contributions of the siberian shelf polynyas to the arctic ocean intermediate and deep water the role of the open water regions or polynyas in the winter ice pack over the siberian continental shelves in the production of arctic ocean intermediate and deep water is examined through use of a combination of passive microwave satellite data coastal weather station data and oceanographic data the satellite data allow us to derive a time series of the open water areas of selected polynyas for the 1978 1982 winters the polynyas which occur north of svalbard around franz josef land along the west coast and north end of novaya zemlya and to the east of severnaya zemlya and the taymyr peninsula are the primary oceanographic contributors the open water time series for these polynyas are used in combination with coastal weather station data to estimate the heat loss from each polynya for the region north of svalbard which is historically known as whalers bay the study shows that the heat loss is sufficient to provide the observed cooling of the west spitsbergen current for the other polynyas the heat loss is used to compute the ice production rates and the oceanic salt flux we then use the historic oceanographic salinities with the salt fluxes to estimate the contribution of each polynya to the arctic ocean water masses if we assume that the salt contributes only to the arctic intermediate water our results show that the shelves are capable of producing about 20 60 of this water alternatively if the salt contributes only to the deep water of the eurasian basin then without consideration of the mixing of the bottom water with the greenland and norwegian sea water the contribution from the shelves yields a renewal time of about 100 years our results imply that there is insufficient water produced in the shelf polynyas to perform all of the roles that have been historically assigned to it

one dimensional evolution of the upper water column in the atlantic sector of the arctic ocean in winter a one dimensional model is employed to reproduce the observed time evolution of hydrographic properties in the upper water column during winter between 26 january and 11 march 2015 in a region north of svalbard in the nansen basin of the arctic ocean from an observed initial state vertical diffusion equations for temperature and salinity give the hydrographic conditions at a later stage observations of microstructure are used to synthesize profiles of vertical diffusivity k representative of varying wind forcing conditions the ice ocean heat and salt fluxes at the ice ocean interface are implemented as external source terms estimated from the salt and enthalpy budgets using friction velocity from the rossby similarity drag relation and the ice core temperature profiles we are able to reproduce the temporal evolution of hydrography satisfactorily for two pairs of measured profiles suggesting that the vertical processes dominated the observed changes sensitivity tests reveal a significant dependence on k variation in other variables such as the temperature gradient of the sea ice the fraction of heat going to ice melt and the turbulent exchange coefficient for heat are relatively less important the increase in salinity as a result of freezing and brine release is approximately 10 significantly less than that due to entrainment 90 from beneath the mixed layer entrainment was elevated during episodic storm events leading to melting the results highlight the contribution of storms to mixing in the upper arctic ocean and its impact on ice melt and mixed layer salt and nutrient budgets

distribution transport and production of volatile halocarbons in the upper waters of the ice covered high arctic ocean 1 volatile halogenated compounds chbr3 ch2br2 chbr2cl and ch2cli were measured in the water column and in sea ice brine across the arctic ocean from barrow alaska to svalbard during the beringia 2005 expedition august september with rv ib oden high concentrations of brominated compounds up to 42 pmol kg 1 of bromoform were found under multiyear ice in the surface waters over the makarov basin and the lomonosov ridge near the north pole even higher concentrations bromoform up to 160 pmol kg 1 were found in sea ice brine we propose that the high load of riverine dissolved organic matter that is transported in the transpolar drift is a main factor responsible for the high concentration of brominated volatile compounds found in sea ice brine and upper waters and that cycles of freezing and thawing during the transport enhance the transfer of halocarbons to the seawater the iodinated compound ch2cli showed a completely different distribution with highest concentrations in water of pacific origin in the mixed layer and upper halocline of the northern canada basin and over the alpha ridge in the southern canada basin low concentrations of halocarbons were found in upper waters higher concentrations in water of pacific origin especially on the continental shelf indicate production in the shelf regions likely in the chukchi sea and the east siberian sea

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

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

the behaviour of manganese in atlantic carbonate sediments abstract manganese porewater and solid phase data are considered from two different atlantic carbonate sediments both with good geochemical characterisation the first case is a continuously accumulated alternating pelagic marl carbonate ooze where there is a correlation in post oxic conditions between mn ii porewater levels and an acetate leachable mn fraction of the sediment this leachable mn appears to have an association with calcite and in this example the leached residue mn content approximates to that of shale in the second case a very recent compositionally homogeneous calcareous turbidite is underlain by mn oxyhydroxide at the former sediment surface which is now acting as a source of mn ii by reduction sorption of mn by the turbidite sediment and shale like leached residue mn levels in anoxic conditions are again observed as mn ii diffuses towards present oxic conditions although no unique equilibrium is achieved similar older buried turbidites have concentration decreases in solid phase mn content preserved from bottom to top as relict evidence that this process has occurred in these turbidites 54 64 of the total mn is leachable by the acetate method and therefore presumed to be sorbed by calcite the oldest example has persisted for 125 kyr it is suggested that the slow breakdown of metastable mn oxyhydroxide and sorption of mn ii to calcite surfaces are important controls on the behaviour of mn in pelagic carbonates in mildly reducing conditions where accumulation fluctuations occur these processes act together with accumulation to limit overall mn migration and to prevent the large mn enrichments seen near the sediment surface in more reducing environments

a relationship between heat transfer to sea ice and temperature salinity properties of arctic ocean waters it is demonstrated that the characteristic temperature salinity relationship shown by thermocline waters of the arctic ocean can be reproduced using a simple model based on transfer of heat directly from these waters to sea ice from this we deduce that there is direct sensible heat flux from waters of atlantic origin to the ice cover such interaction could play a major role in determining the physical properties of arctic water masses

freshwater balance and the sources of deep and bottom waters in the arctic ocean inferred from the distribution of h218o data from sections across the eurasian basin of the arctic ocean occupied in 1987 and 1991 are used to derive information on the freshwater balance of the arctic ocean and on sources of the deep waters of the nansen amundsen and makarov basins using salinity h218o and mass balances we estimate the river runoff and the sea ice melt water fractions contained in the upper waters of the arctic ocean and infer pathways of the river runoff signal from the shelf seas across the central arctic ocean to fram strait the average mean residence time of the river runoff fraction contained in the arctic ocean halocline is determined to be about 11 to 14 years pacific water entering through bering strait is traced using silicate and its influence on the halocline waters of the canadian basin is estimated water column inventories of river runoff and sea ice melt water are calculated for a section just north of fram strait and implications of these inventories for sea ice export through fram strait are discussed comparison of the 18o 16o ratios of shelf water atlantic water and the deep waters of the arctic ocean indicate that the sources of the deep and bottom waters of the eurasian basin are located in the barents and kara seas

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

steady models of arctic shelf basin exchange steady state exchanges between the arctic shelves and the central basins are estimated using an inverse box model estimates based only on mass heat and salt conservation are highly uncertain and cannot determine how the shelf basin exchange is partitioned between dense overflows and surface layer exchange inclusion of 18o conservation greatly reduces the uncertainty with the 18o constraints dense water fluxes from the shelves of 0 2 0 1 sv in the canadian basin and 1 4 0 3 sv in the eurasian basin with a small o 0 1 sv surface layer transport from shelves to basins best satisfy the requirements of steady state up to 3 8 sv of shelfbreak upwelling is consistent within error bars with steady state but none is required water leaving the shelves is replaced primarily from the bering strait the barents sea inflow and runoff and not from the basin surface layer proper representation of these external sources for the shelves is important for capturing the full range of plausible steady solutions the steady state solutions identify the balances which if upset could lead to arctic change

arctic ocean stability the effects of local cooling oceanic heat transport freshwater input and sea ice melt with special emphasis on the nansen basin the arctic loses energy to space and heat is transported northward in the atmosphere and ocean the largest transport occurs in the atmosphere the oceanic heat flux is significantly smaller and the warm water that enters the arctic ocean becomes covered by a low salinity surface layer which reduces the heat transfer to the sea surface this upper layer has two distinct regimes in most of the deep basins it is due to the input of low salinity shelf water ultimately conditioned by net precipitation and river runoff the nansen basin is different here warm atlantic water is initially in direct contact with and melts sea ice its upper part being transformed into less dense surface water the characteristics and depth of this layer are determined as functions of the temperature of the atlantic water and for different energy losses using a one dimensional energy balance model the amount of transformed atlantic water is estimated for two different sea ice melt rates and the assumption of a buoyant boundary outflow to create the upper layer sea ice formed elsewhere has to drift to the nansen basin with reduced ice cover this ice drift might weaken and the ice could disappear by the end of winter the surface buoyancy input would disappear and the upper layer might eventually convect back into the atlantic water reducing the formation of less dense polar water the created ice free areas would release more heat to the atmosphere and affect the atmospheric circulation

seabed erosion on the lomonosov ridge central arctic ocean a tale of deep draft icebergs in the eurasia basin and the influence of atlantic water inflow on iceberg motion 1 the submarine lomonosov ridge which bisects the arctic ocean is covered by 450 m of hemipelagic sediments high resolution chirp sonar and side scan data have documented erosion of a section of the ridge here we present multichannel seismic and chirp sonar data which show removal of unconsolidated sediments along the eurasia basin side of the lomonosov ridge where the central ridge is shallower than 1000 m the incomplete erosion of the hemipelagic drape and probable topographic control of ice motion suggest that the deepest draft glacier ice which reached the central arctic ocean from the eurasia basin was in the form of armadas of large icebergs embedded in sea ice rather than a single continuous floating ice shelf massive rapid discharge of glacier ice was probably required to produce the deepest draft 800 m icebergs eastward and northward drift trajectories from a likely iceberg source area on the kara barents sea margin would reflect the relative strength of atlantic inflow through the fram strait however only icebergs with drafts exceeding bathymetric thresholds on the lomonosov ridge would leave an erosive imprint on the seabed advection of atlantic water may have been relatively strong at times of discharge from the saalian ice sheet icebergs exiting the arctic ocean caused massive erosion and redeposition of the hemipelagic sediments on top of yermak plateau

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

halocline water formation in the barents sea hydrographic data from the first phase of the coordinated eastern arctic experiment cearex are analyzed the data consist of temperature and salinity measurements made by a ship based conductivity temperature depth ctd instrument and by a drifting salargos buoy these data were collected in the autumn and early winter of 1988 1989 in the northern barents sea mostly in ice covered conditions and then across the marginal ice zone miz the data show that relatively warm salty water of atlantic origin is modified by air cooling and ice melting to produce lighter water that has properties identical to lower halocline water found in the arctic ocean this occurs mostly at the miz and to a lesser degree within the ice pack itself at the miz the halocline water subducts underneath the lighter meltwater that resides directly under the ice pack geostrophic velocity calculations indicate that it then turns eastward and flows toward the kara sea in keeping with previous chemical tracer analyses a rough calculation reveals that the amount of halocline water formed in this way in the barents sea and fram strait is 30 50 of that formed by ice growth in eastern arctic polynyas

thermohaline circulation in the arctic mediterranean seas the renewal of the deep north atlantic by the various overflows of the greenland scotland ridges is only one manifestation of the convective and mixing processes which occur in the various basins and shelf areas to the north the arctic ocean and the greenland iceland and norwegian seas collectively called the arctic mediterranean the traditional site of deep ventilation for these basins is the greenland sea but a growing body of evidence also points to the arctic ocean as a major source of deep water this deep water is relatively warm and saline and it appears to be a mixture of dense brine enriched shelf water with intermediate strata in the arctic ocean the deep water exits the arctic ocean along the greenland slope to mix with the greenland sea deep water conversely very cold low salinity deep water from the greenland sea enters the arctic ocean west of spitsbergen within the arctic ocean the lomonosov ridge excludes the greenland sea deep water from the canadian basin leaving the latter warm saline and rich in silica in general the entire deep water sphere of the arctic mediterranean is constrained by the greenland scotland ridges to circulate internally therefore it is certain of the intermediate waters formed in the greenland and iceland seas which ventilate the north atlantic these waters have a very short residence time in their formation areas and are therefore able to rapidly transmit surface induced signals into the deep north atlantic

hydrography of the west spitsbergen current svalbard branch autumn 2001 1 the atlantic inflow is the primary source of water and heat to the arctic ocean a large portion enters through fram strait where it splits into the yermak and svalbard branches in october to november 2001 the uscgc healy occupied five oceanographic transects across the svalbard branch west and north of spitsbergen temperature and salinity sections show the warm salty atlantic water cooling and freshening as it flows along the continental slope for 553 km the temperature in the upper 500 m of the water column decreased by 0 25 c 100 km implying a heat flux across the sea surface of up to 520 w m2 if one assumes a nominal current of speed of 0 1 m s a temperature salinity t s analysis shows that the shape of the t s curves can be explained in terms of the ratio of the atmospheric to ice melt heat flux the observations imply that ice melt accounts for progressively more surface cooling as the flow moves toward the arctic ocean an autonomous underwater vehicle completed a vertical section in the region of maximum water mass gradient and revealed layer interleaving in fine detail data from this cruise extend a long time series of atlantic layer source temperature beginning in 1910 saloranta and haugan 2001 the extended observations show that after the temperature of the atlantic layer inflow reached a peak in 1992 it cooled to a minimum in 1998 and rose again through 2001

a meteoric water budget for the arctic ocean a budget of meteoric water mw river runoff net precipitation minus evaporation and glacial meltwater over four regions of the arctic ocean is constructed using a simple box model regional precipitation evaporation estimates from reanalysis data sets and estimates of import and export fluxes derived from the literature with a focus on the 2003 2008 period the budget indicates an approximate slightly positive balance between mw imports and exports i e no change in storage thus the observed total freshwater increase observed during this time period likely resulted primarily from changes in non mw freshwater components i e increases in sea ice melt or pacific water and or a decrease in ice export further our analysis indicates that the mw increase observed in the canada basin resulted from a spatial redistribution of mw over the arctic ocean mean residence times for mw were estimated for the western arctic 5 7 years eastern arctic 3 4 years and lincoln sea 1 2 years the mw content over the siberian shelves was estimated 14 000 km3 based on a residence time of 3 5 years the mw content over the entire arctic ocean was estimated to be 44 000 km3 the mw export through fram strait consisted mostly of water from the eastern arctic 3 237 1 370 km3 yr 1 whereas the export through the canadian archipelago was nearly equally derived from both the western arctic 1 182 534 km3 yr 1 and lincoln sea 972 391 km3 yr 1

on the ice and heat balance in fram strait the sea ice margin northwest of spitsbergen is schematically represented by a stationary wedge maintained by opposing ice and warm atlantic water advection ice melt and cooling of the surface water generate a mixed layer with properties approximating those found elsewhere in the arctic basin the heat energy required to melt the advancing ice is roughly comparable to the rate of heat loss of the west spitsbergen current and suggests that direct heat exchange with the atmosphere is less important only a small fraction of the nearly fresh water from ice melt exits through eastern fram strait and most of it appears to return to the arctic basin whether or not it contributes to the formation and maintenance of the arctic mixed layer depends on the largely unknown circulation pattern north of fram strait an example of the large interannual variation of the mean wind stress field is shown to illustrate the likelihood of an equally large variance of the ice and surface water circulation

winter convection transports atlantic water heat to the surface layer in the eastern arctic ocean a 1 yr 2009 10 record of temperature and salinity profiles from ice tethered profiler itp buoys in the eurasian basin eb of the arctic ocean is used to quantify the flux of heat from the upper pycnocline to the surface mixed layer the upper pycnocline in the central eb is fed by the upward flux of heat from the intermediate depth 150 900m atlanticwater aw layer thisfluxisestimatedtobe 1wm 22 averaged over one year release of heat from the upper pycnocline through the cold halocline layer to the surface mixed layer is however seasonally intensified occurring more strongly in winter this seasonal heat loss averages 3 4wm 22 between january and april reducing the rate of winter sea ice formation this study hypothesizes that the winter heat loss is driven by mixing caused by a combination of brine driven convection associated with sea ice formation and larger vertical velocity shear below the base of the surface mixed layer sml enhanced by atmospheric storms and the seasonal reduction in density difference between the sml and underlying pycnocline

arctic ocean water mass balance from isotope data the distributions of the oxygen 18 and tritium isotopes and of salinity yield a residence time of 10 years for the surface and halocline waters of the arctic basin we find a yearly net production of 0 59 m of sea ice and an input of 1 16 m of freshwater from continental river runoff local precipitation and bering strait salinity deficiency using the basin area value with these numbers gives long term average total net production and transport rates of 0 15 sv of ice and 0 18 sv of meteoric component bering strait water not included if in addition a reasonable depth profile of relative current velocity is assumed for the outflow a yearly input of 2 8 sv of atlantic and bering strait water is needed to replenish the upper and halocline waters these numbers should be good to 20 and are multiyear averages the isotope data clearly indicate that the barents sea is an inflow area for atlantic water to the basin but that net export of ice occurs there

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

brine driven eddies under sea ice leads and their impact on the arctic ocean mixed layer abstract eddy generation induced by a line shaped salt flux under a sea ice lead and associated salt transport are investigated using a three dimensional numerical model the model is designed to represent a typical condition for the wintertime arctic ocean mixed layer where new ice formation within leads is known to be one of the primary sources of dense water the result shows that along lead baroclinic jets generate anticyclonic eddies at the base of the mixed layer and almost all the lead originated salt is contained inside these eddies these eddies survive for over a month after closing of the lead and transport the lead originated salt laterally consequently the lead origin salt settles only on the top of the halocline and is not used for increasing salinity of the mixed layer sensitivity experiments suggest that the horizontal scale of generated eddies depends only on the surface forcing and is proportional to the cube root of the total amount of salt input this scaling of eddy size is consi

a 2700 cal yr bp extreme flood event revealed by sediment accumulation in amazon floodplains abstract climatic conditions are one of the most important factors affecting hydrological processes in fluvial systems higher discharges are responsible for higher erosion greater transport and also higher deposition consequently sediment accumulation in amazonia floodplain river connected lakes can be directly related to hydrological patterns of the amazon river mainstream in this context we analyzed five sediment cores taken in two floodplain systems situated in the lower amazon river to investigate sediment accumulation patterns during the holocene our records show abrupt fluctuations in sedimentation rates in lakes that can reach more than 2 cm yr during some periods we find that in all cores sediment stratigraphy is characterized by packages of sediments of uniform age which are typically 10 80 cm thick and present a variegated color the 14 c age of the upper package is about 2700 cal yr bp during this abrupt event sediment accumulation rates in floodplain lakes can be at least 200 times higher than those of normal periods this sedimentation event is interpreted as being the consequence of one or several successive extreme floods the 2700 cal yr bp event has been also observed in other sites in south america and other regions in the world although different impacts can be observed in each system this event probably corresponds to a conjunction of favorable conditions for extreme amazon discharge associated with the middle to late holocene increase of austral summer insolation and shifts of the intertropical convergence zone itcz from northern to southern positions in this context a marked negative peak in solar irradiance at 2700 cal yrs bp seems to have provoked cooling on the continents and a southward shift of the itcz associated with a probable reduction in the atlantic meridian overturning circulation

using the nutrient ratio no po as a tracer of continental shelf waters in the central arctic ocean historical nitrate phosphate and dissolved oxygen data from the central arctic ocean are examined with particular emphasis on the conservative parameters no 9 no sub 3 o sub 2 and po 135 po sub 4 o sub 2 the no po ratio is shown to increase with depth in the canada basin being approximately 0 78 in surface and upper halocline waters and approximately 1 0 in the atlantic layer and deep waters lower halocline water is marked by no and po minima and intermediate no po no po ratios from the arctic shelf seas are examined to determine possible source regions for the various water masses the no po ration of canada basin deep water implies an upper bound of approximately 11 shelf water contribution to this water mass a slight oxygen maximum core in the lower halocline water is identified at a salinity of s double bond 34 5 in the vicinity of the alpha ridge this core appears to be diminished by diapycnal mixing and does not extend into the beaufort gyre

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