Atmospheric and
Oceanic Sciences

Weekly Weather Event -Week of November 2nd

November 6, 2020

While Wisconsin is having an unusually warm start to November, the Northern Hemisphere is well into the fall season. In a typical year, this also marks the beginning of sea ice growth in the Northern Hemisphere. Arctic sea ice coverage is at its low during the month of September, but the colder October weather marks a turning point where the Arctic ocean begins to refreeze. This year, however, has seen the slowest growth of sea ice on record for the month of October, rising from 1.5 million square kilometers in September to just 5.4 million square kilometers in October. The ice extent is well below average on the Eurasian side of the Arctic Ocean, as well as in Baffin Bay. Researchers from the National Snow and Ice Center have confirmed that this is the largest departure from average conditions so far in the satellite record.

These extremely low ice records are largely due to a heat wave that hit the Arctic over the summer. Warmer temperatures accelerated ice melt, exposing large swaths of the Arctic Ocean to direct sunlight. This caused the water temperatures to warm by more than 5 degrees Celsius above average, slowing ice growth come fall, especially over the Laptev Sea near Siberia. The Laptev Sea is known to be an important region of ice formation in the Arctic, as offshore winds promote and accelerate ice formation. These flows are then transported throughout the Arctic, helping to cool and freeze the ocean during the colder months.

Given how late in the season this freeze is coming, any sea ice that forms will be thinner and weaker than in previous tears. Younger ice is more likely to melt earlier in the spring, resulting in more warming of the Arctic Ocean and weaker ice come next winter. This process is a well understood positive climate feedback loop, where melting of ice and warming of the oceans contributes to more melting of ice and increased warming of the oceans. As this process continues to happen, the world can expect to see a completely ice-free Arctic summer in the coming decades.