ikaite precipitation in a lacustrine environment implications for palaeoclimatic studies using carbonates from laguna potrok aike patagonia argentina abstract the monoclinic mineral ikaite caco 3 6h 2 o and its pseudomorphs are potentially important archives for palaeoenvironmental reconstructions natural ikaite occurs in a small temperature range near freezing point and is reported mainly from marine and only rarely from continental aquatic environments ikaite transforms to more stable anhydrous forms of caco 3 after an increase in temperature or when exposed to atmospheric conditions the knowledge about conditions for natural ikaite formation its stable isotope fractionation factors and isotopic changes during transformation to calcite is very restricted here for the first time primary precipitation of idiomorphic ikaite and its calcite pseudomorphs are reported from a subsaline lake laguna potrok aike in southern argentina the calculated stable oxygen isotope fractionation factor between lake water and ikaite derived calcite pai 1 0324 at a temperature of 4 1 c is close to but differs from that of primarily inorganically precipitated calcite pseudomorphs after ikaite rapidly disintegrate into calcite powder that is indistinguishable from m sized calcite crystals in the sediment record of laguna potrok aike suggesting an ikaite origin of sedimentary calcites therefore the holocene carbonates of laguna potrok aike have the potential to serve as a recorder of past hydrological variation

a study of oxygen isotopic fractionation during bio induced calcite precipitation in eutrophic baldeggersee switzerland in order to better understand environmental factors controlling oxygen isotope shifts in autochthonous lacustrine carbonate sequences we undertook an extensive one year study march 1995 to february 1996 of water column chemistry and daily sediment trap material from a small lake in central switzerland comparisons between calculated equilibrium isotope values using the fractionation equation of friedman and o neil 1977 and measured oxygen isotope ratios of calcite in the sediment traps reveal that oxygen isotopic values of autochthonous calcite 18o are in isotopic equilibrium with ambient water during most of the spring and summer when the majority of the calcite precipitates in contrast small amounts of calcite precipitated in early spring and again in late autumn are isotopically depleted in 18o relative to the calculated equilibrium values by as much as 0 8 this seasonally occurring apparent isotopic nonequilibrium is associated with times of high phosphorous concentrations elevated ph 8 6 and increased co32 50 mol l in the surface waters the resulting weighted average 18o value for the studied period is 9 6 compared with a calculated equilibrium 18o value of 9 4 these data convincingly demonstrate that 18o of calcite are for the most part a very reliable proxy for temperature and 18o of the water

interpolation of an intertidal digital elevation model from heighted shorelines a case study in the western wash abstract a method of interpolating a spatiotemporal digital elevation model dem of an intertidal zone from a set of heighted shorelines is described the heighted shorelines are obtained by the water line method using remote sensing and hydrodynamic modelling this enables an intertidal dem to be constructed over a large area relatively quickly as well as frequent subsequent updating of the dem to detect changes the dem may be used for studying sediment transport in the intertidal zone and for the development of improved hydrodynamic models the spatiotemporal interpolator is based on universal block kriging and its results are illustrated using data from the wrangle flats area of the western wash u k for a kriging block size of 50 m 50 m 1100 days an average block height estimation standard deviation of 14 3 cm is achieved using shorelines from 33 images collected over the period 1992 1994 this height accuracy is compared with those obtained from dems constructed from beach transect data and is shown to be an improvement over the transect dem accuracies away from transects the construction of dems of improved accuracy 13 cm from combined shoreline and beach transect data using cokriging is discussed ways in which the shoreline accuracies may be improved are also considered

lateglacial and holocene climatic changes in south eastern patagonia inferred from carbonate isotope records of laguna potrok aike argentina abstract first results of strontium calcium carbon and oxygen isotope analyses of bulk carbonates from a 106 m long sediment record of laguna potrok aike located in southern patagonia are presented morphological and isotopic investigations of m sized carbonate crystals in the sediment reveal an endogenic origin for the entire holocene during this time period the calcium carbonate record of laguna potrok aike turned out to be most likely ikaite derived as ikaite precipitation in nature has only been observed in a narrow temperature window between 0 and 7 c the respective carbonate oxygen isotope ratios serve as a proxy of hydrological variations rather than of palaeotemperatures we suggest that oxygen isotope ratios are sensitive to changes of the lake water balance induced by intensity variations of the southern hemisphere westerlies and discuss the role of this wind belt as a driver for climate change in southern south america in combination with other proxy records the evolution of westerly wind intensities is reconstructed our data suggest that weak shw prevailed during the lateglacial and the early holocene interrupted by an interval with strengthened westerlies between 13 4 and 11 3 ka cal bp wind strength increased at 9 2 ka cal bp and significantly intensified until 7 0 ka cal bp subsequently the wind intensity diminished and stabilised to conditions similar to present day after a period of reduced evaporation during the little ice age strontium isotopes 87 sr 86 sr ratio were identified as a potential lake level indicator and point to a lowering from overflow conditions during the glacial 17 ka cal bp to lowest lake levels around 8 ka cal bp thereafter the strontium isotope curve resembles the lake level curve which is stepwise rising until the little ice age the variability of the ca isotope composition of the sediment reflects changes in the ca budget of the lake indicating higher degrees of ca utilisation during the period with lowest lake level

a storm surge prediction model for the northern bay of bengal with application to the cyclone disaster in april 1991 abstract a numerical model for simulating and predicting tides and storm surges in regions that include areas of open sea combined with estuarine channels and intertidal banks is described the model makes use of modified depth averaged equations with a numerical scheme in which the solution of 1d equations for narrow channels 2d equations for the open sea and an approach to modeling inundation are combined within a unified framework this simplifies the construction of realistic models for complex coastal areas and deltas the model is applied to the northern shelf of the bay of bengal and the ganges delta including the coast of bangladesh devastated by a cyclone surge in april 1991 in which about 140 000 people died hindcast and forecast simulations of this event using forcing derived from a semianalytical cyclone model with data supplied by the joint typhoon warning center jtwc are described it is shown that the timing of cyclone landfall and its coincidence with high tide determine the area

measurement of recent intertidal sediment transport in morecambe bay using the waterline method abstract an illustration of how sediment transport may be measured over a large dynamic intertidal area at reasonable cost and spatiotemporal resolution using the waterline method employing remote sensing and hydrodynamic modelling is presented areas and volumes of accretion and erosion were measured in the study area of morecambe bay in north west england over the period 1992 97 tidal asymmetry is considered to be the dominant agent of sediment movement in the bay with waves being of secondary importance waterlines i e land sea boundaries were extracted from 31 synthetic aperture radar images of the bay covering a substantial fraction of the tidal range heights were attached to the waterlines using water elevations from nested hydrodynamic tide surge models interpolation in space and time was carried out to produce a continuous spatiotemporal height map of the intertidal zone height maps with a spatial resolution of about 50 m and height accuracy of about 40 cm were constructed over an area of about 350 km 2 strong temporal decorrelation in the bay limited the height accuracy achievable differences between height maps for 1992 94 and 1995 97 allowed sediment volume changes to be extracted the intertidal region showed a loss of 16 1 4 5 10 6 m 3 over the period almost all the change being due to a significant decrease between mean sea level and the low water mark changes were also measured in three of the main river estuaries within the bay the leven kent and lune these included movement of the leven north east by about 2 km cutting into cartmel wharf accretion seaward of grange over sands and changes in the low water channels at the mouth of the lune these changes could be used to validate sediment transport models of the bay

neoproterozoic cap dolostone deposition in stratified glacial meltwater plume abstract neoproterozoic cap carbonates host distinctive geochemical and sedimentological features that reflect prevailing conditions in the aftermath of snowball earth interpretation of these features has remained contentious with hypotheses hinging upon timescale and synchronicity of deposition and whether or not geochemical signatures of cap carbonates represent those of a well mixed ocean here we present new high resolution sr and mg isotope results from basal ediacaran cap dolostones in south australia and mongolia least altered sr and mg isotope compositions of carbonates are identified through a novel incremental leaching technique that monitors the purity of a carbonate sample and the effects of diagenesis these data can be explained by the formation of these cap dolostones involving two chemically distinct solutions a glacial meltwater plume enriched in radiogenic sr and a saline ocean residue with relatively lower 87sr 86sr ratios model simulations suggest that these water bodies remained dynamically stratified during part of cap dolostone deposition most likely lasting for 8 thousand years our results can potentially reconcile previous conflicts between timescales estimated from physical mixing models and paleomagnetic constraints geochemical data from cap carbonates used to interpret the nature of snowball earth and its aftermath should be recast in terms of a chemically distinct meltwater plume

factors controlling δ13c values of sedimentary carbon in hypertrophic baldeggersee switzerland and implications for interpreting isotope excursions in lake sedimentary records we use stable carbon isotope values d 13 c in sedimented organic matter and carbonate as proxy indicators of productivity changes in a highly eutrophic to hypertrophic lake stable isotope data from a seasonally sampled sediment core recovered from baldeggersee switzerland were compared with direct and inferred total phosphorus p concentrations carbon isotope values of sedimentary organic matter d 13 corg in both seasonal varves and over the past 100 yr are not linearly related to total p concentrations nor do they mirror observed trends in carbonate isotope values d 13 c baldeggersee d 13 corg values are influenced by both variations in the relative inputs of caco3 eukaryotic biomass which becomes enriched in 13 c with increasing primary productivity and the contribution of microbial biomass produced in the expanding anoxic bottom waters which is typically very depleted in 13 c we also examined the fractionation within the organic matter co2 caco3 system calculated as total organic carbon toc 5 10 3 d 13 c 1 1 000 d 13 corg 1 1 000 2 1 thresholds within the measured toc values represent baldeggersee caco3 trophic status more accurately than d 13 corg or d 13 c values alone in alkaline lakes with endogenic carbonate caco3 precipitates toc values can facilitate accurate interpretation of values and trends in organic carbon isotope data and can help to better assess trophic history and lake remediation efforts in lake systems that have been heavily affected by cultural eutrophication

a 14kyr record of the tropical andes the lago chungara sequence 18 s northern chilean altiplano abstract high resolution geochemical analyses obtained using an x ray fluorescence xrf core scanner as well as mineralogical data from the lago chungara sedimentary sequence in the northern andean chilean altiplano 18 s provided a detailed reconstruction of the lacustrine sedimentary evolution during the last 14 000 cal yr bp the high resolution analyses attained in this study allowed to distinguish abrupt periods identify the complex structures of the early and mid holocene arid intervals and to compare their timing with titicaca lake and sajama ice records three main components in the lake sediments have been identified a biogenic component mainly from diatoms b volcanics ash layers from the nearby parinacota volcano and c endogenic carbonates the correlation between volcanic input in lago chungara and the total particles deposited in the nevado sajama ice core suggests the parinacota volcano as the common source the geochemical record of lago chungara indicates an increase in siliceous productivity during the early holocene lagging behind the rise in temperatures inferred from the nevado sajama ice core the regional mid holocene aridity crisis can be characterized as a number of short events with calcite and aragonite precipitation in the offshore lake zones

88 sr 86 sr fractionation and calcite accumulation rate in the sea of galilee abstract this study used the sea of galilee lake kinneret northern israel as a natural laboratory to investigate the fractionation of the stable sr isotope ratio 88 sr 86 sr during precipitation of inorganic primary calcite from the lake s water it was found that the absolute value of the 88 sr 86 sr fractionation factor 88 86 sr increases as a function of calcite accumulation rate 88 86 sr 0 05 to 0 042 log r mol m 2 d 1 where r is the accumulation rate furthermore the 87 sr 86 sr and 88 sr 86 sr ratios in the freshwater and brines that enter the lake were used to calculate the contributions of these sources to the lake sr budget the 87 sr 86 sr and 88 sr 86 sr ratios were measured in primary calcite aragonite shells of live melanopsis lake water and various water sources to the lake while the lake s 87 sr 86 sr ratios are determined by the mixture of freshwater of the jordan river and saline springs the 88 sr 86 sr ratios of the lake reflect a more complex mass balance that includes the effect of isotopic fractionation associated with the precipitation of primary calcite data analysis suggests that long term accumulation of inorganic calcite depleted in the heavy isotope 88 sr results in an increase of the 88 86 sr value of the lake water by 0 05 in contrast to the primary inorganic calcite biogenic aragonite of the melanopsis shells show a rather constant 88 sr 86 sr water caco 3 fractionation of 88 86 sr 0 21 similar 88 86 sr values were reported for the precipitation of coralline and inorganic aragonite from seawater and the precipitation of inorganic calcite from various continental waters the 88 86 sr value of inorganic calcite is modulated by the rate of carbonate precipitation as noted above and shown by precipitation experiments massive precipitation of primary calcite with a wide spread of accumulation rates occurs during the spring phytoplankton bloom in lake kinneret the bloom dictates the degree of calcite saturation in the lake and hence the stable sr isotopic composition of the precipitating calcite the correlation between 88 sr 86 sr and the calcite accumulation rate can be therefore used as a tool to reconstruct environmental and ecological variations in the historical lake by analyzing the 88 sr 86 sr ratio in the primary caco 3 recovered from the lake s sedimentary archives

oxygen isotope disequilibrium precipitation of calcite in lake arreso denmark lake carbonates are generally assumed to precipitate at or very close to oxygen isotopic equilibrium with the ambient water we present results from the eutrophic lake arreso northeastern sealand denmark that demonstrate disequilibrium precipitation of present day calcite according to the temperature equation of epstein et al these calcites are depleted in 18 o by 2 3 when compared to the expected equilibrium values core studies indicate that the development of disequilibrium conditions in lake arreso is correlated with the onset of an enhanced eutrophication a high precipitation rate is suggested as the mechanism responsible for the observed 18 o depletion of the calcite precipitates

biologically induced calcite and its isotopic composition in lake ontario we studied water sediment trap and core samples from eastern lake ontario to reconstruct the factors controlling the biologically induced production and sedimentation of calcite during so called whiting events calcite accumulation and its isotopic composition are controlled by a complex set of interrelated factors including temperature primary productivity and the abundance of pica cyanobacteria during the stratified period calcite precipitation is highly correlated to lake temperature because physical and biological factors interact to produce conditions favorable for whitings during warm years when the lake stratifies early in the seasonal cycle carbonate stratigraphies in multiple cores from eastern lake ontario revealed similar patterns of historical variation in percent carbonate an exponential rise in carbonate accumulation occurred in nine cores after 1930 culminating in peak values in the early 1980s this rise was related to historic increases in primary productivity resulting from increased phosphorus loading to lake ontario superimposed upon this rise were four peaks centered on 1940 1942 1957 1961 1971 1977 and 1983 that correlate with maxima in summer air temperature anomalies from the great lakes region and with strong el niiio events these peaks are also associated with maxima in s c values and minima in s180 values of carbonate lending support to our model that more calcite is precipitated with higher 6 c values during warm years when thermal stratitication occurs early in the seasonal cycle beginning in the mid 1980s calcite accumulation and its 6 c ratio began to decrease suggesting a reduction in primary productivity in surface waters probably related to lower phosphate concentrations in epilimnetic waters of lake ontario during the stratified period reduced summer p loading may be explained either by a lagged response to p abatement measures that began in the late 1970s or by decreased p loading from upstream lake erie beginning in the late 1980s as a result of the establishment of filter feeding zebra mussels

multiproxy paleoaltimetry of the late oligocene pliocene oiyug basin southern tibet the stable isotope compositions of carbonate and organic samples from the oiyug basin in southern tibet allows for model calculations of the oligocene to pliocene paleoelevation of the south central tibetan plateau we measured the oxygen isotope composition of pedogenic and lacustrine calcite dolomite and siderite and the hydrogen isotope composition of n alkanes from plant waxes to reconstruct the 18o and d values of oiyug basin paleometeoric water calculated water isotope values from oiyug basin carbonate and organic samples respectively are in close agreement suggesting the preservation of an unaltered paleometeoric water isotopic signal in these archives late oligocene middle miocene paleoelevation estimates from groundwater pedogenic calcite and lacustrine dolomite indicate basin elevations of 4 1 km 1 2 1 6 km plant wax n alkanes d and lacustrine siderite 18o compositions of middle miocene 15 ma samples indicate paleoelevations of 5 1 km 1 3 1 9 km this estimated elevation is similar to the 5 4 km paleoelevation estimate based on fossil floral physiognomy from the same stratigraphic interval calculated late miocene pliocene paleoelevation estimates derived from the 18o composition of lacustrine marls and carbonate siderite concretions as well as the d from plant wax n alkanes indicate a mean elevation of 5 5 km 1 4 2 0 km at 5 ma although calculated mean paleoelevations for the oiyug basin all fall within the errors associated with the model calculations the close agreement of the different paleoelevation proxies provides an additional degree of confidence in the fidelity of the calculated paleoelevations calculated paleoelevations indicate a possible increase in oiyug basin elevations of 1 4 km between the early and late miocene given the modern oiyug basin elevation of 4 3 km study results allow for a possible 1 km decrease in elevation since the early pliocene these findings in conjunction with other tibetan paleoaltimetry studies are consistent with tectonic models supporting high elevations of the tibetan plateau since the initiation of india asia collision during the eocene and subsequent late cenozoic extensional collapse

calcification generates protons for nutrient and bicarbonate uptake abstract the biosphere s great carbonate deposits from caliche soils to deep sea carbonate oozes precipitate largely as by products of autotrophic nutrient acquisition physiologies protons constitute the critical link calcification generates protons which plants and photosynthetic symbioses use to assimilate bicarbonate and nutrients a calcium atpase based trans mechanism underlies most biological calcification this permits high calcium carbonate supersaturations and rapid carbonate precipitation the competitive advantages of calcification become especially apparent in light and nutrient deficient alkaline environments calcareous plants often dominate the lower euphotic zone in both the benthos and the plankton geographically and seasonally massive calcification concentrates in nutrient deficient environments including alkaline soils coral reefs cyanobacterial mats and coccolithophorid blooms structural and defensive uses for calcareous skeletons are sometimes overrated

understanding the transfer of contemporary temperature signals into lake sediments via paired oxygen isotope ratios in carbonates and diatom silica problems and potential abstract although the oxygen isotope composition 18o of calcite 18ocalcite and to a lesser extent diatom silica 18odiatom are widely used tracers of past hydroclimates especially temperature and surface water hydrology the degree to which these two hosts simultaneously acquire their isotope signals in modern lacustrine environments or how these are altered during initial sedimentation is poorly understood here we present a unique dataset from a natural limnological laboratory to explore these issues this study compares oxygen and hydrogen isotope data 18o 2h of contemporary lake water samples at 2 weekly intervals over a 2 year period 2010 12 with matching collections of diatoms 18odiatom and calcite 18ocalcite from sediment traps at 10 m and 25 m at rostherne mere maximum depth 30 m a well monitored eutrophic seasonally stratified monomictic lake in the uk the epilimnion shows a seasonal pattern of rising temperature and summer evaporative enrichment in 18o and while there is a temperature imprint in both 18odiatom and 18ocalcite there is significant inter annual variability in both of these signals the interpretation of 18odiatom and 18ocalcite values is complicated due to in lake processes e g non equilibrium calcite precipitation especially in spring leading to significant 18ocalcite depletion and for 18odiatom by post mortem depositional and possibly dissolution or diagenetic effects for 2010 and 2011 respectively there is a strong temperature dependence of 18ocalcite and 18odiatom in fresh trap material with the fractionation slope for 18odiatom of ca 0 2 c in agreement with several other studies the 18odiatom data indicate the initiation of rapid post mortem secondary alteration of fresh diatom silica within 6 months with some trap material undergoing partial maturation in situ diatom 18o of the trap material is also influenced by resuspension of diatom frustules from surface sediments notably in summer 2011 with the net effect seen as an enrichment of deep trap 18odiatom by about 0 7 relative to shallow trap values contact with anoxic water and anaerobic bacteria are potentially key to initiating this silica maturation process as deep trap samples that were removed prior to anoxia developing do not show enrichment dissolution perhaps enhanced by anaerobic bacterial communities may also be responsible for changes to 18odiatom that lead to increasing but potentially predictable error in inferred temperatures using this proxy high resolution multi year monitoring can shed light on the complex dynamics affecting 18odiatom and 18ocalcite and supports the careful use of sedimentary 18odiatom and 18ocalcite as containing valuable hydroclimatic signals especially at a multi annual resolution although there remain substantial challenges to developing a reliable geothermometer on paired 18odiatom and 18ocalcite in particular 18odiatom needs cautious interpretation where silica post mortem secondary alteration is incomplete and diatom preservation is not perfect and we recommend dissolution be routinely assessed on diatom samples used for isotopic analyses

sedimentary characteristics and depositional models of two types of homogenites in an eocene continental lake basin shulu sag eastern china abstract homogenites are homogeneous and structureless fine grained rocks they have been studied extensively in marine settings and are typically interpreted as being related to catastrophic events such as earthquakes however studies on lacustrine homogenite like rocks are limited new core data from the shulu sag in china reveal that thick massive calcilutites exist in the lower shahejie 3 formation which formed during the middle eocene rifting stage based on petrographic geochemical and mineralogical data these massive calcilutites are interpreted as homogenites and grouped into two types type a homogenite is composed of intrabasinal materials characterized by high calcite total organic carbon toc content and 13c value type a homogenite has two facies successions the first of which is characterized by homogeneous appearance capped by an erosional interface and the second is characterized by repeated massive laminated calcilutite successions type b homogenite contains abundant allochthonous materials displaying relatively high dolomite content and low calcite toc and 13c content type b homogenite represents the topmost finer portion of a graded megabed which includes from base to top grain supported carbonate conglomerates slumped deformed portions and debrites the whole unit can be considered as a megaturbidite earthquakes are the most reasonable triggers of homogenite formation in the shulu sag type a homogenites are thought to be derived by fluidification resuspension and decantation of lacustrine fines due to shock waves generated by an earthquake type b homogenites might be deposits of distal turbidity currents and turbid clouds transformed from other gravity flows the results of this study provide a better understanding of the formation of homogenites caused by earthquakes in a confined lacustrine basin

paleoclimatic significance of lacustrine microbialites a stable isotope case study of two lakes at torres del paine southern chile article two patagonian lakes studied here lago sarmiento and laguna amarga are located within the orographic rain shadow formed to the east of the southern patagonian ice field in the andes range major thrombolite colonies are present in lago sarmiento whereas widespread stromatolites occur in laguna amarga based on the characterization of the hydrologic system of these two lakes together with an estimation of the isotopic balance and an analysis of the equilibrium conditions between the water and biologically induced carbonates it is concluded that the microbialites of lago sarmiento are better suited as paleotemperature indicators than those of laguna amarga lago sarmiento thrombolites contain unique carbonate mineral species in which carbonate precipitation occurs close to isotopic equilibrium and where the variation in water temperature controls fractionation of the stable oxygen isotope the results indicate that at 1215 cal yr bp the level of the lake was at 85 m a s l with a temperature close to 9 3 c was at 82 m a s l at 600 cal yr bp with a temperature close to 8 5 c this coincides with the timing of the northern hemisphere medieval warming period at 183 cal yr bp the level of the lake was at 80 m a s l with a cooler temperature close to 7 7 c representing a colder period coinciding with the timing of the little ice age lia an interesting outcome of this study is that it reinforces the idea that the 13 c signal in carbonate deposits can be an effective tool in distinguishing between inorganic and biologically induced precipitation

stable isotopic record of hydrological changes in subtropical laguna mar chiquita argentina over the last 230 years laguna mar chiquita a highly variable closed saline lake located in the pampean plains of cetral argentina is presently the largest saline lake in south america 6000km2 the availability of hitorical instrumental lake level and salinity data for the past 100 years allows for the calibration of the isotopic archive recorded in the lake sediments prolonged intervals with either negative or positive hydrlogical balances have severely modified lakewater levels salinity and primary productivity and have also controlled the isotopic composition of both the authigenic carbonate 8ooarb and f133ccarb and sedimetary organic matter 6 c0 extensive evaporation during lowstand stages results in an enrichment of 180 and 13c in the lake waters and is recorded in the sediments as the most positive 8o8arb and 613c carb compositions 0 0 o and 1 9yoo respectively conversely more negative 6f 8ocarb and 813ccarb values 1 8 o and 3 8yoo respectively are the result of increasing freshwater input into

construction of an inter tidal digital elevation model by the water line method progress in the development of a method for constructing a digital elevation model dem of an inter tidal zone using remote sensing and hydrodynamic modelling is described the method allows the construction of an inter tidal dem over large areas relatively quickly as well as frequent subsequent monitoring of the dem to detect changes and is particularly suited to sar satellite data because of the all weather day night capability of sar the resulting dem may be used for the development of improved hydrodynamic models and for studying sediment mass transport in the inter tidal zone

a sensitivity analysis of the waterline method of constructing a digital elevation model for intertidal areas in ers sar scene of eastern england abstract a sensitivity analysis of the waterline method of constructing a digital elevation model dem of an intertidal zone using remote sensing and hydrodynamic modelling is described variation in vertical height accuracy as a function of beach slope is investigated using a set of nine ers synthetic aperture radar sar images of the humber wash area on the english east coast acquired between 1992 and 1994 waterlines from these images are heighted using a hydrodynamic tide surge model and interpolated using block kriging on 1 500 slope beaches an average block height estimation standard deviation of 18 22 cm is achieved this rises to 27 cm on 1 100 slope beaches and 32 cm on 1 30 slope beaches the average heighting error at different slopes is decomposed into components due to waterline heighting error inadequate sensor resolution and interpolation inaccuracy it is shown that at 1 500 slope waterline heighting error and interpolation inaccuracy are the main error sources whilst at 1 30 slope errors due to inadequate sensor resolution become dominant the ability of the technique to generate intertidal dems for almost the entire coastal zone in a complete ers sar scene covering 100 100 km is demonstrated

data assimilation for a coastal area morphodynamic model morecambe bay this paper investigates the use of data assimilation in coastal area morphodynamic modelling using morecambe bay as a study site a simple model of the bay has been enhanced with a data assimilation scheme to better predict large scale changes in bathymetry observed in the bay over a 3 year period the 2dh decoupled morphodynamic model developed for the work is described as is the optimal interpolation scheme used to assimilate waterline observations into the model run each waterline was acquired from a sar satellite image and is essentially a contour of the bathymetry at some level within the inter tidal zone of the bay for model parameters calibrated against validation observations model performance is good even without data assimilation however the use of data assimilation successfully compensates for a particular failing of the model and helps to keep the model bathymetry on track it also improves the ability of the model to predict future bathymetry although the benefits of data assimilation are demonstrated using waterline observations any observations of morphology could potentially be used these results suggest that data assimilation should be considered for use in future coastal area morphodynamic models

a 200 year mid european air temperature record preserved in lake sediments an extension of the δ18op air temperature relation into the past abstract a detailed history of the water oxygen isotope ratios of lake ammersee southern germany was established for the last two centuries by analyzing oxygen isotope ratios of ostracod shells from a sediment core in a three to five year resolution empirical analysis and modelling of the isotope hydrology of the lake show that the oxygen isotopic composition of the lake water is mainly controlled by the isotopic composition of local precipitation for the last 200 years the lake isotope record is strongly correlated to the air temperature record from hohenpeisenberg situated within the lake s catchment area thus the mid european relation between 18 o in precipitation and air temperature documented for the last 20 years can be extended over a longer time and a larger temperature range the results provide further support for the validity of ostracod 18 o from ammersee sediments as a quantitative proxy for mean annual air temperature probably extending back to the last glaciation

lacustrine carbonates of iberian karst lakes sources processes and depositional environments abstract carbonates are the main components of iberian quaternary lake sediments in this review we summarize the main processes controlling carbonate deposition in extant iberian lakes located in mesozoic and tertiary carbonate dominated regions and formed through karstic activity during the late quaternary the lakes relatively small 1 ha to 118 ha and relatively shallow zmax 11 to 40 m provide examples of the large variability of sedimentary facies depositional environments and carbonate sources hydrology is dominated by groundwater inflow except those directly connected to the fluvial drainage nine lakes have been selected for this review and the main facies in palustrine littoral and profundal environments described and interpreted clastic carbonates occur in all iberian lakes due to the carbonate composition of the bedrocks surface formations and soils of the watersheds low temperatures and dilute meteoric waters seem responsible for the low carbonate content of sediments in high elevation lakes in the glaciated terrains in the pyrenees and the cantabrian mountains clastic carbonates are dominant in small karst lakes with functional inlets where sediment infill is dominated by fining upward sequences deposited during flood events re working of littoral carbonates is common in shallow environments and during low lake level stages in most lakes endogenic carbonate production occurs in two settings i littoral platforms dominated by chara and charophyte meadows and ii epilimnetic zone as biologically mediated calcite precipitates continuous preservation of varves since the mid holocene only occurs in one of the deeper lakes montcortes lake up to 30 m where calcite laminae textures massive fining upward and coarsening upward reflect seasonal changes in limnological conditions however varves have been formed and preserved in most of the lakes during short periods associated with increased water depth and more frequent meromictic conditions most iberian lakes are in a mature stage and karstic processes are not very active an outstanding example of a lake with intense karstic activity is banyoles lake where increased spring discharge after long rainy periods causes large remobilization and re suspension of the sediments accumulated in the deepest areas leading to the deposition of thick homogeneous layers homogeinites the iberian karst lake sequences underline the large variability of facies carbonate sources and depositional environments in small lake systems they illustrate how lake types evolve through the existence of a lake basin at centennial or even smaller time scales hydrology is the paramount control on facies and depositional environment patterns distribution and lake evolution and consequently a lake classification is proposed based on hydrology and sediment input a correct interpretation of carbonate sources and depositional history is a key for using lake sequences as archives of past global changes

high resolution late glacial chronology for the gerzensee lake record switzerland δ18o correlation between a gerzensee stack and ngrip oxygen isotope variations were analyzed on bulk samples of shallow water lake marl from gerzensee switzerland in order to evaluate major and minor climatic oscillations during the late glacial to highlight the overall signature of the gerzensee 18o record 18o records of four parallel sediment cores were first correlated by synchronizing major isotope shifts and pollen abundances then the records were stacked with a weighting depending on the differing sampling resolution to develop a precise chronology the 18o stack was then correlated with the ngrip 18o record applying a monte carlo simulation relying on the assumption that the shifts in 18o were climate driven and synchronous in both archives the established chronology on the gicc05 time scale is the basis for 1 comparing the 18o changes recorded in gerzensee with observed climatic and environmental fluctuations over the whole north atlantic region and 2 comparing sedimentological and biological changes during the rapid warming with smaller climatic variations during the bolling allerod period the 18o record of gerzensee is characterized by two major isotope shifts at the onset and at the termination of the bolling allerod warm period as well as four intervening negative shifts labeled gi 1e2 d c2 and b which show a shift of one third to one fourth of the major 18o shifts at the beginning and end of the bolling allerod despite some inconsistency in terminology these oscillations can be observed in various climatic proxies over wide regions in the north atlantic region especially in reconstructed colder temperatures and they seem to be caused by hemispheric climatic variations

geochemical evaluation of fenghuoshan group lacustrine carbonates north central tibet implications for the paleoaltimetry of the eocene tibetan plateau abstract a sedimentologic petrologic and geochemical evaluation of lacustrine carbonates from the eocene oligocene fenghuoshan group of north central tibet provides insight into the paleoenvironmental and paleolimnological setting of the hoh xil basin during the mid tertiary fenghuoshan lacustrine rocks consist primarily of carbonate mudstones and wackestones these carbonates are generally less than 3 m in thickness and are intercalated with siliciclastic lacustrine and fluvial alluvial plain deposits individual limestone beds coarsen and contain increasing amounts of siliciclastic material upward fenghuoshan carbonates also contain abundant ostracode bivalve and charaphyte fossils sedimentologic evidence suggests that carbonate deposition occurred in shallow relatively short lived lacustrine systems that were subsequently filled by alluvial deposits of coeval fluvial systems stable c and o isotopic analysis of fenghuoshan carbonates show 18o values ranging from 11 7 to 10 3 vienna pee de

late holocene climate change in central sweden inferred from lacustrine stable isotope data stable isotopes 18o and 13c of lacustrine carbonates chara spp algae and pisidium spp molluscs from a lake sedimentary sequence in central sweden were analysed to infer changes in lake hydrology and climate during the late holocene results from analysis of lake water isotopes 18o and 2h show that lake blektjarnen water isotope composition is responsive to the balance between evaporation and input water e i ratio a high e i ratio results from a dry and probably warmer climate decreasing the relative importance of precipitation input under such conditions evaporation and atmospheric equilibration probably enrich lake water in 18o and 13c respectively which is reflected in the isotopic composition of the carbonates in the lake from the relatively positive chara 18o values we infer that conditions were dry and warm between 4400 and 4000 cal a bp whereas more negative values indicate that conditions were wetter and probably cooler between 4000 and 3000 cal a bp a drier climate is inferred from more positive values between 2500 and 1000 cal a bp however a successive depletion after ca 1750 cal a bp also detected in several other 18o records carbonate and diatom suggest increasingly wetter conditions in scandinavia after that time which is probably related to increased strength of the zonal flow

tracking the hydro climatic signal from lake to sediment a field study from central turkey palaeo hydrological interpretations of lake sediment proxies can benefit from a robust understanding of the modern lake environment in this study we use nar golu a non outlet monomictic maar lake in central turkey as a field site for a natural experiment using observations and measurements over a 17 year monitoring period 1997 2014 we compare lake water and sediment trap data to isotopic chemical and biotic proxies preserved in its varved sediments nar golu underwent a 3 m lake level fall between 2000 and 2010 18olakewater is correlated with this lake level fall responding to the change in water balance endogenic carbonate is shown to precipitate in isotopic equilibrium with lake water and there is a strong relationship between 18olakewater and 18ocarbonate which suggests the water balance signal is accurately recorded in the sediment isotope record over the same period sedimentary diatom assemblages also responded and conductivity inferred from diatoms showed a rise shifts in carbonate mineralogy and elemental chemistry in the sediment record through this decade were also recorded intra annual changes in 18olakewater and lake water chemistry are used to demonstrate the seasonal variability of the system and the influence this may have on the interpretation of 18ocarbonate we use these relationships to help interpret the sedimentary record of changing lake hydrology over the last 1725 years nar golu has provided an opportunity to test critically the chain of connection from present to past and its sedimentary record offers an archive of decadal to centennial scale hydro climatic change

13c 12c partitioning and kinetics of co2 absorption by hydroxide buffer solutions abstract absorption of co2 gas into a borate buffer solution is a linear function of time the measured absorption rate logr 10 33 mol cm 2 s 1 compares well to a value calculated from the diffusion constant of co2 aq and the rate constant for the reaction of co2 aq with oh the stable carbon isotope composition of the dissolved carbonate is constant as function of time and is depleted in13c by 19 5 with respect to the gas phase the kinetic fractionation due to diffusion is 13d 12d 0 5 1 103 0 7 while that caused by the chemical reaction is 13k 12k 0 5 1 103 18 8 these values have to be taken into account if a borate buffer is used for sample concentration techniques in order to deduce the carbon isotope composition of co2 g absorption of co2 into a ba oh 2 solution is a linear function of time too but the absorption rate varies with the experimental boundary conditions the precipitated baco3 is depleted in13c with respect to the gas phase however 13c values are not constant and decrease as a function of time

a simple waterline approach for tidelands using multi temporal satellite images a case study in the yangtze delta abstract waterline technique based on satellite remote sensing is potentially one of the most effective tools for studying changes in tidal flat environment and coastlines however multi temporal waterlines obtained from satellite images are often difficult to compare directly because fluctuant tidal conditions may produce different elevation of waterlines to overcome the difficulty this study developed a comparable waterline solution to estimate active lateral evolutions using tm satellite images at different tide conditions owing to the dynamic properties the yangtze river mouth was selected as the case example to test the suitability of the approach and totally four time slices were partitioned during 1987 2004 for investigating coastline changes the first step of this technique is to digitize waterlines with various elevations labeling in a time slice in the second step the waterlines were merged to generate dems and contour maps using the linear gridding interpolation method in the last step any interested contour line may be extracted from dems and used for comparison of tideland changes to evaluate the errors in digitizing and interpolation process quantitative checks were examined after the dems were constructed in order to monitoring the rate of coastline spread a proposed approach for estimating mean coastline spread distance between two time spans is developed in this paper to conclude this work demonstrates the importance of tm etm images to provide high frequency historical topography and morphodynamics information for coastal monitoring and evaluation

evaluating shoreline identification using optical satellite images abstract a technique to extract the shoreline location from optical satellite images has been developed and evaluated for the case study site of progreso yucatan mexico a novel method to extract a satellite derived shoreline sds was developed ensuring the maximum contrast between sea and land the area under investigation is an 8 km length of shoreline that faces north into the gulf of mexico the sds was validated using quasi simultaneous in situ shoreline measurements both adjusted to equal water levels in situ shoreline measurements recorded the instantaneous shoreward extent of the wave run up when walking along the beach the validation of sds revealed that the sds is located consistently seawards of the in situ shoreline explained by a the water depth that optical satellite image requires to identify a pixel either as sea or land and b the shoreward extent of the wave run up the overall distance between sds and in situ shoreline is 5 6 m on average with a standard deviation of 1 37 m in the horizontal over 8 km of shoreline confidence bounds considering the shoreward extent of the wave run up inter tidal beach slope variation and tidal uncertainty were computed to assess the accuracy of the sds the sds has been shown to be capable of detecting shoreline changes of less than 10 m and abrupt changes due to storms the success of our method suggests that it should be applicable to other locations after adapting the confidence bounds to the beach conditions

hydrologic and climatic implications of stable isotope and minor element analyses of authigenic calcite silts and gastropod shells from a mid pleistocene pluvial lake western desert egypt abstract authigenic calcite silts at wadi midauwara in kharga oasis egypt indicate the prolonged presence of surface water during the marine isotope stage 5e pluvial phase recognized across north africa exposed over an area of 4 25 km 2 these silts record the ponding of water derived from springs along the libyan plateau escarpment and from surface drainage the 18 o values of these lacustrine carbonates 11 3 to 8 0 pdb are too high to reflect equilibrium precipitation with nubian aquifer water or water of an exclusively atlantic origin mg ca and sr ca of the silts have a modest negative covariance with silt 18 o values suggesting that the water may have experienced the shortest residence time in local aquifers when the water 18 o values were highest furthermore intra shell 18 o sr ca and ba ca analyses of the freshwater gastropod melanoides tuberculata are consistent with a perennially fresh water source suggesting that strong evaporative effects expected in a monsoonal climate did not occur or that dry season spring flow was of sufficient magnitude to mute the effects of evaporation the input of a second isotopically heavier water source to aquifers possibly indian ocean monsoonal rain could explain the observed trends in 18 o and minor element ratios

accurate and efficient determination of the shoreline in ers 1 sar images extraction of the shoreline in sar images is a difficult task to perform using simple image processing operations such as grey value thresholding due to the presence of speckle and because the signal returned from the sea surface may be similar to that from the land a semiautomatic method for detecting the shoreline accurately and efficiently in ers 1 sar images is presented this is aimed primarily at a particular application namely the construction of a digital elevation model of an intertidal zone using sar images and hydrodynamic model output but could be carried over to other applications a coarse fine resolution processing approach is employed in which sea regions are first detected as regions of low edge density in a low resolution image then image areas near the shoreline are subjected to more elaborate processing at high resolution using an active contour model over 90 of the shoreline detected by the automatic delineation process appear visually correct

oxygen isotope geothermometers in lacustrine sediments new insights through combined δ18o analyses of aquatic cellulose authigenic calcite and biogenic silica in lake gościąz central poland abstract two water based oxygen isotope geothermometers calcite cellulose and silica cellulose were tested using well dated intervals of laminated sediment retrieved from lake go ci z a small hardwater lake in central poland five sections spanning ca 90 200 years of deposition were selected and subsampled at approximately decadal resolution to characterize relatively stable climatic and hydrologic conditions during the middle of the younger dryas cold period the rapid environmental changes that occurred at the younger dryas preboreal yd pb boundary and three subsequent periods of relative stability during the early middle and late holocene the two geothermometers are based on the premise that aquatic cellulose 18 o serves as a direct proxy for lakewater 18 o thereby allowing resolution of temperature signals in 18 o records obtained from co existing authigenic calcite or diatom silica qualitatively consistent results from the calcite cellulose geothermometer were obtained for all five intervals clearly showing the expected low epilimnion water temperatures in the mid yd rapid warming during the yd bp transition and maximum temperatures during the early holocene followed by slightly lower temperatures during the middle and late holocene results from the silica cellulose geothermometer also showed lower temperatures during the yd than the late holocene although insufficient diatom silica for analysis was present in the intervening intervals the calcite cellulose geothermometer yielded consistently higher estimates of epilimnion temperatures than the silica cellulose thermometer in the yd and late holocene intervals and unrealistically high values throughout the holocene we speculate that the calcite cellulose geothermometer is influenced by kinetic effects during rapid carbonate precipitation which offsets temperature dependent fractionation and thus leads to high temperature estimates in contrast the silica cellulose geothermometer may be affected by the production of diatom silica early in the spring prior to seasonal warming and isotopic enrichment of the epilimnion thus generating low temperature estimates