dynamics of active layer in wooded palsas of northern quebec abstract palsas are organic or mineral soil mounds having a permafrost core palsas are widespread in the circumpolar discontinuous permafrost zone the annual dynamics and evolution of the active layer which is the uppermost layer over the permafrost table and subjected to the annual freeze thaw cycle are influenced by organic layer thickness snow depth vegetation type topography and exposure this study examines the influence of vegetation types with an emphasis on forest cover on active layer dynamics of palsas in the boniface river watershed 57 45 n 76 00 w in this area palsas are often colonized by black spruce trees picea mariana mill b s p thaw depth and active layer thickness were monitored on 11 wooded or non wooded mineral and organic palsas in 2009 2010 and 2011 snow depth organic layer thickness and vegetation types were assessed the mapping of a palsa covered by various vegetation types and a large range of organic layer thickness were used to identify the factors influencing the spatial patterns of thaw depth and active layer the active layer was thinner and the thaw rate slower in wooded palsas whereas it was the opposite in more exposed sites such as forest openings shrubs and bare ground thicker organic layers were associated with thinner active layers and slower thaw rates snow depth was not an important factor influencing active layer dynamics the topography of the mapped palsa was uneven and the environmental factors such as organic layer snow depth and vegetation types were heterogeneously distributed these factors explain a part of the spatial variation of the active layer over the 3 year long study the area of one studied palsa decreased by 70 in a context of widespread permafrost decay increasing our understanding of factors that influence the dynamics of wooded and non wooded palsas and understanding of the role of vegetation cover will help to define the response of discontinuous permafrost landforms to changing climatic conditions

accelerated thawing of subarctic peatland permafrost over the last 50 years 1 in this study we provide a quantification of the main patterns of change of a subarctic peatland caused by permafrost decay monitored between 1957 and 2003 up thrusting of the peatland surface due to permafrost aggradation during the little ice age resulted in the formation of an extensive peat plateau that gradually fragmented into residual palsas from the 19th century to the present only about 18 of the original surface occupied by permafrost was thawed in 1957 whereas only 13 was still surviving in 2003 rapid permafrost melting over the last 50 years caused the concurrent formation of thermokarst ponds and fen bog vegetation with rapid peat accumulation through natural successional processes of terrestrialization the main climatic driver for accelerated permafrost thawing was snow precipitation which increased from 1957 to present while annual and seasonal temperatures remained relatively stable until about the mid 1990s when annual temperature rose well above the mean contrary to current expectations the melting of permafrost caused by recent climate change does not transform the peatland to a carbon source ecosystem as rapid terrestrialization exacerbates carbon sink conditions and tends to balance the local carbon budget

distinct modes of east asian winter monsoon documented by a southern red sea coral record the large scale boreal winter climatic patterns associated with interannual variability in a coral oxygen isotope 18o record from the southern red sea covering most of the last century are investigated from the early 1930s to the early 1960s the winter coral 18o record reflecting temperature and salinity variations in southern red sea surface waters is associated with global or large scale sea surface temperature sst and 850 mb geopotential height z850 anomalies which project on the corresponding patterns associated with the el nino southern oscillation enso in contrast since the early 1960s the winter coral 18o record is related to a z850 pattern that reflects the enso independent part of the east asian winter monsoon eawm which includes the siberian high the east asian through and the east asian upper tropospheric jet our results indicate a weakening of the enso control on interannual temperature salinity variations in southern red sea surface waters in the early 1960s due to the warming of the indian ocean and suggest that information about the nonstationarity in the relationship between enso and two distinct modes of eawm can be documented in southern red sea coral 18o records

water isotopes in precipitation data model comparison for present day and past climates abstract variations of hdo and h2 18 o concentrations are observed in precipitation both on a geographical and on a temporal basis these variations resulting from successive isotopic fractionation processes at each phase change of water during its atmospheric cycle are well documented through the iaea wmo network isotope concentrations are in middle and high latitudes linearly related to the annual mean temperature at the precipitation site paleoclimatologists have used this relationship to infer paleotemperatures from isotope paleodata extractable from ice cores deep groundwater and other such sources for this application to be valid however the spatial relationship must also hold in time at a given location as the location undergoes a series of climatic changes progress in water isotope modeling aimed at examining and evaluating this assumption has been recently reviewed jouzel et al 1997 with a focus on polar regions and more specifically on greenland we extend this review in comparing the results of two different isotopic agcms nasa giss and echam and in examining with a more global perspective the validity of the above assumption i e the equivalence of the spatial and temporal isotope temperature relationships these results confirm the dominating role of local temperature changes on the paleo isotope signal in most regions however the exact calibration of this valuable paleothermometer is biased by for example the seasonality of precipitation and other factors we forced the two models by the climatic boundary conditions of the mild holocene at 6 kyr bp which only slightly differs from today s climate the isotope response on this weak forcing is quite heterogeneous the only robust common response is the intensification of the hydrological cycle in low latitudes and therefore isotopically more depleted precipitation in the tropics and subtropics we also examine recent progress made in modeling the relationship between the conditions prevailing in moisture source regions for precipitation and the deuterium excess of that precipitation

importance of the indian ocean for simulating rainfall anomalies over eastern and southern africa the relative contributions of the indian ocean and pacific ocean sea surface temperatures ssts to the rainfall variability over eastern central and southern africa during the austral spring summer are examined the variability of african rainfall is statistically related to both oceans but the variability in the two oceans is also related to separate the effects of the indian and pacific oceans a suite of numerical model simulations is presented goga the atmosphere is forced by observed ssts globally ioga the atmosphere is forced by observed ssts only in the indian ocean basin and poga the atmosphere is forced by observed ssts only in the tropical pacific basin while the sst variability of the tropical pacific exerts some influence over the african region it is the atmospheric response to the indian ocean variability that is essential for simulating the correct rainfall response over eastern central and southern africa analyses of the dynamical response s seen in the numerical experiments and in the observations indicate that the pacific and indian oceans have a competing influence over the indian ocean african region this competition is related to the influence of the two oceans on the walker circulation and the consequences of that variability on low level fluxes of moisture over central and southern africa finally given the high correlation found between sst variability in the indian and pacific oceans with the pacific leading by 3 months we speculate on an approach to long lead dynamical climate prediction over central east and southern africa

oxygen isotope constraints on surface ocean temperatures published oxygen isotope results from benthic and planktonic foraminifera are used to constrain the extent to which surface ocean temperatures in the tropics changed between glacial and interglacial time the possible impacts of bioturbation and of the redistribution of 18o16o ratios within the sea putting aside the oxygen isotope results are consistent with the climap project conclusion that tropical ocean temperatures remained within 2 c of their present value

interaction between the enso and the asian monsoon in a coral record of tropical climate the oxygen isotopic composition of a banded coral from the western equatorial indian ocean provides a 150 year long history of the relation between the el nino southern oscillation enso phenomenon and the asian monsoon interannual cycles in the coral time series were found to correlate with pacific coral and instrumental climate records suggesting a consistent linkage across ocean basins despite the changing frequency and amplitude of the enso however decadal variability that is characteristic of the monsoon system also dominates the coral record which implies important interactions between tropical and midlatitude climate variability one prominent manifestation of this interaction is the strong amplitude modulation of the quasi biennial cycle

alkenones and multiproxy strategies in paleoceanographic studies 1 we assess multiproxy strategies involving alkenone based and other paleoceanographic indicators in an effort to define uncertainties and to advance understanding of past oceanic and climatic changes looking to the future we recommend a parallel strategy of applying proxies to the geologic record while continuously seeking refinements in methods and understanding of mechanisms that control each proxy a multiproxy strategy increases confidence in results and provides oceanographic context for more effective interpretation of processes a combination of proxies allows derivation of additional properties such as upper ocean paleosalinity or paleo pco2 for a more complete view of the oceanographic and climate mechanisms involved in changing earth s environment

deconvolving the δ18o seawater component from subseasonal coral δ18o and sr ca at rarotonga in the southwestern subtropical pacific for the period 1726 to 1997 to reconstruct oceanographic variations in the subtropical south pacific 271 year long subseasonal time series of sr ca and delta 18 o were generated from a coral growing at rarotonga 21 5degreess 159 5degreesw in this case coral sr ca appears to be an excellent proxy for sea surface temperature sst and coral delta 18 o is a function of both sst and seawater delta 18 o composition delta 18 o sw here we focus on extracting the delta 18 o sw signal from these proxy records a method is presented assuming that coral sr ca is solely a function of sst and that coral delta 18 o is a function of both sst and delta 18 o sw this method separates the effects of delta 18 o sw from sst by breaking the instantaneous changes of coral delta 18 o into separate contributions by instantaneous sst and delta 18 o sw changes respectively the results show that on average delta 18 o sw at rarotonga explains similar to39 of the variance in delta 18 o and that variations in sst explains the remaining similar to61 of delta 18 o variance reconstructed delta 18 o sw shows systematic increases in summer months december february consistent with the regional pattern of variations in precipitation and evaporation the delta 18 o sw also shows a positive linear correlation with satellite derived estimated salinity for the period 1980 to 1997 r 0 72 this linear correlation between reconstructed delta 18 o sw and salinity makes it possible to use the reconstructed delta 18 o sw to estimate the past interannual and decadal salinity changes in this region comparisons of coral delta 18 o and delta 18 o sw at rarotonga with the pacific decadal oscillation index suggest that the decadal and interdecadal salinity and sst variability at rarotonga appears to be related to basin scale decadal variability in the pacific copyright c 2002 elsevier science ltd

paired coral sr ca and δ18o records from the chagos archipelago late twentieth century warming affects rainfall variability in the tropical indian ocean understanding the relationship between sea surface temperature sst and precipitation is a significant challenge for climate models particularly for the tropics here we present a new monthly coral sr ca record from the tropical indian ocean chagos archipelago that extends from 1950 to 1995 the coral sr ca ratio shows a stationary relationship with local sst and documents a warming of 0 3 c since 1950 previous work has shown that the 18 o values measured in the same coral core provide a proxy record of precipitation in the tropical indian ocean the coral 18 o record shows a nonstationary relationship with local sst and a correlation between 18 o and sst only emerges in the 1970s it was proposed that this nonstationary behavior is due to an increase in mean ssts in the tropical indian ocean during the 1970s ssts reached a critical threshold 28 5 c beyond which small sst anomalies can have a significant impact on atmospheric convection as a result the covariance between sst and precipitation in the tropical indian ocean increased our new sr ca data confirm that the warming of the indian ocean during the late twentieth century affects atmospheric convection and rainfall variability moreover our proxy data show that the relationship between sst and precipitation is nonlinear and characterized by threshold behavior

the human occupation of the northwestern pyrenees in the late glacial new data from the arudy basin lower ossau valley excavated since the 1860s the arudy basin has yielded a number of rich magdalenian sites that enable us to address the question of the human reoccupation of the lower pyrenean valleys at the end of the last glacial maximum until the 1990s it was considered that at arudy this reoccupation started ca 16 000 cal bp in the middle magdalenian and continued into the upper magdalenian until ca 14 000 cal bp however since the mid 2000 s this picture has been modified through a series of new analyses excavations caves of laa 2 and tastet 14c dates and reassessment of ancient collections evidence of human occupation ca 20 000 19 000 cal bp although limited has been identified at laa 2 and tastet consistent with numerous data obtained at pyrenean scale showing a deglaciation of the north pyrenean foothills as early as the end of the global lgm the number of sites with evidence of magdalenian has increased showing that human presence in the basin was more intensive than previously thought the middle and upper magdalenian occupations have been redated to at least 18 000 17 500 cal bp to 15 000 14 500 cal bp with the transition between the two phases probably occurring ca 16 600 16 200 cal bp the faunal records of these sites document an emphasis on horse hunting which is not common in the northern pyrenees but also witness an evolution over time in the range of species hunted furthermore the pyrenean affinities of the arudy groups and their relations with neighboring regions such as spain and the northern part of the aquitaine basin can be addressed through new evidence in particular lithic and osseous raw materials and specific types of projectile tips these results significantly change our view of the nature rhythm and chronology of the late glacial settlement in this area

modulation of the southern africa precipitation response to the el nino southern oscillation by the subtropical indian ocean dipole the climate of southern africa defined as the land area bound by the region 15 s 35 s 12 5 e 42 5 e during the december march rainy season is driven by indo pacific sea surface temperature sst anomalies associated with the el nino southern oscillation enso and the subtropical indian ocean dipole siod the observed december march 1979 2014 southern africa precipitation during the four enso and siod phase combinations suggests that the phase of the siod can disrupt or enhance the southern africa precipitation response to enso here we use a large ensemble of model simulations driven by global sst and enso only sst to test whether the siod modifies the relationship between southern africa precipitation and enso since enso based precipitation forecasts are used extensively over southern africa an improved understanding of how other modes of sst variability modulate the regional response to enso is important enso in the absence of the siod forces an equivalent barotropic rossby wave over southern africa that modifies the regional mid tropospheric vertical motions and precipitation anomalies el nino la nina is related with high low pressure over southern africa that produces anomalous mid tropospheric descent ascent and decreases increases in precipitation relative to average when the siod and enso are in opposite phases the siod compliments the enso related atmospheric response over southern africa by strengthening the regional equivalent barotropic rossby wave anomalous mid tropospheric vertical motions and anomalous precipitation by contrast when the siod and enso are in the same phase the siod disrupts the enso related atmospheric response over southern africa by weakening the regional equivalent barotropic rossby wave anomalous mid tropospheric vertical motions and anomalous precipitation

forward modeling of carbonate proxy data from planktonic foraminifera using oxygen isotope tracers in a global ocean model the distribution and variation of oxygen isotopes in seawater are calculated using the goddard institute for space studies global ocean model simple ecological models are used to estimate the planktonic foraminiferal abundance as a function of depth column temperature season light intensity and density stratification these models are combined to forward model isotopic signals recorded in calcareous ocean sediment the sensitivity of the results to the changes in foraminiferal ecology secondary calcification and dissolution are also examined simulated present day isotopic values for ecology relevant for multiple species compare well with core top data hindcasts of sea surface temperature and salinity are made from time series of the modeled carbonate isotope values as the model climate changes paleoclimatic inferences from these carbonate isotope records are strongly affected by erroneous assumptions concerning the covariations of temperature salinity and 18ow habitat imposed biases are less important although errors due to temperature dependent abundances can be significant

rapid 20th century warming in the caribbean and impact of remote forcing on climate in the northern tropical atlantic as recorded in a guadeloupe coral we have generated 104 year long 1895 1999 monthly 18o and sr ca time series from a fast growing diploria strigosa coral core drilled off guadeloupe island lesser antilles coral sr ca reliably records interannual to decadal surface air temperature sat variations in the region and shows a pronounced warming of approximately 1 5 c since 1950 with the strongest warming 1 2 c occurring since 1975 this warming is also evident in sat measured at guadeloupe which ends in 1951 thus our sr ca series extends the air temperature record by 56 years we find that the past few decades are the warmest years over the entire period of record the accelerated warming since 1950 is accompanied by a pronounced decrease in regional precipitation this dampens the warming signal indicated by coral 18o which is too low only 0 7 0 8 c since 1951 consistently 18osw estimated from the coral proxies also shows a strong decrease since 1950 our data suggest an inverse relationship between sat and precipitation i e warmer and drier for the latter half of the 20th century with the strongest trends since the mid 1970s this is consistent with recent observational and model data which report that while over the tropical oceans rainfall has increased due to an increase in sea surface temperatures precipitation over land regions is reduced a continuation of this warming and drying trend over caribbean land regions would have severe societal consequences especially in the context of anthropogenic warming the el nino southern oscillation enso and the north atlantic oscillation nao are the two major climate modes affecting large scale sst variability in the northern tropical atlantic both sr ca and 18o show a close relationship to enso and the nao a quantitative comparison between extremes in mean march may coral 18o and the nino3 and nao indices imply that climate variability in the northern tropical atlantic is mainly forced by tropical pacific and north atlantic variability spectral analysis suggests that the relative importance of enso and the nao is frequency dependent with enso dominating at interannual and the nao dominating at interdecadal time scales

assessing the biomineralization processes in the shell layers of modern brachiopods from oxygen isotopic composition and elemental ratios implications for their use as paleoenvironmental proxies abstract fossil brachiopod shells are often used as valuable archives to reconstruct paleoenvironmental conditions in deep time however biomineralization processes can impact their fidelity as geochemical proxies brachiopod shells comprise an outer primary layer a secondary fibrous layer and sometimes a tertiary columnar layer therefore it is essential to assess the potential effects of the biomineralization processes in each of the different shell microstructures of modern brachiopods this study analyses the oxygen isotopic composition together with li ca na ca mg ca and sr ca data at high spatial 20 50 m resolution in seven modern brachiopod species focusing on differences between the primary secondary and tertiary layers in all studied species 18o values of the outer primary layer are consistently out of equilibrium with seawater also this shell layer is enriched in li na mg and sr contrary to the primary layer the innermost secondary layer is near or at oxygen isotopic and elemental equilibrium with ambient seawater the columnar tertiary shell layer if present has the least variable and the heaviest oxygen isotopic composition within the range of equilibrium values with seawater this tertiary layer however is depleted in minor and trace elements relative to the other shell layers thus the tertiary layer is more suitable for oxygen isotopic studies whereas the innermost secondary layer of the most mature parts of the shell is the best target in two layered shells while we do not observe any clear interspecific relationships between mg ca and sr ca ratios on one hand and environmental parameters such as temperature salinity and ph on the other hand there is a positive interspecific relationship between na ca and salinity and a negative interspecific relationship between li ca and temperature suggesting their potential use as proxies of physicochemical parameters of seawater

impact of diagenesis and low grade metamorphosis on isotope δ26mg δ13c δ18o and 87sr 86sr and elemental ca mg mn fe and sr signatures of triassic sabkha dolomites abstract dolomite is a common rock forming mineral in the geological record but its value as archive of ancient seawater 26 mg signatures and their variations in time is at present underexplored unknown factors include the sensitivity of 26 mg ratio to processes in the diagenetic and low grade metamorphic domain this paper documents and discusses the first detailed 26 mg data set from early diagenetic and burial dolomites samples come from the upper triassic hauptdolomit dolomia principale the dolomites italy and include coeval dolomicrites that underwent differential burial diagenesis and low grade metamorphosis in a temperature range between about 100 and more than 350 c magnesium isotope data are complemented by dolomite 13 c 18 o and 87 sr 86 sr isotope ratios as well as ca mg mn fe and sr elemental abundances and data on the dolomite crystal structure as indicated by dolomicrite 87 sr 86 sr ratios and petrographic evidence sabkha calcian d1 dolomites precipitated from evaporated seawater and stabilized at an early marine pore water diagenetic stage to d2 dolomites analysed here with increasing burial temperature dolomite 26 mg ratio scatter in the data set decreases with increasing mg ca ratio and degree of order specifically 26 mg ratio variability is reduced from 0 36 2 at burial temperatures beneath 100 c to about 0 14 2 at temperatures in excess of 350 c respectively with mean 26 mg values ranging constantly near 1 9 this suggests that at least for the rock buffered system investigated here dolomicrite 26 mg proxy data are conservative and preserve near pristine values even at elevated burial temperatures at present the main element of uncertainty is the mg isotope fractionation factor between evaporated seawater and dolomite a possible solution to this problem includes the compilation of data from modern sabkha environments including pore water and calcian dolomite 26 mg isotope signatures

variability of the intertropical convergence zone recorded in coral isotopic records from the central indian ocean chagos archipelago we have analyzed the stable oxygen isotopic composition of two porites corals from the chagos archipelago which is situated in the geographical center of the indian ocean coral 18o at this site reliably records temporal variations in precipitation associated with the intertropical convergence zone itcz precipitation maxima occur in boreal winter when the itcz forms a narrow band across the indian ocean the chagos then lies within the center of the itcz and rainfall is strongly depleted in 18o a 120 yr coral isotopic record indicates an alternation of wet and dry intervals lasting 15 to 20 yr the most recent 2 decades are dominated by interannual variability which is tightly coupled to the el nino southern oscillation enso this is unprecedented in the 120 yr of coral record as the itcz is governed by atmospheric dynamics this provides evidence of a major change in the coupled enso monsoon system

three monthly coral sr ca records from the chagos archipelago covering the period of 1950 1995 a d reproducibility and implications for quantitative reconstructions of sea surface temperature variations in order to assess the fidelity of coral sr ca for quantitative reconstructions of sea surface temperature variations we have generated three monthly sr ca time series from porites corals from the lagoon of peros banhos 71 e 5 s chagos archipelago we find that all three coral sr ca time series are well correlated with instrumental records of sea surface temperature sst and air temperature however the intrinsic variance of the single core sr ca time series differs from core to core limiting their use for quantitative estimates of past temperature variations averaging the single core data improves the correlation with instrumental temperature r 0 7 and allows accurate estimates of interannual temperature variations 0 35 c or better all sr ca time series indicate a shift towards warmer temperatures in the mid 1970s which coincides with the most recent regime shift in the pacific ocean however the magnitude of the warming inferred from coral sr ca differs from core to core and ranges from 0 26 to 0 75 c the composite sr ca record from peros banhos clearly captures the major climatic signals in the indo pacific ocean i e the el nino southern oscillation and the pacific decadal oscillation moreover composite sr ca is highly correlated with tropical mean temperatures r 0 7 suggesting that coral sr ca time series from the tropical indian ocean will contribute to multi proxy reconstructions of tropical mean temperatures

climate co variability between south america and southern africa at interannual intraseasonal and synoptic scales this paper investigates and quantifies co variability between large scale convection in the south american and southern african sectors at different timescales interannual intraseasonal and synoptic during the austral summer seasons november february from 1979 to 2012 multivariate analyses canonical correlation analysis and principal component analysis are applied to daily outgoing longwave radiation olr used as a proxy for atmospheric convection anomalies to extract the principal modes of variability and co variability in each and between both regions filtered to consider the appropriate time scales at the interannual timescale results confirm the predominant role of el nino southern oscillation enso favoring enhanced convection over both southeastern brazil and northern argentina on the one hand and tropical africa and the western indian ocean on the other hand at the intraseasonal timescale the leading mode of co variability is related to modulations of large scale atmospheric convection over most of south america and 10 days later tropical southern africa this mode accounts for the impacts of the madden julian oscillation mjo over these regions identifying robust co variability at the intraseasonal timescale between both regions require thus to consider a temporal shift between the two sectors at the synoptic scale however co variability consists mostly of a synchronous modulation of the large scale atmospheric convection over the south american and southern african sectors this results from the development of concomitant rossby waves forming a continuous wave train over the south atlantic in the mid latitudes affecting both the south atlantic and south indian convergence zones among the days when convection shows significant anomalies 30 of the total days in each sector this synchronous mode occurs about 25 of the time individual rossby waves modulating convection over one single region only during the remaining 75 events another mode of co variability involving a single rossby wave modulating the convection first over the americas and 4 days later over africa appears as sensibly weaker than the synchronous mode suggesting that the wave train mode occurs more frequently than the development and propagation of a single wave that could affect both regions

a high resolution investigation of temperature salinity and upwelling activity proxies in corals we present a high resolution study of five geochemical components of a new caledonia coral core minor and trace elements sr ca u ca mg ca ba ca together with oxygen isotopes 18o were investigated at near fortnightly resolution geochemical measurements were compared to sea surface temperature ssttsg and salinity ssstsg recorded by a thermosalinograph tsg located less than 10 m from the coral results show that sr ca mg ca and 18o are temperature dependent correlation coefficient to local ssttsg between 0 74 and 0 84 their robustness as sst tracers is tested against a satellite based data set for a 4 year validation period u ca has a more complex behavior and appears to be linked to both ssttsg and ssstsg despite relatively small local sss variations for the first time this salinity related imprint is quantified in a u ca coralline ratio in addition to sst and sss tracers ba ca measurements provide a possible way to investigate upwelling activity occurrences

calibrations of bermuda corals against large scale sea surface temperature and sea level pressure pattern time series and implications for climate reconstructions 1 proxy records from stony reef corals are established tools for reconstructing climate features however validation procedures for proving the calibrations are often insufficient or even lacking we address this problem by the establishment and validation of statistical regression models for the reconstruction of large scale climate patterns from local coral records upscaling we apply the upscaling technique to the annual growth rates of two coral species from bermuda representing a period of about 140 years the coral records are related to reanalyzed sea surface temperature sst and sea level pressure slp fields in the western north atlantic the correlation maps between the ssts and the single coral records and their leading principal component show similar structures on the basis of regression patterns for limited areas upscaling models are established validation of such models for the sst yields an explained variance of 30 of the low pass filtered data using the first principal component of both corals for the detrended slp time series representing an almost hemispheric slp pattern 21 of the interannual variability is explained by means of only one coral thus different corals from neighboring sites represent similar climate signals however to slightly varying degrees leading to different reconstruction skills problems remain in reconstructing long term trends we conclude that reconstructions from multiple corals are not a priori predominant to those from single corals a calibration to what extent a single coral represents a climate parameter should be the first step before combining multiple corals as the basis for a reconstruction

changes in eastern pacific ocean ventilation at intermediate depth over the last 150 kyr bp the circulation patterns of the deep glacial pacific ocean are still debated difficulties arise due to the scarcity of reliable paleoceanographic records that can document the past movements and properties of pacific ocean water masses here we jointly use delta 13 c and delta 18 o measured on the epibenthic foraminifer cibicidoides wuellerstorfi from the md02 2529 sediment core collected at 1619 m water depth in the eastern equatorial pacific to monitor changes in water mass circulation spanning the past 150 kyr bp after the extraction of short term centennial to millennial scale delta 13 c and delta 18 o changes which were similar to 1 0 and 0 5 parts per thousand respectively we observed that these rapid delta 13 c and 8180 shifts were closely interrelated during the last 150 kyr bp a comparison of md02 2529 with other benthic delta 13 c records localized to the north and south of the core location revealed that md02 2529 was alternately bathed by a northern nutrient rich and a southern nutrient poor water mass the comparison provided a diagnostic for the latitudinal movements of a sharp water mass front that was particularly evident during marine isotope stages 4 and 3 on the millennial timescale by considering that delta 13 c is an indicator of the northern vs southern origin of the water that bathed the md02 2529 coring site in the past we found that a north pacific water mass that occasionally spreads to the eastern pacific ocean as deep as 1600 m and as far south as 8 degrees n was responsible for shifts toward the positive delta 18 o we observed in the past we then used the delta 13 c delta 18 o relationship to reconstruct latitudinal temperature and or salinity gradients of the water mass that were linked to changes in the northern and or the southern water mass end members evolution of the delta 13 c delta 18 o relationship spanning the past 150 kyr bp has shed light on how hydrological processes occurring at northern and southern high latitudes are transmitted to the ocean s interior through water mass advection c 2010 elsevier b v all rights reserved

cooling of the southern high latitudes during the medieval period and its effect on enso abstract a high resolution multiproxy study performed on a marine record from se pacific off southern south america was used to reconstruct past regional environmental changes and their relation to global climate particularly to el nino southern oscillation enso phenomenon during the last 2200 years our results suggest a sustained northward shift in the position of the zonal systems i e the southern westerly wind belt and the antarctic circumpolar current which occurred between 1300 and 750 yr bp the synchrony of the latitudinal shift with cooling in antarctica and reduced enso activity observed in several marine and terrestrial archives across south america suggests a causal link between enso and the proposed displacement of the zonal systems this shift might have acted as a positive feedback to more la nina like conditions between 1300 and 750 yr bp by steepening the hemispheric and tropical pacific zonal sea surface temperature gradient this scenario further suggests different boundary conditions for enso before 1300 and after 750 yr bp

the remnants of younger dryas lithalsas on the hautes fagnes plateau in belgium and elsewhere in the world this paper summarizes all the available information about the viviers of the hautes fagnes i e closed and ramparted depressions which are numerous above 500 m a s l on the highest belgian plateau these features and cross sections in the ramparts are described the ramparts are the result of both mass wasting on the slopes of the mounds and toppling of inside material 14c dating of a peat layer preserved under a rampart allerod volcanic ashes and palynological studies have proved that the viviers formed their origin during the younger dryas in the first place the depressions were interpreted as excavations by prehistoric men from 1956 on they were interpreted as pingo remnants the pingo hypothesis is now abandoned the viviers are remnants of mineral palsas lithalsas features which nowadays exist in hudsony canada present day lithalsas are solely known in subarctic quebec and in lapland they form in the discontinuous permafrost zone close to the tree line i e in zones where mean annual temperature mat ranges from 4 to 6 c and where the average temperature of the warmest month is between 9 and 11 5 c such climatic conditions are rarely encountered nowadays in periglacial regions remnants of lithalsas are very infrequent too they appear like ramparted depressions forming clusters such traces dating from the younger dryas have been described only at elevation above 500 m a s l on the belgian hautes fagnes plateau around 250 m a s l in wales and at sea level in ireland in these few places according to r isarin s palaeoclimatic results climatic conditions during the younger dryas were similar to present day conditions in subarctic quebec where lithalsas are numerous

palaeoecology of a palsa and a filled thermokarst pond in a permafrost peatland subarctic quebec canada radiocarbon dating and macrofossil data from a palsa and a filled thermokarst pond within a subarctic permafrost peatland were used to reconstruct their evolution and to distinguish between allogenic and autogenic processes that had been involved in their development peat began to accumulate in the peatland basin shortly after 6000 cal bp the initial stage was a shallow bay or a salty marsh followed by a wet marsh triggered by a relatively rapid drop in sea level related to a rapid isostatic uplift of land by 5640 cal bp the site had transformed into a rich fen a high rate of peat accumulation led to the establishment of a short lived intermediate fen by 4610 cal bp and to a poor fen from 4200 cal bp until 1760 cal bp low water tables associated with decreased precipitation occurred between 5170 and 4610 cal bp and 3100 and 1760 cal bp between 1760 and the little ice age there was ombrotrophication of the site largely as a result of a thick peat accumulation during this period autogenic processes had controlled the general hydrosere while allogenic processes mainly precipitation had influenced species composition permafrost established during the little ice age leading to palsa formation and it has been melting in response to recent climate warming and precipitation increases macrofossil results from the filled thermokarst pond show that plant succession used the followed hydrosere calliergon giganteum and sphagnum riparium when the pond s depth was at a maximum s riparium and c giganteum when the pond was partly filled in and s lindbergii and s riparium since the pond has been completely filled in

reconstructing seawater δ18o from paired coral δ18o and sr ca ratios methods error analysis and problems with examples from tahiti french polynesia and timor indonesia we compare several statistical routines that may be used to calculate delta o 18 and sss from paired coral sr ca and delta o 18 measurements typically the delta o 18 coral sst relationship is estimated by linear regression of coral delta o 18 vs sst if this method is applied evidence should be given that at a particular site sst and sss do not co vary in the tropical oceans sst and delta o 18 sw sss often co vary and this will bias the estimate of the regression slope of delta o 18 coral sst using a stochastic model we show that covariance leads to a bias in the coefficients of the univariate regression equations as the slope of the delta o 18 coral sst relationship has known we propose to insert this value for gamma 1 in the regression models this requires that the constants of the regression equations are removed to omit the constants we propose to center the regression equations i e to remove the mean values from the variables the statistical error propagation is calculated to assess our ability to resolve past variations in delta o 18 sw sss at tahiti we find that the combined analytical uncertainties of coral delta o 18 and sr ca equal the amplitude of the seasonal cycle of delta o 18 sw sss therefore we cannot resolve the seasonal cycle of sss at tahiti at timor the error of reconstructed delta o 18 sw sss is lower than the magnitude of seasonal variations of delta o 18 sw sss and the seasonal cycle of delta o 18 sw sss can be resolved c 2008 elsevier ltd all rights reserved

an investigation of interannual rainfall variability in africa abstract interannual variations in african rainfall are examined using rotated principal component analysis pca applied to anomalies from the annual mean as well as seasonal anomalies the rotated pca loading patterns suggest several preferred continental scale rainfall anomaly patterns the dominant features of year to year variations in african rainfall appear to be the high spatial coherence of rainfall anomalies over large portions of the continent in addition several dipole regions that is adjacent regions which tend to experience rainfall anomalies of opposite sign are found and discussed one dipole region the sub saharan region appears to have a relationship with a characteristic atlantic sea surface temperature anomaly pattern during boreal summer during austral summer the tendency for a large scale dipole pattern in southeast africa is apparent as is an association of this pattern with the warm and cold phases of the el nin southern oscillation enso phenomenon normalized rainfal

glacial to interglacial vegetation changes in the northern and southern pyrenees deglaciation vegetation cover and chronology abstract new palynological investigations have been carried out in the southern northern and mediterranean part of the pyrenean chain pollen percentage and concentration diagrams are compared for a period including the end of the glacial period the late glacial and postglacial periods from the new results and from comparisons with previous published data the steppe and semi desert vegetation of the end of the last glacial period are described as well as the plant communities of the period 15 13 ka a dry climate was responsible for the early glacial retreat before 30 ka deglaciation was continuous up to about 15 14 ka without any readvance around 20 18 ka different aspects of the late glacial vegetation are studied and the first stages of the postglacial are described the younger dryas event is found everywhere but particularly clearly in the mediterranean area the most important 14 c dates are discussed and a plateau of 14 c ages is clearly visible around 10 000 bp

the influence of pacific sst variability on the precipitation over southern africa this study is an analysis of agcm model results to understand the dynamics of the response of precipitation over southern africa sa to anomalies in the sea surface temperature sst over the pacific ocean the pattern of interannual precipitation anomaly over sa and its temporal variations are quite similar in both the ensemble mean of the control where agcm is forced with observed ssts in all ocean basins and experimental runs where agcm is forced with seasonally varying climatological sst over the pacific ocean however the amplitude of the variability is found to be relatively reduced in the experimental runs this is shown to be a result of the modulation of the walker circulation by the variability of pacific ocean sst the regional teleconnection pattern between the dominant mode of sa precipitation variability and sst anomalies over the eastern indian ocean is also influenced by the variations in pacific sst the nature of the teleconnection between sa precipitation and eastern indian sst is apparent only when the pacific sst variability is excluded this is corroborated from observations as well

global patterns of enso induced precipitation although there have been many analyses of el nino southern oscillation enso induced precipitation anomalies global patterns from these analyses remain incomplete here we combine recent satellite estimates of oceanic precipitation and historical rain gauge records to derive a global climatology of enso induced precipitation anomalies using empirical orthogonal function eof analyses the patterns suggest that the re arrangement of convection centers of the walker circulation during enso events induces large precipitation anomalies in the tropics while associated changes in the monsoon systems through the hadley cell over the pacific indian and atlantic oceans and their interactions with midlatitude westerlies generate coherent anomaly patterns over the extratropics our results can be used to evaluate climate models and forecast enso induced precipitation anomalies

shift in enso teleconnections recorded by a northern red sea coral abstract el nino southern oscillation enso teleconnections over europe and the middle east are evaluated using an oxygen isotope coral time series from the northern red sea and various instrumental datasets a shift in the correlation between the nino 3 index and the red sea coral record in the 1970s is detected and it is shown that this shift can be attributed to nonstationary circulation regimes and related enso teleconnections it is found that positive anomalies of oxygen isotope in the red sea coral record from the middle 1930s to the late 1960s are associated with a strong pacific north atlantic teleconnection accompanied by a weak aleutian low a more zonal flow at midlatitudes and la nina conditions in tropical pacific in contrast positive anomalies of oxygen isotopes in the red sea coral after the 1970s are related to el nino conditions and weaker pan pacific atlantic circulation regimes using the window correlation of the northern red sea coral record with two coral records from the tropi

the guianese paradox how can the freshwater outflow from the amazon increase the salinity of the guianan shore french guiana is notable for the extent of its rain forests which occupy 97 of the country and the influence of the amazon along its shores in fact the shores and estuaries support a mangrove forest typical of saline conditions this paper reports the chemical characteristics conductivity and salinity and the stable isotopes oxygen and deuterium of the rivers and shores between the cayenne area and the border with surinam the results show a quite homogenous freshwater pool over the country however the low slope of the coast a result of the wide mud banks deposited by the amazonian plume have turned the mouths of the smaller rivers to the northwest creating large salty areas where mangroves grow several kilometers inland despite the large amount of amazonian water the guianan coast exhibits high salinity in fact the freshwater itself remains far from the shore following the north brazilian current while only the mud plume arrives at the coast creating this paradox

a new concept for the paleoceanographic evolution of heinrich event 1 in the north atlantic new records of planktonic foraminiferal 18o and lithic and foraminiferal counts from eirik drift are combined with published data from the nordic seas and the ice rafted debris ird belt to portray a sequence of events through heinrich event 1 h1 these events progressed from an onset of meltwater release at not vert similar19 ka bp through the conventional h1 ird deposition phase in the ird belt starting from not vert similar17 5 ka bp to a final phase between 16 5 and not vert similar15 ka bp that was characterised by a pooling of freshwater in the nordic seas which we suggest was hyperpycnally injected into that basin after not vert similar15 ka bp this freshwater was purged from the nordic seas into the north atlantic which preconditioned the nordic seas for convective deep water formation this allowed an abrupt re start of north atlantic deep water nadw formation in the nordic seas at the bolling warming 14 6 ka bp in contrast to previous estimates for the duration of h1 i e 1000 years to only a century or two the total combined composite h1 signal presented here had a duration of over 4000 yrs not vert similar19 14 6 ka bp which spanned the entire period of nadw collapse it appears that deep water formation and climate are not simply controlled by the magnitude or rate of meltwater addition instead the location of meltwater injections may be more important with nadw formation being particularly sensitive to surface freshening in the arctic nordic seas

late holocene mineral palsas and associated vegetation patterns a case study from lac hendry northern quebec canada and significance for european pleistocene thermokarst abstract mineral palsas with thin peat covers are described from the continuous to discontinuous permafrost transition zone they are up to 4 m high and are developed in a clast rich fine grained diamict their development post dates the land emergence ca 4 3 ka bp following isostatic uplift morphological and vegetational data suggest a growth and decay cycle from small emergent sphagnum covered mounds to mature palsas with heath and forest taxa and finally arcuate ridges marking the outline of degraded palsas separated by bogs and open water it is speculated that long term ground water supply within a complex talik structure and allied ice segregation through cryosuction are crucial formative processes field features diagnostic of these mineral palsas are frost heaved erratic blocks surficial sliding of peat blocks seeps of thawed diamict and a complex pattern of thermokarst landforms the palsa fields may be analogues for relict complex thermokarst landforms in parts of western europe formerly subject to permafrost and previously interpreted as relict pingos

western indian ocean marine and terrestrial records of climate variability a review and new concepts on land ocean interactions since ad 1660 we examine the relationship between three tropical and two subtropical western indian ocean coral oxygen isotope time series to surface air temperatures sat and rainfall over india tropical east africa and southeast africa we review established relationships provide new concepts with regard to distinct rainfall seasons and mean annual temperatures tropical corals are coherent with sat over western india and east africa at interannual and multidecadal periodicities the subtropical corals correlate with southeast african sat at periodicities of 16 30 years the relationship between the coral records and land rainfall is more complex running correlations suggest varying strength of interannual teleconnections between the tropical coral oxygen isotope records and rainfall over equatorial east africa the relationship with rainfall over india changed in the 1970s the subtropical oxygen isotope records are coherent with south african rainfall at interdecadal periodicities paleoclimatological reconstructions of land rainfall and sat reveal that the inferred relationships generally hold during the last 350 years thus the indian ocean corals prove invaluable for investigating land ocean interactions during past centuries

environmental processes of the ice age land oceans glaciers epilog knowledge of the state of the earth at the last glacial maximum lgm an interval around 21 000 years ago is an important benchmark for understanding the sensitivity of global environmental systems to change much progress in understanding climates of the lgm has occurred in the 20 years since the end of the climap project of the 1970s climate long range investigation mapping and prediction here we review this progress based on presentations and discussion at a rst open science meeting of the epilog project environmental processes of the ice age land oceans glaciers held in delmenhorst germany may 1999 we outline key controversies and document protocols for epilog contributions so that a new synthesis of the lgm earth can emerge as an open project of the world s community of scientists 2001 elsevier science ltd all rights reserved

the magdalenian in switzerland re colonization of a newly accessible landscape abstract during the last glacial maximum switzerland was almost entirely covered with ice however in the ice free region situated less than 50 km north of the glaciers human occupation is confirmed as early as 23 000 cal bp numerous sedimentary sequences in lakes and mires have produced a wealth of proxy data indicating that environmental conditions improved rapidly after the melting of the glaciers that liberated the swiss plateau at least at c 17 500 cal bp offering severe but possible life conditions to plant animal and human communities contrary to what has long been the prevailing opinion magdalenian re colonization of switzerland did not start with the onset of the warming of greenland interstadial 1e but well before according to most of the recently obtained ams dates the magdalenian occupation falls within the cold treeless environment of the oldest dryas period it is even conceivable that it did not extend into greenland interstadial 1e more than 50 sites among which famous caves and rockshelters such as kesslerloch and schweizersbild as well as large open air campsites like monruz and moosbuhl have produced different techno assemblages that find good comparisons in the rest of europe in contrast to the exploitation of mainly local and regional flint sources the use of exotic ornamental symbolic objects fossil mollusks amber and jet shows widespread multidirectional long distance connections with the upper danube basin the mainz basin the paris basin the atlantic coast the mediterranean and even the baltic regions

oxygen isotope salinity relationship in the northern indian ocean we analyze the surface 18o salinity relationships of the bay of bengal and the arabian sea in the northern indian ocean known for their contrasting hydrological conditions new measurements of these tracers show a very low 18o salinity slope associated with the strong dilution in the bay of bengal but a slope more typical of this latitude in the arabian sea although this region is marked by a complex monsoonal regime numerical modeling using a box model and a general circulation model is able to capture the 18o salinity slope and its geographical variation both models clearly show that the low 18o salinity slope is due to the evaporation minus precipitation balance with an important contribution of the continental runoff in the bay of bengal although the low value of these slopes 0 25 makes past salinity reconstructions uncertain insight into the last glacial maximum conditions shows a probable stability of these slopes and limited error on paleosalinity

modification of the southern african rainfall variability enso relationship since the late 1960s analysis of 149 raingauge series 1946 1988 shows a weak positive correlation between late summer rainfalls january march in tropical southern africa and the southern oscillation index soi the correlation coefficients have been unstable since world war ii they were close to zero before 1970 and significant thereafter before 1970 southern african late summer rainfalls were more specifically correlated with regional patterns of sea surface temperature sst mainly over the southwestern indian ocean after 1970 teleconnections with near global sst anomaly patterns i e over the central pacific and indian oceans dominate the regional connections the increase in the sensitivity of the southern african rainfall to the global so related circulation anomalies is simultaneous with the correlation between soi and more extensive sst anomalies particularly over the southern indian ocean this feature is part of longer term decadal global sst variability as inferred from statistical analyses numerical experiments using the meteo france general circulation model arpege climat are performed to test the impact of the observed sst warming in the southern indian and extratropical oceans during el nino southern oscillation enso events on southern african rainfall simulated results show that enso events which occurred in the relatively cold background of the pre 1970 period in the southern oceans had a little effect on southern africa climatic conditions and atmospheric circulation by contrast more recent enso events with warmer sst over the southern oceans lead to a climatic bipolar pattern between continental southern african and the western indian ocean which is characterized by reduced enhanced deep convection and rainfall over the subcontinent the western indian ocean a weaker subtropical high pressure belt in the southwestern indian ocean is also simulated along with a reduced penetration of the moist southern indian ocean trade winds over the southern african plateau these results are consistent with the strong droughts observed over all southern africa during enso events since 1970

assessment of pingo distribution and morphometry using an ifsar derived digital surface model western arctic coastal plain northern alaska abstract pingos are circular to elongate ice cored mounds that form by injection and freezing of pressurized water in near surface permafrost here we use a digital surface model dsm derived from an airborne interferometric synthetic aperture radar ifsar system to assess the distribution and morphometry of pingos within a 40 000 km2 area on the western arctic coastal plain of northern alaska we have identified 1247 pingo forms in the study region ranging in height from 2 to 21 m with a mean height of 4 6 m pingos in this region are of hydrostatic origin with 98 located within 995 drained lake basins most of which are underlain by thick eolian sand deposits the highest pingo density 0 18 km 2 occurs where streams have reworked these deposits morphometric analyses indicate that most pingos are small to medium in size

the landes de gascogne southwest france periglacial desert and cultural frontier during the palaeolithic abstract during the last glacial period a large part of the aquitaine basin southwest france was a periglacial desert comprising coversands with low relief dune fields surrounded by loess accumulations osl and radiocarbon dates show that the phase of maximum sand deposition coincides with marine isotope stage mis 2 peats and gleyic palaeosoils intercalated within the sands at some sites indicate that vegetation cover was able to develop locally during short events possibly d o interstadials due to raised groundwater levels in interdunal depressions few palaeolithic sites have been discovered in the coversand area in contrast to the peripheral loess region systematic survey along a future highway corridor demonstrates that this paucity of sites is not the result of insufficient survey nor deep site burial but rather reflects an archaeological reality this strongly suggests that the sand area was not attractive for hunter gatherer populations due to its reduced levels of water resources and available vegetation and animal biomass the distribution of cultural markers such as art items and projectile points also shows that the coversand area probably acted as a barrier separating two different cultural sub areas one in the pyrenees and cantabria the other in the perigord as a consequence the commonly accepted view that southwest france as a whole served as a refugia during the cold and arid phases of the pleistocene should be replaced by a more complex one that reflects the fact that a large part of the territory was almost unoccupied and that human populations were concentrated along alluvial valleys

geomorphology and hydrogeological significance of the holocene pingos in the karup valley area traill island northern east greenland many of the geomorphologically diverse hydraulic pingos of holocene age are described from within the catchment of the karup river pingo morphology ranges from single features to complexes with over 10 from mature forms to degraded types evidence for different cycles of reactivation is seen the two instances of active pingo springs are associated with substantial icings landform changes since fritz muller s observations in 1956 are generally minor it is hypothesised that the concentration of hydraulic pingos in east greenland may initially reflect residual higher heat flows following extensive early intrusive tertiary volcanism despite a continuous permafrost climatic environment the undisputed presence of ground water flows and discharges as evidenced by major icings and pingos in the valleys suggests that structural weaknesses are controlling the taliks associated with the intrapermafrost hydrology

a calibration of the oxygen isotope paleothermometer of coral aragonite from porites the oxygen isotopic composition 18oaragonite of coral aragonite is dependent upon two parameters temperature and water oxygen isotopic composition this tracer allows temperature reconstruction in tropical zones different published 18o temperature relationships show a slope derived from the regression 18o against t c which varies between 0 16 and 0 23 for porites genus this implies greater uncertainty for paleoclimatic reconstruction the calibrations were generated differently they were obtained from several colonies collected in different locations or the formula was derived from the same coral head following seasonal variations of temperature the relationships took into account of 18osw fluctuation or 18osw were estimated from salinity or were not considered we show by using isotopic data from weber and woodhead 1972 and assessing the 18osw value by two different methods that a thermodynamically significant formula is generated

climate variability across the last deglaciation in nw iberia and its margin abstract the direct comparison between marine and terrestrial data from the nw iberian margin core md03 2697 allows us to accurately evaluate without chronological ambiguity the vegetation response to north atlantic climate events across the last deglaciation comparison of md03 2697 data with other marine and terrestrial records from a vast area stretching from the azores to western w france iberia and its margin the w mediterranean and nw africa reveals the importance of enhanced winter north atlantic westerlies episodes in driving a heterogeneous regional climatic signal during particular events of the last deglaciation heinrich stadial 1 hs1 oldest dryas is a complex event marked by three synchronous main phases a extremely cold relatively wet b cool dry c relatively warmer increasing moisture availability in regions directly influenced by the north atlantic while it is characterized by a single phase cold and dry in most inland and high altitude areas changes in the strength and position of north atlantic westerlies could explain the variability in moisture during hs1 from w pyrenees to w mediterranean the bolling allerod b a event is marked by a synchronous progressive increase of ocean and atmospheric temperatures and precipitation from the bolling to the allerod in w iberia and w pyrenees contrasting with the greenland temperature pattern mid to high latitudes thermal contrast and the gradual strengthening of the atlantic meridional overturning circulation amoc triggered the continuing enhancement of westerlies and moisture along this period finally the younger dryas yd stadial is characterized by a land ocean synchronous returning cold conditions but not so cold as hs1 and although dry conditions persisted during this period extreme winter precipitation occurrences might have affected the most coastal areas of north and central w iberia and pyrenees in contrast dry conditions persisted during the yd in the western mediterranean regions the westerlies migrated further north following the displacement of the polar front during the deglaciation precluding the input of moisture in the w mediterranean region which persisted very dry during the yd stadial

lithic tool kits a metronome of the evolution of the magdalenian in southwest france 19 000 14 000 cal bp under the magdatis project a new evolutionary model has been proposed for the middle and upper magdalenian based on a review of several lithic assemblages from southwest france the lower magdalenian is not addressed in this article single lithic assemblages and stratigraphic sequences have been compared according to several parameters the origin of the siliceous raw materials the interconnection between domestic tool production and hunting armatures and the typo technology of the microliths alongside the new techno economic data the geographical distribution of certain practices and particular artefacts in southwest france has led to a discussion of the cultural geography of the different phases of the magdalenian between 19 000 and 14 000 cal bp the early middle magdalenian covers an extensive european cultural territory demonstrating social interactions over vast distances both in the circulation of raw materials and in the distribution of certain morphotypes of lithic armament the late middle magdalenian appears to correspond to a phase of population contraction in which cultural emulation is observed among lithic tool kits in the socio economic value placed on large blades the early upper magdalenian coincides with the renewed settlement of the north aquitaine plains among the technological innovations observed is the development of lithic points on small blades leading to a first geographical division of the southwest aquitaine basin versus pyrenees finally the late upper magdalenian confirms this evolution of lithic equipment with new developments in lithic armaments in parallel with some easing off of the technical constraints associated with blade production this period thus coincides with the progressive dilution of magdalenian norms with these four phases of the middle and upper magdalenian it is possible to gain a clearer understanding of the sequence of technical and economic changes observed in an environment in recomposition at the same time population fluctuations over these five millennia can be associated with developing phenomena of regionalism particularly in the southwest of france

nonstationary enso precipitation teleconnection over the equatorial indian ocean documented in a coral from the chagos archipelago d 18 oc o f aporites coral from the chagos archipelago 71 e 5 s only after the mid 1970s a strong enso signal emerges in the d 18 oc during the analyzed period 1950 1994 in the 1970s the increasing sea surface temperature sst shifted the mean sst closer to the deep convection threshold at about 28 5 c enso related sst variability largely controls the deep convection and precipitation in the central equatorial indian ocean ceio when the sst is at this critical level the anomalies in the precipitation induce changes in the isotopic composition of the surface ocean waters the precipitation signal amplifies the sst signal in the coral d 18 oc and raises the correlation to enso the presented results have important implications for the reconstruction of enso indices from corals within the indian ocean citation timm o m pfeiffer and w c dullo 2005 nonstationary ensoprecipitation teleconnection over the equatorial indian ocean documented in a coral from the chagos archipelago geophys res lett 32 l02701 doi 10 1029 2004gl021738

decadal shift in el nino influences on indo western pacific and east asian climate in the 1970s abstract el nino s influence on the subtropical northwest nw pacific climate increased after the climate regime shift of the 1970s this is manifested in well organized atmospheric anomalies of suppressed convection and a surface anticyclone during the summer june august of the el nino decay year jja 1 a season when equatorial pacific sea surface temperature sst anomalies have dissipated in situ observations and ocean atmospheric reanalyses are used to investigate mechanisms for the interdecadal change during jja 1 the influence of the el nino southern oscillation enso on the nw pacific is indirect being mediated by sst conditions over the tropical indian ocean tio the results here show that interdecadal change in this influence is due to changes in the tio response to enso during the postregime shift epoch the el nino teleconnection excites downwelling rossby waves in the south tio by anticyclonic wind curls these rossby waves propagate slowly westward causing persistent sst warmi

mayotte coral reveals hydrological changes in the western indian ocean between 1881 and 1994 we reconstruct the hydrologic history of the tropical western indian ocean by calculating the 18oseawater from coupled coral sr ca and 18o measurements in a massive porites coral from mayotte comoros between 1881 and 1994 we found that the precipitation evaporation balance varies naturally on time scales of 5 6 years and 18 25 years high low ssts are associated with positive negative 18oseawater implying that atmospheric variability is linked with remote climate modes in the indian ocean and the tropical extratropical pacific ocean warm el nino southern oscillation events are associated with a negative freshwater balance at mayotte this case study demonstrates that a much denser network of 18oseawater reconstructions is crucial for understanding the spatial patterns of hydrological conditions

effect of changes in d18o content of the surface ocean on estimated sea surface in past warm climate 1 using a coupled climate model of intermediate complexity including oxygen 18 climber 2 we investigate the evolution of the distribution of surface water 18o composition under warm climate conditions we then determine the impact of changes of the surface water 18o distribution on ocean surface temperatures inferred from calcite oxygen 18 our results show that published temperature reconstructions based on oxygen 18 from calcite are systematically biased by 2 to 4 c in the absence of major oceanic circulation changes and up to 7 c in the presence of major oceanic circulation changes as the bias introduced is shown to vary with latitude our work has major implications on past latitudinal temperature gradient reconstructions based on oxygen 18 measurements

technological evolution of hunting implements among pleistocene hunter gatherers osseous projectile points in the middle and upper magdalenian 19 14 ka cal bp abstract the middle and upper magdalenian have yielded rich and diverse assemblages of osseous hunting technology including projectile points barbed or not foreshafts and spearthrowers within the magdatis project the evolution of this technology at french sites was reassessed by building an extensive dataset of 14c dates on magdalenian hunting implements selecting assemblages with good archeological homogeneity and taking into account questions of manufacture hafting and use a finer four stage chronology was established in coordination with lithic studies a steady evolution was identified marked by the intensification of antler exploitation and the increasing diversity and complexity of osseous armatures this evolution is the continuation of a long term trend that began in the badegoulian and lower magdalenian and that culminated in the late middle early upper magdalenian showing a special emphasis on composite projectile tips and evidence of the long distance circulation of osseous materials and objects a simplification process then takes place with much of the technical innovation now centered on barbed implements to the detriment of the rest of the weapon kit a trait that may announce the azilian

interannual displacements of convection and surface circulation over the equatorial indian ocean the interannual variability of surface observations in the equatorial indian ocean is investigated from 23 years of ship reports 1954 1976 in october and november during certain years the monthly analyses show strong wind anomalies in the eastern and central equatorial indian ocean simultaneously cloud cover anomalies of opposite signs are observed in the eastern indian ocean and in the central indian ocean a linear analysis of heat induced circulation suggests that the surface wind anomalies are forced by anomalies of rainfall this circulation is probably dissipative with time scales in the range two to five days the reasons for the maintenance of anomalous circulations are not well known it is noted that during most el nino events in the pacific ocean anomalies are observed in the indian ocean however there are other years with the same anomalous pattern 1961 for example during the years with anomalously little cloudiness in the eastern indian ocean sea surface temperatures lower than normal are found in the eastern indian ocean this suggests that coupled air sea dynamics must be taken into account to understand the interannual variability

effect of sea ice on the salinity of antarctic bottom waters abstract brine rejection during the formation of antarctic sea ice is known to enhance the salinity of dense shelf waters in the weddell and ross seas as these shelf waters flow off the shelves and descend to the bottom they entrain ambient deep water to create new bottom water it is not uncommon for ocean modelers to modify salinity boundary conditions around antarctica in an attempt to include a sea ice effect in their models however the degree to which antarctic salinities are enhanced is usually not quantified or defended in this paper studies of shelf hydrography and 18o are reviewed to assess the level of salinity enhancement appropriate for ocean general circulation models the relevant quantities are 1 the salinity difference between the water masses modified on the shelves and the final offshelf flow and 2 the flux of salt or freshwater that gives rise to this salinity difference onshelf offshelf salinity changes in the weddell and ross seas appear to be fairly small 0 15 0 20 sa

the glacial origins of relict pingos wales uk ramparted depressions doughnut shaped debris cored ridges with peat and or sediment filled central basins are commonly perceived to represent the relict collapsed forms of permafrost ground ice mounds i e pingos or lithalsas in wales uk ramparted depressions of late pleistocene age have been widely attributed to permafrost related processes however a variety of alternative glacial origins for these enigmatic landforms are also consistent with the available geological and geomorphological evidence although previous studies have barely considered such alternative processes of formation from detailed geophysical sedimentological and remote sensing studies at two field sites we demonstrate that i the wastage of stagnating glacier ice is a viable alternative explanation for the formation of ramparted depressions in wales ii the glacial geomorphology and geology of these landforms is analogous to supraglacial and subglacial landforms from the last laurentide and fennoscandian ice sheets iii these landforms have significant potential for characterising the nature of deglaciation around the margins of the irish sea during the last glacial cycle and may record evidence for the overextension and stagnation of the south eastern margin of the irish sea ice stream and iv investigations of ramparted depressions within formerly glaciated terrains must consider both glacial and periglacial mechanisms of formation

synchronisation of palaeoenvironmental records over the last 60 000 years and an extended intimate event stratigraphy to 48 000 b2k the intimate protocol for the correlation of marine ice core and terrestrial records is here updated reflecting recent developments in palaeoclimate research originally focussed on last glacial to interglacial transition lgit 22 000 11 500 years b p the intimate group has now extended its study period back to 60 000 years as a first step the intimate event stratigraphy has now been extended to include 8000 48 000 b2k based on a combined ngrip and grip isotope profile against a gicc05 chronology and key tephra horizons from iceland and continental european volcanic sources in this lead article of this intimate special issue we introduce some of the recent achievements of the intimate community and discuss the challenges associated with extending the intimate approach back in time focussing in particular on the chronological problems inherent in comparing different proxy records the intimate approach has thus far been limited predominantly to the north atlantic and australasian regions and we also discuss the potential to extend the intimate protocol beyond these regions

ma anshan cave and the origin of bone tool technology in china abstract here we present the results of a techno functional analysis of 17 bone tools recovered from strata 6 5 and 3 of the palaeolithic site of ma anshan cave guizhou province southern china stratum 6 dated to c 35 cal kyr bp has yielded three sharp awls from stratum 5 dated to c 34 cal kyr bp come six probable spear points awls and a cutting tool separated from these layers by a sterile horizon stratum 3 dated 23 cal kyr bp to 18 cal kyr bp has yielded barbed points of two types bone tools were shaped by scraping grinding and in strata 5 and 3 finished by polishing ma anshan cave records the oldest formal bone tools from china and amongst the oldest known evidence of indisputable barbed point manufacture outside africa change in the hunting toolkit between strata 5 and 3 may indicate a shift in prey preference from medium to small size mammals and fish which needs to be verified by supplementary analyses the significance of this evidence is discussed in the context of what is known about the origin of bone tool technology in africa and eurasia

reconstructing paleosalinity from δ18o coupled model simulations of the last glacial maximum last interglacial and late holocene reconstructions of salinity are used to diagnose changes in the hydrological cycle and ocean circulation a widely used method of determining past salinity uses oxygen isotope ow residuals after the extraction of the global ice volume and temperature components this method relies on a constant relationship between ow and salinity throughout time here we use the isotope enabled fully coupled general circulation model gcm hadcm3 to test the application of spatially and time independent relationships in the reconstruction of past ocean salinity simulations of the late holocene lh last glacial maximum lgm and last interglacial lig climates are performed and benchmarked against existing compilations of stable oxygen isotopes in carbonates oc which primarily reflect ow and temperature we find that hadcm3 produces an accurate representation of the surface ocean oc distribution for the lh and lgm our simulations show considerable variability in spatial and temporal ow salinity relationships spatial gradients are generally shallower but within 50 of the actual simulated lh to lgm and lh to lig temporal gradients and temporal gradients calculated from multi decadal variability are generally shallower than both spatial and actual simulated gradients the largest sources of uncertainty in salinity reconstructions are found to be caused by changes in regional freshwater budgets ocean circulation and sea ice regimes these can cause errors in salinity estimates exceeding 4 psu our results suggest that paleosalinity reconstructions in the south atlantic indian and tropical pacific oceans should be most robust since these regions exhibit relatively constant ow salinity relationships across spatial and temporal scales largest uncertainties will affect north atlantic and high latitude paleosalinity reconstructions finally the results show that it is difficult to generate reliable salinity estimates for regions of dynamic oceanography such as the north atlantic without additional constraints

modern and last glacial maximum sea surface δ18o derived from an atmospheric general circulation model the past isotopic contents of sea surface waters 6 cannot be measured directly although they would be a good indicator of ocean circulation through their relationship with sea surface salinities a method of 6 reconstruction is proposed based on the use of outputs from an atmospheric general circulation model including a full isotopic model using the outputs of the nasa giss isotopic gcm and a simple box model we have established that there is a strong correlation r 0 75 between atmospheric fluxes and s measured in the frame of geosecs program indicating that 6 is largely governed by atmospheric fluxes this justifies the use of the present day statistical relationship reflecting essentially the strong atmospheric forcing on sea surface water for different conditions to those prevailing during the last glacial maximum for this period over subtropical areas lower isotopic compositions are obtained in the atlantic ocean whereas higher values are obtained in the indian and pacific oceans thus reducing the isotopic contrast between the atlantic and pacific oceans the pacific and indian oceans show a similar isotopic pattern with the tropical s values accentuated by a marked decrease in the equatorial zone however whereas the predictions from the atlantic and indian oceans exhibit good agreement with proxy data derived from foraminifera important discrepancies exist in the pacific ocean

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

caribbean coral tracks atlantic multidecadal oscillation and past hurricane activity it is highly debated whether global warming contributed to the strong hurricane activity observed during the last decade the crux of the recent debate is the limited length of the reliable instrumental record that exacerbates the detection of possible long term changes in hurricane activity which naturally exhibits strong multidecadal variations that are associated with the atlantic multidecadal oscillation amo the amo itself a major mode of climate variability remains also poorly understood because of limited data here we present the first coral based proxy record 18o that clearly captures multidecadal variations in the amo and the hurricane activity our record obtained from a brain coral situated in the atlantic hurricane domain is equally sensitive to variations in sea surface temperature sst and seawater 18o with the latter being strongly linked to precipitation by this means amplifying large scale climate signals in coral 18o the sst and precipitation signals in the coral provide the longest thus far continuous proxy based record of hurricane activity that interestingly exhibits a long term increase over the last century as multidecadal sst variations in this region are closely related to the amo this study raises new possibilities to extend the limited observations and to gain new insights into the mechanisms underlying the amo and long term hurricane variations

oxygen 18 salinity relationship simulated by an oceanic general circulation model the distribution of h218o in the ocean is simulated using an oceanic general circulation model gcm surface isotopic fluxes prescribed to this model are derived from an atmospheric gcm which ensures their consistency the oceanic gcm is initialized with a homogeneous composition and redistributes isotopic gradients so as to equilibrate with the atmosphere a good agreement is found between the observations and the simulation concerning i the interbasin h218o gradients especially the atlantic being more enriched than the pacific as well as the meridional gradients and ii the h218o salinity relationship

on the weakening relationship between the indian monsoon and enso analysis of the 140 year historical record suggests that the inverse relationship between the el nino southern oscillation enso and the indian summer monsoon weak monsoon arising from warm enso event has broken down in recent decades two possible reasons emerge from the analyses a southeastward shift in the walker circulation anomalies associated with enso events may lead to a reduced subsidence over the indian region thus favoring normal monsoon conditions additionally increased surface temperatures over eurasia in winter and spring which are a part of the midlatitude continental warming trend may favor the enhanced land ocean thermal gradient conducive to a strong monsoon these observations raise the possibility that the eurasian warming in recent decades helps to sustain the monsoon rainfall at a normal level despite strong enso events

oceanic oxygen 18 at the present day and lgm equilibrium simulations with a coupled climate model of intermediate complexity abstract an earth system model of intermediate complexity climber 2 is used to simulate the oxygen 18 content of the water masses h182o in the oceans firstly we forced climber 2 with the fluxes from the atmospheric general circulation model echam simulated oceanic 18o fields for the present day are in good agreement with data secondly a water isotope module was developed to transport 18o in the atmosphere on a large scale and compute the 18o fluxes to the ocean at the atmosphere ocean interface using only variables already computed by climber 2 for the present day we successfully represent oxygen 18 distribution in the atlantic indian and pacific oceans and close agreement is also found when we compare modelled and observed 18ow salinity relationships during the last glacial maximum lgm we find that the major differences in the 18o oceanic fields apart from the global oceanic enrichment due to ice sheet build up are due to surface condition changes surface temperature shift in bottom water formation zones and that no drastic changes occurred in the 18ow salinity spatial relationship in addition we compute a calcite 18oc field for the atlantic and compare it to the available data to assess the variation between the lgm and the present day

modern precipitation stable isotope vs elevation gradients in the high himalaya comment on a new approach to stable isotope based paleoaltimetry implications for paleoaltimetry and paleohypsometry of the high himalaya since the late miocene by david b rowley et al earth planet sci lett 188 2001 253 268