Overview
- Scientists say a Kelvin wave tied to the strong 2026 El Niño is moving north and is expected to reach California waters by October, potentially adding roughly 6 to 12 inches to current Bay Area sea levels.
- Kelvin waves are underwater pulses of warm water that travel east along the equator then turn north as coastally trapped waves, producing an elevated sea state rather than moving large volumes of water.
- The wave will deepen the thermocline and warm nearshore waters, which can weaken cold-water upwelling, stress marine ecosystems and let high tides and storm-driven waves reach farther inland.
- Researchers warn several more Kelvin waves could follow through fall and winter, which may keep sea levels elevated into spring 2027 and raise the chance that high tides coincide with storms to worsen flooding.
- Local officials are taking near-term steps: Sausalito approved $250,000 for mitigation projects and the Port of San Francisco is reviewing storm-response protocols and inspecting stormwater systems.