Since 1993, satellite altimetry has measured the height of the ocean surface with millimeter precision. This animation shows the monthly sea level anomaly (Copernicus/CMEMS, vDT2024) from 1993 to 2025, projected onto the Spilhaus projection, which shows the world ocean as a single connected body of water instead of cutting it into pieces at the map edges.

Three things to look for. First, the long-term shift: blues dominate in the early 1990s and gradually give way to reds by the 2020s, the visible signature of global sea level rise. Second, the swirls: those aren't noise, they're mesoscale eddies, rotating bodies of water tens to hundreds of km across that show up as local sea level bumps and dips. Most drift westward, following the same physics that steers hurricanes, except in the Antarctic Circumpolar Current, the one place on Earth where the dominant flow overwhelms that tendency and eddies get swept eastward instead. Third, the polar regions flicker: that's not missing data by accident, altimeters can't see the sea surface through sea ice, so those patches blink in and out with the seasonal advance and retreat of Arctic and Antarctic ice each year.

Data: Copernicus Marine Service (CMEMS), satellite altimetry, DUACS vDT2024