Comparison of carbon cycle between the western Pacific subarctic and subtropical time-series stations: highlights of the K2S1 project     

Makio C. Honda  Masahide Wakita  Kazuhiko Matsumoto  Tetsuichi Fujiki  Eko Siswanto  Kosei Sasaoka  Hajime Kawakami  Yoshihisa Mino  Chiho Sukigara  Minoru Kitamura  Yoshikazu Sasai  Sherwood L. Smith  Taketo Hashioka  Chisato Yoshikawa  Katsunori Kimoto  Shuichi Watanabe  Toru Kobari  Toshi Nagata  Koji Hamasaki  Ryo Kaneko  Mario Uchimiya  Hideki Fukuda  Osamu Abe  Toshiro Saino 《Journal of Oceanography》2017,73(5):647-667

A comparative study of ecosystems and biogeochemistry at time-series stations in the subarctic gyre (K2) and subtropical region (S1) of the western North Pacific Ocean (K2S1 project) was conducted between 2010 and 2013 to collect essential data about the ecosystem and biological pump in each area and to provide a baseline of information for predicting changes in biologically mediated material cycles in the future. From seasonal chemical and biological observations, general oceanographic settings were verified and annual carbon budgets at both stations were determined. Annual mean of phytoplankton biomass and primary productivity at the oligotrophic station S1 were comparable to that at the eutrophic station K2. Based on chemical/physical observations and numerical simulations, the likely “missing nutrient source” was suggested to include regeneration, meso-scale eddy driven upwelling, meteorological events, and eolian inputs in addition to winter vertical mixing. Time-series observation of carbonate chemistry revealed that ocean acidification (OA) was ongoing at both stations, and that the rate of OA was faster at S1 than at K2 although OA at K2 is more critical for calcifying organisms.  相似文献   

Phytoplankton community structure in Otsuchi Bay,northeastern Japan,after the 2011 off the Pacific coast of Tohoku Earthquake and tsunami     

Aiko Tachibana  Yuichiro Nishibe  Hideki Fukuda  Kyoko Kawanobe  Atsushi Tsuda 《Journal of Oceanography》2017,73(1):55-65

The tsunami caused by the 2011 off the Pacific coast of Tohoku Earthquake seriously damaged the Pacific coast of northeastern Japan. In addition to its direct disturbance, a tsunami can indirectly affect coastal pelagic ecosystems via topographical and environmental changes. We investigated seasonal changes in the phytoplankton community structure in Otsuchi Bay, northeastern Japan, from May 2011, which was 2 months after the tsunami, to May 2013. The phytoplankton species composition in May 2011 was similar to that observed in May 2012 and 2013. The present results are consistent with the dominant species and water-mass indicator species of phytoplankton in past records. These results suggest that there was no serious effect of the tsunami on the phytoplankton community in Otsuchi Bay. Community analysis revealed that two distinct seasonal communities appeared in each year of the study period. The spring–summer community was characterized by warm-water Chaetoceros species, and dinoflagellates appeared from May to September. The fall–winter community was characterized by cold neritic diatoms, which appeared from November to March. The succession from the spring–summer community to the fall–winter community took place within a particular water mass, and the fall–winter community appeared in both the surface water and the Oyashio water mass, suggesting that water-mass exchange is not the only factor that determines the phytoplankton community structure in Otsuchi Bay.  相似文献   

Cyclicity of Solar Activity During the Maunder Minimum Deduced from Radiocarbon Content     

Hiroko Miyahara  Kimiaki Masuda  Yasushi Muraki  Hideki Furuzawa  Hiroaki Menjo  Toshio Nakamura 《Solar physics》2004,224(1-2):317-322

  相似文献   

Modeling three-dimensional forest structures to drive canopy radiative transfer simulations of bidirectional reflectance factor     

Wei Yang  Hideki Kobayashi  Xuehong Chen  Kenlo Nishida Nasahara  Rikie Suzuki  Akihiko Kondoh 《International Journal of Digital Earth》2018,11(10):981-1000

Three-dimensional (3-D) Monte Carlo-based radiative transfer (MCRT) models are usually used for benchmarking in intercomparisons of the canopy radiative transfer (RT) simulations. However, the 3-D MCRT models are rarely applied to develop remote sensing algorithms to estimate essential climate variables of forests, due mainly to the difficulties in obtaining realistic stand structures for different forest biomes over regional to global scales. Fortunately, some of important tree structure parameters such as canopy height and tree density distribution have been available globally. This enables to run the intermediate complexities of the 3-D MCRT models. We consequently developed a statistical approach to generate forest structures with intermediate complexities depending on the inputs of canopy height and tree density. It aims at facilitating applications of the 3-D MCRT models to develop remote sensing retrieval algorithms. The proposed approach was evaluated using field measurements of two boreal forest stands at Estonia and USA, respectively. Results demonstrated that the simulations of bidirectional reflectance factor (BRF) based on the measured forest structures agreed well with the BRF based on the generated structures from the proposed approach with the root mean square error (RMSE) and relative RMSE (rRMSE) ranging from 0.002 to 0.006 and from 0.7% to 19.8%, respectively. Comparison of the computed BRF with corresponding MODIS reflectance data yielded RMSE and rRMSE lower than 0.03 and 20%, respectively. Although the results from the current study are limited in two boreal forest stands, our approach has the potential to generate stand structures for different forest biomes.  相似文献   

Nutrient status of Otsuchi Bay (northeastern Japan) following the 2011 off the Pacific coast of Tohoku Earthquake     

Hideki Fukuda  Ryosuke Katayama  Yanhui Yang  Hiroyuki Takasu  Yuichiro Nishibe  Atsushi Tsuda  Toshi Nagata 《Journal of Oceanography》2016,72(1):39-52

  相似文献   

Determination of U–Pb Ages for Young Zircons using Laser Ablation‐ICP‐Mass Spectrometry Coupled with an Ion Detection Attenuator Device     

Shuhei Sakata  Kentaro Hattori  Hideki Iwano  Takaomi D. Yokoyama  Tohru Danhara  Takafumi Hirata 《Geostandards and Geoanalytical Research》2014,38(4):409-420

We have developed new analytical procedures to measure precise and accurate ²³⁸U–²⁰⁶Pb and ²³⁵U–²⁰⁷Pb ages for young (~ 1 Ma) zircons using laser ablation‐ICP‐mass spectrometry. For young zircons, both careful correction for the background counts and analysis of very small Pb/U ratios (i.e., ²⁰⁶Pb/²³⁸U < 0.00016 and ²⁰⁷Pb/²³⁵U < 0.0001 for 1 Ma zircons) are highly desired. For the correction of the background, the contribution of the background signal intensities for the analytes, especially for the residual signal intensities for ²⁰⁶Pb and ²⁰⁷Pb, was defined through laser ablation of synthesised zircons (ablation blank) containing negligible Pb. The measured signal intensities for ²⁰²Hg, ²⁰⁶Pb and ²⁰⁷Pb signals obtained by the ablation blank were slightly higher than those obtained by data acquisition without laser ablation (gas blank). For the wider dynamic range measurements on Pb/U ratios, an attenuator device for the ion detection system was employed to extend the capability to monitor high‐intensity signals (i.e., > 3 Mcps). Through the attenuator device, the ion currents were reduced to 1/450 of the signal intensity without the attenuator. Because the switching time for the attenuator was shorter than 1 ms, signal intensities for only specific isotopes could be reduced. With attenuation of the ²³⁸U signal, counting statistics on ²⁰⁶Pb and ²⁰⁷Pb isotopes could be improved and counting loss on the ²³⁸U signal could be minimised. To demonstrate the reliability of this new analytical technique, ²³⁸U–²⁰⁶Pb and ²³⁵U–²⁰⁷Pb ages for three young zircon samples (collected from Osaka Group Pink Volcanic Ash, Kirigamine and Bishop Tuff) were measured. The data presented here demonstrate clearly that the present technique could become a major analytical tool for in situ U–Pb age determination of young zircons (~ 1 Ma).  相似文献   

Paleoenvironmental analysis of the Mawaki archaeological site,central Japan,in relation to the stratigraphic position of dolphin bones     

Yasuto Itoh  Keiji Takemura  Toshio Nakamura  Shin Hasegawa  Hideki Takada 《Geoarchaeology》2011,26(4):461-478

In order to elucidate the paleoenvironment associated with the early Holocene Mawaki archaeological site on the Noto Peninsula of central Japan, a high‐resolution stratigraphic study was conducted of 17 boreholes drilled at the archaeological site. We selected three boreholes for which lithological and/or chronological data are reported. Initial magnetic susceptibility was utilized for correlation of clastic core samples with the assistance of 26 radiocarbon dates. Four lithological units (A, B, C, and D in ascending order) were identified and interpreted as a sequence in a cycle of marine transgression and regression. Dated coastal horizons were chosen to indicate former sea levels. A Holocene relative sea level curve was generated on the basis of the geological data, and a rapid rise from 8000cal. yr B.P. to 7000cal. yr B.P. and a succeeding minor sea level fall represent the basic eustatic trend around the Sea of Japan because hydroisostatic and tectonic effects are moderate in the study area. Abundant dolphin bones lay just above the top of the marine sequence (boundary between Units C and D), located in the seashore environment. Cultural artifacts are found in a subaerial deposit (Unit D) near the dolphin bone level that is assigned to a period of high, stable sea level after the post‐glacial eustatic highstand. Dolphin bones are associated with stone artifacts (arrowheads, knives, and scrapers) and ritual wood columns, indicating the presence of a longstanding fishery during the early Holocene on the Sea of Japan coast. © 2011 Wiley Periodicals, Inc.  相似文献   

Metamorphic petrology of the Barchi–Kol metabasites, western Kokchetav ultrahigh-pressure–high-pressure massif, northern Kazakhstan     

Hideki Masago 《Island Arc》2000,9(3):358-378

Abstract In the Barchi–Kol area, located at the westernmost part of the Kokchetav ultrahigh pressure (UHP) to high-pressure (HP) massif, northern Kazakhstan, metabasites from the epidote amphibolite (EA) facies to the coesite eclogite (CEC) facies are exposed. Based on the equilibrium mineral assemblages, the Barchi–Kol area is divided into four zones: A, B, C and D. Zone A is characterized by the assemblage: epidote + hornblende + plagioclase + quartz, with minor garnet. Zone B is characterized by the assemblage: garnet + hornblende + plagioclase + quartz + zoisite. Zone C is defined by the appearance of sodic–augite, with typical assemblage: garnet + sodic–augite + tschermakite–pargasite + quartz ± plagioclase ± epidote/clinozoisite. Zone D is characterized by the typical eclogite assemblage: garnet + omphacite + quartz + rutile, with minor phengite and zoisite. Inclusions of quartz pseudomorph after coesite were identified in several samples of zone D. Chemical compositions of rock-forming minerals of each zone were analyzed and reactions between each zone were estimated. Metamorphic P-T conditions of each zone were estimated using several geothermobarometers as 8.6 ± 0.5 kbar, 500 ± 30 °C for zone A; 11.7 ± 0.5 kbar, 700 ± 30 °C for zone B; 12–14 kbar, 700–815 °C for zone C; and 27–40 kbar, 700–825 °C for zone D.  相似文献   

Mineralizations of Base Metal Deposits of Acid-Sulfate Type Coexisting with Adularia-Sericite Type     

Hideki IMAI 《Resource Geology》1999,49(3):147-156

Abstract: Two types of ores are recognized in the Huanzala mine, Peru. Zinc and lead ore of adularia-sericite type, is accompanied by pyrite body and skarn. Orthoclase (adularia), sericite and calcite are found in the skarn and altered country rocks. On the other hand, copper and silver (tin) ore of acid-sulfate type, is characterized by enargite, luzonite and bornite, accompanied by tin, silver and tellurium minerals. Although sericite and calcite are found only at the earlier stage in the mineralization of acid-sulfate type, kaolinite appears in the country rocks at a subsequent stage. It is interpreted that the ore-forming fluid of the acid-sulfate type separated from the adularia-sericite type by boiling in the early stage of mineralization. The separated fluid was nearly neutral just after boiling and changed into acidic by the oxidation of H₂S into HSO₄^-. Both types of mineralizations are studied in terms of fo₂-fs₂-pH-temperature diagrams. The adularia-sericite type might correspond to the hot-water system of a geothermal area, and the acid-sulfate type to the vapor-dominated system.
The copper ores from the Teine mine, Hokkaido, Japan and the Chinkuashih mine, Taiwan are acid-sulfate type, characterized by the occurrence of enargite and luzonite. However, zinc and lead ores of the adularia-sericite type are also present in these deposits. Both types in the Teine and Chinkuashih deposits are supposed to have formed in the similar relation as in the Huanzala deposits. The enargite and luzonite ores in the Hokuetsu mine, Japan are closely associated with native sulfur of solfataric origin.  相似文献   

Magnetic detection of heated soils at paleolithic sites in Japan     

Hayao Morinaga  Hiroo Inokuchi  Hideki Yamashita  Akira Ono  Takashi Inada 《Geoarchaeology》1999,14(5):377-399

We present a methodological approach to detect heated soil on ancient sites, using magnetic measurements. The method is based on changes in magnetic signals of soil by heating. The following three types of soil were used for testing the method: silty soil (SS), weathered volcanic ash (WVA, = loam) and fairly fresh volcanic ash (VA) called Odori tephra. On heating above 250–600°C, the magnetic susceptibility and remanent magnetization intensity increased for the SS and WVA samples, reflecting chemical alteration of magnetic minerals (from goethites to magnetites through hematites). The VA sample showed no susceptibility change suggesting the absence of goethites within it. On heating below 250°C, only the intensities of all the samples increased. This is possibly due to acquisition of thermal remanent magnetization. The largest change of the magnetic signals was identified for the SS sample and the smallest one was seen for the VA sample. Therefore, the in situ susceptibility measurement, which is the nondestructive and indirect method, seems to be effective to detect heated soil for sites of aqueous deposits as the SS. On the other hand, for sites of aeolian deposits as the WVA (loam) and VA, the intensity measurement of collected soils seems to be the most reliable method to detect evidence of heating. The degree of the magnetic stability (coercivity) against progressive alternating-field demagnetization was also an important parameter, indicating whether the investigated soils were heated or unheated. © 1999 John Wiley & Sons, Inc.  相似文献