TY  - JOUR
A1  - Middelanis, Robin
A1  - Willner, Sven N.
A1  - Otto, Christian
A1  - Kuhla, Kilian
A1  - Quante, Lennart
A1  - Levermann, Anders
T1  - Wave-like global economic ripple response to Hurricane Sandy
JF  - Environmental research letters : ERL / Institute of Physics
N2  - Tropical cyclones range among the costliest disasters on Earth. Their economic repercussions along the supply and trade network also affect remote economies that are not directly affected. We here simulate possible global repercussions on consumption for the example case of Hurricane Sandy in the US (2012) using the shock-propagation model Acclimate. The modeled shock yields a global three-phase ripple: an initial production demand reduction and associated consumption price decrease, followed by a supply shortage with increasing prices, and finally a recovery phase. Regions with strong trade relations to the US experience strong magnitudes of the ripple. A dominating demand reduction or supply shortage leads to overall consumption gains or losses of a region, respectively. While finding these repercussions in historic data is challenging due to strong volatility of economic interactions, numerical models like ours can help to identify them by approaching the problem from an exploratory angle, isolating the effect of interest. For this, our model simulates the economic interactions of over 7000 regional economic sectors, interlinked through about 1.8 million trade relations. Under global warming, the wave-like structures of the economic response to major hurricanes like the one simulated here are likely to intensify and potentially overlap with other weather extremes.
KW  - supply chains
KW  - Hurricane Sandy
KW  - economic ripples
KW  - extreme weather
KW  - impacts
KW  - loss propagation
KW  - natural disasters
Y1  - 2021
U6  - https://doi.org/10.1088/1748-9326/ac39c0
SN  - 1748-9326
VL  - 16
IS  - 12
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Frieler, Katja
A1  - Schauberger, Bernhard
A1  - Arneth, Almut
A1  - Balkovic, Juraj
A1  - Chryssanthacopoulos, James
A1  - Deryng, Delphine
A1  - Elliott, Joshua
A1  - Folberth, Christian
A1  - Khabarov, Nikolay
A1  - Müller, Christoph
A1  - Olin, Stefan
A1  - Pugh, Thomas A. M.
A1  - Schaphoff, Sibyll
A1  - Schewe, Jacob
A1  - Schmid, Erwin
A1  - Warszawski, Lila
A1  - Levermann, Anders
T1  - Understanding the weather signal in national crop-yield variability
JF  - Earths future
N2  - Year-to-year variations in crop yields can have major impacts on the livelihoods of subsistence farmers and may trigger significant global price fluctuations, with severe consequences for people in developing countries. Fluctuations can be induced by weather conditions, management decisions, weeds, diseases, and pests. Although an explicit quantification and deeper understanding of weather-induced crop-yield variability is essential for adaptation strategies, so far it has only been addressed by empirical models. Here, we provide conservative estimates of the fraction of reported national yield variabilities that can be attributed to weather by state-of-the-art, process-based crop model simulations. We find that observed weather variations can explain more than 50% of the variability in wheat yields in Australia, Canada, Spain, Hungary, and Romania. For maize, weather sensitivities exceed 50% in seven countries, including the United States. The explained variance exceeds 50% for rice in Japan and South Korea and for soy in Argentina. Avoiding water stress by simulating yields assuming full irrigation shows that water limitation is a major driver of the observed variations in most of these countries. Identifying the mechanisms leading to crop-yield fluctuations is not only fundamental for dampening fluctuations, but is also important in the context of the debate on the attribution of loss and damage to climate change. Since process-based crop models not only account for weather influences on crop yields, but also provide options to represent human-management measures, they could become essential tools for differentiating these drivers, and for exploring options to reduce future yield fluctuations.
Y1  - 2017
U6  - https://doi.org/10.1002/2016EF000525
SN  - 2328-4277
VL  - 5
SP  - 605
EP  - 616
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Goelzer, Heiko
A1  - Levermann, Anders
A1  - Rahmstorf, Stefan
T1  - Two-way coupling of an ENSO model to the global climate model CLIMBER-3 alpha
N2  - We present a model study that investigates to what extent it is possible to introduce ENSO variability to an Earth system Model of Intermediate Complexity (EMIC). The Zebiak-Cane ENSO model is dynamically coupled to the EMIC CLIMBER-3 alpha, which by itself exhibits no interannual or multidecadal variability. ENSO variability is introduced to CLIMBER-3 alpha by adding ENSO-related sea surface temperature anomalies to the upper layers of the model ocean. For the other coupling direction, changes in the mean CLIMBER-3 alpha climate on decadal time scales are used to change the background state of the ENSO model, achieving a two-way coupling. We compare typical ENSO-related patterns of a fully coupled pre-industrial model run to reanalysis data and point out the possibilities and limitations of this model configuration. Although introduced ENSO-related SST anomalies and other related variables like the Southern Oscillation Index are well reproduced by the EMIC in the forcing domain, teleconnections to other regions are damped, especially in meridional direction. The reason for this limitation is the atmospheric model, which does not sufficiently resolve the necessary transport mechanisms. Despite this limitation the presented coupling method may still be a useful tool in combination with higher resolution atmospheric models as being in development for the successor model CLIMBER-3 and possibly other EMICs.
Y1  - 2009
UR  - http://www.sciencedirect.com/science/journal/14635003
U6  - https://doi.org/10.1016/j.ocemod.2009.03.004
SN  - 1463-5003
ER  - 
TY  - JOUR
A1  - Schleussner, Carl-Friedrich
A1  - Runge, Jakob
A1  - Lehmann, Jasvcha
A1  - Levermann, Anders
T1  - The role of the North Atlantic overturning and deep ocean for multi-decadal global-mean-temperature variability
JF  - Earth system dynamics
Y1  - 2014
U6  - https://doi.org/10.5194/esd-5-103-2014
SN  - 2190-4979
SN  - 2190-4987
VL  - 5
IS  - 1
SP  - 103
EP  - 115
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Reese, Ronja
A1  - Levermann, Anders
A1  - Albrecht, Torsten
A1  - Seroussi, Helene
A1  - Winkelmann, Ricarda
T1  - The role of history and strength of the oceanic forcing in sea level projections from Antarctica with the Parallel Ice Sheet Model
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Mass loss from the Antarctic Ice Sheet constitutes the largest uncertainty in projections of future sea level rise. Ocean-driven melting underneath the floating ice shelves and subsequent acceleration of the inland ice streams are the major reasons for currently observed mass loss from Antarctica and are expected to become more important in the future. Here we show that for projections of future mass loss from the Antarctic Ice Sheet, it is essential (1) to better constrain the sensitivity of sub-shelf melt rates to ocean warming and (2) to include the historic trajectory of the ice sheet. In particular, we find that while the ice sheet response in simulations using the Parallel Ice Sheet Model is comparable to the median response of models in three Antarctic Ice Sheet Intercomparison projects - initMIP, LARMIP-2 and ISMIP6 - conducted with a range of ice sheet models, the projected 21st century sea level contribution differs significantly depending on these two factors. For the highest emission scenario RCP8.5, this leads to projected ice loss ranging from 1:4 to 4:0 cm of sea level equivalent in simulations in which ISMIP6 ocean forcing drives the PICO ocean box model where parameter tuning leads to a comparably low sub-shelf melt sensitivity and in which no surface forcing is applied. This is opposed to a likely range of 9:1 to 35:8 cm using the exact same initial setup, but emulated from the LARMIP-2 experiments with a higher melt sensitivity, even though both projects use forcing from climate models and melt rates are calibrated with previous oceanographic studies. Furthermore, using two initial states, one with a previous historic simulation from 1850 to 2014 and one starting from a steady state, we show that while differences between the ice sheet configurations in 2015 seem marginal at first sight, the historic simulation increases the susceptibility of the ice sheet to ocean warming, thereby increasing mass loss from 2015 to 2100 by 5% to 50 %. Hindcasting past ice sheet changes with numerical models would thus provide valuable tools to better constrain projections. Our results emphasize that the uncertainty that arises from the forcing is of the same order of magnitude as the ice dynamic response for future sea level projections.
Y1  - 2020
U6  - https://doi.org/10.5194/tc-14-3097-2020
SN  - 1994-0416
SN  - 1994-0424
VL  - 14
IS  - 9
SP  - 3097
EP  - 3110
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Martin, Maria A.
A1  - Winkelmann, Ricarda
A1  - Haseloff, M.
A1  - Albrecht, Tanja
A1  - Bueler, Ed
A1  - Khroulev, C.
A1  - Levermann, Anders
T1  - The Potsdam parallel ice sheet model (PISM-PIK) - Part 2: Dynamic equilibrium simulation of the Antarctic ice sheet
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - We present a dynamic equilibrium simulation of the ice sheet-shelf system on Antarctica with the Potsdam Parallel Ice Sheet Model (PISM-PIK). The simulation is initialized with present-day conditions for bed topography and ice thickness and then run to steady state with constant present-day surface mass balance. Surface temperature and sub-shelf basal melt distribution are parameterized. Grounding lines and calving fronts are free to evolve, and their modeled equilibrium state is compared to observational data. A physically-motivated calving law based on horizontal spreading rates allows for realistic calving fronts for various types of shelves. Steady-state dynamics including surface velocity and ice flux are analyzed for whole Antarctica and the Ronne-Filchner and Ross ice shelf areas in particular. The results show that the different flow regimes in sheet and shelves, and the transition zone between them, are captured reasonably well, supporting the approach of superposition of SIA and SSA for the representation of fast motion of grounded ice. This approach also leads to a natural emergence of sliding-dominated flow in stream-like features in this new 3-D marine ice sheet model.
Y1  - 2011
U6  - https://doi.org/10.5194/tc-5-727-2011
SN  - 1994-0416
VL  - 5
IS  - 3
SP  - 727
EP  - 740
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Winkelmann, Ricarda
A1  - Martin, Maria A.
A1  - Haseloff, Monika
A1  - Albrecht, Torsten
A1  - Bueler, Ed
A1  - Khroulev, C.
A1  - Levermann, Anders
T1  - The Potsdam parallel ice sheet model (PISM-PIK) - Part 1: Model description
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - We present the Potsdam Parallel Ice Sheet Model (PISM-PIK), developed at the Potsdam Institute for Climate Impact Research to be used for simulations of large-scale ice sheet-shelf systems. It is derived from the Parallel Ice Sheet Model (Bueler and Brown, 2009). Velocities are calculated by superposition of two shallow stress balance approximations within the entire ice covered region: the shallow ice approximation (SIA) is dominant in grounded regions and accounts for shear deformation parallel to the geoid. The plug-flow type shallow shelf approximation (SSA) dominates the velocity field in ice shelf regions and serves as a basal sliding velocity in grounded regions. Ice streams can be identified diagnostically as regions with a significant contribution of membrane stresses to the local momentum balance. All lateral boundaries in PISM-PIK are free to evolve, including the grounding line and ice fronts. Ice shelf margins in particular are modeled using Neumann boundary conditions for the SSA equations, reflecting a hydrostatic stress imbalance along the vertical calving face. The ice front position is modeled using a subgrid-scale representation of calving front motion (Albrecht et al., 2011) and a physically-motivated calving law based on horizontal spreading rates. The model is tested in experiments from the Marine Ice Sheet Model Intercomparison Project (MISMIP). A dynamic equilibrium simulation of Antarctica under present-day conditions is presented in Martin et al. (2011).
Y1  - 2011
U6  - https://doi.org/10.5194/tc-5-715-2011
SN  - 1994-0416
VL  - 5
IS  - 3
SP  - 715
EP  - 726
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Levermann, Anders
A1  - Clark, Peter U.
A1  - Marzeion, Ben
A1  - Milne, Glenn A.
A1  - Pollard, David
A1  - Radic, Valentina
A1  - Robinson, Alexander
T1  - The multimillennial sea-level commitment of global warming
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Global mean sea level has been steadily rising over the last century, is projected to increase by the end of this century, and will continue to rise beyond the year 2100 unless the current global mean temperature trend is reversed. Inertia in the climate and global carbon system, however, causes the global mean temperature to decline slowly even after greenhouse gas emissions have ceased, raising the question of how much sea-level commitment is expected for different levels of global mean temperature increase above preindustrial levels. Although sea-level rise over the last century has been dominated by ocean warming and loss of glaciers, the sensitivity suggested from records of past sea levels indicates important contributions should also be expected from the Greenland and Antarctic Ice Sheets. Uncertainties in the paleo-reconstructions, however, necessitate additional strategies to better constrain the sea-level commitment. Here we combine paleo-evidence with simulations from physical models to estimate the future sea-level commitment on a multimillennial time scale and compute associated regional sea-level patterns. Oceanic thermal expansion and the Antarctic Ice Sheet contribute quasi-linearly, with 0.4 m degrees C-1 and 1.2 m degrees C-1 of warming, respectively. The saturation of the contribution from glaciers is overcompensated by the nonlinear response of the Greenland Ice Sheet. As a consequence we are committed to a sea-level rise of approximately 2.3 m degrees C-1 within the next 2,000 y. Considering the lifetime of anthropogenic greenhouse gases, this imposes the need for fundamental adaptation strategies on multicentennial time scales.
KW  - climate change
KW  - climate impacts
KW  - sea-level change
Y1  - 2013
U6  - https://doi.org/10.1073/pnas.1219414110
SN  - 0027-8424
VL  - 110
IS  - 34
SP  - 13745
EP  - 13750
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Garbe, Julius
A1  - Albrecht, Torsten
A1  - Levermann, Anders
A1  - Donges, Jonathan
A1  - Winkelmann, Ricarda
T1  - The hysteresis of the Antarctic Ice Sheet
JF  - Nature : the international weekly journal of science
N2  - More than half of Earth's freshwater resources are held by the Antarctic Ice Sheet, which thus represents by far the largest potential source for global sea-level rise under future warming conditions(1). Its long-term stability determines the fate of our coastal cities and cultural heritage. Feedbacks between ice, atmosphere, ocean, and the solid Earth give rise to potential nonlinearities in its response to temperature changes. So far, we are lacking a comprehensive stability analysis of the Antarctic Ice Sheet for different amounts of global warming. Here we show that the Antarctic Ice Sheet exhibits a multitude of temperature thresholds beyond which ice loss is irreversible. Consistent with palaeodata(2)we find, using the Parallel Ice Sheet Model(3-5), that at global warming levels around 2 degrees Celsius above pre-industrial levels, West Antarctica is committed to long-term partial collapse owing to the marine ice-sheet instability. Between 6 and 9 degrees of warming above pre-industrial levels, the loss of more than 70 per cent of the present-day ice volume is triggered, mainly caused by the surface elevation feedback. At more than 10 degrees of warming above pre-industrial levels, Antarctica is committed to become virtually ice-free. The ice sheet's temperature sensitivity is 1.3 metres of sea-level equivalent per degree of warming up to 2 degrees above pre-industrial levels, almost doubling to 2.4 metres per degree of warming between 2 and 6 degrees and increasing to about 10 metres per degree of warming between 6 and 9 degrees. Each of these thresholds gives rise to hysteresis behaviour: that is, the currently observed ice-sheet configuration is not regained even if temperatures are reversed to present-day levels. In particular, the West Antarctic Ice Sheet does not regrow to its modern extent until temperatures are at least one degree Celsius lower than pre-industrial levels. Our results show that if the Paris Agreement is not met, Antarctica's long-term sea-level contribution will dramatically increase and exceed that of all other sources. <br /> Modelling shows that the Antarctic Ice Sheet exhibits multiple temperature thresholds beyond which ice loss would become irreversible, and once melted, the ice sheet can regain its previous mass only if the climate cools well below pre-industrial temperatures.
Y1  - 2020
U6  - https://doi.org/10.1038/s41586-020-2727-5
SN  - 0028-0836
SN  - 1476-4687
VL  - 585
IS  - 7826
SP  - 538
EP  - 544
PB  - Macmillan Publishers Limited
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Reese, Ronja
A1  - Gudmundsson, Gudmundur Hilmar
A1  - Levermann, Anders
A1  - Winkelmann, Ricarda
T1  - The far reach of ice-shelf thinning in Antarctica
JF  - Nature climate change
N2  - Floating ice shelves, which fringe most of Antarctica’s coastline, regulate ice flow into the Southern Ocean1,2,3. Their thinning4,5,6,7 or disintegration8,9 can cause upstream acceleration of grounded ice and raise global sea levels. So far the effect has not been quantified in a comprehensive and spatially explicit manner. Here, using a finite-element model, we diagnose the immediate, continent-wide flux response to different spatial patterns of ice-shelf mass loss. We show that highly localized ice-shelf thinning can reach across the entire shelf and accelerate ice flow in regions far from the initial perturbation. As an example, this ‘tele-buttressing’ enhances outflow from Bindschadler Ice Stream in response to thinning near Ross Island more than 900 km away. We further find that the integrated flux response across all grounding lines is highly dependent on the location of imposed changes: the strongest response is caused not only near ice streams and ice rises, but also by thinning, for instance, well-within the Filchner–Ronne and Ross Ice Shelves. The most critical regions in all major ice shelves are often located in regions easily accessible to the intrusion of warm ocean waters10,11,12, stressing Antarctica’s vulnerability to changes in its surrounding ocean.
Y1  - 2017
U6  - https://doi.org/10.1038/s41558-017-0020-x
SN  - 1758-678X
SN  - 1758-6798
VL  - 8
IS  - 1
SP  - 53
EP  - 57
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Kotz, Maximilian
A1  - Levermann, Anders
A1  - Wenz, Leonie
T1  - The effect of rainfall changes on economic production
JF  - Nature : the international journal of science
N2  - Macro-economic assessments of climate impacts lack an analysis of the distribution of daily rainfall, which can resolve both complex societal impact channels and anthropogenically forced changes(1-6). Here, using a global panel of subnational economic output for 1,554 regions worldwide over the past 40 years, we show that economic growth rates are reduced by increases in the number of wet days and in extreme daily rainfall, in addition to responding nonlinearly to the total annual and to the standardized monthly deviations of rainfall. Furthermore, high-income nations and the services and manufacturing sectors are most strongly hindered by both measures of daily rainfall, complementing previous work that emphasized the beneficial effects of additional total annual rainfall in low-income, agriculturally dependent economies(4,7). By assessing the distribution of rainfall at multiple timescales and the effects on different sectors, we uncover channels through which climatic conditions can affect the economy. These results suggest that anthropogenic intensification of daily rainfall extremes(8-10) will have negative global economic consequences that require further assessment by those who wish to evaluate the costs of anthropogenic climate change.
Y1  - 2022
U6  - https://doi.org/10.1038/s41586-021-04283-8
SN  - 0028-0836
SN  - 1476-4687
VL  - 601
IS  - 7892
SP  - 223
EP  - 227
PB  - Macmillan Publishers Limited, part of Springer Nature
CY  - London
ER  - 
TY  - JOUR
A1  - Ueckerdt, Falko
A1  - Frieler, Katja
A1  - Lange, Stefan
A1  - Wenz, Leonie
A1  - Luderer, Gunnar
A1  - Levermann, Anders
T1  - The economically optimal warming limit of the planet
JF  - Earth system dynamics
N2  - Both climate-change damages and climate-change mitigation will incur economic costs. While the risk of severe damages increases with the level of global warming (Dell et al., 2014; IPCC, 2014b, 2018; Lenton et al., 2008), mitigating costs increase steeply with more stringent warming limits (IPCC, 2014a; Luderer et al., 2013; Rogelj et al., 2015). Here, we show that the global warming limit that minimizes this century's total economic costs of climate change lies between 1.9 and 2 ∘C, if temperature changes continue to impact national economic growth rates as observed in the past and if instantaneous growth effects are neither compensated nor amplified by additional growth effects in the following years. The result is robust across a wide range of normative assumptions on the valuation of future welfare and inequality aversion. We combine estimates of climate-change impacts on economic growth for 186 countries (applying an empirical damage function from Burke et al., 2015) with mitigation costs derived from a state-of-the-art energy–economy–climate model with a wide range of highly resolved mitigation options (Kriegler et al., 2017; Luderer et al., 2013, 2015). Our purely economic assessment, even though it omits non-market damages, provides support for the international Paris Agreement on climate change. The political goal of limiting global warming to “well below 2 degrees” is thus also an economically optimal goal given above assumptions on adaptation and damage persistence.
Y1  - 2019
U6  - https://doi.org/10.5194/esd-10-741-2019
SN  - 2190-4979
SN  - 2190-4987
VL  - 10
IS  - 4
SP  - 741
EP  - 763
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Born, Andreas
A1  - Levermann, Anders
T1  - The 8.2 ka event : abrupt transition of the subpolar gyre toward a modern North Atlantic circulation
N2  - Climate model simulations of the 8.2 ka event show an abrupt strengthening of the Atlantic subpolar gyre that allows us to connect two major but apparently contradictory climate events of the early Holocene: the freshwater outburst from proglacial lakes and the onset of Labrador Sea water formation. The 8.2 ka event is the largest climatic signal of our present interglacial with a widespread cooling in the North Atlantic region about 8200 years before present. It coincides with a meltwater outburst from North American proglacial lakes that is believed to have weakened the Atlantic meridional overturning circulation and northward heat transport, followed by a recovery of the deep ocean circulation and rising temperatures after a few centuries. Marine proxy data, however, date the onset of deep water formation in Labrador Sea to the same time. The subsequent strengthening of the slope current system created a regional signal recorded as an abrupt and persistent surface temperature decrease. Although similarities in timing are compelling, a mechanism to reconcile these apparently contradictory events was missing. Our simulations show that an abrupt and persistent strengthening of the Atlantic subpolar gyre provides a plausible explanation. The intense freshwater pulse triggered a transition of the gyre circulation into a different mode of operation, stabilized by internal feedbacks and persistent after the cessation of the perturbation. As a direct consequence, deep water formation around its center intensifies. This corresponds to the modern flow regime and stabilizes the meridional overturning circulation, possibly contributing to the Holocene's climatic stability.
Y1  - 2010
UR  - http://www.agu.org/journals/gc/
U6  - https://doi.org/10.1029/2009gc003024
SN  - 1525-2027
ER  - 
TY  - JOUR
A1  - Marzeion, Benjamin
A1  - Levermann, Anders
T1  - Stratification-dependent mixing may increase sensitivity of a wind-driven Atlantic overturning to surface freshwater flux
N2  - Stratification-dependent mixing is employed in a coupled climate model of intermediate complexity with a 3- dimensional ocean component. Oceanic vertical diffusivity is calculated as kappa similar to N-alpha, where N is the local buoyancy frequency. The sensitivity of the Atlantic meridional overturning circulation (AMOC) to freshwater forcing is tested for exponents 0 <= a <= 2 by first slowly increasing, then decreasing the freshwater forcing over the North Atlantic, keeping the model close to equilibrium. The surface fresh anomaly imposed between 20 degrees N and 50 degrees N in the Atlantic reaches the deep ocean by vertical diffusion, and by AMOC advection via the northern convection sites. The fresh anomaly leads to enhanced stratification and thereby reduces vertical mixing stronger for higher values of a. Consequently, the freshwater anomaly reaches the northern deep water formation regions less diluted, and reduces the AMOC more strongly compared to lower values of a. Our findings indicate that modeled changes in the AMOC depend critically on the details of the mixing parameterization employed in the model.
Y1  - 2009
UR  - http://www.agu.org/journals/gl/
U6  - https://doi.org/10.1029/2009gl039947
SN  - 0094-8276
ER  - 
TY  - JOUR
A1  - Feldmann, Johannes
A1  - Levermann, Anders
A1  - Mengel, Matthias
T1  - Stabilizing the West Antarctic Ice Sheet by surface mass deposition
JF  - Science Advances
N2  - There is evidence that a self-sustaining ice discharge from the West Antarctic Ice Sheet (WAIS) has started, potentially leading to its disintegration. The associated sea level rise of more than 3m would pose a serious challenge to highly populated areas including metropolises such as Calcutta, Shanghai, New York City, and Tokyo. Here, we show that the WAIS may be stabilized through mass deposition in coastal regions around Pine Island and Thwaites glaciers. In our numerical simulations, a minimum of 7400 Gt of additional snowfall stabilizes the flow if applied over a short period of 10 years onto the region (-2 mm year(-1) sea level equivalent). Mass deposition at a lower rate increases the intervention time and the required total amount of snow. We find that the precise conditions of such an operation are crucial, and potential benefits need to be weighed against environmental hazards, future risks, and enormous technical challenges.
Y1  - 2019
U6  - https://doi.org/10.1126/sciadv.aaw4132
SN  - 2375-2548
VL  - 5
IS  - 7
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schlemm, Tanja
A1  - Feldmann, Johannes
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Stabilizing effect of melange buttressing on the marine ice-cliff instability of the West Antarctic Ice Sheet
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Owing to global warming and particularly high regional ocean warming, both Thwaites and Pine Island Glaciers in the Amundsen region of the Antarctic Ice Sheet could lose their buttressing ice shelves over time. We analyse the possible consequences using the parallel ice sheet model (PISM), applying a simple cliff-calving parameterization and an ice melange-buttressing model. We find that the instantaneous loss of ice-shelf buttressing, due to enforced ice-shelf melting, initiates grounding-line retreat and triggers marine ice sheet instability (MISI). As a consequence, the grounding line progresses into the interior of the West Antarctic Ice Sheet and leads to a sea level contribution of 0.6 m within 100 a. By subjecting the exposed ice cliffs to cliff calving using our simplified parameterization, we also analyse marine ice cliff instability (MICI). In our simulations it can double or even triple the sea level contribution depending on the only loosely constrained parameter that determines the maximum cliff-calving rate. The speed of MICI depends on this upper bound of the calving rate, which is given by the ice melange buttressing the glacier. However, stabilization of MICI may occur for geometric reasons. Because the embayment geometry changes as MICI advances into the interior of the ice sheet, the upper bound on calving rates is reduced and the progress of MICI is slowed down. Although we cannot claim that our simulations bear relevant quantitative estimates of the effect of ice-melange buttressing on MICI, the mechanism has the potential to stop the instability. Further research is needed to evaluate its role for the past and future evolution of the Antarctic Ice Sheet.
Y1  - 2022
U6  - https://doi.org/10.5194/tc-16-1979-2022
SN  - 1994-0416
SN  - 1994-0424
VL  - 16
IS  - 5
SP  - 1979
EP  - 1996
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Albrecht, Torsten
A1  - Levermann, Anders
T1  - Spontaneous ice-front retreat caused by disintegration of adjacent ice shelf in Antarctica
JF  - Earth & planetary science letters
N2  - Antarctic ice-discharge constitutes the largest uncertainty in future sea-level projections. Floating ice shelves, fringing most of Antarctica, exert retentive forces onto the ice flow. While abrupt ice-shelf retreat has been observed, it is generally considered a localized phenomenon. Here we show that the disintegration of an ice shelf may induce the spontaneous retreat of its neighbor. As an example, we reproduce the spontaneous but gradual retreat of the Larsen B ice front as observed after the disintegration of the adjacent Larsen A ice shelf. We show that the Larsen A collapse yields a change in spreading rate in Larsen B via their connecting ice channels and thereby causes a retreat of the ice front to its observed position of the year 2000, prior to its collapse. This mechanism might be particularly relevant for the role of East Antarctica and the Antarctic Peninsula in future sea level.
KW  - Antarctica
KW  - Larsen Ice Shelf
KW  - glaciology
KW  - numerical ice modeling
KW  - sea level
KW  - iceberg calving
Y1  - 2014
U6  - https://doi.org/10.1016/j.epsl.2014.02.034
SN  - 0012-821X
SN  - 1385-013X
VL  - 393
SP  - 26
EP  - 30
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - GEN
A1  - Feldmann, Johannes
A1  - Levermann, Anders
T1  - Similitude of ice dynamics against scaling of geometry and physical parameters
T2  - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe
N2  - The concept of similitude is commonly employed in the fields of fluid dynamics and engineering but rarely used in cryospheric research. Here we apply this method to the problem of ice flow to examine the dynamic similitude of isothermal ice sheets in shallow-shelf approximation against the scaling of their geometry and physical parameters. Carrying out a dimensional analysis of the stress balance we obtain dimensionless numbers that characterize the flow. Requiring that these numbers remain the same under scaling we obtain conditions that relate the geometric scaling factors, the parameters for the ice softness, surface mass balance and basal friction as well as the ice-sheet intrinsic response time to each other. We demonstrate that these scaling laws are the same for both the (two-dimensional) flow-line case and the three-dimensional case. The theoretically predicted ice-sheet scaling behavior agrees with results from numerical simulations that we conduct in flow-line and three-dimensional conceptual setups. We further investigate analytically the implications of geometric scaling of ice sheets for their response time. With this study we provide a framework which, under several assumptions, allows for a fundamental comparison of the ice-dynamic behavior across different scales. It proves to be useful in the design of conceptual numerical model setups and could also be helpful for designing laboratory glacier experiments. The concept might also be applied to real-world systems, e.g., to examine the response times of glaciers, ice streams or ice sheets to climatic perturbations.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 564 
KW  - grounding line motion
KW  - full-stokes model
KW  - West Antarctica
KW  - sheet models
KW  - Pine Island
KW  - stream-B
KW  - shelf
KW  - flow
KW  - sensitivity
KW  - collapse
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-412441
SN  - 1866-8372
IS  - 564
SP  - 1753
EP  - 1769
ER  - 
TY  - JOUR
A1  - Feldmann, Johannes
A1  - Levermann, Anders
T1  - Similitude of ice dynamics against scaling of geometry and physical parameters
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - The concept of similitude is commonly employed in the fields of fluid dynamics and engineering but rarely used in cryospheric research. Here we apply this method to the problem of ice flow to examine the dynamic similitude of isothermal ice sheets in shallow-shelf approximation against the scaling of their geometry and physical parameters. Carrying out a dimensional analysis of the stress balance we obtain dimensionless numbers that characterize the flow. Requiring that these numbers remain the same under scaling we obtain conditions that relate the geometric scaling factors, the parameters for the ice softness, surface mass balance and basal friction as well as the ice-sheet intrinsic response time to each other. We demonstrate that these scaling laws are the same for both the (two-dimensional) flow-line case and the three-dimensional case. The theoretically predicted ice-sheet scaling behavior agrees with results from numerical simulations that we conduct in flow-line and three-dimensional conceptual setups. We further investigate analytically the implications of geometric scaling of ice sheets for their response time. With this study we provide a framework which, under several assumptions, allows for a fundamental comparison of the ice-dynamic behavior across different scales. It proves to be useful in the design of conceptual numerical model setups and could also be helpful for designing laboratory glacier experiments. The concept might also be applied to real-world systems, e.g., to examine the response times of glaciers, ice streams or ice sheets to climatic perturbations.
Y1  - 2016
U6  - https://doi.org/10.5194/tc-10-1753-2016
SN  - 1994-0416
SN  - 1994-0424
VL  - 10
SP  - 1753
EP  - 1769
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Feldmann, Johannes
A1  - Reese, Ronja
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Shear-margin melting causes stronger transient ice discharge than ice-stream melting in idealized simulations
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Basal ice-shelf melting is the key driver of Antarctica's increasing sea-level contribution. In diminishing the buttressing force of the ice shelves that fringe the ice sheet, the melting increases the ice discharge into the ocean.
Here we contrast the influence of basal melting in two different ice-shelf regions on the time-dependent response of an isothermal, inherently buttressed ice-sheet-shelf system. In the idealized numerical simulations, the basal-melt perturbations are applied close to the grounding line in the ice-shelf's (1) ice-stream region, where the ice shelf is fed by the fastest ice masses that stream through the upstream bed trough and (2) shear margins, where the ice flow is slower.
The results show that melting below one or both of the shear margins can cause a decadal to centennial increase in ice discharge that is more than twice as large compared to a similar perturbation in the ice-stream region. We attribute this to the fact that melt-induced ice-shelf thinning in the central grounding-line region is attenuated very effectively by the fast flow of the central ice stream. In contrast, the much slower ice dynamics in the lateral shear margins of the ice shelf facilitate sustained ice-shelf thinning and thereby foster buttressing reduction.
Regardless of the melt location, a higher melt concentration toward the grounding line generally goes along with a stronger response. Our results highlight the vulnerability of outlet glaciers to basal melting in stagnant, buttressing-relevant ice-shelf regions, a mechanism that may gain importance under future global warming.
Y1  - 2022
U6  - https://doi.org/10.5194/tc-16-1927-2022
SN  - 1994-0416
SN  - 1994-0424
VL  - 16
IS  - 5
SP  - 1927
EP  - 1940
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Born, Andreas
A1  - Levermann, Anders
A1  - Mignot, Juliette
T1  - Sensitivity of the Atlantic Ocean circulation to a hydraulic overflow parameterisation in a coarse resolution model : response of the subpolar gyre
N2  - We investigate the sensitivity of a coarse resolution coupled climate model to the representation of the overflows over the Greenland-Scotland ridge. This class of models suffers from a poor representation of the water mass exchange between the Nordic Seas and the North Atlantic, a crucial part of the large-scale oceanic circulation. We revisit the explicit representation of the overflows using a parameterisation by hydraulic constraints and compare it with the enhancement of the overflow transport by artificially deepened passages over the Greenland-Scotland ridge, a common practice in coarse resolution models. Both configurations increase deep water formation in the Nordic Seas and represent the large-scale dynamics of the Atlantic realistically in contrast to a third model version with realistic sill depths but without the explicit overflow transport. The comparison of the hydrography suggests that for the unperturbed equilibrium the Nordic Seas are better represented with the parameterised overflows. As in previous studies, we do not find a stabilising effect of the overflow parameterisation on the Atlantic meridional overturning circulation but merely on the overflow transport. As a consequence the surface air temperature in the Nordic Seas is less sensitive to anomalous surface fresh water forcing. Special attention is paid to changes in the subpolar gyre circulation. We find it sensitive to the overflow transport and the density of these water masses through baroclinic adjustments. The analysis of the governing equations confirms the presence of positive feedbacks inherent to the subpolar gyre and allows us to isolate the influence of the overflows on its dynamics.
Y1  - 2009
UR  - http://www.sciencedirect.com/science/journal/14635003
U6  - https://doi.org/10.1016/j.ocemod.2008.11.006
SN  - 1463-5003
ER  - 
TY  - JOUR
A1  - Zeitz, Maria
A1  - Levermann, Anders
A1  - Winkelmann, Ricarda
T1  - Sensitivity of ice loss to uncertainty in flow law parameters in an idealized one-dimensional geometry
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Acceleration of the flow of ice drives mass losses in both the Antarctic and the Greenland Ice Sheet. The projections of possible future sea-level rise rely on numerical ice-sheet models, which solve the physics of ice flow, melt, and calving. While major advancements have been made by the ice-sheet modeling community in addressing several of the related uncertainties, the flow law, which is at the center of most process-based ice-sheet models, is not in the focus of the current scientific debate. However, recent studies show that the flow law parameters are highly uncertain and might be different from the widely accepted standard values. Here, we use an idealized flow-line setup to investigate how these uncertainties in the flow law translate into uncertainties in flow-driven mass loss. In order to disentangle the effect of future warming on the ice flow from other effects, we perform a suite of experiments with the Parallel Ice Sheet Model (PISM), deliberately excluding changes in the surface mass balance. We find that changes in the flow parameters within the observed range can lead up to a doubling of the flow-driven mass loss within the first centuries of warming, compared to standard parameters. The spread of ice loss due to the uncertainty in flow parameters is on the same order of magnitude as the increase in mass loss due to surface warming. While this study focuses on an idealized flow-line geometry, it is likely that this uncertainty carries over to realistic three-dimensional simulations of Greenland and Antarctica.
Y1  - 2020
U6  - https://doi.org/10.5194/tc-14-3537-2020
SN  - 1994-0416
SN  - 1994-0424
VL  - 14
IS  - 10
SP  - 3537
EP  - 3550
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Clark, Peter U.
A1  - Mix, Alan C.
A1  - Eby, Michael
A1  - Levermann, Anders
A1  - Rogelj, Joeri
A1  - Nauels, Alexander
A1  - Wrathall, David J.
T1  - Sea-level commitment as a gauge for climate policy
T2  - Nature climate change
N2  - A well-defined relationship between global mean sea-level rise and cumulative carbon emissions can be used to inform policy about emission limits to prevent dangerous and essentially permanent anthropogenic interference with the climate system.
Y1  - 2018
U6  - https://doi.org/10.1038/s41558-018-0226-6
SN  - 1758-678X
SN  - 1758-6798
VL  - 8
IS  - 8
SP  - 653
EP  - 655
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Schleussner, Carl-Friedrich
A1  - Rogelj, Joeri
A1  - Schaeffer, Michiel
A1  - Lissner, Tabea
A1  - Licker, Rachel
A1  - Fischer, Erich M.
A1  - Knutti, Reto
A1  - Levermann, Anders
A1  - Frieler, Katja
A1  - Hare, William
T1  - Science and policy characteristics of the Paris Agreement temperature goal
JF  - Nature climate change
Y1  - 2016
U6  - https://doi.org/10.1038/NCLIMATE3096
SN  - 1758-678X
SN  - 1758-6798
VL  - 6
SP  - 827
EP  - 835
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Levermann, Anders
A1  - Feldmann, Johannes
T1  - Scaling of instability timescales of Antarctic outlet glaciers based on one-dimensional similitude analysis
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Recent observations and ice-dynamic modeling suggest that a marine ice-sheet instability (MISI) might have been triggered in West Antarctica. The corresponding outlet glaciers, Pine Island Glacier (PIG) and Thwaites Glacier (TG), showed significant retreat during at least the last 2 decades. While other regions in Antarctica have the topographic predisposition for the same kind of instability, it is so far unclear how fast these instabilities would unfold if they were initiated. Here we employ the concept of similitude to estimate the characteristic timescales of several potentially MISI-prone outlet glaciers around the Antarctic coast. Our results suggest that TG and PIG have the fastest response time of all investigated outlets, with TG responding about 1.25 to 2 times as fast as PIG, while other outlets around Antarctica would be up to 10 times slower if destabilized. These results have to be viewed in light of the strong assumptions made in their derivation. These include the absence of ice-shelf buttressing, the one-dimensionality of the approach and the uncertainty of the available data. We argue however that the current topographic situation and the physical conditions of the MISI-prone outlet glaciers carry the information of their respective timescale and that this information can be partially extracted through a similitude analysis.
Y1  - 2019
U6  - https://doi.org/10.5194/tc-13-1621-2019
SN  - 1994-0416
SN  - 1994-0424
VL  - 13
IS  - 6
SP  - 1621
EP  - 1633
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Kuhla, Kilian
A1  - Willner, Sven N.
A1  - Otto, Christian
A1  - Geiger, Tobias
A1  - Levermann, Anders
T1  - Ripple resonance amplifies economic welfare loss from weather extremes
JF  - Environmental research letters : ERL / Institute of Physics
N2  - The most complex but potentially most severe impacts of climate change are caused by extreme weather events. In a globally connected economy, damages can cause remote perturbations and cascading consequences-a ripple effect along supply chains. Here we show an economic ripple resonance that amplifies losses when consecutive or overlapping weather extremes and their repercussions interact. This amounts to an average amplification of 21% for climate-induced heat stress, river floods, and tropical cyclones. Modeling the temporal evolution of 1.8 million trade relations between >7000 regional economic sectors, we find that the regional responses to future extremes are strongly heterogeneous also in their resonance behavior. The induced effect on welfare varies between gains due to increased demand in some regions and losses due to demand or supply shortages in others. Within the current global supply network, the ripple resonance effect of extreme weather is strongest in high-income economies-an important effect to consider when evaluating past and future economic climate impacts.
KW  - consecutive disasters
KW  - economic ripple resonance
KW  - repercussion resonance
KW  - weather extremes
KW  - supply network
KW  - climate impacts
KW  - climate change
Y1  - 2021
U6  - https://doi.org/10.1088/1748-9326/ac2932
SN  - 1748-9326
VL  - 16
IS  - 11
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Montoya, Marisa
A1  - Born, Andreas
A1  - Levermann, Anders
T1  - Reversed North Atlantic gyre dynamics in present and glacial climates
JF  - Climate dynamics : observational, theoretical and computational research on the climate system
N2  - The dynamics of the North Atlantic subpolar gyre (SPG) are assessed under present and glacial boundary conditions by investigating the SPG sensitivity to surface wind-stress changes in a coupled climate model. To this end, the gyre transport is decomposed in Ekman, thermohaline, and bottom transports. Surface wind-stress variations are found to play an important indirect role in SPG dynamics through their effect on water-mass densities. Our results suggest the existence of two dynamically distinct regimes of the SPG, depending on the absence or presence of deep water formation (DWF) in the Nordic Seas and a vigorous Greenland-Scotland ridge (GSR) overflow. In the first regime, the GSR overflow is weak and the SPG strength increases with wind-stress as a result of enhanced outcropping of isopycnals in the centre of the SPG. As soon as a vigorous GSR overflow is established, its associated positive density anomalies on the southern GSR slope reduce the SPG strength. This has implications for past glacial abrupt climate changes, insofar as these can be explained through latitudinal shifts in North Atlantic DWF sites and strengthening of the North Atlantic current. Regardless of the ultimate trigger, an abrupt shift of DWF into the Nordic Seas could result both in a drastic reduction of the SPG strength and a sudden reversal in its sensitivity to wind-stress variations. Our results could provide insight into changes in the horizontal ocean circulation during abrupt glacial climate changes, which have been largely neglected up to now in model studies.
Y1  - 2011
U6  - https://doi.org/10.1007/s00382-009-0729-y
SN  - 0930-7575
VL  - 36
IS  - 5-6
SP  - 1107
EP  - 1118
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Hattermann, Tore
A1  - Levermann, Anders
T1  - Response of Southern Ocean circulation to global warming may enhance basal ice shelf melting around Antarctica
N2  - We investigate the large-scale oceanic features determining the future ice shelf-ocean interaction by analyzing global warming experiments in a coarse resolution climate model with a comprehensive ocean component. Heat and freshwater fluxes from basal ice shelf melting (ISM) are parameterized following Beckmann and Goosse [Ocean Model 5(2):157-170, 2003]. Melting sensitivities to the oceanic temperature outside of the ice shelf cavities are varied from linear to quadratic (Holland et al. in J Clim 21, 2008). In 1% per year CO2-increase experiments the total freshwater flux from ISM triples to 0.09 Sv in the linear case and more than quadruples to 0.15 Sv in the quadratic case after 140 years at which 4 x 280 ppm = 1,120 ppm was reached. Due to the long response time of subsurface temperature anomalies, ISM thereafter increases drastically, if CO2 concentrations are kept constant at 1,120 ppm. Varying strength of the Antarctic circumpolar current (ACC) is crucial for ISM increase, because southward advection of heat dominates the warming along the Antarctic coast. On centennial timescales the ACC accelerates due to deep ocean warming north of the current, caused by mixing of heat along isopycnals in the Southern Ocean (SO) outcropping regions. In contrast to previous studies we find an initial weakening of the ACC during the first 150 years of warming. This purely baroclinic effect is due to a freshening in the SO which is consistent with present observations. Comparison with simulations with diagnosed ISM but without its influence on the ocean circulation reveal a number of ISM-related feedbacks, of which a negative ISM-feedback, due to the ISM-related local oceanic cooling, is the dominant one.
Y1  - 2010
UR  - http://www.springerlink.com/content/100405
U6  - https://doi.org/10.1007/s00382-009-0643-3
SN  - 0930-7575
ER  - 
TY  - JOUR
A1  - Feldmann, J.
A1  - Albrecht, Torsten
A1  - Khroulev, C.
A1  - Pattyn, F.
A1  - Levermann, Anders
T1  - Resolution-dependent performance of grounding line motion in a shallow model compared with a full-Stokes model according to the MISMIP3d intercomparison
JF  - Journal of glaciology
N2  - Making confident statements about the evolution of an ice-sheet shelf system with a numerical model requires the capability to reproduce the migration of the grounding line. Here we show that the shallow-ice approximation/shallow-shelf approximation hybrid-type Parallel Ice Sheet Model (PISM), with its recent improvements, is capable of modeling the grounding line motion in a perturbed ice-sheet shelf system. The model is set up according to the three-dimensional Marine Ice-Sheet Model Intercomparison Project (MISMIP3d), and simulations are carried out across a broad range of spatial resolutions. Using (1) a linear interpolation of the grounding line with locally interpolated basal friction and (2) an improved driving-stress computation across the grounding line, the reversibility of the grounding line (i.e. its retreat after an advance forced by a local perturbation of basal resistance) is captured by the model even at medium and low resolutions (Delta x > 10 km). The transient model response is qualitatively similar to that of higher-order models but reveals a higher initial sensitivity to perturbations on very short timescales. Our findings support the application of PISM to the Antarctic ice sheet from regional up to continental scales and on relatively low spatial resolutions.
KW  - glacier flow
KW  - ice dynamics
KW  - ice-sheet modelling
Y1  - 2014
U6  - https://doi.org/10.3189/2014JoG13J093
SN  - 0022-1430
SN  - 1727-5652
VL  - 60
IS  - 220
SP  - 353
EP  - 360
PB  - International Glaciological Society
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Geiger, Tobias
A1  - Frieler, Katja
A1  - Levermann, Anders
T1  - Reply to Comment on: High-income does not protect against hurricane losses (Environmental research letters. -  12 (2017))
T2  - Environmental research letters
N2  - Recently a multitude of empirically derived damage models have been applied to project future tropical cyclone (TC) losses for the United States. In their study (Geiger et al 2016 Environ. Res. Lett. 11 084012) compared two approaches that differ in the scaling of losses with socio-economic drivers: the commonly-used approach resulting in a sub-linear scaling of historical TC losses with a nation's affected gross domestic product (GDP), and the disentangled approach that shows a sub-linear increase with affected population and a super-linear scaling of relative losses with per capita income. Statistics cannot determine which approach is preferable but since process understanding demands that there is a dependence of the loss on both GDP per capita and population, an approach that accounts for both separately is preferable to one which assumes a specific relation between the two dependencies. In the accompanying comment, Rybski et al argued that there is no rigorous evidence to reach the conclusion that high-income does not protect against hurricane losses. Here we affirm that our conclusion is drawn correctly and reply to further remarks raised in the comment, highlighting the adequateness of our approach but also the potential for future extension of our research.
KW  - climate change
KW  - tropical cyclones
KW  - damage
KW  - meteorological extremes
KW  - vulnerability
Y1  - 2017
U6  - https://doi.org/10.1088/1748-9326/aa88d6
SN  - 1748-9326
VL  - 12
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Quante, Lennart
A1  - Willner, Sven N.
A1  - Middelanis, Robin
A1  - Levermann, Anders
T1  - Regions of intensification of extreme snowfall under future warming
JF  - Scientific reports
N2  - Due to climate change the frequency and character of precipitation are changing as the hydrological cycle intensifies. With regards to snowfall, global warming has two opposing influences; increasing humidity enables intense snowfall, whereas higher temperatures decrease the likelihood of snowfall. Here we show an intensification of extreme snowfall across large areas of the Northern Hemisphere under future warming. This is robust across an ensemble of global climate models when they are bias-corrected with observational data. While mean daily snowfall decreases, both the 99th and the 99.9th percentiles of daily snowfall increase in many regions in the next decades, especially for Northern America and Asia. Additionally, the average intensity of snowfall events exceeding these percentiles as experienced historically increases in many regions. This is likely to pose a challenge to municipalities in mid to high latitudes. Overall, extreme snowfall events are likely to become an increasingly important impact of climate change in the next decades, even if they will become rarer, but not necessarily less intense, in the second half of the century.
Y1  - 2021
U6  - https://doi.org/10.1038/s41598-021-95979-4
SN  - 2045-2322
VL  - 11
IS  - 1
PB  - Macmillan Publishers Limited, part of Springer Nature
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Wenz, Leonie
A1  - Willner, Sven N.
A1  - Radebach, Alexander
A1  - Bierkandt, Robert
A1  - Steckel, Jan Christoph
A1  - Levermann, Anders
T1  - Regional and sectoral disaggregation of multi-regional input-output tables - a flexible algorithm
JF  - Economic systems research : journal of the International Input-Output Association
N2  - A common shortcoming of available multi-regional input-output (MRIO) data sets is their lack of regional and sectoral detail required for many research questions (e.g. in the field of disaster impact analysis). We present a simple algorithm to refine MRIO tables regionally and/or sectorally. By the use of proxy data, each MRIO flow in question is disaggregated into the corresponding sub-flows. This downscaling procedure is complemented by an adjustment rule ensuring that the sub-flows match the superordinate flow in sum. The approximation improves along several iteration steps. The algorithm unfolds its strength through the flexible combination of multiple, possibly incomplete proxy data sources. It is also flexible in a sense that any target sector and region resolution can be chosen. As an exemplary case we apply the algorithm to a regional and sectoral refinement of the Eora MRIO database.
KW  - Disaster impact analysis
KW  - Disaggregation
KW  - Global supply chains
KW  - Life cycle assessment
KW  - Regionalization
Y1  - 2015
U6  - https://doi.org/10.1080/09535314.2014.987731
SN  - 0953-5314
SN  - 1469-5758
VL  - 27
IS  - 2
SP  - 194
EP  - 212
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Levermann, Anders
A1  - Winkelmann, Ricarda
A1  - Nowicki, S.
A1  - Fastook, J. L.
A1  - Frieler, Katja
A1  - Greve, R.
A1  - Hellmer, H. H.
A1  - Martin, M. A.
A1  - Meinshausen, Malte
A1  - Mengel, Matthias
A1  - Payne, A. J.
A1  - Pollard, D.
A1  - Sato, T.
A1  - Timmermann, R.
A1  - Wang, Wei Li
A1  - Bindschadler, Robert A.
T1  - Projecting antarctic ice discharge using response functions from SeaRISE ice-sheet models
JF  - Earth system dynamics
N2  - The largest uncertainty in projections of future sea-level change results from the potentially changing dynamical ice discharge from Antarctica. Basal ice-shelf melting induced by a warming ocean has been identified as a major cause for additional ice flow across the grounding line. Here we attempt to estimate the uncertainty range of future ice discharge from Antarctica by combining uncertainty in the climatic forcing, the oceanic response and the ice-sheet model response. The uncertainty in the global mean temperature increase is obtained from historically constrained emulations with the MAGICC-6.0 (Model for the Assessment of Greenhouse gas Induced Climate Change) model. The oceanic forcing is derived from scaling of the subsurface with the atmospheric warming from 19 comprehensive climate models of the Coupled Model Intercomparison Project (CMIP-5) and two ocean models from the EU-project Ice2Sea. The dynamic ice-sheet response is derived from linear response functions for basal ice-shelf melting for four different Antarctic drainage regions using experiments from the Sea-level Response to Ice Sheet Evolution (SeaRISE) intercomparison project with five different Antarctic ice-sheet models. The resulting uncertainty range for the historic Antarctic contribution to global sea-level rise from 1992 to 2011 agrees with the observed contribution for this period if we use the three ice-sheet models with an explicit representation of ice-shelf dynamics and account for the time-delayed warming of the oceanic subsurface compared to the surface air temperature. The median of the additional ice loss for the 21st century is computed to 0.07 m (66% range: 0.02-0.14 m; 90% range: 0.0-0.23 m) of global sea-level equivalent for the low-emission RCP-2.6 (Representative Concentration Pathway) scenario and 0.09 m (66% range: 0.04-0.21 m; 90% range: 0.01-0.37 m) for the strongest RCP-8.5. Assuming no time delay between the atmospheric warming and the oceanic subsurface, these values increase to 0.09 m (66% range: 0.04-0.17 m; 90% range: 0.02-0.25 m) for RCP-2.6 and 0.15 m (66% range: 0.07-0.28 m; 90% range: 0.04-0.43 m) for RCP-8.5. All probability distributions are highly skewed towards high values. The applied ice-sheet models are coarse resolution with limitations in the representation of grounding-line motion. Within the constraints of the applied methods, the uncertainty induced from different ice-sheet models is smaller than that induced by the external forcing to the ice sheets.
Y1  - 2014
U6  - https://doi.org/10.5194/esd-5-271-2014
SN  - 2190-4979
SN  - 2190-4987
VL  - 5
IS  - 2
SP  - 271
EP  - 293
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Schleussner, Carl-Friedrich
A1  - Levermann, Anders
A1  - Meinshausen, Malte
T1  - Probabilistic projections of the Atlantic overturning
JF  - Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change
N2  - Changes in the Atlantic overturning circulation have a strong influence on European temperatures, North American sea level and other climate phenomena worldwide. A meaningful assessment of associated societal impacts needs to be based on the full range of its possible future evolution. This requires capturing both the uncertainty in future warming pathways and the inherently long-term response of the ocean circulation. While probabilistic projections of the global mean and regional temperatures exist, process-based probabilistic assessments of large-scale dynamical systems such as the Atlantic overturning are still missing. Here we present such an assessment and find that a reduction of more than 50 % in Atlantic overturning strength by the end of the 21 (s t) century is within the likely range under an unmitigated climate change scenario (RCP8.5). By combining linear response functions derived from comprehensive climate simulations with the full range of possible future warming pathways, we provide probability estimates of overturning changes by the year 2100. A weakening of more than 25 % is found to be very unlikely under a climate protection scenario (RCP2.6), but likely for unmitigated climate change. The method is able to reproduce the modelled recovery caused by climatic equilibration under climate protection scenarios which provides confidence in the approach. Within this century, a reduction of the Atlantic overturning is a robust climatic phenomena that intensifies with global warming and needs to be accounted for in global adaptation strategies.
Y1  - 2014
U6  - https://doi.org/10.1007/s10584-014-1265-2
SN  - 0165-0009
SN  - 1573-1480
VL  - 127
IS  - 3-4
SP  - 579
EP  - 586
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Levermann, Anders
A1  - Bamber, Jonathan L.
A1  - Drijfhout, Sybren
A1  - Ganopolski, Andrey
A1  - Haeberli, Winfried
A1  - Harris, Neil R. P.
A1  - Huss, Matthias
A1  - Krueger, Kirstin
A1  - Lenton, Timothy M.
A1  - Lindsay, Ronald W.
A1  - Notz, Dirk
A1  - Wadhams, Peter
A1  - Weber, Susanne
T1  - Potential climatic transitions with profound impact on Europe Review of the current state of six 'tipping elements of the climate system'
JF  - Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change
N2  - We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize the mechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the 'tipping' potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding.
Y1  - 2012
U6  - https://doi.org/10.1007/s10584-011-0126-5
SN  - 0165-0009
SN  - 1573-1480
VL  - 110
IS  - 3-4
SP  - 845
EP  - 878
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - GEN
A1  - Wenz, Leonie
A1  - Levermann, Anders
A1  - Willner, Sven N.
A1  - Otto, Christian
A1  - Kuhla, Kilian
T1  - Post-Brexit no-trade-deal scenario: short-term consumer benefit at the expense of long-term economic development
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - After the United Kingdom has left the European Union it remains unclear whether the two parties can successfully negotiate and sign a trade agreement within the transition period. Ongoing negotiations, practical obstacles and resulting uncertainties make it highly unlikely that economic actors would be fully prepared to a “no-trade-deal” situation. Here we provide an economic shock simulation of the immediate aftermath of such a post-Brexit no-trade-deal scenario by computing the time evolution of more than 1.8 million interactions between more than 6,600 economic actors in the global trade network. We find an abrupt decline in the number of goods produced in the UK and the EU. This sudden output reduction is caused by drops in demand as customers on the respective other side of the Channel incorporate the new trade restriction into their decision-making. As a response, producers reduce prices in order to stimulate demand elsewhere. In the short term consumers benefit from lower prices but production value decreases with potentially severe socio-economic consequences in the longer term.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1208 
KW  - model
KW  - origins
KW  - chains
KW  - impact
KW  - costs
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-525819
SN  - 1866-8372
IS  - 9
ER  - 
TY  - JOUR
A1  - Wenz, Leonie
A1  - Levermann, Anders
A1  - Willner, Sven N.
A1  - Otto, Christian
A1  - Kuhla, Kilian
T1  - Post-Brexit no-trade-deal scenario: short-term consumer benefit at the expense of long-term economic development
JF  - PLoS ONE
N2  - After the United Kingdom has left the European Union it remains unclear whether the two parties can successfully negotiate and sign a trade agreement within the transition period. Ongoing negotiations, practical obstacles and resulting uncertainties make it highly unlikely that economic actors would be fully prepared to a “no-trade-deal” situation. Here we provide an economic shock simulation of the immediate aftermath of such a post-Brexit no-trade-deal scenario by computing the time evolution of more than 1.8 million interactions between more than 6,600 economic actors in the global trade network. We find an abrupt decline in the number of goods produced in the UK and the EU. This sudden output reduction is caused by drops in demand as customers on the respective other side of the Channel incorporate the new trade restriction into their decision-making. As a response, producers reduce prices in order to stimulate demand elsewhere. In the short term consumers benefit from lower prices but production value decreases with potentially severe socio-economic consequences in the longer term.
KW  - model
KW  - origins
KW  - chains
KW  - impact
KW  - costs
Y1  - 2019
VL  - 15
IS  - 9
PB  - PLOS
CY  - San Francisco
ER  - 
TY  - JOUR
A1  - Glanemann, Nicole
A1  - Willner, Sven N.
A1  - Levermann, Anders
T1  - Paris Climate Agreement passes the cost-benefit test
JF  - Nature Communications
N2  - The Paris Climate Agreement aims to keep temperature rise well below 2 degrees C. This implies mitigation costs as well as avoided climate damages. Here we show that independent of the normative assumptions of inequality aversion and time preferences, the agreement constitutes the economically optimal policy pathway for the century. To this end we consistently incorporate a damage-cost curve reproducing the observed relation between temperature and economic growth into the integrated assessment model DICE. We thus provide an intertemporally optimizing cost-benefit analysis of this century's climate problem. We account for uncertainties regarding the damage curve, climate sensitivity, socioeconomic future, and mitigation costs. The resulting optimal temperature is robust as can be understood from the generic temperature-dependence of the mitigation costs and the level of damages inferred from the observed temperature-growth relationship. Our results show that the politically motivated Paris Climate Agreement also represents the economically favourable pathway, if carried out properly.
Y1  - 2020
U6  - https://doi.org/10.1038/s41467-019-13961-1
SN  - 2041-1723
VL  - 11
IS  - 1
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Albrecht, Tanja
A1  - Martin, M.
A1  - Haseloff, M.
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Parameterization for subgrid-scale motion of ice-shelf calving fronts
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - A parameterization for the motion of ice-shelf fronts on a Cartesian grid in finite-difference land-ice models is presented. The scheme prevents artificial thinning of the ice shelf at its edge, which occurs due to the finite resolution of the model. The intuitive numerical implementation diminishes numerical dispersion at the ice front and enables the application of physical boundary conditions to improve the calculation of stress and velocity fields throughout the ice-sheet-shelf system. Numerical properties of this subgrid modification are assessed in the Potsdam Parallel Ice Sheet Model (PISM-PIK) for different geometries in one and two horizontal dimensions and are verified against an analytical solution in a flow-line setup.
Y1  - 2011
U6  - https://doi.org/10.5194/tc-5-35-2011
SN  - 1994-0416
VL  - 5
IS  - 1
SP  - 35
EP  - 44
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Wenz, Leonie
A1  - Levermann, Anders
A1  - Auffhammer, Maximilian
T1  - North-south polarization of European electricity consumption under future warming
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - There is growing empirical evidence that anthropogenic climate change will substantially affect the electric sector. Impacts will stem both from the supply sidethrough the mitigation of greenhouse gasesand from the demand sidethrough adaptive responses to a changing environment. Here we provide evidence of a polarization of both peak load and overall electricity consumption under future warming for the worlds third-largest electricity marketthe 35 countries of Europe. We statistically estimate country-level doseresponse functions between daily peak/total electricity load and ambient temperature for the period 2006-2012. After removing the impact of nontemperature confounders and normalizing the residual load data for each country, we estimate a common doseresponse function, which we use to compute national electricity loads for temperatures that lie outside each countrys currently observed temperature range. To this end, we impose end-of-century climate on todays European economies following three different greenhouse-gas concentration trajectories, ranging from ambitious climate-change mitigationin line with the Paris agreementto unabated climate change. We find significant increases in average daily peak load and overall electricity consumption in southern and western Europe (similar to 3 to similar to 7% for Portugal and Spain) and significant decreases in northern Europe (similar to-6 to similar to-2% for Sweden and Norway). While the projected effect on European total consumption is nearly zero, the significant polarization and seasonal shifts in peak demand and consumption have important ramifications for the location of costly peak-generating capacity, transmission infrastructure, and the design of energy-efficiency policy and storage capacity.
KW  - electricity consumption
KW  - peak load
KW  - climate change
KW  - adaptation
Y1  - 2017
U6  - https://doi.org/10.1073/pnas.1704339114
SN  - 0027-8424
VL  - 114
SP  - E7910
EP  - E7918
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schewe, Jacob
A1  - Levermann, Anders
T1  - Non-linear intensification of Sahel rainfall as a possible dynamic response to future warming
JF  - Earth system dynamics
Y1  - 2017
U6  - https://doi.org/10.5194/esd-8-495-2017
SN  - 2190-4979
SN  - 2190-4987
VL  - 8
SP  - 495
EP  - 505
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Schewe, Jacob
A1  - Levermann, Anders
T1  - Non-linear intensification of Sahel rainfall as a possible dynamic response to future warming
T2  - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe
N2  - Projections of the response of Sahel rainfall to future global warming diverge significantly. Meanwhile, paleoclimatic records suggest that Sahel rainfall is capable of abrupt transitions in response to gradual forcing. Here we present climate modeling evidence for the possibility of an abrupt intensification of Sahel rainfall under future climate change. Analyzing 30 coupled global climate model simulations, we identify seven models where central Sahel rainfall increases by 40 to 300% over the 21st century, owing to a northward expansion of the West African monsoon domain. Rainfall in these models is non-linearly related to sea surface temperature (SST) in the tropical Atlantic and Mediterranean moisture source regions, intensifying abruptly beyond a certain SST warming level. We argue that this behavior is consistent with a self-amplifying dynamic-thermodynamical feedback, implying that the gradual increase in oceanic moisture availability under warming could trigger a sudden intensification of monsoon rainfall far inland of today's core monsoon region.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 630 
KW  - moisture-advection feedback
KW  - abrupt monsoon transitions
KW  - West African monsoon
KW  - CMIP5
KW  - Holocene
KW  - climate
KW  - ocean
KW  - jet
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-419114
IS  - 630
SP  - 495
EP  - 505
ER  - 
TY  - JOUR
A1  - Otto, Christian
A1  - Willner, Sven N.
A1  - Wenz, Leonie
A1  - Frieler, Katja
A1  - Levermann, Anders
T1  - Modeling loss-propagation in the global supply network: The dynamic agent-based model acclimate
JF  - Journal of economic dynamics & control
N2  - World markets are highly interlinked and local economies extensively rely on global supply and value chains. Consequently, local production disruptions, for instance caused by extreme weather events, are likely to induce indirect losses along supply chains with potentially global repercussions. These complex loss dynamics represent a challenge for comprehensive disaster risk assessments. Here, we introduce the numerical agent-based model acclimate designed to analyze the cascading of economic losses in the global supply network. Using national sectors as agents, we apply the model to study the global propagation of losses induced by stylized disasters. We find that indirect losses can become comparable in size to direct ones, but can be efficiently mitigated by warehousing and idle capacities. Consequently, a comprehensive risk assessment cannot focus solely on first-tier suppliers, but has to take the whole supply chain into account. To render the supply network climate-proof, national adaptation policies have to be complemented by international adaptation efforts. In that regard, our model can be employed to assess reasonable leverage points and to identify dynamic bottlenecks inaccessible to static analyses. (C) 2017 Elsevier B.V. All rights reserved.
KW  - Disaster impact analysis
KW  - Higher-order effects
KW  - Economic network
KW  - Resilience
KW  - Dynamic input-output model
KW  - Agent-based modeling
Y1  - 2017
U6  - https://doi.org/10.1016/j.jedc.2017.08.001
SN  - 0165-1889
SN  - 1879-1743
VL  - 83
SP  - 232
EP  - 269
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ehlert, D.
A1  - Levermann, Anders
T1  - Mechanism for potential strengthening of Atlantic overturning prior to collapse
JF  - Earth system dynamics
N2  - The Atlantic meridional overturning circulation (AMOC) carries large amounts of heat into the North Atlantic influencing climate regionally as well as globally. Palaeo-records and simulations with comprehensive climate models suggest that the positive salt-advection feedback may yield a threshold behaviour of the system. That is to say that beyond a certain amount of freshwater flux into the North Atlantic, no meridional overturning circulation can be sustained. Concepts of monitoring the AMOC and identifying its vicinity to the threshold rely on the fact that the volume flux defining the AMOC will be reduced when approaching the threshold. Here we advance conceptual models that have been used in a paradigmatic way to understand the AMOC, by introducing a density-dependent parameterization for the Southern Ocean eddies. This additional degree of freedom uncovers a mechanism by which the AMOC can increase with additional freshwater flux into the North Atlantic, before it reaches the threshold and collapses: an AMOC that is mainly wind-driven will have a constant upwelling as long as the Southern Ocean winds do not change significantly. The downward transport of tracers occurs either in the northern sinking regions or through Southern Ocean eddies. If freshwater is transported, either atmospherically or via horizontal gyres, from the low to high latitudes, this would reduce the eddy transport and by continuity increase the northern sinking which defines the AMOC until a threshold is reached at which the AMOC cannot be sustained. If dominant in the real ocean this mechanism would have significant consequences for monitoring the AMOC.
Y1  - 2014
U6  - https://doi.org/10.5194/esd-5-383-2014
SN  - 2190-4979
SN  - 2190-4987
VL  - 5
IS  - 2
SP  - 383
EP  - 397
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Levermann, Anders
T1  - Make supply chains climate-smart
JF  - Nature : the international weekly journal of science
Y1  - 2014
SN  - 0028-0836
SN  - 1476-4687
VL  - 506
IS  - 7486
SP  - 27
EP  - 29
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Marzeion, Ben
A1  - Levermann, Anders
T1  - Loss of cultural world heritage and currently inhabited places to sea-level rise
JF  - Environmental research letters
KW  - sea-level rise
KW  - cultural heritage
KW  - chlimate impacts
Y1  - 2014
U6  - https://doi.org/10.1088/1748-9326/9/3/034001
SN  - 1748-9326
VL  - 9
IS  - 3
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Mengel, Matthias
A1  - Feldmann, Johannes
A1  - Levermann, Anders
T1  - Linear sea-level response to abrupt ocean warming of major West Antarctic ice basin
JF  - Nature climate change
N2  - Antarctica’s contribution to global sea-level rise has recently been increasing1. Whether its ice discharge will become unstable and decouple from anthropogenic forcing2,3,4 or increase linearly with the warming of the surrounding ocean is of fundamental importance5. Under unabated greenhouse-gas emissions, ocean models indicate an abrupt intrusion of warm circumpolar deep water into the cavity below West Antarctica’s Filchner–Ronne ice shelf within the next two centuries6,7. The ice basin’s retrograde bed slope would allow for an unstable ice-sheet retreat8, but the buttressing of the large ice shelf and the narrow glacier troughs tend to inhibit such instability9,10,11. It is unclear whether future ice loss will be dominated by ice instability or anthropogenic forcing. Here we show in regional and continental-scale ice-sheet simulations, which are capable of resolving unstable grounding-line retreat, that the sea-level response of the Filchner–Ronne ice basin is not dominated by ice instability and follows the strength of the forcing quasi-linearly. We find that the ice loss reduces after each pulse of projected warm water intrusion. The long-term sea-level contribution is approximately proportional to the total shelf-ice melt. Although the local instabilities might dominate the ice loss for weak oceanic warming12, we find that the upper limit of ice discharge from the region is determined by the forcing and not by the marine ice-sheet instability.
Y1  - 2016
U6  - https://doi.org/10.1038/NCLIMATE2808
SN  - 1758-678X
SN  - 1758-6798
VL  - 6
SP  - 71
EP  - +
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Levermann, Anders
A1  - Albrecht, Tanja
A1  - Winkelmann, Ricarda
A1  - Martin, Maria A.
A1  - Haseloff, Monika
A1  - Joughin, I.
T1  - Kinematic first-order calving law implies potential for abrupt ice-shelf retreat
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Recently observed large-scale disintegration of Antarctic ice shelves has moved their fronts closer towards grounded ice. In response, ice-sheet discharge into the ocean has accelerated, contributing to global sea-level rise and emphasizing the importance of calving-front dynamics. The position of the ice front strongly influences the stress field within the entire sheet-shelf-system and thereby the mass flow across the grounding line. While theories for an advance of the ice-front are readily available, no general rule exists for its retreat, making it difficult to incorporate the retreat in predictive models. Here we extract the first-order large-scale kinematic contribution to calving which is consistent with large-scale observation. We emphasize that the proposed equation does not constitute a comprehensive calving law but represents the first-order kinematic contribution which can and should be complemented by higher order contributions as well as the influence of potentially heterogeneous material properties of the ice. When applied as a calving law, the equation naturally incorporates the stabilizing effect of pinning points and inhibits ice shelf growth outside of embayments. It depends only on local ice properties which are, however, determined by the full topography of the ice shelf. In numerical simulations the parameterization reproduces multiple stable fronts as observed for the Larsen A and B Ice Shelves including abrupt transitions between them which may be caused by localized ice weaknesses. We also find multiple stable states of the Ross Ice Shelf at the gateway of the West Antarctic Ice Sheet with back stresses onto the sheet reduced by up to 90 % compared to the present state.
Y1  - 2012
U6  - https://doi.org/10.5194/tc-6-273-2012
SN  - 1994-0416
VL  - 6
IS  - 2
SP  - 273
EP  - 286
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - VIDEO
A1  - Levermann, Anders
T1  - Kann sich die Meeresströmung plötzlich ändern? : Antrittsvorlesung 2007-06-07
N2  - Bohrkerne zeigen, dass sich die Meeresströmungen im Atlantik während der letzten Eiszeit plötzlich und drastisch verändert haben. Temperatursprünge von bis zu zehn Grad innerhalb von Dekaden waren die Folge. Nicht nur für die zukünftige wirtschaftliche und gesellschaftliche Entwicklung Europas ist es wichtig, ob sich diese Veränderungen wiederholen können. Kann es auch in der heutigen Warmzeit abrupte Klimaveränderungen geben? Diese Frage ist eng an eine scheinbar akademische Diskussion nach den Antriebsmechanismen der Ozeanzirkulation gekoppelt. Mit den Gründen hierfür und den Folgerungen für die klimatische Stabilität beschäftigt sich der Referent in seiner Vorlesung.
Y1  - 2007
UR  - http://info.ub.uni-potsdam.de/multimedia/show_projekt.php?projekt_id=15
PB  - Univ.-Bibl.
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Born, Andreas
A1  - Stocker, Thomas F.
A1  - Raible, Christoph C.
A1  - Levermann, Anders
T1  - Is the Atlantic subpolar gyre bistable in comprehensive coupled climate models?
JF  - Climate dynamics : observational, theoretical and computational research on the climate system
N2  - The Atlantic subpolar gyre (SPG) is one of the main drivers of decadal climate variability in the North Atlantic. Here we analyze its dynamics in pre-industrial control simulations of 19 different comprehensive coupled climate models. The analysis is based on a recently proposed description of the SPG dynamics that found the circulation to be potentially bistable due to a positive feedback mechanism including salt transport and enhanced deep convection in the SPG center. We employ a statistical method to identify multiple equilibria in time series that are subject to strong noise and analyze composite fields to assess whether the bistability results from the hypothesized feedback mechanism. Because noise dominates the time series in most models, multiple circulation modes can unambiguously be detected in only six models. Four of these six models confirm that the intensification is caused by the positive feedback mechanism.
Y1  - 2013
U6  - https://doi.org/10.1007/s00382-012-1525-7
SN  - 0930-7575
VL  - 40
IS  - 11-12
SP  - 2993
EP  - 3007
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Willner, Sven N.
A1  - Glanemann, Nicole
A1  - Levermann, Anders
T1  - Investment incentive reduced by climate damages can be restored by optimal policy
JF  - Nature Communications
N2  - Increasing greenhouse gas emissions are likely to impact not only natural systems but economies worldwide. If these impacts alter future economic development, the financial losses will be significantly higher than the mere direct damages. So far, potentially aggravating investment responses were considered negligible. Here we consistently incorporate an empirically derived temperature-growth relation into the simple integrated assessment model DICE. In this framework we show that, if in the next eight decades varying temperatures impact economic growth as has been observed in the past three decades, income is reduced by similar to 20% compared to an economy unaffected by climate change. Hereof similar to 40% are losses due to growth effects of which similar to 50% result from reduced incentive to invest. This additional income loss arises from a reduced incentive for future investment in anticipation of a reduced return and not from an explicit climate protection policy. Under economically optimal climate-change mitigation, however, optimal investment would only be reduced marginally as mitigation efforts keep returns high.
Y1  - 2021
U6  - https://doi.org/10.1038/s41467-021-23547-5
SN  - 2041-1723
VL  - 12
IS  - 1
PB  - Nature Publishing Group UK
CY  - London
ER  - 
TY  - JOUR
A1  - Feldmann, Johannes
A1  - Levermann, Anders
T1  - Interaction of marine ice-sheet instabilities in two drainage basins: simple scaling of geometry and transition time
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - The initiation of a marine ice-sheet instability (MISI) is generally discussed from the ocean side of the ice sheet. It has been shown that the reduction in ice-shelf buttressing and softening of the coastal ice can destabilize a marine ice sheet if the bedrock is sloping upward towards the ocean. Using a conceptional flow-line geometry, we investigate the possibility of whether a MISI can be triggered from the direction of the ice divide as opposed to coastal forcing and explore the interaction between connected basins. We find that the initiation of a MISI in one basin can induce a destabilization in the other. The underlying mechanism of basin interaction is based on dynamic thinning and a consecutive motion of the ice divide which induces a thinning in the adjacent basin and a successive initiation of the instability. Our simplified and symmetric topographic setup allows scaling both the geometry and the transition time between both instabilities. We find that the ice profile follows a universal shape that is scaled with the horizontal extent of the ice sheet and that the same exponent of 1/2 applies for the scaling relation between central surface elevation and horizontal extent as in the pure shallow ice approximation (Vialov profile). Altering the central bed elevation, we find that the extent of grounding-line retreat in one basin determines the degree of interaction with the other. Different scenarios of basin interaction are discussed based on our modeling results as well as on a conceptual flux-balance analysis. We conclude that for the three-dimensional case, the possibility of drainage basin interaction on timescales on the order of 1 kyr or larger cannot be excluded and hence needs further investigation.
Y1  - 2015
U6  - https://doi.org/10.5194/tc-9-631-2015
SN  - 1994-0416
SN  - 1994-0424
VL  - 9
IS  - 2
SP  - 631
EP  - 645
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Feldmann, Johannes
A1  - Levermann, Anders
T1  - Interaction of marine ice-sheet instabilities in two drainage basins
BT  - simple scaling of geometry and transition time
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Universität
N2  - The initiation of a marine ice-sheet instability (MISI) is generally discussed from the ocean side of the ice sheet. It has been shown that the reduction in ice-shelf buttressing and softening of the coastal ice can destabilize a marine ice sheet if the bedrock is sloping upward towards the ocean. Using a conceptional flow-line geometry, we investigate the possibility of whether a MISI can be triggered from the direction of the ice divide as opposed to coastal forcing and explore the interaction between connected basins. We find that the initiation of a MISI in one basin can induce a destabilization in the other. The underlying mechanism of basin interaction is based on dynamic thinning and a consecutive motion of the ice divide which induces a thinning in the adjacent basin and a successive initiation of the instability. Our simplified and symmetric topographic setup allows scaling both the geometry and the transition time between both instabilities. We find that the ice profile follows a universal shape that is scaled with the horizontal extent of the ice sheet and that the same exponent of 1/2 applies for the scaling relation between central surface elevation and horizontal extent as in the pure shallow ice approximation (Vialov profile). Altering the central bed elevation, we find that the extent of grounding-line retreat in one basin determines the degree of interaction with the other. Different scenarios of basin interaction are discussed based on our modeling results as well as on a conceptual flux-balance analysis. We conclude that for the three-dimensional case, the possibility of drainage basin interaction on timescales on the order of 1 kyr or larger cannot be excluded and hence needs further investigation.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 511 
KW  - Pine Island Glacier
KW  - model PISM-PIK
KW  - West Antarctica
KW  - grounding-line
KW  - Thwaites Glacier
KW  - divide position
KW  - part 1
KW  - stability
KW  - shelf
KW  - accumulation
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-408903
SN  - 1866-8372
IS  - 511
ER  - 
TY  - JOUR
A1  - Katzenberger, Anja
A1  - Levermann, Anders
A1  - Schewe, Jacob
A1  - Pongratz, Julia
T1  - Intensification of very wet monsoon seasons in India under global warming
JF  - Geophysical research letters
N2  - Rainfall-intense summer monsoon seasons on the Indian subcontinent that are exceeding long-term averages cause widespread floods and landslides. 

Here we show that the latest generation of coupled climate models robustly project an intensification of very rainfall-intense seasons (June-September). 
Under the shared socioeconomic pathway SSP5-8.5, very wet monsoon seasons as observed in only 5 years in the period 1965-2015 are projected to occur 8 times more often in 2050-2100 in the multi-model average. 

Under SSP2-4.5, these seasons become only a factor of 6 times more frequent, showing that even modest efforts to mitigate climate change can have a strong impact on the frequency of very strong rainfall seasons. 

Besides, we find that the increasing risk of extreme seasonal rainfall is accompanied by a shift from days with light rainfall to days with moderate or heavy rainfall. Additionally, the number of wet days is projected to increase.
KW  - Indian monsoon
KW  - climate modeling
KW  - extreme seasons
KW  - climate change
KW  - CMIP6
KW  - India
Y1  - 2022
U6  - https://doi.org/10.1029/2022GL098856
SN  - 0094-8276
SN  - 1944-8007
VL  - 49
IS  - 15
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Nowicki, Sophie
A1  - Bindschadler, Robert A.
A1  - Abe-Ouchi, Ayako
A1  - Aschwanden, Andy
A1  - Bueler, Ed
A1  - Choi, Hyeungu
A1  - Fastook, Jim
A1  - Granzow, Glen
A1  - Greve, Ralf
A1  - Gutowski, Gail
A1  - Herzfeld, Ute
A1  - Jackson, Charles
A1  - Johnson, Jesse
A1  - Khroulev, Constantine
A1  - Larour, Eric
A1  - Levermann, Anders
A1  - Lipscomb, William H.
A1  - Martin, Maria A.
A1  - Morlighem, Mathieu
A1  - Parizek, Byron R.
A1  - Pollard, David
A1  - Price, Stephen F.
A1  - Ren, Diandong
A1  - Rignot, Eric
A1  - Saito, Fuyuki
A1  - Sato, Tatsuru
A1  - Seddik, Hakime
A1  - Seroussi, Helene
A1  - Takahashi, Kunio
A1  - Walker, Ryan
A1  - Wang, Wei Li
T1  - Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project II  Greenland
JF  - Journal of geophysical research : Earth surface
N2  - The Sea-level Response to Ice Sheet Evolution (SeaRISE) effort explores the sensitivity of the current generation of ice sheet models to external forcing to gain insight into the potential future contribution to sea level from the Greenland and Antarctic ice sheets. All participating models simulated the ice sheet response to three types of external forcings: a change in oceanic condition, a warmer atmospheric environment, and enhanced basal lubrication. Here an analysis of the spatial response of the Greenland ice sheet is presented, and the impact of model physics and spin-up on the projections is explored. Although the modeled responses are not always homogeneous, consistent spatial trends emerge from the ensemble analysis, indicating distinct vulnerabilities of the Greenland ice sheet. There are clear response patterns associated with each forcing, and a similar mass loss at the full ice sheet scale will result in different mass losses at the regional scale, as well as distinct thickness changes over the ice sheet. All forcings lead to an increased mass loss for the coming centuries, with increased basal lubrication and warmer ocean conditions affecting mainly outlet glaciers, while the impacts of atmospheric forcings affect the whole ice sheet.
KW  - Greenland
KW  - ice-sheet
KW  - sea-level
KW  - model
KW  - ensemble
Y1  - 2013
U6  - https://doi.org/10.1002/jgrf.20076
SN  - 2169-9003
VL  - 118
IS  - 2
SP  - 1025
EP  - 1044
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
A1  - Martin, Maria A.
A1  - Frieler, Katja
T1  - Increased future ice discharge from Antarctica owing to higher snowfall
JF  - Nature : the international weekly journal of science
N2  - Anthropogenic climate change is likely to cause continuing global sea level rise(1), but some processes within the Earth system may mitigate the magnitude of the projected effect. Regional and global climate models simulate enhanced snowfall over Antarctica, which would provide a direct offset of the future contribution to global sea level rise from cryospheric mass loss(2,3) and ocean expansion(4). Uncertainties exist in modelled snowfall(5), but even larger uncertainties exist in the potential changes of dynamic ice discharge from Antarctica(1,6) and thus in the ultimate fate of the precipitation-deposited ice mass. Here we show that snowfall and discharge are not independent, but that future ice discharge will increase by up to three times as a result of additional snowfall under global warming. Our results, based on an ice-sheet model(7) forced by climate simulations through to the end of 2500 (ref. 8), show that the enhanced discharge effect exceeds the effect of surface warming as well as that of basal ice-shelf melting, and is due to the difference in surface elevation change caused by snowfall on grounded versus floating ice. Although different underlying forcings drive ice loss from basal melting versus increased snowfall, similar ice dynamical processes are nonetheless at work in both; therefore results are relatively independent of the specific representation of the transition zone. In an ensemble of simulations designed to capture ice-physics uncertainty, the additional dynamic ice loss along the coastline compensates between 30 and 65 per cent of the ice gain due to enhanced snowfall over the entire continent. This results in a dynamic ice loss of up to 1.25 metres in the year 2500 for the strongest warming scenario. The reported effect thus strongly counters a potential negative contribution to global sea level by the Antarctic Ice Sheet.
Y1  - 2012
U6  - https://doi.org/10.1038/nature11616
SN  - 0028-0836
VL  - 492
IS  - 7428
SP  - 239
EP  - +
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Bindschadler, Robert A.
A1  - Nowicki, Sophie
A1  - Abe-Ouchi, Ayako
A1  - Aschwanden, Andy
A1  - Choi, Hyeungu
A1  - Fastook, Jim
A1  - Granzow, Glen
A1  - Greve, Ralf
A1  - Gutowski, Gail
A1  - Herzfeld, Ute
A1  - Jackson, Charles
A1  - Johnson, Jesse
A1  - Khroulev, Constantine
A1  - Levermann, Anders
A1  - Lipscomb, William H.
A1  - Martin, Maria A.
A1  - Morlighem, Mathieu
A1  - Parizek, Byron R.
A1  - Pollard, David
A1  - Price, Stephen F.
A1  - Ren, Diandong
A1  - Saito, Fuyuki
A1  - Sato, Tatsuru
A1  - Seddik, Hakime
A1  - Seroussi, Helene
A1  - Takahashi, Kunio
A1  - Walker, Ryan
A1  - Wang, Wei Li
T1  - Ice-sheet model sensitivities to environmental forcing and their use in projecting future sea level (the SeaRISE project)
JF  - Journal of glaciology
N2  - Ten ice-sheet models are used to study sensitivity of the Greenland and Antarctic ice sheets to prescribed changes of surface mass balance, sub-ice-shelf melting and basal sliding. Results exhibit a large range in projected contributions to sea-level change. In most cases, the ice volume above flotation lost is linearly dependent on the strength of the forcing. Combinations of forcings can be closely approximated by linearly summing the contributions from single forcing experiments, suggesting that nonlinear feedbacks are modest. Our models indicate that Greenland is more sensitive than Antarctica to likely atmospheric changes in temperature and precipitation, while Antarctica is more sensitive to increased ice-shelf basal melting. An experiment approximating the Intergovernmental Panel on Climate Change's RCP8.5 scenario produces additional first-century contributions to sea level of 22.3 and 8.1 cm from Greenland and Antarctica, respectively, with a range among models of 62 and 14 cm, respectively. By 200 years, projections increase to 53.2 and 26.7 cm, respectively, with ranges of 79 and 43 cm. Linear interpolation of the sensitivity results closely approximates these projections, revealing the relative contributions of the individual forcings on the combined volume change and suggesting that total ice-sheet response to complicated forcings over 200 years can be linearized.
Y1  - 2013
U6  - https://doi.org/10.3189/2013JoG12J125
SN  - 0022-1430
VL  - 59
IS  - 214
SP  - 195
EP  - 224
PB  - International Glaciological Society
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Mengel, Matthias
A1  - Levermann, Anders
T1  - Ice plug prevents irreversible discharge from East Antarctica
JF  - Nature climate change
N2  - Changes in ice discharge from Antarctica constitute the largest uncertainty in future sea-level projections, mainly because of the unknown response of its marine basins(1). Most of West Antarctica's marine ice sheet lies on an inland-sloping bed(2) and is thereby prone to a marine ice sheet instability(3-5). A similar topographic configuration is found in large parts of East Antarctica, which holds marine ice equivalent to 19 m of global sea-level rise(6), that is, more than five times that of West Antarctica. Within East Antarctica, the Wilkes Basin holds the largest volume of marine ice that is fully connected by subglacial troughs. This ice body was significantly reduced during the Pliocene epoch(7). Strong melting underneath adjacent ice shelves with similar bathymetry(8) indicates the ice sheet's sensitivity to climatic perturbations. The stability of the Wilkes marine ice sheet has not been the subject of any comprehensive assessment of future sea level. Using recently improved topographic data(6) in combination with ice-dynamic simulations, we show here that the removal of a specific coastal ice volume equivalent to less than 80 mm of global sea-level rise at the margin of the Wilkes Basin destabilizes the regional ice flow and leads to a self-sustained discharge of the entire basin and a global sea-level rise of 3-4 m. Our results are robust with respect to variation in ice parameters, forcing details and model resolution as well as increased surface mass balance, indicating that East Antarctica may become a large contributor to future sea-level rise on timescales beyond a century.
Y1  - 2014
U6  - https://doi.org/10.1038/NCLIMATE2226
SN  - 1758-678X
SN  - 1758-6798
VL  - 4
IS  - 6
SP  - 451
EP  - 455
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Geiger, Tobias
A1  - Frieler, Katja
A1  - Levermann, Anders
T1  - High-income does not protect against hurricane losses
JF  - Environmental research letters
N2  - Damage due to tropical cyclones accounts for more than 50% of all meteorologically-induced economic losses worldwide. Their nominal impact is projected to increase substantially as the exposed population grows, per capita income increases, and anthropogenic climate change manifests. So far, historical losses due to tropical cyclones have been found to increase less than linearly with a nation's affected gross domestic product (GDP). Here we show that for the United States this scaling is caused by a sub-linear increase with affected population while relative losses scale super-linearly with per capita income. The finding is robust across a multitude of empirically derived damage models that link the storm's wind speed, exposed population, and per capita GDP to reported losses. The separation of both socio-economic predictors strongly affects the projection of potential future hurricane losses. Separating the effects of growth in population and per-capita income, per hurricane losses with respect to national GDP are projected to triple by the end of the century under unmitigated climate change, while they are estimated to decrease slightly without the separation.
KW  - climate change
KW  - tropical cyclones
KW  - damage
KW  - meteorological extremes
KW  - vulnerability
Y1  - 2016
U6  - https://doi.org/10.1088/1748-9326/11/8/084012
SN  - 1748-9326
VL  - 11
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Willner, Sven N.
A1  - Otto, Christian
A1  - Levermann, Anders
T1  - Global economic response to river floods
JF  - Nature climate change
N2  - Increasing Earth’s surface air temperature yields an intensification of its hydrological cycle. As a consequence, the risk of river floods will increase regionally within the next two decades due to the atmospheric warming caused by past anthropogenic greenhouse gas emissions. The direct economic losses caused by these floods can yield regionally heterogeneous losses and gains by propagation within the global trade and supply network. Here we show that, in the absence of large-scale structural adaptation, the total economic losses due to fluvial floods will increase in the next 20 years globally by 17% despite partial compensation through market adjustment within the global trade network. China will suffer the strongest direct losses, with an increase of 82%. The United States is mostly affected indirectly through its trade relations. By contrast to the United States, recent intensification of the trade relations with China leaves the European Union better prepared for the import of production losses in the future.
Y1  - 2018
U6  - https://doi.org/10.1038/s41558-018-0173-2
SN  - 1758-678X
SN  - 1758-6798
VL  - 8
IS  - 7
SP  - 594
EP  - 598
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Albrecht, Torsten
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM)
BT  - part 2: parameter ensemble analysis
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - The Parallel Ice Sheet Model (PISM) is applied to the Antarctic Ice Sheet over the last two glacial cycles (approximate to 210 000 years) with a resolution of 16 km. An ensemble of 256 model runs is analyzed in which four relevant model parameters have been systematically varied using full-factorial parameter sampling. Parameters and plausible parameter ranges have been identified in a companion paper (Albrecht et al., 2020) and are associated with ice dynamics, climatic forcing, basal sliding and bed deformation and represent distinct classes of model uncertainties. The model is scored against both modern and geologic data, including reconstructed grounding-line locations, elevation-age data, ice thickness, surface velocities and uplift rates. An aggregated score is computed for each ensemble member that measures the overall model-data misfit, including measurement uncertainty in terms of a Gaussian error model (Briggs and Tarasov, 2013). The statistical method used to analyze the ensemble simulation results follows closely the simple averaging method described in Pollard et al. (2016). 
This analysis reveals clusters of best-fit parameter combinations, and hence a likely range of relevant model and boundary parameters, rather than individual best-fit parameters. The ensemble of reconstructed histories of Antarctic Ice Sheet volumes provides a score-weighted likely range of sea-level contributions since the Last Glacial Maximum (LGM) of 9.4 +/- 4.1m (or 6.5 +/- 2.0 x 10(6) km(3)), which is at the upper range of most previous studies. The last deglaciation occurs in all ensemble simulations after around 12 000 years before present and hence after the meltwater pulse 1A (MWP1a). Our ensemble analysis also provides an estimate of parametric uncertainty bounds for the present-day state that can be used for PISM projections of future sea-level contributions from the Antarctic Ice Sheet.
Y1  - 2020
U6  - https://doi.org/10.5194/tc-14-633-2020
SN  - 1994-0416
SN  - 1994-0424
VL  - 14
IS  - 2
SP  - 633
EP  - 656
PB  - Copernicus Publ.
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Albrecht, Torsten
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM)
BT  - Part 1: boundary conditions and climatic forcing
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Simulations of the glacial-interglacial history of the Antarctic Ice Sheet provide insights into dynamic threshold behavior and estimates of the ice sheet's contributions to global sea-level changes for the past, present and future. However, boundary conditions are weakly constrained, in particular at the interface of the ice sheet and the bedrock. Also climatic forcing covering the last glacial cycles is uncertain, as it is based on sparse proxy data. <br /> We use the Parallel Ice Sheet Model (PISM) to investigate the dynamic effects of different choices of input data, e.g., for modern basal heat flux or reconstructions of past changes of sea level and surface temperature. As computational resources are limited, glacial-cycle simulations are performed using a comparably coarse model grid of 16 km and various parameterizations, e.g., for basal sliding, iceberg calving, or for past variations in precipitation and ocean temperatures. In this study we evaluate the model's transient sensitivity to corresponding parameter choices and to different boundary conditions over the last two glacial cycles and provide estimates of involved uncertainties. We also discuss isolated and combined effects of climate and sea-level forcing. Hence, this study serves as a "cookbook" for the growing community of PISM users and paleo-ice sheet modelers in general. <br /> For each of the different model uncertainties with regard to climatic forcing, ice and Earth dynamics, and basal processes, we select one representative model parameter that captures relevant uncertainties and motivates corresponding parameter ranges that bound the observed ice volume at present. The four selected parameters are systematically varied in a parameter ensemble analysis, which is described in a companion paper.
Y1  - 2020
U6  - https://doi.org/10.5194/tc-14-599-2020
SN  - 1994-0416
SN  - 1994-0424
VL  - 14
IS  - 2
SP  - 599
EP  - 632
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Lehmann, Jascha
A1  - Coumou, Dim
A1  - Frieler, Katja
A1  - Eliseev, Alexey V.
A1  - Levermann, Anders
T1  - Future changes in extratropical storm tracks and baroclinicity under climate change
JF  - Environmental research letters
N2  - The weather in Eurasia, Australia, and North and South America is largely controlled by the strength and position of extratropical storm tracks. Future climate change will likely affect these storm tracks and the associated transport of energy, momentum, and water vapour. Many recent studies have analyzed how storm tracks will change under climate change, and how these changes are related to atmospheric dynamics. However, there are still discrepancies between different studies on how storm tracks will change under future climate scenarios. Here, we show that under global warming the CMIP5 ensemble of coupled climate models projects only little relative changes in vertically averaged mid-latitude mean storm track activity during the northern winter, but agree in projecting a substantial decrease during summer. Seasonal changes in the Southern Hemisphere show the opposite behaviour, with an intensification in winter and no change during summer. These distinct seasonal changes in northern summer and southern winter storm tracks lead to an amplified seasonal cycle in a future climate. Similar changes are seen in the mid-latitude mean Eady growth rate maximum, a measure that combines changes in vertical shear and static stability based on baroclinic instability theory. Regression analysis between changes in the storm tracks and changes in the maximum Eady growth rate reveal that most models agree in a positive association between the two quantities over mid-latitude regions.
KW  - storm tracks
KW  - baroclinicity
KW  - climate change
Y1  - 2014
U6  - https://doi.org/10.1088/1748-9326/9/8/084002
SN  - 1748-9326
VL  - 9
IS  - 8
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Feldmann, Johannes
A1  - Levermann, Anders
T1  - From cyclic ice streaming to Heinrich-like events: the grow-and-surge instability in the Parallel Ice Sheet Model
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Here we report on a cyclic, physical ice-discharge instability in the Parallel Ice Sheet Model, simulating the flow of a three-dimensional, inherently buttressed ice-sheet-shelf system which periodically surges on a millennial timescale. The thermomechanically coupled model on 1 km horizontal resolution includes an enthalpy-based formulation of the thermodynamics, a nonlinear stress-balance-based sliding law and a very simple subglacial hydrology. The simulated unforced surging is characterized by rapid ice streaming through a bed trough, resulting in abrupt discharge of ice across the grounding line which is eventually calved into the ocean. We visualize the central feedbacks that dominate the subsequent phases of ice buildup, surge and stabilization which emerge from the interaction between ice dynamics, thermodynamics and the subglacial till layer. Results from the variation of surface mass balance and basal roughness suggest that ice sheets of medium thickness may be more susceptible to surging than relatively thin or thick ones for which the surge feedback loop is damped. We also investigate the influence of different basal sliding laws (ranging from purely plastic to nonlinear to linear) on possible surging. The presented mechanisms underlying our simulations of self-maintained, periodic ice growth and destabilization may play a role in large-scale ice-sheet surging, such as the surging of the Laurentide Ice Sheet, which is associated with Heinrich events, and ice-stream shutdown and reactivation, such as observed in the Siple Coast region of West Antarctica.
Y1  - 2017
U6  - https://doi.org/10.5194/tc-11-1913-2017
SN  - 1994-0416
SN  - 1994-0424
VL  - 11
SP  - 1913
EP  - 1932
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Feldmann, Johannes
A1  - Levermann, Anders
T1  - From cyclic ice streaming to Heinrich-like events
BT  - the grow-and-surge instability in the Parallel Ice Sheet Model
T2  - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2  - Here we report on a cyclic, physical ice-discharge instability in the Parallel Ice Sheet Model, simulating the flow of a three-dimensional, inherently buttressed ice-sheet-shelf system which periodically surges on a millennial timescale. The thermomechanically coupled model on 1 km horizontal resolution includes an enthalpy-based formulation of the thermodynamics, a nonlinear stress-balance-based sliding law and a very simple subglacial hydrology. The simulated unforced surging is characterized by rapid ice streaming through a bed trough, resulting in abrupt discharge of ice across the grounding line which is eventually calved into the ocean. We visualize the central feedbacks that dominate the subsequent phases of ice buildup, surge and stabilization which emerge from the interaction between ice dynamics, thermodynamics and the subglacial till layer. Results from the variation of surface mass balance and basal roughness suggest that ice sheets of medium thickness may be more susceptible to surging than relatively thin or thick ones for which the surge feedback loop is damped. We also investigate the influence of different basal sliding laws (ranging from purely plastic to nonlinear to linear) on possible surging. The presented mechanisms underlying our simulations of self-maintained, periodic ice growth and destabilization may play a role in large-scale ice-sheet surging, such as the surging of the Laurentide Ice Sheet, which is associated with Heinrich events, and ice-stream shutdown and reactivation, such as observed in the Siple Coast region of West Antarctica.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 652 
KW  - grounding-line migration
KW  - last glacial period
KW  - West Antarctica
KW  - North Atlantic
KW  - numerical simulations
KW  - iceberg discharges
KW  - creep stability
KW  - basal mechanics
KW  - climate
KW  - ocean
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-418777
SN  - 1866-8372
IS  - 652
ER  - 
TY  - JOUR
A1  - Albrecht, Torsten
A1  - Levermann, Anders
T1  - Fracture-induced softening for large-scale ice dynamics
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Floating ice shelves can exert a retentive and hence stabilizing force onto the inland ice sheet of Antarctica. However, this effect has been observed to diminish by the dynamic effects of fracture processes within the protective ice shelves, leading to accelerated ice flow and hence to a sea-level contribution. In order to account for the macroscopic effect of fracture processes on large-scale viscous ice dynamics (i.e., ice-shelf scale) we apply a continuum representation of fractures and related fracture growth into the prognostic Parallel Ice Sheet Model (PISM) and compare the results to observations. To this end we introduce a higher order accuracy advection scheme for the transport of the two-dimensional fracture density across the regular computational grid. Dynamic coupling of fractures and ice flow is attained by a reduction of effective ice viscosity proportional to the inferred fracture density. This formulation implies the possibility of non-linear threshold behavior due to self-amplified fracturing in shear regions triggered by small variations in the fracture-initiation threshold. As a result of prognostic flow simulations, sharp across-flow velocity gradients appear in fracture-weakened regions. These modeled gradients compare well in magnitude and location with those in observed flow patterns. This model framework is in principle expandable to grounded ice streams and provides simple means of investigating climate-induced effects on fracturing (e. g., hydro fracturing) and hence on the ice flow. It further constitutes a physically sound basis for an enhanced fracture-based calving parameterization.
Y1  - 2014
U6  - https://doi.org/10.5194/tc-8-587-2014
SN  - 1994-0416
SN  - 1994-0424
VL  - 8
IS  - 2
SP  - 587
EP  - 605
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Albrecht, Torsten
A1  - Levermann, Anders
T1  - Fracture field for large-scale ice dynamics
JF  - Journal of glaciology
N2  - Recent observations and modeling studies emphasize the crucial role of fracture mechanics for the stability of ice shelves and thereby the evolution of ice sheets. Here we introduce a macroscopic fracture-density field into a prognostic continuum ice-flow model and compute its evolution incorporating the initiation and growth of fractures as well as their advection with two-dimensional ice flow. To a first approximation, fracture growth is assumed to depend on the spreading rate only, while fracture initiation is defined in terms of principal stresses. The inferred fracture-density fields compare well with observed elongate surface structures. Since crevasses and other deep-reaching fracture structures have been shown to influence the overall ice-shelf dynamics, we propose the fracture-density field introduced here be used as a measure for ice softening and decoupling of the ice flow in fracture-weakened zones. This may yield more accurate and realistic velocity patterns in prognostic simulations. Additionally, the memory of past fracture events links the calving front to the upstream dynamics. Thus the fracture-density field proposed here may be employed in fracture-based calving parameterizations. The aim of this study is to introduce the field and investigate which of the observed surface structures can be reproduced by the simplest physically motivated fracture source terms.
Y1  - 2012
U6  - https://doi.org/10.3189/2012JoG11J191
SN  - 0022-1430
SN  - 1727-5652
VL  - 58
IS  - 207
SP  - 165
EP  - 176
PB  - International Glaciological Society
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Schneider von Deimling, Thomas
A1  - Meinshausen, Malte
A1  - Levermann, Anders
A1  - Huber, Veronika
A1  - Frieler, Katja
A1  - Lawrence, D. M.
A1  - Brovkin, Victor
T1  - Estimating the near-surface permafrost-carbon feedback on global warming
JF  - Biogeosciences
N2  - Thawing of permafrost and the associated release of carbon constitutes a positive feedback in the climate system, elevating the effect of anthropogenic GHG emissions on global-mean temperatures. Multiple factors have hindered the quantification of this feedback, which was not included in climate carbon-cycle models which participated in recent model intercomparisons (such as the Coupled Carbon Cycle Climate Model Intercomparison Project - (CMIP)-M-4). There are considerable uncertainties in the rate and extent of permafrost thaw, the hydrological and vegetation response to permafrost thaw, the decomposition timescales of freshly thawed organic material, the proportion of soil carbon that might be emitted as carbon dioxide via aerobic decomposition or as methane via anaerobic decomposition, and in the magnitude of the high latitude amplification of global warming that will drive permafrost degradation. Additionally, there are extensive and poorly characterized regional heterogeneities in soil properties, carbon content, and hydrology. Here, we couple a new permafrost module to a reduced complexity carbon-cycle climate model, which allows us to perform a large ensemble of simulations. The ensemble is designed to span the uncertainties listed above and thereby the results provide an estimate of the potential strength of the feedback from newly thawed permafrost carbon. For the high CO2 concentration scenario (RCP8.5), 33-114 GtC (giga tons of Carbon) are released by 2100 (68% uncertainty range). This leads to an additional warming of 0.04-0.23 degrees C. Though projected 21st century permafrost carbon emissions are relatively modest, ongoing permafrost thaw and slow but steady soil carbon decomposition means that, by 2300, about half of the potentially vulnerable permafrost carbon stock in the upper 3 m of soil layer (600-1000 GtC) could be released as CO2, with an extra 1-4% being released as methane. Our results also suggest that mitigation action in line with the lower scenario RCP3-PD could contain Arctic temperature increase sufficiently that thawing of the permafrost area is limited to 9-23% and the permafrost-carbon induced temperature increase does not exceed 0.04-0.16 degrees C by 2300.
Y1  - 2012
U6  - https://doi.org/10.5194/bg-9-649-2012
SN  - 1726-4170
SN  - 1726-4189
VL  - 9
IS  - 2
SP  - 649
EP  - 665
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Menon, Arathy
A1  - Levermann, Anders
A1  - Schewe, Jacob
T1  - Enhanced future variability during India's rainy season
JF  - Geophysical research letters
N2  - The Indian summer monsoon shapes the livelihood of a large share of the world's population. About 80% of annual precipitation over India occurs during the monsoon season from June through September. Next to its seasonal mean rainfall, the day-to-day variability is crucial for the risk of flooding, national water supply, and agricultural productivity. Here we show that the latest ensemble of climate model simulations, prepared for the AR-5 of the Intergovernmental Panel on Climate Change, consistently projects significant increases in day-to-day rainfall variability under unmitigated climate change. The relative increase by the period 2071-2100 with respect to the control period 1871-1900 ranges from 13% to 50% under the strongest scenario (Representative Concentration Pathways, RCP-8.5), in the 10 models with the most realistic monsoon climatology; and 13% to 85% when all the 20 models are considered. The spread across models reduces when variability increase per degree of global warming is considered, which is independent of the scenario in most models, and is 8% +/- 4%/K on average. This consistent projection across 20 comprehensive climate models provides confidence in the results and suggests the necessity of profound adaptation measures in the case of unmitigated climate change.
KW  - monsoon
KW  - variability
KW  - CMIP-5
Y1  - 2013
U6  - https://doi.org/10.1002/grl.50583
SN  - 0094-8276
VL  - 40
IS  - 12
SP  - 3242
EP  - 3247
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Wenz, Leonie
A1  - Levermann, Anders
T1  - Enhanced economic connectivity to foster heat stress-related losses
JF  - Science Advances
N2  - Assessing global impacts of unexpected meteorological events in an increasingly connected world economy is important for estimating the costs of climate change. We show that since the beginning of the 21st century, the structural evolution of the global supply network has been such as to foster an increase of climate-related production losses. We compute first- and higher-order losses from heat stress-induced reductions in productivity under changing economic and climatic conditions between 1991 and 2011. Since 2001, the economic connectivity has augmented in such a way as to facilitate the cascading of production loss. The influence of this structural change has dominated over the effect of the comparably weak climate warming during this decade. Thus, particularly under future warming, the intensification of international trade has the potential to amplify climate losses if no adaptation measures are taken.
Y1  - 2016
U6  - https://doi.org/10.1126/sciadv.1501026
SN  - 2375-2548
VL  - 2
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Mengel, Matthias
A1  - Levermann, Anders
A1  - Schleussner, Carl-Friedrich
A1  - Born, Andreas
T1  - Enhanced Atlantic subpolar gyre variability through baroclinic threshold in a coarse resolution model
JF  - Earth system dynamics
N2  - Direct observations, satellite measurements and paleo records reveal strong variability in the Atlantic subpolar gyre on various time scales. Here we show that variations of comparable amplitude can only be simulated in a coupled climate model in the proximity of a dynamical threshold. The threshold and the associated dynamic response is due to a positive feedback involving increased salt transport in the subpolar gyre and enhanced deep convection in its centre. A series of sensitivity experiments is performed with a coarse resolution ocean general circulation model coupled to a statistical-dynamical atmosphere model which in itself does not produce atmospheric variability. To simulate the impact of atmospheric variability, the model system is perturbed with freshwater forcing of varying, but small amplitude and multi-decadal to centennial periodicities and observational variations in wind stress. While both freshwater and wind-stress-forcing have a small direct effect on the strength of the subpolar gyre, the magnitude of the gyre's response is strongly increased in the vicinity of the threshold. Our results indicate that baroclinic self-amplification in the North Atlantic ocean can play an important role in presently observed SPG variability and thereby North Atlantic climate variability on multi-decadal scales.
Y1  - 2012
U6  - https://doi.org/10.5194/esd-3-189-2012
SN  - 2190-4979
SN  - 2190-4987
VL  - 3
IS  - 2
SP  - 189
EP  - 197
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Schleussner, Carl-Friedrich
A1  - Frieler, Katja
A1  - Meinshausen, Malte
A1  - Yin, J.
A1  - Levermann, Anders
T1  - Emulating Atlantic overturning strength for low emission scenarios  consequences for sea-level rise along the North American east coast
JF  - Earth system dynamics
N2  - In order to provide probabilistic projections of the future evolution of the Atlantic Meridional Overturning Circulation (AMOC), we calibrated a simple Stommel-type box model to emulate the output of fully coupled three-dimensional atmosphere-ocean general circulation models (AOGCMs) of the Coupled Model Intercomparison Project (CMIP). Based on this calibration to idealised global warming scenarios with and without interactive atmosphere-ocean fluxes and freshwater perturbation simulations, we project the future evolution of the AMOC mean strength within the covered calibration range for the lower two Representative Concentration Pathways (RCPs) until 2100 obtained from the reduced complexity carbon cycle-climate model MAGICC 6. For RCP3-PD with a global mean temperature median below 1.0 degrees C warming relative to the year 2000, we project an ensemble median weakening of up to 11% compared to 22% under RCP4.5 with a warming median up to 1.9 degrees C over the 21st century. Additional Greenland meltwater of 10 and 20 cm of global sea-level rise equivalent further weakens the AMOC by about 4.5 and 10 %, respectively. By combining our outcome with a multi-model sea-level rise study we project a dynamic sea-level rise along the New York City coastline of 4 cm for the RCP3-PD and of 8 cm for the RCP4.5 scenario over the 21st century. We estimate the total steric and dynamic sea-level rise for New York City to be about 24 cm until 2100 for the RCP3-PD scenario, which can hold as a lower bound for sea-level rise projections in this region, as it does not include ice sheet and mountain glacier contributions.
Y1  - 2011
U6  - https://doi.org/10.5194/esd-2-191-2011
SN  - 2190-4979
SN  - 2190-4987
VL  - 2
IS  - 2
SP  - 191
EP  - 200
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Frieler, Katja
A1  - Mengel, M.
A1  - Levermann, Anders
T1  - Delaying future sea-level rise by storing water in Antarctica
JF  - Earth system dynamics
N2  - Even if greenhouse gas emissions were stopped today, sea level would continue to rise for centuries, with the long-term sea-level commitment of a 2 degrees C warmer world significantly exceeding 2 m. In view of the potential implications for coastal populations and ecosystems worldwide, we investigate, from an ice-dynamic perspective, the possibility of delaying sea-level rise by pumping ocean water onto the surface of the Antarctic ice sheet. We find that due to wave propagation ice is discharged much faster back into the ocean than would be expected from a pure advection with surface velocities. The delay time depends strongly on the distance from the coastline at which the additional mass is placed and less strongly on the rate of sea-level rise that is mitigated. A millennium-scale storage of at least 80% of the additional ice requires placing it at a distance of at least 700 km from the coastline. The pumping energy required to elevate the potential energy of ocean water to mitigate the currently observed 3 mmyr(-1) will exceed 7% of the current global primary energy supply. At the same time, the approach offers a comprehensive protection for entire coastlines particularly including regions that cannot be protected by dikes.
Y1  - 2016
U6  - https://doi.org/10.5194/esd-7-203-2016
SN  - 2190-4979
SN  - 2190-4987
VL  - 7
SP  - 203
EP  - 210
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Frieler, Katja
A1  - Mengel, Matthias
A1  - Levermann, Anders
T1  - Delaying future sea-level rise by storing water in Antarctica
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Even if greenhouse gas emissions were stopped today, sea level would continue to rise for centuries, with the long-term sea-level commitment of a 2 degrees C warmer world significantly exceeding 2 m. In view of the potential implications for coastal populations and ecosystems worldwide, we investigate, from an ice-dynamic perspective, the possibility of delaying sea-level rise by pumping ocean water onto the surface of the Antarctic ice sheet. We find that due to wave propagation ice is discharged much faster back into the ocean than would be expected from a pure advection with surface velocities. The delay time depends strongly on the distance from the coastline at which the additional mass is placed and less strongly on the rate of sea-level rise that is mitigated. A millennium-scale storage of at least 80% of the additional ice requires placing it at a distance of at least 700 km from the coastline. The pumping energy required to elevate the potential energy of ocean water to mitigate the currently observed 3 mmyr(-1) will exceed 7% of the current global primary energy supply. At the same time, the approach offers a comprehensive protection for entire coastlines particularly including regions that cannot be protected by dikes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 533 
KW  - carbon-dioxide emissions
KW  - ice-sheet
KW  - climate-change
KW  - model
KW  - collapse
KW  - commitment
KW  - Greenland
KW  - discharge
KW  - project
KW  - surface
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-410234
SN  - 1866-8372
IS  - 533
ER  - 
TY  - JOUR
A1  - Kotz, Maximilian
A1  - Wenz, Leonie
A1  - Stechemesser, Annika
A1  - Kalkuhl, Matthias
A1  - Levermann, Anders
T1  - Day-to-day temperature variability reduces economic growth
JF  - Nature climate change
N2  - Elevated annual average temperature has been found to impact macro-economic growth. However, various fundamental elements of the economy are affected by deviations of daily temperature from seasonal expectations which are not well reflected in annual averages. Here we show that increases in seasonally adjusted day-to-day temperature variability reduce macro-economic growth independent of and in addition to changes in annual average temperature. Combining observed day-to-day temperature variability with subnational economic data for 1,537 regions worldwide over 40 years in fixed-effects panel models, we find that an extra degree of variability results in a five percentage-point reduction in regional growth rates on average. The impact of day-to-day variability is modulated by seasonal temperature difference and income, resulting in highest vulnerability in low-latitude, low-income regions (12 percentage-point reduction). These findings illuminate a new, global-impact channel in the climate–economy relationship that demands a more comprehensive assessment in both climate and integrated assessment models.
KW  - Climate change
KW  - Climate-change impacts
KW  - Economics
KW  - Environmental economics
KW  - Environmental impact
Y1  - 2021
U6  - https://doi.org/10.1038/s41558-020-00985-5
SN  - 1758-678X
SN  - 1758-6798
VL  - 11
IS  - 4
SP  - 319
EP  - 325
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Menon, Arathy
A1  - Levermann, Anders
A1  - Schewe, Jacob
A1  - Lehmann, J.
A1  - Frieler, Katja
T1  - Consistent increase in Indian monsoon rainfall and its variability across CMIP-5 models
JF  - Earth system dynamics
N2  - The possibility of an impact of global warming on the Indian monsoon is of critical importance for the large population of this region. Future projections within the Coupled Model Intercomparison Project Phase 3 (CMIP-3) showed a wide range of trends with varying magnitude and sign across models. Here the Indian summer monsoon rainfall is evaluated in 20 CMIP-5 models for the period 1850 to 2100. In the new generation of climate models, a consistent increase in seasonal mean rainfall during the summer monsoon periods arises. All models simulate stronger seasonal mean rainfall in the future compared to the historic period under the strongest warming scenario RCP-8.5. Increase in seasonal mean rainfall is the largest for the RCP-8.5 scenario compared to other RCPs. Most of the models show a northward shift in monsoon circulation by the end of the 21st century compared to the historic period under the RCP-8.5 scenario. The interannual variability of the Indian monsoon rainfall also shows a consistent positive trend under unabated global warming. Since both the long-term increase in monsoon rainfall as well as the increase in interannual variability in the future is robust across a wide range of models, some confidence can be attributed to these projected trends.
Y1  - 2013
U6  - https://doi.org/10.5194/esd-4-287-2013
SN  - 2190-4979
SN  - 2190-4987
VL  - 4
IS  - 2
SP  - 287
EP  - 300
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Frieler, Katja
A1  - Clark, Peter U.
A1  - He, Feng
A1  - Buizert, Christo
A1  - Reese, Ronja
A1  - Ligtenberg, Stefan R. M.
A1  - van den Broeke, Michiel R.
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Consistent evidence of increasing Antarctic accumulation with warming
JF  - Nature climate change
N2  - Projections of changes in Antarctic Ice Sheet (AIS) surface mass balance indicate a negative contribution to sea level because of the expected increase in precipitation due to the higher moisture holding capacity of warmer air(1). Observations over the past decades, however, are unable to constrain the relation between temperature and accumulation changes because both are dominated by strong natural variability(2-5). Here we derive a consistent continental-scale increase in accumulation of approximately 5 +/- 1% K-1, through the assessment of ice-core data (spanning the large temperature change during the last deglaciation, 21,000 to 10,000 years ago), in combination with palaeo-simulations, future projections by 35 general circulation models (GCMs), and one high-resolution future simulation. The ice-core data and modelling results for the last deglaciation agree, showing uniform local sensitivities of similar to 6% K-1. The palaeo-simulation allows for a continental-scale aggregation of accumulation changes reaching 4.3% K-1. Despite the different timescales, these sensitivities agree with the multi-model mean of 6.1 +/- 2.6% K-1 (GCMprojections) and the continental-scale sensitivity of 4.9% K-1 (high-resolution future simulation). Because some of the mass gain of the AIS is offset by dynamical losses induced by accumulation(6,7), we provide a response function allowing projections of sea-level fall in terms of continental-scale accumulation changes that compete with surface melting and dynamical losses induced by other mechanisms(6,8,9).
Y1  - 2015
U6  - https://doi.org/10.1038/nclimate2574
SN  - 1758-678X
SN  - 1758-6798
VL  - 5
IS  - 4
SP  - 348
EP  - 352
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Clark, Peter U.
A1  - Shakun, Jeremy D.
A1  - Marcott, Shaun A.
A1  - Mix, Alan C.
A1  - Eby, Michael
A1  - Kulp, Scott
A1  - Levermann, Anders
A1  - Milne, Glenn A.
A1  - Pfister, Patrik L.
A1  - Santer, Benjamin D.
A1  - Schrag, Daniel P.
A1  - Solomon, Susan
A1  - Stocker, Thomas F.
A1  - Strauss, Benjamin H.
A1  - Weaver, Andrew J.
A1  - Winkelmann, Ricarda
A1  - Archer, David
A1  - Bard, Edouard
A1  - Goldner, Aaron
A1  - Lambeck, Kurt
A1  - Pierrehumbert, Raymond T.
A1  - Plattner, Gian-Kasper
T1  - Consequences of twenty-first-century policy for multi-millennial climate
and sea-level change
JF  - Nature climate change
N2  - Most of the policy debate surrounding the actions needed to mitigate and adapt to anthropogenic climate change has been framed by observations of the past 150 years as well as climate and sea-level projections for the twenty-first century. The focus on this 250-year window, however, obscures some of the most profound problems associated with climate change. Here, we argue that the twentieth and twenty-first centuries, a period during which the overwhelming majority of human-caused carbon emissions are likely to occur, need to be placed into a long-term context that includes the past 20 millennia, when the last Ice Age ended and human civilization developed, and the next ten millennia, over which time the projected impacts of anthropogenic climate change will grow and persist. This long-term perspective illustrates that policy decisions made in the next few years to decades will have profound impacts on global climate, ecosystems and human societies - not just for this century, but for the next ten millennia and beyond.
Y1  - 2016
U6  - https://doi.org/10.1038/NCLIMATE2923
SN  - 1758-678X
SN  - 1758-6798
VL  - 6
SP  - 360
EP  - 369
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Sillmann, Jana
A1  - Lenton, Timothy M.
A1  - Levermann, Anders
A1  - Ott, Konrad
A1  - Hulme, Mike
A1  - Benduhn, Francois
A1  - Horton, Joshua B.
T1  - COMMENTARY: No emergency argument for climate engineering
JF  - Nature climate change
Y1  - 2015
SN  - 1758-678X
SN  - 1758-6798
VL  - 5
IS  - 4
SP  - 290
EP  - 292
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Feldmann, Johannes
A1  - Levermann, Anders
T1  - Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - The future evolution of the Antarctic Ice Sheet represents the largest uncertainty in sea-level projections of this and upcoming centuries. Recently, satellite observations and high-resolution simulations have suggested the initiation of an ice-sheet instability in the Amundsen Sea sector of West Antarctica, caused by the last decades' enhanced basal ice-shelf melting. Whether this localized destabilization will yield a full discharge of marine ice from West Antarctica, associated with a global sea-level rise of more than 3 m, or whether the ice loss is limited by ice dynamics and topographic features, is unclear. Here we show that in the Parallel Ice Sheet Model, a local destabilization causes a complete disintegration of the marine ice in West Antarctica. In our simulations, at 5-km horizontal resolution, the region disequilibrates after 60 y of currently observed melt rates. Thereafter, the marine ice-sheet instability fully unfolds and is not halted by topographic features. In fact, the ice loss in Amundsen Sea sector shifts the catchment's ice divide toward the Filchner-Ronne and Ross ice shelves, which initiates grounding-line retreat there. Our simulations suggest that if a destabilization of Amundsen Sea sector has indeed been initiated, Antarctica will irrevocably contribute at least 3 m to global sea-level rise during the coming centuries to millennia.
KW  - West Antarctic Ice Sheet
KW  - sea-level rise
KW  - tipping point
KW  - instability
KW  - marine ice-sheet instability
Y1  - 2015
U6  - https://doi.org/10.1073/pnas.1512482112
SN  - 0027-8424
VL  - 112
IS  - 46
SP  - 14191
EP  - 14196
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Hinkel, Jochen
A1  - Lincke, Daniel
A1  - Vafeidis, Athanasios T.
A1  - Perrette, Mahé
A1  - Nicholls, Robert James
A1  - Tol, Richard S. J.
A1  - Marzeion, Ben
A1  - Fettweis, Xavier
A1  - Ionescu, Cezar
A1  - Levermann, Anders
T1  - Coastal flood damage and adaptation costs under 21st century sea-level rise
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Coastal flood damage and adaptation costs under 21st century sea-level rise are assessed on a global scale taking into account a wide range of uncertainties in continental topography data, population data, protection strategies, socioeconomic development and sea-level rise. Uncertainty in global mean and regional sea level was derived from four different climate models from the Coupled Model Intercomparison Project Phase 5, each combined with three land-ice scenarios based on the published range of contributions from ice sheets and glaciers. Without adaptation, 0.2-4.6% of global population is expected to be flooded annually in 2100 under 25-123 cm of global mean sea-level rise, with expected annual losses of 0.3-9.3% of global gross domestic product. Damages of this magnitude are very unlikely to be tolerated by society and adaptation will be widespread. The global costs of protecting the coast with dikes are significant with annual investment and maintenance costs of US$ 12-71 billion in 2100, but much smaller than the global cost of avoided damages even without accounting for indirect costs of damage to regional production supply. Flood damages by the end of this century are much more sensitive to the applied protection strategy than to variations in climate and socioeconomic scenarios as well as in physical data sources (topography and climate model). Our results emphasize the central role of long-term coastal adaptation strategies. These should also take into account that protecting large parts of the developed coast increases the risk of catastrophic consequences in the case of defense failure.
KW  - coastal flooding
KW  - climate change impact
KW  - loss and damage
Y1  - 2014
U6  - https://doi.org/10.1073/pnas.1222469111
SN  - 0027-8424
VL  - 111
IS  - 9
SP  - 3292
EP  - 3297
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schleussner, Carl-Friedrich
A1  - Donges, Jonathan
A1  - Engemann, Denis A.
A1  - Levermann, Anders
T1  - Clustered marginalization of minorities during social transitions induced by co-evolution of behaviour and network structure
JF  - Scientific reports
N2  - Large-scale transitions in societies are associated with both individual behavioural change and restructuring of the social network. These two factors have often been considered independently, yet recent advances in social network research challenge this view. Here we show that common features of societal marginalization and clustering emerge naturally during transitions in a co-evolutionary adaptive network model. This is achieved by explicitly considering the interplay between individual interaction and a dynamic network structure in behavioural selection. We exemplify this mechanism by simulating how smoking behaviour and the network structure get reconfigured by changing social norms. Our results are consistent with empirical findings: The prevalence of smoking was reduced, remaining smokers were preferentially connected among each other and formed increasingly marginalized clusters. We propose that self-amplifying feedbacks between individual behaviour and dynamic restructuring of the network are main drivers of the transition. This generative mechanism for co-evolution of individual behaviour and social network structure may apply to a wide range of examples beyond smoking.
Y1  - 2016
U6  - https://doi.org/10.1038/srep30790
SN  - 2045-2322
VL  - 6
SP  - 3407
EP  - 3417
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Schewe, Jacob
A1  - Levermann, Anders
A1  - Meinshausen, Malte
T1  - Climate change under a scenario near 1.5 degrees C of global warming: monsoon intensification, ocean warming and steric sea level rise
JF  - Earth system dynamics
N2  - We present climatic consequences of the Representative Concentration Pathways (RCPs) using the coupled climate model CLIMBER-3 alpha, which contains a statistical-dynamical atmosphere and a three-dimensional ocean model. We compare those with emulations of 19 state-of-the-art atmosphere-ocean general circulation models (AOGCM) using MAGICC6. The RCPs are designed as standard scenarios for the forthcoming IPCC Fifth Assessment Report to span the full range of future greenhouse gas (GHG) concentrations pathways currently discussed. The lowest of the RCP scenarios, RCP3-PD, is projected in CLIMBER-3 alpha to imply a maximal warming by the middle of the 21st century slightly above 1.5 degrees C and a slow decline of temperatures thereafter, approaching today's level by 2500. We identify two mechanisms that slow down global cooling after GHG concentrations peak: The known inertia induced by mixing-related oceanic heat uptake; and a change in oceanic convection that enhances ocean heat loss in high latitudes, reducing the surface cooling rate by almost 50%. Steric sea level rise under the RCP3-PD scenario continues for 200 years after the peak in surface air temperatures, stabilizing around 2250 at 30 cm. This contrasts with around 1.3 m of steric sea level rise by 2250, and 2 m by 2500, under the highest scenario, RCP8.5. Maximum oceanic warming at intermediate depth (300-800 m) is found to exceed that of the sea surface by the second half of the 21st century under RCP3-PD. This intermediate-depth warming persists for centuries even after surface temperatures have returned to present-day values, with potential consequences for marine ecosystems, oceanic methane hydrates, and ice-shelf stability. Due to an enhanced land-ocean temperature contrast, all scenarios yield an intensification of monsoon rainfall under global warming.
Y1  - 2011
U6  - https://doi.org/10.5194/esd-2-25-2011
SN  - 2190-4979
SN  - 2190-4987
VL  - 2
IS  - 1
SP  - 25
EP  - 35
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Strauss, Benjamin H.
A1  - Kulp, Scott
A1  - Levermann, Anders
T1  - Carbon choices determine US cities committed to futures below sea level
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Anthropogenic carbon emissions lock in long-term sea-level rise that greatly exceeds projections for this century, posing profound challenges for coastal development and cultural legacies. Analysis based on previously published relationships linking emissions to warming and warming to rise indicates that unabated carbon emissions up to the year 2100 would commit an eventual global sea-level rise of 4.3-9.9 m. Based on detailed topographic and population data, local high tide lines, and regional long-term sea-level commitment for different carbon emissions and ice sheet stability scenarios, we compute the current population living on endangered land at municipal, state, and national levels within the United States. For unabated climate change, we find that land that is home to more than 20 million people is implicated and is widely distributed among different states and coasts. The total area includes 1,185-1,825 municipalities where land that is home to more than half of the current population would be affected, among them at least 21 cities exceeding 100,000 residents. Under aggressive carbon cuts, more than half of these municipalities would avoid this commitment if the West Antarctic Ice Sheet remains stable. Similarly, more than half of the US population-weighted area under threat could be spared. We provide lists of implicated cities and state populations for different emissions scenarios and with and without a certain collapse of the West Antarctic Ice Sheet. Although past anthropogenic emissions already have caused sea-level commitment that will force coastal cities to adapt, future emissions will determine which areas we can continue to occupy or may have to abandon.
KW  - climate change
KW  - climate impacts
KW  - sea-level rise
Y1  - 2015
U6  - https://doi.org/10.1073/pnas.1511186112
SN  - 0027-8424
VL  - 112
IS  - 44
SP  - 13508
EP  - 13513
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Willner, Sven N.
A1  - Levermann, Anders
A1  - Zhao, Fang
A1  - Frieler, Katja
T1  - Adaptation required to preserve future high-end river flood risk at present levels
JF  - Science Advances
N2  - Earth’s surface temperature will continue to rise for another 20 to 30 years even with the strongest carbon emission reduction currently considered. The associated changes in rainfall patterns can result in an increased flood risk worldwide. We compute the required increase in flood protection to keep high-end fluvial flood risk at present levels. The analysis is carried out worldwide for subnational administrative units. Most of the United States, Central Europe, and Northeast and West Africa, as well as large parts of India and Indonesia, require the strongest adaptation effort. More than half of the United States needs to at least double their protection within the next two decades. Thus, the need for adaptation to increased river flood is a global problem affecting industrialized regions as much as developing countries.
Y1  - 2018
U6  - https://doi.org/10.1126/sciadv.aao1914
SN  - 2375-2548
VL  - 4
IS  - 1
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - GEN
A1  - Levermann, Anders
A1  - Petoukhov, Vladimir
A1  - Schewe, Jacob
A1  - Schellnhuber, Hans Joachim
T1  - Abrupt monsoon transitions as seen in paleorecords can be explained by moisture-advection feedback
T2  - Proceedings of the National Academy of Sciences of the United States of America
Y1  - 2016
U6  - https://doi.org/10.1073/pnas.1603130113
SN  - 0027-8424
VL  - 113
SP  - E2348
EP  - E2349
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schewe, Jacob
A1  - Levermann, Anders
T1  - A statistically predictive model for future monsoon failure in India
JF  - Environmental research letters
N2  - Indian monsoon rainfall is vital for a large share of the world's population. Both reliably projecting India's future precipitation and unraveling abrupt cessations of monsoon rainfall found in paleorecords require improved understanding of its stability properties. While details of monsoon circulations and the associated rainfall are complex, full-season failure is dominated by large-scale positive feedbacks within the region. Here we find that in a comprehensive climate model, monsoon failure is possible but very rare under pre-industrial conditions, while under future warming it becomes much more frequent. We identify the fundamental intraseasonal feedbacks that are responsible for monsoon failure in the climate model, relate these to observational data, and build a statistically predictive model for such failure. This model provides a simple dynamical explanation for future changes in the frequency distribution of seasonal mean all-Indian rainfall. Forced only by global mean temperature and the strength of the Pacific Walker circulation in spring, it reproduces the trend as well as the multidecadal variability in the mean and skewness of the distribution, as found in the climate model. The approach offers an alternative perspective on large-scale monsoon variability as the result of internal instabilities modulated by pre-seasonal ambient climate conditions.
KW  - monsoon failure
KW  - climate change
KW  - coupled climate model
KW  - stochastic model
KW  - non-linear dynamics
Y1  - 2012
U6  - https://doi.org/10.1088/1748-9326/7/4/044023
SN  - 1748-9326
VL  - 7
IS  - 4
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Schlemm, Tanja
A1  - Levermann, Anders
T1  - A simple stress-based cliff-calving law
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Over large coastal regions in Greenland and Antarctica the ice sheet calves directly into the ocean. In contrast to ice-shelf calving, an increase in calving from grounded glaciers contributes directly to sea-level rise. Ice cliffs with a glacier freeboard larger than approximate to 100 m are currently not observed, but it has been shown that such ice cliffs are increasingly unstable with increasing ice thickness. This cliff calving can constitute a self-amplifying ice loss mechanism that may significantly alter sea-level projections both of Greenland and Antarctica. Here we seek to derive a minimalist stress-based parametrization for cliff calving from grounded glaciers whose freeboards exceed the 100m stability limit derived in previous studies. This will be an extension of existing calving laws for tidewater glaciers to higher ice cliffs. To this end we compute the stress field for a glacier with a simplified two-dimensional geometry from the two-dimensional Stokes equation. First we assume a constant yield stress to derive the failure region at the glacier front from the stress field within the glacier. Secondly, we assume a constant response time of ice failure due to exceedance of the yield stress. With this strongly constraining but very simple set of assumptions we propose a cliff-calving law where the calving rate follows a power-law dependence on the freeboard of the ice with exponents between 2 and 3, depending on the relative water depth at the calving front. The critical freeboard below which the ice front is stable decreases with increasing relative water depth of the calving front. For a dry water front it is, for example, 75 m. The purpose of this study is not to provide a comprehensive calving law but to derive a particularly simple equation with a transparent and minimalist set of assumptions.
Y1  - 2019
U6  - https://doi.org/10.5194/tc-13-2475-2019
SN  - 1994-0416
SN  - 1994-0424
VL  - 13
IS  - 9
SP  - 2475
EP  - 2488
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Schlemm, Tanja
A1  - Levermann, Anders
T1  - A simple parametrization of mélange buttressing for calving glaciers
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Both ice sheets in Greenland and Antarctica are discharging ice into the ocean. In many regions along the coast of the ice sheets, the icebergs calve into a bay. If the addition of icebergs through calving is faster than their transport out of the embayment, the icebergs will be frozen into a melange with surrounding sea ice in winter. In this case, the buttressing effect of the ice melange can be considerably stronger than any buttressing by mere sea ice would be. This in turn stabilizes the glacier terminus and leads to a reduction in calving rates. Here we propose a simple parametrization of ice melange buttressing which leads to an upper bound on calving rates and can be used in numerical and analytical modelling.
Y1  - 2021
U6  - https://doi.org/10.5194/tc-15-531-2021
SN  - 1994-0416
SN  - 1994-0424
VL  - 15
IS  - 2
SP  - 531
EP  - 545
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Levermann, Anders
A1  - Winkelmann, Ricarda
T1  - A simple equation for the melt elevation feedback of ice sheets
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - In recent decades, the Greenland Ice Sheet has been losing mass and has thereby contributed to global sea-level rise. The rate of ice loss is highly relevant for coastal protection worldwide. The ice loss is likely to increase under future warming. Beyond a critical temperature threshold, a meltdown of the Greenland Ice Sheet is induced by the self-enforcing feedback between its lowering surface elevation and its increasing surface mass loss: the more ice that is lost, the lower the ice surface and the warmer the surface air temperature, which fosters further melting and ice loss. The computation of this rate so far relies on complex numerical models which are the appropriate tools for capturing the complexity of the problem. By contrast we aim here at gaining a conceptual understanding by deriving a purposefully simple equation for the self-enforcing feedback which is then used to estimate the melt time for different levels of warming using three observable characteristics of the ice sheet itself and its surroundings. The analysis is purely conceptual in nature. It is missing important processes like ice dynamics for it to be useful for applications to sea-level rise on centennial timescales, but if the volume loss is dominated by the feedback, the resulting logarithmic equation unifies existing numerical simulations and shows that the melt time depends strongly on the level of warming with a critical slow-down near the threshold: the median time to lose 10% of the present-day ice volume varies between about 3500 years for a temperature level of 0.5 degrees C above the threshold and 500 years for 5 degrees C. Unless future observations show a significantly higher melting sensitivity than currently observed, a complete meltdown is unlikely within the next 2000 years without significant ice-dynamical contributions.
Y1  - 2016
U6  - https://doi.org/10.5194/tc-10-1799-2016
SN  - 1994-0416
SN  - 1994-0424
VL  - 10
SP  - 1799
EP  - 1807
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Levermann, Anders
A1  - Winkelmann, Ricarda
T1  - A simple equation for the melt elevation feedback of ice sheets
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - In recent decades, the Greenland Ice Sheet has been losing mass and has thereby contributed to global sea-level rise. The rate of ice loss is highly relevant for coastal protection worldwide. The ice loss is likely to increase under future warming. Beyond a critical temperature threshold, a meltdown of the Greenland Ice Sheet is induced by the self-enforcing feedback between its lowering surface elevation and its increasing surface mass loss: the more ice that is lost, the lower the ice surface and the warmer the surface air temperature, which fosters further melting and ice loss. The computation of this rate so far relies on complex numerical models which are the appropriate tools for capturing the complexity of the problem. By contrast we aim here at gaining a conceptual understanding by deriving a purposefully simple equation for the self-enforcing feedback which is then used to estimate the melt time for different levels of warming using three observable characteristics of the ice sheet itself and its surroundings. The analysis is purely conceptual in nature. It is missing important processes like ice dynamics for it to be useful for applications to sea-level rise on centennial timescales, but if the volume loss is dominated by the feedback, the resulting logarithmic equation unifies existing numerical simulations and shows that the melt time depends strongly on the level of warming with a critical slow-down near the threshold: the median time to lose 10% of the present-day ice volume varies between about 3500 years for a temperature level of 0.5 degrees C above the threshold and 500 years for 5 degrees C. Unless future observations show a significantly higher melting sensitivity than currently observed, a complete meltdown is unlikely within the next 2000 years without significant ice-dynamical contributions.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 529 
KW  - sea-level rise
KW  - mass-balance
KW  - climate-change
KW  - Greenland
KW  - model
KW  - glacier
KW  - projections
KW  - dynamics
KW  - impact
KW  - 21st-Century
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-409834
SN  - 1866-8372
IS  - 529
ER  - 
TY  - JOUR
A1  - Fürst, Johannes J.
A1  - Levermann, Anders
T1  - A minimal model for wind- and mixing-driven overturning  threshold behavior for both driving mechanisms
JF  - Climate dynamics : observational, theoretical and computational research on the climate system
N2  - We present a minimal conceptual model for the Atlantic meridional overturning circulation which incorporates the advection of salinity and the basic dynamics of the oceanic pycnocline. Four tracer transport processes following Gnanadesikan in Science 283(5410):2077-2079, (1999) allow for a dynamical adjustment of the oceanic pycnocline which defines the vertical extent of a mid-latitudinal box. At the same time the model captures the salt-advection feedback (Stommel in Tellus 13(2):224-230, (1961)). Due to its simplicity the model can be solved analytically in the purely wind- and purely mixing-driven cases. We find the possibility of abrupt transition in response to surface freshwater forcing in both cases even though the circulations are very different in physics and geometry. This analytical approach also provides expressions for the critical freshwater input marking the change in the dynamics of the system. Our analysis shows that including the pycnocline dynamics in a salt-advection model causes a decrease in the freshwater sensitivity of its northern sinking up to a threshold at which the circulation breaks down. Compared to previous studies the model is restricted to the essential ingredients. Still, it exhibits a rich behavior which reaches beyond the scope of this study and might be used as a paradigm for the qualitative behaviour of the Atlantic overturning in the discussion of driving mechanisms.
KW  - Meridional overturning circulation
KW  - Northern sinking
KW  - Critical freshwater threshold
KW  - Overturning sensitivity
KW  - Conceptual model
KW  - Stability
KW  - Atlantic meridional overturning circulation
KW  - Pycnocline depth
KW  - Driving mechanism
Y1  - 2012
U6  - https://doi.org/10.1007/s00382-011-1003-7
SN  - 0930-7575
VL  - 38
IS  - 1-2
SP  - 239
EP  - 260
PB  - Springer
CY  - New York
ER  - 
TY  - GEN
A1  - Frieler, Katja
A1  - Levermann, Anders
A1  - Elliott, J.
A1  - Heinke, J.
A1  - Arneth, A.
A1  - Bierkens, M. F. P.
A1  - Ciais, Philippe
A1  - Clark, D. B.
A1  - Deryng, D.
A1  - Doell, P.
A1  - Falloon, P.
A1  - Fekete, B.
A1  - Folberth, Christian
A1  - Friend, A. D.
A1  - Gellhorn, C.
A1  - Gosling, S. N.
A1  - Haddeland, I.
A1  - Khabarov, N.
A1  - Lomas, M.
A1  - Masaki, Y.
A1  - Nishina, K.
A1  - Neumann, K.
A1  - Oki, T.
A1  - Pavlick, R.
A1  - Ruane, A. C.
A1  - Schmid, E.
A1  - Schmitz, C.
A1  - Stacke, T.
A1  - Stehfest, E.
A1  - Tang, Q.
A1  - Wisser, D.
A1  - Huber, V.
A1  - Piontek, Franziska
A1  - Warszawski, L.
A1  - Schewe, Jacob
A1  - Lotze-Campen, Hermann
A1  - Schellnhuber, Hans Joachim
T1  - A framework for the cross-sectoral integration of multi-model impact projections
BT  - land use decisions under climate impacts uncertainties
T2  - Earth system dynamics
N2  - Climate change and its impacts already pose considerable challenges for societies that will further increase with global warming (IPCC, 2014a, b). Uncertainties of the climatic response to greenhouse gas emissions include the potential passing of large-scale tipping points (e.g. Lenton et al., 2008; Levermann et al., 2012; Schellnhuber, 2010) and changes in extreme meteorological events (Field et al., 2012) with complex impacts on societies (Hallegatte et al., 2013). Thus climate change mitigation is considered a necessary societal response for avoiding uncontrollable impacts (Conference of the Parties, 2010). On the other hand, large-scale climate change mitigation itself implies fundamental changes in, for example, the global energy system. The associated challenges come on top of others that derive from equally important ethical imperatives like the fulfilment of increasing food demand that may draw on the same resources. For example, ensuring food security for a growing population may require an expansion of cropland, thereby reducing natural carbon sinks or the area available for bio-energy production. So far, available studies addressing this problem have relied on individual impact models, ignoring uncertainty in crop model and biome model projections. Here, we propose a probabilistic decision framework that allows for an evaluation of agricultural management and mitigation options in a multi-impact-model setting. Based on simulations generated within the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP), we outline how cross-sectorally consistent multi-model impact simulations could be used to generate the information required for robust decision making.

Using an illustrative future land use pattern, we discuss the trade-off between potential gains in crop production and associated losses in natural carbon sinks in the new multiple crop-and biome-model setting. In addition, crop and water model simulations are combined to explore irrigation increases as one possible measure of agricultural intensification that could limit the expansion of cropland required in response to climate change and growing food demand. This example shows that current impact model uncertainties pose an important challenge to long-term mitigation planning and must not be ignored in long-term strategic decision making.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 457 
KW  - global food demand
KW  - water availability
KW  - elevated CO2
KW  - future
KW  - carbon
KW  - system
KW  - productivity
KW  - agriculture
KW  - emissions
KW  - scarcity
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-407968
ER  - 
TY  - JOUR
A1  - Frieler, Katja
A1  - Levermann, Anders
A1  - Elliott, J.
A1  - Heinke, Jens
A1  - Arneth, A.
A1  - Bierkens, M. F. P.
A1  - Ciais, Philippe
A1  - Clark, D. B.
A1  - Deryng, D.
A1  - Doell, P.
A1  - Falloon, P.
A1  - Fekete, B.
A1  - Folberth, Christian
A1  - Friend, A. D.
A1  - Gellhorn, C.
A1  - Gosling, S. N.
A1  - Haddeland, I.
A1  - Khabarov, N.
A1  - Lomas, M.
A1  - Masaki, Y.
A1  - Nishina, K.
A1  - Neumann, K.
A1  - Oki, T.
A1  - Pavlick, R.
A1  - Ruane, A. C.
A1  - Schmid, E.
A1  - Schmitz, C.
A1  - Stacke, T.
A1  - Stehfest, E.
A1  - Tang, Q.
A1  - Wisser, D.
A1  - Huber, Veronika
A1  - Piontek, Franziska
A1  - Warszawski, Lila
A1  - Schewe, Jacob
A1  - Lotze-Campen, Hermann
A1  - Schellnhuber, Hans Joachim
T1  - A framework for the cross-sectoral integration of multi-model impact projections
BT  - land use decisions under climate impacts uncertainties
JF  - Earth system dynamics
N2  - Climate change and its impacts already pose considerable challenges for societies that will further increase with global warming (IPCC, 2014a, b). Uncertainties of the climatic response to greenhouse gas emissions include the potential passing of large-scale tipping points (e.g. Lenton et al., 2008; Levermann et al., 2012; Schellnhuber, 2010) and changes in extreme meteorological events (Field et al., 2012) with complex impacts on societies (Hallegatte et al., 2013). Thus climate change mitigation is considered a necessary societal response for avoiding uncontrollable impacts (Conference of the Parties, 2010). On the other hand, large-scale climate change mitigation itself implies fundamental changes in, for example, the global energy system. The associated challenges come on top of others that derive from equally important ethical imperatives like the fulfilment of increasing food demand that may draw on the same resources. For example, ensuring food security for a growing population may require an expansion of cropland, thereby reducing natural carbon sinks or the area available for bio-energy production. So far, available studies addressing this problem have relied on individual impact models, ignoring uncertainty in crop model and biome model projections. Here, we propose a probabilistic decision framework that allows for an evaluation of agricultural management and mitigation options in a multi-impact-model setting. Based on simulations generated within the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP), we outline how cross-sectorally consistent multi-model impact simulations could be used to generate the information required for robust decision making.
 Using an illustrative future land use pattern, we discuss the trade-off between potential gains in crop production and associated losses in natural carbon sinks in the new multiple crop-and biome-model setting. In addition, crop and water model simulations are combined to explore irrigation increases as one possible measure of agricultural intensification that could limit the expansion of cropland required in response to climate change and growing food demand. This example shows that current impact model uncertainties pose an important challenge to long-term mitigation planning and must not be ignored in long-term strategic decision making.
Y1  - 2015
U6  - https://doi.org/10.5194/esd-6-447-2015
SN  - 2190-4979
SN  - 2190-4987
VL  - 6
IS  - 2
SP  - 447
EP  - 460
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Schewe, Jacob
A1  - Levermann, Anders
A1  - Cheng, Hai
T1  - A critical humidity threshold for monsoon transitions
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Monsoon systems around the world are governed by the so-called moisture-advection feedback. Here we show that, in a minimal conceptual model, this feedback implies a critical threshold with respect to the atmospheric specific humidity q(o) over the ocean adjacent to the monsoon region. If q(o) falls short of this critical value q(o)(c), monsoon rainfall over land cannot be sustained. Such a case could occur if evaporation from the ocean was reduced, e.g. due to low sea surface temperatures. Within the restrictions of the conceptual model, we estimate q(o)(c) from present-day reanalysis data for four major monsoon systems, and demonstrate how this concept can help understand abrupt variations in monsoon strength on orbital timescales as found in proxy records.
Y1  - 2012
U6  - https://doi.org/10.5194/cp-8-535-2012
SN  - 1814-9324
VL  - 8
IS  - 2
SP  - 535
EP  - 544
PB  - Copernicus
CY  - Göttingen
ER  -