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In this July 19, 2011 photo, attached by rope to a waiting helicopter, researcher Carl Gladish walks back after deploying a GPS seismometer, or GeoPebble, to track glacial movement on Jakobshavn Glacier, near Ilulissat, Greenland. Chief researcher David Holland, hopes to eventually deploy scores of the devices to measure ice loss in Greenland. (AP Photo/Brennan Linsley)

Huge crack discovered in Antarctic glacier

A major glacier in Antarctica is melting unusually quickly because ocean currents are undermining it from below, researchers find. Scientists are gathering meaningful and accurate data of how ice sheets and glaciers are changing over time, and what this means for our planet.