Sea ice production variability in Antarctic coastal polynyas

Abstract

AbstractEnhanced sea ice production (SIP) in Antarctic coastal polynyas forms dense shelf water (DSW), leading to Antarctic Bottom Water (AABW) formation that ultimately drives the lower limb of the meridional overturning circulation. Some studies suggest that the variability of SIP in Antarctic coastal polynyas is driven by the influence of atmospheric forcing, i.e., surface winds and air temperature. Our previous mapping of SIP in 13 major Antarctic coastal polynyas from 1992 to 2007, using a heat flux calculation with ice thickness data derived from satellite data, is extended here to examine the interannual and seasonal variability of SIP from 1992 to 2013. The interannual variability of total ice production correlates more strongly with polynya extent than with atmospheric forcing, with the exception of the Shackleton Polynya, which correlates well with wind. There is no coherent signal in the interannual variability between the major Antarctic coastal polynyas. We find that stochastic changes to the coastal “icescape,” i.e., ice shelves, floating glaciers, fast ice, together with offshore first‐year ice, are also important factors driving SIP variability on multiyear time scales. Both the Ross Ice Shelf Polynya and Mertz Glacier Polynya experienced a significant reduction in SIP due to calving events and the repositioning of icebergs and fast ice. Our results also show opposing trends between polynya‐based SIP and sea ice extent in key regions of Antarctic sea ice change. Close monitoring of coastal icescape dynamics and change is essential to better understand the long‐term impact of coastal polynya variability and its influence on regional AABW production.