Tuesday, February 19, 2013

Climate: New study maps regional sea level rise variation « Summit County Citizens Voice

FRISCO — Intensifying concerns about the potential for sea level rise to swamp low-lying Pacific island nations are justified, according to a new report in Geophysical Research Letters.

Western Australia, Oceania and the small atolls and islands in this region, including Hawaii, are at greatest risk, according to the new study from EU’s ice2sea program.

The results of the modeling mirror observational data that’s been collected by satellites in the past few decades, said David Vaughan, program coordinator for EU’s ice2sea program, which seeks to develop more accurate sea level rise predictions.

“The urgent job now is to understand how global the sea-level rise will be shared out around the world’s coastlines. Only by doing this can we really help people understand the risks and prepare for the future,” Vaughn said, explaining that some regions will actually see relative sea levels decline because of the way land and ice interact globally.

The research team included scientists from Italy’s University of Urbino and the UK’s University of Bristol. The study focussed on three effects that lead to global mean sea-level rise being unequally distributed around the world.

One key factor is the continuing subsidence and emergence of land masses due to a massive loss of ice at the end of the last ice age 10,000 years ago when billions of tons of ice covering parts of North America and Europe melted. This caused a major redistribution of mass on the Earth, but the crust responds to such changes so slowly that the process is still ongoing.

The overall warming of the oceans will also change in the distribution of water across the globe by altering circulation patterns and currents. For example, scientists have documented a depletion of deep, cold water in the Southern Ocean around Antarctica, a reservoir that helps drive ocean currents worldwide.

The new paper also suggests that the loss of ice in Greenland and Antarctica will affect the regional distribution of sea level rise in another way. For now, the sheer mass of water held in ice at the frozen continents like Antarctica and Greenland exerts a gravitational pull on the surrounding liquid water, pulling in enormous amounts of water and raising the sea-level close to those continents. As the ice melts, that gravitational pull will lessen and the water will rush away and slosh toward equatorial regions.

“In the paper we are successful in defining the patterns, known as sea level fingerprints, which affect sea levels,” said University of Urbino Professor Giorgio Spada. “This is paramount for assessing the risk due to inundation in low-lying, densely populated areas. The most vulnerable areas are those where the effects combine to give the sea-level rise that is significantly higher than the global average,” Spada said, adding that, in Europe, sea level will rise but it would be slightly lower than the global average. More