Measurements in Atka Bay

Atka Bay +++ 70° 32’ S, 08° 04’ W +++ -1.9°C, Sunshine and slightly snowing +++
01 January 2015
(by Sandra Schwegmann,
translation: Ina Lefering)

Since 6 days, we are located only a few kilometres from Neumayer III, the German research station in Antarctica, -­‐  just outside Atka Bay. RV Polarstern resupplies Neumayer III with food, scientific and technical equipment as well as fuel, as always around this time of year. But this year, it seems to be particularly difficult to fulfil its task. 5km of dense sea ice is blocking the way to the pier on the shelf ice where all goods are supposed to be unloaded. This solid sea ice cover is called fast ice, and is free of any cracks, which would make it easier to break it.

In the meantime, the sea ice physics team took the opportunity to study this area of thick sea ice in Atka Bay. The measurements are part of the sea ice program (AFIN), which is executed by the overwinterers at Neumayer station. During one of the ice stations, our team studied the surface of the ice from underneath with their ROV (remotely operated vehicle), called Siri. They observed a lot of platelet ice, a special type of sea ice which forms when shelf ice melts from below. This results in an upwelling of lighter, fresh water which then cools and forms new ice platelets. These platelets accumulate underneath the sea ice just, off the shelf ice edge. We observed a layer of platelet ice with a thickness of 1 to 3 m, in addition to the ‘standard’ sea ice thickness of about 3 to 5 m. Together with a layer of 1m snow on top, this forms a pretty thick ice cover.

Our stay in Atka Bay was also used to study sea ice thickness on various scales. This included the basic drilling method but also electromagnetic measurements with an instrument that is towed over the ice on a sledge (GEM). The sledge is thereby pulled by either scientists or a snow scooter. A total of 45 km of ice profiles have been acquired in Atka Bay. The sledge transects repeated the electromagnetic measurements which had previously been conducted from a helicopter with an instrument called EM-­‐Bird. The collected data can now be used to ground-truth the different methods and platforms. Both techniques (sledge and helicopter based) measure ice thickness on different scales and will be merged in the end to provide accurate estimates of ice thicknesses.

Happy New Year to all our readers!