Advertisement

Ocean Science Journal

, Volume 52, Issue 3, pp 307–327 | Cite as

Surface circulation and vertical structure of current off the Keum River estuary, Korea in later spring 2008

  • Sang-Ho LeeEmail author
  • Moon-Jin Kim
  • Chang-Soo Kim
  • Byoung-Ju Choi
  • Hong-Bae Moon
Article
  • 175 Downloads

Abstract

To examine the surface circulation and vertical structure of currents in the region of the Keum River (KR) plume, we analyzed the subinertial surface currents obtained by high frequency radar and the vertical profiles of currents measured at a station (M1) located 10 km distance from the estuary mouth for one month in late spring 2008. Monthly-mean surface circulation is composed of the westward flow from the estuary mouth and the northward flow in the offshore. These surface mean currents are a gradient (geostrophic) current around the monthly-mean plume bulge. Dominant variabilities of the surface currents, winds, and KR-outflow are decomposed by the Empirical Orthogonal Functions (EOF). The first current EOF mode, explaining 39% of total variation, is primarily related to the first wind EOF mode varying along the coast and the second current mode, explaining 33% of total variation, is mainly related to the first KR-outflow EOF mode varying along the mean KR-outflow direction. Meanwhile, vertical profile of the monthly-mean current at M1 shows a two-layer structure of the current flowing offshore (onshore) in the upper (lower) layer because the water column is divided by a pycnocline at 7-9 m depths below the plume water. This two layer structure is a background persisting current structure, at least in spring, maintained by the geostrophic balance induced by the sea level slope and density gradient along the line normal to the westward mean surface current direction due to monthly-mean plume bulge off the KR estuary. EOF analysis of vertical current profiles reveals that the first mode, explaining 43% of total variation, represents the two-layer structure of the current variability. The upper-layer current varies along a line normal to the mainland coastline and the low-layer one varies approximately along a line parallel to the coastline, with direction difference of about 115° between the upper-and low-layer. From the correlation analysis it is found that 60% of the first mode variation is influenced by the first mode of KR-outflow and 36% by the first mode of wind. Any forcing modes of KR-outflow and wind influencing the other current vertical modes could not be found in the present study.

Keywords

Keum River surface plume current two-layer current structure geostrophic balance 

References

  1. Avicola G, Huq P (2003) The role of outflow geometry in the formation of the recirculating bulge region in coastal buoyant outflows. J Mar Res 61(4):411–434CrossRefGoogle Scholar
  2. Barrick DE, Evans MW, Weber BL (1977) Ocean surface currents mapped by radar. Science 198:138–144CrossRefGoogle Scholar
  3. Baek HY (2008) Characteristics of sea level, tidal and subinertial current variations in the Saemangeum coastal area. M.D. Thesis, Kunsan National University, 85 p (in Korean)Google Scholar
  4. Bowden KF (1983) Physical oceanography of coastal waters. Ellis-Horwood, New York, 302 pGoogle Scholar
  5. Chant RJ, Glenn SM, Hunter E, Kohut J, Chen RF, Houghton RW, Bosch J, Schofield O (2008) Bulge formation of a buoyant river outflow. J Geophys Res 113:C01017. doi:10.1029/2007JC004100CrossRefGoogle Scholar
  6. Chao SY (1990) Tidal modulation of estuarine plumes. J Phys Oceanogr 20(7):1115–1123CrossRefGoogle Scholar
  7. Chapman RD, Shay LK, Graber HC, Edson JB, Karachintsev A, Trump CL, Ross DB (1997) On the accuracy of ocean radar surface current measurements: inter-comparisons with shipbased sensors. J Geophys Res 102(C8):18737–18748CrossRefGoogle Scholar
  8. Choi B-J, Wilkin JL (2007) The effect of wind on the dispersal of the Hudson River plume. J Phys Oceanogr 37:1878–1897. doi:10.1175/JPO3081.1CrossRefGoogle Scholar
  9. Choi HY, Lee SH, Yoo KY (1999) Salinity distribution in the mideastern Yellow Sea during the high discharge from the Keum River weir. J Korean Soc Oceanogr 4:1–9 (in Korean)Google Scholar
  10. de Boer GJ, Pietrzak JD, Winterwerp JC (2008) Using the potential energy anomaly equation to investigate tidal straining and advection of stratification in a region of freshwater influence. Ocean Model 22:1–11CrossRefGoogle Scholar
  11. Emery WJ, Thomson RE (2004) Data analysis methods in physical oceanography. Elsevier, Amsterdam, 638 pGoogle Scholar
  12. Ekman WW (1905) On the influence of the earth’s rotation on ocean currents. Ark Mar Astr Fys 2:1–53Google Scholar
  13. Fernandez DM, Vesecky JF, Teague CC (1996) Measurements of upper ocean surface current shear with high frequency radar. J Geophys Res 101(C12):28615–28625CrossRefGoogle Scholar
  14. Fong DA, Geyer WR, Signell RP (1997) The wind-forced response on a buoyant coastal current: observations of the western Gulf of Maine plume. J Marine Syst 12:69–81CrossRefGoogle Scholar
  15. Fong D, Geyer RW (2002) The alongshore transport of freshwater in a surface-trapped river plume. J Phys Oceanogr 32:957–972CrossRefGoogle Scholar
  16. Garvine RW (1995) A dynamical system for classifying buoyant coastal discharges. Cont Shelf Res 15(13):1585–1596CrossRefGoogle Scholar
  17. Halverson MJ, Pawlowicz R (2008) Estuarine forcing of a river plume by river flow and tides. J Geophys Res 113:C09033. doi:10.1029/2008JC004844CrossRefGoogle Scholar
  18. Heaps NS (1972) Estimation of density currents in the Liverpool Bay area of the Irish Sea. Geophys J Roy Astr S 30 415–432CrossRefGoogle Scholar
  19. Hickey BM, Pietrafesa LJ, Jay DA, Boicourt WC (1998) The Columbia River plume study: subtidal variability in the velocity and salinity fields. J Geophys Res 103(C5):10339–10368.CrossRefGoogle Scholar
  20. Hickey B, Geier S, Kachel N, MacFadyen A (2005) A bi-directional river plume: the Columbia in summer. Cont Shelf Res 25: 1631–1656CrossRefGoogle Scholar
  21. Horner-Devine AR, Fong DA, Monismith SG, Maxworthy T (2006) Laboratory experiments simulating a coastal river outflow. J Fluid Mech 555:203–232CrossRefGoogle Scholar
  22. Horner-Devine AR, Jay DA, Orton PM, Spahn EY (2009) A conceptual model of the strongly tidal Columbia River plume. J Marine Syst 78:460–475CrossRefGoogle Scholar
  23. Imasato N (1983) What is tide-induced residual current? J Phys Oceanogr 13:1307–1317CrossRefGoogle Scholar
  24. Jay DA, Pan J, Orton PM, Horner-Devine AR (2009) Asymmetry of Columbia River tidal plume fronts. J Marine Syst 78:442–549. doi:10.1016/j.jmarsys.2008.11.015CrossRefGoogle Scholar
  25. Jurisa JT, Nash JD, Moum JN, Kilcher LF (2016) Controls on turbulent mixing in a strongly stratified and sheared tidal river plume. J Phys Oceanogr 46(8):2373–2388.CrossRefGoogle Scholar
  26. Kim CS, Lee SH, Son YT, Kwon HK, Lee KW, Choi BJ (2008a) Variations in subinertial surface currents observed with HF radar in the coastal waters off the Saemangeum area. J Korean Soc Oceanogr 13(1):56–66 (in Korean)Google Scholar
  27. Kim SR, Terill EJ, Cornuelle BD (2008b) Mapping surface currents from HF radar radial velocity measurements using optimal interpolation. J Geophys Res 113:C10023. doi:10.1029/ 2007JC004244CrossRefGoogle Scholar
  28. Kim SR, Cornuelle BD, Terill EJ (2009) Anisotropic response of surface currents to the wind in a coastal region. J Phys Oceanogr 39(6):1512–1533CrossRefGoogle Scholar
  29. Kundu PK (1976) Ekman veering observed near the ocean bottom. J Phys Oceanogr 6:238–242CrossRefGoogle Scholar
  30. Lee SH, Choi HY, Oh IS (1995) Structure and variability of the Keum River plume in summer. J Korean Soc Oceanogr 30:125–137 (in Korean)Google Scholar
  31. Lee SH, Kwon HK (1999) Physical environment changes in the Keum River estuary by the dyke gate operation. II. Salinity structure and estuary type. J Korean Soc Oceanogr 4:93–100 (in Korean)Google Scholar
  32. Lee SH, Choi HY, Kwon HK (2001) Physical environment changes in the Keum River Estuary due to dike gate pperation: III. Tidal modulation of low-salinity water. J Korean Soc Oceangr 6(3):115–125 (in Korean)Google Scholar
  33. Lee S-H, Choi HY, Son YT, Kwon HK, Kim YK, Yang JS (2003) Low-salinity water and circulation in summer around the Saemangeum area in the west coast of Korea. J Korean Soc Oceanogr 8(2):138–150 (in Korean)Google Scholar
  34. Lee S-H, Moon HB, Baek HY, Kim CS, Son YT, Kwon HK, Choi B-J (2008) On the accuracy of current measurement by HF radar in the coastal sea off the Keum River estuary. J Korean Soc Oceanogr 13(1):42–55 (in Korean)Google Scholar
  35. Lee S-H, Kang CY, Choi B-J, Kim CK (2013) Surface current response to wind and plumes in a bay-shape estuary of the eastern Yellow Sea: ocean radar observation. Ocean Sci J 48(1):117–139CrossRefGoogle Scholar
  36. McCabe RM, MacCready P, Hickey BM (2009) Ebb-tide dynamics and spreading of a large river plume. J Phys Oceanogr 39:2839–2856. doi:10.1175/2009JPO4061.1CrossRefGoogle Scholar
  37. Nash JD, Kilcher LF, Moum JN (2009) Structure and composition of a strongly stratified, tidally pulsed river plume. J Geophys Res 114:C00B12. doi:10.1029/2008JC005036CrossRefGoogle Scholar
  38. Pritchard M, Huntley DA (2006) A simplified energy and mixing budget for a small river plume discharge. J Geophys Res-Oceans 111:C03019. doi:10.1029/2005JC002984Google Scholar
  39. Rikiishi K, Ichiye T (1986) Tidal fluctuation of the surface currents of the Kuroshio in the East China Sea. Prog Oceanogr 17: 193–214CrossRefGoogle Scholar
  40. Shin EJ, Lee S-H, Choi HY (2002) Numerical model study for structure and distribution of the Keum River Plume. J Korean Soc Oceanogr 7:157–170 (in Korean)Google Scholar
  41. Simpson JH (1997) Physical processes in the ROFI regime. J Marine Syst 12:3–16CrossRefGoogle Scholar
  42. Simpson JH, Bowers D (1981) Models of stratification and frontal movements in shelf seas. Deep-Sea Res 28:727–738CrossRefGoogle Scholar
  43. Simpson JH, Brown J, Matthews J, Allen G (1990) Tidal straining, density currents, and stirring in the control of estuarine stratification. Estuaries 13(2):125–132CrossRefGoogle Scholar
  44. Son YT, Lee S-H, Kim CS, Lee JC, Lee GH (2007) Surface current variability in the Keum River Estuary (South Korea) during summer 2002 as observed by high-frequency radar and coastal monitoring buoy. Cont Shelf Res 27:43–63CrossRefGoogle Scholar
  45. Taylor JR, Sarkar S (2008) Stratification effects in a bottom Ekman layer. J Phys Oceanogr 38:2535–2555. doi:10.1175/2008JPO3942.1CrossRefGoogle Scholar
  46. Thompson RORY (1983) Low-pass filters to suppress inertial and tidal frequencies. J Phys Oceanogr 13(6):1077–1083CrossRefGoogle Scholar
  47. Verspecht F, Rippeth TP, Howarth MJ, Souza AJ, Simpson JH, Burchard H (2009) Processes impacting on stratification in a region of freshwater influence: application to Liverpool Bay. J Geophys Res 114:C11022. doi:10.1029/2009JC005475CrossRefGoogle Scholar
  48. Yankovsky AE, Hickey BM, Munchow AK (2001) Impact of variable inflow on the dynamics of a coastal buoyant plume. J Geophys Res 106(C9):19809–19824CrossRefGoogle Scholar

Copyright information

© Korea Institute of Ocean Science & Technology (KIOST) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media B.V. 2017

Authors and Affiliations

  • Sang-Ho Lee
    • 1
    Email author
  • Moon-Jin Kim
    • 1
  • Chang-Soo Kim
    • 1
  • Byoung-Ju Choi
    • 2
  • Hong-Bae Moon
    • 3
  1. 1.Department of Oceanography, Graduate SchoolKunsan National UniversityKunsanKorea
  2. 2.Department of OceanographyChonnam National UniversityGwangjuKorea
  3. 3.Oceantech Co.Deogyang-gu, GoyangKorea

Personalised recommendations