features of coastal current instabilities in the north sea results of a numerical model coastal currents that are forced by buoyancy discharges from rivers often show a tendency to become unstable under certain conditions two such coastal current systems in the north sea the german bight and the skagerrak and their instabilities are investigated and compared here with the help of a fully nonlinear three dimensional baroclinic circulation model differences between the two regions were found with respect to three main aspects first in the skagerrak instabilities contribute to the kinetic energy on a scale that is comparable to the mean kinetic energy this does not hold for the german bight second of the two forms of instabilities fed by baroclinic and barotropic energy conversion in the skagerrak barotropic conversion is as important as baroclinic instability while in the german bight baroclinic conversion clearly dominates finally in the german bight instability tends to occur only if supported by wind in a direction that helps establishing a steep front against strong tidal mixing one explanation for the distinction in the features of the two regions is the water depth german bight is 40 m skagerrak is 300 m and consequently the amount of tidal mixing applied to the near surface coastal current front several deep and shallow water coastal currents outside the north sea are found to exhibit features similar to those presented for the skagerrak and german bight

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

circulation phenomena and frontal dynamics of the norwegian coastal current after a short general description of the norwegian coastal current some recent investigations concerning its variability are reviewed the variability caused by meteorological effects and fresh water fluxes is shown to be the dominant feature the coastal current not only responds to local wind forcing but is also a signal channel of sea level variations in the north sea as a whole the variability at times manifests itself as mesoscale waves and eddies the subsurface frontal region is characterized by interleaving of coastal and atlantic water and strong mixing lateral and longitudinal frontal motions are dealt with in relation to plumes of brackish water from the fjords and outbreaks of brackish and or warm water masses from the skagerrak the inflow of atlantic water through the norwegian trench and the formation of deep and bottom water in skagerrak are discussed

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

air sea co2 fluxes and the continental shelf pump of carbon in the chukchi sea adjacent to the arctic ocean the chukchi sea a shallow sea ice covered coastal sea adjacent to the arctic ocean exhibits an intense bloom of phytoplankton each year due to the exposure of nutrient laden surface waters during the brief summertime retreat and melting of sea ice the impact of phytoplankton production and other factors on the seasonal dynamics of carbon and air sea co2 fluxes were investigated during two survey cruises 5 may 15 june 2002 and 17 july 26 august 2002 as part of the western arctic shelf basins interactions sbi project in springtime most of the chukchi sea was sea ice covered 95 and remnant winter water was present across the shelf surface layer seawater partial pressure of co2 pco2 ranged from 200 320 atm indicative of undersaturation with respect to atmospheric pco2 although sea ice cover kept rates of air to sea co2 flux generally low 80 air to sea co2 fluxes remained generally low 2 mmoles co2 m 2 d 1 seasonal i e may to september and annual net air to sea co2 fluxes from the chukchi sea shelf were estimated at 27 7 tg c yr 1 and 38 7 tg c yr 1 respectively the chukchi sea represents the largest oceanic co2 sink in the marginal coastal seas adjacent to the arctic ocean an active continental shelf pump of carbon driven by the northward transport of nutrient rich water of pacific ocean origin high rates of primary and net community production during the sea ice free period and lateral export of organic carbon maintains the chukchi sea shelf and slope as a perennial ocean co2 sink

hydrographic conditions during the 2002 sbi process experiments abstract a review of the hydrographic data from the 2002 western arctic shelf basin interactions sbi process cruises permits the following conclusions 1 temperature salinity relationships were similar to canonical descriptions but at five stations in the outer shelf slope region warm high salinity atlantic layer water appeared to have risen displaced the lower halocline and mixed with shelf upper halocline water 2 primary production in the sbi study region was strongly influenced by the advection of dissolved inorganic nitrogen din entering via bering strait this import of din ammonium nitrate nitrite is modified by local processes but without the bering strait inflow biological productivity in the sbi region would be much lower 3 in comparison to the inflowing atlantic waters din urea phosphate and din urea silicate ratios in the pacific waters that dominated the upper 150 m of the water column were low they were also low relative to redfield uptake ratios for phytoplankton 4 microbial processes continue to destroy din in significant quantities as the pacific waters transit the sbi region 5 nitrate and ammonium were the principal contributors to din nitrite concentrations were always

coupled wind forced controls of the bering chukchi shelf circulation and the bering strait throughflow ekman transport continental shelf waves and variations of the pacific arctic sea surface height gradient abstract we develop a conceptual model of the closely co dependent bering shelf bering strait and chukchi shelf circulation fields by evaluating the effects of wind stress over the north pacific and western arctic using atmospheric reanalyses current meter observations satellite based sea surface height ssh measurements hydrographic profiles and numerical model integrations this conceptual model suggests bering strait transport anomalies are primarily set by the longitudinal location of the aleutian low which drives oppositely signed anomalies at synoptic and annual time scales synoptic time scale variations in shelf currents result from local wind forcing and remotely generated continental shelf waves whereas annual variations are driven by basin scale adjustments to wind stress that alter the magnitude of the along strait meridional pressure gradient in particular we show that storms centered over the bering sea excite continental shelf waves on the eastern bering shelf that carry northward velocity anomalies northward through bering strait and along the chukchi coast the integrated effect of these storms tends to decrease the northward bering strait transport at annual to decadal time scales by imposing cyclonic wind stress curl over the aleutian basin and the western subarctic gyre ekman suction then increases the water column density through isopycnal uplift thereby decreasing the dynamic height sea surface height and along strait pressure gradient storms displaced eastward over the gulf of alaska generate an opposite set of bering shelf and aleutian basin responses while ekman pumping controls canada basin dynamic heights proshutinsky et al 2002 we do not find evidence for a strong relation between beaufort gyre sea surface height variations and the annually averaged bering strait throughflow over the western chukchi and east siberian seas easterly winds promote coastal divergence which also increases the along strait pressure head as well as generates shelf waves that impinge upon bering strait from the northwest

thermal regimes in the chukchi sea from 1941 to 2008 the summer june october temperature observations in the surface 0 m and subsurface 20 mbottom chukchi sea layers collected from 1941 to 2008 have been analyzed using the self consistent data recovery procedure based on correlation analysis and iterative empirical orthogonal function eof decomposition the analysis of the surface and subsurface eofs identified cold normal and warm thermal states with variability of 2 3 years and also 4 7 years we found that the chukchi sea water temperature has gradually increased since 1941 warming in the surface layer since 1941 has been minimal in the bering strait 0 012 1 cy r 1 total 0 8 1c and maximal in long strait 0 030 0 036 1 cy r 1 total 2 0 2 4 1c in the subsurface layer temperatures have increased about half as much minimal 0 0030 0 0075 1 cy r 1 total 0 2 0 5 1c in long strait and rather uniform 0 010 0 015 1 cy r 1 total 0 7 1 0 1c for the remaining chukchi sea analysis of the satellite sea surface height anomaly data shows that during the warm periods there is a stronger flow through the bering strait and intensification of the northwestward currents in the central chukchi sea extensive correlation analysis shows that the thermal state of the chukchi sea agrees well with the flow of pacific water through the bering strait and by an increase of the global atmospheric temperature in addition typical circulation during warm and cold periods was reconstructed using four dimensional variational 4dvar data assimilation into the ocean model and estimates of volume and heat fluxes in the chukchi sea during cold and warm periods were derived which are consistent with eof and correlation analyses

holocene variability in sea ice cover primary production and pacific water inflow and climate change in the chukchi and east siberian seas arctic ocean in this study we present new detailed biomarker based sea ice records from two sediment cores recovered in the chukchi sea and the east siberian sea these new biomarker data may provide new insights on processes controlling recent and past sea ice changes the biomarker proxy records show i minimum sea ice extent during the early holocene ii a prominent mid holocene short term high amplitude variability in sea ice primary production and pacific water inflow and iii significantly increased sea ice extent during the last ca 4 5k cal a bp this late holocene trend in sea ice change in the chukchi and east siberian seas seems to be contemporaneous with similar changes in sea ice extent recorded from other arctic marginal seas the main factors controlling the millennial variability in sea ice and surface water productivity are probably changes in surface water and heat flow from the pacific into the arctic ocean as well as the long term decrease in summer insolation the short term centennial variability observed in the high resolution middle holocene record is probably related to solar forcing our new data on holocene sea ice variability may contribute to synoptic reconstructions of regional to global holocene climate change based on terrestrial and marine archives

north american origin of pink white layers at the mendeleev ridge arctic ocean new insights from lead and neodymium isotope composition of detrital sediment component abstract dolomite rich layers of distinct pinkish colour are used as lithostratigraphic markers in the amerasian basin of the arctic ocean however origin of dolomite in these sediment units has not been studied in detail in this study lead pb and neodymium nd isotope composition of detrital clay size fraction from different lithofacies were investigated in core ps72 340 5 recovered at the eastern flank of the mendeleev ridge prior to the geochemical analyses grain size distribution was analyzed in order to minimize the grain size effect on the provenance signature for provenance discrimination results of isotope measurements were compared with marine surface sediment data and values for the circum arctic subaerial provinces late quaternary sediment supply variability was analyzed using the mixing model constrained by two tracers 207pb 206pb and end variations of sediment isotopic composition are inferred to result from mixing of volcanic and plutonic components usage of pb isotopic ratios alone does not allow distinction between these two types of sources results confirm that over the last estimated ca 200 ka dolomite rich pink layers at the mendeleev ridge were deposited during events probably associated with intensified iceberg transport from north america in general however sedimentation was mostly controlled by terrigenous input from the chukchi and east siberian seas whereas sediment supply from the laptev sea area remained less important and relatively constant at the studied location

a cyclonic eddy over the continental margin of vancouver island evidence for baroclinic instability abstract this paper describes the circulation water properties and energetics of an observed cyclonic eddy that formed over the continental margin of vancouver island between late july and early september 1980 the eddy was characterized by a depth scale of 1 km a radius of 50 km and a maximum near surface geostrophic flow of 50 cm s 1 within the middepth core of the eddy isopycnal surfaces were domed upward by 50 m and were comprised of relatively warm saline and low dissolved oxygen water that appeared to originate with the california undercurrent the eddy is shown to have been generated through dynamic instability of the seasonal mean flow along vancouver island the appearance in late july of the undercurrent over the slope may have been an important factor in the amplification of the mesoscale meander that eventually deformed into the eddy calculation of each of the terms in the integrated energy balance reveals that both barotropic and baroclinic instability contributed to the amplification

separation of tidal and subtidal currents in ship mounted acoustic doppler current profiler observations a simple method is developed to analyze current measurements obtained from a moving platform the need for this is motivated by the now common use of the ship mounted acoustic doppler current profiler adcp to acquire absolute velocity data during an oceanographic survey of a given region the full potential of this new measurement technique is severely hindered when the presence of high frequency phenomena e g tidal or inertial motions prevents a clear visualization of the lower frequency current structure of interest our analysis method is based on a spatial interpolation scheme using arbitrary functions that allows for the tidal current time variability which then permits the tide induced motions to be subtracted from the adcp data to yield the subtidal current field the method also allows nearby moored and drifter current measurements if available to be combined with the shipboard adcp observations in a single analysis to obtain the best description of the tidal and subtidal currents to illustrate this method we present results from the analysis of adcp data taken during oceanographic surveys in two different continental shelf regions the east china sea and the amazon shelf a 5 day conductivity temperature depth ctd and adcp survey was made in the east china sea near the mouth of the yellow sea during january 1986 there the currents were essentially barotropic and dominated by the semidiurnal tide the adcp derived cotidal chart for the m2 12 42 hours component agrees well with existing charts derived empirically from sea level observations or from regional numerical models the adcp derived steady flow is also consistent with the observed density field and indicates little flow in or out of the yellow sea and a transport of about 1 sv toward the tsushima strait two ctd adcp surveys lasting 21 and 23 days were conducted over the amazon shelf during march and may 1990 simultaneously moored current observations were also obtained at three locations along a cross shelf array 200 km north of the amazon river mouth for a common period of at least 2 months february 12 to april 13 over the shelf tidal and subtidal currents were comparable in magnitude our analysis indicates that the tidal currents were essentially barotropic semidiurnal and polarized in the cross shelf direction increasing in magnitude toward the inner shelf where current values of more than 2 m s are common the adcp derived steady currents were aligned in the along shelf direction and strongly influenced by the north brazil current nbc during both adcp surveys the northwestward flowing nbc was transporting more than 2 sv over the shelf at depths shallower than 100 m

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

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

the distribution of nutrients in the southeastern beaufort sea implications for water circulation and primary production hydrographic data collected above the shelf and slope in the southeastern beaufort sea show marked contrast in surface properties of nutrients temperature salinity and oxygen between august 1974 a year when ice remained close to shore and august 1975 a year with much open water the near surface properties are dominated by river inputs biological activity and the ice regime below the winter mixed zone 40 50 m properties are similar to those observed elsewhere in the arctic ocean bering sea water is detected at 50 60 m as a very weak signal in temperature nutrients and oxygen upwelling in both years was observed at the eastern side of mackenzie canyon this upwelling likely results from the interaction of coastal circulation with topography estimates of new productivity based on nutrient budgets are low 20 g c m 2 yr 1 compared to temperate coastal waters but fall in the range expected for the arctic in 1974 the heavy ice year turbid water and ice cover appear to have reduced new production by about 30 calculations show that this production over the shelf could potentially supply a significant portion of the nutrients found in the upper halocline over a wide region of the arctic ocean by regeneration at the shelf bottom and transport off the shelf in brine drainage

river forced estuarine plumes abstract the development maintenance and dissipation of river forced estuarine plumes with and without seaward sloping bottom are studied by use of a three dimensional primitive equation model inside the estuary discussion is focused on how the coriolis force induces lateral asymmetries in the circulation four physical processes dictate the transient as well as the quasi steady circulation in moderately stratified estuaries 1 upper layer convergence during the transient spinup phase 2 upward entrainment leading to the two layer steady circulation pattern 3 upward stretching of the lower layer vortex during the spindown period and 4 in the presence of a seaward bottom slope the left bounded tendency of the landward undercurrent for all phases of development deviations from the laterally averaged circulation pattern caused by these processes are discussed over the shelf various types of plumes are defined according to the visual appearance of the surface salinity field the four types of p

the east greenland coastal current structure variability and forcing abstract the subtidal circulation of the southeast greenland shelf is described using a set of high resolution hydrographic and velocity transects occupied in summer 2004 the main feature is the east greenland coastal current egcc a low salinity high velocity jet with a wedge shaped hydrographic structure characteristic of other surface buoyancy driven currents the egcc was observed along the entire greenland shelf south of denmark strait while the transect north of the strait showed only a weak shelf flow this observation in conjunction with water mass considerations and other supporting evidence suggests that the egcc is an inner branch of the east greenland current egc that forms south of denmark strait it is argued that bathymetric steering is the most likely reason why the egc apparently bifurcates at this location repeat sections occupied at cape farewell between 1997 and 2004 show that the alongshelf wind stress can have an influence on the structure and strength of the egcc and egc on timescales of 2 3 days accounting for the wind induced effects the volume transport of the combined egcc egc system is roughly constant 2 sv over the study domain from 68 n to cape farewell near 60 n the corresponding freshwater transport increases by roughly 60 over this distance 59 96 msv referenced to a salinity of 34 8 this trend is consistent with a simple freshwater budget of the egcc egc system that accounts for meltwater runoff melting sea ice and icebergs and net precipitation minus evaporation

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

water mass structure and boundaries in the mackenzie shelf estuary the mackenzie shelf is a broad estuarine region bordering the southeastern beaufort sea in the arctic ocean its fields of temperature and salinity result from the modification of offshore water masses by river inflow ice melting and freezing solar insolation and air sea exchange we here relate water masses resident on the mackenzie shelf to the large scale oceanography of the arctic mediterranean the summertime exchange between the shelf and open ocean is largely confined to waters lying above the main halocline s 34 2 psu cross shelf property distributions show that individual water masses maintain their structural identity i e core properties and buoyancy frequency as they move across the shelf and participate in the estuarine circulation shelf waters are strongly influenced by river inflow however the concept of a single plume issuing from the incoming river and forming a strictly two layered structure over uniform shelf water is misleading since a variety of temperature salinity and turbidity fronts co exist on the shelf at any given time

oceanographic characteristics associated with autumn movements of bowhead whales in the chukchi sea abstract each fall bowhead whales in the bering chukchi beaufort bcb population migrate westward from summering grounds in the beaufort sea through the chukchi sea to the northern coast of chukotka russia routes whales use when crossing the chukchi sea vary by year in some years whales migrate directly to the northern coast of chukotka while in other years whales may pause migration and linger presumably to feed in the central chukchi sea to investigate how whale movements may be related to oceanographic variables we examined bowhead whale habitat selection within the chukchi sea in autumn september november at two spatial scales first at the landscape scale i e the chukchi sea we compare oceanographic variables e g temperature salinity and current velocity at locations within used and randomly available tracks i e paths of travel to determine how oceanographic features are associated with where whales cross the chukchi sea in autumn second at a local scale we examine how directed travel or lingering within a whale s track is associated with oceanographic variables e g temperature salinity and current velocity whale location data for 24 bowhead whales were paired with oceanographic data from a pan arctic coupled ice ocean model for 2006 2009 at the landscape scale we found that whales generally followed water of pacific origin characterized by temperatures

ecological characteristics of core use areas used by bering chukchi beaufort bcb bowhead whales 2006 2012 the bering chukchi beaufort bcb population of bowhead whales balaena mysticetus ranges across the seasonally ice covered waters of the bering chukchi and beaufort seas we used locations from 54 bowhead whales obtained by satellite telemetry between 2006 and 2012 to define areas of concentrated use termed core use areas we identified six primary core use areas and describe the timing of use and physical characteristics oceanography sea ice and winds associated with these areas in spring most whales migrated from wintering grounds in the bering sea to the cape bathurst polynya canada area 1 and spent the most time in the vicinity of the halocline at depths 75 m which are within the euphotic zone where calanoid copepods ascend following winter diapause peak use of the polynya occurred between 7 may and 5 july whales generally left in july when copepods are expected to descend to deeper depths between 12 july and 25 september most tagged whales were located in shallow shelf waters adjacent to the tuktoyaktuk peninsula canada area 2 where wind driven upwelling promotes the concentration of calanoid copepods between 22 august and 2 november whales also congregated near point barrow alaska area 3 where east winds promote upwelling that moves zooplankton onto the beaufort shelf and subsequent relaxation of these winds promoted zooplankton aggregations between 27 october and 8 january whales congregated along the northern shore of chukotka russia area 4 where zooplankton likely concentrated along a coastal front between the southeastward flowing siberian coastal current and northward flowing bering sea waters the two remaining core use areas occurred in the bering sea anadyr strait area 5 where peak use occurred between 29 november and 20 april and the gulf of anadyr area 6 where peak use occurred between 4 december and 1 april both areas exhibited highly fractured sea ice whales near the gulf of anadyr spent almost half of their time at depths between 75 and 100 m usually near the seafloor where a subsurface front between cold anadyr water and warmer bering shelf water presumably aggregates zooplankton the amount of time whales spent near the seafloor in the gulf of anadyr where copepods in diapause and possibly euphausiids are expected to aggregate provides strong evidence that bowhead whales are feeding in winter the timing of bowhead spring migration corresponds with when zooplankton are expected to begin their spring ascent in april the core use areas we identified are also generally known from other studies to have high densities of whales and we are confident these areas represent the majority of important feeding areas during the study 2006 2012 other feeding areas that we did not detect likely existed during the study and we expect core use area boundaries to shift in response to changing hydrographic conditions

evolution and dynamics of the flow through herald canyon in the western chukchi sea abstract the flow of summer and winter pacific water masses through herald canyon is investigated using data from a high resolution hydrographic velocity survey conducted in summer 2004 the survey was part of the russian american long term census of the arctic rusalca program and consisted of four cross canyon transects occupied over a 2 day period at the time of the survey dense winter water was entering the western side of the canyon from the chukchi sea flowing alongside a poleward jet of summer water on the canyon s eastern flank as the dense water progressed northward it switched sides of the canyon and underwent a sudden increase in layer thickness this coincided with vertical mixing near the interface of the winter and summer water producing a new water mass mode exiting the canyon all of these features are consistent with the notion of hydraulic activity occurring in the canyon a three layer hydraulic theory is applied to the flow which suggests that it is supercritical and that hydraulic control is likely a lock exchange formulation accurately predicts the northward transport of the winter water the origin of the winter water and the manner in which it drains into the canyon is investigated using satellite ice concentration data atmospheric re analysis fields historical in situ data and a simple circulation model finally the fate of the pacific water exiting the canyon and its connection to the chukchi shelfbreak current is discussed

the upstream spreading of bottom trapped plumes it is well known that numerical simulations of freshwater discharges produce plumes that spread in the direction opposite to that of the propagation of coastally trapped waves the upstream direction the lack of a theory explaining these motions in unforced environments deemed the numerical results suspect thus it became a common practice in numerical studies to add a downstream mean flow to arrest the development of the upstream perturbation this approach is generally unjustified and it remains a matter of interest to determine if the upstream displacement produced by models is a geophysical phenomenon or a consequence of erroneous assumptions in the model setup in this article the results of highly idealized numerical experiments are used to investigate these matters it is shown that this phenomenon is associated with the geostrophic adjustment of the discharge and that upstream motion is endemic to the baroclinic structure of bottom trapped plumes it is also shown that downstream displacements are generated by the cross shelf barotropic pressure gradient generated by the propagation of coastally trapped waves sensitivity experiments indicate that the speed of upstream propagation and the density structure of the plume are affected by bottom friction the slope of the bottom and the magnitude of the density anomaly bottom friction in particular slows down the progression of the plume and changes its density structure producing a more homogeneous downstream region and a more stratified upstream region

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

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

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

a simple theory for the fate of buoyant coastal discharges abstract a simple theory that predicts the vertical structure and offshore spreading of a localized buoyant inflow onto a continental shelf is formulated the theory is based on two competing mechanisms that move the buoyant fluid offshore 1 the radial spread of the lighter water over the ambient water being deflected by the coriolis force and producing an anticyclonic cyclostrophic plume and 2 offshore transport of buoyant water in the frictional bottom boundary layer that moves the entire plume offshore while maintaining contact with the bottom the surface expression of the cyclostrophic plume moves offshore a distance ys 2 3g h0 2i 2g h0 2i 1 2f where g is reduced gravity based on the inflow density anomaly h0 is the inflow depth i is the inflow velocity and f is the coriolis parameter the plume remains attached to the bottom to a depth given by hb 2l ih0f g 1 2 where l is the inflow width both scales are based solely on parameters of the buoyant inflow at its source there

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

northward flow in the bering and chukchi seas the ocean circulation on the bering and chukchi sea shelves is investigated using a barotropic numerical model in the presence of the winter seasonal wind stress from the northeast observed northward transport through bering strait of 0 6 sv for the 8 month winter season 1981 1982 can be driven by a sea level difference of 0 4 m between the pacific and arctic oceans this sea level difference between basins is in agreement with hydrographic estimates in the absence of wind stress a 0 4 m sea level difference drives a northward transport through bering strait of 1 1 sv maximum transport through bering strait is geostrophically limited not frictionally or inertially limited major qualitative circulation features of the region are evident in the simulations westward intensification of the northward transport across the bering sea shelf is confirmed with the major transport occurring in the relatively deep gulf of anadyr in the absence of wind anadyr strait contributes 72 of the northward transport through bering strait with northeasterly winds there is a net clockwise circulation around saint lawrence island within the 20 m isobath norton and kotzebue sounds are little influenced by the general circulation northward transport in the chukchi sea bifurcates in the vicinity of point hope the predominant branch is directed toward the northwest in a broad canyon feature south of herald shoal and the balance becomes the alaskan coastal current between cape lisburne and point barrow

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

the siberian coastal current a wind and buoyancy forced arctic coastal current we describe circulation and mixing in the siberian coastal current scc using fall shipboard measurements collected between 1992 and 1995 in the western chukchi sea the scc forced by winds siberian river outflows and ice melt flows eastward from the east siberian sea it is bounded offshore by a broad 60 km front separating cold dilute siberian coastal water from warmer saltier bering sea water the alongshore flow is incoherent because the current contains energetic eddies and squirts probably generated by frontal baroclinic instabilities these enhance horizontal mixing and weaken the cross shore density gradient along the scc path eventually the scc converges with the northward flow from bering strait whereupon it deflects offshore and mixes with that inflow deflection occurs where the alongshore pressure gradient vanishes that location varies on synoptic and seasonal timescales because this gradient depends on the winds buoyancy fluxes and the sea level difference between the pacific and arctic oceans deflection usually occurs on the chukchi shelf but the scc occasionally flows southward through bering strait such events are short lived 1 10 days and occur mainly in fall and winter under northerly winds scc transport is likely small 0 1 sv but its dilute waters could substantially freshen the bering strait inflow and affect the disposition of pacific waters in the arctic ocean arctic river outflows should preferentially form surface advected fronts rather than bottom advected fronts because vertical mixing energy is low on arctic shelves surface advected fronts are more susceptible to upwelling winds and for the scc the pressure gradient between the pacific and arctic oceans than bottom advected fronts the scc never developed in fall 1995 because of anomalously steady upwelling winds the western chukchi shelf could have formed upper halocline source water in the winter of 1995 1996

early jurassic volcanic rocks in the xiongcun district southern lhasa subterrane tibet implications for the tectono magmatic events associated with the early evolution of the neo tethys ocean abstract early mesozoic late triassic to middle jurassic igneous rocks in the southern lhasa subterrane tibet record important information on the early tectono magmatic evolution of the neo tethys ocean this paper presents petrological geochronological and geochemical data for the xiongcun formation ignimbrites to constrain the petrogenesis and tectonic setting of these rocks in the southern lhasa subterrane the xiongcun formation is dominated by andesitic and dacitic rocks these rocks yield early jurassic 195 176 ma zircon u pb ages and display typical arc like geochemical signatures being enriched in large ion lithophile elements e g rb ba and u and depleted in high field strength elements e g nb ta and ti sr nd pb hf isotopic compositions are highly depleted these chemical and isotopic data suggest that the xiongcun formation ignimbrites probably formed in an intra oceanic island arc setting related to the northward subduction of the neo tethys oceanic slab the parental magmas were derived from a depleted mantle source modified by fluids released from the neo tethys oceanic slab combined with previously reported data we suggest that the volcanic rocks in the early jurassic xiongcun and yeba formations of the southern lhasa subterrane were generated by a single subduction system but developed on oceanic and continental crust respectively

ice export from the laptev and east siberian sea derived from δ18o values ice export from the vast arctic siberian shelf is calculated using o 18 values and salinity data for water samples collected during the international siberian shelf study between august and september 2008 isss 08 the samples represent a wide range of salinities and o 18 values due to river water inputs and sea ice removal we estimate the fraction of water that has been removed as ice by interpreting observed o 18 values and salinities as a result of mixing between river water and sea water end members as well as to fractional ice removal this method does not assume an ice end member of fixed composition which is especially important when applied on samples with large differences in salinity the results show that there is net transport of ice from both the laptev and the eastern siberian seas and in total 3000 km 3 of sea ice is exported from the shelf the annual total export of ice from the entire region calculated from the residence time of water on the shelf is estimated to be 860 km 3 yr 1 thus changes in ice production on the shelf may have great impact on sea ice export from the arctic ocean

the contiguous panarctic riverine coastal domain a unifying concept the riverine coastal domain rcd is a narrow 15 km shallow 10 m contiguous feature that is primarily forced driven by an aggregate of continental runoff sources and which extends clockwise 10 103 km around northern north america we hypothesize that a similar feature extends around northern eurasia the rcd carries a terrestrial signal that affects light nutrient and carbon regimes and provides a coastal pathway for the dispersal and migration of marine biota the physical and biogeochemical variables within the rcd yield a contiguous gradient of environmental conditions along and across the panarctic coastal zone the rcd acts as the initial connector between terrestrial and marine ecosystems and may become even more prominent as terrestrial runoff permafrost thawing and local ice melt are assumed to increase in the near future climate

a one dimensional time dependent model for the vertical stratification of the upper arctic ocean abstract a one dimensional time dependent model of the upper arctic ocean is presented it describes the circulation above a dynamically passive reservoir of atlantic water the model is driven by freshwater runoff from land ice production and export bering strait inflow and wind the mixed layer thickness is controlled by the shortest among the following three length scales the depth to the upper pycnocline the ekman length and the monin obukov length the outflow is assumed to occur as geostrophically controlled coastal currents four integral quantities are defined in order to make objective comparisons between model generated and observed salt and temperature profiles the model generates a seasonally varying mixed layer in qualitative agreement with measurements a halocline with water near the freezing temperature is also generated this structure is sustained by the water coming from the bering strait by comparing the model result with the observed freshwater content in the basin likely value

on the nature and origin of water masses in herald canyon chukchi sea synoptic surveys in summer 2004 2008 and 2009 abstract hydrographic and velocity data from three high resolution shipboard surveys of herald canyon in the northwest chukchi sea in 2004 2008 and 2009 are used to investigate the water masses in the canyon and their possible source regions both summer and winter pacific waters were observed in varying amounts in the different years although in general the summer waters resided on the eastern side of the canyon while the winter waters were located on the western flank the predominant summer water was bering summer water although some alaskan coastal water resided in the canyon in the two later years likely due to wind forcing both newly ventilated and remnant winter waters were found in the canyon but the amount lessened in each successive survey using mooring data from bering strait it is shown that a large amount of bering summer water in the western channel of the strait follows a relatively direct route into herald canyon during the summer months with an estimated advective speed of 10 20 cm s however while the winter water observed in 2004 was consistent with a bering strait source with a slower advective speed of 5 8 cm s the dense water in the canyon during 2008 and 2009 was more in line with a northern source this is consistent with sections to the west of the canyon and with previously reported measurements implying winter water formation on the east siberian shelf large scale wind patterns and polynya activity on the shelf are also investigated it was found that the former appears to impact more strongly the presence of dense water in herald canyon

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

freshwater distribution in the arctic ocean simulation with a high resolution model and model data comparison 1 a high resolution numerical simulation of the arctic ocean is analyzed in order to study the fate of river runoff and freshwater fluxes in the arctic ocean the model is driven by realistic winds and thermodynamic forcing from the european centre for medium range weather forecasting ecmwf reanalysis data set dye tracers have been added to visualize the pathways followed by low salinity water from the major arctic rivers and bering strait inflow the model is spun up using repeated forcing with the 1979 annual cycle for 20 years then the 1979 through 1998 atmospheric forcing is applied under the influence of the 1979 through early 1980s winds a large plume of river runoff exits the broad eurasian shelf seas along the lomonosov ridge starting in about 1985 the locus of shelf to basin transport shifts eastward to the alpha mendeleyev ridge complex this shift in the model output is related to changes in the sea surface height ssh fields which we attribute primarily to shifts in surface wind stresses model resolution runoff inputs and relaxation terms in the lena river delta region are analyzed in detail to expose issues with model performance at boundaries with freshwater inflow suggestions are made for improving future simulations of river runoff in basin scale models

idealized three dimensional modeling of seasonal variation in the alaska coastal current 1 seasonal variation of the buoyancy and downwelling wind forced alaska coastal current acc and the fate of freshwater contained in it is considered using idealized analytical and numerical models of the acc formed from a half line source of buoyant inflow the coastal current initially develops two dimensionally but becomes three dimensional from a balance between coastal influx of buoyancy and its downstream transport which leads to a coastal current depth limit hmax 1 2 where x is along shelf distance q is the line source strength for unit length f is the coriolis frequency and g is the reduced gravity of the buoyant inflow this limit is unchanged under downwelling wind stress and is reached on timescales of less than 1 month for the acc the coastal current width is roughly constant in x and increases in time at the same rate as the two dimensional solution imposition of a downwelling wind stress results in an approximate balance among wind stress and along and cross shelf momentum advection so that the current width is reduced to ywind ld 1 2 where ld is the rossby radius of deformation is the wind stress and 0 is a reference density waves eddying motions eventually grow in the half line source coastal current with wavelengths proportional to the coastal current width and with a downstream phase speed slower than the maximum current speed these features cause an offshore flux of buoyant water a broader coastal current and further accumulation of buoyancy on the shelf increasing downwelling wind stress reduces the effects of the instabilities continual accumulation of buoyancy on the shelf occurs during all model runs but is nearly absent under maximum winter downwelling wind stress it is suggested that freshwater accumulation on the shelf during spring summer and fall may be largely lost downstream during winter

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

extreme chemical heterogeneity of granite derived hydrothermal fluids an example from inclusions in a single crystal of miarolitic quartz magma derived fluids are important in geologic processes e g metal sequestration and ore deposition but are intrinsically transient samples of magmatic fluids represented by fluid inclusions in a single zoned quartz crystal from a miarolitic cavity within a porphyritic leucogranite hosting the industrialnoe tin deposit northeastern russia were studied by using modern in situ analytical methods laser raman spectroscopy proton induced x ray emission the fluid inclusions are either dominated by vapor or by complex multiphase brines the inclusions within a given trapping plane have similar phase relationships however there are significant variations between inclusions in different healed fractures phase and chemical compositions of individual brine inclusions demonstrate significant compositional heterogeneity in terms of absolute element concentrations and ratios of high temperature magmatic fluids accumulated in the miarolitic cavity this finding suggests that fluids leaving a crystallizing magma may have variable initial compositions that are subsequently modified by reactions with the rocks while the fluid is in transit to a miarolitic cavity as well as by processes in the cavity such as mixing crystallization and boiling the inferred chemical diversity and fractionation of granite derived fluids at near magmatic conditions imply that fluids entering a cooler hydrothermal system are extremely complex and their metallogenic signature may differ from that of related ore deposits

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

a holocene record of changing arctic ocean ice drift analogous to the effects of the arctic oscillation 1 the arctic oscillation ao controls the configuration of the transpolar drift tpd if thicker ice from the beaufort gyre were exported the volume of fresh water sea ice in the nordic seas would significantly increase decreasing the formation of north atlantic deep water this would cool large parts of the northern hemisphere and affect global climate therefore in order to understand how the global climate system functions it is imperative to know how the tpd changed over the last millennium or more the provenance of grains in a sediment core located near the confluence of the tpd and the beaufort gyre provides a direct proxy for changes in seaice drift owing to these circulation systems the core has more than 200 cm of holocene sediment with intervals dominated by grains from the russian shelves alternating with intervals of abundant grains from north american sources grains matched to russian shelves indicate that the tpd was shifted toward north america similar to what occurs during a more positive phase of the ao this condition alternated with intervals where few grains matched to russian sources presumably because the tpd was restricted to the russian half of the arctic far from the core site during the last 1300 years increased influx of russian grains occurred approximately every 50 150 years this fluctuation might represent the long term oscillation of the ao which modulates the same tpd shift today