The extreme cold leaves 10 dead in the United States: what is the polar vortex? – 31/01/2019

The extreme cold wave which freezes in those hours in the center west of United States with colder temperatures than in Antarctica and dozens of degrees below zero, he not only put everyday life in the freezer, he also left the tragic toll of 10 dead.

Temperatures dropped to -30 ° C in Chicago and -37 ° C in North Dakota, in an extreme cold wave affecting a total of 250 million people, including 170 million, living at or below 17 degrees.

Local media has confirmed eight storm-related deaths in Illinois, Wisconsin, Iowa and Nebraska. The last victim would have been a student at the University of Iowa.

Wyomissing Pennsylvania police reported that at least 24 people were injured, two seriously, on a shock of several vehicles.

tremors

One fact that attracted attention was the tremors recorded by the cold in Chicago.

"I thought I was crazy, I was up all night because I could not help hearing it," said Chastity Clark Baker at WGN Information Network, a subsidiary from CNN.

"I was scared and I thought it was the oven, I kept walking in the house, I had everyone's jackets on the table in case we were running."

But this noise was not an oven ready to explode, but probably a meteorological phenomenon as overwhelming as the "firenado" or fire tornado: Frostquakes

Tremor due to frost, or "Cryosismo" occurs when groundwater freezes and expands, causing the breaking of the earth and the rock.

According to WGN, the roar usually starts with a sudden drop in temperature.

Meanwhile, the cold snap that seemed to have its most serious spike Wednesday will continue Thursday, with heavy snow and icy winds. And it is expected that by Friday, 20 million people will experience temperatures below -28 degrees.

But the city that broke all records is Grand Forks, North Dakota, where the icy winds brought the temperature to -54 ° C on Wednesday morning. The specialists warned that any part of the body exposed to this cold would freeze in just 5 minutes.

What is the polar vortex?

This radical phenomenon is called "polar vortex". What is it? Does it respond to climate change? Let's see

Experts say this could be the case, but the fact that global warming plays a key role in this phenomenon is still under discussion. Here's why:

The polar vortex is a persistent cyclone (it still exists). It weakens in the summer and intensifies in the winter. "C & # 39; a very cold air mbad which is normally to the right of the North Pole and tends to remain restricted in this area because of the "jet stream", a thermodynamic factor that regulates air circulation in the atmosphere-, says Ben Kirtman , Professor of Atmospheric Sciences at the School of Marine and Atmospheric Sciences Rosenstiel of the University of Miami.

Normally, the jet stream maintains its cold air in the Arctic, but when this current is agitated or weakened, the cold can spread.

Sometimes an arctic air mbad is released by the polar vortex that usually surrounds the North Pole, causing a polar wave "and that's what's happening right now. And if it's very big, it can penetrate a large amorphous mbad of cold air very south"Kirtman said.

According to Weather Channel, the cold of these days "could be the most extreme of the last 20 years in the Midwest and reach record temperatures in some areas."

"It's not out of the limits of the historical record, it happens, you have storms that are larger than other storms, there's a lot of that that's part of the natural climate variability," he said. Kirtman.

The protective strip of the atmosphere that keeps the polar air to the north can oscillate. This is not strange either.

"There are still ripples in the jet stream," said Kirtman.

The strength of the fast current is related to the temperature contrast between the tropics and the poles.

The greater the difference, the more jet stream is strong and, theoretically, the polar air is more likely to remain in the Arctic.

However, this current is sometimes so strong that it can become unstable, which "causes some oscillation in the stream that can cause these meanders," Kirtman said.

Some tests also suggest that when the poles warm up, the contrast with the tropics is less, which can also make the jet stream more oscillating, allowing cold air to descend from the north.

We know that the Arctic it heats twice as fast than the rest of the planet.

"What people are starting to wonder, is if, if the jet stream weakens, we would have more and more powerful outputs from the polar vortex, and if that would prove true, we can connect the most extreme cold to climate change"Kirtman added.

Researchers examine the data in their desire to discover it. "There are signs that this is related to climate change, but I would like to point out that the jury is still deliberating," he said.

Scientists are deciphering the role of climate change in some extreme weather events. Until now, the signs are clearer in phenomena such as rains, drought, heat waves and forest fires.

But when it comes to cold waves, the answers are not so clear: "I would say that science is still incomplete, we have no evidence yet," Kirtman concluded.

Donald Trump referred to this Polar Wave on Twitter on Tuesday not only to warn of low temperatures, but also to raise his particular vision on climate change. "Where is global warming? Come back please, we need you"he wrote.

Source: AFP and dpa