Mar 3, 2017

Sea Ice Extent in Antarctica Bottoming Out at Lowest on Record

Antarctica
by
Bob Henson
,
Category 6
Sea ice extent for the five-day period ending March 2 (right-hand end of pale blue line) is lower than at any point since satellite measurements began in 1979. Averaged over the preceding five days, the extent on Thursday, March 2, was 2.113 million square kilometers. The next-lowest value for this date, in 1997, had about 236,000 more sq km than 2017. Image: NSIDC
Sea ice extent for the five-day period ending March 2 (right-hand end of pale blue line) is lower than at any point since satellite measurements began in 1979. Averaged over the preceding five days, the extent on Thursday, March 2, was 2.113 million square kilometers. The next-lowest value for this date, in 1997, had about 236,000 more sq km than 2017. Image: NSIDC

As summer draws to a close across the Southern Hemisphere, the extent of sea ice ringing Antarctica has fallen to the lowest values ever observed in satellite records dating back to 1979. On Wednesday, March 1, the daily extent data from the National Snow and Ice Data Center (NSIDC) showed 2,109,000 square kilometers of Antarctic sea ice, its lowest value on record. That value nudged up slightly on Thursday, but a more useful measure, the five-day rolling average, hit its lowest value yet on Thursday (see Figure above). Update: The five-day average fell even lower on Friday, March 3, dropping from 2,113,000 to 2,106,000 sq. km.

We can expect the regular autumn rebound in southern ice to kick in very soon now. However, this has been a notably persistent melt season--one that wouldn’t take too much longer to break a record for tardiness. If Thursday’s five-day average turns out to be the lowest for the summer, it will be tied with March 2, 1991 for third-latest minimum behind March 6, 1986 and March 3, 2003.

“It could start trending upward any day,” sea ice expert Walt Meier (NASA Goddard Space Flight Center) told me on Thursday. “Of course, this year has been rather unusual, so it would not surprise me to see it going into unprecedented territory.”