Oral Presentation AMOS Annual Meeting and International Conference on Tropical Meteorology and Oceanography

The role of Southern Ocean cyclones on Antarctic sea ice variability (#39)

Dominic B Thorn 1 , Ian Simmonds 1 , Andrew D King 1
  1. School of Earth Sciences, University of Melbourne, Parkville, Victoria, Australia

Trends in Antarctic sea ice extent underwent a remarkable turnaround in 2016 after almost four decades of steady expansion. In spring of 2016, a dramatic decline was initiated, with sea ice extent reaching record monthly lows for a number of months in late 2016 and 2017, with annual sea ice extent reaching its lowest point in 2017. Recent research has shed light on the possible drivers of these interannual to decadal changes in Antarctic sea ice. In contrast, very little is known about sea ice variability on very short timescales. In particular, little is known about cyclone-sea ice interactions, despite the importance of cyclones for the maintenance of the general circulation of the Southern Hemisphere. Using an automated cyclone tracking scheme, we investigated the effect of cyclones in the Southern Ocean on Antarctic sea ice extent on daily timescales. Although there is considerable variability, it is shown that days with more numerous and intense cyclones correspond to days with increased growth in sea ice extent. Equally, days with fewer cyclones correspond with a contraction of the ice field. This effect can also be seen with sea ice area, suggesting that this effect is both dynamic and thermodynamic. We propose that wind-forced spreading of marginal ice creates areas of open water which rapidly refreeze to form new ice.