Greenland's ice sheet in a changing world

The Greenland ice sheet is thousands of feet thick, so heavy the land it covers is pushed below sea level and so ancient that bubbles visible in the ice today contain air that may be 15,000 years old. Along the ice sheet's edges, glaciers elbow through a rocky rim, sending icebergs the size of Manhattan into the sea. In summer months, as the ice sheet's surface melts, crevasses open, luminous canyons deepen, brilliant blue lakes form. The melt, the cracks, the calving glaciers -- it's all accelerating, an alarming but spectacular evocation of global warming.

Since 2005, James Balog has been photographing the ice sheet -- and glaciers around the world -- in person and with fixed, time-lapse cameras for a project called the Extreme Ice Survey. These images come from Balog's new book, "Ice: Portraits of Vanishing Glaciers," and the ice sheet also stars in a documentary on the Extreme Ice Survey that is showing this week in West Los Angeles at the Nuart Theatre.

James Balog's photographs have been exhibited in museums and galleries worldwide and published in National Geographic, Vanity Fair and the New Yorker. In 2009, he served as a NASA and State Department representative at the U.N. climate change conference in Copenhagen.