Winter Oceanographic Conditions in the Southwestern Part of the Okhotsk Sea and Their Relation to Sea Ice     

Kay I. Ohshima  Genta Mizuta  Motoyo Itoh  Yasushi Fukamachi  Tatsuro Watanabe  Yasushi Nabae  Koukichi Suehiro  Masaaki Wakatsuchi 《Journal of Oceanography》2001,57(4):451-460

In the southwestern part of the Okhotsk Sea, oceanographic and sea-ice observations on board the icebreaker Soya were carried out in February 1997. A mixed layer of uniform temperature nearly at the freezing point extending down to a depth of about 300 m was observed. This is much deeper than has previously been reported. It is suggested that this deep mixed layer originated from the north (off East Sakhalin), being advected along the shelf slope via the East Sakhalin Current, accompanied with the thick first-year ice (average thickness 0.6 m). This vertically uniform winter water, through mixing with the surrounding water, makes the surface water more saline (losing a characteristic of East Sakhalin Current Water) and the water in the 100–300 m depth zone less saline, colder, and richer in oxygen (a characteristic of the intermediate Okhotsk Sea water). The oceanographic structure and a heat budget analysis suggest that new ice zone, which often appears at ice edges, can be formed through preconditioning of thick ice advection and subsequent cooling by the latent heat release due to its melting. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Coastal polynyas off East Queen Maud Land observed from NOAA AVHRR data     

Takayuki Ishikawa  Jinro Ukita  Kay I. Ohshima  Masaaki Wakatsuchi  Takashi Yamanouchi  Nobuo Ono 《Journal of Oceanography》1996,52(3):389-398

Coastal polynyas off East Queen Maud Land in Antarctica are examined using NOAA AVHRR infrared data. From image analyses, two locations of coastal polynyas in this region are identified; one in Breid Bay and the other along the shelf break. The areal coverage of the Breid Bay polynya is significantly related to the strength of katabatic winds, which maintain their strength over the coastal sea due to land topography favoring for their confluence, thereby being capable of removing newly formed ice. Land fast ice in the eastern part of the bay also plays an additional role in the formation mechanism. It is also found that the areal coverage of coastal polynyas in this region fluctuate coherently. Moreover, these fluctuations correspond to the synoptic index, which measures the strength of the offshore wind, with their peaks closely associated with the areal peaks. These facts strongly suggest the influence of synoptic scale weather on the formation and maintenance of polynyas in this region.  相似文献   

Systematic and ecological studies on mysidacea collected by the bottom-net     

Masaaki Murano 《Journal of Oceanography》1970,26(3):137-150

A list of the 21 species represented in the collection by the bottom-net is given. Of these, 5 are impossible to be identified with the already known species, especially 2 are reserved as their genera are undecided. It is found that there are 2 races inHolmesiella affinis Ii, the large-sized and the small-sized, as like as the most related species,H. anomala Ortmann. As to a species,Pteromysis amemiyai Ii, the development of the marsupium is discussed on the basis of an adult female collected by the ORI-net. The occurrence of 2 species,Petalophthalmus oculatus Illig andPseudomma calloplura Holt andTattersall, is a new record in the Pacific. For the former species, moreover, an ecological property of the habitat is discussed.  相似文献   

Water mass exchange and diapycnal mixing at Bussol’ Strait revealed by water mass properties     

Kazuya Ono  Kay I. Ohshima  Tokihiro Kono  Motoyo Itoh  Katsuro Katsumata  Yuri N. Volkov  Masaaki Wakatsuchi 《Journal of Oceanography》2007,63(2):281-291

Intensive CTD observations that resolve the mean and tidal components were done with a total of 129 casts in summer of 2001 at Bussol’ Strait. Based on these data and all the available historical data, we have revealed the outflow from Bussol’ Strait to the Pacific and the significant diapycnal mixing in the strait. In the range 27.0−27.3σ _θ , the water property in Bussol’ Strait is almost identical to that of the Kuril Basin Water (KBW). The KBW out of Bussol’ Strait forms a water mass front with the East Kamchatka Current Water (EKCW). This front also corresponds to the front of the Oyashio Current. In the lower part of the intermediate layer (27.3−27.6σ _θ ), part of the water in the strait is characterized by lower temperature, lower salinity, and higher dissolved oxygen than that of KBW and EKCW, which can be explained only by the diapycnal mixing. The strong diapycnal mixing in the strait can also be shown by the density inversion, occurrence frequency of which corresponds well to the amplitude distribution of the diurnal current. In the density range 26.7−26.8σ _θ , the water in Bussol’ Strait has the lowest potential vorticity, suggesting that it is a source region of the low potential vorticity water. Seasonal change of the water can reach up to a density of 26.8σ _θ around Bussol’ Strait. This leads us to propose that the combination of winter convection and local tidal mixing leads to effective ventilation of the intermediate layer.  相似文献   

MIS11–19 pollen stratigraphy from the 250-m Choshi core, northeast Boso Peninsula, central Japan: Implications for the early/mid-Brunhes (400–780 ka) climate signals     

Masaaki  Okuda  Hiroomi  Nakazato  Norio  Miyoshi  Takeshi  Nakagawa  Hiroko  Okazaki  Saneatsu  Saito  Asahiko  Taira 《Island Arc》2006,15(3):338-354

Abstract   The 250-m Choshi core (CHOSHI-1), drilled from hemipelagic muds of the Inubo Group, has been physically, geochemically and tephrochronologically analyzed back to 1 Ma. We provide pollen results for the 19–169 m section of the core (400–780 ka) bracketed by the marker tephra Ty1 (equivalent to J4) and the Brunhes–Matuyama paleomagnetic boundary. The results show good agreement with the corresponding oxygen isotope (δ¹⁸O) profile, with high δ¹⁸O intervals dominated by boreal conifers Picea , Abies , Pinus (subgen. Haploxylon ) and Tsuga ( diversifolia ), whereas low δ¹⁸O intervals are dominated by temperate conifers Cryptomeria , Taxaceae-Cephalotaxaceae-Cupressaceae and Sciadopitys . In order to confirm pollen-climate relations for the relevant taxa, a modern surface pollen dataset for the Japanese archipelago was consulted. In this analysis, the ratios of Cryptomeria / Picea and temperate/boreal conifers serve as proxies for the 100-kyr glacial/interglacial cycle during the Middle Pleistocene. Distinct signals for marine isotope stages (MIS) 11, 12, 13–15, 16, 17 and 18–19 are recognized in accordance with the tephrochronology and δ¹⁸O of the same core. Application of the criteria to an independent pollen record from Lake Biwa provides an integrated pollen stratigraphy for mid-latitude Japan during the past 800 ky. Some degree of uncertainty remains in the chronology of the MIS13–15 interval, relating to the uncertainty in the eruption age of widespread tephra Ks11.  相似文献   

Relaxation method for pounding action between adjacent buildings at expansion joint          下载免费PDF全文

Hideo Takabatake  Masaaki Yasui  Yoshihisa Nakagawa  Akiko Kishida 《地震工程与结构动力学》2014,43(9):1381-1400

Earthquake‐induced structural pounding frequently causes serious damage to buildings, particularly at the expansion joint (hereafter, EXPJ) between adjacent buildings. Because the EXPJ width in existing reinforced concrete buildings is usually very small, typically about 5 cm for school buildings in Japan, collision avoidance cannot be achieved by seismic retrofitting. This paper presents an experimental investigation into an effective method for reducing severe structural damage due to pounding at the EXPJ between narrowly separated buildings. The method involves inserting a shock‐absorbing material such as rubber into the EXPJ gap. The efficiency of the proposed method is evaluated by laboratory shaking tests using two model buildings. Furthermore, a lumped mass model is used to carry out a collision analysis in order to numerically investigate the influence of such a shock‐absorbing material. Both the numerical and experimental results confirm the effectiveness of the proposed approach. The validity of the proposed method is also demonstrated by numerical simulation of adjacent 10‐story steel buildings with an EXPJ width of 5 cm. The force, acceleration and velocity produced by earthquake‐induced structural pounding are found to be remarkably mitigated by inserting a soft shock‐absorbing material into the EXPJ gap. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Diffuse carbon dioxide emissions from hidden subsurface structures at Asama volcano,Japan     

Masaaki Morita  Toshiya Mori  Ryunosuke Kazahaya  Hiroshi Tsuji 《Bulletin of Volcanology》2016,78(3):17

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Diurnal coastal-trapped waves on the eastern shelf of Sakhalin in the Sea of Okhotsk and their modification by sea ice     

Jun Ono  Kay I. Ohshima  Genta Mizuta  Yasushi Fukamachi  Masaaki Wakatsuchi 《Continental Shelf Research》2008

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Textural varieties in the Indochinese metamorphic rocks: A key for understanding Asian tectonics     

Nobuhiko  Nakano  Yasuhito  Osanai  Masaaki  Owada 《Island Arc》2008,17(1):2-5

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Direct observations of sea-ice thickness and brine rejection off Sakhalin in the Sea of Okhotsk     

Yasushi Fukamachi  Kunio Shirasawa  Anatoliy M. Polomoshnov  Kay I. Ohshima  Ervin Kalinin  Sohey Nihashi  Humfrey Melling  Genta Mizuta  Masaaki Wakatsuchi 《Continental Shelf Research》2009,29(11-12):1541-1548

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