Gravity perturbations measure ice loss
Pretty cool: a pair of satellites is being used to measure subtle changes in the Earth's gravitational field and hence changes in the mass of ice in Greenland and Antartica.
Not cool is that Greenland's ice is melting 3 times faster than thought. When all of Greenland's ice melts, the oceans will be 6.5 meters higher as it contains 10% of Earth's ice-mass.