Indian summer monsoon during the last two millennia     

David M. Anderson  Corinne K. Baulcomb  Alice K. Duvivier  Anil K. Gupta 《第四纪科学杂志》2010,25(6):911-917

The monsoon is a large‐scale feature of the tropical atmospheric circulation, affecting people and economies in the world's most densely populated regions. Future trends due to natural variability and human‐induced climate changes are uncertain. Palaeoclimate records can improve our understanding of monsoon dynamics and thereby reduce this uncertainty. Palaeoclimate records have revealed a dramatic decrease in the Asian summer monsoon since the early Holocene maximum 9 ka BP. Here we focus on the last 2 ka, where some records indicate an increasing trend in the summer monsoon. Analysing Globigerina bulloides upwelling records from the Arabian Sea, we find the weakest monsoon occurred 1500 a BP, with an increasing trend towards the present. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Glacial/interglacial sea surface temperature changes in the Southwest Pacific ocean over the past 360 ka     

Kazuyo Tachikawa  Laurence Vidal  Corinne Sonzogni  Edouard Bard 《Quaternary Science Reviews》2009,28(13-14):1160-1170

The phase relationship between climate parameters during terminations gives insight into deglaciation mechanisms. By combining foraminiferal Mg/Ca and alkenone thermometers with planktonic and benthic foraminiferal δ¹⁸O, we determined the phase relationship between local sea surface temperature (SST) and global seawater δ¹⁸O changes in the Coral Sea in the Southwestern Pacific over the last 360 ka. The onset of the SST warming preceded the seawater δ¹⁸O change by several ka for Termination I, II and III. During Termination I, the SST warming started at 20 ka BP, earlier than atmospheric CO₂ rise suggesting that the greenhouse effect was not the main trigger of this early warming. Compilation of ¹⁴C-dated SST records from the whole Pacific during Termination I reveals that the onset of the warming is generally earlier in the Southern and the tropical Pacific than in the North Pacific. This spatio-temporal warming pattern suggests linkage between the southern ocean and tropical Pacific. The early tropical warming could provide heat and moisture to the northern high latitudes, modifying radiative balance and precipitation over ice sheets at the onset of deglaciation.  相似文献   

Potential risks to freshwater resources as a result of leakage from CO<Subscript>2</Subscript> geological storage: a batch-reaction experiment     

Jiemin Lu  Judson W. Partin  Susan D. Hovorka  Corinne Wong 《Environmental Earth Sciences》2010,60(2):335-348

In assessing the feasibility of widespread deployment of CO₂ geological storage, it is prudent to first assess potential consequences of an error or accident that could lead to CO₂ leakage into groundwater resources above a sequestration interval. Information about the sensitivity of the groundwater system to introduction of CO₂ is needed in order to design groundwater monitoring program. A laboratory-batch experiment was conducted to explore the range of CO₂ impact on groundwater quality of a spectrum of representative aquifers, in the Gulf Coast region, USA. Results show that CO₂ elevated concentrations of many cations within hours or days. Two types of cations were recognized according to their concentration trends. Type I cations—Ca, Mg, Si, K, Sr, Mn, Ba, Co, B, Zn—rapidly increased following initial CO₂ flux and reached stable concentrations before the end of the experiment. Type II cations—Fe, Al, Mo, U, V, As, Cr, Cs, Rb, Ni and Cu—increased at the start of CO₂ flux, but declined, in most cases, to levels lower than pre-CO₂ concentrations. Dissolution of dolomite and calcite caused the largest increase in concentrations for Ca, Mg, Mn, Ba and Sr. Cation release rates decreased linearly as pH increased during mineral buffering. Experiment results suggest that carbonate minerals are the dominant contributor of changes in groundwater quality. Risk assessments of potential degradation of groundwater and monitoring strategies should focus on these fast-reacting minerals. Mobilization risk of Type II cations, however, may be self-mitigated because adsorption occurs when pH rebounds.  相似文献   

LAND-USE CONTROL: AN IMPORTANT PIECE OF THE GROUND-WATER PROTECTION PUZZLE     

Harry E. LeGrand  Donald K. Keech  Steve Ragone  Jay H. Lehr  David M. Nielsen 《Ground water》1983,21(1):2-3

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A creative solution to the NIMBY problem     

Lehr J  Inhaber H 《Ground water》2003,41(4):401-403

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Assessing catchment-scale spatial and temporal patterns of groundwater and stream salinity     

David L. Poulsen  Craig T. Simmons  Corinne Le Galle La Salle  Jim W. Cox 《Hydrogeology Journal》2006,14(7):1339-1359

Understanding catchment-scale patterns of groundwater and stream salinity are important in land- and water-salinity management. A large-scale assessment of groundwater and stream data was undertaken in the eastern Mt Lofty Ranges of South Australia using geographical information systems (GIS), regional scale hydrologic data, hydrograph separation and hydrochemical techniques. Results of the study show: (1) salts were mostly of marine origin (75%), while sulfate and bicarbonate from mineral weathering comprised most of the remainder, (2) elevated groundwater salinities and stable water isotopic compositions similar to mean rainfall indicated that plant transpiration was the primary salt accumulation mechanism, (3) key factors explaining groundwater salinity were geology and rainfall, with overall catchment salinity inversely proportional to average annual rainfall, and groundwater salinity ‘hotspots’ (EC >8 mS/cm) associated with geological formations comprising sulfidic marine siltstones and shales, (4) shallow groundwater correlated with elevated stream salinity, implying that baseflow contributed to stream salt loads, with most of the annual salt load (estimated to be 24,500 tonnes) occurring in winter when baseflow volume was highest. Salt-load analysis using stream data could be a practical, low-cost technique to rapidly target the investigation of problem areas within a catchment.  相似文献   

A new technique to estimate initial spill size using a modified fay-type spreading formula     

W.J. Lehr  R.J. Fraga  M.S. Belen  H.M. Cekirge 《Marine pollution bulletin》1984,15(9):326-329

Estimating oil spill size is important for a variety of economic, environmental and legal reasons. One attempt to determine oil spill size by visually assessing the extent of colour regimes in the spill and multiplying the areas of these regimes by thickness values leads to unsatisfactory results. Previous efforts to estimate oil spill size by inverting spreading using formulae like those of Blokker and Fay have also incurred difficulties related to environmental conditions which influence spill spread rate. Data obtained during a series of field experiments, conducted off the Saudi Arabian coastline during the fall of 1982, were used to devise a modification of Fay's spreading formula. The results agree significantly better with the observed areas of the oil spill than Fay's original formula. The modified area formula is then inverted to obtain a formula for initial volume spilled.  相似文献   

Communicating landscape hydrology — the water cycle in a box          下载免费PDF全文

Christian Lehr  Philipp Rauneker  Marcus Fahle  Tobias L. Hohenbrink  Steven Böttcher  Marco Natkhin  Björn Thomas  Ralf Dannowski  Bernd Schwien  Gunnar Lischeid 《水文研究》2017,31(3):750-752

Physical models are a well‐established tool in education to strengthen hydrological understanding. They facilitate the straightforward visualization of hydrological processes and allow the communication of hydrological concepts, research and questions of general interest to the public. In order to visualize the water cycle in a landscape of postglacial sediments, in particular the subsurface part, a physical model was constructed. In two videos, (1) a detailed construction manual and (2) visualization examples of hydrological concepts and processes are presented. With our contribution, we like to encourage professionals in the field of hydrology to share methods and tools of knowledge transfer and communication of hydrological concepts. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Testing the genetic relationship between fluid alteration and brecciation in CM chondrites     

Maximilien J. Verdier‐Paoletti  Yves Marrocchi  Lionel G. Vacher  Jrme Gattacceca  Andrey Gurenko  Corinne Sonzogni  Matthieu Gounelle 《Meteoritics & planetary science》2019,54(8):1692-1709

Boriskino is a poorly studied CM chondrite with numerous millimeter‐ to centimeter‐scale clasts exhibiting sharp boundaries. Clast textures and mineralogies attest to diverse geological histories with various degrees of aqueous alteration. We conducted a petrographic, chemical, and isotopic study on each clast type of the breccia to investigate if there exists a genetic link between brecciation and aqueous alteration, and to determine the controlling parameter of the extent of alteration. Boriskino is dominated by CM2 clasts for which no specific petrographic type could be assigned based on the chemical compositions and modal abundances of constituents. One clast stands out and is identified as a CM1 lithology, owing to its lack of anhydrous silicates and its overall abundance of dolomite‐like carbonates and acicular iron sulfides. We observe that alteration phases near clast boundaries exhibit foliation features, suggesting that brecciation postdated aqueous alteration. We measured the O‐isotopic composition of Ca‐carbonates and dolomite‐like carbonates to determine their precipitation temperatures following the methodology of Verdier‐Paoletti et al. (2017). Both types of carbonates yield similar ranges of precipitation temperatures independent of clast lithology, ranging from ?13.9 ± 22.4 (2σ) to 166.5 ± 47.3 °C, precluding that temperature alone accounts for the differences between the CM1 and CM2 lithologies. Instead, we suggest that initial water/rock ratios of 0.75 and 0.61 for the CM1 and CM2 clasts, respectively, might control the extent of aqueous alteration. Based on these estimates, we suggest that Boriskino clasts originated from a single parent body with heterogeneous distribution of water either due to local differences in the material permeability or in the initial content of ice available. These conditions would have produced microenvironments with differing geochemical conditions thus leading to a range of degrees of aqueous alteration.  相似文献   

Ground motion prediction with the empirical Green's function technique: an assessment of uncertainties and confidence level     

Ronan Pavic  Martin G. Koller  Pierre-Yves Bard  Corinne Lacave-Lachet 《Journal of Seismology》2000,4(1):59-77

An assessment of uncertainties for ground motion predictions with the aid of the empirical Green's function (EGF) technique is presented. The main input parameters were identified, and their respective uncertainties were assessed by means of an international expert inquiry. The repercussion of these input uncertainties on the final ground motion estimates were investigated by means of the Latin Hypercube Sampling technique. The mean ground motion estimates (response spectra) and their standard deviations were compared with results obtained from empirical attenuation laws. The most sensitive input parameter turned out to be the seismic moment corresponding to the EGF. In general, if the source parameters are well determined, equivalent uncertainties, statistically speaking, can be expected from the EGF technique and from the application of attenuation laws. Therefore, if EGFs with well known source parameters are available, the EGF technique seems to be preferable: site effects are automatically taken into account, and physically realistic acceleration time histories can be obtained. However, further investigations on the reliability of the EGF technique should be performed, and finally, it is recalled that the EGF technique is based on the assumption of linearity. If conditions are such that this assumption cannot be maintained, the EGF technique should be combined with non-linear geotechnical methods.  相似文献