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4. Modelling the snowball Earth: from its inception to its aftermath

Author

Ramstein, G., Le Hir, G., Donnadieu, Y., Godderis, Y., Laboratoire des Sciences du Climat et de l'Environnement (LSCE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
9622 INFORMATION RELATED TO GEOLOGIC TIME / Proterozoic, [SDU]Sciences of the Universe [physics]
Abstract

International audience; The relationship between CO2 variation and Neoproterozoic glaciation has deeply evolved these last years. Through the use of an innovative climate-carbon coupled model, the causes of the CO2 decrease that led to the onset of the global glaciation (Sturtian) has been shown to be strongly related to the dislocation of the Rodinia super continent, promoting CO2 consumption through silicate weathering1. Another important issue is the evolution of atmospheric CO2 during the Snowball episode itself. It appears not to be just a linear accumulation with time through the ongoing solid Earth degassing. Indeed, efficient CO2 diffusion in seawater might have promoted the oceanic crust dissolution, resulting in an asymptotic CO2 rise in the atmosphere2,3, stressing the question of the snowball melting threshold. Indeed, it has been shown that greenhouse climate induced by the storage of the CO2 in the atmosphere invoked to escape a snowball Earth was possibly not sufficient to melt the snowball Earth due to thermal inversion in vertical column4. Therefore, CO2 is may be not the only trigger for the deglaciation. Finally, the super greenhouse climate thought to have followed the snowball episode was explored. We demonstrate that, despite very high temperatures under 0.2 bars of CO2, the amount of rainfall might have been limited by the availability of latent heat which cannot be higher that the total energy provided by the sun. As a consequence of limited increase in the water cycling, CO2 consumption by continental weathering might not exceed 10 times its present day value. The return to normal climatic conditions after the snowball melting should thus have lasted several million of years, further increasing the biological perturbations linked to a snowball event5. The aim of this contribution is to revisit the issue of the role of atmospheric CO2 before, during and after a Snowball Earth and to deliver a new picture of its feedbacks with climate. 1. Donnadieu, Y., Y. Godderis, et al. (2004). "A 'snowball Earth' climate triggered by continental break-up through changes in runoff." Nature 428(6980): 303- 306. 2. Ramstein G., Donnadieu Y., Goddéris Y. Proterozoic glaciations. Comptes Rendus Geoscience 336 (7-8): 639-646 Jun 2004 3. Le Hir G., Goddéris Y., Donnadieu Y., Ramstein G. (2008). A geochemical modelling study of the evolution of the chemical composition of seawater linked to a "snowball" glaciation. Biogeosci. 5, 253-267. 4. Le Hir Guillaume , Goddéris Yves, Donnadieu Yannick , Ramstein Gilles (2008) A scenario for the evolution of the atmopsheric pCO2 during a Snowball Earth, Geology, 36 (1): 47-50 5. Pierrehumbert, R.T. (2004). High levels of atmospheric carbon dioxide necessary for the termination of global glaciation: Nature, v. 429, p. 646-649, doi: 10.1038/nature02640. 6. Le Hir Guillaume, Donnadieu Yannick, Goddéris Y, Pierrehumbert Raymond T., Halverson Galen P., Macouin Mélina, Nédélec Anne b, Ramstein Gilles. (2008).The snowball Earth aftermath: Exploring the limits of continental weathering processes, Earth and Planetary Science Letters, EPSL-09573; No of Pages 11.

Published
2023

5. Transient simulations of the Mid-Holocene with MGV, the IPSL fast ocean-atmosphere-vegetation general circulation model

Author

Gential, L., Ringeval, B., Sepulchre, P., Krinner, G., Ramstein, G., Friedlingstein, P., Laboratoire des Sciences du Climat et de l'Environnement (LSCE), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
[SDU]Sciences of the Universe [physics]
Abstract

International audience; A fast OAVGCM called MGV has been developed at IPSL to handle multi-millennial climate simulations. It couples the ocean and sea-ice OPA-LIM model to the atmosphere-vegetation LMDZ-ORCHIDEE model. The more affordable computing cost compared to the version of the IPSL Climate Model used for the IPCC has been obtained by decreasing the resolution of the atmosphere and vegetation components down to a mesh of 44 per 43 grid points in the horizontal. In ORCHIDEE, the carbon cycle is activated (STOMATE) as well as the dynamic vegetation (based on LPJ). On the other hand, the ocean carbon cycle and atmospheric chemistry are not taken into account yet due to their prohibitive additional computing costs. Two transient runs of the middle Holocene are carried out with the newly designed model. In one of them, the dynamic vegetation is not activated to assess this biospheric feedback on climate. The transient response of the climate system to solar forcings and gas concentrations is analysed with emphasize on changes in vegetation cover (such as the greening of the Sahara) and carbon fluxes. Lake extend (such as Lake Chad) and emissions of methane by wetlands are diagnosed using offline simulations with a refined version of ORCHIDEE recently developed at LSCE.

Published
2023

6. Heinrich event 1: an example of dynamical ice-sheet reaction to oceanic changes

Author

Álvarez Solas, Jorge, Montoya, M., Ritz, C., Ramstein, G., Charbit, S., Dumas, C., Nisancioglu, K., Dokken, T., Ganopolski, A., Álvarez Solas, Jorge, Montoya, M., Ritz, C., Ramstein, G., Charbit, S., Dumas, C., Nisancioglu, K., Dokken, T., and Ganopolski, A.

Abstract

We thank Y. Donnadieu, D. Paillard, D. Roche, F. Remy, F. Pattyn, A. Robinson and E. Lucio for helpful discussions, and two anonymous referees and the editor Andre Paul who helped to improve the manuscript. Figure 5 of this article is based on a similar figure suggested by referee #2. We are also greatful to the PalMA group for useful comments and suggestions. This work was funded under the MOVAC and SPECT-MORE projects. J. A-S was also funded by the Spanish programme of the International Campus of Excellence (CEI)., Heinrich events, identified as enhanced ice-rafted detritus (IRD) in North Atlantic deep sea sediments (Heinrich, 1988; Hemming, 2004) have classically been attributed to Laurentide ice-sheet (LIS) instabilities (MacAyeal, 1993; Calov et al., 2002; Hulbe et al., 2004) and assumed to lead to important disruptions of the Atlantic meridional overturning circulation (AMOC) and North Atlantic deep water (NADW) formation. However, recent paleoclimate data have revealed that most of these events probably occurred after the AMOC had already slowed down or/and NADW largely collapsed, within about a thousand years (Hall et al., 2006; Hemming, 2004; Jonkers et al., 2010; Roche et al., 2004), implying that the initial AMOC reduction could not have been caused by the Heinrich events themselves. Here we propose an alternative driving mechanism, specifically for Heinrich event 1 (H1; 18 to 15 ka BP), by which North Atlantic ocean circulation changes are found to have strong impacts on LIS dynamics. By combining simulations with a coupled climate model and a three-dimensional ice sheet model, our study illustrates how reduced NADW and AMOC weakening lead to a subsurface warming in the Nordic and Labrador Seas resulting in rapid melting of the Hudson Strait and Labrador ice shelves. Lack of buttressing by the ice shelves implies a substantial ice-stream acceleration, enhanced ice-discharge and sea level rise, with peak values 500-1500 yr after the initial AMOC reduction. Our scenario modifies the previous paradigm of H1 by solving the paradox of its occurrence during a cold surface period, and highlights the importance of taking into account the effects of oceanic circulation on ice-sheets dynamics in order to elucidate the triggering mechanism of Heinrich events., MOVAC, SPECT-MORE, Spanish programme of the International Campus of Excellence (CEI), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

Published
2023

7. Influence of global mean sea-level rise on atmospheric and oceanic circulations

Author

Zhang, Z., Jansen, E., Sobolowski, S., Otterå, O., Ramstein, G., Guo, C., Nummelin, A., Bentsen, M., Dong, C., Wang, X., Wang, H., and Guo, Z.

Abstract

Over recent decades, the rate of global mean sea-level (GMSL) rise has increased, though the magnitude of current and projected GMSL change by the end of this century – tens of centimeters – remains small from a geological perspective. Such modest GMSL rise presents challenges when attempting to assess its global climate impacts, as the signal is weak. However, in previous warmer geological periods, GMSL was several or tens of meters higher than the present. These paleoclimate periods offer a unique opportunity to investigate the climate effects of high GMSL. Here, using climate simulations of the Last Interglacial period and a set of present-day sea-level sensitivity experiments, we highlight the importance of GMSL rise in modulating global climate. Lifting a sea-level datum – lowering terrestrial elevation and deepening oceanic bathymetry – reorganizes atmospheric and oceanic circulations. Our simulations of the Last Interglacial show that considering this aspect of GMSL rise, in isolation from changes associated with land-sea masks or freshwater input, reduces the long-lasting model-data mismatch in the Southern Hemisphere. Furthermore, the present-day sensitivity experiments demonstrate that a slight GMSL uplift causes significant adjustments in the global climate, particularly at mid-high latitudes.&nbsp

Published
2023

9. Biogeochemical Cycles and Aerosols Over the Last Million Years

Author

Ramstein, G, Landais, A, Bouttes, N, Sepulchre, P, Govin, A, Bopp, L, Albani, S, Vadsaria, T, Capron, E, Bouttes N., Bopp L., Albani S., Ramstein G., Vadsaria T., Capron E., Ramstein, G, Landais, A, Bouttes, N, Sepulchre, P, Govin, A, Bopp, L, Albani, S, Vadsaria, T, Capron, E, Bouttes N., Bopp L., Albani S., Ramstein G., Vadsaria T., and Capron E.

Abstract

The biogeochemical cycles encompass the exchange of chemical elements between reservoirs such as the atmosphere, ocean, land and lithosphere. Those exchanges involve biological, geological and chemical processes, hence the term “biogeochemical cycles”.

Published
2021

10. Modeling the climate of the Last Glacial Maximum from PMIP1 to PMIP4

Author

Kageyama, Masa, Abe-Ouchi, A., Obase, T., Ramstein, G., Valdes, P.J., Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics (MERMAID), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Modélisation du climat (CLIM), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2021

11. Mid-Pliocene West African Monsoon rainfall as simulated in the PlioMIP2 ensemble

Author

Berntell, E, Zhang, Q, Li, Q, Haywood, AM, Tindall, JC, Hunter, SJ, Zhang, Z, Li, X, Guo, C, Nisancioglu, KH, Stepanek, C, Lohmann, G, Sohl, LE, Chandler, MA, Tan, N, Contoux, C, Ramstein, G, Baatsen, MLJ, von der Heydt, AS, Chandan, D, Peltier, WR, Abe-Ouchi, A, Chan, W-L, Kamae, Y, Williams, CJR, Lunt, DJ, Feng, R, Otto-Bliesner, BL, Brady, EC, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Sub Dynamics Meteorology, Sub Physical Oceanography, Marine and Atmospheric Research, and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, Stratigraphy, Palaeontology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

The mid-Pliocene warm period (mPWP; ∼3.2 million years ago) is seen as the most recent time period characterized by a warm climate state, with similar to modern geography and ∼400 ppmv atmospheric CO2 concentration, and is therefore often considered an interesting analogue for near-future climate projections. Paleoenvironmental reconstructions indicate higher surface temperatures, decreasing tropical deserts, and a more humid climate in West Africa characterized by a strengthened West African Monsoon (WAM). Using model results from the second phase of the Pliocene Modelling Intercomparison Project (PlioMIP2) ensemble, we analyse changes of the WAM rainfall during the mPWP by comparing them with the control simulations for the pre-industrial period. The ensemble shows a robust increase in the summer rainfall over West Africa and the Sahara region, with an average increase of 2.5 mm/d, contrasted by a rainfall decrease over the equatorial Atlantic. An anomalous warming of the Sahara and deepening of the Saharan Heat Low, seen in >90 % of the models, leads to a strengthening of the WAM and an increased monsoonal flow into the continent. A similar warming of the Sahara is seen in future projections using both phase 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5). Though previous studies of future projections indicate a west–east drying–wetting contrast over the Sahel, PlioMIP2 simulations indicate a uniform rainfall increase in that region in warm climates characterized by increasing greenhouse gas forcing. We note that this effect will further depend on the long-term response of the vegetation to the CO2 forcing.

Published
2021

14. Evaluating the large-scale hydrological cycle response within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble

Author

Han, Z, Zhang, Q, Li, Q, Feng, R, Haywood, AM, Tindall, JC, Hunter, SJ, Otto-Bliesner, BL, Brady, EC, Rosenbloom, N, Zhang, Z, Li, X, Guo, C, Nisancioglu, KH, Stepanek, C, Lohmann, G, Sohl, LE, Chandler, MA, Tan, N, Ramstein, G, Baatsen, MLJ, von der Heydt, AS, Chandan, D, Peltier, WR, Williams, CJR, Lunt, DJ, Cheng, J, Wen, Q, Burls, NJ, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modélisation du climat (CLIM), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Sub Dynamics Meteorology, Sub Physical Oceanography, Marine and Atmospheric Research, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), This research has been supported by the Swedish Research Council (Vetenskapsrådet, grant nos. 2013- 06476 and 2017-04232). The article processing charges for this open-access publication were covered by Stockholm University, Zixuan Han acknowledges financial support from the National Natural Science Foundation of China (grant no. 42130610), the Fundamental Research Funds for the Central Universities (grant no. B210201009), and the National Key R&D Program of China (grant no. 2017YFC1502303). Jianbo Cheng acknowledges financial support from the National Natural Science Foundation of China (grant no. 42005012) and the Natural Science Foundation of Jiangsu Province (grant no. BK20201058). Qin Wen acknowledges financial support from the National Natural Science Foundation of China (grant no. 42106016) and a project funded by the China Postdoctoral Science Foundation (grant no. 2021M691623). The EC-Earth3 model simulations and the data analysis were performed using the ECMWF computing and archive facilities and the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputer Centre (NSC), which is partially funded by the Swedish Research Council through grant agreement no. 2018-05973. Charles J. R. Williams acknowledges financial support from the UK Natural Environment Research Council within the framework of the SWEET (Super-Warm Early Eocene Temperatures) project (grant no. NE/P01903X/1). Natalie J. Burls acknowledges support from the National Science Foundation (NSF, grant nos. AGS-1844380 and OCN-2002448) and the Alfred P. Sloan Foundation (as a research fellow). Ran Feng acknowledges sponsorship from the U.S. National Science Foundation (grant nos. 1903650 and 1814029). The contributions of Bette L. Otto-Bliesner, Esther C. Brady, and Nan Rosenbloom are based upon work supported by the National Center for Atmospheric Research, which is a major facility sponsored by the NSF under cooperative agreement no. 1852977. The CESM project is primarily supported by the National Science Foundation (NSF). Computing and data storage resources for the CESM and CCSM4 simulations, including the Cheyenne supercomputer (https://doi.org/10.5065/D6RX99HX), were provided by the Computational and Information Systems Laboratory (CISL) at NCAR. Xiangyu Li acknowledges financial support from the National Natural Science Foundation of China (NSFC, grant no. 42005042) and the China Scholarship Council (grant no. 201804910023). The NorESM simulations benefitted from resources provided by UNINETT Sigma2 – the national infrastructure for high-performance computing and data storage in Norway. The work by Anna S. von der Heydt and Michiel L. J. Baatsen was carried out in the framework of the Netherlands Earth System Science Centre (NESSC) program, which is financially supported by the Ministry of Education, Culture and Science (OCW grant no. 024.002.001). Simulations with CCSM4-Utrecht were performed at the SURFsara Dutch national computing facilities and were sponsored by NWO-EW (Netherlands Organisation for Scientific Research, Exact Sciences, and project nos. 17189 and 2020.022). Christian Stepanek and Gerrit Lohmann acknowledge computational resources from the Computing and Data Centre of the Alfred Wegener Institute, Helmholtz-Zentrum für Polar- und Meeresforschung. Christian Stepanek and Gerrit Lohmann also acknowledge funding from the Helmholtz Climate Initiative REKLIM and the Alfred Wegener Institute's 'Changing Earth-Sustaining our Future' research program. The PRISM4 reconstruction and boundary conditions used in PlioMIP2 were funded by the U.S. Geological Survey Climate and Land Use Change Research and Development Program. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government.

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, Stratigraphy, Palaeontology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

International audience; Abstract. The mid-Pliocene (∼3 Ma) is one of the most recent warm periods with high CO2 concentrations in the atmosphere and resulting high temperatures, and it is often cited as an analog for near-term future climate change. Here, we apply a moisture budget analysis to investigate the response of the large-scale hydrological cycle at low latitudes within a 13-model ensemble from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The results show that increased atmospheric moisture content within the mid-Pliocene ensemble (due to the thermodynamic effect) results in wetter conditions over the deep tropics, i.e., the Pacific intertropical convergence zone (ITCZ) and the Maritime Continent, and drier conditions over the subtropics. Note that the dynamic effect plays a more important role than the thermodynamic effect in regional precipitation minus evaporation (PmE) changes (i.e., northward ITCZ shift and wetter northern Indian Ocean). The thermodynamic effect is offset to some extent by a dynamic effect involving a northward shift of the Hadley circulation that dries the deep tropics and moistens the subtropics in the Northern Hemisphere (i.e., the subtropical Pacific). From the perspective of Earth's energy budget, the enhanced southward cross-equatorial atmospheric transport (0.22 PW), induced by the hemispheric asymmetries of the atmospheric energy, favors an approximately 1∘ northward shift of the ITCZ. The shift of the ITCZ reorganizes atmospheric circulation, favoring a northward shift of the Hadley circulation. In addition, the Walker circulation consistently shifts westward within PlioMIP2 models, leading to wetter conditions over the northern Indian Ocean. The PlioMIP2 ensemble highlights that an imbalance of 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.

Published
2021

15. Mid-Pliocene Atlantic Meridional Overturning Circulation simulated in PlioMIP2

Author

Zhang, Zhongshi, Li, X., Guo, Chuncheng, Ottera, O. H., Nisancioglu, Kerim H., Tan, N., Contoux, C., Ramstein, G., Feng, Ran, Otto-Bliesner, Bette L., Brady, Esther C., Chandan, Deepak, Peltier, W. R., von der Heydt, Anna S., Weiffenbach, Julia E., Stepanek, Christian, Lohmann, Gerrit, Zhang, Q., Li, Q., Chandler, M. A., Sohl, Linda E., Haywood, A. M., Hunter, S. J., Tindall, Julia C., Williams, C., Lunt, D. J., Chan, Wing-Le, Abe-Ouchi, A., Zhang, Zhongshi, Li, X., Guo, Chuncheng, Ottera, O. H., Nisancioglu, Kerim H., Tan, N., Contoux, C., Ramstein, G., Feng, Ran, Otto-Bliesner, Bette L., Brady, Esther C., Chandan, Deepak, Peltier, W. R., von der Heydt, Anna S., Weiffenbach, Julia E., Stepanek, Christian, Lohmann, Gerrit, Zhang, Q., Li, Q., Chandler, M. A., Sohl, Linda E., Haywood, A. M., Hunter, S. J., Tindall, Julia C., Williams, C., Lunt, D. J., Chan, Wing-Le, and Abe-Ouchi, A.

Abstract

In the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2), coupled climate models have been used to simulate an interglacial climate during the mid-Piacenzian warm period (mPWP; 3.264 to 3.025 Ma). Here, we compare the Atlantic Meridional Overturning Circulation (AMOC), poleward ocean heat transport and sea surface warming in the Atlantic simulated with these models. In PlioMIP2, all models simulate an intensified mid-Pliocene AMOC. However, there is no consistent response in the simulated Atlantic ocean heat transport nor in the depth of the Atlantic overturning cell. The models show a large spread in the simulated AMOC maximum, the Atlantic ocean heat transport and the surface warming in the North Atlantic. Although a few models simulate a surface warming of ∼ 8–12 ∘C in the North Atlantic, similar to the reconstruction from Pliocene Research, Interpretation and Synoptic Mapping (PRISM) version 4, most models appear to underestimate this warming. The large model spread and model–data discrepancies in the PlioMIP2 ensemble do not support the hypothesis that an intensification of the AMOC, together with an increase in northward ocean heat transport, is the dominant mechanism for the mid-Pliocene warm climate over the North Atlantic.

Published
2021

18. A return to large-scale features of Pliocene climate: the Pliocene Model Intercomparison Project Phase 2

Author

Haywood, AM, Tindall, JC, Dowsett, HJ, Dolan, AM, Foley, KM, Hunter, SJ, Hill, DJ, Chan, W-L, Abe-Ouchi, A, Stepanek, C, Lohmann, G, Chandan, D, Peltier, WR, Tan, N, Contoux, C, Ramstein, G, Li, X, Zhang, Z, Guo, C, Nisancioglu, KH, Zhang, Q, Li, Q, Kamae, Y, Chandler, MA, Sohl, LE, Otto-Bliesner, BL, Feng, R, Brady, EC, Von der Heydt, AS, Baatsen, MLJ, and Lunt, DJ

Abstract

The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ~ 400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolution and based on new reconstructions of boundary conditions (the Pliocene Model Intercomparison Project Phase 2; PlioMIP2). As a global annual average, modelled surface air temperatures increase by between 1.4 and 4.7 °C relative to pre-industrial with a multi-model mean value of 2.8 °C. Annual mean total precipitation rates increase by 6 % (range: 2 %–13 %). On average, surface air temperature (SAT) increases are 1.3 °C greater over the land than over the oceans, and there is a clear pattern of polar amplification with warming polewards of 60° N and 60° S exceeding the global mean warming by a factor of 2.4. In the Atlantic and Pacific Oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. Although there are some modelling constraints, there is a statistically significant relationship between a model's climate response associated with a doubling in CO2 (Equilibrium Climate Sensitivity; ECS) and its simulated Pliocene surface temperature response. The mean ensemble earth system response to doubling of CO2 (including ice sheet feedbacks) is approximately 50 % greater than ECS, consistent with results from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea-surface temperatures are used to assess model estimates of ECS and indicate a range in ECS from 2.5 to 4.3 °C. This result is in general accord with the range in ECS presented by previous IPCC Assessment Reports.

Published
2020

19. The Pliocene Model Intercomparison Project Phase 2: A return to large-scale features of Pliocene climate sensitivity

Author

Haywood, AM, Tindall, JC, Dowsett, HJ, Dolan, AM, Foley, KM, Hunter, SJ, Hill, DJ, Chan, W-L, Abe-Ouchi, A, Stepanek, C, Lohmann, G, Chandan, D, Peltier, WR, Tan, N, Contoux, C, Ramstein, G, Li, X, Zhang, Z, Guo, C, Nisancioglu, KH, Zhang, Q, Li, Q, Kamae, Y, Chandler, MA, Sohl, LE, Otto-Bliesner, BL, Feng, R, Brady, EC, Von der Heydt, AS, Baatsen, MLJ, Lunt, DJ, Sub Physical Oceanography, Sub Dynamics Meteorology, and Marine and Atmospheric Research

Abstract

The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental 35 consequences of an atmospheric CO2 concentration near ~400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolution and based on new reconstructions of boundary conditions (the Pliocene Model Intercomparison Project Phase 2; PlioMIP2). As a global annual average, modelled surface air temperatures increase by between 1.4 and 4.7°C relative to pre-industrial with a multi-model mean value of 2.8°C. Annual mean total precipitation rates increase by 6% (range: 2%-13%). On 40 average, surface air temperature (SAT) increases are 1.3°C greater over the land than over the oceans, and there is a clear pattern of polar amplification with warming polewards of 60°N and 60°S exceeding the global mean warming by a factor of 2.4. In the Atlantic and Pacific Oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. Although there are some modelling constraints, there is a statistically significant relationship between a model's climate response associated with a doubling in CO2 (Equilibrium Climate Sensitivity; ECS) and its simulated 45 Pliocene surface temperature response. The mean ensemble earth system response to doubling of CO2 (including ice sheet feedbacks) is approximately 50% greater than ECS, consistent with results from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea-surface temperatures are used to assess model estimates of ECS and indicate a range in ECS from 2.5 to 4.3°C. This result is in general accord with the range in ECS presented by previous IPCC Assessment Reports. 50

Published
2020

20. Evaluation of Arctic warming in mid-Pliocene climate simulations

Author

de Nooijer, W, Zhang, Q, Li, Q, Li, X, Zhang, Z, Guo, C, Nisancioglu, KH, Haywood, A, Tindall, J, Hunter, S, Dowsett, HJ, Stepanek, C, Lohmann, G, Otto-Bliesner, BL, Feng, R, Sohl, LE, Chandler, MA, Tan, N, Contoux, C, Ramstein, G, Baatsen, MLJ, von der Heydt, A, Chandan, D, Peltier, WR, Abe-Ouchi, A, Chan, W-L, Kamae, Y, Brierley, CM, Bolin Centre for Climate Research, Stockholm University, Chinese Academy of Sciences [Beijing] (CAS), Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences [Bergen] (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Modélisation du climat (CLIM), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS
Abstract

Palaeoclimate simulations improve our understanding of the climate, inform us about the performance of climate models in a different climate scenario, and help to identify robust features of the climate system. Here, we analyse Arctic warming in an ensemble of 16 simulations of the mid-Pliocene Warm Period (mPWP), derived from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The PlioMIP2 ensemble simulates Arctic (60–90∘ N) annual mean surface air temperature (SAT) increases of 3.7 to 11.6 ∘C compared to the pre-industrial period, with a multi-model mean (MMM) increase of 7.2 ∘C. The Arctic warming amplification ratio relative to global SAT anomalies in the ensemble ranges from 1.8 to 3.1 (MMM is 2.3). Sea ice extent anomalies range from −3.0 to -10.4×106 km2, with a MMM anomaly of -5.6×106 km2, which constitutes a decrease of 53 % compared to the pre-industrial period. The majority (11 out of 16) of models simulate summer sea-ice-free conditions (≤1×106 km2) in their mPWP simulation. The ensemble tends to underestimate SAT in the Arctic when compared to available reconstructions, although the degree of underestimation varies strongly between the simulations. The simulations with the highest Arctic SAT anomalies tend to match the proxy dataset in its current form better. The ensemble shows some agreement with reconstructions of sea ice, particularly with regard to seasonal sea ice. Large uncertainties limit the confidence that can be placed in the findings and the compatibility of the different proxy datasets. We show that while reducing uncertainties in the reconstructions could decrease the SAT data–model discord substantially, further improvements are likely to be found in enhanced boundary conditions or model physics. Lastly, we compare the Arctic warming in the mPWP to projections of future Arctic warming and find that the PlioMIP2 ensemble simulates greater Arctic amplification than CMIP5 future climate simulations and an increase instead of a decrease in Atlantic Meridional Overturning Circulation (AMOC) strength compared to pre-industrial period. The results highlight the importance of slow feedbacks in equilibrium climate simulations, and that caution must be taken when using simulations of the mPWP as an analogue for future climate change.

Published
2020

21. Evaluating the Dominant Components of Warming in Pliocene Climate Simulations

Author

Hill, D. J, Haywood, A. M, Lunt, D. J, Hunter, S. J, Bragg, F. J, Contoux, C, Stepanek, C, Sohl, L, Rosenbloom, N. A, Chan, W.-L, Kamae, Y, Zhang, Z, Abe-Ouchi, A, Chandler, M. A, Jost, A, Lohmann, G, Otto-Bliesner, B. L, Ramstein, G, and Ueda, H

Subjects
Meteorology And Climatology
Abstract

The Pliocene Model Intercomparison Project (PlioMIP) is the first coordinated climate model comparison for a warmer palaeoclimate with atmospheric CO2 significantly higher than pre-industrial concentrations. The simulations of the mid-Pliocene warm period show global warming of between 1.8 and 3.6 C above pre-industrial surface air temperatures, with significant polar amplification. Here we perform energy balance calculations on all eight of the coupled ocean-atmosphere simulations within PlioMIP Experiment 2 to evaluate the causes of the increased temperatures and differences between the models. In the tropics simulated warming is dominated by greenhouse gas increases, with the cloud component of planetary albedo enhancing the warming in most of the models, but by widely varying amounts. The responses to mid-Pliocene climate forcing in the Northern Hemisphere midlatitudes are substantially different between the climate models, with the only consistent response being a warming due to increased greenhouse gases. In the high latitudes all the energy balance components become important, but the dominant warming influence comes from the clear sky albedo, only partially offset by the increases in the cooling impact of cloud albedo. This demonstrates the importance of specified ice sheet and high latitude vegetation boundary conditions and simulated sea ice and snow albedo feedbacks. The largest components in the overall uncertainty are associated with clouds in the tropics and polar clear sky albedo, particularly in sea ice regions. These simulations show that albedo feedbacks, particularly those of sea ice and ice sheets, provide the most significant enhancements to high latitude warming in the Pliocene.

Published
2014
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22. The Pliocene Model Intercomparison Project Phase 2: A return to large-scale features of Pliocene climate sensitivity

Author

Sub Physical Oceanography, Sub Dynamics Meteorology, Marine and Atmospheric Research, Haywood, AM, Tindall, JC, Dowsett, HJ, Dolan, AM, Foley, KM, Hunter, SJ, Hill, DJ, Chan, W-L, Abe-Ouchi, A, Stepanek, C, Lohmann, G, Chandan, D, Peltier, WR, Tan, N, Contoux, C, Ramstein, G, Li, X, Zhang, Z, Guo, C, Nisancioglu, KH, Zhang, Q, Li, Q, Kamae, Y, Chandler, MA, Sohl, LE, Otto-Bliesner, BL, Feng, R, Brady, EC, Von der Heydt, AS, Baatsen, MLJ, Lunt, DJ, Sub Physical Oceanography, Sub Dynamics Meteorology, Marine and Atmospheric Research, Haywood, AM, Tindall, JC, Dowsett, HJ, Dolan, AM, Foley, KM, Hunter, SJ, Hill, DJ, Chan, W-L, Abe-Ouchi, A, Stepanek, C, Lohmann, G, Chandan, D, Peltier, WR, Tan, N, Contoux, C, Ramstein, G, Li, X, Zhang, Z, Guo, C, Nisancioglu, KH, Zhang, Q, Li, Q, Kamae, Y, Chandler, MA, Sohl, LE, Otto-Bliesner, BL, Feng, R, Brady, EC, Von der Heydt, AS, Baatsen, MLJ, and Lunt, DJ

Published
2020

28. Mid-Pliocene Atlantic Meridional Overturning Circulation Not Unlike Modern

Author

Zhang, Z.-S, Nisancioglu, K. H, Chandler, M. A, Haywood, A. M, Otto-Bliesner, B. L, Ramstein, G, Stepanek, C, Abe-Ouchi, A, Chan, W. -L, and Sohl, L. E

Subjects
Meteorology And Climatology
Abstract

In the Pliocene Model Intercomparison Project (PlioMIP), eight state-of-the-art coupled climate models have simulated the mid-Pliocene warm period (mPWP, 3.264 to 3.025 Ma). Here, we compare the Atlantic Meridional Overturning Circulation (AMOC), northward ocean heat transport and ocean stratification simulated with these models. None of the models participating in PlioMIP simulates a strong mid-Pliocene AMOC as suggested by earlier proxy studies. Rather, there is no consistent increase in AMOC maximum among the PlioMIP models. The only consistent change in AMOC is a shoaling of the overturning cell in the Atlantic, and a reduced influence of North Atlantic Deep Water (NADW) at depth in the basin. Furthermore, the simulated mid-Pliocene Atlantic northward heat transport is similar to the pre-industrial. These simulations demonstrate that the reconstructed high-latitude mid-Pliocene warming can not be explained as a direct response to an intensification of AMOC and concomitant increase in northward ocean heat transport by the Atlantic.

Published
2013
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29. Large-Scale Features of Pliocene Climate: Results from the Pliocene Model Intercomparison Project

Author

Haywood, A. M, Hill, D.J, Dolan, A. M, Otto-Bliesner, B. L, Bragg, F, Chan, W.-L, Chandler, M. A, Contoux, C, Dowsett, H. J, Jost, A, Kamae, Y, Lohmann, G, Lunt, D. J, Abe-Ouchi, A, Pickering, S. J, Ramstein, G, Rosenbloom, N. A, Salzmann, U, Sohl, L, Stepanek, C, Ueda, H, Yan, Q, and Zhang, Z

Subjects
Meteorology And Climatology
Abstract

Climate and environments of the mid-Pliocene warm period (3.264 to 3.025 Ma) have been extensively studied.Whilst numerical models have shed light on the nature of climate at the time, uncertainties in their predictions have not been systematically examined. The Pliocene Model Intercomparison Project quantifies uncertainties in model outputs through a coordinated multi-model and multi-mode data intercomparison. Whilst commonalities in model outputs for the Pliocene are clearly evident, we show substantial variation in the sensitivity of models to the implementation of Pliocene boundary conditions. Models appear able to reproduce many regional changes in temperature reconstructed from geological proxies. However, data model comparison highlights that models potentially underestimate polar amplification. To assert this conclusion with greater confidence, limitations in the time-averaged proxy data currently available must be addressed. Furthermore, sensitivity tests exploring the known unknowns in modelling Pliocene climate specifically relevant to the high latitudes are essential (e.g. palaeogeography, gateways, orbital forcing and trace gasses). Estimates of longer-term sensitivity to CO2 (also known as Earth System Sensitivity; ESS), support previous work suggesting that ESS is greater than Climate Sensitivity (CS), and suggest that the ratio of ESS to CS is between 1 and 2, with a "best" estimate of 1.5.

Published
2013
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33. Simulating the amplification of orbital forcing by ocean feedbacks in the last glaciation

Author

Khodri, M., Leclainche, Y., Ramstein, G., Braconnot, P., Marti, O., and Cortijo, E.

Subjects
Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Author(s): M. Khodri (corresponding author); Y. Leclainche; G. Ramstein; P. Braconnot; O. Marti; E. Cortijo According to Milankovitch theory, the lower summer insolation at high latitudes about 115,000 years ago [...]

Published
2001
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38. Impacts of polar ice sheets on the East Asian monsoon during the MIS-13 interglacial

Author

UCL - SST/ELI/ELIC - Earth & Climate, Shi, Feng, Yin, Qiuzhen, Nikolova I., Zhao S., Sun Y., Ramstein G., Guo Z.T., Berger, André, EGU General Assembly, UCL - SST/ELI/ELIC - Earth & Climate, Shi, Feng, Yin, Qiuzhen, Nikolova I., Zhao S., Sun Y., Ramstein G., Guo Z.T., Berger, André, and EGU General Assembly

Published
2018

39. Evolutionary design of strong and stable high entropy alloys using multi-objective optimisation based on physical models, statistics and thermodynamics

Author

European Commission, Comunidad de Madrid, Menou, E., Toda Caraballo, Isaac, Rivera-Díaz-del-Castillo, P.E.J., Pineau, C., Bertrand, E., Ramstein, G., Tancret, F., European Commission, Comunidad de Madrid, Menou, E., Toda Caraballo, Isaac, Rivera-Díaz-del-Castillo, P.E.J., Pineau, C., Bertrand, E., Ramstein, G., and Tancret, F.

Abstract

A new integrated computational HEA design strategy is proposed. It combines a multi-objective genetic algorithm with (i) statistical criteria to guide the formation of a single phase, supplemented by computational thermodynamics (Thermo-Calc) and (ii) models for the estimation of alloy yield stress via solid solution hardening, to be maximised, and alloy density, to be minimised. This strategy is applied to the design of face-centered-cubic (FCC) HEAs and yields several thousands of new alloys. An alloy featuring an interesting combination of predicted stability, strength and density, AlCoFeMoNi (at%), is chosen among them, fabricated by vacuum arc melting and experimentally tested. The microstructure of this new HEA consists in a single FCC solid solution, as evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) mapping. With a density of 7.95 g⋅cm, a Vickers hardness of 1.78 GPa, a yield stress of 215 MPa and an ultimate tensile strength of 665 MPa in the annealed state, its properties surpass those of existing FCC HEAs of comparable density.

Published
2018

40. Computational design of light and strong high entropy alloys (HEA): Obtainment of an extremely high specific solid solution hardening

Author

European Commission, Menou, E., Tancret, F., Toda Caraballo, Isaac, Ramstein, G., Castany, P., Bertrand, E., Gautier, N., Rivera-Díaz-del-Castillo, P.E.J., European Commission, Menou, E., Tancret, F., Toda Caraballo, Isaac, Ramstein, G., Castany, P., Bertrand, E., Gautier, N., and Rivera-Díaz-del-Castillo, P.E.J.

Abstract

A multi-objective optimisation genetic algorithm combining solid solution hardening (SSH) and thermodynamic modelling (CALPHAD) with data mining is used to design high entropy alloys (HEAs). The approach searches for the best compromise between single-phase stability, SSH and density. Thousands of Pareto-optimal base-centred cubic (BCC) HEAs are designed. AlCrMnMoTi (at.%) is chosen for experimental validation. The alloy was cast and characterised. Its microstructure consists of large grains of a single disordered solid solution displaying a Vickers hardness of 6.45 GPa (658 HV) and a density below 5.5 g/cm; uniquely combining exceptional hardness with medium density.

Published
2018

43. Snowball Earth climate dynamics and Cryogenian geology-geobiology

Author

Hoffman, P., Abbot, D., Ashkenazy, Y., Benn, D., Brocks, J., Cohen, P., Cox, G., Creveling, J., Donnadieu, Y., Erwin, D., Fairchild, I., Ferreira, D., Goodman, J., Halverson, Galen, Jansen, M., Le Hir, G., Love, G., Macdonald, F., Maloof, A., Partin, C., Ramstein, G., Rose, B., Rose, C., Sadler, P., Tziperman, E., Voigt, A., Warren, S., Hoffman, P., Abbot, D., Ashkenazy, Y., Benn, D., Brocks, J., Cohen, P., Cox, G., Creveling, J., Donnadieu, Y., Erwin, D., Fairchild, I., Ferreira, D., Goodman, J., Halverson, Galen, Jansen, M., Le Hir, G., Love, G., Macdonald, F., Maloof, A., Partin, C., Ramstein, G., Rose, B., Rose, C., Sadler, P., Tziperman, E., Voigt, A., and Warren, S.

Abstract

Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. Geological evidence indicates that grounded ice sheets reached sea level at all latitudes during two long-lived Cryogenian (58 and =5 My) glaciations. Combined uranium-lead and rhenium-osmium dating suggests that the older (Sturtian) glacial onset and both terminations were globally synchronous. Geochemical data imply that CO2was 102PAL (present atmospheric level) at the younger termination, consistent with a global ice cover. Sturtian glaciation followed breakup of a tropical supercontinent, and its onset coincided with the equatorial emplacement of a large igneous province. Modeling shows that the small thermal inertia of a globally frozen surface reverses the annual mean tropical atmospheric circulation, producing an equatorial desert and net snow and frost accumulation elsewhere. Oceanic ice thickens, forming a sea glacier that flows gravitationally toward the equator, sustained by the hydrologic cycle and by basal freezing and melting. Tropical ice sheets flow faster as CO2rises but lose mass and become sensitive to orbital changes. Equatorial dust accumulation engenders supraglacial oligotrophic meltwater ecosystems, favorable for cyanobacteria and certain eukaryotes. Meltwater flushing through cracks enables organic burial and submarine deposition of airborne volcanic ash. The subglacial ocean is turbulent and well mixed, in response to geothermal heating and heat loss through the ice cover, increasing with latitude. Terminal carbonate deposits, unique to Cryogenian glaciations, are products of intense weathering and ocean stratification. Whole-ocean warming and collapsing peripheral bulges allow marine coastal flooding to continue long after ice-sheet disappearance. The evolutionary legacy of Snowball Earth is perceptible in fossils and living organisms.

Published
2017

45. Using results from the PlioMIP ensemble to investigate the Greenland Ice Sheet during the mid-Pliocene Warm Period

Author

Dolan, A.M., Hunter, S.J., Hill, D.J., Haywood, A.M., Koenig, S.J., Otto-Bliesner, B.L., Abe-Ouchi, A., Bragg, F., Chan, W.-L., Chandler, M.A., Contoux, C., Jost, A., Kamae, Y., Lohmann, G., Lunt, D.J., Ramstein, G., Rosenbloom, N.A., Sohl, L., Stepanek, C., Ueda, H., Yan, Q., Zhang, Z., Dolan, A.M., Hunter, S.J., Hill, D.J., Haywood, A.M., Koenig, S.J., Otto-Bliesner, B.L., Abe-Ouchi, A., Bragg, F., Chan, W.-L., Chandler, M.A., Contoux, C., Jost, A., Kamae, Y., Lohmann, G., Lunt, D.J., Ramstein, G., Rosenbloom, N.A., Sohl, L., Stepanek, C., Ueda, H., Yan, Q., and Zhang, Z.

Abstract

During an interval of the Late Pliocene, referred to here as the mid-Pliocene Warm Period (mPWP; 3.264 to 3.025 million years ago), global mean temperature was similar to that predicted for the end of this century, and atmospheric carbon dioxide concentrations were higher than pre-industrial levels. Sea level was also higher than today, implying a significant reduction in the extent of the ice sheets. Thus, the mPWP provides a natural laboratory in which to investigate the long-term response of the Earth's ice sheets and sea level in a warmer-than-present-day world. At present, our understanding of the Greenland ice sheet during the mPWP is generally based upon predictions using single climate and ice sheet models. Therefore, it is essential that the model dependency of these results is assessed. The Pliocene Model Intercomparison Project (PlioMIP) has brought together nine international modelling groups to simulate the warm climate of the Pliocene. Here we use the climatological fields derived from the results of the 15 PlioMIP climate models to force an offline ice sheet model. We show that mPWP ice sheet reconstructions are highly dependent upon the forcing climatology used, with Greenland reconstructions ranging from an ice-free state to a near-modern ice sheet. An analysis of the surface albedo variability between the climate models over Greenland offers insights into the drivers of inter-model differences. As we demonstrate that the climate model dependency of our results is high, we highlight the necessity of data-based constraints of ice extent in developing our understanding of the mPWP Greenland ice sheet.

Published
2015

46. Using results from the PlioMIP ensemble to investigate the Greenland Ice Sheet during the mid-Pliocene Warm Period

Author

Dolan, A. M., Hunter, S. J., Hill, D. J., Haywood, A. M., Koenig, S. J., Otto-Bliesner, B. L., Abe-Ouchi, A., Bragg, F., Chan, W.-L., Chandler, M. A., Contoux, C., Jost, A., Kamae, Y., Lohmann, Gerrit, Lunt, D. J., Ramstein, G., Rosenbloom, N. A., Sohl, L., Stepanek, Christian, Ueda, H., Yan, Q., Zhang, Z., Dolan, A. M., Hunter, S. J., Hill, D. J., Haywood, A. M., Koenig, S. J., Otto-Bliesner, B. L., Abe-Ouchi, A., Bragg, F., Chan, W.-L., Chandler, M. A., Contoux, C., Jost, A., Kamae, Y., Lohmann, Gerrit, Lunt, D. J., Ramstein, G., Rosenbloom, N. A., Sohl, L., Stepanek, Christian, Ueda, H., Yan, Q., and Zhang, Z.

Abstract

During an interval of the Late Pliocene, referred to here as the mid-Pliocene Warm Period (mPWP; 3.264 to 3.025 million years ago), global mean temperature was similar to that predicted for the end of this century, and atmospheric carbon dioxide concentrations were higher than pre-industrial levels. Sea level was also higher than today, implying a significant reduction in the extent of the ice sheets. Thus, the mPWP provides a natural laboratory in which to investigate the long-term response of the Earth's ice sheets and sea level in a warmer-than-present-day world. At present, our understanding of the Greenland ice sheet during the mPWP is generally based upon predictions using single climate and ice sheet models. Therefore, it is essential that the model dependency of these results is assessed. The Pliocene Model Intercomparison Project (PlioMIP) has brought together nine international modelling groups to simulate the warm climate of the Pliocene. Here we use the climatological fields derived from the results of the 15 PlioMIP climate models to force an offline ice sheet model. We show that mPWP ice sheet reconstructions are highly dependent upon the forcing climatology used, with Greenland reconstructions ranging from an ice-free state to a near-modern ice sheet. An analysis of the surface albedo variability between the climate models over Greenland offers insights into the drivers of inter-model differences. As we demonstrate that the climate model dependency of our results is high, we highlight the necessity of data-based constraints of ice extent in developing our understanding of the mPWP Greenland ice sheet.

Published
2015

47. Challenges in reconstructing terrestrial warming of the Pliocene revealed by data-model discord

Author

Salzmann, U., Dolan, A. M., Haywood, A. M., Chan, W.-L., Voss, J., Hill, D. J., Lunt, D. J., Abe-Ouchi, A., Otto-Bliesner, B., Bragg, F., Chandler, M. A., Contoux, C., Dowsett, H. J., Jost, A., Kamae, Y., Lohmann, Gerrit, Pickering, S. J., Pound, M. J., Ramstein, G., Rosenbloom, N. A., Sohl, L., Stepanek, Christian, Ueda, H., and Zhang, Z.

Abstract

Comparing simulations of key warm periods in Earth history with contemporaneous geological proxy data is a useful approach for evaluating the ability of climate models to simulate warm, high-CO2 climates that are unprecedented in the more recent past. Here we use a global data set of confidence-assessed, proxy-based temperature estimates and biome reconstructions to assess the ability of eight models to simulate warm terrestrial climates of the Pliocene epoch. The Late Pliocene, 3.6–2.6 million years ago, is an accessible geological interval to understand climate processes of a warmer world. We show that model-predicted surface air temperatures reveal a substantial cold bias in the Northern Hemisphere. Particularly strong data–model mismatches in mean annual temperatures (up to 18 °C) exist in northern Russia. Our model sensitivity tests identify insufficient temporal constraints hampering the accurate configuration of model boundary conditions as an important factor impacting on data–model discrepancies. We conclude that to allow a more robust evaluation of the ability of present climate models to predict warm climates, future Pliocene data–model comparison studies should focus on orbitally defined time slices.

Published
2013

48. Qu’apprend-on des paléoclimats ?

Author

Kageyama, M., Ramstein, G., Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modélisation du climat (CLIM), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2013

49. A reassessment of lake and wetland feedbacks on the North African Holocene climate

Author

Krinner, G., Lézine, Anne-Marie, Braconnot, Pascale, Sepulchre, P., Ramstein, G., Grenier, C., Gouttevin, I., Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics (MERMAID), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Modélisation du climat (CLIM), Modélisation Hydrologique (HYDRO), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)

Subjects
4928), Global Change: Land/atmosphere interactions (1218, 3309), Global Change: Regional climate change (4321), 3322), Global Change: Climate dynamics (0429, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Global Change: Earth system modeling (1225, Global Change: Global climate models (3337, 4316)
Abstract

International audience; Large parts of the Sahara were vegetated during the early to mid Holocene. Several positive feedbacks, most notably related to vegetation, have been shown to have favored the northward migration of the desert boundary. During this period, numerous lakes and wetlands existed in the Sahara region and might have acted as a local moisture source. However, earlier model studies of the effects of open water surfaces on the mid-Holocene North African climate suggested that these were weak and did not contribute significantly to this northward migration of the North African climate zones. Using a state-of-the-art climate model, we suggest that the effect of open-water surfaces on the mid-Holocene North African climate might have been much stronger than previously estimated, regionally more than doubling the simulated precipitation rates. It is thus possible that this effect, combined to other known positive feedbacks, favored the appearance of the "Green Sahara".

Published
2012

50. Using results from the PlioMIP ensemble to investigate the Greenland Ice Sheet during the mid-Pliocene Warm Period

Author

Dolan, A. M., primary, Hunter, S. J., additional, Hill, D. J., additional, Haywood, A. M., additional, Koenig, S. J., additional, Otto-Bliesner, B. L., additional, Abe-Ouchi, A., additional, Bragg, F., additional, Chan, W.-L., additional, Chandler, M. A., additional, Contoux, C., additional, Jost, A., additional, Kamae, Y., additional, Lohmann, G., additional, Lunt, D. J., additional, Ramstein, G., additional, Rosenbloom, N. A., additional, Sohl, L., additional, Stepanek, C., additional, Ueda, H., additional, Yan, Q., additional, and Zhang, Z., additional

Published
2015
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