direct correlation of millennial scale changes in western north american vegetation and climate with changes in the california current system over the past 60 kyr terrestrial pollen and marine climate proxies from seven sediment cores taken on the continental margin of western north america between 32 and 43 n show systematically related short term changes superposed on milankovitch scale oscillations of the past 60 kyr during oxygen isotope stage 3 brief warming events in california and oregon appear correlative with interstadial events in waters offshore as do the rapid climate oscillations of the last glacial transition 14 10 ka estimated temperature depression of the coastal lowlands ranges from 10 c in southern california to 5 c in oregon during the last glacial the absence of long distance migration of pacific coastal plant assemblages concurs with marine evidence that southward movement of the polar front during the last glacial maximum was limited correlative changes in terrestrial and marine ecosystems imply that broad reorganizations of circulation in the northeast pacific ocean were synchronous with reorganizations of atmospheric circulation over western north america

assessment of geochemical and micropaleontological sedimentary parameters as proxies of surface water properties in the canary islands region abstract the canary islands region occupies a key position with respect to biogeochemical cycles with the zonal transition from oligotrophic to nutrient rich waters and the contribution of saharan dust to the particle flux we present the distribution of geochemical proxies toc carbonate 15n 13corg c n ratio and micropaleontological parameters diatoms dinoflagellates foraminifera pteropods in 80 surface sediment samples in order to characterise the influence of coastally upwelled water on the domain of the subtropical gyre results of the surface sediment analyses confirmed the high biomass gradient from the coast to the open ocean inferred from satellite data of surface chlorophyll or sst the distribution of total dinoflagellate cysts the planktic foraminifera species globigerina bulloides the diatom resting spore chaetoceros spp and toc concentration coincided well with the areas of strong filament production off cape ghir and cape yubi the warm water planktic foraminifera globigerinoides ruber white the diatom nitzschia spp and the 15n values showed the opposite trend with high values in the open ocean factor analyses on the planktic foraminifera species distribution indicated three major assemblages in the canary islands region that represent the present surface water conditions from the upwelling influenced region via a mixing area towards the subtropical gyre

south atlantic and benthic foraminifer δ13c deviations implications for reconstructing the late quaternary deep water circulation abstract benthic foraminifer species cibicidoides wuellerstorfi and related genera are assumed to secrete calcite very close to the carbon isotope values of the ambient bottom water co2 recently attention has been focused on substantial productivity linked 13c depletions to examine further the productivity effect on benthic 13c deviations we present data from the south atlantic between 15 and 35 s including water samples from 10 hydrographic stations and related surface sediment measurements on c wuellerstorfi we compare open ocean data with observations in the namibia upwelling area as a result 13c co2 values as well as phosphate concentrations in water samples of the upwelling realm differ significantly from those of the open ocean realm at least in the upper and mid depth water masses sacw aaiw ucdw however deviations from the redfield fractionation caused by air sea fractionation remain constant within each water mass which means that the carbon isotope changes toward upwelling areas are exclusively determined by biological cycling in addition to lower 13c co2 values in upwelling areas a depletion in the 13c of epibenthic foraminifer calcite is observed which is most likely explained by the decay of organic matter reducing the 13c 12c ratio in the pore water and influencing the carbon isotopic composition of the c wuellerstorfi shells of highly productive areas the paleoceanographic implication of this effect for reconstructing the late quaternary deep water circulation is discussed using carbon isotope records of several sediment cores within and outside the namibia upwelling area

ocean chemistry during glacial time abstract measurements of co2 to air ratios in the gas trapped in bubbles in ice of glacial age suggest that the co2 content of the atmosphere was considerably lower during peak glacial time than during holocene time the purpose of this paper is to show that such a change must in all likelihood be the result of alterations in the nutrient element chemistry of sea water two possible scenarios are presented one involves alternate storage and erosion of phosphorous leaving residues from shelf sediments the other involves changes in the c p ratio in the organic debris falling to the deep sea means of verifying the nutrient cycle hypothesis are also given it is shown that the 13c record as we know it in planktonic and benthic foraminifera the oxygen record as inferred from benthic foraminifera species distributions and the early post glacial caco3 preservation event as recorded by aragonitic pteropods are consistent with both of the hypotheses presented only if an early post glacial spike in the 13c record for planktonic shells could be found would it be possible to eliminate one of these hypotheses i e that involving shelf storage the implications of these nutrient hypotheses to climate theory are as follows if shelf storage is responsible for the glacial to interglacial co2 increase then the co2 change must be considered an amplifier of some primary cause the reason is that sea level changes are needed to drive deposition on and erosion from the shelves on the other hand if changes in the c p ratio for falling debris are responsible then the co2 change could either be an amplifier or a primary cause for the major glacial to interglacial climatic cycle the latter is possible as self sustained oscillations in ocean chemistry might be driven by interactions between ocean ecology and ocean nutrient chemistry

depth profiles of δ13c in bottom water and core top c wuellerstorfi on the ontong java plateau and emperor seamounts we have measured the carbon isotopic composition of dissolved inorganic carbon in bottom waters of the ontong java plateau western equatorial pacific and on the northern emperor seamounts northwest pacific each of these locations is several hundred miles from the nearest geochemical ocean sections study geosecs stations and the observed 13c values at each site differ substantially from regionally averaged geosecs 13c profiles we discuss the possible causes of these differences including horizontal variability near bottom effects and problems with the pacific geosecs 13c data we also measured the isotopic composition c and o of core top c wuellerstorfi from a depth transect of cores at each location the 18o data are used to verify that our samples are holocene comparison of foraminiferal and bottom water 13c values shows that this species faithfully records bottom water 13c at both sites and demonstrates that there is no depth related artifact in the dissolved inorganic carbon c wuellerstorfi 13c relationship at these sites

the benthic foraminiferal record of the medieval warm period and the recent warming in the gullmar fjord swedish west coast a high resolution study of benthic foraminiferal assemblages was performed on a ca eight metre long sediment core from gullmar fjord on the west coast of sweden the results of pb 210 and ams c 14 datings show that the record includes the two warmest climatic episodes of the last 1500 years the medieval warm period mwp and the recent warming of the 20th century both periods are known to be anomalously warm and associated with positive nao winter indices benthic foraminiferal successions of both periods are compared in order to find faunal similarities and common denominators corresponding to past climate changes during the mwp adercotryma glomerata cassidulina laevigata and nonionella iridea dominated the assemblages judging from dominance of species sensitive to hypoxia and the highest faunal diversity for the last ca 2400 years the foraminiferal record of the mwp suggests an absence of severe low oxygen events at the same time faunas and delta c 13 values both point to high primary productivity and or increased input of terrestrial organic carbon into the fjord system during the medieval warm period comparison of the mwp and recent warming revealed different trends in the faunal record the thin shelled foraminifer n iridea was characteristic of the mwp but became absent during the second half of the 20th century the recent skagerrak kattegat fauna was rare or absent during the mwp but established in gullmar fjord at the end of the little ice age or in the early 1900s also there are striking differences in the faunal diversity and absolute abundances of foraminifera between both periods changes in primary productivity higher precipitation resulting in intensified land runoff different oxygen regimes or even changes in the fjord s trophic status are discussed as possible causes of these faunal differences c 2011 elsevier b v all rights reserved less

deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation the degree of similarity of the 13c records of the planktonic foraminiferal species n pachyderma and of the benthic foraminiferal genus cibicides in the high latitude basins of the world ocean is used as an indicator of the presence of deepwater sources during the last climatic cycle whereas continuous formation of deep water is recognized in the southern ocean the norwegian sea stopped acting as a sink for surface water during isotope stage 4 and the remainder of the last glaciation however deep water formed in the north atlantic south of the norwegian sea during the last climatic cycle as early as isotope substage 5d and this area was also the only active northern source during stages 4 2 a detailed reconstruction of the geographic distribution of 13c in benthic foraminifera in the atlantic ocean during the last glacial maximum shows that the most important deepwater mass originated from the southern ocean whereas the glacial north atlantic deep water cannot be traced south of 40 n at shallower depth an oxygenated 13c rich intermediate water mass extended from 45 n to 15 s in the pacific ocean a ventilation higher than the modern one was also found in open ocean in the depth range 700 2600 m and is best explained by stronger formation of intermediate water in high northern latitudes

multispecies stable isotopes of benthic foraminifers reveal past changes of organic matter decomposition and deepwater oxygenation in the arabian sea 1 the stable isotope composition of one epifaunal and three infaunal benthic foraminiferal species of a sediment core from 1800 m water depth of the western arabian sea was determined to evaluate deepwater oxygenation organic matter remineralization and early diagenetic processes during the past 190 000 years the 18o records reveal species specific metabolic effects susceptibility to changes in carbonate ion concentration and supralysoclinal calcite dissolution the foraminiferal 13c records reveal changes in the stable carbon isotope gradients of pore water dissolved inorganic carbon 13cdic and in the microhabitat depth of infaunal species maximum 13cdic offsets between bottom and pore waters ranged between mean values of 0 8 and 1 2 corresponding to estimates of deepwater oxygen concentration between approximately 1 and 2 7 ml l 1 intervals of improved deepwater oxygenation coincided with high benthic foraminiferal diversity and indicate the admixture of well oxygenated deepwater masses during interglacials during interglacial maxima the 13c difference between epifauna and shallow infauna indicates highest organic matter remineralization rates at times of maximum organic matter fluxes

benthic foraminiferal δ18o in the ocean s temperature salinity density field constraints on ice age thermohaline circulation benthic 18o data from 95 core sites are used to infer possible temperature salinity t s fields of the atlantic and pacific oceans at the last glacial maximum lgm a constraint of stable density stratification yields logically consistent scenarios for both t and s the solutions are not unique but are useful as a thinking tool using geosecs data we solve for the modem relationship between 18owater w and salinity in the deep sea w smow 1 529 s 53 18 as a starting point we assume that the slope of this equation applies to lgm conditions and predict 18ocalcite c gradients in equilibrium with probable t s fields of lgm deep and bottom waters benthic foraminiferal 18o data from the deep pacific 2 4 km depth and the bottom atlantic 4 km depth are 0 1 0 2 lower than from the deep atlantic 2 4 km depth at the lgm if the modern w s slope applies atlantic deep and bottom waters were more dense than pacific deep waters this assumption would imply bottom waters both fresher s 0 5 and colder t 3 c than overlying deep waters in conflict with other data suggesting ice age deep water much colder than at present it is also possible that the observed c gradients are an artifact of laboratory intercalibration if atlantic deep and bottom water c values were similar to deep pacific values this would be consistent with the hypothesis of a stronger southern ocean versus north atlantic source for deep ocean ventilation at the lgm taking the observed gradients at face value however a solution could be that the lgm w s slope in deep and bottom waters was higher than at present conceivably because of a stronger contribution of salt to the deep ocean via more intense sea ice freezing this would allow pacific deep waters and atlantic bottom waters to have a common source again in the antarctic both would be more dense than atlantic deep waters even though the deep waters were much colder than at present to better constrain these inferences drawn from the spatial distribution of benthic 18o we must reduce scatter in the 18o data with more high quality measurements in high sedimentation rate cores this is especially true at bottom water sites also we must intercalibrate mass spectrometers at different isotope laboratories more accurately to insure our isotope data are compatible

marine and terrestrial biomarker records for the last 35 000 years at odp site 658c off nw africa several high resolution proxy environmental records have been obtained for the last 35 kyr from odp hole 658c a well studied site ca 200 km oa cap blanc nw africa the collective assessment based on the marine proxies u k 0 37 sst contents of toc and chlorins upwelling radiolarian index and the percentage of florisphaera profunda surprisingly indicates that the last glacial maximum lgm was characterized by warmer sea surface temperature sst weaker upwelling and lower marine productivity compared with the preceding older glacial and subsequent deglaciation periods of the terrigenous proxies the mean grain size of the non carbonate fraction and the terrigenous alkane content indicate that wind strength and aridity were high the weaker upwelling at the 658 site during the lgm may have resulted from changes in the strength and direction of the wind systems and or shifts in the position and geometry of the upwelling cell 2000 elsevier science ltd all rights reserved

high epibenthic foraminiferal δ13c in the recent deep arctic ocean implications for ventilation and brine release during stadials low planktic and benthic 18o and 13c values in sediments from the nordic seas of cold stadials of the last glaciation have been attributed to brines formed similar to modern ones in the arctic ocean to expand on the carbon isotopes of this hypothesis i investigated benthic 13c from the modern arctic ocean i show that mean 13c values of live epibenthic foraminifera from the deep arctic basins are higher than mean 13c values of upper slope epibenthic foraminifera this agrees with mean high 13c values of dissolved inorganic carbon dic in arctic bottom water abw which are higher than mean 13cdic values from shallower water masses of mainly atlantic origin however adjustments for oceanic 13c suess depletion raise subsurface and intermediate water 13cdic values over abw 13cdic ones accordingly during preindustrial holocene times the 13cdic of abw was as high or even higher than today but lower than the 13cdic of younger subsurface and intermediate water if brine enriched water significantly ventilated abw brines should have had high 13cdic values analogously high 13cdic brines may have been formed in the nordic seas during warm interstadials during cold stadials when most of the arctic ocean was perennially sea ice covered a cessation of high 13cdic brine rejection may have lowered 13cdic values of abw and ultimately the 13cdic in nordic seas intermediate and deep water so in contrast to the idea of enhanced brine formation during cold stadials the results of this investigation imply that a cessation of brine rejection would be more likely

messinian productivity changes in the northeastern atlantic and their relationship to the closure of the atlantic mediterranean gateway implications for neogene palaeoclimate and palaeoceanography the stable isotope composition of planktic and benthic foraminifera and the distribution of selected benthic foraminiferal species from a messinian record of the lower guadalquivir basin northeastern atlantic ocean show that regional productivity changes were linked to glacioeustatic fluctuations glacial periods were characterized by poorly ventilated bottom waters as a result of weak atlantic meridional overturning circulation amoc and by phases of high productivity related to intensified upwelling in contrast well ventilated bottom waters owing to strong amoc the presence of degraded organic matter in the upper slope and high input of degraded terrestrial organic matter derived from fluvial discharge to the outer shelf were recorded during interglacial periods before closure of the adjacent guadalhorce corridor at 6 18 ma which was the final active betic atlantic mediterranean gateway the study area was alternately influenced by well ventilated mediterranean outflow water mow and poorly ventilated atlantic upwelled water auw following closure of the corridor cessation of the mow reduced the amoc and promoted glacial conditions in the northern hemisphere resulting in the establishment of local upwelling cells

recent benthic foraminifera from the continental margin of northwest africa community structure and distribution abstract sediment grab samples were collected at 107 locations along the continental margin of northwest africa these samples form a series of depth transects between the straits of gibraltar and dakar senegal the greater than 250 m size fraction was retained for a census of both the live and dead foraminifera after deleting trace occurrences jaccard and correlation coefficient based cluster analyses were performed to decipher the community structure for this margin the geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth upper slope and shelf middle slope and lower slope and continental rise the biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using jaccard coefficients dendrograms constructed from correlation coefficients emphasize depth related faunal communities dominant species such as cibicides lobatulus trifarina fornasinii planulina ariminensis uvigerina finisterrensis and c wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient based dendrograms other distributions are clearly not depth related but correspond to various environmental variables for example cancris auriculus coarse substrate bolivina subaenariensis oxygen minimum cibicidoides kullenbergi and hoeglundina elegans low organic carbon uvigerina peregrina is also a notable exception to depth dependence in that this dominant species and the province it represents are generally confined to the continental slope south of cape blanc its preference for that region may arise from the high organic carbon and fine grain size of the sediment there from low salinity of the bottom water or from other unknown variables the most important vertical faunal boundary occurs between cape barbas and cape blanc between 22 and 21 n latitude in contrast the canary island ridge intersects the continental margin at a saddle depth of about 1500 m but that physiographic barrier has little effect on provincialism of the deep water benthic foraminifera

glacial and interglacial wind regimes over the eastern subtropical atlantic and north west africa analysis of aeolo marine dust deposits in the subtropical eastern atlantic enables the strength of the major wind patterns during the late quaternary to be evaluated and gives an insight into the climate of north africa

variability of the antarctic intermediate waters in the northern canary box abstract several chemical parameters were measured during four seasonal cruises in 1997 and 1998 within the canary islands acores gibraltar observations project along the transects within the so called northern canary box ncb this area is enclosed between the african coast latitudes 29 n and 32 n and longitude 18 w to the north of the canary islands spain the nutrient and oxygen concentration data are used in order to establish the atlantic antarctic intermediate water aaiw distribution in the area by means of an anomaly method it is established that this water mass is widely found in this zone particularly new to the african coast a volumetric budget indicates that the aaiw volume flowing into the ncb is of the same order as the mediterranean water mw inflow the results indicate that only 40 of the aaiw mass reaching the box flows northwards through the 32 n section whereas 20 returns southwards through the 29 n section

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

nw african climate variations during the last 47 000years evidence from organic walled dinoflagellate cysts nw african climate shows orbital and millennial scale variations which are tightly connected to changes in marine productivity we present an organic walled dinoflagellate cyst dinocyst record from a sediment core off cape yubi at about 27 n in the canary basin covering the time period from 47 to 3 ka before present bp the dinocyst record reflects differences in upwelling intensity and seasonality as well as the influence of fluvial input sea level changes play an important role for the upwelling pattern and productivity signals at the core site within the studied time interval four main phases were distinguished 1 from 45 to 24 ka bp when sea level was mostly about 75 m lower than today high relative abundances of cysts of heterotrophic taxa point to enhanced upwelling activity especially during heinrich events while relatively low dinocyst accumulation rates indicate that filament activity at the core location was strongly reduced 2 at sea level lowstand during the lgm to h1 dinocyst accumulation rates suggest that local filament formation was even more inhibited 3 from the early holocene to about 8 ka bp extraordinary high accumulation rates of most dinocyst species especially of lingulodinium machaerophorum suggest that nutrient supply via fluvial input increased and rising sea level promoted filament formation at the same time the upwelling season prolongated 4 a relative increase in cysts of photoautotrophic taxa from about 8 ka bp onwards indicates more stratified conditions while fluvial input decreased our study shows that productivity records can be very sensitive to regional features from the dinocyst data we infer that marine surface productivity off cape yubi during glacial times was within the scale of modern times but extremely enhanced during deglaciation

atlantic sea surface temperatures estimated from planktonic foraminifera off the iberian margin over the last 40 ka bp abstract sea surface temperatures ssts were reconstructed from planktonic foraminiferal assemblages in two sediment cores off the nw iberian continental margin for the last 40 kyr results of this work were compared with published ssts estimated in six cores from the iberian margin and the 18 o data from ngrip ice core of greenland longitudinal and latitudinal sst changes were identified in several intervals related to alterations in the hydrographic conditions off the iberian peninsula namely the influence of the upwelling system the intensity of paleo portugal and paleo azores currents and the positions of the polar and arctic fronts during the holocene the ssts were quite stable along the west iberian margin when compared with the last glaciation however during the last glacial maximum lgm ssts were not much lower than during the holocene the portugal current as an eastward descending branch of the north atlantic drift should have been quite vigorous in transporting warm water to the west iberian margin which could have moderated the ssts during the lgm however our results suggest a much higher instability during the lgm than previously reported and much lower ssts at 42 n the lowest ssts during the last 40 ka were recorded during the heinrich stadials hs and the younger dryas yd during the hs ssts at the northwest iberian margin were lower than today by about 10 to 16 c as a result of the invasion of cool and low salinity water masses and the increased transport of icebergs from the northern seas the polar front was persistently situated at 42 n for 3 ka during the hs1 and a comparable present day arctic front should have been present up to the latitude of 40 n during the hs2 hs3 and hs4 off the west iberian peninsula the hs were recorded all along the west iberian margin however an overall trend of increasing of mean ssts from north to south of 8 c during the hs1 of 10 c during the hs2b and hs3 of 11 c during the hs2a and of 4 c during the hs4 was recorded these gradients also were present during the yd of 9 c and the lgm of 4 c and may be related to the strong influence of the paleo azores current in southern areas

200 000 yr diatom records from atlantic upwelling sites reveal maximum productivity during lgm and a shift in phytoplankton community structure at 185 000 yr abstract time series of diatom accumulation rates dar and assemblage composition for the last 200 000 yr from the atlantic major coastal upwelling loci of the eastern boundary currents and eastern equator are compared together with independent proxies of export production to upper ocean productivity and to nutrient concentration and utilization fluctuations in dar are concomitant at all sites and in good correspondence to the other independent productivity proxies indicating glacial periods as the most productive times of the past 200 000 yr in both hemispheres of the eastern atlantic maximum productivity about one order of magnitude higher than at present occurred at the last glacial maximum lgm despite the atlantic similarities in both coastal and equatorial upwelling types important regional and site specific variations emerge in the southern hemisphere site a contradiction of proxies diatoms and corg is noted at the base of stage 6 185 000 yr the good correlation found between the corg and the benthic foraminifera fluxes is interpreted as a reflection of a shift in the phytoplankton community structure related to either a change in the n p si ratio or similar nutrient conditions associated with increased water column stratification

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

climatic changes along the northwestern african continental margin over the last 30 kyrs two sediment cores were investigated to study the regional climatic variability of the nw african upwelling over the late quaternary biomarker data and sea surface temperatures ssts predicted from alkenones at 25 n and 21 n exhibited distinct features the amplitude of the last deglaciation was estimated to 4 5 c at 25 n and 2 2 5 c at 21 n at 25 n terrestrial and marine glacial inputs were higher than holocene ones as a result of a strengthening of the trade winds and intensification of oceanic production in contrast at 21 n warmer ssts and lower organic carbon and alkenone productions during the last glacial suggest a regression of the upwelling and therefore a change of wind regime low glacial n alkanols are consistent with the migration of the vegetation belt during the maximum of african aridity while their decrease towards the core top may be indicative of anthropogenic disturbances

the ecology of living stained deep sea benthic foraminifera from the sulu sea the distribution of living rose bengal stained deep sea benthic foraminifera was determined in the upper 20 cm of sediments of eight soutar box cores taken from two depth transects 510 4515 m in the thermospheric 10 c sulu sea despite the uniformity of bottom water temperatures salinities and dissolved oxygen levels below 1000 m significant faunal differences exist at different depths in the low oxygen 1 25 ml l below 1000 m basin the shallowest site 510 m is dominated 10 of the calcareous fauna by cibicidoides uvigerina 150 m and bolivina 63 m while siphonina is codominant with cibicidoides and uvigerina in the 1005 m core the 2000 m cores are dominated by cibicidoides gyroidinoides and oridorsalis while cibicidoides bradyi and oridorsalis umbonatus dominate the 3000 and 4000 m cores infaunal assemblages of valvulineria mexicana are found in the sediments of the 4515 m core relatively low bottom water oxygen values do not necessarily yield typical low oxygen taxa such as bolivina uvigerina chilostomella bulimina and globobulimina changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments an examination of the vertical distributions of foraminiferal assemblages from the 63 m and 150 m fractions reveals that taxa have microhabitat preferences similar to those observed in other regions taxa found in the upper 0 to 1 cm interval epifaunal include cibicidoides wuellerstorfi and hoeglundina elegans while taxa such as chilostomella and globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences cibicidoides bradyi and o umbonatus live in sediment depths from 0 to 4 cm and have transitional preferences with both epifaunal and infaunal occurrences intrageneric differences in test morphologies including pore distribution rounded peripheries and variable spire height are observed in cibicidoides and gyroidinoides and are suggested to be related to microhabitat preferences vertical distributions of a number of taxa found in both the 63 to 150 m and 150 m fractions are similar suggesting that juveniles and adults live under similar microhabitat conditions ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

global variations of surface ocean productivity in low and mid latitudes influence on co2 reservoirs of the deep ocean and atmosphere during the last 21 000 years based on detailed reconstructions of global distribution patterns both paleoproductivity and the benthic 13c record of co2 which is dissolved in the deep ocean strongly differed between the last glacial maximum and the holocene with the onset of termination i about 15 000 years ago the new export production of low and mid latitude upwelling cells started to decline by more than 2 4 gt carbon year this reduction is regarded as a main factor leading to both the simultaneous rise in atmospheric co2 as recorded in ice cores and with a slight delay of more than 1000 years to a large scale gradual co2 depletion of the deep ocean by about 650 gt c this estimate is based on an average increase in benthic 13c by 0 4 0 5 the decrease in new production also matches a clear 13c depletion of organic matter possibly recording an end of extreme nutrient utilization in upwelling cells as shown by sarnthein et al 1987 the productivity reversal appears to be triggered by a rapid reduction in the strength of meridional trades which in turn was linked via a shrinking extent of sea ice to a massive increase in high latitude insolation i e to orbital forcing as primary cause

inflow and outflow facies from the 1993 tsunami in southwest hokkaido abstract we describe in detail the sedimentary facies provenance and grain size distributions of the 1993 tsunami deposits in the lower reaches of usubetsu river only two lithofacies were recognized a gravel lobe facies glf and a sand sheet facies ssf the gravel lobe facies was deposited rapidly by a hydraulic jump in contrast the sand sheet facies which contains both current ripples and dunes was deposited by a traction current under subcritical flow conditions we identified four stratigraphic units unit 1 unit 2 unit 3 and unit 4 in ascending order we interpreted units 1 and 2 as having been deposited by the inflow and outflow events of the first run up and units 3 and 4 by the inflow and outflow events of the second run up respectively units 3 and 4 were more widely distributed and coarser grained than units 1 and 2 because the second run up was larger than the first run up furthermore unit 4 was more widely distributed than unit 3 because the outflow eroded the inflow deposits grain size distributions of the inflow and outflow deposits were clearly different unit 4 deposits had a peak at 2 5 phi p 1 population in contrast unit 3 deposits had a bimodal distribution with peaks at 0 5 1 5 phi p 2 population and at 2 5 phi p 1 population a comparison of the tsunami deposits with other sedimentary deposits near the study area showed that the tsunami deposits were mainly derived from the seabed at depths below 5 5 m in the offshore area where the marine sands are about 2 2 5 phi in size and thus are the source of the p 1 population the p 2 population is derived from coarse 0 5 2 phi fluvial materials eroded during the tsunami run up according to our calculations benthic foraminiferal tests were entrained from the comparatively deep seabed at depths up to 100 m during the tsunami run up and included in the tsunami deposits

the eastern boundary current system between the canary islands and the african coast to study the easternboundarycurrentsystem off northwest africa in detail several ctd adcp sections and long term mooring work were carried out in the channel between lanzarote and africa the observations are compared with a fine resolution model which was developed in the framework of the canigo project the water masses which are observed in this area are characterised and classified in density ranges the current field shows a high spatial and temporal variability with maximum velocities of about 35 cm s seasonal means as well as currents averaged across the channel are only a few cm s in the surface water a steady southward flow in the middle of the channel indicates the canarycurrent in this area during fall a strong northward current is observed close to the african shelf though the canarycurrent strengthens during summer and fall due to an increase of the trade winds the transport in the channel decreases or turns northward during that time due to the enhanced poleward current at the eastern side a northward undercurrent with a mean velocity of 2 3 cm s is observed at the african slope in 950 m depth the poleward transport of aaiw increases during fall and a strong influence of relatively fresh aaiw is observed during that time most of the observations fit well to the results of the canigo model but the occurrence of mw at the bottom of the channel and the corresponding southward flow cannot be resolved by the model

geomorphic effects of rural to urban land use conversion on three streams in the central redbed plains of oklahoma abstract this research evaluates the impact of rural to urban land use conversion on channel morphology and riparian vegetation for three streams in the central redbed plains geomorphic province central great plains ecoregion of oklahoma the deep fork creek watershed is largely urbanized the skeleton creek watershed is largely rural and the stillwater creek watershed is experiencing a rapid transition from rural to urban land cover each channel was divided into reaches based on tributary junctions sinuosity and slope field surveys were conducted at transects in a total of 90 reaches including measurements of channel units channel cross section at bankfull stage and riparian vegetation historical aerial photographs were available for only stillwater creek watershed which were used to document land cover in this watershed especially changes in the extent of urban areas impervious cover the three streams have very low gradients

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

climatic changes in the upwelling region off cap blanc nw africa over the last 70 kyear a multi biomarker approach abstract molecular statigraphic records of core su94 11k 21 n 18 w 1200 m water depth were reconstructed for organic carbon oc carbonates alkenones n alkanols and sterols over the last 70 ky to study past changes of production and paleoceanographic conditions in the coastal upwelling of northwest africa u k 37 derived sea surface temperatures sst show a 2 5 c warming during the last deglaciation surprisingly they also indicate that during the last glacial period between 24 and 15 kyear sst rose by 1 c it can be seen from the values of marine and terrigenous biomarker mass accumulation rates mar that this time interval was also the period of lowest marine production and dust supply suggesting a major change in the north east trade winds system this situation would have lasted until the onset of the deglaciation from which upwelling progressively intensified to produce highest marine biomarker mar at the holocene our data also show a reduced terrigenous supply in late holocene sediments that may reflect lower emission rates from the vegetation and or changes in the wind conditions

sedimentological and geomorphological effects of the sumatra andaman tsunami in the area of khao lak southern thailand the sumatra andaman tsunami left distinctive sedimentological and geomorphological signatures in the area of khao lak fine grained sediments predominantly layers of cohesive carbonate rich fine sandy silt with thicknesses of 1 10 cm erosionally overlying pre tsunami sandy soils and sediments represent the most common tsunami deposits in the study area petrographically they differ significantly from other coastal sediments and affiliated soils due to their grain size and corresponding clay mineral content muddy shelf sediments sub wave base are indicated as a main source the present results suggest that indications of shelf influence although varying regionally might contribute to the identification of fine grained tsunami sediments and their differentiation from storm sediments however the observed differences of tsunami sediments to soils and other coastal sediments especially with respect to carbonate mineralogy might disappear in short geological time under conditions of intensive weathering and bioturbation at cape pakarang hundreds of boulders with up to 24 tons were deposited on the foreshore and upper shoreface applying nott s earth planet sci lett 210 269 276 2003 formulas minimum flow velocities of 3 9 m s are required to transport the largest boulders the devastating tsunami effect of both onshore flow and backflow is documented by damaged human constructions geomorphological effects include intensive widening of estuary mouths and the development of erosional channels now estuary mouths are reduced and erosional channels cut off from the sea due to the formation of a post tsunami beach ridge

carbon and oxygen isotopic disequilibria of recent deep sea benthic foraminifera abstract the carbon and oxygen isotopic compositions of 149 samples of benthic foraminifera from deep sea core tops indicate that none of the nine species studied secrete calcium carbonate in isotopic equilibrium with ambient bottom water uvigerina pyrgo murrhina and oridorsalis tener are the closest to 18o equilibrium with average deviations about 0 4 while planulina wuellerstorfi and p murrhina are the closest to 13c equilibrium with average deviations about 1 p wuellerstorfi shows the most systematic relationship between 13c and bottom water apparent oxygen utilization the intraspecific variabilities in 18o and 13c suggest that estimates of bottom water paleotemperatures can be made to a precision of 0 7 c while estimates of past apparent oxygen utilization aou can be made to 35 mol kg based on intraspecific comparisons of the recent samples with fossils no temporal changes in the degree of either 18o or 13c disequilibrium have been detected for planulina wuellerstorfi uvigerina oridorsalis tener and globocassidulina subglobosa

solar modulation of north atlantic central water formation at multidecadal timescales during the late holocene article i nfo understanding natural climate variability in the north atlantic region is essential not only to assess the sensitivity of atmosphere ocean climate signal exchange and propagation but also to help distinguish between natural and anthropogenic climate change the north atlantic oscillation is one of the controlling modes in recent variability of atmosphere ocean linkages and ice freshwater fluxes between the polar and north atlantic ocean through these processes the nao influences water mass formation and the strength of the atlantic meridional overturning circulation and thereby variability in ocean heat transport however the impact of the nao as well as other forcing mechanisms on multidecadal timescales such as total solar irradiance on eastern north atlantic central water production central water circulation and climate signal propagation from high to low latitudes in the eastern subpolar and subtropical basins remains uncertain here we use a 1200 yr long benthic foraminiferal mg ca based temperature and oxygen isotope record from a 900 m deep sediment core off northwest africa to show that atmosphere ocean interactions in the eastern subpolar gyre are transferred at central water depth into the eastern boundary of the subtropical gyre further we link the variability of the nao over the past 165 yrs and solar irradiance late holocene and their control on subpolar mode water formation to the multidecadal variability observed at mid depth in the eastern subtropical gyre our results show that eastern north atlantic central waters cooled by up to 0 8 0 7 c and densities decreased by 0 3 0 2 during positive nao years and during minima in solar irradiance during the late holocene the presented records demonstrate the sensitivity of central water formation to enhanced atmospheric forcing and ice freshwater fluxes into the eastern subpolar gyre and the importance of central water circulation for cross gyre climate signal propagation during the late holocene 2011 elsevier b v all rights reserved

reconstruction of paleoceanography off nw africa during the last 40 000 years influence of local and regional factors on sediment accumulation abstract a set of 43 sediment cores from around the canary islands is used to characterise this region which intersects meridional climatic regimes and zonal productivity gradients in a high spatial resolution using rapid and nondestructive core logging techniques we carried out fe intensity and magnetic susceptibility ms measurements and created a stack on the basis of five stratigraphic reference cores for which a stratigraphic age model was available from 18 o and 14 c analyses on planktonic foraminifera by correlation of the stack with the fe and ms records of the other cores we were able to develop age depth models at all investigated sites of the region we present the bulk sediment accumulation rates ar of the canary islands region as an indicator of shifts in the upwelling influenced areas for the holocene 0 12 ky the deglaciation 12 18 ky and the last glacial 18 40 ky general observations are an enhanced productivity during glacial times with highest values during the deglaciation the main differences between the analysed time intervals we interpret as result of the sea level effects changes in the extent of high productivity areas and current intensity

upwelling intensity and filament activity off morocco during the last 250 000 years abstract the high productive upwelling area off morocco is part of one of the four major trade wind driven continental margin upwelling zones in the world oceans while coastal upwelling occurs mostly on the shelf biogenic particles derived from upwelling are deposited mostly at the upper continental slope nutrient rich coastal water is transported within the cape ghir filament region at 30 n up to several hundreds of kilometers offshore both upwelling intensity and filament activity are dependent on the strength of the summer trades this study is aimed to reconstruct changes in trade wind intensity over the last 250 000 years by the analysis of the productivity signal contained in the sedimentary biogenic particles of the continental slope and beneath the cape ghir filament detailed geochemical and geophysical analyses toc carbonate c n 13corg 15n 13c of benthic foraminifera 18o of benthic and planktic foraminifera magnetic susceptibility have been carried out at two sites on the upper continental slope and one site located further offshore influenced by the cape ghir filament a second offshore site south of the filament was analyzed toc magnetic susceptibility to distinguish the productivity signal related to the filament signal from the general offshore variability higher productivity during glacial times was observed at all four sites however the variability of productivity during glacial times was remarkably different at the filament influenced site compared to the upwelling influenced continental slope sites in addition to climate related changes in upwelling intensity zonal shifts of the upwelling area due to sea level changes have impacted the sedimentary productivity record especially at the continental slope sites by comparison with other proxies related to the strength and direction of the prevailing winds si al ratio as grain size indicator pollen the productivity record at the filament influenced site reflects mainly changes in trade wind intensity our reconstruction reveals that especially during glacial times trade wind intensity was increased and showed a strong variability with frequencies related to precession

upwelling intensity and ocean productivity changes off cape blanc northwest africa during the last 70 000 years geochemical and micropalaeontological evidence abstract the accumulation of biogeochemical organic carbon calcium carbonates molybdenum and iodine micropalaeontological benthic foraminifera and terrigenous markers grain size si al zr al k al over the last 70 000 years in one core sedorqua 11k on the northwest african margin off cap blanc has been used to reconstruct past variations of local upwelling intensity and oceanic productivity the study demonstrates that productivity in this area increased during stage 3 particularly between 40 000 and 50 000 yr b p and during the last deglaciation between 6000 and 15 000 yr b p during most of isotopic stage 2 and particularly during the last glacial maximum productivity was much lower these variations can be attributed to changes in local wind stress and seasonality that are related to variability in monsoon pressure intensity because of the establishment of upwelling cells over the shelf due to high sea level the conditions of sedimentation during the last 5 6 thousend years on the upper slope site 11k are largely dominated by advection from the shelf leading to strong sorting prior to deposition advection seems to have been minor during the other periods of enhanced productivity a conceptual model is proposed to link the productivity variations to atmospheric circulation in particular to the wind stress direction and seasonality

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

trophic control of benthic foraminiferal abundance and microhabitat in the bathyal gulf of lions western mediterranean sea surface sediment was sampled at two bathyal sites in the southwestern gulf of lions in the western mediterranean sea in february and august 1997 to study the distribution and microhabitat of living rose bengal stained deep sea benthic foraminifera both standing stock and diversity of the faunas and the microhabitat of distinct species mirror the trophic situation and the depth of the oxidised layer at the different sites our results suggest that the faunas do not comprise highly opportunistic species and are adapted to rather stable environments in the axial channel of the lacaze duthiers canyon organic matter fluxes are enhanced due to advective transport of organic matter resulting in elevated oxygen consumption rates in the surface sediment and a rather thin oxidised layer the corresponding benthic foraminiferal fauna is characterised by rather high standing stock and diversity and a well developed deep infauna in addition to freshly deposited phytodetritus more degraded organic matter seems to be an important food source in contrast at the open slope organic matter fluxes and oxygen consumption rates in the surface sediment are lower and the oxidised layer is much thicker than inside the canyon the corresponding benthic foraminiferal fauna comprises mainly epifaunal and shallow infaunal species with much lower standing stocks and clear differences between february and august in august standing stocks are higher and the average living depths of most species shift towards the sediment surface these differences can be attributed to patchiness or represent a seasonal trophic signal

waves coastal boulder deposits and the importance of the pre transport setting the pre transport environment of a coastal boulder along with its shape size and density determines the height of wave required for it to be transported different forces act on sub aerial boulders as opposed to submerged boulders when struck by a wave boulders derived from joint bounded blocks on shore platforms predominantly experience lift force and require a wave of greater height to be transported than boulders in other environments no one equation is applicable to determine the height of palaeo waves responsible for depositing a field or ridge of imbricated coastal boulders a range of equations and their derivation is presented here which can be applied to the respective pre transport environment of a boulder such an approach is necessary when attempting to reconstruct the frequency and magnitude of past coastal wave hazards and for differentiating between tsunami and storm wave deposited boulder fields

last glacial maximum paleoproductivity and water masses off nw africa evidence from benthic foraminifera and stable isotopes abstract last glacial maximum lgm paleoproductivity organic carbon c org fluxes and seasonality was reconstructed from benthic foraminiferal faunas and the stable carbon and oxygen isotopes of foraminiferal calcite sediments of the lgm between 23 000 to 19 000 cal yr bp of sixteen cores from the upwelling region off morocco between cape ghir 31 n and cape yubi 27 5 n were investigated four regions with distinct paleo c org fluxes and seasonality were reconstructed based on faunal assemblages and 13 c values of hoeglundina elegans 1 the cape yubi upwelling region with high paleoproductivity high paleo c org fluxes and very low seasonality as indicated by the bolivina albatrossi uvigerina mediterranea assemblage and lowest mean 13 c h elegans 2 the cape ghir upwelling region with moderate to high paleoproductivity and paleo c org fluxes and low seasonality as indicated by the bulimina mexicana gavelinopsis translucens assemblage and low mean 13 c h elegans 3 the cape yubi filament region with moderate to high paleoproductivity high paleo c org fluxes and high seasonality as indicated by the cassidulina laevigata nonionella iridea assemblage and 13 c h elegans as low as those from the cape ghir upwelling region 4 the cape ghir filament region with highest paleoproductivity high paleo c org fluxes and seasonality as indicated by the epistominella exigua assemblage and highest 13 c h elegans productivities during the lgm and today were compared based on faunal assemblages and 13 c values 13 c 13 c lgm 13 c present of three infaunal species generally during the lgm the upwelling region was characterized by higher paleo c org fluxes particularly in the area between the capes similar seasonality along the coast and higher seasonality further offshore than at present day for the reconstruction of lgm water mass stratification we used the 13 c of cibicidoides wuellerstorfi and equilibrium adjusted 18 o of several species deep water mass stratification is characterized by glacial north atlantic central water above 800 m by glacial mediterranean outflow water between 800 and 1900 m and glacial north atlantic deep water below 1900 m and a southern source deep water mass this means considering the lowered glacial sea level water mass stratification during the lgm was similar to present day conditions

isopollen maps for 18 000 years b p of the atlantic offshore of northwest africa evidence for paleowind circulation distribution patterns of the most important pollen types from southern european and northwest african source areas for the 18 000 years b p time slice are reconstructed from pollen records of 14 well dated deep sea cores located between 37 and 9 n and compared with the modern pollen distribution in this area it is concluded that the belt with maximum african easterly jet transport did not shift latitudinally during the last glacial interglacial transition but remained at about 20 n furthermore it is substantiated that the trade winds did not shift latitudinally during the last glacial interglacial transition this evidence is not compatible with an atmospheric circulation model that assumes a zone of surface westerlies in the northern part of northwest africa trade winds during glacial episodes did however intensify especially from about 36 to 24 n

contrasting paleoceanographic conditions off morocco during heinrich events 1 and 2 and the last glacial maximum abstract past hydrological and primary productivity regimes on the basis of dinocyst and foraminiferal fossil assemblages as well as on stable isotopes o c and alkenones were investigated over the last 30 ka at upwelling site md04 2805 cq off morocco the results show highest upwelling intensity during heinrich event he 1 time coeval with a distinct plateau of heavy planktonic 13 c values high concentrations of pinus pollen and heterotrophic dinocysts caused by an increased northern wind regime in addition we also present regional reconstructions of paleo sea surface temperatures ssts using three different proxy tools dinocyst and foraminiferal transfer functions as well as alkenones u k 37 sst the reconstructed ssts depict coherent scenarios as modulated by the typical northern hemisphere climatic fluctuations furthermore specific occurrences of the dinocyst spiniferites lazus and of the foraminifer turborotalita quinqueloba are noted for he 2 he 1 and the younger dryas whereas in the alboran sea and in peri iberian waters these cold events were accompanied by the dinocyst bitectatodinium tepikiense and the subpolar foraminifer neogloboquadrina pachyderma s both implying a marked southward shift in the planktonic population in response to the migration of polar water masses this very pronounced demarcation between the planktonic communities better seems to attest the presence of a distinct hydrological structure in proximity of the strait of gibraltar which separated at that time african north of morocco from european southern iberia water masses

stable oxygen and carbon isotopes of live benthic foraminifera from the bay of biscay microhabitat impact and seasonal variability we determined the stable oxygen and carbon isotopic composition of live rose bengal stained benthic foraminifera n150 am size fraction of seven taxa sampled along a downslope transect between 140 to 2000 m water depth in the bay of biscay at the five stations hoeglundina elegans cibicidoides pachydermus uvigerina peregrina uvigerina mediterranea preferentially occupy shallow infaunal niches whereas melonis barleeanus and uvigerina elongatastriata occupy an intermediate infaunal microhabitat and globobulimina spp live in a deep infaunal niche close to the zero oxygen boundary when compared with d 18 o values of calcite formed in equilibrium with bottom waters u peregrina forms its test in close equilibrium with bottom water d 18 o all other foraminiferal taxa calcify with a constant offset to calculated equilibrium calcite there is no systematic relationship between the foraminiferal microhabitat depth and the dd 18 o between foraminiferal and equilibrium calcite we calculated correcting factors for the various taxa which are needed for constructing multispecies based oxygen isotope records in paleoceanographic studies of the study area the d 13 c values of foraminiferal taxa investigated in this study do neither record bottom water d 13 cdic in a 1 1 relationship nor with a constant offset but appear to be mainly controlled by microhabitat effects the increase of d 13 c values of shallow infaunal taxa with increasing water depth reflects the decrease of the exported flux of organic carbon along the bathymetric transect and early diagenetic processes in the surface sediment this is particularly the case for the shallow infaunal u peregrina the d 13 c values of deep infaunal globobulimina spp are much less dependent on the exported organic matter flux we suggest that the dd 13 c between u peregrina and globobulimina spp can shed light on the various pathways of past degradation of organic detritus in the benthic environments at a station in 550 m water depth where periodic eutrophication of sediment surface niches was demonstrated previously we performed a two year seasonal survey of the isotopic composition of foraminiferal faunas no marked seasonal changes of the stable carbon isotopic composition of shallow intermediate and deep infaunal foraminiferal taxa were observed thus the d 13 c values of foraminiferal individuals belonging to the n150 am fraction may result from rather long term calcification processes lasting for several weeks or months which limit the impact of ephemeral 12 c enrichment of shallow infaunal niches on the isotope chemistry of adult individuals during eutrophic periods only highly opportunistic taxa reproducing or calcifying during

past circulation along the western iberian margin a time slice vision from the last glacial to the holocene abstract fifteen iberian margin sediment cores distributed between 43 12 n and 35 53 n have been used to reconstruct spatial and temporal sub surface circulation along the iberian margin since the last glacial period time slice maps of planktonic foraminiferal derived summer sea surface temperature sst and export productivity pexp were established for specific time intervals within the last 35 ky the holocene recent and last 8 ky younger dryas yd heinrich stadials hs 1 2a 2b 3 and the last glacial maximum lgm the sst during the holocene shows the same latitudinal gradient along the western iberian margin as present day with cold but productive areas that reflect the influence of coastal upwelling centers the lgm appears as a slightly less warm but more productive period relative to the holocene and present day conditions suggesting that sea level minima forced a westward displacement of the coastal upwelling centers possibly accompanied by a strengthening of northward winds during the yd a longitudinal thermal front is depicted at 10 w with cold polar waters offshore and warmer subtropical waters inshore suggesting that the subtropical paleo iberian poleward current more likely flowed at a more inshore location masking the local sst signal and amplitude of variation a substantial cooling and drop in productivity is observed during all hs in particular hs1 and hs3 reflecting the penetration of icebergs derived meltwater these most extreme southward extensions of very cold waters define a strong sst gradient that marks a possible paleo azores front higher production south of this front was likely fed by frontal nutrient advection

cenozoic deep sea benthic foraminifers tracers for changes in oceanic productivity from late middle eocene through earliest oligocene high latitude regions cooled and by the end of the period continental ice sheets existed in antarctica diversity of planktonic microorganisms declined and modern groups of terrestrial vertebrates originated coeval faunal changes in deep sea benthic foraminifers have been related to cooling of deep waters and increased oxygenation cooling however occurred globally whereas species richness declined at high latitudes and not in the tropics the late eocene and younger lower diversity high latitude faunas typically contain common epistominella exigua and alabaminella weddellensis opportunistic phytodetritus exploiting species that indicate a seasonally fluctuating input of organic matter to the sea floor we speculate that the species richness gradient and increase in abundance of phytodetritus exploiting species resulted largely from the onset of a more unpredictable and seasonally fluctuating food supply especially at high latitudes

vostok ice core provides 160 000 year record of atmospheric co2 direct evidence of past atmospheric co2 changes has been extended to the past 160 000 years from the vostok ice core these changes are most notably an inherent phenomenon of change between glacial and interglacial periods besides this major 100 000 year cycle the co2 record seems to exhibit a cyclic change with a period of some 21 000 years

benthic foraminifera off west africa 1 n to 32 s do live assemblages from the topmost sediment reliably record environmental variability abstract recent benthic foraminifera 125 m were investigated from multicorer samples on a latitudinal transect of 20 stations between 1 n and 32 s along the upper slope off west africa samples were selected from a narrow water depth interval between 1200 and 1500 m so that changes in water masses are minimized but changes in surface productivity are important and the only significant environmental variable live rose bengal stained benthic foraminifera were counted from the surface sediment down to a maximum of 12 cm dead foraminifera were investigated in the top 5 cm of the sediment only five live and five dead benthic foraminiferal assemblages were identified using q mode principal component analysis matching distinct primary productivity provinces characterized by different systems of seasonal and permanent upwelling differences in seasonality quantity and quality of food supply are the main controlling parameters on species composition and distribution of the benthic foraminiferal faunas to test the sensitivity of foraminiferal studies based on the uppermost centimeter of sediment only a comparative q mode principal component analysis was conducted on live and dead foraminiferal data from the top 1 cm of sediment it has been demonstrated that on the upper slope off west africa most of the environmental signals as recorded by species composition and distribution of the total live and dead assemblages i e including live and dead foraminifera from the surface sediment down to 12 cm and 5 cm respectively can be extracted from the assemblages in the top centimeter of sediment only on the contrary subsurface abundance maxima of live foraminifera and dissolution of empty tests strongly bias quantitative approaches based on the calculation of standing stocks and foraminiferal numbers in the topmost centimeter

the gephyrocapsa sea surface palaeothermometer put to the test comparison with alkenone and foraminifera proxies off nw africa abstract recently a new palaeotemperature proxy was developed based on the morphology of the coccolithophore genus gephyrocapsa here we apply and validate this new methodology by comparing gephyrocapsa derived palaeotemperature estimates with temperature estimates obtained from alkenone ratios mg ca ratios in foraminiferal calcite and planktic foraminifera assemblages we investigated a downcore record off cape blanc geob 1048 20 55 n 19 43 w spanning the last 28 000 years in the vicinity of bofs core 31k 19 00 n 20 10 w for which a detailed multiproxy palaeotemperature record has already been established our data show an especially good correspondence between the gephyrocapsa and alkenone derived palaeotemperatures and thus validate the great potential of the new gephyrocapsa proxy to reconstruct sea surface water temperatures ssts both indicate a glacial drop in sst of 3 c compared to holocene values similar to the mg ca palaeotemperature record although the latter is consistently 2 5 c cooler largest discrepancies both in terms of downcore amplitude changes and same age sample estimates are found with available planktic foraminifera transfer function data this can be due to fundamental differences in the season of production ecologic preferences and habitats and or preservation on the other hand it may be a result of differences inherent to the transfer functions used and their original calibration i e regional vs global approach or different temperature ranges covered in addition to the downcore record off cape blanc sediment samples corresponding to the last glacial maximum lgm were selected from a dispersed set of eighteen well dated gravity cores in order to derive palaeo sst maps off northwest africa during this time slice by applying a regional gephyrocapsa transfer function for the first time we show that mean ssts in the canary islands region during the lgm were 4 6 c colder than today we found lowest glacial temperatures 14 15 5 c offshore morocco and south of the volcanic canary islands likely due to intensified upwelling related to stronger trade winds consistent with estimates from climap and other palaeotemperature reconstructions for the same region in contrast for offshore cape blanc today s centre of perennial upwelling our temperature estimates for the lgm are significantly warmer t today lgm 2 5 4 c than proposed by climap t today lgm 6 10 c however our results consistently support temperature reconstructions based on alkenones that also indicate rather small temperature changes t today lgm 2 4 c in this area we show that gephyrocapsa morphotypes may also provide useful qualitative information about relative changes in primary productivity although no linear relationship is apparent in summary our palaeotemperature and palaeoproductivity data support the observation that enhanced glacial productivity appears geographically limited to the northernmost latitudes of the nw african upwelling system whilst upwelling intensity off cape blanc was reduced despite overall enhanced trade wind intensity

a benthic foraminiferal proxy of pulsed organic matter paleofluxes in the temperate open ocean of the modern northeast atlantic the spring bloom of phytoplankton leads to a seasonal pulse of detrital organic material phytodetritus to the ocean floor opportunistic benthic foraminifera rapidly colonise this food resource producing large numbers of individuals whose tests are ultimately added to the sediment one of these taxa epistominella exigua shows periodic peaks in abundance in the fossil record at many open ocean sites previously such peaks have been commonly interpreted to result from changes in physicochemical properties of bottom water mass and thus deep sea circulation the main purpose of this paper is to propose thate exigua may be used as a proxy of pulsed organic matter inputs to the deep ocean and therefore as an indicator of relative changes in productivity

rapid bottom water circulation changes during the last glacial cycle in the coastal low latitude ne atlantic previous paleoceanographic studies along the nw african margin focused on the dynamics of surface and intermediate waters whereas little attention has been devoted to deep water masses currently these deep waters consist mainly of north atlantic deep waters as part of the atlantic meridional overturning circulation amoc however this configuration was altered during periods of amoc collapse we present a high resolution reconstruction of bottom water ventilation and current evolution off mauritania from the last glacial maximum into the early holocene applying redox proxies mo u and mn measured on sediments from off mauritania we describe changes in deep water oxygenation and we infer the evolution of deep water conditions during millennial scale climate oceanographic events in the area the second half of heinrich event 1 and the younger dryas were recognized as periods of reduced ventilation coinciding with events of amoc reduction we propose that these weakening circulation events induced deficient deep water oxygenation in the mauritanian upwelling region which together with increased productivity promoted reducing conditions and enhanced organic matter preservation this is the first time the effect of amoc collapse in the area is described at high resolution broadening the knowledge on basin wide oceanographic changes associated with rapid climate variability during the last deglaciation

biomarker stratigraphic records over the last 150 kyears off the nw african coast at 25 n terrigenous and marine biomarkers were investigated in a core oa northwest africa in the northeast atlantic 25n 16w 1445 m depth to assess changes in the sedimentation pattern of organic carbon oc over the last 150 kyears alkenone derived temperatures recorded a warming of 4 5c during the last deglaciation n alkanol mass accumulation rates mar fluctuated in parallel with northeast trade winds netw intensity oc and sterol mar both increased during glacial times indicating enhanced fertility of the ocean in response to intensified netw alkenone oc ratios were higher by a factor of two over stages 4 6 than stages 1 3 thus reflecting distinct coccolithophorid inputs this transition coincides with a major change of alkenone producers inferred from coccolith counts 2000 elsevier science ltd all rights reserved

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

late glacial to holocene history of the mediterranean outflow evidence from benthic foraminiferal assemblages and stable isotopes at the portuguese margin records of benthic foraminiferal assemblage variations and benthic 13c along 12 sediment cores from the western iberian margin between 36 and 42 n at water depths from 820 to 3580 m are used to monitor fluctuations of the mediterranean outflow water mow during the past 30 ka the chronostratigraphy of the cores is based on planktonic 18o records 14c ams dating and the recognition of heinrich events h1 through h4 increased abundances of suspension feeding benthic foraminifers denoted as epibenthos group closely match areas where the recent mow core layers impinge on the continental slope at 800 and 1300 m water depth and near bottom current velocities are enhanced elevated epibenthos group abundances increased benthic 13c and sedimentological evidence for winnowing and erosion are found in glacial sections up to the earliest termination i in cores at water depths between 1600 and 2200 m off southern portugal the combined evidence reveals enhanced current activity at these depths due to a deep glacial mow the mow advection at the portuguese margin during the last glacial was about 700 m deeper than today conceivably forced by increased mow density due to higher salinity and colder temperatures of mediterranean waters the deep mow current gradually decreased in strength and shoaled to 1300 m water depth during the termination and early holocene a shallow mow core layer became active with the onset of termination i at depths between 600 and 1000 m both the shallow and deep mow current culminated during the younger dryas period the present flow pattern with two mow core layers centred at 800 and 1300 m water depth was established between 7 5 and 5 5 ka

core top evaluation of benthic foraminiferal isotopic ratios for paleo oceanographic interpretations abstract the benthic foraminifera cibicides wuellerstrofi oridforsalis tener and pyrgo rotalaria from twelve core tops in the norwegian greenland sea and c wuellerstorfi o tener and o umbonatus from four core tops on the rio grande rise were analysed for oxygen and carbon isotopes the norwegian greenland sea data yield statistically discrete means for both 18o and 13c for each species the interregional comparison of our data to published data from the east pacific rise shows that c wuellerstorfi 18o and 13c variations reflect oceanographic differences between sites whereas the data on oridorsalis and pyrgo do not we conclude that c wuellerstorfi is a reliable sensor of bottom water conditions whereas other taxa are of unproven utility supportive biological studies and the lack of positive covariance of 18o to 13c among deep sea benthic taxa lead us to reject models calling for incorporation of metabolic co2 to explain the isotopic variation among deep sea benthic foraminifera we propose a within sediment microhabitat hypothesis to explain the 13c variations among taxa

changes in arctic ocean paleoproductivity and hydrography during the last 145 kyr the benthic foraminiferal record the benthic foraminiferal record of two sediment cores at 900 and 2500 m water depth in the marginal arctic ocean reflects fluctuations in paleoproductivity ice sheet extent and atlantic water inflow highest paleoproductivity is observed in interglacial periods and at the termination of interstadials to stadials within oxygen isotope substages ois 6 3 5 3 5 1 3 1 and termination ia stable and high paleoproductivity at the ice edge during terminations is indicated by the melonis zaandami benthic foraminiferal association periods of glacial ice sheet advance or retreat from the core site are dominated by benthic foraminiferal associations related to seasonal organic carbon flux temperate saline atlantic water entered the arctic ocean within ois 6 3 5 5 and the holocene coincident paleoproductivity maxima are related to extended seasonal ice retreat during glacial periods of stagnating atlantic water advection unusual low paleoproductivity values are observed in the arctic ocean indicating increasing ice coverage deep water was poorly ventilated during these periods and the deeper site became exposed to corrosive bottom waters

the δ13c in benthic foraminiferal tests of fontbotia wuellerstorfi schwager relative to the δ13c of dissolved inorganic carbon in southern ocean deep water implications for glacial ocean circulation models on a transect between 20 and 70 s in the eastern atlantic ocean and weddell sea water samples from 19 hydrographic stations and bottom water from 55 surface sediment samples taken with a multiple corer were investigated for the stable carbon isotopic composition of the total dissolved inorganic carbon 13c co2 these measurements were compared to 13c values determined on live specimens of the benthic foraminifer fontbotia wuellerstorfi and closely related genera from the same stations in addition at 16 stations the stable carbon isotope composition of sedimentary organic carbon was measured general deepwater and bottom water mass circulation patterns as inferred from the 13c co2 are in close agreement with those known from other nonconservative tracers very low 13c values of upper circumpolar deep water 0 3 pee dee belemnite pdb in the polar front region and the eastern limb of the weddell gyre coincide with nutrient maxima however a significant decoupling of the dissolved phosphate signal from the 13c co2 signal is indicated in the abyssal weddell sea we attribute this to temperature dependent fractionation processes during gas exchange of surface waters with the atmosphere at sites of bottom water formation multiple corer water from the sediment water interface is slightly 13c depleted relative to deepwater and bottom water 13 co2 the surface sediment organic carbon 13c is 3 to 4 lower south of the polar front than north of it and the 13corg in freshly accumulated phytodetritus is 3 to 4 lower than surface sediment organic carbon 13c comparison of live f wuellerstorfi 13c and related genera with bottom water 13c co2 exhibits at most stations between the subtropical front 41 s and the southern boundary of the antarctic circumpolar current 55 s a significant lowering of foraminiferal 13c values compilation of a mean last glacial interglacial 13c amplitude 13c from six published southern ocean cores results in a shift of 0 99 0 13 pdb this shift is greater than that in all other regions however all of these cores are from positions close to recent oceanic fronts thus for these peripheral areas of the southern ocean we suggest about half of the glacial interglacial shift can be explained by varying frontal zone positions and widths accompanied by a change in mode and height of export production

changes in east atlantic deepwater circulation over the last 30 000 years eight time slice reconstructions using 95 epibenthic 13c records eight time slices were reconstructed to trace the distribution of east atlantic deepwater and intermediate water masses over the last 30 000 years our results show that there have been three distinct modes of deepwater circulation near the stage 3 2 boundary the origin of north atlantic deep water nadw was similar to today mode 1 however after late stage 3 the source region of the nadw end member shifted from the norwegian greenland sea to areas south of iceland mode 2 a reduced nadw flow persisted during the last glacial maximum with constant preformed 13c values the nutrient content of nadw increased markedly near the azores fracture zone from north to south probably because of the mixing of upwelled antarctic bottom water aabw from below which then advected with much higher flux rates into the northeast atlantic later the spread of glacial meltwater over the north atlantic led to a marked short term ventilation minimum below 1800 m about 13 500 14c years ago mode 3 the formation of nadw recommenced abruptly north of iceland 12 800 12 500 years ago and reached a volume approaching that of the holocene in the younger dryas 10 800 10 350 years b p another short term shutdown of deepwater formation followed between 10 200 and 9 600 years b p linked to a further major meltwater pulse into the atlantic each renewal of deepwater formation led to a marked release of fossil co2 from the ocean the likely cause of the contemporaneous 14c plateaus over the last 9000 years deepwater circulation varied little from today apart from a slight increase in aabw about 7000 14c years ago it is also shown that the oxygenated mediterranean outflow varied largely independent of the variations in deepwater circulation over the last 30 000 years

pelagic benthic coupling within an upwelling system of the subtropical northeast atlantic over the last 35 ka bp we present a high resolution multiproxy study of the relationship between pelagic and benthic environments of a coastal upwelling system in the subtropical ne atlantic ocean marine sediments corresponding to late mis3 to the holocene in the radiocarbon dated core geob7926 retrieved off mauritania 21 degrees n were analysed to reconstruct productivity in surface waters and its linkage to deep waters during the last 35 ka bp high latitude cold events and changes in atmospheric and oceanographic dynamics influenced upwelling intensity over this time period subsequently this caused changes in primary productivity off this low latitude coastal upwelling locality the benthic foraminiferal fauna displays four main community shifts corresponding to fundamental climatic events first of all during late mis3 35 28 ka bp secondly from 28 to 19 ka bp including heinrich event 2 and the lgm thirdly within heinrich event 1 the bolling allerod and the younger diyas 18 11 5 ka bp and finally during the holocene 11 5 0 ka bp in particular strong pelagic benthic coupling is apparent in mis 3 as demonstrated by increased primary productivity indicated by moderate dar and the dominance of benthic foraminiferal species which prefer fresh phytodetritus a decline in upwelling intensity and nutrient availability follows which resulted in a proportionately larger amount of older degraded matter provoking a shift in the benthic foraminifera fauna composition this rapid response of the benthic environment continues with a progressive increase in upwelling intensity due to sea level and oceanographic changes and according high surface production during the lgm during heinrich event 1 and the younger dryas extreme levels of primary production actually hindered benthic environment through the development of low oxygen conditions after this period a final change in benthic foraminiferal community composition occurs which indicates a return to more oxygenated conditions during the holocene c 2014 elsevier ltd all rights reserved less

interpretation of the paleo primary production record in the nw african coastal upwelling system as potentially biased by sea level change 1 using a regional circulation ecosystem model subject to a set of boundary conditions that reflect present day pd and last glacial maximum lgm conditions we investigate how changes in preformed subsurface nutrient concentrations as opposed to a local drop in sea level or increase in wind stress influence the biological productivity off the northwest african coastal upwelling area a reduction of subsurface nutrient concentration at lgm reduced the zonally averaged primary production pp the sea level change modifies the shelf morphology the upwelling circulation and the productivity and displaces the high productivity zone according to our model results the sedimentary record of pp is best explained by a simulation considering a doubled wind stress over nw africa we conclude that production regionally along the coast of nw africa during the lgm may have been lower than today despite the fact that most of the sediment cores north of 22 n show local increases in pp during the last glacial period this paradox may be due to the sea level change and the associated eastward shift of the coastline and upwelling system

the tropical rainbelt and productivity changes off northwest africa a 31 000 year high resolution record abstract benthic foraminiferal assemblage compositions and sedimentary geochemical parameters were analyzed in two radiocarbon dated sediment cores from the upwelling area off nw africa at 12 n to reconstruct productivity changes during the last 31 kyr high latitude cold events and variations in low latitude summer insolation influenced humidity wind systems and the position of the tropical rain belt over this time period this in turn caused changes in intensity and seasonality of primary productivity off the southern northwest african continental margin high accumulation rates of benthic foraminifera carbonate and organic carbon during times of north atlantic melt water events heinrich 2 25 4 to 24 3 kyr bp and 1 16 8 to 15 8 kyr bp indicate high productivity dominance of infaunal benthic foraminiferal species and high numbers of deep infaunal specimens during that time indicate a strong and sustained supply of refractory organic matter reworked from the upper slope and shelf a more southerly position of the tropical rainbelt and the northeast trade wind belt during heinrich 2 and 1 may have enhanced wind intensity and almost permanent upwelling driving this scenario a phytodetritus related benthic fauna indicates seasonally pulsed input of labile organic matter but generally low year round productivity during the last glacial maximum 23 to 18 kyr bp the tropical rainbelt is more expanded to the north than during heinrich events and relatively weak ne trade winds resulted in seasonal and weak upwelling thus lower productivity high productivity characterized by a seasonally high input of labile organic matter is indicated for times of orbital forced warming such as the african humid period 9 8 to 7 kyr bp an intensified african monsoon during boreal summer and the northernmost position of the tropical rainbelt within the last 31 kyr resulted in enhanced river discharge from the northward extended drainage area initiating intense phytoplankton blooms in the late holocene 4 to 0 kyr bp strong carbonate dissolution may have been caused by even more enhanced organic matter fluxes to the sea floor increasing aridity on the continent and stronger ne trade winds induced intensive seasonal coastal upwelling

glacial interglacial variability of particle accumulation in the canary basin a time slice approach abstract particle supply and sediment accumulation in the canary basin are strongly modified by seasonal coastal upwelling and dust input from the sahara along an e w depth profile and fertility gradient north of the canary islands we demonstrate an increase in total mass accumulation rates from a low of 1 2 g cm 2 ka 1 in the outer oceanic domain to 6 12 g cm 2 ka 1 closer to the moroccan shelf in holocene sediments during the last glacial maximum lgm oxygen isotopic event 2 2 a steeper gradient was found with two to four times higher mass accumulation rates at the near shore sites total mass accumulation rates during the last interglacial climax lic isotopic event 5 5 and end of the penultimate glaciation epg isotopic event 6 2 resemble holocene values with lowered near shore maxima of 3 and 4 g cm 2 ka 1 respectively analyses of separate sediment components show that total organic carbon total carbonate lithogenic and diatom accumulation rates were generally enhanced during glacial times especially during the lgm in contrast glacial accumulation rates of biogenic carbonate particles coccoliths and planktic foraminifera shells remained constant or were lowered with respect to interglacial time periods at the site closest to the moroccan shelf despite a doubling of bulk carbonate accumulation this could indicate lowered supply from the productive euphotic zone or a latitudinal offshore shift of the main sedimentary depocentre however enhanced carbonate dissolution could by itself account for this decrease in biogenic carbonate accumulation increased glacial input of detrital carbonate derived from the exposed moroccan shelf appears to be responsible for the overall enhanced carbonate accumulation at the same sites east of lanzarote

benthic isotope evidence for changes of the mediterranean outflow during the late quaternary a suit of sediment cores close to and south of the strait of gibraltar 12 36 n 500 2800 m water depth were analyzed for stable isotopes in epibenthic foraminifers cibicidoides wuellerstorfi and planulina ariminensis during peak glacial times the data exhibit higher 13c values of up to 1 6 at intermediate depths near the strait of gibraltar 36 n the values decrease to the south as evidenced by our data but also to the north as revealed by data of intermediate depth cores north of 38 n in duplessy et al 1987 thus the distribution pattern of 13c provides crucial evidence for an increased influence of nutrient depleted mediterranean outflow water mow on the glacial northeast atlantic hydrography during oxygen isotope terminations i and ii the meridional carbon isotope gradient indicates a significantly decreased but still active mow as deduced from the 18o fluctuations the temperatures of the mow in the atlantic were lower during glacial times by as much as 5 c during glacial times and during termination i the maximum 13c values of the mow correlate with minimum values of the north atlantic deep water nadw and vice versa this inverse response to climatic change of the carbon isotope signals of both water masses indicates that the supply of saline mow to the north atlantic may be less important for the formation of nadw than previously assumed

benthic foraminiferal δ13c and accumulation rates of organic carbon uvigerina peregrina group and cibicidoides wuellerstorfi the glacial to interglacial 13c records of the benthic foraminifera cibicidoides wuellerstorfi and the uvigerina peregrina group from deep sea cores cannot be adjusted by a generally valid constant the 13c values of the u peregrina group largely correlate with the accumulation rates of organic carbon suggesting a local habitat effect those of c wuellerstorfi vary independently with respect to the carbon flux and record fluctuations in the 13c of the ambient bottom water isotopic composition