Water exchange through the Kerama Gap estimated with a 25-year Pacific HYbrid Coordinate Ocean Model
Variations in water exchange through the Kerama Gap (between Okinawa Island and Miyakojima Island) from 1979 to 2003 were estimated with the 0.08° Pacific HYbrid Coordinate Ocean Model (HYCOM). The model results show that the mean transport through the Kerama Gap (KGT) from the Pacific Ocean to the East China Sea (ECS) was 2.1 Sv, which agrees well with the observed mean KGT (2.0 Sv) for 2009–2010. Over the time period examined, the monthly KGT varied from -10.9 Sv to 15.8 Sv and had a standard deviation of ± 5.0 Sv. The water mainly enters the ECS via the subsurface layer (300–500 m) along the northeastern slope of the Kerama Gap and mainly flows out of the ECS into the southwest of the Kerama Gap. The seasonal and interannual variations of the KGT and the Kuroshio upstream transport were negatively correlated. The Kuroshio upstream transport was largest in summer and smallest in autumn while the KGT was smallest in summer (1.02 Sv) and largest in spring (2.94 Sv) and autumn (2.44 Sv). The seasonal and interannual variations in the Kuroshio downstream (across the PN-line) transport differed significantly from the Kuroshio upstream transport but corresponded well with the KGT and the sum of the transport through the Kerama Gap and the Kuroshio upstream, which indicates that information about variation in the KGT is important for determining variation in the Kuroshio transport along the PN-line.
KeywordsKerama Gap Kuroshio Ryukyu Current HYbrid Coordinate Ocean Model (HYCOM) water exchange
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The satellite-tracked drifting buoy data are available from the Global Drifter Program (GDP), with support from their website (ftp://ftp.aoml.noaa.gov/pub/phod/buoydata/). The World Ocean Database (WOD) is available from the website (http://www.nodc.noaa.gov/OC5/SELECT/dbsearch/dbsearch. html). The HYCOM data are available for download from the Global Ocean Data Assimilation Experiment (GODAE) from the website (ftp://ftp.hycom.org/datasets/PACa0.08/).
- Boyer T P, Antonov J I, Baranova O K, Garcia H E, Grodsky A, Johnson D R, Locarnini R A, Mishonov A V, O’Brien T D, Seidov D, Smolyar I V, Zweng M M. 2013. World Ocean Database 2013. Data Science Journal, 90(49): 153–173.Google Scholar
- Lin X P, Wu D X, Lan J. 2004. The intrusion and influences of intraseasonal long Rossby waves in the East China Sea. Journal of Hydrodynamics, 16(5): 621–632.Google Scholar
- Morinaga K, Nakagawa N, Osamu K, Guo B. 1998. Flow pattern of the Kuroshio west of the main Okinawa Island. In: Proceedings of Japan-China Joint Symposium on Cooperative Study of Subtropical Circulation System. Seikai National Fisheries Research Institute, Nagasaki, Japan. p.203–210.Google Scholar
- Na H, Wimbush M, Park J H, Nakamura H, Nishina A. 2014. Observations of flow variability through the Kerama Gap between the East China Sea and the Northwestern Pacific. Journal of Geophysical Research: Oceans, 119(2): 689–703.Google Scholar
- Nagano A, Ichikawa H, Miura T, Ichikawa K, Konda M, Yoshikawa Y, Obama K, Murakami K. 2007. Current system east of the Ryukyu Islands. Journal of G eophysical Research: Oceans, 112(C6): 137–154.Google Scholar
- Nakamura H, Nishina A, Liu Z J, Tanaka F, Wimbush M, Park J H. 2013. Intermediate and deep water formation in the Okinawa Trough. Journal of Geophysical Research: Oceans, 118(12): 6881–6893.Google Scholar
- Oka E, Kawabe M. 1998. Characteristics of variations of water properties and density structure around the Kuroshio in the East China Sea. J ournal of O ceanography, 54(6): 605–617.Google Scholar
- Soeyanto E, Guo X Y, Ono J, Miyazawa Y. 2014. Interannual variations of Kuroshio transport in the East China Sea and its relation to the Pacific Decadal Oscillation and mesoscale eddies. Journal of Geophysical Research: Oceans, 119(6): 3595–3616.Google Scholar
- You S H, Yoon J H. 2004. Modeling of the Ryukyu current along the Pacific side of the Ryukyu islands. Pacific Oceanography, 2: 44–51.Google Scholar
- Yuan Y. 1995. The western boundary current east of the Ryukyu Islands. Oceanographic Literature Review, 42(11): 929–930.Google Scholar
- Zheng X T, Liu Q Y, Hu H B, Miyazawa Y, Jia Y L. 2008. The study of the temporal and spatial characteristics of western boundary current East of Ruykyu submarne ridge and the transport of Kuroshio in East China Sea. Acta Oceanologica Sinica, 30(1): 1–9. (in Chinese with English abstract)CrossRefGoogle Scholar
- Zhu X H, Han I S, Park J H, Ichikawa H, Murakami K, Kaneko A, Ostrovskii A. 2003. The northeastward current southeast of Okinawa Island observed during November 2000 to August 2001. Geophysical Research Letters, 30(2): 61–79.Google Scholar