A Tale of Two Glaciers

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By George Hale, IceBridge Science Outreach Coordinator

The glaciers that flow out of the Greenland Ice Sheet move tons of ice out of the ice sheet each year. Many of these rivers of ice meet the ocean where relatively warm currents weaken the glacier’s terminus, causing icebergs to break off in a process known as calving. This forms a cliff-like feature called a calving front, where icebergs break off and fall into the sea.

Jakobshavn Glacier calving front

The calving front of Jakobshavn Glacier and calved icebergs as it appeared in April 2012. Credit: NASA / Jefferson Beck

The presence of these currents is part of the reason why ocean-terminating glaciers are so dynamic. In contrast, land-terminating glaciers move more slowly and lose mass through melting on the surface rather than calving.

On a recent IceBridge flight, instruments aboard the P-3 captured views of two very different glaciers in east Greenland, the De Geer and Wahlenberg glaciers. The images below show the difference between a dynamic, ocean-terminating glacier (De Geer) and a land-terminating glacier that is essentially dormant (Wahlenberg).

DMS mosaic of glacier calving frontAbove is an image mosaic from the Digital Mapping System aboard the NASA P-3 showing the terminus of the De Geer Glacier in east Greenland. The heavily crevassed end of the glacier is to the left of the image and large icebergs are to the right. Credit: NASA / DMS / Eric Fraim

ATM plot of De Geer Glacier

This image, is a plot showing data on De Geer Glacier from the Airborne Topographic Mapper instrument, a laser altimeter that measures ice surface elevation. Here we see the differences in elevation between before and after the calving front and in crevasses on the surface.

ATM plot of Wahlenberg Glacier

In contrast, this ATM plot of the land-terminating Wahlenberg Glacier shows a smoother surface and more gradual change in elevation along its end.

 

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