Larsen C iceberg accelerates ahead of calving

by
Project MIDAS

Comparison of speeds between Sentinel-1 image mosaics in early and late June 2017. The early mosaic combines displacements on the inner shelf measured between 6th and 12th June with similar ones on the outer shelf measured between 3rd and 15th June. The recent mosaic combines inner shelf displacements up to 24th June with outer shelf displacements only 3 days later highlighting a significant acceleration over those three days.

In another sign that the iceberg calving is imminent, the soon-to-be-iceberg part of Larsen C Ice Shelf has tripled in speed to more than ten meters per day between 24th and 27th June 2017. The iceberg remains attached to the ice shelf, but its outer end is moving at the highest speed ever recorded on this ice shelf. We still can’t tell when calving will occur - it could be hours, days or weeks - but this is a notable departure from previous observations.

Comparison of speeds between Sentinel-1 image mosaics in early and late June 2017. The early mosaic combines displacements on the inner shelf measured between 6th and 12th June with similar ones on the outer shelf measured between 3rd and 15th June. The recent mosaic combines inner shelf displacements up to 24th June with outer shelf displacements only 3 days later highlighting a significant acceleration over those three days.

The most recent observations on 27th June do not cover the rift tip, but a low resolution Sentinel-1 image of just after midnight on 28th June shows clearly that the iceberg remains attached to the ice shelf at its western end - for now.

When it calves, the Larsen C Ice Shelf will lose more than 10% of its area to leave the ice front at its most retreated position ever recorded; this event will fundamentally change the landscape of the Antarctic Peninsula. We have previously shown that the new configuration will be less stable than it was prior to the rift, and that Larsen C may eventually follow the example of its neighbour Larsen B, which disintegrated in 2002 following a similar rift-induced calving event.