spinels and mg ilmenites from the noril sk 1 and talnakh intrusions and other mafic rocks of the siberian flood basalt province spinels from the mineralized noril sk 1 and talnakh intrusions show a broad and distinctive compositional spectrum from normal chromite to ti enriched aluminous magnetite in the talnakh intrusion in particular the range of spinel compositions extends across a compositional space where spinels are rare in other layered intrusions spinel compositions vary widely on a scale of individual thin sections and are influenced by the nature of the enclosing silicate phase spinels enclosed in olivines are less ti enriched than those outside olivine grains compositional variance in the spinels is attributed to variable but generally advanced reaction between cumulus chromite grains and solidifying trapped intercumulus liquid the advanced nature of the process is attributed to the open nature of the intrusions continuous prolonged flow through of hot magma enabled cumulates within the intrusions to remain above their solidus temperature for longer than would be normal for sills of comparable thickness the barren chibacheka river intrusion shows some of the same features but differs from talnakh in that spinel olivine pairs record equilibration temperatures higher than those at talnakh temperatures recorded by spinel olivine pairs at talnakh are anomalously low for such a small intrusion again indicating prolonged slow cooling consistent with a flow through model for the sill spinel compositions support a hypothesized comagmatic relationship between the chibacheka river intrusion and the ti cr rich gudchichinsky picritic basalts spinels in the noril sk and talnakh intrusions imply a parent magma with a lower cr al ratio than the gudchichinsky picritic basalts spinels from the siberian intrusions show a similar range in compositions to the feeder intrusions of the karoo flood basalt province jinchuan spinels share the features of high ti contents and anomalously low equilibration temperatures with the noril sk talnakh spinels mg ilmenites are a feature of the siberian and jinchuan intrusions they are attributed to crystallization of ilmenite from evolved trapped intercumulus liquid buffered by surrounding mg rich cumulus phases their existence implies moderately but not unusually ti rich parent magmas consistent with compositions of the siberian traps lavas

has the ozone hole contributed to increased antarctic sea ice extent 1 since the 1970s sea ice extent has decreased dramatically in the northern hemisphere and increased slightly in the southern hemisphere a difference that is potentially explained by ozone depletion in the southern hemisphere stratosphere in this study we consider the impact of stratospheric ozone depletion on antarctic sea ice extent using a climate model forced with observed stratospheric ozone depletion from 1979 to 2005 contrary to expectations our model simulates a year round decrease in antarctic sea ice due to stratospheric ozone depletion the largest percentage sea ice decrease in our model occurs in the austral summer near the coast of antarctica due to a mechanism involving offshore ekman sea ice transport the largest absolute decrease is simulated in the austral winter away from the coast of antarctica in response to an ocean warming that is consistent with a poleward shift of thc large scale pattern of sea surface temperature our model results strongly suggest that processes not linked to stratospheric ozone depletion must be invoked to explain the observed increase in antarctic sea ice extent

rossby waves mediate impacts of tropical oceans on west antarctic atmospheric circulation in austral winter recent studies link climate changearound antarctica to the sea surface temperature of tropical oceans with teleconnections from the pacific atlantic and indian oceans making different contributions to antarctic climate in this study the impacts of each ocean basin on the wintertime southern hemisphere circulation are identified by comparing simulation results using a comprehensive atmospheric model an idealized dynamical core model and a theoretical rossby wave model the results herein show that tropical atlantic ocean warming indian ocean warming and eastern pacific cooling are all able to deepen the amundsen sea low located adjacent to west antarctica while western pacific warming increases the pressure to the west of the international date line encompassing the ross sea and regions south of the tasman sea in austral winter these tropical ocean basins work together linearly to modulate the atmospheric circulation around west antarctica further analyses indicate that these teleconnections critically depend on stationary rossby wave dynamics and are thus sensitive to the background flow particularly the subtropical midlatitude jet nearthesejets wind shearis amplified which strengthens the generation of rossby waves on the other hand near the edges of the jets the meridional gradient of the absolute vorticity is also enhanced as a consequence of the rossby wave dispersion relationship the jet edge may reflect stationary rossby wave trains serving as a waveguide the simulation results not only identify the relative roles of each of the tropical ocean basins in the tropical antarctica teleconnection but also suggest that a deeper understanding of teleconnections requires a better estimation of the atmospheric jet structures

capture of helium and other volatiles during the growth of olivine phenocrysts in picritic basalts from the juan fernandez islands olivine crystals in basalt contain helium that can be extracted for isotopic analysis helium bearing olivine phenocrysts in picritic tholeiites from the juan fernandez islands se pacific crystallized from moderately differentiated liquids none are xenocrysts of mantle peridotite the helium occurs in cavities or bubbles in inclusions best seen at high magnification in the olivine the olivine grew around spinel sulfide and bubbles that preferentially nucleated on crystal surfaces inclusions within these phases range from large cavities to tiny faceted pits arranged in rows many crystals contain curving trains of inclusions along annealed features the inclusions formed during mixing between cooler differentiated magma and hotter olivinecharged magma which accelerated vesiculation bubbles nucleated on the olivine as they do on ice when stirred in carbonated water mixing also induced thermal stress fracturing like the cracking of ice dropped into water cracking irregular extinction and subgrain formation occurred when faceted crystals collided with each other or with conduit walls boundary layer melts and bubbles were drawn quickly into the fractures thus few inclusions contain equilibrium proportions of minerals and vapor mantle derived helium clearly permeated into shallow storage reservoirs including rift zones where magmatic differentiation mixing and vapor exsolution were fairly extensive

the antarctic dipole and its predictability this study investigates the nature of interan nualvariability ofantarcticseaiceanditsrelationshipwith the tropical climate we nd that the dominant interan nual variance structure in the sea ice edge and surface air temperature elds is organized as a quasi stationary wave which we call the antarctic dipole adp it is charac terized by an out of phase relationship between the ice and temperature anomalies in the central eastern pacic and atlantic sectors of the antarctic the dipole consists of a strong standing mode and a weaker propagating motion within each basin s ice eld it has the same wavelength as the antarctic circumpolar wave acw and dominates the acw variance the dipole is clearly associated with tropical enso events it can be predicted with moderate skill using linear regression involving surface temperature two to four months ahead the prediction performs better in extreme warm cold years and best in la ni na years

the significance of pge variations with sr nd isotopes and lithophile elements in the emeishan flood basalt province from sw china to northern vietnam abstract new analyses of siderophile lithophile elements and sr nd isotopes in the permian basalts and picrites from northern vietnam the southernmost occurrence of the emeishan flood basalt province together with previously published data are used to address the question of whether any meaningful correlation between these elements and isotopes exists at a province scale the available data show that negative correlations between e nd 87 sr 86 sr i and mantle normalized nb th n are present in the basalts but not in the associated picrites this indicates that crustal contamination is negligible in the picrites but significant in some of the basalts the picrites and basalts from the entire province show negative correlations between rh ru n pt ru n pd ru n and mg number this indicates that ru behaves compatibly whereas rh pt and pd behave incompatibly during magma differentiation the incompatible behavior of rh in natural basaltic systems is also supported by the fact that pt rh n remains constant with decreasing mg number in the lavas depletions of pd and pt and to a lesser degree cu in some basaltic samples characterized by relatively low e nd and nb th n support the notion that sulfide saturation in the magmas was triggered by a combination of siliceous crustal contamination and addition of external sulfur within the entire flood basalt province only the picrites from song da northern vietnam show clear depletion in ir relative to ru these picrites are also characterized higher al 2 o 3 tio 2 and lower mantle normalized la yb 0 2 2 4 than those from elsewhere in the province possibly due to the involvement of an ir depleted fertile mantle component in magma generation at this location

laboratory experimental study of soil crusting relation between aggregate breakdown mechanisms and crust stucture abstract crusts formation on cores of air dry and prewetted aggregates was studied using a laboratory rainfall simulator samples were taken out during the experiment in order to study changes in water content and aggregates size distribution inside the crust and under the crust pore space geometry of the crusts is described using light optical microscopy and mercury porosimetry in the case of air dry aggregates aggregates become micro cracked macropores at the surface are quickly closed and ponding occurs rapidly with prewetted aggregates microcracking does not occur and only a very slow abrasion of the aggregates is observed porosity remains high and no ponding excess occurs the discussion of these results shows that it is the way of the wetting and the initial water content which determine the breakdown mechanism and therefore the behaviour of the aggregates submitted to rainfall

soil aggregation response to long and short term differences in rainfall amount under arid and mediterranean climate conditions soil structure variables aggregate stability as mean weight diameter mwd microparticles percentage mip and macroparticles percentage map organic matter content om electrical conductivity ec and sodium and potassium adsorption ratio spar were monitored for 3 years at seven research sites the sites are located along a climatic transect extending from the judean mountains mean annual rainfall 700 mm annual mean temperature 17 c to the dead sea mean annual rainfall 100 mm annual mean temperature 23 c and represent four climatic regions multiple regression relating soil structure variables to om spar and ec highlighted the importance of organic matter in determining soil structure a high correlation was found between mean annual rainfall representing its long term effect and annual rainfall variability representing its short term effect and some aggregation variables as increased while mip decreased with decreasing rainfall the rate of change along the climatic transect was non linear a step like threshold exists in the semi arid zone meaning that this area is threatened by land degradation even with a small decrease in mean annual rainfall mip was found to be very sensitive to rainfall amount even at the patch scale no patches of low mip values were found in the arid zone even in a very wet year and no patches of high mip values were found in the mediterranean zone even in a very wet year the main conclusion is that mip is the best indicator for assessing the impact of the expected climate change on soil structure and erosion

deriving indicators of soil degradation from soil aggregation studies in southeastern spain and southern france soil degradation is perceived as a major threat in the mediterranean region due to changes in land use and possible future climate change soil aggregation parameters are used here to demonstrate their potential as a key indicator for land degradation studies the monitoring of these indicators offers a means of establishing the vulnerability and resilience of geo ecosystems soil aggregation stability and distribution were studied on soils with an open shrubby vegetation cover from several places in southeastern spain and southern france by applying drop tests and determining aggregate size distributions aspect and vegetation cover were incorporated in the soil sampling several indices were derived from these analyses to indicate the degree of soil aggregation this was done by referencing to a base level of aggregation bare soil aggregation it was found that soil aggregates were more stable and were often coarser under vegetation when compared to their immediate surrounding bare areas a similar slightly less clear effect was noted on n facing exposed slopes when compared to s facing exposed slopes long term changes were found by studying cultivated land abandoned fields and land covered by semi natural vegetation on comparable substrate and comparable land units it is clear that soil aggregation and aggregate stability increases with time years it is argued that soil aggregation indices can be used as a key indicator for degradation processes at a fine scale with implications for runoff and sediment generating processes at the hillslope scale

controls on pge fractionation in the emeishan picrites and basalts constraints from integrated lithophile siderophile elements and sr nd isotopes picrites from the emeishan large igneous province elip may be divided into those that show lree enrichment and those that are characterized by lree depletion all picrite types have low 87sr 86sr ratios 0 7057 but variable end suggesting that crustal contamination has been negligible and source mantle variation is responsible for their chemical diversity in contrast coeval basalts show strong signatures of crustal contamination calculated mantle potential temperatures are 240 c higher than that in ambient mantle supporting a plume origin for the province a depleted plume source and ancient sub continental lithospheric mantle are inferred to be the most important end members involved in the generation of the emeishan picrites pt and pd values of the picrites show no evidence of depletion pt pd ratios are highly variable and show no correlation with picrite type pge analyses of both picrites and coeval basalts confirm that os ir and ru ipge have behaved compatibly and pt pd and rh have behaved incompatibly during cr spinel and olivine crystallization pge depleted basalts are present in the elip but the most fractionated basalts tend not to show significant depletion in pt and pd this suggests that fractional crystallization alone was not sufficient to induce sulfide saturation in the magmas and that contamination involving crustal sulfur was an important driving mechanism significant depletion of ir relative to ru in some of the basalts regardless of the sulfide saturation state of the parental magma suggests that ir dominant alloys segregated prior to magma eruption depletions of ipge relative to pt and pd in the emeishan picrites are consistent with the notion that ipge alloys are stable in the mantle during partial melting

erosion in mediterranean landscapes changes and future challenges abstract intense erosion processes are widespread in the mediterranean region and include sheet wash erosion rilling gullying shallow landsliding and the development of large and active badlands in both subhumid and semi arid areas this review analyses the main environmental and human features related to soil erosion processes and the main factors that explain the extreme variability of factors influencing soil erosion particularly recent land use changes the importance of erosion in the mediterranean is related to the long history of human activity in a region characterized by low levels of annual precipitation the occurrence of intense rainstorms and long lasting droughts high evapotranspiration the presence of steep slopes and the occurrence of recent tectonic activity together with the recurrent use of fire overgrazing and farming these factors have resulted in a complex landscape in which intensification and abandonment wealth and poverty can co exist the changing conditions of national and international markets and the evolution of population pressure are now the main drivers explaining land use changes including farmland abandonment in mountain areas the expansion of some subsidized crops to marginal lands and the development of new terraces affected by landslides and intense soil erosion during extreme rainstorm events the occurrence of human related forest fires affecting thousands of hectares each year is a significant problem in both the northern and southern areas of the mediterranean basin here we highlight the rise of new scientific challenges in controlling the negative consequences of soil erosion in the mediterranean region 1 to reduce the effects and extent of forest fires and restructure the spatial organization of abandoned landscapes 2 to provide guidance for making the eu agricultural policy more adapted to the complexity and fragility of mediterranean environments 3 to develop field methods and models to improve the identification of runoff and sediment contributing areas 4 to contribute to the conservation of landscapes i e bench terraced fields having high cultural and productivity values 5 to improve knowledge of the hydrological and geomorphological functioning of badlands with the aim of reducing sediment yield and accessibility 6 to better understand the effect of climate change on soil erosion in the mediterranean region and 7 to improve quantitative information on long term soil erosion

soil degradation factors along a mediterranean pluviometric gradient in southern spain article i nfo the modifications to soil properties that resulted from changes in water availability along a pluviometric gradient from 240 to 1100 mm mean annual rainfall were investigated the study was carried out at eight experimental sites in southern spain and assessed the influence of a reduction in annual average rainfall along the pluviometric gradient on various physical chemical and hydrological properties of the topsoil and on the biotic characteristics of the environment the aims were to assess the soil degradation status and to determine if any of the soil variables studied could be used as soil degradation indicators for each experimental site the relationships among a series of edaphic hydrological and biological properties were investigated and the principal factors affecting soil degradation were determined using principal component analysis the properties included the clay silt and sand content organic matter retained organic carbon salinity cation exchange capacity structural stability usle k factor bulk density saturated hydraulic conductivity soil moisture the number of vegetal species and vegetation cover the results show that relationships among biotic and abiotic factors control soil degradation processes from wet to semiarid arid conditions along the mediterranean pluviometric gradient a precipitation based soil degradation threshold of approximately 500 mm year 1 was established as below this level the vegetation is no longer associated with the presence of greater soil moisture content but adapts to degradation as evidenced by the appearance of xerophytic species

influence of soil properties on the aggregation of some mediterranean soils and the use of aggregate size and stability as land degradation indicators abstract soil aggregation in relation to other soil properties was studied along a climatological transect in the southeast of spain three sites were selected along this transect ranging from semiarid to subhumid climatological conditions the aggregate size distribution the macro and microaggregate stability of the superficial soil horizon and their relations with other soil properties were analysed large aggregates 10 10 5 5 2 mm were present in highest proportions in the most arid of the studied areas these large aggregates were associated with high values of water stable microaggregates however they did not improve soil structure and are related to high bulk densities and low water retention aggregates 1 0 105 mm were positively correlated to medium fine very fine sand and silt fractions and to organic matter aggregates water stability of microaggregates showed a positive correlation with clay content while the stability of the macroaggregates depended on the organic matter content when the organic matter content was greater than 5 or 6 below that threshold the carbonate content was strongly correlated with aggregate stability a general conceptual scheme of associations between aggregate size distribution water stable microaggregation and textural characteristics for the area was developed the land use history affecting soil overlaps the pattern of climatological situations and has to be taken into account aggregate size distribution and stability can be used as indicator of soil degradation but not as a unique parameter

linking spatial patterns of soil organic carbon to topography a case study from south eastern spain a key uncertainty in our understanding of the global carbon cycle is the lateral movement of carbon through the terrestrial system soils are the major storage of carbon in the terrestrial biosphere and the inventory of soil organic carbon soc is required for greenhouse gas inventories and carbon mitigation projects the aim of this study is to characterize spatial patterns of the concentrations of topsoil total organic carbon toc in a semi arid mediterranean area in south eastern spain and to assess their relationship to topography we adopt a remote sensing based approach for the spectral determination and quantification of toc with a complete coverage of bare soil surfaces digital terrain analysis and geostatistical techniques are applied to analyze the spatial patterns of toc at different spatial scales we show that accumulation of topsoil soc is dependent on topographic position at the landscape scale with highest values found in valley bottoms at the hill slope scale differences among terrain classes exist regarding the topographic controls on soc while positive correlation between the topographic wetness index twi and toc can be observed on steep slopes that correlation is not significant on wide pediments small scale spatial variability is large on ridges steep slopes and valley bottoms while soc distribution on pediments is relatively homogeneous these differences are most likely governed by the presence of vegetation patches and variable runoff and sediment transport rates among the terrain classes the successful application of hyperspectral remote sensing for the spatial estimation of soc concentrations suggests that it is a promising technique to advance soc inventories in semi arid and arid regions

holocene sediment fluxes in a fragile loess landscape saxony germany abstract the loess region of the central saxon hill country is characterized by a relief of gently rolling hills whose most distinctive landscape elements are well defined shallow valleys called dells the aim of this research is to gather morphodynamic information on the dells in a qualitative and quantitative way by means of high resolution field mapping and laboratory based analyses the intensity of sediment shifting has been modelled via sediment budgeting on a small catchment scale research objectives are to determine the character and magnitude of geomorphic processes for a holocene time frame concerning the absence of currently obtainable dating this study represents a reflection which summarises all sediment shifting related to anthropogenic land use during the holocene as a specific parameter in terms of landscape development the relief is considered to be strongly associated with varying process intensities agrarian land use of the loess region since the late neolithic has resulted in severe soil erosion lower middle slope positions are the apparent spots were soil erosion processes take place in terms of rill erosion a detailed survey of three dells provided a very heterogeneous pattern of the relocation of soil material dell 1 zehren shows medial holocene soil profile truncation of 1090 mm in contrast dell 3 lobschutz shows soil loss of around 660 mm all systems have similarly high slope gradients up to 12 actually the deepening of the dell s depth contours and therewith the extent of erosive slope lengths is varying thus a higher longitudinal decline of the valley floors and a more intensive incision lead to enlarged erosive slope lengths which causes increasing sediment transport hence land use patterns trigger the process of material displacement whereas relief modifies the intensity of geomorphic processes

the characteristic variability and connection to the underlying synoptic activity of the amundsen bellingshausen seas low 1 recent studies have noted an asymmetrical climate change across antarctica with significant warming in west antarctica and the antarctica peninsula and primarily insignificant trends in east antarctica due to its proximity variations in the position and intensity of the amundsen bellingshausen seas low absl are a suspected atmospheric mechanism here we investigate the absl to understand its characteristic variability and underlying synoptic scale influences based on three reanalysis data sets the absl is defined as the minimum monthly pressure in the 45 75 s 180 60 w domain using this criterion a significant north south and east west progression is noted in the climatological 1979 2001 average absl which is strongly tied to the location of the maximum cyclone system density and minimum cyclone central pressures more than 550 cyclones a year were identified in the vicinity of the absl during spring significant trends in their central pressures are noted in the ross sea the implied changes in temperature advection by these stronger systems are consistent with the warming in west antarctica the strongest cyclone events i e the ten with the deepest central pressures also demonstrate a connection to the climatological absl albeit weaker moreover these strong cyclone events are significantly linked to the southern annular mode sam particularly in their annual frequency and location steering in the summer this shows that large scale forcing such as from the sam may influence the strongest cyclones in the region and could allow for the prediction of such events

the origin of ni cu pge sulfide mineralization in the margin of the zhubu mafic ultramafic intrusion in the emeishan large igneous province southwestern china the zhubu magmatic ni cu pge sulfide deposit is hosted in a mafic ultramafic intrusion which is part of the emeishan large igneous province in southwest china the zhubu intrusion is composed of a layered sequence 750 x 400 x 600 m with subhorizontal modal layering and a subvertical marginal zone of 40 m across the marginal zone is composed of iherzolite and olivine websterite with minor gabbroic rocks the layered sequence is composed of iherzolite websterite gabbro and gabbrodiorite from the base to the top the zhubu intrusion can be explained by two stages of formation an early conduit stage for the marginal zone and a late in situ differentiation stage for the layered sequence most important ni cu pge mineralization in the intrusion occurs as disseminated sulfides within the marginal zone olivine crystals from the marginal zone contain 81 to 84 mol fo and 1 600 to 1 900 ppm ni the rims of zoned olivine phenocrysts in the emeishan picrites have similar fo contents but significantly higher ni contents 2 300 2 600 ppm the olivine data indicate that the parental magma of the zhubu ultramafic rocks is similar to the transporting magma of the emeishan picrites in mgo feo ratios but depleted in ni due to sulfide segregation before olivine crystallization the initial concentrations of pge in the zhubu magma estimated from bulk sulfide compositions are 7 ppb pd 9 3 ppb pt and 0 8 ppb ir similar to the values in the emeishan picrites like the emeishan picrites the zhubu intrusive rocks are characterized by light ree enrichments negative nb anomalies relative to th and ta which are rare in the emeishan picrites are present in the zhubu samples the sr 87 sr 86 i and epsilon nd values of the zhubu intrusive rocks vary from 0 709591 to 0 710692 and from 2 to 3 respectively the trace element and isotope compositions indicate that the zhubu magma was contaminated by crustal materials supporting the interpretation that sulfide saturation in the magma was triggered by crustal contamination the area where the lower part of the conduit may have been brought up by faulting should be the focus of future exploration at zhubu

aggregate stability in range sandy loam soils relationships with runoff and erosion abstract the spatial variability of soil aggregate stability and its relationship to runoff and soil erosion were examined in a catena of soils and vegetation in a semiarid environment at the rambla honda field site tabernas almeria se spain to evaluate the validity of structural stability as a soil erosion indicator in sandy loam range soils the influence of soil properties and topography on the variability of aggregate stability was also examined methods include 1 aggregate stability assessment at 12 sites 3 repetitions per site on the hillslope by two methods a aggregate size distribution by dry sieving b water drop test 2 soil organic carbon content 3 particle size distribution determination 4 terrain attributes derived from a digital elevation model 1 m resolution 5 monitoring runoff and erosion for nearly 3 years in eight 10 2 m plots distributed over the hillslope results 41 of the average soil mass is formed by 2 mm aggregates however wet aggregate stability is poor with a mean of a total of 1440 aggregates of only 26 drop impacts necessary to break up a wet aggregate pf 1 significant relationships were found in the number of water drops required for aggregate breakdown and runoff and erosion rates however no significant relationships between the mean weight diameter of aggregates under dry conditions and runoff or erosion rates were observed the relationships of aggregates with other soil properties hillslope position and proximity to plants are also analysed the most significant correlation found was between the number of drop impacts and soil organic matter content the stability of topsoil aggregates seems to be a valuable indicator of field assessed runoff and inter rill erosion of sandy loam range soils under semiarid conditions

anthropogenic and climatic impact on holocene sediment dynamics in se spain a review the climatic and anthropogenic control on holocene sediment dynamics was not well constrained for the western mediterranean basin the paucity of high resolution palaeoenvironmental records long hampered a detailed understanding of the human impact on erosion rates this paper analyses holocene sediment dynamics in the context of regional climatic conditions land cover and human occupation based on an extended compilation of recently published high resolution paleoenvironmental proxy data from both terrestrial and marine environments the palaeoenvironmental reconstruction identified four main aridification episodes a at 5600 4700 a4 4100 3400 a3 2800 2500 a2 and 1900 1300 1200 a1 cal bp most of the severe aridification phases were climatically induced not human driven and well correlated with a large dataset of paleoenvironmental records from the western mediterranean basin and north atlantic ocean the phases of enhanced aridity are generally associated with enhanced sediment dynamics independent of the intensity and type of human occupation in contrast wet climatic conditions are found to be associated with both high and low sediment dynamics dependent on the human impact on the environment the mid late phoenician phoenician ii republican rome civilizations and the christian reconquest are all associated with high human impact on the environment and high erosion rates are reported for the vera basin and ne spain despite the improved hydrological conditions human occupation is not necessarily associated with geomorphic instability as shown by the post argaric omeya and nazarene periods that are characterized by low erosion rates and geomorphic stability

wave zonal flow interaction and ultra low frequency variability in a simplified global circulation model the interactions between baroclinic waves and the zonal mean mid latitude flow are investigated using a multilevel primitive equation model of moderate resolution with idealized surface friction and diabatic heating terms integrations corresponding to 100 years were performed under perpetual solstice conditions empirical orthogonal function eof analyses were carried out on the zonal mean zonal wind u adjustments to the winter hemisphere zonal jet due to the growth and decay of baroclinic waves can be described in terms of the first two eof patterns which exhibit substantial interannual variability for a single lifecycle such adjustments take the form of a circuit of a phase space whose axes are defined by the amplitudes of the two eofs the cumulative effects of multiple lifecycles lead to a low frequency circulation in the phase space with a timescale of about 150 days we suggest that this effect may be intrinsically related to the internal generation of ultra low frequency variability in the model normal mode lifecycle calculations including dissipation reveal similar phase space properties the growth rates of normal mode disturbances are shown to be highly sensitive to the phase of the first eof

interpretation of recent antarctic sea ice variability 1 trends in the satellite derived antarctic sea ice concentrations 1979 2002 show pronounced increase decrease in the central pacific sector bellingshausen western weddell sector by 4 10 per decade confidence levels for these regional trends exceed 95 positive polarities of the antarctic oscillation aao lead to more less ice in the eastern ross amundsen sector bellingshausen northern weddell sector which are qualitatively opposite to the impacts of positive polarities of the el nino southern oscillation enso the mechanisms responsible for the covariability between the ice and the a aao and b enso are demonstrated over the last 24 years a positive aao trend and a slightly negative enso trend produce a spatial pattern of ice changes similar to the regional ice trends however the magnitude of the ice changes associated with the aao and enso is much smaller than the regional ice trends more local or less understood large scale processes should be investigated for the explanations

initial subduction of neo tethyan ocean geochemical records in chromite and mineral inclusions in the pozanti karsanti ophiolite southern turkey abstract chromitites in the pozanti karsanti ophiolite in turkey mainly occur as podiform chromitites within mantle harzburgite and stratiform like chromitites in mantle crust transition zone chromites in chromitites have varing cr from 62 8 to 80 3 and can be divided into two types namely intermediate cr 62 8 69 2 and high cr cr 73 9 80 3 types major elements of the high cr chromitite have an affinity with boninite whereas the intermediate chromitite shows transitional features between morb and boninite the compositional differences in clinopyroxene inclusions between intermediate and high cr chromitite coupled with the relatively high trace element contents e g v ga in the high cr chromitite indicate distinctive parental magmas trace elemental profile analysis of a nodular chromite grain in one nodular chromitite sample pk14 41 demonstrates significant but non systematic variations from the core to the rim which also confirmed the compositional heterogeneity of the parental magmas the presence of primary hydrous mineral inclusions such as amphibole in chromite together with ca rich minerals e g calcite reflect the water rich and ca rich characteristics of the parental magma the higher fo2 of high cr chromitite evidenced by the lower v mn values may be due to more oxidized fluids released from downgoing crustal materials thus we conclude that the parental magmas of the pozanti karsanti chromitite were derived from a proto forearc mantle and evolved to higher fo2 with the subduction initiation at that time but were water and ca rich in general

tropical connections to climatic change in the extratropical southern hemisphere the role of atlantic sst trends abstractthe austral spring relationships between sea surface temperature sst trends and the southern hemisphere sh extratropical atmospheric circulation are investigated using an atmospheric general circulation model agcm a suite of simulations are analyzed wherein the agcm is forced by underlying sst conditions in which recent trends are constrained to individual ocean basins pacific indian and atlantic allowing the impact of each region to be assessed in isolation when forced with observed global sst the model broadly replicates the spatial pattern of extratropical sh geopotential height trends seen in reanalyses however when forcing by each ocean basin separately similar structures arise only when atlantic sst trends are included it is further shown that teleconnections from the atlantic are associated with perturbations to the zonal walker circulation and the corresponding intensification of the local hadley cell the impact of which results in the development of atmospheric rossby w

central west antarctica among the most rapidly warming regions on earth the west antarctic ice sheet is contributing to sea level rise but temperature trends in the region have remained uncertain a complete temperature record for byrd station in central west antarctica spanning from 1958 to 2010 establishes west antarctica as one of the fastest warming regions globally

surface microtopography and soil penetration resistance associated with shrub patches in a semiarid rangeland the surfaces of hillsides in semiarid regions are characterized by vegetative patchiness and an associated pattern of soil characteristics in a semiarid patchy rangeland in the northern negev region of israel the pattern of ground surface microtopography and soil penetration resistance were investigated along transects centred on randomly selected shrubs of sarcopoterium spinosum each transect comprised five segments on the hillslope axis upslope us and downslope ds of the central stem cluster of the shrub patch immediately upslope of the shrub tr an upper intershrub ui segment above tr and a lower intershrub li segment below ds significant differences were found among the different segments with regard to both slope and soil penetration resistance segment us had a relatively shallow slope 9 0 in average and the deepest penetration depth 20 5 mm segment ds had the steepest slope 21 0 and a relatively deep penetration depth 16 4 mm segments ui and li had intermediate values for both slope 15 1 and 13 4 respectively and penetration depth 10 5 and 9 8 mm a spatial relationship between the shrub patches and grazing was found segment tr immediately above the shrub tended to be a flock trampling route and had the lowest values of both slope 5 1 and penetration depth 6 1 mm a conceptual model was proposed to explain these results it suggests that under the prevailing conditions of the study site these relationships regulate the redistribution of soil resources on the hillside

the 1925 meteorite fall near ellemeet and serooskerke the netherlands two meteorites impacted in 1925 around the town of serooskerke on the isle of schouwen the netherlands the largest mass is widely known as the ellemeet diogenite while a second mass heavily weathered due to environmental exposure also survived until the present day this work aims to reconstruct the history of the 1925 fall and for the first time documents the second mass known as the serooskerke by integrating a historical and experimental approach the study of historical news archives and cadastral records redefined the 1925 impact site at n 51 42 086 e 3 49 789 environmental exposure experiments reproducing the effects of rainfall and frost weathering identified the latter as the main cause for the second mass reported disintegration in the field sometime during the 1925 1926 winter the bulk mineralogy of the second mass was established using xrd powder diffraction for a 2 range of 3 70 and was found to be identical to an ellemeet reference sample uv vis nir spectroscopy 300 2500 nm was subsequently used to broadly compare the second mass to hed clan meteorites bouvante eet87503 johnstown and asteroid 4 vesta in order to corroborate its vestan origin the historical and geographic relationship of the two masses and the comparable bulk mineralogy supported the pairing of these two meteorites this makes the serooskerke a valuable legacy of the 1925 fall especially as the location of 50 of the remaining ellemeet mass is presently unknown

soil erosion and climate change the transect approach and the influence of scale abstract studies of geo ecological processes are being made along climatological transects on similar limestone rocks at different locations across the mediterranean the main objectives of the research are firstly to gain insight into the influence of climate on key geomorphological process pattern relationships that characterise different locations along the transect and secondly to obtain a better insight into the possible impact of climate change on ecosystem degradation the paper begins by considering the possible methodological approaches that can be applied to investigate the impact of climate change on ecosystem degradation in complex ecosystems and explains why a nonlinear evolutionary modelling framework was chosen for the transect studies the conceptual basis of the methodology is presented and the transect approach described the research methodology takes into account the influence of climate at four different scales landscape slope response unit and patch field research at these scales is oriented towards identifying and understanding the key processes and to identifying key parameters that can be monitored to establish change some results are presented from the judean desert transect in israel to show how a key indicator in this case aggregate stability varies with temperature and to show how process pattern features vary along the limestone transect from the area having a mediterranean climate to the desert both conceptual and practical models of soil erosion need to address scale issues in particular as time and spatial scales change so also does the relative significance of different processes it is concluded that process pattern phenomena are useful in this context and that they can be applied to the problem of up scaling

compositional variations of olivine and sulfur isotopes in the noril sk and talnakh intrusions siberia implications for ore forming processes in dynamic magma conduits olivine from the noril sk i main and northwestern talnakh ore bearing intrusions in the noril sk region occurs as inclusions discrete grains and poikilitic crystals the original compositions of olivine inclusions have been well preserved by their host oikocrysts from reaction with interstitial silicate and sulfide liquids in contrast the compositions of discrete and poikilitic olivine crystals have been variably modified by reequilibration with trapped silicate and sulfide liquids there are abrupt changes in the contents of nickel in olivine inclusions 500 1 500 ppm between different rock units in all three intrusions which indicates that the different rock units in these intrusions are not related to each other via in situ differentiation of a common parental magma but rather are consistent with separate pulses of magma with variable degrees of differentiation possibly involving olivine crystallization and assimilation of siliceous crustal material in a staging chamber the 34s values of the samples with high sulfur contents 800 ppm sulfur from all three ore bearing intrusions vary between 8 and 14 per mil two sulfur poor samples 600 ppm sulfur from the northwestern talnakh intrusion yield 34s values of 1 5 and 3 6 per mil these values are similar to the values of the sulfur poor rocks from the ore barren intrusions in the region and illustrate the fact that high sulfur contents couple with increasing 34s values such a relationship is consistent with the addition of crustally derived 34s enriched sulfur to the magma of the ore bearing intrusions in contrast to other models of sulfide segregation in closed systems we propose that sulfide segregation occurred in an open system and the magma involved was undersaturated in sulfur and undepleted in chalcophile elements we envision that the 34s enriched sulfur was introduced via circulating fluids that transported sulfur from evaporite in the underlying sedimentary sequence to the magma in a dynamic magma conduit the immiscible sulfide liquids that segregated during sulfur contamination settled down in the wider parts of the conduit as the magma continued to travel successive pulses of new magma entered the conduit reacted with the early sulfide and displaced much of the early magma in the conduit the ore bearing intrusions are thought to have crystallized within the wider parts of the conduits and their voluminous sulfide poor peripheral sills represent some if not all of the magma that flowed out of the conduits

cr spinel olivine and cr spinel liquid nickel partition coefficients from natural samples abstract the nernst partition coefficient of nickel d ni between cr spinel and silicate melt in natural systems has been investigated using mid ocean ridge basalts morb and other volcanic rocks the cr spinel olivine d ni values in volcanic rocks are between 1 2 and 0 3 indicating that the cr spinel liquid d ni values vary from slightly higher to significantly lower than the olivine liquid d ni values in natural systems the cr spinel liquid d ni values from the morb samples vary between 6 and 11 slightly higher than those from the s bearing experiments of satari et al satari p brenan j m horn i and mcdonough w f 2002 experimental constraints on the sulfide and chromite silicate melt partitioning behavior of rhenium and platinum group elements economic geology 97 385 398 the results of the morb samples and the experiments of satari et al 2002 indicate a negative correlation between the cr spinel liquid d ni and the x cr values in cr spinels cr cation number on the basis of 3 total cations in the spinel structure variations of cr spinel liquid d ni values with cr spinel compositions can be estimated from an empirical equation based on the results of the morb samples and the experiments by satari et al 2002 the choice of cr spinel liquid d ni 10 for numerical modeling by righter et al righter k leeman w p and hervig r l 2006 partitioning of ni co and v between spinel structured oxides and silicate melts importance of spinel composition chemical geology 227 1 25 is reasonable for basaltic systems for picritic and komatiitic systems a lower value of 5 is more appropriate

eco geomorphological system response variability to the 2004 06 drought along a climatic gradient of the littoral betic range southern spain abstract one of the main characteristics of the mediterranean climate is the high frequency of droughts which last for a year or more and the appearance of dry spells within the wet season the littoral betic range in the south of the iberian peninsula shows a significant climatic gradient from the straits of gibraltar 1600 mm year 1 to the cabo de gata 150 mm year 1 these differences in climatic conditions result in variations in the elements of the eco geomorphological system at the hillslope scale this study aimed to analyse the immediate consequences of a two year drought period 2004 06 on several elements of the mediterranean eco geomorphological system on three hillslopes under different climatic conditions sub humid dry mediterranean and semi arid the soil water content the pattern of vegetation and some soil properties organic matter content aggregate stability and permeability were analysed before nov 2003 and during nov 2005 the drought period the most important findings were i a reduction in the soil water content which reached values below the wilting point in the wet seasons affecting negatively the water available for vegetation especially in the wettest sites ii a reduction in vegetation cover and the number of plants especially on semi arid field sites iii changes in the organic matter content which aggravate the loss of stability of soil aggregates a process seen more clearly under more arid conditions and iv a reduction of soil permeability in all situations in the climate gradient studied which supposes a priori an increase in erosive processes due to surface runoff these results indicate increased vulnerability of the eco geomorphological system because of the rainfall drought situation

geochronological petrological and geochemical constraints on ni cu sulfide mineralization in the poyi ultramafic troctolitic intrusion in the northeast rim of the tarim craton western china the poyi magmatic ni cu sulfide deposit is situated in the beishan fold belt in the northeastern rim of the tarim craton many permian magmatic ni cu sulfide deposits such as those in east tianshan are present in the adjacent central asian orogenic belt to the north the poyi deposit is hosted in a small dike like ultramafic troctolitic body that was emplaced into a much larger gabbroic intrusion our new zircon u pb isotope data reveal that these two intrusions formed 6 ma apart the ultramafic troctolitic intrusion was emplaced at 269 9 1 7 ma whereas the gabbroic intrusion was emplaced at 276 1 1 9 ma the results show that the poyi deposit is the youngest among the major magmatic ni cu sulfide deposits 0 2 mt ni of permian ages in the beishan tianshan region sulfide mineralization in the poyi deposit occurs as steeply dipping disseminated sulfide lenses mostly associated with wehrlites in the center of the dike olivine from the poyi ultramafic rocks has fo content up to 91 mol which is similar to the lower limit of mantle olivine and the most primitive within the permian beishan tianshan nickel belt like other magmatic sulfide deposits in this belt olivine from the poyi deposit is depleted in ca 1 000 ppm the estimated parental magma for the poyi most primitive ultramafic rocks contains 15 2 wt mgo cotectic olivine sulfide segregation from the poyi magma is inferred from systematic variation of fo ni contents in olivine from some sulfide barren ultramafic rock samples and supported by the occurrence of sulfide droplets as small inclusions in olivine fo90 mol in these rocks the involvement of multiple pulses of sulfide charged magma with different compositions is indicated by the abrupt change of olivine fo content with depth and the presence of olivine with similar fo contents but dramatically different ni abundances in the different parts of the deposit the 87sr 86sr i ratios and nd total of the poyi ultramafic rocks and troctolites range from 0 7042 to 0 7052 and from 4 9 to 6 0 respectively which are close to the isotope compositions of depleted mantle and within the ranges of major magmatic ni cu sulfide deposits of permian ages in east tianshan no more than 5 wt of bulk crustal contamination is required to explain the variations of sr nd isotopes in the poyi ultramafic troctolitic intrusion the abundances of incompatible trace elements in whole rocks and clinopyroxene crystals indicate very weak light ree enrichments coupled by significant negative nb ta anomalies in the parental melts bulk sulfides in the poyi deposit are characterized by positive correlations between any pair of platinum group elements pge indicating that pge tenor variations in the deposit are mainly controlled by variable r factors magma sulfide mass ratios the estimated initial concentrations of pge in the parental magma for the poyi deposit are almost two orders of magnitude lower than the abundances of pge in some continental picrites given that the parental magma for the poyi deposit is as primitive as a primary mantle derived magma the depletion of pge in the poyi deposit is most likely due to previous sulfide segregation at depth based on these observations we conclude that sulfide saturation in the poyi pge depleted mg rich magma was triggered by addition of crustal sulfur during magma ascent and that the poyi deposit was a dynamic conduit used by multiple pulses of olivine and sulfide charged magma

antarctic ice sheet loss driven by basal melting of ice shelves accurate prediction of global sea level rise requires that we understand the cause of recent widespread and intensifying glacier acceleration along antarctic ice sheet coastal margins atmospheric and oceanic forcing have the potential to reduce the thickness and extent of floating ice shelves potentially limiting their ability to buttress the flow of grounded tributary glaciers indeed recent ice shelf collapse led to retreat and acceleration of several glaciers on the antarctic peninsula but the extent and magnitude of ice shelf thickness change the underlying causes of such change and its link to glacier flow rate are so poorly understood that its future impact on the ice sheets cannot yet be predicted here we use satellite laser altimetry and modelling of the surface firn layer to reveal the circum antarctic pattern of ice shelf thinning through increased basal melt we deduce that this increased melt is the primary control of antarctic ice sheet loss through a reduction in buttressing of the adjacent ice sheet leading to accelerated glacier flow the highest thinning rates occur where warm water at depth can access thick ice shelves via submarine troughs crossing the continental shelf wind forcing could explain the dominant patterns of both basal melting and the surface melting and collapse of antarctic ice shelves through ocean upwelling in the amundsen and bellingshausen seas and atmospheric warming on the antarctic peninsula this implies that climate forcing through changing winds influences antarctic ice sheet mass balance and hence global sea level on annual to decadal timescales

cotectic proportions of olivine and spinel in olivine tholeiitic basalt and evaluation of pre eruptive processes the volume distribution texture and composition of coexisting olivine cr spinel and glass has been determined in quenched lava samples from hawaii iceland and mid oceanic ridges the volume ratio of olivine to spinel varies from 60 to 2800 and samples with 0 02 spinel have a volume ratio of olivine to spinel of approximately 100 a plot of wt mgo vs ppm cr for natural and experimental basaltic glasses suggests that the general trend of the glasses can be explained by the crystallization of a cotectic ratio of olivine to spinel of about 100 one group of samples has an olivine to spinel ratio of approximately 100 with skeletal olivine phenocrysts and small 100mm spinel crystals that show evidence of two stages of growth and a volume ratio of olivine to spinel of 100 to well over 1000 the olivine and spinel in this group have crystallized more slowly with little physical interaction and show evidence that they have accumulated in a magma chamber

chrome spinels from the jinchuan ni cu sulfide deposit gansu province people s republic of china chrome spinels occur in olivine rich cumulates in the jinchuan intrusion host to one of the largest known accumulations of magmatic ni cu in the world the chemistry and mode of occurrence of these spinels is compared with those in two other similar but unmineralized mafic ultramafic intrusions in the same belt the jinchuan intrusion contains mg poor chromites with widely varying tio 2 contents showing many features that are typical of chromites in normal tholeiitic layered intrusions wide compositional variance occurs on the scale of single thin sections and is attributed to reaction between cumulus chromite and trapped intercumulus liquid this process operated extensively even on grains that were armored by cumulus olivine crystals different reaction paths correlate with the abundance of sulfides in the rock the unmineralized intrusions show similar reaction trends but are offset from the jinchuan trends yejili spinels are generally higher in al and ga while zangbutai chromites are systematically higher in fe super 3 jinchuan spinel olivine pairs record equilibration temperatures well below the solidus and are slightly but significantly lower than blocking temperatures recorded at yejili the jinchuan ore zone contains low cr high fe super 3 chromites that are unusual and distinctive a plausible model for these unusual compositions is that these grains originated as normal aluminous spinels crystallizing from the parent silicate melt and subsequently became enlarged and modified during crystallization of the sulfide melt ti enriched chromites enclosed within sulfides record a prehistory of extensive reaction with trapped liquid sulfide associated chromites from jinchuan are strongly nickel depleted relative to expected ni values for their fe super 3 content when compared with the barren intrusions this feature combined with the distinctive chemistry of the sulfide related spinels may have applications in the use of heavy resistate minerals during exploration distinctively high ti chromites are also a feature of intrusions associated with the karoo flood basalts suggesting that jinchuan may have a similar affinity however tio 2 enrichment in chromite can be a product of interaction with differentiated trapped liquid as indicated by similar trends in lava lakes layered intrusions and at sudbury and therefore cannot be taken to prove unusually ti rich parent magmas

compositional effects on the solubility of minor and trace elements in oxide spinel minerals insights from crystal crystal partition coefficients in chromite exsolution chromite from los congos and los guanacos in the eastern pampean ranges of cordoba argentinian central andes shows homogenous and exsolution textures the composition of the exsolved phases in chromite approaches the end members of spinel mgal 2 o 4 spl and magnetite fe 2 fe 2 3 o 4 mag that define the corners of the spinel prism at relatively constant cr 3 r 3 ratio where r 3 is cr al fe 3 the exsolution of these phases from the original chromite is estimated to have accounted at 600 c on the basis of the major element compositions of chromite with homogenous and exsolution textures that are in equilibrium with forsterite rich olivine fo 95 the relatively large size of the exsolved phases in chromite up to ca 200 m provided for the first time the ability to conduct in situ analysis with laser ablation inductively coupled plasma mass spectrometry for a suite of minor and trace elements to constrain their crystal crystal partition coefficient between the spinel rich and magnetite rich phases d i spl mag minor and trace elements listed in increasing order of compatibility with the spinel rich phase are ti sc ni v ge mn cu sn co ga and zn d i spl mag values span more than an order of magnitude from d ti spl mag 0 30 0 06 to d zn spl mag 5 48 0 63 our results are in remarkable agreement with data available for exsolutions of spinel rich and magnetite rich phases in other chromite from nature despite their different cr 3 r 3 ratio the estimated crystal crystal partitioning coefficients reflect the effect that crystal chemistry of the exsolved phases from chromite imposes on all investigated elements excepting cu and sc and only slightly for mn the observed preferential partitioning of ti and sc into the magnetite rich phase is consistent with high temperature chromite melt experiments and suggests a significant dependence on fe 3 substitution in the spinel structure a compositional effect of major elements on ga co and zn is observed in the exsolved phases from chromite but not in the experiments this might be due to crystal chemistry differences along the mgfe 1 al 2 fe 2 3 exchange vector which is poorly covered experimentally this inference is supported by the strong covariance of ga co and zn observed only in chromite from layered intrusions where this exchange vector is important a systematic increase of zn and co coupled with a net decrease in ga during hydrous metamorphism of chromitite bodies cannot be explained exclusively by compositional changes of major elements in the chromite which are enriched in the magnetite component the most likely explanation is that the contents of minor and trace elements in chromite from metamorphosed chromitites are controlled by interactions with metamorphic fluids involved in the formation of chlorite

short and long term effects of bioturbation on soil erosion water resources and soil development in an arid environment the importance of vegetal cover on soil erosion processes has been recognized for a long time however the short and long term effects of faunal activity on soil erosion and soil development had been largely overlooked by geomorphologists the study of runoff and erosion processes in the negev desert indicated pronounced systematic differences in sediment concentration and soil erosion rates between rocky and colluvial surfaces erosion rates were always higher on the former than on the latter field observations drew attention to an intense burrowing and digging activity conducted mainly by isopods and porcupines the monitoring of this activity based on a grid system which consists of rows 5 m wide lasted ten consecutive years data obtained suggest the existence of a strong link between the spatial pattern of bioturbation and that of soil erosion the study also examines through feedback processes the regulatory role of bioturbation on the spatial distribution of water availability soil moisture and soil forming processes due to bioturbation two distinct environments were recognised the rocky environment which is characterized by a positive feedback with a high water availability and low soil salinity and the soil covered areas where a negative feedback results in low water availability and a high soil salinity

differences in hillslope runoff and sediment transport rates within two semi arid catchments in southeast spain this paper focuses on hillslope runoff and sediment transport within two catchments in southeast spain five monitoring sites were established on hillslope concavities throughout the two catchments the techniques used were mini crest stage recorders spray painted lines sediment traps and tipping bucket rain gauges established during previous research results show that a storm event in the rambla nogalte on 30 june 2002 of 83 0 mm was responsible for a maximum runoff depth of 12 cm and a maximum hillslope sediment transport of 1886 cm3 m 1 the same storm in the rambla de torrealvilla produced 53 4 mm of rainfall on the 1 july 2002 had a maximum runoff depth of 26 cm and resulted in 2311 cm3 m 1 of sediment transport there is evidence to suggest that measured sediment transport is related to runoff and a qualitative estimate of morphological runoff zones mrz sediment transport and depth of runoff varied dramatically with lithology marl sites produced most runoff and sediment transport followed by the sites of mixed red and blue schist then blue schist these results are important for understanding the behaviour of slopes and show that for short lived storms with high but not rare rainfall intensities and total rainfall amounts runoff can cause significant hillslope sediment transport in semi arid areas

influence of the southern annular mode on the sea ice ocean system 1 the global sea ice ocean model orca2 lim driven by the ncep ncar national centers for environmental prediction national center for atmospheric research reanalysis daily 2 m air temperatures and 10 m winds and by monthly climatologies for precipitation cloud cover and relative humidity is used to investigate the impact of the southern annular mode sam on the antarctic sea ice ocean system our results suggest that the response of the circumpolar southern ocean consists of an annular and a nonannular component for the sea ice cover the non annular component seems to be the most important the annular component strongly affects the overall patterns of the upper ocean circulation when the sam is in its positive phase a northward surface ekman drift a downwelling at about 45 degreess and an upwelling in the vicinity of the antarctic continent are simulated the non annular component has a significant impact at the regional scale especially in the weddell ross amundsen and bellingshausen seas in those regions the pressure pattern associated with the sam induces meridional winds which advect warmer air in the weddell sea and around the antarctic peninsula and colder air in the amundsen and ross seas this implies a dipole response of sea ice to the sam with on average a decrease in ice area in the weddell sea and around the antarctic peninsula and an increase in the ross and amundsen seas during years with a high sam index the long term trend in the observed sea ice area does not appear to be related to the trend in the sam index

widespread acceleration of tidewater glaciers on the antarctic peninsula over the last half century the antarctic peninsula ap has been among the most rapidly warming regions on earth this has led to increased summer snowmelt loss of ice shelves and retreat of 87 of marine and tidewater glacier fronts tidewater glacier flow is sensitive to changes in basal water supply and to thinning of the terminus and faster flow leads directly to sea level rise the flow rates of most ap tidewater glaciers have never been measured however and hence their dynamic response to the recent changes is unknown we present repeated flow rate measurements from over 300 glaciers on the ap west coast through nine summers from 1992 to 2005 we show that the flow rate increased by similar to 12 on average and that this trend is greater than the seasonal variability in flow rate we attribute this widespread acceleration trend not to meltwater enhanced lubrication or increased snowfall but to a dynamic response to frontal thinning we estimate that as a result the annual sea level contribution from this region has increased by 0 047 0 011 mm between 1993 and 2003 this contribution together with previous studies that assessed increased runoff from the area and acceleration of glaciers resulting from the removal of ice shelves implies a combined ap contribution of 0 16 0 06 mm yr 1 this is comparable to the contribution from alaskan glaciers and combined with estimated mass loss from west antarctica is probably large enough to outweigh mass gains in east antarctica and to make the total antarctic sea level contribution positive

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

understanding the sam influence on the south pacific enso teleconnection the relationship between the el nino southern oscillation enso and the southern hemisphere annular mode sam is examined with the goal of understanding how various strong sam events modulate the enso teleconnection to the south pacific 45 70 s 150 70 w the focus is on multi month multi event variations during the last 50 years a significant p 0 10 relationship is observed most marked during the austral summer and in the 1970s and 1990s in most cases the significant relationship is brought about by la nina el nino events occurring with positive negative phases of the sam more often than expected by chance the south pacific teleconnection magnitude is found to be strongly dependent on the sam phase only when enso events occur with a weak sam or when a la nina el nino occurs with a positive negative sam phase are significant south pacific teleconnections found this modulation in the south pacific enso teleconnection is directly tied to the interaction of the anomalous enso and sam transient eddy momentum fluxes during la nina sam and el nino sam combinations the anomalous transient momentum fluxes in the pacific act to reinforce the circulation anomalies in the midlatitudes altering the circulation in such a way to maintain the enso teleconnections in la nina sam and el nino sam cases the anomalous transient eddies oppose each other in the midlatitudes overall acting to reduce the magnitude of the high latitude enso teleconnection

rossby wave propagation and teleconnection patterns in the austral winter abstract observational evidence of and theoretical support for the northern and southern hemisphere teleconnection patterns in the austral southern hemisphere winter are examined through an upper troposphere streamfunction teleconnectivity map and time lag cross correlation analysis using ecmwf initialized analysis 2oo hpa winds for the 11 june august periods from 1979 to 1989 as was previously found for the northern hemisphere winter the regions of strong teleconnectivity particularly in the winter hemisphere tend to he oriented in the zonal direction and coincide with the location of the major jet streams although equatorward propagation from the northern and southern hemispheres is observed little evidence of cross equatorial propagation has been found for comparison the response of a barotropic model linearized about a climatological 300 hpa june august time mean flow to localized forcing is determined it is found that the activity tends to be trapped inside each of the southern hemisphere

climate variability in the amundsen and bellingshausen seas satellite data reveal a 20 decline in sea ice extent in the amundsen and bellingshausen seas in the two decades following 1973 this change is negatively correlated with surface air temperatures on the west side of the antarctic peninsula which have increased 0 58c decade21 since the mid 1940s the recession was strongest during summer when monthly average minima in 1991 92 removed much of the incipient multiyear ice over the continental shelf this would have lowered the regional mean ice thickness impacting snow ice formation brine production and vertical heat flux the northern ice edge contracted by 18 of latitude in all seasons from 1973 79 to 1987 93 returning toward mean conditions in 1993 95 the decline included multiyear cycles of several years in length superimposed on high interannual variability a review of atmospheric forcing shows winds consistent with mean and extreme ice extents and suggests links to larger scale circulation changes in the south pacific historical ocean measurements are sparse in this sector but mixed layer depths and upper pycnoclines beneath the sea ice resemble those in the weddell sea weaker surface currents or changes in the upwelling of circumpolar deep water on the continental shelf could have contributed to the anomaly persistence

the met office hadley centre sea ice and sea surface temperature data set version 2 1 sea ice concentrations we present a new version of the sea ice concentration component of the met office hadley centre sea ice and sea surface temperature data set hadisst 2 1 0 0 passive microwave data are combined with historical sources such as sea ice charts to create global analyses on a 1 grid from 1850 to 2007 climatology was used when no information about the sea ice was available our main aim was to create a homogenous data set by calculating and applying bias adjustments using periods of overlaps between the different data sources used national ice center charts from 1995 to 2007 have been used as a reference to achieve this in particular large bias adjustments have been applied to the passive microwave data in both the antarctic and arctic summers overall hadisst 2 1 0 0 contains more ice than hadisst1 1 with higher concentrations shorter marginal ice zones and larger extents and areas in some regions and periods a new method for estimating the concentrations within the ice pack using the distance from the ice edge has been developed and evaluated this was used when only the extents were known or the original concentration fields were heterogeneous a number of discontinuities in the hadisst1 1 record are no longer found in hadisst 2 1 0 0

observed antarctic interannual climate variability and tropical linkages abstractthis study reviews the mechanisms associated with antarctic tropical climate linkages and presents new analyses of the seasonality and spatial patterns of tropical climate signals in the antarctic for the late 1950s to the present tropical climate signals are primarily communicated to the antarctic via the pacific south america psa pattern and the southern annular mode sam the impacts of these circulation patterns and their tropical linkages are evident in regressions of seasonally stratified antarctic station temperature data and annually resolved ice core records on global fields of sea surface temperature sea level pressure and precipitation temperature and ice core anomalies in the antarctic peninsula region and adjoining areas of west antarctica are significantly impacted by the psa interpreted as a rossby wave train driven by anomalous tropical deep convection during enso events this pattern is most evident in the austral spring consistent with recent studies suggesting that atm

temporal changes in soil aggregates and water erosion after a wildfire in a mediterranean pine forest abstract the evolution of soil structure after a forest fire was studied on two zones representatives of a typical mediterranean pine forest these zones were in opposite slope orientation but with similar topographical and pedological characteristics changes in soil macro aggregation and water stable micro aggregation were monitored seasonally during a year after the fire the water erosion patterns were also studied from august 1993 immediately after the fire to the end of 1996 the first 5 cm of soil depth were the most affected by fire temperature showing clear differences on aggregate distribution and temporal variability between zones in the north facing soil a substantial and gradual recovery on soil aggregation was observed mainly in the fraction greater than 5 mm diameter this reached an increase of 27 in mass of aggregates in the south slope the evolution of aggregation was smooth and restricted to the fraction minor than 0 1 mm these differences between zones are reflected also in their values on soil cohesiveness and compaction being lesser in the south oriented soils values of erosion parameters show that both zones have the higher soil losses during the immediate period 4 months after the fire being more important in the south zone this zone produced more sediment and runoff 52 42 and 29 95 respectively than north facing soils for the whole period studied

petrogenesis of the pt pd mineralized jinbaoshan ultramafic intrusion in the permian emeishan large igneous province sw china the jinbaoshan ultramafic intrusion is a sheet like body with a thick wehrlite unit in the center and thin pyroxenite units at the margins pge are enriched in several disseminated sulfide zones in the intrusion olivine from the intrusion has low fo and depleted ni contents compared to olivine from coeval emeishan picrites whole rock major and trace element concentrations suggest that the jinbaoshan wehrlites originally contained 30 trapped liquid the total amount of sulfide in the rocks exceeds that which could have been dissolved in the trapped liquid the jinbaoshan wehrlites are interpreted to represent residual assemblages formed by dissolution of plagioclase by passing magma no clear evidence of crustal contamination is indicated by s nd and os isotopes we envision that sulfide saturation occurred at depth due to olivine and chromite crystallization immiscible sulfide droplets were transported to the jinbaoshan conduit where they accumulated and reacted with magma successively passing through the conduit to achieve high pge concentrations