Greenland Glacier Gives Birth to Giant Iceberg
True-colour Envisat MERIS image of Petermann glacier on 5 August 2010 showing the iceberg already separated from the main glacier tongue. Cloud coverage prevents obtaining additional MERIS images spanning the actual calving event. (ESA)
Envisat has been observing a rare event in the Arctic since early August - a giant iceberg breaking off the Petermann glacier in North-West Greenland.
The Petermann glacier is one of the largest glaciers connecting the Greenland inland ice sheet with the Arctic Ocean. Upon reaching the sea, a number of these large outlet glaciers extend into the water with a floating ‘ice tongue’.
The ice tongue of the Petermann glacier was the largest in Greenland, with an extension of about 70 km until early August. This tide-water glacier regularly advances towards the ocean at about 1 km per year. During the previous months, satellite images revealed that several cracks had appeared on the glacier surface,suggesting to scientists that a break-up event was imminent.
In the Envisat radar image taken on 3 August, the ice tongue was still intact but, on 4 August, a large part of the floating ice tongue was separated from the glacier, giving birth to what is currently the largest iceberg in the northern hemisphere. Such a process of detachment, called ‘calving’, occurs regularly on the Petermann glacier, with smaller calving events in summer 2008 and 2009. However large calving events are rare, with the last such significant event being documented in 1991 by ESA’s ERS-1 satellite. (more…)
Researchers Witness Overnight Breakup & Retreat of Greenland Glacier
Images courtesy of DigitalGlobe
NASA-funded researchers monitoring Greenland’s Jakobshavn Isbrae glacier report that a 7 square kilometer (2.7 square mile) section of the glacier broke up on July 6 and 7, as shown in the image above. The calving front – where the ice sheet meets the ocean – retreated nearly 1.5 kilometers (a mile) in one day and is now further inland than at any time previously observed. The chunk of lost ice is roughly one-eighth the size of Manhattan Island, New York.
Research teams led by Ian Howat of the Byrd Polar Research Center at Ohio State University and Paul Morin, director of the Antarctic Geospatial Information Center at the University of Minnesota have been monitoring satellite images for changes in the Greenland ice sheet and its outlet glaciers. While this week’s breakup itself is not unusual, Howat noted, detecting it within hours and at such fine detail is a new phenomenon for scientists. (more…)
Greenland Rapidly Rising as Ice Melt Continues
This is a satellite image of Western Greenland, acquired by NASA's MODIS satellite. The narrow grey band in the center of the image is melting ice, between the rocky coast to the left (west) and thicker, non-melting, higher altitude ice to the right (east). Small lakes form in this region during the summer. Arrow points to darker grey zone of rapidly thinning ice near the outlet of Jacobshavn glacier, which also loses mass due to iceberg calving. (Courtesy of NASA)
Greenland is situated in the Atlantic Ocean to the northeast of Canada. It has stunning fjords on its rocky coast formed by moving glaciers, and a dense icecap up to 2 km thick that covers much of the island–pressing down the land beneath and lowering its elevation. Now, scientists at the University of Miami say Greenland’s ice is melting so quickly that the land underneath is rising at an accelerated pace.
According to the study, some coastal areas are going up by nearly one inch per year and if current trends continue, that number could accelerate to as much as two inches per year by 2025, explains Tim Dixon, professor of geophysics at the University of Miami Rosenstiel School of Marine and Atmospheric Science (RSMAS) and principal investigator of the study.
“It’s been known for several years that climate change is contributing to the melting of Greenland’s ice sheet,” Dixon says. “What’s surprising, and a bit worrisome, is that the ice is melting so fast that we can actually see the land uplift in response,” he says. “Even more surprising, the rise seems to be accelerating, implying that melting is accelerating.”
Dixon and his collaborators share their findings in a new study titled “Accelerating uplift in the North Atlantic region as an indicator of ice loss,” The paper is now available as an advanced online publication, by Nature Geoscience. The idea behind the study is that if Greenland is losing its ice cover, the resulting loss of weight causes the rocky surface beneath to rise. The same process is affecting the islands of Iceland and Svalbard, which also have ice caps, explains Shimon Wdowinski, research associate professor in the University of Miami RSMAS, and co-author of the study. (more…)
Greenland Ice Sheet Losing Mass on Northwest Coast
Shfaqat Abbas Khan - Tasiilaq, Greenland
Ice loss from the Greenland ice sheet, which has been increasing during the past decade over its southern region, is now moving up its northwest coast, according to a new international study.
Led by the Denmark Technical Institute’s National Space Institute in Copenhagen and involving the University of Colorado at Boulder, the study indicated the ice-loss acceleration began moving up the northwest coast of Greenland starting in late 2005. The team drew their conclusions by comparing data from NASA’s Gravity and Recovery Climate Experiment satellite system, or GRACE, with continuous GPS measurements made from long-term sites on bedrock on the edges of the ice sheet.
The data from the GPS and GRACE provided the researchers with monthly averages of crustal uplift caused by ice-mass loss. The team combined the uplift measured by GRACE over United Kingdom-sized chunks of Greenland while the GPS receivers monitor crustal uplift on scales of just tens of miles. “Our results show that the ice loss, which has been well documented over southern portions of Greenland, is now spreading up along the northwest coast,” said Shfaqat Abbas Khan, lead author on a paper that will appear in Geophysical Research Letters. (more…)
Greenland Ice Cap Melting Faster Than Ever
Satellite observations and a state-of-the art regional atmospheric model have independently confirmed that the Greenland ice sheet is losing mass at an accelerating rate, reports a new study in Science
Satellite observations and a state-of-the art regional atmospheric model have independently confirmed that the Greenland ice sheet is loosing mass at an accelerating rate, reports a new study in Science.
This mass loss is equally distributed between increased iceberg production, driven by acceleration of Greenland’s fast-flowing outlet glaciers, and increased meltwater production at the ice sheet surface. Recent warm summers further accelerated the mass loss to 273 Gt per year (1 Gt is the mass of 1 cubic kilometre of water), in the period 2006-2008, which represents 0.75 mm of global sea level rise per year.
Professor Jonathan Bamber from the University of Bristol and an author on the paper said: “It is clear from these results that mass loss from Greenland has been accelerating since the late 1990s and the underlying causes suggest this trend is likely to continue in the near future. We have produced agreement between two totally independent estimates, giving us a lot of confidence in the numbers and our inferences about the processes”. (more…)
Sea-level Rise May Pose Greatest Threat to Northeast US, Canada
An aerial view of Long Island shows its low-lying shores, vulnerable to sea-level rise effects. (New York State Department of Environmental Conservation)
The melting of the Greenland Ice Sheet this century may drive more water than previously thought toward the already threatened coastlines of New York, Boston, Halifax and other cities in the northeastern United States and Canada, according to new research.
Results of the study are being published this week in Geophysical Research Letters. They suggest that moderate to high rates of ice melt from Greenland may shift ocean circulation by about 2100, causing sea levels off the northeast coast of North America to rise by about 30 to 51 centimeters (12 to 20 inches) more than other coastal areas.
The research builds on recent reports that have found that sea level rise could adversely affect North America, and its findings suggest that the situation is even more urgent than previously believed. (more…)
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