“A heat wave begins with high atmospheric pressure building up over an area. A downward-moving air column compresses the air that’s closer to the ground, holding it still and heating it up. That high pressure also forces clouds away and around the column, creating an unobstructed line of light between the ground and the sun.
Over a period of days and weeks, the ground absorbs sunlight, and with stagnant air, heat accumulates and temperatures rise. “There’s nothing coming in and nothing going out,” explained Walt Meier, a senior research scientist at the National Snow and Ice Data Center at the University of Colorado Boulder. “It’s kind of like an oven basically.”
That’s the general formula for heat waves around the world. But there are also several unique ingredients contributing to the Arctic one.
In northern latitudes during the summer, there is near-continuous sunlight — even at night. That allows heat to accumulate faster than in areas that experience sunsets and can cool off in the evening.
Another factor this year was the lack of snow. With an unusually warm winter, less snow built up across parts of the Arctic, and with a warm spring, much of it melted away sooner than usual. “The snow is very reflective of the sunlight,” said Meier. “This year, the snow went away earlier, so then you have the bare ground that can absorb more solar energy.”
The warmer ground also dries out in the heat. With less moisture, there is less evaporation that can cool the surrounding air. “The drier ground and the air over the top of it makes it more susceptible to rapid warming when you have the right conditions like we’re seeing now,” Meier said.”
“One of the overarching trends behind the heat wave and the wildfires is climate change. Earth as a whole is warming up due to human emissions of greenhouse gases like carbon dioxide. But every place isn’t warming up at the same rate; the Arctic is warming at double the rate of the rest of the planet, which is why some of the earliest effects of climate change are felt in the region. The north pole also presents a window into the future for the rest of the world.
Those higher average temperatures mean extreme heat will become even more likely and more intense, exacerbating threats like forest fires as vegetation dries out. “The wildfires definitely come from the extreme heat and the dryness,” Meier said.
The loss of these ancient, slow-growing forests will release carbon dioxide into the atmosphere that will take decades to reabsorb, further warming the planet. Warming in the Arctic is also thawing permafrost, which releases even more carbon into the atmosphere.
And while it’s summer in the Arctic right now, the region has also experienced heat waves in the winter. In fact, researchers have found that in general, winters are warming faster than summers. That’s part of the reason why the Arctic is now losing sea ice at its fastest rate in 1,500 years.”
“Antarctica is also warming up. Earlier this year, the continent broke two high-temperature records within a week.”