Inter-annual zonal shift of the formation region of the lighter variety of the North Pacific Central Mode Water

2015 ◽  
Vol 72 (2) ◽  
pp. 225-234 ◽  
Author(s):  
Yuma Kawakami ◽  
Shusaku Sugimoto ◽  
Toshio Suga
Keyword(s):  
North Pacific ◽  
Mode Water ◽  
Formation Region ◽  
The North ◽  
Central Mode Water ◽  
Central Mode ◽  
The North Pacific

Differential Formation and Circulation of North Pacific Central Mode Water

2005 ◽  
Vol 35 (11) ◽  
pp. 1997-2011 ◽  
Author(s):  
Eitarou Oka ◽  
Toshio Suga
Keyword(s):  
North Pacific ◽  
World Ocean ◽  
Subtropical Gyre ◽  
Mode Water ◽  
Formation Region ◽  
The North ◽  
Central Mode Water ◽  
Central Mode ◽  
The Kuroshio ◽  
The North Pacific

Abstract A repeat hydrographic section along 165°E was analyzed to verify a westward extension of the formation region of the North Pacific Ocean Central Mode Water (CMW) suggested by previous synoptic observations, and to investigate the relation between the formation region and thermohaline fronts. The CMW formation region extends at least as far west as 155°E, much farther than recognized in a previous study based on climatology. It is located in two interfrontal regions between the Kuroshio Extension front and the Kuroshio Bifurcation front (KBF), and between the KBF and the subarctic front, where two types of CMW—namely, the lighter variety with potential density of 25.8–26.2 kg m−3 and the denser one of 26.3–26.4 kg m−3—are formed. How this differential formation of CMW is reflected in its gyrewide distribution was examined using one-time sections of the World Ocean Circulation Experiment (WOCE) Hydrographic Program in the North Pacific. The main circulation paths of the two types of CMW diverge east of the date line; the lighter variety is located in the inner part of the eastern subtropical gyre, and the denser variety is located in the outer part. These results demonstrate that the frontal structure around the northern boundary of the subtropical gyre, particularly the existence of KBF, is essential in determining the properties and the gyrewide distribution of CMW.

scholarly journals Distributions of mixed layer properties in North Pacific water mass formation areas: comparison of Argo floats and World Ocean Atlas 2001

Ocean Science ◽  
2006 ◽  
Vol 2 (1) ◽  
pp. 61-70 ◽  
Author(s):  
F. M. Bingham ◽  
T. Suga
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
World Ocean ◽  
Water Masses ◽  
Mode Water ◽  
The North ◽  
Central Mode Water ◽  
Central Mode ◽  
World Ocean Atlas ◽  
The North Pacific

Abstract. Winter mixed layer characteristics in the North Pacific Ocean are examined and compared between Argo floats in 2006 and the World Ocean Atlas 2001 (WOA01) climatology for a series of named water masses, North Pacific Tropical Water (NPTW), Eastern Subtropical Mode Water (ESTMW), North Pacific Subtropical Mode Water (NPSTMW), Light Central Mode Water (LCMW) and Dense Central Mode Water (DCMW). The WOA01 is found to be in good agreement with the Argo data in terms of water mass volumes, average temperature-salinity (T-S) properties, and outcrop areas. The exception to this conclusion is for the central mode waters, DCMW and LCMW, whose outcropping is shown to be much more intermittent than is apparent in the WOA01 and whose T-S properties vary from what is shown in the WOA01. Distributions of mixed layer T-S properties measured by floats are examined within the outcropping areas defined by the WOA01 and show some shifting of T-S characteristics within the confines of the named water masses. In 2006, all the water masses were warmer than climatology on average, with a magnitude of about 0.5°C. The NPTW, NPSTMW and LCMW were saltier than climatology and the ESTMW and DCMW fresher, with magnitudes of about 0.05. In order to put these results into context, differences between Argo and WOA01 were examined over the North Pacific between 20 and 45° N. A large-scsale warming and freshening is seen throughout this area, except for the western North Pacific, where results were more mixed.

scholarly journals Interdecadal temperature variations in the North Pacific Central Mode Water simulated by an OGCM

2004 ◽  
Vol 60 (5) ◽  
pp. 865-877 ◽  
Author(s):  
Shigeki Hosoda ◽  
Shang-Ping Xie ◽  
Kensuke Takeuchi ◽  
Masami Nonaka
Keyword(s):  
North Pacific ◽  
Mode Water ◽  
Temperature Variations ◽  
The North ◽  
Central Mode Water ◽  
Central Mode ◽  
The North Pacific

Interannual Variation of Annual Subduction Rate in the North Pacific Estimated from a Gridded Argo Product

2015 ◽  
Vol 45 (9) ◽  
pp. 2276-2293 ◽  
Author(s):  
Katsuya Toyama ◽  
Aiko Iwasaki ◽  
Toshio Suga
Keyword(s):  
Pacific Decadal Oscillation ◽  
North Pacific ◽  
Mode Water ◽  
Subtropical Mode Water ◽  
The North ◽  
Central Mode Water ◽  
The Pacific ◽  
Central Mode ◽  
Subduction Rate ◽  
The North Pacific

AbstractSpatiotemporal variability of the subduction rate in the North Pacific from 2005 to 2012 is examined based on the Argo observational data. The subduction rate in the subtropical North Pacific varies significantly from year to year between 25 and 50 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1), and it is well correlated with the Pacific decadal oscillation. The temporal change of the subduction rate is largely determined by that of the late winter mixed layer depth through the lateral induction term. The increase (decrease) in the subduction rate in the subtropical mode water areas accompanies densification (lightening) of the mode density class of the subducted water. The subduction rate variability in the central mode water and eastern subtropical mode water regions is anticorrelated as found in the previous study using the output from an ocean GCM. The subduction rate in the central mode water density range changes dramatically, which is very large in 2005 and 2010 but almost disappears in 2009. The subduction rate variability in the western subtropical mode water regions seems to be correlated with the Pacific decadal oscillation with a lag of a few years.

scholarly journals Chlorofluorocarbons (CFCs) in the North Pacific Central Mode Water: Possibility of under-saturation of CFCs in the wintertime mixed layer

2004 ◽  
Vol 38 (6) ◽  
pp. 643-650 ◽  
Author(s):  
Takayuki Tokieda ◽  
Masao Ishii ◽  
Tamaki Yasuda ◽  
Kazutaka Enyo
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
Mode Water ◽  
The North ◽  
Central Mode Water ◽  
Central Mode ◽  
The North Pacific

scholarly journals The Transition Region Mode Water of the North Pacific and Its Rapid Modification

2011 ◽  
Vol 41 (9) ◽  
pp. 1639-1658 ◽  
Author(s):  
Hiroko Saito ◽  
Toshio Suga ◽  
Kimio Hanawa ◽  
Nobuyuki Shikama
Keyword(s):  
Transition Region ◽  
Mixed Layer ◽  
North Pacific ◽  
Water Masses ◽  
Mode Water ◽  
Formation Region ◽  
Argo Float ◽  
The North ◽  
Modification Process ◽  
The North Pacific

Abstract Using Argo float data, this study examined the formation region, spatial distribution, and modification of transition region mode water (TRMW), which is a recently identified pycnostad in the subtropical–subarctic transition region of the North Pacific, the basin-scale boundary region between subtropical and subarctic water masses. Analyses of the formation fields of water masses within and around the transition region reveal that TRMW forms in a wide area from the western to central transition region and is separated from the denser variety of central mode water (D-CMW) to the south by a temperature and salinity front. TRMW has temperatures of 4°–9°C and salinities of 33.3–34.0, making it colder and fresher than D-CMW. TRMW has a density range of 26.3–26.6 σθ, and thick TRMW is widely distributed in the transition region. However, the range of the T–S properties at TRMW cores is substantially reduced downstream within 10°–20° longitude from the formation region by gradually losing its fresh and cold side. It is also demonstrated that a major part of TRMW of 26.4–26.6 σθ is entrained into the mixed layer in the following winter. Quasi-Lagrangian observation by an isopycnal-following Argo float demonstrates that the double-diffusive salt-finger convection plausibly causes not only rapid erosion of the TRMW pycnostads but also an increase of salinity and temperature at the TRMW cores, at least to some degree. It is demonstrated that strong salt fingering within TRMW is probably caused by geostrophic currents with vertical shear crossing the density-compensating T–S front that brings warm and saline water to the upper TRMW and creates instability in the salinity stratification. This modification process could explain why water that is subducted from the transition region and constitutes the pycnocline of the subtropical gyre in the North Pacific has different T–S properties from the winter mixed layer of the transition region. This knowledge about the modification process of subducted water in the transition region would help to model the permanent pycnocline structure more realistically and to clarify how large signals of decadal and multidecadal variability of sea surface temperature in this region are propagated into the ocean interior.

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