A Weakened AMOC Could Cause Southern Ocean Temperature and Sea‐Ice Change on Multidecadal Timescales

Abstract We present the first CMIP6‐era multi‐model intercomparison of the Southern Ocean (SO) temperature and sea‐ice response to substantial Atlantic meridional overturning circulation (AMOC) weakening. Results are based on analysis of the North Atlantic Hosing Model Intercomparison Project, involving eight CMIP6 models under identical North Atlantic freshwater hosing. On multidecadal timescales, we find that southwards ocean heat transport into the SO increases, causing surface warming and sea‐ice loss. Additionally, an atmospheric tropical‐Antarctic teleconnection, identified here for the first time, causes regional temperature and sea‐ice changes in the SO. Unlike previous studies, we find that the Amundsen Sea Low deepens for only some models. Overall, in the multi‐model ensemble mean (multi‐model range in brackets), over years 50–100 after AMOC weakening: SO surface air temperature warms by 0.3 (0.1–0.7)°C, sea level pressure (SLP) decreases by 30 (10–70) Pa, and sea‐ice area decreases by 0.4 (−0.2–1.3) Mkm 2 . The teleconnection leads to regional differences between the response in the Indian sector and the Weddell Sea of 180 (80–320) Pa in SLP, 0.6 (0.5–1.4)°C in surface air temperature, and 0.1 (0.1–0.2) Mkm 2 in sea‐ice area. These SO heat transport, temperature, pressure, and sea‐ice changes are small relative to the changes expected under future anthropogenic warming, despite the large and idealized 0.3 Sv hosing used to weaken the AMOC.

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Publication Details

Journal
Journal of Geophysical Research Oceans
Published
2025-07-01
DOI
https://doi.org/10.1029/2024jc022027
Citations
1
Primary Topic
Oceanographic and Atmospheric Processes
Type
article
Field-Weighted Citation Impact
1.79

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article

A Weakened AMOC Could Cause Southern Ocean Temperature and Sea‐Ice Change on Multidecadal Timescales

Eduardo Alastrué de Asenjo, Gökhan Danabasoglu, Aixue Hu, Johann Jungclaus et al.
1 citations
Journal of Geophysical Research Oceans
Oceanographic and Atmospheric Processes
1.79
article

A Weakened AMOC Could Cause Southern Ocean Temperature and Sea‐Ice Change on Multidecadal Timescales

Eduardo Alastrué de Asenjo, Gökhan Danabasoglu, Aixue Hu, Johann Jungclaus, Didier Swingedouw, Virna Meccia, Katinka Bellomo, Laura Jackson, David Schröeder, Rachel Diamond, Marisa Montoya, Oleg A. Saenko, Louise Claire Sime, Paul R. Holland
article en
1 citations

Abstract

Abstract We present the first CMIP6‐era multi‐model intercomparison of the Southern Ocean (SO) temperature and sea‐ice response to substantial Atlantic meridional overturning circulation (AMOC) weakening. Results are based on analysis of the North Atlantic Hosing Model Intercomparison Project, involving eight CMIP6 models under identical North Atlantic freshwater hosing. On multidecadal timescales, we find that southwards ocean heat transport into the SO increases, causing surface warming and sea‐ice loss. Additionally, an atmospheric tropical‐Antarctic teleconnection, identified here for the first time, causes regional temperature and sea‐ice changes in the SO. Unlike previous studies, we find that the Amundsen Sea Low deepens for only some models. Overall, in the multi‐model ensemble mean (multi‐model range in brackets), over years 50–100 after AMOC weakening: SO surface air temperature warms by 0.3 (0.1–0.7)°C, sea level pressure (SLP) decreases by 30 (10–70) Pa, and sea‐ice area decreases by 0.4 (−0.2–1.3) Mkm 2 . The teleconnection leads to regional differences between the response in the Indian sector and the Weddell Sea of 180 (80–320) Pa in SLP, 0.6 (0.5–1.4)°C in surface air temperature, and 0.1 (0.1–0.2) Mkm 2 in sea‐ice area. These SO heat transport, temperature, pressure, and sea‐ice changes are small relative to the changes expected under future anthropogenic warming, despite the large and idealized 0.3 Sv hosing used to weaken the AMOC.

Journal of Geophysical Research OceansVol. 130(7)
NSF National Center for Atmospheric Research (US), Universidad Complutense de Madrid (ES), Met Office (GB), Centre National de la Recherche Scientifique (FR), U.S. National Science Foundation (US), British Antarctic Survey (GB), Consejo Superior de Investigaciones Científicas (ES), Universität Hamburg (DE), Politecnico di Torino (IT), University of Victoria (CA), University of Cambridge (GB), Institute of Atmospheric Sciences and Climate (IT), Environnements et Paléoenvironnements Océaniques et Continentaux (FR), Centre for Polar Observation and Modelling (GB), National Centre for Earth Observation (GB), NSF NCAR Climate and Global Dynamics Laboratory (US), Environment Park (IT), Instituto de Geociencias (ES), National Research Council (IT), Institut Polytechnique de Bordeaux (FR), Max Planck Institute for Meteorology (DE), University of Reading (GB)
National Science Foundation, National Center for Atmospheric Research, Global Down Syndrome Foundation, Ministerio de Ciencia, Innovación y Universidades, Met Office, European Centre for Medium-Range Weather Forecasts, Office of Nuclear Energy, Horizon 2020 Framework Programme, Natural Environment Research Council, British Antarctic Survey, National Centre for Earth Observation, HORIZON EUROPE European Research Council
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Oceanographic and Atmospheric Processes
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