How changes in sea ice motion influence Antarctic sea ice extent

Till J.W. Wagner, University of North Carolina at Wilmington, Wilmington, NC, United States, Hassan C Mason, University of North Carolina at Wilmington, NC, United States and Ian Eisenman, University of California San Diego, Scripps Institution of Oceanography, La Jolla, United States
Antarctic sea ice extent has increased on average since 1979 despite increasing greenhouse gas concentrations and global warming. Most current comprehensive global climate models fail to capture this increase, instead simulating a shrinking Antarctic sea ice cover in simulations of the past 40 years. Changes in sea ice drift have been proposed in previous studies as a possible explanation for the observed sea ice expansion, but the complex relationship between ice motion and ice extent remains poorly understood. Here we investigate this relationship using an idealized latitudinally- and seasonally-varying model of global climate and sea ice that includes specified sea ice motion. Simulations with idealized ice velocity fields are used to probe the mechanisms by which changes in sea ice drift cause changes in sea ice extent and volume. Building on this, we specify in the model a spatially- and temporally-varying sea ice velocity based on satellite observations. The results are used to investigate the physical mechanisms by which changes in the sea ice drift velocity during recent decades have influenced the observed trend in Antarctic sea ice extent.