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Weddell seals exploring the deep, forever changing Antarctic marine science

It is in the waters that surround Antarctica that the global currents linking all of the World’s oceans are born. Understanding how, where, and when these currents are formed is central to understanding global climate and how that has and continues to change. However, gathering the vital physical information needed to study current formation is not easy and in the deep south is almost impossible in winter when most of the Southern Ocean is a vast impenetrable ice-sheet.

It is this vast ice world and the seas below it that are home to a new generation of super marine scientists – the southern seals. By carrying small data loggers that transmit information to satellites, seals have joined the ranks of the Pasteur and Steven Hawking. While they may not wear white coats, they are helping drive new discoveries The information encoded by these loggers tells us not only what the seals are doing as they swim beneath the ice, but how the oceans are changing. They do this by collecting the very information; depth, water temperature and salinity that we need to describe ocean structure and function. Moreover, because the seals are able to collect this information at a time and place– the harsh Antarctic winter- when most of this area is inaccessible to conventional sampling platforms such as ship or ocean buoys, this information is revolutionising our understanding of the oceans.

Weddell seals inhabit some of the coldest, darkest waters known, deep within the Ross Sea ice. Weddell seals dive very deep below the surface, to nearly 1000m and for more than an hour. As seals are mammals, like us they must surface to breathe and when they surface they can transmit information to circulating satellites. Because Weddell seals inhabit the fast-ice, as they swim up and down below the ice they can collect this high quality oceanographic information on the structure of the water column, right through autumn and winter into early spring. While some traverse wide areas across the Ross Sea, providing broad spatial structure, other Weddell seals appear to act like oceanographic moorings, at a fraction of the cost. This happens when a seal stays in the same area for a long period of time- days or weeks, feeding in a single spot. As they dive to the bottom and back over and over, they provide multiple casts of the water structure in that area. This can allow very precise measurements of ice formation over winter, and of ice melt in spring, information impossible to gather in any other way and advancing our understanding of these crucial ice processes.

As part of a University of Canterbury project lead by Dr Regina Eisert (Gateway Antarctica) and supported by Antarctica New Zealand, an international team of researchers attached satellite-linked Conductively, Temperature and Depth recorders to 10 Weddell seals at the New Zealand station Scott Base last February. Weekly images tracking the seals have been transmitted back during the winter months tracking the activities of the seals. The recorders will be recovered in November when the seals return to the Scott Base area to pup.

The project is part of a larger IMOS Seals as Oceanographers Program which is part of the Australian government’s Integrated Marine Observing System (IMOS) that has been collecting data with seals since 2008. In collaboration with French, American, British and Norwegian and now New Zealand programs, these seals now collect over 70 % of oceanographic profiles south of 60°S. These animals have altered our understanding of the Southern Ocean (the ocean around Antarctica) and its influence on the world’s climate.  

SealTracking
The tracks of the eight female Weddell seals being studied in the Ross Sea from February 2014 to present.

Regina Eisert; Gateway Antarctica – Centre for Antarctic Studies and Research,

University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand

Clive McMahon; Sydney Institute of Marine Science, 19 Chowder Bay Road, Mosman NSW, 2088, Australia

Robert Harcourt; Facility Leader, Australian Animal Tagging & Monitoring System, Department of Biological Sciences, Macquarie University, Sydney NSW 2109, Australia

Mark Hindell; Institute for Marine and Antarctic Studies
Private Bag 129, Hobart Tasmania,700,1 Australia