persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

a stratigraphically controlled multiproxy chronostratigraphy for the eastern mediterranean 1 an accelerator mass spectrometry ams 14c dated multiparameter event stratigraphy is developed for the aegean sea on the basis of highly resolved centimeter to subcentimeter multiproxy data collected from four late glacial to holocene sediment cores we quantify the degree of proportionality and synchroneity of sediment accumulation in these cores and use this framework to optimize the confidence levels in regional marine radiocarbon based chronostratigraphies the applicability of the framework to published lower resolution records from the aegean sea is assessed next this is extended into the wider eastern mediterranean using new and previously published high resolution data from the northern levantine and adriatic cores we determine that the magnitude of uncertainties in the intercore comparison of ams 14c datings based on planktonic foraminifera in the eastern mediterranean is of the order of 240 years 2 se these uncertainties are attributed to synsedimentary and postsedimentary processes that affect the materials dated this study also offers a background age control that allows for vital refinements to radiocarbon based chronostratigraphy in the eastern mediterranean with the potential for similar frameworks to be developed for any other well studied region

evaluation of palaeoenvironmental changes during the last 18 000 years in the myrtoon basin sw aegean sea abstract high resolution last glacial maximum to holocene palaeoenvironmental changes corresponding to a time interval between 200 and 500 years are examined in the myrtoon basin in the sw aegean sea using the abundance variation in foraminifera and pollen in relation to accelerator mass spectrometry 14 c dating and limited oxygen isotope data foram abundance variation shows that from 18 ka to the late glacial holocene boundary at around 10 5 to 9 5 ka the sea surface was cold during this period two intervals of relatively high and low sea surface temperature sst were observed the first high sst occurred at around 14 2 ka whereas the second high sst was centred at around 12 8 ka and appears to correspond to the termination 1a event the first low sst was centred at around 13 7 ka and the second low sst occurred between 11 8 and 10 8 ka the former event may correspond to the heinrich 1 event and the latter to the younger dryas chronozone the holocene started with a sharp warming of sea surface water reaching present day levels and probably associated with a reduction in salinity the formation of the sapropel sequence in the myrtoon basin started at about 10 ka about the same time as the sapropel formation in the other aegean basins which means that the environmental conditions became suitable for the formation of sapropels in the aegean about 800 years earlier than in the adriatic ionian and levantine basins within the sapropel sequence there are two high organic carbon corg content sublayers s 1 a 9 7 9 ka and s 1 b 7 3 6 9 ka separated by a lower corg content sublayer indicating variation in the oceanographic and climatic conditions prevailing in the area during the sapropel sequence formation the depositions of s 1 a and s 1 b coincide with an increase in sst increased temperature and enhanced fresh water inputs from the outflowing rivers in to the aegean sea which later was supplemented by the overflowing of the black sea lowered the sea surface density and reduced the vertical water masses circulation resulting in reduced bottom water ventilation the reduction of o 2 supply to the seabed in combination with increased fluxes of terrigenous and or marine organic matter were responsible for the creation of dysoxic to anoxic conditions in the seabed which led to the formation of sapropel s 1 the sapropel formation ended at 5 2 ka and about the same time the sst attained present day levels during the last glacial maximum and late glacial periods the pollen source area was providing a suitable environment for the growth and survival of arboreal taxa the source area was apparently ice free and was characterized by sufficient humidity and non lethal low temperatures probably only a few degrees colder than present day

foraminiferal ecozones a high resolution proxy for the late quaternary biochronology in the central mediterranean sea the planktic foraminiferal distribution identified in 60 cores collected in different basins of the mediterranean sea allowed to establish an ecostratigraphical scheme which provides a very important tool for the biochronological subdivision of the uppermost quaternary we identified a succession of ten ecozones during the last 23 ka in the tyrrhenian basin and eight ecozones in the adriatic sea during the last 15 ka the ecozones boundaries have been calibrated by 14c ams radiometric data and by the stable oxygen isotope record the chronological framework defined by the successive bioevents shows a very high resolution millenary scale and evidences that the changes in the planktic microfauna occurred more or less synchronously throughout the central mediterranean sea differences due to different oceanographic settings of the basins do not affect the general distributional pattern of planktic foraminifera

late pliocene to early pleistocene astronomically forced sea surface productivity and temperature variations in the mediterranean abstract principal component analysis of late pliocene to early pleistocene planktonic foraminiferal abundances from the mediterranean yielded two significant components which represent first order approximations for sea surface productivity and temperature this interpretation is confirmed by the good fit between the score plots and sea surface productivity and sea surface temperature proxy records based on selected eutrophic and temperature sensitive species using present day habitat characteristics spectral analysis revealed significant peaks in the orbital frequency bands of the spectrum suggesting that variations in sea surface productivity and temperature are controlled by the quasi periodic variations in the earth s orbit precession forced variations are reflected primarily in sea surface productivity and to a lesser degree in sea surface temperature maxima in sea surface productivity and temperature in this frequency band occurred at times of sapropel formation the sea surface productivity maxima can be explained by an increased input of river borne nutrients and by the shoaling of the pycnocline and the associated intensification of the deep chlorophyll maximum dcm layer precession forced variations in sea surface temperature are not related to glacial cycles since this frequency component is almost completely absent in ice volume proxy records for this time interval sapropel bound sea surface temperature maxima presumably reflect periods of maximum insolation during the northern hemisphere summer the contrasting winter signal corresponds to minimum insolation values which may be reflected by peak abundances ofgloborotalia inflata obliquity forced variations are reflected primarily in sea surface temperature and not in sea surface productivity these temperature fluctuations correspond with ice volume changes registered in the oxygen isotope record at the north atlantic dsdp site 607 this shows that obliquity forced sea surface temperature variations in the mediterranean are primarily driven by glacial cycles

planktonic foraminiferal faunal and stable isotopic indices of upwelling a sediment trap study in the san pedro basin southern california bight

scaling of stagnant lid convection with arrhenius rheology and the effects of mantle melting summary on the basis of numerical modelling and scaling analysis a few modifications are proposed for the scaling of stagnant lid convection in order to make it more applicable to the thermal evolution of terrestrial planets the effect of using arrhenius rheology as opposed to more popular linear exponential rheology is first investigated and the stability analysis of top thermal boundary layer is shown to be able to capture systematic differences caused by the different kinds of temperature dependent viscosity the local stability analysis is then extended to handle the effects of mantle melting such as dehydration stiffening and compositional buoyancy a new heat flow scaling law incorporating these effects suggests that mantle melting may reduce the conventional prediction of surface heat flux by up to a factor of 5 10 and its potential impact on our understanding of planetary evolution is briefly discussed

aegean sea as driver of hydrographic and ecological changes in the eastern mediterranean the eastern mediterranean is undergoing a long term increase in net evaporation which may have preconditioned the profound changes that occurred in its deep sea ventilation over the past two decades we test the sensitivity of aegean convective deep water formation to forcing in the opposite sense based on a last interglacial episode of enhanced freshwater injection into the eastern mediterranean we find that aegean subsurface ventilation collapsed completely within 40 20 yr promoting euxinic conditions hostile to aerobic life that expanded toward the photic layer within 650 250 yr similar conditions extended throughout the eastern mediterranean 300 120 yr later these findings emphasize the exceptional sensitivity of aegean deep water formation to climate forcing driving large scale hydrographic adjustments throughout the eastern mediterranean and beyond

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

calcareous nannofossils planktonic foraminifera and oxygen isotopes in the late quaternary sapropels of the ionian sea core m 25 4 12 a long piston core 12 20 m recovered in the ionian sea during cruise m25 4 of the r v meteor summer 1993 at a water depth of 2467 m shows an almost complete sequence of sapropels s 1 s 3 to s 10 over the last 330 ka this paper presents the results of an integrated study based on quantitative biostratigraphic analyses performed on both calcareous nannofossils and planktonic foraminifera coupled with the 18o record a decrease in syracosphaera sp 1 and an increase in the abundance of the genus rhabdosphaera and of helicosphaera carteri florisphaera profunda and of the reworked specimens has been found in the calcareous nannofossil assemblage within the sapropels the planktonic foraminiferal assemblage of the sapropels is characterized by a peak in the frequency of globigerinoides ruber var alba and rosea and neogloboquadrina dutertrei the 18o record of globigerinoides ruber and globigerina bulloides allows recognition of isotope stages 1 to 9 and shows a negative fluctuation that corresponds to the sapropel layers these features support the idea of increased productivity coupled to the presence of reduced salinity surface waters that caused the deposition of the sapropels however the need for a good understanding of the ecological requirements of modern assemblages is stressed this is necessary to correctly interpret fossil assemblages this in turn will allow a better understanding of the palaeoceanographic conditions leading to sapropel deposition

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

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

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

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

multispecies approach to reconstructing eastern equatorial pacific thermocline hydrography during the past 360 kyr 1 stable isotope data from eastern equatorial pacific eep core tr163 19 2 15 n 90 57 w 2348 m are presented for the surface dwelling foraminifers globigerinoides ruber and g sacculifer and thermocline dwelling globorotalia menardii and neogloboquadrina dutertrei using species specific normalization factors derived from experimental and plankton tow data we reconstruct a 360 kyr record of water column hydrography across the past three glacial cycles we demonstrate that g ruber maintains a mixed layer habitat throughout the entire record while g sacculifer records a mixture of thermocline and mixed layer conditions and g menardii and n dutertrei record thermocline properties we conclude that g sacculifer is not appropriate for paleoceanographic applications in regions with steep vertical hydrographic gradients results suggest that this region of the eep had a thicker mixed layer and deeper 13cdic boundary between the surface and equatorial undercurrent during the last two glacial periods a shift in n dutertrei and g sacculifer geochemistry prior to 185 kyr suggests water column structure and chemocline gradients changed possibly due to a shift in the position of the undercurrent relative to this site the timing and magnitude of glacial interglacial 13c variations between species indicates that near surface carbon chemistry is controlled by changes in productivity atmospheric circulation and advected intermediate water sources north of the antarctic polar front these results demonstrate that when properly calibrated for species differences multispecies geochemical data sets can be invaluable for reconstructing water column structure and properties in the past

a dynamic concept for eastern mediterranean circulation and oxygenation during sapropel formation we propose that intermittent bottom water ventilation occurred throughout periods of sapropel deposition and that the recently reported sapropel interruptions represent centennial scale episodes of enhanced frequency intensity of that process in essence the modern high frequency variability in deep water formation affected by climatic variability over the northern basins on seasonal to longer time scales prevailed also at times of sapropel deposition although the overall ventilation state was much reduced this concept is supported by detailed multiple species isotope records for three aegean cores the presence of abundant globorotalia truncatulinoides within especially sapropels s7 and s8 in the western levantine basin observations of three rapid benthic repopulations within sapropel s6 in the deep western levantine basin a report of continuous benthic presence through sapropel s1 at intermediate deep locations offshore libya and further supporting information from the literature in the aegean records concomitant abundance of low oxygen tolerant benthic foraminifera and presence of the more oxyphilic benthic foraminifer uvigerina mediterranea with surface similar 13c values indicate repeated deep water re oxygenation events throughout the deposition of s1 the observations of a continuous benthic presence through s1 offshore from libya imply that no persistent anoxia developed at mid depth levels in that region which is far removed from direct deep ventilation influences the abundance of deep mesopelagic g truncatulinoides through several sapropels from the western levantine basin also suggests the presence of bio available oxygen at many hundreds of meters of depth moreover the rapid intermittent benthic repopulations within sapropels from the deep eastern mediterranean imply that bottom water anoxia was spatially restricted and or of a highly intermittent nature the short time scales of these repopulation events are incompatible with titration of an extensively anoxic water column and subsequent re establishment of water column anoxia we suggest that where anoxic azoic conditions were present they most likely were restricted to a veneer at the sediment water interface the extent of such an anoxic blanket depends on the balance between advective oxygen supply into the deep sea and biological and chemical oxygen demand the demand functions imply a decoupling of oxygenation from water mass advection allowing export production and corg posting rates to the sea floor to delimit the extent of the anoxic blanket in both space and time low productivity regions would develop no anoxic blanket allowing for the observed persistence of deep dwelling planktonic and bottom dwelling benthic faunas

african monsoons an immediate climate response to orbital insolation the croll milankovitch astronomical theory of climate1 3 has received strong support from the evidence of a linear climatic forcing by obliquity and precession although nonlinearity had to be assumed for eccentricity4 5 moreover interglacials have appeared to be controlled by the orbital insolation6 although a phase shift of 6 000 5 000 yr is seen between an astronomical climate index and terrestrial climate indicators dominated by the northern ice sheet dynamics climate proxy data of low latitudes are less directly dependent on the ice sheets here it is shown that during the past 464 000 yr african monsoons signalled by the east mediterranean sapropels were heaviest always and only when a northern summer monsoon index computed from the orbital variation of insolation reached maximum values this occurred during all the interglacials but also twice during glacial periods thus tropical aridity is not the single climatic pattern of glacial periods an immediate terrestrial climate response to orbital variations of insolation is established

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

sub millennial scale climatic oscillations in the central adriatic during the lateglacial palaeoceanographic implications abstract a multi proxy study of a sedimentary core obtained from the central adriatic basin provides evidence of short term events of palaeoceanographic variability during the last glacial lateglacial period grip event stages gi 1 and gs 1 comparison of the adriatic results with other mediterranean records reveals a common sequence of changes in palaeoceanographic conditions variations in foraminiferal assemblage data and in stable isotopic compositions indicate two short term cold oscillations which interrupted an overall cooling trend that commenced at the beginning of the greenland gi 1 episode bolling allerod episode these cold events considered to be contemporaneous with gi 1b and gi d of the grip ice core record are indicated by distinctive foraminiferal assemblages which reflect episodes of high productivity under relatively restricted water circulation with in particular reduced vertical mixing during winter differences in the foraminiferal assemblages indicate that the younger of the two cold spells is characterized by reduced ventilation of bottom waters our results combined with published data from neighbouring marine basins suggest a widespread reduction in deep water formation in the central mediterranean which commenced during the gi 1b episode and reached its maximum effect during the onset of the gs 1 younger dryas episode moreover three intervals with reduced vertical mixing correspond to the two cold spells during gi 1 and the lower phase of the gs 1 episode and show close similarities with the palaeoceanographic changes reported for the north atlantic this similarity indicates that the mediterranean and north atlantic may have been responding more or less synchronously to common forcing mechanisms

seasonality variations in the central mediterranean during climate change events in the late holocene abstract holocene rapid climate change rcc events such as the little ice age lia are thought to have influenced average annual temperatures only marginally but to have affected winter temperatures relatively strongly with summer temperatures relatively unaffected reconstructing climate change at a seasonal resolution is crucial to fully capture holocene climate variability mediterranean climate is highly seasonal being influenced by the subtropical high pressure belt in summer and the mid latitude westerlies combined with outbreaks of polar winds in winter we identified events of high and low detrital input to the gulf of taranto central mediterranean sea anticipated to be linked to humid and dry conditions respectively and thereby potentially reflecting seasonal contrasts these events represent the bronze age ba roman humid period rhp medieval climate anomaly mca lia and present day and were selected for the analysis of single specimen globigerinoides ruber white carbonate chemistry mg ca 18o and 13c the dynamic range found for these parameters for the measured single individuals in the most recent interval reflects the present day seasonal contrasts in temperature and precipitation albeit with a bias towards the summer season these results are compared with high resolution 15 years sample sea surface temperature sst and bottom water temperature bwt reconstructions based on the 18o of g ruber white and mg ca of benthic foraminifer hyalinea balthica although the seasonal temperature contrast remains relatively stable significant winter cooling is observed during the ba and lia connections between high latitude climate winter conditions and low latitude climate summer conditions appear not straightforward during rcc events this results in changes in the moisture balance and in shifts in seasonal dominance between rccs during the lia winter like conditions cold and humid prevail throughout the year in contrast winters are dry and cold during the ba and are accompanied by dry and warm summers suggesting year round aridity and a relatively high seasonal temperature contrast this could have had a profound impact on early agriculture in southern italy

variability of the western mediterranean sea surface temperature during the last 25 000 years and its connection with the northern hemisphere climatic changes sea surface temperature sst profiles over the last 25 kyr derived from alkenone measurements are studied in four cores from a w e latitudinal transect encompassing the gulf of cadiz atlantic ocean the alboran sea and the southern tyrrhenian sea western mediterranean the results document the sensitivity of the mediterranean region to the short climatic changes of the north atlantic ocean particularly those involving the latitudinal position of the polar front the amplitude of the sst oscillations increases toward the tyrrhenian sea indicating an amplification effect of the atlantic signal by the climatic regime of the mediterranean region all studied cores show a shorter cooling phase 700 years for the younger dryas yd than that observed in the north atlantic region 1200 years this time diachroneity is related to an intra yd climatic change documented in the european continent minor oscillations in the southward displacement of the north atlantic polar front may also have driven this early warming in the studied area during the holocene a regional diachroneity propagating west to east is observed for the sst maxima 11 5 10 2 kyr b p in the gulf of cadiz 10 9 kyr b p in the alboran sea and 8 9 8 4 kyr b p in the thyrrenian sea a general cooling trend from these sst maxima to present day is observed during this stage which is marked by short cooling oscillations with a periodicity of 730 40 years and its harmonics

a synthesis of the circulation and hydrography of the south aegean sea and the straits of the cretan arc march 1994 january 1995 abstract four seasonal oceanographic cruises were carried out in the eastern mediterranean sea within the framework of the cec mast mtp project pelagos during 1994 1995 the surveys covered the south aegean sea and the adjacent open sea regions southeastern ionian northwestern levantine analysis of ctd data revealed that a multiscaled circulation pattern prevails in the area it differs from the circulations detected during the 1986 87 thus indicating interannual variability cyclonic and anticyclonic gyres and eddies are interconnected by currents and jets variable in space and time most of the features are persistent others seem transitional or recurrent the hydrological structure is also complex and apart from the upper layer does not present basinwide any significant seasonality dynamical and hydrological regimes are variable in the upper and intermediate layers at the straits of the cretan arc while the deep regime seems rather constant topographic control is evident on the flows through the straits the new very dense deep water mass namely the cretan deep water cdw and a well defined intermediate layer of minimum temperature and salinity the so called transition mediterranean water tmw consists the new important structural elements of the south aegean sea the cdw outflows towards the deep and bottom layers of the eastern mediterranean thus considerably contributing to the formation of the new denser deep and bottom water of the eastern mediterranean which sinks and displaces the eastern mediterranean deep water of adriatic origin in the adjacent sea regions outside the aegean sea

reconstruction of sea surface temperatures from assemblages of planktonic foraminifera multi technique approach based on geographically constrained calibration data sets and its application to glacial atlantic and pacific oceans abstract we present a conceptual framework for a new approach to environmental calibration of planktonic foraminifer census counts this approach is based on simultaneous application of a variety of transfer function techniques which are trained on geographically constrained calibration data sets it serves to minimise bias associated with the presence of cryptic species of planktonic foraminifera and provides an objective tool for assessing reliability of environmental estimates in fossil samples allowing identification of adverse effects of no analog faunas and technique specific bias we have compiled new calibration data sets for the north n 862 and south n 321 atlantic and the pacific ocean n 1111 we show evidence that these data sets offer adequate coverage of the sea surface temperature sst and faunal variation range and that they are not affected by the presence of pre holocene samples and or calcite dissolution we have applied four transfer function techniques including artificial neural networks revised analog method and simmax with and without distance weighting on faunal counts in a last glacial maximum lgm data set for the atlantic ocean 748 samples in 167 cores based on the glamap 2000 compilation and a new data set for the pacific ocean 265 samples in 82 cores and show that three of these techniques provide adequate degree of independence for the advantage of a multi technique approach to be realised the application of our new approach to the glacial pacific lends support to the contraction and perhaps even a cooling of the western pacific warm pool and a substantial 3 c cooling of the eastern equatorial pacific and the eastern boundary currents our results do not provide conclusive evidence for lgm warming anywhere in the pacific the atlantic reconstruction shows a number of robust patterns including substantial cooling of eastern boundary currents with considerable advection of subpolar waters into the benguela current a cooling of the equatorial atlantic by 5 c and steep sst gradients in the mid latitude north atlantic the transfer function techniques generally agree that subtropical gyre areas in both hemispheres did not change significantly since the lgm although the ann technique produced glacial sst in the southern gyre 1 2 c warmer than today we have revisited the issue of sea ice occurrence in the nordic seas and using the distribution of subpolar species of planktonic foraminifera in glacial samples we conclude that the norwegian sea must have been ice free during the summer

late quaternary paleoenvironmental reconstruction and paleoclimatic implications of the aegean sea eastern mediterranean based on paleoceanographic indexes and stable isotopes the late quaternary palaeoenvironmental evolution and the main palaeoceanographic changes of the aegean sea was reconstructed using planktonic foraminifera obtained from the sediments of a northern sk 1 and a southern ns 14 core site multivariate statistical approach including q mode cluster and principal component pca analyses gives an insight into the relationships between sea surface environmental changes between the north and south aegean and furthermore serves as a baseline data set for palaeoclimatic and palaeoceanographic reconstructions of the eastern mediterranean sea stable isotope analyses coupled with additional paleoceanographic sea surface temperature sst productivity ssp stratification s index upwelling u index seasonality sn index proxies provide insights into the sedimentological hydrographic and trophic evolution and ecosystem dynamics of the aegean sea and furthermore serve as a baseline data set for palaeoclimatic and palaeoceanographic reconstructions of the eastern mediterranean sea concentrating on the last 19 ka faunal and isotopic data concur suggesting a series of climatic zones corresponding to well known climatic phases of the last glacial cycle cold and arid conditions during the late glacial period were followed by a warmer and wetter climate trend during deglacial time a marked seasonality characterized by homogenous water column favored by efficient upwelling during the winter and by warm stratified water column during the summer has also been recognized during this period bolling allerod b a in both basins an abrupt switch to cool arid climatic event younger dryas yd suggests a strengthening of winter convection around 12 9 ka which seems to be more evident in the north aegean core however the more pronounced environmental changes between the north and south aegean sea were identified during the holocene and they coincide with the deposition of sapropel s1 and sapropel mid holocene smh the comparison between sk 1 and ns 14 records indicated significant changes in both the productivity and stratification patterns with the former the main factor in north aegean and the latter in south aegean for s1 deposition regarding the localized deposition of smh in the semi enclosed shallow south aegean site the fully oxygenated and less productive water column conditions prevailing during that time 5 4 4 3 ka in the north aegean were the limiting factor for its deposition

approaches to unravel seasonality in sea surface temperatures using paired single specimen foraminiferal δ18o and mg ca analyses 1 seasonal changes in surface ocean temperature are increasingly recognized as an important parameter of the climate system here we assess the potential of analyzing single specimen planktonic foraminifera as proxy for the seasonal temperature contrast seasonality oxygen isotopes and mg ca ratios were measured on single specimens of globigerinoides ruber extracted from surface sediment samples of the mediterranean sea and the adjacent atlantic ocean variability in 18o and mg ca was then compared to established modern seasonal changes in temperature and salinity for both regions the results show that 1 average 18o derived temperatures correlate with modern annual average temperatures for most sites 2 the range in 18o and mg ca derived temperature estimates from single specimen analysis resembles the range in seasonal temperature values at the sea surface 0 50 m in the mediterranean sea and the atlantic ocean and 3 there is no strong correlation between mg ca and 18o derived temperatures from the same specimens in the current data set indicating that other parameters salinity carbonate ion concentration symbiont activity ontogenesis and natural variability potentially affect these proxies

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