Insights from pollen,non-pollen palynomorphs and testate amoebae into the evolution of Lake Simcoe     

Olena Volik  Francine M. G. McCarthy  Nicholas L. Riddick 《Journal of Paleolimnology》2016,56(2-3):137-152

  相似文献   

Application of Aqua MODIS sensor data for estimating chlorophyll a in the turbid Case 2 waters of Lake Erie using bio-optical models     

K. Adem Ali  Joseph Ortiz  Nicholas Bonini  Morgan Shuman  Catherine Sydow 《地理信息系统科学与遥感》2016,53(4):483-505

There is considerable interest in accurately estimating water quality parameters in turbid (Case 2) and eutrophic waters such as the Western Basin of Lake Erie (WBLE). Lake Erie is a large, open freshwater body that supports diverse ecosystem, and over 12 million people in the mid-western part of the United States depend on it for drinking water, fisheries, navigational, and recreational purposes. The increasing utilization of the freshwater has deteriorated the water severely and currently the lake is experiencing recurring harmful algal blooms (HABs). Improving the water quality of Lake Erie requires the use of robust monitoring tools that help water quality managers understand sources and pathways of influxes that trigger HABs. Satellite-based remote sensing sensor such as the moderate resolution imaging spectroradiometer (MODIS) may provide frequent and synoptic view of the water quality indices. In this study, data set from field measurements was used to evaluate the performance of 14 existing ocean color algorithms. Results indicated that MODIS data consistently underestimated the chlorophyll a concentrations in the WBLE, with the largest source of errors from dissolved organic matter and xanthophyll accessory pigments in this data set. Most of the global algorithms, including OC4v4 and the Baltic model, generated near-identical statistical parameters with an average R² of ~0.57 and RMSE ~2.9 μg/l. MODIS performed poorly (R² ~0.18) when its NIR/red bands were used. A slightly improved model was developed using similar band ratio approach generating R² of ~0.62 and RMSE ~1.8 μg/l.  相似文献   

Coastal curios? An analysis of ex situ beach finds for mapping new Palaeolithic sites at Happisburgh,UK     

Rachel Bynoe  Nick M. Ashton  Tim Grimmer  Peter Hoare  Joanne Leonard  Simon G. Lewis  Darren Nicholas  Simon Parfitt 《第四纪科学杂志》2021,36(2):191-210

Recent archaeological discoveries from exposures of the Cromer Forest-bed Formation at Happisburgh, UK, have radically changed interpretations of the nature and timing of early hominin occupation of northern latitudes, but this in situ archaeology is only one part of the picture. Surface finds of Pleistocene mammalian remains have been found along this coastline for centuries, with stone tools adding to this record over the past 7 years. The ex situ nature of these finds, however, means they are often seen as limited in the information they can provide. This work contributes to a growing body of research from a range of landscape and environmental contexts that seeks to demonstrate the value and importance of these ex situ assemblages. Here the focus is on Palaeolithic flint artefacts and Pleistocene mammalian remains recovered by a group of local collectors through systematic, GPS-recorded beach collection from 2013 to 2017, and their use in developing a methodology for working with ex situ Palaeolithic finds in coastal locations. The results demonstrate significant patterning that identifies unexplored exposures both onshore and offshore, considerably expanding the known extent of deposits and facilitating new insights into the wider archaeological landscape associated with the earliest occupation of northern Europe.  相似文献   

Farm-scale adaptation and vulnerability to environmental stresses: Insights from winegrowing in Northern California     

Kimberly A. Nicholas  William H. Durham 《Global Environmental Change》2012,22(2):483-494

The wine industry is increasingly recognized as especially vulnerable to climate change due to the climate sensitivity of both winegrape yields and quality, making it an important model system for the agricultural impacts of global changes. However, agricultural production is strongly influenced by the management decisions of growers, including their practices to modify the microclimate experienced by the growing crop; these adaptations have not been studied at the vineyard level, where managers on the ground are on the front lines of responding to global change.We conducted 20 in-depth interviews with winegrowers to examine farm-scale adaptive responses to environmental stresses, to understand the views and motivations of agricultural managers, and to explore adaptive capacity in practice. We found that growers tend to respond to stresses individually rather than collectively, except when facing severe, unfamiliar pests and diseases. Responses may be reactive or anticipatory; most anticipatory strategies have been short-term, in response to imminent threats. Growers tend to rely on their own experience to guide their management decisions, which may offer poor guidance under novel climate regimes. From using a Vulnerability Scoping Diagram, we find that changing exposure (vineyard location) and sensitivity (planting choices such as vine variety) have the biggest impact on reducing vulnerability, but that adaptations in growing or processing the crop in the vineyard and winery are easier to implement, much more commonly undertaken, and may also offer substantial adaptive capacity. Understanding the context of adaptations, as well as the decision-making processes motivating them, is important for understanding responses to global change.These findings highlight some innovations in adapting to global change, as well as some of the barriers, and point to the need for strategic investments to enhance agricultural resilience to climate change. In particular, strategies to enhance both effective and easy to implement farming adaptations, as well as broader-scale anticipatory, collective responses, could reduce vulnerability in the context of climate change.  相似文献   

Historical discharge measurements on the Middle Mississippi River,USA: no basis for ‘changing history’     

Nicholas Pinter 《水文研究》2010,24(8):1088-1093

This study tests the hypothesis that historical float‐based discharge measurements on the Mississippi River systematically over‐stated actual flood flows by 10% to > 30% relative to measurements using current meters. This assertion has been repeated over the past 25 years and recently has been used to adjust historical discharges used for flood‐frequency analysis. This study tests the hypothesis above using 2150 historical discharge measurements digitized from the three principal gauging stations on the Middle Mississippi River (MMR): data that include 626 float‐based discharges and 1516 meter‐based discharges, including 122 paired measurements. Multiple comparative tests show that the hypothesis above cannot be supported; if anything, the float‐based measurements slightly underestimate flows (not over‐estimate) over a broad range of discharges up to large floods. In response to the purported data bias above (‘changing history’; Dieckmann RJ, Dyhouse GR. 1998. Changing history at St. Louis—adjusting historic flows for frequency analysis. First Federal Inter‐Agency Hydrologic Modeling Conference, April 20–22, 1998. Las Vegas, NV; 4·31–4·36), historical flood discharges on the MMR have been modified, most by 10–20% and several by > 30%. These altered discharges are now being promulgated, in particular, through the Upper Mississippi River System Flow Frequency Study (UMRSFFS). New flow frequencies, flood profiles, and new flood maps from the UMRSFFS may significantly underestimate the actual flood hazard on the MMR if the original hydrologic data have been erroneously altered on the basis of an assumption of data bias. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

An integrated approach to shallow aquifer characterization: combining geophysics and geostatistics   总被引：1，自引：0，他引：1  

Nicholas B. Engdahl  Gary S. Weissmann  Nedra D. Bonal 《Computational Geosciences》2010,14(2):217-229

We present a method of aquifer characterization that is able to utilize multiple sources of conditioning data to build a more realistic model of heterogeneity. This modeling approach (InMod) uses geophysical data to delineate bounding surfaces within sedimentary deposits. The depositional volumes between bounding surfaces are identified automatically from the geophysical data by a region growing algorithm. Simple geometric rules are used to constrain the growth of the regions in 3-D. The nodes within the depositional volume are assigned to categorical lithologies using geostatistical realizations and a dynamic lookup routine that can be conditioned to field data. The realizations created with this method preserve geologically expected features and produces sharp juxtapositions of high and low hydraulic conductivity lithologies along bounding surfaces. The realizations created with InMod also have higher variance than models created only with geostatistics and honor the volumetric distribution of sediments measured from field data.  相似文献   

Earthquakes in Switzerland and surrounding regions during 2009     

Nicholas Deichmann  John Clinton  Stephan Husen  Benjamin Edwards  Florian Haslinger  Donat Fäh  Domenico Giardini  Philipp Kästli  Urs Kradolfer  Iris Marschall  Stefan Wiemer 《Swiss Journal of Geoscience》2010,103(3):535-549

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2009. During this period, 450 earthquakes and 68 quarry blasts were detected and located in the region under consideration. The three strongest events occurred about 15 km NW of Basel in southern Germany (M_L 4.2), near Wildhaus in the Toggenburg (M_L 4.0) and near Bivio in Graubünden (M_L 3.5). Although felt by the population, they were not reported to have caused any damage. With a total of 24 events with M_L ≥ 2.5, the seismic activity in the year 2009 was close to the average over the previous 34 years.  相似文献   

High-Resolution Fibre-Optic Temperature Sensing: A New Tool to Study the Two-Dimensional Structure of Atmospheric Surface-Layer Flow   总被引：1，自引：0，他引：1  

Christoph K. Thomas  Adam M. Kennedy  John S. Selker  Ayla Moretti  Martin H. Schroth  Alexander R. Smoot  Nicholas B. Tufillaro  Matthias J. Zeeman 《Boundary-Layer Meteorology》2012,142(2):177-192

We present a novel approach based on fibre-optic distributed temperature sensing (DTS) to measure the two-dimensional thermal structure of the surface layer at high resolution (0.25 m, ≈0.5 Hz). Air temperature observations obtained from a vertically-oriented fibre-optics array of approximate dimensions 8 m × 8 m and sonic anemometer data from two levels were collected over a short grass field located in the flat bottom of a wide valley with moderate surface heterogeneity. The objectives of the study were to evaluate the potential of the DTS technique to study small-scale processes in the surface layer over a wide range of atmospheric stability, and to analyze the space–time dynamics of transient cold-air pools in the calm boundary layer. The time response and precision of the fibre-based temperatures were adequate to resolve individual sub-metre sized turbulent and non-turbulent structures, of time scales of seconds, in the convective, neutral, and stable surface layer. Meaningful sensible heat fluxes were computed using the eddy-covariance technique when combined with vertical wind observations. We present a framework that determines the optimal environmental conditions for applying the fibre-optics technique in the surface layer and identifies areas for potentially significant improvements of the DTS performance. The top of the transient cold-air pool was highly non-stationary indicating a superposition of perturbations of different time and length scales. Vertical eddy scales in the strongly stratified transient cold-air pool derived from the DTS data agreed well with the buoyancy length scale computed using the vertical velocity variance and the Brunt–Vaisala frequency, while scales for weak stratification disagreed. The high-resolution DTS technique opens a new window into spatially sampling geophysical fluid flows including turbulent energy exchange.  相似文献   

Towards Reconciling the Large-Scale Structure of Turbulent Boundary Layers in the Atmosphere and Laboratory   总被引：1，自引：1，他引：0  

Nicholas Hutchins  Kapil Chauhan  Ivan Marusic  Jason Monty  Joseph Klewicki 《Boundary-Layer Meteorology》2012,145(2):273-306

A collaborative experimental effort employing the minimally perturbed atmospheric surface-layer flow over the salt playa of western Utah has enabled us to map coherence in turbulent boundary layers at very high Reynolds numbers, \({Re_{\tau}\sim\mathcal{O}(10^6)}\) . It is found that the large-scale coherence noted in the logarithmic region of laboratory-scale boundary layers are also present in the very high Reynolds number atmospheric surface layer (ASL). In the ASL these features tend to scale on outer variables (approaching the kilometre scale in the streamwise direction for the present study). The mean statistics and two-point correlation map show that the surface layer under neutrally buoyant conditions behaves similarly to the canonical boundary layer. Linear stochastic estimation of the three-dimensional correlation map indicates that the low momentum fluid in the streamwise direction is accompanied by counter-rotating roll modes across the span of the flow. Instantaneous flow fields confirm the inferences made from the linear stochastic estimations. It is further shown that vortical structures aligned in the streamwise direction are present in the surface layer, and bear attributes that resemble the hairpin vortex features found in laboratory flows. Ramp-like high shear zones that contribute significantly to the Reynolds shear-stress are also present in the ASL in a form nearly identical to that found in laboratory flows. Overall, the present findings serve to draw useful connections between the vast number of observations made in the laboratory and in the atmosphere.  相似文献   

The Relationship between Wellbeing and Indigenous Land,Language and Culture in Australia     

Nicholas Biddle  Hannah Swee 《The Australian geographer》2012,43(3):215-232

A consistent finding in the literature on Indigenous peoples is the importance of the sustainability of land, language and culture. All three are related, with the maintenance of one helping to protect the others. This paper uses a nationally representative, cross-sectional survey of the Indigenous Australian population to look at the factors associated with individual measures of sustainability. Geography matters for those in remote areas who are much more likely to have participated in hunting, fishing and gathering than those in non-remote areas and somewhat more likely to be learning an Indigenous language. However, those in remote areas are somewhat less likely to have participated in Indigenous cultural production. Participation in the mainstream economy is not necessarily a barrier to these aspects of wellbeing as those with high levels of formal education were more likely to speak, understand or be learning an Indigenous language. While important in their own right, such aspects of sustainability also have the potential to directly contribute to narrower measures of social and emotional wellbeing. A positive relationship was found between the sustainability of Indigenous land, language and culture and an Indigenous person's subjective emotional wellbeing.  相似文献