15:45 〜 16:00
[AOS14-02] Dynamics of the upwelling at the upstream of the East Sakhalin Current (ESC)
キーワード：湧昇、傾圧不安定、渦
The resuspension of the sediments at the upstream of ESC was confirmed by ADCP high backscatter events [Ito et al.,2017]. Further observation discovered that the sediments resuspended was frozen into the frazil ice at the surface of the upstream of ESC and might be conveyed to the south to support the next spring broom when the ice melts [Ito et al.,2017; Mustapha et al.,2008], which indicates the vertical mixing, whole depth upwelling typically, was at the upstream of ESC and corresponded with the strong wind event [Ito et al.,2017]. According to the dissolved oxygen distribution [Ohshima et al.,2001 Figure 3(a)], there should be an upwelling at the southwest of the Sea of Okhotsk as well.
Downwelling-favorable wind from Siberia High in winter, buoyancy flux from Amur River carried by ATW, and the bottom friction are the main dynamic sources of the western coastal current of the Sea of Okhotsk, which might contribute to the coastal upwelling. There are many researches investigated the coast responses to different initial conditions. For a stratified coast with an alongshelf current, idealized simulation depicted an upwelling at the shelf break [Benthuysen et al.,2015]. Benthuysen et al 2015 explained it with the well-known buoyancy shutdown process. The geostrophic current is modified by the tilted isopycnal via the thermal wind relation which induces the bottom Ekman transport convergence and the upwelling consequently. The shelf break is one of the main reasons for the isopycnal tilt in their research. A similar process might happen at the coast of the ESC, and the buoyancy instability is contributed to the downwelling favorable wind. In the idealized simulations by Allen and Newberger 1996, and Austin and Lentz 2002, the downwelling favorable wind remains a well-mixed water mass at the coast and a downwelling front shoulder by shoulder. With the freshwater discharge, the well-mixed water mass at the coast might be replaced by a stratified one, which could be the situation of the ESC.
We accomplished a simulation with the COCO, an Ocean General Circulation Model. The initial conditions are the same as the Matsuda et al [2015]. The grid size at the coast is finer to 3 km at the coast of the ESC. The reanalysis datasets ERA-Interim from 1980.01.01 to 2018.12.31 were adopted as the meteorological forces. The freshwater discharge is from Dai and Trenberth [2002]. Analyzing the output of the January mean, the upwelling is simulated at the upstream of the ESC. The buoyancy shutdown takes part in the formation of the upwelling according to the isopycnal distribution. Adjacent to the upwelling it is an anti-clockwise overturning, means the water is stratified with the surface onshore current and bottom offshore current. The eddy generated by the baroclinic instability attempts to maintain the coastal stratification, while the diffusion demolishes the stratification. We are figuring out how the mean current takes its responsibility in the coastal overturning. The reasonable hypothesis is the mean current just works inversely compared to the eddy.
Downwelling-favorable wind from Siberia High in winter, buoyancy flux from Amur River carried by ATW, and the bottom friction are the main dynamic sources of the western coastal current of the Sea of Okhotsk, which might contribute to the coastal upwelling. There are many researches investigated the coast responses to different initial conditions. For a stratified coast with an alongshelf current, idealized simulation depicted an upwelling at the shelf break [Benthuysen et al.,2015]. Benthuysen et al 2015 explained it with the well-known buoyancy shutdown process. The geostrophic current is modified by the tilted isopycnal via the thermal wind relation which induces the bottom Ekman transport convergence and the upwelling consequently. The shelf break is one of the main reasons for the isopycnal tilt in their research. A similar process might happen at the coast of the ESC, and the buoyancy instability is contributed to the downwelling favorable wind. In the idealized simulations by Allen and Newberger 1996, and Austin and Lentz 2002, the downwelling favorable wind remains a well-mixed water mass at the coast and a downwelling front shoulder by shoulder. With the freshwater discharge, the well-mixed water mass at the coast might be replaced by a stratified one, which could be the situation of the ESC.
We accomplished a simulation with the COCO, an Ocean General Circulation Model. The initial conditions are the same as the Matsuda et al [2015]. The grid size at the coast is finer to 3 km at the coast of the ESC. The reanalysis datasets ERA-Interim from 1980.01.01 to 2018.12.31 were adopted as the meteorological forces. The freshwater discharge is from Dai and Trenberth [2002]. Analyzing the output of the January mean, the upwelling is simulated at the upstream of the ESC. The buoyancy shutdown takes part in the formation of the upwelling according to the isopycnal distribution. Adjacent to the upwelling it is an anti-clockwise overturning, means the water is stratified with the surface onshore current and bottom offshore current. The eddy generated by the baroclinic instability attempts to maintain the coastal stratification, while the diffusion demolishes the stratification. We are figuring out how the mean current takes its responsibility in the coastal overturning. The reasonable hypothesis is the mean current just works inversely compared to the eddy.