late quaternary mega lakes fed by the northern and southern river systems of central australia varying moisture sources and increased continental aridity optically stimulated and thermoluminescence ages from relict shorelines along with accelerator mass spectrometer 14c ages from freshwater molluscs reveal a record of variable moisture sources supplied by northern and southern river systems to lake mega frome in southern central australia during the late quaternary additional lacustrine palynological and terrestrial proxies are used to reconstruct a record that extends back to 105 ka confirming that lakes mega frome and mega eyre were joined to create the largest system of palaeolakes on the australian continent as recently as 50 47 ka the palaeohydrological record indicates a progressive shift to more arid conditions with marked drying after 45 ka subsequently lake mega frome has filled independently at 33 31 ka and at the termination of the last glacial maximum to volumes some 40 times those of today further sequentially declining filling episodes to volumes 25 10 those of today occurred immediately prior to the younger dryas stadial in the mid holocene and during the medieval climatic anomaly southern hemisphere summer insolation maxima are a poor predictor of palaeolake filling episodes an examination of multiple active moisture sources suggests that palaeolake phases were driven independently of insolation and at times by some combination of enhanced southern ocean circulation and strengthened tropical moisture sources

short period fluctuations of the diurnal tide observed with low latitude mf and meteor radars during cadre evidence for gravity wave tidal interactions mf and meteor radar data from four equatorial and subtropical sites hawaii christmas island jakarta and adelaide are used to examine diurnal tide amplitude and phase variability at mesosphere and lower thermosphere altitudes all sites exhibit significant seasonal variability with the largest amplitude fluctuations occurring at hawaii and adelaide shorter term variability is found to occur primarily on timescales of 5 to 30 days amplitude and phase fluctuations are well correlated among different sites on occasion but in general the amplitude and phase coherences are low and suggest significant local influences on the tidal structures the temporal behavior of height variations of the diurnal tide amplitude and phase is also examined cross correlations and cross spectra of these tidal parameters especially between the amplitude and phase are examined closely the tendency for phase maxima to lead amplitude maxima is consistent with tidal modulation of gravity wave propagation and momentum fluxes with a corresponding feedback by the gravity wave momentum flux divergences on the observed tidal structures these results substantially extend previous more limited studies of gravity wave tidal interactions and provide a statistical basis for the possible importance of this interaction and its influences on the diurnal tidal structure

late quaternary climates of the australian arid zone a review abstract aridity in australia has generally been associated with glacial intervals of the last few glacial cycles the causes and nature of aridity varied from north to south over the continent in northern and central australia reduced monsoon rain in global cold stages caused lakes and rivers to dry vegetation to become more sparse sand dunes to become active and dust advection to increase while the monsoon is correlated with warmer global temperatures and high sea levels overall the exact timing of the greatest development of the monsoon in stage 5 remains uncertain in southeastern australia the proxy records give a less clear picture while vegetation seems to have been more sparse in cold stages and sand dune activity and dust flux consequently greater records of runoff in rivers and lakes have mixed or opposite behaviour to northern or central australia the nature of aridity in southeastern australia is not analogous to conditions anywhere on the continent today greatly reduced temperatures over the central and southern interior greater influence of snow and periglaciation on runoff high groundwater tables lower rainfall and reduced atmospheric carbon dioxide levels may all have contributed to and interacted to produce the reconstructed picture of a cold sparsely vegetated arid landscape with large rivers and perennial lakes the largest changes in circulation patterns over the glacial cycle probably occurred in the location and or intensity of summer tropical convergence in northern australia over southern australia changes to the temperature and humidity of the westerly circulation have been more significant than the small fluctuations in latitude of the sub tropical high pressure ridge

a radiocarbon chronology from the playa lake tyrrell northwestern victoria australia abstract dating sediments with a low organic carbon content has proved a considerable problem in playa palaeoenvironments conversion of organic carbon contained in sediments to strontium carbonate eases handling of the otherwise large samples needed to obtain radiocarbon dates from such material concentrated carbon samples were used to erect a chronology of sedimentation in the upper levels of lake tyrrell after 10 000 yr b p and comparisons made between radiocarbon ages for comparable stratigraphic horizons in cores from two sites in the northern basin of the lake reference is also made to a third series of dates which have a bearing upon the earlier history of deflation from the lake basin

last glacial to holocene evolution of semi arid rangelands in southeastern australia pollen sequences from playa lakes in the darling anabranch dunefields of southwestern new south wales record vegetation changes over the last glacial period and into the holocene this interval was one of marked taxonomic and structural reorganization with the plant communities that became established after the last glacial maximum lgm 24 18 ka distinct from those that had prevailed over the build up to full glacial conditions 70 24 ka the glacial period was characterized by a gradual reduction of woodland and tall shrubland cover recolonization of the dunefields involved a similar gradual succession from herbfields and low shrublands to tall shrublands and finally woodlands these changes are likely to have been driven by climatic change particularly fluctuations in temperature precipitation and atmospheric co2 as global climate systems entered and emerged from the last glaciation

amplitude phase and period variations of the quasi 2 day wave in the mesosphere and lower thermosphere over london canada 43 n 81 w during 1993 and 1994 because there is as yet no conclusive evidence pointing to the source of the quasi 2 day wave further observations are required in order to resolve questions about the generating mechanism as well as to better understand the role of the wave in the middle atmosphere in this paper we investigate the period amplitude phase and vertical wavelength for the quasi 2 day wave in the mesosphere and lower thermosphere using the university of western ontario 2 mhz radar near london canada and in addition we look at possible coupling with atmospheric tides the results of the present study bring out certain new aspects of the quasi 2 day wave at midlatitude in the northern hemisphere that have not been previously reported in particular we show that the period of the quasi 2 day wave determined from our study is smaller 46 47 hours than the 51 to 52 h period generally suggested by other northern hemisphere results and our periods also showed variability as a function of time we also draw attention to the annual variability and especially highlight the occurrence of the wave in nonsummer months for example a brief occurrence in april is not uncommon our study also contributes additional midlatitude geographical data that should aid in developing a better picture of the quasi 2 day wave

mesospheric momentum flux studies at adelaide australia observations and a gravity wave tidal interaction model abstract we present here the results of an analysis of gravity wave momentum fluxes in the mesosphere and lower thermosphere inferred using a dual beam doppler radar near adelaide australia during june 1984 our analysis reveals that over 70 of the momentum flux and of the inferred zonal drag was due to gravity waves with observed periods less than one hour this suggests that it is the gravity waves with high intrinsic frequencies and small horizontal scales that are most effective at transporting momentum into the middle atmosphere the temporal variations in the momentum flux and flux divergence due to high frequency motions were also examined in detail in addition to daily variability a strong diurnal modulation was observed to occur this was found to be correlated with the phase of large amplitude diurnal tidal motions as a result of these observations a gravity wave tidal interaction model was proposed which accounts for all of the major features of the observed data including a reduction i

continental aridification and the vanishing of australia s megalakes the nature of the australian climate at about the time of rapid megafaunal extinctions and humans arriving in australia is poorly understood and is an important element in the contentious debate as to whether humans or climate caused the extinctions here we present a new paleoshoreline chronology that extends over the past 100 k y for lake mega frome the coalescence of lakes frome blanche callabonna and gregory in the southern latitudes of central australia we show that lake mega frome was connected for the last time to adjacent lake eyre at 50 47 ka forming the largest remaining interconnected system of paleolakes on the australian continent the final disconnection and a progressive drop in the level of lake mega frome represents a major climate shift to aridification that coincided with the arrival of humans and the demise of the megafauna the supply of moisture to the australian continent at various times in the quaternary has commonly been ascribed to an enhanced monsoon this study in combination with other paleoclimate data provides reliable evidence for periods of enhanced tropical and enhanced southern ocean sources of water filling these lakes at different times during the last full glacial cycle

the terdiurnal tide in the mesosphere and lower thermosphere over london canada 43 n 81 w radars have been used successfully for many years to measure atmospheric diurnal and semidiurnal tides but studies of the atmospheric terdiurnal tide have only rarely been reported to date in the literature in this paper we investigate the amplitude phase and vertical wavelength for the terdiurnal tide using the university of western ontario uwo 2 mhz radar near london canada emphasis is placed on short term monthly seasonal and annual variations of the terdiurnal tide the results of the present study bring out certain new aspects of the terdiurnal tide at midlatitudes in the northern hemisphere we show that terdiurnal tides have significant amplitudes in the mesosphere and lower thermosphere indeed the terdiurnal amplitudes are often comparable to the diurnal ones we also draw attention to the annual variability and especially highlight the occurrence of the terdiurnal tide in non winter months for example the occurrence of the terdiurnal tide in spring months is not uncommon thus it seems that the 8 hour component observed over london canada cannot be explained by the terdiurnal tide being due to solar heating alone particular cases of the terdiurnal tide are examined and the observed amplitude and phase profiles of the terdiurnal tide at certain times of the year are discussed in terms of nonlinear interaction between the diurnal and semidiurnal tides we suspect that this effect may also explain the fact that diurnal and semidiurnal tides at our station often seem suppressed relative to other sites thayaparan et al 1995a on the basis of our previous and present observations it is also possible that large terdiurnal amplitudes observed at certain times of the year may be partly explained in terms of tidal gravity wave interactions however this possibility needs to be further investigated in the future

observational evidence of tidal gravity wave interactions using the uwo 2 mhz radar the degree of interaction between atmospheric gravity waves and tides is an issue which is of great importance in middle atmosphere studies it is especially important with regard to tidal variability which is frequently observed in the mesosphere and lower thermosphere but as yet has not been subject to adequate study in this paper we present some strong observational evidence of such interactions made with the uwo 2 mhz radar near london canada our observations show significant correlation between gravity waves and tides diurnal at certain times of the year and the nature of the correlation is intermittent and varies with time of year it is possible that differences between tidal amplitudes at sites with mesoscale separations may be explained in terms of such phenomena we also propose a simple model which is found to be consistent with the major features of the observed data

advanced meteor radar installed at tirupati system details and comparison with different radars an advanced meteor radar viz sri venkateswara university svu meteor radar svu mr operating at 35 25 mhz was installed at sri venkateswara university svu tirupati 13 63 n 79 4 e india in august 2013 for continuous observations of horizontal winds in the mesosphere and lower thermosphere mlt this manuscript describes the purpose of the meteor radar system configuration measurement techniques its data products and operating parameters as well as a comparison of measured mean winds in the mlt with contemporary radars over the indian region it is installed close to the gadanki 13 5 n 79 2 e mesosphere stratosphere troposphere mst radar to fill the region between 85 and 100 km where this radar does not measure winds the present radar provides additional information due to its high meteor detection rate which results in accurate wind information from 70 to 110 km as a first step we made a comparison of svu mr derived horizontal winds in the mlt region with those measured by similar and different mst and mf radars techniques over the indian region as well as model horizontal wind model 2007 data sets the comparison showed an exquisite agreement between the overlapping altitudes 82 98 km of different radars zonal winds compared very well as did the meridional winds the observed discrepancies and limitations in the wind measurement are discussed in the light of different measuring techniques and the effects of small scale processes like gravity waves this new radar is expected to play an important role in our understanding of the vertical and lateral coupling of different regions of the atmosphere that will be possible when measurements from nearby locations are combined

a simple inversion method for determining optimal dispersion model parameters from satellite detections of volcanic sulfur dioxide a simple inversion scheme for optimizing volcanic emission dispersion model parameters with respect to satellite detections is presented in this paper in this scheme multiple dispersion model simulations obtained by varying relevant model parameters are created and compared against satellite detections using pattern correlation as a measure of model agreement with observations it is shown that the scheme is successful in inferring emission source parameters such as those describing the vertical extent of the nascent sulfur dioxide emissions in the november 2010 mount merapi eruption in java indonesia these optimal parameter values then become a basis for improved forecasts of the transport of volcanic emissions

global monsoons in the mid holocene and oceanic feedback the response of the six major summer monsoon systems the north american monsoon the northern africa monsoon the asia monsoon the northern australasian monsoon the south america monsoon and the southern africa monsoon to mid holocene orbital forcing has been investigated using a coupled ocean atmosphere general circulation model foam with the focus on the distinct roles of the direct insolation forcing and oceanic feedback the simulation result is also found to compare well with the ncar csm the direct effects of the change in insolation produce an enhancement of the northern hemisphere monsoons and a reduction of the southern hemisphere monsoons ocean feedbacks produce a further enhancement of the northern africa monsoon and the north american monsoon however ocean feedbacks appear to weaken the asia monsoon although the overall effect direct insolation forcing plus ocean feedback remains a strengthened monsoon the impact of ocean feedbacks on the south american and southern african monsoons is relatively small and therefore these regions especially the south america experienced a reduced monsoon regime compared to present however there is a strong ocean feedback on the northern australian monsoon that negates the direct effects of orbital changes and results in a strengthening of austral summer monsoon precipitation in this region a new synthesis is made for mid holocene paleoenvironmental records and is compared with the model simulations overall model simulations produce changes in regional climates that are generally consistent with paleoenvironmental observations

evidence of gravity wave tidal interaction observed near the summer mesopause at poker flat alaska abstract an analysis of gravity wave tidal interaction observed near the mesopause by the mst radar at poker flat in july of 1986 is presented our observations revealed daily mean wind maxima of 60 m s 1 westward and 20 m s 1 southward with daily mean momentum fluxes contributed by gravity waves with periods less than 1 hour of 4 5 m2 s 2 eastward and 1 2 m2 s 2 northward considerable hourly height variability was found to exist for both winds and momentum fluxes a significant modulation of the fluxes by tidal winds was observed characterized by out of phase correlations over a number of heights diurnal and semidiurnal winds and momentum fluxes exhibited very similar height variations with amplitudes of 5 30 m s 1 and 1 5 m2 s 2 meridional winds leading zonal winds by 90 and maximum fluctuating winds and momentum fluxes at lower levels the observed variations in the amplitude and phase of winds and momentum fluxes provide some support to the gravity wave tidal interaction model proposed

diurnal variation of gravity wave momentum flux and its forcing on the diurnal tide 1 the diurnal variation of gravity wave gw momentum flux is derived from the 5 years of meteor radar wind measurements at maui hawaii the amplitude and phase relationships between the gw forcing and the diurnal tide are analyzed by calculating their equivalent rayleigh frictions the results show that the gw momentum flux is clearly modulated by the diurnal tide the forcing from the momentum flux convergence has strong effects on both the amplitude and phase of the diurnal tide they can reach 80 ms 1 day 1 for the amplitude and 15 h day 1 for the phase the gw forcing tends to increase the diurnal tide amplitude above 90 km but has a small damping effect below 90 km it tends to increase the phase of the diurnal tide throughout all altitudes seasonal variations of the gw forcing exist which result in differences in their effects on the diurnal tide the magnitudes of the forcing are in agreement with recent results from satellite observations but are much larger than values used in general circulation models this work also demonstrates that meteor radar measurements can provide a valuable data set for the study of gw tide interactions

tidal modulation of the gravity wave momentum flux in the antarctic mesosphere airglow imager and dynasonde idi radar wind measurements at halley station antarctica 76degreess 27degreesw have been used to estimate the diurnal variation of the vertical fluxes of horizontal momentum carried by high frequency atmospheric gravity waves the cross correlation coefficients between the vertical and horizontal wind perturbations were calculated from the sodium airglow imager data collected during four consecutive nights of near total darkness during july of 2000 these were combined with wind velocity variances from coincident radar measurements to estimate the upper limit of the vertical flux of horizontal momentum during three hour intervals throughout the period the resulting momentum flux showed a marked semi diurnal oscillation in the zonal and meridional components calculations of the momentum flux through the na airglow show variations in period and phase consistent with the observations implying that tidal propagation and modulated gravity wave forcing may both affect observed wind variations

holocene palaeoecology of the northern flinders ranges south australia based on stick nest rat leporillus spp middens a preliminary overview eight stick nest rat leporillus spp middens from three locations in the northern flinders ranges south australia provide a discontinuous palaeoecological record spanning the holocene evidence from radiocarbon dates pollen plant macrofossils and animal macrofossils is presented both pollen and plant macrofossils show that in the early to mid holocene c 8 8 5 3 ka woodlands with grassy understoreys were more widespread than present this accords with other studies suggesting wetter conditions at this time samples dating of the pleistocene holocene transition 10 9 9 ka are dominated by halophytes it is not yet clear whether this is due to the continuation of pleistocene aridity changes in rainfall seasonality or local influences on vegetation

tidal gravity wave interactions and their influence on the large scale dynamics of the middle atmosphere model results results from a modified version of the quasi geostrophic model of mclandress and mcfarlane 1993 in combination with the tidal model of forbes 1982a b are used to delineate the role of tides in modulating gravity wave momentum fluxes and the ensuing effects on the large scale circulation of the middle atmosphere for solstice conditions the influence of the tidal wind fields on the location and strength of the gravity wave drag is strongest in the mesosphere and lower thermosphere where the tidal winds are of the same order as the zonal mean component due to the nonlinear dependence on the local wind speed the daily mean gravity wave drag in the model can differ significantly depending on whether or not tidal variations are included at middle and low latitudes these differences are largest and occur as a result of the filtering effects of the shorter vertical wavelength diurnal tide at more polar latitudes where the longer wavelength semidiurnal tide dominates a slight increase in drag occurs the interaction between the tidal wind fields and the localized orographic gravity wave momentum flux has important consequences for the in situ generation of planetary scale disturbances in particular the amplification of stationary planetary wavenumber 1 is enhanced by the presence of tides in addition forcing of nonmigrating tidal modes is predicted to occur as a result of the localized drag

stratigraphy sedimentology chronology and palaeohydrology of quaternary lacustrine deposits at madigan gulf lake eyre south australia abstract madigan gulf is a large bay at the southern end of lake eyre north a major ephemerally flooded playa in arid central australia at the southwestern margin of a vast 1 300 000 km2 internal drainage basin the stratigraphy and chronology of the quaternary sequence in the gulf is described from 8 cores and a cliff exposure at the gulf margin a number of depositional environments are recognised and their distinctive sedimentary components are described facies recognised include deep and shallow water lacustrine environments dominated by surface water processes and dry or ephemerally flooded playa environments dominated by groundwater controlled processes sedimentary components include terrigenous clastics from river inflow and shoreline erosion carbonates of detrital inorganic or biological origin and gypsum and halite evaporites carbonates and gypsum evaporites precipitated within the basin are frequently reworked as clastic components the establishment of a preliminary chronology for the sequence by the application of thermoluminescence uranium thorium disequilibrium amino acid racemization and radiocarbon dating techniques has allowed a reconstruction of the last 130 ka of lake eyre palaeohydrology the wettest phase occurred during the last interglacial early in oxygen isotope stage 5 when an enlarged lake eyre was up to 25 m deep subsequently there has been a number of dry periods separating successively less effective wet phases culminating in the deposition of a substantial halite salt crust around the time of the glacial maximum the dry interludes are characterised by deflation of salts and sediment from the basin a process controlled by lowering of the watertable the record from madigan gulf demonstrates the dramatic and repetitive impact of lake deflation on the quaternary record of lake eyre in the early holocene a minor but mostly perennial lacustrine event was terminated at about 3 4 ka when the modern ephemeral playa regime was established the major catchment of lake eyre is located in the monsoon watered areas of northern australia as demonstrated by large floodings of the modern ephemeral regime major lacustrine episodes must indicate enhanced monsoon precipitation in northern australia in the holocene the lake has not risen to levels achieved during the early stage 5 lacustral phase indicating a marked reduction in the effectiveness of the monsoon in the present interglacial by comparison with its predecessor

late quaternary palaeoenvironmental change in the australian drylands in this paper we synthesise existing palaeoenvironmental data from the arid and semi arid interior of the australian continent for the period 40 0 ka moisture is the predominant variable controlli

gravity wave tidal interactions in the mesosphere and lower thermosphere over rothera antarctica 68 s 68 w 1 a simple technique for measuring gravity wave activity has been used to investigate gravity wave tidal interactions in the polar mesosphere and lower thermosphere mlt the technique uses the radial velocities of individual meteors recorded by meteor radar to derive a statistical measure variance of the activity of the high frequency gravity wave field this technique can measure gravity waves with horizontal wavelengths of up to about 400 km and periods up to approximately 3 hours interactions between the observed gravity wave field and the background wind are investigated using data collected between february 2005 and december 2008 by a meteor radar based at rothera antarctica 68 s 68 w the results reveal the presence of significant modulations of the observed gravity wave field at tidal periods of 12 and 24 hours correlations between the hourly zonal winds and the gravity wave field measured by the meteor radar reveal an in phase relationship between the hourly zonal winds and gravity wave variance in winter and an anti phase relationship in summer this is consistent with the theory of filtering by tidal winds acting on a zonally asymmetric gravity wave field in which westward waves dominate in winter and eastward waves dominate in summer the limitations of the technique and the effect this has on the interpretation of these results are also considered the effects of the diurnal cycles in meteor count rates the uncertainty in recorded radial velocities and the uncertainty in the measured heights of meteors are considered

low latitude glacial cooling in the southern hemisphere from amino acid racemization in emu eggshells the record of natural climate variability over glacial interglacial timescales provides a framework from which a better mechanistic understanding of the climate system may be derived but this approach is limited by the number and distribution of well dated and reliable palaeoenvironmental archives particularly vexing is the conflicting evidence for low latitude cooling during the last glacial maximum and the apparent synchrony in glacial activity between the hemispheres despite out of phase insolation forcing1 4 here we utilize the temperature dependent amino acid racemization reaction in radiocarbon dated emu eggshell fragments from the continental interior of australia to reconstruct low altitude subtropical temperatures for the past 45 kyr racemization rate changes indicate that millennial scale average air temperatures were at least 9 c lower between 45 and 16 kyr bp than since 16 kyr bp a temperature change of this magnitude coupled with other low latitude palaeotemperature records that indicate substantial cooling3 4 must reflect global processes which we speculate involved glacial age reduction in atmospheric water vapour content

radiocarbon dating of playa lake hydrologic changes examples from northwestern china and central australia accurate radiocarbon dating of arid zone playas is restricted by shortage of suitable organic matter analyses from two large systems in australia lake frome and china qarhan playa in the qaidam basin demonstrate the problems associated with the use of carbonates for dating organic carbon although requiring treatment of large samples 1 2 kg provides the most accurate basis for establishing chronologic control in qarhan a deposit of halite averaging about 30 m thick extends over an area of 5800 km2 carbonate in the system is dominantly derived as clastics from loess transported by northwesterly winds the large component of dead carbon thus involved explains anomalous patterns of dates derived from these materials such results are consistently much older than those based on organic carbon in lake frome subject to a more maritime climate in central australia the carbonate component is dominantly authigenic lacustrine in origin contaminated by a small detrital component it provides ages about one half life older than those from organic carbon the sequence from qarhan supplemented by evidence of lacustral pluvial episodes in two other sub basins in qaidam kunteyi and xiao qaidam illustrates the presence there of expanded waterbodies persisting from at least 40 000 to about 15 000 yr b p in areas where little surface water persists today the large evaporite deposits formed between about 25 000 to sometime after 15 000 yr b p holocene climate appears to have remained hyperarid like that of today at lake frome an early lacustral phase gave way before 18 000 yr b p to drying and aeolian activity water had returned to the system by 16 000 yr b p signalling a decline if not the end of aridity lacustrine conditions persisted through early holocene with drying and development of playa facies about 7000 yr b p after a brief return to lacustrine conditions between about 6000 4000 yr b p a dry playa environment has continued to the present day the frome and qarhan playas although in comparable latitudes lie in very different climatic and tectonic settings their palaeohydrologic records are neither in phase nor in distinct anti phase emphasizing the complexity of comparing palaeoclimatic records from different circulation systems

measurement of momentum fluxes near the summer mesopause at poker flat alaska abstract observations of the motion field near the summer mesopause using the poker flat mst radar in a symmetric six beam configuration during 8 days of july 1986 were used to examine the mean structure the wave variances and the momentum fluxes due to gravity wave and tidal motions our results reveal a mean horizontal wind structure generally consistent with previous observations but with considerable daily variability and large mean shears particularly significant is a mean downward eulerian vertical velocity of 0 3 m s 1 which implies a significant upward flux of wave energy horizontal and vertical velocity variances are found to be 1500 and 6 m2 s 2 and to remain nearly constant with height momentum flux measurements reveal a largely zonal mean flux of 5 to 15 m2 s 2 that achieves a maximum just below the height of wind reversal daily mean values on the other hand exhibit large variability with maxima as large as 30 to 40 m2 s 2 hourly momentum flux profiles were found to achieve m

a soil chronosequence on lake mega frome beach ridges and its implications for late quaternary pedogenesis and paleoenvironmental conditions in the drylands of southern australia abstract the terminal lake systems of central australia are key sites for the reconstruction of late quaternary paleoenvironments paleoshoreline deposits around these lakes reflect repeated lake filling episodes and such landforms have enabled the establishment of a luminescence based chronology for filling events in previous studies here we present a detailed documentation of the morphology and chemistry of soils developed in four well preserved beach ridges of late pleistocene and mid to late holocene age at lake callabonna to assess changes in dominant pedogenic processes all soil profiles contain evidence for the incorporation of eolian derived material likely via the formation of desert pavements and vesicular horizons and limited illuviation due to generally shallow wetting fronts even though soil properties in the four studied profiles also provide examples of parent material influence or site specific processes related to the geomorphic setting there is an overall trend of increasing enrichment of eolian derived material since at least 33 ka compared to the holocene profiles the derived average accumulation rates for the late pleistocene profiles are significantly lower and may suggest that soils record important regional changes in paleoenvironments and dust dynamics related to shifts in the southern hemisphere westerlies

dynamics of acacia aneura triodia boundaries using carbon 14c and δ 13c and nitrogen δ15n signatures in soil organic matter in central australia abstract soil organic matter som was sampled from soil profiles on a near level sandsheet at the southern limit of the tanami desert in central australia to determine if boundaries of triodia hummock grassland acacia aneura shrublands had changed in the holocene accelerator mass spectrometry ams 14c dating of 16 soil profiles showed that som that had accumulated at 100 to 140 cm depth near the base of most profiles had ages between 1175 and 2630 14c years averaging 1906 14c years the stable carbon isotopic a13c composition of som from the upper 50 cm soil profiles in the a aneura shrubland inhabited by plants with predominantly c3 photosynthetic pathway was significantly more 13c depleted than the comparable soil interval beneath a triodia grassland predominantly c4 photosynthetic pathway mean age of som at 50 cm depth was 830 14c years suggesting the vegetation has been stable for about 1000 years however soil profiles in triodia grassland adjacent to the shrubland boundary had slightly more depleted a13c relative to sites 0 5 km from the boundary with respect to stable nitrogen isotopic values only surface soils in the acacia shrublands were found to be 15n enriched relative to all other soil depths although there were no obvious environmental discontinuities such as change in soil type or slope angle associated with the ecosystem boundaries the acacia shrublands were found to occur on more clayrich soils with higher concentrations of total phosphorus nitrogen and potassium compared with the surrounding grasslands and these trends became more pronounced with increasing distance from the ecotone it is unclear if these differences are a cause or an effect of the vegetation mosaic the concordance of the vegetation boundaries with the a13c and a15n and of soil nutrients are consistent with only minor attrition of the a aneura shrublands in the late holocene at this site

on the equivocal fate of late pleistocene callitris vent cupressaceae woodlands in arid south australia fossil pollen assemblages suggest callitris cupressaceae dominated woodlands were prominent elements in landscapes near lake frome and lake eyre during latest pleistocene times callitris woodlands were present at lake eyre before 30 000 bp but became fragmented and disappeared in the lead up to the last glacial maximum callitris was again prominent from approximately 10 000 bp until about 5000 bp after which time it vanishes from the pollen record and presumably the region at lake frome callitris was abundant between 16 000 bp and 13 000 bp before declining to low modern levels from 11 000 bp at both sites the latest pleistocene or holocene decline in callitris occurrence and its eventual extinction in the vicinity of lake eyre broadly corresponds with archaeological indications of increasing human presence in the landscape in the absence of evidence of significant climatic changes at the times in question these observations lend tentative support to arguments that the composition and structure of modern zone vegetation has been significantly modified by aboriginal land management practices although the charcoal record is ambiguous fire is argued to be the principle agent of the changes wrought during human re colonisation of lands around lake frome and lake eyre

mean winds tides and gravity waves during the westward phase of the mesopause semiannual oscillation msao mf radar observations of mean winds tides and gravity waves in the period range 30 120 min over tirunelveli 8 7 n 77 8 e during april 1993 when the mesopause semiannual oscillation msao was in the westward phase are presented in this work the focus herein is on the observed relationship between these dynamical parameters which is explained in the context of the current understanding of the behavior of msao winds tidal dissipation and gravity wave tide interactions the observed diurnal tide amplitude and phase variations with height indicate 1 1 wave damping and subsequent westward momentum deposition the gravity wave variances are shown to be modulated by the diurnal tide though the analysis does not lead to an estimation of gravity wave contributions to the time mean zonal flow and its shears the observations do suggest that the short term tidal variability contributes either directly or indirectly through the gravity wave tidal interactions to the variation of the strength of the time mean westward flow associated with the msao

holocene palaeoenvironments and change at three quarter mile lake silver plains station cape york peninsula australia pollen and diatom analyses of organic sediments from three quarter mile lake a perched lake on cape york peninsula north queensland indicate that significant changes in vegetation and hydrology occurred during the holocene early holocene grass dominated landscapes were replaced in mid holocene times by increasingly woody vegetation comprising tropical heathlands savanna and rainforest early holocene lake levels fluctuated widely from mid holocene times lake levels stabilized and water became increasingly acidic as a mature swamp forest developed adjacent to the lake and contributed tannins to the lake water the timing and character of changes are consistent with those described from the atherton tableland in wet tropical queensland holocene dry phases described from the northern territory and the western shores of cape york cannot be identified from three quarter mile lake rainforest is currently close to its greatest holocene extent suggesting that the rainforest dependent endemic fauna of no

mesospheric momentum fluxes over adelaide during the 2 day wave results and interpretation estimates of the vertical flux of meridional momentum due to waves of periods between 8 min and 1 hour were obtained over a height range of approximately 80 to 94 km while the 2 day wave was active during january 1987 between 0600 and 1100 lt on the days of the northward phase of the 2 day wave pulses of momentum flux density somewhat larger than the values present at other times were found the interpretation of momentum flux density profiles is considered and the concepts developed are applied to the data presented it is found that the data are generally not consistent with the expected scenario of breaking upgoing gravity waves an alternative explanation involving downgoing waves is tendered

drake antarctic agile meteor radar first results configuration and comparison of mean and tidal wind and gravity wave momentum flux measurements with southern argentina agile meteor radar 1 a new generation meteor radar was installed at the brazilian antarctic comandante ferraz base 62 1 s in march 2010 this paper describes the motivations for the radar location its measurement capabilities and comparisons of measured mean winds tides and gravity wave momentum fluxes from april to june of 2010 and 2011 with those by a similar radar on tierra del fuego 53 8 s motivations for the radars include the hotspot of small scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere mlt centered over the drake passage the maximum of the semidiurnal tide at these latitudes and the lack of other mlt wind measurements in this latitude band mean winds are seen to be strongly modulated at planetary wave and longer periods and to exhibit strong coherence over the two radars at shorter time scales as well as systematic seasonal variations the semidiurnal tide contributes most to the large scale winds over both radars with maximum tidal amplitudes during may and maxima at the highest altitudes varying from 20 to 70 ms 1 in contrast the diurnal tide and various planetary waves achieve maximum winds of 10 to 20 ms 1 monthly mean gravity wave momentum fluxes appear to reflect the occurrence of significant sources at lower altitudes with relatively small zonal fluxes over both radars but with significant and opposite meridional momentum fluxes below 85 km these suggest gravity waves propagating away from the drake passage at both sites and may indicate an important source region accounting in part for this hotspot

a geospatial visualisation and chronological study of a late pleistocene fluvial wetland surface in the semi arid flinders ranges south australia abstract the semi arid flinders ranges of south australia contain abundant remnants of fine grained late pleistocene valley fills we have mapped these deposits using real time kinematic rtk gnss and topographic surveying techniques for data acquisition and integrate the surveyed data in a geographical information system gis to interpolate a 3 dimensional palaeo surface representing the uppermost remnant sediments of the late pleistocene floodplain our analysis of sedimentary and landscape profiles indicates a continuous surface and consistent westward slope suggesting that the remnants present today are still largely consistent with the original alluvial surface in addition secondary levels are identified and interpreted integration of the geospatial landscape characterisation with chronologies from selected sites microfossil and stable isotope data provides new evidence for the timing rates of aggradation and mode of deposition of the late pleistocene fine grained valley fill formation the use of gis for 2 d and 3 d data management analysis and visualisation provides a visual and quantitative model of landscape changes and helps to clarify how the valley fill deposits accumulated

lake eyre palaeohydrology from 60 ka to the present beach ridges and glacial maximum aridity lake eyre is presently an ephemeral playa lake in an extremely large 1 3 million km2 internal drainage basin with most of its inflow derived from monsoon watered northern australia the hydrologic state of the lake has varied in the past in response to climate change from a perennial lake up to 25 metres deep to a groundwater controlled playa marked by substantial sediment deflation this paper is concerned with the stratigraphic record of the last 60 ka of that hydrologic history particularly the character and age of a playa marginal unit formed by deflation from the playa and of stranded high beach ridges a major deflation episode between 60 and 50 ka excavated the present lake eyre basin and deposited a gypsum and clay rich aeolian phase the williams point aeolian unit at a number of sites around the lake after deflation ceased a thick secondary gypsum profile developed on the dune early in oxygen isotope stage 3 evidence for the state of lake eyre at this time is equivocal preliminary results from a substantial suite of amino acid racemization aar analyses of mollusc shell and bird eggshell samples from beach ridges at 5 and 10 m australian height datum ahd suggest that they are oxygen isotope stage 5 in age sedimentologic evidence suggests that it is unlikely that the shells are reworked from older deposits these aar results apparently conflict with early oxygen isotope stage 3 thermoluminescence tl dates from the 5 m ahd beach ridge nanson et al this volume however the age difference is not substantial the calibration of the aar is still at a preliminary stage and only one site was sampled for both techniques further stratigraphic and chronologic work is required to fully assess the apparent discrepancy between about 30 000 and 12 000 yr b p lake eyre was at least as dry as it is today at many sites around madigan gulf a lunette like playa marginal aeolian unit the shelly island unit was deposited during this period formed by material deflated from the playa floor forty ams radiocarbon dates span the period 35 000 to 10 000 yr b p from the shelly island unit 11 and from aeolian sediment close to playa level 29 indicating that the lake was dry during this period this evidence conflicts strongly with 2 tl dates from latest oxygen isotope stage 3 and oxygen isotope stage 2 from the 5 and 10 m ahd beach ridges nanson et al this volume additionally the aar results from the high beach ridges cannot be reconciled with these tl dates after 10 000 yr b p a minor lacustral phase occurred until the modern ephemeral playa regime became established at 3000 4000 yr b p

ams radiocarbon dating in the study of arid environments examples from lake eyre south australia abstract sediments containing small amounts of carbon are difficult to date using traditional radiocarbon techniques this has resulted in less than satisfactory attempts to establish reliable chronologies for sedimentation and environmental change in the australian arid zone we describe here the first application of the ams technique to the radiocarbon dating of salt lake core samples using a chemical pretreatment methodology based on pollen extraction techniques these results indicate that fine grained charcoal and pollen have a similar source and depositional mechanism the data from lake eyre imply a last glacial maximum deposition for the major buried halite layer an early holocene return to lacustrine conditions with a late holocene reduction of net sediment inout to madigan gulf as the present playa conditions were established

changes in vegetation and seasonal climate since the last full glacial at lake frome south australia abstract results are presented from stratigraphy radiocarbon and pollen analysis from lake frome south australia close to the summer winter rainfall boundary at 30 south latitude the pollen sequence shows that tree vegetation was minor around 18 000 yr b p the landscape was dominated by chenopod low shrublands and ephemeral tubuliflorae vegetation by 17 000 yr b p callitris moved in and rose to 25 of the pollen sum values of casuarina myrtaceous shrubs acacia dodonaea and cyperaceae also rose at about the same time between 17 000 and 14 500 yr b p callitris and eucalyptus dominated the tree vegetation with callitris reaching its maximum values eucalpt woodlands were associated with undershrubs belonging to myrtaceae acacia dodonaea and gyrostemonaceae whereas callitris woodlands had probably supported only a sparse understorey chenopodiaceae today distributed mainly in the winter rainfall zone continued to show high values 25 gramineae today associated with high summer rainfall generally remained below 20 the sporadic presence of a number of taxa which now grow in temperate areas further south suggest that average annual temperatures were a little lower than at present from 14 500 to 13 000 yr b p there was a sudden decline in the values of callitris and a more gradual decline in chenopodiaceae and dodonaea the rise of ephemeral vegetation together with a fall in chenopodiaceae would indicate that winter precipitation had started to decline between 13 000 and 4500 yr b p chenopodiaceae and tubuliflorae ephemerals declined and gramineae rose to its highest values tribulus pollen a subtropical tropical taxon first appeared 13 000 yr b p overall plants from the summer rainfall zone became more prominent and taxa from the temperate south declined summer monsoon incursions apparently strengthened and temperature increased during this phase since 4500 yr b p both chenopodiaceae and tubuliflorae returned to high values whereas gramineae declined values of acacia and myrtaceous shrubs rose but those of casuarina declined and callitris remained extremely low these changes were accompanied by the onset of playa environments which have since persisted vegetation during this phase suggests that summer precipitation declined and summer monsoon incursions became rare during the late holocene