Impact of Ocean Physics on Marine Ecosystems in the Kuroshio and Kuroshio Extension Regions

Sasai, Yoshikazu; Honda, Makio C.; Siswanto, Eko; Kato, Sami; Uehara, K.; Sasaki, Hideharu; Nonaka, Masami

doi:10.1002/9781119428428.ch11

Cited by 4 publications

(1 citation statement)

References 60 publications

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“…Eddies associated with the KE jet (Itoh and Yasuda, 2010;Sasaki and Minobe, 2015) are an important agent for water mass exchanges across the KE jet and associated oceanic frontal zones, and influence distributions of temperature (Sugimoto and Hanawa, 2011), potential vorticity (Qiu and Chen, 2006;Oka et al, 2015), nutrients (e.g., Sasai et al, 2019), and oxygen (Oka et al, 2015(Oka et al, , 2019. The eddy activity modifies also the KE jet itself (Ma et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Atmospheric-Driven and Intrinsic Interannual-to-Decadal Variability in the Kuroshio Extension Jet and Eddy Activities

et al. 2020

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To investigate the influences of oceanic intrinsic/internal variability and its interannualto-decadal modulations on the Kuroshio Extension (KE) jet speed and associated eddy activity, a ten-member ensemble integration of an eddy-resolving ocean general circulation model forced by the 1965-2016 atmospheric reanalysis is conducted. We found a distinct timescale dependence in the ratio of forced and intrinsic variability of the KE jet speed. On the decadal time scale, the ratio of the magnitude of intrinsic variability to that of the atmospheric-driven variability is 0.73, suggesting it is largely atmospheric-driven. In contrast, on the interannual time scales, the KE jet speed has a large ensemble spread, indicating that it is strongly affected by intrinsic variability and has substantial uncertainty. For eddy activity, the ratios of atmospheric-driven and intrinsic variability also depend on the region. In the downstream KE [32 •-38 • N, 153 •-165 • E], variability in the atmospheric-driven eddy activity dominates (1.36 times) over the intrinsic variability on the decadal time scale, and is positively correlated with the current speed. Consistent with the westward propagation of atmospheric-driven jet speed anomalies shown by the ensemble mean, the eddy activity in the downstream KE region is correlated with the current speed variability in the central North Pacific 4 years earlier. This linkage is robust even for each ensemble member with the significant lagged correlation found in seven out of ten ensemble members as well as the ensemble mean (r = 0.59), suggesting the possibility of prediction of the eddy activity. In contrast, the eddy activity in the upstream KE [32 •-38 • N, 141 •-153 • E] shows a very large intrinsic and limited atmospheric-driven variability with a ratio of the former to the latter of 2.73. These results suggest that the intrinsic variability needs to be considered in the interannual variability of strong ocean jet. The dependence of these findings to the model specificities needs to be further explored.

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Section: Introductionmentioning

confidence: 99%

Atmospheric-Driven and Intrinsic Interannual-to-Decadal Variability in the Kuroshio Extension Jet and Eddy Activities

et al. 2020

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Dominant Forcing Regions of Decadal Variations in the Kuroshio Extension Revealed by a Linear Rossby Wave Model

Tamura

Tozuka

2023

Geophysical Research Letters

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The Kuroshio Extension (KE) is a strong eastward inertial jet in the western North Pacific formed after the Kuroshio separates from the Japanese coast. Since the Kuroshio transports a large volume of warm water from the tropics to the midlatitudes, a huge amount of heat is released from the sea surface over the KE region (Sugimoto & Hanawa, 2011;Tomita & Kubota, 2005). Moreover, a sharp gradient of sea surface temperature (SST) associated with convergence of the KE and the Oyashio Extension (Kida et al., 2015), a cold current flowing north of the KE, can affect stormtrack activity in the overlying atmosphere and the large-scale atmospheric circulation (Nakamura et al., 2004). Because of these effects on the atmosphere, the KE region is supposed to influence weather (

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Simulated decadal variations of surface and subsurface phytoplankton in the upstream Kuroshio Extension region

Tozuka

Sasai²,

Yasunaka³

et al. 2022

Prog Earth Planet Sci

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Using outputs from an ecosystem model embedded in an eddy-resolving ocean general circulation model that can realistically simulate decadal modulations of the Kuroshio Extension (KE) between stable and unstable states, decadal variations of phytoplankton concentration in the upstream KE region are investigated. During stable states of the KE, surface phytoplankton concentrations are anomalously suppressed to the south of the KE front, while those to the north are anomalously enhanced. Although the surface phytoplankton concentration anomalies are prominent only during winter to spring, significant subsurface anomalies centered around 60 m depth persist even in summer and autumn. Anomalies persist throughout the year in phytoplankton biomass integrated over the upper 100 m despite the strong surface anomalies during the spring bloom season. An analysis of nitrogen concentration anomalies suggests that the vertical movement of the isopycnal surfaces, vertical mixing of nutrients, and meridional shifts in the KE jet contribute to the anomalous phytoplankton biomass.

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Impact of Ocean Physics on Marine Ecosystems in the Kuroshio and Kuroshio Extension Regions

Cited by 4 publications

References 60 publications

Atmospheric-Driven and Intrinsic Interannual-to-Decadal Variability in the Kuroshio Extension Jet and Eddy Activities

Atmospheric-Driven and Intrinsic Interannual-to-Decadal Variability in the Kuroshio Extension Jet and Eddy Activities

Dominant Forcing Regions of Decadal Variations in the Kuroshio Extension Revealed by a Linear Rossby Wave Model

Simulated decadal variations of surface and subsurface phytoplankton in the upstream Kuroshio Extension region

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