large sea ice outflow into the nares strait in 2007 1 sea ice flux through the nares strait is most active during the fall and early winter ceases in mid to late winter after the formation of ice arches along the strait and re commences after breakup in summer in 2007 ice arches failed to form this resulted in the highest outflow of arctic sea ice in the 13 year record between 1997 and 2009 the 2007 area and volume outflows of 87 103 km2 and 254 km3 are more than twice their 13 year means this contributes to the recent loss of the thick multiyear arctic sea ice and represents 10 of our estimates of the mean ice export at fram strait clearly the ice arches control arctic sea ice outflow the duration of unobstructed flow explains more than 84 of the variance in the annual area flux in our record seasonal stoppages are always associated with the formation of an arch near the same location in the southern kane basin additionally close to half the time another ice arch forms just north of robeson channel prior to the formation of the kane basin arch here we examine the ice export with satellite derived thickness data and the timing of the formation of these ice arches

glacial dispersal train of paleozoic erratics central baffin island n w t canada a glacial dispersal train of erratics derived from paleozoic bedrock has been delineated stretching east northeast west southwest across central baffin island the lithologies of these erratics suggest a derivation from strata of member b of the ordovician ship point formation to the west which are presently either submerged or covered by quaternary sediment in the eastern part of foxe basin these paleozoic erratics were carried from foxe basin onto the baffin upland and the western edge of the davis highlands they can be inferred to have reached at least ekalugad fiord and the eastern part of home bay

detrital carbonate peaks on the labrador shelf a 13 7 ka template for freshwater forcing from the hudson strait outlet of the laurentide ice sheet into the subpolar gyre abstract the laurentide ice sheet lis was a large dynamic ice sheet in the early holocene the glacial events through hudson strait leading to its eventual demise are recorded in the well dated labrador shelf core md99 2236 from the cartwright saddle we develop a detailed history of the timing of ice sheet discharge events from the hudson strait outlet of the lis during the holocene using high resolution detrital carbonate ice rafted detritus ird 18o and sediment color data eight detrital carbonate peaks dcps associated with ird peaks and light oxygen isotope events punctuate the md99 2236 record between 11 5 and 8 0 ka we use the stratigraphy of the dcps developed from md99 2236 to select the appropriate r to calibrate the ages of recorded glacial events in hudson bay and hudson strait such that they match the dcps in md99 2236 we associate the eight dcps with h0 gold cove advance noble inlet advance initial retreat of the hudson strait ice stream hsis from hudson strait opening of the tyrrell sea and drainage of glacial lakes agassiz and ojibway the opening of foxe channel and retreat of glacial ice from foxe basin are represented by a shoulder in the carbonate data r of 350 years applied to the radiocarbon ages constraining glacial events h0 through the opening of the tyrell sea provided the best match with the md99 2236 dcps r values and ages from the literature are used for the younger events a very close age match was achieved between the 8 2 ka cold event in the greenland ice cores dcp7 8 15 ka bp and the drainage of glacial lakes agassiz and ojibway our stratigraphic comparison between the dcps in md99 2236 and the calibrated ages of hudson strait bay deglacial events shows that the retreat of the hsis the opening of the tyrell sea and the catastrophic drainage of glacial lakes agassiz and ojibway at 8 2 ka are separate events that have been combined in previous estimates of the timing of the 8 2 ka event from marine records sw iceland shelf core md99 2256 documents freshwater entrainment into the subpolar gyre from the hudson strait outlet via the labrador north atlantic and irminger currents the timing of freshwater release from the lis hudson strait outlet in md99 2236 matches evidence for freshwater forcing and lis icebergs carrying foreign minerals to the sw iceland shelf between 11 5 and 8 2 ka the congruency of these records supports the conclusion of the entrainment of freshwater from the retreat of the lis through hudson strait into the subpolar gyre and provides specific time periods when pulses of lis freshwater were present to influence climate

variations in the provenance of sediment from ice sheets surrounding baffin bay during mis 2 and 3 and export to the labrador shelf sea site hu2008029 0008 davis strait based on quantitative x ray diffraction mineralogical analysis of cores hu2008029 0006 0008 857 m water depth located south of the davis strait sill we seek answers to two questions i the temporal correlation of nw labrador shelf sea heinrich h and baffin bay detrital carbonate bbdc events and ii the provenance of the sediments a sediment unmixing model sedunmix is used to determine provenance variations although 12 radiocarbon dates were obtained there were many age reversals and we favour a depth age model for hu2008029 0008pc based on correlations to well dated neighbouring cores north and south of davis strait we find no correlation between h and bbdc events except for h 0 which appears to be a broadly synchronous event along the ne canadian margin and is correlative with an episode of major moraine building along this flank of the laurentide ice sheet unmixing of the sediment composition based on six potential glacial source regions indicates that the bulk of the sediment in 0008pc is derived from glacial erosion of west greenland but is punctuated by intervals when dolomite rich sediments derived from outcrops north of baffin bay dominate the composition estimated dates on these bbdc events are 13 25 and 30 38 cal ka bp copyright 2013 john wiley sons ltd

holocene and pleistocene dissolution cycles in deep sea cores of baffin bay and davis strait palaeoceano graphic implications abstract calcium carbonate dissolution has been studied in several grab samples and piston cores from baffin bay and davis strait ranging in water depth from 200 to 2300 m the intensity of dissolution was determined from examining 1 the ratio of arenaceous to calcareous benthonic foraminifera 2 the ratio of benthonic to planktonic foraminifera 3 the relationships between the dissolution susceptible and dissolution resistant foraminifera 4 the degree of foraminiferal test fragmentation and 5 the relationships between plankton tows and the fauna in the surface sediments all core tops and grab samples from baffin bay surface sediments below 600 900 m water depth demonstrated intense dissolution of calcium carbonate sediments below 900 m were biogenic carbonate free indicating 100 foraminiferal loss due to dissolution possible causes of substantial undersaturation in calcium carbonate of baffin bay bottom water are very low temperatures and higher concentrations of carbon dioxide all cores also demonstrated intense dissolution during interglacial or interstadial isotope stages 1 3 5 7 and 9 similarities in planktonic foraminiferal assemblages suggested the presence of similar bottom water masses during these periods the preservation state of biogenic carbonate debris in glacial isotope stages 2 4 6 8 and 10 is similar to the assemblage found in the water at present

latest quaternary and holocene paleoceanography of the eastern baffin island continental shelf canada benthic foraminiferal evidence foraminiferal zones radiocarbon ages on shells and corrected ages on pretreated organic sediment from four cores from the eastern baffin island continental shelf suggest a three stage deglacial to postglacial history late wisconsin to holocene the earliest sediments in the cores contain foraminiferal species elphidium excavatum cassidulina reniforme islandiella helenae indicative of distal glaciomarine environments that lasted at least several thousand years an oceanographic change about 8500 years ago is indicated by a melonis zaandamae zone in northern and central shelf cores collected from 200 800 m water depth the presence of m zaandamae in the north and its absence in the south suggest warmer and more saline postglacial water in northern baffin bay whose influence became diluted with cooler coastal meltwater as the current flowed south along the baffin island shelf sediments after 6000 years ago on the northern and central shelf are dominated by agglutinated foraminifera suggesting dis

asynchronous instability of the north american arctic and greenland ice sheets during the last deglaciation abstract the chronology of deglacial meltwater pulses from the laurentide ice sheet is well documented however the deglacial history of the north american arctic north eastern laurentide and innuitian and western greenland ice sheets draining into the labrador sea via baffin bay is less well constrained here we present new high resolution radiocarbon dated records from the central baffin bay spanning 17 to 10 kyr bp and documenting the full deglacial history of baffin bay sedimentological and geochemical data confirm the presence of two periods of enhanced detrital carbonate delivery termed baffin bay detrital carbonate events bbdcs these events are dated to 14 2 13 7 kyr bp and 12 7 11 kyr bp they are synchronous across baffin bay and their mineralogical signature indicates a common source of detrital carbonate from northern baffin bay the first event bbdc 1 postdates heinrich event 1 and the second event bbdc 0 predates the recently revised timing of heinrich event 0 the onset of the bbdc events appears not to be systematically linked to greenland temperature change as they occur during both interstadial and stadial periods this indicates that deglaciation of north american arctic and western greenland ice sheets with the associated iceberg and meltwater discharge were decoupled from the dominant north atlantic climate mode where iceberg discharge events from the laurentide ice sheet occurred during stadial periods

the variability of baffin bay seafloor sediment mineralogy the identification of discrete glacial sediment sources and application to late quaternary downcore analysis quantitative x ray diffraction qxrd mineralogy of bedrock ice rafted and fluvial clasts 239 seafloor samples 2 mm and samples from two long piston cores were used to i define regional pa

the geochemical evolution of halite structures in hypersaline lakes the dead sea israel depressions in the floor of the southern basin of the dead sea contain dense 1 26 l 29 g cm 3 brines which formed by evaporation at the lake s surface absorbance of solar radiation heats these brines by about 2 4 c d l as long as the density gradient of the lake prevents overturn as a result bottom halite is dissolved in the warmer brines at about 0 4 g nacl liter c i continuous heating of the brine of these holes and cooling of the overlying liquids at night causes frequent overturns of the brine column followed by mixing and cooling of the nacl rich brine the extra load of halite is precipitated near the holes in the form of halite cones and mushroomlike structures whereas the initial nacl supply to the growing halite structures comes from the floor of the lake the later growth stage is supported by nacl supplied from the upper evaporating brine layer crude mass and heat balances show that the proposed model may well explain the occurrence and distribution of halite islands in the dead sea the model may be applicable to any shallow enough a few meters hypcrsaline lake that is saturated with respect to halite the dead sea is composed of a ca chloridic brine the evolution of which has been proposed by starinsky 1974 the physiography limnology and sedimentological regime of the lake have been studied and described by neev and emery 1967 among many others the dead sea is comprised of two parts a northern basin 300 m deep which forms the bulk of the lake s volume and area and a southern shallow mostly 2 4 m deep basin fig 1 dwindling precipitation since about 1930 klein 1985 and diversion of water from the dead sea drainage system for agricultural needs resulted in the continuous lowering of the lake level at a rate of 50 cm yr l finally toward the end of the 1 960s the two basins became separated since then the brine level in the southern basin is maintained artificially evaporation of the brine results in enrichment of most of its dissolved salts with respect to their concentrations in the northern basin exceptions are na and s042 which are precipitated from

prediction of iceberg trajectories for the north atlantic and arctic oceans icebergs are a well known hazard for shipping their study also provides information about diverse geophysical processes as varied as ocean circulation air sea fluxes calving rates of glaciers or the mass balance of ice sheets as a first step to obtaining this information from iceberg data we have developed a model of iceberg drift driven by ocean and atmospheric forcing derived from general circulation models we have applied the drift model to a distribution of typical icebergs released from the main tidewater glaciers of the north atlantic and arctic oceans we demonstrate that the main driving force of iceberg motion is rooted in the unsteady component of oceanic advection from simulated trajectories we are able to reproduce the observed southwards limit of iceberg penetration and demonstrate sometimes surprising geographical links between iceberg origin and ultimate melting zones

a seismological model for earthquakes induced by fluid extraction from a subsurface reservoir a seismological model is developed for earthquakes induced by subsurface reservoir volume changes the approach is based on the work of kostrov 1974 and mcgarr 1976 linking total strain to the summed seismic moment in an earthquake catalog we refer to the fraction of the total strain expressed as seismic moment as the strain partitioning function a probability distribution for total seismic moment as a function of time is derived from an evolving earthquake catalog the moment distribution is taken to be a pareto sum distribution with confidence bounds estimated using approximations given by zaliapin et al 2005 in this way available seismic moment is expressed in terms of reservoir volume change and hence compaction in the case of a depleting reservoir the pareto sum distribution for moment and the pareto distribution underpinning the gutenberg richter law are sampled using monte carlo methods to simulate synthetic earthquake catalogs for subsequent estimation of seismic ground motion hazard we demonstrate the method by applying it to the groningen gas field a compaction model for the field calibrated using various geodetic data allows reservoir strain due to gas extraction to be expressed as a function of both spatial position and time since the start of production fitting with a generalized logistic function gives an empirical expression for the dependence of on reservoir compaction probability density maps for earthquake event locations can then be calculated from the compaction maps predicted seismic moment is shown to be strongly dependent on planned gas production

diagenetic cycling of nutrients in seafloor sediments and the carbonate silica balance in a paleozoic cool water carbonate system sverdrup basin canadian arctic archipelago abstract seafloor processes are often destructive of biogenic remains while at the same time promoting growth of authigenic minerals such as hematite fluorapatite glauconite and chalcedony middle to late permian sedimentary rocks in the sverdrup basin are cool water marine sandstones shales limestones and cherts rich in carbonate and siliceous biotic components the authigenic minerals hematite fluorapatite glauconite and chalcedony are abundant from the interactions of nutrient elements silica phosphorus and iron with carbonate and siliceous biotas in ramp environments of variable energy and sediment accumulation rate these authigenic phases represent in part faunas that are no longer preserved and should not be viewed simply as diagenetic products early middle permian siliciclastic rocks the assistance formation contain carbonate heterozoan biotas with widespread siderite and hematite and local void filling phosphate deposited under moderate sediment accumulation rates sponge spicules were dissolved unless encased in hematite or siderite and incorporated in silica cement in contrast more slowly deposited younger middle permian inboard cherty limestones the lower trold fiord formation underwent frequent physical and biological reworking resulting in dissolution of biogenic silica and precipitation of glauconite and carbonate fluorapatite sediment reworking also excavated and produced rounded glauconite and phosphate clasts much of the glauconite was then oxidized to hematite on the seafloor again unless encased in phosphate sponge spicules were dissolved and the silica precipitated as glauconite or chalcedony coeval deeper water phosphatic cherty limestones the degerbols formation do however contain sponge spiculites reduced sediment reworking led to retention of silica in pore fluids and slowed dissolution of sponge spicules resulting in local preservation of sponge spiculite facies late permian organic rich cherts the lindstrom formation with prolific siliceous sponges and a less plentiful carbonate biota accumulated relatively slowly sponge spicules were preserved and carbonate biota partially dissolved in these organic rich deposits implying that the biota had to be overwhelmingly dominated by siliceous components to overcome ambient silica undersaturation in pore fluids each succession has a distinct composition depending upon the rate of sediment accumulation the original benthic biota and the nature and abundance of silica phosphate and iron in seawater at any given time these characteristics controlled the formation of authigenic minerals and the preservation or dissolution of carbonate and silica biotas

changes in the silt and clay size mineralogy of sediments at ocean drilling program site 645b baffin bay site 645b ocean drilling program odp leg 105 was cored in 2010 m water depth off the eastern margin of baffin island a 279 m core was dated as extending back to ca 2 ma samples of sediment were analyzed for their silt and clay size mineralogy using x ray diffraction techniques constrained cluster analysis on these data defined three units which indicated that significant changes in mineralogies occurred at approximately 75 m below sea floor bsf ca 0 5 ma and 155 m bsf ca 1 15 ma these boundaries coincide closely with units ia ib and ib ii as designated in the odp shipboard reports and which were based on detrital carbonate and sand contents unit ii 1 2 2 ma is characterized by zero clay size calcite and high amounts of clay size smectite and silt size mica unit ib 0 5 1 15 ma is noteworthy for the first presence of clay size calcite high amounts of detrital dolomite and a peak in clay size kaolinite the uppermost unit ia 0 0 5 ma is characterized by consistently high value

geologic and topographic controls on fast flow in the laurentide and cordilleran ice sheets ice streams are fast flowing arteries which play a vital role in the dynamics and mass balance of present day ice sheets although not fully understood fast flow dynamics are intimately coupled with geologic topographic thermal and hydrologic conditions of the underlying bed these are difficult observables beneath contemporary ice sheets hindering elucidation of the processes which govern ice streaxn behavior for past ice sheets the problem is antithetic geologic evidence of former ice streams exists but spatim and temporal histories are uncertain however detailed knowledge of bed geology and topography is available in many places we take advantage of this information to compile terrain characteristics relevant to fast flow dynamics in the laurentide and cordilleran ice sheets using seed points where fast flowing wisconsinan ice has been geologically inferred discriminant analysis of a suite of north american geologic and topographic properties yields a concise measure of ice bed coupling strength our analysis suggests that the interior plains and continental shelf regions of north america have low basal coupling relative to areas of variable relief or exposed bedrock in the cordillera and on the canadian shield we conclude that the interior plains and continental shelves are both topographically and geologically predisposed to large scale basal flows i e ice streaxns or surge lobes this result holds independent of whether the mechanism of fast flow is sediment deformation or decoupled sliding over the bed

ice stream retreat following the lgm and onset of the west greenland current in uummannaq trough west greenland the deglacial history and oceanography of uummannaq trough central west greenland continental shelf was investigated using foraminiferal sedimentological and bathymetric records together with a radiocarbon chronology providing a timeline for the retreat of glacial ice after the last glacial maximum lgm to map ice stream retreat data were collected from cores from the outer jr175 vc45 and jr175 vc43 and inner jr175 vc42 uummannaq trough a large ice stream fed by confluent glaciers draining the interior of the greenland ice sheet extended across the outer shelf during the lgm and was in retreat by 15 0 cal kyr bp foraminiferal data indicate that the warm west greenland current wgc was established prior to 14 0 cal kyr bp which is the hitherto earliest record of atlantic water found on the west greenland shelf for each of the cores foraminifera indicate that ice sheet retreat was followed quickly by incursion of the wgc suggesting that the warm water may have enhanced ice retreat prior to the younger dryas cold event the radiocarbon chronology indicates that the ice sheet retreated to the mid shelf where it subsequently stabilised and formed a large grounding zone wedge gzw after the younger dryas around 11 5 cal kyr bp the ice retreated rapidly from the gzw and into the fjords

source to sink statistical identification of regional variations in the mineralogy of surface sediments in the western nordic seas 58 n 75 n 10 w 40 w the non clay and clay mineralogies of the 2 mm sediment fraction from 157 seafloor samples in the western nordic seas is calculated by quantitative x ray diffraction analysis our sample coverage includes the iceland shelf the ice impacted east greenland margin and the greenland iceland and irminger seas the bedrock geology of source areas includes precambrian basement rocks devonian red beds and younger marine and fluvial sediments and large outcrops of early tertiary to recent flood basalts and other volcanic facies sediment erosion and transport in the area are associated with ice sea ice and icebergs and glacial meltwater and fluvial sediment plumes we use principal component analysis fuzzy k means clustering and discriminant function analysis to reduce the original 31 minerals 157 sites matrix to more manageable 5 regional coherent clusters of sites which are well discriminated by the weight of six minerals namely quartz pyroxene illites magnetite and maghemite amorphous silica e g glass and muscovite the close spatial relationship between bedrock geology and discrete cluster membership stresses the importance of this variable and indicates that far distant sediment transport by sea ice icebergs or other mechanisms although occurring does not radically change the mineral composition of present day sea floor sediments our improved knowledge of the regional mineral assemblages allows for tracking distinct eastern greenland and icelandic sources

biomarker determination as a provenance tool for detrital carbonate events heinrich events fingerprinting quaternary glacial sources into baffin bay sedimentary deposits associated with heinrich events are anomalously rich in detrital carbonate off hudson strait the dominant carbonate is calcite whereas at distal sites in the north atlantic dolomite is dominant more diagnostic a significant source for dolomite is its outcrop at the northern end of baffin bay where major ice streams from the laurentide innuitian and greenland ice sheets converged the provenance of samples containing detrital carbonate mainly dolomite from a core in baffin bay has been confirmed using organic geochemistry to distinguish between alternative sources based upon the thermal maturity of organic matter in carbonates of the source region the core contained five distinct carbonate units dating between 14 and 51 cal ka bp and indicates significant ice stream instability associated with iceberg calving and significant volumes of meltwater the exact temporal relationship to heinrich events is not yet clear a long mid wisconsin interval 38 to 22 cal ka bp devoid of detrital carbonate suggests a major reduction in ice extent at high northern latitudes the core samples yield thermally sensitive biomarker ratios comparable to those from laurentian carbonates in the canadian arctic islands but unlike those from north greenland identifying the former region as their provenance however a late holocene sample from off newfoundland shows a stronger affinity with greenland 2007 elsevier b v all rights reserved

fram strait ice export during the nineteenth and twentieth centuries reconstructed from a multiyear sea ice index from southwestern greenland abstract historical observations of multiyear ice called storis in the southwest greenland waters exist from the period 1820 2000 obtained from ship logbooks and ice charts it is argued that this ice originates in the arctic ocean and has traveled via the fram strait southward along the greenland coast in the east greenland current and around the southern tip of greenland therefore it is hypothesized that these observations can be used as proxies for reconstructing the fram strait ice export on an annual basis an index describing the storis extent is extracted from the observations and a linear statistical model formulated relating this index to the fram strait ice export the model is calibrated using ice export values from a hindcast study with a coupled ocean ice model over the period 1949 98 subsequently the model is used to reconstruct the fram strait annual ice export in the period 1820 2000 the model has significant skill calculated on independent data based on this reconstruction

the laurentide and innuitian ice sheets during the last glacial maximum the late wisconsinan advance of the laurentide ice sheet started from a middle wisconsinan interstadial minimum 27 30 14 c ka bp when the ice margin approximately followed the boundary of the canadian shield ice extent in the cordillera and in the high arctic at that time was probably similar to present ice advanced to its late wisconsinan stage 2 limit in the northwest south and northeast about 23 24 14 c ka bp and in the southwest and far north about 20 21 14 c ka bp in comparison to some previous reconstructions of ice extent our current reconstruction has substantially more late wisconsinan ice in the high arctic where an innuitian ice sheet is generally acknowledged to have existed in the atlantic provinces where ice is now thought to have extended to the continental shelf edge in most places and on eastern baffin island where ice probably extended to the fiord mouths rather than to the fiord heads around most of the ice margin the late wisconsinan maximum ice extent either exceeded the extent of earlier wisconsinan advances or it was similar to the early wisconsinan advance ice marginal recession prior to 14 14 ck a bp occurred mainly in deep water and along the southern terrestrial fringe however heinrich event 1 probably drew down the entire central ice surface at 14 5 14 c ka bp sufficiently to displace the labrador sector outflow centre 900 km eastward from the coast of hudson bay the onset of substantial ice marginal recession occurred about 14 14 c ka bp in the northwest southwest and south but not until about 10 11 14 c ka bp in the northeast and in the high arctic thus the period of maximum ice extent in north america generally encompasses the interval from b24 21 to 14 14 c ka bp or considerably longer than the duration of the lgm defined as occurring during a period of low global sea level as well as during a time of relative climate stability b18 14 c ka bp the interval of advance of much of the laurentide ice sheet to its maximum extent between b27 14 c ka bp and b24 14 c ka bp coincides with a suggested interval of rapid fall in global sea level to near lgmlevels r 2001 elsevier science ltd all rights reserved

how glaciers entrain and transport basal sediment physical constraints abstract simple insights from the physics of ice water and sediment place constraints on the possible sediment transport behavior of glaciers and ice sheets because glaciers concentrate runoff streams generated by glaciers transport much sediment and may erode bedrock rapidly deforming glacier beds also can transport much sediment particularly in marginal regions rapid sediment entrainment producing thick debris rich basal zones may occur by regelation into subglacial materials and by freeze on from rising supercooled waters numerous other mechanisms may be important but primarily near ice margins especially those of advancing or fluctuating glaciers several sediment entrainment mechanisms may be active beneath a single glacier but one process is likely to be dominant at any place and time

late quaternary sedimentation in baffin bay baffin bay is a small ocean basin that connects the arctic and atlantic oceans the adjacent continental shelves have been extensively reworked during quaternary glaciation the shelf break generally lies between 200 and 500 m the continental slope passes directly into the abyssal plain of baffin bay basin without any major submarine canyon deep sea fan system being present except for a large smooth sediment apron in northern baffin bay on the basis of over 50 piston cores six quaternary sediment facies are distinguished from detrital mineralogy reflected in colour and sediment texture facies a b and c are predominantly ice rafted or are debris flow deposits each with a distinct mineralogy facies d is turbidites and bottom current sorted sands silts and muds facies e is hemipelagic sediment facies f consists of sediments ranging from slumps through debris flow deposits to fine grained turbidites with a distinctive provenance in northern baffin bay these sediment facies appear to be part

last glacial maximum ice sheet dynamics in arctic canada inferred from young erratics perched on ancient tors along standing debate regarding the reconstruction of former ice sheets revolves around the use of relative weathering of landscapes i e the assumption that highly weathered landscapes have not been recently glaciated new cosmogenic isotope measurements from upland bedrock surfaces and erratics along the northeastern margin of the laurentide ice sheet lis shed light on this debate 10 be and 26 al concentrations from three perched erratics yielding cosmogenic exposure ages of 17 11 ka are much lower than those measured in two unmodified highly weathered tors upon which they lie which yield cosmogenic exposure ages of 60 ka these findings suggest that non erosive ice covered weathered upland surfaces along the northeastern margin of the lis during the last glacial maximum these data challenge the use of relative weathering to define the margins of pleistocene ice sheets the juxtaposition of non erosive ice over upland plateaus and erosive ice in adjacent fiords requires strong gradients in basal thermal regimes suggestive of an ice stream mode of glaciation r 2003 elsevier science ltd all rights reserved

the deglaciation of clyde inlet northeastern baffin island arctic canada the behaviour of ice sheets as they retreated from their last glacial maximum lgm positions provides insights into lateglacial and early holocene ice sheet dynamics and climate change thepatternofdeglaciationofthelaurentideicesheet lis inarcticfiordlandscapescannow bewelldatedusingcosmogenicexposuredating weusecosmogenicexposureandradiocarbonages to constrain the deglaciation history of clyde inlet a 120km long fiord on northeastern baffin island the lis reached the continental shelf during the lgm retreated from the coastal lowlands by 12 5 0 7ka n 3 and from the fiord mouth by 11 7 2 2ka n 4 rapid retreat from the outer fiord occurred 10 3 1 3ka n 6 with the terminus reaching the inner fiord shortly after 9 4ka n 2 where several moraine systems were deposited between ca 9 4 and ca 8 4ka these moraines represent fluctuations of the lis during the warmest summers since the last interglaciation and this suggests that the ice sheet was responding to increased snowfall before retreating from the head of clyde inlet the lis margin fluctuated at least twice between ca 7 9 and ca 8 5ka possibly in response to the 8 2ka cold event copyright 2006 john wiley sons ltd

environmental magnetism a practical guide j walden f oldfield j and smith eds technical guide no 6 quaternary research association london 1999 243 pp price 17 00 9 00 to qra members isbn 0 907780 42 3

determination of sediment provenance by unmixing the mineralogy of source area sediments the sedunmix program abstract along the margins of areas such as greenland and baffin bay sediment composition reflects a complex mixture of sources associated with the transport of sediment in sea ice icebergs melt water and turbidite plumes similar situations arise in many contexts associated with sediment transport and with the mixing of sediments from different source areas the question is can contributions from discrete sediment bedrock sources be distinguished in a mixed sediment by using mineralogy and if so how accurately to solve this problem four end member source sediments were mixed in various proportions to form eleven artificial mixtures two of the end member sediments are felsic and the other two have more mafic compositions end member and mixed sediment mineralogies were measured for the

late quaternary chronostratigraphic framework of deep baffin bay glaciomarine sediments from high resolution paleomagnetic data 1 the late quaternary baffin bay sediments provide exclusive records of greenland innuitian and laurentide ice sheet margin activities as well as information about the arctic and northern atlantic ocean linkages through the canadian arctic archipelago because of specific oceanographic conditions foraminiferal 18o stratigraphies and radiocarbon ages fail to provide reliable chronologies here we propose an original chronostratigraphy spanning the last glacial cycle based on high resolution paleomagnetic investigations on a 741 cm long core hu2008 029 016pc raised from the deep central baffin bay near odp site 645 two major difficulties were encountered 1 the high frequency occurrence of rapidly deposited layers related to short ice sheet margin events e g ice surges and 2 the magnetic grain size variability physical and magnetic mineralogical properties were used to screen out unreliable magnetic sediment layers the obtained relative paleointensity rpi proxy matches reference paleomagnetic stacks and regional records moreover the resulting record depicts two major excursions which were assigned to the laschamp and the norwegian greenland sea events it has thus been possible to derive a robust 115 ka chronology for the cored sequence we concluded that even under such a dynamic sedimentary regime magnetic properties of the sediments can provide a reliable chronostratigraphy together with information on sedimentary processes

north eastern laurentide western greenland and southern innuitian ice stream dynamics during the last glacial cycle precise relationships between high frequency ice sheet dynamics and late quaternary climate variability are still poorly understood notably with regard to their relative timing and causal mechanisms baffin bay is of particular interest in this regard due to the influence of ice streaming activities from the north eastern laurentide southern innuitian and western greenland ice margins on its sedimentary regimes during glacial times here we document such ice margin dynamics using a sedimentological analysis performed on a piston core from central baffin bay and spanning the last 115 ka lithofacies analysis and mineralogical assemblages are used to reconstruct sediment sources using the sedunmix program and depositional mechanisms coarse detrital carbonate dc dolomite rich layers are attributed either to north eastern laurentide and innuitian ice stream surges or to pervasive ice rafted debris delivery processes at distinct periods out of phase fine grained glaciomarine sediments with a mineralogical signature from western greenland linked to uummannaq ice streaming activity are interbedded with the coarse dc layers the new results suggest that during the last glacial cycle the north eastern laurentide and southern innuitian ice streams were sensitive to high frequency climate fluctuations such as the dansgaard oeschger events while the western greenland margins were more sensitive to large scale climatic oceanic reorganizations such as relative sea level changes and or advection of warmer atlantic waters into the bay copyright 2013 john wiley sons ltd

evaluation of the relative roles of global versus local sedimentary controls on middle to late pleistocene formation of continental margin strata canterbury basin new zealand determining the relative influence of eustasy versus local sedimentary processes on strata formation is a fundamental challenge in the study of continental margin stratigraphy in this paper the relative contribution of these factors on continental margin evolution during the middle to late pleistocene is evaluated using samples from integrated ocean drilling program expedition 317 core logging biostratigraphy and quantitative x ray diffraction mineralogy are used to delineate continental shelf sedimentary systems major lithological unconformities bound stratigraphic sequences that contain recurring compositional patterns and that resemble other examples of middle to upper pleistocene sequences however a preliminary chronology suggests that sequence boundary formation cannot be linked one to one with eustatic cycles and therefore these sequences can contain multiple ca 100 ka eustatic cycles smaller amplitude higher frequency transitions in sediment composition are interpreted as stratigraphic sequences driven by more rapid perturbations in the interplay of accommodation and sediment supply their stratigraphy is variable in time and across the shelf suggesting a strong influence of local sedimentary forcing in their formation changes in sediment composition after the middle pleistocene transition indicate that sediment transfer from onshore sources in the glaciated southern alps to the middle shelf occurred over a single 100 ka glacio eustatic cycle with an additional 100 ka lag before the mineralogical signal was preserved on the outer shelf this phenomenon is coincident with rapid shelf progradation in this basin suggesting a causal relation between across shelf sediment transport and margin progradation this is one of very few studies that provide insights at the core scale into the processes driving continental margin evolution during the middle to late pleistocene this work shows that compositional changes in mud dominated successions can lead to a sequence stratigraphic interpretation and the identification of high frequency sequences which may not be possible using a conventional stratigraphic approach

calcium carbonate saturation states in the waters of the canadian arctic archipelago and the labrador sea 1 ocean acidification is predicted to occur first in polar oceans we investigated the saturation state of waters with respect to calcite cal and aragonite arg in six sections along an arctic outflow pathway through the canadian arctic archipelago caa and into the northwestern atlantic using dissolved inorganic carbon and total alkalinity measurements from 2003 to 2005 the study area a key region connecting the arctic and the north atlantic includes smith sound barrow strait baffin bay davis strait hudson strait and the labrador sea the average arg in the arctic outflow was 1 18 0 17 in barrow strait and 1 31 0 14 in smith sound with areas where arg 1 the arctic outflow through the caa has a high content of pacific waters which have a low saturation state these waters can be traced along the western baffin bay to davis strait south of davis strait this outflow is modified by mixing with slope and offshore waters of atlantic origin and with the outflow from hudson strait despite the mixing low saturation state water can still be identified on the southern labrador shelf the aragonite saturation horizon is found at 150 m in barrow strait at 200 m in baffin bay davis strait and hudson strait and at 2300 m in the labrador sea this study provides baseline data of the saturation states for the waters of the caa and the northwest atlantic it also illustrates the downstream evolution of low saturation state arctic outflow in the northwest atlantic

u and th series isotopes in deep baffin bay sediments tracers of detrital sources and of contrasted glacial interglacial sedimentary processes abstract uranium u and thorium th series have been used to document the sedimentary sources processes and fluxes of the last 115 ka in central baffin bay a major gateway between the arctic ocean and the north atlantic ocean which has been fed throughout the last ice age by sediments and meltwaters from the northeastern laurentide ice sheet the innuitian ice sheet and the western greenland ice sheet measurements have been made with a 1 6 ka time resolution in sedimentary core hu2008 029 016pc 70 27 n 64 39 w 2063 m water depth the lack of correlation between u concentration 234 u 238 u activity ratio 234 u 238 u ar organic carbon and redox sensitive elements suggests minimum early diagenetic u uptake if any likely due to very low organic matter sedimentary fluxes in such a subarctic environment throughout the last glaciation u and th concentrations and their mass ratio as well as 234 u 238 u ar do not show either any unequivocal linkage with detrital dolomitic carbonate and or detrital silicate fluxes data rather suggest sedimentary supplies with singular u and th series signatures linked to specific glacial margin ice streaming events and highlighting the diversity of sedimentary sources surrounding this small oceanic basin large surplus of 230 th 230 th xs 0 well above the production from dissolved u decay in the overlying water column are observed throughout the last glacial interval in response to sediment focusing and high sedimentation rates in the deepest part of the bay during this interval high frequency fluctuations in 230 th xs 0 indicate either a similar variability in sedimentation rates not captured by the age model used and or grain size or mineralogical dependent 230 th xs scavenging rates in the much lower sedimentation rate holocene core top section the 230 th xs 0 inventory falls below production in the overlying water column despite evidence for some primary productivity revival as suggested by the higher organic carbon content 230 th xs losses through lateral advection via baffin bay water masses overflowing through davis strait might account for this pattern pointing to ocean circulation drastically differing from that of the glacial interval

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

large scale reorganization and sedimentation of terrestrial ice streams during late wisconsinan laurentide ice sheet deglaciation glacial geomorphological mapping of shuttle radar topography mission srtm data from the western canadian prairies demonstrates that during the last late wisconsinan deglaciation of the laurentide ice sheet terrestrial ice streams underwent a major reorganization of their flow configuration this reorganization involved a 90 shift in flow direction and was accompanied by a corresponding increase in the influence of topography on streaming flow ice streams included both topographically confined and pure ice streams that flowed independent of topography streaming flow is recorded by suites of highly elongate 60 km long subglacial bedforms bounded sharply at their lateral margins by prominent moraines initial streaming flow was unconfined by topography but was replaced progressively and crosscut by younger topographically confined flows flow reorganization is inferred to have been caused by temporal and spatial variations in the interaction between frozen and thawed bed conditions with thinning and shutdown of one ice stream ultimately triggering initiation of others this highlights the role of internal glaciodynamically driven reorganization in triggering streaming flow within large ice sheets and shows that large scale flow reorganization can occur over the time scale of a single deglaciation in terrestrial ice streams

contrasting glacimarine sedimentary environments of two arctic fiords on disko west greenland abstract two fiords kangerluk and akulliit on the island of disko central west greenland have very different sedimentary regimes caused by differences in the characteristics of their drainage basins and in the exposure of their waters to the open sea of baffin bay their insular location also results in much lower input of water and sediment than in nearby fiords on the mainland of greenland that are affected by glaciers from the greenland ice cap akulliit has a small drainage basin and low input of water and sediment it is directly exposed to the higher energy wave environment of baffin bay as a consequence the mean thickness of holocene glacimarine sediment assessed in acoustic records is less than 6 m in the inner and middle reaches of the fiord mean holocene accumulation 0 4 mm a and about 11 m 1 mm a near the mouth dated core sediment indicates that rates are less than 0 5 mm a in the outer fiord in the last 2 ka the larger more glacier covered drainage basin of kangerluk contributes much larger loads of sediment to a fiord environment protected from the open sea as a result holocene glacimarine sediment is more than 80 m thick in the inner fiord mean holocene accumulation up to 5 mm a decreasing to 10 40 m about 1 mm a in the middle reaches accumulation rates in kangerluk are within the range of arctic fiords including those of baffin island but those in akulliit are near the lower limit the decrease in thickness distally in kangerluk is typical of arctic fiords but the opposite trend in akulliit is probably due to erosion and re distribution of sediment in the higher energy environment there

rapid changes in ice discharge from greenland outlet glaciers using satellite derived surface elevation and velocity data we found major short term variations in recent ice discharge and mass loss at two of greenland s largest outlet glaciers their combined rate of mass loss doubled in less than a year in 2004 and then decreased in 2006 to near the previous rates likely as a result of fast re equilibration of calving front geometry after retreat total mass loss is a fraction of concurrent gravity derived estimates pointing to an alternative source of loss and the need for high resolution observations of outlet dynamics and glacier geometry for sea level rise predictions

paleoenvironments during younger dryas early holocene retreat of the greenland ice sheet from outer disko trough central west greenland paleoenvironments during the late younger dryas through early holocene retreat of the greenland ice sheet from the outer shelf in the disko trough system of central west greenland were investigated via lithofacies foraminifera dinocysts and sediment provenance analyses in radiocarbon dated sediment cores from the upper slope jr175 vc35 and outer shelf jr175 vc20 and hu2008029 070cc core data show that the ice margin retreated rapidly from the outer shelf by calving beginning by 12 2k cal a bp under cold paleoceano graphic conditions with up to 11 months of sea ice ice retreat into disko bugt was well underway by 10 9k cal a bp enhanced ice sheet ablation in disko bugt and elsewhere along the west greenland coast is inferred from cold glacial marine conditions associated with high sedimentation rates between 10 9 and 9 5k cal a bp on the outer shelf glacial marine conditions are recorded on the outer shelf until 7 8k cal a bp detrital carbonate bearing sediments rich in 2 mm clasts deposited between 11 6 and 10 6k cal a bp indicate that icebergs calved from northern baffin bay ice margins were melting and releasing sediments along west greenland while the greenland ice sheet margin was retreating into disko bugt copyright 2013 john wiley sons ltd

abrupt changes in marine conditions sunneshine fiord eastern baffin island nwt during the last deglacial transition younger dryas and h 0 events

varying sediment sources hudson strait cumberland sound baffin bay to the nw labrador sea slope between and during heinrich events 0 to 4 core hu97048 007pc was recovered from the continental labrador sea slope at a water depth of 945 m 250 km seaward from the mouth of cumberland sound and 400 km north of hudson strait cumberland sound is a structural trough partly floored by cretaceous mudstones and paleozoic carbonates the record extends from 10 to 58 ka on board logging revealed a complex series of lithofacies including buff colored detrital carbonate rich sediments heinrich h events frequently bracketed by black facies we investigate the provenance of these facies using quantitative x ray diffraction on drill core samples from paleozoic and cretaceous bedrock from the se baffin island shelf and on the 2 mm sediment fraction in a transect of five cores from cumberland sound to the nw labrador sea a sediment unmixing program was used to discriminate between sediment sources which included dolomite rich sediments from baffin bay calcite rich sediments from hudson strait and discrete sources from cumberland sound results indicated that the bulk of the sediment was derived from cumberland sound but baffin bay contributed to sediments coeval with h 0 younger dryas whereas hudson strait was the source during h events 1 4 contributions from the cretaceous outcrops within cumberland sound bracket h events thus both leading and lagging hudson strait sourced h events copyright 2012 john wiley sons ltd

the central labrador sea facies and dispersal patterns of clastic sediments in a small ocean basin abstract the upper 500 m of the 2 km thick sedimentary section in the central labrador sea consists of upper pliocene pleistocene clastic sediments associated with the globally unique submarine trunk channel of the northwest atlantic mid ocean channel namoc and its system of tributaries turbidity currents in the namoc fractionate their sediment load into fine grained mostly silty clayey spill over sediments on the natural levees and coarse grained channel fill sediments the natural levees of the namoc are composite features containing shallow second order channels tributaries and satellite channels which have their own subdued levees these shallow channels are much less efficient in fractionating the sediment into coarse and fine fractions compared to the namoc the second order levees are sandy based on high resolution seismic profiles and sediment cores eight different facies have been differentiated in the surface sediments of the central labrador basin 1 deep channel fill facies on the namoc floor 2 slide and slump facies on the namoc walls 3 spill over facies on the namoc levees 4 channel fill facies of shallow second order channels 5 sandy spill over facies of shallow second order channels 6 debris flow deposits on the namoc levees 7 pelagic sediments with ice rafted debris and 8 contourites

baffin bay paleoenvironments in the lgm and hs1 resolving the ice shelf question abstract core hu2008029 12pc from the disko trough mouth fan on the central west greenland continental slope is used to test whether an ice shelf covered baffin bay during the last glacial maximum lgm and at the onset of the deglaciation we use benthic and planktic foraminiferal assemblages stable isotope analysis of planktic forams algal biomarkers ice rafted detritus ird lithofacies characteristics defined from ct scans and quantitative mineralogy to reconstruct paleoceanographic conditions sediment processes and sediment provenance the chronology is based on radiocarbon dates on planktic foraminifers using a r of 140 30 14 c years supplemented by the varying reservoir estimates of stern and lisiecki 2013 that provide an envelope of potential ages hu2008029 12pc is bioturbated throughout sediments between the core base at 11 3 m and 4 6 m lgm through hs1 comprise thin turbidites plumites and hemipelagic sediments with greenlandic provenance consistent with processes active at the greenland ice sheet margin grounded at or near the shelf edge abundance spikes of planktic forams coincide with elevated abundance of benthic forams in assemblages indicative of chilled atlantic water meltwater and intermittent marine productivity ird and ip 25 are rare in this interval but brassicasterol an indicator of marine productivity reaches and sustains low levels during the lgm these biological characteristics are consistent with a sea ice covered ocean experiencing periods of more open water such as leads or polynyas in the sea ice cover with chilled atlantic water at depth rather than full ice shelf cover they do not support the existence of a full baffin bay ice shelf cover extending from grounded ice on the davis strait initial ice retreat from the west greenland margin is manifested by a pronounced lithofacies shift to bioturbated diatomaceous mud with rare ird of greenlandic origin at 467 cm 16 2 cal ka bp r 140 yrs within hs1 a spike in foraminiferal abundance and ocean warmth indicator benthic forams precedes the initial ice retreat from the shelf edge at the end of hs1 ip 25 brassicasterol and benthic forams indicative of sea ice edge productivity increase indicating warming interstadial conditions within the bolling allerod interstadial a strong rise in ip 25 content and ird spikes rich in detrital carbonate from northern baffin bay indicate that northern baffin bay ice streams were retreating and provides evidence for increased open water advection of atlantic water in the west greenland current and formation of an ird belt along the w greenland margin

significant differences in late quaternary bedrock erosion and transport east versus west greenland 70 n evidence from the mineralogy of offshore glacial marine sediments

quantitative assessment of carbonate dissolution in marine sediments from foraminifer linings vs shell ratios davis strait northwest north atlantic a new method to evaluate quantitatively the degree of calcium carbonate preservation and dissolution in high latitude marine sediments is proposed on the basis of relative abundance of caco 3 shells and organic linings of benthic foraminifers this method was applied to a late quaternary sequence from davis strait in the northwest north atlantic and shows that caco 3 dissolution in sediments has increased since the last glacial maximum ca 18 000 b p and peaked when subpolar interglacial conditions were established in surface waters the dissolution in davis strait sediments appears to be closely related to organic biogenic production in surface waters with a regional pattern of bottom water formation and circulation

epitaxial salt reefs and mushrooms in the southern dead sea salt usually accumulates in shallow ephemeral brines as simple flat beds however in permanent brines deepening in solar evaporation ponds in the southern dead sea salt accumulation is complicated by the growth of isolated vegetable like salt structures

source analysis of acoustic emissions in aue granite cores under symmetric and asymmetric compressive loads the effect of stress anisotropy on the brittle failure of granite is investigated under uniaxial compression non standard asymmetric compression tests are performed on cores of aue granite diameter 52 mm length 100 mm in which 20 per cent of the core top surface remains unloaded the edge of the asymmetric steel loading plate acts as a stress concentrator from where a shear rupture is initiated the propagation of the fracture related process zone from top to bottom of the core is mapped by microcrack induced acoustic emissions compared to standard uniaxial tests with symmetric loading in the asymmetric tests both a greater quantity and more localized distributions of emission event hypocentres are observed the maximum event density doubles for asymmetric 20 events per 10 6 m3 compared to symmetric tests the cluster correlation coefficient a measure of strain localization in the faulting process reaches 0 15 for symmetric and 0 30 for asymmetric tests the clustering of events however is found post failure only three different amplitudes are used to determine b values discussed as a possible failure precursor focal amplitudes determined at a 10 mm source distance and maximum amplitudes measured at eight piezoceramic sensors lead to b values that drop before rock failure first pulse amplitudes automatically picked from emission wavelets show no anomaly first motion polarity statistics of amplitudes indicate that a shear crack type radiation pattern is responsible for 70 per cent of the failure of granite irrespective of stress boundary conditions for type s events with an equal percentage of dilatational and compressional first motions focal mechanisms are determined by fitting measured first pulse amplitudes to an assumed double couple radiation pattern while hypocentres of large type s events align parallel to the later fracture plane their fault plane solutions show no coherent pattern spatial views of fracture planes reconstructed from x ray computed tomograms reveal local small scale changes in fracture plane orientation nodal planes from average fault plane solutions of the microscopic acoustic emission events coincide with the overall orientation of the macroscopic fracture plane azimuth strike angle determined from thin sections and tomograms

quantitative mineralogy of the yukon river system changes with reach and season and determining sediment provenance the mineralogy of yukon river basin sediment has been studied by quantitative x ray diffraction bed beach bar and suspended sediments were analyzed using the rockjock computer program the bed sediments were collected from the main stem and from selected tributaries during a single trip down river from whitehorse to the yukon river delta during the summer of 2001 beach and bar sediments were collected from the confluence region of the tanana and yukon rivers during the summer of 2003 suspended sediments were collected at three stations on the yukon river and from a single station on the tanana river at various times during the summers of 2001 through 2003 with the most complete set of samples collected during the summer of 2002 changes in mineralogy of yukon river bed sediments are related to sediment dilution or concentration effects from tributary sediment and to chemical weathering during transport carbonate minerals compose about 2 wt of the bed sediments near whitehorse but increase to 14 wt with the entry of the white river tributary above dawson thereafter the proportion of carbonate minerals decreases downstream to values of about 1 to 7 wt near the mouth of the yukon river quartz and feldspar contents of bed sediments vary greatly with the introduction of pelly river and white river sediments but thereafter either increase irregularly quartz from 20 to about 50 wt or remain relatively constant feldspar at about 35 wt with distance downstream clay mineral content increases irregularly downstream from about 15 to about 30 wt the chief clay mineral is chlorite followed by illite smectite there is little to no kaolinite the total organic carbon content of the bed sediments remains relatively constant with distance for the main stem generally 1 to 2 wt with one exception but fluctuates for the tributaries 1 to 6 wt the mineralogies of the suspended sediments and sediment flow data were used to calculate the amount of mineral dissolution during transport between eagle and pilot station a distance of over 2000 km we estimate that approximately 3 wt of the quartz 15 wt of the feldspar 1 wt of the alkali and 25 wt of the plagioclase and 26 wt of the carbonates 31 wt of the calcite and 15 wt of the dolomite carried by the river dissolve in this reach the mineralogies of the suspended sediments change with the season for example during the summer of 2002 the quartz content varied by 20 wt with a minimum in mid summer the calcite content varied by a similar amount and had a maximum corresponding to the quartz minimum these modes are related to the relative amount of sediment flowing from the white river system which is relatively poor in quartz but rich in carbonate minerals suspended total clay minerals varied by as much as 25 wt with maxima in mid july and suspended feldspar varied up to 10 wt suspended sediment data from the summers of 2001 and 2003 support the 2002 trends a calculation technique was developed to determine the proportion of various sediment sources in a mixed sediment by unmixing its quantitative mineralogy results from this method indicate that at least three sediment sources can be identified quantitatively with good accuracy with this technique sediment mineralogies can be used to calculate the relative flux of sediment from different tributaries thereby identifying sediment provenance

acceleration of jakobshavn isbrae triggered by warm subsurface ocean waters observations over past decades show a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning in 1997 this switch is associated with a doubling in glacier velocity hydrographic data show a concurrent sudden increase in subsurface ocean temperatures along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were triggered by the arrival of relatively warm water originating from the irminger sea observations over the past decades show a rapid acceleration of several outlet glaciers in greenland and antarctica1 one of the largest changes is a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning2 in 1997 associated with a doubling in glacier velocity3 suggested explanations for the speed up of jakobshavn isbrae include increased lubrication of the ice bedrock interface as more meltwater has drained to the glacier bed during recent warmer summers4 and weakening and break up of the floating ice tongue that buttressed the glacier5 here we present hydrographic data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were instead triggered by the arrival of relatively warm water originating from the irminger sea near iceland we trace these oceanic changes back to changes in the atmospheric circulation in the north atlantic region we conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets

sediment color record from the northeast atlantic reveals patterns of millennial scale climate variability during the past 500 000 years a 500 000 yr long deep sea sediment color record from the northeast atlantic was investigated to reconstruct the evolution of late pleistocene climate variability on millennial time scales variations of the red green color intensity are probably caused by climatically induced changes in the ice rafted input of red colored iron bearing terrigenous material to the core site the resolution of the age model impedes the detection of distinct spectral features at sub milankovitch periodicities hence millennial scale climate variability is quantified as time dependent variance of the high pass filtered color time series the course of the estimated variance shows distinct patterns which can be linked to continental ice mass during the past 500 000 yr large amplitude millennial scale climate variability occurs only if continental ice mass exceeds a threshold level equivalent to sea level at approximately 40 of the lowering during the last glacial maximum

late quaternary detrital carbonate dc layers in baffin bay marine sediments 67 74 n correlation with heinrich events in the north atlantic abstract episodes of glaciation in the region north of baffin bay resulted in the erosion of paleozoic carbonate outcrops in nw greenland and the canadian high arctic these events are recognized in the marine sediments of baffin bay bb as a series of detrital carbonate rich dc layers bbdc layers thin southward within baffin bay thus the contribution of baffin bay ice rafted carbonate rich sediments to the north atlantic is probably slight especially compared with sediment output from hudson strait during heinrich events we reexamine cf aksu 1981 a series of nine piston cores from the axis of baffin bay and across the davis strait sill and provide a suite of 21 ams 14 c dates on foramininfera which bracket the ages of several dc layers the onset of the last dc event is dated in six cores and has an age of ca 12 4 ka in northern and central baffin bay a thick dc layer occurs at around 4 m in the cores and is dated 40 ka there were three to six dc intervening events the youngest bbdc event possibly a double event lags heinrich event 1 h 1 off hudson strait dated at 14 5 ka but it is coeval with the pronounced warming seen in gisp2 records from the greenland ice sheet during interstadial 1 we hypothesize that bbdc episodes are coeval with major interstadial 18 o peaks from gisp2 and other greenland ice core records and are caused by or associated with the advection of atlantic water into baffin bay cf hiscott et al 1989 and the subsequent rapid retreat of ice streams in the northern approaches to baffin bay

laser vs settling velocity differences in silt grainsize measurements estimation of palaeocurrent vigour the use of grain size distribution of muds for the reconstruction of past deep ocean currents is becoming established and applied in the palaeoceanographic community the methods are also applicable to shallow marine and tidal flat muds with similar inferences concerning the energy of wave and current sorting being drawn fine sediment grain size distributions can be obtained using a variety of instruments based on fundamentally different theoretical principles these machines may give varying sometimes misleading results giving divergent interpretations of flow speed history the new evidence presented here combined with earlier work suggests that of the three most commonly used analytical methods for fine silts with clays settling velocity sedigraph should be the method and instrument of choice with electrical resistance pulse counters e g coulter counter as a suitable alternative the data also show that laser particle sizers should be avoided for palaeocurrent reconstructions because the measured size of platey minerals can be dominated by their large projected area this causes them to be recorded as the same size as larger equant grains although they have much smaller settling velocity and were deposited in aggregates this produces results with a weaker relationship to the dynamics of deposition the central problem is thus that some coarse clay fine silt is recorded as medium to coarse silt the key size in the sortable silt mean size method of inferring changes in flow speed for coarse silts e g loess the laser gives more satisfactory results

along slope variations in sediment lithofacies and depositional processes since the last glacial maximum on the northeast baffin margin canada abstract twelve piston cores were used to characterize late quaternary lithofacies depositional processes and deglacial history along the baffin bay slope between lancaster sound and home bay core investigations show four distinct laterally correlatable lithofacies along the slope basal and upper diamicton laminated red brown mud tan carbonate gravelly sandy mud and bioturbated brown mud basal diamicton largely represents glacigenic debris flow deposits during a glacial advance from baffin island at 25 cal ka the distribution and character of laminated red brown mud suggests a lateral supply to baffin bay slope from ice proximal meltwater plumes and turbidity currents sourced in glacial ice from both baffin bay shelf and home bay between 41 5 cal ka to 14 2 cal ka an upper diamicton records a lesser localized glacial advance that ended at about 14 2 cal ka tan carbonate mud events represent ice rafted enhanced detrital carbonate delivery to the slope between 25 cal ka and 11 cal ka a gradual thinning of these events from northern to southern baffin bay corroborates a northern baffin bay lancaster sound or nares strait iceberg source proglacial facies seaward of home bay contain beds with slightly elevated detrital carbonate that may represent the distal edge of carbonate ice rafted from lancaster sound baffin bay is a type example of a polar glacial basin in which direct glacial supply predominates over the effects of glacial meltwater as a result axial supply from the large ice streams north of baffin bay particularly lancaster sound is dominant in the baffin bay basin and lateral supply from smaller ice streams on baffin island predominates on the ne baffin slope

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

margin segmentation of baffin bay davis strait eastern canada based on seismic reflection and potential field data abstract the continental margin of baffin island was interpreted from a compilation of seismic reflection and potential field data based on these data it was divided into volcanic and non volcanic segments in the northernmost area coast parallel grabens and continental basement highs are superseded beneath the slope by irregular basement topography in combination with the velocities from refraction data and the lack of a magnetic slope anomaly we propose a non volcanic margin in the central region the seismic data show a limited region with a seaward dipping reflector sequence that may be intercalated with a sedimentary section both north and south of cape dyer extensive volcanic rocks are interpreted at and below seabed consistent with a volcanic margin in the southern region the depth to basement drops rapidly offshore a thick prograding sedimentary wedge produces a high amplitude long wavelength free air gravity anomaly that was previously confused with the continent ocean boundary although some volcanic rocks are mapped in the region this area is adjacent to the non volcanic labrador sea margin and is interpreted to be of similar structure segmentation of the margin by major faults can explain the abrupt transitions from volcanic to non volcanic margin segments the continent ocean boundary for the region is determined based on the potential field and seismic data along the greenland plate in davis strait the continent ocean boundary coincides with the ungava fault zone the continent ocean boundary is used in conjunction with published poles of rotation to evaluate plate reconstructions at chrons 33n and 27n the earlier reconstruction produces an extensive overlap of boundaries in the north the later reconstruction shows a gap in the southern region thus additional information is required to refine the reconstructions

holocene variations in mineral and grain size composition along the east greenland glaciated margin ca 67 70 n local versus long distance sediment transport quantitative x ray diffraction qxrd analysis of the 2 mm sediment fraction from surface sea floor samples and marine sediment cores that span the last 10 12 cal ka bp are used to describe spatial and temporal variations in non clay mineral compositions for an area between kangerlussuaq trough and scoresby sund 67 70 n east greenland bedrock consists primarily of an early tertiary alkaline complex with high weight of pyroxene and plagioclase farther inland and to the north the bedrock is dominantly felsic with a high fraction of quartz and potassium feldspars principal component pc analysis of the non clay sediment compositions indicates the importance of quartz and pyroxene as compositional end members with an abrupt shift from quartz and k feldspar dominated sediments north of scoresby sund to sediments rich in pyroxene and plagioclase feldspars offshore from the early tertiary basaltic outcrop coarse 2 mm or 1 mm ice rafted sediments are largely absent from the trough sediments between 8 and 5 cal ka bp but then increase in the last 4 cal ka bp compositional unmixing of the sediments in grivel basin and kangerlussuaq trough indicate the dominance of local over long distance sediment sources with pulses of sediment from tidewater glaciers in kangerlussuaq and nansen fjords reaching the inner shelf during the neoglaciation the change in ird is more dramatic in the sediment grain size proxies than in the quartz wt forty to seventy percent of the variance in the quartz records from either side of denmark strait is explained by low frequency trends but the data from the grivel basin east greenland are distinctly different with an approximate 2500 yr periodicity

distinguishing current effects in sediments delivered to the ocean by ice ii glacial to holocene changes in high latitude north atlantic upper ocean flows abstract shallow ocean flows in the northern north atlantic are of key importance in the regulation of earth s climate in the northern north atlantic nutrient rich cold arctic ocean outflow of modified atlantic water plus pacific and ice melt waters flow in the east greenland current egc and in the baffin island current which feeds into the labrador current the outflows east of greenland carry a substantial amount of warm salty north atlantic water that flows into the nordic seas mixes recirculates much of it via the arctic ocean and contributes to both shallow and deep overflows a key to understanding oceanic control of earth s climate therefore resides in establishing the changes in these high latitude currents we have analysed 28 cores comprising 2900 measured samples in the high latitude n atlantic and arctic oceans of which 80 pass the reliability test of a correlation coefficient between sortable silt mean and percentage r 0 5 mccave and andrews 2019 quat sci rev 212 92 107 there is a close similarity between the pattern of holocene decrease in the strength of the irminger current inflow to the nordic seas and outflow recorded in the egc and in deep overflow east of reykjanes ridge this suggests that the flow of the egc is strongly influenced by the influx of north atlantic water rather than supply of fresher water from ice sheet melt or pacific origin in contrast to the flows east of greenland those west of greenland show a slow holocene increase in flow the freshest coldest deep denmark strait overflow recorded at orphan knoll as well as labrador sea water flow on the slope north of the grand banks also show this gradual increase this points to control on deep water overflows by the flux of cold fresh water from greenland and the arctic some of which may have come from the pacific via the bering strait models also show a holocene east west difference in deep water formation with increase in the labrador sea and decrease in the nordic seas in almost all cases holocene flow speed maxima lag the local holocene thermal maxima by between 0 and 1000 years it is therefore highly unlikely that the local holocene thermal maxima are responses to increased flow of shallow currents in the adjacent ocean areas decelerations in flow speed accompany holocene coolings while accelerations accompany warmings the lgm was a period of slow flow and meltwater events usually show slowdowns as well however heinrich events show slowdowns in some regions and faster flow in others

seismicity and deformation induced by magma accumulation at three basaltic volcanoes we analyzed the evolution of volcano tectonic vt seismicity and deformation at three basaltic volcanoes kilauea mauna loa piton de la fournaise during phases of magma accumulation we observed that the vt earthquake activity displays an accelerating evolution at the three studied volcanoes during the time of magma accumulation at the same times deformation rates recorded at the summit of kilauea and mauna loa volcanoes were not accelerating but rather tend to decay to interpret these observations we propose a physical model describing the evolution of pressure produced by the accumulation of magma into a reservoir this variation of pressure is then used to force a simple model of damage where damage episodes are equivalent to earthquakes this model leads to an exponential increase of the vt activity and to an exponential decay of the deformation rate during accumulation phases seismicity and deformation data are well fitted by such an exponential model the time constant deduced from the exponential increase of the seismicity is in agreement with the time constant predicted by the model of magma accumulation this vt activity can thus be a direct indication of the accumulation of magma at depth and therefore can be seen as a long term precursory phenomenon at least for the three studied basaltic volcanoes unfortunately it does not allow the prediction of the onset of future eruptions as no diverging point i e critical time is present in the model

palaeo ice streams in the foxe baffin sector of the laurentide ice sheet in this paper we describe mapping of palaeo ice streams in the foxe baffin sector of the laurentide ice sheet by means of geomorphological interpretation of high resolution satellite images our interpretations were guided by a glaciological inversion scheme aided by digital elevation models publicly available sonar surveys and field studies as a result we produced a map depicting the location geometry and relative temporal changes of palaeo ice streams and analysed their palaeoglaciological implications for the foxe baffin sector we conclude that in the period between the last glacial maximum and approximately 7 0 kyr bp the foxe baffin sector was largely drained by topographically controlled outlet glaciers and ice streams which were organized in a relatively stable pattern during this time large areas of melville peninsula and central baffin island were subject to cold based conditions between 7 0 and 6 0 kyr bp the foxe baffin sector collapsed catastrophically in the foxe basin after which its remnant portion became confined to baffin island during this collapse rapid successions of small transient ice streams occurred along wide loosely defined topographical corridors in two sectors of baffin island the presently available landform archive on emerged land is not sufficient to conclusively support the existence of fully scaled ice streams along the whole length of hudson strait as an alternative solution we propose that topographically controlled ice streams might have occurred along the deepest parts of hudson strait with attendant cold based ice zones on marginal areas and islands at the head of the strait

surface sea floor and near surface box cores sediment mineralogy in baffin bay as a key to sediment provenance and ice sheet variations to better understand the glacial history of the ice sheets surrounding baffin bay and to provide information on sediment pathways samples from 82 seafloor grabs and core tops and from seven box cores were subjected to quantitative x ray diffraction weight percent wt analysis of the 2000 m all show an abrupt drop in calcite wt post 5 cal ka bp following a major peak in detrital carbonate mainly dolomite this dolomite rich detrital carbonate dc event in jr175bc06 is possibly coeval with the younger dryas cold event four possible glacial sourced end mem bers were employed in a compositional unmixing algorithm to gain insight into down core changes in sediment provenance at the deep central basin estimates of the rates of sediment accumulation in the central basin are only in the range of 2 to 4 cm cal ka surprisingly low given the glaciated nature of the surrounding land

holocene sediment properties of the east greenland and iceland continental shelves bordering denmark strait 64 68 n north atlantic the oceanographic polar front separates the east greenland and iceland margins surface water temperatures across denmark strait vary by 8 12 c and represent one of the steepest oceanographic gradients on earth the eastgreenland margin is a polar environment with extensive sea ice cover and calving glacier margins in contrast the iceland shelf is much more temperate and freshwater run off is a key component in land ocean sediment transfers average sediment properties from these two contrasting climate and oceanographic continental shelf environments are compared in the spatial domain at 13 sites the data represent the last 10 000 radiocarbon years of normal marine sedimentation for the two regions the two regions have similar average rates of sediment accumulation around 43 5 cm kyr 1 so that this key variable is factored out in explaining any differences in sediment properties dry sediment density moisture content hygroscopic moisture total organic carbon and carbonate contents mass magnetic susceptibility and the percentages of sand and silt are compared focusing on 1 median values for sediment properties and 2 downcore variability measured by the coefficient of variation cv there are significant differences in all but one hygroscopic moisture of the sediment properties between iceland and east greenland in four cases the sense of the differences was not as predicted in terms of downcore variation cv no difference was found between the two regions nor between the 13 sites whereas there are some significant differences between the variables carbonate and mass magnetic susceptibility have the largest spreads and moisture content and dry sediment density are the least variable protocols are developed to identify the type core in a regional series of sites the results indicate a need to develop a regional perspective on sediment properties both as inputs to models of sedimentary processes in different polar arctic environments and as an indication of which sediment properties might be best suited for palaeoenvironmental downcore time series

baffin bay nares strait surface seafloor sediment mineralogy further investigations and methods to elucidate spatial variations in provenance the goal of the paper is to ascertain whether there are significant regional variations in sediment mineral composition that might be used to elucidate ice sheet histories the weight percentages o

coalescent greenland and innuitian ice during the last glacial maximum revising the quaternary of the canadian high arctic abstract this paper constitutes a fundamental revision of the author s earlier research and resolves a long standing debate concerning the late quaternary history of the canadian high arctic supporting its inundation by glaciers during the last glacial maximum lgm a transect along east ellesmere island demonstrates that ice advanced northward and southward along the axis of nares strait during the late wisconsinan debouching from a central saddle in kane basin the configuration of ellesmere island and greenland ice is based on moraines meltwater channels and erratics the youngest ams 14c date obtained on shelly till suggests ice buildup after 19 ka bp whereas many other dates are younger than 30 ka bp furthermore the lowest youngest detectable amino acid ratios on shells from till postdate the robeson aminozone 70 ka bp and are separated from holocene ratios by a narrow gap wholly consistent with the occupation of the strait by late wisconsinan ice re entry of the sea throughout nares strait is shown by a series of paleogeographic maps based on geomorphic evidence and radiocarbon dates on shells associated with marine limit deglaciation at the north end of the strait occurred by 10 1 ka bp and at the south end by 9 0 ka bp nares strait may still have been blocked by ice north of kane basin at 8 ka bp however by 7 5 ka bp it provided an unobstructed seaway from the arctic ocean to baffin bay the prominent ice margins within the fiords of eastern ellesmere island previously considered to mark the last ice limit record regional stabilization of land based ice after breakup of preceding marine based margins other implications of this study are that ice buildup occurred post 30 ka bp and possibly post 19 ka bp during an interval widely assumed to be constrained by severe aridity in the high arctic and that coalescent greenland and ellesmere island ice during the lgm promoted thickening of the eastern ellesmere island ice divide causing enhanced westward flow across the island to eureka sound sizeable postglacial emergence 80 120 m on eastern ellesmere island is associated with the retreat of thick ice 1 km from the strait greater emergence in eureka sound which extends southward into the central arctic islands confirms the previously proposed axis of the innuitian ice sheet further clarification of the extent geometry and retreat of the innuitian ice sheet will provide new opportunities for glaciological and geophysical modelling and help to identify late quaternary sediment sources for the arctic ocean and baffin bay

nd and pb isotope signatures of the clay size fraction of labrador sea sediments during the holocene implications for the inception of the modern deep circulation pattern holocene on the basis of sediment supply variations for the last 12 kyr three sources have contributed to the sediment mixture the north american shield the pan african and variscan crusts and the mid atlantic ridge clay isotope signatures indicate two mixtures of sediment sources the first mixture 12 2 6 5 ka is composed of material derived from the north american shield and from a young crustal source from 6 5 ka onward the mixture is characterized by a young crustal component and by a volcanic component characteristic of the midatlantic ridge since the significant decrease in proximal deglacial supplies the evolution of the relative contributions of the sediment sources suggests major changes in the relative contributions of the deep water masses carried by the western boundary undercurrent over the past 8 4 kyr the progressive intensification of the western boundary undercurrent was initially associated mainly with the transport of the northeast atlantic deep water mass until 6 5 ka and with the denmark strait overflow water thereafter the establishment of the modern circulation at 3 ka suggests a reduced influence of the denmark strait overflow water synchronous with the full appearance of the labrador seawater mass our isotopic data set emphasizes several changes in the relative contribution of the two major components of north atlantic deep water throughout the holocene index terms 4267 oceanography general paleoceanography 4558 oceanography physical sediment transport 1040 geochemistry isotopic composition chemistry 9325 information related to geographic region atlantic ocean 9604 information related to geologic time cenozoic keywords clay size fraction sedimentary mixings deep circulation nd and pb isotopes north atlantic labrador sea

ocean forcing of ice sheet retreat in central west greenland from lgm to the early holocene publisher elsevier articletitle ocean forcing of ice sheet retreat in central west greenland from lgm to the early holocene journaltitle earth and planetary science letters articlelink http dx doi org 10 1016 j epsl 2017 05 007 content type article copyright 2017 elsevier b v all rights reserved

glacimarine lithofacies provenance and depositional processes on a west greenland trough mouth fan along the west greenland continental margin adjoining baffin bay bathymetric data show a series of large submarine fans located at the mouths of cross shelf troughs one of these fans termed here uummannaq fan is a trough mouth fan built largely by debris delivered from a fast flowing outlet of the greenland ice sheet during past glacial maxima cores from this fan provide the first information on glacimarine sedimentary facies within a major west greenland trough mouth fan and on the nature of late weichselian holocene glacigenic sediment delivery to this region of the baffin bay margin glacigenic debris flows deposited on the upper slope and extending to at least 1800 m water depth in front of the trough mouth are related to the remobilization of subglacial debris that was delivered onto the upper slope at times when an ice stream was positioned at the shelf edge in contrast sedimentary facies from the northern sector of the fan are characterized by hemipelagic and ice rafted sediments and turbidites glacigenic debris flows are notably absent in cores from this region quantitative x ray diffraction studies of the 2 mm sediment fraction indicate that the bulk of the sediment in the fan is derived from uummannaq trough but there are distinct intervals when sediment from northern baffin bay sources dominates especially on the northern limit of the fan these data demonstrate considerable variation in the nature of sediment delivery across the uummannaq fan when the greenland ice sheet was at the shelf edge they highlight the variability of glacimarine depositional processes operating on trough mouth fans on high latitude continental margins during the last glacial maximum and indicate that glacigenic debris flows are just one of a number of mechanisms by which such large depocentres form copyright 2012 john wiley sons ltd

the circulation water masses and sea ice of baffin bay abstract the oceanographic meteorological and sea ice conditions in baffin bay are studied using historical hydrographic satellite and meteorological data and a set of current meter data from a mooring program of the bedford institute of oceanography baffin bay is partially covered by sea ice all year except august and september the interannual variation of the ice extent is shown to be correlated with winter air temperature available hydrographic data were used to study the water masses and the horizontal and vertical distribution of temperature salinity three water masses can be identified arctic water in the upper 100 300 m of all regions except the southeast west greenland intermediate water at 300 800 m in most of the interior of baffin bay and deep baffin bay water in all regions below 1200 m the temperature and salinity in baffin bay have limited seasonal variability except in the upper 300 m of eastern davis strait northern baffin bay and the mouth of lancaster sound summer data have a temperature minimum at 100 m which suggests winter convection does not penetrate deeper than this depth current meter data and results of a circulation model indicate that the mean circulation is cyclonic the seasonal variation of the currents is complex overall summer and fall tend to have stronger currents than winter and spring at all depths among the different regions the largest seasonal variation occurs at the mouth of lancaster sound and the baffin island slope model generated velocity fields show a basic agreement with the observed currents and indicate strong topographic control in the vicinity of davis strait and on the greenland shelves the model also produces a southward counter current on the greenland slope which may explain the observed high horizontal shears over the greenland slope estimates of the volume and fresh water transports through lancaster jones and smith sounds are reviewed transports through davis strait are computed from the current meter data the balance of freshwater budget and sensitivity of the thermohaline circulation to freshwater transport are discussed

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research