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- Title
Multiple thermal AMOC thresholds in the intermediate complexity model Bern3D.
- Authors
Adloff, Markus; Pöppelmeier, Frerk; Jeltsch-Thömmes, Aurich; Stocker, Thomas F.; Joos, Fortunat
- Abstract
Variations of the Atlantic Meridional Overturning Circulation (AMOC) are associated with Northern Hemispheric and global climate shifts. Thermal thresholds of the AMOC have been found in a hierarchy of numerical circulation models, and there is an increasing body of evidence for the existence of highly sensitive AMOC modes where small perturbations can cause disproportionately large circulation and hence climatic changes. We discovered such thresholds in simulations with the intermediate complexity Earth system model Bern3D, which is highly computationally efficient allowing for studying this non-linear behaviour systematically over entire glacial cycles. By simulating the AMOC under different magnitudes of orbitally-paced changes in radiative forcing over the last 800,000 years, we show that up to three thermal thresholds are crossed during glacial cycles in Bern3D, and that thermal forcing could have destabilised the AMOC repeatedly. We present the circulation and sea ice patterns that characterise the stable circulation states between which the model oscillates during a glacial cycle, and assess how often and when thermal forcing could have preconditioned the AMOC for abrupt shifts over the last 800 kyr.
- Subjects
ATLANTIC meridional overturning circulation; SEA ice; RADIATIVE forcing; CLIMATE change; CIRCULATION models
- Publication
Climate of the Past Discussions, 2023, p1
- ISSN
1814-9324
- Publication type
Article
- DOI
10.5194/cp-2023-82