A recent study of the Greenland ice sheet found that glaciers receded in almost every part of the island while undergoing other physical changes. Some of these changes cause the transformation of freshwater rivers under ice.
In a study by Twila Moon, led by the National Snow և Ice Data Center, researchers looked in detail at 225 physical changes in the glaciers ending in the Greenland Ocean. The narrow fingers of ice that flow from the ice sheet to the ocean. They found that none of the glaciers had advanced significantly since 2000, with 200 retreating.
The map at the top of this page shows the speed measurements of ice in Greenland, which are measured by satellites. The data was compiled through the ITS_LIVE Interagency Time Series (ITS_LIVE), which combines glacier observations collected by multiple Landsat satellites from 1985 to 2015 into a single database open to the scientific community.
About 80 percent of Greenland is covered by ice, also known as the Continental Glacier, which is up to 3 kilometers (2 miles) thick. As glaciers flow into the sea, they are usually replenished by new snow on the inside of the ice, which compacts the ice. Numerous studies have shown that the balance between melting and replenishing the glacier changes, as does the birth of an iceberg. As the air’s ocean temperature rises, the ice loses mass at an accelerating rate, լրացուցիչ additional melt water flows into the sea.
“Greenland’s coastline is undergoing a major transformation,” said Alex Gardner, a snow and ice scientist. NASAJet Propulsion Laboratory և Co-author of the study. “We are already seeing the ice sheet receding into new parts of the ocean և fjord, and now we have evidence of changes in these freshwater flows. Thus, the loss of ice is not just a change in sea level, but also a change in Greenland’s coastline, a change in coastal ecology.
Although the findings of Mooney, the Gardner և colleagues coincide with other Greenland observations, the new study describes a trend that was not apparent in previous work. As individual glaciers recede, they change in ways that are likely to alter the freshwater flows beneath the ice. For example, glaciers change in thickness not only when hot air melts ice from their surfaces, but also as their flow rate changes. Both scenarios can lead to a change in the pressure distribution under the ice. This in turn can change the course of sub-glacial rivers, as water will always flow at the lowest resistance (lowest pressure).
Referring to previous studies of Greenland ecology, the authors note that the freshwater rivers under the ice sheet carry nutrients to the gulfs, deltas and fjords around Greenland. In addition, icy rivers enter the ocean, where they meet ice և pebbles, which are often located far below the ocean surface. Relatively vibrant freshwater rises to the surface of the nutrient-rich deep ocean, where nutrients can be consumed by phytoplankton. Studies have shown that glacial melt rivers directly affect the productivity of phytoplankton, which serve as the basis of the marine food chain. As glaciers երի retreat, new fjords’s ocean segments open up, and these changes transform the local environment.
“The rate of ice loss in Greenland is staggering,” Moon said. “When the edge of ice responds to the rapid loss of ice, the nature and behavior of the system as a whole change, can affect ecosystems and the people who depend on them.”
NASA Earth Observatory image by Osh Oshua Stevens using Landsat data from the US Geological Survey’s Intermediate Ice Rail Height (ITS_LIVE) program time series /JPL:-Caltech ընդհանուր Overall Batimetric Chart of Oceans (GEBCO). Story by Calla Cofield with Mike Carlowich of the Jet Engine Lab.