an integrated carbon isotope record of an end permian crater lake above a phreatomagmatic pipe of the siberian traps abstract the largest mass extinction in earth history occurred at the end permian 252 million years ago and is marked by a global negative carbon isotope excursion and the onset of siberian trap volcanism prompting diverse hypotheses on the link between flood basalt volcanism carbon cycle perturbations and mass extinction phreatomagmatic pipes associated with siberian trap volcanism have been proposed as conduits for the release of 12c enriched carbon gases from thermogenic and or magmatic sources to the end permian atmosphere some of the pipes have preserved crater lake sediments of volcaniclastic origin this study examined the preserved evidence for 12c enriched carbon release into the western oktyabrsk crater in east siberia from the underlying volcanic basin we find that the 13c 12c ratio of the carbonate cement organic matter and long chain n alkanes in the lacustrine crater sediments support the hypothesis that 12c enriched carbon infiltrated the basal crater sediments and lake water immediately after crater formation the values and trends of 13ccarb 13ctoc and 13cn alkanes in the crater sediments are consistent with 12c enriched carbon with isotopic values similar to that of carbon sourced from thermogenic and or 12c enriched magmatic sources this implies that carbon release through the pipes in the tunguska basin may explain the source of the global negative carbon isotope perturbations and their coincidence with siberian trap volcanism at the end permian

propagation of low level circulation features in the vicinity of mountain ranges abstract the local influence of mountains upon large and synoptic scale low level atmospheric circulations is investigated in this study the sea level pressure associated with low frequency fluctuations exhibit phase propagation of monopolar structures around mountains in an anticyclonic sense while the corresponding 500 mb height patterns are relatively stationary and evolve in a manner consistent with the concept of rossby wave dispersion on a sphere the sea level pressure patterns in the high pass filtered data exhibit characteristics of synoptic scale baroclinic waves and are steered around mountain ranges in an anticyclonic sense while the corresponding 500 mb height patterns propagate nearly parallel to the time mean flow in the middle troposphere it is hypothesized that the phase propagation of lower tropospheric circulation patterns is a reflection of the conservation of potential vorticity in flows over variable terrain most of the observations presented in this study are interpreted as th

geochemistry of coal measure source rocks and natural gases in deep formations in songliao basin ne china abstract the natural gases developed in deep volcanic rock reservoirs of the songliao basin ne china are characterized by enriched 13 c value for methane and frequently reversal carbon isotopic distribution pattern although many researchers consider such gas type as an abiogenic origin we believe the natural gases have a biogenic origin mainly except little inorganic gases and the reversal carbon isotopic distribution pattern of gases is caused by mixing of different origin gases methane carbon isotopic values for majority samples fall in the range from 24 to 32 which is heavier than typical coal type gases in other chinese basins there are several reasons caused heavy carbon isotope of methane 1 carbon isotopic values of source kerogen are 3 5 heavier than these from other basins 2 source rocks are at extremely high maturity stage with vitrinite reflectance mostly above 3 0 3 portion of gas is derived from basement mudrock or slate with higher maturity the observation on the organic from deep formation reveals that there is a relatively high content for liptinite which reaches approximately 8 to 10 the macerals component of source rock shows that the source rocks have some ability to generate oil small portion of oil was generated from high hydrogen content macerals in coals and shales as proof by oil found in microcrack and in micropore of coal and oil bearing fluid inclusions grown in volcanic reservoir the occurrence of pyrobitumen in volcanic reservoir indicates preexisted oil had been cracked into wet gas and this kind of gas had also been found in gas pools heavy isotopic methane is derived from coal at extremely high maturity stage there may be little inorganic alkane gases in deep layers for their geochemistry and special geological setting of songliao basin artificial mixing experiments of different origins gases confirm that inorganic gas such as gas from well fs1 mixed with other end members can turn out full reversal isotopic distribution pattern based on simple calculations of 13 c 1 values it can be concluded that the deep natural gases in songliao basin are mainly derived from coal

bitumen biomarkers in the mid proterozoic ilimaussaq intrusion southwest greenland a challenge to the mantle gas theory abstract gc and gc ms ms analysis on rock extracts has shown that the bitumen in the peralkaline ilimaussaq intrusion previously assumed to be abiogenic is biotic in origin a biotic origin is in accordance with previously published stable carbon isotopic data on bituminous matter in the rocks the biomarker distribution in the bitumen including the less common bicadinanes resembles that of oil seeps on the central west greenland coast 2200 km farther north whose source rocks and migration history are relatively well established we use a recent re construction of the subsidence and later exhumation of the west greenland coastal region during the mesozoic cenozoic japsen et al 2006a b to anticipate that hydrocarbons migrated from deeper parts of the basin offshore west of greenland the rocks of ilimaussaq were probably more deeply invaded than the surrounding granites due to their higher proportion of corroded minerals which may explain why bitumen has not been observed elsewhere in the area hydrocarbon gases c1 c5 present in fluid inclusions were also analysed after having been released by treatment with hydrochloric acid that resulted in an almost complete disintegration of the ilimaussaq intrusion rocks the acid extraction method proved generally more efficient than the crushing procedure applied by others but gave similar results for the chemical composition of the gas ch4 88 97 and isotopic ratios 13 c ch 4 1 6 to 5 0 13 c c 2 h 6 9 2 to 12 5 with the exception of hydrocarbons hosted in quartz which showed significantly lower isotopic values for methane graser et al 2008 previous researchers have suggested an abiotic origin for these hydrocarbon gases but we suggest a biotic origin for the majority of them not just those in quartz assuming that the isotopic ratio of the constituents have changed due to loss of gas by diffusion the assumption of gas loss via diffusion is supported by published studies on micro fissures in minerals typical of the ilimaussaq and field investigations showing diffusive loss of gas from the peralkaline khibina and lovozero massifs on the kola peninsula russia which are in many respects of mineralogy and hydrocarbon content similar to the ilimaussaq intrusion both the hydrocarbon gases and bitumen in the khibina and lovozero massifs have been cited as prime examples of a deep mantle source although the carbon isotopic ratio of the bitumen clearly pointed to an organic origin the trends in carbon isotopic ratio of methane released with time from freshly exposed rocks also supports our hypothesis of 13c enrichment of the methane remaining within the rock thus there is good evidence that the hydrocarbons in the kola alkaline massifs are mostly biotic in origin in which case the probability of finding economic hydrocarbon accumulations from a deep mantle source seems exceedingly small

organic inclusions in salt part 3 oil and gas inclusions in cambrian evaporite deposit from east siberia a contribution to the understanding of nitrogen generation in evaporites abstract halite in cambrian kcl deposits from the southern part of the siberian platform which have been thermally overprinted by dolerite intrusions commonly contains inclusions dominantly composed of co2 and less commonly host inclusions composed of hydrocarbons four types of hydrocarbon inclusions have been identified in samples taken from locations devoid of dolerite intrusions these are 1 monophase gaseous inclusions i e n2 ch4 or n2 ch4 2 aliphatic oil inclusions 3 two phase l1 l2 hydrocarbon brine inclusions and 4 n2 hydrocarbon inclusions the area where the n2 rich inclusions occur is associated with ammonium free k chlorides by comparing different types of k salt environments the origin of the nitrogen could be identified first ammonium ions are produced by deamination of organic matter and stored in k chlorides and thereafter n2 is released from nh4 k minerals by oxidation in zones rich in iron oxides and or by 40k radiolysis

abiogenic hydrocarbon isotopic signatures in granitic rocks identifying pathways of formation abstract the stability and isotopic composition of hydrocarbons formed in the mantle are controversial subjects knowing the range in isotopic compositions of abiogenically derived hydrocarbons is important for recognising biological signatures in ancient and extra terrestrial materials in an effort to enhance this database stable isotope results are reported here for hydrocarbon bearing fluid inclusions hosted in two peralkaline igneous complexes from lovozero russia and strange lake canada based on the distribution of isotopic compositions we propose three pathways for abiogenically generated hydrocarbons type 1 13cch4 13cco2 and 13cc2 represents mantle derived hydrocarbons generated in equilibrium with hyperagpaitic magmas in the upper mantle and suggests that mantle ch4 and c2h6 13c and 2h could have values of 5 3 and 112 and 10 8 and 162 respectively type 2 13cco2 13cch4 13cc2 represents fischer tropsch type hydrocarbon generation in quartz bearing peralkaline rocks with co2 as the initial magmatic gas phase for type 2 13cco2 values are 2 whereas 13cch4 and 2hch4 values range from 32 to 20 and 170 and 160 respectively the 13cc2h6 values are slightly lower than associated 13cch4 values type 3 13cco2 13cch4

cold surges in tropical and extratropical south america the strong event in june 1994 the authors investigate one case of surges of polar air that occasionally propagate into southeastern brazil during wintertime and are harmful to coffee production because of the freezing conditions associated with them the cooling is also observed in southern and with less intensity in western amazonia the event of 26 june 1994 is studied the frost event caused a sharp drop in coffee production and similarly dramatic increases in coffee prices the event was characterized by the presence of an anticyclonic perturbation off the coast of chile that enters south america and crosses the andes mountains south of 458s hours later the anticyclone center tracks equatorward until it reaches 208 308s and then shifts eastward toward the atlantic based on a diagnostic analysis using the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis a two stage process can be distinguished in the starting period midtropospheric troughing is established east of the andes over central argentina due to stretching and or vorticity advection this troughing is responsible for cold advection along the eastern flank of the andes which produces substantial temperature drops and deepens the upper trough locally the increase in the magnitude of the zonal temperature gradients east of the cold advection zone at levels near 700 hpa is another result of the cooling process this feature would ensure that the cold advection be extended eastward producing an upper level trough local deepening there this intensification would produce an increase in the cyclonic vorticity advection which would tend to produce sea level pressure drops underneath this near surface low pressure area would eventually contribute to the southeastern brazil sb cooling due to the associated southerly winds another feature is the near surface local anticyclonic generation due to midtropospheric cold advection associated with descending motions low level divergence and anticyclonic growth eventually this high pressure would also contribute to produce southwesterlies to transport cold air to sb the paper is divided in two sections the first part is a study of synoptic and climatic aspects of the cold surge episodes by using daily surface climatic observations the purpose of the second part is to analyze the dynamic aspects of this cold episode and to study the cooling mechanisms by using the four times daily surface and upper air ncep ncar reanalysis as well as to look for possible predictors

orographic influences on the distribution and generation of atmospheric variability in a gcm abstract the effect of large scale mountains on atmospheric variability is studied in a series of gcm experiments in which a single mountain is varied in height from 0 to 4 km high frequency 30 days variability are largest in the jet exit region while the intermediate frequency 7 30 days variability has its maximum upstream of the mountain where it exhibits enhanced equatorward propagation high and intermediate frequencies change from zonal wave trains to localized wave packets as orographic forcing is increased but they retain their characteristic scale and frequency the dominant pattern of low frequency is variability changes from a zonally symmetric oscillation for which transient eddy zonal flow interaction is the dominant mechanism to a more localized oscillation of the jet downstream of the mountain the transient eddy forcing still plays a significant role in maintaining the variations of this more localized jet however the total amount of wave

a new perspective on southern hemisphere storm tracks abstract a detailed view of southern hemisphere storm tracks is obtained based on the application of filtered variance and modern feature tracking techniques to a wide range of 45 yr european centre for medium range weather forecasts ecmwf re analysis era 40 data it has been checked that the conclusions drawn in this study are valid even if data from only the satellite era are used the emphasis of the paper is on the winter season but results for the four seasons are also discussed both upper and lower tropospheric fields are used the tracking analysis focuses on systems that last longer than 2 days and are mobile move more than 1000 km many of the results support previous ideas about the storm tracks but some new insights are also obtained in the summer there is a rather circular strong deep high latitude storm track in winter the high latitude storm track is more asymmetric with a spiral from the atlantic and indian oceans in toward antarctica and a subtropical jet related lower latitu

atmospheric gas in modern and ancient halite fluid inclusions a screening protocol abstract halite possesses great potential for hosting and storing information vital to the reconstruction of earth s ancient climate seawater chemistry and evolving atmosphere here we propose a screening protocol that not only distinguishes between primary and secondary halite but also identifies fluid inclusions that carry original gas trapped during the primary crystallization process an integrated multi analytical protocol is presented for sample preparation petrographic evaluation analytical measurements and distinguishing original gases and contents from contaminants the screening protocol starts with the visual inspection of halite for primary chevron and hopper features and or milky appearance then petrography is used to distinguish between primary and secondary diagenetic crystal fabrics and inclusions the trace element and isotope geochemistry speak directly to the composition of the depositional and or diagenetic fluids and to the formation in marine non marine or diagenetic settings furthermore rare earth elements and redox sensitive elements may address the redox conditions of the salt pan flat brines whereas microthermometry helps characterize the depositional diagenetic environment s temperature finally gas extracted by quadrupole mass spectrometer from gas bubbles in fluid inclusions is screened with concomitant ch4 co2 and ar contents to distinguish and quantify organic matter decomposition contributions and with 40ar 36ar to monitor modern atmospheric gas diffusion leakage issues and thus contamination of the primary gas contents our test case shows that halite collected from cores is well suited in maintaining its original mineralogical texture chemistry and gas content our integrated screening protocol suggests that the 815 myr old halite from the tonian browne formation of the officer basin australia formed under atmospheric conditions of about 10 9 po2 back calculation or 9 6 po2 mean calculation the coeval neoproterozoic gypsum collected in outcrop from minto inlet victoria island canada underwent some mineralogical alteration however experiments suggest that depositional gypsum from outcrop core may have potential of retaining vestiges of original gas in fluid inclusions

magnetic fingerprint of the late holocene inception of the rio de la plata plume onto the southeast brazilian shelf abstract measurement of changes in the assembly of magnetic particles in sediment records is useful both for paleoclimatic and paleoceanographic reconstructions and for assessing provenance and pathways of sediment transport in this study we provide detailed rock magnetic analysis along with scanning electron microscopy sem ti ca ratio and particle size distribution of the decarbonated fraction of sediments to trace terrigenous source changes during the last 6 cal kyr bp in core 7610 collected on the se brazilian continental shelf magnetic mineralogy data indicate a gradual shift between two distinct sources of sediments 1 dust from southern south america patagonia central western argentina and puna altiplano plateau and 2 sediments eroded from the weathered volcanics of parana basin these materials reached the continental margin off argentina and uruguay by different pathways and were transported northward by the brazilian coastal current bcc the chronology of events related to the environmental record of core 7610 indicates that between 6 and 4 7 cal kyr bp dry conditions over continental south america resulted in enhanced eastward eolian transport of the argentinean loess and a limited discharge of the rdlp river load into the atlantic ocean at this time the sedimentary magnetic fraction that reached the se brazilian shelf reflect predominantly loessic sources transported from the pampean terraces to the argentinean and uruguay shelves and then distributed northward by the shelf current system from 4 7 to 2 cal kyr bp the climate became gradually wetter over the continent and the contribution of oxidized phases from the weathered parana basin mainly from the basaltic and acidic volcanics started to become important this change in climate overlaps in time a with the late holocene sea level fall recorded along the se south american coast later from 2 up to 0 9 cal kyr bp even wetter conditions were prevalent in s and se south america and the rdlp sedimentary load became the main source of sediments transported to the se brazilian shelf by the bcc the magnetic record of core 7610 reported here together with other paleoenvironmental tracers palynology geochemistry and stable isotopes thus indicates that the inception of the rdlp plume onto the se brazilian shelf started as early as 4 7 cal kyr bp and has been strengthened since then mostly due to changes in precipitation over south america and to a smaller extent by sea level changes

long term vegetation climate and ocean dynamics inferred from a 73 500 years old marine sediment core geob2107 3 off southern brazil abstract long term changes in vegetation and climate of southern brazil as well as ocean dynamics of the adjacent south atlantic were studied by analyses of pollen spores and organic walled dinoflagellate cysts dinocysts in marine sediment core geob2107 3 collected offshore southern brazil covering the last 73 5 cal kyr bp the pollen record indicates that grasslands were much more frequent in the landscapes of southern brazil during the last glacial period if compared to the late holocene reflecting relatively colder and or less humid climatic conditions patches of forest occurred in the lowlands and probably also on the exposed continental shelf that was mainly covered by salt marshes interestingly drought susceptible araucaria trees were frequent in the highlands with a similar abundance as during the late holocene until 65 cal kyr bp but were rare during the following glacial period atlantic rainforest was present in the northern lowlands of southern brazil during the recorded last glacial period but was strongly reduced from 38 5 until 13 0 cal kyr bp the reduction was probably controlled by colder and or less humid climatic conditions atlantic rainforest expanded to the south since the lateglacial period while araucaria forests advanced in the highlands only during the late holocene dinocysts data indicate that the brazil current bc with its warm salty and nutrient poor waters influenced the study area throughout the investigated period however variations in the proportion of dinocyst taxa indicating an eutrophic environment reflect the input of nutrients transported mainly by the brazilian coastal current bcc and partly discharged by the rio itajai the major river closest to the core site this was strongly related to changes in sea level a stronger influence of the bcc with nutrient rich waters occurred during marine isotope stage mis 4 and in particular during the late mis 3 and mis 2 under low sea level evidence of nothofagus pollen grains from the southern andes during late mis 3 and mis 2 suggests an efficient transport by the southern westerlies and argentinean rivers then by the malvinas current and finally by the bcc to the study site major changes in the pollen spore and dinocyst assemblages occur with similar pacing indicating strongly interlinked continental and marine environmental changes proxy comparisons suggest that the changes were driven by similar overarching factors of which the most important was orbital obliquity

the influence of the andes cordillera on transient disturbances abstract the influence of the andes cordillera on transient disturbances is investigated in this study using a lag correlation analysis this analysis shows that the unfiltered geopotential height data have a wavelike pattern moving to the east while tilting to the west in the vertical when the wave approaches the andes cordillera it exhibits orographic effects such as anticyclonic turning of a low level disturbance trajectory a zonal trajectory in the upper levels distortions of the isolines of correlation and an elongation of maximum correlation on the lee side of the andes the anticyclonic turning of the trajectory in the low attitude levels and a zonal trajectory in upper levels implies a decrease in the vertical tilt of the system on the windward side and an increase in the tilt on the lee side the increase of baroclinicity on the lee side results in baroclinic development as predicted from a linearly obtained normal mode solution in the presence of mountains a cross correlation analysis of t

the composition of gases in fluid inclusions of late permian zechstein marine evaporites in northern germany abstract in order to understand the generation of gases in late permian marine evaporites and the migration of gases in salt domes 428 gas bearing fluid inclusions of the gorleben salt dome northern germany were analysed using laser raman spectrometry lrs the investigations were divided in two parts in the first part only gas rich inclusions were analysed involving samples from different stratigraphic layers of the zechstein 2 stasfurt serie and zechstein 3 leine serie and from different locations within the salt dome for the second part only the gaseous components in brines rich inclusions of the zechstein 2 were measured the compositional range of all inclusions investigated can be subdivided into two main groups with rare exceptions the first group of n 2 and n 2 o 2 inclusions reveals a n 2 o 2 ratios close to that of modern atmosphere thus indicating trapped paleoatmosphere the second group is represented by inclusions that contain mixtures of n 2 ch 4 occasionally h 2 and or h 2 s the most abundant subgroups are n 2 ch 4 and n 2 ch 4 h 2 mixtures these gas mixtures can be produced by the decomposition of organic material under anoxic conditions it is noted that n 2 in both main groups can also be generated by degassing of underlying early permian rotliegendes or carboniferous c org rich sedimentary rocks and an entrapment in early stages of the zechstein halokinesis the different origin of both main groups is supported by stratigraphic correlation in the stratigraphic layers which contain mainly mixtures of n 2 and o 2 or pure n 2 inclusions of the n 2 ch 4 h 2 h 2 s group are rare and vice versa layers which are rich in n 2 ch 4 h 2 h 2 s do not contain many n 2 o 2 inclusions the majority of layers investigated frequently contains inclusions of the n 2 o 2 group only two anhydrite rich layers of zechstein 3 main anhydrite and anhydrite intercalated salt contain mainly inclusions of the second group the zechstein 3 potash seam as well as secondary halites contain more or less the same population of inclusions from every main group a comparison of the gas rich inclusions and the gases in the brine rich inclusions of the zechstein 2 layer main rock salt 3 shows distinct differences whereas the gas rich inclusions are of the n 2 o 2 group the gases from the brine rich inclusions are of the n 2 ch 4 group emphasising different origins the latter is a product of anhydrite rich parts or potash seams that have migrated later into the overlying main rock salt 3

structure and evolution of baroclinic waves as inferred from regression analysis abstract the structure of transient disturbances with periods shorter than a week is documented an the basis of one point regression maps and longitude height sections derived from the national meteorological center nmc operational analyses for nine winter seasons the reference time series for the regression coefficients is highpass filtered normalized 500 mb height at a grid point in the pacific stormtrack the field variables that were regreesed on the reference time series were not filtered the regression statistics yield quantitative estimates of the amplitudes of the high frequency fluctuations in the geopotential height temperature wind ageostrophic wind vorticity divergence vertical velocity and outgoing longwave radiation fields the observed high frequency fluctuations exhibit a vertical and meridional structure suggestive of baroclinic waves evolving through the mature phase of their life cycle most of the results are in qualitative agreement with previous studies but the ageostrop

a diagnostic study of cold air outbreaks over south america midlatitude disturbances such as intense cold fronts and cutoff lows are a very important cause of severeweather events over the southern part of south america particularly during the austral winter months behind cold fronts cold air from higher latitudes is forced to flow equatorward to the east of the andes occasionally fronts might produce cold surges in tropical latitudes with freezing temperatures referred as to geadas in portuguese over crop growing areas of southern southeastern and central brazil the structure and dynamical processes of winter synoptic scale waves associated with cold surges over south america are documented in this paper it is shown that the rotated extended empirical orthogonal function technique is capable of extracting well defined regional patterns from 850 hpa meridional wind perturbation fields over south america waves behave very differently in the lower and middle troposphere while upperlevel waves propagate northeastward as they cross the andes evolving in a manner consistent with the concept of rossby wave dispersion at lower levels waves tend to conform to the shape of the mountain range in agreement with the theory of topographic rossby waves however it was found that cold surges do not seem to result from the generation of rotationally trapped waves significant differences have been found between synoptic scale patterns associated with cold surges over extratropical south america no geada composites and synoptic scale patterns associated with major coldair outbreaks that produce extreme low temperatures at tropical regions geada composites while both surges are characterized by a long wave pattern consisting of a cyclonic perturbation over south america and anticyclonic perturbation behind over the southern pacific ocean at the early stages of geada composites two additional features were identified a subpolar and subtropical short wave pattern the presence of the upperlevel subtropical cyclonic perturbation is associated with the subtropical jetstream location farther north which would facilitate the equatorward penetration of frontal systems in addition this cyclonic perturbation enhances rising motion at subtropical and tropical latitudes that is associated with a well defined secondary circulation with its descending branch over central argentina it is shown that this configuration favors the rapid and equatorward penetration of the subpolar short wave trough the temperature decrease over southern brazil and the anticyclone intensification over central argentina thus the presence of the subtropical upper level feature plays a key role on the cold surge occurrence over tropical regions of south america

millennial scale precipitation changes in southern brazil over the past 90 000 years 1 a u th dated 90 000 year long speleothem oxygen isotope record from southern brazil anti correlates remarkably with the cave calcite records from eastern china but positively correlates with the speleothem record from northeastern brazil suggesting an interhemispheric anti phasing of rainfall on both millennial and orbital timescales likely related to displacement in the mean position of the intertropical convergence zone and associated asymmetry in hadley circulation the phase relationships among these records are consistent with the hypothesis that abrupt climate events during the last glacial period are triggered by oceanic circulation changes in the high latitudes and enhanced by tropical feedbacks

interhemispheric anti phasing of rainfall during the last glacial period abstract we have obtained a high resolution oxygen isotopic record of cave calcite from caverna botuvera 27 13 s 49 09 w southern brazil which covers most of the last 36 thousand years ka with an average resolution of a few to several decades the chronology was determined with 46 u th ages from two stalagmites tests for equilibrium conditions show that oxygen isotopic variations are primarily caused by climate change we interpret our record in terms of meteoric precipitation changes hence the variability of south american monsoon sam intensity the oxygen isotopic profile broadly follows local insolation changes and shows clear millennial scale variations during the last glacial period with amplitudes as large as 3 but with smaller centennial scale shifts 1 during the holocene the overall record is strikingly similar to but strongly anti correlated with a number of records from the northern hemisphere we compared our record to other precisely dated contemporaneous records from hulu cave eastern china minima in 18o wet periods intense sam at our site are synchronous with maxima in 18o dry periods weak east asian monsoon eam in eastern china within precise dating errors and vice versa this anti phased precipitation relationship between two low latitude locations may be interhemispheric in extent based on comparison with records from other sites precipitation anti phasing may be related to north south shifts in the mean position of the intertropical convergence zone itcz and asymmetry in hadley circulation in two hemispheres associated not with seasonal changes as observed today but with millennial scale climate shifts the millennial scale atmospheric see saw patterns that we observe could have important controls and feedbacks on climate within hemispheres because of water vapor s greenhouse properties

cold air incursions over subtropical south america mean structure and dynamics abstract synoptic scale incursions of midlatitude air moving into subtropical south america to the east of the andes cordillera are observed to occur year round with a periodicity of about 1 2 weeks during wintertime they have a profound impact upon the low level temperature field and extreme episodes produce freezing conditions from central argentina to southern brazil and bolivia warm season episodes produce less dramatic variations of temperature but they organize deep convection in the form of synoptic scale bands of convective cloudiness along the leading edge of the cool air on the basis of 17 yr of ncep ncar reanalysis and outgoing longwave radiation fields the mean synoptic scale structure and evolution of these incursions is documented using a simple compositing technique the underlying physical mechanisms responsible for the occurrence of these incursions are also investigated by diagnosing the leading dynamic and thermodynamic forcing of their development

shell sclerochronology and stable isotopes of the bivalve anomalocardia flexuosa linnaeus 1767 from southern brazil implications for environmental and archaeological studies abstract this study presents the first stable isotopic and sclerochronological calibration of the bivalve anomalocardia flexuosa linnaeus 1767 in relation to environmental variables in a subtropical coastal area of southern brazil we investigate incremental shell growth patterns and 18o and 13c values of modern specimens collected alive from the laguna lagoonal system lls shells of anomalocardia flexuosa are also one of the main biological components of pre columbian archaeological shell mounds and middens distributed along the brazilian coastline we therefore selected archaeological specimens from a local late holocene shell mound cabecuda to compare their stable carbon and oxygen isotope values with those of modern specimens shell growth increments 18o and 13c values respond to a complex of environmental conditions involving for example the effects of temperature and salinity the isotopic information extracted from archaeological specimens from cabecuda shell midden in the lls indirectly indicates that environmental conditions during the late holocene were different from present day in particular intra shell 18o and 13c values of archaeological shells reveal a stronger marine influence at 3 ka cal bp which is in contrast to the seasonal freshwater seawater balance that currently prevails at the lls

the energy cycle and structural evolution of cyclones over southeastern south america in three case studies 1 in this paper the lorenz energy cycle over a limited area was applied for three cyclones with different origins and evolutions where each of them was formed in an important cyclogenetic region near southeastern south america the synoptic conditions and energetics were analyzed during each system s life cycle and showed important relationships between their energy cycle and the evolution of their vertical structure in the case of the weak baroclinic cyclone which formed on brazil s south southeastern coast the analysis showed that it originated through a midlevel cutoff low with contribution from barotropic instability its evolution would indicate potential transition to a hybrid system if the convective activity were stronger the system that occurred in the la plata river mouth had features of an oceanic bomb type cyclogenesis and showed an important contribution from the available potential energy generation term through the latent heat release by the convection meanwhile the system of the southern argentina coast presented a classical baroclinic development of extratropical cyclogenesis in the energy cycle from the wave amplification up to the final occlusion of the associated frontal system these analyses revealed that the development of some cyclones that occur in eastern south america can present different mechanisms that are not related to the classical extratropical cyclogenesis

multiple origins of methane in the earth methane occurrences in the earth s crust are predominantly of biogenic origin i e their ultimate source is biologically formed organic matter methane can also form through inorganic reactions and is consequently termed abiogenic biogenic methanes can either form through bacterial or thermogenic processes bacterial processes follow a co2 reduction and or fermentation pathway the fermentation processes are quantitatively more important in recent fresh sediments and swamps methane formed by co2 reduction however is most common in older sediments and commercial gasfields temperature organic substrate and age may be the major factors controlling the relative importance of the two pathways stable isotope concentrations in thermogenic methanes seem to be controlled by the extent of conversion of organic matter the timing of gas expulsion and trapping the different character of methane in individual sedimentary basins may be a result of the geologic history geothermal methanes are most likely derived from pyrolysis of organic matter abiogenic methane occurs in hydrothermal vents and ophiolite complexes inorganic reactions either surficial or deep seated are the likely source of such methanes a uniform mantle origin of methane is not supported by the observed isotope variations in naturally occurring methanes

characteristics of the southern hemisphere winter storm track with filtered and unfiltered data abstract the structure and evolution of the fluctuations in synoptic scales in the southern hemisphere sh during winter are discussed using six years of european centre for medium range weather forecasts analyses it is shown that patterns from unfiltered meridional wind series in the sh display all the features needed to represent the synoptic scale waves typical periods and wavelengths are similar to those observed in the northern hemisphere 4 days 4000 km although over the pacific ocean they can be as high as 7 8 days and 4700 km respectively as in the northern hemisphere tilts are not geographically fixed but change with the stage of the evolution of the wave the phase speed of the waves agrees with the low level winds in extensive areas of the middle latitudes and ranges from 12 m s 1 in the indian ocean to 6 m s 1 in the pacific ocean the estimated group velocities achieve maximum values of about 38 m s 1 also in the indian ocean and agree with the upper level maximum winds in accor

variability in warm season atmospheric circulation and precipitation patterns over subtropical south america relationships between the south atlantic convergence zone and large scale organized convection over the la plata basin warm season precipitation variability over subtropical south america is characterized by an inverse relationship between the south atlantic convergence zone sacz and precipitation over the central and western la plata basin of southeastern south america this study extends the analysis of this south american seesaw precipitation dipole to relationships between the sacz and large long lived mesoscale convective systems llcss over the la plata basin by classifying sacz events into distinct continental and oceanic categories and building a logistic regression model that relates llcs activity across the region to continental and oceanic sacz precipitation a detailed account of spatial variability in the out of phase coupling between the sacz and large scale organized convection over the la plata basin is provided enhanced precipitation in the continental sacz is found to result in increased llcs activity over northern northeastern and western sections of the la plata basin in association with poleward atmospheric moisture flux from the amazon basin toward these regions and a decrease in the probability of llcs occurrence over the southeastern la plata basin increased oceanic sacz precipitation however was strongly related to reduced atmospheric moisture and decreased probability of llcs occurrence over nearly the entire la plata basin these results suggest that continental sacz activity and large scale organized convection over the northern and eastern sections of the la plata basin are closely tied to atmospheric moisture transport from the amazon basin while the warm coastal brazil current may also play an important role as an evaporative moisture source for llcss over the central and western la plata basin

a stalagmite record of changes in atmospheric circulation and soil processes in the brazilian subtropics during the late pleistocene we present a high resolution 116 000 year carbon stable isotope record from a stalagmite from southern brazil which has been precisely dated using the u series method evaluation of carbon and oxygen isotope ratios together with the speleothem growth history suggest that the carbon isotopic composition of the speleothem is primarily controlled by biogenic co2 supply from the soil which is in turn affected by temperature and secondarily rainfall amount thus the speleothem provides evidence of paleoenvironmental change in southern brazil during the last glacial period predominantly high d 13 c values and low stalagmite growth rates reflect persistent cool conditions during most of the glacial period in subtropical brazil this cooling is probably related to an intensified extratropical circulation with more frequent and intense cold surges reaching a maximum at approximately 19 ky b p this cooling tendency is interrupted during periods of high obliquity values within the full glacial period at 93 85 and 47 40 ky b p and after 19 ky b p when a dramatic decrease in d 13 c marks the deglaciation time in the continent unlike d 18 o the d 13 c record does not exhibit a strong response to precessional forcing instead it shows a strong 40 ky obliquity signal here we propose that local temperature and thus the biological processes in the soil are primarily steered by the gradients of temperature between low and mid high latitudes which influence the meridional heat transport these gradient changes in turn are paced by obliquity r 2006 published by elsevier ltd

subpolar high anomaly preconditioning precipitation over south america abstract the mechanisms associated with the intraseasonal variability of precipitation over south america during the spring season are investigated with emphasis on the influence of a quasi stationary anomalous circulation over the southeastern south pacific ocean sep a spectral analysis performed to the bandpass filtered time series of daily precipitation anomalies for the la plata basin lpb and the south atlantic convergence zone sacz regions revealed several statistically relevant peaks corresponding to periods of roughly 23 days and 14 16 days with the lower higher frequency peaks more prevalent for the sacz lpb the large scale circulation patterns preconditioning precipitation variability over both regions were explored by means of a regression analysis performed on the daily 500 hpa geopotential anomaly field provided by the ncep ncar reanalysis dataset the most prominent feature of the regression fields is the presence of a quasi stationary anomalous anticyclonic cyclonic circulation

methane origin in the samail ophiolite comment on modern water rock reactions in oman hyperalkaline peridotite aquifers and implications for microbial habitability geochim cosmochim acta 179 2016 217 241

origin of convectively coupled kelvin waves over south america convectively coupled kelvin waves over the south american continent are examined through the use of temporal and spatial filtering of reanalysis satellite and gridded rainfall data they are most prominent from november to april the season analyzed herein the following two types of events are isolated those that result from preexisting kelvin waves over the eastern pacific ocean propagating into the continent and those that apparently originate over amazonia forced by disturbances propagating equatorward from central and southern south america the events with precursors in the pacific are mainly upper level disturbances with almost no signal at the surface those events with precursors over south america on the other hand originate as upper level synoptic wave trains that pass over the continent and resemble the cold surges documented by garreaud and wallace as the wave train propagates over the andes it induces a southerly low level wind that advects cold air to the north precipitation associated with a cold front reaches the equator a few days later and subsequently propagates eastward with the characteristics of a kelvin wave the structures of those waves originating over the pacific are quite similar to those originating over south america as they propagate to eastern south america and into the atlantic south america kelvin waves that originate over neither the pacific nor the midlatitudes of south america can also be identified in a composite sense these form over the eastern slope of the andes mountains close to the equator there are also cases of cold surges that reach the equator yet do not form kelvin waves the interannual variability of the pacific originating events is related to sea surface temperatures in the central eastern pacific ocean when equatorial oceanic conditions are warm there tends to be an increase in the number of disturbances that reach south america from the pacific

assessing pedogenic calcite stable isotope values can positive linear covariant trends be used to quantify palaeo evaporation rates abstract palaeoclimate models suggest enhanced evaporation rates in subtropical regions 15 30 latitude during greenhouse world conditions however there are no empirical data to support these estimates laboratory evaporation experiments have shown that calcites precipitated from variably saturated solutions yield a positive linear covariant trend plct in 18 o calcite versus 13 c calcite values the goal of the present controlled laboratory experiments is to develop a method to quantify regional palaeo evaporation rates from palaeosol calcrete plcts samples of powdered caco 3 were dissolved in de ionized water in pressure sealed containers with a range of elevated atmospheric p co 2 concentrations for 24 h the solution was then allowed to evaporate completely from an open container within an incubator with the time of calcite crystallization noted and aliquots removed for analysis every 24 h the precipitated calcite produced an array of 18 o calcite versus 13 c calcite values that fall upon a plct projected from a theoretical meteoric calcite line mcl water analyses yielded 18 o water enrichments from an initial value of 4 75 vsmow ranging up to between 10 0 and 14 8 the experimental results show that solutions formed under higher p co 2 conditions precipitated calcite very early on during evaporation and thus have 18 o calcite and 13 c calcite values that are slightly enriched relative to the mcl the solutions that formed under low p co 2 conditions precipitated calcite after much of the fluid had evaporated and thus yield more enriched 18 o calcite and 13 c calcite values repeat trials with varying temperature and relative humidity show that the plct is steeper under both higher temperature and low relative humidity the wide range of p co 2 temperature and relative humidity conditions used simulate meteoric phreatic and meteoric vadose conditions that may affect a calcrete horizon over time during numerous dissolution precipitation reactions the results of these experiments show that a dominant factor in the precipitation of vadose calcite is the saturation state of the fluid with respect to caco 3 while the primary factors affecting the magnitude and steepness of the plct are vadose zone temperature relative humidity the starting 18 o water value and saturation state of the fluid with respect to caco 3 since the p co 2 of the rooting zone is cross controlled by the local soil and surface ecology the magnitude of the plct enrichment may not be a direct proxy for palaeo evaporation rates

structure and characteristics of submonthly scale waves along the indian ocean itcz this study examines wave disturbances on submonthly 6 30 day timescales over the tropical indian ocean during southern hemisphere summer using japanese reanalysis jra25 jcdas products and national oceanic and atmospheric administration outgoing longwave radiation data the analysis period is december february for the 29 years from 1979 1980 through 2007 2008 an extended empirical orthogonal function eeof analysis of daily 850 hpa meridional wind anomalies reveals a well organized wave train pattern as a dominant mode of variability over the tropical indian ocean daily lagged composite analyses for various atmospheric variables based on the eeof result show the structure and evolution of a wave train consisting of meridionally elongated troughs and ridges along the indian ocean intertropical convergence zone itcz the wave train is oriented in a northeast southwest direction from sumatra toward madagascar the waves have zonal wavelengths of about 3 000 5 000 km and exhibit westward and southwestward phase propagation individual troughs and ridges as part of the wave train sequentially travel westward and southwestward from the west of sumatra into madagascar meanwhile eastward and northeastward amplification of the wave train occurs associated with the successive growth of new troughs and ridges over the equatorial eastern indian ocean this could be induced by eastward and northeastward wave energy dispersion from the southwestern to eastern indian ocean along the mean monsoon westerly flow in addition the waves modulate the itcz convection correlation statistics show the average behavior of the wave disturbances over the tropical indian ocean these statistics and other diagnostic measures are used to characterize the waves obtained from the composite analysis the waves appear to be connected to the monsoon westerly flow the waves tend to propagate through a band of the large meridional gradient of absolute vorticity produced by the mean monsoon westerly flow this suggests that the monsoon westerly flow provides favorable background conditions for the propagation and maintenance of the waves and acts as a waveguide over the tropical indian ocean the horizontal structure of the wave train may be interpreted as that of a mixture of equatorial rossby waves and mixed rossby gravity wavelike gyres

the modification of baroclinic waves by the rocky mountains abstract the author diagnoses two observed cases of rocky mountain lee cyclogenesis and perform several idealized simulations to understand the effect of the mountains on incident baroclinic waves several issues are examined 1 in what sense is the effect of the mountains cyclolytic and why 2 what is the effect of adding a mean surface wind 3 what sorts of behavior may result in differing mean flows and 4 what is a useful conceptual framework in which to view lee cyclogenesis the dynamical underpinning for analysis of observations and idealized simulations is the quasigeostrophic qg equations the author finds that the most important effect of the mountains is to alter the mean distribution of surface potential temperature and hence change the propagation characteristics of the incident baroclinic wave the presence of a mountain enhances the gradient of the qg approximation to surface potential temperature to the north of the peak and decreases it to the south thus the component of the b

stable isotopic composition of soil calcite o c and gypsum s overlying cu deposits in the atacama desert chile implications for mineral exploration salt sources and paleoenvironmental reconstruction abstract soils overlying two porphyry cu deposits spence gaby sur and the pampa del tamarugal atacama desert northern chile were collected in order to investigate the extent to which saline groundwaters influence soil chemistry in regions with thick miocene and younger sediment cover soil carbonate calcite was analyzed for c and o isotopes and pedogenic gypsum for s isotopes soil calcite is present in all soils at the spence deposit but increases volumetrically above two fracture zones that cut the miocene gravels including gravels that overlie the deposit the c isotope composition of carbonate from the soils overlying fracture zones is indistinguishable from pedogenic carbonate elsewhere at the spence deposit all 13 c vpdb values fall within a narrow range 1 40 4 23 consistent with the carbonate having formed in equilibrium with atmospheric co 2 however 18 o vpdb for carbonate over both fracture zones is statistically different from carbonate elsewhere average 18 o vpdb 0 82 vs 2 23 respectively suggesting involvement of groundwater in their formation the composition of soils at the tamarugal anomaly has been most strongly affected by earthquake related surface flooding and evaporation of groundwater 13 c vpdb values 4 28 to 2 04 are interpreted to be a mixture of dissolved inorganic c dic from groundwater and atmospheric co 2 at the spence deposit soils only rarely contain sufficient so 4 for s isotope analysis the so 4 bearing soils occur only above the fracture zones in the gravel results are uniform 3 7 4 9 34 s cdt which is near the middle of the range for so 4 in groundwater 0 9 7 3 sulfur in soils at the gaby sur deposit 3 8 6 1 34 s cdt is dominated by gypsum which primarily occurs on the flanks and tops of hills suggesting deposition from so 4 rich fogs sulfate in gaby sur deposit gypsum is possibly derived by condensation of airborne so 4 from volcanic so 2 from the nearby andes at the gaby sur deposit and tamarugal anomaly pedogenic stable isotopes cannot distinguish between s from porphyry or redeposited so 4 from interior salars the three sites studied have had different histories of salt accumulation and display variable influence of groundwater which is interpreted to have been forced to the surface during earthquakes the clear accumulation of salts associated with fractures at the spence deposit and shifts in the isotopic composition of carbonate and sulfate in the fractures despite clear evidence of relatively recent removal of salts indicates that transfer from groundwater is an ongoing process the interpretation that groundwaters can influence the isotopic composition of pedogenic calcrete and gypsum has important implications for previous studies that have not considered this mechanism

diagnostic study of explosive cyclogenesis during fgge abstract two rapidly developing extratropical maritime cyclones are studied using the european centre for medium range weather forecasting ecmwf level iii b analyses from the first garp global experiment fgge the first cyclone forms over the western north pacific ocean along an intense frontal zone south of japan while the second develops in a polar air mass over the north atlantic ocean quasi lagrangian diagnostic techniques in isobaric coordinates are used in a synoptic investigation and mass and vorticity budget diagnostic evaluation of storm development reliable diagnostics are obtained from the ecmmwf analyses over these ocean areas using 0000 and 1200 utc data although the cyclones develop under almost unperturbed upper level flow resembling petterssen type a development rapid deepening in both cases occurs when an approaching upper tropospheric jet with appreciable shear vorticity advection becomes favorably superposed over the surface low stability decreases in the low troposphere durin

influence of surface sensible heat flux on incipient marine cyclogenesis abstract incipient marine cyclogenesis is investigated as an instability process of a mean baroclinic state with a vertically nonuniform static stability under the influence of a self induced surface sensible heat flux in the context of a quasigeostrophic model framework the analytic solution of such a model is first presented the surface sensible heat flux induces strongly unstable short waves in the meso range and an e folding time of the order of one day under supposedly relevant parameter conditions those modes have a shallow vertical structure near the surface with a pronounced westward tilt with height the latter facilitates a release of enough potential energy from the basic state to overcompensate the destruction of potential energy by the surface heat exchange itself the diabatic destabilization by surface sensible heat flux is therefore an alternative mechanism for initiating small marine cyclones without upper level forcing a potential vorticity interpretation of this instability proces

links between topography moisture fluxes pathways and precipitation over south america the andes cordillera plays a role in driving moisture and heat from tropical onto subtropical south america it forces the development of a lee side trough that covers most of western argentina and a low level jet that maximizes over paraguay eastern bolivia and northern argentina and is tightly linked to precipitation variability over much of central and southeastern south america its steep slopes and the large zonal gradients in topography between the equator and 40 s are misrepresented in climate simulations using global climate models gcm with resolutions coarser than about 100 km since they naturally have a poor representation of the andes and related circulation features this paper analyses the impact of varying artificially the altitude of the andes cordillera in a gcm as well as increasing the horizontal resolution to study how these variations determine moisture fluxes and precipitation over selected regions of south america results show that the height of the andes is crucial in shaping moisture fluxes pathways onto subtropical south america all year long in particular the low level jet is only simulated when the andes heights are doubled at the same time the relationship between the andes shape and the location of the bolivian high in summer is also discussed in terms of precipitation the lowest bias in the simulations is achieved when the horizontal resolution is increased while in particular near the andes foothills the simulated annual rainfall is largely determined by the mountains shape

statistical behavior of transient eddies near mountains and implications for theories of lee cyclogenesis abstract we examine the nature and spatial structure of meteorological high frequency variability in two selected areas one including the alps and the other the rocky mountains seven years of geopotential height data derived from ecmwf analysis set have been filtered in order to remove periods longer than 6 7 days statistical analysis performed on the filtered series include one point lag correlations and composites that reveal changes in the typical horizontal structure and path of traveling eddies as they move from the oceans to the adjacent mountainous regions the important modifying action of the orography is shown and lee cyclogenesis is interpreted as one aspect of such action cross correlation maps between upper and lower tropospheric levels reveal the effect that mountains also exert on the vertical structure of baroclinic eddies these statistical results are discussed and compared with those predicted by theories of cyclogenesis in the lee of the alps and the rocky mountains and by the

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

composition of groundwaters associated with porphyry cu deposits atacama desert chile elemental and isotopic constraints on water sources and water rock reactions abstract groundwaters were collected around the spence porphyry copper deposit atacama desert northern chile to study water porphyry copper ore bodies interaction and test hypotheses regarding transport of metals through thick overburden leading to the formation of soil geochemical anomalies the deposit contains 400 mt of 1 cu and is completely buried by piedmont gravels of miocene age groundwaters were recovered from the eastern up hydraulic gradient upflow margin of the spence deposit from within the deposit and for two kilometers down flow from the deposit water table depths decrease from 90 m at the upflow margin to 30 m 1 5 km down flow groundwaters at the spence deposit are compositionally variable with those upflow of the deposit characterized by relatively low salinities 900 7000 mg l and na so42 type compositions these waters have compositions and stable isotope values similar to regional groundwaters recovered elsewhere in the atacama desert of northern chile in contrast groundwaters recovered within and down flow of the deposit range in salinity from 10 000 to 55 000 mg l one groundwater at 145 000 mg l and are dominantly na cl type waters dissolved sulfate values are however elevated compared to upflow waters and 34scdt decreases into the deposit from 4 to 2 consistent with increasing influence of sulfur derived from oxidation of sulfide minerals within the deposit the increase in salinity and conservative tracers cl br li and na and the relationship between oxygen and hydrogen isotopes suggests that in addition to water rock reactions within the deposit most of the compositional variation can be explained by groundwater mixing with perhaps a minor role for evaporation a groundwater mixing scenario implies a deeper more saline groundwater source mixing with the less saline regional groundwater flow system flow of deeper more saline groundwater along pre existing structures has important implications for geochemical exploration and metal transport models

observed southern hemisphere eddy statistics at 500 mb frequency and spatial dependence abstract nearly eight years of daily southern hemisphere analyses at 500 mb have been used to define the spatial dependence of the variance fields of geopotential height and the two geostrophic wind components the corresponding covariance fields and the transient kinetic energy the fields are further examined in the frequency domain by using lorenz 1979 poor man s spectral analysis technique in view of the small variation in eddy statistics as a function of the time of the year in the sh this study removes the first four harmonies of the annual cycle and then considers all data together so that contributions from all time scales from 2 to 4096 days 11 years can be resolved the main results are based on analyses from may 1972 january 1978 but are verified with analyses from the relatively data rich fgge period results for the zonal mean statistics are compared with those from previous studies the zonal means of the geopotential height and westerly wind component have spectra which roughly

extratropical forcing of tropical wave disturbances along the indian ocean itcz the role of extratropical waves in the excitation of tropical waves on submonthly timescales is explored along the indian ocean intertropical convergence zone itcz during the austral summer using japanese reanalysis products and noaa outgoing longwave radiation data the analysis period is december february of 1979 1980 to 2008 2009 the submonthly tropical waves are regarded as a type of rossby wave propagating along the mean monsoon westerly flow they play an important role in modulating the indian ocean itcz convection the linkage between the tropical and extratropical waves which is responsible for the formation and strengthening of tropical waves is examined composite analysis results linked to the tropical wave train development show that the midlatitude rossby wave train progresses eastward and northeastward from the south atlantic into the subtropical indian ocean as a trough and ridge that form part of the midlatitude wave train approach the southern africa southwest indian ocean swio region a southwest northeast oriented wave train is subsequently established originating from this feature and is strengthened across the tropical indian ocean the midlatitude wave propagation toward the subtropics induces the growth of the trough and ridge over the swio wave activity flux diagnostics indicate that the amplified trough and ridge over the swio act as an energy source for northeastward amplification of the tropical waves through the wave energy dispersion process the results suggest that the propagation of the midlatitude wave toward the swio is the fundamental mechanism behind the development of the tropical waves along the indian ocean itcz

extensive and rapid changes in seawater chemistry during the phanerozoic evidence from br contents in basal halite abstract variation of seawater chemical composition during the phanerozoic is still a contentious subject br concentration in primary marine basal halites was used to indicate variations in seawater composition during the past 550 ma evaporation experiments and thermodynamic modelling suggests that the partition coefficient of br in halite depends on the composition of the seawater a combination of this correlation with the time dependent models for ocean chemistry of hardie leads to a prediction of br in basal halite during the phanerozoic this prediction is in good agreement with data from different ancient evaporite basins the br data give evidence for rapid and massive changes in seawater chemistry during the phanerozoic and are thus a first independent test for the hardie model

evidence of rainfall variations in southern brazil from trace element ratios mg ca and sr ca in a late pleistocene stalagmite trace element ratios in the bt2 stalagmite from botuveracave southern brazil are explored as a proxy for changes in the local rainfall recharge during the last 116 ky bp mg ca and sr ca ratios measured with an electron microprobe are signif icantly positively correlated with one another throughout the entire record and vary in a way that is very consistent with variations of d 18 o in the same speleothem during the last glacial period we suggest that prior calcite precipitation in the vadose zone of the cave system is the main factor affecting the incorporation of mg and sr into calcite of the stalagmite this interpretation is supported by trace element correlation patterns and by results from a hydrochemistry study performed in a cave located in the same region and in a similar environmental setting therefore we conclude that higher lower mg ca and sr ca values are associated with lower higher levels of recharge into the karstic aquifer as such conditions lead to an increase decrease in the volume of calcite precipitated in the unsaturated zone above the cave during dry wet climate periods trace element variations point to generally dryer wetter conditions during lower high phases of summer insolation in the southern hemisphere these periods coincide with decreased increased activity of the south american summer monsoon as revealed by d 18 o stalagmite records in addition trace element variations show that rather wet conditions persisted through out most of the last glacial period from approximately 70 to 17 ky bp we suggest that during this period the glacial boundary conditions especially ice volume buildup in the northern hemisphere played an important role for monsoon rainfall inten sification in the region 2007 elsevier ltd all rights reserved

weathering on land and transport of chromium to the ocean in a subtropical region misiones nw argentina a chromium stable isotope perspective abstract we have investigated the pathway of chromium from its mobilization on land and along its riverine transport in a subtropical region of south america misiones province argentina in an attempt to link cr stable isotope compositions recently measured in seawater with signals prevailing in rivers and ultimately with cr isotope effects observed during oxidative surface weathering in subtropical red soils cr concentrations and stable cr isotopic compositions expressed as 53cr values in two typical and representative surface profiles of weathered basalt show significant depletion of cr in the soils of up to 50 together with pronounced negatively fractionated 53cr values which are indicative of oxidative mobilization of heavy cr vi into the run off the behavior of cr in the studied weathering profiles is not correlated with that of other redox sensitive elements such as ce and u this is essentially due to the affinity of ree and u but not cr with secondary phosphates which form during weathering processes smaller tributaries in nw argentina to the parana river second largest river in south america carry dissolved cr in the order of 0 7 1 4 ppb 13 27 nm with 53cr values of 0 2 to 0 4 balancing the negatively fractionated weathering products the isotope composition and concentration of dissolved cr in the ca 1200 km long parana river from misiones to its estuary and discharge area into the south atlantic ocean remains relatively constant with an average cr concentration around 2 4 ppb 46 nm and an average 53cr value of 0 32 the cr concentration in the estuary itself drops by ca 50 but with only minor change in its cr isotope composition results from the parana estuary are identical with recently analyzed surface seawater from the argentine basin with cr contents of 0 3 ppb 6 nm and 53cr values 0 4 bonnand et al 2013 and indicate that there is only a minimal cr isotopic variability during riverine transport even during long transport distances as shown in our example of the parana river simple cr input flux calculations reveal that the parana river accounts for 5 of the total yearly cr flux to the world s oceans today and that its isotopic signature seems to be at least locally imparted to the surface seawater of the argentine basin whether or not this cr isotope signature is generally exhibited by the world s oceans needs further investigations particularly the characterization of seawater around the globe

reconstruction of regional atmospheric circulation features during the late pleistocene in subtropical brazil from oxygen isotope composition of speleothems two high resolution oxygen isotope records of speleothems from caves located in subtropical brazil provide a broad view of regional climate variations and related forcing during the late pleistocene and holocene here we present a new record precisely dated by u series extending back to 131 kyr bp from a speleothem collected in santana cave comparison with the 116 kyr bp record from botuvera cave confirms that the seasonal change in regional rainfall distribution is primarily controlled by variations in summer insolation on milankovitch timescales however significant negative anomalies of 18 o from 60 kyr bp to 10 kyr bp in the records suggest that the northern hemisphere glacial boundary conditions in particular heinrich events impacted the mean location and or convective activity of the south american summer monsoon sasm resulting in enhanced transport of depleted moisture from the amazon basin into the region in addition comparison of the two records indicates a steep north south gradient in 18 o of rainfall throughout which is interpreted as reflecting different relative contribution of extratropical and monsoonal precipitation to the two locations for some time periods more pronounced negative 18 o anomalies occur in the northern part and more positive anomalies in the southern part of the region which appear to be associated with more abundant monsoonal and extratropical rainfall respectively the last interglacial period is characterized by the highest 18 o values in the entire st8 record indicating a dominance of extratropical winter rainfall and thus the most northward position of the summer sasm for the last 131 kyr bp 2006 elsevier b v all rights reserved

the signature of the midlatitude tropospheric storm tracks in the surface winds abstract storm track analysis is applied to the meridional winds at 10 m and 850 hpa for the winters of 1999 2006 the analysis is focused on the north atlantic and north pacific ocean basins and the southern ocean spanning the region south of the indian ocean the spatial patterns that emerge from the analysis of the 850 hpa winds are the typical free tropospheric storm tracks the spatial patterns that emerge from the analysis of the surface winds differ from the free tropospheric storm tracks the spatial differences between the surface and free tropospheric storm tracks can be explained by the influence of the spatial variability in the instability of the atmospheric boundary layer strongly unstable boundary layers allow greater downward mixing of free tropospheric momentum momentum mixing and this may be the cause of the stronger surface storm tracks in regions with greater instability in the time mean principal component analysis suggests that the basin scale variability that is reflected in th

mesoscale convective systems over southeastern south america and their relationship with the south american low level jet abstract prior studies have shown that the low level jet is a recurrent characteristic of the environment during the initiation and mature stages of mesoscale convective systems mcss over the great plains of the united states the south american low level jet sallj over southeastern south america sesa has an analogous role advecting heat and moisture from the amazon basin southward into the central plains of southeastern south america generating ideal environmental conditions for convection initiation and growth into mcss this research has two purposes one is to describe the characteristics of a 3 yr mcs sample in south america south of the equator and its related geographical distribution of convection frequency the other is to advance the knowledge of the evolution of favorable environmental conditions for the development of large mcss specifically those that mature under sallj conditions high horizontal and temporal resolution satellite images are used to detect mcss in the area for the

a model of rocky mountain lee cyclogenesis abstract a quasi geostrophic model of cyclogenesis in the lee of the rocky mountains treats the cyclogenesis as a forecasting problem and uses an initial value approach the model consists of the interaction of a growing baroclinic wave with an infinitely long mountain ridge this transient interaction simulates many of the observed features of the phenomena including the formation of a lee trough concurrent with the poleward displacement of the incident low on the upstream side of the mountain and the development of a lee cyclone equatorward of the unperturbed storm track despite this development the low is weakened by its interaction with the orography these results are explained physically and compared with those using a normal mode approach to lee cyclogenesis

the shape propagation and mean flow interaction of large scale weather systems abstract for a zonal average operator the eliassen palm flux provides a diagnostic of both eddy behavior and the feedback of the eddies onto the mean flow this paper addresses the diagnosis problem for other averaging operators and in particular for time averaging which has proved in recent years such a powerful means of viewing the three dimensional tropospheric flow the horizontal velocity correlation tensor gives a measure of the characteristic horizontal eddy shape at a point it also implies the direction of the group velocity relative to the mean flow in cases where such a concept is valid however the major emphasis here is on the mean flow feedback of eddies in this respect the eddy vorticity flux is determined by derivatives of the components of the anisotropic part of the tensor making a reasonable approximation allows the eddy vorticity flux convergence to be written in terms of e v 2 u 2 u v a simple interpretation of the mean flow feedback of eddies is then possible a sligh

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

characteristics of wave packets in the upper troposphere part ii seasonal and hemispheric variations abstract gridded 300 hpa meridional wind data produced by the ecmwf reanalysis project were analyzed to document the seasonal and hemispheric variations in the properties of upper tropospheric wave packets the properties of the wave packets are mainly illustrated using time lagged one point correlation maps performed on based on indices that show the coherence of wave propagation as well as examination of correlation maps schematic waveguides were constructed for the summer and winter seasons of both hemispheres along which waves preferentially propagate with greatest coherence in the summers the waveguides basically follow the position of the midlatitude jets in the northern hemisphere winter the primary waveguide follows the subtropical jet over southern asia into the pacific but there is a secondary branch running across russia joining the primary waveguide near the entrance to the pacific storm track over the atlantic the waveguide passes east southeastward toward north africa then bac

large scale carbon isotope fractionation in evaporites and the generation of extremely 13c enriched methane petrographic fluid inclusion geochemical and gas stable isotope data are reported here for a permian zechstein evaporite sequence this deposit is a geochemically unaltered sequence bromine concentrations show a continuous evaporation profile with little postdepositional alteration in halite chemistry bacterial fermentation gases identified in primary inclusions change from an n 2 h 2 s composition in the lower middle halite series to a ch 4 h 2 composition in the upper halite and potash series carbon isotope results for ch 4 show a 1 3 c enrichment up sequence from typical biogenic values of 45 to 50 to extremely unusual 1 3 c enriched values as high as 21 the d values for these 1 3 c enriched ch 4 gases range from 240 to 377 a model is proposed for the formation of the ch 4 gases whereby the dominant isotopic fractionation process controlling the system was evaporation of the brines this generated a progressive 1 3 c enrichment in the carbon in the residual brines due to preferential loss of 1 2 co 2 to the atmosphere the resulting ch 4 generated in the sediments as evaporation and precipitation advanced recorded this 1 3 c enrichment in the carbon reservoir therefore the isotopic profile observed in this sequence today represents a primary feature with little evidence for postdepositional migration

vertical structure of wintertime teleconnection patterns abstract orthogonal rotated principal component analysis of the wintertime northern hemisphere 5 day mean sea level pressure field yielded five modes which are of some dynamical interest one can be identified with the well known north atlantic oscillation and another with the pacific north american pattern three of the other modes are highly baroclinic in the sense that their sea level pressure patterns and their associated 500 mb height patterns are different in shape and opposite in polarity over substantial areas these more baroclinic patterns attain their largest amplitudes in the vicinity of the himalayas and rockies their spatial patterns evolve very differently in the lower and middle troposphere the sea level pressure patterns exhibit a distinctive eastward and or equatorward phase propagation parallel to contours of surface elevation along the northern and or eastern side of the mountain ranges while the corresponding 500 mb patterns evolve in a manner consistent with the concept of ros