Thursday, February 21, 2013

New projections of 'uneven' global sea-level rise

EurekAlert via the British Antarctic Survey: Sophisticated computer modelling has shown how sea-level rise over the coming century could affect some regions far more than others. The model shows that parts of the Pacific will see the highest rates of rise while some polar regions will actually experience falls in relative sea levels due to the ways sea, land and ice interact globally.

Reporting in the journal Geophysical Research Letters researchers have looked ahead to the year 2100 to show how ice loss will continue to add to rising sea levels. Scientists have known for some time that sea level rise around the globe will not be uniform, but in this study the team of ice2sea researchers show in great detail the global pattern of sea-level rise that would result from two scenarios of ice-loss from glaciers and ice sheets.

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."....

From NASA, the first flight of Operation Ice Bridge’s Antarctic campaign flew Oct. 16, 2009, along the Amundsen Coast. The aircraft’s downward-looking Digital Mapping System camera captured images of sea ice from an altitude of at least 20,000 feet.

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