Oceanic vertical mixing of the lower halocline water in the Chukchi Borderland and Mendeleyev Ridge
Abstract: Oceanic vertical mixing of the lower halocline water (LHW) in the Chukchi Borderland and Mendeleyev Ridge was studied based on in-situ hydrographic and turbulent observations. The depth-averaged turbulent dissipation rate of LHW demonstrates a clear topographic dependence, with a mean value of 1.2×10–9 W·kg–1 in the southwest of Canada Basin, 1.5×10–9 W·kg–1 in the Mendeleyev Abyssal Plain, 2.4×10–9 W·kg–1 on the Mendeleyev Ridge, and 2.7×10–9 W·kg–1 on the Chukchi Cap. Correspondingly, the mean depth-averaged vertical heat flux of the LHW is 0.21 W·m–2 in the southwest Canada Basin, 0.30 W·m–2 in the Mendeleyev Abyssal Plain, 0.39 W·m–2 on the Mendeleyev Ridge, and 0.46 W·m–2 on the Chukchi Cap. However, in the presence of Pacific Winter Water, the upward heat released from Atlantic Water through the lower halocline can hardly contribute to the surface ocean. Further, the underlying mechanisms of diapycnal mixing in LHW—double diffusion and shear instability—was investigated. The mixing in LHW where double diffusion were observed is always relatively weaker, with corresponding dissipation rate ranging from 1.01×10–9 to 1.57×10–9 W·kg–1. The results also show a strong correlation between the depth-average dissipation rate and strain variance in the LHW, which indicates a close physical linkage between the turbulent mixing and internal wave activities. In addition, both surface wind forcing and semidiurnal tides significantly contribute to the turbulent mixing in the LHW.
Figure 1. Hydrographic and turbulent stations of the 7th Chinese National Arctic Research Expedition in the Chukchi Borderland and Mendeleyev Ridge of the Arctic Ocean in the summer of 2016. CTD stations are marked as red dots; stations with quality sADCP data were marked as red squares; and VMP stations are marked as red circles. The colormap shows the bathymetry.
Table 1. Comparison of the depth averaged diffusivity between observation and parameterization where double diffusion occurred in LHW.
Station Name Observed dissipation rate
Diffusivity derived from observed
dissipation rate κ/×10–6 m2·s-2
Diffusivity based on double-diffusive
theory κ/×10–6 m2·s-2
E24 1.57 7.90 5.16 E26 1.14 6.69 6.49 R20 1.47 7.89 5.38 R21 1.44 9.55 5.90 P26 1.01 6.75 5.05
 Aagaard K, Coachman L K, Carmack E. 1981. On the halocline of the Arctic Ocean. Deep Sea Research Part A. Oceanographic Research Papers, 28(6): 529–545  Aksenov Y, Ivanov V V, Nurser A J G, et al. 2011. The Arctic circumpolar boundary current. Journal of Geophysical Research: Oceans, 116(C9): C09017  Alford M H. 2003. Improved global maps and 54-year history of wind-work on ocean inertial motions. Geophysical Research Letters, 30(8): 1424  Carmack E, Polyakov I, Padman L, et al. 2015. Toward quantifying the increasing role of oceanic heat in sea ice loss in the new Arctic. Bulletin of the American Meteorological Society, 96(12): 2079–2105. doi: 10.1175/BAMS-D-13-00177.1  Coachman L K, Aagaard K. 1974. Physical oceanography of Arctic and subarctic seas. In Herman Y, eds. Marine Geology and Oceanography of the Arctic Seas. Berlin, Heidelberg: Springer, 1–72.  D'Asaro E A, Morison J H. 1992. Internal waves and mixing in the Arctic Ocean. Deep Sea Research Part A. Oceanographic Research Papers, 39(2): S459–S484  Dmitrenko I A, Kirillov S A, Serra N, et al. 2014. Heat loss from the Atlantic water layer in the northern Kara Sea: Causes and consequences. Ocean Science, 10(4): 719–730. doi: 10.5194/os-10-719-2014  Erofeeva S, Egbert G. 2020. Arc5km2018: Arctic Ocean Inverse Tide Model on a 5 kilometer grid, 2018. Dataset. https:/doi.org/10.18739/A21R6N14K.  Fer I. 2009. Weak vertical diffusion allows maintenance of cold halocline in the central Arctic. Atmospheric and Oceanic Science Letters, 2(3): 148–152. doi: 10.1080/16742834.2009.11446789  Fer I, Voet G, Seim K S, et al. 2010. Intense mixing of the Faroe Bank Channel overflow. Geophysical Research Letters, 37(2): L02604  Fer I, Bosse A, Ferron B, et al. 2018. The dissipation of kinetic energy in the Lofoten Basin Eddy. Journal of Physical Oceanography, 48(6): 1299–1316. doi: 10.1175/JPO-D-17-0244.1  Flanagan J D, Radko T, Shaw W J, et al. 2014. Dynamic and double-diffusive instabilities in a weak pycnocline. Part II: Direct numerical simulations and flux laws. Journal of Physical Oceanography, 44(8): 1992–2012. doi: 10.1175/JPO-D-13-043.1  Gregg M C, D'Asaro E A, Riley J J, et al. 2018. Mixing efficiency in the ocean. Annual Review of Marine Science, 10: 443–473. doi: 10.1146/annurev-marine-121916-063643  Guthrie J D, Morison J H, Fer I. 2013. Revisiting internal waves and mixing in the Arctic Ocean. Journal of Geophysical Research: Oceans, 118(8): 3966–3977. doi: 10.1002/jgrc.20294  Hibler III W D. 1979. A dynamic thermodynamic sea ice model. Journal of Physical Oceanography, 9(4): 815–846. doi: 10.1175/1520-0485(1979)009<0815:ADTSIM>2.0.CO;2  Itoh M, Shimada K, Kamoshida T, et al. 2012. Interannual variability of Pacific Winter Water inflow through Barrow Canyon from 2000 to 2006. Journal of Oceanography, 68(4): 575–592. doi: 10.1007/s10872-012-0120-1  Jackson J M, Carmack E C, McLaughlin F A, et al. 2010. Identification, characterization, and change of the near‐surface temperature maximum in the Canada Basin, 1993–2008. Journal of Geophysical Research: Oceans, 115(C5): C05021  Jones E P, Anderson L G. 1986. On the origin of the chemical properties of the Arctic Ocean halocline. Journal of Geophysical Research: Oceans, 91(C9): 10759–10767. doi: 10.1029/JC091iC09p10759  Jones E P, Anderson L G, Swift J H. 1998. Distribution of Atlantic and Pacific waters in the upper Arctic Ocean: implications for circulation. Geophysical Research Letters, 25(6): 765–768. doi: 10.1029/98GL00464  Kunze E, Firing E, Hummon J M, et al. 2006. Global abyssal mixing inferred from lowered ADCP shear and CTD strain profiles. Journal of Physical Oceanography, 36(8): 1553–1576. doi: 10.1175/JPO2926.1  Lenn Y D, Wiles P J, Torres-Valdes S, et al. 2009. Vertical mixing at intermediate depths in the Arctic boundary current. Geophysical Research Letters, 36(5): L05601  Lincoln B J, Rippeth T P, Lenn Y D, et al. 2016. Wind‐driven mixing at intermediate depths in an ice-free Arctic Ocean. Geophysical Research Letters, 43(18): 9749–9756. doi: 10.1002/2016GL070454  Lique C, Guthrie J D, Steele M, et al. 2014. Diffusive vertical heat flux in the Canada Basin of the Arctic Ocean inferred from moored instruments. Journal of Geophysical Research: Oceans, 119(1): 496–508. doi: 10.1002/2013JC009346  Liu Zhiyu, Lozovatsky I. 2012. Upper pycnocline turbulence in the northern South China Sea. Chinese Science Bulletin, 57(18): 2302–2306. doi: 10.1007/s11434-012-5137-8  Lozovatsky I, Liu Zhiyu, Fernando H J S, et al. 2013. The TKE dissipation rate in the northern South China Sea. Ocean Dynamics, 63(11-12): 1189–1201. doi: 10.1007/s10236-013-0656-7  Meyer A, Fer I, Sundfjord A, et al. 2017. Mixing rates and vertical heat fluxes north of Svalbard from Arctic winter to spring. Journal of Geophysical Research: Oceans, 122(6): 4569–4586. doi: 10.1002/2016JC012441  Munk W, Wunsch C. 1998. Abyssal recipes II: energetics of tidal and wind mixing. Deep Sea Research Part I: Oceanographic Research Papers, 45(12): 1977–2010. doi: 10.1016/S0967-0637(98)00070-3  Nagasawa M, Niwa Y, Hibiya T. 2000. Spatial and temporal distribution of the wind-induced internal wave energy available for deep water mixing in the North Pacific. Journal of Geophysical Research: Oceans, 105(C6): 13933–13943. doi: 10.1029/2000JC900019  Nasmyth P W. 1970. Oceanic turbulence [dissertation]. Vancouver: University of British Columbia.  Osborn T. R 1980. Estimates of the local rate of vertical diffusion from dissipation measurements. Journal of Physical Oceanography, 10(1): 83–89. doi: 10.1175/1520-0485(1980)010<0083:EOTLRO>2.0.CO;2  Padman L, Dillon T M. 1991. Turbulent mixing near the Yermak Plateau during the coordinated Eastern Arctic Experiment. Journal of Geophysical Research: Oceans, 96(C3): 4769–4782. doi: 10.1029/90JC02260  Perovich D K, Light B, Eicken H, et al. 2007. Increasing solar heating of the Arctic Ocean and adjacent seas, 1979–2005: attribution and role in the ice-albedo feedback. Geophysical Research Letters, 34(19): L19505. doi: 10.1029/2007GL031480  Polzin K L, Toole J M, Schmitt R W. 1995. Finescale parameterizations of turbulent dissipation. Journal of Physical Oceanography, 25(3): 306–328. doi: 10.1175/1520-0485(1995)025<0306:FPOTD>2.0.CO;2  Qiu Bo, Chen Shuiming, Carter G S. 2012. Time-varying parametric subharmonic instability from repeat CTD surveys in the northwestern Pacific Ocean. Journal of Geophysical Research: Oceans, 117(C9): C09012  Qiu Chunhua, Huo Dan, Liu Changjian, et al. 2019. Upper vertical structures and mixed layer depth in the shelf of the northern South China Sea. Continental Shelf Research, 174: 26–34. doi: 10.1016/j.csr.2019.01.004  Rainville L, Winsor P. 2008. Mixing across the Arctic Ocean: microstructure observations during the Beringia 2005 expedition. Geophysical Research Letters, 35(8): L08606  Rippeth T P, Lincoln B J, Lenn Y D, et al. 2015. Tide-mediated warming of Arctic halocline by Atlantic heat fluxes over rough topography. Nature Geoscience, 8(3): 191–194. doi: 10.1038/ngeo2350  Rudels B, Anderson L G, Jones E P. 1996. Formation and evolution of the surface mixed layer and halocline of the Arctic Ocean. Journal of Geophysical Research: Oceans, 101(C4): 8807–8821. doi: 10.1029/96JC00143  Rudels B, Jones E P, Schauer U, et al. 2004. Atlantic sources of the Arctic Ocean surface and halocline waters. Polar Research, 23(2): 181–208. doi: 10.1111/j.1751-8369.2004.tb00007.x  Shaw W J, Stanton T P. 2014a. Vertical diffusivity of the Western Arctic Ocean halocline. Journal of Geophysical Research: Oceans, 119(8): 5017–5038. doi: 10.1002/2013JC009598  Shaw W J, Stanton T P. 2014b. Dynamic and double-diffusive instabilities in a weak pycnocline. Part I: observations of heat flux and diffusivity in the vicinity of Maud Rise, Weddell Sea. Journal of Physical Oceanography, 44(8): 1973–1991. doi: 10.1175/JPO-D-13-042.1  Shimada K, Carmack E C, Hatakeyama K, et al. 2001. Varieties of shallow temperature maximum waters in the western Canadian Basin of the Arctic Ocean. Geophysical Research Letters, 28(18): 3441–3444. doi: 10.1029/2001GL013168  Simmons H L, Hallberg R W, Arbic B K. 2004. Internal wave generation in a global baroclinic tide model. Deep Sea Research Part II: Topical Studies in Oceanography, 51(25–26): 3043–3068. doi: 10.1016/j.dsr2.2004.09.015  Sirevaag A, Fer I. 2012. Vertical heat transfer in the Arctic Ocean: the role of double-diffusive mixing. Journal of Geophysical Research: Oceans, 117(C7): C07010  Spreen G, Kaleschke L, Heygster G. 2008. Sea ice remote sensing using AMSR-E 89-GHz channels. Journal of Geophysical Research: Oceans, 113(C2): C02S03  Steele M, Morison J H. 1993. Hydrography and vertical fluxes of heat and salt northeast of Svalbard in autumn. Journal of Geophysical Research: Oceans, 98(C6): 10013–10024. doi: 10.1029/93JC00937  Steele M, Morison J, Ermold W, et al. 2004. Circulation of summer Pacific halocline water in the Arctic Ocean. Journal of Geophysical Research: Oceans, 109(C2): C02027  Thorndike A S, Colony R. 1982. Sea ice motion in response to geostrophic winds. Journal of Geophysical Research: Oceans, 87(C8): 5845–5852. doi: 10.1029/JC087iC08p05845  Timmermans M L, Proshutinsky A, Golubeva E, et al. 2014. Mechanisms of Pacific summer water variability in the Arctic's Central Canada Basin. Journal of Geophysical Research: Oceans, 119(11): 7523–7548. doi: 10.1002/2014JC010273  Timmermans M L, Toole J, Krishfield R, et al. 2008. Ice-Tethered Profiler observations of the double-diffusive staircase in the Canada Basin thermocline. Journal of Geophysical Research: Oceans, 113(C1): C00A02  Toole J M, Timmermans M L, Perovich D K, et al. 2010. Influences of the ocean surface mixed layer and thermohaline stratification on Arctic Sea ice in the central Canada Basin. Journal of Geophysical Research: Oceans, 115(C10): C10018  Turner J S. 2010. The melting of ice in the Arctic Ocean: the influence of double-diffusive transport of heat from below. Journal of Physical Oceanography, 40(1): 249–256. doi: 10.1175/2009JPO4279.1  Woodgate R A, Aagaard K, Swift J H, et al. 2007. Atlantic water circulation over the Mendeleev Ridge and Chukchi Borderland from thermohaline intrusions and water mass properties. Journal of Geophysical Research: Oceans, 112(C2): C02005  Yang Jiayan. 2009. Seasonal and interannual variability of downwelling in the Beaufort Sea. Journal of Geophysical Research: Oceans, 114(C1): C00A14  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: 10.1175/JPO-D-16-0256.1  Zhang Jinlun, Steele M. 2007. Effect of vertical mixing on the Atlantic Water layer circulation in the Arctic Ocean. Journal of Geophysical Research: Oceans, 112(C4): C04S04  Zhao Jinping, Wang Weibo, Kang S H, et al. 2015. Optical properties in waters around the Mendeleev Ridge related to the physical features of water masses. Deep Sea Research Part II: Topical Studies in Oceanography, 120: 43–51. doi: 10.1016/j.dsr2.2015.04.011  Zhong Wenli, Zhao Jinping. 2014. Deepening of the Atlantic Water core in the Canada Basin in 2003–11. Journal of Physical Oceanography, 44(9): 2353–2369. doi: 10.1175/JPO-D-13-084.1  Zhong Wenli, Guo Guijun, Zhao Jinping, et al. 2018. Turbulent mixing above the Atlantic Water around the Chukchi Borderland in 2014. Acta Oceanologica Sinica, 37(3): 31–41. doi: 10.1007/s13131-018-1198-0  Zhong Wenli, Steele M, Zhang Jinlun, et al. 2019. Circulation of Pacific winter water in the Western Arctic Ocean. Journal of Geophysical Research: Oceans, 124(2): 863–881. doi: 10.1029/2018JC014604
- 文章访问数: 26
- HTML全文浏览量: 12
- 被引次数: 0