Preprints
https://doi.org/10.5194/tc-2022-151
https://doi.org/10.5194/tc-2022-151
 
12 Sep 2022
12 Sep 2022
Status: this preprint is currently under review for the journal TC.

Antarctic sea ice regime shift associated with decreasing zonal symmetry in the Southern Annular Mode

Serena Schroeter1, Terence J. O'Kane1,2, and Paul A. Sandery1 Serena Schroeter et al.
  • 1CSIRO Oceans and Atmosphere, Hobart, Tasmania, Australia
  • 2Australian Centre for Excellence in Antarctic Science, Hobart, Tasmania, Australia

Abstract. Across the long-term (~43 year) satellite record, Antarctic sea ice extent shows a small overall circumpolar increase, resulting from opposing regional sea ice concentration anomalies. Running short-term samples of the same sea ice concentration data, however, show that the long-term trend pattern is skewed towards the earliest years of the satellite record. Compensating regional anomalies diminish over time, and in the most recent decade, these tend towards spatial homogeneity instead. Running 30-year trends show the regional pattern of sea ice behaviour reversing over time; while in some regions, trend patterns abruptly shift in line with the record anomalous sea ice behaviour of recent years, in other regions a steady change predates these record anomalies. The shifting regression patterns are co-located with enhanced north-south flow due to an increasingly wave-3-like structure of the Southern Annular Mode. Sea surface temperature anomalies also shift from a circumpolar cooling to a regional pattern that resembles the increasingly asymmetric structure of the Southern Annular Mode, with warming in regions of previously increasing sea ice such as the Ross Sea.

Serena Schroeter et al.

Status: open (until 11 Nov 2022)

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  • RC1: 'Comment on tc-2022-151', Anonymous Referee #1, 28 Sep 2022 reply

Serena Schroeter et al.

Serena Schroeter et al.

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Short summary
Antarctic sea ice has increased over much of the satellite record, but we show that the early, strongly-opposing regional trends diminish and reverse over time, leading to overall negative trends in more recent decades. The dominant pattern of atmospheric flow has changed from strongly east-west to more wave-like with enhanced north-south winds. Sea surface temperatures have also changed from circumpolar cooling to regional warming, suggesting recent record low sea ice will not rapidly recover.