A giant crack 29km long, 73m wide and 58m deep is splitting the Pine Island ice shelf, Nasa reports. Scientists said it is widening by 1.8m each day.

The iceberg expected to calve off will have an area of about 900sq km. The crack was found during Nasa’s third annual airborne survey to measure and map changes in Antarctic glaciers. The Pine Island ice shelf is known to periodically calve off large icebergs, most recently in 2007.

Although the crack is unrelated to climate change, the larger glacier that the ice shelf is part of shows what Nasa calls “one of the most significant climate change response trends” worldwide.

The glacier lost 46 gigatonnes of mass last year, the equivalent of 46 trillion litres of water. That’s a huge increase in its melt rate. In 2005, it lost just six gigatonnes.