First Map of the Thawed Areas Under the Greenland Ice Sheet
The Greenland Ice Sheet covers roughly 80% of the country, and is over 2,400 kilometers long from top to bottom. Being the second largest ice sheet in the world after the South Pole’s Antarctic Ice Sheet, it is a key area to study for insights into climate change.
Mapping Greenland Matters
Using multiple technologies in harmony, NASA has been able to produce a map showing the state of the land and deeper ice under the ice sheet itself. This is a monumental achievement because “knowing whether Greenland’s ice lies on wet, slippery ground or is anchored to dry, frozen bedrock is essential for predicting how this ice will flow in the future” (NASA). The map that is now available shows the areas of the bottom of the ice sheet that are still frozen against those that are thawed, indicating which areas could potentially lead to heavier melting.
Scientists have also indicated that the melting of the Greenland Ice Sheet could disrupt water currents in the North Atlantic Ocean and beyond. This disruption could have effects on climate patterns worldwide.
“If the ice at its bottom is at the melting point temperature, or thawed, then there could be enough liquid water there for the ice to flow faster and affect how quickly it responds to climate change.” - Joe MacGregor, glaciologist at NASA’s Goddard Space Flight Center
Combined Data
The team that created the map had to combine the data from four separate measuring methods.
They used data from eight recent computer models of the ice sheet, which predict basal temperatures. Next they studied the layers of the ice sheet itself, which are detected by radars onboard NASA’s Operation IceBridge aircraft and suggest where the bottom of the ice is melting rapidly. Third, they looked at where the ice surface speed measured by satellites exceeds its “speed limit”, the maximum velocity at which the ice could flow and still be frozen to the rock beneath it. Finally, they examined images from the Moderate Resolution Imaging Spectroradiometers on the NASA Terra and Aqua satellites looking for rugged surface terrain that is usually indicative of ice sliding over a thawed bed (NASA).
“Each of these methods has strengths and weaknesses. Considering just one isn’t enough. By combining them, we produced the first large-scale assessment of Greenland’s basal thermal state…” - Joe MacGregor
Ice Sheet Covers Two Grand Canyons?
In 2013 National Geographic released an article detailing that the Greenland Ice Sheet sits atop a canyon the equivalent of two times the size of the Grand Canyon in Arizona. While this is a staggering amount of frozen water, it differs to the terrain underneath the Antarctic Ice Sheet, which is composed of several very large lakes.
Scientists must consider every aspect of the land surrounding the ice sheets, both beside and underneath them, to be able to predict where melted ice might flow.
Discovering when the ice sheets might significantly change size is another matter. And while the ice sheets have been here for thousands upon thousands of years and will likely be here for many more, we will need to know if we are speeding up the process of the melting.
As one researcher put it, “If we carry on warming up the planet, the ice is going to melt faster than we want it to. It really depends on what we do to the planet, doesn’t it?”
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