Formation of Central Mode Water based on two zonal hydrographic sections in spring 2013 and 2016

Two zonal high-density hydrographic sections along 41° N and 37.5° N east of Japan were occupied in April 2013 and June 2016 to examine the formation of Central Mode Water (CMW) and Transition Region Mode Water (TRMW) in relation to fronts and eddies. In the 41° N section traversing the meandering s...

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Bibliographic Details
Published in:Journal of oceanography 2020-10, Vol.76 (5), p.373-388
Main Authors: Oka, Eitarou, Kouketsu, Shinya, Yanagimoto, Daigo, Ito, Daiki, Kawai, Yoshimi, Sugimoto, Shusaku, Qiu, Bo
Format: Article
Language:English
Subjects:
Alliances
Bifurcations
Current rings
Earth and Environmental Science
Earth Sciences
Eddies
Freshwater & Marine Ecology
Fronts
Hydrographic sections
Meandering
Oceanography
Original Article
Potential vorticity
Subduction
Vortices
Vorticity
Water
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Summary:Two zonal high-density hydrographic sections along 41° N and 37.5° N east of Japan were occupied in April 2013 and June 2016 to examine the formation of Central Mode Water (CMW) and Transition Region Mode Water (TRMW) in relation to fronts and eddies. In the 41° N section traversing the meandering subarctic front, the denser variety of CMW (D-CMW) and TRMW was formed continuously on both sides of the front, except for the part of the section located south of the Kuroshio bifurcation front where the lighter variety of CMW (L-CMW) and D-CMW was formed instead. L-CMW and D-CMW were also formed in the eastern part of the 37.5° N section between the Kuroshio Extension front and the Kuroshio bifurcation front, but were hardly formed in the western part of the section west of the bifurcation point of the two fronts. D-CMW and TRMW pycnostads in the western part of the 41° N section observed in April 2013 tended to exhibit more than one core (vertical minimum of potential vorticity), which might be formed by destruction of deep winter mixed layers. Such multiple-core structure was also observed in L-CMW and D-CMW pycnostads in the eastern part of both the sections south of the Kuroshio bifurcation front in June 2016, being particularly abundant in three anticyclonic eddies. It was likely to be formed by the exchange of low-potential vorticity water among the eddies and the ambient region in association with eddy-to-eddy interaction, suggesting a new mechanism of mode water subduction.
ISSN:0916-8370
1573-868X
DOI:10.1007/s10872-020-00551-9