NASA downplays Antarctic snow record, blames ozone depletion, ocean dynamics
By Chelsea Schilling
Ice melt on the world’s coldest continent was the lowest in 30 years during the 2008-2009 melt season, according to new research.
The finding was published in the journal Geophysical Research Letters last month by Marco Tedesco, a research scientist at the Joint Center for Earth Systems Technology, cooperatively managed by NASA’s Goddard Space Flight Center; and Andrew Monaghan, National Center for Atmospheric Research scientist.
“A 30-year minimum Antarctic snowmelt record occurred during austral summer 2008–2009 according to spaceborne microwave observations for 1980-2009,” their abstract states. “Strong positive phases of both the El-Niño Southern Oscillation (ENSO) and the Southern Hemisphere Annular Mode (SAM) were recorded during the months leading up to and including the 2008–2009 melt season.”
World Climate Report posted the following line graph to illustrate the Antarctic snow melt index (October-January) from 1980-2009:
The report included a list of NASA stories that highlight record high amounts of ice melting across Greenland. In recent years, NASA has written extensively on increasing snow melt and published findings by scientist Marco Tedesco.
A May 2007 NASA report declared, “In 2006, Greenland experienced more days of melting snow and at higher altitudes than average over the past 18 years, according to a new NASA-funded project using satellite observations.”
On Sept. 25, 2007, NASA reported once again that Greenland snow melt hit record highs.
NASA also reported extensive snowmelt in Antarctica in 2007 and 2008.
“On the world’s coldest continent of Antarctica, the landscape is so vast and varied that only satellites can fully capture the extent of changes in the snow melting across its valleys, mountains, glaciers and ice shelves,” NASA reported. “In a new NASA study, researchers using 20 years of data from space-based sensors have confirmed that Antarctic snow is melting farther inland from the coast over time, melting at higher altitudes than ever and increasingly melting on Antarctica’s largest ice shelf.”
NASA warns that “Antarctica contains 90 percent of Earth’s fresh water, making it the largest potential source of sea level rise.”
In March 2008, NASA reported the Wilkins Ice Shelf on the Antarctic Peninsula disintegrated, something it said was “an indication of warming temperatures in the region.”
But now that Tadesco and Monaghan confirm a 30-year minimum Antarctic snowmelt record, NASA has published research from scientists who claim increasing sea ice could be due to ozone depletion, changing ocean dynamics or the flooding of sea ice.
“Since the ozone hole began developing, researchers believe the Antarctic stratosphere has cooled between 2°C and 6°C (3.6°F and 10.8°F),” NASA reports. “Such cooling changes the dynamics between the stratosphere and lower layers of the atmosphere and strengthens Antarctica’s already fierce winds.”
The fierce winds are said to produce sustained periods of freezing temperatures unlike any other place in the world.
“The new model suggests that colder, stormier, and faster winds are rushing over the waters encircling Antarctic – especially the Ross Sea, where ice growth has been the most rapid,” NASA wrote in a September report. “The winds create areas of open water near the coast – known as polynyas – that promote sea ice production.”
According to the NASA report, changes in ocean circulation may also play a role.
“If global air temperatures warm, the model indicates that the amount of rain and snowfall could increase, and surface waters could freshen,” it states. “Since fresh water is less dense and less apt to mix with the heavier, saltier, and warmer water below, the layer at the ocean’s surface could become more stratified and mix less. This, in turn, would reduce the amount of heat flowing upward, allowing surface ice to expand.”
Another possibility, according to NASA, could be that accumulating snow is pressing down on the sea ice until it’s nearly submerged.
“When that happens, waves cause ocean water to spill on top of the ice and into the snow, forming a layer that eventually freezes and becomes ‘snow ice,’” NASA reported.
World Climate Report questioned why NASA wouldn’t report specifically on Tedesco and Monaghan’s findings concerning a 30-year record low for ice melt.
“[T]his time around, nothing, nada, zippo from NASA when their ice melt go-to guy Marco Tedesco reports that Antarctica has set a record for the lack of surface ice melt (even more interestingly coming on the heels of a near-record low ice-melt year last summer),” World Climate Report states. “So, seriously, NASA, what gives? If ice melt is an important enough topic to warrant annual updates of the goings-on across Greenland, it is not important enough to elucidate the history and recent behavior across Antarctica?”
ICE is expanding in much of Antarctica, contrary to the widespread public belief that global warming is melting the continental ice cap.
The results of ice-core drilling and sea ice monitoring indicate there is no large-scale melting of ice over most of Antarctica, although experts are concerned at ice losses on the continent’s western coast.
Antarctica has 90 per cent of the Earth’s ice and 80 per cent of its fresh water, The Australian reports. Extensive melting of Antarctic ice sheets would be required to raise sea levels substantially, and ice is melting in parts of west Antarctica. The destabilisation of the Wilkins ice shelf generated international headlines this month.
However, the picture is very different in east Antarctica, which includes the territory claimed by Australia.
East Antarctica is four times the size of west Antarctica and parts of it are cooling. The Scientific Committee on Antarctic Research report prepared for last week’s meeting of Antarctic Treaty nations in Washington noted the South Pole had shown “significant cooling in recent decades”.
Australian Antarctic Division glaciology program head Ian Allison said sea ice losses in west Antarctica over the past 30 years had been more than offset by increases in the Ross Sea region, just one sector of east Antarctica.
“Sea ice conditions have remained stable in Antarctica generally,” Dr Allison said.
The melting of sea ice – fast ice and pack ice – does not cause sea levels to rise because the ice is in the water. Sea levels may rise with losses from freshwater ice sheets on the polar caps. In Antarctica, these losses are in the form of icebergs calved from ice shelves formed by glacial movements on the mainland.
Last week, federal Environment Minister Peter Garrett said experts predicted sea level rises of up to 6m from Antarctic melting by 2100, but the worst case scenario foreshadowed by the SCAR report was a 1.25m rise.
Mr Garrett insisted global warming was causing ice losses throughout Antarctica. “I don’t think there’s any doubt it is contributing to what we’ve seen both on the Wilkins shelf and more generally in Antarctica,” he said.
Dr Allison said there was not any evidence of significant change in the mass of ice shelves in east Antarctica nor any indication that its ice cap was melting. “The only significant calvings in Antarctica have been in the west,” he said. And he cautioned that calvings of the magnitude seen recently in west Antarctica might not be unusual.
“Ice shelves in general have episodic carvings and there can be large icebergs breaking off – I’m talking 100km or 200km long – every 10 or 20 or 50 years.”
Ice core drilling in the fast ice off Australia’s Davis Station in East Antarctica by the Antarctic Climate and Ecosystems Co-Operative Research Centre shows that last year, the ice had a maximum thickness of 1.89m, its densest in 10 years. The average thickness of the ice at Davis since the 1950s is 1.67m.
A paper to be published soon by the British Antarctic Survey in the journal Geophysical Research Letters is expected to confirm that over the past 30 years, the area of sea ice around the continent has expanded.