著者

今井 圭理 渡邉 豊

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:13461842)

巻号頁・発行日

vol.65, no.2, pp.111-116, 2015-08-20

---

Massive radioactive cesium was released to the North Pacific Ocean by the accident of the TEPCO Fukushima Dai-ichi Nuclear Power Plant from March 2011. Using the T/S "Oshoro-Maru" cruise, we started monitoring the concentration of radioactive cesium radioactive cesium(134Cs and 137Cs) in the North Pacific surface water from May 2011. Until December 2014, the samplings were carried out at 394 stations in the North Pacific Ocean including the Japan Sea and the Bering Sea. High concentration of radioactive cesium has been observed off Tohoku in 2011, and afterwards spread through the eastern side of the North Pacific by the Kuroshio Extension. In the most region, the radioactive cesium in the surface water reduced by less than the detection limit by the end of 2012. In order to clarify the spatiotemporal change of radioactive cesium in the ocean in future, the continuous monitoring by using the T/S "Oshoro-Maru" cruise be useful.

著者

三宅 誠音 磯田 豊 今井 圭理 小熊 健治 澤田 光希

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.1-11, 2020-08-24

---

The shelf slope off Cape Erimo is very steep, and its slope width (L~30 km) is smaller than the internal radius deformation (λi~50 km). A simple model is used to investigate the dynamic response of Oyashio barotropic flow passing through this local steep slope area. Model results suggest that near-bottom Oyashio water cannot intrude from shelf area off Cape Erimo to Hidaka Trough, because inverse flow accompanied by the bottom trapped shelf wave is generated over the steep slope under the physical condition of L <λi. To confirm the existence of such inverse flow, hydrographic data at upstream and downstream both sides of shelf area off Cape Erimo were examined.

著者

樋口 淳也 河合 俊郎 宇治 利樹 今井 圭理

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.71, no.1, pp.21-28, 2021-08-03

---

Seven specimens of fishes and three specimens of crabs were collected with drifting algae by T/S Oshoro-maru from off the Pacific coast of Tohoku region, northern Japan. In fishes, a single specimen was identified as Histrio histrio (Linnaeus, 1758), five specimens as Oplegnathus punctatus (Temminck and Schlegel, 1844) and a single specimen as Stephanolepis cirrhifer (Temminck and Schlegel, 1850). In crabs, except a single specimen of megalopa, a single specimen was identified as Guinusia dentipes (De Haan, 1835) and a single specimen as Portunus (Portunus) sanguinolentus sanguinolentus (Herbst, 1783). Because previous northernmost records of P. (P.) sanguinolentus sanguinolentus were reported from Boso Peninsula in the Pacific Ocean and Akita Prefecture in the Sea of Japan, the present specimen represents the northernmost record of the species in the Pacific Ocean.