Interdecadal Variability in an Ocean Model Driven by a Small, Zonal Redistribution of the Surface Buoyancy Flux

Abstract

Abstract An idealized, three-dimensional model, of size comparable to the Atlantic, is used to study interdecadal variability of the thermohaline circulation (THC). In most of the model experiments, salinity is kept uniform and constant, the model being driven by surface heat flux only. When the model is driven by the surface heat flux diagnosed from a restoring spinup experiment no oscillations occur. Driving the model by a time-independent, surface heat flux, obtained by applying a “small” zonal redistribution to the diagnosed flux, leads to strong interdecadal oscillations; “small” means that the modification to the diagnosed flux is within the error bars on estimates of surface heat flux based on observations. The model sea surface temperature (SST) anomalies are similar to the observed pattern of SST anomalies in the North Atlantic and to the SST anomalies associated with the interdecadal oscillation in the GFDL fully coupled ocean-atmosphere model. For redistributions that weaken the east-west varia...