PNNL

Abstract

Vertical motions in the ocean exchange gases, heat, nutrients, and pollutants between the surface and the ocean interior, impacting ocean carbon sequestration, air-sea exchange, and marine environments. The vertical exchange is enhanced within ocean fronts, yet due to challenges in conducting field campaigns to sample these ephemeral features, such exchange at small spatial and temporal scales is not yet well characterized. Using high-resolution ocean observations and simulations of the northern Gulf of Mexico, we demonstrate how a land-sea breeze generates rapid vertical exchange at ocean fronts. We show that the interaction between the land-sea breeze and the fronts leads to convergence/divergence in the surface mixed layer, which further facilitates an slantwise circulation that subducts surface water along isopycnals into the interior and upwells bottom waters to the surface. This process causes significant vertical displacements of water parcels and creates a ventilating channel of the bottom oxygen-deficient water in the northern Gulf that can bypass the stratification barrier set by the Mississippi River plume