Glacial 'aftershock' spawns Antarctic iceberg the size of Manhattan

Chiara Palazzo

Antarctica's rapidly melting Pine Island Glacier has shed an iceberg the size of Manhattan, the latest evidence of the ice shelf’s fragility.

Nasa released photographs showing the block of ice separating from the southwest coast of the continent taken between January 26 and January 31.

The sequence, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on Nasa’s Terra satellite, shows the berg when it first broke and then as it drifts in the bay.

According to Ian Howat, a glaciologist at Ohio State University, the event was about 10 times smaller than in July 2015, when a 30-kilometre-long (20-mile) rift developed below the ice surface, then broke through and calved an iceberg spanning 583 square kilometers (225 square miles).

“I think this event is the calving equivalent of an ‘aftershock’ following the much bigger event,” Mr Howat said. “Apparently, there are weaknesses in the ice shelf - just inland of the rift that caused the 2015 calving - that are resulting in these smaller breaks.”

Pine Island Glacier

Scientists have observed other small rifts in the glacier which are predicted to bring more calving in the near future. 

“Such ‘rapid fire’ calving does appear to be unusual for this glacier,” Mr Howat said. But the phenomenon “fits into the larger picture of basal crevasses in the centre of the ice shelf being eroded by warm ocean water, causing the ice shelf to break from the inside out.”

Scientists have been closely monitoring Pine Island, one of the main glaciers responsible for moving ice from the interior of the West Antarctic Ice Sheet to the ocean, and its connection to rising sea levels.

They have observed an increase in the speed of the loss of ice which ultimately would contribute to sea level rise.