Submesoscale-enhanced filaments and frontogenetic mechanism within mesoscale eddies of the South China Sea
Tóm tắt
Submesoscale activity in the upper ocean has received intense studies through simulations and observations in the last decade, but in the eddy-active South China Sea (SCS) the fine-scale dynamical processes of submesoscale behaviors and their potential impacts have not been well understood. This study focuses on the elongated filaments of an eddy field in the northern SCS and investigates submesoscale-enhanced vertical motions and the underlying mechanism using satellite-derived observations and a high-resolution (∼500 m) simulation. The satellite images show that the elongated highly productive stripes with a typical lateral scale of ∼25 km and associated filaments are frequently observed at the periphery of mesoscale eddies. The diagnostic results based on the 500 m-resolution realistic simulation indicate that these submesoscale filaments are characterized by cross-filament vertical secondary circulations with an increased vertical velocity reaching O(100 m/d) due to submesoscale instabilities. The vertical advections of secondary circulations drive a restratified vertical buoyancy flux along filament zones and induce a vertical heat flux up to 110 W/m2. This result implies a significant submesoscale-enhanced vertical exchange between the ocean surface and interior in the filaments. Frontogenesis that acts to sharpen the lateral buoyancy gradients is detected to be conducive to driving submesoscale instabilities and enhancing secondary circulations through increasing the filament baroclinicity. The further analysis indicates that the filament frontogenesis detected in this study is not only derived from mesoscale straining of the eddy, but also effectively induced by the subsequent submesoscale straining due to ageostrophic convergence. In this context, these submesoscale filaments and associated frontogenetic processes can provide a potential interpretation for the vertical nutrient supply for phytoplankton growth in the high-productive stripes within the mesoscale eddy, as well as enhanced vertical heat transport.
Tài liệu tham khảo
Adams K A, Hosegood P, Taylor J R, et al. 2017. Frontal circulation and submesoscale variability during the formation of a Southern Ocean mesoscale eddy. Journal of Physical Oceanography, 47(7): 1737–1753, doi: https://doi.org/10.1175/JPO-D-16-0266.1
Bachman S D, Fox-Kemper B, Taylor J R, et al. 2017. Parameterization of frontal symmetric instabilities. I: theory for resolved fronts. Ocean Modelling, 109: 72–95, doi: https://doi.org/10.1016/j.ocemod.2016.12.003
Boccaletti G, Ferrari R, Fox-Kemper B. 2007. Mixed layer instabilities and restratification. Journal of Physical Oceanography, 37(9): 2228–2250, doi: https://doi.org/10.1175/JPO3101.1
Brannigan L, Marshall D P, Naveira-Garabato A, et al. 2015. The seasonal cycle of submesoscale flows. Ocean Modelling, 92: 69–84, doi: https://doi.org/10.1016/j.ocemod.2015.05.002
Bryden H L, Brady E C. 1989. Eddy momentum and heat fluxes and their effects on the circulation of the equatorial Pacific Ocean. Journal of Marine Research, 47(1): 55–79, doi: https://doi.org/10.1357/002224089785076389
Capet X, McWilliams J C, Molemaker M J, et al. 2008. Mesoscale to submesoscale transition in the California current system. Part II: Frontal processes. Journal of Physical Oceanography, 38(1): 44–64, doi: https://doi.org/10.1175/2007JPO3672.1
Carton J A, Giese B S. 2008. A reanalysis of ocean climate using simple ocean data assimilation (SODA). Monthly Weather Review, 136(8): 2999–3017, doi: https://doi.org/10.1175/2007MWR1978.1
Chelton D B, DeSzoeke R A, Schlax M G, et al. 1998. Geographical variability of the first baroclinic Rossby radius of deformation. Journal of Physical Oceanography, 28(3): 433–460, doi: https://doi.org/10.1175/1520-0485(1998)028<0433:GVOTFB>2.0.CO;2
Chelton D B, Gaube P, Schlax M G, et al. 2011a. The Influence of nonlinear mesoscale eddies on near-surface oceanic chlorophyll. Science, 334(6054): 328–332, doi: https://doi.org/10.1126/science.1208897
Chelton D B, Schlax M G, Samelson R M. 2011b. Global observations of nonlinear mesoscale eddies. Progress in Oceanography, 91(2): 167–216, doi: https://doi.org/10.1016/j.pocean.2011.01.002
Chen Gengxin, Hou Yijun, Chu Xiaoqing. 2011. Mesoscale eddies in the South China Sea: mean properties, spatiotemporal variability, and impact on thermohaline structure. Journal of Geophysical Research: Oceans, 116(C6): C06018
da Silva A M, Young C C, Levitus S. 1994. Atlas of surface marine data 1994, volume 1: algorithms and procedures. Washington, DC: U. S. Department of Commerce, NOAA, NESDIS
D’Asaro E, Lee C, Rainville L, et al. 2011. Enhanced turbulence and energy dissipation at ocean fronts. Science, 332(6027): 318–322, doi: https://doi.org/10.1126/science.1201515
Dauhajre D P, McWilliams J C, Uchiyama Y. 2017. Submesoscale coherent structures on the continental shelf. Journal of Physical Oceanography, 47(12): 2949–2976, doi: https://doi.org/10.1175/JPO-D-16-0270.1
Dong Changming, McWilliams J C, Liu Yu, et al. 2014. Global heat and salt transports by eddy movement. Nature Communications, 5(1): 3294, doi: https://doi.org/10.1038/ncomms4294
Dong Jihai, Zhong Yisen. 2018. The spatiotemporal features of submesoscale processes in the northeastern South China Sea. Acta Oceanologica Sinica, 37(11): 8–18, doi: https://doi.org/10.1007/s13131-018-1277-2
Dong Jihai, Zhong Yisen. 2020. Submesoscale fronts observed by satellites over the northern South China Sea shelf. Dynamics of Atmospheres and Oceans, 91: 101161, doi: https://doi.org/10.1016/j.dynatmoce.2020.101161
Fox-Kemper B, Ferrari R, Hallberg R. 2008. Parameterization of mixed layer eddies. Part I: theory and diagnosis. Journal of Physical Oceanography, 38(6): 1145–1165, doi: https://doi.org/10.1175/2007JPO3792.1
Gula J, Molemaker M J, McWilliams J C. 2014. Submesoscale cold filaments in the Gulf Stream. Journal of Physical Oceanography, 44(10): 2617–2643, doi: https://doi.org/10.1175/JPO-D-14-0029.1
Guo Lin, Xiu Peng, Chai Fei, et al. 2017. Enhanced chlorophyll concentrations induced by Kuroshio intrusion fronts in the northern South China Sea. Geophysical Research Letters, 44(22): 11565–11572, doi: https://doi.org/10.1002/2017GL075336
Hosegood P J, Gregg M C, Alford M H. 2013. Wind-driven submesoscale subduction at the north Pacific subtropical front. Journal of Geophysical Research: Oceans, 118(10): 5333–5352, doi: https://doi.org/10.1002/jgrc.20385
Hoskins B J. 1974. The role of potential vorticity in symmetric stability and instability. Quarterly Journal of the Royal Meteorological Society, 100(425): 480–482, doi: https://doi.org/10.1002/qj.49710042520
Hoskins B J. 1982. The mathematical theory of frontogenesis. Annual Review of Fluid Mechanics, 14: 131–151, doi: https://doi.org/10.1146/annurev.fl.14.010182.001023
Jing Zhiyou, Fox-Kemper B, Cao Haijin, et al. 2021. Submesoscale fronts and their dynamical processes associated with symmetric instability in the northwest Pacific subtropical ocean. Journal of Physical Oceanography, 51(1): 83–100, doi: https://doi.org/10.1175/JPOD-20-0076.1
Klein P, Lapeyre G. 2009. The oceanic vertical pump induced by mesoscale and submesoscale turbulence. Annual Review of Marine Science, 1: 351–375, doi: https://doi.org/10.1146/annurev.marine.010908.163704
Klein P, Lapeyre G, Roullet G, et al. 2011. Ocean turbulence at meso and submesoscales: connection between surface and interior dynamics. Geophysical & Astrophysical Fluid Dynamics, 105(4–5): 421–437
Klymak J M, Shearman R K, Gula J, et al. 2016. Submesoscale streamers exchange water on the north wall of the Gulf Stream. Geophysical Research Letters, 43(3): 1226–1233, doi: https://doi.org/10.1002/2015GL067152
Lapeyre G, Klein P. 2006. Dynamics of the upper oceanic layers in terms of surface quasigeostrophy theory. Journal of Physical Oceanography, 36(2): 165–176, doi: https://doi.org/10.1175/JPO2840.1
Large W G, McWilliams J C, Doney S C. 1994. Oceanic vertical mixing: a review and a model with a nonlocal boundary layer parameterization. Reviews of Geophysics, 32(4): 363–403, doi: https://doi.org/10.1029/94RG01872
Lévy M, Klein P, Treguier A M. 2001. Impact of sub-mesoscale physics on production and subduction of phytoplankton in an oligotrophic regime. Journal of Marine Research, 59(4): 535–565, doi: https://doi.org/10.1357/002224001762842181
Li Jiajun, Jiang Xin, Li Gang, et al. 2017. Distribution of picoplankton in the northeastern South China Sea with special reference to the effects of the Kuroshio intrusion and the associated mesoscale eddies. Science of the Total Environment, 589: 1–10, doi: https://doi.org/10.1016/j.scitotenv.2017.02.208
Li Ruihuan, Xu Jie, Cen Xianrong, et al. 2021. Nitrate fluxes induced by turbulent mixing in dipole eddies in an oligotrophic ocean. Limnology and Oceanography, 66(7): 2842–2854, doi: https://doi.org/10.1002/lno.11794
Lin Hongyang, Liu Zhiyu, Hu Jianyu, et al. 2020. Characterizing meso- to submesoscale features in the South China Sea. Progress in Oceanography, 188: 102420, doi: https://doi.org/10.1016/j.pocean.2020.102420
Mahadevan A. 2016. The impact of submesoscale physics on primary productivity of plankton. Annual Review of Marine Science, 8: 161–184, doi: https://doi.org/10.1146/annurev-marine-010814-015912
Martin A P. 2003. Phytoplankton patchiness: the role of lateral stirring and mixing. Progress in Oceanography, 57(2): 125–174, doi: https://doi.org/10.1016/S0079-6611(03)00085-5
Mason E, Pascual A, McWilliams J C. 2014. A new sea surface height-based code for oceanic mesoscale eddy tracking. Journal of Atmospheric and Oceanic Technology, 31(5): 1181–1188, doi: https://doi.org/10.1175/JTECH-D-14-00019.1
McGillicuddy D J Jr. 2016. Mechanisms of physical-biological-biogeochemical interaction at the oceanic mesoscale. Annual Review of Marine Science, 8: 125–159, doi: https://doi.org/10.1146/annurev-marine-010814-015606
McGillicuddy D J Jr, Anderson L A, Doney S C, et al. 2003. Eddy-driven sources and sinks of nutrients in the upper ocean: results from a 0.1° resolution model of the North Atlantic. Global Biogeochemical Cycles, 17(2): 1035
McWilliams J C. 2017. Submesoscale surface fronts and filaments: secondary circulation, buoyancy flux, and frontogenesis. Journal of Fluid Mechanics, 823: 391–432, doi: https://doi.org/10.1017/jfm.2017.294
McWilliams J C, Colas F, Molemaker M J. 2009a. Cold filamentary intensification and oceanic surface convergence lines. Geophysical Research Letters, 36(18): L18602, doi: https://doi.org/10.1029/2009GL039402
McWilliams J C, Gula J, Molemaker M J, et al. 2015. Filament frontogenesis by boundary layer turbulence. Journal of Physical Oceanography, 45(8): 1988–2005, doi: https://doi.org/10.1175/JPO-D-14-0211.1
McWilliams J C, Molemaker M J, Olafsdottir E I. 2009b. Linear fluctuation growth during frontogenesis. Journal of Physical Oceanography, 39(12): 3111–3129, doi: https://doi.org/10.1175/2009JPO4186.1
Munk W, Armi L, Fischer K, et al. 2000. Spirals on the sea. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 456(1997): 1217–1280
Nan Feng, Xue Huijie, Xiu Peng, et al. 2011. Oceanic eddy formation and propagation southwest of Taiwan. Journal of Geophysical Research: Oceans, 116(C12): C12045, doi: https://doi.org/10.1029/2011JC007386
Omand M M, D’Asaro E A, Lee C M, et al. 2015. Eddy-driven subduction exports particulate organic carbon from the spring bloom. Science, 348(6231): 222–225, doi: https://doi.org/10.1126/science.1260062
Penven P, Debreu L, Marchesiello P, et al. 2006. Evaluation and application of the ROMS 1-way embedding procedure to the central california upwelling system. Ocean Modelling, 12(1–2): 157–187, doi: https://doi.org/10.1016/j.ocemod.2005.05.002
Qiu Bo, Chen Shuiming. 2010. Interannual variability of the North Pacific Subtropical Countercurrent and its associated mesoscale eddy field. Journal of Physical Oceanography, 40(1): 213–225, doi: https://doi.org/10.1175/2009JPO4285.1
Read J F, Pollard R T, Allen J T. 2007. Sub-mesoscale structure and the development of an eddy in the subantarctic front north of the Crozet Islands. Deep-Sea Research Part II: Topical Studies in Oceanography, 54(18–20): 1930–1948, doi: https://doi.org/10.1016/j.dsr2.2007.06.013
Risien C M, Chelton D B. 2008. A global climatology of surface wind and wind stress fields from eight years of QuikSCAT scatterometer data. Journal of Physical Oceanography, 38(11): 2379–2413, doi: https://doi.org/10.1175/2008JPO3881.1
Shakespeare C J, Taylor J R. 2013. A generalized mathematical model of geostrophic adjustment and frontogenesis: uniform potential vorticity. Journal of Fluid Mechanics, 736: 366–413, doi: https://doi.org/10.1017/jfm.2013.526
Shchepetkin A F, McWilliams J C. 2005. The regional oceanic modeling system (ROMS): a split-explicit, free-surface, topography-following-coordinate oceanic model. Ocean Modelling, 9(4): 347–404, doi: https://doi.org/10.1016/j.ocemod.2004.08.002
Spall M A. 1995. Frontogenesis, subduction, and cross-front exchange at upper ocean fronts. Journal of Geophysical Research: Oceans, 100(C2): 2543–2557, doi: https://doi.org/10.1029/94JC02860
Stone P H. 1966. On non-geostrophic baroclinic stability. Journal of the Atmospheric Sciences, 23(4): 390–400, doi: https://doi.org/10.1175/1520-0469(1966)023<0390:ONGBS>2.0.CO;2
Su Zhan, Torres H, Klein P, et al. 2020. High-frequency submesoscale motions enhance the upward vertical heat transport in the global ocean. Journal of Geophysical Research: Oceans, 125(9): e2020JC016544
Su Zhan, Wang Jinbo, Klein P, et al. 2018. Ocean submesoscales as a key component of the global heat budget. Nature Communications, 9(1): 775, doi: https://doi.org/10.1038/s41467-018-02983-w
Sullivan P P, McWilliams J C. 2018. Frontogenesis and frontal arrest of a dense filament in the oceanic surface boundary layer. Journal of Fluid Mechanics, 837: 341–380, doi: https://doi.org/10.1017/jfm.2017.833
Tang Qunshu, Jing Zhiyou, Lin Jianmin, et al. 2021. Diapycnal mixing in the subthermocline of the Mariana Ridge from high-resolution seismic images. Journal of Physical Oceanography, 51(4): 1283–1300, doi: https://doi.org/10.1175/JPO-D-20-0120.1
Tarry D R, Essink S, Pascual A, et al. 2021. Frontal convergence and vertical velocity measured by drifters in the Alboran Sea. Journal of Geophysical Research: Oceans, 126(4): e2020JC016614
Taylor J R, Ferrari R. 2009. On the equilibration of a symmetrically unstable front via a secondary shear instability. Journal of Fluid Mechanics, 622: 103–113, doi: https://doi.org/10.1017/S0022112008005272
Thomas L N, Taylor J R, Ferrari R, et al. 2013. Symmetric instability in the Gulf Stream. Deep-Sea Research Part II: Topical Studies in Oceanography, 91: 96–110, doi: https://doi.org/10.1016/j.dsr2.2013.02.025
Thompson A F, Lazar A, Buckingham C, et al. 2016. Open-ocean submesoscale motions: a full seasonal cycle of mixed layer instabilities from gliders. Journal of Physical Oceanography, 46(4): 1285–1307, doi: https://doi.org/10.1175/JPO-D-15-0170.1
Wang Dongxiao, Xu Hongzhou, Lin Jing, et al. 2008. Anticyclonic eddies in the northeastern South China Sea during winter 2003/2004. Journal of Oceanography, 64(6): 925–935, doi: https://doi.org/10.1007/s10872-008-0076-3
Woodruff S D, Worley S J, Lubker S J, et al. 2011. ICOADS Release 2.5: extensions and enhancements to the surface marine meteorological archive. International Journal of Climatology, 31(7): 951–967, doi: https://doi.org/10.1002/joc.2103
Yang Qingxuan, Nikurashin M, Sasaki H, et al. 2019. Dissipation of mesoscale eddies and its contribution to mixing in the northern South China Sea. Scientific Reports, 9(1): 556, doi: https://doi.org/10.1038/s41598-018-36610-x
Yang Qingxuan, Zhao Wei, Liang Xinfeng, et al. 2017. Elevated mixing in the periphery of mesoscale eddies in the South China Sea. Journal of Physical Oceanography, 47(4): 895–907, doi: https://doi.org/10.1175/JPO-D-16-0256.1
Zhang Yanwei, Liu Zhifei, Zhao Yulong, et al. 2014. Mesoscale eddies transport deep-sea sediments. Scientific Reports, 4: 5937
Zhang Zhengguang, Qiu Bo. 2020. Surface chlorophyll enhancement in mesoscale eddies by submesoscale spiral bands. Geophysical Research Letters, 47(14): e2020GL088820
Zhang Zhiwei, Tian Jiwei, Qiu Bo, et al. 2016. Observed 3D structure, generation, and dissipation of oceanic mesoscale eddies in the South China Sea. Scientific Reports, 6(1): 24349, doi: https://doi.org/10.1038/srep24349
Zhang Zhiwei, Zhang Yuchen, Qiu Bo, et al. 2020. Spatiotemporal characteristics and generation mechanisms of submesoscale currents in the northeastern South China Sea revealed by numerical simulations. Journal of Geophysical Research: Oceans, 125(2): e2019JC015404
Zheng Quanan, Xie Lingling, Xiong Xuejun, et al. 2020. Progress in research of submesoscale processes in the South China Sea. Acta Oceanologica Sinica, 39(1): 1–13, doi: https://doi.org/10.1007/s13131-019-1521-4
Zhong Yisen, Bracco A, Tian Jiwei, et al. 2017. Observed and simulated submesoscale vertical pump of an anticyclonic eddy in the South China Sea. Scientific Reports, 7(1): 44011, doi: https://doi.org/10.1038/srep44011