Dr Mike Williams, NIWA
Wednesday 7th December, 12:00 – 12:50 pm
Old IASOS seminar room, Room 205, Centenary building
Abstract:
The base of Antarctica’s ice shelves provide a direct connection between the world’s oceans and the Antarctic ice sheet. A relationship that has traditionally been viewed through the prism of the oceans impact of the ice shelf. Over the past decade McMurdo Sound, in the southwestern Ross Sea, Antarctica has been used as a natural laboratory for understanding interactions between sea ice, oceans and the adjacent Ross and McMurdo Ice Shelves. McMurdo Sound is a conduit for flow between the seasonally-open ocean of the Ross Sea, and the vast cavity beneath the Ross and McMurdo Ice Shelves, allowing the sound to “see” and be influenced by signals from tidal to seasonal time scales. First and multi-year ice in the sound has acted to form a proxy ice shelf cavity, which has allowed us to easily access the ice-water interface. Our research has shown that instead of the traditional view there are complex feedbacks between sea ice, ice shelves and oceans. The ice shelf cools the ocean generating Ice Shelf Water, and supercooled water (up to 50 mK). This cold water in turn augments sea ice production and the formation of platelet ice. Variations in sea ice modify the ocean through water mass formation processes and localized diffusive mixing. In addition over the 2010-11 season we have been able to expand our observational program to the front of the Ross Ice Shelf, early results from here also show complex feedback relationships, in particular between the Ross Sea polynya and the currents under the ice shelf.