One of the few ways to find climate records of the Earth's early history is to drill into the planet's deepest ice, and one of the best places to do that is Greenland. Researchers first started digging pits there in the 1930s, and have since graduated to decade-long expeditions in Greenland with high-tech ice coring drills. "Greenland has holes punched all over it," says Mary Davis, a geologist at Ohio State University.
But the existing Greenland ice cores are lacking crucial data: records from the last interglacial period, called the Eemian, about 115,000 years ago. The Eemian period was warm, much like today, and the gasses trapped in this ice are important for understanding present-day climate change.
Since 2007, Danish scientists
have been drilling for this ice at two sites in northwest Greenland called NorthGRIP and NEEM. There the conditions are best for finding Eemian ice. The bedrock is flat, which fosters even ice layers; the precipitation is high, which makes layers easier to detect; and the ice is more than 1.5 miles thick, suggesting that the ice at the bottom has been around for a long time--maybe as long ago as the Eemian period, scientists hope.