a gradual drowning of the southwestern black sea shelf evidence for a progressive rather than abrupt holocene reconnection with the eastern mediterranean sea through the marmara sea gateway core m02 45 recovered 9 5 m of a 12 m thick transgressive succession on the sw black sea shelf the underlying transgressive unconformity a deepens toward the shelf edge so that the coresite was never isolated from the open black sea fourteen radiocarbon dates indicate sedimentation from 9 3 ka to the present with only one hiatus at 270 cm depth spanning 4 5 2 5 ka three units are present in the core unit a 0 270 cm burrowed mud with laminated silt beds and mollusc shells of mediterranean affinity accumulation rate 125 cm ky unit b 270 525 cm silty mud with shelly interbeds containing truncatella subcylindrica mytilus galloprovincialis parvicardium exiguum rissoa spp and modiolula phaseolina rate 85 cm ky unit c 525 950 cm burrowed silty mud with graded beds of silt and fine sand and shells of t subcylindrica p exiguum and dreissena polymorpha rate 360 cm ky unit c developed below storm wave base at a time when proponents of a catastrophic flood in the black sea claim that the shelf was subaerially exposed clearly it was not ostracoda of caspian affinity indicate 5 salinity until 7 5 ka dinocysts and foraminifera confirm a low but rising salinity after 8 6 ka an increase of d 34 s from 5 30 through 8 4 7 6 ka is attributed to a first pulse of sulfate rich aegean water into an already high black sea after which this sulfate was quantitatively precipitated as sulfide d 34 s then dropped at 8k a to 20 as dysoxia and water column stratification were established because of the initiation of two way flow through the bosphorus earlier water exchange with the mediterranean was likely impeded by strong black sea outflow which prevented easy access of the aegean water mass r 2006 published by elsevier ltd

a revised calendar age for the last reconnection of the black sea to the global ocean abstract during the last decade a debate arose regarding the timing and pattern of the last reconnection of the black sea lake with the global ocean on a geochemical basis the radiocarbon age of black sea lake surface water during the time of reconnection was determined to be 8400 14c a bp despite the potential bias induced by the hard water effect in lakes the reconnection age was calibrated without any reservoir age correction which led to an estimate of 9400 cal a bp since knowledge for the actual calendar age has important hydrologic implications that would provide new insights regarding the mechanism of reconnection determining the actual calendar age for the last reconnection remains important based upon modeling experiments and micropaleontological reconstructions the black sea lake reconnection occurred in two steps as follows 1 initial marine inflow imi followed by 2 a period of increasing basin salinity that led to the disappearance of lacustrine species dls in order to better define the actual calendar age for the last reconnection a review of the sedimentary expressions of the imi and dls boundaries was performed in order to correlate them throughout the black sea sedimentary environments this correlation reconciles the apparent inconsistency in the published radiocarbon dataset and provides the atmospheric radiocarbon age of the last reconnection which represents the reference for reservoir age calculations and which can be directly calibrated we determine reservoir ages for the water column as well as the reconnection calendar age to be 9000 cal a bp at the reconnection with the global ocean black sea lake reservoir ages were non negligible and water depth dependent consistent with a weak water column stratification during the early holocene the calibrated age of initial marine inflow 9000 cal a bp implies that the former bosphorus sill was shallower by 10 m than is commonly assumed in the literature compared to the sedimentary context of the sakarya coastal plain this result suggests that the level of the isolated black sea was below the former bosphorus sill depth at the time of the last reconnection furthermore a lag of 900 yr between initial marine inflow and the disappearance of lacustrine species indicates that approximately ten centuries were needed to establish the currently observed two way flow exchange with the global ocean

numerical simulation of katabatic flow with changing slope angle a large eddy simulation les model and the advanced regional prediction system arps model which does not resolve turbulent eddies are used to study the effect of a slope angle decrease on the structure of katabatic slope flows for a simple uniform angle slope simulations from both models produce turbulence kinetic energy and momentum budgets that are in good overall agreement simulations of a compound angle slope are compared to a uniform angle slope to demonstrate how a changing slope angle can strongly affect the strength of katabatic flows both arps and the les model show that slopes with a steep upper slope followed by a shallower lower slope concave shape generate a rapid acceleration on the upper slope followed by a transition to a slower evolving structure characterized by an elevated jet over the lower slope in contrast the case with uniform slope having the same total height change yields a more uniform flow profile with stronger winds at the slope bottom higher average slope in the uniform slope angle case generates greater gravitational potential energy which is converted to kinetic energy at the bottom of the slope analysis of the total energy budget of slope flows indicates a consistent structure where potential energy generated at the top of the slope is transported downslope and converted into kinetic energy near the slope base

molecular diversity and spatial distribution of benthic foraminifera of the seamounts and adjacent abyssal plains in the tropical western pacific ocean abstract deep sea systems are among the least understood ecosystems on earth forming large proportions of deep sea benthic communities benthic foraminifera play important roles however their molecular diversity and distribution patterns in the deep sea seamounts and abyssal plains of the tropical western pacific ocean are poorly known in this study using next generation sequencing we investigated the molecular diversities and community compositions of benthic foraminifera of the tropical western pacific ocean seamounts and adjacent abyssal plains with water depth ranging between 263 and 5900 m a region of the small subunit ssu rrna gene about 300 bp was amplified with the foraminiferal specific primers s14f3 s17 and the pr2 database was selected as the reference database for sequence assignment monothalamiids were assigned most of the 1399 operational taxonomic units otus obtained the foraminifera genetic novelty with an average similarity of 91 33 to reference sequences in the deep sea was extremely high comparing the different habitats the foraminiferal diversities of the seamounts investigated were both higher than those of their adjacent abyssal plains clustering of results showed the foraminifera community composition of the y3 seamount to be most like that of its adjacent abyssal plain our study indicates that the foraminiferal diversity distribution patterns and community structures between the two seamounts differ yet they resemble those of their adjacent abyssal plain areas we infer the possibilities that seamounts are diversity hotspots possessing particularly high benthic species richness and that foraminifera spread from them to the adjacent abyssal plains the results also revealed variations in foraminifera at different water depths and temperatures in seamounts and adjacent abyssal plains additionally an extremely high genetic novelty of foraminifera was observed in these habitats which points to a hotspot for the discovery of new foraminifera species in deep sea systems

lateglacial and holocene sea level changes in semi enclosed seas of north eurasia examples from the contrasting black and white seas abstract a comparison of the black and white seas which differ in their tectonic glacial and climatic history but which share a strong dependence upon limited water exchange with the world ocean represents an opportunity for the identification of major factors controlling sea level changes during the lateglacial and holocene and for the correlation of these changes existing data were critically analyzed and compared with the results of geological geomorphological and palaeohydrological studies obtained by the present authors during the past two decades we conclude that glacioeustatic processes played a major role in relative sea level changes on most coasts of both areas however along several coastlines other factors overwhelm glacioeustasy during some time intervals in the black sea water level rose from its minimum position 100 120 m at 18 17 ka bp to 20 30 m at nearly 9 ka bp in the white sea the decreasing trend in relative sea level is well illustrated on the kola peninsula and in karelia subject to glacioisostatic emergence a drastic sea level fall from 15 to 25 m occurred with the drainage of glacial lakes in the eastern white sea 12 5 9 5 ka bp the black and white sea histories changed drastically in the early holocene or in the beginning of the middle holocene 9 5 7 5 ka bp due to the intrusion of water from the mediterranean and the barents seas respectively during this period the white sea developed under the strong influence of the formation of ice shelves and dead ice blocks retreating glaciers as well as of glacioisostatic and related processes the black sea history however was determined by water exchange with the mediterranean via the shallow dardanelles and bosporus straits outflow from the black sea 10 9 5 ka bp and inflow from 9 7 5 ka bp according to various data and partially by river discharge variations caused by climatic changes on the russian plain the hypothesis of a catastrophic sea level rise from 120 150 to 15 20 m nearly 7550 calendar years bp is not supported by our data water intrusion from the mediterranean was fast but not catastrophic in the black sea periods of high sea levels after the intrusion of mediterranean waters are dated from four sedimentary complexes vityazevian kalamitian dzhemetian and nymphaean from nearly 7 5 7 6 5 5 4 5 and 2 2 1 7 ka bp respectively a fluctuating pattern of sea level change was established in the white sea after the drainage of proglacial lakes and intrusion of ocean waters at the end of the early holocene nearly 8 5 8 2 ka bp major periods of sea level rise in the white sea are dated from the late boreal early atlantic 8 5 7 5 ka bp late atlantic 6 5 5 2 ka bp middle subboreal 4 5 4 ka bp and middle subatlantic 1 8 1 5 ka bp fluctuations of relative sea level during the middle and late holocene were possibly on the order of several meters from 2 3 to 2 3 m in the black sea and from 3 5 to 2 3 m in the white sea lower estimates of regressive stages are principally derived from archaeological data on ancient settlements in tectonically submerging deltaic areas and cannot be regarded as reliable palaeohydrological analysis does not indicate that intensive 15 25 m or greater sea level fluctuations were present in the black sea or in the white sea during the middle and late holocene instead such analysis provides independent evidence to support the argument that significant differences in water level between the black sea and the mediterranean could not be maintained for an extended period of time

ancient dna derived from alkenone biosynthesizing haptophytes and other algae in holocene sediments from the black sea 1 holocene sea surface temperatures sst of the black sea have been reconstructed using sedimentary c37 unsaturated alkenones assumed to be derived from the coccolithophorid haptophyte emiliania huxleyi whose fossil coccoliths are an important constituent of the unit i sediments however alkenones can also be biosynthesized by haptophyte species that do not produce microscopic recognizable coccoliths a species specific identification of haptophytes is important in such u37k based past sst reconstructions since different species have different alkenone sst calibrations we showed that 18s rdna of e huxleyi made up only a very small percentage less than 0 8 of the total eukaryotic 18s rdna within the up to 3600 year old fossil record obtained from the depocenter 2000 m of the black sea the predominant fossil 18s rdna was derived from dinoflagellates gymnodinium spp which are predominant members of the summer phytoplankton bloom in the modern black sea using a polymerase chain reaction denaturing gradient gel electrophoresis method selective for haptophytes we recovered substantial numbers of a preserved 458 base pair bp long 18s rdna fragment of e huxleyi from the holocene black sea sediments additional fossil haptophyte sequences were not detected indicating that the e huxleyi alkenone sst calibration can be applied for at least the last 3600 years the ancient e huxleyi dna was well protected against degradation since the dna alkenone ratio did not significantly decrease throughout the whole sediment core and 20 of 2700 year old fossil e huxleyi dna was still up to 23 000 base pairs long we showed that fossil dna offers great potential to study the holocene paleoecology and paleoenvironment of anoxic deep sea settings in unprecedented detail

dna and lipid molecular stratigraphic records of haptophyte succession in the black sea during the holocene abstract previous studies suggest that the coccolithophorid haptophyte emiliania huxleyi entered the black sea 3400 yrs ago and since then a coccolith ooze defined as unit i has developed unit i sediments contain long chain alkenones derived from e huxleyi whereas the alkenone distribution of the deeper coccolith free sapropel unit ii is rather unusual alkenone derived past sea surface temperature sst estimates suggest a large difference between unit ii and unit i which is likely a result of unusual biological precursors of the alkenones in unit ii here we report a high resolution stratigraphic analysis of ancient haptophyte dna to establish the holocene succession of haptophytes as sources of the alkenones in the black sea haptophytes related to brackish isochrysis spp were the initial sources of alkenones and appeared immediately after the onset of sapropel deposition 7550 yrs before present a bp as salinity increased isochrysis related haptophytes were slowly replaced by a complex suite of e huxleyi strains as sources of alkenones our paleogenetic data showed that e huxleyi colonized the black sea shortly after the onset of sapropel deposition 4000 yrs earlier than previously recognized based on their preserved coccoliths e huxleyi strains were the most likely source of the previously reported abundant and unusual c36 di unsaturated black sea alkenone strong haptophyte species and strain specific effects were observed on the level of unsaturation of alkenones which resulted in spurious alkenone derived sst estimates before 5250 a bp in contrast from 5250 a bp onwards a relatively stable haptophyte assemblage dominated by a different suite of e huxleyi strains yielded robust alkenone sst values and indicated a gradual cooling from 19 c to 15 c at the top of the record 450 a bp

sedimentological and stable isotope evolution of lakes in the vestfold hills antarctica the sedimentological chemical and isotopic characteristics of sediment cores from three slightly saline to hypersaline lakes highway ace and organic lakes and two marine inlets ellis fjord and taynaya bay in the vestfold hills antarctica have been examined sections of the cores deposited in marine environments are characterized by uniform regularly laminated fine grained organic rich sediments with uniform organic 13c values 18 0 to 19 4 vs pdb and sulfur contents in contrast sediments deposited in lacustrine environments are extremely heterogeneous varying from finely laminated mat like sequences to poorly sorted clastic rich sediments authigenic monohydrocalcite and aragonite occur in some lake sediments the 13c values of organic matter in the lacustrine sediments exhibit an extremely wide range 10 5 to 25 3 that can be related to variations in physico chemical conditions in the lake waters strongly negative organic 13c values coupled with high sulfur contents are indicative of an anoxic zone in the overlying lake waters whereas less negative organic 13c values coupled with low sulfur contents are indicative of well mixed oxic conditions particularly high organic 13c values result during high levels of microbial activity in the lakes due to high rates of photosynthetic co2 fixation the large shifts in organic 13c are not necessarily accompanied by any change in macroscopic sedimentological characteristics illustrating the utility of isotopic investigations in these environments the 13c composition of authigenic carbonate in hypersaline organic lake sediments provides a record of changes in palaeoproductivity while the 18o of the carbonate provides information on rates of meltwater input and evaporation in the lake 14c dating suggests that highway lake was isolated from the sea by isostatic uplift at least 4600 yr before present b p whereas organic lake was isolated at approximately 2700 yr b p apparent emergence rates calculated from the 14c ages range from 1 0 to 2 1 mm yr 1 the reservoir effect in the lacustrine and marine environments is variable but probably does not exceed 1000 yr in any of the lakes examined

the interaction of katabatic flow and mountain waves part ii case study analysis and conceptual model via numerical analysis of detailed simulations of an early september 1993 case night the authors develop a conceptual model of the interaction of katabatic flow in the nocturnal boundary layer with mountain waves mki a companion paper part i describes the synoptic and mesoscale observations of the case night from the atmospheric studies in complex terrain ascot experiment and idealized numerical simulations that manifest components of the conceptual model of mki presented herein the reader is also referred to part i for detailed scientific background and motivation the interaction of these phenomena is complicated and nonlinear since the amplitude wavelength and vertical structure of the mountain wave system developed by flow over the barrier owes some portion of its morphology to the evolving atmospheric stability in which the drainage flows develop simultaneously katabatic flows are impacted by the topographically induced gravity wave evolution which may include significantly changing wavelength amplitude flow magnitude and wave breaking behavior in addition to effects caused by turbulence including scouring perturbations to the leeside gravity wave structure at altitudes physically distant from the surface based katabatic flow layer can be reflected in the katabatic flow by transmission through the atmospheric column the simulations show that the evolution of atmospheric structure aloft can create local variability in the surface pressure gradient force governing katabatic flow variability is found to occur on two scales on the meso due to evolution of the mountain wave system on the order of one hour and on the microscale due to rapid wave evolution short wavelength and wave breaking induced fluctuations it is proposed that the mki mechanism explains a portion of the variability in observational records of katabatic flow

the co evolution of black sea level and composition through the last deglaciation and its paleoclimatic significance abstract the black sea was an inland lake during the last ice age and its sediments are an excellent potential source of information on eurasian climate change showing linkages between regionally and globally recognized millennial scale climate events of the last deglaciation here we detail changes from the last glacial maximum lgm through the transition to an anoxic marginal sea using isotopic strontium and oxygen and trace element sr ca ratios in carbonate shells which record changing input sources and hydrologic conditions in the basin and surrounding region sr isotope records show two prominent peaks between 18 and 16 ka bp cal reflecting anomalous sedimentation associated with meltwater from disintegrating eurasian ice sheets that brought black sea level to its spill point following a sharp drop in sr isotope ratios back toward glacial values two stages of inorganic calcite precipitation accompanied increasing oxygen isotope ratios and steady sr isotope ratios these calcite peaks are separated by an interval in which the geochemical proxies trend back toward glacial values the observed changes reflect negative water balance and lake level decline during relatively warm periods bolling allerod and preboreal and increasing river input less evaporation resulting in higher lake levels during the intervening cold period the younger dryas a final shift to marine values in sr and oxygen isotope ratios at 9 4 ka bp cal corresponds to connection with the global ocean and marks the onset of sedimentation on the black sea continental shelf this date for the marine incursion is earlier than previously suggested based on the appearance of euryhaline fauna and the onset of sapropel formation in the deep basin

the holocene black sea reconnection to the mediterranean sea new insights from the northeastern caucasian shelf abstract recent findings about the evolution of palaeogeographic conditions of the black sea during the holocene have significantly improved our understanding of the profound environmental changes that took place around 9 ka ago when the neoeuxinian lake reconnected to the global ocean in contrast to the western and southeastern regions where numerous studies have been recently performed the northeast region remains relatively under investigated we carried out the first multi proxy continuous study of a sediment core ak 2575 from the northeastern black sea shelf that includes benthic calcareous fossils ostracods molluscs and foraminifers dinoflagellate cysts dinocysts and sedimentology thus providing reconstructions of surface and bottom water conditions the age model of the core is based on 10 ams 14 c dates calibrated ages are used throughout the manuscript the first appearance of mediterranean elements is documented at 9 6 cal ka bp our data provide evidence of sustained cohabitation of benthic species of caspian and mediterranean origins represented by different ontogenetic stages from at least 7 8 or even 8 8 to 6 7 cal ka bp with the gradual disappearance of brackish species suggesting a gradual increase in salinity and most likely a change in the salt composition dinocyst assemblages show species succession that is coherent across the black sea basin with brackish taxa dominating until 8 5 cal ka bp and being slowly replaced by euryhaline species the occurrences of authigenic gypsum crystals especially abundant at 7 4 and 6 5 cal ka bp suggest the temporal appearance of hydrogen sulphide at the shelf edge which during certain periods appears to reduce the abundance of benthic fauna

flow regimes over a basin induced by upstream katabatic flows an idealized modeling study abstractidealized two dimensional model simulations are performed to study the frequent nocturnal occurrence of downslope windstorm type flows in arizona s meteor crater the model topography is a simplified representation of the meteor crater and its surroundings with an approximately 1 mesoscale slope upstream and downstream of the crater basin a strong surface based inversion and a katabatic flow develop above the mesoscale slope as a result of radiational cooling the temperature and flow profiles are evaluated against observations over low angle slopes from two field campaigns showing that the model s turbulence parameterization has a strong impact on the near surface conditions the interaction of the katabatic flow with the basin topography leads to the formation of waves and hydraulic jumps over the basin the simplified two dimensional simulations show good qualitative agreement with observations of downslope windstorm type flows from the meteor crater the sensitivity of the flow solution ov

geochemical evidence for a large methane release during the last deglaciation from marmara sea sediments abstract recent methane inventories have revealed the potential impact of gas hydrates on the global carbon cycle and hence in climate change milkov 2004 however only a few studies have traced methane release in the geologic record here we show geochemical evidence for a large scale methane release at mid latitudes during the last deglaciation the sea of marmara an enclosed sea between the mediterranean and black seas is located in a tectonically active basin with gas hydrate expulsion and the formation of shallow gas hydrates since depths in the basin are shallower than 1100 m future global temperatures are expected to have a great influence in destabilizing methane clathrates among the suite of biomarkers we have focused on diplopterol and diploptene profiles in core md012430 retrieved from the central basin in the marmara sea our results indicate that during the last 15 000 years hopanoids showed important concentration variations with a pronounced peak during the deglaciation the lack of a relationship between diplopterol diploptene and phytoplanktonic biomarker concentrations as well as a depleted isotopic composition have linked the hopanoid maxima to methanotrophic activity suggesting that an intense methane release occurred at the onset of deglaciation in the marmara sea the vulnerability of the hydrate stability zone to changes in temperature and pressure under this range of shallow water depths as well as the relative timing of the hopanoid maxima and sea surface temperature rise points to thermal destabilization of hydrates as a trigger for methane release in the water column

quantitative estimation of holocene surface salinity variation in the black sea using dinoflagellate cyst process length reconstruction of salinity in the holocene black sea has been an ongoing debate over the past four decades here we calibrate summer surface water salinity in the black sea sea of azov and caspian sea with the process length of the dinoflagellate cyst lingulodinium machaerophorum we then apply this calibration to make a regional reconstruction of paleosalinity in the black sea calculated by averaging out process length variation observedatfourcore sites fromtheblack seawithhigh sedimentation rates anddatedbymultiple mollusk shell ages results show averygradual change of salinity from w14 0 91 psu around 9 9 cal ka bp to a minimum w12 3 0 91 psu around 8 5 cal ka bp reaching current salinities ofw17 1 0 91 psu around

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

first high resolution marinopalynological stratigraphy of late quaternary sediments from the central part of the bulgarian black sea area abstract spores pollen and dinoflagellate cysts of late pleistocene and holocene sediments were analyzed from giant gravity core 18 from the black sea continental slope recovered from a water depth of 971 m the investigated length of the core is 203 5 cm it includes 3 lithological units light grey clay sapropels and coccolith bearing ooze the core was sampled at 5 10 cm intervals sampling of the interval 141 5 126 cm was carried out at every cm ams radiocarbon dating of bulk organic carbon was performed on 18 selected sediment layers this chronological data allowed the first high resolution pollen stratigraphy of late quaternary sediments from the western black sea area to be presented the percentage spore pollen diagram is divided into 6 local pollen assemblage zones the trends in the vegetation dynamics and climate changes and the early history of migration of the majority of the arboreal taxa that nowadays occur in the eastern balkan range were traced out the palynological record suggests that open oak forests were spread in the eastern balkan range at the beginning of the holocene and shows early migration of the major temperate arboreal species such as quercus ulmus tilia and carpinus betulus this vegetation palaeosuccession continues with the spreading of mixed oak forests from 8950 until 2620 cal bp 8650 40 until 3120 35 14c bp followed by destructive changes due to human impact and climate deterioration a cooling of holocene climate that is well known in the north atlantic region as the 8200 yrs cold event is identified for the first time in marine records from the bulgarian black sea area the assemblages of dinoflagellate cysts and acritarchs were investigated to provide a reconstruction of surface seawater salinity and surface seawater temperature changes two main dinoflagellate cyst assemblages one dominated by fresh to brackish water species such as spiniferites cruciformis and pyxidinopsis psilata and a subsequent one that is characterized by euryhaline marine mediterranean species such as lingulodinium machaerophorum spiniferites belerius spiniferites bentorii operculodinium centrocarpum and acritarchs cymatiosphaera globulosa testified a change in sss from low salinity

organic carbon accumulation in the holocene sapropel of the black sea the modern laminated coccolith marl unit 1 of the black sea containing 2 6 wt organic carbon overlies a finely laminated sapropel unit 2 containing 5 20 wt organic carbon however the accumulation rate of organic carbon in the sapropel is not significantly different from that in unit 1 in contrast the accumulation rates of either caco 3 or lithogenous matter clay are significantly lower in the sapropel compared with unit 1 thus the sapropel has very high organic carbon contents because of lesser dilution of the organic fraction by the other bulk components because the accumulation rate of organic carbon in the sapropel is similar to that in unit 1 which is not significantly different from accumulation rates in oxygenated environments in similar settings the black sea sapropel is not necessarily characteristic of anoxic basins

effects of inversion height and surface heat flux on downslope windstorms abstractsimulations are presented focusing on the role of temperature inversions in controlling the formation and strength of downslope wind storms three mechanisms are examined depending on the relative height of the inversion with respect to the mountain and the stability of vertically propagating mountain waves for low level inversions flows are generated that closely resemble a reduced gravity shallow water hydraulic response with a large vertical displacement of the inversion on the lee side of the mountain for higher level inversion cases simulated flows more closely followed a stratified hydraulic behavior with the inversion acting as a rigid reflective lid in the third mechanism downslope winds were forced by a self induced critical layer located below the inversion height the presence of the inversion in this case had little effect on the resulting downslope winds observations made on the falkland islands show that downslope windstorms may preferentially occur in early morning even withou

a salinity related occurrence of a novel alkenone and alkenoate in late pleistocene sediments from the japan sea abstract the novel alkenoate ethyl tetratriacontadienoate c34 2ee has been found in late quaternary sediments of the japan sea by using gas chromatography mass spectrometry gc ms it accompanied hexatriacontadien 3 one c36 2ek previously found in black sea sediments a linear relationship between c36 2ek and c34 2ee concentrations points to both compounds being derived from the same source most likely a specific haptophyte the relative abundance of c34 2ee in total alkenones and alkenoates was significantly higher during the last glacial maximum when the 18o in planktonic foraminifera was anomalously light strongly suggesting that c34 2ee is associated with low salinity environments as samples with abundant c34 2ee also possessed anomalously high u 37 k values low salinity may have an ecological or physiological influence on both the unsaturation and carbon chain length of alkenones and alkenoates

late glacial to holocene climate and sedimentation history in the nw black sea abstract gravity cores from the continental slope in the northwestern black sea were studied using high resolution stable isotope grain size and xrf scanning data the measurements provide a 30 000 years ams 14c dated record of variations in the hydrological regime of the black sea and give insight into changing paleoenvironments in the surrounding areas stable climatic conditions during the last glacial maximum were followed by a series of meltwater pulses most likely originating from the scandinavian ice sheet between 18 000 and 15 500 yr bp 1 this meltwater input rose the level of the caspian sea to a point that caspian water could spill into the black sea via the manych depression north of the caucasian mountains high frequency oscillations in the xrf data during this period suggest a probable link to the arctic climate regime later during the bolling allerod and the early holocene prevailing high temperatures led to authigenic calcite precipitation through increased phytoplankton activity interrupted by the younger dryas and the 8200 yr bp cold event with dominant clastic sedimentation

late glacial to holocene paleoenvironmental evolution of the black sea reconstructed with stable oxygen isotope records obtained on ostracod shells high resolution stable oxygen isotope d 18 o on ostracod shells xrf scanning and bulk grain size data obtained on a transect of 6 gravity cores from the continental slope in the northwestern black sea give new insight into the hydrological evolution of the black sea since the last glacial maximum lgm stable climatic conditions during the lgm were followed by a series of meltwater pulses between 18 and 15 5 kyr bp that resulted in temporary isotopic depletion of the black sea waters subsequently steadily increasing d 18 o values in all cores are mainly caused by isotopically enriched precipitation at the onset of the allerod bolling warm period a comparison of the major trends in d 18 o at different water depths suggests evaporation driven deep water formation since 14 5 kyr bp while the two shallowest cores from 168 and 465 m water depth were under the influence of increased warming in the upper water column since 14 5 and 12 5 kyr bp respectively the core from 168 m depth seems to be additionally influenced by freshwater input of the danube this core provides a high resolution record from the younger dryas allerod boundary and suggests that a nao like climate mode was governing the interannual variability in the run off of the danube which implies that this climate mode has been a persistent climatic feature over central europe the inflow of saline mediterranean waters occurs between 9 and 8 kyr bp where a merging of all d 18 o records signals an initial homogenisation of the water column

black sea chemocline oscillations during the holocene molecular and isotopic studies of marginal sediments we measured d 13 c values of free and sulfur bound lipids and framboidal pyrite size distributions in three sediment cores from the southern margins of the black sea the margin cores show a marked diaerence in the occurrence of biomarkers from green sulfur bacteria compared with the deep basin cores as a result of deepening of the chemocline resulting from enhanced mixing and or decreased light penetration as a consequence of high turbidity and productivity in shelf waters quantitation of biomarkers suggests that photic zone anoxia along the shelf margin was generally absent during the deposition of unit i although occurred during the deposition of unit iib at two sites 2000 elsevier science ltd all rights reserved

an abrupt drowning of the black sea shelf abstract during latest quaternary glaciation the black sea became a giant freshwater lake the surface of this lake drew down to levels more than 100 m below its outlet when the mediterranean rose to the bosporus sill at 7 150 yr bp 1 saltwater poured through this spillway to refill the lake and submerge catastrophically more than 100 000 km2 of its exposed continental shelf the permanent drowning of a vast terrestrial landscape may possibly have accelerated the dispersal of early neolithic foragers and farmers into the interior of europe at that time

observations of flow and turbulence in the nocturnal boundary layer over a slope measurements were conducted on an eastern slope of the salt lake basin slb as a part of the vertical transport and mixing experiment vtmx conducted in october 2000 of interest was the nocturnal boundary layer on a slope in particular katabatic flows in the absence of significant synoptic influence extensive measurements of mean flow turbulence temperature and solar radiation were made from which circulation patterns on the slope and the nature of stratified turbulence in katabatic winds were inferred the results show that near the surface 25 50 m the nocturnal flow is highly stratified and directed downslope but at higher levels winds strongly vary in magnitude and direction with height and time implying the domination of upper levels by air intrusions these intrusions may peel off from different slopes surrounding the slb have different densities and flow at their equilibrium density levels the turbulence was generally weak and continuous but sudden increases of turbulence levels were detected as the mean gradient richardson number dropped to rig about unity with a short timescale fluctuated on the order of a few tens of seconds while modulating with rig a longer along slope internal waves sloshing timescale of about half an hour the mixing efficiency or the flux richardson number of the flow was found to be a strong function of similar to that found in laboratory rig experiments with inhomogeneous stratified shear flows the eddy diffusivities of momentum and heat were evaluated and they showed a systematic variation with when scaled with the shear length scale and the rms rig vertical velocity of turbulence

organic matter production and preservation and evolution of anoxia in the holocene black sea dating of sediments collected in gravity cores during leg 1 of the 1988 r v knorr expedition to the black sea suggests that the onset of water column anoxia at 7 5 ka was virtually synchronous across the basin over a depth range of 200 2250 m a finely laminated organic carbon oc rich sapropel unit ii was produced as a result of this anoxia the trigger for increased oc production and development of anoxia was the spillover of saline waters through the bosporus that probably began at 9 0 ka and peaked between 7 0 and 5 5 ka this spillover enhanced vertical mixing and nutrient cycling and caused a short term 2 3 kyr burst in surface water productivity during the early part of unit ii deposition continued incursion of saline waters enhanced vertical stability and inhibited mixing of nutrients into surface waters thus limiting primary production and decreasing the oc flux to sediments beginning 5 5 ka concentration accumulation rate and degree of preservation of organic matter all decreased in the upper part of unit ii as a result of decreasing productivity but anoxia persisted throughout most of the water column the end of unit ii sapropel deposition was synchronous across the black sea as the result of the first blooms of the coccolith emiliania huxleyi which presumably marked an increase in surface water salinity above 11 and the beginning of unit i deposition the high coccolith carbonate fluxes that occurred during deposition of unit i diluted the oc concentration in the sediments but oc accumulation rates are about the same as those in upper part of unit ii

paleoenvironmental and paleoclimatic variations around lake van eastern turkey recorded by sedimentary source specific biomarkers 250 130 ka mis7 and mis6 abstract paleoclimatic changes during mis7 and mis6 remain poorly described in the near east we quantified source specific biomarkers in lake van sediments during the interglacial glacial cycle mis7 mis6 long chain n alkanes produced by land derived vegetation as well as long chain alkenones and sterols namely brassicasterol and dinosterol produced by aquatic algae were investigated stable hydrogen isotopic measurements 2h on n c29 alkanes were used as a proxy for aridity and revealed three wetter periods interrupted by two drier intervals during mis7 in contrast during the mis6 glaciation a generally drier climate was predominant during the warmer and wetter periods of mis7 a higher input of aquatic organic matter to lake van sediments was recorded by higher concentrations of long chain alkenones dinosterol and brassicasterol long chain alkane abundances do not show a pattern related to aridity and were observed in higher concentrations in wetter as well as drier periods generally in the eastern mediterranean a wetter interglacial interrupted by drier episodes followed by a dry glacial period was the common feature observed during the mis7 mis6 interglacial glacial cycle however in comparison to the last interglacial glacial cycle the extreme dry glacial period registered around lake van from mis5d to mis2 was apparently unique and not equaled by a similar event within the last 250 ka

varve calibrated records of carbonate and organic carbon accumulation over the last 2000 years in the black sea sedimentologic and geochemical studies of box and gravity cores recovered from the black sea during the first leg of a multileg international black sea expedition in 1988 allow reconstruction of the basinwide holocene environmental history of the black sea in the deeper parts of the basin box cores typically recovered a flocculent surface layer fluff laminated coccolith marls of unit i 25 45 cm thick and the upper 5 10 cm of finely laminated dark colored sapropels of unit ii fine grained homogeneous mud turbidites are interbedded with units i and ii over much of the basin but the stratigraphie position of these turbidites differs from site to site the deposition of individual turbidites up to 15 cm thick does not appear to have significantly disturbed underlying laminae sediment trap deployments in the black sea suggest that light and dark laminae couplets represent annual increments of sedimentation i e varves we have therefore constructed a varve chronology for the sequence in order to correlate and date distinctive sedimentation and paleoenvironmental events distinctive groups of laminae in unit i can be correlated across the entire deeper basin a distance of more than 1000 km this implies a remarkable homogeneity in production accumulation and preservation of biogenic material over much of the black sea during deposition of unit i the change from deposition of finely laminated organic carbon rich sapropels unit ii to laminated more calcareous coccolith rich marls unit i is thought to represent the crossing of a salinity threshold for emiliania huxleyi the varve chronology sets this change at about 1 63 ka 1633 100 yr b p but the record of magnetic secular variation measured in several cores produces an age estimate of about 2 0 ka for the base of unit i or about 1 2 times the varve age the average of six calibrated accelerator mass spectrometry radiocarbon ages for the base of unit i is 2 7 ka or about 1 7 times the varve age following the initial change to coccolith dominated sedimentation deposition of sapropel resumed for at least one significant period 1 56 1 25 ka since 1 25 ka cycles of carbonate deposition with quasi decadal periodicities have produced characteristic darker and lighter assemblages of laminae these cycles may have been climatically driven geochemical analyses coupled with the varve ages adopted herein indicate that accumulation rates of carbonate are nearly an order of magnitude higher in unit i averaging 35 45 g m 2 yr 1 than in sapropelic unit ii which contains primarily detrital carbonate the accumulation of lithogenic components in parts of unit i is only 1 5 times the rate in unit ii deepwater organic carbon accumulation rates are somewhat higher in unit i 3 5 4 5 g m 2 yr 1 than in the upper part of unit ii organic carbon accumulation rates in unit i are somewhat antithetic to those of carbonate and on the basis of this and additional constraints placed by pyrolysis and carbon isotopic analyses of organic material it appears that terrestrial organic matter is an important component perhaps 25 of total organic carbon burial in the basin unit i in the western part of the black sea has a higher terrestrial organic component and higher accumulation rates of terrigenous clastic material than unit i in the eastern part this difference between eastern and western black sea is to be expected because of the major rivers that empty into the western black sea from eastern europe ukraine and russia shallow slope sites but still within euxinic bottom waters have lower organic carbon accumulation rates and lower pyrolysis hydrogen indices than deepwater basinal sites suggesting selective resuspension and oxidation of organic matter at basin margins and focusing of organic matter deposition toward the basin center a comparison of the black sea data with those from several open ocean sites with similar water depths showed no significant difference between organic carbon accumulation rates under oxic and anoxic conditions for a given bulk accumulation rate the organic carbon accumulation rates normalized to primary productivity are about the same in both settings

black sea impact on the formation of eastern mediterranean sapropel s1 evidence from the marmara sea abstract water exchange between the black sea and the mediterranean sea has been a major focus of the paleohydrography of the eastern mediterranean glacial melt water released from the black sea is a potential factor in the formation of sapropel s1 an organic rich sediment layer that accumulated during the early holocene a high resolution study done on sediments from the marmara sea the gateway between the mediterranean and the black sea sheds light on the holocene exchange processes past sea surface temperature and sea surface salinity sss were derived from stable oxygen isotope ratios 18o of foraminiferal calcite and alkenone unsaturation ratios uk 37 heavy 18o values and high sss in the marmara sea suggest absence of low salinity water from the black sea during s1 the comparison with data from the levantine basin and southern aegean sea outlines gradients of freshening in the eastern mediterranean sea whereby the major sources of freshwater were closer to the levantine basin it is thus concluded that the black sea was not a major freshwater source contributing to formation of s1 given the absence of a low salinity layer the deposition of organic rich sediments corresponding to s1 in the marmara sea is likely the result of the global transgression and the concomitant re organization of biogeochemical cycles leading to enhanced productivity as shown by globigerina bulloides

flow during the evening transition over steep alpine slopes a field campaign the slope experiment near la fouly self 2010 was conducted to monitor the evening transition of slope flows on clear sky days from july to september 2010 in a narrow valley of the swiss alps a steep west facing slope with inclinations ranging from 25 to 45 was instrumented from 1900mto 2200mabove sea level detailed measurements were made along a linear transect of the slope with two turbulence towers two weather stations five surface temperature measurement stations and a tethered balloon system the present study focuses on nine exemplary convective days characterized by weak synoptic flow and clear sky conditions during which thermal circulations prevail the analysis of the observational data shows that topographic shading triggers the evening transition the topographic configuration around the experimental site results in a sharply defined shading front propagating up slope causing a sudden decrease in incoming short wave radiation on the order of several hundreds of wm 2 within a few minutes the slope surface rapidly responds to the advancing shading front in some cases reductions in surface temperatures of some 10 c in less than 10 min are observed this is rapidly followed by an early evening calm period with very small turbulent kinetic energy tke 0 05m2 s 2 and extremely light wind speeds 0 5ms 1 when the inertia driven upslope flow is fully stopped by the katabatic acceleration a shallow local drainage flow forms and reaches a quasi equilibrium 1 5 h after the local sunset an analysis of the tke budget close to the surface shows that the buoyancy flux is much greater than the shear production in the last hours before the local sunset possibly due to valley curvature effects copyright c 2012 royal meteorological society

sediment accumulation in the central western black sea over the past 5100 years the postdepositional particle flux accumulation rate over the last 5100 years was studied in the anoxic sediment units i and ii from the central western black sea deposition of unit ii sapropel in the deep black sea basin was divided further into two subunits the beginning of the deposition of the sapropel in the black sea 5100 3100 years b p subunit iib was characterized by higher organic carbon accumulation rates due largely to higher primary production accumulation rates of lithogenic matter were at a minimum compared to younger units during the subsequent 2100 years 3100 1000 years b p subunit iia organic carbon accumulation rates decreased considerably while accumulation rates of lithogenic matter increased to the present level at 1000 years b p unit i total mass accumulation rates increased by a factor of 3 this increase was largely a result of an increase in carbonate accumulation rates by a factor of 11 which was caused by the rapid appearance of emiliania huxleyi in the black sea higher carbonate accumulation rates in unit i are mainly the cause for the considerably lower organic carbon content compared to unit ii since the organic carbon accumulation rate in unit i did not decrease general correspondence of accumulation rates of lithogenic matter in different cores through time suggests overregional long term 100 year scale climatic effects on the terrigenous particle supply to the black sea

large eddy simulation of a katabatic jet along a convexly curved slope part 1 statistical results abstractlarge eddy simulation is performed to study a katabatic jet along a convexly curved slope with a maximum angle of about 35 5 the design of this numerical simulation of turbulent shear flow is discussed and a qualitative assesment of the method is proposed the katabatic flow is artificialy generated by ground surface cooling and a stable atmospheric boundary layer with constant stratification is considered as a reference state a quantitative statistical analysis is used to describe the present turbulent flow with a focus on the outer layer shear of the katabatic jet which extends about 50 m above the jet maximum the prandtl model for a katabatic jet is applied to the present results and revisited versions of the model found in the literature are discussed with an emphasis on specific momentum and turbulent heat diffusion the vertical and downslope variability of the turbulent kinetic energy budget is also discussed and it is shown that advection and production contributions in the downslope

the shelf to basin iron shuttle in the black sea revisited continental shelf sediments are a major source of iron fe for phytoplankton in surface waters in this study we investigate the mechanisms that control release of fe from shelf sediments and its lateral transport shuttling in oxic and hypoxic waters on the northwestern black sea shelf we find that at two coastal stations near the outflow of the danube river high input of organic matter drives strong reductive dissolution of fe oxyhydr oxides henceforth termed fe oxides in surface sediments supporting high rates of fe release to oxygenated bottom waters 0 36 mmol m 2 d 1 we suggest that bioirrigation plays a key role in the release of fe from these sediments at four stations further offshore organic matter deposition is lower resulting in limited mobilization of fe2 in the sediment and low benthic fluxes of fe 0 2 m in the lower part of the water column likely through repeated deposition and resuspension of fe oxides from surface sediments using synchrotron based x ray spectroscopy and sequential chemical extractions we demonstrate that the suspended matter and surface sediments are enriched in easily reducible fe oxides mostly ferrihydrite and fe associated with clay the mobilization of fe in the coastal zone and subsequent lateral transport of these fe bearing particles results in higher ratios of fe al in surface sediments at outer shelf stations ca 1 2 to 2 wt wt 1 than at coastal stations ca 0 5 to 0 9 wt wt 1 however below the sediment surface layer fe al ratios are similar at all stations indicating limited burial of the laterally transported fe our results highlight the critical role of organic matter input associated biological activity and riverine fe input as drivers of fe shuttling on continental shelves we also show that in shelf areas where sediments receive low inputs of organic matter physical transport controls the ultimate fate of the shuttled fe

latitudinal variation in spectral properties of the lunar maria and implications for space weathering abstract space weathering alters the optical properties of exposed surfaces over time complicating the interpretation of spectroscopic observations of airless bodies like asteroids mercury and the moon solar wind and micrometeoroids are likely the dominant agents of space weathering but their relative contributions are not yet well understood based primarily on clementine mosaics we report a previously unrecognized systematic latitudinal variation in the near infrared spectral properties of the lunar maria and show that the characteristics of this latitudinal trend match those observed at lunar swirls where magnetic fields alter local solar wind flux without affecting the flux of micrometeoroids we show that the observed latitudinal color variations are not artifacts of phase angle effects and cannot be accounted for by compositional variation alone we propose that reduced solar wind flux which should occur both at swirls and toward higher latitudes is the common mechanism behind these color variations this model helps us quantify the distinct effects of solar wind and micrometeoroid weathering and could aid in interpreting the spectra of airless bodies throughout the solar system

constraints on black sea outflow to the sea of marmara during the last glacial interglacial transition new cores from the upper continental slope off romania in the western black sea provide a continuous high resolution record of sedimentation rates clay mineralogy calcium carbonate content and stable isotopes of oxygen and carbon over the last 20 000 yr in the western black sea these records all indicate major changes occurring at 15 000 12 800 8400 and 7100 yr before present these results are interpreted to reflect an evolving balance between water supplied by melting glacial ice and other river runoff and water removed by evaporation and outflow the marked retreat of the fennoscandian and alpine ice between 15 000 and 14 000 yr is recorded by an increase in clays indicative of northern provenance in black sea sediments a short return toward glacial values in all the measured series occurs during the younger dryas cold period the timing of the first marine inflow to the black sea is dependent on the sill depths of the bosporus and dardanelles channels the depth of the latter is known to be 80 5 m which is consistent with first evidence of marine inundation in the sea of marmara around 12 000 yr the bedrock gorge of the bosporus reaches depths in excess of 100 m relative to present sea level though it is now filled with sediments to depths as shallow as 32 m two scenarios are developed for the connection of the black sea with the sea of marmara one is based on a deep bosporus sill depth effectively equivalent to the dardanelles and the other is based on a shallow bosporus sill less than 35 m in the deep sill scenario the black sea s surface rises in tandem with the sea of marmara once the latter connected with the aegean sea and black sea outflow remains continuous with inflowing marine water gradually displacing the freshwater in the deep basin the increase in the 18 o of mollusk shells at 12 800 yr and the simultaneous appearance of inorganic calcite with low 18 o is compatible with such an early marine water influx causing periodic weak stratification of the water column in the shallow sill scenario the black sea level is decoupled from world sea level and experiences rise and fall depending on the regional water budget until water from the rising sea of marmara breaches the shallow sill in this case the oxygen isotope trend and the inorganic calcite precipitation is caused by increased evaporation in the basin and the other changes in sediment properties reflect climate driven river runoff variations within the black sea watershed the presence of saline ponds on the black sea shelf circa 9600 yr support such evaporative drawdown but a sensitive geochemical indicator of marine water one that is not subject to temperature salinity or biological fractionation is required to resolve whether the sill was deep or shallow

investigation of upstream boundary layer influence on mountain wave breaking and lee wave rotors using a large eddy simulation abstract interactions between a turbulent boundary layer and nonlinear mountain waves are explored using a large eddy simulation model simulations of a self induced critical layer which develop a stagnation layer and a strong leeside surface jet are considered over time wave breaking in the stagnation region forces strong turbulence that influences the formation and structure of downstream leeside rotors shear production is an important source of turbulence in the stagnation zone and along the interface between the stagnation zone and surface jet as well as along the rotor edges buoyancy perturbations act as a source of turbulence in the stagnation zone but are shown to inhibit turbulence generation on the edges of the stagnation zone surface heating is shown to have a strong influence on the strength of downslope winds and the formation of leeside rotors in cases with no heating a series of rotor circulations develops capped by a region of increased winds weak heating disrupts this system an

late quaternary dinoflagellate cysts from the black marmara and aegean seas variations in assemblages morphology and paleosalinity abstract the link between sea surface salinity sss and dinoflagellate cyst morphology was studied quantitatively in cores of late quaternary mud from the black marmara and aegean seas where oxygen isotopic and planktonic foraminiferal data show salinities of about 5 19 15 22 and 36 39 ppt respectively in the black sea late glacial muds contain low diversity assemblages of the cruciform species spiniferites cruciformis and pyxidinopsis psilata with most s cruciformis cysts having expanded septal membranes form 1 circular outline form 2 irregular the assemblage is associated with surface salinities of in the northeast aegean core stenohaline species and morphotypes are rare occurring only as low percentages of s cruciformis forms 3 and 4 and o centrocarpum var truncatum in a mid holocene sapropel that was deposited during a period of high runoff and black sea water outflow marmara sea cores record surface salinities of 14 18 ppt during late glacial sapropel deposition and 20 22 ppt for the overlying marine sediments the sapropel is dominated by s cruciformis forms 1 and 2 and by p psilata with common l machaerophorum clavate and normal forms in surface sediments l machaerophorum is co dominant with o centrocarpum normal and truncate forms brigantedinium and spiniferites spp percentages of s cruciformis five forms and l machaerophorum two forms plotted against proxy salinity data however show no clear correlation indicating that morphological variation is not a simple function of salinity

unusual c35 to c38 alkenones in mid holocene sediments from a restricted estuary charlotte harbor florida unusual c 35 to c 38 alkenones were identified in mid holocene 8 3 5 kyr bp sediments from a restricted estuary in southwest florida charlotte harbor the distribution was dominated by a c 36 diunsaturated omega 15 20 ethyl ketone identical to the one present in black sea unit 2 sediments other unusual alkenones were tentatively assigned as a c 35 2 omega 15 20 methyl ketone a c 37 2 omega 17 22 methyl ketone and a c 38 2 omega 17 22 ethyl ketone in late holocene sediments 3 5 kyr bp the common c 37 to c 39 alkenones were found compound specific c 14 c 13 and d isotope measurements were used to constrain the possible origin of the alkenones conventional radiocarbon ages of alkenones and higher plant derived long chain n alcohols indicated no significant difference in age between mid holocene alkenones and higher plant n alcohols both alcohols and alkenones were offset vs calibrated ages of shell fragments in the same sediment core which suggests they were pre aged by 500 800 yr implying resuspension and redistribution of the fine grained sedimentary particles with which they are associated the hydrogen isotopic delta d composition 190 parts per thousand to 200 parts per thousand of the c 37 and c 38 alkenones in the late holocene sediments is in line with values for coastal haptophytes in brackish water however the unusual c 36 and c 38 alkenones from the mid holocene sediments were enriched in d by ca 100 parts per thousand vs the late holocene alkenones also delta c 13 values of mid holocene alkenones were consistently offset compared with late holocene alkenones 21 parts per thousand to 22 parts per thousand and 22 parts per thousand to 23 parts per thousand respectively we suggest that the alkenones in charlotte harbor were produced by unknown alkenone producing haptophyte

phylogenetic diversity and evolutionary relatedness of alkenone producing haptophyte algae in lakes implications for continental paleotemperature reconstructions alkenones have been found in an increasing number of lakes around the world making them a promising new tool for continental paleoclimate reconstruction however individual lakes may harbor different species of haptophyte algae with different sensitivities to temperature variations thus presenting a significant challenge to the use of lacustrine alkenones for paleotemperature reconstructions to explore the extent of lacustrine haptophyte diversity we conducted the first comprehensive phylogenetic and geochemical survey of lacustrine alkenone producers we sampled 15 alkenone containing lake surface sediments from a variety of geographic locales and inferred identities of environmental sequences using 18s ribosomal rna rrna gene based phylogenies for two lakes brayaso in southwest greenland and tso ur on the tibetan plateau we also analyzed both surface and downcore sediments to characterize haptophyte populations through time in parallel with phylogenetic analyses we determined the alkenone distributions including c37 c38 ratios and the presence absence of c38 methyl ketones and c40 compounds in all the samples the resulting alkenone profiles from this study do not all align with traditional marine versus coastal lacustrine alkenone profiles additionally our genetic data indicate the presence of multiple haptophyte species from a single lake sediment sample these distinct haptophyte populations could not be discerned from the alkenone profiles alone these results show that alkenone profiles are not a reliable way to assess the haptophyte algae in lakes and that dna fingerprinting is a preferred approach for species identification although closely related haptophyte species or subspecies may not warrant different temperature calibrations our results emphasize the importance of genetic data for inferring haptophyte identities and eventually selecting alkenone temperature calibrations for paleoclimate reconstructions

carbon accumulation rates and the origin of the holocene sapropel in the black sea a detailed radiocarbon chronology obtained by accelerator mass spectrometry together with organic carbon and carbonate measurements on two black sea cores has been used to compare and contrast the burial fluxes of organic carbon in the holocene sapropel and the modern sediment at both deep water and eastern slope sites the sapropel is separated from the modern facies by a variable thickness of compositionally homogeneous sediment with low levels of organic carbon and anomalously old radiocarbon ages this homogeneous unit probably represents deposition by slumping or mudflow the age limits of the sapropel are 1600 6600 b p at the deep water site and 4000 6000 b p radiocarbon years before 1950 a d at the shallow water site the carbon accumulation rate in the deep water sapropel is higher than that in the modern deep water facies by a factor of 2 and is approximately the same as that in the modern sediment in shallow water the revised chronology of sapropel formation and the differences in the carbon accumulation rates probably indicate that the sapropel was formed by increased production during the transition from the premodern lake to the modern marine phases of the black sea this conclusion is consistent with the clear marine carbon isotope signal in the organic mattermore in the sapropel in both cores results to be reported elsewhere in contrast to the mixed source of carbon in the other facies less

organic carbon geochemistry in the north western black sea danube river system abstract the isotopic and chemical composition of organic matter from sediments collected on the north western shelf of the black sea and the danube river are discussed the 13 c distribution pattern in organic carbon from surface sediments 0 1 cm of the western part of the black sea has been established it reveals a rather complicated picture reflecting the superposition of several factors local marine primary productivity terrestrial input to the danube river discharge and possible contribution from anaerobic microbial activity the analysis of organic carbon by a pyrolysis chromatography technique showed that the h o indices of organic matter from marine sediments are in correlation with 13 c values this is an indication of the mixed origin of the organic carbon in the littoral sediments however samples from the zone where h 2 s conditions prevail deviate from the correlation line of 13 c vs h o indices we believe that this is due to the contribution of the biomass of chemosynthetic bacteria in the sediments thus we argue that in the danube black sea system several consecutive zones are distinguished river discharge delivers organic carbon with 13 c values from 28 to 26 psu is used mixing of the land derived material with autochtonous marine primary production gives 13 c values of about 26 to 23 for the organic carbon in coastal sediments on the shelf area beyond significant influence of both terrestrial and sulphide regime factors plankton material dominates as a source of organic carbon in sediments in the hydrogen sulphide zone chemosynthetic bacteria produce additional amounts of organic matter with hydrogen to oxygen indices similar to those of plankton but with different isotopic composition which results in the appearance of relatively isotopically light organic carbon in the deep sea sediments

meltwater events and the mediterranean reconnection at the saalian eemian transition in the black sea abstract the last glacial interglacial transition or termination i t i is well documented in the black sea whereas little is known about climate and environmental dynamics during the penultimate termination t ii here we present a multi proxy study based on a sediment core from the se black sea covering the penultimate glacial and almost the entire eemian interglacial 133 5 0 7 122 5 1 7 ka bp proxies comprise ice rafted debris ird o and sr isotopes as well as sr ca mg ca and u ca ratios of benthic ostracods organic and inorganic sediment geochemistry as well as tex 86 and u k 37 derived water temperatures the ending penultimate glacial mis 6 133 5 to 129 9 0 7 ka bp is characterised by mean annual lake surface temperatures of about 9 c as estimated from the tex 86 palaeothermometer this period is impacted by two black sea melt water pulses bswp ii 1 and 2 as indicated by very low sr ca ostracods but high sedimentary k al values anomalously high radiogenic 87 sr 86 sr ostracod values max 0 70945 during bswp ii 2 suggest a potential himalayan source communicated via the caspian sea the t ii warming started at 129 9 0 7 ka bp witnessed by abrupt disappearance of ird increasing 18 o ostracod values and a first tex 86 derived temperature rise of about 2 5 c a second abrupt warming step to ca 15 5 c as the prelude of the eemian warm period is documented at 128 3 ka bp the mediterranean black sea reconnection most likely occurred at 128 1 0 7 ka bp as demonstrated by increasing sr ca ostracods and u ca ostracods values the disappearance of ostracods and toc contents 2 document the onset of eemian sapropel formation at 127 6 ka bp during sapropel formation tex 86 temperatures dropped and stabilised at around 9 c while u k 37 temperatures remain on average 17 c this difference is possibly caused by a habitat shift of thaumarchaeota communities from surface towards nutrient rich deeper and colder waters located above the gradually establishing halo and redoxcline

dinoflagellate cysts freshwater algae and fungal spores as salinity indicators in late quaternary cores from marmara and black seas abstract seismic profiles and mollusks have been used to suggest that from 12 500 to 7000 yr bp the black sea was an isolated freshwater lake containing potable water and implying a surface salinity of 24 and that spiniferites cruciformis spiniferites inaequalis peridinium ponticum polykrikos spp and quinquecuspis concreta characterize the lower salinity of the marmara and or black seas the core top data and correlatable down core assemblage changes in time equivalent sapropelic and brown muds show that there is no evidence for differential aerobic decay of dinocysts in the study area the main acritarchs are sigmopollis psilatum concentricystes cf c rubinus and cf acritarch 8 of traverse 1978 all of which are absent from the aegean sea and decrease in abundance with increasing salinity the first two taxa have been reported previously as freshwater species fungal remains show a similar distribution pattern to the freshwater acritarchs indicating their origin from terrestrial environments freshwater chlorococcales are almost confined to the black sea but they have rare occurrences in the aegean indicating long distance transport microforaminiferal linings are abundant in the marmara sea but are absent in deep water of the black sea in the marmara sea mid late holocene assemblages

combined dna and lipid analyses of sediments reveal changes in holocene haptophyte and diatom populations in an antarctic lake preserved ribosomal dna of planktonic phototrophic algae was recovered from holocene anoxic sediments of ace lake antarctica and the ancient community members were identified based on comparative sequence analysis the similar concentration profiles of dna of haptophytes and their traditional lipid biomarkers alkenones and alkenoates revealed that fossil rdna also served as quantitative biomarkers in this environment the dna data clearly revealed the presence of six novel phylotypes related to known alkenone and alkenoate biosynthesizing haptophytes with isochrysis galbana uio 102 as their closest relative the relative abundance of these phylotypes changed as the lake chemistry particularly salinity evolved over time changes in the alkenone distributions reflect these population changes rather than a physiological response to salinity by a single haptophyte using this novel paleo ecological approach of combining data from lipid biomarkers and preserved dna we showed that the post glacial development of ace lake from freshwater basin to marine inlet and the present day lacustrine saline system caused major qualitative and quantitative changes in the biodiversity of the planktonic populations over time

palynological evidence for climatic change anthropogenic activity and outflow of black sea water during the late pleistocene and holocene centennial to decadal scale records from the black and marmara seas abstract previous marine palynology studies of pollen and dinoflagellate cysts dinocysts in the black sea mediterranean corridor were made on short cores allowing only millennial century scale reconstruction of past climates we now describe pollen accumulation rates for 5 cores with eleven 14c ages over 30 000 years and new decadal scale data for a holocene core with fourteen 14c ages pollen influxes show pinus abies quercus forest steppe and deteriorating climate from 29 8 24 kyr bp then colder drier pre and post lgm conditions with artemisia cheno ams and ephedra that lasted through the bolling interstade deciduous oak returns by the younger dryas and rapidly expands followed by pistacia by 9 3 kyr bp foraminiferal 18o shows 4 c cooler than present late glacial summers and rapid holocene warming by 9 bp influxes from quercus cerris tilia fagus castanea ulmus shade ferns aquatics swamp plants and 18o indicate warm winters 5 c or more and year round precipitation 600 1000 mm not the dry conditions that would be required for black sea drawdown there is mid holocene expansion of carpinus evergreen quercus and pistacia walnut olive and cereal pollen suggest early cultivation attempts but no sustained farming before 4 5 kyr bp dinocyst assemblages show major changes traceable throughout the corridor variability in process length marks low diversity n 13 pleniglacial early holocene spiniferites cruciformis assemblages suggesting fluctuating salinity like the modern caspian sea with brackish to saline conditions 5 16 distributions of euryhaline cysts spiniferites mirabilis and spiniferites bentorii show the aegean and marmara seas were connected by 11 kyr bp and linked to black sea by 9 3 kyr bp there is no palynological evidence of either freshwater salinity

alkenone producers inferred from well preserved 18s rdna in greenland lake sediments 1 the 18s ribosomal dna rdna sequences of haptophyte algae were successfully amplified using the polymerase chain reaction pcr from water filtrate surface sediments and a late holocene sediment sample 1000 years old from a group of lakes in the sondre stromfjord region of west greenland the dna of the algal primary producer is extremely well preserved in the laminated lake sediments which have been deposited in cold 1 2c anoxic and sulphidic bottom water phylogenetic analyses of the greenland haptophyte rdna sequences suggest that alkenones in the greenland lake sediments are produced by haptophyte algae of the class prymnesiophyceae the 18s rdna sequences from the greenland samples cluster within a distinct phylotype differing from both marine haptophytes and from those reported previously from ace lake antarctica the similarity of haptophyte rdna sequences among all samples in this study suggests a single alkenone based temperature calibration may be applied to these lakes for at least the past 1000 years these sedimentary archives hold great promise for highresolution alkenone based paleotemperature reconstruction of southern west greenland a region sensitive to atmospheric oceanic climate phenomena such as the north atlantic oscillation nao

molecular isotopic and dinoflagellate evidence for late holocene freshening of the black sea abstract the black sea is the world s largest anoxic basin with oxygen free conditions below water depths of approximately 100 m resulting from strong density stratification the salinity of its surface water likely varied substantially over time due to variations in freshwater input from large rivers and in the saline bottom water of mediterranean origin coming across the shallow sill of the bosporus however long term reconstructions of surface water salinities are lacking the invasion of the coccolithophorid emiliania huxleyi in the black sea at approximately 2720 a responsible for a marked change in sediment composition lithology has been commonly attributed to salinity levels rising above 11 we analyzed the d values of long chain alkenones produced by haptophyte algae mainly e huxleyi in a core from the eastern basin of the black sea to reconstruct past variations in sea surface salinities and combined this with relative salinity changes generated from organic walled dinoflagellate cyst dinocyst distributions from the same core combined results indicate a substantial freshening of black sea surface waters in the last 3000 years suggesting that sea surface salinity was substantially higher than the present day salinity of approximately 18 at the time e huxleyi invaded the black sea

organic geochemical and palynological evidence for terrigenous origin of the organic matter in aegean sea sapropel s1 abstractorganic geochemistry and micropaleontology are used to determine the origin of sapropel s1 in the aegean sea low molecular weight c 15 c 17 and c 19 n alkane data show that net primary productivity npp increased from 14 000to 10 000 yr bp at the glacial interglacial transition but the onset of s1 at 9600 yr bp marks a sharp decline in npp whichremained low until 8200 yr bp the start of sapropel deposition is marked by increased total organic carbon toc and pollen spore concentrations together with increased high molecular weight c 27 c 29 c 31 and c 33 n alkanes pollenassemblages show large in ux of tree pollen from central northern european forests increases in high molecular weightn alkanes suggest greater in ux of fresh vascular plant material at the start of s1 although the amount is small comparedto other insoluble organic matter palynological studies showed that most of this insoluble organic matter are ocksof dark brown amorphous kerogen typical of terrigenous humic compounds from 8200 yr bp to the top of s1at 6400 yr bp there is a decline in high molecular weightn alkanes and terrigenous kerogen and an increase inlow molecular weightn alkanes suggesting that npp recovered during the later deposition of s1 in the aegean sea theincrease in low molecular weightn alkanes coincides with the recovery of coccolithophores and dino agellates suggestingthat these phytoplankton are primarily responsible for the low molecular weightn alkane variations these data from theaegean sea support the model for sapropel deposition resulting from increased in ux of toc during times of stagnantbottom water but disagree with mediterranean models prescribing a large increase in marine productivity 1999 elsevierscience b v all rights reserved keywords sapropel s1 aegean sea fatty acids n alkanes palynology

an intercomparison of subgrid models for large eddy simulation of katabatic flows we present an intercomparison of three subgrid scale sgs models for large eddy simulation les of katabatic flows the sgs closures we study include the smagorinsky formulation a scale invariant dynamic model and a scale dependent dynamic model downslope fluxes of mass and buoyancy deficit are highly sensitive to sgs closure choice due to strong shear and strong stratification the dynamic models show a reduction of the smagorinsky coefficient near the surface relative to the smagorinsky model furthermore results from both scale dependent dynamic models suggest that the assumptions of scale invariance in the dynamic model are violated we present a second set of experiments which focus on grid resolution requirements of eddy resolving simulations of drainage flows downslope buoyancy and mass flux predictions produced by the scale dependent dynamic model are more robust with respect to grid resolution and grid anisotropy than the scale invariant dynamic and smagorinsky sgs models predictions of vertically integrated downvalley mass and buoyancy fluxes are more sensitive to vertical grid resolution than horizontal grid resolution

subsurface migration of h2o at lunar cold traps 1 permanently shaded areas near the poles of the moon and mercury may harbor water ice we develop a physical model for migration of water molecules in the regolith and discover two pathways that can lead to accumulation of h2o in the subsurface a small fraction of water molecules delivered either continuously or abruptly to permanently cold areas diffuses into the regolith and can remain there longer than on the surface higher temperatures lead to deeper burial at constant temperature this diffusive migration produces less than one molecular layer of volatile h2o on grains because it is driven by differences in surface concentrations the water is therefore expected to be in adsorbed form and the amount stored in this fashion could be at most a few hundred ppm of h2o a second pathway is pumping by diurnal temperature oscillations from a transient ice cover that may have formed during a large comet impact it can lead to high ground ice densities but the ground ice layer lasts not long beyond the disappearance of the ice cover both types of subsurface charging mechanism work best for temperatures typical of permanently shaded areas with sunlit surfaces in their field of view

last glacial holocene paleoceanography of the black sea and marmara sea stable isotopic foraminiferal and coccolith evidence multi proxy data and radiocarbon dates from several key cores from the black sea and marmara sea document a complex paleoceanographic history for the last v30 000 yr the marmara sea was isolated from both the black sea and the aegean sea during glacial periods when global sea level lowering subaerially exposed the shallow sills at the straits of bosphorus and dardanelles i e lake stage and reconnected through both straits during interglacial periods when rise of global sea level breached the shallow sills i e gateway stage micropaleontological data show that during the lake stage the surface water masses in both the marmara sea and black sea became notably brackish however during the gateway stages there was a low salinity surface layer and normal marine water mass beneath two sapropel layers are identified in the marmara sea cores sapropels m2 and m1 were deposited between v29 5 and 23 5 ka and v10 5 and 6 0 ka respectively micropaleontological and stable isotopic data show that the surface water salinities were reduced considerably during the deposition of both sapropel layers m2 and m1 and calculation using planktonic foraminiferal transfer functions shows that sea surface temperatures were notably lower during these intervals the presence of fauna and flora with black sea affinities and the absence of mediterranean fauna and flora in sapropels m1 and m2 strongly suggest that communication existed with the black sea during these times a benthic foraminiferal oxygen index shows that the onset of suboxic conditions in the marmara sea rapidly followed the establishment of fully marine conditions at v11 10 5 ka and are attributed to black sea outflow into the marmara sea since 10 5 ka these suboxic conditions have persisted to the present the data discussed in this paper are completely at odds with the flood hypothesis of ryan et al 1997 and ryan and pitman 1999 crown copyright 2002 elsevier science b v all rights reserved

evidence for surface water ice in the lunar polar regions using reflectance measurements from the lunar orbiter laser altimeter and temperature measurements from the diviner lunar radiometer experiment abstract we find that the reflectance of the lunar surface within 5 of latitude of the south pole increases rapidly with decreasing temperature near 110 k behavior consistent with the presence of surface water ice the north polar region does not show this behavior nor do south polar surfaces at latitudes more than 5 from the pole this south pole reflectance anomaly persists when analysis is limited to surfaces with slopes less than 10 to eliminate false detection due to the brightening effect of mass wasting and also when the very bright south polar crater shackleton is excluded from the analysis we also find that south polar regions of permanent shadow that have been reported to be generally brighter at 1064 nm do not show anomalous reflectance when their annual maximum surface temperatures are too high to preserve water ice this distinction is not observed at the north pole the reflectance excursion on surfaces with maximum temperatures below 110 k is superimposed on a general trend of increasing reflectance with decreasing maximum temperature that is present throughout the polar regions in the north and south we attribute this trend to a temperature or illumination dependent space weathering effect e g hemingway et al 2015 we also find a sudden increase in reflectance with decreasing temperature superimposed on the general trend at 200 k and possibly at 300 k this may indicate the presence of other volatiles such as sulfur or organics we identified and mapped surfaces with reflectances so high as to be unlikely to be part of an ice free population in this south we find a similar distribution found by hayne et al 2015 based on uv properties in the north a cluster of pixels near that pole may represent a limited frost exposure

ancient dna from marine sediments precautions and considerations for seafloor coring sample handling and data generation the study of ancient dna adna from sediments sedadna offers great potential for paleoclimate interpretation and has recently been applied as a tool to characterise past marine life and environments from deep ocean sediments over geological timescales using sedadna palaeo communities have been detected including prokaryotes and eukaryotes that do not fossilise thereby revolutionising the scope of marine micropalaeontological research however many studies to date have not reported on the measures taken to prove the authenticity of sedadna derived data from which conclusions are drawn adna is highly fragmented and degraded and extremely sensitive to contamination by non target environmental dna contamination risks are particularly high on research vessels drilling ships and platforms where logistics and facilities do not yet allow for sterile sediment coring and due consideration needs to be given to sample processing and analysis following adna guidelines this review clarifies the use of adna terminology discusses common pitfalls and highlights the urgency behind adopting new standards for marine sedadna research with a focus on sampling optimisation to facilitate the incorporation of routine sedadna research into international ocean discovery program iodp operations currently available installations aboard drilling ships and platforms are reviewed improvements suggested analytical approaches detailed and the controls and documentation necessary to support the authenticity of adna retrieved from deep sea sediment cores is outlined beyond practical considerations concepts relevant to the study of past marine biodiversity based on sedadna and the applicability of the new guidelines to the study of other contamination susceptible environments permafrost and outer space are discussed

foehn warming distributions in nonlinear and linear flow regimes a focus on the antarctic peninsula the structure of lee side warming during foehn events is investigated as a function of cross barrier flow regime linearity two contrasting cases of westerly flow over the antarctic peninsula ap are considered one highly nonlinear the other relatively linear westerly flow impinging on the ap provides one of the best natural laboratories in the world for the study of foehn owing to its maritime setting and the larsen c ice shelf lcis providing an expansive homogeneous and smooth surface on its east side numerical simulations with the met office unified model at 1 5 km grid size and aircraft observations are utilized in case a relatively weak southwesterly cross peninsula flow and an elevated upwind inversion dictate a highly nonlinear foehn event with mountain wave breaking observed the consequent strongly accelerated downslope flow leads to high amplitude warming and ice shelf melt in the immediate lee of the ap however this foehn warming diminishes rapidly downwind due to upward ascent of the foehn flow via a hydraulic jump in case c strong northwesterly winds dictate a relatively linear flow regime there is no hydraulic jump and strong foehn winds are able to flow at low levels across the entire ice shelf mechanically mixing the near surface flow preventing the development of a strong surface inversion and delivering large fluxes of sensible heat to the ice shelf consequently in case c ice melt rates are considerably greater over the lcis as a whole than in case a our results imply that although nonlinear foehn events cause intense warming in the immediate lee of mountains linear foehn events will commonly cause more extensive lee side warming and over an ice surface higher melt rates this has major implications for the ap where recent east coast warming has led to the collapse of two ice shelves immediately north of the lcis

sedimentary alkenone distributions reflect salinity changes in the baltic sea over the holocene the baltic sea has had a complex salinity history since the last deglaciation here we show how distributions of alkenones and their d values varied with past fluctuations in salinity in the baltic sea over the holocene by examining a holocene record 11 2 0 1 cal kyr bp from the arkona basin major changes in the alkenone distribution i e changes in the fractional abundance of the c37 4 me alkenone the c38 2 et alkenone and a c36 2 me alkenone the latter which has not been reported in the baltic sea previously correlated with known changes in salinity both alkenone distributions and hydrogen isotopic composition suggest a shift in haptophyte species composition from lacustrine to brackish type haptophytes around 7 7 7 2 cal kyr bp corresponding with a salinity change that occurred when the connection between the basin and the north sea was re established a similar salinity change occurred in the black sea previously published alkenone distributions and their d values from the black sea were used to reconstruct holocene changes in surface water salinity and hence it was shown that the unusual c36 2 alkenone dominates the alkenone distribution at salinities of 2 8 ppt g kg this information was used to corroborate the interpretations made about salinity changes from the data presented for the baltic sea low and variable salinity waters in the baltic sea over the holocene have led to a variable alkenone producing haptophyte community composition including low salinity adapted species hindering the use of the unsaturation ratios of long chain alkenones for sea surface temperature reconstruction however these alkenone based indices are potentially useful for studying variations in salinity regionally as well as in the past

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

alkenone distribution in lake van sediment over the last 270 ka influence of temperature and haptophyte species composition abstract fossil long chain alkenones have been used for several decades to reconstruct past ocean surface water temperatures and gained recent interest as a paleotemperature proxy for continental lake settings however factors besides temperature can affect alkenone distributions in haptophyte algae and alkenone compositions can differ between haptophyte species alkenone biosynthesizing haptophyte algae are genetically much more diverse in lakes than in the marine realm and species level variations in alkenone compositions could have implications for alkenone paleothermometry here we performed a paired analysis of alkenone distributions and haptophyte species compositions using ancient dna in up to 270 ka old sediments of lake van in turkey to reveal a possible species effect on fossil alkenone distributions and paleotemperature estimates the same predominant haptophyte in lake van today prevailed also since the last 100 ka however a calibration of alkenone paleotemperature especially in the oldest analyzed intervals is complicated due to a more complex haptophyte species composition predominated by a haptophyte lvhap 6 which is phylogenetically different from sequences recovered from currently existing lakes including lake van and from haptophyte species existing in culture the predominance of lvhap 6 coincided with the presence of alkenone mec38 3 and relatively high mec37 3 4 2 4 and mec38 4 5 ratios 3 0 uk37 index values in the sediment core over the last 270 ka reflect relative changes in past temperature and are additionally linked to haptophyte species composition a sustained period of high salinity as indicated by pore water salinity measurements could potentially have triggered the succession of haptophytes as sources of alkenones in lake van

composition age and provenance of organic matter in nw african dust over the atlantic ocean 1 eolian dust deposited on a meteorology buoy over the boreal winter and spring of 1992 1993 in the northeast atlantic off northwest africa 18 n 22 w afforded sufficient material for detailed assessment of its biogeochemical characteristics and provenance the sample was subjected to microscopic examination and bulk elemental isotopic black carbon and molecular lignin lipid analyses the bulk elemental composition and organic carbon oc content 1 02 dry weight establishes the dust s origin as continental upper crust and is typical of dusts that emanate from west africa these data are in accord with the extensive satellite imagery documenting the transit of dust clouds from the sahara and sahel regions e g nasa toms aerosol index microscopic examination reveals that charcoal like particles from vegetation fires black carbon bc are the most abundant morphologically distinct organic components accelerator mass spectrometry ams 14c analysis yields conventional 14c ages for bulk oc of 1260 40 years and bc of 2070 35 years taken together with corresponding stable carbon isotopic compositions 13c 18 9 and 15 1 respectively these results suggest the presence of biomass and burning residues derived from predominantly c4 vegetation that accumulated in soils over the late holocene molecular level measurements are also consistent with this scenario for example lignin derived phenols in the dustfall sample indicate a significant contribution of angiosperm grass type tissue the altered nature of the lignin suggests storage as residues in soils solvent extractable lipid constituents include a marked leaf wax type component with a molecular and stable carbon isotopic composition similar to those observed in surface marine sediments in this region the hydrocarbon fraction contained some diesel type contamination but the n alkanes c23 c33 retained a prominent odd even distribution with 13c ranging from 26 7 to 28 5 the suite of even carbon numbered n alkanols c22 c32 is 14c dated at 647 150 years with 13c values ranging from 23 9 to 30 4 the long chain n alkanoic acids c22 c32 exhibited 13c values ranging from 22 6 to 27 4 these waxes are evidently a mixed signal derived from contemporary c3 and c4 vegetation and from ablated soils and desiccated lake sediments of middle to late holocene age this molecular approach shows promise as a tool for continental paleoenvironmental assessment particularly with respect to past vegetation cover regional aridity and wind systems

long chain alkenones in baltic sea surface sediments new insights abstract c 37 alkenones produced by certain haptophytes of the isochrysidales are valuable sedimentary biomarkers used to estimate sea surface temperature sst in the open ocean however in coastal seas the role of salinity gradients on alkenone producing species and sst estimates is poorly known alkenones were analyzed in surface sediments from the marine skagerrak region and the entire brackish baltic sea three types of alkenone distribution patterns were identified type a distribution which resembles the distribution in emiliania huxleyi type b distribution which is similar to ruttnera lamellosa isochrysis galbana and pseudoisochrysis paradoxa distributions although these haptophytes are absent from the baltic sea and type c distribution which is also found in worldwide lake sediments these types of distribution are apparent in the percentage of c 37 4 alkenone c 37 4 which is significantly negatively correlated to sea surface salinity sss the distribution of alkenones very likely results from distinct alkenone producing haptophytes whose spatial distribution is ultimately related to sss as supported by the hydrogen isotope fractionation between alkenones and water u 37 k and u 37 k correlate more significantly than u 37 k with both sst and sss probably due to the superimposed effect of changing alkenone producing species the application of u 37 k and u 37 k as sst proxies results in unrealistic holocene temperature records for the southern baltic sea but c 37 4 as a sss proxy reveals reasonable salinity changes interestingly a c 32 hopanoic acid was found abundantly as the methyl ester in the ketone fractions and may represent a marker for cyano bacterial biomass in the baltic sea

an observational and numerical study of a regional scale downslope flow in northern arizona 1 boundary layer observations taken during the metcrax field study in october of 2006 near winslow in northern arizona revealed the frequent presence of a near surface wind maximum on nights with relatively quiescent synoptic conditions data from a sodar a radar wind profiler several surface stations and frequent high resolution rawinsonde soundings were used to characterize this boundary layer wind phenomenon and its relation to synoptic conditions and the ambient environment the data analyses are augmented by high resolution mesoscale numerical modeling it is found that the observed nocturnal low level wind maximum is part of a regional scale downslope flow converging from high terrain of the colorado plateau toward the little colorado river valley the depth of this downslope flow is between 100 and 250 m with a peak speed of 4 6 m s 1occurring usually within the lowest 50 m above ground opposing ambient winds lead to a longer evening transition period shallower slope flows and a smaller horizontal extent as compared to supporting synoptic winds a simple analytical solution based on local equilibrium appears to agree fairly well with the observed layer mean downslope wind speed but the classic prandtl solution for maximum downslope wind speed fails to match the observations the properties of the flow appear to be insensitive to changes in soil moisture land cover and surface roughness length the contribution to the low level wind maximum by inertial oscillation at night is found to be insignificant

late glacial to holocene benthic foraminifera in the marmara sea implications for black sea mediterranean sea connections following the last deglaciation benthic foraminifera were studied from four gravity cores that penetrated holocene marine sediments in the marmara sea morphogroup and assemblage analyses reveal that the holocene sea level rise did not result in a catastrophic flooding event as proposed by w b f ryan and others whereby well oxygenated saline mediterranean waters rapidly inundated a low lying low salinity black sea lake at v7 15 ka popularly known as the noah s flood hypothesis rather the benthic foraminiferal data confirm the hypothesis that the dardanelles sill was breached by the mediterranean at v12 ka allowing saline waters to penetrate the marmara sea these saline waters reached the level of the bosphorus sill at v9 5 ka but were unable to penetrate into the black sea until after v9 1 ka because of the persistent strong outflow of brackish to fresh water from the black sea the initial colonisation of the marmara sea by benthic foraminifera is essentially synchronous with the re establishment of marine connections through the dardanelles strait at v12 ka by v10 ka ammonia dominated faunas developed on the strait exit delta v1 at the southern end of the bosphorus and at v9 1 ka the appearance of fully marine species documents the establishment of a more stratified water column over v1 finally the increase in abundance of planktonic foraminifera at the southern exit of the bosphorus after v6 1 ka reflects a decreased volume of outflow water from the black sea quantitative analysis of benthic foraminiferal morphogroups reveals that the oxygen content of subhalocline water was low below v1 5 ml l throughout the holocene and the occurrence of sapropel sediment in the deeper part of the basin suggests bottom waters may have been anoxic at times after v4 5 ka an increase in benthic foraminiferal oxic morphotypes suggests a reduction in black sea outflow and weakening of the halocline the strong and persistent stratification of the water column in the marmara sea throughout the holocene is entirely incompatible with the noah s flood hypothesis 2002 elsevier science b v all rights reserved

group i alkenones and isochrysidales in the world s largest maar lakes and their potential paleoclimate applications abstract the espenberg maar lakes on the seward peninsula alaska are the largest volcanic crater lakes in the world and contain the longest known lacustrine sedimentary archives in alaska the lack of glacial aged marine sedimentary archives around the bering land bridge due to exposure of the shelf during sea level low stands makes these lakes highly valuable for understanding the region s past climate and environmental changes located en route to humanity s last colonized american continents the seward peninsula s climate and environments during the last glacial period bear major anthropological significance however a lack of quantitative proxies has so far hampered exploration of these lakes for paleoclimate reconstructions here we report for the first time the discovery of abundant group i alkenones and isochrysidales in surface sediments from three maar lakes white fish north killeak and devil mountain using a combination of lipid biomarker and 18s rrna gene sequencing analyses our discovery adds to the expanding list of oligotrophic freshwater lakes where group i alkenones are found and water chemistry data contribute to the understanding of the environmental controls on group i isochrysidales our results further confirm the use of the u 37 k index of group i alkenones as a proxy for the mean temperature of the spring isotherm mtsi and rik37 as a quantitative measurement for isochrysidales group mixing we also demonstrate the analytical challenges for analyzing alkenones in freshwater lakes and the effectiveness of eliminating coelution using silver thiolate chromatographic material agtcm

establishment of euxinic conditions in the holocene black sea the paleoenvironmental evolution of the black sea is closely linked to the ingression of mediterranean seawater over the bosporus sill after the last glacial maximum we have reconstructed the temporal and spatial development of the black sea suboxic chemocline which divides oxic surface water from anoxic sulfi dic euxinic deep water by combining high resolution geochemical records of bulk parameters carbonate total organic carbon sulfur trace metals cu mo v and an isotopic proxy 56 fe from seven sediment cores in the black sea we generated a single composite geochemical core log that serves as a reference archive for the entire basin our proxy records refl ect the changing depositional and redox conditions of the black sea and permit us to estimate the infl ow budget of mediterranean seawater throughout the holocene our data indicate a gradual rise of the chemocline until ca 5 3 ka when suboxic waters fl ooded the shelf for the fi rst time trace metal and isotopic inventories document one major descent of the chemocline since the onset of brackish marine conditions before the present stable situation was established

north atlantic control on precipitation pattern in the eastern mediterranean black sea region during the last glacial based on proxy records from western black sea cores we provide a comprehensive study of climate change during the last glacial maximum and late glacial period in the black sea region for the first time we present a record of relative changes in precipitation for nw anatolia based on variations in the terrigenous supply expressed as detrital carbonate concentration the good correspondence between reconstructed rainfall intensity in nw anatolia and past western mediterranean sea surface temperatures ssts implies that during the glacial period the precipitation variability was controlled like today by mediterranean cyclonic disturbances periods of reduced precipitation correlate well with low ssts in the mediterranean related to heinrich events h1 and h2 stable oxygen isotopes and lithological and mineralogical data point to a significant modification in the dominant freshwater sediment source concomitant to the meltwater inflow after 16 4 cal ka bp this change implies intensification of the northern sediment source and with other records from the mediterranean region consistently suggests a reorganization of the atmospheric circulation pattern affecting the hydrology of the european continent the early deglacial northward retreat of both atmospheric and oceanic polar fronts was responsible for the warming in the mediterranean region leading simultaneously to more humid conditions in central and northern europe