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.
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 -