Natural hazards in Australia: droughts   总被引：3，自引：0，他引：3  

Anthony S. Kiem  Fiona Johnson  Seth Westra  Albert van Dijk  Jason P. Evans  Alison O’Donnell  Alexandra Rouillard  Cameron Barr  Jonathan Tyler  Mark Thyer  Doerte Jakob  Fitsum Woldemeskel  Bellie Sivakumar  Raj Mehrotra 《Climatic change》2016,139(1):37-54

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Natural hazards in Australia: floods     

Fiona Johnson  Christopher J. White  Albert van Dijk  Marie Ekstrom  Jason P. Evans  Dörte Jakob  Anthony S. Kiem  Michael Leonard  Alexandra Rouillard  Seth Westra 《Climatic change》2016,139(1):21-35

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A spreadsheet‐based (Microsoft Excel) point surface energy balance model for glacier and snow melt studies     

Ben W. Brock  Neil S. Arnold 《地球表面变化过程与地形》2000,25(6):649-658

This paper describes a point surface energy balance model which runs within the Microsoft Excel spreadsheet package. The study incorporates a large amount of previous energy balance work and presents it in a useable form. The core model calculates the net shortwave and longwave radiation fluxes, the turbulent sensible and latent heat fluxes and the surface melt rate at a point on a melting ice or snow surface, from hourly inputs of incoming shortwave radiation, vapour pressure, air temperature and wind speed data. The latitude, longitude, slope angle, aspect, elevation, local temperature lapse rate, albedo and aerodynamic roughness of the study site, and the elevation of the meteorological station, can all be specified in the model. An output file containing the hourly and daily rates, and the totals of the energy fluxes is generated. The main advantages of the model are: first, that it requires only a PC or laptop computer running standard Microsoft Windows software, enabling it to be used at a desktop or in the field; and second, that it can be adapted quickly to different sites, meteorological data formats and other application requirements. Model calculations are compared with measured surface melt rates at five points on Haut Glacier d'Arolla, Switzerland, over a 115 day ablation period. Allowing for differences in shading between the meteorological station and the glacier, the root mean square error of the calculated melt rates is 2·0 mm day⁻¹ water equivalent melt (mean error +1·2 mm day⁻¹), for measured melt rates in the range 23 to 42 mm day⁻¹ water equivalent melt. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Hydropyrolysis as a new tool for radiocarbon pre-treatment and the quantification of black carbon     

P.L. Ascough  M.I. Bird  F. Brock  T.F.G. Higham  W. Meredith  C.E. Snape  C.H. Vane 《Quaternary Geochronology》2009,4(2):140-147

The first results concerning the potential of hydrogen pyrolysis (hypy) as a new tool for the quantification and isolation of Black Carbon (BC) for radiocarbon analysis are reported. BC is a highly stable form of carbon, produced during pyrolysis of biomass to materials such as charcoal. Isolation and quantification of this component is therefore of great interest in radiocarbon measurement, particularly for more ancient samples, where contamination issues become more critical. Hypy has been demonstrated to reliably separate labile and refractory carbonaceous sample components for engineering and geological applications, but its potential in ¹⁴C geochronological investigation has previously been unexplored. Here, we test the hypy technique using a selection of soil standard samples and ancient charcoals from deposits of geological and archaeological significance. The results show that hypy can effectively and reproducibly isolate different carbon fractions within a variety of sample types and thus has the potential to provide a rapid and robust pre-treatment technique for radiocarbon analysis. Hypy has the additional advantage that the non-BC fraction removed from a sample can be quantitatively collected for subsequent further analysis. The technique represents a promising new approach not only for ensuring reliable decontamination of pyrogenic carbon samples prior to radiocarbon dating, but also for BC quantification in a variety of environmental matrices.  相似文献   

Jökulhlaup initiation by ice‐dam flotation: the ­significance of glacier debris content     

Fiona S. Tweed 《地球表面变化过程与地形》2000,25(1):105-108

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Wetter isn't better: global warming and food security in the Congo Basin     

David Wilkie  Gilda Morelli  Fiona Rotberg  Ellen Shaw   《Global Environmental Change》1999,9(4):613

Over 20 million forest farmers practice slash and burn agriculture in the forests of the Congo Basin (Bahuchet and de Maret, 1995. State of Indigenous Populations Living in Rainforest Areas, European Commission DG XI Environment, Brussels). They rely on the long dry season (December–February north of the equator) to ensure that their new fields, cleared from regrowth forest, burn sufficiently well to deposit nutrients into the soil and to minimize the labor required to prepare the field for planting. Data from the Ituri forest in northeastern Democratic Republic of Congo show that the strength of the annual dry season (a) has a direct positive impact on the size of fields cleared each year by slash and burn farmers, and consequently on food production and the severity of the subsequent year's pre-harvest hunger period; and (b) is inversely related to total annual rainfall. These results suggest that the 1 mm/d increase in rainfall predicted for much of the Congo Basin by the 2050s may cause a basin wide increase in the frequency of heavy rains during the dry season, causing a reduction in the size of slash and burn farmers’ fields, and potentially a substantial increase in the food insecurity of poor rural families across the region.  相似文献   

Optically stimulated luminescence dating of single and multiple grains of quartz from perennially frozen loess in western Yukon Territory, Canada: Comparison with radiocarbon chronologies for the late Pleistocene Dawson tephra     

M. Demuro  R.G. Roberts  D.G. Froese  L.J. Arnold  F. Brock  C.Bronk Ramsey 《Quaternary Geochronology》2008,3(4):346-364

Optically stimulated luminescence (OSL) dating of perennially frozen loess was tested on quartz grains extracted from deposits associated with the late Pleistocene Dawson tephra in western Yukon Territory, Canada. OSL samples were obtained from ice-rich loess bracketing the Dawson tephra, while radiocarbon (¹⁴C) samples were collected from the bulk sediments directly underlying the tephra and from a ground-squirrel burrow 2.7 m below the tephra. Here we report the OSL characteristics and ages of the extracted quartz grains, as well as additional radiocarbon ages for samples described in Froese [2002. Age and significance of the late Pleistocene Dawson tephra in eastern Beringia. Quaternary Science Reviews 21, 2137–2142; 2006. Seasonality of the late Pleistocene Dawson tephra and exceptional preservation of a buried riparian surface in central Yukon Territory, Canada. Quaternary Science Reviews 25, 1542–1551]. We refine the time of Dawson tephra deposition to between 25,420±70 and 25,290±80 ¹⁴C a BP. Bayesian analysis of constraining radiocarbon ages places the deposition of the Dawson tephra at between 30,433 and 30,032 cal a BP. Linear modulation (LM) OSL analysis of multi-grain aliquots of quartz showed that the initial part of the decay curve is dominated by a rapidly bleached (‘fast’) component; these samples, however, had relatively dim continuous wave (CW) OSL signals at the multi-grain aliquot (each composed of 80 grains) and single-grain scales of analysis. The single-aliquot regenerative-dose protocol was applied to multi-grain aliquots and single grains to obtain equivalent dose (D_e) values for samples collected from below and above the Dawson tephra. The D_e values were examined graphically and numerically, the latter using the central age, minimum age, and finite mixture models. For multi-grain aliquots, the central age model gave weighted mean D_e values between 30 and 50 Gy, which greatly underestimated the expected D_e of 74–81 Gy for both samples studied. Possible reasons for these underestimations are discussed, and a solution proposed based on single-grain analysis. Measurements of single grains produced D_e values in agreement with the expected D_e, and yielded OSL ages of 28±5 and 30±4 ka for the samples taken from above and below the Dawson tephra, respectively. Examination of individual grains with differing luminescence behaviors showed that a significant number of the measured quartz grains exhibited anomalous luminescence properties that would have compromised the results obtained from multi-grain aliquots. We therefore recommend analysis of individual grains to overcome the age-shortfall from multi-grain analysis of these and similar samples of quartz.  相似文献   

New quantitative approaches for classifying and predicting local-scale habitats in estuaries     

Fiona J. Valesini  Mathew Hourston  Michelle D. Wildsmith  Natasha J. Coen  Ian C. Potter 《Estuarine, Coastal and Shelf Science》2010

This study has developed quantitative approaches for firstly classifying local-scale nearshore habitats in an estuary and then predicting the habitat of any nearshore site in that system. Both approaches employ measurements for a suite of enduring environmental criteria that are biologically relevant and can be easily derived from readily available maps. While the approaches were developed for south-western Australian estuaries, with a focus here on the Swan and Peel-Harvey, they can easily be tailored to any system.  相似文献   

Sacred ground; the Maipés necropolis of north‐west Gran Canaria     

Valentin R. Troll  Alejandro Rodriguez‐Gonzalez  Frances M. Deegan  Francisco Jos Perez‐Torrado  Juan Carlos Carracedo  Konstantinos Thomaidis  Harri Geiger  Fiona C. Meade 《Geology Today》2019,35(2):55-62

Gran Canaria, like most of the Canary Islands, shows evidence for young basaltic volcanism in the form of cinder cones and valley‐hugging lava flows. These landforms were of no particular use to the aboriginal population, nor to the subsequent Spanish settlers, and young lava flows and lava fields are still referred to as ‘malpaís’ (badlands) in the Canary Islands. In north‐west Gran Canaria, one such lava flow fills the bottom of a steep‐sided valley, which reaches the sea at the present day village of Agaete. The lava flow erupted c. 3030 ± 90 yr bp and displays a total length of ～ 11 km. At its distal end, just outside Agaete, it hosts one of Europe’s largest and most important pre‐historic burial sites constructed of volcanic rock: the Maipés necropolis. Over 700 pre‐historic tombs (or tumuli) constructed from the aa‐type clinker materials have been identified on top of the valley‐filling lava flow. The up to soccer‐ball sized vesicular clinker fragments are sufficiently low in density to provide abundant, workable basalt blocks for the construction of the tumuli, allowing the pre‐hispanic aboriginal population to create a large and magnificent ‘sacred ground’ in an otherwise barren landscape.  相似文献   

Microbiological studies of thermal habitats of the central volcanic region,North Island,New Zealand     

T. D. Brock  M. Louise Brock 《新西兰海洋与淡水研究杂志》2013,47(2):233-258

This account of studies on the algae and bacteria of North Island thermal areas records temperature, pH and species found in these microbial habitats, with special attention to organisms living at the highest temperatures. Thermal features were studied at Rotorua (Whakarewarewa and Ohinemutu), Waiotapu (Tourist Reserve and Lady Knox Geyser), Orakei Korako, Taupo Spa, Waikite Springs, Wairakei thermal valley, Wairakei geothermal field, Tikitere, Ketetahi, Lake Rotokawa (Taupo region), Waimangu, De Brett Thermal Hotel (Taupo).

The upper temperature limit for blue‐green algae in New Zealand is 60–65°c, and the species living at the thermal limit is generally Mastigocladus laminosus, although in some cases Phormidium sp. or Synechococcus sp. was found. The Synechococcus sp. characteristic of high temperatures (73–74°c) present in North America was not found in New Zealand. In virtually all boiling pools (99–101°c) with pH values in the neutral and alkaline range bacteria were found, but in acidic boiling pools, bacteria were absent. The presence in New Zealand of the eucaryotic algae Cyanidium caldarium and Zygogonium sp. is reported for the first time. Further records for the hot spring brine fly Ephydrella thermarum and other ephydrids are given. The observations are compared with previous data on thermal habitats in Yellowstone Park, in Iceland, and in other parts of the world.  相似文献