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Warmer Ocean Waters Threaten Glaciers, Ice Sheets Worldwide

NASA scientist says higher temperatures creeping into Earth's cold areas

Pieces of a years-old scientific puzzle have come together to confirm that warmer water temperatures are creeping into the Earth's colder areas, a NASA scientist says.

Those warm waters are increasing melting and accelerating ice flow in polar areas, according to a March 23 NASA press release.

The conclusion appears in an article by Robert Bindschadler, a glaciologist at NASA's Goddard Space Flight Center in Maryland, published in the March 24 issue of Science magazine.

Water temperatures collected by ships and buoys showed a warming of all oceans. That increase began before satellite sensors detected temperature increases of sea surfaces.

Most warming was limited to the oceans' upper 1,000 meters, except in the North Atlantic. In the cold North Atlantic waters, heat penetrated even deeper. This warming has increased the melting of sea ice in the North Atlantic.

Overall ocean heat content changes are monitored by ocean altimetry (altitude-measuring) satellites like TOPEX and Jason-1. The seagoing Argo network of ocean buoys broadcasts ocean temperature measurements to a satellite.

MELTING, ACCELERATING ICE FLOW IN GREENLAND

Bindshadler's research reveals another effect that potentially could be of great significance to sea-level rise - the warm waters are starting to melt the underside of the floating fringes of the Greenland ice sheet, even at great depths. These fringes have been holding back vast stores of ice locked up in the Greenland ice sheet, and as this ice has been melting, the glaciers have hastened their flow to the sea.

A recent assessment in the changes in speed and the amount of snow and ice around Greenland confirms a large melting of outflow glaciers and acceleration of ice flow.

Three large glaciers - the Kangerdlugssuaq, Helheim and Jakobshavns Isbrae - have been melting at a rapid rate over the past several years. Jakobshavns, the largest glacier on Greenland's east coast, has been thinning at 15 meters annually since 1997.

The other two glaciers also have been thinning - Kangerdlugssuaq at 40 meters per year and Helheim at 25 meters per year - a phenomenon that cannot be explained by normal melting. All these glaciers also have been accelerating in their meltdown.

This rapid melt is not just happening in Greenland; scientists also are seeing similar behavior in Antarctica.

"Deep outlet glaciers around both major ice sheets are accelerating, and thinning means warm water has reached them," Bindschadler said. "I see no process to reverse this and expect increased ice sheet discharge to continue and probably to spread, with the result being further accelerations to sea-level rise."

"Understanding just how significant these rapid losses are to the overall ice sheet balance requires a comprehensive look at melt, accumulation and flow characteristics over the entire ice sheet," said Waleed Abdalati, head of the Cryospheric Sciences Branch at Goddard.

Abdalati said satellite and aircraft observations are providing this critical information and that the story still is unfolding, but the evidence is clear to Bindschadler that increased snowfall predicted in a warmer climate cannot possibly keep up with the overall ice sheet balance.

His conclusions cannot be verified without new measurements, and NASA is compiling them with satellites like ICESat. ICESat enables scientists to measure precisely changes in the elevation of ice and snow on glaciers and ice sheets as they respond to a changing climate.

In an effort to understand these changes, NASA continues to monitor sea surface temperatures and the behavior of glaciers and ice sheets around the world.

Source: U.S. Department of State

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