An interlaboratory comparison of piston-cylinder pressure calibration using the albite-breakdown reaction     

W. Johannes  P. M. Bell  H. K. Mao  A. L. Boettcher  D. W. Chipman  J. F. Hays  R. C. Newton  F. Seifert 《Contributions to Mineralogy and Petrology》1971,32(1):24-38

The pressure of the reaction albite=jadeite and quartz was measured at 600° C by workers in six geophysical laboratories for the purpose of comparing pressure calibration procedures for the solid-pressure piston-cylinder apparatus. All groups used the same starting mix of crystalline reactant and products and all obtained hydrothermal reversals of the equilibrium. Solid pressure media used included talc, NaCl, boron nitride, pyrophyllite, pyrex glass and crushable ceramic. Various means of calibration were used, including internal standardization by transitions in indicator substances and the piston-in, piston-out bracketing method.There was agreement among all groups—the average preferred value of 16.3 kilobars at 600° C is enclosed by all of the error brackets assigned by the various investigators. This average preferred value is lower by nearly two kilobars than the often-quoted extrapolation of Birch and LeComte's data (1960). It will be important for both petrology and high-pressure technology to test this result in a very high gas pressure apparatus.  相似文献   

Oceanographic conditions associated with high abundances of the radiolarian Cycladophora davisiana     

Joseph J. Morley  James D. Hays 《Earth and Planetary Science Letters》1983

The cosmopolitan radiolarian Cycladophora davisiana usually comprises less than 5% of the radiolarian fauna in Holocene sediments. In recent sediments from the Sea of Okhotsk, however, this species frequently represents more than 20% of the radiolarian assemblage. At times during the late Pleistocene, abundances of this species in excess of 40% are recorded in marine sediments from high-latitude oceans (> 40°) of both hemispheres. The Sea of Okhotsk apparently represents a modern analogue of climatic and oceanographic conditions that existed throughout large portions of high-latitude oceans at times during the late Pleistocene.The near-surface water structure of the Sea of Okhotsk is characterized by a low-salinity surface layer with a strong temperature minimum near its base. The low surface salinities are responsible for maintaining near-freezing subsurface temperatures as well as establishing relatively stable temperatures and salinities at depths below the temperature minimum. This water structure is produced, at least in part, by intense freezing of sea ice in winter with subsequent summer melting. The physical characteristics of the upper water column affect the abundance and activity of shallow-dwelling flora and fauna, while providing a stable subsurface environment for deeper-dwelling fauna.  相似文献   

The last interglacial ocean     

William F. Ruddiman  Rose Marie L. Cline  James D. Hays  Warren L. Prell  William F. Ruddiman  Ted C. Moore  Nilva G. Kipp  Barbara E. Molfino  George H. Denton  Terence J. Hughes  William L. Balsam  Charlotte A. Brunner  Jean-Claude Duplessy  James L. Fastook  John Imbrie  Lloyd D. Keigwin  Thomas B. Kellogg  Peter R. Thompson 《Quaternary Research》1984,21(2):123-224

The final effort of the CLIMAP project was a study of the last interglaciation, a time of minimum ice volume some 122,000 yr ago coincident with the Substage 5e oxygen isotopic minimum. Based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean, last interglacial sea-surface temperatures (SST) were compared with those today. There are small SST departures in the mid-latitude North Atlantic (warmer) and the Gulf of Mexico (cooler). The eastern boundary currents of the South Atlantic and Pacific oceans are marked by large SST anomalies in individual cores, but their interpretations are precluded by no-analog problems and by discordancies among estimates from different biotic groups. In general, the last interglacial ocean was not significantly different from the modern ocean. The relative sequencing of ice decay versus oceanic warming on the Stage 6/5 oxygen isotopic transition and of ice growth versus oceanic cooling on the Stage 5e/5d transition was also studied. In most of the Southern Hemisphere, the oceanic response marked by the biotic census counts preceded (led) the global ice-volume response marked by the oxygen-isotope signal by several thousand years. The reverse pattern is evident in the North Atlantic Ocean and the Gulf of Mexico, where the oceanic response lagged that of global ice volume by several thousand years. As a result, the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years. These regional lead-lag relationships agree with those observed on other transitions and in long-term phase relationships; they cannot be explained simply as artifacts of bioturbational translations of the original signals.  相似文献   

Dissolved nutrient fluxes through a sandy estuarine beachface (Cape Henlopen,Delaware, U.S.A.): Contributions from fresh groundwater discharge,seawater recycling,and diagenesis     

Rebecca L. Hays  William J. Ullman 《Estuaries and Coasts》2007,30(4):710-724

The sandy beachface at Cape Henlopen, Delaware, receives dissolved nutrient inputs from fresh upland groundwater and estuarine seawater and exports nutrients through intertidal and submarine groundwater discharge. The discharge of brackish beachface waters indicates that there must be additional diagenetic nutrient sources and sinks within the porous beachface aquifer. At some times of the year, diagenetic processes within the beachface remove nitrate from waters draining the beachface consistent with the stoichiometry of either denitrification or dissimilatory nitrate reduction to ammonium. Up to 50–100% of the nitrate load from the upland groundwaters is apparently reduced to N₂O/N₂ gas or ammonium during these periods. At other times, ammonium and nitrate are added to beachface waters consistent with the stoichiometry of organic matter remineralization and nitrification. Dissolved reactive phosphorus and silica are similarly consumed and produced by beachface processes at different times of the year, presumably by adsorption or desorption. Infiltration of reactive estuarine particles may be an additional source of nutrients and carbon that supports the diagenetic activity in the beachface aquifer. These observations suggest that sandy beachfaces are biogeochemically reactive systems that can serve as sources, sinks, and temporary reservoirs of nutrients to support the primary and secondary production of the adjacent intertidal zone.  相似文献   

Origin of lunar feldspathic rocks     

D. Walker  T.L. Grove  J. Longhi  E.M. Stolper  J.F. Hays 《Earth and Planetary Science Letters》1973,20(3):325-336

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The westward thermospheric jet-stream of the evening auroral oval     

D. Rees  T.J. Fuller-Rowell  M.F. Smith  R. Gordon  T.L. Killeen  P.B. Hays  N.W. Spencer  L. Wharton  N.C. Maynard 《Planetary and Space Science》1985,33(4):425-456

One of the most consistent and often dramatic interactions between the high latitude ionosphere and the thermosphere occurs in the vicinity of the auroral oval in the afternoon and evening period. Ionospheric ions, convected sunward by the influence of the magnetospheric electric field, create a sunward jet-stream in the thermosphere, where wind speeds of up to 1 km s^?1 can occur. This jet-stream is nearly always present in the middle and upper thermosphere (above 200 km altitude), even during periods of very low geomagnetic activity. However, the magnitude of the winds in the jet-stream, as well as its location and range in latitude, each depend on geomagnetic activity. On two occasions, jet-streams of extreme magnitude have been studied using simultaneous ground-based and satellite observations, probing both the latitudinal structure and the local time dependence. The observations have then been evaluated with the aid of simulations using a global, three-dimensional, time-dependent model of thermospheric dynamics including the effects of magnetospheric convection and particle precipitation. The extreme events, where sunward winds of above 800 ms^?1 are generated at relatively low geomagnetic latitudes (60–70°) require a greatly expanded auroral oval and large cross-polar cap electric field ( ~ 150 kV). These in turn are generated by a persistent strong Interplanetary Magnetic Field, with a large southward component. Global indices such as K_p are a relatively poor indicator of the magnitude and extent of the jet-stream winds.  相似文献   

Line shape of the non-thermal 6300 Å O(¹D) emission     

G.A. Schmitt  V.J. Abreu  P.B. Hays 《Planetary and Space Science》1982,30(5):457-461

The line shape of the non-thermal O(¹D) 6300 Å emission is calculated using the two population model of Schmitt, Abreu and Hays (Planet. Space Sci.29, 1095, 1981). The calculated line shapes simulate observations made from a space platform at different zenith angles and altitudes. The non-thermal line shapes observed at zenith angles other than the local vertical have been obtained by using the Addition theorem for spherical harmonics of a Legendre polynomial expansion of the non-thermal population distribution function.  相似文献   

The high latitude circulation and temperature structure of the thermosphere near solstice     

R.G. Roble  R.E. Dickinson  E.C. Ridley  B.A. Emery  P.B. Hays  T.L. Killeen  N.W. Spencer 《Planetary and Space Science》1983,31(12):1479-1499

The neutral gas temperature and circulation of the thermosphere are calculated for December solstice conditions near solar cycle maximum using NCAR's thermospheric general circulation model (TGCM). High-latitude heat and momentum sources significantly alter the basic solar-driven circulation during solstice. At F-region heights, the increased ion density in the summer hemisphere results in a larger ion drag momentum source for the neutral gas than in the winter hemisphere. As a result there are larger wind velocities and a greater tendency for the neutral gas to follow the magnetospheric convection pattern in the summer hemisphere than in the winter hemisphere. There is about three times more Joule heating in the summer than the winter hemisphere for moderate levels of geomagnetic activity due to the greater electrical conductivity in the summer E-region ionosphere.

The results of several TGCM runs are used to show that at F-region heights it is possible to linearly combine the solar-driven and high-latitude driven solutions to obtain the total temperature structure and circulation to within 10–20%. In the lower thermosphere, however, non-linear terms cause significant departures and a linear superposition of fields is not valid.

The F-region winds at high latitudes calculated by the TGCM are also compared to the meridional wind derived from measurements by the Fabry-Perot Interferometer (FPI) and the zonal wind derived from measurements by the Wind and Temperature Spectrometer (WATS) instruments onboard the Dynamics Explorer (DE−2) satellite for a summer and a winter day. For both examples, the observed and modeled wind patterns are in qualitative agreement, indicating a dominant control of high latitude winds by ion drag. The magnitude of the calculated winds (400–500 m s⁻¹) for the assumed 60 kV cross-tail potential, however, is smaller than that of the measured winds (500–800 m s⁻¹). This suggests the need for an increased ion drag momentum source in the model calculations due to enhanced electron densities, higher ion drift velocities, or some combination that needs to be further denned from the DE−2 satellite measurements.  相似文献   

Atmospheric scattering effects on ground-based measurements of thermospheric winds     

V.J. Abreu  G.A. Schmitt  P.B. Hays  J.W. Meriwether  C.A. Tepley  L.L. Cogger 《Planetary and Space Science》1983,31(3):303-310

Inherent in observations of thermospheric winds from the ground with the Fabry-Perot interferometer is the assumption that the measured Doppler shift is a property of the source medium viewed by the instrumental line of sight. However, ground based airglow observations in regions of weak airglow emission near large intensity gradients may be contaminated by scattered light. Light from areas where the emission is strong can be scattered by the lower atmosphere into the field of view of the observations. Thermospheric winds deduced from the observed Doppler shifts will then show apparent convergence or divergence with respect to the site of observation. Examples of this effect are found in observations by the Michigan Airglow Observatory station located near the auroral zone at Calgary, Alberta. Simulation calculations based upon an experimental model for a significant scattering atmosphere also showed results with either convergence or divergence in the apparent neutral wind field observed by the station.  相似文献   

The evolution and variability of atmospheric ozone over geological time   总被引：1，自引：0，他引：1  

Joel S. Levine  Paul B. Hays  James C.G. Walker 《Icarus》1979,39(2):295-309

The rise of atmospheric O₃ as a function of the evolution of O₂ has been investigated using a one-dimensional steady-state photochemical model based on the chemistry and photochemistry of O_x(O₃, O, O(¹D)), N₂O, NO_x(NO, NO₂, HNO₃), H₂O, and HO_x(H, OH, HO₂, H₂O₂) including the effect of vertical eddy transport on the species distribution. The total O₃ column density was found to maximize for an O₂ level of 10^?1 present atmospheric level (PAL) and exceeded the present total O₃ column by about 40%. For that level of O₂, surface and tropospheric O₃ densities exceeded those of the present atmosphere by about an order of magnitude. Surface and tropospheric OH densities of the paleoatmosphere exceeded those of the present atmosphere by orders of magnitude. We also found that in the O₂-deficient paleoatmosphere, N₂O (even at present atmospheric levels) produces much less NO_x than it does in the present atmosphere.  相似文献