Turbulent mixing in the upper ocean of the northwestern Weddell Sea, Antarctica

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• 作者：Guijun Guo ; Jiuxin Shi ; Yutian Jiao
• 关键词：mixing ; dissipation rate ; turbulent diffusivity ; upper ocean ; Weddell Sea
• 刊名：Acta Oceanologica Sinica
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：35
• 期：3
• 页码：1-9
• 全文大小：1,931 KB
• 参考文献：D’Asaro E A, Eriksen C C, Levine M D, et al. 1995. Upper-Ocean inertial currents forced by a strong storm. Part I: data and comparisons with linear theory. J Phys Oceanogr, 25(11): 2909–2936CrossRef
  Fahrbach E, Rohardt G, Schröder M, et al. 1994. Transport and structure of the Weddell Gyre. Ann Geophys, 12(9): 840–855CrossRef
  Gill A E. 1984. On the behavior of internal waves in the wakes of storms. J Phys Oceanogr, 14(7): 1129–1151CrossRef
  Gordon A L, Huber B A, Hellmer H H, et al. 1993. Deep and bottom water of the Weddell Sea’s western rim. Science, 262(5130): 95–97CrossRef
  Gordon A L, Mensch M, Dong Zhaoqian, et al. 2000. Deep and bottom water of the Bransfield Strait eastern and central Basins. J Geophys Res, 105(C5): 11337–11346CrossRef
  Gordon A L, Visbeck M, Huber B. 2001. Export of Weddell Sea deep and bottom water. J Geophy Res, 106(C5): 9005–9017CrossRef
  Huang Ruixin. 1999. Mixing and energetics of the oceanic thermohaline circulation. J Phys Oceanogr, 29(4): 727–746CrossRef
  Jayne S R. 2009. The impact of abyssal mixing parameterizations in an Ocean general circulation model. J Phys Oceanogr, 39(7): 1756–1775CrossRef
  Kitade Y, Shimada K, Tamura T, et al. 2014. Antarctic bottom water production from the Vincennes Bay Polynya, East Antarctica. Geophys Res Lett, 41(10): 3528–3534CrossRef
  Kunze E, Firing E, Hummon J M, et al. 2006. Global abyssal mixing inferred from lowered ADCP shear and CTD strain profiles. J Phys Oceanogr, 36(8): 1553–1576CrossRef
  Ledwell J R, Laurent L C S, Girton J B, et al. 2011. Diapycnal mixing in the antarctic circumpolar current. J Phys Oceanogr, 41(1): 241–246CrossRef
  Levine M D, Padman L, Muench R D, et al. 1997. Internal waves and tides in the western Weddell Sea: observations from Ice Station Weddell. J Geophys Res, 102(C1): 1073–1089CrossRef
  Liang Xinfeng, Thurnherr A M. 2012. Eddy-modulated internal waves and mixing on a midocean ridge. J Phys Oceanogr, 42(7): 1242–1248CrossRef
  Matano R P, Gordon A L, Muench R D, et al. 2002. A numerical study of the circulation in the northwestern Weddell Sea. Deep-Sea Res Part II, 49(21): 4827–4841CrossRef
  Moum J N, Farmer D M, Smyth W D, et al. 2003. Structure and generation of turbulence at interfaces strained by internal solitary waves propagating shoreward over the continental shelf. J Phys Oceanogr, 33(10): 2093–2112CrossRef
  Muench R D, Gordon A L. 1995. Circulation and transport of water along the western Weddell Sea margin. J Geophys Res, 100(C9): 18503–18515CrossRef
  Muench R D, Padman L, Howard S L, et al. 2002. Upper ocean diapycnal mixing in the northwestern Weddell Sea. Deep-Sea Res Part II, 49(21): 4843–4861CrossRef
  Nikurashin M, Ferrari R. 2010. Radiation and dissipation of internal waves generated by geostrophic motions impinging on smallscale topography: theory. J Phys Oceanogr, 40(5): 1055–1074CrossRef
  Nash J D, Kunze E, Toole J M, et al. 2004. Internal tide reflection and turbulent mixing on the continental slope. J Phys Oceanogr, 34(5): 1117–1134CrossRef
  Oakey N S. 1982. Determination of the rate of dissipation of turbulent energy from simultaneous temperature and velocity shear microstructure measurements. J Phys Oceanogr, 12(3): 256–271CrossRef
  Ohshima K I, Fukamachi Y, Williams G D, et al. 2013. Antarctic bottom water production by intense sea-ice formation in the Cape Darnley polynya. Nat Geoscience, 6(3): 235–240CrossRef
  Orsi A H, Nowlin W D, Whitworth T. 1993. On the circulation and stratification of the Weddell Gyre. Deep-Sea Res Part I, 40(1): 169–203CrossRef
  Osborn T R. 1980. Estimates of the local rate of vertical diffusion from dissipation measurements. J Phys Oceanogr, 10(1): 83–89CrossRef
  Padman L, Fricker H A, Coleman R, et al. 2002. A new tide model for the Antarctic ice shelves and seas. Ann Glaciol, 34(1): 247–254CrossRef
  Rainville L, Lee C M, Woodgate R A. 2011. Impact of wind-driven mixing in the Arctic Ocean. Oceanography, 24(3): 136–145CrossRef
  Robertson R, Padman L, Levine M D. 1995. Fine structure, microstructure, and vertical mixing processes in the upper ocean in the western Weddell Sea. J Geophy Res, 100(C9): 18517–18535CrossRef
  Schodlok M P, Hellmer H H, Beckmann A. 2002. On the transport, variability and origin of dense water masses crossing the South Scotia Ridge. Deep-Sea Res Part II, 49(21): 4807–4825CrossRef
  Thompson A F, Heywood K J. 2008. Frontal structure and transport in the northwestern Weddell Sea. Deep-Sea Res Part I, 55(10): 1229–1251CrossRef
  von Gyldenfeldt A-B, Fahrbach E, Garcia M A, et al. 2002. Flow variability at the tip of the Antarctic Peninsula. Deep-Sea Res Part II, 49(21): 4743–4766CrossRef
  Wolk F, Yamazaki H, Seuront L, et al. 2002. A new free-fall profiler for measuring biophysical microstructure. J Atmos Oceanic Technol, 19(5): 780–793CrossRef
  Zhang Jubao, Schmitt R W, Huang Ruixing. 1999. The relative influence of diapycnal mixing and hydrologic forcing on the stability of the Thermohaline Circulation. J Phys Oceanogr, 29(6): 1096–1108CrossRef
  
• 作者单位：Guijun Guo (1) (2)
  Jiuxin Shi (1) (2)
  Yutian Jiao (1)
  
  1. Key Laboratory of Physical Oceanography, Ocean University of China, Qingdao, 266003, China
  2. College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao, 266100, China
  
• 刊物主题：Oceanography; Climatology; Ecology; Engineering Fluid Dynamics; Marine & Freshwater Sciences; Environmental Chemistry;
• 出版者：Springer Berlin Heidelberg
• ISSN：1869-1099

文摘

Turbulent mixing in the upper ocean (30–200 m) of the northwestern Weddell Sea is investigated based on profiles of temperature, salinity and microstructure data obtained during February 2014. Vertical thermohaline structures are distinct due to geographic features and sea ice distribution, resulting in that turbulent dissipation rates (ε) and turbulent diffusivity (K) are vertically and spatially non-uniform. On the shelf north of Antarctic Peninsula and Philip Ridge, with a relatively homogeneous vertical structure of temperature and salinity through the entire water column in the upper 200 m, both ε and K show significantly enhanced values in the order of O(10–7)–O(10–6) W/kg and O(10–3)–O(10–2) m2/s respectively, about two or three orders of magnitude higher than those in the open ocean. Mixing intensities tend to be mild due to strong stratification in the Powell Basin and South Orkney Plateau, where ε decreases with depth from O(10–8) to O(10–9) W/kg, while K changes vertically in an inverse direction relative to ε from O(10–6) to O(10–5) m2/s. In the marginal ice zone, K is vertically stable with the order of 10–4 m2/s although both intense dissipation and strong stratification occur at depth of 50–100 m below a cold freshened mixed layer. Though previous studies indentify wind work and tides as the primary energy sources for turbulent mixing in coastal regions, our results indicate weak relationship between K and wind stress or tidal kinetic energy. Instead, intensified mixing occurs with large bottom roughness, demonstrating that only when internal waves generated by wind and tide impinge on steep topography can the energy dissipate to support mixing. In addition, geostrophic current flowing out of the Weddell Sea through the gap west of Philip Passage is another energy source contributing to the local intense mixing.