abrupt change of antarctic moisture origin at the end of termination ii the deuterium excess of polar ice cores documents past changes in evaporation conditions and moisture origin new data obtained from the european project for ice coring in antarctica dome c east antarctic ice core provide new insights on the sequence of events involved in termination ii the transition between the penultimate glacial and interglacial periods this termination is marked by a north south seesaw behavior with first a slow methane concentration rise associated with a strong antarctic temperature warming and a slow deuterium excess rise this first step is followed by an abrupt north atlantic warming an abrupt resumption of the east asian summer monsoon a sharp methane rise and a co 2 overshoot which coincide within dating uncertainties with the end of antarctic optimum here we show that this second phase is marked by a very sharp dome c centennial deuterium excess rise revealing abrupt reorganization of atmospheric circulation in the southern indian ocean sector

holocene shifts of the southern westerlies across the south atlantic the southern westerly winds sww exert a crucial influence over the world ocean and climate nevertheless a comprehensive understanding of the holocene temporal and spatial evolution of the sww remains a significant challenge due to the sparsity of high resolution marine archives and appropriate sww proxies here we present a north south transect of high resolution planktonic foraminiferal oxygen isotope records from the western south atlantic our proxy records reveal holocene migrations of the brazil malvinas confluence bmc a highly sensitive feature for changes in the position and strength of the northern portion of the sww through the tight coupling of the bmc position to the large scale wind field the records allow a quantitative reconstruction of holocene latitudinal displacements of the sww across the south atlantic our data reveal a gradual poleward movement of the sww by about 1 1 5 from the early to the mid holocene afterward variability in the sww is dominated by millennial scale displacements on the order of 1 in latitude with no recognizable longer term trend these findings are confronted with results from a state of the art transient holocene climate simulation using a comprehensive coupled atmosphere ocean general circulation model proxy inferred and modeled sww shifts compare qualitatively but the model underestimates both orbitally forced multimillennial and internal millennial sww variability by almost an order of magnitude the underestimated natural variability implies a substantial uncertainty in model projections of future sww shifts

links between salinity variation in the caribbean and north atlantic thermohaline circulation variations in the strength of the north atlantic ocean thermohaline circulation have been linked to rapid climate changes1 during the last glacial cycle through oscillations in north atlantic deep water formation and northward oceanic heat flux2 3 4 the strength of the thermohaline circulation depends on the supply of warm salty water to the north atlantic which after losing heat to the atmosphere produces the dense water masses that sink to great depths and circulate back south2 here we analyse two caribbean sea sediment cores combining mg ca palaeothermometry with measurements of oxygen isotopes in foraminiferal calcite in order to reconstruct tropical atlantic surface salinity5 6 during the last glacial cycle we find that caribbean salinity oscillated between saltier conditions during the cold oxygen isotope stages 2 4 and 6 and lower salinities during the warm stages 3 and 5 covarying with the strength of north atlantic deep water formation7 at the initiation of the bolling allerod warm interval caribbean surface salinity decreased abruptly suggesting that the advection of salty tropical waters into the north atlantic amplified thermohaline circulation and contributed to high latitude warming

prolonged warming of the brazil current precedes deglaciations abstract paleoceanographic reconstructions from the brazil current are scarce and lack the required temporal resolution to appropriately represent its variability during key periods of the last glacial interglacial cycles here we present the first high temporal resolution multiproxy reconstruction of the brazil current at 24 s covering the last 185 ka during the last and penultimate glacial periods our mg ca derived sea surface temperature sst record shows a strong cooling at ca 47 and ca 156 ka respectively that is followed by a warming trend from late marine isotope stage mis 3 to mis 1 and from late mis 6 to mis5e respectively importantly the brazil current warmed uninterruptedly towards termination i ii after the low sst at ca 47 and ca 156 ka with no sst minima during the last glacial maximum or penultimate glacial maximum the reason for the strong cooling and the warming trend during late mis 3 and late mis 6 could reside in the favorable obliquity configuration however this mechanism is not sufficient to sustain the warming observed for the rest of the last and penultimate glacial periods we propose that the change in the atlantic meridional overturning circulation amoc as described in the literature from a warm to a cold mode for mis 2 and mis 6 is responsible for the accumulation of warm waters in the subtropical western south atlantic preventing sst minima during the last and penultimate glacial maxima in the region change in benthic 13 c corroborates that a fundamental modification in the amoc mode might have triggered the heat accumulation our data also show a sudden increase in sst and surface salinity during the last glacial descent mis 4 indicating that the western portion of the subtropical gyres may have acted as a heat and salt reservoir while higher latitude climates transited to a glacial background our findings imply that the amoc cold mode induces heat storage in the subtropical western south atlantic and because of that the last two regional sst minima occurred out of phase with the glacial maxima of higher latitudes

south atlantic interocean exchange as the trigger for the bolling warm event the north atlantic ocean underwent an abrupt temperature increase of 9 c at high latitudes within a couple of decades during the transition from heinrich event 1 h1 to the bolling warm event but the mechanism responsible for this warming remains uncertain here we address this issue presenting high resolution last deglaciation planktic and benthic foraminiferal records of temperature and oxygen isotopic composition of seawater 18 osw for the subtropical south atlantic we identify a warming of 6 5 c and an increase in 18 o sw of 1 2 at the permanent thermocline during the transition and a simultaneous warming of 3 5 c with no significant change in 18 o sw at intermediate depths most of the warming can be explained by tilting the south atlantic east west isopycnals from a flattened toward a steepened position associated with a collapsed h1 and strong bolling atlantic meridional overturning circulation amoc however this zonal seesaw explains an increase of just 0 3 in permanent thermocline 18 o sw considering that 18 o sw at the south atlantic permanent thermocline is strongly influenced by the inflow of salty indian ocean upper waters we suggest that a strengthening in the agulhas leakage took place at the transition from h1 to the bolling and was responsible for the change in 18 o sw recorded in our site our records high light the important role played by indian atlantic interocean exchange as the trigger for the resumption of the amoc and the bolling warm event

dependence of abrupt atlantic meridional ocean circulation changes on climate background states abrupt decadal climate changes during the last glacial interglacial cycle are less pronounced during maximum glacial conditions and absent during the holocene to further understand the underlying dynamics we conduct hosing experiments for three climate states pre industrial pi 32 kilo years before present ka bp and last glacial maximum lgm our simulations show that a stronger temperature inversion between the surface and intermediate layer in the south labrador sea induces a faster restart of convective processes 32 ka bp lgm pi during the initial resumption of the atlantic meridional overturning circulation amoc a few decades later an amoc overshoot is mainly linked to the advection of warmer and saltier intermediate layer water from the tropical atlantic into the south labrador sea which causes a stronger deep water formation than that before the freshwater perturbation this mechanism is most pronounced during the 32 ka bp weaker during the lgm and absent during the pi

estimated strength of the atlantic overturning circulation during the last deglaciation the atlantic meridional overturning circulation affects the latitudinal distribution of heat and is a key component of the climate system proxy reconstructions based on sedimentary 231 pa 230 th ratios and the difference between surface and deep water radiocarbon ages indicate that during the last glacial period the overturning circulation was reduced during millennial scale periods of cooling 1 5 however much debate exists over the robustness of these proxies 6 8 here we combine proxy reconstructions of sea surface and air temperatures and a global climate model to quantitatively estimate changes in the strength of the atlantic meridional overturning circulation during the last glacial period we find that relative to the last glacial maximum the overturning circulation was reduced by approximately 14 sv during the cold heinrich event 1 during the younger dryas cold event the overturning circulation was reduced by approximately 12 sv relative to the preceding warm interval these changes are consistent with qualitative estimates of the overturning circulation from sedimentary 231 pa 230 th ratios in addition we find that the strength of the overturning circulation during the last glacial maximum and the holocene epoch are indistinguishable within the uncertainty of the reconstruction the atlantic meridional overturning circulation amoc is an important feature of the earth s climate system it is characterized by northward flowing water masses at the surface ocean deepwater formation in the north atlantic and southward flowing water masses in the intermediate to deep ocean this overturning cell is complemented by an underlying generally weaker reversed overturning cell that originates in the southern ocean in the following we use amoc to refer only to the upper overturning cell owing to the large heat capacity of water the northwardflowing near surface waters contribute effectively to the heat transport from the tropics to the mid and high latitudes and therefore affect the regional climate around the north atlantic 9 10 hence changes of the amoc strength can substantially influence climate in the north especially in europe the depth of the southward flowing waters and the strength of the circulation have changed in the past during the last glacial period abrupt warming events of several degrees within a few decades followed by slower cooling were detected in greenland ice cores 11 as effects of the so called dansgaardoeschger events were found far beyond the greenland ice sheet 1214 with patterns reminiscent of varying inter hemispheric heat distribution 15 16 they are believed to be the result of rapid changes of the amoc strength 17 other examples of a reduction or even a complete shutdown of the

the oxygen isotope composition of planktonic foraminifera from the cariaco basin venezuela seasonal and interannual variations material collected during a three year sediment trapping experiment in the cariaco basin venezuela january 1997 to december 1999 is used to examine both temporal and inter species variability in the oxygen isotope composition of planktonic foraminifera specifically this study compares the oxygen isotope composition of six species of planktonic foraminifera globigerinoides ruber pink globigerina bulloides neogloboquadrina dutertrei orbulina universa globorotalia menardii and globorotalia crassaformis with the climatology and hydrography of the region and evaluates the application of each species for use in paleoceanographic reconstructions the isotope results are consistent with known depth habitats for all six species the lowest 18 o values 1t o 2 were measured on g ruber pink and g bulloides two species that live in the surface mixed layer values for deeper dwelling species such as n dutertrei g menardii and g crassaformis are higher predominantly ranging from 0 to 0 5 temperature estimates derived using species specific paleotemperature equations indicate that g ruber pink accurately estimates sea surface temperatures ssts throughout the year while g bulloides temperature estimates are similar to measured surface temperatures only during the upwelling season january april for the remainder of the year the 18 o derived temperatures for g bulloides typically are lower than the measured sst although the maximum flux of all species occurs during upwelling the flux weighted annual mean isotopic composition of the six species indicates that only g bulloides is biased towards this season therefore we conclude that the sediment 18 o record of g ruber pink is most suitable for estimating past values of mean annual sst while g bulloides provides information on conditions during spring upwelling the depth of calcification of n dutertrei varies seasonally in response to changes in the depths of the thermocline and chlorophyll maximum as a result the 18 o difference between g ruber pink and n dutertrei provides an estimate of the annual surface to thermocline temperature gradient in the basin 2006 elsevier b v all rights reserved

magnetic properties of deep sea sediments off southwest greenland evidence for major differences between the last two deglaciations high resolution rock magnetic data atomic mass spectroscopy 14 c dates 18 o and grain size analyses from a piston core hu90 013 013 located off southwest greenland provide a record of the last two deglaciations during termination i a welldefined interval having high volumetric magnetic susceptibility k and a low ratio of anhysteretic susceptibility to volumetric magnetic susceptibility k arm k postdates the younger dryas and the 18 o change marking the stage 2 1 boundary and correlates with sedimentological and geomorphological evidence for greenland ice sheet retreat from the coastline to the continental interior during termination ii a very similar magnetic signal coincides with the 18 o shift marking the stage 6 5 glacial interglacial transition and continues throughout substage 5e we suggest that this magnetic signal during both termination i and termination ii marks continental meltwater carried detritus from greenland if so the synchronous changes in magnetic and oxygen isotopic records at termination ii indicate very early and rapid deglaciation of greenland in contrast to the relatively late deglaciation observed for termination i distinct fluctuations in k and k arm k occur below the onset of the 18 o change at termination i where they occur at 16 900 yr b p and at termination ii these fluctuations are interpreted as due to sudden influxes of detritus into the basin caused by unpinning of ice from the continental shelf at the inception of deglaciation

the sequence of events surrounding termination ii and their implications for the cause of glacial interglacial co2 changes events surrounding termination ii as preserved in the vostok ice core provide a number of clues about the mechanisms controlling glacial to interglacial climate change antarctic temperature and the atmosphere s co2 content increased together over a period of 8000 years this increase is bounded by a drop in dust flux at its onset and by a drop in the 18o of trapped air at its finish a similar lag between dust flux and foraminiferal 18o is seen in a southern ocean marine record suggesting that the 18o in air trapped in vostok ice is a valid proxy for ice volume the synchronous change of atmospheric co2 and southern hemisphere temperature thus preceded the melting of the northern hemisphere ice sheets this observation coupled with the fact that nutrient reorganization in the north atlantic occurs with or after the sea level rise eliminates many scenarios proposed to explain the co2 rise including those which rely on sea level change conveyor related nutrient redistribution or north atlantic cooling southern ocean scenarios become the front runners but the most popular mechanism iron fertilization has two problems in explaining the co2 rise before termination ii first much of the dust demise occurs prior to the change in co2 so if iron is the villain a threshold value of its supply must be called upon above which productivity does not continue to increase second the co2 rise continues for some 4 5 kyr after the dust flux has fallen to close to zero these problems may be solved if the increased iron supply in dust caused higher rates of nitrogen fixation during the glacial periods in this case the residence time of oceanic nitrate of a few thousand years would enable decreasing productivity to be a global rather than a local phenomenon and would explain the slow rampup of atmospheric co2

why there was not a younger dryas like event during the penultimate deglaciation abstract the younger dryas cold event is a relatively unique feature of the last deglaciation when compared to previous deglaciations suggesting a unique trigger rather than the commonly held forcing mechanism of north american freshwater routing to the north atlantic here i compare the last t i and penultimate t ii deglaciations and provide new support for the argument that the lack of a younger dryas like event during t ii is due to the rapidity of northern hemisphere ice sheet retreat under greater boreal summer insolation forcing faster ice retreat suppressed atlantic meridional overturning circulation amoc until near the end of t ii while during t i amoc increased relatively early during t i the eastward routing of freshwater that caused the younger dryas happened after amoc resumption whereas during t ii this routing occurred prior to the resumption of amoc thus the increased flux of freshwater to the north atlantic during t ii had little effect on amoc explaining the lack of a younger dryas like climate oscillation during this deglaciation

impact of abrupt deglacial climate change on tropical atlantic subsurface temperatures both instrumental data analyses and coupled ocean atmosphere models indicate that atlantic meridional overturning circulation amoc variability is tightly linked to abrupt tropical north atlantic tna climate change through both atmospheric and oceanic processes although a slowdown of amoc results in an atmospheric induced surface cooling in the entire tna the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths here we reconstruct high resolution temperature records using oxygen isotope values and mg ca ratios in both surface and subthermocline dwelling planktonic foraminifera from a sediment core located in the tna over the last 22 ky our results show significant changes in the vertical thermal gradient of the upper water column with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the younger dryas furthermore we present new analyses of a climate model simulation forced with freshwater discharge into the north atlantic under last glacial maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of amoc weakening consistent with the reconstructed record together our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high latitude north atlantic climate to the tropical atlantic during periods of reduced amoc across the last deglacial transition

the impact of the amoc resumption in the western south atlantic thermocline at the onset of the last interglacial after glacial terminations large amounts of heat and salt were transferred from low to high latitudes which is a crucial phenomenon for the reestablishment of the atlantic meridional overturning circulation amoc however how different glacial terminations evolved in the sub tropics is still poorly documented here we use foraminifera oxygen 18o and carbon 13c stable isotopes to show that the north atlantic heat piracy following the amoc resumption at the early last interglacial affected the thermocline 18o levels of the subtropical western south atlantic because of the cooling imposed by this process glacial 18o persisted in the thermocline for 7 kyr after the onset of the last interglacial dampening the effect of sea level rise usually imprinted on foraminifera 18o during terminations faunal composition and 13c also suggest the existence of a colder and thicker south atlantic central water coeval with the amoc recovery this process apparently did not occur during the last deglaciation

millennial scale changes in atmospheric co2 levels linked to the southern ocean carbon isotope gradient and dust flux the rise in atmospheric co2 concentrations observed at the end of glacial periods has at least in part been attributed to the upwelling of carbon rich deep water in the southern ocean1 2 the magnitude of outgassing of dissolved co2 however is influenced by the biological fixation of upwelled inorganic carbon and its transfer back to the deep sea as organic carbon the efficiency of this biological pump is controlled by the extent of nutrient utilization which can be stimulated by the delivery of iron by atmospheric dust particles3 changes in nutrient utilization should be reflected in the 13c gradient between intermediate and deep waters here we use the 13c values of intermediate and bottom dwelling foraminifera to reconstruct the carbon isotope gradient between thermocline and abyssal water in the subantarctic zone of the south atlantic ocean over the past 360 000 years we find millennial scale oscillations of the carbon isotope gradient that correspond to changes in dust flux and atmospheric co2 concentrations as reported from antarctic ice cores4 5 we interpret this correlation as a relationship between the efficiency of the biological pump and fertilization by dust borne iron as the correlation is exponential we suggest that the sensitivity of the biological pump to dust borne iron fertilization may be increased when the background dust flux is low

rapid coupling between ice volume and polar temperature over the past 150 000 years a new approach to dating a continuous sea level record using speleothem u th ages shows that past variations in global ice volume occurred within centuries of polar climate change with rates of sea level rise reaching at least 1 metre per century

the oxygen isotopic composition of seawater during the last glacial maximum high resolution oxygen and hydrogen isotope measurements were made on pore fluids from deep sea sediments from sites in the north and south atlantic the data provide direct measurements of changes in the isotopic composition of bottom waters during the last glacial maximum lgm results from ocean drilling program odp site 981 in the north atlantic currently bathed in north atlantic deep water nadw reproduces previous results from the ceara and bermuda rises constraining the glacial interglacial change in 18 o of the deep atlantic to be 0 7 0 8 results from site 984 which is located north of site 981 and at a shallower water depth yield a similar value 0 8 providing insight into the properties of glacial north atlantic intermediate water gnaiw sites from odp leg 177 in the south atlantic span the modern boundary between northern and southern sources of deep water data from the northern site 1088 yield a similar result to sites in the tropical and north atlantic 0 7 at the southern site 1093 located south of the polar front the change is substantially larger 1 1 representing the change in 18 o of southern source waters since the lgm these results confirm previous estimates that the global average change in 18 o of seawater is 1 0 0 1 hydrogen isotopes measured on pore fluids from three sites are consistent with the oxygen isotopes from these locations giving further support to these results at all sites studied the temperature of the deep ocean during the lgm calculated by combining the pore fluid results with oxygen isotope data from benthic foraminifera was within 1 c of the freezing point of seawater

the influence of air and sea exchange on the carbon isotope distribution in the sea we explore here the influence of the temperature dependence of isotope fractionation between atmospheric co2and ocean co2 on the distribution of carbon isotopes in the ocean this is accomplished by an analysis of departures from the expected redfield tie between po4 and 13c we find that for the surface ocean the temperature influence largely compensates for the biologic influence in the deep ocean the temperature influence imprinted at the sites of deepwater formation reduces somewhat the biologically induced difference between the carbon isotope ratios for deep waters produced in the northern atlantic and in the antarctic these same features are reproduced in the hamburg ocean model in order to assess the impact of changes in the ratio of ocean mixing rate to wind speed we have made a model run in which co2 exchange rates between air and sea were everywhere doubled as expected the influence of the thermodynamic effect on the oceanic carbon isotope distribution is magnified

strong and deep atlantic meridional overturning circulation during the last glacial cycle extreme abrupt northern hemisphere climate oscillations during the last glacial cycle 140 000 years ago to present were modulated by changes in ocean circulation and atmospheric forcing1 however the variability of the atlantic meridional overturning circulation amoc which has a role in controlling heat transport from low to high latitudes and in ocean co2 storage is still poorly constrained beyond the last glacial maximum2 3 4 here we show that a deep and vigorous overturning circulation mode has persisted for most of the last glacial cycle dominating ocean circulation in the atlantic whereas a shallower glacial mode with southern sourced waters filling the deep western north atlantic prevailed during glacial maxima3 5 our results are based on a reconstruction of both the strength and the direction of the amoc during the last glacial cycle from a highly resolved marine sedimentary record in the deep western north atlantic parallel measurements of two independent chemical water tracers the isotope ratios of 231pa 230th and 143nd 144nd 6 7 8 which are not directly affected by changes in the global cycle reveal consistent responses of the amoc during the last two glacial terminations any significant deviations from this configuration resulting in slowdowns of the amoc were restricted to centennial scale excursions during catastrophic iceberg discharges of the heinrich stadials severe and multicentennial weakening of north atlantic deep water formation occurred only during heinrich stadials close to glacial maxima with increased ice coverage probably as a result of increased fresh water input in contrast the amoc was relatively insensitive to submillennial meltwater pulses during warmer climate states and an active amoc prevailed during dansgaard oeschger interstadials greenland warm periods

the european small mammal faunas related to the first half of the middle pleistocene abstract by now the abundant european small mammal data have been collected from the deposits of the first part of the middle pleistocene mis 18 mis 11 the significant number of global climatic events glaciations and interglacials corresponds to this period we analyzed the evolutional changes of small mammals of the middle pleistocene revealed the reactions of small mammals on the different climatic events glaciations interglacials and correlated the western and the eastern european faunas the collected data also help us to divide the geological deposits age and permit to reconstruct the palaeogeographic picture of the past the obtained results may serve as an important component for compiling biostratigraphic schemes of the middle pleistocene and the pleistocene in general

planktonic foraminifera in the sediment of a western boundary upwelling system off cabo frio brazil abstract the distribution of planktonic foraminifera in box core tops under the influence of a western boundary upwelling system along the southeastern brazilian continental margin was examined to evaluate the similarity percentage simper and to create a biofacies model for paleoenvironmental applications species associated with warm and oligotrophic water were distributed in the rio de janeiro sector of the campos basin while productive water species were most abundant in the rio de janeiro sector of the santos basin and cold water species were most abundant in the cabo frio upwelling system cfus four major biofacies are associated with the oceanographic setting of the cfus one from the campos basin a brazil current front one from the santos basin b mixture of coastal and oceanic waters and two associated with the cabo frio high in the northern biofacies c and southern biofacies d the distribution of biofacies c and d was associated with temperature differences biofacies c represents a mixture of upwelling and tropical waters while biofacies d represents a mixture of cold nutrient rich and santos basin waters these biofacies were also defined in core cf10 01b in which six main paleoceanographic phases were characterized during the last 9 cal kyr predominantly showing alternating dominance between biofacies c and d from 9 0 to 5 0 cal kyr before the present bp the system was dominated by biofacies c between 4 0 and 3 5 cal kyr bp biofacies d was dominant between 3 5 and 2 5 cal kyr bp a strong influence of coastal waters and weakened upwelling activity were indicated by the dominance of biofacies b c d the last 2 5 cal kyr was dominated by biofacies d the sst in this core was reconstructed using the modern analog technique mat which revealed 0 35 c of variability indicating no sst changes during the holocene the weak sensitivity of the mat was due to the interplay among different oceanographic features

the structure of termination ii penultimate deglaciation and eemian in the north atlantic abstract a study of the 140 100 ka interval in core t90 9p from the north atlantic 45 n 25 w based on analysis of oxygen and carbon isotope records from planktonic and benthonic foraminifera and from the bulk sediment fine fraction facilitates a detailed paleoceanographic reconstruction of the penultimate deglaciation termination ii and of the eemian interglacial 18o stage 5e the first step of termination ii was characterised by low productivity and a mixed water column which was a remnant of glacial conditions a 3 ka period of relatively stable conditions with a stratified water column termination ii pause occurred half way through termination ii and preceeded a second and more rapid climatic shift the end of the deglaciation eemian maximum i e isotopic event 5 53 initiated the establishment of strong seasonal water column stratification north atlantic deep water nadw production remained low during the complete glacial interglacial transition after the eemian maximum nadw prodution was restored and bottom waters remained quite stable during the course of the eemian while surface waters gradually cooled in the second half of the stage a short surface water cooling event accompanied by a reduced seasonal water column stratification and nutrient instability occurred at approximately 117 ka bp

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

mg ca of globorotalia inflata as a recorder of permanent thermocline temperatures in the south atlantic 1 we present a species specific mg ca calcification temperature calibration for globorotalia inflata from a suite of 38 core top samples from the south atlantic from 8 s to 49 s g inflata is a deep dwelling planktonic foraminifer commonly occurring in subtropical to subpolar conditions which qualifies it for reconstructions of the permanent thermocline apparent calcification depths and calcification temperatures were determined by comparing measured 18o with equilibrium 18o of calcite based on water column properties based on our core top samples g inflata apparent calcification depth is constant throughout the south atlantic midlatitudes with a depth of 350 400 m within the permanent thermocline the resulting mg ca calcification temperature calibration is mg ca 0 72 0 045 0 042 exp 0 076 0 006 calcification temperature r2 0 81 and covers the temperature range 3 1 c 16 5 c we applied our mg ca calibration to gravity core ps2495 3 from the mid atlantic ridge at 41 s to test its validity by reconstructing a low resolution record covering the last two glacial interglacial cycles our paleotemperature record reveals large changes in temperature for terminations i and ii when permanent thermocline temperature increased by as much as 8 c the g inflata paleotemperature record suggests that oceanic fronts repeatedly migrated over the location of core ps2495 3 during the last 160 kyr this study shows the potential of g inflata mg ca to reconstruct paleotemperatures in the permanent thermocline

intermediate depth warming in the tropical atlantic related to weakened thermohaline circulation combining paleoclimate data and modeling results for the last deglaciation 1 benthic foraminiferal oxygen isotope ratios from two sediment cores recovered at 426 and 1299 m water depth in the eastern and western tropical atlantic show that a slowdown of the thermohaline circulation thc during heinrich event h1 and the younger dryas was accompanied by rapid and intense warming of intermediate depth waters millennial scale covariations of low paleosalinities in the subpolar north atlantic with decreased benthic oxygen isotope ratios in the eastern tropical atlantic throughout the past 10 000 years suggest that thc weakening might be related to middepth warming during the holocene period as well climate model experiments simulating a strong reduction of the thc in the atlantic ocean under present day and glacial conditions reveal that the increase of temperature in the middepth tropical and south atlantic is a common feature for both climatic states caused by a reduced ventilation of cold intermediate and deep waters in conjunction with downward mixing of heat from the thermocline from the similarity of the paleoclimatic records with the model simulations we infer that the characteristic pattern of temperature change in the atlantic ocean related to weakened thermohaline circulation can serve as an indicator of present day and future thc slowdown

planktonic foraminifera from modern sediments reflect upwelling patterns off iberia insights from a regional transfer function abstract quantitative and qualitative analyses of planktonic foraminiferal assemblages from 134 core top sediment samples collected along the western iberian margin were used to assess the latitudinal and longitudinal changes in surface water conditions and to calibrate a sea surface temperature sst transfer function for this seasonal coastal upwelling region q mode factor analysis performed on relative abundances yielded three factors that explain 96 of the total variance factor 1 50 is exclusively defined by globigerina bulloides the most abundant and widespread species and reflects the modern seasonal may to september coastal upwelling areas factor 2 32 is dominated by neogloboquadrina pachyderma dextral and globorotalia inflata and seems to be associated with the portugal current the descending branch of the north atlantic drift factor 3 14 is defined by the tropical sub tropical species globigerinoides ruber white globigerinoides trilobus trilobus and g inflata and mirrors the influence of the winter time eastern branch of the azores current in conjunction with satellite derived sst for summer and winter seasons integrated over an 18 year period the regional foraminiferal data set is used to calibrate a sst transfer function using imbrie kipp mat and simmaxndw techniques similar predicted errors rmsep correlation coefficients and residuals deviation from sst estimated for both techniques were observed for both seasons all techniques appear to underestimate sst off the southern iberia margin an area mainly occupied by warm waters where upwelling occurs only occasionally and overestimate sst on the northern part of the west coast of the iberia margin where cold waters are present nearly all year round the comparison of these regional calibrations with former atlantic and north atlantic calibrations for two cores one of which is influenced by upwelling reveals that the regional one attests more robust paleo ssts than for the other approaches