Iceberg, Jakobshavn Fjord, Greenland, 2007
Photograph by James Balog
At four miles (six kilometers) wide and several thousand feet thick Jakobshavn Isbræ disgorges icebergs like these faster than any other of Greenland's glaciers. Its output, accelerated by global warming, totals some 11 cubic miles (45 cubic kilometers) of ice each year.
