Development of an operational coastal model of the Seto Inland Sea,Japan     

Kei Sakamoto  Goro Yamanaka  Hiroyuki Tsujino  Hideyuki Nakano  Shogo Urakawa  Norihisa Usui  Mikitoshi Hirabara  Koji Ogawa 《Ocean Dynamics》2016,66(1):77-97

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High resolution OSL dating back to MIS 5e in the central Sea of Okhotsk   总被引：1，自引：0，他引：1  

Saiko Sugisaki  Jan-Pieter Buylaert  Andrew Murray  Sumiko Tsukamoto  Yoshifumi Nogi  Hideki Miura  Saburo Sakai  Koichi Iijima  Tatsuhiko Sakamoto 《Quaternary Geochronology》2010,5(2-3):293-298

Marine sediments contain important archives of past ocean and climate changes, but at high latitudes the absence of carbonate has prevented the construction of accurate chronological models. We have begun a study to (1) determine the accuracy of luminescence ages in deep-sea marine sediments, e.g. by comparison with marine oxygen isotope stratigraphy where possible, (2) describe changes in sedimentation rate through time, and (3) test whether it is possible to date back to marine isotope stage 5e (MIS 5e). We show here that optical dating of fine grains of quartz from the central Sea of Okhotsk is able to provide an accurate and precise chronology for the reconstruction of the palaeoceanic and palaeoclimatic environment at our site. The upper 6.5 m of the 18.42 m long core MR0604-PC07A is believed, based on its magnetic susceptibility and the oxygen isotope (δ¹⁸O) records to contain the last ～150 ka. Forty OSL samples were taken from this upper part of the core. The single-aliquot regenerative-dose (SAR) procedure is used for equivalent dose (D_e) determination. The luminescence characteristics of fine-grained quartz (4–11 μm) extracted from the core are described. The OSL signal is dominated by the fast component and a dose recovery test shows that we can accurately measure a known dose given in the laboratory prior to any heat treatment. Dose rates were determined using high-resolution gamma spectrometry, and vary between 0.4 and 1.6 Gy/ka. The OSL ages from this section lie between ～140 ka and ～15 ka and are in very good agreement with the δ¹⁸O stratigraphy up to MIS 5e. A clear change in sedimentation rate is identified: between ～139 and 110 ka, the sedimentation rate was ～0.09 m/ka, but then from ～110 to 15 ka, the sedimentation rate decreases to a constant value of ～0.04 m/ka. Our data confirm that OSL dating using widely distributed fine-grain quartz has great potential for dating deep-sea sediments. Because luminescence methods use clastic materials, they do not depend on the presence of biogenic carbonate. As a result it is now likely that we can establish a chronology in regions of the ocean that were previously undatable.  相似文献   

Tunnelling through squeezing rock in two large fault zones of the Enasan Tunnel II     

Fuminori Kimura  Nobuyuki Okabayashi  Toshikazu Kawamoto 《Rock Mechanics and Rock Engineering》1987,20(3):151-166

Summary In spite of the high content of clay in the rock, blasting technique had to be adopted for excavation because the hydrothermally altered clay was interbedded in the hard rock. Problems with groundwater did not arise owing to the dewatering effect of the pilot tunnel.  相似文献   

An overview of decadal climate predictability in a multi-model ensemble by climate model MIROC   总被引：1，自引：1，他引：0  

Yoshimitsu Chikamoto  Masahide Kimoto  Masayoshi Ishii  Takashi Mochizuki  Takashi T. Sakamoto  Hiroaki Tatebe  Yoshiki Komuro  Masahiro Watanabe  Toru Nozawa  Hideo Shiogama  Masato Mori  Sayaka Yasunaka  Yukiko Imada 《Climate Dynamics》2013,40(5-6):1201-1222

Decadal climate predictability is examined in hindcast experiments by a multi-model ensemble using three versions of the coupled atmosphere-ocean model MIROC. In these hindcast experiments, initial conditions are obtained from an anomaly assimilation procedure using the observed oceanic temperature and salinity with prescribed natural and anthropogenic forcings on the basis of the historical data and future emission scenarios in the Intergovernmental Panel of Climate Change. Results of the multi-model ensemble in our hindcast experiments show that predictability of surface air temperature (SAT) anomalies on decadal timescales mostly originates from externally forced variability. Although the predictable component of internally generated variability has considerably smaller SAT variance than that of externally forced variability, ocean subsurface temperature variability has predictive skills over almost a decade, particularly in the North Pacific and the North Atlantic where dominant signals associated with Pacific decadal oscillation (PDO) and the Atlantic multidecadal oscillation (AMO) are observed. Initialization enhances the predictive skills of AMO and PDO indices and slightly improves those of global mean temperature anomalies. Improvement of these predictive skills in the multi-model ensemble is higher than that in a single-model ensemble.  相似文献   

Liquid waveguide spectrophotometric measurements of arsenate and particulate arsenic,as well as phosphate and particulate phosphorus,in seawater     

Fuminori Hashihama  Shuhei Suwa  Jota Kanda 《Journal of Oceanography》2017,73(4):439-447

Sensitive methods for the determination of arsenate and particulate arsenic (PAs), as well as phosphate and particulate phosphorus (PP), in seawater are described. The method for arsenate and phosphate was established by applying automated liquid waveguide spectrophotometry. Because the reaction time for the formation of the arsenate-molybdate complex is longer than that for the phosphate-molybdate complex, a long Teflon tube submerged in a heating bath was installed in the conventional phosphate flow system. The arsenate was quantified as the difference between absorbances of molybdenum blue dyes with (only phosphate) and without (phosphate + arsenate) arsenate reduction treatment. Contamination was observed in the reagent for arsenate reduction and must be corrected. Linear dynamic ranges up to 1000 nM were confirmed for arsenate and phosphate. The detection limits for arsenate and phosphate were 5 and 4 nM, respectively. Freezing was a reliable sample preservation technique for both arsenate and phosphate. The method for PAs and PP was established by combining conventional persulfate oxidation of PP and the automated liquid waveguide spectrophotometry of arsenate and phosphate. The digestion efficiencies of organic As analogs were >93%. Contamination in the glass fiber filter was negligible. Field tests confirmed that the coefficients of variation (CVs) of 10–19 nM arsenate and 4–151 nM phosphate were 7–20 and 1–25%, respectively, while the CVs of 0.9 nM PAs and 10.2 nM PP were 11 and 4%, respectively.  相似文献