Scientists have examined the about 100 km wide Whillans Ice Stream, one of the fast-moving streams that feed
The team used magnetotellurica sounding that measures the penetration into the earth of natural electromagnetic energy generated high in the planet's atmosphere. As scientists note, ice, fresh and salt water, sediment and bedrock conduct electromagnetic energy differently.
Study area. Map: Chloe Gustafson, Columbia University
By measuring these differences, the researchers compiledmap of "underground" structures. In addition, the scientists also re-analyzed the natural seismic waves studied by the other team to distinguish between bedrock, sediment and ice.
The analysis showed that sedimentary rocks extendfrom half a kilometer to two kilometers from the base of the ice. As scientists note, these sedimentary deposits are filled with liquid water throughout. Moreover, the deeper these groundwaters are located, the more saline they become.
Researchers believe that sedimentary rocksformed long ago in sea water. During the last major warming, about 5 - 7 thousand years ago, ocean waters covered these rocks, saturating the sediments with salt water. After the expansion of the ice that covered this area, fresh meltwater, formed under pressure from above, went into the upper part of the sedimentary rocks.
Scientists believe that this slow departure is insipidwater in ground deposits protects the glacier from rapid growth. Measurements made by other scientists at the ground line of the ice stream—the point where the land-based ice stream meets the floating ice shelf—show that the water here is somewhat less salty. This suggests that fresh water is flowing through sediment into the ocean, making room for more meltwater to enter and keeping the system stable, the scientists say.
The researchers believe the discovery will help better understand the formation of glaciers, the impact of climate change on Antarctica, and the influence of Antarctica on climate change.
“The amount of groundwater that we foundwas so significant that it probably affects the formation of ice currents. Now we need to learn more and figure out how to incorporate the new data into the models,” says Chloe Gustafson, study co-author at Columbia University.
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