Resumen del producto

¹ Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas

The tropical branch of the California Current (TBCC) converges with tropical waters in the Pacific off Mexico, generating thermal fronts whose hydrographic structure and ecological implications remain poorly understood. Using satellite-derived sea surface temperature (SST) data (2003–2021) and in situ measurements from four oceanographic cruises, this study examines the spatiotemporal variability of thermal fronts and their relationship with chlorophyll-a (CHL) as a proxy for productivity. Fronts were persistent along the peninsular coast, driven by coastal upwelling, with seasonal shifts in distribution: spring showed the highest frontal prevalence south of 24 °N, while summer activity shifted northward (26–28 °N). Autumn and winter exhibited minimal frontal activity. Seasonal variability explained 20–50 % of frontal occurrence in coastal zones and the oceanic zone south of 23 °N but was negligible offshore. The cold phase of ENSO (La Niña) correlated with enhanced frontal activity and elevated CHL, particularly south of 24 °N. A significant positive correlation between frontal probability and mesoscale CHL anomalies highlighted two key oceanic regions where fronts likely boost productivity: near Punta Eugenia (25–29 °N) and Cabo San Lucas (20–24 °N), especially in spring and summer. In situ data revealed that spring fronts featured steep thermocline slopes and coincided with CHL gradients, whereas autumn fronts lacked vertical structure and ecological influence. These findings underscore the role of thermal fronts in modulating productivity in the TBCC, particularly during spring and summer, while emphasizing the limited ecological impact of density-compensated fronts in autumn.

Palabras clave: Thermal fronts; Front probability; Chlorophyll a; Tropical branch of the California current

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