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Science

Ungrounded Glaciers Are Unpredictable

A new study shows that glaciers that lose their attachment to the seafloor and begin floating start behaving very erratically.

The study, led by Scripps Institution of Oceanography, UC San Diego glaciologist Fabian Walter and colleagues, to be published in the journal Geophysical Research Letters, present the first detailed observations of a glacier detaching from the seafloor and becoming a floating glacier.

“We’re seeing more tidewater glaciers retreat,” Walter said. “As they retreat, they thin and that increases the likelihood that they’ll come afloat.”

Iceberg calving is one of the least understood processes in ice mass loss and, as a result, sea level rise, as icebergs are thought to be a large contributor to the increase in sea levels. Calving occurs when fractures in the ice meet up and cause a piece of ice to become entirely fragmented from the larger glacier, causing it to fall into the ocean as seen below.

[youtube=http://www.youtube.com/v/kD88ksW5srk&hl=en_US&fs=1]

Columbia Glacier, one of Alaska’s many tidewater glaciers and one of the fastest receding glaciers in the world, is currently detaching from the seafloor beneath it. All Alaskan tidewater glaciers – glaciers that flow directly into the ocean, ending at a cliff in the sea where icebergs are formed – were believed to be resting on the ocean floor and unable to float without totally disintegrating.

That being said, Columbia Glacier developed a floating extension in 2007 that has continued to exist despite researchers theories. The Scripps led research team believe that this extension has been caused and persisted by the speed at which the glacier is retreating, some 4 kilometres (2.49 miles) since 2004 and nearly 20 kilometres (12.43 miles) since 1980.

The research team installed a seismometer on Columbia Glacier to measure seismic waves that are produced in geologic formations, including earthquakes, landslides, and most importantly, glacier calving. They collected and studied data from 2004-2005 and 2008-2009 that allowed them to compare the glacier’s activity before and after it began floating.

This study should help scientists begin to analyse the mechanics of the calving process in both floating and grounded glaciers, as well as ice shelves, and allow them to better understand and predict iceberg production from glaciers and ice sheets like Antarctica.

From these predictions will come the all important data to help accurately estimate global sea level rise in the coming decades.

Source: University of California – San Diego

Image Source: A tea but no e via Flickr




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