Anatomical study of Tsushima Warm Current system: Determination of Principal Pathways and its Variation

Yabe, Itsuka; Kawaguchi, Yusuke; Wagawa, Taku; Fujio, Shinzou

doi:10.1016/j.pocean.2021.102590

Cited by 26 publications

(17 citation statements)

References 23 publications

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“…Although PT and PD at each layer fluctuated with an amplitude, particularly at Sta. PM5 in the Yamato Basin where the mesoscale eddies are active (Lee et al, 2000;Morimoto et al, 2000;Watanabe et al, 2009;Yabe et al, 2021), the overall trends of the ship-based PT and PD coincide well with those of the Argo-based yearly mean values in both areas.…”

Section: Resultssupporting

confidence: 59%

Changes in Mid-Depth Water Mass Ventilation in the Japan Sea Deduced From Long-Term Spatiotemporal Variations of Warming Trends

Senjyu

2022

Front. Mar. Sci.

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The influence of global warming on mid-depth water mass ventilation in the Japan Sea was investigated using both Argo-based and ship-based hydrographic datasets. The Argo-based dataset of the entire Japan Sea area revealed a warming trend during the past two decades in the upper portion of the Japan Sea Proper Water (UJSPW), which lies at intermediate depths from just under the main thermocline to approximately 1000 m. The warming rates in the southern Japan Sea are generally greater than those in the northern sea by a factor of 2–3. Long-term hydrographic data obtained over the last five decades in the northeast and southeast of the sea revealed that higher warming rates in the southern sea began from 2008, although a significant warming in both northern and southern seas was initiated from the late 1980s. A stagnation in the UJSPW formation from the late 1980s was suggested by a positive shift in the winter sea surface temperature in its formation region and a decreasing trend in dissolved oxygen concentration during the 1990s. In addition, a vertical multi-box model demonstrated that an imbalance between the heating from the upper layer and the cold water supply from its source region induces a warming in the UJSPW. We conclude that a significant change in the mid-depth water mass ventilation occurred in the entire Japan Sea in the late 1980s due to a stagnation in the UJSPW formation. Subsequently, a modest event in the mid-depth water mass ventilation have occurred since 2008. The higher warming rates in the southern sea than those in the northern sea in the event suggest a reduction in cold UJSPW supply to the southern sea from its formation region.

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Section: Resultssupporting

confidence: 59%

Changes in Mid-Depth Water Mass Ventilation in the Japan Sea Deduced From Long-Term Spatiotemporal Variations of Warming Trends

Senjyu

2022

Front. Mar. Sci.

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“…Figure 8 shows the climatological horizontal geostrophic current fields during the time period 1993-2020 and the decadal changes between 1993-2002 and 2011-2020 (the latter minus the former). Yabe et al (2021) reported that the SPF Current (SFC) turns to flow eastward at about 40°N. This implies that the SFC has strengthened in the upstream region over the past decades, resulting in stronger MSSTG advection (Figure 8B).…”

Section: Contributions From Geostrophic Advectionmentioning

confidence: 94%

“…Moreover, the non-steric effect is affected by the volume transport from the upstream. As shown in Figure 8A, one branch of the TWC originating from the west channel of the KTS and flowed poleward along the Korean Peninsula, namely East Korea Warm Current (EKWC, Yoon and Kim (2009)), while the SFC is an extension of the EKWC at about 39-40°N (Yabe et al, 2021). Figure 8B shows the acceleration of the EKWC.…”

Section: Contributions From Geostrophic Advectionmentioning

confidence: 98%

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Decadal intensified and slantwise Subpolar Front in the Japan/East Sea

et al. 2022

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The Subpolar Front in the Japan/East Sea (JES) could far-reaching influence the atmospheric processes over the downstream regions. However its variability on decadal timescale remains less understood. In this study, the decadal trends in the intensity and position of the SPF in the JES during the time period 1985−2020 are analyzed by using four categories of satellite observed high-resolution sea surface temperature products. The results show that there is a significant intensification trend of the SPF at a rate of 0.37°C/100km/decade. The SPF is further divided into three regions based on the meridional sea surface temperature gradient (MSSTG): the eastern (135−138°E), central (130−135°E) and western (128−130°E) regions, respectively. These three regions showed different meridional movements with the eastern SPF moving poleward by 0.08°/decade, the central SPF moving equatorward by −0.11°/decade and the western SPF showing no significant displacements. The reverse meridional movements between the central and eastern SPF increased its skewness. The frontogenesis rate equation is employed to identify the mechanisms of these decadal trends. Results show that the geostrophic advection term, especially its zonal component, had a crucial role in the decadal trends of the intensity and position of the central and eastern SPF. The decadal trend of the central SPF was mainly attributed to the zonal geostrophic advection of the MSSTG associated with the enhancement of the Subpolar Front Current (SFC) in the upstream region, whereas the decadal trend in the eastern SPF was mainly driven by the zonal geostrophic shear advection controlled by the shear of the SFC in the downstream region. Before 2002, the eastern SPF moved poleward at a rate of 0.27°/decade, whereas there was no obvious trend after 2002. Further decomposition showed that this shift was caused by meridional Ekman advection of the MSSTG.

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“…Topography of the JES. Red/blue arrows represent warm/cold currents (Yabe et al, 2021). Black dots indicate the in-situ observation stations of chlorophyll-a concentration, as derived from the WOD18.…”

Section: Study Regionmentioning

confidence: 99%

Satellite-detected phytoplankton blooms in the Japan/East Sea during the past two decades: Magnitude and timing

et al. 2022

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The Japan/East Sea (JES) is known as a mid-latitude “Miniature Ocean” that features multiscale oceanic dynamical processes. Using principal component analysis (PCA), we investigate the variability of the sea surface chlorophyll-a concentration (SSC) and its bloom timing in the JES based on satellite remote sensing products spanning 1998–2019. The JES SSC exhibits strong seasonal variability and blooms twice annually. The spring bloom is induced under combined factors of increased photosynthetically active radiation (PAR), weakened wind speeds and sea ice melting, and terminated by the enhanced stratification. The fall bloom is induced by destratification and active dynamic processes (such as upwelling and front), and terminated by decreased PAR. The interannual variability of spring and fall bloom occur along the northwestern coast of the JES and in the deep Japan Basin, respectively. The positive SSC anomalies along the northwestern coast of the JES in spring is associated with more sea ice in the previous winter, weaker wind speed, and stronger stratification induced by the El Niño events. No significant relationship has been found between the fall bloom and the El Niño events. The bloom timing is controlled by the critical depth hypothesis. The initiation/termination timing of spring blooms has shifted earlier by 0.37/0.45 days, and the counterpart of fall blooms has shifted 0.49/1.28 days earlier per year. The duration and magnitude are independent with each other for spring bloom at interannual time scale. In contrast, they are positively correlated for fall bloom, because of both bloom timing and magnitude are dominated by active oceanic dynamical processes in fall.

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Anatomical study of Tsushima Warm Current system: Determination of Principal Pathways and its Variation

Cited by 26 publications

References 23 publications

Changes in Mid-Depth Water Mass Ventilation in the Japan Sea Deduced From Long-Term Spatiotemporal Variations of Warming Trends

Changes in Mid-Depth Water Mass Ventilation in the Japan Sea Deduced From Long-Term Spatiotemporal Variations of Warming Trends

Decadal intensified and slantwise Subpolar Front in the Japan/East Sea

Satellite-detected phytoplankton blooms in the Japan/East Sea during the past two decades: Magnitude and timing

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