Observation of summertime upwelling off the eastern and northeastern coasts of Hainan Island, China
- 289 Downloads
Using cruise observations and reanalysis data, this study analyzes the effects of wind, freshwater, and turbulent mixing on the two upwellings: one is off the eastern coast of Hainan Island (HEU) and the other is off the northeastern coast of Hainan Island (HNEU). During the cruise in 2009, the HNEU occurred with southwesterly to southeasterly wind. The relative large values of turbulent kinetic energy dissipation rate and diffusivity estimated from the Thorpe scale indicate that the upwelling water is further uplifted to the surface by strong turbulent mixing in the HNEU region. But the HEU was not observed under the southeasterly wind. During the cruise in 2012, the HNEU disappeared in the upper layer with freshwater covered and southeasterly wind, while the apparent HEU only accompanied with southwesterly wind. To obtain the general characteristics, we define three types of upwelling patterns, i.e., the intensified HEU, the intensified HNEU, and both HEU and HNEU in one day, using the reanalysis data. The composites of sea surface temperature (SST), wind, and precipitate for each upwelling pattern identify that the HNEU is associated with the prevailing southeasterly wind and can be limited in the lower layer when it is covered by freshwater. But the HEU is mainly driven by southwesterly wind but is not remarkably affected by freshwater.
KeywordsUpwelling off Hainan Island Wind Freshwater Turbulent mixing Fuzzy c-means algorithm
The authors appreciate two anonymous reviewers for suggestions that improved this manuscript. This work is supported by the National Basic Research Program of China projects 2015CB954004 and 2009CB421208, and the National Natural Science Foundation of China projects 41276006 and U1405233. The authors also thank the crew of R/V Dongfanghong 2 for help with the cruise survey and Shaoling Shang for helpful comments.
- Alford MH, MacKinnon JA, Nash JD, Simmons H, Pickering A, Klymak JM, Pinkel R, Sun O, Rainville L, Musgrave R, Beitzel T, Fu KH, Lu CW (2011) Energy flux and dissipation in Luzon Strait: two tales of two ridges. J Phys Oceanogr 41(11):2211–2222Google Scholar
- Guo F, Shi M, Xia Z (1998) Two-dimension diagnose model to calculate upwelling on offshore of the east coast of Hainan Island. Acta Oceanol Sin 20(6):109–116 (in Chinese with English abstract)Google Scholar
- Han Y, Wang M, Ma K (1990) The lowest surface water temperature area of China Sea in summer-the upwelling along the east coast of Hainan Island. Oceanol Et Limnol Sin 21(3):267–275 (in Chinese with English abstract)Google Scholar
- Li L (1990) A study on the summer upwellings in shelf waters west to Zhujiang River mouth. J Oceanogr Taiwan Strait 9(4):338–346 (in Chinese with English abstract)Google Scholar
- Lin P, Cheng P, Gan J, Hu J (2016) Dynamics of wind-driven upwelling off the northeastern coast of Hainan Island. J Geophys Res Oceans 121. doi: 10.1002/2015JC011000
- Mamayev OI (1975) Temperature-salinity analysis of world oceans. Elsevier oceanography series, New york Google Scholar
- Xie L, Zhang S, Zhao H (2012) Overview of studies on Qiongdong upwelling. J Trop Oceanogr 31(4):35–41 (in Chinese with English abstract)Google Scholar
- Yu W (1987) A preliminary approach of the upwelling for the northern South China Sea. Mar Sci 6:7–10 (in Chinese with English abstract)Google Scholar