holocene climate optimum and last glacial maximum in the mediterranean the marine oxygen isotope record reconstructions with comprehensive estimates of confidence intervals are presented of changes in the w e stable oxygen isotope gradient in mediterranean surface waters between the holocene climate optimum and the present and between the last glacial maximum and the present rigorous statistical assessment is made of the significances of the mean geographic trends observed in these reconstructions firstly it is concluded that any reconstruction should strictly be based on values obtained by analyses of one single foraminiferal species throughout the basin as different species are found to respond with isotopic variations of different amplitudes to climatic hydrographic change this difference is tentatively related to differences between the habitats and seasons of growth of the various species secondly a significant increase of roughly a factor 3 is found in the mediterranean w e oxygen isotope gradient during the last glacial maximum relative to the present this difference is almost entirely due to increased glacial values in the levantine sea which are considered to be a result of a combination of increased evaporation rates and or somewhat cooler than anticipated surface water conditions thirdly an eastward increase of roughly half the present day magnitude is found for the w e oxygen isotope gradient during the holocene climate optimum values in the levantine sea appear to have undergone up to 0 3 more depletion than those elsewhere in the eastern mediterranean however no significant trends are found between the eastern and western parts of the levantine sea nor between values near the nile delta and those from elsewhere in the levantine sea the holocene climate optimum s eastward increase in the mediterranean oxygen isotope gradient although weaker than the present suggests that the mediterranean continued to function as a concentration basin albeit in a less vigorous way than today finally simple mixing arguments are used to argue that inferred oxygen isotope ratios of surface waters may not be used as an indication of conservative property e g salinity distribution on geological timescales but instead show amplitudes of response to climatic hydrographic changes that likely are 2 times larger than the corresponding amplitudes of response for truly conservative properties

variations in mode of formation and temperature of oceanic deep waters over the past 125 000 years marked changes in the deep water temperature of the different oceanic basins during the past 125 kyr are revealed by a detailed comparison of the oxygen isotopic composition ofbenthicforaminiferafrom sediment cores taken from the norwegian sea and the pacific atlantic and southern oceans the last interglacial deep water temperatures were similar to the modern ones at the 5e 5d transition around 115 kyr bp the deep water temperatures dropped below approximately 0 c in the pacific and southern indian oceans in the atlantic ocean the deep water temperature dropped in 2 successive steps at 115 and 75ky bp the global ocean deep water temperatures were in the 0 to 1 c range for the whole of the last ice age isotope stages 4 2

oxygen isotope analyses and pleistocene ice volumes abstract the oxygen isotope record from fossil foraminifera in deep sea sediments is commonly used as a proxy for global ice volume the linkage between 18 o and ice volume however is probably nonlinear we have developed a simple numerical model of the isotopic response of the oceans to ice volume change the major features it simulates are 1 the changing mean isotopic composition of snow as a function of ice volume colder snow temperatures forced by climate change and higher elevation accumulation areas imply more negative mean 18 o 2 the nonequilibrium isotopic composition of ice sheets the past history of an ice sheet is integrated into its mean isotopic composition which introduces a lag of isotopic ice volume i e the measured 18 o record scaled to ice volume units behind true ice volume 3 selective preservation of isotopically more negative colder higher latitude ice this geographic effect can selectively amplify or dampen the isotopic response to the ice volume signal we illustrate the response of our model to simple hypothetical ice volume transitions of ice growth and ice decay sensitivity tests are illustrated for all model parameters the results suggest that oxygen isotope records reproduce the general patterns of ice volume change fairly accurately the foraminiferal isotope record however may misrepresent the true amplitude of the ice volume signal and lag true ice volume by 1000 to 3000 yr

holocene trends in 18o in land snail shells from the negev desert and their implications for changes in rainfall source areas abstract the 18o value of the carbonate of land snail shells is related to the 18o content of precipitation which in turn relates to the source region and trajectory of the rain bearing air masses analyses of 18o of the shell carbonate of 76 radiocarbon dated holocene samples of the land snail trochoidea seetzeni from the northern negev desert in southern israel were carried out and the results were compared to modern snails from the same region early holocene 18o values are similar to modern but during the period centered around 6500 6000 yr b p a depletion of some 2 below modern is observed a change in the atmospheric circulation pattern for this period is thus indicated most likely an increase in the frequency of storm systems reaching the region from north eastern africa by 3500 yr b p 18o values had reached modern levels and indicate a stable pattern of atmospheric circulation since that time

stable isotope anomalies in mediterranean pleistocene records oxygen and carbon isotope records of twelve mediterranean cores raised from west alboran sea to east off israel and of four atlantic cores raised from the western side of gibraltar and located respectively inside below and beyond the modern mediterranean outflow are compared to open ocean records of core 71 139c from the north atlantic and core v19 30 from the east pacific oxygen isotope stratigraphies can be established for deep mediterranean records and the major events of the last 150 ka are easily identifiable for instance the five substages of stage 5 or the 18 ka event stage 2 are identified but the 10 ka event younger dryas is only recorded by globigerina bulloides and benthic foraminifera suggesting that the cooling affected only winter sst 14c dates for the two terminations ia and ib of the last deglaciation which are recorded in sediment cores from areas with high sedimentation rates faro ridge alboran sea sicilian strait are in good agreement with the dates published for the same termination in atlantic cores an intermediate step however has been identified in some cores at 14 ka and divides termination ia into two phases oxygen isotope anomalies are recorded by the shallow water species globigerinoides ruber they correspond to 1 a higher amplitude glacial interglacial change in 18o values which exceeds that of the open ocean by 1 in the western basin and by 1 7 in the eastern basin 2 large isotopic depletions during the deposition of sapropel s1 s3 and s5 they are interpreted as the result of fresh water run off responsible for a strong dilution in the shallower layers of the east mediterranean waters the isotopic effect of this dilution averages 0 75 for sapropel s1 and 1 6 for sapropel s5 during the last glacial maximum the mediterranean still acted as a concentration basin and a gradient of 18o values similar to the modern one 0 75 existed from west to east in the deep waters apparently deep water temperatures were lower during the last glacial but the decrease did not exceed 4 c in the eastern basin major anomalies are also contained in the 13c records of g bulloides and benthic foraminifera the 13c records from surface intermediate and deep waters of the eastern basin and from intermediate and deep waters of the western basin are opposite to that of the open ocean during glacial time 13c values were higher in intermediate and deep waters of the whole mediterranean and also in surface water of the eastern basin at the same time the 13c gradient of surface to deep waters was low this gradient increased during the last deglaciation while 13c values of g bulloides and benthic foraminifera decreased this decrease interrupted at 10 ka may have been related to increased fresh water run off from the bordering contintents due to increased precipitation especially in the tropical belt the 13c depletion is clearly recorded in the levantine and deep water masses and can be traced westward in the mediterranean outflow oxygen and carbon isotope anomalies recorded simultaneously in the east mediterranean by the shallow water species globigerinoides ruber during sapropel deposition indicate that increased precipitation on the bordering continents and strong fresh water run off during the time of the last deglaciation may have caused a density stratification and deep stagnation in the eastern basin uncertainties arise from the fact that in the mixing model deglacial mediterranean waters are mixed with continental fresh waters the isotopic characteristics of which are not entirely understood although increased surface water production of biogenic material can not be excluded as a possible cause of 13c depletion it appears that the river discharge including the nile as well as black sea input are also plausible sources for the fresh water layering

distribution patterns of live planktic foraminifers as related to regional hydrography and productive systems of the mediterranean sea abstract distribution patterns of live planktic foraminifers are examined at two times of the year late summer and late winter through horizontal plankton towing along a nw se transect across the west and east mediterranean basins and in the alboran sea french oceanographic cruises vicomed i ii and iii respectively foraminiferal production is significantly different in the two sampling periods and across the west and east mediterranean foraminiferal density is higher in winter than summer e g in the western basin 3700 specimens 1000 m3 in winter against 200 600 specimens 1000 m3 in summer the production averaged for the two sampling sets is higher in the western basin than in the eastern one however in late summer peaks of maximal production are observed in the central mediterranean strait of sicily and ionian basin 1000 to 2000 specimens 1000 m3 where the assemblages are dominated by globigerinoides ruber rosea and g ruber alba in the mediterranean sea frontal regions and semipermanent eddies which are essentially controlled by regional hydrography represent a significant portion of the regional production they also elicit a higher diversity of species their influence is observed in summer as well as in winter at the end of summer the rather shallow mixed layer hosts spinose symbiont bearing species such as g ruber alba g ruber rosea o universa and g trilobus at that season in the western basin the nutrient content of the mixed layer is generally low and the surface layer is rapidly nutrient depleted summer foraminiferal production remains low at the surface with respect to the winter production in the eastern basin late summer and autumn correspond to the biological spring summer foraminiferal production in surface waters is higher than in winter but standing crops are lower than in the western basin for the same species at the same period in summer however frontal structures and eddies are generally better developed than in winter in some particular cases frontal boundaries in the western basin eddies south of cyprus nutrients from intermediate layers can be upwelled through isopycnal or diapycnal mixing to the photic zone and allow for secondary blooms in the western basin these blooms favour the development of grazers at depth globorotalia truncatulinoides g inflata south of cyprus in the eastern basin oligotrophic conditions promote the development of heterotrophic organisms and predatory foraminifers have higher standing stocks g ruber alba g ruber rosea in winter the break down of the thermocline combined with deep turbulent mixing in the northwestern basin and the deepening of the mixed layer in the alboran sea and along the north african coast result in increased phytoplankton biomass and favour reproduction and proliferation of species such as g truncatulinoides or g inflata our observations indicate that the geographic and depth distribution of live foraminiferal species cannot be entirely explained by the general temperature and salinity differences among the different mediterranean basins but that they are strongly related to regional hydrographic patterns hydrography controls the seasonality and depth of the turbulent mixing which differ between the western and the eastern basins the depth of the mixed layer and its seasonal stratification and the strength of the pycnocline nutrient supply and primary production are mostly regulated by these dynamics one may therefore expect that the species assemblages on the sea floor and in deep sea cores will also correlate to the various hydrographic parameters of the overlying water masses

african monsoon variability during the previous interglacial maximum abstract little is known about centennial to millennial scale climate variability during interglacial times other than the holocene we here present high resolution evidence from anoxic unbioturbated sediments in the eastern mediterranean sea that demonstrates a sustained 800 yr climate disturbance in the monsoonal latitudes during the eemian interglacial maximum 125 ka bp results imply that before and after this event the intertropical convergence zone itcz penetrated sufficiently beyond the central saharan watershed 21 n during the summer monsoon to fuel flooding into the mediterranean along the wider north african margin through fossil river wadi systems that to date have been considered only within a holocene context relaxation in the itcz penetration during the intra eemian event curtailed this flux but flow from the nile with its vast catchment area was not affected previous work suggests a concomitant eurasian cooling event with intensified impact of the higher latitude climate on the mediterranean basin the combined signals are very similar to those described for the holocene cooling event around 8 ka bp the apparent type of concurrent changes in the monsoon and higher latitude climate may reflect a fundamental mechanism for variability in the transfer of energy latent heat between the tropics and higher latitudes

northern levantine and adriatic quaternary planktic foraminifera reconstruction of paleoenvironmental gradients rohling e j jorissen f j vergnaud grazzini c and zachariasse w j 1993 northern levantine and adriatic quaternary planktic foraminifera reconstruction of paleoenvironmental gradients mar micropaleontol 21 191 218 a detailed study of the planktic foraminiferal records of three cores recovered near crete shows very consistent changes unfortunately the record of t87 2 13g our shallowest core is bioturbated too much for detailed comparisons but it can still be used to discuss the general trends the mutual record of the other two cores t87 2 20g and t87 2 27g extends back to about 125 000 yr b p principal components analyses performed on the combined records of t87 2 20g and t87 2 27g yield two axes that can be interpreted paleoecologically namely a temperature axis and an annual stability axis the latter is a measure of stratification within the euphoric layer in this study we consider t87 2 20g and t87 2 27g to be reference cores for the eastern mediterranean subsequently we interprete the faunal variation in two cores from the adriatic sea in 68 5 and in 68 9 containing records extending back to 15 000 and 18 000 yr b p in the context of these reference cores this is done by calculating scores of the adriatic records along the two relevant pca axes derived from the northern levantine records also cluster analyses of the adriatic and northern levantine records are compared on the average the adriatic sea appears to have been considerably colder than the region around crete during the past 18 000 years this temperature difference was largest during the pleniglacial and only small during the holocene we found no distinct expression of a younger dryas cooling event in the adriatic records neither on our pca axis nor in the oxygen isotope record this contradicts previous paleoclimatic reconstructions based mainly on paleobotanical evidence which suggests that the younger dryas event greatly influenced circum mediterranean areas as yet we have no ready explanation for this discrepancy low annual stability values dominate both the pleniglacial and the holocene intervals of the adriatic records this suggests that homothermal conditions were as prevalent in the adriatic euphoric layer at pleniglacial times as they are at present in the present day adriatic homothermal conditions are associated with deep convection and subsequent eastern mediterranean deep water emdw formation and therefore our data suggest that emdw formation was as effective at pleniglacial times as it is at present high annual stability values in the transitional interval from 12 700 to 9600 yr b p in the adriatic records are suggestive of low emdw formation rates at that time in combination with high productivity throughout the eastern mediterranean which has previously been inferred from the planktic foraminiferal record these low emdw formation rates may have preconditioned the eastern mediterranean for sapropel formation

adriatic deep water formation during the holocene implication for the reoxygenation of the deep eastern mediterranean sea under modern conditions the reoxygenation of eastern mediterranean deep water is the result of the formation of dense bottom water in the southern adriatic sea oxygen isotopic records of planktonic foraminfera used as a paleosalinity tracer show that po river and or the alpine glaciers meltwater are not directly responsible of the inhibition of the deep water formation in the adriatic during sapropel s1 formation at 9 000 years b p sedimentological evidence indicates that fully oxygenated conditions in the deep adriatic occurred only by 1 650 100 years b p a long time after the total reoxygenation of the deep eastern mediterranean organic carbon content and isotopic ratio indicate that persistence of a reduced sediment phase until 1 650 years b p does not result from increased primary productivity or large input of terrestrial organic matter

surface water temperature salinity and density changes in the northeast atlantic during the last 45 000 years heinrich events deep water formation and climatic rebounds we developed a new method to calculate sea surface salinities sss and densities ssd from planktonic foraminiferal 18o and sea surface temperatures sst as determined from planktonic foraminiferal species abundances sst sss and ssd records were calculated for the last 45 000 years for biogeochemical oceanic flux study bofs cores 5k and 8k recovered from the northeast atlantic the strongest feature is the dramatic drop in all three parameters during the heinrich ice rafting events we modelled the possibility of deepwater formation in die northeast atlantic from the ssd records by assuming that the surface waters at our sites cooled as they flowed further north comparison with modelled north atlantic deepwater densities indicates that there could have been periods of deepwater formation between 45 000 and 30 000 14c years b p interrupted by iceberg meltwater input of heinrich event 3 and 4 at 27 000 and 38 000 14c years b p and during the holocene no amount of cooling in the northeast atlantic between 30 000 and 13 000 years could cause deep water to form because of the low salinities resulting from the high meltwater inputs from icebergs our records indicate that after each heinrich event there were periods of climatic rebound with milder conditions persisting for up to 2000 years as indicated by the presence of warmer and more saline water masses after these warm periods conditions returned to average glacial levels these short term cold and warm episodes in the northeast atlantic are superimposed on the general trend towards colder conditions of the last glacial maximum lgm heinrich event 1 appears to be unique as it occurs as insolation rose and was coeval with the initial melting of the fennoscandian ice sheet we propose that meltwater input of heinrich event 1 significantly reduced north atlantic deep water formation reducing the heat exchange between the low and high latitudes thus delaying deglaciation by about 1500 radiocarbon years 2000 calendar years

rainy periods and bottom water stagnation initiating brine accumulation and metal concentrations 1 the late quaternary a working hypothesis is proposed to account for the present accumulation of brines in isolated pockets of the ocean floor and for the formation of the underlying organic and metal rich sediments these are the tyro and bannock basins in the east mediterranean the red sea deeps and the orca basin in the northern gulf of mexico initiation of brine derived deposition in the red sea deeps and orca basin occurred between 12 000 and 8000 years b p this time bracket also encompasses the formation of the latest east mediterranean sapropel and the wettest global climate since the last glacial maximum this wet period first appeared in the tropics around 12 000 years b p then in the subtropical and middle latitudes during the same period the 23 000 year precession cycle brought the summer insolation of the northern hemisphere to its peak at 11 000 years b p with retreating northern hemisphere ice sheets the red sea deeps and the orca basin became anoxic during this humid period and metal rich sapropel deposition then began in contrast the tyro and bannock basins began accumulating a brine long before and persisted beyond this climatic stage the hypothesis involves two propositions 1 as in the eastern mediterranean sea marine anoxia was mainly the consequence of the large influx of continental runoff and local precipitation longer residence time of bottom waters so called stagnation in silled rimmed basins would have resulted from lower salinity at the sea surface in areas of deep water formation in the eastern mediterranean the red sea and the gulf of mexico and 2 miocene or older evaporites underlie these basins or outcrop on their flanks leaching from these evaporites was an ongoing process before the quasi stagnation phase but the initial leachate much less saline than the present brines was continuously flushed by bottom circulation the climate induced quiescence of bottom waters in these basins enabled the leachate to accumulate the feedback of stagnation by increased density progressively raised the salinity of entrapped bottom waters to the present brine concentration the high density has resisted brine removal by bottom circulation until present time long after cessation of the initiating wet period the brines therefore are stagnant fossil waters

nile water as a cause of eastern mediterranean sapropel formation evidence for and against during the late pleistocene sapropels layers of organic carbon rich sediment formed throughout the entire eastern mediterranean basin in close association with glacial interglacial transitions the current theory for the mechanism of sapropel formation involves a density stratification of the water column due to the invasion of a large quantity of low saline water which resulted in oxygen depletion of the bottom waters most workers believe that this low salinity water was glacial meltwater that entered the mediterranean via the black sea and a series of interconnected glacial lakes but the suggestion also has been made that the freshwater originated from the nile river in this study the oxygen isotope values of planktonic foraminifera globigerinoides ruber have been examined in six gravity cores and one piston core from the southern levantine basin and compared with the oxygen isotope records ofg ruber from other areas of the eastern mediterranean this study deals mainly with the latest sapropel which was deposited approximately 7000 to 9000 years ago results indicate that nile discharge probably does reduce salinities somewhat in the immediate area surrounding the mouth of the nile but this water is rapidly mixed with the highly saline waters of the easternmost mediterranean using a mixing equation and surface water salinity limitations an approximate oxygen isotope balance of surface waters was calculated for the time of latest sapropel deposition this calculation shows that neither nile river discharge nor black sea input nor both together are large enough to account for the large scale oxygen isotope depletion associated with latest sapropel deposition in the eastern mediterranean this suggests that part of the isotopic change at termination i is probably due to increased surface water salinities during the last glacial maximum in addition evidence from the timing of sapropel 1 deposition and the dissolved oxygen balance indicates that deposition of the latest sapropel is associated with increased surface water production of biogenic material as much as three times higher than that of present day

error analysis of paleosalinity calculations a detailed error analysis is performed for the calculation of open ocean salinity changes from carbonate oxygen 18 proxy data measurement errors are generally negligible however errors due to the goodness of fit of various regressions used in the calculation are significant depending on the method used and on the proxies available error bars 1 for the salinity range from 0 6 to 1 8 in particular expected errors for the midlatitude and tropical salinity differences at the last glacial maximum are around 1 1 to 2 5 the largest errors occur because of the differences between temporal and spatial seawater oxygen 18 salinity relationships and through the use of nonconcurrent temperature measurements methods of improving paleosalinity estimates should focus on eliminating these large sources of uncertainty

the timing of mediterranean sapropel deposition relative to insolation sea level and african monsoon changes the mediterranean basin is sensitive to global sea level changes and african monsoon variability on orbital timescales both of these processes are thought to be important to the deposition of organic rich sediment layers or sapropels throughout the eastern mediterranean yet their relative influences remain ambiguous a related issue is that an assumed 3 kyr lag between boreal insolation maxima and sapropel mid points remains to be tested here we present new geochemical and ice volume corrected planktonic foraminiferal stable isotope records for sapropels s1 holocene s3 s4 and s5 marine isotope stage 5 in core lc21 from the southern aegean sea the records have a radiometrically constrained chronology that has already been synchronised with the red sea relative sea level record and this allows detailed examination of the timing of sapropel deposition relative to insolation sea level and african monsoon changes we find that sapropel onset was near synchronous with monsoon run off into the eastern mediterranean but that insolation sapropel monsoon phasings were not systematic through the last glacial cycle these latter phasings instead appear to relate to sea level changes we propose that persistent meltwater discharges into the north atlantic e g at glacial terminations modified the timing of sapropel deposition by delaying the timing of peak african monsoon run off these observations may reconcile apparent model data offsets with respect to the orbital pacing of the african monsoon our observations also imply that the previous assumption of a systematic 3 kyr lag between insolation maxima and sapropel midpoints may lead to overestimated insolation sapropel phasings finally we surmise that both sea level rise and monsoon run off contributed to surface water buoyancy changes at times of sapropel deposition and their relative influences differed per sapropel case depending on their magnitudes sea level rise was clearly important for sapropel s1 whereas monsoon forcing was more important for sapropels s3 s4 and s5

contrast in surface water δ18o distributions between the last glacial maximum and the holocene in the southern south china sea abstract published core data of planktonic foraminiferal 18o and alkenone sea surface temperature sst are used to investigate seawater 18o w distributions in the south china sea scs during the last glacial maximum lgm and the holocene the holocene w distributions show a pattern correlated to modern salinity distributions displaying an increasing trend from the south to the north however the lgm w distributions show a different pattern displaying increasing values from the central to the southern scs and the lgm holocene differences in w w corrected by ice volume effect though negative in values display decreasing amplitude toward the south both of which could suggest increasing salinity toward the south by conventional approach this is somewhat counter intuitive because enhanced freshening could be expected for the southern scs due to extra discharge from the river systems on the emerged sunda land during the lgm here we propose an alternative explanation to reconcile the lgm w and w distributions with the above expectation in the proposal changes in w salinity relationship i e lowering the w salinity slope due to significant runoff contributions to freshwater input and less 18o depleted precipitation during the lgm are deeply discussed to reasonably explain the abnormity in lgm w distributions

late glacial holocene paleoclimatic and paleoceanographic evolution of the aegean sea micropaleontological and stable isotopic evidence abstract late glacial to holocene paleoclimatic and paleoceanographic changes are examined using records of calcareous and organic walled marine microfossils pollen and terrestrial spores and oxygen isotope data in cores from the aegean sea basins planktic foraminiferal coccolith and dinoflagellate data show that the late glacial holocene transition in the region was associated with a large warming of surface water mediterranean based paleotransfer functions for planktic foraminifera show a 5 10 c increase in surface water temperature from 14 000 to 9600 yr b p estimates of surface water oxygen isotopic composition 18 o w derived from planktic foraminiferal oxygen isotopic and transfer function data indicate that this warming was associated with a 2 0 to 2 5 reduction in 18 o w transfer function results indicate corresponding 1 0 to 1 5 salinity reductions for this tim ca 6400 9600 yr b p throughout the aegean sea pollen dinoflagellate and isotopic data show that the early holocene excess fresh water originated from rapid melting of the northern european and siberian ice sheets supplied primarily from the black sea by the opening of bosphorus and dardanelles channels during the post glacial sea level rise and supplemented by major rivers entering the aegean sea continuous outflow of fresh water into the aegean sea provided a low salinity surface lid preventing the ventilation of the deep water benthic foraminifera shows a major turn over that indicates low dissolved oxygen however bottom waters were not anoxic sapropel level s1 resulted from a combination of stagnant deep water in isolated depressions increased terrigenous organic matter and periods of high primary productivity as indicated by pollen and dinocysts respectively the surface water temperature and salinity reached present day values at 6400 yr b p with little subsequent change despite the major deforestation onshore

pluvial conditions in the eastern sahara following the penultimate deglaciation implications for changes in atmospheric circulation patterns with global warming during the transition from the penultimate glacial to the last interglacial period isotope stages 6 5e or terminal ii large freshwater lakes abruptly infilled sandy depressions in arid regions of the eastern sahara geochemical and mineralogical studies of samples from lacustrine sequences in the western desert of southern egypt indicate 1 the sediments are chalk composed of authigenic chemical precipitates predominantly low mg calcite with carbonate contents averaging about 80 the low dilution of the chemical precipitate by detrital input implies that physical erosion and transport of detrital grains were minimized by extensive vegetation cover in the catchment area the fauna and flora associated with the lake deposits and middle paleolithic occupation sites on the paleo shorelines attest to a more amenable environment 2 vastly different rainfall or atmospheric circulation patterns than at present must have existed based on consistently negative 18opdb values for the chalk as low as 9 5 which would require precipitation from lake waters significantly more depleted in 18o than the modern local spring water 18osmow 1 8 3 the lakes were stable perennial water bodies with relatively long residence times sufficient to produce isotopic covariant signals in the chalks apparently the lakes disappeared as abruptly as they appeared without going through a terminal phase of evaporative enrichment extremely arid conditions again prevailed during the transition from the last glacial to the present interglacial terminal i a similar change from arid to pluvial conditions occurred thus it is proposed that during transitions from glacial to interglacial climates rapid global warming can lead to temporary alteration to atmospheric circulation with an intersification of the southwest monsoons bringing large quantities of isotopically light moisture to the eastern sahara

the nature distribution and origin of a sapropelic layer in sediments of the silicia basin northeastern mediterranean a sapropelic layer with organic carbon contents of 1 0 1 5 in contrast to the usual 0 2 0 5 of adjacent normal basin sediments is found to be widespread in sediment cores collected from the cilicia basin northeastern mediterranean the horizon is thought to be equivalent to the s1 sapropel of other workers it is finely laminated with no evidence of bioturbation has a very markedly low magnetic susceptibility and contains a significantly higher content of pollen and plant debris than is found in the normal basin sediment the stable oxygen and carbon isotope values suggest that the layer formed during post glacial climatic warming when fresh nutrient rich surface water flowed into the cilicia basin from the surrounding land to produce a stratified water mass which allowed the development of anoxic bottom waters the distribution of the sapropelic layer indicates that anoxic conditions extended to within approximately 350 m of sea level during deposition a depth shallower than previously recorded in the eastern mediterranean

cenomanian turonian and δ13c and δ18o sea level and salinity variations at pueblo colorado stable isotopes of the surface dwelling planktic foraminifera hedbergella planispira its abundance variations and mineralogical analysis of the cenomanian turonian at pueblo co reveal cyclic variations in surface salinity due to changes in precipitation freshwater influx marine incursions and long term sea level fluctuations hedbergella planispira is a proxy for salinity variations as indicated by 2 4 more negative 18o values in intervals of peak abundances as compared to intervals with reduced populations negative 18o values reflect periods of brackish surface waters caused by freshwater influx during wet humid periods accompanied by increased clastic transport more positive 18o values reflect more normal marine salinities as a result of arid periods and or marine incursions and correlate with intervals of increased biogenic carbonate deposition the magnitude of salinity variations during the low sea level of the hartland shale is twice that during the sea level transgression of the bridge creek limestone the rapid positive 13c shift that marks the onset of oceanic anoxic event 2 oae 2 at pueblo occurred over a period of about 100 ky 93 90 94 00 ma and coincided with the major sea level transgression that culminated in the deposition of the basal bridge creek limestone a positive 13c shift also occurred in the rotalipora cushmani zone prior to oae 2 and coincided with a sea level rise and enhanced preservation of terrestrial organic matter the likely cause for oae 2 is depletion of 12c in the water column as a result of high primary productivity whereas an earlier r cushmani zone event was primarily caused by increased input of terrigenous organic matter both 13c events are associated with enhanced organic matter preservation and anoxic or dysoxic bottom waters

three hundred eighty thousand year long stable isotope and faunal records from the red sea influence of global sea level change on hydrography stable isotope and faunal records from the central red sea show high amplitude oscillations for the past 380 000 years positive 18o anomalies indicate periods of significant salt buildup during periods of lowered sea level when water mass exchange with the arabian sea was reduced due to a reduced geometry of the bab el mandeb strait salinities as high as 53 and 55 are inferred from pteropod and benthic foraminifera 18o respectively for the last glacial maximum during this period all planktonic foraminifera vanished from this part of the red sea environmental conditions improved rapidly after 13 ka as salinities decreased due to rising sea level the foraminiferal fauna started to reappear and was fully reestablished between 9 ka and 8 ka spectral analysis of the planktonic 18o record documents highest variance in the orbital eccentricity obliquity and precession bands indicating a dominant influence of climatically driven sea level change on environmental conditions in the red sea variance in the precession band is enhanced compared to the global mean marine climate record specmap suggesting an additional influence of the indian monsoon system on red sea climates

sonic and gamma ray astrochronology cycle to cycle calibration of atlantic climatic records to mediterranean sapropels and astronomical oscillations a high resolution analysis of cyclical patterns in gamma ray and sonic logs of the lower pliocene sediments from the gulf of cadiz southern spain was carried out results suggest that these cycles can be successfully used for a bed to bed correlation with the global reference section for the astronomical time scale in capo rossello sicily cycle patterns were used to tune the logs to the astronomical solutions of j laskar the gamma ray and sonic cyclicity was interpreted in terms of precession induced oscillations of annual rainfall in southern spain that were in part responsible for the increasing input of freshwater into the mediterranean at times of sapropel formation we demonstrate that gamma ray and sonic astrochronology can be successfully used for interregional correlation and astronomical dating with errors not higher than 20 k y

oxygen isotopic composition of the mediterranean sea since the last glacial maximum constraints from pore water analyses abstract interstitial waters recovered from ocean drilling program leg 161 site 976 in the western mediterranean sea are used in conjunction with a numerical model to constrain the 18o of seawater in the basin since the last glacial maximum including sapropel event 1 to resolve the oxygen isotopic composition of the deep mediterranean we use a model that couples fluid diffusion with advective transport thus producing a profile of seawater 18o variability that is unaffected by glacial interglacial variations in marine temperature comparing our reconstructed seawater 18o to recent determinations of 1 0 for the mean ocean change in glacial interglacial 18o due to the expansion of global ice volume we calculate an additional 0 2 increase in mediterranean 18o caused by local evaporative enrichment this estimate of 18o change due to salinity variability is smaller than previous studies have proposed and demonstrates that mediterranean records of foraminiferal calcite 18o from the last glacial period include a strong temperature component paleotemperatures determined in combination with a stacked record of foraminiferal calcite depict almost 9 c of regional cooling for the last glacial maximum model results suggest a decrease of 1 1 in seawater 18o relative to the modern value caused by increased freshwater input and reduced salinity accompanying the formation of the most recent sapropel the results additionally indicate the existence of isotopically light water circulating down to bottom water depths at least in the western mediterranean supporting the existence of an anti estuarine thermohaline circulation pattern during sapropel event 1

a review of ecogeochemistry approaches to estimating movements of marine animals ecogeochemistry the application of geochemical techniques to fundamental questions in population and community ecology has been used in animal migration studies in terrestrial environments for several decades however the approach has received far less attention in marine systems this review includes comprehensive meta analyses of organic zooplankton 13c and 15n values at the base of the food web dissolved inorganic carbon 13c values and seawater 18o values to create for the first time robust isoscapes for the atlantic ocean these isoscapes present far greater geographic variability in multiple geochemical tracers than was previously thought thus forming the foundation for reconstructions of habitat use and migration patterns of marine organisms we review several additional tracers including trace element to calcium ratios and heavy element stable isotopes to examine anadromous migrations we highlight the value of the ecogeochemistry approach by examining case studies on three components of connectivity dispersal and natal homing functional connectivity and migratory connectivity we also discuss recent advances in compound specific stable carbon and nitrogen isotope analyses for tracking animal movement a better understanding of isotopic routing and fractionation factors particularly of individual compound classes is necessary to realize the full potential of ecogeochemistry

modeling a 200 yr interruption of the holocene sapropel s1 an oceanic general circulation model previously used to simulate the conditions associated with the holocene sapropel s1 is used to simulate the effects of a climate deterioration represented as a cooling event on the sapropelic circulation mode the enhanced cooling 2 3 c induces deep convection in the adriatic and the gulf of lions and intermediate water formation in the aegean where in all cases there had previously been only stagnant unventilated waters the depths of ventilation to 1250 m are in agreement with core data from this period the short decadal timescales involved in modifying the sapropelic circulation suggest that such a climatic deterioration may be associated with the interruption of s1 between 7100 and 6900 14c yr b p which divided the sapropel into two subunits

glacial holocene salinity changes in the mediterranean sea hydrographic and depositional effects oxygen isotope changes as recorded by pleistocene foraminifera from open ocean sediments are primarily a function of changes in the isotopic composition of the global seawater reservoir caused by ice volume changes with a secondary temperature component1 oxygen isotope records from marginal basins such as the gulf of mexico2 the mediterranean sea3 5 and the red sea6 also exhibit the global signal but are far more complicated owing to the strong overprint of local climate conditions in particular glacial interglacial changes in continental aridity and river runoff produce significant salinity changes in these semi enclosed basins using available oxygen isotope records we estimate that glacial 18 000 yr bp salinities in the eastern and western mediterranean sea were 2 7 and 1 2 higher respectively than at present these elevated glacial salinities played an important part in preconditioning the eastern mediterranean for the eventual accumulation of organic carbon rich sediments sapropels at the end of deglaciation

the oxygen and carbon isotope distribution in the mediterranean water masses abstract the oxygen and carbon stable isotope compositions of the present day mediterranean waters have been measured in order to evaluate their variability which is related to the specific climatic and hydrological conditions within the basin the experimental equation between the 18 o value and the salinity of water based on 300 measurements on surface intermediate and deep waters sampled during the vicomed 2 and 3 cruises in the western central and eastern mediterranean has a slope of 0 27 a value which is significantly lower than the slope of 0 45 as defined in the northeast atlantic ocean this difference in the 18 o salinity relationship which occurs immediately in the alboran basin is basically a characteristic of the climatic regime of the mediterranean i e of an excess evaporation over fresh water input the largest variations of these two parameters 18 o of water and 13 c of co 2 are observed in the surface waters mostly in the western mediterranean this evolution mirrors the progressive eastward restriction which separates the less evaporated and more productive western basins from the more evaporated and less productive eastern basins the intermediate waters constitute a homogeneous layer however their 18 o values decrease eastward by 0 35 at maximum due to progressive dilution by mixing with overlying and underlying water masses their 13 c values decrease also eastward by 0 35 at maximum due to an increasing input of nutrients issued from the regeneration of sinking organic particles the deep waters have similar 18 o values but slightly higher 13 c values often by less than 0 1 than the overlying intermediate waters indicating generally well ventilated conditions due to active winter convection

oxygen isotopes from phorcus osilinus turbinatus shells as a proxy for sea surface temperature in the central mediterranean a case study from malta abstract the marine topshell phorcus osilinus turbinatus is a common component of many archaeological sites in the mediterranean this species has been successfully used as a palaeoclimate proxy in italy to test whether 18 o from p turbinatus shells can serve as a reliable palaeoclimate archive for other regions of the mediterranean we collected live p turbinatus from the northeast coast of malta each month for a year the 18 o shell values of the outermost growth increments of these live collected shells ranged between 0 4 and 2 4 these values correspond to growing temperatures calculated from shell edge 18 o of between 15 c and 27 c calculated shell edge sea surface temperatures are highly correlated with instrumental records of sea surface temperature recorded over the period of collection the individuals analysed for this study are smaller than p turbinatus from populations studied elsewhere in the mediterranean nonetheless 18 o shell provides a robust record of sea surface temperatures suggesting that smaller younger shells in archaeological deposits can still provide reliable palaeothermometry records this study extends the upper growth limit p turbinatus by 2 c compared with the previous studies of p turbinatus in the mediterranean and suggests that contrary to the previous studies growth shutdown does not occur in all p turbinatus when sea surface temperatures exceed 25 c this may reflect the higher sample resolution that can be obtained from smaller faster growing shells or it may reflect actual higher growth tolerances of p turbinatus populations in malta by showing that p turbinatus precipitate their shells in 18 o equilibrium with surrounding sea water this study reinforces the potential for the stable isotope chemistry of p turbinatus shells preserved in mediterranean archaeological sites to provide a window into the climate and seasonality regimes of the past

eastern mediterranean palaeoclimates from 26 to 5 ka b p documented by pollen and isotopic analysis of a core in the anoxic bannock basin continuous pollen and isotopic records were established for core ban 84 09 gc retrieved from the anoxic bannock basin in the eastern mediterranean on the basis of two 14c dates they document the palaeoclimate between about 25 7 ka b p and 5 2 ka b p in the northern borderlands of the ionian basin the upper half of the core has been redeposited the isotopic record displays a correlation with pollen percentages that is strong and positive for artemisia sage brush and negative for quercus oak the last glacial maximum and the deglaciation are identified by these combined taxa together with chenopodiaceae the glacial maximum around 18 ka b p which has elsewhere been dated from 20 to 15 ka b p has pollen percentages that are high for artemisia and low for quercus the climate in the pollen source area was arid cold in winter briefly warm in summer and sustained the vegetation of a semi desert the onset of deglaciation after 18 ka b p coincides with that of the decline in artemisia pollen percentage however this decline does not indicate reduced aridity because it is accompanied by a pollen percentage rise of the even more arid herbs chenopodiaceae and ephedra throughout the deglaciation from 18 to 11 ka b p the aridity progressively increases culminating at 11 ka b p this trend is briefly interrupted by a more humid event shown by a peak in artemisia pollen percentage and a smaller peak in oak these two peaks are coeval with the bolling allerod chronozone 13 11 ka b p maximum aridity occurs during the younger dryas chronozone 11 10 ka b p afterwards the oak pollen percentage begins a steady increase and its maximum value is coeval with the lowest isotopic value dated at 8760 170 yr b p this period was one of high moisture warm summers and according to altitude mild to cool winters this climate sustained forests that were mediterranean in the lowlands and warm temperate in the uplands a high pollen concentration is observed during this period and reveals the presence of sapropel s1 which is otherwise unrecognizable in this entirely black core during the following period between 8760 170 and 5200 yr b p the 180 reverts to slightly higher values and the quercus pollen percentage decreases while the pollen percentage of the wetter ostrya the oriental hornbeam increases the high pollen concentration during the deposition of sapropel s1 cannot have been caused by increased pollen input into the sea this pollen being wind borne nor by increased pollen production for all taxa both trees and herbs we conclude that it is entirely due to increased preservation of this allochtonous organic material by the deep anoxia of the bottom water below a thick anoxic water column the coincidence of sapropel deposition with warm and humid local climate as well as with the second global meltwater pulse suggests that the cessation of bottom water ventilation was due to decreased surface water density resulting from less saline incoming atlantic surface water increased local runoff and warmer winters

on the late pleistocene holocene sapropel record of climatic and oceanographic variability in the eastern mediterranean sapropels and intercalated marls in a piston core from the eastern mediterranean are chemically and mineralogical distinct kaolinite smectite and total s contents fe a1 ba a1 co a1 mo a1 and v a1 are higher whereas quartz mg calcite illite contents si a1 ti a1 k a1 rb a1 and zr a1 are lower in the sapropels missing and ghost sapropels are identified by mineralogical and chemical properties that are not prone to diagenesis primary production was higher ba a1 and bottom water and or interstitial oxygenation was lower co a1 mo a1 ni a1 and v a1 during sapropel formation wind speeds quartz clay si a1 and zr a1 and bottom water salinities mg calcite calcite were higher during periods of marl formation sapropels represent a fundamentally different sedimentary facies whose formation is linked to changes in the hydrological balance in the basin driven by precessionally modulated changes in monsoon strength and subtropical precipitation changes which altered circulation production and sediment source areas

reef drowning during the last deglaciation evidence for catastrophic sea level rise and ice sheet collapse elevations and ages of drowned acropora palmata reefs from the caribbean atlantic region document three catastrophic metre scale sea level rise events during the last deglaciation these catastrophic rises were synchronous with 1 collapse of the laurentide and antarctic ice sheets 2 dramatic reorganization of ocean atmosphere circulation and 3 releases of huge volumes of subglacial and proglacial meltwater this correlation suggests that release of stored meltwater periodically destabilized ice sheets causing them to collapse and send huge fleets of icebergs into the atlantic massive inputs of ice not only produced catastrophic sea level rise drowning reefs and destabilizing other ice sheets but also rapidly reduced the elevation of the laurentide ice sheet flipping atmospheric circulation patterns and forcing warm equatorial waters into the frigid north atlantic such dramatic evidence of catastrophic climate and sea level change during deglaciation has potentially disastrous implications for the future especially as the stability of remaining ice sheets such as in west antarctica is in question

nature of the antarctic peninsula ice sheet during the pliocene geological evidence and modelling results compared abstract in this paper we examine the nature of the pliocene antarctic peninsula ice sheet by comparing the terrestrial and marine geological records of the antarctic peninsula and surrounding sea floor with estimated net snow accumulation in the region derived from numerical palaeoclimate model experiments pliocene geological data and our new modelling results are consistent and mutually supportive in suggesting that an ice sheet was present even during the warmest episodes of the pliocene the combined results suggest that the ice sheet in the antarctic peninsula is more robust to globally warmer conditions than is generally assumed at least up to the climatic limits examined in our study

ocean surface water response to short term climate changes revealed by coccolithophores from the gulf of cadiz ne atlantic and alboran sea w mediterranean the response of coccolithophore assemblages to short term millennial and centennial climatic changes over the last 50 kyr is studied in core m39029 7 from the gulf of cadiz atlantic ocean and core md95 2043 from the alboran sea western mediterranean sea the nannoplankton data are compared with oxygen isotopes u37k sst and other biogeochemical and sedimentological proxies to obtain a new perspective of the paleoceanography and paleoecology of the area during these short term climatic changes coccolithophores indicate that heinrich events he were characterised by the presence of cold low salinity and turbid water masses on both sides of the strait of gibraltar high abundances of the lower photic zone lpz species florisphaera profunda in the gulf of cadiz synchronous with he are interpreted as being an evidence of upper water column stratification on the atlantic side these episodes coincided with input of terrigenous material especially during h2 surface waters during dansgaard oeschger do stadials were also cold and turbid while most of do interstadials were characterised by warm water flora the increase in small placoliths small gephyrocapsa and emiliania huxleyi 4 m which is considered here as a cold water indicator the sharp decrease in large specimens of e huxleyi related to the warming trend in the last deglaciation can be used as a biostratigraphic reference level that marks at least approximately the deglaciation and the beginning of the holocene peaks of f profunda are observed during termination 1 t1 in the alboran sea they are isochronous with the organic rich layer 1 recognised in the western mediterranean in this interval the water column of the region was stratified as a consequence of the global increase in the sea level following the deglaciation quantitative analyses of the coccolithophore assemblage allow us to interpret that coccolithophore production has been higher in the alboran sea than in the gulf of cadiz during the holocene

aridity of the mediterranean sea at the last glacial maximum a reinterpretation of the δ18o record paleoclimate data show conflicting evidence for aridity in the mediterranean basin at the last glacial maximum lgm two recent modeling studies of the lgm mediterranean using water balance biome and ocean general circulation models respectively suggest that evaporation over the basin was reduced at the lgm compared with today in apparent conflict with these results is the strongly enhanced 18o signature of the lgm mediterranean surface waters particularly in the eastern basin which has been ascribed to a much higher salinity in an alternative interpretation presented here a box model of the balance between paleoclimate model evaporation and rainfall and paleoceanographic model advective terms shows that the observed lgm 18o signature can be reproduced without the need for an enhanced salinity with advection playing the dominant role in the 18o budget the box model also shows that the 18o data alone are insufficient to determine the type of exchange between the eastern and western basins the results emphasize that regional paleoceanographic water balances should consider all relevant processes and not just the evaporative flux

circulation changes and nutrient concentrations in the late quaternary aegean sea a nonsteady state concept for sapropel formation sapropel forming conditions we identify the start of seasonal stratification and highlight a lag in d 18 o response of the planktonic foraminifer n pachyderma to termination t1b as identified in the d 18 o record of g ruber by use of a simple model we determine that this offset cannot be a function of bioturbation effects the lag is of the order of 1 kyr and suggests that isolation of intermediate deep water preceded the start of sapropel formation by up to 1 5 kyr using this discovery we propose an explanation for the major unresolved problem in sapropel studies namely the source of nutrient supply required for export productivity to reach levels needed for sustained sapropel deposition we suggest that nutrients had been accumulating in astagnant basin for 1 1 5 kyr and that these accumulated resources wereutilized duringthe deposition of s1 in addition we provide a first quantitative estimate of the diffusive 1 e mixing timescale for the eastern mediterranean in its stratified sapropel mode which is of the order of 450 years index terms 1050 geochemistry marine geochemistry 4835 4850 3030 marine geology and geophysics micropaleontology 3339 meteorology and atmospheric dynamics ocean atmosphere interactions 0312 4504 4267 oceanography general paleoceanography 4870 oceanography biological and chemical stable isotopes keywords sapropel mediterranean holocene foraminifera climate variability

palaeoceanographic record of the last deglaciation in the strait of sicily abstract the palaeoceanographic evolution of the levantine waters during the last deglacial time is investigated using the sedimentary record of a deep sea core cs 70 5 from the linosa basin 35 44 4 n 13 11 0 e 1486 m water depth radiocarbon dating and oxygen isotope stratigraphy based on 18 o changes in globigerina bulloides allow us to recognize and to date the different steps of the deglaciation these steps are synchronous with those reported in the north atlantic but correspond to a 18 o decrease of higher amplitude than in the alboran sea or in the north atlantic ocean major faunal events permit the establishment of a local biozonation which differs from those reported either for the alboran sea or the eastern mediterranean basin major breaks in the faunal assemblages occurred during termination i a within the first step of the deglaciation around 14 kyr b p and near 10 6 kyr b p within the younger dryas the onset of the last deglaciation induced important changes in the characteristics of the levantine and atlantic water masses which occupied the strait of sicily the 13 c records of globigerina bulloides and cibicidoides pachyderma indicate that the modifications observed in the assemblages of deep faunas are controlled by the oxygenation of the water column 13 c records of globigerina bulloides are similar throughout the west mediterranean as well as in sediments located below the present mediterranean outflow the distributional pattern as well as its 13 c record suggest that this species could be a good recorder of the upper levantine waters and more precisely of the mixing layer of the overlying atlantic waters with the levantine ones major influxes of atlantic waters during terminations i a and i b could have slowed down the vertical mixing of the different water layers present in the strait of sicily and caused a decrease in the oxygenation of the water column during termination i b the effect of atlantic influxes was reinforced by the occurrence of a low salinity layer in the eastern basin which led to the stagnation of the deep waters the two episodes of decreased oxygenation in the levantine waters also favored the precipitation of inorganic magnesium calcite

postglacial connection of the black sea to the mediterranean and its relation to the timing of sapropel formation the opening of the connection between the mediterranean and black seas as sea level rose above the bosporus sill has long been associated with the formation of the most recent holocene sapropel deposit s1 in the eastern mediterranean but the mechanism has remained elusive we present a model for the opening of the black sea based on hydraulics arguments which demonstrates that increased freshwater flux out of the black sea began 500 1000 years after sea level reached sill depth and that the timescale for the increased freshwater flux that drained the freshwater reservoir of the black sea is about 2500 3500 years we argue that the increased freshwater discharge out of the black sea would lead to decreased deep water formation and higher productivity in the surface waters in the eastern mediterranean two conditions generally associated with sapropel formation the delay in increased freshwater flux after the opening of the black sea and the period of increased freshwater discharge appear to match the onset and duration of sapropel deposits in the eastern mediterranean

holocene paleoenvironment 7200 4000 cal bp of the los castillejos archaeological site se spain inferred from the stable isotopes of land snail shells abstract neolithic copper age and modern land snail shells from the los castillejos archeological site 37 20 n se iberian peninsula were analyzed for 13 c 12 c and 18 o 16 o ratios to estimate the paleoenvironmental conditions during shell deposition modern and ancient 13 c values ranged from 9 2 to 7 7 and from 13 6 to 5 7 respectively and they differed among taxa 13 c values were similar for neolithic 13 c 8 1 2 3 copper age 13 c 8 4 0 6 and modern 13 c 8 4 0 5 herbivorous cernuella specimens alternatively fossil shells of the herbivorous ferussacia folliculum 13 c 9 9 1 2 and the omnivorous rumina decollata 13 c 11 1 2 showed substantially lower 13 c values than modern specimens which may suggest lower water stress during the early to mid holocene than today the 18 o values from modern specimens ranged from 1 1 to 0 6 while the 18 o values from fossil specimens ranged from 6 7 to 0 and they differed among species cernuella exhibited shell 18 o values that increased from the neolithic 18 o 2 3 1 8 and copper age 18 o 1 7 0 6 to the present 18 o 0 3 0 5 the 18 o values of fossil shells of f folliculum 18 o 3 7 1 0 and r decollata 18 o 4 0 1 6 were also lower than modern shells calculations of a published snail flux balance mixing model for 18 o values indicate that early to mid holocene shells precipitated during times when relative humidity was greater than today the se iberian peninsula was noticeably wetter 7200 cal bp and experienced drier conditions thereafter the results are consistent with other regional paleoclimatic proxies and reinforce the potential use of land snail shells as paleoenvironmental archives

tyrrhenian sea tephrochronology of the oxygen isotope record for the past 60 000 years abstract a chronology of the marine oxygen isotope record of the past 60 ka is proposed by correlating eight marine ash layers with terrestrial volcanic deposits dated by the 14c and or k ar methods detailed oxygen isotope analyses were made on the planktonic foraminifera of three cores collected in the central tyrrhenian sea the origin of the ash layers was determined by major and trace elements analyses then the major pyroclastic terrestrial deposits were sampled and analysed in order to provide land sea correlations two ash layers occurred during the warm event that followed the first step of the deglaciation and which was dated at 12 6 0 5 ka b p another ash layer is present near the last glacial maximum that we have dated at 17 5 0 3 ka b p during isotopic stage 3 five ash layers were recognized and dated which allowed us to assign ages to the isotopically light oxygen peaks warmer interstadials at 31 1 5 ka and 33 4 1 6 ka denekamp at 37 5 2 ka hengelo and successively at 49 2 ka 52 4 2 2 ka 57 2 2 ka and 60 5 2 2 ka moershoofd complex

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

holocene snail shell isotopic record of millennial scale hydrological conditions in western mediterranean data from bauma del serrat del pont ne iberian peninsula land snail shells are a common component in mediterranean holocene archaeological deposits providing the opportunity to explore their potential as source of information concerning human behaviour and palaeoclimatic conditions many well preserved shells of the caenogastropod pomatias elegans were recovered along the holocene succession of bauma del serrat del pont bsp in the iberian peninsula their oxygen 18os and carbon 13cs isotopic compositions were analysed and compared with that of modern shells of the same species collected in two distinct areas near the archaeological site modern shells from site a shady and b sunny show distinctly different oxygen isotopic ratios possibly due to the effect of microenvironmental conditions e g temperature and relative humidity carbon isotopes by contrast reveal similar values isotope mass balance suggests a prevalent contribution of vegetation 70 integrated with foreign carbonates 30 to 13cs of modern snails early late holocene shells 9 2 5 cal ka bp have lower 18os compared with modern counterparts which is consistent with prevailing wetter conditions compared with present day the 13cs reveals distinct hydrological regimes wet and dry conditions from early to late holocene respectively in general shell isotopic records from western and central mediterranean regions suggest wetter conditions during the middle holocene with a possible reduction in humidity from 4 cal ka bp the 18os indicates a possible latitudinal difference in hydrological balance between mediterranean and atlantic europe as inferred by previous studies of regional palaeoclimatic records carbon isotopes by contrast do not provide a clear climatic picture probably due to the effect of distinct vegetation structure and composition comparisons with other environmental archives reinforce the concept of regional shell oxygen isotopic response to millennial scale changes in hydrological condition over the western and central mediterranean during the late quaternary

review and new aspects concerning the formation of eastern mediterranean sapropels abstract in this paper it is proposed that the formation of eastern mediterranean sapropels occurred in an anti estuarine type of circulation which was to some degree weakened relative to the present in response to reduction of the eastern mediterranean excess of evaporation over freshwater input this reduction of excess evaporation would have been imposed by intensifications of 1 the indian ocean summer sw monsoon influencing the eastern mediterranean via increased nile discharge and 2 the system of mediterranean depressions an element of the westerly atlantic system causing increased precipitation and decreased evaporation both the indian ocean summer monsoon and the westerly atlantic system would be intensified in response to the occurrence of distinct minima in the cycle of precession it is demonstrated that reduced excess evaporation whether or not coinciding with global phases of deglaciation would lead to reduction of surface water salinities in the eastern mediterranean causing isolation of previously formed high salinity cooler deep water thus mixing was severely reduced possibly even restricted to eddy diffusion with only occasional convective events that because of the existing density gradient hardly ever would reach the deepest parts of the basin the consequently diminished oxygen advection down from a few hundred meters in the water column favoured preservation of the sinking organic matter this would however suffice only to enable the formation of sapropels with low organic carbon contents the high organic carbon contents observed in various sapropels are argued to reflect superimposed increases of export production the described scenario accounts for previously reported 1 increases of organic carbon content with increasing depth of deposition within individual sapropels and 2 asymmetrical sequences of sapropel deposition characterized by gradual build up and rather abrupt ending it is furthermore in agreement with 3 isotopic and faunal reconstructions of the history of exchange transports through both the strait of sicily and the strait of gibraltar and 4 faunal and floral reflections of the presence or absence of a distinct deep chlorophyll maximum with its associated increases in export production indicating the presence or absence of a shallow pycnocline within the euphotic layer moreover the described scenario 5 is in no way conflicting with the reports of sapropels in the western mediterranean and 6 seems to be endorsed by occasionally intercalated intervals suggestive of somewhat improved oxygenation amidst anoxic benthic desert levels a situation that has been observed in a few quaternary and pliocene sapropels

exchange through the strait of gibraltar to measure the exchange between the atlantic and mediterranean through the strait of gibraltar an array of current meter moorings was deployed for a year in the strait during 1985 1986 a novel aspect of these measurements is the inclusion of conductivity as well as temperature and pressure sensors on each current meter so that the salinity of the flows could be monitored continuously these salinity measurements determine the water mass characteristics of the flows crossing the sill they allow definition of the 37 psu isohaline as the interface between inflowing fresher atlantic water and outflowing saltier mediterranean water and they enable time series to be developed for the depth of this interface for the upper layer inflow and for the lower layer outflow from these measurements the time averaged outflow of mediterranean water is estimated to be 0 68sv 1sv 1 106m3s 1 and the outflow salinity transport defined to be the outflow times the salinity excess above a basic atlantic water salinity of 36 1 psu is estimated to be 1 50 103m3s 1 1sv 1psu 1 103m3s 1 equivalent to a net evaporation over the mediterranean basin of 52cm y 1 extrapolated measurements of the inflow from current meters generally deployed below 100m depth yield an estimate for the time averaged inflow of 0 93sv which is believed to be unrealistically high in view of the better measured outflow and net evaporation thus a more realistic estimate of the inflow is 0 72sv equal to the sum of the outflow and net evaporation as required by the mass budget for the mediterranean sea such estimates of the exchange are smaller by almost a factor of 2 than previous values for the exchange by lacombe and richez 1982 the exchange across the gibraltar sill is found to be due in nearly equal parts to the mean currents and to the tidal fluctuations the mean currents are smaller than had been expected reaching a peak value of only about 60 cm s 1 in the deep outflow over the sill the tidal exchange is due to a strong correlation over the tidal period between the depth of the interface and the strength of the inflowing currents for the m2 tide at the sill the amplitude of the interface depth is 51 m and the amplitude of the tidal currents is 1 2m s 1 furthermore the inflow and interface depth have similar phases as a consequence the upper layer is deep on the inflowing tide so that a large slug of atlantic water crosses the sill into the mediterranean on the outflowing tide the interface is shallow so that a large slug of mediterranean water crosses the sill into the atlantic similar processes occur for the s2 o1 and k1 tides though the amplitude are smaller in this manner tidal oscillations lead to a time averaged exchange of water masses across the gibraltar sill the inflow and outflow defined to be the instantaneous transports above and below the 37psu isohaline interface exhibit m2 tidal amplitudes of 2 3 sv and 1 3sv respectively thus the tides are large enough to reverse the mean upper layer inflow and lower layer outflow daily averaged inflow and outflow transports exhibit low frequency fluctuations with standard deviations of 0 37sv and 0 22sv respectively such low frequency fluctuations have been shown previously to be associated with barotropic flows through the strait of gibraltar compensating for sea level variations over the mediterranean due to atmospheric pressure fluctuations candela winant and bryden 1989 finally from these measurements there appear to be little fortnightly or annual period fluctuations in the exchange through the strait of gibraltar

contourites of the gulf of cadiz a high resolution record of the paleocirculation of the mediterranean outflow water during the last 50 000 years the mediterranean outflow water mow paleocirculation during the last 50 000 years has been inferred from the grain size distribution of contourite beds in core md99 2341 from the gulf of cadiz southern iberian margin atlantic ocean three main contourite facies are described their vertical succession defines two contourite sequences that reveal past variations of the mow bottom current velocity a comparison of contourite sequences and the planktonic 18o record of core md99 2341 with the 18o record from greenland ice core gisp2 show a close correlation of sea surface water conditions and deep sea contouritic sedimentation in the gulf of cadiz with northern hemisphere climate variability on millennial timescales a high mow velocity prevailed during dansgaard oeschger stadials heinrich events and the younger dryas cold climatic interval the mow velocity was comparatively low during the warm dansgaard oeschger interstadials bolling allerod and the early holocene rapid sea level fluctuations on the order of 35 m during marine oxygen isotope stage 3 are considered to have exerted limiting controls on the mow volume transport and thus positively modulated the mow behaviour during the last 50 kyr

seasonal salinity changes during mediterranean sapropel deposition 9000 years b p evidence from isotopic analyses of individual planktonic foraminifera using stable isotopic analyses of individual tests of planktonic foraminifera with different seasonal and depth habitats we have investigated temporal variations in surface water salinities in the eastern mediterranean during the past 13 000 years low oxygen isotopic values document the presence of anomalously low salinity conditions in the eastern mediterranean at about 13 000 years b p 4000 years before the deposition of the youngest sapropel by 11 000 years b p during the deposition of presapropel sediments low salinity surface waters were more pervasive but were restricted to summer months and only affected the surface of the water column at the onset of sapropel deposition about 9000 years b p surface salinities in the eastern mediterranean had decreased by almost 4 and had extended to depths of at least 75 m the low salinity surface lens was not however a permanent feature of the eastern mediterranean during sapropel deposition low salinity surface conditions occurred in the fall and winter seasons but normal sea surface salinities returned during spring months on a seasonal and or interannual basis thus a low salinity surface lens could have existed continuously for months or decades at a time but would have been interrupted intermittently by a return to normal conditions any triggering mechanism proposed for mediterranean sapropels must account for the seasonal fluctuations and ephemeral nature of low salinity conditions in the eastern mediterranean despite normal salinities returning occasionally during spring months a low salinity surface lens may have greatly inhibited the production of levantine intermediate water prevented the formation of adriatic deep water and consequently reduced ventilation of the eastern mediterranean

late quaternary central mediterranean biochronology jorissen f j asioli a borsetti a m capotondi l de visser j p hilgen f j rohling e j van der borg k vergnaud grazzini c and zachariasse w j 1993 late quaternary central mediterranean biochronology mar micropaleontol 21 169 189 a high resolution biochronology is presented for the late quaternary of the central mediterranean in the late pleistocene holocene successions three assemblage zones are distinguished on the basis of frequency patterns of planktic foraminifera the age of these zones is determined by accelerator mass spectrometry ams t4c dating the zonal boundaries are dated at 12 700 yr b p the end of termination la and 9600 yr b p the start of termination ib respectively the ams dates show that major changes in the planktic and benthic realms occurred synchronously over wide areas although records of individual species may show important regional differences in the studied areas resedimentation processes revealed by anomalous successions of 14c dates play a far more important role than indicated by the sedimentological and micropaleontological data possibly these processes contribute to the very high accumulation rates in the glacial zone ill although the ams technique has increased the accuracy of lac measurements of older carbonate may still lead to substantial age differences between areas with different sedimentary regimes

eastern mediterranean surface water temperatures and d18o composition during deposition of sapropels in the late quaternary 0indices and d 18 o of planktonic foraminifer calcite d 18 ofc across late pleistocene sapropel intervals show that d 18 ofc decreased between 1 and 4 6 and sst increased between 0 7 and 6 7 c maximal d 18 oseawater depletion of eastern mediterranean surface waters at the transition is between 0 5 and 3 0 and in all but one case exceeded the depletion seen in a western mediterranean core the depletion in d 18 oseawater is most pronounced at sapropel bases in agreement with an initial sudden input of monsoon derived freshwater most sapropels coincide with warming trends of sst the density decrease by initial freshwater input and continued warming of the sea surface pooled fresh water in the surface layer and prohibited deep convection down to ageing deep water emplaced during cold and arid glacial conditions an exception to this pattern is glacial sapropel s6 its largest d 18 oseawater depletion 3 is almost matched by the depletion in the western mediterranean sea and it is accompanied by surface water cooling following an initially rapid warming phase a second period of significant isotopic depletion is in isotope stage 6 at the 150 kyr insolation maximum while not expressed as a sapropel due to cold sst it is in accord with a strengthened monsoon in the southern catchment index terms 1055 geochemistry organic geochemistry 1620 global change climate dynamics 3309 4267 oceanography general paleoceanography 9604 information related to geologic time cenozoic keywords mediterranean sea sapropels sea surface temperatures oxygen isotopes quaternary citation emeis k c et al eastern mediterranean surface water temperatures and d 18 o composition during deposition of sapropels

a window into africa s past hydroclimates the sisal_v1 database contribution africa spans the hemispheres from temperate region to temperate region and has a long history of hominin evolution although the number of quaternary palaeoclimatic records from the continent is increasing much of the history of spatial and temporal climatic variability is still debated speleothems as archives of terrestrial hydroclimate variability can help reveal this history here we review the progress made to date with a focus on the first version of the speleothem isotopes synthesis and analysis sisal database the geology of africa has limited development of large karst regions to four areas along the northern coast bordering the mediterranean eastern africa and the horn of africa southwestern africa and southern africa exploitation of the speleothem palaeoclimate archives in these regions is uneven with long histories of research e g in south africa but large areas with no investigations such as west africa consequently the evidence of past climate change reviewed here is irregularly sampled in both time and space nevertheless we show evidence of migration of the monsoon belt with enhanced rainfall during interglacials observed in northeast africa southern arabia and the northern part of southern africa evidence from eastern africa indicates significant decadal and centennial scale rainfall variability in northwestern and southern africa precession and eccentricity influence speleothem growth largely through changing synoptic storm activity

late pleistocene variability of the carbon isotopic composition of organic matter in the eastern mediterranean monitor of changes in carbon sources and atmospheric co2 concentrations the organic carbon isotopic record of the sapropels s1 and s3 s10 and intercalated marl oozes has been determined in a 12 m piston core from the eastern mediterranean the 13corganic values are systematically lighter mean 21 0 0 82 in all sapropels and heavier mean 18 8 1 07 in the marl oozes these differences are not due to variable marine and terrestrial organic matter mixtures because all values are heavier than modern plankton in the mediterranean there is no relationship between the corganic n ratios and the isotopic values and published information on the abundance and distribution of organic biomarkers shows that terrestrial material constitutes a minor fraction of the total organic matter temperature effects on isotope fractionation are also discounted because the change in 13corganic values between glacial and interglacial horizons is in the opposite sense diagenesis which can produce relatively small changes in the carbon isotopic composition of sedimentary organic matter under certain circumstances is unlikely to have caused the observed differences because this mechanism would cause an enrichment in 12c implying that all values were even heavier originally and there is no secular trend in the 13corganic record the observed differences in 13corganic between the two lithologies are probably produced by changes in the isotopic composition and the concentration of dissolved co2 first freshwater flooding during the formation of the sapropels caused the isotopic composition of the dissolved inorganic carbon in the surface waters of the mediterranean to become lighter because of the 13c deficiency in fresh waters hence photosynthesis would have produced isotopically lighter organic material second changes in atmospheric pco2 between glacial and interglacial periods as shown by the vostok ice core caused marked changes in the concentration of free dissolved co2 in the mixed layer lower values during glacial maxima caused a smaller fractionation of the carbon isotopes by phytoplankton whereas levels were less limiting during the interglacials concentrations of dissolved co2 could also have been much higher during the deposition of the sapropels because of the supply of regenerated co2 to the mixed layer by upwelling and this could have further lightened the 13corganic values in the sapropels themselves carbon isotope records may provide an alternative method for estimating atmospheric pco2 levels over longer time periods than can be obtained from ice cores

palaeoceanography of the last deglaciation in the alboran sea western mediterranean stable isotopes and planktonic foraminiferal records abstract oxygen isotope changes of the foraminiferal species globigerina bulloides and uvigerina peregrina eleven radiocarbon dates on the sediment fraction above 50 m and 13 biostratigraphical events allow us to correlate and to date the sediment record of the last climatic cycle in four cores from the alboran sea nine ecozones are recognized which differ from those previously established for atlantic sediments cored immediately west of gibraltar these ecozones can be grouped into two broad phases from the last glacial maximum up to near 9 500 yr b p cold north atlantic microfaunas are the major component of the assemblages during this interval dominant species replace each other according to the varying temperature and density stratification of the water masses from 9 500 yr b p up to the present time subtropical forms from the central atlantic dominate the northern atlantic forms an abrupt increase in the percentages of g inflata occurred near 7 000 b p this event was diachronous within the mediterranean during the last glacial g inflata was endemic inside the mediterranean and its abrupt increase near the end of the deglaciation did not result from replenishment from the atlantic between 4 000 and 5 000 yr b p percentages of g bulloides also increased abruptly warming conditions associated with the onset of a seasonal thermal stratification and a contrasting winter vertical convection are strongly suggested

divergent mediterranean seawater circulation during holocene sapropel formation reconstructed using nd isotopes in fish debris and foraminifera abstract the recurrent deposition of organic rich sapropel layers in the eastern mediterranean sea ems has been attributed to deep water stagnation and enhanced biological production however the underlying climatic interactions paleoceanographic processes and associated ventilation dynamics are still debated here we present a basin wide reconstruction of circulation systematics during sapropel s1 formation 10 8 6 1 kyr bp using the nd isotope composition e nd as paleo seawater tracer our e nd data from fish debris and foraminifera tests are remarkably radiogenic compared to today and spatially and temporally constant these results predominantly reflect enhanced nile versus atlantic contributions and indicate that ems deep water stagnation prevailed below 800 m water depth during s1 formation additional e nd records obtained from bulk sediment leachates show that such stagnation was preconditioned thousand s of years prior to s1 initiation by intensified nile flooding whereas it terminated with a basin wide deep water renewal in addition decoupling of deep waters between the ems and western mediterranean sea wms is evident for the s1 period using a box model for nd in the ems the observed e nd distribution can be most adequately explained by a 2 fold increase in nile discharge and a 50 decrease in the ems wms exchange that was mostly limited to the surface waters alone the corresponding circulation during s1 was more sluggish and shallow for the ems but largely unaffected for the wms this implies that deep water stagnation is a prerequisite for sapropel formation

glacial meltwater input to the alaska coastal current evidence from oxygen isotope measurements results of a study of the oxygen isotopic composition of coastal pelagic and fresh waters from the northern gulf of alaska region are presented this study was undertaken to investigate whether isotopic tracers could be of use in determining the important freshwater inputs to the alaska coastal current acc and whether they could confirm the presence of the acc in coastal waters west of kodiak island the alaska coastal current the major coastal circulation feature of the northern gulf of alaska can be distinguished from oceanic waters on the basis of its lower salinity at least as far west as kodiak island this study adds significantly to the small amount of oxygen isotopic information available for the waters of this region the isotopic results suggest that in late summer glacial meltwater may provide a substantial portion of the total freshwater runoff into the acc and that the acc does extend as far to the west as unimak pass

high resolution holocene record in the southeastern bay of biscay global versus regional climate signals abstract core ks10b north east atlantic 43 50 n 2 03 w water depth 550 m was recovered at a location of high sediment deposition and hence includes a high resolution palaeoclimatic record for the southeastern bay of biscay over the last 9000 cal yr bp the effect of global and regional climatic forcing factors e g orbital forcing north atlantic oscillation nao and their subsequent control on water temperature sea level hydrology and continental influence were investigated by studying planktic and benthic foraminiferal faunas 150 m sedimentology and stable isotopes results indicate probable episodic long term incursions of the warm and salty iberian poleward current ipc into the bay of biscay during the holocene by the intermittent presence of subtropical globigerinoides ruber in the otherwise temperate fauna these incursions seem to be triggered by negative nao like conditions our data show five main climatic periods which are in general agreement with the literature data on the climatic variability in the north atlantic and the iberian peninsula the early holocene 9000 7400 cal yr bp is characterized by low sea level significant downslope transport eutrophic benthic settings and high surface water productivity these environmental characteristics are probably due to the general wet and warm climate under a prevailing negative nao increasing precipitation and river runoff and favouring the incursion of the ipc into the bay of biscay the climatic optimum appears between 7400 and 6000 cal yr bp under a generally positive nao index in the following 6000 3500 cal yr bp surface water cooling is matching a steep decline of the northern hemisphere summer insolation meanwhile benthic settings are changing progressively towards present day trophic conditions the time interval from 3500 to 1800 cal yr bp encompasses the iberian roman humid period characterized by warm and humid conditions and increasing primary production under a prevailing negative nao index the last 1800 years were characterized by stable cool conditions reflecting a change towards a positive nao state

the age and origin of the younger dryas climate event in greenland ice cores 230th 234u and 14c dating of barbados corals has extended the calibration of 14c years b p to calendar years b p beyond the 9200 year tree ring series bard et al 1990 this now permits the conversion of 14c chronozones which delimit major climate shifts in western europe to calendar years the younger dryas chronozone defined as 11 000 to 10 000 14c years b p corresponds to 13 000 to 11 700 calendar years b p this calibration affects the interpretation of an intensely studied example of the younger dryas climate event the 18o anomaly between 1785 and 1793 m in dye 3 ice core the end of the 18o anomaly in dye 3 ice core has been dated by measurements of 14c in air bubbles andree et al 1984 1986 and by annual layer counting hammer et al 1986 the older 14c dates fall out of the range of the tree ring calibration series but can now be calibrated to calendar years using the barbados 230th 234u calibration the 14ccorrected age for the end of the 18o event is 10 300 400 calendar years b p compared to the annual layer counting age of 10 720 150 years b p thus the younger dryas event in the dye 3 ice core ends in the preboreal chronozone 11 700 to 10 000 calendar years b p and is not correlative with the end of the younger dryas event identified in pollen records marking european vegetation changes the end of the dye 3 18o event is however correlative with the end of meltwater pulse ib fairbanks 1989 marking a period of intense deglaciation with meltwater discharge rates exceeding 13 000 km yr

paleosalinity and δ18o a critical assessment in paleoceanography a traditional application of oxygen isotope ratios in fossil carbonate from deep sea cores concerns the reconstruction of paleotemperatures recently isotopic data have been increasingly employed in the reconstruction of paleosalinities as well this application involves a number of basic assumptions a critical review of which is presented here as the calculation of paleosalinity from 18o residuals assumes constant and linear surface water salinity s 18o relationships we investigate this basic assumption for areas with important and variable freshwater budget and or sea ice influences we show that it is particularly unwarranted to assume such temporally invariant linearity in temperate and subpolar seas because of the effects of freezing and melting more critically we argue that the determinant of many regions s 18o is advection not the local water balance so that the basic 18o of seawater in many regions of the world ocean would likely have changed in a manner somewhat different from that expected from the ice volume record although the differences may not be significant for the gross reconstruction of such features as past sea level we believe they do potentially bias paleosalinity reconstructions mostly toward high salinities to fully exploit the potential of oxygen isotope records as quantitative paleosalinity indicators both the spatial and temporal variabilities need to be constrained hence we recommend that 1 for any time slice of specific interest to paleoceanographic and paleoclimatological studies a coupled ocean atmosphere isotope model or at least an ocean isotope model driven by a paleoclimate isotope model should be used to define the distribution of the base mixing end member 18o of sea water 2 much further regional scale research is needed on flux rates and isotopic compositions of the various terms in the freshwater budget as well as on the variability in the various advective terms the latter variability may be assessed from reconstructions of past seaice distributions and of volume fluxes isotopic compositions of outflow from marginal seas and through sea straits passages

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

impact of iceberg melting on mediterranean thermohaline circulation during heinrich events down core samples of planktonic and benthic foraminifera were analyzed for oxygen and carbon isotopes in international marine past global changes study images core md99 2343 in order to study the interactions between climate change in the northern hemisphere and the western mediterranean thermohaline circulation at times of heinrich events he our results confirm the antiphase correlation between enhanced north atlantic deep water formation and low ventilation in the mediterranean however this study reveals that this antiphase relationship in deepwater formation between the north atlantic and mediterranean was interrupted during times of he when the injection of large volumes of water from melting icebergs reached the entrance to the mediterranean these events which lasted less than 1000 years are represented by pronounced decreases in both planktonic d18o and benthic d13c signals lower salinities of mediterranean surface water resulted in a slowdown of western mediterranean deepwater overturn even though cold sea surface temperatures and drier climate should have resulted in enhanced deepwater formation

hydrographic changes of the southern ocean southeast indian sector over the last 230 kyr hydrographical changes of the southern indian ocean over the last 230 kyr is reconstructed using a 17 m long sediment core md 88 770 46 01 s 96 28 e 3290m the oxygen and carbon isotopic composition of planktonic n pachyderma sinistra and g bulloides and benthic cibicidoides wuellerstorfi epistominella exigua and melonis barleeanum foraminifera have been analysed changes in sea surface temperatures sst are calculated using diatom and foraminiferal transfer functions a new core top calibration for the southern ocean allows an extension of the method developed in the north atlantic to estimate paleosalinities duplessy et al 1991 the age scale is built using accelerator mass spectrometry ams 14c dating of n pachyderma s for the last 35 kyr and an astronomical age scale beyond changes in surface temperature and salinity clearly lead by 3 to 7 kyr deep water variations thus changes in deep water circulation are not the cause of the early response of the surface southern ocean to climatic changes we suggest that the early warming and cooling of the southern ocean result from at least two processes acting in different orbital bands and latitudes 1 seasonality modulated by obliquity affects the high latitude ocean surface albedo sea ice coverage and heat transfer to and from the atmosphere 2 low latitude insolation modulated by precession influences directly the atmosphere dynamic and related precipitation evaporation changes which may significantly change heat transfer to the high southern latitudes through their control on latitudinal distribution of the major frontal zones and on the conditions of intermediate and deep water formation

levantine intermediate water hydrodynamic and bottom water ventilation in the northern tyrrhenian sea over the past 56 000 years new insights from benthic foraminifera and ostracods abstract foraminifera and ostracods have been quantitatively studied in core md01 2472 from the upper continental slope at water depth of 501 m to evaluate their relationship with bottom water condition variability and decipher the control of the levantine intermediate water liw current on benthic faunas the occurrence of reworked ostracod species originating from the continental shelf and the presence of shallow water elphidium ammonia benthic foraminifera are used to estimate the degree of along slope transport at the core site this has revealed two intervals of along slope transport also associated with coarse grained contourite deposits deposited during the yd and hs2 episodes planktonic benthic foraminiferal and ostracod assemblages reflect climate oscillations peaks of the polar planktonic neogloboquadrina pachyderma left coiling s may be used to identify heinrich events interstadials are marked by abundant ostracod species such as paracypris sp argilloecia acuminata and cytheropteron alatum and the presence of benthic foraminifera like bulimina marginata bulimina costata and gyroidina altiformis the b a and holocene are characterized by abundant warm water species of planktonic foraminifera and by the ostracod species polycope sp we hypothesize that there is relationship between liw intensification during cold rapid climate events and benthic fauna assemblage variations due to changes in 1 bottom water ventilation and 2 the export of nutrients and or sediment particles by bottom currents

quaternary neotectonics of the south aegean arc abstract the sedimentary and tectonic quaternary evolution of the south aegean arc has been interpreted from 8000 line km of sparker seismic reflection profiles the older parts of basins formed by e w trending faults and accumulated hemipelagic sediment younger active faulting trends nnw in the western part of the arc and ene in the eastern arc the ene trending faults record sinistral strike slip motion broadly parallel to the convergence direction of the aegean anatolian and african plates the north south faults in the western arc are similar to those on land in the south peloponnese chronology is estimated from sedimentation rates in cores and from stacked progradational units on basin margins controlled by eustatic changes in sea level the younger fault pattern developed at 0 6 0 8 ma in the western and central arc but progressively younger in the southeastern part of the arc the older basin fill with e w faults is of early quaternary and pliocene age an older regional unconformity corresponds to an early pleistocene unconformity in the cretan basin particularly in the area east of santorini faulting has resulted in startling changes in palaeogeography such that some areas were late pliocene basins positive features during the pleistocene and then subsided 600 m in the last 0 2 ma such rapid basin inversion resulted in uplift of stratified hemipelagic muds which were deformed by creep or failure so that debris flow deposits accumulated in valleys and ponded basins these fundamental tectonic changes in the past two million years indicate that much of the deformation resulting from the interaction of the eurasian african and anatolian aegean plates is taken up at the southern margin of the aegean microplate probably because subduction of the african plate has slowed as a result of collision of continental crust regional fault patterns are a consequence of spatially varying effects of subduction roll back

riverine supply to the eastern mediterranean during last interglacial sapropel s5 formation a basin wide perspective abstract organic rich sapropel sediments were repeatedly deposited in the eastern mediterranean sea ems in response to insolation driven freshwater forcing however the exact freshwater sources and causal associated paleoclimate related processes remain unresolved sapropel s5 formed during the insolation maximum of the last interglacial is one of the most intensely developed sapropels of the late quaternary here detrital sediments of sapropel s5 obtained from 8 cores together with 13 ems surface samples are analyzed for major elements rare earth elements ree and sr and nd isotopes this permits a basin wide investigation of the source and distribution of river borne material to the ems for sapropel s5 and its comparison to the present day and the holocene sapropel s1 period during the sapropel s5 there was minor saharan dust input the marked east west geochemical gradient in s5 detrital sediments across the ems is therefore attributed to mixing between fluvial contributions being nile discharge aegean adriatic riverine inputs and libyan tunisian paleodrainage fluxes the offshore distribution of nile sediments during sapropel s5 was comparable to those during s1 and the present the nile sediment contribution appears to be only dominant for the levantine basin decreasing to negligible values south of crete this rather limited sediment delivery despite inferred increased runoff during s5 is related to denser vegetation cover on the ethiopian highlands by contrast small rivers around the aegean and adriatic sea brought large amounts of detrital material into the ems this is particularly noticeable around crete and the northern ionian sea the enhanced riverine input is probably due to strong precipitation seasonality over the northern ems borderlands particularly for the early phase of the last interglacial maximum furthermore there are substantial fluvial contributions from the libyan tunisian margin to the ionian sea sediments in particular during the last part of sapropel s5 the inferred river borne material was transported via paleodrainage systems reactivated by intensified monsoon precipitation and derived from central saharan mountains compared to sapropel s1 these s5 related paleodrainage fluxes were not only stronger but also had a more predominant provenance from eastern rather than western libya in addition a similar averaged endmember of saharan dust sources is revealed by ree signatures

mediterranean pluvial periods and sapropel formation over the last 200 000 years abstract three mediterranean deep sea cores have been studied to reconstruct the hydrological conditions at the time of deposition of interglacial and glacial sapropels during the time interval 200 60 kyr bp the isotopic and sea surface temperature records of planktonic foraminifera were used to estimate the oxygen isotopic composition of surface water w in the tyrrhenian sea and levantine basin our results show a strong w salinity decrease in both basins associated with each sapropel these w decreases reflect a drastic change in the local freshwater budget and were comparable to that observed during the last sapropel s 1 centred at ca 8 kyr bp a strong precipitation increase transformed the whole mediterranean sea into a non concentration basin the low surface salinity was responsible for the water column stratification while nutrients brought in by the runoff enhanced productivity it resulted in a significant reduction in the rate of deep water oxygenation and sapropel formation in the eastern basin in addition the mediterranean sea 18 o record is very similar to that of the bay of bengal as the latter is very sensitive to the summer monsoon rain this similarity suggests that both glacial and interglacial sapropels result from enhanced monsoon like precipitation due to an increase in summer insolation driven by precession variations

slow rates of subduction erosion and coastal underplating along the andean margin of chile and peru comment and reply reply we thank encinas and finger 2007 1 for their comments on our paper clift and hartley 2007 2 as they add detail to the model we presented while leaving intact the essential idea of neogene tectonic erosion along the andean margin being followed by accretion and underplating since 2 ma

central mediterranean mid pleistocene paleoclimatic variability and its association with global climate abstract planktonic foraminiferal assemblages were studied at high resolution in core kc01b from the ionian sea quantitative analysis allowed us to distinguish the main climatic features and associated paleoceanographic changes that occurred between marine isotopic stages mis 13 and 9 500 300 ka mis 12 and mis 10 are characterized by relatively temperate conditions and an oligotrophic oceanographic regime in the early part and by colder conditions and nutrient supply in the sub surface water masses in the upper part during these intervals small but distinct peaks of neogloboquadrina pachyderma sinistral sin are detected at times of extremely negative values of the planktonic foraminifera paleoclimatic curve their co occurrence with similar episodes in the atlantic suggests that the climate in the central mediterranean was associated with north atlantic millennial scale climate instability mis 11 and mis 9 are dominated by surficial warm water taxa the climate optimum is reached in the middle part of each of these stages as denoted by the presence of globigerinoides sacculifer and persists for approximately 20 and 6 ka during mis 11 and mis 9 respectively this warming is not constant but is characterized by three distinct intervals with elevated winter temperatures and or weak winter mixing distribution of globigerina bulloides turborotalita quinqueloba and n pachyderma dextral dex indicates that significant environmental changes occur across the transitions from glacial to interglacial mis 12 mis 11 termination v and mis 10 mis 9 termination iv the studied record documents a close linkage between mediterranean climate evolution and higher and lower latitude climate change throughout mis 13 9