It happened over a month ago. The picture above was taken on 22 July 2013. It shows a buoy anchored near a remote webcam at the North Pole, surrounded by a lake of melted ice:

• Becky Oskin, North Pole now a lake, LiveScience, 23 July 2013.

Instead of snow and ice whirling on the wind, a foot-deep aquamarine lake now sloshes around a webcam stationed at the North Pole. The meltwater lake started forming July 13, following two weeks of warm weather in the high Arctic. In early July, temperatures were 2 to 5 degrees Fahrenheit (1 to 3 degrees Celsius) higher than average over much of the Arctic Ocean, according to the National Snow & Ice Data Center.

Meltwater ponds sprout more easily on young, thin ice, which now accounts for more than half of the Arctic’s sea ice. The ponds link up across the smooth surface of the ice, creating a network that traps heat from the sun. Thick and wrinkly multi-year ice, which has survived more than one freeze-thaw season, is less likely sport a polka-dot network of ponds because of its rough, uneven surface.

This particular meltwater pond was “just over 2 feet deep and a few hundred feet wide”, according to this article:

• Hannah Hickey, Santa’s workshop not flooded—but lots of melting in the Arctic, 30 July 2013.

The pond drained out through cracks in the ice late July 27.

More important is the overall trend in the the total sea ice volume as estimated by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS).

The trend line from 1979 to 2011 shows that Arctic sea ice is melting at an average rate of roughly 3,000 cubic kilometers per decade.

In 2010, 2011 and 2012, so much ice melted that the volume fell more than 2 standard deviations below from the trend line—that’s why the jagged curve falls below the shaded region at the far right of the graph. At the end of July this year, it was just about 2 standard deviations below the trend line. The ice volume seems unlikely to break last year’s record low.

As usual, click the picture for more details.