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Submesoscale eddies (1-10 km diameter) were identified using surface velocity observations obtained from a high-frequency radar system (HFR) operated in Todos Santos Bay (TSB), Baja California, Mexico. Eddies were detected through a special case of the Okubo-Weiss parameter for divergent flows in the form of eigenvalues of the Jacobian matrix. The detection method, applied for a surface velocity grid, shows encouraging results in the recognition and tracking of submesoscale features in TSB. The detection method is rapid and efficient. Results show the formation and persistence of an eddy structure inside the Bay in December 6, 2010, displaying a trajectory from NE to SW until disappearing at the center of the Bay. The eddy is approximately 4 km in diameter with a frequency of ~0.1f (f is the Coriolis parameter). The real part of the Okubo-Weiss parameter ranged between − 4 × 10 − 9 to − 1 × 10 − 9 s − 2, and outlined the eddy for approximately 9 hours. Although it is difficult to identify the origin of the detected submesoscale eddy, its appearance coincided with a drop in relative atmospheric humidity suggesting land-ocean Santa Ana winds as a possible generating mechanism.

In this work we present the exchange flows between a semi-enclosed Bay and the adjacent ocean as measured by a real-time coastal observing system in Baja California, Mexico. Several sources of information as numerical modeling, currents profile data, high frequency radar observations and drifters tracking, all together show an interesting three-dimensional structure to the exchange flows. The northern entrance (relatively shallow, ∼40 m at its deepest portion) showed an estuarine-like exchange pattern, with a net outflow at the shallow parts and inflow at the deepest, suggesting that the frictional effect is more important than the earth's rotation, as typically observed in relatively small bodies of water like estuaries and coastal lagoons. On the other hand, the southern entrance (with a ∼400 m deep canyon) is more complex, with recurrent anticyclonic exchange pattern with inflows at the western limit and outflows at the east. We suggest that the vertical structure of this circulation may be sustained by the deep canyon which lowers the thermocline, but further investigation is needed.

Climatological data indicate that Gulf of California (GC) waters are warmed in spring by the exchange of waters with the Pacific Ocean. To better understand this exchange, hydrographic observations were collected across the entrance to the GC during 19–21 April 2013. Results indicated an anticyclonic exchange with the Pacific Ocean. Strong outflow of Gulf of California Water (GCW) occurred over the outer continental shelf and slope of Sinaloa with maximum velocities of 0.5 m·s–1 at ~60 m depth and reaching ~500 m depth. Inflow close to the Baja California Peninsula was weaker (0.1–0.2 m·s–1) and transported both California Current Water and GCW. Satellite altimeter data indicated a possible reason for this flow pattern at the entrance to the GC: a couple of eddies to the east blocked the usual path of California Current flow toward Sinaloa. Horizontal transports integrated across the gulf were calculated with observed velocity and geostrophic balance. Transports were greatest in the upper 200 m, with outflow above 500 m depth, implying a net cooling of these upper layer waters in the gulf. Observations were compared with data collected in early May 1992. April 2013 exhibited much greater thermohaline variability in the upper ocean than May 1992, when a well developed cyclonic flow was observed at the entrance to the GC. The transports estimated with Pegasus for April–May 1992 were very different from those estimated for April 2013, when inflow (and heat gain) dominated above 500 m depth. The contrast between the 2013 and 1992 measurements is an example of how mesoscale eddies can reverse normal seasonal exchanges at the entrance to the GC.

Fernández-Barajas et al. (1994) reportan los resultados de mediciones hidrográficas realizadas en la entrada del Golfo de California en agosto de 1992. Durante ese crucero, el CTD se encontraba calibrado inadecuadamente, teniendo como resultado mediciones anómalas de altas temperaturas y bajas salinidades. Fernández-Barajas et al. (1994) incorrectamente atribuyeron estas condiciones anómalas al fenómeno El Niño de 1991- 1993 y a la tormenta tropical Lester. Fernández-Barajas et al. (1994) report results of hydrographic measurements at the entrance to the Gulf of California in August 1992. During this cruise, the CTD was improperly calibrated, and this resulted in anomalously high (low) near-surface temperatures (salinities) being reported. Fernández-Barajas et al. (1994) incorrectly attribute these anomalous surface conditions to the 1991-1993 El Niño and tropical storm Lester.