Kevin Myatt is The Roanoke Times' weather columnist.

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The extent of Arctic Ocean ice at the end of the summer melt season was a little larger than in 2007 or 2008, but still the third-least ice in the Arctic since satellite records began in the late 1970s.

Arctic ice concentration is a focus of global warming discussions. But the effects of Arctic ice extent on any particular North American winter are not clear-cut.

The advance of cold air in the Northern Hemisphere during fall is caused by lengthening nights and lessening sun angle. The rapid re-freezing of Arctic Ocean ice in the autumn is more a result of seasonal cooling rather than a primary cause.

That said, a frozen Arctic does enhance the cooling of air above it. Unfrozen water absorbs warming sun rays and emits heat into the air. Ice reflects solar rays away from Earth, allowing more cooling.

Also, the physical act of freezing itself releases a small amount of heat into the air. The more open water there is to freeze, the more of this heat is released.

But unfrozen water is also easier to evaporate into precipitation, which this time of year is almost exclusively snow in the Arctic Circle and surrounding areas.

Abundant snowfall on land areas surrounding the Arctic Ocean can allow masses of cold air to build above the surface, as snowpack reflects sunlight and chills the lower atmosphere. If these cold air masses become dense enough, they can start pushing southward early in the season.

So, while tracking Arctic ice is important in the big picture of long-term climate, the effects on year-to-year winter weather at our latitude are not easy to determine or predict.