isolation basins sea level changes and the holocene history of the greenland ice sheet abstract isolation basins are natural topographic depressions that at various times in their history may be connected to or isolated from the sea by changes in relative sea level rsl they provide a valuable source of data for tracking large scale tens of meters changes in rsl over millennia as well as quiet water depositional environments where abrupt changes caused by tsunami iceberg roll or storms may be recorded in this paper we review isolation basins as sources of rsl data with a particular focus on their use in greenland to constrain the holocene history of the ice sheet a new rsl curve from disko fjord west greenland is presented which shows that local ice free conditions were established at c 11 k cal yr bp after which rsl fell rapidly from a marine limit at c 80 m to reach close to present sea level by c 4 k cal yr bp we compare this record with other isolation basin rsl data from six other sites in disko bugt and note a strong northwest southeast differential rebound across the area during the early and mid holocene that reflects variations in ice load history we compare the disko bugt data with other previously published isolation basin rsl records from sisimiut central west greenland nanortalik south greenland and ammassalik southeast greenland rsl fell below present during the early holocene at nanortalik c 10 k cal yr bp and during the mid to late holocene elsewhere before rising to present these differences reflect variations in the timing and amount of greenland ice load change since the last glacial maximum as well as non greenland processes notably the collapse of the laurentide forebulge and also changes in ice equivalent sea level isolation basin data have relatively small age and height uncertainties compared with other rsl indicators enabling them to resolve between different earth and ice sheet models especially during periods of large ice load and rsl change

evidence for storegga tsunami run up at the head of nordfjord western norway numerical simulations show that the storegga tsunami 8 150 cal a bp penetrated into fjords and sounds along the norwegian coast because of its large wavelengths of about 600 800 km despite this deposits from the tsunami have not previously been reported from the innermost fjord district probably because suitable sedimentary archives are lacking in the steep fjord landscape here we describe a persistent and well defined depositional unit up to 3 m thick found in a lake sequence at the head of the 106 km long nordfjord which we interpret as a deposit from the storegga tsunami the unit is identified and mapped in seismic profiles as a continuous semi transparent unit which in places cut deeply into the underlying strata in sediment cores the unit consists of grey silt with sub units containing shell or plant fragments gravel and sand clasts and redeposited lake mud radiocarbon ages date the deposit to the time of the storegga tsunami 8 150 cal a bp we estimate a minimum run up of 1 7 5 m for the tsunami based on the inferred elevation of the lake outlet relative to sea level at that time

consistently large marine reservoir ages in the norwegian sea during the last deglaciation with the exception of the gs 1 younger dryas coldperiodmarine reservoir ages for the last deglaciation in the north atlantic norwegian sea are generally assumed to have been around 400 500 radiocarbon years in magnitude earth planet sci lett 126 1994 275 radiocarbon 37 1995 53 quat res 52 1999 104 nature 412 2001 724 by comparing the climate records obtained from the grip ice core nature 359 1992 311 j quat sci 13 4 1998 283 andfrom north atlantic norwegian sea cores quat res 52 1999 104 geology 23 12 1995 1059 nature 356 1991 757 nature 356 1992 757 paleoceanography 3 1 1988 1 nature 343 1990 612 earth planet sci lett 126 1994 275 with radiocarbon dated european continental records we show that marine reservoir ages in the norwegian sea were of the order of 1000 14 c yr including large uncertainties this approach rests on the reasonable assumption that climate changes throughout the ne atlantic andeurope were more or less synchronous at the centennial scale fairly large variations in reservoir ages over time may have been causedby changing atmospheric 14 c content the results indicate that detailed land sea correlations for the north atlantic during the last deglaciation are not feasible using radiocarbon dating alone r 2003 elsevier science ltd all rights reserved

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

sensitivity of palaeotidal models of the northwest european shelf seas to glacial isostatic adjustment since the last glacial maximum abstract the spatial and temporal distribution of relative sea level change over the northwest european shelf seas has varied considerably since the last glacial maximum due to eustatic sea level rise and a complex isostatic response to deglaciation of both near and far field ice sheets because of the complex pattern of relative sea level changes the region is an ideal focus for modelling the impact of significant sea level change on shelf sea tidal dynamics changes in tidal dynamics influence tidal range the location of tidal mixing fronts dissipation of tidal energy shelf sea biogeochemistry and sediment transport pathways significant advancements in glacial isostatic adjustment gia modelling of the region have been made in recent years and earlier palaeotidal models of the northwest european shelf seas were developed using output from less well constrained gia models as input to generate palaeobathymetric grids we use the most up to date and well constrained gia model for the region as palaeotopographic input for a new high resolution three dimensional tidal model roms of the northwest european shelf seas with focus on model output for 1 ka time slices from the last glacial maximum taken as being 21 ka bp to present day we demonstrate that spatial and temporal changes in simulated tidal dynamics are very sensitive to relative sea level distribution the new high resolution palaeotidal model is considered a significant improvement on previous depth averaged palaeotidal models in particular where the outputs are to be used in sediment transport studies where consideration of the near bed stress is critical and for constraining sea level index points

the deep accumulation of 10be at utsira southwestern norway implications for cosmogenic nuclide exposure dating in peripheral ice sheet landscapes cosmogenic nuclide exposure dating is a widely used method for constraining past ice sheet histories we scrutinize a recently published data set of cosmogenic 10be data from erratic boulders in norway used to constrain the deglaciation of the western scandinavian ice sheet to 20 ka our model of the 10be inventory in glacial surfaces leads us to conclude that the chronology may be afflicted by the deep subsurface accumulation of 10be during long lasting ice free periods that resulted in 10be ages 10 too old we suggest that the majority of the dated erratic boulders contain a uniform level of inherited muon produced 10be and were derived from bedrock depths 2 5 m and most likely 4 m the implication of our finding is that for landscapes that experience long ice free periods between brief maximum glacial phases glacial erosion of 5 m is required to remove detectable traces of inherited 10be

late quaternary ice sheet history of northern eurasia the maximum limits of the eurasian ice sheets during four glaciations have been reconstructed 1 the late saalian 140 ka 2 the early weichselian 100 80 ka 3 the middle weichselian 60 50 ka and 4 the late weichselian 25 15 ka the reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in russia and siberia and with marine seismic and sediment core data the barents kara ice sheet got progressively smaller during each glaciation whereas the dimensions of the scandinavian ice sheet increased during the last ice age the barents kara ice sheet attained its maximum size as early as 90 80 000 years ago when the ice front reached far onto the continent a regrowth of the ice sheets occurred during the early middle weichselian culminating about 60 50 000 years ago during the late weichselian the barents kara ice sheet did not reach the mainland east of the kanin peninsula with the exception of the nw fringe of taimyr a numerical ice sheet model forced by global sea level and solar changes was run through the full weichselian glacial cycle the modeling results are roughly compatible with the geological record of ice growth but the model underpredicts the glaciations in the eurasian arctic during the early and middle weichselian one reason for this is that the climate in the eurasian arctic was not as dry then as during the late weichselian glacial maximum

marine 14c reservoir ages for 19th century whales and molluscs from the north atlantic abstract in order to compare radiocarbon dates on marine and terrestrial samples the former have to be corrected for a reservoir age we present reservoir ages from dating 21 whales collected 1860 1901 and recalculating dates of 23 molluscs collected 1857 1926 most of the whales were caught along the coast of norway but one is from france and one from iceland we assume the former mainly lived in the north and equatorial atlantic and in the norwegian sea whales feed only on pelagic organisms and will provide the reservoir age for the open ocean surface water however they travel long distances and will integrate the reservoir ages of the different water masses along their way molluscs dated from norway spitsbergen and arctic canada are stationary and monitor the sea water passing their dwelling site but some also take up carbon from particulate food or sediment pore water coastal water also often contains some continental carbon we present two different views on how to analyze and interpret the data mangerud recommends to use reservoir ages based on a combination of the whale and mollusc dates i e 380 30 and 360 30 yr relative to intcal04 and british oak respectively and a r value of 20 30 for the surface water in the n atlantic and norwegian sea bondevik and gulliksen maintain that the reservoir age and r along the norwegian coast is latitude dependant with r values increasing from 3 22 in the south to 105 24 at spitsbergen whales reflecting north atlantic open ocean surface water have lower r 7 11 than most molluscs

late glacial sea level and ocean margin environmental changes interpreted from biostratigraphic and lithostratigraphic studies of isolation basins in northwest scotland

changes in north atlantic radiocarbon reservoir ages during the allerod and younger dryas estimates of the radiocarbon age of seawater are required in correlations between marine and terrestrial records of the late quaternary climate we radiocarbon dated marine shells and terrestrial plant remains deposited in two bays on norway s west coast between 11 000 and 14 000 years ago a time of large and abrupt climatic changes that included the younger dryas yd cold episode the radiocarbon age difference between the shells and the plants showed that sea surface reservoir ages increased from 400 to 600 years in the early yd stabilized for 900 years and dropped by 300 years within a century across the yd holocene transition

middle and late weichselian devensian glaciation history of south western norway north sea and eastern uk data from eastern england scotland the northern north sea and western norway have been compiled in order to outline our current knowledge of the middle and late weichselian glacial history of this region radiometric dates and their geological context from key sites in the region are presented and discussed based on the available information the following conclusions can be made i prior to 39 cal ka and most likely after ca 50 cal ka scotland and southern norway were extensively glaciated most likely the central north sea was not glaciated at this time and grounded ice did not reach the shelf edge ii during the time interval between 29 and 39 ka periods with ameliorated climate including the alesund sandnes and tolsta interstadials alternated with periods of restricted glaciation in scotland and western norway iii between 29 and 25 ka maximum weichselian glaciation of the region occurred with the fennoscandian and british ice sheets coalescing in the central north sea iv decoupling of the ice sheets had occurred at 25 ka with development of a marine embayment in the northern north sea v between 22 and 19 ka glacial ice expanded westwards from scandinavia onto the north sea plateau in the tampen readvance vi the last major expansion of glacial ice in the offshore areas was between 17 5 and 15 5 ka at this time ice expanded in the north western part of the region onto the maloy plateau from norway and across caithness and orkney and to east of shetland from the moray firth the norwegian channel ice stream ncis which drained major parts of the south western fennoscandian ice sheet was active at several occasions between 29 and 18 ka

the early mid holocene transgression tapes at the norwegian coast comparing observations with numerical modelling abstract the early to mid holocene transgression dated between approximately 10 000 and 7000 cal yr bp inundated a significant part of the coastal areas of norway in this paper we compare observations of the amplitude of the transgression with numerical modelling the observations of the transgression along the coast vary from a couple of meters to more than 20 m and depend on the distance from the margin of the last ice sheet over fennoscandia we reviewed and evaluated the uncertainty of the data and present here the most reliable observations of the transgression data derived from the analysis of isolation basins from 17 locations spread along the norwegian coast the numerical model simulates the response of the earth to the deglaciation and changing sea level and shows that the transgression is mainly a result of the rising sea level and movements of the earth due to postglacial rebound our earth model consists of two viscous layers overlain by an elastic lithosphere we found a good match to the observations in southern norway with a weak effective elastic lithosphere 30 km this is consistent with a previous study of tilt of the raised late glacial shorelines in southwestern norway in northern norway however the same earth model and ice model give significant mismatch to the observations the best fit model for northern norway has a significantly thicker effective elastic lithosphere an alternative explanation for the mismatch could be a later deglaciation of the barents sea than generally assumed or neo tectonism in the area

quantifying variable rates of postglacial relative sea level fall from a cluster of 24 isolation basins in southern norway abstract sediment sequences obtained from 24 isolation basins located on the skagerrak coastline are used to develop new sea level index points for southern norway the basins are located near a common shoreline isobase and extend from marine limit at c 83 m asl to present sea level the abundance of bedrock isolation basins within the small study area enables a high resolution reconstruction of postglacial relative sea level change for most of the basin records 3 5 samples of terrestrial plant macrofossils were radiocarbon dated across the biostratigraphically defined isolation boundary eight of the isolation events were further constrained by bayesian modelling of the radiocarbon age results the overall reconstructed sea level history is as expected for a formerly glaciated coastline consisting of a rapid regression from marine limit followed by a slower pace of relative sea level fall from early mid holocene to present the new dataset of sea level index points however further delineates century scale oscillations in rates of sea level regression which record past changes in sea surface height and vertical land motion glacial isostatic adjustments gia results provide new constraints for future numerical models aimed at reducing uncertainty in century scale relative sea level projections for fennoscandia

late weichselian vegetation climate and floral migration at liastemmen north rogaland south western norway palynological results from liastemmen indicate a tripartite division of the late weichselian in the pleniglacial period from deglaciation ca 14000 bp to ca 13000 bp artemisia dominated pioneer vegetation on disturbed mineral soil was strongly influenced by cold winters and katabatic winds the late weichselian interstadial ca 13000 bp ca 11000 bp comprises a salix shrub consolidation phase and from ca 12700 bp a tree birch phase in the last 500 years of this period july and january means are estimated to about 16 c and between 2 c and 6 c respectively in the younger dryas stadial ca 11000 bp ca 10200 bp artemisia dominated vegetation returns three brief climatic deteriorations ca 12 250 bp 11 700 bp and 11 300 bp unfavourable to woody vegetation on humus soils are demonstrated within the interstadial critical climatic factors include cool winters and strong winds exposing vegetation and soil to frost drought and erosion the oldest and strongest oscillation probably involving local deforestation is correlated with the older dryas deterioration boreal circumpolar eurasiatic and arctic alpine plants dominated the late glacial flora for the majority of the late glacial taxa a northward migration is demonstrated this may also apply for papaver radicatum pinguicula alpina and primula scandinavica all with bicentric distributions in norway today

postglacial relative sea level history of the prince rupert area british columbia canada this paper presents a history of relative sea level rsl change for the last 15 000 years in the prince rupert region on the northern coast of british columbia canada one hundred twenty three radiocarbon ages of organic material from isolation basin cores sediment sequence exposures and archaeological sites having a recognized relation to past sea levels constrain postglacial rsl the large number of new measurements relating to past sea level provides a well constrained rsl curve that differs in significant ways from previously published results after deglaciation following the last glacial maximum the region experienced an isostatically induced rapid rsl drop from as much 50 m asl to as low as 6 3 m asl in as little as a few centuries between 14 500 bp and 13 500 bp after a lowstand below current sea level for about 2000 years during the terminal pleistocene rsl rose again to a highstand at least 6 m asl after the end of the younger dryas rsl slowly dropped through the holocene to close to its current position by 2000 1500 bp with some potential fluctuations between 3500 and 1500 bp this study highlights variation in rsl histories across relatively short distances which must be accounted for by local rsl reconstructions such as this one this rsl curve aided in the identification of an 8000 9000 year old archaeological site on a 10 12 m asl terrace which is currently the earliest dated archaeological site in the area and it provides guidance for searching for even older archaeological remains we highlight the utility and potential of this refined rsl history for developing surveys for other archaeological sites associated with paleoshorelines

tectonic and geodynamic setting of oil and gas basins of the soviet union within the territory of the soviet union and its offshore economic zone are about 70 sedimentary basins containing oil and gas the basins include almost all basin types described in present day plate tectonic classifications namely 1 intracontinental and pericontinental rifts suprarift syneclises and zones of pericratonic downwarps 2 ancient passive margins of continents with adjacent overthrust fold system 3 modern passive margins of continents 4 zones of convergence of lithospheric plates i e zones of subduction of oceanic plates below continental plates and 5 zones of collision of continental lithospheric plates basins of the first type include the pripyat dnieper donets aulacogen the viluy aulacogen of siberia the huge west siberian supra aulacogen basin the analogous yenisei khatanga basin and others the second type includes the volga urals basin with the ural foredeep azov kuban basin and terek caspian basin with the greater caucasus foredeeps and others the difference between these two types is rather arbitrary because the passive margins of continents also undergo the rift stage of development though their main stage of oil and gas accumulation corresponds to the post rift stage the third type is represented by the poorly studied prospective basins of the arctic margin of the soviet union the fourth includes numerous but relatively small basins of the far eastern and northe stern soviet union of which the east sakhalin west kamchatka and anadyr basins have proved to contain oil and gas rifting also played a role in the formation of the back arc group of these basins basins in central asia fergana south tadjik and the transcaucasia region south caspian belong to the fifth basin type the central asian basins lie within the area of secondary epiplatform orogenesis whereas the transcaucasian basins are with the area of primary epigeosynclinal orogenesis so far the only type of basin not identified within the territory of the soviet union is the pull apart basin the location and distribution of oil and gas deposits in the section of a basin prevailing types of traps and scale of potential resources are all features influenced by the geodynami type of the basin

late devensian and holocene records of relative sea level changes in northwest scotland and their implications for glacio hydro isostatic modelling raised tidal marshes and isolation basins lakes that were once connected to the sea in northwest scotland record changes in relative sea level following deglaciation during the late devensian to the present the kentra to arisaig area which was covered by relatively thick ice c 900 m at the last glacial maximum lgm shows a regression from a marine limit between 36 5 m od and 40 m od at c 15 9 kyr cal bp range 15 6 16 3 kyr cal bp through to an early holocene minimum a range of sites in the same area record a mid holocene maximum indicative of mean sea level c 6 5 m above present the maximum is not a well developed and short duration highstand as predicted by a number of models but is an extended period 8 0 5 0 kyr cal bp with sea level within c 1 m of the maximum sites to the north in kintail show no late devensian record because much of the area lies within the younger dryas ice limit the altitude of the mid holocene maximum in kintail is not well constrained but occurred 7 9 8 1 kyr cal bp further north sites on the applecross peninsula record a late devensian fall in sea level and a holocene maximum for mean sea level no higher than c 3 0 m above present in coigach the furthest north of the new sites and well outside the younger dryas ice limit there is no evidence recorded of late devensian sea levels above present the holocene maximum here was around c 2 5 m above present these observations of sea level change all standardised to change in mean sea level relative to present constrain the glacio hydroisostatic rebound model parameters earth models comprising three mantle layers with lateral viscosity and elastic parameters give a satisfactory description of rebound the parameters h lithosphere thickness 65 km g 6 upper mantle viscosity 4 1020 pa 14c seconds and g lower mantle viscosity 1022 pa 14c seconds give the best overall agreement but discrepancies between observations and predictions remain an increase of 10 in ice thickness north of the great glen compared to the previous optimum ice model provides good agreement for many sites but important discrepancies remain for the northern sites and indicate inadequacies in the model of the british ice sheet several alternative ice models are examined but the various combinations of earth and ice model illustrate the non uniqueness of the solution a combination of more extensive ice limits especially onto the hebridean shelf and west shetland shelf and some changes to ice thicknesses over the mainland should produce a better agreement but the spatial coverage of observations remains a limitation to producing a unique solution the characteristics of the holocene highstand age duration and amplitude at the di erent sites refutes the assumption that globally deglaciation ceased abruptly 7000 yr ago the observations are consistent with an ice model that includes c 3 m of melting over the last 7000 yr 2000 elsevier science ltd all rights reserved

dynamics of mixed bottom boundary layers and its implications for diapycnal transport in a stratified natural water basin here we report on two field experiments from lake alpnach surface area 4 8 km 2 maximum depth 34 m that were designed to study the process of boundary mixing and to estimate its efficiency the ratio between the turbulent kinetic energy converted into potential energy and dissipated into heat for diapycnal tracer transport lake alpnach is particularly suited for this purpose because it is known from earlier experiments that 1 its currents follow a regular oscillatory pattern associated with basin wide standing internal waves seiches period similar to 0 5 days and 1 day respectively and 2 diapycnal tracer transport is mainly caused by boundary mixing during one of the experiments reported here strong seiches were excited regularly and damped on a timescale of the order of 3 days during the other experiment seiching motion was comparably weak if seiching is excited regularly we find a persistent well mixed bottom layer of 4 5 m height at the deepest part of the lake in the absence of regular seiching the layer disappears within 10 20 days on the sloping bottom boundaries the well mixed layers 1 are of much more transient nature 2 exhibit different thermal structure and 3 decrease in thickness toward shallower depth inversely proportionally to the stability at the same depth in the lake interior their reduced thickness is possibly the result of repeatedly occurring intrusions of boundary mixed water masses that are observed to extend horizontally similar to 100 200 m into the lake interior as a consequence of repeated generation of intrusions mixing on the sloping boundaries is expected to be considerably more efficient compared to mixing over flat bottom boundaries the observed mixing efficiency the ratio of the rate of change of potential energy below depth z caused by turbulence to the energy loss by bottom friction below depth z increases indeed from 0 01 0 01 in the deepest well mixed layers to 0 15 0 04 in the upper pycnocline

calendar year age estimates of allerod younger dryas sea level oscillations at os western norway a detailed shoreline displacement curve documents the younger dryas transgression in western norway the relative sea level rise was more than 9 m in an area which subsequently experienced an emergence of almost 60 m the sea level curve is based on the stratigraphy of six isolation basins with bedrock thresholds effort has been made to establish an accurate chronology using a calendar year time scale by 14c wiggle matching and the use of time synchronic markers the vedde ash bed and the post glacial rise in betula birch pollen the sea level curve demonstrates that the younger dryas transgression started close to the allerod younger dryas transition and that the high stand was reached only 200 yr before the younger dryas holocene boundary the sea level remained at the high stand for about 300 yr and 100 yr into holocene it started to fall rapidly the peak of the younger dryas transgression occurred simultaneously with the maximum extent of the ice sheet readvance in the area our results support earlier geophysical modelling concluding a causal relationship between the younger dryas glacier advance and younger dryas transgression in western norway we argue that the sea level curve indicates that the younger dryas glacial advance started in the late allerod or close to the allerod younger dryas transition copyright 2004 john wiley sons ltd

evidence of early deglaciation 18 000 cal a bp and a postglacial relative sea level curve from southern karmoy south west norway

a major re growth of the scandinavian ice sheet in western norway during allerod younger dryas abstract distinct younger dryas yd moraines are mapped more or less continuously around the scandinavian ice sheet in most areas there is no evidence to suggest that a glacial re advance took place during the yd either because it did not happen or because older deposits have been removed by glacial erosion in contrast we here present 90 radiocarbon dates from 36 different sites that were overrun by a major ice sheet advance in the area between hardangerfjorden and sognefjorden sw norway thus this region is exceptional for examining the glacial response to the climate shifts across allerod yd the re growth of the ice sheet in this sector commenced during the allerod interstadial it expanded along 600 800 m deep fjords reaching a thickness of up to 2000 m we produce time distance diagrams for two lobes for both the outermost coast became ice free close to 15 cal ka bp i e at the onset of the bolling the hardangerfjorden lobe re advanced during the older dryas 14 cal ka bp an event that was not replicated for the herdla lobe farther north both lobes reached their most landward position before re advancing at 13 5 13 0 cal ka and obtained their maximum extent at the very end of the yd 11 5 cal ka the late culmination of the advance is accurately dated and differs from most of the scandinavian ice sheet margin where the maximum was reached during early or middle yd we also present a time distance diagram from the last glacial maximum to the ice divide showing two step retreat fast retreat occurs 21 20 and 11 5 10 cal ka bp separated by a period of almost no net retreat 20 11 5 cal ka bp which contrasts with much more even retreat in other parts of the scandinavian ice sheet

relative sea level changes and crustal movements in britain and ireland since the last glacial maximum abstract the new sea level database for britain and ireland contains 2100 data points from 86 regions and records relative sea level rsl changes over the last 20 ka and across elevations ranging from 40 to 55 m it reveals radically different patterns of rsl as we move from regions near the centre of the celtic ice sheet at the last glacial maximum to regions near and beyond the ice limits validated sea level index points and limiting data show good agreement with the broad patterns of rsl change predicted by current glacial isostatic adjustment gia models the index points show no consistent pattern of synchronous coastal advance and retreat across different regions 100 500 km scale indicating that within estuary processes rather than decimetre and centennial scale oscillations in sea level produce major controls on the temporal pattern of horizontal shifts in coastal sedimentary environments comparisons between the database and gia model predictions for multiple regions provide potentially powerful constraints on various characteristics of global gia models including the magnitude of mwp1a the final deglaciation of the laurentide ice sheet and the continued melting of antarctica after 7 ka bp

a multi proxy approach to assessing isolation basin stratigraphy from the lofoten islands norway article i nfo article history received 14 november 2009 available online 24 september 2010 this study takes a comprehensive approach to characterizing the isolation sequence of heimerdalsvatnet a coastal lake in the lofoten islands northern norway we use established methods and explore new techniques to assess changes in marine influence bathymetric and sub bottom profiles were acquired to examine basin wide sedimentation and a 5 8 m sediment core spanning the last 7800 cal yr bp was analyzed we measured magnetic susceptibility bulk organic matter properties molecular biomarkers diatom assemblages and elemental profiles acquired by scanning x ray fluorescence these characteristics of the sediment reflect detailed changes in salinity and water column conditions as the lake was progressively isolated three distinct litho chemo stratigraphic units represent a restricted marine phase 7800 6500 cal yr bp a transitional phase characterized by intermittent marine influence 6500 4900 cal yr bp and complete isolation and freshwater sedimentation 4900 cal yr bp to present although there are uncertainties in the estimate of the threshold elevation of the lake the timing of these phases generally corresponds with previous interpretations of the local relative sea level history this record captures sea level regression following the tapes transgression and supports the interpretation of a subsequent sea level stillstand dated in heimerdalsvatnet from 6500 to 4900 cal yr bp

a younger dryas ash bed in western norway and its possible correlations with tephra in cores from the norwegian sea and the north atlantic abstract a bed of volcanic ash up to 23 cm thick is found in lacustrine and marine sediments in western norway it is formally mamed the vedde ash bed and its age is approximately 10 600 yr b p i e mid younger dryas the bed consits of pure glass having a bimodal basaltic and rhyolitic somposition the geochemistry of the glass shards suggests an icelandic source by means of stratigraphic position and geochemistry the ash is correlated with ash zones found in cores from the continental shelf the norwegian sea and the north atlatic

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

eurasian ice sheet collapse was a major source of meltwater pulse 1a 14 600 years ago rapid sea level rise caused by the collapse of large ice sheets is a threat to human societies in the last deglacial period the rate of global sea level rise peaked at more than 4 cm yr 1 during meltwater pulse 1a which coincided with the bolling warming event some 14 650 years ago however the sources of the meltwater have proven elusive and the contribution from eurasian ice sheets has been considered negligible here we present a regional carbon 14 calibration curve for the norwegian sea and recalibrate marine 14c dates linked to the eurasian ice sheet retreat we find that marine based sectors of the eurasian ice sheet collapsed at the bolling transition and lost an ice volume of 4 5 7 9 m sea level equivalents sle over 500 years during peak melting 3 3 6 7 m sle of ice was lost potentially explaining up to half of meltwater pulse 1a a mean meltwater flux of 0 2 sv over 300 years was injected into the norwegian sea and the arctic ocean at a time when proxy evidence suggests vigorous atlantic meridional overturning circulation our reconstruction shows that massive marine based ice sheets can collapse in as little as 300 500 years marine based sections of the eurasian ice sheet collapsed rapidly during a warming event 14 600 years ago and contributed to the meltwater pulse 1a event according to a recalibrated age model for sediments from the norwegian sea

a model of greenland ice sheet deglaciation constrained by observations of relative sea level and ice extent an ice sheet model was constrained to reconstruct the evolution of the greenland ice sheet gris from the last glacial maximum lgm to present to improve our understanding of its response to climate change the study involved applying a glaciological model in series with a glacial isostatic adjustment and relative sea level rsl model the model reconstruction builds upon the work of simpson et al 2009 through four main extensions 1 a larger constraint database consisting of rsl and ice extent data model improvements to the 2 climate and 3 sea level forcing components 4 accounting for uncertainties in non greenland ice the research was conducted primarily to address data model misfits and to quantify inherent model uncertainties with the earth structure and non greenland ice our new model termed huy3 fits the majority of observations and is characterised by a number of defining features during the lgm the ice sheet had an excess of 4 7 m ice equivalent sea level iesl which reached a maximum volume of 5 1 m iesl at 16 5 cal ka bp modelled retreat of ice from the continental shelf progressed at different rates and timings in different sectors southwest and southeast greenland began to retreat from the continental shelf by 16 to 14 cal ka bp thus responding in part to the bolling allerod warm event c 14 5 cal ka bp subsequently ice at the southern tip of greenland readvanced during the younger dryas cold event in northern greenland the ice retreated rapidly from the continental shelf upon the climatic recovery out of the younger dryas to present day conditions upon entering the holocene 11 7 cal ka bp the ice sheet soon became land based during the holocene thermal maximum htm 9 5 cal ka bp air temperatures across greenland were marginally higher than those at present and the gris margin retreated inland of its present day southwest position by 40 60 km at 4 cal ka bp which produced a deficit volume of 0 16 m iesl relative to present in response to the htm warmth our optimal model reconstruction lost mass at a maximum centennial rate of c 103 4 gt yr our results suggest that remaining data model discrepancies are affiliated with missing physics and sub grid processes of the glaciological model uncertainties in the climate forcing lateral earth structure and non greenland ice particularly the north american component finally applying the huy3 greenland reconstruction with our optimal earth model we generate present day uplift rates across greenland due to past changes in the ocean and ice loads with explicit error bars due to uncertainties in the earth structure present day uplift rates due to past changes are spatially variable and range from 3 5 to 7 mm a including earth model uncertainty

marine reservoir age variability and water mass distribution in the iceland sea abstract lateglacial and holocene tephra markers from icelandic source volcanoes have been identified in five sediment cores from the north icelandic shelf and correlated with tephra layers in reference soil sections in north iceland and the grip ice core land sea correlation of tephra markers that have been radiocarbon dated with terrestrial material or dated by documentary evidence provides a tool for monitoring reservoir age variability in the region age models developed for the shelf sediments north of iceland based on offshore tephrochronology on one hand and on calibrated ams 14c datings of marine molluscs on the other display major deviations during the last 4500 years the inferred temporal variability in the reservoir age of the regional water masses exceeds by far the variability expected from the marine model calculations the observed reservoir ages are generally considerably higher by up to 450 years than the standard model ocean it is postulated that the intervals with increased and variable marine reservoir age reflect incursions of arctic water masses derived from the east greenland current to the iceland sea and the north icelandic shelf

sea level fluctuations imply that the younger dryas ice sheet expansion in western norway commenced during the allerod after the first emergence following deglaciation relative sea level rose by 10 m in western norway and culminated late in the younger dryas yd the relative sea level history reconstructed by dating deposits in isolation basins shows a sea level low stand between 13 640 and 13 080 cal yr bp a 10 m sea level rise between 13 080 and 11 790 cal yr bp and a sea level high stand between 11 790 and 11 550 cal yr bp shortly after the yd holocene boundary sea level fell abruptly by 37 m the shorelines formed during the sea level low stand in the mid allerod and during the sea level high stand in the yd have almost parallel tilts with a gradient of 1 3 m km 1 indicating that hardly any isostatic movement has taken place during this period of sea level rise we conclude that the transgression was caused by the major re advance of the scandinavian ice sheet that took place in western norway during the lateglacial the extra ice load halted the isostatic uplift and elevated the geoid due to the increased gravitational attraction on the sea our results show that the crust responded to the increased load well before the yd starting 12 900 cal yr bp with a sea level low stand at 13 640 cal yr bp and the subsequent yd transgression starting at 13 080 cal yr bp thus we conclude that the so called yd ice sheet advance in western norway started during the allerod possibly more than 600 years before the allerod yd transition r 2007 elsevier ltd all rights reserved

high resolution x ray fluorescence core scanning analysis of les echets france sedimentary sequence new insights from chemical proxies the les echets sediment sequence has recently been the subject of a high resolution multi proxy study which revealed shifts in lake productivity linked to greenland stadials and interstadials over the last 40 ka wohlfarth et al 2008 rapid ecosystem response to abrupt climate changes during the last glacial period in western europe 40 16 ka geology 36 407 410 here we present new elemental data for this sequence as acquired using an x ray fluorescence core scanning system which provides in situ high resolution continuous multi element analyses it was found that the strength of associations between the studied elements ti rb k zr si ca sr mn and fe varied over time with changes in lake status which are ultimately driven by changes in climate increases in fine grained detrital input as indicated by ti rb k and zr rb overlap with independently established periods of lower lake productivity and are interpreted to represent more arid conditions several of these arid periods are coincident with low diatom concentrations and the timing of heinrich events h4 h3 and h2 the duration of the environmental impacts linked to the h events varied by proxy with elemental data ti and zr rb estimating shorter events than the diatom data periods of lower detrital input and coarser grain sizes agreed in time with periods of higher lake productivity the elemental data provide new insights into hydrological changes and related sediment processes within the catchment and highlight the need for multi element and multi proxy approaches when reconstructing climate change using lacustrine sediment sequences copyright 2011 john wiley sons ltd

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

early break up of the norwegian channel ice stream during the last glacial maximum 10be dating last glacial maximum abstract we present 18 new cosmogenic 10 be exposure ages that constrain the breakup time of the norwegian channel ice stream ncis and the initial retreat of the scandinavian ice sheet from the southwest coast of norway following the last glacial maximum lgm seven samples from glacially transported erratics on the island utsira located in the path of the ncis about 400 km up flow from the lgm ice front position yielded an average 10 be age of 22 0 2 0 ka the distribution of the ages is skewed with the 4 youngest all within the range 20 2e20 8 ka we place most confidence on this cluster of ages to constrain the timing of ice sheet retreat as we suspect the 3 oldest ages have some inheritance from a previous ice free period three additional ages from the adjacent island karmoy provided an average age of 20 9 0 7 ka further supporting the new timing of retreat for the ncis the 10 be ages from utsira and karmoy suggest that the ice stream broke up about 2000 years earlier than the age assignment based on 14 c ages on foraminifera and molluscs from marine sediment cores we postulate that the scandinavian ice sheet flowed across the norwegian channel to denmark and onto the north sea plateau during early phases of the lgm when the ncis started to operate this ice supply to the north sea was cut off and the fast flow of the ncis also led to a lowering of the ice surface along the norwegian channel and thereby drawdown of the entire ice sheet this facilitated rapid calving of the ice front in the north sea and we reconstruct a large open bay across the entire northern north sea by 20 ka based on our 10 be ages in the

intcal13 calibrated ages of the vedde and saksunarvatn ashes and the younger dryas boundaries from krakenes western norway from krakenes lake in western norway there exist 118 accelerator mass spectrometry 14c dates for the time interval 12 000 8000 14c a bp that we earlier calibrated using the intcal09 data set these yielded the most accurate and precise ages available for the younger dryas boundaries and the vedde and saksunarvatn ashes here we present a new calibration using the recently published intcal13 data set all differences between the two sets of calibrated ages are within the 1 error of the original intcal09 results the most significant differences are that the error for the allerod younger dryas boundary decreased that this boundary became slightly older and that the length of the younger dryas increased slightly