Tidally generated island wakes and surface water cooling over Izu Ridge

Kodaira, Tsubasa; Waseda, Takuji

doi:10.1007/s10236-019-01302-1

Cited by 6 publications

(6 citation statements)

References 31 publications

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“…L1 is about 1 km behind the island, and the SST of the wake area (27.3 °C) can reach 2.1 °C lower than that of the Kuroshio water (29.4 °C) as seen in Figure 4. The Chl-a concentration reached 0.23 mg m 3 ⁄ , which was three times that of the Kuroshio water (0.07 mg m 3 ⁄ ). We can use this case to quantify the magnitude of the horizontal gradient of SST and Chl-a.…”

Section: Spatial Structure Of Island Wakementioning

confidence: 83%

“…Island wakes have been studied for many years in the global oceans. Different driving forces cause this phenomenon and these wakes have different characteristics according to the island's scale and water depth [1][2][3][4]. Green Island, a small island located off southeast of Taiwan, is on the path of the Kuroshio to the East China Sea (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Temporal Variation and Spatial Structure of the Kuroshio-Induced Submesoscale Island Vortices Observed from GCOM-C and Himawari-8 Data

Hsu

Lee

et al. 2020

Remote Sensing

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Dynamics of ocean current-induced island wake has been an important issue in global oceanography. Green Island, a small island located off southeast of Taiwan on the Kuroshio path was selected as the study area to more understand the spatial structure and temporal variation of well-organized vortices formed by the interaction between the Kuroshio and the island. Sea surface temperature (SST) and chlorophyll-a (Chl-a) concentration data derived from the Himawari-8 satellite and the second generation global imager (SGLI) of global change observation mission (GCOM-C) were used in this study. The spatial SST and Chl-a variations in designed observation lines and the cooling zone transitions on the left and right sides of the vortices were investigated using 250 m spatial resolution GCOM-C data. The Massachusetts Institute of Technology general circulation model (MITgcm) simulation confirmed that the positive and negative vortices were sequentially detached from each other in a few hours. In addition, totals of 101 vortexes from July 2015 to December 2019 were calculated from the 1-h temporal resolution Himawari-8 imagery. The average vortex propagation speed was 0.95 m/s. Totals of 38 cases of two continuous vortices suggested that the average vortex shedding period is 14.8 h with 1.15 m/s of the average incoming surface current speed of Green Island, and the results agreed to the ideal Strouhal-Reynolds number fitting curve relation. Combined with the satellite observation and numerical model simulation, this study demonstrates the structure of the wake area could change quickly, and the water may mix in different vorticity states for each observation station.

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Section: Spatial Structure Of Island Wakementioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Temporal Variation and Spatial Structure of the Kuroshio-Induced Submesoscale Island Vortices Observed from GCOM-C and Himawari-8 Data

Hsu

Lee

et al. 2020

Remote Sensing

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“…The different models between the LORA and JCOPE2M are not likely to make large impacts on the forecast accuracy, and consequently the JCOPE2M is suitable for comparing validation results from the LORA-WNP. The JCOPE2M has been adopted for physical and biogeochemical oceanography studies (Kodaira and Waseda 2019;Hasegawa et al 2021;Ishizu et al 2021) and has provided operational information on Kuroshio and Oyashio prediction for the Kuroshio-Oyashio Watch website (https:// www. jamst ec.…”

Section: Validationmentioning

confidence: 99%

LORA: a local ensemble transform Kalman filter-based ocean research analysis

2023

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We have produced an eddy-resolving local ensemble transform Kalman filter (LETKF)-based ocean research analysis (LORA) for the western North Pacific (WNP) and Maritime Continent (MC) regions (LORA-WNP and LORA-MC, respectively). This paper describes the system configuration and validation comparisons with Japan Coastal Ocean Predictability Experiment 2M (JCOPE2M) reanalysis and Archiving, Validation, and Interpretation of Satellite Oceanographic Data (AVISO) observational datasets. The results show that the surface horizontal velocity in the LORA-WNP is closer to independent drifter buoy observations in the mid-latitude region, especially along the Kuroshio Extension (KE), and is less close in the subtropical region than the JCOPE2M, although the AVISO is the closest over the whole domain. The sea surface temperatures (SSTs) in the LORA-WNP correspond better to assimilated satellite observations than the JCOPE2M over most of the domain except for coastal regions. The results using an independent buoy south of the KE indicate that better fit of temperature in the LORA-WNP may be limited to the upper 300 m depth, probably because of the prescribed vertical localization cutoff length of 370 m. In the MC region, the surface velocity in the LORA-MC is closer to the independent drifter buoys in the equatorial coastal region and is less close in the offshore region than the AVISO. The SSTs in the LORA-MC correspond better to the assimilated satellite observations in the offshore region than the nearshore region. Therefore, the LORA-WNP and LORA-MC have sufficient accuracy for geoscience research applications as well as for fisheries, marine transport, and environment consultants.

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“…The "island mass effect" summarizes various coupled physical-biogeochemical mechanisms that enhance plankton productivity near an island, or groups of islands (Doty and Oguri, 1956). Mechanisms include the interaction of oceanic flows with the island topography (Mann and Lazier, 2005), tidal mixing around islands (Kodaira and Waseda, 2019), tidally induced internal waves (Griffin et al, 1987), turbulent mixing in island wakes (Hasegawa et al, 2021), and other factors such as nutrient intake from island runoff (Bell, 1992), atoll flushing (Gove et al, 2016), groundwater discharge (Street et al, 2008) and human activities that increase nearshore nutrient concentrations above natural levels (Vitousek et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

On the wind-driven formation of mesoscale plankton patches in island wakes

Kämpf

2023

Preprint

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Using a three-dimensional coupled physical-biological model, this paper explores the creation of phytoplankton blooms around tropical islands in the presence of ambient currents and short-lived (~4 days) wind events. The ambient flow creates a retention zone of weak flows in the lee of the island, which is a typical feature of island wakes. Findings reveal that wind-induced upwelling effects are essential for the initial nutrient enrichment and phytoplankton growth that occur mainly in this retention zone. Oscillating flow, typical of island wakes, occasionally releases mesoscale patches of upwelled water and its phytoplankton load into the ambient ocean. The phytoplankton continues to grow within floating structures that are of up to 20 km in diameter. This mechanism complements the plankton growth associated with the formation of mesoscale eddies.

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Tidally generated island wakes and surface water cooling over Izu Ridge

Cited by 6 publications

References 31 publications

Temporal Variation and Spatial Structure of the Kuroshio-Induced Submesoscale Island Vortices Observed from GCOM-C and Himawari-8 Data

Temporal Variation and Spatial Structure of the Kuroshio-Induced Submesoscale Island Vortices Observed from GCOM-C and Himawari-8 Data

LORA: a local ensemble transform Kalman filter-based ocean research analysis

On the wind-driven formation of mesoscale plankton patches in island wakes

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