Echoing numerous reports over the last few weeks, scientists from NASA reported yesterday that the extent of Arctic sea ice shrank to its lowest level ever recorded. (For perspective on the unprecedented melt, read How Fast Is The Arctic Melting?) This widely recognized harbinger of global warming has been offset -- in the minds of some climate science skeptics -- by conflicting reports about melting on the other end of the globe, where different ice shelves and edges of Antarctica have been shown to be disintegrating in some cases, but growing in others.
Yesterday, NASA released the results of another new study -- to considerably less fanfare than the Arctic data has received -- showing that over that in 2004-2005, Antarctica showed melting further inland, at higher altitudes, during a greater number of days, and to a greater extent on its largest ice shelf, than at any time in a quarter century: This image shows, in green, areas of persistent melting -- the first documented since studies began in 1987 -- as detected by the Special Sensor Microwave Imager radiometer aboard the Defense Meteorological Satellite Program's satellites.
Unlike visible sensors, Microwave instruments can also detect melting below the snow surface. NASA/Rob Simmon The study highlights the importance of continued investment in earth-observing satellite programs at NASA -- an area of research that has been persistently pared down and de-emphasized during the Bush Administration.
Threat of Sea-Level Rise Antarctica is 1.5 times the size of the United States, and holds 90% of the world's fresh water -- making it the world's largest potential source of sea level rise. Whereas floating Arctic sea ice melting poses relatively little threat of sea-level rise (imagine an ice cube melting in a glass of water) melting of ice locked on a continent holds huge potential. Despite persistently cold temperatures on the continent, NASA documented melting as far as 500 miles inland from the coast, and at altitudes as high as 1.2 miles above sea level in 2005.
The melting wasn't uniform across the continent, but worrying melting occurred on the Ross Ice Shelf, which acts as a "braking system" for glaciers inland behind it. If it disintegrates, those glaciers come sliding into the sea, where they will melt and increase the level of the sea. "Snow melting is very connected to surface temperature change, so it's likely warmer temperatures are at the root of what we've observed in Antarctica," lead author Marco Tedesco, said in a statement released to the press.
He is a research scientist at the Joint Center for Earth Systems Technology cooperatively managed by NASA's Goddard Space Flight Center, Greenbelt, Md., and the University of Maryland at Baltimore County, Baltimore. The study will be published on Sept. 22 in the American Geophysical Union's Geophysical Research Letters. It is seen as an important, but still early, contribution to the understanding of Antarctica's role in future sea level rise, given various global warming scenarios.
A Cascade of Effects The melting of sea ice can contribute to a cycle of warming: Lose icy reflective ice and the darker water that's left behind absorbs more heat from the sun, and melts more ice, which exposes more water -- and on and on. On land, the melting on the surface can cause water to infiltrate cracks in glaciers, lubricating their otherwise slide to the sea. n the Arctic, the winter is setting in, and sea ice is beginning to reform. The coming years will tell us how much that spiral has progressed. How the melting in the Antarctic could speed up warming is still a matter ripe for research.
What both milestones show is that the melting at the poles is significant, and climate scientists agree that the warming climate is showing its first -- and most pronounced -- affects there. Not only that, but those effects are -- often -- being documented far earlier than previously predicted. How quickly will the cascade of other effects -- wildfires, droughts, floods, heat waves, the inundation of coastal communities, the spread of tropical diseases, the loss of endangered species -- will occur is unknown.
There's some indication that some effects are already being observed, and the speed with which the Earth's poles are responding to the climate is a worrying indicator of more catastrophes closer to home -- if nothing is done to slow the pace of global warming.
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