another consequence of arctic warming: A weakened polar vortex
Introduction
Another consequence of the melting summer sea ice is the alteration of atmospheric pressures resulting in a weakened polar vortex
First of all, just what is the polar vortex? Breaking the term in two: polar means it resides in the higher latitudes, both near the North and South Poles; vortex means it is a persistent and closed circular pattern of upper atmospheric winds flowing from west to east around the Arctic regions. When it is strong it keeps the coldest of the cold air hemmed in. Usually the vortex is at its most robust in the winter — when the large difference between temperatures from the equator to the pole makes for the strongest winds. But it can, and does, weaken, allowing that cold air to make a break for it and spill southward[1].
It is also not a storm, like a winter storm or blizzard, but a standard feature of the Earth's atmosphere. It is semi-permanent, meaning it is not something new, and was not suddenly "discovered" in January 2014. (There is also a Southern Hemispheric version of the polar vortex within which depletion of the upper-atmospheric ozone layer has occurred).
The easiest way to conceptualise this is in terms of a wall. A stronger polar vortex effectively helps to wall off cold Arctic air from the mid-latitudes, and retains the cold Arctic air masses north of the Arctic Circle, but when the polar vortex is weak as the result of anomalously weak low pressures in the Arctic, it is less able to constrain cold Arctic air masses, allowing them to invade the middle latitudes to the south, delivering outbreaks of cold weather and increased snowfall.
Another way of describing it, favoured by American theoretical physicist Michio Kaku is as “a swirling bucket of cold air” with walls that are weakening, causing cold air to spill out. Researchers think the reason the polar vortex is weakening is because of the gradual heating up of the North Pole. “The North Pole is melting. That excess heat generated by all the warm water is destabilizing this gigantic bucket of cold air, weakening this low pressure region, causing cold air to spill out over the United States. So that’s the irony, that heating can cause gigantic storms of historic proportions,”[2], prolonged heat waves, stalled hurricanes, relentless rains and more intense fire seasons[3].
[1] https://weather.com/science/weather-explainers/news/polar-vortex-cold-outbreak-feb2016
[2] http://www.cbsnews.com/news/extreme-weather-polar-vortex-and-jet-stream-unstable-expert-says/
[3] Jennifer A Francis, op cit.
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First of all, just what is the polar vortex? Breaking the term in two: polar means it resides in the higher latitudes, both near the North and South Poles; vortex means it is a persistent and closed circular pattern of upper atmospheric winds flowing from west to east around the Arctic regions. When it is strong it keeps the coldest of the cold air hemmed in. Usually the vortex is at its most robust in the winter — when the large difference between temperatures from the equator to the pole makes for the strongest winds. But it can, and does, weaken, allowing that cold air to make a break for it and spill southward[1].
It is also not a storm, like a winter storm or blizzard, but a standard feature of the Earth's atmosphere. It is semi-permanent, meaning it is not something new, and was not suddenly "discovered" in January 2014. (There is also a Southern Hemispheric version of the polar vortex within which depletion of the upper-atmospheric ozone layer has occurred).
The easiest way to conceptualise this is in terms of a wall. A stronger polar vortex effectively helps to wall off cold Arctic air from the mid-latitudes, and retains the cold Arctic air masses north of the Arctic Circle, but when the polar vortex is weak as the result of anomalously weak low pressures in the Arctic, it is less able to constrain cold Arctic air masses, allowing them to invade the middle latitudes to the south, delivering outbreaks of cold weather and increased snowfall.
Another way of describing it, favoured by American theoretical physicist Michio Kaku is as “a swirling bucket of cold air” with walls that are weakening, causing cold air to spill out. Researchers think the reason the polar vortex is weakening is because of the gradual heating up of the North Pole. “The North Pole is melting. That excess heat generated by all the warm water is destabilizing this gigantic bucket of cold air, weakening this low pressure region, causing cold air to spill out over the United States. So that’s the irony, that heating can cause gigantic storms of historic proportions,”[2], prolonged heat waves, stalled hurricanes, relentless rains and more intense fire seasons[3].
[1] https://weather.com/science/weather-explainers/news/polar-vortex-cold-outbreak-feb2016
[2] http://www.cbsnews.com/news/extreme-weather-polar-vortex-and-jet-stream-unstable-expert-says/
[3] Jennifer A Francis, op cit.
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