controls of eustasy and diagenesis on the 238u 235u of carbonates and evolution of the seawater 234u 238u during the last 1 4 myr using a leaching protocol designed for the study of u isotopes in recent carbonates we measured the u isotope composition both 238 u 235 u and 234 u 238 u of modern and ancient corals n 6 a limestone and a dolostone as well as 43 shallow water carbonate sediments from the odp leg 166 site 1009 drill core on the slope of the bahamas platform although bulk corals record the seawater 238 u value within 0 02 differences of up to 0 30 in the 238 u of individual leachates suggest a control of the coral structure and a more positive 238 u 235 u ratio in the centers of calcification the drill core 238 u data shows that the 238 u 235 u ratio of shallow water carbonates is controlled mainly by 1 variations in sea level through the mixing of different amounts of platform derived sediments with 238 u 0 50 0 60 heavier than seawater and pelagic sediments with seawater like 238 u values 2 authigenic u enrichment via pore watercirculation and u reduction both on the platform and down to 5 m below the surface mbsf after deposition of the sediment and to a lesser extent by 3 early diagenetic processes i e carbonate dissolution and or recrystallization during sediment burial the global effect of these processes leaves the 238 u values of shallow water carbonates offset relative to that of seawater by carbonates sw 0 24 0 06 95 ci including all samples this shift can be used in seawater paleoredox reconstructions based on carbonates deposited on shallow water platform shelf and slope environments i e most of the carbonate sedimentary record prior to the mesozoic to account for the average effect of carbonate diagenesis assuming that the 238 u 235 u ratio of carbonate platform sediments directly records the seawater 238 u 235 u ratio would underestimate the extent of ocean seafloor anoxia by at least a factor 10 the rapid fluctuations in 238 u values due to sea level changes i is a factor that should be considered before interpreting 238 u variations as reflecting changes in oceanic paleoredox conditions and ii reinforces the need for statistically meaningful data sets the 234 u data suggest that the 234 u 238 u ratio of the seawater has remained within 20 of the modern seawater value during the last 1 1 4 myr furthermore we find that small scale 1 15 variations in seawater 234 u mirror sea level changes during the penultimate glacial interglacial period 140 to 200 ka thus confirming the record of lower 234 u sw during periods of low sea level stand and expanding it to at least the last two glacial interglacial events i e 0 23 ma such fluctuations in 234 u initial values should be taken into account when screening carbonate sediments u th ages on the basis of the initial 234 u 238 u ratios of the samples

depositional and sea level history from mis 6 termination ii to mis 3 on the southern continental shelf of south africa abstract pleistocene shoreline deposits comprised of calcified shallow marine palaeobeach and aeolian palaeodune facies found along mid latitude coastlines can be useful indicators of past sea levels here we describe a succession of such deposits that are presently exposed both above subaerial and below submerged mean sea level along the southern cape coast of south africa 18 km east of the town of mossel bay the submerged units provide a window on late pleistocene coastal processes as palaeoshoreline deposits in this study extend to water depths of up to 55 m on the mid shelf five sedimentary facies were identified in the strata and were compared to modern depositional environments of the local littoral zone which include aeolian dune upper shoreface foreshore intertidal swash and back barrier settings twenty two geological units were observed and mapped some of these units were directly dated with optically stimulated luminescence osl dating osl ages were obtained for ten samples from the subaerial and twelve samples from the submerged deposits those geological units not directly dated were interpreted based on sedimentology and field stratigraphic relationships to dated units the stratigraphy and chronology of the succession indicates a record of initial deposition during termination ii t ii meltwater events preceding and leading to marine isotope stage mis 5e indicators for multiple sea level fluctuations between mis 5d and mis 4 and sediment deposition at the end of mis 4 and start of mis 3 are also found both regressive and transgressive depositional cycles are well preserved in the succession we propose that palaeodune and palaeobeach deposits along the south coast of south africa have no clear preference for deposition during sea level transgressions or regressions sediment deposition more closely mirrors the rate of sea level change with deposition and preservation either during times of rapid sea level movement or oscillation around still stand events periods of relatively slow average rise or fall of sea level are represented by erosional planation surfaces in this record

u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

open system coral ages reveal persistent suborbital sea level cycles sea level is a sensitive index of global climate that has been linked to earth s orbital variations with a minimum periodicity of about 21 000 years although there is ample evidence for climate oscillations that are too frequent to be explained by orbital forcing suborbital frequency sea level change has been difficult to resolve primarily because of problems with uranium thorium coral dating here we use a new approach that corrects coral ages for the frequently observed open system behavior of uranium series nuclides substantially improving the resolution of sea level reconstruction this curve reveals persistent sea level oscillations that are too frequent to be explained exclusively by orbital forcing

anatomy of a late quaternary carbonate island constraints on timing and magnitude of sea level fluctuations west caicos turks and caicos islands bwi abstract the data set of the island of west caicos consists of a combination of high resolution lidar and digital imagery radiometric data and amino acid racemization aar d l values as well as extraordinary preservation of sedimentary and bio constructed deposits on the island together with a well established regional stratigraphic framework from the neighboring bahamian island chain and detailed field mapping the west caicos data set provides an opportunity to advance our understanding of the link between carbonate stratigraphy and the controlling parameters of sea level sediment supply tectonics and climate the exceptionally well preserved stratigraphic record of the mid late pleistocene from west caicos allows recognition of marine isotope stages mis 9 11 5e and holocene the west coast of the island provides a continuous 8 4 km exposure of the mis 5e record that enhances our understanding of the intra mis 5e bipartite succession in this region and supports a sea level lowering that occurred during the last interglacial lig west caicos accreted as a series of eolian foreshore shoreface barrier reef and fringing reef facies shoreline positions for all but the mis 7 and mis 5a c deposits are now captured in the sub meter geodetic quality topobathy lidar survey the star town unit of mis 9 11 age forms the southern margin of the island as well as the central karst modified spine with uranium thorium u th coral ages of between 368 and 365 thousand years ago ka and a d l glu average of 0 60 early mis 5e strata include the railroad ridge unit in the center of the island which was previously identified as one of the older units the railroad ridge unit is a north south linear dune ridge that has a d l glu average of 0 52 and indicates the onset of sediment sources from the east associated with a flooded central caicos platform approximately synchronously the early mis 5e south reef unit 3 75 4 m sea level elevation nucleated on the western coast of west caicos attached to the middle pleistocene star town unit the south reef corals yield an average coral u th age of 126 5 ka with an average d l glu from skeletal matrix of 0 46 this transitional barrier fringing reef is unconformably overlain by the late mis 5e boat cove unit corals in the basal transgressive phase of this upper mis 5e boat cove unit yield an average 120 6 ka u th and average d l glu of 0 45 shallow marine foreshore and eolian facies of the late mis 5e rest on a wave cut terrace that cuts the early mis 5e south reef unit by as much as 3 m down to a 0 5 m above present sea level elevation the upper mis 5e boat cove unit displays a maximum of 4 5 m elevation above present day sea level measured from the middle of the foreshore this estimate may be a minimum value as the exposures on the west coast are part of a forced regressive foreshore sequence last stages of the upper mis 5e deposition are seen in a series of regressive dune beach ridge deposits referred to as the northeast ridges unit with sea level positions ranging from 4 5 m early in the central part of west caicos to 0 5 m on the far northeast coast eventually building down below present day sea level this sea level history fits well with previously documented records in the bahamas and globally and the extensive erosion supports a short lived between 126 and 120 ka intra mis 5e relative sea level fall holocene deposition on west caicos is restricted to northern and eastern margins of the island as a combination of strandplain and dune ridge mixed skeletal oolitic units using the high resolution digital elevation model dem and linked digital geologic map makes it possible to compare areas of the different pleistocene and holocene units quantitatively and to constrain volumetric assessments and accumulation rates on the island for different units the peak sediment volume production accumulation rate between 6 5 and 8 106 m3 or between 2 2 and 2 7 106 m3 per ka is observed in the upper mis 5e unit this rate is 5 times greater than the 0 5 106 m3 per ka estimated for the holocene ooid dune ridge strandplain complex suggesting that the combination of higher sea level greater wave and wind energy and warmer ocean temperatures may have fostered the higher rate of chemically precipitated sediment supply

lack of evidence for a substantial sea level fluctuation within the last interglacial during the last interglacial global mean sea level reached approximately 6 to 9 m above the present level this period of high sea level may have been punctuated by a fall of more than 4 m but a cause for such a widespread sea level fall has been elusive reconstructions of global mean sea level account for solid earth processes and so the rapid growth and decay of ice sheets is the most obvious explanation for the sea level fluctuation here we synthesize published geomorphological and stratigraphic indicators from the last interglacial and find no evidence for ice sheet regrowth within the warm interglacial climate we also identify uncertainties in the interpretation of local relative sea level data that underpin the reconstructions of global mean sea level given this uncertainty and taking into account our inability to identify any plausible processes that would cause global sea level to fall by 4 m during warm climate conditions we question the occurrence of a rapid sea level fluctuation within the last interglacial we therefore recommend caution in interpreting the high rates of global mean sea level rise in excess of 3 to 7 m per 1 000 years that have been proposed for the period following the last interglacial sea level lowstand

fuzzy based spatial modeling approach to predict island karst distribution a conceptual model previous studies have shown that island karst could successfully indicate paleoclimate change in the quaternary period however because of the relative inaccessibility of carbonate islands and their rural settings the exploration of island karst features has been limited to enhance future research remote sensing and geospatial modeling were used in this study to improve the island karst exploration record the results showed that fuzzy based spatial modeling could successfully predict the island karst distributions on a simple carbonate island the accuracy of the model was above 90 this method could apply to other coastal karst regions and carbonate islands in the future

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

reconciliation of sea level observations in the western north atlantic during the last glacial cycle abstract a south to north gradient of increasing marine isotope substage mis 5a 80 ka bp sea level has been recorded across the caribbean and surrounding region relative to present mis 5a sea levels range from 19 m to more than 3 m between barbados haiti the bahamas florida bermuda and the us atlantic coast in contrast no gradient in sea level is observed for the last interglacial period mis 5e 128 118 ka bp at tectonically stable localities in the same region with deposits generally lying several metres above present we demonstrate here that these controversial observations are reconciled by taking into account the isostatic response of the earth to glacial loading and unloading a fundamental effect that is commonly overlooked in the interpretation of sea level observations from different locations to define a global sea level curve furthermore the observed gradient can be used to place constraints on earth rheology and is an important indicator of the behaviour of the north american ice sheets during the last glacial cycle

diurnal boundary layer development over sloping terrain abstract a one dimensional prognostic model of the atmospheric boundary layer coupled to a surface energy budget is described which utilizes a profile formulation non local for exchange coefficients in the daytime convective boundary layer and an exchange coefficient scheme based on local richardson number for the stable nocturnal boundary layer this combined local and non local model is used to simulate the full diurnal cycle of the boundary layer behavior of days 33 34 of the wangara experiment results of the simulation indicate that these simplified exchange coefficient schemes simulate the mean features of the boundary layer as well as the more complex and computationally expensive higher order closure models this diurnal boundary layer formulation is incorporated into a two dimensional mesoscale model employing a terrain following coordinate system to examine boundary layer behavior over sloping terrain similar to that of the great plains of the united states particular emphasis is placed on th

uranium series dating of fossil coral reefs extending the sea level record beyond the last glacial cycle abstract absolutely dated records of past sea level change are extremely important for understanding the advance and retreat of the large ice sheets when combined with other complementary climate archives and climate models such records offer the potential to gain an improved understanding of earth s natural climate cycles providing a firmer basis for assessing the role of anthropogenic effects such as greenhouse gas emissions in modifying climate the u series dating of fossil coral reefs has been widely utilized to provide absolutely dated records of past sea level change and numerous observations now exist for the past 130 000 years spanning the last glacial cycle despite this controversies still exist regarding the exact timing and character of sea level events within this time interval and extending the sea level history further back in time on the basis of robust and independent age constraints for older fossil reefs remains very elusive this is primarily due to a progressive loss in the resolution of the u series chronometer as one goes further back in time coupled to a lack of well preserved dateable coral in older fossil reefs to overcome these limitations the primary challenges are three fold first new analytical protocols are required to improve the resolution of the u series chronometer enhanced analytical precision must be coupled to accuracy through continued refinement of the u series decay constant determinations and via the implementation of rigorous inter laboratory calibration exercises second efforts should continue to be focussed on gaining an improved understanding of the mechanisms controlling open system exchange of the u series isotopes in fossil reef systems this will allow the number of reliable u series observations to be extended third alternative dateable archives of past sea level change must continue to be emphasized to further complement the coral reef database these limitations are discussed in the context of current developments that further advance the application of u series chronology to older fossil reef systems formed prior to the last glacial cycle

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

arsenic within the secondary environment resulting from geogenic inputs harlech dome united kingdom there has been a growing awareness of as in the environment due to both anthropogenic and geogenic loading this study quantifies the presence of as in river water river sediment and groundwater within the harlech dome region of the uk an area underlain by cambro ordovician aged mineralization published data regarding as levels in uk groundwater are relatively rare compared to elsewhere arsenic levels in groundwater 0 1 18 g l 1 and river sediment 1 5 142 mg kg 1 exceed environmental quality guidelines and indicate the release of as into the secondary environment from predominantly geogenic sources modelling of dissolved as speciation using orp ph diagrams predicts the presence of as in both arsenate as5 and arsenous acid as3 species which possess differing solubilities and mobilities calculation of enrichment factors efs for as in river sediments using al as a reference element indicates highest efs and therefore as release occurs in streams draining the coed y brenin region in the south east of the harlech dome this area is underlain by an as yet unexploited porphyry copper deposit data indicate that the presence of potentially harmful elements within the environment may occur with or without the presence of major anthropogenic activity

growth and development of notch speleothems from cayman brac british west indies response to variable climatic conditions over the last 125 000 years abstract the spectacular wave cut notch on cayman brac which is 6 m above sea level formed during marine isotope stage 5e highstand 128 000 to 116 000 years ago on cayman brac the notch is commonly decorated with speleothems mostly stalactites that are formed of calcite aragonite and micrite these notch speleothems are characterized by numerous growth zones that are delimited by minor and major hiatal surfaces u th dating indicates that the major growth phases which took place 73 000 to 59 000 years ago 46 000 to 49 000 years ago and 4000 to 1000 years ago were separated by periods when erosion and minimal precipitation were the norm the 18ovpdb values range from 6 5 to 0 3 with a mode between 2 and 4 and an average of 3 1 whereas the 13cvpdb values range from 10 5 to 1 9 with one mode between 2 0 and 3 0 a second mode between 7 0 and 8 0 and an overall average of 6 1 the 18o and 13c values co vary the 18ovpdb and 13cvpdb values are similar to those from the young 125 000 years cave speleothems today with the little evidence of active speleothem growth in the notch or caves cayman brac is characterized by dry sub tropical forest and shrubland with xeric components on the elevated eastern end of the island available data indicate that most of the speleothem growth took place during the transitions from marine isotope stage mis 5a to 4 and mis2 to 1 these transitional periods which define the onset and termination of glaciation in the northern latitudes were probably characterized by higher rainfall and development of tropical rainforests it is evident that notch speleothems like those from cayman brac are valuable archives of the paleoclimate conditions that have existed since the highstand associated with mis5e

the uncertainties involved in extracting amplitude and frequency of orbitally driven sea level fluctuations from shallow water carbonate cycles in outcrops shallow water carbonates often form thick vertically stacked metre scale exposure bounded depositional packages here called carbonate cycles because the facies within carbonate cycles can be tied precisely to water depths they are considered ideal for reconstructing past sea level changes there is however increasing evidence that these depositional cycles are unreliable recorders of both the frequency and the amplitude of orbitally driven sea level fluctuations carbonate cycles record only a fraction of the amplitude of a sea level cycle a portion of the rise and nothing of the fall cores through the pleistocene cycles on great bahama bank illustrate this shortcoming although the amplitudes of the last nine sea level changes are each a hundred metres or more the thickness of the cycles varies from a few metres to ca 15 m the lack of correlation between sea level amplitude and cycle thickness is not eliminated for cycles deposited during times of lower sea level amplitudes for example the cretaceous upper cretaceous cycles on the maiella platform margin document the irregularly filled accommodation space and the resultant variability in cycle thickness and frequency uncertainties in assessing the frequencies of sea level changes from shallow water carbonate cycles are caused by missed beats and metre scale oscillations of sea level within highstands that potentially produce cycles of very short duration the random amplitude variability during the last 57 glacio eustatic sea level changes illustrates the difficulty of assessing missed beats where a sea level fluctuation is not recorded because the sea level rise does not reach the platform top missed beats are also produced by the depositional topography that is created by irregularly filled accommodation space as a result variable numbers of cycles are deposited across the platform further complicating orbital frequency analyses are decametre scale oscillations of the sea level during highstands the amplitude of these sub orbital sea level oscillations up to 17 m within the last interglacial marine isotope stage 5e are sufficient to expose shallow platforms like great bahama bank and subsequently produce an additional depositional cycle with similar facies successions the combined effects of missed beats and oscillations within highstands are likely to produce cycles and hiatuses of variable duration that are difficult to extract from the rock record consequently estimates of the orbital forcing mechanisms and frequencies from ancient shallow water carbonate cycles carry large uncertainties

a case study of the summertime great plains low level jet abstract a case study of the kinematical and dynamical evolution of the summertime great plains low level jet llj is presented airborne radar altimetry was used to discern the x and y components of the geostrophic wind at three levels in the lower atmosphere throughout the llj episode results appear to confirm previous theoretical and numerical studies regarding the importance of the diurnal cycle of heating over sloping terrain in producing an oscillating horizontal pressure gradient force inertial turning of the llj as a result of frictional decoupling was also documented it is concluded that the inertial oscillation resulting from the sudden decrease in friction in the lower atmosphere during the early evening is the dominant mechanism in forcing this example of a summertime great plains llj

simulating arctic climate warmth and icefield retreat in the last interglaciation in the future arctic warming and the melting of polar glaciers will be considerable but the magnitude of both is uncertain we used a global climate model a dynamic ice sheet model and paleoclimatic data to evaluate northern hemisphere high latitude warming and its impact on arctic icefields during the last interglaciation our simulated climate matches paleoclimatic observations of past warming and the combination of physically based climate and ice sheet modeling with ice core constraints indicate that the greenland ice sheet and other circum arctic ice fields likely contributed 2 2 to 3 4 meters of sea level rise during the last interglaciation

high precision u series dating of corals from western australia and implications for the timing and duration of the last interglacial abstract u series ages using methods of thermal ionisation mass spectrometry tims are reported for last interglacial fossil reefs along the stable coastal margin of western australia thorium isotope ratios were measured with superior precision using methods of charge collection high levels of precision in the measurement of both uranium and thorium isotopes has reduced the age uncertainty due to analytical errors excluding the uncertainty in the decay constants by a factor of four over the precisions reported by many earlier tims workers uncertainties in 234u t determined from both 230th 238u and 234u 238u are also significantly smaller than previously reported allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified strict criteria were adopted to screen the new western australian data reliable ages range from 127 to 122 ka published tims observations from other localities have been assessed using the same strict criteria when these are combined with glacio hydro isostatic sea level models they indicate that the last interglacial period occurred from at least 130 to 117 ka however these age constraints are largely determined from single data points and need to be verified with additional ages before considering them to be robust estimates for the timing of onset and termination of the last interglacial globally the main episode of reef growth appears to be confined to a narrow interval occurring from 127 to 122 ka in direct agreement with the narrow range in ages obtained from the western australian sites this may indicate that the last interglacial was of short duration extending from 127 to 122 ka only alternatively this interval may reflect a major reef building event in the middle of a longer duration 130 117 ka interglacial interval

on the role of sloping terrain in the forcing of the great plains low level jet abstract the summertime great plains low level jet llj has been the subject of numerous investigations during the past several decades characteristics of the llj include nighttime development of a pronounced wind maximum of typically 15 20 m s 1 at levels 300 800 m above the surface and a clockwise rotation of the wind maximum during the course of the night maximum frequency of occurrence of the llj is found in the southern great plains theories proposed to explain the diurnal wind maximum of the great plains llj include inertial oscillation of the ageostrophic wind the diurnal oscillation of the horizontal pressure field associated with heating and cooling of the sloping terrain and the western boundary current interpretations a simple equation system and output from the 12 km horizontal resolution weather research and forecasting nonhydrostatic mesoscale model nam for july 2008 are used to provide evidence as to the importance of the great plains topography in driving the llj summertime heati

speleothem constraints on marine isotope stage mis 5 relative sea levels yucatan peninsula mexico rates of sea level fall at the termination of the last interglacial are poorly defined and archives from which sea level elevations are constrained during marine isotope stage mis 5 in the western north atlantic caribbean region are restricted spatially to a few key sites here growth periods of presently submerged but subaerially deposited speleothems from the yucatan peninsula south east mexico are dated using the 230 th 234 u multi collector inductively coupled plasma mass spectrometric method the growth periods used to constrain maximum elevations of relative sea level are in agreement with glacio isostatic adjustment models for the near to intermediate region of the former north american ice sheets furthermore our data provide additional constraints on the timing of peak relative sea levels during mis 5a and 5c and the timing of the regression following the last interglacial highstand combining our data with coral archives of minimum relative sea level from the same region provides a novel approach to calculating the rate of relative sea level fall although initial estimates are poorly constrained because of the wide range in ages observed for the most suitable corals copyright 2013 john wiley sons ltd

source and pathways of lead in humans from the broken hill mining community an alternative use of exploration methods to assist in recommendations for the most suitable lead abatement policies in broken hill new south wales australia knowledge of the sources and pathways of the lead into humans is critical we have approached these problems using the lead isotope fingerprinting method combined with mineral speciation and bioavailability tests approaches which have in the past been largely applied to mineral exploration high precision lead isotope ratio measurements and lead contents were determined by thermal ionization mass spectrometry on biological samples blood urine and environmental samples from 27 families encompassing 60 children 41 female adults and 17 male adults environmental samples analyzed not from every household included soils gutter sweepings ceiling dust vacuum cleaner dust long term dust surface dust wipes external and internal air food water and gasoline sources of lead have been identified in the blood of children using lead isotopes with dominant contributions from the broken hill orebody but with individual cases having a dominant source of lead from gasoline or paint nevertheless of 28 children with a blood lead level pb b 15 mu dl approximately 30 percent have more than 50 percent of their pb b from sources other than orebody lead female adults generally have a low pb b 100 percent mean 47 or 38 n 5 from vacuum cleaner dusts thus the currently suggested amounts of approximately 100 mg d ingested soil dirt and dust for a broken hill child can readily account for the elevated lead levels compared with the amounts for children in many other mining communities based on these investigations it is possible to construct a flow sheet of sources and pathways for the lead into humans at broken hill on which to base correct remedial actions

an open system model for u series age determinations of fossil corals the source of excess 234u in fossil corals and its relationship to u series age determinations has been an outstanding problem in geochronology for more than 20 years with increasing numbers of u series isotope measurements in corals and significant improvements in analytical precision through mass spectrometry it is increasingly apparent that a substantial fraction of observed isotope ratios cannot be reasonably explained by closed system decay moreover observations of a positive correlation between 234u 238u and 230th 238u ratios in corals from the same terrace are difficult to explain however the decay of dissolved uranium and recoil mobilization of uranium daughters produce particle reactive 234th and 230th and the coupled addition of these th isotopes could simultaneously increase coral 234u 238u and 230th 238u here we present a quantitative model based on decay dependent redistribution of 234th and 230th permitting calculation of open system coral ages these equations provide a general solution to the recoil redistribution problem applicable to any alpha decay series while measured isotope ratios of corals from the three youngest stratigraphically defined barbados terraces are inconsistent with closed system decay they fall in broadly linear arrays agreeing with model predictions isotopic arrays of older barbados corals and corals from terraces around the world are also consistent with model predictions suggesting the open system model is generally applicable corals with extreme isotopic compositions that are impossible to produce by closed system decay are consistent with the limited range of isotopic compositions predicted by the model at ages older than 600 ka for corals from a single terrace 234th and 230th redistribution appears to be a source of systematic conventional age error even for corals with slightly elevated 234u however open system ages are consistent even for corals with extremely elevated 234u for the youngest three barbados terraces mean open system terrace ages are consistent with mean conventional terrace ages calculated from pristine samples if the most accurate conventional ages are from corals with an initial 234u 238u identical to modern seawater then the open system model will improve the accuracy of coral u series age determinations and dramatically increase the number of reliable ages

re evaluation of the composition of sediments from the murray darling basin of australia as a potential source area for airborne dust to epica dome c in antarctica reply to comment on lead isotopic evidence for an australian source of aeolian dust to antarctica at times over the last 170 000 years by p de deckker m norman i d goodwin a wain and f x gingele

late quaternary uplift along the north america caribbean plate boundary evidence from the sea level record of guantanamo bay cuba abstract the tectonic setting of the north america caribbean plate boundary has been studied intensively but some aspects are still poorly understood particularly along the oriente fault zone guantanamo bay southern cuba is considered to be on a coastline that is under a transpressive tectonic regime along this zone and is hypothesized to have a low uplift rate we tested this by studying emergent reef terrace deposits around the bay reef elevations in the protected inner part of the bay are 11 12 m and outer coast wave cut benches are as high as 14 m uranium series analyses of corals yield ages ranging from 133 ka to 119 ka correlating this reef to the peak of the last interglacial period marine isotope stage mis 5 5 assuming a span of possible paleo sea levels at the time of the last interglacial period yields long term tectonic uplift rates of 0 02 0 11 m ka supporting the hypothesis that the tectonic uplift rate is low nevertheless on the eastern and southern coasts of cuba east and west of guantanamo bay there are flights of multiple marine terraces at higher elevations that could record a higher rate of uplift implying that guantanamo bay may be anomalous southern cuba is considered to have experienced a measurable but modest effect from glacial isostatic adjustment gia processes thus with a low uplift rate guantanamo bay should show no evidence of emergent marine terraces dating to the 100 ka mis 5 3 or 80 ka mis 5 1 sea stands and results of the present study support this

sea level oscillations during the last interglacial highstand recorded by bahamas corals whether sea level was stable during the last interglacial remains a subject of debate an analysis of the u th ages of coral reefs in the bahamas corrected for open system behaviour confirms the presence of at least one oscillation within the sea level highstand

a global compilation of coral sea level benchmarks implications and new challenges i present a quality controlled compilation of sea level data from u th dated corals encompassing 30 studies of 13 locations around the world the compilation contains relative sea level rsl data from each location based on both conventional and open system u th ages i have applied a commonly used age quality control criterion based on the initial 234u 238u activity ratios of corals in order to select reliable ages and to reconstruct sea level histories for the last 150 000 yr this analysis reveals scatter of rsl estimates among coeval coral benchmarks both within individual locations and between locations particularly during marine isotope stage mis 5a and the glacial inception following the last interglacial the character of data scatter during these time intervals imply that uncertainties still exist regarding tectonics glacio isostacy u series dating and or coral position to elucidate robust underlying patterns with confidence limits i performed a monte carlo style statistical analysis of the compiled coral data considering appropriate age and sea level uncertainties by its nature such an analysis has the tendency to smooth obscure millennial scale and finer details that may be important in individual datasets and favour the major underlying patterns that are supported by all datasets this statistical analysis is thus functional to illustrate major trends that are statistically robust what we know trends that are suggested but still are supported by few data what we might know subject to addition of more supporting data and improved corrections and which patterns data are clear outliers unlikely to be realistic given the rest of the global data and possibly needing further adjustments prior to the last glacial maximum and with the possible exception of the 130 120 ka period available coral data generally have insufficient temporal resolution and unexplained scatter which hinders identification of a well defined pattern with usefully narrow confidence limits this analysis thus provides a framework that objectively identifies critical targets for new data collection improved corrections and integration of coral data with independent stratigraphically continuous methods of sea level reconstruction

natural enrichment of arsenic in loch lomond sediments abstract concentrations of arsenic in surface or near surface sediment in 12 of 13 cores from the three major basins of loch lomond are substantially enhanced up to 675 mg kg compared with background values of 15 50 mg kg sedimentary as profiles are attributed to post depositional enrichment processes since there are no recent significant sources of environmental as contamination anthropogenic or natural in the loch lomond area the enrichments can be interpreted in terms of post depositional diagenetic remobilization processes in sediment reducing zones followed by upward migration of as through interstitial waters and oxidation adsorption precipitation reactions in near surface oxidizing layers confirmation of the diagenetic adsorption hypothesis is provided directly by the analysis of as species 1 5 81 g l in pore water and indirectly via comparison with sedimentary phosphorus

u series dating of diagenetically altered fossil reef corals initial 234u 238u activity ratios higher than those expected from closed system evolution of seawater are an outstanding problem in u series dating of fossil reef corals the increased activity ratios are ascribed to post depositional diagenesis we analysed six last interglacial and one holocene coral of the genus porites collected near the northern end of the gulf of aqaba northern red sea together with three recent corals from this location as a modern reference while the values measured on the recent samples show no deviation from expected values the holocene and last interglacial corals display highly elevated 234u 238u activity ratios as well as increased 238u and 232th concentrations 234u 238u activity ratios are strongly correlated with 230th 238u and total uranium content a model assuming different degrees of uranium addition and subsequent loss in different sub samples of one coral produces straight lines isochrons on a 234u 238u 230th 238u plot and predicts that the true age of the coral can be calculated by intersecting this isochron with the seawater evolution curve we used the strong correlation detected in the aqaba corals to calculate isochron ages the isochron age of the holocene coral 3116 167 156 yr is concordant with its calibrated 14c age 2963 92 103 yr the ages of the last interglacial corals are between 121 6 7 5 3 and 121 9 7 0 6 3 kyr for a higher terrace 7 10 m asl and 106 4 8 9 8 1 and 117 1 19 7 15 3 kyr for a lower terrace 4 5 m asl one last interglacial coral with an aragonite content of 85 could not be dated the elevation and ages of the fossil terraces are consistent with existing sea level reconstructions from the red sea

high rates of sea level rise during the last interglacial period sea level during the last interglacial stood at least 4 m higher than at present with evidence of short term fluctuations of up to 10 m a new continuous sea level record from the red sea and coral ages suggest that during these fluctuations sea level changes were on the order of 1 6 m per century

precise chronology of the last interglacial period 234u 230th data from fossil coral reefs in the bahamas a detailed study of 238 u 234 u 230 th ages was made for different coral species from two bahamian reefs to determine the time scale of the sea level high during the last interglacial period using recently developed mass spectrometric techniques for the measurement of u and th isotopes thirty seven coral samples were analyzed in replicate typical errors at 125 ky are 1 5 ky 2 and 3 ky time intervals appear to be well resolved this high precision permits detailed chronologic study with time resolution adequate to define stages of the reef s history these data demonstrate that the time between transgression and regression of the ocean in the last interglacial was about 12 ky after which sea level fell rapidly at more than 2 m ky the high sea level stand began possibly by 132 ky and certainly by 129 ky ago when sea level reached 6 m above present mean low sea level high sea level was sustained until 120 ky and then fell rapidly this time period covers the milankovitch insolation peak at 65 n but is not sharply defined and the sea level high lasted from about 4 ky before the insolation peak to 8 ky after it we find no evidence for a double peak of sea level rise in the last interglacial episode that is high stands at both 125 and 142 ky there appears to be some discrepancy between this precise chronology for a coral reef on a tectonically stable platform and the chronology assigned to deep sea sediments the present results show that the duration of the last interglacial led to a 12 ky period of high sea level stand which is much longer than the insolation peak the study area consists of two sizeable bank barrier coral reefs of sangamon age that crop out along the coast northwest of cockburn town on san salvador island and at devil s point on great inagua island the initial stage of reef development is not revealed at either site but the main parts of both reefs are well preserved at cockburn town the beginning of the reef was marked by colonization of acropora palmata on hardground areas and possibly other corals at 132 ky ago patch reefs at the southeastern flank of the developing reef were growing by 129 to 126 ky ago by 126 to 123 ky ago the crest of the reef was formed by the frame building coral a palmata and associated patch reefs flourished along its flanks a palmata coral heads grew upward to a mean low sea level 6 m above the present one the reef began to decline as sea level dropped at about 123 to 120 ky ago near two measured profiles at devil s point the top of a rubblestone dominated by a cervicornis and patch reef corals preserved in growth position have been beveled off and represent an ancient wave cut surface 230 th ages on corals below and above this surface indicate that it was cut at about 125 1 ky ago

rapid sea level rise abstract several global and regional factors contribute to observed sea level change along any particular coast global processes include changes in ocean mass glacio eustasy from ice melt ocean volume steric effects viscoelastic land movements glacioisostatic adjustment gia and changes in terrestrial water storage regional processes often connected to steric and glacial changes include changes in ocean circulation meridional overturning circulation moc glacial melting local gia regional subsidence and others paleoclimate instrumental and modeling studies show that combinations of these factors can cause relatively rapid rates of sea level rise exceeding 3 mm yr 1 over various timescales along particular coasts this paper discusses patterns and causes of sea level rise with emphasis on paleoclimatological records it then addresses the hypothesis of late holocene pre 20th century sea level stability in light of paleoclimatic evidence notably from reconstructions of sea surface temperature and glacial activity for significant climate and sea level variability during this time the practical difficulties of assessing regional sea level sl patterns at submillennial timescales will be discussed using an example from the eastern united states

the influence of mesoscale orography on a coastal jet and rainband abstract the role of mesoscale orography along the central california coast in the development and evolution of a coastal jet and rainband is investigated using a high resolution triply nested nonhydrostatic numerical model comparison of the model simulations which use horizontal grid increments of 5 and 2 km on the inner computational meshes with a coastal mesoscale observation network indicates that the finescale structure of the jet and rainband dynamics are adequately simulated although phase and orientation errors occur the observed and simulated near surface winds have maximum speeds that exceed 22 m s 1 and a direction nearly parallel to the coastline and topography force balance analysis indicates that blocking in the lowest 500 m and flow over the coastal range above this layer contribute to mesoscale pressure perturbations including pressure ridging upstream of the coastal mountains which forces the ageostrophic dynamics of the coastal jet pressure perturbations associated with the to

the role of the indian summer monsoon variability on arabian peninsula summer climate this study investigates the influence of the indian summer monsoon ism on the atmospheric circulation over the arabian peninsula ap using the european centre for medium range weather forecasts twentieth century reanalysis era 20c for the period 1901 2010 after describing the summer climate of the ap using various dynamic and thermodynamic parameters we investigate the link between extreme isms and atmospheric circulation over the ap on inter annual time scale analysis of composites of different parameters during extreme monsoon strong and weak years reveals that the ism plays an important role in the summer circulation over the ap and adjoining regions the major noticeable changes in modulating circulation during extreme monsoons are 1 a strengthening of lower tropospheric northerly winds westerly winds passing through the tokar gap shamal winds and the upper tropospheric easterly jet stream during strong ism 2 a northward southward shift of the subtropical westerly jet stream during strong weak monsoon years 3 the development of strong upper level ridge above the surface thermal low during strong ism years which result in a baroclinic structure over the ap and adjoining regions 4 an increase in adiabatic warming and hence aridity over the ap during strong monsoon years caused by intense subsidence of the middle to upper troposphere due to zonal overturning circulation and 5 convective instability during strong monsoon years caused by an intensification of the upward motion over the southern ap furthermore during strong monsoons the availability of excess moisture leads to atmospheric instability which in turn triggers the formation of clouds that lead to more rainfall over the southwestern ap finally the westward propagation of a gill type rossby waves induced by the ism play an important role in the variations of the ap summer climate by enhancing the warm core structure over the ap and through their interaction with the midlatitude westerlies during strong monsoons

mass spectrometric 234u 230th ages from the key largo formation florida keys united states constraints on diagenetic age disturbance new mass spectrometric 234 u 230 th ages for the key largo formation confirm earlier less precise alpha counting measurements that place the unit within marine oxygen isotope stage 5 ages derived from the petrographically freshest samples 99 aragonite of this study range from 125 to 138 ka despite careful sample selection and preparation the initial 234 u 238 u activity ratios denoted 234 u 238 u t range from 1 163 to 1 176 and so are all significantly higher than modern day or inferred last interglacial seawater this result indicates open system behavior of u series nuclides as has been observed in many other pleistocene coral samples and casts doubt on the accuracy of our age determinations we have used our samples to investigate the processes and magnitudes of age perturbations repeats of the same sample dissolution analytical reproducibility are within measured uncertainties which are generally less than 1 k y in contrast different parts of the same coral similarly screened for alteration can show age differences of as much as 3 k y evidence from this study and others suggests that alteration generally increases 234 u 230 th ages we were able to determine by using field relationships that the differences in 234 u 230 th ages of samples lying on either side of an erosion feature are at least 5 k y in error the stratigraphically younger corals above the erosion surface have 234 u 230 th ages that are at least 5 k y too old notably these apparently more perturbed samples have lower 234 u 238 u t ratios than the underlying corals this observation emphasizes that although 234 u 238 u t is a sensitive indicator of open system behavior the 234 u 238 u t ratio does not provide a simple index of the magnitude of age disturbance diagenetic additions of both 234 u and 230 th to corals seem necessary to explain both elevated ages and 234 u 238 u t ratios we argue that these additions result from redistribution of nuclides during meteoric alteration of the reef in the first 40 k y after formation variations in the amount of 230 th added relative to 234 u can be used to model the spread of ages at similar 234 u 238 u ratios although variable amounts of recent u loss may also have been important the youngest age of this study 125 ka just below an erosion surface is compatible with the ages of similar features in the southern bahamas we suggest that 125 ka is the maximum age of a short lived sea level lowstand within the last interglacial 5e highstand

the summertime low level jet and marine boundary layer structure along the california coast abstract this paper examines the strong summertime northerly low level jet llj that frequently exists along the california coast the persistent synoptic scale pressure distribution north pacific high to the west thermal low to the east and baroclinity created by the juxtaposition of the heated continent and the cool marine layer produce the mean structure of this llj strong diurnal thermal forcing coupled with topographic influences on the flow modulate the jet structure position and intensity a mesoscale model is used to examine many of the complex facets of the llj flow dynamics several sensitivity studies in addition to a control experiment aid in this investigation principal findings of this study include the following the pronounced east west slope of the marine planetary boundary layer mpbl is not due primarily to colder sst values along the coast dynamically forced low level coastal divergence coupled with synoptic scale divergence appears to be dominant in determining mpbl i

coriolis effects in mesoscale flows with sharp changes in surface conditions a general linearized shallow layer perturbation model where the approximately neutral lower layer of thickness h0 is situated below a stable upper layer i e an inversion with temperature change t is developed for steady mesoscale atmospheric flows over low lying topography whose height is less than h0 with the coriolis parameter f sharp changes in surface conditions surface roughness terrain elevation heat flux are modelled as a distributed body force through the lower layer the froude number of this layer is small typical cases of mesoscale discontinuities are examined the results are compared with those of a continuously stratified model and observations and with numerical mesoscale model results for a meteorological case study over the dover straits region of the english channel the main results are i if the wind direction is parallel to the edge line separating the change in surface roughness there are marked increases and decreases in these coastal winds whose maxima can occur over the sea within a distance of order h0 1 km of a coast the strength of these wind jets which do not occur in the absence of coriolis force decrease away from the edge line gradually over transverse length scales of the order of the rossby deformation radius changes to surface roughness lead to an increase in the wind speed perturbation in the downwind direction until limited by non linear effects when the wind is at an angle to a roughness change or coast the maxima occur at the coastline ii where there are sharp changes in the orientation of contours of constant roughness length e g at capes or bays on the coastline or wakes of high drag areas detached jets are formed in the downwind direction iii changes in surface elevation at a coast produce effects different from those of roughness a positive wind jet forms parallel to the coast in the direction of the wind when the coast is on the right looking downwind and a negative jet when the coast is on the left these jets do not increase in strength along the flow and do not persist downwind iv coriolis effects also determine how the inversion height varies near coastlines and surface roughness changes for example increasing decreasing inland over a distance lr when stable airflow approaches from the sea and the coast is on the right left of an observer looking downwind opposite in the southern hemisphere this mechanism is consistent with observed increasing decreasing cloudiness inland from a coast v other effects occur where the surface elevation changes gradually over a distance of order lr e g a wide shallow valley frictional effects are comparable with buoyancy and coriolis forces and flows perpendicular to the elevation change are deflected to the left in the northern hemisphere as observed in the rhine valley vi the shallow layer model simulates the major features of the low level flow field computed using the numerical mesoscale model with a horizontal resolution of 2 km i e of order h0 broad features were captured using a coarser resolution of 12 km vii the analysis provides a method of estimating errors associated with finite grid size in numerical mesoscale models copyright 2004 royal meteorological society

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

radar duct and boundary layer characteristics over the area of the gulf radar duct characteristics and the associated atmospheric boundary layer over the the gulf 50 n 28 e on 28 april 1996 were simulated with the ncar penn state mm5v3 numerical model the model was validated against meteorological observations and duct data gathered in a special observational programme a benchmark study with horizontal grid length of 5 km revealed complete coverage of the gulf by ducts throughout the whole twenty four hours over land ducts existed only at night over the gulf meso scale variation occurred shallow 250 m surface ducts existed within about 200 km of the north coast elevated ducts over 500 m deep near the southern coast and s shaped ducts about 400 m deep over the majority of the area duct strength also increased from north to south these features were related to the marine internal boundary layer mibl that formed over the gulf in the ambient north west wind meso scale variations in duct top height occurred within 200 km of the north coast immediately downwind of qatar and off the central east and west coasts duct characteristics were influenced at the meso scale by coastal configuration and at the meso scale by sea surface temperature sst land sea temperature difference orography and ambient wind an increase in grid length to 25 km lost much of the meso scale structure but retained the meso scale features at the meso scale duct top height and strength were consistently lower in the sensitivity runs than those in the control run because of changes in the depth of the mibl elimination of the north south sst gradient resulted in a shallower and more stable mibl maximizing the land sea temperature difference increased the subsidence associated with the stronger sea breeze circulation in the sensitivity case and therefore decreased the depth of the mibl when the orography was much reduced the lower wind speeds in the sensitivity run were again associated with a shallower mibl the lower wind speeds resulted from the lack of the thermal wind effect induced by the high orography around much of the gulf the explicit reduction of the ambient wind also led to a reduction in depth of the mibl duct type also changed in the sensitivity studies surface ducts replacing s shaped ducts in those areas where the depth of the mibl decreased of the meso scale factors influencing the ducts ambient wind speed was most important closely followed by orography the distribution of sst had the smallest effect copyright 2005 royal meteorological society

a radiometric calibration of the specmap timescale the astronomical theory of climate change asserts that earth s climate is affected by changes in its orbit which vary the seasonal and latitudinal distribution of solar radiation this theory is the basis of the orbitally tuned specmap timescale a key constraint for this important chronology was the mid point of the penultimate deglaciation initially dated to 127 000 years ago recent work suggests this event may be considerably older casting doubt on the astronomical theory the specmap timescale and the accuracy of orbitally tuned chronologies difficulties with u th coral dating of sea level events have impeded progress on this problem because most corals are not closed systems here we use a new approach to u th dating that corrects for open system behavior and produces a sea level curve of sufficient resolution to confidently correlate with specmap over the last 240 000 years permitting a reassessment of both this critical chronology and a central tenet of climate change theory high precision ages for 24 oxygen isotope events provide a 240 000 year chronology for marine 18o records that is independent of orbital tuning assumptions although there appear to be significant differences between the radiometric and orbitally tuned timescales near the lastglacial maximum and at the marine isotope stage 7 6 boundary a comparison of radiometric and specmap ages for identical isotope events suggest that the specmap timescale is quite accurate and that its errors were in general overestimated despite suborbital complexity orbital cyclicity is clearly evident in our record high amplitude sea level oscillations at periods greater than 20 000 years are very close in phase to summer insolation in the northern hemisphere although sea level changes cannot be uniquely tied to a specific season or latitude of insolation forcing the simplest explanation is that long period high amplitude sea level change is linked to northern hemisphere insolation forcing these results validate the principles of orbital tuning and suggest such timescales are generally robust

effects of coastal orography on landfalling cold fronts part i dry inviscid dynamics abstract in this study the interaction of cold fronts with idealized coastal terrain typical of the western united states and canada is considered two issues are examined first what are the factors that determine the strength of the coastal winds and second what are the orographic effects on the frontal evolution to address these issues the authors utilize a two dimensional boussinesq terrain following coordinate numerical model in which a uniform prescribed flow is forced to move over a plateau the resultant across mountain velocities are characterized by a zone of strongly decelerated flow upstream of the windward slope and a train of inertia gravity waves downstream a barrier jet oriented parallel to the mountain is produced by the coriolis force the variations of the magnitude of the upstream deceleration and the barrier jet over a wide range of froude numbers and rossby numbers are described steady linear theory applied to flow over a plateau shows that the upstream deceleration is dete

three dimensional idealized simulations of barrier jets along the southeast coast of alaska abstract three dimensional idealized simulations using the fifth generation pennsylvania state university ncar mesoscale model mm5 down to 6 km grid spacing were performed in order to understand how different ambient conditions wind speed and direction stability and inland cold pool and terrain characteristics impact barrier jets along the southeastern alaskan coast the broad inland terrain of western north america is important in alaskan jet development since it rotates the impinging flow cyclonically more coast parallel well upstream of the coast thus favoring more low level flow blocking while also adding momentum and width to the barrier jet near the steep coastal terrain the largest wind speed enhancement factor 1 9 2 0 in the terrain parallel direction relative to the ambient onshore directed wind speed occurs at relatively low froude numbers fr 0 3 0 4 these low froude numbers are associated with 10 15 m s 1 ambient wind speeds and wind directions orientated 30 45 from terra

frontogenesis over a mountain ridge abstract the interaction of developing two dimensional cold and warm frontal systems with a mesoscale mountain ridge is examined the flow of the rotating model atmosphere is assumed to be inviscid adiabatic and boussinesq the geostrophic momentum approximation is made an imposed horizontal deformation field forces the frontogenesis the nonlinear model equations are solved numerically in physical space using terrain following coordinates which incorporate the fully nonlinear lower boundary condition comparison of the model results with and without topography enables assessment of the impact of the mountain on the frontogenesis a scale analysis indicates that the most general problem of frontal interaction with an infinite mountain ridge encompasses a seven dimensional parameter space the scale analysis provides justification for die two dimensional geostrophic momentum approximation and defines an inverse richardson number as a measure of the importance of the ageostrophic advection sensitivity

testing glacial isostatic adjustment models of last interglacial sea level history in the bahamas and bermuda abstract part of the spatial variation in the apparent sea level record of the last interglacial lig period is due to the diverse response of coastlines to glacial isostatic adjustment gia processes particularly where coastlines were close to the laurentide ice sheet during the past two glacial periods we tested modeled lig paleo sea levels on new providence island npi bahamas and bermuda by investigating emergent coral patch reefs and oolitic peloidal beach deposits corals with closed system histories collected from patch reefs on npi have ages of 128 118 ka and ooids peloids from beach ridges have closed system ages of 128 116 ka elevations of patch reefs indicate a lig paleo sea level of at least 7 m to 9 m above present beach ridge sediments indicate paleo sea levels of 5 m to 14 m assuming subsidence 7 m to 16 m above present during the lig some though not all of these measurements are in good agreement with gia models of paleo sea level that have been simulated for the bahamas on bermuda corals with closed system histories collected from marine deposits have ages of 126 114 ka although coral bearing marine deposits on bermuda lack the precise indication of paleo sea level provided by patch reefs and oolitic beach ridges these sediments nevertheless provide at least a first order estimate of paleo sea level paleo sea level records on bermuda are consistently lower 2 m to 7 m than what gia models simulate for the lig the reason for the reasonable agreement with models for the bahamas and poor agreement for bermuda is not understood but needs further investigation in light of the probability of a higher sea level in the near future

heavy metal pollution of coastal river sediments north eastern new south wales australia lead isotope and chemical evidence heavy metal and metalloid concentrations within stream estuary sediments 180 m size fraction in north eastern new south wales largely represent natural background values however element concentrations ag as cd cr cu hg ni pb sb zn of hunter river sediments within the heavily industrialized and urbanized newcastle region exceed upstream background values by up to one order of magnitude high element concentrations have been found within sediments of the newcastle harbour and throsby creek which drains into urbanized and light industry areas observed pb enrichments and low 208pb 204pb 207pb 204pb and 206pb 204pb ratios are likely caused by atmospheric deposition of pb additives from petrol and subsequent pb transport by road run off waters into the local drainage system sediments of the richmond river and lower manning macleay clarence brunswick and tweed river generally display no evidence for anthropogenic heavy metal and metalloid contamination ag as cd cr cu hg ni pb sb zn however the rivers and their tributaries possess localized sedimentary traps with elevated heavy metal concentrations cu pb zn lead isotope data indicate that anthropogenic pb provides a detectable contribution to investigated sediments such contributions are evident at sample sites close to sewage outlets and in the vicinity of the pacific highway in addition as concentrations of richmond river sediments gradually increase downstream this geochemical trend may be the result of as mobilization from numerous cattle dip sites within the region into the drainage system and subsequent accumulation of as in downstream river and estuary sediments

the timing of high sea levels over the past 200 000 years the 230 th ages and 234 u 238 u ratios were determined for barbados corals that grew during periods of high sea level within the last 200 000 years the similarity of the initial 234 u 238 u ratios of some of the corals to the modern marine value suggests that these samples are pristine and that the marine 234 u 238 u ratio 83 000 and 200 000 years ago was within 2 per mil of the modern value the accuracies of the 230 th ages are evaluated on the basis of the 234 u 238 u values and a model of the behavior of uranium and thorium isotopes during diagenesis for the last three interglacial and two intervening interstadial periods sea level peaked at or after peaks in summer insolation in the northern hemisphere this overall pattern supports the idea that glacial interglacial cycles are caused by changes in earth9s orbital geometry the sea level drop at the end of the penultimate interglacial the last interglacial and a subsequent interstadial period lagged behind the decrease in insolation by 5 000 to 10 000 years

the analysis of last interglacial mis 5e relative sea level indicators reconstructing sea level in a warmer world the last interglacial mis 5e 128 116 ka is among the most studied past periods in earth s history the climate at that time was warmer than today primarily due to different orbital conditions with smaller ice sheets and higher sea level field evidence for mis 5e sea level was reported from thousands of sites but often paleo shorelines were measured with low accuracy techniques and in some cases there are contrasting interpretations about paleo sea level reconstructions for this reason large uncertainties still surround both the maximum sea level attained as well as the pattern of sea level change throughout mis 5e such uncertainties are exacerbated by the lack of a uniform approach to measuring and interpreting the geological evidence of paleo sea levels in this review we discuss the characteristics of mis 5e field observations and we set the basis for a standardized approach to mis 5e paleo sea level reconstructions that is already successfully applied in holocene sea level research application of the standard definitions and methodologies described in this paper will enhance our ability to compare data from different research groups and different areas in order to gain deeper insights into mis 5e sea level changes improving estimates of last interglacial sea level is in turn a key to understanding the behavior of ice sheets in a warmer world

the persian gulf summertime low level jet over sloping terrain there are few observational and numerical studies of the summertime low level jet llj over the persian gulf known as the shamal in this study the weather research and forecasting wrf model accurately simulates the llj s vertical structure nocturnal features and strong diurnal variation of the wind the case study period is divided into a period during which the shamal is spatially extended strong winds over the gulf and iraq and a period during which it is less spatially extended strong flow only over the gulf orography mountain slope and land sea breeze are found to be key factors for the shamal diurnal variation of wind speed and wind direction the blackadar mechanism appears to be secondary to the heating in forcing the shamal the zagros mountains not only channel the northwesterly winds but also provide a barrier for the easterly monsoon airflow which maximizes the wind speed only during the less extensive period does the zagros mountains slope significantly affect the shamal wind intensity and direction both shallow and steep mountain slope sensitivity studies feature a jet like flow over the persian gulf the steep slopes cause larger wind speeds however the shallow slopes reveal a stronger diurnally varying wind direction due to larger heating and cooling of the sloping terrain it is also shown that during the less extensive period the land breeze and the lower friction over the sea increase the intensity of the nocturnal jet over the gulf copyright 2011 royal meteorological society

isotopic record of lead pollution in lake sediments from the northeastern united states abstract although it is common knowledge that pb concentrations have increased in lake sediments in the northeastern united states over the last 150 years the processes responsible have been the subject of debate in this study differences in lead isotopic compositions and concentrations in sediment from large lakes lake erie ontario and michigan and small ones deep lake and lake andrus are used to infer temporal changes in the source s of anthropogenic pb in the great lakes region a natural background component of pb is present in sediment deposited prior to 1860 in lake erie and the other lakes as indicated from low pb concentrations and uniform lead isotopic compositions changes in isotopic ratios of lake sediment reflect differing sources of anthropogenic pb superimposed on the natural component such as regional deforestation from 1860 1890 followed by coal combustion and ore smelting through 1930 combustion of leaded gasoline was the dominant anthropogenic pb source to the atmosphere and by inference to lake sediment from 1930 1980 temporal changes in lead isotopic compositions in lake sediment suggest that the source of the pb used in gasoline additives gradually changed from 1930 to present the best example is a distinct shift in lead isotopic ratios in lake sediment deposited after 1970 which corresponds to increased pb production from the viburnum trend deposits in missouri present in all lakes except ontario however the changes in lead isotopic compositions are much less variable than and do not parallel those calculated on the basis of annual united states mine production and imports rather anthropogenic recycling of pb as well as natural mixing processes during emission transport and deposition of pb in lake sediment control most of the variation in lead isotope ratios differences in lead isotopic ratios in lake michigan erie and deep lake sediment preserve regional differences in lead isotopic ratios from u s and canadian sources first noted in aerosols by sturges and barrie 1987 more localized sources of pb such as point discharges are needed to explain the results from lake ontario and andrus

coral indicators of past sea level change a global repository of u series dated benchmarks fossil corals provide valuable data for reconstructing past sea levels as they are often well preserved in the fossil record and can be dated with u series methods here we present a global and internally consistent database of usingle bondth dated fossil coral sea level indicators including full consideration of all known associated uncertainties both vertical and chronological we include carefully determined taxon specific depth distributions rather than blanket depth uncertainty terms as used in most previous work this is based on a synthesis of extensive modern ecological information on depth ranges these ranges are found to be spatially variable between ocean basins between regions and on sub regional scales because depth itself is not limiting instead depth distributions arise from complex physical chemical and biological interactions with coral reef growth distribution and composition one of the main causes for recognition of the greater depth variability of coral taxa has been the routine inclusion of deep diving and rov surveys in coral ecological studies over the past few decades which has broken through the shallow water bias of early surveys by adding frequent observations on deeper occurrences although more are needed it is also clear from our assessment that coral habitat depth distributions must be determined on the species level to reduce uncertainties in reconstructions of past sea levels and that application to sea level studies then requires these studies also to identify fossil corals to the species level samples identified only to the genus level give rise to wide uncertainties in habitat depth and hence sea level our database contains extensive metadata to assist evaluations of dating quality as well as geomorphic and stratigraphic metadata we demonstrate with examples how such metadata can help to evaluate sea level reconstructions for example by identifying outlier points one example discusses the last interglacial lig where we use the available data with their uncertainties to assess probabilistically the time at which local sea levels exceed that of the present which yields a mean age of 124 6 ka with 95 probability bounds at 118 5 and 129 5 ka we conclude with identification of key outstanding issues relating to i current incomplete understanding of tectonic setting including the current lack of independent verification of uplift subsidence rates and reliance of somewhat unsatisfactory and circular use of the elevation of last interglacial deposits ii the depth distributions of coral taxa and iii the complete documentation of stratigraphic geomorphological and other contextual information with suggestions for strategies to address these issues

similarities and dissimilarities between the last two deglaciations and interglaciations in the north atlantic region abstract sea surface temperatures ssts recorded by alkenones and oxygen isotopes in the alboran basin are used here to describe at an unprecedented fine temporal resolution the present interglaciation pig initiated at 11 7 ka bp the last interglaciation lig onset approximately at 129 ka and respective deglaciations similarities and dissimilarities in the progression of these periods are reviewed in comparison with ice cores and stalagmites cold spells coeval with the heinrich events h described in the north atlantic include multi decadal scale oscillations not previously obvious up to 4 c in less than eight centuries within the stadials associated with h1 and h11 ca 133 ka and 17 ka respectively these abrupt oscillations precede the accumulation of organic rich layers deposited when perihelion moves from alignment with nh spring equinox to the summer solstice a reference for deglaciations events observed during the last deglaciation at 17 ka 14 8 ka and 11 7 ka are reminiscent of events occurred during the penultimate deglaciation at ca 136 ka 132 ka and 129 ka respectively the sst trend during the pig is no more than 2 c from 20 c to 18 c up to 0 2 c ka the trend is steeper during the lig i e up to a 5 c change from the early interglaciation to immediately before the glacial inception from 23 c to 18 c up to 0 4 c ka events are superimposed upon a long term trend towards colder ssts beginning with sst maxima followed by temperate periods until perihelion aligned with the nh autumn equinox before ca 5 3 ka for the pig and 121 ka for the lig a cold spell of around eight centuries at 2 8 ka during the pig was possibly mimicked during the lig at ca 118 ka by a sst fall of around 1 c in a millennium these events led interglacial sst to stabilise at around 18 c the glacial inception barely evident at the beginning ca 115 ka north atlantic event c25 after perihelion passage in the nh winter solstice culminated with a sst drop of at least 2 c in two millennia event c24 ca 111 ka the little ice age 0 7 ka also occurred after the latest perihelion passage in the nh winter solstice and could be an example of how a glacial pre inception event following an interglaciation might be

the role of the north american topography on the maintenance of the great plains summer low level jet abstract summer precipitation over the central united states depends strongly on the strength of the great plains low level jet llj the geophysical fluid dynamics laboratory s new generation of the atmospheric general circulation model gcm and the linear and nonlinear stationary wave models are used in this study to examine the role of north american topography in maintaining the great plains summer mean llj and precipitation atmospheric gcm experiments were first performed with and without the north american topography and with prescribed climatological sea surface temperatures results show that the great plains llj disappears completely in the experiment when the north american topography is removed while the summer seasonal mean llj is well simulated in the experiment with full earth topography in the absence of the north american topography the summer precipitation is significantly reduced over the central united states and increased along the gulf states and northeast mexico linear and non

reply to comments on anatomy of a late quaternary carbonate island constraints on timing and magnitude of sea level fluctuations west caicos turks and caicos islands bwi by wanless and dravis quat sci rev doi 10 1016 j quascirev 2020 106216 abstract we address concerns raised by wanless and dravis 2020 on our paper documenting the late quaternary evolution of west caicos island we negate the claim that omitting their paper dravis and wanless 2017 had any consequences for our interpretations we also provide reasoning and data to demonstrate that our interpretation of the quaternary stratigraphy of the island was derived from detailed field work and high resolution remote sensing data which was subsequently corroborated by aar and u th age dating control the opposite of the claim by wanless and dravis

quaternary tectonic stability of the bahamian archipelago evidence from fossil coral reefs and flank margin caves abstract throughout the islands of the bahamian archipelago fossil coral reefs are found from current sea level up to a maximum elevation of 4 m 234 u 230 th radiometric dates obtained from in situ corals from these reefs by both alpha count and mass spectrometric techniques indicates that they were all formed during oxygen isotope substage 5e ca 125 000 years ago those data are consistent with a maximum sea level highstand of 6 m during substage 5e and either no vertical motion of the bahamas or possible isostatic subsidence of up to 2 m during the past 120 000 years no older in situ fossil corals or other subtidal deposits have been found subaerially exposed anywhere in the bahamas that finding suggests that late quaternary at least the past 300 000 years isostatic subsidence has occurred at a rate of 1 2 m per hundred thousand years and or no pre 5e highstands were above modern sea level an independent corroboration of the conclusions drawn about sea level amplitude and tectonic stability of the bahamas from the coral reef data is available from examination of abundant flank margin caves horizontal phreatic dissolution caves found above modern sea level throughout the bahamas these horizontally extensive air filled caves have dissolutional ceilings with elevations that are restricted to 1 to 7 m which is consistent with formation at the margin of a thin freshwater lens elevated by a past 6 m sea level highstand the restricted cave elevations and the lack of stalagmites in these caves that are older than 100 000 years are also consistent with cave formation during substage 5e and possible subsequent isostatic subsidence of a few metres the subsurface geology of the southeastern bahamas contains a long term record millions of years that has been attributed to past tectonic activity along the north american caribbean plate boundary while that record suggests differential subsidence across the bahamas in the tertiary period the data from fossil coral reefs and subtidal deposits and flank margin caves indicate that all bahamian banks on which there are islands have been tectonically stable and behaving similarly for at least the past several hundred thousand years

geological geochemical and mineralogical characteristics of ree bearing las mercedes bauxite deposit dominican republic abstract bauxite deposits traditionally the main source of aluminum have been recently targeted for their remarkable contents in rare earth elements ree with ree lanthanoids sc y concentrations systematically higher than 1400 ppm av 1530 ppm the las mercedes karstic bauxites in the dominican republic rank as one of the ree richest deposits of its style the bauxitic ore in the las mercedes deposit is mostly unlithified and has a homogeneous massive lithostructure with only local cross stratification and graded bedding the dominant arenaceous and round grained texture is composed of bauxite particles and subordinate ooids pisoids and carbonate clasts mineralogically the bauxite ore is composed mostly of gibbsite and lesser amounts of kaolinite hematite boehmite anatase goethite chromian spinel and zircon identified ree minerals include cerianite and monazite ce whose composition accounts for the steady enrichment in light relative to medium and heavy ree of the studied bauxites considering the paleo geomorphology of the study area we propose that bauxites in the las mercedes deposit are the product of the erosion and deposition of lithified bauxites located at higher elevations in the bahoruco ranges based on the available data we suggest a mixed lithological source for the bauxite deposits at the district scale bedrock carbonates and an igneous source of likely mafic composition

global sea level fluctuations during the last interglaciation mis 5e the geomorphology and morphostratigraphy of numerous worldwide sites reveal the relative movements of sea level during the peak of the last interglaciation marine isotope stage mis 5e assumed average duration between 13072 and 11972 ka because sea level was higher than present deposits are emergent exposed and widespread on many stable coastlines correlation with mis 5e is facilitated by similar morphostratigraphic relationships a low degree of diagenesis uranium thorium u th ages and a global set of amino acid racemization aar data this study integrates information from a large number of sites from tectonically stable areas including bermuda bahamas and western australia and some that have experienced minor uplift 2 5 m 100 ka including selected sites from the mediterranean and hawaii significant fluctuations during the highstand are evident at many mis 5e sites revealed from morphological stratigraphic and sedimentological evidence rounded and flat topped curves derived only from reef tracts are incomplete and not representative of the entire interglacial story despite predictions of much different sea level histories in bermuda the bahamas and western australia due to glacio and hydro isostatic effects the rocks from these sites reveal a nearly identical record during the last interglaciation the last interglacial highstand is characterized by several defined sea level intervals slis that include sli 1 post glacial mis 6 5e termination ii rise to above present before 130 ka sli 2 stability at 2 to 3 m for the initial several thousand years 130 to 125 ka during which fringing reefs were established and terrace morphology was imprinted along the coastlines sli 3 a brief fall to near or below present around 125 ka sli 4 a secondary rise to and through 3 4 m 124 to 122 ka followed by sli 5 a brief period of instability 120 ka characterized by a rapid rise to between 6 to 9 m during which multiple notches and benches were developed and sli 6 an apparently rapid descent of sea level into mis 5d after 119 ka u th ages are used to confirm the last interglacial age of the deposits but unfortunately in only two cases was it possible to corroborate the highstand subdivisions using radiometric ages sea levels above or at present were relatively stable during much of early mis 5e and the last 6 7 ka of mis 1 encouraging a comparison between them the geological evidence suggests that significant oceanographic and climatic changes occurred thereafter midway through and continuing through the end of mis 5e fluctuating sea levels and a catastrophic termination of mis 5e are linked to the instability of grounded and marine based ice sheets with the greenland gis and west antarctic wais ice sheets being the most likely contributors late mis 5e ice volume changes were accompanied by oceanographic reorganization and global ecological shifts and provide one ominous scenario for a greenhouse world r 2007 elsevier ltd all rights reserved