postglacial emergence and distribution of late weichselian ice sheet loads in the northern barents and kara seas russia reconstructions of late weichselian glacier coverage on the continental shelves of the russian arctic range from a large ice sheet terminating in northern siberia to isolated ice caps restricted to arctic archipelagos this disparity in glacier reconstructions reflects the lack of chronological control on glacial and deglacial landforms we present new holocene relative sea level data from franz josef land and northern novaya zemlya russia that place the thickest glacier loads in the northern barents sea and not over novaya zemlya radiocarbon ages from shelf and terrestrial areas at the former ice sheet margin support deglaciation of the northern barents sea between 13 0 and 10 3 ka considerably later than inferred from isotopic records for the arctic ocean this analysis indicates that the barents sea ice sheet was a dominant sea level reservoir in northern eurasia and that glacier loading of novaya zemlya was comparatively limited during the last glaciation

past ice sheet flow east of svalbard inferred from streamlined subglacial landforms the pattern of late weichselian ca 20 ka ice flow in the northern barents sea is not well known due mainly to a lack of marine data east of svalbard several years with little summer sea ice have allowed acquisition of swath bathymetric imagery of well preserved subglacial landforms characterizing late weichselian ice flow directions over 150 000 km2 of the northwestern barents sea we show that a major ice dome was located on easternmost spitsbergen or southern hinlopen strait at least 500 km west of its previously inferred position in the northern barents sea this dome controlled the regional flow pattern ice flowed eastward around kong karls land into franz victoria trough and north through hinlopen strait an ice dome west of kong karls land is required to explain the observed ice flow pattern but does not preclude an additional ice dome to the southeast discrepancies with earlier ice sheet reconstructions reflect the lack of previous seafloor observations with evidence limited mainly to past ice loading and postglacial rebound the new pattern of ice flow directions shows predominantly eastward rather than northward flow with franz victoria trough a major drainage pathway with a full glacial balance flux of 40 km3 yr 1

impact of eastern arctic shelf waters on the nansen basin intermediate layers the eurasian shelves supply water to the nansen basin intermediate layers in two ways as buoyancy driven plumes of dense winter water and as permanent inflow of the barents sea branch of atlantic water while the plumes are local and seasonal phenomena the barents sea flow is part of the large scale circulation both interact with atlantic water which enters the arctic ocean through fram strait and moves as a subsurface boundary current eastward along the continental slope during the polarstern cruise ark ix 4 in summer 1993 the fram strait branch was observed as a narrow core within tens of kilometers of the barents sea shelf edge here several patches of cold low salinity water spread across the slope down to about 500 m depth their origin is assumed to be the northern barents sea they mix with the warm saline fram strait branch water fsbw so that the core properties of the latter become modified downstream in the eastern nansen basin the fram strait branch is displaced toward the inner basin by inflow of the barents sea branch of atlantic water bsbw this inflow appears as a broad 200 km wedge extending from 200 to 1300 m depth bsbw is colder and less saline than water of the fram strait branch and it is less dense and less stratified than the ambient water both branches appear to undergo vigorous mixing while spreading eastward so that any eastward continuation of the boundary flow transports about 50 bsbw and 50 fsbw above 600 m and about 80 bsbw and 20 fsbw below that level toward the canadian basin according to available observations the barents and kara seas are the only source areas for shelf waters ventilating the nansen basin below the halocline and these waters constitute a freshwater input rather than a salt input winter shelf water from the laptev sea cannot contribute to layers deeper than the upper halocline

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

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

late quaternary sediment yield from the high arctic svalbard area late quaternary sediment yields from the isfjorden drainage area 7327 km 2 a high arctic region on svalbard characterized by an alpine landscape have been reconstructed by using seismic stratigraphy supported by sediment core analysis the sediments that accumulated in the fjord during and since deglaciation can be divided into three stratigraphic units the volumes of these units were determined and converted into sediment yield rates averaged over the drainage basin during deglaciation 13 to 10 ka the sediment yield was sim 860 tons t cdot km 2 cdot yr 1 in the early holocene it decreased to 190 t cdot km 2 cdot yr 1 and then increased to 390 t cdot km 2 cdot yr 1 during the late holocene little ice age when normalized to the approximate glacierized area these rates correspond to a sediment yield of sim 800 t cdot km 2 cdot yr 1 sediment yield from non glacierized parts of the drainage is estimated to be 35 t cdot km 2 cdot yr

deglacial warming of the northeastern atlantic ocean correlation with the paleoclimatic evolution of the european continent abstract isotopic micropaleontologic and pollen analyses of deep sea cores from the bay of biscay and the northeastern atlantic ocean show that the deglacial warming of this oceanic area was closely correlated with the paleoclimatic evolution of the adjacent european continent temperatures were at least as warm as those of today in the bay of biscay between 13 300 and 11 000 b p coinciding with the combined bolling allerod warm continental events a major spread of polar water occurred between 11 000 and 10 000 b p during this event which coincides with the younger dryas continental cold event marine temperatures were almost as low as those of the last glacial maximum the final deglacial warming of the norteastern atlatntic ocean occurred during the following 3000 yr

effects of ice coverage and ice rafted material on sedimentation in the fram strait as little is known about pelagic sedimentation processes in arctic environments1 the interpretation of biological and chemical processes as well as the reconstruction of ancient conditions including those in the glacial north atlantic is difficult here we provide sediment trap results which show that the position of the sea ice boundary significantly influences the particle flux the seasonal variability of the particle flux differed markedly in the various sediment trap sites in fram strait depending on the behaviour of the sea ice under complete ice cover sedimentation is very low whereas maximum sedimentation is found at the ice margin the highest particle flux observed showing a large lithogenic component was observed at the ice edge where the water was warmer 2 c we find that high biogenic opal fluxes are characteristic of the summer ice margin indicating that the sedimentary record of opal fluxes may allow the position of ice margins in the past to be reconstructed

moisture supply for northern ice sheet growth during the last glacial maximum during the last ice age the barents sea ice sheet began to grow 22 kyr ago1 only 8 kyr before it began to disintegrate2 this implies that the ice must have grown very rapidly from the coast to the edge of the continental shelf such rapid growth of a large ice sheet requires significant amounts of moisture3 but the origin of this moisture has been unclear particularly as the climap climate reconstruction suggests4 5 that the greenland iceland norwegian gin seas were perennially ice covered during this period here we present data from deep sea sediment cores from the fram strait which suggest that relatively warm water from the north atlantic ocean was advected into the gin seas in two short term events 27 22 5 and 19 5 14 5 kyr ago we suggest that the resulting seasonally ice free waters were an important regional moisture source for the barents sea ice sheet and that the gin seas played a much more active role in climate during the last glaciation than has previously been supposed

late quaternary stratigraphy and sedimentology of orphan basin implications for meltwater dispersal in the southern labrador sea abstract orphan basin is a deep water basin on the continental margin off newfoundland which throughout the late quaternary received proglacial sediment from local ice that crossed the continental shelf sediment from more distant sources was transported southward in the labrador current as proglacial plumes and in icebergs five sedimentary facies related to glacial processes are distinguished in cores recovered from orphan basin hemipelagic sediment nepheloid layer deposits layered mud beds rich in ice rafted detritus ird sand and mud turbidites and glaciogenic debris flow deposits ird rich beds correspond to periods of intensified iceberg calving and layered mud turbidites and glaciogenic debris flow deposits with glacial meltwater discharge in the late wisconsinan eight periods of meltwater discharge and iceberg calving from the newfoundland ice sheet are interpreted from the sediment facies in orphan basin these discharges coincide with the terminations of the colder periods of the d o cycles recorded in greenland ice cores the oldest minor meltwater event 27 5 28 5 cal ka corresponds to the first late wisconsinan ice advance across the grand banks and ne newfoundland shelf the following three meltwater discharges 23 23 5 23 8 24 5 and 25 27 cal ka deposited sand turbidites and glaciogenic debris flow deposits seaward of trinity trough which was occupied by an ice stream at this time and mud turbidites in the southern part of the basin derived from a mid shelf ice margin on the grand banks four periods of meltwater discharge occurred during the deglaciation and are centered at 15 18 5 19 75 and 20 75 cal ka the youngest is correlated to heinrich event 1 in the literature the 18 5 and 20 75 cal ka events have been recorded in multiple glacial settings in the north atlantic and therefore are interpreted as large scale events of meltwater discharge and iceberg calving but in orphan basin the 19 75 cal ka event is also of similar scale

retreat patterns and dynamics of the sentralbankrenna glacial system central barents sea accepted manuscript version published version available at https doi org 10 1016 j quascirev 2017 06 004 accepted manuscript version licensed cc by nc nd 4 0

two step deglaciation of the southeastern barents sea marine geologic evidence from the western barents sea shelf leaves little doubt that theareawascoveredbygroundediceduringthelastglaciation butthepatternandtiming of the subsequent deglaciation were not well determined here we reconstruct the timing and mechanism of ice sheet retreat as constrained by seismic stratigraphy and lithostratigraphy and accelerator mass spectrometer 14 c dating of foraminifera and mollusc shellsinsedimentboringsfromthesoutheasternbarentssea 1000kmfromthewestern shelf edge and former ice sheet margin the deposition of ice proximal glaciomarine sediments upon till began at or shortly before 12 7 ka indicating that the ice sheet retreat whichmostlikelycommencedalongthewesternmarginofthebarentsseashelfat15 14 5 ka reached the southeastern part of the shelf in 2 ka the subsequent accumulation of glaciomarinesedimentstookplaceintwodistinctpulses 12 7 12 1kaand 10 5 9 4ka separatedbyanintervalofnondepositionlasting 1 5ka thetwopulsesofsedimentation were coeval with periods of increasing surface water and air temperatures in the northern atlanticregionandacceleratedeustaticsea levelrise suggestingthattheremainingretreat of the barents shelf ice sheet was paced by these factors

ice sheet variability around the north atlantic ocean during the last deglaciation millennial scale variability in the flux of ice rafted detritus to north atlantic sediments during the last glacial period has been interpreted to reflect a climate forced increase in the discharge of icebergs from ice sheet margins surrounding the northern north atlantic ocean 1 but the relationship between ice sheet variability and climate change is not clear as both the sources of ice rafted detritus and the ice marginal processes are varied and complex 2 4 terrestrial records are helpful in unravelling this complexity because they can demonstrate the scale of ice sheet oscillations and whether the ice sheet or sector was advancing or retreating with respect to climate change here we constrain the age and anatomy of a prominent readvance of the british ice sheet in the northern irish sea region at similar to 14 14 c kyr bp similar to 16 4 calendar kyr bp the analysis indicates that the british ice sheet participated in an iceberg discharge episode known as heinrich event 1 comparison with other terrestrial and marine ice sheet records suggests that the dynamic collapse of the laurentide ice sheet beginning at 14 6 15 0 c 14 kyr bp1 4 similar to 17 2 17 6 calendar kyr bp 5 initiated varied responses from other ice sheet margins around the northern north atlantic region these observations support the argument that the release of icebergs and meltwater during heinrich event 1 disrupted the north atlantic thermohaline circulation 6 8 leading to a delay or reversal of deglaciation of the northern hemisphere and at least as far south as 40 degrees s for two to three thousand years 5 9 10 suggesting a climate forcing and response similar to that of the ensuing younger dryas cold snap 11 12

late weichselian ice sheets in arctic and pacific siberia abstract interpretation of space images coupled with field data on glacial geomorphology and glacial geology of northern eurasia have provided compelling evidence for a continuous late weichselian ice sheet covering the entire arctic margin of the continent in addition to the scandinavian ice sheet three ice sheets of the same order the karan east siberian and beringian are identified within the major eurasian ice sheet also there is evidence and other considerations suggesting a former ice sheet in the sea of okhotsk ice spreading centers of the ice sheets were situated on the continental shelves off the siberian coasts thus we can term the ice sheets siberian so far the conventional stratigraphic approach to the problem of siberian glaciation has proven fruitless and yielded nothing but uncertainty while geomorphological studies have discovered a wealth of glacial landforms in arctic siberia it was these landforms and their spacing that made the existence of former siberian ice sheets evident the east siberian ice sheet rested on the shelves of the eastern laptev and east siberian seas and its flow was directed radially including up the yana and indigirka rivers the beringian ice sheet was grounded on the chukchi bering and beaufort sea shelves overriding the chukchi and seward peninsulas from the north and flowing through the bering strait it was continued by a thick floating ice shelf buttressed by the submarine aleutian commander ridge the okhotsk ice sheet was grounded on the okhotsk shelf specific gemorphic signatures of marine ice sheets the glacially cut corners have been identified on all promontories jutting out into the bering and okhotsk seas the beringian and okhotsk ice sheets are consistent with the results of deep sea drilling in the adjacent north pacific during leg 145 of d v joides resolution

glaciomarine sedimentation in epicontinental seas exemplified by the northern barents sea abstract sediments on high arctic shelves result from modern processes and the effect of former glaciations based on data from the northern barents sea an area with input from large and numerous surging glaciers we define two principal zones with different environmental regimes and corresponding sedimentary facies 1 a glacier proximal zone influenced by grounding line processes and the immediately adjacent areas affected by glacial sediment input and 2 a glacier distal sea ice and current controlled zone which also includes a wide sediment starved region dominated by biogenic carbonate accumulation characteristic of the glacier proximal zone are glacial surges which affect sedimentation rates and leave a diagnostic pattern of sea floor morphologies extensive ice gouging causes a homogeneous sediment texture in the glacier distal zone fine grained mud supplied from sea ice and infrequent coarser material deposited from icebergs is reworked by modern oceanographic processes on shallow banks in 30 50 m of water carbonates accumulate from a prolific bottom fauna formed in response to extensive reworking and nutrient supply

migration and stratigraphic fill of an underfilled foreland basin middle late cenomanian belle fourche formation in southern alberta canada abstract the geometry of a foreland basin is mainly a product of a complex dynamic balance between the orogenic loading erosion and sedimentation and lithospheric flexural response to improve our understanding of the relationships between these processes and the foreland basin stratigraphy a detailed stratigraphic and sedimentologic study of the middle late cenomanian belle fourche formation in the subsurface of southern alberta is presented in this paper the middle cenomanian lower belle fourche formation and the late cenomanian upper belle fourche formation were deposited in underfilled conditions showing prominent forebulge zones it is demonstrated that during the late cenomanian with the cratonward migration of the uplifting forebulge zones the axes of backbulge zones also migrated cratonwards and a wide uplifted forebulge zone was formed during the last stage of the underfilled condition the foreland basin had a relatively flat topography and fine sands were deposited along the flank of the uplifting forebulge a qualitative model for the migration and stratigraphic fill of an underfilled foreland basin is proposed this model provides a qualitative pattern of the cratonward migration of the forebulge zone and backbulge zone within a several million year tectonically driven cycle it is suggested that during the early underfilled period the basin geometry is mainly controlled by the orogenic loading and a prominent forebulge zone with an approximately fixed location is formed during the late underfilled period the basin geometry is mainly controlled by the sediment loading and the forebulge zone move very fast along with the rapid cratonward shift of the sediment loading center over a longer time period and between different tectonically driven cycles along with the cratonward propagation of the thrusting wedge the orogenic loading plays a more important role than the sediment loading for the migration of the forebulge zone

late quaternary sedimentation and glacial history of the western svalbard continental margin abstract glacigenic sediments recovered in shallow cores from the western svalbard continental slope are subdivided into five facies associations based on grain size sedimentary structure mineralogy petrography and geochemistry two diamicton facies are recognised one of which is interpreted as hemipelagic mud with variable amounts of ice rafted debris ird and the other as a product of mass movement the diamictons are associated with melting of icebergs during glacial melt events and debris flow deposition on the submarine fans during peak glaciation respectively laminated to layered mud and turbidites seem to be closely related to eustatic fall in sea level and erosion of banks located on the continental shelf resulting in accumulation of fine grained organic rich deposits and thin silt and sand layers on the continental slope middle weichselian was characterised by several phases of extensive iceberg production and input of ird the first phase 60 55 ka is correlated with a glacier advance on svalbard but the following phases 54 44 ka can not be correlated with glacier advances on land this demonstrates that there may have been more glaciations than recorded on svalbard and that ice sheets at high northern latitudes fluctuated more frequently than previously assumed the composition of the ird deposited after 54 ka suggests that the ice sheets during these advances were located in the eastern svalbard barents sea area the late weichselian growth of the svalbard barents sea ice sheet occurred probably in two steps nucleation of a continental based ice sheet between 27 and 22 5 ka followed by a rapid advance to the shelf edge when the ice margin reached the soft clay rich sediments on the continental shelf eustatic lowering of the sea level during the initial phase led to bank exposure and erosion bringing large quantities of fine grained organic rich sediments to the deep sea during peak glaciation glaciers provided a localised supply of sediments to the shelf troughs and the upper slope which were redistributed by debris flows the marine based svalbard barents sea ice sheet started to retreat around 14 5 ka through massive iceberg discharge the retreat was interrupted by a short lived advance accompanied by erosion of the shelf banks and redistribution of organic rich sediments to the continental slope the final ice recession started around 12 ka and ended close to 9 ka when the fjords of svalbard were essentially ice free large amounts of meltwater released during the removal of the svalbard barents sea ice sheet cooled down the surface waters of the norwegian greenland sea and formed a widespread sea ice cover between 12 and 8 ka input of terrigenous material was greatly reduced during the early part of holocene the present interglacial is characterised by erosion of the shelf and upper slope by bottom currents leaving a prominent lag deposit

the growth and decay of the late weichselian ice sheet in western svalbard and adjacent areas based on provenance studies of marine sediments the history of the late weichselian northwestern barents shelf including western svalbard has been investigated by provenance sedimentologist studies of five cores from the continental shelf and slope west of svalbard the chronostratigraphy of the cores is based on ams 14c dates and oxygen isotope analyses interpretations of the cores suggest that the ice sheets of western svalbard and northwestern barents sea experienced advances and retreats in two steps the first significant ice advance beyond the present coastline occurred ca 22 000 14c yr b p and was followed by an ice advance to the shelf edge ca 18 000 14c yr b p ice recession from the outer shelf and the southwestern barents sea began 14 800 14c yr b p and was followed by a second ice recession between 13 000 and 12 000 14 c yr b p during which ice withdrew from the inner shelf a minor readvance of the ice sheet on the shelf west of svalbard occurred close to 12 400 14c yr b p the first deglaciation event was associated with release of icebergs containing ice rafted detritus while the later episode also included significant amounts of meltwater and fine grained sediment

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

detrital carbonate rich sediments northwestern labrador sea implications for ice sheet dynamics and iceberg rafting heinrich events in the north atlantic much of the bed of the central and eastern sectors of the laurentide ice sheet was underlain by paleozoic carbonates we propose that pulses of detrital carbonate rich sediments in two cores from the northwestern labrador sea reflect episodes when an ice stream from the hudson strait extended to the shelf break and delivered sediment onto the slope and deep sea plain atomic mass spectroscopy 14 c dating of planktonic foraminifera in cores hu75 009 iv 55 2 4 km water depth and hu87 033 009 1 4 km water depth and 150 km north northwest indicates that the youngest event occurred between ca 14 and 15 ka and another occurred between 19 and 21 ka the two carbonate intervals in northwestern labrador sea cores are coeval with heinrich events 1 and 2 in the eastern north atlantic lat 45 50 n long 20 w where they are associated with an increase in lithic fragments and a drastic reduction in the numbers of foraminifera these changes have been linked with the massive production of icebergs associated with ice sheet surges our evidence indicates that heinrich events 1 and 2 are associated with the dynamics of the hudson strait ice stream and denote considerable glaciological instability

the relative importance of gravity induced versus current controlled sedimentation during the quaternary along the mideast u s outer continental margin revealed by 3 5 khz echo character abstract a detailed echo character map based on more than 50 000 km of 3 5 khz echograms reveals the relative importance of contour currents turbidity currents and mass wasting processes for the upper 50 100 m of sea floor sediments along the u s continental margin between southern georges bank and cape hatteras nineteen individual echo types are mapped and interpreted as deposits produced either by current controlled or gravity induced processes based on echo type distribution analysis of selected sediment core samples and the published results of other workers turbidity currents and mass wasting have apparently been the primary depositional agents throughout 60 of the region in contrast contour currents alone appear to have influenced only 10 of the region however combined processes i e non separable interaction between downslope and parallel to contour processes have influenced an estimated 25 of the margin the remaining 5 of the study area constitutes the outermost continental shelf echo types here reflect the influence of fluvial deltaic and shallow marine sedimentary processes changes in the relative distributions of various echo types with sea floor depth indicate that the dominant sedimentary processes change downslope and are significantly different within each physiographic province deposits formed by mass wasting dominate the continental slope where 50 of the sea floor is eroded and gullied by slides slumps and the heads of debris flows deposits developed under the influence of combined processes are most wide spread on the upper continental rise and cover 40 of the sea floor primarily in the form of deep sea channel levees modified by contour currents on the lower continental rise turbidites form more than 50 of the sea floor deposits the downslope deposits turbidity currents slumps debris flows etc were emplaced primarily during the pleistocene glacioeustatic sea level lowering moved beaches and rivers across the exposed continental shelf to the shelf edge where massive fluxes of terrigenous sediment could be delivered to the continental slope and rise by turbidity currents significant amounts of this sediment were transported through submarine canyons and leveed deep sea channels to the lower continental rise and formed the lower continental rise terrace a flat turbidite basin ponded behind the hatteras outer ridge southwest of the wilmington channel this glacially derived influx was diminished however depositional patterns indicate that downslope processes continued to be dominant at least as far south as cape hatteras where rapid deposition on the continental slope and uppermost continental rise created instabilities slope failure produced slumps slides and debris flows and provided an additional volumetrically important redistribution of sediment downslope the influence of contour currents is clearly observed only in those areas topographically shielded from the masking effects of downslope processes in particular along the seaward side of the buried chesapeake drift and the hatteras outer ridge

late weichselian glaciation of the russian high arctic a numerical ice sheet model was used to reconstruct the late weichselian glaciation of the eurasian high arctic between franz josef land and severnaya zemlya an ice sheet was developed over the entire eurasian high arctic so that ice flow from the central barents and kara seas toward the northern russian arctic could be accounted for an inverse approach to modeling was utilized where ice sheet results were forced to be compatible with geological information indicating ice free conditions over the taymyr peninsula during the late weichselian the model indicates complete glaciation of the barents and kara seas and predicts a maximum sized ice sheet for the late weichselian russian high arctic in this scenario full glacial conditions are characterized by a 1500 m thick ice mass over the barents sea from which ice flowed to the north and west within several bathymetric troughs as large ice streams in contrast to this reconstruction a minimum model of glaciation involves restricted glaciation in the kara sea where the ice thickness is only 300 m in the south and which is free of ice in the north across severnaya zemlya our maximum reconstruction is compatible with geological information that indicates complete glaciation of the barents sea however geological data from severnaya zemlya suggest our minimum model is more relevant further east this in turn implies a strong paleoclimatic gradient to colder and drier conditions eastward across the eurasian arctic during the late weichselian

late quaternary stage 2 and 3 meltwater and heinrich events northwest labrador sea two major meltwater events are documented in cores from the nw labrador sea one occurred ca 20 000 14c yr b p in association with deposition of a major detrital carbonate unit both prior to and after this event 18o values of near surface planktonic foraminifera were 4 5 indicating fully enriched glacial values a younger event ca 14 000 14 c yr b p is characterized by a dramatic change in 18o from 4 5 to 2 0 and coincided with the retreat of ice from the outer se baffin shelf possibly into hudson strait these meltwater events coincide with heinrich h layers 1 and 2 from north atlantic sediments the 14 000 14c yr b p meltwater event indicates that the eastern margin of the laurentide ice sheet also underwent rapid retreat at approximately the same time as other ice sheet margins around the ne north atlantic a third major detrital carbonate event at the base of hu87 033 009 possibly correlative with heinrich layer 3 occurred ca 33 960 675 14 c yr b p however this is older than the accepted date for h 3 of 27 000 14c yr b p and may be h 4

radiocarbon content of pre bomb marine mollusks and variations in the 14c reservoir age for coastal areas of the barents and kara seas russia fourteen mollusks collected alive between 1900 and 1945 from the russian barents and kara seas were analyzed by ams 14c dating to evaluate variations in the 14c marine reservoir for arctic coastal sites which is important for correcting ages in paleoenvironmental time series and advancing understanding of the exchange of carbon the 14c ages on the mollusks reveal a range of marine reservoir values r t from 159 14c yr to 764 14c yr the oldest r t values of 764 to 620 14c yr are for the bivalve portlandia arctica which often inhabit cold and low salinity waters and muddy substrates the depleted 14c content for this bivalve reflects possibly the incorporation of old carbon from freshwater inputs and or the consumption of old organic matter from the underlying sediments and pore waters other mollusks with sessile habitats and pelagic food sources gave significantly lower r t values between 159 and 344 14c yr the youngest r t values indicate enrichment in 14c and may partially reflect enhanced transfer of 14c enriched co2 from the atmosphere to the ocean surface with wind generated wave agitation this study underscores that a variety of processes can lead to variable 14c depletion and enrichment of surface waters yielding a ca 600 year age span for contemporaneous arctic mollusks there may be added uncertainty in the 14c reservoir correction for deposit feeder species such as portlandia sp and perhaps for certain benthic foraminifera e g nonion labradoricum because these taxa often incorporate old organic matter from the substrate a reservoir correction of 700 years may be more appropriate for infaunal deposit eater species particularly in glacier dominated environments mollusks and foraminifera with sessile habits and pelagic food sources should be selected preferentially for 14c dating because their shells may more closely reflect the 14c content of the global ocean mixed layer

late weichselian deglacial history of the svyataya saint anna trough northern kara sea arctic russia abstract marine sediment core and seismic records from the svyataya saint anna trough provide new insight into the distribution of late weichselian glacial coverage ice retreat pattern and post glacial environments in the northern barents and kara seas these records indicate that the saint anna trough was filled with grounded glacier ice which likely reached the shelf edge during the late weichselian maximum several radiocarbon dates suggest early deglaciation of the deep axial part of the trough prior to 13 3 ka two sandy beds in the deglacial section of the cores imply distinct pulses of iceberg calving and or melting which were probably associated with stepwise retreat of the ice margin morainic ridges and glacial sole markings in the western part of the saint anna trough indicate that the northern central barents sea was a site of a large ice mass during deglaciation a smaller ice cap is inferred for the northern kara plateau at later stages ice retreat on the western flank of the trough was directed towards franz josef land and was presumably facilitated by a separation of the barents sea and novaya zemlya ice domes deglaciation of the saint anna trough was completed by ca 10 ka high post glacial sediment fluxes between 10 and 8 ka were probably related to sea floor coastal erosion and or siberian river discharge during the rising sea level

late glacial and holocene paleoceanography and sedimentary environments in the st anna trough eurasian arctic ocean margin based on stratigraphical analysis of twelve sediment cores from the saint anna trough we reconstruct changes in paleoceanography and sedimentary environment during the last deglaciation and the holocene detailed analysis of benthic and planktic foraminiferal fauna stable oxygen and carbon isotope analysis lithostratigraphy and radiocarbon dates are used to reconstruct the following evolution after the deglaciation of the saint anna trough 13 300 yr b p until 9500 yr b p the environment was mainly characterised by low biogenic production carbonate dissolution and deposition of proximal to distal glaciomarine sediments intervals with high abundance of the benthic foraminifer cassidulina teretis may indicate influx of atlantic water at bottom the transition into the present interglacial started at 9500 yr b p reflected by increased production of foraminifera and bivalves after 8000 yr b p there was a marked drop in planktic 18o followed by a rise in planktic foraminifera and subsequently an increase of c teretis these paleoceanographic changes reflect increased heat transport into the area and are coupled to changes in nordic seas the early holocene warming of the saint anna trough were delayed by ca 2000 years relative to the northeast nordic seas early holocene sedimentation rates were relatively high 100 cm 1000 yr declining drastically after 8000 yr b p 50 cm 1000 yr this was presumably caused by reduction in winnowing and or riverine input

the last glacial maximum of svalbard and the barents sea area ice sheet extent and configuration abstract the timing extent and configuration of the late weichselian barents ice sheet has been debated for several decades this debate has arisen largely because of the limited or conflicting field evidence on which most models have been based in particular reconstruction of the marine parts of the former barents ice sheet has been controversial this paper aims to review the geological observations and interpretations regarding the size and timing of the late weichselian ice sheet combined with numerical modelling of its formation in order to produce a reconstruction of ice sheet extent and behaviour sub glacial till with overlying glacimarine deposits dated to the late weichselian is found over most of the barents sea floor and the continental shelf west of svalbard glacially induced debris flow deposits on the large bjonoya and isfjorden trough mouth fans strongly support the idea of ice sheet extension to the shelf edge during maximum glaciation isobase maps show a centre of post glacial uplift in the north central barents sea and glaciological and isostatic modelling suggest that the ice sheet was 2000 3000 m thick in this area the ice sheet was confluent with ice over the kara sea but the interaction between the barents and kara ice sheets is not yet fully understood the deglaciation of the barents ice sheet started ca 15 ka probably by calving within the deeper troughs by 12 ka most of the central barents sea was ice free and ice remained over the svalbard franz josef land and novaja zemlya archipelagos and adjacent shallow shelf areas the coasts and fjords of these islands were ice free by 10 ka

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

glacimarine sedimentary processes and facies on the polar north atlantic margins abstract major contrasts in the glaciological oceanic and atmospheric parameters affecting the polar north atlantic both over space between its eastern and western margins and through time from full glacial to interglacial conditions have lead to the deposition of a wide variety of sedimentary facies in these ice influenced seas the dynamics of the glaciers and ice sheets on the hinterlands surrounding the polar north atlantic have exterted a major influence on the processes rates and patterns of sedimentation on the continental margins of the norwegian and greenland seas over the late cenozoic the western margin is influenced by the cold east greenland current and the svalbard margin by the northernmost extent of the warm north atlantic drift and the passage of relatively warm cyclonic air masses in the fjords of spitsbergen and the northwestern barents sea glacial meltwater is dominant in delivering sediments in the fjords of east greenland the large numbers of icebergs produced from fast flowing outlets of the greenland ice sheet play a more significant role in sedimentation during full glacials sediments are delivered to the shelf break from fast flowing ice streams which drain huge basins within the parent ice sheet large prograding fans located on the continental slope offshore of these ice streams are made up of stacked debris flows large scale mass failures turbidity currents and gas escape structures also rework debris in continental slope and shelf settings even during interglacials both the margins and the deep ocean basins beyond them retain a glacimarine overprint derived from debris in far travelled icebergs and sea ice under full glacial conditions the glacier influence is correspondingly stronger and this is reflected in the glacial and glacimarine facies deposited at these times

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

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

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

the barents sea ice sheet a model of its growth and decay during the last ice maximum on the basis of geomorphological and sedimentological data we believe that the entire barents sea was covered by grounded ice during the last glacial maximum 14c dates on shells embedded in tills suggest marine conditions in the barents sea as late as 22 ka bp and models of the deglaciation history based on uplift data from the northern norwegian coast suggest that significant parts of the barents sea ice sheet calved off as early as 15 ka bp the growth of the ice sheet is related to glacioeustatic fall and the exposure of shallow banks in the central barents sea where ice caps may develop and expand to finally coalesce with the expanding ice masses from svalbard and fennoscandia the outlined model for growth and decay of the barents sea ice sheet suggests a system which developed and existed under periods of maximum climatic deterioration and where its growth and decay were strongly related to the fall and rise of sea level

neogloboquadrina pachyderma sinistral coiling as paleoceanographic tracers in polar oceans evidence from northeast water polynya plankton tows sediment traps and surface sediments the abundance and chemistry of the planktonic foraminifera neogloboquadrina pachyderma sinistral coiling have long been used as tools for monitoring polar surface ocean changes and for correlating these changes to atmospheric and thermohaline circulation fluctuations however due to its remote habitat very little is known about how modern n pachyderma s respond to changing environmental conditions in the polar seas modern samples of n pachyderma s from the northeast water polynya provide a means for studying how environmental conditions affect the vertical distribution and chemistry of this species highest abundances of n pachyderma s were associated with the chlorophyll maximum in the surface 20 80 m where they are exploiting their primary food source evidence suggests that the addition of a calcite crust modifies the calcite tests of some n pachyderma s between 50 and 200 m increasing shell density and modifying shell chemistry the shell mass of encrusted forms is 3 4 times greater than the nonencrusted forms between 50 and 200 m the oxygen isotope composition of n pachyderma s shells increase by 1 5 in response to local water column gradients the 13c values of n pachyderma s are basically invariant with depth in this region are consistently 1 0 depleted in comparison with the 13c for equilibrium calcite and remain basically constant during the shell thickening process mass balance calculations suggest that encrustation occurs at all depths but abundance counts suggest that the process occurs mostly at the depth of the main pycnocline sediment fluxes of n pachyderma s occur during a 2 week bloom event and decrease to almost zero below complete ice cover the decoupling of the processes controlling abundances and shell chemistry explain the discrepancies between transfer function and isotopically derived paleotemperature estimates of surface conditions in some oceanic settings the ability of 18o to record surface ocean conditions will depend on vertical water column gradients as evidenced by the differences in core top calibrations between the north and south atlantic

numerical modeling of the late weichselian svalbard barents sea ice sheet abstract previous reconstructions of the ice cover of the svalbard barents sea region during the late weichselian have ranged from small ice masses on svalbard to complete inundation of the barents shelf region by an ice sheet several kilometers thick we have used a time dependent finite difference numerical model to undertake a new glaciological reconstruction for the svalbard barents sea ice sheet over the last 30 000 yr the numerical model requires environmental forcing functions in the form of air temperature and precipitation and their behavior with respect to altitude together with sea level change and an iceberg calving relation ice buildup on svalbard is calculated to have begun 28 000 yr ago and maximum dimensions were reached by 20 000 yr ago covering svalbard and the northwestern barents sea with a center of mass 1 3 km thick around eastern svalbard decay was complete by about 10 000 yr ago the margin of the modeled ice sheet at its maximum is in good agreement with observed sea floor morphological features but there are discrepancies in timing between the modeled ice sheet decay and i a dated meltwater spike in fram strait and ii the observed rebound curves for svalbard an inverse approach was used to predict ice sheet decay and it was found that increasing the rate of iceberg calving within the model produces a deglaciation some 2000 yr earlier which is compatible with these two independent datasets the reconstruction is also compatible with geological evidence on the isostatic response of bjornoya close to the southern limit of the ice sheet and seismically observed deposits interpreted to be ice proximal facies located in the northwestern barents sea our time dependent model reconstructions of the svalbard barents sea ice sheet indicate ice cover over only the northwestern barents sea during the late weichselian but this does not preclude the presence of ice derived from fennoscandia and the kara sea region elsewhere in the barents sea

the north atlantic atmosphere sea surface 14c gradient during the younger dryas climatic event abstract we attempt to quantify the 14c difference between the atmosphere and the north atlantic surface during a prominent climatic period of the last deglaciation the younger dryas event yd our working hypothesis is that the north atlantic may have experienced a measurable change in 14c reservoir age due to large changes of the polar front position and variations in the mode and rate of north atlantic deep water nadw production we dated contemporaneous samples of terrestrial plant remains and sea surface carbonates in order to evaluate the past atmosphere sea surface 14c gradient we selected terrestrial vegetal macrofossils and planktonic foraminifera neogloboquadrina pachyderma left coiling mixed with the same volcanic tephra the vedde ash bed which occurred during the yd and which can be recognized in north european lake sediments and north atlantic deep sea sediments based on ams ages from two norwegian sites we obtained about 10 300 yr bp for the atmospheric 14c age of the volcanic eruption foraminifera from four north atlantic deep sea cores selected for their high sedimentation rates 10 cm kyr 1 were dated by ams 21 samples for each core the raw 14c ages assigned to the ash layer peak is significantly older than the 14c age obtained on land part of this discrepancy is due to bioturbation which is shown by numerical modelling nevertheless after correction of a bioturbation bias the mean 14c age obtained on the planktonic foraminifera is still about 11 000 11 100 yr bp the atmosphere sea surface 14c difference was roughly 700 800 yr during the yd whereas today it is 400 500 yr a reduced advection of surface waters to the north atlantic and the presence of sea ice are identified as potential causes of the high 14c reservoir age during the yd

deep pleistocene iceberg plowmarks on the yermak plateau sidescan and 3 5 khz evidence for thick calving ice fronts and a possible marine ice sheet in the arctic ocean the southern yermak plateau northwest of spitsbergen was investigated with 11 12 khz sidescan sonar and 3 5 khz profiler to test whether thick pleistocene ice streams ever calved into the arctic ocean and or whether a continuous arctic ice sheet existed in either case the ice would have grounded on the plateau crest on its way out of the arctic several distinct sets of relict iceberg plowmarks were discovered at present water depths from less than 450 m to at least 850 m perhaps recording the deepest iceberg keels known the plateau crest 510 530 m is nearly bare of plowmarks perhaps because of beveling by an ice rise formed of grounding shelf ice this implies continuous 400 600 m thick grounded ice consistent with but not proving the postulated existence of an arctic ice sheet most plowmarks are probably late pleistocene products of the calving of barents kara ice sheets into the arctic ocean plowmarks in 450 850 m deep water require unusually deep ice sheet grounding lines e g svyataya anna trough and or drat increasing capsizing events even if sea levels were 100 50 m lower than today at water depths of 800 to 1800 m the sidescan texture and topography suggest bottom currents descending the northeast slope of the plateau

constraints on the late weichselian ice sheet over the barents sea from observations of raised shorelines abstract direct evidence for late weichselian grounded glacier ice over extensive areas of the barents sea is based largely on indirect observations including elevations of old shorelines on svalbard and arguments of isostatic rebound such isostatic models are discussed here for two cases representing maximum and minimum ice sheet reconstructions in the former model the ice extends over the kara sea whereas in the latter the ice is limited to the barents sea and island archipelagos comparisons of predictions with observations from a number of areas including spitsbergen nordaustlandet edgeoya kong karls land franz josef land novaya zemlya and finnmark support arguments for the existence of a large ice sheet over the region at the time of the last glacial maximum this ice sheet is likely to have had the following characteristics conclusions that are independent of assumptions made about the earth s rheological parameters i the maximum thickness of this ice was about 1500 2000 m with the centre of the load occurring to the south and east of kong karls land ii the ice sheet extended out to the western edge of the continental shelf and its maximum thickness over western spitsbergen was about 800 m iii to the north of svalberg and frans josef land the ice sheet extended out to the northern shelf edge iv retreat of the grounded ice across the southern barents sea occurred relatively early such that this region was largely ice free by about 15 000 bp v by 12 000 bp the grounded ice had retreated to the northern archipelagos and was largely gone by 10 000 bp vi the ice sheet may have extended to the kara sea but ice thicknesses were only a fraction of those proposed in those reconstructions where the maximum ice thickness is centered on novaya zemlya models for the palaeobathymetry for the barents sea at the time of the last glacial maximum indicate that large parts of the barents sea were either very shallow or above sea level providing the opportunity for ice growth on the emerged plateaux as well as on the islands but only towards the end of the period of fennoscandian ice sheet build up

pleistocene iceberg dynamics on the west svalbard margin evidence from bathymetric and sub bottom profiler data large icebergs leave evidence of their drift via ploughing of the seabed thereby providing a geological record of episodes of calving from thick ice sheets we interpret large scale curvilinear depressions on the western svalbard margin as ploughmarks produced by the keels of icebergs that grounded on the seafloor as they drifted through this area iceberg ploughmarks were identified at modern water depths between 300 m and 1000 m and in two distinct stratigraphic units combining data from sediment cores with seismic stratigraphy from sub bottom profiler data suggests that the ploughmarks developed in two phases 1 during marine isotope stage mis 6 and 2 during mis 2 indicating the presence of large drifting icebergs on the western svalbard margin during both the late saalian and late weichselian glaciations sediment core data along the western svalbard margin indicate a sharp increase in mass transported sediments dated at 23 7 0 2 ka consistent with the mis 2 age of the younger iceberg ploughed surface the ploughmarks are oriented in two main directions sw ne and s n s n oriented ploughmarks which shallow to the north indicate iceberg drift from the south with a sw ne component marking the zone of splitting of the west spitsbergen current wsc into the yermak slope current ysc and north spitsbergen current nsc large mis 6 and mis 2 icebergs most likely had an arctic ocean source we suggest that these icebergs probably left the arctic ocean southward through fram strait and circulated within the norwegian greenland sea before being transported northwards along the svalbard margin by the wsc an additional likely source of icebergs to the western svalbard margin during mis 2 was the ice sheet terminating in the western barents sea from which icebergs drifted northward

submarine landforms and glacimarine sedimentary processes in lomfjorden east spitsbergen understanding the role of fjords in modulating the long term interaction between ice sheets and glaciers with the surrounding ocean requires the investigation of glacigenic landform and sediment archives in svalbard there is a wealth of data from fjords in west spitsbergen that constrains the glacial history of this sector of the svalbard barents sea ice sheet sbis since the last glacial maximum lgm and the nature and timing of subsequent ice retreat in contrast however very little is known about the glacial history of fjords in east spitsbergen this paper combines multibeam swath bathymetry sub bottom profiles lithological data and radiocarbon dates from lomfjorden svalbard to provide the first insights into the dynamics of tidewater glaciers and associated glacimarine sedimentary processes in a northeast spitsbergen fjord at the lgm a fast flowing ice stream drained the sbis through lomfjorden serving as a tributary to a south north flowing ice stream in hinlopenstretet ice advance is recorded by streamlined bedrock glacial lineations and drumlins a radiocarbon date of 9 7 ka bp from the outer fjord provides a minimum date for retreat of this ice stream and suggests that lomfjorden was ice free earlier than fjords in west spitsbergen ice retreat occurred in a slow and step wise manner indicated by the presence of recessional moraines and de geer moraines by 4 5 ka bp the local tidewater glaciers had probably retreated inland of their present positions the limited extent of glacigenic landform assemblages in front of these glaciers implies that any holocene re advances were probably restricted the principal sedimentary processes during deglaciation were suspension settling from meltwater causing deposition of weakly stratified bioturbated mud in ice distal settings at rates of 0 02 0 08 cm a 1 and gravitational mass flows forming sandy turbidites in ice proximal areas iceberg ploughmarks and ice rafted debris provide evidence for the presence of large icebergs during deglaciation our data suggest an early and extensive deglaciation in east spitsbergen fjords and show that previous reconstructions of the extent of the sbis need to be revised as new data emerges from east spitsbergen the data confirm that tidewater glaciers from different regions of spitsbergen behaved differently since the lgm and that variations in landform sediment assemblages occur even within geographically adjacent fjords

stable isotope stratigraphy sedimentation rates and salinity changes in the latest pleistocene to holocene eastern central arctic ocean a high resolution study including oxygen and carbon stable isotopes as well as carbonate and total organic carbon contents has been performed on undisturbed near surface 0 40 cm sediment sequences taken in the eastern arctic ocean during the international arctic 91 expedition based on the oxygen stable isotope records measured on neogloboquadrina pachyderma sin and ams 14c dating the upper 10 to 20 cm of the sediment sequences represent isotope stage 1 and the base of termination i 15 7 ka can be identified very well stage 1 sedimentation rates vary between 0 4 and 2 0 cm kyr in general glacial stage 2 sedimentation rates are probably lower and vary between 0 4 and 0 7 cm kyr the glacial interglacial shifts in 18o values of n pachyderma sin may reach values of 1 3 to 2 5 indicating 1 that in addition to the glacial interglacial global ice volume signal changes in surface water salinity have effected the isotope records and 2 that these salinity changes have varied laterally glacial interglacial differences in salinity were small in the lomonosov ridge area 0 0 4 and relatively high in the morris jesup rise area up to 1 4 this implies that the supply of low saline waters onto the eurasian shelves and its further transport into the central arctic ocean via the transpolar drift should have continued during the last glacial and should have significantly influenced the surface water characteristics in parts of the central arctic on the morris jesup rise on the other hand the glacial low saline water signal at that time was strongly reduced in comparison to the modern situation at the glacial interglacial stage 12 boundary a strong meltwater signal is recorded in a sharp depletion in 18o as well as 13c this central arctic ocean meltwater event can be correlated from the makarov basin through the lomonosov ridge and amundsen basin to the eastern gakkel ridge the beginning of this event is ams 14c dated at 15 7 ka i e significantly older than the major decrease in the global ice volume signal which occurs between 9 and 13 5 ka large amounts of freshwater meltwater were probably supplied from the eurasian continent due to the decay of the barents sea ice sheet causing this distinct early meltwater anomaly in the central arctic ocean the extension of a well oxygenated surface near water mass in the arctic ocean and at least seasonal open ice conditions and some increased bioproductivity were probably established at the end of termination i as indicated by the increase in 13c to modern values as well as increased carbonate i e foraminifers coccoliths ostracodes and total organic carbon contents

deglaciation of a major palaeo ice stream in disko trough west greenland recent work has confirmed that grounded ice reached the shelf break in central west greenland during the last glacial maximum lgm here we use a combination of marine sediment core data including glacimarine lithofacies and ird proxy records and geomorphological and acoustic facies evidence to examine the nature of and controls on the retreat of a major outlet of the western sector of the greenland ice sheet gris across the shelf retreat of this outlet which contained the ancestral jakobshavns isbrae ice stream from the outer shelf in disko trough was rapid and progressed predominantly through iceberg calving however minor pauses in retreat tens of years occurred on the middle shelf at a trough narrowing forming subtle grounding zone wedges by 12 1 cal kyr bp ice had retreated to a basalt escarpment and shallow banks on the inner continental shelf where it was pinned and stabilised for at least 100 years during this time the ice margin appears to have formed a calving bay over the trough and melting became an important mechanism of ice mass loss fine grained sediments muds were deposited alternately with ird rich sediments diamictons forming a characteristic deglacial lithofacies that may be related to seasonal climatic cycles high influxes of subglacial meltwater emanating from the nearby ice margins deposited muddy sediments during the warmer summer months whereas winters were dominated by iceberg calving leading to the deposition of the diamictons this is the first example of this glacimarine lithofacies from a continental shelf setting and we suggest that the calving bay configuration of the ice margin plus the switching between calving and melting as ablation mechanisms facilitated its deposition by channelling meltwater and icebergs through the inner trough the occurrence of a major stillstand on the inner shelf in disko trough demonstrates that the ice dynamical response to local topography was a crucial control on the behaviour of a major outlet in this sector of the gris during retreat

glacigenic sediments on a passive continental margin as exemplified by the barents sea abstract reflection seismics data borehole data and gravity cores have been used to map the sedimentary facies of the epicontinental southwestern barents sea its continental margin and adjacent coastal areas an upper unconformity with a glacially eroded morphology extends over most of the continental shelf up to 300 m of stratiform glacigenic sediments overlie this unconformity these sediments can be grouped into seismic units which are separated by smooth or irregular erosional surfaces each sequence may be up to 150 m thick normally with a lateral extent of 100 300 km three dominant seismic signatures may be discerned semi transparent stratified and chaotic reflection patterns these sediments are partly glacifluvial in origin but on the whole they represent more or less tectonized glacimarine deposits the deeper troughs on the continental shelf contain an undeformed postglacial glacimarine marine trough fill the greatest thickness up to 1000 m of glacigenic sediments occurs at the shelf break and below the upper slope the depocentres are situated at trough mouth fans the sediments comprise several prograding sequences with a complex sigmoid oblique character indicating alternating upbuilding and depositional bypass erosion in the topset segment small and large scale slide scars are observed on the upper slope and debris lobes on the lower slope a marked progradation seems to have occurred during the plio pleistocene glacial periods this progradation also resulted in an unstable slope with various types of sediment gravity flows currents flowing along the slope were established during interglacials and gullying by cold dense shelf water and downslope transport occurred maximum net sedimentation rates are 0 2 m ka continental slope 0 4 m ka shelf break 0 1 m ka shelf stratiform diamictons 1 m ka shelf trough fills and 60 m ka fjord trough fills

mechanisms of unrest and eruption at persistently restless volcanoes insights from the 2015 eruption of telica volcano nicaragua many of earth s volcanoes experience well defined states of quiescence and unrest with unrest occasionally culminating in eruption some volcanoes however experience an unusually protracted i e decades long period of noneruptive unrest and are thus categorized as persistently restless volcanoes prvs the processes that drive persistently restless volcanism are poorly understood as our knowledge of prvs is currently based on a small number of case studies here we examine multidisciplinary observations of the 2015 eruptive episode at telica volcano nicaragua in the context of its long term behavior we suggest that the latter phases of the 2015 eruption were ultimately driven by destabilization of its shallow magma reservoir based on previous geodetic seismic studies of telica geirsson et al 2014 https doi org 10 1016 j jvolgeores 2013 11 009 rodgers et al 2013 https doi org 10 1016 j jvolgeores 2013 08 010 and 2015 https doi org 10 1016 j jvolgeores 2014 11 012 and on multiparameter observations at telica over a 7 year period we propose that three distinct states of unrest occur at telica over decadal timescales a stable open state involving steady conduit convection and two distinct unstable states that may lead to eruptions in the weak sealing state phreatic explosions result from steady conduit convection underlying a weak seal in the destabilized state destabilization of the top of the convecting magma in the conduit leads to rapid accumulation of high pressures leading to strong impulsive phreatomagmatic explosions our observations and interpretations suggest that continuous seismic ground based deformation gas emission and thermal monitoring and interpretation of these data within a paradigm of sustained conduit convection modulated by episodes of sealing and destabilization of shallow magma reservoirs may allow robust forecasting of eruption potential energy and duration at telica and similar prvs worldwide

quaternary history of sea ice and paleoclimate in the amerasia basin arctic ocean as recorded in the cyclical strata of northwind ridge the 19 middle early pleistocene to holocene bipartite lithostratigraphic cycles observed in high resolution piston cores from northwind ridge in the amerasia basin of the arctic ocean provide a detailed record of alternating glacial and interglacial climatic and oceanographic conditions and of correlative changes in the character and thickness of the sea ice cover in the amerasia basin glacial conditions in each cycle are represented by gray pelagic muds that are suboxic laminated and essentially lacking in microfossils macrofossils trace fossils and generally in glacial erratics interglacial conditions are represented by ochre pelagic muds that are oxic and bioturbated and contain rare to abundant microfossils and abundant glacial erratics the synglacial laminated gray muds were deposited when the central amerasia basin was covered by a floating sheet of sea ice of sufficient thickness and continuity to reduce downwelling solar irradiance and oxygen to levels that precluded photosynthesis maintenance of a biota and strong oxidation of the pelagic sediment except during the early part of 3 of the 19 synglacial episodes when it was periodically breached by erratic bearing glacial icebergs the floating arctic ocean sea ice sheet was sufficiently thick to block the circulation of icebergs over northwind ridge and presumably other areas of the central arctic ocean interglacial conditions were initiated by abrupt thinning and breakup of the floating sea ice sheet at the close of glacial time which permitted surges of glacial erratic laden icebergs to reach northwind ridge and the central arctic ocean where they circulated freely and deposited numerous and relatively thick erratic clast rich beds breakup of the successive synglacial sea ice sheets initiated deposition of the interglacial ochre mud units under conditions that allowed sunlight and increased amounts of oxygen to enter the water column resulting in photosynthesis and biologic productivity and strong oxidization of the pelagic sediment the lithostratigraphy of northwind ridge suggests that during at least late pleistocene time glacial conditions in the arctic ocean were initiated abruptly and continued unabated until terminated also abruptly by onset of the succeeding interglacial warming variations in abundance of glacial erratics within the interglacial units of the late pleistocene indicate that during at least most interglacial episodes northern north america was glaciated but with generally diminishing severity until onset of the succeeding continental glaciation magnetostratigraphy suggests that the glacial interglacial cycles on northwind ridge had an average periodicity of approximately 93 5 k y during the brunhes normal and approximately 105 k y during the latter part of the matuyama reverse polarity zone these average periodicities are close to the 100 k y temperature cycles found in north atlantic deep water sediments of the brunhes normal polarity chron which have been ascribed to forcing by a milankovitch eccentricity cycle they are also close however to the average interval 101 k y between the aperiodic glacial terminations in the 500 k y pleistocene continental climate record from devil s hole nevada which have been ascribed to nonlinear feedbacks within the earth s atmosphere ice sheet ocean system

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

arctic ocean glacial history while there are numerous hypotheses concerning glacial interglacial environmental and climatic regime shifts in the arctic ocean a holistic view on the northern hemisphere s late quaternary ice sh

late quaternary ice flow and sediment delivery through hinlopen trough northern svalbard margin submarine landforms and depositional fan abstract the morphology and distribution of submarine landforms in hinlopen trough northern svalbard margin and the upper continental slope beyond are investigated using swath bathymetric data together with side scan sonar acoustic profiler records and sediment cores sun illuminated images reveal a number of landform assemblages on the sea floor of hinlopen trough and confirm that this depression was occupied by an ice stream during the late weichselian glaciation around 20 ka before present the geomorphology of the inner shelf is characterised by bedrock drumlins and ice sculpted bedrock there is a middle shelf transition from a rock bed to an unconsolidated sedimentary bed that contains highly attenuated drumlins and megaflutes formed within a dark grey matrix supported diamict interpreted as subglacial till outer shelf landforms are mainly iceberg ploughmarks the geomorphological imprint identified from hinlopen trough is similar to that of many former ice streams the trough is dominated by elongate landforms orientated parallel to the inferred flow direction and is lacking in transverse features indicative of inter ice stream locations a characteristic down flow progression in landform elongation is also observed suggesting an increase in ice velocity across the continental shelf the lack of grounding zone features imaged from swath bathymetric data implies that deglaciation was probably rapid within the trough a large depositional fan exists on the upper continental slope beyond the trough characterised by debris flow deposits relating to the down slope transport of glacigenic sediment order of magnitude calculations of the volume of glacigenic sediment on the continental slope indicate that the ice stream provided high rates of debris delivery of around 5 7 5 m ka this suggests that hinlopen trough ice stream represented a major route for the transfer of ice and debris to the hinlopen fan on the northern continental margin of svalbard during the late weichselian glaciation

late glacial holocene clay minerals elucidating glacial history in the sw barents sea abstract detailed investigations of the distribution of clay minerals of late glacial holocene sediments from the sw barents sea provide important new information about the provenance and transport paths of the sediments this information leads to better understanding of the onset of the last deglaciation and subsequent advances retreats of the barents sea and fennoscandian ice sheets the results show interaction and changes in the fennoscandian ice sheet and bjornoyrenna ice stream during the last deglaciation high illite content and maximum kaolinite content 18 700 cal yr b p indicate glacial erosion from both the fennoscandian ice sheet and bjornoyrenna ice stream lgm ii the occurrence of a c reniforme dominated benthic foraminiferal assemblage 18 700 cal yr b p indicates that the northern most cores site in ingoydjupet had already been deglaciated and was probably situated in a glacier distal environment in addition smectite content reaching its highest level concurrent with the presence of neogloboquadrina pachyderma sin dominated planktic foraminifera can be related to the strengthening of the atlantic current the inflow of the atlantic water may have triggered deglaciation of the fennoscandian ice sheet bolling interstadial a rapid increase in illite content reflecting strong melting of the fennoscandian ice sheet 15 000 cal yr b p indicates the onset of deglaciation in a core closer to the continent decrease of illite and ird content together with the deposition of laminated sediments during the older dryas stadial 15 000 14 000 cal yr b p indicates colder conditions and formation of at least seasonal sea ice in addition increased kaolinite content indicates increased glacial erosion of the bjornoyrenna ice stream the highest values of illite content and increased ird content 14 000 13 000 cal yr b p can be related to strong melting of the fennoscandian ice sheet a slight indication of the younger dryas cold period is given by the decrease in illite and ird contents all clay contents are more stable during holocene compared to lgm and the last deglaciation

evidence from fram strait 78 n for early deglaciation recent syntheses of the history of the last northern hemisphere glaciation and deglaciation illustrate that understanding of the mechanisms and timing of deglaciation before approximately 12 000 years bp1 5 is limited after 12 000 yr bp however there is sufficient evidence from radiocarbon dated moraines raised beaches varved lake sediments and pollen records to provide a reasonable temporal and geographic picture of the decay of the ice sheets here we report on the first oxygen isotope record from the norwegian greenland sea that is radiocarbon dated directly by accelerator mass spectrometry a significant light oxygen isotope event is recorded at approximately 15 000 years bp which suggests that the marine based barents shelf ice sheet disintegrated rapidly at this time recent studies6 7 have estimated that the decay of this ice sheet could have contributed as much as 15 metres to eustatic sea level rise the decay of the barents shelf ice sheet is the earliest major deglacial event yet dated and may have triggered subsequent deglacial events through eustatic sea level effects

trough mouth fans palaeoclimate and ice sheet monitors abstract trough mouth fans are fans at the mouth of transverse troughs channels on glaciated continental shelves on the northwest european glaciated continental margin eight trough mouth fans varying in size between 2700 and 215 000 km 2 have been identified the trough mouth fans are depocentres dominated by debris flows accumulated in front of ice streams draining the former large northwest european ice sheets the debris flow units are separated by hemmipelagic interglacial interstadial sediments it is inferred that the number of debris flow units record the number of shelfbreak positions of the ice sheet margins the number found varies between three in the south and eight in the north typical trough mouth fans and related debris flow units seem to have been formed later than the early mid pleistocene thus the north european ice sheets did not form ice streams extending to the shelfbreak in any appreciable length before the mid pleistocene besides being loci for sediment deposition the trough mouth fans were also the main sites of fresh water supply to the ocean in the form of icebergs during the mid late pleistocene ice ages

the last ice sheet of the kara sea terrestrial constraints on its age abstract the ice dispersal features on the siberian mainland unanimously indicate that the last ice domes were positioned on the kara sea shelf and adjacent coastal plains the age of the last glacial maximum evokes much controversy the problem may be solved by sorting out the available radiocarbon dates both statistically and using geological common sense over 200 finite radiocarbon dates have been analysed 77 of the entire population represent sediments overlying the topmost till including dating the most reliable organics such as mammoth remains the rest of the dates 23 have been obtained from the underlying sediments mostly on materials readily prone to redeposition and contamination such as driftwood and shells the last culmination of the shelf ice sheet must have occurred beyond the range of the conventional radiocarbon method and after the last warm water sea transgression correlative to the eemian the early weichselian age for the last kara sea ice sheet is also supported by the lack of proglacial lacustrine sediments with finite radiocarbon dates in periglacial west siberia