See the Ocean Breathe: Sentinel-6B Tracks El Niño and Rising Sea Levels Across 90% of Earth

Washington, D.C., Source :.

Hundreds of miles above Earth, satellites are watching the ocean breathe. The surface rises and falls with warmth, and those small changes tell a huge story about the planet. Sentinel-6B joined that story in November 2025, and it is already showing what a single satellite can do.

This mission brings together NASA and international partners in a U.S.-European effort. It surveys about 90 percent of the world's oceans. Radar altimeters measure the height of the sea surface down to the centimeter. Those tiny measurements reveal where heat is stored, how currents move, and when the Pacific is about to shift.

One of the most useful things Sentinel-6B can do is detect El Niño and La Niña. These natural climate patterns influence weather nearly everywhere on Earth. La Niña cools the central and eastern Pacific. El Niño warms it. Both change winds, rainfall, and marine life in ways that affect food supply, water resources, and disaster preparedness.

In late 2025, a weak La Niña appeared across the equatorial Pacific. Cooler surface waters were paired with heavier rain over the Amazon basin. That rainfall stayed on land in rivers, wetlands, and reservoirs, so the global sea level rise for 2025 slowed compared with the previous year. All the while, the ocean continued absorbing record amounts of heat.

By early 2026, the Pacific began to shift. Sea level data collected from March to May by the Sentinel-6 Michael Freilich satellite showed a wide area of higher, warmer water moving east from the western Pacific. The swell reached the coasts of Colombia, Ecuador, and Peru in a band hundreds of miles wide. By early June, satellite readings showed it growing stronger. That is how El Niño starts.

Warm water expands, so sea surface height offers an early signal. Weak trade winds let the warm water that usually gathers near Asia surge eastward across the ocean. This slow wave carries heat with it. Once it arrives in the eastern Pacific, it shifts storm paths, changes ocean ecosystems, and influences rainfall for millions of people. The satellite allows scientists to see that journey unfolding.

Sentinel-6B follows in the path of TOPEX/Poseidon and the Jason satellites. That lineage transformed oceanography from a field with few observations into one with continuous, reliable data. The same measurements now support weather models, marine navigation, hurricane forecasts, and coastal flood plans. Anyone who lives on the coast, works on a ship, or plans a farm can benefit from these eyes in the sky.

Global sea levels are rising as the climate warms. Superimposed on that trend are natural oscillations like El Niño and La Niña that make the yearly numbers speed up or slow down. Sentinel-6B tracks both the long-term rise and these natural pulses. That separation helps scientists predict coastal flooding, support national security planning, and design a more resilient future.