ASLO Aquatic Sciences Meeting 2012, Otsu, Japan.

Transient thermal plume dispersal in the Hudson Riverestuary
Uchiyama, Y. Ishii, S., Tuy, P.N.M., Wells, J.C., Kirkey, W.D., Islam, M.S. and Bonner,J.S.
Abstract:
A three-dimensional, transient thermal plume dispersal in the Hudson River estuary is
examined with Regional Oceanic Modeling System (ROMS) with an empiricalnear-field buoyant source submodel for approximately two spring-neap cycles.

We

focus on the area of 13.4 km x 67.7 km between the USGS monitoring stations atPoughkeepsie and Piermont, resolved by 160 x 800 longitudinally-stretched curvilinear
horizontal grids with 20 vertical sigma layers. The Indian Point Power Plant, locatedabout 65 km upstream from the mouth, continuously discharges thermal effluent at
109.8 m^3/s heated by +9.6 deg. C from the intake. The model output is comparedwith the USGS gauges and HADCP data at West Point to show a reasonableagreement. With a modest mean river discharge, the thermal plume from the planttends to be restricted near the source location, generally traveling back andforth. However, the topographically-generated eddies and vorticity significantlyenhance the mechanical and buoyant mixing.

Tidally-driven longitudinal flows arehighly skewed in the lateral direction near the bend, leading to substantial secondary
circulations.

ASLO Aquatic Sciences Meeting 2012, Otsu, Japan.

Interaction between the Kuroshio intrusion and intrinsic
variabilityin Seto Inland Sea, Japan
Kuriyama, T., Uchiyama, Y. and Miyazawa, Y.
Abstract:
The estuarine circulation in Seto Inland Sea, Japan, has been reported to be largely
affected by the intrusion of the Kuroshio water through its two narrow channels, theBungo Channel to the west and the Kii Channel to the east. In addition, freshwater
inputs and the complicated coastline, topography and over 3,000 islands could skew theKuroshio influxes through nonlinear processes, and substantially enhance intrinsic
variability in the estuary. In the present study, a doubly-nested oceanic modelingframework based on ROMS (Regional Oceanic Modeling System) downscaled from theJCOPE2 (Japan Coastal Ocean Predictability Experiment) dataset is developed toexamine the interaction between estuarine and Kuroshio waters at a horizontalresolution up to 600 m. To accurately account for the mass, momentum and buoyancy
fluxes from Kuroshio to the estuary, a careful diagnosis on the reproducibility ofKuroshio paths, thermocline slope and density structure is conducted by comparing todata. Tidal and subtidal variabilities of the mass exchange at the two channels andseveral cross-sections along the longitudinal axis of the estuary and their impacts on thecirculation are discussed.

ASLO Aquatic Sciences Meeting 2012, Otsu, Japan.

A downscaling experiment on reproducibility of the Kuroshio
off JapanIshii, S., Uchiyama, Y. and Miyazawa, Y.
Abstract:
Whereas the Kuroshio flowing up off the eastern side of Japan is known to becontrolled by the mesoscale dynamics, effects of the submesoscale dynamics on themean structure, eddies, frontal processes, stratification, etc. has not been fully
understood. In prior to designing a submesoscale Kurhoshio modeling, a detailed
numerical downscaling experiment is performed with ROMS at a horizontal resolutionof 3 km, forced by the assimilative JCOPE2 at 1/10 deg. as the boundary
condition. Three nesting configurations are prototyped for an assessment of surface
kinetic energy: 1) a free run without any controls 2) with a homogeneous constanthorizontal eddy viscosity of 100 m2/s, and 3) a three-dimensional T-S nudging towards
the JCOPE2 at a nudging time scale of 20 days. Among the others, the T-S nudging isfound to best reproduce the Koroshio including its paths, surface KE and EKE,
thermocline slopes and stratification. In turn, the free run substantially overestimates
the KE and EKE because of the lack of subgrid-scale energy dissipation associated withthe submesoscale turbulence leading to overly meandered paths and more isolated
warm/cold-core rings.