Observations taken during tile course of the Northern California Coastal Circulation Study (NCCCS) pilot experiment from March through August of 1987 show that shelf currents often converge near Cape Mendocino, resulting in offshore transport. This convergence occasionally, though not always, is accompanied by convergence in the large-scale winds. A cyclonic eddy, roughly 20 km in diameter, is commonly found on the south side of the Cape, where, on the shelf, the average currents are directed to the north. The water temperature in this area is colder than that observed north of the Cape, where the average current is to the south. Correlation between currents aim the local wind near the Cape is lower than expected from previous results obtained during the Coastal Ocean Dynamics Experiment (CODE) conducted in the same general region, though farther south, along a straight section of the coast. Similarly, temperature and wind fluctuations at a given location are less correlated than they were during CODE.

These patterns are not those expected for typical coastal upwelling areas. The coincidence of coldest surface temperatures and persistent northward shelf flow is particularly intriguing, as is the lack of correlation between currents and wind. Interactions between the shelf flow and the California Current, variations in the large-scale structure of the wind, the influence of poleward-traveling shelf waves, and the role of Cape Mendocino in determining flow in the atmosphere as well as in the ocean are discussed as possible causes of the observed convergence. Some of these effects may be responsible for enhanced upwelling near other capes and headlands.

The NCCCS Group. 1990. Convergent shelf flow at Cape Mendocino. Oceanography 3(1):4, https://doi.org/10.5670/oceanog.1990.14.

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