21 July 2016
The Gravity in Greenland is Dropping, No Really.
Posted by Dan Satterfield
Check out this NASA movie showing the changes in sea level since 2002.
Blue areas show rising oceans, and yellow/red show dropping sea levels. Watch the movie, and pay attention to the area near Greenland.
So WHY is the sea level dropping around Greenland??
NASA has the answer. The Greenland ice sheet is melting, and therefore there is less mass. Less mass, means less gravity pulling the ocean water toward the coast, and the water level drops.
Here is what NASA has to say about the data:
Cumulative sea level change since April 2002
An animation showing “sea level fingerprints,” or patterns of rising and falling sea levels across the globe in response to changes in Earth’s gravitational and rotational fields. Major changes in water mass can cause localized bumps and dips in gravity, sometimes with counterintuitive effects. Melting glaciers, for example, actually cause nearby sea level to drop; as they lose mass, their gravitational pull slackens, and sea water migrates away. In this animation, computed from data gathered by the twin GRACE satellites since 2002, sea level is dropping around rapidly melting Greenland (orange, yellow). But near coastlines at a sufficient distance, the added water causes sea levels to rise (blue). The computational method is described in Adhikari et al. (2016, Geoscientific Model Development). And, these solutions are presented in Adhikari and Ivins (2016, Science Advances).
Note also the annual pulse of water from the Amazon, and the beginnings of ice loss in West Antarctica and southern Chile.