sea ice motion in response to geostrophic winds it is an old rule of thumb that sea ice moves with a speed of about 2 of the surface wind and about 45 to the right of the wind a similar relationship between the ice velocity and the geostrophic wind is examined here it is found that only about half of the long term several month average ice motion is directly related to the geostrophic wind the other half being due to the mean ocean circulation on shorter time scales and in all seasons more than 70 of the variance of the ice velocity in the central arctic ocean is explained by the geostrophic wind within about 400 km of the coasts the geostrophic wind is less successful in explaining the ice motion the spatial variations in ice velocity are also partly explained by the geostrophic wind about half of the variance in the large scale ice vorticity and shear are accounted for on the other hand none of the large scale ice divergence can be explained by the wind the long term average ocean current is estimated by subtracting the share of the ice motion caused by the wind from the total ice motion

statistical analysis of atmospheric forcing of north pole ice draft variations a series of correlation experiments and regression models are used to explore the atmospheric forcing of observed interannual variability in north pole ice drafts as measured by u s navy submarine sonar from 1982 to 1992 mean ice drafts as well as ice draft distributions are used in the analysis nearby drifting buoys are used to approximate a full 2 year motion history of the north pole ice parcels prior to submarine underpass drawing from theoretical work and empirical observation predictors of north pole ice draft variation are selected which embody accumulated ice exposure to subfreezing air temperature ice divergence and patterns of ice motion the timescales of the predictors are based on systematic evaluations of the lag dependence of the predictor predictand relationships linear correlation of each predictor with the observed ice draft distribution shows accumulated ice exposure to subfreezing air temperature is weakly correlated with reductions in shallow 0 to 2 5 m drafts ice divergence a week prior to draft measurement correlates most closely with the redistribution of ice drafts shallower than 3 5 m ice divergence and ice deflection from its wind forced motion during the 6 months prior to observation correlate with deeper ice drafts deeper than 6 8 and 4 6 m respectively together these two parameters explain more than 80 of the variance of the observed mean ice draft the accumulated ice exposure to subfreezing air temperatures colder than the 1980 1992 mean in the 2 years prior to ice arrival at the north pole adds little to an explanation of the interannual variance of the mean ice draft the results imply that 1 a realistic formulation of sea ice dynamics is a first order priority for model simulations of ice draft and 2 north pole ice thickness is not a simple function of arctic air temperature

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

clay minerals as indicators of sources of terrigenous sediments their transportation and deposition bering basin russian alaskan arctic abstract cluster analysis of clay mineral abundances in surficial sediments from 52 stations revealed the presence of four station cluster groups within the bering basin and contiguous eastern aleutian trench forearc these results can be explained using two end members of terrigenous clay mineral sources and their admixtures the first end member cluster group i consists of the highest average concentration of illite 48 and chlorite plus kaolinite 40 and lowest of expandable minerals 12 in contrast the second end member cluster group iv has the highest concentration of expandable minerals 43 and lowest concentrations of illite 30 and chlorite plus kaolinite 27 the group i assemblages come from two regions the eastern aleutian trench forearc and the northwestern margin of the bering basin off koryak mountains east siberia clays in the former region are derived primarily from the meta sedimentary and meta volcanic rocks of the chugach mountains with infiltrations from alaska peninsula and are transported from the southeastern kodiak shelf of the gulf of alaska to the trench forearc by the alaska current alaskan stream similar clays are derived from the koryak mountains group iv clays located within the komandorsky and bowers basins and unmak plateau originated from the mio pliocene andesites and basalts of the eastern kamchatka peninsula and aleutian islands respectively it is postulated that group ii clays in the southcentral aleutian basin and bowers ridge basin area and group iii clays in the northern aleutian basin are mixtures obtained primarily from terrigenous sources of group i and iv the distribution patterns and boundaries of the cluster groups reflect the dispersal pathways of clays from the primary sources and the extent of their mixing by regional and local surface currents and mesoscale gyres eddies presumably the minor infiltration of anadyr river clays into group iii is a result of clay transport by episodic turbidity currents most of the clays derived from the alaska mainland and russia proper do not reach the bering basin as these clays are trapped within the bering sea shelf

a key source area and constraints on entrainment for basin scale sediment transport by arctic sea ice combining field measurements remote sensing and numerical modelling a key site for ice entrainment and basinwide dispersal of sediments by sea ice has been identified near the new siberian islands the total ice bound sediment export of 18 5 x 10 6 t for an entrainment event documented in 1994 95 is of the same order of magnitude as annual sediment supply to the deep sea sector of the eurasian arctic and the greenland sea satellite imagery and ancillary data indicate that ice advection from this source may play an important role in sedimentation downstream in the transpolar drift

mechanisms controlling the distribution of helium and neon in the arctic seas the case of the knipovich ridge abstract helium concentration and isotopic ratio in the ocean are influenced by four sources the mantle atmosphere crust and tritium decay in addition the concentration of dissolved gases can be altered by air injection and ice related mechanisms such as brine rejection sea ice melting and glacial melting especially in the high latitude seas the knipovich ridge a northern continuation of the mid atlantic ridge 74 79 n 6 8 e is potentially affected by all the sources and mechanisms mentioned above this suggests that the ridge should be a good place to investigate these mechanisms during the knipovich 2000 expedition water samples were collected for helium and neon analysis along the axis of the ridge although mn and ch 4 results suggest the existence of hydrothermal activity in the ridge we could not detect a significant increase of helium isotopic ratio 3 he 4 he at corresponding water depths instead the bottom waters in the northern section of the ridge were supersaturated by up to 40 for 4 he the helium isotopic ratio of 1 3 10 6 indicates the dominance of atmospheric helium using he and ne saturation anomalies we further explored the mechanisms affecting the distribution of helium and neon in the ridge around 5 supersaturation of he and ne at most deep waters is explained by air injection and brine rejection however the large excess in the northern ridge was attributed to the input of 2 5 glacial meltwater possibly originating from the glacier covered islands svalbard

seasonal variations of sea ice motion in the canada basin and their implications ice velocities and sea level pressure data from arctic drifting buoys for 1979 85 are used to examine the seasonal variation of sea ice drift in the canada basin a recurring reversal of the mean anticyclonic gyre is demonstrated in late summer in response to changes in atmospheric forcing the identification of this reversal of ice motion is significant for numerical modeling of arctic atmosphere ocean ice interactions

sources of sediment found in sea ice from the western arctic ocean new insights into processes of entrainment and drift patterns 1 the geochemical fingerprint of entrained fe oxide mineral grains in arctic ocean sea ice is used to determine precise sources of this sediment this approach substantiates the importance of the laptev sea as a source of sea ice and even the presence of russian ice in the beaufort sea off alaska fe oxide grains from the laptev sea were found in floes in the beaufort sea chukchi borderland and central arctic ocean demonstrating the importance of sea ice in distributing itself throughout the arctic ocean and the potential of transporting sediment from russian rivers to north american shelves banks island shelf is the most important source of sediment sampled from ice floes in the beaufort sea northern chukchi sea and chukchi borderland area although most of the entrained sediment fits the criteria for suspension freezing in shallow water the presence of winter polynyas with offshore winds and not the size of shallow areas appears to be the critical factor for sea ice entrainment seven of the 18 ice floes sampled contained fe oxide grains from more than one source area the two most common sources that are found in the same ice floes are banks island and the laptev sea multiple sources in ice floes suggest that either mingling of fragmented ice floes occurs or that a source area containing grains from both these sources has yet to be located the addition of fine sand sized windblown sediment is not thought to be significant

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

constituent material properties and clast size distribution of volcanic breccia abstract volcanic breccia is a representative heterogeneous rock as a preliminary study for determining its mechanical properties in laboratory and field experiments its material properties and structural features were described three dimensional clast size distribution was also estimated for the study site using the theory of stereology with this distribution determined a numerical simulation was performed to investigate the relationship between the volumetric proportion of clasts in a sample and the areal proportion and maximum length of clasts on a lateral surface of the sample the following observations were made 1 coefficients of variation for volumetric proportion are dependent on the size of the sample and became large when the size of the sample is small 2 samples with a small coefficient of variation can be selected at any size if a restriction is placed on the ratio dmax d0 of the maximum length of clasts to the size of the sample and 3 the volumetric proportion of clasts in each sample can be estimated from the observed areal proportions within an error range that depends on the whole volumetric proportion

sea ice motion as a drunkard s walk observations of sea ice displacement over short periods of time are used to deduce some statistics of the ice motion over long periods of time the objective is to follow the trajectory of a piece of ice starting at a randomly selected time and location and ending when the ice either melts or leaves the arctic basin trajectories are also followed backward in time to the time and location where the piece of ice was formed statistical properties considered are the age and remaining lifetime of ice in various locations and the probability that ice presently occupying a particular location was originally created or will ultimately melt in certain regions possible applications are to the distribution of pollutants by sea ice and to the design of experiments involving drifting measurement platforms

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

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

chemostratigraphy across the cretaceous tertiary boundary and a critical assessment of the iridium anomaly the elevated concentration of iridium one of the platinum group elements pge at the cretaceous tertiary boundary is still the most generally accepted evidence that a large bolide struck the earth at the time of the end cretaceous mass extinctions new chemostratigraphic data for cross boundary sections from both hemispheres are not easily explained in terms of such an impact event for example the observation that the pge patterns show marked differences between the hemispheres the new constraints indicate that models of mantle derived pge should be seriously considered and that pge anomalies might not be as useful as previously thought as unambiguous identifiers of large impact events in the earth s history

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

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

river runoff sea ice meltwater and pacific water distribution and mean residence times in the arctic ocean hydrographic and tracer data collected during ark iv 3 fs polarstern in 1987 arctic91 ib oden and aos94 ccgs louis s st laurent expeditions reveal the evolution of the near surface waters in the arctic ocean during the late 1980s and early 1990s salinity nutrients dissolved oxygen and 18 o data are used to quantify the components of arctic freshwater river runoff sea ice meltwater and pacific water the calculated river runoff fractions suggest that in 1994 a large portion of water from the pechora ob yenisey kotuy and lena rivers did not flow off the shelf closest to their river deltas but remained on the shelf and traveled via cyclonic circulation into the laptev and east siberian seas river runoff flowed off the shelf at the lomonosov ridge and most left the shelf at the mendeleyev ridge arctic91 and aos94 pacific water fraction estimates of upper halocline water the traditionally defined core of the pacific water mass document a decrease in extent compared to historical data the front between atlantic water and pacific water shifted from the lomonosov ridge location in 1991 to the mendeleyev ridge in 1994 the relative age structure of the upper waters is described by using the 3 h 3 he age the mean 3 h 3 he age measured in the halocline within the salinity surface of 33 1 0 3 is 4 3 1 7 years and that for the 34 2 0 2 salinity surface is 9 6 4 6 years lateral variations in the relative age structure within the halocline and atlantic water support the well known cyclonic boundary current circulation

large scale drift of arctic sea ice retrieved from passive microwave satellite data a method of determining the large scale sea ice drift using 85 5 ghz special sensor microwave imager data are presented a cross correlation method is applied to sequential images of gridded data covering the entire arctic individual correlation results are validated with ice velocities derived from buoy data the satellite derived mean drift values and the variabilities of the ice drift correspond closely with the buoy data similarly time series of buoy data and associated satellite data are in good agreement even over large time periods an example of a satellite retrieved 3 day mean drift field demonstrates the potential of the method for providing large scale ice circulation patterns mean drift fields of the winter periods 1987 1988 and 1992 1993 indicate a considerable interannual variability of the sea ice drift pattern in the arctic ocean the arctic region is divided into seven larger areas and the area flux between these regions has been derived the kara sea and the laptev sea show the largest area ice export with 0 02 and 0 015 km 2 s 1 respectively the central arctic export through fram strait amounts to 0 12 sv during the winter of 1992 1993 with a maximum of 0 15 sv in january

reconstructing the origin and trajectory of drifting arctic sea ice recent studies have indicated that drifting arctic sea ice plays an important role in the redistribution of sediments and contaminants here we present a method to reconstruct the back ward trajectory of sea ice from its sampling location in the eurasian arctic to its possible site of ori gin on the shelf based on historical drift data from the international arctic buoy program this method is verified by showing that origins derived from the backward trajectories are generally con sistent with other indicators such as comparison of the predicted backward trajectories with known buoy drifts and matching the clay mineralogy of sediments sampled from the sea ice with that of the seafloor in the predicted shelf source regions the trajectories are then used to identify regions where sediment laden ice is exported to the transpolar drift stream from the new siberian islands and the central kara plateau calculation of forward trajectories shows that the kara sea is a major contributor of ice to the barents sea and the southern limb of the transpolar drift stream

physical characteristics of summer sea ice across the arctic ocean sea ice characteristics were investigated during july and august on the 1994 transect across the arctic ocean properties examined from ice cores included salinity temperature and ice structure salinities measured near zero at the surface increasing to 3 4 at the ice water interface ice crystal texture was dominated by columnar ice comprising 90 of the ice sampled surface albedos of various ice types measured with radiometers showed integrated shortwave albedos of 0 1 to 0 3 for melt ponds 0 5 for bare discolored ice and 0 6 to 0 8 for a deteriorated surface or snow covered ice aerial photography was utilized to document the distribution of open melt ponds which decreased from 12 coverage of the ice surface in late july at 76 n to almost none in mid august at 88 n most melt ponds were shallow and depth bore no relationship to size sediment was pervasive from the southern chukchi sea to the north pole occurring in bands or patches it was absent in the eurasian arctic where it had been observed on earlier expeditions calculations of reverse trajectories of the sediment bearing floes suggest that the southernmost sediment was entrained during ice formation in the beaufort sea while more northerly samples probably originated in the east siberian sea some as far west as the new siberian islands

particulate matter in pack ice of the beaufort gyre ice observations and sediment samples were collected in the beaufort gyre in 1988 fine sediment occurred in very small patches of turbid ice as thin spotty surface layers in mud pellets or in old snowdrifts the latter were widespread south of 74 n containing an estimated 22 tonnes of silt and clay km 2 average particle concentration in sea ice 40 mg l 1 was much higher than in sea water 0 8 mg l 1 or in new snow but the sediment load was significantly smaller and of finer texture compared to that observed in a shelfal source area after a major entrainment event

upper ocean velocities in the beaufort gyre a 23 month time series of upper ocean velocities in the beaufort gyre was obtained from an autonomous drifting buoy equipped with an acoustic doppler current profiler the buoy was deployed in the beaufort sea and drifted over the canada basin chukchi shelf and chukchi plateau time evolving spectral analysis was used to examine velocity variability in three frequency bands an eddy band 2 5 day periods a diurnal band and a semidiurnal band the eddy band and the semidiurnal band dominated the horizontal kinetic energy although eddy energy was clearly confined to the beaufort sea and canada basin eddies were found further to the south and west than in previous observations the semidiurnal band was dominated by near inertial motions with amplitude that varied seasonally largest in late summer and smallest in late winter diurnal tides were weak 1 cm s 1 except over a shallow portion of the chukchi shelf

canadian basin freshwater sources and changes results from the 2005 arctic ocean section 1 we present measurements of oxygen isotope ratios and nutrient concentrations along the 2005 arctic ocean section aboard the icebreaker oden the data are used to estimate freshwater contributions from meteoric water mainly river runoff sea ice meltwater and chukchi sea shelf water itself a combination of pacific and indigenous arctic water types nutrients ratios are combined to form quasi conservative water mass tracers phosphate star n star and the empirical arctic n p relationship and used along with salinity and 18o which are conservative in the ocean interior disagreements between two different freshwater analyses in the western arctic are largely resolved using a salinity dependent redfield ratio a new estimate of the pacific end member and an analysis of the bering strait inflow contribution to detraining shelf waters freshwater components from 2005 are placed into the context of the overlapping 1994 arctic ocean section aboard the louis st laurent and a time series of hydrographic tracer casts between 1987 and 1992 in the canada basin compared to 1987 1994 the 2005 transect exhibits increased meteoric water concentrations in the northern part of the canadian basin and a decrease in the southern part this pattern is related to changes in the distribution of wind stress curl during the several years prior to each sampling campaign in addition a previously observed correlation between sea ice formation and river runoff disappears over the central arctic in 2005 a change that we attribute to a northward shift of sea ice formation resampling approximately every 3 years should resolve the dynamics driving changes in freshwater and nutrient distributions

late cenozoic sedimentary environments in the amundsen basin arctic ocean analyses of sediment cores recovered on the arctic 91 cruise with rv polarstern to the amundsen basin and lomonosov ridge identify four main sedimentary facies and associated depositional sedimentary processes these include 1 homogenous mud facies interpreted as hemipelagic deposits most abundant in the central parts of the amundsen basin 2 fining upward cycle facies interpreted as fine grained distal turbidite deposits present in all amundsen basin cores but most abundant laterally in the basin 3 massive diamicton facies found in the north pole core and 4 laminated diamicton facies abundant in the upper parts of lomonosov ridge cores both diamictons are heavily influenced by ice rafted debris and the massive diamicton may result from redeposition of laminated diamicton downslope from the lomonosov ridge the lomonosov ridge core exhibits a sedimentation rate of 29 mm ka while the sedimentation rates of turbidite rich sediments of the amundsen basin may be up to 10 times as high clay minerals show that the eastern kara sea and the laptev sea is the source area for most of the sediments while some clay mineral zones may have their source in northern greenland or the barents sea shelf

holocene paleoenvironmental implications of diatom and organic carbon records from the southeastern kara sea siberian margin diatom assemblages and organic carbon records from two sediment cores located within an estuarian bay of the inner kara sea trace changes in yenisei river runoff and postglacial depositional environments paleosalinity and sea ice reconstructions are based on modern relationships of local diatom assemblages and summer surface water salinity approximately 15 500 cal yr b p rivers and bogs characterized the study area when sea level reached the 38 to 40 m paleo isobath approximately 9300 cal yr b p the coring site was flooded from 9300 9100 cal yr b p estuarine conditions occurred proximal to the depocenter of fluvially derived material and salinity was 7 8 paleosalinity increased to 11 13 by 7500 cal yr b p following postglacial sea level rise and the southward shift of the siberian coast sharp decreases in diatom accumulation rates total sediment and organic carbon also occurred suggesting the presence of brackish conditions and greater distance between the coast and study site maximum paleosalinity up to 13 was recorded between 7500 and 6000 cal yr b p which was likely caused by the enhanced penetration of atlantic waters to the kara sea stepwise decreases to modern salinity levels happened over the last 6000 cal yr

seasonal variations in sea ice motion and effects on sea ice concentration in the canada basin drifting buoy data surface pressure and geostrophic wind analyses from the arctic ocean buoy program are used to examine seasonal features of the sea ice motion in the canada basin for 1979 1985 although the 7 year annual mean motion in this region is clockwise the month to month motion is highly variable in late summer to early autumn the circulation can become net anticlockwise for periods lasting at least 30 days results from a linear model demonstrate that these reversals of ice motion in the beaufort gyre are a wind driven response to persistent cyclonic activity that contrasts sharply with the predominantly anticyclonic regimes of spring late autumn and winter model predicted ice divergences of 0 5 or more per day which can occur during periods of anticlockwise ice motion are in good agreement with values calculated from optimally interpolated velocity gradient fields visible band imagery and passive microwave data confirm associated large areal reductions in ice concentration of approximately 20 data from under ice submarine sonar transects and surface pressure records prior to the study period point to frequent recurrences of these late summer to early autumn ice conditions

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

drifting arctic sea ice archives changes in ocean surface conditions 18o profiles in drifting arctic sea ice are coupled with back trajectories of ice drift and an ice growth model to reconstruct the surface hydrography of the arctic ocean interior the results compare well with 18o values obtained by traditional oceanographic methods and known water mass distributions analysis of the stable isotopic composition of sea ice floes sampled at strategic and relatively accessible locations e g fram strait could aid in mapping spatial and temporal variations in arctic ocean surface waters