Melt water driven stream and groundwater stage fluctuations on a glacier forefield (Dammagletscher,Switzerland)          下载免费PDF全文

Jan Magnusson  Florian Kobierska  Stephan Huxol  Masaki Hayashi  Tobias Jonas  James W. Kirchner 《水文研究》2014,28(3):823-836

In many mountain regions, large land areas with heterogeneous soils have become ice‐free with the ongoing glacier retreat. On these recently formed proglacial fields, the melt of the remaining glaciers typically drives pronounced diurnal stream level fluctuations that propagate into the riparian zone. This behaviour was measured on the Damma glacier forefield in central Switzerland with stage recorders in the stream and groundwater monitoring wells along four transects. In spite of the large groundwater stage variations, radon measurements in the near‐stream riparian zone indicate that there is little mixing between stream water and groundwater on daily time scales. At all four transects, including both losing and gaining reaches, the groundwater level fluctuations lagged the stream stage variations and were often damped with distance from the stream. Similar behaviours have been modelled using the diffusion equation in coastal regions influenced by tidal sea level variations. We thus tested the ability of such a model to predict groundwater level fluctuations in proglacial fields. The model reproduced several key features of the observed fluctuations at three of four locations, although discrepancies also arise due to non representative input data and model simplifications. Nevertheless, calibration of the model for the individual transects yielded realistic estimates of hydraulic diffusivities between the stream and groundwater monitoring wells. We conclude that studying diurnal groundwater fluctuations can provide important information about the subsurface hydrology of alpine watersheds dominated by glacier melt. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Simulating preferential flow and snowmelt partitioning in seasonally frozen hillslopes     

Aaron A. Mohammed  Edwin E. Cey  Masaki Hayashi  Michael V. Callaghan 《水文研究》2021,35(8):e14277

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Biomarker records from core GH02-1030 off Tokachi in the northwestern Pacific over the last 23,000 years: Environmental changes during the last deglaciation     

Masaki Inagaki  Masanobu Yamamoto  Yaeko Igarashi  Ken Ikehara 《Journal of Oceanography》2009,65(6):847-858

We investigated marine and terrestrial environmental changes at the northern Japan margin in the northwestern Pacific during the last 23,000 years by analyzing biomarkers (alkenones, long-chain n-alkanes, long-chain n-fatty acids, and lignin-derived materials) in Core GH02-1030. The U ₃₇^K′-derived temperature in the last glacial maximum (LGM) centered at 21 ka was ∼10°C, which was 2°C lower than the core-top temperature (∼12°C). This small temperature drop does not agree with pollen evidence of a large air temperature drop (more than 4°C) in the Tokachi area. This disagreement might be attributed to a bias of U ₃₇^K′-derived temperature within 2.5°C by a seasonal shift in alkenone production. The U ₃₇^K′-derived temperature was significantly low during the last deglaciation. Because this cooling was significant in the Kuroshio-Oyashio transition zone, the temperature drops are attributable to the southward displacement of the Kuroshio-Oyashio boundary. Abundant lignin-derived materials, long-chain n-alkanes and long-chain n-fatty acids indicate a higher contribution of terrigenous organic matter from 17 to 12 ka. This phenomenon might have resulted from an enhanced coastal erosion of terrestrial soils due to marine transgression and/or an efficient inflow of higher plant debris to river waters from 17 to 12 ka.  相似文献   

Eclogite from the Kumon range,Myanmar: Petrology and tectonic implications     

Masaki Enami  Motohiro Tsuboi 《Gondwana Research》2012,21(2-3):548-558

This paper presents the first report on the occurrence of eclogite from the Kumon range of the Western province in Myanmar, which is in the southeastern extension of the Himalayan orogenic belt. The eclogite is mainly composed of omphacite, garnet, hornblende/edenite/katophorite/taramite, biotite, quartz, and rutile. The garnet grains in the eclogite usually show textures of barrier reef, atoll, and table reef types, and have a wide compositional range of Alm_58–70Sps_1–2Prp_9–16Grs_14–31. Omphacite grains that occur as garnet inclusions and as isolated crystals in the matrix have similar compositions of Jd_34–45 and Jd_37–44, respectively. Lesser amounts of jadeitic clinopyroxene (Jd_21–38), phengite, biotite, albite, and quartz occur in the lagoon of barrier reef and atoll garnet grains. The matrix omphacite is partly replaced by symplectite of sodic clinopyroxene of Jd_20–29 and albite. The lower limits of the pressure/temperature during the eclogite stage, which are defined by the assemblage of garnet, omphacite (Jd_40–45), and quartz, are 1.2–1.3 GPa/530–615 °C. The finding of eclogite from Myanmar suggests the possibility of a wide occurrence of high-pressure metamorphic rocks in the ophiolite zone along the southeastern extension of the Indus-Yarlung Zangbo suture in Myanmar and Indochina.  相似文献   

Watershed-scale response of groundwater recharge to inter-annual and inter-decadal variability in precipitation (Alberta,Canada)     

Masaki Hayashi  Christopher R. Farrow 《Hydrogeology Journal》2014,22(8):1825-1839

Groundwater recharge sets a constraint on aquifer water balance in the context of water management. Historical data on groundwater and other relevant hydrological processes can be used to understand the effects of climatic variability on recharge, but such data sets are rare. The climate of the Canadian prairies is characterized by large inter-annual and inter-decadal variability in precipitation, which provides opportunities to examine the response of groundwater recharge to changes in meteorological conditions. A decadal study was conducted in a small (250 km²) prairie watershed in Alberta, Canada. Relative magnitude of annual recharge, indicated by water-level rise, was significantly correlated with a combination of growing-season precipitation and snowmelt runoff, which drives depression-focussed infiltration of meltwater. Annual precipitation was greater than vapour flux at an experimental site in some years and smaller in other years. On average precipitation minus vapour flux was 10 mm y^?1, which was comparable to the magnitude of watershed-scale groundwater recharge estimated from creek baseflow. Average baseflow showed a distinct shift from a low value (4 mm y^?1) in 1982–1995 to a high value (15 mm y^?1) in 2003–2013, indicating the sensitivity of groundwater recharge to a decadal-scale variability of meteorological conditions.  相似文献   

Influences of catchment characteristics on nitrogen concentration in largely forested streams during the base flow period     

Baolin Su  So Kazama  Seiichiro Katayama  Masaki Sawamoto 《水文研究》2006,20(20):4391-4403

Based on measured stream nitrogen concentrations at outlets of 12 small sub‐areas (1·3–54·7 km²) in a largely forested catchment during the base flow period, we investigated the influences of discharges and different catchment characteristics on stream nitrogen concentration. Our field surveys were carried out during the 11‐month's period from April 2001 to February 2002 and the correlations between nitrogen concentrations and catchment characteristics were studied. The results showed that the vegetation cover was strongly correlated to total nitrogen (TN) and nitrate + nitrite ? nitrogen (NO_x‐N) concentrations. That is, the TN and NO_x‐N concentrations had positive correlations with mean normalized difference vegetation cover index (NDVI) of each sub‐area during dormant seasons (mean NDVI < 0 · 70) and had negative correlations during the growing season (mean NDVI ≥ 0 . 70). The significance of catchment characteristics to TN and NO_x‐N concentrations was ranked as vegetation cover > soil > topography > land use, and the best models can account for 55–64% of the variance of TN and NO_x‐N concentrations. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

High pressure phase equilibria in the system CaTiO3-CaSiO3: stability of perovskite solid solutions     

Atsushi Kubo  Toshihiro Suzuki  Masaki Akaogi 《Physics and Chemistry of Minerals》1997,24(7):488-494

Phase relations in the system CaTiO₃-CaSiO₃ were experimentally examined at 5.3–14.7 GPa and 1200–1600 °C with a 6–8 type multianvil apparatus. As pressure increases, stability field of perovskite solid solution extends from CaTiO₃ to CaSiO₃, and the perovskite becomes stable for the entire composition range above about 12.3 GPa. The stability field of Ca(Ti_1?X, Si_X)₂O₅ (0.78<x≦1) titanite solid solution +Ca₂SiO₄ larnite exists in the CaSiO₃-rich composition range at 9.3–12.3 GPa and 1200 °C. Perovskite solid solutions containing CaSiO₃ component of 0 to 66 mol% could be quenched to 1 atm. The composition-molar volume relationship of perovskite solid solution showed that molar volume of perovskite solid solution linearly reduces from the value of CaTiO₃ to that of CaSiO₃.  相似文献   

A Review of the Tetrapod Track Record in China,with Special Reference to Type Ichnospecies:Implications for Ichnotaxonomy and Paleobiology     

Martin G. LOCKLEY  LI Jianjun  LI Rihui  Masaki MATSUKAWA  Jerald D. HARRIS  XING Lida 《《地质学报》英文版》2013,87(1):1-20

<正>"Splitting" and "lumping" are perpetual problems in vertebrate,especially dinosaur, ichnotaxonomy.Chinese dinosaur ichnotaxonomy,which began in 1940,provides a series of interesting case studies,highlighting the dual problems of historical and dubious ichnotaxonomy. Chinese Mesozoic tetrapod track types have been placed into 63 ichnospecies(one Triassic,28 Jurassic,and 34 Cretaceous),exclusive of other,non-type ichnospecies or ichnotaxa identified from China.Fifty-two(～83%) of these 63 tetrapod ichnospecies were placed in monospecific ichnogenera. At the ichnogenus level,we prune—either by recognizing nomina dubia or by synonymy—17 from the list of 53 dinosaurian ichnogenera(a 32%reduction),leaving 36 ichnotaxa that we consider valid. Most of the cuts affect Jurassic theropod ichnotaxa,which are reduced from 23 to only nine because most ichnogenera are subjective junior synonyms of Grallator and Eubrontes.Fewer Chinese Cretaceous ichnotaxa(only six of 21 ichnogenera) are obvious nomina dubia or subjective synonyms, suggesting greater east Asian endemism during this time.Because ichnospecies differences are subtle, we provisionally retain ichnospecies as valid pending detailed comparative analyses of congeneric ichnospecies.This synthesis is long overdue and is necessary to address problems of historical and provincial ichnotaxonomy,which severely hamper comparisons of tetrapod ichnofaunas in space and time.  相似文献   

Measuring saturated hydraulic conductivity and anisotropy of peat by a modified split-container method   总被引：1，自引：0，他引：1  

Ranjeet M. Nagare  Robert A. Schincariol  Aaron A. Mohammed  William L. Quinton  Masaki Hayashi 《Hydrogeology Journal》2013,21(2):515-520

Long-term changes in the physical and hydraulic properties of peat result from the decomposition and consolidation processes. The saturated hydraulic conductivity (K _s) of peat is depth-dependent and could increase or decrease with depth; therefore, K _s determination on a large number of samples is required to more accurately assess field variability. The cube method is a popular laboratory procedure to determine K _s because it allows use of smaller sample dimensions, while minimizing edge effects. This article describes the design and use of an alternate split container to enclose undisturbed peat cubes during measurement of K _s and the application of this method to a field site in Northwest Territories, Canada. The method allows for simpler and more controlled K _s measurements while also permitting anisotropy measurements. Matched tests on identical samples (K _s range 21–314 m/d), using the split-container and wax methods, showed a good agreement for intermediate K _s values; however, significant deviations occurred for low and high K _s values. Hydraulic-conductivity measurements taken on field samples showed a decrease with depth and exhibited anisotropic hydraulic conductivity as expected based on previous studies.  相似文献   

Effects of Snowfall on Drifting Snow and Wind Structure Near a Surface     

Masaki Nemoto  Takeshi Sato  Kenji Kosugi  Shigeto Mochizuki 《Boundary-Layer Meteorology》2014,152(3):395-410

Wind-tunnel and numerical experiments were performed to investigate the effects of snowfall on the wind profile and the development of drifting snow. Wind profiles and mass-flux profiles of drifting snow were measured with and without artificial snowfall over a snow surface within the tunnel. Wind and shear-stress profiles and the impact speeds of the snowflakes during snowfall were also investigated numerically. During snowfall, snowflakes transfer part of their horizontal momentum to the air, which increases the stress close to the snow surface; however, the resultant modifications of the wind profiles are small. Because snowflakes have large momentum, the decomposed snow crystals that result from their collision with a surface can form a saltation layer, even over a hard snow surface where entrainment of the grains from the surface does not occur. Additionally, during snowfall, the threshold friction velocity can be lower than the impact threshold because snowflake fragmentation facilitates snow drifting. The broken crystals contribute to the increase in the number of drifting snow grains, even below the impact threshold.  相似文献