ON THE GREENLAND ICE SHEET • The midnight sun still gleamed at 1am across the brilliant expanse of the Greenland ice sheet.
Mr Brandon Overstreet, a doctoral candidate in hydrology at the University of Wyoming, picked his way across the frozen landscape, clipped his climbing harness to an anchor in the ice and crept towards the edge of a river that rushed downstream towards an enormous sinkhole.
If he fell in, "the death rate is 100 per cent", said Mr Overstreet's friend and fellow researcher, Mr Lincoln Pitcher.
But Mr Overstreet's task, to collect critical data from the river, is essential to understanding one of the most consequential impacts of global warming.
The scientific data he and a team of six other researchers collect here could yield ground-breaking information on the rate at which the melting of Greenland ice sheet, one of the biggest and fastest-melting chunks of ice on earth, will drive up sea levels in the coming decades.
The rivers melt down faster than the surrounding ice, like a knife through butter... The ice sheet is porous, like Swiss cheese. We didn't know that until this year.
DR LAURENCE C. SMITH, head of the geography department at the University of California, Los Angeles, and the leader of the team that worked in Greenland
The full melting of Greenland's ice sheet could increase sea levels by about 6m.
"We scientists love to sit at our computers and use climate models to make those predictions," said Dr Laurence C. Smith, head of the geography department at the University of California, Los Angeles, and the leader of the team that worked in Greenland.
"But to really know what's happening, that kind of understanding can come about only through empirical measurements in the field."
For years, scientists have studied the impact of the planet's warming on the Greenland and Antarctic ice sheets. But they have little on-the-ground information and so have trouble predicting precisely how fast sea levels will rise.
Scientists know that the melting of Greenland is accelerating. As the temperature rises, large lakes form on the surface of the ice, which in turn create a network of rivers.
"The rivers melt down faster than the surrounding ice, like a knife through butter," Dr Smith said.
The rivers then flow down into giant holes in the ice, called moulins, which drain through tunnels in the ice sheet and out into the ocean.
"The ice sheet is porous, like Swiss cheese," Dr Smith said. "We didn't know that until this year."
Earlier this year in Greenland, the scientists set up camp on the ice, where they hoped to capture the first comprehensive measurements of the rate of melting. Their research could yield valuable information to help scientists figure out how rapidly sea levels will rise in the 21st century, and thus how people in coastal areas from New York to Bangladesh could plan for the change.
But the research is under increasing fire by some US Republican leaders , who deny or question the scientific consensus that human activities contribute to climate change.
Leading the Republican charge on Capitol Hill is Representative Lamar Smith of Texas, chairman of the House science committee, who has sought to cut US$300 million (S$419 million)from Nasa's budget for earth science and has started an inquiry into some 50 National Science Foundation grants.
Any cuts could directly affect the work of Dr Smith and his team, who are supported by a three-year, US$778,000 grant from Nasa, which must cover everything, including researchers' salaries, flights, food, computers, scientific instruments and camping, safety and extreme cold-weather gear.
Every scientist, Dr Smith said, is keenly aware that the research costs "a tremendous amount of taxpayer money".
In July, Dr Smith's team arrived in Kangerlussuaq, Greenland, a dusty outpost of 512 people which serves as a base for researchers to prepare for fieldwork on the ice sheet.
The scientists were excited but anxious as they prepared to travel inland by helicopter to do the fieldwork: For 72 hours, every hour on the hour, they would stand watch by a supraglacial watershed, taking measurements - velocity, volume, temperature and depth - from the icy bank of the rushing river.
"No one has ever collected a data set like this," said Professor Asa Rennermalm, a professor of geography at the Rutgers University Climate Institute who was running the project with Dr Smith.
Everyone knew the team would be working just upriver from the moulin - the sinkhole that would sweep anyone who fell into it.
The scientists will use the data, which they expect to publish in the coming months, to test whether climate models are accurate. The data can then be used to create a new model to estimate the amount of water flowing from thousands of similar rivers.
The data gathered from the river at the top of the sheet will be compared with measurements the scientists have taken at its foot. They might even learn, Dr Smith said, that the water is refreezing within the ice sheet and that sea levels are rising more slowly than models project.
NEW YORK TIMES