the formation of polar surface water the ice export and the exchanges through the fram strait abstract the polar surface water is formed from two parent water masses inflowing atlantic water and fresh from river run off and net precipitation two possible modes for this formation are considered 1 a entrainment driven by mechanical stirring takes place over the entire polar ocean and brings atlantic water into the surface layer 2 b the interaction between the atlantic water and the fresh water supply occurs only on the s shelves while the mixing in the interior is inhibited by a thick advective layer of intermediate density formed on the shelves the exchanges between the polar ocean and the north atlantic and the resulting stratification are determined for the two cases the derived transports are much smaller than those often encountered in the literature which mode dominates depends upon the fresh water discharge from the analysis it is found that a larger fresh water contribution favours mixing on the shelves while the entrainment in the interior becomes more important as the run off diminishes the present day situation is probably one where the shelf processes dominate however a modest decrease in the river run of the ocean it is found that a complete removal of the river run off may not affect the extent of the ice cover too seriously so that comparatively high ice export can be maintained this is because the higher salinity of the polar surface water gradually increases the fresh water buffer present in the pacific inflow

relationships between dinoflagellate cyst assemblages in surface sediment and hydrographic conditions in the bering and chukchi seas palynological analyses were performed on 52 surface sediment samples from the eastern part of the bering sea and chukchi sea in order to document the regional distribution of dinoflagellate cyst assemblages and their relationship with sea surface conditions the assemblages present a relatively high species diversity 20 taxa are recovered routinely especially in the bering sea where they are dominated by operculodinium centrocarpum and the cyst of pentapharsodinium dalei accompanied mainly by spiniferites elongatus s l spiniferites ramosus impagidinium pallidum brigantedinium spp islandinium minutum selenopemphix quanta selenopemphix nephroides quinquecuspis concreta and the cyst of polykrikos kofoidii the percentages of the main taxa vary with latitude and principal component analysis shows that the distribution of assemblages is closely related to hydrographic conditions notably the seasonal duration of sea ice cover and the sea surface temperature in february the dinoflagellate cyst assemblages from the bering sea differ significantly from those of subarctic seas of the north atlantic with respect to their species composition and relationships with sea surface conditions in particular the occurrence of the cyst of polykrikos kofoidii and quinquecuspis concreta and the positive correlation between the percentages of operculodinium centrocarpum and the extent of sea ice constitute peculiar features in the bering sea assemblages copyright 2001 john wiley sons ltd journal of quaternary science

an arctic ocean cold core eddy detailed physical and chemical observations were obtained during september 1997 of a cold core eddy situated in the southern central canada basin of the arctic ocean the eddy was about 20 km in diameter had maximum current speeds exceeding 20 cm s 21 and extended from the base of the upper mixed layer near 40 m down to 400 m excess salt in the eddy core was consistent with addition of brine from 1mo f ice formation core tracer distributions indicated a lifetime exceeding 1 year and were consistent with an origin as near surface pacific water with some admixed terrestrial runoff the eddy was probably formed in association with a polynya along the alaskan chukchi sea coast through local water densification from surface ice formation followed by development of frontal instabilities formation and subsequent migration of such eddies which may have lifetimes of several years provide a mechanism for transporting water from the beaufort and chukchi sea coastal and shelf regions into the interior canada basin and for contributing to maintenance of the permanent halocline present light ice conditions throughout the arctic ocean favor the formation of such eddies and may contribute to enhanced ventilation of the halocline waters

carbonate chemistry dynamics in bering strait and the chukchi sea fall dynamics of the carbonate system in the shallow chukchi sea is a result of the interaction between physical and biological processes such as mixing of different water masses cooling photosynthesis respiration the study area acts as a sink for atmospheric co2 the general trend in surface pco2 distribution is a decrease towards the ice edge which is determined by the temperature decrease whereas mesoscale variability of the carbonate parameters is controlled by the interaction between different waters the calculated september 1996 flux of co2 from the air into the sea on eastern chukchi sea is about 1 1012 g c

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

aspects of the marine nitrogen cycle of the chukchi sea shelf and canada basin abstract as a highly productive seasonally ice covered sea with an expansive shallow continental shelf the chukchi sea fuels high rates of sedimentary denitrification this contributes to its fixed nitrogen n deficit relative to phosphorus p which is among the largest in the global ocean making the chukchi sea severely n limited during the phytoplankton growth season here we examine aspects of the n cycle on the chukchi sea shelf and the downstream canada basin using nutrients dissolved oxygen o 2 and the stable isotopes of nitrate no 3 in the northward flow path across the chukchi shelf bottom waters experienced strong o 2 drawdown from which we calculated a nitrification rate of 1 3 mmol m 2 d 1 this nitrification was likely primarily in sediments and directly fueled sedimentary denitrification historically measured at similar rates we observed significant accumulations of ammonium nh 4 in bottom waters of the chukchi shelf up to 5 m which were inversely correlated with 15 n no 3 indicating a sediment source of 15 n enriched nh 4 this is consistent with a process of coupled partial nitrification denitrification cpnd which imparts significant 15 n enrichment and 18 o depletion to pacific origin no 3 this cpnd mechanism is consistent with a significant decrease in 18 o no 3 relative to bering sea source waters indicating that at least 58 of no 3 populating the pacific halocline was regenerated during its transit across the north bering and chukchi shelves rather than arriving preformed from the bering sea slope this pacific origin no 3 propagates into the canada basin and towards the north atlantic being significantly 15 n enriched and 18 o depleted relative to the underlying atlantic waters

an annual study of inorganic and organic nitrogen and phosphorus and silicic acid in the southeastern beaufort sea 1 water column samples from the mackenzie shelf the beaufort sea and the amundsen gulf were obtained during 2003 2004 to investigate nutrient dynamics in an arctic ecosystem influenced by a large river and flaw lead polynya nutrient inventories in the upper water column showed a significant seasonal drawdown of nitrate no3 and silicic acid si oh 4 1 1 75 mol mol and subsequent accumulation of nitrite no2 and ammonium nh4 dissolved organic nitrogen and phosphorus concentrations don and dop were elevated in surface waters during the time of peak phytoplankton growth bloom and postbloom phases and covaried in a 17 1 molar ratio vertical profiles showed the typical middepth maxima in no3 po43 and si oh 4 at salinity 32 33 1 the concentration of dop 0 76 0 27 mol p l 1 was also 2 times higher in this layer compared to the surface average and inversely correlated with the water mass tracer n n no3 16 po43 2 9 0 87 suggesting that pacific derived waters were a source of the enrichment below the mixed layer don was generally constant with depth although averaged profiles like those of urea suggested the presence of subsurface maxima at 50 m and between 250 and 300 m regeneration ratios varied with depth and were approximately 9 0 mol o2 mol no3 and 122 5 mol o2 mol po43 in shallow pacific derived waters halocline layer and 17 4 and 193 5 in deep atlantic waters atlantic layer respectively deep waters of the amundsen gulf contained an excess of 1 7 mol no3 l 1 0 12 mol po43 l 1 and 6 2 mol si oh 4 l 1 and a deficit in o2 relative to waters of similar density in the beaufort sea in proportions consistent with the remineralization ratios derived from oxygen nutrient regressions enhanced export of particulate matter from the overlying polynya and subsequent remineralization at depth are hypothesized to create this nutrient enrichment

the nutrient salinity and stable oxygen isotope composition of bering and chukchi seas waters in and near the bering strait seawater nutrient salinity and oxygen 18 data collected from 1990 to 1993 in the bering and chukchi seas were used to identify potential sources of nutrients and water masses that result in formation of the arctic ocean upper halocline and its associated nutrient maximum water matching the delta sup 18 o values of the arctic ocean upper halocline and containing sufficient or a nearly sufficient nutrient and salinity concentration was collected in subsurface waters in the summer in portions of the bering sea particularly the gulf of anadyr however nutrient concentrations significantly declined in this north flowing water over the shallow continental shelf before it reached the bering strait as a consequence of biological utilization and dilution with nutrient poor and oxygen 18 depleted fresh water therefore it does not appear likely that the flow of unaltered water through the bering strait in the summer plays a critical role in the formation of the arctic ocean upper halocline the role of other mechanisms for contributing pacific derived waters to the arctic ocean nutrient maximum is considered copyright 1997 american geophysical union

the summer hydrography and surface circulation of the east siberian shelf sea during the ice free summer season in 1995 the authors deployed and subsequently tracked 39 surface drifters to test the hypothesis that the discharge from the kolyma river forces a buoyancy driven coastal current from the east siberian sea toward bering strait the observed mean flow is statistically significant at the 95 level of confidence but its direction contradicts their initial hypothesis instead of a coastally trapped eastward flow the authors find a laterally sheared westward flow with maximum velocities offshore that correlate only weakly with the local winds at a daily wind dominated timescale the drifter data reveal spatially coherent flows of up to 0 5 m s21 the lagrangian autocorrelation scale is about 3 days and the lagrangian eddy length scale reaches 40 km this spatial scale exceeds the nearshore internal deformation radius by a factor of 3 however it more closely corresponds to the internal deformation radius associated with the offshore ice edge bulk estimates of the horizontal mixing coefficient resemble typical values of isotropic open ocean dispersion at midlatitudes hydrographic observations and oxygen isotope ratios of seawater indicate a low proportion of riverine freshwater relative to sea ice melt in most areas of the east siberian sea except close to the kolyma delta the observations require a reevaluation of the conceptual view of the summer surface circulation of the east siberian sea eastward buoyancy driven coastal currents do not always form on this shelf despite large river discharge instead ice melt waters of a retreating ice edge act as a line source of buoyancy that in 1995 forced a westward surface flow in the east siberian sea

characteristics of colored dissolved organic matter cdom in the arctic outflow in the fram strait assessing the changes and fate of terrigenous cdom in the arctic ocean absorption coefficients of colored dissolved organic matter cdom were measured together with salinity delta o 18 and inorganic nutrients across the fram strait a pronounced cdom absorption maximum between 30 and 120 m depth was associated with river and sea ice brine enriched water characteristic of the arctic mixed layer and upper halocline waters in the east greenland current egc the lowest cdom concentrations were found in the atlantic inflow we show that the salinity cdom relationship is not suitable for evaluating conservative mixing of cdom the strong correlation between meteoric water and cdom is indicative of the riverine terrigenous origin of cdom in the egc based on cdom absorption in polar water and comparison with an arctic river discharge weighted mean we estimate that a 49 59 integrated loss of cdom absorption across 250 600 nm has occurred a preferential removal of absorption at longer wavelengths reflects the loss of high molecular weight material in contrast cdom fluxes through the fram strait using september velocity fields from a high resolution ocean sea ice model indicate that the net southward transport of terrigenous cdom through the fram strait equals up to 50 of the total riverine cdom input this suggests that the fram strait export is a major sink of cdom these contrasting results indicate that we have to constrain the c dom budgets for the arctic ocean much better and examine uncertainties related to using tracers to assess conservative mixing in polar waters citation granskog m a c a stedmon p a dodd r m w amon a k pavlov l de steur and e hansen 2012 characteristics of colored dissolved organic matter cdom in the arctic outflow in the fram strait assessing the changes and fate of terrigenous cdom in the arctic ocean j geophys res 117 c12021 doi 10 1029 2012jc008075

on the origin of the chemical properties of the arctic ocean halocline profiles of chemical constituents in seawater above the alpha ridge in the central arctic ocean obtained during the canadian expedition to study the alpha ridge cesar support a model in which the halocline is maintained by dense saline water produced on the continental shelves within the arctic ocean by the formation of sea ice it is argued that nutrient regeneration on the continental shelves largely accounts for the nutrient maximum that has been observed in the upper halocline over a wide region of the arctic ocean and that while the bering sea and north altantic can be recognized as origins of halocline water water masses from these regions undergo sufficient changes in their chemical properties within the arctic ocean significant that they no longer retain their identity in the halocline

density driven vertical transport of saltwater through the freshwater lens on the island of baltrum germany following the 1962 storm flood abstract due to the growing vulnerability of low lying coastal zones to flooding by seawater there is a current need for studies of the impact of such inundations on fresh groundwater resources the knowledge from the literature is biased towards tropical atoll environments and only few studies specifically investigated the effect of density driven downward flow even though its importance is widely acknowledged the present study is based on previously unpublished hydrochemical data collected on the island of baltrum following a devastating storm in 1962 which uniquely show the impact of seawater inundation on a freshwater lens in a siliciclastic aquifer the field data show that about 3 kg of cl per m 2 of inundated land area or 18 cm of seawater infiltrated and that elevated salinities persisted at the measurement depths of 4 and 6 m for at least 4 years and at least for 6 years at greater depths numerical models support the assertion that the shape of the measured salinographs i e an initial sharp rise in the salt concentration with time followed by a continually slowing decrease must be attributed to density driven salt fingering models that did not consider density effects fail to simulate the observed patterns transient recharge model dimension and lateral flow modify the details of the simulation results but in all models density driven vertical flow dominates the overall system behaviour the diminishing importance of density driven flow at greater depths however in combination with slow recharge driven flow rates prolongs flushing times and enhances the risk of brackish water up coning when pumping is resumed too soon

sediment transport by sea ice in the chukchi and beaufort seas increasing importance due to changing ice conditions abstract sediment laden sea ice is widespread over the shallow wide siberian arctic shelves with off shelf export from the laptev and east siberian seas contributing substantially to the arctic ocean s sediment budget by contrast the north american shelves owing to their narrow width and greater water depths have not been deemed as important for basin wide sediment transport by sea ice observations over the chukchi and beaufort shelves in 2001 02 revealed the widespread occurrence of sediment laden ice over an area of more than 100 000 km2 between 68 and 74 n and 155 and 170 w ice stratigraphic studies indicate that sediment inclusions were associated with entrainment of frazil ice into deformed multiple layers of rafted nilas indicative of a flaw lead environment adjacent to the landfast ice of the chukchi and beaufort seas this is corroborated by buoy trajectories and satellite imagery indicating entrainment in a coastal polynya in the eastern chukchi sea in february of 2002 as well as formation of sediment laden ice along the beaufort sea coast as far eastward as the mackenzie shelf moored upward looking sonar on the mackenzie shelf provides further insight into the ice growth and deformation regime governing sediment entrainment analysis of radarsat synthetic aperture sar imagery in conjunction with bathymetric data help constrain the water depth of sediment resuspension and subsequent ice entrainment 20 m for the chukchi sea sediment loads averaged at 128 t km 2 with sediment occurring in layers of roughly 0 5 m thickness mostly in the lower ice layers the total amount of sediment transported by sea ice mostly out of the narrow zone between the landfast ice edge and waters too deep for resuspension and entrainment is at minimum 4 106 t in the sampling area and is estimated at 5 8 106 t over the entire chukchi and beaufort shelves in 2001 02 representing a significant term in the sediment budget of the western arctic ocean recent changes in the chukchi and beaufort sea ice regimes reduced summer minimum ice extent ice thinning reduction in multi year ice extent altered drift paths and mid winter landfast ice break out events have likely resulted in an increase of sediment laden ice in the area apart from contributing substantially to along and across shelf particulate flow an increase in the amount of dirty ice significantly impacts sub ice algal production and may enhance the dispersal of pollutants

the freshwater budget and under ice spreading of mackenzie river water in the canadian beaufort sea based on salinity and 18o 16o measurements in water and ice observations of salinity and oxygen isotope composition 18o were made for the beaufort shelf mackenzie estuary waters in september 1990 just prior to ice formation and for both the water column and ice in april may 1991 at the end of winter these measurements are used to determine the apportioning of fresh water in the estuary between its two main sources runoff and sea ice melt changes in disposition of water between seasons and amounts frozen into the growing ice sheet are also derived two domains are considered in order to construct a freshwater budget for the mackenzie shelf the nearshore within which landfast ice grows in winter and the outer shelf most of the winter inflow from the mackenzie river appears to remain impounded as liquid under the ice within the landfast zone at the end of winter and about 15 of it is incorporated into the landfast ice oxygen isotopes 18o in ice cores collected from across the shelf record the progress beneath the ice of new mackenzie inflow as it invades the nearshore throughout winter rates of spreading are about 0 2 cm s 1 away from the coast and 1 3 cm s 1 along the coast as this inflow spreads across the shelf it progressively shuts off convection driven by brine production at locations within the landfast ice salinity and 18o in the offshore water column suggest that about 3 m of sea ice was formed in the outer shelf domain since both brine and newly formed sea ice can be advected off the shelf a complete budget for brine or sea ice production cannot be established without first measuring the advection of one of these two components

variations in the proportions of melted sea ice and runoff in surface waters of the chukchi sea a retrospective analysis 1990 2012 and analysis of the implications of melted sea ice in an under ice bloom abstract retrospective analysis of apparent freshwater isotopic end members through use of salinity 18 o mixing lines for 15 research cruises from 1990 to 2012 indicates that the freshwater contributed by melted seasonal sea ice does not directly reflect the large change in seasonal sea ice extent in the chukchi sea observed over the past several decades instead the freshwater that appears to be contributed by melting sea ice relative to runoff is highly dependent upon cruise track e g proximity to runoff and sampling capabilities in sea ice icebreakers sample waters with less melted sea ice although under certain circumstances including later seasonal sampling and recurrent cruise tracks between years increased melted sea ice in surface waters can be readily detected this suggests a more ephemeral influence of melted sea ice on ecosystem properties despite the significant decadal changes in sea ice extent as a recent case study the freshwater component present in waters within an under ice bloom in the chukchi sea reported by arrigo et al 2012 included a significant fraction 10 or more of freshwater primarily from melted sea ice these results suggest that this under ice bloom which extended more than 60 km under solid ice still might be reasonably interpreted as being part of a continuum with other ice melt associated blooms and not independent of sea ice retreat and dissolution

late winter water column and sea ice conditions in the northern bering sea 1 seasonal sea ice concentration and thickness were evaluated on a weekly basis during two years with contrasting ice coverage 1998 1999 and 2000 2001 using data provided by the u s national ice center ice in the bering sea during 1998 1999 was extensive and thick but by contrast in 2000 2001 winter sea ice formed late with thin ice and ice melt proceeded earlier during spring the presence and timing of a winter polynya an area of relatively open water or thin ice surrounded by heavier ice located south of st lawrence island also varied between these two winters shipboard measurements south of st lawrence island during two late winter early spring cruises in 1999 and 2001 showed that some brine injected water was present resulting in localized areas of bottom water with salinities approaching or exceeding 33 psu the mean salinity of bottom water was significantly higher in 2001 32 6 psu than in 1999 32 3 psu these varying degrees of brine injection associated with large differences in ice conditions heavy in 1998 1999 light in 2000 2001 influenced bottom water salinity and density but there were indications that variation in water mass structure also can explain differences in salinity observed between the two winters the mean 18oh2o values of bottom seawater were significantly higher in 2001 0 78 0 16 sd than in 1999 0 98 0 20 sd consistent with a more saline nutrient rich water being present in 2001 consistent with these indications inorganic nutrients nitrate phosphate and silicate in bottom water were significantly higher in 2001 than in 1999 although it is seemingly paradoxical that salinities were higher in 2001 light ice than in 1999 heavy ice when brine injection might have been more prevalent the sampling period was approximately 1 month earlier in 2001 when ice formation may have been more active in addition 18oh2o values indicate a higher proportion of anadyr water with higher salinity and nutrients in 2001 despite these differences in both ice conditions and water mass nutrient chemistry water column chlorophyll was uniformly low in both years this indicates that changes in bering sea ice regimes during the late winter months such as may occur under various climate change scenarios will not necessarily lead to any higher productivity or an earlier onset of seasonal biological production despite relatively high inorganic nutrient concentrations in both years a well mixed water column was observed with low water column chlorophyll a chl a concentrations these observations suggest that there was little primary production during either cruise in spite of the relatively open water and high water column nutrient concentrations during 2001 strong southerly winds during winter likely impeded ice formation vertically mixed the water column and prevented early spring open water primary production

winter currents and hydrographic conditions on the northern central bering sea shelf current observations obtained from the northern bering shelf region in winter 1984 1985 indicate that midwinter circulation patterns differed from those during the rest of the year annual mean circulation in this region is dominated by vigorous northward currents from 10 cm s in shpanberg strait to more than 50 cm s in bering strait these northward currents are accompanied by a weak northwestward coastal flow south of st lawrence island in february april 1985 however flow was weakly 0 5 cm s southward through shpanberg strait and southeastward south of st lawrence island while remaining northward through anadyr and bering straits comparison with current data obtained from previous years suggests that midwinter reversal of flow in shpanberg strait is a recurrent winter feature it generally occurs at about the same time that the winter ice cover undergoes its major advance and it is associated with strong northerly winds northward flow through anadyr strait persists conversely through the winter and is the northward extension of a western intensified northward flow over the bering shelf its source is bering sea water farther south rather than water from the northern central shelf the resultant trapping of shelf water on the northern central shelf coupled with intensive regional ice formation during the same period as the flow reversal led in 1985 to significant about 1 5 brine enrichment this salinity increase agrees qualitatively with historical data which suggest that the northern central bering shelf is the site both of sluggish winter circulation and of elevated salinities due to brine enrichment from ice formation

forward modeling of carbonate proxy data from planktonic foraminifera using oxygen isotope tracers in a global ocean model the distribution and variation of oxygen isotopes in seawater are calculated using the goddard institute for space studies global ocean model simple ecological models are used to estimate the planktonic foraminiferal abundance as a function of depth column temperature season light intensity and density stratification these models are combined to forward model isotopic signals recorded in calcareous ocean sediment the sensitivity of the results to the changes in foraminiferal ecology secondary calcification and dissolution are also examined simulated present day isotopic values for ecology relevant for multiple species compare well with core top data hindcasts of sea surface temperature and salinity are made from time series of the modeled carbonate isotope values as the model climate changes paleoclimatic inferences from these carbonate isotope records are strongly affected by erroneous assumptions concerning the covariations of temperature salinity and 18ow habitat imposed biases are less important although errors due to temperature dependent abundances can be significant

uplift of beta regio three dimensional models 1 three dimensional models of the uplift of beta regio caused by a mantle plume satisfy constraints on gravity topography rheology and the uplift rate substantially better than two dimensional models in particular the uplift time of beta regio is reduced to an acceptable 800 million years three dimensional models give the plume formation depth around 3000 km which approximately corresponds to the core mantle boundary the results depend only weakly on the initial lithospheric thickness at the time of global resurfacing including a very thin initial lithosphere this implies that the thick present day lithosphere 400 km suggested by our models can be reconciled with a thin lithosphere 100 200 km inferred from the melt generation rates and the flexural rigidity models

the deglacial history of surface and intermediate water of the bering sea the lithology of deglacial sediments from the bering sea includes intervals of laminated or dysaerobic sediments these intervals are contemporaneous with the occurrence of laminated sediments from the california margin and gulf of california which suggests widespread low oxygen conditions at intermediate depths in the north pacific ocean the cause could be reduced intermediate water ventilation increased organic carbon flux or a combination of the two we infer abrupt decreases of planktonic foraminifer d 18 o at 14 400 and 11 650 yr bp which may be a combination of both freshening and warming on the shirshov ridge the abundance of sea ice diatoms of the genus nitzschia reach local maxima twice during the deglaciation the latter of which may be an expression of the younger dryas these findings expand the extent of the expression of deglacial millennial scale climate events to include the northernmost pacific r 2005 elsevier ltd all rights reserved

ocean acidification and biologically induced seasonality of carbonate mineral saturation states in the western arctic ocean calcium carbonate caco3 mineral saturation states for aragonite aragonite and calcite calcite are calculated for waters of the chukchi sea shelf and canada basin of the western arctic ocean during the shelf basin interactions project from 2002 to 2004 on the chukchi sea shelf a strong seasonality and vertical differentiation of aragonite and calcite saturation states was observed during the summertime sea ice retreat period high rates of phytoplankton primary production and net community production act to increase the aragonite and calcite of surface waters while subsurface waters become undersaturated with respect to aragonite due primarily to remineralization of organic matter to co2 this seasonal phytoplankton carbonate saturation state interaction induces strong undersaturation of aragonite aragonite 10 the seasonal aragonite undersaturation of waters observed on the chukchi sea shelf is likely a recent phenomenon that results from the uptake of anthropogenic co2 and subsequent ocean acidification with seasonality of saturation states superimposed by biological processes these undersaturated waters are potentially highly corrosive to calcifying benthic fauna e g bivalves and echinoderms found on the shelf with implications for the food sources of large benthic feeding mammals e g walrus gray whales and bearded seals the benthic ecosystem of the chukchi sea and other arctic ocean shelves is thus potentially vulnerable to future ocean acidification and suppression of caco3 saturation states

east west differences in water mass nutrient and chlorophyll a distributions in the sea ice reduction region of the western arctic ocean 1 the r v mirai conducted hydrographic surveys in the western arctic ocean during summer 2004 across a front between cold arctic water and warm water from the pacific ocean where sea ice cover has been largely reduced in recent summers the hydrographic data indicate a new type of vertical temperature minimum water west of the front along isohaline surfaces with approximate salinity s of 32 which is fresher than the typical temperature minimum s 33 caused by spreading of pacific winter water pww mainly to the east of the front both of the temperature minimum waters are characterized by low potential vorticity with near freezing temperature suggesting that they are formed by winter convection with sea ice formation a difference between the waters results from a large contribution of sea ice meltwater to the fresh temperature minimum frtmin water of s 32 the distributions of the sea ice meltwater contribution and nitrogen deficit suggest that summer shelf water largely influenced by the sea ice melt in the chukchi sea is modified by winter convection on its way to the chukchi abyssal plain to form the frtmin water this water supplies nutrients through the water distribution to the west of the front at depths shallower than the nutrient maximum layer caused by the pww spreading the shallower nutrient supply by the frtmin water combined with light penetration without sea ice cover could produce a prominent chlorophyll a maximum layer west of the front

evaluation of shelf basin interaction in the western arctic by use of short lived radium isotopes the importance of mesoscale processes shelf basin exchange in the western arctic was evaluated by use of water column analyses of 228 ra 226 ra ratios and the first measurements of the short lived 224 ra t1 2 3 64 d in the arctic during the 2002 shelf basin interaction sbi program excess 224 ra was detected over the shelf but was not found seaward of the shelf break similarly the 228 ra 226 ra ratio dropped rapidly from the shelf across the shelf break consequently the model age gradient elapsed time since shelf residence northward across the chukchi shelf increased from 1 5 years nearshore to approximately 14 years in surface waters sampled off shelf at the southern margin of the beaufort gyre this steep gradient is consistent with very slow exchange between the chukchi shelf and the beaufort gyre whereby bering strait inflow is constrained by the earth s rotation to follow local isobaths and does not easily move into deeper water the strong dynamic control inhibiting water that enters the system through bering strait from flowing north across isobaths also would lead to a long recirculation time of river water emptied into the beaufort gyre possible mechanisms that can generate cross shelf currents that break the topographic constraint to follow isobaths and thereby transport water and associated properties off the shelves include wind induced upwelling downwelling meandering jets and eddies evidence of such a process was found during the icex project in the beaufort sea in april 2003 when excess 224 ra was measured over 200 km from any shelf source this required an ne offshore flow of 40 cm s 1 assuming that the source water derives from the mouth of barrow canyon a weak northeastward flow was measured using an ladcp within the upper 300 m of the ocean but was of lower speed than required by the 224 raxs at the time of the icex occupation

observations of banding in first year arctic sea ice 1 horizontal banding features alternating dark and bright horizontal bands apparent in ice cores and stratigraphic cross sections have long been observed in first year sea ice and are frequently associated with bands of high and low brine or gas porosity observations on the land fast ice near barrow alaska in recent years have revealed particularly striking banding patterns and prompted a study of their macroscopic and microscopic characteristics the banding patterns are quantified from photographs of full depth sections of the ice and examples are presented from the chukchi sea and elson lagoon statistics on band spacing are presented and the growth records for three seasons are employed to estimate their time of formation these data provide insight into the periodicity of the underlying phenomena micrographs are used to examine the microstructural variations associated with various banding features and to quantify the geometry of the constituent brine inclusions associated with high and low porosity bands the micrography revealed that the area fraction of brine inclusions varied by a factor of nearly 3 through the more pronounced high and low porosity bands vertical micrographs obtained shortly after the materials removal from the ice sheet showed that significantly larger inclusions form abruptly at the start of the high porosity bands and frequently terminate abruptly at the end of the band crystallographic observations indicated that the high porosity bands supported the nucleation and growth of crystals having substantially different orientations from the very well aligned columnar structure that characterized the bulk of the sheet

variability of sea ice melt and meteoric water input in the surface labrador current off newfoundland the respective contributions of saline atlantic and pacific water and freshwater sea ice melt meteoric water components in the surface labrador current are quantified using salinity 18o and nutrient data collected between 2012 and 2015 east of newfoundland to investigate the seasonal variability of salinity in relation with the different freshwater contributions nutrient data indicate that the surface saline water is composed on average over 2012 2015 of roughly 62 atlantic water and 38 pacific water a large salinity seasonal cycle of 1 5 peak to peak amplitude is found over the middle continental shelf which is explained by the freshwater input seasonal variability 2 3 of the amplitude of the salinity seasonal cycle can be explained by meteoric water input and 1 3 by the sea ice melt a smaller seasonal salinity cycle 1 3 is observed over the inner shelf compared to the middle shelf because of smaller variability in the large meteoric water inputs furthermore the data reveal that sea ice melt sim input was particularly important during july 2014 following a larger extension of sea ice over the labrador shelf during the 2013 2014 winter season compared to both previous winter seasons some patches of large sim contribution observed during july 2014 and april 2015 were located on the continental slope or further offshore the comparison of 2012 2015 data with data collected in 1994 1995 shows that the surface water over the newfoundland shelf and slope is strongly affected by sea ice processes in both periods and suggests a larger contribution of brines over the slope during 1994 1995

on exchange of water between the gulf of alaska and the bering sea through unimak pass we present the first long term current and bottom pressure observations from unimak pass alaska and adjacent locations on the gulf of alaska and bering sea shelves vector mean current recorded between march and august 1980 was 12 cm s toward 284 t or onto the bering sea shelf however magnitude decreased from 20 cm s to 6 cm s between the first and second halves of the record at shorter periods 3 10 days current fluctuations in the pass were strongly coherent k2 0 7 with the pressure difference measured along the axis of the pass and this was coherent with geostrophic wind estimates the results indicated that wind induced sea level perturbation was the dominant forcing mechanism for fluctuations relations among current bottom pressure pressure difference and geostrophic wind time series also showed that dynamic variaton on the gulf of alaska shelf was primarily responsible for current fluctuations in the pass hydrographic data indicated that a baroclinic current existed along the gulf of alaska coast and this flow became the long term mean flow through the pass we suggest that this feature was the extension of the kenai current the historic supposition that water is transported from the gulf of alaska into the bering sea was verified however the waters are of coastal origin rather than from the alaskan stream

circulation on the north central chukchi sea shelf abstract mooring and shipboard data collected between 1992 and 1995 delineate the circulation over the north central chukchi shelf previous studies indicated that pacific waters crossed the chukchi shelf through herald valley in the west and barrow canyon in the east we find a third branch through the central channel onto the outer shelf the central channel transport varies seasonally in phase with bering strait transport and is 0 2 sv on average although some of this might include water entrained from the outflow through herald valley a portion of the central channel outflow moves eastward and converges with the alaskan coastal current at the head of barrow canyon the remainder appears to continue northeastward over the central outer shelf toward the shelfbreak joined by outflow from herald valley the mean flow opposes the prevailing winds and is primarily forced by the sea level slope between the pacific and arctic oceans current variations are mainly wind forced but baroclinic forcing associated with upstream dense water formation in coastal polynyas might occasionally be important winter water mass modification depends crucially on the fall and winter winds which control seasonal ice development an extensive fall ice cover delays cooling limits new ice formation and results in little salinization in such years bering shelf waters cross the chukchi shelf with little modification in contrast extensive open water in fall leads to early and rapid cooling and if accompanied by vigorous ice production within coastal polynyas results in the production of high salinity 33 shelf waters such interannual variability likely affects slope processes and the transport of pacific waters into the arctic ocean interior

the contribution of alaskan siberian and canadian coastal polynyas to the cold halocline layer of the arctic ocean numerous arctic ocean circulation and geochemical studies suggest that ice growth in polynyas over the alaskan siberian and canadian continental shelves is a source of cold saline water which contributes to the maintenance of the arctic ocean halocline the purpose of this study is to estimate for the 1978 1987 winters the contributions of arctic coastal polynyas to the cold halocline layer of the arctic ocean the study uses a combination of satellite oceanographic and weather data to calculate the brine fluxes from the polynyas then an oceanic box model is used to calculate their contributions to the cold halocline layer of the arctic ocean this study complements and corrects a previous study of dense water production by coastal polynyas in the barents kara and laptev seas recurrent polynyas form on the canadian and alaskan coasts from banks island to the bering strait and on the siberian coast from the bering strait to the new siberian islands in the bering sea polynyas form in norton sound south and west of st lawrence island and in the gulf of anadyr two regions that account for almost 50 of the total dense water production are the siberian coastal polynyas in the adjacent regions of the gulf of anadyr and anadyr strait and the alaskan coastal polynyas which occur along the coast from cape lisburne to point barrow for all of the western arctic coastal regions examined the mean annual total brine flux is 0 5 0 2 sv combination of this flux with the contribution from the barents kara and laptev seas which is recalculated from data in the earlier study shows that over the entire arctic coastal polynyas generate about 0 7 1 2 sv of dense water this compares well with the theoretical estimates of 1 1 5 sv because an unknown fraction of the barents kara and laptev brine flux must go to the eurasian basin deep water the coastal polynyas alone cannot renew the halocline layer other potential brine generation mechanisms include overall freezing on the shelves and the response of the ice to infrequent violent storms for example during february 1982 an intense storm generated a large region of low ice concentration in the eastern chukchi sea over barrow canyon the refreezing of the region was followed by the flow of a dense plume down barrow canyon although the ocean dynamical response to this refreezing needs to be established the possible response of a barrow canyon flow to this refreezing event suggests that the overall refreezing in response to infrequent violent storms may be a potential source of the additional brine needed to maintain the arctic ocean halocline

geochemical profiles in the central arctic ocean their relation to freezing and shallow circulation temperature salinity nutrient tritium and oxygen isotope data collected during the lomonosov ridge experiment along a drift track between the makarov and fram basins over the lomonosov ridge are presented the relationship of these quantities to the processes that maintain the halocline in particular to the production of more saline waters by addition of brines formed during the freezing of seawater is described the results support the idea that the wide continental shelves of the arctic ocean play an important role in maintaining the halocline productivity and to the chemical and physical effects of freezing sea water a comparison of this ocean with its low productivity at least during winter with other oceanic regions should help to elucidate some of the effects of biological activity on marine chemistry for example trace metal cycling and speciation aagaard et al 1981 discussed the way in which the cold waters of the halocline which lie immediately below the surface mixed layer and extend to the top of the warm atlantic layer could be produced on the wide continental margins surrounding the arctic ocean the processes in volve freezing with release of highly saline brines having a temperature close to the freezing point of surface sea water this water flows over the shelves and into the central basin sinking then to the appropriate density surface the distribu tions of various chemical parameters will be affected in predictable ways by these processes as a part of the lomonosov ridge experiment lorex which ran from late march until the end of may 1979 a program was undertaken aimed at describing more accurate ly the hydrography of the central arctic ocean and studying the geochemistry of selected trace elements in this unusual environment to this end water samples were collected from a drifting ice station lorex satellite camp 1 for the measurement of salinity silicate phosphate 5 80 trace metals moore 1981 1983 carbon 14 tritium helium 3 caesium 137 caesium 134 strontium 90 plutonium ameri cium h d livingston et al manuscript in preparation 1983 alkalinity and ph ice cores were collected to investi gate the possibility of deducing the extent of temporal changes in the tritium content of the surface waters

influence of the st lawrence island polynya upon the bering sea benthos the influence of a polynya a persistent ice free region on water column production and subsequent transport to the shallow continental shelf benthos of the bering sea was evaluated by studying spatial patterns of organic material deposition benthic biomass community sediment metabolism benthic population structure and other potential indicators of enhanced organic carbon transport to benthic communities underlying the st lawrence island polynya despite suggestions that polynyas may be important localized centers of primary production in polar waters we found that the st lawrence island polynya does not obviously enhance the biomass of benthic communities directly below the polynya however southward flowing baroclinic currents generated as a result of brine injection at the polynya edge do appear to have an influence on the biomass and ecological structure of bering sea benthic communities south of st lawrence island these currents appear to affect mean sediment oxygen consumption surface organic carbon nitrogen ratios total organic content and bottom water ammonia by sweeping phytodetrital matter south and to the west of the island a particle reactive short lived natural radioisotope 7be used as an indicator of rapid days to weeks deposition of particulate material from the water column was detected only in surface sediments to the southwest of the island indicating enhancement of particle deposition to the southwest of the island finally the 18o content of tunicate cellulose was highest in the polynya region consistent with increased filter feeding in the late winter when the polynya is present and presumably promoting primary production in the open water the anadyr current consisting of nutrient rich deeper bering sea water that is upwelled onto the shelf in the gulf of anadyr flows west to east in the region south of st lawrence island throughout the year and is the major forcing function for high production in the region the interaction of anadyr water with the winter spring ephemeral polynya and associated baroclinic currents combine to positively influence benthic communities

distribution of atlantic and pacific waters in the upper arctic ocean implications for circulation the atlantic and pacific oceans provide source waters for the arctic ocean that can be distinguished by their differing nitrate and phosphate concentration relationships using these relationships we estimate the amount of atlantic and pacific waters in the surface layer top 30 m of the arctic ocean atlantic source water is dominant in most of the eurasian basin and is present in significant amounts in the makarov basin north of the east siberian sea pacific source water is dominant in most of the canadian basin and is present in significant amounts in the amundsen basin north of greenland we deduce circulation patterns from the distributions of atlantic and pacific source waters in the surface layer of the arctic ocean and conclude that the flow within the surface layer differs from ice drift along the north american and european boundaries of the polar basin

modification of no po and no po during flow across the bering and chukchi shelves implications for use as arctic water mass tracers the no and po tracers 9 no3 o2 and 135 po4 o2 respectively and their derivative no po have found increasing use in arctic water mass analyses for identifying the specific basin or shelf areas from which surface waters originate based upon assumed differences in pacific and atlantic derived content and basin to basin differences within the arctic following shipboard sampling in june september 1993 and may june 1994 both north and south of bering strait we have found evidence that pacific derived waters flowing north to bering strait do not necessarily have any unique no po or no po identity that would permit unequivocal use as a water mass tracer in particular no po ratios in the bering sea continental shelf 150 m waters varied from 0 7 to 1 1 which encompasses ratios previously reported for arctic continental shelf and atlantic origin waters in the arctic ocean the highest no po ratios 1 in the bering sea were observed to the southwest of st lawrence island close to where high nutrient waters are first upwelled onto the shelf and seasonally early in the biological production cycle by contrast later in the summer north of bering strait at the depth of the arctic ocean nutrient maximum the highest concentrations of silica 60 m were associated with low no po ratios 0 7 apparent increases in the proportions of sea ice melt in these waters inferred from 18o and salinity regressions were associated with lower no po ratios this pattern the potential for sea air exchange and a significant relationship between decreases in nitrate phosphate ratios and both no po ratios and silica concentrations indicate that biological and physical processes north and south of bering strait affect the fidelity of these nutrient based tracers these results indicate the need for consideration of shelf based processes before no po ratios and other nutrient based tracers can be successfully applied as arctic circulation tracers

freshwater composition of the waters off southeast greenland and their link to the arctic ocean 1 the freshwater composition of waters on the southeast greenland shelf and slope are described using a set of high resolution transects occupied in summer 2004 which included hydrographic velocity nutrient and chemical tracer measurements the nutrient and tracer data are used to quantify the fractions of pacific water sea ice melt and meteoric water present in the upper layers of the east greenland current egc and east greenland coastal current egcc the egc egcc system dominates the circulation of this region and strongly influences the observed distribution of the three freshwater types sea ice melt and meteoric water fractions are surface intensified reflecting their sources and generally increase southward from denmark strait to cape farewell as well as shoreward significant fractions of pacific water are found in the subsurface layers of the egcc supporting the idea that this inner shelf branch is directly linked to the egc and thus to the arctic ocean a set of historical sections is examined to investigate the variability of pacific water content in the egc and egcc from 1984 to 2004 in the vicinity of denmark strait the fraction of pacific water increased substantially in the late 1990s and subsequently declined to low levels in 2002 and 2004 mirroring the reduction in pacific water content reported previously at fram strait this variability is found to correlate significantly with the arctic oscillation index lagged by 9 years suggesting that the arctic ocean circulation patterns bring varying amounts of pacific water to the north atlantic via the egc egcc

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

estimation of sea ice production in the bering sea from amsr e and amsr2 data with special emphasis on the anadyr polynya

age characteristics of a shelf break eddy in the western arctic and implications for shelf basin exchange 1 radioisotope evaluation of a cold core anticyclonic eddy surveyed in september 2004 on the chukchi sea continental slope was used to determine its age since formation over the shelf environment because the eddy can be shown to have been generated near the shelf break initial conditions for several age dependent tracers could be relatively well constrained a combination of 228ra 226ra excess 224ra and 228th 228ra suggested an age on the order of months this age is consistent with the presence of elevated concentrations of nutrients organic carbon suspended particles and shelf derived neritic zooplankton within the eddy compared to ambient offshore water in the canada basin but comparable to values measured in the chukchi shelf and shelf break environment hence this feature at the edge of the deep basin was poised to deliver biogeochemically significant shelf material to the central arctic ocean

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

late spring nitrate distributions beneath the ice covered northeastern chukchi shelf measurements of late springtime nutrient concentrations in arctic waters are relatively rare due to the extensive sea ice cover that makes sampling difficult during the subice cruise in may june 2014 an extensive survey of hydrography and pre bloom concentrations of inorganic macronutrients oxygen particulate organic carbon and nitrogen and chlorophyll a was conducted in the northeastern chukchi sea cold 1 5 c winter water was prevalent throughout the study area and the water column was weakly stratified nitrate no3 concentration averaged 12 6 1 92 m in surface waters and 14 0 1 91 m near the bottom and was significantly correlated with salinity the highest no3 concentrations were associated with winter water within the central channel flow path no3 concentrations were much reduced near the northern shelfbreak within the upper halocline waters of the canada basin and along the eastern side of the shelf near the alaskan coast net community production ncp estimated as the difference in depth integrated no3 content between spring this study and summer historical varied from 28 38 g c m 2 a 1 this is much lower than previous ncp estimates that used no3 concentrations from the southeastern bering sea as a baseline these results demonstrate the importance of using profiles of no3 measured as close to the beginning of the spring bloom as possible when estimating local ncp they also show that once the snow melts in spring increased light transmission through the sea ice to the waters below the ice could fuel large phytoplankton blooms over a much wider area than previously known

phytoplankton blooms beneath the sea ice in the chukchi sea in the arctic ocean phytoplankton blooms on continental shelves are often limited by light availability and are therefore thought to be restricted to waters free of sea ice during july 2011 in the chukchi sea a large phytoplankton bloom was observed beneath fully consolidated pack ice and extended from the ice edge to 4100 km into the pack the bloom was composed primarily of diatoms with biomass reaching 1291 mg chlorophyll a m 2 and rates of carbon fixation as high as 3 7 g c m 2 d 1 although the sea ice where the bloom was observed was near 100 concentration and 0 8 1 2 m thick 30 40 of its surface was covered by melt ponds that transmitted 4 fold more light than adjacent areas of bare ice providing sufficient light for phytoplankton to bloom phytoplankton growth rates associated with the under ice bloom averaged 0 9 d 1

on the processes controlling shelf basin exchange and outer shelf dynamics in the bering sea abstract we use a 9 km pan arctic ice ocean model to better understand the circulation and exchanges in the bering sea particularly near the shelf break this region has historically been undersampled for physical chemical and biological properties very little is known about how water from the deep basin reaches the large shallow bering sea shelf to address this we examine here the relationship between the bering slope current and exchange across the shelf break and resulting mass and property fluxes onto the shelf this understanding is critical to gain insight into the effects that the bering sea has on the arctic ocean especially in regard to recent indications of a warming climate in this region the bering sea shelf break region is characterized by the northwestward flowing bering slope current previously it was thought that once this current neared the siberian coast a portion of it made a sharp turn northward and encircled the gulf of anadyr in an anticyclonic fashion our model results indicate a significantly different circulation scheme whereby water from the deep basin is periodically moved northward onto the shelf by mesoscale processes along the shelf break canyons along the shelf break appear to be more prone to eddy activity and therefore are associated with higher rates of on shelf transport the horizontal resolution configured in this model now allows for the representation of eddies with diameters greater than 36 km however we are unable to resolve the smaller eddies

freshwater budget of the canada basin arctic ocean from salinity δ18o and nutrients 1 the contribution of freshwater components e g meteoric sea ice and pacific water in the canada basin is quantified using salinity 18o and nutrient data collected in 2003 and 2004 the penetration depth of sea ice meltwater is limited to the upper 30 m and brine rejected during sea ice formation is observed from 30 to 250 m depth the fraction of meteoric water is high in the upper 50 m and decreases with depth pacific water entering via bering strait is the main source of freshwater below 50 m depth bering strait throughflow which transports pacific water with salinity 32 5 together with meteoric water supplied upstream of the bering strait contributes up to 75 of freshwater input 3200 km3 a 1 to the canada basin the mean residence time of pacific water in the canada basin is estimated to be 11 years precipitation and river runoff from both north american and eurasian continents add 800 km3 a 1 and sea ice formation removes 900 km3 a 1 0 6 m a 1 of fresh water the export of ice and liquid fresh water from the canada basin contributes 40 of the freshwater flux from the arctic ocean to the north atlantic ocean

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

stable isotope profiles of last interglacial pelukian transgression mollusks and paleoclimate implications in the bering strait region abstract the marine paleoclimate during the last interglaciation in the bering strait region is inferred from the stable oxygen and carbon isotope profiles of fossil bivalve mollusks specimens were collected from the marine highstand deposits of the pelukian transgression from the arctic alaskan coastal plain the nome coastal plain st lawrence island and the val katlen suite on the chukotka peninsula as a calibration modern mollusks were obtained from the major water masses in the bering chukchi seas system and from coastal environments near the fossil localities the 18 o composition of the modern mollusks accurately reflects the seawater 18 o differences among the water masses and the ambient temperature range at each site seasonal paleotemperature ranges are estimated from the 18 o profiles of the fossils by comparison with those of the modern specimens a simple model is developed to correct the paleotemperature ranges for the influence of differences in seawater 18 o between water masses and seasonal variations caused by freshwater discharge paleotemperatures calculated for the skull cliff site alaskan arctic coastal plain are close to but slightly cooler than those of modern specimens from peard bay and icy cape the isotopic composition of a pelukian specimen collected near wainwright shows the obvious influence of locally reduced salinities with a correction for lower seawater 18 o this profile yields a summer temperature of 13 c which is 3 c warmer than that from the modern icy cape specimen the isotope records of two specimens from the nome coastal plain suggest salinities that were 3 5 psu lower than the modern eastern bering shelf the paleotemperature range of 0 15 c is consistent with modern conditions in norton sound the character of the isotope profiles of the pelukian specimens from st lawrence island is very different than that of modern specimens near the island but matches the 18 o values of shells from deeper sites in anadyr water this suggests that the fossil mollusks were living in anadyr strait and were transported by a glacial advance from the chukotka peninsula the last interglacial specimens from the val katlen suite have isotope profiles with large seasonal 18 o ranges and the clear influence of a reduced salinity coastal water mass calculated paleotemperatures from the val katlen specimens range from 0 to 13 c differences in the 13 c of shell carbonate between sites appears to reflect the regional distribution of the 13 c of sedimentary organic matter som which is a mixture between terrestrial organic matter mean 13 c of 24 and marine phytoplankton 21 partitioning of 13 c between shallow and deep waters by phytoplankton productivity and remineralization may also affect the regional distribution differences in shell 13 c between taxa may relate to feeding mode and the type and isotopic composition of ingested particles the filter feeders mya and astarte typically have 13 c values 1 2 more positive than the deposit feeders macoma and serripes this effect is attributed to a 13 c difference between marine phytoplankton and som with a component of terrestrial organic carbon

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

composition and modification of water masses in the mackenzie shelf estuary the distributions of 18o salinity temperature and nutrients have been used to quantify water sources to the mackenzie shelf in the beaufort sea comparison of water mass analyses with satellite imagery confirms that the meteoric runoff water is associated with the mackenzie plume the seasonally variable surface layer for the shelf is viewed as cycling between a reverse estuary in winter when the polar mixed layer pml is formed and a positive estuary in summer when the shelf waters respond to freshwater inputs runoff and ice melt we infer a standing stock of 3 7 m fresh water at the end of summer 1986 of which 30 owes its origin to the melting of sea ice our data coupled with river flow imply a freshwater flushing time for the mackenzie shelf at about 150 days to re form the pml during winter requires the removal of this seasonal fresh water through the combined processes of flushing and ice formation once this fresh water has been removed continued ice growth can produce new brine which would be observed as a deeper and saltier pml from the previous year a simple geochemical model shows that autumn conditions freshwater accumulation and the rate of flushing are important controls on the potential of the shelf to produce new brine and that winter runoff were it to distribute evenly across the shelf is sufficient to inhibit brine production

oxygen isotopic composition of bottom seawater and tunicate cellulose used as indicators of water masses in the northern bering and chukchi seas oxygen isotopic composition of bottom seawater and tunicate cellulose were used as short term and long term indicators respectively of water mass characteristics in the northern bering and chukchi seas oxygen isotopic composition of northeastern bering sea waters is influenced by yukon river inflows of sup 18 o depleted continental water mixing with relatively sup 18 o enriched waters contributed by the anadyr current tunicate cellulose sampled under alaska coastal water is more depleted in sup 18 o than that collected under bering shelf and anadyr waters which reflects the oxygen isotopic composition of these waters tunicate cellulose collected under the mixed bering shelf water displays intermediate delta sup 18 o values oxygen isotopic analyses of bottom seawater were used to determine the spatial location and influence of continental and coastal derived precipitation and of sea ice formation on water mass structure on the continental shelf of the northern bering and chukchi seas results indicate that the oxygen isotopic composition of tunicate cellulose averaged over multiple seasons may serve as a long term biochemical indicator of water mass patterns in ice covered polar regions where continuous sampling is impractical

processes of multibathyal aragonite undersaturation in the arctic ocean during three years of study 2010 2012 the western arctic ocean was found to have unique aragonite saturation profiles with up to three distinct aragonite undersaturation zones this complexity is produced as inflow of atlantic and pacific derived water masses mix with arctic derived waters which are further modified by physiochemical and biological processes the shallowest aragonite undersaturation zone from the surface to 30 m depth is characterized by relatively low alkalinity and other dissolved ions besides local influence of biological processes on aragonite undersaturation of shallow coastal waters the nature of this zone is consistent with dilution by sea ice melt and invasion of anthropogenic co2 from the atmosphere a second undersaturated zone at 90 220 m depth salinity 31 8 35 4 occurs within the arctic halocline and is characterized by elevated pco2 and nutrients the nature of this horizon is consistent with remineralization of organic matter on shallow continental shelves bordering the canada basin and the input of the nutrients and co2 entrained by currents from the pacific inlet finally the deepest aragonite undersaturation zone is at greater than 2000 m depth and is controlled by similar processes as deep aragonite saturation horizons in the atlantic and pacific oceans the comparatively shallow depth of this deepest aragonite saturation horizon in the arctic is maintained by relatively low temperatures and stable chemical composition understanding the mechanisms controlling the distribution of these aragonite undersaturation zones and the timescales over which they operate will be crucial to refine predictive models this article is protected by copyright all rights reserved

spatial and temporal variability of air sea co2 exchange of alongshore waters in summer near barrow alaska alongshore water off barrow alaska is a useful area for studying the carbon cycle of the arctic coastal sea because the different coastal characteristics extant in the area likely represent much larger regions of the coastal water of the western arctic ocean especially noteworthy is the inflow shelf water transferred northward by the arctic coastal current into the chukchi sea from the north pacific and turbid water in the elson lagoon where a significant amount of coastal erosion has been reported along the extensive coastal line and where a part of the water from the lagoon drains into the beaufort sea adjacent to the chukchi sea to investigate spatial and temporal variations of air sea co2 flux co2 flux of the alongshore water partial pressure of co2 of surface seawater pco2sw was measured in summer 2007 and 2008 and co2 flux was directly measured by eddy covariance at a fixed point for the beaufort sea in summer 2008 measured pco2sw in the chukchi sea side was the lowest in the beginning of the measurement season and increased later in the season both in 2007 and 2008 the average co2 flux estimated based on pco2sw in the chukchi sea side was 0 10 mmol m 2 s 1 0 1 s d using the sign convention of positive fluxes into the atmosphere from the ocean pco2sw in the beaufort sea and the elson lagoon was relatively higher in early summer and decreased in the middle of the summer the overall average co2 flux was 0 07 mmol m 2 s 1 0 1 s d for the beaufort sea side and 0 03 mmol m 2 s 1 0 07 s d for the elson lagoon respectively indicating a sink of co2 despite high carbon inflows from the terrestrial margin into the elson lagoon a strong sink of co2 was often observed from the beaufort sea by eddy covariance in the middle of the summer this sink activity in the middle summer in the beaufort sea and elson lagoon was likely due to biological carbon uptake as inferred by low apparent oxygen utilization and high chlorophyll concentration that offset a potential source of co2 due to terrestrial carbon inputs

sources of dissolved inorganic carbon to the canada basin halocline a multitracer study we examine the dissolved inorganic carbon maximum in the canada basin halocline using a suite of geochemical tracers to gain insight into the factors that contribute to the persistence of this feature hydrographic and geochemical samples were collected in the upper 500 m of the southwestern canada basin water column in the summer of 2008 and fall of 2009 these observations were used to identify conservative and nonconservative processes that contribute dissolved inorganic carbon to halocline source waters including shelf sediment organic matter remineralization air sea gas exchange and sea ice brine export our results indicate that the remineralization of organic matter that occurs along the bering and chukchi sea shelves is the overwhelming contributor of dissolved inorganic carbon to pacific winter water that occupies the middle halocline in the southwestern canada basin nonconservative contributions from air sea exchange and sea ice brine are not significant the broad salinity range associated with the dic maximum compared to the narrow salinity range of the nutrient maximum is due to mixing between pacific and atlantic water and not abiotic addition of dic

linkages among runoff dissolved organic carbon and the stable oxygen isotope composition of seawater and other water mass indicators in the arctic ocean 1 flow weighted dissolved organic carbon doc concentrations and 18o values were determined from major arctic rivers specifically the ob yenisey lena kolyma mackenzie and yukon during 2003 2004 these data were considered in conjunction with marine data for doc 18o values nutrients salinity and fluorometric indicators of doc obtained during sampling at the shelf basin boundary of the chukchi and beaufort seas on the basis of these data freshwater in the sampled marine waters is likely derived from regional sources such as the mackenzie the bering strait inflow and possibly eastern siberian rivers including the kolyma or the lena but not rivers farther west in the eurasian arctic freshwater from melted sea ice is insignificant over annual cycles although melted sea ice was a locally dominant freshwater component following summer sea ice retreat in 2002 doc concentrations were correlated with the runoff fraction with an apparent meteoric water doc concentration of 174 1 m this is lower than the flow weighted concentrations measured at river mouths of the five largest arctic rivers 358 to 917 m indicating removal of doc during transport through estuaries shelves and in the deep basin flow weighted doc concentrations in the two largest north american arctic rivers the yukon 625 m and the mackenzie 358 m are lower than in the three largest eurasian arctic rivers the ob 825 m the yenesey 858 m and the lena 917 m a fluorometer responding to chromophoric dissolved organic matter cdom was not correlated with doc concentrations in pacific influenced surface waters unlike previous observations in the atlantic layer nutrient distributions concentrations and derived ratios suggest the cdom fluorometer may be responding to the release of chromophoric materials from shelf sediments shipboard incubations of undisturbed sediment cores indicate that sediments on the bering and chukchi sea shelves are a net source of doc to the arctic ocean

composition and fluxes of freshwater through davis strait using multiple chemical tracers 1 freshwater transport through davis strait can supply additional buoyancy to the deep convection region of the labrador sea which influences the strength of the meridional overturning circulation and consequently the global climate the freshwater contribution from local sea ice meltwater meteoric water fluvial glaciofluvial and precipitation and the arctic outflow were quantified using oxygen isotope composition 18o salinity and nutrient relationships in september october 2004 freshwater transported by the arctic outflow was isolated using a modified nutrient relationship method and further deconvoluted into sea ice meltwater meteoric water and pacific water for the first time fluxes of individual freshwater components were estimated using observations of the velocity field derived from mooring arrays and geostrophic currents from hydrography the arctic outflow dominated in western davis strait 60 and its influence extended eastward close to the greenland slope the sea ice meltwater fraction was small 6 and attributed to glacial meltwater the freshwater inventory of the 0 100 m layer was equivalent to 7 4 m in western davis strait 8 m from the arctic outflow and 0 6 m from brine rejection in eastern davis strait the freshwater inventory was 4 m 3 m from meteoric water and 1 m from sea ice meltwater the arctic outflow contributed 82 99 msv to the southward freshwater transport about 67 81 of the total glacial meltwater contributed the largest northward transport of 10 30 msv

circulation of summer pacific halocline water in the arctic ocean 1 we present an analysis of arctic ocean hydrographic and sea ice observations from the 1990s with a focus on the circulation of water that originates in the north pacific ocean previous studies have shown the presence of two varieties of relatively warm summer halocline water in the vicinity of the chukchi sea i e the relatively fresh alaskan coastal water acw and the relatively saltier summer bering sea water sbsw here we extend these studies by tracing the circulation of these waters downstream into the arctic ocean we find that acw is generally most evident in the southern beaufort gyre while sbsw is strongest in the northern portion of the beaufort gyre and along the transpolar drift stream we find that this separation is most extreme during the early mid 1990s when the arctic oscillation was at historically high index values this leads us to speculate that the outflow to the north atlantic ocean through the canadian archipelago and fram strait may be similarly separated as arctic oscillation index values fell during the later 1990s acw and sbsw began to overlap in their regions of influence these changes are evident in the area north of ellesmere island where the influence of sbsw is highly correlated with a 3 year lag with the arctic oscillation index we also note the presence of winter bering sea water wbsw which underlies the summer varieties all together this brings the number of distinct pacific water types in our arctic ocean inventory to three acw sbsw and wbsw

ocean circulation and exchanges through the northern bering sea 1979 2001 model results abstract we have developed and run a model with sufficiently high resolution 9 km and 45 levels and a large enough spatial domain to allow for realistic representation of flow through the narrow and shallow straits in the northern bering sea this is potentially important for quantification of long term mean and time dependent ocean circulation and water mass and property exchanges between the pacific and arctic oceans over a 23 year interval 1979 2001 mean transport through bering strait is estimated to be 0 65 sv comparison of our model results with published observations indicates that ocean circulation is not only variable at seasonal to interdecadal scales but it is also responsive to short term atmospheric forcing one of such events occurred during the winter of 2000 2001 with reversed oceanic flow in some areas and much reduced sea ice cover analyses of eddy kinetic energy fields identify some high biological productivity regions of the chirikov basin coincident with persistent high energy up to 2700 cm 2 s 2 in the surface layer and up to 2600 cm 2 s 2 at mid depth throughout the annual cycle model output in the bering strait region is validated against several time series of moored observations of water mass properties comparison with shipboard observations of near bottom salinity from late winter through autumn indicates that the model reasonably represents the major water mass properties in the region the modeled vertical water column structure in the northern bering sea allows increased understanding of the mechanisms of water transformation and transport northward through bering strait into the chukchi and beaufort seas we conclude that the long term model results for the northern bering sea provide important insights into the ocean circulation and fluxes and they are a useful frame of reference for limited observations that are short term and or cover only a small geographic region

glacial meltwater input to the alaska coastal current evidence from oxygen isotope measurements results of a study of the oxygen isotopic composition of coastal pelagic and fresh waters from the northern gulf of alaska region are presented this study was undertaken to investigate whether isotopic tracers could be of use in determining the important freshwater inputs to the alaska coastal current acc and whether they could confirm the presence of the acc in coastal waters west of kodiak island the alaska coastal current the major coastal circulation feature of the northern gulf of alaska can be distinguished from oceanic waters on the basis of its lower salinity at least as far west as kodiak island this study adds significantly to the small amount of oxygen isotopic information available for the waters of this region the isotopic results suggest that in late summer glacial meltwater may provide a substantial portion of the total freshwater runoff into the acc and that the acc does extend as far to the west as unimak pass

use of ammonium and other nitrogen tracers to investigate the spreading of shelf waters in the western arctic halocline 1 the contribution of nutrient regeneration in summer to the nutrient maximum associated with bering sea winter water bsww is estimated from the ammonium data which was obtained in the outer shelf region of the chukchi sea for the first time by the r v mirai in 2002 the contribution rate reaches 20 30 which is larger than the rate studied earlier inside the chukchi shelf such bsww influenced by the regeneration spreads to the chukchi shelf slope up to the isobath of 3000 m however was not found in the canada basin the ammonium and a nitrogen deficit are also useful tracers to study the spreading of shelf waters that are less saline than bsww in the canada basin a small amount of ammonium 2 m was observed east of the northwind ridge this small amount of ammonium would be associated with the spreading of eastern chukchi summer water via the barrow canyon around the chukchi borderland a prominent nitrogen deficit layer was found it would be accompanied by western chukchi summer water via the hope valley herald valley channel the water flows into the chukchi abyssal plain and then spreads eastward to the west of the northwind ridge with the decrease of nitrogen deficit signal

impact of an unusually large warm core eddy on distributions of nutrients and phytoplankton in the southwestern canada basin during late summer early fall 2010 1 recent freshening of the arctic ocean due to melting of sea ice and enhanced ekman pumping has deepened the nutricline over the canada basin and reduced nutrient concentrations in the euphotic zone cold core eddies frequently transport nutrient rich shelf water to the canada basin but the eddies are much deeper than the euphotic zone because warm core eddies appear near the surface or at a depth range shallower than that of the cold core eddies they may play a crucial role in determining nutrient distributions in the euphotic zone and hence may affect primary production during late summer early fall 2010 we conducted detailed surveys of a warm core eddy which was unusually large 100 km in diameter we suggest that this warm core eddy which contained high ammonium shelf water could supply ammonium to the euphotic zone in the southwestern canada basin and may sustain 30 higher biomass of picophytoplankton 2 m than that in the surrounding water in the basin the role of warm core eddies in supplying nutrients to the euphotic zone and controlling phytoplankton distributions seems to be more important than previously because the recent deepening of the nutricline in the canada basin has decreased the nutrient supply to the euphotic zone

variability in the meteoric water sea ice melt and pacific water contributions to the central arctic ocean 2000 2014 fourteen years 2000 2014 of bottle chemistry data collected during the north pole environmental observatory were compiled to examine variations in the composition of freshwater meteoric water net sea ice meltwater and pacific water over mixed layer of the central arctic ocean in addition to significant spatial and interannual variability there was a general decrease in meteoric water mw fractions at the majority of stations reoccupied over the duration of the program that was approximately balanced by a concomitant increase in freshwater from sea ice melt sim fw between 2000 and 2012 inventories 0 120 m of mw and sim fw computed using available data between 2005 and 2012 exhibited similar variations over the study area allowing for first order estimates of the mean annual changes in mw 389 194 km3 yr 1 and sim fw 292 97 km3 yr 1 for the central arctic region these mean annual changes were attributed to the diversion of siberian river runoff to the beaufort gyre and the overall reduction of sea ice volume across the arctic respectively in addition to this lower frequency variability spatial gradients and interannual variations in mw sim fw and pacific water contributions to specific locations were attributed to shifts in the transpolar drift that advects waters of eastern and western arctic origin through the study area

effects of a shelf polynya on flow and water properties in the northern bering sea we present long term 230 day measurements from three moorings in the vicinity of saint lawrence island on the northern bering sea shelf one mooring was deployed near the polynya which often exists south of the island these data confirm the existence of strong 0 15 m s 1 flow toward bering strait northwest of the island in anadyr strait and suggest that regional circulation results in a moderate 0 03 5 m s 1 mean flow eastward along the southern coast of saint lawrence island coherent variations in the regional circulation and variations in the geostrophic wind account for much of the low frequency current fluctuation south of saint lawrence island however there were 11 events when offshore northerly winds coincided with the temperature following the freezing point increasing salinity and reversal of the current this suggests that ice formation and the ensuing brine rejection affect flow in the vicinity of the polynya scaling of a simplified momentum equation indicates that the cross shelf density gradient was a possible mechanism for some of the reversals salinity data show a seasonal cycle as well as individual events of brine rejection during an average event time of 65 hours the salinity increased by 8 10 3 g kg 1 h 1 the heat flux can be estimated as 535 wm 2 these fluxes correspond to an ice production of 5 m during winter 1981 extrapolation of our results and comparison with the freshwater cycle suggest that brine rejection is an important component of the regional salt budget

linkages between sea ice coverage pelagic benthic coupling and the distribution of spectacled eiders observations in march 2008 2009 and 2010 northern bering sea icebreaker based sampling in the northern bering sea south of st lawrence island in march of 2008 2009 and 2010 has provided new data on overall ecosystem function early in the annual productive cycle while water column chlorophyll concentrations 5 m these data together with other physical biological and nutrient data are presented here in conjunction with observed sea ice dynamics and the distribution of an apex predator the spectacled eider somateria fischeri sea ice dynamics in addition to benthic food availability as determined by sedimentation processes play a role in the distribution of spectacled eiders which cannot always access the greatest biomass of their preferred bivalve prey overall the data and observations indicate that the northern bering sea is biologically active in late winter but with strong atmospheric and hydrographic controls these controls pre determine nutrient and chlorophyll distributions water column mixing as well as pelagic benthic coupling

seasonal variability of water mass distribution in the southeastern beaufort sea determined by total alkalinity and δ18o 1 we examined the seasonal variability of water mass distributions in the southeastern beaufort sea from data collected between september 2003 and august 2004 salinity total alkalinity ta and isotopic composition 18o of seawater were used together as tracers of freshwater input i e meteoric water and sea ice meltwater we used an optimum multiparameter analysis to identify the different water masses including the mackenzie river sea ice melt sim winter polar mixed layer pml upper halocline water uhw with core salinity of 33 1 psu pacific origin and atlantic water computed values of co2 fugacity in seawater fco2 sw show that the surface mixed layer sml remains mostly undersaturated 328 55 atm n 552 with respect to the average atmospheric co2 concentration 380 5 atm over the study period the influence of the mackenzie river fco2 sw 500 atm was relatively small in the southeastern beaufort sea and significant fractions were only observed on the inner mackenzie shelf the contribution of sea ice melt fco2 sw 600 atm was usually located between 120 and 180 m depth but could contribute to the sml during wind driven upwelling events in summer and autumn and during brine driven eddies in winter

circulation dense water formation and outflow on the northeast chukchi shelf we investigated circulation and water mass modification processes in the chukchi sea using 1 temperature salinity and velocity data collected between september 1991 and september 1992 from moorings in bering strait and the northeast shelf and 2 meteorological data and ice concentrations derived from special sensor microwave imager ssm i imagery in october 1991 and from february to august 1992 the mean monthly circulation was steady and northward from november to january strong northeast winds diverted the low salinity bering inflow onto the western shelf and weakened and reversed flow over the northeast shelf the winds also opened extensive polynyas wherein cold hypersaline salinity 34 waters formed the fall winter circulation enhanced dense water formation by diverting low salinity waters away from and prolonging the residence time of water within the polynyas alongshore convergence of the coastal flow swept some of the cold hypersaline water offshore across isobaths but the coastal current carried most of it into the arctic ocean through barrow canyon the dense outflow mixed little during its descent through the upper canyon where bottom friction and rotation but not entrainment were important in the plume momentum balance if the outflow is not diluted by mixing in the lower canyon where theory suggests this will occur then the densest shelf waters can ventilate layers deeper than the halocline salt rejection estimates using ssm i data and surface heat budget calculations agree within a factor of 2 with independent estimates from the mooring hence remote sensing techniques can monitor winter salt rejection rates in the chukchi sea

seasonal discharge of estuarine freshwater to the western chukchi sea shelf identified in stable isotope profiles of mollusk shells 1 oxygen and carbon isotope profiles of bivalve mollusks serripes groenlandicus and macoma calcarea record distinct changes of water mass properties in the bering strait region associated with the seasonal discharge of estuarine freshwater from kolyuchin bay into the western chukchi sea cycles in the 18o profiles are correlated with shell growth bands and interpreted as annual maximum 18o values corresponding to coldest water temperatures coincide with dark internal bands in the shell that mark slower growth during winter a 0 5 offset between the baseline winter 18o values of two specimens hx68 and hx65 at different distances from the estuarine discharge is attributed to a difference in seawater 18o between the two sites and indicates that the influence of the estuarine water persists through much of the year the isotope profiles of specimen ak55 collected north of bering strait in the chukchi sea reflect the bering shelf anadyr water flowing from south of bering strait comparison of the 13c profiles shows that hx68 collected closer to kolyuchin bay has high amplitude negative 13c excursions associated with incorporation of dissolved inorganic carbon that is isotopically depleted in 13c probably from terrestrial runoff the significant positive correlation between 18o and 13c values in these specimens suggests that the properties of the ambient water masses are reflected in the stable isotope profiles these results show that the stable isotope profiles of mollusk shells can serve as proxy indicators of water mass properties particularly during runoff events in arctic coastal regions that are logistically difficult to sample directly

composition of freshwater in the spring of 2014 on the southern labrador shelf and slope the labrador current is an important conduit of freshwater from the arctic to the interior north atlantic subpolar gyre here we investigate the spatial variability of the freshwater sources over the southern labrador shelf and slope during may june 2014 using measurements of seawater properties such as temperature salinity nutrients and oxygen isotopic composition we estimate the respective contributions of saline water of atlantic and pacific origins of brines released during sea ice formation and of freshwater from sea ice melt and meteoric water origins on the southern labrador shelf we find a large brine signal and pacific water influence indicating a large contribution of water from the canadian arctic the brine signal implies that more than 4 m of sea ice formed upstream either in the arctic or in baffin bay and the northern labrador sea over the midshelf and slope at 52 n we find a stronger influence of slope water from the west greenland current with a smaller contribution of pacific water and no brine signal thus there is advection of water from the slope region to the midshelf between 55 n and 52 n very freshwater with high meteoric content is found close to the coast in june 2014 observations from 1995 and 2008 suggest a higher fraction of brine and pacific water on the shelf compared to that observed in 2014

strong hydrographic controls on spatial and seasonal variability of dissolved organic carbon in the chukchi sea abstract a detailed analysis of dissolved organic carbon doc distribution in the western arctic ocean was performed during the spring and summer of 2002 and the summer of 2003 doc concentrations were compared between the three cruises and with previously reported arctic work concentrations of doc were highest in the surface water where they also showed the highest degree of variability spatially seasonally and annually over the canada basin doc concentrations in the main water masses were 1 surface layer 71 4 m ranging from 50 to 90 m 2 bering sea winter water 66 2 m ranging from 58 to 75 m 3 halocline layer 63 3 m ranging from 59 to 68 m 4 atlantic layer 53 2 m ranging from 48 to 57 m and 5 deep arctic layer 47 1 m ranging from 45 to 50 m in the upper 200 m doc concentrations were correlated with salinity with higher doc concentrations present in less saline waters this correlation indicates the strong influence that fluvial input from the mackenzie and yukon rivers had on the doc system in the upper layer of the chukchi sea and bering strait over the deep basin there appeared to be a relationship between doc in the upper 10 m and the degree of sea ice melt water present we found that sea ice melt water dilutes the doc signal in the surface waters which is contrary to studies conducted in the central arctic ocean

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

transit time of river water in the bering and chukchi seas estimated from δ 18 o and radium isotopes abstract seawater samples for the measurements of 226ra 228ra and stable oxygen isotope 18o were collected from the bering and chukchi seas in the summer of 2014 the fractions of meteoric water fmw and sea ice melted water fsim were estimated based on the mass balance of salinity and 18o with a three end member mixing model our results showed that the average fmw increased northward from the bering basin to the canada basin while the fsim distributed homogeneously the lowest fmw and 228ra 226ra a r values were found in the upper bering basin with little terrestrial input the highest fmw but low 228ra 226ra a r appeared in the northern chukchi sea and the canada basin ascribing to the current driven accumulation of freshwater and its long residence time more abundant sea ice melted water was found on the pack ice edge indicating the trap of earlier melted waters by the ice pack based upon the linear relationships between 228ra 226ra a r and fmw in the bering shelf and the chukchi shelf the transit time for the pacific inflow was constrained the transit time of river water from the bering shelf to the chukchi shelf was estimated as 0 2 4 4 years with an average of 1 6 1 5 years while that from the chukchi shelf to the canada basin was 10 2 13 2 years with an average of 11 8 1 1 years the spatial variation of the transit time was mainly affected by the current intensity our study highlights the importance of in depth evaluation for the subarctic arctic exchange