Sea-level rise over the coming century could affect some regions far more than others, according to a numerical model which projects that parts of the Pacific will see the highest rates of rise while some polar regions will experience falls in relative sea levels due to the ways sea, land and ice interact globally.

In their Geophysical Research Letters article the researchers simulated out to the year 2100 to calculate how ice loss will continue to add to rising sea levels. It's well known that sea level rise around the globe will not be uniform, but the ice2sea researchers say 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 U.K.'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 focused on three effects that lead to global mean sea-level rise being unequally distributed around the world.:

First, 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. 

Second, the warming of the oceans leads to a change in the distribution of water across the globe. 

Third, 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" and the other was the upper limit of what could happen.  

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."

Co-author Jonathan Bamber of Bristol University, said, "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."

Citation: G. Spada1, J. L. Bamber, R. T. W. L. Hurkmans, 'The gravitationally consistent sea-level fingerprint of future terrestrial ice loss', Geophysical Research Letters Article first published online: 13 FEB 2013 DOI: 10.1029/2012GL053000