for National Geographic Today
Today the world's ice is restless. Warmer temperatures are melting ice and eroding glaciers from Greenland to Antarctica. But scientists do not know how global warming may affect Earth's two major ice sheets, in Greenland and Antarctica, which hold 77 percent of the world's fresh waterenough to potentially raise the sea level approximately 225 feet (70 meters).
In early December, NASA plans to launch ICESat, a satellite dedicated to the study of ice and how it moves.
ICESat will use lasers to measure the surface elevation of the Greenland and Antarctic ice sheets, which cover 700,000 and 5.3 million square miles (1.7 million and 13.7 million square kilometers), respectively.
These two ice sheets alone, which average 8,000 feet (2,500 meters) thick, cover 10 percent of Earth's land surface.
The new satellite, with a three- to five-year life span, will enable scientists to get a global perspective on how ice sheets grow and shrink.
A Place by the Icebergs
For the residents of Ilulissat, on the west coast of Greenland, ice is part of the landscape. About 10 percent of all Greenland's icebergs come from Ilulissat, which means "place by the icebergs."
A nearby glacier called Sermeq Kujalleqthe most prolific glacier in the Northern Hemisphere and the source of the icebergsproduces 22 million tons of ice each day.
But now, residents of the town say the ice is changing.
"I remember when I was navigating around and the icebergs were so big," says Thorvald Jensen, a former fisherman and skipper of the Esle, a fishing boat converted for tours. "We had one, we called it Matterhorn, and it was measured to be 104 meters [342 feet]. But we don't see them any more. They are not so tall."
Ilulissat's people have an intimate relationship with ice. They fight it and they love it. Melting ice enriches the sea with fresh water and oxygen, which attracts an abundance of fish and fosters a thriving fishing industry. The ice's beauty lures tourists, who pay guides to take them for boat rides amid the icebergs.
Sermeq Kujalleq is about 3,300 feet (1,000 meters) tall, but only 300 feet (100 meters) rise above the water. The glacier breaks up in a fjord near Ilulissat, birthing bergs that drift past the town like visiting mountains.
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