The impact of coastal runoff on ocean color during an El Niٌo year in Central California

The introduction of the SeaWiFS ocean-color instrument in the autumn of 1997 coincided with the onset of perhaps the largest El Niño event of the century, providing us with the opportunity to monitor the impact of such events on biological and bio-optical properties in central California. The increased importance of coastal runoff (both sediments and fresh water) during the winter of 1998 have been striking. Here we evaluate the effects of riverine input to central California immediately following the largest El Niño-influenced winter storm event in central California of February 1998 using shipboard, mooring, and satellite observations from the sea-viewing wide field-of-view sensor (SeaWiFS). Two models were employed to estimate colored dissolved organic matter, (CDOM), which provided similar spatial and temporal patterns of CDOM, but differing absolute concentrations. We observed a 5-fold increase in SeaWiFS-derived chlorophyll concentrations, with a corresponding CDOM signal (estimated absorption at 300 nm greater than 0.30 m−1) extending to approximately 300 km offshore. This event, while anomalous, demonstrates the potential influence of riverine input on the bio-optical properties of the coastal environment extending to several hundred kilometers offshore.