* Pine Island glacier shrank 8,000 years ago, lasted decades* New melt similar, will add to sea level rise-Science studyBy Alister Doyle, Environment CorrespondentOSLO, Feb 20 (Reuters) - A thawing
A thawing Antarctic glacier that is the biggest contributor to rising sea levels is likely to continue shrinking for decades, even without an extra spur from global warming, a study showed on Thursday.
Scientists said the Pine Island Glacier, which carries more water to the sea than the Rhine River, also thinned 8,000 years ago at rates comparable to the present, in a melt that lasted for decades, perhaps for centuries.
A creeping rise in sea levels is a threat to low-lying coasts from Bangladesh to Florida, and to cities from London to Shanghai. Of the world's biggest glaciers, in Antarctica and Greenland, Pine Island is the largest contributor.
The trigger of the ancient thinning, of about a metre (3 ft) a year, was probably a natural climate shift that warmed the sea and melted the floating end of the glacier, removing a buttress that let ice on land slide more quickly into the sea.