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Tuesday, April 5, 2011
Glaciers in Chile ‘melt at fastest rate in 350 years
San Rafael Glacier in Patagonia, one of the 270 glaciers included in this study, has retreated about 8km since the peak of the ‘Little Ice Age’
Melting mountain glaciers are making sea levels rise faster now than at any time in the last 350 years, according to new research.
Universities at Aberystwyth, Exeter and Stockholm looked at longer timescales than usual for their study.
They mapped changes in 270 of the largest glaciers between Chile and Argentina since the “Little Ice Age”.
Studies showed glaciers have lost volume on average “10 to 100 times faster” in the last 30 years.
The rapid melt rate is linked to their contribution to global sea level.
The new research was published in the journal Nature Geoscience on Sunday.
Their survey centred on remotely sensed images of outlet glaciers of the south and north Patagonian icefields, but used longer timescales than previous studies.
Satellite image of Upsala Glacier in Patagonia, which has retreated about 13km since 1750
The glaciers straddle the Andes, on the border between Chile and Argentina.
The northern icefield extends for nearly 200 km and covers a surface of 4,200 square km, while the southern icefield is more than 350km long, covering 13,000 square km.
The scientists mapped changes in the position of the glaciers since the “Little Ice Age”.
This took place around 1870 for the north icefield and around 1650 for the southern icefield, the last time that they were much larger in the recent past.
Lead author, Professor Neil Glasser of Aberystwyth University, said: “Previous estimates of sea-level contribution from mountain glaciers are based on very short timescales.
“They cover only the last 30 years or so when satellite images can be used to calculate rates of glacier volume change.
“We took a different approach by using a new method that allows us to look at longer timescales.
‘Above-average’”We knew that glaciers in South America were much bigger during the Little Ice Age so we mapped the extent of the glaciers at that time and calculated how much ice has been lost by the retreat and thinning of the glaciers.”
Their calculations showed that in recent years the mountain glaciers have rapidly increased their melt rate and thus their contribution to global sea level.
Dr Stephen Harrison of the University of Exeter, added: “The work is significant because it is the first time anyone has made a direct estimate of the sea-level contribution from glaciers since the peak of the industrial revolution (between 1750-1850). “
He said their results showed that estimates taken a decade ago of rates of glacier contribution to sea-level rise are “well above” the long-term averages, which cover 1650/1750 to 2010 and 1870-2010.