Damping of Climate-Scale Oceanic Variability by Mesoscale Eddy Turbulence

Abstract

AbstractThe impact of mesoscale eddy turbulence on long-term, climatic variability in the ocean’s buoyancy structure is investigated using observations from a mooring deployed in the Drake Passage, Southern Ocean. By applying the temporal-residual-mean framework and characterizing the variance contributors and the buoyancy variance budget, we identify the main source and sink of long-term buoyancy variance. Long-term buoyancy variance amplitude is set by long-term vertical velocity fluctuations acting on the steady stratification. This baroclinic buoyancy flux is also the main source of the variance, indicative of the effect of large-scale baroclinic instability. This source is balanced by a sink of long-term buoyancy variance associated with the vertical advection of the steady stratification by the eddy-induced circulation. We conclude that mesoscale eddy turbulence acts as a damping mechanism for long-term, climatic variability in the region of the observations, consistent with an “eddy saturated” behavior of the Antarctic Circumpolar Current.