Open water ahead as SA Agulhas heads south for Antarctica

Dec 8, 2004
Author: Ian Hunter - South African Weather Service

The SA Agulhas is due to leave Cape Town on her annual relief voyage to the South African Antarctic Base on 14 December. Last year the higher latitude weather buoy deployments had to be shifted northwards because of the unusually large area of pack ice still remaining in the eastern Weddell Sea.

Consider the attached comparison of early December sea ice cover, 2003 versus current. This information comes courtesy of the Marine Modelling and Analysis Branch of the US National Weather Service. The imagery gives a good overall representation of actual sea ice concentrations - red for low, blue for high.

What is of particular interest is the large area of relatively open water on the SA Agulhas’ intended track at about 67S (centre right of image). This is what is known as a polyna – an area of reduced ice concentration or open water surrounded by pack ice, which often forms annually in roughly the same location. In December 2003 this feature was considerably smaller. Further comparison shows lower ice concentrations along the coast where the SA Agulhas will construct a ramp into the shelf ice for unloading her cargo (see attached photo, courtesy of Smit Marine SA).

Hopefully this year’s voyage will be significantly less affected by the pack ice – and the buoy deployment positions won’t have to be adjusted to avoid offloading them on to solid ice!

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