Melting Glaciers Contribute to Sea Level Rise as much as Ice Sheets

Sea level rise has the potential to make a major impact on coastal nations across the globe. Now, researchers have some more disturbing news. The massive, melting glaciers across Earth contributed as much to sea rise as the Greenland and Antarctic ice sheets combined from 2003 to 2009.

While a lot of attention is being given to ice sheets, less is being given to the glaciers that span the globe. Alaska alone has more than 600 named glaciers, though the Alaska Almanac estimates that the state has approximately 100,000 glaciers total. These massive chunks of ice lock the Earth's water in place, though that changes with warmer temperatures.

In order to examine exactly how much glaciers were contributing to sea rise, researchers examined how much mass glaciers lost from 2003 to 2009. More specifically, they compared traditional ground measurements to satellite data from NASA's Ice, Cloud and Land Elevation Satellite (ICESat) and the Gravity Recovery and Climate Experiment (GRACE) missions.

In the end, the researchers found that all glacial regions lost mass over the course of the years that were examined. The biggest ice losses occurred in Arctic Canada, Alaska, coastal Greenland, the southern Andes and the Himalayas. In fact, they found that glaciers outside of the Greenland and Antarctic sheets lost an average of roughly 260 billion metric tons of ice annually during the study period. This, in turn, caused the oceans to rise .03 inches per year.

"For the first time, we've been able to very precisely constrain how much these glaciers as a whole are contributing to sea level rise," said Alex Gardner of Clark University, the lead study author, in a news release. "These smaller ice bodies are currently losing about as much mass as the ice sheets."

There's a reason that glaciers haven't been receiving as much attention as ice sheets, though. Current estimates actually predict that if all glaciers in the world were to melt, they would raise sea levels by about two feet. In contrast, an entire Greenland ice sheet melt would raise sea levels by about 20 feet. A completely melted Antarctica, in contrast, would raise levels by nearly 200 feet.

"Because the global glacier ice mass is relatively small in comparison with the huge ice sheets covering Greenland and Antarctica, people tend not to worry about it," said Tad Pfeffer, study co-author, in a news release. "Buts it's like a little bucket with a huge hole in the bottom: it may not last for very long, just a century or two, but while there's ice in those glaciers, it's a major contributor to sea level rise."

The new findings highlight the unprecedented level of melting in these glaciers, and could help researchers better estimate levels of sea rise. While the glaciers remain, they are a significant source of melting ice.

The findings are published in the journal Science.