Seasonal variation of global surface pressure and water vapor

Previous studies have shown that the seasonal variation of global-mean surface pressure ( p _s) results from variation of global-mean water vapor pressure ( p _w). The current study, employing the global data generated by Version 1 of the Goddard Earth Observing System (GEOS-1) Data Assimilation System, shows that seasonal variations of regional p _s and p _w tend to be out of phase (particularly in the subtropics of the two hemispheres) and that the magnitude of the former variation is generally much larger than that of the latter. The seasonal variations of these two quantities are maintained by airmass and water vapor transports by the global divergent circulation, which is driven by the latent heat released by cumulus convection over the water vapor sink, as the "water mass forcing" mechanism predicted. Since p _w and p _s are used often in depicting the climate system, assessments of climate change in terms of the global-mean and regional variations of these two variables should be interpreted with caution.     

Thermobarometry and Pressure-Temperature Paths in the Grenville Province of Ontario

To constrain the tectonic and metamorphic history of the GrenvilleProvince of southern Ontario we have quantitatively evaluatedchanges in peak metamorphic pressures and temperatures in theregion. Pressures increase northwest from the Frontenac Axistowards the Grenville Front, and they increase from 4–6kb near Madoc to 10–11 kb south of North Bay. Furtherto the north pressures decrease to 8–9 kb in the GrenvilleFront Tectonic Zone north of the French and Mattawa Rivers.Temperatures form a broad high, reaching 800?C northeast ofParry Sound, and decreasing to 400–500?C in the HastingsLow near Madoc, 600–650?C east towards the Ottawa River,and 650–700?C near Sudbury. This regional P-T distributionis in good agreement with constraints available from the distributionof aluminosilicate polymorphs. Comparison of thermobarometric results with regional tectonicfeatures shows a sharp discontinuity across the Mattawa andFrench Rivers, with a 1–2-kb pressure drop to the north.This implies that the major movement along this zone since theGrenville event was ‘south-side-up’ rather than‘north-side-up’ as suggested by Lumbers (1971).Large P-T discontinuities are not apparent across the domainboundaries mapped by Davidson and co-workers east of Parry Sound,but small discontinuities may exist. Sparse data may indicatethat the Central Metasedimentary Belt equilibrated at 1–2kb lower pressures than the Central Gneiss Terrane. Zoning profiles in garnet-pyroxene pairs have been used to placeconstraints on the metamorphic pressure-temperature-time pathin the Parry Sound, Port Severn, Bancroft, and Mattawa areasof the Grenville Province, Ontario. A nonlinear fitting routinewas used to obtain best-fit core and rim analyses for garnetsand pyroxenes. These results were combined with plagioclasecore/rim analyses to obtain estimates of peak and retrogradeconditions. The resultant retrograde P-Tpath has a slope of7 ? 10 b/?C, and involves pressure changes of 0?6–2?1kb for temperature changes of 60–130?C. Present address: Department of Geosciences, University of Arizona, Tucson, Arizona 85721     

Regulating Land Use Conflict on the Urban Fringe: Two contrasting case studies from the Australian poultry industry

Land use conflict involving farm externalities represents an increasing policy concern in Australia as agricultural activities intensify and as the nation's metropolitan areas continue to expand outwards. A review of the rural-urban fringe literature reveals a noticeable absence of research exploring the intensity of conflict experienced by farmers. Similarly, inadequate attention has been given to the policies adopted by government to manage conflict. This article contrasts the regulatory system that has been implemented to manage conflict involving poultry farming on the metropolitan fringe of two Australian state capitals: Perth, Western Australia and Sydney, New South Wales. Spatial variation in the nature of government intervention is uncovered. In the discussion that follows reasons are identified to help explain such variation including state ideology, metropolitan growth, industry activism, geographical constraints and farm characteristics. It is concluded that where agricultural industries experience internal political divisions and a geographically dispersed membership it becomes more difficult to influence government policy.     

FLOW SEPARATION IN UNDISTURBED SOILS USING MULTIPLE ANIONIC TRACERS. PART 1. ANALYTICAL METHODS AND UNSTEADY RAINFALL AND RETURN FLOW EXPERIMENTS

Tracers provide one of the few ways of obtaining realistic information on the flows of water and solutes in undisturbed structured soils. Three fluorinated organic acids [pentafluorobenzoic acid, 2,6-diflurobenzoic acid and o-(trifluoromethyl) benzoic acid] and bromide were tested as anionic tracers in situations where the separation of different flow components is of interest. The fluorobenzoates were relatively conservative (approximately 90% for loam soil) although, in some instances, co-elution or complexation may lead to apparently non-conservative behaviour. Tracer mixtures applied to soils, were separated and quantified by high-performance liquid chromatography. The relative mobilities of the tracers were studied during unidirectional steady flow in large undisturbed soil columns brought back to the laboratory. The breakthrough curves showed highly dispersive behaviour, with very early breakthrough of solute and a long tail. Contributions to the column outflow of different simultaneous applications of rainfall and return flow, labelled with different tracers, were separated using multicomponent mixing equations. The results show the importance of preferential flow and relatively immobile storage in the transport process.     

FLOW SEPARATION IN UNDISTURBED SOIL USING MULTIPLE ANIONIC TRACERS. PART 2. STEADY-STATE CORE-SCALE RAINFALL AND RETURN FLOWS AND DETERMINATION OF DISPERSION PARAMETERS

A series of experiments designed to study the separation of flow components from two large undisturbed cores under steady-state rainfall (downward) and return (upward) flows under near-saturated conditions is summarized. The experiments were conducted on soil columns collected from Lancaster University and the Slapton Wood catchment, Devon. The use of the relatively conservative tracers, potassium bromide, o-(trifluoromethyl)benzoic acid and 2,6-difluorobenzoic acid and a combination of application rates made it possible to quantify the different sources of water contributing to the discharge hydrographs. There is significant retention of tracer within the cores, despite the application of several pore volumes of water. The use of steady flow conditions allowed the determination of dispersion coefficients, dispersivity and proportion of ‘mobile’ water content parameters of the advection–dispersion equation. It was found that there were significant differences between the dispersivities at different flow-rates under upward and downward flux conditions and that in the undisturbed cores studied here the apparent proportions of mobile pore water ranged between 0.33 and 1.0, with an apparently complex relationship to flux rate. Prediction of transport in undisturbed soil remains problematic and tracer experiments will continue to be needed to provide a fundamental understanding of the complex flow processes involved.     

Pressure, Temperature and C-O-H Fluid Fugacities across the Amphibolite-Granulite Transition, Northwest Adirondack Mountains, New York

Pressures, temperatures, water activities (a_H2O) and fugacitiesof the other C-O-H fluid species have been estimated on a traverseacross the amphibolite-granulite facies boundary in the MajorParagneiss, northwest Adirondacks, N.Y. Two-feldspar pairs givetemperatures ranging from 650?C in the central portion of theunit to 760?C towards the northeast. Biotite-garnet pairs giveerratic temperatures compared to two-feldspar temperatures.This discrepancy appears to be due to retrograde resetting asdetermined from compositional zoning patterns in biotites andgarnets. Some of the discrepancy may also be due to non-idealityof pyrope-almandine mixing or to non-ideality from other components.Pressures ranging from 5?4 kb for the southwestern portion ofthe unit to 8?0 kb in the northeast were determined from anorthite-grossular-sillimanite-quartzbarometry. Minimum pressures of 5?8 kb were also determinedfrom coexisting garnet + rutile. Values of a_H2O of 0?08-0?5estimated from biotite and muscovite dehydration reactions showno correlation with grade. The variability in a_H2O suggeststhat it is locally controlled and that a homogeneous, pervasivefluid was not present during high grade metamorphism. Graphiteequilibria indicate that f_O2 was less than 0?5 log units belowQFM and that if a fluid was present, it was rich in CO₂ andH₂O. P-T-a_H2O values suggest that partial melting did not occurduring metamorphism. Pervasive flooding with CO₂ does not appearto have occurred. The amphibolite-granulite transition at thislocality is characterized by increasing temperature and pressure.     

Mineralogy and Petrology of the Red Hill Alkaline Igneous Complex, New Hampshire, U.S.A.

The Red Hill intrusion, New Hampshire is one of the alkalineintrusions making up the White Mountain Magma Series. Earlierwork has shown that it consists of several units with ring-or plug- like form, in order of intrusion: Outer Coarse Syenite(OCS) plus Nepheline Sodalite Syenite (NSS Fire Tower Sycnite(FTS); Garland Peak Syenite (GPS) Watson Ledge Quartz Syenite(WLQS) Interior Fine Granite (IFG). New studies have revealedtrends of increasing alkalinity in both the OCS (OCS-AOCS-B)and NSS (NSS-A-B-C). Conventional K-Ar and Rb-Sr age datingon separated minerals and bulk rocks show that the OCS, NSS,FTS, and GPS have indistinguishable ages at 198.5?1.5 Ma whilethe IFG formed about 10 Ma later. These values are believedto represent intrusion ages. Amphiboles from the NSS vary from ferro-pargasites through taramitesto katophontes and pyroxenes from ferrosalites to aegirine-augitesthese trends follow the increasing degree of under- saturationin the NSS-A-C series. The NSS-A contain mafic syenite xenolithsas well as partially resorbcd salitic pyroxene cores withinamphiboles. Mineral and isotope data are consistent with theseinclusions being cognate suggesting derivation from more-basicparental magmas. Pyroxenes and amphiboles from saturated andoversaturated rocks vary from ferro-salites to ferro-hedenbergitesand hastingsites to ferro-edenites, respectively, but OCS-Bshow fractionation towards aegirine-augites and katophorites. Mineral assemblages crystallized close to the quartz-fayalite-magnetitebuffer at a pressure of about 1–1.5 kb under essentiallyfluid-saturated conditions. It seems likely that the complexformed by emplacement of fractionated magmas derived from alower-level magma chamber which initially contained a basalticparent magma. The first pulse of magma had an overall compositionsimilar to OCS plus NSS and was intruded as a sheet-like bodywhich differentiated in situ to give a central unit of highlyundersaturated magma (NSS-C). NSS-C samples with relativelyradiogenic Sr isotope compositions were modified by introductionof country-rock Sr via circulating fluids. Fractional crystallizationof alkali-rich amphiboles from critically undersaturated magma(NSS-A?) in the lower- level chamber led to the developmentof saturated and oversaturated magmas. These were intruded intothe OCS/NSS unit along ring fractures to form the FTS and GPSunits. Rock and mineral compositions, including isotope data,are consistent with the IFG forming by partial melting of countryrock and being intruded along pre-existing planes of weaknesssome 10 Ma after the main complex was formed.     

Seasonal and spatial variability of particulate matter of a muddy intertidal flood front

The concentration and composition of suspended particulate matter (SPM) were measured weekly for a period of one year in the flood front waters traversing a muddy tidal flat. SPM concentrations were lowest in the winter when portions of the tidal flat were covered with ice, and biological activity was minimal. In contrast, the summer months had the highest SPM concentrations which reflected increased bottom resuspension. The two main sources of SPM were suspended matter carried in from offshore on the flooding tide and resuspended in situ bottom sediments. The offshore source was characterized by low SPM concentrations, coarse textures, and a high content of protein and chlorophyll ‘a’. Samples taken during resuspension events (storms/showers) had high SPM concentrations, finer textures, and were enriched in dead detrital organic material (phaeophytin). At any one time the SPM was primarily an admixture of these two sources. The highest SPM measurements were taken during storm events, with rainfall seeming to play a dominant physical role in aiding resuspension. SPM concentrations, textures, and compositions collected during the storms closely approximated SPM measurements made over newly dug ‘clam flats’.     

The late Miocene to Pleistocene ice-rafting history of southeast Greenland

Analysis of a Miocene-Pleistocene ice-rafted debris (IRD) record from the western Irminger Basin provides evidence for the initiation and long-term behavior of the SE portion of the Greenland Ice Sheet. In the late Miocene (~7.3 Ma), IRD supply to Ocean Drilling Program site 918 increased significantly indicating that glaciers large enough to reach sea level were present in SE Greenland long before the onset of widespread Northern Hemisphere glaciation. IRD accumulated at this site throughout the Pliocene and Pleistocene, supporting the hypothesis that SE Greenland was a key nucleation area for the formation of the Greenland Ice Sheet. Since glacial onset, the western Irminger Basin IRD record is characterized by a succession of episodes with high IRD mass accumulation rates (MARs). The site 918 IRD record indicates that greatest iceberg production in SE Greenland occurred during major climatic transitions (e.g. widespread Northern Hemisphere glacial expansion at 2.7 Ma and the mid-Pleistocene climate shift at 0.9 Ma), and that SE Greenland sometimes also led the northern North Atlantic region in glacial response to climatic forcing (e.g. glacial intensification at ~4.8 and, along with NE Greenland, at ~3.5 Ma).     

A comparison of scavenging and deposition processes in global models: results from the WCRP Cambridge Workshop of 1995

We report on results from a World Climate Research Program workshop on representations of scavenging and deposition processes in global transport models of the atmosphere. 15 models were evaluated by comparing simulations of radon, lead, sulfur dioxide, and sulfate against each other, and against observations of these constituents. This paper provides a survey on the simulation differences between models. It identifies circumstances where models are consistent with observations or with each other, and where they differ from observations or with each other. The comparison shows that most models are able to simulate seasonal species concentrations near the surface over continental sites to within a factor of 2 over many regions of the globe. Models tend to agree more closely over source (continental) regions than for remote (polar and oceanic) regions. Model simulations differ most strongly in the upper troposphere for species undergoing wet scavenging processes. There are not a sufficient number of observations to characterize the climatology (long‐term average) of species undergoing wet scavenging in the upper troposphere. This highlights the need for either a different strategy for model evaluation (e.g., comparisons on an event by event basis) or many more observations of a few carefully chosen constituents.