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Abstract El Niño Southern Oscillation (ENSO) has been linked to climate anomalies throughout the world. This paper presents an overview of global ENSO-streamflow teleconnection and identifies regions where the relationship may be exploited to forecast streamflow several months ahead. The teleconnection is investigated by fitting a first harmonic to 24-month El Niño streamflow composites from 581 catchments worldwide and the potential for forecasting is investigated by calculating the lag correlation between streamflow and two indicators of ENSO. The analyses indicate clear ENSO-streamflow teleconnections in many catchments, some of which are consistent across large geographical regions. Strong and regionally consistent ENSO-streamflow teleconnections are identified in Australia and New Zealand, South and Central America, and weaker signals are identified in some parts of Africa and North America. The results suggest that the ENSO-streamflow relationship and the serial correlation in streamflow can be used to successfully forecast streamflow. The streamflow forecasts can be used to help manage water resources, particularly in systems with high interannual variability in Australia, southern and drier parts of Africa and some areas of North America. 相似文献
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The Signature of Amphibole in Mafic Alkaline Lavas, a Study in the Northern Canadian Cordillera 总被引：2，自引：8，他引：2
Despite evidence for its involvement, the importance of amphibolein controlling the compositions of mafic alkaline magmas remainsunder-appreciated. Relatively small variations in large ionlithophile elements (LILE) with respect to other incompatibleelements, such as light rare-earth elements (LREE) or Th, requirethat amphibole was an important residual phase during the productionof Late Tertiary to Recent olivine nephelinite (Ol-NEPH) magmasbeneath the northern Canadian Cordillera. The erupted maficmagma types define a continuous array from Ol-NEPH to hypersthene-normativeolivine basalt (Hy-NORM AOB). The overall compositional arrayhas a sense of curvature which is counter to binary mixing,but can be modeled by two distinct linear melting trends: onefrom Ol-NEPH to basanite (BASAN) compositions, during whichamphibole controlled the composition of the melt, and the ratiosof LILE/LREE change significantly, but the ratios of high fieldstrength elements (HFSE) remain relatively constant; the otherfrom BASAN to Hy-NORM AOB corresponding to the melting of alherzolite assemblage, following the exhaustion of amphibole,across which the ratios of LILE/LREE remain relatively constant,but the ratios of HFSE change significantly. Other intraplate alkaline suites, such as those of the HawaiianIslands, show similar evidence for the involvement of residualamphibole in the genesis of Ol-NEPH to BASAN magmas. The meltingof any amphibole-bearing mantle assemblage is likely to be atwo-step process, regardless of whether the amphibole is segregatedas veins or distributed interstitially. In a water-undersaturatedenvironment, the first stage of melting is controlled by thebreakdown of amphibole, which produces silica-saturated liquidsbelow 12 kbar and silica-undersaturated liquids at greater depths,with little contribution from other mineral phases. In the secondstage, following the exhaustion of amphibole, the major elementcompositions of subsequent melts change rapidly to equilibratewith a lherzolite mineralogy, but the incompatible trace-elementcharacteristics of the former amphibole persist. KEY WORDS: amphibole; mafic alkaline magmas; northern Canadian Cordillera; trace elements
*Corresponding author 相似文献
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Anaerobic diagenesis within Recent, Pleistocene, and Eocene marine carbonate frameworks 总被引：2，自引：0，他引：2
FRANCIS J. SANSONE† GORDON W. TRIBBLE ‡ CHRISTINE C. ANDREWS† JEFFREY P. CHANTON§ 《Sedimentology》1990,37(6):997-1009
Porewaters from a variety of Recent, Pleistocene, and Eocene lithified marine carbonate frameworks displayed similar chemical characteristics: highly depleted concentrations of dissolved oxygen (>20 μM), elevated levels of dissolved methane (25-5000 nM), and near-seawater sulphate levels. These porewaters also had low pH values (7·5-7·9), and contained elevated concentrations of sulphide (4–10 μM), dissolved inorganic carbon (2·05–2·46 mM), and inorganic nutrients. Hydrocarbon composition data indicate that the methane is biogenic, whereas the methane δ13C values (–47·4 ± 2·7%0) suggest that it has been subject to oxidation. The porewater dissolved inorganic carbon δ13C values varied from –0·6 to –39%0, suggesting input of carbon dioxide from organic matter oxidation. We conclude that anaerobic diagenesis involving bacterial degradation of organic matter is a common process in lithified marine carbonates and hypothesize that it may be an important factor controlling their carbonate geochemistry. 相似文献
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Polar fossil forests 总被引：1，自引：0，他引：1
JANE E. FRANCIS 《Geology Today》1990,6(3):92-95
In the Arctic and Antarctic there are spectacular fossil forests. They are true 'polar forests' because not only are they found as fossils in high latitudes today-they actually grew in the polar regions. They provide important evidence that the climate of the Earth was once much warmer, and that the trees must have been adapted to the strange polar light-regime of winter darkness and continuous summer sunlight. 相似文献
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The Mantle Source for Olivine Nephelinite, Basanite, and Alkaline Olivine Basalt at Fort Selkirk, Yukon, Canada 总被引：2，自引：1，他引：1
Olivine nephelinite, basanite, and transitional alkaline basaltlavas of the Quaternary Fort Selkirk volcanic complex in thecentral Yukon represent three distinct alkaline magma serieswhich have evolved along diverging paths. They cannot be relatedby low-pressure crystal-liquid fractionation, and systematicisotopic differences make it difficult to derive them by variabledegrees of melting of a common mantle source. Field evidencerequires, however, that these three magma series are intimatelyrelated in time and space, and they share a number of anomalouschemical characteristics including low Ca/Na ratios with respectto the majority of terrestrial equivalents. When the effectsof differential olivine fractionation are ignored, the compositionalspectrum of the Fort Selkirk lavas approximates a binary mixingline between transitional alkaline basalt and olivine nephelinite.A population gap along this mixing line, located between thecompositions of the nephelinite and basanite lavas, coincideswith the compositions of amphibole and/or amphibole–garnet–clinopyroxeneassemblages observed in mantle xenoliths. This compositionalgap may represent a thermal divide separating two minimum-meltcompositions in a mantle source consisting of a lherzolite hostcut by amphibole–garnet–clinopyroxenite veins. Theolivine nephelinite endmember may have been derived by earlymelting in the amphibole–garnet–clinopyroxeniteveins, whereas the transitional alkaline basalt would representmore extensive melting of the host lherzolite. 相似文献
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FRANCIS M. MUTUA 《水文科学杂志》2013,58(3):235-244
Abstract For a long time now, the hydrologist has been faced with the problem of finding which of the many possible probability distribution functions can be used most effectively in flood frequency analyses. This problem has been mainly due to the insufficiency of the conventional goodness-of-fit procedures when used with the typically skewed flood probability distributions. In this study, the Akaike Information Criterion (AIC) goodness-of-fit test is used to identify more objectively the optimum model for flood frequency analysis in Kenya from a class of competing models. The class is comprised of (a) seven three-parameter density functions, namely, log-normal, Pearson, log-Pearson, Fisher-Tippet, log-Fisher-Tippet, Walter Boughton and log-Walter Boughton; and (b) two five-parameter density functions, namely, Wakeby and log-Wakeby. The AIC is also used in this study as a method of testing for the existence of outlier peak-flow values in the peak annual data used. A modified version of the chi-square goodness-of-fit test is also used, but only for the sake of comparison with the AIC. 相似文献
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A common fault of atmospheric general circulation models (AGCMs) is an overestimation of orographic precipitation. One basic reason is that water vapour advection schemes do not use information about the local temperature. When water vapour is advected from a warm grid point to a colder one, supersaturation may occur on the way, and the water vapour advected may partly precipitate before reaching the latter. This process is particularly important when moisture is advected upward mountain slopes along terrain‐following coordinates. Not taking it in account, i.e., letting all the moisture reach the colder point, leads to artificial drying of the windward valleys and foothills, and to overestimation of rainfall over summits and plateaux. This spurious behaviour is amplified by the resulting biases in the circulation, due to misplacement of the moisture convergence. It is a general bias, although its magnitude may be reduced, for instance when σ-coordinates are replaced by hybrid coordinates, or increased by highly diffusive schemes such as the upstream finite differencing. A simple way of correcting this bias is to test the advected water vapour with respect to saturation values, and redistribute it accordingly over the grid points found along the advecting path. This method is tested on a finite difference model using σ-coordinates and an upstream advection scheme. The effect on the distribution of moisture and rainfall is dramatic: precipitation is displaced from summits and plateaux to slopes and foothills, leading to much more realistic patterns, in particular for the Indian and Amazonian monsoons. 相似文献
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Transport and accumulation of actinide elements in the near-shore environment: field and modelling studies 总被引：2，自引：0，他引：2
OLIVIA J. MARSDEN† LIAM ABRAHAMSEN† NICHOLAS D. BRYAN† J. PHILIP DAY† L. KEITH FIFIELD‡ CLARISSA GENT† PHILLIP S. GOODALL§ KATHERINE MORRIS¶ FRANCIS R. LIVENS 《Sedimentology》2006,53(1):237-248
Nuclear facilities in coastal locations often discharge low‐level liquid wastes into the sea and the radioisotopes in these discharges are of interest both in assessing possible environmental impacts and as tracers for coastal processes. The distributions of a range of artificial radionuclides, derived from the authorized discharges from British Nuclear Fuels (BNFL) Sellafield, have been determined in the sediments of an intertidal salt marsh in the Esk Estuary, Cumbria, UK. Where published discharge histories exist (for 137Cs, 238Pu, 239,240Pu and 241Am), the sediment core‐profile distributions of these radionuclides have been compared with the releases from Sellafield, and consistent values of the accumulation rate (0·226 ± 0·007 g cm?2 yr?1) are obtained. A quantitative model has been developed, describing association of radionuclides with suspended particulate material, which is then accumulated and mixed in an offshore mud patch before resuspension and deposition in the salt marsh. The model has been used to describe radionuclide distributions observed in both the mud patch and the salt marsh, and to identify isotopes for which post‐depositional remobilization or solution transport from the discharge point are important. The behaviour of the commonly studied isotopes (137Cs, 238Pu, 239,240Pu and 241Am) is similar to that observed at this and other nearby locations. The activation product isotope 236U is enhanced in these sediments over the natural baseline by four to eight orders of magnitude, and the results suggest that Sellafield‐derived uranium is comparably mobile to 137Cs in these sediments although the processes governing the behaviour of these two elements may be different. In situ production of 241Am by decay of its 241Pu parent has generated only 17% of the current sediment inventory of this isotope, insufficient to account for the increase over the last 20–25 years, and suggesting that the input material for these sediments is preferentially enriched in Am relative to Pu during transport from the offshore mud patch. The discharge history of 244Cm, which is unknown, has also been reconstructed from the sediment profile and the model. 相似文献
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INGRID U. OLSSON FRANCIS A. N. OSADEBE 《Boreas: An International Journal of Quaternary Research》1974,3(4):139-146
The formulas for correcting 14 C measurements are explained. The expected ranges of the δ13 C values for some types of samples are given. It is pointed out that the corrections are approximate because of the choice of correction formula, and that all samples arc normalized to wood samples instead of to carbon dioxide of the air. Some results from the Uppsala laboratory for plant materials and carbonates are given. 相似文献