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Calving glaciers give up their secrets to C3W researchers

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E-mail: vsj@aber.ac.uk

 

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Many of the world’s glaciers contribute to sea-level rise through ice breaking off into the ocean in a process called ‘calving’. However, the way ice calves from a glacier, which is poorly understood, may not occur in the way previously thought, according to a study published this week in Nature Geoscience by C3W scientists from Swansea University.

Over the summers of 2010 and 2011, Timothy James and colleagues from Swansea’s Glaciology Group monitored the front of a large glacier called Helheim on Greenland’s southeast coast using consumer-grade cameras and specialised mapping methods to produce daily 3D models of the glacier as it flowed into the ocean.

During the study, the authors recorded a spectacular calving event at Helheim glacier with time-lapse photography. In the video (above), the glacier flows downhill from the ice sheet towards the ocean at the right hand side of the frame. After a crack forms along the front of the glacier, a large iceberg begins to calve through a backward rotation eventually disintegrating into the already ice- clogged water. Helheim glacier is one of the largest glaciers in southeast Greenland. It is over 200 km long, 6 km wide and can flow as fast as 30 m a day.
They found that large icebergs, which can be over one cubic kilometre in size, form as a result of the bending of the glacier as it tries to float and the widening of crevasses from the glacier’s base. The study highlights that surface crevasses, often the focus for predicting when glaciers calve, are less important for large glaciers than previously thought. James, who led the study said:

“This is an important finding because computer models that try to predict glacier behaviour currently do not account for this way of losing glacier ice to the sea.”

Understanding glacier behaviour is very important for predicting how much and how fast sea-level will rise in a warming climate and measurements like these will help to improve these predictions.

This research received support from The Leverhulme Trust, the Climate Change Consortium for Wales (C3W) and the Royal Geographical Society (with IBG), the European Union 7th Framework Programme, and the Welsh Institute for Sustainable Environments (WISE).

The authors are part of the Swansea University’s Glaciology Group, world leaders in understanding the processes that drive changes in the earth’s ice stores and measuring past and future glacier contributions to sea-level rise.

Buoyant flexure and basal crevassing in dynamic mass loss at Helheim Glacier Timothy D. James*, Tavi Murray, Nick Selmes, Kilian Scharrer and Martin O’Leary Nature Geoscience, published online 13 July 2014. Abstract (http://dx.doi.org/10.1038/ngeo2204)

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