Circulation at the Entrance to the Gulf of California

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Intellectual merit: An eight-day survey of waters at the mouth of the Gulf of California will be conducted during the return transit of R/V Point Sur from Palmer Station, Antarctica, to Moss Landing, California, in April 2013. Flow rates and transports between the Pacific Ocean and Gulf of California will be measured using closely spaced CTD observations which extend from the ocean surface to the bottom as well as from observations of currents using vessel mounted acoustic Doppler current profilers. Similar observations will be carried out along the southern coast of Baja California in order to determine the fate of waters formed in the Gulf of California when they reach the Pacific Ocean. These observations will complement a 20-year program of observations carried out jointly by the Universidad Autonoma de Baja California (UABC) in Ensenada, Mexico, and the Naval Postgraduate School (NPS) in Monterey, CA. Surface waters at the mouth of the Gulf are highly productive, in part due to mixing of Gulf and Pacific waters, while subsurface waters contain very little dissolved oxygen, about 2-4 micro mole per kg. The latter is of concern as subsurface waters which flow out of the Gulf along Baja California join the California Undercurrent and flow poleward along the West Coast of the United States, perhaps contributing to declining oxygen values in the Southern California bight. 2013 observations of water properties at the mouth of the Gulf will be compared to those obtained in 1991 to see if systematic changes of water properties are occurring with time. Broader impacts: This collaborative research will contribute to graduate and undergraduate teaching programs at UABC and graduate programs at NPS. Students will be involved with collection, processing, and interpretation of shipboard data. The project will also foster continued cooperative ocean studies with Mexican oceanographers which are necessary to understand joint management of common ocean resources. Examples include "dead zones" which occur when low oxygen waters flow onto the continental shelf and the ecological perturbations which occur when Humboldt squid move northward into California waters. All the collected data will be submitted to the National Oceanographic Data Center (NODC) for archiving and distribution.