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We are presently sampling in a deep (900 m) hole in Watt Bay, the next bay to the east from Commonwealth Bay. Overnight we completed a line of CTD stations crossing a deep depression on the continental shelf, and then moved east to the huge iceberg B9-B. We have completed further stations (12 in the last 24 hours) between B9-B and the Antarctic continent. This area is the location of an active polynya in winter. A polynya is an area within the sea ice pack that remains free of ice all winter. Because there is no cover of sea ice to insulate the ocean, the ocean loses huge amounts of heat to the cold winter air and starts to freeze. But as soon as the ice crystals form, they are blown down-wind by the strong katabatic winds flowing off the continent in this region, so the area remains free of sea ice. We’re in the region Mawson called “The Home of the Blizzard” and cold air roars off the continent in winter to freeze the ocean. When the ocean freezes, the salt in the sea water gets left behind and makes the water beneath the ice saltier; the colder and saltier the water gets, the heavier it is. A major focus of this voyage is on how this process works, how much of this dense water is formed here, and how things might have changed as a result of the calving of the Mertz Glacier. We’ve done very well to get as far east on the inshore side of the iceberg B9-B as we have. While the weather has been OK for working (winds of 30-40 knots for the last 18 hours), I don’t think we’ve seen the sun for a week or more. Last night the fog and blowing snow lifted enough to reveal amazing scenes of drift blowing off the top of numerous icebergs, the continent to starboard and an island-sized iceberg to port, glowing under a scudding sky.
REGARDS: Steve, Fred and Penny
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.