oxygen and carbon isotope record of east pacific core v19 30 implications for the formation of deep water in the late pleistocene north atlantic abstract a detailed oxygen and carbon isotope record has been obtained from benthic foraminifera in core v19 30 from the carnegie ridge on the south side of the panama basin expressing these records and the oxygen and carbon isotope records previously published for atlantic core m 12392 on a common timescale it is apparent that the oxygen isotope records are very similar but that the carbon isotope records are quite different by obtaining the carbon isotope gradient between the two sites as a function of time we show that the production of north atlantic deep water has varied over a wide range during the late pleistocene and that the pattern of variation is not simply related to the well known oxygen isotope record although the two oxygen isotope records are very similar changes in the interoceanic gradient are detectable and support the hypothesis that in the glacial mode the north atlantic was colder and less oxygenated than it is today shackleton s 1 1977 interpretation whereby the carbon isotope record from the atlantic core reflects changes in the terrestrial biomass is an over simplification however the record from the pacific core v19 30 probably can be explained in these terms since it probably approximates the carbon isotope record of global mean oceanic dissolved co 2

variations in mode of formation and temperature of oceanic deep waters over the past 125 000 years marked changes in the deep water temperature of the different oceanic basins during the past 125 kyr are revealed by a detailed comparison of the oxygen isotopic composition ofbenthicforaminiferafrom sediment cores taken from the norwegian sea and the pacific atlantic and southern oceans the last interglacial deep water temperatures were similar to the modern ones at the 5e 5d transition around 115 kyr bp the deep water temperatures dropped below approximately 0 c in the pacific and southern indian oceans in the atlantic ocean the deep water temperature dropped in 2 successive steps at 115 and 75ky bp the global ocean deep water temperatures were in the 0 to 1 c range for the whole of the last ice age isotope stages 4 2

silicon isotope fractionation during nutrient utilization in the north pacific the distribution of silicon in the north pacific is controlled by the utilization of silicic acid by diatoms a process that fractionates silicon si isotopic compositions silicon isotope variations are presented for six water column profiles from the surface mixed layer down to the deep waters of the north pacific ocean although the observed si isotopic variations display an apparently simple inverse relationship with dissolved nutrient concentrations in fact they reflect mixing of surface waters undergoing active si isotope fractionation and deep waters with more uniform concentrations and isotope compositions samples from the surface of the subtropical gyre have the lowest dissolved si concentrations and heaviest si isotope compositions of marine waters measured thus far fractionation in the surface waters follows a typical rayleigh type distillation curve for a closed surface water reservoir resulting from stratification of the surface layer in the subarctic region in contrast an open system prevails within the subtropical gyre where there is significant recycling of silicic acid in the upper water column and lateral transport of silicon within surface currents for deep waters the si isotope composition distinguishes between the northern north pacific deep water npdw and the southerly derived bottom water the relatively light si isotope compositions measured from waters within the subarctic gyre provides evidence for isolation of the nutrient pool in the north pacific

primary production in the glacial north atlantic and north pacific oceans the conditions controlling primary production are very different in the modern north atlantic and north pacific oceans1 a difference that is reflected in the composition of diatom fossils in surface sediments by contrast i report here evidence that during the last glacial interval the diatom assemblage and by extrapolation the primary production was very similar in the two regions the modern analogues of these assemblages occur in sediments of baffin bay and the sea of okhotsk both highly productive seas where ice is present i infer that during the last glacial interval plankton biomass was at least as high as it is today in the north atlantic and was as much as an order of magnitude higher in the north pacific the glacial assemblage occurs in lithologies dominated by ice rafted detritus which is generally believed to indicate the presence of icebergs2 6 i hypothesize that the presence of numerous icebergs possibly associated with sea ice supported high production by physical mechanisms such as turbulent mixing and enhanced density stratification and or biogeochemical ones such as supply of major or trace nutrients

a 15 000 year paleoenvironmental record from meiji seamount far northwestern pacific late glacial and holocene hemipelagic sediments from meiji seamount in the far northwest pacific contain common to abundant planktonic and benthic foraminifera for ams 14c dating for stable isotope analysis and for interpreting paleoclimate change we present here chronostratigraphic faunal and geochemical results from a piston core which indicate that during glacial times as young as 14 000 yrs bp the northwest pacific sea surface salinity was at least as low as today effectively inhibiting convective overturn between 12 000 and 13 000 yrs ago after a major flux of ice rafting there is faunal and 18o evidence of an abrupt decrease in surface ocean salinity coincident with this event was an increase in biological productivity shown by higher fluxes of calcium carbonate organic carbon opal and greater abundances and lower 13o of the benthic foraminifera uvigerina oxygen isotope ratios in uvigerina and cibicidoides show step like decreases at about 13 000 14 000 11 000 10 000 and 6000 8000 yrs bp these events may be analogous to steps in the north atlantic 18o record during meltwater events if this interpretation is correct then the temperature and salinity history of the deep pacific lags that of the north atlantic by about 1000 yrs consistent with the transport time of deep water from the north atlantic to the north pacific

the joint global ocean flux study canada in the ne subarctic pacific abstract this volume of dsr ii is dedicated to the canadian joint global ocean flux study jgofs in the ne subarctic pacific this oceanic province is one of three high nitrate low chlorophyll hnlc regions in the world oceans furthermore this region is characterised by a shallow ca 100 120 m permanent pycnocline during winter which permits relatively high numbers of phytoplankton and micro grazers to subsist over winter which in turn strongly influences pelagic community structure the 5 year field study encompassed two phases phase 1 seven voyages between september 1992 and may 1995 and the intensive phase 2 six voyages between september 1995 and june 1997 each voyage transected line p from the coastal ocean westward to the open ocean in addition to the jgofs study this volume also includes analyses of long time series 20 yr data sets from ocean station papa osp 50 n 145 w and other stations in the coastal and open ocean

boundary scavenging in the pacific ocean a comparison of 10be and 231pa concentrations of u th 231pa and 10be were measured in holocene sediments from two cores collected off the west coast of south america two cores from the east pacific rise two from the equatorial pacific and one from the south pacific central gyre our results together with data from 5 cores reported in the literature show that boundary scavenging plays a major role in the removal of 10be from the pacific ocean deposition rates of 10be at three margin sites are more than an order of magnitude greater than at sites of red clay accumulation in the deep central pacific deposition of 231pa is 4 to 5 fold greater at the margin sites the residence time of 10be with respect to chemical scavenging defined as its inventory in the water column divided by its rate of removal to the sediments varies regionally from 1000 years at the red clay sites in the deep central pacific to 100 years at the margin sites different factors control boundary scavenging of pa and be for example scavenging of 231pa is enhanced by metal oxide coatings of particles whereas this seems to have little influence on the scavenging of 10be 1990

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

millennial scale deep water oscillations reflections of the north atlantic in the deep pacific from 10 to 60 ka northeast pacific benthic foraminiferal 18o and 13 reveal repeated millennial scale events of strong deep sea ventilation associated with nutrient depletion and or high gas exchange during stadial cool high ice volume episodes from 10 to 60 ka opposite the pattern in the deep north atlantic two climate mechanisms may explain this pattern north pacific surface waters chilled by atmospheric transmission from a cold north atlantic and made saltier by reduced freshwater vapor transports could have ventilated the deep pacific from above alternatively faster turnover of pacific bottom and mid depth waters driven by southern ocean winds may have compensated for suppressed north atlantic deep water production during stadial intervals during the younger dryas event 11 6 13 0 cal ka ventilation of the deep ne pacific 2700 m lagged that in the santa barbara basin 450 m by 500 years suggesting that the ne pacific was first ventilated at intermediate depth from above and then at greater depth from below this apparent lag may reflect the adjustment time of global thermohaline circulation

changes in redox conditions in deep sea sediments of the subarctic north pacific ocean possible evidence for the presence of north pacific deep water cores of upper quaternary and holocene sediment from the subarctic north pacific north of about 48 n contain one or more layers of oxidized brown sediment interbedded within predominantly reduced green sediment the brown layers are enriched in several trace elements especially mn mo ni and co relative to the green layers where multiple oxidized layers are present the intensity of the brown coloration and the magnitude of trace element enrichment often decrease with depth suggesting that the oxidized layers are unstable and are being chemically reduced at depth the oxidized layers represent a change in redox conditions between the north pacific red clay province and the subarctic biosiliceous green clay province the redox change may have been caused by an increase in supply of dissolved oxygen to bottom waters during glacial interglacial transitions as the result of the periodic formation of a seasonal bottom water mass in the northeastern pacific ocean

glacial to interglacial changes in carbonate and clay sedimentation in the atlantic ocean estimated from 230th measurements abstract the cause of the climatically controlled fluctuations in the carbonate content of deep sea sediments remains the subject of uncertainty and debate three variables are involved supply of biogenic carbonate loss by dissolution and dilution by non carbonate phases it is suggested that 230 th which is produced in the ocean at a constant rate provides a reliable reference for measuring variations in rate of sedimentation on a regional scale results of a preliminary analysis based on published data indicate that for depths at and above the lysocline the carbonate fluctuations observed in cores from the north atlantic ocean are due primarily to variations in the terrigenous clay input which was 2 5 times higher during glacials than during interglacials carbonate deposition appears to have been somewhat reduced during glacials but probably not by more than a factor of 2 from published 230 th 232 th profiles it appears that the south atlantic ocean also received increased inputs of terrigenous clay during glacial periods

glacial interglacial modulation of the marine nitrogen cycle by high latitude o2 supply to the global thermocline 1 an analysis of sedimentary nitrogen isotope records compiled from widely distributed marine environments emphasizes the global synchrony of denitrification changes and provides evidence for a strong temporal coupling of these variations to changes in nitrogen fixation as previously inferred we explain the global coherence of these records by a simple physical control on the flux of dissolved oxygen to suboxic zones and the coupling to fixation via the supply of phosphorus to diazotrophs in suitable environments according to our hypothesis lower glacial stage sea surface temperature increased oxygen solubility while stronger winds in high latitude regions enhanced the rate of thermocline ventilation the resultant colder rapidly flushed thermocline lessened the spatial extent of denitrification and consequently n fixation during warm periods sluggish circulation of warmer less oxygen rich thermocline waters caused expansion of denitrification zones and a concomitant increase in n fixation local fluctuations in export productivity would have modulated this global signal

living diatom assemblages from north pacific and bering sea surface waters during summer 1999 diatom assemblages collected during july august 1999 along an e w transect comprising sixty two north pacific and bering sea surface water samples were identified and enumerated absolute abundance profiles of centric and raphid pennate diatoms show that the former group dominates in shallow coastal waters and through island passes whilst the latter group though less numerous dominates the oceanic regions this pattern is interpreted as nutrient related with centric diatoms especially chaetoceros section hyalochaete minidiscus and thalassiosira spp preferring eutrophic and upwelling conditions and raphid pennate diatoms especially nitzschioid genera like fragilariopsis neodenticula and pseudo nitzschia preferring oligotrophic pelagic conditions the absolute abundances of the two sections of chaetoceros chaetoceros ex phaeoceros and hyalochaete and some species belonging to the thalassiosirales and bacillariaceae show distribution patterns that can be interpreted as preferences for shallow or oceanic waters subtropical or subarctic waters or ice related arctic conditions r 2005 elsevier ltd all rights reserved

coastal atmospheric forcing in the northern gulf of alaska a comparison of winds over the northern gulf of alaska found measured winds to be significantly weaker than calculated geostrophic winds the latter required more than the standard 30 reduction to correct for frictional effects in the maritime boundary layer an additional 11 is calculated based on principal axis analysis a counterclockwise rotation of the instantaneous geostrophic wind vectors of 44 59 total beyond the standard 15 was required to align them with those measured at a coastal weather station however events in these two wind sets were well correlated throughout the year and the rotary coherence was significant for frequencies lower than 0 895 cpd on the basis of empirical orthogonal function analysis most of the seasonal variability in this coastal current is associated with wind changes freshwater discharge is also important in driving the alongshore baroclinic flow and a secondary cross shelf flow

dust impact on marine biota and atmospheric co2 during glacial periods 1 we assess the impact of high dust deposition rates on marine biota and atmospheric co2 using a state of the art ocean biogeochemistry model and observations our model includes an explicit representation of two groups of phytoplankton and colimitation by iron silicate and phosphate when high dust deposition rates from the last glacial maximum lgm are used as input our model shows an increase in the relative abundance of diatoms in today s iron limited regions causing a global increase in export production by 6 and an atmospheric co2 drawdown of 15 ppm when the combined effects of changes in dust temperature ice cover and circulation are included the model reproduces roughly our reconstruction of regional changes in export production during the lgm based on several paleoceanographic indicators in particular the model reproduces the latitudinal dipole in the southern ocean driven in our simulations by the conjunction of dust sea ice and circulation changes in the north pacific the limited open ocean data suggest that we correctly simulate the east west gradient in the open ocean but more data are needed to confirm this result from our model data comparison and from the timing of the dust record at vostok we argue that our model estimate of the role of dust is realistic and that the maximum impact of high dust deposition on atmospheric co2 must be 30 ppm

water mass conversion in the glacial subarctic pacific 54 n 148 w physical constraints and the benthic planktonic stable isotope record benthic uvigerina spp cibicidoides spp gyroidinoides spp and planktonic n pachyderma sinistral g bulloides stable isotope records from three core sites in the central gulf of alaska are used to infer mixed layer and deepwater properties of the late glacial subarctic pacific glacial interglacial amplitudes of the planktonic 18o records are 1 1 1 3 less than half the amplitude observed at core sites at similar latitudes in the north atlantic these data imply that a strong negative w anomaly existed in the glacial subarctic mixed layer during the summer which points to a much stronger low salinity anomaly than exists today if true the upper water column in the north pacific would have been statically more stable than today thus suppressing convection even more efficiently this scenario is further supported by vertical i e planktic versus benthic 18o and 13c gradients of 1 which suggest that a thermohaline link between pacific deep waters and the subarctic pacific mixed layer did not exist during the late glacial epibenthic 13c in the subarctic pacific is more negative than at tropical subtropical pacific sites but similar to that recorded at southern ocean sites suggesting ventilation of the deep central pacific from mid latitude sources e g from the sea of japan and sea of okhotsk still convection to intermediate depths could have occurred in the subarctic during the winter months when heat loss to the atmosphere sea ice formation and wind driven upwelling of saline deep waters would have been most intense this would be beyond the grasp of our planktonic records which only document mixed layer temperature salinity fields extant during the warmer seasons also we do not have benthic isotope records from true intermediate water depths of the subarctic pacific

paleoenvironmental implications of the insoluble microparticle record in the gisp2 greenland ice core during the rapidly changing climate of the pleistocene holocene transition oscillations in the time series of insoluble microparticle characteristics between 0 7 and 11 0 m in the greenland ice sheet project 2 gisp2 ice core reflect changes in environmental conditions in the northern hemisphere from 10 500 to 14 000 yr ago elevated values in microparticle number and mass especially during the younger dryas are related to northern hemisphere aridity and the subsequent increase in dust available for long range transport to greenland this scenario occurs with the colder climatic conditions that result from a more expanded spatially and temporally polar vortex peaks in mean grain size based on number mean number diameter are a proxy for increased strength in zonal winds westerlies highs in mean number diameter in the earlier part of the record often coincide with number and mass peaks reflecting the increased temperature and pressure gradients with an expanded polar vortex highs in mean grain size based on mass mean mass diameter reflect greater deposition of the coarser size fraction and thus are a proxy for increased storminess associated with better developed synoptic scale pressure systems in the northernmost atlantic region peaks in mean mass diameter often lead these other parameters by 100 200 yr suggesting an increase in storminess with the initial southward migration of the mean position of the polar front prior to full development of a more expanded polar vortex the general decline in number and mass trends decreased aridity with a contracting polar vortex together with increasing mean number diameter trends strengthening zonal winds following the maxima in the early younger dryas suggest an expansion of mid latitude circulation systems subtropical highs thereby maintaining latitudinal temperature and pressure gradients increased variability in mean mass diameter during the warm preboreal compared to the colder younger dryas may be a function of the greater seasonality during warmer climatic periods and thus more frequent storms associated with higher frequency oscillations in the position of the polar front with changing seasons and increased interannual variability in climate

micropaleontology and palynology of core par87a 10 a 23 000 year record of paleoenvironmental changes in the gulf of alaska northeast north pacific micropaleontological data of core par87a 10 reveal that the last glacial interval prior to 13 ka was marked by low biogenic fluxes and poor caco3 preservation quantitative estimates of sea surface conditions based on dinocyst assemblages suggest that cold temperatures and freezing winter conditions existed during this period the glacial to interglacial transition i e the 13 8 ka interval was characterized by an increase in fluxes of microfossils indicating enhanced productivity in surface waters a higher biogenic carbonate production probably resulted in better preservation of caco3 this interval was marked by relatively low salinity and by sea surface temperatures increasing toward modern values relatively high pollen flux during the transition suggests nutrient inputs through atmospheric and or fluvial transport from the adjacent north american continent after 8 ka diminished fluxes of plankton concomitant with a decline in pollen input are associated with decreasing nutrient supply as predominantly eastward winds became established over the north pacific

middle pleistocene to holocene palynostratigraphy of ocean drilling program site 887 in the gulf of alaska northeastern north pacific a palynological investigation was undertaken on the upper 29 m of sediment at ocean drilling program odp site 887 spanning the last 430 000 years i e isotopic stages 12 to 1 pollen and dinocyst assemblages reveal a major ecostratigraphical boundary at the middle late pleistocene transition the middle pleistocene pollen data doc ument the occurrence of a spruce forest vegetation in the source area likely located on the adjacent alaskan coast whereas the late pleistocene is marked by higher inputs of pine shrub and herb taxa suggesting predominant inputs from a more open landscape the middle pleistocene is characterized by a low diversity in dinocyst assemblages which are dominated by operculodinium centrocarpum whereas the late pleistocene is marked by the significant oc currence of pentapharsodinium dalei pyxidinopsis reticulata and by high percentages of brigantedinium spp such as semblages suggest open oceanic and cool temperate conditions during the middle pleistocene changing toward generally colder and less saline conditions during the late pleistocene in addition large fluctuations in the dinocyst assemblages during the late pleistocene are recorded in phase with the main shifts in the isotopic stratigraphy a new dinocyst taxon spiniferites alaskensis sp nov exclusively recorded in sediments of the isotopic substage 5e is de scribed herein resume une analyse palynologique a ete realisee sur une sequence sedimentaire de 29 metres prelevee au site odp 887 et couvrant les derniers 430 000 ans soit les stades isotopiques 12 a 1 les assemblages de pollen et de dinokystes revelent une transition ecostratigraphique majeure entre le pleistocene moyen et le pleistocene superieur les assembla ges polliniques du pleistocene moyen indiquent la presence d une vegetation dominee par l epinette et l aulne dans la region source qui etait sans doute localisee le long des cotes de l alaska de forts pourcentages de pin et des taxons arbustifs et herbaces au pleistocene superieur indiquent des apports issus d un paysage plus ouvert le pleistocene moyen est caracterise par une faible diversite dans les assemblages de dinokystes et par la dominance de operculodi nium centrocarpum tandis que le pleistocene superieur est marque par pentapharsodinium dalei pyxidinopsis reticulata et des pourcentages eleves de brigantedinium spp les assemblages suggerent des conditions oceaniques temperees fraiches pendant le pleistocene moyen et des eaux de surface plus froides et moins salines au cours du pleistocene su perieur par ailleurs de larges fluctuations sont enregistrees dans les assemblages de dinokystes au pleistocene supe rieur en phase avec la stratigraphie isotopique parmi les dinokystes une nouvelle espece spiniferites alaskensis sp nov observee exclusivement pendant le sous stade isotopique 5e est decrite ici marret et al 386

cordilleran ice sheet growth fueled primary productivity in the gulf of alaska northeast pacific ocean fertilization of the ocean by eolian dust and icebergs is an effective mechanism to enhance primary productivity in particular high nutrient low chlorophyll hnlc areas where phytoplankton growth is critically iron limited such as the subarctic pacific ocean and the southern ocean are proposed to respond to increases in bioavailable fe supply with enhanced phytoplankton productivity and carbon export to the seafloor while fe fertilization from dust is widely acknowledged to explain a higher export production during glacial periods in the southern ocean paleoceanographic records supporting links between productivity and eolian dust and or icebergs in the north pacific are scarce by combining independent proxies indicative of ice sheet dynamics and ocean productivity from a single marine sedimentary record integrated ocean drilling program iodp site u1417 we present a comprehensive data set of phytoplankton response to different fertilization mechanisms in the subarctic northeast pacific between 1 5 and 0 5 ma including the mid pleistocene transition importantly the timing of the fertilization events is more strongly controlled by local ice sheet extent than by glacial interglacial climate variability our findings indicate that fertilization by glacigenic debris results in productivity events in hnlc areas adjacent to ice sheets and that this mechanism may represent an important yet rarely considered driver of phytoplankton growth

paleoclimatic significance of eolian carbonates supplied to the japan sea during the last glacial maximum laminated sediments deposited under anoxic bottom waters in the japan sea during the last glacial maximum lgm contain extremely well preserved calcareous microfossils and eolian carbonates the radiocarbon age difference between bulk sediment and monospecific planktonic foraminifera in discrete laminae from a core in the southern japan sea implies that 40 of the total carbonates in the sediments at the lgm are of eolian origin extrapolation of this result yields a rate of supply of eolian carbonates of 2800 tons d 1 to the entire japan sea during the lgm the climatic significance of this flux potentially lies in its broader geographic extension particularly in the interaction of the carbonate bearing dust with shallow corrosive north pacific waters and with rain in the atmosphere by increasing the alkalinity of such waters and by enhancing the biological pump the dust flux could have increased co2 absorption by both the ocean and rain during the lgm

glacial age hydrography of the far northwest pacific ocean stable isotope data on benthic foraminifera from more than 30 cores on the northern emperor seamounts and in the okhotsk sea are synthesized in paleohydrographic profiles spanning the depth range 1000 4000 m holocene core top benthic foraminiferal 18o and 13c data are calibrated to modern hydrographic properties through measurements of 13c of co2 and 18o of seawater cibicidoides stable isotope ratios are close to the 13c and equilibrium 18o of seawater whereas uvigerina 18o and 13c are variably offset from cibicidoides glacial maximum 13c of cibicidoides displays a different vertical profile than that of the holocene when results are adjusted by 0 32 to account for the secular change in 13c during the last glacial maximum the data coincide with the modern seawater and foraminiferal curves deeper than 2 km however at shallower depths 13c gradually increases by as much as 1 above the modern value furthermore above 2 km the benthic 18o decreases by 0 5 these results are consistent with a benthic front at 2 km in the north pacific see herguera et al 1992 but they differ from interpretations based on trace metal data which indicate a source of nutrient depleted deep water during glaciation the isotopic data suggest that during glaciation there was a better ventilated watermass at intermediate depths in the far northwestern pacific it was relatively fresher than deep waters there and deep waters were as nutrient rich as today

timing of late quaternary productivity pulses in the panama basin and implications for atmospheric co2 high resolution percent corg and 18oforam records obtained from panama basin core atlantis ii 54 25pc and additional data from nearby core p7 show that enhanced burial of organic carbon has characterized every major glacial period for the last 500 kyr in that area both corg concentration and mass accumulation rate profiles exhibit a sawtooth pattern with maxima occurring typically in the later stages of glacial periods comparison with dust records suggests that the carbon accumulation rate profile reflects both the upwelling history and a variable rate of iron input during the late quaternary the sawtooth character may derive from increased wind velocities and rates of upwelling during glacials which are indirectly related to ice volume sarnthein et al 1988 the rapid decline in export production at the end of glacials in the equatorial pacific may be attributed to the retreat of ice sheets thus reduced wind velocities and upwelling coupled with a coincident decline in atmospheric dust load and or delivery rate the corg accumulation rate profiles do not correlate well with atmospheric co2 records for example atmospheric co2 was already at a minimum 40 kyr ago when production in the panama basin began increasing dramatically commensurate with an increase in global dust levels using the relationship between the degree of photosynthetic fractionation and the concentration of free co2 in the surface ocean postulated by popp et al 1989 13corg measurements made on core p7 show that panama basin surface waters have been supplying co2 to the atmosphere continually for at least the last 50 kyr there is no evidence for a flux of co2 into the surface ocean in this area at any time during this period despite the higher production if the panama basin cores are representative of the eastern and central equatorial pacific then these observations weaken the influence on co2 drawdown postulated for increased glacial productivity at low latitudes

productivity and sedimentary δ15n variability for the last 17 000 years along the northern gulf of alaska continental slope 1 biogenic opal organic carbon organic matter stable isotope and trace metal data from a well dated high resolution jumbo piston core ew0408 85jc 59 33 3 n 144 9 21 w 682 m water depth recovered from the northern gulf of alaska continental slope reveal changes in productivity and nutrient utilization over the last 17 000 years maximum values of opal concentration 10 occur during the deglacial bolling allerod b a interval and earliest holocene 11 2 to 10 8 cal ka bp moderate values 6 occur during the younger dryas 13 0 to 11 2 cal ka bp and holocene and minimum values 3 5 occur during the late glacial interval lgi when converted to opal mass accumulation rates the highest values 5000 g cm 2 kyr 1 occur during the lgi prior to 16 7 cal ka bp which points to a strong influence by lgi glacimarine sedimentation regimes similar patterns are also observed in total organic carbon and cadmium paleoproductivity proxies mid holocene peaks in the terrestrial organic matter fraction at 5 5 4 7 3 5 and 1 2 cal ka bp indicate periods of enhanced delivery of glaciomarine sediments by the alaska coastal current the b a and earliest holocene intervals are laminated and enrichments of redox sensitive elements suggest dysoxic to anoxic conditions in the water column the laminations are also associated with mildly enriched sedimentary 15n ratios indicating a link between productivity nitrogen cycle dynamics and sedimentary anoxia after applying a correction for terrestrial 15n contributions based on end member mixing models of terrestrial and marine organic matter the resulting b a marine 15n 6 3 0 4 ratios are consistent with either mild denitrification or increased nitrate utilization these findings can be explained by increased micronutrient fe availability during episodes of rapid rising sea level that released iron from the previously subaerial coastal plain iron input from enhanced terrestrial runoff and or the intermittent presence of seasonal sea ice resulting from altered ocean atmospheric circulation during the b a in the gulf of alaska

late pleistocene eolian sand sheets in alaska abstract nonglaciated lowlands in central and southwestern alaska contain extensive deposits of upper quaternary eolian sand derived largely from major outwash rivers although surface dunes are common deep exposures consistently reveal that subhorizontally stratified sand and silt deposits dominate over dune cross strata we hypothesize that 1 many of the subhorizontally stratified deposits represent full glacial eolian sand sheets formed when sand supply was limited by seasonally variable combinations of ice cementation snow cover high groundwater tables and vegetation and 2 many surface dunes reflect late glacial and postglacial reworking under conditions of increased short term availability of loose sand the morphology of some surface dunes may therefore reflect mainly the intensity of reworking since the last glacial maximum rather than full glacial paleowind vectors or the age of the bulk of the underlying deposits

controls on carbon isotope fractionation by diatoms in the peru upwelling region the fractionation of carbon isotopes during photosynthesis by phytoplankton is quantified for samples of suspended material collected along two transects across the peru continental margin in 1992 the magnitude of fractionation is estimated using the 13c of 24 methylcholesta 5 24 28 dien 3 ol diatoms and compared to that of c37 2 alkenone haptophytes isotopic fractionation by diatoms exhibits a wide range and large scatter when plotted against the reciprocal of the concentration of co2 aq while a strong correlation is observed for fractionation by alkenone bearing haptophytes diatom growth rates calculated from silicate concentrations and assuming monod growth kinetics normalized to co2 aq are well correlated to diatom fractionation factors these results support the concept that growth rates in addition to co2 concentrations impose a control on the fractionation of carbon isotopes by both taxonomic groups of algae in addition the very small fractionation factors for diatoms indicate that species in the peru upwelling region employed mechanisms which actively transport inorganic carbon into cells a size dependence is observed for the 13c of the diatom sterol 24 methylcholesta 5 24 28 dien 3 ol is enriched in 13c in samples of suspended material 20 m relative to the 20 m fraction this suggests that surface area to volume ratios also impose a control on the fractionation of carbon isotopes by diatoms a proposition that is supported by detailed cell geometry and isotopic data for two larger size fractions from one sample

distribution of biogenic silica and quartz in recent deep sea sediments all available quartz and biogenic silica concentrations from deep sea surface sediments were intercalibrated plotted and contoured on a calcium carbonate free basis the maps show highest concentrations of biogenic silica opal along the west african coast along equatorial divergences in all oceans and at the polar front in the southern indian ocean these are all areas where upwelling is strong and there is high biological productivity quartz in pelagic sediments deposited far from land is generally eolian in origin its distribution reflects dominant wind systems in the pacific but in much of the atlantic and indian oceans the distribution pattern is strongly modified by turbidite deposition and bottom current processes

late pleistocene variability of the carbon isotopic composition of organic matter in the eastern mediterranean monitor of changes in carbon sources and atmospheric co2 concentrations the organic carbon isotopic record of the sapropels s1 and s3 s10 and intercalated marl oozes has been determined in a 12 m piston core from the eastern mediterranean the 13corganic values are systematically lighter mean 21 0 0 82 in all sapropels and heavier mean 18 8 1 07 in the marl oozes these differences are not due to variable marine and terrestrial organic matter mixtures because all values are heavier than modern plankton in the mediterranean there is no relationship between the corganic n ratios and the isotopic values and published information on the abundance and distribution of organic biomarkers shows that terrestrial material constitutes a minor fraction of the total organic matter temperature effects on isotope fractionation are also discounted because the change in 13corganic values between glacial and interglacial horizons is in the opposite sense diagenesis which can produce relatively small changes in the carbon isotopic composition of sedimentary organic matter under certain circumstances is unlikely to have caused the observed differences because this mechanism would cause an enrichment in 12c implying that all values were even heavier originally and there is no secular trend in the 13corganic record the observed differences in 13corganic between the two lithologies are probably produced by changes in the isotopic composition and the concentration of dissolved co2 first freshwater flooding during the formation of the sapropels caused the isotopic composition of the dissolved inorganic carbon in the surface waters of the mediterranean to become lighter because of the 13c deficiency in fresh waters hence photosynthesis would have produced isotopically lighter organic material second changes in atmospheric pco2 between glacial and interglacial periods as shown by the vostok ice core caused marked changes in the concentration of free dissolved co2 in the mixed layer lower values during glacial maxima caused a smaller fractionation of the carbon isotopes by phytoplankton whereas levels were less limiting during the interglacials concentrations of dissolved co2 could also have been much higher during the deposition of the sapropels because of the supply of regenerated co2 to the mixed layer by upwelling and this could have further lightened the 13corganic values in the sapropels themselves carbon isotope records may provide an alternative method for estimating atmospheric pco2 levels over longer time periods than can be obtained from ice cores

multiple late quaternary episodes of exceptional diatom production in the gulf of alaska abstract hole 887b of the ocean drilling program odp comprises a 44 m 750 kyr long continuous section recovered from the patton murray rise an elevated plateau that is largely isolated from turbidite deposition the patton murray area is centered under the alaska gyre a region characterized by the domal upwelling of nutrient rich waters marked increases in productivity and rapid settling of biogenic matter are suggested throughout the section by the episodic accumulation of diatomaceous oozes up to 1 m thick that are accompanied by barium enrichments significant 13corg maxima in the major diatomaceous bands suggest that mixed layer co2 aq may have been drawn down significantly during some of the productivity events the episodes of enhanced productivity at site 887 occur synchronously with short lived minima in planktonic foram 18o suggesting a direct link to low salinity or less likely warming events in the gulf of alaska there is no obvious explanation for the events but they may be related to seasonal incursions of meltwater from alaska we speculate that episodic input of meltwater or dust borne iron from asian or alaskan sources may have promoted the extraordinary diatom production events recorded in the sedimentary record

the deglacial transition on the southeastern alaska margin meltwater input sea level rise marine productivity and sedimentary anoxia 1 oxygen isotope data from planktonic and benthic foraminifera on a high resolution age model 44 14c dates spanning 17 400 years document deglacial environmental change on the southeast alaska margin 59 33 32 n 144 9 21 w 682 m water depth surface freshening i e 18o reduction of 0 8 began at 16 650 170 cal years b p during an interval of ice proximal sedimentation likely due to freshwater input from melting glaciers a sharp transition to laminated hemipelagic sediments constrains retreat of regional outlet glaciers onto land circa 14 790 380 cal years b p abrupt warming and or freshening of the surface ocean i e additional 18o reduction of 0 9 coincides with the bolling interstade of northern europe and greenland cooling and or higher salinities returned during the allerod interval coincident with the antarctic cold reversal and continue until 11 740 200 cal years b p when onset of warming coincides with the end of the younger dryas an abrupt 1 reduction in benthic 18o at 14 250 290 cal years b p likely reflects a decrease in bottom water salinity driven by deep mixing of glacial meltwater a regional megaflood event or brine formation associated with sea ice two laminated opal rich intervals record discrete episodes of high productivity during the last deglaciation these events precisely dated here at 14 790 380 to 12 990 190 cal years b p and 11 160 130 to 10 750 220 cal years b p likely correlate to similar features observed elsewhere on the margins of the north pacific and are coeval with episodes of rapid sea level rise remobilization of iron from newly inundated continental shelves may have helped to fuel these episodes of elevated primary productivity and sedimentary anoxia

what controls opal preservation in tropical deep sea sediments measurements of opal preservation in deep sea sediment cores have been presented in three ways the opal concentration as a fraction of total dry weight opaltot the opal concentration normalized to calcite free dry weight opalcalcite free and me opal accumulation rate opal mar it is tempting to interpret changes in these indices as indicators of rates of biological production in past oceans based on theoretical constraints we argue that in typical tropical and subtropical sediments both opalcalcite free and opal mar reflect a significant artifact of dilution by other phases thus the band of high opalcalcite free in the equatorial pacific appears to be caused in large part by the high calcite in that region rather than by high opal productivity the best candidate for a reliable paleoproductivity proxy appears to be opaltot unfortunately present day opaltot data from tropical and subtropical regions show little or no systematic trend with the rain rate of opal pore water silica concentration data reveal that the apparent pore water opal solubility is not constant but correlates regionally with the rain rate of opal to the seafloor a model that treats opal as a single homogeneous phase with a single well defined solubility product predicts a strong dependence of opal concentration on rain rate in stark contrast to the data and a constant asymptotic pore water si two models representing opal as multiple heterogeneous phases with different solubilities are able to reproduce the observed asymptotic pore water si rain rate relationship but not the lack of rain rate trend in the opal concentration data only by assuming a systematic trend in the quality of opal i e the solubility as a function of opal production can we reproduce the observed pattern of opal preservation the implication of this study is that changes in opal preservation in the geologic record cannot simply be interpreted in terms of changes in surface ocean productivity until our understanding of opal diagenesis can be improved

subarctic pacific evidence for a glacial deepening of the oceanic respired carbon pool abstract measurements of benthic foraminiferal cadmium calcium cd ca have indicated that the glacial interglacial change in deep north pacific phosphate po4 concentration was minimal which has been taken by some workers as a sign that the biological pump did not store more carbon in the deep glacial ocean here we present sedimentary redox sensitive trace metal records from ocean drilling program odp site 882 nw subarctic pacific water depth 3244 m to make inferences about changes in deep north pacific oxygenation and thus respired carbon storage over the past 150 000 yr these observations are complemented with biogenic barium and opal measurements as indicators for past organic carbon export to separate the influences of deep water oxygen concentration and sedimentary organic carbon respiration on the redox state of the sediment our results suggest that the deep subarctic pacific water mass was depleted in oxygen during glacial maxima though it was not anoxic we reconcile our results with the existing benthic foraminiferal cd ca by invoking a decrease in the fraction of the deep ocean nutrient inventory that was preformed rather than remineralized this change would have corresponded to an increase in the deep pacific storage of respired carbon which would have lowered atmospheric carbon dioxide co2 by sequestering co2 away from the atmosphere and by increasing ocean alkalinity through a transient dissolution event in the deep sea the magnitude of change in preformed nutrients suggested by the north pacific data would have accounted for a majority of the observed decrease in glacial atmospheric pco2

lacustrine sedimentation in a semiarid alpine setting an example from ladakh northwestern himalaya abstract the lamayuru lacustrine strata in ladakh typify many of the carbonate rich pleistocene alpine lakes found in the semiarid environment of the northern himalaya created by a 200 m thick landslide the lake was in existence by at least 35 000 yr ago and may have persisted until 500 1000 yr ago represented in the center by thin turbidites and laminated muds the lacustrine sedimentation along the lake margins and low relief deltas characteristically displays a marked contrast between 1 clastic lenses representing rapid sporadic matrix poor debris flows and periglacial inputs from the alpine slopes and 2 abundant diverse shallow water biologically dominated carbonate strata among which organism rich chalky beds and oncolithic and encrusted stem rich strata predominate resemblances of the lamayuru lacustrine strata and their setting to those of former lakes throughout areas north of the greater himalayan crest suggest that the alpine semi arid environment would favor diversified spacially restricted carbonate sedimentation punctuated by occasional clastic influxes such a depositional regime contrasts strongly with that found immediately south of the himalayan crest where more humid conditions promote a more continuous clastic influx into intramontane lakes

tropical forcing of north pacific intermediate water distribution during late quaternary rapid climate change abstract evidence is presented demonstrating intermediate water 500 m temperature variability at odp hole 893a in santa barbara basin during submillennial climate change 11 60 ka benthic 18 o oscillations are considered to result primarily from shifts in intermediate water temperature at the site detailed comparison of both benthic and planktonic records from the basin provide crucial evidence for differing surface and intermediate water mass temporal responses to rapid climate change gradual warming of intermediate water compared to abrupt cooling suggests mechanistic differences between processes controlling north pacific intermediate water expansion and contraction relative to southern component intermediate waters comparisons suggest intermediate water warming preceded by 60 200 years the most rapid interval of surface warming inferred to be associated with north pacific atmospheric reorganization tropical forcing of sea level anomalies in the eastern pacific via trade wind strength may control california undercurrent flow 300 500 m and be the cause of early intermediate water warming in santa barbara basin

does sedimentary organic δ13c record variations in quaternary ocean co2 aq ocean surface water co2 aq variations based on glacial interglacial changes in sediment delta 13corg are shown to compare favorably with reconstructions based on ice core co2 in particular an approximate 80 microatmospheres increase in atmospheric pco2 during the last glacial interglacial transition is calculated to correspond to a 3 4 micromolar increase in ocean surface water co2 aq at atmospheric equilibrium a widespread marine delta 13corg decrease of 1 2 accompanied this event and was not preceded by an equivalent isotopic change in surface water total dissolved inorganic carbon these observations support the hypothesis that co2 aq influences photosynthetic isotope fractionation between marine inorganic and organic carbon pools and therefore that plankton sediment delta 13corg may serve as a proxy for surface water co2 aq

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

a record of past ocean atmosphere radiocarbon differences from the northeast pacific a record of the 14c age differences between atmosphere and the mixed layer of the northeast pacific ocean was obtained from 58 radiocarbon measurements on shells and associated wood from coastal sediments in british columbia this series of mixed layer reservoir ages spans the holocene and extends into the period of the younger dryas cold event in the north atlantic and surrounding regions the data reflect the extent of upwelling in the northeast pacific and thus constrain models of carbon cycling and ocean circulation most of the reservoir ages are only slightly less than than the present preindustrial value of about 800 years and may be identical when probable sampling errors are taken into account either the north pacific reached a state close to its present mode of circulation at or before the end of the younger dryas or a different circulation fortuitously produced a similar reservoir age our results support the hypothesis that slow changes in atmospheric radiocarbon concentrations over the holocene arose from 14c production rate changes data corresponding to a radiocarbon age of around 6400 years b p give a reservoir age of 1200 years if this result is confirmed it indicates a much greater variability for the holocene ocean circulation than was previously believed possible

nutrient leakage from the north pacific to the bering sea iodp site u1341 following the onset of northern hemispheric glaciation 1 intergrated ocean drilling program expedition 323 recovered a sediment record covering the last 4 3 ma from the bering sea integrated ocean drilling program site u1341 bowers ridge 2177 m water depth to resolve pliocene pleistocene paleoenvironmental changes in this marginal basin 190 sediment samples were analyzed for their bulk element composition aluminium contents in bowers ridge sediments are variable but overall higher toward younger sediments probably related to the intensification of the northern hemispheric glaciation and increasing sea ice transport in the bering sea the gradual increase of terrigenous input is mirrored by decreasing sio2 and excess si sixs contents but the overall si enrichment of the deposits reflects continuous opal deposition since the pliocene at bowers ridge unlike in the north pacific the sixs record at site u1341 does not support a dramatic decrease in opal export following the onset of the northern hemispheric glaciation around 2 7 ma but sio2xs have higher accumulation rates up to 8 g cm2 ka between 2 6 and 1 8 ma bp during this period the major oceanic opal deposition centers shifted globally from open marine high latitude regions to upwelling areas we here discuss how the onset of north pacific stratification at 2 7 ma bp may have caused leakage of nutrient rich deep intermediate north pacific water into the bering sea via the deep kamtchatka strait leading to increased opal deposition and likely reactive organic matter export at bowers ridge as a result magnetic and geochemical records were overprinted by intensified diagenesis significantly affecting their applications as paleoceanographic proxies

influences of oceanic rheostats and amplifiers on atmospheric co2 content during the late quaternary abstract although a clear explanation has yet to emerge for the observed decline in atmospheric co2 content during glacial episodes numerous hypotheses have been offered selected examples are reviewed or evaluated here a strengthened biological pump resulting from intensified upwelling at low latitudes was suggested early on as a likely direct cause of the glacial co2 drawdown two problems have since arisen with this hypothesis first on some upwelling continental margins for example off california oregon northwestern mexico peru and parts of nw africa organic matter accumulation decreased in some areas markedly during the last glacial maximum lgm second upwelled cool co2 rich water degasses carbon dioxide in warm regions and for a key area such as the modern equatorial pacific to become a net sink for atmospheric co2 rather than a source as it is today the rate of downward organic carbon export must exceed the rate of degassing recent sedimentary carbon and nitrogen isotopic data suggest however that the equatorial pacific has remained a strong co2 source for at least the last 40 000 yr and probably much longer although the direct extraction of carbon from surface waters and burial in the sediments in productive regions now appears unlikely to provide the sought for explanation indirect effects related to export productivity may hold the key these can modulate the chemical character of the ocean so as to increase its uptake of co2 a rheostat effect or they could increase indirectly the nutrient inventory of the sea an amplifier effect for example it is now recognized that denitrification was greatly reduced during glacial maxima in all three principal oxygen minimum zones in the oceans i e the subtropical north and south pacific and the arabian sea the implication is that nitrate the limiting nutrient in the modern ocean must have been more abundant during glacial periods and that this surfeit would have supported increased export production in the meso or oligotrophic areas that are today nitrate limited dust may represent another rheostat increases in atmospheric turbidity during glacials are clearly recorded by ice and marine sediment cores in both hemispheres in addition to fostering enhanced export production by adding needed iron to nitrate rich areas it has been suggested recently that increased dust inputs to nitrate depleted regions during glacials might have encouraged growth of iron hungry n2 fixing cyanobacteria thus alleviating nitrate limitation no sedimentary 15 n data yet exist to support this hypothesis but it remains viable finally regional changes in physical hydrography may have played a major and hitherto underestimated role for example in the glacial southern ocean south of the polar front recent nitrogen isotope and other data imply that the upper water column was well stratified during the lgm by limiting upwelling this would have reduced the ocean atmosphere co2 leak in the area this could have made a significant contribution to the pco2 drawdown

dissolution and preservation of antarctic diatoms and the effect on sediment thanatocoenoses abstract comparison of southern ocean diatom populations from i surface ocean production ii underlying antarctic sediments and iii laboratory dissolution experiments demonstrates that dissolution can account for the temporal and spatial variations in sedimentary diatom assemblages observed in southern ocean sediments increasing dissolution causes relative depletions in n kerguelensis k enrichments in t lentiginosa l and slight enrichments in e antarctica a this reflects the relative susceptibility to dissolution of the three species that dominate antarctic sediments we have devised a preservation index for the southern ocean based on the ratio k k l to estimate relative extents of dissolution and applied it to natural assemblages holocene southern ocean sediments display increasing opal preservation toward higher latitudes but south of the antarctic polar front preservation decreases in the order well preserved se indian s atlantic sw indian se pacific poorly preserved dissolution also accounts for the pattern of diatom assemblages in the last glacial maximum lgm sediments of the indian and pacific sectors but in the atlantic increased e antarctica abundances at lgm must have resulted from an increase in surface ocean production of this species holocene and lgm diatoms in atlantic and pacific sector sediments are equally well preserved but in the indian sectors holocene sediments are better preserved than those of lgm age paleoceanographic and paleoclimatic transfer functions derived from factor analyses of variations in the sedimentary abundances of these three diatoms have ignored the effects of differential dissolution on thanatocoenosis and thus should be interpreted with caution

characterization of carbon and nitrogen stable isotope gradients in the northern gulf of alaska using terminal feed stage copepodite v neocalanus cristatus abstract individual terminal feeding copepodite v stage neocalanus cristatus were collected systematically in the northern gulf of alaska goa near 60 n from 1998 to 2004 from which the natural abundance of stable carbon and nitrogen isotopes was measured the data confirmed the existence of an isotopic cross shelf gradient such that values low in 13 c content are diagnostic of oceanic production from the goa when measured in organisms taken from prince william sound pws the mean 13 c 12 c cross shelf gradient of 3 4 delta units was relatively strong with generally good separation between goa and prince william sound observations whereas the mean 15 n 14 n gradient of 2 delta units was relatively weak with frequent overlap between goa and pws observations there was a seasonal 15 n 14 n increase in the goa the 13 c 12 c values observed in pws were more consistent over time than those observed in the goa distinctively high 13 c 12 c values that were similar to those typical of pws were observed at the continental slope during three of the mays in the 1998 2004 period the circulation pattern associated with mesoscale eddies when they occurred just south of the sampling line based on satellite sea surface height anomaly data suggested that cross shelf flow in the offshore direction drove high slope 13 c 12 c values these observations led to positing that high 13 c 12 c values reflect coastal carbon isotope signatures and diatom blooms based on samples from may 1996 the three goa neocalanus congeners had concordant isotopic patterns with relatively small systematic species differences confirming that the isotopic patterns observed for n cristatus apply to other zooplankton

controls on deglacial changes in biogenic fluxes in the north pacific ocean the subarctic north pacific ocean holds a large co2 reservoir that is currently isolated from the atmosphere by a low salinity layer it has recently been hypothesized that the reorganization of these high co2 waters may have played a crucial role in the degassing of carbon dioxide to the atmosphere during the last deglaciation this reorganization would leave some imprint on paleo productivity records here we present 230th normalized biogenic fluxes from an intermediate depth sediment core in the northwest pacific rc10 196 54 7 n 177 1 e 1007 m and place them within the context of a synthesis of previously published biogenic flux data from 49 deep sea cores north of 20 n ranging from 420 to 3968 m water depth the 230th normalized opal carbonate and organic carbon fluxes from rc10 196 peak approximately 13 000 calendar years bp during the bolling allerod b a period our data synthesis suggests that biogenic fluxes were in general lowest during the last glacial period increased somewhat in the northwest pacific during heinrich event 1 and reached a maximum across the entire north pacific during the b a period we evaluate several mechanisms as possible drivers of deglacial change in biogenic fluxes in the north pacific including changes in preservation sediment focusing sea ice extent iron inputs stratification and circulation shifts initiated in the north atlantic and north pacific our analysis suggests that while micronutrient sources likely contributed to some of the observed changes the heterogeneity in timing of glaciogenic retreat and sea level make these mechanisms unlikely causes of region wide contemporaneous peaks in export production we argue that paleoobservations are most consistent with ventilation increases in both the north pacific during h1 and north atlantic during b a being the primary drivers of increases in biogenic flux during the deglaciation as respectively they were likely to bring nutrients to the surface via increased vertical mixing and shoaling of the global thermocline

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds