Distribution and Modification of North Pacific Intermediate Water in the Kuroshio-Oyashio Interfrontal Zone

Yasuda, Ichiro; Okuda, Kuniaki; Shimizu, Yoshihisa

doi:10.1175/1520-0485(1996)026<0448:damonp>2.0.co;2

Cited by 229 publications

(199 citation statements)

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“…Those two fronts are meridionally separated by the Kuroshio-Oyashio mixed water region (Yasuda et al 1996, and references therein). Variability of the two fronts could be governed by different dynamics, and if so, they would not necessarily vary in a coherent manner as simulated in the GCM experiments with coarse horizontal resolutions in the previous studies.…”

Section: Introductionmentioning

confidence: 93%

“…From a macroscopic view the KOE region is a zonally oriented SST frontal zone associated with strong eastward surface currents, forming the boundary of the oceanic subtropical and the subpolar gyres (e.g., Yasuda et al 1996). Detailed investigations have shown that SST anomalies (SSTAs) in the KOE region (more specifically, the subarctic frontal zone) associated with decadal variability exhibit no significant simultaneous correlation with those either in the subtropical central North Pacific (specifically, in the subtropical frontal zone) or in the tropical Pacific (Nakamura et al 1997;Nakamura and Yamagata 1999;Tomita et al 2001).…”

Section: Introductionmentioning

confidence: 99%

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Decadal Variability in the Kuroshio–Oyashio Extension Simulated in an Eddy-Resolving OGCM

et al. 2006

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Through analysis of a hindcast integration of an eddy-resolving quasi-global ocean general circulation model, decadal variability in the Kuroshio-Oyashio Extension region is investigated, with particular emphasis on that of the subarctic (Oyashio) and the Kuroshio Extension (KE) fronts. The KE front is deep and accompanied by sharp sea surface height (SSH) gradient with modest sea surface temperature (SST) gradient. In contrast, the subarctic front is shallow and recognized as a zone of tight gradient in SST but not SSH.As a decadal-scale change from a warm period around 1970 to a cool period in the mid-1980s, those fronts in the model migrate southward as observed, and the associated pronounced cooling is confined mainly to those frontal zones. Reflecting the distinctive vertical structures of the fronts, the mixed-layer cooling is the strongest along the subarctic front, whereas the subsurface cooling and the associated salinity changes are the most pronounced along the KE front. Concomitantly with their southward migration, the two fronts have undergone decadal-scale intensification. Associated with reduced heat release into the atmosphere, the cooling in the frontal zones can be attributed neither to the direct atmospheric thermal forcing nor to the advective effect of the intensified KE current, while the advective effect by the intense Oyashio can contribute to the cooling in the subarctic frontal zone.In fact, their time evolution is not found completely coherent, suggesting that their variability may be governed by different mechanisms. Decadal SSH variability in the KE frontal zone seems to be largely explained by propagation of baroclinic Rossby waves forced by anomalous Ekman pumping in the central North Pacific. This process alone cannot fully explain the corresponding variability in the subarctic frontal zone, where eastward propagating SSH anomalies off the Japanese coast seem to be superimposed on the Rossby wave signals.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Decadal Variability in the Kuroshio–Oyashio Extension Simulated in an Eddy-Resolving OGCM

et al. 2006

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“…Yasuda [1997] showed that coastal Oyashio water of the Okhotsk Sea origin intrudes into the Mixed Water Region. Flowing eastward along the Kuroshio Extension and being modified by the mixing with the warm and saline Kuroshio water [Yasuda et al, 1996], Oyashio water feeds North Pacific Intermediate Water (NPIW) [e.g., Sverdrup et al, 1942;Reid, 1965]. Sarmiento et al [2004] pointed out that NPIW formation is crucial in determining low latitude biological productivities, because NPIW with the properties of Oyashio water is rich in nutrients.…”

Section: Introductionmentioning

confidence: 99%

Interdecadal variations of the coastal Oyashio from the 1970s to the early 1990s

Tatebe

Yasuda

2005

Geophysical Research Letters

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The interdecadal migration of the southernmost latitude of the coastal Oyashio is investigated using a simple layered model. Being influenced by the changes of the Aleutian low which shows two dominant oscillations with bi‐decadal and penta‐decadal periods, the southernmost latitude gradually migrated southward from the 1970s to the early 1990s with less bi‐decadal signals. The westward baroclinic Rossby waves on the be‐decadal period could be attenuated effectively by the local wind stress anomalies which changed their signs on the characteristics of the Rossby waves. As a result, only the penta‐decadal signal can survive and reach the western boundary region, and the coastal Oyashio can be affected. In the analyzed period from the 1970s to the 1990s, the transient responses of the North Pacific ocean to the interdecadal changes of the Aleutian low could play a role in cutting off the bi‐decadal signals.

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“…The Kuroshio/Oyashio Interfrontal Zone (K/O zone: Yasuda et al, 1996) is a key area when considering the transport of heat, freshwater and chemical substances across the subpolar front in the North Pacific. Complex mixing of the subtropical-gyre-originated Kuroshio water with the subarctic-gyre-originated Oyashio water occurs in the K/O zone and achieves effective cross-gyre transport (Talley, 1993;Talley et al, 1995;Yasuda et al, 1996;Maksimenko et al, 1997;Yasuda, 1997).…”

Section: Introductionmentioning

confidence: 99%

“…Complex mixing of the subtropical-gyre-originated Kuroshio water with the subarctic-gyre-originated Oyashio water occurs in the K/O zone and achieves effective cross-gyre transport (Talley, 1993;Talley et al, 1995;Yasuda et al, 1996;Maksimenko et al, 1997;Yasuda, 1997). In the subtropical gyre, North Pacific Intermediate Water (NPIW) formed in the K/O zone efficiently spreads the Oyashio-oriented substances farther into the gyre (Tsunogai et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Chemical alternation of waters in the Kuroshio/Oyashio Interfrontal Zone

et al. 1998

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An intensive survey has been conducted of the distributions of some chemical properties (dissolved oxygen, nutrients and carbonate properties) in the Kuroshio/Oyashio Interfrontal Zone. Many low-salinity water patches were found down to depths of 640 m. Each chemical property also showed anomalies in these patches, but the degree of variation showed a low correlation with salinity. This may be due to the high variability of biological processes in the surface waters where these patches are formed. Vertical profiles of the chemical properties were also observed along the Kuroshio extension axis from 140.50°E to 146.75°E. The concentrations of nutrients and total carbonate (TC) in the water having densities greater than σ θ = 26.60 can be regarded as being formed by the isopycnal mixing of the Kuroshio component water and Oyashio component water and biological degradation within the density surfaces. This implies that the transport of chemical properties by the diapycnal mixing is negligible in these density layers in the K/O zone.

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Distribution and Modification of North Pacific Intermediate Water in the Kuroshio-Oyashio Interfrontal Zone

Cited by 229 publications

References 0 publications

Decadal Variability in the Kuroshio–Oyashio Extension Simulated in an Eddy-Resolving OGCM

Decadal Variability in the Kuroshio–Oyashio Extension Simulated in an Eddy-Resolving OGCM

Interdecadal variations of the coastal Oyashio from the 1970s to the early 1990s

Chemical alternation of waters in the Kuroshio/Oyashio Interfrontal Zone

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