Hydrologic and water isotope characterization of a regulated Canadian Shield river basin     

Nancy England  April L. James  Krystopher J. Chutko  Richard S. Pyrce  Huaxia Yao 《水文研究》2019,33(6):905-919

Stable water isotope surveys have increasingly been integrated into river basins studies, but fewer have used them to evaluate impact of hydropower regulation. This study applies hydrologic and water isotope survey approaches to a Canadian Shield river basin with both regulated and natural flows. Historical streamflow records were used to evaluate the influence of three hydroelectric reservoirs and unregulated portions of the basin on downstream flows and changes in water level management implemented after an extreme flood year (1979). In 2013, water isotope surveys of surface and source waters (e.g., rainfall, groundwater, snowmelt) were conducted to examine spatial and temporal variation in contributions to river flow. Seasonal changes in relative groundwater contribution were assessed using a water‐isotope mass balance approach. Within the basin, two regulated reservoirs exhibited inverted hydrographs with augmented winter flows, whereas a third exhibited a hydrograph dominated by spring snowmelt. In 2013, spatial variation in rain‐on‐snow and air temperatures resulted in a critical lag in snowmelt initiation in the southern and northern portions of the basin resulting in a dispersed, double peak spring hydrograph, contrasting with 1979 when a combination of rain‐on‐snow and coincident snowmelt led to the highest flood on record. Although eastern basin reservoirs become seasonally enriched in δ¹⁸O and δ²H values, unregulated western basin flows remain less variable due to groundwater driven baseflow with increasing influence downstream. Combined analysis of historical streamflow (e.g., flood of 1979, drought of 2010) and the 2013 water isotope surveys illustrate extreme meteorological conditions that current management activities are unable to prevent. In this study, the influence of evaporative fractionation on large surface water reservoirs provides important evidence of streamflow partitioning, illustrating the value of stable water isotope tracers for study of larger catchments.  相似文献   

Effect of polychromatic X‐ray microtomography imaging on the amino acid content of the Murchison CM chondrite     

Jon M. Friedrich  Hannah L. McLain  Jason P. Dworkin  Daniel P. Glavin  W. Henry Towbin  Morgan Hill  Denton S. Ebel 《Meteoritics & planetary science》2019,54(1):220-228

X‐ray microcomputed tomography (μCT) is a useful means of characterizing cosmochemical samples such as meteorites or robotically returned samples. However, there are occasional concerns that the use of μCT may be detrimental to the organic components of a chondrite. Small organic compounds such as amino acids comprise up to ~10% of the total solvent extractable carbon in CM carbonaceous chondrites. We irradiated three samples of the Murchison CM carbonaceous chondrite under conditions akin to and harsher than those typically used during typical benchtop X‐ray μCT imaging experiments to determine if detectable changes in the amino acid abundance and distribution relative to a nonexposed Murchison control sample occurred. After subjecting three meteorite samples to ionizing radiation dosages between ~300 Gray (Gy) and 3 kGy with bremstrahlung X‐rays, we analyzed the amino acid content of each sample. Within sampling and analytical errors, we cannot discern differences in the amino acid abundances and amino acid enantiomeric ratios when comparing the control samples (nonexposed Murchison) and the irradiated samples. We conclude that a polychromatic X‐ray μCT experiment does not alter the abundances of amino acids to a degree greater than how well those abundances are measured with our techniques and therefore any damage to amino acids is minimal.  相似文献   

Detailing the impact of the Storegga Tsunami at Montrose,Scotland     

Mark D. Bateman  Tim C. Kinnaird  Jon Hill  Robert A. Ashurst  Jenna Mohan  Rebecca B. I. Bateman  Ruth Robinson 《Boreas: An International Journal of Quaternary Research》2021,50(4):1059-1078

The Storegga tsunami, dated in Norway to 8150±30 cal. years BP, hit many countries bordering the North Sea. Run-ups of >30 m occurred and 1000s of kilometres of coast were impacted. Whilst recent modelling successfully generated a tsunami wave train, the wave heights and velocities, it under-estimated wave run-ups. Work presented here used luminescence to directly date the Storegga tsunami deposits at the type site of Maryton, Aberdeenshire in Scotland. It also undertook sedimentological characterization to establish provenance, and number and relative power of the tsunami waves. Tsunami model refinement used this to better understand coastal inundation. Luminescence ages successfully date Scottish Storegga tsunami deposits to 8100±250 years. Sedimentology showed that at Montrose, three tsunami waves came from the northeast or east, over-ran pre-existing marine sands and weathered igneous bedrock on the coastal plain. Incorporation of an inundation model predicts well a tsunami impacting on the Montrose Basin in terms of replicate direction and sediment size. However, under-estimation of run-up persisted requiring further consideration of palaeotopography and palaeo-near-shore bathymetry for it to agree with sedimentary evidence. Future model evolution incorporating this will be better able to inform on the hazard risk and potential impacts for future high-magnitude submarine generated tsunami events.  相似文献   

Improving Automated Geological Logging of Drill Holes by Incorporating Multiscale Spatial Methods     

Hill  E. June  Pearce  Mark A.  Stromberg  Jessica M. 《Mathematical Geosciences》2021,53(1):21-53

Mathematical Geosciences - Manually interpreting multivariate drill hole data is very time-consuming, and different geologists will produce different results due to the subjective nature of...  相似文献   

Erratum: Seasonal Occurrence of Cownose Rays (<Emphasis Type="Italic">Rhinoptera bonasus</Emphasis>) in North Carolina’s Estuarine and Coastal Waters     

M. April Goodman  Paul B. Conn  Eric Fitzpatrick 《Estuaries and Coasts》2011,34(3):652-652

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Memory in place     

Stephen Hill 《New Zealand geographer》2011,67(1):16-20

Geographers and psychologists both seek to understand people's behaviour and their cognitive and emotional lives so it is somewhat surprising that there has not been more theoretical cross‐fertilisation of the two disciplines. ‘On time, place and happiness’ is a rare but welcome exception, showing how research in social‐cognitive psychology might usefully clarify thinking about temporality, place and well‐being. This commentary examines several additional human memory phenomena that geographers might like to consider in their theorising about these matters.  相似文献   

On the energy integral for first post-Newtonian approximation     

Joseph O’Leary  James M. Hill  James C. Bennett 《Celestial Mechanics and Dynamical Astronomy》2018,130(7):44

The post-Newtonian approximation for general relativity is widely adopted by the geodesy and astronomy communities. It has been successfully exploited for the inclusion of relativistic effects in practically all geodetic applications and techniques such as satellite/lunar laser ranging and very long baseline interferometry. Presently, the levels of accuracy required in geodetic techniques require that reference frames, planetary and satellite orbits and signal propagation be treated within the post-Newtonian regime. For arbitrary scalar W and vector gravitational potentials \(W^j (j=1,2,3)\), we present a novel derivation of the energy associated with a test particle in the post-Newtonian regime. The integral so obtained appears not to have been given previously in the literature and is deduced through algebraic manipulation on seeking a Jacobi-like integral associated with the standard post-Newtonian equations of motion. The new integral is independently verified through a variational formulation using the post-Newtonian metric components and is subsequently verified by numerical integration of the post-Newtonian equations of motion.  相似文献   

Solar-Cycle Variation of Subsurface Zonal Flow     

R. Komm  R. Howe  I. González Hernández  F. Hill 《Solar physics》2014,289(9):3435-3455

We study the solar-cycle variation of the zonal flow in the near-surface layers of the solar convection zone from the surface to a depth of 16 Mm covering the period from mid-2001 to mid-2013 or from the maximum of Cycle 23 through the rising phase of Cycle 24. We have analyzed Global Oscillation Network Group (GONG) and Helioseismic and Magnetic Imager (HMI) Dopplergrams with a ring-diagram analysis. The zonal flow varies with the solar cycle showing bands of faster-than-average flows equatorward of the mean latitude of activity and slower-than-average flows on the poleward side. The fast band of the zonal flow and the magnetic activity appear first in the northern hemisphere during the beginning of Cycle 24. The bands of fast zonal flow appear at mid-latitudes about three years in the southern and four years in the northern hemisphere before magnetic activity of Cycle 24 is present. This implies that the flow pattern is a direct precursor of magnetic activity. The solar-cycle variation of the zonal flow also has a poleward branch, which is visible as bands of faster-than-average zonal flow near 50° latitude. This band appears first in the southern hemisphere during the rising phase of the Cycle 24 and migrates slowly poleward. These results are in good agreement with corresponding results from global helioseismology.  相似文献   

A Full-Sun Magnetic Index from Helioseismology Inferences     

I. González Hernández  M. Díaz Alfaro  K. Jain  W. K. Tobiska  D. C. Braun  F. Hill  F. Pérez Hernández 《Solar physics》2014,289(2):503-514

Solar magnetic indices are used to model the solar irradiance and ultimately to forecast it. However, the observation of such indices is generally limited to the Earth-facing hemisphere of the Sun. Seismic maps of the far side of the Sun have proven their capability to locate and track medium–large active regions at the non-visible hemisphere. We present here the possibility of using the average signal from these seismic far-side maps, combined with similarly calculated near-side maps, as a proxy to the full-Sun magnetic activity.  相似文献   

Solar-Cycle Variation of Subsurface Meridional Flow Derived with Ring-Diagram Analysis     

R. Komm  I. González Hernández  R. Howe  F. Hill 《Solar physics》2015,290(11):3113-3136

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