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

arctic ocean circulation processes and water masses a description of observations and ideas with focus on the period prior to the international polar year 2007 2009 abstract the evolving knowledge of the arctic ocean its hydrography and its water masses and their transformations and circulation is reviewed starting with the observations made on fram 1893 1896 and extending to the international polar year ipy 2007 2009 the expeditions and observations after fram to the mid 20th century as well as the more extensive and systematic studies of water masses and circulation made from ice stations and airborne expeditions from the late 1940s to the late 1970s are briefly described the early concepts of the connections and exchanges between the arctic ocean and the world ocean are also discussed in the 1980s scientific icebreakers were beginning to enter the inner parts of the arctic ocean and large international programmes were launched culminating in the ipy the changes in the arctic ocean first noted in the atlantic layer in 1990 and shortly after in the upper layers are described the exchanges between the arctic ocean and the surrounding seas through the four main openings fram strait barents sea bering strait and the canadian arctic archipelago as well the volume and freshwater balances of the arctic ocean are examined

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

reconstruction of ice conditions in the northern chukchi sea during recent centuries geochemical proxy compared with observed data abstract this paper presents the first results of the quantitative reconstruction of ice conditions in the arctic based on a comparison of the data for periods of meteorological observations with variations in the chemical compositions of the sediments accumulated during the same times the biogenic elements br ca and sr and some redox sensitive as and fe elements are the most informative for the reconstruction of changes in ice conditions with positive correlations and the lithogenic elements k and ti are predominantly negatively correlated the reconstruction results for the last 300 400 years of average annual air temperature anomalies for all cores in general terms coincide with the reconstruction for the northern hemisphere the common features of all reconstructions are low temperatures during the little ice age lia and a rapid warming in the middle of the 19th century and in the last decades of the 20th and first decades of the 21st centuries the results of the reconstruction of the duration of the ice free period generally coincide with the temperature changes for the last two centuries although for lia there is an inverse correlation between the variations in temperature and the duration of the ice free period a possible reason for this may be changes in the structure of the surface currents in the chukchi sea and the northern part of the bering sea because of which the inflow of warm and freshened waters through the bering strait to the arctic increased occasionally

renewal and circulation of intermediate waters in the canadian basin observed on the scicex 96 cruise during the summer of 1996 the nuclear submarine uss pogy occupied a line of stations extending through the middle of the canadian basin between about 88 n 44 w lomonosov ridge and about 78 n 144 w center of the canada basin ctd niskin bottle casts extending to 1600 m were carried out at eight stations providing the first high quality temperature salinity cfc tritium and 3he data obtained from this region although xctd data had previously been collected in this region these data along with data from stations at the basin boundary to the south and west reveal the presence of well ventilated intermediate water beneath the halocline in the center of the canada basin indicating renewal times of the order of 1 2 decades the least ventilated intermediate water was observed at the northern end of the canada basin along the southern flank of the alpha ridge intermediate water is derived from the atlantic ocean and enters the arctic ocean through fram strait and the barents sea it flows around the arctic basins in boundary currents and splits in the eastern amundsen basin with one branch crossing the lomonosov ridge and flowing along the east siberian continental slope and the other flowing along the eurasian flank of the lomonosov ridge from the 1996 scientific ice expedition scicex 96 observations we conclude that the branch that flows along the east siberian continental slope transports this water to the chukchi rise where it apparently enters the central canada basin with some flow continuing along the boundary to the southern canada basin the fram strait branch water mixes extensively with waters from the canadian basin during its transit along the east siberian continental slope being diluted by a factor of about 5 by the time it reaches the central canada basin the barents sea branch water does not undergo such extensive mixing and is diluted by a factor of only about 2 when it reaches the central canada basin

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

penetration of the 1990s warm temperature anomaly of atlantic water in the canada basin 1 penetration of the 1990s warm temperature anomaly wta of the fram strait branch of atlantic water fsbw in the canada basin is described using available temperature salinity and velocity data the core temperatures of fsbw show distinct pathways over the chukchi borderland advective velocities of the fsbw are well correlated with bottom topography the resulting multifarious pathways over the chukchi borderland act to modulate and substantially increase the time scale of wta spreading and advancement further downstream two wta tongues are observed one tongue followed the beaufort slope and along this pathway the core temperatures of fsbw decreased rapidly the depth integrated value of heat content remained near constant however suggesting enhanced vertical mixing the second tongue debouched from the northern tip of the northwind ridge and spread eastward into the deep canada basin suggesting a complex recirculation structure within the beaufort gyre index terms 4532 oceanography physical general circulation 4536 oceanography physical hydrography 4512 oceanography physical currents citation shimada k f mclaughlin e carmack a proshutinsky s nishino and m itoh 2004 penetration of the 1990s warm temperature anomaly of atlantic water in the canada basin geophys res lett 31 l20301

deepening of the atlantic water core in the canada basin in 2003 11 abstractin 2004 a cold mode of atlantic water aw entered the western canada basin replacing the anomalously warm aw that resided in the basin since the 1990s this slightly colder aw was denser than the 1990s warm mode it gradually filled most of the western basin by 2009 the enhanced surface stress curl led to the spinup of the beaufort gyre and convergence of freshwater the spinup also resulted in a deepening of the aw core at the center of the gyre and in shoaling of the aw core at the margins of the gyre the density versus depth relationship revealed in this study shows that the depth of the maximum aw temperature was mainly controlled by the density structure before 2007 thus it is the case when the denser water was deeper and the case when the lighter water was shallower around the basin however this relationship was reversed to become the case when the denser water was shallower and the case when the lighter water was deeper since 2008 inside the beaufort gyre the combined effect of de

ice tethered profiler observations of the double diffusive staircase in the canada basin thermocline vertical heat fluxes through the staircase are in the range 0 05 0 3 w m 2 only about one tenth of the estimated mean surface mixed layer heat flux to the sea ice it is thus concluded that the vertical transport of heat from the atlantic water in the central basin is unlikely to have a significant impact to the canada basin ocean surface heat budget icebreaker conductivity temperature depth data from the beaufort gyre freshwater experiment show that the staircase is absent at the basin periphery turbulent mixing that presumably disrupts the staircase might drive greater flux from the atlantic water at the basin boundaries and possibly dominate the regionally averaged heat flux

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

biomass of zooplankton in the eastern arctic ocean a base line study abstract only a few historical assessments of the zooplankton biomass in the arctic ocean exist are difficult to compare due to methodological differences including incomplete sampling of the water column we present assessments of the zooplankton biomass for 66 locations scattered over the eurasian and makarov basins of the arctic ocean and analyze regional variability and factors affecting the biomass distribution the study is based on material from several summer expeditions of rv polarstern 1993 1998 that was collected and processed using consistent methods i e stratified sampling of the entire water column from the bottom to the surface with very similar gear and standardized calculation of biomass total zooplankton biomass varied strongly from 1 9 to 23 9 g dw m 2 dry mass regional variability was mainly related to the circulation pattern but local food availability was also important a belt of elevated biomass along the eurasian continental margin was associated with the advection of atlantic pelagic populations within the arctic ocean boundary current along the siberian shelves and returning branches along mid ocean ridges biomass was highest in the core of the atlantic inflow and remained rather stable along the continental margins but species composition changed pointing to different adaptation levels to local conditions by advected species biomass gradually decreased towards the shelves and basins and was lowest in the centers of the basins north of 85 n in the slope region three calanus species c hyperboreus c glacialis c finmarchicus and metridia longa contributed most to the biomass chaetognaths eukrohnia hamata were also important in the basins c hyperboreus was dominant copepods made up to 97 of total biomass vertical distribution was similar at all stations with biomass maxima in the upper 50 m layer except for stations near fram strait and northern kara sea the gateways of atlantic water to the arctic ocean where maxima where between 25 and 100 m as there was only very little interannual variability of temperature and current velocity in the regions of the atlantic inflow we suggest that the majority of our samples collected in 1993 and 1995 represents the phase of the 1990s warm event in the nordic seas

numerical modeling of late glacial laurentide advance of ice across hudson strait insights into terrestrial and marine geology mass balance and calving flux a time dependent finite element model was used to reconstruct the advance of ice from a late glacial dome on northern quebec labrador across hudson strait to meta incognita peninsula baffin island and subsequently to the 9 9 9 6 ka 14c gold cove position on hall peninsula terrestrial geological and geophysical information from quebec and labrador was used to constrain initial and boundary conditions and the model results are compared with terrestrial geological information from baffin island and considered in the context of the marine event dc 0 and the younger dryas cooling we conclude that advance across hudson strait from ungava bay to baffin island is possible using realistic glacier physics under a variety of reasonable boundary conditions production of ice flux from a dome centered on northeastern quebec and labrador sufficient to deliver geologically inferred ice thickness at gold cove hall peninsula appears to require extensive penetration of sliding south from ungava bay the discharge of ice into the ocean associated with advance and retreat across hudson strait does not peak at a time coincident with the start of the younger dryas and is less than minimum values proposed to influence north atlantic thermohaline circulation nevertheless a significant fraction of freshwater input to the north atlantic may have been provided abruptly and at a critical time by this event

representing topographic stress for large scale ocean models abstract interaction of eddies with seafloor topography can exert enormous systematic forces on the ocean circulation this interaction has been considered previously under idealized circumstances theoretical results are here simplified and extended toward practical application in large scale ocean circulation models among the suggestions is that coarse resolution models can correct a depth independent part of the velocity field toward a velocity given by z flh where z is the vertical unit vector f is coriolis form l is a length scale o 10 km and h is the total depth absence of this tendency may be implicated in a number of systematic defects that appear in present ocean models

arctic warming evolution and spreading of the 1990s warm event in the nordic seas and the arctic ocean 1 observations in the arctic ocean revealed changes in oceanic temperature salinity and ice cover of the 1990s as compared with earlier data with a numerical model we favorably reproduce the development and subsequent propagation of temperature anomalies in water of atlantic origin in the 1980s and 1990s these propagated into the arctic ocean via the barents sea and the fram strait two warm anomalies entered the arctic ocean through these passages while the first smaller anomaly only warmed up the western eurasian basin the second large anomaly spread far into the eastern eurasian basin and across the lomonossov ridge into the western arctic basins intensified boundary currents during the high nao state in the first half of the 1990s significantly influenced the amplitude and speed of propagation of the temperature anomalies inside the arctic ocean in contrast to the notion of a continuous warming process during the 1990s our model results suggest the warming of the atlantic layer in the arctic ocean occurred in the form of events the event with the largest anomalous heat input during the modeled period entered the arctic between 1989 and 1994 it is possible to trace back the additional heat input into the arctic to an increased volume inflow via the faroer scotland passage and reduced heat loss to the atmosphere in the early 1990s after a weaker warm inflow in the second half of the 1990s the most recent observations and the model results point to a recurring warm anomaly in the inflow from 1999 onward

iodine 129 137cs and cfc 11 tracer transit time distributions in the arctic ocean 1 time series measurements of the nuclear fuel reprocessing tracers 129i and 137cs and ventilation tracer cfc 11 were used to determine circulation time scales for atlantic water aw in the arctic ocean measurements in surface water are consistent with an advection model and transit times from the north sea of 1 4 years to the barents sea 3 6 years to the kara sea and 9 12 years to the north pole tracer ages for intermediate waters do not support an advection model because they vary with time the tracer relationships were employed to determine transit time distributions ttd using inverse gaussian functions that implicitly incorporate the effects of mixing in simulating fluid flow tracer concentrations were used to constrain the ratio of the width of the ttd to the mean age a measure of the relative importance of mixing giving values for most intermediate water regimes of 1 these results are in contrast to values 1 typical of the north atlantic indicating the greater relative importance of advection compared to mixing in the arctic ocean mean ages for aw increase from 12 20 years in the southern makarov basin to 30 40 years near the arctic outflow north of greenland a decline in with distance along the direction of aw boundary flow from the makarov into the canada basin may indicate relatively stronger mixing in regimes upstream of the makarov basin but also implies that ttds may differ from inverse gaussian functions for flow in the arctic domain

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

influence of coriolis force upon bottom boundary layers in a large scale gravity current experiment implications for evolution of sinuous deep water channel systems oceanic density currents in many deep water channels are strongly influenced by the coriolis force the dynamics of the bottom boundary layer in large geostrophic flows and low rossby number turbidity currents are very important for determining the erosion and deposition of sediment in channelized contourite currents and many large scale turbidity currents however these bottom boundary layers are notoriously difficult to resolve with oceanic field measurements or in previous small scale rotating laboratory experiments we present results from a large 13 m diameter rotating laboratory platform that is able to achieve both stratified and highly turbulent flows in regimes where the rotation is sufficiently rapid that the coriolis force can potentially dominate by resolving the dynamics of the turbulent bottom boundary in straight and sinuous channel sections we find that the coriolis force can overcome centrifugal force to switch the direction of near bed flows in channel bends this occurs for positive rossby numbers less than 0 8 defined as ror

circulation features in the central arctic ocean revealed by nuclear fuel reprocessing tracers from scientific ice expeditions 1995 and 1996 measurements of the tracer radionuclides 129 i and 137 cs were conducted on seawater samples collected during the scientific ice expedition cruises to the arctic ocean of the u s navy nuclear submarines uss cavalla and uss pogy in 1995 and 1996 respectively these radionuclides are derived mainly from discharges from the sellafield england united kingdom and la hague france nuclear fuel reprocessing plants and are subsequently transported with atlantic water into the arctic ocean through fram strait and the barents sea iodine 129 results from halocline waters water depths of 59 and 134 m collected virtually synoptically throughout the central arctic ocean during the uss cavalla cruise clearly show the front between atlantic origin water having high 129 i levels 100 10 7 atoms l 1 and pacific origin water labeled mainly by fallout 30 10 7 atoms l 1 measured in central regions of the canada basin indicate that the interior is more efficiently ventilated than previously thought possibly by separation from boundary currents flowing over the continental margin north of the chukchi plateau the 129 i and 137 cs data were interpreted using a transit time model that provided estimates of 6 7 years 0 5 years for the passage of halocline and atlantic water from the norwegian coastal current 60 n to the continental slope of the makarov basin and a lower limit of 8 years for transport to interior regions of the makarov and amundsen basins

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

western arctic ocean temperature variability during the last 8000 years 1 we reconstructed subsurface 200 400 m ocean temperature and sea ice cover in the canada basin western arctic ocean from foraminiferal do ostracode mg ca ratios and dinocyst assemblages from two sediment core records covering the last 8000 years results show mean temperature varied from 1 to 0 5 c and 0 5 to 1 5 c at 203 and 369 m water depths respectively centennial scale warm periods in subsurface temperature records correspond to reductions in summer sea ice cover inferred from dinocyst assemblages around 6 5 ka 3 5 ka 1 8 ka and during the 15th century common era these changes may reflect centennial changes in the temperature and or strength of inflowing atlantic layer water originating in the eastern arctic ocean by comparison the 0 5 to 0 7 c warm temperature anomaly identified in oceanographic records from the atlantic layer of the canada basin exceeded reconstructed atlantic layer temperatures for the last 1200 years by about 0 5 c citation farmer j r t m cronin a de vernal g s dwyer l d keigwin and r c thunell 2011 western arctic ocean temperature variability during the last 8000 years geophys res lett 38 l24602 doi 10 1029 2011gl049714

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

observing global ocean topostrophy 1 recent publications have evaluated topostrophy f v d where is f coriolis v is velocity and d is gradient of total depth as a means of comparing models circulations some results are striking comparing four global models two with modest grid size and two with fine grids merryfield and scott 2007 show that finer grid models are characterized by more positive especially at greater depths and higher latitudes among nine arctic ocean models holloway et al 2007 find in three of the models quite distinct from the other six a result shown to depend upon subgrid eddy parameterization from different choices of numerical method within the same model penduff et al 2007 show that improved numerical representations support more positive can these model results be compared with observations a global compilation has been prepared from 17120 current meter records spanning 83087 current meter months the compilation tends to confirm modeling progress achieved by finer resolution improved parameterizations and better representations a new characterization of global ocean circulation emerges with suggestive dynamical insights

diffusive vertical heat flux in the canada basin of the arctic ocean inferred from moored instruments 1 observational studies have shown that an unprecedented warm anomaly has recently affected the temperature of the atlantic water aw layer lying at intermediate depth in the arctic ocean using observations from four profiling moorings deployed in the interior of the canada basin between 2003 and 2011 the upward diffusive vertical heat flux from this layer is quantified vertical diffusivity is first estimated from a fine scale parameterization method based on ctd and velocity profiles resulting diffusive vertical heat fluxes from the aw are in the range 0 1 0 2 w m 2 on average although large over the period considered the variations of the aw temperature maximum yields small variations for the temperature gradient and thus the vertical diffusive heat flux in most areas variations in upward diffusive vertical heat flux from the aw have only a limited effect on temperature variations of the overlying layer however the presence of eddies might be an effective mechanism to enhance vertical heat transfer although the small number of eddies sampled by the moorings suggest that this mechanism remains limited and intermittent in space and time finally our results suggest that computing diffusive vertical heat flux with a constant vertical diffusivity of 2 10 6 m2 s 1 provides a reasonable estimate of the upward diffusive heat transfer from the aw layer although this approximation breaks down in the presence of eddies

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