calibrating a viscoelastic sea ice model for wave propagation in the arctic fall marginal ice zone this paper presents a wave in ice model calibration study data used were collected in the thin ice of the advancing autumn marginal ice zone of the western arctic ocean in 2015 where pancake ice was found to be prevalent multiple buoys were deployed in seven wave experiments data from four of these experiments are used in the present study wave attenuation coefficients are calculated utilizing wave energy decay between two buoys measuring simultaneously within the ice covered region wavenumbers are measured in one of these experiments forcing parameters are obtained from simultaneous in situ and remote sensing observations as well as forecast hindcast models cases from three wave experiments are used to calibrate a viscoelastic model for wave attenuation dispersion in ice cover the calibration is done by minimizing the difference between modeled and measured complex wavenumber using a multi objective genetic algorithm the calibrated results are validated using two methods one is to directly apply the calibrated viscoelastic parameters to one of the wave experiments not used in the calibration and then compare the attenuation from the model with measured data the other is to use the calibrated viscoelastic model in wavewatch iii over the entire western beaufort sea and then compare the wave spectra at two remote sites not used in the calibration both validations show reasonable agreement between the model and the measured data the completed viscoelastic model is believed to be applicable to the fall marginal ice zone dominated by pancake ice

in situ observations of wave induced sea ice breakup ocean waves can propagate hundreds of kilometers into sea ice leaving behind a wake of broken ice floes three floe breakup events were observed during the second sea ice physics and ecosystem experiment sipex 2 we show that the three breakup events were likely influenced by ocean waves we compare the observations to a wave induced floe breakup model which includes an empirical wave attenuation model and show that the model underestimates the extent of floe breaking for long period waves

evolution of directional wave spectra in the marginal ice zone a new model tested with legacy data abstractfield experimental data from a 1980s program in the greenland sea investigating the evolution of directional wave spectra in the marginal ice zone are reanalyzed and compared with the predictions of a new phase resolving three dimensional model describing the two dimensional scattering of the waves by the vast number of ice floes that are normally present the model is augmented with a dissipative term to account for the nonconservative processes affecting wave propagation observations reported in the experimental study are used to reproduce the ice conditions and wave forcing during the experiments it is found that scattering alone underestimates the attenuation experienced by the waves during their passage through the ice field with dissipation however the model can replicate the observed attenuation for most frequencies in the swell regime model predictions and observations of directional spreading are in agreement for short to midrange wave periods where the wave field quickly becomes

wave attenuation through an arctic marginal ice zone on 12 october 2015 1 measurement of wave spectra and ice features from sentinel 1a a storm with significant wave heights exceeding 4 m occurred in the beaufort sea on 11 13 october 2015 the waves and ice were captured on 12 october by the synthetic aperture radar sar on board sentinel 1a with interferometric wide swath images covering 400 x 1 100 km at 10 m resolution this data set allows the estimation of wave spectra across the marginal ice zone miz every 5 km over 400 km of sea ice since ice attenuates waves with wavelengths shorter than 50 m in a few kilometers the longer waves are clearly imaged by sar in sea ice obtaining wave spectra from the image requires a careful estimation of the blurring effect produced by unresolved wavelengths in the azimuthal direction using in situ wave buoy measurements as reference we establish that this azimuth cutoff can be estimated in mixed ocean ice conditions wave spectra could not be estimated where ice features such as leads contribute to a large fraction of the radar backscatter variance the resulting wave height map exhibits a steep decay in the first 100 km of ice with a transition into a weaker decay further away this unique wave decay pattern transitions where large scale ice features such as leads become visible as in situ ice information is limited it is not known whether the decay is caused by a difference in ice properties or a wave dissipation mechanism the implications of the observed wave patterns are discussed in the context of other observations plain language summary our work entitled wave attenuation through an arctic marginal ice zone on 12 october 2015 1 measurement of wave spectra and ice features from sentinel 1a uses a newly developed method to extract wave spectra from radar imagery over sea ice this is possible since the sea ice rapidly removes the short waves which usually distort the radar imagery we are able to estimate thousands of wave spectra across several hundred kilometers at kilometer scale resolution for the first large scale view of wave attenuation across the marginal ice zone our results show a unique wave attenuation pattern described by a piecewise exponential decay that changes by a factor of 10 the transition between the different wave attenuation regions occurs near a change in sea ice conditions we estimate from the sar backscatter this suggests the wave ice interaction mechanisms are indeed changing over these large scales

finite floe wave reflection and transmission coefficients from a semi infinite model a model to describe the reflection and transmission of ocean waves by a single ice floe is developed from the semi infinite model of fox and squire 1990 1991 this is done by considering the coefficients for the transition from ice to water in the semi infinite case in terms of those from water to ice finite floe reflection and transmission coefficients r and t respectively are then found as the solution of a set of four simple simultaneous equations the properties of r and t are investigated and examples of their absolute values are given for several geometries r compares well with the predictions of a precise model in the case of deep water these results suggest that the analytical model described has applications to defining the sea state within marginal ice zones given the floe size and ice thickness distributions and the incoming sea wave spectrum

swell and sea in the emerging arctic ocean ocean surface waves sea and swell are generated by winds blowing over a distance fetch for a duration of time in the arctic ocean fetch varies seasonally from essentially zero in winter to hundreds of kilometers in recent summers using in situ observations of waves in the central beaufort sea combined with a numerical wave model and satellite sea ice observations we show that wave energy scales with fetch throughout the seasonal ice cycle furthermore we show that the increased open water of 2012 allowed waves to develop beyond pure wind seas and evolve into swells the swells remain tied to the available fetch however because fetch is a proxy for the basin size in which the wave evolution occurs thus both sea and swell depend on the open water fetch in the arctic because the swell is regionally driven this suggests that further reductions in seasonal ice cover in the future will result in larger waves which in turn provide a mechanism to break up sea ice and accelerate ice retreat

measuring ocean waves in sea ice using sar imagery a quasi deterministic approach evaluated with sentinel 1 and in situ data measurements of wave heights in marginal ice zones are limited to very few in situ data here we revisit the linear and quasilinear theories of synthetic aperture radar imaging of waves in the particular case of waves in sea ice instead of only working with spectra we have developed an iterative nonlinear algorithm to estimate phase resolved deterministic maps of wave induced orbital velocities from which elevation spectra can be derived application of this algorithm to sentinel 1a wave mode images in the southern ocean shows that it produces reasonable results for swells in all directions except when they propagate at a few degrees off the range direction the estimate of wave parameters is expected to work best when the shortest wave components those which cause a pixel displacement of the order of the dominant wavelength in azimuth can be neglected otherwise short waves produce a blurring of the image increasing exponentially with the azimuthal wavenumber and reducing the estimated wave amplitude given the expected spatial attenuation of waves in ice covered regions our deterministic method should apply beyond a few tens of kilometers in the ice without any correction for short wave effects in situ data collected around the ice edge as part of the 2015 seastate dri cruise in the beaufort confirm the progressive image blurring caused by such short waves and the apparent reduction in the wave modulation when short waves propagate from the open ocean towards the ice this blurring can produce an unrealistic apparent increase of wave height from the open ocean up to a few tens of kilometers inside the ice

spaceborne synthetic aperture radar observations of ocean waves traveling into sea ice 1 damping of ocean waves by sea ice is studied using spaceborne synthetic aperture radar sar images of the marginal ice zone miz acquired by the european remote sensing satellite ers 2 sar imaging of waves damped by sea ice is analyzed theoretically the impact of sea ice on the azimuthal cutoff is studied by simulation of the azimuthal sar image autocorrelation function as well as the two dimensional sar image spectrum typical imaging artifacts like spiky wave crests and wave refraction seen on sar scenes of the miz are reproduced by simulation sensitivity studies are performed using models for wind sea and swell systems it is shown that the degradation of the azimuthal sar image resolution is dominated by the orbital velocity variance of the waves while the coherence time of the complex radar reflectivity has a minor impact a first order analysis of wave damping observed on sar scenes is carried out using a technique that was originally developed for wind estimation by kerbaol et al 1998 the method does not require a priori information and is insensitive to real aperture modulation the azimuthal sar image cutoff wavelength is estimated and related to the orbital velocity variance of the sea surface by regression the model is fitted on the basis of a global set of model ocean wave spectra the technique is applied within the sea ice and in the open water in front of the ice boundary on the basis of simple models for wind sea and swell ocean wave attenuation rates are obtained from the observed orbital velocity decrease of waves entering the ice the required wind information is derived from calibrated sar data using the cmod method two case studies showing examples from the greenland and the weddell seas are given it is shown that the estimated wave damping is consistent with damping parameters found in earlier field campaigns carried out in the weddell sea and the bering sea an inversion technique providing estimates for the two dimensional wave spectra behind and in front of the ice boundary as well as a two dimensional filter function characterizing the sea ice impact is introduced the technique is based on simultaneous inversion of the two dimensional image spectra in the open water and within the ice using a priori information from an ocean wave model it is shown that the technique gives results consistent with the first order analysis based on the cutoff estimation

the attenuation rates of ocean waves in the marginal ice zone during field operations in the greenland and bering seas in 1978 1979 and 1983 a number of experiments were carried out in which wave energy was measured along a line of stations running from the open sea deep into an icefield wave buoys in the water and accelerometer packages on floes were the instruments employed with airborne vertical photography to supply information on floe size distribution it was found that the decay of waves is exponential with a decay coefficient which generally increases with frequency except for a roll over at the highest frequencies the observations can be fitted reasonably well to a theory of one dimensional scattering

in situ measurements of an energetic wave event in the arctic marginal ice zone r v lance serendipitously encountered an energetic wave event around 77 n 26 e on 2 may 2010 onboard gps records interpreted as the surface wave signal show the largest waves recorded in the arctic region with ice cover comparing the measurements with a spectral wave model indicated three phases of interaction 1 wave blocking by ice 2 strong attenuation of wave energy and fracturing of ice by wave forcing and 3 uninhibited propagation of the peak waves and an extension of allowed waves to higher frequencies above the peak wave properties during fracturing of ice cover indicated increased groupiness wave ice interaction presented binary behavior there was zero transmission in unbroken ice and total transmission in fractured ice the fractured ice front traveled at some fraction of the wave group speed findings do not motivate new dissipation schemes for wave models though they do indicate the need for two way wave ice coupling

the use of sar to measure ocean wave dispersion in frazil pancake icefields abstract icefields composed of frazil and pancake ice play important roles in both polar regions in winter during the early to midwinter period pancake ice is a major component of the antarctic sea ice cover while in the arctic the odden ice tongue in the greenland sea associated with deep convection is composed mainly of pancake ice the retrieval of sea ice thickness by remote sensing is in general a very difficult task in this paper the change in dispersion of ocean waves as they penetrate into pancake ice is considered so as to gain insight into its possible relationship with thickness spectral analysis of subscenes from ers 2 second european remote sensing satellite synthetic aperture radar sar images yields the wavelength and direction of the principal spectral component both outside and inside the ice cover there is a decrease of wavelength at the ice edge as well as refraction toward the normal and a loss of amplitude the analysis is complex because the true wave spectrum must be re

airborne synthetic aperture radar observations and simulations for waves in ice the canada centre for remote sensing cv 580 aircraft collected c band synthetic aperture radar sar data over the marginal ice zone off the east coast of newfoundland during the labrador ice margin experiment limex in march 1989 one component of the limex 89 program was the study of ocean waves penetrating the marginal ice zone in this paper we consider nearly coincidental observations of waves in ice by airborne sar and wave induced ice motion measurements we explain the wave patterns observed in the sar imagery and the corresponding sar image spectra in terms of sar wave imaging models these include the well known tilt cross section modulation linear quasi linear and nonlinear velocity bunching forward mapping models fmms and the assertion that the concept of coherence time limitation applies differently to the cases of waves in ice and open water we modify the concept of the scene coherence time to include two parts first a decorrelation time deduced from the inherent azimuth cutoff in the nonlinear velocity bunching fmm and second the intrinsic scene coherence time which is a measure of the time scale over which an open water bragg scattering patch retains its phase structure either of these coherence time scales could dominate the sar image formation process depending upon the environmental conditions the wave spectrum and the wind speed for example these two coherence time scales are independently estimated based upon a quasi linear velocity bunching fmm applied to some of the limex 89 observations observed sar image spectra and forward mapped ice motion package spectra are favorably compared

airborne remote sensing of ocean wave directional wavenumber spectra in the marginal ice zone interactions between surface waves and sea ice are thought to be an important but poorly understood physical process in the atmosphere ice ocean system in this work airborne scanning lidar was used to observe ocean waves propagating into the marginal ice zone miz these represent the first direct spatial measurements of the surface wave field in the polar miz data were compared against two attenuation models one based on viscous dissipation and one based on scattering both models were capable of reproducing the measured wave energy the observed wavenumber dependence of attenuation was found to be consistent with viscous processes while the spectral spreading of higher wavenumbers suggested a scattering mechanism both models reproduced a change in peak direction due to preferential directional filtering floe sizes were recorded using co located visible imagery and their distribution was found to be consistent with ice breakup by the wave field

theory of synthetic aperture radar ocean imaging a marsen view this paper reviews basic synthetic aperture radar sar theory of ocean wave imaging mechanisms using both known work and recent experimental and theoretical results from the marine remote sensing marsen experiment several viewpoints that have contributed to the field are drawn together in a general analysis of the backscatter statistics of a moving sea surface a common focus for different scattering models is provided by the mean image impulse response function which is shown to be identical to the spatially varying frequency variance spectrum of the local complex reflectivity coefficient from the analysis has emerged a more complete view of the sar imaging phenomenon than has been previously available a new generalized imaging model is proposed

in situ measurements and analysis of ocean waves in the antarctic marginal ice zone in situ measurements of ocean surface wave spectra evolution in the antarctic marginal ice zone are described analysis of the measurements shows significant wave heights and peak periods do not vary appreciably in approximately the first 80km of the ice covered ocean beyond this region significant wave heights attenuate and peak periods increase it is shown that attenuation rates are insensitive to amplitudes for long period waves but increase with increasing amplitude above some critical amplitude for short period waves attenuation rates of the spectral components of the wavefield are calculated it is shown that attenuation rates decrease with increasing wave period further for long period waves the decrease is shown to be proportional to the inverse of the period squared this relationship can be used to efficiently implement wave attenuation through the marginal ice zone in ocean scale wave models

metallogenic provinces geochemical provinces and regional geology what causes large scale patterns in low density geochemical maps of the c horizon of podzols in arctic europe the 2 mm fraction of 605 samples of the c horizon of podzols collected from an area of 188 000 km2 in the european arctic was analysed for more than 40 chemical elements the results were used to construct geochemical maps which showed clear regional distribution patterns notwithstanding the very low sample density of 1 site per 300 km2 some of these patterns fit established lithological boundaries others fit lineament structures in the area and underline the relative importance of certain tectonic directions some of which have not yet been delineated on existing geological maps some mark large scale hydrothermal events and related alteration finally some are connected with prominent known ore deposits occurring in the area however several large deposits and even famous metallogenic provinces fe ni cu are hardly or not at all reflected in the regional geochemical maps in their present definitions geochemical provinces and metallogenic provinces are thus not necessarily related special geochemical features can occur at very different scales the term geochemical province is so imprecise in terms of processes leading to regional scale geochemical features that it should be avoided low density geochemistry can be used to aid the interpretation of the geological evolution of large regions it can also be used to find prospective areas within such regions

air ice ocean momentum exchange part 1 energy transfer between waves and ice floes abstract the energy exchange between ocean surface waves and ice floes in the marginal ice zone miz involves the scattering and attenuation of wave energy and the excitation of oscillation modes of the ice floes as open ocean waves propagate into the miz heave pitch and roll modes of oscillation are linked to estimation of wave scattering and attenuation a model is presented for wave attenuation and compared to measurements from the marginal ice zone experiments in the greenland sea as reported by wadhams et al

a 15 year climatology of northern hemisphere 500 mb closed cyclone and anticyclone centers abstract a 15 year 1963 77 northern hemisphere 2 5 degree latitude longitude gridded dataset of 500 mb geopotential heights has been used to construct a climatology of 500 mb closed circulation centers these centers defined by at least one closed 30 m contour around a central minimum or maximum geopotential height value were identified objectively between 24 and 82 n from the twice daily analysis grids tracks for all closed circulation centers were computed to establish genesis and lysis distributions and to examine the monthly seasonal and interannual variability characteristics of the closed circulation center distributions for specified regions the occurrence of closed cyclone centers is maximized north of and within the main belt of westerlies extending from northeast asia to the gulf of alaska near 50 n and extending from eastern canada and the extreme northeast united states to southeast of greenland and west of the united kingdom their occurrence is also maximized south of the main be

sea ice floes dissipate the energy of steep ocean waves a laboratory experimental model of an incident ocean wave interacting with an ice floe is used to validate the canonical solitary floe version of contemporary theoretical models of wave attenuation in the ice covered ocean amplitudes of waves transmitted by the floe are presented as functions of incident wave steepness for different incident wavelengths the model is shown to predict the transmitted amplitudes accurately for low incident steepness but to overpredict the amplitudes by an increasing amount as the incident wave becomes steeper the proportion of incident wave energy dissipated by the floe in the experiments is shown to correlate with the agreement between the theoretical model and the experimental data thus implying that wave floe interactions increasingly dissipate wave energy as the incident wave becomes steeper

a wave based model for the marginal ice zone including a floe breaking parameterization 1 the marginal ice zone miz is the boundary between the open ocean and ice covered seas where sea ice is significantly affected by the onslaught of ocean waves waves are responsible for the breakup of ice floes and determine the extent of the miz and floe size distribution when the ice cover is highly fragmented its behavior is qualitatively different from that of pack ice with large floes therefore it is important to incorporate wave ice interactions into sea ice ocean models in order to achieve this goal two effects are considered the role of sea ice as a dampener of wave energy and the wave induced breakup of ice floes these two processes act in concert to modify the incident wave spectrum and determine the main properties of the miz a simple but novel parameterization for floe breaking is derived by considering alternatively ice as a flexible and rigid material and by using current estimates of ice critical flexural strain and strength this parameterization is combined with a wave scattering model in a one dimensional numerical framework to evaluate the floe size distribution and the extent of the miz the model predicts a sharp transition between fragmented sea ice and the central pack thus providing a natural definition for the miz reasonable values are found for the extent of the miz given realistic initial and boundary conditions the numerical setting is commensurate with typical ice ocean models with the future implementation into two dimensional sea ice models in mind

observed cyclone anticyclone tropopause vortex asymmetries relatively little is known about coherent vortices near the extratropical tropopause even with regard to basic facts about their frequency of occurrence longevity and structure this study addresses these issues through an objective census of observed tropopause vortices the authors test a hypothesis regarding vortex merger asymmetry where cyclone pairs are repelled and anticyclone pairs are attracted by divergent flow due to frontogenesis emphasis is placed on arctic vortices where jet stream influences are weaker in order to facilitate comparisons with earlier idealized numerical simulations results show that arctic cyclones are more numerous persistent and stronger than arctic anticyclones an average of 15 cyclonic vortices and 11 anticyclonic vortices are observed per month with maximum frequency of occurrence for cyclones anticyclones during winter summer there are are about 47 more cyclones than anticyclones that survive at least 4 days and for longer lifetimes 1 day survival probabilities are nearly constant at 65 for cyclones and 55 for anticyclones mean tropopause potential temperature amplitude is 13 k for cyclones and 11 k for anticyclones with cyclones exhibiting a greater tail toward larger values an analysis of close proximity vortex pairs reveals divergence between cyclones and convergence between anticyclones this result agrees qualitatively with previous idealized numerical simulations although it is unclear to what extent the divergent circulations regulate vortex asymmetries