Hoarfrost covered the snow where researchers crossed a lagoon in Utqiagvik, Alaska, in April 2019. (Bonnie Jo Mount/The Washington Post)

A heat wave of historic proportions is gripping the Central Arctic, with the region setting a milestone for being so warm relative to average so early in the year.

According to a regional climate database that goes back to 1958, this week’s temperature spike in the Arctic, as defined as the region north of 80 degrees latitude, is unprecedented during that time period.

This period of unusually mild Arctic weather is only the latest of many such episodes in recent years as the region rapidly warms in response to increasing amounts of greenhouse gases in the atmosphere. The Arctic as a whole is warming at more than twice the rate of the rest of the world, owing to feedbacks in the climate system, and this is leading to sweeping changes in the way of life for the area’s 4 million residents, as well as a cascade of knock-on effects to ecosystems.

According to Martin Stendel, a climate scientist at the Danish Meteorological Institute (DMI), the temperature data set, which is known as a reanalysis, shows how unusual the Arctic temperature anomalies are in the context of the past several decades.

“Concerning the Arctic temperature, that is indeed quite extraordinary. In the time series which is based on ERA40 and therefore goes back to 1958, there is no similar event so early in the season,” Stendel wrote in an email. “There is (again) very little sea ice in the Arctic (only 2019 had less),” Stendel noted.

A reanalysis is a way to put together a thorough record of how weather and climate conditions have varied over time.

Unusually mild temperatures across the Arctic Ocean are projected by the American GFS model for the next seven days. (Karsten Haustein)

The temperature spike, which is in part related to unusually mild air for this time of year flowing northward from the Russian Arctic, may have significant consequences. The milder temperatures and unusually clear skies could accelerate ice melt of sea and land ice across the vast region, particularly if cold snaps do not quickly follow.

For example, Friday is likely to mark the official start of the Greenland melt season, which requires three consecutive days with more than 5 percent of the ice sheet surface area melting at least part of the day. There have already been two straight days.

Extent of surface melting seen on the Greenland ice sheet so far in 2020 (red) compared to average (blue). (NSIDC)

Rapid Arctic warming is bringing sweeping changes to the Far North, and these impacts are not staying contained to this region, either. For example, a federal report released in 2019 found that a dreaded Arctic feedback involving the release of billions of tons of greenhouse gases that will thaw Arctic permafrost is in fact underway.

Above-freezing temperatures are showing up in the Central Arctic about one month earlier than average this week, according to Ted Scambos, a senior research scientist at CIRES, an atmospheric research institute operated by the National Oceanic and Atmospheric Administration and the University of Colorado at Boulder.

Zack Labe, a graduate student at the University of California at Irvine who studies Arctic climate change, said he’s not convinced there is an early-season record for Arctic temperature departures from average because the reanalysis in use is older and less precise than more updated records.

“While it’s representative of warm or cold periods, I don’t think we can’t say much about ‘records’ from using it,” Labe said of the temperature reanalysis. “Regardless of records, this is definitely an unusually warm period across the entire Arctic Ocean. I think a weather pattern like this, but in June, would be particularly bad for sea ice.”

Computer model projections show mild temperature anomalies covering a vast expanse, stretching from the Barents and Kara seas near Siberia (which itself is unusually mild for this time of year) to the Chukchi Sea off the Alaskan coast.

These anomalous readings are reflected in the average temperature over the high Arctic (north of 80 degrees latitude), which has spiked in recent days, rising about 16 degrees (9C).

This unusually mild air mass is expected to stay in place for at least the next seven to 10 days, possibly longer, computer model projections show. A high-pressure area parked over the Central Arctic will also ensure clear skies, which is a key ingredient in warm season extreme melt events due to feedback loops involving melting snow and sea ice.

While sea ice melt tends to kick into gear in June, Scambos says the weather this week could cause the snowpack on top of the sea ice to “ripen” early in the season, which would cause the snow to get some liquid meltwater in it, lowering its reflectivity, or albedo, and absorbing more incoming solar energy. This would precondition the sea ice to more rapid and widespread melting earlier in the season, depending on the weather.

Melting on the Greenland ice sheet has also ticked up in recent days, according to satellite observations, but it is not unprecedented in its severity or timing, scientists say. “It looks like although the melt the last few days was widespread, it wasn’t particularly intense,” Ruth Mottram, a climate scientist with the DMI, wrote in an email.

[The Greenland ice sheet poured 197 billion tons of water into the North Atlantic in July alone]

Most of the melting during the summer takes place in July, Stendel said. If the melt season were to start on Friday, as is anticipated, that would be about two weeks early. However, the 2016 melt season began significantly earlier, on April 11. The ice sheet is going into the 2020 melt season with below average snowfall in many areas, which could tip the scale toward a lower surface mass balance as the spring and summer progress.

Last year, the Greenland ice sheet saw a sudden sharp uptick in melting during July, a month when 197 billion tons of water poured into the North Atlantic Ocean, contributing to global sea level rise. In late July, the ice sheet saw its biggest single day loss of ice since 1950.