Temperature Inverted Haloclines Provide Winter Warm-Water Refugia for Manatees in Southwest Florida     

Bradley M. Stith  James P. Reid  Catherine A. Langtimm  Eric D. Swain  Terry J. Doyle  Daniel H. Slone  Jeremy D. Decker  Lars E. Soderqvist 《Estuaries and Coasts》2011,34(1):106-119

Florida manatees (Trichechus manatus latirostris) overwintering in the Ten Thousand Islands and western Everglades have no access to power plants or major artesian springs that provide warm-water refugia in other parts of Florida. Instead, hundreds of manatees aggregate at artificial canals, basins, and natural deep water sites that act as passive thermal refugia (PTR). Monitoring at two canal sites revealed temperature inverted haloclines, which provided warm salty bottom layers that generally remained above temperatures considered adverse for manatees. At the largest PTR, the warmer bottom layer disappeared unless significant salt stratification was maintained by upstream freshwater inflow over a persistent tidal wedge. A detailed three-dimensional hydrology model showed that salinity stratification inhibited vertical convection induced by atmospheric cooling. Management or creation of temperature inverted haloclines may be a feasible and desirable option for resource managers to provide passive thermal refugia for manatees and other temperature sensitive aquatic species.  相似文献   

The Diagnostic Potential of Transition Region Lines Undergoing Transient Ionization in Dynamic Events     

J. G. Doyle  A. Giunta  A. Singh  M. S. Madjarska  H. Summers  B. J. Kellett  M. O’Mullane 《Solar physics》2012,280(1):111-124

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A contribution to the crystal chemistry of the voltaite group: solid solutions, Mössbauer and infrared spectra, and anomalous anisotropy     

Juraj Majzlan  Hannes Schlicht  Maria Wierzbicka-Wieczorek  Gerald Giester  Herbert Pöllmann  Beatrix Brömme  Stephen Doyle  Gernot Buth  Christian Bender Koch 《Mineralogy and Petrology》2013,107(2):221-233

Voltaite is a mineral of fumaroles, solfatares, coal-fire gas vents, and acid-mine drainage systems. The nominal composition is K₂Fe₅ ²⁺Fe₃ ³⁺Al(SO₄)₁₂·18H₂O and the nominal symmetry is cubic, $Fd\overline{3}c$ . The tetragonal (I4₁/acd) superstructure of voltaite is known as the mineral pertlikite. In this study, we investigated 22 synthetic voltaite samples in which Fe²⁺ was partially or completely replaced by Mg, Zn, Mn, or Cd, by single-crystal and powder X-ray diffraction (both in-house and synchrotron). Two samples contained NH₄ ⁺ instead of K⁺. The structure of voltaite is based on a framework defined by kröhnkite-like heteropolyhedral chains which host both M³⁺ and M²⁺ in octahedral coordination. Unit cell dimensions of the end-members scale almost linearly with the size of M²⁺. In the Fe²⁺-Mg-Zn solid solutions, the Fe²⁺-Mg and Fe²⁺-Zn solutions are linear (ideal) in terms of their lattice-parameter variations. The Mg-Zn solid solution, however, is strongly non-ideal. A detailed analysis of the topology of the chains showed that this behavior originates in expansion and contraction of individual M²⁺-O bonds within the chains. In the Mg-Zn solid solution, some of the M²⁺-O bonds expand while none contract. In the other solid solutions, expansion of some M²⁺-O bonds is always compensated by contraction of the other ones. Parts of the nominally cubic crystals are optically anisotropic and their symmetry is found to be tetragonal by single crystal X-ray diffraction measurements. The coexistence of cubic and tetragonal sectors within a single crystal without any detectable difference in their chemical composition is difficult to explain in terms of growth of such composite crystals. Mössbauer and infrared spectra collected on our synthetic crystals conform with previously published data.  相似文献   

Seismic velocities from explosions off the central coast of New South Wales     

H. A. Doyle  R. Underwood  E. J. Polak 《Australian Journal of Earth Sciences》2013,60(2):355-372

Travel times from explosions fired on the continental shelf off the central coast of New South Wales were observed at permanent stations and spreads of seismic exploration instruments, and combined with existing results to give a seismic crustal profile across part of southeastern Australia. An intermediate layer, dipping to the southwest, underlies the surface rocks and has a P velocity of about 6–52 km./sec. Beneath Sydney, its top may either be in contact with the basin sediments at a depth of about 5 km., or separated from them by a wedge of a few kilometres of 6 km./sec. material. The Mohorovi?i? discontinuity (M) is at a depth of 25 km., dips to the southwest at about 4 degrees, and the velocity under it is about 7.86 km./sec. The depth to the top of the intermediate layer under the Snowy Mountains is about 20 km., and the revised depth to M is about 42 km. M dips at about 2° to the southwest in this region, and the velocity at the top of the mantle is 8.1 km./sec.  相似文献   

Impact d’une crise environnementale majeure sur les espèces,les populations et les communautés : la fragmentation de la forêt africaine à la fin de l’Holocène     

Anne-Marie Lézine  Doyle McKey 《Comptes Rendus Geoscience》2013,345(7-8):263-265

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Radiocarbon-dated ferricrete provides a record of natural acid rock drainage and paleoclimatic changes     

G. Furniss  N. W. Hinman  G. A. Doyle  D. D. Runnells 《Environmental Geology》1999,37(1-2):102-106

 Ancient deposits of ferricrete (stratified iron oxyhydroxide or clastic sediment cemented by stratified iron oxyhydroxide) are present in headwater streams draining an historic mining district in the Rocky Mountains, USA. These deposits, which form under conditions of low pH and high metal concentrations, are present in streams draining many other mineralized areas. Radiocarbon dating of wood fragments entombed within the ferricrete indicates dates of deposition as old as 8840±50 years before present (b.p.). The ferricrete deposits provide evidence that natural, metal-rich acid rock drainage has been occurring in this mineralized region for thousands of years, due to the weathering and oxidation of exposed or near-surface massive sulfide ore deposits. The dating and chemical composition of the ferricrete deposits have applications to the environmental remediation of historic mining sites and to environmental issues related to natural background chemistry. In addition, the radiocarbon dates of the ferricrete deposits correlate closely with warm–wet periods in the Holocene record, showing that ferricrete deposits may represent a previously untapped source of paleoclimatic information. Received: 6 October 1997 · Accepted: 23 March 1998  相似文献   

Solar physics in Dublin     

R Erdélyi  L Fletcher  G J Doyle 《Astronomy& Geophysics》2003,44(3):3.13-3.15

This year's annual UK Solar Physics meeting took place in Dublin from 7–11 April 2003, overlapping with the National Astronomy Meeting. R Erdélyi, L Fletcher and G J Doyle summarize.  相似文献   

Influence of climate,water content and leaching on seasonal variations in potential water repellence     

Marcus A. Hardie  William E. Cotching  Richard B. Doyle  Shaun Lisson 《水文研究》2012,26(13):2041-2048

Seasonal variation in potential water repellence has not been widely reported in the literature, and little is known of the processes that cause changes in potential water repellence. In this study, the severity and stability of potential water repellence varied seasonally from being weakly hydrophobic in July 2009 (water drop penetration time, 0.19 min; water entry potential, 0.0 cm) to severely hydrophobic (water drop penetration time, 54 min; water entry potential, 14.3 cm) in May 2009. Seasonal variation in the stability of potential water repellence was significantly correlated with cumulative rainfall, air temperature and soil water deficit, which indicated that the accumulation of water‐repellent compounds, presumably polar waxes, resulted from microbial or plant inputs to the soil. Laboratory experiments demonstrated that saturating and mixing the soil resulted in a two to three order of magnitude reduction in the stability of potential water repellence, even after oven drying at 40 °C and 60 °C. Repeated leaching resulted in sequential reduction in both the stability and severity of water repellence. The significant correlation between soil water repellence and dissolved organic carbon content of the leachate, together with pedological evidence of organic staining of ped faces in the clay subsoil indicate that seasonal rainfall leached soluble water‐repellent compounds from the topsoil. The reestablishment of water repellence after saturation and leaching required the input of new water‐repellent compounds. These findings suggest that the use of surfactants before sowing may assist to leach water‐repellent compounds from the topsoil, allowing improved infiltration and reduced runoff through the remainder of the cropping season. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Deriving the coronal hole electron temperature: electron density dependent ionization / recombination considerations     

John Gerard Doyle  Steven Chapman  Paul Bryans  David Pérez-Suárez  Avninda Singh  Hugh Summers  Daniel Wolf Savin 《中国天文和天体物理学报》2010,10(1)

Comparison of appropriate theoretically derived line ratios with observational data can yield estimates of a plasma’s physical parameters,such as electron density or temperature.The usual practice in the calculation of the line ratio is the assumption of excitation by electrons/protons followed by radiative decay.Furthermore,it is normal to use the so-called coronal approximation,i.e.one only considers ionization and recombination to and from the ground-state.A more accurate treatment is to include ionizati...  相似文献   

Nature of Quiet Sun Oscillations Using Data from the Hinode, TRACE, and SOHO Spacecraft     

G. R. Gupta  S. Subramanian  D. Banerjee  M. S. Madjarska  J. G. Doyle 《Solar physics》2013,282(1):67-86

We study the nature of quiet-Sun oscillations using multi-wavelength observations from TRACE, Hinode, and SOHO. The aim is to investigate the existence of propagating waves in the solar chromosphere and the transition region by analyzing the statistical distribution of power in different locations, e.g. in bright magnetic (network), bright non-magnetic and dark non-magnetic (inter-network) regions, separately. We use Fourier power and phase-difference techniques combined with a wavelet analysis. Two-dimensional Fourier power maps were constructed in the period bands 2??C?4?minutes, 4??C?6?minutes, 6??C?15?minutes, and beyond 15?minutes. We detect the presence of long-period oscillations with periods between?15 and 30?minutes in bright magnetic regions. These oscillations were detected from the chromosphere to the transition region. The Fourier power maps show that short-period powers are mainly concentrated in dark regions whereas long-period powers are concentrated in bright magnetic regions. This is the first report of long-period waves in quiet-Sun network regions. We suggest that the observed propagating oscillations are due to magnetoacoustic waves, which can be important for the heating of the solar atmosphere.  相似文献