LAUSR

Satellite observations from the Moderate Resolution Imaging Spectroradiometer and Sea-viewing Wide Field-of-view Sensor reveal a “tongue” of elevated near-surface chlorophyll that extends into the Southern California Bight from Point Conception. A local chlorophyll maximum at the western edge of the bight, near the Santa Rosa Ridge, indicates that the chlorophyll is not solely due to advection from Point Conception but is enhanced by local upwelling. Chlorophyll in the bight peaks in May and June, in phase with the seasonal cycle of wind stress curl. The spatial structure and seasonal variability suggest that the local chlorophyll maximum is due to a combination of bathymetric influence from the Santa Rosa Ridge and orographic influence from the coastline bend at Point Conception, which causes sharp wind stress curl in the bight. High-resolution glider observations show thermocline doming in May–June, in support of the local upwelling effect. Despite the evidence for local wind stress curl-forced upwelling in the bight, we cannot rule out alternative mechanisms for the local chlorophyll maximum, such as iron supply from the ridge. Covariability between chlorophyll, surface wind stress, and sea surface temperature (SST) indicates that nonseasonal chlorophyll variability in the bight is closely related to SST, but the spatial patterns of SST influence vary by time scale: Subannual chlorophyll variability is linked to local wind-forced upwelling, while interannual chlorophyll variability is linked to large-scale SST variations over the northeast Pacific. This suggests a greater role for nonlocal processes in the bight’s low-frequency chlorophyll variability. Plain Language Summary Satellite observations of ocean color reveal a “tongue” of enhanced chlorophyll in the Southern California Bight, indicating that this is a region of high biological productivity. The satellite observations and local observations from automated gliders suggest that the enhanced chlorophyll in the bight is due to local upwelling, rather than chlorophyll being simply carried downstream from Point Conception. The seasonal cycle of chlorophyll is in phase with the local wind stress forcing, which peaks in May and June. In contrast to the seasonal variability, the substantial year-to-year chlorophyll variations are controlled by large-scale climate variability over the northeast Pacific, that is, El Niño and marine heat wave events.