Thursday 13 May 2010, 11:30 AM (AAD Theatrette)

Roger Stevens

University of Tasmania

Untangling processes of ice-edge movements in the Southern Ocean

Abstract: The location of the Antarctic sea ice edge is determined by the interplay between the dynamic and thermodynamic processes at the ocean-ice-atmosphere interface. This session will present results from a numerical model which we use to investigate the relative contributions of the physical processes impacting on the ice edge. Firstly, results of the ice-edge location from an 11 year simulation of the ice model have been verified against satellite observations from 1998 – 2008. We find that the relative contributions to the modelled ice-edge advance/retreat vary as the ice edge moves north/south during the seasons. In autumn the advance of the sea ice edge is primarily due to thermodynamic processes with substantial dynamic contributions only found between 60º-70º E and 310º-340º E. In these regions, winds with a southerly component not only cause northward ice advection but also induce thermodynamic growth of new ice, which occurs at the highest rate just southward of the 15% ice concentration contour. As the ice moves equatorward into warmer water it melts, consequently pushing the ocean mixed layer freezing point contour northwards. The melting processes become dominant as the year progresses through spring to ice decay. The Southern Ocean summer produces broad bands of thin ice, especially in the Weddell and Ross seas, accompanied by seasonally high fresh-water fluxes.

About the speaker: Roger Stevens is a PhD candidate within the QMS program of IMAS at the University of Tasmania investigating the dynamic and thermodynamic processes impacting on the sea ice edge with the use of a numerical model. His supervisors are Dr Petra Heil (AAD, ACE), Dr Kelvin Michael (IMAS, ACE) and Dr Steve Rintoul (CSIRO, ACE). Roger completed a Masters by research in the area of artificial life at the computing school at Griffith University and his undergraduate degree was in mechanical engineering at the University of Queensland.