A sustained oscillation in a toy-model of the coupled atmosphere-ocean system

TL;DR

This paper models the coupled atmosphere-ocean system using idealized spectral models, revealing a sustained oscillation driven by the interaction of atmospheric bimodality and ocean Rossby dynamics, with implications for understanding climate variability.

Contribution

It introduces a coupled low-order spectral model that demonstrates a persistent oscillation arising from atmosphere-ocean interactions, highlighting the role of topography and Rossby waves.

Findings

Coupled system exhibits two stable flow patterns.

A sustained oscillation occurs due to atmosphere-ocean interaction.

Oscillation period ranges from inter-annual to inter-decadal.

Abstract

Interaction between atmospheric mid-latitude flow and wind-driven ocean circulation is studied coupling two idealized low-order spectral models. The barotropic Charney-DeVore model with three components simulates a bimodal mid-latitude atmospheric circulation in a channel with two stable flow patterns induced by topography. The wind-driven ocean double gyre circulation in a square basin (of half the channel length) is modeled by an equivalent barotropic formulation of the Veronis model with 21 components, which captures Rossby-wave dynamics and nonlinear decadal variability. When coupled, the atmosphere forces the ocean by wind-stress while, simultaneously, the ocean affects the atmosphere by thermal forcing in terms of a vorticity source. Coupled atmosphere-ocean simulations show two stable flow patterns associated with the topographically induced atmospheric bimodality and a sustained oscillation due to interaction between atmospheric bimodality and oceanic Rossby dynamics. The oscillation is of inter-annual to inter-decadal periodicity and occurs in a reasonably wide parameter domain.