Recent Warming In The San Francisco Bay And California Coastal Ocean

During 2014 exceptionally warm water temperatures developed across a wide area off the California coast and within San Francisco Bay (SFB) and persisted through the middle of 2016. Observations and numerical model output are used to document this warming and its origins. The coastal warming was mostly confined to the upper 100 meters of the ocean and was manifested strongly in the two leading modes of upper ocean (0-100 m) temperature variability in the extra-tropical eastern Pacific. Observations in the suggest that the coastal warming in 2014 propagated into nearshore regions from the west and later indicate a warming influence that propagates from south to north into the region associated with the 2015-16 El Nio event. An analysis of the upper ocean (0-100 m) heat budget in a Regional Ocean Modeling System hindcast simulation confirmed this scenario. The results from a set of sensitivity runs with the model in which the lateral boundary conditions varied supports the conclusions drawn from the heat budget analysis. Concerning the warming in the SFB, an examination of the observations and the heat budget in an unstructured-grid numerical model simulation suggests that the warming during the second half of 2014 and early 2016 originates in the adjacent California coastal ocean and propagates through the Golden Gate into the Bay. The finding that the coastal and Bay warming are due to the relatively slow propagation of signals from remote sources raise the possibility that such warming events may be predictable several months in advance.