해양순환모형에서 열염분순환의 수평해상도에 대한 민감도:동안경계류의 생성

Abstract

Through an idealized modeling study, the dependence of thermally driven circulation from a depth level coordinate general ocean circulation model (GFDL/MOM) on horizontal resolution is investigated while focusing on the eastern boundary current. In general the circulation patterns do not show significant sensitivity to the resolution except the northern and the eastern boundaries. When the resolution is low, as in earlier studies the zonal flow driven by the meridional sea surface temperature gradient sinks to the intermediate level at the eastern wall. As the resolution becomes higher, a northward eastern boundary current emerges. The current continues along the along the perimeter of the basin cyclonically and supplies warm water to polar ocean while changing the temperature and velocity structures along its path to make the model results realistic and physical. A simple scaling analysis shows that the eastern boundary current is caused by the vortex column stretching due to the downwelling of the zonal flow at the eastern wall. The vortex column stretching whose magnitude increases linearly with the resolution is balanced by the lateral friction and beta effect both of which require a northward flow along the eastern wall. The scaling analysis also shows that the magnitude of the boundary current, if there is one, is inversely proportional to the horizontal resolution as consistent with the model results.