a high resolution record of the last deglaciation in the central mediterranean sea palaeovegetation and palaeohydrological evolution abstract a high resolution palynological and stratigraphical record of a marine deep sea core in the adriatic sea documents marine and continental palaeoenvironmental changes in the basin during the last deglaciation and early holocene a chronology is derived from the oxygen isotope stratigraphy three periods of aridity marked by the development of a semi desert rich in artemisia occurred between 18 5 and 16 kyr between 14 4 and 12 7 kyr and between 11 1 and 9 7 kyr consistent with the last glacial maximum the oldest dryas and the younger dryas they are correlated with increases in productivity and intensification of the levantine water formation in the eastern mediterranean basin during the warmer bolling allerod 12 7 11 1 kyr the presence of the cold temperate dinocyst bitectatodinium tepikiense is interpreted as indicating the establishment of a strong seasonal thermal gradient probably linked to seasonal cold freshwater runoff from the po river attested by the unique presence of pollen of freshwater plants the expansion of forest and the development of the warmer dinocysts start with termination ib during the holocene three tree phases are recognized and are contemporaneous with the preboreal boreal and atlantic chronozones of europe the two phases of sapropel deposition are marked by higher pollen and dinocyst concentrations and a high representation of brigantedinium spp which indicate higher preservation of organic material and or freshwater runoff of the po river

environmental control on mediterranean salinity and δ18o a box model is presented to simulate changes in mediterranean long term average salinity and 18o over the past 20 000 years simulations are validated by comparison with observations sensitivity tests illustrate robustness with respect to the main assumptions and uncertainties the results show that relative humidity over the mediterranean remained relatively constant around 70 apparently narrowly constrained to the lower end of the range observed globally over sea surfaces by the basin s land locked character isotopic depletion in run off relative to the present is identified as the main potential cause of depletions in the mediterranean 18o record also slight increases in relative humidity of the order of 5 might have caused very pronounced isotopic depletions such as that in sapropel s5 of the penultimate interglacial maximum the model shows distinctly non proportional responses of 18o and salinity to environmental change which argues against the use of isotope residuals in mediterranean paleosalinity reconstructions

transgressive dune formation along a cliffed coast at 75 ka in sardinia western mediterranean a record of sea level fall and increased windiness transgressive dunes develop frequently along strandplain coastlines however they may also form along rocky coasts dominated by cliffs and embayments two lithified transgressive dune systems developed along the cliffed alghero coast nw sardinia italy have been investigated one aeolian system forms a cliff front anchored aeolian dune accumulation the other is a valley head anchored sand ramp system optically stimulated luminescence ages indicate that both systems formed around 75 ka this period which corresponds to the beginning of mis 4 was characterized by a relatively low sea level stand 15 m below the present sea level and was preceded by a sea level highstand 1 m asl around 81 ka mis 5a our results show that this rapid sea level fall exposed an enormous amount of marine sand which was transported inland by strong northerly winds and deposited in front of cliffs or in valley heads therefore sediment supply and sea level fall seem to be critical factors controlling dune formation along rocky coasts which generate time transgressive aeolianites terra nova 00 000 000 2010

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

size sorting in marine muds processes pitfalls and prospects for paleoflow speed proxies the basis for and use of fine grain size parameters for inference of paleoflow speeds is reviewed here the basis resides in data on deposited sediment taken in conjunction with flow speed measurements in the field experimental data on suspended sediment transport and deposition and theoretical treatments of the generation of size distributions of deposits from suspension controlled by particle settling velocity and flow speed in the deep sea sorting events occur under resuspension deposition events in benthic storms at flow speeds below 10 15 cm s 1 size in the noncohesive sortable silt 10 63 m range is controlled by selective deposition whereas above that range removal of finer material by winnowing also plays a role the best particle size instruments to measure a flow speed related grain size employ the settling velocity method while laser diffraction sizers can yield misleading results because of particle shape effects potential problems including source effects downslope supply on continental margins spatial variability of flow over bedforms and influence of ice rafted detritus are examined a number of studies using the sortable silt flow speed proxy are reviewed and inverse modeling of grain size distributions is examined outstanding problems are that corroboration is sparse because almost no studies have yet used the full range of proxies for flow rate and water mass identification and that the sortable silt mean size is not yet properly calibrated in terms of flow speed

the levantine intermediate water experiment liwex group levantine basin a laboratory for multiple water mass formation processes 1 in winter 1995 the last major field work of the physical oceanography of the eastern mediterranean poem program was carried out the levantine intermediate water experiment liwex in this study a thorough analysis is presented of the data set collected during three successive surveys in january february and march april 1995 the major overall result is that the levantine basin is shown to be the site for multiple and different water mass formation processes levantine deep water ldw was formed in the rhodes gyre with the preconditioning phase starting in december 1994 in late january the chimney was ventilating to the atmosphere in february the strong mixing phase is documented by the convective cell vertically homogeneous to 900 m depth in march april recapping has occurred in the upper 200 m ldw remained confined inside the rhodes gyre cyclonic circulation levantine intermediate water liw is instead deeply affected by the upper thermocline circulation shallow ventilating chimneys with the liw thermostads were found in the january survey inside the cyclonic region of the northern levantine the formation process of liw does not involve deep penetrative convection winter surface cooling and evaporation are sufficient to produce a surface mixed layer 100 m deep with liw characteristics at the mixed layer basis liw subducts and spreads along isopycnal surfaces along pathways determined by the cyclonic anticyclonic structures of the upper thermocline circulation

magnetobiostratigraphic chronology and palaeoenvironmental history of cenozoic sequences from odp sites 1165 and 1166 prydz bay antarctica a transect of three sites was drilled during leg 188 of the ocean drilling program odp proximal to the east antarctic ice sheet eais across the prydz bay continental shelf site 1166 slope site 1167 and rise site 1165 we present results of a palaeomagnetic and rock magnetic study of sediments recovered at sites 1165 and 1166 magnetostratigraphic interpretations are presented for both holes and are mainly constrained by diatom and radiolarian biostratigraphies interpreted in the light of recent refinements to southern ocean zonal schemes and datum calibrations for these microfossil groups site 1165 records a history of sedimentation on the continental rise extending back to earliest miocene times about 22 ma several long term changes characterise this record including an overall trend of decreasing sedimentation rates from the bottom to the top of the hole there is a progressive decrease in the sedimentation rate above about 308 mbsf meters below sea floor which is marked by a transition from dark grey fissile claystones to greenish grey diatom bearing clays at this transition ice rafted debris sand grains and total clay content also increase the chronology presented here indicates a middle miocene age 14 3 ma for the lithological transition correlation to odp hole 747a from the kerguelen plateau suggests that this lithological transition coincides with the base of the mi 3 3a 18o event which suggests palaeoclimatic control on middle miocene sedimentation changes at site 1165 core recovery was poor at site 1166 consequently the magnetostratigraphic data are of limited value the deepest cores recovered at site 1166 record brief intervals in the early history of the eais for the prydz bay region extending back through the early stage of glaciation to pre glacial times an early cretaceous fluvio lacustrine unit lagoonal deposits and sandy fluvio deltaic units of mid late eocene age contain a sporadic record of the transition from humid and mild conditions to cool temperate conditions

primary productivity variability on the atlantic iberian margin over the last 70 000 years evidence from coccolithophores and fossil organic compounds 1 this study analyzes coccolithophore abundance fluctuations e g emiliania huxleyi gephyrocapsa specimens and florisphaera profunda in core md01 2444 sediment strata retrieved at the iberian margin northeastern atlantic ocean coccolithophores are calcareous nannofossils a major component of the oceanic phytoplankton which provide information about past ecological and climatological variability results are supported by data on fossil organic compounds sea surface temperatures alkenones and n hexacosan 1 ol index and geochemical analyses benthic 13ccc and planktonic 18occ isotopes three scenarios are taken into account for this location at centennial scale resolution over the last 70 000 years the holocene and the stadial and interstadial modes the different alternatives are described by means of elements such as nutrients upwelling phenomena temperatures at surface and subsurface level or the arrival of surface turbid fresh and cold waters due to icebergs low sea level increased aridity and dust during the holocene moderate primary productivity was observed mainly concentrated in e huxleyi specimens surface temperatures were at maxima while the water column was highly ventilated by northern sourced polar deep waters and warmer subsurface nutrient poor subtropical waters over most of the last glacial stadials surface productivity weakened higher f profunda and reworked specimen percentages and lower diunsaturated and triunsaturated c37 alkenones the arrival of cold arctic surface waters traced by tetraunsaturated c37 peaks and large e huxleyi together with powerful ventilated southern sourced polar deep waters disturbed in all likelihood the delicate vertical equilibrium while preventing significant upwelling mixing finally during the last glacial interstadials lower f profunda percentages nonreworked material and higher diunsaturated and triunsaturated c37 alkenones a combined signal is observed warm surface temperatures were concurrent with generally low oxygenation of the deep sea floor moderate arrival of northern sourced deep waters and subsurface cold nutrient rich recently upwelled waters probably of polar origin these particular conditions may have promoted vertical mixing while enhancing surface primary productivity mainly of gephyrocapsa specimens

intensified deep pacific inflow and ventilation in pleistocene glacial times the production of cold deep waters in the southern ocean is an important factor in the earth s heat budget1 the supply of deep water to the pacific ocean is presently dominated by a single source the deep western boundary current east of new zealand here we use sediment records deposited under the influence of this deep western boundary current to reconstruct deep water properties and speed changes during the pleistocene epoch in physical and isotope proxies we find evidence for intensified deep pacific ocean inflow and ventilation during the glacial periods of the past 1 2 million years the changes in throughflow may be directly related to an increased production of antarctic bottom water during glacial times possible causes for such an increased bottom water production include increasing wind strengths in the southern ocean or an increase in annual sea ice formation leaving dense water after brine rejection and thereby enhancing deep convection we infer also that the global thermohaline circulation was perturbed significantly during the mid pleistocene climate transition between 0 86 and 0 45 million years ago

sortable silt and fine sediment size composition slicing parameters for palaeocurrent speed and palaeoceanography fine sediment size 63 ixm is best measured by a sedimentation technique which records the whole size distribution repeated size measurement with intermediate steps of removal of components by dissolution allows inference of the size distribution of the removed component as well as the residue in this way the size of the biogenic and lithogenic noncarbonate fractions can be determined observations of many size distributions suggest a minimum in grain size frequency curves at 8 to 10 ixm the dynamics of sediment erosion deposition and aggregate breakup suggest that fine sediment behavior is dominantly cohesive below 10 1xm grain size and noncohesive above that size thus silt coarser than 10 ixm displays size sorting in response to hydrodynamlc processes and its properties may be used to infer current speed silt that is f mer than 10 ixm behaves in the same way as clay 2 xm useful parameters of the distribution are the 10 63 ixm mean size and the percentage 10 63 ixm in the fine fraction we cannot use size distributions to distinguish the nature of the currents therefore to infer water mass advection speeds i e the mean kinetic energy of the flow ku regions of high eddy kinetic energy ke must be avoided at the present such abyssal regions lie under the high surface k e of major current systems gulf stream kuroshio agulhas antarctic circmpolar current and brazil falldand currents in the argenthe basin this is probably a satisfactory guide for the pleistocene with regard to the carbonate subfraction of the size spectrum size modes due to both cocco iths and foramlnlferal fragments can be recognized and analyzed with the boundary between them again at about 10 lm the flux of less than 10 lm carbonate at pelagic sites above the lysocline is another candidate for a productivity indicator

millennial scale variability in the productivity signal from the alboran sea record western mediterranean sea primary productivity of the alboran sea western mediterranean is reconstructed for the time interval 48 000 to 28 000 years bp using the following geochemical proxies calcium carbonate barium excess baexcess total organic carbon toc and alkenone concentration the records show a consistent pattern that indicates enhanced productivity during dansgaard oeschger d o warm periods at the same time deep water conditions were favorable for organic matter preservation in the sediments as indicated by the variation in redox sensitive elements such as mn cr or v and by the 13c record of benthic foraminifers the alboran sea productivity variation during d o cycles is explained by the succession of two climatic scenarios that led to latitudinal shifts of the westerly wind system this mechanism would also account for the variability in the deep water ventilation of the western mediterranean sea

rapid environmental changes in southern europe during the last glacial period oxygen isotope records from greenland ice cores1 2 indicate numerous rapid climate fluctuations during the last glacial period north atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of ice rafted debris3 4 5 in contrast very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents here we present high resolution geochemical physical and pollen data from lake sediments in italy and from a mediterranean sediment core linked by a common tephrochronology our lacustrine sequence extends to the past 102 000 years many of its features correlate well with the greenland ice core records demonstrating that the closely coupled ocean atmosphere system of the northern hemisphere during the last glacial4 extended its influence at least as far as the central mediterranean region numerous vegetation changes were rapid frequently occurring in less than 200 years showing that the terrestrial biosphere participated fully in last glacial climate variability earlier than 65 000 years ago our record shows more climate fluctuations than are apparent in the greenland ice cores together the multi proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials and provide a step towards determining the underlying mechanisms of the centennial millennial scale variability

abrupt cold spells in the northwest mediterranean hitherto unknown abundance peaks of left coiling l c neogloboquadrina pachyderma from a gulf of lions piston core indicate that abrupt cold spells associated with atlantic heinrich events affected the mediterranean n pachyderma l c is typical of sub polar waters in the open ocean the southern edge of its glacial north atlantic bioprovince reached south portugal only trace abundances of n pachyderma l c are known from quaternary mediterranean sediments suggesting that no significant invasions occured via the strait of gibraltar the gulf of lions abundance peaks therefore seem to reflect area specific thriving of a normally rare but indigenous taxon in the western mediterranean through local favorable habitat development the general planktonic foraminiferal record suggests that the basic hydrographic regime in the gulf of lions with wintertime deep convective overturn was relatively stable over the past 60 kyr under these conditions high abundances of n pachyderma l c would essentially imply temperature reductions of the order of 5 8 relative to the present

environmental and biological effects on the stable isotope composition of recent deep sea benthic foraminifera from the western mediterranean sea abstract the influence of microhabitat organic matter flux and metabolism on the stable oxygen and carbon isotope composition of live rose bengal stained and dead empty tests deep sea benthic foraminifera from the gulf of lions western mediterranean sea have been studied the total range of observed foraminiferal isotope values exceeds 1 0 for 18o and 2 2 for 13c demonstrating a wide range of coexisting disequilibria relative to 18o of equilibrium calcite 18oeq and 13c of bottom water dissolved inorganic carbon 13cdic the mean 18o values reveal strongest disequilibria for the studied epifaunal to shallow infaunal species cibicidoides pachydermus uvigerina mediterranea uvigerina peregrina while values approach equilibrium in deep infaunal species globobulimina affinis globobulimina pseudospinescens the mean 13c values decrease with increasing average living depths of the different species thus reflecting a dominant microhabitat pore water signal at the axis of the lacaze duthier canyon a minimum 13cdic pore water gradient of approximately 2 1 is assessed for the upper 6 cm of the surface sediment although live individuals of u mediterranea were found in different depth intervals their mean 13c values are consistent with calcification at an average living depth around 1 cm the deep infaunal occurrence of u mediterranea specimens suggests association with macrofaunal burrows creating a microenvironment with geochemical characteristics similar to the topmost centimeter this also explains the excellent agreement between stable isotope signals of live and dead individuals the ontogenetic enrichment in both 18o and 13c values of u mediterranea suggests a slow down of metabolic rates during test growth similar to that previously observed in planktic foraminifera enhanced organic carbon fluxes and higher proportion of resuspended terrestrial organic material at the canyon axis are reflected by 13c values of u mediterranea on average 0 58 lower than those from the open slope these results demonstrate the general applicability of the 13c signal of this species for the reconstruction of past organic matter fluxes in the mediterranean sea further studies on live specimens are needed for a more quantitative paleoceanographic approach

orbital and sub orbital scale climate impacts on vegetation of the western mediterranean basin over the last 48 000 yr article i nfo high resolution pollen analysis of alboran sea core md95 2043 provides a 48 ka continuous vegetation record that can be directly correlated with sea surface and deep water changes the reliability of this record is supported by comparison with that of padul sierra nevada spain marine isotope stage mis 3 was characterised by fluctuations in quercus forest cover in response to dansgaard oeschger climate variability mis 2 was characterised by the dominance of semi desert vegetation despite overall dry and cold conditions during mis 2 heinrich events hes 2 and 1 were distinguished from the last glacial maximum by more intensely arid conditions taxon specific vegetation responses to a tripartite climatic structure within the hes are observed in mis 1 the bolling allerod was marked by rapid afforestation while a re expansion of semi desert environments occurred during the younger dryas the maximum development of mixed quercus forest occurred between 11 7 and 5 4 cal ka bp with forest decline since 5 4 cal ka bp on orbital timescales a long term expansion of semi desert vegetation from mis 3 into mis 2 reflects global ice volume trends while holocene arboreal decline reflects summer insolation decrease the influence of precession on the amplitude of forest development and vegetation composition is also detected

a hydraulic box model study of the mediterranean response to postglacial sea level rise 1 this paper quantifies the role of changing sea level in affecting mediterranean stratification using a new model of the strait basin system which allows for explicit time dependence during the last deglaciation fairbank s meltwater peak 1b leads to rapidly rising global sea levels and a freshening of the oceans and hence increasing influx of ever freshening atlantic water into the mediterranean basin owing to long residence times the salinity of the deep and intermediate water reservoirs would have decreased more slowly so that the basin was more stably stratified for a period with possible implications for sapropel formation our model is used to estimate the size of this reservoir effect in comparison to the freshwater influx from the opening of the black sea at the bosphorus it is found that this mechanism affects the stratification to a similar degree as the black sea opening other climatic mechanisms have also affected the freshwater budget of the mediterranean at this time but their sizes are more difficult to quantify

phase relationships between millennial scale events 64 000 24 000 years ago a core recovered on the iberian margin off southern portugal can be correlated with greenland ice cores using oxygen isotope variability in planktonic foraminifera which closely matches the ice core records of temperature over greenland our age model identifies the base of every interstadial between 64 000 and 24 000 years ago and uses the greenland ice core project grip timescale the oxygen isotope signal in benthic foraminifera on this grip based timescale is quite different from the planktonic record and resembles the temperature record over antarctica when this is synchronized with greenland using the record of methane in the atmospheric air in the polar ice cores we interpret the benthic record as indicating significant fluctuations in ice volume during millennial events and we suggest that antarctic temperature changed as a function of ice volume

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

the seasonal characteristics of the circulation in the north mediterranean basin and their relationship with the atmospheric climatic conditions the greater heat losses sustained by the ligurian provencal basin in winter appear to be the major factor leading to the periodic intrusions of the warmer tyrrhenian water from the east this is the main conclusion of a 3 year oceanographic investigation carried out in the eastern ligurian provencal basin in order to monitor the long term characteristics of its exchanges with the tyrrhenian sea the analysis of the whole data set collected in this period shows that two currents converge north of corsica after having flowed along the northwestern side of corsica the west corsican current and through the corsican channel the tyrrhenian current while the former does maintain nearly steady properties year round the latter crosses the strait only during the coldest season thus showing a clear seasonal trend that begins again every year the comparison with the meteorological parameters of the ligurian provencal basin indicates that the winter intrusions of the tyrrhenian current are tightly associated with the heat and water losses through the rise induced in the upper basin density in addition to reintegrating the heat lost to the atmosphere the tyrrhenian flow might also restore the volume of the basin upper layer involved in the deep water formation processes this enables us to infer that a unique circulation pattern mostly driven by atmospheric climatic conditions involves the northern part of the western mediterranean sea

flux forced simulations of the paleocirculation of the mediterranean 1 a series of experiments with an ocean general circulation model of the mediterranean forced by artificial but realistic surface fluxes of heat and freshwater are performed the model has a stable thermohaline circulation under the baseline fluxes small decreases in excess evaporation 8 produce a linear weakening of the thermohaline circulation with less water formation and smaller strait transports levantine intermediate water production is shown to be very sensitive to additional freshwater input the dominant circulation mode in wetter climates is one with adriatic intermediate water formation and dispersal leading to ventilation of intermediate depths of the basin although the deep layers are not ventilated stratification is generally weak as the excess evaporation decreases stratification increases a 60 80 decrease leads to conditions closest to those suggested for sapropel s1 with a west east salinity gradient of half of today

ecological thresholds and patterns of millennial scale climate variability the response of vegetation in greece during the last glacial period the regional expression of millennial scale climate variability during the last glacial is examined with particular reference to the vegetation response in greece inspection of three pollen records from contrasting bioclimatic areas suggests that differences in the magnitude of cold events as recognized in the north atlantic and western mediterranean are expressed in terms of tree population changes only in areas with a range of favorable habitats by contrast records from sites where populations approach their tolerance threshold do not appear to resolve differences in the amplitude of the climate oscillations understanding the importance of local factors in modulating the biological response to climate change is critical when attempting to establish the spatial pattern of millennial variability

turbidite emplacement on the southern balearic abyssal plain western mediterranean sea during marine isotope stages 1 3 an application of itrax xrf scanning of sediment cores to lithostratigraphic analysis the upper part 0 20 m of a long piston core from the se balearic abyssal plain spanning the past 50 ka has been studied using the itrax micro xrf core scanner to obtain downcore elemental profiles the ca fe ratio was found to be an effective parameter to distinguish between turbidites and pelagites because turbidites generally have higher fe contents and lower ca contents compared with pelagic intervals beds that were obscure when visually logged could be identified as turbidites or pelagites on their geochemical characteristics allowing more complete subdivision of the sequence into genetic units the itrax xrf data also provide useful information on textural grading bioturbative mixing identification of geochemically distinctive marker beds indications of differences in provenance and confirm or query the presence of early arrivals during turbidite emplacement a chronostratigraphic framework for the core based on accelerator mass spectrometry ams radiocarbon dating and correlation with oxygen isotope stages of pelagic intervals in other cores using calcium carbonate stratigraphy was also established this shows that turbidite emplacement on this part of the balearic abyssal plain has been modulated strongly by climate and sea level change with turbidite emplacement most frequent during the early holocene when the rate of post glacial sea level rise was greatest deposition of the coarsest i e sand and silt based turbidites at the core site was restricted to the full and late glacial 11 25 ka turbidite emplacement during oxygen isotope stage 3 was rare most of the turbidites at the site are distal but some coarse grained based turbidites are characterized by higher sr ca ratios possibly indicating a higher aragonite content higher ca and lower fe contents compared to other turbidites and are interpreted as having a more proximal shelf source such turbidites are generally rare however and restricted to full glacial and younger dryas time there is little evidence for large scale seismogenic turbidites expected to be seen as randomly timed emplacement seemingly independent of eustatic control at the core site despite proximity to the seismically active algerian margin 100 km to the south this suggests that seismogenic turbidites must largely bypass this part of the plain although the itrax core scanner provides a rapid and non destructive means of characterizing downcore geochemical distributions in great detail interpretation of the data requires caution and assessment from an informed standpoint analytical artefacts such as those caused by water or organic content degree of compaction grain size and mineral effects unevenness of the cut core surface and poor discrimination of closely spaced element xrf peaks need identification and elimination

synchroneity between marine and terrestrial responses to millennial scale climatic variability during the last glacial period in the mediterranean region land sea climatic proxies have been obtained from the last glacial section of images core md95 2043 western mediterranean sea vegetation and alkenone derived sst curves indicate rapid 150 years and synchronous terrestrial and marine climatic changes paralleling the dansgaard oeschger d o climatic variability over greenland this frequency of climate change can be related to shifts between the two modes of operation of the north atlantic oscillation nao transfer functions applied to the pollen data indicate that there was an amplification of the climatic signal during heinrich events hes in comparison with other d o stadials the development and persistence of both scandinavian and atlantic mobile polar highs over southwestern europe may explain the extreme cooling 10 c and dryness 400 mm during heinrich events 5 and 4 in the mediterranean region comparison of the results of core md95 2043 with similar climatic data from images core md95 2042 located off portugal indicates that thermal and precipitation gradients occurred between the mediterranean and the atlantic sides of iberia within hes hes 4 and 5 are associated with more humid conditions in the atlantic by 200 mm than in the mediterranean site as is the case at the present time this comparison also illustrates the different behaviour of these areas during the d o stadials in contrast with the mediterranean site the atlantic site shows similar precipitation and temperature drops for all the d o stadials including those related to the hes here we propose the operation of different mobile polar highs mph as the driving mechanism for this difference in behaviour between the atlantic and mediterranean sides of iberia hes are related to a stronger influence of the scandinavian mph forcing a severe aridification and cooling of the full iberian peninsula the atlantic mph may have been dominant during the other stadials which would preferentially affect southwestern iberia

benthic foraminiferal evidence for reduced deep water circulation during sapropel deposition in the eastern mediterranean abstract an analysis of deep sea benthic foraminifera from six eastern mediterranean piston cores was carried out to determine the faunal response to the deposition of sapropel s5 formed between 125 000 and 116 000 yrs b p the pre s5 population is the most diverse being composed of miliolids articulina tubulosa gyroidina spp and various rotaliids an assemblage found near the base and top of s5 is dominated by chilostomella mediterranensis globobulimina affinis and bolivina spp and the post s5 fauna is dominated by a tubulosa and gyroidina spp the faunal data are interpreted in terms of the microhabitat preferences of the fauna based on living stained benthic foraminiferal data and associated morphological characteristics from the north atlantic epifaunal species dominate pre s5 and post s5 sediments and are associated with low organic carbon values ranging from 0 1 to 0 4 infaunal species occurring near or within sapropel layers are found with organic carbon values of 0 7 and live in environments characterized by low dissolved oxygen levels the dominance of epifaunal species within the pre s5 and post s5 sediments is interpreted to reflect low levels of food in a well oxygenated environment while the low abundance and dominance of infaunal taxa at the base and top of s5 reflects low food and low oxygen conditions although an increase in surface productivity may have occurred immediately preceding and during the deposition of s5 the critical factor in deposition of sapropel s5 is anoxia resulting from reduced ventilation of the deep waters the similarity of the faunal patterns in the six cores suggests that bathyal environmental conditions were uniform in the eastern mediterranean at depths ranging from 2042 to 3150 m during deposition of sapropel s5

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

proliferation and demise of deep sea corals in the mediterranean during the younger dryas abstract uranium series and radiocarbon ages are reported for deep sea corals madrepora oculata desmophyllum dianthus lophelia pertusa and caryophyllia smithii from the mediterranean sea u series dating indicates that deep sea corals have persisted in the mediterranean for over 480 000 years especially during cool interstadial periods the most prolific period of growth however appears to have occurred within the younger dryas yd period from 12 900 to 11 700 years bp followed by a short 330 years phase of post yd coral growth from 11 230 to 10 900 years bp this indicates that deep sea corals were prolific in the mediterranean not only during the return to the more glacial like conditions of the yd but also following the rapid deglaciation and transition to warmer conditions that followed the end of the yd surprisingly there is a paucity last glacial maximum lgm coral ages implying they were largely absent during this period when cold water conditions were more prevalent radiocarbon ages show that the intermediate depth waters of the mediterranean generally had 14 c compositions similar to surface waters indicating that these waters were extremely well ventilated the only exception is a narrow period in the yd 12 500 100 years bp when several samples of lophelia pertusa from the ionian sea had 14 c values falling significantly below the marine curve using a refined approach isolation ages isol of 300 years to 500 years are estimated for these intermediate 800 1000 m depth waters relative to surface marine waters indicating a reduction or absence of deep water formation in the ionian and adjacent adriatic seas during the yd contrary to previous findings we find no evidence for widespread intrusion of low 14 c atlantic waters into the mediterranean prolific growth of deep sea corals in the mediterranean ended abruptly at 10 900 years bp with many of the coral bearing mounds on the continental slopes being draped in a thin veneer of mud their demise is attributed to a number of factors including the direct loss of habitat due to high sedimentation that accompanied glacial meltwater pulses together with rising temperatures that would have finally pervaded the deeper water of the mediterranean following the onset of holocene warming

topographic control of oceanic flows in deep passages and straits saddle points between neighboring deep ocean basins are the sites of unidirectional flow from one basin to the next depending on the source of bottom water flow in these sites appears to be topographically controlled so the interface between the bottom water and the water above adjusts itself to permit bottom water flow from the basin that contains a source of bottom water into the next examples in the atlantic include flow in the romanche fracture zone the vema channel the ceara abyssal plain the anegada jungfern passage and the discovery gap but there are many more theoretical predictions of volume flux using a method that requires only conductivity temperature depth data archives and detailed knowledge of bathymetry near the saddle point are compared with volume flux estimates using current meters and or geostrophic estimates for seven cases the ratio of prediction to volume flux estimate ranges from 1 0 to 2 7 some ocean straits that separate adjacent seas are also found to critically control bidirectional flows between basins theory of the influence of rotation on such critical flows is reviewed predictions of volume flux in eight cases are compared with ocean estimates of volume flux from traditional methods

paleoceanography of the deep western boundary undercurrent on the north american continental margin for the past 25 000 yr temporal fluctuations of silt mean particle size and foraminiferal indices were used to examine fluctuations in velocity and position of the axis of the deep western boundary undercurrent dwbuc on the north american continental margin from 25 to 17 ka the dwbuc axis was 500 m shallower and farther inshore than its present position on the lower rise current speed was high from 25 to 20 ka and then waned until 17 ka between 17 and 7 ka the major axis of the dwbuc shallowed to 4000 m current speed increased from 17 to 11 ka but slowed from h to 7 ka since 7 ka the dwbuc axis has deepened to its modern position at 4900 m the zone of maximum carbonate dissolution remained below the dwbuc the most intense dissolution was from 22 to 9 ka and 5 to 2 ka highest abundance of uvigerina and highest percent benthic foraminifera were immediately above the dwbuc from 22 to 7 ka after which values of both parameters fell to near zero

high resolution stratigraphy of the mediterranean outflow contourite system in the gulf of cadiz during the late pleistocene the impact of heinrich events abstract a detailed high resolution stratigraphic analysis of the mediterranean outflow contourite system at the continental slope of the gulf of cadiz has been carried out through the correlation between a dense network of seismic reflection profiles sparker airgun 3 75 khz and parametric echosounder topas calypso giant piston and standard gravity cores from such correlation we determine a stacking pattern constituted by four main seismic units a d that are internally structured into ten subunits each subunit shows a single sequence formed by transparent seismic facies at the base to smooth parallel reflectors of moderate to high amplitude facies at the top being well correlated in the cores with a coarsening upward sequence the latest pleistocene holocene deposits form glacial interglacial depositional sequences related to cycles with a frequency range below the milankovitch band that corresponds to millennial timescale climatic changes such as dansgaard oeschger 1 5 ka and bond cycles 10 15 ka oxygen isotope records of planktonic foraminifera and the occurrence of ice rafted debris ird in the most recent contourite subunits show clear evidence of the influence of the north atlantic climatic conditions especially the climatic heinrich events h in the slope sedimentation of the gulf of cadiz and then in the circulation of the mediterranean outflow water mow the coarser contourite deposits are mostly associated with the last glacial maximum younger dryas and heinrich events on the central area of the middle slope during globally cooler conditions the mow was denser so that it was more active in deeper areas than today on the other hand during warm periods the mow became less dense favoring an increased intensity of the mow on the distal area of the upper slope therefore spatial and vertical fluctuations of the mow contourite system are strongly affected by global climate and oceanographic changes being clearly influenced by iceberg discharges and probably also by the resumption of thermohaline circulation in the north atlantic ocean during ice melting periods

regional synthesis of mediterranean atmospheric circulation during the last glacial maximum atmospheric circulation leaves few direct traces in the geological record making reconstructions of this crucial element of the climate system inherently difficult we produced a regional mediterranean synthesis of paleo proxy data from the sea surface to alpine altitudes this provides a detailed observational context for change in the three dimensional structure of atmospheric circulation between the last glacial maximum lgm 23 000 to 19 000 years ago and the present the synthesis reveals evidence for frequent cold polar air incursions topographically channeled into the northwestern mediterranean anomalously steep vertical temperature gradients in the central mediterranean imply local convective precipitation we find the lgm patterns to be analogous though amplified to previously reconstructed phases of enhanced meridional winter circulation during the maunder minimum the little ice age

a dynamic explanation for the origin of the western mediterranean organic rich layers the eastern mediterranean sapropels are among the most intensively investigated phenomena in the paleoceanographic record but relatively little has been written regarding the origin of the equivalent of the sapropels in the western mediterranean the organic rich layers orls orls are recognized as sediment layers containing enhanced total organic carbon that extend throughout the deep basins of the western mediterranean and are associated with enhanced total barium concentration and a reduced diversity dysoxic but not anoxic benthic foraminiferal assemblage consequently it has been suggested that orls represent periods of enhanced productivity coupled with reduced deep ventilation presumably related to increased continental runoff in close analogy to the sapropels we demonstrate that despite their superficial similarity the timing of the deposition of the most recent orl in the alboran sea is different than that of the approximately coincident sapropel indicating that there are important differences between their modes of formation we go on to demonstrate through physical arguments that a likely explanation for the origin of the alboran orls lies in the response of the western mediterranean basin to a strong reduction in surface water density and a shoaling of the interface between intermediate and deep water during the deglacial period furthermore we provide evidence that deep convection had already slowed by the time of heinrich event 1 and explore this event as a potential agent for preconditioning deep convection collapse important differences between heinrich like and deglacial like influences are highlighted giving new insights into the response of the western mediterranean system to external forcing

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

variability of the large scale general circulation of the mediterranean sea from observations and modelling a review abstract in this paper we present an overview of the most recent findings about the mediterranean sea present day circulation structure both historical observations and numerical model simulations are presented outlining the differences and agreement the model simulations are presented for both an eddy resolving and a coarse resolution numerical model and the results are intercompared the importance of the mesoscales in modifying the large scale flow field is elucidated the critical point is the discovery of the large amplitude interannual variability of the circulation and water mass structure associated with the anomalies of atmospheric forcing over the basin the seasonal variability can be strictly related to changes in heat and momentum fluxes while the interannual variability has a component which is related to the mesoscale field the latter is very intense in the algerian current region and levantine basin but different in structure in the two regions results are shown which confirm the importance of wind driving in establishing the kinetic energy of the flow field by comparing the current transport at the strait of corsica with observations in conclusion the essential characteristics of the present day circulation are associated with the atmospheric forcing and the basin topographic structure results from palaeoceanographic simulations for the last 20 000 years show that changing the atmospheric forcing can cause large changes in the circulation structure which may have affected sapropel formation

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

enhanced rainfall in the western mediterranean during deposition of sapropel s1 stalagmite evidence from corchia cave central italy a stable isotope record from a stalagmite collected from antro del corchia cave apuan alps central italy supported by 17 uranium series ages indicates enhanced regional rainfall between ca 8 9 and 7 3 kyr cal bp at the time of sapropel s1 deposition within this phase the highest rainfall occurred between 7 9 and 7 4 kyr cal bp comparison with different marine and lake records and in particular with the soreq cave record israel suggests substantial in phase occurrence of enhanced rainfall between the western and eastern mediterranean basins there is no convincing evidence for major climatic change at the time of the 8 2 kyr event

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

a sensitivity study of the general circulation of the western mediterranean sea part ii the response to atmospheric forcing abstract this paper investigates the influence of sea surface thermohaline fluxes and wind stress on the circulation of the western mediterranean sea using a high resolution 3d primitive equation model an 18 year experiment was forced with the daily output of a fine grid mesh numerical weather prediction model the major characteristics of the circulation are well reproduced the basin surface circulation is cyclonic over all of the basin the two anticyclonic alboran gyres are present the instabilities of the algerian current generate large anticyclonic eddies that invade the whole algerian basin the liguro provencal catalan current is well marked deep water convection down to the bottom only occurs during the first 3 years then winter intermediate water is produced the north south gradient of the atmospheric thermohaline fluxes induces a northward surface transport of water from the algerian basin into the liguro provencal basin this pattern can be associated with the balearic front sensitivity

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

the greenland ice sheet project 2 depth age scale methods and results the greenland ice sheet project 2 gisp2 depth age scale is presented based on a multiparameter continuous count approach to a depth of 2800 m using a systematic combination of parameters that have never been used to this extent before the ice at 2800 m is dated at 110 000 years b p with an estimated error ranging from 1 to 10 in the top 2500 m of the core and averaging 20 between 2500 and 2800 m parameters used to date the core include visual stratigraphy oxygen isotopic ratios of the ice electrical conductivity measurements laser light scattering from dust volcanic signals and major ion chemistry gisp2 ages for major climatic events agree with independent ages based on varve chronologies calibrated radiocarbon dates and other techniques within the combined uncertainties good agreement also is obtained with greenland ice core project ice core dates and with the specmap marine timescale after correlation through the 18 o of o 2 although the core is deformed below 2800 m and the continuity of the record is unclear we attempted to date this section of the core on the basis of the laser light scattering of dust in the ice

seismo stratigraphic characters of paleocontourites along the calabro tyrrhenian margin southern tyrrhenian sea abstract buried contourites located offshore capo suvero calabria southern italy have been investigated using analysis of sparker profiles the deposits onlap an erosional surface produced by a slide in the upper slope pleistocene units the overall seismic characters of the deposits suggest an interpretation as infilling drift deposits formed by the activity of a northward bottom current flowing along the paleoslope the deposits with thickness up to 140 m are made up of 3 units including 8 sub units with an upward convex shape on dip profile and a lenticular shape on strike profile the stacking pattern of sub units highlights a general upslope migration interrupted by two downslope shifts accompanied by erosion a general migration toward the north has also been recognized this evolution could be explained by autocyclic processes due to the seafloor modification during the growth of the deposits otherwise it could also be related to variations of the oceanographic conditions or eventually to sea level changes formation of the deposits located in the present day 110 240 m bathymetric range could have been significantly deeper than present location as a consequence of the regional uplift affecting the area since pleistocene under this hypothesis an intermediate current may be inferred for the formation of the deposits these deposits are quite rare along the tyrrhenian margins and their formation preservation seems to be related to the peculiar morphological setting of the area characterized by a morpho structural high and a slide scar their presence is relevant for the stratigraphy of the eastern tyrrhenian margin as they underline the importance of bottom current processes with implications on paleocirculation reconstructions of the mediterranean basin

yes some of the mediterranean outflow does come from great depth in 1973 stommel et al predicted that the western mediterranean deep water wmdw contributes directly to the mediterranean outflow through the strait of gibraltar strommel et al 1973 hydrographic data obtained in november 1985 showed unambiguous evidence of wmdw west of the major gibraltar sill thus confirming the prediction

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

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

deglacial meltwater pulse 1b and younger dryas sea levels revisited with boreholes at tahiti reconstructing sea level changes during the last deglaciation provides a way of understanding the ice dynamics that can perturb large continental ice sheets the resolution of the few sea level records covering the critical time interval between 14 000 and 9 000 calendar years before the present is still insufficient to draw conclusions about sea level changes associated with the younger dryas cold event and the meltwater pulse 1b mwp 1b we used the uranium thorium method to date shallow living corals from three new cores drilled onshore in the tahiti barrier reef no significant discontinuity can be detected in the sea level rise during the mwp 1b period the new tahiti sea level record shows that the sea level rise slowed down during the younger dryas before accelerating again during the holocene

a 130 000 year record of levantine intermediate water flow variability in the corsica trough western mediterranean sea abstract sortable silt particle size data and stable isotope analyses from the corsica trough western mediterranean sea provide a continuous palaeoceanographic record of the inflow ventilation and vertical fluctuations of the levantine intermediate water liw in the northern tyrrhenian sea for the last 130 000 years the results presented herein reveal that climate changes drive the mediterranean intermediate circulation on milankovitch to millennial time scales intensified intermediate inflow and ventilation in the corsica trough occurred throughout the last glacial interval with a cold faster warm slower pattern existing between the dansgaard oeschger climatic oscillations including heinrich events and the liw variability by contrast a weak intermediate ventilation characterised the holocene and the last interglacial period especially during insolation maxima and the sapropel deposition in the eastern mediterranean this variability probably reflects the changes of the eastern mediterranean net evaporation as well as the propagation to the western mediterranean of the profound hydrographic adjustments of the levantine sea and adjacent areas to climate forcing the implications for the formation and ventilation of the western mediterranean deep water wmdw in the northwestern mediterranean basin as well as for mediterranean atlantic exchange through the strait of gibraltar are discussed

evidence for enhanced mediterranean thermohaline circulation during rapid climatic coolings molecular biomarkers c37 alkenones n nonacosane and n hexacosanol and toc are used together with benthic 18o and 13c data to document the hydrographic response of the western mediterranean sea to rapid climatic variability these proxies are recorded in core md 95 2043 alboran sea affording the study of the dansgaard oeschger d o and heinrich he variability during the last glacial period the results suggest that rapid changes in the western mediterranean thermohaline circulation occurred in parallel to sea surface temperature oscillations enhanced deep water ventilation occurred during cold intervals he and d o stadials probably driven by a strengthening of north westerly wind over the north western mediterranean sea in contrast decreased intensity of the thermohaline circulation is detected during warm intervals d o interstadials which led to low oxygenated deep water masses and better preservation of the organic matter in the sediment

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

evidence of abrupt changes in western mediterranean deep water circulation during the last 50kyr a high resolution marine record from the balearic sea abstract the images core md99 2343 recovered from a sediment drift north of the island of minorca in the north western mediterranean sea holds a high resolution sequence that is perfectly suited to study the oscillations of the overturning system of the western mediterranean deep water wmdw detailed analysis of grain size and bulk geochemical composition reveals the sensitivity of this region to climate changes at both orbital and centennial millennial temporal scales during the last 50 kyr the dominant orbital pattern in the k al record indicates that sediment supply to the basin was controlled by the insolation evolution at 40 n which forced changes in the fluvial regime with more efficient sediment transport during insolation maxima this orbital control also modulated the long term pattern of the wmdw intensity as illustrated by the silt clay ratio however deep convection was particularly sensitive to climatic changes at shorter time scales i e to centennial millennial glacial and holocene oscillations that are well documented by all the paleocurrent intensity proxies si al ti al and silt clay ratios benthic isotopic records 13c and 18o show a dansgaard oeschger d o pattern of variability of wmdw properties which can be associated with changing intensities of the deep currents system the most prominent reduction on the wmdw overturning was caused by the post glacial sea level rise three main scenarios of wmdw overturning are revealed a strong mode during d o stadials a weak mode during d o interstadials and an intermediate mode during cooling transitions in addition d o stadials associated with heinrich events hes have a very distinct signature as the strong mode of circulation typical for the other d o stadials was never reached during he due to the surface freshening induced by the inflowing polar waters consequently the wmdw overturning system oscillated around the intermediate mode of circulation during he though surface conditions were more stable during the holocene the wmdw overturning cell still reacted synchronously to short lived events as shown by increments in the planktonic 18o record triggering quick reinforcements of the deep water circulation overall these results highlight the sensitivity of the wmdw to rapid climate change which in the recent past were likely induced by oceanographic and atmospheric reorganizations in the north atlantic region

neodymium isotopes in the mediterranean sea comparison between seawater and sediment signals nine depth profiles of dissolved nd concentrations and isotopic ratios epsilon nd were obtained in the levantine basin the ionian the aegean the alboran seas and the strait of gibraltar thirteen core top sediments and nile river particle samples were also analyzed leached with 1 n hcl acetic acid or hydroxylamine hydrochloride the seawater epsilon nd values become more radiogenic during the eastward circulation in the mediterranean sea the relationship between salinity and the seawater epsilon nd shows that the nd isotopic signature is more conservative than salinity in the mediterranean sea the water mass with the highest epsilon nd 4 8 is found at about 200 m in the easternmost levantine basin the average epsilon nd value for deep waters is 7 0 in the eastern basin 2 5 epsilon units higher than in the western basin by examining the sensitivity of seawater epsilon nd to nd inputs from the nile we conclude that the most significant radiogenic nd source is partially dissolved nile river particles the nd flux from the nile river water has a minor influence on the mediterranean seawater end except for the easternmost levantine basin the leachate epsilon nd values are consistent with the seawater values in the easternmost levantine basin the leachate end values obtained with hcl leaching are systematically higher than the seawater values the relationship between leachate and residual epsilon nd values indicates that the hcl leaching partially dissolves lithogenic nd so the dissolution of nile river particles is the cause of the observed shift some end values obtained with hydroxylamine hydrochloride leaching are higher than those obtained with hcl leaching although the reason for this shift is not clear sr 87 sr 86 successfully detects the presence of a nonmarine component in the leachate our results suggest that leaching performance may vary with the mineralogy of marine sediments at least in the case of the mediterranean sea copyright c 2004 elsevier ltd

mediterranean outflow strengthening during northern hemisphere coolings a salt source for the glacial atlantic abstract high resolution grain size and magnetic susceptibility records from the eastern gulf of cadiz site md99 2339 1170 m water depth reveal contourites formed by the mediterranean outflow mow during the last 47 kyr bp oscillations in the mow s intensity occurred in phase with greenland temperature variations with a stronger outflow during northern hemisphere coolings such as dansgaard oeschger stadials heinrich events and the younger dryas benthic 13c data implies the western mediterranean deep water as one of the main sources feeding the outflow current while differential changes in the properties of the mediterranean source and entrained north atlantic central water largely control the mow s strength detailed studies for heinrich events 1 4 and 5 show that the flow strength peaked only when subtropical surface waters prevailed in the eastern gulf of cadiz while incursions of icebergs and subpolar surface water were not favorable for the mow s intensification as the mow was strong when the atlantic s thermohaline circulation thc was weakened the heat and salt injected by the mow into the intermediate north atlantic waters might have preconditioned the thc to switch from the stadial to the interstadial mode

glacial to interglacial changes in the settling depth of the mediterranean outflow plume we present micropalaeontological and grain size records for a set of sediment cores from the gulf of cadiz southwest spain that reflect changes in the position and strength of the mediterranean outflow mo current the cores sample a sediment drift the gil eanes drift that is positioned lower on the slope in the gulf of cadiz than the position of the main current today the data indicate that the drift is of glacial age and that the glacial mo current was positioned lower on the slope than today but also that it was active over a considerably reduced area of the slope we argue that this observation is consistent with physical constraints on the gibraltar exchange and on the likely settling and spreading behavior of the mo plume along the iberian margin under glacial environmental and sea level conditions the deeper settling of the mo is likely to have influenced the formation of glacial north atlantic intermediate water and also may have exerted indirect influence on the formation of glacial north atlantic deep water

surface and deep water conditions in the sicily channel central mediterranean at the time of sapropel s5 deposition abstract new centennial scale data of benthic foraminifera assemblages and of stable isotopes of foraminifera shells from the sicily channel representative of surface and bottom waters over the interval between about 140 and 110 kyr bp are presented during this period anoxia developed on the eastern mediterranean basin and sapropel s5 deposited although anoxic sediments have not been deposited in the sicily channel this area is strategic to study the character of intermediate waters whose chemical physical properties strongly precondition the eastern mediterranean deep water formation so far no data from these water masses have been obtained apart from the isotopic composition of shells of the planktonic foraminifera species neogloboquadrina pachyderma which lives at about 200 m depth thus quite far from the intermediate water core we conclude that although with a reduced rate the flowing of intermediate waters coming from the eastern basin together with the surface water masses with a clear western affinity implies the maintenance of an anti estuarine circulation pattern across the sicily channel and in the mediterranean sea also during one of the most severe episodes of anoxia of the late pleistocene

promotion of meridional overturning by mediterranean derived salt during the last deglaciation we demonstrate that changes in the behavior of the mediterranean outflow water mow prior to and through the last deglaciation played an important role in promoting meridional overturning circulation moc estimation of past mow salt and heat fluxes indicates that they gradually increased through the last deglaciation between 17 5 and 14 6 thousand years ago ka b p where b p references year 1950 net evaporation from the mediterranean exported sufficient fresh water from the north atlantic catchment to cause an average salinity increase of 0 5 psu throughout the upper 2000 m of the entire north atlantic to the north of 25

palaeoclimate and the formation of sapropel s1 inferences from late quaternary lacustrine and marine sequences in the central mediterranean region abstract synchronous responses to climatic changes during the late pleistocene holocene transition are inferred from marine and lacustrine stratigraphic records in the central mediterranean region new stratigraphic data are presented from well dated sequences in the meso adriatic depression mad two crater lakes in the lazio region and in the tyrrhenian sea the sequences all span the last termination and the holocene but we focus here on the evidence in each record for the time period during which sapropel s1 formed in the mediterranean ca 9 0 to 6 8 cal kyr b p the new records provide evidence of palaeoenvironmental changes on land and sea that can be reconstructed at a high temporal resolution and which throw some light on the processes which led to the formation of s1 the collective evidence indicates that i organic rich sediments occurred in both the marine and the crater lake sites during the time of formation of the s1 sapropel ii there is evidence of increased stratification and anoxia in the sea water column during the period of s1 formation iii the s1 period in the study area is divisible into two sub phases s1a and s1b which reflect short term variations in oceanographic conditions stratification and anoxia iv changes in stratification in the marine column were contemporaneous with regional climate variations that are inferred from the terrestrial records we conclude that the key factor that initiated the formation of s1 was increased discharge of freshwater into the mediterranean following a change post 9 0 cal kyr b p to a warmer and wetter climate furthermore the period of s1 formation was interrupted by a short lived episode ca 500 years of comparatively cooler and drier conditions during the early middle holocene transition emht

a possible influence of the north atlantic oscillation on the circulation of the western mediterranean sea a current time series spanning from 1985 to 1996 in the corsica channel shows that seasonal and interannual variabilities are stable components of the circulation of the northern part of the western mediterranean sea for the first time these characteristics are related to the state of the north atlantic oscillation during winter we have found that this large scale control is mainly maintained through the air sea interaction processes which take place in the northern basin these results provide new elements for a consistent explanation of the major features of the basin circulation such as the seasonal increase of the boundary current and deep water formation

hydrothermal he and co2 at wudalianchi intra plate volcano ne china 3 he abstract chemical and isotopic compositions have been measured for co2 rich bubbling gases discharging from cold springs in wudalianchi intra plate volcanic area ne china observed 3 he 4 he ratios 2 3 ra and d 13 c values of co2 5 to 3 indicate the occurrence of a mantle component released and trans ferred to the surface by the cenozoic extension related magmatic activities the co2 3 he ratios are in wide range of 0 4 97 10 9 based on the apparent mixing trend in a

variable bottom water in the western mediterranean basin the deep water of the western mediterranean has long been considered to have practically constant values of s and between 1909 1910 the thor expedition and the 1970 cruise of the jean charcot the deep water at more than 1800 m depth showed very little variation the small changes which appeared through the years could be due in part to changes in instrumentation analysis and methods of sampling in 1972 and 1973 during the medoc cruises a bottom layer of 200 300 m thickness was found its temperature and salinity showed a small gradient producing at the bottom an increase of potential temperature of about 0 01 to 0 02 c and an increase in salinities of about 0 010 00 relative to a minimum of and s in the deep water at 1800 2000 m these minima of and s were found to be homogeneous horizontally at all stations occupied in the medoc area and in the ligurian sea in 1973 interestingly the bottom layer was not present in 1974 however in november 1981 during the cruise mediprod iv the variable bottom water was again present extending from the ligurian sea and medoc areas along the western coasts of corsica and sardinia to the eastern alboran sea in most cases the maximum values of and s were recorded at the bottom and were higher than the 1973 values by about 0 03 c and up to 0 0150 00 but with a rather high spatial variability by february 1982 cruise dyome ii the situation had become more complicated not only was a layer of minimum and s present but it was underlain by a layer of maximum and s below which a decrease appeared producing a new minimum at the very bottom in addition a number of stations displayed higher values of by about 0 05 c and of s by about 0 0150 00 in the layers of minimum and maximum characteristics as well as on the bottom in contrast to the situation in 1973 high spatial variability was found in the deep layering the variability may have been due to patchy deep convention activity possibly in the ligurian sea the phenomenon of variable bottom water and the processes which produce it may be relevant to our understanding of water mass formation

dominant northern hemisphere climate control over millennial scale glacial sea level variability abstract based on a radiocarbon and paleomagnetically dated sediment record from the northern red sea and the exceptional sensitivity of the regional changes in the oxygen isotope composition of sea water to the sea level dependent water exchange with the indian ocean we provide a new global sea level reconstruction spanning the last glacial period the sea level record has been extracted from the temperature corrected benthic stable oxygen isotopes using coral based sea level data as constraints for the sea level oxygen isotope relationship although the general features of this millennial scale sea level records have strong similarities to the rather symmetric and gradual southern hemisphere climate patterns we observe in constrast to previous findings pronounced sea level rises of up to 25 m to generally correspond with northern hemisphere warmings as recorded in greenland ice core interstadial intervals whereas sea level lowstands mostly occur during cold phases corroborated by climber 2 model results the close connection of millennial scale sea level changes to northern hemisphere temperature variations indicates a primary climatic control on the mass balance of the major northern hemisphere ice sheets and does not require a considerable antarctic contribution

suborbital climate variability during marine isotopic stage 5 in the central mediterranean basin evidence from calcareous plankton record abstract new faunal and floral records from ocean drilling project hole 963a resolved at 80 year spacing provide evidence of suborbital scale climate variability in the central mediterranean sea throughout marine isotope stage mis 5 cold events in the central mediterranean sea indicated by low abundances of warm species and high abundances of cold species are also evident in a planktonic foraminifera paleoclimatic curve they have been linked to ngrip greenland ice core c events and appear correlative with similar sub millennial climate fluctuations identified in the north atlantic region and in the alboran basin westernmost mediterranean low resolution benthic and planktonic oxygen isotope fluctuations parallel trends in the surface records evidenced by planktonic assemblage fluctuations bolstering their interpretation as climate proxies climate events also occur in the mediterranean between named c events and may be coeval with additional climate events identified recently in the western subtropical atlantic hence we propose that frequent climate oscillations during mis 5 characterize both sides of the mid latitude north atlantic perhaps indicating millennial scale variations in mid latitude atmospheric patterns

climatic forcing of eastern mediterranean deep water formation and benthic ecosystems during the past 22 000 years abstract lateglacial and holocene faunal and stable isotope records from benthic foraminifers in the eastern mediterranean sea ems suggest a high spatiotemporal variability of deep water oxygenation and biogeochemical processes at the sea floor during that time changes in the oxygenation and food availability of the deep sea ecosystems are closely linked to the hydrology of the ems borderlands they reflect orbital and suborbital climate variations of the high northern latitudes and the african monsoon system during the last glacial maximum cool surface waters and high evaporation resulted in maximum convection and oxic deep waters in all sub basins strong wind induced mixing fostered surface water production with seasonal phytodetritus fluxes during the glacial termination and the holocene oxygenation and food availability of deep sea benthic ecosystems were characterized by a pronounced regional differentiation local deep water formation and trophic conditions were particularly variable in the northern aegean sea as a response to changes in riverine runoff and black sea outflow during the interval of sapropel s1 formation in the early holocene average oxygen levels decreased exponentially with increasing water depth suggesting a basin wide shallowing of vertical convection superimposed by local signals in the northernmost aegean sea deep water ventilation persisted during the early period of s1 formation owing to temperature driven local convection and the absence of low salinity black sea outflow at the same time severe temporary anoxia occurred in the eastern levantine basin at water depths as shallow as 900 m this area was likely influenced by enhanced nutrient input of the nile river that resulted in high organic matter fluxes and related high oxygen consumption rates in the water column in the southern aegean and levantine seas we observe a gradual increase in deep water residence times preceding s1 formation by approximately 1 1 5 kyr once oxygen levels fell below a critical threshold the benthic ecosystems collapsed almost synchronously with the onset of s1 deposition the recovery of benthic ecosystems during the terminal phase of s1 formation is controlled by subsequently deeper convection and re ventilation over a period of approximately 1500 years after the re ventilation of the various sub basins had been completed during the middle and late holocene deep water renewal was more or less similar to recent rates during that time deep sea ecosystem variability was driven by short term changes in food quantity and quality as well as in seasonality all of which are linked to millennial scale changes in riverine runoff and associated nutrient input

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