A global view of air–sea thermal coupling and related non-Gaussian SST variability

Article history: Received 10 March 2008 Received in revised form 24 June 2008 Accepted 19 August 2008 Available online xxxx Two recent studies of observed sea surface temperature (SST) variations have provided striking evidence that their non-Gaussian statistics can be understood within the context of linear stochastically forced models in which the amplitude of the noise forcing depends linearly on the SST. One study is based on a general 1-d Langevin model, whereas the other considers an explicitly coupled 2-d model of SST and local surface air temperature, and emphasizes the crucial role of thermal air–sea coupling in generating the non-Gaussian statistics. It is shown here that these studies are not necessarily mutually inconsistent. In particular, it is shown that the 1-dmodel can be derived from the 2-dmodel as a special case, inwhich the air temperature is approximated as comprising a part linearly dependent on SST plus a pure noise part. This version of the 1-d model, however, can only predict positive SST skew given the observed thermal damping and coupling constants over the globe. The fact that the more general 1-d model can also capture the essence of the local SST dynamics in regions of negative SST skew therefore implies that other physical mechanisms not included in simple local thermally coupledmodels, such as stochasticity in oceanic heat transports, may also be important in those regions. © 2008 Elsevier B.V. All rights reserved.