HR: 10:20h
AN: OS52B-01    [Abstracts]
TI: Spontaneous interannual to decadal scale variations in the Kuroshio and its recirculation in a high-resolution North Pacific Model
AU: * Ishikawa, I
EM: iishikaw@mri-jma.go.jp
AF: Meteorological Research Institute, 1-1, Nagamine, Tsukuba, 305-0052 Japan
AU: Ishizaki, H
EM: hishizak@mri-jma.go.jp
AF: Meteorological Research Institute, 1-1, Nagamine, Tsukuba, 305-0052 Japan
AB: Interannual to decadal scale variations of the Kuroshio and its recirculation are investigated using an eddy-permitting North Pacific numerical model. The model is a z-coordinate free-surface OGCM (one version of MRI.COM; MRI Community Ocean Model). Horizontal resolution is $1/6^{\circ}$ in the latitudinal and $1/4^{\circ}$ in the longitudinal direction, with 44 vertical levels. The model domain is the Pacific north of $15^{\circ}$S. Integration is carried out for 150 years, including the initial restoring body forcing of temperature and salinity to the observed state for the first six years. Data from the last 50 years of integration are used for analysis. The model is forced by climatological wind stresses, and the temperature and salinity are restored to climatology at the surface, at the southern boundary, and in the Okhotsk and Bering Seas. Without interannual change in the forcing, it is found that there are variations of about three-year period in mass transports of the Kuroshio through the Tokara Strait and the Ryukyu Current, flowing northeastward east of the Ryukyu Islands. The Tokara transport lags that of the Ryukyu Current for about 9 months. The Tokara transport is also found to be in opposite phase with the extent of the recirculation gyre, which is defined here as an area encircled by some closed contour of the barotropic stream function. During the analysis period, the Kuroshio south of Japan takes the large meander path, the strait path, or unstable paths. The path variation is rather irregular in comparison with the mass transport described above. The stable large meander path that persists for longer than a couple of years appears four times within the fifty-year period. Thus, the periods between the transitions from the strait path ( or unstable paths ) to the large meander path are about twelve years on average, which is longer than the time scale of the mass transport variation, and the path variation looks uncorrelated to the mass transport.
DE: 4255 Numerical modeling
DE: 4532 General circulation
DE: 4576 Western boundary currents
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting