From: Roger Greenway, ENN
Published October 3, 2014 08:52 AM

Sediment from melting Greenland glaciers visible in satellite images

The glaciers on Greenland are melting, and this is releasing visible plumes of sediments to surrounding waters. NASA has released some new images showing these plumes.

Toward the end of the 21st century, melting from the Greenland Ice Sheet could result in global sea level rise of 4-21 centimeters (2-8 inches), according to the Fifth Assessment Report from the Intergovernmental Panel on Climate Change. Toward refining that estimate, some scientists are taking a close look at the colorful plumes that pepper the ocean around Greenland's perimeter.

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About half of the mass lost from the Greenland Ice Sheet is from icebergs calving from glaciers; the other half is lost via meltwater runoff either from the top of the ice or from below (subglacial). According to Vena Chu of University of California, Los Angeles, one of the biggest science questions relating to the ice sheet is: what is the contribution to sea level rise from meltwater?

Measuring the amount of meltwater leaving the ice sheet—as opposed to water that is stored or refrozen after melting—is a huge challenge. One way to better understand the hydrology of the ice sheet is by observing the buoyant bits of dust, minerals, and soil that exit the fjords of large glaciers. "The sediment wonderfully stands out behind the blue marine waters," Chu said, "and makes it easy to see in remotely sensed satellite imagery."

Scientists working in 2008 in Greenland's Kangerlussuaq Fjord found that higher sediment concentrations coincided with lower salinity levels in coastal waters, confirming that the presence of a sediment plume is a strong marker for subglacial freshwater leaving the ice sheet. Subsequent research showed that satellite imagery can be used to map the size and location of these sediment plumes.

"This is especially important in fjords of marine-terminating glaciers, where we have no way of measuring the amount of runoff, as opposed to land-terminating glaciers that end in rivers, where it is difficult but possible to measure runoff more traditionally," Chu said.

The image above, acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite on September 9, 2014, shows sediment plumes from meltwater exiting glaciers in southwest Greenland.

Read more at NASA.

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