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We have not seen any icebergs or bergy bits for the last 12 or 18 hours, so we may now be far enough north to well and truly left the ice. In the last 24 hours we have completed another four CTD stations, pumped water from the surface and the ‘deep chlorophyll maximum’ for filtering, and deployed another Argo float. We have been receiving the first few profiles from the special Argo floats deployed when we were in the Mertz area. These floats are made more rugged to survive encounters with sea ice. In order to keep them in the area of the Mertz polynya (or what’s left of it), we have programmed them to descend and sit on the sea floor between profiles, rather than drift with the ocean currents. We hope in this way to measure how the water properties in this region are changing throughout the year, and not just when we are there in a ship. The floats have already shown some interesting things, including an outflow of ‘super-cooled’ melt-water from the base of the Mertz Glacier. The freezing point of sea water depends on the pressure. The floats have measured temperatures less than -2.1C, well below the freezing point at the sea surface. The cold temperatures tell us that relatively warm ocean waters have been melting the floating glacial ice from below, at depths greater than about 300 m.
Regards, Steve and Barbara
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.