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CTD sampling of waters from the sea-surface to the seabed continues around the clock for the CASO (Climate of Antarctica and the Southern Ocean) part of V3. CASO is a major multinational project for the International Polar Year involving scientists from 18 nations and is led by Australia. CASO will provide the first circumpolar snapshot of the physical and biogeochemical state of the Southern Ocean as a benchmark for the assessment of past and future change. It will also demonstrate the feasibility of a sustained Southern Ocean observing system. CASO will continue on V6, during which a transect from Hobart to Antarctica will be sampled. On V3, CASO is focused on the region close to the Antarctic continental shelf and the fate of cold, dense ‘Antarctic Bottom Water’ from the Mertz Polynya. This region is one of the few places in the ocean where surface waters are made sufficiently dense to allow them to sink to the deep ocean. This transfer of water from the surface to the abyss is part of a global system of ocean currents known as the overturning or thermohaline circulation, which strongly influences Earth's climate. Our measurements on V3 are aimed at understanding how the Antarctic contribution to this global current system works and whether it is changing. We are presently re-occupying sites first measured on Aurora Australis in the 1994-5 season and are making excellent progress in unusually calm conditions. Last night we sampled the northern-most site, nearly 250 miles from the continent and are now heading east to sample some of the deepest sites which are about 4 kilometres from the surface to the seabed. Being this far north, we experienced our first, brief nightfall for the year last night. Regards, Martin and Sarah.
Map
A map showing Australia and Antarctica. The map shows the journey of one voyage that has occured in the season, with each route highlighted in a distinct colour.