An east Greenland glacier seen from the NASA P-3 in April 2014. Image Credit: NASA/Jim Yungel

Global Warming? Nasa Satellite Images, Data Help Scientists Map Melting Layers Deep Beneath Greenland Ice Sheet

NASA’s Operation IceBridge has helped scientists to find new evidence of a drained and refilled sub-glacial lake beneath Greenland’s Flade Ice Cap, a rare sub-ice body of water detected that sheds light on how global warming affects the Greenland Ice Sheet.

Subglacial lakes are found in Antarctica and recent have mathematically predicted hundreds of them in Greenland but few have actually been found. To find bodies of water beneath the ice, either you need an ice-penetrating radar or conclude by observing rapid changes in ice surface elevation such as bulges or basins.

However, a new study published in the journal Nature by Michael Willis, a glaciologist at Cornell University in Ithaca, New York, and his team revealed that a large basin was formed beneath Greenland’s ice over a 21-day period in the summer of 2011 using satellite images provided by NASA, the first-ever comprehensive map of layers deep inside the Greenland Ice Sheet.

The size of the basin was consistent with a drained subglacial lake, but its location remained questionable about the source of water. Where did the water in the lake come from?

Subglacial lakes usually form beneath an ice sheet either due to friction or trapped heat from bedrock below. But to accommodate this, ice needs to move quickly or be thick enough to protect the ice sheet base from cold air at the surface. or below from the bedrocks.

The research team used weather data and ice thickness measurements from IceBridge flights to calculate the temperature beneath the ice and found that it was not much that is needed for normal basal melt. Further observation showed that the basin floor rose significantly in the next summer concurrent with a nearby surface meltwater drained into cracks along the basin’s edge.

This led the team to hypothesize that water from surface melting was refilling a lake beneath the ice and the ice movement accounted for a portion of the basin’s rise, with meltwater estimates filling in the rest of the increase.

Extrapolating the study to the possibility of similar meltwater-filled subglacial lakes in other parts of Greenland, researchers said an extensive network of sub-ice drainage channels in Greenland that are thought to quickly move surface melt along the bed and to the ocean.

The presence of subglacial lakes in Greenland could affect the movement of ice sheet, adding heat to the base and softening ice. Researchers now plan further research to make projections of how the ice sheet will change in response to future global warming.

What is Operation IceBridge?

NASA’s Operation IceBridge has so far completed four additional surveys of the Antarctic, bringing the mission’s six-week-long field campaign to a close on Nov. 15, 2014.

IceBridge carried out study on the Institute Ice Stream near the Ronne Ice Shelf and collected data on surface elevation, sub-ice bedrock and water depth along paths previously measured by NASA’s Ice, Cloud and Land Elevation Satellite, or ICESat, from 2003 to 2009.

This region has been studied since the 1950s, including an airborne research by a joint U.S.–Danish project in the 1970s and an effort by Germany’s Alfred Wegener Institute in the 1990s.

Previously IceBridge had flown one line in this area in 2012, expanding the mission’s record of measurements in Antarctica. Researchers were able to collect data for an entire day with the exception of one five minute stretch where low clouds blocked laser and camera instruments.

In addition, ice-penetrating radar detected two steep sidewalls in the bedrock in the Hercules Inlet.”IceBridge surveyed previously unexplored parts of the Greenland ice sheet and did it using state-of-the-art CReSIS radars,” said co-author, Mark Fahnestock from the Geophysical Institute at University of Alaska.

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