Cyclonic circulation in Amundsen Sea Polynya and its inter-annual variation.

Abstract

Amundsen Sea recently attracted particular interest, because it is most rapidly warming in the Western Antarctic (WA). The strong seasonal cyclonic eddy in Amundsen Sea Polynya was found from the shipborne measurements LADCP data during 2010/2011 and 2011/2012 IBRV Araon expeditions. Also this ocean surface circulation was reconfirmed from the OSCAR (Ocean Surface Current Analysis) what calculated from quasi-linear and steady flow momentum equations using sea surface height, surface vector wind and sea surface temperature obtained from satellites. A polynya larger than 200 km in diameters formed effect of wind and ocean currents in front of DIS (Dotson Ice Shelf) during austral summer season. The strong upwelling induced by latitudinal varying of westward wind velocities and sea ice condition at the northern boundary of Polynya. Such upwelling generates the cyclonic eddy that maximum current speed is larger than 10 cm s-1. However, during austral winter, polynya was almost closed, so upwelling is reduced compared to the summer season and disappear the cyclonic eddy in front of DIS. This seasonal variation in the strong ocean surface circulation may be influence on oceanic heat transport to ice selves. Also, such cyclonic circulation in front of DIS shows the inter-annual variation depended on the variability of sea ice condition and local wind pattern during austral summer.