Observation of the Kyucho in the Bungo Channel by HF radar

Takeoka, Hidetaka; Tanaka, Yoshio; Ohno, Yoshiki; Hisaki, Yukiharu; Nadai, Akitsugu; Kuroiwa, Hiroshi

doi:10.1007/bf02235460

Cited by 29 publications

(12 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(2) The G. ruber shells in sediment trap samples collected before 'Kyucho' indicate that frequent intrusions into the surface layer of the BC from the Pacific (Takeoka et al, 1995) are rare (M. Kuwae, unpublished data, 2008), suggesting that sedimentation of shells in the BC is dependent on transportation, ie, intrusions of the KC water into the BC. For those reasons, the main shell-forming area lies in the KC region.…”

Section: Planktonic Foraminiferal Mg/ca Recordmentioning

confidence: 97%

See 1 more Smart Citation

Using foraminiferal Mg/Ca ratios to detect an ocean-warming trend in the twentieth century from coastal shelf sediments in the Bungo Channel, southwest Japan

et al. 2009

Self Cite

View full text Add to dashboard Cite

report.html) indicated 0.17 m of mean sea level rise in the world's oceans during the twentieth century. Long-term sea level records from the western margins of the North Atlantic have provided the first indication that modern rates of relative sea level rise (last 100 years) in these regions might be more rapid than the long-term rate of rise (over the last 800-1000 years), and that the timing of these accelerations may reflect a link with human-induced global Abstract: To assess abnormal warming of temperature in southwest Japan's coastal seas during the twentieth century, we developed a 200 yr interannually resolved record of planktonic and benthic foraminiferal Mg/Cabased temperature using neritic coastal sediment cores. The winter to late spring bottom temperature (50 m) record, based on benthic foraminiferal (Nonion japonicum) Mg/Ca ratios in the Bungo Channel (BC), showed consistent variation with observed temperatures on a five-year average basis. The BC bottom temperature record showed a significant increasing trend of 1.5°C /100 yr during the twentieth century, which was never apparent in nineteenth century. That result suggests that our Mg/Ca-based thermometry approach using coastal benthic foraminifera can detect abnormally rising temperatures in neritic coastal seas in southwest Japan. The abnormal warming of winter to late spring bottom temperature in the BC contrasts with the lack of an increasing trend in the Globigerinoides ruber-based summer to autumn temperature for the upper 20 m in the slope region of southwest Japan and the lack of an increasing trend in the steric sea level in the region. These results indicate a warming trend of the neritic coastal ocean in southwest Japan, especially in winter to late spring. The timing of the onset of the prolonged abnormal high-temperature stage, which started in the early twentieth century, suggests a link of the neritic coastal ocean in Japan with human-induced global warming.

show abstract

Section: Planktonic Foraminiferal Mg/ca Recordmentioning

confidence: 97%

“…Warm surface KC waters and cold deeper waters often intrude into the BC when the KC path flows nearshore ( Figure 1); they are so-called 'Kyucho' (Takeoka et al, 1995) and 'bottom intrusion' (Kaneda et al, 2002). These observations suggest a strong influence of the KC waters on water exchange between the BC and the KC region.…”

Section: Regional Settingmentioning

confidence: 98%

Using foraminiferal Mg/Ca ratios to detect an ocean-warming trend in the twentieth century from coastal shelf sediments in the Bungo Channel, southwest Japan

et al. 2009

Self Cite

View full text Add to dashboard Cite

show abstract

“…Knowledge of ocean surface wave spectra is important in a wide variety of marine applications, such as physical oceanography, wave forecasting, ship routine, and coastal engineering. One promising method of measuring spatially evolving current and wave fields is to use high-frequency (HF) ocean radar, which measures ocean surface currents (e.g., Takeoka et al 1995;Hisaki et al 2001;Hisaki and Naruke 2003) and waves (Hisaki 1996(Hisaki , 2002(Hisaki , 2004 by radiating high-frequency radio waves and analyzing backscattered signals from the ocean. Since a Doppler spectrum can be expressed in terms of the wave directional spectrum, we can estimate that spectrum by inverting the integral equation that relates the Doppler spectrum to the wave spectrum (e.g., Wyatt 1990;Hisaki 1996;Hashimoto and Tokuda 1999;Hashimoto et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Ocean Wave Directional Spectra Estimation from an HF Ocean Radar with a Single Antenna Array: Methodology

Hisaki

2006

Journal of Atmospheric and Oceanic Technology

Self Cite

View full text Add to dashboard Cite

A method to estimate ocean wave directional spectra using a high-frequency (HF) ocean radar was developed. The governing equations of wave spectra are integral equations of first-and second-order radar cross sections, the wave energy balance equation, and the continuity equation of surface winds. The parameterization of the source function is the same as that in WAM. Furthermore, the method uses the constraints that wave spectral values are smooth in both wave frequency and direction and that the propagation terms are small. The unknowns to be estimated are surface wind vectors at radial grids whose centers are the radar position, and wave spectral values at radial and wave frequency-direction grids. The governing equations are discretized in the radial and wave frequency-direction grids and are converted into a nonlinear minimization problem. Identical twin experiments showed that the present method can estimate wave spectra and dynamically extrapolate wave spectra, even in an inhomogeneous wave field.

show abstract

“…We analyzed ocean surface currents observed by HF ocean radars. HF ocean radar is used to measure ocean surface currents [e.g., Barrick et al, 1977;Prandle and Ryder, 1985;Takeoka et al, 1995;Hisaki et al, 2001;Hisaki and Naruke, 2003] and surface waves [e.g., Hisaki, 1996Hisaki, , 2002Hisaki, , 2004Hisaki, , 2005Hisaki, , 2006 over broad spatial areas. The method is to radiate high-frequency radio waves and analyze the backscattered signals from the ocean.…”

Section: Introductionmentioning

confidence: 99%

“…HF ocean radar is useful to investigate the spatial variability of the surface currents. For example, Takeoka et al [1995] was the first to use HF ocean radars to detect intrusion of the western boundary current (Kuroshio). The intrusion of the Gulf Stream has also been detected by HF radars [Marmorino et al, 1998].…”

Section: Introductionmentioning

confidence: 99%

Southward recirculation of the East China Sea Kuroshio west of Okinawa Island

Hisaki

Imadu

2009

J. Geophys. Res.

Self Cite

View full text Add to dashboard Cite

[1] The surface current of the Kuroshio recirculation region in the East China Sea is investigated. The surface currents in the west of Okinawa Island observed by HF radars and the assimilation results of the Japan Coastal Ocean Predictability Experiment (JCOPE) are analyzed. It appeared that currents in the easternmost edge of the Kuroshio bifurcate southward and flow into the west of Okinawa Island from JCOPE data. The currents are called Kuroshio southward recirculation currents. The currents are controlled by the bottom topography. The wind stress curl in the area where the bifurcated current can be seen in JCOPE data is negative, while the curl is positive in the eastern portion of the Kuroshio. The Kuroshio southward recirculation currents are sometimes enhanced, and their enhancement coincides with that of the positive and negative wind stress curls.

show abstract

Observation of the Kyucho in the Bungo Channel by HF radar

Cited by 29 publications

References 6 publications

Using foraminiferal Mg/Ca ratios to detect an ocean-warming trend in the twentieth century from coastal shelf sediments in the Bungo Channel, southwest Japan

Using foraminiferal Mg/Ca ratios to detect an ocean-warming trend in the twentieth century from coastal shelf sediments in the Bungo Channel, southwest Japan

Ocean Wave Directional Spectra Estimation from an HF Ocean Radar with a Single Antenna Array: Methodology

Southward recirculation of the East China Sea Kuroshio west of Okinawa Island

Contact Info

Product

Resources

About