Greenland Ice Sheet more Dynamic than Previously Thought

The Greenland Ice Sheet is of major concern to scientists the world over in a world that is warming rapidly and causing massive ice melt to occur. However, recent research has shown that the Greenland Ice Sheet may in fact be more robust and dynamic than previously thought.

The research was conducted by the University of Copenhagen in conjunction with the Technical University of Denmark (DTU) and the Danish National Survey and Cadastre (KMS) and Aarhus University in collaboration with an international team of scientists.

The massive calving front of the second most southerly tributary of the Upernavik Icestream, Northwest Greenland. The fast-flowing ice stream is evident as the heavily crevassed zone adjacent to the slower-moving ice, which appears as a smoother surface. The rolled-over iceberg in the center of the picture is roughly 200 m across.

“That air temperatures have increased and melting has intensified is relatively well-understood,” explained University of Copenhagen Associate Professor Kurt H. Kjær. “On the other hand, the UN’s climate panel, the IPCC, has for many years called for greater knowledge in relation to the other major effect on the Greenland Ice Sheet – the ‘thinning of the ice sheet’ which is the effect of the largest glaciers in Greenland flowing faster into the ocean than previously measured.

“Over the past three years a number of scientific articles have addressed the issue and pointed to a sea-level rise of one metre or more. These reports presuppose that the melting will accelerate to the same degree as during the past decade. This is a question to which we have been able to provide a qualified answer. It turns out that the ice sheet, in relation to this point, behaves more dynamically and is able to more quickly stabilise itself in comparison to what many other models and computer calculations otherwise predict.”

A Historically Robust Greenland Ice Sheet

The Greenland Ice Sheet is seeing more than 240 billion tonnes of fresh water melt away into the surrounding oceans each year. However, according to new research findings from University of Copenhagen and the Technical University of Denmark (DTU) in conjunction with an international team of researchers, the Greenland Ice Sheet is actually more robust than we thought. The new research is the result of combining contemporary satellite data against old aerial photographs of the ice sheet in northwestern Greenland, a location on the ice sheet that has seen a lot of thinning and glacial ice runoff.

“We’ve used a combination of old aerial photographs from the 80’s to construct a digital elevation map and recent satellite data,” said senior researcher Shfaqat Abbas Khan of the Technical University of Denmark (DTU). “In this way we’ve been able to gain an overview of the thinning of the ice sheet over the last 30 years in northwestern Greenland. We are the first who have been able to show that the Greenland Ice Sheet was on as a dramatic diet at the end of the 80’s as it is today. On the positive side our results show that despite a significant thinning in peripheral regions from 1985-1992; the thinning slowed and then died out.”

Thanks Heavens for Old Photos

It was Associate Professor Kurt H. Kjær of the University of Copenhagen who had the idea to create new and comparable elevation models of the ice sheet based on data gathered from the old photos, providing researchers with a means in which to delve into the ice sheet’s past.

“Our results show that the thinning of the ice sheet at the end of the 80’s and beginning of the 90’s eased over a 4-8 year period, after which a period of stability occurred until 2003,” Kurt H. Kjær said. “Our conclusion is therefore, that if we judged against longer periods of time, the current thinning of the ice sheet is likely to ease within an 8-year period.”

“These variations in the amount of thinning that we are able to document since the 80’s make it difficult to predict how much the world’s oceans will rise over a longer period of time – a century for instance – as a result of Greenland glacial melt-water runoff. However, it is certain that many of the present calculations and computer models of ice sheet conditions that built upon a short range of years since 2000 must be reassessed.

“It is too early to proclaim the ‘ice sheet’s future doom’ and subsequent contribution to serious water problems for the world. In this context it should be mentioned that the Greenland bedrock rises as the ice sheet in the peripheral regions and especially near the coast is in retreat and becoming thinner. This highlights the enormous forces that are at play in Greenland and of how difficult it is to predict what it means for Greenland as well as the rest of the world.”

Source: University of Copenhagen
Image Source: Niels J. Korsgaard, Natural History Museum of Denmark

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