The chief culprit? Global warming. The potential upshot? Longer and more intense extreme-weather events such as heat waves, cold spells, and droughts. (Read more about extreme weather in National Geographic magazine.)

In August, the sea ice disappeared at an average rate of about 39 square miles (a hundred square kilometers)—or about twice as normal, NSIDC scientists say.

Moreover, the area of Arctic sea ice around the North Pole had shrunk to 1.58 million square miles (4.1 million square kilometers)—the smallest measurement since 1979, when satellite observations began.

The worst news of all? The new record probably won't last long. With up to three more weeks of the melting season left, said Stroeve, the total is likely to shrink further.

"It will be below 4 million square kilometers (1.5 million square miles) before it's all said and done."