Fifty years of the 137°E repeat hydrographic section in the western North Pacific Ocean     

Eitarou Oka  Masao Ishii  Toshiya Nakano  Toshio Suga  Shinya Kouketsu  Masatoshi Miyamoto  Hideyuki Nakano  Bo Qiu  Shusaku Sugimoto  Yusuke Takatani 《Journal of Oceanography》2018,74(2):115-145

The 137°E repeat hydrographic section of the Japan Meteorological Agency across the western North Pacific was initiated in 1967 as part of the Cooperative Study of the Kuroshio and Adjacent Regions and has been continued biannually in winter and summer. The publicly available data from the section have been widely used to reveal seasonal to decadal variations and long-term changes of currents and water masses, biogeochemical and biological properties, and marine pollutants in relation to climate variability such as the El Niño-Southern Oscillation and the Pacific Decadal Oscillation. In commemoration of the 50th anniversary in 2016, this review summarizes the history and scientific achievements of the 137°E section during 1967–2016. Through the publication of more than 100 papers over this 50-year span, with the frequency and significance of the publication increasing in time, the 137°E section has demonstrated its importance for future investigations of physical–biogeochemical–biological interactions on various spatiotemporal scales, and thereby its utility in enhancing process understanding to aid projections of the impact of future climate change on ocean resources and ecosystems over the twenty-first century.  相似文献   

An extreme flood caused by a heavy snowfall over the Indigirka River basin in Northeastern Siberia     

Shunsuke Tei  Tomoki Morozumi  Shin Nagai  Shinya Takano  Atsuko Sugimoto  Ryo Shingubara  Rong Fan  Alexander Fedorov  Tuyara Gavrilyeva  Nikita Tananaev  Trofim Maximov 《水文研究》2020,34(3):522-537

Flooding is one of the greatest disasters that produces strong effects on the ecosystem and livelihoods of the local population. Flood frequency is expected to increase globally making its risk assessment an urgent issue. In spring-summer 2017, an extreme flooding occurred in the Indigirka River lowland of Northeastern Siberia that inundated a large area. In this study, the extent and climatic drivers of the flooding were determined using the results of field observations, satellite images, and climate reanalysis dataset, and its possible effects on the ecosystem were discussed. In 2017, a significant lowland area of around 16,016 km² was covered with water even in July, which was 5,217 km² (around 4% of the total area) greater than the water-covered area in 2015 when usual hydrological condition in the area was observed. The hydrographic signature obtained for the Indigirka River water level in 2017 was unusual. Although the water level rose sharply at the end of May (which was typical for the Arctic region), it did not fall afterwards and even increased again to an annual daily maximum value in the middle of July. The climate reanalysis dataset obtained for the temporal–spatial variations of snow water equivalent, snowmelt, and runoff over the lowland revealed that a large amount of snowmelt runoff in June and July 2017 produced a large water-covered area and unusually high river water levels that lasted until summer. Snow depth from winter to spring was largest in 2017 over the period from 2009 to 2017, and the surface of the lower reach of the lowland was partially covered with snow even in the end of June due to the extreme snowfall that occurred in October 2016. Such unusual hydrological conditions waterlogged most trees over the lowland, which caused serious ecosystem devastation and changes in the material cycle.  相似文献   

A new index for evaluation of risk of complex disaster due to typhoons     

Tomokazu Murakami  Shinya Shimokawa  Jun Yoshino  Takashi Yasuda 《Natural Hazards》2015,79(1):29-44

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Hydrogeological and ground-water resource analysis using a geotechnical database     

Katsuaki Koike  Toshiaki Minta  Shinya Ishizaka  Michito Ohmi 《Natural Resources Research》1996,5(1):23-32

An application of a geotechnical database system for primary evaluation of ground-water resources in a sedimentary basin is proposed. The database consists of 1200 borehole logs including geologic columns,in situ test results, ground-water level, water quality data, and resistivity logs. The Kumamoto plain, situated in southwest Japan, is chosen as a study area. The evaluation process consists of two steps: (1) modeling of shapes of water-bearing strata, and (2) modeling of distribution of physical quantity which has some relationship with the porosity of those strata. In step (1), the shapes of upper and/or lower surface of the pyroclastic flow deposits and the andesitic lava were determined, whereas the three-dimensional distribution model of resistivity was constructed from resistivity logging data obtained from 100 boreholes and using the proposed interpolation method in the step (2). An empirical equation between the porosity and the resistivity of the lava was also identified. The integration of two types of model and the empirical equation contributed to an estimate of the total volume of the ground-water under the study area.  相似文献   

Current Structure and Behavior of the River Plume in Suo-Nada     

Shinya Magome  Atsuhiko Isobe 《Journal of Oceanography》2003,59(6):833-843

The behavior of a river plume in Suo-Nada, Japan, has been studied using a primitive equation numerical model, the Princeton Ocean Model. Special attention has been paid to the current structure and behavior of the anticyclonic eddy (bulge) induced by high freshwater inflow changing on a timescale of one week. First, the freshwater is supplied from a river to a rectangular basin with a simple topography. When the river discharge subsides after reaching its peak value, the bulge propagates upstream (i.e., opposite to the direction of the Kelvin wave propagation). Next, the freshwater is supplied from eight major rivers to the basin with realistic topography. The less saline water mass in the southern part of Suo-Nada propagates to the west (i.e., upstream) after the river discharge subsides. This is consistent with an observed phenomenon, viz., that the less saline water mass appears in the western part of Suo-Nada, suggesting that the upstream propagation of the bulge is possible in the real ocean. Finally, the cause of the upstream propagation is considered. Onshore currents appear in the bottom layer beneath the bulge, propagating upstream. They produce an anticyclonic barotropic eddy due to the conservation of potential vorticity. The current component associated with the eddy crosses normally to the isohaline in the upper layer, and therefore transports the bulge upstream. No other current component (such as surface current velocity minus vertically-averaged value) is responsible for the upstream propagation of the bulge. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Ecosystem shift resulting from loss of eelgrass and other submerged aquatic vegetation in two estuarine lagoons, Lake Nakaumi and Lake Shinji, Japan     

Masumi Yamamuro  Jun-Ichi Hiratsuka  Yu Ishitobi  Shinya Hosokawa  Yoshiyuki Nakamura 《Journal of Oceanography》2006,62(4):551-558

Zostera marina L. was intensively harvested until the early 1950s in Lake Nakaumi, a eutrophic estuarine lagoon. We have estimated the amount of nitrogen (N) and phosphorus (P) removed from the lagoon through Z. marina harvesting. Lake Nakaumi lies in Tottori and Shimane prefectures, and the annual harvest of Z. marina in the late 1940s in Tottori was recorded as at least 56,250 t wet weight. The nutrient content of 56,250 t of Z. marina was calculated to be 61.9 t of N and 12.9 t of P, which is equivalent to 5.3% and 11%, respectively, of present annual nutrient loads to the lake. The nutrients formerly used by Z. marina were likely used by phytoplankton after the Z. marina started to decline in the mid-1950s at Lake Nakaumi. This shift in the chief primary producer, from benthic macrophytes to phytoplankton, caused a subsequent shift in secondary producers. Benthic fish and crustacean populations decreased and the non-commercial filter-feeding bivalve, Musculus senhausia, increased in Lake Nakaumi after the decline of seagrass beds. This affected the local economy, inducing not only eutrophication but also the collapse of local fisheries. On the other hand, at adjacent Lake Shinji, loss of submerged aquatic vegetation induced an increase of the commercial filter-feeding bivalve, Corbicula japonica, which doubled the fishery yield in the lake.  相似文献   

The REVEALS model,a new tool to estimate past regional plant abundance from pollen data in large lakes: validation in southern Sweden     

Sofie Hellman  Marie‐José Gaillard  Anna Broström  Shinya Sugita 《第四纪科学杂志》2008,23(1):21-42

The REVEALS model was developed to reconstruct quantitatively regional vegetation abundance (in a 10⁴–10⁵ km² area) from pollen assemblages in large lakes (≥100–500 ha). This model corrects for biases in pollen percentages caused by inter‐taxonomic differences in pollen productivity and dispersal. This paper presents the first case study to validate REVEALS, using empirical data from southern Sweden. Percentage cover of modern regional vegetation in Skåne and Småland, two contrasting vegetation regions, was predicted with REVEALS for 26 key taxa, using pollen assemblages from surface sediments in 10 large lakes, and compared to the actual vegetation within 10⁴ km² compiled from satellite data, forestry inventories, crop statistics, aerial photographs, and vegetation inventories. REVEALS works well in predicting the percentage cover of large vegetation units such as total trees (wooded land), total herbs (open land), total conifers and total broad‐leaved trees, and it provides reasonable estimates for individual taxa, including Pinus, Picea, Betula, Corylus, Alnus, Tilia, Salix spp., Juniperus, Poaceae, Cyperaceae, Cerealia and Secale. The results show great potential for REVEALS applications, including (1) quantitative reconstructions of past regional land cover important for palaeoclimatology and nature conservation, and (2) local‐scale reconstruction of vegetation (<1 km² up to ～ 5 km² area) relevant for palaeoecology and archaeology. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Numerical investigation on the failure criterion of normally consolidated clays     

Shinya Tachibana  Atsushi Iizuka  Katsuyuki Kawai  Ichizou Kobayashi  Thirapong Pipatpongsa  Hideki Ohta 《国际地质力学数值与分析法杂志》2007,31(6):809-833

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Pyrolysis of Transvaal kerogens. II. An evaluation of vacuum pyrolysis with polyethylene,polystyrene and their mixtures with minerals     

Hiroshi Ogino  Bartholomew Nagy 《Precambrian Research》1981,15(2):113-130

A series of experiments have been conducted with polyethylene and polystyrene standards in an attempt to define the advantages and limitations of a vacuum pyrolysis—gas chromatography—mass spectrometry procedure for the characterization of kerogen and other macromolecular substances. Effects of variations in pyrolysis temperatures and times, sample sizes (weights) and thickness were evaluated together with the reproducibility of the nature and abundances of pyrolyzates. The effects of minerals (illite and quartz) admixed in the polymers were also considered with reference to the nature of the breakdown products. Optimal pyrolysis conditions, where primary pyrolyzates were sufficiently abundant and secondary products did not hinder characterization, were attained at 450°C and 60–90 min. The reproducibility of the nature and quantities of pyrolyzates was rather satisfactory at this temperature and pyrolysis time. However, relatively large samples of macromolecular matter, which is considerably volatile at this temperature, led to the synthesis of an abundant yield of secondary products, but sample thickness does not affect the nature of pyrolyzates. Admixed mineral matter affected the nature and relative abundances of the pyrolyzates but did not impede characterization of samples, as primary breakdown products were discernible. Macromolecular substances of limited volatility, heterogeneous chemical composition and containing intractable mineral matter, such as many kerogens, need to be pyrolyzed as relatively large samples. The vacuum procedure used in these studies may be to advantage, as compared with some other methods, to pyrolyze such samples. This method seems to be also suitable for the pyrolysis of volatile macromolecular matter, provided that small samples are employed.  相似文献   

Reflections on post-pandemic university teaching,the corresponding digitalisation of education and the lecture attendance crisis     

Shinya Uekusa 《New Zealand geographer》2023,79(1):33-38

This short commentary discusses effective university teaching in the context of the pandemic, the corresponding digitalisation of tertiary education, and the recent lecture attendance crisis. By critically reflecting on my own experience as a university educator and as a student in a teacher education course, I suggest that the attendance crisis presents an opportunity to explore effective teaching in a rapidly changing context. To improve our teaching and learning, we can reflect on what students and teachers have gone through and seek to understand who our students are.  相似文献