distribution of clay minerals in surface sediments from the eastern barents and south western kara seas surface samples from the eastern barents and south western kara seas have been analysed for clay mineralogy transport paths the role of regional sources and local bedrock outcrops and the influence of hydrodynamic and glacigenous processes for clay distribution on the shelves are discussed in relation to central arctic ocean deep sea and sea ice sediments franz josef land and novaya zemlya show significantly different clay mineral associations although smectite concentrations are fairly high franz josef land can be excluded as a source for central arctic sea ice sediments which are relatively rich in smectite in the kara sea smectite concentrations in coastal sediments surpass even the franz josef land concentrations the large cyclonic gyre in the eastern barents sea between novaya zemlya and franz josef land which serves as a mixing zone between arctic and north atlantic water is apparently reflected within the smectite distribution pattern with the exception of franz josef land the area of investigation is typically low in kaolinite in particular coastal areas and areas north of novaya zemlya influenced by the inflow of arctic waters show the lowest kaolinite concentrations a high kaolinite occurrence within the nansen basin is most probably related to franz josef land and emphasizes the importance of long range downslope transport of sediments across the continental slope the surface water circulation pattern in close interaction with local outcrops onshore novaya zemlya and locally restricted occurrences within the eastern barents sea significantly alter the illite dispersal pattern illite concentrations are lowest around franz josef land chlorite is generally low in the area of investigation submarine outcrops and important chlorite occurrences onshore novaya zemlya bias its distribution pattern

causes and consequences of arctic freshwater routing into the nordic seas during late marine isotope stage 5 sediment core ps1904 reveals continuous records of planktic and benthic foraminiferal stable isotopes 18o 13c from the north eastern greenland continental margin the data show good comparability with other records from the nordic seas allowing the stratigraphic range of ps1904 to be dated to marine isotope stage mis 6 focusing on mis 5 reveals light 18o values during mis 5a compared to the last interglacial peak mis 5e which indicates that surface and bottom water layers were strongly affected by freshwater during the former event we present two possible scenarios explaining the origin and routing of the freshwater i drainage of a eurasian proglacial lake coupled with the collapse of the kara sea ice sheet at the mis 5b a boundary and ii destabilization and melting of the nearby greenland ice sheet although both scenarios could have acted simultaneously sediment records from the eurasian sector of the arctic ocean hint at the proglacial lake system in north western siberia as the largest freshwater source regardless of the actual source the freshwater lowered the surface ocean salinity causing water column stratification and sea ice expansion increased sea ice abundance led to a higher albedo and probably contributed to the cooling and global ice sheet growth that occurred subsequently during mis 4

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

the paleogeography of arctic shelf and coastal zone of eurasia at the time of the last glaciation 18 000 yr b p abstract paleogeographic maps showing reconstructed environments of the eurasian arctic shelf and coastal zone during the last glacial maximum 18 000 yr b p were compiled within the project igcp 200 sea level correlations and applications the reconstruction shows conspicuous difference between eastern and western sectors of the arctic shelf of eurasia large glaciers existed in the west while the eastern arctic shelf was an emerged ice free lowland dominated by tundra landscapes and built of unconsolidated sediments with a variety of genesis

field observations of slush ice generated during freeze up in arctic coastal waters abstract in some years large volumes of slush ice charged with sediment are generated from frazil crystals in the shallow beaufort sea during strong storms at the time of freeze up such events terminate the navigation season and because of accompanying hostile conditions little is known about the processes acting the water saturated slush ice which may reach a thickness of 4 m exists for only a few days before freezing from the surface downward arrests further wave motion or pancake ice forms movements of small vessels and divers in the slush ice occurs only in phase with passing waves producing compression and rarefaction and internal pressure pulses where in contact with the seafloor the agitated slush ice moves cobble size material generates large sediment ripples and may possibly produce a flat rampart observed on the arctic shoreface in some years processes charging the slush ice with as much as 1000 m 3 km 2 of sediment remain uncertain but our field observations rule out previously proposed filtration from turbid waters as a likely mechanism sedimentary particles apparently are only trapped in the interstices of the slush ice rather than being held by adhesion since wave related internal pressure oscillations result in downward particle movement and cleansing of the slush ice this loss of sediment explains the typical downward increase in sediment concentration in that part of the fast ice canopy composed largely of frazil ice the congealing slush ice in coastal water does not become fast ice until grounded ridges are formed in the stamukhi zone one to two months after freeze up begins during this period of new ice mobility long range sediment transport occurs the sediment load held by the fast ice canopy in the area between the colville and sagavanirktok river deltas in the winter of 1978 1979 was 16 times larger than the yearly river input to the same area this sediment most likely was rafted from canada more than 400 km to the east during a brief time period in the previous fall ocean turbulence is greatly reduced while the congealing slush ice drifts about therefore new ice then forming in intervening open water areas is clean these events explain the patchy appearance of the fast ice after the summer snowmelt more work on the important phenomena reported here is needed to close a major gap in the knowledge of the arctic marine environment

polynya dynamics a review of observations and modeling 1 polynyas are nonlinear shaped openings within the ice cover ranging in size from 10 to 105 km2 polynyas play an important climatic role first winter polynyas tend to warm the atmosphere thus affecting atmospheric mesoscale motions second ocean surface cooling and brine rejection during sea ice growth in polynyas lead to vertical mixing and convection contributing to the transformation of intermediate and deep waters in the global ocean and the maintenance of the oceanic overturning circulation since 1990 there has been an upsurge in polynya observations and theoretical models for polynya formation and their impact on the biogeochemistry of the polar seas this article reviews polynya research carried out in the last 2 decades focusing on presenting a state of the art picture of the physical interactions between polynyas and the atmosphere sea ice ocean system observational and modeling studies the surface heat budget and water mass transformation within these features are addressed

concentrations provenance and flux of aerosol trace elements during us geotraces western arctic cruise gn01 abstract the arctic region is undergoing significant changes in climate with a notable decrease in summertime sea ice coverage over the past three decades this trend means an increasing proportion of arctic ocean surface waters can receive direct deposition of material from the atmosphere potentially influencing marine biogeochemical cycles and delivery of pollutants to the arctic ecosystem here we present aerosol concentrations of selected trace elements al ti v mn fe co ni cu zn cd and pb measured during the us geotraces western arctic cruise gn01 also known as hly1502 in august october 2015 concentrations of lithogenic elements al ti v mn fe and co were similar to those measured in remote and predominantly marine influenced air masses in previous studies reflecting the remoteness of the arctic ocean from major dust sources concentrations of ni cu zn pb and cd showed significant enrichments over crustal values and were often of similar magnitude to concentrations measured over the north atlantic in air masses of north american or european provenance we use 7be inventory and flux data from gn01 to estimate a bulk atmospheric deposition velocity during the study period and combine it with our aerosol concentrations to calculate atmospheric deposition fluxes of the trace elements in the arctic region during late summer the resulting estimates for mineral dust and fe deposition fall at the low end of global estimates and confirm the arctic ocean as a low dust environment during the summer months this article is part of a special issue entitled conway geotraces edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

character paleoenvironment rate of accumulation and evidence for seismic triggering of holocene turbidites canada abyssal plain arctic ocean abstract four box cores and one piston core show that holocene sedimentation on the southern canada abyssal plain for the last 8010 120 yr has consisted of a continuing rain of pelagic organic and ice rafted clastic sediment with a net accumulation rate during the late holocene of 10 mm 1000 yr and episodically emplaced turbidites 1 5 m thick deposited at intervals of 830 to 3450 yr average 2000 yr the average net accumulation rate of the mixed sequence of turbidites and thin pelagite interbeds in the cores is about 1 2 m 1000 yr physiography suggests that the turbidites originated on the mackenzie delta or its clinoform and 13c values of 27 to 25 in the turbidites are compatible with a provenance on a delta extant displaced neritic and lower slope to basin plain calcareous benthic foraminifers coexist in the turbidite units their joint occurence indicates that the turbidites originated on the modern continental shelf and entrained sediment from the slope and rise enroute to their final resting place on the canada abyssal plain the presence of middle pleistocene diatoms in the turbidites suggests in addition that the turbidites may have originated in shallow submarine slides beneath the upper slope or outer shelf small but consistent differences in organic carbon content and 13c values between the turbidite units suggest that they did not share an identical provenance which is at least compatible with an origin in slope failures the primary provenance of the ice rafted component of the pelagic beds was the glaciated terrane of northwestern canada and the provenance of the turbidite units was pleistocene and holocene sedimentary deposits on the outer continental shelf and upper slope of the mackenzie delta largely local derivation of the sediment of the canada abyssal plain indicates that sediment accumulation rates in the arctic ocean are valid only for regions with similar depositional sources and processes and that these rates cannot be extrapolated regionally the location of an elliptical zone of active seismicity over the inferred provenance of the turbidites suggests that they were triggered by large earthquakes distal turbidite sediment accumulation rates were more than two orders of magnitude greater than pelagic sediment accumulation rates on the canada abyssal plain during the last 8000 years this disparity reconciles the discrepancy between the high accumulation rates assumed by some for the arctic ocean because of the numerous major rivers and large ice sheets that discharge into this small mediterranean basin and the low pelagic sedimentation rates that have been reported from the arctic ocean

distribution of chlorite and kaolinite in eastern atlantic sediments off north africa chlorite in the atlantic sediments is predominantly derived from the atlas mountains kaolinite originates in the southern sahara and sahel zone these minerals may be used to reconstruct the tracks of two superimposed wind systems trade winds and harmattan wind a modified method for determining relative abundances of chlorite and kaolinite is presented

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

sea ice sediment entrainment and rafting in the arctic abstract large areas of first year sea ice containing disseminated loads of silt and clay sized materials are common off the northern coast of alaska sand and coaser material is also found in this ice in the form of distinct masses of sediment laden ice sediment is entrained into the sea ice cover during fall storms when frazil or small discs of ice in suspension is actively forming in the supercooled water column at this time sea ice is unconsolidated and very mobile making long range ice rafting possible sediment rich ice may be advected off the shelf and upon melting deposit material in the deep arctic basin the amount of sediment incorporated into the ice cover varies considerably from year to year depending on the location and severity of storms accompanying freezeup in 1978 the seasonal ice cover in an area off northern alaska carried 16 times as much sediment as the total annual suspended sediment input from adjacent coastal rivers sea ice sediment transport is important in the overall sediment budget in northern polar regions particularly the transport of fine grained material but entrainment mechanisms are poorly understood

organic carbon carbonate and clay mineral distributions in eastern central arctic ocean surface sediments abstract results from a detailed sedimentological investigation of surface sediments from the eastern arctic ocean indicate that the distribution of different types of sediment facies is controlled by different environmental processes such as sea ice distribution terrigenous sediment supply oceanic currents and surface water productivity in comparison to other open ocean environments total organic carbon contents are high with maximum values in some deep basin areas as well as west and north of svalbard in general the organic carbon fraction is dominated by terrigenous material as indicated by low hydrogen index values and high c n ratios probably transported by currents and or sea ice from the eurasian shelf areas the amount of marine organic carbon is of secondary importance reflecting the low productivity environment described for the modern ice covered arctic ocean in the area north of svalbard some higher amounts of marine organic matter may indicate increased surface water productivity controlled by the inflow of the warm westspitsbergen current wsc into the arctic ocean and reduced sea ice cover this influence of the wsc is also supported by the high content of biogenic carbonate recorded in the yermak plateau area the clay mineral distribution gives information about different source areas and transport mechanisms illite the dominant clay mineral in the eastern central arctic ocean sediments reaches maximum values in the morris jesup rise area and around svalbard indicating north greenland and svalbard to be most probable source areas kaolinite reaches maximum values in the nansen basin east of svalbard and in the barents sea possible source areas are mesozoic sediments in the barents sea and franz josef land in contrast to the high smectite values determined in sea ice samples smectite contents are generally very low in the underlying surface sediments suggesting that the supply by sea ice is not the dominant mechanism for clay accumulation in the studied area of the modern central arctic ocean

ice rafting of fine grained sediment a sorting and transport mechanism beaufort sea alaska abstract the presence of turbid sediment rich fast ice in the arctic is a major factor affecting transport of fine grained sediment turbid ice was found to be present in a zone 10 to 20 km wide along the coast of the beaufort sea sediment concentrations observed in cores taken in seasonal fast ice ranged from 3 to more than 1 600 g m3 finely disseminated silt and clay sized particles dominated discoloring the upper segments of the cores in a layer up to 1 m thick in almost all of the cores the upper most 10 cm of ice was relatively less turbid and the relief at the base of the turbid layer was 10 to 20 cm over distances of 1 to 2 m observers have documented the widespread sporadic occurrence of sediment rich fast ice in both the beaufort and bering seas the known sources a d transport relations of suspended sediment did not explain this distribution of turbid ice the occurrence of sediment in only the upper part of the seasonal fast ice indicates that sediment rich ice forms early during ice growth the most likely mechanism for the formation of sediment laden ice and preferential sorting of fine sediments requires resuspension of nearshore bottom sediment during storms accompanied by formation of frazil ice and subsequent lateral advection before the fast ice is stabilized we estimate that the sediment incorporated in the beaufort ice canopy formed a significant proportion of the seasonal influx of terrigenous fine grained sediment the dominance of fine grained sediment suggests that in the arctic and sub arctic these size fractions may be ice rafted in greater volumes than the coarse fraction of traditionally recognized ice rafted sediment the incorporation and transport mechanism may be a significant factor in the transport of fine grained sediments in the arctic basin

anchor ice seabed freezing and sediment dynamics in shallow arctic seas diving investigations confirm previous circumstantial evidence of seafloor freezing and anchor ice accretion during freeze up storms in the alaskan beaufort sea these related bottom types were found to be continuous from shore to 2 m depth and spotty to 4 5 m depth spotty anchor ice occurred as pillow shaped crystal aggregates on buried slabs of frozen sand surrounded by unfrozen sand considerations of required conditions for ice bonding and anchor ice growth allows regional extrapolation and suggests the possibility of anchor ice growth out to 20 m depth the estimated maximum depth of supercooling during fall storms anchor ice and seabed freezing apparently do not develop during a calm freeze up because of the abrupt growth of anchor ice during a freezing storm and its release soon after formation of a surface ice cover this ice type has not been documented before the concretelike nature of frozen bottom where present should prohibit sediment transport by any conceivable wave or current regime during the freezing storm but elsewhere particularly where the bonded crust is broken by grounded ice anchor ice lifts coarse material off the bottom and incorporates it into the ice canopy thereby leading to significant ice rafting of shallow shelf sediment and likely sediment loss to the deep sea

sediments in arctic sea ice implications for entrainment transport and release despite the arctic sea ice cover s recognized sensitivity to environmental change the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood sea ice sediment inclusions were studied in the central arctic ocean during the arctic 91 expedition and in the laptev sea east siberian arctic region expedition 1992 results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central arctic ocean this study documents the regional distribution and composition of particle laden ice investigates and evaluates processes by which sediment is incorporated into the ice cover and identifies transport paths and probable depositional centers for the released sediment in april 1992 sea ice in the laptev sea was relatively clean the sediment occasionally observed was distributed diffusely over the entire ice column forming turbid ice observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment in the central arctic ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes the surface sediment accumulation in central arctic multi year sea ice exceeds by far the amounts observed in first year ice from the laptev sea in april 1992 sea ice sediments are generally fine grained although coarse sediments and stones up to 5 cm in diameter are observed component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles the biogenous components namely shells of pelecypods and benthic foraminiferal tests point to a shallow benthic marine source area apparently sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing clay mineralogy of ice rafted sediments provides information on potential source areas a smectite maximum in sea ice sediment samples repeatedly occurred between 81 n and 83 n along the arctic 91 transect indicating a rather stable and narrow smectite rich ice drift stream of the transpolar drift the smectite concentrations are comparable to those found in both laptev sea shelf sediments and anchor ice sediments pointing to this sea as a potential source area for sea ice sediments in the central arctic ocean sea ice clay mineralogy is significantly different from deep sea clay mineral distribution patterns the contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms

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

biomarker distributions in surface sediments from the kara and laptev seas arctic ocean indicators for organic carbon sources and sea ice coverage studies of spatial and temporal changes in modern and past sea ice occurrence may help to understand the processes controlling the recent decrease in arctic sea ice cover here we determined concentrations of ip25 a novel biomarker proxy for sea ice developed in recent years phytoplankton derived biomarkers brassicasterol and dinosterol and terrigenous biomarkers campesterol and sitosterol in the surface sediments from the kara and laptev seas to estimate modern spatial seasonal sea ice variability and organic matter sources c25 hbi dienes and trienes were determined as additional palaeoenvironmental proxies in the study area furthermore a combined phytoplankton ip25 biomarker approach pip25 index is used to reconstruct the modern sea ice distribution more quantitatively the terrigenous biomarkers reach maximum concentrations in the coastal zones and estuaries reflecting the huge discharge by the major rivers ob yenisei and lena maxima in phytoplankton biomarkers indicating increased primary productivity were found in the seasonally ice free central part of the kara and laptev seas neither ip25 nor pip25 however shows a clear and simple correlation with satellite sea ice distribution in our study area due to the complex environmental conditions in our study area and the transportation process of sea ice diatom in the water column differences in the diene ip25 and triene ip25 ratios point to different sources of these hbis and different environmental conditions the diene ip25 ratio seems to correlate positively with sea surface temperature while negatively with salinity distributions

coastal environments of the western kara and eastern barents seas abstract satellite images from the kara sea show that until july fast ice extends along the coast and fills the estuaries of the ob and yenisey rivers it is separated from offshore drift ice by a region of open water comprising a flaw lead polynya by august much of the fast and drift ice has melted and retreated from the southwestern kara sea leaving behind a persistent patch of sea ice east of novaya zemlya because both the of and yenisey rivers discharge water throughout the winter the fast ice is likely to incorporate river borne contaminants by bottom adfreezing during peak river discharge in june the fast ice remains in place and is potentially influenced by the river outflow throughout the length of the estuary breakup and melting of the fast ice in july could release contaminants to the surface waters by late july and august when the fast ice has disappeared the river discharge is observed primarily along the shore in a zone that extends offshore more than 100 km in fall newly forming ice may incorporate contaminants from the river plume while in late winter convection penetrating to the sea floor may allow resuspended sediments to be entrained in ice forming in the flaw lead polynya drift ice formed in this region could then advect contaminants offshore the potential for exchange of water ice and contaminants with the barents sea through karskiye vorota south of novaya zemlya is discussed in the context of the temperature and turbidity distribution observed in the satellite images

seabed erosion on the lomonosov ridge central arctic ocean a tale of deep draft icebergs in the eurasia basin and the influence of atlantic water inflow on iceberg motion 1 the submarine lomonosov ridge which bisects the arctic ocean is covered by 450 m of hemipelagic sediments high resolution chirp sonar and side scan data have documented erosion of a section of the ridge here we present multichannel seismic and chirp sonar data which show removal of unconsolidated sediments along the eurasia basin side of the lomonosov ridge where the central ridge is shallower than 1000 m the incomplete erosion of the hemipelagic drape and probable topographic control of ice motion suggest that the deepest draft glacier ice which reached the central arctic ocean from the eurasia basin was in the form of armadas of large icebergs embedded in sea ice rather than a single continuous floating ice shelf massive rapid discharge of glacier ice was probably required to produce the deepest draft 800 m icebergs eastward and northward drift trajectories from a likely iceberg source area on the kara barents sea margin would reflect the relative strength of atlantic inflow through the fram strait however only icebergs with drafts exceeding bathymetric thresholds on the lomonosov ridge would leave an erosive imprint on the seabed advection of atlantic water may have been relatively strong at times of discharge from the saalian ice sheet icebergs exiting the arctic ocean caused massive erosion and redeposition of the hemipelagic sediments on top of yermak plateau

arctic perennial ice cover over the last 14 million years knowledge of the long term history of the perennial ice is an important issue that has eluded study because the cenozoic core material needed has been unavailable until the recent arctic coring expedition acex detrital fe oxide mineral grains analyzed by microprobe from the last 14 ma 164 m of the acex composite core on the lomonosov ridge were matched to circum arctic sources with the same mineral and 12 element composition these precise source determinations and estimates of drift rates were used to determine that these sand grains could not be rafted to the acex core site in less than a year thus the perennial ice cover has existed since 14 ma except for the unlikely rapid return to seasonal ice between the average sampling interval of about 0 17 ma both north america and russia contributed significant fe grains to the acex core during the last 14 ma

revised magnetostratigraphies confirm low sedimentation rates in arctic ocean cores the general lack of an age diagnostic biostratigraphy in the neogene sediments of the abyssal arctic ocean has emphasized the importance of magnetostratigraphy in providing chronostratigraphic control in these sediments sedimentation rates interpreted from early magnetostratigraphic studies of cores taken from the t3 ice island in the western mendeleev plain were estimated to be on the order of 1 mm io3 yr however recent amino acid epimerization studies of a core from the same area have suggested sedimentation rates of almost 15 mm io3 yr this controversy has led us to reexamine the paleomagnetism of several of these cores our alternating field demagnetization studies indicate that many of these cores have an intense high coercivity overprint acquired after the core was opened that is adequately removed only after treatment at 20 to 70 mt we have remeasured samples from two cores after demagnetizations up to 80 mt and can confirm the position of the bnmheslmatuyama boundary originally identified in the cores in addition the jaramillo and olduvai subchrons are identified average sedimentation rates in these two cores are 2 3 mm io3 yr similar to the original estimates based on reversal stratigraphy as well as those determined from recent radiocarbon studies but incompatible with the amino acid based dates

geochemistry of surficial and ice rafted sediments from the laptev sea siberia the laptev sea as a part of the world s widest continental shelves surrounding the arctic ocean is a key area for understanding the land ocean interaction in high latitude regions with a yearly freshwater input of 511 km3 the lena river one of the eight major world rivers has an influencing control over the environment of this arctic marginal sea which is ice covered during most of the year in this paper the first measurements are presented of the major and trace element distribution within the 20 m grain size fraction of surficial sediments and of particulate matter in new and young ice from the laptev sea siberian arctic the concentration and distribution of major and trace elements have been determined in 51 surficial sediment samples covering the whole laptev sea shelf south of the 50 m isobath thirty one samples of particulate matter in newly formed ice were taken during the freeze up period in 1995 median concentration levels of heavy metals in surficial sediments ni 46 g g 1 cu 26 g g 1 zn 111 g g 1 and pb 21 g g 1 are within the concentration range of marine unpolluted sediments also the sediment laden ice showed no indication of anthropogenic perturbation of the trace metal inventory spatial distribution patterns of heavy metals are mainly determined by variation of mineral composition and different fluvial sediment sources in the eastern and western laptev sea the laptev sea shelf is cut by five north south trending submarine valleys enrichment of manganese in the oxic surficial sediment layer within these valleys and the occurrence of small ferromanganese nodules are caused by a high input of dissolved and particulate mn from the lena river and a strong diagenetic cycling of mn on the laptev sea shelf evidence is given that the content of as in surficial sediments is also strongly affected by diagenetic cycling this causes surficial sediment as concentrations of more than 100 g g 1 enrichment of mn and as was mainly observed in the submarine valleys distant from the major river mouth the sediment dilution due to higher sedimentation rates near the river outlets and a strong sediment re working by ice gouging in the shallow areas are the principle causes for the absence of diagenetic accumulation in this region during the formation of new ice scavenging of riverine suspended matter and resuspension of sediments followed by an incorporation of particles into the ice are important processes for the river shelf ocean transport of particulate trace elements it could be shown that particle loaded ice posseses the same geochemical signatures as the suspended matter and surficial seafloor sediments in the area of ice origin this has also strong implications for the contaminant transport on the arctic shelves and allows to use the geochemical signature of sea ice for the reconstruction of ice drift pattern within the arctic ocean

diffuse spectral reflectance of surficial sediments indicates sedimentary environments on the shelves of the bering sea and western arctic abstract visible diffuse spectral reflectance dsr has been described by previous workers as an efficient tool for extracting lithological compositions clay minerals iron oxyhydroxides carbonates and diatoms in sedimentary material the spatial patterns of these components are essential to understanding the processes driving their distribution and accumulation in the marine environment some of these processes include sea ice variability nutrient supply current flow patterns current strength sediment supply provenance and bathymetry the dsr derivatives and varimax rotated principal component analysis vpca of the spectral data collected from 234 core samples identified five leading components that account for variations in sediment lithology of the surface samples from the bering sea and western arctic these spectral components were then matched to spectral standards to identify the mineral assemblages responsible for them the components responsible for the vpca trends are chlorite muscovite goethite phycoerythrin phycocyanin smectite calcite dolomite and illite chlorophyll a the spatial pattern of the inorganic components is indicative of provenance and processes controlling their transportation and depositional patterns while the organic components are indicative of areas of primary productivity and driving mechanisms the chlorite muscovite assemblage which is sourced dominantly from the yukon river has maximum values on the bering sea shelf this is the source of the chlorite muscovite transport to the chukchi sea the chlorite muscovite assemblage also has a main transport route to the aleutian basin in the northern bering sea shelf the chukchi sea on the western arctic ocean shelf is a region of highly reducing condition this is based on the lowest values for the goethite phycoerythrin phycocyanin assemblage supported by the high carbonate concentrations at this location the carbonate distribution pattern on the bering sea shelf also appears to be tidally influenced this is because their spatial pattern divides the bering shelf into three domains which are similar to the three hydrographic domains on the bering shelf a function of tidal influence the smectite assemblage reaches maximum values along the coast of the chukotka peninsula in the chukchi sea denoting the chukotka peninsula as a major source area of smectite and supporting the notion for volcanically derived sediment to the chukchi sea another likely source of smectite to the chukchi sea is via the bering strait the illite in the illite chlorophyll a assemblage shows maximum values and distribution on the western arctic ocean shelf indicating the western arctic ocean shelf to be a main province of illite all the high values of the illite chlorophyll a component on the bering sea shelf are chlorophyll a from diatoms our results support the usefulness of the dsr method as an effective and efficient tool for provenance analysis and understanding the processes controlling sediment and biologic distribution in this case in the marine environment

deposition of organic carbon in arctic ocean sediments terrigenous supply vs marine productivity during the arctic 91 expedition with rv polarstern several kastenlot cores were recovered along a profile crossing the eastern part of the arctic ocean in this paper we present results of detailed sedimentological and organic geochemical investigations on three of these cores which have yielded a wide range of data for the interpretation of the flux and type of organic matter in general the high organic carbon content of the sediments is derived from a high input of terrigenous organic matter the variation in content and composition of the organic carbon in the sediments of core ps2174 5 reflect glacial interglacial changes interglacial stages 7 and 5e reveal a low organic carbon content 0 5 and as indicated by high hydrogen indices low c n ratios higher content of n alkanes c 17 and c 19 and a high opal content reflect higher marine productivity during the glacial stages stages 6 upper 5 and 4 organic carbon values are significantly higher 0 7 1 3 low hydrogen indices high c n ratios low short chain n alkanes and low opal contents provide evidence for a higher input of terrigenous organic matter and reduced marine productivity changes in the content and composition of the organic carbon are believed to vary with the fluctuations in sea level and sea ice coverage

suspension freezing of bottom sediment and biota in the northwest passage and implications for arctic ocean sedimentation ice observations and sediment collected in a summer transit through the northwest passage provide insights on suspension freezing the most important sediment entrainment mechanism for the arctic ocean no evidence was seen for entrainment by bottom adfreezing bluff slumping river flooding dragging ice keels or significant eolian transport from land to sea lack of eolian sediment loading in the northwest passage together with that already reported for northern alaska eliminates wind as an important source for fine sediment in the pack of the beaufort gyre and related parts of the transpolar drift muddy sediment with pebbles and cobbles algae with holdfasts ostracodes with appendages and well preserved mollusks and sea urchins were collected from two sites in a 50 km long stretch of turbid ice these materials indicate that suspension freezing reaching to a water depth of 25 30 m during the previous fall was responsible for entrainment this mechanism requires rapid ice formation in open shallo

effects of advancing freeze fronts on distributions of fine grained sediment particles in seawater and freshwater slush ice slurries abstract experiments were performed to evaluate the effects of advancing freeze fronts on movements of fine grained sediment particles in seawater and freshwater slush ice slurries in the freshwater experiment the horizontal migrations of clay sized particles in response to a laterally advancing freeze front were documented photographically differential migration of particles as a function of their size was also noted in the seawater slush ice experiment involving downward movement of a freeze front through a sediment laden slush ice layer time series measurements were taken for 1 accumulations of sediment released from the ice into the underlying water column 2 decreases in temperature in the ice matrix and 3 increases in salinity in the water beneath the ice results of the latter experiment support the contention that a downward congealing slush ice matrix can purge itself of at least a portion of an entrained sediment load during an evolving freezing process however most of the sediment load initially carried by the slush ice remained at the conclusion of the experiment this observation has implications for the importance of spatial transport and deposition of ice rafted sediments to overall sediment budgets in regions affected by sea ice in summary migration of sediment particles in congealing slush ice matrices due to freeze front advances can be important to geological physical and biological processes as well as commercial activities in arctic marine and nearshore regions

millennial scale depositional cycles related to british ice sheet variability and north atlantic paleocirculation since 45 kyr b p barra fan u k margin lithology lithic petrology planktonic foraminiferal abundances and clastic grain sizes have been determined in a 30 m long core recovered from the barra fan off northwest scotland the record extends back to around 45 kyr b p with sedimentation rates ranging between 50 and 200 cm kyr the abundance of ice rafted debris indicates 16 glacimarine events including temporal equivalents to heinrich events 1 4 enhanced concentrations of basaltic material derived from the british tertiary province suggest that the glacimarine sediments record variations in a glacial source on the hebrides shelf margin glacimarine zones are separated by silty intervals with high planktonic foraminifera concentrations that reflect an interstadial circulation regime in the rockall trough the results suggest that the last british ice sheet fluctuated with a periodicity of 2000 3000 years in common with the dansgaard oeschger climate cycle

thermohaline circulation in the arctic mediterranean seas the renewal of the deep north atlantic by the various overflows of the greenland scotland ridges is only one manifestation of the convective and mixing processes which occur in the various basins and shelf areas to the north the arctic ocean and the greenland iceland and norwegian seas collectively called the arctic mediterranean the traditional site of deep ventilation for these basins is the greenland sea but a growing body of evidence also points to the arctic ocean as a major source of deep water this deep water is relatively warm and saline and it appears to be a mixture of dense brine enriched shelf water with intermediate strata in the arctic ocean the deep water exits the arctic ocean along the greenland slope to mix with the greenland sea deep water conversely very cold low salinity deep water from the greenland sea enters the arctic ocean west of spitsbergen within the arctic ocean the lomonosov ridge excludes the greenland sea deep water from the canadian basin leaving the latter warm saline and rich in silica in general the entire deep water sphere of the arctic mediterranean is constrained by the greenland scotland ridges to circulate internally therefore it is certain of the intermediate waters formed in the greenland and iceland seas which ventilate the north atlantic these waters have a very short residence time in their formation areas and are therefore able to rapidly transmit surface induced signals into the deep north atlantic

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

arctic ocean deep sea record of northern eurasian ice sheet history the sediment composition of deep sea cores from the central arctic ocean the fram strait and the yermak plateau was analyzed for several parameters to reconstruct the history of marine paleoenvironment and terrestrial glaciation in the last 200 000 years layers with high amounts of coarse terrigenous ice rafted debris ird and often high contents of smectite were deposited during extensive glaciations in northern eurasia when ice sheets reached the northern continental margins of the barents and kara seas and discharged icebergs into the arctic ocean intercalated layers with relatively low ird and smectite contents but abundant planktic foraminifers in the coarse fraction were deposited during periods of atlantic water inflow to the arctic ocean and seasonally open waters leads in a sea ice cover with only few icebergs in the arctic ocean high ird contents in the sediments reflect the presence of ice sheets on the kara and barents seas shelves and the hinterland during the entire oxygen isotope stage 6 ca 190 130 ka in substage 5b ca 90 80 ka at the stage boundary 5 4 around 75 ka and in late stage 4 early stage 3 ca 65 50 ka these results are in excellent correlation with those from recent field work in northern scandinavia european russia siberia and on the shelves relatively low amounts of ird in central arctic ocean sediments from the late weichselian glacial maximum ca 24 18 ka correlate well with the recent reconstruction of a very limited eastern ice sheet extension during this time oxygen and carbon isotope records of planktic foraminifers from the analyzed sediment cores show a number of prominent excursions which can be interpreted as evidence for freshwater events in the arctic ocean the synchroneity of freshwater events and ird input suggests a common source strongest events were associated with deglaciations of the barents and kara seas after the ice sheets had blocked the outflow of large rivers for several millennia the outflow of freshwater from large ice dammed lakes occurred at ca 130 80 75 and 52 ka freshwater events in the central arctic ocean during the last deglaciation ca 18 ka were relatively small compared to the previous events this indicates that during most of the late weichselian glacial maximum a river outflow from northern siberia to the arctic ocean was possible atlantic water inflow to the arctic ocean and seasonally open waters in the ice leads occurred during the interglacials ofoxygen isotope stage 1 and substage 5e during several interstadials stage 3 substages 5a and 5c and to a lesser degree within stadials and glacials stages 2 4 and 6 with the exception ofthe interglacials these periods were times ofstrong ice growth on the continents as revealed by terrestrial data the coincidence suggests that open waters in the arctic ocean and the nordic seas were an important moisture source in addition to more southerly sources which fostered the growth of ice sheets on northern eurasia

a model for entrainment of sediment into sea ice by aggregation between frazil ice crystals and sediment grains avertical numerical model has been developed that simulates tank experiments of sediment entrainment into sea ice physical processes considered were turbulent vertical diffusion of heat salt sediment frazil ice and their aggregates differential growth of frazil ice crystals secondary nucleation of crystals and aggregation between sediment and ice the model approximated the real size distribution of frazil ice and sediment using five classes of each frazil crystals 25 m to 1 5 cm were modelled as discs with a constant thickness of their diameter each class had a constant rise velocity based on the density of ice and drag forces sediment grains 1 600 m were modelled as constant density spheres with corresponding sinking velocities the vertical diffusion was set constant for experiments based on calculated turbulent rms velocities and dissipation rates from current data the balance between the rise sinking velocities and the constant vertical diffusion is an important feature of the model the efficiency of the modeled entrainment process was estimated through a an aggregation factor values for a are in the range but average values are often close to 0 01 entrainment increases with increasing sediment concentration and turbulence of the water and heat flux to the air

microfeatures of modern sea ice rafted sediment and implications for paleo sea ice reconstructions distinguishing sea ice rafted debris sird from iceberg rafted debris is crucial to an interpretation of ice rafting history however there are few paleo sea ice proxies this study characterizes quartz grain microfeatures of modern sird from the arctic ocean and compares these results with microfeatures from representative glacial deposits to potentially differentiate sird from ice rafted sediments which have been recently subjected to glacial processes this allows us to evaluate the use of grain microfeatures as a paleo sea ice proxy sird grains were largely subrounded with medium relief pervasive silica dissolution and a high abundance of breakage blocks and microlayering the glacial grains were more angular with lower relief and higher abundances of fractures and striations gouges discriminate analysis shows a distinct difference between sird and glacial grains with 7 of the sird grains containing typical glacial microtextures suggesting this method is a useful means of inferring paleo sea ice presence in the marine record we propose that differences in microfeatures of sird and glacial ice rafted debris reflect differences in sediment transport and weathering histories sediment transported to a coastal setting and later rafted by sea ice would be subject to increased chemical weathering whereas glaciers that calve icebergs would bypass the coastal marine environment thus preserving their glacial signature

a lower cretaceous syn extensional magmatic source for a linear belt of positive magnetic anomalies the pacific margin anomaly pma western palmer land antarctica ar ar laserprobe dating suggests that in western palmer land plutons associated with a curvilinear belt of positive magnetic anomalies along the pacific margin of the antarctic peninsula the pacific margin anomaly pma are early cretaceous in age the new ages combined with published structural and geochemical studies suggest that highly magnetically susceptible gabbroic to tonalitic granodioritic rocks the probable source of the palmer land segment of the pma were generated during early cretaceous extension when mantle derived basaltic magma intruded mafic lower to middle crust continued extension uplifted newly generated lower to middle crust through the curie isotherm ca 600 c forming the magnetic anomaly the pma broadly tracks an arc parallel band in western palmer land where crustal extension and uplift of lower crust were greatest the close spatial relationship between the pma and early cretaceous syn extensional plutons suggests that anomaly area can be used as a crude proxy for the volume of a related plutonic complex the areal extent of the pma indicates that a significant proportion of the arc crust was newly generated during the early cretaceous in western palmer land

styles of behavioral complexity recorded by selected trace fossils abstract at least four styles of complex behavior are recorded in trace fossils 1 intricate programmed behavior that is recorded in complex trace fossils such as spirophyton and zoophycos 2 behavior that is complex in consisting of multiple simple behaviors performed by a single organism as indicated by one trace fossil merging into another compound trace fossils 3 behavior in which an animal constructs both complex and simple structures as demonstrated by direct connection between the two structures 4 two scales of complex behavior reflected in multiple specimens of one trace fossil arranged in a pattern to produce a distinctive larger scale structure until recently complex trace fossils e g zoophycos alone have served as proxies for complex behavior recognition and reconstruction of diverse modes of behavioral complexity allow more biological information to be gleaned from the trace fossil record

tracking nutrient and productivity variations over the last deglaciation in the arctic ocean we have reconstructed the surface water environment of the arctic ocean over the last 50 000 years using measurements of the organic nitrogen and carbon isotope ratios carbonate and total organic carbon concentrations toc and terrestrial biomarkers lignin and long chain n alkanes in four multicores variations in nitrogen isotope ratios that are concordant with toc and carbonate concentrations representing foraminifera and excluding ice rafted debris reflect differences in relative nutrient utilization of phytoplankton in the surface waters however 15n variations also appear to be dependent on the stratification of the water column and therefore potentially track the exchange of nutrients between deep and surface waters low last glacial maximum lgm 15n values and higher holocene values are opposite to those recorded in the southern ocean the arctic ocean with higher nutrient utilization today compared to the lgm therefore acts as a counterpart to the southern ocean although the global impact on carbon dioxide variations compared to the southern ocean is probably low

thickness structure and properties of level summer multiyear ice in the eurasian sector of the arctic ocean in august and september 1991 thickness structure and properties of level multiyear ice were studied at 66 locations in the eurasian sector of the arctic ocean the mean ice thickness was 2 86 m with 0 31 m of freeboard including 0 08 m deteriorated ice of mean density 370 kg m 3 on the basis of the study of ice cores 61 of the ice cover consisted of undeformed columnar ice the remaining 39 consisted of a mixture of ice types including frazil 18 and deformed ice 9 through microstructural studies six main classes of pores could be identified the mean density of the ice cover increased from 720 kg m 3 at the top to 880 kg m 3 below 0 4 m depth sea ice salinities mean value 2 1 correlate with ice thickness on average salinity profiles exhibit a linear increase from values close to 0 at the top to 2 at 1 m depth with less steep salinity gradients below sampling from different depths within the ice cover indicates that the brine in summer sea ice is strongly stratified the influence of meltwater percolation is evident with salinities around 5 and ph values 15 and 8 at greater depths brine volumes ranging from 80 to 150 are controlled by the thermodynamic equilibrium between the solid and liquid phases gas volumes decrease from 200 at the top to 50 below 1 m depth pore microstructure is highly variable even on small scales salinity and other ice properties do not vary to a large degree between different regions the evolution of level multiyear sea ice is discussed with particular reference to hidden occurrence of deformed ice and the importance of ablation processes

distribution patterns of diatom surface sediment assemblages in the laptev sea arctic ocean abstract the modern diatom distribution in the laptev sea arctic ocean was investigated in 89 surface sediment samples diatom concentrations are relatively low showing values between 0 01 10 6 and 6 7 10 6 valves per gram dry sediment based on a factor analysis using seventeen taxa or taxa groups five diatom surface sediment assemblages can be defined the ice diatom assemblage of the central region of the laptev sea the chaetoceros assemblage of the eastern and southeastern shelf the thalassiosira antarctica assemblage of the continental slope and deep sea the freshwater diatom assemblage in the vicinity of river mouths and deltas and the thalassiosira nordenskioeldii assemblage which shows a patchy occurrence on the central laptev sea shelf the distribution pattern of diatom assemblages in surface sediment is significantly related to oceanographic conditions of surface water masses the main factors controlling the distribution of diatoms in the laptev sea are the riverine freshwater input during the summer which strongly affects the salinity conditions and the sea ice extent furthermore the composition of the thalassiosira antarctica assemblage of the continental slope is largely influenced by dissolution and lateral transport processes

imprint of late pleistocene continental processes visible in ice rafted grains from the central arctic ocean abstract ice rafted quartz sand grains of sediment samples representing marine isotope stages mis 3 and 4 from the lomonosov ridge arctic ocean are here analysed with a scanning electron microscope sem to characterise processes in the sediment source area the microtextural characteristics of the grains were observed and their microtexture frequencies calculated specific sets of microtextures were identified and classified group i iii using principal component analysis pca and cluster analysis the statistically analysed microtextural data were used to identify signals of continental processes that operated during the late pleistocene mis 4 to mis 3 in the eurasian arctic the microtextures of group i generally formed as a result of prolonged fluvial alluvial or aeolian transport the glacial microtextures of groups ii and iii indicate subglacial conditions and transport based on the data two principal components seem to characterise late pleistocene continental environmental conditions glacial and non glacial there is a signal of non glacial continental processes in the ice rafted grains at around 62 64 and 67 ka ago a signal of subglacial processes was observed in the grains at around 26 34 42 and 45 ka and concurrent with non glacial at around 62 and 64 ka ago we suggest that these signals in mis 4 sediments are related to deglaciation with an increased supply of glacial sediment to the arctic ocean whereas during mis 3 they were probably related more to iceberg calving from the oscillating barents kara ice sheet

entrainment and export of laptev sea ice sediments siberian arctic sea ice sediments sis sediments rafted by ice and shelf surface deposits from the siberian laptev sea were analyzed to study turbulent entrainment processes this study focused on the silt and clay fractions on average representing 63 4 and 30 4 total 93 7 of the bulk sis respectively generally the sis contains 50 more silt than the shelf deposits while the clay percentages in both sample groups are similar sand sized particles are less abundant in sis than in bottom sediment although sis is clearly enriched in silt no evidence was found for preferential ice entrainment of any silt subfraction coarse medium fine statistical tests of sis and shelf silt parameters and the similar clay mineral compositions of both sample groups provide evidence for entrainment of laptev bottom deposits into newly forming ice the entrainment is related to the mechanism known as suspension freezing accordingly coarser clasts sand and plant debris may be lifted upward by buoyant anchor ice while coarse silt particles are supposed to be transported to the surface by rising frazil aggregates additionally turbulent interaction of convergent langmuir circulation and near surface frazil ice streaks is proposed to support ice entrainment of the finest particles 6 4 phi 12 m entrainment and export of sis from the laptev sea were assessed for ten individual flaw leads extended narrow polynyas separating fast and drifting ice using particle concentrations in ice samples and new ice formation rates the results show that roughly 20 mt of sis can be annually exported from the laptev sea by lead ice only thus formation and export of sediment laden lead ice may play a major geological role in siberian arctic shelf erosion and coastal retreat

arctic ocean chronology confirmed by accelerator 14c dating the role of the arctic ocean in earth s climatic and oceanographic development is significant but has become controversial because of disagreements concerning a reliable arctic chronology the first arctic ocean chronology based on u th and 14c data was in agreement with magnetostratigraphy developed later but these data have been challenged by recent amino acid diagenesis dates new accelerator 14c data support the earlier u th magnetostratigraphic dates and confirm the reliability of the established arctic ocean chronology