An estimation of oceanic eddy heat transport in a high resolution Ocean General Circulation Model

本研究首次利用地球模拟器进行的全球涡旋分辨海洋环流模式(OGCM)估计了海洋中尺度变率(如中尺度涡旋)在世界大洋引起的经向热输送。西部边界流和南极绕极流一般以极地涡热输送为主，赤道地区以向赤道方向涡热输送为主，这与以往用较高分辨率OGCM研究的结果类似。正如线性斜压不稳定理论所预期的那样，中纬度海洋中如此显著的极地涡热输送表明，涡旋起到了减弱经向背景温度梯度的作用。然而，有趣的是，特别是对于黑潮延伸区和墨西哥湾流，沿这些洋流南岸的次表层发生了向赤道方向的涡热输送。不同洋流对赤道向涡热输送的主导机制不同。对于黑潮延伸区，如果海流路径向赤道倾斜，原本分布在海流路径上的暖水被赤道流向赤道平流。对于墨西哥湾流，在墨西哥湾流上形成的圆形暖涡沿南环流环流东缘向赤道方向迁移。

The present study, for the first time, estimates meridional heat transport induced by oceanic mesoscale variability such as mesoscale eddy in the World Ocean using a global eddy-resolving Ocean General Circulation Model(OGCM) conducted by the Earth Simulator. Poleward eddy heat transports are generally predominant for the Western Boundary Currents and the Antarctic Circumpolar Current, and along with equatorward eddy heat transport in the equatorial region, as similar to the results from previous studies with coarser resolution OGCMs. Such a significant poleward eddy heat transport in mid-latitude oceans suggests that the eddies act to weaken strong meridional background temperature gradients as expected from the linear baroclinic instability theory. However, interestingly, especially for the Kuroshio Extention and the Gulf Stream, equatorward eddy heat transport occurs in subsurface layer along the southern frank of these currents. The dominant mechanism of the equatorward eddy heat transport is different between these currents. For the Kuroshio Extension, warm water originally distributed on the current path is advected equatorward by equatorward current in the event of equatorward meandaring of the current path. For the Gulf Stream, warm eddies with circular shape formed on the Gulf Stream migrates equatorward along eastern rim of the southern recirculation gyre.