Helheim Glacier, Greenland
Location of Helheim Glacier in Greenland. (Source: UNEP Atlas of our Changing Environment) The Helheim Glacier (66.4°N, 38°W) is a flow of ice that orginates from the much larger Greenland ice Sheet, through a narrow rift in the coastal mountain range and down into the sea at a rate of several kilometers (miles) per year. In the sea, the glacier's weight keeps it firmly resting on the ocean floor, as long as the water depth is less than about nine-tenths of the glacier's thickness. Where the water is deep enough to cause the end of the glacier to float, its front becomes brittle, breaking into numerous icebergs.
Helheim glacier’s calving front positions overlain on an ASTER VNIR-band false color image acquired July 19, 2005. Margin positions were mapped from geo-registered ASTER images acquired on the dates shown in black. (Credit: image and caption, I. Howat et al. 2005) After years of melting back at a relatively stable speed, Helheim Glacier in southern Greenland has dramatically accelerated its retreat. According to a research paper published in the scientific journal Geophysical Research Letters by Ian Howat, I. Joughin, S. Tulaczyk, and S. Gogineni, the glacier's rate of flow has increased from 8 kilometer (km) per year (5 miles per year) in 2000 to 11 km per year (6.8 miles per year) in 2005. In addition to flowing more rapidly the glacier thinned by 40 meters (130 feet) between 2001 and 2003. The calving front of the glacier ? the area where the ice breaks away and falls into the ocean ? has retreated by approximately 5 km (3.1 miles).
This image shows the calving front, or break-off point into the ocean, of Helheim Glacier, located in southeast Greenland. The image, taken in May 2005, shows high calving activity associated with faster Glacial flow. This glacier is now one of the fastest moving glaciers in the world. (Image credit: NASA/Wallops) The center of the Greenland Ice Sheet is only 240 km (150 miles) inland, and the researchers worry that the effects of the glacier's retreat will continue to move inland, ultimately decreasing the thickness of the whole ice sheet. Overall, the margins of the Greenland Ice Sheet have been thinning by tens of meters over the last decade. The likely underlying cause of these changes is higher air and water temperatures in the area of Southern Greenland. However, the study also identifies a relationship between the retreating front of outlet glaciers such as Helheim and an increase in the rate of flow (as the front of the glacier retreats it offers less resistance to the glacier's movement). The dynamic interactions of temperature, glacier flow rates, and ice thickness complicate the modeling of future changes in the Greenland Ice Sheet. These processes are likely to continue to accelerate under prevailing climate change scenarios.
The overall Greenland Ice Sheet contains approximately 10 percent of the world's freshwater and is up to 3.2 km (two miles) thick. If the entire Greenland Ice Sheet were to melt it would raise sea level by 5 to 6 meters (15 to 20 feet). Ian Howat and his coauthors also state that the processes which are accelerating the thinning and retreat of Helheim Glacier are occurring at other outlet glaciers along the coastal margins of Greenland.
Further Reading
- Howat, I. M., I. Joughin, S. Tulaczyk, and S. Gogineni (2005). Rapid retreat and acceleration of Helheim Glacier, east Greenland. Geophysical Research Letters, 32, L22502, doi:10.1029/2005GL024737.
- NASA Earth Observatory - Retreat of the Helheim Glacier, Greenland.
- Tierney, John. Greenland Redux. New York Times. May 3, 2007.
- UNEP Atlas of our Changing Environment
- University of California (Santa Cruz). - Currents Newspaper
