the tropospheric stratospheric mean zonal flow in winter latitude height cross sections of the mean zonal geostrophic flow at 500 0 4 mbar about 5 55 km were derived for individual months of the winters 1975 1976 to 1978 1979 vtpr radiation data from noaa satellites were used to obtain data above radiosonde heights these cross sections are supplemented by time height cross sections at 65 n for 2 month periods of stratospheric warming activity in each winter our mean latitude height cross section for winter shows marked differences from an earlier cross section published by murgatroyd 1970 although some of the differences are due to the use of observed rather than geostrophic winds in the latter the cross sections for individual months show a strong dispersal between 25 and 65 n of the latitude of maximum wind in the lower mesospheric jet which often appears as a split system in contrast to a single jet in murgatroyd s representation the modulation of the zonal wind pattern from month to month and winter to winter is evidently related to the cross tropopause propagation of planetary waves the time height cross sections for stratospheric warming periods show wind minima and maxima with apparent upward and downward propagation across the tropopause the minima which include cases of reversed zonal flow easterly are associated with high latitude stratospheric warming and can be related further to the vertical propagation of planetary zonal height waves 1 and or 2

planetary wave modelling of the middle atmosphere the importance of travelling wave components a linerized stationary planetary wave model is applied to mean data for a chosen quiescent winter month december 1979 comparison with observations from the stratosperic sounding unit on board noaa 6 shows that both the amplitude and height of propagation of wavenumber one are significantly underpredicted this behaviour is not substantially modified by extension to more sophisticated model formulation and representation of dissipative processes it is shown that the response to forcing varies appreciably with travelling wave frequency even at periods greater than one month and it is suggested that this sensitivity is a significant limitation on the applicability of stationary wave models based only on time mean behaviour

assessing cave internal aerology in understanding carbon dioxide co 2 dynamics implications on calcite mass variation on the wall of lascaux cave france carbon dioxide gas is a key component in dissolution and precipitation of carbonates in karst and cave systems therefore characterizing the internal aerology of a cave is essential to obtain the spatiotemporal distribution of temperature and co2 level in this research lascaux cave france an important adorned cavity was studied first the spatiotemporal distribution of co2 and temperatures were examined using continuous monitoring at a per minute basis high resolution spatial measurements 14 pco2 locations and 27 locations for temperature were carried out for a year in the epikarst and the cave february 2015 to february 2016 the spatiotemporal analysis presents that air and rock temperatures vary for less than a degree celsius 12 4 12 9 c these are controlled by the conduction of the external thermal waves through the overlying calcarenite massif as a consequence two seasonal internal aerologic regimes were identified stratification and convection these regimes govern the spatiotemporal distribution of the co2 levels 1 1 3 7 showing that this parameter is a good natural marker of the internal air movements second a method was proposed to estimate the calcite mass potentially affected by condensation water dissolution process and exfiltration water precipitation process this method based on numerical simulations relies on co2 and air and rock temperature spatiotemporal distributions in the cave third the method was applied using the case of the left wall of the hall of the bulls one of the most adorned part of the cave results showed that the calcite mass possibly dissolved varies from 0 0002 to 0 006 g when the mass potentially precipitated is higher from 0 013 to 0 067 g depending on the aerologic conditions this method allows determining which alteration process e g precipitation or dissolution could eventually lead to the largest variation of calcite on the wall the results can serve as useful data to the cave experts of the french ministry of culture and communication in terms of lascaux cave management policies

divergent trends in land and ocean temperature in the southern ocean over the past 18 000 years reconstructions of land and ocean temperatures over the past 18 000 years in the high southern latitudes have shown conflicting trends analyses of temperatures on campbell island south of new zealand confirm this behaviour and lead to the suggestion that it reflects changes in the position and intensity of the westerly winds over the past 18 000 years sea surface temperatures for the southern ocean do not align with those of the adjacent high latitude landmasses during the late glacial period the ocean surface warmed rapidly to present day temperatures1 whereas the land warmed only slowly as evidenced by the lagged response of forest and glaciers2 3 however in the holocene epoch land based records suggest strong warming whereas marine records indicate that ocean surface temperatures cooled here we present reconstructions of summer temperature for campbell island in the southern ocean over the past 16 500 years based on fossil pollen we find a pronounced warming 12 500 11 000 years ago a cooling until 9 200 years ago and a rapid warming to a peak between 6 000 and 5 000 years ago followed by minor cool intervals from 5 200 4 000 3 000 1 700 and 700 100 years ago as expected our temperature reconstructions show a late glacial lag behind nearby records of sea surface temperature6 7 and opposing trends in the holocene we suggest that this discrepancy arises because land based reconstructions record summer temperatures whereas marine proxies generally reflect annual temperatures we conclude that the divergence of the records therefore reflects changes in the seasonality of atmospheric heat transport as atmospheric heat transport is tied to the southern hemisphere westerly winds we attribute our observed changes to shifts in the position and intensity of the southern westerlies

hydrogeochemistry of a clayey till 2 sources of co2 the spatial distributions of inorganic and organic carbon in gas aqueous and solid phases were studied in an 18 m thick surficial deposit of fractured clayey calcareous till large pco2 increases were observed with increasing depth at the bottoms of vadose zones from which solid organic carbon had been depleted hydrochemical reaction simulations indentified a reaction path consistent with pco2 o2 major element chemistry 13c and 14c isotope observations this path is open to a biogenic co2 reservoir with pco2 higher than and 14c composition considerably different from that of the soil zone such co2 reservoirs occurring in deep vadose shallow saturated zones and thus isolated by overlying sediments from temperature fluctuations which limit soil zone respiration may be common in the western glaciated plains as evidenced by prevalence of hard high pco2 waters in the region s intertill aquifers carbon 14 data suggest that in the till both dissolved organic c and dissolved inorganic c have two sources soil organic matter and kerogen in the till matrix regardless of source s initial 14c activities of both aqueous c pools at the water table are diluted substantially relative to the actual residence time of the water unappreciated this could cause large relative errors in the calculation of radiocarbon based groundwater age dates

a review of glacial and holocene paleoclimate records from southernmost patagonia 49 55 s southern south america is the only landmass intersecting the southern westerly wind belt sww that influences the large scale oceanography and controls for example the outgassing of co2 in the southern ocean therefore paleo reconstructions from southernmost patagonia are of global interest and an increasing number of paleoclimate records have been published during the last decades we provide an overview on the different records mostly covering the holocene but partly extending into the late glacial based on a large variety of archives and proxies we particularly discuss possible reasons for regionally diverging palaeoclimatic interpretations and summarize potential climate forcing mechanisms the deglacial and holocene temperature evolution of the region including the adjacent pacific ocean indicates antarctic pattern and timing consistent with glacier re advances during the antarctic cold reversal some records indicate a significant accumulation control on the glacier fluctuations related to changes in sww strength and or position reconstructions of holocene changes in the sww behaviour provide partly inconsistent and controversially discussed pattern while records from the hyperhumid side point to a stronger or southward displaced sww core during the early holocene thermal maximum records from the lee side of the andes show either no long term trend or the opposite suggesting enhanced westerlies during the late holocene neoglacial likewise centennial scale global or hemispheric cold intervals such as the little ice age have been interpreted in terms of enhanced and reduced sww strength some sww variations can be linked to changes in the el nino southern oscillation enso consistent with instrumental climate data sets and might be ultimately forced by solar variability resolving these inconsistencies in southernmost patagonian sww records is a prerequisite for improving hemispheric comparisons and links to atmospheric co2 changes

heterogeneous distributions of co 2 may be more important for dissolution and karstification in coastal eogenetic limestone than mixing dissolution mixing dissolution a process whereby mixtures of two waters with different chemical compositions drive undersaturation with respect to carbonate minerals is commonly considered to form cavernous macroporosity e g flank margin caves and banana holes in eogenetic karst aquifers on small islands macroporosity commonly originates when focused dissolution forms globular chambers lacking entrances to the surface suggesting that dissolution processes are decoupled from surface hydrology mixing dissolution has been thought to be the primary dissolution process because meteoric water would equilibrate rapidly with calcium carbonate as it infiltrates through matrix porosity and because pco2 was assumed to be homogeneously distributed within the phreatic zone here we report data from two abandoned well fields in an eogenetic karst aquifer on san salvador island bahamas that demonstrate pco2 in the phreatic zone is distributed heterogeneously the pco2 varied from less than log 2 0 to more than log 1 0 atm over distances of less than 30 m generating dissolution in the subsurface where water flows from regions of low to high pco2 and cementation where water flows from regions of high to low pco2 using simple geochemical models we show dissolution caused by heterogeneously distributed pco2 can dissolve 2 5 to 10 times more calcite than the maximum amount possible by mixing of freshwater and seawater dissolution resulting from spatial variability in pco2 forms isolated globular chambers lacking initial entrances to the surface a morphology that is characteristic of flank margin caves and banana holes both of which have entrances that form by erosion or collapse after cave formation our results indicate that heterogeneous pco2 rather than mixing dissolution may be the dominant mechanism for observed spatial distribution of dissolution cementation and macroporosity generation in eogenetic karst aquifers and for landscape development in these settings copyright 2015 john wiley sons ltd

advancements in the use of speleothems as climate archives abstract speleothems have become a cornerstone of the approach to better understanding earth s climatic teleconnections due to their precise absolute chronologies their continuous or semicontinuous deposition and their global terrestrial distribution we review the last decade of speleothem related research building off a similar review by mcdermott 2004 in three themes i investigation of global teleconnections using speleothem based climate reconstructions ii refinement of climate interpretations from speleothem proxies through cave monitoring and iii novel technical methods of speleothem based climate reconstructions speleothem records have enabled critical insight into the response of global hydroclimate to large climate changes this includes the relevant forcings and sequence of climatic responses involved in glacial terminations and recognition of a global monsoon response to climate changes on orbital and millennial time scales we review advancements in understanding of the processes that control speleothem 13 c values and introduce the idea of a direct atmospheric pco 2 influence we discuss progress in understanding kinetic isotope fractionation which with further advances may help quantify paleoclimate changes despite non equilibrium formation of speleothems this feeds into the potential of proxy system modeling to consider climatic hydrological and biogeochemical processes with the objective of quantitatively interpreting speleothem proxies finally we provide an overview of emerging speleothem proxies and novel approaches using existing proxies most recently technical advancements made in the measurement of fluid inclusions are now yielding reliable determinations of paleotemperatures

microclimatic characterization of a karstic cave human impact on microenvironmental parameters of a prehistoric rock art cave candamo cave northern spain the candamo cave contains an impor tant group of paleolithic paintings which have been seriously deteriorated due to mass tourism in this work an analysis was carried out of different cli matic parameters co2 temperature humidity 222 rn during annual cycles with the cave closed to the public and during an experimental period of controlled visits the effect of visits on the geo chemical characteristics of karstic water was also analyzed together with the cave ventilation the natural variations in the cave air co2 were above 3000 ppm the increase produced through visits was only 100 110 ppm and since the humidi ty is almost permanently at saturation point the critical parameter which limits the visitor capacity becomes air temperature the temperature changes during the annual cycle are of the order of 1 7c in the external part and less than 0 5 7c in the internal part of the cave and a maximum increase of 0 13 7c was observed during the period of the visits the 222 rn and co2 concentration minimums in the summer period july october show that this is the most propitious time for visits since the greatest ventilation is produced in the cave at this time and therefore the greatest capacity for recovery the geochemistry of the water on the other hand indi cated that this is the period of the year in which processes of wall corrosion can be most easily in troduced although this would be of limited magni tude the visitor capacity calculated was 29 visi tors day

the younger dryas relevant in the australian region an assessment of australian climate during the younger dryas chronozone ydc is presented this review focuses on securely dated records from sites of continuous deposition placing greatest emphasis on temperature reconstructions with records of effective precipitation i e the combined effect of precipitation minus evapotranspiration also considered while there is a paucity of australian records covering the last glacial interglacial transition particularly those which directly infer temperature sufficient data exist to examine ydc climate from southern and eastern australia temperature reconstructions from tasmania based on both chironomid and pollen data show no evidence for younger dryas cooling by contrast there is evidence for cooling associated with the antarctic cold reversal from tullabardine dam pollen data and the sediment organic content from eagle and platypus tarns in tasmania records from a number of eastern australian mainland sites provide no evidence of effective precipitation shifts concurrent with the younger dryas chronozone similarly reconstructions of discharge from the murray darling basin which covers a large proportion 14 of the australian continent and dust transport from a larger portion of the continent also show no evidence of climate shifts concomitant with the younger dryas of research published in the past decade only one study located in the great australian bight claims evidence of a ydc cooling andres et al 2003 by contrast this review suggests that there is no conclusive evidence for cooling or indeed any distinctive climate patterning during the younger dryas chronozone in australia

unconformities and porosity development in carbonate strata ideas from a hedberg conference the purpose of this paper is to highlight ideas from a hedberg conference concerning detection of unconformities and associated porosity in carbonate strata many types of information including cores and outcrops seismic data eustatic sea level curves wireline logs biostratigraphic data stable isotope trends cycle stacking patterns and tectonic and basin evolution models can be used to predict and or detect subaerial unconformities all methods of detecting subaerial exposure with these types of information have limits and pitfalls detailed analysis of the stratigraphy sedimentology and diagenetic history of a rock sequence from outcrop or core data is considered the most reliable means of detecting subaerial exposure though an integrated approach using all a ailable information is recommended the relationship between subaerial exposure and subsurface porosity in carbonates is not simple or easily predicted subsurface porosity is the product of many factors operating during deposition subaerial exposure and burial several concepts should be recognized when evaluating porosity associated with subaerial unconformities 1 carbonate diagenesis during subaerial exposure rearranges pore networks but usually does not increase the total porosity near surface dissolution can simply lower a topographic surface without increasing porosity within the host limestone in many cases total porosity in carbonates under unconformities is actually reduced during subaerial exposure 2 permeability is likely to change more than porosity during subaerial exposure increasing in some c ses but decreasing in others 3 pore systems evolve with time during subaerial exposure short periods of subaerial exposure 10 000 400 000 yr are often associated with greater porosity than long intervals of subaerial exposure 1 20 million yr prolonged subaerial exposure may change permeability less than porosity because high permeability karst related conduits can form quickly and persist for millions of years 4 many carbonates subjected to subaerial exposure have little or no porosity in the deep subsurface because compaction cementation and stratal collapse reduce porosity during burial 5 unconformity related diagenesis may enhance reservoir potential by creating pore systems that are resistant to compaction during deeper burial 6 vugs caverns and breccias can fo m in the deep subsurface because of dissolution by basinal fluids independent of subaerial exposure 7 lithologic changes at unconformities like shales overlying carbonates can influence the flow of subsurface fluids during end page 857 deeper burial resulting in deep burial dissolution localized along unconformities if subaerial exposure and exposure surfaces are integrated into a sequence stratigraphic paleogeographic and climatic framework systematic and hopefully predictable patterns will emerge however we do not fully understand the complex interplay between the factors critical to creating and preserving porosity in carbonates additional research is needed to quantify critical processes and products so we can reliably predict porosity associated with subaerial exposure during exploration in frontier basins and on a smaller scale during reservoir analysis

carbon dioxide and dissolution rate dynamics within a karst underflow overflow system savoy experimental watershed arkansas usa abstract within numerical models of karst development geochemical and hydrological boundary conditions are typically assumed to be constant however rates of calcite dissolution in natural karst systems can vary substantially in time in particular variation in carbon dioxide co2 concentrations has been shown to produce time variability in dissolution rates in karst streams but controls on co2 variation within karst systems are relatively poorly quantified here we analyze hourly in situ measurements of dissolved co2 discharge and specific conductance at a pair of karst underflow overflow springs and examine potential drivers of variability in co2 and dissolution rates the springs display strong seasonal variability in co2 and saturation state as well as moderate variation during storm events though both springs have elevated co2 concentrations in the summer season the overflow spring experiences a substantial decrease in dissolved co2 below a critical discharge threshold we hypothesize that this decrease results from ventilation within the overflow portion of the system as segments of the flow path transition from full pipe to open channel flow the overflow spring experiences substantially lower average dissolution rates than the underflow spring despite larger discharge and chemical variability during high flow events at the overflow spring though open systems are frequently presumed to have higher dissolution rates because of their ability to replenish co2 that is consumed in the dissolution process these data suggest that dissolution rates within the closed portion of the system may in some cases be higher due to the inability of closed flow paths to ventilate excess co2 to the atmosphere such conditions are likely to occur in conduits where co2 concentrations are elevated above atmospheric levels and average flow through times are short compared to the time scale over which water reaches equilibrium with respect to calcite

planetary wave modelling of the middle atmosphere the importance of transients a linear planetary wave model of the middle atmosphere is used to diagnose the wavenumber 1 structure for a day during december 1979 given the wave forcing and the time derivative terms the time derivatives are calculated using data from the stratospheric sounding unit ssu on noaa 6 for days on either side of the principal day of interest the effect of the time derivative terms is significant and the model is found to be in fair agreement with the data in high latitudes although low latitude features are poorly reproduced the influence of the transient wave components is discussed and in particular some dissipation like effects are demonstrated which might clarify the role of rayleigh friction in planetary wave models

carbon dioxide ground air and carbon cycling in gibraltar karst we put forward a general conceptual model of co2 behaviour in the vadose zone of karst aquifers based on physical principles of air flow through porous media and caves combined with a geochemical interpretation of cave monitoring data this gibraltar model links fluxes of water air and carbon through the soil with the porosity of the vadose zone the circulation of ground air and the ventilation of caves gibraltar hosts many natural caves whose locations span the full length and vertical range of the rock we report results of an 8 year monitoring study of carbon in soil organic matter and bedrock carbonate dissolved inorganic carbon in vadose waters and gaseous co2 in soil cave and ground air results show that the regime of cave air co2 results from the interaction of cave ventilation with a reservoir of co2 enriched ground air held within the smaller voids of the bedrock the pco2 of ground air and of vadose waters that have been in close contact with it are determined by multiple factors that include recharge patterns vegetation productivity and root respiration and conversion of organic matter to co2 within the soil the epikarst and the whole vadose zone mathematical modelling and field observations show that ground air is subject to a density driven circulation that reverses seasonally as the difference between surface and underground temperatures reverses in sign the gibraltar model suggests that cave air pco2 is not directly related to co2 generated in the soil or the epikarstic zone as is often assumed ground air co2 formed by the decay of organic matter om washed down into the deeper unsaturated zone is an important additional source of pco2 in gibraltar the addition of om derived co2 is the dominant control on the pco2 of ground air and the ca hardness of waters within the deep vadose zone the seasonal regime of co2 in cave air depends on the position of a cave in relation to the density driven ground air circulation pattern which is itself determined by the topography as well as by the high permeability conduits for air movement provided by caves themselves in the steep topography of gibraltar caves in the lower part of the rock act as outflow conduits for descending ground air in summer and so have higher pco2 in that season caves in the upper rock have high pco2 in winter when they act as outflow conduits for rising currents of co2 enriched ground air understanding seasonal flows of ground air in the vadose zone together with the origins and seasonal regimes of co2 in cave air underpins robust interpretation of speleothem based climate proxy records

origin of caves and other solution openings in the unsaturated vadose zone of carbonate rocks a model for co2 generation the enigma that caves and other solution openings form in carbonate rocks at great depths below land surface rather than forming from the surface downward can be explained by the generation of co 2 within the aquifer system in the proposed model co 2 is generated by the oxidation of particulate and or dissolved organic carbon that is transported from the land surface deep into the unsaturated zone by recharging ground water the organic material is oxidized to co 2 by aerobic bacteria utilizing oxygen that diffuses in from the atmosphere because gas transport in the unsaturated zone is controlled largely by diffusion steady state generation of even minute amounts of co 2 deep in the unsaturated zone results in the creation of large concentrations of co 2 at depth as it establishes a concentration gradient to the surface or other sink ground water descending into these areas of high co 2 concentration becomes thermodynamically subsaturated with respect to carbonate minerals and is able to dissolve them thus forming the observed solution opening at depth

interhemispheric atlantic seesaw response during the last deglaciation the asynchronous relationship between millennial scale temperature changes over greenland and antarctica during the last glacial period has led to the notion of a bipolar seesaw which acts to redistribute heat depending on the state of meridional overturning circulation within the atlantic ocean here we present new records from the south atlantic that show rapid changes during the last deglaciation that were instantaneous within dating uncertainty and of opposite sign to those observed in the north atlantic our results demonstrate a direct link between the abrupt changes associated with variations in the atlantic meridional overturning circulation and the more gradual adjustments characteristic of the southern ocean these results emphasize the importance of the southern ocean for the development and transmission of millennial scale climate variability and highlight its role in deglacial climate change and the associated rise in atmospheric carbon dioxide

the southern westerlies in central chile during the two last glacial cycles as documented by coastal aeolian sand deposits and intercalating palaeosols abstract changes in the position and intensity of the southern westerly winds sww and related causal processes during the quaternary are controversial and not well understood here we present a record from continental central chile based on coastal aeolian sand and dunes with intercalated palaeosols reaching back 190 ka in time sixteen samples for luminescence dating and additional samples for geochemical procedures were analysed from three locations in the norte chico la serena los vilos las ventanas besides the recent bw horizons four palaeosols btb1 btb2 btb3 btb4 are identified they formed in periods with stable surface conditions and a relatively dense vegetation cover whereas sand accumulation reflects increased aeolian activity under dry conditions and in parts glacial sea level lowering three of these soils are well bracketed by luminescence data to

post glacial regional climate variability along the east antarctic coastal margin evidence from shallow marine and coastal terrestrial records we review the post glacial climate variability along the east antarctic coastline using terrestrial and shallow marine geological records and compare these reconstructions with data from elsewhere nearly all east antarctic records show a near synchronous early holocene climate optimum 11 5 9 ka bp coinciding with the deglaciation of currently ice free regions and the optimum recorded in antarctic ice and marine sediment cores shallow marine and coastal terrestrial climate anomalies appear to be out of phase after the early holocene warm period and show complex regional patterns but an overall trend of cooling in the terrestrial records a mid to late holocene warm period is present in many east antarctic lake and shallow coastal marine records although there are some differences in the regional timing of this warm period it typically occurs somewhere between 4 7 and 1 ka bp which overlaps with a similar optimum found in antarctic peninsula terrestrial records the differences in the timing of these sometimes abrupt warm events in different records and regions points to a number of mechanisms that we have yet to identify nearly all records show a neoglacial cooling from 2 ka bp onwards there is no evidence along the east antarctic coastline for an equivalent to the northern hemisphere medieval warm period and there is only weak circumstantial evidence in a few places for a cool event crudely equivalent in time to the northern hemisphere s little ice age there is a need for well dated high resolution climate records in coastal east antarctica and particularly in terre adelie dronning maud land and enderby land to fully understand the regional climate anomalies the disparity between marine and terrestrial records and to determine the significance of the heterogeneous temperature trends being measured in the antarctic today 2010 elsevier b v

formation of phreatic caves in an eogenetic karst aquifer by co2 enrichment at lower water tables and subsequent flooding by sea level rise formation of extensive phreatic caves in eogenetic karst aquifers is widely believed to require mixing of fresh and saltwater extensive phreatic caves also occur however in eogenetic karst aquifers where fresh and saltwater do not mix for example in the upper floridan aquifer these caves are thought to have formed in their modern settings by dissolution from sinking streams or by convergence of groundwater flow paths on springs alternatively these caves have been hypothesized to have formed at lower water tables during sea level low stands these hypotheses have not previously been tested against one another analyzing morphological data and water chemistry from caves in the suwannee river basin in north central florida and water chemistry from wells in the central florida carbonate platform indicates that phreatic caves within the suwannee river basin most likely formed at lower water tables during lower sea levels consideration of the hydrological and geochemical constraints posed by the upper floridan aquifer leads to the conclusion that cave formation was most likely driven by dissolution of vadose co2 gas into the groundwater sea level rise and a wetter climate during the mid holocene lifted the water table above the elevation of the caves and placed the caves tens of meters below the modern water table when rising water tables reached the land surface surface streams formed incision of surface streams breached the pre existing caves to form modern springs which provide access to the phreatic caves phreatic caves in the suwannee river basin are thus relict and have no causal relationship with modern surficial drainage systems neither mixing dissolution nor sinking streams are necessary to form laterally extensive phreatic caves in eogenetic karst aquifers dissolution at water tables potentially driven by vadose co2 gas offers an underappreciated mechanism to form cavernous porosity in eogenetic carbonate rocks copyright 2012 john wiley sons ltd

hydrothermal alteration veining and fluid inclusion characteristics of the kalzas wolframite deposit yukon kalzas is a sheeted vein and stockwork wolframite deposit crosscutting continental margin sedimentary rocks of the proterozoic windermere supergroup in central yukon mineralization is synchronous with cretaceous post tectonic granites of the selwyn plutonic suite parallel sets of planar quartz veins contain coarse euhedral wolframite and are generally oriented perpendicular to southeast plunging fold axes widespread alteration of the host rocks and intense stockwork veining surround the veins alteration and mineralization show a distinct concentric zonation across a 2 5 km long southeast trending oval the core zone is characterized by orthoclase contained within quartz tourmaline wolframite veins minor phases include apatite molybdenite bismuthinite pyrite chalcopyrite and pyrrhotite host rocks are prevasively tourmalinized and sericitized hydrothermal alteration here at the core of the system overprints early biotitization of the host rocks the biotitization appears to have been the result

palaeoclimate southern westerlies and co2 the southern hemisphere westerly winds affect the exchange of carbon dioxide between the ocean and atmosphere climate reconstructions from the southern mid latitudes may reveal variability in the strength and position of the wind belt since the last glacial maximum

antarctic deglacial pattern in a 30 kyr record of sea surface temperature offshore south australia 1 comparison of ice cores from greenland and antarctica shows an asynchronous two step warming at these high latitudes during the last termination however the question whether this asynchrony extends to lower latitudes is unclear mainly due to the scarcity of paleorecords from the southern hemisphere new data from a marine core collected off south australia 36s allows a detailed reconstruction of sea surface temperatures over the last termination this confirms the existence of an antarctic type deglacial pattern and shows no indication of cooling associated with the northern hemisphere yd event the sst record also provides a new comparison with the more extensive paleoclimatic data available from continental australia this shows a strong climatic link between onshore and offshore records for australia and to southern hemisphere paleorecords we also show a progressive sst drop over the last 6 5 kyr not seen before for the australian region citation calvo e c pelejero p de deckker and g a logan 2007 antarctic deglacial pattern in a 30 kyr record of sea surface temperature offshore south australia geophys res lett 34 l13707 doi 10 1029 2007gl029937

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

climatic influence of the latest antarctic isotope maximum of the last glacial period aim4 on southern patagonia abstract this paper presents the first detailed paleoclimate reconstruction of the latest antarctic isotope maximum aim4 33 29 ka cal bp at 52 s in continental southeastern argentine patagonia high resolution sedimentological and geochemical analyses of sediments from the maar lake potrok aike pta reveal a decrease in the thickness of flood induced turbidites and a series of wind burst deposits during aim4 both pointing to increasingly drier conditions this interpretation is also supported by a significant amount of runoff driven micropumices incorporated within the sediments that suggests a lower lake level with canyons incising thick tephra deposits around the lake increased gustiness and or dust availability in southeast patagonia together with intensified antarctic circumpolar circulation in the drake passage dust deposition in the scotia sea and in antarctica ice shelf are consistent with a southward shift of the southern westerly winds sww during the aim4 in contrast to other warmer aims the sww during the aim4 did not migrate far enough south to generate upwelling in the southern ocean and they did not reach 52 s in se patagonia as revealed by unchanged values of the rock magnetic proxy of wind intensity obtained from the same pta core nevertheless the sww displacement during aim4 imposed drier conditions at 52 s in southeast patagonia likely by blocking precipitation from the atlantic ocean in a way similar to modern seasonal variations and the other antarctic warm events

revised interpretations of stable c and o patterns in carbonate rocks resulting from meteoric diagenesis abstract a positive correlation between the 13c and 18o values of carbonate rocks is a screening tool widely used to identify the overprint of meteoric diagenesis on the original isotopic composition of a sample in particular it has been suggested that systematic change from negative to positive 13c and 18o values with increasing depth in the core is an indicator of alteration within the zone of mixing between meteoric and marine waters in this paper we propose that such covariance is not generated within the traditionally defined mixing zone and that positive correlations between 13c and 18o values in marine carbonates are not necessarily indicators of meteoric alteration this new interpretation is based on data collected from the shallow sub surface of the bahamas a region unequivocally influenced by meteoric waters to depths of at least 200 m below the current sediment water interface the classic interpretation of the diagenetic environments based on changes in the 13c and 18o values would suggest the maximum penetration of freshwater occurs between 65 and 100 m below seafloor below these depths a strong positive covariation between the 13c and 18o values exists and would traditionally be defined as the mixing zone however based upon known changes in sea level the penetration of the freshwater lens extends significantly below this limit we contend that the zone showing covariance of 13c and 18o values is actually altered within the freshwater lens and not the mixing zone as previously proposed the co varying trend in 13c and 18o values is the result of diagenetic processes occurring at the interface between vadose and phreatic zones significantly greater rates of recrystallization and neomorphism are driven by the increased rates of oxidation of organic matter at this transition with progressively less alteration occurring with increasing depth as sea level oscillates the position of this interface moves through the deposit causing cumulative alteration throughout the section hence we propose that the covariation between 13c and 18o values is a consequence of varying degrees of alteration rather than the result of diagenesis occurring within the zone where marine and freshwater fluids mix furthermore within the pervasively altered vadose zone there is little correlation between 13c and 18o values and therefore covariation between 13c and 18o values is not an unequivocal indicator of meteoric diagenesis

holocene environmental changes on nightingale island south atlantic based on diatom floristic changes in an infilled pond a holocene diatom stratigraphy of 2nd pond a small filled pond on nightingale island 37 degrees 25 s 12 degrees 29 w was analyzed and interpreted to infer paleolimnological changes on tristan da cunha south atlantic the diatom assemblage of 2nd pond has the character of an acidic oligotrophic wetland and the diatom record suggests that 2nd pond most likely has been a bog wetland throughout most of the holocene the flora is largely dominated by pinnularia viridis a species typically found in peat bogs the flora also includes benthic and epiphytic gomphonema sp achnanthes saxonica frustulia cf rhomboides staurosira venter as well as pinnularia cf divergens var decrescens and eunotia paludosa var paludosa peaks of aerophytic diatom i e mostly diadesmis spp and luticola spp abundances and concentrations correspond to increased magnetic susceptibility and slightly higher c n ratios and are interpreted to be the result of increased catchment erosion due to precipitation and following increased in wash of terrestrial diatoms the diatom record suggests dry conditions in the early holocene followed by recurrent periods of increased precipitation in the region at 8600 5600 cal a bp and at 2200 1700 cal a bp the main causes for these hydrological changes are probably changes in intensity and or position of the southern hemisphere west wind belt c 2013 elsevier b v all rights reserved less

antarctic timing of surface water changes off chile and patagonian ice sheet response marine sediments from the chilean continental margin are used to infer millennial scale changes in southeast pacific surface ocean water properties and patagonian ice sheet extent since the last glacial period our data show a clear antarctic timing of sea surface temperature changes which appear systematically linked to meridional displacements in sea ice westerly winds and the circumpolar current system proxy data for ice sheet changes show a similar pattern as oceanographic variations offshore but reveal a variable glacier response time of up to 1000 years which may explain some of the current discrepancies among terrestrial records in southern south america

ages of travertine deposits in eastern grand canyon national park arizona abstract travertine deposits in eastern grand canyon national park arizona are inferred to have formed under conditions of effective wetness that were greater than present uranium series dating of 17 samples indicates that the deposits formed at about 15 000 71 000 111 000 171 000 and 338 000 yr b p intervals of travertine deposition are essentially contemporaneous with dated high paleolake levels montane glacial maxima and high paleowater table levels from several great basin localities

radiocarbon evidence for decomposition of aged organic matter in the vadose zone as the main source of speleothem carbon 2015 elsevier ltd several recent studies have used records of the radiocarbon 14c bomb peak in speleothems to inversely model the soil a 14co 2 and the age distribution of soil organic material som above caves in part to investigate the potential of speleothems as sensitive records of past som dynamics the results of these modeling studies have suggested that soil co 2 at karst sites is derived primarily from the decomposition of som with turnover times on the order of decades to centuries this result is in stark contrast with observations of soil a 14co 2 at non karst sites which indicate that soil co 2 is derived primarily from root respiration and decomposition of som with much shorter turnover times this discrepancy suggests that som in karst settings may have a very different age distribution than sites that have been studied previously and or that soil co 2 is not the main source of speleothem carbon to help resolve this discrepancy we present an improved inverse model which we use to estimate the age of co 2 above several caves we also present results from a detailed case study of soil carbon dynamics at heshang cave china this work demonstrates that som in karst sites may be much older than som in non karst soils that have been studied previously but that co 2 produced in the shallow soil zone is unlikely to be the main source of speleothem carbon a review of the literature suggests that the most likely explanation for the aforementioned discrepancy is that decomposition of down washed som in the vadose zone is the dominant source of speleothem carbon

holocene changes in the position and intensity of the southern westerly wind belt the position and intensity of the southern westerly wind belt varies seasonally as a consequence of changes in sea surface temperature during the austral winter the belt expands northward and the wind intensity in the core decreases conversely during the summer the belt contracts and the intensity within the core is strengthened reconstructions of the westerly winds since the last glacial maximum however have suggested that changes at a single site reflected shifts throughout the entire southern wind belt 1 4 here we use sedimentological and pollen records to reconstruct precipitation patterns over the past 12 500 yr from sites along the windward side of the andes precipitation at the sites located in the present core and northern margin of the westerlies is driven almost entirely by the wind belt 5 and can be used to reconstruct its intensity rather than varying coherently throughout the holocene epoch we find a distinct anti phasing of wind strength between the core and northern margin over multi millennial timescales during the early holocene the core westerlies were strong whereas the northern margin westerlies were weak we observe the opposite pattern in the late holocene as this variation resembles modern seasonal variability we suggest that our observed changes in westerly wind strength can best be explained by variations in sea surface temperature in the eastern south pacific ocean chile is ideally located to reconstruct past variability of the southern westerly wind belt sww as the sww almost entirely controls precipitation on the western side of the andes in southern south america with an extreme northsouth

late glacial and early holocene cyclic changes in paleowind conditions and lake levels inferred from diatom assemblage shifts in laguna potrok aike sediments southern patagonia argentina abstract pasado is a multidisciplinary potrok aike sediment archive drilling project which was conducted from 2008 to 2013 focusing on the sedimentary record of the volcanic crater maar laguna potrok aike 52 s 70 w 116 m asl in southern patagonia argentina it represents one of the few non glacial and extra andean sediment archives studied so far on the continental landmass between subtropical south america and antarctica that covers the entire holocene and the late glacial in this study a high resolution diatom analysis of the late glacial time interval situated between 15 60 and 10 51 ka cal bp was performed on the pasado sediment core this period is of particular interest as it encompasses the antarctic cold reversal acr as well as the younger dryas yd chronozone to better refine the variability of environmental and climatic conditions of this late glacial time interval we combined our data with those of a microsedimentological analysis conducted on the same sediments and for the same period to infer changes in lake level and water column stratification our study revealed that diatoms are an ideal proxy to complement microsedimentological analyses by providing important independent information on the past limnological dynamics of laguna potrok aike and the paleoclimatic conditions that prevailed during the late glacial in the study area and allows a new way of explaining shifts in the position of southern hemisphere westerly winds sww during the late glacial peaks of planktonic diatoms particularly cyclostephanos patagonicus correspond to previously detected total organic carbon toc ca si ca and mn peaks and support the hypothesis that relatively high lake levels and weaker sww have prevailed during the late glacial moreover a cyclic pattern observed both in the biological and geochemical indicators suggests at least five shifts in the position of the sww from the beginning of the acr to the end of the yd the periodicity of these shifts seems to be related to antarctic ice sheet discharge aid events in the scotia sea that coincide with enhanced iceberg flux from the antarctic ice sheet

changes in holocene climate and the intensity of southern hemisphere westerly winds based on a high resolution palynological record from sub antarctic south georgia sub antarctic south georgia is a key region for studying climate variability in the southern hemisphere because of its position at the core of the southern hemisphere westerly wind belt and between the antarctic circumpolar current and the polar frontal zone here we present a 5 8 m long high resolution pollen record from fan lake on annenkov island dominated by local sub polar vegetation with acaena and poaceae being present throughout the last 7000 years palynological and sedimentological analyses revealed a warm late holocene climate optimum between 3790 and 2750 cal yr bp which was followed by a gradual transition to cool and wet conditions this cooling was interrupted by slightly warmer environmental conditions between 1670 and 710 cal yr bp that partly overlap with the northern hemisphere medieval climate anomaly increases in non native and long distance pollen grains transported from south america e g nothofagus podocarpus indicate that stronger southern hemisphere westerly winds over south georgia possibly occurred during some colder phases of the late holocene most notably between c 2210 and 1670 cal yr bp and after 710 cal yr bp

the importance of nonlinear wave processes in a quiescent winter stratosphere linear wave modelling about a zonally symmetric state is often assumed to be able to simulate accurately time averaged planetary wave geopotential heights in the stratosphere during quiescent winter periods we test this linear assumption by using a time dependent three dimensional primitive equation model of the stratosphere and mesosphere to simulate the quiescent winter stratospheric circulation during december 1980 the results from this simulation together with two other idealized integrations indicate that nonlinear wave interactions were crucial in accounting for the observed monthly mean wavenumber 1 planetary wave amplitude particularly in the upper stratosphere our results suggest that in general such interactions cannot be ignored for quantitatively accurate simulations of the middle atmosphere

holocene dynamics of the southern westerly winds over the indian ocean inferred from a peat dust deposition record abstract the southern westerly winds sww play a major role in climate variability in southern hemisphere mid and high latitudes regulating rainfall ocean circulation and the southern ocean carbon sink despite their importance little is known about millennial scale changes in the sww and how they have influenced the climate system in the past and interacted with the earth s surface elements such as dust nutrients and carbon here we present a dust record from a 6 6 kyr old peat core in amsterdam island ams situated at the northern edge of the sww 37 s in the southern indian ocean mineral dust flux was used to track atmospheric dust production long distance transport and subsequent deposition dust provenance was determined from rare earth element ree and nd isotopic signatures end in the peat core compared with a reference dataset of southern hemisphere dust sources using a multi proxy mixing model the end and ree ratios show a relatively uniform mixture of ca 40 local 15 southern african and 45 southern south american dust sources since 6 6 cal kyr bp however from 1910 ad onwards there is a doubling in the contribution from southern africa 32 two mineral dust flux minima occur at 6 2 4 9 cal kyr bp and 3 9 2 7 cal kyr bp interpreted as periods with equatorward shifted and or strengthened sww at the northern edge of the wind belt conversely periods of higher dust flux at 6 6 6 2 cal kyr bp 4 9 3 9 cal kyr bp and 1 4 cal kyr bp onwards are interpreted as poleward shifted and or weakened sww these interpretations are based on the findings that higher lower wind speeds lead to enhanced less removal of distal dust on the way to ams by wet deposition and turbulence published holocene sww records at the northern edge of the wind belt 33 41 s covering south america southern africa and australia show much variability over the last 6 6 kyr we suggest this reflects complex regional climate variability in the different sh longitudinal sectors indicating that sww are not zonally homogeneous at the northern edge of the wind belt the recent shift in dust provenance is not accompanied by enhanced total dust deposition at ams we therefore suggest that human impact e g land use changes and drier climate conditions in southern africa have led to enhanced dust mobilization

multi proxy analyses of a peat bog on isla de los estados easternmost tierra del fuego a unique record of the variable southern hemisphere westerlies since the last deglaciation we have analyzed an almost 14 000 year old peat sequence on the island of isla de los estados 55 degrees s 64 degrees w east of tierra del fuego in the core of the southern hemisphere westerlies a multitude of methods have been used high resolution c 14 dating detailed lithologic descriptions including humification degree loss on ignition magnetic susceptibility bulk density pollen and spore analysis and determination of aeolian sand influx by combining proxies for wind and precipitation we have been able to reconstruct how the westerlies have varied over time in the atlantic sector of the southern ocean it shows that this westerly wind belt was most intense at the onset of the record 13 600 13 200 cal bp coinciding with the mid to late part of the antarctic cold reversal followed by a gradual decline at 12 200 cal bp the westerlies seem to have shifted to a position south of tierra del fuego and this phase the calmest and driest period on the island throughout the sequence ended at 10 000 cal bp when the westerlies moved equatorward again since then the westerlies have been present but with a variable impact on the 55 degrees s latitude of the atlantic mostly conditions have been fairly similar to today but occasionally with a wider or narrower and or weaker or stronger wind belt at 7200 cal bp wind intensity began to increase and between 4500 and 3500 cal bp these southern latitudes experienced a distinct wind and precipitation maximum both in terms of perseverance and intensity our results show a both wide and strong wind belt with possible niveo aeolian activity in tierra del fuego in winter and possibly creating milder summers around the antarctic peninsula in the later part of the holocene expansion contraction phases of the wind belt especially in winter seem to have been a common phenomenon c 2012 elsevier ltd all rights reserved

glacier advance in southern middle latitudes during the antarctic cold reversal the geographic extent of cooling associated with the antarctic cold reversal is unclear dating of glacial moraines in new zealand suggests that the cooling extended into the southern mid latitudes possibly as a result of the northward migration of the southern subtropical front

vadose co2 gas drives dissolution at water tables in eogenetic karst aquifers more than mixing dissolution most models of cave formation in limestone that remains near its depositional environment and has not been deeply buried i e eogenetic limestone invoke dissolution from mixing of waters that have different ionic strengths or have equilibrated with calcite at different pco2 values in eogenetic karst aquifers lacking saline water mixing of vadose and phreatic waters is thought to form caves we show here calcite dissolution in a cave in eogenetic limestone occurred due to increases in vadose co2 gas concentrations and subsequent dissolution of co2 into groundwater not by mixing dissolution we collected high resolution time series measurements 1 year of specific conductivity spc temperature meteorological data and synoptic water chemical composition from a water table cave in central florida briar cave we found spc pco2 and calcite undersaturation increased through late summer when briar cave experienced little ventilation by outside air and decreased through winter when increased ventilation lowered cave co2 g concentrations we hypothesize dissolution occurred when water flowed from aquifer regions with low pco2 into the cave which had elevated pco2 elevated pco2 would be promoted by fractures connecting the soil to the water table simple geochemical models demonstrate that changes in pco2 of less than 1 along flow paths are an order of magnitude more efficient at dissolving limestone than mixing of vadose and phreatic water we conclude that spatially or temporally variable vadose co2 g concentrations are responsible for cave formation because mixing is too slow to generate observed cave sizes in the time available for formation while this study emphasized dissolution gas exchange between the atmosphere and karst aquifer vadose zones that is facilitated by conduits likely exerts important controls on other geochemical processes in limestone critical zones by transporting oxygen deep into vadose zones creating redox boundaries that would not exist in the absence of caves copyright 2014 john wiley sons ltd