Advertisement

Journal of Oceanography

, Volume 71, Issue 1, pp 1–17 | Cite as

Observations of current and mixing around the shelf break in Pribilof Canyon in the Bering Sea

  • T. Tanaka
  • I. Yasuda
  • H. Onishi
  • H. Ueno
  • M. Masujima
Original Article

Abstract

Tide-induced vertical mixing along the shelf break in the eastern Bering Sea is considered one of the main physical processes that sustain local summertime high biological production. However, observations based on microstructure measurements that show enhanced tidal mixing are scarce. In this study, repeated casts of current and turbulence in the vicinity of the shelf break within Pribilof Canyon were conducted over a day in June 2012, enabling us to evaluate the representativeness of the vertical mixing intensity during one day and to detect the relationship between turbulence and tidal current. The cross-sectional distributions of the one-day averaged vertical diffusivity and the turbulent energy dissipation rate showed that strong vertical mixing occurred at the subsurface within about 15 km of the shelf break and near the seabed of the outer shelf. This result agrees with prior observations that were made by us and based on a single profile at each station, which indicated that the observed spatial pattern of turbulence is robust. Diurnal and semidiurnal tidal currents dominated the flow variations off the shelf break, and a statistically significant positive correlation was detected between the vertical shear of the horizontal tidal currents and the turbulent energy dissipation rate. This result suggests that the high turbulent energy dissipation and the enhanced vertical mixing off the shelf break were induced by the strong vertical shear of tidal currents.

Keywords

Vertical turbulent mixing Microstructure observation Tidal current Pribilof Canyon 

Notes

Acknowledgments

This paper forms a part of Ph.D. thesis (Tanaka 2014; Graduate School of Science, The University of Tokyo). We appreciate helpful comments from Profs. T. Hibiya, Y. Masumoto, K. Iga, M. Uematsu, and Y. Tanaka, and two anonymous reviewers. We are grateful to Prof. K. Kuma for kindly providing data on iron concentration. We are also grateful to the officers and crew of the T/S Oshoro-maru and to all of the scientists onboard it for their assistance in conducting observations and their thoughtful arrangement of the field observations. This work was supported by a JSPS Research Fellowship and Grant-in-Aid for Scientific Research (KAKENHI, 20221002/25257206/25121503). We thank Dr. R. Saito for his help obtaining AVISO data.

References

  1. Aguilar-Islas AM, Hurst MP, Buck KN, Sohst B, Smith JG, Lohan MC, Bruland KW (2007) Micro- and macronutrients in the southeastern Bering Sea: insight into iron-replete and iron-depleted regimes. Prog Oceanogr 73:99–126CrossRefGoogle Scholar
  2. Asahara Y, Takeuchi F, Nagashima K, Harada N, Yamamoto K, Oguri K, Tadai O (2012) Provenance of terrigenous detritus of the surface sediments in the Bering and Chukchi Seas as derived from Sr and Nd isotopes: implications for recent climate change in the Arctic regions. Deep Sea Res II 55:155–171. doi: 10.1016/j.dsr2.2011.12.004 CrossRefGoogle Scholar
  3. Carter GS, Gregg MC, Lien R-C (2005) Internal waves, solitary-like waves, and mixing on the Monterey Bay shelf. Cont Shelf Res 25:1499–1520CrossRefGoogle Scholar
  4. Coachman LK (1986) Circulation, water masses, and fluxes on the southeastern Bering Sea shelf. Cont Shelf Res 5:23–108CrossRefGoogle Scholar
  5. Coachman LK, Walsh JJ (1981) A diffusion model of cross-shelf exchange of nutrients in the southeastern Bering Sea. Deep-Sea Res 28:819–846CrossRefGoogle Scholar
  6. Efron B, Gong G (1983) A leisurely look at the bootstrap, the jackknife, and cross-validation. Am Stat 37(1):36–48. doi: 10.2307/2685844 Google Scholar
  7. Egbert GD, Erofeeva SY (2002) Efficient inverse modeling of barotropic ocean tides. J Atmos Oceanic Technol 19:183–204CrossRefGoogle Scholar
  8. Fischer J, Visbeck M (1993) Deep velocity profiling with self-contained ADCPs. J Atmos Ocean Technol 10:764–773CrossRefGoogle Scholar
  9. Foreman MGG, Cummins PF, Cherniawsky JY, Stabeno PJ (2006) Tidal energy in the Bering Sea. J Mar Res 64:797–818CrossRefGoogle Scholar
  10. Gill AE (1982) Atmosphere–ocean dynamics. Academic, San DiegoGoogle Scholar
  11. Hunt GL Jr, Stabeno PJ, Strom S, Napp JM (2008) Patterns of spatial and temporal variation in the marine ecosystem of the southeastern Bering Sea, with special reference to the Pribilof Domain. Deep Sea Res II 55:1919–1944. doi: 10.1016/j.dsr2.2008.04.032 CrossRefGoogle Scholar
  12. Hurst MP, Aguilar-Islas AM, Bruland KW (2010) Iron in the southeastern Bering Sea: elevated leachable particulate Fe in shelf bottom waters as an important source for surface waters. Cont Shelf Res 30:467–480CrossRefGoogle Scholar
  13. Katsumata K, Yasuda I, Kawasaki Y (2001) Direct current measurements at Kruzenshterna Strait in summer. Geophys Res Lett 28:319–322. doi: 10.1029/2000GL011489 CrossRefGoogle Scholar
  14. MacKinnon JA, Gregg MC (2003) Mixing on the late-summer New England shelf: solibores, shear, and stratification. J Phys Oceanogr 33:1476–1492CrossRefGoogle Scholar
  15. MacKinnon JA, Gregg MC (2005) Spring mixing: turbulence and internal waves during restratification on the New England shelf. J Phys Oceanogr 35:2425–2443CrossRefGoogle Scholar
  16. Marshall J, Adcroft A, Hill C, Perelman L, Heisey C (1997) A finite-volume, incompressible Navier–Stokes model for studies of the ocean on parallel computers. J Geophys Res 102(C3):5753–5766Google Scholar
  17. Miura T, Suga T, Hanawa K (2002) Winter mixed layer and formation of dichothermal water in the Bering Sea. J Oceanogr 58:815–823Google Scholar
  18. Mizobata K, Wang J, Saitoh S (2006) Eddy-induced cross-slope exchange maintaining summer high productivity of the Bering Sea shelf break. J Geophys Res 111:C10017. doi: 10.1029/2005JC003335 CrossRefGoogle Scholar
  19. Oakey NS (1982) Determination of the rate of dissipation of turbulent energy from simultaneous temperature and velocity shear microstructure measurements. J Phys Oceanogr 12:256–271CrossRefGoogle Scholar
  20. Osafune S, Yasuda I (2010) Bidecadal variability in the Bering Sea and the relation with 18.6 year period nodal tidal cycle. J Geophys Res 115:C02014. doi: 10.1029/2008JC005110 Google Scholar
  21. Osborn TR (1980) Estimates of the local-rate of vertical diffusion from dissipation measurements. J Phys Oceanogr 10:83–89CrossRefGoogle Scholar
  22. Palmer MR, Rippeth TP, Simpson JH (2008) An investigation of internal mixing in a seasonally stratified shelf sea. J Geophys Res 113:C12005. doi: 10.1029/2007JC004531 CrossRefGoogle Scholar
  23. Schumacher JD, Reed RK (1992) Characteristics of currents over the continental slope of the eastern Bering Sea. J Geophys Res 97:9423–9433CrossRefGoogle Scholar
  24. Simpson JH, Sharples J (2012) Introduction to the physical and biological oceanography of shelf seas. Cambridge University Press, New York 424 ppCrossRefGoogle Scholar
  25. Springer AM, McRoy CP, Flint MV (1996) The Bering Sea Green Belt: shelf-edge processes and ecosystem production. Fish Oceanogr 5:205–223Google Scholar
  26. Stabeno PJ, Schumacher JD, Ohtani K (1999) The physical oceanography of the Bering Sea. In: Loughlin TR, Ohtani K (eds) Dynamics of the Bering Sea: a summary of physical, chemical, and biological characteristics, and a synopsis of research on the Bering Sea. AK-SG-99-03. University of Alaska Sea Grant (PICES), Fairbanks, pp 1–28Google Scholar
  27. Stabeno PJ, Bond NA, Kachel NB, Salo SD, Schumacher JD (2001) On the temporal variability of the physical environment over the south-eastern Bering Sea. Fish Oceanogr 10(1):81–98CrossRefGoogle Scholar
  28. St.Laurent LS, Stringer S, Garrett D, Perrault Joncas D (2003) The generation of internal tides at abrupt topography. Deep Sea Res I 50:987–1003CrossRefGoogle Scholar
  29. Tanaka T, Yasuda I, Kuma K, Nishioka J (2012) Vertical turbulent iron flux sustains the Green Belt along the shelf break in the southeastern Bering Sea. Geophys Res Lett 39:L08603. doi: 10.1029/2012GL051164 Google Scholar
  30. Tanaka T, Yasuda I, Tanaka Y, Carter GS (2013) Numerical study on tidal mixing along the shelf break in the Green Belt in the southeastern Bering Sea. J Geophys Res Oceans 118:6525–6543. doi: 10.1002/2013JC009113 CrossRefGoogle Scholar
  31. Tanaka Y, Yasuda I, Osafune S, Tanaka T, Nishioka J, Volkov YN (2014) Internal tides and turbulent mixing observed in the Bussol Strait. Prog Oceanogr 126:98–108CrossRefGoogle Scholar
  32. Vlasenko V, Stashchuk N, Hutter K (2005) Baroclinic tides: theoretical modeling and observational evidence. Cambridge University Press, Cambridge, p 351CrossRefGoogle Scholar
  33. Walsh JJ et al (1989) Carbon and nitrogen cycling with the Bering/Chukchi Seas: sources regions for organic matter affecting AOU demands of the Arctic ocean. Prog Oceanogr 22:277–359CrossRefGoogle Scholar
  34. Wang T, Chen X, Jiang W (2012) Laboratory experiments on the generation of internal waves on two kinds of continental margin. Geophys Res Lett 39:L04602. doi: 10.1029/2011GL049993 Google Scholar
  35. Whitney FA (2011) Nutrient variability in the mixed layer of the subarctic Pacific Ocean, 1987–2010. J Oceanogr 67:481–492CrossRefGoogle Scholar
  36. Yagi M, Yasuda I (2012) Deep intense vertical mixing in the Bussol Strait. Geophys Res Lett 39:L01602. doi: 10.1029/2011GL050349
  37. Yagi M, Yasuda I, Tanaka T, Tanaka Y, Ono K, Ohshima KI, Katsumata K (2014) Re-evaluation of turbulent mixing vertical structure in the Bussol strait and its impact on water-masses in the Okhotsk Sea and the North Pacific. Prog Oceanogr 126:121–134CrossRefGoogle Scholar

Copyright information

© The Oceanographic Society of Japan and Springer Japan 2014

Authors and Affiliations

  • T. Tanaka
    • 1
  • I. Yasuda
    • 1
  • H. Onishi
    • 2
  • H. Ueno
    • 2
  • M. Masujima
    • 3
  1. 1.Atmosphere and Ocean Research InstituteThe University of TokyoKashiwaJapan
  2. 2.Faculty of Fisheries ScienceHokkaido UniversityHakodateJapan
  3. 3.National Research Institute of Fisheries ScienceFisheries Research AgencyYokohamaJapan

Personalised recommendations