Approximately two years ago, a huge rift was detected on the Larsen C Ice Shelf on the eastside of the Antarctic Peninsula. Now, scientists have discovered that the crack has increased rapidly and only another 20 km of ice are left to crack before one of the largest icebergs ever recorded will be born. Satellite observations from December 2016 suggest that the iceberg with an area of up to 5,000 km² is likely to calve soon.

Tabular icebergs are born when pieces of an ice shelf break off and start drifting in the adjacent ocean currents. Ice shelves themselves are tongues of several glaciers flowing together into the coastal areas of Antarctica. Picture: Michael Wenger
Tabular icebergs are born when pieces of an ice shelf break off and start drifting in the adjacent ocean currents. Ice shelves themselves are tongues of several glaciers flowing together into the coastal areas of Antarctica. Picture: Michael Wenger

British Antarctic Survey researchers have a long running research program to monitor ice shelves from both above and below to understand the causes and implications of the rapid changes observed in the region. During the current Antarctic field season, a glaciology research team has been on Larsen C using seismic techniques to survey the seafloor beneath the ice shelf.  Because a break up looks likely the team has not set up camp on the ice as usual.  Instead they have made field trips by twin otter aircraft supported from Rothera Research Station. Scientists from Swansea University are on the forefront of the MIDAS project, which investigates the impact of melt on ice shelf dynamics and stability.

A field team of scientists on the Larsen C Shelf with a Twin Otter plane in the back. Due to the looming break off, no camp could be established on the shelf. Picture: Peter Bucktrout, BAS
A field team of scientists on the Larsen C Shelf with a Twin Otter plane in the back. Due to the looming break off, no camp could be established on the shelf. Picture: Peter Bucktrout, BAS

Ice shelves in normal situations produce an iceberg every few decades. There is not enough information to know whether the expected calving event on Larsen C is an effect of climate change or not, although there is good scientific evidence that climate change has caused thinning of the ice shelf. Once the iceberg has calved the big question is whether the entire ice sheet may collapse. This is something that British Antarctic Survey teams have been monitoring and why glaciologists were deployed to work on Larsen C in the past few weeks. Glaciologist Professor David Vaughan OBE, Director of Science at British Antarctic Survey, said, “The calving of this large iceberg could be the first step of the collapse of Larsen C ice shelf, which would result in the disintegration of a huge area of ice into a number of icebergs and smaller fragments. Because of the uncertainty surrounding the stability of the Larsen C ice shelf, we chose not to camp on the ice this season.  Researchers can now only do day trips from our Rothera Research Station with an aircraft nearby on standby.”

The crack which was detected and described in a 2015 publication by an international research team stretches along the northern part of the shelf and has been monitored since 2013. However, in the last few months the rift advanced 18 km instead of the proposed 2.5 km per year. Picture: NASA
The crack which was detected and described in a 2015 publication by an international research team stretches along the northern part of the shelf and has been monitored since 2013. However, in the last few months the rift advanced 18 km instead of the proposed 2.5 km per year. Picture: NASA

Dr Andrew Fleming, Remote Sensing Manager at British Antarctic Survey, said, “We use regular satellite images provided by the European Sentinel satellites to monitor cracks in the ice shelf. These images are perfect for following these changes since they provide detailed information, day or night and regardless of cloud cover.” When the ice shelf calves, the Larsen C Ice shelf will loose approximately 10 percent of its total area. The implications and impact on the shelf stability, the sea level and other factors cannot be determined yet.

The map shows the Larsen C Ice shelf and colored lines display the rift which eventually will lead to the calving of an ice berg with an area of approximately 5’000 km2, a quarter of the size of Wales. Map: A. Luckman, Swansea University
The map shows the Larsen C Ice shelf and colored lines display the rift which eventually will lead to the calving of an ice berg with an area of approximately 5’000 km2, a quarter of the size of Wales. Map: A. Luckman, Swansea University

Source: British Antarctic Survey / NASA