Journal of Oceanography

, Volume 68, Issue 1, pp 79–92 | Cite as

Roles of mode waters in the formation and maintenance of central water in the North Pacific

Special Section: Original Article New developments in mode-water research: Dynamic and climatic effects


This study describes the three-dimensional distributions of the Turner angle (Tu) and the potential vorticity (PV) of the main pycnocline water in the subtropical North Pacific (10–50°N, 120°E–120°W) using a large in situ CTD data set taken by the Argo profiling floats during June to October of 2001–2009 to clarify the detailed distribution of the central water and the mode waters as well as the relationship between these water masses. The ventilated part of the main pycnocline water (σ θ < 26.7 kg m−3) in the subtropical gyre generally displays a sharp peak in Tu value of 59° in the histogram. The Tu histograms for 10° × 10° geographical boxes mostly show that the mode for the Tu value is 59° too, but they also show some regional differences, suggesting some types of relations with the North Pacific mode waters. To further investigate this relationship, the appearance probability density function of the central water (defined as the main pycnocline water with Tu = 56°–63°) and those of the mode waters with PVs lower than the critical value on each isopycnal surface were analyzed. The distribution area of the central mode water (CMW) corresponds so well with that of the central water that a direct contribution of the CMW to the formation and maintenance of the central water is suggested. On the other hand, the distribution areas of subtropical mode water (STMW), Eastern STMW, and transition region mode water do not correspond to that of the central water. Nevertheless, indirect contributions of these mode waters to the formation and maintenance of the central water through salt finger type convection or diapycnal mixing are suggested.


Mode water Central water Argo 



The authors wish to express their gratitude to members of the Physical Oceanography Group at Tohoku University and to two anonymous reviewers for their valuable comments. The first author (KT) was supported by the 21st-Century Center-Of-Excellence (COE) Program, “Advanced Science and Technology Center for the Dynamic Earth (E-ASTEC),” and the Global COE Program, “Global Education and Research Center for Earth and Planetary Dynamics” at Tohoku University. This study was partly supported by funds from a grant-in-aid for Scientific Research in Priority Areas—“Western Pacific Air–Sea Interaction Study (W-PASS)”—under grants 19030004 and 21014004 from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan, and from “Studies on Prediction and Application of Fish Species Alteration (SUPRFISH)” sponsored by the Agriculture, Forestry, and Fisheries Research Council (AFFRC), Japan.


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Copyright information

© The Oceanographic Society of Japan and Springer 2011

Authors and Affiliations

  1. 1.Department of Geophysics, Graduate School of ScienceTohoku UniversitySendaiJapan
  2. 2.Japan Agency for Marine-Earth Science and TechnologyYokosukaJapan

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