Drilling into Earth's icy past.

Drilling into Earth's icy past

It seems appropriate that investigators travel to the top of Greenland's ice cap to gather clues about Earth's glacial ages. U.S. and European scientists recently finished their first of four field seasons, drilling a pair of unprecedented research holes into Greenland's ice cap. The two teams are extracting cores of ice containing particles and air bubbles dating back over 200,000 years. Like a tree, the ice cap grows in annual layers. This enables scientists to trace a year-by-year history of climate change through the last two ice ages by analyzing the particles and gases locked within the annual layers.

The U.S. team, led by Paul A. Mayewski of the University of New Hampshire in Durham, is drilling a 3,200-meter-deep hole about 30 kilometers from the ice cap's summit, the site of the European drilling. The two teams will compare findings.

The cores will reach back through the last ice age, which began about 120,000 years ago, into the warm interglacial time, and then back into the previous ice age. Meanwhile, Soviets continue to drill the Vostok hole into the Antarctic ice sheet -- a hole that presently reaches back more than 160,000 years.