Warming temperatures and melting glaciers are accelerating Arctic warming: Bob McDonald

2015 was a record year for high temperatures andmelting glaciers in western Greenland, a heatingeffect that is amplifying itself and could lead to accelerated warming in the Arctic.

A new reportfrom the Lamont-Doherty Earth Observatory at Columbia Universityattributes the warming to a shift in the jet stream that brought higher temperatures to much more northerly latitudes than normal last year.

The warmer air and melting ice magnifyeach other in a feedback loop called Arctic amplification.

In the same way thatwhite clothing feels cooler than black on a sunny summer day, white ice reflects sunlight,keeping temperatures at the surface low. When the icemelts, dark sea waterand dark land areexposed. Theseabsorb sunlight rather than reflecting it, thusraising temperatures andcausingmore melting. The cycle continues, and even speeds up, as the dark areas grow larger and white ice disappears.

This is one reason the Arctic is heating up faster than other parts of the globe.

A similar feedback loop has been taking place over the Arctic Ocean, with the increasing loss of sea ice each summer. Thishas warmed the ocean waters.

Many scientists believe that thewarmer Arctic air has alsoaffected the shape of the jet stream, causing it to be more wavy, with troughs dipping farther southand ridges looping farther north. That shiftdelivered last winter's extra cold temperatures over central North America, and broughtwarm air over Greenland.

The jet stream is the boundary between cold polar air and warm tropical air, a river of fast moving air that circles the globe like the soft brim of a floppy hat. When the temperature difference between northern cold and tropical warmth is large, the waves in the jet stream tend to smooth out more, but when the Arctic warms up and that difference shrinks, the stream becomes more wavy.

We don't know whether this change in shape of the jet stream is due to human-induced climate change at this point, because records on its shape don't go back far enough, but the effect is there.

• Arctic heat waves cause exceptional Greenland melt, says new study
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A third feedback loop is caused by air pollution from the south settling on the ice, making it darker and causing it tomelt faster.

None of this is good news for the Greenland ice sheetthe second largest in the world. Although it will take centuries for it all tomelt,the accelerated melting that is alreadytaking place is having far-reachingeffects.

Glacial runoff is cold, fresh water that floats on top of salty ocean water. Its presence can affect ocean currents, such as the Gulf Stream, as well as fish habitats. That,in turn, affects the birds that feed on the fish.

In other words, everything in the North is affected by climate change, and all systems in the air, on land and in the seas are connected. These feedback loops collectively pressharder on the accelerator pedal, speeding up the rate of warming which only increasesthe urgency for usto take actionto slow thingsdown.