As glaciers shrink, the Alps get taller.

As massive glaciers melt in the Alps, the reduction in weight on those peaks is causing them--and the entire region--to gain altitude.

Recent surveys of Alpine glaciers suggest that the ice masses as a whole are losing more than 1.5 billion tons each year, says Claudio Smiraglia, a glaciologist at the University of Milan in Italy. As glacial melt flows to the sea, immense pressures from deep within Earth that had been counterbalanced by glacial weight cause the planet's crust to spring upward. While some altitude gain occurs almost immediately, the remainder takes place over centuries.

Computer models suggest that in the immediate effects of recent melting, the entire Alpine region is rising about 0.15 millimeter each year, Smiraglia and his colleagues report in the July 28 Geophysical Research Letters. In areas with large, rapidly melting glaciers, such as the Austrian Alps, peaks are rising annually at rates of 0.4 mm or more. Mont Blanc, the tallest peak in the mountain chain, is growing by about 0.9 mm annually, the team estimates.

The models also show a long-term effect of the melting of 155 cubic kilometers of Alpine ice since 1850. That effect contributes an additional altitude gain of 0.32 mm per year, the researchers note.