Marine geomorphology

Diagnostics of mixed-layer thermodynamics in the formation regime of the North Pacific subtropical mode water

  • BO Ai-Jun ,
  • MO Xiao-Fang- ,
  • Liu-Qin-Yu-
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  • 1 . Environment and Dynamics Laboratory, Third Institute of Oceanography, Xiamen 361005, China ; 2 . Physical Oceanography Laboratory, Ocean University of China , Qingdao 266003, China

Received date: 2011-11-01

  Revised date: 2011-11-01

  Online published: 2011-11-01

Abstract

Diagnostics of the contributions from the surface heat forcing, vertical entrainment, Ekman advection, and geostrophic advection to the formation of the North Pacific subtropical mode water are performed using the National Centers for Environmental Prediction (NCEP) ocean data and the Comprehensive Ocean-Atmosphere Data Set ( COADS) fluxes. The results suggest that both the surface heat forcing and vertical entrainment dominate the cooling tendency of the wintertime mixed layer in all three mode water formation regions, with relative contributions of 67% and 19% in the North Pacific Subtropical Mode Water (NPSTMW) formation region, respectively; 53% and 21% in the North Pacific Central Mode Water (NPCMW) formation region, and 65% and 30% in the Eastern Subtropical Mode Water (ESMW) formation region. In addition, both the Ekman and geostrophic advection are warm advection in the ESMW formation region, while only the latter is warm advection in the other two mode water formation regions. Further analysis indicates that on interannual and decadal timescales, contributions from the surface heat forcing and geostrophic advection to the wintertime mixed layer cooling trend are 62% and 32% in the NPSTMW formation region, respectively. In the NPCMW formation region, the interannual and decadal variability derives from the combination of Ekman advection (32%), geostrophic advection (30%), and surface heat forcing (25%). By contrast, the surface heat forcing is the most prominent contributor (67%) in in ESMW formation region.

Cite this article

BO Ai-Jun , MO Xiao-Fang- , Liu-Qin-Yu- . Diagnostics of mixed-layer thermodynamics in the formation regime of the North Pacific subtropical mode water[J]. Journal of Tropical Oceanography, 2011 , 30(5) : 8 -18 . DOI: 10.11978/j.issn.1009-5470.2011.05.008

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