January to April temperature departures from average, showing the most significant temperature anomalies across Russia, including Siberia. (Berkeley Earth)

Siberia is in the throes of a heat wave that would be considered warm even by the standards of those living outside the Arctic Circle.

In Washington, for example, the temperature has been stuck in the 60s all week, reaching a maximum of 73 degrees Thursday. Yet several stations in North Central Siberia, including areas near or above the Arctic Circle, are seeing temperatures climb well into the 80s.

On Friday, the town of Khatanga, Siberia, located well north of the Arctic Circle, recorded a temperature of 78 degrees, some 46 degrees above normal. The typical maximum temperature for the day at that location is 32 degrees. The town obliterated its previous record high for the date of 54 by some 24 degrees and its monthly record of 68 by about 10 degrees.

The Siberian warmth in May is not a fluke event, either; instead, it’s been a consistent feature since the winter. Temperature departures from average in Europe and Asia have helped push global average surface temperatures to record highs this year, and on global temperature maps, these regions stand out as splotches of crimson red.

The warmth in Siberia is already having repercussions on Arctic ecosystems, with unusually large Siberian wildfires already burning this year, snow cover plummeting unusually quickly and sea ice cover in areas such as the Kara Sea, which lies to the north of Central Siberia, at a record low for the date, having begun its seasonal melt more than a month earlier than is typical.

In recent years, scientists have raised growing concerns about the stability of Arctic permafrost, including stretches of permanently frozen soil located throughout Siberia. When the permafrost thaws, carbon dioxide and other planet-warming greenhouse gases that had been locked away for centuries is freed up, constituting an accelerant to global warming.

Scientists refer to this phenomena as the somewhat innocuous-sounding “positive climate feedback,” which in reality is not a good thing.

According to Zack Labe, a graduate student at the University of California at Irvine who researches Arctic climate change, what has recently been taking place in Siberia has been extraordinary.

“Although Siberia is known for wild temperature swings, the persistence and magnitude of warmth over the region so far this year has been astonishing,” he said via email. “This week is an example of an extreme event, with summer-like temperatures over parts of Western Siberia thanks to a strong upper level ridge. We can already see this reflected in snow cover data, as there are large negative departures of snow extent stretching across the entire Siberian coast of the Arctic,” he said.

Labe noted that ice in the Kara Sea has reached a record low for the date, and ice cover is thinner than average along the entire coastline of northern Siberia. He said the warmth is likely conditioning the ice to melt further by melting snow cover lying on top of the sea ice.


The intense ridge of high pressure, or “heat dome,” parked over Siberia. (Tomer Burg)

This turns highly reflective ice cover into snow and ice that has a lower reflectivity, known as its albedo, which means that it absorbs more incoming solar radiation.

“This may make the sea ice more vulnerable to melting later in the summer, if weather conditions permit,” Labe said. “Overall, the weather patterns in June through August will dictate the extent of melting closer to the September minimum.”

This year, Siberian fires have gotten off to a fast, and unusually expansive, start. Russian officials have stated they expect the summer will potentially be the hottest the region has seen, with an unusually destructive fire season. Fires in the vast forests of Siberia burned 7 million acres last year, an area larger than the state of Maryland, and sent smoke drifting around the world.

This year, 1.5 million acres have burned. Mark Parrington, a senior scientist at the European Center for Medium-Range Weather Forecasts (ECMWF) in Reading, England, said via email that fire-related emissions around the Arctic Circle and Siberia’s Sakha Republic have not exceeded average data from 2003 through 2019.

However, Labe said there have been trends of fires showing up shortly after snow cover melts, which is a topic of discussion in the fire science community. Some scientists are noting how quickly the hot spots are showing up on satellite imagery and questioning whether these are actually “zombie fires” from last summer that survived the winter by burning in layers of vegetation under the snow.

The temperature departures from average in Siberia this year are some of the highest of any area on Earth. Since January, the region has been running at least 5.4 degrees (3 Celsius) above the long-term average, according to a recent report from the National Oceanic and Atmospheric Administration.

According to Robert Rohde of Berkeley Earth, which monitors global temperature trends, Russia averaged a temperature anomaly of nearly 11 degrees (6 Celsius) above average for the January to April time period.

“That’s not only a new record anomaly for Russia,” Rhode wrote via Twitter. “That’s the largest January to April anomaly ever seen in any country’s national average.”

The polar vortex is helping lead to record warmth

Several factors conspired to produce such a mild winter in Siberia, and are still working to bring freak warmth now. Among them? The polar vortex spent much of the winter near or at record strength.

When the polar vortex is strong, it forms a frigid upper-air doughnut of winds that doesn’t permit much Arctic chill to slip south to the mid-latitudes. When that happens, areas along the vortex’s periphery that would usually experience frigid weather remain just outside its frosty sphere of influence.

In recent weeks, the vortex has undergone its annual spring collapse, making it easier for intense ridges of warm high pressure to build in.

Most recently, a prominent bubble of high pressure, referred to as a heat dome, slipped even farther northward, spanning from northern Siberia into the Central Arctic ocean — smack dab over much of the sea ice pack.

In fact, the high-altitude “heat dome” is more intense than any other on the planet, and likely anything forecast to develop globally in the coming weeks. The dome of heat has also helped to deflect inclement weather and storm systems away from Siberia, with sinking air eroding cloud cover and precipitation.

The alignment of weather systems is just one side of the coin in a world facing the growing impacts and severity of human-induced climate change.

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.

“This heat wave occurs mostly at the area which has been anomalously warm during the whole 2020,” said Mika Rantanen, a researcher at the Finnish Meteorological Institute, via email. “It could be that lack of snow/dry soils can play a role, so they now favor high temperatures as the [solar] energy [is] not consumed [by] melting of snow.”

“One thing which I found noteworthy is that Russia just experienced a record-warm winter. And [it] looks like the warmth or heat still continues.”