Advertisement

Acta Oceanologica Sinica

, Volume 37, Issue 3, pp 51–62 | Cite as

On the subtropical Northeast Pacific mixed layer depth and its influence on the subduction

  • Ruibin Xia
  • Chengyan Liu
  • Chen Cheng
Article

Abstract

The present climate simulations of the mixed layer depth (MLD) and the subduction rate in the subtropical Northeast Pacific are investigated based on nine of the CMIP5 models. Compared with the observation data, spatial patterns of the MLD and the subduction rate are well simulated in these models. The spatial pattern of the MLD is nonuniform, with a local maximum MLD (>140 m) region centered at (28°N, 135°W) in late winter. The nonuniform MLD pattern causes a strong MLD front on the south of the MLD maximum region, controls the lateral induction rate pattern, and then decides the nonuniform distribution of the subduction rate. Due to the inter-regional difference of the MLD, we divide this area into two regions. The relatively uniform Ekman pumping has little effect on the nonuniform subduction spatial pattern, though it is nearly equal to the lateral induction in values. In the south region, the northward warm Ekman advection (–1.75×10–7 K/s) controls the ocean horizontal temperature advection (–0.85×10–7 K/s), and prevents the deepening of the MLD. In the ensemble mean, the contribution of the ocean advection to the MLD is about–29.0 m/month, offsetting the sea surface net heat flux contribution (33.9 m/month). While in the north region, the southward cold advection deepens the MLD (21.4 m/month) as similar as the heat flux (30.4 m/month). In conclusion, the nonuniform MLD pattern is dominated by the nonuniform ocean horizontal temperature advection. This new finding indicates that the upper ocean current play an important role in the variability of the winter MLD and the subduction rate.

Keywords

mixed layer depth mixed layer depth front subduction horizontal temperature advection nonuniform 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Notes

Acknowledgments

The authors appreciate World Climate Research Programme’s Working Group on Coupled Modeling, which is responsible for CMIP5, and thank the climate modeling groups (listed in Table 1) for producing and making available their model output.

References

  1. Carton J A, Giese B S. 2008. A reanalysis of ocean climate using Simple Ocean Data Assimilation (SODA). Monthly Weather Review, 136(8): 2999–3017CrossRefGoogle Scholar
  2. Dawe J T, Thompson L A. 2007. PDO-related heat and temperature budget changes in a model of the North Pacific. Journal of Climate, 20(10): 2092–2108CrossRefGoogle Scholar
  3. de Boyer Montégut C, Madec G, Fischer A S, et al. 2004. Mixed layer depth over the global ocean: an examination of profile data and a profile-based climatology. Journal of Geophysical Research, 109(C12): C12003CrossRefGoogle Scholar
  4. Deser C, Blackmon M L. 1995. On the relationship between tropical and North Pacific sea surface temperature variations. Journal of Climate, 8(6): 1677–1680CrossRefGoogle Scholar
  5. Dong Shenfu, Sprintall J, Gille S T, et al. 2008. Southern Ocean mixedlayer depth from Argo float profiles. Journal of Geophysical Research, 113(C6): C06013CrossRefGoogle Scholar
  6. Dunne J P, John J C, Adcroft A J, et al. 2012. GFDL’s ESM2 global coupled climate-carbon earth system models. Part I: physical formulation and baseline simulation characteristics. Journal of Climate, 25(19): 6646–6665Google Scholar
  7. Hu Haibo, Liu Qinyu, Zhang Yuan, et al. 2011. Variability of subduction rates of the subtropical North Pacific mode waters. Chinese Journal of Oceanology and Limnology, 29(5): 1131–1141CrossRefGoogle Scholar
  8. Kara A B, Rochford P A, Hurlburt H E. 2003. Mixed layer depth variability over the global ocean. Journal of Geophysical Research, 108(C3): 3079CrossRefGoogle Scholar
  9. Kraus E B. 1972. Atmospheric–Ocean Interaction. London: Oxford University Press, 255Google Scholar
  10. Levitus S. 1982. Climatological atlas of the world ocean. Eos, Transactions American Geophysical Union, 64(49): 962–963CrossRefGoogle Scholar
  11. Levitus S, Boyer T P. 1994. World Ocean Atlas 1994. Volume 4, Temperature. Washington, DC: National Environmental Satellite, Data, and Information ServiceGoogle Scholar
  12. Liu Chengyan, Wang Zhaomin. 2014. On the response of the global subduction rate to globalwarming in coupled climate models. Advances in Atmospheric Sciences, 31(1): 211–218CrossRefGoogle Scholar
  13. Liu Chengyan, Wang Zhaomin, Li Bingrui, et al. 2017. On the response of subduction in the South Pacific to an intensification of westerlies and heat flux in an eddy permitting ocean model. Advances in Atmospheric Sciences, 34(4): 521–531CrossRefGoogle Scholar
  14. Liu Chengyan, Wu Lixin. 2012. An intensification trend of South Pacific mode water subduction rates over the 20th century. Journal of Geophysical Research, 117(C7): C07009Google Scholar
  15. Luo Yiyong, Liu Qinyu, Rothstein L M. 2009. Simulated response of North Pacific Mode Waters to global warming. Geophysical Research Letters, 36(23): L23609CrossRefGoogle Scholar
  16. Marshall J C, Nurser A J G, Williams R G. 1993. Inferring the subduction rate and period over the North Atlantic. Journal of Physical Oceanography, 23(7): 1315–1329CrossRefGoogle Scholar
  17. Monterey G I, Levitus S. 1997. Climatological Cycle of Mixed Layer Depth in the World Ocean. Washington DC: U.S. Government Printing Office, NOAA NESDIS, 5Google Scholar
  18. Pan Aijun, Wan Xiaofang, Liu Qinyu. 2011. Diagnostics of mixed-layer thermodynamics in the formation regime of the North Pacific subtropical mode water. Journal of Tropical Oceanography (in Chinese), 30(5): 8–18Google Scholar
  19. Pond S, Pickard G L. 1983. Introductory Dynamical Oceanography. 2nd ed. New York: Pergamon, 379Google Scholar
  20. Qiu Bo. 2002. The Kuroshio Extension system: its large-scale variability and role in the midlatitude ocean-atmosphere interaction. Journal of Oceanography, 58(1): 57–75CrossRefGoogle Scholar
  21. Qiu Bo, Chen Shuiming. 2006. Decadal variability in the formation of the North Pacific Subtropical Mode Water: oceanic versus atmospheric control. Journal of Physical Oceanography, 36(7): 1365–1380CrossRefGoogle Scholar
  22. Qiu Bo, Kelly K A. 1993. Upper-ocean heat balance in the Kuroshio Extension region. Journal of Physical Oceanography, 23(9): 2027–2041CrossRefGoogle Scholar
  23. Qu Tangdong, Chen Ju. 2009. A North Pacific decadal variability in subduction rate. Geophysical Research Letters, 36(22): L22602CrossRefGoogle Scholar
  24. Stommel H. 1979. Determination of water mass properties of water pumped down from the Ekman layer to the geostrophic flow below. Proceedings of the National Academy of Sciences of the United States of America, 76(7): 3051–3055CrossRefGoogle Scholar
  25. Suga T, Motoki K, Aoki Y, et al. 2004. The North Pacific climatology of winter mixed layer and Mode Waters. Journal of Physical Oceanography, 34(1): 3–22CrossRefGoogle Scholar
  26. Toyoda T, Awaji T, Ishikawa Y, et al. 2004. Preconditioning of winter mixed layer in the formation of North Pacific Eastern Subtropical Mode Water. Geophysical Research Letters, 31: L17206CrossRefGoogle Scholar
  27. Taylor K E, Stouffer R J, Meehl G A. 2012. An overview of CMIP5 and the experiment design. Bulletin of the American Meteorological Society, 93(4): 485–498CrossRefGoogle Scholar
  28. Tsujino H, Yasuda T. 2004. Formation and circulation of mode waters of the North Pacific in a high-resolution GCM. Journal of Physical Oceanography, 34(2): 399–415CrossRefGoogle Scholar
  29. Williams R G. 1991. The role of the mixed layer in setting the potential vorticity of the main thermocline. Journal of Physical Oceanography, 21(12): 1803–1814CrossRefGoogle Scholar
  30. Woods J D. 1985. The physics of pycnocline ventilation. In: Nihoul J C J, ed. Coupled Ocean-Atmosphere Models. London: Elsevier, 543–590CrossRefGoogle Scholar
  31. Xia Ruibin, Liu Qinyu, Xu Lixiao, et al. 2015. North Pacific eastern subtropical mode water simulation and future projection. Acta Oceanologica Sinica, 34(3): 25–30CrossRefGoogle Scholar
  32. Xie Shangping, Deser C, Vecchi G A, et al. 2010. Global warming pattern formation: sea surface temperature and rainfall. Journal of Climate, 23(4): 966–986CrossRefGoogle Scholar
  33. Xie Shangping, Kunitani T, Kubokawa A, et al. 2000. Interdecadal thermocline variability in the North Pacific for 1958-97: a GCM simulation. Journal of Physical Oceanography, 30(11): 2798–2813CrossRefGoogle Scholar
  34. Xie Shangping, Xu Lixiao, Liu Qinyu, et al. 2011. Dynamical role of mode water ventilation in decadal variability in the central subtropical gyre of the North Pacific. Journal of Climate, 24(4): 1212–1225CrossRefGoogle Scholar
  35. Xu Lixiao, Li Peilaing, Xie Shangping, et al. 2016. Observing mesoscale eddy effects on mode-water subduction and transport in the North Pacific. Nature Communications, 7: 10505CrossRefGoogle Scholar
  36. Xu Lixiao, Xie Shangping, Liu Qinyu, et al. 2012. Response of the North Pacific subtropical countercurrent and its variability to global warming. Journal of Oceanography, 68(1): 127–137CrossRefGoogle Scholar

Copyright information

© The Chinese Society of Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Polar Climate System and Global Change LaboratoryNanjing University of Information Science & TechnologyNanjingChina

Personalised recommendations