As an April snowstorm strikes the U.S. Northeast, major global weather stories related to climate change are unfolding in real time. For today, we again find that none of the key climate zones feature below average temperatures even as a ten-day-long Arctic warm spell appears to be on tap.

Very Warm Arctic in Early April

(Another big Arctic warm-up drives cold air southward. The result is snow over the U.S. Northeast even as parts of the Arctic Ocean are experiencing an early thaw. Image source: Climate Reanalyzer.)

Warm winds driving northward over eastern Siberia, on the back side of a high pressure ridge, are delivering yet one more big dose of near or above freezing temperatures to this Arctic region. From the Chukchi Sea through the Bering Strait and on into East Siberia, temperatures range from 10 to 22 degrees Celsius above average. The Bering itself has been mostly swept clean of sea ice — with severe record low ice extent readings for this zone during early April.

Throughout winter, the Bering and Chukchi have received wave after wave of much warmer than normal air from the ocean zone to the south. This tendency for warm air propagating northward through the Pacific is one that is often triggered by La Nina — a periodic pattern of Pacific Equatorial surface water cooling that became a dominant feature of 2018 winter weather. However, globally warmer than normal ocean waters and, in particular, much warmer than normal sea surface temperatures in the Northeastern Pacific appear to have greatly enhanced the heat influx.

(Much warmer than normal sea surface temperatures in the Northeastern Pacific this year have provided a pathway for warm air to invade the Arctic. Meanwhile, La Nina and Polar Amplification generate a combined influence that weakens the Jet Stream and facilitates atmospheric ridges in this zone. Image source: Earth Nullschool.)

These warm waters at the middle to northern latitudes have developed a pathway that enhances the northward flow of tropical air masses over the Pacific Ocean. Meanwhile La Nina’s Equatorial cooling combines with climate change’s amplified polar warming to slow down the Jet Stream — further enabling this south-to-north heat transfer. As we have seen time and time again, human-forced global warming generated chiefly by fossil fuel burning is developing an atmospheric and oceanic handshake with past understood synoptic trends to produce an out-sized Arctic warming.

Bering Sea Almost Completely Cleared of Ice

This severe warming is plainly visible as open water is driven by outlandish temperatures well north and through the Bering Strait during early April. A time when ocean ice typically extends more than 150 miles south of Ninivak — bridging the water zone from Bristol Bay to the Kamchatka Peninsula.

(The Bering Sea is typically ice-choked during April. And during a normal year all the water zones in the above image would be covered with ice. But this spring, sea ice extent there is at never-before-seen record low levels. Image source: NASA Worldview.)

The impact is quite dramatic. During February, Bering Sea Ice hit 100,000 square kilometers below previous record lows for the Month. These record low extents continued throughout March and into early April when, today, we find that Bering sea ice extent is between 150,000 to 200,000 square kilometers below the previous record lows for the day and about half a million square kilometers below the seasonal average.

Putting this loss into context, half a million square kilometers is a region that splits the difference in size between the land mass area of California and Texas.

According to GFS model runs, the present Bering-East Siberia warm spell should last for another 2-3 days even as larger Arctic warming in the range of 2.4 to 3.2 degrees Celsius above average for the entire 66 North Latitude zone and on poleward is expected to continue through the ten day horizon. These warmer than normal temperatures should retard typical seasonal sea ice thickening in the far northern regions even as edge ice zones like those in the Bering, Baffin Bay, and the Sea of Okhotsk experience early spring melt and erosion.

New England Spring Snow

As warm air invades the Arctic — a feature that has become more and more prevalent as the globe itself has heated up — it tends to drive cold air southward over the North American, Asian, and European Continents. In this case, the warm air invasion coming from the Siberian side is displacing Arctic air over North America. As a result, and much to the delight of myth-enraptured climate change deniers everywhere, we have been treated to a rare, if not unheard of, spring April snowstorm in New England.

(Increasingly, there have been indications that polar warming related to global warming is influencing storm tracks and ridge and trough patterns in the Northern Hemisphere Jet Stream. The result is a stronger influence on Mid-Latitude Northern Hemisphere weather. Image source: Arctic Change and Possible Influence on Mid-Latitude Climate and Weather.)

According to local weather reports, as much as 7 inches of snow were dumped in intense 2-inch-per-hour bursts over parts of New England last night as a brief but intense storm roared through the region. The cold air, driven south by the recent warm polar air invasion, encountered high atmospheric moisture levels bleeding off a much warmer than normal Gulf Stream lurking just off-shore. The result, as has been the case during recent intense rain and snowstorms, was enhanced convection. This greater atmospheric uplift, in turn, produced an out-sized spring precipitation event. With below freezing temperatures driven far to the south by warm air entering the Arctic, the Northeast saw its first significant April snow event since 1982.

An April 6th to 7th Snowstorm for the U.S. South on the Way?

Further fodder for the climate change denial community supported by the anti-information campaigns of Fox News and others, may emerge by next weekend as another big push of cold air could help to develop a snow and ice storm stretching from Oklahoma through the Carolinas. Cold air driven out of the Arctic and southward over the Eastern and Central U.S. could result in 10 to 18 degree Celsius below average temperatures in that region. Moisture bleeding off the much warmer than normal Gulf of Mexico and Atlantic Ocean could be injected into this cold trough as a related storm develops. The result is a potentially unusual snow and ice storm. And an intense event off this kind, should it develop, would be a very odd weather event during U.S. spring-time.

(Another odd spring U.S. Snowstorm may be on the way for April 6th and 7th according to GFS model forecasts. Image source: Tropical Tidbits.)

Meanwhile, the U.S. tendency in the model forecasts is for warmer than normal temperatures in the West, cooler than normal temperatures in the East through the middle of April. It’s worth noting that the forecast also shows highly variable temperatures with strong swings between warm and cold throughout this period for most U.S. regions. As a result, as the Arctic remains much warmer than normal over the next ten days, the U.S. is likely to experience periods of both extreme warmth and extreme cold relative to climatological averages for this time of year.

Final Points — Intense U.S. Spring Snowfall Events a Likely Upshot of Polar Warming

Putting all these dynamics into context, we can sum up by making the following statements:

April snow and even April blizzards are not unheard of for the U.S. East. That said, the recent events are odd and outside the context of regular U.S. weather patterns — particularly when it comes to precipitation intensity. Arctic warming and loss of regional sea ice, such as that seen in the Bering, is historically unprecedented during 2018. This is a continuation of an observed trend of polar amplification and severe warming seen during recent years. No major global climate zones show below normal temperatures on April 2, 2018. That said, a high variance in middle latitude northern hemisphere temperatures presently exists — with regions of intense cool and intense warmth interspersed. Snowstorms in the U.S. Northeast during April do not disprove global warming or a related shift to increasing climate extremes. In fact, they appear to be an aspect of it.