infaunal density biomass and bioturbation in the sediments of the arctic ocean abstract little is known about the benthic communities of the arctic ocean s slope and abyssal plains here we report on benthic data collected from box cores along a transect from alaska to the barents abyssal plain during the arctic ocean section of 1994 we determined 1 density and biomass of the polychaetes foraminifera and total infauna 2 concentrations of potential sources of food pigment concentration and percent organic carbon in the sediments 3 surficial particle mixing depths and rates using downcore 210pb profiles and 4 surficial porewater irrigation using nabr as an inert tracer metazoan density and biomass vary by almost three orders of magnitude from the shelf to the deep basins e g 47 403 individuals m 2 on the chukchi shelf to 95 individuals m 2 in the barents abyssal plain water depth is the primary determinant of infaunal density explaining 39 of the total variability potential food concentration varies by almost two orders of magnitude during the late summer season e g the phaeopigment concentration integrated to 10 cm varies from 36 16 mg m 2 on the chukchi shelf to 0 94 mg m 2 in the siberia abyssal plain but is not significantly correlated with density or biomass of the metazoa most stations show evidence of particle mixing with mixing limited to 3 cm below the sediment water interface and enhanced pore water irrigation occurs at seven of the nine stations examined particle mixing depths may be related to metazoan biomass while enhanced pore water irrigation beyond what is expected from diffusion alone appears to be related to total phaeopigment concentration the data presented here indicate that arctic benthic ecosystems are quite variable but all stations sampled contained infauna and most stations had indications of active processing of the sediment by the associated infauna

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

central arctic surface ocean environment during the past 80 000 years stable oxygen and carbon isotope and sedimentological paleontological investigations supported by accelerator mass spectrometry 14 c datings were carried out on cores from north of 85 degrees n in the eastern central arctic ocean significant changes in accumulation rates provenance of ice rafted debris ird and planktic productivity over the past 80 000 years are documented during peak glacials i e oxygen isotope stages 4 and 2 the arctic ocean was covered by sea ice with decreased seasonal variation limiting planktic productivity and bulk sedimentation rates in early stage 3 and during termination i major deglaciations of the circum arctic regions caused lowered salinities and poor oxygenation of central arctic surface waters a meltwater spike and an associated ird peak dated to similar to 14 12 14 c ka can be traced over the southern eurasian basin of the arctic ocean this event was associated with the early and rapid deglaciation of the marine based barents sea ice sheet a separate termination ib meltwater event is most conspicuous in the central arctic and is associated with characteristic dolomitic carbonate ird this lithology suggests an origin of glacial ice from northern canada and northern greenland where lower paleozoic platform carbonates crop extensively out

deep mesoscale eddies in the canada basin arctic ocean 1 numerous eddies have been identified in a seven year time series of mooring observations in the canada basin arctic ocean we focus on a series of deep eddies centered at 1200 m depth and occupying up to 1500 m of the water column the deep eddies are found to be spatially localized only ever being observed at one of four mooring sites of the beaufort gyre observing system in the canada basin however despite only a few previously reported observations of deep eddies in the arctic ocean we find that they are the most prevalent eddy type at this location based on this observation together with an analysis of the temperature salinity structure and the exclusively anticyclonic rotation of the deep eddies we hypothesize that they are formed by a density driven outflow from the chukchi borderland region we also describe a simple analytical model to explain the observed vertical scales of the eddies

joint effects of boundary currents and thermohaline intrusions on the warming of atlantic water in the canada basin 1993 2007 1 the 1990 1991 influx of atlantic water both anomalously warm and in greater volume than in the past enveloped the chukchi borderland in the western canada basin by 2002 and spread across the southeastern canada basin by 2007 warmer younger more ventilated and less dense fram strait branch waters have replaced colder older and denser waters increasing the temperature of the fram strait branch core from a 50 year or more mean of 0 45 c to 0 7 c physical and geochemical data collected from 1993 to 2007 show that the two main transport mechanisms are the boundary current and thermohaline intrusions established by large thermal gradients the boundary current operates in a cyclonic direction whereas the thermohaline intrusions operate in an anticyclonic direction because of the influence of the beaufort gyre this shows that the beaufort gyre s effect on ocean circulation extends into the fram strait branch of the atlantic layer the boundary current a fully pan arctic structure is much slower in the canada basin than in basins upstream with an effective speed of 0 5 cm s the effective spreading rate of the thermohaline intrusions relative to the core is 0 2 cm s thermohaline intrusions show signs of dissipation near the northwind ridge in 2007 suggesting that as temperature gradients between inflowing and resident waters decrease they will disappear from the canada basin

the arctic ocean warms from below 1 the old 450 year isolation age and near homogenous deep waters of the canada basin cbdw that are found below 2700 m warmed at a rate of 0 0004 c yr 1 between 1993 and 2010 this rate is slightly less than expected from the reported geothermal heat flux fg 50 mw m 2 a deep temperature minimum tmin layer overlies cbdw within the basin and is also warming at approximately the same rate suggesting that some geothermal heat escapes vertically through a multi stepped 300 m thick deep transitional layer double diffusive convection and thermobaric instabilities are identified as possible mechanisms governing this vertical heat transfer the cbdw found above the lower continental slope of the deep basin maintains higher temperatures than those in the basin interior consistent with geothermal heat being distributed through a shallower water column and suggests that heat from the basin interior does not diffuse laterally and escape at the edges

evolution of the deep water in the canadian basin in the arctic ocean abstract an overflow of magnitude 0 25 sv sv 106 m 3 s 1 has been predicted to enter the makarov basin part of the canadian basin in the arctic ocean from the eurasian basin via a deep gap in the dividing lomonosov ridge the authors argue that this overflow does not ventilate the deep makarov basin below 2400 m where the water is too warm and salty to be compatible with such a large cold fresh inflow however complete isolation of the homogeneous bottom layer of the makarov basin must be ruled out because changes there are too small to arise from more than a small fraction of the measured geothermal heat flux into the basin a small cold fresh inflow of about 0 01 sv from the amundsen basin seems to be required this could occur if the gap in the dividing lomonosov ridge is shallower than previously thought it could also occur if there is active mixing and dilution of the predicted overflow in the gap leaving only a small fraction to descend into the deep makarov basin hydraulic theory and hy

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

mixing in the west spitsbergen current abstract twenty eight profiles of temperature and salinity down to 1 km depth have been measured in the area north from the coast of svalbard to latitude 84 40 n between 0 and 32 e longitude they show atlantic waters of the west spitsbergen current entering the arctic ocean in a bifilimentary mode one filament following the coastline and the other 300 km farther north apparently following the continental shelf break the profiles show these filaments mixing into the ambient water in a series of intrusive layers which are remarkably uniform over distances of hundreds of kilometers a triple peak structure at the atlantic water maximum is the dominant oceanographic characteristic of the area with salt fingering occurring on the upper surface of the cold intrusions and indications of double diffusive exchanges through the lower surface a system or eddies or meanders is postulated as the mechanism for the production of multiple fronts allowing the intrusive layers to extend to distances much greater t

flow of winter transformed pacific water into the western arctic abstract the dynamics of the flow of dense water through barrow canyon is investigated using data from a hydrographic survey in summer 2002 the focus is on the winter transformed bering water the highest volumetric mode of winter water in the chukchi sea which drains northward through the canyon in spring and summer the transport of this water mass during the time of the survey was 0 2 0 3 sv as the layer flowed from the head of the canyon to the mouth it sank decelerated and stretched strong cyclonic relative vorticity was generated on the seaward side of the jet which compensated for the stretching this adjustment was incomplete however in that it did not extend across the entire current possibly because of internal mixing due to shear instabilities the resulting vorticity structure of the flow at the canyon mouth was conducive for baroclinic instability and eddy formation multiple eddies of winter transformed bering water were observed along the chukchi beaufort shelfbreak those to the west of barrow canyon were in the process of being spawned by the eastward flowing shelfbreak current emanating from herald canyon while the single eddy observed to the east originated from the barrow canyon outflow it is argued that such an eddy formation is a major source of the ubiquitous cold core anti cyclones observed historically throughout the canada basin implications for the ventilation of the upper halocline of the western arctic are discussed

a model for the thickness and salinity of the upper layer in the arctic ocean and the relationship between the ice thickness and some external parameters abstract this paper presents a dynamical model for the salinity and thickness of the upper layer in the arctic the parameters are the river runoff to the arctic the buoyancy supply through the bering strait the export of ice from the arctic and a parameter characterizing the vertical mixing an ice model is formulated having the following two important properties 1 the horizontal surface area of the exported ice is essentially determined by external parameters the wind field over the arctic and 2 there is a relationship between the ice thickness and the fraction of open water in the arctic the model for the upper layer and the ice model are used together with a heat budget for the arctic also including the effect of different albedo for ice and open water a relationship between the freshwater supply and the ice thickness is derived also investigated are the effects on the ice thickness of a changed export of ice area and changed properties of the flow through the bering strait it is found t

distribution of convective lower halocline water in the eastern arctic ocean 1 we investigate the distribution of convectively formed lower halocline water clhw in the eastern arctic ocean using observational and climatological data the clhw can be defined as the water mass in the cold halocline layer formed by winter convection the presence of clhw is indicated by temperatures close to the freezing point and a sharp bend in the s curve near the salinity of clhw results from ice drifting buoy observations in 2002 show differences in water mass characteristics in the upper ocean among the amundsen basin over the arctic mid ocean ridge and in the nansen basin in 2000 2002 clhw was present over the arctic mid ocean ridge and the nansen basin but was largely absent from the amundsen basin using climatological data we find that clhw was confined to the nansen basin prior to 1990 in the early 1990s clhw still covered only the nansen basin but extended to the northern side of the arctic mid ocean ridge in the mid 1990s and covered the whole of the amundsen basin by the late 1990s in the early 2000s the area of clhw moved back to its present boundary on the northern side of the arctic mid ocean ridge these results correspond roughly to other changes in the arctic ocean circulation and water mass structure but with a time delay we hypothesize that general circulation changes and the cutoff of source water for advective convective modification of the lhw are causes of the change in clhw distribution the lag in changes to clhw distribution behind other changes in the atmosphere and upper ocean are likely related to differences in circulation change with depth and the transit time from clhw formation

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

a changing arctic seasonal ice zone observations from 1870 2003 and possible oceanographic consequences 1 changes in the extent of seasonal ice were investigated using historical and satellite observations for the period 1870 2003 the seasonal ice zone siz has been gradually expanding since 1870 with a marked acceleration over the past three decades and has migrated north to encompass all peripheral arctic seas the expansion of the siz may be increasing the salinity of the upper arctic ocean consistent with recent observations the migration of the siz over continental shelves may also be enhancing the formation rate and salinity of arctic deep waters which are subsequently advected to the convective region of the greenland iceland norwegian sea thereby influencing the formation of north atlantic deep waters and related global thermohaline circulation

arctic ocean warming and its consequences for the denmark strait overflow 1 two anomalously warm inflow pulses into the atlantic water layer of the arctic ocean have occurred since the late 1980s as a consequence temperatures of the arctic basins at 200 800 m depth have increased considerably in comparison to earlier decades the warm inflow pulses also had a low density owing to the decadal time scale of the circulation in the atlantic water layer large pools of anomalously light water have thereby formed in the arctic ocean these will slowly drain back south into the nordic seas we submit that they will be able to influence the overflows into the atlantic across the greenland scotland ridges the atlantic meridional overturning is fed by these overflows our model experiments indicate that the low density anomalies from the arctic ocean may be able to reduce the denmark strait overflow 15 25 years after the entrance of the original signal through fram strait into the arctic ocean the actual size of the reduction depends on the exact path and speed of the anomalies inside the arctic proper and on local processes in the arctic ocean and the nordic sea

water masses and circulation in the eurasian basin results from the oden 91 expedition the oden 91 north pole expedition obtained oceanographic measurements on four sections in the nansen and amundsen basins of the eurasian basin and in the makarov basin of the canadian basin thereby proving the feasibility of carrying out a typical oceanographic program using an icebreaker in the arctic ocean the data show greater spatial variability in water structure and circulation than was apparent from previous data the results show that a clear front exists between the eurasian and canadian basins such that upper halocline water in the canadian basin is almost absent from the eurasian basin the lower halocline water produced in the barents kara sea region permeates much of the eurasian basin and flows along the continental slope into the canadian basin the deeper circulation is strongly influenced by topography three return flows of the atlantic layer are identified one over the nansen gakkel ridge one over the lomonosov ridge and a third flowing from the canadian basin the slight differences observed in salinity and temperature characteristics of the deeper waters of the nansen and amundsen basins do not lead to an obvious explanation of their origin or flow pattern

variability in arctic sea ice drift 1 analysis of arctic sea ice drift from 1979 1997 using a lagrangian perspective shows the complexities of ice drift response to variations in atmospheric conditions changes in ice dynamics influence the redistribution of ice and any transported material from different source areas sources of ice exported to fram strait shifted in about 1986 87 from dominance of the kara sea and severnaya zemlya to the new siberian islands east siberian sea and chukchi sea average travel time of multiyear ice within the perennial pack of the central arctic basin reached a maximum in 1987 88 and decreased by at least 1 year between 1984 1989 and 1990 1997 consistent with the observations of other investigators this decrease in ice travel time occurred following a major export or surge of old ice to fram strait from the beaufort gyre in 1988 through 1990 which decreased the fraction of thick ridged ice within the central basin

a large eddy in the central arctic ocean 1 long term moored measurements of temperature salinity and velocity over the abyssal plain near the north pole show a rich array of eddy like structures over a wide range of depths here we demonstrate an anticyclone that extends from the surface to at least 1700 m is about 60 km across and has a likely origin along the eurasian continental margin

surface freshening in the arctic ocean s eurasian basin an apparent consequence of recent change in the wind driven circulation 1 data collected by an autonomous ice based observatory that drifted into the eurasian basin between april and november 2010 indicate that the upper ocean was appreciably fresher than in 2007 and 2008 sea ice and snowmelt over the course of the 2010 drift amounted to an input of less than 0 5 m of liquid freshwater to the ocean comparable to the freshening by melting estimated for those previous years while the observed change in upper ocean salinity over the melt period implies a freshwater gain of about 0 7 m results of a wind driven ocean model corroborate the observations of freshening and suggest that unusually fresh surface waters observed in parts of the eurasian basin in 2010 may have been due to the spreading of anomalously fresh water previously residing in the beaufort gyre this flux is likely associated with a 2009 shift in the large scale atmospheric circulation to a significant reduction in strength of the anticyclonic beaufort gyre and the transpolar drift stream

circulation and water mass transformation in a model of the chukchi sea 1 the circulation and water mass transformation in a regional ocean ice model of the chukchi sea are discussed the model has horizontal resolution of o 4 km is forced by fluxes derived from daily ncep reanalysis fields and has seasonally varying transport temperature and salinity imposed at bering strait many of the observed characteristics of the mean circulation and seasonal cycle in the chukchi sea are reproduced the discussion focuses on the branching of the inflow transport into pathways following herald canyon central channel and the alaskan coast the pattern of ice melt and the water mass transformation and formation of winter water and hypersaline water the ice melt pattern and timing is strongly influenced by advection through bering strait high frequency forcing results in a larger region of ice melt particularly over the shoals and in the northern chukchi sea compared to monthly mean forcing in the model the seasonal cycle of salinity in the southern and central chukchi sea is dominated by advection through bering strait while local atmospheric forcing and brine rejection are more important north of herald and hanna shoals and in barrow canyon however since the residence time in the chukchi sea is generally less than 1 year interannual variability in the bering strait salinity will be reflected in the salinity across the chukchi sea and at barrow canyon

jellies under ice rov observations from the arctic 2005 hidden ocean expedition abstract in order to provide a baseline understanding of gelatinous zooplankton biodiversity and distribution in the rapidly changing arctic ocean 12 stations were sampled across the canada basin northwind ridge and chukchi plateau with detailed deep water rov observations and multinet tows down to 3000 m the complex multi origin water layers of the arctic ocean provided the backdrop for examining the vertical and horizontal distributions of the poorly understood meso and bathypelagic gelatinous taxa over 50 different gelatinous taxa were observed across the stations with cnidarians being the most common group medusae accounted for 60 of all observations siphonophores for 24 larvaceans for 10 ctenophores for 5 and numerous interesting and rarer taxa constituted the remaining 1 of observations several new species were found and many major range extensions were observed both the vertical and horizontal distribution of species appear to be linked to water mass characteristics as well as bottom topography and geographic location within the study area shallow slope and ridge areas around the canada basin and chukchi plateau appear to harbor substantially lower gelatinous zooplankton biomass and diversity than the deeper locations shallow stations not only show reduced abundance but also different relative abundance of the major taxa where the shallow water stations are dominated by large numbers of siphonophores and ctenophores the deep stations are dominated by medusae taxonomic issues and ecological observations of several important species are discussed aided by the live collection of many undamaged and fragile species

observations of small eddies in the beaufort sea the horizontal and vertical variations of velocity temperature density and turbulent kinetic energy dissipation in the central beaufort sea were measured with helicopter borne expendable current profilers and conductivity temperature depth units almost all velocity differences larger than 0 05 m s 1 could be consistently interpreted as being due to nearly circular eddies with a diameter of 10 20km a thickness of 50 500 m peak velocities of 0 07 0 3 m s 1 and little expression at the top of the ocean four such eddies were found two anticyclones were found and accurately sampled two cyclones were found but were only poorly sampled both were beneath and close to one of the anticyclones relative vorticity could be computed for two anticyclones and one cyclone within experimental error the two anticyclones and all historical beaufort sea anticyclones had a relative vorticity of and thus zero potential vorticity at the center the cyclone had a central relative vorticity of about 0 5 and thus a different value of potential vorticity than the surrounding fluid one anticyclonic eddy b was sampled seven times over a period of 23 days its measured velocity and density fields were in approximate gradient wind balance its central core contained values of temperature nitrate and silicate that were different from those outside the core at the same density it moved eastward at about 0 02 m s 1 through the surrounding fluid measurements of turbulent kinetic energy dissipation were almost always less than the noise level of the instrument about 10 9 w kg 1 corresponding to a mean dissipation much less than this and a minimum decay time due to turbulence much longer than 0 3 year the nondimensional strength rossby number and shape burger number of anticylcone b are very similar to those of other beaufort sea anticyclones and similar to those of small mid latitude eddies each of the eddies observed here was centered on a temperature maximum associated with one of the warm water masses that advect into the arctic ocean the two anticyclones were centered on temperature maxima originating in the pacific ocean whereas the two cyclones were centered on temperature maxima from the atlantic ocean this is consistent with the hypothesis that the eddies are formed as these water masses enter the arctic ocean

determining the existence of the fine sediment flocculation in the three gorges reservoir abstractseveral proofs for the existence of flocculation in the three gorges reservoir tgr are found through field measurements and laboratory experiments the suspended particles and bed sediments are fine and the particle diameters stay the same along the water depth indicating that flocculation may occur both the vertical distributions of sediment concentrations at low flow velocities and measured settling velocities suggest that the effective settling velocities are larger than those of the primary particles providing strong evidence for flocculation the flow velocity zones of deposition and transportation are found and the demarcation velocity of the two zones is approximately 0 5 0 6 m s it is thought that flocculation occurs when the flow velocity is smaller than the demarcation velocity otherwise the flocs will be disrupted by turbulent shear laboratory experiments are conducted by using the sampled bed sediments and floc structures are also observed confirming the existence of fl

sedimentation patterns of fine grained particles in the dam area of the three gorges project 3d numerical simulation abstractthis paper is focused on the sedimentation processes of fine grained particles in a 14 km long section upstream of the three gorges dam referred to as the dam area during the period from march 2003 to october 2006 field measurements indicated that sediment deposits in the dam area were mostly found at the bottom of the main channel where a new river bed was formed with a flat nearly horizontal surface in contrast very little deposits could be found on the bank slopes of the channel the observations disagree with the previous predictions based on numerical models which suggested more evenly distribution of deposits over the cross section this paper explains the discrepancy by identifying the motion of muddy deposits by gravity as a key process in the dam area a three dimensional 3d full reynolds averaged navier stokes rans model is applied to calculate the flow and sediment transport processes a critical slope method csm is used to estimate the downslope movement of muddy deposits

arctic sea ice circulation and drift speed decadal trends and ocean currents 1 we examine the basinwide trends in sea ice circulation and drift speed and highlight the changes between 1982 and 2009 in connection to regional winds multiyear sea ice coverage ice export and the thinning of the ice cover the polarity of the arctic oscillation ao is used as a backdrop for summarizing the variance and shifts in decadal drift patterns the 28 year circulation fields show a net strengthening of the beaufort gyre and the transpolar drift especially during the last decade the imprint of the arctic dipole anomaly on the mean summer circulation is evident 2001 2009 and enhances summer ice area export at the fram strait between 2001 and 2009 the large spatially averaged trends in drift speeds winter 23 6 decade summer 17 7 decade are not explained by the much smaller trends in wind speeds winter 1 46 decade summer 3 42 decade notably positive trends in drift speed are found in regions with reduced multiyear sea ice coverage over 90 of the arctic ocean has positive trends in drift speed and negative trends in multiyear sea ice coverage the increased responsiveness of ice drift to geostrophic wind is consistent with a thinner and weaker seasonal ice cover and suggests large scale changes in the air ice ocean momentum balance the retrieved mean ocean current field from decadal scale average ice motion captures a steady drift from siberia to the fram strait an inflow north of the bering strait and a westward drift along coastal alaska this mean current is comparable to geostrophic currents from satellite derived dynamic topography

observed increases in bering strait oceanic fluxes from the pacific to the arctic from 2001 to 2011 and their impacts on the arctic ocean water column 1 mooring data indicate the bering strait throughflow increases 50 from 2001 0 7 sv to 2011 1 1 sv driving heat and freshwater flux increases increase in the pacific arctic pressure head explains two thirds of the change the rest being attributable to weaker local winds the 2011 heat flux 5 1020j approaches the previous record high 2007 due to transport increases and warmer lower layer ll temperatures despite surface temperature sst cooling in the last decade warmer ll waters arrive earlier 1 6 1 1 days yr though winds and sst are typical for recent decades maximum summer salinities likely set in the bering sea remain remarkably constant 33 1 psu over the decade elucidating the stable salinity of the western arctic cold halocline despite this freshwater flux variability strongly driven by transport exceeds variability in other arctic freshwater sources remote data winds sst prove insufficient for quantifying variability indicating interannual change can still only be assessed by in situ year round measurements

phytoplankton production from melting ponds on arctic sea ice 1 recently the areal extent of melt ponds within sea ice has rapidly increased during the arctic ocean summer however the biological impacts of melt ponds on the arctic marine ecosystem have rarely been studied carbon and nitrogen uptake rates of phytoplankton were measured at 26 different melt ponds in 2005 and 2008 using a 13c 15n dual stable isotope tracer technique generally the open ponds had relatively higher nutrients than closed ponds but the nutrient concentrations in the open ponds were within a range similar to those in surrounding surface seawaters chlorophyll a chl a concentrations in melt ponds ranged from 0 1 to 2 9 mg chl a m 3 with a mean of 0 6 mg chl a m 3 sd 0 8 mg chl a m 3 in the canada basin in 2005 whereas the range of the chl a concentrations was from 0 1 to 0 3 mg chl a m 3 with a mean of 0 2 mg chl a m 3 sd 0 1 mg chl a m 3 in the central arctic ocean in 2008 the average annual carbon production in sea ice melt ponds was 0 67 g c m 3 sd 1 03 g c m 3 in the arctic ocean based on this study recent annual carbon production of all melt ponds was roughly estimated to be approximately 2 6 tg c which is less than 1 of the total production in the arctic ocean

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

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

characterizing the eddy field in the arctic ocean halocline ice tethered profilers itp deployed in the arctic ocean between 2004 and 2013 have provided detailed temperature and salinity measurements of an assortment of halocline eddies a total of 127 mesoscale eddies have been detected 95 of which were anticyclones the majority of which had anomalously cold cores these cold core anticyclonic eddies were observed in the beaufort gyre region canadian water eddies and the vicinity of the transpolar drift stream eurasian water eddies an arctic wide calculation of the first baroclinic rossby deformation radius rd has been made using itp data coupled with climatology rd 13 km in the canadian water and 8 km in the eurasian water the observed eddies are found to have scales comparable to rd halocline eddies are in cyclogeostrophic balance and can be described by a rankine vortex with maximum azimuthal speeds between 0 05 and 0 4 m s the relationship between radius and thickness for the eddies is consistent with adjustment to the ambient stratification eddies may be divided into four groups each characterized by distinct core depths and core temperature and salinity properties suggesting multiple source regions and enabling speculation of varying formation mechanisms

deep water flow over the lomonosov ridge in the arctic ocean the arctic ocean likely impacts global climate through its effect on the rate of deep water formation and the subsequent influence on global thermohaline circulation here the renewal of the deep waters in the isolated canadian basin is quanitified using hydraulic theory and hydrographic observations the authors calculate the magnitude of this renewal where circumstances have thus far prevented direct measurements a volume flow rate of q 0 25 0 15 sv sv 10 6 m 3 s 1 from the eurasian basin to the canadian basin via a deep gap in the dividing lomonosov ridge is estimated deep water renewal time estimates based on this flow are consistent with 14 c isolation ages the flow is sufficiently large that it has a greater impac to n the canadian basin deep water than either the geothermal heat flux or diffusive fluxes at the deep water boundaries

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

deterioration of perennial sea ice in the beaufort gyre from 2003 to 2012 and its impact on the oceanic freshwater cycle time series of ice draft from 2003 to 2012 from moored sonar data are used to investigate variability and describe the reduction of the perennial sea ice cover in the beaufort gyre bg culminating in the extreme minimum in 2012 negative trends in median ice drafts and most ice fractions are observed while open water and thinnest ice fractions 0 3 m have increased attesting to the ablation or removal of the older sea ice from the bg over the 9 year period monthly anomalies indicate a shift occurred toward thinner ice after 2007 in which the thicker ice evident at the northern stations was reduced differences in the ice characteristics between all of the stations also diminished so that the ice cover throughout the region became statistically homogenous the moored data are used in a relationship with satellite radiometer data to estimate ice volume changes throughout the bg summer solid fresh water content decreased drastically in consecutive years from 730 km3 in 2006 to 570 km3 in 2007 and to 240 km3 in 2008 after a short rebound solid fresh water fell below 220 km3 in 2012 meanwhile hydrographic data indicate that liquid fresh water in the bg in summer increased 5410 km3 from 2003 to 2010 and decreased at least 210 km3 by 2012 the reduction of both solid and liquid fresh water components indicates a net export of approximately 320 km3 of fresh water from the region occurred between 2010 and 2012 suggesting that the anticyclonic atmosphere ocean circulation has weakened

wind driven shelf basin exchange on an arctic shelf the joint roles of ice cover extent and shelf break bathymetry 1 the efficiency of shelf basin exchange sbe in polar regions during summer is strongly moderated by the location of the ice edge relative to underlying topography numerical model calculations suggest that upwelling favorable winds generate very little sbe so long as the ice edge remains shoreward of the shelf break but an abrupt onset of shelf break upwelling takes place when the ice edge retreats beyond the shelf break a climatology 1968 2000 of ice conditions from the canadian shelf of the beaufort sea shows large interannual variability in ice edge extent and duration of ice free conditions in summer similarly available hydrographic data reflect a corresponding variability in water mass properties under scenarios of climate warming associated with greenhouse gas build up both the extent and duration of summer melt back are predicted to increase and this may have dramatic impacts on sbe and biological productivity

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

effects of ocean acidification warming and melting of sea ice on aragonite saturation of the canada basin surface water 1 in 2008 surface waters in the canada basin of the arctic ocean were found to be undersaturated with respect to aragonite this is associated with recent extensive melting of sea ice in this region as well as elevated sea surface temperature and atmospheric co2 concentrations we have estimated the relative contribution of each of these controlling factors to the calcium carbonate saturation state w from observations of dissolved inorganic carbon total alkalinity and oxygen isotope ratio results indicate that the increase in atmospheric co2 has lowered surface w by 0 3 in the canada basin since the preindustrial period recent melting of sea ice has further lowered mean w by 0 4 and of this half was due to dilution of surface water and half was due to the change in air sea disequilibrium state surface water warming has generally counteracted the mean decrease in w by 0 1 citation yamamoto kawai m f a mclaughlin and e c carmack 2011 effects of ocean acidification warming and melting of sea ice on aragonite saturation of the canada basin surface water geophys res lett 38 l03601 doi 10 1029 2010gl045501

role of shelfbreak upwelling in the formation of a massive under ice bloom in the chukchi sea abstract in the summer of 2011 an oceanographic survey carried out by the impacts of climate on ecosystems and chemistry of the arctic pacific environment icescape program revealed the presence of a massive phytoplankton bloom under the ice near the shelfbreak in the central chukchi sea for most of the month preceding the measurements there were relatively strong easterly winds providing upwelling favorable conditions along the shelfbreak analysis of similar hydrographic data from summer 2002 in which there were no persistent easterly winds found no evidence of upwelling near the shelfbreak a two dimensional ocean circulation model is used to show that sufficiently strong winds can result not only in upwelling of high nutrient water from offshore onto the shelf but it can also transport the water out of the bottom boundary layer into the surface ekman layer at the shelf edge the extent of upwelling is determined by the degree of overlap between the surface ekman layer and the bottom boundary layer on the outer shelf once in the ekman layer this high nutrient water is further transported to the surface through mechanical mixing driven by the surface stress two model tracers a nutrient tracer and a chlorophyll tracer reveal distributions very similar to that observed in the data these results suggest that the biomass maximum near the shelfbreak during the massive bloom in summer 2011 resulted from an enhanced supply of nutrients upwelled from the halocline seaward of the shelf the decade long trend in summertime surface winds suggests that easterly winds in this region are increasing in strength and that such bloom events will become more common

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

waters of the makarov and canada basins abstract hydrographic measurements from the 1994 arctic ocean section show how the makarov and canada basins of the arctic ocean are related and demonstrate their oceanographic connections to the eurasian basin the inflow into the makarov basin consists largely of well ventilated water within a broad band of densities from a boundary flow over the siberian end of the lomonosov ridge the boundary flow contains a significant component of dense shelf water likely originating in the barents kara and laptev seas earlier ice camp data show that the canada basin is relatively more isolated from this ventilation source in the canada basin shelf sources influenced by bering sea water appear to add cold waters with high silicate concentrations to the halocline and deeper in 1994 the halocline silicate maximum over the central makarov basin was absent evidence of the recent displacement of the upper s 33 1 halocline water from the chukchi east siberian sea region by water from the eurasian basin much of the makarov basin water in and below the halocline is in fact from the eurasian basin with admixture of waters from the canada basin suggested by their higher silicate concentrations mid depth eddies may transport anomalous properties into the central arctic and create property gradients or fronts in mid depth and deep waters the complex topography of the mendeleyev ridge chukchi plateau region also may assist spreading of water from the boundary into the interior atlantic layer characteristics in 1994 differed from previous general depictions in particular the core temperatures at the chukchi mendeleyev boundary were at least 0 2 c warmer on average than indicated in earlier work the recent warming at intermediate depth has resulted from inflow of atlantic waters that have been cooled relatively little during their transit of the norwegian sea

mooring based observations of double diffusive staircases over the laptev sea slope abstracta yearlong time series from mooring based high resolution profiles of water temperature and salinity from the laptev sea slope 2003 04 2686 m depth 78 26 n 125 37 e shows six remarkably persistent staircase layers in the depth range of 140 350 m encompassing the upper atlantic water aw and lower halocline despite frequent displacement of isopycnal surfaces by internal waves and eddies and two strong aw warming pulses that passed through the mooring location in february and late august 2004 the layers preserved their properties using laboratory derived flux laws for diffusive convection the authors estimate the time averaged diapycnal heat fluxes across the four shallower layers overlying the aw core to be 8 w m 2 temporal variability of these fluxes is strong with standard deviations of 3 7 w m 2 these fluxes provide a means for effective transfer of aw heat upward over more than a 100 m depth range toward the upper halocline these findings suggest that double diffusion is an imp

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

cryosphere warmth from the deep unusual wind patterns and the albedo feedback effect played crucial roles in the rapid reduction of arctic sea ice cover in recent years evidence is now building that a warmer ocean has also contributed to the thinning of arctic ice

arctic warming through the fram strait oceanic heat transport from 3 years of measurements we present estimates of volume and heat transport through fram strait for the period 1997 to 2000 from data of moored instruments full depth volume transports at 78 55 n were in the order of 10 sv both northwards and southwards with an annual mean net transport between 2 and 4 sv to the south the temperature of the northward flow of atlantic water had a strong seasonality with a minimum in winter nevertheless the northward heat transport was highest in winter caused by the winter maximum of northward volume transport during the three years of observation the heat transport in the west spitsbergen current increased from 28 to 46 tw as a result of both increased speed and temperature in contrast to the west spitsbergen current the volume and heat transport of east greenland current remained fairly constant an integration over a subsection of the east greenland current showed similar values of volume transport to that obtained by measurements in the 1980s foldvik et al 1988 the southward heat transport through modified atlantic water weakened slightly between 1997 and 1999 despite increased temperatures

non equilibrium sediment transport in the three gorges reservoir based on field data analysis and mathematical model simulation the non equilibrium sediment transport law in the three gorges reservoir under large water depth was studied it is revealed that after the reservoir was put into operation the flood propagates in the form of gravity wave and the suspended sediment transported from the cuntan to huanglingmiao is lagged behind the flood for a long time by considering the unsteady flood process the calculated sediment deposited in the reservoir is more than that predicted in the past most fine sediment particles are deposited in the reservoir and the different percentage of particles in size does not obviously change the calculation result this phenomenon can not be explained by non equilibrium sediment transport theory if the flocculatiou is not considered when flocculation of fine sediment is taken into account the simulated reservoir outlet concentration is in good agreement with observation data it implies that the flocculation may exist in the reservoir and further study on this phenomenon is needed

relaxation of central arctic ocean hydrography to pre 1990s climatology 1 upper ocean hydrography in the central arctic ocean has relaxed since 2000 to near climatological conditions that pertained before the dramatic changes of the 1990s the behavior of the anomalies of temperature and salinity in the central arctic ocean follow a first order linear response to the ao with time constant of 5 years and a delay of 3 years

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

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

benthic macrofauna and megafauna assemblages in the arctic deep sea canada basin abstract the benthic component of an interdisciplinary expedition on icebreaker uscg healy analyzed box core samples and seafloor photographs to quantify deep sea assemblages in the canada basin and chukchi borderland area soft bottom metazoan macrofauna 250 m were collected with 33 box cores at 11 stations ranging from 817 to 3961 m water depth in the high arctic canada basin from 28 june to 25 july 2005 megabenthic epifauna was quantified with a digital camera platform suspended 2 89 2722 ind m 2 and total biomass ranged from 0 2 to 1 6 g wet weight 0 06 m 2 2 macrofauna diversity numbered between 8 and 55 taxa per station abundance biomass number of taxa and diversity indices of macrofauna declined significantly with water depth polychaetes crustaceans and bivalves dominated the macrofaunal densities biomass and species numbers the megafauna visible in the seabed photographs was assigned to a total of 67 provisional taxa the lowest taxon count per station was 11 and the highest was 51 at the pockmark station epifauna abundance was also highest in this pockmark mean 5 8 ind m 2 and generally lower at deepest stations 0 1 0 9 ind m 2 but was skewed by large numbers of the holothuroid kolga hyalina epifauna observed in the center of the pockmark was significantly different from all other station groups but did not include known chemosynthetic fauna or bacterial mats multivariate analysis indicated that station groupings chukchi slope canada basin abyss and the chukchi cap were significantly different in community composition in the macrofauna box corer samples but could not be similarly distinguished as such in the epifauna photographs

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

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

kugmallit valley as a conduit for cross shelf exchange on the mackenzie shelf in the beaufort sea 1 kugmallit valley spans the midsection of a transect across the mackenzie shelf of the beaufort sea its greatest relief is 20 m and its width is 20 km using a yearlong record of ice drift ocean current temperature and salinity acquired near the center of the valley we describe a pattern of flow that is correlated with wind stress and ice motion and discuss its similarity to flow within larger submarine canyons that cut through the shelf break as in such canyons there is enhanced cross shelf transport within kugmallit valley during upwelling favorable surface stress the data also document the down valley flow of dense water from a flaw lead

atlantic water circulation over the mendeleev ridge and chukchi borderland from thermohaline intrusions and water mass properties 1 hydrographic and tracer data from 2002 illustrate atlantic water pathways and variability in the mendeleev ridge and chukchi borderland cblmr region of the arctic ocean thermohaline double diffusive intrusions zigzags dominate both the fram strait fsbw and barents sea branch waters bsbw in the region we show that details of the zigzags temperature salinity structure partially describe the water masses forming the intrusions furthermore as confirmed by chemical tracers the zigzags peaks contain the least altered water allowing assessment of the temporal history of the atlantic waters whilst the fsbw shows the 1990s warming and then a slight cooling the bsbw has continuously cooled and freshened over a similar time period the newest boundary current waters are found west of the mendeleev ridge in 2002 additionally we show the zigzag structures can fingerprint various water masses including the boundary current using this tracer data and the advection of the 1990s warming we conclude the strongly topographically steered boundary current order 50 km wide and found between the 1500 m and 2500 m isobaths crosses the mendeleev ridge north of 80 n loops south around the chukchi abyssal plain and north around the chukchi rise with the 1990s warming having reached the northern but not the southern northwind ridge by 2002 pacific waters influence the atlantic layers near the shelf and over the chukchi rise the northwind abyssal plain is comparatively stagnant being ventilated only slowly from the north there is no evidence of significant boundary current flow through the chukchi gap

hypsometry and volume of the arctic ocean and its constituent seas 1 this paper presents an analysis of the arctic ocean and its constituent seas for seafloor area distribution versus depth and ocean volume the bathymetry from the international bathymetric chart of the arctic ocean ibcao is used together with limits defining this ocean and its constituent seas from the international hydrographic organization iho as well as redefined limits constructed to confine the seas to the shallow shelves ibcao is a bathymetric grid model with a resolution of 2 5 2 5 km which significantly improved the portrayal of the arctic ocean seafloor through incorporation of newly released bathymetric data including echo soundings from u s and british navies scientific nuclear submarine cruises and icebreaker cruises this analysis of seafloor area and ocean volume is the first for the arctic ocean based on this new and improved portrayal of the seafloor as represented by ibcao the seafloor area and volume are calculated for different depths starting from the present sea level and progressing in increments of 10 m to a depth of 500 m and in increments of 50 m from 550 m down to the deepest depth within each of the analyzed seas hypsometric curves expressed as simple histograms of the frequencies in different depth bins and depth plotted against cumulative area for each of the analyzed seas are presented the area and volume calculations show that the entire iho defined arctic ocean makes up 4 3 of the total ocean area but only 1 4 of the volume furthermore the iho arctic ocean is the shallowest mean depth 1201 m of all the major oceans and their adjacent seas the continental shelf area from the coasts out to the shelf break make up as much as 52 9 of the total area in the arctic ocean defined in this work as consisting of the oceanic deep arctic ocean basin the broad continental shelves of the barents kara laptev east siberian chukchi and beaufort seas the white sea and the narrow continental shelf off both the canadian arctic archipelago and northern greenland this result indicates that the arctic ocean has significantly larger continental shelves compared with all the other oceans where previous studies show that the proportion of shelves from the coasts out to the foot of the continental slopes only ranges between about 9 1 and 17 7 furthermore the derived hypsometric curves show that most of the arctic ocean shelf seas besides the barents sea beaufort sea and the shelf off northern greenland have a similar shape with the largest seafloor area between 0 and 50 m the east siberian and laptev seas in particular show area distributions concentrated in this shallow depth range and together with the chukchi sea they form a large flat shallow shelf province composing as much as 22 of the entire arctic ocean area but only 1 of the volume this implies that the circulation in the arctic ocean might be very sensitive to eustatic sea level changes one of the aims with this work is to make up to date high resolution area and volume calculations for the arctic ocean at various depths available for download

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

formation of gold deposits a metamorphic devolatilization model a metamorphic devolatilization model can explain the enrichment segregation timing distribution and character of many goldfields such as those found in archean greenstone belts slate belts and other gold only provinces in this genetic model hydrated and carbonated greenschist facies rocks particularly metabasic rocks are devolatilized primarily across the greenschist amphibolite facies boundary in an orogenic setting devolatilization operates on the scale of individual mineral grains extracting not just h2o and co2 but also s and in turn au elevated gold in solution is achieved by complexing with reduced s and by h2co3 weak acid buffering near the optimal fluid ph for gold solubility the buffering is more important than being at the point of maximum gold solubility low salinity ensures low base metal concentrations in the auriferous metamorphic fluid migration of this fluid upwards is via shear zones and or into hydraulic fracture zones in rocks of low tensile strength the geometry of the shear zones dictates the kilometre scale fluid migration paths and the degree of fluid focusing into small enough volumes to form economic accumulations of gold deposition of gold from solution necessitates breakdown of the gold thiosulphide complex and is especially facilitated by fluid reduction in contact with reduced carbon bearing host rocks and or by sulphidation of wallrocks to generate iron bearing sulphide and precipitated gold as such black slate carbon seams banded iron formation tholeiitic basalt magnetite bearing diorite and differentiated tholeiitic dolerite sills are some of the important hosts to major goldfields gold deposition is accompanied by carbonation sulphidation and muscovite biotite alteration where the host rock is of suitable bulk composition the correlation of major gold deposits with rock type even when the gold is primarily in veins argues for rock dominated depositional systems not fluid dominated ones as a consequence a general role in gold deposition for fluid mixing temperature decrease and or fluid pressure decrease and boiling is unlikely although such effects may be involved locally several geological features that are recorded at gold only deposits today reflect subsequent modifications superimposed upon the products of this generic metamorphic devolatilization process overprinting by higher grade metamorphism and deformation and or palaeo weathering may provide many of the most obvious features of goldfields including their mineralogy geochemistry geometry small scale timing features geophysical response and even mesoscopic gold distribution

role of panama uplift on oceanic freshwater balance comparison between planktic foraminiferal oxygen isotope records from the caribbean sea ocean drilling program odp site 999 and the equatorial east pacific odp site 851 suggests an increase in caribbean surface water salinity between 4 7 and 4 2 ma the modern atlantic pacific salinity contrast of about 1 became fully established at 4 2 ma as reflected by a 0 5 planktic foraminifera 18o enrichment in the caribbean sea this is interpreted as the result of restricted surface water exchange between the tropical atlantic and pacific in response to the shoaling of the central american seaway as a consequence the atlantic and pacific surface ocean circulation regime changed as did the freshwater balance between the major ocean basins simultaneous shifts in benthic carbon isotope records in the caribbean sea suggest an intensification in north atlantic thermohaline circulation these results indicate that the panamanian isthmus formation caused several new ocean atmosphere feedback mechanisms that have affected climate since the early pliocene

the arctic circumpolar boundary current abstract the main water transformations in the arctic mediterranean take place in the boundary current of atlantic water which crosses the greenland scotland ridge from the north atlantic into the eastern norwegian sea it enters and flows around the arctic ocean before it exits the arctic mediterranean as the east greenland current primarily through denmark strait on route it experiences numerous branchings and mergings by examining how the properties of this circumpolar boundary current evolve it is possible to identify and describe the processes causing the water mass transformations in the arctic mediterranean it is also possible to follow the arctic ocean deep waters as they spread into the nordic seas and eventually provide 40 of the overflow water supplying the north atlantic deep water

ventilation rate of the deep arctic ocean from carbon 14 data application of mass balances of 18o tritium and salt plus 14c data show that the deep eurasian basin exchanges water with the subarctic atlantic ocean on a time scale of 10 to 100 years while the deep canada basin has an exchange time scale of about 700 years only small fractions less than 10 to 15 of the deep waters originate from the shelves the deep canada basin cannot consist of fossil water from glacial time or from the latest cool climate spell just 100 to 300 years ago