From: Andy Soos, ENN
Published September 7, 2010 03:11 PM

As Greenland Melts

The Greenland ice sheet is a vast body of ice covering 660,235 square miles, roughly 80% of the surface of Greenland. It is the second largest ice body in the World, after the Antarctic Ice Sheet. The ice sheet is almost 1,500 miles long in a north south direction, and its greatest width is 680 miles at a latitude of 77°N, near its northern margin. Scientists investigating the geophysical and hydrological conditions beneath the Greenland ice sheet say their analysis will be vital for helping understand how the massive ice sheet will respond to climate change.

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The ice in the current ice sheet is as old as 100,000 years. It is generally thought that the Greenland Ice Sheet formed in the late Pliocene or early Pleistocene. It apparently developed very rapidly with the first continental glaciation.

The massive weight of the ice has depressed the central Greenland; the bedrock surface is near sea level over most of the interior of Greenland, but mountains occur around the periphery, confining the sheet along its margins. If the ice were to disappear, Greenland would most probably appear as a group of islands at least until the lanmd rises higher as a result of the ice sheet's great weight being removed. The ice surface reaches its greatest height on two north-south elongated domes, or ridges. That height is about 10,000 feet above sea level

Large outlet glaciers, which are restricted tongues of the ice sheet, move through bordering valleys around the periphery of Greenland to calve off into the ocean, producing the numerous icebergs that sometimes occur in North Atlantic shipping lanes.

Researchers from the University of Bristol, who have carried out extensive fieldwork in Greenland over the past few years, are to lead a series of new experiments, which could yield important information about the wider risks to global sea levels.

The Bristol stream tracing project will reveal how melt water generated on the surface of the ice sheet is transferred to the base. They will work alongside colleagues from the universities of Edinburgh and Aberystwyth, to tackle the challenging task of tracing water flow over 50 miles and in sub-surface rivers with double the discharge of the River Thames. The huge volumes of water generated on the surface of the Greenland Ice Sheet makes it challenging to detect any ordinary tracers injected in the water runoff.

Bristol’s Dr Jemma Wadham, who is leading the project said: “We know little about how water flows beneath the Greenland Ice Sheet because the toolkit available to scientists to trace waters under such challenging conditions has been very limited. We aim to employ a new suite of highly sensitive tracing methods, developed in Bristol, to solve this mystery.”

The airborne geophysics project, lead by the University of Cambridge, will focus on ten major outlet glaciers across the ice sheet and will use radar, gravity and magnetic data to characterize the sub-glacial environment of the glaciers and, in particular, the presence of water and sediment at the bed.

Over the past 15 years, rising temperatures have led to increasing water mass loss from the ice sheet and an increase in global sea level. This increased loss has been due to a roughly equal increase in the speed of glaciers flowing into the ocean and increased melting at the surface.

Results from the studies will help determine essential information about the internal structure of the ice sheet and the conditions at the bed, including basal melting and the routing of basal water. That information will make a help develop computer modeling of the ice sheet, and help show how it may respond to changes in air and ocean temperature over the coming decades.

If the entire Greenland ice sheet were to melt, global sea levels would theoretically rise 23.6 feet. Some climate models project that local warming in Greenland will exceed 3 °C (5.4 °F) during this century. Such a rise would inundate almost every major coastal city in the World. How fast the melt would eventually occur is a matter of discussion. The current project would help project a possible answer.

For further information: http://www.bristol.ac.uk/news/2010/7204.html

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