The Role of Sea Ice Insulation Effects on the Probability of AMOC Transitions

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Abstract

Recent simulations performed with the Community Earth System Model (CESM) have suggested a crucial role of sea ice processes in Atlantic meridional overturning circulation (AMOC) hysteresis behavior under varying surface freshwater forcing. Here, we further investigate this issue using additional CESM simulations and a novel conceptual ocean–sea ice box model. The CESM simulations suggest that the presence of sea ice gives rise to the existence of statistical equilibria with a weak AMOC strength. This is confirmed in the conceptual model, which captures similar AMOC hysteresis behavior as in the CESM simulation and where steady states are computed versus freshwater forcing parameters. In the conceptual model, transition probabilities between the different equilibrium states are determined using rare event techniques. The transition probabilities from a strong AMOC state to a weak AMOC state increase when considering sea ice insulation effects and indicate that sea ice promotes these transitions. On the other hand, sea ice insulation effects strongly reduce the probabilities of the reverse transition from a weak AMOC state to a strong AMOC state and this implies that sea ice also limits AMOC recovery. The results here indicate that sea ice effects play a dominant role in AMOC hysteresis width and influence transition probabilities between the different equilibrium states.

Original languageEnglish
Pages (from-to)6269-6284
Number of pages16
JournalJournal of Climate
Volume37
Issue number23
DOIs
Publication statusPublished - 1 Dec 2024

Bibliographical note

Publisher Copyright:
Ó 2024 American Meteorological Society.

Funding

FundersFunder number
Inner Mongolia Agricultural University
Michael Kliphuis
European Research Council
NWO-SURF17239
ERC-AdG101055096
Horizon 2020 Framework Programme956170
Horizon 2020 Framework Programme

    Keywords

    • Dynamical system model
    • Idealized models
    • Nonlinear dynamics
    • Numerical analysis/modeling
    • Ocean circulation
    • Ocean models

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