An evaluation of the relative importance of the effects of climate change and groundwater extraction on seawater intrusion in coastal aquifers in Atlantic Canada     

N. R. Green  K. T. B. MacQuarrie 《Hydrogeology Journal》2014,22(3):609-623

To investigate the relative importance of projected sea-level rise, climate change effects on recharge, and groundwater extraction on seawater intrusion in important coastal aquifers in Atlantic Canada, a three-dimensional numerical model of density-dependent groundwater flow coupled with solute transport was developed for the Richibucto region of New Brunswick. The model was used, with an efficient 2^k factorial design approach, to perform simulations for the period 2011–2100. The results of the factorial analyses indicate that the relative importance of the three factors investigated varies depending on the model location considered. The effect of declining recharge is most significant at shallow to intermediate depths along the freshwater–seawater transition zone, while the effect of increasing pumping rates dominates at a location relatively close to the well field. The effect of sea-level rise is shown to be significant only at the much deeper inland toe of the transition zone. The spatial variation in importance is related to how different model boundary conditions influence freshwater flow at the different locations within the model domain. This investigation indicates that sea-level rise has the least significant effect (of the three factors considered) on future seawater intrusion in sandstone aquifers in the Richibucto region.  相似文献   

Coherence of river and ocean conditions along the US West Coast during storms     

Tara A. Kniskern  Jonathan A. Warrick  Katherine L. Farnsworth  Robert A. Wheatcroft  Miguel A. Goñi 《Continental Shelf Research》2011,31(7-8):789-805

The majority of water and sediment discharge from the small, mountainous watersheds of the US West Coast occurs during and immediately following winter storms. The physical conditions (waves, currents, and winds) within and acting upon the proximal coastal ocean during these winter storms strongly influence dispersal patterns. We examined this river–ocean temporal coherence for four coastal river–shelf systems of the US West Coast (Umpqua, Eel, Salinas, and Santa Clara) to evaluate whether specific ocean conditions occur during floods that may influence coastal dispersal of sediment. Eleven years of corresponding river discharge, wind, and wave data were obtained for each river–shelf system from USGS and NOAA historical records, and each record was evaluated for seasonal and event-based patterns. Because near-bed shear stresses due to waves influence sediment resuspension and transport, we used spectral wave data to compute and evaluate wave-generated bottom-orbital velocities. The highest values of wave energy and discharge for all four systems were consistently observed between October 15 and March 15, and there were strong latitudinal patterns observed in these data with lower discharge and wave energies in the southernmost systems. During floods we observed patterns of river–ocean coherence that differed from the overall seasonal patterns. For example, downwelling winds generally prevailed during floods in the northern two systems (Umpqua and Eel), whereas winds in the southern systems (Salinas and Santa Clara) were generally downwelling before peak discharge and upwelling after peak discharge. Winds not associated with floods were generally upwelling on all four river–shelf systems. Although there are seasonal variations in river–ocean coherence, waves generally led floods in the three northern systems, while they lagged floods in the Santa Clara. Combined, these observations suggest that there are consistent river–ocean coherence patterns along the US West Coast during winter storms and that these patterns vary substantially with latitude. These results should assist with future evaluations of flood plume formation and sediment fate along this coast.  相似文献   

Europrobe seismic reflection profiling across the eastern Middle Urals and West Siberian Basin     

M. Friberg  C. Juhlin  A.G. Green  H. Horstmeyer  J. Roth  A. Rybalka  & M. Bliznetsov 《地学学报》2000,12(6):252-257

New deep seismic reflection data provide images of the crust and uppermost mantle underlying the eastern Middle Urals and adjacent West Siberian Basin. Distinct truncations of reflections delineate the late-orogenic strike-slip Sisert Fault extending vertically to ∼28 km depth, and two gently E-dipping reflection zones, traceable to 15–18 km depth, probably represent normal faults associated with the opening of the West Siberian Basin. A possible remnant Palaeozoic subduction zone in the lower crust under the West Siberian Basin is visible as a gently SW-dipping zone of pronounced reflectivity truncated by the Moho. Continuity of shallow to intermediate-depth reflections suggest that Palaeozoic accreted island-arc terranes and overlying molasse sequences exposed in the hinterland of the Urals form the basement for Triassic and younger deposits in the West Siberian Basin. A highly reflective lower crust overlies a transparent mantle at about 43 km depth along the entire 100 km long seismic reflection section, suggesting that the lower crust and Moho below the eastern Middle Urals and West Siberian Basin have the same origin.  相似文献   

Thermal history of the Hodgkinson Province and Laura Basin,Queensland: Multiple cooling episodes identified from apatite fission track analysis and vitrinite reflectance data     

S. J. Marshallsea  P. F. Green  J. Webb 《Australian Journal of Earth Sciences》2013,60(4):779-797

Apatite fission track analysis and vitrinite reflectance data from outcrop and well samples in the Hodgkinson Province and Laura Basin reveal regional Cretaceous cooling. Apatite fission track analysis appears to define two discrete cooling episodes, in the mid‐Cretaceous (110–100 Ma) and Late Cretaceous (80–70 Ma), although in most samples data allow only definition of a single episode. Rocks now at outcrop cooled from Cretaceous palaeotemperatures generally between 50 and 130°C in the south of the region, and from >100°C in the north. Some samples from the Hodgkinson Province also show evidence for an Early Jurassic cooling episode, characterised by maximum palaeotemperatures varying from at least 95°C (from apatite fission track analysis) to ～200–220°C (from vitrinite reflectance), with cooling beginning at around 200 Ma. Apatite fission track analysis data do not reveal the earlier event in the Laura Basin, but on the basis of vitrinite reflectance data from Permian? units this event is also inferred to have affected the pre‐Jurassic basin units in this region. The regional extent of the Cretaceous cooling episode in the Hodgkinson Province suggests that the elevated palaeotemperatures in this region were most likely due to greater depth of burial, with subsequent cooling due to kilometre‐scale denudation. For a palaeogeothermal gradient of 30°C/km and a palaeosurface temperature of 25°C the total degree of Cretaceous cooling experienced by the samples corresponds to removal of between ～0.8 and >3.0 km of Triassic and younger section removed by denudation, beginning some time between ca 110 and 80 Ma. Higher palaeogradients would require correspondingly lower amounts of removed section. The geology of the Laura Basin suggests that an explanation of the observed Cretaceous palaeotemperatures in this region in terms of deeper burial may be untenable. Heating due to hot fluid flow may be a more realistic mechanism for producing the observed Cretaceous palaeothermal effects in the Laura Basin.  相似文献   

Composition of jovian dust stream particles     

Frank Postberg  Sascha Kempf  Simon F. Green  Neil McBride 《Icarus》2006,183(1):122-134

The Cassini spacecraft encountered Jupiter in late 2000. Within more than 1 AU of the gas giant the Cosmic Dust Analyser onboard the spacecraft recorded the first ever mass spectra of jovian stream particles. To determine the chemical composition of particles, a comprehensive statistical analysis of the dataset was performed. Our results imply that the vast majority (>95%) of the observed stream particles originate from the volcanic active jovian satellite Io from where they are sprinkled out far into the Solar System. Sodium chloride (NaCl) was identified as the major particle constituent, accompanied by sulphurous as well as potassium bearing components. This is in contrast to observations of gas in the ionian atmosphere, its co-rotating plasma torus, and the neutral cloud, where sulphur species are dominant while alkali and chlorine species are only minor components. Io has the largest active volcanoes of the Solar System with plumes reaching heights of more than 400 km above the moons surface. Our in situ measurements indicate that alkaline salt condensation of volcanic gases inside those plumes could be the dominant formation process for particles reaching the ionian exosphere.  相似文献   

A power spectrum description of Galactic neutral hydrogen     

D. A. Green 《Astrophysics and Space Science》1994,216(1-2):201-205

Angular power spectra for neutral hydrogen towardsl = 140°,b = 0° on scales from ≈ 1° to 1/10° are presented. The spectra are generally well fitted by a power-law dependence on radius in theuv-plane, with an index between ≈ -2.2 and ≈ -3.0. The more distant hydrogen, which corresponds to larger physical scales, tends to have a more negative index than does the nearer material. There is no preferred angular scale apparent at any velocity. For the distant hydrogen there is no obvious difference between the slope of power spectra for emission aligned perpendicular compared with that parallel to the Galactic plane.  相似文献   

Experimental petrology of peridotites,including effects of water and carbon on melting in the Earth’s upper mantle   总被引：1，自引：0，他引：1  

David H. Green 《Physics and Chemistry of Minerals》2015,42(2):95-122

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Key natural analogue input required to build a safety case for direct disposal of spent nuclear fuel in Japan     

Ian G. McKinley  Hideki Kawamura  Susie M. L. Hardie  Elizaveta Klein  Tara M. Beattie 《Swiss Journal of Geoscience》2015,108(1):147-154

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Shocked molecular hydrogen towards the Tornado nebula     

J. S. Lazendic  M. Wardle  M. G. Burton  F. Yusef-Zadeh  A. J. Green  J. B. Whiteoak 《Monthly notices of the Royal Astronomical Society》2004,354(2):393-400

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Phytochemical changes in leaves of subtropical grasses and fynbos shrubs at elevated atmospheric CO₂ concentrations     

D. Hattas  W.D. Stock  W.T. Mabusela  I.R. Green 《Global and Planetary Change》2005,47(2-4):181

The effects of elevated atmospheric CO₂ concentrations on plant polyphenolic, tannin, nitrogen, phosphorus and total nonstructural carbohydrate concentrations were investigated in leaves of subtropical grass and fynbos shrub species. The hypothesis tested was that carbon-based secondary compounds would increase when carbon gain is in excess of growth requirements. This premise was tested in two ecosystems involving plants with different photosynthetic mechanisms and growth strategies. The first ecosystem comprised grasses from a C₄-dominated, subtropical grassland, where three plots were subjected to three different free air CO₂ enrichment treatments, i.e., elevated (600 to 800 μmol mol⁻¹), intermediate (400 μmol mol⁻¹) and ambient atmospheric CO₂. One of the seven grass species, Alloteropsis semialata, had a C₃ photosynthetic pathway while the other grasses were all C₄. The second ecosystem was simulated in a microcosm experiment where three fynbos species were grown in open-top chambers at ambient and 700 μmol mol⁻¹ atmospheric CO₂ in low nutrient acid sands typical of south western coastal and mountain fynbos ecosystems. Results showed that polyphenolics and tannins did not increase in the grass species under elevated CO₂ and only in Leucadendron laureolum among the fynbos species. Similarly, foliar nitrogen content of grasses was largely unaffected by elevated CO₂, and among the fynbos species, only L. laureolum and Leucadendron xanthoconus showed changes in foliar nitrogen content under elevated CO₂, but these were of different magnitude. The overall decrease in nitrogen and phosphorus and consequent increase in C:N and C:P ratio in both ecosystems, along with the increase in polyphenolics and tannins in L. laureolum in the fynbos ecosystem, may negatively affect forage quality and decomposition rates. It is concluded that fast growing grasses do not experience sink limitation and invest extra carbon into growth rather than polyphenolics and tannins and show small species-specific chemical changes at elevated atmospheric CO₂ concentrations. Responses of fynbos species are varied and were species-specific.  相似文献