http://www.juneauempire.com/stories/index.htmlThe fact that these two glaciers are behaving so differently, and at such rapid speeds in recent years, brings scientists from around the state and the world to Juneau every summer. Their studies can help predict how the landscape of Southeast Alaska will change in the coming years, and they can help document how the region's climate has changed over millennia. Some scientists believe the glaciers can indicate what's happening to the global climate today.
The glaciers flowing out of the Juneau Icefield are "the most delicate indicator of climate change that we have anywhere on the planet," said Maynard Miller, a scientist with the University of Idaho. He founded the Juneau Icefield Research Project in 1946, and has sent students and scientists to the ice every summer since to study the size and movement of its glaciers.
The Juneau Icefield is ideal because it is situated right where the low-pressure weather patterns over the Gulf of Alaska meet the high-pressure systems over the continent, Miller said. The arctic front, the name given for the area where these two systems meet, is where the most snow falls over the icefield.
In recent years, the arctic front has moved further east over the continent - a trend that, Miller said, is indicative of a global warming trend.
"One, we're observing the intensity of the changes due to global warming and, two, the rapidity of those changes," said Miller.
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About 90 percent of the glaciers in Alaska are retreating, Motyka said. Only one glacier on the Juneau Icefield bucks this trend: the Taku.
"The Taku is the maverick," said Motyka.
The surging Taku
About 100 years ago, when the Taku was about four miles further up the valley from its present location, it was a tidewater glacier, meaning the ocean and the glacier's face were in direct contact. Icebergs frequently broke off the glacier, a process called calving, and were carried by currents and tides down Taku Inlet and up into Gastineau Channel.
As a tidewater glacier, the Taku moved much more quickly than glaciers that aren't in direct contact with water. But glacier dynamics eventually slowed that movement.
"As (glaciers) advance, they build themselves a moraine, a pile of debris at the terminus," Motyka said. "A tidewater glacier does this submarine. It keeps pushing the debris up, and pretty soon it's got a wall there that protects it from the ocean water, so it stabilizes."
Motyka and his colleagues recorded this stabilization in the 1980s. But while there was little movement of the terminus of the glacier, the thickness of the ice at the terminus was increasing. In the summer of 2001, Motyka returned to the glacier and found it moving.
"We knew that the glacier had to start advancing again sometime because it was getting so thick," Motyka said.
One of Motyka's theories for the Taku's advance is that the high amount of precipitation received at the head of the glacier, on the Juneau Icefield, is overriding the melting at the terminus of the glacier caused by the higher temperatures.
Using the movement of the Taku Glacier to prove or refute any global warming theory is too simplistic, though, Motyka said.
http://www.juneauempire.com/stories/index.htmlAccording to the National Climatic Data Center, a division of the National Oceanic and Atmospheric Administration, global surface temperatures have increased by about 0.6 degrees Celsius, or about 1 degree Fahrenheit, since the late 19th century.
This claim is little disputed among scientists. Scientists also do not dispute the fact that the concentration of carbon dioxide, a greenhouse gas, has increased in Earth's atmosphere in the last century.
What is disputed, among scientists, politicians, industry officials and environmental activists, is the cause and implications of the change.
Many scientists, including those at the U.S. Environmental Protection Agency and the National Oceanic and Atmospheric Administration, believe that the increased amount of carbon dioxide and other so-called "greenhouse gases" in the Earth's atmosphere are causing the rise in temperatures.
They believe these gases are produced by the burning of fossil fuels for energy
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