central arctic surface ocean environment during the past 80 000 years stable oxygen and carbon isotope and sedimentological paleontological investigations supported by accelerator mass spectrometry 14 c datings were carried out on cores from north of 85 degrees n in the eastern central arctic ocean significant changes in accumulation rates provenance of ice rafted debris ird and planktic productivity over the past 80 000 years are documented during peak glacials i e oxygen isotope stages 4 and 2 the arctic ocean was covered by sea ice with decreased seasonal variation limiting planktic productivity and bulk sedimentation rates in early stage 3 and during termination i major deglaciations of the circum arctic regions caused lowered salinities and poor oxygenation of central arctic surface waters a meltwater spike and an associated ird peak dated to similar to 14 12 14 c ka can be traced over the southern eurasian basin of the arctic ocean this event was associated with the early and rapid deglaciation of the marine based barents sea ice sheet a separate termination ib meltwater event is most conspicuous in the central arctic and is associated with characteristic dolomitic carbonate ird this lithology suggests an origin of glacial ice from northern canada and northern greenland where lower paleozoic platform carbonates crop extensively out

10be records of sediment cores from high northern latitudes implications for environmental and climatic changes the 10be records of four sediment cores forming a transect from the norwegian sea at 70 n core 23059 via the fram strait core 23235 to the arctic ocean at 86 n cores 1533 and 1524 were measured at a high depth resolution although the material in all the cores was controlled by different sedimentological regimes the 10be records of these cores were superimposed by glacial interglacial changes in the sedimentary environment core sections with high 10be concentrations 1 109 at g are related to interglacial stages and core sections with low10be concentrations 0 5 109 at g are related to glacial stages climatic transitions e g termination ii 5 6 are marked by drastic changes in the 10be concentrations of up to one order of magnitude the average 10be concentrations for each climatic stage show an inverse relationship to their corresponding sedimentation rates indicating that the 10be records are the result of dilution with more or less terrigenous ice rafted material however there are strong changes in the 10be fluxes e g termination ii into the sediments which may also account for the observed oscillations most likely both processes affected the 10be records equally amplifying the contrast between lower glacials and higher interglacials 10be concentrations the sharp contrast of high and low 10be concentrations at climatic stage boundaries are an independent proxy for climatic and sedimentary change in the nordic seas and can be applied for stratigraphic dating 10be stratigraphy of sediment cores from the northern north atlantic and the arctic ocean

high resolution climate records from the north atlantic during the last interglacial the two deep ice cores recovered by the grip1 and gisp22 projects at summit greenland agree in detail over the past 100 000 years3 and demonstrate dramatic climate variability in the north atlantic region during the last glacial before the current period of holocene stability this glacial climate instability has subsequently been documented in the marine sedimentary record of surface ocean conditions in the north atlantic4 before 100 kyr ago the two ice core records are discrepant however casting doubt on whether the oxygen isotope fluctuations during the last interglacial eemian seen in the grip core1 5 represent a true climate signal here we present high resolution records of foraminiferal assemblages and ice rafted detritus from two north atlantic cores for the interval 65 kyr to 135 kyr ago extending the surface ocean record back to the eemian the correlation between our records and the greenland ice core records is good throughout the period in which the two ice cores agree suggesting a regionally coherent climate response during the eemian our marine records show a more stable climate than that implied by the grip ice core suggesting that localized phenomena may be responsible for the variability in the latter record during the eemian

south pacific origin of the decadal enso like variation as simulated by a coupled gcm 1 the hypothesis of the south pacific origin of the decadal 7 35 years enso like variation is investigated based on 200 year outputs of the echam4 opa oasis coupled gcm associated with the decadal warm cold sst anomalies in the tropical pacific an anomalous cyclonic anticyclonic circulation which is tilted in a southeast northwest direction appears in the south pacific this results in anomalous upward downward ekman pumping along the northeastern edge of the anomalous circulation and hence shallowing deepening the oceanic thermocline there such an external source of heat content tends to slowly discharge recharge the tropical ocean on the decadal timescale the above result is consistent with the observational study of luo and yamagata 2001 besides the model reproduces amazingly a high lagged correlation between the global land surface temperature and the decadal nino3 sst despite the model biases this suggests a potential prediction skill of the global warming based on the enso like decadal variation

optically stimulated luminescence dating supports central arctic ocean cm scale sedimentation rates 1 this paper presents new results from optically stimulated luminescence osl dating on a sediment core raised from the crest of the lomonosov ridge in the central arctic ocean there has been much debate about dating sediment cores from the central arctic ocean and by using an independent absolute dating technique we aim to test whether or not relatively fast cm scale ka sedimentation rates were typical of arctic s pleistocene depositional mode on the basis of mainly paleomagnetic reversal stratigraphy many previous studies suggest mm scale ka sedimentation rates a common feature in these studies is that the first down core paleomagnetic negative inclination is consistently interpreted as the brunhes matuyama boundary at about 780 ka our osl dating results indicate that this assumption is not generally valid and that the first encountered negative inclination represents younger age excursions within the brunhes chron implying reinterpretation of many published core studies where paleoenvironmental reconstructions have been made for the central arctic ocean our dating results furthermore corroborates a correlation of the uppermost 2 3 m of the lomonosov ridge cores to a well dated core located off the barents kara sea margin that in turn is correlated to cores in the fram strait valuable information on the paleoceanographical evolution in the arctic ocean from mis 6 to the holocene is given through this correlation of records from the central arctic ocean to records off the eurasian continental margin

stable oxygen and carbon isotopes in planktic foraminifers from arctic ocean surface sediments reflection of the low salinity surface water layer planktic foraminifers neogloboquadrina pachyderma sin from 87 eastern and central arctic ocean surface sediment samples were analyzed for stable oxygen and carbon isotope composition additional results from 52 stations were taken from the literature the lateral distribution of 18o full size image 33 atlantic waters entering the arctic ocean through the fram strait 18o values decrease both to the barents shelf and to the north pole in accordance with the decreasing salinities of the halocline waters in the nansen basin a strong n s 18o gradient is in contrast with a relatively low salinity change and suggests contributions from different freshwater sources i e salinity reduction from sea ice meltwater in the south and from light isotope waters meteoric precipitation and river runoff in the northern part of the basin north of the gakkel ridge 18o and salinity gradients are in good accordance and suggest less influence of sea ice melting processes the 13c full size image 1 k values of n pachyderma sin from arctic ocean surface sediment samples are generally high 0 75 0 95 lower values in the southern eurasian basin appear to be related to the intrusion of atlantic waters the high 13c values are evidence for well ventilated surface waters because the perennial arctic sea ice cover largely prevents atmosphere ocean gas exchange ventilation on the seasonally open shelves must be of major importance lack of 13c gradients along the main routes of the ice drift from the siberian shelves to the fram strait suggests that primary production i e co2 consumption does probably not change the co2 budget of the arctic ocean significantly

global ice volume fluctuations north atlantic ice rafting events and deep ocean circulation changes between 130 and 70 ka multiproxy data from north atlantic deep sea sediment core neap18k provide a detailed record of climate through oxygen isotope stage ois 5 seven distinct large scale episodes of ice rafting c25 c19 were identified between 126 and 70 ka global ice volume reconstructions based on high resolution benthic 18 o records indicate that major ice rafting events were not confined to ice volume maxima at ois 5d and 5b but also occurred during periods of ice sheet growth and disintegration however iceberg discharges were restricted to times when sea levels were 40 65 m below present values ice rafting episode c25 the first large scale cooling of mid atlantic surface waters after the last interglacial occurred during the gradual buildup of continental ice sheets at the ois 5e 5d transition major ice sheet collapses allied to ice rafting events c24 and c21 were associated with rapid sea level increases of 20 and 40 m respectively suborbital climatic fluctuations in the neap18k sedimentary record denoted by prominent 7 5 4 5 and 3 k y cyclicities appear to correlate with both greenland atmospheric temperatures and changes in thermohaline circulation patterns inferred from benthic 13 c values and hence provide clear evidence of a highly interconnected north atlantic climatic regime during ois 5

freshwater pulses in the eastern arctic ocean during saalian and early weichselian ice sheet collapse abstract improved multiparameter records from the northern barents sea margin show two prominent freshwater pulses into the arctic ocean during mis 5 that significantly disturbed the regional oceanic regime and probably affected global climate both pulses are associated with major iceberg rafted debris ird events revealing intensive iceberg sea ice melting the older meltwater pulse occurred near the mis 5 6 boundary 131 000 yr ago its 2000 year duration and high ird input accompanied by high illite content suggest a collapse of large scale saalian glaciation in the arctic ocean movement of this meltwater with the transpolar drift current into the fram strait probably promoted freshening of nordic seas surface water which may have increased sea ice formation and significantly reduced deep water formation a second pulse of freshwater occurred within mis 5a 77 000 yr ago its high smectite content and relatively short duration is possibly consistent with sudden discharge of early weichselian ice dammed lakes in northern siberia as suggested by terrestrial glacial geologic data the influence of this mis 5a meltwater pulse has been observed at a number of sites along the transpolar drift through fram strait and into the nordic seas it may well have been a trigger for the north atlantic cooling event c20

the classic marine isotope substage 5e since its identi cation nearly fty years ago marine iso tope stage 5 mis 5 has been placed onto absolute time scaleson the basis of three independent approaches cesare emiliani who set up the isotope stages emiliani 1955 depended onuranium series dating of the sediments a method that today isregarded as not generally capable of yielding useful precisionor accuracy broecker and van donk 1970 pioneered the ap proach of correlating to radiometrically dated marine coral ter races thishasbeenmuchaidedinrecentyearsbyimprovementsin the precision and accuracy of these age determinations thathave owed from the development of thermal ionization massspectrometry tims for uranium series dating edwards

the δ18o record along the greenland ice core project deep ice core and the problem of possible eemian climatic instability over 70 000 samples from the 3029 m long greenland ice core project grip ice core drilled on the top of the greenland ice sheet summit have been analyzed for 8o a highly detailed and continuous 8o profile has thus been obtained and is discussed in terms of past temperatures in greenland we also discuss a three core stacked annual 8o profile for the past 917 years the short term 50 years variability of the annual 8o signal is found to be 1 in the holocene and estimates for the coldest parts of the last glacial are 3 or higher these data also provide insights into possible disturbances of the stratigraphic layering in the core which seems to be sound down to the onset of the eemian spectral analysis of highly detailed sequences of the profile helps determine the smoothing of the 8o signal which for the holocene ice is found to be considerably stronger than expected we suggest this is due to a process involving diffusion of water molecules along crystal boundaries in the recrystallizing ice matrix deconvolution techniques were employed for restoring with great confidence the highly attenuated annual 8o signal in the holocene we confirm earlier findings of dramatic temperature changes in greenland during the last glacial cycle abrupt and strong climatic shifts are also found within the eem sangamon interglaciation which is normally recorded as a period of warm and stable climate in lower latitudes the stratigraphic continuity of the eemian layers is consequently discussed in section 3 of this paper in terms of all pertinent data which we are not able to reconcile

surface and deep water changes in the subpolar north atlantic during termination ii and the last interglaciation to reconstruct the history of water mass exchange between the ne atlantic and the nordic seas sediment cores from 2 km water depth were studied across termination ii tii and through the last interglaciation mis5e during early tii the sudden appearance of the low latitude planktonic foraminifera beella megastoma is noted in both regions along with a steep decrease in benthic foraminiferal 18o since other proxies indicate that surface waters were cold and stratified because of meltwater conditions which prevented near surface thermohaline circulation and vertical convection in the nordic seas water mass exchange between the two areas occurred at the subsurface during later tii surface conditions changed and this subsurface circulation style was eventually replaced by vertical convection in the nordic seas b megastoma vanished from the record together with ice rafted debris ird at the end of tii while subpolar foraminiferal abundance rose peak interglacial conditions with intensive vertical convection now fully developed generating a bottom water temperature gradient of 4 c between the two areas however surface water temperatures deteriorated in the nordic seas already notably before ird recurred and 18o increased at the end of mis5e

glaciology enigmatic arctic ice sheets to what extent was the arctic ocean glaciated in the past heavily according to data gathered by a submarine which show considerable ice scouring of topography in parts of the ocean basin

a multiproxy approach to reconstruct the environmental changes along the eurasian continental margin over the last 150 000 years abstract sediment cores located along the eurasian continental margin arctic ocean have been studied to reconstruct the environmental changes in terms of waxing and waning of the barents kara sea ice sheets atlantic water inflow and sea ice distribution over the last 150 kyr the stratigraphy of the cores is based on stable oxygen isotopes ams 14 c and paleomagnetic data we studied variations in marine and terrigenous input by a multiproxy approach involving direct comparison of sedimentological and organo geochemical data extensive episodes of northern barents sea ice sheet growth during marine isotope stages mis 6 and 2 have been supported by at least subsurface atlantic water inflow moisture bearing storms low summer insolation and minimal calving of ice ice advance during mis 4 was probably restricted to the shallow shelf between mis 4 and mis 2 large ice sheet fluctuations correspond to contemporary laurentide surging events and indicate short term climatic changes in the arctic ocean as has been recorded in lower latitudes in contrast in low precipitation areas in eastern eurasia glacial activity was rather limited only distinct ice rafted debris ird input during termination ii and early mis 3 reflects severe glaciations on the northern severnaya semlya margin during mis 6 and mis 4 we conclude that 1 oscillations of ice sheets are less frequent along the eastern eurasian margin than in areas with continuous moisture supply like the western eurasian margins and that 2 major fluctuations of the kara sea ice sheet during the last 150 kyr apparently followed the major interglacial glacial mis 5 4 and mis 7 6 transitions rather than the precession 23 kyr and the tilt 41 kyr cyclicity of the earth s orbit as observed for the scandinavian sis and the svalbard ice sheets respectively mangerud j jansen e landvik j y 1996 late cenozoic history of the scandinavian and barents sea ice sheets in solheim a riis f elverhoi a faleide j j jensen l n cloetingh s eds impact of glaciations on basin evolution data and models from the norwegian margins and adjacent basins global and planetary chance special issue 12 pp 11 26 surface and or subsurface atlantic water masses coupled with seasonally ice free conditions penetrated continuously to at least the franz victoria trough during the last 150 kyr however sustained periods of open water were largely restricted to substages 5 5 5 1 and the holocene as indicated by distinct carbonate dissolution and higher accumulation of marine organic matter mom signals of periodic open water conditions along the northern margin of severnaya semlya are of less importance higher production of foraminifera probably due to atlantic water inflow occurred between 38 and 12 14 c kyr and corresponds to periodic atlantic water advection penetrating into the arctic ocean however marine organic proxies indicate a continuous decrease of surface water productivity from the western to the eastern eurasian continental margin due to a more extensive sea ice cover over the last 150 kyr

arctic ocean evidence for late quaternary initiation of northern eurasian ice sheets a high resolution multiparameter stratigraphy allows the identification of late quaternary glacial and interglacial cycles in a central arctic ocean sediment core distinct sandy layers in the upper part of the otherwise fine grained sediment core from the lomonosov ridge lat 87 5 n correlate to four major glacials since ca 0 7 ma the composition of these ice rafted terrigenous sediments points to a glaciated northern siberia as the main source in contrast lithic carbonates derived from north america are also present in older sediments and indicate a northern north american glaciation since at least 2 8 ma we conclude that large scale northern siberian glaciation began much later than other northern hemisphere ice sheets

implications of stratigraphic and paleoclimatic records of the last interglaciation from the nordic seas climatic reconstruction of glacial to interglacial episodes from oxygen isotopes in sediment cores from the nordic seas is complicated by strong local meltwater contributions to the oxygen isotope changes combination of benthic and planktic foraminiferal isotope data with foraminiferal abundances and ice rafted debris ird allows separation of local and global effects and subdivision of the marine oxygen isotope events 6 2 5 4 which include the last interglaciation into 1 a meltwater phase after glacial stage 6 recorded by large amounts of ird and low foraminiferal abundance indicating surface water warming 2 an ird free period with high deposition rates of subpolar foraminifera and other caco3pelagic components recognized here as the full interglaciation and 3 a phase with the recurrence of ird and the demise of subpolar species comparison of ice core records and marine data implies that the global climate during the last full interglaciation and that during the postdeglacial holocene were similar the records show no significantly different variations in the proxy data in contrast the oxygen isotopes of planktic foraminifera and ice cores indicate significant differences during each of the deglacial transitions terminations i and ii that preceded these two interglaciations these suggest that during termination ii the climatic evolution in the nordic seas was less affected by abrupt changes in ocean atmosphere circulation than during the last glacial to interglacial transition

late pleistocene paleo oceanography of the norwegian greenland sea benthic foraminiferal evidence fluctuations in benthic foraminiferal faunas over the last 130 000 yr in four piston cores from the norwegian sea are correlated with the standard worldwide oxygen isotope stratigraphy one species cibicides wuellerstorfi dominates in the holocene section of each core but alternates downcore with oridorsalis tener a species dominant today only in the deepest part of the basin o tener is the most abundant species throughout the entire basin during periods of particularly cold climate when the norwegian sea presumably was ice covered year round and surface productivity lowered portions of isotope stages 6 3 and 2 are barren of benthic foraminifera this is probably due to lowered benthic productivity perhaps combined with dilution by ice rafted sediment there is no evidence that the norwegian sea became azoic the holocene and substage 5e the last interglacial are similar faunally this similarity combined with other evidence supports the presumption that the norwegian sea was a source of dense overflows into the north atlantic during substage 5e as it is today oxygen isotope analyses of benthic foraminifera indicate that norwegian sea bottom waters warmer than they are today from substage 5d to stage 2 with the possible exception of substage 5a these data show that the glacial norwegian sea was not a sink for dense surface water as it is now and thus it was not a source of deep water overflows the benthic foraminiferal populations of the deep norwegian sea seem at least as responsive to near surface conditions such as sea ice cover as they are to fluctuations in the hydrography of the deep water benthic foraminiferal evidence from the norwegian sea is insufficient in itself to establish whether or not the basin was a source of overflows into the north atlantic at any time between the substage 5e 5d boundary at 115 000 yr b p and the holocene

stable isotope composition δ 18 o δ 13 c of living planktic foraminifers in the outer laptev sea and the fram strait abstract the upper water column in the fram strait and the outer laptev sea was sampled for water column isotopes and living planktic foraminifer species neogloboquadrina pachyderma sinistral coiling ehrenberg 1861 and turborotalita quinqueloba natland 1938 their shell 18o and 13c values are compared to water oxygen and dissolved inorganic carbon isotope data to determine the environmental influence on the foraminifers isotopic ratio major controls on the oxygen isotope composition of both species are the shallow depth habitat under permanent ice coverage the low salinity surface layer and the rate of metabolic activity none of the specimens precipitated its shell in isotopic equilibrium with the ambient sea water they are all depleted in 13c and 18o attributed to a species specific vital effect for nonencrusted n pachyderma sin in the 125 250 m size class this vital effect amounts to 1 3 in 18o and 2 0 in 13c it increases to higher values in waters under permanent ice cover t quinqueloba reveals a mean vital effect of about 1 3 in 18o and 2 6 in 13c the general isotopic trends are similar for n pachyderma sin and t quinqueloba differences in the species isotope ratio at the same sites are caused by different calcification depths and metabolic activity the oxygen isotope composition of n pachyderma sin shows a relationship to salinity measurements and indicates that it is a good quantitative proxy for salinity reconstructions while no relationship exists in this region between n pachyderma sin oxygen isotopes and water temperature

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

long lived vortices as a mode of deep ventilation in the greenland sea the greenland sea is one of a few sites in the world ocean where convection to great depths occurs1 2 3 4 a process that forms some of the densest waters in the ocean but the role of deep convective eddies which result from surface cooling and mixing across density surfaces followed by geostrophic adjustment5 has not been fully taken into account in the description of the initiation and growth of convection6 here we present tracer float and hydrographic observations of long lived 1 year and compact 5 km core diameter vortices that reach down to depths of 2 km the eddies form in winter near the rim of the greenland sea central gyre and rotate clockwise with periods of a few days the cores of the observed eddies are constituted from a mixture of modified atlantic water that is warm and salty with polar water that is cold and fresh we infer that these submesoscale coherent eddies contribute substantially to the input of atlantic and polar waters to depths greater than 500 m in the central greenland sea

variations of continental discharge pattern in space and time implications from the laptev sea continental margin arctic siberia variations in sediment input and distribution to the laptev sea continental margin during the holocene and termination i could be identified based on radiocarbon dated magnetic susceptibility logs and sediment thickness in high resolution seismic profiles magnetic susceptibility of surface samples reveals an increased input of magnetic grains to the laptev sea deriving from the anabar and khatanga river catchments exposed magnetite schists and volcanic rocks of the anabar shield and putoran plateau respectively function as major source of magnetic material the distribution of magnetic susceptibility in association with the thickness of the holocene sediments indicates bottom current induced sediment transport guided by major submarine valleys on the laptev sea shelf the sites of filled paleoriver channels identified in the seismic profiles suggest that during the late weichselian sea level lowstand river runoff continued through four of the major valleys on the exposed laptev sea shelf the sediments at the top of the lowstand deposits in front of the anabar khatanga valley represented in the seismic profiles by prograding deltas are characterized by outstandingly high magnetic susceptibility values radiocarbon datings approximate the deposition of these high magnetic sediments between 10 and 13 4 ka it is suggested that this increased input of magnetic material is related to the deglaciation of the anabar shield and the putoran plateau and thus support their glaciation during marine isotope stage mis 2