California Ocean Observing Systems: Tracking El Niño

Updated: October 23rd, 2026

A persistent warm anomaly has been observed along much of the California coast since September 2025 (see Coastal Conditions, Offshore Conditions).
El Niño temperature signals are now evident in Southern California, both at shore stations and along the glider lines (see Gliders).
The ocean off Central California is warming in a way that points to El Niño. Instruments on MBARI’s M1 mooring, a long-running ocean observing buoy in Monterey Bay, are recording unusually warm water 60 meters (about 200 feet) below the surface (see Moorings). Warming at depth like this is a classic sign that El Niño has reached our coast.
In Northern California, upwelling has brought short bursts of cooling. These dips interrupt the warm anomaly but haven’t reversed it (see Upwelling).
Much of this warmth started as a marine heatwave before El Niño arrived. Earlier this year, glider temperature anomalies on Lines 66.7 and 80 were the largest in the 20-year glider record.
California’s ocean observing systems provide real-time and forecast data to track El Niño’s arrival and impacts along the coast.

Impacts Monitored

Water Levels & Waves

CalOOS collects measurements on sea state (waves, winds, waterlevels), and works across observing programs to deliver actionable information to protect lives and livelihoods.

Coastal Erosion (coming soon)

Ocean Heat

Increased marine heat and persistent marine heatwaves can contribute to higher tides and bigger waves and storms, and threaten ecosystems.

Coastal Conditions
Offshore Conditions

Ecosystem Response

Changes in ocean and coastal conditions related to El Nino-driven heat, freshwater inputs (salinity), and other biogeochemical parameters can result in altered ecosystems, including kelp habitats, algae communities, and species distribution.

Upwelling
Ecosystem Impacts (coming soon)

Updated: October 23rd, 2026

Warm, but not everywhere. Nearshore waters off Southern and Central California have run warm since fall 2025. The warmth comes from a marine heatwave that began before the current El Niño. Earlier this year, glider temperature anomalies on Lines 66.7 and 80 were the largest in the 20-year glider record. North of San Francisco, coastal temperatures have mostly been near average to slightly above average.
El Niño's signal is starting to show in Southern California. The latest warming at Southern California shore stations and on glider Line 90 (off Dana Point) is likely the first direct El Niño influence. The tropical El Niño is very strong, and its effects along the coast usually lag by a few months, so expect more warming through late fall and winter.
Upwelling is causing short cool-downs in Central and Northern California. Upwelling-favorable winds keep bringing brief cooling to these regions. The dips interrupt the warm conditions but haven't ended them (see the Upwelling page). If El Niño weakens the upwelling winds this winter, these cool breaks may become less frequent.

Sea Surface Temperature: Northern California

Conditions summary: Northern California shore stations have seen water temperatures near average to slightly above average in recent weeks, without the persistent heat recorded farther south. Short cool-downs from upwelling have repeatedly interrupted warm spells, so the past six months look variable rather than steadily warming. El Niño warming usually reaches the north coast later than Southern California, so temperatures here may climb through late fall and winter.

About the data: Automated shore stations on piers, wharves and other coastal sites (such as Humboldt, Santa Cruz Wharf and Scripps Pier) measure nearshore seawater temperature every few minutes, as part of the CeNCOOS and SCCOOS networks. Each plot compares recent readings with the station’s long-term record: the average, the minimum and maximum, and the 90th percentile, which is the usual threshold for a marine heatwave. Data are quality-controlled following national (QARTOD) standards, and full records are available on the CalOOS Data Portal.

Conditions summary: Glider surveys show the marine heatwave reached well below the surface. Averaged over the upper 100 m within 200 km of shore, temperature anomalies on Lines 66.7 (Monterey Bay) and 80 (Point Conception) earlier this year were the largest in the 20-year glider record. Recent warming on Line 90 (off Dana Point) is the first sign of the current El Niño in the glider data.

About the data: The California Underwater Glider Network uses autonomous Spray gliders, operated by Scripps Institution of Oceanography, to survey fixed lines running hundreds of kilometers offshore. The gliders dive repeatedly from the surface to depth, measuring temperature, salinity and other properties. Several lines have been sampled almost continuously since the mid-2000s (Rudnick et al. 2017).

Data citation: Rudnick, D. L., K. D. Zaba, R. E. Todd, and R. E. Davis, 2017: A climatology of the California Current System from a network of underwater gliders. Progress in Oceanography, 154, 64-106; doi: 10.1016/j.pocean.2017.03.002

Impacts Monitored

Water Levels & Waves

Ocean Heat

Ecosystem Response

Sea Surface Temperature: Northern California

Sea Surface Temperature: Central California

Sea Surface Temperature: Southern California

Subsurface Conditions: Moorings

Multi-scale Ultra-high Resolution (MUR) SST Anomaly

Coastal Erosion

Ecosystem Impacts

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