AWI glaciologist Dr Daniela Jansen and a team of British researchers have discovered a large rift in the Larsen C Ice Shelf in Antarctica which in time will dramatically reduce its area and could affect its stability.

This MODIS AQUA satellite image was acquired on 3rd December 2014. The Larsen C Ice Shelf, fringed by the Antarctic Peninsula mountains, is the smooth grey expanse filling the frame. The rapidly growing rift, highlighted in red, threatens to remove at least 10% of the area of the ice shelf. Credit: NASA
This MODIS AQUA satellite image was acquired on 3rd December 2014. The Larsen C Ice Shelf, fringed by the Antarctic Peninsula mountains, is the smooth grey expanse filling the frame. The rapidly growing rift, highlighted in red, threatens to remove at least 10% of the area of the ice shelf. Credit: NASA

Following the disintegrations in 1995 and 2002 of the Larsen A and Larsen B ice shelves on the Antarctic Peninsula, scientists have been keenly studying their much larger neighbour, the Larsen C Ice shelf, for evidence of change. In new research, submitted to the journal The Cryosphere, a team of researchers has highlighted a large rift which is growing rapidly and threatens to destabilise the whole ice shelf. "Rifting and calving of this magnitude is rare but not unusual.” 

The MIDAS project, funded by the Natural Environment Research Council, and including researchers from the Swansea University, the Alfred Wegener Institute in Germany, Aberystwyth University, and the British Antarctic Survey, used satellite data from NASA to detect an acceleration in the progress of a large rift during 2014.

Analysis of rift propagation using Landsat data. Background image, in which the rift is visible, is from 4 December 2014. Inset graph shows the development of rift length with respect to the 2010 tip position, and rift width at the 2010 tip position, measured from 15 Landsat images (crosses). Circles and labels on the map, and dotted red lines on the graph, show the positions of notable stages of rift development.
Analysis of rift propagation using Landsat data. Background image, in which the rift is visible, is from 4 December 2014. Inset graph shows the development of rift length with respect to the 2010 tip position, and rift width at the 2010 tip position, measured from 15 Landsat images (crosses). Circles and labels on the map, and dotted red lines on the graph, show the positions of notable stages of rift development.

When the ice eventually calves away, the ice shelf, with an area as big as the German federal state Lower Saxony, will be reduced by at least 10% to reach a new minimum. Crucially, using computer modelling, the team has shown that the resulting configuration may be unstable and at risk of further collapse. "The critical thing is that our model shows that even for the most modest of projected calving extents, the remaining ice is significantly less stable than at present," says first author Daniela Jansen. 

Ice shelves are permanent extensions of an ice sheet, several hundred meters thick, which float on the ocean fringing Antarctica. The Larsen C Ice Shelf is the fourth largest in the world.

The impact of an ice shelf collapse will not be felt immediately because the ice is already floating. If a significant area of the Larsen C Ice Shelf is lost, however, ice covering the mountains of the Antarctic Peninsula, currently held back by the ice shelf, will eventually be able to contribute much more quickly to sea level rise.

The development of this rift cannot be attributed directly to climate change, and may be part of a natural cycle of growth and calving. It is, however, the latest in a succession of evidence of ongoing erosion of ice shelves in the region. The Antarctic Peninsula is one of the fastest warming places on Earth and ice shelves are vulnerable to increased melting from both the atmosphere above, and the ocean below.

Antarctic_Peninsula

Source: AWI, Bremerhaven