In the large image, the area behind the shoreline is pockmarked by marshes, ponds, and hummocks characteristic of "thermokarst," landscapes created by the melting and refreezing of permafrost.

But if warming is occurring across a wider area than previously observed, that could increase the possibility of large ice shelves melting off the continent and changing sea levels around the world.

Similarly, at the other end of the planet, near the South Pole, scientists have found new evidence of snow melting in West Antarctica across an area as large as California.