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[1] The Ballenas-Salsipuedes Channel (BSC) is considered an oceanographic province on its own within the Gulf of California. In this region, tidal mixing is modulated by quarterdiurnal, semidiurnal, diurnal, and fortnightly frequencies, producing a strong outcropping of cold and nutrient-rich waters. In this work we analyze the temporal and spatial variability of sea surface temperature (SST) data recorded simultaneously over a period of 1 year in six bays along the BSC. Minimum mean SST differences ( 2.5°C) were recorded in June. The monthly SST anomaly showed that from late October to late January, the channel behaved as a very well mixed region. In contrast, SST anomalies of up to 2.2°C among bays were observed from May to September, indicating intense heat gain in summer and highlighting spatial heterogeneity in the intensity of vertical mixing. Besides the seasonal temperature cycle, influenced by solar irradiation, four main periods (0.25, 0.5, 1, and 15 days) were identified, corresponding to the main timescales of variability induced by the tides. This work demonstrates that the main source of temporal SST variability in BSC is the tide-induced fortnightly modulation, suggesting the possibility of a pulsation mechanism in the outcropping of nutrient-rich waters reaching the surface layer throughout the channel; this could play a crucial role in explaining the exceptionally high biological production of this region.

espanolEl Estero de Punta Banda, localizado dentro de la Bahia de Todos Santos, en el noroeste de la Peninsula de Baja California, se encuentra delimitado hacia el mar por una barra arenosa de 8 km de longitud. De 1972 a 2003 la barra tuvo un crecimiento longitudinal neto de 420 m, lo que redujo el ancho de la boca del estero en mas de 400 m. A pesar de dicho crecimiento, se ha sugerido que la boca del estero no se ha cerrado debido a la existencia de un balance anual en los volumenes de sedimento que se transportan en ambas direcciones a lo largo de la barra. Mientras que mediciones directas indican que en las epocas de primavera, verano y otono la direccion del transporte litoral de sedimento es hacia el noreste, se ha planteado la hipotesis de que durante la epoca invernal el transporte litoral en la barra deberia ser hacia el suroeste En este trabajo se analizan mediciones de oleaje realizadas de noviembre de 2004 a marzo de 2005 frente a la barra del Estero de Punta Banda y se infiere por primera vez la magnitud y direccion del trasporte litoral de sedimento en esta barra durante la epoca invernal. Los resultados muestran que durante la epoca invernal el oleaje dominante que arriba a la bahia proviene del oeste-noroeste, aproximandose a la barra del estero con direccion oeste franco, lo que en combinacion con la orientacion de la barra induce un transporte litoral de sedimento en direccion noreste, hacia la boca del estero. Este resultado contradice la hipotesis de que durante el invierno la direccion del transporte litoral es hacia el sur y permite establecer que a lo largo de un ano tipico la direccion dominante del transporte litoral de sedimento en la barra del estero es hacia el noreste. El hecho de que la boca del estero no se haya cerrado debe ser atribuible a otros procesos fisicos, como por ejemplo a aportes pluviales extraordinarios durante la epoca de lluvias o posibles desigualdades entre las velocidades del flujo y reflujo de la marea al estero. EnglishPunta Banda Estuary, located within Todos Santos Bay, on the northwest coast of the Baja California Peninsula, is separated from the bay by a single sandbar, approximately 8 km long. From 1972 to 2003 this sandbar showed a longitudinal net growth of 420 m, which decreased the width of the estuary mouth by more than 400 m. Despite the bar’s rapid growth it has been suggested that the estuary mouth remains open because in spring, summer and autumn the longshore sand transport is northeastward, but during winter the longshore sand transport should be toward the southwest, away from the mouth, establishing a balance between the amount of sediment transported both ways. In this study we analyze wave data acquired from November 2004 to March 2005 on the bay side of the sandbar, and for the first time provide the magnitude and direction of the longshore sand transport during winter. The results show that during this season the dominant waves approach the bay from the west-northwest and the sandbar from the west, inducing a net longshore sand transport of 817 m3 day–1 to the northeast. This result contradicts the hypothesis of a longshore sand transport balance, and shows that throughout a typical year the net longshore sand transport is to the northeast. The fact that the estuary mouth has not closed up should be attributed to other causes, such as extraordinary amounts of rain during the rainy season or inequalities between the ebb and flood tidal current velocities to the estuary.