The jagged line shows how much ice Greenland has lost since May 2002, expressed in gigatonnes (billions of metric tons) of ice mass – the “weight” of the ice. (See an animated map of these changes.) The blue line (seen when you click and drag to zoom in) shows how much uncertainty, high or low, is associated with these measurements.
These measurements come from the retired GRACE (Gravity Recovery and Climate Experiment) satellites, and GRACE Follow-On, the successor mission to GRACE that launched in 2018.
Greenland’s ice is melting rapidly, and the melt is accelerating, making it a canary in a coal mine for climate change. For every 360 gigatonnes of ice lost, the ocean rises by 1 millimeter. Since 2002, sea levels have risen by about 2.5 inches, or 63 millimeters. Sea level rise increases coastal flooding and eventually will inundate some coastal communities.