Arctic sea ice melts to its lowest extent. The dotted yellow line indicates the average area from 1979 to 2000

POLAR BEARS: Some 23,000 of these magnificent predators roam the Arctic today. By 2100 dwindling ice could wipe them out.

Shoveling snow during arctic survival training at Eielson Air Force Base, Alaska.

An Arctic tern.

The crew of the Greenpeace ship My Arctic Sunrise construct a heart with the flags of the 193 country members of the United Nations on an ice floe north of the Arctic Circle on September 14, 2012.

Arctic sea ice extent for August 26, 2012 (right) was 4.10 million square kilometers (1.58 million square miles), which was 70,000 square kilometers (27,000 square miles) below the September 18, 2007 daily extent of 4.17 million square kilometers (1.61 million square miles)

A sign reading "Gas!" in Novy Urengoi, just below the Arctic Circle in far northern Russia

Arctic sea ice is melting so fast that most of it could be gone in 30 years, according to a report in April 2009

This visualization shows the extent of Arctic sea ice on Aug. 26, 2012, the day the sea ice dipped to its smallest extent ever recorded in more than three decades of satellite measurements, according to scientists from NASA and the National Snow and Ice Data Center.

An unknown blob floats in the Arctic Ocean off Alaska's North Slope

The Russian Arctic base.

Beyond these mountains lies the Arctic National Wildlife Refuge's coastal plain, a magnificent battleground

Two polar bears on a chunk of ice in the Arctic off Northern Alaska.

Polar bears near the Norwegian island of Spitsbergen, which borders the Arctic Ocean