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

• Published in: Climate of the Past
• Main Authors: Alvarez-Solas, J., Montoya, M., Ritz, C., Ramstein, G., Charbit, S., Dumas, C., Nisancioglu, K., Dokken, T., Ganopolski, A.
• Other Authors: Departamento de Astrofisica y Ciencias de la Atmósfera, Universidad Complutense de Madrid = Complutense University of Madrid Madrid (UCM), 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)), Instituto de Geociencias (UCM-CSIC), Facultad de Ciencias Fisicas, Laboratoire de glaciologie et géophysique de l'environnement (LGGE), 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)-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), Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences Bergen (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), Potsdam Institute for Climate Impact Research (PIK), MOVAC and SPECT-MORE projects
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Hudson Strait; Ice Sheet; Ice Shelves; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://insu.hal.science/insu-00843368; https://insu.hal.science/insu-00843368/document; https://insu.hal.science/insu-00843368/file/Alvarez-Solas_2011.pdf; https://doi.org/10.5194/cp-7-1297-2011

International audience Heinrich events, identified as enhanced ice-rafted detritus (IRD) in North Atlantic deep sea sediments ( Hein- rich , 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, specif- ically 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 simula- tions 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 acceler- ation, 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 ef- fects of oceanic circulation on ice-sheets dynamics in order to elucidate the triggering mechanism of Heinrich events.