Flecks of dust, falling seasonally, enable glaciologists to count the years down the ice core's length. Isotopes of oxygen, in minute air bubbles trapped in the ice, vary with temperature and so tell researchers how ancient climate shifted. Other clues — chemicals, surrounding geology, trapped and frozen vegetation or insects — tell high-altitude investigators still more.
The 59-year-old Thompson's assault on Puncak Jaya, planned for May-June 2009, will take his crew into isolated, mist-shrouded highlands seldom visited even by tribes in the area, across Papua New Guinea's border in the Indonesian half of this island. In 2006, a biological expedition to its uncharted tropical forests reported finding new species of birds, frogs, even a tree kangaroo.
The last scientific expedition to the glaciers took place in 1973, when Australian glaciologist Ian Allison and colleagues trekked seven days through the wilderness past gushing rivers and groves of tree ferns, with gear borne by a train of near-naked tribesmen.
"In the fourth or fifth day you see in the distance the sheer limestone cliffs with the ice on top, and it's really quite a sight," Allison recalled by phone from Australia.
Thompson should have an easier time scaling those 10,000-foot cliffs.
The mining company Freeport-McMoRan, operating nearby, has agreed to airlift his dozen-member team to Puncak Jaya's heights by helicopter, along with six tons of equipment — electro-mechanical and thermal drill systems, radar to gauge ice thickness and map the underlying rock, winch and cable, boxes to preserve core segments, high-altitude camping gear and supplies.
They'll find glaciers very different from those Allison saw.
Although ever-present cloud cover complicates satellite surveillance, meticulous research by Texas A&M University geographers has determined that the glaciers are shrinking rapidly.
"We're tracking their demise by satellite images," the university's Andrew Klein said from College Station, Texas. "If current retreat rates continue, they will disappear in a few decades. This is similar to what's happening to tropical glaciers around the world."
Puncak Jaya's Meren Glacier, one of five ice masses surveyed in the 1972-73 Australian expeditions, vanished completely sometime between 1994 and 2000, the Texas researchers report. In two years alone, between 2000 and 2002, the remaining glaciers lost more than 7% of their area.
The researchers estimate that since about 1850, as heat-trapping industrial emissions accumulated in the atmosphere, Puncak Jaya's ice has shrunk from covering 7 square miles to less than one square mile.
Michael Prentice, an Indiana University paleoclimatologist, or climate historian, believes temperature increases in the New Guinea uplands have far exceeded — "really out of sight" — the 1-degree Fahrenheit average rise recorded globally in the past century.
With Inape and Australian and Indonesian scientists, Prentice is organizing the project to collect and analyze existing climate data, and to emplace or upgrade automatic weather stations at sites including Puncak Jaya.
New Guinea lies on the fringe of the Western Pacific Warm Pool, a center of warm water that generates El Nino disturbances and influences climate from India's monsoons to the Amazon's droughts. Because of that, Prentice said, what the glacier ice tells Thompson about the region's past will help climatologists understand what lies ahead.