Cross-Front Mixing and Frontal Upwelling in a Controlled Quasi-Permanent Density Front in the Gulf of St. Lawrence

Abstract

Abstract CTD data obtained from three transects across a controlled quasi-permanent density front in the Gulf of St. Lawrence were analyzed for the purpose of investigating cross-front mixing, mechanisms for frontal convergence, secondary circulation induced by the front and relationship between surface mixed-layer properties and frontal structure. Water mass analysis indicates that mixing takes place mainly in the ambient water, from the lower boundary of the frontal layer down to ∼100 m. On the side of heavier water, there is a region of low surface temperature. The water masses have a distribution suggestive of upwelling in the low surface temperature region. The thickness of the surface mixed layer varies across he front. Outside the frontal zone there is a well-developed mixed layer of a thickness of about 25 m. It disappears completely in the low surface temperature zone and is re-established in the frontal layer with a reduced thickness. Horizontal intrusions below the frontal layer and interleavin...