2 trillion tons of ice in Alaska, Antarctica and Greenland melted since 2003, NASA says
About 2 trillion tons of ice in Alaska, Antarctica and Greenland has melted since 2003, NASA scientists say, due to accelerating climate change.
Analyzing data from NASA’s Gravity Recovery and Climate Experiment, GRACE, in which two orbiting satellites are used to measure the “mass balance” of a glacier, that is the net difference between ice accumulation and ice loss each year, NASA geophysicist Scott Luthcke says the losses are colossal.
“The ice tells us in a very real way how the climate is changing,” said Luthcke. “A few degrees of change [in temperature] can increase the amount of mass loss, and that contributes to sea level rise and changes in ocean current.”
Greenland has lost about 160 gigatons (one billion tons) each year for 5 consecutive years, enough to raise global sea levels about .5 mm per year, according to another NASA researcher, Jay Zwally.
“Every few extra inches of sea level have very significant economic impacts, because they change the sea level, increase flooding and storm damage,” said Zwally. “It’s a warning sign.”
“We’re seeing the impacts of global warming in many areas of our own lives, like agriculture,” he said.
Citing the pine beetle infestation in the forests of Colorado and western Canada [how about Alaska?] he said: “[The pests] were believed to be spreading because the winter was not cold enough to kill them, and that’s destroying forests.”
Sermersuaq (Humboldt) Glacier, Greenland
acquired August 30, 2008 – NASA Earth Observatory
acquired August 30, 2000 – NASA Earth Observatory
Stretching about 90 kilometers across Kane Bassin in the Nares Strait, northwestern Greenland’s Sermersuaq Glacier, also called Humboldt Glacier, is the Northern Hemisphere’s widest tidewater glacier—a glacier that begins on land, but terminates in water. The Sermersuaq is a major source of icebergs in the strait, which connects the Lincoln Sea in the north to Baffin Bay in the south.
This pair of images shows the retreat of the Sermersuaq Glacier between 2000 and 2008. In these natural-color images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, the approximate terminus of the glacier on August 31, 2000 (bottom image), is traced with a yellow line on an image from August 30, 2008 (top). Although the southern part of the terminus showed little change during the period, significant retreat is visible in the northern part, where a fast-flowing ice stream is located. In both images, the deep blue waters of Kane Bassin are littered with ice, which may include icebergs and sea ice.
Having a “toe” in the water adds complexity to the natural cycle of advance and retreat that a glacier experiences in response to climate changes. The behavior of tidewater glaciers is affected not only by melting and snowfall on land, but also by the shape of the fjord or coastline where the glacier enters the water, the depth of the water, tides, and the thickness of the moraine (a shoal of sediment and rock) that builds up underwater at the tip of the glacier.
Even in the absence of human-caused climate change, tidewater glaciers naturally experience century-long cycles that include phases of rapid retreat. After decades of slow advance, the terminus of the glacier eventually becomes grounded on its own moraine. The shoal can become so thick that it stops icebergs from calving for extended spans of time. The support of the shoal allows the glacier to grow larger than it could if it were free-floating.
A small amount of thinning or retreat at the terminus can trigger a rapid retreat once the glacier—too large to float—is ungrounded from the shoal. The initial thinning or retreat of a tidewater glacier may result from a warming climate, but the extremely rapid retreat thereafter has as much to do with topography and the laws of physics as it does with the current climate.
NASA image created by Jesse Allen, using data obtained from the Goddard Level 1 and Atmospheric Archive and Distribution System (LAADS). Caption by Rebecca Lindsey.
- Instrument: Terra – MODIS
- Date Acquired: August 30, 2008