by Natura Naturans
The Arctic freeze-up season is well underway, with ice extent increasing faster than average for most regions in November. Exceptions were in the Chukchi and Barents Seas, where the ice has been slow to form. Meanwhile, November snow cover over North America was the most extensive since 1966, the National Snow and Ice Data Center (NSIDC) reported in their analysis released December 4, 2018.
Arctic sea ice extent for November averaged 9.80 million km2 (3.78 million mi2), the center reports. This was the 9th lowest November in the 1979 to 2018 satellite record, falling 900 000 km2 (347 000 mi2) below the 1981 to 2010 average, yet 1.14 million km2 (440 000 mi2) above the record November low in 2016.
Sea ice extent increased quite rapidly during the early part of the month, bringing the extent within the interdecile range of the 1981 to 2010 climatology during the latter half of the month. This was due in part to the Laptev Sea finally freezing up after having extensive open water through the end of October, as discussed in their previous post.
There was also considerable ice growth in Hudson Bay, Baffin Bay, the Chukchi Sea, and the Kara Sea. This rapid growth is not particularly surprising, NSIDC scientists said.
As the sun has set in the Arctic, the atmosphere has strongly cooled. As soon as the remaining open ocean water loses its heat to the atmosphere, ice growth occurs. Further, the increased area of open water in summer had led to increased frequency of rapid ice growth events in mid to late autumn, in which more than 1 million km2 (386 000 mi2) of ice can form within a 7-day period (see Stroeve and Notz, 2018).
An early start to the snow season for much of North America
While parts of Alaska had their latest first snowfall, based on data at the Rutgers Global Snow Lab, North America as a whole had the highest November snow extent in the 1966 to 2018 record.
Above average snow cover was particularly notable over central and eastern Canada.
Over Eurasia, snow cover was slightly above average for this time of year. The extensive snow cover over eastern Canada was related to low pressure over the North Atlantic that brought cold air from the Arctic into the region.