Surface current and vertical thermal structure on the continental slope in Tosa Bay

Kuroda, Hiroshi; Shimizu, Manabu; Hirota, Yuichi; Ambe, Daisuke; Akiyama, Hideki

doi:10.1007/s10872-008-0006-4

Cited by 12 publications

(5 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These contraction and expansion processes are explained by the thermal gradients formed by the warm Kuroshio Current, rather than by simple latitudinal gradients. As long-term (1950–2004) mean surface current patterns related to the Kuroshio Current generate an anticlockwise circulation in Tosa Bay ( Kuroda et al 2008 ; Fig. 1 ), SST isotherms should be the lowest in the western side of Tosa Bay with the longer path of the warm inflow and be higher in both the northern and southern ends of Tosa Bay directly struck by the Kuroshio Current.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Warming off southwestern Japan linked to distributional shifts of subtidal canopy‐forming seaweeds

Tanaka

Taino²,

Haraguchi

et al. 2012

Ecology and Evolution

138

120

View full text Add to dashboard Cite

To assess distributional shifts of species in response to recent warming, historical distribution records are the most requisite information. The surface seawater temperature (SST) of Kochi Prefecture, southwestern Japan on the western North Pacific, has significantly risen, being warmed by the Kuroshio Current. Past distributional records of subtidal canopy-forming seaweeds (Laminariales and Fucales) exist at about 10-year intervals from the 1970s, along with detailed SST datasets at several sites along Kochi's >700 km coastline. In order to provide a clear picture of distributional shifts of coastal marine organisms in response to warming SST, we observed the present distribution of seaweeds and analyzed the SST datasets to estimate spatiotemporal SST trends in this coastal region. We present a large increase of 0.3°C/decade in the annual mean SST of this area over the past 40 years. Furthermore, a comparison of the previous and present distributions clearly showed the contraction of temperate species' distributional ranges and expansion of tropical species' distributional ranges in the seaweeds. Although the main temperate kelp Ecklonia (Laminariales) had expanded their distribution during periods of cooler SST, they subsequently declined as the SST warmed. Notably, the warmest SST of the 1997–98 El Niño Southern Oscillation event was the most likely cause of a widespread destruction of the kelp populations; no recovery was found even in the present survey at the formerly habitable sites where warm SSTs have been maintained. Temperate Sargassum spp. (Fucales) that dominated widely in the 1970s also declined in accordance with recent warming SSTs. In contrast, the tropical species, S. ilicifolium, has gradually expanded its distribution to become the most conspicuously dominant among the present observations. Thermal gradients, mainly driven by the warming Kuroshio Current, are presented as an explanation for the successive changes in both temperate and tropical species' distributions.

show abstract

Section: Discussionmentioning

confidence: 99%

“…Thin arrows show observation periods. Thick and medium arrows show the main axis of the warm Kuroshio Current and the long-term dominant surface current inflow to Tosa Bay, respectively ( Kuroda et al 2008 ). Enclosed names show SST measurement locations.…”

Section: Introductionmentioning

confidence: 99%

Warming off southwestern Japan linked to distributional shifts of subtidal canopy‐forming seaweeds

Tanaka

Taino²,

Haraguchi

et al. 2012

Ecology and Evolution

138

120

View full text Add to dashboard Cite

show abstract

“…The main spawning season of S. melanostictus is February and March in the subtropical Pacific Ocean off Japan (Watanabe et al 1996), and their major spawning ground is Tosa Bay. Tosa Bay is an open-type bay off the southern coast of Japan, and the hydrography is strongly affected by the Kuroshio Current (Kuroda et al 2008). During the spawning season of S. melanostictus, another commercially important clupeoid species, the Pacific round herring Etrumeus teres, also dominates the larval community (Djumanto et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Molecular-based diet analysis of the early post‑larvae of Japanese sardine Sardinops melanostictus and Pacific round herring Etrumeus teres

Hirai¹,

Hidaka²,

Nagai³

et al. 2017

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

show abstract

“…Although Tosa Bay is an open bay with a semicircular shelf-slope topography (Figure 1), the warm water of the Kuroshio does not flow directly through the bay. The most dominant current pattern is a counterclockwise circulation interacting with a cold eddy (Fujimoto, 1987;Kuroda et al, 2008). This circulation appears to be induced by the combined effect of changes in the position of the Kuroshio axis and the irregular topography of the continental margin (Awaji et al, 1991).…”

Section: Resultsmentioning

confidence: 99%

“…This circulation appears to be induced by the combined effect of changes in the position of the Kuroshio axis and the irregular topography of the continental margin (Awaji et al, 1991). The surface current, subsurface temperature, and vertical thermal structure on the continental slope in Tosa Bay are markedly influenced by the position of the Kuroshio axis, the counterclockwise circulation being enhanced as the Kuroshio axis moves near shore south of the Ashizuri and Muroto peninsulas (Kuroda et al, 2008). Therefore, the seafloor environment is affected by low-salinity coastal water only at depths shallower than 80-90 m in Tosa Bay, and the seafloor below 100 m is predominantly influenced by water originating from the Kuroshio.…”

Section: Resultsmentioning

confidence: 99%

Oxygen Isotope Equilibrium of the Shallow-Water Benthic Foraminifer Hanzawaia nipponica Asano in Tosa Bay, Southwest Japan

Ikehara¹,

Kita²,

Kawagata³

2021

Front. Earth Sci.

View full text Add to dashboard Cite

Oxygen isotopic compositions (δ18O) of benthic foraminifer tests are widely used for reconstructing paleoceanographic changes, such as global ice volumes during glacial–interglacial cycles. Although deep-sea benthic foraminifers have been well characterized and are considered reliable indicators, little attention has been paid to the geochemistry of shallow-water benthic foraminifers. In this study we evaluated δ18O in the shallow-water benthic foraminifer Hanzawaia nipponica Asano, which lives in surface sediments on continental shelves and upper slopes under the influence of two warm currents, the Kuroshio and Tsushima currents, in the East China Sea, northwest Pacific, and southwestern Japan Sea. To evaluate oxygen isotope equilibrium, we analyzed δ18O of H. nipponica and ambient seawater on the continental shelf in Tosa Bay, southwest Japan. Seawater δ18O and salinity in Tosa Bay are similar to those of surface and subsurface waters in the Kuroshio region in the Okinawa Trough and the northwest Pacific. Vertical profiles of seawater δ18O show no variation with water depth (0–200 m) in Tosa Bay. However, tests of living H. nipponica (as determined by staining with Rose Bengal) and fossil (non-stained) H. nipponica, picked from samples of the top centimeter of seafloor sediment, yielded carbonate δ18O values that clearly increase with water depth, suggesting a temperature-dependent relationship. A comparison of carbonate δ18O values in living H. nipponica and those predicted on the basis of seawater δ18O and annual mean bottom temperature shows that H. nipponica tests are in oxygen isotopic equilibrium with ambient seawater. We determined the linear equations of δ18O–temperature relationship, and the slope of −5.26 (0.19‰°C−1) for living and −4.50 (0.22‰°C−1) for the fossil H. nipponica, respectively. The carbon isotopic compositions (δ13C) of H. nipponica also closely match seawater δ13C. Thus, we propose that the carbonate δ18O and δ13C of H. nipponica are useful proxies to reconstruct shallow-water paleoenvironmental changes in the northwest Pacific and its marginal seas.

show abstract

Surface current and vertical thermal structure on the continental slope in Tosa Bay

Cited by 12 publications

References 8 publications

Warming off southwestern Japan linked to distributional shifts of subtidal canopy‐forming seaweeds

Warming off southwestern Japan linked to distributional shifts of subtidal canopy‐forming seaweeds

Molecular-based diet analysis of the early post‑larvae of Japanese sardine Sardinops melanostictus and Pacific round herring Etrumeus teres

Oxygen Isotope Equilibrium of the Shallow-Water Benthic Foraminifer Hanzawaia nipponica Asano in Tosa Bay, Southwest Japan

Contact Info

Product

Resources

About