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

validation of the ice 3g model of wurm wisconsin deglaciation using a global data base of relative sea level histories a global data base consisting of radiocarbon controlled relative sea level rsl histories from 392 different geographic locations has been compiled for use in analyses of the glacial isostatic adjustment process these data may be employed to constrain both the spatiotemporal characteristics of the last deglaciation event of the current ice age and the rheological structure of the planetary interior in a previous paper in this series tushingham and peltier 1991 we employed the rsl data in this set from sites that were once ice covered to refine the apriori model of deglaciation that had been delivered by past research in the area of pleistocene geomorphology peltier and andrews 1976 wu and peltier 1983 to produce a new global model of this event that we have called ice 3g in the present paper following a description of the full data base and of the methods used to compile it we employ data from the sites that were not ice covered 200 time series to verify the plausibility of this refined model of deglaciation and to test the extent to which the totality of the observations constrain the radial viscoelastic structure of the planet the analysis of solutions to the forward problem presented here reinforce previous inferences of a preference for a thick lithosphere by rsl data from sites along the u s east coast and a preference by data from most near field sites for an increase in viscosity across the 670 km discontinuity in the mantle by a factor of approximately 2 when the viscosity of the upper mantle is fixed to the value of 1021 pa s originally deduced by haskel 1935 on the basis of his analysis of the data from fennoscandia

late quaternary stratigraphy glacial limits and paleoenvironments of the marresale area western yamal peninsula russia stratigraphic records from coastal cliff sections near the marresale station on the yamal peninsula russia yield new insight on ice sheet dynamics and paleoenvironments for northern eurasia field studies identify nine informal stratigraphic units from oldest to youngest the marresale formation labsuyakha sand kara diamicton varjakha peat and silt oleny sand baidarata sand betula horizon nenets peat and chum sand that show a single glaciation and a varied terrestrial environment during the late pleistocene the kara diamicton reflects regional glaciation and is associated with glaciotectonic deformation from the southwest of the underlying labsuyakha sand and marresale formation finite radiocarbon and luminescence ages of ca 35 000 to 45 000 yr from varjakha peat and silt that immediately overlies kara diamicton place the glaciation 40 000 yr ago eolian and fluvial deposition ensued with concomitant cryogenesis between ca 35 000 and 12 000 cal yr b p associated with the oleny and the baidarata sands there is no geomorphic or stratigraphic evidence of coverage or proximity of the yamal peninsula to a late weichselian ice sheet the nenets peat accumulated over the baidarata sand during much of the past 10 000 yr with local additions of the eolian chum sand starting ca 1000 yr ago a prominent betula horizon at the base of the nenets peat contains rooted birch trees ca 10 000 to 9000 cal yr old and indicates a 200 km shift northward of the treeline from the present limits corresponding to a 2 to 4 c summer warming across northern eurasia

holocene raised beach ridges and sea ice pushed boulders on the kola peninsula northwest russia indicators of climatic change the primary aim of this paper is to describe and discuss the palaeoclimatic significance of mid to late holocene fields of raised beach ridges at matalaniemi and sea ice pushed boulders at kutovaya

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

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

the late weichselian glacial maximum on western spitsbergen inferred from offshore sediment cores abstract the late weichselian glacial history of the continental shelf off western spitsbergen is discussed based on acoustic sub bottom records and sediment cores the outer part of isfjorden and the inner shelf to the west of this fjord are characterized by a thin veneer 10 20 m of glacigenic sediments and absence of ice marginal features towards the outer shelf the sediment thickness increases significantly and exceeds 500 m at the shelf edge possible moraine complexes were identified in this outer part sediment cores from the inner shelf sampled a firm diamicton interpreted as till beneath soft glaciomarine sediments radiocarbon dates on shells from the clay resting directly on the till suggest an age of around 12 500 yrs b p for the base of the marine sequence we argue that grounded ice covered the sites shortly before in contrast to suggestions that the fjords and coast were partly ice free during the late weischselian we conclude that the ice must have reached out onto the continental shelf

holocene relative sea level history of franz josef land russia one of the largest uncertainties in ice volume changes during the late quaternary period is the extent of ice sheets over the barents and kara seas field research on central and eastern franz josef land russia provide new observations on postglacial emergence and deglaciation that further constrain the magnitude and timing of late weichselian glaciations radiocarbon dating of driftage from raised marine sequences place deglacial unloading prior to 9 4 ka at a number of localities within 1 to 2 km of the present glacier margin in situ shells from raised marine sediments yield 14c ages between 9 7 and 8 4 yr b p evidence that outlet glaciers were at or behind present margins by the early holocene period the altitude of the marine limit on franz josef land ranges from 49 to 20 m above sea level asl and is low compared to eastern svalbard 110 to 60 m asl the age of the marine limit ranges from 10 4 ka to ca 6 0 ka and exhibits greater diachrony where emergence is 35 m a low initial rate of emergence reflects glacio isostatic compensation offset by a eustatic rise in sea level and perhaps an additional component from renewed water loading of the barents sea after deglaciation the presence of raised beaches at 1 to 4 m asl that are 1 to 2 ka indicates that uplift is incomplete an exponential extrapolation of uplift data for franz josef land and eastern svalbard yields current maximum uplift estimates of 0 7 to 1 6 mm yr an inferred 5 5 m of uplift remaining these values are at least 50 to 80 lower than the inferred uplift residual for a modeled ice sheet in the barents and kara seas the discrepancy indicates that further refinement is needed for this ice sheet model the compilation of emergence data from franz josef land svalbard and novaya zemlya confine maximum glacio isostatic compensation to the barents sea comparatively minor ice sheet loads were over novaya zemlya and the southeastern barents sea emergence isobases since 5 and 9 ka descend northward across franz josef land indicating a diminishing glacio isostatic response into the arctic ocean

neodymium isotope constraints on chemical weathering and past glacial activity in svalbard abstract neodymium nd isotopes in leached authigenic components of marine sediments have been increasingly used as a tracer of past ocean water masses despite the general assumption that the nd isotopic composition of solutes released during chemical weathering fingerprints the source rocks on continents preferential dissolution of easily dissolvable phases may result in significant deviations in nd isotopic composition between the solutes and the source rocks with potential implications for the utility of nd isotopes in paleoenvironmental studies here we present the nd isotopic compositions of leached and detrital fractions separated from bedrock and marine sediment samples from the svalbard archipelago our goal is to further understand the behaviour of nd isotopes during chemical weathering in glacial catchments and evaluate how glacier fluctuations and associated weathering congruency may have affected the export of dissolved nd isotope signatures to seawater our results confirm that terrestrial weathering on svalbard causes considerable nd isotopic decoupling between the leached and detrital fractions of fjord sediments end resulting from the preferential dissolution of marine precipitates in glaciated catchments dominated by sedimentary rocks we also show that the degree of nd isotopic decoupling has fluctuated in response to climate variability on svalbard during the holocene which is also as suggested by the occurrence of generally higher end values during periods of glacier advances in sediment cores retrieved from two different fjords dicksonfjorden and woodfjorden we posit that the high end values can be ascribed to incongruent chemical weathering of fresh rock flour produced by glacial abrasion this finding suggests that the degree of nd isotopic decoupling could be used as a new proxy for tracing glacial fluctuations and associated glacier derived nutrient inputs to the marine realm

late weichselian glacier retreat in kongsfjorden west spitsbergen svalbard the chronology of late weichselian to holocene deglaciation of kongsfjorden west spitsbergen has been reconstructed based on the geomorphic and stratigraphic record of ice retreat relative sea level relationships and 14c dating of associated marine organic materials the seaward extent of glacial drift and fjord bathymetry constrain a secure reconstruction for the ice sheet near the mouth of the fjord at ca 13 000 yr b p but do not rule out the possibility that more extensive glaciation was achieved earlier during the late weichselian regional shoreline relations rates of emergence and radiocarbon dating of foraminifera deposited just above till indicate that deglaciation occurred in two steps one beginning during or just prior to the late weichselian marine limit phase at 13 000 12 000 yr b p and another beginning at 10 000 9500 yr b p the fjord was completely deglaciated by 9440 130 yr b p a period of stable relative sea level began 10 700 yr b p and ended between 10 000 and 9500 yr b p which we take to indicate renewed glacial loading during the younger dryas glacier readvance within kongsfjorden at this time was diminutive suggesting that most of the younger dryas ice sheet growth was confined to the eastern part of the archipelago and or to the barents shelf the two step deglaciation of kongsfjorden occurred during intervals of accelerated global ice sheet melting and rapid oceanic and atmospheric warming in more temperate latitudes of the circum atlantic region this coincidence most likely resulted from contemporaneous increases in the poleward transport of oceanic heat

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

ice age paleotopography a gravitationally self consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the last glacial maximum lgm the results show that lgm ice volume was approximately 35 percent lower than suggested by the climap reconstruction and the maximum heights of the main laurentian and fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level use of these ice age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the climap data set

accuracy of north american human skeleton ages accelerator mass spectrometry ams radiocarbon dates fail to provide conclusive evidence that all new world human fossils are younger than approximately 11 000 yr because fossil bones vary widely in preservation their radiocarbon dates are not equally accurate molecular level radiocarbon dating which used individual amino acids to assess fossil diagenesis revealed that dates on known age noncollagenous bone were underestimated by at least 2000 to 9000 yr the significance is that 11 000 yr old fossil bones with poor preservation would yield holocene and not pleistocene radiocarbon ages regardless of what chemical pretreatment or 14c counting method was used irreplaceable evidence for pleistocene age fossils in the new world could be lost if the diagenesis of fossil bones is not evaluated before the bones are radiocarbon dated in contrast radiocarbon ages for collagenous fossils can be determined more accurately if 14c is measured in several individual amino acids that are isolated from collagenous bone protein molecular level radiocarbon dating will greatly improve not only the accuracy of chronologies for human migrations and animal extinctions but of all late quaternary chronologies that are based upon the 14c dating of fossil proteins

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

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

glacial isostatic deformation of the great lakes region tilting of ancient shorelines of the great lakes region has been studied for more than a century nevertheless fundamental disagreements exist among both glacial geologists trying to understand the chronology of lake events geophysicists investigating the causes of tilting and glaciologists attempting to reconstruct ice sheet thickness along the southern perimeter of the laurentide ice sheet fundamental to many of these studies is the belief that the southern part of the great lakes region has been geodynamically stable for at least the past 11 000 yr results of our numerical model of the glacio isostatic process for a spherical layered self gravitating viscoelastic earth suggest constraints upon earth models shoreline chronologies and ice sheet thickness as a test of the model predictions were compared to observations of outlet chronology and isobases of both ancient shorelines and modern tilting indicated by lake level gauges earth models with a uniform viscosity mantle resulted in the best fit to observed shorelines earth models with a low viscosity asthenosphere or a high viscosity lower mantle do not predict deformation consistent with known outlet chronologies an ice sheet with thickness of 2 000 m over the region results in an excessive amount of tilting in most instances whereas a much thinner ice sheet 700 m although in better agreement with the data generally resulted in underestimates none of the results suggests stability in the southern great lakes region at any time predictions indicate instead that submergence of ancient shorelines has complicated the record there

hydrodynamics and sediment transport in the swash zone a review and perspectives the dominant hydrodynamic forcing and resulting sediment transport mechanisms in the swash zone are reviewed combined with a discussion of future measurement and modelling requirements the importance of swash zone processes in the overall behaviour of the nearshore littoral zone are identified with the paper subsequently focusing on aspects that directly relate to sediment transport on beaches the review considers analytical and numerical modelling work and both field and laboratory data the hydrodynamics of the swash zone are first discussed with reference to the surf zone boundary swash characteristics forcing mechanisms and shoreline oscillations subsequent sections consider more micro scale processes such as the internal flow kinematics turbulence the bed boundary layer and infiltration exfiltration through permeable beds the second part of the paper outlines the fundamental mechanics of sediment transport in the swash zone followed by a more detailed discussion of sediment transport modes induced by the dominant hydrodynamic conditions modelling concepts are reviewed and the strengths and weaknesses of different approaches identified a final summary and future modelling perspectives conclude the paper

late weichselian and holocene relative sea level history of broggerhalvoya spitsbergen abstract radiocarbon dated whalebones from raised beaches record a relative sea level history for broggerhalvoya western spitsbergen that suggest a two step deglaciation on svalbard at the end of the late weichselian glaciation the late weichselian marine limit was reached at about 13 000 yr b p and was followed by relatively slow emergence until about 10 000 yr b p either in response to ice unloading in the barents sea initial retreat of local fjord glaciers or some combination of the two rare whale skeletons dating between 13 000 and 10 000 yr b p indicate that the norwegian sea was at least seasonally ice free during that interval deglaciation of spitsbergen is recorded by the rapid emergence of broggerhalvoya after 10 000 yr b p this was followed by a transgression during the mid holocene here named the talavera transgression and another in modern times raised beach morphologies suggest striking differences in nearshore depositional processes before and after 10 000 yr b p that are probably related to changes in the rate of uplift and in sea ice conditions

glaciotectonised quaternary sediments at cape shpindler yugorski peninsula arctic russia implications for glacial history ice movements and kara sea ice sheet configuration the coastal cliffs of cape shpindler yugorski peninsula arctic russia occupy a key position for recording overriding ice sheets during past glaciations in the kara sea area either from the kara sea shelf or the uplands of yugorski peninsula polar urals this study on late quaternary glacial stratigraphy and glaciotectonic structures of the cape shpindler coastal cliffs records two glacier advances and two ice free periods older than the holocene during interglacial conditions a sequence of marine to fluvial sediments was deposited this was followed by a glacial event when ice moved southwards from an ice divide over novaya zemlya and overrode and disturbed the interglacial sediments after a second period of fluvial deposition under interstadial or interglacial conditions the area was again subject to glacial overriding with the ice moving northwards from an inland ice divide the age control suggests that the older glacial event could possibly belong to marine oxygen isotope stage mois 8 drenthe 300 250 ka and that the underlying interglacial sediments might be holsteinian 300 ka one implication of this is that relict glacier ice buried in sediments and incorporated into the permafrost may survive several interglacial and interstadial events the younger glacial event recognised in the cape shpindler sequence is interpreted to be of early to middle weichselian age it is suggested to correlate to a regional glaciation around 90 or 60 ka the cape shpindler record suggests more complex glacial dynamics during that glaciation than can be explained by a concentric ice sheet located in the kara sea as suggested by recent geological and model studies copyright 2003 john wiley sons ltd

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

out of the woods driftwood insights into holocene pan arctic sea ice dynamics the collation of 913 driftwood samples from across the western arctic with spatiotemporal distribution and available provenance data enabled the production of a high resolution proxy based reconstruction of holocene arctic ocean surface current and sea ice dynamics regionally bounded driftwood based sea ice reconstructions studies suggest spatiotemporally complex past arctic sea ice extent and movement however a large scale compilation of holocene arctic driftwood has not previously been developed sparse driftwood in the early holocene 8 2 cal ka b p deglacial period was followed by increased driftwood deposition in the warmer mid holocene 8 2 4 2 cal ka b p characterized by an enhanced transpolar drift tpd 7 cal ka b p leading to sea ice loss through the fram strait driftwood incursion peaks show spatial e w progression from the eurasian archipelagos to greenland and the canadian arctic archipelago suggesting a progressive shift in the orientation of the tpd on centennial millennial time scales and intermediate phases in the arctic oscillation late holocene cooling 4 2 cal ka b p is indicated by increased influx of probably north american picea via a strengthened beaufort gyre bg which enhanced sea ice recirculation starting in the western arctic and progressing eastward in recent millennia 2 cal ka b p a more variable driftwood record alternates between bg and tpd dominance on centennial time scales to further constrain a spatiotemporal reconstruction of variations in holocene ocean current and sea ice dynamics a more definitive determination of driftwood provenance is recommended to build upon the current framework such as through radiogenic isotope tracing and adna analysis

freshwater and atlantic water inflows to the deep northern barents and kara seas since ca 13 14 c ka foraminifera and stable isotopes foraminiferal stable isotopes and assemblages from franz victoria and st anna troughs provide a valuable record of freshwater and atlantic water flows to the northern barents and kara seas from deglaciation to present the d 18 o and d 13 c of planktonic neogloboquadrina pachyderma s and benthic elphidium excavatum were up to1 4 lower than present at ca 13 11 5 and 10 14 c ka global sea level corrected mostly reflecting substantial freshwater inputs coincident with glacial marine sediment deposition cassidulina teretis exceeded 40 of benthic foraminifera ca 13 and 10 14 c ka indicating subsurface penetrations of atlantic water the transition to postglacial marine conditions is marked by a 1 rise in foraminiferal d 18 o and a sharp fall in c teretis soon after 10 14 c ka these changes imply reduced inputs of freshwater and atlantic water subsequent isotopic and foraminiferal assemblage variations reflect changing atlantic water conditions upstream in the nordic seas and shifts between the warm fram strait and cold barents sea branches of atlantic water we hypothesize that glacial isostatically induced deepening by up to 150 m influenced atlantic water inflows to the northern barents sea during deglaciation and the holocene thus effects of isostatic recovery have to be factored into paleoceanographic reconstructions 2001 elsevier science ltd all rights reserved

paleo methane emissions recorded in foraminifera near the landward limit of the gas hydrate stability zone offshore western svalbard we present stable isotope and geochemical data from four sediment cores from west of prins karls forland ca 340 m water depth offshore western svalbard recovered from close to sites of active methane seepage as well as from shallower water depths where methane seepage is not presently observed our analyses provide insight into the record of methane seepage in an area where ongoing ocean warming may be fueling the destabilization of shallow methane hydrate the 13c values of benthic and planktonic foraminifera at the methane seep sites show distinct intervals with negative values as low as 27 8 that do not coincide with the present day depth of the sulfate methane transition zone smtz these intervals are interpreted to record long term fluctuations in methane release at the present day landward limit of the gas hydrate stability zone ghsz shifts in the radiocarbon ages obtained from planktonic foraminifera toward older values are related to methane derived authigenic carbonate overgrowths of the foraminiferal tests and prevent us from establishing the chronology of seepage events at shallower water depths where seepage is not presently observed no record of past methane seepage is recorded in foraminifera from sediments spanning the last 14 ka cal bp 14c ams dating 13c values of foraminiferal carbonate tests appear to be much more sensitive to methane seepage than other sediment parameters by providing nucleation sites for authigenic carbonate precipitation foraminifera thus record the position of even a transiently stable smtz which is likely to be a characteristic of temporally variable methane fluxes

late weichselian local ice dome configuration and chronology in northwestern svalbard early thinning late retreat the chronology and configuration of the svalbard barents sea ice sheet sbsis during the late weichselian lw are based on few and geographically scattered data thus the timing and configuration of the sbsis has been a subject of extensive debate we present provenance data of erratic boulders and cosmogenic 10be ages of bedrock and boulders from northwest spitsbergen nws svalbard to determine the thickness configuration and chronology during the lw we sampled bedrock and boulders of mountain summits and summit slopes along with erratic boulders from coastal locations around nws we suggest that a local ice dome over central nws during lw drained radially in all directions provenance data from erratic boulders from northern coastal lowland reinsdyrflya suggest northeastward ice flow through liefdefjorden 10be ages of high elevation erratic boulders in central nws 687 836 m above sea level ranging from 18 3 1 3 ka to 21 7 1 4 ka indicate that the centre of a local ice dome was at least 300 m thicker than at present 10be ages of all high elevation erratics 400 m above sea level central and coastal locations indicate the onset of ice dome thinning at 25 20 ka 10be ages from erratic boulders on reinsdyrflya ranging from 11 1 0 8 ka to 21 4 1 7 ka indicate an ice cover over the entire reinsdyrflya during lw and a complete deglaciation prior to the holocene but apparently later than the thinning in the mountains lack of moraine deposits but the preservation of beach terraces suggest that the ice covering this peninsula possibly was cold based and that reinsdyrflya was part of an inter ice stream area covered by slow flowing ice as opposed to the adjacent fjord which possibly was filled by a fast flowing ice stream despite the early thinning of the ice sheet 25 20 ka we find a later timing of deglaciation of the fjords and the distal lowlands several bedrock samples 10be from vertical transects in the central mountains of nws pre date the lw and suggest either ice free or pervasive cold based ice conditions our reconstruction is aligned with the previously suggested hypothesis that a complex multi dome ice sheet configuration occupied svalbard and the barents sea during lw with numerous drainage basins feeding fast ice streams separated by slow flowing possibly cold based inter ice stream areas

gas slug ascent through changes in conduit diameter laboratory insights into a volcano seismic source process in low viscosity magmas seismic signals generated during the flow and degassing of low viscosity magmas include long period lp and very long period vlp events whose sources are often attributed to dynamic fluid processes within the conduit we present the results of laboratory experiments designed to investigate whether the passage of a gas slug through regions of changing conduit diameter could act as a suitable source mechanism a vertical liquid filled glass tube featuring a concentric diameter change was used to provide canonical insights into potentially deep or shallow seismic sources as gas slugs ascend the tube we observe systematic pressure changes varying with slug size liquid depth tube diameter and liquid viscosity gas slugs undergoing an abrupt flow pattern change upon entering a section of significantly increased tube diameter induce a transient pressure decrease in and above the flare and an associated pressure increase below it which stimulates acoustic and inertial resonant oscillations when the liquid flow is not dominantly controlled by viscosity net vertical forces on the apparatus are also detected the net force is a function of the magnitude of the pressure transients generated and the tube geometry which dictates where and hence when the traveling pressure pulses can couple into the tube in contrast to interpretations of related volcano seismic data where a single downward force is assumed to result from an upward acceleration of the center of mass in the conduit our experiments suggest that significant downward forces can result from the rapid deceleration of relatively small volumes of downward moving liquid

marine molluscs and late quaternary environmental studies with particular reference to the late glacial period in northwest europe a review abstract although it is now commonly thought that temperature is a minor factor in limiting the distribution of marine invertebrates particularly on a local scale there is evidence to suggest that some boreal molluscs particularly those which occur in similar environments on both sides of the north atlantic are valuable as oceanic temperature indicators this applies particularly to planktotrophic species whose northern limits of distribution are apparently controlled by summer surface temperature the oceanography of the eastern north atlantic is briefly considered in relation to zoogeographic subdivisions based on temperature and it is concluded that the latter are fairly crude and apply only to shelf seas most glaciomarine molluscan faunas are not specific to that environment an exception being that dominated by the bivalve portlandia arctica the role of marine molluscs in palaeoenvironmental research at the local level for the 13 11 ka bp period is illustrated by a site at inchinnan scotland it is concluded that a shell bed at this locality consists partly of a little modified life assemblage and partly of shells which have been gently reworked under conditions of generally rapid deposition during the same time interval the changing composition of molluscan faunas on the nw european seaboard suggests that a weak drift of north atlantic water replaced polar water at or a little later than 13 ka bp off scotland and a few hundred years later off northern norway evidence for relatively warm intervals early and late in the 13 11 ka bp period has been found particulary on the scottish coast and to a lesser extent more generally the later warm interval may be related to the southward movement of the polar front at the beginning of the younger dryas the value of the bivalve shell itself in the determination of temperature seasonality and calendar years is briefly discussed

sea level changes in the holocene over the last 30 years the emphasis in studies of the recovery from low last glaciation sea levels has changed significantly the search for a eustatic sea level curve having global relevance has ended studies into the rheology of the earth s crust and recognition that the geoid has not remained stable over time have resulted in the recognition that there must have been regional differences in eustatic response to deglaciation as a part of this re appraisal there has been a growing appreciation that crustal isostatic response to the removal of the weight of ice sheets has been accompanied by a consequential hydro isostatic response particularly in the areas of the shelf seas in the later part of the post war period attention has additionally been focussed on the much greater potential for error over the whole field of palaeoenvironmental reconstruction in the holocene including not only errors in dating but also a large number of possible sources of errors in heighting as a result of this an increasing number of scientists are withholding judgement on the nature of sea level rise and more particularly on the problem of higher than present late holocene eustatic sea levels the problems outstanding in the early 1960s have not yet been resolved but the bases of uncertainty have changed

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

late weichselian iceberg surface melt and sediment production from the eurasian ice sheet results from numerical ice sheet modelling abstract results from a numerical ice sheet model were matched with geological evidence detailing the extent and timing of the late weichselian ice sheet in the eurasian arctic through simple adjustments in the model s environmental inputs the numerical model predicts the spatial and temporal variation in 1 subglacial sediment transport and deposition 2 rates of iceberg calving and 3 rates of supraglacial melting over the past 30 000 yr the ice sheet is characterised by a series of ice streams occupying bathymetric troughs in the barents sea and west of norway which act as sources for glacial sediment build up and iceberg production our model indicates that significant volumes of sediment are deposited over the bear island fan 3000 km 3 in 12 000 yr franz victoria trough fan 500 km 3 in 8000 yr and a series of smaller fans west of norway which combine to yield 4000 km 3 in 12 000 yr the norwegian channel ice stream operated for only 4000 yr during which time 400 km 3 of sediments were deposited on the adjacent fan the ice sheet experienced two major periods of iceberg production where the rate of calving increased by 50 at about 15 000 and 12 500 yr ago however the time dependent response of iceberg calving to sea level rise for individual ice streams is shown to be more complicated than the generalised ice sheet response the marine portions of the ice sheet decayed after 15 000 yr ago resulting in several embayments at the mouths of bathymetric troughs a second pulse of enhanced iceberg calving at 12 500 yr ago caused further decay of the marine ice sheet and the ice margin retreated back to the shorelines of island archipelagos in the northern barents sea ice loss through surface melting was restricted mostly to the southern margin of the ice sheet

emergence of the varanger peninsula arctic norway and climate changes since deglaciation fields of glacioisostatically uplifted beach ridges on the eastern varanger peninsula coast in northern norway record the occurrence of major storms since deglaciation more than 70 radiocarbon dat

holocene relative sea level history of novaya zemlya russia and implications for late weichselian ice sheet loading abstract we present six new radiocarbon dated emergence curves that provide a detailed record of postglacial emergence of northern novaya zemlya and ages which constrain the emergence of vaygach island in the southern archipelago radiocarbon ages on hiatella sp from a lateral moraine in russkaya gavan and abundances of foraminifea in a marine core from nordenskiold bay 300 km south of our study area indicate that coastal deglaciation occurred prior to 10 000 cal yr b p however postglacial emergence commenced 7000 cal yr b p with stabilization of global sea level the total emergence is 13 11 m above sea level asl with apparent uplift rates of 1 2 mm yr for the past 2000 yr indicating modest glacier loads 11 000 cal yr b p deglaciation or both the isobase pattern showing no east west tilt across novaya zemlya and offshore moraines suggest a separate ice dispersal center over novaya zemlya for the later stages of the late weichselian glacial cycle and possibly earlier

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

post glacial relative sea level history of northwestern spitsbergen svalbard the late weichselian and holocene raised beach sequences on northwestern spitsbergen provide a detailed record of sea level oscillations during the last deglacial hemicycle initial emergence commenced at 13 ka coincident with local deglaciation and until 10 5 ka was characterized by a relative slow rate of emergence 1 5 to 5 m ka interrupted by minor stillstands or transgressions associated with possible glacier re advances the orientation of paleo spits and the paucity of whale remains at the late weichselian marinelimit indicate that the prevailing westerly fetch was dampened by a semi permanent sea ice cover allowing long shore drift to predominate a period of accelerated emergence 15 to 30 m ka between 10 5 and 9 ka is correlative with rapid deglaciation of fiords the middle and late holocene is characterized by two brief transgressions one between 6 5 and 5 0 ka that did not exceed 7 m asl and a present probable slow rise in sea level that commenced 2 to 1 ka the strandline tilts in northwestern spitsbergen and the pattern and rate of emergence on svalbard indicate that the maximum glacier loads during the late weichselian were centered on nordaustlandet and on the central and eastern part of the archipelago northwestern and southwestern spitsbergen were marginal to glacial loading and were deglaciated early 13 ka which is presently incompatible with maximum ice sheet extent and the timing and position of deglacial margins recently reconstructed for the barents sea and svalbard mountain ranges and large fiords probably confined major outlet glaciers to the central part of the archipelago preventing inundation of much of western spitsbergen by an inferred large ice sheet based in eastern svalbard and the barents sea

postglacial emergence of western franz josef land russian and retreat of the barents sea ice sheet uncertainty remains on the timing and extent of late weichselian glaciers over the qsr barents and kara sea shelves franz josef land russia is a critical area for deciphering the record of glacier fluctuations and postglacial relative sea level change coastal forelands on the archipelago are covered by a well preserved raised beach sequence containing abundant and pristine driftwood whalebone and shell 4c dating of these materials provides site specific emergence records for the archipelago and some of the oldest ages on deglaciation of 10 400 bp three apparent still stands in emergence are inferred from morphology of the raised beach sequence and 4c dating between 9900 and 6200 bp and at ca 5500 bp and 3500 bp the earliest sea level arrest after formation of the marine limit reflects a balance between glacio isostasy and eustasy concomitant with the final phase of global sea level rise the latter two sea level arrests during the middle to late holocene are less pronounced and may indicate increased height of the ocean surface with greater storminess and extended open water conditions raised beaches at 1 2 m a s l and j4c dated at 1000 to 2000 bp give contemporary emergence rates of 1 to 2 mm year the low current rates of emergence on franz josef land are similar to areas in fennoscandinavia that sustained modest late weichselian glacier loads 1500 m within a few 100s of km of the inferred ice sheet margin the pattern of postglacial emergence and strandline tilts indicates that past glacier loads were greater over the adjacent barents sea than franz josef land marine and terrestrial records from franz josef land place retreat of glaciers from coastal areas by 10 400 bp whereas the adjacent franz victoria trough was deglaciated by 13 000 bp retreat of the barents sea ice sheet was probably underway by 13 500 bp coincident with rising global sea level and elevated summer insolation we infer that iceberg calving through the deep troughs bordering the barents sea particularly with rapidly rising sea level ca 12 000 bp was an important process controlling the demise of the barents sea ice sheet copyright 1996 elsevier science ltd

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

the determination of rates of land uplift in norway it is the task and the responsibility of the geodetic section within the geographical survey of norway to establish and maintain the national horizontal and vertical geodetic primary control networks of that country provided that relative crustal movements take place within norway they will cause deformations to these networks there is no geodetic proof that any horizontal deformations of the surface layer of the crust take place in continental norway and there is no established geological evidence of such movements either in 1984 a small geodetic control network was established and measured for the first time across a possibly active fault it is not expected that horizontal movements will cause any serious problems in the maintenance of the horizontal network vertical movements of the ground however are causing us problems both in the establishment and in the maintenance of a national height system

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

the last glacial maximum on spitsbergen svalbard most scientists have concluded previously that the west coast of spitsbergen svalbard remained ice free during the late weichselian between 25 000 and 10 000 yr b p we conclude that the glaciation was more extensive terraces that were postulated to have been ice free are covered by a thin late weichselian till sudden drop in the marine limit and basal radiocarbon dates of raised glaciomarine sediments demonstrates that the glaciers in the main fjords isfjorden and van mijenfjorden terminated west outside of the fjord mouths basal radiocarbon dates from glaciomarine clay above till in cores from the continental shelf west of spitsbergen yielded ages of about 12 500 yr b p from which we conclude that the ice extended to the shelf edge based on the extent of amino acid diagenesis in radiocarbon dated molluscs the duration of the maximum extension of the late weichselian glaciation was short certainly less than 10 000 years during the ice free period preceding that glaciation at least back to 40 000 yr b p the glaciers on svalbard were not significantly larger than at present as shown by marine deposits close to the glacier snouts many radiocarbon dates place deglaciation of the outer coast at about 12 500 yr b p at about 10 000 yr b p the rest of the archipelago rapidly became ice free

elevation changes measured on svalbard glaciers and ice caps from airborne laser data precise airborne laser surveys were conducted during spring in 1996 and 2002 on 17 ice caps and glaciers in the svalbard archipelago covering the islands of spitsbergen and nordaustlandet we present the derived elevation changes lower elevation glaciers in south spitsbergen show the largest thinning rates of 0 5 m a 1 while some of the higher more northerly ice caps appear to be close to balance the pattern of elevation change is complex however due to several factors including glacier aspect microclimatological influences and the high natural annual variability in local accumulation and ablation rates anomalous changes were observed on fridtjovbreen which started surging in 1996 at the start of the measurement period on this glacier thinning of 0 6 m a 1 w as observed in the accumulation area coincident with thickening at lower elevations asymmetric thinning was found on two ice caps on nordaustlandet with the largest values on the eastern side of vestfonna but the western slopes of vegafonna the mean elevation change for all ice masses was 0 19 m a 1 w e which is 1 6 times the net mass balance value determined for the last 30 years using mass balance sensitivity estimates for svalbard suggests that the implied increase in negative balance is linked to warmer air temperatures in the late 1990s multiple linear regression suggests that mass balance is most closely correlated with latitude rather than mean altitude or longitude

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

holocene glacier and climate fluctuations on franz josef land arctic russia 80 n fluctuations in glacier extent provide the first comprehensive record of holocene paleoclimate for franz josef land glacier fluctuations were constrained using 45 14c ages from 16 glacier margins many glaciers were behind present margins before 9 4 kyr possibly as early as 10 3 kyr and probably remained so until at least 4 4 kyr where kyr 14c yr b p 1000 subsequently glaciers expanded probably reaching present margins before 3 2 kyr but certainly by 2 kyr a prominent neoglacial advance occurred ca 1 kyr and was followed by little ice age advances including one in the middle 1600s a d glaciers were larger than present at the turn of the century followed by widespread retreat soon after the holocene glacier record closely mimics that of svalbard 500 to 1000 km to the west suggesting similar glacier mass balance changes over a broad region of the eurasian arctia independent paleoclimate evidence from svalbard indicates higher than present summer air temperatures during the early to middle holocene when glaciers were behind present margins followed by generally cooler summer conditions and intermittent glacier advances and retreats holocene glacier variations were probably more influenced by summer temperature than winter precipitation

mantle viscosity and ice age ice sheet topography ice age paleotopography and mantle viscosity can both be inferred from observations of earth s response to the most recent deglaciation event of the current ice age this procedure requires iterative application of a theoretical model of the global process of glacial isostatic adjustment results demonstrate that the iterative inversion procedure converges to a paleotopography that is extremely close to that from the ice 4g model the accompanying mantle viscosity profile is furthermore shown to reconcile the requirements of aspherical geoid anomalies related to the mantle convection process thus resolving a fundamental issue concerning mantle rheology the combined model also explains postglacial sea level histories for the east coast of the united states

amino acid geochronology resolution and precision in carbonate fossils changes in indigenous proteins preserved in carbonate skeletons can be used to estimate the time elapsed since death of the organism racemization the most widely used reaction in amino acid geochronology refers to the inversion of l amino acids to their d configuration for the protein amino acid l isoleucine racemization occurs about only one of the two chiral carbon atoms this reaction epimerization proceeds from an initial dl ratio near zero to an equilibrium ratio of about 1 30 the reaction rate is controlled primarily by temperature and to a lesser degree by the nature of the proteins themselves a variable related to taxonomy and the extent of protein degradation analyzing monospecific samples minimizes the taxonomic variable the resolving power of dl ratios as relative age indices is a function of the reaction rate degree of natural variability and analytical uncertainty natural variability is defined as the spread in ratios in five well preserved shells of the same age from a single stratum and is primarily related to taxonomy it can range from 20 or more in taxa of low reliability to 1 in taxa of greatest integrity 5 to 10 is to be expected analytical uncertainty within a single laboratory is relatively insignificant amounting to no more than 2 but interlaboratory comparisons suggest caution in comparing ratios determined at different laboratories or by different techniques sampling appropriate portions of a shell is essential to minimize variability in dl ratios site temperature exerts the greatest control on reaction rate hence resolving power for tropical sites 25 c age differences 1 ka can be resolved within the holocene and ca 5 to 10 ka for older samples as the rate decreases equilibrium is attained after 150 to 300 ka the reaction rate is substantially lower at mid latitude sites ca 10 c where equilibrium requires about 2 ma and resolution within the last glacial cycle is no better than 10 to 20 ka arctic sites 10 c show almost no measurable racemization within the holocene and in extreme cases even within the last 100 ka equilibrium is not attained in 10 ma the extent of amino acid racemization epimerization in carbonate fossils provides chronological information for the critical time period beyond radiocarbon dating dl ratios can be used directly as relative age indices and with suitable calibration can provide reasonable estimates of absolute age and or effective diagenetic temperature improving the accuracy of racemization based age estimates requires a better understanding of racemization kinetics in carbonate systems

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

late quaternary stratigraphy of western yamal peninsula russia new constraints on the configuration of the eurasian ice sheet ice sheet reconstructions for the last glacial maximum in northern eurasia range from nearly complete coverage by a contiguous marine based ice sheet to large unglaciated areas stratigraphic records from yamal peninsula russia provide new insight on the eastern limit of the eurasian ice sheet in the kara sea radiocarbon and infrared stimulated luminescence ages from coastal cliff sections date the emplacement of the kara diamicton as older than ca 40 ka reflecting regional glaciation ice wedge growth peat accumulation and eolian and fluvial deposition characterized the past 40 k y and do not support coverage of yamal peninsula by an ice sheet or proximity to a glacier margin thus the late weichselian eurasian ice sheet was largely confined to barents sea and its global sea level contribution is reduced to 7 m of sea level equivalent

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

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

depositional history of the north taymyr ice marginal zone siberia a landsystem approach the sediment landform associations of the northern taymyr peninsula in arctic siberia tell a tale of ice sheets advancing from the kara sea shelf and inundating the peninsula probably three times during the weichselian in each case the ice sheet had a margin frozen to its bed and an interior moving over a deforming bed the north taymyr ice marginal zone ntz comprises ice marginal and supraglacial landsystems dominated by thrust block moraines 2 3 km wide and large scale deformation of sediments and ice large areas are still underlain by remnant glacier ice and a supraglacial landscape with numerous ice walled lakes and kames is forming even today the proglacial landsystem is characterised by subaqueous e g deltas or terrestrial e g sandar environments depending on location altitude and time of formation dating results osl c 14 indicate that the ntz was initiated ca 80 kyr bp during the retreat of the early weichselian ice sheet and that it records the maximum limit of a middle weichselian glaciation ca 65 kyr bp during both these events proglacial lakes were dammed by the ice sheets part of the ntz was occupied by a thin late weichselian ice sheet 20 12 kyr bp resulting in subaerial proglacial drainage copyright c 2002 john wiley sons ltd

9 400 yr b p the mortality of mollusk shell mya truncata at high arctic is associated with a sudden cooling event an 118 cm long well preserved sediment profile was collected from a paleo notch formed by ocean wave action before rising to the terrace on ny alesund svalbard norway a large number of mollusk shell fragments predominantly mya truncata were found in the sediment profile ams 14c dating and stable oxygen and carbon isotope analyses were performed on the shell fragments samples the reservoir corrected radiocarbon ages averaged 9 400 yr b p which accurately dates the raised terrace and the upper marine limit after kongsfjorden was completely deglaciated the calibrated aragonite isotopic temperature equation was established for ny alesund by comparing the 18o profiles of modern mollusks as follows t c 16 26 3 68 18oaragonite pdb 18owater vsmow the reconstructed paleotemperature range was 0 52 to 4 78 c warmer than today by about 1 c which was further confirmed by reconstructed sea surface temperature sst in west svalbard moreover the mortality of mollusks was very likely caused by an abrupt cooling event at about 9 400 yr b p which was triggered by reduced insolation weakened thermohaline circulation and abruptly decreased sst more evidences for this distinct but short cooling event centered at about 9 400 yr b p were found in northern siberia north atlantic alps and eastern europe

a comparison of different ways of dealing with isostasy examples from modelling the antarctic ice sheet during the last glacial cycle the bedrock isostatic response exerts a strong control on ice sheet dynamics and is therefore always taken into account in ice sheet models this paperreviews the various methods normally used in the ice sheet modeling community to deal with the bedrock response and compares these with a moresophisticated full earth model each of these bedrock treatments five in total are coupled with a three dimensional thermomechanical ice sheet model underthe same forcing conditions to simulate the antarctic ice sheet during the last glacial cycle the outputs of the simulations are compared on the basis of thetime dependent behavior for the total ice volume and the mean bedrock elevation during the cycle and of the present rate of uplift over antarctica thiscomparison confirms the necessity of accounting for the elastic bending of the lithosphere in order to yield realistic bedrock patterns it furthermoredemonstrates the deficiencies inherent to the diffusion equation in modeling the complex deformation within the mantle nevertheless when characteristicparameters are varied within their range of uncertainty differences within one single method are often of the same order as those between the variousmethods this overview finally tries to point out the main advantages and drawbacks of each of these methods and to determine which one is mostappropriate depending on the specific modeling requirements

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

the margin of the last barents kara ice sheet at markhida northern russia the markhida moraine is a broad zone of ice marginal landforms and deposits running e w across the pechora lowland in northern russia it was formed along the southern margin of an ice sheet advancing onto the coast from the kara sea previous researchers grosswald 1980 1983 1994a grosswald et al 1974 concluded that the moraine was formed during a readvance of the barents kara ice sheet after 9000 14c yr b p this conclusion was based on the occurrence of deformed lacustrine sediments dated 9000 to 10 000 14c yr b p between two presumed basal tills in the type section at markhida a reinvestigation of the section by the authors revealed only one basal till overlain by lacustrine sediments and diamictons yielding radiocarbon dates between 9000 and 10 000 14c yr b p luminescence dating from the sand underlying the till gave middle weichselian ages deformation structures and fabric in the sediments overlying the till solely reflect gravity driven processes not glaciotectonic deformation as claimed by previous investigators we conclude that most of these sediments were finally deposited during very slow retarded melting of a large body of buried glacier ice and the underlying permafrost thus the markhida moraine as an ice marginal feature was formed prior to 10 000 14c yr b p probably during the late weichselian but possibly as early as the middle weichselian

new constraints on the limits of the barents kara ice sheet during the last glacial maximum based on borehole stratigraphy from the pechora sea a new 14 c verified borehole stratigraphy provides the first age controlled reconstruction of the late quaternary glacial history of the pechora sea southeasternmost barents sea a complete glaciation of the pechora sea is confirmed for middle weichselian time prior to ca 35 40 ka composition of glacial erratics indicates that ice was moving from or across southernmost novaya zemlya and vaygach island after a brief interstadial period with normal marine conditions the pechora sea was affected by a drop in sea level and a drier climate subsequently the late weichselian barents kara ice sheet occupied the northwestern part of the pechora sea but did not reach the coast of the pechora lowland as previously believed these data provide a new constraint on the last glacial maximum lgm ice sheet limits in the eurasian arctic the inferred direction of the last glacial maximum ice movement in the pechora sea was from the northeast but with a stronger northern component than the penultimate glaciation the ice sheet retreated early ca 13 ka after which the shallow pechora sea was subjected to strong erosion during the postglacial sea level rise

an inter ice stream glaciated margin submarine landforms and a geomorphic model based on marine geophysical data from svalbard well preserved submarine landforms from the continental shelf and fjords of northwest ernmost svalbard provide an example of ice sheet deposition in an inter ice stream setting em1002 swath bathymetric imagery covering 1280 km 2 was examined at the shelf edge a distinctive and continuous belt of hum mocky topography represents the grounding zone of a slow moving late weichselian ice sheet active ice on the outer shelf is inferred from subtle lineations orientated parallel to fl ow low amplitude transverse moraines crosscut the lineations suggesting ice retreat across the outer shelf with brief stillstands on the middle and inner shelf large moraine ridges indicate multiple stillstands during de glaciation there are arcuate moraine ridges at fjord mouths streamlined crag and tail landforms are preserved from when ac tive full glacial ice fl owed out of the fjords clusters of smaller transverse ridges indi cate slow retreat of grounded ice through the fjords holocene sedimentation is by rainout from sediment rich meltwater producing smooth basin fi ll small slides from the fjord walls are common little ice age glacier readvance produced another set of terminal moraines and smaller retreat moraines in the innermost fjords a schematic model of this inter ice stream glacial landform assem blage summarizes the geomorphic record it is compared with a model derived from sev eral svalbard cross shelf troughs occupied by fast fl owing late weichselian ice streams in general the seafl oor morphology of continen tal margins affected by ice streams is domi nated by streamlined subglacially produced landforms oriented in the former ice fl ow direction interrupted by major grounding zone wedges formed during temporary halts in ice retreat by contrast between ice streams shelf and fjord morphology records submarine landforms of various dimensions oriented mainly transverse to ice fl ow pro duced at slowly retreating grounded ice sheet margins there is little evidence for channeled subglacial water fl ow in the form of eskers and ice contact fans on the sval bard margin implying that basal water is drained or advected mainly within soft sub glacial sediments

paleoceanographic reconstructions of surface ocean conditions in the greenland iceland and norwegian seas through the last 14 ka based on diatoms prior reconstructions of the last glacial maximum and the holocene did not include detailed paleoclimate data from the greenland iceland and norwegian gin seas which cover sensitive areas for oceanographic boundaries sea ice distribution and deep water formation in order to fill this gap we studied nine well dated sediment cores from this area and reconstructed the paleoceanographic conditions of the surface gin seas at 2000 year intervals since 13 400 bp based on the diatom record results show that a n s extending sea ice free corridor had opened along norway already at 13 400 bp indicating a northward flow of a branch of the north atlantic drift possibly caused by a change in the jet stream flow due to the decreased height of the north american ice sheet a major change of climatic conditions occurred over the gin seas as the insolation anomaly reached its maximum around 9000 bp when the sea ice cover and the oceanic fronts retreated to a northwesterly position along greenland and the ocean temperatures rose the first half of the holocene is recorded as the warmest period during the last 13 400 bp in the gin seas the duration of this climatic optimum decreased both toward the north and toward the margins of the area the second half of the holocene is characterized by a cooling trend in step with the decreasing insolation these results support the proposal of imbrie et al 1992 that the gin seas region acts as an initial responder to insolation changes

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