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Increasingly Rapid Greenland Ice Melting May be Connected to Warming Fjords

February 21, 2010

In the last several years, one of the key things learned is that our previous assumptions about the time it would take to melt enormous sheets of ice — say, for example, Greenland, or the rest of the Arctic — was wildly underestimated.

One of the key components of increased melting is the presence of water, particularly in cracks in the ice.

There are multiple reasons for this. Cracks in the ice allow for warmer temperatures to reach down into the ice, into areas that otherwise would be well blocked and insulated from warmer temperatures.  Then the melting is further accelerated because ice melts much faster in water than in air. Increased pressure from water build up (from, for example, small lakes forming atop of ice sheets, with water permeating deeply through cracks underneath) also accelerates the process.

In Greenland, a team of scientists, led by Fiammetta Straneo of the Woods Hole Institute, are also looking at the role that continually replenishing warmer water may be playing in the melting of glaciers at the ocean ice interface. From the journal Nature Geoscience:

Here we present oceanographic data collected in Sermilik Fjord, East Greenland, by ship in summer 2008 and from moorings. Our data reveal the presence of subtropical waters throughout the fjord. These waters are continuously replenished through a wind-driven exchange with the shelf, where they are present all year. The temperature and renewal of these waters indicate that they currently cause enhanced submarine melting at the glacier terminus.

This has been offered as one possible explanation for the increasingly rapid melting of the outer ice shelf areas.   It would also seem to be dependent up ocean currents that bring warmer waters up from the south to the shelf of Greenland.  Ocean patterns are changing, and while many effects of increased atmospheric forcing are starting to accelerate, it is conceivable, it seems, that this process could slow if the ocean currents that bring up warmer tropic waters, were to shut off.

A Fjord is a cut area left by a glacier via abrasion, forming a valley that fills with water.  A big part of the rapidly accelerating warming, the scientists theorize, is also due to shifting wind patters that is bringing in (relatively) warmer water (perhaps 38 to 40 degrees Fahrenheit.)  The original source of the water is of course warmth brought up from further south as part of the ocean’s circulatory patterns.

What the scientists theorize is that some of the increased melting is due to a combination of ocean and atmospheric changes; increasing shore-ward winds drive the warmer waters off the continental shelf into the Fjords, where the waters then lead to increased melting (which would cool those waters) with the water being constantly replenished by waters from the warmer continental shelf.

It is just a theory. But the Woods Hole team, as noted above, was able to at least test the theory and confirm the continued replenishment of continental shelf (warmer) water in the fjords at the ocean/ice terminus.