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Thermodynamics Drive Post-2016 Changes in the Antarctic Sea Ice Seasonal Cycle
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  • Kenza Himmich,
  • Martin Vancoppenolle,
  • Sharon Stammerjohn,
  • Marion Bocquet,
  • Gurvan Madec,
  • Jean-Baptiste Sallée,
  • Sara Fleury
Kenza Himmich
Sorbonne Université, Laboratoire d'Océanographie et du Climat, CNRS/IRD/MNHN, Paris, France

Corresponding Author:[email protected]

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Martin Vancoppenolle
Sorbonne Université
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Sharon Stammerjohn
U. of Colorado, Boulder
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Marion Bocquet
University of Toulouse
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Gurvan Madec
LOCEAN
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Jean-Baptiste Sallée
LOCEAN-IPSL, CNRS
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Sara Fleury
University of Toulouse
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Abstract

Antarctic sea ice extent has been persistently low since late 2016, possibly owing to changes in atmospheric and oceanic conditions. However, the relative contributions of the ocean, the atmosphere and the underlying mechanisms by which they have affected sea ice remain uncertain. To investigate possible causes for this sea-ice decrease, we establish a seasonal timeline of sea ice changes following 2016, using remote sensing observations. Anomalies in the timing of sea ice retreat and advance are examined along with their spatial and interannual relations with various indicators of seasonal sea ice and oceanic changes. They include anomalies in winter ice thickness, spring ice removal rate due to ice melt and transport, and summer sea surface temperature. We find that the ice season has shortened at unprecedented rate and magnitude, due to earlier retreat and later advance. We attribute this shortening to a winter ice thinning, in line with the ice-albedo feedback, with ice transport playing a more minor role. Reduced ice thickness has accelerated spring ice area removal as thinner sea ice requires less time to melt. The consequent earlier sea ice retreat has in turn increased ocean solar heat uptake in summer, ultimately delaying sea ice advance. We speculate that the observed winter sea ice thinning is consistent with previous evidence of subsurface warming of the Southern Ocean.