해양대순환모형의 북태평양 해향혼합층 깊이 변동성

Abstract

We have investigated variability of MLD obtained from a global OGCM and its dependency on three different vertical mixing schemes, based on comparisons among model simulations, as well as comparison of model simulations with climatological data (NMLD). All vertical mixing schemes have successfully captured the well-known distinct patterns of seasonal variations of MLD, which are considerably large in mid-latitude and marginal in equatorial regions, while producing notable difference of the seasonality at high latitudes (north of 45N). The constant vertical mixing scheme underestimates annual-mean MLD over most regions of the North Pacific Ocean, except the Kuroshio and its recirculation region where all vertical mixing schemes overestimate the annual-mean MLD. The Pacanowski-Philander scheme shows poor performance in high latitudes, implying that vertical mixing in high latitude may not be represented properly by simple internal mixing mechanism such as stratification or vertical shear of horizontal velocity. On the other hand, the new vertical mixing scheme based on a turbulence mixed layer model gives most reasonable MLD and its variability. These results suggest that parameterization of vertical mixing has significant effects on simulation of the seasonal and spatial variability of MLD over the North Pacific Ocean.