Parts of America’s normally frozen north appear to be on the edge of some sort of time warp wherein the climate months – as opposed to the calendar months – jump from March right into May.
Temperatures in Alaska’s largest city on Wednesday hit a high of 50 degrees with a low of 34 and a daily average of 42.
And this isn’t due to some weird, one-day anomaly. Following a late-February cold snap, the Anchorage metropolitan area – home to more than half of the state’s population – started warming up and since the start of March the weather has generally been tracking the norms for April.
It’s as if the whole month had been grabbed and shifted to the right on the Weather Service graph of normal temperatures.
Blame the polar vortex and the Arctic oscillation yet again. Instead of spinning northern climates smoothly around the North Pole all winter, the PV and AO have been causing havoc.
That’s been bad for the U.S. Midwest and parts of Europe, if you prefer warm weather to cold, and good for Alaska, if you prefer warm weather to cold. If you prefer cold weather to warm, on the other hand, it’s all the opposite.
What’s going on here is not global warming, though that might play some small part, but pressure ridging in the atmosphere. Think of the air above as looking like the sea ice where pressure ridges regularly pop up when moving sheets of ice collide.
Much the same happens in the atmosphere when moving masses of air interact. The ridges then serve to influence winds that naturally want to move north to south and west to east, at least in the northern hemisphere.
It’s all complicated and simple at the same time. The cold, dense air of the Arctic wants to sink. The warm, light air of the tropics wants to rise. And they constantly interact as they are pulled around a planet spinning ever eastward.
Ridges serve to stabilize things at least temporarily. When high pressure ridges form over western North America, more warm, tropical air gets forced north across the Pacific Ocean and Alaska warms up.
“Across North America, the (latest) minor PV disruption spawned a strong blocking high centered near Alaska,” Judah Cohen, and MIT climatologist and authority on the polar climate, observed earlier this week.
The blocking high forced what one might think of as the Pacific Northwest weather of March to slide north, causing the big warm up that brought rain to the lower Yukon River during the Iditarod Trail Sled Dog race earlier in the month and helped contribute to the open water of the Bering Sea off Nome.
Cohen believes the latter could now further effect air movements.
“I think this blocking high could be hard to dissipate,” he writes. “Sea ice is extremely low or even completely absent from the Bering Sea. I believe that heating from the open waters could help to anchor the ridge that has developed in the atmosphere above.”
That might make it possible the April-like temperatures of March in parts of Alaska could give way to May-like temperatures in April.
The U.S. Climate Prediction Center appears in general agreement with this view. The 8- to 14-day outlook it issued today predicts a 50 percent or greater probability for Alaska to be warmer than normal.
How much warmer it doesn’t say, but this is the time of year when Alaska is already making a rapid transition from the long, dark winter to the glorious days of midnight sun.
Temperature norms track the increasing sunlight. Anchorage daytime highs average 24.9 degrees from November through February with the monthly start of that run weighing in at 27.7 degrees on average and the end at 25.8.
The March average, however, jumps almost 8 degrees above the February average, and the April average jumps more than 10 degrees above March with May topping April by another 11 degrees to push into the mid-50s before leveling off into the 60-degree months of July, July an August.
Comfortable, not cooked
The state is warm in summer, but never quite the “Cancun” weather heralded on the internet when Klawock hit 70 degrees on Tuesday.
Eight of the top-10 hottest days in Anchorage are colder than the average for Cancun in March, and those Anchorage temperatures cover a span of 38 years from the 82 degrees in August 1977 to the 83 degrees in June of 2015.
At the moment, the ripple in the atmosphere that caused the ridging that shifted temperatures appears the driving cause for the shift.
As Gizmodo noted, “the heat didn’t stop at the (U.S.-Canada) border, either. Record-setting warmth spread over western Canada and the Pacific Northwest as monthly records fell across British Columbia, Alberta, the Northwest Territories, and the Yukon. And not to be outdone by the ’70s in Alaska, temperatures topped 81 degrees Fahrenheit in Quillayute on Washington’s Olympic Peninsula and 79 degrees Fahrenheit in Seattle. Both are all-time March records.”
Like climate change and how exactly it will manifest itself (maybe this is it?), the link between global warming and polar ice is now a very hot topic.
Sea ice has obviously always been involved in influencing the planet’s temperature, but Norwegian scientists early this month published a peer-reviewed paper at Science Advances saying they found evidence that losses in sea ice, possibly caused by “an increasing influence of warm and saline Atlantic waters flowing into the Norwegian Sea at the surface and/or subsurface,” might have precipitated global warming and not the other way around.
About 35,000 years ago, an abrupt change – “known as Dansgaard–Oeschger climate events – had global implications and comprised temperature shifts of up to 15°C (about 27F) over the Greenland ice sheet and happened within decades,” Lachlan Gilbert at the Univesity of South Wales wrote in a laymen’s summary at Phys.org.
“While the underlying mechanisms of these dramatic changes are not yet fully understood….it is now believed that initial sea ice reduction started before the abrupt warming over Greenland, and that sea ice expansion started before the end of the warm periods in the same area.”
With Alaska so warm, Alaskans can now ponder whether global warming is melting the sea ice or the melting sea-ice is warming the globe, or maybe a little of both?