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81.
Luminescence dating of Middle Pleistocene proglacial deposits from northern Switzerland: methodological aspects and stratigraphical conclusions 下载免费PDF全文
Sally E. Lowick Marius W. Buechi Dorian Gaar Hans R. Graf Frank Preusser 《Boreas: An International Journal of Quaternary Research》2015,44(3):459-482
Optically stimulated luminescence (OSL) dating was applied to proglacial deposits from the Klettgau Valley in northern Switzerland, which is understood to record several phases of glaciation prior to the Last Interglacial. The aim was to provide an independent chronology for the different sedimentary units to understand better the complex depositional history of the region. This time range requires care when assessing the reliability of the luminescence protocols applied. Equivalent doses for fine‐ and coarse‐grain quartz remained below 300 Gy, while dose response curves for both fractions continued to display growth above 500 Gy. Dose recovery tests confirmed the ability of the single aliquot regenerative (SAR) protocol to recover laboratory doses of a similar size to burial doses, and isothermal decay measurements confirmed the stability of the quartz signal. Having passed rigorous testing criteria, quartz OSL ages of up to ~200 ka were considered reliable but significantly underestimated expected ages and prompt a reconsideration of earlier interpretations of the stratigraphy for this site. Rather than representing three separate glaciations, quartz luminescence ages instead suggest that these deposits record up to four independent ice advances during Marine Isotope Stage 6. For both single grain and single aliquot feldspar dating, it was not possible to separate the conflicting influences of anomalous fading and partial bleaching. However, uncorrected feldspar central age model ages were found to be in reasonable agreement with quartz age estimates, and suggest that feldspar ages may still offer useful additional information in this region. 相似文献
82.
Information included in this summary is based on more detailed reports published in the Bulletin of the Global Volcanism Network,
vol. 34, no. 12, December 2009 (on the Internet at ). Edited by scientists at the Smithsonian, this bulletin includes reports provided by a worldwide network of correspondents.
The reports contain the names and contact information for all sources. Please note that these reports are preliminary and
subject to change as events are studied in more detail. The Global Volcanism Program welcomes further reports of current volcanism,
seismic unrest, monitoring data, and field observations. 相似文献
83.
Edward Venzke Sally Kuhn Sennert Richard Wunderman Jen Fela Jacquelyn Gluck 《Bulletin of Volcanology》2010,72(9):1137-1138
Information included in this summary is based on more detailed reports published in the Bulletin of the Global Volcanism Network,
vol. 35, no. 4, April 2010 on the Internet at (). Edited by scientists at the Smithsonian, this bulletin includes reports provided by a worldwide network of correspondents.
The reports contain the names and contact information for all sources. Please note that these reports are preliminary and
subject to change as events are studied in more detail. The Global Volcanism Program welcomes further reports of current volcanism,
seismic unrest, monitoring data, and field observations. 相似文献
84.
How much does dry‐season fog matter? Quantifying fog contributions to water balance in a coastal California watershed 下载免费PDF全文
The seasonally‐dry climate of Northern California imposes significant water stress on ecosystems and water resources during the dry summer months. Frequently during summer, the only water inputs occur as non‐rainfall water, in the form of fog and dew. However, due to spatially heterogeneous fog interaction within a watershed, estimating fog water fluxes to understand watershed‐scale hydrologic effects remains challenging. In this study, we characterized the role of coastal fog, a dominant feature of Northern Californian coastal ecosystems, in a San Francisco Peninsula watershed. To monitor fog occurrence, intensity, and spatial extent, we focused on the mechanisms through which fog can affect the water balance: throughfall following canopy interception of fog, soil moisture, streamflow, and meteorological variables. A stratified sampling design was used to capture the watershed's spatial heterogeneities in relation to fog events. We developed a novel spatial averaging scheme to upscale local observations of throughfall inputs and evapotranspiration suppression and make watershed‐scale estimates of fog water fluxes. Inputs from fog water throughfall (10–30 mm/year) and fog suppression of evapotranspiration (125 mm/year) reduced dry‐season water deficits by 25% at watershed scales. Evapotranspiration suppression was much more important for this reduction in water deficit than were direct inputs of fog water. The new upscaling scheme was analyzed to explore the sensitivity of its results to the methodology (data type and interpolation method) employed. This evaluation suggests that our combination of sensors and remote sensing allows an improved incorporation of spatially‐averaged fog fluxes into the water balance than traditional interpolation approaches. 相似文献
85.
Mathias Ritter Mathias D. Müller Oriol Jorba Eberhard Parlow L.-J. Sally Liu 《Meteorology and Atmospheric Physics》2013,119(1-2):59-70
This study evaluates the impact of different chemical and meteorological boundary and initial conditions on the state-of-the-art Weather Research and Forecasting (WRF) model with its chemistry extension (WRF-Chem). The evaluation is done for July 2005 with 50 km horizontal resolution. The effect of monthly mean chemical boundary conditions derived from the chemical transport model LMDZ-INCA on WRF-Chem is evaluated against the effect of the preset idealized profiles. Likewise, the impact of different meteorological initial and boundary conditions (GFS and Reanalysis II) on the model is evaluated. Pearson correlation coefficient between these different runs range from 0.96 to 1.00. Exceptions exists for chemical boundary conditions on ozone and for meteorological boundary conditions on PM10, where coefficients of 0.90 were obtained. Best results were achieved with boundary and initial conditions from LMDZ-INCA and GFS. Overall, the European simulations show encouraging results for observed air pollutant, with ozone being the most and PM10 being the least satisfying. 相似文献
86.
Chad S. Lane Sally P. Horn Claudia I. Mora Kenneth H. Orvis David B. Finkelstein 《Journal of Paleolimnology》2011,45(3):323-338
Continuous terrestrial records of paleoclimate and paleovegetation that extend to the late Pleistocene are rare for the circum-Caribbean
uplands. In this study we analyzed the bulk and compound-specific carbon isotope composition of lake sediments spanning this
period from Lago de las Morrenas 1 (LM1), a glacial lake in the highlands of southern Costa Rica, for evidence of climate
and vegetation changes that may not have been apparent in previous analyses. The stable carbon isotope ratios of n-alkanes typically derived from terrestrial plants (δ13CC27–C33) indicate an increased abundance of C4 plant taxa during the late Pleistocene and earliest Holocene that may be related to decreased atmospheric carbon dioxide
concentrations, increased aridity, or habitat availability. These n-alkane isotope ratios also provide evidence of more arid conditions during the early and late Holocene, and more mesic conditions
during the middle Holocene, a pattern prevalent in other paleoclimate records from the region that is thought to be related
to millennial-scale dynamics of the intertropical convergence zone (ITCZ). The sensitivity of the LM1 paleorecord to trade
wind dynamics provides further support for the role of millennial-scale shifts in ITCZ dynamics in driving neotropical environmental
change, and indicates that the effects of ITCZ migration were not limited to the lowlands. 相似文献
87.
88.
Sally Meese 《Marine Policy》1983,7(2):123-124
Emphasis on mining of manganese nodules has led to a rules, regulations and procedures lacuna in the provisions for non-nodule minerals mining. Unless the regime governing the exploitation of‘other minerals’ is improved, the mining of polymetallic sulphides and other non-nodule minerals will be seriously affected. 相似文献
89.
90.
When properly calibrated, Holocene pollen data provide an important source of quantitative information about Holocene climates. Multiple linear regression of modern climate and pollen data allows the development of statistical calibration functions that transform percentages of certain pollen types into quantitative estimates of climatic variables, and these functions, when applied to Holocene pollen data, yield estimates of climatic variables for past times. Confidence intervals for the climatic variables provide estimates of the statistical errors. These interval estimates are based upon the following statistical assumptions: (1) the regression model is appropriate; (2) the errors in measuring the climate variables are independent, normally distributed and have constant variance; and (3) no outliers are present. We outline the steps to be followed in calculating calibration functions, including (1) selecting the calibration region; (2) selecting a pollen sum; (3) analyzing scatter diagrams of a given climate variable against each pollen type; (4) deleting outliers and transforming pollen data; (5) performing the regression; and (6) testing the appropriateness of the statistical assumptions. We used available computer programs for most of this study. In addition, we developed new software to compute the Moran statistic to test for spatial autocorrelation among the regression residuals, using the dual of the Voronoi diagram to describe the spatial relationships among the sites. In order to illustrate the sequence of procedures, we used data from the lower peninsula of Michigan to develop a calibration function for July mean temperature and then used Holocene pollen data from central lower Michigan to estimate past temperatures. 相似文献