Early thaw in Greenland...

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The summit of the Greenland ice sheet has also been record warm. On Tuesday, it reached 20.3°F (-6.5°C) which while obviously below freezing, is still record mild for this time of year and is roughly 40°F above normal. And the wamrth isn't over yet.

Temperatures could reach as high as 57°F above normal this week. It's distinctly possible more temperatures records could fall before the week is out.
And while normal temperatures are expected to return, the impacts of this warm stretch will remain with the ice sheet. Energy of all that melting ice is expected to wend its way a bit deeper into the ice pack, making it easier for continued melt later in the season.

The Greenland ice sheet represents one of the most massive stores of ice on the planet. If it were all to melt, it would raise oceans about 20 feet. Melting ice is also affecting ocean circulation and even the drift of the North Pole.

Climate change has been cutting into Greenland’s icy reserves, with warm air and water temperatures leading to the loss of millions of tons of ice each year. Dust and soot from forest fires in Canada and Siberia have also expedited the ice sheet’s melt.

But how this melt season progresses depends a lot on the weather. Last year, a cool spring kept Greenland mostly solid before a summer heat wave led to a rapid meltdown of the ice sheet. And in July 2012, a record-setting 95 percent of the ice sheet experienced surface melting due to high temperatures and soot from wildfires in Siberia.