in a global ocean general circulation model

Abstract. We examine mixed layer temperatures in a global ocean general circulation model subjected to seasonally varying climatological forcing. Harmonic analysis of monthly mixed layer temperatures and cli-matological sea surface temperatures (SSTs) shows that, on the average, the annual harmonic accounts for 90 % of the total seasonal variance in both fields, while the semiannual harmonic accounts for about 8%. The semiannual signal is mostly confined to equatorial and high-latitude regions. The model mixed layer tempera-tures underestimate the mean amplitude of the annual harmonic in middle latitudes (657lhuhl107) by about 26%, while lagging climatological SSTs by 22 days, on average. In several parameter sensitivity experiments, these differences could be reduced to as little as 12% and 12.5 days, respectively, though most of this gain occurred when the mixed layer was unrealistically shal-low (mean depth less than 65 m). At least part of the differences in amplitudes and phases of the annual har-monic is linked to the uncoupled formulation of the surface heat flux, which is computed using specified and seasonally varying climatological air temperatures. In ice-free areas, seasonal amplitudes and phases of air temperatures are almost identical to those of climato-logical SSTs. Thus, differences between model mixed layer temperatures and climatological SSTs give rise to Newtonian relaxation to SSTs, which then leads to am-plitude damping and time lags in mixed layer tempera-tures relative to the SSTs