Sensitivity of Internally-Generated Climate Oscillations to Ocean Model Formulation

Abstract

The simulation of climate on Pleistocene time scales requires coupling subsystems with response time scales which vary over several orders of magnitude. Most models of the coupled atmosphere-ocean-cryosphere (AOC) system have treated the global ocean as a single isothermal reservoir, resulting in a relatively slow surface temperature response time scale. We use a series of one-dimensional box ocean models and a box-advection diffusion ocean model to demonstrate that the ocean temperature does not respond with a single time scale. In particular, the first half or more of the mixed layer response to a radiative perturbation is governed by the relatively small mixed layer thermal inertia, rather than by the deep ocean thermal inertia. We implement the box and box-advection-diffusion ocean models in the AOC model of (7), which uses a single isothermal ocean reservoir and exhibits internal oscillations. We find that internal oscillations are no longer a solution to their model, thereby confirming the importance of distinguishing between the mixed layer and deeper ocean thermal response time scales.