contrasting compositions of mariana trough fallout tephra and mariana island arc volcanics a fractional crystallization link discrete quaternary 400 ka tephra fallout layers mostly 1 cm thick within the siliceous oozes of the central mariana trough at 18 n are characterized by medium k to high k subalkalic volcanic glasses k2o 0 8 3 2 wt with high large ion lithophile elements lile high field strength elements hfse ratios and nb depletion ba la 35 ba zr 3 5 la nb 4 typical for convergent margin volcanic rocks compositional zoning within layers ranges from basaltic to dacitic sio2 48 71 wt mgo 0 7 6 5 wt all layers contain basaltic andesites the tephra layers are interpreted as single explosive eruptive events tapping chemically zoned reservoirs the sources being the mariana arc volcanoes mav due to their proximity 100 400 km and similar element ratios mav ba la 36 7 ba zr 3 5 0 9 the glasses investigated however contrast with the contemporaneous basaltic to dacitic lavas of the mav by being more enriched in tio2 1 2 wt mav 0 8 wt feo 10 wt mav 8 9 wt k2o 1 1 wt mav 0 8 wt and p2o5 0 4 wt mav 0 2 wt semi incompatible trace elements including rare earth elements ree of the basaltic andesitic and dacitic glasses match those of the dacitic mav lavas which became enriched by fractional crystallization moreover the glasses follow a tholeiitic trend of fractionation in contrast to mav transitional trends and have a characteristic p2o5 trend that reaches a maximum of 0 6 wt p2o5 at 57 wt sio2 whereas mav lavas increase linearly in p2o5 from 0 1 to 0 3 wt with increasing silica both explosive and effusive series are interpreted to have evolved in common magma reservoirs by convective fractionation similar parental magmas are suggested to have separated into coexisting si andesitic to dacitic and basaltic melts by in situ crystallization the differentiated melt is interstitial in an apatite saturated crystalline mush of plag px ox ol at the cooler chamber margins in contrast to the less differentiated basaltic to basaltic andesitic magmas which are not yet saturated in apatite and occupy the chamber interior reinjection of interstitial melt into the chamber interior and mixing with larger melt fractions of the interior liquid mixing ratios about 1 8 9 can explain the paradoxical behavior of apatite controlled p and mree variation in the basaltic andesite glasses and their mav dacite like fractionation patterns the process may also account for the exclusively tholeiitic trend of fractionation of the glass shard series but in situ crystallization alone cannot cause their absolute enrichment in semi incompatible elements the newly mixed melt is suggested to form the basaltic end member of the glass shard series however it must have become physically separated from the main mav magma body possibly by density driven convective fractionation in order to allow for further evolution of the contrasting geochemical paths as well as differentiation

mariana trough basalts mtb trace element and srnd isotopic evidence for mixing between morb like and arc like melts abstract mariana trough basalt mtb glasses from zones of of active seafloor volcanism have incompatible trace element compositions which are intermediate between normal morb and basaltic rocks from the active northern mariana island arc miab the chemical variation is observed in trace elemental abundances and ratios such as lil lil and lil hfs mtb glasses with high lil hfs and ba sm ratios and low k rb k ba and sm nd ratios have more enriched sr and nd isotopic compositions comparison of the sr nd isotopic compositions of mtb and miab suggests that the source region within the mantle wedge is heterogeneous the diverse trace element and isotopic compositions of mtb glasses both within and between dredge sites near 18 n imply small scale source heterogeneity correlation between sm nd and143nd 144nd of the mtb glasses is interpreted as due to recent binary mixing rather than closed system evolution of a common homogeneous source mixing of melts at or near the source region between a mantle component with long term lree and lil element depletion morb like and a relatively enriched component with lower integrated143nd 144nd arc like is suggested by trends of the mtb data on ratio ratio ratio element and element element plots

investigation of the causes of historical changes in the subsurface salinity minimum of the south atlantic in this study we investigate the subsurface salinity changes on decadal timescales across the subtropical south atlantic ocean using two ocean reanalysis products the latest version of the simple ocean data assimilation and the estimating the circulation and climate of the ocean phase ii as well as using additional climate model experiments results show that there is a recent significant salinity increase at the core of the salinity minimum at intermediate levels the main underlying mechanism for this subsurface salinity increase is the lateral advective gyre changes due to the southern annular mode variability which conditions an increased contribution from the indian ocean high salinity waters into the atlantic the global warming signal has a secondary but complementary contribution latitudinal differences at intermediate depth in response to large scale forcing are in part caused by local variation of westward propagation features and by compensating contributions of salinity and temperature to density changes

the connection between the southern annular mode and a feature based perspective on southern hemisphere midlatitude winter variability abstractthis article provides a reconciling perspective on the two main but contradictory interpretations of the southern annular mode sam sam was originally thought to characterize meridional

present day south american climate abstract this paper documents the main features of the climate and climate variability over south america on the basis of instrumental observations gathered during the 20th century it should provide a modern reference framework for paleoclimate research in south america targeting high resolution proxies over the past few centuries several datasets suitable for present day climate research are first described highlighting their advantages as well as their limitations we then provide a basic physical understanding of the mean annual cycle of the precipitation and atmospheric circulation over the continent and the adjacent oceans in particular the diversity of precipitation temperature and wind patterns is interpreted in terms of the long meridional extent of the continent and the disruption of the large scale circulation caused by the andes cordillera the contrasting oceanic boundary conditions and the landmass distribution similarly the intensity and timing of the interannual and interdecadal climatic fluctuations exhibit considerable geographical dependence as some regions are more influenced by large scale phenomena rooted in the tropical oceans while others are more influenced by high latitude phenomena the impact of these large scale phenomena over south america is documented by a regression analysis between selected atmospheric indices and the precipitation and temperature fields we have included a discussion on the seasonality and long term stability of such impacts and complemented our general description by an updated review of the literature on climate variability over specific regions

zonal asymmetry of the antarctic oscillation 1 in this research the zonal asymmetry of the southern annular mode or the antarctic oscillation aao is studied it is indicated that apparent zonal asymmetry exists in the normalized sea level pressure differences between the middle and high latitudes during the boreal summer among different longitudes especially between the western and eastern hemispheres results show that the southern oscillation so is responsible for part of the zonal asymmetry in aao the western hemisphere and the eastern hemisphere parts of aao are correlated at 0 23 and 0 52 respectively for the period of 1959 1998 before and after the linear regressions on the southern oscillation index soi have been removed from the time series the paper also discusses the relationship between the precipitation in the east asia and the aao before and after removing the linear regressions on so index soi indicating the stable relationship between the east asian precipitation and the zonal symmetric component of aao

teleconnection stationarity variability and trends of the southern annular mode sam during the last millennium the southern annular mode sam is the leading mode of atmospheric interannual variability in the southern hemisphere sh extra tropics here we assess the stationarity of sam spatial correlations with instrumental and paleoclimate proxy data for the past millennium the instrumental period shows that temporal non stationarities in sam teleconnections are not consistent across the sh land areas this suggests that the influence of the sam index is modulated by regional effects however within key regions with good proxy data coverage south america tasmania new zealand teleconnections are mostly stationary over the instrumental period using different stationarity criteria for proxy record selection we provide new austral summer and annual mean sam index reconstructions over the last millennium our summer sam reconstructions are very robust to changes in proxy record selection and the selection of the calibration period particularly on the multi decadal timescale in contrast the weaker performance and lower agreement in the annual mean sam reconstructions point towards changing teleconnection patterns that may be particularly important outside the summer months our results clearly portend that the temporal stationarity of the proxy climate relationships should be taken into account in the design of comprehensive regional and hemispherical climate reconstructions the summer sam reconstructions show no significant relationship to solar greenhouse gas and volcanic forcing with the exception of an extremely strong negative anomaly following the ad 1257 samalas eruption furthermore reconstructed pre industrial summer sam trends are very similar to trends obtained by model control simulations we find that recent trends in the summer sam lie outside the 5 95 range of pre industrial natural variability

tropical oceanic causes of interannual to multidecadal precipitation variability in southeast south america over the past century abstract observations atmosphere models forced by historical ssts and idealized simulations are used to determine the causes and mechanisms of interannual to multidecadal precipitation anomalies over southeast south america sesa since 1901 about 40 of sesa precipitation variability over this period can be accounted for by global sst forcing both the tropical pacific and atlantic oceans share the driving of sesa precipitation with the latter contributing the most on multidecadal time scales and explaining a wetting trend from the early midcentury until the end of the last century cold tropical atlantic sst anomalies are shown to drive wet conditions in sesa the dynamics that link sesa precipitation to tropical atlantic sst anomalies are explored cold tropical atlantic sst anomalies force equatorward flowing upper tropospheric flow to the southeast of the tropical heating anomaly and the vorticity advection by this flow is balanced by vortex stretching and ascent which drives the increased prec

southern hemisphere circulation features associated with el nino southern oscillation events abstract composite seasonal mean and anomaly fields prepared from operational numerical analyses have been used to describe the southern hemisphere sh circulation features associated with el nino southern oscillation enso events the period of analyses available 1972 83 has limited the composites to include only three enso events the reliability and stability of the composites has been tested using multiple permutation methods and by comparison with the results obtained using a longer period 1950 79 of sh rawinsonde station data in the sh winter a weak equivalent barotropic wavetrain pattern of anomalies extends over australia and the south pacific ocean to south america this wavetrain pattern is quite variable in amplitude and location between enso events although it is more stable over the subtropical pacific in the sh summer the circulation anomalies are more zonally symmetric with increased height at low and high latitudes and decreased height in middle latitudes the circulation anoma

230 th 238 u disequilibrium in island arcs evidence from the aleutians and the marianas complex models for magma generation in island arcs have recently been proposed which require varying contributions from three possible sources 1 the mantle 2 subducted altered oceanic crust and 3 sediments see for example refs 1 6 these models involve partial melting of metasomatized mantle the metasomatizing liquids derive from the subducted slab and are large ion lithophile lil element bearing fluids or are themselves partial melts further modification of the chemical composition of the lavas may occur by processes such as shallow level fractional crystallization because the th u ratio is quite different for each of the three possible magma sources mentioned above and as th and u may behave differently during fractionation processes particularly if volatile transport is involved studies of 230 th 238 u disequilibrium have great potential in investigations of arc lavas our data given here imply that the th u ratio in the sources of mariana and aleutian island arc lavas is similar to ocean ridge basalt sources although there is a hint of a somewhat lower th u component in the aleutian source the data also confirm and extend the observations by gill and allegre and condomines that oceanic arc lavas are distinguished from magmas erupted in virtually all other volcanic environments by activity ratios 230 th 238 u 1 implying relative enrichment of uranium

230th 238u radioactive disequilibria in tholeiites from the famous zone mid atlantic ridge 36 50 n th and sr isotopic geochemistry we analyzed u th and230th 232th activity ratios for a few tholeiites from the mid atlantic ridge famous zone at 36 50 n the results show a fairly wide scatter for both th u and 230th 232th ratios seawater contamination appears to be responsible for this scatter and for the uranium produces an increase in content yielding a 234u 238u ratio greater than 1 and for the th an increase of the 230th 232th ratio which is a very sensitive indicator for contamination also the latter often is selective u th and sr are not affected in the same manner when discarding all data for contaminated samples the famous zone appears to be very homogeneous with ath u ratio value of 3 05 and a 230th 232th ratio value of 1 24 comparison with other active volcanic areas reveals a negative correlation between 230th 232th and87sr 86sr ratios for present lavas which is indicative of a consistency in th u and rb sr fractionation in the source regions of these magmas the th isotopic geochemistry can thus provide useful information for the study of present volcanism information as valuable as that from sr pb or nd isotopes

relationships between low frequency variability in the southern hemisphere and sea surface temperature anomalies abstract long term trends and interannual variations of circulation anomalies in the southern hemisphere are examined using the national centers for environmental prediction national center for atmospheric research reanalysis from 1949 to 1998 the changes in planetary circulation regimes are linked to global sea surface temperature anomalies sstas empirical orthogonal function eof analysis was performed on 500 hpa height anomalies the leading mode eof1 shows a strong zonal symmetry with a phase reversal between height anomalies in high and midlatitudes apart from zonal symmetry a zonal wavenumber 3 is evident with three centers located in three southern oceans in the low frequency band with fluctuations longer than 60 months eof1 is associated with the second rotated eof mode of sstas with positive loadings over three southern oceans and negative loadings in the north pacific and the north atlantic the next two modes are the pacific south american psa patterns they depict wave 3 patterns in

reply to comment by riccardo caputo and marcello bianca on late cenozoic uplift of southern italy deduced from fluvial and marine sediments coupling between surface processes and lower crustal flow by rob westaway and david bridgland improved uplift modelling of the gulf of taranto marine terraces the well developed pleistocene marine terrace staircase along the gulf of taranto coastline southern italy has been extensively studied over many decades the rivers in this region have also formed long timescale terrace staircases our paper late cenozoic uplift of southern italy deduced from fluvial and marine sediments coupling between surface processes and lower crustal flow quaternary international 175 86 124 presented original field observations aimed at testing contradictory hypotheses for the mode of origin of this marine terrace staircase and developed age models for the marine and fluvial successions we also proposed on the basis of physics based numerical modelling that the quaternary uplift of this region is primarily the isostatic response to erosion and has thus been driven by climate which has forced the erosion despite the location within a plate boundary zone however bianca and caputo quaternary international 204 98 102 have questioned our use of the data and disputed the logic of our numerical modelling notwithstanding minor corrections and updating from which we present revised uplift modelling we uphold the substantial content of our original paper as valid and consider it to be a tenable interpretation of the terrace record in the study region we also discuss underlying issues including strategies for age control and the causes of fluvial terrace development

indian ocean dipole influence on south american rainfall 1 the rainfall anomalies over south america are found to be influenced by the indian ocean dipole iod between subtropical la plata basin and central brazil the iod excites a dipolar pattern in rainfall anomalies rainfall is reduced enhanced over latter former during austral spring when iod reaches its peak phase a rossby wave train extends from the subtropical south indian ocean to the subtropical south atlantic the associated anomaly in surface circulation suggests an intensification of the south atlantic high the anomalous anticyclone in the lower troposphere causes anomalous divergence convergence of moisture over central brazil subtropical la plata basin these results based on the university of delaware precipitation analysis and the ncep ncar reanalysis data are corroborated by that of the scale interaction experiment frontier version 1 sintex f1 coupled general circulation model

timing and intensity of groundwater movement during egyptian sahara pluvial periods by u series analysis of secondary u in ores and carbonates abstract wet climatic episodes are known to have prevailed in the egyptian sahara several times during the late quaternary most recently during the holocene 8000 yr ago earlier wet episodes have been recognized as having occurred during the past 300 000 yr and have been dated by u series methods in speleothems and in lake travertines we show here that the times of enhanced groundwater movement can also be determined by 230 th 234 u dating of secondary u in ores of uranium iron and phosphate we also present evidence that such acceleration of groundwater movements is indicated by relatively low 234 u 238 u activity ratios in the secondary uranium our new data show that pluvial periods in egypt occurred during marine oxygen isotope stages 4 5 6 and 7 and therefore are consistent with the view that the wet episodes are the results of migration of the tropical monsoonal belt driven primarily by the 23 000 yr precession cycle of the milankovich curve modulated by the 100 000 yr eccentricity cycle

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

ar ar dating of late cenozoic basaltic volcanism in northern syria implications for the history of incision by the river euphrates and uplift of the northern arabian platform 1 ar ar dating of basalt flows capping terrace deposits of the river euphrates in northern syria has provided a new quantitative chronology for the late cenozoic evolution of this important river system and for the associated history of surface uplift of the northern arabian platform through which it flows a region of relatively strong crust that has experienced only slow deformation notably fluvial deposits 65 m above the euphrates are overlain by basalt dated to 2717 20 ka those 45 m above the river are overlain by basalt dated to 2116 39 ka and those 8 9 m above the river are overlain by basalt dated to 402 11 ka these new dates require the previous dating scheme based on paleolithic archaeology to be revised the euphrates terrace deposits and the associated incised valley are much older than was previously thought rates of incision by the euphrates providing a proxy for regional surface uplift that is inferred to be the isostatic response to regional erosion have varied significantly over the past 3 ma with indications that between 1 2 and 0 9 ma there was regional subsidence which gave rise to fluvial aggradation this unusual pattern involving reversals in the sense of vertical crustal motions is interpreted to be a consequence of a relatively cold and thin mobile lower crustal layer no more than 5 km thick evidently due to the presence of a much thicker underlying layer of mafic underplating at the base of the crust this study thus indicates previously unsuspected complexity in the isostatic response to regional erosion in an area of high crustal stability

late cenozoic surface uplift revealed by incision by the river euphrates at birecik southeast turkey incision by the river euphrates has created a dramatic erosional landscape in the northern arabian platform in se turkey we obtain accurate heights of its terrace deposits in the birecik area using differential gps and summarise evidence regarding heights of late miocene basalt flows and low altitude wetland sediments we thus estimate 600 m of uplift since the early late miocene 9 ma represented by 270 m of fluvial incision the difference reflecting downstream channel lengthening as the coastline has retreated to the persian gulf 1400 km away the oldest recognised sediments inset below this level form a thick aggradation between 100 and 130 m above the present level of the euphrates we estimate that this accumulated during 5 3 ma when uplift rates were low such that aggradation was necessary to maintain a downstream channel gradient in response to the coastal retreat palaeolithic artefacts have been reported locally in euphrates deposits up to 80 m above present river level which we tentatively date to 1 8 ma the euphrates subsequently incised to within 10 m of its present level before aggrading 45 m higher in the late early pleistocene the final 55 m of incision reflects the increase in uplift rates observed worldwide in the early middle pleistocene following the mid pleistocene revolution

a test of a quartz eclogite source for parental aleutian magmas a mass balance approach the observation that magmatic conduits evolve with time has provided a new framework within which to interpret aleutian compositional and isotopic data accordingly a two stage physical model of aleutian magma genesis has been developed and used to model quantitatively geochemical and isotopic mass balance relations parental magmas approximated by high alumina basalts are presumed to be generated by partial melting of eclogite and subducted sediment the incorporation of sediment produces elevated parental magma sr and pb isotopic ratios but lowered epsilon nd relative to morb if these magmas ascend along well established conduits their isotopic characteristics are little changed during ascent in immature conduits interaction with oceanic lithosphere produces significant isotopic variability according to this model the isotopic and geochemical characteristics of parental magmas are fixed by mixing eclogite and sediment melts as a test we have quantitatively examined the mass balance rel

isotopic and incompatible element constraints on the genesis of island arc volcanics from cold bay and amak island aleutians and implications for mantle structure reply to a critical comment by m r perfit and r w kay

a station based southern annular mode index from 1884 to 2005 atmospheric pressure observations from the southern hemisphere are used to estimate monthly and annually averaged indexes of the southern annular mode sam back to 1884 this analysis groups all relevant observations in the following four regions one for antarctica and three in the subtropical zone continuous surface pressure observations are available at a number of locations in the subtropical regions since the end of the nineteenth century however year round observations in the subpolar region near the antarctic continent began only during the 1940 60 period the shorter antarctic records seriously compromise the length of a traditionally estimated sam index to improve the situation proxy estimates of antarctic sea level pressure anomalies are provided based on the concept of atmospheric mass conservation poleward of 208s this allows deriving a longer sam index back to 1884 several aspects of the new record its statistical properties seasonal trends and the regional pressure anomaly correlations are presented

230th 238u disequilibrium systematics in oceanic tholeiites from 21 n on the east pacific rise significant disequilibrium occurs between 230 th and its parent 238 u in a suite of fresh basalt glasses from the rise project study area at 21 n on the east pacific rise the 230 th 232 th activity ratios observed for eight of nine samples from the crest of the axis at this site are constant within analytical uncertainty with a value of 1 22 this observed homogeneity of 230 th 232 th has two possible interpretations first the measured 230 th 232 th can be considered to indicate a mantle source for the rise basalts with th u of 2 5 this interpretation however conflicts with the proposed correlation between 230 th 232 th and 87 sr 86 sr 1 which predicts that 230 th 232 th should equal 1 33 at the rise site a second possible interpretation is that radioactive decay of 230 th in the basalts themselves or in a magma chamber has decreased 230 th 232 th from 1 33 to the observed values the required time span is 11 000 to 100 000 years however petrologic arguments rule against long residence time in a magma chamber and the spreading rate of this section of the east pacific rise 6 cm yr predicts that the maximum age for axis basalts is 27 000 years both interpretations of the measured 230 th 232 th imply a low th u ratio for the rise basalt source and suggest that the morb source at this location is depleted in th with respect to u relative to primitive mantle or bulk earth in spite of their constant 230 th 232 th the basalts from 21 n have wide ranges of measured th u and thorium and uranium concentrations in apparent conflict with the common assumption that these two elements have very small similar crystal liquid partition coefficients participation of an accessory phase with high th and u concentrations during partial melting or fractional crystallization appears to be required to explain this anomaly major and other trace element compositions provide more information about petrogenetic processes although fractional crystallization can explain the variations in major element composition a more complex process such as continuous melting is required to account for the observed trends in trace element compositions in addition to its use as a tracer the 230 th 238 u disequilibrium technique is capable of putting some constraints on the timing of fractionation events and it may eventually lead to a method for dating very young mid ocean ridge basalts

southern hemisphere origins for interannual variations of snow cover over the western tibetan plateau in boreal summer abstractthe climate response to the tibetan plateau tp snow cover tpsc has been receiving extensive concern however relatively few studies have been devoted to revealing the potential factors

recycling of crystal mush derived melts and short magma residence times revealed by u series disequilibria at stromboli volcano abstract the presence of crystal mushes in the feeding system of active volcanoes is generally revealed by antecrysts representing the crystalline portion of old magmas recycled in the juvenile material but very little is known about the fate of interstitial liquid hosted within the crystal rich mush i e antemelt u series disequilibria measured in magmas erupted in the past 18 years at stromboli volcano provide the first geochemical evidence of the involvement of antemelt and help constraining the timescales of the processes occurring in the plumbing system of the volcano despite almost constant major and trace element composition significant variations in isotope ratios are observed 230 th 232 th decreases with time whilst 238 u 232 th 226 ra 230 th and 87 sr 86 sr are different in the two types of magma erupted magma with low phenocryst content lp is erupted as pumices during paroxysm and is thought to belong to a deep reservoir highly porphyritic magma hp is erupted during the normal strombolian activity as scoria and during the effusive events as lavas and it is considered to derive from the former one within a shallow reservoir through degassing driven crystallisation mixing and incorporation of antecrysts the distinct 238 u 232 th of lp and hp magma requires the involvement of a component with high 87 sr 86 sr and 238 u 232 th deriving from older magmas erupted earlier in the volcano history up to 2 5 ka the incompatibility of u and th in major mineral phases limits the possible effect of antecrysts hence requiring the involvement of a u and th rich antemelt the decrease of 226 ra excess from lp to hp magmas provides further and independent evidence for the involvement of a few thousands years old antemelt the variation with time of 230 th 232 th within lp and hp magmas is exploited to constrain the residence time of magmas in the deep and shallow reservoir of the volcano to 55 yrs inferred reservoir volume 0 5 km 3 and 2 10 yrs inferred reservoir volume 0 02 0 09 km 3 respectively our results show the occurrence of magmatic processes operating at different timescale within the feeding system of a so called steady state volcano such as stromboli we show that while most of the magma is erupted within few years a portion of it made of both crystals antecrysts and residual liquid antemelt can be stored in the plumbing system for thousands of years to be eventually rejuvenated and mixed back into the shallow reservoir the presence of antemelts may also affect the eruptive mechanism by promoting heat transfer in locked crystal mushes hence favouring their remobilisation

seasonal zonal asymmetries in the southern annular mode and their impact on regional temperature anomalies abstractthe southern hemisphere annular mode sam is the dominant mode of climate variability in the extratropical southern hemisphere representing variations in pressure and the corresponding changes to the circumpolar zonal flow it is typically thought of as an annular or ringlike structure however on seasonal time scales the zonal symmetry observed in the sam in monthly or annual mean data is much less marked this study further examines the seasonal changes in the sam structure and explores temperature signals across the southern hemisphere that are strongly tied to the asymmetric sam structure the sam asymmetries are most marked in the pacific sector and in austral winter and spring related to changes in the jet entrance and exit regions poleward of 30 s depending on the season the asymmetric sam structure explains over 25 of the variance in the overall sam structure and has strong connections with enso or zonal wavenumber 3 in austral summer and autumn the sam has been becoming more zona

uranium and 10 be enrichments by fluids in andean arc magmas volcanic rocks from subduction settings frequently contain 10be enrichments that have been attributed to sediment subduction1 6 and are often characterized by 238u 230th ratios greater than unity in contrast to mid ocean ridge and ocean island basalts7 8 here we report such an excess of 238u over 230th in historic lavas from the southern volcanic zone of chile 33 42 s the greatest uranium excess is found south of 39 s where 10be 9 be ratios are highest and the trench is filled with sediment these features suggest that both u and 10be enrichments result from preferential partitioning of u and be into a fluid phase during dehydration of the recently subducted sediments the presence of strong 238u 230th disequilibria in basaltic magmas of the southern volcanic zone suggests that the timescale for dehydration melting and eruption in this arc is probably less than 20 000 yr

marine isotope stage 9 environments of fluvial deposits at hackney north london uk middle pleistocene deposits at hackney north london comprise a thick unit of organic sands and silts occupying a channel near the confluence of the river thames in south eastern england and its left bank tributary the river lea they represent a short time interval perhaps no more than a few years within a late middle pleistocene interglacial the organic sediments are overlain by unfossiliferous sands and gravels indicating deposition on the floodplain of a braided river under cool or cold climatic conditions the fossil plant insect mollusc and vertebrate remains from the interglacial deposits all indicate climatic conditions with summers warmer than the present in se england and winters with a similar thermal climate the biostratigraphic evidence suggests that the time period represented by the organic unit is part of mis 9 although the geochronological evidence for such an age is inconclusive the palaeontological evidence strongly suggests that this temperate stage was warmer than the succeeding temperate stage mis 7 or the holocene and approaching the ipswichian miss 5e in its warmth the multidisciplinary description of the hackney deposits is one of the first to reconstruct terrestrial conditions in marine isotope stage 9 in western europe

interannual extremes in new zealand precipitation linked to modes of southern hemisphere climate variability abstract interannual extremes in new zealand rainfall and their modulation by modes of southern hemisphere climate variability are examined in observations and a coupled climate model north island extreme dry wet years are characterized by locally increased reduced sea level pressure slp cold warm sea surface temperature sst anomalies in the southern tasman sea and to the north of the island and coinciding reduced enhanced evaporation upstream of the mean southwesterly airflow during extreme dry wet years in south island precipitation an enhanced reduced meridional slp gradient occurs with circumpolar strengthened weakened subpolar westerlies and an easterly westerly anomaly in zonal wind in the subtropics as a result via ekman transport anomalously cold warm sst appears under the subpolar westerlies while anomalies of the opposite sign occur farther north the phase and magnitude of the resulting sst and evaporation anomalies cannot account for the rainfall extremes over t

u series isotope data on lau basin glasses the role of subduction related fluids during melt generation in back arc basins new thermal ionization mass spectrometry u series disequilibrium data are presented for 24 basaltic to dacitic glasses from active spreading centres in the back arc lau basin sw pacific together with additional inductively coupled plasma mass spectrometry trace element analyses and sr nd pb isotope data valu fa ridge samples adjacent to the arc front have high u th and 230th 238u 1 implying a recent 350 ka addition of a u rich slab derived fluid the valu fa data can be combined with existing 230th 238u data for the central tonga arc to infer a fluid addition event at 50 ka the similar sources and time scales for fluid transfer beneath the valu fa ridge and beneath the arc itself suggest that the valu fa ridge is propagating into the arc front region central lau basin samples further behind the arc have lower u th and 230th 238u 1 similar to typical mid ocean ridge basalts morb within the central lau basin a water rich subduction component is seen only in samples closest to the arc and this fluid does not have the high u th composition of the fluid at valu fa melt generation in the central lau basin appears to be dominated by normal ridge type processes but the relatively low 230th 238u for these shallow ridges compared with global morb could be a consequence of increased melt productivity as a result of the elevated water contents the transition from 238u to 230th excesses within the back arc basin is not a smooth function of decreasing addition of a u rich fluid moving away from the arc front but also reflects the complex dynamics between two major mantle domains within the mantle wedge pacific beneath valu fa ridge indian beneath the central lau basin

coupled ocean atmosphere ice response to variations in the southern annular mode abstract the coupled ocean atmosphere ice response to variations in the southern annular mode sam is examined in the national center for atmospheric research ncar community coupled climate model version 2 the model shows considerable skill in capturing the predominantly zonally symmetric sam while regional deviations between model and observation sam winds go a long way in explaining the generally small differences between simulated and observed sam responses in the ocean and sea ice systems vacillations in the position and strength of the circumpolar winds and the ensuing variations in advection of heat and moisture result in a dynamic and thermodynamic forcing of the ocean and sea ice both meridional and zonal components of ocean circulation are modified through ekman transport which in turn leads to anomalous surface convergences and divergences that strongly affect the meridional overturning circulation and potentially the pathways of intermediate water ventilation a heat budget analysis de

cold season synoptic scale waves over subtropical south america the most active winter synoptic scale wave patterns over south america are identified using an extended empirical orthogonal function eeof technique and are physically diagnosed using composite methods results show that the leading modes of short timescale variability propagate along two main paths over the subtropical jet latitudes 308s and over the subpolar jet latitudes 608s this research focuses on the subtropical mode and its evolution over south america the observed structure of the systems associated with the subtropical mode resembles that of midlatitude baroclinic waves both cyclonic and anticyclonic perturbations display significant modifications in their threedimensional structure as they evolve over extratropical and subtropical south america while the upper level perturbations are mostly unaffected when moving eastward the lower level perturbations advance following the shape of the andes mountains and exhibit an abrupt equatorward migration at the lee side of the mountains as a result of such detachment smaller eddy heat fluxes are observed in the vicinity of the orography and consequently a weaker eddy baroclinic growth is observed once the upper level system is on the lee side the perturbations acquire a more typical baroclinic wave structure and low level intensification of the system occurs the latter is largest around 1000 km east of the orography where enhanced moisture transports from tropical latitudes along the eastern portion of the low level cyclone favor precipitation occurrence over southeastern south america those precipitation processes seem to provide a diabatic source of energy that further contributes to the strengthening of the low level cyclone in addition an intensification of the cyclone once over the ocean was found in 60 of the situations considered which is consistent with previous research suggesting an additional source of moisture and heat flux due to the warm waters of the brazil current

the reliability of uranium series mollusc dates from the western mediterranean basin abstract fossil mollusc shells from western mediterranean raised beach deposits have been dated using u series techniques sub sampling has allowed intra shell isotopic variability to be assessed although most of the calculated ages appear plausible and some internal consistency exists closer scrutiny of the data reveals that the shells have behaved as geochemically open systems and all the ages therefore must be considered suspect some previously published u series mollusc data from the same region may also contain evidence of open system behaviour and are considered equally unreliable simple modelling suggests considerable variation in isotopic uptake behaviour both within and between shells

flow in the lower continental crust as a mechanism for the quaternary uplift of south east england constraints from the thames terrace record abstract the sequence of terraces of the river thames in south east england has been shown to date from the early pleistocene onwards and to provide an indication of the quaternary uplift history of the region using this evidence supplemented by altitudes of pliocene and early pleistocene marine sediments we have determined the pliocene and quaternary uplift histories of five representative localities clacton colchester and dartford for the lower thames and cookham and reading for the middle thames these uplift histories have been modelled using a physics based technique which calculates the isostatic response involving flow in the lower continental crust induced by cyclic loading at the earth s surface our results suggest that the late pliocene and early pleistocene part of the uplift history of our study region was initiated following the deterioration in climate starting at 3 1 ma which marked the start of upland glaciation elsewhere in europe the later increase in uplift rates in the middle pleistocene followed the start of intensified cyclic loading by very large continental ice sheets during and after oxygen isotope stage ois 22 at 0 87 ma dartford cookham and reading in the interior of south east england are all shown to have begun to uplift quite rapidly at rates of up to 0 1 mm a 1 following the start of forcing at 3 1 ma they have since uplifted by distances which increase gradually westward from 200 to 250 m of which a uniform 70 m has occurred since ois 22 at 0 87 ma in contrast clacton and colchester near the present north sea coastline experienced slow subsidence until the late early pleistocene but have nonetheless uplifted since ois 22 by similar distances to the other sites

holocene long and short term climate changes off adelie land east antarctica diatom data from a marine sediment core give insight on holocene changes in sea surface conditions and climate at high southern latitudes off adelie land east antarctica the early to mid holocene was warmer than the late holocene with a transition at 4000 calendar years b p sea ice was less present and spring summer growing season was greater during the warm period relative to the cold one thus limiting sea ice diatom production and favoring more open ocean diatom to develop the long term holocene climatic evolution in east antarctica is explained by a combination of a delayed response to local seasonal insolation changes coupled to the long memory of the southern ocean abrupt variations of the diatom relative abundances indicating rapid climate changes are superimposed to the holocene long term trends spectral analyses calculate robust frequencies at 1600 a where a is years 1250 a 1050 a 570 a 310 a 230 a 150 125 a 110 a 90 a and 66 a such periods are very close to solar activity cyclicities except for the periods at 310 a and 1250 a which are close to internal climate variability cyclicities wavelet analyses estimate the same periods but indicate nonstationary cyclicities rapid climate changes at high southern latitudes may therefore be explained by a combination of external solar and internal thermohaline circulation forcings

238u decay series systematics of young lavas from batur volcano sunda arc abstract activities of 238u decay series radioisotopes have been determined for both postcaldera basalts erupted between 1849 and 1974 and genetically related young precaldera dacites from batur volcano bali sunda arc all rocks possess 230th 238u 1 within 2 sigma error indicating that little if any fractionation between th and u occurred during their genesis or in their source regions within approximately the last 350 ka both the basaltic and the dacitic rocks possess 230th 232u 0 71 consistent with both having a common mantle source with an unusually high th u weight ratio of 4 4 and with the dacitic magma having formed by closed system convective fractionation of the same basaltic magma from which the postcaldera lavas were derived the historical basalts possess 226 ra 230 th 1 indicating a significant ra enrichment relative to th and u within approximately the last 8 ka the highest degree of 226ra enrichment occurs in the most mafic basaltic lavas which form a cycle of mafic volcanism between 1888 and 1926 if ra enrichments were produced during mantle melting as a result of its greater incompatibility relative to th then variations in 236ra 230th may reflect the presence at batur of a periodically replenished but poorly mixed open system magma chamber in addition this result implies that the primitive batur basaltic magmas take considerably less than about 8 ka to travel from their mantle source through the batur magma chamber to the surface whole rock 210 pb 226 ra 1 in the youngest historical basalts indicates that pb has been enriched relative to ra within about 100 years of their eruption because pb is expected to be less incompatible then ra during mantle melting the enrichments are probably due to late stage processes such as accumulation of 210pb rich plagioclase phenocrysts or post eruptive condensation of volatile pb salts in vesicles

enhanced rainfall in the western mediterranean during deposition of sapropel s1 stalagmite evidence from corchia cave central italy a stable isotope record from a stalagmite collected from antro del corchia cave apuan alps central italy supported by 17 uranium series ages indicates enhanced regional rainfall between ca 8 9 and 7 3 kyr cal bp at the time of sapropel s1 deposition within this phase the highest rainfall occurred between 7 9 and 7 4 kyr cal bp comparison with different marine and lake records and in particular with the soreq cave record israel suggests substantial in phase occurrence of enhanced rainfall between the western and eastern mediterranean basins there is no convincing evidence for major climatic change at the time of the 8 2 kyr event

aleutian lead isotopic data additional evidence for the evolution of lithospheric plumbing systems abstract lead isotopic ratios and concentrations have been measured in lavas from the aleutian volcanic centers of adak 12 and atka 12 whereas lavas from atka have very small pb isotopic ranges 206 pb 204 pb 18 78 18 86 207 pb 204 pb 15 55 15 62 208 pb 204 pb 38 31 38 52 those from adak have ranges nearly twice as large 206 pb 204 pb 18 34 18 86 207 pb 204 pb 15 47 15 63 208 pb 204 pb 37 81 38 56 on lead lead isotopic diagrams atka data form tight clusters whereas those from adaak define a well developed linear trend extending from the atka field toward less radiogenic values at a given 206 pb 204 pb the lavas from both islands plot in the morb trend for 208 pb 204 pb but atka lavas plot above the morb 207 pb 204 pb 206pb 204pb trend and those from adak fall both within and above the trend lead contents in lavas from atka increase four fold 5 21 ppm over the compositional range of the volcanic suite 49 68 sio2 in contrast actak lavas 49 65 have concentration levels of 0 6 13 ppm and display no simple correlation with sio2 the lead isotopic data alone can be explained by three different processes model 1 assigns lead isotopic differences to original magma source heterogeneity according to model 2 the isotopic ratios of a primary non radiogenic component from the mantle are elevated by the addition of an isotopically enriched slab derived component in contrast model 3 assumes a primary radiogenic magma produced by melting of the slab is contaminated by a non radiogenic lithospheric component during conduit formation because these models all adequately explain the lead isotopic data supplementary geologic petrographic geochemical and isotopic data must be used to select the most likely model careful consideration of the evidence suggests model 3 best explains our extensive lead isotopic data as well as other characteristics of aleutian lavas our study suggests detailed isotopic studies of individual volcanic centers arc or otherwise can be extremely useful in understanding the complex processes of magma generation extraction ascent and evolution

state of the antarctic and southern ocean climate system this paper reviews developments in our understanding of the state of the antarctic and southern ocean climate and its relation to the global climate system over the last few millennia climate over this and earlier periods has not been stable as evidenced by the occurrence of abrupt changes in atmospheric circulation and temperature recorded in antarctic ice core proxies for past climate two of the most prominent abrupt climate change events are characterized by intensification of the circumpolar westerlies also known as the southern annular mode between 6000 and 5000 years ago and since 1200 1000 years ago following the last of these is a period of major trans antarctic reorganization of atmospheric circulation and temperature between ad1700 and 1850 the two earlier antarctic abrupt climate change events appear linked to but predate by several centuries even more abrupt climate change in the north atlantic and the end of the more recent event is coincident with reorganization of atmospheric circulation in the north pacific improved understanding of such events and of the associations between abrupt climate change events recorded in both hemispheres is critical to predicting the impact and timing of future abrupt climate change events potentially forced by anthropogenic changes in greenhouse gases and aerosols special attention is given to the climate of the past 200 years which was recorded by a network of recently available shallow firn cores and to that of the past 50 years which was monitored by the continuous instrumental record significant regional climate changes have taken place in the antarctic during the past 50 years atmospheric temperatures have increased markedly over the antarctic peninsula linked to nearby ocean warming and intensification of the circumpolar westerlies glaciers are retreating on the peninsula in patagonia on the sub antarctic islands and in west antarctica adjacent to the peninsula the penetration of marine air masses has become more pronounced over parts of west antarctica above the surface the antarctic troposphere has warmed during winter while the stratosphere has cooled year round the upper kilometer of the circumpolar southern ocean has warmed antarctic bottom water across a wide sector off east antarctica has freshened and the densest bottom water in the weddell sea has warmed in contrast to these regional climate changes over most of antarctica near surface temperature and snowfall have not increased significantly during at least the past 50 years and proxy data suggest that the atmospheric circulation over the interior has remained in a similar state for at least the past 200 years furthermore the total sea ice cover around antarctica has exhibited no significant overall change since reliable satellite monitoring began in the late 1970s despite large but compensating regional changes the inhomogeneity of antarctic climate in space and time implies that recent antarctic climate changes are due on the one hand to a combination of strong multi decadal variability and anthropogenic effects and as demonstrated by the paleoclimate record on the other hand to multi decadal to millennial scale and longer natural variability forced through changes in orbital insolation greenhouse gases solar variability ice dynamics and aerosols model projections suggest that over the 21st century the antarctic interior will warm by 3 4 1oc and sea ice extent will decrease by 30 ice sheet models are not yet adequate enough to answer pressing questions about the effect of projected warming on mass balance and sea level considering the potentially major impacts of a warming climate on antarctica vigorous efforts are needed to better understand all aspects of the highly coupled antarctic climate system as well as its influence on the earth s climate and oceans

climate variability in southern south america associated with el nino and la nina events a comprehensive view is given of the precipitation and circulation anomalies associated with the various stages of el nino en and la nina ln events all over southern south america ssa this view comprises the delineation of coherent regions with respect to precipitation anomalies the identification of the seasons of maximum anomalies the indication of their magnitude and the assessment of their consistency during those events in addition the spatial and temporal variability of these anomalies is detailed by calculating the expected precipitation percentiles and the consistency of wet and dry anomalies for each station and each three month running season during en and ln events composites of circulation anomalies and an assessment of their consistency are also presented and their connection with the precipitation anomalies is discussed southern brazil presents the strongest average signal in en events the general behavior toward opposite signals in the precipitation and circulation anomalies over ssa during almost the same periods of the en and ln events indicates a large degree of linearity in the response to these events the timing of the anomalies changes throughout ssa leading to the identification of eight different coherent regions in the en case and six in the ln case this regionalization is mostly caused by different processes leading to precipitation anomalies in ssa during those events all these regions show a significant response in some part of each event the magnitude and consistency of this response show a large spatial variability and some areas present very strong and consistent anomalies sometimes not disclosed when large coherent regions are analyzed in spite of the differences in timing some features of the precipitation anomalies are rather uniform throughout the region during en and ln events in en episode there is a tendency to lower than median precipitation in the year before the event which continues until march of the year of the event in a vast region east of the andes the strongest positive precipitation anomalies occur in spring of this year when the circulation anomalies concur to enhance rainfall over several regions during the summer of the mature stage the positive precipitation anomalies almost disappear and then reappear in some regions in late summer early autumn and in winter of the year following the starting year of the event this description holds partially for the ln event but with opposite signs although there is a larger spatial variability in the ln related anomalies in the following year and some shifts in timing as for precipitation the symmetry of the geopotential height anomaly fields with opposite signs between ln and en cases is also remarkable especially during the year 0

influence of the tropics on the southern annular mode abstractperturbations in the southern annular mode sam are shown to be significantly correlated with sst anomalies in the central tropical pacific during austral winter and sst anomalies in the eastern tropical pacific during austral summer the sam signature in the pacific sector resembles a tropically forced rossby wave train the so called pacific south american pattern while the signature in the indian ocean sector is a zonally elongated meridional dipole thus the sam contains strong zonally asymmetric variability and tends to behave differently in the eastern and western hemispheres with internal dynamics prevailing in the indian ocean sector and the forced response to tropical sst anomalies exerting a strong influence in the pacific sector the tropically forced component of the sam in the pacific sector is related to a geographically fixed active rossby wave source to the east of australia within the core of the subtropical jet in addition to the well documented positive trend in summer the

boreal spring southern hemisphere annular mode indian ocean sea surface temperature and east asian summer monsoon 1 the relationships among the boreal spring southern hemisphere annular mode sam the indian ocean io sea surface temperature sst and east asian summer monsoon easm are examined statistically in this paper the variability of boreal spring sam is closely related to the io sst when the sam is in its strong positive phase in boreal spring with low pressure anomalies over the south pole and high pressure anomalies over middle latitudes sstover the subtropics and middle latitudes of the south indian ocean sio increases which persists into the summer following the positive sst anomalies over the subtropics and midlatitudes of the sio sst in the equatorial indian ocean and bay of bengal increases in summer moreover the variability of sst in the equatorial indian ocean and bay of bengal is closely related to easm when sst in the equatorial indian ocean and bay of bengal increases easm tends to be weak therefore the io sst may play an important role bridging boreal spring sam and easm the atmospheric circulations and surface heat exchanges contribute to the sst anomalies in the sio when the spring sam is in its strong positive phases the regional ferrel cell weakens and the anomalous upward motions at 20s 30s cause an increase of low cloud cover and downward longwave radiation flux the surface atmospheric circulations also transport more less warmer cooler air from middle latitudes north of 50s high latitudes south of 60s into 50s 60s and warm the air which reduces the temperature difference between the ocean and atmosphere and consequently reduces sensible heat flux from the ocean to atmosphere the increased downward longwave radiation and decreased sensible heat are responsible for the sst increase in the sio the atmospheric circulation and surface heat flux anomalies are of opposite signs following the strong negative phases of sam

midsummer low level circulation and precipitation in subtropical south america and related sea surface temperature anomalies in the south atlantic abstract the midsummer interannual variability of the low level tropospheric circulation and of the precipitation field in subtropical south america sa associated to the sea surface temperature sst anomalies in the western subtropical south atlantic ocean wssa is investigated using reanalyses regional precipitation datasets and monthly ssts the region of the wssa where sst has the strongest relation with precipitation in subtropical sa was identified using canonical correlation analysis this region extends from 20 to 30 s and from 30 to 50 w composites corresponding to extreme ssts in this area show two well differentiated patterns in the low level circulation and in the precipitation fields in the composite corresponding to the more positive sst anomalies in this area the mainstream of the low level flow and of the moisture transport from the continental low latitudes starts to follow a southeastward direction at 10 s and converges with the west flow at 35 s over the atlantic ocean on t

poleward shift and change of frontal activity in the southern hemisphere over the last 40 years abstractseveral studies have documented the poleward shift of the midlatitude westerly jet of the southern hemisphere during the last decades of the twentieth century mainly during the warm season in this work the consistency between this change and the seasonal changes in frontal activity and precipitation are explored the authors also attempt to identify the correlation between frontal activity and precipitation changes frontal activity is defined using the 40 yr european centre for medium range weather forecasts ecmwf re analysis era 40 dataset for the period 1962 2001 as the temperature gradient times the relative vorticity at 850 hpa considering cyclonic systems only an enhancement of the frontal activity at high latitudes in the last two decades is apparent however the pattern of frontal activity change is not zonally symmetric with the zonal asymmetries consistent with the climate change signal of the zonal anomaly of the 300 hpa geopotential height the pattern of precipitation change

re examining southern hemisphere westerly wind behavior insights from a late holocene precipitation reconstruction using new zealand fjord sediments abstract the behavior of the southern hemisphere westerly winds sww is inherently linked with climate variability understanding past sww climate feedbacks is key to predicting future climate change however we are limited by a lack of sww reconstructions particularly from the southwest pacific here we examine fjord sediments from fiordland new zealand 44 5 46 5 s to determine how the sww have fluctuated in position and strength in response to regional late holocene climate change and we compare our record to patagonia climate reconstructions in order to evaluate large scale sww behavior sww flow over the southern alps of new zealand drives orographic rainfall that is recorded within fjord sediments as changes in the relative contributions of terrestrial to marine organic matter which can be measured by bulk sediment 13 c and organic c n ratios using these proxies cores from three new zealand fjords show that precipitation decreased between 1400 1100 and 750 150 cal yr bp with short duration shifts toward drier conditions at 1900 and 900 cal yr bp precipitation increased 2100 1400 and 1100 700 cal yr bp with a short interval of wetter conditions around 400 cal yr bp these results indicate that westerly airflow over new zealand was stronger weaker during intervals of relatively warm cool climate our comparison of precipitation reconstructions from fiordland and patagonia shows dissimilarities in sww flow between regions while to date most mechanisms for changing the sww have invoked purely zonal shifts our results suggest that meridional changes in sww flow occurred in addition to zonal shifts in fiordland the meridional airflow associated with sam and or el nino like climate phenomena may be responsible for wet intervals while sam and or la nina like phenomena may promote dry conditions

late quaternary activity of the scorciabuoi fault southern italy as inferred from morphotectonic investigations and numerical modeling 1 following a detailed morphotectonic analysis of the fluvial terraces of the sauro river basilicata southern italy the present research documents for the first time the late quaternary tectonic activity of the scorciabuoi fault and discusses its inferred seismogenic potential on the basis of both remote sensing techniques and detailed field investigations four fill terraces have been recognized and mapped along the sauro valley showing differential cumulative displacements across the fault these terraces are genetically correlated with four highstand sea level periods following stratigraphic and geological age constraints and on the basis of the correlation with a sequence of marine and fluvial terraces characterizing the lower agri valley the sauro terraces likely formed between 80 or 100 ka and present the inferred long term slip rate of the scorciabuoi fault ranges between 0 5 and 1 0 mm a numerical simulations based on a crustal elastic deformation model also contribute to separate and tentatively quantify the regional uplift rate 1 0 1 4 mm a and to improve the overall reconstruction of the late quaternary evolution of the area the synergic but distinct roles played by eustatism regional uplift and faulting are eventually appreciated

links between the antarctic oscillation and winter rainfall over western south africa 1 relationships between the antarctic oscillation aao and winter rainfall over western south africa are investigated this region receives most of its annual rainfall during austral winter and often experiences severe drought it is found that 6 6 of the 7 8 wettest driest winters jja during 1948 2004 occur during negative positive aao phase i e positive negative pressure anomalies over antarctica and negative positive anomalies over the midlatitudes the mechanisms by which the aao appears to influence winter rainfall involve shifts in the subtropical jet and changes in the low level moisture flux upstream over the south atlantic and in the mid level uplift low level convergence and relative vorticity over the region the anomalous circulation patterns extend into spring thus the springs following the identified winters also show similar rainfall anomalies

on the functioning of the southern oscillation in the south american sector part i surface climate abstract the functioning of the southern oscillation so over south america and the surrounding tropical atlantic and eastern pacific oceans is studied through analyses of bimonthly patterns of correlation between an so index and the fields of pressure wind temperature and rainfall hydrometeorological anomalies being further ascertained from river discharge and lake level records and measurements of outgoing longwave radiation most pronounced is the anomalously low pressure over the eastern pacific during the negative so phase defined by anomalously low high pressure at tahiti darwin consistently positive so pressure correlations over the eastern tropical pacific extend eastward into the north atlantic region and southern south america during the respective winter semester during the austral winter the tendency for anomalously abundant rainfall in central chile during the negative so phase appears related to an anomalously weak and northward displaced south pacific subtropical high while relativ

regional sediment sources versus the indus river system the plio pleistocene of the peshawar basin nw pakistan abstract sedimentary archives within the peshawar basin in northwest pakistan preserve a record of siliciclastic supply patterns during the plio pleistocene epoch the basin fill consists of fluvial floodplain clays overlain by thick lacustrine glaciofluvial rhythmites with deposits of multiple alluvial fans in the southern parts of the basin and topped by loess deposits in ideal vertical successions framework mineralogical composition and bulk sediment geochemical proxies of these sediments indicate detritus derivation from dominantly acidic igneous sources with contribution from medium grade metamorphic rocks there appears to be no significant contribution from ultramafic mafic or very high grade metamorphic sources in addition sediments from the southern part of the basin support supply from low grade metamorphic rocks and carbonate sediments overall sedimentation occurred in an active continental margin setting under conditions of insignificant chemical weathering the uplift of the attock cherat range during the late pliocene 2 8 ma restricted the indus river from shedding its detritus into the basin therefore the sediments of the peshawar basin do not reflect signatures of the indus river siliciclastics and thus lack the basic igneous geochemical signal which is otherwise typical for the himalayas hinterland on the contrary the geochemical signatures of these sediments favour predominant detritus flux from the acidic rocks of the peshawar plain alkaline igneous complex ppaic and associated metasediments therefore the kabul swat river and other local tributaries of this smaller river system that originated within the ppaic and associated mountains are considered the major transporting agents which contributed siliciclastics into the peshawar basin during the plio pleistocene additionally in the southern part of the basin the uplifting attock cherat range appeared to have contributed detritus in the form of alluvial fluvial fan deposits

changma onset definition in korea using the available water resources index and its relation to the antarctic oscillation this study defines the changma onset using the available water resources index awri for 25 years 1985 2009 and verifies the validity of this definition the three conditions for defining the changma onset are established as follows i the first day exceeding the june awri threshold averaged over the 25 year period ii the continuation of the value over the threshold for at least 1 week after the onset iii after the continuation of more than 1 week the non continuation of the value under the threshold for at least 1 week the 25 year average changma onset date is 24 june with a standard deviation of 9 days the defined changma onset is verified through the analysis on the relationship with the antarctic oscillation aao aao in june shows a high correlation with not only the changma onset but also the june precipitation awri in korea these three variables are influenced by mascarene and australian positive aao pattern highs from in the preceding march when these two pressure systems develop the cold cross equatorial flow in the direction from the region around australia to the equator is intensified which in turn forces a western north pacific high wnph to develop northward this eventually drives the rain belt north as a result the changma begins early in the positive aao phase and the june precipitation increases in korea in addition a wnph that develops more northward increases the landfalling frequency of tropical cyclones in korea which plays an important role in increasing the june precipitation

wave mean flow feedback and the persistence of simulated zonal flow vacillation abstract the structure of eddies forcing the vacillation of the southern midlatitude tropospheric zonal mean zonal wind and the significance of wave mean flow feedbacks on its persistence are assessed using a 100 yr 8 h dataset simulated by the commonwealth scientific and industrial research organisation csiro mark 2 general circulation model using time lagged regression and composite analyses relative to the vacillation index it is shown that high frequency hf eddy momentum flux anomalies near the mean jet latitude provide much of the forcing of the zonal mean anomalies as in observations low frequency lf eddies also contribute while the cross frequency flux enhances short term variation of the index the hf band also provides a positive feedback which is partly countered by an lf negative feedback high and low index composites of representative midtropospheric waves zonal wavenumbers 7 for hf and 3 for lf are constructed including those for waves phase shifted relative to the wave at th

usercalc a web based uranium series calculator for magma migration problems 1 measured departures from secular equilibrium in the uranium series decay chains provide important constraints on the rates of recent mantle and crustal processes nevertheless the inferences drawn from these observations depend upon the models used to interpret them while several useful models for u series exist they are not all equally easy to use and it is often the ease of use rather than the utility of the model that determines which models are applied the purpose of this paper is to level the playing field by making some of the more general u series transport models accessible to a wider community through the usercalc web site available from lamont doherty earth observatory at www ldeo columbia edu mspieg usercalc these models calculate the effects of both melting and melt transport on two u series chains 238u 230th 226ra and 235u 231pa and allow the user to input their own petrological insight and data to explore the behavior of this model the purpose of the site is to provide a tool that can spur additional collaborations between geophysicists and geochemists as well as drive more rapid exploration evolution of u series models

antarctic oscillation signal on precipitation anomalies over southeastern south america 1 the relation between the antarctic oscillation aao and the precipitation in southeastern south america sesa is examined the aao influence is particularly strong during winter and late spring although of opposite sign in particular during spring aao positive negative phases are associated with the intensification of an upper level anticyclonic cyclonic anomaly weakened enhanced moisture convergence and decreased increased precipitation over sesa the combined influence of both enso and aao on sesa precipitation was also explored and significant correlation values between both oscillations are only observed during spring results show that during that particular season aao activity produces a strong modulation of the enso signal on sesa precipitation

zonal flow vacillation and eddy forcing in a simple gcm of the atmosphere abstract zonal flow vacillation with very long time scales is observed in a 3070 day simple gcm simulation with zonally symmetric forcing the long lasting zonal wind anomalies suggest that zonal flow vacillation is self maintained wave mean flow interactions are investigated by composite analysis and transform eulerian momentum budget analysis nonlinear life cycle simulations are conducted to demonstrate that each extreme phase of the zonal flow vacillation is a quasi stable state and is self maintained by the embedded synoptic eddies the firm eof mode of zonal mean wind shows an out of phase relation between anomalies at 60 s and at 40 s with a barotropic structure this structure is similar to the dominant vacillation pattern observed in the southern hemisphere the composite jet stream in the high low index phase of zonal flow vacillation shifts poleward equatorward from the time mean location and becomes broader narrower and weaker stronger composite eddies in the high index phase tilt nw

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

magma cumulate mixing identified by u th disequilibrium dating magma mixing is believed to be important in magmagenesis1 particularly in volcanic arcs2 where its influence is revealed by heterogeneous phenocryst populations3 and quenched inclusions4 nevertheless isotope studies particularly of uranium series dis equilibria have concentrated on the analysis of bulk rock samples5 9 comprehensive u th mineral separate data from arc volcanics are scarce10 14 here we present the first u th isotopic evidence for mixing between a crystal mush and a magma in an andesite from the island of santorini in the aegean arc the lava contains crystal populations from two sources of distinct thorium isotope composition one from a basic cumulate the other phenocrysts from a dacite magma the crystal populations have statistically indistinguishable crystallization ages of 79 14 12kyr and 93 29 22kyr and are thought to have physically intermingled just before eruption the crystals did not re equilibrate and hence retain the isotopic compositions and ages of the parental materials

nonstationary impacts of the southern annular mode on southern hemisphere climate abstract the temporal stability of the southern annular mode sam impacts on southern hemisphere climate during austral spring is analyzed results show changes in the typical hemispheric circulation pattern associated with sam particularly over south america and australia between the 1960s 70s and 1980s 90s in the first decades the sam positive phase is associated with an anomalous anticyclonic circulation developed in the southwestern subtropical atlantic that enhances moisture advection and promotes precipitation increase over southeastern south america sesa on the other hand during the last decades the anticyclonic anomaly induced by the sam s positive phase covers most of southern south america and the adjacent atlantic producing weakened moisture convergence and decreased precipitation over sesa as well as positive temperature anomaly advection over southern south america some stations in the australia new zealand sector and africa exhibit significant correlations between the sam and prec

precipitation interannual variability in south america from the wcrp cmip3 multi model dataset the ability of coupled climate models from the wcrp cmip3 multi model dataset to reproduce the interannual seasonal variability of precipitation in south america and the influence of the southern annular mode sam and el nino southern oscillation enso on such variability is examined models are able to reproduce the northward migration of the precipitation variability maximum during autumn and winter and its later return towards the south during spring and summer as well as the high variability throughout the year in southern chile nevertheless most of them have problems in representing accurately the variability associated with the south atlantic convergence zone during summer and the typical maximum of variability in the subtropical continent during autumn and winter the annular like structure characteristic of the sam influence on the southern hemisphere circulation is basically simulated by all models but they have serious deficiencies in representing the observed relationship between sam and both precipitation and circulation anomalies in south america in addition most of the models are not able to reproduce the typical wavetrains observed in the circulation anomalies in the southern hemisphere associated to enso only few models previously identified as those with reasonable enso representation at the equatorial pacific have evidences of such wavetrains coherently they exhibit the best representation of the enso signal in the south american precipitation results show that considerable improvement in the model representation of the climate variability in south america and in the associated large scale teleconnections is still needed

large scale control on the patagonian climate abstractpatagonia located in southern south america is a vast and remote region holding a rich variety of past environmental records but a small number of meteorological stations precipitation over this region is mostly produced by disturbances embedded in the westerly flow and is strongly modified by the austral andes uplift on the windward side leads to hyperhumid conditions along the pacific coast and the western slope of the andes in contrast downslope subsidence dries the eastern plains leading to arid highly evaporative conditions the authors investigate the dependence of patagonia s local climate precipitation and near surface air temperature year to year variability on large scale circulation anomalies using results from a 30 yr long high resolution numerical simulation variations of the low level zonal wind account for a large fraction of the rainfall variability at synoptic and interannual time scales zonal wind also controls the amplitude of the air temperature annual cycle by changi

morphometric analysis and amino acid geochronology of uplifted shorelines in a tectonic region near reggio calambria south italy the tectonic coastline of the calabrian peninsula provides an opportunity to study the morphology and history of elevated marine shorelines near capo dell armi eleven shorelines are preserved between sea level and 256 m with some correlation difficulties posed by the dissection of the area by intermittent streams we are able to correlate several of the shorelines across the entire study area with the support of correlations provided by amino acid geochronology we have identified four shorelines dating from the last interglacial period isotope stage 5 the oldest two both contain the strombus bubonius fauna and are of indistinguishable early last interglacial ages stage 5e aminozone e ca 125 ka the highest terrace vii is associated with a shoreline at 157 m and the lower with a shoreline around 125 105 m a s l of the two younger stage 5 without strombus bubonius the higher v lies at about 90 100 m and produces amino acid ratios slightly younger than but statistically indistinguishable from those of aminozone e however the youngest last interglacial shoreline deposits iv have produced amino acid ratios correlated to late stage 5 5a elsewhere in the mediterranean basin amino acid and geomorphic data have shown that uplift varies the study area from 0 85 to 1 03 m ka and suggeststhat constant uplift along any one traverse is unlikely