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第317回 大気海洋物理学・気候力学セミナー のおしらせ

日　時： 12月27日(木) 9:30 - 12:00
Date ： Thu., 27 Dec. 9:30−12:00　
場　所： 低温科学研究所 3階 講堂
Place ： Institute of Low Temperature Science, 3F Auditorium

Speaker:Chou Hung-Wei (Institute of Low Temperature Science/D2)
Title:Dynamic of Barotropical water exchange between the Sea of Okhotsk and the Pacific by tidal forcing
発表者: 水田元太（地球環境科学研究院/助教）
Speaker:Genta Mizuta(Faculty of Environmental Earth Science/Assistant Professor)
題目:続流ジェットの再循環 -- 数値実験と概念モデルの比較

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Dynamic of Barotropical water exchange between the Sea of Okhotsk and the Pacific by tidal forcing
Chou Hung-Wei 発表要旨:

Since the dense water generated in Sea of Okhotsk is a major source of 
North Pacific Intermediate Water (NPIW), which is spreading the 
biochemical nutrients and driving the overturning circulation in North 
Pacific, the understanding of water exchange between two basins is 
necessary for NPIW water properties variation analysis.

The pattern of exchange flow between two basins is a system composed by 
an Okhotsk-ward inflow through Kruzenshtern strait in north and a 
Pacific-ward outflow through Bussol strait in south. One of major 
theories for explaining the dynamic of water exchange through Kuril 
Island Chain is EKC（East Kamchatka Current）driven machism. EKC driven 
mechanism is based on the total friction balanced around Kuril islands.  
When friction is enhanced by western boundary current on the right hand 
side of islands, an Okhotsk-ward inflow in north and a Pacific-ward 
outflow in south would formed automatically to keep the friction 
balanced. However,  EKC driven mechanism does not consider the 
complexcity of bathymetric in Kuril islands area: western boundary 
current tends to overshot the Kuril islands instead of approching.

By setting the tidal force as controlled variable, results from 
realistic model COCO show only the case with tidal forcing can 
consistent with the exchange flow pattern as historical observation. 
Further, simple idealized model experiments provide the evidence of 
connection between the topographic trapped wave above a seamount in 
Pacific side of north strait and the Okhotsk-ward inflow. The tidal 
seamount trapped wave enhanced the residual inflow in north strait, 
therefore the EKC driven mechanism should be modified as the friction 
gaining in north strait leads the western boundary current gradually to 
apporach the island for circular balance. 


続流ジェットの再循環 -- 数値実験と概念モデルの比較
水田元太(Genta Mizuta)発表要旨:

黒潮続流や湾流に代表される西岸境界流の続流ジェットの付近では、渦による非線型性に 
よって再循環とよばれる流れが形成される。再循環の形成要因としてRhines and Young 

(1982)による渦位一様化の考え方が古くから知られていたが、この考え方では実際の続流 
ジェットでの渦位輸送の向きを必ずしも正しく説明出来ない。一方Haidvogel and Rhines  
(1983)、 Waterman and Jayne (2011)等は概念モデルを用いてジェットから生じるロス 
ビー波が再循環を形成するという説を提唱した。この概念モデルは渦位輸送の向きを定性 
的に正しく再現することができるが、実際の続流ジェットで同様のしくみが働いているか 
は十分明らかでない。そこで本研究では実際の数値実験でロスビー波が再循環と渦位輸送 
の形成に寄与するかについて検討する。Holland and Rhines (1980)は渦位輸送の向きを 
エンストロフィーの収支から診断的に求める方法を提唱したが、その妥当性についても議 
論する。

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