iron and humic type fluorescent dissolved organic matter in the chukchi sea and canada basin of the western arctic ocean 1 the concentrations of dissolved fe d fe total dissolvable fe t fe humic type fluorescence intensity humic f intensity as humic type fluorescent dissolved organic matter and nutrients were vertically determined in the shelf slope and basin regions chukchi sea and canada basin of the western arctic ocean during 1 27 september 2008 in all stations the remarkably high d fe and humic f intensity were found at depths between 25 and 200 m with the subsurface maxima of d fe 1 0 3 2 nm and humic f intensity 4 5 quinine sulfate units in the upper halocline layer upper hl being associated with a prominent nutrient maximum the high d fe and humic f intensity within the upper hl are probably attributed to the fe iii complexation with natural organic ligands such as marine dissolved humic substances resulting from main processes of the brine rejection during sea ice formation and interactions with sediments on the shelves however subsurface maxima 10 50 nm of t fe were found in the lower halocline layer beneath the upper hl of all slope and basin regions and are mainly attributed to the resuspension of sedimentary particles in the shelf region the finding of subsurface iron maxima in the halocline water of all regions may be the first confirmation for the lateral iron transport into the halocline layer from the shelves to the arctic basin

halocline structure in the canada basin of the arctic ocean 1 we examine the varieties and spatial distributions of pacific and eastern arctic origin halocline waters in the canada basin using 2002 2003 hydrographic data the halocline structure in the canada basin is different from the eastern arctic halocline because it includes fresher pacific winter waters that form a cold halostad which lies above the eastern arctic origin lower halocline waters the structure of the halostad in the canada basin however is not spatially uniform and depends on the pathway and history of the source water pacific winter water entering through the bering strait becomes salty due to sea ice formation and this in turn is dependent on the occurrence and distribution of polynyas in particular saline water from the eastern chukchi sea forms thick halostad and causes depression of the isohalines in the southern canada basin this depression influences thermohaline structure of the oceanic beaufort gyre

beaufort shelf break eddies and shelf basin exchange of pacific summer water in the western arctic ocean detected by satellite and modeling analyses 1 mesoscale eddies and shelf basin exchange of pacific summer water in the western arctic ocean are examined using satellite data sets and an eddy resolving coupled sea ice ocean model several surface eddy like features along the beaufort shelf break are detected by the moderate resolution imaging spectroradiometer modis sea surface temperature and the global imager gli radiance image the quikscat sea wind vectors indicate that summertime shelf wide wind is an important factor for interannual variations in the eddy properties a realistic numerical experiment reveals that the origin of shelf break warm eddies and timing of their generation can be classified into three types type i eddies are frequently produced in the vicinity of the barrow canyon throughout the summer season by a combination of outflow of pacific summer water with a low potential vorticity from the barrow canyon and lateral velocity shear of the canyon jet surface wind variability modulates the timing of generation type ii and type iii eddies originate from an eastward current along the beaufort shelf break although origin depth and background hydrographic structure differ between them type ii eddies are spawned from the shelf slope at middepth during early summer type iii eddies are generated from the surface isopycnal front over the shelf break during late summer the shift from type ii eddies to type iii eddies is caused by surface buoyancy input in the upstream region a sensitivity experiment using different atmospheric forcing data suggest that the mechanism controlling pacific water transport from the chukchi shelf to the canada basin differs depending on surface wind fields in the shelf region the mesoscale eddies primarily induce the shelf to basin transport under weak or westerly wind conditions during summer while wind driven ekman transport is a major driver in the easterly wind regime year 2003 2007 corresponds to the former latter case

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

microstructure observations of turbulent heat fluxes in a warm core canada basin eddy abstractan intrahalocline eddy was observed on the chukchi slope in september of 2015 using both towed ctd and microstructure temperature and shear sections the core of the eddy was 6 c significa

optical properties in waters around the mendeleev ridge related to the physical features of water masses abstract irradiance profiles were measured during the korean 2012 summer arctic ocean cruise and optical properties were studied the optical attenuation coefficient in all surface waters was low as the nutrients in the surface layers became exhausted and phytoplankton growth was only possible at the subsurface where optimal conditions of nutrients and sufficient illumination existed this high attenuation zone was at about 40 60 m the attenuation properties were categorized to three types type 1 waters had weaker maximum attenuation coefficients and were located at the chukchi plateau and the north margin of the study region type 2 water had an intense maximum of attenuation coefficient up to 0 56 m located on west flank of mendeleev ridge and continental slope of east siberian sea two integral parameters attenuation depth and optical thickness were mapped by spatial distribution the attenuation depth was basically shallower 40 m to the west and deeper to the east 100 m the averaged optical thickness at the level of 30 60 m was the main zone of high attenuation both the optical attenuation property and the physical features of the water indicated two subsurface water masses one is the cold shelf water well mixed with river water and transported to the east by a subsurface current along the east siberian slope the other is the warmer water from the pacific with lower nutrients and transported to the northwest along the north margin of the observed region a cyclonically re circulated branch of shelf water passing over the chukchi abyssal plain was described in this study

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

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

application of aerosondes to high resolution observations of sea surface temperature over barrow canyon 1 continuous observation of sea surface temperature sst were obtained for a period of 27 hours over barrow canyon on 20 21 september 2002 using a small robotic aircraft called the aerosonde these observations demonstrated significant spatial and temporal variations in the sst at scales that would be very difficult to measure using mooring and satellite observations over a region of 25 km2 sst values varied from 1 6 c a sharp sst front with a temperature gradient of 3 c was observed over the northwestern shelf of barrow canyon which moved northward during the observation period relatively cold water was transported from the southwest into the region current speeds were estimated using the time series of observations this analysis demonstrates new technology for oceanographic observations and supports previous evidence that the flow through barrow canyon has a strongly sheared flow into the arctic ocean

experimental formation of spiky calcite through organically mediated dissolution abstract cultures of known species of fungi placed on crystals of iceland spar calcite resulted in extensive dissolution of the calcite this organically mediated dissolution produced large patches of spiky calcite within a period of 253 days the dissolution of the calcite occurred via surface reaction controlled kinetic processes that were mediated by the fungi this occurred despite the lack of vast quantities of fluids undersaturated with respect to calcite locally at least 10 m of calcite was removed from the original crystal surface

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

early summer water mass transformation in the eastern chukchi sea abstract pacific water entering the chukchi sea through bering strait can be modified by physical processes such as surface heating and cooling and internal mixing here we document the existence of a previously unobserved water mass in the eastern chukchi sea during the early summer using hydrographic and velocity data from the june july 2010 icescape survey the water mass in question is as salty as pacific winter water pww but is much warmer with temperatures typical of summer waters we label the water mass dense chukchi summer water dcsw which is dense enough to ventilate the upper halocline of the western arctic ocean normally ventilated by the much colder pww satellite sea surface temperature data long term mooring data from bering strait and the beaufort shelfbreak and atmospheric reanalysis fields are used to characterize the spatial and temporal variability of the dcsw and explore potential forcing scenarios that can lead to its formation in 2010 the dcsw did not enter the chukchi sea through bering strait hence it had to be formed locally on the shelf two distinct forcing mechanisms are considered 1 mixing of very warm alaskan coastal water with the cold pww when the two water masses come in contact in the energetic alaskan coastal current and 2 warming of pww when it experiences solar heating within the coastal polynya in the northeastern chukchi sea during the spring melt season finally we explore the conditions under which the springtime polynya has formed over the past three decades as it relates to the formation of dcsw

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

the profile of the rare earth elements in the canada basin arctic ocean we analyzed the dissolved rare earth element ree content of three water column profiles two shelf sites and one deep basin site in the canada basin in order to better constrain the behavior of rees in the arctic ocean dissolved concentrations of the rees in the surface are 1 3 to 1 9 times higher than deep water 500 m concentrations which are constant with depth la 19 23 pm nd 14 17 pm yb 4 0 4 3 pm the dominant source of rees to the surface waters of the canada basin is most likely pacific water flowing through the bering strait and chukchi sea and or the mackenzie river dissolved rees in the intermediate and deep waters are constant and appear to behave conservatively allowing us to investigate this aspect of ree behavior in the oceans calculated deep ocean residence times of the rees in the canada basin range from 450 700 years and match the age of these waters we postulate that these values are likely applicable to global deep ocean reservoirs and that observed deviations from this conservative value can help to constrain non conservative processes acting on the rees this article is protected by copyright all rights reserved

on the record reduction in 1998 western arctic sea ice cover during summer 1998 record reductions in ice cover occurred in the beaufort and chukchi seas open water formed earlier than in prior years and september ice extent in this region was 25 percent less than the previous minimum for 1953 1997 seven percent of the arctic basin that had been perennially ice covered was ice free in 1998 this reduction in western arctic ice extent can be attributed in part to preconditioning by light ice cover in autumn 1997 and to atmospheric circulation patterns during the following winter through autumn that favored southerly and easterly winds such decreases in northerly winds and the associated weakening or displacement of the beaufort gyre is found to be typical of winters that precede years with below normal ice extent in the western arctic

varieties of shallow temperature maximum waters in the western canadian basin of the arctic ocean the properties and spreading pathways of shallow temperature maximum waters stms in the western canadian basin are investigated using ctd and mooring data obtained in 1997 98 as part of the sheba surface heat budget of the arctic ocean drift experiment and available historical data three distinct varieties of stm are recognized on the basis of salinity range 1 surface mixed layer water smlw with s 32 psu these stms carry sufficient heat within the upper layers of the ocean to significantly affect the rates of ice cover and decay for example during the winter of 1997 98 anomalously warm stm 0 c originating from ecsw was observed to spread northwards along the northwind ridge and chukchi plateau where the maximum reduction of the ice covers was subsequently observed in late summer 1998 maslanik et al 1999 regional climate variability and ice cover in the western canadian basin are thus affected not only by anomalous atmospheric circulation patterns but also by the circulation of upper ocean water masses

vertical diffusivity of the western arctic ocean halocline a nearly year long series of upper ocean temperature conductivity and temperature microstructure profiles were collected from an ice camp drifting in the beaufort gyre as part of the 1997 1998 surface heat budget of the arctic experiment sheba geographically the record includes portions over the deep canada basin and the steep bathymetry of the chukchi borderlands region hydrographically the record includes cool pacific origin haloclines which contain a variety of subsurface temperature maxima and cold haloclines typical of the eurasian basins we present estimates of the vertical turbulent diffusivity derived from the dissipation rate of thermal variance and calculations of the associated vertical heat fluxes we find that vertical diffusion proceeds at molecular rates in the deep basins and away from topographic features while still relatively small diffusivity is enhanced by 1 order of magnitude near and above the chukchi borderlands the enhanced diffusivity is correlated to an increase in water column strain variance above the borderlands providing a linkage between bathymetry internal wave activity and turbulence the chukchi borderlands play a significant role in heat transport in the western arctic they are a pathway for horizontal heat transport and a hot spot for vertical heat transport vertical fluxes make a substantial contribution to the energy balance of the sea ice cover in this region heat fluxes between the halocline and underlying atlantic water are shown to be small and lacking vertical connection near surface waters

vertical structure and temporal variability of currents over the chukchi sea continental slope abstract observations from a single mooring site on the northern chukchi sea continental slope near the 1000 m isobath are presented this site was occupied consecutively for three years spanning september 2014 august 2017 vertically the flow divides into three depth ranges the upper 200 m 200 850 m and near bottom flow in the upper 200 m the mean flow was northwestward and strongest in the summer months during winter months currents decreased in magnitude and in some years even reversed in direction satellite tracked drifter trajectories drogue depth 30 m show this along slope flow persists at least from 156 to 165 w with an average velocity of 17 cm s 1 this northwestward flowing current is the chukchi slope current from 250 m to 850 m the flow reversed this weak flow is the arctic wide cyclonic boundary current advecting atlantic water the mean flow at 900 m is weak and on an annual time scale not significantly different from 0 cm s 1 it consists of arctic deep water in the upper two layers currents vary on the scale of days to seasons with short term reversals common currents below 40 m were not significantly correlated with local winds nor wind stress curl we hypothesize that the northwestward flowing chukchi slope current is a consequence of dynamics associated with the beaufort gyre

pacific freshwater river water and sea ice meltwater across arctic ocean basins results from the 2005 beringia expedition 1 pacific water sea ice meltwater and river water are the primary sources of freshwater in the arctic ocean we have determined their relative fractions on a transect across the arctic ocean section 2005 expedition onboard ib oden which took place from 21 august to 23 september 2005 the transect began north of alaska continued through the central canada basin to the alpha ridge and into the makarov basin and ended in amundsen basin pacific freshwater and river water were the major sources of freshwater throughout the central canada basin and into makarov basin with river water fractions sometimes considerably higher than pacific water in the top 50 m pacific freshwater extended to depths of about 200 m pacific water found over the alpha ridge and in the amundsen basin is suggested to have been transported there in the transpolar drift the inventories of pacific freshwater and river water were roughly constant along the section through most of the canada and makarov basins river water fractions were greater than those of pacific freshwater in the amundsen basin sea ice meltwater fractions were negative reflecting net ice formation or near zero throughout most of the section a comparison of freshwater inventories with those at stations occupied during expeditions in 1991 1994 and 1996 indicated an increase in river water inventories in the makarov and amundsen basins on the eurasian side of the arctic ocean

holocene sea ice history and climate variability along the main axis of the northwest passage canadian arctic 1 palynological geochemical and physical records were used to document holocene paleoceanographic changes in marine sediment core from dease strait in the western part of the main axis of the northwest passage core 2005 804 006 pc latitude 68 59 552 n longitude 106 34 413 w quantitative estimates of past sea surface conditions were inferred from the modern analog technique applied to dinoflagellate cyst assemblages the chronology of core 2005 804 006 pc is based on a combined use of the paleomagnetic secular variation records and the cals7k 2 time varying spherical harmonic model of the geomagnetic field the age depth model indicates that the core spans the last 7700 cal years b p with a sedimentation rate of 61 cm ka 1 the reconstructed sea surface parameters were compared with those from barrow strait and lancaster sound cores 2005 804 004 pc and 2004 804 009 pc respectively which allowed us to draw a millennial scale holocene sea ice history along the main axis of the northwest passage manwp overall our data are in good agreement with previous studies based on bowhead whale remains however dinoflagellate sea surface based reconstructions suggest several new features the presence of dinoflagellate cysts in the three cores for most of the holocene indicates that the manwp was partially ice free over the last 10 000 years this suggests that the recent warming observed in the manwp could be part of the natural climate variability at the millennial time scale whereas anthropogenic forcing could have accelerated the warming over the past decades we associate holocene climate variability in the manwp with a large scale atmospheric pattern such as the arctic oscillation which may have operated since the early holocene in addition to a large scale pattern more local conditions such as coastal current tidal effects or ice cap proximity may have played a role on the regional sea ice cover these findings highlight the need to further develop regional investigations in the arctic to provide realistic boundary conditions for climatic simulations

plio pleistocene trends in ice rafted debris on the lomonosov ridge although more than 700 sediment cores exist from the arctic ocean the plio pleistocene evolution of the basin and its marginal seas remains virtually unknown this is largely due the shallow penetration of most of these records and difficulties associated with deriving chronologies for the recovered material the integrated ocean drilling program s iodp expedition 302 arctic coring expedition acex recovered 197 m of neogene quaternary sediment from the circumpolar regions of the lomonosov ridge as detailed analyses of this material emerge research is beginning to formulate a long term picture of paleoceanographic changes in the central arctic ocean this paper reviews the acex plio pleistocene age model identifies uncertainties and addresses ways in which these may be eliminated within the established stratigraphic framework a notable reduction in the abundance of ice rafted debris ird occurs in the early part of the pleistocene and persists until marine isotope stage 6 mis 6 therefore while global oceanographic proxies indicate the gradual growth of terrestrial ice sheets during this time ird delivery to the central arctic ocean remained comparatively low and stable within the resolution of existing data the pleistocene reduction in ird is synchronous with predicted changes in both the inflow of north atlantic and pacific waters which in modern times are known to exert a strong influence on sea ice stability

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

iron nutrients and humic type fluorescent dissolved organic matter in the northern bering sea shelf bering strait and chukchi sea 1 the concentrations of dissolved fe dfe total dissolvable fe humic type fluorescence intensity humic f intensity as humic type fluorescent dissolved organic matter humic type fdom and nutrients were determined vertically in the northern bering sea shelf yukon river estuary region and st lawrence island polynya region the eastern chukchi sea shelf chukchi shelf polynya region and the central bering strait during 30 july to 12 august 2007 and 30 june to 12 july 2008 in early july 2008 with a nearly peak river water discharge period remarkably high humic f intensity and high dfe were found with a decrease in salinity s 26 30 in the surface water of the yukon river estuarine region these results suggest that riverine humic type fdom is responsible for dfe in coastal waters with natural organic ligand complexation of fe iii apparently playing an important role in iron transport to the northern bering sea shelf in the st lawrence island and chukchi shelf polynya regions cold dense waters t 1 5 to 1 7 c and 26 2 to 26 7 were found in deep and bottom waters the cold waters are characterized by high nutrient and iron concentrations and high humic f intensity probably resulting from two main processes brine rejection during sea ice formation and transport across the sediment water interface during early diagenesis in the central bering strait the waters are vertically uniform with high salinity s 32 5 and high nutrient and iron concentrations these waters appear to originate from the outer shelf of the bering sea and are not affected by denitrification occurring in bottom sediments of the bering shelf

the western arctic boundary current at 152 w structure variability and transport abstract from august 2002 to september 2004 a high resolution mooring array was maintained across the western arctic boundary current in the beaufort sea north of alaska the array consisted of profiling instrumentation providing a timeseries of vertical sections of the current here we present the first year velocity measurements with emphasis on the pacific water component of the current the mean flow is characterized as a bottom intensified jet of o 15 cm s 1 directed to the east trapped to the shelfbreak near 100 m depth its width scale is only 10 15 km seasonally the flow has distinct configurations during summer it becomes surface intensified as it advects buoyant alaskan coastal water in fall and winter the current often reverses flows westward under upwelling favorable winds between the storms as the eastward flow re establishes the current develops a deep extension to depths exceeding 700 m in spring the bottom trapped flow advects winter transformed pacific water emanating from the chukchi sea the year long mean volume transport of pacific water is 0 13 0 08 sv to the east which is less than 20 of the long term mean bering strait inflow this implies that most of the pacific water entering the arctic goes elsewhere contrary to expected dynamics and previous modeling results possible reasons for this are discussed the mean atlantic water transport to 800 m depth is 0 047 0 026 sv also smaller than anticipated

seasonal to mesoscale variability of water masses and atmospheric conditions in barrow canyon chukchi sea abstract twenty four repeat hydrographic transects occupied across barrow canyon from 2010 to 2013 are used to study the seasonal evolution of water masses in the canyon from july october as well as the occurrence of upwelling the mean sections revealed that the alaskan coastal water is mainly confined to the eastern flank of the canyon corresponding to a region of sloped isopycnals indicative of the surface intensified alaskan coastal current which advects the water the pacific origin winter water is found at depth banked against the western flank of the canyon its isopycnal structure is consistent with a bottom intensified flow of this dense water mass out of the canyon for the months that were sampled the alaskan coastal water is most prevalent in august and september while the coldest winter water is observed in the month of august it is argued that this newly ventilated winter water is delivered to the canyon via pathways on the central chukchi shelf as opposed to the coastal pathway roughly a third of the hydrographic sections were preceded by significant up canyon winds and hence were deemed to be under the influence of upwelling during these periods anomalously salty water is found throughout the eastern flank of the canyon and on occasion atlantic water fills the deepest part of the section using atmospheric reanalysis data it is shown that upwelling occurs when the beaufort high is strengthened and the aleutian low is deepened two modes of storm tracks were identified northward progressing storms mode 1 and eastward progressing storms mode 2 both of which can drive upwelling mode 1 is prevalent in july august while mode 2 is more common in september october these seasonal patterns appear to be dictated by regional variations in blocking highs

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

sources and distribution of fresh water in the east greenland current abstract fresh water flowing from the arctic ocean via the east greenland current influences deep water formation in the nordic seas as well as the salinity of the surface and deep waters flowing from there this fresh water has three sources pacific water relatively fresh cf atlantic water river runoff and sea ice meltwater to determine the relative amounts of the three sources of fresh water in may 2002 we collected water samples across the east greenland current in sections from 81 5 n to the irminger sea south of denmark strait we used nitrate phosphate relationships to distinguish pacific waters from atlantic waters salinity to obtain the sum of sea ice melt water and river runoff water and total alkalinity to distinguish the latter river runoff contributed the largest part of the total fresh water component in some regions with some inventories exceeding 12 m pacific fresh water pacific source water s 32 cf atlantic source water s 34 9 typically provided about 1 3 of the river runoff contribution sea ice meltwater was very nearly non existent in the surface waters of all sections likely at least in part as a result of the samples being collected before the onset of the melt season the fresh water from the arctic ocean was strongly confined to near the greenland coast we thus conjecture that the main source of fresh water from the arctic ocean most strongly impacting deep convection in the nordic seas would be sea ice as opposed to fresh water in the liquid phase i e river runoff pacific fresh water and sea ice meltwater

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

western arctic shelfbreak eddies formation and transport abstract the mean structure and time dependent behavior of the shelfbreak jet along the southern beaufort sea and its ability to transport properties into the basin interior via eddies are explored using high resolution mooring data and an idealized numerical model the analysis focuses on springtime when weakly stratified winter transformed pacific water is being advected out of the chukchi sea when winds are weak the observed jet is bottom trapped with a low potential vorticity core and has maximum mean velocities of o 25 cm s 1 and an eastward transport of 0 42 sv 1 sv 106 m3 s 1 despite the absence of winds the current is highly time dependent with relative vorticity and twisting vorticity often important components of the ertel potential vorticity an idealized primitive equation model forced by dense weakly stratified waters flowing off a shelf produces a mean middepth boundary current similar in structure to that observed at the mooring site the model boundary current is also highly v

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

modeling the formation and fate of the near surface temperature maximum in the canadian basin of the arctic ocean 1 a numerical model is used to investigate the time and space extent of the near surface temperature maximum nstm of the canadian basin of the arctic ocean over the years 2000 2009 the nstm is formed from local summertime absorption of solar radiation which in some circumstances descends through the fall and early winter to form a warm subsurface layer just below the winter mixed layer we find that winter survival of this layer is confined largely to the beaufort gyre of the canadian basin where ekman convergence and downwelling push the summer warm layer down below the winter mixing depth in recent years summer stratification has increased downwelling has accelerated and the nstm has warmed as the sea ice cover in the beaufort gyre has thinned the result is a strengthening nstm which contained enough heat by the end of winter 2007 2008 to melt about 20 cm of sea ice northwest of alaska the model also simulates a second deeper temperature maximum layer that forms from advection of saltier summer pacific water however this layer is difficult to adequately resolve and maintain given the model s resolution

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

incorporation of satellite derived thin ice data into a global ogcm simulation the presence of thin sea ice is indicative of active freezing conditions in the polar ocean we propose a simple yet effective method to incorporate information of thin ice category into coupled ocean sea ice model simulations in our approach the thin ice distribution restricts thick ice extent and constrains atmosphere ocean heat exchange through the sea ice our model simulation with the incorporation of satellite derived thin ice data for the arctic ocean showed much improved representation of sea ice and upper ocean fields including sea ice thickness in the canadian archipelago and the region north of greenland mixed layer depth over the central arctic and surface layer salinity over the open ocean enhanced sea ice production by the thin ice data constraint increased the total sea ice volume of the arctic ocean by 5 times 10 3 10 times 10 3 km3 subsequent sea ice melting was also enhanced leading to the greater amplitude of the seasonal cycle by approximately 2 times 10 3 km3 15 of the baseline value from the experiment without the thin ice data incorporation overall our results demonstrate that the incorporation of satellite derived information on thin sea ice has great potential for the improvement of coupled ocean sea ice simulations

changes to the near surface waters in the canada basin arctic ocean from 1993 2009 a basin in transition 1 increased sea ice melt and decreased surface albedo have changed the near surface water mass structure of the canada basin from 1993 2009 the near surface temperature maximum nstm and remnant of the previous winter s mixed layer rwml warmed by about 1 5 c and 0 5 c and freshened by about 4 and 2 practical salinity units respectively results from a 1 d model suggest rwml warming can be explained by heat diffusion from both the nstm and pacific summer water psw the same model predicts salinization of the rwml whereas freshening was observed this suggests that changes to the rwml are from both diffusion and the accumulation of freshwater the rwml s salinity was associated with distance from the center of the beaufort gyre the rwml at stations inside the gyre was on average 1 9 salinity units fresher than at stations outside in addition the salinity of psw in the canada basin defined by its local temperature maximum freshened from about 30 32 in 1993 to 28 32 in 2008 order of magnitude calculations suggest that neither changes in psw source waters nor changes in advection pathways of psw explain this freshening our model suggests that salt diffused from psw to the freshening rwml this diffusion increased and freshened the psw salinity range as the rwml freshened these results show that surface effects through warming and ice melt are felt to at least the depth of psw observations from 2009 show the appearance of a third temperature maximum from an as yet unknown source

two configurations of the western arctic shelfbreak current in summer abstractdata from a closely spaced array of moorings situated across the beaufort sea shelfbreak at 152 w are used to study the western arctic shelfbreak current with emphasis on its configuration during the summer season two dynamically distinct states of the current are revealed in the absence of wind with each lasting approximately one month the first is a surface intensified shelfbreak jet transporting warm and buoyant alaskan coastal water in late summer this is the eastward continuation of the alaskan coastal current it is both baroclinically and barotropically unstable and hence capable of forming the surface intensified warm core eddies observed in the southern beaufort sea the second configuration present during early summer is a bottom intensified shelfbreak current advecting weakly stratified chukchi summer water it is baroclinically unstable and likely forms the middepth warm core eddies present in the interior basin the mesoscale instabilities extract energy from the mean flow such

absorption and fluorescence of dissolved organic matter in the waters of the canadian arctic archipelago baffin bay and the labrador sea the optical properties of dissolved organic matter dom were investigated for the first time in the canadian arctic archipelago caa baffin bay bb and labrador sea ls as part of the international polar year canada s three oceans project c3o the dynamics and composition of absorbing dom i e colored dom or cdom and fluorescent dom fdom were evaluated in several distinct water masses occupying the three regions surface waters arctic outflow waters west greenland intermediate waters wgiw upper labrador sea waters ulsw and bottom baffin deep water bbdw four fluorescent components were identified by applying parallel factor analysis parafac to 522 excitation emission matrix eem spectra three humic like and one protein like the fdom in surface waters of the caa and bb differed considerably in character from those of the ls with higher fluorescence intensity in the former the fluorescence intensities of the two terrestrial humic like components c1 and c3 were linearly correlated with apparent oxygen utilization aou in the caa arctic outflow and the wgiw whereas only humic like c3 was significantly correlated with aou in ulsw these findings suggest that the humic like components were produced in situ as organic matter was bio oxidized the slopes of the linear relationship between humic like intensity and aou were significantly greater in the wgiw relative to the arctic outflow waters which implies that fdom in the arctic derived deeper layer was less prone to mineralization

enhanced diapycnal mixing due to near inertial internal waves propagating through an anticyclonic eddy in the ice free chukchi plateau abstractthe arctic ocean is known to be quiescent in terms of turbulent kinetic energy tke associated with internal waves to investigate the current state of tke in the seasonally ice free chukchi plateau arctic ocean this study performed a 3 week fixed point observation fpo using repeated microstructure hydrographic and current measurements in september 2014 during the fpo program the microstructure observation detected noticeable peaks of tke dissipation rate e during the transect of an anticyclonic eddy moving across the fpo station particularly e had a significant elevation in the lower halocline layer near the critical level reaching the order of 10 8 w kg 1 the adcp measured current displayed energetic near inertial internal waves niws propagating via the stratification at the top and bottom of the anticyclone according to spectral analyses of horizontal velocity the waves had almost downward energy propagation and its current amplitude reached 10 cm s 1 the wkb scaling inco

hydrographic changes in the lincoln sea in the arctic ocean with focus on an upper ocean freshwater anomaly between 2007 and 2010 hydrographic data from the arctic ocean show that freshwater content in the lincoln sea north of greenland increased significantly from 2007 to 2010 slightly lagging changes in the eastern and central arctic the anomaly was primarily caused by a decrease in the upper ocean salinity in 2011 upper ocean salinities in the lincoln sea returned to values similar to those prior to 2007 throughout 2008 2010 the freshest surface waters in the western lincoln sea show water mass properties similar to fresh canada basin waters north of the canadian arctic archipelago in the northeastern lincoln sea fresh surface waters showed a strong link with those observed in the makarov basin near the north pole the freshening in the lincoln sea was associated with a return of a subsurface pacific water temperature signal although this was not as strong as observed in the early 1990s comparison of repeat stations from the 2000s with the data from the 1990s at inline image showed an increase of the atlantic temperature maximum which was associated with the arrival of warmer atlantic water from the eurasian basin satellite derived dynamic ocean topography of winter 2009 showed a ridge extending parallel to the canadian archipelago shelf as far as the lincoln sea causing a strong flow toward nares strait and likely fram strait the total volume of anomalous freshwater observed in the lincoln sea and exported by 2011 was close to inline image approximately 13 of the total estimated fw increase in the arctic in 2008

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

zooplankton inside an arctic ocean cold core eddy probable origin and fate abstract in september 2004 an extensive survey of a cold core eddy in the canada basin western arctic was carried out with high horizontal resolution physical and chemical sampling and lower horizontal resolution biological sampling the eddy was located over the continental slope north of the chukchi shelf and had a radius of 8 km its core was centered at a depth of 160 m water mass characteristics and the presence of copepods from the north pacific ocean neocalanus flemingeri and metridia pacifica demonstrated that the core contained water of pacific origin vertical distributions of zooplankton were associated with the physical structure of the water column for most taxa concentrations in the eddy core were elevated compared with those in similar density water in the surrounding basin based on tracer age estimates and previous observations of eddy formation the eddy is believed to have been formed during the previous spring summer from the chukchi shelfbreak jet surprisingly the eddy also contained elevated abundances of arctic origin copepods metridia longa and calanus glacialis analysis of a shelf basin transect occupied in the region in august 2004 showed that these species were present in high abundances in relatively shallow water 50 m inshore of the shelfbreak due to upwelling of deeper basin water and copepods onto the shelf in response to easterly winds if the formation of the observed eddy occurred during or shortly after a period of such winds upwelled arctic origin copepods on the shelf might have been entrained into the feature our observations suggest that formation and subsequent migration of such eddies may provide a mechanism for transporting zooplankton from the chukchi shelf into the interior canada basin the periodic input of high abundances of zooplankton from productive shelf areas could affect food webs in the less productive basin

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

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

mechanisms of pacific summer water variability in the arctic s central canada basin pacific water flows northward through bering strait and penetrates the arctic ocean halocline throughout the canadian basin sector of the arctic in summer pacific summer water psw is modified by surface buoyancy fluxes and mixing as it crosses the shallow chukchi sea before entering the deep ocean measurements from ice tethered profilers moorings and hydrographic surveys between 2003 and 2013 reveal spatial and temporal variability in the psw component of the halocline in the central canada basin with increasing trends in integrated heat and freshwater content a consequence of psw layer thickening as well as layer freshening and warming it is shown here how properties in the chukchi sea in summer control the temperature salinity properties of psw in the interior by subduction at isopycnals that outcrop in the chukchi sea results of an ocean model forced by idealized winds provide support to the mechanism of surface ocean ekman transport convergence maintaining psw ventilation of the halocline

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

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

shoaling of the nutricline with an increase in near freezing temperature water in the makarov basin 1 the water mass changes in the makarov basin and adjacent areas associated with the recent loss of arctic sea ice had not been studied in detail we combined data obtained from multiple cruises in these regions and used chemical tracers to investigate the spatial and temporal changes in water masses our data show that a previously present temperature maximum water has disappeared from the makarov basin and chukchi abyssal plain due to enhanced cooling and convection in the east siberian sea in addition a large volume of water has formed by cooling and convection and is flowing into the makarov basin producing a temperature minimum with relatively high nutrients and resulting in a shoaling of the nutricline this temperature minimum water likely originated from the eastern part of the east siberian sea where significant open water areas appeared after 2005 in the freeze up season the water mass boundary between this temperature minimum water and the pacific origin temperature minimum water shifted westward from the chukchi plateau in the early 2000s to the mendeleyev ridge in the late 2000s probably owing to a westward flow of the enhanced beaufort gyre associated with recent sea ice loss in the canada basin although the shoaling of the nutricline in the makarov basin could increase phytoplankton production such production could decrease in the southern makarov basin because a large amount of sea ice meltwater covers that region and might decrease the nutrient supply from the subsurface layer