UT Scientist Maps History of Greenland Ice Sheet


Imagine that Texas is covered in ice. (Difficult, right?) Now imagine that three Texases are covered in ice. That’s about the size of the Greenland ice sheet—the 656,000-square-mile mass of glacier that covers nearly the entire island. It is second in size only to Antarctica, and if it melted, sea levels would rise up to 20 feet. This means that understanding the ice sheet is key to understanding climate change.

Joe MacGregor, a research associate with UT’s Institute for Geophysics (UTIG), is hoping to make the history of the Greenland ice sheet a little bit easier to understand. Working closely with NASA’s Operation IceBridge, MacGregor has used data collected from ice cores and ice-penetrating radar to develop a detailed 3-D map of the ice sheet. Then, by examining the characteristics of the vertical layers of ice, MacGregor and his colleagues have been able to date the ice and examine its behavior since as early as 130,000 years ago. Their work is available to the public in a study published online last week.

“What I’m primarily interested in doing is trying to understand why the ice sheet flows as it does now and how it might have changed in the past, and then finally, what that might tell us about how it might change in the future,” MacGregory says. “Layering tells us what the ice sheet experienced and how it responded to those changes.”

MacGregor describes Greenland’s problems as twofold. First, as ocean circulation changes, warmer water melts the ice sheet’s edges. Second, the surface of the ice sheet faces annual melts as a result of arctic warming. The new map provides insight into how the ice sheet responded to similar changes throughout its history—and that helps scientists predict what will happen next. “The important thing to realize is that although these changes are probably occurring much more quickly than they have in the past due to ongoing anthropogenic climate change, the ice sheet has experienced changes like that back in time of a similar magnitude,” he says.

While the study does not offer any long-term solutions, it will certainly help scientists understand how Greenland might respond to climate change and affect sea-levels worldwide. In particular, MacGregor and his colleagues will closely examine the ice sheet’s behavior over the last millennium as they continue to unravel the information collected through Operation IceBridge. While 130,000 years may sound like an enormous timespan to most, MacGregor describes this period of time as “much closer to the present” than one might think, when viewed in the mind-boggling scale of geologic time. If scientists can understand the ice sheet’s recent past, he explains, they have a better chance of predicting its near future.

While MacGregor searches Greenland’s history to understand its future, he is sure to note that he too is deeply indebted to the past. Operation IceBridge collected its first transect of ice nearly 22 years ago, and scientists are still relying on that data today. “This was an effort that involved many people over many decades,” he says. Relative to the history of the Greenland Ice Sheet, of course, that’s just a drop in the bucket.

Image courtesy NASA


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