Estimating sea-surface temperature transport fields from stochastically-forced fluctuations

In this article we introduce a method to quantify the transport of sea surface temperature (SST) from SST fluctuations. Previous studies have estimated the advective transport of SST from time-lag correlation of SST anomalies. However this approach does not consider diffusive SST transport or relaxation to atmospheric temperatures. To quantify the transport more completely we use a response function (Greenʼs function) which solves the SST continuity equation for an impulsive forcing. The response function is estimated from SST anomalies using a fluctuation-dissipation approach. An assumption of spatial locality in the linear operator used to produce the response significantly improves the accuracy of the method. Using 100 years of data from a stochastically-forced prototypical SST model, the method estimates the SST transport response function to within 10% error. Decomposing the linear operator into symmetric, anti-symmetric, and divergent operators enables estimates of the modelʼs spatially dependent velocity vector, diffusivity tensor, and relaxation rate which converge at the same rate as the response function.