38. Mechanisms leading to the last glacial inception over North America: Results from the CLIMBER-GREMLINS atmosphere-ocean-vegetation northern hemisphere ice-sheet model

• Main Authors: Kageyama, Masa, Charbit, Sylvie, Ritz, Catherine, Khodri, Myriam, Ramstein, Gilles
• Other Authors: 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), Observatoire des Sciences de l'Univers de Grenoble (OSUG), 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), NOAA Geophysical Fluid Dynamics Laboratory (GFDL), National Oceanic and Atmospheric Administration (NOAA)
• Format: Book Part
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Ice Sheet; Sea ice
• Online Access: https://hal.science/hal-03030440; https://doi.org/10.1016/S1571-0866(07)80063-7

International audience The CLIMBER-GREMLINS model is an atmosphere-ocean-vegetation-northern hemisphere ice-sheet model able to simulate ice-sheet growth in response to the transient forcings (insolation and CO2 changes) of the period 126-106kyr BP. In the present version of the model, this growth mainly occurs over North America and reaches an equivalent of 17 m in sea-level drop. To quantify the role of the vegetation, ocean and icesheet feedbacks in this glaciation of North America, we have conducted sensitivity experiments in which the feedback of each of these components is sequentially switched off. These experiments show that, in this model. (1) glacial inception does not occur when vegetation is fixed to its interglacial state (experiment testing the response of the atmosphere-ocean-boreal land-ice system), (2) glacial inception occurs faster than in the standard experiment when the ocean surface characteristics (surface temperature and sea ice extent) are prescribed to their interglacial seasonal cycle (experiment testing the sensitivity of the atmosphere-vegetation-boreal land-ice system), (3) the ice-sheet albedo and altitude feedbacks are not crucial for starting the glaciation, but the albedo feedback doubles the ice volume growth rate, (4) the potential effect of a reduction in the thermohaline circulation is tested via an additional experiment in which we have forced it to its ‘off’ mode. The results show that this mode favours the fastest land ice growth of all our experiments.