Quantifying the response of cotton production in eastern Australia to climate change   总被引：1，自引：0，他引：1  

Allyson Williams  Neil White  Shahbaz Mushtaq  Geoff Cockfield  Brendan Power  Louis Kouadio 《Climatic change》2015,129(1-2):183-196

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Chlorophyll production,in response to nutrient additions,by the algae in Lake Taupo water     

E. White  G. W. Payne 《新西兰海洋与淡水研究杂志》2013,47(3):501-507

In batch cultures of Lake Taupo water, phosphorus was the nutrient limiting plant growth from January to June, and nitrogen took over this role from July to December. Chlorophyll production by algae was often stimulated by trace element additions, but it was uncertain whether total cytoplasmic production was also involved.  相似文献   

Observed winds,turbulence, and dispersion in built-up downtown areas of Oklahoma City and Manhattan   总被引：2，自引：2，他引：0  

Steven Hanna  John White  Ying Zhou 《Boundary-Layer Meteorology》2007,125(3):441-468

Wind and tracer data from the Oklahoma City Joint Urban 2003 (JU2003) and the Manhattan Madison Square Garden 2005 (MSG05) urban field experiments are being analyzed to aid in understanding air flow and dispersion near street-level in built-up downtown areas. The mean winds are separately calculated for groups of anemometers having similar exposures such as “near street level” and “on building top”. Several general results are found, such as the scalar wind speed at street level is about 1/3 of that at building top. Turbulent standard deviations of wind speed components and temperature, and vertical fluxes of momentum and sensible heat, are calculated from sonic anemometers near street level at 20 locations in JU2003 and five locations in MSG05, and from two rooftop locations in MSG05. The turbulence observations are consistent with observations in the literature at other cities, although the JU2003 and MSG05 data are unique in that many data are available near street level. For example, it is found that the local (i.e., at the measuring height) averages about 1.5 and the local averages about 0.25 in the two cities, where is the standard deviation of vertical velocity fluctuations, is the friction velocity, and u is the wind speed. The ratio of temperature fluctuations to temperature scale, , averages about −3 in both cities, consistent with similarity theory for slightly unstable conditions, where is the standard deviation of temperature fluctuations, and is the temperature scale. The calculated Obukhov length, L, is also consistent with slightly unstable conditions near street level, even at night during JU2003. The SF₆ tracer concentration observations from JU2003 are analyzed. Values of for the continuous releases are calculated for each release and arc distance, where is the 30-min average arc maximum concentration, Q is the continuous source emission rate, and u is the spatial-averaged wind speed in the downtown area. The basic characteristics of the JU2003 plot of averaged agree reasonably well with similar plots for other urban experiments in Salt Lake City and London (i.e., at . A is found to be about 3 during the day and about 10 during the night.  相似文献   

Arctic sea-ice motion and its relation to pressure field   总被引：5，自引：0，他引：5  

Yunhe Zhao  Antony K. Liu 《Journal of Oceanography》2007,63(3):505-515

Daily Arctic sea-ice motion maps during the winter seasons (December–March) from December 1988 to March 2003 derived from NSCAT, QuikSCAT, SSM/I, and AMSRE data by a wavelet analysis method have been merged with those derived from buoy data. These merged sea-ice motion data have been used to study the circulation regimes and winter-to-winter variability of Arctic sea-ice motion. The relation between sea-ice motion and the pressure field in the Arctic Ocean was also studied by applying Principal Component Analysis (PCA) to the monthly merged sea-ice motion data and the monthly pressure field data from IABP. The mean Arctic sea-ice motion map of the 15 winter seasons has two distinct features: the Beaufort Gyre and a cyclonic circulation system in the Eurasian Basin, which moves ice from the Laptev Sea to Fram Strait. The strengths and sizes of the two features change from one winter season to another. Seasons with a strong or normal Beaufort Gyre alternate with seasons with a weak or no Beaufort Gyre every one to three seasons. The principal components of the first two modes of PCA of the monthly sea-ice motion are closely correlated with their counterparts of the monthly pressure field in the Arctic Ocean. The mode-one components of these two anomalies alternate between anticyclonic and cyclonic circulation systems. The correlation between Arctic Oscillation indexes and the principal components of the first mode of PCA of the monthly Arctic sea-ice motion is low but statistically significant.  相似文献   

Temporal and geochemical evolution of the Cenozoic intraplate volcanism of Zealandia     

Christian Timm  Kaj Hoernle  Reinhard Werner  Folkmar Hauff  Paul van den Bogaard  James White  Nick Mortimer  Dieter Garbe-Schönberg 《Earth》2010,98(1-2):38-64

In order to constrain better the distribution, age, geochemistry and origin of widespread Cenozoic intraplate volcanism on Zealandia, the New Zealand micro-continent, we report new ⁴⁰Ar/³⁹Ar and geochemical (major and trace element and Sr–Nd–Hf–Pb isotope) data from offshore (Chatham Rise, Campbell and Challenger Plateaus) and onland (North, South, Auckland, Campbell, Chatham and Antipodes Islands of New Zealand) volcanism on Zealandia. The samples include nephelinite, basanite through phonolite, alkali basalt through trachyte/rhyolite, and minor tholeiite and basaltic andesite, all of which have ocean island basalt (OIB)-type trace element signatures and which range in age from 64.8 to 0.17 Ma. Isotope ratios show a wide range in composition (⁸⁷Sr/⁸⁶Sr = 0.7027–0.7050, ¹⁴³Nd/¹⁴⁴Nd = 0.5128–0.5131, ¹⁷⁷Hf/¹⁷⁶Hf = 0.2829–0.2831, ²⁰⁶Pb/²⁰⁴Pb = 18.62–20.67, ²⁰⁷Pb/²⁰⁴Pb = 15.54–15.72 and ²⁰⁸Pb/²⁰⁴Pb = 38.27–40.34) with samples plotting between mid-ocean-ridge basalts (MORB) and Cretaceous New Zealand intraplate volcanic rocks.Major characteristics of Zealandia's Cenozoic volcanism include longevity, irregular distribution and lack of age progressions in the direction of plate motion, or indeed any systematic temporal or spatial geochemical variations. We believe that these characteristics can be best explained in the context of lithospheric detachment, which causes upwelling and melting of the upper asthenospheric mantle and portions of the removed lithosphere. We propose that a large-scale seismic low-velocity anomaly, that stretches from beneath West Antarctica to Zealandia at a depth of > 600 km may represent a geochemical reservoir that has been in existence since the Cretaceous, and has been supplying the upper mantle beneath Zealandia with HIMU-type plume material throughout the Cenozoic. In addition, the sources of the Cenozoic intraplate volcanism may be at least partially derived through melting of locally detached Zealandia lower lithosphere.  相似文献   

The Quaternary history of the Wash fluvial network, UK     

Steve Boreham  Tom S. White  Andy J. Howard 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(4):393-449

This paper appraises and compares the Middle-Upper Pleistocene sedimentary sequences preserved in the fluvial systems draining into the Fenland Basin and the Wash estuary. Of the main Fenland rivers the longest records, which extend back to the initial Anglian (glacial) formation of the basin, are found in the Great Ouse and its tributaries, particularly the Cam and the Nar. These sequences preserve sediments representing all four post-Anglian interglacials. The Nene also has an extensive post-Anglian history, with evidence for a Hoxnian estuary that is presumed to have been the precursor of the Wash. North of the Nene, however, the Welland and Witham (proto-Trent) have relatively short sequences, which are thought to commence with a later (post-Anglian-pre-Devensian) glaciation that affected Lincolnshire and fed the previously-recognized Tottenhill outwash delta south of Kings Lynn. Prior to Devensian deglaciation the Witham valley was occupied by the Trent, which was the trunk river of the late Middle Pleistocene Wash system. During periods of low sea level the river would have extended north-eastwards across what is now the floor of the North Sea, possibly via the Inner Silver Pit. Several of the central Fenland sequences show evidence of infrequent terrace formation during the late Quaternary, although this might in part be due to poor vertical separation between terraces, so that differentiating them has been difficult; this has been exacerbated by mixed biostratigraphical signals due to the preservation of sediments representing more than one interglacial beneath a single terrace surface. In several of the systems there is evidence for valley rejuvenation to the lowest terrace or valley-floor level during the MIS 4-3 transition. The observed differences within what, during the predominant periods of lower sea level, would have been a single Wash river system are difficult to explain.  相似文献   

Evidence from the Trent terrace archive, Lincolnshire, UK, for lowland glaciation of Britain during the Middle and Late Pleistocene   总被引：1，自引：1，他引：0  

Tom S. White  Andy J. Howard 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):141-153

The late Middle Pleistocene fluvial terrace sequence of the lower Trent system, Lincolnshire (eastern England), provides an excellent record of environmental change, including evidence for the last two interglacial episodes. It also provides important stratigraphical evidence for the timing and extent of three separate glaciations. Two of these, the Anglian and Devensian, are well-established correlatives of Marine Isotope Stages (MIS) 12 and 2 respectively; the third is a hitherto un-named post-Anglian-pre-Devensian glaciation in eastern England that has been the subject of much previous speculation, but can now be attributed with some confidence to MIS 8. Crucially, the recognition of MIS 7 interglacial deposits within the Balderton-Southrey terrace of the proto-Trent indicates that the underlying Wragby Till, which is ascribed to this additional glaciation, was emplaced no later than MIS 8. The oldest terrace preserved within the lower Trent staircase, the Eagle Moor-Martin Terrace, is considered to be a complex glacial outwash terrace related to the Wragby Till glaciation. It is suggested that deposits representing MIS 11-9, which are conspicuously absent throughout the Trent system, were removed by this glaciation. This is a departure from previous interpretations, which have suggested MIS 10 or MIS 6 as the most likely stages in which an extensive post-Anglian-pre-Devensian lowland glaciation might have occurred in Britain. However, the widespread preservation of undisrupted post-MIS 8 fluvial sequences throughout the Trent valley and in neighbouring systems, within which MIS 7 interglacial deposits have now been recognized at a number of localities, indicates that ice sheets are unlikely to have advanced further into this catchment during MIS 6 than during the Devensian (MIS 2). Recognition of a British glaciation during MIS 8 corresponds with widespread evidence in Europe, which suggests that glacial deposits classified as ‘Saalian’ represent both MIS 8 and MIS 6; in many areas, distinguishing these remains controversial, as confident correlation with either stage is often only possible where glacial sediments interdigitate with well-constrained fluvial records.  相似文献   

Heat capacity, entropy, and magnetic properties of jarosite-group compounds     

Juraj Majzlan  Peter Glasnák  Robert A. Fisher  Mary Anne White  Michel B. Johnson  Brian Woodfield  Juliana Boerio-Goates 《Physics and Chemistry of Minerals》2010,37(9):635-651

Jarosite phases are common minerals in acidic, sulfate-rich environments. Here, we report heat capacities (C _p) and standard entropies (S°) for a number of jarosite samples. Most samples are close to the nominal composition AFe₃(SO₄)₂(OH)₆, where A = K, Na, Rb, and NH₄. One of the samples has a significant number of defects on the Fe sites and is called the defect jarosite; others are referred to as A-jarosite. The samples, their compositions, and the entropies at T = 298.15 K are:

Sample	Chemical composition	S o/(J mol−1 K−1)
K-jarosite	K0.92(H3O)0.08Fe2.97(SO4)2(OH)5.90(H2O)0.10	427.4 ± 0.7
Na-jarosite	Na0.95(H3O)0.05Fe3.00(SO4)2(OH)6.00	436.4 ± 4.4
Rb-jarosite	RbFe2.98(SO4)2(OH)5.95(H2O)0.05	411.9 ± 4.1
NH4-jarosite	(NH4)0.87(H3O)0.13Fe3.00(SO4)2(OH)6.00	447.2 ± 4.5
Defect jarosite	K0.94(H3O)0.06Fe2.34(SO4)2(OH)4.01(H2O)1.99	412.7 ± 4.1

There are additional configurational entropies of 13.14 and 8.23 J mol⁻¹ K⁻¹ in defect and NH₄-jarosite, respectively. A detailed analysis of the synchrotron X-ray diffraction patterns showed a large anisotropic peak broadening for defect and NH₄-jarosite. The fits to the low-temperature (approx. <12 K) C _p data showed that our samples can be divided into two groups. The first group is populated by the K-, Na-, Rb-, and NH₄-jarosite samples, antiferromagnetic at low temperatures. The second group contains the H₃O-jarosite (studied previously) and the defect jarosite. H₃O- and defect jarosite are spin glasses and their low-T C _p was fit with the expression C _p = γT + ΣB _j T _j , where j = (3, 5, 7, 9). The linear term is typical for spin glasses and the sum represents the lattice contribution to C _p. Surprisingly, the C _p of the K-, Na-, Rb-, and NH₄-jarosite samples, which are usually considered to be antiferromagnetic at low temperatures, also contains a large linear term. This finding suggests that even these phases do not order completely, but have a partial spin-glass character below their Néel transition temperature.  相似文献   

Management of freshwater lenses on small Pacific islands   总被引：3，自引：0，他引：3  

Ian White  Tony Falkland 《Hydrogeology Journal》2010,18(1):227-246

The nature of shallow aquifers and the impacts of seawater intrusion in small islands within the Pacific Ocean are reviewed. Many Pacific islands rely on shallow fresh groundwater lenses in highly permeable aquifers, underlain and surrounded by seawater, as their principal freshwater source. It is argued here that, in small islands, the nature of fresh groundwater lenses and their host aquifers coupled with frequent natural and ever-present anthropogenic threats make them some of the most vulnerable aquifer systems in the world. A simple steady-state approximation is used to provide insight into the key climatic, hydrogeological, physiographic, and management factors that influence the quantity of, and saline intrusion into freshwater lenses. Examples of the dynamic nature of freshwater lenses as they respond to these drivers are given. Natural and human-related threats to freshwater lenses are discussed. Long dry periods strongly coupled to sea surface temperatures impact on the quantity and salinity of fresh groundwater. The vulnerability of small island freshwater lenses dictates careful assessment, vigilant monitoring, appropriate development, and astute management. Strategies to aid future groundwater sustainability in small islands are presented and suggested improvements to donor and aid programs in water are also advanced.  相似文献   

The Value of Practice-Based Knowledge     

Edward P. Weber  Jill M. Belsky  Denise Lach  Antony S. Cheng 《社会与自然资源》2014,27(10):1074-1088

Increasing recognition of the value of practice-based or experiential knowledge in natural resource management justifies the creation of a new category of articles in Society & Natural Resources that we are calling Practice-Based Knowledge (PBK). The rationale for focusing on PBK is due to its key role in the emergence of hybrid governance institutions across state, market, and civil society, understanding the complexity of dynamic socioecological systems, recognizing the challenges of multiple knowledge systems and context-specific practices, embracing the power of informal institutions and civic science, and engaging debates on the growing prevalence of market-oriented conservation. The goal is to provide a dedicated space within the published, peer-reviewed literature for scholars, government officials, nonprofit managers, and engaged citizens to share experiences informed by practical action. Relevant and timely practice-based insights may improve understanding and management of social and ecological processes and systems, while also offering the potential to contribute to theory.  相似文献