extensive liquid meltwater storage in firn within the greenland ice sheet surface melt water from the greenland ice sheet can become trapped in firn delaying its journey to the sea radar and ice core observations provide direct evidence of a perennial aquifer in the firn layer in southern greenland that represents a potentially significant contribution to the greenland mass budget

computation of wind wave spectra in coastal waters with swan on unstructured grids abstract an unstructured grid procedure for swan is presented it is a vertex based fully implicit finite difference method which can accommodate unstructured meshes with a high variability in geographic resolution suitable for representing complicated bottom topography in shallow areas and irregular shoreline the numerical solution is found by means of a point to point multi directional gauss seidel iteration method requiring a number of sweeps through the grid the approach is stable for any time step while permitting local mesh refinements in areas of interest a number of applications are shown to verify the correctness and numerical accuracy of the unstructured version of swan

numerical modeling of the morphodynamic response of a low lying barrier island beach and foredune system inundated during hurricane ike using xbeach and cshore abstract follet s island fi is a sediment starved barrier island located on the upper texas coast a stretch of coastline along the gulf of mexico that experiences on average four hurricanes and four tropical storms per decade during hurricane ike water levels and wave heights at fi exceeded the 100 year and 40 year return values respectively leading to significant overtopping and morphology changes of this low lying barrier island the physical processes governing the real time morphodynamic response of the beach and dune system during 96 h of hurricane impact were modeled using xbeach 2d and cshore 1d hydrodynamic boundary conditions were obtained from adcirc swan model runs validated with measured buoy and wave gauge data while lidar surveys provided pre and post storm measured topography xbeach displayed a decent model skill of 0 34 and provided numerical outputs of the entire 2d domain such as topography suspended sediment load and bed load which was very useful in visualizing erosion and deposition patterns cshore also displayed a decent model skill of 0 33 and was able to accurately predict the post storm beach slope and shoreline but was less effective at simulating the foredune morphology modeling results show that the complete morphodynamic response of fi to hurricane ike was governed by a sequence of impact regimes including swash collision overwash inundation and storm surge ebb

a high resolution coupled riverine flow tide wind wind wave and storm surge model for southern louisiana and mississippi part ii synoptic description and analysis of hurricanes katrina and rita abstract hurricanes katrina and rita were powerful storms that impacted southern louisiana and mississippi during the 2005 hurricane season in part i the authors describe and validate a high resolution coupled riverine flow tide wind wave and storm surge model for this region herein the model is used to examine the evolution of these hurricanes in more detail synoptic histories show how storm tracks winds and waves interacted with the topography the protruding mississippi river delta east west shorelines manmade structures and low lying marshes to develop and propagate storm surge perturbations of the model in which the waves are not included show the proportional importance of the wave radiation stress gradient induced setup

characterization and formation of melt layers in polar snow observations and experiments from west antarctica author posting international glaciological society 2005 this article is posted here by permission of international glaciological society for personal use not for redistribution the definitive version was published in journal of glaciology 51 2005 307 312 doi 10 3189 172756505781829395

differentiating bubble free layers from melt layers in ice cores using noble gases melt layers are clear indicators of extreme summer warmth on polar ice caps the visual identification of refrozen meltwater as clear bubble free layers cannot be used to study some past warm periods because in deeper ice bubbles are lost to clathrate formation we present here a reliable method to detect melt events based on the analysis of kr ar and xe ar ratios in ice cores and apply it to the detection of melt in clathrate ice from the eemian at neem greenland additionally melt layers in ice cores can compromise the integrity of the gas record by dissolving soluble gases or by altering gas transport in the firn which affects the gas chronology we find that the easily visible 1 mm thick bubble free layers in the wais divide ice core do not contain sufficient melt to alter the gas composition in the core and do not cause artifacts or discontinuities in the gas chronology the presence of these layers during winter and the absence of anomalies in soluble gases suggests that these layers can be formed by processes other than refreezing of meltwater consequently the absence of bubbles in thin crusts is not in itself proof of a melt event

wetting front advance and freezing of meltwater within a snow cover 1 observations in the canadian arctic in a naturally stratified snow cover the movement of meltwater into dry snow is complicated by the interaction of the wetting front with stratigraphic horizons field observations showed that when the wetting front reached premelt stratigraphic horizons water ponded at the interface and then flow fingers developed and penetrated the lower stratum the flux in these fingers which was increased to about twice that of the surface flux was used to feed water to the impeding horizons where it froze to form ice layers these ice layers were the major source of latent heat released within the snow cover and they were responsible for the warming of the snow and the underlying soil these continuous ice layers grew only at stratigraphic boundaries because of this ice layer growth the wetting front advance was retarded and the arrival of meltwater at the snow cover base was significantly delayed owing to a cold substrate the strong heat flux from the snow into the soil delays the warming of the snow cover and limits runoff after the snow is isothermal at 0 c by the refreezing of soil infiltration and the development of a basal ice layer

early formation of preferential flow in a homogeneous snowpack observed by micro ct we performed x ray microtomographic observations of wet snow metamorphism during controlled continuous melting and melt freeze events in the laboratory three blocks of snow were sieved into boxes and subjected to cyclic superficial heating or heating cooling to reproduce vertical water infiltration patterns in snow similarly to natural conditions periodically samples were taken at different heights and scanned results suggest that wet snow metamorphism dynamics are highly heterogeneous even in an initially homogeneous snowpack consistent with previous work we observed an increase with time in the thickness of the ice structure which is a measure of grain size however this was coupled with large temporal scatter between consecutive measurements of the specific surface area and of the statistical moments of grain thickness distributions because of marked differences in the right tail grain thickness distributions did not show shape invariance with time contrary to previous analyses in our experiments wet snow metamorphism showed two strikingly different patterns homogeneous coarsening superimposed by faster heterogeneous coarsening in areas that were affected by preferential percolation of water liquid water movement in snow and fast structural evolution may be thus intrinsically coupled by early formation of preferential flow at local scale these observations suggest that further experiments are highly needed to fully understand wet snow metamorphism and infiltration patterns in a natural snowpack

a basin to channel scale unstructured grid hurricane storm surge model applied to southern louisiana abstract southern louisiana is characterized by low lying topography and an extensive network of sounds bays marshes lakes rivers and inlets that permit widespread inundation during hurricanes a basin to channel scale implementation of the advanced circulation adcirc unstructured grid hydrodynamic model has been developed that accurately simulates hurricane storm surge tides and river flow in this complex region this is accomplished by defining a domain and computational resolution appropriate for the relevant processes specifying realistic boundary conditions and implementing accurate robust and highly parallel unstructured grid numerical algorithms the model domain incorporates the western north atlantic the gulf of mexico and the caribbean sea so that interactions between basins and the shelf are explicitly modeled and the boundary condition specification of tidal and hurricane processes can be readily defined at the deep water open boundary the unstructured grid enables highly refi

diagnosis of frontal instabilities over the southern ocean the development of three fronts over the southern ocean is described using seawinds on quikscat scatterometer surface winds and an attribution technique to partition the wind field in three components nondivergent and irrotational components at the scale of the front and the remaining harmonic component or environmental flow induced by the synoptic scale flow the front and the environment in which the front is embedded are analyzed separately a frontal wave is shown to develop out of the first front when the large scale alongfront stretching decreases the environmental flow becomes frontolytic and a connection with the upper levels is established in the second case the stretching remains relatively strong and no frontal wave develops the third front exhibits a developing wave but is not in a favorable configuration with the upper levels the frontal wave does not deepen significantly

storm surge from hurricane irma along the florida peninsula abstract hurricane irma impacted the entire florida peninsula in september 2017 the combination of irma s strength size and track provided a unique opportunity to study hurricane effects on storm surge on both sides of a peninsula storm surge characteristics on the west coast of florida were markedly different from those on the east coast on the west coast the maximum storm surge was 1 6 m at naples which was attributed to onshore winds and an atmospheric pressure of 970 hpa a stunning negative surge of 2 7 m appeared at cedar key in the peninsula s northwestern quarter after 10 h of oblique offshore and divergent winds on the east coast the maximum surge was 2 4 m at fernandina beach where wind velocity displayed horizontal convergence a revealing finding of this investigation was that wind divergence is an essential component for predicting storm surge

thermal tracking of meltwater retention in greenland s accumulation area 1 poorly understood processes controlling retention of meltwater in snow and firn have important implications for greenland ice sheet s mass balance and flow dynamics here we present results from a 3 year 2007 2009 field campaign studying firn thermal profiles and density structure along an 85 km transect of the percolation zone of west greenland we installed one or two thermistor strings at 14 study sites each string having 32 sensors spaced between 0 and 10 m depth data from our network of over 500 sensors were collected at 15 60 min intervals for 1 2 years thereby recording the thermal signature of meltwater infiltration and refreezing during annual melt cycles we document three types of heating of firn related to different mechanisms of meltwater motion and freezing including heterogeneous breakthrough events wetting front advance and year round heating from freezing of residual deep pore water vertically infiltrating meltwater commonly penetrates through cold firn accumulated over decades even where ice layers are present at the previous summer surface and where ice layer thickness exceeds several decimeters the offset between the mean annual air temperature and the 10 m firn temperature reveals the elevation dependency of meltwater retention along our transect the firn is 10 c warmer than the mean annual air temperature at the region where meltwater runoff initiates during 2007 2009 runoff was limited to elevations lower than 1500 m with no sharp runoff limit rather the ratio of retention to runoff transitioned from all retention to all runoff across a 20 km wide zone

retention of greenland runoff by refreezing implications for projected future sea level change melting produced at the surface of subfreezing permeable firn does not freely percolate but instead refreezes near its point of origin raising the firn temperature and decreasing the pore space if sufficient meltwater is introduced the firn will warm to 0 c and subsequent water will fill the remaining pore space without freezing only after the residual water content of the firn is exceeded will water flow through the firn and possibly escape as runoff this process prevents summer melt on high arctic glaciers and ice caps from escaping in its entirety and it must be accounted for in modeling glacier runoff on the basis of surface energy balance a model is presented here which describes in a simple way the transient process of infiltration refreezing and runoff in a future warming climate the model is applied to greenland for which predictions of runoff induced sea level rise that do not consider the refreezing process could be as much as 5 0 cm too high over 150 years

the mass balance of mccall glacier brooks range alaska u s a its regional relevance and implications for climate change in the arctic mccall glacier has the only long term mass balance record in arctic alaska average annual balances over the periods 1958 72 and 1972 93 were 15 and 33cm respectively recent annual balances 1993 96 are about 60 cm and the mass balance gradient has increased for an arctic glacier with its low mass exchange rate this marks a significant negative trend recently acquired elevation profiles of mccall glacier and ten other glaciers within a 30 km radius were compared with topographic maps made in 1956 or 1973 most of these glaciers had average annual mass balances between 25 and 33 cm while mccall glacier averaged 28 cm for 1956 93 indicating that it is representative of the region in contrast changes in terminus position for the different glaciers vary markedly thus mass balance trends in this region cannot be estimated from fractional length changes at time scales of a few decades we developed a simple degree day accumulation mass balance model for mccall glacier the model was tested using precipitation and radiosonde temperatures from weather stations at inuvik canada and barrow kaktovik and fairbanks alaska and was calibrated with the measured balances the inuvik data reproduce all measured mass balances of mccall glacier well and also reproduce the long term trend towards more negative balances data from the other stations do not produce satisfactory model results we speculate that the arctic front oriented east west in this region causes the differences in model results

a comparative study of storm surge and wave setup in the east china sea between two severe weather events abstract the coastal regions of the east china sea are frequently threatened by the increased sea level induced by intense tropical cyclones in this study a coupled wave circulation model adcirc swan is used to investigate the spatial and temporal characteristics of storm surges and wave setup heights in the southeastern coastal area of china during two severe weather events with different tracks typhoon saomai which made direct landfall and the bypassing typhoon chan hom by definition the storm surge is attributable to the wind forcing while the wave setup results from the wave radiation stress the simulated sea levels agree well with the observations with improved results when the wave setup was considered the simulation results showed clearly different spatial patterns depending on the track type the maximum storm surge resulted from the cumulative effect of the local onshore wind forcing occurring on the right side of the typhoon saomai track and the left side of the typhoon chan hom track significant surge levels along the coast on the left side of the typhoon track were well observed in both cases resulting from the coastal trapped shelf waves the saomai track type is more likely to cause extremely high storm surges along the coast due to the stronger cumulative effect of the onshore wind forcing the maximum wave setup was governed by the swell and slope of the sea floor the locations of the maximum wave setup and surge level were spatially close during typhoon saomai but they were separated during typhoon chan hom

hurricane gustav 2008 waves and storm surge hindcast synoptic analysis and validation in southern louisiana abstracthurricane gustav 2008 made landfall in southern louisiana on 1 september 2008 with its eye never closer than 75 km to new orleans but its waves and storm surge threatened to flood the city easterly tropical storm strength winds impacted the region east of the mississippi river for 12 15 h allowing for early surge to develop up to 3 5 m there and enter the river and the city s navigation canals during landfall winds shifted from easterly to southerly resulting in late surge development and propagation over more than 70 km of marshes on the river s west bank over more than 40 km of caernarvon marsh on the east bank and into lake pontchartrain to the north wind waves with estimated significant heights of 15 m developed in the deep gulf of mexico but were reduced in size once they reached the continental shelf the barrier islands further dissipated the waves and locally generated seas existed behind these effective breaking zones the hardening and innovative deployment of gauges since hur

implications from the comparisons between two and three dimensional model simulations of the hurricane ike storm surge 1 we apply the finite volume coastal ocean model to simulate the hurricane ike storm surge using two dimensional 2 d and three dimensional 3 d formulations the high resolution unstructured grid extends over the gulf of mexico with open boundaries in the straits of florida and the yucatan channel with the same wind and pressure forcing the bottom drag coefficients for the baseline 2 d and 3 d simulations are determined by spatially varying manning coefficients and constant bottom roughness respectively the baseline 2 d model simulates both the forerunner and the surge whereas the baseline 3 d model simulates the surge but underestimates the forerunner increasing the minimum manning coefficient reduces the 2 d forerunner and the surge manning coefficient and bottom roughness parameterizations produce different bottom drag coefficients using the same bottom drag coefficient the 2 d simulation yields a smaller surge than in three dimensions this is investigated for scenarios of either constant or variable bottom roughness where the bottom roughness is determined through manning coefficient transformation these sensitivity studies indicate that storm surges simulated either in two dimensions or three dimensions depend critically upon the parameterizations and the parameter values used for specifying bottom stress and similar may be said of surface stress given suitable calibration 2 d and 3 d models may adequately simulate storm surge however it is unclear that a calibration for a given storm and location may apply generally hence additional experimental guidance is required on the parameterizations and the parameter values used for both the surface and bottom stresses under severe wind conditions

observations of snowpack ripening in the sierra nevada california u s a the transition from a dry sub freezing snow cover to isothermal snow freely conducting water was observed near timberline in the sierra nevada california u s a although there were few major stratigraphic boundaries in the snowpacks observed minor textural discontinuities were sufficient to both route water laterally downslope and later create ice layers at these strata during the first few days of snowmelt downslope movement of water parallel to the strata allowed water to bypass lower layers of the snow cover on slopes and converge in microtopographic depressions on level terrain creating isolated drains through the snowpack in addition to these drains flow fingers associated with holes in the ice sheets delivered water to the base of the snow several days prior to the thorough wetting of the snowpack formation of a series of ice lenses just below the snow surface every night released much more latent heat than did ice layer development within the hulk of the snowpack or at its base

investigations of meltwater refreezing and density variations in the snowpack and firn within the percolation zone of the greenland ice sheet the mass balance of polythermal ice masses is critically dependent on the proportion of surface generated meltwater that subsequently refreezes in the snowpack and firn in order to quantify this effect and to characterize its spatial variability we measured near surface 26 resulting in a 32 increase in net accumulation this seasonal densification increased at lower elevations rising to 47 10km closer to the ice sheet margin at 1860 m a s l density depth profiles from nine sites within 1 km 2 at similar to 1945ma s l reveal complex stratigraphies that change over short spatial scales and seasonally we conclude that estimates of massbalance change cannot be calculated solely from observed changes in surface elevation but that near surface densification must also be considered however predicting spatial and temporal variations in densification may not be straightforward further the development of complex firn density profiles both masks discernible annual layers in the near surface firn and ice stratigraphy and is likely to introduce error into radar derived estimates of surface elevation

the treatment of meltwater retention in mass balance parameterisations of the greenland ice sheet retention of melt water runoff by percolation and or refreezing in the snowpack cannot be neglected when studying the surface mass balance of the greenlandice sheet in this paper we make a detailed comparison of several treatments proposed in the literature to account for this process in large scale mass balanceparameterizations the melt on the greenland ice sheet is calculated with a revised degree day model using updated datasets of surface elevation and precipitationrate on a 5 km grid crucial model parameters are recalibrated by comparing mass balance characteristics with available observations on a regional basis wediscuss the role of meltwater retention in the light of the overall mass balance of the greenland ice sheet and its sensitivity to climatic change and displaypatterns of effective retention fractions for the various methods as a main conclusion it appears that overall results are quite similar for the various models butthat meltwater retention has a large spatial variation not described by the simple treatments using the most comprehensive retention model the sensitivity of therunoff is found to be 0 35 mm deg c of sea level change per year we also present a new map of the different zones facies that characterize the accumulationarea of the greenland ice sheet that is useful for interpreting field data and calibrating satellite observations

remote forcing contribution to storm induced sea level rise during hurricane dennis 1 numerical model experiments are conducted to address the previously unexplained anomalously high storm surge along the florida coast of apalachee bay during hurricane dennis 2005 the 2 3 m surge observed during this storm cannot be obviously explained by the relatively weak local winds over this bay 275 km east of the storm center realistic and idealized numerical experiments demonstrate that the along shore winds to the east of the storm center built a high sea level anomaly along the coast which traveled northward to apalachee bay as a topographic rossby wave the wave was amplified as the storm moved nearly parallel to the shelf and at comparable speed to the wave phase speed these results suggest that enlarging the domain of the storm surge forecasting models can improve the surge forecast for a storm moving along a similar track and have now been applied to operational use

correlation lengths of meltwater flow through ripe snowpacks colorado front range usa the flowpaths of meltwater through snow is known to be an inhomogeneous process the spatial distribution of meltwater flowing from the bottom of melting snowpacks is the result of horizontal and vertical flow paths within the snowpack the ability to characterize the spatial distribution of these meltwater flowpaths would be useful in developing models of snow melt runoff which could better characterize snow melt hydrographs we analyzed near infrared aerial photos of melting snow using a moving window analysis which can characterize correlation lengths in the reflectance of the snow surface near infrared is sensitive to snow grain size which in turn may indicate higher amounts of meltwater the grains grow faster if the liquid water content is higher correlation lengths were live to seven metres and the probability of finding such correlation lengths increased from 0 22 in may 1997 when the melt had just started to 0 68 by late june when melt was well established liquid water content at the snow surface was sampled with a dielectric sensor at 0 5 m intervals on 100 m 2 and 75 m 2 grids semi variograms showed a sill at five to six metres the liquid water measurements at the snow surface suggest that the correlation lengths derived from the infrared aerial photos represent surface expressions of higher flow density through the melting snowpack a circular array of 16 snow melt lysimeters each with areas of 0 2 m 2 was operated for two years at niwot ridge in the colorado front range variograms indicated that flows were correlated over a distance of five to seven metres these three independent methods all suggest a spatial organization of five to seven metres for flowpaths draining ripe snowpacks in the rocky mountains

determination of timing and location of water movement and ice layer formation by temperature measurements in sub freezing snow measurements of temperature in snow along a vertical profile during the onset of spring melting are used to calculate spatial and temporal temperature gradients and terms of the conduction equation with an internal energy production term are calculated heat transfer information is combined with stratigraphic observations made during melting and allow detailed determination of the timing and location of heterogeneous water movement and of refreezing internal energy production is interpreted as latent heat of refreezing of percolated meltwater times and locations of flow and refreezing of meltwater are calculated and compared to stratigraphic observations of layering and changes in density and liquid water content sequences of melt piping layering and refreezing seen in calculations and in stratigraphy demonstrate retarded flow at fine to coarse transitions flow along such transitions and refreezing at the transitions to form ice layers downslope flow is also observed in the absence of an impermeable horizon to redirect flow from the vertical

kelvin type coastal surges generated by tropical cyclones abstract measurements of sea level along the coat of western australia during the period 1969 to 1982 when 12 southward moving tropical cyclones occurred showed distinct peaks with amplitudes of about 1 to 2 m propagating southwards with speeds ranging between 400 600 km day 1 similar observations of sea level along the east coast of australia during the period 1971 to 1980 of 7 southward moving tropical cyclones showed no such peaks these data suggest that the large peaks occurring on the west coast are a result of a resonance phenomenon when the southward component of the cyclone speed is close to that of southward propagating shallow water kelvin waves 11 is shown that the coastal response to moving atmospheric forcing fields may be described by a kelvin type disturbance which at any instant is confined to a localized coastal region dependent on the kelvin wave speed and the longshore speed of the tropical cyclone this region expands in the longshore direction at a rate equal to the difference

origin of the hurricane ike forerunner surge 1 a large unpredicted water level increase appeared along a substantial section of the western louisiana and northern texas latex coasts 12 24 hrs in advance of the landfall of hurricane ike 2008 with water levels in some areas reaching 3 m above mean sea level during this time the cyclonic wind field was largely shore parallel throughout the region a similar early water level rise was reported for both the 1900 and the 1915 galveston hurricanes the ike forerunner anomaly occurred over a much larger area and prior to the primary coastal surge which was driven by onshore directed winds to the right of the storm track we diagnose the forerunner surge as being generated by ekman setup on the wide and shallow latex shelf the longer forerunner time scale additionally served to increase water levels significantly in narrow entranced coastal bays the forerunner surge generated a freely propagating continental shelf wave with greater than 1 4 m peak elevation that travelled coherently along the coast to southern texas and was 300 km in advance of the storm track at the time of landfall this was at some locations the largest water level increase seen throughout the storm and appears to be the largest freely propagating shelf wave ever reported ekman setup driven forerunners will be most significant on wide shallow shelves subject to large wind fields and need to be considered for planning and forecasting in these cases

modeling wave effects on storm surge and coastal inundation abstract we present a parametric study of surface wave effects on storm surge and coastal inundation hurricane wind forcing terms atmosphere pressure gradient terms and radiation open boundary conditions are implemented into an existing quasi 3d nearshore model nearcom tvd which uses a shock capturing tvd scheme and can better simulate the wetting drying process during inundation than a conventional finite difference model systematic numerical experiments are carried out in an idealized continental shelf beach land system to identify the role of waves in modeling storm surge and inundation under different storm characteristics four storm parameters including storm intensity storm size translation speed and incident angle are investigated modeling results reveal that the presence of waves can increase the maximum storm surge heights significantly through wave setup and the contribution of waves varies considerably depending on the storm characteristics in addition to direct wave forcing the wave enhanced bottom stress in the surfzone also promotes higher wave setup and hence higher surge heights waves also have a major influence on the maximum inland inundation distance however we find that waves do not always favor more inundation as expected for storms traveling at very slow translation speeds or nearly parallel to the coast waves surprisingly exert a negative effect on the maximum inundation distance we argue that wave enhanced bottom stress combined with longer forcing duration in such storms counteract the positive effect of wave setup and thus less inundation is predicted in wave current coupled simulations our results highlight the necessity of fully incorporating wave effects in storm surge and inundation modeling

wind and waves in extreme hurricanes waves breaking at the ocean surface are important to the dynamical chemical and biological processes at the air sea interface the traditional view is that the white capping and aero dynamical surface roughness increase with wind speed up to a limiting value this view is fundamental to hurricane forecasting and climate research but it has never been verified at extreme winds here we show with observations that at high wind speeds white caps remain constant and at still higher wind speeds are joined and increasingly dominated by streaks of foam and spray at surface wind speeds of 40 m s the streaks merge into a white out the roughness begins to decrease and a high velocity surface jet begins to develop the roughness reduces to virtually zero by 80 m s wind speed rendering the surface aero dynamically extremely smooth in the most intense part of extreme or major hurricanes wind speed 50 m s a preliminary assessment shows that cross swell dominant in large regions of hurricanes allows the roughness under high wind conditions to increase considerably before it reduces to the same low values

backscatter model for the unusual radar properties of the greenland ice sheet a number of planetary objects exhibit large radar reflectivity and polarization ratios and more recently a similar behavior has been observed over a vast portion of the earth s surface the percolation facies of the greenland ice sheet surface based ranging radar data and snow stratigraphy studies demonstrated that the radar properties of that portion of greenland are caused by enhanced scattering from massive large solid ice bodies buried in the top few meters of the dry cold clean snowy surface of the ice sheet and created by seasonal melting and refreezing events from author

wetting front advance and freezing of meltwater within a snow cover 2 a simulation model a simulation model is developed which incorporates the effect of flow fingers at the leading edge of the wetting front ice layer growth within and at the base of the snow cover and meltwater infiltration into the underlying frozen soils the model results demonstrated that ice layers grow rapidly over a 24 to 36 hour period due to the conduction of heat into the snow and underlying soil sufficient water is frozen as ice layers to slow the finger wetting front and to account for the rapid snow and soil warming wetting front advance and ice layer growth were found to be sensitive to snow temperature thermal conductivity volume of flow in the fingers and irreducible water saturation simulation of a warm snow cover showed that with reduced ice layer growth the flow fingers were able to transmit rapidly water to the snow cover base before the entire snow cover was wet in the arctic situation the soil was sufficiently cold to ensure basal ice growth throughout the melt period basal ice growth was found to be sensitive to soil infiltration length of the growing period and the snowmelt rate as a result of the negative soil heat flux all meltwater is not available for runoff until both the liquid and thermal requirements of the snow and soil have been satisfied

high frequency observations of melt effects on snowpack stratigraphy kahiltna glacier central alaska range with an increased volume of melt on many of the world s glaciers study of how meltwater affects the properties of glacial snowpack becomes essential to our understanding of how glaciers will respond to climate change we address this problem by studying how snow properties changed on sub daily timescales on the kahiltna glacier alaska between may 26 and june 10 2010 during this period we dug 1 8 m deep snow pits twice daily to record the stratigraphy of melt layers snow hardness grain size and density and sampled for hydrogen isotopic composition d on four occasions from these data we show that 65 of the melted surface snow infiltrates and refreezes in the snowpack this leads to a densification of the snow a 729 increase in volume of melt layers and a homogenization of isotopic and physical snow properties from visual and stratigraphic observations we show that meltwater flow within the snowpack is conducted primarily along lenses and pipes where melt layers later form but that more homogeneous capillary based flow is also important finally we show using isotope ratios that post depositional alteration is exacerbated with increased melt extent using the d profile below a volcanic ash layer as a case study in the future similar studies would benefit from this high frequency monitoring approach to assessing snowpack evolution as it allows for a greater understanding of short duration processes new directions for study would include longer term monitoring efforts over a wider spatial snow pit network copyright 2012 john wiley sons ltd

analysis and modeling of melt water refreezing in dry snow a dynamic zone of thermal disequilibrium is described which separates wet snow at 0 c from dry sub freezing snow the dynamic zone tends to be eliminated by thermal equilibrium through freezing but is sustained and propagated into the sub freezing snow by water flow from the wet snow the width of the dynamic zone is controlled by the rate of water inflow and by the rate of freezing of water on to sub freezing ice grains which is in turn controlled by the ice water geometry two ice water geometries are investigated isolated ice spheres and capillary tubes of ice into which water is pulled by capillary suction the rate of freezing of water is calculated for the two models for various initial dimensions and temperatures equilibrium times are short typically about 0 5 s but depend on the assumed geometry which is poorly constrained by existing data equilibration times and freeze on mass fluxes are calculated for a variety of general conditions these results can be used in numerical models of wetting front propagation into cold snow

a high resolution coupled riverine flow tide wind wind wave and storm surge model for southern louisiana and mississippi part i model development and validation abstract a coupled system of wind wind wave and coastal circulation models has been implemented for southern louisiana and mississippi to simulate riverine flows tides wind waves and hurricane storm surge in the region the system combines the noaa hurricane research division wind analysis system h wind and the interactive objective kinematic analysis ioka kinematic wind analyses the wave model wam offshore and steady state irregular wave stwave nearshore wind wave models and the advanced circulation adcirc basin to channel scale unstructured grid circulation model the system emphasizes a high resolution down to 50 m representation of the geometry bathymetry and topography nonlinear coupling of all processes including wind wave radiation stress induced set up and objective specification of frictional parameters based on land cover databases and commonly used parameters riverine flows and tides are validated for no storm conditions while winds wind waves hydrographs and high wa

u s ioos coastal and ocean modeling testbed evaluation of tide wave and hurricane surge response sensitivities to mesh resolution and friction in the gulf of mexico 1 this paper investigates model response sensitivities to mesh resolution topographical details bottom friction formulations the interaction of wind waves and circulation and nonlinear advection on tidal and hurricane surge and wave processes at the basin shelf wetland and coastal channel scales within the gulf of mexico tides in the gulf of mexico are modestly energetic processes whereas hurricane surge and waves are highly energetic the unstructured mesh coupled wind wave and circulation modeling system swan adcirc is implemented to generate modeled tidal harmonic constituents and hurricane waves and surge for a hurricane ike 2008 hindcast in the open ocean mesh resolution requirements are less stringent in achieving accurate tidal signals or matching hurricane surge and wave responses however coarser resolution or the absence of intertidal zones decreases accuracy along protected nearshore and inland coastal areas due to improper conveyance and or lateral attenuation bottom friction formulations are shown to have little impact on tidal signal accuracy but hurricane surge is much more sensitive especially in shelf waters where development of a strong shore parallel current is essential to the development of ike s geostrophic setup the spatial and temporal contributions of wave radiation stress gradients and nonlinear advection were charted for ike nonlinear advection improves model performance by capturing an additional 10 20 cm of geostrophic setup and increasing resonant cross shelf waves by 30 40 cm wave radiation stress gradients improve performance at coastal stations by adding an extra 20 40 cm to water levels

calibrating a surface mass balance model for austfonna ice cap svalbard austfonna 8120 km 2 is by far the largest ice mass in the svalbard archipelago there is considerable uncertainty about its current state of balance and its possible response to climate change over the 2004 05 period we collected continuous meteorological data series from the ice cap performed mass balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground penetrating radar along several profile lines these data are used to drive and test a model of the surface mass balance the spatial accumulation pattern was derived from the snow depth profiles using regression techniques and ablation was calculated using a temperature index approach model parameters were calibrated using the available field data parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably testing model results against multiple criteria is an efficient method to cope with non uniqueness in doing so a range of different data and observations was compared to several different aspects of the model results we find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation which suggests that refreezing processes play an important role to represent these effects in the model a simple pmax approach was included in its formulation used as a diagnostic tool the model suggests that the surface mass balance for the period 29 april 2004 to 23 april 2005 was negative 318 mm w e

observation of a fast continental shelf wave generated by a storm impacting newfoundland using wavelet and cross wavelet analyses abstract wavelet and cross wavelet power spectra of sea level records from tide gauges along the atlantic coast of canada showed a low frequency barotropic response after hurricane florence crossed the newfoundland shelf in september 2006 in comparison with two other storms the results showed that florence was the only one that excited a propagating sea level disturbance with a period range similar to the passage time of the storm over the shelf 26 30 h and phase shifts consistent with a barotropic continental shelf wave csw the high amplitude of the oscillations generated by florence along the shore diminished from approximately 45 to 12 cm as the csw propagated from the south coast of newfoundland to the southern nova scotia seaboard this paper presents the first direct measurement of a remarkably high alongshore group speed 11 4 5 9 m s 1 in the manner of free barotropic csw by examination of sea level wavelet power spectra at different locations furthermore using cross wavelet analysis

measurement and simulation of snow and superimposed ice at the kongsvegen glacier svalbard spitzbergen 1 multiyear glaciometeorological data have been collected at about the equilibrium line of kongsvegen glacier in svalbard during the first summer of the investigation period about 0 6 m of superimposed ice si was built up because of effective meltwater refreeze upon the former glacier surface thus winter accumulation is completely retained from runoff and latent heat is released equivalent to 27 of july net radiation this ice layer as well as part of the former year s ice disappeared during the subsequent summer using a physically based snow model the evolution of the snow pack properties as well as the observed amount of si is successfully reproduced however the latter is only possible by modifying the model s water transport routine to also treat effects of ponding water which have been observed two distinct phases of si formation can be distinguished a first one 15 cm is initiated as soon as meltwater has penetrated to the underlying cold glacier ice toward the end of the melt period however the remaining body of si is rapidly formed because of intense atmospheric cooling the availability of ponding water plays an essential role in this context during the following summer the initial refreezing phase was terminated by exposure of the newly built si at the surface the whole amount of the actual year and the major part of the former year s si was melted then a positive ice albedo feedback process plays an additional role there sensitivity studies prove that the model results and their interpretation do not critically depend on possible uncertainties of input data and model parameters despite their local nature these studies are valuable steps toward understanding the regional distribution of si on arctic glaciers as well as their climate sensitivity remote sensing studies indicate that si presently covers 35 of kongsvegen s surface area

cryosphere greenland s lurking aquifer runoff estimates from the greenland ice sheet carry uncertainty because the fate of surface melt in permanently snow covered regions is unconstrained in situ and airborne observations reveal large scale liquid water storage in buried layers of aged and compacted snow

storm driven erosion and inundation of barrier islands from dune to region scales abstract barrier islands are susceptible to erosion overwash and breaching during intense storms however these processes are not represented typically in large domain models for storm surge and coastal inundation in this study we explore the requirements for bridging the gap between dune scale morphodynamic and region scale flooding models a high resolution xbeach model is developed to represent the morphodynamics during hurricane isabel 2003 in the north carolina nc outer banks the model domain is extended to more than 30 km of hatteras island and is thus larger than in previous studies the predicted dune erosion is in good agreement with post storm observed topography and an excellent skill score of 0 59 is obtained on this large domain sensitivity studies show the morphodynamic model accuracy is decreased as the mesh spacing is coarsened in the cross shore direction but the results are less sensitive to the alongshore resolution a new metric to assess model skill water overpassing area w o a is introduced to account for the available flow pathway over the dune crest together these findings allow for upscaled parameterizations of erosion in larger domain models the updated topography obtained from xbeach prediction is applied in a region scale flooding model thus allowing for enhanced flooding predictions in communities along the outer banks it is found that even using a fixed topography in region scale model the flooding predictions are improved significantly when post storm topography from xbeach is implemented these findings can be generalized to similar barrier island systems which are common along the u s gulf and atlantic coasts

data and numerical analysis of astronomic tides wind waves and hurricane storm surge along the northern gulf of mexico the northern gulf of mexico ngom is a unique geophysical setting for complex tropical storm induced hydrodynamic processes that occur across a variety of spatial and temporal scales each hurricane includes its own distinctive characteristics and can cause unique and devastating storm surge when it strikes within the intricate geometric setting of the ngom while a number of studies have explored hurricane storm surge in the ngom few have attempted to describe storm surge and coastal inundation using observed data in conjunction with a single large domain high resolution numerical model to better understand the oceanic and nearshore response to these tropical cyclones we provide a detailed assessment based on field measurements and numerical simulation of the evolution of wind waves water levels and currents for hurricanes ivan 2004 dennis 2005 katrina 2005 and isaac 2012 with focus on mississippi alabama and the florida panhandle coasts the developed ngom3 computational model describes the hydraulic connectivity among the various inlet and bay systems gulf intracoastal waterway coastal rivers and adjacent marsh and built infrastructure along the coastal floodplain the outcome is a better understanding of the storm surge generating mechanisms and interactions among hurricane characteristics and the ngom s geophysical configuration the numerical analysis and observed data explain the 2 m s hurricane induced geostrophic currents across the continental shelf a 6 m s outflow current during ivan the hurricane induced coastal kelvin wave along the shelf and for the first time a wealth of measured data and a detailed numerical simulation was performed and was presented for isaac