By Tom Randall
Sir Isaac Newton's law of gravity states that the pull of an object depends on its mass. This means that when the Earth's mass shifts, so does its field of gravity.
The first accurate measurement of melting glaciers in Greenland came from gravitational readings by the twin satellites known as GRACE (Gravity Recovery and Climate Experiment), which produced this rendering of Earth's gravity field. The satellites found that global warming reduced Greenland's ice shield by 240 gigatons of mass each year from 2002 to 2011, corresponding to a global sea level rise of 0.7 millimeters per year.
The uneven distribution of mass both within the Earth and on its surface causes variability in gravity, reflected in the planet's irregular shape. The rendering also shows increased gravity mounds over North America and Scandinavia, where a mile-thick ice sheet melted after the last ice age. With ice's surface pressure gone, the Earth's mantle shifted and the dense crust to began to rise.
-0- Mar/28/2012 15:08 GMT