Another anomalous warming event will be underway this week into next week in the Arctic, potentially impacting the Arctic Ocean sea ice. Basin average air temperature anomalies exceeding +3-4 C (~5.5-7 F) relative to pre-industrial/anthropogenic warming which began in the 18th and 19th centuries (the baseline for these maps is very recent…1981-2010, with an acceleration in global warming occurring just during that time). The Arctic has been warming much faster than the globe as a whole (twice as fast overall, 3-4 times faster in the interior Arctic). The Arctic had its warmest winter on record in 2017-18 with what were effectively “heat wave” events generated by either huge upper-atmospheric ridges of high pressure from a very high amplitude (very wavy) jet stream producing areas of intense warming; or “atmospheric rivers” of intense heat and moisture transport via intense ocean storms moving in from the Atlantic and Pacific eroding the sea ice sheet in the middle of winter by warm temperatures, high wave action and even rainfall. The Bering-Chukchi Seas of the far northern Pacific and Arctic Oceans have been the lowest sea ice extent on record, likely going back to the mid-19th century (the earliest records can be reconstructed).
Climate change-related warming is melting sea ice rapidly, exposing more dark-blue ocean during the warm season, warming it and the atmosphere, contributing to further warming. It also has led to a weakening of the jet stream and winter time upper-atmospheric polar vortex which stabilizes the Arctic climate and upper-atmospheric circulation pattern, “vortex splitting” and much increases “waviness” in the jet stream, with increasingly extreme Northern Hemisphere winters (persistent areas of abnormal cold, warmth, with wet or dryness and very wild swings between the two states in some regions with strong mid-latitude cyclones produced by the temperature gradients). I discussed this more in a detailed post related to my personal observations of the effect the wild temperature variability has had on seasonality on the Great Plains.
For the Arctic, this new very abnormal warming period is unusual in that this is the middle of Spring and temperature variability typically decreases somewhat after winter. But the jet stream continues with its very high amplitude or “wavy” pattern. Lots of abnormal warmth across the Northern Hemisphere mid-latitudes, a couple notable cold spots, but now the Arctic will get assaulted by more heat from the warming mid-latitudes.
But this will be May warmth, not the warmth of January or February. The current sea ice extent, which is around the same as 2016 (which ended the year with the second lowest September minimum on record) may begin decreasing at higher rate, particularly as a days long period of abnormal warmth hits the Central Arctic Basin, which has relatively normal sea ice extent, but record low sea ice area (which subtracts areas within the max extent which are free of sea ice). So bringing in more heat is no good. The Arctic may become ice free in the warm season over the next decade and could do so abruptly.
-Below are Global Forecast System model depictions of temperature anomalies (relative to 1981-2010) over the Arctic over the next several days as storms move over the Arctic Ocean from Siberia and the far North Atlantic. The last image is the mean temperature anomaly over the next 7 days.
Here’s what those temperature anomalies actually translate too in actual air temperatures (forecast by the American GFS model). No part of the Arctic Ocean is below zero F, with the large swath above freezing on Sunday (and earlier).
I’ll also note, I saw evidence of this warming event in long-range models mid last week…and noticed it will coincide with the beginning of an extensive period of abnormal heat over Western North America (literally from the western US to portions of Alaska), with cooler than normal conditions over the Great Lakes and eastern Canada, with abnormal heating of Europe as well. Parts of Europe have already had periods of record heat in April, including Germany.
–Meteorologist Nick Humphrey