Winter view: Arctic sea ice has been getting thinner, even faster than its area has been shrinking.
Greenland's estimated ice loss each year from 2004 through 2007.
Greenland has been losing large amounts of ice into the sea Ã¢Â€Â“ enough to collect into rafts the size of states.
Greenland has been shedding billions of tons of ice in 2007, the melted equivalent of draining San Francisco Bay every 10 days.
Alaska has been losing tremendous volumes of ice to the sea.
Alaska has been shedding large amounts of ice into the sea - on average, enough to fill a daily freight train around the world.
Arctic sea ice acts like a heat shield, reflecting most of the sun's energy. As the ice has melted back, it reflects less, and the planet is absorbing more heat.
NASA satellites have watched Arctic sea ice for three decades now, and the record shows more and more melting over time.