Mixing in the meandering Kuroshio Extension and the formation of North Pacific Intermediate Water

Citation
Tm. Joyce et al., Mixing in the meandering Kuroshio Extension and the formation of North Pacific Intermediate Water, J GEO RES-O, 106(C3), 2001, pp. 4397-4404
Citations number
11
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
ISSN journal
2169-9275 → ACNP
Volume
106
Issue
C3
Year of publication
2001
Pages
4397 - 4404
Database
ISI
SICI code
0148-0227(20010315)106:C3<4397:MITMKE>2.0.ZU;2-K
Abstract
Synoptic hydrographic and velocity data were obtained in the first meander crest and trough of the Kuroshio Extension (KE) from measurements aboard th e R/V Soyo-maru in late May and early June 1998. Measurements indicated tha t the eastward flowing KE had significant (up to 20 cm s(-1)) flow at 1400 in depth and that a subsurface velocity maximum could be seen on the equato rward side of the current. Large salinity differences were found on potenti al densities from 26.2 to 27.2 kg m(-3) that reflected cold, fresh waters o f northern origin and warm, salty subtropical waters. Approaching the first meander crest, northward moving water was saltier than southward moving wa ter at the same density on the downstream side of the crest, approaching th e first trough. The velocity-salinity covariance was high and consistent wi th an eddy diffusivity of order 10(4) m(2) s(-2). With an assumption of qua si-steady meanders, supported by altimeter results, density advection can b e used to infer vertical velocities of 50-100 m d(-1) in the meanders. Asce nding water was found to be saltier than the descending water, especially i n a potential density range about 26.8 kg m(-3) within the core of North Pa cific Intermediate Water (NPIW)). However, the two patterns of horizontal v elocity-salinity covariance and vertical velocity-salinity covariance were not consistent with one another. The mixing of Oyashio and Kuroshio source waters, thought to be critical to the formation of NPIW, is clearly tied to cross-frontal flows within the meandering KE, with Kuroshio water ejected northward as water parcels approach the first meander crest and Oyashio wat er injected southward into the flow as parcels approach the first trough.