There's some good news from the atmosphere. The ozone hole over Canada's arctic has finally closed and it was a massive one. Freezing cold temperatures and ozone-depleting substances are to blame.

According to the U.N. World Meteorological Organization, ozone depletion over the arctic was at a record level in March but the huge hole that opened up is now closed.

It formed in late February and persisted all the way through to April before it was finally done.

When the temperature dips below -78 C in the stratosphere, the small amount of water forms polar stratospheric clouds.

Those clouds play a role in chemical reactions that lead to atoms being released which then go and break up ozone molecules.

During the winter, there was a very strong polar vortex that brought record-setting cold temperatures to the stratosphere in March.

With those freezing cold temperatures that were long-lasting and brought on by the polar vortex and ozone-depleting substances in the atmosphere, the huge hole opened up.

Now that there's been enough of a warm-up, those polar stratospheric clouds have gone away which allowed the hole to close again.

The big gap ranged from Hudson's Bay all the way to Siberia and extended about one million square kilometres.

According to The Weather Network, this hole over the arctic is similar to the one that forms over Antarctica but up here it's rare.

Even though this was huge, it's nothing compared to the one that happens at the south pole.

That one can be around 20 million square kilometres and last for three to four months.

This large opening in the ozone was actually predicted back in the fall according to the National Oceanic and Atmospheric Administration.

According to Amy Butler, polar vortex expert for CIRES/NOAA Chemical Sciences Laboratory, "long-range models were predicting this event as far back as last fall."

Mini-ozone holes have been observed over the arctic in the past that are just temporary gaps or thin areas.

Those usually form because of weather patterns that lead to pile-ups in the ozone, not because of a freezing cold polar vortex.

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