Barrier Layers in a High-Resolution Model in the Eastern Tropical Pacific

This study examines salinity barrier layers (BLs) in the eastern tropical North Pacific in the region of the Salinity Processes in the Upper ocean Regional Studies-2 field campaign. We utilize a high-resolution numerical model to study BLs and their relationship to frontal features and small-scale ocean variability, focusing on two specific events. One is associated with a large outbreak of BL presence near 7 degrees N along 125 degrees W. The other is a relatively isolated but persistent BL that forms near 13 degrees N, again along 125 degrees W. In both cases we find that the BL is proximate to a salinity frontal feature in which isohalines tilt toward the fresh side of the front at its base. The BLs studied are associated with divergent flow at the surface on the fresh side of the front and convergent flow on the salty side. Tilting of the front is invoked to explain this, with an additional mechanism involving a vertical circulation which causes the base of the front to tilt preferentially.