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Glaciers
Ruben Herrera
Physical Geology
Spring 2006
 
 

MELTING GLACIERS

 

            Studies continues to show that 84 percent of the Antarctic glaciers are in withdraw over the past 50 years in response to a warmer climate. The scientists who performed the work based in on 2,000 aerial satellite photos, some taken in the 1940s, and they said that the climate in the region has warmed by more than 4.5 degrees Fahrenheit (2.5 Celsius) in the last 50 years.

 

"The widespread retreat of the glaciers on the Antarctic Peninsula over the last 50 years was largely caused by climate change," said David Vaughan of the British Antarctic Survey in Cambridge. "Are humans responsible? 

 

 About 10 percent of Earth's land is covered with glaciers.

During the last Ice Age, glaciers covered 32 percent of land.

Glaciers store about 75 percent of the world's fresh water.

Antarctic ice is more than 2.6 miles (4,200 meters) thick in some areas.

If all land ice melted, sea level would rise approximately 230 feet (70 meters) worldwide. SOURCE:NOAA

            Among the most comprehensive surveys ever done was one by Alison Cook and is detailed in the April 22 issue of the journal Science), it looked at floating glacier-ice shelves, which are connected to the land-based glacier from which they flowed, and tidewater glaciers that rest on land and break off into the ocean when they reach the water. Of those that retreated, the average retreat was 1,970 feet (600 meters) since 1953. The Sjogren Glacier retreated 8 miles (13 kilometers) since 1993. Ocean temperatures may also play a role in the retreats, but there is no solid data on how those might have changed, the researchers said. (Britt) 

 

A map of the change in thickness of mountain glaciers since 1970.  Thinning in orange and red, thickening in blue.
 

A map of the change in thickness of mountain glaciers since 1970. Thinning in orange and red, thickening in blue.

           

            Glacial retreat is a complex phenomenon that often involves thinning of the glacier, too. As glaciers melt, they sometimes move toward the sea more quickly, exacerbating the melting. Where a glacier meets the sea, an ice shelf can hold it back. When those ice shelves break apart, however, a glacier can become a runaway. Whether the planet is actually warming has been controversial. Last fall, however, two separate reports concluded that Earth's overall climate has warmed by about 1 degree Fahrenheit since 1900. A separate recent study said that regardless of what humans do or don't do, the world's oceans are destined to rise at least 4 inches (10 centimeters) in the next century because of climate wheels already in motion. Half a century ago, most Antarctic glaciers that flowed from the mountains to the sea were slowly growing in length, Cook said, "but since then this pattern has reversed. In the last 5 years the majority were actually shrinking rapidly."(Britt) 

 

 

Pasterze

1875 photo courtesy H. Slupetzky/University of Salzburg

Pasterze

 

Alaska's glaciers are receding at twice the rate previously thought, according to a new study published in the July 19, 2002 Science journal. These two images show Portage Glacier, near Anchorage, Alaska, in about 1950 and in July 2001. The ice has pulled back nearly out of sight.

 

 

Portage Glacier 1914
Portage Glacier 1914

Portage Glacier 2004
Portage Glacier 2004
 

            The loss of glaciers not only directly causes landslides, flash floods and glacial lake overflow, but also increases annual variation in water flows in rivers. Glacier runoff declines in the summer as glaciers decrease in size, this decline is already observable in several regions. Glaciers retain water on mountains in high precipitation years, since the snow cover accumulating on glaciers protects the ice from melting. In warmer and drier years, glaciers offset the lower precipitation amounts with a higher meltwater input.  

 

WORK CITED

 

Wikipedia: The Free Encyclopedia

http://en.wikipedia.org/wiki/Effects_of_global_warming

 

Antarctic Glaciers Melting Rapidly by Robert Roy Britt

LiveScience Senior Writer posted: 21 April 2005

http://www.livescience.com/environment/050421_glacial_retreat.html