US facing ice age? Polar vortex changes sending Northern Hemisphere into deep freeze
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How polar vortex cause cold snaps
How stratospheric patterns steer cold air
In today's times, when experts, scientists, and leaders across the globe are contemplating ways to tackle the simmering issue of global warming amid rising temperatures, winters in the Northern Hemisphere are still marked by cold snaps and extreme snowfall events. The Northern Hemisphere often sees snowfall events to some extent, such as the 2021 deep freeze in Texas and Oklahoma that caused over $1 billion in damage.A new study has surfaced that suggests these cold extremes are due to a rising common pattern in the polar vortex . According to LiveScience.com, it is the zone of low pressure that usually circulates over the Arctic. When this vortex gets disturbed, it changes shape and sends cold air into Canada and the U.S. This is happening more often because the Arctic is getting warmer."Overwhelmingly, extreme cold and severe winter weather, heavy snowstorms, and deep snow are associated with these stretched events," study co-author Judah Cohen, the director of seasonal forecasting at Atmospheric and Environmental Research and a visiting scientist at MIT, told Live Science.The study carried out by Cohen and his team looked at how these events evolve in the stratosphere, the middle layer of the atmosphere that starts about 12 miles (19 kilometers) up. Understanding how these patterns shift could help meteorologists make longer-range forecasts, said Andrea Lopez Lang, an atmospheric scientist at the University of Wisconsin, Madison, who was not involved in the research."Knowing this information is useful for a lot of applications in energy and applications in insurance or reinsurance," Lang told Live Science. "How cold is it going to get? Are pipes going to burst? Are insurance claims going to spike this winter?" she added.The polar vortex quite often circulates the North Pole like a spinning top, and occasionally, it collapses dramatically. This usually leads to polar air rushing toward northern Europe and Asia. These collapses can sometimes cause cold snaps in North America , but not always. "There's been this big question mark over what happens in North America," Lang stated.Cohen and his team studied satellite data on the stratosphere and winter weather records from 1980 to 2021. They discovered that, short of total collapse, the polar vortex often wobbles and stretches, like a figure skater flinging out an arm for balance in a tricky spin. The researchers reported in the journal Science Advances that there were five different common patterns in the stratosphere, and two in particular were connected to cold weather dipping into Canada and the U.S. during these stretch events. Stretch events are increasing in general, Cohen said, but there has also been a shift in the type of stretches.One stratospheric pattern usually brings cold air to the East Coast, while another chills the Midwest and Plains. Since 2015, researchers have noticed the westerly pattern happens more often. It's not clear why, but this change seems linked to La Niña, a pattern of unusually cold temperatures in the equatorial Pacific Ocean. In the last couple of decades, there have been multiple multiyear La Niña events. In the past twenty years, there have been several La Niña events that lasted for more than one year.The researchers were able to detect some regularities in the way the polar vortex shifts between the five patterns, which might help improve forecasts over the two- to six-week period, Cohen said. "In that shorter range is the poorest accuracy," he said. "This paper can be helpful in that timeframe." One big question is how these polar vortex trends might change over time as the globe warms, Lang said.Cohen and his team have been looking at that question as well. The polar vortex is controlled by waves in the atmosphere, he said, and right now the most influential standing wave is over Eurasia, with a warm ridge to the west and a cooler trough to the east, which in turn is driven by patterns of warming in the Arctic.Currently, melting sea ice is contributing to the increase in the temperature differences between the west and the east, strengthening the wave that can disrupt the vortex, Cohen said. If the sea ice disappeared, the pattern might collapse and flip. Instead of surprisingly cold winter events despite overall global warming, winter might suddenly become much toastier. "We could become more like the Southern Hemisphere, where you rarely get a breakdown of the polar vortex," Cohen said, "and it would probably mean warmer midlatitudes and a colder Arctic."
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