13Jul2020

The 100km-long "A-68" iceberg, which calved from Antarctica in 2017, is now 1000km away from birthplace and shrinking.

When it calved, A-68 was about twice the size of Luxembourg and one of the largest icebergs on record, changing the outline of the Antarctic Peninsula forever. Despite its size, however, it is remarkably thin, just a couple of hundred metres thick.

Over the last three years, satellite missions such as the European Space Agency's Copernicus Sentinel-1 have been used to track the berg as it drifted in the Southern Ocean. For the first two years, it remained close to its parent ice sheet, impeded by sea ice.

However, it lost a chunk of ice almost immediately after being calved, resulting in it being renamed A-68A, and its offspring became A-68B. More recently, in April 2020, A-68A lost another chunk: A-68C.

Antarctic icebergs are named from the Antarctic quadrant in which they were originally sighted, then a sequential number, then, if the iceberg breaks, a sequential letter. Although A-68A is a relatively thin iceberg, it has held together reasonably well, but satellites will be key to monitoring how it changes in open waters.

Pace of drift increasing

Captured by the Copernicus Sentinel-1 radar mission, the image above shows the berg on 5 July 2020, a few days before its third birthday. Satellites carrying radar continue to deliver images regardless of the dark and bad weather, which is indispensable when monitoring the remote polar regions which are shrouded in darkness during the winter months.

Other maps available from ESA show the different positions of A-68A during its three-year journey. The map not only highlights how long it remained close to the Larsen C ice sheet, but how, over the past year or so, its pace of drift has increased considerably. The map also includes historic iceberg tracks, based on data from a number of satellites including ESAs ERS-1 and ERS-2, and shows that A-68A is following this well-trodden path.

Link:

Copernicus Sentinel-1 tracks progress of giant iceberg over three years - Optics.org