@article{KatzenbergerLevermannScheweetal.2022,
author = {Katzenberger, Anja and Levermann, Anders and Schewe, Jacob and Pongratz, Julia},
title = {Intensification of very wet monsoon seasons in India under global warming},
series = {Geophysical research letters},
volume = {49},
journal = {Geophysical research letters},
number = {15},
publisher = {American Geophysical Union},
address = {Washington},
issn = {0094-8276},
doi = {10.1029/2022GL098856},
pages = {10},
year = {2022},
abstract = {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.},
language = {en}
}
@article{AlbrechtWinkelmannLevermann2020,
author = {Albrecht, Torsten and Winkelmann, Ricarda and Levermann, Anders},
title = {Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM)},
series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
volume = {14},
journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
number = {2},
publisher = {Copernicus},
address = {G{\"o}ttingen},
issn = {1994-0416},
doi = {10.5194/tc-14-599-2020},
pages = {599 -- 632},
year = {2020},
abstract = {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.
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.
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.},
language = {en}
}
@article{OttoWillnerWenzetal.2017,
author = {Otto, Christian and Willner, Sven N. and Wenz, Leonie and Frieler, Katja and Levermann, Anders},
title = {Modeling loss-propagation in the global supply network: The dynamic agent-based model acclimate},
series = {Journal of economic dynamics \& control},
volume = {83},
journal = {Journal of economic dynamics \& control},
publisher = {Elsevier},
address = {Amsterdam},
issn = {0165-1889},
doi = {10.1016/j.jedc.2017.08.001},
pages = {232 -- 269},
year = {2017},
abstract = {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.},
language = {en}
}
@article{FeldmannAlbrechtKhroulevetal.2014,
author = {Feldmann, J. and Albrecht, Torsten and Khroulev, C. and Pattyn, F. and Levermann, Anders},
title = {Resolution-dependent performance of grounding line motion in a shallow model compared with a full-Stokes model according to the MISMIP3d intercomparison},
series = {Journal of glaciology},
volume = {60},
journal = {Journal of glaciology},
number = {220},
publisher = {International Glaciological Society},
address = {Cambridge},
issn = {0022-1430},
doi = {10.3189/2014JoG13J093},
pages = {353 -- 360},
year = {2014},
abstract = {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.},
language = {en}
}
@article{HinkelLinckeVafeidisetal.2014,
author = {Hinkel, Jochen and Lincke, Daniel and Vafeidis, Athanasios T. and Perrette, Mah{\´e} and Nicholls, Robert James and Tol, Richard S. J. and Marzeion, Ben and Fettweis, Xavier and Ionescu, Cezar and Levermann, Anders},
title = {Coastal flood damage and adaptation costs under 21st century sea-level rise},
series = {Proceedings of the National Academy of Sciences of the United States of America},
volume = {111},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = {9},
publisher = {National Acad. of Sciences},
address = {Washington},
issn = {0027-8424},
doi = {10.1073/pnas.1222469111},
pages = {3292 -- 3297},
year = {2014},
abstract = {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.},
language = {en}
}
@article{SchleussnerLevermannMeinshausen2014,
author = {Schleussner, Carl-Friedrich and Levermann, Anders and Meinshausen, Malte},
title = {Probabilistic projections of the Atlantic overturning},
series = {Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change},
volume = {127},
journal = {Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change},
number = {3-4},
publisher = {Springer},
address = {Dordrecht},
issn = {0165-0009},
doi = {10.1007/s10584-014-1265-2},
pages = {579 -- 586},
year = {2014},
abstract = {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.},
language = {en}
}
@article{SchleussnerFrielerMeinshausenetal.2011,
author = {Schleussner, Carl-Friedrich and Frieler, Katja and Meinshausen, Malte and Yin, J. and Levermann, Anders},
title = {Emulating Atlantic overturning strength for low emission scenarios consequences for sea-level rise along the North American east coast},
series = {Earth system dynamics},
volume = {2},
journal = {Earth system dynamics},
number = {2},
publisher = {Copernicus},
address = {G{\"o}ttingen},
issn = {2190-4979},
doi = {10.5194/esd-2-191-2011},
pages = {191 -- 200},
year = {2011},
abstract = {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.},
language = {en}
}
@article{AlbrechtMartinHaseloffetal.2011,
author = {Albrecht, Tanja and Martin, M. and Haseloff, M. and Winkelmann, Ricarda and Levermann, Anders},
title = {Parameterization for subgrid-scale motion of ice-shelf calving fronts},
series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
volume = {5},
journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
number = {1},
publisher = {Copernicus},
address = {G{\"o}ttingen},
issn = {1994-0416},
doi = {10.5194/tc-5-35-2011},
pages = {35 -- 44},
year = {2011},
abstract = {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.},
language = {en}
}
@article{ScheweLevermannCheng2012,
author = {Schewe, Jacob and Levermann, Anders and Cheng, Hai},
title = {A critical humidity threshold for monsoon transitions},
series = {Climate of the past : an interactive open access journal of the European Geosciences Union},
volume = {8},
journal = {Climate of the past : an interactive open access journal of the European Geosciences Union},
number = {2},
publisher = {Copernicus},
address = {G{\"o}ttingen},
issn = {1814-9324},
doi = {10.5194/cp-8-535-2012},
pages = {535 -- 544},
year = {2012},
abstract = {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.},
language = {en}
}
@article{LevermannAlbrechtWinkelmannetal.2012,
author = {Levermann, Anders and Albrecht, Tanja and Winkelmann, Ricarda and Martin, Maria A. and Haseloff, Monika and Joughin, I.},
title = {Kinematic first-order calving law implies potential for abrupt ice-shelf retreat},
series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
volume = {6},
journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union},
number = {2},
publisher = {Copernicus},
address = {G{\"o}ttingen},
issn = {1994-0416},
doi = {10.5194/tc-6-273-2012},
pages = {273 -- 286},
year = {2012},
abstract = {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.},
language = {en}
}
@article{LevermannBamberDrijfhoutetal.2012,
author = {Levermann, Anders and Bamber, Jonathan L. and Drijfhout, Sybren and Ganopolski, Andrey and Haeberli, Winfried and Harris, Neil R. P. and Huss, Matthias and Krueger, Kirstin and Lenton, Timothy M. and Lindsay, Ronald W. and Notz, Dirk and Wadhams, Peter and Weber, Susanne},
title = {Potential climatic transitions with profound impact on Europe Review of the current state of six 'tipping elements of the climate system'},
series = {Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change},
volume = {110},
journal = {Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change},
number = {3-4},
publisher = {Springer},
address = {Dordrecht},
issn = {0165-0009},
doi = {10.1007/s10584-011-0126-5},
pages = {845 -- 878},
year = {2012},
abstract = {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.},
language = {en}
}
@article{HattermannLevermann2010,
author = {Hattermann, Tore and Levermann, Anders},
title = {Response of Southern Ocean circulation to global warming may enhance basal ice shelf melting around Antarctica},
issn = {0930-7575},
doi = {10.1007/s00382-009-0643-3},
year = {2010},
abstract = {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.},
language = {en}
}
@misc{Levermann2007,
author = {Levermann, Anders},
title = {Kann sich die Meeresstr{\"o}mung pl{\"o}tzlich {\"a}ndern? : Antrittsvorlesung 2007-06-07},
publisher = {Univ.-Bibl.},
address = {Potsdam},
year = {2007},
abstract = {Bohrkerne zeigen, dass sich die Meeresstr{\"o}mungen im Atlantik w{\"a}hrend der letzten Eiszeit pl{\"o}tzlich und drastisch ver{\"a}ndert haben. Temperaturspr{\"u}nge von bis zu zehn Grad innerhalb von Dekaden waren die Folge. Nicht nur f{\"u}r die zuk{\"u}nftige wirtschaftliche und gesellschaftliche Entwicklung Europas ist es wichtig, ob sich diese Ver{\"a}nderungen wiederholen k{\"o}nnen. Kann es auch in der heutigen Warmzeit abrupte Klimaver{\"a}nderungen geben? Diese Frage ist eng an eine scheinbar akademische Diskussion nach den Antriebsmechanismen der Ozeanzirkulation gekoppelt. Mit den Gr{\"u}nden hierf{\"u}r und den Folgerungen f{\"u}r die klimatische Stabilit{\"a}t besch{\"a}ftigt sich der Referent in seiner Vorlesung.},
language = {de}
}