Role of horizontal density advection in seasonal deepening of the mixed layer in the subtropical Southeast Pacific

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• 作者：Qinyu Liu ; Yiqun Lu
• 关键词：mixed layer ; seasonal deepening ; Southeast Pacific ; heat flux ; density advection
• 刊名：Advances in Atmospheric Sciences
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：33
• 期：4
• 页码：442-451
• 全文大小：981 KB
• 参考文献：AVISO, 2008: SSALTO/DUACS User Handbook: (M)SLA and (M)ADT Near-Real Time and Delayed Time Products. Collecte Localisation Satellites, Agne, France, 39 pp.
  Colbo, K., and R. Weller, 2007: The variability and heat budget of the upper ocean under the Chile-Peru stratus. J. Mar. Res., 65, 607–637.CrossRef
  de Boyer MontéGut, C., G. Madec, A. S. Fischer, A. Lazar, and D. Iudicone, 2004: Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology. J. Geophys. Res, 109, C12003, 481–497.
  Deser, C., M. A. Alexander, and M. S. Timlin, 1996: Upper ocean thermal variations in the North pacific during 1970–1991. J. Climate, 9, 1840–1855.CrossRef
  Huang, R. X., 2010. Oceanic Circulation: Wind-driven and Thermohaline Processes. Cambridge University Press, Cambridge, 360–369.
  Kara, A. B., P. A. Rochford, and H. E. Hurlburt, 2003: Mixed layer depth variability over the global ocean. J. Geophys. Res.: Oceans (1978–2012), 108(C3), 209.
  Large, W. G., and S. G. Yeager, 2008: The global climatology of an interannually varying air-sea flux data set. Climate Dyn., 24, 341–364, doi: 10.1007/s00382-008-0441-3.
  Liu, C. Y., and Z. M. Wang, 2014: On the response of the global subduction rate to global warming in coupled climate models. Adv. Atmos. Sci., 31(1), 211–218, doi: 10.1007/s00376-013-2323-9.CrossRef
  Liu, H. L., W. Y. Lin, and M. H. Zhang, 2010: Heat budget of the upper ocean in the south-central Equatorial Pacific. J. Climate, 23(7), 1779–1792. doi: 10.1175/2009JCLI3135.1CrossRef
  Liu, L. L., and R. X. Huang, 2012: The global subduction/obduction rates: Their interannual and decadal variability. J. Climate, 25(4), 1096–1115.CrossRef
  Luo, Y. Y., Q. Y. Liu, and L. M. Rothstein, 2011: Increase of South Pacific eastern subtropical mode water under global warming. Geophys. Res. Lett., 38, L01601.CrossRef
  Nishikawa, S., and A. Kubokawa, 2012: Mixed layer depth front and subduction of low potential vorticity water under seasonal forcings in an idealized OGCM. Journal of Oceanography, 68(1), 53–62.CrossRef
  Pan, A. J., Q. Y. Liu, and Z. Y. Liu, 2008: Formation mechanism of the “Stability Gap” and the North Pacific central mode water. Chinese Journal of Geophysics, 51(1), 77–87. (in Chinese)CrossRef
  Qiu, B., and R. X. Huang, 1995: Ventilation of the North Atlantic and North Pacific: Subduction versus obduction. J. Phys. Oceanogr., 25, 2374–2390.CrossRef
  Sato, K., and T. Suga, 2009: Structure and modification of the South Pacific eastern subtropical mode water. J. Phys. Oceanogr., 39, 1700–1714.CrossRef
  Williams, R. G., 1991: The role of the mixed layer in setting the potential vorticity of the main thermocline. J. Phys. Oceanogr., 21, 1803–1814.CrossRef
  Wong, A. P. S., and G. C. Johnson, 2003: South Pacific eastern subtropical mode water. J. Phys. Oceanogr., 33(7), 1493–1509.CrossRef
  Xie, P. P., and P. A. Arkin, 1997: Global precipitation: A 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull. Amer. Meteor. Soc., 78, 2539–2558.CrossRef
  Xie, S. P., L. X. Xu, Q. Y. Liu, and F. Kobashi, 2011: Dynamical role of mode water ventilation in decadal variability in the central subtropical gyre of the North Pacific. J. Climate, 24, 1212–1225.CrossRef
  Xu, L. X., S. P. Xie, J. L. McClean, Q. Y. Liu, and H. Sasaki, 2014: Mesoscale eddy effects on the subduction of North Pacific mode waters. J. Geophys. Res.-Oceans, 119, 4867–4886, doi: 10.1002/2014JC009861.CrossRef
  Yu, L. S., 2007: Global variations in oceanic evaporation (1958–2005): The role of the changing wind speed. J. Climate, 20(21), 5376–5390.CrossRef
  Yu, L. S., and R. A. Weller, 2007: Objectively analyzed air-sea heat fluxes for the global ice-free oceans (1981–2005). Bull. Amer. Meteor. Soc., 88(4), 527–539.CrossRef
  Yu, L. S., X. Z. Jin, and R. A. Weller, 2006: Role of net surface heat flux in seasonal evolutions of sea surface temperature in the tropical Atlantic Ocean. J. Climate, 19, 6153–6169.CrossRef
  
• 作者单位：Qinyu Liu (1)
  Yiqun Lu (1)
  
  1. Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology, Key Laboratory of Ocean–Atmosphere Interaction and Climate in Universities of Shandong, Ocean University of China, Qingdao, 266100, China
  
• 刊物主题：Atmospheric Sciences; Meteorology; Geophysics/Geodesy;
• 出版者：Springer Berlin Heidelberg
• ISSN：1861-9533

文摘

The mechanisms behind the seasonal deepening of the mixed layer (ML) in the subtropical Southeast Pacific were investigated using the monthly Argo data from 2004 to 2012. The region with a deep ML (more than 175 m) was found in the region of (22°–30°S, 105°–90°W), reaching its maximum depth (~200 m) near (27°–28°S, 100°W) in September. The relative importance of horizontal density advection in determining the maximum ML location is discussed qualitatively. Downward Ekman pumping is key to determining the eastern boundary of the deep ML region. In addition, zonal density advection by the subtropical countercurrent (STCC) in the subtropical Southwest Pacific determines its western boundary, by carrying lighter water to strengthen the stratification and form a “shallow tongue” of ML depth to block the westward extension of the deep ML in the STCC region. The temperature advection by the STCC is the main source for large heat loss from the subtropical Southwest Pacific. Finally, the combined effect of net surface heat flux and meridional density advection by the subtropical gyre determines the northern and southern boundaries of the deep ML region: the ocean heat loss at the surface gradually increases from 22?S to 35?S, while the meridional density advection by the subtropical gyre strengthens the stratification south of the maximum ML depth and weakens the stratification to the north. The freshwater flux contribution to deepening the ML during austral winter is limited. The results are useful for understanding the role of ocean dynamics in the ML formation in the subtropical Southeast Pacific. Keywords mixed layer seasonal deepening Southeast Pacific heat flux density advection