The Arctic Ocean's sea ice is in a "death spiral" due to rising temperatures, scientists said in 2008. Many marine species, such as these narwhals swimming through a bay in Nunavut, Canada, depend on the ice throughout their life cycles. Experts predict that summer Arctic ice may completely disappear within a few decades.

Icebergs, including one with a sapphire pool of meltwater, clutter Greenland's Jakobshavn Fjord near the village of Ilulissat. The glacier that produced this flotilla has receded some four miles (six kilometers) since the year 2000. Glaciers such as Jakobshavn are calving icebergs much faster than scientific models had predicted they would. The ongoing Extreme Ice Survey hopes to shed some light on why these so-called tidewater glaciers, which end in water instead of land, are being lost at such a rapid rate.

Permafrost—the frozen soil that forms the backbone of the Arctic tundra—is melting due to climbing global temperatures. In Alaska, the mercury may rise by 1 to 5 degrees Celsius (1.8 to 9 degrees Fahrenheit) by 2100. In this false-color image of Alaska's North Slope, taken by NASA's Terra satellite, the blue-black color shows the many ponds of meltwater that collected on the coast in July 2007. Photograph courtesy Goddard Space Flight Center