impact of eastern arctic shelf waters on the nansen basin intermediate layers the eurasian shelves supply water to the nansen basin intermediate layers in two ways as buoyancy driven plumes of dense winter water and as permanent inflow of the barents sea branch of atlantic water while the plumes are local and seasonal phenomena the barents sea flow is part of the large scale circulation both interact with atlantic water which enters the arctic ocean through fram strait and moves as a subsurface boundary current eastward along the continental slope during the polarstern cruise ark ix 4 in summer 1993 the fram strait branch was observed as a narrow core within tens of kilometers of the barents sea shelf edge here several patches of cold low salinity water spread across the slope down to about 500 m depth their origin is assumed to be the northern barents sea they mix with the warm saline fram strait branch water fsbw so that the core properties of the latter become modified downstream in the eastern nansen basin the fram strait branch is displaced toward the inner basin by inflow of the barents sea branch of atlantic water bsbw this inflow appears as a broad 200 km wedge extending from 200 to 1300 m depth bsbw is colder and less saline than water of the fram strait branch and it is less dense and less stratified than the ambient water both branches appear to undergo vigorous mixing while spreading eastward so that any eastward continuation of the boundary flow transports about 50 bsbw and 50 fsbw above 600 m and about 80 bsbw and 20 fsbw below that level toward the canadian basin according to available observations the barents and kara seas are the only source areas for shelf waters ventilating the nansen basin below the halocline and these waters constitute a freshwater input rather than a salt input winter shelf water from the laptev sea cannot contribute to layers deeper than the upper halocline

matrix association effects on hydrodynamic sorting and degradation of terrestrial organic matter during cross shelf transport in the laptev and east siberian shelf seas this study seeks an improved understanding of how matrix association affects the redistribution and degradation of terrigenous organic carbon terroc during cross shelf transport in the siberian m

origin of freshwater and polynya water in the arctic ocean halocline in summer 2007 extremely low summer sea ice coverage in the arctic ocean in 2007 allowed extensive sampling and a wide quasi synoptic hydrographic and 18o dataset could be collected in the eurasian basin and the makarov basin up to the alpha ridge and the east siberian continental margin with the aim of determining the origin of freshwater in the halocline fractions of river water and sea ice meltwater in the upper 150 m were quantified by a combination of salinity and 18o in the eurasian basin two methods applying the preformed phosphate concentration po and the nitrate to phosphate ratio n p were compared to further differentiate the marine fraction into atlantic and pacific derived contributions while po based assessments systematically underestimate the contribution of pacific derived waters n p based calculations overestimate pacific derived waters within the transpolar drift due to denitrification in bottom sediments at the laptev sea continental margin within the eurasian basin a west to east oriented front between net melting and production of sea ice is observed outside the atlantic regime dominated by net sea ice melting a pronounced layer influenced by brines released during sea ice formation is present at about 30 to 50 m water depth with a maximum over the lomonosov ridge the geographically distinct definition of this maximum demonstrates the rapid release and transport of signals from the shelf regions in discrete pulses within the transpolar drift the ratio of sea ice derived brine influence and river water is roughly constant within each layer of the arctic ocean halocline the correlation between brine influence and river water reveals two clusters that can be assigned to the two main mechanisms of sea ice formation within the arctic ocean over the open ocean or in polynyas at the continental slope where relatively small amounts of river water are found sea ice formation results in a linear correlation between brine influence and river water at salinities of about 32 to 34 in coastal polynyas in the shallow regions of the laptev sea and southern kara sea sea ice formation transports river water into the shelf s bottom layer due to the close proximity to the river mouths this process therefore results in waters that form a second linear correlation between brine influence and river water at salinities of about 30 to 32 our study indicates which layers of the arctic ocean halocline are primarily influenced by sea ice formation in coastal polynyas and which layers are primarily influenced by sea ice formation over the open ocean accordingly we use the ratio of sea ice derived brine influence and river water to link the maximum in brine influence within the transpolar drift with a pulse of shelf waters from the laptev sea that was likely released in summer 2005

semidiurnal tides on the laptev sea shelf with implications for shear and vertical mixing the arctic continental shelf seas hold a globally significant source of freshwater that impacts arctic ocean stratification circulation and climate this freshwater can be injected below the surface mixed layer by intense turbulent kinetic energy dissipation events as resolved by laptev sea microstructure observations the tides provide a major source of energy that can be dissipated and hence drive diapycnal mixing in the laptev sea multiyear adcp mooring records from locations across the shelf reveal that semidiurnal tides are dominated by them2 and s2 constituents with the largest amplitudes on the outer shelf throughoutmost of the shelf tides are clockwise polarized and sheared by stratification as characteristic near the m2 critical latitude interannual variations of the tidal and shear structures on the inner shelf aremainly determined by the stratification setting lena river freshwater plume in all locations m2 tides are enhanced under sea ice and therefore changes in the seasonal ice cover may lead to changes in tides and water column structure the main conclusions of this study are that i tides play a comparatively greater role year round on the outer shelf relative to the inner shelf ii a sea ice reduction will overall decrease the predictability of the currents especially on the inner shelf and iii the freshwater distribution directly impacts diapycnal mixing by setting the vertical tidal structure these combined effects imply that future sea ice loss will increase the variability and vertical mixing of freshwater particularly on the inner shelf where the lena river first enters the laptev sea

evidence for warming of atlantic water in the southern canadian basin of the arctic ocean results from the larsen 93 expedition potential temperature and salinity s data obtained along the perimeter of the southern canadian basin north of the east siberian sea in 1993 aboard the ccgs henry larsen show higher temperatures in waters of atlantic origin than in available climatological data for the canadian basin in particular a front is observed near the mendeleyev ridge which separates the cooler atlantic waters of the canada basin from the warmer atlantic waters observed in the makarov basin the front is further characterized by a change in the s slope of arctic thermocline water and by thermohaline intrusions and s reversals within the atlantic layer the idea that this warm variety of atlantic water has come recently from the eurasian basin is supported by its higher level of the tracer cfc 11

ba ca in neogloboquadrina pachyderma as an indicator of deglacial meltwater discharge into the western arctic ocean 1 down core samples of the planktonic foraminifer neogloboquadrina pachyderma sinistral from the mendeleyev ridge in the western arctic ocean have been analyzed for ba ca and 18o the apparent distribution coefficient for n pachyderma sin is estimated at dba 0 22 0 02 a meltwater event is identified at around 11 8 14c kyr bp and is coincident with elevated ba ca ratios the barium enrichment is believed to be the result of enhanced weathering and erosion following glaciation additionally barium may have desorbed from shelf sediments as sea level rose changes in ba ca correlate with the retreat of the laurentide ice sheet and the evolution of the mackenzie river drainage basin therefore maximum ba ca in arctic surface waters at 11 8 ka may be indicative of an increase in the export of freshwater from the arctic to the north atlantic potentially contributing to the onset of the younger dryas this work suggests that ba ca in planktonic foraminifera may be a useful indicator of the timing and processes associated with deglaciation

surface freshening of the canada basin 2003 2007 river runoff versus sea ice meltwater 1 the extent of summer arctic sea ice has reduced dramatically in recent years and simultaneously we have observed surface freshening over the canada basin in 2006 and 2007 in order to identify the source of this fresh water either meteoric or sea ice meltwater salinity 18o and alkalinity were analyzed results show that sea ice meltwater increased in the surface water over the central part of the basin in 2006 and 2007 corresponding to the melting of an additional 2 7 m 1 3 m a 1 of sea ice anomalously fresh surface water observed in the southern part in 2007 however was mostly attributed to mackenzie river water extending into the basin interior a source that was mainly absent in the early 2000s comparison with previous data shows that the meltwater component of surface water in the southern part of the canada basin has progressively increased at a mean rate of 0 27 m a 1 since 1987 this can be explained by a reduction of winter sea ice formation rate by 0 45 m or more during the past two decades the runoff component showed larger variability in the southern basin but no obvious temporal trend in the central basin the river runoff component showed an increasing trend of 0 7 m a 1

two circulation regimes of the wind driven arctic ocean the major goal of this paper is to demonstrate the existence in the arctic ocean of two regimes of wind forced circulation we simulated the vertically averaged currents sea level heights and ice drift in the arctic ocean from 1946 to 1993 using a two dimensional wind forced barotropic model that includes frictional coupling between the ocean and ice the model has a spatial resolution of 55 5 km and is driven by winds river runoff and an imposed but realistic sea level slope between the pacific and the atlantic oceans there is a good agreement between velocities from observed buoy motions and velocities of modeled ice drift even though the model lacks ocean baroclinicity and ice thermodynamics the results indicate that wind driven motion in the central arctic alternates between anticyclonic and cyclonic circulation with each regime persisting for 5 7 years based upon our analysis of the modeled sea level and ice motion anticyclonic wind driven motion in the central arctic appeared during 1946 1952 1958 1963 1972 1979 and 1984 1988 and cyclonic motion appeared during 1953 1957 1964 1971 1980 1983 and 1989 1993 shifts from one regime to another are forced by changes in the location and intensity of the icelandic low and the siberian high the two regimes may help explain the significant basin scale changes in the arctic s temperature and salinity structure observed recently the great salinity anomaly and the variability of ice conditions in the arctic ocean

freshwater balance and the sources of deep and bottom waters in the arctic ocean inferred from the distribution of h218o data from sections across the eurasian basin of the arctic ocean occupied in 1987 and 1991 are used to derive information on the freshwater balance of the arctic ocean and on sources of the deep waters of the nansen amundsen and makarov basins using salinity h218o and mass balances we estimate the river runoff and the sea ice melt water fractions contained in the upper waters of the arctic ocean and infer pathways of the river runoff signal from the shelf seas across the central arctic ocean to fram strait the average mean residence time of the river runoff fraction contained in the arctic ocean halocline is determined to be about 11 to 14 years pacific water entering through bering strait is traced using silicate and its influence on the halocline waters of the canadian basin is estimated water column inventories of river runoff and sea ice melt water are calculated for a section just north of fram strait and implications of these inventories for sea ice export through fram strait are discussed comparison of the 18o 16o ratios of shelf water atlantic water and the deep waters of the arctic ocean indicate that the sources of the deep and bottom waters of the eurasian basin are located in the barents and kara seas

physical and geochemical properties across the atlantic pacific water mass front in the southern canadian basin temperature salinity nutrients oxygen and halocarbon data collected in the arctic ocean reveal a frontal structure previously unrecognized in the hydrography of the canadian basin samples were collected on a 1300 km section extending from the beaufort sea in the canada basin to the east siberian sea in the makarov basin these data collected in 1993 aboard the ccgs henry larsen reveal a lateral boundary between water masses of atlantic and pacific origin the term water mass assembly is introduced to describe the basic arrangement or vertical stacking of water masses found in the arctic ocean recognizing that water mass components within each assembly may differ from basin to basin using historical data two primary water mass assemblies are defined each consisting of three layers an upper layer an atlantic layer and a deep layer these two assemblies are marked by important differences one assembly here defined as the western arctic wa assembly is characterized by an upper layer of relatively fresh high nutrient water of pacific origin below this by an atlantic layer with a core temperature generally below 0 5 c and finally by a deep layer of higher salinities and colder temperatures about 0 5 c than found in the overlying atlantic layer the second assembly here defined as eastern arctic ea assembly is characterized by the absence of pacific water in the upper layer below this by an atlantic layer core as warm as 2 to 3 c and by a colder about 0 9 c deep layer because the presence or absence of pacific origin water is a key characteristic distinguishing the two assemblies we will refer to the water mass boundary between the two assemblies as the atlantic pacific front earlier research indicated that water masses in the arctic ocean were separated by a front above the lomonosov ridge into the canadian and eurasian basins although all larsen 93 stations from the canada basin a1 d1 display classic wa assembly characteristics the makarov basin station e1 shows ea assembly characteristics in the upper and atlantic layers and a wa assembly deep layer this suggests a relocation in the position of the atlantic pacific boundary away from the lomonosov ridge further larsen 93 data show the transition region between the atlantic and deep layers is fresher in the makarov basin than corresponding water in either the canada or eurasian basins implying a source of cold low salinity water perhaps from the laptev and east siberian shelves the front separating these two assemblies lies above the mendeleyev ridge and is marked by large lateral gradients in all measured properties in particular the penetration of anthropogenic halocarbons is 2 to 3 times deeper in the makarov basin than in the canada basin implying enhanced rates of ventilation this suggests that direct exchange between the canadian and eurasian basins has occurred recently near the perimeter and that physical and chemical properties including contaminants may have been transported by boundary currents more quickly from one basin to the other

tracing pacific water in the north atlantic ocean 1 in the arctic ocean pacific source water can be distinguished from atlantic source water by nitrate phosphate concentration relationships with pacific water having higher phosphate concentrations relative to those of nitrate furthermore pacific water originally from the inflow through bering strait is clearly recognizable in the outflows of low salinity waters from the arctic ocean to the northern north atlantic ocean through the canadian arctic archipelago and through fram strait in the canadian arctic archipelago we observe that almost all of the waters flowing through lancaster and jones sounds most of the water in the top 100 m in smith sound containing the flow through nares strait and possibly all waters in hudson bay contain no water of atlantic origin significant amounts of pacific water are also observed along the western coast of baffin bay along the coast of labrador and above the 200 m isobath of the grand banks there is a clear signal of pacific water flowing south through fram strait and along the east coast of greenland extending at least as far south as denmark strait pacific water signature can be seen near the east coast of greenland at 66 n but not in data at 60 n temporal variability in the concentrations of pacific water has been observed at several locations where multiple year observations are available

changes in temperature and tracer distributions within the arctic ocean results from the 1994 arctic ocean section abstract major changes in temperature and tracer properties within the arctic ocean are evident in a comparison of data obtained during the 1994 arctic ocean section to earlier measurements 1 anomalously warm and well ventilated waters are now found in the nansen amundsen and makarov basins with the largest temperature differences as much as 1 c in the core of the atlantic layer 200 400 m thus thermohaline transition appears to follow from two distinct mechanisms narrow order 100 km topographically steered cyclonic flows that rapidly carry new water around the perimeters of the basins and multiple intrusions 40 60 m thick which extend laterally into the basin interiors 2 altered nutrient distributions that within the halocline distinguish water masses of pacific and atlantic origins likewise point to a basin wide redistribution of properties 3 distributions of cfcs associated with inflows from adjacent shelf regions and from the atlantic demonstrate recent ventilation to depths exceeding 1800 m 4 concentrations of the pesticide hch in the surface and halocline layers are supersaturated with respect to present atmospheric concentrations and show that the ice capped arctic ocean is now a source to the global atmosphere of this contaminant 5 the radionuclide 129i is now widespread throughout the arctic ocean although the current level of 129i level poses no significant radiological threat its rapid arrival and wide distribution illustrate the speed and extent to which waterborne contaminants are dispersed within the arctic ocean on pathways along which other contaminants can travel from western european or russian sources

glacial freshwater discharge events recorded by authigenic neodymium isotopes in sediments from the mendeleev ridge western arctic ocean the freshwater budget of the arctic ocean is a key component governing the deep water formation in the north atlantic and the global climate system we analyzed the isotopic composition of neodymium end in authigenic phases of marine sediments on the mendeleev ridge in the western arctic ocean spanning an estimated time interval from present to about 75 ka bp this continuous record was used to reconstruct the end of the polar deep water pdw and changes in freshwater sources to the pdw through time three deviations in end from a long term average of 10 2 were identified at estimated 46 51 35 39 and 13 21 ka bp the estimated 46 51 ka bp event can be traced to bursting of ice dammed lakes accompanying the collapse of the barents kara ice sheet which would have released radiogenic nd to the eastern arctic ocean the cyclonic surface circulation in the eastern arctic ocean must have been stronger than at present for the event to be recorded on the mendeleev ridge for the 35 39 and 13 21 ka bp events it is likely that the laurentide ice sheet lis supplied the unradiogenic freshwater the configuration of the anticyclonic circulation in the western arctic was probably similar to today or expanded eastward our simple mass balance calculations suggest that large amounts of freshwater were released but due to significant deep water formation within the arctic ocean the effect on the formation of nadw was probably minor

partial recovery of the arctic ocean halocline 1 the evolution during the 1990 s of the cold halocline layer chl of the arctic ocean is investigated using data from icebreaker and scicex submarine cruises the chl disappearance and subsequent partial recovery is described along repeated transects through the central arctic ocean from the alpha ridge to the nansen basin salinity at the top of the halocline is used as a measure of halocline development with high salinity corresponding to a poorly developed halocline in the nansen amundsen and makarov basins upper ocean salinity increased from 1991 to 1998 as the chl disappeared then decreased from 1998 to 2000 as it recovered salinity was higher over the study region through the 1990 s than at any time during the prior 40 year period hence the 1990 s chl recovery was only partial disappearance of the chl from the eurasian basin in the early 1990 s was due to a shift from the laptev to east siberian seas of the region for seaward flow of low salinity siberian shelf waters ice velocities and sea level pressure fields suggest that the reappearance of the chl in 1999 corresponded to a shift of this flow back to the laptev sea region

the 2003 bam se iran earthquake precise source parameters from satellite radar interferometry summary differential radar interferometry provided high quality near field deformation data for the 2003 bam earthquake and therefore strong constraints on its source parameters the ruptured fault segments could be clearly detected by using a sobel edge filter on the phase unwrapped deformation field the estimated total rupture length is about 24 km more than 80 per cent of the seismic moment was released from its southern segment of about 13 km where the slip reached a maximum of up to 270 cm resulting in a stress drop of at least 6 mpa in addition optical remote sensing data show that the bam fault is not a single fault but consists of a 4 5 km wide fault system with the known main branch running between the city of bam and baravat the fault ruptured by the bam earthquake appears to continue the nw branch of this fault system from bam city southwards based on these results we suggest that the bam earthquake ruptured a hidden or new fault and that in this process an unusually strong asperity was involved

post glacial variability of sea ice cover river run off and biological production in the western laptev sea arctic ocean a high resolution biomarker study abstract multi proxy biomarker measurements were applied on two sediment cores ps51 154 ps51 159 to reconstruct sea ice cover ip25 biological production brassicasterol dinosterol and river run off campesterol sitosterol in the western laptev sea over the last 17 ka with unprecedented temporal resolution the absence of ip25 from 17 2 to 15 5 ka in combination with minimum concentration of phytoplankton biomarkers suggests that the western laptev sea shelf was mostly covered with permanent sea ice very minor river run off and restricted biological production occurred during this cold interval from 16 ka until 7 5 ka a long term decrease of terrigenous riverine organic matter and a coeval increase of marine organic matter reflect the gradual establishment of fully marine conditions in the western laptev sea caused by the onset of the post glacial transgression intensified river run off and reduced sea ice cover characterized the time interval between 15 2 and 12 9 ka including the bolling allerod warm period 14 7 12 9 ka prominent peaks of the dip25 index coinciding with maximum abundances of subpolar foraminifers are interpreted as pulses of atlantic water inflow on the western laptev sea shelf after the warm period a sudden return to severe sea ice conditions with strongest ice coverage between 11 9 and 11 ka coincided with the younger dryas 12 9 11 6 ka at the onset of the younger dryas a distinct alteration of the ecosystem reflected in a distinct drop in terrigenous and phytoplankton biomarkers was detected during the last 7 ka the sea ice proxies reflect a cooling of the laptev sea spring summer season this cooling trend was superimposed by a short term variability in sea ice coverage probably representing bond cycles 1500 500 ka that are related to solar activity changes hence atmospheric circulation changes were apparently able to affect the sea ice conditions on the laptev sea shelf under modern sea level conditions

the canada basin 1989 1995 upstream events and far field effects of the barents sea 1 the effects of upstream events on southern canada basin waters were examined using physical and geochemical data collected at one location between 1989 and 1995 these events included atlantic layer warming relocation of the atlantic pacific water mass boundary and increased ventilation of boundary current waters early signals of change in the canada basin first appeared in 1993 along the continental margin and by 1995 were evident in the basin interior and farther downstream differences in physical and geochemical properties nutrients oxygen 129i and cfcs were observed between 150 and 1600 m of the water column by 1995 the boundary between pacific and atlantic origin water was shallower and atlantic origin water occupied more of the canada basin water column atlantic origin lower halocline water was colder and more ventilated fram strait branch water was colder fresher and more ventilated and barents sea branch water was warmer fresher more ventilated and occupied a larger volume of the water column than in previous years water mass analysis showed that the composition of atlantic origin water in the canada basin in 1995 included 20 more water from the barents sea two related events upstream appear to be the source of this change an atmospheric regime shift in 1989 that increased cyclonic circulation a transition unprecedented within the latter half of the 20th century in magnitude geographic reach and apparent oceanographic impacts and a large volume of dense water flowed from the barents sea to the arctic ocean between 1988 and 1989 these two phenomena illustrate the close relationship between atmospheric and oceanic events whose combined influence was evident 6 years later and 5100 km downstream in the canada basin at depths 1000 m

arctic ocean variability derived from historical observations 1 this study has been motivated by reports of extraordinary change in the arctic ocean observed in recent decades most of these observations are based on synoptic measurements while evaluation of anomalies requires an understanding of the underlying long term variability historical climatologies give reference means and while these datasets are a reliable source of the mean atlantic layer temperature they significantly underestimate variability using historical data we calculated statistical parameters for selected arctic ocean regions they demonstrate a high level of atlantic layer temperature variability in the nansen basin and sea surface salinity fluctuations on the siberian shelf and the amundsen basin these estimates suggest strong limitations on our ability to define amplitudes of anomalies by comparing recent synoptic measurements with climatologies especially for regions characterized by strong variability

when will the summer arctic be nearly sea ice free 1 the observed rapid loss of thick multiyear sea ice over the last 7 years and the september 2012 arctic sea ice extent reduction of 49 relative to the 1979 2000 climatology are inconsistent with projections of a nearly sea ice free summer arctic from model estimates of 2070 and beyond made just a few years ago three recent approaches to predictions in the scientific literature are as follows 1 extrapolation of sea ice volume data 2 assuming several more rapid loss events such as 2007 and 2012 and 3 climate model projections time horizons for a nearly sea ice free summer for these three approaches are roughly 2020 or earlier 2030 10 years and 2040 or later loss estimates from models are based on a subset of the most rapid ensemble members it is not possible to clearly choose one approach over another as this depends on the relative weights given to data versus models observations and citations support the conclusion that most global climate model results in the cmip5 archive are too conservative in their sea ice projections recent data and expert opinion should be considered in addition to model results to advance the very likely timing for future sea ice loss to the first half of the 21st century with a possibility of major loss within a decade or two

a sea ice free summer arctic within 30 years an update from cmip5 models interpreted as sea ice extent less than 1 0 million km 2 w e consider this estimate to be still valid based on projections of updated climate models cmip5 and observational data similar to previous models cmip3 cmip5 still shows a wide spread in hindcast and projected sea ice loss among different models further there is no consensus in the scientific literature for the cause of such a spread in results for cmip3 and cmip5 while cmip5 model mean sea ice extents are closer to observations than cmip3 the rates of sea ice reduction in most model runs are slow relative to recent observations all cmip5 models do show loss of sea ice due to increased anthropogenic forcing relative to preindustrial control runs applying the same technique of model selection and extrapolation approach to cmip5 as we used in our previous paper the interval range for a nearly sea ice free arctic is 14 to 36 years with a median value of 28 years relative to a 2007 baseline this suggests a nearly sea ice free arctic in the 2030s citation wang m and j e overland 2012 a sea ice free summer arctic within 30 years an update from cmip5 models geophys res lett 39 l18501

kara sea freshwater transport through vilkitsky strait variability forcing and further pathways toward the western arctic ocean from a model and observations siberian river water is a first order contribution to the arctic freshwater budget with the ob yenisey and lena supplying nearly half of the total surface freshwater flux however few details are known regarding where when and how the freshwater transverses the vast siberian shelf seas this paper investigates the mechanism variability and pathways of the fresh kara sea outflow through vilkitsky strait toward the laptev sea we utilize a high resolution ocean model and recent shipboard observations to characterize the freshwater laden vilkitsky strait current vsc and shed new light on the little studied region between the kara and laptev seas characterized by harsh ice conditions contrasting water masses straits and a large submarine canyon the vsc is 10 20 km wide surface intensified and varies seasonally maximum from august to march and interannually average freshwater volume transport is 500 120 km3 a 1 0 53 0 08 sv with a baroclinic flow contribution of 50 90 interannual transport variability is explained by a storage release mechanism where blocking favorable summer winds hamper the outflow and cause accumulation of freshwater in the kara sea the year following a blocking event is characterized by enhanced transports driven by a baroclinic flow along the coast that is set up by increased freshwater volumes eventually the vsc merges with a slope current and provides a major pathway for eurasian river water toward the western arctic along the eurasian continental slope kara and laptev sea freshwater transport is not correlated with the arctic oscillation but rather driven by regional summer pressure patterns

composition and fate of terrigenous organic matter along the arctic land ocean continuum in east siberia insights from biomarkers and carbon isotopes abstract climate warming is predicted to translocate terrigenous organic carbon terroc to the arctic ocean and affect the marine biogeochemistry at high latitudes the magnitude of this translocation is currently unknown so is the climate response the fate of the remobilized terroc across the arctic shelves represents an unconstrained component of this feedback the present study investigated the fate of permafrost carbon along the land ocean continuum by characterizing the terroc composition in three different terrestrial carbon pools from siberian permafrost surface organic rich horizon mineral soil active layer and ice complex deposit and marine sediments collected on the extensive east siberian arctic shelf esas high levels of lignin phenols and cutin acids were measured in all terrestrial samples analyzed indicating that these compounds can be used to trace the heterogeneous terrigenous material entering the arctic ocean in esas sediments comparison of these terrigenous biomarkers with other terroc proxies bulk 13c 14c and hmw lipid biomarkers highlighted contrasting across shelf trends these differences could indicate that terroc in the esas is made up of several pools that exhibit contrasting reactivity toward oxidation during the transport in this reactive spectrum lignin is the most reactive decreasing up to three orders of magnitude from the inner to the outer shelf while the decrease of hmw wax lipid biomarkers was considerably less pronounced alternatively degradation might be negligible while sediment sorting during the across shelf transport could be the major physical forcing that redistributes different terroc pools characterized by different matrix association despite the marked decrease shown by lignin the fingerprint of lignin phenols such as the acid aldehyde ratio of vanillyl and syringyl phenols showed a lack of any across shelf trends and exhibited an extremely wide range of values in all terrestrial samples by contrast the 3 5 dihydroxybenzoic vanillyl phenols ratio exhibited a clear across shelf trend suggesting either increasing degradation with distance from the coast or terroc sorting along the sediment dispersal system the ratio of syringyl vanillyl phenols indicated that gymnosperm tissues are more important than angiosperm tissues in surface sediments in particular off the lena river mouth consistent with the vegetation in its watershed conversely the fingerprint of p hydroxybenzenes suggests lack of substantial input of moss derived material finally autochthonous lipid and protein derived cuo reaction products displayed a strong along shelf gradient likely reflecting the inflow of nutrient rich pacific waters from the bering strait that stimulate primary productivity in the eastern esas in particular short chain fatty acids showed a clear frontal transition zone between pacific influenced and river influenced waters approximately along the 160 e longitude considering the labile nature of phytoplankton priming and co metabolism processes might stimulate degradation of terroc in the easternmost region of the siberian shelf this study demonstrated the need to consider multiple terroc proxies at isotopic molecular levels to differentiate the fate for different allocthonous components in arctic sediments and the need to assess how these terroc pools are distributed in different density size and settling fractions to better discriminate between the extent of hydrodynamic sorting versus degradation

differentiating fluvial components of upper canada basin waters on the basis of measurements of dissolved barium combined with other physical and chemical tracers 1 the utility of dissolved barium ba as a quasi conservative tracer of arctic water masses has been demonstrated previously here we report distributions of salinity temperature and ba in the upper 200 m of the canada basin and adjacent areas observed during cruises conducted in 2003 2004 as part of the joint western arctic climate study and beaufort gyre exploration project a salinity oxygen isotope mass balance is used to calculate the relative contributions from sea ice melt meteoric and saline end members and ba measurements are incorporated to resolve the meteoric fraction into separate contributions from north american and eurasian sources of runoff large fractions of eurasian runoff as high as 15 5 were observed in the surface layer throughout the canada basin but significant amounts of north american runoff in the surface layer were only observed at the southernmost station occupied in the canada basin in 2004 nearest to the mouth of the mackenzie river smaller contributions from both eurasian and north american runoff were evident in the summer and winter pacific derived water masses that comprise the underlying upper halocline layer in the canada basin significant amounts of eurasian and north american runoff were observed throughout the water column at a station occupied in amundsen gulf in 2004 this suggests the export of runoff from both sources through the passages of the canadian arctic archipelago

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

a meteoric water budget for the arctic ocean a budget of meteoric water mw river runoff net precipitation minus evaporation and glacial meltwater over four regions of the arctic ocean is constructed using a simple box model regional precipitation evaporation estimates from reanalysis data sets and estimates of import and export fluxes derived from the literature with a focus on the 2003 2008 period the budget indicates an approximate slightly positive balance between mw imports and exports i e no change in storage thus the observed total freshwater increase observed during this time period likely resulted primarily from changes in non mw freshwater components i e increases in sea ice melt or pacific water and or a decrease in ice export further our analysis indicates that the mw increase observed in the canada basin resulted from a spatial redistribution of mw over the arctic ocean mean residence times for mw were estimated for the western arctic 5 7 years eastern arctic 3 4 years and lincoln sea 1 2 years the mw content over the siberian shelves was estimated 14 000 km3 based on a residence time of 3 5 years the mw content over the entire arctic ocean was estimated to be 44 000 km3 the mw export through fram strait consisted mostly of water from the eastern arctic 3 237 1 370 km3 yr 1 whereas the export through the canadian archipelago was nearly equally derived from both the western arctic 1 182 534 km3 yr 1 and lincoln sea 972 391 km3 yr 1

retreat of the cold halocline layer in the arctic ocean we present a comparison of arctic ocean hydrographic data sets from the 1990s with a focus on changes in the upper few hundred meters of the eurasian basin the most recent observations discussed here were collected during the spring 1995 scientific ice expedition scicex 95 the second in a series of scientific cruises to the arctic ocean aboard u s navy nuclear submarines although the 1990s have seen an abundance of synoptic cruises to the arctic this was the only one to take place in winter spring conditions other data considered here were collected during the first scicex cruise in summer 1993 scicex 93 and during an icebreaker cruise to the eurasian basin in summer 1991 oden 91 a new russian american winter climatology is also used as a reference these comparisons reveal that the eurasian basin cold halocline layer has retreated during the 1990s to cover significantly less area than in previous years specifically we find a retreat from the amundsen basin back into the makarov basin the latter is the only region with a true cold halocline layer during scicex 95 changes are also seen in other halocline types and in the atlantic water layer heat content and depth since the cold halocline layer insulates the surface layer and thus the overlying sea ice from the heat contained in the atlantic water layer this should have profound effects on the surface energy and mass balance of sea ice in this region using a simple mixing model we calculate maximum ice ocean heat fluxes of 1 3 w m 2 in the eurasian basin where during scicex 95 the surface layer lay in direct contact with the underlying atlantic water layer the overall cause of water mass changes in the 1990s might have been a shift in the atmospheric wind forcing and resulting sea ice motion during the late 1980s which we speculate influenced the location where fresh shelf waters flow into the deeper basins of the arctic ocean finally we discuss two different mechanisms that have been proposed for cold halocline water formation and we propose a compromise that best fits these data

impact of siberian coastal polynyas on shelf derived arctic ocean halocline waters hydrographic and stable oxygen isotope h218o h216o sampling was carried out within the west new siberian wns coastal polynyas in the southern laptev sea in late winters 2008 and 2009 the impact of sea ice formation on the water column was quantified by a salinity lower case delta 18o mass balance several stations had vertically homogeneous physical properties in april may 2008 and featured polynya formed local bottom water with elevated signals of brine released during sea ice formation and elevated fractions of river water the polynya formed bottom water was fresher than surrounding bottom waters at other stations salinity lower case delta 18o correlation showed well defined mixing lines for bottom and surface layers in march april 2009 surface waters were strongly influenced by lena river water and local polynya activity with elevated brine signals reached to intermediate depth but did not penetrate the bottom layer in the highly stratified water column inventory values of sea ice formation were comparable in both years but freshwater distributions from the preceding summers were different therefore the observed difference in the impact of polynya activity on the water column is not primarily controlled by the amount of sea ice formed during winter but by preconditioning from the preceding summer only in years when the river plume is mostly absent in the polynya region stratification is weak and allows winter sea ice formation to reach the bottom layer thus summer stratification controls the influence of local polynya water on the shelf s bottom hydrography and as bottom water is exported impacts on the source water of shelf derived halocline waters

the freshwater composition of the fram strait outflow derived from a decade of tracer measurements the composition of the fram strait freshwater outflow is investigated by comparing 10 sections of concurrent salinity 18o nitrate and phosphate measurements collected between 1997 and 2011 the largest inventories of net sea ice meltwater are found in 2009 2010 and 2011 the 2009 2011 sections are also the first to show positive fractions of sea ice meltwater at the surface near the core of the egc sections from september 2009 2011 show an increased input of sea ice meltwater at the surface relative to older september sections this suggests that more sea ice now melts back into the surface in late summer than previously comparison of april july and september sections reveals seasonal variations in the inventory of positive sea ice meltwater with maximum inventories in september sections the time series of sections reveals a strong anti correlation between meteoric water and net sea ice meltwater inventories suggesting that meteoric water and brine may be delivered to fram strait together from a common source we find that the freshwater outflow at fram strait exhibits a similar meteoric water to net sea ice meltwater ratio as the central arctic ocean and siberian shelves suggesting that much of the sea ice meltwater and meteoric water at fram strait may originate from these regions however we also find that the ratio of meteoric water to sea ice meltwater inventories at fram strait is decreasing with time due to an increased surface input of sea ice meltwater in recent sections

arctic ocean water mass balance from isotope data the distributions of the oxygen 18 and tritium isotopes and of salinity yield a residence time of 10 years for the surface and halocline waters of the arctic basin we find a yearly net production of 0 59 m of sea ice and an input of 1 16 m of freshwater from continental river runoff local precipitation and bering strait salinity deficiency using the basin area value with these numbers gives long term average total net production and transport rates of 0 15 sv of ice and 0 18 sv of meteoric component bering strait water not included if in addition a reasonable depth profile of relative current velocity is assumed for the outflow a yearly input of 2 8 sv of atlantic and bering strait water is needed to replenish the upper and halocline waters these numbers should be good to 20 and are multiyear averages the isotope data clearly indicate that the barents sea is an inflow area for atlantic water to the basin but that net export of ice occurs there

exchange of laptev sea and arctic ocean halocline waters in response to atmospheric forcing combined delta o18 salinity data reveal a distinctive water mass generated during winter sea ice formation which is found predominantly in the coastal polynya region of the southern laptev sea export of the brine enriched bottom water shows interannual variability in correlation with atmospheric conditions summer anticyclonic circulation is favoring an offshore transport of river water at the surface as well as a pronounced signal of brine enriched waters at about 50 m water depth at the shelf break summer cyclonic atmospheric circulation favors onshore or an eastward alongshore water transport and at the shelf break the river water fraction is reduced and the pronounced brine signal is missing while on the middle laptev sea shelf brine enriched waters are found in high proportions residence times of bottom and subsurface waters on the shelf may thereby vary considerably an export of shelf waters to the arctic ocean halocline might be shut down or strongly reduced during onshore cyclonic atmospheric circulation while with offshore anticyclonic atmospheric circulation brine waters are exported and residence times may be as short as 1 year only

tracer derived freshwater composition of the siberian continental shelf and slope following the extreme arctic summer of 2007 we investigate the freshwater composition of the shelf and slope of the arctic ocean north of the new siberian islands using geochemical tracer data 18o ba and po 4 collected following the extreme summer of 2007 we find that the anomalous wind patterns that partly explained the sea ice minimum at this time also led to significant quantities of pacific derived surface water in the westernmost part of the makarov basin we also find larger quantities of meteoric water near lomonosov ridge than were found in 1995 dissolved barium is depleted in the upper layers in one region of our study area probably as a result of biological activity in open waters increasingly ice free conditions compromise the quantitative use of barium as a tracer of river water in the arctic ocean

wind driven transport pathways for eurasian arctic river discharge distributions of temperature salinity and barium in near surface waters depth 50 m of the laptev sea and adjacent areas of the arctic ocean are presented for the summers of 1993 1995 and 1996 the tracer data indicate that while fluvial discharge was largely confined to the shelf region of the laptev sea in the summer of 1993 surface waters containing a significant fluvial component extended beyond the shelf break and over the slope and basin areas north of the laptev sea in the summers of 1995 and 1996 these distributions of fluvial discharge are consistent with local winds and suggest two principal pathways by which river waters can enter the central arctic basins from the laptev sea when southerly to southeasterly wind conditions prevail river waters are transported northward beyond the shelf break and over the slope and adjacent basin areas these waters can then enter the interior arctic ocean via upper layer flow in the vicinity of the lomonosov ridge under other wind conditions river waters are steered primarily along the inner laptev shelf and into the east siberian sea as part of the predominantly eastward coastal current system these waters then appear to cross the shelf and enter the interior arctic ocean via upper layer flow aligned roughly along the mendeleyev ridge the extent to which either pathway is favored in a given year is largely determined by local wind patterns during the summer months when fluvial discharge is greatest and shelf waters are at the lowest salinity of their annual cycle

the tracing of riverine u in arctic seawater with very precise 234u 238u measurements abstract the riverine flux of u that enters the deep oceans is not well constrained since the net losses during estuarine mixing are difficult to quantify riverine dissolved u normally has a higher 234 u 238 u activity ratio 234 u 238 u ar than the uniform value that characterizes open ocean seawater and could be used as a tracer of riverine inputs if one could resolve subtle variations in seawater composition using new mass spectrometry techniques we achieve a long term reproducibility 0 3 on 234 u 238 u ar which permits the tracing of riverine u in seawater samples from the arctic a partially restricted basin that is ideal for such a study we find that surface waters from the arctic basins carry elevated 234 u 238 u ar when compared with deep ocean seawater samples from the canada basin have a significant freshwater component and provide evidence that the mackenzie river loses 65 of its u in the mackenzie shelf estuary zone before entering the deeper basin this is in contrast to samples from the makarov basin which provide evidence that all of the freshwater input is derived from the major yenisey river alone despite the proximity of the lena and ob rivers the differing behaviour of u between the mackenzie and yenisey rivers is most likely a consequence of the strong binding of u to dissolved organic matter doc or secondary phases in these rivers the yenisey river appears to transport the majority of the doc through the shelf and into the makarov basin in contrast the mackenzie river appears to lose a significant amount of doc 50 in the estuary shelf zone which may lead to loss of associated u these findings offer a more detailed picture of the fresh riverine water flow patterns in the arctic ocean when compared to other geochemical proxies the non conservative behaviour of u in the mackenzie river through the shelf estuaries has important implications for u input into oceans and the total marine budget

cross shelf transport of warm and saline water in response to sea ice drift on the laptev sea shelf 1 oceanographic moorings and conductivity temperature depth ctd surveys from september 2009 to september 2010 are used to describe recent changes in the laptev sea hydrography and to highlight wind and ice driven surface ekman transport as the mechanism to translate these changes from the outer to the inner shelf bottom waters in february 2010 moored oceanographic instruments recorded a sudden increase in temperature 0 8 c and salinity 3 near the bottom of the inner laptev sea shelf such warm and saline waters had not been previously observed on the inner shelf in winter they likely originated from the basin and were first observed during a summer 2009 ctd survey in the northwestern shelf break region subsequently spreading east and shoreward across the laptev sea shelf the changes were introduced to the mooring site by the first of a series of bottom intensified flow events with velocities reaching 20 cm s 1 topographically guided along a relic submarine river valley each of the flow events coincided with negative pressure anomalies at the mooring site and offshore directed upwelling favorable winds and ice drift we suggest that the observations to first order resemble a simplified two dimensional two layered ocean where offshore surface ekman transport is compensated for by a barotropic shoreward response flow near the bottom in this paper we use one of the first comprehensive long term laptev sea datasets to highlight ice ocean atmosphere interactions in early and late winter and discuss the role of freshwater stratification and ice mobility on under ice circulation on the laptev sea shelf

the interior shelves of the arctic ocean physical oceanographic setting climatology and effects of sea ice retreat on cross shelf exchange abstract the interior shelves of the arctic mediterranean are the shelves of the kara sea laptev sea east siberian sea and beaufort sea they comprise approximately 40 of the total arctic shelf area 2 5 10 6 km 2 and are distinguished from inflow and outflow shelves by their principal forcing dynamics along their southern continental boundary the interior shelves are dominated by the major arctic rivers receiving over 80 of the total freshwater input to the arctic ocean in the mid shelf region wind and ice motion surface stresses dominate mixing and circulation resulting in high variability along their northern seaward boundary they are forced by upwelling and downwelling favourable surface stresses which drive shelf basin exchanges with atlantic and pacific origin cyclonic boundary currents over the upper slope shelf basin exchange is further modified by shelf break morphometry e g canyons valleys headlands and bottom slope here we review the physical oceanographic settings and forcing of the interior shelves and then focus on shelfbreak exchange and supply of nutrients for new primary production due to upwelling across the shelfbreak as a proxy for this nutrient supply we show seasonal and annual time series of along shelfbreak surface stress due to wind and ice motion from 1979 to 2011 we apply this analysis to the shallow shelves from the kara sea to the beaufort sea and comment on recent increases due to atmospheric changes and sea ice retreat

landfast ice affects the stability of the arctic halocline evidence from a numerical model landfast ice covers large surface areas of the winter siberian seas the immobile landfast ice cover inhibits divergent and convergent motion hence dynamical sea ice growth and redistribution decouples winter river plumes in coastal seas from the atmosphere and positions polynyas at the landfast ice edge offshore in spite of the potentially large effects state of the art numerical models usually do not represent landfast ice in its correct extent a simple parametrization of landfast ice based on bathymetry and internal sea ice strength is introduced and its effects on the simulated arctic ocean are demonstrated the simulations suggest that the siberian landfast ice impacts the arctic halocline stability through enhanced brine production in polynyas located closer to the shelf break and by redirecting river water to the canadian basin these processes strengthen the halocline in the canadian basin but erode its stability in the makarov and eurasian basins

investigation of subsurface water flow along the continental margin of the eurasian basin using the transient tracers tritium 3he and cfcs during august september 1993 the r v polarstern expedition ark ix 4 was made to the eurasian continental margin of the arctic ocean sections of oceanographic stations leading from the outer shelf over the continental slopes toward the deep eurasian basin were occupied north of the barents and laptev seas the distributions of the transient tracers cfc 11 cfc 12 tritium and 3he were measured along these sections and are discussed in relation to water mass distribution and circulation along the continental margin of the eurasian basin the tracer data strongly corroborate the temperature and salinity data schauer et al 1997 clearly showing the inflow of atlantic water in two branches the fram strait branch and the barents sea branch high cfc and tritium concen trations extended down to 1300 m over the laptev continental slope indicating strong inflow of the barents sea branch between franz josef land and severnaya zemlya the apparent ages of water in the fram strait branch were estimated to be about 2 years north of the barents sea and 6 years at the eastern end of the nansen basin which corresponds to an apparent mean current speed of about 1 cm s 1 the age of the core of the barents sea branch was also estimated to be about 6 years over the laptev slope region and to increase by 0 5 years as it flowed through this region a lower limit for the inflow of newly formed barents sea branch water was estimated to be 0 5 sv and an overall transport for the sum of fram strait branch plus barents sea branch flow of 4 sv was estimated from this aging in the deep water there was clear evidence for the inflow of norwegian sea deep water through fram strait but there appeared to be no significant input of shelf derived water from the santa anna trough if there was any shelf derived input to eurasian basin bottom water it entered at a deeper depth than was sampled on the slope sections in the laptev sea or its flow is intermittent and was not occurring during the ark ix 4 expedition

connections among ice runoff and atmospheric forcing in the beaufort gyre during sheba thin ice and freshening of the arctic ocean surface in the beaufort sea led to speculation that perennial sea ice was disappearing mcphee et al 1998 since 1987 we have collected salinity 18o and ba profiles near the initial sheba site and in 1997 we ran a section out to sheba resolving fresh water into runoff and ice melt we found a large background of mackenzie river water with exceptional amounts in 1997 explaining much of the freshening at sheba ice melt went through a dramatic 4 6 m jump in the early 1990s coinciding with the atmospheric pressure field and sea ice circulation becoming more cyclonic the increase in sea ice melt appears to be a thermal and mechanical response to a circulation regime shift should atmospheric circulation revert to the more anticyclonic mode ice conditions can also be expected to revert although not necessarily to previous conditions

wind driven summer surface hydrography of the eastern siberian shelf 1 high interannual variability of summer surface salinity over the laptev and east siberian sea shelves derived from historical records of the 1950s 2000s is attributed to atmospheric vorticity variations in the cyclonic regime positive vorticity the eastward diversion of the laptev sea riverine water results in a negative salinity anomaly to the east of the lena delta and farther to the east siberian sea and a positive anomaly to the north of the lena delta anticyclonic negative vorticity results in negative salinity anomalies northward from the lena delta due to freshwater advection toward the north and a corresponding salinity increase eastward

barium as a tracer of arctic halocline and river waters dissolved barium ba concentrations are reported for water samples collected during six oceanographic cruises to the arctic in 1993 and during the 1994 arctic ocean section upper arctic 75 nmol ba 1 1 observed in the surface mixed layer of the arctic interior i e beyond the 200 m isobath occurred in the canada basin as a result of the biological removal of ba from surface waters of the chukchi sea and the tendency of the bering inflow to enter the arctic interior at depths below the relatively fresher mixed layer we hypothesize that the mackenzie river is the dominant source of the high ba observed in the surface waters of the canada basin features characterized by local salinity minima and ba maxima in surface waters down to depths of 30 50 m were observed over the arlis plateau and mendeleyev ridge in both 1993 and 1994 and over the makarov basin and lomonosov ridge in 1994 the physical and chemical properties of these waters suggest that they have been significantly influenced by fluvial discharge it could not be determined from available data whether these features arose from offshore transport of eurasian river discharge from the russian arctic seas meanders of the mackenzie river influenced beaufort gyre or a branch of bering inflow that crossed the chukchi shelf and entrained river water from north american and or eurasian sources in both 1993 and 1994 ba concentrations in the upper halocline layer as defined by a core salinity of 33 1 ranged between 42 and 77 nmol ba 1 1 with highest values observed in the canada basin the ba maximum and the related nutrient maxima and oxygen minimum that characterize the upper halocline in the canada basin suggest sources in the chukchi and beaufort seas and that the mechanism by which these waters are formed is linked with the influx of water through the bering strait the ba distributions for 1993 and 1994 delineate the lateral extent of upper halocline waters with canada basin character and show them to be chemically distinct from upper halocline waters in the eurasian basin the front separating these water types ran roughly along the mendeleyev and alpha ridges consistent with reports that the boundary between atlantic and pacific water mass assemblies in the arctic has recently been displaced from its historical position over the lomonosov ridge lateral gradients in both ba and the no parameter were observed within the lower halocline layer defined by an no minimum and core salinity of 34 2 34 4 along the 1994 arctic ocean section indicating that lower halocline waters receive additional inputs as they transit to the canadian basin from their region of formation in the eurasian sector of the arctic

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

variability in river runoff distribution in the eurasian basin of the arctic ocean 1 the distribution of freshwater within the arctic ocean and its export from it are intimately involved in climate and climate change processes both within and outside the arctic ocean river runoff in the arctic ocean constitutes a major part of the arctic ocean freshwater budget within the arctic ocean variability in the distribution of river runoff will be reflected in the location of the cold halocline that isolates the sea ice from the warm atlantic layer outside the arctic ocean such variability will impact on the salinity of north atlantic waters great salinity anomaly and on deep convection areas of the north atlantic ocean and thereby potentially on global thermohaline circulation rivers entering the arctic ocean have high levels of total alkalinity that contribute significantly to the total alkalinity of the surface polar mixed layer we exploit total alkalinity data to trace river runoff in the surface polar mixed layer and to observe variability in the river runoff distribution in the eurasian basin over the period 1987 2001 the river runoff front changed from a position over the gakkel ridge in 1987 and 1991 to over the lomonosov ridge in 1996 and returned to a midpoint between the two ridges in 2001 wind field changes as characterized by the arctic oscillation index are considered to be a major factor in determining ice and surface water flow we note a correlation with 4 6 years delay between changes in river runoff distribution and the arctic oscillation index we show that the delay can be inferred from a geostrophic flow calculation

formation and evolution of the surface mixed layer and halocline of the arctic ocean fresh water from summer ice melt and the total freshwater content of the arctic ocean water column above the thermocline are estimated from vertical profiles of temperature and salinity observed on the i b oden 1991 cruise the seasonal ice melt ranges from 0 5 m to slightly above 1 m and is moderately uniform over the observation area regions of lower melting are seen over the morris jesup plateau the freshwater content is calculated relative to the salinity just above the thermocline north of the barents sea the freshwater content increases toward the interior of the arctic ocean showing that fresh water is advected from other regions into the observation area regions of different freshwater content are separated by fronts over the nansen gakkel ridge over the lomonosov ridge and in the western eurasian basin between waters derived from the eurasian and canadian basins denser water homogenized north of the barents sea is recognized by a temperature minimum layer the absence of the temperature minimum near the nansen gakkel ridge indicates that heat is transferred from the atlantic layer over a longer time than the shortest route would allow this observation can be explained if the layer circulates together with the atlantic layer i e toward the east and returns above the nansen gakkel ridge and along the amundsen basin north of the laptev sea this water formed north of the barents sea becomes covered by low salinity shelf water the increased freshwater content limits the winter convection so it no longer reaches the thermocline and an intermediate halocline is formed the halocline in the eurasian basin consists of water originating from winter convection in the arctic ocean north of the barents sea which then circulates around the basin such a formation mechanism also explains the observed distribution of low no water the strong density increase limits vertical exchange and the vertical diffusion coefficient in the halocline is small 1 10 6 m2 s 1 the increased temperature of the halocline shows that the heat lost upward by the atlantic layer mainly by double diffusive convection is trapped below the mixed layer

quantitative considerations of dissolved barium as a tracer in the arctic ocean 1 dissolved barium ba was measured along transects across fram and denmark straits as part of the 1998 ark xiv 2 polarstern expedition results are combined with other available tracer observations to analyze water mass composition at fram strait a combination of pacific water and eurasian river runoff dominated 80 and 10 of the total mass respectively the upper east greenland current egc while the remainder of the section was dominated by north atlantic water a much smaller contribution of pacific water to the egc 50 at fram strait in 1987 suggests that this component can be quite variable in time north american river water was not detectable at fram strait in 1998 presumably the eurasian river water we observed at fram strait transited eastward along shelf within the arctic mixed with pacific water in the vicinity of the east siberian sea and was borne by the transpolar drift across the arctic ocean in the absence of significant net ice formation along the way such a pathway can be expected to produce more pronounced freshening of the egc than when eurasian river water mixes more directly off shelf into salty atlantic waters and pacific water is diverted largely through the canadian archipelago existing measurements at the main arctic gateways were used to construct a ba budget for the arctic ocean under conditions of simultaneous mass heat and salt conservation this preliminary budget is statistically consistent with the steady state hypothesis on the arctic basin scale ba appears to be conservative

changes in distribution of brine waters on the laptev sea shelf in 2007 combined salinity and 18o data from summer 2007 reveal a significant change in brine production in the laptev sea relative to summer 1994 the distribution of river water and brine enriched waters on the laptev sea shelf is derived based on mass balance calculations using salinity and 18o data while in 1994 maximal influence of brines is seen within bottom waters bauch et al 2009a in 2007 the influence of brines is highest within the surface layer and only a moderate influence of brines is observed in the bottom layer in contrast to 2007 salinity and 18o data from summer 1994 clearly identify a locally formed brine enriched bottom water mass as mixing endmember between surface layer and inner shelf waters on one side and with higher salinity water from the outer laptev sea on the other side in 2007 the brine enriched waters are predominantly part of the surface regime and the mixing endmember between surface layer and outer shelf waters is replaced by a relatively salty bottom water mass this relatively salty bottom water probably originates from the western laptev sea the inverted distribution of brines in the water column in 2007 relative to 1994 suggests a less effective winter sea ice formation in winter 2006 2007 combined with advection of more saline waters from the western laptev sea or the outer shelf precedent to 1 the climatically extreme summer 2007 the observed changes result in an altered export of waters from the laptev sea to the arctic ocean halocline

correlation of river water and local sea ice melting on the laptev sea shelf siberian arctic hydrographic and stable isotope 18o data from 4 summer surveys in the laptev sea are used to derive fractions of sea ice meltwater and river water sea ice meltwater fractions are found to be correlated to river water fractions while initial heat of river discharge is too small to melt the observed 0 158 km3 of sea ice meltwater arctic rivers contain suspended particles spm and colored dissolved organic material cdom that preferentially absorb solar radiation accordingly heat content in surface waters is correlated to river water fractions but in years when river water is largely absent within the surface layer absolute heat content values increase to considerably higher values with extended exposure time to solar radiation and sensible heat nevertheless no net sea ice melting is observed on the shelf in years when river water is largely absent within the surface layer the total freshwater volume of the central eastern laptev sea 72 76 n 122 140 e varies between 1000 1500 km3 34 92 reference salinity it is dominated by varying river water volumes 1300 1800 km3 reduced by an about constant freshwater deficit 350 400 km3 related to sea ice formation net sea ice melt 109 158 km3 is only present in years with high river water budgets intermediate to bottom layer 25 salinities contain 60 and 30 of the river budget in years with low and high river budgets respectively the average mean residence time of shelf waters was 2 3 years during 2007 2009

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