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

searching for eustasy in deglacial sea level histories abstract perturbations to the earth s gravity field and solid surface associated with glacial isostatic adjustment gia cause the total observable sea level change to depart from the eustatic curve which is defined as a spatially uniform height shift of the ocean surface to accommodate any mass gained lost from grounded ice in this study we apply a state of the art model of gia induced sea level change to quantify the magnitude and spatial form of this departure at the global scale for a range of model parameters with an aim to identify regions that are well suited to obtain accurate and precise estimates of eustatic sea level and therefore past grounded ice volume in general our results indicate that eustatic sea level is not a directly measurable quantity and so must be estimated by subtracting a model derived estimate of non eustatic contributions from observations in this regard we use our results to isolate regions where this procedure can be applied with optimal accuracy and precision that is where 1 the gia predictions are relatively insensitive to plausible ranges in input parameters and 2 where the non eustatic contribution is small i e the predicted sea level closely approximates the eustatic value we present maps that can be employed by the field community to identify areas where sea level reconstructions would be well suited to arrive at robust estimates of eustatic sea level note that sea level changes associated with tectonic motion and changes in ocean water temperature salinity which also lead to departures from eustasy are not considered in this analysis

ostracod assemblages in late quaternary varved glaciomarine clay of the baltic sea yoldia stage in eastern middle sweden abstract four cored sites in eastern middle sweden have been analysed for their content of calcareous fossils the investigated sediments consist of late quaternary varved clay deposited during the baltic sea yoldia stage four regional palaeoecological units a d have been established unit a reflects ice proximal conditions unit b optimal conditions for the benthic fauna and unit c the termination of a saline phase in unit c oxygen deficiency might have occurred in the fourth unit d no fossils were found the fauna recorded is poor in taxa and indicates a weak marine influence the salinity was higher in the western part of the investigated area due to the proximity to the inlet of marine water the meltwater influx was high and the salinity probably fluctuated considerably the ostracod cytheromorpha macchesneyi brady and crosskey is reported for the first time in quaternary deposits from northwestern europe and indicates that a connection could have existed between the baltic and the white sea in late glacial times

energetic subthermocline currents observed east of mindanao abstract two cruises of the jamstec ship kaiyo during october 1999 and september 2000 included lowered acoustic doppler current profiler adcp measurements to 2000 m depth on zonal sections extending east from the mindanao coast on the second cruise the lowered adcp profiles were augmented by profiles to 1000 m from a 38 khz shipboard adcp all zonal ladcp sections 7 n 8 10 showed southward flow along the coast extending to at least 2000 m depth although the mindanao current in the upper 500 m forms a continuous narrow stream along the coast the deeper southward flow appears to be part of a set of subthermocline eddies within 300 km of the coast northward flow was found 100 200 km offshore during both cruises currents mapped by the shipboard adcp on the second cruise indicate that cyclonic eddies were centered near 7 5 n 128 e and 10 2 n 127 e maximum speeds of 0 6 m s 1 were observed at 800 m depth on the 10 n section and speeds of 0 2 0 3 m s 1 were found below 1500 m on all sections

comparison study of the modern ostracod associations in the kara and laptev seas ecological aspects recent ostracod assemblages were investigated from coretop sediment samples collected in the eastern kara sea from water depths down to 300 m a total of 45 species were identified 27 of them were reported for the kara sea for the first time the kara sea data were compared with our results on the distribution of ostracods in the eastern laptev sea the spatial distribution of recent taxa and the ecological groupings demonstrate a clear relation to dominant environmental factors which range from estuarine to full marine conditions four assemblages related to average summer bottom water salinities were established 1 a freshwater assemblage from the inner estuaries of the ob and yenisei rivers with salinities less than 2 and from thermokarst lagoons of the southern laptev sea coast with strong salinization in winter 2 a brackishwater assemblage of the outer estuaries of the ob and yenisei rivers with salinities up to 26 3 a mixed euryhaline marine assemblage dominated by euryhaline species paracyprideis pseudopunctillata and heterocyprideis sorbyana from the inner shelf river affected zone of the kara and laptev seas where salinities range between 26 and 32 4 a taxonomically diverse marine assemblage dominated by shallow water marine taxa from the northern parts of the kara and laptev shelves and upper continental slope with stable bottom environments and a salinity higher than 32 abundant euryhaline species found at greater water depths are identified as part of an ice rafted assemblage they are possibly entrained into the newly formed fast ice during autumn storms and freeze up period and then transported to the distal open sea areas during summer

hydraulics of subglacial outburst floods new insights from the spring hutter formulation using a slightly modified form of the spring hutter equations glacial outburst floods are simulated from three classic sites hazard lake yukon canada summit lake british columbia canada and grimsvotn iceland in order to calibrate the hydraulic roughness associated with subglacial conduits previous work has suggested that the manning roughness of the conduits is remarkably high but the new calibration yields substantially lower values that are representative of those for natural streams and rivers the discrepancy can be traced to a poor assumption about the effectiveness of heat transfer at the conduit walls the simulations reveal behaviour that cannot be interred from simplified theories 1 during flood onset water pressure over much of the conduit can exceed the confining pressure of surrounding ice 2 local values of fluid potential gradient can differ substantially from the value averaged over the length of the conduit contradicting an assumption of simple theories 3 as the flood progresses the location of flow constrictions that effectively control the flood magnitude can jump rapidly over large distances 4 predicted water temperature at the conduit outlet exceeds that suggested by measurements of exit water temperature

reconstruction of the holocene seismic history of a seabed fault using relative sea level curves reconstructed by ostracode assemblages case study on the median tectonic line in iyo nada bay western japan abstract relative sea level curves of cores k1 k2 s1 and s2 collected from iyo nada bay western japan were reconstructed using ostracode assemblages these curves clearly show a holocene history of seismic subsidence comparing the curves with sea level histories from a tectonically stable area of japan demonstrates that iyo nada bay has undergone subsidence through the holocene this subsidence was probably caused by movements of the median tectonic line mtl fault system in iyo nada bay comparison of relative sea level curves of the lower and upper plates elucidated a detailed seismic history of the kaminada oki kita and shimonada oki minami faults the kaminada oki kita fault moved vertically about 7 m at ca 5500 0 cal yr bp in addition this fault may have moved vertically about 5 m and 9 m at ca 7500 6000 cal yr bp and ca 10 000 9000 cal yr bp respectively the shimonada oki minami fault has moved vertically about 15 m over the last 6500 years this fault also might have had a large movement around 10 000 cal yr bp this study provided a robust method for reconstruction of the holocene seismic history using ostracode assemblages found in seabed drilling cores

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

an analysis of tropical instability waves in a numerical model of the pacific ocean 2 generation and energetics of the waves this work was supported by the department of com merce noaa under grant na56gp0026 one of the au thors sm was partially supported by a nasa global change fellowship ngt 30288 another author ab was supported by a ucar postdoctoral fellowship

effects of the november 13 1985 eruption on the snow pack and ice cap of nevado del ruiz volcano colombia abstract about twenty five to thirty percent of the ice on the ice cap of nevado del ruiz was fractured and destabilized by earthquakes and explosive activity on november 13 1985 comparison of aerial and ground photographs taken before and after the eruption allows calculation of the volume of snow and ice removed from each glacial basin during the eruption about 16 4 2 km 2 of the surface area of the ice and snow was lost the corresponding volume is estimated to be close to 0 06 km 3 or 9 of the total volume of ice and snow at least four distinct processes including explosions ice avalanches surficial erosion of snow and slush avalanches were responsible for transporting snow firn and ice downslope heat from pyroclastic flows and surges and their deposits was responsible for melting snow and ice both at the surface of the ice cap in situ and during its downslope transport voluminous lahars were triggered in 3 of the 4 main drainages on the volcano by the approximately 43 million m 3 of liquid water about 62 million m 3 of snow firn and ice produced by these combined processes thermal and mechanical effects of the pyroclastic flows and surges included scouring direct melting and entraining snow firn and ice which left several erosional features on the ice cap and deposits both on the ice and on the edges of the ice cap subsurface and englacial drainage of water through crevasses was deduced from depositional and morphological features at the ice margins some meltwater might have been trapped in reservoirs but some water was also released shortly after the eruption the estimated volume of released meltwater is about 43 million m 3 i e 2 4 times more than the approximate 11 12 million m 3 of water incorporated into the lahars thus roughly 21 million m 3 of water were released but did not contribute to lahar generation this non contributing water was 1 included in snow avalanches and sediment laden slush avalanches outside the lahars channels or bound up in the wet pyroclastic surge deposits 2 incorporated in the phreatic explosive products or saturated firn by meltwater which issued from the thermal effect of the tephra fall 3 sublimated into steam during the passage of the pyroclastic flows or 4 stored within the ice meltwater may still be be trapped within the ice cap and may be a potential source of water for future lahars

submarine landforms and ice sheet flow in the kvitoya trough northwestern barents sea high resolution geophysical and sediment core data are used to investigate the pattern and dynamics of former ice flow in kvitoya trough northwestern barents sea a new swath bathymetric dataset identifies three types of submarine landform in the study area streamlined landforms meltwater channels and cavities iceberg scours subglacially produced streamlined landforms provide a record of ice flow through kvitoya trough during the last glaciation flow directions are inferred from the orientations of streamlined landforms drumlins crag and tail features ice flowed northward for at least 135 km from an ice divide at the southern end of kvitoya trough a large channel cavity system incised into bedrock in the southern trough indicates that subglacial meltwater was present at the former ice sheet base modest landform elongation ratios and a lack of mega scale glacial lineations suggest that although ice in kvitoya trough was melting at the bed and flowed faster than the likely thin and cold based ice on adjacent banks a major ice stream probably did not occupy the trough retreat was relatively rapid after 14 13 5 14c kyr b p and probably progressed via ice sheet bed decoupling in response to rising sea level there is little evidence for still stands during ice retreat or of ice proximal deglacial sediments relict iceberg scours in present day water depths of more than 350 m in the northern trough indicate that calving was an important mass loss mechanism during retreat

equatorial pacific 13 c water eddies in the eastern subtropical south pacific ocean abstract argo float profile data are used to analyze warm salty weakly stratified subthermocline eddies of tropical origin in the eastern subtropical south pacific ocean these eddies contain anomalous signatures of the equatorial pacific 13 c water that is carried poleward within the peru chile undercurrent pcu as it flows along the west coast of south america from their source along the chilean coast between 29 and 39 s the eddies spread westward and slightly northward likely at least partly advected by the subtropical gyre the eddy water properties contrast strongly with the colder fresher more strongly stratified waters of subantarctic origin being carried northward then westward by the gyre near the eddy source about 6 of argo profiles sample eddies that are above selected thresholds for both salinity and potential vorticity anomalies relative to maps of the mean distributions of these properties on and around the core isopycnal for the eddies the proportion of such profiles dimini

englacial vs lacustrine origin of volcanic table mountains evidence from iceland detailed facies analysis of hyaloclastites and associated lavas from eight table mountains and similar hyaloclastite volcanoes in the icelandic rift zone contradict a rapid and continuous monogenetic entirely subglacial evolution of most volcanoes studied the majority of the exposed hyaloclastite deposits formed in large stable lakes as indicated by widespread up to 300 m thick continuous sections of deep water shallow water and emergent facies salient features include extensively layered or bedded successions comprising mainly debris flow deposits turbidites base surge and fallout deposits consisting of texturally and compositionally variable slightly altered hyaloclastites as well as sheet and pillow lavas in contrast chaotic assemblages of coarser grained more poorly sorted and more strongly palagonitized hyaloclastite tuffs and breccias as well as scoria and lava are interpreted to have formed under sub or englacial conditions in small chimney like ice cavities or ice bound lakes irregularly shaped and erratically arranged hyaloclastite bodies produced at variable water levels appear to have resulted mainly from rapid changes of the eruptive environment due to repeated build up and drainage of ice bound lakes as well as the restricted space between the ice walls we distinguish a deep water facies formed during high water levels of the lake a hydroclastic shallow water and emergent facies leakage of the lake or growth of the volcano above the water surface our model implies the temporary existence of large stable lakes in iceland probably formed by climatically induced ice melting the highly complex edifices of many table mountains and similar volcanoes were constructed during several eruptive periods in changing environments characterized by contrasting volcanic and sedimentary processes

semiannual variation in the western tropical pacific ocean 1 analysis of altimeter data combined with results from a high resolution general circulation model has revealed the existence of a semiannual variation in the western tropical pacific the semiannual variation cannot be explained by local ekman pumping alone but is also related to the westward propagation of rossby waves originating in the central tropical pacific corresponding in the northern hemisphere with the inter tropical convergence zone and in the southern hemisphere with the south pacific convergence zone this signal intensifies toward the western boundary and appears to have a notable impact on the circulation there in the mindanao current the semiannual variation is of comparable strength with the annual variation this finding is supported by a moored acoustic doppler current profile measurement during the period from october 1999 to july 2002

subthermocline eddies observed by rapid sampling argo floats in the subtropical northwestern pacific ocean in spring 2014 in spring 2014 two subthermocline eddies stes were observed by rapid sampling argo floats in the subtropical northwestern pacific stnwp the first one is a warm salty and oxygen poor lens with its temperature salinity dissolved oxygen t s do anomalies reaching 1 16 c 0 21 practical salinity unit psu 29 9 mol kg respectively near the 26 62 0 surface the other is a cold fresh and oxygen rich lens with its t s do anomalies reaching 1 95 c 0 34 psu 88 0 mol kg respectively near the 26 54 0 surface the vertical extent of the water mass anomalies in the warm cold ste is about 190 m 150 m and its horizontal length scale is 22 7 km 18 10 km according to their water mass properties we speculate that the warm and cold stes are generated in the north pacific subtropical and subarctic front region respectively the observed stes may play an important role in modifying the intermediate layer water properties in the stnwp and this needs to be confirmed by more focused observations in the future

observed features of the halmahera and mindanao eddies 1 the structure and variability of the halmahera and mindanao eddies he and me which are thought to be quasi stationary eddies are described based on onboard and time series observations in the gateway region of the indonesian throughflow itf the he was found to have a clear anticyclonic eddy structure during all cruises it tilted northward and or westward with increasing depth the he mixes waters from the northern and southern hemispheres and transfers this mixed water to the eastern route of the itf the he shifted northwestward in the boreal summer and the cold phase of enso el nino and southern oscillation and southeastward in the boreal winter and the warm phase of enso in contrast the me with its cyclonic eddy structure was observed only once and seems not to be a quasi stationary eddy it appears in the mean field and is confined above the thermocline the stationary northward undercurrent the mindanao undercurrent was also not found at 7 n east of mindanao but the northern tip of the he was found at this latitude

younger dryas sea level and meltwater pulse 1b recorded in barbados reef crest coral acropora palmata the younger dryas climate event occurred during the middle of the last deglacial cycle and is marked by an abrupt shift in the north atlantic polar front almost to its former glacial position trending east to west using high precision and high accuracy u th dated barbados reef crest coral acropora palmata we generate a detailed sea level record from 13 9 to 9000 years before present kyr b p and reconstruct the ice volume response to the younger dryas cooling from the mid allerod 13 9 kyr b p to the end of the younger dryas 11 65 kyr b p rates of sea level rise decreased smoothly from 20 mm yr 1 to 4 mm yr 1 culminating in a 400 year slow stand before accelerating into meltwater pulse 1b mwp 1b the mwp 1b event at barbados is better constrained as beginning by 11 45 kyr b p and ending at 11 1 kyr b p during which time sea level rose 14 2 m and rates of sea level rise reached 40 mm yr 1 we propose that mwp 1b is the direct albeit lagged response of the northern hemisphere ice sheets to the rapid warming marking the end of the younger dryas coinciding with rapid warming in the circum north atlantic region and the polar front shift from its zonal to meridional position 11 65 kyr b p as predicted by glaciological models the ice sheet response to rapid north atlantic warming was lagged by 400 years due to the thermal inertia of large ice sheets the regional circum north atlantic younger dryas climate event is elevated to a global response through sea level changes starting with the global slowdown in sea level rise during the younger dryas and culminating with mwp 1b no meltwater pulses are evident at the initiation of the younger dryas climate event as is often speculated

deglacial holocene svalbard paleoceanography and evidence of meltwater pulse 1b abstract better understanding of deglacial meltwater pulses mwps is imperative for future predictions of human induced warming and abrupt sea level change because of their potential for catastrophic damage however our knowledge of the second largest meltwater pulse mwp 1b that occurred shortly after the start of the holocene interglacial remains very limited here we studied fossil ostracods as paleoenvironmental indicators of water depth salinity and temperature in two marine sediment cores from storfjorden svalbard margin the arctic ocean to investigate near field i e areas located beneath continental ice sheets at the last glacial maximum evidence of mwp 1b the depositional environment changed from a cold bathyal environment to a warmer bathyal environment at 11 300 yr bp indicating incursion of warm atlantic water into the nordic seas and eventually to a cold neritic environment by 11 000 yr bp because of melting of the svalbard barents sea ice sheet and resultant isostatic rebound this process corresponds to rapid relative sea level fall of 40 80 m of mwp 1b from 11 300 to 11 000 yr bp

lateglacial and early holocene climatic oscillations on the western svalbard margin european arctic abstract a multi proxy sediment core record on the continental margin off western svalbard european arctic reflects large climatic and oceanographic oscillations at the lateglacial early holocene transition based on studies of planktonic foraminifera their stable oxygen and carbon isotopic composition and ice rafted debris we have reconstructed the last 14 cal ka bp the period 14 13 5 cal ka bp was characterized by highly unstable climatic conditions short lived episodes of warming alternated with meltwater pulses and enhanced iceberg rafting this period correlates to a regional warming of the northern north atlantic an overall decrease in meltwater took place during the deglaciation 14 10 8 cal ka bp the late younger dryas and subsequent transition into the early holocene is characterized by a reduced flux of planktonic foraminifera and increased iceberg rafting a major warming took place from 10 8 to 9 7 cal ka bp the influence of meltwater ceased and the flux of warm atlantic water increased from 9 7 to 8 8 cal ka bp the western svalbard margin surface waters were significantly warmer than today this warm period the thermal maximum was followed by an abrupt cooling at 8 8 cal ka bp caused by an increased influence of arctic water from the arctic ocean the results document that the european arctic was very sensitive to climatic and oceanographic changes at the end of the last glacial and during the holocene

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

holocene paleoceanography and glacial history of the west spitsbergen area euro arctic margin two sediment cores from the west spitsbergen area euro arctic margin md99 2304 and md99 2305 have been investigated for paleoceanographic proxies including benthic and planktonic foraminifera benthic foraminiferal stable isotopes and ice rafted debris core md99 2304 is located on the upper continental margin reflecting variations in the influx of atlantic water in the west spitsbergen current core md99 2305 is located in van mijenfjord picturing variations in tidewater glacier activity as well as fjordocean circulation changes surface water warmer than today was present on the margin as soon as the van mijenfjord was deglaciated by 11 200 cal years bp relatively warm water invaded the fjord bottom almost immediately after the deglaciation a relatively warm early holocene was followedby an abrupt cooling at 8800 cal years bp on the continental margin another cooling in the fjord record 8000 4000 cal years bp is documented by an increase in ice rafted debris and an increase in benthic foraminiferal d 18 o the ird record indicates that central spitsbergen never was completely deglaciated during the holocene relatively cool andstable cond itions similar to the present were establishedabout 4000 cal years bp

a census of meddies tracked by floats recent subsurface float measurements in 27 mediterranean water eddies meddies in the atlantic are grouped together to reveal new information about the pathways of these energetic eddies and how they are often modified and possibly destroyed by collisions with seamounts twenty meddies were tracked in the iberian basin west of portugal seven in the canary basin during february 1994 14 meddies were simultaneously observed 11 of them in the iberian basin most 69 of the newly formed meddies in the iberian basin translated southwestward into the vicinity of the horseshoe seamounts and probably collided with them some meddies 31 passed around the northern side of the seamounts and translated southwestward at a typical velocity of 2 0 cm s into the canary basin some meddies observed there were estimated to be up to 5 yr old four meddies in the canary basin collided with the great meteor seamounts and three meddies were inferred to have been destroyed by the collision overall an estimated 90 of meddies collided with major seamounts the mean time from meddy formation to a collision with a major seamount was estimated to be around 1 7 yr combined with the estimated meddy formation rate of 17 meddies yr from previous work this suggests that around 29 meddies co exist in the north atlantic therefore during february 1994 we observed about half of the population of meddies

a mesoscale eddy dipole in the offshore california current there is a transition zone in the california current system between inshore coastal and offshore oceanic flow this transition zone is associated with the main core of the california current and is populated with offshore mesoscale eddies the structure of isolated eddies and dipole eddy pairs found within the transition zone is examined using water mass analysis spiciness and dissolved oxygen the analyses show that these offshore mesoscale eddies have cores which contain california undercurrent water these observations and independent observations of the sitka eddy near sitka alaska support the conclusion that a bathymetrically induced instability of the california undercurrent is a likely generation mechanism for the offshore eddies this conclusion also is consistent with mathematical models of eddy generation in a subsurface poleward baroclinic current the similarity between long term mean conditions caicofi conditions observed during january 1981 and july 1985 and those of the sitka eddy coupled with the bathymetric effects provides a plausible explanation for the recurrence of offshore mesoscale eddies at preferred locations within the transition zone

cretaceous tertiary high latitude palaeoenvironments james ross basin antarctica high latitude settings are sensitive to climatically driven palaeoenvironmental change and the resultant biotic response climate change through the peak interval of cretaceous warmth late cretaceous cooling onset and expansion of the antarctic ice sheet and subsequently the variability of neogene glaciation are all recorded within the sedimentary and volcanic successions exposed within the james ross basin antarctica this site provides the longest onshore record of cretaceous tertiary sedimentary and volcanic rocks in antarctica and is a key reference section for cretaceous tertiary global change the sedimentary succession is richly fossiliferous yielding diverse invertebrate vertebrate and plant fossil assemblages allowing the reconstruction of both terrestrial and marine systems the papers within this volume provide an overview of recent advances in the understanding of palaeoenvironmental change spanning the mid cretaceous to the neogene of the james ross basin and related biotic change and will be of interest to many working on cretaceous and tertiary palaeoenvironmental change

energetics of eddy mean flow interactions along the western boundary currents in the north pacific abstractthe energetics of eddy mean flow interactions along two western boundary currents of the north pacific the kuroshio and ryukyu currents are systematically investigated using 22 years of n

sediment dynamics driven by contour currents and mesoscale eddies along continental slope a case study of the northern south china sea abstract based upon 3 d seismic reflection data published drill core studies oceanographic observations and numerical modelling this study identifies a small scale contourite depositional system that is locally confined by canyons slope failures erosional terraces and erosional slopes on the jianfeng slope northern south china sea 1500 to 2300 m water depth possible oceanic driving mechanisms for the spatial heterogeneity in sedimentation and erosion within the quaternary deposits in this complex slope system are investigated numerical simulations show that the quasi steady south china sea deep water circulation which affects the study area is characterised by low velocities maximum 4 cm s with a slight modulation by tides 1 cm s this quasi steady deep water thermohaline circulation is able to keep sediment particles in suspension rather than to erode seafloor sediment the bottom hydrodynamic regime becomes energetic when mesoscale eddies horizontal scale of 10 to 100 km approach our modelling study indicates that both surface and bottom mesoscale eddies are essential to account for the spatial heterogeneity in sedimentation pattern along the northern south china sea continental slope according to simulation the eddy front contains the highest flow velocity over a mesoscale eddy cycle 45 days exceeding the threshold for resuspension of unconsolidated sediment 15 cm s as a consequence massive resuspension is produced at various sites and redistributed by sub mesoscale horizontal scale of 1 to 10 km circulations originated from an eddy topography interaction in contrast to the surrounding areas which are subject to erosional forcing for a relatively long part 7 of an eddy cycle both the locally confined drift and a further upstream large elongated mounded drift experience little erosion

rapid glaciation and a two step sea level plunge into the last glacial maximum the approximately 10 000 year long last glacial maximum before the termination of the last ice age was the coldest period in earth s recent climate history1 relative to the holocene epoch atmospheric carbon dioxide was about 100 parts per million lower and tropical sea surface temperatures were about 3 to 5 degrees celsius lower2 3 the last glacial maximum began when global mean sea level gmsl abruptly dropped by about 40 metres around 31 000 years ago4 and was followed by about 10 000 years of rapid deglaciation into the holocene1 the masses of the melting polar ice sheets and the change in ocean volume and hence in gmsl are primary constraints for climate models constructed to describe the transition between the last glacial maximum and the holocene and future changes but the rate timing and magnitude of this transition remain uncertain here we show that sea level at the shelf edge of the great barrier reef dropped by around 20 metres between 21 900 and 20 500 years ago to 118 metres relative to the modern level our findings are based on recovered and radiometrically dated fossil corals and coralline algae assemblages and represent relative sea level at the great barrier reef rather than gmsl subsequently relative sea level rose at a rate of about 3 5 millimetres per year for around 4 000 years the rise is consistent with the warming previously observed at 19 000 years ago1 5 but we now show that it occurred just after the 20 metre drop in relative sea level and the related increase in global ice volumes the detailed structure of our record is robust because the great barrier reef is remote from former ice sheets and tectonic activity relative sea level can be influenced by earth s response to regional changes in ice and water loadings and may differ greatly from gmsl consequently we used glacio isostatic models to derive gmsl and find that the last glacial maximum culminated 20 500 years ago in a gmsl low of about 125 to 130 metres

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

brine formation in relation to climate changes and ice retreat during the last 15 000 years in storfjorden svalbard 76 78 n storfjorden svalbard is an area of intense brine formation the brine is cold dense rich in oxygen and co2 and has reduced ph storfjorden is unique because it contains well preserved agglutinated foraminifera dating back to the beginning of the last deglaciation we have investigated the distribution of calcareous and agglutinated benthic foraminifera benthic oxygen and carbon isotopes calcium carbonate total organic carbon and ice rafted debris in five cores from storfjorden comprising the holocene and the deglaciation the purpose of the study is to reconstruct brine formation in the past under different climate scenarios the data indicate that in storfjorden the ratio of agglutinated to calcareous benthic foraminifera can be taken as a measure of the strength of brine formation the foraminiferal data which are supported by stable isotopes degree of fragmentation and geochemical parameters signify that brine formation intensified during cold periods and weakened during warm periods during the deglaciation increased brine flow coincides with the older dryas the intra allerod cold period and the younger dryas brine formation increased from circa 8200 years b p reaching periodic maxima during the last 4000 years b p in response to the unstable climate maximum brine production correlates with the dark ages cold period circa 1500 1100 years b p and the little ice age circa 600 100 years b p lower production correlates with the roman warm period circa 2500 2000 years b p and the medieval warm period circa 1000 700 years b p

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

snow contact volcanic facies and their use in determining past eruptive environments at nevados de chillan volcano chile studies of the eruptive products from volcanoes with variable ice and snow cover and a long history of activity enable reconstruction of erupted palaeoenvironments as well as highlighting the hazards associated with meltwater production such as jokulhlaups and magma water interaction existing difficulties include estimation of ice snow thicknesses and discrimination between ice and snow contact lithofacies we present field evidence from the cerro blanco subcomplex of nevados de chillan stratovolcano central chile which has erupted numerous times in glacial and non glacial periods and most recently produced andesitic lava flows in the 1861 1865 eruption from the santa gertrudis cone on the northwest flank of the volcano the main period of lava effusion occurred during the winter of 1861 when the upper flanks of the volcano were reportedly covered in snow and ice the bases and margins of the first lava flows produced are cut by arcuate fractures which are interpreted as snow contact features formed when steam generated from the melting of snow entered tensional fractures at the flow base in contrast the interiors and upper parts of these flows as well as the overlying flow units have autobrecciated and blocky textures typical of subaerial conditions due to insulation by the underlying lava similar textures found in a lava flow dated at 90 0 0 6 ka that was emplaced on the northwest flank of cerro blanco are also inferred to be ice and snow contact features these textures have been used to infer that a small valley glacier overlain by snow existed in the santa gertrudis valley at the time of the eruption such reconstructions are important for determining the long term evolution of the volcano as well as assessing future hazards at seasonally snow covered volcanoes

variability and linkages of new guinea coastal undercurrent and lower equatorial intermediate current abstract velocity at depths of 700 800 m was measured between september 1998 and october 2002 at 2 5 s 142 e off the new guinea coast and at 0 138 e to examine the new guinea coastal undercurrent ngcuc and the current on the equator carrying antarctic intermediate water aaiw velocity characteristics before november 1999 were markedly different from those after november 1999 the typical state occurred during the second period the intermediate ngcuc and the lower equatorial intermediate current leic varied markedly with an annual cycle in opposite phases in austral winter the ngcuc flowed west northwestward strongly 14 cm s 1 285 t especially in may july during which the leic disappeared and eddylike equatorial variations with periods of 20 60 days were significant in austral summer the leic flowed westward strongly 12 cm s 1 270 t especially in october december whereas the ngcuc reversed its direction repeatedly to flow east southeastward in november february thus the intermediat

subthermocline eddies in the western equatorial pacific as shown by an eddy resolving ogcm abstractsporadic in situ observations have shown evidence that subthermocline eddies exist off the mindanao coast these subthermocline eddies are believed to play an important role in the heat freshwater and other ocean property transports of the region but their characteristics and in particular their pathway and source of energy are poorly explored because of the lack of long term observations analysis of results from an eddy resolving general ocean circulation model has revealed that most subthermocline eddies off the mindanao coast originate from the equatorial south pacific ocean to the west of the ninigo group these eddies propagate northward along the new guinea coast cross the equator in the far western pacific and reach the mindanao coast at a typical propagation speed of 0 12 m s 1 the dominant time scales of these eddies range between 50 and 60 days

holocene glacial history of svalbard status perspectives and challenges abstract we synthesize the current understanding of glacier activity on svalbard from the end of the late pleistocene 12 000 yrs before present to the end of the little ice age c 1920 ad our glacier history is derived from the svalhola database the first compilation of holocene geochronology for svalbard and the surrounding waters including over 1 800 radiocarbon terrestrial cosmogenic nuclide and optically stimulated luminescence ages data have been categorized by geological setting uniformly re calibrated quality assessed and ultimately used to constrain glacier fluctuations deglaciation ice free conditions glacier re advances and ice marginal positions we advance existing knowledge by mapping the extent and distribution of ice cover during the holocene glacial maximum and the glacial minimum as well as present retreat rates and percentages within early holocene fjord systems throughout the holocene svalbard glaciers have responded to a varying combination of climatic environmental and dynamic driving factors which influence both the extent and behavior of ice margins we discuss the complexities of glacier systems and their dynamics in response to changes in climate this review provides a holistic state of the art of holocene glaciers on svalbard suitable for orienting future works which address gaps in our current knowledge

northern north sea benthic ostracoda modern distribution and palaeoenvironmental significance the ostracod faunas of the northern north sea exhibit a depth related distribution that is controlled by substrate and hydrographic conditions four biofacies are defined on the basis of total live dead counts sandy substrates shallower than 110 m are characterized by robertsonites tuberculatus and cytheropteron latissimum these species are replaced by acanthocythereis dunelmensis and palmenella limicola on sandy muds in the fladen ground 110 150 m muellerina abyssicola dominates from 175 250 m in the norwegian channel giving way to krithe praetexta at greater depths on soft bottom substrates the results are compared with data from the skagerrak and the western european shelf area temperature ranges for the commonest taxa show that north sea faunas contain endemic western european species temperature range on average 2 20 c some southern species 5 26 c and taxa that range to high latitudes 2 to 14 c southern species are confined to the southern and western margins of the north sea

recent ostracoda from the laptev sea arctic siberia species assemblages and some environmental relationships ostracod assemblages from coretop sediments collected at 26 localities at different depths of the laptev sea shelf and upper continental slope were investigated for assemblage studies a total of 41 species belonging to 19 genera and 12 families have been identified three assemblages have been established that could be linked to environmental factors such as water depth bottom salinities water mass circulation and sea ice transportation the species rich and abundant assemblages of the western and central laptev sea were related to the atlantic waters occupying the upper continental slope these include relatively deep water forms that show clear affinities to north atlantic and arctic ocean assemblages cytheropteron biconvexa c testudo c simplex c nodosoalatum c inflatum c porterae krithe glacialis k minima pseudocythere caudata polycope punctata p orbicularis in the eastern middle shelf region the assemblage is comprised of acanthocythereis dunelmensis together with other normal marine species semicytherura complanata elofsonella concinna cluthia cluthae this assemblage seems connected to the winter flaw polynya which is believed to be the main area of sediment entrainment into sea ice the inner shelf assemblage of the southern laptev sea is dominated by shallow water euryhaline species paracyprideis pseudopunctillata and heterocyprideis sorbyana with admixture of the brackish water species roundstonia macchesneyi the unusual occurrence of a number of shallow water ostracod species on the upper continental slope may be explained by ice rafting which these ostracods are probably able to survive

glacimarine processes and inductive lithofacies modelling of ice shelf and tidewater glacier sediments based on quaternary examples abstract three variables control the type of glacial debris source and where and when debris is introduced to an ocean 1 type of glacial ice source ice sheet or valley glacier 2 condition of a grounded glacier melting freezing or frozen base and cold or warm internal ice and 3 type of glacier front ice shelf or tidewater using these variables in different combinations eight glacimarine regimes are postulated to exist by integrating information from holocene sediment and pleistocene glacimarine sequences with the eight inductive regimes lithofacies relationships are predicted and modelled the models show a complexity of glacimarine lithofacies the importance of recognizing this complexity lies in realistic interpretations of ancient sequences ice shelf sediment may be limited in the geologic record because of tectonic and climatic constraints required for ice shelf formation alternatively in some tidewater glacier regimes larger volumes of glacimarine sediment are produced than in ice shelf regimes ice proximal sediment is distinctive especially near subglacial meltwater stream effluxes ice shelves and tidewater glaciers may produce similar ice proximal lithofacies e g morainal bank associations and laminites in certain regimes however details of lithofacies may aid in distinguishing ice shelf from tidewater regimes ice shelf and tidewater iceberg zone sediment can be distinguished from each other if basal and high level englacial debris can be distinguished ice shelf zone sediment out from the grounding line has a basal debris source high level englacial debris is deposited in more distal ice shelf zones resulting in sediment by pass in corresponding positions of a tidewater glacier regime iceberg rafted debris comprises mixed basal and high level englacial debris deeper water zones receive large volumes of sediment when a melting freezing base grounding line is at the edge of a continental shelf when the grounding line retreats sediment supply may be drastically reduced because of a back sloping continental shelf and trapping by morainal banks cool water bioclastic carbonates may accumulate once a grounding line has retreated although ice shelf iceberg zones are more extensive than those in tidewater regimes ice shelf icebergs have low debris content and resulting ice rafted debris may be scarce the smallest volume of sediment is produced by a frozen base ice sheet ending as a tidewater front and the largest volume by a melting freezing base valley tidewater glacier glacimarine sediment has a relatively high preservation potential near continental interiors or margins however at continental margins mass flow olistostrome and tectonic melange deposits may be preserved with glacimarine diamictites these deposits may be difficult to distinguish from each other especially if metamorphosed such as at a convergent margin the models presented do not fully represent the glacimarine environment because many other variables are omitted however the principal concepts of generating glacimarine lithofacies associations are considered continued research will verify if each regime exists and will provide data on those regimes that exist today to compare and modify these models

miocene glaciomarine sedimentation in the northern antarctic peninsula region the stratigraphy and sedimentology of the hobbs glacier formation james ross island the onshore record of cenozoic glaciation in the antarctic peninsula region is limited to a number of isolated localities on alexander island the south shetland islands and in the james ross island area in the james ross island area late cretaceous sedimentary rocks are unconformably overlain by a unit of diamictites and tuffs which occur at the base of the james ross island volcanic group these rocks are here defined as the hobbs glacier formation and on the basis of palynological studies are assigned to a miocene late miocene age the diamictites are interpreted as representing glaciomarine sedimentation close to the grounding line of either a floating ice shelf or a grounded tidewater glacier in a marine basin provenance studies indicate that the glacier was flowing from the antarctic peninsula towards the southeast volcanic tuffs conformably overlie the diamictites and are interpreted as representing deposition in a periglacial delta front setting in either a marine or non marine basin away from direct glacial influence the hobbs glacier formation and overlying james ross island volcanic group help to enhance our understanding of the neogene glacial chronology of west antarctica

reconstruction of glacier variability from lake sediments reveals dynamic holocene climate in svalbard abstract the arctic is warming faster than anywhere else on earth holocene proxy time series are increasingly used to put this amplified response in perspective by understanding arctic climate processes beyond the instrumental period however available datasets are scarce unevenly distributed and often of coarse resolution glaciers are sensitive recorders of climate shifts and variations in rock flour production transfer this signal to the lacustrine sediment archives of downstream lakes here we present the first full holocene record of continuous glacier variability on svalbard from glacier fed lake hajeren this reconstruction is based on an undisturbed lake sediment core that covers the entire holocene and resolves variability on centennial scales owing to 26 dating points a toolbox of physical geochemical xrf and magnetic proxies in combination with multivariate statistics has allowed us to fingerprint glacier activity in addition to other processes affecting the sediment record evidence from variations in sediment density validated by changes in ti concentrations reveal glaciers remained present in the catchment following deglaciation prior to 11 300 cal bp culminating in a holocene maximum between 9 6 and 9 5 ka cal bp correspondence with freshwater pulses from hudson strait suggests that early holocene glacier advances were driven by the melting laurentide ice sheet lis we find that glaciers disappeared from the catchment between 7 4 and 6 7 ka cal bp following a late hypsithermal glacier reformation around 4250 cal bp marks the onset of the neoglacial supporting previous findings between 3380 and 3230 cal bp we find evidence for a previously unreported centennial scale glacier advance both events are concurrent with well documented episodes of north atlantic cooling we argue that this brief forcing created suitable conditions for glaciers to reform in the catchment against a background of gradual orbital cooling these findings highlight the climate sensitivity of the small glaciers studied which rapidly responded to climate shifts the start of prolonged neoglacial glacier activity commenced during the little ice age lia around 700 cal bp in agreement with reported advances from other glaciers on svalbard in conclusion this study proposes a three stage holocene climate history of svalbard successively driven by lis meltwater pulses episodic atlantic cooling and declining summer insolation

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

deglacial meltwater pulse 1b and younger dryas sea levels revisited with boreholes at tahiti reconstructing sea level changes during the last deglaciation provides a way of understanding the ice dynamics that can perturb large continental ice sheets the resolution of the few sea level records covering the critical time interval between 14 000 and 9 000 calendar years before the present is still insufficient to draw conclusions about sea level changes associated with the younger dryas cold event and the meltwater pulse 1b mwp 1b we used the uranium thorium method to date shallow living corals from three new cores drilled onshore in the tahiti barrier reef no significant discontinuity can be detected in the sea level rise during the mwp 1b period the new tahiti sea level record shows that the sea level rise slowed down during the younger dryas before accelerating again during the holocene

glacial isostatic adjustment associated with the barents sea ice sheet a modelling inter comparison the 3d geometrical evolution of the barents sea ice sheet bsis particularly during its late glacial retreat phase remains largely ambiguous due to the paucity of direct marine and terrestrial based evidence constraining its horizontal and vertical extent and chronology one way of validating the numerous bsis reconstructions previously proposed is to collate and apply them under a wide range of earth models and to compare prognostic isostatic output through time with known relative sea level rsl data here we compare six contrasting bsis load scenarios via a spherical earth system model and derive a best fit 2 parameter using rsl data from the four main terrestrial regions within the domain svalbard franz josef land novaya zemlya and northern norway poor 2 values allow two load scenarios to be dismissed leaving four that agree well with rsl observations the remaining four scenarios optimally fit the rsl data when combined with earth models that have an upper mantle viscosity of 0 2 2 1021 pa s while there is less sensitivity to the lithosphere thickness ranging from 71 to 120 km and lower mantle viscosity spanning 1 50 1021 pa s gps observations are also compared with predictions of present day uplift across the barents sea key locations where relative sea level and gps data would prove critical in constraining future ice sheet modelling efforts are also identified

formation regions of subantarctic mode water detected by ofes and argo profiling floats 1 we investigated the distribution of the deep mixed layer in the southern ocean where subantarctic mode water samw forms by using argo profiling floats and the ocean general circulation model for the earth simulator ofes the mixed layer depth mld generally increased eastward from 50 180 e and from 180 80 w with distinct local maxima near major bathymetric features a sudden transition from deep to shallow mixed layer was found along the equatorward limit of the deep mixed layer this diagnosed mld front coincides with the line of ug s 0 indicating the distributions of the general deepening and local maxima of mld were affected by near surface geostrophic flow the flow is steered by the major bottom topographies and the local mld maxima occurred where the flow direction was deflected southward this implies a link between the bathymetric features and formation of thick samw

the svalbard barents sea ice sheet historical current and future perspectives abstract the history of research on the late quaternary svalbard barents sea ice sheet mirrors the developments of ideas and the shifts of paradigms in glacial theory over the past 150 years since the onset of scientific research there in the early 19th century svalbard has been a natural laboratory where ideas and concepts have been tested and played an important but rarely acknowledged role in the break through of the ice age theory in the 1870 s the history of how the scientific perception of the svalbard barents sea ice sheet developed in the mid 20th century also tells a story of how a combination of fairly scattered and often contradictory observational data and through both deductive and inductive reasoning could outline a major ice sheet that had left but few tangible fingerprints since the 1980 s with increased terrestrial stratigraphical data ever more marine geological evidence and better chronological control of glacial events our perception of the svalbard barents sea ice sheet has changed the first reconstructions depicted it as a static concentric single domed ice sheet with ice flowing from an ice divide over the central northern barents sea that expanded and declined in response to large scale late quaternary climate fluctuations and which was more or less in tune with other major northern hemisphere ice sheets we now increasingly perceive it as a very dynamic multidomed ice sheet controlled by climate fluctuations relative sea level change as well as subglacial topography substrate properties and basal temperature in this respect the svalbard barents sea ice sheet will increasingly hold the key for understanding the dynamics and processes of how marine based ice sheets build up and decay

theoretical analysis of snow dam decay snow dams have been observed in many stream channels in the arctic and the sub arctic but there is no theoretical analysis of their decay processes these processes include snowmelt seepage erosion down cutting snow slope failure and flotation of the snow dam snowmelt can be determined by the energy balance seepage of water will cause serious erosion at the point where the stream or pond level in front of the dam intersects the dam face erosion by water overflowing the dam is due to down cutting under cutting and thermal erosion down cutting increases with discharge but decreases with the shear strength of the snow where a hydraulic jump occurs downstream of the dam under cutting can accelerate dam decay thermal erosion depending mainly on water temperature may be less significant than the previous two processes slope failure occurs when the driving forces exceed the resisting forces and these are affected by snow property and snow load when the stream or pond level downstream of the dam rises rapidly the dam is prone to float as peak flow often occurs during the break up period results of the theoretical study of the mechanisms of snow dam decay will improve flood forecasting for arctic streams

deep arctic ocean warming during the last glacial cycle in the arctic ocean the cold and relatively fresh water beneath the sea ice is separated from the underlying warmer and saltier atlantic layer by a halocline ongoing sea ice loss and warming in t

semiannually alternating exchange of intermediate waters east of the philippines intermediate water exchange in the northwest tropical pacific is explored with the temperature salinity and current measurements of a mooring system deployed at 8 degrees n 127 05 degrees e during 2010 2014 for the first time prominent semiannual variability sav with the maximum power at similar to 187days of subthermocline meridional flow along the mindanao coast is revealed a significant correlation between meridional flow and salinity is found at intermediate depths this provides direct evidence for the alternating transports of south pacific and north pacific intermediate waters by northward and southward undercurrents respectively further analysis with an eddy resolving ocean general circulation model demonstrates that the sav is generated locally near the western boundary manifesting as large scale subthermocline recirculation and leading to alternating northward and southward flows near the mindanao coast which plays an efficient role in the intermediate water exchange of the northwest tropical pacific mechanisms underlying the observed sav are discussed

deglaciation of the eurasian ice sheet complex the eurasian ice sheet complex eisc was the third largest ice mass during the last glacial maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea level lowering whilst recent terrestrial and marine empirical insights have improved understanding of the chronology pattern and rates of retreat of this vast ice sheet a concerted attempt to model the deglaciation of the eisc honouring these new constraints is conspicuously lacking here we apply a first order thermomechanical ice sheet model validated against a diverse suite of empirical data to investigate the retreat of the eisc after 23 ka bp directly extending the work of patton et al 2016 who modelled the build up to its maximum extent retreat of the ice sheet complex was highly asynchronous reflecting contrasting regional sensitivities to climate forcing oceanic influence and internal dynamics most rapid retreat was experienced across the barents sea sector after 17 8 ka bp when this marine based ice sheet disintegrated at a rate of 670 gigatonnes per year gt a 1 through enhanced calving and interior dynamic thinning driven by oceanic atmospheric warming and exacerbated by eustatic sea level rise from 14 9 to 12 9 ka bp the eisc lost on average 750 gt a 1 peaking at rates 3000 gt a 1 roughly equally partitioned between surface melt and dynamic losses and potentially contributing up to 2 5 m to global sea level rise during meltwater pulse 1a independent glacio isostatic modelling constrained by an extensive inventory of relative sea level change corroborates our ice sheet loading history of the barents sea sector subglacial conditions were predominately temperate during deglaciation with over 6000 subglacial lakes predicted along with an extensive subglacial drainage network moreover the maximum eisc and its isostatic footprint had a profound impact on the proglacial hydrological network forming the fleuve manche mega catchment which had an area of 2 5 106 km2 and drained the present day vistula elbe rhine and thames rivers through the seine estuary during the bolling allerod oscillation after c 14 6 ka bp two major proglacial lakes formed in the baltic and white seas buffering meltwater pulses from eastern fennoscandia through to the younger dryas when these massive proglacial freshwater lakes flooded into the north atlantic ocean deglaciation temporarily abated during the younger dryas stadial at 12 9 ka bp when remnant ice across svalbard franz josef land novaya zemlya fennoscandia and scotland experienced a short lived but dynamic re advance the final stage of deglaciation converged on present day ice cover around the scandes mountains and the barents sea by 8 7 ka bp although the phase lagged isostatic recovery still continues today

reconstruction of inflow of atlantic water to isfjorden svalbard during the holocene correlation to climate and seasonality abstract the distribution patterns of benthic foraminifera faunas stable isotopes and ice rafted debris ird have been studied in piston core jm98 845 pc from isfjorden western svalbard to reconstruct changes in the flow of atlantic water during the holocene interglacial the paleoenvironmental conditions in isfjorden and the inflow of the atlantic water followed closely the changes in insolation with strong seasonality in the early holocene and weaker seasonality in the middle to late holocene a summer temperature maximum of the bottom water occurred in the early holocene 10 500 c 8200 years bp cooling began at 9000 years bp with stepwise coolings at c 8200 7400 and 4000 years bp the cooling correlated with an increase in ice rafting and increased influence of polar water and seasonal sea ice cover between 4000 and 2000 years bp bottom water temperatures reached a minimum after 2000 years bp episodic inflow of warmer atlantic water at the bottom of the fjord occurred and conditions became more unstable the data indicate close interaction of the flow of atlantic water with the development of the terrestrial climate and the amount of polar meltwater and sea ice

the permeability of a melting snow cover data from snow lysimeters in california and vermont are used to find the saturated permeability of a melting snow cover in the range of 10 40 10 10 m2 depending on snow density the unsaturated permeability increases as about the third power of liquid saturation the gravity flow theory is shown to be an accurate representation of meltwater drainage from snow covers in two diverse areas even though the snow covers are treated as homogeneous units the variation of saturated permeability with snow density occurs about as predicted by shimizu s formula for dry snow although ice layers decrease the permeability somewhat

lava and ice interaction at stratovolcanoes use of characteristic features to determine past glacial extents and future volcanic hazards structures resulting from lava and ice interaction are common at glaciated stratovolcanoes during summit eruptions at stratovolcanoes meltwater is produced and travels freely down steep slopes and thin permeable valley glaciers eroding the ice and enlarging preexisting glacial drainages as a result eruptions in this environment have produced few catastrophic floods lava flowing into the open channels and voids in the glaciers becomes confined and grows thicker filling the available space and producing steep sided bodies with smooth bulbous contact surfaces quenching of lava against ice or by water forms small scale features such as tensional fractures and glass as the amount of meltwater in contact with the lava increases the type and abundance of smaller scale features become similar to those produced during subglacial eruptions into meltwater lakes identification of large and small scale lava ice contact features in the field can be used to reconstruct paleoglacial extent and combined with geochronology of lavas to determine past paleoclimate an understanding of lava ice interaction allows us to better assess the hazards posed by future eruptions at glaciated volcanoes

reconstruction of ice sheet retreat after the last glacial maximum in storfjorden southern svalbard abstract storfjorden is a large north south trending sound located in the southern part of svalbard in the northwestern barents sea presently several glaciers drain into the northern and western part of storfjorden our study area covers the southern part of the sound which is divided by a north south striking basement ridge the mid ridge into a narrow western trough little storfjorden and a broader eastern trough storfjorden in the latter three grounding zone wedges gzws were discovered in 2005 showing evidence of former grounded ice here we confirm the existence and map the extent of the gzws and reconstruct the pattern and timing of ice retreat in storfjorden during the deglaciation the study is based on high resolution seismic and shallow acoustic profiles and swath bathymetry combined with information of lithology and radiocarbon dates from sediment cores the results show that the three gzws stretch across the fjord and that all three are located south of higher basement areas that were upstream of the gzws and which acted as pinning points during ice retreat the mid ridge imposed a lateral drag to the ice resulting in an uneven ice retreat across the fjord outside of the gzws only a thin cover of glacial deposits was found the cores were taken in vicinity of the gzws and all reached till deposits overlain by glacimarine or hemipelagic sediments enabling dating of the gzws altogether we find that the fjord and basement topography played an important role in the ice retreat ams 14c dates show that the formation of the three gzws correlate with three well known atmospheric warming phases start of bolling interstadial allerod interstadial and holocene interglacial respectively associated with inflows of warm atlantic water indicating a strong ocean climate control on the deglaciation of storfjorden

the relative importance of supraglacial versus subglacial meltwater escape in basaltic subglacial tuya eruptions an important unresolved conundrum the hydraulic behaviour of meltwater during subglacial basaltic eruptions in temperate ice is of paramount importance in understanding the eruptive processes lithofacies and architecture of the edifices formed hydraulics also determines the timing location and volume of meltwater discharge which may be sudden and catastrophic and via subglacial and or supraglacial routes increasing our knowledge of meltwater hydraulics is therefore important for understanding predicting and mitigating the impact of meltwater release on vulnerable human communities new observations about eruption related meltwater hydraulics are presented for well exposed glaciovolcanic lava fed deltas on james ross island antarctica and accounts of historical eruptions are also re examined to identify the major meltwater discharge routes the study provides the first conceptual model for how meltwater escapes supraglacially in the absence of a crevassed layer which will dominate any meltwater flow overflowing may be initiated by enhanced rates of seepage despite the intrinsically low hydraulic conductivities of snow and firn once overflowing is established the rate of spillway incision is a likely overriding control on the evolution of the system and whether the discharge is unstable fast or stable slower the james ross island sequences demonstrate that meltwater discharge is highly dynamic and may have involved both subglacial and supraglacial escape subglacial discharge probably occurs throughout basaltic tuya eruptions but some periods may be dominated by concurrent overflowing it is still unclear if overflowing systems are sufficiently stable to enable the growth of laterally extensive glaciovolcanic lava fed deltas

dating high arctic holocene relative sea level changes using juvenile articulated marine shells in raised beaches high arctic raised beaches provide evidence for changes in relative sea level rsl sea ice extent storminess and variations in sediment supply in many high arctic areas driftwood and whale bone are usually the preferred targets for radiocarbon dating with marine shells a third choice because of their often large age and height uncertainties with respect to former sea level here we detail a new approach to sampling marine shells that reduces these problems by targeting juvenile articulated specimens of astarte borealis that are washed onto the beach under storm conditions and become incorporated into the beach crest radiocarbon dates from articulated valves of a borealis from eight raised beaches from billefjorden svalbard provide a chronology for holocene beach ridge formation and rsl change that compares favourably to the most precise records developed from elsewhere in svalbard using driftwood or whale bone we demonstrate the value of this new approach by comparing our record with previously published rsl data from eastern svalbard to test different models of late weichselian ice load in this region we find support for a major ice dome centred south and east of kong karls land but no evidence for a significant ice dome located over easternmost spitsbergen or southern hinlopen strait as proposed from recent marine geophysical survey the approach is potentially applicable elsewhere in svalbard and the high arctic to address questions of rsl change and beach ridge chronology and hence wider questions regarding palaeoclimate and ice load history

anti correlated variability in subduction rate of the western and eastern north pacific oceans identified by an eddy resolving ocean gcm analysis of results from an eddy resolving ocean general circulation model has revealed the existence of an anti correlated variability in subduction rate of the western and eastern north pacific oceans consistent with the leading mode of pacific decadal oscillation pdo a composite analysis shows that during the positive phase of pdo the winter mixed layer depth mld generally gets deeper in the west and shallower in the east being closely related to the variability in surface heat flux stemming from an enhanced aleutian low and the situation during the negative phase of pdo is reversed changes in mld are primarily responsible for the anti correlated variability in subduction rate though changes in subtropical gyre circulation also play a role the result also provides useful evidence for the interior and western boundary pathways through which variability in eastern subtropical mode water can be conveyed into the equatorial region citation chen j t qu y n sasaki and n schneider 2010 anti correlated variability in subduction rate of the western and eastern north pacific oceans identified by an eddy resolving ocean gcm geophys res lett 37 l23608 doi 10 1029 2010gl045239

distribution lithofacies and environmental context of neogene glacial sequences on james ross and vega islands antarctic peninsula considerable controversy exists concerning the stability of the antarctic ice sheet during the neogene period the northern antarctic peninsula is in a critical position in this debate as it represents a peripheral area of the ice sheet and is therefore likely to have been sensitive to climatic changes this paper is concerned with neogene glacial deposits that occur on james ross and vega islands they occur between a thick volcanic sequence the james ross island volcanic group and upper cretaceous sedimentary rocks they also occur within the volcanic sequence itself the glacial deposits where dated give a series of snapshots of glacial conditions in neogene time the deposits are characterized by diamictite and sandy mudstone published 87sr 86sr ages on shelly fossils in some deposits range from 9 9 to 4 7 ma although additional 40ar 39ar ages on interbedded volcanic rocks suggest that younger sedimentary deposits are also present on james ross island the basal diamictite is interpreted as glaciomarine sediment that has undergone subaqueous mass movement and on vega island as basal till originating from the west provenance studies indicate that the antarctic peninsula ice sheet expanded sufficiently to deposit these sediments these diamictites in places are overlain by waterlain tuffaceous rocks that include a minor ice rafted component complex deformation of sedimentary and volcanic deposits and contact metamorphism relationships confirm that volcanism was contemporaneous with glaciation later glacial events within the volcanic sequence are characterized by glacial erosion of basalt followed by basal till and possibly glaciofluvial deposition the clasts in the latter are almost exclusively local hence later glaciation was as a small ice cap constructed on the growing volcanic complex of james ross island

northward intrusion of antarctic intermediate water in the western pacific abstract the northward intrusion of antarctic intermediate water aaiw is examined using historical data combined with synoptic observations from a repeated hydrographic section in the western pacific ocean the results of this analysis suggest that aaiw is traced as a salinity minimum to only about 15 n via the new guinea coastal undercurrent and the mindanao undercurrent there is no northward extension of aaiw farther to the north along the western boundary although relatively high oxygen water does exist in the okinawa trough it is connected with high oxygen water in the south china sea scs through the luzon strait but not from the south as an extension of aaiw local circulation seems to play an essential role in localizing the oxygen maximum in the scs evidence exists to suggest that high oxygen water enters the scs as part of the pacific deep water around the still depth 2000 m of the luzon strait from there part of it upwells and is entrained into shallower isopycnal surfaces by vertica

past ice flow in wahlenbergfjorden and its implications for late quaternary ice sheet dynamics in northeastern svalbard wahlenbergfjorden is a fjord situated in the western part of nordaustlandet in northern svalbard it leads into the 400 m deep hinlopen strait located between nordaustlandet and spitsbergen high r