Effect of Oceanic Advection on the Potential Predictability of Sea Surface Temperature

The effect of oceanic advection on the predictability of sea surface temperature (SST) is investigated in the framework of a linear stochastic model. An analytical solution of a one-dimensional model shows that even though advection can give rise to a pair of low-frequency normal modes, no enhancement in the predictability is found in terms of domain-averaged error variance. However, a predictable component analysis shows that advection can play a role in redistributing the predictable variance. When forced with a spatially coherent stochastic forcing, advection enables certain regions to be more predictable than others. This analytical result is further examined in a more realistic two-dimensional North Atlantic model with observed mean currents. It is shown that the predictability of SST averaged over the whole North Atlantic basin is determined by the thermal damping time scale (∼3 months), not the advective time scale (∼6 years). However, the most predictable pattern reveals that the predictable variance along the west boundary is substantially enhanced by the strong currents, and the potential predictability limit in this region is on the order of 5 months.