Ice cores offer a window into the history of Earth's climate. Layers of ice reveal past temperatures, and gases trapped in bubbles reveal past atmospheric composition. The oldest continuous ice core so far comes from Dome C in East Antarctica and extends back 800,000 years. But a tantalizing clue recently offered the possibility to go back even further. A collaborative study now pinpoints a location where an entire million years of undisturbed ice might be preserved intact. The team gathered observations in Antarctica's Allan Hills Blue Ice Area, named for the blue ice that is exposed at the surface when ice above gets vaporized. This windy, desert area gets less than 1 centimeter of snow accumulation per year. Researchers used snow machines to tow ice-penetrating radar around the region. The radar sends radio waves into the ice, which reflect off of layers of ice with different chemistries and densities, providing an image of the structure below. A computer model of glacier flow incorporating the data from those surveys suggests that million-year-old ice is about 25 to 35 meters (about 100 feet) above the bedrock. Regardless of whether the million-year-old ice is there, the record is likely to be valuable.
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