Arctic ice melting rapidly, study says

This satellite image released by NASA shows the concentration of Arctic sea ice in 2005....

Arctic sea ice in winter is melting far faster than before, two new

NASA studies reported Wednesday, a new and alarming trend that researchers say threatens the ocean's delicate ecosystem.

Scientists point to the sudden and rapid melting as a sure sign of man-made global warming.

"It has never occurred before in the past," said NASA senior research scientist Josefino Comiso in a phone interview. "It is alarming... This winter ice provides the kind of evidence that it is indeed associated with the greenhouse effect."