Drivers of extreme Antarctic ice extents in summer over the period 1979-2022 

Abstract

<p>The Antarctic sea ice variability and its underlying drivers remain overall unsettled, particularly since the sea ice extent (SIE) during the last two decades has first exhibited a slight increase, somewhat in contrast with the global warming trend, followed by a rapid reduction in the more recent years. The unprecedented SIE minimum registered in February 2022 has received great attention and already constitutes an important case study, as the prior record low in 2017. However, other extreme anomalous events are present in the observational record, and a comprehensive analysis of both minima and maxima in the summer SIE is essential to identify and separate potential common drivers from event-specific dynamics, ultimately advancing our general understanding of the Antarctic sea ice and climate variability.</p><p>In this work, we aim at assessing the relative roles of atmospheric and oceanic processes in the summer SIE extremes and at disentangling the dynamic contributions to sea ice changes - such as wind-driven transport and divergence - from the thermodynamic part (freezing and melting). Furthermore, we identify the key regions at play during such events, the local dominant mechanisms, and the mutual interactions that result in a total maximum or minimum. The timing and persistence of the sea ice, atmosphere and ocean anomalies in the prior months are also examined to clarify the time scales of the processes during the melting season that lead to the summer extremes.</p><p>We use observations and reanalysis data over the satellite period (1979-2022) and compare our main findings with results obtained from an ocean-sea ice model (NEMO-LIM) driven by prescribed atmospheric fields from ERA5 on the same period. While the model may not be able to capture all the extremes in the observational record, examining its own variability provides valuable insights on the dynamics of the Antarctic sea ice extremes.</p><p> </p>