OCEANS SET TO RISE MANY METRES

An analysis of records left by the Last Interglacial led by the University of Arizona has found that most of the 8-metre rise in sea-levels was due to the melting of ice-sheets, not thermal expansion, and that average ocean temperatures then were only 0.7 degrees Celsius above what they are now.

'This means that even small amounts of warming may have committed us to more ice sheet melting than we previously thought. The temperature during that time of high sea levels wasn't that much warmer than it is today,' said Nicholas McKay, a doctoral student at the UA's department of geosciences and the paper's lead author.

McKay pointed out that even if ocean levels rose to similar heights as during the Last Interglacial, they would do so at a rate of up to a metre per century.

'Even though the oceans are absorbing a good deal of the total global warming, the atmosphere is warming faster than the oceans. Moreover, ocean warming is lagging behind the warming of the atmosphere. The melting of large polar ice sheets lags even farther behind. As a result, even if we stopped greenhouse gas emissions right now, the Earth would keep warming, the oceans would keep warming, the ice sheets would keep shrinking, and sea levels would keep rising for a long time.'

Jonathan Overpeck, co-director of the UA's Institute of the Environment and a professor with joint appointments in the department of geosciences and atmospheric sciences, said: 'This study marks the strongest case yet made that humans--by warming the atmosphere and oceans--are pushing the Earth's climate toward the threshold where we will likely be committed to four to six or even more metres of sea level rise in coming centuries.'

Overpeck, who is McKay's doctoral advisor and a co-author of the study, said: 'Unless we dramatically curb global warming, we are in for centuries of sea level rise at a rate of up to three feet per century, with the bulk of the water coming from the melting of the great polar ice sheets--both the Greenland and Antarctic Ice Sheets.'

Full story at ScienceDaily.