behaviour of dissolved organic matter during formation of natural and artificially grown baltic sea ice during sea ice formation the dissolved constituents of water are rejected from ice crystals the initial fractionation of dissolved organic matter dom in the baltic sea ice was studied through two freezing experiments and by sampling natural sea ice dom was characterized by the spectral absorption of chromophoric dom cdom and the parallel factor analysis of dom fluorescence molecular weight measurements of dom were applied to assess changes in the molecular size distribution of dom in new sea ice relative to parent sea water both in the newly formed artificial and the natural sea ice cdom was enriched by 34 39 relative to salinity the same three identified dom fluorophores were present both in sea water and ice but enriched by 15 54 relative to salinity in ice after the incorporation of dom into ice the ageing of ice decreased the spectral slope coefficient and the molecular weight of dom this study shows that physical processes during freezing of brackish water enrich chromo and fluorophoric dom relative to salts in sea ice

colored dissolved organic matter dynamics across the shelf basin interface in the western arctic ocean 1 spatial variations in the concentration and nature of colored dissolved organic matter cdom in the western arctic ocean were examined by three dimensional excitation emission matrix 3 d eem spectroscopy cdom profiles showed distinctive features well correlated with hydrographic characteristics cdom fluorescence was particularly high at depths between 40 and 200 m up to 3 fluorescence units fl u in both chukchi sea and beaufort sea transects penetration of the high cdom signal formed on the shelves into the canada basin was confined to the upper halocline layer salinity of 33 1 this layer had distinctive 3 d eem fingerprints in fluorescence spectra showing a marked terrestrial humic signature the presence of cdom in the halocline layer likely resulted from two main processes the brine rejection during sea ice formation and transport across the sediment water interface during early diagenesis despite the high primary productivity in the chukchi shelf cdom contribution from in situ production seemed to have little influence on the overall cdom distributions in the study area

physical structural and isotopic characteristics and growth processes of fast sea ice in lutzow holm bay antarctica a sea ice ocean study was conducted off queen maud land and enderby land antarctica from 1990 to 1991 by the japanese antarctic research expedition observations of multiyear land fast sea ice were made in lutzow holm bay over a period of 2 years to determine the snow and ice characteristics and ice growth processes the snow depth in the bay reached large values of 1 0 to 1 5 m during the winter season at offshore locations from the analysis of ice thickness measurements it is confirmed that the fast ice with deep snow cover grew little in winter but substantially thickened during the summer months on the basis of ice core structure salinity and stable isotopic composition we conclude that the summer growth was caused by upward growth at the top of the ice to which snow ice and superimposed ice formation contribute these processes were the primary contributors to sea ice growth and characteristics only where the snow accumulation was large in areas of low snow accumulation there was no surface growth superimposed ice formation on sea ice in antarctica has not been reported previously evidence for snow cover melting which is a prerequisite for superimposed ice formation was also found

carbon dynamics in sea ice a winter flux time series 1 a winter time series of the inorganic carbon system above within and beneath the landfast sea ice of the southern beaufort sea confirmed that sea ice is an active participant in the carbon cycle of polar waters eddy covariance measurements above the ice identified significant vertical co2 fluxes mostly upward away from the ice but with short periods of downward fluxes as well a novel in situ method revealed extremely high pco2 values within the ice that are not inconsistent with theory the total carbon content of the ice increased slightly through the winter season and increasing variability in the vertical profiles as spring began indicated that the inorganic carbon became mobile as the ice began to melt during early winter as the ice formed inorganic carbon concentrations in the surface waters increased dramatically along with salinity partly because of rejection from the ice and partly from advective mixing brine drainage was apparently not sufficient to initiate convection and the excess carbon remained in the surface waters into the summer

modeling the winter spring transition of first year ice in the western weddell sea a new halodynamic scheme is coupled with the los alamos sea ice model to simulate western weddell sea ice during the winter spring transition one dimensional temperature and salinity profiles are consistent with the warming and melt stages exhibited in first year ice cores from the 2004 ice station polarstern ispol expedition results are highly sensitive to snowfall simulations which use reanalysis precipitation data do not retain a snow cover beyond mid december and the warming transition occurs too rapidly model performance is greatly improved by prescribing a snowfall rate based on reported snow thicknesses during ice growth prior to ispol simulations indicate a period of thick snow and upper ice salinity enrichment gravity drainage model parameters impact the simulation immediately while effects from the flushing parameter snow porosity at the ice top appear as the freeboard becomes negative simulations using a snow porosity of 0 3 consistent with that of wet snow agree with salinity observations the model does not include lateral sources of sea water flooding but vertical transport processes account for the high upper ice salinities observed in ice cores at the start of the expedition as the ice warms a fresh upper ice layer forms and the high salinity layer migrates downward this pattern is consistent with the early spring development stages of high porosity layers observed in antarctic sea ice that are associated with rich biological production future extensions of the model may be valuable in antarctic ice biogeochemical applications

characteristics of colored dissolved organic matter cdom in the arctic outflow in the fram strait assessing the changes and fate of terrigenous cdom in the arctic ocean absorption coefficients of colored dissolved organic matter cdom were measured together with salinity delta o 18 and inorganic nutrients across the fram strait a pronounced cdom absorption maximum between 30 and 120 m depth was associated with river and sea ice brine enriched water characteristic of the arctic mixed layer and upper halocline waters in the east greenland current egc the lowest cdom concentrations were found in the atlantic inflow we show that the salinity cdom relationship is not suitable for evaluating conservative mixing of cdom the strong correlation between meteoric water and cdom is indicative of the riverine terrigenous origin of cdom in the egc based on cdom absorption in polar water and comparison with an arctic river discharge weighted mean we estimate that a 49 59 integrated loss of cdom absorption across 250 600 nm has occurred a preferential removal of absorption at longer wavelengths reflects the loss of high molecular weight material in contrast cdom fluxes through the fram strait using september velocity fields from a high resolution ocean sea ice model indicate that the net southward transport of terrigenous cdom through the fram strait equals up to 50 of the total riverine cdom input this suggests that the fram strait export is a major sink of cdom these contrasting results indicate that we have to constrain the c dom budgets for the arctic ocean much better and examine uncertainties related to using tracers to assess conservative mixing in polar waters citation granskog m a c a stedmon p a dodd r m w amon a k pavlov l de steur and e hansen 2012 characteristics of colored dissolved organic matter cdom in the arctic outflow in the fram strait assessing the changes and fate of terrigenous cdom in the arctic ocean j geophys res 117 c12021 doi 10 1029 2012jc008075

new insights into sea ice nitrogen biogeochemical dynamics from the nitrogen isotopes we report nitrogen n isotopic measurements of nitrate total dissolved nitrogen and particulate nitrogen from antarctic pack ice in early and late spring salinity normalized concentrations of total fixed n are approximately twofold higher than in seawater indicating that sea ice exchanges fixed n with seawater after its formation the production of low 15n immobile organic matter by partial nitrate assimilation and the subsequent loss of high 15n nitrate during brine convection lowers the 15n of total fixed n relative to the winter supplied nitrate the effect of incomplete nitrate consumption in sea ice is thus similar to that in the summertime surface ocean but the degree of nitrate consumption is greater in ice leading to a higher 15n for organic n 3 9 than in the open antarctic zone 0 6 relative to previous findings of very high 15n organic matter in sea ice up to 41 this study indicates that it would be difficult for sea ice to explain the high 15n of ice age antarctic sediments the partitioning of n isotopes between particulate and dissolved forms of reduced n suggests that primary production evolved from new to regenerated production from early to late spring even though nitrate assimilation raises the 15n of nitrate the 15n of sea ice nitrate is frequently lower than that of seawater providing direct evidence that the regeneration of reduced n in the ice includes nitrification with mass and isotopic balances suggesting that nitrification supplies a substantial fraction up to 70 of nitrate assimilated within antarctic spring sea ice

selective retention in saline ice of extracellular polysaccharides produced by the cold adapted marine bacterium colwellia psychrerythraea strain 34h the retention of salts in laboratory grown ice was compared to the retention of extracellular polysaccharide substances eps produced by the cold adapted marine gammaproteo bacterium colwellia psychrerythraea strain 34h saline ice was formed by means of a cold finger apparatus from artificial sea water solutions containing either native dissolved eps from strain 34h the same eps but heat treated or dissolved eps from the uninoculated growth medium results indicated that only the native unheated eps of strain 34h was retained preferentially in the ice temperature and volumetric measurements of the ice further suggested a link between the heat labile fraction of this eps of marine bacterial origin and potential habitat alteration bacterial eps may join algal eps in our understanding of how extracellular polymers help to establish and sustain the microbial community that inhabits sea ice

determination of the earth s plasmapause location from the ce 3 euvc images the moon based extreme ultraviolet camera euvc aboard china s chang e 3 ce 3 mission has successfully imaged the entire earth s plasmasphere for the first time from the side views on lunar surface an euvc image on 21 april 2014 is used in this study to demonstrate the characteristics and configurations of the moon based euv imaging and to illustrate the determination algorithm of the plasmapause locations on the magnetic equator the plasmapause locations determined from all the available euvc images with the minimum l algorithm are quantitatively compared with those extracted from in situ observations defense meteorological satellite program time history of events and macroscale interactions during substorms and radiation belt storm probes excellent agreement between the determined plasmapauses seen by euvc and the extracted ones from other satellites indicates the reliability of the moon based euvc images as well as the determination algorithm this preliminary study provides an important basis for future investigation of the dynamics of the plasmasphere with the moon based euvc imaging

the plasmapause response to the southward turning of the imf derived from sequential euv images 1 we statistically examined the plasmapause response to the southward turning of the interplanetary magnetic field imf using sequential global images of the plasmasphere in order to understand how the convection electric field propagates to the inner magnetosphere the extreme ultraviolet euv imager on the imager for magnetopause to aurora global exploration satellite clearly observed inward motion of the plasmapause driven by the southward turning of the imf we surveyed the euv data in the 2000 2001 period and found 16 events using the sequential euv images we calculated the plasmapause radial velocity and then estimated the time development of the convection electric field at the plasmapause epp epp and the solar wind electric field derived from the measurement by the ace satellite had very similar variations each other but there surely was a time lag consequently our research indicates that the plasmapause response to the southward turning of the imf takes 10 30 min this timescale suggests that the convection electric field penetrates from the magnetopause to the inner magnetosphere through the ionosphere

tank study of physico chemical controls on gas content and composition during growth of young sea ice during an ice tank experiment samples were taken to study the processes of acquisition and alteration of the gas properties in young first year sea ice during a complete growth warming cooling cycle the goal was to obtain reference levels for total gas content and concentrations of atmospheric gases o2 n2 co2 in the absence of significant biological activity the range of total gas content values obtained 3 5 to 18 ml of gas per kilo of ice was similar to previous measurements or estimates however major differences occurred between the current and quiet basins showing the role of water dynamics at the ice water interface in controlling bubble nucleation processes extremely high co2 concentrations were observed in all the experiments up to 57 in volume parts it is argued that these could have resulted from two unexpected biases in the experimental settings concentrations of bubbles nucleated at the interface are controlled by diffusion both from the ice water interface towards the well mixed reservoir and between the interface water and the bubble itself this double kinetic effect results in a transition of the gas composition in the bubbles from values close to solubility in sea water towards values close to atmospheric as the ice cover builds up

equations for determining the gas and brine volumes in sea ice samples on a etabli des equations utilisables pour determiner le taux de gaz inclus dans la glace de mer a partir de mesures de densite de salinite et de temperature dans des gammes de temperatures entre 2 c et 30 c inversement ces relations peuvent etre utilisees pour calculer la densite de la glace de mer en fonction de la temperature et de la salinite en prenant en compte a la fois la presence de gaz et de cristaux de sel dans la glace on donne aussi des equations qui permettent le calcul du volume de gaz et d eau salee dans la glace a des temperatures autres que celle pour laquelle la densite a ete determinee

chemical properties of brackish water ice in the bothnian bay the baltic sea the behavior of major ions 18 o dissolved organic carbon doc and trace elements was studied during the initial freezing of low saline water 3 practical salinity units in a freezing experiment samples were also collected from first year sea ice from pack ice in the bothnian bay northern baltic sea during initial ice formation the major ion ratios in sea ice indicated variable behavior with some ions showing relative enrichment sulfate calcium and magnesium conservative behavior sodium or relative depletion potassium compared to sea water at the same salinity doc iron and aluminum showed enrichment in the ice while zinc was depleted to salinity lead was detected in surface snow ice layers only implying atmospheric accumulation first year sea ice with a variable growth and thermal history showed behavior for major ions similar to that observed in new ice however for trace elements the picture was much more complicated most likely due to active secondary processes such as atmospheric supply and biological activity ice growth has a potential impact on the chemical budgets and cycling of some elements especially those which are selectively rejected retained during sea ice formation particularly in the shallow parts of the bothnian bay covered with a land fast ice cover

moon based euv imaging of the earth s plasmasphere model simulations the euv imager on board the chang e 3 lunar lander will image the earth s plasmasphere from a lunar perspective to focus on some of the open questions in plasmaspheric researches i e global structures erosion and refilling of plasmasphere in order to achieve the understanding of the plasmaspheric dynamics in relation to these euv images in lunar perspective the he 30 4nm emission intensities and global structures of the plasmasphere viewed from the moon are investigated using a dynamic global core plasma model embedded with ts07 magnetic field model and w05 electric field model two typical storms observed by the image euv imager are systematically simulated from the perspectives of the moon it is found from the simulations that the maximum emission intensity of the plasmasphere is similar to 12 3 r which is greater than that detected from polar orbit and the global shapes and temporal evolutions of large scale plasmaspheric structures plasmapause shoulder and plume also have different patterns in moon based simulated images it is also shown that the plasmaspheric structures extracted from moon based euv images are in agreement with those from image euv images systematic simulations demonstrate that specific latitudinal distribution of the plasmaspheric structures can only be imaged at specific positions in lunar orbit it is expected that this investigation provides us with an overall understanding on moon based euv images and helps to identify the plasmaspheric structures and evolution patterns in future moon based euv imaging

comparisons of sea ice velocity fields from ers 1 sar and a dynamic model numerical models for sea ice thickness distribution and velocity are used for ice dynamics research and ice forecasting in the modeling work ers 1 sar is an excellent tool in particular by providing spatial ice velocity fields as described in the present baltic sea study ice velocities were extracted from sar data with 3 and 6 day time intervals using the optical flow method a considerable stiffening of the ice pack was observed due to the change in the character of ice deformation under compression from rafting to ridging as the minimum ice thickness increased from 10 to 3o cm the coastal alignment was strong in the ice motion and the coastal boundary layer width was 20 30 km an analysis of the sar data with an ice dynamics model showed that the observed overall ice velocity field could be produred using the hibler viscous plastic ice rheology the compressive strength of the ice over 10 km sc ales was 2 5x 10 4 n m 2 50 for ridging and negligible for rafting of very thin ice the shear strength was significant and the normal yield ellipse aspect ratio of 2 was valid the 3 day time interval is val id for updating an ice model but for detailed ice dynamics investigations a data frequency of 1 d 1 or higher would be preferable

seasonal variations in the properties and structural composition of sea ice and snow cover in the bellingshausen and amundsen seas antarctica sixty three ice cores were collected in the bellingshausen and amundsen seas in august and september 1993 during a cruise of the r v nathaniel b palmer the structure and stable isotopic composition 18 o 16 o of the cores were investigated in order to understand the growth conditions and to identify the key growth processes particularly the contribution of snow to sea ice formation the structure and isotopic composition of a set of 12 cores that was collected for the same purpose in the bellingshausen sea in march 1992 are reassessed frazil ice and congelation ice contribute 44 and 26 respectively to the composition of both the winter and summer ice core sets evidence that the relatively calm conditions that favour congelation ice formation are neither as common nor as prolonged as the more turbulent conditions that favour frazil ice growth and pancake ice formation both frazil and congelation ice layers have an av erage thickness of 0 12 m in winter evidence that congelation ice and pancake ice thicken primarily by dynamic processes the thermodynamic development of the ice cover relies heavily on the formation of snow ice at the surface of floes after sea water has flooded the snow cover snow ice layers have a mean thickness of 0 20 and 0 28 m in the winter and summer cores respectively and the contribution of snow ice to the winter 24 and summer 16 core sets exceeds most quantities that have been reported previously in other antarctic pack ice zones the thickness and quantity of snow ice may be due to a combination of high snow accumulation rates and snow loads environmental conditions that favour a warm ice cover in which brine convection between the bottom and top of the ice introduces sea water to the snow ice interface and bottom melting losses being compensated by snow ice formation layers of superimposed ice at the top of each of the summer cores make up 4 6 of the ice that was examined and they increase by a factor of 3 the quantity of snow entrained in the ice the accumulation of superimposed ice is evidence that melting in the snow cover on antarctic sea ice floes ran reach an advanced stage and contribute a significant amount of snow to the total ice mass

effect of plasmaspheric drainage plumes on solar wind magnetosphere coupling evidence is uncovered that plasmaspheric drainage plumes flowing into the dayside reconnection site mass load the reconnection rate and thereby reduce the coupling of the solar wind to the earth s magnetosphere solar wind magnetosphere coupling is statistically analyzed with the 1963 2003 omni2 data set matched up with the ae au and pci geomagnetic indices times when plasmaspheric drainage plumes are flowing are discerned using multiple spacecraft with plasma detectors in geosynchronous orbit it is found that for a given value of vbz of the solar wind the geomagnetic indices ae au and pci are statistically lower when plasmaspheric drainage plumes are present than when plumes are not present this is taken as a measure of a weakened coupling of the solar wind to the earth s magnetosphere caused by the plumes an addendum examines the effects of polar cap saturation on the auroral electrojet index

classification seasonality and persistence of low frequency atmospheric circulation patterns abstract orthogonally rotated principle component analysis rpca of northern hemisphere 1 month mean 700 mb heights is used to identify and describe the seasonality and persistence of the major modes of interannual variability the analysis is detailed and comprehensive in that 1 a high resolution approximately equal area 358 point grid is used for the virtually maximum possible 35 year period of record 2 a positive bias in the nmc data base in the early 1950s in the subtropics is largely eliminated for the first time and 3 homogeneous separate analyses of each month of the year are carried out detailing the mouth to month changes in the dominant circulation patterns winter results are similar to those of other recent rpca and teleconnection studies except that some less obvious patterns are identified and further detail of the better known patterns is provided two north south dipole patterns are found over the pacific ocean west pacific oscillation and east pacific pattern and over the atla

modelling of superimposed ice formation during the spring snowmelt period in the baltic sea development of landfast sea ice and its snow cover was monitored in the gulf of bothnia baltic sea for a period of 4 weeks during the early melt season of 2004 during this period approximately 90 of the snow layer was transformed into superimposed ice while the rest sublimated a one dimensional thermodynamic snow ice model was used to simulate this process the modelled snowmelt and superimposed ice growth were consistent with the observations but the net accumulation of superimposed ice was slightly overestimated the errors in calculation of temporal variations of the refreezing were probably due to the uncertainties in the external forcing and simplification of snow processes in the model the modelled snow thickness was sensitive to the atmospheric forcing and the influence was amplified when the albedo was parameterized as a function of surface temperature in the sensitivity tests without this feedback the direct effect of the inaccuracy in the albedo parameterization was minor errors in the parameterized longwave radiation were critical for the modelled snow surface temperature during night time but did not have a large effect on the mass balance during this spring melt period

experimental evidence for carbonate precipitation and co2 degassing during sea ice formation chemical and stable carbon isotopic modifications during the freezing of artificial seawater were measured in four 4 m3 tank incubations three of the four incubations were inoculated with a non axenic antarctic diatom culture the 18 days of freezing resulted in 25 to 27 cm thick ice sheets overlying the residual seawater the ice phase was characterized by a decrease in temperature from 1 9 to 2 2oc in the under ice seawater down to 6 7oc in the upper 4 cm of the ice sheet with a concurrent increase in the salinity of the under ice seawater and brine inclusions of the ice sheet as a result of physical concentration of major dissolved salts by expulsion from the solid ice matrix measurements of ph total dissolved inorganic carbon ct and its stable isotopic composition d13ct all exhibited changes which suggest minimal effect by biological activity during the experiment a systematic drop in ph and salinity normalized ct by up to 0 37 phsws units and 376 mol c kg 1 respectively at the lowest temperature and highest salinity part of the ice sheet were coupled with an equally systematic 13c enrichment of the ct calculations based on the direct ph and ct measurements indicated a steady increase in the in situ concentration of dissolved carbon dioxide co2 aq with time and increasing salinity within the ice sheet partly due to changes in the dissociation constants of carbonic acid in the low temperature high salinity range within sea ice the combined effects of temperature and salinity on the solubility of co2 over the range of conditions encountered during this study was a slight net decrease in the equilibrium co2 aq concentration as a result of the salting out overriding the increase in solubility with decreasing temperature hence the increase in the in situ co2 aq concentration lead to saturation or supersaturation of the brine inclusions in the ice sheet with respect to atmospheric pco2 3 5x10 4 atm when all physico chemical processes are considered we expect co2 degassing and carbonate mineral precipitation from the brine inclusions of the ice sheet which were saturated or highly supersaturated with respect to both the anhydrous calcite aragonite vaterite and hydrated ikaite carbonate minerals

behaviour of dissolved organic matter and inorganic nutrients during experimental sea ice formation it is well established that during sea ice formation crystals aggregate into a solid matrix and dissolved seawater constituents including inorganic nutrients are rejected from the ice matrix however the behaviour of dissolved organic matter dom during ice formation and growth has not been studied to date dom is the primary energetic substrate for microbial heterotrophic activity in seawater and sea ice and therefore it is at the base of the trophic fluxes within the microbial food web the aim of our study was to compare the behaviour of dom and inorganic nutrients during formation and growth of sea ice experiments were conducted in an indoor basin at 15 c three 1 m3 tanks to which synthetic seawater nutrients and dissolved organic compounds diatom extracted dom had been added were sampled over a period of 5 days during sea ice formation samples were collected throughout the experiment from water underlying the ice and at the end from the ice as well brine was obtained from the ice by centrifuging ice cores inorganic nutrients nitrate and phosphate were substantially enriched in brine in comparison to water and ice phases consistent with the processes of ice formation and brine rejection dissolved organic carbon doc was also enriched in brine but was more variable and enriched in comparison to the dilution line no difference in bacteria numbers was observed between water ice and brine no bacteria growth was measured and therefore had no influence on the doc levels we conclude that the incorporation of dissolved organic compounds in newly forming ice is conservative however since the proportions of doc in the brine were partially higher than those of the inorganic nutrients concentrating effects of doc in brine might be different compared to salts

on the recognition of areas with problematic sulphidic sediments using multi disciplinary data increased concentrations of several trace elements have been observed in water draining areas with sulphidic sediments along the baltic sea coast of sweden and finland some of these elements are harmful to the water environment the increased leaching of trace elements is often caused by antrophogenic activities such as ditching which cause oxidation of the sulphides and thereby acid soil conditions it is therefore important to recognise areas with sulphidic sediments and if possible avoid land use which causes sulphide oxidation the aim of this study was to find time effective methods which can be used to delineate areas with sulphidic sediments three areas in sweden with known occurrences of sulphidic sediments were studied data obtained from the mapping program at the geological survey of sweden sgu were first studied selected sites were thereafter visited and geoelectrical measurements were carried out by the use of several instruments the results imply that areas with sulphidic sediments are reflected as areas with high trace element contents on sgus biogeochemical maps which are based on analyses of trace elements in aquatic plants the same deposits are often shown as gyttja clay on the maps of quaternary deposits furthermore models derived from airborne electromagnetic measurements show that areas with sulphidic sediments often have a lower electric resistivity than surrounding sediments also the results from ground geoelectrical measurements suggest that the sulphidic sediments have a lower resistivity than surrounding fine grained deposits that interpretation was verified after stratigraphical studies and analyses of the sulphur contents of the sediments it is therefore suggested that data from ground geophysical measurements can be used for a detailed delineation of sulphidic sediments whereas data obtained from airborne geophysical and geological maps give an overview over potential areas with these sediments the absolute resistivity of the sulphidic sediments varies however between the three investigated areas complementary corings and stratigraphical descriptions are therefore always necessary to verify the occurrence of these sediments

18o concentrations in sea ice of the weddell sea antarctica we present data on ice texture salinity and delta o 18 obtained from identical sections of ice cores during the winter weddell sea project 1986 on rv polarstern from july through august 1986 in the longitude range between 5 degrees w and 7 degrees e we find no uniquely definable relationship between delta o 18 values and ice texture in a particular section however most of the snow ice as well as some sections of frazil ice ar found to have negative delta o 18 concentrations this is due to varying degrees of admixtures of meteoric ice snow and sea water during formation of snow ice in contrast to common assumptions our results seem to indicate that a snow cover contributes positively to sea ice growth rather than slowing down the overall growth rate based on a simple model we have estimated the contributions of meteoric ice mean of 3 3 and the combined meteoric ice sea water fraction a minimum of 7 6 to the total ice thickness for the majority of the sampled floes although this is only a moderate contribution to the overall mass balance in the absence of congelation growth it nevertheless enhances ice growth in general this hypothesis is dependently supported by our snow and ice thickness data wadhams and others 1987 which demonstrate that the depression of the snow ice interface below the water line i e a negative freeboard and the formation of snow ice is a common occurrence in the weddell sea therefore we hypothesize that the major part of the observed apparent increase in ice thickness between our inbound and outbound tracks of wwsp 86 may not be derived from regular thermodynamically driven congelation growth but rather from the snow ice component in floes of the weddell sea

snow contribution to first year and second year arctic sea ice mass balance north of svalbard the salinity and water oxygen isotope composition 18o of twenty nine first year fyi and second year syi arctic sea ice cores total length 32 0 m from the drifting ice pack north of svalbard were examined to quantify the contribution of snow to sea ice mass five cores total length 6 4 m were analyzed for their structural composition showing variable contribution of 10 30 by granular ice in these cores snow had been entrained in 6 to 28 of the total ice thickness we found evidence of snow contribution in about three quarter of the sea ice cores when surface granular layers had very low 18o values snow contributed 7 5 9 7 to sea ice mass balance on average including also cores with no snow using 18o mass balance calculations in syi cores snow fraction by mass 12 7 16 3 was much higher than in fyi cores 3 3 4 4 while the bulk salinity of fyi 4 9 was distinctively higher than for syi 2 7 we surmise that oxygen isotopes and salinity profiles can give information on the age of the ice and allows to distinguish between fyi and syi or older ice in the area north of svalbard this article is protected by copyright all rights reserved

an airborne tensor vlf system from concept to realization1 radio signals from very low frequency vlf transmitters distributed world wide have been used for several decades to study the lateral variations of the electrical conductivity in the upper few hundred metres of the earth s crust traditionally in airborne applications the total magnetic fields from one or two transmitters are measured to form the basis for construction of maps that primarily show those conductive structures that are parallel or subparallel to the direction to the transmitters the tensor vlf technique described in this paper makes use of all signals available in a predefined frequency band to construct transfer functions relating the vertical magnetic field and the two horizontal magnetic field components these transfer functions are uniquely determined for a particular measuring site and contain information about the lateral conductivity variations in all directions first experiences with real field data acquired during a test survey in sweden show that maps of the so called peaker the spatial divergence of the transfer functions give an image of the conducting structures most of the structures can be correlated to small valleys filled with conducting sediments or valleys underlain by conductive fracture zones in the crystalline rocks

groundwater exploration using combined controlled source and radiomagnetotelluric techniques radiomagnetotelluric rmt 14 250 khz combined with controlled source magnetotelluric csmt 1 12 khz measurements were applied to the exploration of groundwater located in sandy formations at depths as great as 20 m below thick clay lenses a combination of approximately 30 radio frequencies and controlled source frequencies is essential for penetrating the thick clay layers the electromagnetic transfer functions of impedance tensor and tipper vectors point toward a structure that is largely two dimensional although clear three dimensional effects can be observed where the sandy formation is close to the surface the determinant of the impedance tensor was chosen for inversion using two dimensional models the final two dimensional model fits the data to within twice the estimated standard errors which is considered quite satisfactory given that typical errors are on the level of 1 on the impedance elements comparison with bore hole results and shallow reflection seismic sections show that the

simulating the ice thickness distribution in a coupled climate model climate simulations in a global coupled model are investigated using a dynamic thermodynamic sea ice and snow model with sophisticated thermodynamics and a subgrid scale parameterization for multiple ice thicknesses in addition to the sea ice component the model includes a full primitive equation ocean and a simple energy moisture balance atmosphere we introduce a formulation of the ice thickness distribution that is lagrangian in thickness space the method is designed to use fewer thickness categories because it adjusts to place resolution where it is needed most and it is free of diffusive effects that tend to smooth eulerian distributions experiments demonstrate that the model does reasonably well in simulating the mean arctic climate we find the climate of the arctic and northern north atlantic is sensitive to resolving the ice thickness distribution when comparing the model results to a simulation with a two level sea ice model the ice thickness distribution causes ice export through fram strait to be more variable and more strongly linked to meridional overturning in the north atlantic ocean the lagrangian formulation of the ice thickness distribution allows for the inclusion of a vertical temperature profile with relative ease compared to an eulerian method we find ice growth rates and ocean surface salinity differ in our model with a well resolved vertical temperature profile in the ice and snow and an explicit brine pocket parameterization compared to a simulation with semtner zero layer thermodynamics although these differences are important for the climate of the arctic the effects of an ice thickness distribution are more dramatic and extend into the northern north atlantic sensitivity experiments indicate that five ice thickness categories with 50 cm vertical temperature resolution capture the effects of the ice thickness distribution on the heat and freshwater exchange across the surface in the presence of sea ice in these simulations

formation of density troughs embedded in the outer plasmasphere by subauroral ion drift events a dynamic global core plasma model dgcpm is used to investigate the effects of subauroral ion drift said events on the formation of trough density profiles in the outer plasmasphere during periods of high magnetic activity the dgcpm includes the influences of convection on the changing flux tube volumes as well as daytime refilling and nighttime draining of plasma to calculate the plasma tube contents and equatorial plasma density distribution versus time throughout the magnetosphere saids are regions of latitudinally narrow westward flow of plasma equatorward of the auroral zone we present dgcpm results for various presumed said locations and durations relative to enhanced substorm convection onset and decay to parametrically elicit the formation of plasmaspheric density trough structures resulting from said effects it is found that imposing a said event in the dusk evening sector for 30 min leads to the formation of a narrow less than 1 re near the equatorial plane embedded plasma density trough in the dusk bulge region the modeled plasmasphere density profiles with troughs generally resemble plasmasphere density profiles observed from de 1 measurements

ridging and strength in modeling the thickness distribution of arctic sea ice a theory describing evolution of the ice thickness distribution the probability density of ice thickness was proposed by thomdike et al 1975 and has been used in several sea ice models the advantage of this theory over the widely used two level formulation is that it treats ridging explicitly as a redistribution of ice thickness and ice strength as a function of energy losses incurred by ridge formation however the parameterization of these processes remains rather speculative and largely untested and so our purpose here is to explore these parameterizations using a numerical model based on this theory the model uses a 160 km resolution grid of the arctic and 7 years of observed atmospheric forcing data 1979 1985 monthly oceanic heat flux and current fields are obtained from a 40 km resolution coupled ice ocean model run separately with the same forcing by requiring the computed monthly mean ice drift to have the same magnitude as observed buoy drift we estimate the primary strength parameter the ratio of total to potential energy change during ridging this ratio depends on the value of other parameters however the standard case has a ratio of 17 which is within the range estimated by hopkins 1994 in simulations of individual ridging events the effects of ridge redistribution and shear ridging parameters are illustrated by a series of sensitivity studies and comparisons between observed and modeled ice thickness distributions and ridge statistics in addition these comparisons highlight the following shortcomings of the thickness distribution theory as it is presently implemented first the process of first year to multiyear ridge consolidation is ignored and second the observed preferential melt of thick ridged ice is not reproduced

relation of ice growth rate to salt segregation during freezing of low salinity sea water bothnian bay baltic sea salt segregation and isotopic fractionation during sea ice formation can be parameterized as a function of the ice growth rate we performed a study to investigate if the salt segregation models derived for saline sea ice studies are pertinent during the growth of baltic sea ice in brackish water we used a time series of ice salinity profiles and modeled growth rates to examine the relationship between effective salt segregation and growth rate the results show that models derived for saline sea water are not directly applicable for use in the brackish waters of the baltic sea we derived a simple model for the effective salt segregation in relation to ice growth rate for a wide range of growth rates pertinent for use in low salinity baltic sea conditions and in the future development of a baltic sea ice salinity model

a numerical study of open water formation in sea ice 1 a multicategory sea ice model that explicitly takes into account redistribution of undeformed ice into categories of ridged and rafted ice is introduced with the intention of investigating the simulation of the open water fraction within sea ice the performance of this model is compared with that of a reduced model that accounts for only two categories the latter type of sea ice model being most widely used in global climate models two idealized scenarios are considered polynya formation along a coastline under offshore winds and a low pressure system passing over an ice field furthermore the two models are compared under more real world forcing conditions as they exist in the weddell sea in simplified situations both models produce identical results upon introduction of more realistic ambient conditions however the multicategory model produces larger open water fractions than the two level model concomitantly and consistently with earlier findings the multicategory model produces thicker ice this is a result of the larger horizontal gradients of ice motion which in turn are due to the weaker ice strength that arises from a higher abundance of thinner ice this leads to more open water as well as increased dynamical growth of ice the open water fraction is of relevance in global ocean circulation models where the amount of open water influences the deep and bottom water formation rates such as in conjunction with antarctic coastal polynyas

geochemistry and partitioning of trace metals in acid sulphate soils in sweden and finland before and after sulphide oxidation abstract acid sulphate soils ass are formed on sulphidic sediments along the baltic coasts of sweden and finland the sulphides in the fine grained sediments were once formed in an anoxic environment some centimetres below an oxic sediment water interface in earlier investigations high concentrations of many trace elements have been observed in streams draining such areas we compared the trace element contents in soils formed in sulphidic and non sulphidic clays the results show that the total contents of cd ni mn co and cu in the sulphidic sediments are not higher than in non sulphidic clays from adjacent areas however the mobilisation of cd and ni is higher from acid sulphate soils than from soils formed on sulphide free clays to understand the processes causing the mobilisation we studied the partitioning of trace metals before and after oxidation of sulphidic sediments cadmium ni mn co zn and to some extent cu were found to be mobilised from acid sulphate soils due to increased weathering caused by the low ph in these soils iron and cr are only mobilised to a limited extent copper mo and fe mobilised from weathering are precipitated in oxides that form in the oxidised bg horizons nickel co mn mo and cu were shown to be partly bound in pyrite and are mobilised from acid sulphate soils during the pyrite oxidation however mobilisation of trace elements from pyrite was not found to be an important quantitative contributor to trace element leaching any elements that are mobilised are likely to be transported down through the characteristic cracks which occur frequently in the oxidised horizons evidence of this was found at the groundwater table where the most easily extractable fraction of mobilisable elements occurred at higher concentrations

influence of the arctic oscillation and el nino southern oscillation enso on ice conditions in the baltic sea the wavelet approach 1 variability in time series of ice conditions in the baltic sea is examined within the context of atmospheric circulation represented by the north atlantic oscillation nao and arctic oscillation ao winter indices using the wavelet approach we develop methods of assessing statistical significance and confidence intervals of cross wavelet phase and wavelet coherence cross wavelet power for the time series indicates that the times of largest variance in ice conditions are in excellent agreement with significant power in the ao at 2 2 3 5 5 7 7 8 and 12 20 year periods similar patterns are also seen with the southern oscillation index soi and nino3 sea surface temperature nino3 series wavelet coherence shows in phase linkages between the 2 2 7 8 and 12 20 year period signals in both tropical and arctic atmospheric circulation and also with ice conditions in the baltic sea these results are consistent with gcm simulations showing dynamical connections between high latitude surface conditions tropical sea surface temperatures mediated by tropical wave propagation the wintertime polar vortex and the ao and with models of sea ice and oceanic feedbacks at decadal periods

evidence for significant protein like dissolved organic matter accumulation in sea of okhotsk sea ice absorption and fluorescence of chromophoric dissolved organic matter cdom in sea ice and surface waters in the southern sea of okhotsk was examined sea water cdom had featureless absorption increasing exponentially with shorter wavelengths sea ice showed distinct absorption peaks in the ultraviolet especially in younger ice older first year sea ice had relatively flat absorption spectra in the ultraviolet range parallel factor analysis parafac identified five fluorescent cdom components two humic like and three protein like sea water was largely governed by humic like fluorescence in sea ice protein like fluorescence was found in considerable excess relative to sea water the accumulation of protein like cdom fluorescence in sea ice is likely a result of biological activity within the ice nevertheless sea ice does not contribute excess cdom during melt but the material released will be of different composition than that present in the underlying waters thus at least transiently the cdom introduced during sea ice melt might provide a more labile source of fresher protein like dom to surface waters in the southern sea of okhotsk keywords sea ice sea ice ecology

dynamics of pco2 and related air ice co2 fluxes in the arctic coastal zone amundsen gulf beaufort sea we present an arctic seasonal survey of carbon dioxide partial pressure pco 2 dynamics within sea ice brine and related air ice co 2 fluxes the survey was carried out from early spring to the beginning of summer in the arctic coastal waters of the amundsen gulf high concentrations of pco 2 up to 1834 matm were observed in the sea ice in early april as a consequence of concentration of solutes in brines caco 3 precipitation and microbial respiration caco 3 precipitation was detected through anomalies in total alkalinity ta and dissolved inorganic carbon dic this precipitation seems to have occurred in highly saline brine in the upper part of the ice cover and in bulk ice as summer draws near the ice temperature increases and brine pco 3 shifts from a large supersaturation 1834 matm to a marked undersaturation down to almost 0 matm this decrease was ascribed to brine dilution by ice meltwater dissolution of caco 3 and photosynthesis during the sympagic algal bloom the magnitude of the co 2 fluxes was controlled by ice temperature through its control on brine volume and brine channels connectivity and the concentration gradient between brine and the atmosphere however the state of the ice interface clearly affects air ice co 2 fluxes

on the numerical resolution in a thermodynamic sea ice model the numerical integration of the heat conduction equation is one of the main components in a thermodynamic sea ice model the spatial resolution in the ice normally varies from a minimum of three layers up to a few tens of layers the temporal resolution varies from a few minutes up to hours in this paper the impact of numerical resolution on the prediction of a one dimensional thermodynamic ice model is studied analytical solutions for idealized cases were derived and compared with the numerical results for the full ice model groups of simulations were made applying average climatic weather forcing data corresponding to the ice freezing ice thermal equilibrium and ice warm up seasons special attention was paid to the effect of model spatial resolution early in the freezing season the influence of resolution on model predictions is not significant when the shortwave radiation becomes large its absorption within the ice or snow cover was found to modulate the effect of numerical resolution on predictions of ice temperature and surface heat fluxes e g the model run with a coarse spatial resolution yielded large daily variations in surface temperature resolution also affects the in ice temperature profile for process studies a two layer scheme for the solar radiation penetrating into the ice is suitable for a fine spatial resolution ice model

ice drift in the weddell sea in 1990 1991 as tracked by a satellite buoy ice drift in the weddell sea has been studied by using a satellite buoy deployed on an ice floe the buoy survived for a 20 month period indicating a drift trajectory of 10 000 km and yielding 13 months of marine meteorological data the drift of the ice floe was studied with respect to the winds measured by the buoy in the central weddell sea the mean drift speed of the ice floe was 0 15 m s which was about 3 of the wind speed more specifically the drift ratio was 3 4 in the marginal ice zone and 2 4 in the inner pack ice field on average the drift was directed 36 left of the wind direction but the turning angle was larger during the austral summer and smaller during the winter on time scales of days the drift was primarily wind dependent except for cases during winter periods of high ice concentration and internal ice resistance for time scales of several months purely wind based simulations of the drift resulted in a discrepancy between the observed and simulated trajectories but the inclusion of a slow 0 02 m s residual current made the simulations significantly better the geostrophic wind based on european centre for medium range weather forecasts pressure analyses was estimated for a 1 month period and the ice floe was found to drift almost parallel to the geostrophic wind with a speed of 2 of the geostrophic wind speed inertial type motion superimposed on the wind induced drift was found to be a characteristic feature in the marginal ice zone during the austral summer but it could not be found from the drift in winter when kinetic energy was transferred to larger scales of motion and dissipated into the ice field

modeling brine and nutrient dynamics in antarctic sea ice the case of dissolved silica sea ice ecosystems are characterized by microalgae living in brine inclusions the growth rate of ice algae depends on light and nutrient supply here the interactions between nutrients and brine dynamics under the influence of algae are investigated using a one dimensional model the model includes snow and ice thermodynamics with brine physics and an idealized sea ice biological component characterized by one nutrient namely dissolved silica dsi in the model dsi follows brine motion and is consumed by ice algae depending on physical ice characteristics the brine flow is either advective diffusive or turbulent the vertical profiles of ice salinity and dsi concentration are solutions of advection diffusion equations the model is configured to simulate the typical thermodynamic regimes of first year antarctic pack ice the simulated vertical profiles of salinity and dsi qualitatively reproduce observations analysis of results highlights the role of convection in the lowermost 5 10 cm of ice convection mixes saline nutrient poor brine with comparatively fresh nutrient rich seawater this implies a rejection of salt to the ocean and a flux of dsi to the ice in the presence of growing algae the simulated ocean to ice dsi flux increases by 0 115 compared to an abiotic situation in turn primary production and brine convection act in synergy to form a nutrient pump the other important processes are the flooding of the surface by seawater and the percolation of meltwater the former refills nutrients near the ice surface in spring the latter if present tends to expell nutrients from the ice in summer

crystal structure stable isotopes δ18o and development of sea ice in the ross amundsen and bellingshausen seas antarctica the crystal structure and oxygen isotopic composition of ice cores obtained from floes at the end of summer in the eastern ross sea the amundsen sea and the western bellingshausen sea were investigated to determine the ice growth processes and conditions that contribute to sea ice development in the eastern pacific sector of the southern ocean the isotope data indicate that a moderate amount of snow contributes to the development of the sea ice however even the combined use of isotopes and crystal structure analysis does not unambiguously explain the means by which all of the snow is entrained in the ice nevertheless it seems clear that much of the snow is contained in granular snow ice that results from seawater flooding of floes and the base of the snow cover the snow cover in the ross amundsen region was as much as 2 m deep and supported by 7 to 8 m thick floes primarily composed of frazil ice in the bellingshausen region the snow cover and the floes were thinner than in the ross amundsen region the bellingshausen cores were composed primarily of multiple layers of frazil and congelation ice in addition in both regions there were numerous tipped or inclined blocks of congelation ice and layers of rafted nilas in the cores the data indicate that the sea ice develops by multiple mechanisms in a turbulent environment

formation of an aggregate scale in arctic sea ice 1 the ice pack covering northern seas is a mixture of thick ridged and rafted ice undeformed ice and open water conventional eulerian arctic sea ice models use a plastic yield surface to characterize the constitutive behavior of the pack an alternative is to adopt a discontinuous lagrangian approach and explicitly model the formation of leads and pressure ridges we use a lagrangian ice model that consists of thousands of discrete polygonal floes 1 4 km in width at the beginning of a simulation the ice floes are frozen together in a square domain we apply a linearly varying wind stress that deforms the pack by stretching the viscous elastic joints between adjacent floes fractures propagate along joints forming a crack pattern in the model ice pack the crack pattern defines a system of large plates 10 100 km in width that are aggregates of many individual floes the average size of the plates is determined by a competition between the rate of crack creation and the speed of the relaxation wave that travels outward from a newly broken joint and reduces stresses in the surrounding pack simulation results are used to characterize the formation of the aggregate structure and to determine how the rate of crack creation and the average area of the aggregate plates depends on tensile strength the wind stress gradient and the size of the individual floes after the formation of the aggregate scale plate structure subsequent deformation occurs at the plate boundaries since the usual state of the ice pack is a state of failure an interesting situation is created in which the initial wind driven deformation creates the material conditions or aggregate structure under which subsequent deformation occurs

coast of departure and coast of arrival two important concepts for the formation and structure of convective snowbands over seas and lakes abstract a case with intense convective snowbands over the baltic sea is examined using the high resolution limited area model the intention is to gain a better insight into the importance of the shape of the coasts the orography and the surface roughness on the formation and evolution of the snowbands among the factors studied are the shape of the coast from which the air departs and that to which it arrives these factors are so important that two new concepts coast of departure and coast of arrival are introduced

boat towed radio magnetotellurics a new technique and case study from the city of stockholm we have developed a new data acquisition system and technique to measure the radio magnetotelluric rmt signals from distant radio transmitters with the objective of mapping and modeling electric

bio optical properties of arctic drift ice and surface waters north of svalbard from winter to spring we have quantified absorption by cdom acdom k particulate matter ap k algal pigments aph k and detrital material anap k coincident with chlorophyll a in sea ice and surface waters in winter and spring 2015 in the arctic ocean north of svalbard the acdom k was low in contrast to other regions of the arctic ocean while ap k has the largest contribution to absorption variability in sea ice and surface waters ap 443 was 1 4 2 8 times and 1 3 1 8 times higher than acdom 443 in surface water and sea ice respectively aph k contributed 90 and 81 to ap k in open leads and under ice waters column and much less 53 74 in sea ice respectively both acdom k and ap k followed closely the vertical distribution of chlorophyll a in sea ice and the water column we observed a tenfold increase of the chlorophyll a concentration and nearly twofold increase in absorption at 443 nm in sea ice from winter to spring the acdom k dominated the absorption budget in the uv both in sea ice and surface waters in the visible range absorption was dominated by aph k which contributed more than 50 and acdom k which contributed 43 to total absorption in water column detrital absorption contributed significantly 33 only in surface ice layer algae dynamics explained more than 90 variability in ap k and aph k in water column but less than 70 in the sea ice this study presents detailed absorption budget that is relevant for modeling of radiative transfer and primary production

dissolved organic matter in antarctic sea ice sea ice supports highly dynamic and at times highly productive assemblages of auto and heterotrophic organisms central to the biogeochemical cycling of carbon and nitrogen within sea ice is the production and lability of dissolved organic matter dom dom is produced through excretion mortality cell lysis and amplified by inefficient feeding by grazers it has been hypothesised that there are significant dom pools in sea ice systems although measurements of dom in sea ice have only rarely been made the significance of dom for ice based productivity and carbon turnover therefore remains highly speculative the dissolved organic carbon and nitrogen doc don of sea ice from the amundsen bellingshausen and weddell seas were investigated in 1992 1994 and 1997 measurements were made on melted sea ice sections in 1994 and 1997 and in sea ice brines in 1992 these studies confirm that doc and don can reach up to 30 and 8 times higher concentrations compared to those in surface waters respectively this dom tends to be carbon enriched with a mean doc don ratio of 14 measurements made on a limited data set showed that carbohydrates constitute on average 35 of the doc pool with highly variable contributions

sea ice structure and biological activity in the antarctic marginal ice zone ice cores obtained during october november 1981 from weddell sea pack ice were analyzed for physical chemical and biological parameters frazil ice which is associated with dynamic turbulent conditions in the water column predominated 70 both floe thickness and salinity indicate ice which is less than 1 year old chemical analyses particularly with regard to the nutrients revealed a complex picture phosphate values are scattered relative to the dilution curve nitrate and silicate values are lower than expected from simple scaling with salinity and suggest diatom growth within the ice nitrite values are higher in the ice than in adjacent waters frazil ice formation which probably concentrates algal cells from the water column into ice floes results in higher initial chlorophyll a concentrations in the ice than in adjacent waters this mechanical concentration is further enhanced by subsequent reproduction within the ice ice core chlorophyll ranged from 0 09 to 3 8 mg m3 comparable to values previously reported for this area but significantly lower than values for antarctic coastal fast ice the dominance of frazil ice in the weddell is one of the major differences between this area and others consequently we believe that ice structural conditions significantly influence the biological communities in the ice

potentials and problems of building detailed dust records using peat archives an example from store mosse the great bog sweden mineral dust deposition is a process often overlooked in northern mid latitudes despite its potential effects on ecosystems these areas are often peat rich providing ample material for the reconstruction of past changes in atmospheric deposition the highly organic up to 99 in some cases matrix of atmospherically fed mires however makes studying the actual dust particles grain size mineralogy challenging here we explore some of the potentials and problems of using geochemical data from conservative lithogenic elements al ga rb sc y zr th ti and ree to build detailed dust records by using an example from the 8900 yr peat sequence from store mosse the great bog which is the largest mire complex in the boreo nemoral region of southern sweden the four dust events recorded at this site were elementally distinct suggesting different dominant mineral hosts the oldest and longest event 6385 5300 cal yr bp sees a clear signal of clay input but with increasing contributions of mica feldspar and middle ree rich phosphate minerals over time these clays are likely transported from a long distance source 100 km while dust deposition was reduced during the second event 5300 4370 cal yr bp this is the most distinct in terms of its source character with eu eu ucc revealing the input of plagioclase feldspar from a local source possibly active during this stormier period the third 2380 2200 cal yr bp and fourth 1275 1080 cal yr bp events are much shorter in duration and the presence of clays and heavy minerals is inferred elemental mass accumulation rates reflect these changes in mineralogy where the relative importance of the four dust events varies by element the broad changes in major mineral hosts grain size source location and approximated net dust deposition rates observed in the earlier dust events of longer duration agree well with paleoclimatic changes observed in northern europe the two most recent dust events are much shorter in duration which in combination with evidence of their local and regional character may explain why they have not been seen elsewhere

a new lagrangian model of arctic sea ice a new lagrangian sea ice model for the arctic ocean has been developed to accommodate the assimilation of integral measures of ice displacement over periods of days or weeks the model is a two layer thick ice and open water dynamic model with 600 700 cells spaced at roughly 100 km the force balance equation is solved for each cell with standard wind and water stress terms a coriolis term and an internal ice stress term the internal stress is found using a viscous plastic rheology and an elliptical yield curve the strain rate is determined by the smoothed particle hydrodynamics formalism which determines the spatial derivatives of the velocity by a weighted summation of the velocities of adjacent cells a length scale of 150 km is used the model is driven with observed geostrophic winds and climatological mean ocean currents ice growth and melt are found from a seasonal and thickness based lookup table because the current focus is on the model dynamics the model ice velocity simulations are compared to observed buoy motion over the 5 yr period 1993 97 the correlation of the daily averaged model velocity with buoy velocities is r 5 0 76 n 5 42 553 rms difference 5 0 072 m s21 speed bias 51 0 009 m s21 angle bias 5 8 08 this compares favorably with the correlation of a state of the art eulerian coupled ice ocean model where r 5 0 74 in the summer and 0 66 in the winter over the same 5 yr period

long term characteristics of simulated ice deformation in the baltic sea 1962 2007 1 the north atlantic oscillation nao index is a frequently used measure for the mean winter conditions in northern europe a positive high index is associated with strong westerlies and anomalous warm temperatures the effects on sea ice conditions in the baltic sea are twofold warm temperatures prevent sea ice formation if ice is present nevertheless the strong winds can promote the formation of ice ridges which hinders ship traffic we use an ocean sea ice model to investigate the nao impact on the ridged ice area fraction in the baltic during 1962 2007 our simulations indicate that in the northern bothnian bay a high nao index is related to an anomalous accumulation of ridges while in the rest of the baltic sea the relationship is contrary the nao explains locally at most only 20 25 of the ridged ice fraction interannual variability which indicates the systems complexity however we find high skill with local correlations around 0 8 for annually averaged ridged ice fraction reconstructed from multilinear regression using winter averaged wind extremes surface air temperature and sea surface temperature sst this suggests that the amount of ridged ice in late winter can be derived from these routinely measured quantities in large parts of the basin it is sufficient to use the atmospheric parameters as a predictor while in the eastern bothnian bay and southern gulf of finland the sst is required to reconstruct the bulk of the ridged ice fraction

geophysics of sea ice in the baltic sea a review abstract with improved observation methods increased winter navigation and increased awareness of the climate and environmental changes research on the baltic sea ice conditions has become increasingly active sea ice has been recognized as a sensitive indicator for changes in climate although the inter annual variability in the ice conditions is large a change towards milder ice winters has been detected from the time series of the maximum annual extent of sea ice and the length of the ice season on the basis of the ice extent the shift towards a warmer climate took place in the latter half of the 19th century on the other hand data on the ice thickness which are mostly limited to the land fast ice zone basically do not show clear trends during the 20th century except that during the last 20 years the thickness of land fast ice has decreased due to difficulties in measuring the pack ice thickness the total mass of sea ice in the baltic sea is however still poorly known the ice extent and length of the ice season depend on the indices of the arctic oscillation and north atlantic oscillation sea ice dynamics thermodynamics structure and properties strongly interact with each other as well as with the atmosphere and the sea the surface conditions over the ice covered baltic sea show high spatial variability which cannot be described by two surface types such as ice and open water only the variability is strongly reflected to the radiative and turbulent surface fluxes the baltic sea has served as a testbed for several developments in the theory of sea ice dynamics experiences with advanced models have increased our understanding on sea ice dynamics which depends on the ice thickness distribution and in turn redistributes the ice thickness during the latest decade advance has been made in studies on sea ice structure surface albedo penetration of solar radiation sub surface melting and formation of superimposed ice and snow ice a high vertical resolution has been found as a prerequisite to successfully model thermodynamic processes during the spring melt period a few observations have demonstrated how the river discharge and ice melt affect the stratification of the oceanic boundary layer below the ice and the oceanic heat flux to the ice bottom in general process studies on ice ocean interaction have been rare in the future increasingly multidisciplinary studies are needed with close links between sea ice physics geochemistry and biology

optical properties of melting landfast sea ice and underlying seawater in santala bay gulf of finland 1 in march and early april 2000 spectral irradiance measurements were conducted on 10 occasions above and beneath the landfast sea ice in santala bay near the entrance to the gulf of finland the measurements included the spectral albedo and transmittance of the sea ice and the downwelling and upwelling spectral irradiance at different depths in the water column spectral albedos integrated over 400 700 nm photosynthetically active radiation par were in the range of 0 16 0 58 with most common values between 0 33 and 0 42 maximum transmittances for the ice are found close to 570 nm decreasing toward shorter and longer wavelengths correspondingly diffuse attenuation coefficients for both seawater and sea ice agree well with earlier measurements in the baltic sea and have a par attenuation of 0 4 0 7 and 3 1 4 7 m 1 respectively during the measurement period the ice reached its maximum thickness of 28 cm and thereafter started to decay the sea ice was snow free however the formation of high scattering melt freeze layers above the freeboard largely increased the surface reflectance discharged meltwater was retained beneath the sea ice forming a low salinity layer which only disappeared as the ice ablated in april compared with many parts of the arctic the sea ice and seawater in santala bay contain higher amounts of dissolved and particulate matter which are indicated by high absorption at wavelengths below 700 nm and thus potentially increase the melt rate of the sea ice

combined magnetic electromagnetic and resistivity study over a highly conductive formation in orrivaara northern sweden different geophysical methods were used to determine the characteristics of a highly conductive structure in northern sweden first discovered on airborne data airborne electromagnetic very low frequency data indicate a high conductivity structure coincident with low magnetic patterns the airborne data were processed in different ways to enhance various structures features in particular we introduce a new transformation to current density that is suitable for delineating conductive structures ground measurements of the total magnetic field radiomagnetotelluric measurements and resistivity imaging provided valuable information that was used in the compilation of a new bedrock map over the area the results of our measurements indicate that the conducting structure consists of metasedimentary rocks containing thin horizons of pyrrhotite and graphite

atmospheric and oceanic conditions and the extremely low bothnian bay sea ice extent in 2014 2015 the winter of 2014 2015 was the first for which we can be certain that the northernmost embayment of the baltic sea the bothnian bay remained partially ice free we assess atmospheric and oceanic drivers responsible for this extreme event in terms of atmospheric drivers mild bothnian bay winters are characterized by positive north atlantic oscillation nao associated with the advection of air from the north atlantic in winter 2014 2015 nao was at a record high level and resulted in a northerly storm track associated with vigorous southwesterlies that drove ice toward the northeastern end of the bay furthermore we found that the 1985 2015 baltic sea ice extent distribution differs from any other preceding 30 winter period since 1720 with a high confidence based on climate projections it is very likely that in the next 50 years partially ice free bothnian bay will go from being an extremely rare event to a new normal

geochemistry of stream water in a catchment in finland affected by sulphidic fine sediments abstract the impact of sediment type on stream water geochemistry was studied in a catchment in finland affected by sulphidic fine grained sediments stream water samples for general characterisation of water quality ph electrical conductivity were taken at the basin outlet during various hydrological conditions while samples for detailed geochemical analysis were collected at 119 sites in the catchment on one single occasion during high water flow in autumn the occurrence of sulphidic fine sediments was estimated based on data from an airborne electromagnetic survey carried out by the geological survey of finland growing symbol maps which were prepared for each of the studied variables in water and statistical calculations including factor analysis and spearman correlations show that the concentrations of al ga u and tl all the lanthanides and several alkali and alkaline earth metals k mg na li ca rb sr transition metals cd co cu zn sc mn ni y hf and non metals s br i si increase in water when the proportion of the catchment cover of sulphidic fine sediments increases it is therefore argued that these elements are released and mobilised in considerable amounts by the oxidation and subsequent acidification and weathering of this type of sediment other elements are either slightly depleted in streams in areas of sulphidic fine sediments v nb pb zr have a distribution unrelated to sediment type fe cr cs mo or are only weakly impacted by the occurrence of sulphidic sediments in the catchment as ti ba it is argued that these elements are not leached extensively from the oxidising sulphidic sediments and that their distributions at least partly may be controlled by the contents of dissolved humic material and or suspended organic and inorganic phases in the water

seasonal development of the properties and composition of landfast sea ice in the gulf of finland the baltic sea 1 the seasonal development of the structure salinity and stable oxygen isotopic composition 18o of landfast sea ice was studied during the winter seasons 1999 2001 in the gulf of finland in the baltic sea the main focuses were on the seasonal and the interannual variability in ice properties and composition and on the contribution of meteoric ice to sea ice mass balance results provide a first statistical description of the seasonal evolution of sea ice in mild ice climate conditions the ice has a characteristic structure with an upper granular ice layer composed almost exclusively of superimposed ice and snow ice averaging at 20 35 of the total ice thickness the remaining is composed of columnar or intermediate granular columnar ice depending on growth conditions while salinity shows a uniform profile through the ice 18o shows lower values in the surface because of meteoric ice formation the thin ice cover is susceptible to changes in atmospheric conditions and rapid changes in ice salinity are connected to changes in the ice thermal regime and flooding the contribution of meteoric ice varied from 0 to 35 by mass depending on season and year superimposed ice formation is a recurring process and significantly contributed to ice growth up to 20 by mass especially late in the season during snowmelt freeze cycles liquid precipitation also cause formation of intermittent superimposed ice layers at these latitudes the contribution of meteoric ice to sea ice mass balance is largely dependent on the amount and timing of snow accumulation and timing of snowmelt freeze processes which all showed large year to year variation the conditions presented here may start to occur at higher latitudes if global warming continues

influence of sea ice on the seasonal variability of hydrography and heat content in tvarminne gulf of finland the seasonal variability of hydrography heat content freshwater budget and sea ice is examined for the past century in tvarminne gulf of finland the aim was to evaluate the seasonal sea ice impact on the physical properties of the coastal waters which can also be subject to riverine influences the gulf of finland is an optimal location for such a study given the high interannual variability of the ice conditions this is the first time annual cycles of physical properties have been analyzed based on such a long term dataset in the archipelago sea the maximum water temperature occurred in august at the sea surface and at the bottom in september with the 1month lag due to vertical heat diffusion the annual salinity cycle varied greatly in the surface layer the variations were largely connected to sea ice formation and break up processes and the ice cover which prevented wind mixing of the surface waters the largest heat loss occurred in november december 150wm 2 and the highest heat gain in june 180wm 2 especially in april latent heat released absorbed in sea ice formation break up contributed to a seasonal variation in heat budget of 40wm 2

variability of fast ice thickness in spitsbergen fjords detailed measurements of sea ice thickness and snow on sea ice were recorded at different locations in fjords along the western coast of spitsbergen the largest island in the svalbard archipelago in 2004 data corresponding to the ice situation before and after melt onset were collected for kongsfjorden and van mijenfjorden while hornsund was investigated once during early spring profiles of total thickness snow plus ice thickness were measured together with some snow thickness measure ments total thicknesses were measured with a portable electromagnetic instrument and at selected sites by drilling the three fjords show some differences in measured thicknesses connected to individual conditions however total thickness does not differ substantially between the three fjords before melt onset the modal total thickness for all three fjords before melt onset was 1 075 m and the corresponding modal snow thickness was 0 225 m bin width 0 05 m long term kongsfjorden ice thickness data since 1997 show that the maximum ice thickness varies significantly interannually as observed at other arctic sites the average maximum ice thickness for kongsfjorden was 0 71 m years 1997 98 2000 and 2002 05 and the respective average maximum snow thickness was 0 22 m in kongsfjorden 2004 was the year with highest maximum total thickness and snow thickness relative to the other years

global response of the plasmasphere to a geomagnetic disturbance 1 global images of the plasmasphere obtained by the extreme ultraviolet euv imager on the image satellite are used to study the evolving structure of the plasmasphere during two geomagnetic disturbances by tracking the location of the plasmapause as a function of l shell and magnetic local time quantitative measurements of radial and azimuthal motions of the boundary are made for intervals 7 hours in duration with a time resolution of 10 min the two cases presented are 26 27 june 2001 a relatively weak but isolated geomagnetic disturbance and 9 10 june 2001 a moderate event with a multistaged onset and recurring substorm activity after the main disturbance in both cases the onset of the disturbance correlated with a southward turning of the imf is characterized by inward motion or erosion of the plasmapause and a smoothing of any existing azimuthal variations across the nightside over a period of many hours a plasmaspheric plume forms in the afternoon sector as a result of sunward flows from dusk and corotational flows across the dayside azimuthal variations in the plasmapause radius tend to form in the local time sector from dawn to the western edge of the plume including mesoscale 0 5 in l and 2 hours in local time crenulations and larger scale shoulder features while the nightside boundary remains featureless in the 26 27 june 2001 case the magnetosphere entered a period of deep quiet after the main disturbance and the plasmaspheric plume began to corotate with the main plasmasphere from the afternoon sector across the nightside in contrast the plume in the 9 10 june 2001 event became wrapped around the main plasmasphere and a second plume formed in the afternoon sector perhaps due to continued substorm activity in situ density data for these events show highly irregular density structure within the plumes as measured at geosynchronous orbit whereas a measurement by image rpi suggests that there may be less structure near the base of the plume closer to the main plasmasphere

idealized study of a 2 d coupled sea ice atmosphere model during warm air advection we present a two dimensional coupled mesoscale atmosphere sea ice model and apply it to simulate the air ice interaction during warm air advection the model was run into a steady state under various conditions with respect to the season cloud cover and wind speed the spatial and temporal evolution of the thermodynamics of the ice show and the atmospheric boundary layer abl were investigated the development of the stably stratified abl downwind of the ice edge depended above all on the wind speed and cloud cover if the turbulent heat flux from air to show was large enough to compensate the radiative cooling of the surface a downward conductive heat flux was generated in the upper ice and snow layers the stronger was the surface heating strong wind overcast skies and the shorter its duration on a scale down to a few hours the wider was the region where this downward flux occurred from the point of view of abl modelling the interactive coupling between air and ice was most important when the wind was strong while from the point of view of ice thermodynamic modelling the coupling was most important when the wind was weak

on the modelling of ice thickness redistribution an ice thickness distribution model based on physical ice classes is formulated pack ice is subdivided into open water two different types of undeformed ice and rafted rubble and ridged ice evolution equations for each ice class are formulated and a redistribution between the ice classes is calculated according to a functional form depending on the ice compactness thickness and velocity divergence the ice thickness distribution model has been included in a coupled ice ocean model and numerical experiments have been carried out for a simulation of the baltic sea ice season the extended ice classification allows separation of thermally and mechanically produced ice inherent thermodynamic growth melting rates of the ice classes can be introduced into the model giving a more detailed seasonal evolution of the pack ice in addition the model provides more information about the surface properties of pack ice numerical experiments for the baltic sea show that both the sub basin and inter basin ice characteristics were realistically simulated by the model deformed ice production was related to storm activity most of the deformation was produced in the coastal zone which is also an important region for thermodynamically produced ice because of the ice growth in leads the modelled mechanical growth rates of ice were 0 5 3 cm d on a basin scale close to the thermodynamic ice production rates the deformed ice fraction was 0 2 in mid winter and increased to 0 5 1 0 during spring

spatial variation of biogeochemical properties of landfast sea ice in the gulf of bothnia baltic sea horizontal variation of landfast sea ice properties was studied in the gulf of bothnia baltic sea during march 2004 in order to estimate their variability among and within different spatial levels 72 ice cores were sampled on five spatial scales with spacings of 10 cm 2 5 m 25 m 250 m and 2 5 km using a hierarchical sampling design entire cores were melted and bulk ice salinity concentrations of chlorophyll a chl a phaeophytin phaeo dissolved nitrate plus nitrite din as well as dissolved organic carbon doc and nitrogen don were determined all sampling sites were covered by a 5 5 23 cm thick layer of snow ice thicknesses of cores varied from 26 to 58 cm with bulk ice salinities ranging between 0 2 and 0 7 as is typical for baltic sea ice observed values for chl a range 0 8 6 0 mg chl a l 1 median 2 9 mg chl a l 1 and doc range 37 397 mm median 95 mm were comparable to values reported by previous sea ice studies from the baltic sea analysis of variance among different spatial levels revealed significant differences on the 2 5 km scale for ice thickness doc and phaeo with the latter two being positively correlated with ice thickness for salinity and chl a the 250 m scale was found to be the largest scale where significant differences could be detected while snow depth only varied significantly on the 25 m scale variability on the 2 5 m scale contributed significantly to the total variation for ice thickness salinity chl a and din in the case of don none of the investigated levels exhibited variation that was significantly different from the considerable amount of variation found between replicate cores results from a principal component analysis suggest that ice thickness is one of the main elements structuring the investigated ice habitat on a large scale while snow depth nutrients and salinity seem to be of secondary importance

analyzing electric field morphology through data model comparisons of the geospace environment modeling inner magnetosphere storm assessment challenge events 1 the storm time inner magnetospheric electric field morphology and dynamics are assessed by comparing numerical modeling results of the plasmasphere and ring current with many in situ and remote sensing data sets two magnetic storms are analyzed 22 april 2001 and 21 23 october 2001 which are the events selected for the geospace environment modeling gem inner magnetosphere storms im s assessment challenge imsac the imsac seeks to quantify the accuracy of inner magnetospheric models as well as synthesize our understanding of this region for each storm the ring current atmosphere interaction model ram and the dynamic global core plasma model dgcpm were run together with various settings for the large scale convection electric field and the nightside ionospheric conductance while keeping all other simulation settings the same dgcpm plasmaspheric parameters were compared with image euv plasmapause extractions and lanl mpa plume locations and velocities ram parameters were compared with dst lanl mpa fluxes and moments image mena images and image hena images both qualitative and quantitative comparisons were made to determine the electric field morphology that allows the model results to best fit the plasma data at various times during these events the simulations with self consistent electric fields were in general better than those with prescribed field choices this indicates that the time dependent modulation of the inner magnetospheric electric fields by the nightside ionosphere is quite significant for accurate determination of these fields and their effects it was determined that a shielded volland stern field description driven by the 3 hour kp index yields accurate results much of the time but can be quite inconsistent the modified mcilwain field description clearly lagged in overall accuracy compared to the other fields but matched some data sets like dst quite well the rankings between the simulations varied depending on the storm and the individual data sets indicating that each field description did well for some place time and energy range during the events as well as doing less well in other places times and energies several unresolved issues regarding the storm time inner magnetospheric electric field are discussed

surface albedo measurements over sea ice in the baltic sea during the spring snowmelt period the snow ice albedo was studied during a 4 week field experiment over first year sea ice in the gulf of bothnia baltic sea in spring 2004 observations were made on radiative fluxes cloud cover wind air temperature and humidity as well as snow ice temperature thickness density and grain size the albedo variation during the observation period was large the daily mean albedo ranged from 0 79 over a new snow cover to 0 30 over bare melting ice the evolution of the albedo was related to the surface properties but existing parameterizations based on arctic data did not explain the observations well the snow thickness was found to be the most critical factor affecting the albedo a new parameterization was derived for the albedo dependence on snow thickness to be applied over the baltic sea in spring when periods of melting and freezing alternate but the ice is still relatively thick about 0 6 m the diurnal cycle of solar radiation was large and the snow ice metamorphism due to the melting during daylight and refreezing during the night caused a diurnal albedo cycle with a maximum in the early morning and a minimum in the afternoon with an albedo difference up to 0 14 between the two

high turnover rates indicated by changes in the fixed n forms and their stable isotopes in antarctic landfast sea ice we report concentration and nitrogen and oxygen isotopic measurements of nitrate total dissolved nitrogen and particulate nitrogen from antarctic landfast sea ice covering almost the complete seasonal cycle of sea ice growth and decay from april to november when sea ice forms in autumn ice algae growth depletes nitrate and accumulates organic n within the ice subsequent low biological activity in winter imposes minor variations in the partitioning of fixed n in early spring the coupling between nitrate assimilation and brine convection at the sea ice bottom traps a large amount of fixed n within sea ice up to 20 times higher than in the underlying seawater at this time remineralization and nitrification also accelerate yielding nitrate concentrations up to 5 times higher than in seawater nitrate 15n and 18o are both elevated indicating a near balance between nitrification and nitrate assimilation these findings require high microbially mediated turnover rates for the large fixed n pools including nitrate when sea ice warms in the spring ice algae grow through the full thickness of the ice the warming stratifies the brine network which limits the exchange with seawater causing the once elevated nitrate pool to be nearly completely depleted the nitrate isotope data point to light limitation at the base of landfast ice as a central characteristic of the environment affecting its n cycling e g allowing for nitrification and impacting algal physiology e g as reflected in the n and o isotope effects of nitrate assimilation

development structure and composition of land fast sea ice in the northern baltic sea the structural and stable oxygen isotopic properties of sea ice samples collected on land fast sea ice in the northern baltic sea at 60 2 65 7 n 21 3 26 9 e were used to estimate the contribution of snow ice in the total sea ice thickness and the fraction of snow in the snow ice layers and in the total sea ice thickness the textural analysis of the sea ice cores revealed a general structure of granular surface layer and a columnar basal layer using different isotopic criteria to distinguish snow ice layers we estimate that snow ice layers contributed on average 24 32 of the total ice thickness in the study region transition ice intermediate granular columnar ice also contributed significantly to the total ice thickness the snow in the snow ice layers contributed on average 18 21 of the total sea ice thickness by mass a significant contribution when compared to other regions with sea ice cover the methods used could be improved to give more accurate estimates especially by improving knowledge of the temporal variability of the isotropic properties of the snow incorporated into the sea ice cover however our results can be regarded is plausible estimates for the contribution of snow ice and snow to sea ice growth in the study area

strong hydrographic controls on spatial and seasonal variability of dissolved organic carbon in the chukchi sea abstract a detailed analysis of dissolved organic carbon doc distribution in the western arctic ocean was performed during the spring and summer of 2002 and the summer of 2003 doc concentrations were compared between the three cruises and with previously reported arctic work concentrations of doc were highest in the surface water where they also showed the highest degree of variability spatially seasonally and annually over the canada basin doc concentrations in the main water masses were 1 surface layer 71 4 m ranging from 50 to 90 m 2 bering sea winter water 66 2 m ranging from 58 to 75 m 3 halocline layer 63 3 m ranging from 59 to 68 m 4 atlantic layer 53 2 m ranging from 48 to 57 m and 5 deep arctic layer 47 1 m ranging from 45 to 50 m in the upper 200 m doc concentrations were correlated with salinity with higher doc concentrations present in less saline waters this correlation indicates the strong influence that fluvial input from the mackenzie and yukon rivers had on the doc system in the upper layer of the chukchi sea and bering strait over the deep basin there appeared to be a relationship between doc in the upper 10 m and the degree of sea ice melt water present we found that sea ice melt water dilutes the doc signal in the surface waters which is contrary to studies conducted in the central arctic ocean

superimposed ice formation and surface energy fluxes on sea ice during the spring melt freeze period in the baltic sea the development of land fast sea ice and overlying snow was monitored during a 4 week period until the snow cover had completely disappeared at a site in the gulf of bothnia baltic sea 63 57 n 19 85 e the meteorological and radiative boundary conditions were continuously recorded during the observation period a 15 cm thick snow layer on the ice was transformed into a 7 cm thick granular ice layer superimposed ice on the ice surface contributing significantly about 11 to the total ice thickness approximately 1 cm w e of the snow was sublimated neither snow ice formation nor basal ice growth was significant during the same period the salinity and isotopic 18 o composition of the ice indicated that prior to the experiment a 7 cm layer of superimposed ice had already formed hence superimposed ice layers contributed 22 of the total ice thickness by the time all snow had disappeared the advancing spring decrease in surface albedo diurnal cycle in the incoming solar radiation and synoptic scale changes in the cloud cover and the air ice turbulent heat fluxes caused variations in the heat budget of the snowpack superimposed ice formation due to refreezing of meltwater occurred during most nights of the study period and the most important refreezing periods were under such synoptic conditions that the air and snow surface temperatures also remained below zero during daytime in contrast to typical summer conditions in polar oceans low snow surface temperatures acted as the primary heat sink for the refreezing of meltwater