Note: ICCI often gets questions about the unusually cold weather that occasionally has begun to hit sub-Arctic Europe and North America. Below in brief is an explanation and direction to other resources and articles:
The so-called “polar vortex” is a regular upper-atmosphere phenomenon that normally, stays centered over the North Pole. It comprises very high-level winds (even above the jet stream) that normally keep Arctic cold (temperatures well below -25C/0 F) locked well inside the Arctic circle, especially during the winter night. Occasionally however, these winds break down, “splitting” the vortex and allowing portions to spin into lower latitudes, bringing this severe cold with them.
This is what occurred both in mid-January, and at the end of January 2019. Often these affect only one section of the northern hemisphere, but these two events impacted both Europe and North America with vortex “splits.” Researcher Zac Lawrence tweeted a great animation of the mid-January event:
— Zac Lawrence (@zd1awrence) January 14, 2019
Most researchers believe this is occurring due to a rapidly warming Arctic (which as most reading this will know, is occurring at twice the global rate). This winter has been usually warm, with Arctic sea ice at record lows since about December 1, 2018 (figure from Jan. 28, 2019 below; see daily updates at: http://nsidc.org/arcticseaicenews/ .)
Indeed most of the Arctic (Alaska, Greenland, northern Scandinavia) is actually warmer as of this writing (January 29) than the mid-latitudes experiencing this extreme cold: Minneapolis, Minnesota will hit -33C (-27F) tonight; while Fairbanks, Alaska is hovering just below freezing and even Murmansk, Russia is “just” at -14C (7F).
So while it may seem counter-intuitive, today’s extreme cold events are actually one more indication of a changing and warming planet. For more resources and popular science articles on this issue, see some links below – and, stay warm!
Pam Pearson, Director, ICCI