JIJITANG2014-07-23 4:03 PM

ANTARCTIC GLACIER IS RAPIDLY MELTING FROM THE BOTTOM UP

Thwaites Glacier, the large, rapidly changing outlet of the West Antarctic Ice Sheet, is not only being eroded by the warming ocean, it’s also being melted from below by geothermal heat, researchers report.

The glacier is on the way to collapsing, but more data and computer modeling are needed to determine when the collapse will begin in earnest and at what rate the sea level will increase as it proceeds, scientists say.

Using radar techniques to map how water flows under ice sheets, researchers were able to estimate ice melting rates and then identify that significant sources of geothermal heat under the glacier are distributed over a wider area—and are much hotter than previously assumed.

The geothermal heat contributes significantly to melting of the underside of the glacier, and might be a key factor in allowing the ice sheet to slide, affecting its stability and its contribution to future sea level rise.

The cause of the variable distribution of heat beneath the glacier is thought to be the movement of magma and associated volcanic activity arising from the rifting of the Earth’s crust beneath the West Antarctic Ice Sheet.

MOST COMPLEX THERMAL ENVIRONMENT
Knowing the pattern of heat distribution beneath the glacier is crucial information that enables ice sheet modelers to more accurately predict the response of the glacier to the presence of a warming ocean.

Until now, scientists have been unable to measure the strength or location of heat flow under the glacier. Current ice sheet models have assumed that heat flow under the glacier is uniform like a pancake griddle with even heat distribution across the bottom of the ice.

But the new findings, published in the Proceedings of the National Academy of Sciences, show that the glacier sits on something more like a multi-burner stovetop with burners putting out heat at different levels at different locations.

“It’s the most complex thermal environment you might imagine,” says coauthor Don Blankenship, a senior research scientist at University of Texas Institute of Geophysics. “And then you plop the most critical dynamically unstable ice sheet on planet Earth in the middle of this thing, and then you try to model it. It’s virtually impossible.”

RISE IN GLOBAL SEA LEVELS
That’s why, getting a handle on the distribution of geothermal heat flow under the ice sheet has been considered essential for understanding it, he says.

Gathering knowledge about Thwaites Glacier is crucial to understanding what might happen to the West Antarctic Ice Sheet. An outlet glacier the size of Florida located in the Amundsen Sea Embayment, the glacier is up to 4,000 meters thick and is considered a key question mark in making projections of global sea level rise.

The glacier is retreating in the face of the warming ocean and is thought to be unstable because its interior lies more than two kilometers below sea level while, at the coast, the bottom of the glacier is quite shallow.

Because its interior connects to the vast portion of the West Antarctic Ice Sheet that lies deeply below sea level, the glacier is considered a gateway to the majority of West Antarctica’s potential sea level contribution.

The collapse of the Thwaites Glacier would cause an increase of global sea level of between 1 and 2 meters, with the potential for more than twice that from the entire West Antarctic Ice Sheet.

100 MILLIWATTS PER SQUARE METER
Researchers had previously used ice-penetrating airborne radar sounding data to image two vast interacting subglacial water systems under Thwaites Glacier. The results from this earlier research on water systems formed the foundation for the new work, which used the distribution of water beneath the glacier to determine the levels and locations of heat flow.

In each case, lead author Dusty Schroeder, who received his PhD in May, used techniques he had developed to pull information out of data collected by the radar.

The findings show that the minimum average geothermal heat flow beneath Thwaites Glacier is about 100 milliwatts per square meter, with hotspots over 200 milliwatts per square meter. For comparison, the average heat flow of the Earth’s continents is less than 65 milliwatts per square meter.

The presence of water and heat present significant challenges, Schroeder says.

“The combination of variable subglacial geothermal heat flow and the interacting subglacial water system could threaten the stability of Thwaites Glacier in ways that we never before imagined.”

Original Article: 
《Evidence for elevated and spatially variable geothermal flux beneath the West Antarctic Ice Sheet》, Published on Journal 《PNAS》in May 8, 2014. 

KEYWORDS

SHARE & LIKE

COMMENTS

ABOUT THE AUTHOR

JIJITANG

0 Following 3 Fans 0 Projects 310 Articles

SIMILAR ARTICLES

Changes to the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) have resulted in families eating more fruits and vegetable

Read More

In contests drawn from game theory, chimpanzee pairs consistently outperform humans in games that test memory and strategic thinking.A new study, condu

Read More

Publishing is one of the most ballyhooed metrics of scientific careers, and every researcher hates to have a gap in that part of his or her CV. Here’s

Read More

Pornography triggers brain activity in people with compulsive sexual behaviour -- known commonly as sex addiction -- similar to that triggered by drugs

Read More

In a recent survey, academic staff at the University identified the interrelated skills of writing and reasoning as the two most important skills for s

Read More

In a recent survey, academic staff at the University identified the interrelated skills of writing and reasoning as the two most important skills for s

Read More

Reading cautionary tales like The Boy Who Cried Wolf and Pinocchio to little kids might not be the best way to teach them to tell the truth.New researc

Read More

Those flat, glassy solar panels on your neighbor’s roof may be getting a more efficient makeover, thanks to a new class of solar-sensitive nanoparticle

Read More

Physicists have overcome a major challenge in the science of measurement using quantum mechanics. They’ve used multiple detectors to measure photons in

Read More

If you want to slow down long enough to smell the proverbial roses, you might want to move to a neighborhood with fewer drive-thru restaurants, researc

Read More