Multiple causes of the Younger Dryas cold period

• Published in: Nature Geoscience
• Main Authors: Renssen, Hans, Mairesse, Aurélien, Goosse, Hugues, Mathiot, Pierre, Heiri, Oliver, Roche, Didier M., Nisancioglu, Kerim, H., Valdes, Paul
• Other Authors: Department of Earth Sciences Amsterdam, Vrije Universiteit Amsterdam Amsterdam (VU), Earth and Life Institute Louvain-La-Neuve (ELI), Université Catholique de Louvain = Catholic University of Louvain (UCL), British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Oeschger Centre for Climate Change Research (OCCR), Universität Bern / University of Bern (UNIBE), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), 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)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Modélisation du climat (CLIM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-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)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), University of Bergen (UiB), Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences Bergen (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), School of Geographical Sciences Bristol, University of Bristol Bristol, European Project: 243908,EC:FP7:ENV,FP7-ENV-2009-1,PAST4FUTURE(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; North Atlantic
• Online Access: https://hal.science/hal-03218176; https://hal.science/hal-03218176/document; https://hal.science/hal-03218176/file/Renssen_etal_resubm_NatureGS_Submitted.pdf; https://doi.org/10.1038/ngeo2557

International audience The Younger Dryas cooling event disrupted the overall warming trend in the North Atlantic region during the last deglaciation. Climate change during the Younger Dryas was abrupt, and thus provides insights into the sensitivity of the climate system to perturbations. The sudden Younger Dryas cooling has traditionally been attributed to a shutdown of the Atlantic Meridional Overturning Circulation by meltwater discharges1 However, alternative explanations such as strong negative radiative forcing and a shift in atmospheric circulation have also been offered. Here we investigate the importance of these different forcings in coupled climate model experiments constrained by data assimilation. We find that the Younger Dryas climate signal as registered in proxy evidence is best simulated using a combination of processes: a weakened Atlantic Meridional Overturning Circulation, moderate negative radiative forcing and an altered atmospheric circulation. We conclude that none of the individual mechanisms alone provide a plausible explanation for the Younger Dryas cold period. We suggest that the triggers for abrupt climate changes such as the Younger Dryas are more complex than suggested so far, and that studies on the response of the climate system to perturbations should account for this complexity.