By Nina Chestney
LONDON (Reuters) - Greenland's ice sheet is melting at a faster rate than previously thought and continued global warming will accelerate thawing and contribute to rising sea levels, scientists said in a paper published on Wednesday.
Rising seas threaten low-lying cities, islands and industries worldwide. Forecasts for how high and how soon the rise will come vary greatly, partly because scientists lack clarity on how fast warming oceans are melting polar ice sheets.
Melting ice in Greenland, home to the second largest mass of ice after Antarctica, is thought to add 0.8 millimetres of water to global ocean levels annually, more than any other region, according to NASA.
In a paper published in the journal Nature, scientists from the United States, Belgium and the Netherlands analysed melt layers in ice cores in western Greenland to develop a record spanning 350 years.
The magnitude of Greenland ice sheet melting is "exceptional" over at least the last 350 years and continued growth of global average temperature will accelerate the melting and contribute to sea level rise, the study said.
Ice sheet melting began to increase soon after the mid-1800s. Surface melting was the most extensive in 2012 than any time over the past 350 years and the period of 2004-2013 had more sustained and intense melting than any other 10-year period recorded.
"We are seeing levels of Greenland ice melt and runoff that are already unprecedented over recent centuries (and likely millennia) in direct response to warming global temperatures since the pre-Industrial era," Sarah Das, co-author of the report and scientist at the U.S.-based Woods Hole Oceanographic Institution said in a statement.
The study showed that although a minor warming event in the past might have had little or no impact on the melting, the same event in a warmer climate in the future could produce a larger melt effect.
"What this means for the future is that for every further degree of warming, we will lose much more ice, on the order of a
doubling or more (leading to faster rates of sea level rise), than we did for the same degree of warming in the past," Das said.
Low-lying tropical island states from the Maldives to Tuvalu view Greenland's 3,000-metre (10,000 ft) thick ice sheet with foreboding since it contains enough ice to raise world sea levels by around 7 metres if it all melted, over many centuries.
A U.N. report in October said that marine ice sheet instability in Antarctica and/or the irreversible loss of the Greenland ice sheet could result in a multi-metre rise in the sea level over hundreds to thousands of years.
Around 190 countries are currently meeting in Poland to work out the details of the 2015 Paris Agreement which aims to limit temperature rise to below 2 degrees Celsius this century.
(Reporting by Nina Chestney; Editing by Elaine Hardcastle)