JAKOBSHAVN GLACIER, Greenland — Gripping a bottle of Jack Daniel's between his knees, Jay Zwally savored the warmth inside the tiny plane as it flew low across Greenland's biggest and fastest-moving outlet glacier.
Mile upon mile of the steep fjord was choked with icy rubble from the glacier's disintegrated leading edge. More than six miles of the Jakobshavn had simply crumbled into open water.
"My God!" Zwally shouted over the hornet whine of the engines.
From satellite sensors and seasons in the field, Zwally, 67, knew the ice sheet below in a way that few could match. Even after a lifetime of study, the raffish NASA glaciologist with a silver dolphin in one pierced ear was dismayed by how quickly the breakup had occurred.
Wedged between boxes of scientific instruments, tent bags, duffels and survival gear, Zwally had no room to turn inside the cramped passenger compartment of the twin-engine Otter. He passed the whiskey bottle over his shoulder to geophysicist Jose Rial from the University of North Carolina, squeezed on a jump seat between a surveyor and a sleeping climatologist.
Homeward bound -- windburned, bone-chilled and greasy after weeks on this immense ice cap tilted like a beret flopped across the top of the world -- they all had been in a celebratory mood.
Somber now, Zwally and Rial shared a drink in silence as the shadow of the plane slipped across azure meltwater lakes, rust-red tundra and silver tongues of ice.
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The Greenland ice sheet -- two miles thick and broad enough to blanket an area the size of Mexico -- shapes the world's weather, matched in influence by only Antarctica in the Southern Hemisphere.
It glows like milky mother-of-pearl. The sheen of ice blends with drifts of cloud as if snowbanks are taking flight.
In its heartland, snow that fell a quarter of a million years ago is still preserved. Temperatures dip as low as 86 degrees below zero. Ground winds can top 200 mph. Along the ice edge, meltwater rivers thread into fraying brown ropes of glacial outwash, where migrating herds of caribou and musk ox graze.
The ice is so massive that its weight presses the bedrock of Greenland below sea level, so all-concealing that not until recently did scientists discover that Greenland actually might be three islands.
