Second in a three-part series.

SUMMIT STATION, Greenland -- At first glance, this research station on the highest point of Greenland's vast ice sheet doesn't look like much.

A scattering of trailers perch on stilts high above the snow, with a neat grid of small yellow tents off to one side. There's a tall metal tower, a few outhouses. A pile of fuel bladders stands in stark contrast next to the carefully groomed ice runway.

But this nondescript outpost is a magnet for scientists trying to answer some very big questions. Do clouds and tiny aerosol particles help warm or cool Greenland's ice and the air above it? How fast is the climate here changing? How quickly is Greenland's ice sheet melting?

Researchers established the first camp here in 1989, at the start of an international effort that drilled the 3,053-meter-long Greenland Ice Sheet Project-2 ice core, retrieving a record of climate over the previous 110,000 years.

That project ended in 1993. It wasn't until nearly a decade later, in 2000, that the National Science Foundation turned the camp perched on the apex of Greenland's ice, 2 miles above bedrock, into a year-round research hub. The station, manned by a six-person crew in winter, hosts up to 50 people at a time during the bustling summer research season.

This year, Summit's list of long-term visitors includes Brandon Strellis, an environmental engineering graduate student from the Georgia Institute of Technology studying how aerosols influence how much energy is reflected and absorbed by Greenland's ice -- and where those particles are coming from.

One aerosol, black carbon, is of increasing concern for Arctic nations worried about the pace of climate change in the far north, which is warming twice as fast as the global average. Sooty particles of black carbon, produced by burning fossil fuels, wood and dung, warm the atmosphere by absorbing heat from the sun. And when they land on Greenland's snow and ice, their ability to absorb heat from sunlight increases surface melting.

Probing mysteries of soot and clouds
A study released in May by the Arctic Council suggests that, while countries below 40 degrees north latitude collectively contribute the lion's share of the world's black carbon output, Nordic countries' soot is the most damaging, because it has the shortest distance to travel to the Arctic.

Strellis said the project he's working on, organized by Georgia Tech professor Michael Bergin, seeks to determine whether black carbon is reaching the interior of Greenland's ice, and how it gets there.

"Long term, policy-wise, if we can say what percentage is from [man-made] sources, policymakers can see where to cut pollution," said Strellis, who spent most of May, June and July at Summit collecting and analyzing snow samples for the project.

Across camp, in a trailer on skis known as the "Mobile Science Facility," researchers are training their eyes to the sky. The tiny shelter is jammed with expensive science equipment designed to measure the clouds high above.

"Clouds are one of the major feedbacks in cooling and heating the surface" of the ice, said Nate Miller, an atmospheric science graduate student at the University of Wisconsin, Madison. But it's not clear which effect predominates in the Arctic, he explained, since different types of clouds have different effects on climate, depending on whether they're made of ice or snow, whether they're thick or thin, and how high they sit in the atmosphere.

Next door, in the "Temporary Atmospheric Watch Observatory," or "TAWO," the National Oceanic and Atmospheric Administration tracks the level of greenhouse gases and ozone-depleting chemicals in the atmosphere.

"When we figure out how to measure to our standards, we never stop measuring," said Brian Vasel, field operations manager for NOAA's global network of observatories, explaining his agency's philosophy. "We're the world standard for tracking carbon dioxide, carbon monoxide, methane and sulfur hexafluoride."

Ground truth for satellite data For other researchers, Summit Camp is a brief stop on longer journeys to the uninhabited interior of Greenland's ice sheet.

Liz Morris, a glaciologist from the Scott Polar Institute at Cambridge University, spent a few days at the station in mid-July, organizing her supplies for a monthlong, 500-mile expedition across the ice.

It's the seventh such journey Morris has undertaken since 2004, all of them aimed at measuring the density of the top layer of snow covering the ice sheet. Morris uses the information she gathers on these trips to check the accuracy of data collected by a European satellite, Cryosat-2, that tracks changes in the thickness of polar ice -- information that tells scientists how quickly that ice is thawing.

"The problem about satellites is that they will give you the change in height [of snow] but not change in mass," Morris said. That doesn't provide a full picture of snow accumulation, since it doesn't take into account the density of the snow layers that pile on the ice.

That's where Morris and her assistant, John Sweeny, come in. The pair left Summit Station on July 17 equipped with a pair of Ski-Doo snowmobiles pulling cargo sleds. They planned to spend a month traveling an established track along Greenland's ice, along the way drilling boreholes to measure the density of the topmost layers of snow.

Several recent studies, most based on satellite data, have concluded that warming has accelerated ice loss from Greenland's massive ice sheet. But Morris noted that most of that loss occurs at the margins of the ice sheet, particularly in areas where the edges of glacial ice are in contact with the ocean.

It's not clear whether the ice in Greenland's interior, which rests on bedrock, is as vulnerable to warming, Morris said -- a question that the data she collects could help answer.

"At the end of the day, it's clear that if the world gets warmer, ice is going to melt," she said. "The question is, is this just a response to short-term ocean warming, and will it continue?"

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500