1985 – 2015
A recent study of Greenland’s ice sheet found that glaciers are retreating in almost every area of the island, while other physical changes are also taking place. Some of these changes are causing the regeneration of freshwater rivers under ice.
In a study led by Tavilla Moon of the National Snow and Ice Data Center, researchers looked in detail at the physical transformation of Greenland’s 225 sea-ending glaciers, the narrow fingers of ice that flow into the ocean from the interior of the ice sheet. They found that none of these glaciers had moved significantly since 2000 and that 200 of them were retreating.
The map at the top of this page shows the measurement of ice velocity in Greenland as measured by satellites. The data was compiled by the Inter-Mission Time Series of Land Ice Velocity and Elevation Project (ITS_Live), which brings together observations of glaciers collected by multiple Landset satellites between 1985 and 2015 in a dataset open to scientists and the public.
About 0% of Greenland is covered by ice sheets, also known as continental glaciers, which can reach up to a kilometer (2 miles) thick. As glaciers flow into the ocean, they are usually replenished by new snowfalls in the interior of the ice sheet that are compacted into ice. Multiple studies have shown that the balance between glacier melting and refilling is changing, as is the proposed rate of snowfall. Due to rising air and sea temperatures, the ice sheet is losing mass at an accelerated rate and flowing into the extra molten sea.
“The marine environment in Greenland is changing dramatically,” said Alex Gardner, ice and snow scientist. NASACo-author of the Jet Propulsion Laboratory and study. “We are already seeing new parts of the ocean and the ice sheet is retreating, and now we have evidence of a change in the flow of this fresh water. So losing ice is not just about changing sea levels, it’s also about reshaping Greenland’s beaches and changing the marine environment. “
Although the findings by Moon, Gardner and colleagues are consistent with other Greenland observations, the new survey finds a trend that is not apparent in previous work. As individual glaciers retreat, they are also changing in such a way that there is a potential for freshwater flow under the ice. For example, as glaciers change in thickness, not only does hot air melt ice from its surface, but it also changes the speed of its flow. Both scenarios could lead to a change in the distribution of pressure under the ice. In turn, subglacial rivers may change course, as water will always take the path of least resistance (lowest pressure).
Referring to previous studies on greenland ecology, the authors note that freshwater rivers under the ice sheet deliver nutrients to bays, deltas, and around Greenland. In addition, rivers below the ice enter the ocean where ice and bedrock meet, often below sea level. Increases in relatively excited freshwater, which carries nutrient-rich ocean deep sea water to the surface, where poputants eat by phytoplankton. Research has shown that icy melted rivers directly affect the productivity of phytoplankton, which serves as the foundation of the seafood chain. Combined with the retreat of glaciers and ice shelfs and the opening of new offshore and ocean sections, this change is similar to the change in the local climate.
“The pace of ice loss in Greenland is spectacular,” Moon said. “As ice sheets respond to rapid ice loss, the character and behavior of the entire system is changing, with the potential to affect ecosystems and the people who depend on them.”
Image of the NASA Earth Observatory taken by Joshua Stevens, using Landset data from the U.S. Geological Survey, and the inter-mission time series of the Land Ice Velocity and Elevation (ITS_Live) project at NASA.JPL-General Bathimetric Chart of Caltech and Ocean (GEBCO). The story of K Prop La Cofield, Jet Propulsion Laboratory with Mike Carloix.
