Preprints
https://doi.org/10.5194/cp-2020-155
https://doi.org/10.5194/cp-2020-155

  22 Dec 2020

22 Dec 2020

Review status: this preprint is currently under review for the journal CP.

Evaluating seasonal sea-ice cover over the Southern Ocean from the Last Glacial Maximum

Ryan A. Green1,2,3, Laurie Menviel1,2, Katrin J. Meissner1,2, and Xavier Crosta4 Ryan A. Green et al.
  • 1Climate Change Research Centre, University of New South Wales, Sydney, Australia
  • 2ARC Centre of Excellence for Climate System Science, Sydney, Australia
  • 3Earth and Planetary Sciences, University of California, Santa Cruz, USA
  • 4Université de Bordeaux EPOC, UMR 5805, Pessac, France

Abstract. Sea-ice cover over the Southern Ocean responds to and impacts Southern Ocean dynamics and, thus, mid to high latitude climate in the Southern Hemisphere. In addition, sea-ice cover can significantly modulate the carbon exchange between the atmosphere and the ocean. As climate models are the only tool available to project future climate changes, it is important to assess their performance in simulating past changes. The Last Glacial Maximum (LGM, ∼21,000 years ago) represents an interesting target as it is a relatively well documented period with climatic conditions and a carbon cycle very different from pre-industrial conditions. Here, we study the changes in seasonal Antarctic sea-ice cover as simulated in numerical PMIP3 and LOVECLIM simulations of the LGM, and their relationship with windstress and ocean temperature. Simulations and paleo-proxy records suggest a fairly well constrained glacial winter sea-ice edge at 51.5° S (1 sigma range: 50°–55.5° S). Simulated glacial summer sea-ice cover however differs widely between models, ranging from almost no sea ice to a sea-ice edge reaching 55.5° S. The austral summer multi-model mean sea-ice edge lies at ∼60.5° S (1 sigma range: 57.5°–70.5° S). Given the lack of strong constraints on the summer sea-ice edge based on sea-ice proxy records, we extend our model-data comparison to summer sea-surface temperature. Our analysis suggests that the multi-model mean summer sea ice provides a reasonable, albeit upper end, estimate of the austral summer sea-ice edge allowing us to conclude that the multi-model mean of austral summer and winter sea-ice cover seem to provide good estimates of LGM conditions. Using these best estimates, we find that there was a larger sea-ice seasonality during the LGM compared to the present day.

Ryan A. Green et al.

 
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Ryan A. Green et al.

Data sets

LOVECLIM ocean and sea-ice results Green, Ryan, Menviel, Laurie, and Meissner, Katrin https://doi.org/10.26190/K6XA-T076

Model code and software

Multi-model mean Southern Ocean sea-ice edge for austral summer and austral winter during the LGM Green, Ryan, Menviel, Laurie, and Meissner, Katrin https://doi.org/10.26190/vbrq-9a36

Ryan A. Green et al.

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Short summary
Climate models are used to predict future climate changes and as such it is important we assess their performance in simulating past climate changes. We analyze the seasonal Antarctic sea-ice cover simulated from numerical PMIP3 and LOVECLIM simulations during the Last Glacial Maximum (LGM). Comparing these simulations to proxy data, we constrain a best estimate of the LGM sea-ice edge during summer and winter. We also find a larger sea-ice seasonality during the LGM compared to the present day.