The IMOS Animal Tagging team returns to Macquarie Island after more than a decade and their new elephant seals research redefines Southern Ocean bathymetry.
This year we were fortunate to see the Integrated Marine Observing System (IMOS) Animal Tagging team return to Macquarie Island in the Southern Ocean for the first time in more than a decade to gather urgent oceanographic information.
Antarctic conditions are fundamental in understanding our global climate as they influence the pattern of global ocean circulation. Antarctic ocean conditions and the Antarctic circumpolar current are largely unknown due to challenges with accessibility and extreme environmental conditions.
The team enlisted the help of southern elephant seals (Mirounga leonina) fitted with Conductivity-Temperature Depth Satellite Relay Data Loggers (CTD-SRDLs) to record information at areas and depths otherwise inaccessible to humans. Their findings are made publicly accessible in their newly published paper Southern Ocean pinnipeds provide bathymetric insights on the East Antarctic continental shelf.
Image Credit – Rob Harcourt
Image Credit – Rob Harcourt
The expedition was a success, with the team tagging 21 seals that quickly went to work, reporting vital information up to 1km below the surface of the water and ice.
From more than 500,000 seal dives, Dr. Clive McMahon and his team were able to redefine bathymetry of the poorly studied Antarctic continental shelf. Their work showed that around one quarter of the 500,000 data points included dives to depths at least 220m deeper than the seafloor was previously defined by the International Bathymetric Chart of the Southern Ocean (IBCSO V2).
This invaluable information allowed the team to discover the presence of new bathymetric features such as the troughs off the Shackleton Ice Shelf and Underwood Glacier, and a deep canyon near the Vanderford Glacier that the researchers hope to name ‘Mirounga-Nuyina’ Canyon after their Mirounga seal subjects and the expedition vessel, the RSV Nuyina.
This expedition has been fundamental in understanding this poorly understood region and informing on pivotal Southern Ocean dynamics. This research and the recent discovery of the Mirounga-Nuyina Canyon will give invaluable insight into understanding how quickly the East Antarctic ice sheet is melting, and where warming water enters shelf cavities to measure melt rates.
The team notes the necessity for further study to improve our understanding and modelling of Antarctic coastal ocean processes and ice-sheet dynamics.
