Decadal variability of the upper ocean in the western part of the midlatitude North Pacific simulated by Meteorological Research Institute Community Ocean Model (MRI.COM)

HR: 0800h
AN: OS21C-1268 [Abstracts]
TI: Decadal variability of the upper ocean in the western part of the midlatitude North Pacific simulated by Meteorological Research Institute Community Ocean Model (MRI.COM)
AU: * Yasuda, T
EM: tyasuda@mri-jma.go.jp
AF: Meteorological Research Institute, 1-1 Nagamine, Tsukuba, 305-0052 Japan
AB: Decadal variability of the North Pacific upper ocean is simulated by Meteorological Research Institute Community Ocean Model (MRI.COM). We analyzed the results focusing on the changes in the heat content and the sea surface height (SSH) in the western part of the midlatitude North Pacific, and the North Pacific Subtropical Mode Water (NPSTMW). Simulated heat content and SSH in the western part of the midlatitude North Pacific has bidecadal variability in conjunction with the observed sea level changes on the Japan coast, and their variability has two distinct modes. The first SSH anomaly mode exhibits a large-scale feature centered at 40N, and is strongly related to the meridional shift of the westerlies over the central North Pacific. The second SSH anomaly mode, which indicates a north-south dipole structure, is determined by the change in the magnitude of the westerlies. The meridional shift and change in the magnitude of westerlies yield the anomalous wind stress curl at the 40N and 30N, respectively. Then, these wind stress curl anomalies dynamically force the thermocline below, and finally affect each mode of the sea level variability in the western North Pacific through the baroclinic Rossby waves for 3 years (at 30N) to 5 years (at 40N). NPSTMW characterize the upper thermal structure in the western part of the midlatitude North Pacific. Decadal variability in the NPSTMW is caused by change in the horizontal heat advection into the NPSTMW formation area due to the meridional shift of the westerlies. Though surface heat flux compensates for the horizontal heat advection in 1970s and 1980s, both heat budget terms change in the same phase in the 1990s and 2000s, resulting in the large variations of the NPSTMW characteristics.
DE: 4215 Climate and interannual variability (3309)
DE: 4255 Numerical modeling
DE: 4283 Water masses
DE: 4572 Upper ocean processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting