Royal Geographical Society - Geography resources for teachers

January 2014

In early January 2014 North America experienced heavy snow storms and freezing weather. On 7 January all 50 US states had temperatures below freezing. Many states are used to sub-zero temperatures in the winter but usually some states will stay above freezing (typically those which border the Gulf of Mexico such as Florida, Texas or Louisiana).

The extreme snow storms and plummeting temperatures were largely blamed on a shift in the pattern of a phenomenon known as the polar vortex, sending colder air further south than usual.

In the Members' Area:

What is a polar vortex?
How did the movement of the polar vortex affect the US?
How do the temperatures compare?
References

What is a polar vortex?

A polar vortex (sometimes called a polar cyclone) is circulating air pattern that flows around the low pressure system that typically lies over the Arctic (and Antarctic) and are typically stronger during the winter. The circulation pattern usually keeps the cold air circulating within the polar regions.

The extreme weather in the US was in thought to have been caused by a weakening of the polar vortex which meant that, rather than being more confined to the polar regions, cold air shifted further south (as shown below).

There are suggestions that this has been caused by an alteration in the heat balance between the North Pole and the Equator caused by warming of the Arctic in summer. This in turn has affected movement of the jet stream (narrow bands of wind found high in the atmosphere) which usually holds the polar vortex in place (Independent, 2014).

Cold air spreads as the polar vortex is pushed further south than usual

How did the movement of the polar vortex affect the US?

The freezing storms covered some areas with up to 61cm of snow and with so much of North America covered in snow and ice the effects of this weather were widespread:

187 million people affected by the severe weather
21 people have died as a result of the cold
Estimates suggest that around US$5 billion has been lost in revenue due to closure of businesses and disruption caused
With many roads blocked and airports on limited capacity, travelling became very difficult around the country
The freezing winds threatened crops and livestock across the American agricultural belt, across the Deep South which usually doesn’t experience such extreme temperatures
Niagara Falls froze in sections forming ice bridges. This happens very rarely, and historical records suggest the last time was in 1848
Even the Polar bears in Lincoln Zoo, Chicago were brought inside as they didn’t have enough insulating fat to cope with the sub-zero temperatures
It also provided for some eye catching experiments with people being able to throw boiling water into the air and see it freeze instantaneously (as can be seen in this YouTube clip)

On the shores of Lake Michigan giant ice boulders developed (the size of beach balls). These are thought to have been caused when pieces of ice broke away from large sheets of ice that had formed in the lake. The motion of the waves eroded the edges of the ice creating the spheres that eventually reached the shores. As they were made of ice they were less dense than the surrounding water and so continued to float on the lakes edge. A video of the giant boulders is available.

How do the temperatures compare?

The US Authorities have declared that 7 January was the coldest in recent records. New York City's Central Park broke a 118-year-old record when the temperature dropped to -15oC but in other areas of the US it was much colder:

Lowest temperature reported was in Embarrass, Minnesota -35oC (if you account for wind chill factor (-43oC). This is colder than some temperatures recorded on Mars by the Mars Rover
It was -26oC in Chicago (wind chills means this fell to -53oC which is cold enough to freeze human skin in under one minute)
On the same day it was -22oC in Almaty, Kazakhstan, -23oC in Mongolia and -33oC in Irkutsk in Siberia
According to the World Meteorological Organisation the coldest temperature recorded in North America was on 3 February 1947 in Yukon Territory, Canada when it reached -63oC. The coldest temperature recorded on Earth was in Antarctica on 21 July 1983 when temperatures dropped to -89.2oC in Vostok.