Scientists at the European Space Agency have found an enormous hole in the Earth’s ozone layer, and it is unusual because it is over the North Pole.  The hole is three times the size of Greenland, and fortunately, is likely to close on its own in the coming weeks, but until then residents of the far north may need to apply sunscreen to protect themselves from the sun’s ultraviolet light.

Why This Matters:  This is believed to be the largest hole ever to have formed above the Arctic.  While a hole in the ozone layer is an annual occurrence in the southern hemisphere (though it is getting smaller in recent years), a hole in the northern hemisphere is quite rare.  It is still only 1 million sq km, which is much smaller than the Antarctic hole, which can reach a size of around 20 to 25 million sq km, and this hole will last only about a month as compared with a normal duration of around 3 to 4 months for the Antarctic hole.

Why Do Ozone Holes Form?

According to LiveScience, holes form in the ozone layer, which is a sheet of gas in Earth’s atmosphere that absorbs much of the harmful ultraviolet light emitted by the sun, due to a combination of cold temperatures and pollution.  During the winter, clouds form due to the cold and HFCs and CFCs and other chemical pollutants containing chlorine and bromine trigger reactions in these clouds that eat away at the surrounding ozone gas.  The Arctic is not as cold as the Antarctic and so it does not typically have the same conditions that trigger ozone depletion there.  However, this year powerful winds trapped cold air in a “polar vortex” above the Arctic., which created the colder conditions leading to more high-altitude clouds than normal.  That is also the reason why the winter was milder here in the northern hemisphere.