the meridional temperature gradient in the eastern north atlantic during mis 11 and its link to the ocean atmosphere system temporal and spatial patterns in eastern north atlantic sea surface temperatures sst were reconstructed for marine isotope stage mis 11c using a submeridional transect of five sediment cores the sst reconstructions are based on planktic foraminiferal abundances and alkenone indices and are supported by benthic and planktic stable isotope measurements as well as by ice rafted debris content in polar and middle latitudes additionally the larger scale dynamics of the precipitation regime over northern africa and the western mediterranean region was evaluated from iron concentrations in marine sediments off nw africa and planktic 13c in combination with analysis of planktic foraminiferal abundances down to the species level in the mediterranean sea compared to the modern situation it is revealed that during entire mis 11c sensu stricto ss i e between 420 and 398 ka according to our age models a cold sst anomaly in the nordic seas co existed with a warm sst anomaly in the middle latitudes and the subtropics resulting in steeper meridional sst gradients than during the holocene such a sst pattern correlates well with a prevalence of a negative mode of the modern north atlantic oscillation we suggest that our scenario might partly explain the longer duration of wet conditions in the northern africa during mis 11c compared to the holocene

links between marine and atmospheric processes oscillating on a millennial time scale a multi proxy study of the last 50 000 yr from the alboran sea western mediterranean sea abstract the large dataset obtained from the extensive study of images core md95 2043 recovered from the alboran sea western mediterranean shows the periodicities and phase relationships of oceanographic and atmospheric processes on a millennial time scale the 1470 yr cycle is the most significant with the exception of the records reflecting climatic or environmental changes on land which show statistically significant 3300 and 8000 frequency bands the investigation of these core records on a millennial scale resolution allows us to establish the evolution of oceanographic and atmospheric mechanisms that influenced the western mediterranean region in the course of the dansgaard oeschger cycles accordingly possible land sea interactions can be identified and situated in the context of the temporal succession of the different climatic processes for instance saharan dust supply from northern africa appears to lead high latitude climate changes suggesting that low latitude feedback processes were involved in forcing the millennial climatic variability in the westernmost mediterranean

coupled deep water flow and climate variability in the middle pleistocene north atlantic abrupt changes in the strength of the atlantic meridional overturning circulation comprising northward flow of warm water and a cold southward return flow are implicated in abrupt climate changes in the late pleistocene a sensitive place to assess this circulation is in the cold return flow of deep western boundary currents here in records of flow speed and isotopic composition of surface and bottom waters from a deep western boundary current location near the northern source of north atlantic deep water we show both orbital and millennial scale coupling between deep ocean flow and climate in the middle pleistocene 0 75 0 87 ma when the boundary conditions in terms of the mean state and amplitude of climate change were different from more recent periods the coupling appears as a phased series of events initiated by reduced vertical density gradients and initial ventilation of deep waters the occurrence of these events in interglacials during the middle pleistocene suggests that the millennial scale climate variability in the north atlantic was more pronounced at that time than previously thought this demonstrates that given the right boundary conditions rapid climate shifts can also occur during relatively warm climate conditions

determining the natural length of the current interglacial terglacials can be used to draw analogies with the present provided their duration is known here we propose that the minimum age of a glacial inception is constrained by the onset of bipolar seesaw climate variability which requires ice sheets large enough to produce iceberg discharges that disrupt the ocean circulation we identify the bipolar seesaw in ice core and north atlantic marine records by the appearance of a distinct phasing of interhemispheric climate and hydrographic changes and ice rafted debris the glacial inception during marine isotope sub stage 19c a close analogue for the present interglacial occurred near the summer insolation minimum suggesting that the interglacial was not prolonged by subdued radiative forcing 7 assuming that ice growth mainly responds to insolation and co2 forcing this analogy suggests that the end of the current interglacial would occur within the next 1500 years if atmospheric co2 concentrations did not exceed 240 5 ppmv

paleoenvironmental changes at the lower pleistocene montalbano jonico section southern italy global versus regional signals abstract integrated high resolution data from calcareous plankton assemblages foraminifera and nannofossils together with geochemical and mineralogical investigations have been collected at the on land montalbano jonico section southern italy in order to reconstruct the paleoenvironmental changes through marine isotope stages mis 23 37 time series analysis on globigerina bulloides and cassidulina carinata 18o records and on selected calcareous plankton proxies mainly revealed the occurrence of precession and obliquity forcing the deposition of sapropel layers which are interbedded in the montalbano jonico section was driven by water column stratification insolation cycle i 104 and enhanced sea surface water productivity insolation cycle i 112 i 102 and i 86 different paleoenvironmental conditions mark the sedimentary evolution of the section from 1240 to 1082 ka mis 37 mis 32 high percentage abundances of warm and oligotrophic planktonic foraminifera and calcareous nannofossil taxa indicate the establishment of oligotrophic and stratified surface water conditions a key paleoenvironmental change occurred during mis 31 from about 1080 to 1065 ka which was a very warm interglacial characterized by an increase of tropical subtropical globigerinoides ruber group and globigerinoides trilobus and low salinity braarudosphaera bigelowii sea surface water taxa during this interval more humid climate conditions coupled with changes in local paleomorphology may have triggered a higher and unusual freshwater input and the creation of a new entry point for sediment supply into the basin from a different drainage area from about 1065 to 1010 ka mis 30 mis 29 a cool and dry climate prevailed in the circum mediterranean area during a time of precession maxima this favored lowered sea surface temperatures and an increase of polar water neogloboquadrina pachyderma left coiling there are also indications of a reduction of the terrigenous input from the new source area from 1010 ka upward mis 28 mis 23 the higher abundances of globigerina bulloides turborotalita quinqueloba and calciosolenia spp indicate enhanced productivity conditions probably related to high turbidity of sea surface waters triggered by a more conspicuous sediment input from land analysis of the long term trends in the multiproxy patterns suggests that the major paleoenvironmental changes occurred as a consequence of the combined effect of orbitally controlled global climate and regional processes

new mis 19 epica dome c high resolution deuterium data hints for a problematic preservation of climate variability at sub millennial scale in the oldest ice marine isotope stage 19 mis 19 is the oldest interglacial period archived in the epica dome c ice core 780 ky bp and the closest orbital analogue to the holocene albeit with a different obliquity amplitude and phase with precession new detailed deuterium measurements have been conducted with a depth resolution of 11 cm corresponding time resolution of 130 years they confirm our earlier low resolution profile 55 cm showing a relatively smooth shape over the mis 20 to mis 18 time period with a lack of sub millennial climate variability first thought to be due to this low resolution the mis 19 high resolution profile actually reveals a strong isotopic diffusion process leading to a diffusion length of at least 40 cm erasing sub millennial climate variability we suggest that this diffusion is caused by water veins associated with large ice crystals at temperatures above 10 c temperature conditions in which the mis 19 ice has spent more than 200 ky this result has implications for the selection of the future oldest ice drilling site

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

reconciling astrochronological and 40ar 39ar ages for the matuyama brunhes boundary and late matuyama chron when five matuyama brunhes m b boundary records from the north atlantic are placed on isotope age models produced by correlation of the 18o record directly or indirectly to an ice volume model the m b boundary lies consistently at the young end of marine isotope stage 19 with a mean age for the midpoint of the reversal of 773 1 ka standard deviation 0 4 kyr 7 kyr younger than the presently accepted astrochronological age for this polarity reversal 780 781 ka two recently proposed revisions of the age of the 40ar 39ar fish canyon sanidine fcs standard to 28 201 0 046 ma and 28 305 0 036 ma would adjust 40ar 39ar ages applicable to the m b boundary and other reversals and excursions back to 1 2 ma to ages older than the new astrochronological ages by 8 24 kyr the variables used to construct the ice volume models cannot account for the discrepancy the fcs standard age that best fits the astrochronological ages is 27 93 ma which is within the uncertainty associated with the commonly used value of 28 02 0 16 ma but younger than the recently proposed fcs ages the edc2 and edc3 age models in the dome c antarctic ice core yield ages of 771 7 ka and 766 4 ka respectively for the 10be flux peak that denotes the paleointensity minimum at the reversal boundary implying that the edc2 rather than edc3 age model is consistent with the observations from marine sediments at least close to the m b boundary

stress and velocity fields in glaciers part ii sliding and basal stress distribution numerical methods are used to examine the interaction between the spatial distribution of the basal shear traction and the corresponding basal velocity for an inclined slab geometry in our improved treatment we reject the common assumption that basal velocity is a simple function of local variables in favour of a non local treatment that includes normal deviatoric stress and takes basal velocity to be an integrated response to spatially varying influences computationally one must either iterate the basal velocity with a friction parameterization that relates basal shear traction to basal velocity or alternatively prescribe the basal shear traction that results from bed decoupling and substrate deformation the average of basal shear traction over the entire bed of the ice mass is invariant under changes in sliding distribution and thus constitutes a useful reference any local relative reduction of traction leads to basal movement either sliding over the bed or moving with a deforming subglacial layer the local stress reduction is accompanied by a concentration of traction up and down glacier of the moving base growth decay and possible migration ofbasal stress concentrations may be closely related to short lived sliding events and to surges

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

changes in vegetation and marine environments in the eastern mediterranean rhodes greece during the early and middle pleistocene pollen records marine faunal associations and stable isotope compositions of sediments from rhodes greece have been determined to track environmental changes in the eastern mediterranean during the early and middle pleistocene a detailed chronostratigraphic curve based on magnetostratigraphic data was obtained by correlating pollen spectra with the mediterranean oxygen isotopic curve of ocean drilling program site 975 five sedimentary sequences that correspond to marine oxygen isotope stage mis 31 27 and to mis 20 17 have been investigated in the confined tsampika microbasin high amplitude pinus variations confirm glacio eustatic changes deduced from changes in marine faunal associations and sedimentary depositional environments reflecting climatic cycles identified in the marine carbonate oxygen isotope record eight vegetation successions characterized by the dominance first of mesothermic elements then of mid and high altitude elements with pinus and ending with maxima in herb and steppe elements have been documented most of them were probably driven by changes in insolation occurring in high northern latitudes obliquity impact during the late early pleistocene and early middle pleistocene

binge purge oscillations of the laurentide ice sheet as a cause of the north atlantic s heinrich events ice rafted debris in sediment cores from the north atlantic suggests that the laurentide ice sheet lis periodically disgorged icebergs in brief but violent episodes which occurred approximately every 7 000 years here i propose that heinrich events i e what these episodes are called were caused by free oscillations in the flow of the laurentide ice sheet which arose because the floor of hudson bay and hudson strait is covered with soft unconsolidated sediment that forms a slippery lubricant when thawed the proposed heinrich event cycle has two phases the growth phase occurs when the sediment is frozen and the lis is stranded immobile on a rigid bed the volume of the lis slowly grows during this phase at a rate dictated by snow accumulation the purge phase occurs when the basal sediment thaws and a basally lubricated discharge pathway i e an ice stream such as those which occur in west antarctica today developes through hudson strait the volume of the lis rapidly equilibrates to the reduced basal friction during this phase by dumping icebergs into the labrador sea the periodicity t k sl2g 2 7000 years of the proposed heinrich event cycle is a function of the thermal conductivity and diffusivity of ice k and respectively the atmospheric sea level temperature sl in degrees celsius and the excess geothermal heat flux defined by g g k where is the atmospheric lapse rate and g is the geothermal heat flux agreement between the predicted t and the apparent periodicity implied by the marine record is the main virtue of the free oscillation mechanism i propose an alternative mechanism in which heinrich events are forced by periodic variations in external climate is implausible because periodic atmospheric temperature perturbations are strongly attenuated with depth in an ice sheet

ice shelf collapse from subsurface warming as a trigger for heinrich events episodic iceberg discharge events from the hudson strait ice stream hsis of the laurentide ice sheet referred to as heinrich events are commonly attributed to internal ice sheet instabilities but their systematic occurrence at the culmination of a large reduction in the atlantic meridional overturning circulation amoc indicates a climate control we report mg ca data on benthic foraminifera from an intermediate depth site in the northwest atlantic and results from a climate model simulation that reveal basin wide subsurface warming at the same time as large reductions in the amoc with temperature increasing by approximately 2 c over a 1 2 kyr interval prior to a heinrich event in simulations with an ocean model coupled to a thermodynamically active ice shelf the increase in subsurface temperature increases basal melt rate under an ice shelf fronting the hsis by a factor of approximately 6 by analogy with recent observations in antarctica the resulting ice shelf loss and attendant hsis acceleration would produce a heinrich event

marine and terrestrial climate variability in the western mediterranean sea during marine isotope stages 20 and 19 abstract the climate variability within late marine isotope stage mis 20 and mis 19 is examined with particular reference to the response of marine and terrestrial realms in the area surrounding the alboran sea western mediterranean sea sediment samples from the ocean drilling program site 976 were used to derive high temporal resolution average resolution of 450 years palynological pollen and spores and calcareous plankton coccolithophores and foraminifera records these data together with the new 18og bulloides make it possible to discuss the paleoenvironmental changes within a well constrained chronological frame cooler phases including late mis 20 and several cold spells during mis 19b a are marked on land by the expansion of open vegetation formations dominated by steppe and semi desert taxa at the same time the western mediterranean sea is marked by the incursion of north atlantic polar water planktonic taxa mis 19c and interstadials of mis 19b a are characterized by the spread of prevalent temperate forest taxa that parallel the expansion of warm water calcareous plankton taxa during periods of lighter 18o climate variations at both precessional and millennial to sub millennial time scales expressed by on land and marine signals highlight the sensitivity of the western mediterranean area to both orbital forcing and rapid internal oscillations of the climate systems involving remote connections with north hemisphere high latitudes the correlation within the central western mediterranean and north atlantic climate dynamics including the time spatial gradients related to regional and global climate processes contributes to the reconstruction of the earth climate dynamics and marine vs land responses in full early middle pleistocene transition these new evidences also provide an opportunity to improve knowledge of mis 19c now considered due to its orbital geometry the best orbital analogue to the holocene

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

nutricline variation in the equatorial atlantic coincident with the younger dryas variations in nutricline depth during the last deglaciation are recorded by the phytoplankton species florisphaera profunda a stacked record of six deep sea cores shows that across the entire equatorial atlantic there was a brief shallowing of the nutricline centered on 11 ka coincident with the younger dryas this shallowing is linked with high latitude north atlantic deglacial events we invoke high albedo and cool sea surface temperatures in the northern latitudes during 11 ka which steepened an already higher than expected winter insolation and hence temperature gradient for a time of june perihelion we postulate that the resultant increased pressure gradient caused an intensification of the northern hemisphere winter tropical easterlies which in turn caused equatorial divergence to occur in boreal winter

shell size variation of the planktonic foraminifer neogloboquadrina pachyderma sin in the norwegian greenland sea during the last 1 3 myrs implications for paleoceanographic reconstructions we present measurements of the maximum diameter of the planktonic foraminifer neogloboquadrina pachyderma sin from six sediment cores ocean drilling program sites 643 644 907 909 985 and 987 from the norwegian greenland sea our data show a distinct net increase in mean shell size of n pachyderma sin at all sites during the last 1 3 ma with largest shell sizes reached after 0 4 ma external factors such as glacial interglacial variability and carbonate dissolution alone cannot account for the observed variation in mean shell size of n pachyderma sin we consider the observed shell size increase to mirror an evolutionary trend towards better adaptation of n pachyderma sin to the cold water environment after 1 1 1 0 ma probably the mid pleistocene climate shift and the associated change of amplitude and frequency of glacial interglacial fluctuations have triggered the evolution of this planktonic foraminifer oxygen and carbon stable isotope analyses of diverent shell size classes indicate that the observed shell size increase could not be explained by the functional concept that larger shells promote increasing sinking velocities during gametogenesis for paleoceanographic reconstructions the evolutionary adaptation of neogloboquadrina pachyderma sin to the cold water habitat has significant implications carbonate sedimentation in highest latitudes is highly dependent on the presence of this species in the norwegian greenland sea carbonate poor intervals before 1 1 ma are therefore not necessarily related to severe glacial conditions they are probably attributed to the absence of this not yet polar adapted species further transfer function and modern analog techniques used for the reconstruction of surface water conditions in high latitudes could therefore contain a large range of errors if they were applied to samples older than 1 1 1 0 myrs 2000 elsevier science b v all rights reserved

vegetation and climate across the early middle pleistocene transition at montalbano jonico southern italy abstract pollen analysis of the montalbano jonico marine succession mjs southern italy provides a continuous vegetational record between 858 ka and 745 13 ka which includes marine isotope stage mis 19 now considered the closest orbital analogue to the holocene a comparison between paleoclimate proxies and global signals of past climate change allows the pollen record to be interpreted in terms of major environmental and climate modifications through mis 21 18 at the orbital and sub orbital scale this is also central to understanding migration patterns of the genus homo interglacials are expressed by the dominance of a mesophilic vegetation typical of a warm temperate and relatively humid climate deciduous quercus dominated fully temperate arboreal forest already devoid of subtropical taxa wooded steppes to steppes expanded during glacials when cold and dry conditions prevailed at mjs the main expansion of temperate forest dominated by broad leaved trees correlates to mis 19 3 whereas the expansion of steppe vegetation during drier conditions marks mis 19 2 directly above the volcaniclastic layer v4 dated at 773 9 1 3 ka more intensively arid conditions developed during mis 20 and mis 18 the pollen temperature index reaches its minimum in uppermost mis 20 in agreement with a significant cold and arid climate phase of wide significance in the north hemisphere as documented by prominent peaks in north atlantic ice rafted debris ird and mediterranean aeolian dust records on the other hand artemisia a significant component of steppes shows its maximum expansion during earlier phases of mis 18 millennial to sub millenial scale climate variability is evidenced by two abrupt short term pollen events within mis 19 3 which show a dominant increase of the cosmopolitan herbaceous component at around 783 54 ka and 774 84 ka respectively the vegetational and inferred climate changes for mis 19 offer two possibilities 1 to investigate the interglacial climate variability and discuss the linkage between climate and changes in geomagnetic field intensity close to the matuyama brunhes paleomagnetic boundary mbb and 2 to help evaluate the role of the mbb in defining the middle pleistocene global boundary stratotype section and point gssp with respect to point 2 a comparison of data at mjs with the pollen record at the nearby and coeval valle di manche section is relevant and evidences the complex response of vegetation to climate events possibly under the effects of both astronomical and local factors

precessional forcing of nutricline dynamics in the equatorial atlantic climate control of nutricline depth in the equatorial atlantic can be monitored by variations in the abundance of the phytoplankton species florisphaera profunda a conceptual model based on in situ evidence associates high abundances of f profunda with a deep nutricline and low abundances with a shallow nutricline a 200 000 year record of f profunda relative abundances obtained from a deep sea core sited beneath the region of maximum equatorial divergence at 10 w has 52 percent of its variance centered on the 23 000 year precessional band cross spectral analysis between the signals of f profunda and sea surface temperature independently derived from zooplankton species shows their 23 000 year cycles to be coherent and nearly in phase abundance minima of f profunda coincide with times of december perihelion whereas abundance maxima coincide with june perihelion these relations indicate that nutricline dynamics in the divergence region of the equatorial atlantic are controlled by variations in the tropical easterlies forced by the precessional component of orbital insolation on time scales greater than 10 000 years

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

northern hemisphere storm tracks during the last glacial maximum in the pmip2 ocean atmosphere coupled models energetic study seasonal cycle precipitation mid latitude eddies are an important component of the climatic system due to their role in transporting heat moisture and momentum from the tropics to the poles and also for the precipitation associated with their fronts especially in winter we study northern hemisphere storm tracks at the last glacial maximum lgm and their influence on precipitation using ocean atmosphere general circulation model oagcm simulations from the second phase of the paleoclimate modelling intercomparison project pmip2 the difference with pmip1 results in terms of sea surface temperature forcing fundamental for storm track dynamics is large especially in the eastern north atlantic where sea ice extends less to the south in oagcms compared to atmospheric only gcms our analyses of the physics of the eddies are based on the equations of eddy energetics all models simulate a consistent southeastward shift of the north pacific storm track in winter related to a similar displacement of the jet stream partly forced by the eddies themselves precipitation anomalies are consistent with storm track changes with a southeastward displacement of the north pacific precipitation pattern the common features of north atlantic changes in the lgm simulations consist of a thinning of the storm track in its western part and an amplification of synoptic activity to the southeast in the region between the azores islands and the iberian peninsula which reflects on precipitation this southeastward extension is related to a similar displacement of the jet partly forced by the eddies in the western north atlantic the synoptic activity anomalies are at first order related to baroclinic generation term anomalies but the mean flow baroclinicity increase due to the presence of the laurentide ice sheet is partly balanced by a loss of eddy efficiency to convert energy from the mean flow moisture availability in this region is greatly reduced due to more advection of dry polar air by stationary waves leading to less synoptic scale latent heat release and hence less precipitation also in terms of seasonality the stormy season is shifted later in the year by a few days to a month depending on the season and the model considered this shift does not directly reflect on the first order seasonal cycle of precipitation which also depends on other mechanisms especially in summer

saharan dust inputs to the western mediterranean sea depositional patterns geochemistry and sedimentological implications data are presented for a number of parameters for aerosols and rainwaters collected at a station on sardinia the findings are interpreted with special reference to saharan dusts and are compared to other data on these dusts obtained from a variety of sites around the mediterranean sea at the sardinia site the particle size distribution of the saharan outbreaks exhibits a bimodal structure the two modes being between 2 and 4 m and 15 and 30 m the presence of giant particles strongly affects the deposition velocities of the saharan aerosols source markers for the saharan dusts are palygorskite kaolinite calcite dolomite and rounded quartz grains the input of saharan dust has important effects on the chemistry of the mediterranean aerosols these include i increases in the atmospheric concentrations and sea surface fluxes of crust controlled trace metals e g al fe ii decreases in the efcrust values of non crust controlled trace metals e g cu zn and pb in the aerosols and iii changes in the solid state speciation of cu zn and pb which decrease their solubilities in seawater the saharan dusts also affect the composition of rainwater by raising the ph following the dissolution of calcium and by decreasing the solubility of trace metals such as cu zn and pb wet deposition controls the flux of saharan dust to the mediterranean sea but dry deposition can also be important the dust transport occurs in the form of pulses and the annual dust flux can be controlled by a few episodes of saharan outbreaks e g sometimes a single outbreak can account for 40 80 of the flux saharan dust deposition fluxes range from 2 to 25 g m 2 average 10 in the west mediterranean between 39 and 42 n from 6 to 46 g m 2 average 20 in the east mediterranean and from 0 4 to 1 0 g m 2 over the alps on continental europe the present day saharan dust fluxes 1 mg cm 2 year 1 account for about 10 20 of the recent deep sea sedimentation in the western mediterranean 3 15 mg cm 2 year 1

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

coccolithophore productivity and surface water dynamics in the alboran sea during the last 25kyr abstract coccolithophore productivity and surface water dynamics for the last 25 kyr in the alboran sea western mediterranean are described in a study of high resolution sedimentary records from two cores her gc t1 and ceuta10pc08 whose locations are currently characterized by different hydrographic conditions fossil coccolithophore assemblages and oxygen isotopes and alkenone and planktonic foraminifera derived sea surface temperature sst records allowed a reconstruction of the properties of the inflowing atlantic water aw which have proved to be a primary control of the variations in productivity in the neighborhood of the strait of gibraltar other local factors such as fluvial discharge wind induced and eddy induced upwelling are proposed to have influenced marine productivity in more distant areas the entrance of cold and less saline aw during the stadials associated with heinrich events 2 and 1 prevented primary productivity which increased along the last glacial maximum probably due to a greater fluvial discharge during terminations 1a and 1b the upper water column was affected by stratification although wind induced upwelling occurred locally the bolling allerod was characterized by a gradual increase in productivity and the development of the organic rich layer two phases of the younger dryas are recognized a first phase which was colder followed by a second phase which was warmer and wetter differences in productivity between both locations during these two phases can be attributed to fluvial discharge and the changing properties of the aw local hydrography such as the dynamics of the western anticyclonic gyre gained greater importance in determining productivity and its variations during the holocene which was the most productive period

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

a middle pleistocene northeast atlantic coccolithophore record paleoclimatology and paleoproductivity aspects abstract changes in paleoclimate and paleoproductivity patterns have been identified by analysing in conjunction with other available proxy data the coccolithophore assemblages from core md03 2699 located in the portuguese margin in the time interval from the marine isotope stage mis 13 14 boundary to mis 9 535 to 300 ka during the mid brunhes event the assemblages associated with the eccentricity minima are characterised by higher nannoplankton accumulation rate nar values and by the blooming of the opportunistic genus gephyrocapsa changes in coccolithophore abundance are also related to glacial interglacial cycles higher nar and numbers of coccoliths g mainly occurred during the interglacial periods while these values decreased during the glacial periods superimposed on the glacial interglacial cycles climatic and paleoceanographic variability has been observed on precessional timescales the structure of the assemblages highlights the prevailing long term influence of the portugal pc and iberian poleward ipc currents following half and full precession harmonics related to the migration of the azores high ah pressure system small gephyrocapsa and coccolithus pelagicus braarudii are regarded as good indicators for periods of prevailing pc influence gephyrocapsa caribbeanica syracosphaera spp rhabdosphaera spp and umbilicosphaera sibogae denote periods of ipc influence our data also highlights the increased percentages of coccolithus pelagicus pelagicus during the occurrence of episodes of very cold and low salinity surface water probably related to abrupt climatic events and millennial scale oscillations of the ah icelandic low il system

paleoceanography of the mid pleistocene the fossil record of the pleistocene calcareous nannoplankton indicates that during the mid pleistocene 0 93 1 25 my occurred an episode of overwhelming dominance of smallgephyrocapsa during this episode normally abundant large size specimens of this genus mainlygephyrocapsa oceanica were virtually excluded from the phytoplankton of tropical and subtropical oceans the best modern analog of this dominantly smallgephyrocapsa assemblage is the subpolaremiliania huxleyi assemblage which implies that nutrient content was significantly greater and water temperature was lower in the photic water column of the tropical oceans than they are today increased equatorial upwelling in the oceans on a scale much greater than today may explain the above pattern to achieve such broad equatorial upwelling there must be a source and a drive for cold dense water the arctic ocean which was probably seasonally free of ice during this interval of the mid pleistocene is capable of providing the requisite source as well as a drive for the inferred equatorial upwelling the energy balance of a predominantly ice free arctic ocean requires an approximately three to seven fold increase of hydrospheric heat transport from the north atlantic to the arctic ocean which dictates a corresponding or even greater increase in the volume of warm water entering the arctic ocean at the surface and cold dense water exiting at depth to the north atlantic such enhanced dense water formation in the arctic ocean could drive the intensified equatorial upwelling implied by the smallgephyrocapsa dominance interval if the above scenario is correct then the climate of the earth s northern hemisphere during the mid pleistocene may have been very different from the younger pleistocene climate one manifestation of this difference may be the mid pleistocene shift in climatic cycle periodicity from 40 ky to 100 ky another important aspect is that the enhanced greenhouse effect expected during the next century because of an increase of atmospheric co2 is thought to lead directly to melting of the arctic ocean ice cover and of the greenland ice sheet thus the greenhouse arctic ocean and its attendant ocean circulation would resemble the inferred mid pleistocene conditions

orbital forcing of continental climate during the pleistocene a complete astronomically tuned climatic record from lake baikal se siberia abstract a new composite bdp 96 biogenic silica record over the entire pleistocene was generated by splicing bdp 96 1 and bdp 96 2 drill cores from lake baikal crosschecked against a similar record from a nearby bdp 98 drill core a new astronomically tuned age model is proposed based on correlating peak biogenic silica responses with the timing of september perihelia this target is derived from analysis of regional climate proxy responses during the holocene the last interglacial and around paleomagnetic reversals by resolving virtually every precessional cycle during the pleistocene the new age model represents a major improvement compared with previously reported lake baikal timescales the astronomically tuned ages of the pleistocene paleomagnetic reversals are consistent with published dates the minimal tuning approach we used precession only has also aligned high signal power in a narrow obliquity band confirming the strong presence of orbital forcing there are also strong ca 100 ka scale cycles but these are not aligned with the orbital eccentricity despite the location of lake baikal in a continental interior that is highly sensitive to insolation forcing the tuned biogenic silica record reveals a consistent phase difference of 32 ca 4 ka relative to insolation in the obliquity band an inherent lag embedded in a continental proxy record not driven by global ice volume is an intriguing finding another new observation is that long term changes in sedimentation rates in lake baikal appear to be related to the amplitude of orbital forcing both amplitudes and sedimentation rates undergo significant changes during mis 24 mis 19 interval corresponding to the middle pleistocene transition with potential for linking continental and marine climato stratigraphies the new baikal record serves a new benchmark correlation target in continental eurasia as an alternative to june 65 n insolation and odp correlated timescales

enso like forcing on oceanic primary production during the late pleistocene late pleistocene changes in oceanic primary productivity along the equator in the indian and pacific oceans are revealed by quantitative changes in nanoplankton communities preserved in nine deep sea cores we show that variations in equatorial productivity are primarily caused by glacial interglacial variability and by precession controlled changes in the east west thermocline slope of the indo pacific the precession controlled variations in productivity are linked to processes similar to the southern oscillation phenomenon and they precede changes in the oxygen isotopic ratio which indicates that they are not the result of ice sheet fluctuations the 30 000 year spectral peak in the tropical indo pacific ocean productivity records is also present in the antarctica atmospheric co2 record suggesting an important role for equatorial biological productivity in modifying atmospheric co2

calcareous nannofossil changes during the mid pleistocene revolution paleoecologic and paleoceanographic evidence from north atlantic site 980 981 abstract new quantitative data on calcareous nannofossil assemblages through 583 1138 thousand years ago kyr have been acquired in high sample resolution 2 3 ky at northern atlantic odp ocean drilling program site 980 981 assemblage composition reflects a temperate paleobioprovince suggesting significant influx of warm north atlantic current at the site location during the mid pleistocene transition between marine isotope stage mis 35 and 15 three intervals have been described based on changes in nannofossil composition and abundance fluctuations of taxa reticulofenestrids are abundant just in the first interval mis 35 22 which is also characterised by the absence of gephyrocapsa 4 m and c pelagicus s l the latter occurring in upper mis 24 only the second interval corresponds to the expanded warm mis 21 that is accompanied by high carbonate content absence of both nannofossil reworking and ice rafted debris ird higher abundance of c leptoporus 5 8 m and h carteri and absence of c pelagicus s l and medium gephyrocapsids the third interval mis 20 15 records the occurrence of c pelagicus s l and medium gephyrocapsa generally higher abundance and higher amplitude fluctuations of helicoliths and absence of reticulofenestrids the major changes in nannofossil assemblages seem to be the result of combined paleoenvironmental factors related to sea surface water features temperature and nutrient availability sea ice cover and possibly to deep and intermediate water production of both northern and southern hemisphere origin during glacial and interglacial phases complex inter relationships between environmental parameters and evolutionary ecological factors are inferred to explain the patterns of coccolithus pelagicus subspecies whose distribution and abundance fluctuations are compared with the available patterns of turborotalia quinqueloba and neogloboquadrina pachyderma left coiled at site 980 and with the c pelagicus subspecies patterns from north atlantic dsdp deep sea drilling project site 607 and south atlantic odp site 1090 data collected provide additional information on stratigraphic distribution of selected taxa the first occurrence fo of gephyrocapsa omega is confirmed as a diachronous event even in the atlantic ocean while the first and last common occurrence fco lco of r asanoi appear as diachronous and synchronous events respectively on a global scale

early middle pleistocene transitions linking terrestrial and marine realms abstract marked by a progressive increase in the amplitude of climate oscillations an evolving waveform and a shift towards a quasi 100 ky frequency the early middle pleistocene transition empt previously known as the mid pleistocene transition or mid pleistocene revolution 1 4 0 4 ma represents a fundamental transformation in the earth s climate state the empt began with a substantial change in climate dynamics and ended with the mid brunhes event signaling the establishment of a new steady state the reasons for the empt while uncertain appear to involve a non linear response of the earth climate system the physical and biotic responses to this transition amplified by the growth of northern hemisphere ice sheets have been profound two important chronostratigraphic markers characterize the empt the jaramillo subchron 1 070 0 988 ma and the matuyama brunhes chron boundary 773 ka the latter has been chosen as the primary guide for the lower middle pleistocene subseries boundary as it lies at the approximate midpoint of the empt and aids in global recognition both in marine and terrestrial deposits the jaramillo subchron has received less attention but the late early pleistocene is important in europe because it saw the progressive transition from the villafranchian to galerian mammal faunas and expansion of hominins into western and northern europe the jaramillo subchron is represented by marine isotope stages mis 31 to 28 with mis 30 already showing the asymmetrical sawtooth pattern characteristic of the middle pleistocene indeed while variation in the 40 ky band obliquity remains strong throughout the empt low frequency variability begins at around 1250 1200 ky which coincides with a progressive increase in global ice volume against a backdrop of increasingly severe glacial cycles notably during mis 36 34 24 22 the so called 0 9 ma event 16 and 12 pronounced phases of warming are also documented globally including the super interglacial mis 31 the early phase of the empt is characterized by important glaciations beginning with mis 36 and continuing to mis 24 22 a major intensification of the east asian monsoon system intensification of loess deposition in northern europe development of open landscapes in western siberia increased fluvial incision higher amplitude sea level change and spread of large mammals across northern eurasia and a strong reduction in the north atlantic thermohaline circulation in europe the loss of thermophilous plant taxa during the empt and indeed throughout the quaternary is a reminder of the progressive cooling that took place here and elsewhere

reconstruction of precipitation in morocco since 1100 a d based on cedrus atlantica tree ring widths annual october through september precipitation from 1100 a d to modern times is reconstructed for morocco using cedrus atlantica endl carriere tree ring chronologies both multiple regression on principal components and the bootstrap method are used to calibrate tree ring width with precipitation precipitation variation is reconstructed for three climatically distinct areas the humid subhumid and arid regions of morocco a series of successive wet and dry periods is identified for the past 1000 years the maximum length of the 13 dry periods during which precipitation was at least 1 sigma below normal is six years twenty one years are identified during which precipitation fell more than 2 sigma below normal there is no significant correspondence in climatic variation in morocco europe and the sahel during this time period

late neogene paleoceanography of the eastern caribbean the gulf of mexico and the eastern equatorial pacific abstract calcareous nannofossil census data from the late neogene of the caribbean the gulf of mexico and the eastern equatorial pacific were subjected to a multifold analysis in order to extract the paleoceanographic history of the region a detailed nannofossil biostratigraphy is the basic time framework the paleoenvironmental signals are deduced from fluctuations of diversity dominance and equitability through time by clustering of assemblages through time and examining the composition of cluster groups by comparison of fluctuations in carbonate content and coarse fraction with time and by factor analysis of the assemblage these measures variously reflect surface water characteristics such as productivity bottom water characteristics such as corrosiveness dissolution and conditions of sedimentation such as dilution of the pelagic biogenic carbonate diversity dominance and equitability which are determined by surface water characteristics show similar trends often in considerable detail in the caribbean and the gulf of mexico from the late miocene through pleistocene broad but definite similarities exist in these measures between the caribbean gulf of mexico and the eastern equatorial pacific in the late miocene to mid pliocene but not in the late pliocene clustering groups assemblages in a broad biostratigraphic pattern corresponding approximately to a major assemblage zone the structure and composition of cluster groups indicate strong similarity between the caribbean and the gulf of mexico during the late miocene through pleistocene but only weak similarity of the caribbean and gulf of mexico to the eastern equatorial pacific and only during the early pliocene surface water productivity is generally similar at the three locations into the late pliocene but seemingly diverges in the eastern equatorial pacific after about 2 4 m y variations in dissolution intensity have generally similar trends in the late miocene and early pliocene in the caribbean and the gulf of mexico but the trends diverge in the late pliocene and are dissimilar in the pleistocene in the eastern equatorial pacific dissolution intensity increases with the inferred thermal subsidence of the crust variations in the calcium carbonate content of the sediment essentially pelagic carbonate follow different trends at the three sites which is attributable to different sedimentary histories at the sites tectonic plus eustatic sea level changes for the caribbean eustatic sea level changes alone for the gulf of mexico and dilution by biogenic silica plus dissolution for the eastern equatorial pacific the various measured and derived parameters indicate that as late as the mid pliocene approximately 3 8 m y a deep water connection existed between the pacific and the caribbean gulf of mexico a shallower seaway permitting exchange of surface water between the pacific and gulf of mexico seems to have existed into the late pliocene to between 3 0 to 2 2 m y and final closure probably coincided with the sea level draw down associated with the initial buildup of a northern hemisphere ice sheet during the late pliocene and early pleistocene surface productivity oscillates markedly but seemingly with different intensities in the caribbean and the gulf of mexico the most important floral change occurs in both basins at about 0 9 m y when the smallgephyrocapsa dominated high productivity nannoflora of the preceeding 0 3 m y was replaced abruptly by a moderate productivity flora this turnover marks a major change in ocean circulation towards a relatively warm stably stratified tropical surface ocean which seems to have been affected remarkably little by some of the intense late pleistocene high latitude climatic changes

decadal resolution record of winter monsoon intensity over the last two millennia from planktic foraminiferal assemblages in the northeastern arabian sea the indian monsoon system is an important climate feature of the northern indian ocean small variations of the wind and precipitation patterns have fundamental influence on the societal agricultu

planktonic response to main oceanographic changes in the alboran sea western mediterranean as documented in sediment traps and surface sediments abstract in order to determine the influence of seasonal oceanographic changes to the export of particulates and the flux of organisms as well as its corresponding integrated signal left in the bottom sediments of the alboran sea western mediterranean two mooring lines alb 1f and alb 1d were deployed from july 1997 to may 1998 on the continental slope south of malaga at 36 01 n 04 16 w and 36 14 n 04 28 w and a water depth of 1004 and 958 m respectively the mooring locations are under the influence of the incoming atlantic surface water asw at the northern and productive edge of the western alboran gyre wag and of the wind induced upwelling offshore the spanish coast additionally a total of five core tops located in the same area were studied the results are compared to information based on seawifs images of chlorophyll a concentration sst meteorological data on wind direction and intensity and fluvial discharges from the main rivers of the alboran basin the temporal oceanographic evolution of the alboran sea during the studied period was divided into five episodes e1 july 1997 e2 august october 1997 e3 november to mid december 1997 e4 december march 1998 and e5 april may 1998 the episodes represent different oceanographic conditions in the alboran sea during the studied period detailed analyses of the recorded pattern of bulk components calcareous nannoplankton planktonic foraminifera diatoms and phytoliths reflect seasonal changes in the main hydrographic regimes in the western alboran sea all biogenic bulk components as well as the annual evolution of the floral and faunal assemblages follow a tri modal pattern with maximum fluxes recorded during e1 e3 and e5 representing periods of higher productivity and wind induced upwelling during these periods species such as the small gephyrocapsa group gephyrocapsa muellerae and calcidiscus leptoporus the foraminifer globigerina bulloides and the diatom chaetoceros resting spores rs were dominant gephirocapsa oceanica and globorotalia inflata were coupled to the evolution of the atlantic surface water asw or related to surface water stability e2 and e4 the diatom leptocylindrus danicus responded to upwelling relaxation and water stratification e1 e2 and e4 and benthic diatoms were related to eddy intensity at bottom phytolith fluxes were directly related to wind intensities and the prevailing westerly winds e3 and e5 the distribution of microfossils in surface sediments differs from the biogenic assemblages recorded in the sediment traps in this sense during 1997 1998 the strongest el nino event in the last century took place which could have forced an unusual seasonality in the alboran sea reflecting an exceptional micropaleontological signal not observed in the surface sediments

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

calcareous plankton response to orbital and millennial scale climate changes across the middle pleistocene in the western mediterranean abstract the paleoenvironmental conditions through mis 15 9 at the mediterranean ocean drilling program odp site 975 were interpreted by high resolution study of calcareous plankton assemblages compared with available 18o and 13c records and high resolution paleoclimate proxies from the atlantic ocean sea surface temperatures ssts have been estimated from planktonic foraminiferal assemblages using the artificial neural networks method calcareous plankton varied dominantly on a glacial interglacial scale as testified by the sst record foraminiferal diversity total coccolith abundance and changes in warm water calcareous nannofossil taxa a general increase in foraminiferal diversity and of total coccolith abundance is observed during interglacials warmest ssts are reached during mis 11 while mis 12 and mis 10 represent the coldest intervals of the studied record during mis 12 one of the most extreme glacials of the last million years occurrence of globorotalia inflata and of neogloboquadrinids indicates a shoaling of the interface between atlantic inflowing and mediterranean outflowing waters among calcareous nannofossils the distribution of gephyrocapsa margereli gephyrocapsa muellerae 4 m also supports a reduced atlantic mediterranean exchange during mis 12 superimposed on glacial interglacial variability six short term coolings are recognized during mis 12 and 10 which appear comparable in their distribution and amplitude to the heinrich type events documented in the atlantic ocean in the same interval during these h type events neogloboquadrina pachyderma s and g margereli g muellerae 4 m increase as a response to the enhanced inflow of cold atlantic water into the mediterranean via the strait of gibraltar mediterranean surface water hydrography appears to have been most severely affected at termination v during the h type event ht4 possibly as a response to a large volume of atlantic meltwater inflow via the strait of gibraltar and or to freshwater terrigenous input deriving from local mountain glaciers three additional sst coolings are recorded through mis 14 16 but these are not well correlated with heinrich type events documented in the atlantic ocean in the same interval during these cooling episodes only the subpolar turborotalita quinqueloba increases these results highlight the sensitive response of the mediterranean basin to millennial scale climate variations related to northern hemisphere ice sheet instability and support the hypothesis that the tight connection between high latitude climate dynamics and mediterranean sea surface water features can be traced through the middle pleistocene

h4 abrupt event and late neanderthal presence in iberia heinrich event 4 h4 is well documented in the north atlantic ocean and the adjacent continents as a cooling event 39 000 yr before present bp to quantify the impact of this event with respect to climate and vegetation over the iberian peninsula we perform numerical experiments using a high resolution general circulation model forced by sea surface temperatures before and during h4 our model simulates an expansion of aridity over the peninsula during h4 a desertification of the south and a replacement of arboreal by herbaceous plants in the north all of which are in agreement with contemporaneous pollen sequences from marine cores located off the iberian peninsula our simulations demonstrate that the h4 marine event imprinted drastic changes over southern iberia which would not have favoured its occupation by anatomically modern humans therefore providing a plausible explanation for the delayed extinction of neanderthals in this region inferred from the archaeological record

enhanced seasonality of precipitation in the mediterranean during the early part of the last interglacial the deposition of sapropels in the eastern mediterranean sea is thought to occur during intervals of intensified african monsoon and increased precipitation in the mediterranean borderlands speleothem and pollen records however reveal conflicting evidence for a mediterranean wide precipitation increase suggesting that seasonal changes in the hydrological regime may be important using a multiproxy record we present the first independent evidence for seasonality of precipitation during the early last interglacial ca 130 119 ka from the tenaghi philippon peatland in northeast greece during the early part of the interglacial mineralogical macrofossil and pollen records from the same core show a shift from mire to lacustrine conditions simultaneous with an expansion of sclerophyllous vegetation and the presence of acicular aragonite indicating the onset of highly evaporative summer conditions this indicates enhanced seasonality of precipitation and reconciles the apparent incongruity between mediterranean pollen and speleothem records it also provides evidence for significantly increased winter precipitation coeval with the deposition of sapropel s5 one of the most prominent sapropels of the pleistocene we suggest that in addition to the summer african monsoon component increased winter precipitation from the northern mediterranean borderlands may have contributed to maintaining reduced surface water salinities in the mediterranean sea over the entire year

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

insolation cycles as a major control of equatorial indian ocean primary production analysis of a continuous sedimentary record taken in the maldives indicates that strong primary production fluctuations 70 to 390 grams of carbon per square meter per year have occurred in the equatorial indian ocean during the past 910 000 years the record of primary production is coherent and in phase with the february equatorial insolation whereas it shows diverse phase behavior with 18o depending on the orbital frequency eccentricity obliquity or precession examined these observations imply a direct control of productivity in the equatorial oceanic system by insolation in the equatorial indian ocean productivity is driven by the wind intensity of westerlies which is related to the southern oscillation therefore it is suggested that a precession forcing on the southern oscillation is responsible for the observed paleoproductivity dynamics

high resolution palaeoenvironmental reconstruction of odp hole 963d sicily channel during the last deglaciation based on calcareous nannofossils abstract a palaeoenvironmental reconstruction of ocean drilling program odp hole 963d sicily channel has been obtained on the basis of quantitative abundance fluctuations in the calcareous nannofossil assemblages the studied hole is characterized by a very high sedimentary resolution and covers the last ca 20 kyr a new palaeoclimatic curve based on the gephyrocapsa muellerae upper photic zone upz group ratio permitted the detection of the rapid climatic fluctuations that characterized the last deglaciation cold water masses occupied the sicily channel during the glacial period and the younger dryas whereas they were generally warm during the bolling allerod and the holocene an approach based on a direct relationship between actualistic data water samples and palaeontological records in the coccolithophores has been attempted in order to obtain the palaeoecological characterization with the proposition of two floristic groups pertaining to the upper photic zone and the lower photic zone lpz further information has been provided by several additional taxa during the investigated time interval stratification in the water column and oligotrophic conditions are always linked to the warm periods while high productivity caused by continuous convection of nutrient fluxes existed during the cold periods finally a simple model with two end members is proposed to explain the relative abundance of the deep dwelling species florisphaera profunda relative to other coccolithophores and to the physical conditions of the photic zone

a high resolution record of the last deglaciation in the sicily channel based on foraminifera and calcareous nannofossil quantitative distribution abstract relative abundance fluctuations in planktic foraminiferal and calcareous nannofossil assemblages are reported on the basis of a high resolution study of odp leg 160 hole 963d drilled in the sicily strait near capo rossello southern sicily with its 8 m of undisturbed sediments the core covers the interval from 1 5 to 23 kyr allowing a 50 100 yr sampling resolution all the short warm and cold events and sub events recorded in this time interval in the grip greenland ice core and at several mediterranean sites were recognized on this basis a total number of nine ecozones based on planktic foraminifera and seven ecozones based on calcareous nannofossils were identified a short interval of climatic amelioration identified above the base of the holocene precedes the segment contemporaneous with the deposition of sapropel s1 which has no lithological expression in the local sedimentary record this segment has been subdivided into the two warm s1a and s1b phases separated by a cold intermediate event a gradual climatic deterioration is recorded above the top of the interval correlated with sapropel s1 it is interrupted by short cold spells tentatively correlated with similar short duration cold events reported for this interval in the recent literature

changes in calcareous nannofossil assemblages during the mid pleistocene revolution the distribution of calcareous nannofossils are quantitatively analysed in high resolution deep sea core samples from north atlantic dsdp site 607 and eastern mediterranean odp site 967 between marine oxygen isotope stage mis 35 and 15 in order to observe the response of calcareous nannofossils to the mid pleistocene revolution mpr nannofossil abundance patterns show major variations through mis 25 22 and distinct higher amplitude changes from mis 21 upward sometime clearly correlatable to glacial interglacial cycles high amplitude short term fluctuations of small placoliths and f profunda characterize the interval through mis 24 to 22 21 suggesting strong instability in nutricline dynamics and surface water productivity principal component analysis and shannon weaver indices diversity and dominance highlight significant shifts mainly related to variations in the characteristics of surface waters in both sites a minimum in diversity is recorded at mis 22 21 corresponding to a maximum in the dominance of reticulofenestra spp at site 607 and of pseudoemiliania lacunosa at site 967 above mis 21 the increase in abundance of various taxa c leptoporus umbilicosphaera spp syracosphaera spp rhabdosphaera spp oolithotus spp and a general increase in diversity are related to a distinct trend toward more stable and oligotrophic surface waters in contrast to the higher productivity and less stratified surface waters of the early pleistocene in addition power spectral analysis was performed on calcareous nannofossil abundances shannon index diversity values and factor 1 of principal component analysis these show significant peaks in the obliquity 41 kyr and eccentricity 100 kyr frequency bands indicating that the quasi periodic oscillations in the climate proxy data are controlled by these orbital parameters a relationship between changes in abundance of calcareous nannofossils and production of glacial north atlantic deep water is inferred

vegetation response to obliquity and precession forcing during the mid pleistocene transition in western mediterranean region odp site 976 abstract the odp leg 161 site 976 alboran sea is a deep sea section sampled at a water depth of 1108 m in the western mediterranean sea pollen analysis provides a vegetation and climate record of the mid pleistocene transition mpt roughly one million years ago the age model tied to biostratigraphic events was revised by aligning the pollen climate index pci to mediterranean kc01b and global lr04 oxygen isotope records the studied time slice spans the interval 1 09 ma mis 31 to 0 90 ma mis 23 across this interval past phytogeography of nowadays extinct taxa which were rare allows a successful application of the modern analogues technique mat to quantitative climate reconstructions for the mpt five long term obliquity related vegetation successions o1 to o5 and eight short term precession related vegetation successions p1 to p8 are observed within the studied interval these vegetation successions regardless of their duration show the same pattern the progressive replacement of temperate trees by mountainous taxa and then by herbs and steppe maxima precession related successions correspond therefore to as dramatic vegetation changes as those driven by obliquity including a final steppe phase under deteriorated climate conditions wavelet analysis of the pci record shows that the western mediterranean experienced a shift at 1 01 ma from precession dominated frequencies 1 05 1 01 ma to obliquity dominated frequencies 1 01 0 9 ma there is therefore an apparent discrepancy between wavelet analysis results and vegetation dynamic analysis which suggests that obliquity and precession are recorded throughout the entire studied interval this discrepancy could result from the fact that the pci record sums somehow similar vegetation changes wet to dry occurring at different periodicities such a complex vegetation dynamics is mathematically rendered through a single parameter i e principal component which does not successfully catch the subtle combinations of variability occurring at two close periodicities furthermore the pollen inferred early pleistocene vegetation dynamic and climate of the western mediterranean region does not show a decrease of the obliquity response relative to the precession response at the onset of the mpt

millennial scale coccolithophore paleoproductivity and surface water changes between 445 and 360 ka marine isotope stages 12 11 in the northeast atlantic abstract a high resolution coccolithophore study was carried out in order to improve the understanding of the paleoceanographic evolution and changes in paleoproductivity occurring off the iberian margin im between 445 and 360 ka i e during late marine isotope stage 12 to 11 coccolithophore assemblages allowed reconstructing surface water changes characterized by millennial scale oscillations 1 5 kyr cycles involving portugal or iberian poleward currents pc and ipc prevalence changes in paleoproductivity possibly related to the upwelling of eastern north atlantic central waters enacw of sub tropical enacwst or sub polar origin enacwsp were also recognized this study also permitted detecting abrupt events stadial interstadial type oscillations and revealed that changes in paleoproductivity are related to opposite dynamics during glacial and interglacial stages with the reversed setting being established during the deglaciation furthermore a possible control of half and fourth precessional cycle components on the occurrence of abrupt changes within the assemblages structure during the deglaciation is proposed on the basis of wavelet analysis results applied to selected taxa

wet to dry climatic trend in north western iberia within heinrich events abstract the direct sea land correlation applied to core md99 2331 retrieved from the north western iberian margin shows a two phase pattern within heinrich events 4 2 and 1 in the ocean and in the adjacent landmasses changes between wet cold and dry cool conditions in the iberian peninsula detected during these extreme events cannot be explained by a simple oceanographic mechanism related to changes in the strength of the atlantic meridional overturning circulation here we propose an additional atmospheric mechanism able to produce this scenario based on the comparison between the md99 2331 record and other available palaeoclimate sequences from the north atlantic region 18 75 n and 0 75 w the climatic asymmetry observed between mid and subtropical eastern north atlantic latitudes wet dry and the blake outer ridge dry wet during h4 h2 and h1 can be explained by changes in the position of the atlantic jet stream during the first phase of h4 h2 and h1 the atlantic jet stream was located further south following the southward displacement of the oceanic thermal front as far south as 35 37 n on the contrary during the second phase of h4 h2 and h1 the jet stream was located further north following the northward displacement of this thermal front as far north as 42 n from the atmospheric point of view these two phases are reminiscent of the present day negative and positive prevailing modes of the north atlantic oscillation nao respectively but high resolution studies of additional north atlantic key sites and climate simulations are needed to confirm the hypothesis of a nao like mechanism operating on millennial timescales

the role of orbital forcing in the early middle pleistocene transition abstract the early middle pleistocene transition empt is the term used to describe the prolongation and intensification of glacial interglacial climate cycles that initiated after 900 000 years ago during the transition glacial interglacial cycles shift from lasting 41 000 years to an average of 100 000 years the structure of these glacial interglacial cycles shifts from smooth to more abrupt saw toothed like transitions despite eccentricity having by far the weakest influence on insolation received at the earth s surface of any of the orbital parameters it is often assumed to be the primary driver of the post empt 100 000 years climate cycles because of the similarity in duration the traditional solution to this is to call for a highly nonlinear response by the global climate system to eccentricity this eccentricity myth is due to an artefact of spectral analysis which means that the last 8 glacial interglacial average out at about 100 000 years in length despite ranging from 80 000 to 120 000 years with the realisation that eccentricity is not the major driving force a debate has emerged as to whether precession or obliquity controlled the timing of the most recent glacial interglacial cycles some argue that post empt deglaciations occurred every four or five precessional cycle while others argue it is every second or third obliquity cycle we review these current theories and suggest that though phase locking between orbital forcing and global ice volume may occur the chaotic nature of the climate system response means the relationship is not consistent through the last 900 000 years

an atlantic lead over pacific deep water change across termination i implications for the application of the marine isotope stage stratigraphy globally synchronous changes in glacioeustatic sea level provide a particularly useful stratigraphic reference in the study of glacial interglacial climate change and form the basis for the marine isotope stage mis system which posits a dominant glacioeustatic signal in benthic foraminferal 18o however benthic 18o strictly does not represent a pure sea level record and it is shown here that due to local changes in deep water hydrography the mis 2 1 boundary i e benthic 18o change occurred 4000 years later in the deep eastern equatorial pacific than in the deep northeast atlantic this discrepancy is too large to be attributed entirely to the pacific lag that may be expected due to the mixing time of the ocean basins instead multiple proxies including benthic foraminiferal mg ca suggest that the large offset in benthic 18o most probably resulted from a late rise in deep water temperature at the pacific site and a series of coupled deep water temperature and 18o changes at the northeast atlantic site these findings have important implications for the application of the mis stratigraphy and the interpretation of benthic 18o records in general as they show that benthic 18o fluctuations and mis boundaries from different hydrological settings may be significantly diachronous these results call into question the leads and lags that we might infer from a naive interpretation of benthic 18o as a sea level proxy with a direct bearing on the mechanisms that we may propose to explain glacial interglacial climate transitions

coccolithophores as proxy of seawater changes at orbital to millennial scale during middle pleistocene marine isotope stages 14 9 in north atlantic core md01 2446 quantitative coccolithophore analyses were performed in core md01 2446 located in the midlatitude north atlantic to reconstruct climatically induced sea surface water conditions throughout marine isotope stages mis 14 9 the data are compared to new and available paleoenvironmental proxies from the same site as well as other nearby north atlantic records that support the coccolithophore signature at glacial interglacial to millennial climate scale total coccolithophore absolute abundance increases during interglacials but abruptly drops during the colder glacial phases and deglaciations coccolithophore warm water taxa wwt indicate that mis11c and mis9e experienced warmer and more stable conditions throughout the whole photic zone compared to mis13 mis11 was a long lasting warmer and stable interglacial characterized by a climate optimum during mis11c when a more prominent influence of the subtropical front at the site is inferred the wwt pattern also suggests distinct interstadial and stadial events lasting about 4 10 kyr the glacial increases of gephyrocapsa margereli g muellerae 3 4 m along with higher values of corg additionally supported by the total alkenone abundance at site u1313 indicate more productive surface waters likely reflecting the migration of the polar front into the midlatitude north atlantic distinctive peaks of g margereli muellerae 4 m c pelagicus pelagicus neogloboquadrina pachyderma left coiling and reworked nannofossils combined with minima in total nannofossil accumulation rate are tracers of heinrich type events during mis12 and mis10 additional heinrich type events are suggested during mis12 and mis14 based on biotic proxies and we discuss possible iceberg sources at these times our results improve the understanding of mid brunhes paleoclimate and the impact on phytoplankton diversity in the midlatitude north atlantic region

seven ambiguities in the mediterranean palaeoenvironmental narrative abstract a review of seven outstanding issues on mediterranean palaeoenvironments is presented these are related to the dominant orbital pacing of climate variability the length of the interglacial vegetation succession the influence of the african summer monsoon the seasonality of precipitation during boreal insolation maxima the moisture balance during glacial maxima and the appearance of the mediterranean type climate rhythm and evolution of mediterranean sclerophyllous plants what emerges is that 1 marine 18oplanktonic and sst records show that precession has been a fundamental tempo of mediterranean climate change representing both a low latitude signal runoff from north africa and the direct influence of insolation at mediterranean latitudes but high latitude glacial effects 41 kyr and 100 kyr cycles became superimposed after 2 8 ma sapropel and dust deposition patterns in marine cores reveal that obliquity also has an effect on mediterranean climate through dry wet oscillations which are independent of glacial interglacial variability 2 the temperate part of interglacial vegetation succession has a duration of approximately half a precession cycle this persisted during the interval of obliquity dominated glacial cycles 2 8 1 ma with distinct forest successions following the precessional cycles however these are not always separated by an open vegetation phase because of minimal ice growth producing an impression of a prolonged interglacial forest interval 3 the effect of an enhanced african monsoon during summer insolation maxima has been mainly indirect in terms of nile discharge and runoff along the north african coast leading to increased freshwater input into the mediterranean sea reduced deep water ventilation and sapropel deposition 4 the notion of an accentuated summer rain regime in the northern mediterranean borderlands also contributing to a freshening of the mediterranean sea during boreal insolation maxima is not supported by the available evidence which suggests increased summer aridity 5 recent improvements in chronological precision and data resolution point to an increase in aridity and decreased temperatures during the last glacial maximum 21 2 ka but suggest an increase in effective moisture during the immediately preceding interval of 24 27 ka 6 the mediterranean type climate is not exclusively a post 3 6 ma phenomenon but may have appeared intermittently during the course of the tertiary or before 7 if that is the case then the paradigm that the sclerophyllous evergreen habit represents a pre adaptation to summer drought may need re evaluation

northern hemisphere storm tracks in present day and last glacial maximum climate simulations a comparison of the european pmip models abstract extratropical weather systems are an essential feature of the midlatitude climate and global circulation at the last glacial maximum lgm the formation of regions of high transient activity referred to as storm tracks is strongly affected by the presence of large ice sheets over northern america and scandinavia and by differences in sea surface temperature sst distributions in the framework of the palaeoclimate modelling intercomparison project simulations of the lgm climate have been run with a wide range of atmospheric general circulation models agcms using the same set of boundary conditions allowing a valuable comparison between simulations of a climate very different from the present one in this study the authors focus on the storm track representation in the models and its relationship with the surface temperatures the mean flow and the precipitation storm tracks are described using transient eddy diagnostics such as mean sea level pressure variance and three dimensional

microplankton response to environmental conditions in the alboran sea western mediterranean one year sediment trap record abstract the present work analyses the seasonal evolution of planktonic assemblages and particle fluxes through the water column in the eastern alboran sea western mediterranean at 35o55 47 n 01o30 77 w a sediment trap was deployed below the influence of the almeria oran front aof a semi permanent geostrophic front during july 1997 to june 1998 overall the temporal variability of coccolithophore planktonic foraminifer diatom benthic and wind carried biogenic particle fluxes is linked to the seasonal evolution of sea surface hydrological structures maximum planktonic fluxes were found during high productivity periods and wind induced upwelling following a trimodal pattern with maximum fluxes in july 1997 november december 1997 and april may 1998 these periods were characterized by vertical mixing and the full development of anticyclonic gyres in the alboran sea the annual flux of coccolithophores was dominated by the small gephyrocapsa group and emiliania huxleyi whereas turborotalita quinqueloba and globigerina bulloides dominated the foraminiferal fluxes and chaetoceros resting spores rs were predominant in the diatom assemblage benthic specimens were also collected with the sediment trap suggesting a variable influence of bottom water activity wind driven particles phytoliths and fresh water diatoms were collected along the year but their fluxes followed the local wind regime the high sea surface temperature sst during fall due to weaker than usual westerly winds and the pressure anomaly prevailing in the alboran sea during early winter were reflected in the planktonic assemblages by the proliferation of warm lower photic layer inhabitants and or oligotrophic taxa of coccolithophores florisphaera profunda planktonic foraminifers globigerinoides ruber and globorotalia inflata and diatoms leptocylindrus danicus these unusual climatic conditions in the eastern alboran sea must have been caused by the 1997 1998 enso event

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

surface circulation in the alboran sea western mediterranean inferred from remotely sensed data 1 in this study for the first time at regional scale the combined use of remote sensing data altimetry and sea surface temperature records provides a description of the persistent recurrent and transient circulation regimes of the alboran sea circulation the analysis of 936 altimeter derived weekly absolute dynamic topography adt and surface geostrophic current maps for 1993 2010 reveals the presence of a dominant annual signal and of two interannual modes of variability the winter spring phase is characterized by two stable gyral scale features the well known western anticyclonic gyre within the western area and the central cyclonic gyre a new structure not identified in former studies occupying the central and eastern parts of the alboran sea a double anticyclonic gyre regime constitutes the stable circulation system of the summer autumn period when the eastern anticyclonic gyre is formed within the eastern alboran basin in this case the central cyclonic gyre is narrower and located closer to the western anticyclonic gyre they represent two stable states of the system robust at the decadal time scale whereas transient changes reflect perturbations on these stable states and are mainly observed at an interannual scale the circulation variability and the gyral features development may be dynamically linked to the corresponding changes of the gibraltar transport rates citation renault l t oguz a pascual g vizoso and j tintore 2012 surface circulation in the alboran sea western mediterranean inferred from remotely sensed data j geophys res 117 c08009 doi 10 1029 2011jc007659

paleoenvironmental conditions at core kc01b ionian sea through mis 13 9 evidence from calcareous nannofossil assemblages quantitative analyses on calcareous nannofossil assemblages on high temporal resolution 600e800 years have been carried out from core kc01b in the ionian sea eastern mediterranean throughout marine isotope stage mis 13e9 between 500 and 300 ka this is an interval of considerable climate changes known as the mid brunhes event which includes mis 11 considered as a possible analogue for future interglacial conditions in the mediterranean core the interval is characterized by the dominance of gephyrocapsaspp as also known fromocean records calcareous nannofossil abundance fluctuations have been interpreted in terms of modification of sea surface primary productivity water stratification and temperature specifically the increase in abundance of gephyrocapsa caribbeanica and small gephyrocapsa coupled with decreases of florisphaera profunda syracosphaera spp and rhabdosphaera spp suggests enhanced primary productivity mixed surface waters during interglacial stages and at the terminations which can be interpreted in terms of interaction between climate changes and mesoscale oceanographic circulation on the other hand distributions of calciosolenia spp oolithotus spp and umbilicosphaera sibogae which are inphase with d 18 o curve showing higher abundances at the lighter values of the marine

depositional and organofacies influences on the petroleum potential of an unusual marine source rock waipawa formation paleocene in southern east coast basin new zealand abstract the paleocene waipawa formation is a widespread 2 80 m thick marine mudstone that occurs in several new zealand basins it is relatively enriched in organic matter om and is the inferred source of a sub commercial oil discovery and several correlated oil seeps to determine the organofacies and depositional influences on the petroleum potential of the formation we have undertaken a high resolution multidisciplinary study of the taylor white section in the central east coast basin this section is the thickest stratigraphically coherent surface exposure of the formation and includes contacts with the bounding whangai and wanstead formations bathymetric indicators within the foraminiferal assemblages indicate a slope setting for the section deepening from middle to lower bathyal through the waipawa wanstead succession significantly the whangai formation in this section is barren of foraminifera dinoflagellate and calcareous nannofossil biostratigraphy provides somewhat conflicting age control but a resulting age model indicates a tenfold increase in compacted sediment accumulation rate during waipawa deposition from 1 to 10 cm ky our multivariate statistical analysis of geochemical and paleontological data reveals systematic variation in paleoenvironmental and source rock parameters within the section with samples forming four distinct clusters or organofacies om rich and om poor waipawa organofacies whangai and wanstead organofacies the two waipawa organofacies are distinguished by enrichments in total organic carbon toc and organic 13c dominance of phytoclasts mainly degraded woody plant matter 66 98 and low amounts of amorphous organic matter whangai and wanstead organofacies are characterised by a greater proportion of marine om but are distinguished from each other by differences in om preservation om is well preserved with indications of hypoxia in the whangai organofacies but is poorly preserved in the wanstead organofacies geochemical fingerprinting identifies an interval of whangai organofacies that separates two phases of waipawa organofacies deposition the lower phase comprises four alternations between om rich and om poor waipawa organofacies and the upper phase comprises a single pulse of om rich waipawa facies bounded by om poor intervals overall waipawa formation in this section has toc and pyrolysable hydrocarbon s2 values of 0 2 4 6 mean 2 2 wt and 0 1 12 4 mean 3 9 mg hc g rock respectively one third of s2 values exceed 5 mg hc g rock indicating good very good bulk petroleum potential with the remainder having poor fair potential petroleum potential s2 increases with increasing toc r2 0 85 hydrogen index hi values range from 21 to 295 mg hc g toc averaging just 147 mg hc g toc in line with these modest hi values quantitative pyrolysis gas chromatography confirms that the petroleum potential is primarily for gas or gas condensate with relatively little oil potential of the total paraffinic petroleum yield gas n c1 5 contributes 80 100 whilst total n c6 and non volatile n c15 paraffinic oil contribute 20 and 6 respectively despite the low paraffinic oil potentials n c6 and n c15 correlate relatively strongly with hi and less strongly with toc the overall gas condensate prone nature of the waipawa organofacies at taylor white reflects the predominance of woody phytoclasts which are unlikely to produce paraffinic oil the small paraffinic oil component is instead more likely to be associated with the marine algal component although this component is volumetrically subordinate the higher paraffinic oil potential appears to result from the combination of high productivity of specific marine algae i e pelagophytes hypoxic depositional conditions and most importantly increased preservation of om including through sulfurisation this raises the possibility of more algal rich oil prone facies existing within the waipawa formation in areas with higher toc or alternatively in areas beyond the direct reach of the terrestrial influxes yet still sufficiently influenced by low water column oxygen levels and high sulfur contents that promote enhanced om preservation

the marine isotope stage 19 in the mid latitude north atlantic ocean astronomical signature and intra interglacial variability abstract since the seminal work by hays et al 1976 a plethora of studies has demonstrated a correlation between orbital variations and climatic change however information on how changes in orbital boundary conditions affected the frequency and amplitude of millennial scale climate variability is still fragmentary the marine isotope stage mis 19 an interglacial centred at around 785 ka provides an opportunity to pursue this question and test the hypothesis that the long term processes set up the boundary conditions within which the short term processes operate similarly to the current interglacial mis 19 is characterised by a minimum of the 400 kyr eccentricity cycle subdued amplitude of precessional changes and small amplitude variations in insolation here we examine the record of climatic conditions during mis 19 using high resolution stable isotope records from benthic and planktonic foraminifera from a sedimentary sequence in the north atlantic integrated ocean drilling program expedition 306 site u1313 in order to assess the stability and duration of this interglacial and evaluate the climate system s response in the millennial band to known orbitally induced insolation changes benthic and planktonic foraminiferal 18o values indicate relatively stable conditions during the peak warmth of mis 19 but sea surface and deep water reconstructions start diverging during the transition towards the glacial mis 18 when large cold excursions disrupt the surface waters whereas low amplitude millennial scale fluctuations persist in the deep waters as recorded by the oxygen isotope signal the glacial inception occurred at 779 ka in agreement with an increased abundance of tetra unsaturated alkenones reflecting the influence of icebergs and associated meltwater pulses and high latitude waters at the study site after having combined the new results with previous data from the same site and using a variety of time series analysis techniques we evaluate the evolution of millennial climate variability in response to changing orbital boundary conditions during the early middle pleistocene suborbital variability in both surface and deep water records is mainly concentrated at a period of 11 kyr and additionally at 5 8 and 3 9 kyr in the deep ocean these periods are equal to harmonics of precession band oscillations the fact that the response at the 11 kyr period increased over the same interval during which the amplitude of the response to the precessional cycle increased supports the notion that most of the variance in the 11 kyr band in the sedimentary record is nonlinearly transferred from precession band oscillations considering that these periodicities are important features in the equatorial and intertropical insolation these observations are in line with the view that the low latitude regions play an important role in the response of the climate system to the astronomical forcing we conclude that the effect of the orbitally induced insolation is of fundamental importance in regulating the timing and amplitude of millennial scale climate variability

causes and consequences of a middle pleistocene origin of the modern planktonic foraminifer neogloboquadrina pachyderma sinistral switches in coiling direction of shells of the planktonic foraminifer neogloboquadrina pachyderma have been extensively used as a paleotemperature proxy from the late miocene through the quaternary exploiting the specific modern polar affinity of the sinistrally coiled form here we have reexamined the origin of the modern sinistral form in pliocene and pleistocene sediments from ocean drilling program site 1014 in the eastern north pacific by using morphometric and stable isotope data we show that pliocene and pleistocene sinistral forms of n pachyderma are morphologically and ecologically different and that modern type sinistral form first appeared ca 1 ma these findings suggest that n pachyderma sinistral should not be used for calibrated paleoceanographic reconstructions prior to the middle pleistocene and reinforce the need to assess the origin of specific ecological affinities of other modern planktonic foraminifer species the first appearance of the modern form and the subsequent evolution of its mean shell size appear to have been synchronous in the north pacific and the north atlantic such hemispheric evolutionary synchronicity implies existence of trans arctic gene flow the modern type shell morphology and the specific cold water affinity of n pachyderma sinistral may have evolved in response to the onset of the 100 k y climate regime in the middle pleistocene

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

history of the last deglaciation in the alboran sea western mediterranean and adjacent north atlantic as revealed by coccolith floras abstract a series of cores recovered from the alboran sea western mediterranean and the adjacent part of the north atlantic has revealed very high rates of accumulation which have enabled us to identify the stages of the last deglaciation in great detail isotopic analyses of the cores show the two steps of the deglaciation terminations 1a and 1b separated by the bolling allerod warm phase 14 c dating of the cores has allowed the dating og the climatic succession we have identified each event of the deglaciation on the basis of changes in the coccolith flora especially in species of the genus gephyrocapsa such changes reflect surface water changes since coccolith live only in the photic zone the abundance of g muellerae in the cold intervals prior to each termination is greater than that in the bolling allerod and holocene warm intervals which follow the terminations coversely g oceanica is virtually absent during cold intervals but becoms more common during the warmer periods during the first deglacial warming there is a large influx of fine grained detrital material presumably derived from increased run off from the nearby mountains of southern spain and north west africa in the alboran sea cores with the most expanded sections there is a marked increase in the percentage of syracosphaera histrica at the beginning of this increase of detritus no increase was found in the atlantic core at this time

sea surface dynamics and palaeoenvironmental changes in the north atlantic ocean iodp site u1313 during marine isotope stage 19 inferred from coccolithophore assemblages abstract coccolithophore assemblages recovered from integrated ocean drilling program iodp site u1313 are investigated to reconstruct the palaeoceanographic evolution of a sector of the north atlantic during marine isotope stage mis 19 790 760 ka at orbital suborbital and millennial time scales the end of the glacial mis 20 is marked by the arrival of cold waters deriving from ice melting at higher latitudes as recorded by coccolithus pelagicus pelagicus the mis 19c is characterised by an extension of warmer north atlantic transitional waters natw reflecting the intensification of subtropical gyre influence on site u1313 identified by an increase in warm species umbilicosphaera sibogae the influence on the site of cooler natw is inferred from higher percentages of gephyrocapsa margereli which starts increasing from 779 ka finally the transition from mis 19a to mis 18 is characterised by a southward shift of the palaeoceanographic system due to a southward extension of the subpolar front as indicated by an increase of cold subspecies c pelagicus pelagicus the evolution of the palaeoproductivity proxy records number of coccoliths g of sediment and nannofossil accumulation rate nar and the abundances of small gephyrocapsa g margereli u sibogae and c pelagicus pelagicus show that fluctuations in sea surface productivity and alternations between cooling and warming phases occurred on the precessional timescale spectral analyses of u sibogae number of coccoliths g of sediment and nar indicate a significant concentration of variance close to half precession 10 kyr this reflects a nonlinear response of the mid latitude north atlantic surface ocean to low latitude insolation forcing furthermore millennial to multi centennial instability in sea surface dynamics is highlighted by spectral and wavelet analyses of u sibogae g margereli and c pelagicus pelagicus percentages number of coccoliths g of sediment and nar which reveal the occurrence of rapid events related to stadial and interstadial type conditions

short term climate changes in the southern aegean sea over the last 48 000 years abstract high resolution palaeoenvironmental changes corresponding to a mean time interval of 450 years covering the last 48 000 years were examined in a core from the cretan basin in the southern aegean sea the intensity and duration of the climatic and oceanographic events were determined by examining the compositional changes in the planktonic foraminifera and pollen assemblages along with the 18o signal of globigerinoides ruber a reconstruction of sea surface temperatures was attempted using the modern analogue technique mat in total 10 stadials and 6 interstadials occurred over the last 48 000 years these fluctuations in climatic conditions coincide with fluctuations documented in the western and central mediterranean and seem to be associated with dansgaard oeschger events some of these climatic fluctuations are correlated with changes in the vegetation in the surrounding land between 48 and 10 cal kyr bp the most pronounced stadials occurred at 41 cal kyr bp c69 st10 and at 13 cal kyr bp c69 st4 these events are characterized by i high positive 18o values of globigerinoides ruber ii drops in sst and iii increases in aridity these events may be correlated with the heinrich h4 event and the younger dryas event respectively two other stadials at 23 cal kyr bp c69 st6 and at 16 cal kyr bp c69 st5 which are characterized by increases in the abundance of the cold plaktonic foraminifera species and increases in aridity may be correlated with the h2 and h1 events respectively the dominant planktonic foraminiferal species during the stadials witch are correlated with the heinrich events were turborotalita quinqueloba and globorotalia scitula the most pronounced interstadials occurred between 39 5 and 38 5 cal kyr bp c69 ist6 and between 25 and 24 cal kyr bp c69 ist3 and are characterized by depletion in 18o values increases in sst and increases in humidity the former event coincides with the formation of the sapropelitic layer s2 in the holocene the most pronounced stadial occurred between 8 and 6 5 cal kyr bp c69 st2 during the interruption of s1 and is characterized by a reduction in sst and an increase in aridity the most pronounced interstadials of holocene occurred during the formation of s1a and s1b between 9 and 8 cal kyr bp c69 ist1 and between 6 5 and 5 5 cal kyr bp c69 ist2 respectively these events are characterized by depletion in 18o values increased sst and an increase in humidity as is indicated by the expansion of temperate evergreen and mediterranean taxa in the pollen record

pollen record from colle curti and cesi early and middle pleistocene mammal sites in the umbro marchean apennine mountains central italy the palynological record from the colle curti and cesi continental deposits has been examined in order to identify the main palaeofloristic and vegetational changes between 0 99 and 0 6 0 7 ma these data show a progressive increase in aridity as well as a progressive decrease in temperature which are associated with the transition in dominance from the 41 to 100 ka cyclicity in the milankovitch orbital record during the middle pleistocene the disappearance of tsuga recorded during the lower part of the brunhes chron also has been related to a shift in global aridity during the successive open vegetational phases glacials chenopodiaceae and artemisia progressively increase whereas cyperaceae decrease forest phases interglacials are successively dominated by tsuga abies with picea and finally pinus but all lack significant expansion of broad leaved deciduous taxa palynological and sedimentological data in addition to taphonomic interpretations demonstrate the occurrence of several hiatuses in the lower parts of the interglacials these hiatuses are considered to represent the palaeoenvironmental response to climatic changes affecting local sedimentological and geomorphological conditions copyright 2000 john wiley sons ltd

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

similarities and dissimilarities between the last two deglaciations and interglaciations in the north atlantic region abstract sea surface temperatures ssts recorded by alkenones and oxygen isotopes in the alboran basin are used here to describe at an unprecedented fine temporal resolution the present interglaciation pig initiated at 11 7 ka bp the last interglaciation lig onset approximately at 129 ka and respective deglaciations similarities and dissimilarities in the progression of these periods are reviewed in comparison with ice cores and stalagmites cold spells coeval with the heinrich events h described in the north atlantic include multi decadal scale oscillations not previously obvious up to 4 c in less than eight centuries within the stadials associated with h1 and h11 ca 133 ka and 17 ka respectively these abrupt oscillations precede the accumulation of organic rich layers deposited when perihelion moves from alignment with nh spring equinox to the summer solstice a reference for deglaciations events observed during the last deglaciation at 17 ka 14 8 ka and 11 7 ka are reminiscent of events occurred during the penultimate deglaciation at ca 136 ka 132 ka and 129 ka respectively the sst trend during the pig is no more than 2 c from 20 c to 18 c up to 0 2 c ka the trend is steeper during the lig i e up to a 5 c change from the early interglaciation to immediately before the glacial inception from 23 c to 18 c up to 0 4 c ka events are superimposed upon a long term trend towards colder ssts beginning with sst maxima followed by temperate periods until perihelion aligned with the nh autumn equinox before ca 5 3 ka for the pig and 121 ka for the lig a cold spell of around eight centuries at 2 8 ka during the pig was possibly mimicked during the lig at ca 118 ka by a sst fall of around 1 c in a millennium these events led interglacial sst to stabilise at around 18 c the glacial inception barely evident at the beginning ca 115 ka north atlantic event c25 after perihelion passage in the nh winter solstice culminated with a sst drop of at least 2 c in two millennia event c24 ca 111 ka the little ice age 0 7 ka also occurred after the latest perihelion passage in the nh winter solstice and could be an example of how a glacial pre inception event following an interglaciation might be

export production of coccolithophores in an upwelling region results from san pedro basin southern california borderlands a seven month long time series sediment trap project was carried out in san pedro basin southern california borderlands in order to evaluate the response of calcareous nannoplankton to seasonal hydrographic changes this region is periodically influenced by upwelling particularly during the spring and early summer the highest fluxes of both whole coccospheres and individual coccoliths occurred during winter january february a period when the fluxes of diatoms and planktic foraminifera were low the highest coccolithophore fluxes were recorded in the mid february with 860 106 coccoliths m 2 day 1 8 106 whole coccospheres m 2 day 1 and 80 mg of coccolith carbonate m 2 day 1 coccolith carbonate fluxes in january and february account for most of the total carbonate fluxes measured during this period the season of maximum coccolithophore production in this region winter is correlated with weak stratification of the upper water column low total primary production low nutrient contents and low temperatures emiliania huxleyi and florisphaera profunda are the two most abundant species in this region while e huxleyi displays no distinct seasonal changes in flux f profunda shows a clear preference for cold low nutrient water conditions and low light levels helicosphaera spp flux is positively correlated to the total coccosphere fluxes and is indicative of high coccolithophore productivity

distribution of coccoliths in surface sediments of the south eastern south atlantic ocean ecology preservation and carbonate contribution abstract recent coccoliths from 52 surface sediment samples recovered from the south eastern south atlantic were examined qualitatively and quantitatively in order to assess the controlling mechanisms for their distribution patterns such as ecological and preservational factors and their role as carbonate producers total coccolith abundances range from 0 2 to 39 9 coccoliths 109 g 1 sediment four assemblages can be delineated by their coccolith content characterising the northern benguela the middle to southern benguela the walvis ridge and the deeper water distinctions are based on multivariate ordination techniques applied on the relative abundances of the most abundant taxa emiliania huxleyi calcidiscus leptoporus gephyrocapsa spp coccolithus pelagicus and subtropical to tropical species the coccolith distribution seems to be temperature and nutrient controlled co varying with the seaward extension of the upwelling filament zone in the benguela a preservation index cex based on the differential dissolution behaviour of the delicate e huxleyi and gephyrocapsa ericsonii versus the robust c leptoporus is applied in order to detect the position of the coccolith lysocline although some samples were recognised as dissolution affected the distribution of the coccoliths in the surface sediments reflects the different oceanographic surface water conditions mass estimations of the coccolith carbonate reveal coccoliths to be only minor contributors to the carbonate preserved in the surface sediments the mean computed coccolith carbonate content is 17 wt equivalent to a mean contribution of 23 to the bulk carbonate

the last 1 35 million years at tenaghi philippon revised chronostratigraphy and long term vegetation trends abstract in addition to being of interest to ancient greek and roman historians the site of philippi ne greece has long been noted in quaternary circles for providing the longest continuous european pollen record spanning the last one million years here the original age model is re evaluated and a new marine terrestrial correlation is proposed an astronomical calibration procedure based on a correspondence between changes in certain vegetation elements and march and june perihelion configurations suggests that the base of the sequence extends back to 1 35 million years ago the revised chronological framework for the tenaghi philippon sequence provides an opportunity to examine the long term behaviour of individual taxa and vegetation trends within the context of global climate changes comparisons reveal a close correspondence between the terrestrial and marine records in terms of orbital and suborbital variability however joint time frequency analysis of the arboreal pollen record shows that the obliquity and eccentricity precession signals persist into the 100 kyr and 41 kyr worlds respectively suggesting the operation of additional climate mechanisms that are independent of high latitude glacial interglacial effects unlike ice core and marine sequences no change in the magnitude of interglacial tree population expansions is observed after the mid brunhes event instead the tenaghi philippon record suggests a major shift in the vegetational composition of interglacials after mis 16 with the establishment of forests of reduced diversity and a modern appearance

impact of the azores front on the distribution of planktic foraminifers shelled gastropods and coccolithophorids abstract the azores front current system south of the azores islands has been studied in order to reveal the direct impact of an open oceanic thermohaline front on the distribution of the calcareous plankton planktic foraminifers pteropods heteropods and coccolithophorids were sampled from the upper 2500 m of the water column during august 1997 and january 1999 in addition the hydrography was recorded across the frontal jet on combined ctd and xbt transects in august 1997 a strong seasonal thermocline capped the azores front af at about 60 90 m water depth below the thermocline a distinct hydrographic front was indicated by temperature and salinity gradients the central af was an area of low planktic foraminiferal gastropod and coccolithophorid production and was a faunal barrier for shallow and deep dwelling species highest numbers of planktic foraminifers gastropods and coccolithophores were recorded from above the thermocline north of the af the most frequent planktic foraminiferal and pteropod species were globigerinoides ruber white and limacina inflata respectively below 100 m planktic foraminifers were most frequent north of the af and gastropod shells were rare in particular the deep dwelling planktic foraminifer globorotalia scitula was frequent only at sampling sites north of the af in january 1999 the surface water temperature of the azores front current system was lower and the thermocline was deeper than in august 1997 the planktic foraminiferal standing stock was three times higher than in august 1997 and no water depth related faunal changes occurred the fauna was dominated by globorotalia truncatulinoides and turborotalita humilis was frequent during both january and august the fauna from south of the azores was different from that to the southeast recording the occurrence of two different water masses in this study we present a micropaleontological definition of the af in order to provide a paleoceanographic tool that may be used to decipher the late quaternary current system of the north atlantic ocean

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