Scientists at NASA are keeping an eye on the plumes of sediment that appear in the ocean as glacial meltwater deposits sand, soil and rocks. The plumes, which are visible via satellite imagery, may be able to help scientists ascertain exactly how much ice mass glaciers are losing to the ocean via meltwater runoff.

NASA's Earth Observatory recently captured a beautiful image of the Greenland Ice Sheet. The image shows the whitish turquoise sediment plumes snaking out from the glacial fjords of Greenland and into the Labrador Sea. "The sediment wonderfully stands out behind the blue marine waters," said UCLA researcher Vena Chu, "and makes it easy to see in remotely sensed satellite imagery."

Understanding how much glacial mass is lost each year to the ocean is key to determining the long-term effects of melting on sea level rise. And while keeping tabs on the ice lost by way of calving icebergs, melting -- both the runoff from the top of glaciers and the even less visible subglacial kind -- is much more difficult to measure.

But now, geologists and climatologists think satellite imagery could help them map and measure sediment plumes, thus providing a more accurate way to determine how much runoff reaches the ocean and what portion is refrozen along the way.

"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 solution isn't perfect, however. Some runoff and subglacial meltwater filters into the ocean water many feet below the surface -- so the sediment that's actually visible may only tell part of a much larger story.

"Not all of the sediment makes it to the surface, a lot of it settles out," Chu said. "It is important that we make more detailed oceanographic studies looking at the vertical structure of these plumes."