In the Southern Hemisphere, after January 11 sea ice began tracking low, leading to a January average extent that was the second lowest on record. The lowest extent for this time of year was in 2017. Extent is below average in the Ross Sea and the West Amundsen Seas, while elsewhere extent remains close to average.
The low ice extent is puzzling, given that air temperatures at the 925 hPa level are near average or below average (relative to the 1981 to 2010 period) over much of the Southern Ocean.
The Weddell and Amundsen Seas were 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) below average. Slightly above-average temperatures were the rule in the northwestern Ross Sea.