During the last few weeks, extreme warmth has been widespread in much of the Arctic region. It’s not unprecedented; it has happened before. Of greater concern is the fact it’s been happening more often recently and is tied to the warming climate, which is advancing more rapidly in the Arctic than anywhere else on the globe.
The physics behind Arctic warming are not all that complex. The Arctic Ocean is quite different from Antarctica, where much of the ice lies on a vast land continent. When Arctic sea ice melts, it is replaced by dark ocean waters. Those dark waters absorb solar heat instead of reflecting it back into space, as did the white ice replaced by the water. I wrote on this polar contrast last autumn.
Winter air temperatures are something of a different matter. Temperatures in the Arctic have now spiked in two consecutive winter seasons. Click here to view a forecast from the American GFS model, reproduced in the Washington Post, for temperature anomalies (blue=colder than average; red=warmer) run on Feb. 22.
The forecast verified. At that time, much of the Arctic was running 45 degrees above average, while the eastern United States was also quite mild. According to the Danish Meteorological Institute, the world’s northernmost weather instrument station at the far northern edge of Greenland, at Cape Morris Jesup, stayed above freezing for more than 24 hours. This is in the 24-hour darkness of Arctic winter. At the same time, temperatures were running 40 to 45 degrees above average in far north Alaska.
This past weekend on WKBW, I marveled how Lake Erie ice had shrunk rapidly to less than 25 percent ice coverage from a previous high of greater than 90 percent in just a few weeks. InsideClimateNews, an online news organization, reported to the Washington Post that more than a third of Bering Sea ice off Alaska had disappeared in only one week in February. Many Alaskan villages on the shore, normally buffered by sea ice, are being pounded and seriously damaged by waves from winter storms.
Zack Labe, doctoral climate science candidate at the University of California, Irvine, reports that the entire Arctic region above 80 degrees latitude has run more than 10 degrees above average since Jan. 1. Because of the enormous spike later in February, this has been the warmest February ever recorded in the Arctic. In that spike, satellite extrapolation suggests the North Pole itself rose above freezing, though there are no surface instruments there. Some individual locations probably ran to an astounding 60 degrees above average.
Such jumps in temperature also occurred in November 2016 and December 2015. That’s what I meant by these spikes having occurred more frequently in recent years. A study published in NATURE demonstrates the shrinkage that has occurred in Arctic sea ice has enabled these warm surges to occur more often. Arctic ice cover in January was the lowest on record for the month. This is normally the time when ice cover is thickest and maximized in areal coverage. But as of now, ice cover continues at the lowest in recorded history for mid- and late-winter months.
These record warm surges occurred four times between 1980 and 2010, but they have recurred four times in the last five years alone. What is really a “canary in the coal mine” for ice sheet specialist Mike MacFerrin at the University of Colorado is the observation of open water north of Greenland at this sunless time of the year, where thick ice can normally be found. The National Oceanic and Atmospheric Administration/NOAA reports there are no signs of Arctic ice cover returning to climatalogical norms in the foreseeable future.
Ironically, this Arctic warming and reduced sea ice can cause occasional exceptional cold and storm outbreaks in the Great Lakes and Western New York amidst a warming global climate (as well as elsewhere in the northern hemisphere).
Researcher Jennifer Francis of Rutgers’ Institute of Marine and Coastal Sciences theorizes that Arctic warming reduces the temperature difference between the Arctic and mid-latitudes. In her hypothesis, the reduced thermal contrast weakens the velocity of the polar jet stream. When that occurs, the polar jet can become wavier and take more frequent dips to the south, transporting colder air to places like the Great Lakes and Northeast, and lend support to development of great Atlantic storms. This past week has been one of the coldest ever observed over much of Eurasia, with snow reaching the Mediterranean and even dusting the Egyptian pyramids.
On the other hand, that waviness in the polar jet can transport warm ridges of high pressure to the north, as has occurred in February and which also warmed Western New York so dramatically during the second half of the month.
Francis’ ideas were first thought of as controversial, but they have drawn greater academic acceptance in recent years in peer review. Of course, temperature extremes occurred long before human-related warming accelerated, as did heavy precipitation events. But these extremes, most warm and some cold, are occurring with much greater frequency with the warming, as had been predicted by most climate models. So far, the effects on Western New York from the warming climate have been far less extreme than in other parts of the northern hemisphere.
Part of that blessing is the moderation of the atmosphere brought on by the waters and the marine layer of the Great Lakes. We’re lucky that way.