About 2 trillion tons of ice have melted in Greenland , Antarctica , Alaska since 2003 . Lost amount of water could fill up Chesapeake Bay 21 times , NASA scientist says . NASA 's Gravity Recovery and Climate Experiment , or GRACE , mission uses two orbiting satellites to measure the `` mass balance '' of a glacier , or the net annual difference between ice accumulation and ice loss . `` A few degrees of change [ in temperature ] can increase the amount of mass loss , and that contributes to sea level rise and changes in ocean current , '' Luthcke said . Comment: mm annually . Scientist says sea levels rising 50 percent faster than 15 years ago .
About 2 trillion tons of ice have melted in Greenland , Antarctica , Alaska since 2003 . Lost amount of water could fill up Chesapeake Bay 21 times , NASA scientist says . Comment: mm annually . Scientist says sea levels rising 50 percent faster than 15 years ago .