[1] Hydrographic data acquired during 2001 by Argo profiling floats deployed in the Kuroshio recirculation region are used to verify the inference that mesoscale eddies prevailing in the recirculation region play an important role in the formation and transport of North Pacific Subtropical Mode Water (NPSTMW). That is, the deeper winter mixed layer is formed preferentially where the thermocline is deeper in association with anticyclonic eddies. In the succeeding seasons, mesoscale eddies retain NPSTMW during their southwestward movement from the NPSTMW formation region, so that anticylonic eddies contribute substantially to the NPSTMW transportation. The spatial distributions of the mixed layer depth in winter and the NPSTMW thickness in the succeeding seasons, based on the float data, suggest that they are affected by mesoscale eddies. The float data also provide the statistical relations of these quantities against the thermocline depth, which are consistent with our inference.
Causes of the multidecadal-scale warming of the intermediate water in the Okhotsk Sea and the western subarctic North Pacific during 1980-2008 are investigated using an ice-ocean coupled model with interannually varying atmospheric forcing. A hindcast experiment qualitatively reproduces the warming and decadal fluctuations of the intermediate water that are similar to those of observations: the warming is significant along the western part of the Okhotsk Sea and subarctic frontal region. The effects of the thermohaline-and wind-driven ocean circulation on the warming are evaluated from perturbation experiments on thermohaline (turbulent heat and freshwater fluxes) and wind causes, respectively. The thermohaline causes are shown to contribute positively to warming in the Okhotsk Sea Intermediate Water (OSIW). The heat budget analysis for the OSIW indicates that the warming is related to a decrease in cold and dense shelf water (DSW) flux, which is caused by a decrease in sea ice and surface water freshening. In contrast, the wind cause has a cooling effect in the OSIW through an increase in DSW. In the subarctic frontal region, the warming is mainly caused by the wind stress change. The heat budget analysis indicates that the warming is related to an increase in the northward advection of the subtropical warm water. These results imply that both thermohaline-and winddriven ocean circulation changes are essential components of the warming in the intermediate water. The atmospheric conditions responsible for the warming are related to a weakened Aleutian low and Siberian high in early and late winter.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.