Variability in concentrations of cloud condensation nuclei in the marine cloud–topped boundary layer     

M. B. BAKER 《Tellus. Series B, Chemical and physical meteorology》1993,45(5):458-472

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Geochemical Evidence for Subduction Fluxes, Mantle Melting and Fractional Crystallization Beneath the South Sandwich Island Arc   总被引：31，自引：11，他引：20  

PEARCE  JULIAN A.; BAKER  PETER E.; HARVEY  PETER K.; LUFF  IAN W. 《Journal of Petrology》1995,36(4):1073-1109

The volcanoes of the South Sandwich island arc follow threedistinct series: low-K tholeiitic (followed by Zavodovski, Candlemas,Vindication, Montagu and Bristol), tholeiitic (followed by Visokoi,Saunders and Bellinghausen) and calcalkaline (followed by Leskov,Freehand and part of Cook and Thule). Flux calculations indicatethat the percentage contribution of the subduction componentto the mantle source of all three series varies from undetectable(e.g. Zr) through small (e.g. Nd=20%) and moderate (e.g. La,Ce, Sr=50–80%) to dominant (e.g. Pb, K, Ba, Rb, Cs >90%)with little change along the arc. Isotope systematics (Pb, Nd,Sr) show that this subduction component obtains a greater contributionfrom altered oceanic crust than from pelagic sediment. Elementsfor which the subduction contribution is small show that themantle is already depleted relative to N-MORB mantle (equivalentto loss of an 2•5% melt fraction) before melting beneaththe arc. After addition of the subduction component, dynamicmelting of this depleted mantle then causes the variations inK that distinguish the three series. The estimated degree ofpartial melting (20%) is slightly greater than that beneathocean ridges, though geothermometry suggests that the primarymagma temperature (1225C) is similar to that of primary MORB.About half of the melting may be attributed to volatile addition,and half to decompression. Dynamic melting involving three-dimensional,two-phase flow may be needed to explain fully the inter-islandvariations. KEY WORDS: geochemistry; petrology; fluxes; melting; subduction ^*Corresponding author  相似文献   

Stable Isotopic Evidence for Fluid-Rock Interactions in the Ivrea Zone, Italy     

BAKER  A. J. 《Journal of Petrology》1990,31(1):243-260

Stable isotope compositions of Ivrea Zone marbles and associatedlithologies are in general heterogeneous. The oxygen isotopecomposition of quartz in pelites ranges from ¹⁸O +9 to + 17(SMOW) and does not vary systematically with metamorphic grade.Peridotites retain oxygen isotope signatures close to mantlevalues. Marble calcites vary in isotopic composition from ¹³C + 2(PDB),¹⁸0 +24(SMOW)to ¹³C –6(PDB), ¹⁸O + 13 (SMOW).Depletions in ¹⁸O and ¹³C may be explained dominantly by interactionwith fluids derived from within the observed metasedimentarysequence during prograde metamorphism. ¹⁸O and ¹³C show gradients of greater than 5/m across marblemargins and within marbles. The preservation of such isotopicgradients is not consistent with the long-term presence of grain-boundary-scaleinterconnected fluid films in and around marbles. There is ageneral lowering of ¹⁸O within individual marble bodies althoughlarge carbon and oxygen isotopic gradients are present. Calcitein marbles may attain oxygen isotope equilibrium, but rarelycarbon isotope equilibrium, with surrounding metapelites. Infiltrationof marbles must involve a component of channelized fluid flow. The general lack of isotopic equilibration within the sequencerequires channelized fluid flow and limited fluid-rock ratios.Large pervasive mantle to crust fluid fluxes are not consistentwith the observations. ^*Present address: Natural Environment Research Council, Polaris House, North Star Avenue, Swindon SN2 1EU, England  相似文献   

TransCom 3 CO₂ inversion intercomparison: 1. Annual mean control results and sensitivity to transport and prior flux information     

KEVIN ROBERT GURNEY  RACHEL M. LAW  A. SCOTT DENNING  PETER J. RAYNER  DAVID BAKER  PHILIPPE BOUSQUET  LORI BRUHWILER  YU-HAN CHEN  PHILIPPE CIAIS  SONGMIAO FAN  INEZ Y. FUNG  MANUEL GLOOR  MARTIN HEIMANN  KAZ HIGUCHI  JASMIN JOHN  EVA KOWALCZYK  TAKASHI MAKI  SHAMIL MAKSYUTOV  PHILIPPE PEYLIN  MICHAEL PRATHER  BERNARD C. PAK  JORGE SARMIENTO  SHOICHI TAGUCHI  TARO TAKAHASHI  CHIU-WAI YUEN 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):555-579

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APPLICATION OF A GROUPED RESPONSE UNIT HYDROLOGICAL MODEL TO A NORTHERN WETLAND REGION     

ALAIN PIETRONIRO  TERRY PROWSE  LAURENCE HAMLIN  NICK KOUWEN  RIC SOULIS 《水文研究》1996,10(10):1245-1261

Applications of hydrological models to northern wetland-dominated regions have been limited in the past to a few case studies on small basins employing ‘lumped’ models. Only recently have there been attempts to apply the grouped response unit (GRU) distributed modelling approach using terrain classifications to these same basins. This study summarizes recent efforts in applying such a model. For the purposes of implementing the GRU approach, terrain types that are hydrologically significant and characteristic to the wetland-dominated regime were successfully discriminated using a principal component analysis and a hybrid unsupervised/supervised classification technique on Landsat–Thematic Mapper imagery. The terrain classifications were then used as input into a distributed hydrological model for calibration and validation using recorded spring runoff events. Preliminary model applications and results are described. Calibration to a historic spring runoff event yielded an r² value of 0.86. Model validation, however, yielded much poorer results. The problems of model applicability to this region and limitations of sparse data networks are highlighted. The need for more field research in this type of hydrological regime, and associated improvements to the model parameter set are also identified.  相似文献   

Meteorites at Meridiani Planum provide evidence for significant amounts of surface and near‐surface water on early Mars     

Alberto G. FAIRÉN  James M. DOHM  Victor R. BAKER  Shane D. THOMPSON  William C. MAHANEY  Kenneth E. HERKENHOFF  J. Alexis P. RODRÍGUEZ  Alfonso F. DAVILA  Dirk SCHULZE‐MAKUCH  M. Ramy EL MAARRY  Esther R. UCEDA  Ricardo AMILS  Hirdy MIYAMOTO  Kyeong J. KIM  Robert C. ANDERSON  Christopher P. McKAY 《Meteoritics & planetary science》2011,46(12):1832-1841

Abstract– Six large iron meteorites have been discovered in the Meridiani Planum region of Mars by the Mars Exploration Rover Opportunity in a nearly 25 km‐long traverse. Herein, we review and synthesize the available data to propose that the discovery and characteristics of the six meteorites could be explained as the result of their impact into a soft and wet surface, sometime during the Noachian or the Hesperian, subsequently to be exposed at the Martian surface through differential erosion. As recorded by its sediments and chemical deposits, Meridiani has been interpreted to have undergone a watery past, including a shallow sea, a playa, an environment of fluctuating ground water, and/or an icy landscape. Meteorites could have been encased upon impact and/or subsequently buried, and kept underground for a long time, shielded from the atmosphere. The meteorites apparently underwent significant chemical weathering due to aqueous alteration, as indicated by cavernous features that suggest differential acidic corrosion removing less resistant material and softer inclusions. During the Amazonian, the almost complete disappearance of surface water and desiccation of the landscape, followed by induration of the sediments and subsequent differential erosion and degradation of Meridiani sediments, including at least 10–80 m of deflation in the last 3–3.5 Gy, would have exposed the buried meteorites. We conclude that the iron meteorites support the hypothesis that Mars once had a denser atmosphere and considerable amounts of water and/or water ice at and/or near the surface.  相似文献   

Stratospheric aerosol measurements in the Arctic winter of 1996/1997 with the M‐55 Geophysika high‐altitude research aircraft     

STEPHAN BORRMANN  REAS THOMAS  VLADIMIR RUDAKOV  VLADIMIR YUSHKOV  BORIS LEPUCHOV  TERRY DESHLER  NIKOLAI VINNICHENKO  VYACHESLAV KHATTATOV  LEOPOLDO STEFANUTTI 《Tellus. Series B, Chemical and physical meteorology》2000,52(4):1088-1103

In‐situ aerosol measurements were performed in the northern hemispheric stratosphere up to altitudes of 21 km between 13 November 1996 and 14 January 1997, inside and outside of the polar vortex during the Airborne Polar Experiment (APE) field campaign. These are measurements of particle size distributions with a laser optical particle counter of the FSSP‐300 type operated during 9 flights on the Russian M‐55 high‐altitude research aircraft Geophysika. For specific flights, the FSSP‐300 measurements are compared with balloon‐borne data (launched from Kiruna, Sweden). It was found that the stratospheric aerosol content reached levels well below the background concentrations measured by the NASA operated ER‐2 in 1988/89 in the northern hemisphere. During the APE campaign, no PSC particle formation was observed at flight altitudes although the temperatures were below the NAT condensation point during one flight. The measured correlations between ozone and aerosol give an indication of the subsidence inside the 1996/97 polar vortex. Despite the lower aerosol content in the winter 1996/97 compared to the 1989 background, the heterogeneous reactivity of the aerosol (as calculated from the measured data with additional model input) is comparable. This is due to the dependency of the reactive uptake coefficients on the atmospheric water vapor content. Under the described assumptions the reaction rates on the background aerosol are significantly smaller than for competing gas phase chlorine activation, as can be expected for stratospheric background conditions especially inside the polar vortex.  相似文献   

Preparing For Hyperseed MAC: An Observing Campaign To Monitor The Entry Of The Genesis Sample Return Capsule     

PETER JENNISKENS  PAUL WERCINSKI  JOE OLEJNICZAK  GARY ALLEN  PRASUN N. DESAI  GEORGE RAICHE  DEAN KONTINOS  DOUG REVELLE  JASON HATTON  RICHARD L. BAKER  RAY W. RUSSELL  MIKE TAYLOR  FRANS RIETMEIJER 《Earth, Moon, and Planets》2004,95(1-4):339-360

The imminent return of the Genesis Sample Return Capsule (SRC) from the Earth’s L1 point on September 8, 2004, represents the first opportunity since the Apollo era to study the atmospheric entry of a meter-sized body at or above the Earth’s escape speed. Until now, reentry heating models are based on only one successful reentry with an instrumented vehicle at higher than escape speed, the 22 May 1965 NASA “FIRE 2” experiment. In preparation of an instrumented airborne and ground-based observing campaign, we examined the expected bolide radiation for the reentry of the Genesis SRC. We find that the expected emission spectrum consists mostly of blackbody emission from the SRC surface (T∼ ∼2630 K@peak heating), slightly skewed in shape because of a range of surface temperatures. At high enough spectral resolution, shock emission from nitrogen and oxygen atoms, as well as the first positive and first negative bands of N₂⁺, will stand out above this continuum. Carbon atom lines and the 389-nm CN band emission may also be detected, as well as the mid-IR 4.6-μm CO band. The ablation rate can be studied from the signature of trace sodium in the heat shield material, calibrated by the total amount of matter lost from the recovered shield. A pristine collection of the heat shield would also permit the sampling of products of ablation.  相似文献   

Six Well-Preserved Australites from the Port Campbell—Princetown Region,Western Australia     

GEORGE BAKER 《Meteoritics & planetary science》1968,4(1):43-56

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Structures of Well Preserved Australite Buttons from Port Campbell,Victoria, Australia     

GEORGE BAKER 《Meteoritics & planetary science》1967,3(4):179-217

Abstract. Complete and nearly complete australite buttons in good states of preservation from Port Campbell, Victoria, show excellent structural details and are of great scientific importance. Some of the features on their posterior surfaces are doubtfully assigned a primary origin in an extraterrestrial birthplace but have been modified by terrestrial solution-etching. Secondary features on their anterior surfaces are due to the effects of aerodynamic frictional heating during transit with stable orientation at supersonic velocity through the earth's atmosphere. Tertiary processes such as subaerial weathering have played some part in slightly modifying their shape and sculpture patterns. They contrast strongly with the many thousands of australites collected from the arid and sub-arid regions of Australia, and with a considerable number that were abraded by stream or gravity transportation in the more temperate zones of the strewnfield. The majority of such specimens have been more severely weathered with the resultant loss of much or all of their primary and secondary features.  相似文献