Massive Iceberg – 10 Times the Size of San Francisco – Breaks Off Brunt Ice Shelf in Antarctica

A giant iceberg, approximately 1.5 times the size of Greater Paris [or about 10 times the size of San Francisco], broke off from the northern section of Antarctica’s Brunt Ice Shelf on Friday 26th February. New radar images, captured by the Copernicus Sentinel-1 mission, show the 1270 sq km iceberg breaking free and moving away rapidly from the floating ice shelf.

Glaciologists have been closely monitoring the many cracks and chasms that have formed in the 150 m thick Brunt Ice Shelf over the past years. In late-2019, a new crack was spotted in the portion of the ice shelf north of the McDonald Ice Rumples, heading towards another large crack near the Stancomb-Wills Glacier Tongue.

This latest rift was closely monitored by satellite imagery, as it was seen quickly cutting across the ice shelf. Recent ice surface velocity data derived from Sentinel-1 data indicated the region north of the new crack to be the most unstable – moving around 5 m per day. Then, in the early hours of Friday 26th, the newer crack widened rapidly before finally breaking free from the rest of the floating ice shelf.

ESA’s Mark Drinkwater said, “Although the calving of the new berg was expected and forecasted some weeks ago, watching such remote events unfold is still captivating. Over the following weeks and months, the iceberg could be entrained in the swift south-westerly flowing coastal current, run aground or cause further damage by bumping into the southern Brunt Ice Shelf. So we will be carefully monitoring the situation using data provided by the Copernicus Sentinel-1 mission.”

Although currently unnamed, the iceberg has been informally dubbed ‘A-74’. 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.

The calving does not pose a threat to the presently unmanned British Antarctic Survey’s Halley VI Research Station, which was re-positioned in 2017 to a more secure location after the ice shelf was deemed unsafe.

Routine monitoring by satellites offer unprecedented views of events happening in remote regions like Antarctica, and how ice shelves manage to retain their structural integrity in response to changes in ice dynamics, air and ocean temperatures. The Copernicus Sentinel-1 mission carries radar, which can return images regardless of day or night and this allows us year-round viewing, which is especially important through the long, dark, austral winter months.