🧂 The ocean is a rain gauge

There are no rain gauges in the middle of the Pacific. But every drop that evaporates leaves its salt behind, and every drop of rain dilutes what is already there, so the ocean keeps its own record of the water cycle written in salinity.

This globe shows how that record has changed from 2010 to 2025. Brown means the surface is getting saltier, blue-green means it is getting fresher.

Since 1993, oceanographers have tracked sea surface salinity from space and ships alike. This animation shows the monthly global distribution (CMEMS multi-observation product) on the Spilhaus projection, in PSU (practical salinity units), the actual field, not an anomaly, because the structure itself is the story here.

A companion piece to the recent Spilhaus animation of monthly salinity: this globe shows the 1993-2025 mean sea surface salinity (CMEMS multi-observation), in PSU. Land is grey.

The surface both is colored and deformed by salinity, but here the reference point isn't zero, it's the ocean's own global mean. Water saltier than that average bulges outward; fresher water sinks in. As with the rest of this series, that's a visual device, not a physical measurement.