Es di Antartika Tidak Mencair Bahkan Sebaliknya
(Antarctic ice is growing, not melting away)
By Greg Roberts
The Australian
April 18, 2009
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Cool down ... ice is expanding in much of the Antarctic, experts say / Reuters |
Ice expanding in much of Antarctica Eastern coast getting colder Western section remains a concernICE 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.
Comments on this story
Andrew Glikson Posted at 9:36am today
Andrew Glikson Posted at 9:36am today
It is to be hoped that, despite global warming in other parts of the Earth (a global mean of 0.6 degrees C since the mid 1970s) the East Antarctic continental ice holds, since otherwise progressive melting would result in major sea level rises. Melting of the cryosphere is not a regular or smooth process, some areas melt and some cool. Large parts of the Arctic Sea, northern Siberia and west Antarctica have warmed over the last 30-40 years by almost 3 degrees C and in some cases 4 degrees C, relative to the 1951-1980 baseline, which accounts for extensive melting. Based on a combination of ground stations and satellite observations, NASA/GISS reports a mean temperature increase of +0.12 degrees C per-decade for the entire continent of Antarctica, and +0.17 degrees C per-decade for west Antarctica during 1957-2006 (NASA, 21.1.2009). Manifestations of warming include reduced concentration and thickness of sea ice around parts of Antarctica and the disintegration of ice shelves due to the effect of warming seas. While sea ice grows in other parts, it is its thickness which is the problem. In particular part of west Antarctica which overlies sub-sea level basement is vulnerable to sea water-induced melting. While most of the peripheral near-coastal zones of west and east Antarctica display various degrees of warming and glacier melt, small area in east Antarctica have been cooling, a likely result of ozone depletion above Antarctica, ozone being a greenhouse gas, as well as acceleration and wind-chill effect of the Antarctic wind vortex. Larger evaporation over warming oceans results in heavier snowfalls in parts of Antarctica. The concern is that, should overall warming continue, as over the last 50 years ( +0.12 degrees C per-decade for the entire continent), the net ice loss of the cryosphere in both the NH and SH, and associated feedback processes (decrease in albedo due to melting ice and increase in the exposure of infrared abosbing water, which in turn melt more ice), would result in further increase in sea level.
Michael Chiu of Fall City, WA. USA Posted at 2:01am today
I think opinions expressed civilly are heard more clearly. The expansion of sea ice in the southern polar region is not conflicting with the theory of global warming. This phenomena was predicted in models in 2005 (see Science Daily 6/30/05) and illlustrates the asymmetry of global warming affect (see www.artic.atmos.uiuc ). Caution should be exercised when reading short media accounts of complex scientific matters. One should NEVER reach a conclusion based upon one event, in one geographical location, at one point in time. To do so would be grasping at convenient truths!! The discussion is not if global warming is occurring but rather causation and effect. Politicians and media outlets do not help clarify the causation question with their spin. Neither does vehement attacks and snipes upon each other.
Andre Barreto of Brazil Posted at 11:49pm April 20, 2009
This is just my opinion, but I'm a scientist. Not a glaciologist, but an oceanographer. I read a lot of those reports and news about Global warming (GW), and most of the problems come from half-truths. Like when the article says ¿Antarctica has 90 per cent of the Earth's ice¿, it's not wrong but not entirely right. Antartica hold's 90% of the _over_land_ice_, and this makes a BIG difference. GW is a fact, there's no arguing with that. But what scientists are discussing is how much warmer and _where_ it'll get warmer. Earth isn't a homogeneous sphere... Some places will get warmer and others (some simulations predict) will get cooler. The most severe effects of GW will be in the northern hemisphere, because most land masses are there. The oceans have a great 'heat-trap' effect, due to water's specific heat. So different distributions of oceans leads to different GW effects. Thus Antarctica may be cooling even if we have a GW going on. Science is about facts, not opinions, as some here have pointed out. But as some governments have tried to modify scientific reports in order to support their political views, we must always try to read all the info available and decide for ourselves.
