Spectral analysis of continuous redox data reveals geochemical dynamics near the stream–aquifer interface     

Corey D. Wallace  Audrey H. Sawyer  Rebecca T. Barnes 《水文研究》2019,33(3):405-413

Changes in streamflow and water table elevation influence oxidation–reduction (redox) conditions near river–aquifer interfaces, with potentially important consequences for solute fluxes and biogeochemical reaction rates. Although continuous measurements of groundwater chemistry can be arduous, in situ sensors reveal chemistry dynamics across a wide range of timescales. We monitored redox potential in an aquifer adjacent to a tidal river and used spectral and wavelet analyses to link redox responses to hydrologic perturbations within the bed and banks. Storms perturb redox potential within both the bed and banks over timescales of days to weeks. Tides drive semidiurnal oscillations in redox potential within the streambed that are absent in the banks. Wavelet analysis shows that tidal redox oscillations in the bed are greatest during late summer (wavelet magnitude of 5.62 mV) when river stage fluctuations are on the order of 70 cm and microbial activity is relatively high. Tidal redox oscillations diminish during the winter (wavelet magnitude of 2.73 mV) when river stage fluctuations are smaller (on the order of 50 cm) and microbial activity is presumably low. Although traditional geochemical observations are often limited to summer baseflow conditions, in situ redox sensing provides continuous, high‐resolution chemical characterization of the subsurface, revealing transport and reaction processes across spatial and temporal scales in aquifers.  相似文献   

The Zn abundance and isotopic composition of diatom frustules,a proxy for Zn availability in ocean surface seawater     

Morten B. Andersen  Derek Vance  Corey Archer  Robert F. Anderson  Michael J. Ellwood  Claire S. Allen 《Earth and Planetary Science Letters》2011,301(1-2):137-145

We have developed cleaning methods for extracting diatomopal from bulk marine sediment samples, for measurement of both zinc (Zn) abundance and isotope composition. This cleaning technique was then applied to a set of Holocene core-top samples from the Southern Ocean. The measured δ⁶⁶Zn (reported relative to the JMC_Lyon standard) and Zn/Si ratios from the Southern Ocean diatom_opal samples range from 0.7 to 1.5‰, and from 14 to 0.9 μmol/mol, respectively. The Zn abundance and isotope composition data show a clear correlation with opal burial rates and other oceanographic parameters. In common with previous work, we interpret the systematic changes in the Zn/Si ratio to be linked to the variability in the concentrations of bioavailable Zn in the ambient surface seawater where the diatom opal is formed. This variability is likely to be primarily controlled by the degree to which Zn is taken up into phytoplankton biomass. The observed systematic pattern in the δ⁶⁶Zn compositions of the diatom_opal core-top samples is, similarly, likely to reflect changes in the δ⁶⁶Zn composition of the ambient Zn in the surface waters above the core-top sites, which is progressively driven towards isotopically heavier values by preferential incorporation of the lighter isotopes into phytoplankton organic material. Thus, the systematic relationship between Zn isotopes and abundance observed in the core-top diatom_opal samples suggests a potential tool for investigating the biogeochemical cycling of Zn in the past surface ocean for down-core diatom_opal material. In this respect, it may be possible to test hypotheses that attribute variations in atmospheric CO₂ on glacial–interglacial timescales to the degree to which trace metals limited primary productivity in HNLC zones.  相似文献   

Application of Proper Orthogonal Decomposition (POD) to inverse problems in saturated groundwater flow     

Corey Winton  Jackie Pettway 《Advances in water resources》2011,34(12):1519-1526

We develop a new Proper Orthogonal Decomposition (POD) reduced order model for saturated groundwater flow, and apply that model to an inverse problem for the hydraulic conductivity field. We use sensitivities as the POD basis. We compare the output when the optimizer uses the reduced order model against results obtained with a full PDE based model. The solutions generated using the POD reduced model are comparable in residual norm to the solutions formed using only the full-scale model. The material parameters are similarly comparable. The time to solution when using the reduced model is reduced by at least an order of magnitude, as are the number of calls to the full model.  相似文献   

Biological characteristics of a resident population of Atlantic cod (Gadus morhua L.) in southern Labrador     

Morris  Corey J.; Green  John M. 《ICES Journal of Marine Science》2002,59(4):666-678

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A New Quantitative Bottom Sampler for Meiof auna     

Corey  Susan; Craib  J. S. 《ICES Journal of Marine Science》1966,30(3):346-353

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Erratum to: The oceanic cycles of the transition metals and their isotopes     

Derek Vance  Corey Archer  Susan H. Little  Michael Köbberich  Gregory F. de Souza 《中国地球化学学报》2018,37(1):151-151

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Do weather fluctuations cause people to seek information about climate change?     

Corey Lang 《Climatic change》2014,125(3-4):291-303

Learning about the causes and consequences of climate change can be an important avenue for supporting mitigation policy and efficient adaptation. This paper uses internet search activity data, a distinctly revealed preference approach, to examine if local weather fluctuations cause people to seek information about climate change. The results suggest that weather fluctuations do have an effect on climate change related search behavior, however not always in ways that are consistent with the projected impacts of climate change. While search activity increases with extreme heat in summer and extended periods of no rainfall and declines in extreme cold in winter, search activity also increases with colder winter and spring average temperatures. Some of the surprising results are magnified when heterogeneity by political ideology and educational attainment in responsiveness is modeled, which could suggest that different people have different perceptions about what types of weather define climate change or that climate science deniers seek information through Google. However, the results also indicate that for all groups in the political and educational spectrum, there exist weather events consistent with the predicted impacts of climate change that elicit increased information seeking.  相似文献   

Comparison of results from several AOGCMs for global and regional sea-level change 1900–2100     

J. M. Gregory  J. A. Church  G. J. Boer  K. W. Dixon  G. M. Flato  D. R. Jackett  J. A. Lowe  S. P. O'Farrell  E. Roeckner  G. L. Russell  R. J. Stouffer  M. Winton 《Climate Dynamics》2001,18(3-4):225-240

 Sea-level rise is an important aspect of climate change because of its impact on society and ecosystems. Here we present an intercomparison of results from ten coupled atmosphere-ocean general circulation models (AOGCMs) for sea-level changes simulated for the twentieth century and projected to occur during the twenty first century in experiments following scenario IS92a for greenhouse gases and sulphate aerosols. The model results suggest that the rate of sea-level rise due to thermal expansion of sea water has increased during the twentieth century, but the small set of tide gauges with long records might not be adequate to detect this acceleration. The rate of sea-level rise due to thermal expansion continues to increase throughout the twenty first century, and the projected total is consequently larger than in the twentieth century; for 1990–2090 it amounts to 0.20–0.37 m. This wide range results from systematic uncertainty in modelling of climate change and of heat uptake by the ocean. The AOGCMs agree that sea-level rise is expected to be geographically non-uniform, with some regions experiencing as much as twice the global average, and others practically zero, but they do not agree about the geographical pattern. The lack of agreement indicates that we cannot currently have confidence in projections of local sea-level changes, and reveals a need for detailed analysis and intercomparison in order to understand and reduce the disagreements. Received: 1 September 2000 / Accepted: 20 April 2001  相似文献   

Euro-politics of scale: competing visions of the region in eastern Germany     

Corey Johnson 《GeoJournal》2008,72(1-2):75-89

As John Agnew (Political geography: a reader, 1997) has argued, political and economic change often occasions competing visions of the scales that are appropriate for organizing particular political and economic activities. Nowhere is this more evident than in the European Union, and eastern Germany offers compelling evidence of the contested nature of contemporary scalar politics. Yet a recent debate in human geography (see, e.g. Marston et al., Transactions of the Institute of British Geographers 30:416–432, 2005) calls into question the very concept of scale and rejects its hierarchical conceptualization. In light of this debate, it is appropriate to draw on real-world case studies to examine the ways in which geography figures into policy. Drawing on field work in Saxony, evidence is offered in the form of competing visions of regionalism in the EU context. The evidence presented complicates both hierarchical and flat notions of scale. The current process of querying space to identify those scales that are best-suited for the globalized economy offers insights into both the socially constructed nature of scale as well as the ways in which scalar lenses help to illuminate the geographical aspects (and consequences) of strategies for coping with structural changes.  相似文献   

Acid Neutralization by Gulf Coast Sediments     

Linn E. Fink  Winton G. Aubert  William J. Bernard 《Ground water》1991,29(4):489-494

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