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Greenland 'lurched upward' in 2010 as 100bn tons of ice melted

Maybe not time to panic just yet, though

The smart choice: opportunity from uncertainty

Parts of southern Greenland apparently lurched upwards by as much as 20mm as glaciers melted and ran off into the sea during 2010, according to scientists. It's thought that as much as 100 billion tons more ice than usual may have vanished from the island's ice sheet that year.

Professor Michael Bevis outlined his findings in a presentation at a conference in San Francisco on Friday. Bevis is lead boffin in charge of a network of groundbased GPS stations placed on bedrock outcrops around the Greenland coast, which were set up to measure rises in the rock as the weight of ice atop it diminishes. The stations were set up when gravity-measuring satellite measurements appeared to show colossal rates of ice loss from Greenland, in the range of 300 billion tons annually.

However the stations showed that the initial satellite calculations had failed to properly estimate the bedrock's rebound, and in fact scientists now think that losses from Greenland are probably more in the range of 100 billion tonnes a year, which might cause a worldwide sea level rise in the order of a quarter of a millimetre annually. Prof Bevis's possible extra 100 billion tonnes could thus mean that an extra quarter-mm occurred from Greenland in 2010.

“Really, there is no other explanation," he argues. "The uplift anomaly correlates with maps of the 2010 melting day anomaly. In locations where there were many extra days of melting in 2010, the uplift anomaly is highest.”

This doesn't seem to mean anything very significant for sea levels globally, however. Throughout the 20th century (about as long as consistent records have been kept) sea levels rose slowly and steadily at around 1.7mm each year, and they have been rising for tens of thousands of years since the last ice age. Like world temperatures, sea levels vary a lot year to year, so they must be measured over a long period to detect any trend.

Various global-warming models and predictions suggest that sea-level rise might accelerate massively in a runaway positive feedback loop if global temperatures climb, and so become a major problem - probably the main reason to worry about global warming, if such massive accelerations in the rate of rise actually occur. However the warming seen in the latter half of the 20th century in fact produced no such acceleration. Indeed recent research indicates that the normal rise of the seas may be slowing down somewhat. Even the reliably alarmist IPCC acknowledges that "no long-term acceleration of sea level has been identified using 20th-century data alone".

Against such a background a possible extra quarter-mm of sea level rise in 2010 doesn't mean a whole lot, then. But a major land mass surging upwards (well, parts of it - "stations in the North of Greenland barely moved at all", says Bevis) as gigatons of ice runs off into the sea makes for a good exciting press release, anyway. ®

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