Oceanographic and climatic variability in the Lower Gulf of California: Links with the tropics and North Pacific

The links between climate and oceanography in the lower Gulf of California (LGC) and the observed physical variability in the open Pacific were studie d on interannual to decadal timescales. Two indices reflect the North Pacif ic's oceanic and climatic variability: the El Nino Southern Oscillation ind ex (ENSO) and the North Pacific Decadal Oscillation index (PDO). The sea su rface temperatures, wind speed, precipitation and sea level records of La P az region, Baja California Sur (Mexico) in the LGC were used to compare the m with the PDO and ENSO indices. The most important forcing processes were observed coming from the tropical and the equatorial Pacific, represented b y the ENSO index, significantly associated with precipitation, sea surface temperature (SST) and sea level. The Northern Pacific influence, represente d by the PDO index, is associated with the winds and to a lesser extent wit h SSTs and precipitation. These results show that SST variability in the re gion is controlled by both indices. A model is proposed to explain the cont rol that each of them exerts on the LGC SST variability. In this model the excess heat brought by surface tropical waters, especially after the intens ification of ENSO events since the 1980s, in addition to the long term warm ing observed over the past century, is partially dissipated by stronger win ter winds in the gulf. These stronger and cooler winds, derived from change s in the atmospheric circulation patterns of the North Pacific and captured by the PDO positive anomalies, act as negative feedback to the warming dis sipating part of the accumulated heat and dampening the raise in SSTs. This process is proposed to operate, especially after the 1970s sign shift of t he PDO, when no change in the SSTs' trend occurs showing an opposite behavi or in respect to wind variability, which was not observed for previous deca des.