holocene palaeoclimate and sea level fluctuation recorded from the coastal barker swamp rottnest island south western western australia abstract the holocene palaeoclimatic history of south western western australia swwa has received little attention compared to south eastern australia and this has resulted in conflicting views over the impact of climate variability in the region we present here a well dated high resolution record from two overlapping sediment cores obtained from the centre of barker swamp rottnest island offshore perth the records span the last 8 7 ka with the main lacustrine phase occurring after 7 4 ka this site preserves both pollen and several ostracod taxa the pollen record suggests a long term shift from the early mid holocene to the late holocene to drier conditions with less shrubland and more low ground cover and less fire activity a salinity transfer function was developed from ostracod faunal assemblage data and trace metal ratios mg ca sr ca and na ca and stable isotopes 18 o and 13 c analysed on selected ostracod valves these provide a detailed history of evaporation precipitation e p differences that clearly shows that the swwa region was subjected to significant climatic shifts over the last 7 4 ka with a broad shift towards increased aridity after 5 ka the swamp ranged from fresh to saline as recorded in the ostracod valve chemistry and the independently derived salinity transfer function the ostracod record also indicates that a sea level highstand occurred between ca 4 5 and 4 3 ka with probable step wise increases at 6 75 6 2 and 5 6 ka with the last vestiges of salt water intrusion at ca 1 ka after about 2 3 ka the fresh groundwater lens that underlies the western portion of the island intersected the swamp depression influencing the hydrology of the swamp the broad climatic changes recorded in barker swamp are also compared with data from southern south africa and it is suggested that the southern annular mode appears to have been the dominant driver in the climate of these regions and that the indian ocean dipole is of little importance in the southern regions of the south western cape of africa and south western western australia

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

orographic clouds in terrain blocked flows an idealized modeling study abstract idealized numerical simulations of moist strongly stratified flow over topography are used to study the processes that control orographic clouds in terrain blocked flows as a joint function of the nondimensional flow parameter nh u the horizontal topographic aspect ratio and the rossby radius of deformation nh f the simulations show the competition between enhanced upstream condensation in the secondary vertically propagating gravity wave and the reduction of condensation owing to enhanced low level flow deflection as nh u increases above about 1 5 the tendency for flow to be deflected around the barrier reduces cloud formation in the primary gravity wave over the ridge while increasing expands low level clouds over a broader upstream area ice clouds may form aloft in the secondary vertically propagating gravity wave and extend upstream for several hundred kilometers in terrain blocked flows more than half of the condensate mass develops upstream of the barrier in the secondary gravi

autumnal precipitation distribution on the southern flank of the alps a numerical model study of the mechanisms during the autumn there are frequent events of heavy precipitation on the southern slopes of the meso scale alpine chain moreover the accompanying climatology exhibits a distinctive spatial distribution with some meso scale regions of enhanced precipitation such as the wet spot in the vicinity of lago maggiore possible mechanisms to account for the observed spatial distribution are established using a heuristic model based approach it is shown using a mesoscale model that the response to a steady horizontally uniform and moisture laden flow impinging upon a comparatively realistic representation of the alpine chain can reproduce both the overall meso scale precipitation distribution and its meso scale sub structure the nature of the simulated flow regime over around or intermediate is sensitive to the strength of the ambient geostrophic flow and its modification in the planetary boundary layer contrariwise the simulated precipitation distribution in the lago maggiore wet spot is comparatively insensitive to the changes in direction of the incident geostrophic flow from south to south west and in strength in the range 10 30 m s 1 although there is a marked change in the structure of the near alpine flow this systematic precipitation enhancement appears to be related to the relative strength and compensating effects of an easterly barrier jet tracking along the zonally elongated part of the alps and an air stream channelled between the maritime alps and the apennines further evidence to the above interpretation of the meso scale precipitation distribution is given with simulations conducted using a smoothed and schematic representation of the alpine chain likewise the sensitivity to the presence of a lago maggiore like indentation of the topography is tested and evidence is provided of a further indentation induced precipitation enhancement at the local scale copyright 2004 royal meteorological society

australasian evidence for mid holocene climate change implies precessional control of walker circulation in the pacific abstract at its simplest the pacific cell of the walker circulation may be regarded as a thermal circulation driven by the temperature contrast between the west and east pacific evidence from australasia is summarized indicating that this circulation was greatly weakened in the early holocene but was enhanced at about 5000 bp the initial effect of this enhancement was the intensification of the northern australian monsoon within the australian tropics but this was reversed abruptly after 3700 bp the enhancement is attributed to an increased polar equator pressure gradient after 5000 bp with consequent intensification of the overall circulation pattern in the southern hemisphere including the mid latitude westerlies and the trade winds this in turn appears to be a result of increased southern hemisphere seasonality driven by the precessional cycle it is proposed that increased wind speeds off south america after 5000 bp in both mid and low latitudes enhanced upwelling and reduced sea surface temperatures ssts this created a greater east west surface temperature contrast across the pacific compounding a pre existing trend towards enhanced circulation and flipping climates in the southern hemisphere pacific basin from an early holocene mode to a late holocene mode under reduced circulation conditions early holocene climates at low latitudes in the southern hemisphere may have been dominated by monsoonal heat transfers

holocene rainfall variability in southern chile a marine record of latitudinal shifts of the southern westerlies geochemical and clay mineral parameters of a high accumulation marine sediment core from the chilean continental slope 41 s provide a 7700 yr record of rainfall variability in southern chile related to the position of the southern westerlies we especially use the iron content measured with a time resolution of ca 10 yr on average of 14 caccelerator mass spectrometry dated marine sediments as a proxy for the relative input of iron poor coastal range and iron rich andean source rocks variations in this input are most likely induced by rainfall changes in the continental hinterland of the core position based on these interpretations we find a pronounced rainfall variability on multicentennial to millennial time scales superimposed on generally more arid conditions during the middle holocene 7700 to 4000 cal yr b p compared to the late holocene 4000 to present this variability and thus changes in the position of the southern westerlies are first compared to regional terrestrial paleoclimate data sets from central and southern chile in order to derive possible wider implications and forcing mechanisms of the holocene latitudinal shifts of the southern westerlies we then compare our data to ice core records from both tropical south america and coastal antarctica these records show similar bands of variability centered at ca 900 and 1500 yr comparisons of band pass filters suggest a close connection of shifts of the southern westerlies to changes within the tropical climate system the correlation to climate conditions in coastal antarctica shows a more complicated picture with a phase shift at the beginning of the late holocene coinciding with the onset of the modern state of el nin o southern oscillation system the presented data provide further evidence that the well known millennial scale climate variability during the last glacial continued throughout the holocene fl 2001 elsevier science b v all rights reserved

paleomagnetic evidence for the miocene counter clockwise rotation of northeast japan rifting process of the japan arc paleomagnetic results have been obtained from more than 700 oriented samples in igneous rocks of cretaceous to miocene age from northeast japan the remanent magnetizations of welded tuffs with age between 32 ma and 21 ma old from 17 widely distributed sampling sites in northeast japan are fairly well grouped with a mean ofd 41 2 i 56 5 95 7 2 the remanent magnetization of welded tuffs of 14 ma and 11 ma from 4 sites shows a northerly direction d 11 7 i 60 5 95 15 3 these data imply that northeast japan was apparently subjected to a counter clockwise rotation through 47 14 about a vertical axis on the representative point of northeast japan 141 e 39 n during the past 21 ma comparing with the period of the clockwise rotation of southwest japan the differential rotation between northeast japan and southwest japan is concluded to have occurred concurrently during the period between 21 ma and 12 ma a rifting model of the japan arc is proposed northeast japan rotated counter clockwise through 50 about a northern pivot at 146 e 44 n while southwest japan rotated clockwise through 54 about a southern pivot at 129 e 34 n the differential rotation about different rotation pivots gives rise to the opening of a diamond shaped back arc basin the japan sea

analysis and simulation of local and regional conditions for the rainfall over the lago maggiore target area during map iop 2b the mesoscale alpine programme map operational and research network collected a large variety of measurements during the two days of intensive observing period iop 2b 19 and 20 september 1999 which is one of the most intense rainfall episodes during the special observing period over the lago maggiore area the synoptic situation is a typical one of a southerly flow and associated convection over alpine orography simulations with the non hydrostatic meso nh model are used to describe the rainfall conditions and are successfully validated at the different scales allowed by the map data the two types of pre frontal orographically triggered convective episodes are described 1 sporadic and shallow convection occurs over the coastal mountains and propagates over the po valley the chronology and the intensity of these convective episodes are driven by two main features the low level humidity anomalies and the middle troposphere dry anomaly present over the mediterranean sea 2 the lago maggiore orographic convection has a very long duration and is mainly controlled by both the intensity of the easterly low level wind in the north part of the po valley and the upper level clouds of the cold front the different origins of the air masses transported by this easterly barrier wind and the associated local circulations are detailed copyright 2003 royal meteorological society

sampling sediment under warm deep water abstract the following devices and their operation are described a modifications to the mackereth corer allowing 12 m long cores to be taken routinely b a development of the frozen finger which recovers two plates of mud each 120 cm 12 cm at each operation together with equipment for facilitating its sub sampling and c a new design of hammer driven piston corer

exploring the relationship between aboriginal population indices and fire in australia over the last 20 000 years abstract the extent of prehistoric human impact on the environment is a contentious topic in various palaeo environmental sciences the long history of humans in australia and its extensive fire prone biota makes this continent a key research area for better characterization of prehistoric human fire interactions here we use statistically robust cross correlation of archaeological radiocarbon data n 4102 ages from 1616 sites and a new synthesis of charcoal records n 155 sites to test for any relationship between people and fire over the last 20 000 years at continental and regional 25 45 s scales we find that the statistical correlation between the two datasets is weak at both spatial scales with short lived synchronous responses only in the terminal pleistocene holocene transition at the onset of the mid holocene climatic optimum 10 7 ka and during significant transitions of el nino southern oscillation 5 4 ka and 1 2 0 8 ka one interpretation of this is that aboriginal populations were implementing fire stick farming only intermittently during periods of societal stress resulting from climatic variability however the synchronicity of the correlations with climate changes along with the low populations through much of this time suggests that both datasets were independently responding to external climatic forcing under either scenario a lack of significant change in the charcoal record implies that there were no long lasting impacts to the environmental biota and macro scale palaeoenvironmental records prior to european colonization largely reflect responses to non human influences while we do not discount the possibility of systematic or deliberate manipulation of fire regimes at local spatial scales we conclude that human control of fire by prehistoric people in australia is not evident at broad landscape levels this conclusion contradicts persistent suggestions of australian wide land management and the pervasiveness of the impacts of fire stick farming

a review of holocene solar linked climatic variation on centennial to millennial timescales physical processes interpretative frameworks and a new multiple cross wavelet transform algorithm article i nfo wereportontheexistenceandnature of holocene solar andclimaticvariationson centennialto millennial time scales we introduce a new solar activity proxy based on nitrate no3 concentration from the talos dome ice core east antarctica we also use a new algorithm for computing multiple cross wavelet spectra in time fre quency space that is generalized for multiple time series beyond two our results provide a new interpretive framework for relating holocene solaractivity variations on centennial to millennial timescales to co varying cli mate proxies drawn from a widespread area around the globe climatic proxies used represent variation in the north atlantic ocean western pacific warm pool southern ocean and the east asian monsoon regions our wavelet analysis identifies fundamental solar modes at 2300 yr hallstattzeit 1000 yr eddy and 500 yr unnamed periodicities leaves open the possibility that the 1500 1800 yr cycle may either be fundamental or derived and identifies intermediary derived cycles at 700 yr and 300 yr that may mark rectified responses of the atlantic thermohaline circulation to external solar modulation and pacing dating uncertainties suggest that the 1500 yr and 1800 yr cycles described in the literature may represent either the same or two separate cycles but in either case and irrespective too of whether it is a fundamental or derived mode in the sense of dima and lohmann 2009 the 1500 1800 yr periodicity is widely represented in a large number of paleoclimate proxy records it is obviously premature to reject possible links between changing solar activity at these multiple scales and the variations that are commonly observed in paleoclimatic records

a continental narrative human settlement patterns and australian climate change over the last 35 000 years drawing on the recent synthesis of australian palaeoclimate by the oz intimate group reeves et al 2013a we consider the effects of climate systems on past human settlement patterns and inferred demography we use 5044 radiocarbon dates from 1750 archaeological sites to develop regional time series curves for different regions defined in the oz intimate compilation as the temperate tropics interior and southern ocean sectors to explore human climate relationships in australia over the last 35 000 years correlations undertaken with improved palaeoclimatic data and archaeological records indicate that the regional time series curves are robust and can be used as a proxy for human behaviour however interrogation of the datasets is essential with artificial peaks and taphonomic over correction being critical considerations the time series curves are interpreted as reflecting population growth stasis and even decline in phase with terminal pleistocene early holocene climatic fluctuations this coupling however decreases during the last 5000 years most likely due to increased population levels greater territoriality technological solutions to stress and social and ideational innovation curves from all sectors show exponential population growth over the last 5000 years we identify future research priorities highlighting the paucity of archaeological records across several parts of australia 1 dated site 4 000 km2 especially around the fringes of the arid zone and the need for improved taphonomic correction techniques finally we discuss how these time series curves represent a first order framework not dissimilar to global climate models which researchers can continue to test and refine with local regional and continental records

control of reservoir geometry and stratigraphic trapping by erosion surface e5 in the pembina carrot creek area upper cretaceous cardium formation alberta canada 1 seven major erosion e surfaces are found within the 100 m thick cardium formation in the subsurface of alberta erosion surface e5 has up to 20 m of erosional relief in the carrot creek area and is cut into originally horizontal open marine sandstones and mudstones the e5 surface has been correlated into the pembina area by construction of a structure map based on 2470 resistivity logs the e5 surface is characterized by a series of sub parallel southeast trending steps with lower areas between the steps this topography is interpreted to have formed during erosional shoreface retreat in a period of alternating transgression and stillstand of relative sea level tectonic tilting of the basin floor is also suggested by the topography of the erosion surface the tilti g is related to the accretion of exotic terranes and loading the continental margin the erosion surface is overlain by a continuous veneer of conglomerate interpreted as a transgressive lag this conglomerate thickens to 20 m in the lower areas at carrot creek where it is interpreted as a shoreface deposit rather than an offshore bar these shoreface conglomerates form important reservoirs the veneer also thickens to about 9 m in parts of pembina but the thick conglomerates occur not in the lows but on top of the steps reconstruction of the geometry of the steps indicates that at times of unusually high sediment supply during transgression conglomerates were deposited as local bars in the lower shoreface the sandstones and mudstones below the erosion surface at pembina shale out northeastward partly forming a stratigraphic trap however these sediments are also truncated by the e5 erosion surface and buried by transgressive mudstones these mudstones contribute significantly to updip stratigraphic trapping the long narrow sand body trends mapped in pembina and adjacent fields are due to the erosive dissection of an originally extensive and continuous sheet of interbedded sandstones and mudstones and not as has been suggested to an offshore bar origin for the fields

dramatic reduction in size of the lowland macquarie river in response to late quaternary climate driven hydrologic change palaeochannels of lowland rivers provide a means of investigating the sensitivity of river response to climate driven hydrologic change about 80 palaeochannels of the lower macquarie river of southeastern australia record the evolution of this distributive fluvial system six macquarie palaeochannels were dated by single grain optically stimulated luminescence the largest of the palaeochannels quombothoo median age 54 ka was on average 284 m wide 12 times wider than the modern river 24 m and with 21 times greater meander wavelength palaeo discharge then declined resulting in a younger narrower group of palaeochannels bibbijibbery 125 m wide 34 ka billybingbone 92 m 20 ka milmiland 112 m 22 ka and mundadoo 86 m 5 6 ka yet these channels were still much larger than the modern river and were continuous downstream to the confluence with the barwon darling river at 5 5 ka a further decrease in river discharge led to the formation of the narrow modern river the ecologically important macquarie marshes and marra creek palaeochannel 31 m 2 1 ka and diminished sediment delivery to the barwon darling river as palaeo discharge fell further the hydrologic changes suggest precipitation was a driving forcing on catchment discharge in addition to a temperature driven runoff response

early mid holocene climatic variations in tasmania australia multi proxy records in a stalagmite from lynds cave mass spectrometric uranium series dating and c o isotopic analysis of a stalagmite from lynds cave northern tasmania australia provide a high resolution record of regional climate change between 5100 and 9200 yr before present bp combined delta 18 o delta 13 c growth rate initial u 234 u 238 and physical property color transparency and porosity records allow recognition of seven climatic stages stage i 9080 yr bp a relatively dry period at the beginning of stalagmite growth evidenced by elevated u 234 u 238 stage ii 9080 8600 yr bp a period of unstable climate characterized by high frequency variability in temperature and bio productivity stage 111 8600 8000 yr bp a period of stable and moderate precipitation and stable and high bio productivity with a continuously rising temperature stage iv 8000 7400 yr bp the warmest period with high evaporation and low effective precipitation rainfall less evaporation stage v 7400 7000 yr bp the wettest period with highest stalagmite growth and enhanced but unstable bio productivity stage vi 7000 6600 yr bp a period with a significantly reduced precipitation and bio productivity without noticeable change in temperature stage vii 6600 5100 yr bp a period of lowest temperature and precipitation marking a significant climatic deterioration overall the records suggest that the warmest climate occurred between 8000 and 7400 yr bp followed by a wettest period between 7400 and 7000 yr bp these are broadly correlated with the so called mid holocene optimum previously proposed using pollen and lake level records however the timing and resolution of the speleothem record from lynds cave are significantly higher than in both the pollen and lake level records this allows us to correlate the abrupt change in physical property delta 18 o delta 13 c growth rate and initial u 234 u 238 of the stalagmite at similar to8000 yr bp with a global climatic event at early mid holocene transition c 2001 elsevier science b v all rights reserved

upstream effects of mesoscale mountains abstract the alpine experiment alpex has revealed that low level air is typically diverted around the alps without reaching the mountaintop in pursuit of an understanding of the physical basis of this phenomenon and of its generality we have explored the characteristics of orographic blocking of a rotating continuously stratified quid as revealed in a simple model problem retaining full nonlinear and transient effects hydrostatic dynamics is assumed and the obstacle is taken to be an infinitely long ridge with height h x the key questions treated are the strength of the upstream deceleration of cross mountain flow and the length scale over which the decelerated region extends by means of scale analysis the controlling parameters are found to be the rossby number ro u fl and the froude number fr nhm u where u is the speed of the oncoming flow f is the coriolis parameter l the mountain half width n the brunt vaisala frequency and hm is the maximum mountain height the scale analysis also

estimates of late holocene soil production and erosion in the snowy mountains australia soil production in actively uplifting or high precipitation alpine landscapes is potentially rapid however these same landscapes are also susceptible to erosion and can be sensitive to changes in climate and anthropogenic activity which can upset the balance between soil production and erosion the snowy mountains southeastern australia are a tectonically stable low relief moderate precipitation mountain environment the alpine area is extensively blanketed by soil that has been subjected to more intensive episodes of erosion during past periods of anthropogenic disturbance and under cold climate conditions of the late quaternary in this study rates of soil development and hillslope erosion were investigated using radiocarbon dating fallout radionuclides and sediment cores collected from lakes and reservoirs estimated holocene soil development rates were 20 220 t km y erosion rates determined from the radionuclides cs and pb were equivocal due to the inherent spatial variability of radionuclide inventories relative to apparent erosion rates estimated average erosion rates over the past 100 years determined from pb inventories were 60 t km y 95 ci 10 90 inventories of cs observed at the same site implied that more recent erosion rates over the past 60 years was below the detection limits of the sampling method applied here i e 70 t km y the upper estimate of 90 t km y is comparable to the mean erosion rate estimated using the radionuclide method for uncultivated sites in australia and is significantly lower than that measured at sites were vegetation cover was disturbed by livestock grazing prior to its exclusion from the alpine area in the 1940s ce low erosion and high soil production rates relative to the lowland soils are likely related to extensive vegetation cover which in this context protects soils against erosion and contributes to the formation of organic alpine soils that rapidly accumulate organic matter by comparison to other soil types

progradational sequences in miocene shoreline deposits southeastern caliente range california abstract an exceptionally well exposed marine nonmarine transition in middle miocene strata exists in the southeastern caliente range california about 50 individual progradational sequences form a succession that ranges in thickness from approximately 1000 m where predominantly nonmarine to more than 2500 m where predominantly marine paleogeographic evidence in basalt flows near the top of the succession and in overlying fluvial deposits indicates that these middle miocene strata were deposited across a north northwest trending shoreline a complete progradational sequence typically is several meters to a few tens of meters thick and includes strata that represent three intertonguing stratigraphic units individual sequences generally rest on a thin gravel deposit interpreted as a transgressive lag on an erosional surface the gravel is overlain by structureless siltstone or fine grained sandstone deposited at water depths where the rate of faunal mixing exceeded that of production of structures by physical processes these rocks grade upward into bedded fine sandstone deposited closer to shore where physical processes exceeded bioturbation crossbedded lenses of coarse sand or fine gravel in the upper part of this facies suggest the presence of fairly long period surface waves the bedded fine sandstone is sharply ove lain by a cross bedded coarse sandstone facies that is interpreted as a combined offshore bar rip channel surf zone assemblage cross strata dip dominantly offshore suggesting substantial deposition from rip currents a secondary shoreparallel mode of cross strata direction suggests longshore currents produced by surface waves from the northwest the crossbedded coarse grained sandstone grades upward into planar bedded medium grained sandstone that is interpreted as a beach foreshore this facies grades upward through structureless medium grained sandstone into nonmarine or lagoonal red and green mudstone of the caliente formation the middle miocene succession was deposited in a subsiding basin that was otherwise remarkably stable tectonically the position of the strand line differed no more than a few kilometers through a period of 1 to 3 m y the average duration of the transgressive regressive cycles a few tens of thousands of years together with their distribution in groups of three or four in the lower two thirds of the succession is consistent with the pattern of long term climatic cycles produced by periodicity of the earth s solar orbit and may be related to eustatic sea level changes attendant to the development of the antarctic ice cap changes in the pattern of progradation in the upper part of the succession and nearby basaltic eruptions may have been precursors to the onset of movement along th san andreas fault in this area 12 14 m y ago

groundwater interactions control dolomite and magnesite precipitation in saline playas in the western district volcanic plains of victoria australia abstract in this paper a review is offered on lacustrine sites in australia where both dolomite and magnesite are found to precipitate today but not through diagenesis and have been doing so during the holocene information thus far obtained in the coorong region of se south australia is provided and this follows with a discussion of the published literature from the volcanic plains of western victoria where modern dolomite and magnesite are also precipitating in saline playa lakes today the work presented here clearly identifies that the volcanic rises and topographic highs in western victoria such as warrion hill play a vital role in groundwater recharge first with subsequent flow paths towards the low plains in the region where saline playas are located in the topographically high recharge areas the waters are predominantly rich in ca and as water progressively flows towards the playas ca is lost through calcite precipitation in scorias and soils and is also presumably exchanged for k with a considerable enrichment of the groundwaters with respect to mg ca and k ca this cationic exchange is thought to occur on clays in the subsurface which are the by product of weathering of the local quaternary basalts eventually the lake waters become supersaturated with respect to mg rich minerals and both dolomite and magnesite precipitate naturally in the lake waters to finally settle on the lake floors it is more than likely that a brine pool occurs below each lake and it is from this that precipitation occurs once that pool waters reaches the lake surface high levels of bicarbonate are found in the groundwaters principally as a result of carbonic acid supplied through rain and also from hydrolysis of silicate minerals that originally occurred in the basalts the high concentrations of bicarbonate contribute to the precipitation of the carbonate minerals chemical analyses of the groundwaters and the lakes are tabled and help understand the chemical changes along the groundwater flow paths in addition examination of the 18o and 13c of the western victorian lake sediments by analogy with those of coorong lakes indicates that although the carbonates in the coorong lakes are precipitated as a result of sulphate bacterial reduction this appears not to be the case for the western victorian lakes due to the high turbidity of the western victorian dolomite precipitating lakes as well because of their very high salinities often 50tds there are no macrophytes and little if any algal growth

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

sedimentary successions formed by fifth order glacio eustatic cycles in the middle to upper quaternary formations of the oga peninsula northeast japan abstract the northern coast of the oga peninsula is a type locality for quaternary sedimentary exposures on the sea of japan side of northeast japan middle to late pleistocene shallow marine to nonmarine sediments are continuously exposed on sea cliffs along the anden coast these sediments have been mapped and classified into nine sedimentary facies based on grain size sedimentary structures intensity of bioturbation and associated fossils the depositional environments and paleo water depths of each facies have been estimated based on comparison with the present sub bottom sedimentary features observed in coastal systems around the oga peninsula on the basis of sedimentary facies analysis variations in the depositional depth through time have been reconstructed and correlated with the specmap 18o curve using four marker tephras as time controls the two curves generally agree between approximately 80 and 450 ka suggesting that the sedimentary cycles at the anden coast faithfully record 5th and 6th order glacio eustatic sea level changes peak to peak comparison between the reconstructed depositional depth curve and the 18o curve reveals that 1 unconformities are formed during the late eustatic sea level falls and or the following lowstands 2 transgressive lag deposits are mainly formed below wave base 3 deepening upward successions which sometimes occur below the ravinement surfaces are formed in the inner part of estuary or barrier island environments where wave action was minor 4 shoaling upward successions formed during eustatic sea level falls are deposited under the influence of intense wave action in a strand plain coastal plain system and 5 the characteristic combination of thinner deepening upward successions and thicker shoaling upward successions reflects the asymmetric pattern of glacio eustatic sea level changes and or lower sediment supply during transgression

abrupt cooling of antarctic surface waters and sea ice expansion in the south atlantic sector of the southern ocean at 5000 cal yr b p antarctic surface waters were warm and ice free between 10 000 and 5000 cal yr b p as judged from ice rafted debris and microfossils in a piston core at 53 s in the south atlantic this evidence shows that about 5000 cal yr b p sea surface temperatures cooled sea ice advanced and the delivery of ice rafted detritus ird to the subantarctic south atlantic increased abruptly these changes mark the end of the hypsithermal and onset of neoglacial conditions they coincide with an early neoglacial advance of mountain glaciers in south america and new zealand between 5400 and 4900 cal yr b p rapid middle holocene climate changes inferred from the taylor dome ice core antarctica cooling and increased ird in the north atlantic and the end of the african humid period the near synchrony and abruptness of all these climate changes suggest links among the tropics and both poles that involved nonlinear response to gradual changes in northern hemisphere insolation sea ice expansion in the southern ocean may have provided positive feedback that hastened the end of the hypsithermal and african humid periods in the middle holocene

flow over mountains coriolis force transient troughs and three dimensionality some issues concerning uniform stratified flow over a three dimensional mountain that have not been fully explored are studied using primitive equation models when the froude number fr is small e g fr 0 5 we find that the coriolis force cannot be neglected for flow over small scale mountains characteristic length l 50 km even though the rossby number ro is large when the coriolis force is neglected a pair of symmetric vortices is induced on the lee side irrespective of the scale of the mountain as long as fr lies roughly between 0 1 and 0 5 the major effect of the coriolis force is to modify or diminish the lee vortices due to the leftward deflection on the upstream side of the mountain the coriolis deflection also reduces the upstream propagation when fr is 1 most of the flow goes over the mountain and the coriolis effect is small for the same ro therefore the importance of the coriolis effect is determined by both ro and fr as the scale of the mountain increases from small scale to mesoscale 100 km l 300 km the upstream flow is deflected more to the left by the coriolis effect and a trough develops on the lee side the length scale of the trough depends on the scale of the mountain in the along flow direction for smaller scale mountains small vortices can be generated within the lee side trough when fr is small when the mountain scale is increased the lee side vortices disappear and only a lee side trough remains depending on the mean wind speed and the mountain scale the lee side trough can be advected by the anticyclonic flow over the mountain to the south and remain attached to the mountain for a long time a train of troughs is generated on the lee side of an elliptic mountain associated with the lee side gravity waves simulations of flows over mountains in two dimensional and three dimensional models with the same cross sectional profile are compared for small scale mountains l 100km the two dimensional model overestimates the amount of airflow over the mountain and also the lee side downslope wind

blocking and frontogenesis by two dimensional terrain in baroclinic flow part i numerical experiments the shallow atmospheric fronts that develop in the early winter along the east coast of north america have been attributed in various modeling and observational studies to the land sea contrasts in both surface heating and friction however typical synoptic conditions are such that these coastal fronts could also be a type of upstream influence by the appalachian mountain chain generalized models have suggested that relatively cold air can become trapped on the windward side of a mountain range during episodes of warm advection without a local contribution from differential surface fluxes such a process was proposed decades ago in a study of observations along the coast of norway could coastal frontogenesis be primarily a consequence of a mountain circulation acting on the large scale temperature gradient a two dimensional terrain following numerical model is used to find conditions under which orography may be sufficient to cause blocking and upstream frontogenesis in a baroclinic environment the idealized basic flow is taken to have constant vertical shear parallel to a topographic ridge and a constant perpendicular wind that advects warm or cold temperatures toward the ridge land sea contrasts are omitted in the observed cases the mountain is narrow in the sense that the rossby number is large this by itself increases the barrier effect but the experiments show that large scale warm advection is still crucial for blocking for realistic choices of ambient static stability and baroclinicity the flow can be blocked by a range like the northern appalachians if the undisturbed incident wind speed is around 10 m s21 cold advection weakens the barrier effect the long term behavior of the front in strongly blocked cases is described and compared to observations because of the background rotation and large scale temperature advection blocked solutions cannot become steady in the assumed environment however the interface between blocked and unblocked fluid can settle into a balanced configuration in some cases a simple argument suggests that in the absence of dissipation the frontal slope should be similar to that of the ambient absolute momentum surfaces

palaeohydrology of lowland rivers in the murray darling basin australia abstract this study derives a new function describing the relationship of channel bankfull discharge qbf to channel width in modern rivers of the murray darling basin mdb of southeastern australia and applies this to dated palaeochannels of seven rivers to quantify late quaternary discharge history in this important basin all rivers show high mis3 and mis2 qbf declining in the holocene the qbf of modern mdb rivers is correlated with total catchment precipitation but comparison with palaeochannel qbf estimates shows that while enhanced runoff efficiency is necessary to account for much larger late pleistocene palaeochannels either lower or higher precipitation rates could have prevailed a strong association between relative palaeo qbf enhancement and temperature suggests a temperature mediated mechanism controlling river discharge such as the fraction of precipitation stored as snow and thawing in spring the enhancement of orographic rainfall or co2 feedbacks with vegetation cover significantly enhanced mis3 qbf requires an additional mechanism such as increased rainfall these findings are consistent with others that increased moisture availability was associated with past colder climates although this was not necessarily the result of enhanced precipitation

geomagnetic secular variation from recent lake sediments ancient fireplaces and historical measurements in southeastern australia abstract compilations of historical observations archaeomagnetic data from ancient fireplaces and palaemagetic results from short cores of sediment from lakes in southeastern australia particularly lake keilambete provide a detailed record of the geomagnetic secular variation during the last 3000 years the independent sets of data are in good agreement if the radiocarbon time scale for the lacustrine record is about 450 years too old the error is attributed to systematic incorporation of ancient carbon into the lake floor sediments mainly through erosion of sediment on the crater walls at times of low water level a significant lag between deposition and the acquisition of stable magnetic remanence is ruled out inclination has been abnormally steep during the last 500 years but remained fairly close to the axial dipole field value prior to that during the last 1000 years the predominant sense of looping of the magnetic vector corresponds to westward drift of the nondipole field secular variations on a time scale of 100 years can be resolved by the lacustrine record

moist dynamics and orographic precipitation in northern and central california during the new year s flood of 1997 abstract the dynamics of moist orographic flows during the january 1997 floods in northern and central california are investigated using numerical simulations computed with the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 early in the event 31 december 1996 1 january 1997 the low level winds offshore of california s central coast were blocked by the topography of the santa lucia range and the low level winds in the central valley were blocked by the topography of the central sierra nevada range in contrast moisture laden winds along the northern coast ranges and the northern sierra nevada flowed over topographic barriers as the core of humid air migrated to the south over 24 h the low level barrier jets weakened as the atmospheric stability decreased bringing heavy rainfall to the central and southern sierra nevada at the end of the event the heavy precipitation during this event was largely controlled by the interactio

effect of stable layer formation over the po valley on the development of convection during map iop 8 during intensive observation period iop 8 of the mesoscale alpine program there was a stable layer of air in the lowest levels of the po valley and just upstream of the apennines in this study the effects of the stable layer on the formation of convection in the southern alpine region were investigated through a series of two dimensional idealized experiments the goals of this study were twofold 1 to determine if stable layer strength affected the placement of convection and 2 to test the notion that the stable layer during iop 8 behaved as an effective mountain to accomplish the first objective three simulations were compared in which the strength of the inversion and low level cooling in the po valley and upstream of the apennines was varied the results of these simulations show that the stronger the inversion and low level cooling the farther south the convection was positioned additionally it was found that convection developed as a result of the formation of a broad region of moist instability over the stable layer cellular convection developed in this region of moist instability the second objective was tested through a simulation where the cold pool was replaced by terrain mmtn as in the reference or stb10 simulation the upslope of the terrain in the mmtn simulation was characterized by a wide zone of moist instability however wave structures to the lee of the apennines were markedly different in the stb10 and mmtn simulations this led to different convective and precipitation patterns with the mmtn simulation exhibiting heavier convection over the po valley while the heaviest convection in stb10 was upstream of the apennines these results suggest that at best the stable layer in the stb10 simulation can only be roughly approximated by terrain

radar observations of precipitation and airflow on the mediterranean side of the alps autumn 1998 and 1999 this study constructs and analyses composite three dimensional fields of doppler radar observed radial velocity and reflectivity for all precipitation events occurring in the lago maggiore region on the mediterranean side of the alps during autumn 1998 and 1999 mean patterns for the two years are in close agreement with each other the radar data are consistent with previous rain gauge studies in showing that the rain was heaviest over the lower windward slopes and decreased toward higher terrain the three dimensional reflectivity fields show that precipitation growth occurred mainly at low altitudes the composite radar data show that the precipitation was most intense when the mean flow around the 2 km level was southerly or south easterly i e when the mean flow was most perpendicular to the alpine barrier sounding data from milan indicated the froude number of the flow upstream of the lago maggiore region when the froude number was high the flow proceeded directly up and over the terrain of the lower alpine slopes under these unblocked conditions the low level flow including the layer from the surface to 2 km above mean sea level rose directly up and over the terrain and the precipitation was greatly enhanced over the lower windward slopes and over the portions of the po valley just upstream of the mountains under unblocked conditions the precipitation enhancement only extended a short distance a few tens of kilometres upstream of the alps when the upstream froude number computed from the milan sounding was low blocked conditions the doppler radial velocities indicated that the low level flow in the layer below 2 km above mean sea level turned cyclonically as it approached the alpine barrier instead of rising over the terrain the composite radar reflectivity data showed less precipitation enhancement directly over the windward slope but in contrast to the unblocked case showed that the precipitation was enhanced 140 km or more upstream of the terrain evidently the low level flow began rising far in advance of the barrier in blocked conditions the 1998 and 1999 autumn data sample further indicates the relative roles of wind speed and stability which are combined in the froude number when the wind speed upstream was strong 8 m s 1 significant precipitation enhancement occurred on the windward slope of the alps in the lago maggiore region regardless of the static stability however the enhancement was far greater under unstable conditions when the wind speed was weak 8 m s 1 the precipitation was generally near or below average except when the stability was low and some patchy enhancement occurred over the po valley just upwind of the alps a diurnal precipitation maximum occurred in the early morning hours 0700 1000 lst possibly where down valley flow converged with synoptic scale up valley flow

strontium content of ostracods indicates lacustrine palaeosalinity individual non marine ostracod valves contain sr in proportion to the sr content of their host lake water two commonly coexisting large planktonic species mytilocypris praenuncia and australocypris robusta have a sr distribution coefficient kd sr ca of 0 082 which is independent of temperature in the range 10 18 c if the relationship between salinity and the sr content of a hydrologically simple lake is known palaeosalinities can be calculated from fossil ostracods we present here palaeosalinities for the past 10 000 yr for lake keilambete victoria calculated from ostracod sr ca of fossil material which are in striking agreement with independent interpretations of palaeosalinity the range of salinity spans 14 95 we also show that a reliable quantitative continuous indicator of lacustrine palaeosalinity is important for the elucidation of continental palaeoenvironments for palaeoclimatology and archaeology and ocean continent climatic correlations and interactions

low froude number flow past three dimensional obstacles part i baroclinically generated lee vortices abstract we study the flow of a density stratified fluid past a three dimensional obstacle using a numerical model our special concern is the response of the fluid when the froude number is near or less than unity linear theory is inapplicable in this range of froude number and the present numerical solutions show the rich variety of phenomena that emerge in this essentially nonlinear flow regime two such phenomena which occupy parts i and ii of this study are the formation of a pair of vertically oriented vortices on the lee side and a zone of flow reversal on the windward side of the obstacle the ice vortices have been explained as a consequence of the separation of the viscous boundary layer from the obstacle however this boundary layer is absent by design in the present experiments and lee vortices still occur we argue that a vertical component of vorticity develops on the lee side owing to the tilting of horizontally oriented vorticity produced baroclinically as the isentropes deform in r

orographic precipitation and air mass transformation an alpine example a case of orographic precipitation in the alps on 20 september 1999 was studied using several models along with rain gauge and radar data the objective of the study is to describe the orographic transformation of an air mass including multi scale aspects several new and some conventional diagnostic quantities are estimated including drying ratio precipitation efficiency buoyancy work condensed water residence time parcel changes in heat moisture and altitude and dominant space and time scales for the case considered the drying ratio was about 35 precipitation efficiency values are ambiguous due to repeated ascent and descent over small scale terrain the sign of buoyancy work changed during the event indicating a shift from stratiform orographic to weak convective clouds cloud water residence times are different for the two mesoscale models 400 compared to 1000 s due to different cloud physical formulations the two mesoscale models agree that the dominant spatial scale of lifting and precipitation is about 10 km smaller than the scale of the main alpine massif trajectory analysis of air crossing the alps casts doubt on the classic model of fohn few parcels exhibit classic pattern of moist ascent followed by dry descent parcels that gain latent heat descend only briefly before rising into the middle troposphere parcels that descend along the lee slope originate in the middle troposphere and gain little or even lose latent heat during the transit as parcels seek their proper buoyancy level downstream a surprising scrambling of the air mass occurs radar data confirm the model prediction that the rainfall field is tightly controlled by local terrain on scales as small as 10 km rather than the full 100 km cross alpine scale a curious pulsing of the precipitation is seen indicating either drifting moisture anomalies or weak convection copyright 2003 royal meteorological society

a multiscale analysis of the extreme weather events over western russia and northern pakistan during july 2010 abstractthis manuscript presents a detailed multiscale analysis using observations model analyses and ensemble forecasts of the extreme heat wave over russia and historic floods over pakistan during late july 2010 with an emphasis on the floods over northern pakistan the results show that recirculation of air and dynamically driven subsidence occurring with the intensification of the blocking anticyclone in late july 2010 were key factors for producing the exceptionally warm temperatures over western russia downstream energy dispersion from the blocking region led to trough deepening northwest of pakistan and ridge building over the tibetan plateau thereby providing the linkage between the russian heat wave and pakistan flood events on the large scale in agreement with previous studies the extratropical downstream energy dispersion and enhanced convective outflow on the large scale associated with the active phase of the madden julian oscillation facilitated the formation of an intense upper level

climate variability over the last 35 000 years recorded in marine and terrestrial archives in the australian region an oz intimate compilation abstract the australian region spans some 60 of latitude and 50 of longitude and displays considerable regional climate variability both today and during the late quaternary a synthesis of marine and terrestrial climate records combining findings from the southern ocean temperate tropical and arid zones identifies a complex response of climate proxies to a background of changing boundary conditions over the last 35 000 years climate drivers include the seasonal timing of insolation greenhouse gas content of the atmosphere sea level rise and ocean and atmospheric circulation changes our compilation finds few climatic events that could be used to construct a climate event stratigraphy for the entire region limiting the usefulness of this approach instead we have taken a spatial approach looking to discern the patterns of change across the continent the data identify the clearest and most synchronous climatic response at the time of the last glacial maximum lgm 21 3 ka with unambiguous cooling recorded in the ocean and evidence of glaciation in the highlands of tropical new guinea southeast australia and tasmania many terrestrial records suggest drier conditions but with the timing of inferred snowmelt and changes to the rainfall runoff relationships driving higher river discharge at the lgm in contrast the deglaciation is a time of considerable south east to north west variation across the region warming was underway in all regions by 17 ka post glacial sea level rise and its associated regional impacts have played an important role in determining the magnitude and timing of climate response in the north west of the continent in contrast to the southern latitudes no evidence for cooling during the younger dryas chronozone is evident in the region but the antarctic cold reversal clearly occurs south of australia the holocene period is a time of considerable climate variability associated with an intense monsoon in the tropics early in the holocene giving way to a weakened monsoon and an increasingly el nino dominated enso to the present the influence of enso is evident throughout the southeast of australia but not the southwest this climate history provides a template from which to assess the regionality of climate events across australia and make comparisons beyond our region

forced regressions in a sequence stratigraphic framework concepts examples and exploration significance sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level on the shelf lowstand deposits which form during falls and subsequent stillstands of relative sea level can be recognized by the presence of an unconformity at the base the isolated and basinward position relative to the previous shoreline and the abrupt seaward translation of shallow water and shoreline facies into the basin across an unconformity surface this seaward translation of facies and shoreline regression in response to relative sea level lowering is termed a forced regression a forced regression is independent of variations of sediment flux and is in contrast with normal regressions that occur in response to excess sediment flux relative to space available on the shelf i e accommodation forced regressions commonly are associated with a zone of sedimentary bypass subaerial exposure and possible fluvial erosion between the newly formed and preceding shorelines certain shelf sands previously interpreted as offshore or mid shelf sand bodies thus can be reinterpreted as stranded lowstand shorelines associated with forced regressions this alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries with the potential for development of new play types and enhanced recovery in o der fields examples of forced regression can be observed at a variety of scales and ages several such examples include the modern east coulee fan delta and the lower cretaceous viking formation in alberta canada the quaternary rhone delta and the quaternary hudson valley system

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

slope shelf nearshore depositional sequences with transgressive conglomerate in a miocene backarc and arc junction setting central japan abstract several third order slope shelf nearshore depositional sequences are found in the middle to late miocene aoki and ogawa formations in the southern part of the northern fossa magna region central japan each depositional sequence consists of a transgressive systems tract varying in thickness from several tens of centimetres to about 10 m a falling stage systems tract several tens of metres in thickness and a highstand systems tract 20 80 m thick the highstand systems tract and falling stage systems tract are bounded by the regressive surface of marine erosion each depositional sequence mainly consists of coarse grained sediments the materials of the transgressive conglomerate beds were derived from the gravelly foreshore and upper shoreface by transgressive shoreface erosion the thin and conglomeratic transgressive systems tract indicates that these slope shelf nearshore sequences were deposited on the steep slope area under a rapid transgression therefore these sequences were formed in response to excess sediment supply and a rapid rise in relative sea level at an active margin of the backarc side of the arc trench system

wave formed coarse grained ripples and their relationship to hummocky cross stratification abstract wave formed coarse grained ripples cgr form in water depths ranging from 3 to 160 m on transgressive surfaces in upper and lower shoreface sediments and in finer grained offshore transition deposits cgr have crest spacings of 0 25 3 0 m with amplitudes of 5 35 cm internal stratification is rarely preserved but where present crossbeds dip en echelon away from the ripple crest and individual laminae feather out away from the crest waves that form cgr commonly have wavelengths on the order of 2 5 m with periods of 8 to 14 sec these are not large storm events especially on a geological scale cgr commonly occur in close association laterally and vertically with hummocky cross stratification it is postulated that if sediment is medium to very coarse grained sand or pebbly sand then two dimensional cgr will be formed from oscillatory or oscillatory dominant flow if however sediment is very fine to fine grained sand then three dimensional hummocky cross stratification will be formed the wave conditions under which cgr form are similar to those which would form hummocky cross stratification it is only the grain size that is different reported and calculated wave conditions for hummocky cross stratification are almost identical to those for cgr modern cgr crests trend parallel to the local shoreline and bathymetry as such ancient ripple crests are a useful tool for basin reconstruction

further results on moist nearly neutral flow over a ridge abstract in a recent study the authors performed numerical simulations of moist nearly neutral flows over a ridge using the weather research and forecasting wrf model in a regime where the coriolis force can be neglected and with the simple kessler warm rain microphysical scheme in the present work further numerical solutions using more general and realistic experimental conditions are discussed the upstream propagating disturbance which was found in the author s previous study to desaturate the initially saturated sounding for intermediate mountain heights is present for all the simulations with taller mountains considered in the present work the inclusion of the coriolis force however suppresses the upwind propagation of the dry region and weakens the downstream development of convective cells the sensitivity to different microphysical schemes has also been investigated the simple kessler scheme was compared with a more complete scheme by lin et al which includes ice species some differ

numerical simulations of the 12 13 august 2002 flooding event in eastern germany in this paper high resolution numerical simulations of the 12 13 august 2002 flooding event in eastern germany are presented the simulations are performed with the penn state national center for atmospheric research mesoscale model mm5 in a four domain configuration with a finest horizontal resolution of 1 km sensitivity experiments are performed with coarser resolutions 3 and 9 km with different cloud microphysical parametrizations and with a different date of initialization moreover tests with i km resolution but the smoothed topography of the 9 km runs are conducted in order to isolate the contribution of the model topography to the differences between the 1 km runs and the 9 km runs the results show that the high resolution runs reproduce the observed structure of the precipitation field very well in particular the location of the rainfall maximum is correct to within 15 km the quantitative agreement between model results and observations is fairly good in regions with light to moderate rain but large amounts of precipitation tend to be underpredicted for observed 36 hour rainfall accumulations exceeding 200 mm the negative bias typically ranges between 15 and 30 with fairly little dependence on the microphysical parametrization in the coarser resolved runs the bias at high precipitation amounts becomes even more pronounced and it is found that this behaviour is not only due to the fact that a coarser resolution is associated with a smoother topography this indicates a systematic deficiency in the microphysical parametrizations limiting their ability to simulate heavy precipitation

vegetation and environments since the last glacial maximum in the southern tablelands new south wales regional changes in vegetation and environment in the last 16 ka have been reconstructed from micalong swamp and willigobung swamp 35 s on the western southern tablelands of new south wales nsw micalong swamp lies at 980m above sea level a s l which is close to the subalpine treeline at this latitude willigobung swamp 780m a s l approaches the modern ecotone between dry and wet montane forest formations the sites are sensitive to shifts in temperature and precipitation and are the first reported pollen records from the western montane slopes of nsw a radiocarbon based chronology indicates that micalong swamp was a swampy gravel floodplain surrounded by alpine grassland before 16 1 ka subalpine woodland may have become established at 1000m by 16 14 ka organic fen sedimentation developed 11 8 ka at willigobung and 11 7 ka at the higher elevation micalong swamp wet forest elements were present at both sites around 10 ka and persisted for 3 4 ka sedimentation in a shallow lake or fen between 10 and 8 ka supports this evidence for wetter conditions in the early holocene in the late holocene an expansion of subalpine flora between 2 7 and 0 9 ka preceded by shallow lake fen sedimentation is consistent with regional evidence for neoglacial cooling copyright 2014 john wiley sons ltd

late quaternary lake level changes and climates of australia abstract spatial and temporal patterns in lake level data from 38 sites in australia and papua new guinea provide a basis for reconstructing changes in water balance and atmospheric circulation during the past 30 000 years the reconstructions are consistent with hydrological changes inferred from pollen analysis and palaeowind directions inferred from dunes generally wetter conditions between 30 000 and 24 000 bp are consistent with a strong walker circulation with the sta near its present position general aridity at the glacial maximum until 12 000 bp with higher than present lake levels in the southeastern interior of australia implies that the southern margin of the subtropical anticyclone belt was expanded southward and the southern westerlies were correspondingly displaced this southward shift appears in all gcm simulations of the 18 000 bp climate and may be a result of the increased vigour of the northern hemisphere circulation a northward migration of the belt of high lake levels between 11 000 and 6000 bp suggests that the sta shifted back equatorward to north of its present position relaxation to modern conditions occurred after 6000 bp interrupted by an unexplained dry phase 6000 5000 bp in tasmania and queensland

late holocene climatic variability indicated by three natural archives in arid southern australia three terrestrial climate proxies are used to investigate the evolution of holocene palaeoenvironments in southern central australia all of which present a coherent record of palaeohydrology single grain optically stimulated luminescence from sediments supplemented by 14c from charcoal and lacustrine shells was obtained to date shoreline deposits lake callabonna and the adjacent mt chambers creek alluvial fan our findings are complemented by a u th based record of speleothem growth in the mt chambers creek catchment which we interpret to reflect increased precipitation together these archives shed light on the timing of and possible sources of water for holocene pluvial intervals we identified several phases of elevated lake levels dated at 5 8 5 2 4 5 3 5 2 7 and 1 kyr most of which correspond to fluvial activity resulting from increased precipitation in the adjacent ranges the enhanced hydrology during phases of the late holocene likely increased the reliability of resources for regional human populations during a time of reduced winter rainfall when considered within the framework of the current understanding of holocene palaeoclimate in central australia our data suggest that the pattern of landscape response was broadly synchronous with larger scale climatic variability and punctuated by pluvial periods greater than today

a model aided investigation of winter thermally driven circulation on the italian tyrrhenian coast a case study 1 data collected during a campaign carried out in and around rome in february 1996 using sodars tethered balloon and surface data suggest the development of a winter sea breeze that could not be detected by conventional data and analyses a model aided study is performed to verify the development of thermally driven local circulation and to prove the onset of a winter sea breeze regime propagating inland and interacting with the urban heat island uhi the area of interest for the study is the central part of italy latitude 41 43n longitude 10 16e the mm5 mesoscale model was used at high resolution three nested domains with up to 3 km of grid resolution were used in the area where the sea breeze was observed to highlight the effect of the sea breeze a simulation with a thick cloud layer in the innermost domain was performed by removing the cloud layer the diurnal evolutionofthehorizontaltemperature gradientledtothedevelopmentoftheseabreezeand the uhi circulation in agreement with the data sensitivity tests were carried out to evaluate the effect of land use resolution and of satellite retrieved climatological sea surface temperatureonthesimulationresults doppler sodardatarecordedatthreesites tethersonde profiles and surface data were used to verify the results as expected using high resolution land use and the daily sea surface temperature retrieved by satellite observations led to improvementsinthelocalcirculationproducedbythemodel however themodelfallsshort in reproducing some of the sea breeze characteristics it finds that the sea breeze starts too early and lasts for a shorter time than the observed one does and the wind direction shows a too strong northerly component also it slightly underestimates the daily temperature pattern the interaction of the urban heat islands of rome and ostia with the sea breeze flow is analyzed to explain the causes of these discrepancies index terms 3307 meteorology and atmospheric dynamics boundary layer processes 3322 meteorology and atmospheric dynamics land atmosphere interactions 3329 meteorology and atmospheric dynamics mesoscale meteorology keywords sea breeze modeling urban heat island citation ferretti r g mastrantonio s argentini r santoleri and a viola a model aided investigation of winter thermally driven circulation on the italian tyrrhenian coast a case study j geophys res 108 d24 4777 doi 10 1029 2003jd003424 2003

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

mechanisms of intense alpine rainfall abstract numerical studies by the authors and others of the 1994 piedmont flood show that the orographically modified flow was a critical element for the production of extraordinary rainfall to uncover the precise mechanism of orographic rainfall occurring in full physics mm5 simulations of the 1994 piedmont flood the authors carried out simulations with the same real data initial and boundary conditions but with the real orography replaced by an idealized one with excellent agreement between real and idealized orography on the rainfall rate versus time in the piedmont area analysis of the idealized orography simulation provides a clear picture of the model s mechanism of orographically induced rainfall as noted in previous studies of the 1994 piedmont case a moist saturated airflow has a reduced effective static stability and tends to flow over the mountains while an unsaturated airstream is stable and tries to flow around toward the left in the northern hemisphere in the 1994 piedmont case t

mechanisms producing different precipitation patterns over north eastern italy insights from hymex sop1 and previous events during the first hymex special observation period sop1 field campaign the target site of north eastern italy nei experienced a large amount of precipitation locally exceeding the climatological values and distributed among several heavy rainfall episodes in particular two events that occurred during the last period of the campaign drew our attention these events had common large scale patterns and a similar mesoscale setting characterised by southerly low level flow interacting with the alpine orography but the precipitation distribution was very different during intensive observing period iop18 31 october 1 november 2012 convective systems were responsible for intense rainfall mainly located over a flat area of the eastern po valley well upstream of the orography conversely during iop19 4 5 november 2012 heavy precipitation affected only the alpine area in addition to iop18 and iop19 the present study analyses other heavy precipitation episodes that display similar characteristics and which occurred over nei during the autumn of recent years a high resolution 2 km grid spacing non hydrostatic nwp model and available observations are used for this purpose the two different observed precipitation patterns are explained in terms of interaction between the impinging flow and the alps depending on the thermodynamic profile convection can be triggered when the impinging flow is forced to rise over a pre existing cold air layer at the base of the orography in this situation a persistent blocked flow condition and upstream convergence are responsible for heavy rain localized over the plain conversely if convection does not develop flow over conditions are established and heavy rain affects the alps numerical parameters proposed in the literature are used to support the analysis finally the role of evaporative cooling beneath the convective systems is evaluated it turns out that the stationarity of the systems upstream of the alps is mainly attributable to persistent blocked flow conditions while convective outflow slightly modifies the location of precipitation

an oceanic cold reversal during the last deglaciation a detailed deuterium excess profile measured along the dome c epica european project for ice coring in antarctica core reveals the timing and strength of the sea surface temperature changes at the source regions for dome c precipitation we infer that an oceanic cold reversal took place in the southern indian ocean 800 years after the antarctic cold reversal the temperature gradient between the oceanic moisture source and antarctica is similar to the dome c sodium profile during the deglaciation illustrating the strong link between this gradient and the strength of the atmospheric circulation

a fine resolution palaeoclimatic reconstruction of the last 2000 years from lake keilambete southeastern australia a fine resolution analysis of pollen charcoal magnetic susceptibility sediment fractions and total carotenoids was used to investigate the last 2000 years of environmental history at lake keilambete in western victoria australia the chronology of sedimentation was based on three radiocarbon dates supplemented by inferences from 22 previous radiocarbon ages from the site spanning approximately the last 7500 years changes in the analysed parameters infer a relatively higher effective moisture from approximately 2000 to 1800 cal bp increased instability in the lake keilambete catchment from 1750 to 1425 cal bp may reflect a decreased moisture availability and cooler temperatures at about 1450 cal bp a period of considerable environmental change is suggested at lake keilambete warmer temperatures or an increased moisture supply seem likely between 1415 and 1320 cal bp from around c 1150 until 800 cal bp overlapping the medieval warm period a series of changes in the composition of the la

lacustrine fluvial interactions in australia s riverine plains climatic forcing of fluvial systems has been a pre occupation of geomorphological studies in australia since the 1940s in the riverine plain southeastern australia the stable tectonic setting and absence of glaciation have combined to produce sediment loads that are amongst the lowest in the world surficial sediments and landforms exceed 140 000 yr in age and geomorphological change recorded in the fluvial fluvio lacustrine and aeolian features have provided a well studied record of quaternary environmental change over the last glacial cycle the region includes the willandra lakes whose distinctive lunette lakes preserve a history of water level variations and ecological change that is the cornerstone of australian quaternary chronostratigraphy the lunette sediments also contain an ancient record of human occupation that includes the earliest human fossils yet found on the australian continent to date the lake level and palaeochannel records in the lachlan willandra system have not been fully integrated making it difficult to establish the regional significance of hydrological change here we compare the willandra lakes environmental record with the morphology and location of fluvial systems in the lower lachlan an ancient channel belt of the lachlan willandra creek acted as the main feeder channel to willandra lakes before channel avulsion caused the lakes to dry out in the late pleistocene electromagnetic surveys geomorphological and sedimentary evidence are used to reconstruct the evolution of the first new channel belt following the avulsion single grain optical dating of floodplain sediments indicates that sedimentation in the new middle billabong palaeochannel had commenced before 18 4 1 1 ka a second avulsion shifted its upper reaches to the location of the present lachlan river by 16 2 0 9 ka the timing of these events is consistent with palaeohydrological records reconstructed from willandra lakes and with the record of palaeochannels on the lachlan river upstream willandra lakes shows high inflows during the last glacial maximum 22 ka but their subsequent drying between 20 5 ka and 19 ka was caused by river avulsion rather than regional aridity this case study highlights the benefits of combining fluvial with lacustrine archives to build complementary records of hydrological change in lowland riverine plains

a numerical study of appalachian cold air damming and coastal frontogenesis abstract a 24 h numerical simulation is used to study features of the wedge shaped pressure ridge and the coastal front which occur in eastern united states during winter and often cause substantial errors in operational models specifically the penn state national center for atmospheric research mesoscale model mm is used as a diagnostic tool to investigate the mesoscale structure of these phenomena associated with the appalachian ice storm of 13 14 january 1980 the mm which used 15 vertical levels 8 below 800 mb a 50 km horizontal mesh size and a multi level boundary layer parameterization produced a better forecast of boundary layer temperature and sea level pressure than did the national meteorological center s operational model for this case study period to the east of the mountains the mm maintained the wedge ridge pattern and produced the low level northerly flow which is characteristic of the damming region the mm also provided reasonable vertical profiles of temperature and wind

holocene lake level fluctuations in lakes keilambete and gnotuk southwestern victoria australia reconstructed holocene lake level curves from two saline hydrologically closed maar crater lakes in southwestern victoria australia show near synchronous lake level changes throughout the holocene we show that lake levels reconstructed from sediment particle size and ostracod valve chemistry 18o and sr ca have undergone rapid 10 m fluctuations throughout the holocene finer sampling resolution shows a more sensitive response to holocene climate than was previously presented for lake keilambete both maar crater lakes show a short lived maximum in holocene lake levels around 7 2 ka the period of lake filling leading to peak lake levels matches the phase of most effective precipitation 7 4 7 0 ka reconstructed from a high resolution speleothem record from northern tasmania water levels declined in both lakes during the mid holocene with a more substantive decline after 5 ka which coincides with the end of the southern hemisphere hypsithermal water levels continued to oscil

lower pleistocene to present structural deformation and sequence stratigraphy of the continental shelf offshore eel river basin northern california seismic stratigraphic sequences and deformational features are mapped beneath the continental shelf of the offshore eel river basin of northern california using a closely spaced high resolution multichannel seismic grid geometries of sequences and morphologies of bounding unconformities reflect competing tectonic and glacioeustatic influences producing shifting sedimentation patterns in the offshore basin during the last v1 myr estimated timing of unconformity formation correlates generally with a deep ocean global n 18 o curve both before and after a v500kyr transition from 41 kyr to 100 kyr dominated cycles we suggest that glacioeustatic fluctuations are the dominant control on unconformity formation basinwide however regional tectonic influences on sequence development are also observed folding associated with gorda north america plate convergence ended progressively from south to north between v1 0 ma and v500 ka in response to northward migration of the mendocino triple junction mtj since v500 ka continued encroachment of the mtj produces rotation of preexisting structures uplift of the table bluff anticline tba related periods of channel incision south of the tba and generally reduced sediment preservation across the shelf mtj related uplift may also have induced formation of eel canyon over the past v1 0 myr a dominant northern sediment source becomes progressively less important a southern source probably the paleo eel river has become dominant since v750 ka seismic unconformities fall into two categories 1 irregular surfaces of limited mappable extent interpreted as incision exposure surfaces forming during relative sea level lowstands and 2 smooth laterally extensive regional unconformities interpreted as ravinement surfaces that erode lowstand surfaces in all but deeply incised areas during sea level transgressions a sequence stratigraphic model for sediment deposition and preservation on the eel river shelf predicts that preserved sediment on the eel margin is dominated by fluvially derived highstand silts and muds deposited by longshore directed currents and waves lowstand sediments are preserved only in fluvial channels infilled during late lowstand early transgression preserved transgressive sediments are likely limited to a thin veneer of well sorted coarse sediment or shell debris deposited above the transgressive ravinement future deep coring will be required to confirm these predictions 2002 elsevier science b v all rights reserved

alkalinity control on the partition coefficients in lacustrine ostracodes from australia the partition coeffi cients k d guiding the uptake of mg and sr in the low mg calcite valves of ostracodes in australian saline lakes have been reviewed in line with new information on the bicarbonate content and the mg ca of the ambient waters strongly alkaline and very high mg ca 20 waters cause the partition coeffi cients of ostracodes to differ signifi cantly from those found in other lakes with lower mg ca values water salinity does not affect the uptake of mg or sr in ostracode valves whereas the hco 3 of the water strongly correlates to k d sr with high hco 3 resulting in a signifi

6000 years of environmental changes recorded in blue lake south australia based on ostracod ecology and valve chemistry abstract a 4 m long core taken from the freshwater blue lake crater near the township of mount gambier in southeastern south australia provided a high resolution palaeoclimatic record for the last six millennia accelerator mass spectrometry ams radiocarbon 14 c dates were obtained from organic plant fibres and biogenic carbonates from the laminated sequence of the core and from a modern water sample large discrepancies between the radiocarbon ages determined from plant fibres and biogenic carbonates indicate the presence of a time variable lacustrine reservoir which is consistent with what is known of the lake s hydrology ostracod assemblages associated with stable isotope 13 c 18 o analyses and in combination with mg ca sr ca and na ca analyses done on ostracod valves infer salinity temperature and water level changes in blue lake over the last 6 millenia the influence of local aquifers through time has also been determined from the na ca of ostracod valves approximately 900 year cycles are evident in the 13 c record from 5 4 ka to 1 8 ka the history of blue lake records an initial period of high hydrological variability around 6 ka becoming increasingly deeper as groundwater flowed into the basin by 4 ka the lake had reached steady state with the lake level fluctuating by as much as 9 m although significant geochemical variations represent temperature fluctuations until european settlement near the lake in 1839

orographic effects on rainfall in map cases iop 2b and iop 8 although the large scale flow was similar important differences in mesoscale atmospheric structure made the difference between moderately intense rain in intensive observing period iop 2b and relatively light rain in iop 8 in the lago maggiore target area lmta this conclusion is supported here through analysis of data from and numerical simulations of these two cases analysis of the large scale data shows that there was in both cases a moist tongue of southerly flow moving from the west to the east of the alpine south side mesoscale data analysis and numerical simulations suggest that the most important difference between the two cases was the presence of a cold stable air mass in the po valley in iop 8 which persisted through the period in which the large scale moist tongue was progressing eastward and prevented the most humid air from reaching the lmta another difference contributing to the greater rainfall in the lmta in iop 2b was the development of conditional instability with associated convective rain due to the effect of the alps on the eastward passage of the moist tongue in iop 8 the atmosphere remained locally stable throughout the period copyright 2003 royal meteorological society

boron isotope geochemistry of australian salt lakes boron isotope geochemistry has been investigated in brines groundwaters and sediments from the modern australian salt lakes of victoria south australia and western australia by applying negative thermal ionization mass spectrometry techniques the geochemical history of the brines has been reconstructed by using 11b bcl and nacl ratios the victorian volcanic crater lakes of southeastern australia have water salinities of up to 60 g l molar nacl ratios 0 87 similar to the marine ratio molar bcl ratios of 2 9 10 4 to 4 9 10 4 and 11b values of 54 to 59 relative to nbs 951 the depletion of total b and the high positive 11b values relative to seawater bclratio 7 9 10 4 11b 39 are attributed to a marine cyclic salt origin together with adsorption processes in closed systems with low water sediment wr ratios in contrast salt lakes from south australia and western australia which are large shallow playas associated with halite gypsum and detrital clay minerals have interstitial and surface brines characterized by salinities of 80 to 280 g l molar nacl ratios of 0 85 to 1 molar bcl ratios of 4 10 6 to 4 10 4 and 11 values of 25 to 48 the 11 values of these brines are different from those of groundwaters from the great artesian basin 11 15 9 to 2 2 with high molar bcl ratios of 1 10 3 to 3 8 10 2 country rocks 11b 8 7 to 6 8 and modern detrital sediments present in these salt lakes 11b 3 2 to 12 3 the 11b values of these salt lakes overlap with those of surface and brackish waters 11b 28 to 35 and with the b isotopic composition of seawater 11b 39 both low molar nacl ratios 39 of some brines indicate interaction of the brines with detrital sediments within the salt lake systems 11 values 39 suggest mixing of brines of marine origin from which b was partly removed by adsorption with waters of terrestrial origin with low 11 values nacl ratios are used as indicators of the origin of the salts as well as of halite dissolution precipitation the 11 values and bcl ratios are sensitive to a marine or non marine origin adsorption of boron onto clays and the effective water sediment ratio at low wr ratios the preferential removal of 10b from the solution affects the bulk solution whereas at high wr ratios the 11 value of a solution is not affected by adsorption although the 11 value of borate minerals may be a discriminant of marine or non marine origin boron isotopes are less distinctive in evaporative environments where boron is not an abundant component and where water sediment interaction occurs

rain shadow development during the growth of mountain ranges an atmospheric dynamics perspective 1 an idealized atmospheric model is used to explore the links between climate and topography in the development of orographic rain shadows during orogenesis the atmospheric dynamics theory of density stratified fluid flow over topography is used to interpret the results the controlling nondimensional parameter is nh u where n is the brunt vaisala frequency a measure of atmospheric stability h is the terrain relief and u is the initial horizontal wind speed rain shadow development is found to be a nonlinear and nonunique function of both topography and atmospheric state indicating that geological records of orographic aridity cannot be interpreted in terms of relief alone when upstream topography exceeds nh u 1 during surface uplift downstream orographic precipitation vanishes and downstream orographic cloud mass decreases by as much as 90 upstream blocking of air flow can generate a forward projecting rain shadow in which a relatively low ridge nh u 1 may be decoupled from the atmospheric flow by a zone of flow stagnation extending upstream of the high terrain such an effect may occur if the valley separating the two ranges is narrower than the length scale of flow stagnation in the model configuration used here lateral widening of a relatively low nh u 1 range increases downstream cloud mass by up to a factor of 3 these results help to refine interpretations of climate tectonic interactions in shaping the geological record of the sierra nevada and andes

a theoretical study of cold air damming abstract the dynamics of cold air damming are examined analytically with a two layer steady state model the upper layer is a warm and saturated cross mountain easterly or southeasterly onshore flow the lower layer is a cold mountain parallel northerly jet trapped on the windward eastern side of the mountain the interface between the two layers represents a coastal front a sloping inversion layer coupling the trapped cold dome with the warm onshore flow above through pressure continuity an analytical expression is obtained for the inviscid upper layer flow with hydrostatic and moist adiabatic approximations blackadar s pbl parameterization of eddy viscosity is used in the lower layer equations solutions for the mountain parallel jet and its associated secondary transverse circulation are obtained by expanding asymptotically upon a small parameter proportional to the square root of the inertial aspect ratio the ratio between the mountain height and the radius of inertial oscillation the geometr

40ar 39ar geochronology reveals rapid change from plume assisted to stress dependent volcanism in the newer volcanic province se australia here we present 40ar 39ar ages of volcanic features in the cenozoic intraplate newer volcanic province in southeast australia the 5 ma volcanic products in the newer volcanic province can be subdivided into tholeiitic valley filling newer plains basalts and alkaline scoria cones lava shields and maars of the newer cones series plateau ages range from 3 76 0 01 to 4 32 0 03 ma 2 all sources of uncertainties included for the newer plains series with production rates of volcanism decreasing post 4 ma we suggest that magmatism is related to the complex interplay of magma upwelling due to edge driven convection and the cosgrove track mantle plume located in the northeast of the province at 6 5 5 ma plateau ages range from 1290 20 to 41 1 2 2 ka 2 for the newer cones series with a diffuse age progression in the onset of volcanism for these features from east to west analyses of the distribution and geomorphology of these volcanic features indicates a strong control of basement faults on volcanism reflected in alignment of volcanic features along paleozoic north south oriented basement faults in the east and cretaceous northwest southeast oriented extensional features in the west this age progression can be explained by a westerly migration of stress derived from the left lateral strike slip tasman fracture zone this suggests that the general mechanism of volcanism changed from upwelling due to plume assisted edge driven convection prior to 4 ma to stress dependent upwelling at around 1 3 ma

effect of the andes cordillera on precipitation from a midlatitude cold front the effects of the andes cordillera the major mountain range in south america on precipitation patterns of baroclinic systems approaching from the southeast pacific remain largely unstudied this study focuses on a case in late may 2008 when an upper level trough and surface cold front produced widespread precipitation in central chile the primary goal was to analyze the physical mechanisms responsible for the structure and evolution of the precipitation weather research and forecasting wrf model simulations indicate that as an upper level trough approached central chile midtropospheric flow below 700 hpa was blocked by the high topography and deflected poleward in the form of a barrier jet this northerly jet had wind maxima in excess of 15 m s 21 was centered around 925 hpa and extended westward 200 km from the mountains it intersected the cold front which approached from the south near the coast thereby increasing convergence along the frontal surface slowing its equatorward progress and enhancing rainfall over central chile another separate region of heavy precipitation formed over the upwind slopes of the cordillera a trajectory analysis confirmed that the barrier jet moved low level parcels from their origin in the moist southeast pacific boundary layer to the coast when model topography was reduced to twenty percent of its original height the cold front advanced more rapidly to the northeast generated less precipitation in central chile between 338 and 368s and produced minimal orographic precipitation on the upwind andean slopes based on these findings the high topography appears responsible for not only orographic precipitation but also for substantially increasing precipitation totals over the central coast and valley

mid holocene drylands a multi model analysis using paleoclimate modelling intercomparison project phase iii pmip3 simulations this study examines changes in aridity levels during the mid holocene approximately 6000 cal yr ago using multi model simulations from the paleoclimate modelling intercomparison project phase ii

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