a microwave technique for mapping thin sea ice a technique is presented for mapping the distribution of new young and first year sea ice in seasonal sea ice zones that utilizes microwave spectral and polarization information from the defense meteorological satellite program special sensor microwave imager the motivation for this work stems from the need for accurate estimates of open water and thin ice within the arctic ice pack the technique utilizes the microwave polarization and spectral characteristics of these three ice types through two microwave radiance ratios the 19 4 ghz polarization and the spectral gradient ratio which is a measure of the spectral difference between the 19 4 ghz and the 37 0 ghz vertically polarized radiance components the combined use of the spectral gradient ratio and polarization reduces the low ice concentration bias generally associated with the presence of thin ice types the microwave polarization which is sensitive to changes in ice thickness and ice surface characteristics is used to classify new young and first year ice types the polarization varies from about 0 3 for calm ice free water to about 0 15 for new ice and to 0 03 for thick first year ice on the basis of this parameterization improved sea ice concentration maps and maps of new young and first year ice type distributions are derived examples from the bering sea are presented and comparisons are made with analyzed noaa avhrr imagery

effects of regional fast ice and iceberg distributions on the behaviour of the mertz glacier polynya east antarctica an observational account of research carried out in july august 1999 shows that grounded iceberg and related fast ice distributions and periodic break outs of fast ice in winter as well as at other times have an important impact on the size and behaviour of the mertz glacier polynya east antarctica and a smaller polynya to the east analysis of satellite and in situ data shows that a semi constant stream of thick broken out fast ice and other large floes from the east extends westwards from north of the glacier terminus to form a compact barrier to the net west northwesterly export of ice formed in the polynya an annual fast ice promontory to the west further narrows the outlet path as a result of this and high ice production rates the polynya periodically back fills significantly reducing the open water area present intervening flush outs by synoptic storm events clear the polynya region to some extent before it back fills again this cycle continued from mid march until early october in 1999 when a significant change in the regional ice drift occurred a preliminary comparison with data from 1998 indicates that the timing and magnitude of the processes may vary interannually similar morphological features were also observed in 1963 on a declassified photoreconnaissance satellite image

mapping of sea ice production in the arctic coastal polynyas 1 high ice production in coastal polynyas over the continental shelves in the arctic ocean is responsible for the formation of cold saline water which contributes to the maintenance of the arctic ocean halocline the accurate detection of coastal polynyas including an estimate of thin ice thickness is essential for the estimation of sea ice production this paper presents an algorithm that estimates thin ice thickness using special sensor microwave imager ssm i data in the arctic ocean detection and estimation of sea ice thicknesses of 0 15 m are based on the ssm i 85 and 37 ghz polarization ratios pr85 and pr37 through a comparison with sea ice thicknesses estimated from the advanced very high resolution radiometer avhrr data in the three different arctic coastal polynyas thus for the entire arctic ocean the algorithm can be used for the detection of coastal polynyas and for the estimation of sea ice production through combination with heat flux calculation this study provides the first circumpolar mapping of sea ice production in coastal polynyas over the entire arctic ocean high ice production is confined to the major arctic coastal polynyas with the highest ice production rate being in the north water polynya this study also presents the interannual variability of sea ice production in the 10 major coastal polynyas from 1992 to 2007 in general interannual variability in sea ice production has good correlation with polynya extent rather than surface air temperature the mapping also provides surface heat and salt flux conditions in the ice covered region which have not been well understood to date

helicopter borne observations with portable microwave radiometer in the southern ocean and the sea of okhotsk accurately measuring and monitoring the thickness distribution of thin ice is crucial for accurate estimation of ocean atmosphere heat fluxes and rates of ice production and salt flux in ice affected oceans here we present results from helicopter borne brightness temperature tb measurements in the southern ocean in october 2012 and in the sea of okhotsk in february 2009 carried out with a portable passive microwave pmw radiometer operating at a frequency of 36 ghz the goal of these measurements is to aid evaluation of a satellite thin ice thickness algorithm which uses data from the spaceborne advanced microwave scanning radiometer earth observing system amsr e or the advanced microwave scanning radiometer ii amsr ii amsr e and amsr ii tb agree with the spatially collocated mean tb from the helicopter borne measurements within the radiometers precision in the sea of okhotsk in february 2009 the amsr e 36ghz tb values are closer to the mean than the modal tb values measured by the helicopter borne radiometer in an antarctic coastal polynya in october 2012 the polarization ratio of 36ghz vertical and horizontal tb is estimated to be 0 137 on average our measurements of the tb at 36ghz over an iceberg tongue suggest a way to discriminate it from sea ice by its unique pmw signature

polynya dynamics a review of observations and modeling 1 polynyas are nonlinear shaped openings within the ice cover ranging in size from 10 to 105 km2 polynyas play an important climatic role first winter polynyas tend to warm the atmosphere thus affecting atmospheric mesoscale motions second ocean surface cooling and brine rejection during sea ice growth in polynyas lead to vertical mixing and convection contributing to the transformation of intermediate and deep waters in the global ocean and the maintenance of the oceanic overturning circulation since 1990 there has been an upsurge in polynya observations and theoretical models for polynya formation and their impact on the biogeochemistry of the polar seas this article reviews polynya research carried out in the last 2 decades focusing on presenting a state of the art picture of the physical interactions between polynyas and the atmosphere sea ice ocean system observational and modeling studies the surface heat budget and water mass transformation within these features are addressed

thickness distribution texture and stratigraphy and a simple probabilistic model for dynamical thickening of sea ice in the southern sea of okhotsk 1 sea ice thickness data and sea ice samples were analyzed to examine the characteristics of the ice thickness distribution and ice texture and to understand ice growth processes in the southern sea of okhotsk ice thickness data and samples were obtained aboard the icebreaker soya in early february the ice growth season ice thickness data which were obtained with a video monitoring system installed on the side deck of the ship each winter from 1991 to 2000 except 1995 show that the average thickness ranges from 19 7 to 55 23 cm and that it matches the characteristics of a poisson distribution ice structure analysis reveals that granular texture occupies about three quarters of the total ice thickness and that the ice exhibits a layered structure with unit thickness averaging 5 to 10 cm stratigraphy and stable isotopic composition of the ice indicate that snow ice accounts for 10 and frazil ice accounts for 64 of the total ice thickness this suggests that dynamic ice thickening processes such as frazil ice growth and piling up are more significant than congelation growth on the basis of these characteristics which resemble more those of antarctic than arctic sea ice we propose a conceptual model for the ice thickening process in this region it is shown that this model can explain the shape of the ice thickness distribution well and is analogous with the concept of the pancake cycle and multiple rafting of antarctic sea ice growth and thickening

multisensor data and thermodynamic sea ice model based sea ice thickness chart with application to the kara sea arctic russia we introduce a method to construct an ice thickness chart using two satellite datasets and a one dimensional high resolution thermodynamic snow and sea ice model hightsi thin ice thickness up to 40 cm is retrieved using modis ice surface temperature data for thicker ice thickness is retrieved from a combination of sar image and background level ice thickness chart h i provided by hightsi because h i is inherently static we utilize passive microwave data based sea ice concentration charts to introduce mesoscale ice dynamics into h i in order to create the thickness chart the value of modified h i is scaled by a factor which depends on the magnitude of backscattering coefficient 0 the proposed method is effective in cold winter conditions we calculated a series of ice thickness charts covering the kara sea arctic russia during winter 2008 09 the ice thickness charts were validated against russian ice charts our method gave realistic results in the thickness range 30 120 cm and was uncertain for the detection of thinner ice areas due to the limitations in our reference dataset more validation work is needed to establish the accuracy in more detail our thickness charts can be used for operational purposes and in climate studies

putting transport into water rock interaction models new quantitative models for water rock interaction are needed that explicitly couple fluid flow and chemical reactions one such model is based on the finite difference method and is applicable to both one and two dimensional reactive flow in applying the model we find that ignoring the coupling between hydrodynamic dispersion and chemical reactions leads to incorrect predictions of the rates of reactions along fluid flow paths and in cases of which reactions will occur

circumpolar mapping of antarctic coastal polynyas and landfast sea ice relationship and variability abstractsinking of dense water from antarctic coastal polynyas produces antarctic bottom water aabw which is the densest water in the global overturning circulation and is a key player in climate change as a significant sink for heat and carbon dioxide very recent studies have suggested that landfast sea ice fast ice plays an important role in the formation and variability of the polynyas and possibly aabw however they have been limited to regional and case investigations only this study provides the first coincident circumpolar mapping of antarctic coastal polynyas and fast ice the map reveals that most of the polynyas are formed on the western side of fast ice indicating an important role of fast ice in the polynya formation winds diverging from a boundary comprising both coastline and fast ice are the primary determinant of polynya formation the blocking effect of fast ice on westward sea ice advection by the coastal current would be another key factor these effects on the variability in

numerical study of winter water formation in the chukchi sea roles and impacts of coastal polynyas winter water formation is examined in the chukchi sea for the winters of 1992 2006 using a primitive equation ocean model forced by ncep wind and surface salinity flux derived from ssm i thin ice thickness estimates the model is also forced by an external inflow of 0 8 sv through the bering strait the model successfully reproduces the oceanic circulation on the chukchi shelf thus providing numerous insights into behaviors of salt enriched water produced on the shelf the experiments show that under northeasterly winds northward throughflow across barrow canyon is reduced this results in salinity buildup under freezing conditions and ultimately in greater enhancement of salinity of the waters carried into the arctic basin the flow and salinity enhancement of the flow through herald canyon is less extreme but more steady than through barrow canyon together with moored salinity in the bering strait the model results estimate the actual salinity to be 32 9 0 8 psu and 32 7 0 3 psu respectively for waters moving through the barrow and herald canyons both estimates are less than 33 1 psu that is typically observed for the cold halostad layer in the canada basin suggesting the importance of diapycnal mixing with saltier atlantic origin water

modelling weathering processes at the catchment scale the witch numerical model a numerical model of chemical weathering in soil horizons and underlying bedrock witch has been coupled to a numerical model of water and carbon cycles in forest ecosystems aspects to simulate the concentration of major species within the soil horizons and the stream of the strengbach granitic watershed located in the vosges mountains france for the first time simulations of solute concentrations in soil layers and in the catchment river have been performed on a seasonal basis the model is able to reproduce the concentrations of most major species within the soil horizons as well as catching the first order seasonal fluctuations of aqueous calcium magnesium and silica concentrations however the witch model underestimates concentrations of mg2 and silica at the spring of the catchment stream and significantly underestimates ca2 concentration the deficit in calculated calcium can be compensated for by dissolution of trace apatite disseminated in the bedrock however the resulting increased ca2 release yields important smectite precipitation in the deepest model layer in contact with the bedrock and subsequent removal of large amount of silica and magnesium from solution in contrast the model accurately accounts for the concentrations of major species ca mg and silica measured in the catchment stream when precipitation of clay minerals is not allowed the model underestimation of mg2 and h4sio4 concentrations when precipitation of well crystallized smectites is allowed strongly suggests that precipitation of well crystallized clay minerals is overestimated and that more soluble poorly crystallized and amorphous materials may be forming in agreement with observations on other watersheds draining granitic rocks this study indicates that highly soluble trace calcic phases control the aqueous calcium budget in the strengbach watershed

on the description of the basin effective drainage structure abstract the relationships between the local properties of the morphological elements of a drainage basin and its drainage structure are analysed two theoretical approaches are used for which hydro dynamics and basin morphology are respectively assumed to represent the lowest and the highest starting scale level the results show a convergence toward the idea of slope scaling with contributing area in river networks this concept is then used as an indicator of channel initiation and maintenance for the identification of the effective drainage structure of the basin on the basis of existing digital elevation models dems integral properties of the single dem pixel are finally introduced to reduce the noise owing to a possible dem low accuracy e g in the estimation of the local slope value from the elevation data set the resulting network is characterized by a non uniform drainage density as expected for natural river networks

estimation of thin ice thickness and discrimination of ice type from amsr e passive microwave data detection of thin ice thickness with microwave radiometers such as the advanced microwave scanning radiometer earth observing system amsr e is very effective for the estimation of sea ice production which causes dense water driving ocean thermohaline circulation in previous thin ice thickness algorithms ice thickness is estimated by utilizing a negative correlation between ice thickness and polarization ratio pr of amsr e however in these thin ice algorithms the relationship has large dispersion we consider that the problem is caused by not taking account of ice type we classified thin ice regions around antarctica into two ice types 1 active frazil comprising frazil and open water and 2 thin solid ice areas of the relatively uniform thin ice using moderate resolution imaging spectroradiometer and advanced synthetic aperture radar data for each ice type we examined the relationship between the amsr e pr of 36 ghz and ice thickness showing that the active frazil type has a much smaller thickness than the thin solid ice type for the same pr the two ice types can be discriminated by a simple linear discriminant method in the plane of the pr and gradient ratio of amsr e with the misclassification of 3 from these results we propose a new thin ice algorithm the two ice types are classified by the linear discriminant method and then empirical equations are used to obtain the ice thickness for each ice type this algorithm significantly improves the accuracy of the thin ice thickness

estimation of thin sea ice thickness from noaa avhrr data in a polynya off the wilkes land coast east antarctica antarctic coastal polynyas are major areas of intense ocean atmosphere heat and moisture flux and associated high sea ice production and dense water formation their accurate detection including an estimate of thin ice thickness is therefore very important in this paper we apply a technique originally developed in the arctic to an estimation of sea ice thickness using us national oceanic and atmospheric administration noaa advanced very high resolution radiometer avhrr data and meteorological data in the vincennes bay polynya off wilkes land east antarctica the method is based upon the heat flux calculation using sea ice surface temperature estimates from the satellite thermal infrared data combined with global objective analysis european centre for medium range weather forecasts ecmwf data the validity of this method is assessed by comparing results with independent ice surface temperature and ice thickness data obtained during an australian led research cruise to the region in 2003 in thin ice polynya regions ice thicknesses estimated by the heat flux calculation using avhrr and ecmwf data show reasonable agreement with those estimated by a applying the heat flux calculation to in situ radiation thermometer and meteorological data and b in situ observations the standard deviation of the difference between the avhrr derived and in situ data is 0 02 m comparison of the avhrr ice thickness retrievals with coincident satellite passive microwave polarization ratio data confirms the potential of the latter as a means of deriving maps of thin sea ice thickness on the wider scale uninterrupted by darkness and cloud cover

chemical weathering in granitic environments abstract factors controlling chemical weathering in granitic environments are deduced using an extensive database from the literature based on a transition state theory model we evaluated the effects on chemical weathering of runoff temperature and ph the dependence between temperature and runoff and chemical weathering is complicated by other factors such as the presence depth of soil cover soil cover favors chemical weathering when it is thin and rich in weatherable minerals in contrast it reduces chemical weathering when is thick and poor in primary minerals processes that increase the contact time and the surface of the water rock interactions such as physical denudation increase chemical weathering rates in granitic environments the effect of temperature can be quantified assuming an apparent activation energy value of 48 7 kj mol to describe chemical weathering of silica in granitic crystalline environment under high runoff conditions

estimation of the thin ice thickness and heat flux for the chukchi sea alaskan coast polynya from special sensor microwave imager data 1990 2001 1 one of the largest arctic polynyas occurs along the alaskan coast of the chukchi sea between cape lisburne and point barrow for this polynya a new thin ice thickness algorithm is described that uses the ratio of the vertically and horizontally polarized special sensor microwave imager ssm i 37 ghz channels to retrieve the distribution of thicknesses and heat fluxes at a 25 km resolution comparison with clear sky advanced very high resolution radiometer data shows that the ssm i thicknesses and heat fluxes are valid for ice thicknesses less than 10 20 cm and comparison with several synthetic aperture radar sar images shows that the 10 cm ice ssm i ice thickness contour approximately follows the sar polynya edge for the twelve winters of 1990 2001 the ice thicknesses and heat fluxes within the polynya are estimated from daily ssm i data then compared with field data and with estimates from other investigations the results show the following first our calculated heat losses are consistent with 2 years of over winter salinity and temperature field data second comparison with other numerical and satellite estimates of the ice production shows that although our ice production per unit area is smaller our polynya areas are larger so that our ice production estimates are of the same order because our salinity forcing occurs over a larger area than in the other models the oceanic response associated with our forcing will be modified index terms 4540 oceanography physical ice mechanics and air sea ice exchange processes 3360 meteorology and atmospheric dynamics remote sensing 4504 oceanography physical air sea interactions 0312 4572 oceanography physical upper ocean processes 4207 oceanography general arctic and antarctic oceanography keywords chukchi sea coastal polynya remote sensing

estimation of thin ice thickness from the advanced microwave scanning radiometer eos for coastal polynyas in the chukchi and beaufort seas in this paper a thin ice thickness algorithm for coastal polynyas in the chukchi and beaufort seas has been attempted which uses the advanced microwave scanning radiometer earth observing system amsr e 89 ghz brightness temperature data at a 6 25 km resolution thermal ice thickness estimated from the moderate resolution imaging spectroradiometer modis ice surface temperature data for a set of control points is used in conjunction with the amsr e brightness temperature data to develop a regression relationship between the thermal ice thickness and the passive microwave polarization ratio the modis thermal ice thickness has been determined from the calculation of conductive heat flux through the ice air interface the relationship is then applied across the polynyas to derive thin ice thickness information at different points in the development of the algorithm the modis derived thermal thickness is assumed to be the standard reference validation of the algorithm has been carried out using an independent modis derived thermal ice thickness data set it is observed that the model error is 1 3 cm within the thickness range of 1 10 cm this method is expected to be useful in high latitudes where in situ observations are sparse

the distribution and formative processes of latent heat polynyas in east antarctica a study of polynya characteristics in east antarctica was undertaken using ice concentrations derived from special sensor microwave imager data for the period july 1987 august 1994 the areas of polynyas were defined as having an ice concentration 75 the analysis revealed a total of 28 coastal polynyas within the study region the spatial and temporal variability in areal extent was quantified the timing of mean maximum areal extent varied from june to october the bathymetry and wind regime at each polynya site was examined to gauge the relative importance of these parameters in polynya formation and maintenance in 20 locations shallow banks and shoals form grounding zones for icebergs and anchoring sites for fast ice which form barriers to the predominantly westward drift of the pack ice elsewhere north south coastal protrusions or alignments form similar barriers the subsequent removal of newly formed sea ice from the lee of such barriers by katabatic and synoptic winds maintains areas of reduced ice concentration and open water very few coastal polynyas are attributed solely to katabatic outflow the combined influence of bathymetry topography and winds is responsible for the characteristics of the majority of polynyas many were considered to be marginal characterised by occasional periods when the ice concentration falls below 75 an analysis of annual winter totals of areas with ice concentrations 75 shows no trends in total polynya areal extent over the period 1987 94 known locations of emperor penguin aptenodytes forsteri rookeries were also found to be associated with the locations of coastal polynyas

contributions of water rock interactions to the composition of groundwater in areas with a sizeable anthropogenic input a case study of the waters of the fundao area central portugal we used a combination of a grouping algorithm and a weathering algorithm to assess the contributions made by chemical weathering and anthropogenic inputs to the groundwater composition in a granitoid area the first algorithm is based on the mathematical concept of equivalent relations between objects and is used to find groups of water samples using the grouping algorithm we identified groups with similar chemistries in a set of data relating to the water composition in 160 springs and wells in the fundao area portugal the second algorithm is based on stoichiometries mass and charge balances in weathering reactions and is used to relate the water composition of each identified group to water mineral interactions in the area background information on the petrology and mineralogy of the area allowed us to choose the most realistic water mineral interactions we also had information about the use and composition of fertilizers in this agricultural area in applying the weathering algorithm we considered all dissolved silica and bicarbonate to be produced by chemical weathering and all dissolved chloride sulphate and nitrate to be derived from other sources mainly from fertilizers the anthropogenic contributions to the water chemistries in the area are high despite the high background concentrations derived from pollution we were able to assess the contribution of weathering to the water chemistries we obtained realistic results with the two algorithms supported by the fact that the spatial distribution of the samples belonging to the various groups shows a good correlation with the geology and petrology of the area

thickness and production of sea ice in the okhotsk sea coastal polynyas from amsr e 1 from comparisons with thickness of sea ice from advanced very high resolution radiometer avhrr and ice profiling sonar data we have developed an advanced microwave scanning radiometer eos amsr e thin ice thickness algorithm for the sea of okhotsk this algorithm can estimate ice thickness of 0 2 m without snow using the polarization ratio of amsr e brightness temperature at a 36 5 ghz channel from a linear relationship with avhrr ice thickness when a snow cover exists on the thin ice surface as occurred a few times in each winter it is shown that the algorithm cannot detect the thin ice sea ice and dense shelf water dsw production in coastal polynya are estimated on the basis of heat flux calculation with the daily amsr e ice thickness for three winters december march of 2002 2003 to 2004 2005 the ice production is largest in the northwest shelf nws polynya which accounts for 45 of the sum of ice production in major coastal polynyas the ice production in major coastal polynyas would cover the maximum ice area of the okhotsk sea if the average ice thickness is assumed to be 1 m variability of the ice production is mainly modulated by air temperature in the nws polynya which is the main dsw production area the annual dsw formation rate is estimated to be 0 36 sv

drying front in a sloping aquifer nonlinear effects 1 the profiles for the water table height h x t in a shallow sloping aquifer are reexamined with a solution of the nonlinear boussinesq equation we demonstrate that the previous anomaly first reported by brutsaert 1994 that the point at which the water table h first becomes zero at x l at time t t c remains fixed at this point for all times t t c is actually a result of the linearization of the boussinesq equation and not as previously suggested brutsaert 1994 verhoest and troch 2000 a result of the dupuit assumption rather by examination of the nonlinear boussinesq equation the drying front i e the point x f at which h is zero for times t greater than or equal to t c actually recedes downslope as physically expected this points out that the linear boussinesq equation should be used carefully when a zero depth is obtained as the concept of an average depth loses meaning at that time

integrating topography hydrology and rock structure in weathering rate models of spring watersheds weathering rate models designed for watersheds combine chemical data of discharging waters with morphologic and hydrologic parameters of the catchments at the spring watershed scale evaluation of morphologic parameters is subjective due to difficulties in conceiving the catchment geometry besides when springs emerge from crystalline massifs rock structure must be accounted in formulas describing the area of minerals exposed to the percolating fluids for a realistic evaluation of the rates these particular features are not included in the available approaches and for that reason a new model was developed coined throw model this is a lumped approach that integrates t opography h ydrology ro ck structure and w eathering in a single algorithm the study area comprises several stream watersheds and spring sites of the vouga river basin northern portugal shaped on granites firstly the throw model couples a terrain modeling analysis with hydrologic models based on discharge rates to determine hydraulic conductivities k effective porosities ne and annual recharges vr at the stream watershed scale subsequently these parameters are used in a water balance model to estimate concomitant groundwater travel times t the mean k 4 7 3 2 10 7 m s 1 and ne 2 0 1 3 10 2 values are adopted as proxies for the spring watersheds and a firm regression equation is defined between time and stream watershed area a secondly two more runs of terrain modeling analysis are executed to extrapolate morphologic parameters for the spring watersheds the first run hinges on scaling properties of the drainage networks known as horton laws and is used to scale watershed areas across stream orders i the scaling function is described by another regression equation the second run evaluates the order of a spring watershed defined as equivalent order ieq and equated to the mean order of the surrounding stream watersheds having calculated the ieq spring watershed areas and travel times were downscaled using the regression equations a 10 km2 and t 1 4 2 8 year standing on the physical and hydrologic parameters of the spring watersheds the throw model finally calculates plagioclase weathering rates in the vicinity of the spring sites the sib model pacheco and van der weijden 1996 was used before to estimate the contribution of plagioclase dissolution to the chemical composition of these springs van der weijden and pacheco 2006 the chemical data were now coupled with k ne and t in a rate equation to estimate chemical weathering rates of plagioclase in the basin in the throw model the rate equation describes the exposed surface area as a function of fracture spacings openings and porosities pacheco and alencoao 2006 the calculated rates wpl 2 5 1 2 10 14 mol m 2 s 1 are consistent with previous reports and with results of experimental kinetic models the sib results predict formation of halloysite and gibbsite along the flow path which were indeed close to equilibrium with the dissolved al and si activities o develop a weathering model that incorporates rock structure in the rate equation o conceive a weathering model especially designed for fracture artesian springs o create a model that integrates topography hydrology rock structure and weathering

modelling the chemical weathering fluxes at the watershed scale in the tropics mule hole south india relative contribution of the smectite kaolinite assemblage versus primary minerals we investigate the chemical weathering processes and fluxes in a small experimental watershed sew through a modelling approach the study site is the mule hole sew developed on a gneissic basement located in the climatic gradient of the western ghats south india the model couples a lumped hydrological model simulating the water budget at the watershed scale to the witch model estimating the dissolution precipitation rates of minerals using laboratory kinetic laws forcing functions and parameters of the simulation are defined by the field data the coupled model is calibrated with stream and groundwater compositions through the testing of a large range of smectite solubility and abundance in the soil horizons we found that despite the low abundance of smectite in the dominant soil type of the watershed 4 vol their net dissolution provides 75 of the export of dissolved silica while primary silicate mineral dissolution releases only 15 of this flux overall smectites modelled as montmorillonites are not stable under the present day climatic conditions furthermore the dissolution of trace carbonates in the saprolitic horizon provides 50 of the calcium export at the watershed scale modelling results show the contrasted behavior of the two main soil types of the watershed red soils 88 of the surface are provider of calcium while black soils smectite rich and characterized by a lower drainage consumes calcium through overall carbonate precipitation our model results stress the key role played by minor accessory minerals and by the thermodynamic properties of smectite minerals and by the drainage of the weathering profiles on the weathering budget of a tropical watershed c 2010 elsevier b v all rights reserved

ground surface slope as a basin scale parameter a simple and relatively rapid method of determining the characteristic or typical slope of a basin is proposed the expression for the parameter which is given by savg l hsu hso2 a cos was developed from considerations of basin geometry and basic geomorphologic facts and involves only quantities that can be easily extracted from topographic maps characteristic basin slope values of 19 appalachian plateau watersheds which range in size from 7 4 to 178 2 km2 were determined by the proposed method these values were compared with corresponding values obtained by horton s intersection line method and with those derived from county soil survey reports and maps the comparisons showed very close agreement between the three sets of values indicating the high accuracy of the method developed here similar comparisons involving values determined by previous slope methods indicated that these values are at best poorly related to actual average basin slope and that most of them are incapable of detecting small differences in slope between similar watersheds moreover the proposed method significantly reduces the amount of work required by other slope methods of comparable accuracy

arise antarctic remote ice sensing experiment in the east 2003 validation of satellite derived sea ice data products preliminary results are presented from the first validation of geophysical data products ice concentration snow thickness on sea ice hs and ice temperature ti from the nasa eos aqua amsr e sensor in east antarctica in september october 2003 the challenge of collecting sufficient measurements with which to validate the coarse resolution amsr e data products adequately was addressed by means of a hierarchical approach using detailed in situ measurements digital aerial photography and other satellite data initial results from a circumnavigation of the experimental site indicate that at least under cold conditions with a dry snow cover there is a reasonably close agree ment between satellite and aerial photo derived ice concentrations i e 97 2 3 6 for nt2 and 96 5 2 5 for bba algorithms vs 94 3 for the aerial photos in general the amsr e concentration represents a slight overestimate of the actual concentration with the largest discrepancies occurring in regions containing a relatively high proportion of thin ice the amsr e concentrations from the nt2 and bba algorithms are similar on average although differences of up to 5 occur in places again related to thin ice distribution the amsr e ice temperature ti product agrees with coincident surface measurements to approximately 0 58c in the limited dataset analyzed regarding snow thickness the amsr hs retrieval is a significant underestimate compared to in situ measurements weighted by the percentage of thin ice and open water present for the case study analyzed the underestimate was 46 for the overall average but 23 compared to smooth ice measurements the spatial distribution of the amsr e hs product follows an expected and consistent spatial pattern suggesting that the observed difference may be an offset at least under freezing conditions areas of discrepancy are identified and the need for future work using the more extensive dataset is highlighted

hydrogeochemistry in the vouga river basin central portugal pollution and chemical weathering abstract to quantify and explain the contributions by pollution and chemical weathering to their composition we studied the chemistries of springs and surface waters in the mountainous part of the vouga river basin water samples were collected during a number of consecutive summer campaigns recharge rates were derived from monitored discharge rates within the basin very large contributions by meteoric agricultural and domestic sources to the water chemistries were found identified by the chloride sulfate and nitrate concentrations on average only 1 4 to 1 3 of the solutes could be attributed to chemical weathering two petrologic units characterize the river basin granites and metasediments the waters collected within metasediment units are distinct from those in granite terrain by a higher magnesium concentration on that basis it could be estimated that the rio vouga when leaving the mountainous part of the basin has for some 2 5 a signature determined by chemical weathering in the metasediments the dominant primary minerals subject to chemical weathering are plagioclase pl and biotite in granite or pl and chlorite in metasediment kaolinite gibbsite and vermiculite are the major weathering products where annual precipitation p 1000 mm y 1 and kaolinite vermiculite and smectite where p was lower using an algorithm based on the ratio of dissolved silica to bicarbonate the contributions of chemical weathering of primary minerals could be unraveled the results show that in granite the export rate as mol ha 1 y 1 wt mineral 1 of oligoclase pl with an10 30 was 5 0 2 6 and of biotite 3 2 2 6 while in metasediment these rates for albite pl with an0 10 are 16 5 8 9 and for chlorite are 0 5 0 5 the observed decrease of dissolved silica in surface waters relative to springs was ascribed to summer uptake by aquatic biota

thin ice thickness from satellite thermal imagery sea ice thickness is an important parameter in the surface energy exchange and mass balance of the polar oceans remote sensing offers the opportunity to monitor thin ice routinely we combine measurements of surface temperature from an advanced very high resolution radiometer avhrr with a thermodynamic ice growth model to estimate thin ice and its thickness distribution during the cold season in a beaufort sea area of perennial ice we find that thin ice up to a meter thick had a concentration of 18 in december 1990 and 3 in april 1991 thin ice concentrations near the ice edge in the greenland sea range from 20 to 50 these avhrr derived estimates generally compare well with thickness observations from upward looking sonar given the uncertainties in all the model inputs estimated from avhrr such as radiative and turbulent heat flux components and surface albedo we find that ice thickness is estimated with an uncertainty of roughly 50 the uncertainty in the cumulative thickness distribution is about 3 for ice less than 20 cm thick and about 9 for ice around 1 m thick these magnitudes are significantly smaller than the variations in thin ice observed by satellite in different months and regions we conclude that avhrr is capable of resolving the regional and seasonal variations in thin ice to a level of accuracy useful both for establishing a climatology and for testing ice models

an analytic model for the prediction of wave setup longshore currents and sediment transport on beaches with seawalls an analytic model is developed to predict the time and depth averaged cross shore and longshore hydrodynamics as well as the longshore sediment transport on a planar beach backed by a seawall similar to the classical no seawall derivations of the problem the model assumes shallow water small angle of wave incidence and spilling breakers the reflected wave energy flux is conserved while the increased energy in the surf zone due to the reflected wave is assumed to be dissipated in the incident wave a partial standing wave develops in front of the seawall causing modulations of the radiation stresses the bottom stress and the resulting wave setup longshore current and longshore sediment transport the influence of these modulations increases as the beach slope decreases due to a greater number of standing waves that develop across the wider surf zone the total water depth slope including wave setup is steeper on a beach with a seawall than on a non armored beach both the longshore current and the longshore sediment transport are strongly influenced by the cross shore location of the seawall on steep beaches the total sediment transport is less than that for a natural beach for milder sloped beaches the modulations due to partial standing waves become significant and the transport may be either more or less than that for a beach with no wall depending on the location of the seawall these mixed results help to explain some of the confusion and contradictions found in the available seawall literature and may aid in focusing future research on the seawall problem

decadal variations of sea ice thickness in the amundsen bellingshausen and weddell seas retrieved from icesat and icebridge laser altimetry 2003 2017

mapping of sea ice production for antarctic coastal polynyas 1 active sea ice production in antarctic coastal polynyas causes dense water formation finally leading to antarctic bottom water aabw formation this study gives the first mapping of sea ice production in the antarctic ocean based on heat flux calculation with ice thickness data derived from satellite data the highest ice production occurs in the ross ice shelf polynya region the ice production there decreased by 30 from the 1990s to the 2000s which can be one candidate for causing the recent freshening of aabw the cape darnley polynya in east antarctica is found to be the second highest production area suggesting a possible aabw formation area according to our estimation around 10 of southern ocean sea ice is produced in the major antarctic coastal polynyas the mapping provides surface heat and salt flux conditions in the ice covered region which have not been well understood

improved mapping of sea ice production in the arctic ocean using amsr e thin ice thickness algorithm new and improved estimates of sea ice production in the arctic ocean are derived from amsr e satellite and atmospheric reanalysis data for the period 2002 2011 at a spatial resolution of 6 25 km and using a newly developed fast ice mask high ice production in the major coastal polynyas is well demonstrated the total annual cumulative ice production in the major 10 polynya regions is about 1180 70km 3 the interannual variability of the ice production for each polynya is presented during 2002 2011 no obvious relationship is noted between the ice production and the recent drastic reduction in the preceding summer arctic sea ice extent most polynya regions exhibit maximum ice production in autumn october november before areas offshore have been covered with consolidated pack ice sea ice production from october to november in the marginal ice zone of the pacific ocean sector is negatively correlated with summer ice extent there the ice production from october to november of 2007 a record minimum summer ice extent was about twice as large as that in other years the high ice production area shifted to higher latitudes i e toward the deep canada basin due to the retreat of the summer ice edge we speculate that the resultant increase in brine input could change the oceanic structure in the basin specifically deepening the winter mixed layer 2014 american geophysical union all rights reserved

theoretical approach to evaluating plagioclase dissolution mechanisms abstract the more rapid dissolution of ca rich feldspars relative to na k rich feldspars has been attributed to the preferential leaching of al deep within the feldspar structure evidence from surface microanalysis e g hellmann et al 2003 however shows that preferential dissolution of al is confined to the top layers of the feldspar lattice and that the amorphous surface layer most likely results from precipitation versus dissolution it is thus critical to examine the extent of preferential al removal here we present a theoretical study of plagioclase dissolution behavior using parameterized monte carlo simulations two different dissolution mechanisms a mechanism involving preferential leaching of al and an interfacial dissolution reprecipitation mechanism are tested using compositions representing the entire plagioclase solid solution series our modeling results indicate that under the control of the preferential al leaching mechanism the influence of al si disorder on the dissolution rate is significant at a fixed composition an increase in the degree of al si disorder yields an increased dissolution rate with an 8 fold increase in dissolution rate observed for highly disordered albite an 0 compared to low albite increasing anorthite content tends to decrease the variation in the dissolution rate due to disorder the difference in the dissolution rate of 293 tested oligoclase configurations with a composition of an 20 is 3 fold and the difference is reduced to 2 fold among 107 andesine configurations of an 30 furthermore feldspar configurations with completely disordered al si distributions yield a consistent log linear dependence of dissolution rate on the anorthite content an while other feldspar configurations with modest degrees of al si disorder exhibit rates less than this trend in contrast when al removal is confined to the top surface layers a variety of feldspar configurations with different al si disorder but a single fixed composition have similar dissolution rates and the dissolution rate of ca rich feldspars departs positively from its log linear relationship with anorthite content this departure occurs around an 80 and is in good agreement with previous experimental studies subsequent modeling results of aluminum inhibition g dependence and formation of altered surface layers in the framework of the interfacial dissolution reprecipitation mechanism are all comparable with experimental investigations and these results suggest that an interfacial dissolution reprecipitation mechanism governs the dissolution of plagioclase feldspars

the unit response of groundwater outflow from a hillslope subsurface flow from a hillslope can be described by hydraulic groundwater theory as formulated by the boussinesq equation solution of its linear version brings out some of the essential features of this phenomenon arbitrary inputs can be accommodated by simple convolution of the sudden drawdown problem the relative magnitude of the driving mechanisms namely the streamwise pressure gradient resulting in diffusion and gravity i e slope resulting in advection can be determined by a simple dimensionless parameter

streamflow recession in basins with multiple water storages abstract a streamflow recession formula for natural basins is derived by linear hydrologic routing of the sum of inflows from discrete independent water storages through a channel storage water storages include depression detention snow and ice channel bank aquifer and cavern evapotranspiration is incorporated in the recession formula but seasonal effects and basin wetness and storage conditions before storms are not considered data from seven basins involving 156 precipitation free recessions are used to test the performance of two and three parameter approximations to the theoretical recession formula recessions are defined to last at least 2 weeks and to begin 2 days after the peak of a basin outflow hydrograph or at a point on the falling limb 2 days after any precipitation occurs recessions end when precipitation recommences or when daily flow data stop decreasing an inverse square formula explains most variance in the two parameter case in contrast to the simple exponential formula usually recommended for recession modelling with three parameters equally good performance is shown by formulae involving a constant plus an inverse square or inverse cubic or simple exponential term these theoretically based formulae should be useful at basin scale for interpolating or extrapolating recession data particularly in basins where little is known about water storage behaviour

observations of ice thickness and frazil ice in the st lawrence island polynya from satellite imagery upward looking sonar and salinity temperature moorings 1 for the 1999 winter this paper examines the behavior of the bering sea st lawrence island polynya using a combination of advanced very high resolution radiometer avhrr radarsat synthetic aperture radar sar meteorological data over winter moored upward looking sonars uls and seabird salinity temperature sensors we define a thermal ice thickness from the avhrr retrieval of ice surface temperature combined with meteorological observations and a heat flux model south of the island we compare the uls and thermal thicknesses for congelation and frazil ice when the satellites observe congelation ice over the ulss the uls and thermal ice thicknesses generally agree when sar observes langmuir plumes over the ulss which indicate frazil ice formation the ulss show scatterers at 5 20 m depths in the water column and the seawater temperatures are either within 0 01 c of freezing or are slightly supercooled this suggests that during frazil events crystals either nucleate at depth or are transported to depth by the langmuir circulation the combination of the sar imagery and uls observations also allow measurement of the pack ice advection velocity the polynya width and the downwind frazil accumulation thickness giving widths of 10 to 30 km and thicknesses of 0 1 0 2 m substitution of these observed values with the heat flux into the pease polynya model yields polynya widths that approximately agree with the observed