Melting glaciers signal global warming

May 28, 2001

For several years, evidence has been mounting that the global climate is steadily getting warmer. But whether the unusual weather patterns alarming environmentalists -- increasing temperatures, reduced snowfall, and rising sea levels -- are evidence of global warming or just passing blips in the earth's notoriously bumpy weather record continues to stir controversy. Before world leaders unanimously heed their cries of "wolf," scientists studying climate change must be able to tease apart regional climate changes and short-term weather fluctuations, such as El Niño, from permanent changes that are happening worldwide.

ASU geologist Rick Wessels is part of an international team of scientists studying the climate of the entire earth over several years with the Global Land Ice Measurement from Space (GLIMS) project. The team, led by United States Geological Survey (USGS) scientist Hugh Kieffer, is monitoring climate change by tracking the melting of glaciers across the earth. The global scale combined with a long study period will give the scientists the broad perspective needed to determine whether worldwide changes in climate are actually taking place. But in only seven months of monitoring, Wessels has already seen melting in glaciers all over Earth, which provides some solid evidence -- or liquid evidence -- for global warming.

At the Spring Meeting of the American Geophysical Union in Boston, May 29 to June 2, Wessels and co-author Jeff Kargel, a USGS geologist, will present the first round of results from this project in a talk titled "GLIMS: Documenting the Demise of the Earth's Glaciers using ASTER." Wessels will present evidence that thousands of glaciers are melting, corroborating similar arguments made by many other researchers over the last few years. Like shrinking ice cubes in an increasingly steamy atmospheric brew, glaciers around the world appear to be getting thinner or even disappearing entirely, says Wessels. The flooding caused by runoff from these melting glaciers could have disastrous consequences for people living nearby.

Using images of the earth taken from space, Wessels, along with over 50 other GLIMS researchers from 23 countries, is tracking changes in nearly all of the 160,000 glaciers around the world, only about 1,000 of which have been previously studied. Wessels's newest data come from NASA-operated ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer), which takes detailed color and infrared images of the entire earth.

Data collection using ASTER is still in the early stages, but by comparing the newest data with older records, Wessels and his colleagues have already noted some major changes in the sizes of many glaciers around the world. "The majority of these glaciers are receding," says Wessels.

Some growing and shrinking is normal for glaciers, and debris-rimmed lakes within some glaciers may come and go. Despite these fluctuations, glaciers usually maintain their size over the long term. But Wessels has seen a shift in the balance of this cycle. "At first glance, there's more shrinkage than growing," he says, "and there's now a trend for the lakes to stay and grow," rather than drying up or freezing over.

The newest images show that, in the Alps, where many years of records track the mountains' ice formations, several glaciers have disappeared in as little as 40 years. In Argentina, glaciers in the Patagonian ice fields have receded by an average of 1.5 kilometers over 13 years. And in the Himalayan mountains, glaciers are losing bulk as continued melting feeds lakes that sometimes run off to flood surrounding areas. Recently, a lake atop one Himalayan glacier threatened to overflow its natural dam within days, forcing local Nepalese engineers to quickly perform a controlled drain.

Because the melting and retreat is occurring at such a rapid pace, Wessels and his colleagues think global warming is the most likely explanation for the loss of glacial ice. "There is definitely a global climate change," Wessels asserts. Whether the climate warming is a natural cycle or caused by human activity, such as burning fossil fuels, is still being debated.
Danika Painter
Contact: James Hathaway, 480-965-6375

Arizona State University

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