Mini Lesson

Stability and Change: Monitoring Sea Level

The Earth's system exemplifies stability and change. Change and rates of change can be observed and quantified over very short or long periods of time and various spatial scales (e.g., from landscape level to global processes). Understanding stability and change in Earth processes contributes to a more complete understanding of the Earth system.

Sea level: The phrase itself suggests our ocean and seas have a uniform height. But in fact, the surface of Earth's ocean is not level at all. The height of the ocean surface varies by several feet across the globe because of currents, winds, and temperature fluctuations that cause seawater to expand or contract. For over two decades, NASA and other space agencies have taken precise satellite measurements of sea level, down to the millimeter. The data for this visualization comes from instruments called "altimeters," which have been included on TOPEX/Poseidon, Jason-1, and Jason-2 satellites.

The data reveal a surface layer in constant flux, marked by local ripples that rise and fall and massive swells that span oceans. Understanding what causes these differences will only become more important in coming decades, as scientists expect rising sea levels to affect some regions more intensely than others. Watch the visualization for a look at how sea level fluctuates around the world. Ocean surface height is indicated by "bumpiness" and color: average (white), 20 inches (~500mm) above average (dark red), 20 inches (~500 mm) below average (dark blue).

Credit: NASA Scientific Visualization Studio