Elephant Seals as Polar Ocean Explorers – Uncovering new sources of dense shelf water formation for Antarctic Bottom Water production and more
Speaker: Guy Williams (AUV / Sea Ice Specialist - ACE CRC, University of Tasmania)
Date: TUESDAY 7 August 2012, 11:00 AM
Venue: Theatrette, Australian Antarctic Division, 203 Channel Highway, KINGSTON, Tasmania
New oceanographic datasets from instrumented marine mammals have been addressing critical spatial and temporal gaps in our understanding of the polar oceans. This is particularly true south of the Antarctic continental shelf break in the coastal polynya regions that form dense shelf water for the production of Antarctic Bottom Water (AABW). In 2011, IMOS instrumented southern elephant seals (Mirounga leonina) from Davis Station and Kerguelen Island foraged extensively over the Prydz Bay/Cape Darnley region (65-80ºE) from February to October. Historically this eastern sector of the Weddell-Enderby Basin was identified from offshore bottom properties as having a local source of AABW. The dense shelf water source was speculated to be Prydz Bay, but never confirmed. Recent satellite analyses found that the Cape Darnley polynya, directly west of Prydz Bay, had the 2nd highest sea ice production around Antarctica. A subsequent Japanese IPY mooring program in 2008 revealed the first direct observations of new AABW production offshore from Cape Darnley, but could not sample the shelf region due to logistic constraints. The elephant seals deployed in 2011 have not only confirmed the presence of very High Salinity Shelf water west of Cape Darnley (up to 34.9), relative to dense shelf water from the Prydz Bay region, but have also captured very rare wintertime observations of the modified shelf water overflows to depths of ~1700m in wintertime. This talk will present these results and showcase other unique insights the IMOS seals are delivering on the East Antarctic margin of the southern ocean.