Mass loss from Alaskan glaciers largely overestimated say researchers

A team of international researchers has said that previous studies have largely overestimated mass loss from Alaskan glaciers over the past 40-plus years.

The research team, led by Etienne Berthier of the Laboratory for Space Studies in Geophysics and Oceanography at the Universite de Toulouse in France, said that glacier melt in Alaska between 1962 and 2006 contributed about one-third less to sea-level rise than previously estimated.

According to Erik Schiefer, a Northern Arizona University geographer, melting glaciers in Alaska originally were thought to contribute about .0067 inches to sea-level rise per year.

The team's new calculations put that number closer to .0047 inches per year.

The numbers sound small, but as Schiefer said, "It adds up over the decades."

While the team looked at three-fourths of all the ice in Alaska, Schiefer noted, "We're also talking about a small proportion of ice on the planet. When massive ice sheets (such as in the Antarctic and Greenland) are added in, you're looking at significantly greater rates of sea-level rise."

Schiefer and his colleagues used data from the SPOT 5 French satellite and the NASA/Japanese ASTER satellite and converted the optical imagery to elevation information.

They then compared this information to the topographical series maps of glacial elevations dating back to the 1950s.

While the team determined a lower rate of glacial melt during a greater than 40-year span, Schiefer said other studies have demonstrated the rate of ice loss has more than doubled in just the last two decades.

"With current projections of climate change, we expect that acceleration to continue," Schiefer said.

This substantial increase in ice loss since the 1990s is now pushing up the rise in sea level to between .0098 inches and .0118 inches per year-more than double the average rate for the last 40 years.