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We recovered the fifth and final mooring at dawn today, in near-perfect conditions. Recovering the moorings was always going to be the trickiest part of the voyage (except, perhaps, landing a party at Commonwealth Bay), so it is a great relief to have them all safely on board. The mooring string recovered this morning was 4 km long, with instruments at 6 depths plus a profiler measuring water properties and currents between 4000 and 4500 m depth. The aft part of the ship is now jammed with instruments. Five bright yellow foam spheres, each nearly 2 m in diameter, have sprouted like mushrooms on the trawl deck. In the Wet Lab, instruments are secured to every available bulkhead or tie down point and a shipping container on the trawl deck is full of the heavy duty glass balls used for flotation. Congratulations to the mooring team, deck crew and officers on a job well done (and thanks to Lance and Jan, who supplied ideal weather and ice conditions, respectively). We will use the mooring data to tackle several different science questions. The moored profilers will give us an unprecedented view of how the dense bottom water sinking around Antarctica varies in time, including before and after the calving of the Mertz Glacier Tongue. The measurements of current speed and direction will allow us for the first time to make accurate estimates of how much water is carried by the ocean currents in this part of Antarctica. Present estimates vary over a huge range: the moorings will allow us to pin this down. Finally, comparison of our new measurements to those made in the past will tell us how rapidly the ocean is changing and how these changes might influence climate, sea level rise and the carbon cycle.
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.