evolution of the large scale temperature field in the greenland sea during 1988 89 from tomographic measurements the greenland sea ocean acoustic tomography experiment was conducted during 1988 89 as one component of the international greenland sea project to study deep water formation and the response of the gyre to variations in wind stress and ice cover six acoustic transceivers moored in an array 200 km across transmitted to one another at four hour intervals near the end of february 1989 a sub surface temperature maximum at several hundred meters depth disappeared over a surprisingly large area of the central greenland sea while the water column was modified to about 1000 m depth over much of the gyre the surface remained colder than the deeper water contrary to what might be expected from simple models of convective renewal

physical and biological controls on oxygen saturation variability in the upper arctic ocean employing continuous in situ measurements of dissolved o2 ar and o2 in the arctic ocean we investigate the mechanisms controlling the physical abiotic and biological oxygen saturation state variability in the surface ocean beneath sea ice o2 ar measurements were made underway using equilibrator inlet mass spectrometry eims during an icebreaker survey transiting the upper arctic ocean across the north pole in late summer 2011 using concurrently collected measurements of total oxygen we devolve biological oxygen saturation and physical oxygen ar saturation signals at unprecedented horizontal resolution in the surface ocean in the nansen basin ar is undersaturated up to 7 while biological oxygen supersaturation peaks at 18 4 we attribute this to ice melt atlantic water influence and or cooling in the canadian basin ar is supersaturated up to 3 likely because of ar injection from freezing processes and long residence times of gas under ice cover the overall canadian basin to eurasian basin gradient of ar supersaturation to undersaturation may reflect net freezing in the canadian basin and net melting in the eurasian basin over several seasons either by pacific to atlantic sector ice transport or local changes over time ar saturation could thereby provide large scale high resolution estimates of current and future changes in these processes o2 ar supersaturation averages 4 9 with peaks up to 9 8 where first year ice and abundant melt ponds likely allow sufficient light for blooms in ice covered regions

advances in marine chemistry 1979 1982 these four years saw advances in many areas further developments in sampling and analytical techniques have opened new avenues of exploration for trace elements and particulate matter the impact of the geosecs expedition was further felt in the field of marine chemistry as the results were still being published a major field effort occurred as a follow on to the geosecs work tto and intensive sampling was performed in the newly discovered submarine hydrothermal vent fields an important and unresolved controversy has arisen regarding the ability to measure preformed co2 in the seawater system in many respects the field of marine chemistry appears to be gaining a momentum spurred by both improvements in analytic techniques and an increasing social and economic relevance

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

on the hydrography of the northeast water polynya the water masses and circulation in the area of the northeast water polynya located on the east greenland shelf north of 79 n are described on the basis of an r v polarstern cruise during spring and summer 1993 the baroclinic flow shows northward components close to the east greenland coast and eastward components at the northern limit of the polynya an anticyclonic half circle is formed by this and the southward flowing east greenland current in the south the circle is not closed the upper water column occupied by polar water is affected by this circulation pattern while deeper waters in the trough system of the area seem to spread independently different types of deep waters are found in different troughs all being of atlantic origin though they seem not to be directly connected to return atlantic water it is shown that what is called polar water must be formed at least partly on the greenland shelf and that deepwater formation does not occur in the investigated area

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

plutonium 241am and 137cs ratios inventories and vertical profiles in washington and oregon continental shelf sediments abstract continental shelf sediments from nine locations off washington and oregon have 239 240 pu inventories which average 8 0 2 6 mci km 2 the columbia river and seawaters advecting over the shelf supply pu which is removed to underlying sediments principally through scavenging by inorganic paniculate matter mass balance calculations argue that less than 20 percent of the advected pu need be scavenged from the water column to balance river input and total shelf sediment inventories the percentage of the pu removed through scavenging is consistent with observed participate concentrations in shelf waters and published sediment water distribution coefficients no marked separation of pu from 137 cs is observed with depth in pacific shelf sediments as has been reported in atlantic coastal sediments this interocean distinctness can be explained by differences in particle mixing and downward diffusion of cs in sediments of varying porosities the transuranic inventories and pu cs ratios in the pacific sediments do not support the hypothesis of livingston and bowen that pu is remobilized within the sediment column by complexone formation with principally organic substances excess 210 pb 239 240 pu inventory ratios in eight representative cores from the washington shelf average 100 19 even though absolute values of both inventories vary by much larger factors this reasonably constant ratio for a given water depth permits estimation of total pu inventories and prediction of sites of unusual pu accumulation from data on the more easily measured natural radionuclide

stochastic synthesis of earthquake catalogs a model of earthquake occurrence is proposed that is based on results of statistical studies of earthquake catalogs we assume that each earthquake generates additional a probability that depends on time as t 1 this assumption together with one regarding the independence of branching events on adjacent branches of the event tree is sufficient to permit the generation of complete catalogs of earthquakes that have the same time magnitude statistical properties as real earthquake catalogs if is about 0 5 the process generates sequences that have statistical properties similar to those for shallow earthquakes many well known relations are reproduced including the magnitude frequency law omori s law of the rate of aftershock and foreshock occurrence the duration of a recorded seismic event versus its magnitude the self similarity or lack of scale of rate of earthquake occurrence in different magnitude ranges etc a value of closer to 0 8 or 0 9 seems to simulate the statistical properties of intermediate and deep shocks a formula for seismic risk prediction is proposed and the implications of the model for risk evaluation are outlined the possibilities of the determination of long term risk from real or synthetic catalogs that have the property of self similarity are dim

storm driven mixing and potential impact on the arctic ocean 1 observations of the ocean atmosphere and ice made by ice ocean environmental buoys indicate that mixing events reaching the depth of the halocline have occurred in various regions in the arctic ocean our analysis suggests that these mixing events were mechanically forced by intense storms moving across the buoy sites in this study we analyzed these mixing events in the context of storm developments that occurred in the beaufort sea and in the general area just north of fram strait two areas with quite different hydrographic structures the beaufort sea is strongly influenced by inflow of pacific water through bering strait while the area north of fram strait is directly affected by the inflow of warm and salty north atlantic water our analyses of the basin wide evolution of the surface pressure and geostrophic wind fields indicate that the characteristics of the storms could be very different the buoy observed mixing occurred only in the spring and winter seasons when the stratification was relatively weak this indicates the importance of stratification although the mixing itself was mechanically driven we also analyze the distribution of storms both the long term climatology and the patterns for each year in the past 2 decades the frequency of storms is also shown to be correlated but not strongly to arctic oscillation indices this study indicates that the formation of new ice that leads to brine rejection is unlikely the mechanism that results in the type of mixing that could overturn the halocline on the other hand synoptic scale storms can force mixing deep enough to the halocline and thermocline layer despite a very stable stratification associated with the arctic halocline the warm subsurface thermocline water is not always insulated from the mixed layer

acoustic scattering losses in the greenland sea marginal ice zone during the 1988 89 tomography experiment using arrival amplitude data from the 1988 89 greenland sea tomography experiment the effects of ice scattering at 250 hz in the marginal ice zone miz are estimated the resolution of the arrivals is examined first showing that arrivals are resolved as rays from about 8 to 13 launch angle and a normal modes for low angles below about 4 launch angle the under ice reflection losses of resolved rays and modes are then considered using two methods first the ratio of arrival amplitudes during ice free and ice covered periods is estimated second the ratio of members of a ray group with different reflection numbers is used showing similar but not identical results to the first method for higher grazing angle reflections fast field calculations using the program safari are observed to model the data reasonably using a combination of measured and historical ice parameter values for the low angle arrivals the amplitudes of the arrivals are observed to depend strongly upon both the details of th

fine grained sediment deposition on mussel beds in the oosterschelde the netherlands determined from echosoundings radio isotopes and biodeposition field experiments sedimentation rates of 5 20 cm year 1 were calculated from 137 cs 134 cs activity profiles and echosoundings in a mussel cultivation area in the western part of the oosterschelde sedimentation rates based on 210 pb activity profiles are far too low mainly due to the deposition of aged sediment i e sediment eroded elsewhere inside the basin and not fully enriched with 210 pb at the moment of deposition also specific adsorption to the finest sediment components mixing winnowing and mobilization of the caesium have affected the lead and caesium profiles field experiments on mussel plots showed that mussels deposit 5 10 cm of fine grained sediment during the summer this biodeposition about equals the settling from flocculation in the water column micro fabric microscope studies revealed that pellets do not dominate the sediments indicating that some of the pellets are broken down or resuspended

transport and deposition of plutonium in the ocean evidence from gulf of mexico sediments abstract a study of sediments in the gulf of mexico shows dramatic gradients in pu content and isotope ratios from the continental shelf to the sigsbee abyssal plain in terms of predicted direct fallout inventory of pu one shelf core contains 745 of the predicted inventory while abyssal plain sediments contain only 15 20 of the predicted value absolute pu concentrations of shelf sediments are also conspicuously high up to 110 dpm kg compared to 13 5 dpm kg in mississippi river suspended sediment there is no evidence of pu remobilization in gulf of mexico shelf sediments based on comparison of pu profiles with mn al and fe al profiles horizontal transport of fallout nuclides from the open ocean to removal sites in ocean margin sediments is concluded to be the source of both the high concentrations and high inventories of pu reported here the shelf sediments show 240 pu 239 pu ratios close to 0 179 the average stratospheric fallout value but the ratios decrease progressively across the gulf to low values of 0 06 in abyssal plain sediments the source of low ratio pu in deep water sediments may be debris from low yield tests transported in the troposphere alternatively it may represent a fraction of the pu from global stratospheric fallout which has been separated in the water column from the remainder of the pu in the ocean in either case the low ratio material must have been removed rapidly to the sea floor where it composes a major fraction of the pu in abyssal plain sediments pu delivered by global atmospheric fallout from the stratosphere has apparently remained for the most part in the water or has been transported horizontally and removed into shallow water sediments

on the effects of small scale variability on acoustic propagation in fram strait the tomography forward problem acoustic tomography systems have been deployed in fram strait over the past decade to complement existing observing systems there the observed acoustic arrival patterns are unusual however consisting of a single broad arrival pulse with no discernible repeating patterns or individual ray arrivals the nature of these arrivals is caused by vigorous acoustic scattering from the small scale processes that dominate ocean variability in fram strait simple models for internal wave and mesoscale variability were constructed and tailored to match the variability observed by moored thermisters in fram strait the internal wave contribution to variability is weak acoustic propagation through a simulated ocean consisting of a climatological sound speed plus mesoscale and internal wave scintillations obtains arrival patterns that match the characteristics of those observed i e pulse width and travel time variation the scintillations cause a proliferation of acoustic ray paths however reminiscent of ray chaos this understanding of the acoustic forward problem is prerequisite to designing an inverse scheme for estimating temperature from the observed travel times

boundary layer upper ocean and ice observations in the greenland sea marginal ice zone during the 1984 marginal ice zone experiment a coordinated ocean boundary layer and mixed layer experiment was carried out in concert with a complete heat and mass balance study in the summer marginal ice zone miz of the greenland sea the measurements were made at two drifting ice stations and included observations of ocean boundary layer turbulence profiles of water temperature salinity and velocity ice ablation ice concentration solar radiation and spectral albedos ocean conditions were found to be extremely variable the ice and water velocities were heavily influenced by tidal and inertial motions with amplitudes from 6 to 12 cm s 1 in the course of the drift a 30 km eddy was crossed wherein ice and water velocities exceeded 15 cm s 1 the northern extension of the east greenland polar front was encountered and a northward flow of atlantic water into the arctic basin was observed below the eastern edge of the front but the drift station never moved quite far enough west to be caught in the southward transport of arctic surface water heat from the ocean was a major factor in ice melt and when the ice was over atlantic water it was the dominant factor the events that had the greatest impact on the ice were two outbreaks during which off ice winds blew the ice across warm ice edge ocean fronts once south of these fronts and over surface water as warm as 1 c the ice bottom melted at rates up to 100 kg m 2 d 1 the rapid changes in stratification associated with the outbreaks had a dramatic impact on the drag and heat transfer coefficients the drag coefficient relative to the square of the relative water velocity at 30 m ranged from 0 002 to 0 02 and averaged 0 006 the heat transfer coefficient relative to the friction velocity u and the mixed layer temperature elevation above freezing ranged from 0 0025 to 0 009 and averaged 0 0038 in agreement with the idea that stratification inhibits turbulent exchange the heat transfer coefficient decreased when stratification increased in fact the observed melt rates can be simulated well if molecular heat and salt transfer through a thin near surface laminar boundary layer are accounted for as well as transfer through the turbulent outer boundary layer also in agreement with turbulent boundary layer theory the drag coefficient decreased when stratification increased slightly above neutral however for the large increases in surface stratification the drag coefficient increased this was due to the generation of internal gravity waves by ice bottom roughness because the surface exchange coefficients are so sensitive to surface stratification which is in turn highly variable in the miz accurate simulations of ice motion and ice melt will require realistic estimates of stratification and a good understanding of the relation between the ice ocean interactions and upper ocean conditions

modeled acoustic propagation through an ice edge eddy in the east greenland sea marginal ice zone a detailed modeling study of the relationship between the various oceanographic features of a cyclonic eddy located at the ice edge off the coast of northeastern greenland and the eddy s effects on the propagation of acoustic energy is presented the effects of the eddy on acoustic propagation as a function of location depth and frequency of the acoustic source and depth of the receiver for nominal frequencies of 50 hz and 1 khz are discussed significant differences sometimes greater than 20 db in the acoustic field were observed for variations in any of the source and receiver parameters the sound speed structure of the eddy makes propagation loss and acoustic modes very dependent on direction and location a significant finding is that the interior environment of the eddy can generate a frequency dependence on propagation loss so that 1 khz sustains a loss as much as 20 db smaller than does 50 hz i e dispersion phenomenon a similar propagation loss anomaly was observed and appears to be due to a combination of marginal ice zone miz fine structure and interference patterns created by reflections from the sea surface such an anomaly can exist in the miz with or without the eddy environment both of these frequency anomalies are a function of source and receiver depth low frequency 50 hz energy in the presence of the eddy can experience stronger downward refraction and thereby possibly suffer greater bottom interaction than high frequencies 1 khz as compared to the noneddy environment propagation in the presence of the eddy for any of the source and receiver depths studied can result in changes in the levels and distribution of energy in the acoustic field by more than 10 db as well as changes in the mode of propagation of some rays e g refracted surface reflected to refracted refracted

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

organic carbon cycling and modern phosphorite formation on the east australian continental margin an overview during 1987 the australian bureau of mineral resources conducted a multidisciplinary investigation of the modern phosphorites on the continental margin of southeastern australia between 28 and 32 s the objectives of the work were to examine the processes controlling the cycling of organic carbon and bioactive elements nitrogen phosphorus sulphur and iron in the sediments and to investigate the roles which these processes played in the formation of the modern phosphorites bacterial productivities sulphate reduction rates sedimentary oxygen and pore water concentrations of nitrate ammonia phosphate iron sulphate and fluoride were measured at sea the highest rates of microbial productivity were found in the surficial 0 20 mm sediments of the modern phosphorite zone in 350 460 m water depth these rates were about double those in shallower shelf 300 m sediments and 3 4 fold those rates in mid slope 600 1000 m sediments aerobic and anaerobic oxidation rates of organic matter calculated from sediment oxygen profiles and sulphate reduction rates were highest in the surface sediments in the modern phosphorite zone the recycling of sedimentary iron via reductive dissolution of iron oxyhydroxides and reprecipitation at the oxic anoxic boundary results in a near surface sedimentary trap for iron in the phosphorite zone sediments phosphate released from organic matter in the interfacial sediments and fluoride from seawater are scavenged by iron oxyhydroxides in the top few centimetres of sediment phosphorus in this way is decoupled from organic carbon in the near surface sediments and linked to the redox cycling of iron phosphate and fluoride scavenged onto iron oxyhydroxides and concentrated in the surficial sediments are subsequently released to pore waters in the anoxic sediments when iron oxyhydroxides are buried and dissolve the recycling process releases phosphate and fluoride for incorporation into apatite fluoride is depleted from pore waters at depths 18 cm phosphorite nodules form within anoxic sediments at depths 18 cm and continue to accumulate iron and phosphorus while resident in the mixed layer combinations of rapid sediment mixing rates a slow sedimentation rate and a mixed layer to about 18 cm result in an average particle residence time in the phosphorite zone sediments which is about ten fold that of the mid slope sediments long residence times and rapid mixing promote the oxidation of organic carbon and release of phosphate while the continuous recycling of iron and phosphate concentrates the phosphorus for apatite precipitation and accumulation into phosphorite nodules phosphorite nodules are not found in mid slope sediments probably because of combinations of relatively rapid sedimentation rates ineffective iron phosphorus and fluoride recycling and trapping mechanisms plus dilution and dissemination of any incipient apatite

integral measurements of mass transport and heat content in the strait of gibraltar from acoustic transmissions three view the mathml sourceacoustic transceivers were deployed on either side of the eastern entrance of the strait of gibraltar during april may 1996 to determine the feasibility of using acoustic methods to make routine rapidly repeated horizontally integrated measurements of flow and temperature in straits reciprocal transmissions between the transceivers were used to test the feasibility of using traditional ray differential travel times to monitor the component of flow along the acoustic paths transmissions directly across the strait were used to test the feasibility of using horizontal arrival angle fluctuations and acoustic intensity scintillations to monitor the flow perpendicular to the acoustic path the geometry was selected to provide ray paths that only sample the lower layer mediterranean water so that the feasibility of monitoring the mediterranean outflow using the various methods could be evaluated the acoustic scintillation method did not yield useful current estimates but the experimental parameters were not optimized for this approach since the low frequency variability in log amplitude was found to be highly correlated at receivers view the mathml source apart it is possible that acoustic scintillation measurements using different receiver spacings and more rapid sampling might yield better results the horizontal deflection method gave encouraging results at the time of neap tides but less so during spring tides for this approach both theoretical estimates and measured phase differences between the horizontally separated receivers suggest that internal wave induced horizontal arrival angle fluctuations may fundamentally limit the precision with which arrival angles can be measured further work is needed to determine if a smaller horizontal spacing and higher signal to noise ratios would yield better results reciprocal travel time measurements diagonally across the strait performed the best of the three methods giving absolute flow estimates consistent with those derived from current meter data the fractional uncertainty variance for the lower layer tidal transport from a single tomographic path was estimated to be 0 017 i e 98 of the a priori tidal transport variance was resolved the spatial scales of the sub tidal flow are thought to be significantly shorter than those of the tidal flow however which means that a more elaborate monitoring network is required to achieve the same performance for sub tidal variability finally sum travel times from the reciprocal transmissions were found to provide good measurements of the temperature and heatcontent in the lower layer

sedimentary processes in the inner new york bight evidence from excess210pb and239 240pu abstract particle reactive radionuclides were determined in sediments from the inner new york bight to trace transport and storage of fine grained sediments and associated reactive materials seven sediment cores 20 50 cm in length were analyzed for water content loss on ignition loi and excess 210 pb three of these were also analyzed for 239 240 pu excepting some depth horizons in a core from a dredge spoil dumpsite every sample analyzed contained excess 210 pb variations in the concentration of excess 210 pb with depth in the sediment at all stations correlated strongly with loi which apparently traces that fraction of the sediment which is active in removing reactive elements from the water column in the cores analyzed for 239 240 pu every sample contained finite pu and pu concentrations correlated strongly with excess 210 pb the radionuclide distributions may be simply viewed as products of steady state sediment accumulation or of mixing geochemically reasonable accumulation rates are very high 0 5 2 6 g cm 2 y and could probably only be sustained by offshore transport of dumped materials at the other extreme the relationships between excess 210 pb and loi are compatible with rapid mixing of a 210 pb carrier phase traced by loi into the pre existing substrate with little or no actual accumulation other non steady state processes such as sediment gravity flow could also explain the observed distributions measured sediment inventories dpm cm 2 of excess 210 pb and pu at these stations are greatly in excess of those supportable by direct atmospheric deposition lateral supply is required incorporation of sedimentary fines into the sand substrate could make the inner new york bight an important repository of reactive materials

mesoscale eddies in the fram strait marginal ice zone during the 1983 and 1984 marginal ice zone experiments during the summer marginal ice zone experiment in fram strait in 1983 and 1984 fourteen mesoscale eddies in both deep and shallow water were studied between 78 o and 81on sampling combined satellite and aircraft remote sensing observations conductivity temperature depth observations drift of surface and subsurface floats and current meter measurements typical scales of these eddies were 20 40 km rotation was mainly cyclonic with a maximum speed in several cases subsurface of up to 40 cm s observations further suggest that the eddy lifetime was at least 20 to 30 days five generation sources are suggested for these eddies several of the eddies were topographically trapped while others primarily formed by combined baroclinic and barotropic instability moved as much as 10 15 km d with the mean current the vorticity balance in the nontrapped eddies is dominated by the stretching of isopycnals accompanied by a change in the radial shear in the most completely observed eddy south of 79on the available potential energy exceeded the kinetic energy by a factor of 2 quantitative estimates suggest that the abundance of these eddies enhances the ice edge melt up to 1 2 km d

melting of floating ice and sea level rise 1 contrary to popular belief the melting of floating ice in the form of ice shelves icebergs and sea ice may have a non zero impact on sea level this is because the melting process cools and dilutes the oceans on average and unless these opposing effects exactly balance each other there will be a net change in the ocean density we discuss how these subtle effects can be quantified and put bounds on the potential sea level rise associated with melting of the ice masses that are currently afloat in the world s oceans

geochemistry and deposition of 7be in river estuarine and coastal waters the atmospheric flux of cosmogenic 7be 53 3 day half life and the mode of 7be deposition in river estuarine and coastal environments have been examined the atmospheric flux of 7be commonly supports inventories ranging from 1 0 to 2 0 pci cm2 1 pci 0 037 bq beryllium 7 concentrations in water phase samples collected across salinity gradients in several estuaries along the eastern coastline of the united states range from 0 03 to 0 53 pci l and primarily reflect variations in 7be supply and sorption kinetics the major process controlling the concentration of 7be on estuarine suspended particles appears to be the length of time that these particles remain in the water column field particle to water distribution coefficients for 7be have a median value of about 4 104 but range over an order of magnitude reflecting short term variations in 7be input particle dynamics and particulate iron content rather than equilibrium sorption desorption responses to changes in water salinity or particle type residence times of 7be in the water column range from a few days in estuarine areas of rapid fine particle deposition to several weeks in high energy environments where pronounced sediment resuspension reintroduces deposited 7be back into the water column inventories of 7be in sediments range from nondetectable to 3 3 pci cm2 with the highest inventories in areas where fine particles are accumulating rapidly such sites are also major repositories for other particle reactive substances a 7be budget for the james estuary indicates that less than 5 of the expected 7be input is in the water column and that the short term estuarine trapping efficiency for atmospherically derived 7be is somewhere between 50 and 100

wintertime heat flux to the underside of east antarctic pack ice in the sea ice zone there is a delicate balance between the heat loss from the surface of the snow covered sea ice and the heat supplied to the underside of the ice by the deep ocean the difference between these two heat fluxes determines the amount of ice growth or melt in global atmospheric models the ocean heat flux is often prescribed and has been shown to be an important parameter in determining how thick sea ice will grow thermodynamically although this ocean heat flux is a critical component in climate models there are relatively few direct measurements in the antarctic sea ice region in this study we use measurements of the temperature gradient through the sea ice and of ice growth during a field experiment to estimate the ocean heat flux in the east antarctic region around 140 e 65 s during august 1995 we find an average ocean heat flux of 13 0 14 5 w m 2 this is more than twice the winter values reported in the western weddell sea under multiyear sea ice but similar to the 19 w m 2 that has been estimated for the entire weddell gyre during august 1995 the air temperature showed large variations ranging from near freezing to 30 c this resulted in the thicker ice floes 50 60 cm alternating between a no growth or melting condition and an active ice growth at the base however it is likely that the thicker 60 cm ridged portions of the floes were continually melting

the fram strait acoustic tomography system the deep and wide fram strait between greenland and spitzbergen is the main influx and efflux gate to the arctic basin although major resources are invested in measurements of current and temperature here http asof npoar no the flux estimates still have significant deficiencies and errors our objective is to build test validate and use an innovated integrated observing and modeling system including acoustic tomography for improved monitoring of volume heat and freshwater transports in the fram strait as part of the damocles ip developing arctic modeling and observing capabilities for long term environmental studies integrated project a first step acoustic tomography system is to be installed in the fram strait between east greenland and west spitzbergen in august 2008 the first step tomography system consists of one acoustic source near the svalbard shelf and one receiver array in the middle of the fram strait an extended acoustic system serving both tomography and glider navigation i

plutonium and210pb distributions in northeast atlantic sediments subsurface anomalies caused by non local mixing abstract the depth distributions of 210 pb and 239 240 pu measured in a suite of box cores collected from water depths of 4000 5000 m in the northeast atlantic ocean exhibit pronounced subsurface maxima caused by sediment reworking by benthic infauna small scale spatial heterogeneity in bioturbation rates is indicated by large differences in tracer profiles from duplicate cores separated only by a few centimeters 210 pb and 239 240 pu activity distributions from each subcore exhibit a high degree of correlation and most tracer profiles exhibit one or more subsurface maxima one dimensional biodiffusion analogue models do not adequately simulate the principal features of this data set however an inverse conveyer belt mixing model which simulates subsurface egestion or a functionally equivalent process of surficial material which is enriched both in organic debris and radioactive tracers can reproduce the subsurface tracer maxima single event and continuous subsurface egestion models have been formulated and solved for different feeding rates and background biodiffusive fields the single event model provides a better fit to the data and in particular ensures the observed high degree of correlation between the 210 pb and 239 240 pu activity profiles regardless of the different tracer input functions the most likely candidate responsible for subsurface tracer egestion is a large infaunal worm of the phylum sipunculida which dominates the biomass below a depth of 3 cm

use of packrat middens to determine rates of cliff retreat in the eastern grand canyon arizona packrat midden data can be used to calculate rates of cliff retreat by relating midden age to the distance between cliff face and midden regression analysis using 14 radiocarbon dated packrat deposits from the mississippian redwall limestone in the eastern grand canyon suggests that the redwall has been retreating at an average rate of 0 45 m 103 14c yr this rate of cliff retreat which is comparable to other cliff retreat rates reported from arid environments implies that the colorado river cut through the redwall limestone in the vicinity of horseshoe mesa about 3 7 m y b p

transport mechanism for pb 210 cs 137 and pu fallout radionuclides through fluvial marine systems abstract pb 210 cs 137 and pu 239 240 sediment depth profiles in an anoxic unbioturbated estuarine depositional regime at the head of the saguenay fjord que exhibit a seasonally modulated component caused by pulsed inputs of silts and sands during high energy spring river discharge events superimposed on an ambient depositional pattern of finer grained clays and organic matter a precise sediment timestratigraphy has been determined by the inverse correlation of the pb 210 activity with the rate of river discharge during the period 1963 1976 the historical record of cs 137 and pu 239 240 sediment fluxes has been reconstructed through the normalization of fallout radionuclide activities to the excess pb 210 activity profile radionuclide flux geochronologies have been interpreted on the basis of a fluvial marine transport model which distinguishes between inputs due to direct adsorption of radionuclides onto particles in the water column and inputs resulting from the erosion of particle associated radionuclides from the drainage basin rate constants corresponding to residence times of one year for cs 137 and pu 239 240 in the water column and 1500 years for each radionuclide in the drainage basin provide reasonable agreement between the model and experimental results although there is some evidence for a slightly longer drainage basin residence time for plutonium both the threshold for the initial appearance of pu 238 derived from the atmospheric burnup of a snap 9a satellite reactor in 1964 and the magnitude of its isotopic dilution by drainage basin inputs of pu 239 240 are also in agreement with model predictions

ice edge eddies in the fram strait marginal ice zone five prominent ice edge eddies in fram strait on the scale of 30 to 40 kilometers were observed over deep water within 77 n to 79 n and 5 w to 3 e the use of remote sensing a satellite tracked buoy and in situ oceanographic measurements showed the presence of eddies with orbital speeds of 30 to 40 centimeters per second and lifetimes of at least 20 days ice ablation measurements made within one of these ice ocean eddies indicated that melting which proceeded at rates of 20 to 40 centimeters per day is an important process in determining the ice edge position these studies give new insight on the formation propagation and dissipation of ice edge eddies

bottom ablation and heat transfer coefficients from the 1983 marginal ice zone experiments bottom ablation in the marginal ice zone miz is a fundamental process that controls the ice edge position in both the winter and the summer during the east and west marginal ice zone experiments mizex west and mizex east in 1983 periodic sonic distance measurements between the overlying ice and transducers fixed on masts below ice floes determined the bottom ablation the melt rates for floes within 15 km of the ice edge ranged from near zero when the ice was in water at the freezing point to 0 5 m d 1 when the ice entered warm water greater than 3 k to the south simultaneous velocity and temperature measurements at 2 m below the ice in mizex west and at 2 m and 10 m below the ice in mizex east show the response of the melt rate to changing oceanographic conditions for the first time the combined oceanographic and ablation measurements allow the direct calculation of the bulk heat transfer coefficient ch between the ice and the ocean at 2 m and 10 m below the ice for the bering sea experiment ch was 8 10 4 while for the fram strait experiment ch varied from 2 10 4 to 4 10 4 within each set of experiments ch remained nearly constant over a wide range of melt rates relative ice water speeds and seawater temperatures

effects of sea ice cover on acoustic ray travel times with applications to the greenland sea tomography experiment the travel time effects of a sea ice cover on an acoustic pulse are estimated using generalized ray theory this expands upon the previous work done by jin and wadhams prog oceanogr 22 249 275 1989 by including the effects of frequency dispersion and different sets of ice parameters travel time changes due to single reflections are approximated by plane wave reflection theory and compared to the generalized ray theory results statistical effects for multiple reflections such as the ice thickness probability distribution function fresnel zone averaging and shadowing are considered finally the effects of ice induced travel time changes on tomographic inversions for water column oceanography are considered the implications of this work on the 1988 89 greenland sea tomography experiment are considered in detail

ice thickness in the arctic ocean the statistical reliability of experimental data the statistical reliability of ice thickness distributions derived from submarine sonar data sets of finite length is examined focusing on the standard error eh l in the mean ice draft h derived from a record of length l km this is important in assessing the significance or otherwise of quoted temporal or spatial differences in mean ice draft estimates for eh 50 are derived from four different submarine surveys each of which involved repeated sampling of apparently homogeneous ice fields values ranged from 7 18 to 15 29 of the mean for climate related comparisons of data sets from different years in the same location a value of 12 75 is recommended derived from data gathered at the north pole this value is used to reassess the significance of published data on ice draft variability quoted variability at the north pole over the 1977 1990 period is found to be not statistically significant but a difference in area averaged ice draft over the eurasian basin between 1976 and 1987 remains highly significant using hitherto unreported 1987 data from the north pole area the statistical variability of other parameters of the ice cover is examined the frequency of lead occurrence the width of leads the fractional cover of smooth ice and the frequency of keel occurrence all show standard errors of 22 24 in their mean values while mean keel draft has a 4 error all over a 50 km track length finally unreported 1987 data for an area extending from the pole to 72 n along the prime meridian and the east greenland shelf break are examined in 1 bins using eh l to assess the significance of variations in the mean a statistically significant decline in mean ice draft is observed starting at 86 n and continuing to 72 n a linear regression gives a thinning rate of 0 22 m deg the decline within the arctic basin itself is tentatively ascribed to a mixture of under ice melt and mixing of ice types since data on young ice occurrence show that divergence did not occur north of fram strait

acoustic propagation in the western greenland sea frontal zone a study utilizing numerical experiments of the environmental acoustic effects of the western greenland sea frontal zone in the summer of 1983 along a 185 km west to east transect is presented the transect begins at the edge of the marginal ice zone in the east greenland current then crosses the east greenland polar front and terminates in the water of the greenland sea gyre the transect contains several mesoscale eddylike features and a sharp front between return atlantic intermediate water and greenland arctic intermediate water whose effects on an acoustic field have not been previously reported this front can impart 15 db increase in loss in 10 db in the sensitivity of propagation loss to changes in receiver depth 10 150 m compared to the nonfrontal zone environment a significant finding is that a longer transmission range 93 km through the waters of a frontal zone can reduce the effects of crossing the front itself by as much as 15 db it was also observed that 75 km of upslope propagation that included two oceanic fronts was unaffected by a decrease in bottom depth of 2000 m within the 75 km range

sea ice melting in the marginal ice zone the heat and salt flux boundary conditions together with the freezing curve relationship are a necessary component of any ice sea water thermodynamic model a neutral two layer oceanic planetary boundary layer model that incorporates these boundary conditions gives the following results the interfacial salinity is within 10 of the far field salinity for conditions commonly encountered in the miz and depends only on the turbulent lewis number and the far field temperature and salinity the predicted melt rates agree with the limited field observations of the order of 1 m day 1 the obukov lengths determined from the predicted interface conditions and melt rates are generally much greater than the ekman layer thicknesses hence the surface buoyancy flux has little effect on the turbulence in the planetary boundary layer

fallout 210pb as a soil and sediment tracer in catchment sediment budget investigations a review increasing anthropogenic pressures coupled with climate change impacts on natural resources have promoted a quest for innovative tracing techniques for understanding soil redistribution processes and assessing the environmental status of soil resources among the different existing tracers the fallout component of the radioisotope lead 210 also termed unsupported or excess lead 210 pb 210 ex when referring to its presence in soil or sediment arguably offers the broadest potential for environmental applications due to its origin and relatively long half life for more than five decades pb 210 ex has been widely used for dating sediments to investigate sedimentation processes and since the 1990s to provide information on the magnitude of soil and sediment redistribution the aim of this review is to provide a comprehensive evaluation and discussion of the various applications of pb 210 ex as a tracer in terrestrial and aquatic environments with particular emphasis on catchment sediment budget investigations this paper summarizes the state of the art related to the use of this tracer the main assumptions the requirements including the need for accurate analytical measurements and for parallel validation and the limitations which must be recognised when using this fallout radionuclide as a soil and sediment tracer lessons learned and current and future research needs in the environmental and radiochronological application of pb 210 ex are also presented and discussed c 2014 elsevier b v all rights reserved

radionuclide tracer profiles at the cesar ice station and canadian ice island in the western arctic ocean abstract water column profiles of naturally occurring 210pb 210po 226ra and fallout 137cs 239 240pu radionuclides measured at the canadian ice island in 1985 1986 and 1989 over the arctic ocean continental shelf were compared to profiles measured at the cesar ice station in the central arctic ocean in 1983 cesium 137 concentrations at cesar decreased from a mean value of 4 2 bq m3 in the surface mixed layer to less than 1 0 bq m3 in the atlantic layer and deep waters cesium 137 concentrations were similar to cesar values in the surface mixed layer at the ice island but in halocline water they were lower than values measured at comparable water depths at cesar indicating that the arrival of fallout 137cs in the ice island halocline had been delayed compared to its arrival in the cesar halocline these data are consistent with a combination of mixing box and lateral advection models with mixing occurring over the russian continental shelves followed by lateral advection through the interior halocline waters of the canada basin dissolved 210pb and 210po concentrations were higher in nutrient maximum water at the ice island compared to cesar low values at cesar are caused by scavenging of particle reactive radionuclides during modification of bering sea water in continental shelf environments the elevated 210pb and 210po concentrations measured in nutrient maximum water at the ice island are assumed to result from ingrowth of 210pb from 226ra during lateral advection of upper halocline water between the cesar and ice island locations a process that is estimated to take approximately 11 years plutonium 239 240 is also depleted relative to 137cs in the surface mixed layer and upper halocline at the ice island owing to its scavenging during modification of pacific water in shelf environments the 239 240 pu 137 cs ratio increases to values approaching fallout levels in lower halocline and atlantic water owing to both reduced 239 240pu removal in source waters and vertical transport of 239 240pu with sinking particles

particle mixing rates in sediments of the eastern equatorial pacific evidence from 210pb 239 240pu and 137cs distributions at manop sites abstract particle mixing rates db calculated from excess 210pb gradients in sediments of the east equatorial pacific range from 0 04 to 0 5 cm2 y with variation of a factor of 3 4 at a single site diffusion of the 236ra daughter 222rn may affect 210pb distributions under conditions of slow mixing and low 210pb flux to the seafloor as shown by a siliceous ooze clay core which contained the fallout radionuclides 239 240pu and 137cs but no excess 210pb relative to 226ra there is no clear relationship between 210pbderived mixing rates and sediment type accumulation rate or organic carbon flux to the sediments comparison of 210pb mixing rates with those calculated from 239 240pu and 137cs distributions reveals better agreement for a pulse input of the fallout radionuclides db 0 03 0 4 cm2 y than for continuous input at a constant rate db 0 1 1 6 cm2 y although the pu and 137cs data are better fit by the latter model the agreement may be fortuitous because 239 240pu and 137cs appear significantly deeper than 210pb in at least one core tracer separation could be caused by particle size selective mixing by the benthic fauna or by chemical mobilization if the fallout radionuclides are scavenged from surface waters by large organic rich particles such as fecal pellets their release and migration may result from decomposition of the carrier in surface sediments either a relatively unreactive form of pu e g oxidized pu has been released by this process or a one dimensional model is inadequate to explain its observed penetration into the sediments activity ratios of 239 240 pu 137 cs in the sediments decrease with increasing north latitude and the trend reflects higher fluxes of 239 240pu near the weapons test site at christmas island 2 n the 239 240 pu 137 cs ratios and fluxes to the sediment assuming constant input at the siliceous ooze red clay site are consistent with published sediment trap data from a nearby site thus if fallout radionuclide fluxes to the sea floor were higher in the past both 239 240pu and 137cs have been released from sinking particles

3 d water properties and geostrophic circulation on the eastern bering sea shelf abstract the national oceanic and atmospheric administration s noaa alaska fisheries science center bottom trawl survey samples demersal fish at over 350 sites on the eastern bering sea continental shelf each summer on a 37 37 km 2 grid rugged conductivity temperature depth sensors ctds were added to the net hauls to obtain gridded data sets of temperature and salinity measurements for 2008 2010 results reveal the three dimensional thermohaline structure of the shelf including the cold pool and areas of fresher water around st matthew island and in bristol bay horizontal gradients are often strongest roughly along the 50 m and 100 m isobaths that traditionally separate the inner and outer shelf from the middle shelf centered along the 70 m isobath the summer mixed layer depth is less than 30 m over much of the region it reaches the bottom along the alaska peninsula in water depths greater than 70 m showing that the boundary of the well mixed inner shelf is not always at the 50 m isobath the greatest upper to lower layer density difference is found across the shelf north of 59 n the salinity difference is the main contributor to this density difference over most of the region in 2008 and 2010 but the temperature difference dominates in 2009 due to decreased ice melt and reduced freshening near st matthew island the geostrophic velocity relative to the bottom shows northwestward flow seaward of the 100 m isobath and northwestward transports integrated across the shelf of 0 10 0 25 10 6 m 3 s in 2008 and 2010 there was clockwise circulation in a region of less saline water around st matthew island in 2009 that fresher lens did not exist and flow was more concentrated along the 100 m isobath bringing saltier water across the shelf

natural radionuclides and plutonium in sediments from the western arctic ocean sedimentation rates and pathways of radionuclides abstract sediment cores collected during r v polar sea aos94 expedition from the chukchi shelf to the north pole were analyzed for several decay series natural radionuclides and pu isotopes to study sedimentation rates and pathways of radionuclides in the western arctic ocean the measured sedimentation rates vary by more than three orders of magnitude along the transect from 210pb based rates of 200 700 cm kyr 1 over the chukchi shelf and 89 cm kyr 1 at the chukchi slope to 230th based rates of 0 02 0 3 cm kyr 1 at various settings in the deep basin 230thex profiles in the central western arctic basin are characterized by a cyclic pattern and a pronounced sub surface maximum superimposed on an overall decrease with depth sediment inventories of excess 210pb and 230th in the deep basin as a whole cannot account for their in situ production and 210pb fall out the opposite is true at the slope and shallower waters we contend that as with other ocean basins boundary scavenging also exists in the arctic ocean the broad continental shelves and the slope region may have the potential of removing all or most of the particle reactive radionuclides unaccounted for in the deep basin the pu isotope data are consistent with the notion of boundary scavenging sediment inventories and concentrations of pu decrease rapidly offshore isotopic composition of pu suggests mixing of fall out pu which decreases with increasing latitudes and fuels reprocessing pu derived from the russian and atlantic sides of the arctic ocean although fuel reprocessing pu has impinged on the chukchi slope its existence over the chukchi shelf is not evident and probably overshadowed by fall out pu

accumulation rates and sediment deposition in the northwestern mediterranean abstract as part of the eros 2000 programme sediment mixing and accumulation rates in the northwestern mediterranean sea were determined applying the 210 pb dating method to a total of 49 cores and the results from 29 sediment cores are presented here on the basis of the results from the 49 sediment cores an attempt was made to present a general picture of sediment accumulation for the area of the northwestern mediterranean the total deposition of sediment in the area is estimated to be of the order of 34 15 10 6 ton year 1 which is half the value reported earlier by got and aloisi 1990 continental shelf research 10 841 855 for the same region the activity depth profiles of 210 pb show the presence of intensive mixing in the upper layer of near shore sediments but little or no mixing is observed in the deep water sediments based on a diffusion model sediment mixing rates calculated from excess 210 pb gradients vary from 0 002 to 7 cm 2 year 1 and the deposition rates from 0 01 to 0 60 cm year 1 a linear dependence of sedimentation rate on water depth derived from the sediment cores indicates an inverse correlation between these two the relatively high sedimentation rates and mixing rates found near the rho ne river suggest that the contribution from the river dominates the deposition system in the northwestern mediterranean in the deep water basin however atmospheric input and biological production are clearly more important

the geochemistry of plutonium in fresh and marine water environments abstract the chemical behaviour of plutonium in the hydrosphere is a subject of both great practical and intrinsic importance the production and eventual disposal of pu and other artificial radionuclides dictates that this be the case the main objective of this paper is to provide a synthesis and critical examination of currently published data and interpretations on the geochemistry of pu in natural waters and sediments where appropriate an attempt is made to reinterpret published data with the aim of establishing the relationships between geochemical and biological processes and the distribution concentration and speciation of pu particular attention is paid to the question of the potential for the chemical remobilization of pu from the solid to the aqueous phase approximately one third of the text deals with freshwaters mostly lakes while two thirds discusses the estuarine coastal and open ocean environments

inventory fluxes and residence times from the depth profiles of naturally occurring 210pb in marine sediments of mumbai harbor bay measurements of the vertical concentration profile of deposited 210pb and its parent 226ra in cores of recent marine sediment of mumbai harbor bay mhb were made to determine the various depth distribution parameters sedimentation rate age of sediment total inventory fluxes residence times scavenging rate linear attenuation coefficient and relaxation mass depth overall the profile distributions of 226ra and 210pb showed a decreasing trend with increasing the depth the mean of sedimentation rate in the studied area was obtained to be about 0 76 cm year 1 which corresponds to average age of sediment of about 56 years the average total deposited 210pb for the studied sediment profile was 9 68 k bq m 2 and correspondingly the average value of fluxes of total 210pb and excess 210pb atmospheric flux were 0 59 and 0 32 k bq m 2 year 1 respectively the residence time of 210pb was in the range of 26 226 years throughout the sediment profile and showed generally an increasing trend from top to bottom the mean relaxation mass depth h0 derived from the depth profile of 210pb at the studied area was about 190 kg m 2 the negative association between clay content of cores and the h0 of 210pb indicates that as the clay content increases the penetration depth of deposited 210pb in sediment profile decreases

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

heat transfer from atlantic waters to sea ice in the arctic ocean evidence from dissolved argon in an attempt to determine whether the temperature and salinity properties of arctic ocean waters above the atlantic water temperature maximum are the result of heat transfer to sea ice dissolved ar has been measured as a temperature tracer consistent with such a hypothesis it is found that there is a transition from supersaturation of ar in the upper waters to undersaturation below a depth of 275m using the known dependence of the solubility of ar on t and s assuming that the water was originally equilibrated with the atmosphere at 760mm hg it has been calculated that ca 0 6c of cooling can be attributed to transfer of heat to sea ice

tomographic resolution of mesoscale eddies in the marginal ice zone a preliminary study the adequacy of ocean acoustic tomography to resolve mesoscale eddies in the marginal ice zones miz in the vertical plane containing the acoustic multipaths connecting a pair of transceivers is studied using simulation inversions based on realistic eddy profiles obtained from conductivity temperature depth data resolution in this plane is seen to be strongly dependent upon the characteristics of the sound channel for optimal minimum mean square error estimators resolution is directly related to accuracy with better resolution implying higher accuracy for unaided acoustic tomography i e no supplementary measurements using only non bottom interacting paths horizontal and vertical resolution lengths of the order of 40 km and 200 m respectively are found in the upper water column for a transmission range of 150 km the implication is that the horizontal resolution is marginally adequate to resolve miz eddies but the vertical resolution is not since the horizontal scale of the eddies is of the same order whereas the vertical scale is much shorter the incorporation of bottom reflected arrivals is found to improve resolution significantly however the improvement only occurs in the horizontal direction and saturates when more than 14 of these arrivals are included beyond this point additional travel time observations give mostly redundant information on the other hand the disappearance of less stable non bottom interacting ray paths can result in a significant loss of resolution but only vertically the deficiency in vertical resolution is a result of the upward refracting nature of the miz sound channel it is also demonstrated that the inclusion of point temperature measurements on the acoustic transceiver moorings can dramatically increase the vertical resolution of the overall system particularly within a horizontal correlation length of the mooring with the inclusion of satellite radiometry surface temperature measurements adequate vertical resolution is achieved over the entire range considered

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

resolution identification and stability of broadband acoustic arrivals in fram strait fram strait is the only deep water connection between the arctic and the world oceans an acoustic system for tomography glider navigation and passive listening was installed in the central deep water part of the strait during 2010 2012 with the primary objective of improving the estimates of transport through the strait previous tomographic measurements have relied on the travel times of resolved identified and stable acoustic arrivals the oceanographic conditions and highly variable sea ice in fram strait provide an acoustic environment that differs substantially from those in other tomographic experiments however and results in complex arrival patterns comparisons of the measured arrival patterns with predictions based on hydrographic sections show that it is difficult to resolve and identify individual arrivals in the early part of the arrival patterns in addition the early arrivals are unstable with the arrival structure changing significantly over time later arrivals that are surface reflected bottom reflected tend to be easier to resolve and identify as well as more stable the implication is that inverse methods need to use fluctuations in the overall structure of the early arrivals which tend to sample the ocean similarly in combination with the travel times of the later arrivals

the heard island feasibility test in january 1991 the heard island feasibility test hift was carried out to establish the limits of usable long range acoustic transmissions coded acoustic signals transmitted from a source near heard island in the southern indian ocean were monitored at 16 sites in the north and south atlantic the north and south pacific the indian ocean and the southern ocean the question posed by hift whether at such global ranges the signals would permit phase coherent processing and thus yield favorable signal to noise levels was answered in the affirmative there was no evidence of distress by the local marine mammal population in response to the acoustic transmissions hift was prerequisite to a program for acoustic thermometry of ocean climate atoc the principal challenges to such a program are discussed

the impact of stored solar heat on arctic sea ice growth high resolution measurements of ocean temperature and salinity in the arctic ocean s canada basin reveal the importance of the release of solar derived stored ocean heat on sea ice growth locally absorbed summer solar heat is stored in a near surface temperature maximum nstm layer underlying the mixed layer the heat content of the nstm layer was anomalously large following summer 2007 which saw considerable sea ice losses and intense solar absorption into the exposed surface ocean measurements provide evidence for the entrainment of nstm layer heat in fall winter 2007 2008 by shear driven mixing and convective mixing by the release of dense salty plumes during sea ice growth while at least a portion of the nstm layer was eroded deeper warm ocean layers remained unaffected it is shown that the release of solar heat stored following summer 2007 was sufficient to have reduced sea ice thickness at the end of the 2008 growth season by about 25

numerical simulation of remote acoustic sensing of ocean temperature in the fram strait environment an important part of the general problem of the arctic climate change is the monitoring of the fram strait which lies between greenland and spitsbergen for this reason it is reasonable to apply acoustic methods which are proven to be effective in acoustic ocean thermometry acoustic tomography etc knowledge of the main peculiarities of sound signal propagation in this region is needed to estimate the feasibility of applying remote acoustic methods to this end computer simulation of sound signal propagation in the fram strait environment was performed based on oceanographic data obtained by the r v polarstern expedition the presence of stable eigenrays in fram strait environmental conditions is demonstrated typical values of acoustic signal travel time fluctuations due to environmental variations are determined and the temperature effect on the signal travel time variation is considered sensitivity estimates for measurement of the average ocean temperature across fram strait is considered in two approaches by calculating travel time changes along selected stable eigenrays and by determining the cumulative sum of the whole envelope of the signals passed along water borne paths

pathways of meltwater export from petermann glacier greenland abstractintrusions of atlantic water cause basal melting of greenland s marine terminating glaciers and ice shelves such as that of petermann glacier in northwest greenland the fate of the resulting glacial meltwater is largely unknown it is investigated here using hydrographic observations collected during a research cruise in petermann fjord and adjacent nares strait onboard icebreaker i b oden in august 2015 a three end member mixing method provides the concentration of petermann ice shelf meltwater meltwater from petermann is found in all of the casts in adjacent nares strait with the highest concentration along the greenland coast in the direction of kelvin wave phase propagation the meltwater from petermann mostly flows out on the northeast side of the fjord as a baroclinic boundary current with the depth of maximum meltwater concentrations approximately 150 m and shoaling along its pathway at the outer sill which separates the fjord from the ambient ocean approximately 0 3 msv 1 sv

thermal evolution of the greenland sea gyre in 1988 1989 slice inverses of temperature and heat content from the 1988 1989 greenland sea tomography experiment and other observations including standard conductivity temperature depth stations moored thermistors surface meteorological variables and surface ice cover are combined to better understand the thermodynamics of the greenland sea gyre thermal evolution of the gyre center seems to divide naturally into the following three periods a preconditioning phase november january during which surface salinity is increased by brine rejection from ice formation and by entrainment but in which the mixed layer deepens only slowly to a depth of some 150 200 m a deep mixing phase february march during which the surface mixed layer deepens rapidly to approximately 1500 m in the gyre center purely under the influence of local surface cooling and a restratification phase during which the products of deep mixing are replaced by arctic intermediate water flowing in from the gyre edges the onset of the deep mixing phase occurs after ice formation in the gyre center stops resulting in an area of open water where large heat fluxes can occur in surrounding regions including the odden region to the south ice is still being formed to the north and west closer to the steep topography of the continental shelf the inverse results show significant variability due to advection and large temperature and heat content fluctuations with a period of about 50 days are seen

hydrography and vertical fluxes of heat and salt northeast of svalbard in autumn temperature and salinity data collected by a salargos buoy during october 1988 northeast of svalbard norway as part of the coordinated eastern arctic research experiment are analyzed as the buoy drifted across the continental slope the data show a transition from central arctic conditions where the thermocline lies below the halocline to shelf conditions where the two coincide surface waters on the shelf were above the freezing point losing heat to sea ice advected southward by the wind the atlantic inflow current was also observed on the continental slope with a maximum temperature above 3 c a storm caused upwelling and entrainment of this current leading to strong ice ocean heat fluxes and ice melting the resulting flux of fresh water stabilized the surface layer and shut off further entrainment this episodic process can lead to bigger heat losses from the atlantic inflow current than previously considered for ice covered conditions

acoustic travel time perturbations due to shallow water internal waves and internal tides in the barents sea polar front theory and experiment during august 1992 a combined acoustics physical oceanography experiment was performed to study both the acoustical properties and the ocean dynamics of the barents sea polar front in the region near bear island oceanographic observations from shipboard hydrography and moored sensors allowed the construction of the internal wave frequency spectrum for the area a rapidly sampled tomographic section from a 224 hz 16 hz bandwidth acoustic source to a 16 element vertical receiving array enabled the monitoring of travel time fluctuations over the internal wave frequency band to describe the measured acoustic fluctuations theoretical expressions have been developed for the travel time variances which are functions of the internal wave oceanographic field the local acoustic propagation characteristics and the acoustical system s properties both ray and mode theory expressions are generated as the experiment was performed in shallow water and both ray and mode arrivals were resolvable comparison of the

sedimentation rates on the continental slope off eastern taiwan abstract 230th and 210pb were measured to determine sedimentation rate and mass flux for several cores collected from the continental slope off eastern taiwan in the slope northeast of taiwan at 490 m depth the sedimentation rate as determined from a box core by the excess 210pb method was 0 28 cm yr for the past 60 years in the deep slope off eastern taiwan the rates as determined from two piston cores by the excess 230th method were similar at about 2 3 cm kyr in gravity core located near lutao farther south the sedimentation rate dropped to 0 6 cm kyr these rates suggest that the river input and runoff from the east coast of taiwan contribute a significant mass of sediments to the slope off the east coast the sedimentation rate obtained on the northern continental slope is about 100 times greater than that on the slope off the east coast suggesting that the major sediment source for the former site is probably the east china sea shelf there are indications that the sediments from both the yangtze and yellow rivers are transported southward by the coastal current and then deflected eastward just north of taiwan when the coastal current encounters the north flowing taiwan warm current sediment traps deployed near the coring site on the northern slope yield an apparent particulate flux that varies periodically with time the flux ranges between 2 2 and 2 8 g m2 day the high variability of trapped particulate flux was found to be closely correlated with the tidal current the mass flux estimated from the sedimentation rate 0 28 cm yr and dry bulk density is about 11 g m2 day about four to five times higher than the trapped particulate flux this discrepancy may be mainly due to horizontal transport near bottom below the trap deployment depth an alternative interpretation for the high mass flux on the northeastern slope is that the sediments have been transported from north to south along the shelf break by the counter current just immediately to the west of the kuroshio

the near surface hydrography beneath the odden ice tongue as part of the european subpolar ocean programme esop the german research icebreaker polarstern worked in the greenland sea in the late winter of 1993 whilst on passage the ship encountered a severe winter storm with winds consistently above 20 m s 1 coupled to air temperatures of below 10 degrees c the underway sensors revealed heat fluxes of greater than 700 w m 2 across most of the nordic basin peaking at greater than 1200 w m 2 when the ship crossed the cold fresh water of the jan mayen current this large heat flux coupled to the unique hydrographic conditions present in the jan mayen current allowed sea ice generation in the form of frazil ice at a rate of 28 cm d 1 this frazil ice then developed into pancake ice measurements also were made in the late winter beneath this pancake ice in two remnants of the odden in the jan mayen current hydrographic conditions are such that the ice can exist for a long period of time before eventually decaying due to short wave radiation at the surface towards the centre of the greenland sea hydrographic measurements reveal that the ice is more transient and decays four times more rapidly than ice in the jan mayen current we discuss the development of the odden ice tongue in light of these results and add evidence to the argument that the eventual fate of the water stored in the ice is important and could be a relevant factor in the formation of greenland sea deep water c 1999 elsevier science ltd all rights reserved

vertical concentration profiles of lead in the central pacific at 15 n and 20 s concentrations of lead were measured in a surface transect and at two vertical profile stations 15 n and 20 s in the central pacific these measurements complement similar measurements made earlier in the north pacific at 33 n and in the northwest atlantic at 34 n as well as recent measurements of eolian lead input fluxes near each of these locations the new transect of surface water concentrations of lead corroborates previous measurements which decrease from 13 ng kg at 30 n to 4 ng kg at 17 s in the central pacific this transect gradient is shown to overlie a similar geographic gradient of subsurface maximum concentrations of lead in the three pacific vertical profile stations decreasing from 14 ng kg at 33 n to 11 ng kg at 14 n to 2 5 ng kg at 20 s lead concentrations at each of those locations exhibit maxima at 400 m decreasing concentrations to 2500 m and approximately concentrations of 0 8 1 1 ng kg below that depth the subsurface maximum at the northwest atlantic profile station 36 ng kg at 34 n is also congruent with surface water lead concentrations which decrease from 806 ng kg to 32 ng kg in an offshore transect from rhode island to 34 n 66 w and the shape of the atlantic profile is congruent with those in the pacific there is a positive correlation between the magnitudes of eolian lead input fluxes and the magnitudes of the upper water maxima in lead concentration profiles at corresponding locations as follows south pacific easterlies 3 ng cm 2 yr vs 2 5 ng kg north pacific easterlies 6 ng cm 2 yr vs 11 ng kg north pacific westerlies 50 ng cm 2 yr vs 14 ng kg and north atlantic westerlies 170 ng cm 2 yr vs 36 ng kg this relationship enables one to view the anthropogenic perturbations of the marine lead cycle on a global scale since the industrial origin of eolian and seawater lead has been established by correlations between geographic patterns of industrial lead emissions to the atmosphere and isotopic ratios of industrial leads and by geographic patterns of pb silicate dust ratios and lead isotopic ratios in ocean surface waters these new data coupled with earlier biogeochemical data indicate that surface water concentrations of lead in the north pacific and north atlantic are now conservatively estimated to be 8 to 20 fold greater and those in the south pacific are 2 fold greater than natural concentrations because of industrial emissions of lead to the atmosphere

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

acoustic monitoring of flow through the strait of gibraltar the strait of gibraltar acoustic monitoring experiment was conducted during april may 1996 to determine the feasibility of using acoustic methods to make routine rapidly repeated transport measurements in the strait of gibraltar as well as to explore the acoustic scattering caused by the internal wave bores generated in the strait three different approaches to monitoring the flow were explored i high frequency 2 khz reciprocal transmissions ii high frequency 2 khz horizontal arrival angle measurements of ray bending due to currents and iii one way transmissions from a low frequency 250 hz source to a vertical receiving array on the opposite side of the strait extensive independent measurements of the temperature salinity and velocity fields were also made the deep turning rays are stable and yield differential travel times that give reasonable values for the current components along the acoustic paths horizontal arrival angles phase differences are strongly correlated with rough

growth rate and salinity profile of first year sea ice in the high arctic this paper describes the growth of sea ice and the salinity profiles observed in eclipse sound near pond inlet baffin island canada during the winter of 1977 78 a numerical method of calculation has been developed to incorporate the variations in snow conditions and physical properties of ice and snow during the growth season it is shown that the growth rate can be predicted reasonably well it is also shown that the vertical salinity profile in the ice towards the end of the season provides a record of previous climatological conditions a dependence has been shown between the predicted growth rate and the measured salinity

changes in arctic sea ice result in increasing light transmittance and absorption 1 arctic sea ice has declined and become thinner and younger more seasonal during the last decade one consequence of this is that the surface energy budget of the arctic ocean is changing while the role of surface albedo has been studied intensively it is still widely unknown how much light penetrates through sea ice into the upper ocean affecting sea ice mass balance ecosystems and geochemical processes here we present the first large scale under ice light measurements operating spectral radiometers on a remotely operated vehicle rov under arctic sea ice in summer this data set is used to produce an arctic wide map of light distribution under summer sea ice our results show that transmittance through first year ice fyi 0 11 was almost three times larger than through multi year ice myi 0 04 and that this is mostly caused by the larger melt pond coverage of fyi 42 vs 23 also energy absorption was 50 larger in fyi than in myi thus a continuation of the observed sea ice changes will increase the amount of light penetrating into the arctic ocean enhancing sea ice melt and affecting sea ice and upper ocean ecosystems

numerical simulation of the transverse current monitoring in the fram strait the numerical simulation of transverse current monitoring in the fram strait environment is performed using horizontal refraction modal tomography hrmt the simplified west spitsbergen current profile is constructed in the framework of geostrophic approach and calculation of the modal phase difference between signals arriving along the two paths of acoustical interferometer due to horizontal refraction is made for the sound signal frequencies 100 200 hz and different sound source depth it was demonstrated that the measurable modal phase difference in a range of 80 160 can be expected for an averaged current velocity in the strait cross section of 0 3 m s at higher frequency of the sound signal the sensitivity of the hrmt increases but the space coherency decreases so the optimal frequency has to be chosen the strong mode coupling effect presented in such a complex environment was apparently weakened by using the signals propagating along the closed paths

239 240pu and excess210pb inventories along the shelf and slope of the northeast u s a abstract sedimentary pu and excess 210 pb inventory data are examined from a large number of sites along the u s north atlantic shelf and slope from these data an estimate can be made of the magnitude and location of pu and 210 pb accumulation in this region a major feature of the data is a decrease in the pu and 210 pb inventories with water depth which appears to reflect a decrease in the net scavenging of these elements off shore when pu and 210 pb inventories are summed over water depths less than 4000 m in the north atlantic shelf and slope region the sediments can account for 24 8 of the expected pu and 83 15 of the expected 210 pb inputs at water depths greater than 4000 m in this region we find a greater deficiency in the measured inventories of both 210 pb and pu which cannot be accounted for in the shallower sediments this suggests that the northwest atlantic continental margin is not a major site of pu or 210 pb removal and storage when compared to atmospheric in situ and lateral inputs of these radionuclides