Ten years ago, glaciologists believed the great Greenland ice sheet was pretty much frozen to its bed of old, cold Precambrian crust. Thus anchored, the ice sheet crept viscously to the sea, where the ice melted away. Annual snowfall balanced whatever thinning the flow produced.
That appealingly simple paradigm was upset in 1992 when Mark Fahnestock, then at NASA’s Goddard Space Flight Center, and his colleagues discovered a stream of fast-moving ice, tens of kilometers wide, running northeast from central Greenland to the Arctic Ocean 500 km away. Glaciologists had identified ice streams before in Western Antarctica, but not in Greenland.
Now, Fahnestock, who has since moved to the University of Maryland in College Park, has uncovered the source of the stream’s rapid motion: a region of unusually warm bedrock at the head of the stream. Most likely volcanic in origin, the warm rock melts the ice, creating a lubricating...
