development and refinement of proxy climate indicators from peats peat especially from acidic mires bogs is a natural archive of past environmental change reconstructions of past climate from bogs commenced in the 19th century through examination of visible peat stratigraphy and later formed the basis for a postglacial climatic scheme widely used in northwest europe nevertheless misconceptions as to how bogs grow led to a 50 year lacuna in peat climate study before the concept of cyclic regeneration in bogs was refuted in recent decades research using proxy climate indicators from bogs has burgeoned a range of proxies for past hydrological change has been developed as well as use of pollen bog oaks and pines and other data to reconstruct past temperatures most of this proxy climate research has been carried out in northern europe but peat based research in parts of asia and north america has increased particularly during the last decade while research has also been conducted in australia new zealand and south america this paper reviews developments in proxy climate reconstructions from peatlands chronicles use of a range of palaeo proxies such as visible peat stratigraphy plant macrofossils peat humification testate amoebae and non pollen palynomorphs and explains the use of wiggle match radiocarbon dating and relationship to climate shifts it details other techniques being used increasingly such as biomarkers stable isotopes inorganic geochemistry and estimation of dust flux and points to new proxies under development although explicit protocols have been developed recently for research on ombrotrophic mires it must be recognised that not all proxies and techniques have universal applicability owing to differences in species assemblages mire formation topographic controls and geochemical characteristics

variable density flow and solute transport simulation of regional aquifers containing a narrow freshwater saltwater transition zone variable density flow and solute transport simulation of aquifer systems containing narrow transition zones between freshwater and saltwater requires particular attention to certain aspects of the numerical method and its application to be successful typically only cases involving wide transition zones have been simulated with variable density transport models possibly because of inaccuracies in the modeling approaches used the major components of a successful approach are threefold first functionally consistent approximation of terms involved in fluid velocity calculations is necessary in the case of galerkin finite element methodology a significant modification is required to the standard approach in order to achieve consistency second the simulator must be verified in a particular series of tests the usual tests using henry s problem for verification of density dependent transport simulators are inadequate to check for consistency of the velocity approximations and for the accuracy of simulating flow driven by bouyancy forces third adequately fine spatial discretization is required when applying the simulator for spatial stability of the numerical transport solution and to allow accurate representation of narrow transition zones and the effects of low transverse dispersivity the effectiveness of this approach is demonstrated through simulation of the flow of fresh and saline groundwater in the layered basalt aquifer of southern oahu hawaii the transition zone in this regional flow system is narrow except near the discharge area where it is broadly dispersed simulation of this common situation with an inconsistent approximation gives grossly incorrect results while simulation with a consistent model provides a robust tool for analysis of system hydrology

a centennial scale record of vegetation and climate variability from 312 to 240 ka marine isotope stages 9c a 8 and 7e from tenaghi philippon ne greece abstract based on a new centennial scale resolution pollen record from the terrestrial site of tenaghi philippon ne greece we report a series of high amplitude millennial scale forest expansion events during the interval from 312 to 240 ka equivalent to isotopic substages c a of marine isotope stage mis 9 mis 8 and the onset of mis 7e pollen based indices support the climatic interpretation of the forest expansion events as indicators of abrupt increases in temperature and moisture availability in the mediterranean region long term changes in vegetation cover and composition during the studied interval permit the definition of glacial substages early middle and late analogous to the glacial substages of the last climatic cycle within this framework forest expansion events occurred during the early glacial equivalent to mis 9c a and the later part of the middle glacial mid to late mis 8 but are absent from the early part of the middle glacial early mis 8 forest expansion events are also detected during the lateglacial and onset of mis 7 associated with a millennial scale climate oscillation across the glacial interglacial transition i e termination iii t iii a peak for peak match between forest expansion events and antarctic temperature maxima suggests interhemispheric coupling of millennial scale climate variability via global oceanic circulation change and synergistic variability in atmospheric circulation consistent with the bipolar see saw the resolution of our record mean 290 yr also permits the characterisation of climate evolution over the course of interstadial episodes following forest expansion events and highlights differences in the characteristics of early and middle glacial interstadials saw tooth vs plateau profile these differences point to an influence of long term boundary conditions especially global ice volume on the characteristics of millennial scale events

mathematical modelling of sea water intrusion nauru island a two dimensional finite element model for density dependent groundwater flow was calibrated to simulate sea water intrusion in nauru island in the central pacific ocean nauru island occupies an area of 22 km2 and supports a population of 8500 the island has been mined for its phosphate deposits and current reserves indicate that the mine has about eight years life remaining the water supply of the island is about one third dependent on imported water which is also used as ballast on the phosphate ships imported water will not be available in the future and a hydrogeological investigation shows that the island is underlain by a fresh water layer less than 5 m thick the freshwater layer overlies a thick transition zone of brackish water which in turn overlies sea water simulation of several management options shows that it is possible to substitute current importation of fresh water by careful extraction from the groundwater resources of the island

lateglacial and holocene vegetation dynamics in the aegean region an integrated view based on pollen data from marine and terrestrial archives to elucidate the vegetation dynamics in the aegean region during the last 20 kyr we have studied terrestrial palynomorphs in marine core geotu sl152 mount athos basin northern aegean sea at centennial scale 125 to 300 yr resolution the robust chronology of the core allows us to reliably date signals of short term vegetation change in the aegean region for the pleniglacial interval until 14 6 kyr bp our data document steppe vegetation suggesting dry climatic conditions in the borderlands of the aegean sea subaerially exposed parts of the shelf were probably colonized by pinus dominated vegetation until shelf areas were flooded during lateglacial sea level rise the final rapid decrease of pinus pollen percentages between 14 and 13 kyr bp appears to be connected to meltwater pulse mwp 1a the lateglacial interstadial complex ie meiendorf bolling and allerod is characterized by the spread of oak trees but also by the continuous presence of steppe elements indicating only slightly increas

reconstruction of late glacial and holocene climate evolution in southern china from geolipids and pollen in the dingnan peat sequence we have carried out a multi proxy analysis of a radiocarbon dated peat core that records the history of paleoclimate change dating from 18 ka in the dingnan region of southern china fatty acid and hydrocarbon distributions total organic carbon toc concentrations pollen assemblages and sediment lithology reveal a succession of three major paleoclimate intervals plant waxes are the predominant origin of the n alkanoic acid and n alkane compositions of this sedimentary sequence contributions of these geolipid components vary relative to toc and with changes in lithology and help to refine a pollen based reconstruction of local paleoclimate evolution a period of cool and fairly wet climate 15 630 10 450 cal abp follows accumulation of coarse fluvial sediments under relatively dry deglacial conditions the second period 10 450 6040 cal abp experienced the warmest climate and the highest precipitation indicated by a minimum c18 1 c18 0 ratio together with the low cpi values of n alkanes and high acl values the third time interval 6040 3800 cal abp was a moderately dry and cool period the climate record of the most recent period 3800 cal abp is obscured by agricultural disturbance the younger dryas 12 900 11 600 cal abp appears in this record as a period of variable and very wet climate during the interval 10 450 6040 cal abp both temperature and the precipitation evaporation ratio maximized therefore we consider this period to represent the holocene optimum which coincides with that of the northern hemisphere moreover our results do not fit the spatially asynchronous pattern of the east asian monsoon holocene optimum in china suggested by previous studies they instead parallel the pattern of global paleoclimate change and consequently show that the evolution of holocene paleoclimate in southern china is consistent with changes in northern hemisphere solar radiation

late quaternary paleoclimate in the eastern mediterranean region from stable isotope analysis of speleothems at soreq cave israel abstract the eastern mediterranean continental paleoclimate during the past 25 000 years was determined by a high resolution petrographic stable isotopic and age study of speleothems from soreq cave israel 18o 13c trends indicate that all speleothems older than 7000 yr formed under conditions that differ from those of today the period from 25 000 to 17 000 yr b p was characterized by the highest 18o and 13c values which indicate deposition at temperatures of 12 16 c annual rainfall of 300 450 mm and vegetation typical of a mixed c3 c4type from 17 000 to 10 000 yr b p deglaciation in northern europe 18o values dropped progressively correlative with warming 2 3 c and a gradual increase in precipitation a simultaneous decrease in 13c gives a range expected for c3 type vegetation this period also shows significant 18o and 13c spikes which are correlatable with global events e g heinrich events and the younger dryas stade the speleothems that grew between 10 000 and 7000 yr b p have a unique petrography showing irregular thin laminae of various colors and much detritus they have the lowest 18o corresponding to 1000 mm rain coupled with the highest 13c caused by flooding events which stripped the soil cover from 7000 to 1000 yr b p conditions became closer to those of today this study demonstrates that global events which were recognized in northern europe and north africa are also evident in the eastern mediterranean and are reflected principally by large changes in the rainfall rate

a model for archaeologically relevant holocene climate impacts in the aegean levantine region easternmost mediterranean abstract a repeating pattern of multi centennial scale holocene climate events has been widely globally documented and they were termed rapid climate change rcc events non seasalt potassium ion k series in greenland ice cores provide well constrained timings for the events and a direct timing relationship has been inferred between these events and the frequency of northerly cold polar continental air outbreaks over the eastern mediterranean sea through gaps in the mountain ranges along the northern margin of the basin there also appears to be a remarkable timing agreement with major archaeological turnover events in the aegean levantine region yet no physically consistent assessment exists for understanding the regional climatic impacts of the events around this critical region we present a simple 2 dimensional lagrangian model which yields a broad suite of physically coherent simulations of the impacts of frequency changes in winter time northerly air outbreaks over the aegean levantine region we validate this with existing reconstructions from palaeoclimate proxy data with emphasis on well validated sea surface temperature reconstructions and a highly resolved cave speleothem stable oxygen isotope record from lebanon given that the rccs were clearly marked by negative sea surface temperature anomalies in the region we find that the predominant climatic impacts of this winter time mechanism were cold and wet in contrast with intercalated warmer and more arid conditions of non rcc periods more specifically the rccs are found to be periods of highly variable conditions with an overall tendency toward cold and wet conditions with potential for flash flooding and for episodic snow cover at low altitudes at least in the lower altitude lower 1 1 5 km regions of crete and the levant the modelled winter anomaly process cannot address underlying longer term astronomically forced trends or the relatively warm and arid anomalies in between rccs the latter require further study for example with respect to potential summer time extension of evaporative subtropical conditions over the region finally our results imply that the amount effect observed in levantine cave 18o and precipitation or drip water 18o may not reflect the conventional concept related to temperature dependent fractionation and rayleigh distillation instead it appears to arise from a complex and somewhat counter intuitive mixing in shifting proportionalities between advected external and evaporated mediterranean moisture

environmental influences over the last 16 ka on compound specific δ13c variations of leaf wax n alkanes in the hani peat deposit from northeast china compound specific carbon isotope ratios 13c of leaf wax n alkanes c21 c33 odd carbon numbered n alkanes were measured in the hani peat sequence from northeast china these data were compared with lipid biomarker compositions to assess changes in local vegetation and paleoclimate for the last 16 ka the 13c values of n alkanes range between 36 6 and 30 7 showing that the compounds originate from c3 plants much larger variations 5 4 in the n alkane 13c values than those of atmospheric co2 during the last 16 ka 0 5 indicate that the isotopic values were affected by environmental factors in addition to the postglacial 13c variations in the atmospheric reservoir the stratigraphic records of 13c reveal decoupled fluctuations among the individual n alkanes particularly between 15 5 and 11 4 ka synchronous excursions in the 13c offsets among individual n alkanes 13c and lipid biomarker paleoplant proxies paq and c23 c31 and c27 c31 from 14 9 to 13 2 ka and 12 7 to 11 6 ka suggest that vegetational changes are the most likely causes for the decoupled 13c variations parallel fluctuations of the 13c values of terrestrial higher plant derived c29 and c31n alkanes and the n alkane average chain length acl from 11 to 6 ka indicate that the 13c variations responded to net evaporation changes negative shifts in the n alkane 13c values coinciding with the acl decreases at 10 5 9 3 ka and 8 1 ka indicate the short term onset and fluctuations of the summer monsoon strength in eastern china during the early holocene

a north to south transect of holocene southeast atlantic continental margin sediments relationship between aerosol transport and compound specific δ13c land plant biomarker and pollen records 1 we examined near surface late holocene deep sea sediments at nine sites on a north south transect from the congo fan 4 s to the cape basin 30 s along the southwest african continental margin contents distribution patterns and molecular stable carbon isotope signatures of long chain n alkanes c27 c33 and n alkanols c22 c32 are indicators of land plant vegetation of different biosynthetic types which can be correlated with concentrations and distributions of pollen taxa in the same sediments calculated clusters of wind trajectories and satellite aerosol index imagery afford information on the source areas for the lipids and pollen on land and their transport pathways to the ocean sites this multidisciplinary approach on an almost continental scale provides clear evidence of latitudinal differences in lipid and pollen composition paralleling the major phytogeographic zonations on the adjacent continent dust and smoke aerosols are mainly derived from the western and central south african hinterland dominated by deserts semi deserts and savannah regions rich in c4 and cam plants the northern sites congo fan area and northern angola basin which get most of their terrestrial material from the congo basin and the angolan highlands may also receive some material from the chad region very little aerosol from the african continent is transported to the most southerly sites in the cape basin as can be expected from the present position of the phytogeographic zones the carbon isotopic signatures of the n alkanes and n alkanols both become isotopically more enriched in 13c from north to south the results of the study suggest that this combination of pollen data and compound specific isotope geochemical proxies can be effectively applied in the reconstruction of past continental phytogeographic developments

paleohydrological changes in the eastern mediterranean region during the early to mid holocene recorded in plant wax n alkane distributions and δ13ctoc new data from tenaghi philippon ne greece abstract holocene climate dynamics have strongly influenced precipitation patterns in the eastern mediterranean region this holds particularly true for the 8 2 kyr bp climatic event arguably the strongest perturbation of early to mid holocene climate here we present a biomarker record of leaf wax derived n alkane distributions and stable isotopic composition of total organic carbon 13 c toc along with palynological data from the fen peat archive of tenaghi philippon tp ne greece spanning the interval from 8 7 to 7 5 kyr bp our record documents the response of in situ vegetation within the philippi peatland to changing hydrological conditions and addresses the applicability of organic proxies such as the aquatic index p aq average chain length acl and 13 c toc as indicators of peat surface moisture conditions at the study site the long chain n alkanes n c 27 n c 29 and n c 31 typical of vascular terrestrial plants dominated the peat sequence a period of relatively dry surface conditions indicated by low values of p aq and elevated acl values in concert with elevated 13 c toc values preceded the 8 2 kyr bp climatic event from ca 8 7 to 8 2 kyr bp slightly wetter more humid conditions suggested by an increase in p aq as well as reduced acl and 13 c toc values characterized the interval of the 8 2 kyr bp climatic event notably the increase in surface wetness as indicated by the biomarker record coincided with a marked rise in fern spore proportion as well as increasing proportion of pollen from aquatic taxa following the 8 2 kyr bp event a distinct change in paleohydrology at tp became apparent from ca 7 9 kyr bp onward an increase in the abundance of the mid chain length n alkanes n c 23 and n c 25 indicative of an increased contribution from aquatic plants to the sediment together with a steep increase in p aq and a decrease in acl as well as variation in 13 c toc imply considerably elevated surface moisture levels likely caused by the increased activity of the karstic system of the surrounding mountains collectively the biomarker proxies and pollen data reveal a concise picture of changing moisture conditions at tp in response to the 8 2 kyr bp climatic event

mediterranean climate and oceanography and the periodic development of anoxic events sapropels mediterranean sapropels are layers with elevated organic carbon concentrations that contrast with surrounding sediments which are organic poor sapropels occur quasi periodically in sedimentary sequences of the last 13 5 million years and exist both in the eastern and western mediterranean sub basins they have been the subject of extensive study based on records from both short conventional and long ocean drilling program sediment cores and from a wide variety of uplifted marine sediment sequences on the basin margins and islands previous syntheses in the 1990s and 2000s have discussed how the formation of sapropels is commonly ascribed to deep sea anoxia enhanced export productivity or a combination of these effects however a wealth of new evidence and insights has emerged during the past 1 2 decades based on traditional and novel proxy data as well as modelling which has revealed intriguing new aspects and nuances to the reconstructed conditions hence it is timely to present a new synthesis of current understanding of the processes behind the formation of sapropels which have over the past decade also become a matter of commercial interest in sub salt hydrocarbon exploration in this review we present a context of modern mediterranean climate and oceanography followed by an integrated assessment of the growing understanding of climatological and ocean circulation changes that were associated with sapropel deposition we find that sapropels predominantly formed during astronomically timed episodes when climatic and oceanographic conditions and ecological responses broadly preconditioned the basin for sapropel deposition there is strong correspondence with times of monsoon intensification fuelling runoff from north africa into the mediterranean sea while preconditioning due to sea level rise and regional precipitation and runoff may have contributed as well within these broad episodes of surface buoyancy gain and resultant decline in deep water ventilation specific deposition under dysoxic anoxic or even euxinic conditions occurred within a clearly dynamic system that was characterised by complex spatial and depth dependent patterns gradients with distinct temporal variability on at least decadal to centennial millennial timescales in the final section we evaluate the implications of different modes of deep water removal from silled basins to investigate why sapropels are more frequently and often more intensely developed in the eastern mediterranean than in the western mediterranean

n alkane parameters from a deep sea sediment transect off southwest africa reflect continental vegetation and climate conditions abstract an isobathic transect of marine surface sediments from 1 n to 28 s off southwest africa was used to further evaluate the potential of the chain length distribution and carbon stable isotope composition of higher plant n alkanes as proxies for continental vegetation and climate conditions we found a strong increase in the n c 29 33 weighted mean average 13 c values from 33 near the equator to around 26 further south additionally c 25 35 n alkanes reveal a southward trend of increasing average chain length from 30 0 to 30 5 the data reflect the changing contribution of plants employing different photosynthetic pathways c 3 and c 4 and or being differently influenced by the environmental conditions of their habitat the c 4 plant proportions calculated from the data ca 20 for rivers draining the rainforest to ca 70 at higher latitude correspond to the c 4 plant abundance in continental catchment areas postulated by considering prevailing wind systems and river outflows furthermore the c 4 plant contribution to the sediments correlates with the mean annual precipitation and aridity at selected continental locations in the postulated catchment areas suggesting that the c 4 plant fraction in marine sediments can be used to assess these environmental parameters

early and middle holocene in the aegean sea interplay between high and low latitude climate variability changes in the orbital parameters solar output and ocean circulation are widely considered as main drivers of the holocene climate yet the interaction between these forcings and the role that they play to produce the pattern of changes observed in different domains of the climate system remain debated here we present new early to middle holocene season specific sea surface temperature sst and d 18 oseawater results based on organic walled dinoflagellate cyst and planktonic foraminiferal data from two sediment cores located in the central sl21 and south eastern lc21 aegean sea eastern mediterranean today this region is affected by high to mid latitude climate in winter and tropical subtropical climate in summer the reconstructed d 18 o seawater from lc21 displays a marked w1 3 negative shift between 10 7 and 9 7 ka bp which represents the regional expression of the orbitally driven african monsoon intensification and attendant freshwater flooding into the eastern mediterranean a virtually contemporaneous shift of the same sign and magnitude is apparent in the d 18 ospeleothem record from soreq cave northern israel an important part of which may therefore reflect a change in the isotopic composition of the moisture source region aegean and levantine seas our sst reconstructions show that aegean winter ssts decreased in concert with intensifications of the siberian high as reflected in the gisp2 nss k record specifically three distinct sea surface cooling events at

plant wax δd values record changing eastern mediterranean atmospheric circulation patterns during the 8 2 kyr b p climatic event abstract throughout the holocene the climate of the mediterranean region has been strongly influenced by variability in the atmospheric circulation of the high and low latitudes a prominent example for such holocene climate perturbations is the 8 2 kyr b p climatic event reorganization of northern hemisphere atmospheric circulation patterns resulted in variations of temperature and precipitation distribution across the mediterranean the effects of changing high and low latitude atmospheric circulation on mediterranean climate in relation to the 8 2 kyr b p climatic event are however not well understood here we present a high resolution record of stable hydrogen isotope composition of plant wax n alkanes dwax across the 8 2 kyr b p climatic event from the tenaghi philippon peat deposit ne greece in order to characterize patterns of precipitation and changes in atmospheric circulation in the eastern mediterranean region our record reveals pronounced changes in dwax that correlate closely with previously published palynological data a long term decline in dwax values characterizes the lower part of the section the 8 2 kyr b p climatic event itself is connected to two distinct positive dwax excursions a minor shift in dwax around 8 2 kyr b p and a major shift in dwax between ca 8 1 and 8 0 kyr b p the upper part of the section shows a progressive trend towards higher dwax values we link shifts in dwax to changes in mediterranean air mass trajectories supplying precipitation to ne greece caused by variations in the relative contributions of northerly derived d depleted moisture and southerly derived d enriched moisture possible control mechanisms for alternating air mass trajectories include changes in the influence of the siberian high and differences in the influence of the african and asian monsoon circulation on anticyclonic conditions in the mediterranean region as well as regional inflow of moist air masses from the aegean sea

carbon isotope constraints on the deglacial co2 rise from ice cores the stable carbon isotope ratio of atmospheric co2 13catm is a key parameter in deciphering past carbon cycle changes here we present 13catm data for the past 24 000 years derived from three independent records from two antarctic ice cores we conclude that a pronounced 0 3 per mil decrease in 13catm during the early deglaciation can be best explained by upwelling of old carbon enriched waters in the southern ocean later in the deglaciation regrowth of the terrestrial biosphere changes in sea surface temperature and ocean circulation governed the 13catm evolution during the last glacial maximum 13catm and atmospheric co2 concentration were essentially constant which suggests that the carbon cycle was in dynamic equilibrium and that the net transfer of carbon to the deep ocean had occurred before then

rapid atmospheric co2 changes associated with the 8 200 years b p cooling event by applying the inverse relation between numbers of leaf stomata and atmospheric co2 concentration stomatal frequency analysis of fossil birch leaves from lake deposits in denmark reveals a century scale co2 change during the prominent holocene cooling event that occurred in the north atlantic region between 8 400 and 8 100 years b p in contrast to conventional co2 reconstructions based on ice cores from antarctica quantification of the stomatal frequency signal corroborates a distinctive temperature co2 correlation results indicate a global co2 decline of 25 ppm by volume over 300 years this reduction is in harmony with observed and modeled lowering of north atlantic sea surface temperatures associated with a short term weakening of thermohaline circulation

late postglacial paleoenvironmental change in the northeastern mediterranean region combined palynological and molecular biomarker evidence three gravity cores collected from the ne mediterranean nemr across a transect from the northern aegean sea north skyros basin to the south cretan margin scm were investigated for pollen and terrestrial biomarkers derived from epicuticular waxes of vascular plants during the last 20 ky pollen data show diversified mixed temperate forest in the northern borderlands and enhanced mediterranean vegetation in the southern areas documenting an n s climatic trend terrestrial plant biomarkers and their diagnostic geochemical indices exhibit latitudinal patterns which are interpreted in terms of the different delivery pathways fluvial runoff vs atmospheric transport resulting from the climate conditions during different periods during the late glacial and early deglaciation periods 20 14 ka bp relatively increased humidity h index is recorded in the north aegean sea while in the south drier climate was the limiting factor for vegetation development during this interval terrestrial n alkanes showed increased accumulation rates suggesting massive transport of terrestrial organic matter through runoffs and rivers followed by weaker input after 14 ka bp after 11 ka bp a major expansion of forest cover is evidenced in the nemr accompanied by a higher h index because of the climatic amelioration the forest vegetation exhibited regionally different characteristics with cool temperate taxa being more abundant in the aegean cores while the scm record is being featured by mediterranean elements at the onset of the holocene and throughout the holocene climatic optimum the delivery of terrestrial biomarkers increased and became more significant in the aegean sites compared to the scm site within the holocene the average chain length acl of long chain n alkanes exhibits lower values in the northern aegean than in the southeastern aegean and scm indicating the predominance of warmer species southwards finally the h index records a conspicuous humidity increase between 5 4 and 4 3 ka bp in the south aegean that coincides with an increase in the terrestrial biomarker supply and the deposition of a distinct sapropel like layer smh sapropel mid holocene similar trends in t temperature and h indices are slightly delayed and attenuated in the northern aegean and are accompanied by an increase in the acl index a noticeable increase in the accumulation rates ars of terrestrial biomarkers and the hpa index values during this period are clearly recorded in all three cores indicative of enhanced terrigenous inputs of organic matter along with higher in situ preservation

climate dynamics in the borderlands of the aegean sea during formation of sapropel s1 deduced from a marine pollen record abstract to unravel the climatic and environmental dynamics in the borderlands of the aegean sea during the early and middle holocene and notably for the interval of sapropel s1 s1 formation we have analysed terrestrial palynomorphs from a marine core in the northern aegean sea the qualitative results were complemented by quantitative pollen based climate reconstructions a land sea correlation was established based on pollen data and sediment lightness measurements from the same core and previously published benthic foraminifer data from a nearby core the borderlands of the aegean sea underwent a transition from an open vegetation to oak dominated woodlands between 10 4 and 9 5 ka cal bp a coeval increase in winter precipitation suggests that moisture availability was the main factor controlling holocene reforestation the 50 higher winter precipitation during s1 formation relative to pre sapropelic conditions suggests a strong contribution from the borderlands of the aegean sea to the freshwater surplus during s1 formation the humid and mild winter conditions during s1 formation were repeatedly punctuated by short term climatic events that caused a partial deforestation and a reorganisation within the broad leaved arboreal vegetation in the marine realm these events are documented by improved benthic oxygenation the strongest event represents the regional expression of the 8 2 ka cold event and led to an interruption in s1 formation except for the interval of s1 formation the pollen derived winter temperatures correlate with the smoothed gisp2 k series they support the previously published marine based concept that the intensity of the siberian high strongly controlled the winter climate in the aegean region during s1 formation in the aegean sea however climate conditions in the borderlands were more strongly affected by the monsoonally influenced climate system of the lower latitudes

the 8k event cause and consequences of a major holocene abrupt climate change abstract a prominent abrupt climate event about 8200 years ago brought generally cold and dry conditions to broad northern hemisphere regions especially in wintertime in response to a very large outburst flood that freshened the north atlantic changes were much larger than typical climate variability before and after the event with anomalies up to many degrees contributing to major displacement of vegetative patterns this 8k event provides a clear case of cause and effect in the paleoclimatic realm and so offers an excellent opportunity for model testing the response to north atlantic freshening has the same general anomaly pattern as observed for older events associated with abrupt climate changes following north atlantic freshening and so greatly strengthens the case that those older events also reflect north atlantic changes the north atlantic involvement in the 8k event helps in estimating limits on climate anomalies that might result in the future if warming caused ice melt and hydrologic cycle intensification at high latitudes lead to major changes in north atlantic circulation few model experiments have directly addressed the 8k event and most studies of proxy records across this event lack the time resolution to fully characterize the anomalies so much work remains to be done

the marine isotope stage 1 5 cryptotephra record of tenaghi philippon greece towards a detailed tephrostratigraphic framework for the eastern mediterranean region abstract the iconic climate archive of tenaghi philippon tp ne greece allows the study of short term palaeoclimatic and environmental change throughout the past 1 3 ma to provide high quality age control for detailed palaeoclimate reconstructions based on the tp archive crypto tephra studies of a peat core tp 2005 have been carried out for the 0 130 ka interval the results show that the tp basin is ideally positioned to receive tephra fall from both the italian and aegean arc volcanic provinces two visible tephra layers the santorini cape riva y 2 c 22 ka and the campanian ignimbrite ci y 5 c 39 8 ka tephras and six primary cryptotephra layers namely the early holocene e1 tephra from the aeolian islands c 8 3 ka the campanian y 3 c 29 ka and x 6 tephras c 109 5 ka as well as counterpart tephras tm 18 1d c 40 4 ka tm 23 11 c 92 4 ka and tm 33 1a c 116 7 ka from the lago grande di monticchio sequence southern italy were identified along with repeatedly redeposited y 2 and ci tephra material bayesian modelling of the ages of seven of the primary tephra layers 60 radiocarbon measurements and 20 palynological control points have been applied to markedly improve the chronology of the tp archive this revised chronology constrains the age of tephra tm 18 1d to 40 90 41 66 cal ka bp 95 4 range several tephra layers identified in the tp record form important isochrons for correlating this archive with other terrestrial e g lago grande di monticchio sulmona basin and lake ohrid and marine e g adriatic sea core prad 1 2 and aegean sea core lc21 palaeoclimate records in the mediterranean region

the high resolution palaeoclimatic and palaeoceanographic history of the last 24 000 years in the central aegean sea greece abstract the palaeoclimatic and palaeoceanographic history of the n skyros basin central aegean sea was studied based on the planktonic foraminifera and the stable isotopes obtained from the sediments of a sediment core selected in this area the data were further supported by pollen and dinoflagellate cyst data the data correspond to a mean sampling interval of about 170 yrs and cover the last 24 000 yrs the variations in almost all of the records showed synchronicity suggesting the occurrence of a series of climatic changes the most pronounced climatic changes during the last glacial and late glacial periods are as follows i a brief relatively warm and humid event at 19 5 kyr ii two cold spells at 17 ka and 15 8 ka iii the climatic oscillation during the gi 1 event and iv the development of the younger dryas gs 1 event in two phases during the holocene epoch five brief cold and or arid phases occurred at around 10 5 ka 8 2 ka 7 ka to 6 ka 5 0 ka and 3 0 ka the most warm and humid holocene events correspond to the time of the deposition of the two sapropel sublayers s1a and s1b almost all of these brief climatic changes are coeval with equivalent changes in high northern latitude areas and with changes in the intensity of the siberian high suggesting a climatic link between the studied area and the high latitude areas the prevalence of holocene arid events which coincide with equivalent events recorded in north eastern africa and the middle east suggests a climatic link between the eastern and south eastern regions of the mediterranean sea

simulation of groundwater interception at lake ranfurly victoria incorporating variable density flow and solute transport abstract the movement of salt from lake ranfurly west towards the river murray and the associated groundwater interception scheme has been modelled in cross section using the sutra model recharge from irrigation areas and saline seepage from the lake have been taken into account owing to the salinity contrast between lake ranfurly west and groundwater it was considered appropriate to simulate density dependent flow behaviour concentration profiles in the aquifers and salt loads to the river under various management scenarios were computed under conditions of both density dependent and non density dependent flow the model simulations have shown that the salt load to the river is 1 dependent on the rate of pumping from interception bores 2 dependent on the aquifer s in which groundwater is intercepted and 3 marginally greater 11 15 for density dependent flow behaviour at less than full interception compared with calculations which neglect density dependent flow

massive perturbation in terrestrial ecosystems of the eastern mediterranean region associated with the 8 2 kyr b p climatic event the climatic perturbation at ca 8 2 kyr b p is the strongest short term climate anomaly within the holocene it is generally attributed to a meltwater induced slowdown of the thermohaline circulation in the north atlantic model simulations and available proxy data suggest that it was strongest in the high to middle latitudes around the north atlantic based on new pollen data from tenaghi philippon northeastern greece we provide evidence for a massive climate induced turnover in terrestrial ecosystems of the aegean region associated with the 8 2 kyr b p event the reconstructed winter temperature decline of 4 c is much stronger than suggested by model simulations and proxy data from more northern latitudes of europe although the latter provide a direct downstream response to a north atlantic thermohaline circulation slowdown we attribute this discrepancy to mesoclimatic effects a stronger influence of the siberian high during the 8 2 kyr b p event may have enhanced the katabatic air flow from the mountains bordering the study site via a larger longer persisting snow cover our data demonstrate that high amplitude temperature anomalies and increased seasonality connected to the 8 2 kyr b p event may also have occurred in the lower mid latitudes much farther south than previously thought the magnitudes of these anomalies appear to have been strong enough to have seriously affected neolithic settlers in the northeastern mediterranean region

lipid biomarkers in the zoige hongyuan peat deposit indicators of holocene climate changes in west china abstract lipid biomarkers extracted from a peat core obtained from the northeast edge of the tibetan plateau have provided a 13 kyr record of regional climate change a period of warmer climate corresponding to the holocene optimum between 9 ka and 5 ka is evident in greater alteration of n alkanoic acids and n alkanols and in the appearance of biomarkers indicative of greater microbial activity concomitant increases in local precipitation that raised the water level of the peat bog are recorded by increases in the proportions of c23 and c25 n alkanes that are mainly derived from submerged floating plants alternations in submergent and emergent plant n alkane proxies reveal multi decimeter scale rises and falls in the bog water level that relate to variation in precipitation on the tibetan plateau during the holocene major low water level events occurred around 12 6 11 3 10 7 9 4 8 3 6 0 4 5 3 1 2 1 and 1 0 ka these events correlate well with cold dry events recorded in same region from other climatic proxies that reflect millennial scale holocene instability in the asian monsoon system our biomarker results also indicate that peat accumulation and preservation on the tibetan plateau are more sensitive to variability in monsoonal precipitation than in annual temperature

holocene atmosphere ocean interactions records from greenland and the aegean sea we compare paleoclimate proxy records from central greenland and the aegean sea to offer new insights into the causes timing and mechanisms of holocene atmosphere ocean interactions a direct atmospheric link is revealed between aegean sea surface temperature sst and high latitude climate the major holocene events in our proxies of aegean sst and winter spring intensity of the siberian high gisp2 k record follow an 2300 year spacing recognised also in the 14c record and in worldwide holocene glacier advance phases suggesting a solar modulation of climate we argue that the primary atmospheric response involved decadal centennial fluctuations in the meridional pressure gradient driving aegean sst events via changes in the strength duration and or frequency of northerly polar continental air outbreaks over the basin the observed natural variability should be accounted for in predictions of future climate change and our timeframe for the aegean climate events in addition provides an independent chronostratigraphic argument to middle eastern archaeological studies

impact of lateglacial cold events on the northern aegean region reconstructed from marine and terrestrial proxy data marine palynomorph data paired with other indicators of sea surface hydrography planktic foraminiferal assemblages and oxygen isotopes were used to decipher the impact of cold events on the northern aegean region during the last glacial to interglacial transition the data which were derived from marine sediment cores geotusl152 and geotusl148 point to a strong impact of the heinrich 1 and younger dryas cold events on surface water conditions in the northern aegean sea shifts in marine palynomorph assemblages correlate with changes in terrestrial vegetation and climate i e precipitation and temperature reconstruc tions based on pollen assemblages in the northern borderlands of the aegean sea the climate responses of the aegean region to heinrich event 1 h1 ca 17 5 to ca 15 7 cal ka bp and younger dryas ca 12 6 to ca 11 7 cal ka bp events appear similar in magnitude with mean annual temperatures between 6 and 108c and mean annual precipitation between 300 and 450 mm however the annual temperature decline during the h1 relative to the preceding already cold conditions was minor 38c the transition from the relatively warm and humid local equivalent of the allerod interstadial to the younger dryas on the other hand witnessed an annual temperature decline of 68c and an annual precipitation decrease of 300 mm the latter occurring abruptly within only ca 150 a the return to warmer conditions in the northern aegean region after the younger dryas was completed at ca 11 6 cal ka bp copyright 2011 john wiley sons ltd

a review of molecular organic proxies for examining modern and ancient lacustrine environments molecular organic geochemical proxies are increasingly being utilized to reconstruct past environmental conditions as new tools continue to be discovered and developed to date organic geochemical proxies have been developed mainly for use in marine systems and are widely used in paleoceanography in contrast organic proxies have been less commonly used on lacustrine sedimentary records one reason for this is that the wide range in the physical and chemical properties of lakes complicates application of some organic geochemical proxies in lacustrine settings furthermore in comparison to marine studies presently only a small number of studies have conducted or are currently conducting fundamental research aimed at developing organic geochemical proxies for use in lacustrine settings despite this an increasing number of paleo limnological studies are currently applying organic geochemical techniques to examine present and past environmental conditions in this manuscript we review the use of a number of commonly utilized organic geochemical and isotopic proxies and discuss their potential for environmental reconstruction in quaternary lacustrine deposits

paleoclimate variability in central taiwan during the past 30 kyrs reflected by pollen δ13ctoc and n alkane δd records in a peat sequence from toushe basin abstract a total of 233 samples from the upper 16 m of the toushe peat core retrieved in central taiwan were measured for toc and 13ctoc values from these samples 17 selected samples with large 13ctoc fluctuations were analyzed for n alkane and d of the c27 and c29 n alkanes combining with the detailed high resolution pollen and geochemical records this study reveals more detailed climatic variations in terms of temperature and precipitation as well as abrupt climatic events during the past 30 kyrs before the last glacial maximum lgm climate was cold and damp with predominantly woodland vegetation in toushe basin and turned to cold and dry after 25 kyr bp climatic conditions there were the worst during lgm over the past 30 kyrs especially around 23 and 18 kyr bp when the woodland was diminished and c4 grass was dominated although short durations of relatively wet conditions could be found at 17 16 and 14 kyr bp cold and dry climates were prevailing during 29 5 28 24 22 17 15 and 13 11 5 kyr bp corresponding to heinrich h events 3 2 1 and younger dryas yd respectively during the early holocene dry climate occurred at 11 10 9 7 9 2 and 8 kyr bp whereas wet condition appeared at 10 3 9 8 9 7 5 kyr bp in the middle holocene climate kept warm and moderate wet in the first half period but many dry events existed in the second half following a cold and dry event at 6 kyr bp after a sharply warm peak at 5 2 kyr bp the climate in toushe turned to cold quickly and tree shrub vegetation disappeared completely with the replacement of c3 grasses in the late holocene climate was relatively wetter with predominant c3 grasses in the basin our climatic interpretations based on the peat records agree well with the greenland ice core and chinese speleothem records on millennium time scales during the last glacial period dry climates corresponding to weakening of the east asian summer monsoon easm during the heinrich events and younger dryas in central taiwan and eastern china demonstrate the climatic forcing on such long time scales in concert with regional monsoon climate however the discrepancies exist between our peat record and the dongge hulu stalagmite record on 1 the age of h2 2 climate intensities of lgm and h1 and 3 wetness condition during holocene these observations call for further study on high resolution climatic changes especially on moisture budget in the east asian monsoonal region

density driven groundwater flow near salt domes active halite dissolution occurs around numerous salt domes in louisiana forming brines with as much as 300 g l 1 tds tds total dissolved solids most of which is na and cl we numerically modeled the possible dynamics of 1 brine density flow induced by solute concentration gradients and 2 thermal convection induced by temperature gradients around hypothetical salt domes calculated maximum flow velocities due to brine density flow range from 0 01 to 1 m yr 1 even in low permeability sediments much greater than velocities due to thermal convection immense quantities of halite can be dissolved by brine density flow up to 3 km3 myr 1 and formation of brine plumes can occur very rapidly in some cases requiring 1 myr maximum flow velocities increase with bulk permeability and decrease with increasing anisotropy geopressured waters bleeding upward into the hydropressured zone may affect brine formation in the hydropressured zone provided permeability of the geopressured zone is sufficiently high

behavior of dense aqueous phase leachate plumes in homogeneous porous media surface contaminant plumes emanating from waste disposal facilities are often denser than the ambient groundwater under certain conditions these dense plumes may become unstable contaminating larger regions of an aquifer the behavior of contaminant plumes with different densities was examined in three flow containers packed with homogeneous porous media simulating unconfined aquifers glass beads and a medium sand were used as the porous media a horizontal ambient groundwater stream was established in each flow container using deionized water the contaminant plumes consisted of nai or nabr solutions introduced into each flow container from a line source located on top of the porous medium and extending over the total width of the container optical tracers were added to the salt solutions to allow flow visualization results show that for a given porous medium dense plumes were either stable or unstable depending on the magnitude of the horizontal flow velocity the contaminant leakage rate and the density difference between the contaminant solution and the ambient groundwater when a dense plume becomes unstable lobe shaped gravitational instabilities develop which are unsteady and three dimensional our experimental results suggest that the behavior of dense contaminant plumes overlying a less dense groundwater stream in a homogeneous porous medium depends on the magnitude of certain nondimensional parameters it appears that gravitational instabilities begin to develop when the values of these nondimensional parameters exceed certain critical values

organic geochemical evidence of late glacial holocene climate instability in the north aegean sea sedimentary molecular biomarker compositions organic carbon and caco3 concentrations and bulk organic 13c and total 15n values document a series of paleoclimatic changes that have affected organic matter production and sedimentation in the north aegean sea from the termination of the latest glacial maximum through the middle holocene continental environmental conditions have been inferred from land plant biomarkers paleoproductivity patterns of diatoms prymnesiophytes dinoflagellates and nannoplankton were discerned from marine derived biomarkers although organic matter is predominantly marine variations in the proportion of marine and land contributions and in its general preservation are evident rapid changes in the eastern mediterranean thermohaline circulation evidently occurred in parallel to sea surface temperature oscillations enhanced deep water ventilation accompanied cold intervals in the late last glacial the younger dryas and during an interruption of deposition of the s1 sapropel probably in response to strengthening of north winds over the region in contrast decreased thermohaline circulation occurred during the warm interval associated with the s1 sapropel during this period increased freshwater inputs diminished ventilation of deep water masses and enhanced organic matter production and preservation intriguing fluctuations in sea surface temperatures and the concentrations of marine and terrestrial biomarkers within the sapropelic layer most prominently in the interruption from 8 2 to 7 8 calibrated radiocarbon conventional kyr bp support the hypothesis that several distinct events of deep water reoxygenation occurred in the north aegean sea during deposition of the s1 sapropel these events reflect centennial excursions to the more common low productivity and well ventilated conditions of the mediterranean that may possibly be related to north atlantic oscillation cycles

analysis of saltwater upconing beneath a pumping well abstract aquifer systems that contain freshwater and saltwater are usually stratified with the more dense saltwater underlying the freshwater a groundwater well discharging from the freshwater zone causes the saltwater to move upwards towards the well this phenomenon is known as saltwater upconing two methods of analysis the sharp interface method and the fluid density dependent solute transport method are used to simulate saltwater upconing numerical experiments including comparisons of the two methods indicate 1 for low to moderate pumpages the 50 isochlor and sharp interface correlate well 2 the well can discharge significant concentrations of saltwater even though a stable cone according to the sharp interface method exists below the well screen 3 an almost linear relationship exists between the well discharge rate and the concentration of the discharge at low pumping rates that maintain a stable cone and 4 upconing is sensitive to transverse dispersivity whereas it is insensitive to longitudinal dispersivity a simulation of upconing at test site no 4 truro cape cod massachusetts indicates that the appropriate field value of transverse dispersivity is very small this supports the validity of the sharp interface assumption for analyzing the behavior of systems with thin saltwater freshwater transition zones

holocene carbon cycle dynamics based on co2 trapped in ice at taylor dome antarctica a high resolution ice core record of atmospheric co2 concentration over the holocene epoch shows that the global carbon cycle has not been in steady state during the past 11 000 years analysis of the co2 concentration and carbon stable isotope records using a one dimensional carbon cycle model uggests that changes in terrestrial biomass and sea surface temperature were largely responsible for the observed millennial scale changes of atmospheric co2 concentrations

biomarker geochemistry of the miocene monterey formation west san joaquin basin california implications for petroleum generation abstract much of the miocene monterey formation of california is rich in biogenic sediment especially organic matter and silica because of the geologic structure the monterey in the subsurface near lost hills in the san joaquin basin forms a natural laboratory for the study of the diagenetic responses of these materials rocks of similar age and lithology are buried to depths ranging between 500 and 3500 m and are thus exposed to a temperature range of 45 130 c the diagenetic progression of silica from opal a to opal ct to microquartz is well documented in monterey burial history studies however diagenetic indicators need to be established below the depth of complete conversion of opal ct to quartz which may be very shallow 1500 m or less at lost hills conventional maturity indicators are problematic the scarcity of vitrinite in many monterey samples hampers reflectance measurements in addition values that are measured may be anomalously low maximum pyrolysis temperatures are depressed due in part to high heavy bitumen content biomarker geochemistry provides effective alternative maturity indicators of particular interest are the stereochemical variations observed in the assemblages of steranes and triterpanes extracted from oil well core samples for example the 20s 20r ratio of 5 h 14 h 17 h 24 ethylcholestane increases from 0 09 to 0 56 over the depth range cited samples from petroleum accumulation zones are distinguished by anomalously mature biomarker assemblages considering their depth of burial this indicates that these bitumens are as mature as the deepest non production zone sample 3430 m even though they are from much shallower depths 580 1572 m other maturity and or migration indicators confirm this such as the relative increases in amounts of 14 h 17 h steranes rearranged steranes and tricyclic terpanes thus it appears that any immature indigenous bitumen in production zone samples is overwhelmed by a mature component which presumably migrated updip from deeper warmer strata since much oil is produced from shallow organic rich fractured monterey shales early in situ generation has previously been hypothesized however while both source and reservoir rock are lithologically similar and lie within the same formation biomarker geochemistry indicates that substantial generation occurs only in deeply buried monterey shales

late glacial holocene climate variability at the south eastern margin of the aegean sea abstract new micropaleontological palynological and geochemical results from a relatively shallow 500 m sediment core ns 14 in the south eastern aegean sea provide a detailed picture of the regional expression of sapropel s1 formation in this sub basin of the eastern mediterranean sea specifically freshwater input during 10 6 10 0 ka bp has preceded the deposition of s1 further decrease in surface water salinity is evidenced between 10 0 and 8 5 ka bp at the lower part of s1a which in respect to s1b is featured by warmer 19 5 c and more productive surface waters associated with dysoxic bottom conditions a series of coolings detected within the s1 depositional interval may be linked to outbursts of cold northerly air masses and relevant pulses in the deep intermediate water ventilation that caused the s1 interruption between 7 9 and 7 3 ka bp and culminated during the deposition of s1b with the decline of deep chlorophyll maximum dcm at 6 5 ka bp the climate instability and the relevant absence of anoxia weakened the organic matter preservation in the shallow south eastern aegean margin during the s1 times ns 14 record provides evidence for a distinct mid holocene warm up to 25 c and wet phase associated with the deposition of the sapropel like layer smh sapropel mid holocene between 5 4 and 4 3 ka bp the smh layer could represent evidence of on going albeit weak african monsoon forcing only expressed at the south eastern edge of the aegean sea its end is associated with the 4 2 ka bp northern hemisphere mega drought event and the termination of the african humid period at 3 8 ka bp

centennial scale climate cooling with a sudden cold event around 8 200 years ago the extent of climate variability during the current interglacial period the holocene is still debated temperature records derived from central greenland ice cores show one significant temperature anomaly between 8 200 and 8 100 years ago which is often attributed to a meltwater outflow into the north atlantic ocean and a slowdown of north atlantic deep water formation this anomaly provides an opportunity to study such processes with relevance to present day freshening of the north atlantic anomalies in climate proxy records from locations around the globe are often correlated with this sharp event in greenland but the anomalies in many of these records span 400 to 600 years start from about 8 600 years ago and form part of a repeating pattern within the holocene more sudden climate changes around 8 200 years ago appear superimposed on this longer term cooling the compounded nature of the signals implies that far field climate anomalies around 8 200 years ago cannot be used in a straightforward manner to assess the impact of a slowdown of north atlantic deep water formation and the geographical extent of the rapid cooling event 8 200 years ago remains to be determined

the 8 2 kyr bp event simulated by a global atmosphere sea ice ocean model seven freshwater perturbation experiments were performed with a global atmosphere sea ice ocean model to study the mechanism behind the 8 2 kyr bp holocene cooling event these experiments differed in initial state and duration of the applied freshwater pulse while the amount of freshwater was kept constant 4 67x10 14 m 3 one of the scenarios with freshwater added to the labrador sea at a rate of 0 75 sv during 20 years resulted in weakening of the north atlantic thermohaline circulation during 320 years and surface cooling varying from 1 to 5 degreesc over adjacent continents this result is consistent with proxy data suggesting that a meltwater induced weakening of the thermohaline circulation caused the event moreover our results indicate that the time scale of the meltwater release and the initial state are important as both have a strong effect on the magnitude and duration of the produced model response

δd values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record abstract the compound specific hydrogen isotope composition d of sedimentary n alkanes is increasingly used as a palaeoclimate proxy to explore the origin of the hydrogen isotope signal of n alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n alkane composition and d values of 31 plant biomass samples birch betula beech fagus oak quercus alder alnus hornbeam carpinus and myrtle myrtus as well as non stomata containing sphagnum cladonia and moss from 14 sites along a climatic gradient from northern finland to southern italy eleven of the sites were previously investigated for the n alkane d values in adjacent lake sediments and are compared to the leaf wax n alkane d values the distribution of terrestrial n alkanes in lake sediments was not found to be characteristic of the dominant vegetation around the lake evidently n alkane distributions within the same species at different sites were found to be variable these findings complicate the use of certain n alkane distributions in sediments as a palaeoenvironmental indicator d values of plant biomass n alkanes show a significant positive correlation with the precipitation d values biomass n alkane d values are in general less negative than the associated sedimentary n alkanes of terrestrial origin possibly due to the stronger evapotranspiration during the summer when sampling took place this suggests that n alkanes in leaves show seasonal variations and the sedimentary organic matter receives the lighter isotope signal of the autumn when most leaves are incorporated into the sediment the variability of the d values from non stomata containing plants is much higher than for broadleaf trees since stomata can regulate water loss through evapotranspiration the average chain length acl of n alkanes from deciduous tree leaves increases from north to south with increasing acl the hydrogen isotopic fractionation e between source water and n alkanes also increases our results prove that terrestrial n alkane d values record the d value of precipitation modified by the amount of isotope enrichment in the leaf water due to plant anatomy stomata vs no stomata and site specific meteorological conditions such as evapotranspiration relative humidity and soil moisture therefore terrestrial n alkanes in lake sediments can deliver information on changes in these parameters over geological timescales in lake sediments where aquatic n alkanes such as n c 17 record the lake water d value the isotopic difference between terrestrial and aquatic n alkanes could therefore be used to reconstruct changes in evapotranspiration

modelling density dependent flow and solute transport at the lake tutchewop saline disposal complex victoria abstract intercepted saline groundwaters and drainage effluent from irrigation are commonly stored in both natural and artificial saline disposal basins throughout the murray darling basin of australia their continued use as wastewater evaporation sites requires an understanding of existing groundwater dynamics the useful of individual basins their sustainability and possible environmental impacts remain largely unknown in this work the movement of salt to the underlying groundwater system from lake tutchewop a saline disposal complex in north central victoria was modelled in cross section due to the salinity contrast between the hypersaline basin waters and the regional groundwater it was necessary to simulate density dependent flow behaviour under certain conditions these density stratified systems may become unstable leading to the onset of convective behaviour which greatly increases the movement of salt from the basin to the groundwater system modelled concentration profiles in the aquifer system and calculated seepage rates from the basin show that lake tutchewop is stable under its present operating regime the downward movement of salt is mainly controlled by diffusion and dispersion the calibrated model was used to assess the impact of several management scenarios using time dependent boundary conditions for lake salinity and water levels the influence of heterogeneous basin linings on ensuing salt flux rates is examined and results show that increased solute transport will occur under such conditions a sensitivity analysis performed on governing variables showed that salt fluxes were most sensitive to lake salinity levels a solute rayleigh number defined in terms of basin salinity and hydrogeologic parameters is seen to be an effective tool for predicting the long term behaviour of such saline disposal basins the models and concepts developed in this work may find application in the design and management of saline disposal complexes

effect of lake evaporation on δd values of lacustrine n alkanes a comparison of nam co tibetan plateau and holzmaar germany compound specific hydrogen isotope ratio values of lacustrine n alkanes from two contrasting ecosystems the semiarid to arid nam co central tibet and the humid holzmaar germany were compared in order to assess whether or not these environmental conditions are recorded in the isotopic signatures of biomarkers increased evaporation of lake water at nam co is recorded by the n alkanes of aquatic origin hence isotopic enrichment results in a di erence between terrestrial and aquatic n alkanes in the opposite direction 68 from that known for humid climate conditions 30 predominating at holzmaar based on this isotopic di erence between terrestrial and aquatic n alkanes evaporation to inflow ratio e i values were estimated and suggest that the isotopic di erence is indicative of the general hydroclimatic characteristics of a lake system moreover the comparison with e i values calculated with actual stable water isotope data showed that the dd values of aquatic and terrestrial lacustrine n alkanes serve as a proxy for the relative isotopic di erences between lake and inflow waters and can be used to assess the proportion of water undergoing evaporation relative to the inflow and thus to reconstruct the lake water balance in the past 2008 published by elsevier ltd

carbon cycle perturbation and stabilization in the wake of the triassic jurassic boundary mass extinction event 1 the triassic jurassic boundary mass extinction event t j 199 6 ma is associated with major perturbations in the carbon cycle recorded in stable carbon isotopes two rapid negative isotope excursions in bulk organic carbon 13corg occur within the immediate boundary interval at multiple locations and have been linked to the outgassing of 12c enriched co2 from the central atlantic magmatic province in british columbia a positive 13corg excursion of 5 vienna peedee belemnite v pdb spans part or all of the subsequent hettangian stage here we examine the significance of these carbon isotope excursions as records of global carbon cycle dynamics across the t j boundary and test the link between carbon cycle perturbation stabilization and biotic extinction recovery patterns a combination of 13corg and palynological analyses from the late triassic to early jurassic in the mingolsheim core germany suggests that organic carbon isotope variations are best explained as the result of both compositional changes in terrestrial versus marine input and disturbance and recovery patterns of major terrestrial plant groups across the t j boundary a new high resolution 13ccarb record from the val adrara section in the southern alps italy spanning from the uppermost rhaetian through lower sinemurian does not exhibit a negative excursion at the t j boundary but does record a large positive 13ccarb excursion of 4 v pdb in bulk carbonate that begins at the t j boundary and reaches a local maximum at the early late hettangian boundary values then gradually decrease reaching 0 5 at the hettangian sinemurian boundary and remain relatively constant into the early sinemurian complementary 13ccarb data from 4 more sections that span the hettangian sinemurian boundary support carbon cycle stabilization within the upper hettangian our analyses suggest that isotope changes in organic carbon reservoirs do not necessarily require a shift in the global exogenic carbon reservoir and that the positive excursion in the carbonate carbon isotope record is best explained as the combined result of an increase in atmospheric pco2 leading to accelerated carbon cycling decreased skeletal carbonate production and increased organic carbon burial lasting several hundred thousand years the termination of the positive inorganic carbon isotope excursion coincides with the recovery of marine skeletal carbonate producers and coeval changes in terrestrial vegetation and reflects the gradual reduction in pco2 and the stabilization of the global carbon cycle during the sinemurian

holocene seasonality changes in the central mediterranean region reconstructed from the pollen sequences of lake accesa italy and tenaghi philippon greece this study presents pollen based climate reconstructions of holocene temperature and precipitation seasonality for two high resolution pollen sequences from the central lake accesa central italy and eastern mediterranean tenaghi philippon greece regions the quantitative climate reconstruction uses multiple methods to provide an improved assessment of the uncertainties involved in palaeoclimate reconstructions the multimethod approach comprises partial least squares regression weighted average partial least squares regression the modern analogues technique and the non metric multidimensional scaling generalized additive model method we find two distinct climate intervals during the holocene the first is a moist period from 9500 to 7800 cal bp characterised by wet winters and dry summers resulting in a strongly seasonal hydrological contrast stronger than today that is interrupted by a short lived event around 8200 cal bp this event is characterised by wet winters and summers at accesa wh

molecular proxies for paleoclimatology we summarize the applications of molecular proxies in paleoclimatology marine molecular records especially are proving to be of value but certain environmentally persistent compounds can also be measured in lake sediments loess deposits and ice cores the fundamentals of this approach are the molecular parameters the compound abundances and carbon hydrogen nitrogen and oxygen isotopic contents which can be derived by the analysis of sediment extracts these afford proxy measures which can be interpreted in terms of the conditions which control climate and also reflect its operation we discuss two types of proxy those of terrigenous and those of aquatic origin and exemplify their application in the study of marine sediments through the medium of ten case studies based in the atlantic mediterranean and pacific oceans and in antarctica the studies are mainly for periods in the present the holocene and particularly the last glacial interglacial but they also include one study from the cretaceous the terrigenous proxies which are measures of continental vegetation are based on higher plant leaf wax compounds i e long chain circa c30 hydrocarbons alcohols and acids they register the relative contributions of c3 vs c4 type plants to the vegetation in the source areas the two marine proxies are measures of sea surface temperatures sst the longer established one u37k is based on the relative abundances of c37 alkenones photosynthesized by unicellular algae members of the haptophyta the newest proxy tex86 is based on c86 glycerol tetraethers gdgts synthesized in the water column by some of the archaeal microbiota the crenarchaeota

molecular and isotopic stratigraphy in an ombrotrophic mire for paleoclimate reconstruction a 40 cm deep sphagnum dominated peat monolith from bolton fell moss in northern england was systematically investigated by lipid molecular stratigraphy and compound specific 13c and d analysis using gas chromatography gc gc mass spectrometry gc ms gc combustion isotope ratio ms gc c irms and gc thermal conversion irms gc tc irms techniques 210pb dating showed the monolith accumulated during the last ca 220 yr a period encompassing the second part of little ice age while the distributions of lipids including n alkan 1 ols n alkan 2 ones wax esters sterols n alkanoic acids alkandioic acids and hydroxy acids display relatively minor changes with depth the cooler climate event was recorded in the concentrations of n alkanes and organic carbon cpi values of n alkanes and n alkanoic acids and the ratio of 5 n alkylresorcinols sterols superimposed on the fossil fuel effect the relatively cooler climate event was also recorded by 13c values of individual hydrocarbons especially the c23n alkane a major compound in certain sphagnum spp the d values of the c29 and c33n alkanes correlated mainly with plant composition and were relatively insensitive to climatic change in contrast the c23n alkane displayed variation that correlated strongly with recorded temperature for the period represented by the monolith agreeing with previously reported deuterium records in tree ring cellulose spanning the same period in scotland germany and the usa with more negative values occurring during the second part of little ice age these biomarker characteristics including the compound specific 13c and d records provide a new set of proxies of climatic change potentially independent of preserved macrofossils which will be of value in deeper sections of the bog where the documentary records of climate are unavailable and humification is well advanced

postglacial climate change record in biomarker lipid compositions of the hani peat sequence northeastern china abstract the peat sequence at hani in northeastern china accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system the molecular compositions of n alkanes n alkanols and n alkanoic acids extracted from the hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat forming vegetation long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n alkane distributions throughout the hani peat sequence the paleoclimate integrity of these biomarker molecules appears to be well preserved most of the n alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants in contrast n alkanoic acid distributions are dominated by secondary components that record the importance of post depositional microbial activity in this peat sequence which evidently can be extensive in a percolation mire elevated n alkane paq values and c23 c29 ratios which are both molecular proxies for water loving plants record an especially moist local climate in the bolling allerod 14 5 to 12 9 ka younger dryas 12 9 to 11 5 ka and pre boreal 11 5 to 10 5 ka portions of the hani peat sequence depressed paq values and c23 c29 ratios and larger n alkane average chain length values indicate that the holocene climatic optimum 10 5 to 6 ka was a period of warmer climate with lower effective precipitation which contrasts with evidence of wetter climates in most of east asia

characterising flow regime and interrelation between surface water and ground water in the fuente de piedra salt lake basin by means of stable isotopes hydrogeochemical and hydraulic data summary this research reports the characterisation of ground and surface water interaction in the fuente de piedra salt lake basin in southern spain by a combined approach using hydraulic hydrogeochemical and stable isotope data during three sampling campaigns february 2004 2005 and october 2005 ground and surface water samples were collected for stable isotope studies 18 o d and for major and minor ion analysis hydraulic measurements at multilevel piezometers were carried out at four different locations around the lake edge conductivity logs were performed at four piezometers located along a profile at the northern lake border and at two deeper piezometers in the miocene basin at a greater distance from the lake to describe processes that control the brine evolution different hydrogeochemical simulations were performed hydrogeochemical data show a variety of brines related to thickness variations of lacustrine evaporites around the lake salinity profiles in combination with stable isotope and hydraulic data indicate the existence of convection cells and recycled brines furthermore restricted ground water inflow into the lake was detected dedolomitisation processes were identified by hydrogeochemical simulations and different brine origins were reproduced by inverse modelling approaches