Ocean mass is the “weight” of the ocean, determined by its gravitational pull.
The plot shows satellite measurements of the ocean's mass since 2002. The increase since 2002 comes largely from melting land ice that adds water to the ocean. The black line tracks the measurements, while blue shows how much uncertainty, up or down, 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. These satellites observe bumps and dips in Earth’s gravitational field as they pass over land, water, and ice.
Increasing ocean mass causes sea levels to rise along the coasts, increasing flood risk and submerging coastlines over time.