Antarctic ice should set record, but Arctic dwindles

Though the amount of sea ice at the Antarctic should set an all-time record high this month, Arctic ice shrank to its sixth-lowest level on record, scientists from the National Snow and Ice Data Center reported this week.

September is the month when Antarctic ice usually reaches its highest extent of the year, at the end of the Southern Hemisphere winter. It's also when Arctic ice typically reaches its annual minimum, as our summer draws to a close.

Sea ice is frozen ocean water that melts each summer, then refreezes each winter.

"Antarctic sea ice is poised to set a record maximum this year, now at 7.6 million square miles and continuing to increase," the ice center noted on its website. Sea ice data goes back to 1979, when satellites first began to measure it.

What does this say about global warming?

Multiple factors — including the geography of Antarctica, the region's winds, as well as air and ocean temperatures — affect the ice around the world's coldest continent.

The amount and volume of ice in Antarctica depend on a complex relationship among air, water, wind and ozone depletion, involving natural and man-made influences, scientist Ted Scambos of the data center said this year.

Two studies in recent years concluded that changing wind patterns were responsible for the expanding sea ice, Scambos said.

Arctic sea ice extent this week was at 1.96 million square miles, well below the long-term average. The average minimum Arctic ice extent each summer, based on data from 1979 to 2010, is about 2.37 million square miles.

"The Northwest Passage remains closed, while the Northern Sea Route is still largely clear of ice," the ice data center reported.

Arctic sea ice extent, overall, has been steadily diminishing over the years because of man-made climate change. Some of the Earth's most extreme rate of warming (when compared with the average) has been over the Arctic over the past few decades.