weichselian and holocene growth of the northern high latitude lofoten contourite drift on the continental slope of norway abstract the weichselian and holocene sediments in the lofoten drift comprise six lithofacies brown sandy mud olive grey mud olive grey laminated mud dark brown mud massive sand and dark grey sandy mud during the weichselian the sediment input to the lofoten drift was from two main sources i e glacimarine sedimentation and ocean current winnowing during the holocene the sediment input was only from winnowing the sediment source area was the voring margin and the continental margin further south the sedimentation rate was 190 cm ka during the late weichelian and 9 cm ka during the holocene the weichselian rates are high compared with the deep sea contourite drifts comprising highly bioturbated sediments and probably explain why bioturbation is less pronounced in these slope drift sediments drifts on glaciated margins as exemplified by the lofoten contourite drift represent areas of high sedimentation rate during glacial maxima sediment input was not restricted to glacial maximum periods for sediments also accumulated during other stadial and interstadial periods

sediment fluxes along the northeastern european margin inferring hydrological changes between 20 and 8 kyr abstract in an attempt to delineate past hydrographic conditions on the northeastern atlantic ocean margin along a latitudinal transect 37 63 n and link the eastern north atlantic ocean with the norwegian sea we have investigated planktonic and benthic stable oxygen isotopes as well as abundances and fluxes of planktonic and benthic foraminifera calcium carbonate organic carbon and detrital grains in six sediment cores studied by the enam project in our joint approach we focused on the major climatic events of the last 20 kyr that is the last glacial maximum lgm the heinrich event 1 h1 the younger dryas yd and the holocene climatic optimum hco simmax temperature estimates suggest glacial ssts off portugal similar to holocene values contradicting the proposed polar front position of climap project members 1976 besides increased planktonic and benthic foraminiferal fluxes in the norwegian sea and the faeroe islands cores point to nordic seas partially ice free with seasonally productive polynas multiple ird spikes observed at the faeroe islands and norwegian sea sites coeval with h1 suggest multiple pulses of the fenno scandian ice sheet at the same time the presence of ird on the portuguese margin cores confirms the southward influence of icebergs the increase in foraminiferal abundances and fluxes that parallel ird spikes at all sites suggests that times of increased productivity either succeed or occur simultaneously with the iceberg surges in the open north atlantic productivity conditions similar to those observed during h1 are also registered during the yd even though planktonic foraminiferal assemblages suggest less cold conditions

numerical reconstructions of lgm climate across the eurasian arctic abstract although limits of the eurasian ice sheet at the last glacial maximum lgm are known relatively well from geological evidence the palaeoclimate coexistent with this ice sheet has yet to be identified confidently a simple ice sheet model has been used to determine lgm climate conditions by finding the ice sheet mass balance configuration that permits model results to match with geological data relating to the extent of lgm ice cover these conditions are compared with atmospheric general circulation model agcm calculations of the climate at the lgm which reveal the meteorological conditions associated with the ice sheet mass balance the western margin of scandinavia is characterised by a maritime climate influenced by the nearby warm seasonally sea ice free ocean conditions however further east the warming effect of the north atlantic diminishes and an extreme polar desert climate dominates across the kara sea similar to east antarctica today the lgm climate that we establish is in contrast to many previous reconstructions involving snow laden warm westerly winds originating from the north atlantic affecting the entire eurasian arctic severely cold conditions across the eurasian arctic are compatible with a stable circulation cell over the kara sea that isolates the region climatically and or cold dry westerly winds from the fennoscandian ice sheet that flow across the rest of the eurasian arctic

late glacial and deglacial palaeoceanographic changes at vestnesa ridge fram strait methane seep versus non seep environments abstract two cores from 1200 m water depth from vestnesa ridge on the western svalbard margin have been investigated for the distribution of benthic and planktic foraminiferal assemblages oxygen and carbon isotopes geochemical and sedimentological parameters including magnetic susceptibility total organic carbon toc and caco 3 content of the sediment vestnesa ridge is known for the presence of numerous pockmarks where methane gas is bubbling out from the seafloor one core was taken from a pockmark with active seepage of methane while the second core was taken just outside the seepage area for comparison the purpose of the study is to reconstruct the palaeoceanography and compare to published palaeoceanographic records from the area and evaluate if seepage of methane have had any impact on the distribution patterns of benthic foraminiferal species and the sedimentary environments through time the results indicate almost continuous presence of atlantic water throughout the last 43 000 years during the heinrich h1 interval ca 18 000 15 300 years atlantic water flowed subsurface along the bottom and the period stands out with the highest bottom water temperatures of the last 43 000 years settlement of a community of chemo synthesizing bivalves indicates increase in the release of methane beginning during h1 however in both records of seep versus non seep environments the distribution patterns of benthic foraminiferal species diversity and productivity of the specimens were the same indicating that seepage of methane had no influence on the foraminiferal faunas our results show that the palaeoceanographic development at vestnesa ridge was similar to the development over the western svalbard margin and the fram strait confirming previously published results we conclude that the benthic foraminifera at the methane seep site were mainly controlled by palaeoceanographic changes and associated changes in the sedimentary environment and palaeoproductivity overprinting any eventual influence of seepage of methane

rapid climatic shifts during isotope stages 2 4 in the polar north atlantic sediment cores from the polar north atlantic provide evidence of six periods of sea ice breakup during isotope stages 4 3 and 2 probably caused by inflow of north atlantic surface water into the polar north atlantic these periods are characterized by having a high number of foraminifera g they last from 2000 to 10000 yr and constitute 50 of the total time span these periods of sea ice breakup correlate temporarily to the heinrich events and the early temperature maximum in the bond cycles of the north atlantic and greenland ice record our hypothesis is that massive iceberg discharges that flooded the north atlantic during each heinrich event probably triggered an oceanographic regime that gave a much more vigorous surface circulation pattern in the polar north atlantic which contributed to the breakup of the sea ice cover open water conditions in the polar north atlantic are inversely related to terrestrial interstadials of coastal norway suggesting ice sheet starvation during the cold periods and ice sheet growth when an open water surface circulation existed in the polar north atlantic our data document synchronous variations on a october 1900 yr time scale between arctic oceanic climate northern hemisphere ice sheet dynamics and ocean atmosphere temperature changes

sedimentary environment and glacial history during the last 40 ka of the voring continental margin mid norway abstract this study is based on detailed investigation of sediment cores and high resolution seismics we identified and describe five lithofacies on the voring plateau and eight on the mid norwegian continental slope the various lithofacies are mainly related to the fluctuations of the fennoscandian ice sheet and the varying intensity of bottom currents and inflow of atlantic water masses ocean circulation was highly variable between 40 and 22 14 c ka bp being vigorous during interstadials and sluggish during stadials between ca 22 and 15 14 c ka bp the sedimentary environment was significantly influenced by fluctuations of the fennoscandian ice sheet repeatedly reaching the outermost shelf these fluctuations are reflected in the sedimentary record as ice rafted debris ird accumulation peaks deposition of stratified diamicton and glacigenic debris flows on the continental slope during this period the sediment accumulation rate increased bottom currents influenced the sedimentary pattern and surface waters were seasonally ice free indicating inflow of atlantic waters subsequent to ca 15 14 c ka bp the glacier influence decreased as the margin of the fennoscandian ice sheet retreated to reach the coast before 12 5 14 c ka bp the modern sedimentary environment is characterised by relatively strong bottom current action causing winnowing or non deposition down to approximately 1000 m water depth

sortable silt cycles in svalbard slope sediments 74 0 ka the grain size of sortable silt ss 10 63 m was studied in sediment core jm04 025pc from a sediment drift on the lower part of the western svalbard slope the study aims to reconstruct the bottom current activity and intermediate water circulation in the greenland sea the ss record covers the last 74 ka and shows consistent millennial scale oscillations in grain size the youngest part of the record 25 ka is well correlated with the few available previously published reconstructions of grain size from the north atlantic ocean and the nordic seas fining of ss occurs during four well known regional cold climatic intervals the 8 2 ka cold spell the younger dryas and north atlantic heinrich events h1 and h2 as well as during a local meltwater event at 14 4 14 7 ka possibly coinciding with the older dryas also before 25 ka grain size oscillated in pace with the northern hemisphere climate with finer grain sizes during cold periods and coarser grain sizes during warm periods the fining of ss indicates reduced bottom current strength and reduced water exchange between the greenland sea and the arctic ocean during regional climate cooling events and probably also reduced deep ocean convection in the greenland sea gyre

dynamics of atlantic water advection to the norwegian greenland sea a time slice record of carbonate distribution in the last 300 ky abstract short term variability in volume and configuration of atlantic water advection to the norwegian greenland sea ngs has recently been identified as a new and significant element for northern hemisphere glacial interglacial climatic fluctuations the amount of salt heat and moisture transferred by atlantic waters to the high arctic effectively influences northern hemisphere climates and is critical for the overall oceanic turnover rate in particular determining the extent and duration of atlantic water intrusions in the ngs is essential because of 1 its effect on the climate of the nordic continents and 2 its trigger function on the stability of the ice sheets with a weak inflows of atlantic water during glacials promoting an increase in ice volume by moisture supply to polar areas and b positive feed back mechanisms of atlantic water intrusions during ice sheet decay in this study the dynamics of surface water mass regimes in the ngs have been reconstructed for the past 300 ky by means of time slice compilations of calcium carbonate distribution and micropaleontologic proxies in addition carbonate preservation records are used to quantify deep water ventilation and production rates in contrast to the climap scenario but in accordance with many recent publications results of this study indicate that atlantic water advection was also a common feature during most glacial periods but varied strongly in volume and configuration significant modes recognized are 1 the full interglacial mode with a wide inflow of warm atlantic waters covering a broad area in the eastern sector of the ngs and extending far north combined with excellent carbonate preservation and very efficient deep water formation stages 1 and 5 5 1 2 the moderate interglacial mode with a rather small extension of atlantic waters along a narrow corridor in the southeastern sector of the ngs but still very efficient deep water exchange stages 9 isotopic events 7 5 7 3 7 1 5 3 and 5 1 3 pronounced cool phases during interglacials with only a very narrow inflow of atlantic waters into the southeastern ngs while the coastal areas off norway were still affected by iceberg drift substages 7 4 and 5 2 carbonate preservation records indicate ongoing deep water formation in the ngs 4 the normal glacial mode characterized by a variable but persistent inflow of cool temperate atlantic water lower stage 8 repetitively during stages 6 4 3 1 and 2 carbonate preservation records indicate ongoing deep water formation in the ngs 5 short glacial and deglacial periods characterized by episodic high inputs of ird evidenced by a wide coverage of diamicton deposition and strong carbonate dissolution e g episodically within stages 10 6 and 2 the 6 5 4 3 and 2 1 transitions some of these ngs diamicton layers correlate with heinrich layers in the north atlantic but generally ngs diamicton layers occur more frequently than heinrich layers the role of atlantic water influence during these events remains enigmatic but atlantic water influence is frequently found just above and below these sections a scenario with rapid ice sheet disintegration induced by atlantic water advection via increase of the thermal regime along the ice margin possibly triggered by small scale sea level rise might be envisaged more obviously the short term cessation of deep water formation in the ngs as evidenced by the dissolution spikes may be correlated with contemporaneous ventilation minima in the north atlantic

climatic dependence of the organic matter contributions in the north eastern norwegian sea over the last 15 000 years abstract lipids are used for the evaluation of the different organic matter contributions in the north eastern norwegian sea m23258 site 75 n 14 e over the last 15 000 years development of a mass balance model based on the down core quantification of the c 37 alkenones the odd carbon numbered n alkanes a odd and the unresolved complex mixture of hydrocarbons ucm has allowed three main organic matter inputs involving marine continental and ancient reworked organic matter to be recognized the model shows good agreement between measured and reconstructed toc values similarly a strong parallelism is observed between predicted components such as marine toc and carbonate content which was determined independently representation of the model results within a time scale based on 15 ams 14 c measurements shows that the main changes in organic matter constituents are coincident with the major climatic events of the last 15 000 years thus the predominance of reworked organic matter is characteristic of termination ia up to 70 continental organic matter was dominant during the bolling allerod b a and younger dryas yd periods about 85 and a strong increase of marine organic matter occurred in the holocene between 50 and 75 this agreement reflects the main hydrographic changes that determined the deposition of sedimentary materials between 0 and 15 cal ka ice rafted detritus from the barents continental platform ice melting waters from the arctic fluvial system discharging into the barents sea and dominance of north atlantic currents respectively in this respect the high resolution down core record resulting from the mass balance and lipid measurements allows for the identification of millennial scale events such as the increase of reworked organic matter at the final retreat of the barents ice sheet at the end of the deglaciation period termination ib

variation in surface and deep water circulation in the denmark strait north atlantic during marine isotope stages 3 and 2 1 the paleoceanography in the denmark strait north atlantic is reconstructed based on down core analysis of planktonic foraminifera carbon and oxygen isotopes carbonate and ice rafted debris ird the stratigraphy spans 57 to 6 calibrated cal ka years and reveals sea surface temperatures that covary with greenland ice core temperatures throughout marine isotope stages mis 3 and 2 planktonic 18o minima interpreted as meltwater events follow sea surface warming ird from both the greenland and iceland ice sheets was delayed by 2 ka relative to the north atlantic heinrich events ventilation of bottom water was mostly sustained through open ocean convection associated with north atlantic deep water production or by convection of glacial north atlantic intermediate water except for two episodes at 54 cal ka mis 3 31 and 18 15 cal ka termination i during these two periods we suggest that deep water ventilation was accomplished mainly by brine formation

geological significance of seismic reflections in collision belts geological problems raised by the interpretation of deep seismic reflections in collision belts result from the structural complexity of the crust and the lack of surface control and well documeted references some of these problems are illustrated by examples coming from various tectonic settings in france and adjacent areas and tentative interpretations are proposed

late weichselian submarine debris flow deposits on the bear island trough mouth fan sedimentary processes on the bear island trough mouth fan during the last glacial were studied using high resolution reflection seismics and gravity cores the fan succession is dominated by large debris flow deposits of up to 24 km in width and 50 m thick debris lobes can be followed over 100 km downslope and the largest cover an area of 1880 km2 the large debris flows were generated when the barents sea ice sheet reached the shelf break glacigenic sediments transported to the grounding line were temporarily stored on the upper slope due to the high sedimentation rate the sediments were unstable and earthquakes oversteepening and or build up of excess pore pressure triggered sediment release generating large debris flows sediments were also eroded and incorporated during the downslope flow debris flows were the most important sediment distributing process due to the relatively high shear strength low flow mobility of the glacigenic diamicton and the low fan gradient the weichselian evolution of the fan was characterized by a relatively low sedimentation rate during the early and mid weichselian the barents sea ice sheet might have reached the shelf break twice during the late weichselian on average one large debris flow comprising 18 km3 of sediments was released between every 35 to 75 years during the last glacial maximum

quaternary dinoflagellate cysts in the arctic ocean potential and limitations for stratigraphy and paleoenvironmental reconstructions abstract the arctic ocean is a siliciclastic depositional environment which lacks any rock forming biogenic calcareous and siliceous components during large parts of its quaternary history these hemipelagic sediments are nevertheless suitable for the study of organic walled microfossils of which the fossil remains of dinoflagellates dinoflagellate cysts are the most important group dinoflagellate cysts have become an important tool in paleoceanography of the high northern latitudes but their potential for quaternary biostratigraphy has remained largely unexplored dinoflagellate cysts are the dominant marine palynomorph group which is more continuously present in the marginal seas e g barents sea bering sea than in the arctic ocean itself throughout the quaternary most species have long stratigraphic ranges are temporary absent and show abundance variations on glacial interglacial timescales of the more than 30 taxa recorded only habibacysta tectata and filisphaera filifera became extinct in the pleistocene the highest persistent occurrence of h tectata at ca 2 0 ma and the top of f filifera acme at ca 1 8 ma can be used for supra regional stratigraphic correlation between the arctic ocean and adjacent basins these events corroborate a slow sedimentation rate model for the quaternary section on the central lomonosov ridge but a combination of different methods will have to be applied to provide a detailed chronostratigraphy the occurrence of cysts of phototrophic dinoflagellates in certain stratigraphic intervals on lomonosov ridge supports published evidence of episodic opening of the multiyear arctic sea ice cover during the quaternary probably related to a stronger inflow of atlantic water this contradicts the hypothesis of a permanently ice covered central arctic ocean in the quaternary

water mass exchange between the nordic seas and the arctic ocean on millennial timescale during mis 4 mis 2 1 the climate of the last glaciation circa 65 000 25 000 years ago was interrupted by about 15 abrupt temperature fluctuations the so called dansgaard oeschger events consisting of warm interstadials and cold stadials recorded in greenland ice cores the largest fluctuations occur in the north atlantic region but they have been registered over the most of the world the events are linked to changes in deep water formation in the nordic seas and north atlantic disrupting the thermohaline circulation yet dansgaard oeschger events have so far not been recorded north of the convection areas in the central nordic seas and it is not known if they affected the water exchange between the nordic seas and the arctic ocean in this study we analyze core jm05 31gc from the northern fram strait at the very entrance to the arctic ocean the core contains sediments from marine isotope stages miss 4 2 the results show millennial timescale shifts in all the investigated proxies including the distribution of planktonic and benthic foraminifera planktonic and benthic oxygen and carbon isotopes and several sedimentological parameters in jm05 31gc the interstadials are characterized by relatively high surface and low bottom water temperatures low content of ice rafted debris and well ventilated bottom water stadials are characterized by the presence of icebergs and decreasing surface water and increasing bottom water temperatures due to increased inflow of atlantic subsurface water ventilation decreased during heinrich events and most stadials the results show that the dansgaard oeschger events strongly affected the water exchange between the nordic seas and the arctic ocean

abrupt shifts of productivity and sea ice regimes at the western barents sea slope from the last glacial maximum to the bolling allerod interstadial abstract advanced knowledge of spatio temporal constraints on the barents sea ice sheet during the late weichselian glaciation overshadows relatively limited understanding of seasonal sea ice experiencing an annual advance retreat cycle and primary productivity trends accompanying massive abrupt climate changes during glacial deglacial cycles such paleo reconstructions are crucial prerequisites for improved comprehension and prediction of current and future climate change here we investigate sea ice and phytoplankton biomarker distributions in a barents sea sediment core covering ca 25 8 15 4 cal kyr bp to elucidate abrupt shifts of spring summer sea ice concentrations and relative sympagic pelagic productivity trends at the southwestern continental slope despite significant presence of seasonal sea ice the last glacial maximum lgm and initial shelf edge deglaciation sedg at the core site are characterised by occurrence of productive coastal polynya adjacent to the maximum ice sheet extent the onset of perennial i e multi year ice cover and near zero productivity during heinrich stadial 1 hs1 ca 18 0 16 3 cal kyr bp accompanies significant meltwater fluxes from ice sheet debuttressing and the consequent stagnation of thermohaline circulation rapid sea ice retreat and unprecedented pelagic productivity observed after 16 3 cal kyr bp coincides with areal ice sheet deglaciation and is potentially linked to the release of sub surface heat and nutrient reservoirs together with reinvigorated deep water circulation following millennial heating of the deep ocean during hs1 we find that a multivariate fingerprinting approach involving assessment of both downcore and surface biomarker distributions is able to distinguish relative ice algal and pelagic diatom productivity driven by sea ice dynamics

quaternary glaciations in southern fennoscandia evidence from southwestern norway and the northern north sea region abstract based on records from the northern north sea and southern norway quaternary fennoscandian glaciations are described and discussed maximum glaciation defined as the presence of shelf edge glaciation an ice stream flowing out of the norwegian channel and most likely an ice divide over the central part of fennoscandia sweden gulf of bothnia occurred for the first time in the late cenozoic at ca 1 1 myr the fedje glaciation this glaciation was followed by a ca 600 kyr period with at least two glaciations with ice extension somewhat larger than the younger dryas event in the region the first maximum glaciation of the bruhnes chron was during isotope stage 12 and was followed by repeated maximum glaciations within each of the light isotopic stages until stage 2 during the weichselian the southwestern part of the fennoscandian ice sheet reached maximum position three times sometime between 22 and 28 37 and 50 and 60 and 80 ka limited glaciations probably occurred during stadials between the early and middle weichselian interstadials between 500 ka and 1 1 myr and most likely also prior to 1 1 myr deep norwegian sea ice rafted detritus ird records reflecting contributions from several different ice sheets fennoscandian barents sea iceland and greenland each with large variations in history of ice extent to their respective margins yet to some degree they reflect the glaciation of the northern north sea region with an increasing ird input around 1 1 myr and a relatively low input of north sea components during some cycles around the b m boundary maximum glaciations occurred during insolation minima in the earlier part of the middle pleistocene however not all such minima are reflected by maximum glaciation in southern parts of fennoscandia the relatively poor chronological control and non continuous character of the data on weichselian interstadials stadials precludes a clear relationship to atmospheric changes recorded in greenland ice cores as well as to precession and or obliquity cycles in insolation

late quaternary development of the storfjorden and kveithola trough mouth fans northwestern barents sea abstract the development of two arctic trough mouth fans tmfs the storfjorden and kveithola tmfs is investigated by means of sub bottom and seismic reflection profiles multibeam bathymetry and sediment samples allowing their detailed stratigraphic architecture to be defined we find that the tmfs mainly consist of an alternation of rapidly deposited glacigenic debris flows during glacial maxima and a sequence of well layered plumites and hemipelagic sediments which were mainly deposited during the deglaciation phase of the adjacent glacial trough we have identified eight units above regional reflector r1 which indicate that the ice sheet reached the shelf edge within the storfjorden trough on at least three occasions during the last 200 ka a shallow subsurface unit of glacigenic debris flows suggests that the ice sheet had a short re advance over the northern and central part of storfjorden after the last glacial maximum from stratigraphy core and literature data we estimate that ice sheets reached the shelf edge between 19 5 to 22 5 ka 61 to 65 ka and 135 to 167 ka detailed seismic imaging allows us to refine the sedimentary model of arctic tmfs the main differences to previous models involve gully formation during not only the deglaciation phase but also during interglacials by dense shelf water cascading and a specific timing for the occurrence of slope failures i e shortly after the deglaciation phase high mean sedimentation rates during glacial maxima of up to 18 kg m 2 yr 1 likely allow excess pore pressure to develop in the water rich plumites and hemipelagic sediments deposited in the previous deglacial period particularly where such plumites attain a significant thickness the position of the submarine landslides in the stratigraphic record suggest that such excess pore pressure is not enough to trigger the slope failures and suggests that earthquakes related to isostatic rebound are likely involved in the final activation

sedimentation of deep water slope base and inner fan deposits the drosgol formation ashgill west central wales abstract the sedimentology of the drosgol formation is summarised in terms of nine sedimentary facies with particular attention given to the pebbly mudstones and major arenites sedimentary facies geometry and palaeocurrents suggest the interpretation of the major arenites as inner fan channel deposits locally preserving their levees the lower less organised part of the formation suggests a slope base environment with small scale channelling slumping and development of mass flow deposits a new definition of the upper boundary of the formation is proposed and map references are given to key localities

high resolution record of late glacial and deglacial sea ice changes in fram strait corroborates ice ocean interactions during abrupt climate shifts the transition from last glacial to deglacial and subsequently to modern interglacial climate conditions was accompanied by abrupt shifts in the palaeoceanographic setting in the subpolar north atlantic knowledge about the role that sea ice coverage played during these rapid climate reversals is limited since most marine sediment cores from the higher latitudes provide only a coarse temporal resolution and often poorly preserved microfossils here we present a highly resolved reconstruction of sea ice conditions that characterised the eastern fram strait a key area for water mass exchange between the arctic ocean and the north atlantic for the past 30 ka bp this reconstruction is based on the distribution of the sea ice biomarker ip25 and phytoplankton derived biomarkers in a sediment core from the continental slope of western svalbard during the late glacial 30 ka to 19 ka bp recurrent advances and retreats of sea ice characterised the study area and point to a hitherto less considered oceanic and or atmospheric variability a long lasting perennial sea ice coverage in eastern fram strait persisted only at the very end of the last glacial maximum i e from 19 2 to 17 6 ka bp and was abruptly reduced at the onset of heinrich event 1 coincident with or possibly even inducing the collapse of the atlantic meridional overturning circulation amoc further maximum sea ice conditions prevailed during the younger dryas cooling event and support the assumption of an amoc reduction due to increased formation and export of arctic sea ice through fram strait a significant retreat of sea ice and sea surface warming are observed for the early holocene

asynchronous deposition of ice rafted layers in the nordic seas and north atlantic ocean instabilities in ice stream flow within the north american laurentide ice sheet leading to the periodic release of armadas of icebergs into the north atlantic ocean over the past 60 000 years have produced extensive layers of coarse grained iceberg rafted debris heinrich layers in north atlantic sediments1 2 correlation of these layers with iceberg discharge events from the ice sheets on greenland iceland and scandinavia suggested in previous studies for some heinrich layers and in some areas3 4 5 would imply that ice sheet instability had been synchronous across the north atlantic presumably in response to a common environmental cause here we show a lack of widespread systematic correlations both between ice rafted debris layers in different sediment cores from the nordic seas and between the nordic layers and the north atlantic heinrich layers this suggests that the full glacial nordic ice sheets did not exhibit unstable behaviour coincident with iceberg discharge from the vast hudson bay drainage basin of the laurentide ice sheet6 7 off the hudson strait significant ice sheet discharge of melt water is indicated by size sorted sandy and muddy turbidite sediments different from the poorly sorted debris flows which dominate sedimentation on the margins of the nordic seas8 9 10 together these results suggest that the dynamics of quaternary ice sheets surrounding the nordic seas were different from the outlet glacier draining the hudson bay basin and they provide evidence against a common circum north atlantic mechanism driving the discharge of icebergs

late pleistocene sediments and environmental change at plaza creek falkland islands south atlantic late pleistocene organic rich sediments exposed in coastal bluffs near the head of plaza creek east falkland have yielded conventional and ams 14c dates of between 36 and 28 ka bp and possess a pollen spectrum dominated by grasses indicating a vegetation assemblage similar to that of the present day although some sample dates are anomalous and contamination by non contemporaneous carbon cannot be ruled out entirely the age estimates are consistent with evidence and dates from antarctica south america and the amphi north atlantic for climate shifts to interstadial conditions at around that time the organic rich units are developed in and enclosed by deposits attributed to processes of periglacial mass wasting grain size characteristics suggest that these sediments may have been emplaced by solifluction shallow translational landsliding and surface wash in at least five mass wasting episodes some of the mass wasting sediments might correlate with solifluction deposits above and below a podsolic soil dated to 26 ka bp at san carlos east falkland and with periods of cirque and valley glaciation identified in the uplands of the falkland islands the similarity between late pleistocene interstadial holocene and present day pollen assemblages and the lack of vegetation change within these periods is characteristic of most cool temperate southern ocean islands and may reflect the lack of sensitivity of the vegetation to climate change and or a lack of climate variability for the time intervals covered 1998 john wiley sons ltd

glacial history and paleoceanography of the southern yermak plateau since 132 ka bp abstract the southern yermak plateau yp is situated at the entrance to the arctic ocean in the narrow marginal ice zone miz between the polar and arctic fronts north west of svalbard a gravity core jm10 02gc has been analysed in order to reconstruct paleoceanographic conditions and the movement of the sea ice margin as well as the glacier ice conditions of the svalbard barents sea ice sheet sbis during the last interglacial glacial cycle the distribution of planktic and benthic foraminifera planktic and benthic oxygen and carbon isotopes and variations in ice rafted debris ird has been investigated the sediment core covers the time interval from the marine isotope stage mis 6 5e transition termination ii c 132 ka bp to the early holocene during termination ii tii the sbis retreated and the sea ice margin was in distal position whereas during mis 5 to mis 4 the sea ice margin was close to the core site several core intervals interpreted as representing mis 5e mis 5c mis 5a mis 3 and mis 1 were barren of calcareous microfossils whereas the intervals representing mis 4 and mis 2 were characterised by high productivity hp of planktic and benthic foraminifera these glacial hp zones were associated with the open water conditions resulting from the advection of atlantic water aw and retreat of the sea ice margin the barren zones during mis 5 mis 3 and mis 1 resulted from the proximity of the sea ice margin whereas during mis 2 the likely cause was an advance of the sbis

a review of postglacial emergence on svalbard franz josef land and novaya zemlya northern eurasia the pattern of postglacial emergence in the barents sea is pivotal to constraining the timing of deglaciation and extent and thickness of the last ice sheet in northern eurasia this review unites records of holocene relative sea level from svalbard franz josef land and novaya zemlya to better understand the geometries of past ice sheet loads emergence data from northern eurasia confine the maximum area of glacier loading to the northwestern barents sea where 100 m of emergence is measured on kongs ya deglacial unloading commenced on western and northern spitsbergen c 13 12 14 c ka ago and by c 10 5 14 ck a on eastern svalbard and more distal sites on franz josef land and novaya zemlya the marine limit phase c 13 12 14 c ka on western and northern spitsbergen is characterized by the construction of spits indicating a dominance of long shore drift over stormgenerated fetch reflecting extensive sea ice coverage of coastal areas at sites in proximity to the ice sheet margin on western and northern spitsbergen there is evidence for a transgressive regressive cycle c 6 4 14 c ka possibly reflecting back migration of displaced mantle material a modern transgression is inferred from the marine erosion of 17th century cultural features and 14 c ages of whalebone and terrestrial peat buried by modern storm gravels that place sea level at its present position by c 2 to 1 ka ago the greatest observed emergence on franz josef land occurs on bell island with a marine limit at 49 m aht formed c 10 14 c ka available emergence data since 9 ka show rising strandlines toward the southwest at b0 3 m km the northern limit of emergence on franz josef land is poorly constrained because relative sea level data is sparse north of 80 30 0 n in contrast to svalbard and franz josef land the marine limit on northern novaya zemlya is only 10 15 m above high tide and formed between 6 5 and 5 0 14 c ka when global sea level was stabilizing all sites show little apparent emergence during the past 2 ka with the youngest raised landforms at identical heights to storm beaches this minimal glacio isostatic signature on novaya zemlya and on vaygach island where deglaciation commenced 10 ka ago indicates ice sheet thicknesses of o1 5 km the spatial variation in emergence for the barents sea indicates that western and northern spitsbergen and novaya zemlya were near the reactive margin of the ice sheet and these areas sustained the briefest ice coverage 2 6 ka and were probably not in isostatic equilibrium in contrast central and eastern svalbard and southern franz josef land were beneath a substantial ice load and probably sustained this load for c 10 14 c ka and achieved isostatic equilibrium isostasy residual from an ice sheet model portrays well the general pattern of uplift and load response at the centre of ice sheets but deviates substantial at the ice sheet margin or areas covered by thin ice like novaya zemlya

oceanic and atmospheric variations during the last deglaciation in the fram strait arctic ocean a coupled high resolution organic geochemical and sedimentological study abstract from a high sedimentation rate core obtained from the yermak slope arctic ocean we deduced short term climatic fluctuations of the last deglaciation lasting from 17 000 to 9000 years bp by using a coupled organic geochemical and sedimentological approach we reconstructed near bottom current conditions and assessed their significance in relation with comparable global thermohaline circulation patterns and surface water conditions highest concentrations and fluctuations of specific marine phytoplankton biomarkers were obtained in the bolling allerod when the major deglaciation of the svalbard barents sea ice sheet sbis occurred the marine biomarker record and the sedimentological record are consistent with climate reconstructions obtained from greenland ice cores and thermohaline circulation variations however beginning with the younger dryas yd episode bottom currents decreased during this time period but surface waters remained very productive the atmospheric conditions of the western fram strait reconstructed from biomarker data and thermohaline circulation signals reconstructed from sedimentological data were decoupled in the yd maximum insolation values of solar radiation and fohn like winds enabled open water conditions and increased productivity values in the northern fram strait at least in summer

northeast atlantic sea surface circulation during the past 30 10 14c kyr b p a study was made of three cores from the faeroe shetland gateway based on planktonic foraminifera oxygen isotopes accelerator mass spectrometry 14c dates magnetic susceptibility and counts of ice rafted debris ird the data covering the period 30 10 ka show that during the last glacial maximum the arctic front occupied a position close to the faeroes allowing a persisting inflow of atlantic surface water into the faeroe shetland channel the oceanographic environment during deposition of two ird layers is influenced by atlantic surface water masses during the lower ird layer with transport of icebergs from n nw polar surface water conditions prevailed only during deposition of the upper ird layer there is no indication of surface meltwater influence in the region during the deglaciation but there is a persistent influence of atlantic surface water masses in the region thus we conclude that during almost the entire period 30 10 ka the faeroe shetland channel was a gateway for transport of atlantic surface water toward the norwegian sea

terrigenous events and climate history of the sophia basin arctic ocean periods of enhanced terrigenous input to the ocean s basins of the north atlantic have been reported for the last glacial period we present a set of new sediment cores recovered from the sophia basin north of svalbard which exhibit widespread ice rafted debris layers reflecting enhanced terrigenous input throughout the last 200 ka b p their consistent stratigraphic position sedimentological character high sedimentation rate and geochemical characteristic point to synchronously deposited layers which we name terrigenous input events ties owing to their higher densities they generate excellent reflectors for sediment penetrating acoustic devices and prominent acoustic layers in the imagery of sedimentary structures therefore ties can be used for regional acoustic stratigraphy each of the events can be linked to major glacial activity on svalbard however the early weichselian glaciation is not recorded as a tie and in agreement with other work might not have occurred on svalbard as a major glacial advance to the shelf break nonsynchronous timing of western and northern sources on svalbard points against sea level induced iceberg discharge events

arctic ocean deep sea record of northern eurasian ice sheet history the sediment composition of deep sea cores from the central arctic ocean the fram strait and the yermak plateau was analyzed for several parameters to reconstruct the history of marine paleoenvironment and terrestrial glaciation in the last 200 000 years layers with high amounts of coarse terrigenous ice rafted debris ird and often high contents of smectite were deposited during extensive glaciations in northern eurasia when ice sheets reached the northern continental margins of the barents and kara seas and discharged icebergs into the arctic ocean intercalated layers with relatively low ird and smectite contents but abundant planktic foraminifers in the coarse fraction were deposited during periods of atlantic water inflow to the arctic ocean and seasonally open waters leads in a sea ice cover with only few icebergs in the arctic ocean high ird contents in the sediments reflect the presence of ice sheets on the kara and barents seas shelves and the hinterland during the entire oxygen isotope stage 6 ca 190 130 ka in substage 5b ca 90 80 ka at the stage boundary 5 4 around 75 ka and in late stage 4 early stage 3 ca 65 50 ka these results are in excellent correlation with those from recent field work in northern scandinavia european russia siberia and on the shelves relatively low amounts of ird in central arctic ocean sediments from the late weichselian glacial maximum ca 24 18 ka correlate well with the recent reconstruction of a very limited eastern ice sheet extension during this time oxygen and carbon isotope records of planktic foraminifers from the analyzed sediment cores show a number of prominent excursions which can be interpreted as evidence for freshwater events in the arctic ocean the synchroneity of freshwater events and ird input suggests a common source strongest events were associated with deglaciations of the barents and kara seas after the ice sheets had blocked the outflow of large rivers for several millennia the outflow of freshwater from large ice dammed lakes occurred at ca 130 80 75 and 52 ka freshwater events in the central arctic ocean during the last deglaciation ca 18 ka were relatively small compared to the previous events this indicates that during most of the late weichselian glacial maximum a river outflow from northern siberia to the arctic ocean was possible atlantic water inflow to the arctic ocean and seasonally open waters in the ice leads occurred during the interglacials ofoxygen isotope stage 1 and substage 5e during several interstadials stage 3 substages 5a and 5c and to a lesser degree within stadials and glacials stages 2 4 and 6 with the exception ofthe interglacials these periods were times ofstrong ice growth on the continents as revealed by terrestrial data the coincidence suggests that open waters in the arctic ocean and the nordic seas were an important moisture source in addition to more southerly sources which fostered the growth of ice sheets on northern eurasia

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

earthquake clustering inferred from pliocene gilbert type fan deltas in the loreto basin baja california sur mexico a stacked sequence of pliocene gilbert type fan deltas in the loreto basin was shed from the footwall of the dextral normal loreto fault and deposited at the margin of a marine basin during rapid fault controlled subsidence fan delta parasequences coarsen upward from marine siltstone and sandstone at the base through sandy bottomsets and gravelly foresets to gravelly nonmarine topsets each topset unit is capped by a thin shell bed that records marine flooding of the delta plain several mechanisms may have produced repetitive vertical stacking of gilbert deltas 1 autocyclic delta lobe switching 2 eustatic sea level fluctuations 3 climatically controlled fluctuations in sediment input and 4 episodic subsidence produced by temporal clustering of earthquakes we favor hypothesis 4 for several reasons but hypotheses 2 and 3 cannot be rejected at this time earthquake clustering can readily produce episodic subsidence at spatial and temporal scales consistent with stratigraphic trends observed in the loreto basin this model is supported by comparison with paleoseismological studies that document clustering on active faults over a wide range of time scales earthquake clustering is a new concept in basin analysis that may be helpful for understanding repetitive stratigraphy in tectonically active basins

the late weichselian glaciation of the franz victoria trough northern barents sea ice sheet extent and timing high resolution seismic profiles parasound 4 khz and three sediment cores from the franz victoria trough and the adjacent continental slope were studied in order to constrain the timing and extent of the northern svalbard barents sea ice sheet during the late weichselian glaciation stacked debris flow lobes and layers of glacimarine diamicton on the lower continental slope indicate that large quantities of glacially derived sediments were deposited by the northern svalbard barents sea ice sheet directly onto the upper continental slope at approximately 23 14 c ka a grounding line advance to the shelf break is supported by the identification of diamicton interpreted as till in the seismic profile near the shelf break after several ice sheet instabilities marked by significant input of ice rafted detritus to the continental margin the disintegration of the northern svalbard barents sea ice sheet termination ia is indicated by a distinct pulse of ice rafted detritus at 15 4 14 c ka and the transition to an isotopically defined meltwater signal the drastic change in sedimentary pattern on the upper continental slope dated to about 13 4 14 c ka is interpreted as grounding line retreat from the shelf edge a further stepwise retreat of the northern svalbard barents sea ice sheet is indicated by pulses of ice rafted detritus which appear to be contemporaneous with the onset of distinct ice rafting events in adjacent areas and pulses of glacimarine sedimentation in the southwestern barents sea q 2000 elsevier science b v all rights reserved

surface water conditions and calcium carbonate preservation in the fram strait during marine isotope stage 2 28 8 15 4 kyr 1 we present a high resolution record of calcium carbonate preservation alongside the distribution pattern of planktic foraminifera from the fram strait the record covers the marine isotope stage mis 2 28 8 to 15 4 kyr including the last glacial maximum lgm and the early deglaciation in multidecadal temporal resolution the investigation is based on the distribution patterns of planktic foraminifera stable isotopes mean shell weight of neogloboquadrina pachyderma the degree of fragmentation of planktic shells caco3 content and geochemical and sedimentological data the dissolution proxies indicate long lasting periods of markedly reduced preservation of calcium carbonate at 28 8 27 2 24 1 23 2 and 16 6 15 4 kyr in addition to a number of short lasting periods 300 year during the lgm these periods are accompanied by a simultaneous and significant reduction in specimens of subpolar planktic foraminifera indicating a southward expansion of arctic surface water masses prolonged periods with high abundances of subpolar foraminiferal species and good preservation of calcium carbonate are attributed to increased influence of atlantic water masses which appears to persist throughout most of the mis 2 comparison to holocene mis 1 shell weight records shows that the preservation during mis 2 was overall better even during the events of dissolution this was probably a reflection of the low concentration of atmospheric co2 at the time

abrupt changes heinrich events in late quaternary north atlantic marine environments a history and review of data and concepts in the last several years evidence has mounted that a series of abrupt changes in sediment delivery and palaeoceanography effected the north atlantic they are recorded in a variety of proxy records but most dramatically in changes of grain size and mineralogy associated with postulated iceberg rafting events specifically heinrich h events this review paper examines the evidence for such evidence prior to the development of the heinrich event concept 1988 1992 and then examines the explosion of data and correlations that stemmed from the acceptance and use of this paradigm specific attention is focused on ideas pertaining to the cause s of glaciological mechanisms sediment delivery and sediment source and major gaps in our understanding of the underlying glaciological glacial geological and glacial marine processes are stressed abrupt changes across boundaries associated with h 2 in the labrador sea are illustrated from core hu87033 009lcf the case is made that correlations between records need to be more rigorous especially within the range of radiocarbon dating but it appears that abrupt changes in the delivery of iceberg rafted debris which characterize these intervals are multisourced it is unclear how global climate can simultaneously influence the abrupt behaviour of ice margins in different parts of the world for marine based margins changes in relative sea level are one possibility a qualitative model is presented for triggering h events which includes global changes in mass balance changes in relative sea level at ice margins due to glacial isostasy and changes in the basal thermal regime of tidewater ice streams 1998 john wiley sons ltd

new aspects of organic carbon deposition and its paleoceanographic implications along the northern barents sea margin during the last 30 000 years we studied variations in terrigenous tom and marine organic matter mom input in a sediment core on the northern barents sea margin over the last 30 ka using a multiproxy approach we reconstructed processes controlling organic carbon deposition and investigated their paleoceanographic significance in the north atlantic arctic gateways variations in paleo surface water productivity are not documented in amount and composition of organic carbon the highest level of mom was deposited during 25 23 ka as a result of scavenging on fine grained reworked and tom rich material released by the retreating svalbard barents sea ice sheet during the late weichselian a second peak of mom is preserved because of sorptive protection by detrital and terrigenous organic matter higher surface water productivity due to permanent intrusion of atlantic water and high suspension load release by melting sea ice during 15 9 11 2 ka

numerical reconstructions of the eurasian ice sheet and climate during the late weichselian abstract geological investigations undertaken through the quaternary environments of the eurasian north programme established ice sheet limits for the eurasian arctic at the last glacial maximum lgm sedimentary records of palaeo ice streams and uplift information relating to ice sheet configuration and the pattern of deglaciation ice sheet numerical modelling was used to reconstruct a history of the eurasian ice sheet compatible with these geological datasets the result was a quantitative assessment of the time dependent behaviour of the ice sheet its mass balance and climate and predictions of glaciological products including sediments icebergs and meltwater at the lgm ice cover was continuous from scandinavia to the arctic ocean margin of the barents sea to the north and the kara sea to the east in the west along the continental margin between the norwegian channel and svalbard the ice sheet was characterised by fast flowing ice streams occupying bathymetric troughs which fed large volumes of sediment to the continental margin that were deposited as a series of trough mouth fans ice streams may also have been present in bathymetric troughs to the north between svalbard and franz josef land further east however the ice sheet was thinner across the kara sea the ice thickness was predicted to be less than 300 m while on severnaya zemlya the ice cover may have been thinner at the lgm than at present it is likely that the taymyr peninsula was mainly free of ice at the lgm in the south the ice margin was located close to the shoreline of the russian mainland the climate associated with this ice sheet is maritime to the west and in stark contrast desert like in the east atmospheric general circulation modelling has revealed that such a contrast is possible under relatively warm north atlantic conditions because a circulation system develops across the kara sea isolating it from the moisture laden westerlies which are diverted to the south ice sheet decay began through enhanced iceberg calving in the deepest regions of the barents sea which caused a significant ice embayment within the bear island trough by about 12 000 years ago further iceberg calving reduced ice extent to the northern archipelagos and their surrounding shallow seas ice decay was complete by about 10 000 years ago

late pleistocene and holocene meltwater events in the western arctic ocean accelerator mass spectrometer 14 c dated stable isotope data from neogloboquadrina pachyerma in cores raised from the mendeleyev ridge and slope provide evidence for significant influx of meltwater to the western arctic ocean during the early part of marine oxygen isotope stage 1 ois 1 and during several intervals within ois 3 the strongest ois 3 meltwater event occurred before ca 45 ka conventional radiocarbon age and was probably related to the deglaciation at the beginning of ois 3 major meltwater input to the western arctic ocean during the last deglaciation coincides closely with the maximum rate of global sea level rise as determined from the barbados sea level record demonstrating a strong link between the global record and changes in the central arctic ocean ois 2 which includes the last glacial maximum is very condensed or absent in the cores abundance and 13 c values for n pachyderma in the middle part of ois 3 are similar to modern values indicating high productivity and seasonal ice free areas along the arctic margin at that time these records indicate that the arctic ocean was a source of heat and moisture to the northern polar atmosphere during parts of ois 3

paleoenvironments in the fram strait during marine isotope stages 2 6 based on planktonic paleobiological and stable isotope proxies and ice rafted debris abstract two sediment cores from the knipovich ridge in the fram strait have been studied to examine paleoceanographic and climatic changes in the polar north atlantic during the late middle and late pleistocene as inferred from the data on foraminifers nannofossils diatoms ird oxygen isotope values and ams 14 c ages the recovered deposits span the interval of mis 2 6 several beds marked by a high productivity of microplankton and often by a great ird content are recorded in mis 2 mis 5a 5c 5e and mis 6 suggesting a repeated occurrence of seasonally ice free waters and strong meridional circulation in the eastern fram strait the planktonic foraminifers globigerinoides ruber globorotalia scitula g crassaformis and pink colored globigerina rubescens exotic for this latitude were identified in three points of the section a hiatus in one of the cores studied was revealed from comparison of ird variations and the occurrence of pullenia bulloides

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

paleoceanographic evolution of the sw svalbard margin 76 n since 20 000 14c yr bp abstract two cores from the southwestern shelf and slope of storfjorden svalbard taken at 389 m and 1485 m water depth have been analyzed for benthic and planktic foraminifera oxygen isotopes and ice rafted debris the results show that over the last 20 000 yr atlantic water has been continuously present on the southwestern svalbard shelf however from 15 000 to 10 000 14c yr bp comprising the heinrich event h1 interval the bolling allerod interstades and the younger dryas stade it flowed as a subsurface water mass below a layer of polar surface water in the benthic environment the shift to interglacial conditions occurred at 10 000 14c yr bp due to the presence of a thin upper layer of polar water surface conditions remained cold until ca 9000 14c yr bp when the warm atlantic water finally appeared at the surface neither extensive sea ice cover nor large inputs of meltwater stopped the inflow of atlantic water its warm core was merely submerged below the cold polar surface water

abrupt climatic change during the last interglacial glacial cycle in the polar north atlantic abstract we have investigated five sediment cores from the margin and abyssal plain off western svalbard barents sea in the polar north atlantic we discuss the palaeoceanography and its relationship to glacial history during the last interglacial glacial cycle based on detailed stratigraphic analyses of planktic and benthic foraminiferal fauna oxygen and carbon isotopes on foraminifera ice rafted debris grains 500 m and radiocarbon dates the sediment cores combined cover the last interglacial glacial cycle including marine isotope stage mis 5 1 sedimentation rates are generally high ranging from 3 to 100 cm 1000 years atlantic water repeatedly reached the polar north atlantic during the last interglacial glacial cycle and was present for at least 50 of the total time interval periods having atlantic water advection termed hp zones hp high productivity are characterised by high planktic foraminiferal production a small increase of benthic and subpolar planktic foraminifera benthic foraminiferal and stable isotope data indicate active deep water formation during the hp zones in substage 5e there are indications of sea surface temperatures similar to those of today the major glaciations on svalbard during the last interglacial glacial cycle are related to hp zones some hp zones correspond to an early build up phase of the ice sheets peak glacials all correspond to one hp zone that subsequently is terminated by a meltwater event however periods with advection of atlantic water during mid mis 3 do not correlate to a glacial phase on svalbard but rather to the western fennoscandian ice sheet the records in the present study are correlated to the northeast atlantic the arctic ocean and to the greenland ice core record and show parallel millennial scale variability

pb isotopes and geochemical monitoring of arctic sedimentary supplies and water mass export through fram strait since the last glacial maximum 1 elemental and pb isotope measurements were performed on leachates and residues from surface sediments and two 50 cm cores mc04 and mc16 collected along a ne sw transect through fram strait geochemical and isotopic properties of residues from surface sediments define three distinct spatial domains within the strait 1 the easternmost edge of the strait 2 the eastern part of the strait off the svalbard margins and 3 the western part of the strait influenced by supplies from svalbard the nordic seas with possible contributions from northwestern siberian margins and sea ice and water outflow from the arctic respectively core mc16 in the third domain beneath the outflowing arctic waters spans the last glacial maximum present interval sediments from this core were leached to obtain detrital residues and exchangeable leachates fractions detrital supplies to core mc16 are believed to originate mainly from melting of the overlying sea ice and thus can be used to document changes in arctic sedimentary sources detrital 206pb 204pb and 208pb 206pb ratios illustrate two mixing trends trends a and b corresponding to the pre and post younger dryas yd intervals respectively these trends represent binary mixtures with a common end member canadian margins and either a siberian trend a or greenland trend b margin end member the yd is marked by an isotopic excursion toward the canadian end member suggesting a very active beaufort gyre possibly triggered by massive drainage of the laurentide ice sheet pb isotope compositions of leachates thought to represent the signature of the overlying water masses define a unique linear trend coincident with trend a this suggests that water masses acquired their signature through exchange with particulate fluxes along the canadian and siberian continental margins

last glacial benthic foraminiferal δ18o anomalies in the polar north atlantic a modern analogue evaluation modern processes are evaluated to understand the possible mechanisms behind last glacial benthic foraminiferal 18o anomalies that occurred concurrent with meltwater events in the polar north atlantic such anomalies in the nordic seas were recently interpreted to be caused by brine formation despite intensive sea ice production on circumarctic shelves modern data show that brines ejected from sea ice formation containing low 18o water do not significantly contribute to deep waters in the arctic ocean today assuming that this process was nevertheless responsible for 18o anomalies in nordic seas deep water during the last glaciation a broad shallow shelf area adjacent to the nordic seas such as the barents sea had to be seasonally free of sea ice in order to serve as an area for brine formation another process which may explain 18o depleted water at depth is found in the weddell sea today where a low 18o signal in deep waters originates from ice shelf interactions if temperature were considered the main mechanism for the low benthic 18o values an increase of 4 c must have occurred in the deep water an analogous situation with a reversed water temperature pattern due to a subsurface inflow of warm atlantic water is found today in the eastern arctic ocean and deep water warming is observed in the greenland gyre in the absence of deep convection because paleoproxy data also indicate an atlantic water inflow into the nordic seas during such benthic 18o anomalies temperature as a principal mechanism of changing 18o cannot be excluded

arctic ocean during the last glacial maximum atlantic and polar domains of surface water mass distribution and ice cover on the basis of 52 sediment cores analyzed and dated at high resolution the paleoceanography and climate of the last glacial maximum lgm were reconstructed in detail for the fram strait and the eastern and central arctic ocean sediment composition and stable isotope data suggest three distinct paleoenvironments 1 a productive region in the eastern to central fram strait and along the northern barents sea continental margin characterized by atlantic water advection frequent open water conditions and occasional local meltwater supply and iceberg calving from the barents sea ice sheet 2 an intermediate region in the southwestern eurasian basin up to 84 85 n and the western fram strait characterized by subsurface atlantic water advection and recirculation a moderately high planktic productivity and a perennial ice cover that breaks up only occasionally and 3 a central arctic region north of 85 n in the eurasian basin characterized by a low salinity surface water layer and a thick ice cover that strongly reduces bioproduction and bulk sedimentation rates although the total inflow of atlantic water into the arctic ocean may have been reduced during the lgm its impact on ice coverage and halocline structure in the fram strait and southwestern eurasian basin was strong

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints