28 Feb 2023
 | 28 Feb 2023
Status: this preprint is currently under review for the journal TC.

Multidecadal Variability and Predictability of Antarctic Sea Ice in GFDL SPEAR_LO Model

Yushi Morioka, Liping Zhang, Thomas Delworth, Xiaosong Yang, Fanrong Zeng, Masami Nonaka, and Swadhin Behera

Abstract. Using a state-of-the-art coupled general circulation model, physical processes underlying Antarctic sea ice multidecadal variability and predictability are investigated. Our model simulations constrained with atmospheric reanalysis and observed sea surface temperature broadly capture the observed sea ice extent (SIE) variability with a low sea ice state (late 1970s–1990s) and a high sea ice state (2000s–early 2010s), although the model overestimates the SIE decrease over the Weddell Sea around the 1980s. The low sea ice state is largely due to an occurrence of strong deep convection in the Southern Ocean that subsequently induces anomalous warming of the upper ocean. During the high sea ice period (post-2000s), the deep convection substantially weakens, so that surface wind variability plays greater roles in the SIE variability. Decadal retrospective forecasts started from the above-mentioned constrained model results demonstrate that the Antarctic sea ice multidecadal variability can be skillfully predicted 6–10 years in advance, showing a moderate correlation with the observation (0.4). Ensemble members with a stronger deep convection tend to predict a larger sea ice decrease in the 1980s, whereas the members with a larger surface wind variability tend to predict a larger sea ice increase after the 2000s. Therefore, skillful simulation and prediction of the Antarctic sea ice multidecadal variability require accurate simulation and prediction of both the Southern Ocean deep convection and surface wind variability in the model.

Yushi Morioka et al.

Status: open (until 25 Apr 2023)

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  • RC1: 'Comment on tc-2023-18', Anonymous Referee #1, 23 Mar 2023 reply

Yushi Morioka et al.

Yushi Morioka et al.


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Short summary
Antarctic sea ice extent shows decadal variations with its decrease in the 1980s and increase after the 2000s until 2015. Here we show that our climate model can predict the sea ice decrease by simulating deep convection in the Southern Ocean and the sea ice increase by capturing the surface wind variability. These results suggest that accurate simulation and prediction of subsurface ocean and atmosphere conditions are important for those of Antarctic sea ice variability on a decadal timescale.