winter to summer oceanographic observations in the arctic ocean north of svalbard oceanographic observations from the eurasian basin north of svalbard collected between january and june 2015 from the n ice2015 drifting expedition are presented the unique winter observations are a key contribution to existing climatologies of the arctic ocean and show a 100m deep winter mixed layer likely due to high sea ice growth rates in local leads current observations for the upper 200m show mostly a barotropic flow enhanced over the shallow yermak plateau the two branches of inflowing atlantic water are partly captured confirming that the outer yermak branch follows the perimeter of the plateau and the inner svalbard branch the coast atlantic water observed to be warmer and shallower than in the climatology is found directly below the mixed layer down to 800m depth and is warmest along the slope while properties inside the basin are quite homogeneous from late may onwards the drift was continually close to the ice edge and a thinner surface mixed layer and shallower atlantic water coincided with significant sea ice melt being observed this article is protected by copyright all rights reserved

fine structure microstructure and vertical mixing processes in the upper ocean in the western weddell sea the upward flux of heat from the subsurface core of warm deep water wdw to the perennially ice covered sea surface over the continental slope in the western weddell sea is estimated using data obtained during february june 1992 from a drifting ice station through the permanent pycnocline the diapycnal heat flux is estimated to be about 3 w m 2 predominantly because of double diffusive convection there is no evidence that shear driven mixing is important in the pycnocline the estimated mean rate of heat transfer from the mixed layer to the ice is 1 7 w m 2 although peak heat fluxes of up to 15 w m 2 are found during storms it is hypothesized that isopycnal mixing along sloping intrusions also contributes to the loss of heat from the wdw in this region however we are unable to quantify the fluxes associated with this process intrusions occur intermittently throughout this experiment but are most commonly found near the boundary of the warm core current and the shelf modified water to the east these heat fluxes are significantly lower than the basin averaged value of 19 w m 2 fahrbach et al 1994 that is required to balance the heat budget of the weddell gyre other studies suggest that shelf processes to the west of the ice station drift track and more energetic double diffusive convection in the midgyre to the east could account for the difference between our flux estimates for this region and those based on the basin scale heat budget

turbulent mixing near the yermak plateau during the coordinated eastern arctic experiment during the ice camp component of the coordinated eastern arctic experiment cearex in march april 1989 1500 profiles of temperature conductivity and velocity shear microstructure were obtained near the yermak plateau the dominant signal in isopycnal displacements was the diurnal variability near the plateau consistent with the enhanced diurnal currents found in this region previously from the fram iii and fram iv ice camps the dissipation rate of turbulent kinetic energy e reached maximum values of about 10 6 w kg 1 in two distinct regions the surface mixing layer and the pycnocline between 120 and 220 m there was a significant component of diurnal variability in e in each region in the surface layer e was proportional to the cube of the ice relative current speed at 30 m below the ice and it decayed approximately exponentially with increasing depth major mixing events in the pycnocline were correlated with large amplitude short duration isopycnal displacements the lowest dissipation rates were recorded over the deep nansen basin north of the plateau and in the subsurface core of a submesoscale baroclinic eddy in northern fram strait the time averaged vertical eddy diffusivity near the slope of the plateau was about 2 5 10 4 m2 s 1 in the pycnocline above the atlantic layer implying an upward heat flux of 25 w m 2 although only a small fraction of this heat reached the base of the mixed layer the results confirm that current interactions with steep topography are critical to the modification of atlantic water in the eastern arctic ocean

semidiurnal tides on the laptev sea shelf with implications for shear and vertical mixing the arctic continental shelf seas hold a globally significant source of freshwater that impacts arctic ocean stratification circulation and climate this freshwater can be injected below the surface mixed layer by intense turbulent kinetic energy dissipation events as resolved by laptev sea microstructure observations the tides provide a major source of energy that can be dissipated and hence drive diapycnal mixing in the laptev sea multiyear adcp mooring records from locations across the shelf reveal that semidiurnal tides are dominated by them2 and s2 constituents with the largest amplitudes on the outer shelf throughoutmost of the shelf tides are clockwise polarized and sheared by stratification as characteristic near the m2 critical latitude interannual variations of the tidal and shear structures on the inner shelf aremainly determined by the stratification setting lena river freshwater plume in all locations m2 tides are enhanced under sea ice and therefore changes in the seasonal ice cover may lead to changes in tides and water column structure the main conclusions of this study are that i tides play a comparatively greater role year round on the outer shelf relative to the inner shelf ii a sea ice reduction will overall decrease the predictability of the currents especially on the inner shelf and iii the freshwater distribution directly impacts diapycnal mixing by setting the vertical tidal structure these combined effects imply that future sea ice loss will increase the variability and vertical mixing of freshwater particularly on the inner shelf where the lena river first enters the laptev sea

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

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

a barotropic inverse tidal model for the arctic ocean 1 we describe high resolution 5 km grid linear dynamics and inverse models of arctic ocean barotropic tides obtained with the osu tidal inversion software otis package the 8 constituent dynamics based model uses the latest ibcao bathymetry and open boundary forcing from the recent tpxo 6 2 global barotropic tidal solution this model performs significantly better than the present benchmark arctic tidal model 14 km grid by z kowalik and a proshutinsky as judged by comparisons with 300 coastal tide gauges the greatest improvements are found in the canadian arctic archipelago nares strait and the baffin bay and labrador sea and can be explained by the higher resolution of the new model in these topographically complex regions the new arctic inverse model assimilates coastal and benthic tide gauges and topex poseidon and ers altimetry for further improvements of the 4 dominant constituents m2 s2 k1 and o1

does rotation influence double diffusive fluxes in polar oceans abstractthe diffusive or semiconvection regime of double diffusive convection ddc is widespread in the polar oceans generating staircases consisting of high gradient interfaces of temperature and salinity separated by convectively mixed layers using two dimensional direct numerical simulations support is provided for a previous theory that rotation can influence ddc heat fluxes when the thickness of the thermal interface sufficiently exceeds that of the ekman layer this study finds therefore that the earth s rotation places constraints on small scale vertical heat fluxes through double diffusive layers this leads to departures from laboratory based parameterizations that can significantly change estimates of arctic ocean heat fluxes in certain regions although most of the upper arctic ocean thermocline is not expected to be dominated by rotation

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

vertical mixing at intermediate depths in the arctic boundary current microstructure and hydrographic observations during september 2007 in the boundary current on the east siberian continental slope document upper ocean stratification and along stream water mass changes a thin warm surface layer overrides a shallow halocline characterized by a 40 m thick temperature minimum layer beginning at 30 m depth below the halocline well defined thermohaline diffusive staircases extended downwards to warm atlantic water intrusions found at 200 800 m depth observed turbulent eddy kinetic energy dissipations are extremely low epsilon 10 6 w m 3 such that double diffusive convection dominates the vertical mixing in the upper ocean the diffusive convection heat fluxes f dc h 1 w m 2 are an order of magnitude too small to account for the observed along stream cooling of the boundary current our results implicate circulation patterns and the influence of shelf waters in the evolution of the boundary current waters

toward a warmer arctic ocean spreading of the early 21st century atlantic water warm anomaly along the eurasian basin margins we document through the analysis of 2002 2005 observational data the recent atlantic water aw warming along the siberian continental margin due to several aw warm impulses that penetrated into the arctic ocean through fram strait in 1999 2000 the aw temperature record from our long term monitoring site in the northern laptev sea shows several events of rapid aw temperature increase totaling 0 8 c in february august 2004 we hypothesize the along margin spreading of this warmer anomaly has disrupted the downstream thermal equilibrium of the late 1990s to earlier 2000s the anomaly mean velocity of 2 4 2 5 0 2 cm s was obtained on the basis of travel time required between the northern laptev sea and two anomaly fronts delineated over the eurasian flank of the lomonosov ridge by comparing the 2005 snapshot along margin data with the aw pre 1990 mean the magnitude of delineated anomalies exceeds the level of pre 1990 mean along margin cooling and rises above the level of noise attributed to shifting of the aw jet across the basin margins the anomaly mean velocity estimation is confirmed by comparing mooring derived aw temperature time series from 2002 to 2005 with the downstream along margin aw temperature distribution from 2005 our mooring current meter data corroborate these estimations

improved offset tracking for predisaster deformation monitoring of the 2018 jinsha river landslide tibet china abstract synthetic aperture radar sar remote sensing is a potential technique for long term monitoring of landslide prone areas pixel offset tracking methods work well for fast moving landslides more than tens of cm yr however existing methods may present some limitations such as i a high dependence of estimation window design on experience ii a tradeoff between the accuracy of single points and the overall efficiency and iii a low confidence in the results caused by heterogeneous in window samples in this paper an improved offset tracking method is proposed to address these problems first the workflow is optimized by a preseparation step added before offset estimation to distinguish between feature matching and speckle pattern matching the optimized workflow is more efficient for natural scenes containing both feature and non saliency regions second an improved algorithm called adaptive incoherence speckle offset tracking based on homogeneous samples aisot hs is proposed for non saliency regions its two key points are i adaptive design of the optimal estimation windows by introducing a coherence map as a guide and ii offset estimation without heterogeneous samples we apply the proposed method to study the evolution of the 2018 jinsha river landslide tibet china using sar data from the gaofen 3 gf 3 satellite and the phased array type l band synthetic aperture radar 2 palsar 2 system onboard the advanced land observing satellite alos satellite compared with the traditional method the proposed method improves the efficiency and reduces the uncertainty we also analyze the spatiotemporal displacement pattern of this landslide which shows that the jinsha river landslide was most likely a thrust load caused landslide this study demonstrates the role of sar remote sensing in global landslide monitoring especially where ground truth data are scarce

effective diffusivities within oceanic thermohaline staircases a scale for the thickness of layers in regular diffusive type thermohaline staircases derived from dimensional analysis is found to collapse oceanic data combining this scale with laboratory derived double diffusive flux laws we formulate effective diffusivities for salt heat and density the diffusivities depend on the turner number r but are independent of the brunt vaisala frequency for r near 1 the diffusivities for salt and heat are approximately equal 10 4 m2 s 1 they decrease roughly as r 4 and r 2 respectively over the oceanic range 1 r 10

trace metal storage in recent floodplain sediments along the dill river central germany abstract trace metals are stored in near channel floodplain sediments along many rivers in industrial and mined watersheds of western european countries such as germany in this paper i document the distribution of cu pb and zn in 13 cores collected from near channel floodplain sediments along a 25 km reach of the dill river in central germany mean concentrations of the three trace metals exceed background concentrations an indication of anthropogenic enrichment along the study reach many individual samples have concentrations several times the background levels and exceed standards for trace metals contained in the german federal soil protection act metal concentrations generally peak at depths of 0 2 to 0 7 m below the floodplain surface and are assumed to represent the period of maximum metal releases to the environment through upstream industrial activity ore mining or both in eight of the cores radiocarbon ages obtained below the depth of peak metal concentrations provide maximum dates for sediment accumulation of between 90 and 1700 years ago with most ages clustering in the period of 90 to 300 years ago the ages and depth to peak metal concentrations indicate 0 6 to 1 0 m of floodplain sedimentation over the last 150 to 300 years 0 3 0 4 cm y 1 which exceed sedimentation amounts and rates found in surrounding watersheds surface sediments contain lower metal concentrations suggesting deposition recently of cleaner sediments trace metals stored along the dill river serve as a reminder that stores of contaminants exist in geomorphically sensitive locations of the fluvial system these legacy sediments bear the chemical imprint of industrial or mining activities that no longer occur in the watershed

oceanographic implications of laboratory experiments on diffusive interfaces abstract this paper contains a summary of the results from some laboratory and theoretical studies on the diffusive interface in double diffusive convection paying particular attention to the recent work of fernando a simple model is developed which predicts the thickness of the convecting layers in a thermohaline staircase structure the laboratory buoyancy flux measurements and the model results are extrapolated for oceanic situations and comparisons are made with field measurements

floodplain storage of sediment contaminated by mercury and copper from historic gold mining at gold hill north carolina usa abstract previous research on the environmental consequences of mining has shown that metal contaminants can have long lasting impacts on water quality and aquatic ecosystems because of the remobilization of sediment associated contaminants that have been stored in floodplains we examined the magnitude and distribution of mercury hg and copper cu contamination of floodplain deposits associated with nineteenth century gold au mining activities in the gold hill mining district north carolina a comparison of post mining metal concentrations in overbank deposits with sediment quality guidelines indicates that overall about 21 are contaminated above the probable effect concentration pec above which adverse effects are expected to occur more often than not for both cu and hg the highest contamination occurs upstream near the mine source where 51 of the samples exceed the pec for hg and 57 exceed the pec for cu of the three different methods used to estimate metal mass storage the most reliable estimate suggests that about 6 8 mg of hg and 619 mg of cu currently reside in floodplain deposits within this watershed although overbank sediment storage increases downstream and with valley width about 75 of the hg and cu mass are stored in the upstream portion of the watershed hg mass storage displays a strong negative relationship with cross sectional stream power but the relationship between cu mass storage and stream power is insignificant we used vertical changes in overbank metal concentrations and the mining history to estimate a mean sedimentation rate of 2 7 cm y 1 during the most intensive period of au mining at gold hill 1842 1856 that is three times the long term 1842 2007 rate of 0 9 cm y 1 long term average rates at gold hill are comparable to those reported elsewhere in the eastern piedmont the downstream increase in long term rates may indicate a spatial and temporal lag effect where the locus of deposition shifts downstream with time

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

what determines the thickness of layers in a thermohaline staircase the article of record as published may be found at http dx doi org 10 1017 s0022112004002290

the chemical and physical speciation of trace metals in fine grained overbank flood sediments in the tyne basin north east england deposition of fine sediment contaminated by heavy metals on floodplains in the tyne basin north east england during a major flood in august 1986 provided an unusual opportunity to investigate the chemical and physical speciation of metals in overbank fines selective extractions and heavy liquid analyses were used to assess the chemical forms of sediment associated metal and the relationship between grain size density and metal concentration and to identify sources of metalliferous material generally the highest concentrations of trace metals were found in the 500 250 m size range and in the heavier density fractions 3 3 gml 1 though more than 60 of metals reported to the lightest 3 3 gml 1 density product the principal source of metals appeared to be reworked alluvium contaminated by historic mining activity metal concentrations in flood sediment decrease downstream from former mining areas though at varying rates depending on the physical propeties and chemical phase of individual metals with the exception of cu dominated by lithogenic fraction metals are primarily associated with fe mn oxides pb zn and to a lesser extent with carbonates cd zn organic matter zn cu and an operationally defined exchangeable cd component in the upper and middle parts of the tyne basin physical processes of downstream sediment metal content reduction were found to predominate while in the lower reaches of the tyne sediment metal transport appears to be governed by chemical sorption desorption processes associated with fe mn oxides and organic material finally the results of the study are discussed in a wider context of particulate metal transport in rivers and recommendations are made for refining density based models of metal dispersal

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

observational and laboratory insights into salt finger convection improving observational capabilities in the ocean are revealing a substantial body of evidence that the double diffusive instability known as salt fingers is widely present and plays a significant role in oceanic mixing this evidence includes unique fine and microstructure features in particular regions and distinct patterns in the temperature and salinity variations over large areas laboratory experiments have also advanced our understanding of salt fingers the insights gleaned from both laboratory and ocean are reviewed and related to large scale ocean structure and climate modeling

impact of channel incision on the hydraulics of flood flows examples from polish carpathian rivers abstract channel deepening may result from channel incision or river metamorphosis changing a wide and shallow channel to a narrow and deep one as only the first type of channel change leads to increased flow capacity of the channel a lowering of water stage associated with a given discharge rather than a lowering of river bed should be used to identify channel incision a lowering of minimum annual stage at gauging stations is typically used to assess the relative importance of channel incision along a river or within a particular region rivers of the polish carpathians incised by 0 5 3 8 m over the twentieth century with the amount of incision being greater in their lower and middle courses than in the upper ones variability in the hydraulic importance of channel incision with increasing river size is analysed by comparing changes in the frequency of valley floor inundation at gauging stations located along the seventh order dunajec river despite a lower absolute amount of channel incision in the upper river course here incision has increased channel conveyance and reduced the frequency of valley floor inundation considerably more than in the lower course hydraulic effects of channel incision depend also on lateral stability of an incising river low energy rivers from the eastern part of the polish carpathians remained laterally stable during channel incision this has resulted in substantial lowering of stages for low flood discharges and markedly smaller one for high magnitude floods whereas velocity of the flows conveyed over the highly elevated floodplains has decreased considerably in high energy rivers from the western part of the polish carpathians alternation of incision and lateral channel migration has led to the formation of incised meander belts with substantially lowered stages for all flood discharges and increased velocity of the flows conveyed over the newly formed low lying floodplains

mechanics of merging events for a series of layers in a stratified turbulent fluid this study attempts to explain the evolutionary pattern of a series of well mixed layers separated by thin high gradient interfaces frequently observed in stratified fluids such layered structures form as a result of the instability of the equilibrium with uniform stratification and their subsequent evolution is characterized by a sequence of merging events which systematically increase the average layer thickness the coarsening of layers can take one of two forms depending on the realized vertical buoyancy flux law layers merge either when the high gradient interfaces drift and collide or when some interfaces gradually erode without moving vertically the selection of a preferred pattern of coarsening is rationalized by the analytical theory the merging theorem which is based on linear stability analysis for a series of identical layers and strongly stratified interfaces the merging theorem suggests that the merger by erosion of weak interfaces occurs when the vertical buoyancy flux decreases with the buoyancy variation across the step if the buoyancy flux increases with step height then coarsening of a staircase may result from drift and collision of the adjacent interfaces our model also quantifies the time scale of merging events and makes it possible to predict whether the layer merging continues indefinitely or whether the coarsening is ultimately arrested the merging theorem is applied to extant one dimensional models of turbulent mixing and successfully tested against the corresponding fully nonlinear numerical simulations it is hypothesized that the upscale cascade of buoyancy variance associated with merging events may be one of the significant sources of the fine scale 10 m variability in the ocean

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

a review of oceanic salt fingering theory salt fingering is a potentially important mechanism for mixing different water masses in those parts of the ocean where warm salty waters overlie cooler fresher this review surveys advances in salt fingering theory as they pertain to ocean mixing basic equations are presented along with steady maximum buoyancy flux and fastest growing finger solutions attempts to quantify theoretically finger induced fluxes of heat salt and buoyancy and to understand staircase formation and maintenance are described also considered are the confounding influences of internal wave shear and strain and intermittent internal wave shear driven turbulence which are present in the ocean but in few theories finally outstanding theoretical questions about the role of salt fingers in the ocean are raised

estimation of ice shelf melt rate in the presence of a thermohaline staircase abstractdiffusive convection favorable thermohaline staircases are observed directly beneath george vi ice shelf antarctica a thermohaline staircase is one of the most pronounced manifestations of double diffusive convection cooling and freshening of the ocean by melting ice produces cool freshwater above the warmer saltier water the water mass distribution favorable to a type of double diffusive convection known as diffusive convection while the vertical distribution of water masses can be susceptible to diffusive convection none of the observations beneath ice shelves so far have shown signals of this process and its effect on melting ice shelves is uncertain the melt rate of ice shelves is commonly estimated using a parameterization based on a three equation model which assumes a fully developed unstratified turbulent flow over hydraulically smooth surfaces these prerequisites are clearly not met in the presence of a thermohaline staircase the basal melt rate is estimated by applying an ex

trace metals distribution pattern in floodplain sediments of a lowland river in relation to contemporary valley bottom morphodynamics the distribution of trace metals in alluvial sediments depends on their natural background concentrations and on the dynamics of contemporary depositional and erosional mainly flood induced processes geological and geochemical investigations were carried out in the valley of vistula river near magnuszew central poland sediment samples were collected from a depth of 35 cm and comprise sediments of all defined geomorphological features identification and geological interpretation of the morphodynamic sediment features was supported by aerial photographs and high resolution satellite images these studies revealed that the distribution of trace metals is closely linked to the morphogenesis of the alluvial floodplain the highest concentrations of cu co zn v cr and ni were observed in crevasse splays deposits by contrast sr pb and as were concentrated in deposits which fill oxbow lakes partly infilled with organic deposits the lowest concentrations of trace metals were detected in flood sediments deposited within erosional troughs the geomorphological and sedimentological history of the fluvial features explains the pattern of heavy metal distribution on the current floodplain surface copyright 2014 john wiley sons ltd

pollutant dispersal in groundwater and sediments of gaining and losing river reaches affected by metal mining the presented work couples groundwater and sediment chemistry in the metal mining polluted przemsza river valley in southern poland to reveal regularities in pollutant distribution and to relate them to sedimentary processes and surface water groundwater exchange ten piezometers were installed in transects across the low gradient meandering losing river reach and in the incised channelised gaining reach at each sampling site cores of sediments were sampled for heavy metals and groundwater samples were collected over a year for standard physicochemical analysis as well as zn pb cd mg and fe in the losing river reach the magnitude of pollution of groundwater in the levee zone was similar to that in the river and declined in the backswamp in the levee zone of the incised reach minimum groundwater pollution adjacent to the highly polluted river was related to gaining relatively clean groundwater in the losing reach the dispersal of heavy metals in the levee zone is controlled mainly by overbank accumulation of polluted sediments post depositional changes of metal concentrations in profiles of the losing reach indicate the important role of groundwater in metal dispersal in the gaining river reach the redistribution of metals in the profiles was not ascertained due to a much lower groundwater table

modelling floodplain flows using a two dimensional finite element model a prototype two dimensional finite element flow model for depth averaged free surface flows was developed for floodplain environments limited refinement of the model s physical representation was undertaken and the enhanced scheme applied to an 11 km river channel floodplain reach in the u k preliminary model results indicate that this modelling approach can be used to identify dynamic variations in the flow field parameters over length scales of the order of 10 100 m potentially such data have the ability to permit detailed analysis of short term floodplain sedimentary dynamics

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

estimating mean flow velocity in channel and floodplain areas and its use for explaining the pattern of overbank deposition and floodplain retention abstract stage discharge curves for out of bank flows are derived from direct discharge measurements and theoretical calculations of channel and floodplain conveyance at a station and comparisons of volumes of flood waves at successive stations a method was developed which permits estimation of the mean flow velocity in the channel and floodplain zones at a given total discharge taken from a rating curve out of bank channel flows are estimated under the assumption that the interface planes between the channel zone and the floodplain are included in the wetted perimeter for the channel subarea the floodplain flows are then calculated as the residual values after subtracting the flow in the channel zone from the total discharge results obtained using the method are presented for three cross sections located on mountain foothill and piedmont rivers within the upper vistula drainage basin southern poland and are considered in relation with the pattern of floodplain sedimentation caused by a major flood of july 1997 high rates of lateral thinning and fining of overbank deposits were observed for the piedmont vistula river which is characterized by a marked contrast in mean velocity between the channel and floodplain flows on the mountain skawa river and the foothill skawinka river mean velocity of the floodplain flow was high both in absolute values and when compared with that of the channel flow overbank deposits were generally thin there and showed minor changes in thickness mean size and sorting across the floodplains this study shows that the proposed method of estimating mean flow velocity in channel and floodplain areas may yield valuable information about hydraulics of out of bank flows which may be used for explaining the observed pattern of floodplain deposition the results also demonstrate that the floodplain of the vistula acts mainly as a storage reservoir at low out of bank flows but its efficiency in carrying flood water grows when flow exceeds that of 12 year frequency on the other hand retention potential of the skawa floodplain is very low but flow becomes increasingly stored after water starts to spread rapidly onto the higher terrace at a discharge of 14 year recurrence interval

the relationship between double diffusive intrusions and staircases in the arctic ocean abstractthe origin of double diffusive staircases in the arctic ocean is investigated for the particular background setting in which both temperature and salinity increase with depth motivated by observations that show the coexistence of thermohaline intrusions and double diffusive staircases a linear stability analysis is performed on the governing equations to determine the conditions under which staircases form it is shown that a double diffusive staircase can result from interleaving motions if the observed bulk vertical density ratio is below a critical vertical density ratio estimated for particular lateral and vertical background temperature and salinity gradients vertical background temperature and salinity gradients dominate over horizontal gradients in determining whether staircases form with the linear theory indicating that perturbations to stronger vertical temperature gradients are more likely to give rise to a staircase examination of arctic ocean temperature and salinity measurements

vertical heat transfer in the arctic ocean the role of double diffusive mixing 1 microstructure profiles collected in the central amundsen basin are analyzed in order to quantify the role of double diffusive mixing for vertical heat transfer from the atlantic layer in the profiles a persistent but laterally incoherent thermohaline staircase structure is identified in the 200 260 m depth range the staircase contains homogeneous layers with average height of 1 3 m and thin high gradient interfaces with average temperature and salinity jumps of about 0 065 c and 0 015 respectively when inferred from a commonly used diffusive convection parameterization the average vertical heat flux within the staircase is 0 6 w m 2 this is one order of magnitude larger than the molecular diffusion alone and of the same order as the overall heat loss from the atlantic layer in the deep basins of the arctic ocean the parameterization is evaluated using observed turbulent heat fluxes and is found to overestimate diffusive convective fluxes with up to an order of magnitude especially for weak thermal forcing small temperature jumps in staircase staircases coexist with thermohaline intrusions in the vertical temperature and salinity profiles lomonosov ridge is identified as a potential region for formation of intrusions it is found that salt fingering is the dominant process during intrusion growth whereas diffusive convection is the dominant process in maintaining the intrusions at steady state in the deep basins

floodplain storage of mine tailings in the belle fourche river system a sediment budget approach arsenic contaminated mine tailings that were discharged into whitewood creek at lead south dakota from 1876 to 1978 were deposited along the floodplains of whitewood creek and the belle fourche river the resulting arsenic contaminated floodplain deposit consists mostly of overbank sediments and filled abandoned meanders along white wood creek and overbank and point bar sediments along the belle fourche river arsenic concentrations of the contaminated sediments indicate the degree of dilution of mine tailings by uncontaminated alluvium about 13 per cent of the 110 106 mg of mine tailings that were discharged at lead were deposited along the whitewood creek floodplain deposition of mine tailings near the mouth of whitewood creek was augmented by an engineered structure about 29 per cent of the mine tailings delivered by whitewood creek were deposited along the belle fourche river floodplain about 60 per cent of that sediment is contained in overbank deposits deposition along a segment of the belle fourche river was augmented by rapid channel migration the proportions of contaminated sediment stored along whitewood creek and the belle fourche river are consistent with sediment storage along the floodplains of perennial streams in other similar sized watersheds

early spring oceanic heat fluxes and mixing observed from drift stations north of svalbard abstract from several drifting ice stations north of svalbard norway observations were made in early spring of the ocean turbulent characteristics in the upper 150 m using a microstructure profiler and close to the under ice surface using eddy correlation instrumentation the dataset is used to obtain average heat fluxes at the ice water interface in the mixed layer across the main pycnocline as well over different water masses in the region the results are contrasted with proximity to the branches of the warm and saline atlantic water current the west spitsbergen current wsc which is the main oceanic heat and salinity source both to the region and to the arctic ocean hydrographic properties show that the surface water mass modification is typically due to atmospheric cooling with relatively less influence of ice melting surface heat fluxes of o 100 w m 2 are found within the branches of the wsc and over shelf areas with elevated levels of mixing due to strong tides away from the shelves and

spatial variability of the arctic ocean s double diffusive staircase the arctic ocean thermohaline stratification frequently exhibits a staircase structure overlying the atlantic water layer that can be attributed to the diffusive form of double diffusive convection the staircase consists of multiple layers of o 1 m in thickness separated by sharp interfaces across which temperature and salinity change abruptly through a detailed analysis of ice tethered profiler measurements from 2004 2013 the double diffusive staircase structure is characterized across the entire arctic ocean we demonstrate how the large scale arctic ocean circulation influences the small scale staircase properties these staircase properties layer thicknesses and temperature and salinity jumps across interfaces are examined in relation to a bulk vertical density ratio spanning the staircase stratification we show that the lomonosov ridge serves as an approximate boundary between regions of low density ratio approximately 3 to 4 on the eurasian side and higher density ratio approximately 6 to 7 on the canadian side we find that the eurasian basin staircase is characterized by fewer thinner layers than that in the canadian basin although the margins of all basins are characterized by relatively thin layers and the absence of a well defined staircase a double diffusive 4 3 flux law parametrization is used to estimate vertical heat fluxes in the canadian basin to be o 0 1 wm 2 it is shown that the 4 3 flux law may not be an appropriate representation of heat fluxes through the eurasian basin staircase here molecular heat fluxes are estimated to be between o 0 01 wm 2 and o 0 1 wm 2 however many uncertainties remain about the exact nature of these fluxes this article is protected by copyright all rights reserved

use of mining contaminated sediment tracers to investigate the timing and rates of historical flood plain sedimentation abstract changes in land use practices following european settlement in the 1830s produced accelerated sedimentation on virtually all valley floors in the blue river watershed wisconsin the contamination of sediments by pb and zn mining allowed us to calculate cross valley rates of flood plain sedimentation for three time periods the pre mining period 1830 1900 the mining period 1900 1920 and the post mining period 1920 1997 most of the eight valley floors examined contained multiple presettlement surfaces significantly higher rates of sedimentation occurred on the lower flood plain surfaces while the terraces were high enough to prevent sedimentation from most floods higher rates of sedimentation on the lower surfaces eventually reduced valley floor relief and consequently lateral differences in sedimentation rates tributaries and larger valleys downstream exhibited differences in the timing and rates of historical flood plain sedimentation while rates of sedimentation were high during the pre mining period in tributary valleys the lower valleys were receiving little or no pre mining alluvium little pre mining alluvium was found in mid basin reaches suggesting that most of the pre mining sedimentation was limited to headwater locations during the mining period lateral channel migration and the development of meander belts increased the conveyance capacity of tributary and mid basin channels which decreased overbank flooding and produced lower rates of sedimentation during the post mining period the meander belt channels also had an effect on the lower portion of the watershed by increasing flood magnitudes and the transport of sediment downstream thereby shifting the locus of sedimentation from the tributaries to the larger lower valleys sedimentation rates in the largest most downstream site were an order of magnitude higher during the post mining period than any of the sites upstream

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

thresholds and the spatial variability of flood power during extreme floods abstract analysis of the effects of extreme events on overall landscape form has shifted geomorphic attention away from a focus on the magnitude and frequency relationship of discharge to a focus on flood power this paper analyzes the variation in flood power both at a station and downstream in a basin of differing lithologies and discusses the geologic and geomorphic controls on flood power design floods ranging from the 2 year discharge tothe 500 year discharge are routed trough a drainage basin and channel boundary shear stress and unit stream power are calculated using hec 2 along 21 cross valley transects because of the strong lithologic control on valley width and channel slope an irregular downstream pattern of flood power emerges which reflects primarily the pattern in valley width narrow valleys correspond to a greater percent of channel conveyance during large magnitude floods and increasing rates of depth increases thus maximizing flood power in these zones the opposite occurs in anomalously wide valleys where flood power is minimized a downstream spatial pattern emerges reflecting both local and general controls for a given probability event flood power varies at least threefold within the basin with a maximum occuring in a specific downstream section holding flood power constant produces an extremely wide range in flow probabilities in order to establish a link between critical flood power magnitude and flow frequency minimum flood powers are developed from an analysis of previous work on catastrophic flooding for humid alluvial channels these minimum thresholds tentatively correspond to 100 n m2 or 300 w m2 for shear stress and unit stream power respectively discharges required to attain these critical flood powers vary from events roughly twice the 100 year flood to a maximum of roughly 18 times the discharge of the 100 year flood

effects of the 1997 flood on the transport and storage of sediment and mercury within the carson river valley west central nevada abstract intense warm rains falling on a heavy snowpack in the sierra nevada at the end of december 1996 produced some of the largest floods on record in west central nevada within the carson river basin a peak discharge of 632 cm was recorded at the fort churchill gaging station on january 3 1997 a flow exceeding the 100 yr event geomorphic impacts of the event and the redistribution of mercury hg released to the carson river valley by comstock mining operations during the mid to late 1800s were assessed by combining field data with the interpretation of aerial photographs geomorphic impacts included significant increases in channel width measuring up to 280 of preflood conditions and large scale shifts in channel position ranging from 10 to 110 m both changes in channel width and position vary as a function of valley morphometry width and slope and differ from the long term trends measured from 1965 to 1991 the 1997 flood also produced widespread overbank deposits that vary morpholo

hydraulic controls on the entrapment of heavy metal polluted sediments on a floodplain of variable width the upper vistula river southern poland distribution of heavy metal polluted overbank sediments deposited by a major flood in july 2001 in three gauging sections of different width on the vistula river southern poland was investigated and related to reconstructed pattern of flow velocity during the event the mean velocity of the flow over the floodplain was low and showed a marked contrast with mean velocity in the channel zone in the smolice and the sieroslawice cross sections 4 5 and 9 times wider than the respective channel widths high rates of lateral thinning and fining of overbank deposits were observed at sieroslawice the heavy metal concentrations first rapidly increased with distance from the channel and then remained high over most of the floodplain at smolice concentrations were relatively low within the levee deposits and high over the rest of the floodplain in both cross sections the loads of heavy metals were highest close to the channel margins and decreased exponentially with increasing distance from the channel due to the rapid lateral thinning of the flood deposits the mean velocity of the flow over the floodplain was high in the bielany cross section only 2 6 times wider than the channel width sediments deposited on the narrow floodplain were mostly sand slowly thinning laterally while the concentrations of various heavy metals increased gradually with increasing distance from the channel their loads varied across the floodplain the highest load of some metals occurred near the channel margin and that of others away from the channel this study indicates that floodplain width and the resultant flow hydraulics exert a significant influence on the lateral distribution of floodplain sediments and entrapped heavy metals in wider floodplain sections the largest amounts of heavy metals accumulate near the channel margin and may be remobilized in the future due to bank erosion

physical and chemical characteristics of a metal contaminated overbank deposit west central south dakota u s a a metal contaminated overbank deposit in west central south dakota resulted from the discharge of a large volume of mine tailings into a river system between the late 1800s and 1977 the deposit along the belle fourche river is typically up to 2 m thick and extends about 90 m away from the channel along the insides of meander bends the sediments contain above background levels of copper iron manganese zinc and particularly arsenic which is commonly two orders of magnitude above background level in the contaminated sediments carbonate minerals in the deposit limit the desorption of arsenic by preventing acid formation arsenic concentrations provide a measure of the dilution of mine tailings by uncontaminated sediment the arsenic appears to have been transported and deposited as arsenopyrite but is now at least partially associated with iron oxides and hydroxides within individual samples arsenic concentration has an inverse relation with grain size that results from the more efficient accumulation of arsenic on the greater surface area of the smaller particles arsenic concentration is inversely related to the sample weight percent finer than 16 m however as a consequence of the dilution of the contaminated sediments by uncontaminated sediment with a finer grain size distribution dilution by uncontaminated sediment from tributaries cause arsenic concentrations to decrease by a factor of 3 along 100 km of floodplain an influx at high streamflow of uncontaminated sediment from terraces and the premining floodplain as well as from tributaries causes arsenic concentrations in parts of the contaminated deposit that are farthest away from the channel to be two to three times less than arsenic concentrations in overbank sediment that is immediately adjacent to the channel

mixing across the arctic ocean microstructure observations during the beringia 2005 expedition 1 turbulent scale temperature and conductivity were measured during the pan arctic beringia 2005 expedition the rates of dissipation of thermal variance and diapycnal diffusivities are calculated along a section from alaska to the north pole across deep flat basins canada and makarov basins and steep ridges alpha mendeleev and lomonosov ridges the mixing rates are observed to be small relative to lower latitudes but also remarkably non uniform relatively elevated turbulence is found over deep topography confirming the dominant role of bottom generated internal waves measured patterns of mixing in the arctic are also associated with other mechanisms such as double diffusive structures and deep overflows a better knowledge of the distribution of mixing is essential to understand the dynamics of the changing arctic environment

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

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

textural analysis and modelling of a flood deposit river severn u k samples of sediment collected from the severn floodplain between worcester and gloucester following the severe flooding in january and february 1990 were analysed for their grain size distribution the results show that most sand was deposited within 20 m of the channel bank but that fine sand may contribute to flood sediment across the width of the floodplain james 1985 numerical model of overbank sedimentation attempts to predict the transfer of sediment to the floodplain during flooding geometrical and hydraulic data relating to the severn flood are used as input for a computer program of james 1985 model the pattern of sediment concentrations predicted by the model was compared with that obtained from statistical analysis of the flood sediment the patterns were found to be similar so james 1985 model was considered to predict in a relative sense the distribution of flood sediment

human induced sedimentation patterns of a channelized lowland river channelization of the severely polluted odra and vistula rivers in poland induced intensive accumulation of fine grained deposits rich in organic matter and heavy metals these sediments have been identified in vertical profiles in a narrow zone along river banks both in groyne created basins and on the floodplain grain size organic matter zinc zn lead pb copper cu content and cesium 137 137cs was used for sediment dating and stratigraphy and chemistry have been diagnostic features for these deposits named industrial alluvium in the most polluted river reaches stabilized by bank reinforcements and groynes 2 m thick slack water groyne deposits are composed of uniform strata of polluted silts with organic matter content over 10 zn content over 1000 mg kg and average cu and pb over 100 mg kg the average rate of sediment accretion in groynes is higher than on the floodplain and reaches 5 cm yr stratification which appears at higher levels in the groyne fields and on the levees reflects a change from in channel to overbank deposition and is typified by dark layers separated by bright sandy and less polluted strata stratified 4 m thick sediment sequences have been found in groyne fields of incised river reaches the average rate of sediment accretion in these reaches is of the order of 5 cm yr in stable and relatively less polluted river reaches vertical accretion organic deposits are finely laminated and the average rate of deposition amounts to a few millimeters per year investigations indicate that groyne construction favors conditions for long term storage of sediments at channel banks for this reason groynes should be considered as structures that efficiently limit sudden release of sediment associated heavy metals stored in channels and in floodplains of the historically polluted rivers copyright 2014 john wiley sons ltd

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

sedimentology of a fine grained aggrading floodplain abstract historical land use changes accelerated both soil erosion and subsequent floodplain alluviation within the galena river basin wisconsin a cross valley transect in a low gradient downstream section of this watershed permitted documentation of the lateral and vertical sedimentological properties occurring during this aggradational phase mechanical and statistical analyses of 97 sediment samples reveal two dominant controls determining the resulting floodplain sedimentology firstly the initial fine grained loessial texture dominated the particle size of the early post settlement alluvium generally yielding fine textured sediments across the valley bottom further landscape de stabilization promoted upland gullying into coarser textured residuum below the loess with a concomitant particle size increase in the foodplain alluvium thus the resulting foodplain stratigraphy exhibits a coarsening upward sequence secondly distance from the stream channel exerts a strong control on overall sedimentological properties distal settings possess massive high clay content sediments usually with less than 1 sand samples become coarser and more stratified near the modern stream channel with channel fill facies containing approximately 20 sand in the upper sections the fine grained loessial sediment source affected numerous sedimentological properties of the deposited alluvium sorting correlates negatively with particle size because all particle sizes were entrained during large overbank floods dominance of silt in this loess mantled basin maintains the maintains the median of the particle size distribution within a fairly narrow range only the tails of the distribution vary and they are primarily controlled by the distance to the stream channel in distal settings the fine tail emerges whereas the coarse tail appears in the channel fill and proximal settings although all sediments were deposited in an overbank floodplain environment passega s cm diagrams erroneously indicate a pelagic depositional environment

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

the diffusive regime of double diffusive convection the diffusive regime of double diffusive convection is discussed with a particular focus on unresolved issues that are holding up the development of large scale parameterizations some of these issues such as interfacial transports and layer interface interactions may be studied in isolation laboratory work should help with these however we must also face more difficult matters that relate to oceanic phenomena that are not represented easily in the laboratory these lie beneath some fundamental questions about how double diffusive structures are formed in the ocean and how they evolve in the competitive ocean environment

floodplain sedimentation quantities patterns and processes this paper presents the result of measurements of floodplain sedimentation using sediment traps the study was carried out on two embanked floodplains along the rivers rhine and meuse in the netherlands during a 3 day flood in january 1993 raster maps of sediment accumulation were made by interpolating the measurements from the traps using block kriging the sediment maps show clear patterns in sediment accumulation together with the estimated interpolation errors average sediment accumulation ranges between 0 57 and 1 0 kg m 2 high sediment accumulation is found on the levees 4 kg m 2 or more and on low lying areas 1 6 kg m 2 sediment accumulation decreases with distance from the main channel the sedimentation patterns are related to floodplain topography and sediment transporting mechanisms sediment transport by turbulent diffusion as well as by convection can be recognized also flood duration and the process of sediment settling out in ponding water in closed depressions are important the applied method allows comparison of the results with raster based sedimentation models

circulation and transformation of atlantic water in the eurasian basin and the contribution of the fram strait inflow branch to the arctic ocean heat budget abstract the inflows of atlantic water from the nordic seas to the arctic ocean through fram strait and over the barents sea are examined and their pathways and transformations in the eurasian basin are described based primarily on hydrographic observations from two cruises with rv polarstern in 2007 and 2011 the contrast between the high salinity atlantic water core in the nansen basin and the lower atlantic water salinity in the amundsen basin combined with a salinity minimum below the atlantic layer suggest that the fram strait branch mainly remains in the nansen basin while the barents sea branch continues along the continental slope enters the amundsen basin and provides most of the atlantic water in the makarov and canada basins to examine the consequences of such a circulation pattern recently published estimates of the in and outflows of volume and liquid freshwater through the barents sea bering strait and the canadian arctic archipelago as well as river runoff net precipitation and ice export are reviewed and added together to achieve volume and freshwater balances net outflows through fram strait of 2 3 sv and 100 msv respectively are required this is reasonably close to the recently reported fram strait transport estimates the net outflows are separated into two parts upper layer transports less dense than the entering atlantic water and lower layer transports as dense as or denser than the atlantic water the largest net volume outflow occurs in the lower layer 1 65 sv while the liquid freshwater is almost exclusively exported in the 0 64 sv net outflow in upper layer leading to unrealistically low salinities in the upper layer compared with observations atlantic water is north of svalbard transformed into less saline surface water through melting of sea ice which can supply the necessary higher salinity halocline water to the upper layer 1 23 sv of halocline water of salinity 34 2 must be added to obtain a more realistic salinity of 33 1 leading to a total export of 1 84 sv upper layer water in the east greenland current existing observations of the net transports into and out of the arctic ocean through fram strait in different temperature classes are used to estimate the heat loss of the atlantic water entering the arctic ocean through fram strait about 10 tw are supplied to the atmosphere in addition to the loss of 24 tw occurring in connection with the formation of the halocline water if the hypothesis that the fram strait branch remains in the nansen basin is true it implies a heat loss between 5 and 15 w m 2 in the nansen basin depending upon how much heat is temporarily stored in the water column this is high compared to the 2 w m 2 commonly cited as the ocean heat flux to the atmosphere in the arctic ocean

observational validation of the diffusive convection flux laws in the amundsen basin arctic ocean the low levels of mechanically driven mixing in many regions of the arctic ocean make double diffusive convection virtually the only mechanism for moving heat up from the core of atlantic water towards the surface in an attempt to quantify double diffusive heat fluxes in the arctic ocean a temperature microstructure experiment was performed as a part of the north pole environmental observatory npeo 2013 field season from the drifting ice station barneo located in the amundsen basin near the lomonosov ridge 89 5 n 75 w a diffusive convective thermohaline staircase was present between 150 and 250 m in nearly all of the profiles typical vertical heat fluxes across the high gradient interfaces were consistently small o 10 1 w m 2 our experiment was designed to resolve the staircase and differed from earlier arctic studies that utilized inadequate instrumentation or sampling our measured fluxes from temperature microstructure agree well with the laboratory derived flux laws compared to previous studies which could find agreement only to within a factor of two to four correlations between measured and parameterized heat fluxes are slightly higher when using the more recent flanagan et al 2013 laboratory derivation than the more commonly used derivation presented in kelley 1990 nusselt versus rayleigh number scaling reveals the convective exponent to be closer to 0 29 as predicted by recent numerical simulations of single component convection rather than the canonical 1 3 assumed for double diffusion however the exponent appears to be sensitive to how convective layer height is defined

future of the arctic sea ice cover implications of an antarctic analog recent observations reveal a significant change in the upper ocean characteristics of the eastern arctic in 1995 the change is manifested through the loss of a near surface layer known as the cold halocline layer chl without the chl the arctic water column looks and behaves like the antarctic water column the expected local impact is the appearance of significant winter ocean heat fluxes 15 20 w m and reduction of winter ice growth by 70 80 relative to years in which the chl was present preliminary results suggest a partial recovery of the chl in the late 1990 s tracking the weakening of the arctic oscillation

cross shelf transport of warm and saline water in response to sea ice drift on the laptev sea shelf 1 oceanographic moorings and conductivity temperature depth ctd surveys from september 2009 to september 2010 are used to describe recent changes in the laptev sea hydrography and to highlight wind and ice driven surface ekman transport as the mechanism to translate these changes from the outer to the inner shelf bottom waters in february 2010 moored oceanographic instruments recorded a sudden increase in temperature 0 8 c and salinity 3 near the bottom of the inner laptev sea shelf such warm and saline waters had not been previously observed on the inner shelf in winter they likely originated from the basin and were first observed during a summer 2009 ctd survey in the northwestern shelf break region subsequently spreading east and shoreward across the laptev sea shelf the changes were introduced to the mooring site by the first of a series of bottom intensified flow events with velocities reaching 20 cm s 1 topographically guided along a relic submarine river valley each of the flow events coincided with negative pressure anomalies at the mooring site and offshore directed upwelling favorable winds and ice drift we suggest that the observations to first order resemble a simplified two dimensional two layered ocean where offshore surface ekman transport is compensated for by a barotropic shoreward response flow near the bottom in this paper we use one of the first comprehensive long term laptev sea datasets to highlight ice ocean atmosphere interactions in early and late winter and discuss the role of freshwater stratification and ice mobility on under ice circulation on the laptev sea shelf

ocean to ice heat flux at the north pole environmental observatory 1 data from drifting buoys deployed in april 2002 as part of the north pole environmental observatory project have been analysed to estimate ocean heat flux in the time period from 1 may 2002 to 11 mar 2003 prior to late january the observatory remained in deep water but subsequently drifted directly over the yermak plateau a relatively shallow feature north of svalbard while over deep water heat flux was dominated by storage and release of solar energy in the ocean boundary layer during summer the most likely annual average value for 2002 was 2 6 w m 2 less than previous determinations in the western arctic over yermak plateau heat flux at the interface came from mixing of warmer water into the boundary layer from below when the observatory was in water with depths less than 1200 m the average heat flux was around 22 w m 2

influences of the ocean surface mixed layer and thermohaline stratification on arctic sea ice in the central canada basin 1 variations in the arctic central canada basin mixed layer properties are documented based on a subset of nearly 6500 temperature and salinity profiles acquired by ice tethered profilers during the period summer 2004 to summer 2009 and analyzed in conjunction with sea ice observations from ice mass balance buoys and atmosphere ocean heat flux estimates the july august mean mixed layer depth based on the ice tethered profiler data averaged 16 m an overestimate due to the ice tethered profiler sampling characteristics and present analysis procedures while the average winter mixed layer depth was only 24 m with individual observations rarely exceeding 40 m guidance interpreting the observations is provided by a 1 d ocean mixed layer model the analysis focuses attention on the very strong density stratification at the base of the mixed layer in the canada basin that greatly impedes surface layer deepening and thus limits the flux of deep ocean heat to the surface that could influence sea ice growth decay the observations additionally suggest that efficient lateral mixed layer restratification processes are active in the arctic also impeding mixed layer deepening

regional dependence in the timing of onset of rapid decline in arctic sea ice concentration arctic sea ice concentration from satellite passive microwave measurements is analyzed to assess the form and timing of the onset of decline of recent ice loss and the regional dependence of the response the timing of the onset is estimated using an objective method and suggests differences of up to 20 years between the various subregions a clear distinction can be drawn between the recent onset times of the atlantic sector beginning in 2003 and the much earlier onset times associated with the pacific sector where the earliest transition to rapid loss is found in 1992 rates of decline prior to and following the transition points are calculated and suggest that the postonset rate of loss is greatest in the barents sea and weakest in the pacific sector covariability between the seasons is noted in the sic response both at interannual and longer time scales for two case regions potential mechanisms for the onset time transitions are briefly analyzed in the barents sea the onset time coincides with a redistribution of the pathways of ice circulation in the region while along the alaskan coast the propagation of the regional signal can be traced in the age of the sea ice the results presented here indicate a series of spatially self consistent regional responses and may be useful in understanding the primary drivers of recent sea ice loss

eastern arctic ocean diapycnal heat fluxes through large double diffusive steps abstractthe diffusive layering dl form of double diffusive convection cools the atlantic water aw as it circulates around the arctic ocean large dl steps with heights of homogeneous layers of

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

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

characterization of double diffusive convection steps and heat budget in the deep arctic ocean 1 in this paper we explore the hydrographic structure and heat budget in the deep canada basin by using data measured with mclane moored profilers mmp bottom pressure recorders bpr and conductivity temperature depth ctd profilers upward from the bottom a homogeneous bottom layer and its overlaying double diffusive convection ddc steps are well identified at mooring a 75 n 150 w we find that the deep water is in weak diapycnal mixing because the effective diffusivity of the bottom layer is 1 8 10 5 m2s 1 while that of the other steps is 10 6 m2s 1 the vertical heat flux through the ddc steps is evaluated by using different methods we find that the heat flux 0 1 11 mwm 2 is much smaller than geothermal heating 50 mwm 2 this suggests that the stack of ddc steps acts as a thermal barrier in the deep basin moreover the temporal distributions of temperature and salinity differences across the interface are exponential whereas those of heat flux and effective diffusivity are found to be approximately lognormal both are the result of strong intermittency between 2003 and 2011 temperature fluctuations close to the sea floor were distributed asymmetrically and skewed toward positive values which provide a direct observation that geothermal heating was transferred into the ocean both bpr and ctd data suggest that geothermal heating and not the warming of the upper ocean is the dominant mechanism responsible for the warming of deep water as the ddc steps prevent vertical heat transfer geothermal heating is unlikely to have a significant effect on the middle and upper arctic ocean

tracing provenance and pathways of late holocene fluvio deltaic sediments by heavy metal spatial distribution po plain northern apennines system italy

one more step toward a warmer arctic this study was motivated by a strong warming signal seen in mooring based and oceanographic survey data collected in 2004 in the eurasian basin of the arctic ocean the source of this and earlier arctic ocean changes lies in interactions between polar and sub polar basins evidence suggests such changes are abrupt or pulse like taking the form of propagating anomalies that can be traced to higher latitudes for example an anomaly found in 2004 in the eastern eurasian basin took 1 5 years to propagate from the norwegian sea to the fram strait region and additional 4 5 5 years to reach the laptev sea slope while the causes of the observed changes will require further investigation our conclusions are consistent with prevailing ideas suggesting the arctic ocean is in transition towards a new warmer state

double diffusion in saline powell lake british columbia powell lake contains a deep layer of relic seawater separated from the ocean since the last ice age permanently stratified and geothermally heated from below this deep layer is an isolated geophysical domain suitable for studying double diffusive convection high resolution ctd and microstructure measurements showseveraldouble diffusivestaircases rr 51 6to6 inthedeepwater separatedverticallybysmoothhighgradientregionswithmuchlargerdensityratios theloweststaircasecontainsstepsthatarelaterallycoherent on the basin scale and have a well defined vertical structure on average temperature steps in this staircase are 4mk salinity steps are 2mgkg 21 and mixed layer heights are 70cm the ctd is capable of measuring bulk characteristics of the staircase in both temperature and salinity microstructure measurements are limited to temperature alone but resolve the maximum temperature gradients in the center of selected laminar interfaces two different algorithms for characterizing the staircase are compared consistent estimates of the steady state heat flux 27mwm 22 are obtained from measurements above and below the staircase as well as from microstructure measurements in the center of smooth interfaces estimates obtained from bulk interface gradients underestimate the steady state flux by nearly a factor of 2 the mean flux calculated using a standard 4 3 flux law parameterization agrees well with the independent estimates but inconsistencies between the parameterization and the observations remain these inconsistencies are examined by comparing the underlying scaling relationship to the measurements