Scientists are saying a global warming "tipping point" in the Arctic seems to be happening before their eyes.

Data show that sea ice in the Arctic Ocean is at its second lowest level in about 30 years.

The National Snow and Ice Data Center reports ice now covers slightly more than two million square miles. The lowest point since satellite measurements began in 1979 was 1.65 million square miles set last September. And with about three weeks left in the Arctic summer, scientists say this year could wind up breaking that previous record low.

Arctic ice always melts in summer and refreezes in winter. But over the years, more of the ice is lost to the sea, with less of it recovered in winter. While ice reflects the sun's heat, the open ocean absorbs more heat and the melting accelerates warming in other parts of the world.

Sea ice also serves as primary habitat for threatened polar bears.