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| Sea ice around Antarctica [Credit: British Antarctic Survey] |
The team, from Italy's University of Urbino and the UK's University of Bristol, found that ice melt from glaciers, and the Greenland and Antarctic ice sheets, is likely to be of critical importance to regional sea-level change in the Equatorial Pacific Ocean where the sea level rise would be greater than the average increase across the globe. This will affect in particular, Western Australia, Oceania and the small atolls and islands in this region, including Hawaii.
The study focussed on three effects that lead to global mean sea-level rise being unequally distributed around the world. Firstly, land is subsiding and emerging 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 it is still deforming. Secondly, the warming of the oceans leads to a change in the distribution of water across the globe. Thirdly 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 its pull decreases and the water previously attracted rushes away to be redistributed around the globe.
Co-author Professor Giorgio Spada says, "In the paper we are successful in defining the patterns, known as sea level fingerprints, which affect sea levels.
"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."
He added that in Europe the sea level would rise but it would be slightly lower than the global average.
"We believe this is due to the effects of the melting polar ice relatively close to Europe – particularly Greenland's ice. This will tend to slow sea-level rise in Europe a little, but at the expense of higher sea-level rise elsewhere."
The team considered two scenarios in its modelling. One was the "most likely" or "mid-range" and the other closer to the upper limit of what could happen.
Professor Spada said, "The total rise in some areas of the equatorial oceans worst affected by the terrestrial ice melting could be 60cm if a mid-range sea-level rise is projected, and the warming of the oceans is also taken into account." David Vaughan, ice2sea programme coordinator, says, "In the last couple of years programmes like ice2sea have made great strides in predicting global average sea-level rise. 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."
Co-author Jonathan Bamber, of Bristol University, says, "This is the first study to examine the regional pattern of sea level changes using sophisticated model predictions of the wastage of glaciers and ice sheets over the next century."
Source: British Antarctic Survey via EurekAlert! [February 18, 2013]