By Greg Roberts - The Australian
April 18, 2009
RUSSIAN sea captain Dimitri Zinchenko has been steering ships through the pack ice of Antarctica for three decades and is waiting to see evidence of the global warming about which he has heard so much.
Zinchenko’s vessel, the Spirit of Enderby, was commissioned in January last year to retrace the steps of the great Antarctic explorer Ernest Shackleton, marking the century of his Nimrod expedition of 1907-09.
Spirit of Enderby was blocked by a wall of pack ice at the entrance to the Ross Sea, about 400km short of Shackleton’s base hut at Cape Royds. Zinchenko says it was the first time in 15 years that vessels were unable to penetrate the Ross Sea in January. The experience was consistent with his impression that pack ice is expanding, not contracting, as would be expected in a rapidly warming world. “I see just more and more ice, not less ice.”
Rodney Russ, whose New Zealand company Heritage Expeditions has operated tourist expeditions to Antarctica for 20 years, agrees. He says ships regularly used to able to reach the US base of McMurdo in summer, but ice has prevented them from doing so for several years.
“Vessels are usually stopped 8km to 14km short of the base. A few years ago, that was often open water,” Russ says. “We have experienced quite severe ice conditions over the past decade. I have seen nothing in this region to suggest global warming is having an effect.”
Such observations are not in step with the popular perception of what global warming is doing to the polar icecaps. Reports last week that an ice bridge had snapped in west Antarctica, threatening the disintegration of the Wilkins Ice Shelf, generated international headlines. Environment Minister Peter Garrett insisted that although he had not received any scientific advice about the Wilkins break-up, he was in no doubt about the implications.
“It’s a big event. There are many others that have been identified in and around the Antarctic, which I think tells us unequivocally that we’re seeing climate change impacts,” Garrett said.
The real story about ice and Antarctica, however, is more complicated.
With Antarctica holding 80 per cent of the world’s fresh water and 90 per cent of its ice, a meltdown of the icecap would raise sea levels worldwide by a catastrophic 70m. With the depth of the icecap averaging 4km, nothing like that is on the horizon. But is there cause for concern about what is happening with the weather in Antarctica?
Climatologists say if temperatures rise by 4C to 6C by the end of the century – the upper limit predicted by the UN Intergovernmental Panel on Climage Change – the melting of ice sheets in west Antarctica and Greenland would raise sea levels by up to 1.5m, enough to create problems in coastal areas.
What is less certain is whether ice shelf losses in west Antarctica, such as Wilkins, are being offset by cooling conditions and ice expansion in east Antarctica, which is four times the size of west Antarctica.
Unlike the Arctic, there has been no certainty that global warming is having an effect across Antarctica, although temperatures have risen in parts of west Antarctica, especially on the Antarctic Peninsula. The peninsula is geologically more an extension of the Andes of South America than part of the Antarctic continent. The crucial distinction between west Antarctica and the much larger east Antarctica is rarely mentioned in media reports of ice shelf break-ups.
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