The Monitoring Network of the Vancouver 2010 Olympics   总被引：1，自引：0，他引：1  

Paul Joe  Bill Scott  Chris Doyle  George Isaac  Ismail Gultepe  Douglas Forsyth  Stewart Cober  Edwin Campos  Ivan Heckman  Norman Donaldson  David Hudak  Roy Rasmussen  Paul Kucera  Ron Stewart  Julie M. Thériault  Teresa Fisico  Kristen L. Rasmussen  Hannah Carmichael  Alex Laplante  Monika Bailey  Faisal Boudala 《Pure and Applied Geophysics》2014,171(1-2):25-58

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Re-Os study of Fe-Ti-V oxide and Fe-Cu-Ni sulfide deposits, Suwałki Anorthosite Massif, northeast Poland   总被引：1，自引：0，他引：1  

J. W. Morgan  H. J. Stein  J. L. Hannah  R. J. Markey  J. Wiszniewska 《Mineralium Deposita》2000,35(5):391-401

The Suwałki anorthosite massif, located in extreme northeast Poland beneath more than a kilometer of Phanerozoic cover, hosts major Fe-Ti-V deposits. These deposits, discovered in 1962, are contained in Fe and Ti oxide minerals that coexist with subordinate quantities of Fe, Cu, Ni, and Co sulfides in massif-style anorthosites, norites, and gabbronorites. Accessibility and other considerations preclude development of this natural resource in the present economic climate. Detailed work by Polish geologists during the last 35 years provides a sound geologic framework for this Re-Os study of the age and origin of oxide and sulfide deposits associated with a major, but lesser known anorthosite massif. Rhenium and osmium abundances and Os isotopic compositions were measured for nine sulfides and four titanomagnetites from the Suwałki anorthosite massif. The titanomagnetites are over an order of magnitude lower in Re (0.4–1.5 ppb) and Os (0.036–0.144 ppb) concentrations than co-precipitated pyrrhotite, pyrite, and chalcopyrite that yield consistent concentrations for Re (30–55 ppb) and Os (1–6 ppb). Parallel lines connecting co-existing titanomagnetite and sulfides have slopes of ∼1 on Re versus common Os concentration plots, indicating that both Re and Os behave similarly during crystallization in their high preference for any sulfide phase over magnetite. Samples from three deposits within the anorthosite massif were analyzed. An age of 1559 ± 37 Ma (n=10) with an initial ¹⁸⁷Os/¹⁸⁸Os of 1.16 ± 0.06 for the Jezioro Okrągłe and Krzemianka deposits is essentially identical to an age of 1556 ± 94 Ma (n=3) for the Udryń deposit. Udryń, however, yielded a marginally lower initial ¹⁸⁷Os/¹⁸⁸Os of 0.87 ± 0.20. The high initial ¹⁸⁷Os/¹⁸⁸Os combined with the Proterozoic Re-Os age indicates that the source for Suwałki oxides-sulfides is older crust, and hypothetically, could involve Archean rocks. An average crustal value of 50 for ¹⁸⁷Re/¹⁸⁸Os yields a 2777 Ma age for Suwałki source rocks. Widespread Phanerozoic cover severely limits knowledge of basement rocks in Poland, however, and no Archean rocks are known in the immediate region. More likely, ¹⁸⁷Re/¹⁸⁸Os ratios may be higher than average continental crust, reflecting mafic crust in the source, and may move the source age for Suwałki anorthosite and mineral deposits toward younger values that easily include ∼2.0 Ga Proterozoic rocks. This more favorable case also accommodates Paleoproterozoic Nd model ages. Regardless of Archean or Proterozoic source age, the high initial ¹⁸⁷Os/¹⁸⁸Os ratios derived from the Re-Os isochron indicate that the source for the oxide-sulfide mineral deposits is more likely the crust and not the mantle. Given that these deposits are clearly magmatic, the Re-Os results add a new dimension to the long-standing “origin of anorthosite” problem, implying a crustal source for the anorthosite as well. The 1559 Ma Suwałki age is compatible with a well-exposed east-west band of 1530-1660 Ma rapakivi granite-anorthosite magmatism to the immediate north, transecting western Russia, southern Finland, Estonia and Latvia, and central Sweden. In particular, the age and isotopic character of Suwałki are not unlike those of the well-studied Salmi rapakivi granite-anorthosite batholith in western Russia (Karelia). Received: 4 December 1998 / Accepted: 11 November 1999  相似文献   

Influence of landscape and hydrological factors on stream–air temperature relationships at regional scale     

Aurélien Beaufort  Florentina Moatar  Eric Sauquet  Pierre Loicq  David M. Hannah 《水文研究》2020,34(3):583-597

Identifying the main controlling factors of the stream temperature (Tw) variability is important to target streams sensitive to climate and other drivers of change. The thermal sensitivity (TS), based on relationship between air temperature (Ta) and Tw, of a given stream can be used for quantifying the streams sensitivity to future climate change. This study aims to compare TS for a wide range of temperate streams located within a large French catchment (110,000 km²) using 4 years of hourly data (2008–2012) and to cluster stations sharing similar thermal variabilities and thereby identify environmental key drivers that modify TS at the regional scale. Two successive classifications were carried out: (a) first based on Ta–Tw relationship metrics including TS and (b) second to establish a link between a selection of environmental variables and clusters of stations. Based on weekly Ta–Tw relationships, the first classification identified four thermal regimes with differing annual Tw in terms of magnitude and amplitudes in comparison with Ta. The second classification, based on classification and regression tree method, succeeded to link each thermal regime to different environmental controlling factors. Streams influenced by both groundwater inflows and shading are the most moderated with the lowest TS and an annual amplitude of Tw around half of the annual amplitude of Ta. Inversely, stations located on large streams with a high distance from source and not (or slightly) influenced by groundwater inflows nor shading showed the highest TS, and so, they are very climate sensitive. These findings have implications for guiding river basin managers and other stakeholders in implementing thermal moderation measures in the context of a warming climate and global change.  相似文献   

Simulation of the hydrological impacts of climate change on a restored floodplain     

Julian R. Thompson  Honeyeh Iravani  Hannah M. Clilverd  Carl D. Sayer  Catherine M. Heppell  Jan C. Axmacher 《水文科学杂志》2017,62(15):2482-2510

Thirty UK Climate Projections 2009 (UKCP09) scenarios are simulated using a MIKE SHE/MIKE 11 model of a restored floodplain in eastern England. Annual precipitation exhibits uncertainty in direction of change. Extreme changes (10 and 90% probability) range between ?27 and +30%. The central probability projects small declines (相似文献   

Land-use dominates climate controls on nitrogen and phosphorus export from managed and natural Nordic headwater catchments     

Heleen A. de Wit  Ahti Lepistö  Hannu Marttila  Hannah Wenng  Marianne Bechmann  Gitte Blicher-Mathiesen  Karin Eklöf  Martyn N. Futter  Pirkko Kortelainen  Brian Kronvang  Katarina Kyllmar  Jelena Rakovic 《水文研究》2020,34(25):4831-4850

Agricultural, forestry-impacted and natural catchments are all vectors of nutrient loading in the Nordic countries. Here, we present concentrations and fluxes of total nitrogen (totN) and phosphorus (totP) from 69 Nordic headwater catchments (Denmark: 12, Finland:18, Norway:17, Sweden:22) between 2000 and 2018. Catchments span the range of Nordic climatic and environmental conditions and include natural sites and sites impacted by agricultural and forest management. Concentrations and fluxes of totN and totP were highest in agricultural catchments, intermediate in forestry-impacted and lowest in natural catchments, and were positively related %agricultural land cover and summer temperature. Summer temperature may be a proxy for terrestrial productivity, while %agricultural land cover might be a proxy for catchment nutrient inputs. A regional trend analysis showed significant declines in N concentrations and export across agricultural (−15 μg totN L⁻¹ year⁻¹) and natural (−0.4 μg NO₃-N L⁻¹ year⁻¹) catchments, but individual sites displayed few long-term trends in concentrations (totN: 22%, totP: 25%) or export (totN: 6%, totP: 9%). Forestry-impacted sites had a significant decline in totP (−0.1 μg P L⁻¹ year⁻¹). A small but significant increase in totP fluxes (+0.4 kg P km⁻² year⁻¹) from agricultural catchments was found, and countries showed contrasting patterns. Trends in annual concentrations and fluxes of totP and totN could not be explained in a straightforward way by changes in runoff or climate. Explanations for the totN decline include national mitigation measures in agriculture international policy to reduced air pollution and, possibly, large-scale increases in forest growth. Mitigation to reduce phosphorus appears to be more challenging than for nitrogen. If the green shift entails intensification of agricultural and forest production, new challenges for protection of water quality will emerge possible exacerbated by climate change. Further analysis of headwater totN and totP export should include seasonal trends, aquatic nutrient species and a focus on catchment nutrient inputs.  相似文献   

European quaternary refugia: a factor in large carnivore extinction?     

Hannah J. O'Regan  Alan Turner  David M. Wilkinson 《第四纪科学杂志》2002,17(8):789-795

The extinction of large carnivores in Europe during the Quaternary is reviewed and the potential role of glacial refugia in these extinctions is investigated using the VORTEX model for population viability analysis. A model was built for a medium sized big cat similar to the extinct Panthera gombaszoegensis utilising life history data from the modern jaguar Panthera onca. This approach highlighted the potential importance of glacial refugia in the extinction process. Even model refugia the size of the Italian peninsula did not guarantee persistence of a population over a 1000 yr time span, illustrating the role of chance in survival in such a refugium. An area the size of the largest Mediterranean island was unable to support a big cat population for a period of 1000 yr. The models also demonstrated the importance of inbreeding as a mechanism for extinction in refugia. It is suggested that repeated genetic bottlenecks during successive glaciations would tend to remove lethal recessive alleles from the population, increasing the probability of survival in refugia in subsequent glaciations. The history of extinction of large carnivores in the European Quaternary is interpreted in the light of these results. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Visible–near infrared spectral indices for mapping mineralogy and chemistry with OSIRIS‐REx     

Hannah H. Kaplan  Victoria E. Hamilton  Ellen S. Howell  F. Scott Anderson  M. Antonella Barrucci  John Brucato  Thomas H. Burbine  Beth E. Clark  Ed A. Cloutis  Harold C. Connolly  Elisabetta Dotto  Joshua P. Emery  Sonia Fornasier  Cateline Lantz  Lucy F. Lim  Frederic Merlin  Alice Praet  Dennis C. Reuter  Scott A. Sandford  Amy A. Simon  Driss Takir  Dante S. Lauretta 《Meteoritics & planetary science》2020,55(4):744-765

The primary objective of the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS‐REx) mission is to return to Earth a pristine sample of carbonaceous material from the primitive asteroid (101955) Bennu. To support compositional mapping of Bennu as part of sample site selection and characterization, we tested 95 spectral indices on visible to near infrared laboratory reflectance data from minerals and carbonaceous meteorites. Our aim was to determine which indices reliably identify spectral features of interest. Most spectral indices had high positive detection rates when applied to spectra of pure, single‐component materials. The meteorite spectra have fewer and weaker absorption features and, as a result, fewer detections with the spectral indices. Indices targeting absorptions at 0.7 and 2.7–3 μm, which are attributable to hydrated minerals, were most successful for the meteorites. Based on these results, we identified a set of 17 indices that are most likely to be useful at Bennu. These indices detect olivines, pyroxenes, carbonates, water/OH‐bearing minerals, serpentines, ferric minerals, and organics. Particle size and albedo are known to affect band depth but had a negligible impact on interpretive success with spectral indices. Preliminary analysis of the disk‐integrated Bennu spectrum with these indices is consistent with expectations given the observed absorption near 3 μm. Our study prioritizes spectral indices to be used for OSIRIS‐REx spectral analysis and mapping and informs the reliability of all index‐derived data products, including a science value map for sample site selection.  相似文献   

Prediction of river temperature surges is dependent on precipitation method     

Danny Croghan  Anne F. Van Loon  Jon P. Sadler  Chris Bradley  David M. Hannah 《水文研究》2019,33(1):144-159

Urban river systems are particularly sensitive to precipitation‐driven water temperature surges and fluctuations. These result from rapid heat transfer from low‐specific heat capacity surfaces to precipitation, which can cause thermally polluted surface run‐off to enter urban streams. This can lead to additional ecological stress on these already precarious ecosystems. Although precipitation is a first‐order driver of hydrological response, water temperature studies rarely characterize rain event dynamics and typically rely on single gauge data that yield only partial estimates of catchment precipitation. This paper examines three precipitation measuring methods (a statutory automatic weather station, citizen science gauges, and radar estimates) and investigates relationships between estimated rainfall inputs and subhourly surges and diurnal fluctuations in urban river water temperature. Water temperatures were monitored at 12 sites in summer 2016 in the River Rea, in Birmingham, UK. Generalized additive models were used to model the relationship between subhourly water temperature surges and precipitation intensity and subsequently the relationship between daily precipitation totals and standardized mean water temperature. The different precipitation measurement sources give highly variable precipitation estimates that relate differently to water temperature fluctuations. The radar catchment‐averaged method produced the best model fit (generalized cross‐validation score [GCV] = 0.30) and was the only model to show a significant relationship between water temperature surges and precipitation intensity (P < 0.001, R² = 0.69). With respect to daily metrics, catchment‐averaged precipitation estimates from citizen science data yielded the best model fit (GCV score = 0.20). All precipitation measurement and calculation methods successfully modelled the relationship between standardized mean water temperature and daily precipitation (P < 0.001). This research highlights the potential for the use of alternative precipitation datasets to enhance understanding of event‐based variability in water quality studies. We conclude by recommending the use of spatially distributed precipitation data operating at high spatial (<1 km²) and temporal (<15 min) resolutions to improve the analysis of event‐based water temperature and water quality studies.  相似文献   

Riparian vegetation and island formation along the gravel‐bed Fiume Tagliamento,Italy     

A. M. Gurnell  G. E. Petts  D. M. Hannah  B. P. G. Smith  P. J. Edwards  J. Kollmann  J. V. Ward  K. Tockner 《地球表面变化过程与地形》2001,26(1):31-62

After more than 300 years of river management, scientific knowledge of European river systems has evolved with limited empirical knowledge of truly natural systems. In particular, little is known of the mechanisms supporting the evolution and maintenance of islands and secondary channels. The dynamic, gravel‐bed Fiume Tagliamento, Italy, provides an opportunity to acquire baseline data from a river where the level of direct engineering intervention along the main stem is remarkably small. Against a background of a strong alpine to mediterranean climatic and hydrological gradient, this paper explores relationships between topography, sediment and vegetation at eight sites along the active zone of the Tagliamento. A conceptual model of island development is proposed which integrates the interactions between large woody debris and vegetation, geomorphic features, sediment calibre and hydrological regime. Islands may develop on bare gravel sites or be dissected from the floodplain by channel avulsion. Depositional and erosional processes result in different island types and developmental stages. Differences in the apparent trajectories of island development are identified for each of the eight study sites along the river. The management implications of the model and associated observations of the role of riparian vegetation in island development are considered. In particular, the potential impacts of woody debris removal, riparian tree management, regulation of river flow and sediment regimes, and changes in riparian tree species' distribution are discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

An observation-based method to quantify the human influence on hydrological drought: upstream–downstream comparison     

Sally Rangecroft  Héctor Maureira  Koen Verbist  David M. Hannah 《水文科学杂志》2019,64(3):276-287

In this present era of the Anthropocene, human activities affect hydrology and droughts. Quantifying this human influence improves our understanding and builds fundamental knowledge for water resource management. Analysis of observation data is useful in progressing this knowledge as these human activities and feedbacks are intrinsically included. Therefore, here we present an observation-based approach, the upstream–downstream comparison, to quantify changes in hydrological drought downstream of a human activity. We demonstrate this approach in a basin in northern Chile, where a reservoir was introduced. A sensitivity analysis is performed to assess how different choices of drought analysis threshold can affect the results and interpretation. We find that many commonly used choices do not exclude human activities from the threshold and therefore could be underestimating the change detected due to the human influence. The upstream–downstream comparison avoids this through the application of the upstream station threshold rather than the human-influenced downstream station.  相似文献