We examine whether the reduced meridional temperature gradients of past greenhouse climates might have reduced oceanic overturning, leading to a more quiescent subsurface ocean. A substantial reduction of the pole-toEquator temperature difference is achieved in a coupled climate model via an altered radiative balance in the atmosphere. Contrary to expectations, we find that the meridional overt...

Two idealized, three-dimensional, analytical models of mid-depth meridional overturning in a basin with a southern-hemisphere circumpolar connection are described. In the first, the overturning circulation can be understood as a ‘pump and valve’ system, in which the wind forcing at the latitudes of the circumpolar connection is the pump, and surface thermodynamic exchange at high northern latit...

The heat and salt input from the Indian to Atlantic Oceans by Agulhas Leakage is found to influence the Atlantic overturning circulation in a low-resolution Ocean General Circulation Model (OGCM). The model used is the Hamburg Large-Scale Geostrophic (LSG) model, which is forced by mixed boundary conditions. Agulhas Leakage is parameterized by sources of heat and salt in the upper South Atlanti...

Using a nonhydrostatic numerical model, this work demonstrates that onshore winds are a principal agent of overturning and vigorous vertical mixing in nearshore water of lakes and inner continental shelves. On short (superinertial) timescales of a few hours, onshore winds create surface currents pushing water against the shore which, via the associated pressure gradient force, creates an underc...

In contrast to conventional expectations based on the stability of steady shear flows, elementary time-periodic stratified flows that are unstable at arbitrarily large Richardson numbers are presented here. The fundamental instability is a parametric one with twice the period of the basic state. This instability spontaneously generates local shears on buoyancy time scales near a specific angle ...

A Lagrangian for strongly nonlinear unsteady water waves ~including overturning waves! is obtained. It is shown that the system of quadratic equations for the Stokes coefficients, which determine the shape of a steady wave ~discovered by Longuet-Higgins 100 years after Stokes derived his system of cubic equations! directly follows from the canonical system of Lagrange equations. Applications to...

The Modeling Eddies in the Southern Ocean (MESO) project uses numerical sensitivity studies to examine the role played by Southern Ocean winds and eddies in determining the density structure of the global ocean and the magnitude and structure of the global overturning circulation. A hemispheric isopycnal-coordinate ocean model (which avoids numerical diapycnal diffusion) with realistic geometry...