Arctic sea ice reaches its largest ice cover in 11 years

Arctic sea ice reaches its largest ice cover in 11 years
Arctic sea ice reaches its largest ice cover in 11 years
Anonim

Winters were mild throughout most of Eurasia and North America. Meanwhile, the cold air that remained in the Arctic Circle has helped the Arctic Sea reach its largest February ice cover in 11 years.

As shown in the animation below, there is an Arctic rapid sea ice rise between September 2019 and February 2020:

The second animation shows the build-up of Arctic sea ice between September 2019 and February 2020:

Here is a chart of the extent of polar sea ice:

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Polar vortex and arctic fluctuations

Arctic Oscillations (AR) are atmospheric circulation patterns characterized by counterclockwise winds circulating around the Arctic at about 55 ° N.

The most obvious reflection of the phase of this oscillation is the location of storms from north to south, a mid-latitude jet stream.

Positive Arctic Oscillation

When AO is "positive," a ring of strong winds circulating around the North Pole acts to confine colder air in the polar regions.

With a positive AO, the atmospheric pressure below the mean over the Arctic is associated with the pressure above the mean over the northern part of the Pacific and Atlantic oceans.

The jet stream is further north than average under these conditions.

Thus, in the mid-latitudes of North America, Europe, Siberia, and East Asia, there are usually fewer outbreaks of cold air than usual.

Negative Arctic Oscillation

In its negative phase, AR is weaker and distorted, which allows colder Arctic air masses to penetrate southward and intensify the storm in mid-latitudes.

In this case, the AR has a higher than average atmospheric pressure over the Arctic region and a lower than average pressure over the northern Pacific and Atlantic oceans.

The jet stream under these conditions shifts to the equator, so the air river encircling the globe is south of its middle position.

Consequently, in mid-latitudes in winter, outbreaks of cold polar air most often occur.

Positive Arctic Oscillation Now

We are currently in a positive state, with a very strong jet stream, farther north than average, and cold air concentrated in the polar regions.

This "positive" Arctic Oscillation is responsible for:

- mild winters in the United States and parts of Europe, - turning the North Atlantic into a weather bomb

- Ice recovery is currently taking place around the North Pole.

Meanwhile, on the other side of the world, in Antarctica, scientists have recorded the warmest temperature ever measured on the continent.

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