Mechanisms of Buoyancy Transport through Mixed Layers and Statistical Signatures from Isobaric Floats

Abstract

Idealized nonhydrostatic numerical calculations that resolve both plumes and geostrophic eddies are used to mimic isobaric float observations taken in the Labrador Sea Deep Convection Experiment and study mechanisms of buoyancy transport through mixed layers. The plumes and eddies are generated in a periodic channel, initialized with a vertical profile of temperature, and cooled by surface heat loss varying across the channel. Probability density functions and time series of vertical velocity and temperature computed from the floats are interpreted in terms of the kinematics of plumes and geostrophic eddies, and their role in buoyancy transport. Estimates from Eulerian time series from the numerical model suggest that geostrophic eddies and plumes have a comparable contribution to vertical heat flux.