Ocean mass since 2002
Key takeaways
- The ocean has gained enough water since 2002 to raise sea level by about … mm.
- Most of the added water comes from melting glaciers and the Greenland and Antarctic ice sheets.
- Added mass now accounts for roughly 60 percent of global sea level rise.
What is ocean mass?
Ocean mass is the weight of all the water in the ocean. When ice on land melts or water moves from rivers, lakes and soils into the sea, the ocean gets heavier and sea level rises. Changes are expressed here in millimeters of sea level so they can be compared directly with the total rise.
What are we looking at?
The twin GRACE satellites (2002 to 2017) and their successors, GRACE Follow-On (since 2018), measure tiny changes in the distance between two spacecraft flying about 220 km apart. Those changes reveal month to month shifts in Earth's gravity field, which in turn tell us where mass has moved. Over the ocean, the result is a direct measurement of water added or removed.
Why do we care?
Ocean mass ties sea level to its sources. By comparing it with ice sheet and glacier loss and with water stored on land, scientists can say how much each source contributes and watch how that mix changes. Ocean mass also responds to El Niño and La Niña as rain is stored on and released from the continents.
Data: GRACE and GRACE-FO JPL mascon solution (RL06.3), via the NASA Sea Level Change portal. Reference: Watkins, M.M. et al. (2015), doi:10.1002/2014JB011547.