Journal of Oceanography

, Volume 65, Issue 1, pp 1–16 | Cite as

Mixed layer depth climatology of the North Pacific based on Argo observations

  • Yuko Ohno
  • Naoto Iwasaka
  • Fumiaki Kobashi
  • Yoshiko Sato
Original Articles


A monthly mean climatology of the mixed layer depth (MLD) in the North Pacific has been produced by using Argo observations. The optimum method and parameter for evaluating the MLD from the Argo data are statistically determined. The MLD and its properties from each density profile were calculated with the method and parameter. The monthly mean climatology of the MLD is computed on a 2° × 2° grid with more than 30 profiles for each grid. Two bands of deep mixed layer with more than 200 m depth are found to the north and south of the Kuroshio Extension in the winter climatology, which cannot be reproduced in some previous climatologies. Early shoaling of the winter mixed layer between 20–30°N, which has been pointed out by previous studies, is also well recognized. A notable feature suggested by our climatology is that the deepest mixed layer tends to occur about one month before the mixed layer density peaks in the middle latitudes, especially in the western region, while they tend to coincide with each other in higher latitudes.


Mixed layer depth Argo data mixed layer climatology 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Akima, H. (1970): A new method of interpolation and smooth curve fitting based on local procedures. J. Associ. Comput. Mach., 17, 589–602.Google Scholar
  2. Alexander, M. A., M. S. Timlin and J. D. Scott (2001): Winter-to-winter recurrence of sea surface temperature, salinity and mixed layer depth anomalies. Prog. Oceanogr., 49, 41–61.CrossRefGoogle Scholar
  3. Argo Data Management Team (2002): Report of the Argo Data Management Meeting. Proc. Argo Data Management Third Meeting, Ottawa, ON, Canada, Marine Environmental Data, 42 pp.Google Scholar
  4. Babu, K. N., R. Sharma, N. Agarwal, V. K. Agarwal and R. A. Weller (2004): Study of the mixed layer depth variations within the north Indian Ocean using a 1-D model. J. Geophys. Res., 109, C08016, doi:10.1029/2003JC002024.CrossRefGoogle Scholar
  5. Bindoff, N. L., J. Willebrand, V. Artale, A, Cazenave, J. Gregory, S. Gulev, K. Hanawa, C. Le Quéré, S. Levitus, Y. Nojiri, C. K. Shum, L. D. Talley and A. Unnikrishnan (2007): Observations: Oceanic climate change and sea level. In Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, ed. by S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor and H. L. Miller. Cambridge University Press, Cambridge, United Kingdom and New York, NY, U.S.A.Google Scholar
  6. Brainerd, K. E. and M. C. Gregg (1995): Surface mixed and mixing layer depths. Deep-Sea Res. I, 42, 1521–1543.CrossRefGoogle Scholar
  7. Conkright, M. E, S. Levitus and T. P. Boyer (1994): World Ocean Atlas 1994, Volume 1: Nutrients. NOAA Atlas NESDIS 1, 150 pp.Google Scholar
  8. Conkright, M. E., J. I. Antonov, O. Baranova, T. P. Boyer, H. E. Garcia, R. Gelfeld, D. Johnson, R. A. Locarnini, P. P. Murphy, T. D. O’Brien, I. Smolyar and C. Stephens (2002): NOAA Atlas NESDIS 42, WORLD OCEAN DATABASE 2001 Volume 1: Introduction. U.S. Gov. Printing Office, Washington, D.C., 160 pp.Google Scholar
  9. 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 profile-based climatology. J. Geophys. Res., 109, C12003, doi:10.1029/2004JC002378.CrossRefGoogle Scholar
  10. Deser, C., M. A. Alexander and M. T. Timlin (1996): Upper-ocean thermal variations in the North Pacific during 1970–1991. J. Climate, 9, 1840–1855.CrossRefGoogle Scholar
  11. Freeland, H., K. Denman, C. S. Wong, F. Whitney and R. Jacques (1997): Evidence of change in the winter mixed layer in the Northeast Pacific. Deep-Sea Res. I, 44, 2117–2129.CrossRefGoogle Scholar
  12. Hanawa, K. and S. Sugimoto (2004): ’Reemergence’ areas of winter sea surface temperature anomalies in the world’s oceans. Geophys. Res. Lett., 31, L10303, doi:10.1029/ 2004GL019904.CrossRefGoogle Scholar
  13. Hanawa, K. and L. D. Talley (2001): Mode water. p. 373–386. In Ocean Circulation and Climate, ed. by G. Siedler et al., Academic Press, New York.CrossRefGoogle Scholar
  14. Hautala, S. L. and D. H. Roemmich (1998): Subtropical mode water in the Northeast Pacific Basin. J. Geophys. Res., 103, 13055–13066.CrossRefGoogle Scholar
  15. Iwasaka, N. and K. Hanawa (1990): Climatologies of marine meteorological variables and surface fluxes in the North Pacific computed from COADS. Tohoku Geophysical Journal, 33, 185–239.Google Scholar
  16. Iwasaka, N., F. Kobashi, Y. Kinoshita and Y. Ohno (2006): Seasonal variations of the upper ocean in the western North Pacific observed by an Argo float. J. Oceanogr., 62, 481–492.CrossRefGoogle Scholar
  17. Josey, S. A., E. C. Kent and P. K. Taylor (1998): The Southampton Oceanography Centre (SOC) Ocean—Atmosphere heat, momentum and freshwater flux atlas. Report of the Southampton Oceanography Centre (6), p. 1–30.Google Scholar
  18. Kara, A. B., P. A. Rochford and H. E. Hurlburt (2000a): An optimal definition for ocean mixed layer depth. J. Geophys. Res., 105, 16,803–16,821.Google Scholar
  19. Kara, A. B., P. A. Rochford and H. E. Hurlburt (2000b): Mixed layer depth variability and barrier layer formation over the North Pacific Ocean. J. Geophys. Res., 105, 16,783–16,801.Google Scholar
  20. Kara, A. B., P. A. Rochford and H. E. Hurlburt (2003): Mixed layer depth variability over the global ocean. J. Geophys. Res., 108, 3079, doi:10.1029/2000JC000736.CrossRefGoogle Scholar
  21. Kubokawa, A. and T. Inui (1999): Subtropical Countercurrent in an Idealized Ocean GCM. J. Phys. Oceanogr., 29, 1303–1313.CrossRefGoogle Scholar
  22. Lorbacher, K., D. Dommenget, P. P. Niiler and A. Koh (2006): Ocean mixed layer depth: A subsurface proxy of ocean-atmosphere variability. J. Geophys. Res., 111, C07010, doi:10.1029/2003JC002157.CrossRefGoogle Scholar
  23. Monterey, G. and S. Levitus (1997): Seasonal variability of mixed layer depth for the world ocean. NOAA Atlas NESDIS, 14, U.S. Gov. Printing Office, Washington, D.C., 100 pp.Google Scholar
  24. Nishikawa, S. and A. Kubokawa (2007): Mixed layer depth front and subduction of low potential vorticity water in an idealized ocean GCM. J. Oceanogr., 63, 125–134.CrossRefGoogle Scholar
  25. Ohno, Y., T. Kobayashi, N. Iwasaka and T. Suga (2004): The mixed layer depth in the North Pacific as detected by the Argo floats. Geophys. Res. Lett., 31, L11306, doi:10.1029/ 2004GL019576.CrossRefGoogle Scholar
  26. Oka, E. (2002): A simulation for deployment of ARGO floats. ARGO Technical Report FY2001, JAMSTEC, 1–8.Google Scholar
  27. Oka, E. and T. Suga (2005): Differential formation and circulation of North Pacific Central Mode Water. J. Phys. Oceanogr., 35, 1997–2011.CrossRefGoogle Scholar
  28. Oka, E., L. D. Talley and T. Suga (2007): Temporal variability of winter mixed layer in the mid-to high-latitude North Pacific. J. Oceanogr., 63, 293–307.CrossRefGoogle Scholar
  29. Pavlidis, T. and S. L. Horowitz (1974): Segmentation of plan curves. IEEE Trans. Comput., C-23, 860–870.CrossRefGoogle Scholar
  30. Polovina, J. J., G. T. Mitchum and G. T. Evans (1995): Decadal and basin-scale variation in mixed layer depth and the impact on biological production in the central and North Pacific 1960–88. Deep-Sea Res., 42, 1701–1716.CrossRefGoogle Scholar
  31. Saito, H., T. Suga, K. Hanawa and T. Watanabe (2007): New type of pycnostad in the western subtropical-subarctic transition region of the North Pacific: Transition Region Mode Water. J. Oceanogr., 63, 589–600.CrossRefGoogle Scholar
  32. Sprintall, J. and M. Tomczak (1992): Evidence of the barrier layer in the surface layer of the tropics. J. Geophys. Res., 97, 7305–7316.CrossRefGoogle Scholar
  33. Suga, T. and K. Hanawa (1990): The mixed-layer climatology in the northwestern part of the North Pacific subtropical gyre and the formation area of Subtropical Mode Water. J. Mar. Res., 48, 543–566.Google Scholar
  34. Suga, T., K. Motoki, Y. Aoki and A. MacDonald (2004): The North Pacific climatology of winter mixed layer and mode waters. J. Phys. Oceanogr., 34, 3–22.CrossRefGoogle Scholar
  35. Takeuchi, E. and I. Yasuda (2003): Wintertime shoaling of oceanic surface mixed layer. Geophys. Res. Lett., 30, 22, 2152, doi:10.1029/2003GL018511.CrossRefGoogle Scholar
  36. The Argo Science Team (2000): Report of the Argo Science Team 2nd Meeting (AST-2) March 7–9, 2000, Southampton Oceanography Centre, Southampton, U.K.Google Scholar
  37. The Open University (1995): Seawater: Its Composition, Properties and Behaviour. 2nd ed., Butterworth-Heinemann, Oxford, Boston, Johannesburg, Melbourne, New Delhi, Singapore.Google Scholar
  38. Thomson, R. E. and I. V. Fine (2003): Estimating mixed layer depth from oceanic profile data. J. Atmos. Oceanic Technol., 20, 319–329.CrossRefGoogle Scholar
  39. Uda, M. and K. Hasunuma (1969): The eastward subtropical countercurrent in the western North Pacific Ocean. J. Oceanogr. Soc. Japan, 25, 201–210.Google Scholar
  40. Uehara, H., T. Suga, K. Hanawa and N. Shikama (2003): A role of eddies in formation and transport of North Pacific Subtropical Mode Water. Geophys. Res. Lett., 30, 13, 1705, doi:10.1029/2003GL017542.CrossRefGoogle Scholar
  41. Ueno, H. and I. Yasuda (2005): Temperature inversions in the subarctic North Pacific. J. Phys. Oceanogr., 35, 2444–2456.CrossRefGoogle Scholar
  42. UNESCO (1983): Algorithms for computation of fundamental properties of seawater. UNESCO Technical Paper in Marine Science 44, 53 pp.Google Scholar
  43. Weller, R. A., A. S. Fischera, D. L. Rudnickb, C. C. Eriksenc, T. D. Dickeyd, J. Marrae, C. Foxf and R. Leben (2002): Moored observations of upper-ocean response to the monsoons in the Arabian Sea during 1994–1995. Deep-Sea Res. II, 49, 2195–2230.CrossRefGoogle Scholar
  44. Wong, A. P. S., G. C. Johnson and W. B. Owens (2003): Delayed-mode calibration of autonomous CTD profiling float salinity data by θ-S cimatology. J. Atmos. Oceanic Technol., 20, 308–318.CrossRefGoogle Scholar
  45. Yasuda, I. (2003): Hydrographic structure and variability in the Kuroshio-Oyashio transition area. J. Oceanogr., 59, 389–402.CrossRefGoogle Scholar
  46. Yasuda, I. and T. Watanabe (2007): Chlorophyll a variation in the Kuroshio Extension revealed with a mixed-layer tracking float: Implication on the long-term change of Pacific saury (Cololabis saira). Fish. Oceanogr., 16, 482–488.CrossRefGoogle Scholar
  47. Yasuda, I., K. Okuda and Y. Shimizu (1996): Distribution and modification of North Pacific Intermediate Water in the Kuroshio-Oyashio interfrontal zone. J. Phys. Oceanogr., 26, 448–465.CrossRefGoogle Scholar
  48. Yuan, X. and L. D. Talley (1996): The subarctic frontal zone in the North Pacific: Characteristics of frontal structure from climatological data and synoptic surveys. J. Geophys. Res., 101, C7, 16491–16508.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Yuko Ohno
    • 1
    • 2
  • Naoto Iwasaka
    • 1
    • 3
  • Fumiaki Kobashi
    • 1
  • Yoshiko Sato
    • 1
    • 4
  1. 1.Tokyo University of Marine Science and TechnologyKoto-ku, TokyoJapan
  2. 2.Kisarazu National College of TechnologyChibaJapan
  3. 3.Institute of Observational Research for Global ChangeJAMSTECKanagawaJapan
  4. 4.Shinko Co. Ltd.TokyoJapan

Personalised recommendations