Articles | Volume 20, issue 9
https://doi.org/10.5194/cp-20-2001-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-20-2001-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
12 Sep 2024
Research article |
| 12 Sep 2024
| 12 Sep 2024
Glacial AMOC shoaling despite vigorous tidal dissipation: vertical stratification matters
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany
Frontiers Science Center for Deep Ocean Multispheres and Earth System/Physical Oceanography Laboratory, Ocean University of China, Qingdao, 266100, China
Pengyang Song
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany
Xianyao Chen
Frontiers Science Center for Deep Ocean Multispheres and Earth System/Physical Oceanography Laboratory, Ocean University of China, Qingdao, 266100, China
Laoshan Laboratory, Qingdao, 266100, China
Gerrit Lohmann
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany
University of Bremen, 28334 Bremen, Germany
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Hartmut Heinrich and Gerrit Lohmann
EGUsphere, https://doi.org/10.5194/egusphere-2026-896, https://doi.org/10.5194/egusphere-2026-896, 2026
This preprint is open for discussion and under review for Earth System Dynamics (ESD).
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To date, models have not been very successful in linking Heinrich events (He) with Dansgaard-Oeschger (D-O) cycles, nor in identifying the driver. Here, we present a concept based on CO2 exchange between the atmosphere and the ocean, and on the input of Fe-rich dust during the cold phases of the systems. Cooling trend during a D-O cycle is interrupted by a precessionally maximized Atlantic circulation causing a He. The subsequent strong release of CO₂ from the ocean triggers a D-O new cycle.
Jochen Knies, Christian Stepanek, Simon T. Belt, Stijn De Schepper, and Gerrit Lohmann
EGUsphere, https://doi.org/10.5194/egusphere-2026-4723, https://doi.org/10.5194/egusphere-2026-4723, 2026
This preprint is open for discussion and under review for Climate of the Past (CP).
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The Arctic is rapidly approaching seasonally ice-free ("blue") conditions. Using proxy data to evaluate simulations of past warm climates, we show that enhanced ocean mixing substantially improves agreement with evidence for a blue Arctic and reveals multiple pathways for Arctic warming during the Early Pliocene. Our findings highlight the importance of accurately representing ocean processes in climate models to improve projections of future Arctic climate.
Xiaoxu Shi, Xiya Liu, Jiping Liu, Martin Werner, Hu Yang, Francisco W. Cruz, Chaoyuan Yang, and Gerrit Lohmann
EGUsphere, https://doi.org/10.5194/egusphere-2026-3894, https://doi.org/10.5194/egusphere-2026-3894, 2026
This preprint is open for discussion and under review for Climate of the Past (CP).
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Cave stalagmites record the oxygen isotope of past rainfall and are used to reconstruct how monsoons changed, but due to the complexity of isotope impacting factors, what these records tell us is debated. We performed a 8300-year simulation with an isotope-enabled climate model, and show that rainfall amount is the key stable driver across global monsoons, while temperature and moisture pathways vary with region and time. Single-site records are noisy, but regional averages recover the signal.
Tobias Spiegl, Norel Rimbu, Franziska Kappenberger, Xiaojie Hao, Wenjuan Huo, Stephan Thober, Ulrike Langematz, and Gerrit Lohmann
EGUsphere, https://doi.org/10.5194/egusphere-2026-3630, https://doi.org/10.5194/egusphere-2026-3630, 2026
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Natural solar signals are not fixed in time. During past centennial-scale solar minima, reduced solar activity promoted summer heavy precipitation through coupled changes in ozone, sea ice and storm tracks. In a warmer future climate, this pathway weakens, showing that anthropogenic warming can reshape how natural forcings translate into regional weather extremes.
Clemens Schannwell, Marie-Luise Kapsch, Matteo Willeit, Lars Ackermann, Gregor Knorr, Uta Krebs-Kanzow, Gerrit Lohmann, Katharina D. Six, Christian Stepanek, and Uwe Mikolajewicz
EGUsphere, https://doi.org/10.5194/egusphere-2026-3384, https://doi.org/10.5194/egusphere-2026-3384, 2026
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We present long-term future projections of the Greenland ice sheet based on three numerical models which all explicitly account for feedbacks between the climate and the Greenland ice sheet. We find that projections vary considerably across the models, particularly beyond 2100. The main reasons for this is the different modelled climate as well as how the modelled climate is translated into snowfall and melt in each of the models.
Gerrit Lohmann
EGUsphere, https://doi.org/10.5194/egusphere-2026-3085, https://doi.org/10.5194/egusphere-2026-3085, 2026
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Climate models often simplify Earth’s atmosphere and oceans to make complex calculations possible. This study examines how such simplifications can unintentionally change the mathematical structures that determine large-scale climate variability and wave behavior. Using examples from global temperature balance and ocean–atmosphere waves, the paper shows that some common approximations may alter the set of physically allowed patterns of variability rather than simply simplifying them.
Alessandro Gagliardi, Norel Rimbu, Gerrit Lohmann, and Monica Ionita
Clim. Past, 22, 935–955, https://doi.org/10.5194/cp-22-935-2026, https://doi.org/10.5194/cp-22-935-2026, 2026
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This study shows that stable oxygen isotope ratios from Greenland ice cores can help identify extreme winter events in Europe. In years with a lack of the heavier oxygen isotope, we found changes in the atmospheric circulation over Europe. These changes bring warmer, wetter conditions to the Norwegian coast and colder, drier conditions to southern Europe. The pattern appears in both recent and past periods, staying stable over the last 400 years.
Yufei Liu, Hu Yang, Haowen Dang, Gerrit Lohmann, Tao Lian, Zhengyao Lu, Xiaoxu Shi, Jiping Liu, Hang Wang, Feng Jiang, Xinyue Deng, Xiaoming Hu, and Dake Chen
EGUsphere, https://doi.org/10.21203/rs.3.rs-7865695/v1, https://doi.org/10.21203/rs.3.rs-7865695/v1, 2026
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Observations and reconstructions show that ENSO is influenced by astronomical precession in addition to anthropogenic warming. Using ~10,000-year simulations, we reconstruct a full tropical precession cycle and find that present ENSO activity is relatively strong within it. This results from asymmetric continental heating that alters the background climate and the threshold for ENSO development, linking astronomical forcing to tropical climate variability.
Lianne Sijbrandij, Uta Krebs-Kanzow, Paul Gierz, Gregor Knorr, Lu Niu, Shan Xu, and Gerrit Lohmann
EGUsphere, https://doi.org/10.22541/essoar.174861028.86292675/v2, https://doi.org/10.22541/essoar.174861028.86292675/v2, 2026
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Towards the end of the last ice age large proglacial lakes formed at the margins of the retreating ice sheets, staying cold due to the influence of melting ice. Modeling shows these lakes lowered summer air temperatures, increased snowfall, and in total reduced surface melt by 18–27 % for nearby ice sheets. If lakes stayed below 4 °C, melt dropped by 23–35 %, providing a substantial negative feedback for retreating of ice sheets.
Ruijian Gou, Yaocheng Deng, Yingzhe Cui, Qi Shu, Hong Wang, Shengpeng Wang, Lixin Wu, and Gerrit Lohmann
EGUsphere, https://doi.org/10.5194/egusphere-2025-5296, https://doi.org/10.5194/egusphere-2025-5296, 2025
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Under anthropogenic warming, Arctic warming is nearly four times faster than global average. One key reason is the ice-albedo feedback – sea ice melting reveals the darker ocean water, which absorbs more solar radiation. Using a climate model of more refined grids, we find that the ocean absorbs more solar radiation. We attribute it to the better represented short-term extreme ocean warming events. They cause more short-term sea ice melting, allowing the ocean to absorb more solar radiation.
Fernanda DI Alzira Oliveira Matos, Dmitry Sidorenko, Xiaoxu Shi, Lars Ackermann, Janini Pereira, Gerrit Lohmann, and Christian Stepanek
Ocean Sci., 21, 2895–2914, https://doi.org/10.5194/os-21-2895-2025, https://doi.org/10.5194/os-21-2895-2025, 2025
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The Atlantic Meridional Overturning Circulation (AMOC) is responsible for about 25 % of the poleward ocean heat transport. Currently, the AMOC strength is mostly calculated in depth space (z-AMOC). However, we argue that, in warmer climates, the AMOC should be calculated in density space (ρ-AMOC). We performed simulations with CO2 forcing of 280 ppmv (PI) and 1120 ppmv of (4xCO2) and find that ρ-AMOC provides more physical and meaningful information about the AMOC in warmer climates.
Hu Yang, Xiaoxu Shi, Xulong Wang, Qingsong Liu, Yi Zhong, Xiaodong Liu, Youbin Sun, Yanjun Cai, Fei Liu, Gerrit Lohmann, Martin Werner, Zhimin Jian, Tainã M. L. Pinho, Hai Cheng, Lijuan Lu, Jiping Liu, Chao-Yuan Yang, Qinghua Yang, Yongyun Hu, Xing Cheng, Jingyu Zhang, and Dake Chen
Clim. Past, 21, 1263–1279, https://doi.org/10.5194/cp-21-1263-2025, https://doi.org/10.5194/cp-21-1263-2025, 2025
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For 1 century, the hemispheric summer insolation is proposed as a key pacemaker of astronomical climate change. However, an increasing number of geologic records reveal that the low-latitude hydrological cycle shows asynchronous precessional evolutions that are very often out of phase with the summer insolation. Here, we propose that the astronomically driven low-latitude hydrological cycle is not paced by summer insolation but by shifting perihelion.
Lutz Schirrmeister, Margret C. Fuchs, Thomas Opel, Andrei Andreev, Frank Kienast, Andrea Schneider, Larisa Nazarova, Larisa Frolova, Svetlana Kuzmina, Tatiana Kuznetsova, Vladimir Tumskoy, Heidrun Matthes, Gerrit Lohmann, Guido Grosse, Viktor Kunitsky, Hanno Meyer, Heike H. Zimmermann, Ulrike Herzschuh, Thomas Böhmer, Stuart Umbo, Sevi Modestou, Sebastian F. M. Breitenbach, Anfisa Pismeniuk, Georg Schwamborn, Stephanie Kusch, and Sebastian Wetterich
Clim. Past, 21, 1143–1184, https://doi.org/10.5194/cp-21-1143-2025, https://doi.org/10.5194/cp-21-1143-2025, 2025
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Geochronological, cryolithological, paleoecological, and modeling data reconstruct the Last Interglacial (LIG) climate around the New Siberian Islands and reveal significantly warmer conditions compared to today. The critical challenges in predicting future ecosystem responses lie in the fact that the land–ocean distribution during the LIG was markedly different from today, affecting the degree of continentality, which played a major role in modulating climate and ecosystem dynamics.
Xiaoyu Wang, Longjiang Mu, and Xianyao Chen
Ocean Sci., 21, 577–586, https://doi.org/10.5194/os-21-577-2025, https://doi.org/10.5194/os-21-577-2025, 2025
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The East Siberian Sea has nearly 80 % of the subsea permafrost worldwide. The cold layer with a temperature around −1.5 ºC above the seafloor prevents heat transporting from above to melt permafrost and release methane from sediments. However, we observed a warming trend at the seafloor caused by wave-induced vertical mixing in the shelf. The intensified mixing can transport enormous heat downward, leading to warming of more than 3 °C at the bottom, putting the subsea permafrost at high risk.
Wee Wei Khoo, Juliane Müller, Oliver Esper, Wenshen Xiao, Christian Stepanek, Paul Gierz, Gerrit Lohmann, Walter Geibert, Jens Hefter, and Gesine Mollenhauer
Clim. Past, 21, 299–326, https://doi.org/10.5194/cp-21-299-2025, https://doi.org/10.5194/cp-21-299-2025, 2025
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Using a multiproxy approach, we analyzed biomarkers and diatom assemblages from a marine sediment core from the Powell Basin, Weddell Sea. The results reveal the first continuous coastal Antarctic sea ice record since the Last Penultimate Glacial. Our findings contribute valuable insights into past glacial–interglacial sea ice responses to a changing climate and enhance our understanding of ocean–sea ice–ice shelf interactions and dynamics.
Lars Ackermann, Thomas Rackow, Kai Himstedt, Paul Gierz, Gregor Knorr, and Gerrit Lohmann
Geosci. Model Dev., 17, 3279–3301, https://doi.org/10.5194/gmd-17-3279-2024, https://doi.org/10.5194/gmd-17-3279-2024, 2024
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We present long-term simulations with interactive icebergs in the Southern Ocean. By melting, icebergs reduce the temperature and salinity of the surrounding ocean. In our simulations, we find that this cooling effect of iceberg melting is not limited to the surface ocean but also reaches the deep ocean and propagates northward into all ocean basins. Additionally, the formation of deep-water masses in the Southern Ocean is enhanced.
Viorica Nagavciuc, Simon L. L. Michel, Daniel F. Balting, Gerhard Helle, Mandy Freund, Gerhard H. Schleser, David N. Steger, Gerrit Lohmann, and Monica Ionita
Clim. Past, 20, 573–595, https://doi.org/10.5194/cp-20-573-2024, https://doi.org/10.5194/cp-20-573-2024, 2024
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The main aim of this paper is to present the summer vapor pressure deficit (VPD) reconstruction dataset for the last 400 years over Europe based on δ18O records by using a random forest approach. We provide both a spatial and a temporal long-term perspective on the past summer VPD and new insights into the relationship between summer VPD and large-scale atmospheric circulation. This is the first gridded reconstruction of the European summer VPD over the past 400 years.
Uta Krebs-Kanzow, Christian B. Rodehacke, and Gerrit Lohmann
The Cryosphere, 17, 5131–5136, https://doi.org/10.5194/tc-17-5131-2023, https://doi.org/10.5194/tc-17-5131-2023, 2023
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We compare components of the surface energy balance from two datasets, ERA5 and ERA-Interim, which can be used to estimate the surface mass balance (SMB) on the Greenland Ice Sheet (GrIS). ERA5 differs significantly from ERA-Interim, especially in the melt regions with lower temperatures and stronger shortwave radiation. Consequently, methods that previously estimated the GrIS SMB from ERA-Interim need to be carefully recalibrated before conversion to ERA5 forcing.
Xiaoxu Shi, Martin Werner, Hu Yang, Roberta D'Agostino, Jiping Liu, Chaoyuan Yang, and Gerrit Lohmann
Clim. Past, 19, 2157–2175, https://doi.org/10.5194/cp-19-2157-2023, https://doi.org/10.5194/cp-19-2157-2023, 2023
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The Last Glacial Maximum (LGM) marks the most recent extremely cold and dry time period of our planet. Using AWI-ESM, we quantify the relative importance of Earth's orbit, greenhouse gases (GHG) and ice sheets (IS) in determining the LGM climate. Our results suggest that both GHG and IS play important roles in shaping the LGM temperature. Continental ice sheets exert a major control on precipitation, atmospheric dynamics, and the intensity of El Niño–Southern Oscillation.
Xin Ren, Daniel J. Lunt, Erica Hendy, Anna von der Heydt, Ayako Abe-Ouchi, Bette Otto-Bliesner, Charles J. R. Williams, Christian Stepanek, Chuncheng Guo, Deepak Chandan, Gerrit Lohmann, Julia C. Tindall, Linda E. Sohl, Mark A. Chandler, Masa Kageyama, Michiel L. J. Baatsen, Ning Tan, Qiong Zhang, Ran Feng, Stephen Hunter, Wing-Le Chan, W. Richard Peltier, Xiangyu Li, Youichi Kamae, Zhongshi Zhang, and Alan M. Haywood
Clim. Past, 19, 2053–2077, https://doi.org/10.5194/cp-19-2053-2023, https://doi.org/10.5194/cp-19-2053-2023, 2023
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We investigate the Maritime Continent climate in the mid-Piacenzian warm period and find it is warmer and wetter and the sea surface salinity is lower compared with preindustrial period. Besides, the fresh and warm water transfer through the Maritime Continent was stronger. In order to avoid undue influence from closely related models in the multimodel results, we introduce a new metric, the multi-cluster mean, which could reveal spatial signals that are not captured by the multimodel mean.
Ryan Love, Lev Tarasov, Heather Andres, Alan Condron, Xu Zhang, and Gerrit Lohmann
EGUsphere, https://doi.org/10.5194/egusphere-2023-2225, https://doi.org/10.5194/egusphere-2023-2225, 2023
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Freshwater injection into bands across the North Atlantic are a mainstay of climate modelling when investigating topics such as climate change or the role of glacial runoff in the glacial climate system. However, this approach is unrealistic and results in a systematic bias in the climate response to a given flux of freshwater. We evaluate the magnitude of this bias by comparison to two other approaches for introducing freshwater into a coupled climate model setup for glacial conditions.
Xiaoxu Shi, Alexandre Cauquoin, Gerrit Lohmann, Lukas Jonkers, Qiang Wang, Hu Yang, Yuchen Sun, and Martin Werner
Geosci. Model Dev., 16, 5153–5178, https://doi.org/10.5194/gmd-16-5153-2023, https://doi.org/10.5194/gmd-16-5153-2023, 2023
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We developed a new climate model with isotopic capabilities and simulated the pre-industrial and mid-Holocene periods. Despite certain regional model biases, the modeled isotope composition is in good agreement with observations and reconstructions. Based on our analyses, the observed isotope–temperature relationship in polar regions may have a summertime bias. Using daily model outputs, we developed a novel isotope-based approach to determine the onset date of the West African summer monsoon.
Di Cai, Gerrit Lohmann, Xianyao Chen, and Monica Ionita
EGUsphere, https://doi.org/10.5194/egusphere-2023-1646, https://doi.org/10.5194/egusphere-2023-1646, 2023
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Our study reveals how a decline in autumn sea ice in the Barents-Kara Seas leads to severe winters in Europe. Using observational data, we illustrate that Arctic sea ice loss isn't just a local issue – it impacts harsh winter conditions globally. Current climate models struggle to reflect these effects accurately, indicating a need for more research. Gaining a more nuanced understanding of this relationship will enhance our climate predictions and preparation for future extremes.
Pengyang Song, Dmitry Sidorenko, Patrick Scholz, Maik Thomas, and Gerrit Lohmann
Geosci. Model Dev., 16, 383–405, https://doi.org/10.5194/gmd-16-383-2023, https://doi.org/10.5194/gmd-16-383-2023, 2023
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Tides have essential effects on the ocean and climate. Most previous research applies parameterised tidal mixing to discuss their effects in models. By comparing the effect of a tidal mixing parameterisation and tidal forcing on the ocean state, we assess the advantages and disadvantages of the two methods. Our results show that tidal mixing in the North Pacific Ocean strongly affects the global thermohaline circulation. We also list some effects that are not considered in the parameterisation.
Julia E. Weiffenbach, Michiel L. J. Baatsen, Henk A. Dijkstra, Anna S. von der Heydt, Ayako Abe-Ouchi, Esther C. Brady, Wing-Le Chan, Deepak Chandan, Mark A. Chandler, Camille Contoux, Ran Feng, Chuncheng Guo, Zixuan Han, Alan M. Haywood, Qiang Li, Xiangyu Li, Gerrit Lohmann, Daniel J. Lunt, Kerim H. Nisancioglu, Bette L. Otto-Bliesner, W. Richard Peltier, Gilles Ramstein, Linda E. Sohl, Christian Stepanek, Ning Tan, Julia C. Tindall, Charles J. R. Williams, Qiong Zhang, and Zhongshi Zhang
Clim. Past, 19, 61–85, https://doi.org/10.5194/cp-19-61-2023, https://doi.org/10.5194/cp-19-61-2023, 2023
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We study the behavior of the Atlantic Meridional Overturning Circulation (AMOC) in the mid-Pliocene. The mid-Pliocene was about 3 million years ago and had a similar CO2 concentration to today. We show that the stronger AMOC during this period relates to changes in geography and that this has a significant influence on ocean temperatures and heat transported northwards by the Atlantic Ocean. Understanding the behavior of the mid-Pliocene AMOC can help us to learn more about our future climate.
Hao Huang, Pengyang Song, Shi Qiu, Jiaqi Guo, and Xueen Chen
Geosci. Model Dev., 16, 109–133, https://doi.org/10.5194/gmd-16-109-2023, https://doi.org/10.5194/gmd-16-109-2023, 2023
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The Oceanic Regional Circulation and Tide Model (ORCTM) is developed to reproduce internal solitary wave dynamics. The three-dimensional nonlinear momentum equations are involved with the nonhydrostatic pressure obtained via solving the Poisson equation. The validation experimental results agree with the internal wave theories and observations, demonstrating that the ORCTM can successfully describe the life cycle of nonlinear internal solitary waves under different oceanic environments.
Jan Streffing, Dmitry Sidorenko, Tido Semmler, Lorenzo Zampieri, Patrick Scholz, Miguel Andrés-Martínez, Nikolay Koldunov, Thomas Rackow, Joakim Kjellsson, Helge Goessling, Marylou Athanase, Qiang Wang, Jan Hegewald, Dmitry V. Sein, Longjiang Mu, Uwe Fladrich, Dirk Barbi, Paul Gierz, Sergey Danilov, Stephan Juricke, Gerrit Lohmann, and Thomas Jung
Geosci. Model Dev., 15, 6399–6427, https://doi.org/10.5194/gmd-15-6399-2022, https://doi.org/10.5194/gmd-15-6399-2022, 2022
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We developed a new atmosphere–ocean coupled climate model, AWI-CM3. Our model is significantly more computationally efficient than its predecessors AWI-CM1 and AWI-CM2. We show that the model, although cheaper to run, provides results of similar quality when modeling the historic period from 1850 to 2014. We identify the remaining weaknesses to outline future work. Finally we preview an improved simulation where the reduction in computational cost has to be invested in higher model resolution.
Xiaoxu Shi, Martin Werner, Carolin Krug, Chris M. Brierley, Anni Zhao, Endurance Igbinosa, Pascale Braconnot, Esther Brady, Jian Cao, Roberta D'Agostino, Johann Jungclaus, Xingxing Liu, Bette Otto-Bliesner, Dmitry Sidorenko, Robert Tomas, Evgeny M. Volodin, Hu Yang, Qiong Zhang, Weipeng Zheng, and Gerrit Lohmann
Clim. Past, 18, 1047–1070, https://doi.org/10.5194/cp-18-1047-2022, https://doi.org/10.5194/cp-18-1047-2022, 2022
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Since the orbital parameters of the past are different from today, applying the modern calendar to the past climate can lead to an artificial bias in seasonal cycles. With the use of multiple model outputs, we found that such a bias is non-ignorable and should be corrected to ensure an accurate comparison between modeled results and observational records, as well as between simulated past and modern climates, especially for the Last Interglacial.
Ryan A. Green, Laurie Menviel, Katrin J. Meissner, Xavier Crosta, Deepak Chandan, Gerrit Lohmann, W. Richard Peltier, Xiaoxu Shi, and Jiang Zhu
Clim. Past, 18, 845–862, https://doi.org/10.5194/cp-18-845-2022, https://doi.org/10.5194/cp-18-845-2022, 2022
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Climate models are used to predict future climate changes and as such, it is important to assess their performance in simulating past climate changes. We analyze seasonal sea-ice cover over the Southern Ocean simulated from numerical PMIP3, PMIP4 and LOVECLIM simulations during the Last Glacial Maximum (LGM). Comparing these simulations to proxy data, we provide improved estimates of LGM seasonal sea-ice cover. Our estimate of summer sea-ice extent is 20 %–30 % larger than previous estimates.
Sebastian Hinck, Evan J. Gowan, Xu Zhang, and Gerrit Lohmann
The Cryosphere, 16, 941–965, https://doi.org/10.5194/tc-16-941-2022, https://doi.org/10.5194/tc-16-941-2022, 2022
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Proglacial lakes were pervasive along the retreating continental ice margins after the Last Glacial Maximum. Similarly to the marine ice boundary, interactions at the ice-lake interface impact ice sheet dynamics and mass balance. Previous numerical ice sheet modeling studies did not include a dynamical lake boundary. We describe the implementation of an adaptive lake boundary condition in PISM and apply the model to the glacial retreat of the Laurentide Ice Sheet.
Justus Contzen, Thorsten Dickhaus, and Gerrit Lohmann
Geosci. Model Dev., 15, 1803–1820, https://doi.org/10.5194/gmd-15-1803-2022, https://doi.org/10.5194/gmd-15-1803-2022, 2022
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Climate models are of paramount importance to predict future climate changes. Since many severe consequences of climate change are due to extreme events, the accurate behaviour of models in terms of extremes needs to be validated thoroughly. We present a method for model validation in terms of climate extremes and an algorithm to detect regions in which extremes tend to occur at the same time. These methods are applied to data from different climate models and to observational data.
Daniel Balting, Simon Michel, Viorica Nagavciuc, Gerhard Helle, Mandy Freund, Gerhard H. Schleser, David Steger, Gerrit Lohmann, and Monica Ionita
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2022-47, https://doi.org/10.5194/essd-2022-47, 2022
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Vapor pressure deficit is a key component of vegetation dynamics, soil science, meteorology, and soil science. In this study, we reconstruct the variability of the vapor pressure deficit in the past and examine the changes in future scenarios using climate models. In this way, past, present and future changes of the vapor pressure deficit can be detected locally, regionally, and continentally with higher statistical significance.
Stephan Krätschmer, Michèlle van der Does, Frank Lamy, Gerrit Lohmann, Christoph Völker, and Martin Werner
Clim. Past, 18, 67–87, https://doi.org/10.5194/cp-18-67-2022, https://doi.org/10.5194/cp-18-67-2022, 2022
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We use an atmospheric model coupled to an aerosol model to investigate the global mineral dust cycle with a focus on the Southern Hemisphere for warmer and colder climate states and compare our results to observational data. Our findings suggest that Australia is the predominant source of dust deposited over Antarctica during the last glacial maximum. In addition, we find that the southward transport of dust from all sources to Antarctica happens at lower altitudes in colder climates.
Martin Wegmann, Yvan Orsolini, Antje Weisheimer, Bart van den Hurk, and Gerrit Lohmann
Weather Clim. Dynam., 2, 1245–1261, https://doi.org/10.5194/wcd-2-1245-2021, https://doi.org/10.5194/wcd-2-1245-2021, 2021
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Northern Hemisphere winter weather is influenced by the strength of westerly winds 30 km above the surface, the so-called polar vortex. Eurasian autumn snow cover is thought to modulate the polar vortex. So far, however, the modeled influence of snow on the polar vortex did not fit the observed influence. By analyzing a model experiment for the time span of 110 years, we could show that the causality of this impact is indeed sound and snow cover can weaken the polar vortex.
Kim H. Stadelmaier, Patrick Ludwig, Pascal Bertran, Pierre Antoine, Xiaoxu Shi, Gerrit Lohmann, and Joaquim G. Pinto
Clim. Past, 17, 2559–2576, https://doi.org/10.5194/cp-17-2559-2021, https://doi.org/10.5194/cp-17-2559-2021, 2021
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We use regional climate simulations for the Last Glacial Maximum to reconstruct permafrost and to identify areas of thermal contraction cracking of the ground in western Europe. We find ground cracking, a precondition for the development of permafrost proxies, south of the probable permafrost border, implying that permafrost was not the limiting factor for proxy development. A good agreement with permafrost and climate proxy data is achieved when easterly winds are modelled more frequently.
Zixuan Han, Qiong Zhang, Qiang Li, Ran Feng, Alan M. Haywood, Julia C. Tindall, Stephen J. Hunter, Bette L. Otto-Bliesner, Esther C. Brady, Nan Rosenbloom, Zhongshi Zhang, Xiangyu Li, Chuncheng Guo, Kerim H. Nisancioglu, Christian Stepanek, Gerrit Lohmann, Linda E. Sohl, Mark A. Chandler, Ning Tan, Gilles Ramstein, Michiel L. J. Baatsen, Anna S. von der Heydt, Deepak Chandan, W. Richard Peltier, Charles J. R. Williams, Daniel J. Lunt, Jianbo Cheng, Qin Wen, and Natalie J. Burls
Clim. Past, 17, 2537–2558, https://doi.org/10.5194/cp-17-2537-2021, https://doi.org/10.5194/cp-17-2537-2021, 2021
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Understanding the potential processes responsible for large-scale hydrological cycle changes in a warmer climate is of great importance. Our study implies that an imbalance in interhemispheric atmospheric energy during the mid-Pliocene could have led to changes in the dynamic effect, offsetting the thermodynamic effect and, hence, altering mid-Pliocene hydroclimate cycling. Moreover, a robust westward shift in the Pacific Walker circulation can moisten the northern Indian Ocean.
Arthur M. Oldeman, Michiel L. J. Baatsen, Anna S. von der Heydt, Henk A. Dijkstra, Julia C. Tindall, Ayako Abe-Ouchi, Alice R. Booth, Esther C. Brady, Wing-Le Chan, Deepak Chandan, Mark A. Chandler, Camille Contoux, Ran Feng, Chuncheng Guo, Alan M. Haywood, Stephen J. Hunter, Youichi Kamae, Qiang Li, Xiangyu Li, Gerrit Lohmann, Daniel J. Lunt, Kerim H. Nisancioglu, Bette L. Otto-Bliesner, W. Richard Peltier, Gabriel M. Pontes, Gilles Ramstein, Linda E. Sohl, Christian Stepanek, Ning Tan, Qiong Zhang, Zhongshi Zhang, Ilana Wainer, and Charles J. R. Williams
Clim. Past, 17, 2427–2450, https://doi.org/10.5194/cp-17-2427-2021, https://doi.org/10.5194/cp-17-2427-2021, 2021
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In this work, we have studied the behaviour of El Niño events in the mid-Pliocene, a period of around 3 million years ago, using a collection of 17 climate models. It is an interesting period to study, as it saw similar atmospheric carbon dioxide levels to the present day. We find that the El Niño events were less strong in the mid-Pliocene simulations, when compared to pre-industrial climate. Our results could help to interpret El Niño behaviour in future climate projections.
Nele Lamping, Juliane Müller, Jens Hefter, Gesine Mollenhauer, Christian Haas, Xiaoxu Shi, Maria-Elena Vorrath, Gerrit Lohmann, and Claus-Dieter Hillenbrand
Clim. Past, 17, 2305–2326, https://doi.org/10.5194/cp-17-2305-2021, https://doi.org/10.5194/cp-17-2305-2021, 2021
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We analysed biomarker concentrations on surface sediment samples from the Antarctic continental margin. Highly branched isoprenoids and GDGTs are used for reconstructing recent sea-ice distribution patterns and ocean temperatures respectively. We compared our biomarker-based results with data obtained from satellite observations and estimated from a numerical model and find reasonable agreements. Further, we address caveats and provide recommendations for future investigations.
Saeid Bagheri Dastgerdi, Melanie Behrens, Jean-Louis Bonne, Maria Hörhold, Gerrit Lohmann, Elisabeth Schlosser, and Martin Werner
The Cryosphere, 15, 4745–4767, https://doi.org/10.5194/tc-15-4745-2021, https://doi.org/10.5194/tc-15-4745-2021, 2021
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In this study, for the first time, water vapour isotope measurements in Antarctica for all seasons of a year are performed. Local temperature is identified as the main driver of δ18O and δD variability. A similar slope of the temperature–δ18O relationship in vapour and surface snow points to the water vapour isotope content as a potential key driver. This dataset can be used as a new dataset to evaluate the capability of isotope-enhanced climate models.
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Short summary
Our study examines the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial Maximum (LGM), a period with higher tidal dissipation. Despite increased tidal mixing, our model simulations show that the AMOC remained relatively shallow, consistent with paleoproxy data and resolving previous inconsistencies between proxy data and model simulations. This research highlights the importance of strong ocean stratification during the LGM and its interaction with tidal mixing.
Our study examines the Atlantic Meridional Overturning Circulation (AMOC) during the...
