quantitative remote sensing study indicates doubling of coastal erosion rate in past 50 yr along a segment of the arctic coast of alaska a new quantitative coastal land gained and lost method uses image analysis of topographic maps and landsat thematic mapper short wave infrared data to document accelerated coastal land loss and thermokarst lake expansion and drainage the data span 1955 2005 along the beaufort sea coast north of teshekpuk lake in the national petroleum reserve in alaska some areas have undergone as much as 0 9 km of coastal erosion in the past 50 yr land loss attributed to coastal erosion more than doubled from 0 48 km2 yr 1 during 1955 1985 to 1 08 km2 yr 1 during 1985 2005 coastal erosion has breached thermokarst lakes causing initial draining of the lakes followed by marine flooding although inland thermokarst lakes show some uniform expansion lakes breached by coastal erosion display lake expansion several orders of magnitude greater than inland lakes

the palisades is a key reference site for the middle pleistocene of eastern beringia new evidence from paleomagnetics and regional tephrostratigraphy abstract the palisades in central alaska is one of the most prominent exposures of quaternary sediments on the yukon river perennially frozen silt and sand at the palisades are presently thought to preserve paleoenvironmental records from the holocene to marine isotope stage mis 8 and beneath a major unconformity the earliest pleistocene 2 ma we present new paleomagnetic and tephrochronologic constraints that substantially revise the age of the sediments at the palisades we describe 15 new tephra beds including five beds below the prominent pal tephra that correlate to known tephra with independent age control from other sites in eastern beringia these five known tephra include chester bluff tephra which is present in east central alaska and the yukon and the newly named alyeska pipeline and taylor highway tephra from central alaska all are constrained to the middle pleistocene paleomagnetic transects from the base of the bluff to the mis 5e forest bed yield normal polarity with the exception of a brief reversal event between old crow tephra 124 10 ka and the mis 5e forest bed that is likely the first documentation of the blake paleomagnetic event in alaskan loess the detailed tephrostratigraphy and paleomagnetic data collectively suggest that most of the sedimentary record at the palisades is middle pleistocene in age the palisades thus preserves a rare record of late to middle pleistocene paleoenvironments with multiple regionally distributed tephra beds

discontinuous grain growth of quartz in metacherts the influence of mica on a microstructural transition abstract the microstructure of quartz in metacherts of the ryoke metamorphic belt in central japan develops from polygonal through duplex to irregular with increasing metamorphic grade the polygonal microstructure is composed of small mostly 90 160 m equant equigranular polygonal quartz grains whereas the irregular microstructure is characterized by large 300 m grains with irregular grain boundaries the duplex microstructure is a mixture of small polygonal and large irregular grains the development of these microstructures is interpreted as being due to secondary recrystallization the size of polygonal grains is greatly influenced by the presence of second phase minerals such as mica whereas that of large irregular grains is unaffected by second phase minerals there seems to be a critical grain size for quartz to occur as polygonal aggregates no polygonal aggregates occur in rocks with larger than the critical grain size the size about 140 m decreases slightly with increasing volume fraction of mica the mean grain sizes of polygonal quartz d and coexisting mica d in the duplex microstructure are systematically related to the volume fraction of mica f by d 0 728d 1 f 0 629

arctic sea ice variability revisited this paper explores spatial and temporal relationships between variations in arctic sea ice concentration summer and winter and near surface atmospheric temperature and atmospheric pressure using multivariate statistical techniques trend empirical orthogonal function eof and singular value decomposition svd analyses are used to identify spatial patterns associated with covariances and correlations between these fields results show that 1 in winter the arctic oscillation still explains most of the variability in sea ice concentration from 1979 to 2006 and 2 in summer a decreasing sea ice trend centered in the pacific sector of the arctic basin is clearly correlated to an arctic wide air temperature warming trend these results demonstrate the applicability of multivariate methods and in particular svd analysis which has not been used in earlier studies for assessment of changes in the arctic sea ice cover results are consistent with the interpretation that a warming signal has now emerged from the noise in the arctic sea ice record during summer our analysis indicates that such a signal may also be forthcoming during winter

infrared microspectroscopy analysis of water distribution in deformed and metamorphosed rocks infrared microspectroscopy has been applied to thin sections of various deformed and metamorphosed rocks in order to investigate water content of quartz in these rocks the broad ir band absorbance around 3400 cm 1 probably due to fluid inclusion molecular water h2o was used to calculate water contents deformed granitic rocks from the yanazawa kamimura area near the median tectonic line mtl showed an increase of water content in quartz from about 300 ppm to 2500 ppm toward the mtl with increasing degree of deformation metacherts from sambagawa metamorphic rocks asemigawa route showed a systematic decrease of water content in quartz from about 1000 ppm to 200 ppm with increasing metamorphic degree from chlorite garnet albite biotite to oligoclase biotite zones an archaean metachert from the napier complex granulite facies has only 40 ppm water comparing this with an inuyama unmetamorphosed chert sample having water contents of 3500 to 7000 ppm a starting point of metamorphism the systematic decrease of water in quartz with increasing metamorphic grade may extend from unmetamorphosed cherts to the highest grade metacherts water contents in high pressure metamorphic rocks in japan are mostly of the order of 500 ppm 300 700 ppm except for those from kurosegawa with a water content as high as 1700 ppm these results represent an exploratory analysis of intragranular water contents in quartz in various deformed and metamorphosed rocks further micro ft ir studies of the distribution of water in crustal rocks will provide a quantitative basis for examining the geochemical cycle of water in the earth s crust

modern thermokarst lake dynamics in the continuous permafrost zone northern seward peninsula alaska 1 quantifying changes in thermokarst lake extent is of importance for understanding the permafrost related carbon budget including the potential release of carbon via lake expansion or sequestration as peat in drained lake basins we used high spatial resolution remotely sensed imagery from 1950 51 1978 and 2006 07 to quantify changes in thermokarst lakes for a 700 km2 area on the northern seward peninsula alaska the number of water bodies larger than 0 1 ha increased over the entire observation period 666 to 737 or 10 7 however total surface area decreased 5 066 ha to 4 312 ha or 14 9 this pattern can largely be explained by the formation of remnant ponds following partial drainage of larger water bodies thus analysis of large lakes 40 ha shows a decrease of 24 and 26 in number and area respectively differing from lake changes reported from other continuous permafrost regions thermokarst lake expansion rates did not change substantially between 1950 51 and 1978 0 35 m yr and 1978 and 2006 07 0 39 m yr however most lakes that drained did expand as a result of surface permafrost degradation before lateral drainage drainage rates over the observation period were stable 2 2 to 2 3 per year thus analysis of decadal scale high spatial resolution imagery has shown that lake drainage in this region is triggered by lateral breaching and not subterranean infiltration future research should be directed toward better understanding thermokarst lake dynamics at high spatial and temporal resolution as these systems have implications for landscape scale hydrology and carbon budgets in thermokarst lake rich regions in the circum arctic

stratocumulus cloud top height estimates and their climatic implications a depth dependent boundary layer lapse rate was empirically deduced from 156 radiosondes released duringsixmonth longresearchcruisestothe southeastpacificsamplingavarietyofstratocumulusconditions thelapse ratedependenceonboundarylayerheightisweak decreasingfromabestfitof7 6to7 2k km 21 as theboundarylayerdeepensfrom800mto2km ship basedcloud baseheightsupto800mcorrespondwellto liftingcondensationlevels indicatingwell mixedconditions withcloud bases 800moften 200 600m higher than the lifting condensation levels the lapse rates were combined with moderate resolution imaging spectrometer 11 mm derived cloud top temperatures and satellite microwave derived sea surface temperatures to estimate stratocumulus cloud top heights the october mean cloud top height structure of the southeast pacific was then spatially and diurnally characterized coastal shoaling is apparent but so is a significant along coast cloud top height gradient with a pronounced elevation of the cloud top heights above thearicabightat 208s diurnalcloud topheightvariations inferredfromirregular4 times dailysampling can locally reach 250 m in amplitude and they can help to visualize offshore propagation of free tropospheric vertical motions a shallow boundary layer associated with the chilean coastal jet expands to its north and west in the afternoon cloud top heights above the arica bight region are depressed in the afternoon which may mean that increased subsidence from sensible heating of the andes dominates an afternoon increase in convergence upward motion at the exit of the chilean coastal jet in the southeast atlantic during october thestratocumuluscloud topheightsaretypicallylowerthanthoseinthesoutheastpacific acoastaljetregion can also be identified through its low cloud top heights coastal shoaling of the south atlantic stratocumulus region is mostly uniform with latitude in keeping with the more linear namibian angolan coastline the southeast atlantic shallow cloudy boundary layer extends farther offshore than in the southeast pacific particularly at 158s

view angle dependence of cloud optical thicknesses retrieved by moderate resolution imaging spectroradiometer modis 1 this study examines whether cloud inhomogeneity influences the view angle dependence of modis cloud optical thickness retrieval results the degree of cloud inhomogeneity is characterized through the local gradient in 11 m brightness temperature the analysis of liquid phase clouds in a 1 year long global data set of collection 4 modis data reveals that while optical thickness retrievals give remarkably consistent results for all view directions if clouds are homogeneous they give much higher values for oblique views than for overhead views if clouds are inhomogeneous and the sun is fairly oblique the mean optical thickness retrieved for the most inhomogeneous third of cloudy pixels is more than 40 higher for oblique views than for overhead views if the solar zenith angle exceeds 60 after considering a variety of possible scenarios the paper concludes that the most likely reason for the increase lies in three dimensional radiative interactions that are not considered in current one dimensional retrieval algorithms namely the radiative effect of cloud sides viewed at oblique angles seems to contribute most to the enhanced optical thickness values the results presented here will help understand and estimate cloud retrieval uncertainties related to cloud inhomogeneity and may eventually help correct for the observed view angle dependent biases

cryostratigraphy of the klondike muck deposits west central yukon territory four late quaternary cryostratigraphic units are recognized in the unconsolidated valley bottom deposits of the klondike area yukon territory three of the units in ice rich loessal sediments of pre wisconsinan or wisconsinan age collectively compose the king solomon formation they are overlain by a holocene organic unit the units are distinguished by their cryostratigraphic characteristics and oxygen isotope ratios of included ground ice the basal unit is the last chance creek member a pre late wisconsinan deposit containing preserved ice wedges 18o 28 to 26 d 225 to 209 the overlying quartz creek member a late wisconsinan unit is dominated by organic rich loess massive ice is noticeably absent although the sediments are ice rich the isotopic composition of ice in this unit is characteristic of full glacial conditions 18o 32 to 29 d 234 to 257 an abrupt change to warmer and wetter conditions at the end of glaciation prior to the holocene is recorded by the i

observations of three dimensional radiative effects that influence modis cloud optical thickness retrievals abstract when cloud properties are retrieved from satellite observations current calculations apply one dimensional 1d theory to the three dimensional 3d world they consider only vertical processes and ignore horizontal interactions this paper proposes a novel approach that estimates 3d effects in cloud optical thickness retrievals the proposed method combines visible and thermal infrared images to see whether 3d radiative effects make clouds appear asymmetric that is whether cloud surfaces tilted toward the sun are systematically brighter than surfaces tilted away from it the observed asymmetries are then used to estimate 3d effects for 1 km size pixels as well as 50 km size areas initial results obtained for moderate resolution imaging spectroradiometer modis images reveal that 3d effects cause abundant uncertainties in the 1 km resolution 1d retrievals averaging over 50 km by 50 km areas greatly reduces the errors but does not remove them completely conservative estimates show that the m

sediment and particulate organic carbon budgets of a subarctic estuarine fjard lake melville labrador abstract sediment and particulate organic carbon poc budgets constructed for oceanic regions provide a means to quantify the burial of poc providing a baseline against which future change can be measured here we developed the first mass balance budgets of sediment and poc terrestrial and marine for the lake melville system lms goose bay and lake melville in central labrador using previously published data 210pb based mass accumulation rates river discharge and total suspended solids together with measurements of oc and 13c signatures within dated sediment cores collected from the lms basins and water from main tributaries and groswater bay a two end member mixing model was used to establish fractions of terrigenous and marine poc overall our mass balance budgets show that the churchill river is the major supply of sediment 16 7 7 8 108 kg y 1 and pocterr 18 4 6 6 106 kg y 1 to the lms accounting for 47 and 56 of the total input to the system respectively although the churchill river drains directly into goose bay along with the smaller goose river the majority of sediment 12 9 7 8 108 kg y 1 and pocterr 11 8 7 0 106 kg y 1 is transported eastward through the surface water plume into lake melville inputs of pocmar from autochthonous primary production estimated by applying an empirical relationship between sediment surface flux of pocmar and water depth to goose bay 1 8 106 kg y 1 and lake melville 98 3 4 7 106 kg y 1 increase with increasing distance from the churchill river to investigate the potential changes to the sediment load of the churchill river to the lms following impoundment at muskrat falls we calculated the sediment increase using the median reservoir shoreline erosion potential this approach showed that the delivery of sediment and pocterr to the lms by the churchill river may double during the two years following impoundment of the lower churchill river

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

holocene sea level history of the canadian beaufort shelf new radiocarbon ages pertaining to the holocene sea level history of the canadian beaufort shelf are presented the ages were obtained on samples of freshwater and tidal marsh peat beds from offsho

microstructural development of fine grained quartz aggregates by syntectonic recrystallization abstract experimental study of syntectonic recrystallization of fine grained quartz aggregates was carried out in order to simulate the development of some natural microstructures of quartz tectonites and to understand their formation condition agate was axially compressed with a constant strain rate apparatus experiments were conducted at 4 kbar solid confining pressure 700 1000 c and 10 4 10 6 sec 1 to 10 45 strain in all runs deformation has proceeded under wet condition caused by dehydration of pyrophyllite used as pressure medium two different types of microstructure were distinguished in the deformed specimens one is p type which is characterized by equant equidimensional and polygonal grains the other is s type which is characterized by the highly oblate grains with the largest dimension perpendicular to the compression axis the p type microstructure is developed at higher temperatures and slower strain rates while the s type developed at lower temperatures and faster strain rates the transition between the s and p types is found to be very sharp

grain size properties and organic carbon stock of yedoma ice complex permafrost from the kolyma lowland northeastern siberia the organic carbon stock in permafrost is of increasing interest in environmental research because during the late quaternary a large pool of organic carbon accumulated in the sedimentary deposits of arctic permafrost because of its potential to degrade and release organic carbon the organic matter inventory of yedoma ice complex deposits is relevant to current concerns about the effects of global warming in this context it is essential to improve the understanding of preserved carbon quantities and characteristics the paper aims to clarify the yedoma ice complex origin and to develop an approach for volumetric organic matter quantification therefore we analyzed the grain size and the organic matter characteristics of the deposits exposed at the stratigraphic key site duvanny yar lower kolyma river northeast siberia a distinct bimodal grain size distribution confirms a polygenetic origin of the frozen sediments from a flood plain environment the total organic carbon content averages 1 5 1 4 wt while the volumetric organic carbon content averages 14 8 kg m however large scale extrapolations for yedoma ice complex deposits in general are not reasonable yet because of their rather unclear spatial distribution we conclude that yedoma ice complex formation at duvanny yar was dominated by water related alluvial fluvial lacustrine as well as aeolian processes the total organic carbon content of the studied deposits is low if compared to other profiles but it is still a significant pool

reflected solar radiances from broken cloud scenes and the interpretation of scanner measurements if an adequate model of the reflection characteristics of a given scene is available the reflected solar irradiance from the scene may be determined from radiance measurements made by satellite borne scanning radiometers a theoretical analysis of the reflection functions of broken cloud scenes is presented using monte carlo simulations of the radiative transfer in various three dimensional geometries it is shown that the reflection functions of horizontally extensive stratiform and horizontally limited cumuliform clouds are generally quite different the differences are greatest for nadir and limb views but tend to vanish for reflected radiances with a zenith angle of 60 deg applications to satellite observations suggest potential errors of a factor of 2 in the inferred irradiance are likely due to scene misidentification when the radiances are interpreted indiscriminantly selection of preferred satellite viewing directions however can significantly reduce this error

global distribution of modern shallow marine shorelines implications for exploration and reservoir analogue studies abstract deposits of marginal marine depositional systems make up significant hydrocarbon reservoirs in the rock record these systems are deposited by a complex interaction between competing depositional processes which can result in heterogeneous and compartmentalized reservoirs shallow marine systems are described using a ternary classification describing the relative importance of wave tide and fluvial processes at the coastline with the advent of freely available remote sensing data modern systems are being increasingly used as analogues for the ancient however to date there has been no systematic quantification of global modern paralic systems the aim of the present study has been to map and classify all the world s shorelines by ternary process and to consider the distribution and controls on different shoreline types the semi automated classification of marginal marine clastic shorelines has been achieved by combining data from a series of proxies for the ternary processes combined with coastline morphology an algorithm predicts shoreline classification with an 85 success rate when compared to manual interpretation using this algorithm the global shoreline has been subdivided into 246 777 5 km segments and the distribution and proportions of these analyzed the first order classification subdivides 28 of the world s coastlines as depositional within the depositional coastlines 62 are wave dominated 35 tide dominated and 3 fluvial dominated analysis of shoreline type distribution suggests a complex network of inter related controlling factors of these climate and tectonic setting are reasonably well constrained in the ancient and can be used to predict the probability of a specific shoreline type in addition to shedding insight into the controls on the distribution of different shoreline types the results of this study can also be used to identify suitable modern analogues for ancient systems which in turn can be used to extract data for better reservoir characterization

cryostratigraphy of late pleistocene syngenetic permafrost yedoma in northern alaska itkillik river exposure abstract extremely ice rich syngenetic permafrost or yedoma developed extensively under the cold climate of the pleistocene in unglaciated regions of eurasia and north america in alaska yedoma occurs in the arctic foothills the northern part of the seward peninsula and in interior alaska a remarkable 33 m high exposure along the lower itkillik river in northern alaska opened an opportunity to study the unmodified yedoma including stratigraphy particle size distribution soil carbon contents morphology and quantity of segregated wedge and thermokarst cave ice the exposed permafrost sequence comprised seven cryostratigraphic units which formed over a period from 48 000 to 5 000 14c yr bp including 1 active layer 2 intermediate layer of the upper permafrost 3 4 two yedoma silt units with different thicknesses of syngenetic ice wedges 5 buried peat layer 6 buried intermediate layer beneath the peat and 7 silt layer with short ice wedges this exposure is comparable to the well known mus khaya and duvanny yar yedoma exposures in russia based on our field observations literature sources and interpretation of satellite images and aerial photography we have developed a preliminary map of yedoma distribution in alaska

late holocene syngenetic ice wedge polygons development bylot island canadian arctic archipelago the initial configuration of the syngenetic ice wedge polygons that developed in the outwash plain of glacier c 79 after 6000 bp was modified by the accumulation of wind blown and organic sediments that began after 3670 110 bp the late holocene sedimentation led to an increase in the thermal contraction coefficient of the soil and the formation of third and fourth order contraction cracks partially explaining the current configuration of the polygonal network the upturning of the sedimentary strata bordering the ice wedges was associated with the summer thermal expansion and resulting internal creep of the soil the mean annual soil displacement coefficient was in the order of 2 5 2 7 10 5 c at the thousand year scale the late holocene sedimentary strata under the centre of the polygons were undisturbed which will make it possible to use this sedimentary record in further studies to attempt paleoenvironmental reconstructions from cores

case study of inhomogeneous cloud parameter retrieval from modis data 1 cloud parameter retrieval of inhomogeneous and fractional clouds is performed for a stratocumulus scene observed by modis at a solar zenith angle near 60 the method is based on the use of neural network technique with multispectral and multiscale information it allows to retrieve six cloud parameters i e pixel means and standard deviations of optical thickness and effective radius fractional cloud cover and cloud top temperature retrieved cloud optical thickness and effective radius are compared to those retrieved with a classical method based on the homogeneous cloud assumption subpixel fractional cloud cover and optical thickness inhomogeneity are compared with their estimates obtained from 250m pixel observations this comparison shows a fairly good agreement the cloud top temperature appears also retrieved quite suitably

the deep permafrost carbon pool of the yedoma region in siberia and alaska estimates for circumpolar permafrost organic carbon oc storage suggest that this pool contains twice the amount of current atmospheric carbon the yedoma region sequestered substantial quantities of oc and is unique because its deep oc was incorporated into permafrost during ice age conditions rapid inclusion of labile organic matter into permafrost halted decomposition and resulted in a deep long term sink we show that the deep frozen oc in the yedoma region consists of two distinct major sub reservoirs yedoma deposits late pleistocene ice and organic rich silty sediments and deposits formed in thaw lake basins generalized as thermokarst deposits we quantified the oc pool based on field data and extrapolation using geospatial datasets to 83 61 57 gt for yedoma deposits and to 128 99 96 gt for thermokarst deposits the total yedoma region 211 160 153 gt is a substantial amount of thaw vulnerable oc that must be accounted for in global models

massive ice of the tuktoyaktuk area western arctic coast canada the extensive coastal exposure of massive underground ice at peninsula point southwest of tuktoyaktuk northwest territories is believed to be intrasedimental ice the ice grew beneath a frozen d

conceptualizing delta forms and processes in arctic coastal environments climate warming in the arctic directly causes two opposite changes in arctic coastal systems increased melt water discharge through rivers induces extra influx of sediments and extended open water season increases wave impact which reworks and erodes the shores a shoreline change analysis along the southern coast of disko island in western greenland was conducted with aerial photographs and satellite images from 1964 1985 and 2012 the decadal morphologic evolution of this 85 km section showed that large parts of the coast had undergone very limited changes however two deltas were highly dynamic and popped up as hotspots the tuapaat delta and skansen delta showed large progradation rates 1 5 and 7 m yr and migration of the adjacent barriers and spits the dynamic behavior at the delta mouths was mainly caused by classic delta channel lobe switching at one delta tuapaat and by a breach of the fringing spit at the other delta skansen the longshore and cross shore transports are responsible for reworking the sediment with a result of migrating delta mouths and adjacent subaqueous mouth bars seaward progradation of the deltas is limited due to the steep nature of the bathymetry in disko bay finally a schematic conceptual overview of processes and associated morphological responses for deltas in arctic environments is presented including the climate drivers affecting delta evolution copyright 2016 john wiley sons ltd

comparison of sea ice extent and ice edge location estimates from passive microwave and enhanced resolution scatterometer data passive microwave sea ice concentration fields provide some of the longest running and most consistent records of changes in sea ice scatterometry based sea ice fields are more recently developed data products but now they provide a record of ice conditions spanning several years resolution enhancement techniques applied to scatterometer fields provide much higher effective resolutions 10km than are available from standard scatterometer and passive microwave fields 25 50km here we examine ice extent fields from both sources and find that there is general agreement between scatterometer data and passive microwave fields though scatterometer estimates yield substantially lower ice extents during winter comparisons with ice edge locations estimated from avhrr imagery indicate that enhanced scatterometer data can sometimes provide an improved edge location but there is substantial variation in the results depending on the local conditions a blended product using both scatterometer and passive microwave data could yield improved results

pan arctic ice wedge degradation in warming permafrost and its influence on tundra hydrology ice wedges are common features of the subsurface in permafrost regions they develop by repeated frost cracking and ice vein growth over hundreds to thousands of years ice wedge formation causes the archetypal polygonal patterns seen in tundra across the arctic landscape here we use field and remote sensing observations to document polygon succession due to ice wedge degradation and trough development in ten arctic localities over sub decadal timescales initial thaw drains polygon centres and forms disconnected troughs that hold isolated ponds continued ice wedge melting leads to increased trough connectivity and an overall draining of the landscape we find that melting at the tops of ice wedges over recent decades and subsequent decimetre scale ground subsidence is a widespread arctic phenomenon although permafrost temperatures have been increasing gradually we find that ice wedge degradation is occurring on sub decadal timescales our hydrological model simulations show that advanced ice wedge degradation can significantly alter the water balance of lowland tundra by reducing inundation and increasing runoff in particular due to changes in snow distribution as troughs form we predict that ice wedge degradation and the hydrological changes associated with the resulting differential ground subsidence will expand and amplify in rapidly warming permafrost regions the polygonal patterns in permafrost regions are caused by the formation of ice wedges observations of polygon evolution reveal that rapid ice wedge melting has occurred across the arctic since 1950 altering tundra hydrology

sea ice thickness variability in the chukchi sea spring and summer 2002 2004 abstract measurements of sea ice thickness were obtained from drill holes an ice based electromagnetic induction instrument iem and a ship borne electromagnetic induction instrument sem during the early melt season in the southern chukchi sea in 2002 and 2004 and in late summer 2003 at the time of minimum ice extent in the northern chukchi sea an ice roughness criterion was applied to distinguish between level and rough or ridged ice ice thickness modes in the probability density functions pdfs derived from drill hole and iem measurements agreed well with modes at 1 5 1 6 and 1 8 1 9 m for all data from level ice the pdfs derived from sem measurements show that the primary modes are at 0 1 and 1 1 m in 2003 and 0 7 m in 2004 in 2002 and 2004 significant fractions between one third and one half of level ice were found to consist of rafted ice segments snow depth varied significantly between years with 2004 data showing more than half the snow cover on level ice to be at or below 0 05 m depth in late spring ice growth simulations and examination of ice drift and deformation history indicate that impacts of atmospheric and oceanic warming on level ice thickness in the region over the past few decades are masked to a large extent by variability in snow depth and the contribution of deformation processes in comparison with submarine sonar ice thickness data from previous decades a reduction in ice thickness by about 0 5 1 m is in part explained by the replacement of multi year with first year ice over the chukchi and beaufort shelves

inference of marine stratus cloud optical depths from satellite measurements does 1d theory apply abstract the validity of plane parallel 1d radiative transfer theory for cloudy atmospheres is examined by directly comparing calculated and observed visible reflectances for one month of global area coverage advanced very high resolution radiometer satellite observations of marine stratus cloud layers off the coasts of california peru and angola marine stratus are an excellent testbed as they arguably are the closest to plane parallel found in nature optical depths in a 1d radiative transfer model are adjusted so that 1d model reflectances match those observed at nadir on a pixel by pixel basis the 1d cloud optical depth distributions are then used in the plane parallel model to generate reflectance distributions for different sun earth satellite viewing geometries these reflectance distributions are directly compared with the observations separate analyses are performed for overcast and broken cloud layers as identified by the spatial coherence method when 1d reflectances are directly compare

the potential for improved boundary layer cloud optical depth retrievals from the multiple directions of misr abstract the multiangle imaging spectroradiometer misr views the earth with nine cameras ranging from a 70 zenith angle viewing forward through nadir to 70 viewing aft misr does not have an operational cloud optical depth retrieval algorithm but previous research has hinted that solar reflection measured in multiple directions might improve cloud optical depth retrievals this study explores the optical depth information content of misr s multiple angles using a retrieval simulation approach hundreds of realistic boundary layer cloud fields are generated with large eddy simulation les models for stratocumulus small trade cumulus and land surface forced fair weather cumulus reflectances in misr directions are computed with three dimensional radiative transfer from the les cloud fields over an ocean surface and averaged to misr resolution and sampled at misr 275 m pixel spacing neural networks are trained to retrieve the mean and standard deviation of optical depth over different size pixel pa

theories and applicability of grain size piezometers the role of dynamic recrystallization mechanisms abstract the average grain size d arising from dynamic recrystallization drx is often used as an indicator of flow stress however a theoretical basis for the scaling relation between d and has yet to be well established in this paper theories for the development of recrystallized grain size are reviewed and their applicability is examined special attention is paid to the dependence of the d relation on drx mechanisms steady state drx is classified into discontinuous drx with bulging blg nucleation grain boundary migration gbm and continuous drx with subgrain rotation sgr nucleation gbm the nucleation and growth model derived from derby ashby theory describes the former case whereas that derived from shimizu theory applies to the latter a static energy balance model derived from twiss theory is applicable to subgrain size but not to recrystallized grain size the lower limit of grain size is possibly constrained by a change in deformation mechanism from dislocation creep to diffusion creep because deformation induced grain size reduction ceases in the diffusion creep field scaling relations determined in the laboratory support the shimizu model in the case of sgr gbm the theoretical piezometer calibrated for quartz suggests significant temperature effects under low temperature metamorphic conditions

permafrost of the east siberian arctic shelf and coastal lowlands in the past decade within the framework of joint russian german marine and terrestrial studies on the arctic shelf new siberian islands and coastal lowlands of the laptev and east siberian seas fundamentally new data have been obtained on terrestrial and offshore permafrost in this area field and laboratory investigations supplemented with numerical modeling and generalization of the results of numerous geological surveys exploratory works and scientific researches performed in previous years have made it possible to revise existing knowledge about the distribution thickness physical state and history of development of terrestrial and offshore permafrost in the east siberian part of the arctic the main results of these studies and their interpretation are discussed in this paper

wind and wave climate in the arctic ocean as observed by altimeters abstracttwenty years 1996 2015 of satellite observations were used to study the climatology and trends of oceanic winds and waves in the arctic ocean in the summer season august september the atlantic side seas exposed to the open ocean host more energetic waves than those on the pacific side trend analysis shows a clear spatial regional and temporal interannual variability in wave height and wind speed waves in the chukchi sea beaufort sea near the northern alaska and laptev sea have been increasing at a rate of 0 1 0 3 m decade 1 found to be statistically significant at the 90 level the trend of waves in the greenland and barents seas on the contrary is weak and not statistically significant in the barents and kara seas winds and waves initially increased between 1996 and 2006 and later decreased large scale atmospheric circulations such as the arctic oscillation and arctic dipole anomaly have a clear impact on the variation of winds and waves in the atlantic sector comparison

modeling erosion of ice rich permafrost bluffs along the alaskan beaufort sea coast the arctic climate is changing inducing accelerating retreat of ice rich permafrost coastal bluffs along alaska s beaufort sea coast erosion rates have increased roughly threefold from 6 8 to 19 m yr 1 since 1955 while the sea ice free season has increased roughly twofold from 45 to 100 days since 1979 we develop a numerical model of bluff retreat to assess the relative roles of the length of sea ice free season sea level water temperature nearshore wavefield and permafrost temperature in controlling erosion rates in this setting the model captures the processes of erosion observed in short term monitoring experiments along the beaufort sea coast including evolution of melt notches topple of ice wedge bounded blocks and degradation of these blocks model results agree with time lapse imagery of bluff evolution and time series of ocean based instrumentation erosion is highly episodic with 40 of erosion is accomplished during less than 5 of the sea ice free season among the formulations of the submarine erosion rate we assessed we advocate those that employ both water temperature and nearshore wavefield as high water levels are a prerequisite for erosion any future changes that increase the frequency with which water levels exceed the base of the bluffs will increase rates of coastal erosion the certain increases in sea level and potential changes in storminess will both contribute to this effect as water temperature also influences erosion rates any further expansion of the sea ice free season into the midsummer period of greatest insolation is likely to result in an additional increase in coastal retreat rates

recent changes in arctic sea ice melt onset freezeup and melt season length 1 in order to explore changes and trends in the timing of arctic sea ice melt onset and freezeup and therefore melt season length we developed a method that obtains this information directly from satellite passive microwave data creating a consistent data set from 1979 through present we furthermore distinguish between early melt the first day of the year when melt is detected and the first day of continuous melt a similar distinction is made for the freezeup using this method we analyze trends in melt onset and freezeup for 10 different arctic regions in all regions except for the sea of okhotsk which shows a very slight and statistically insignificant positive trend 0 4 d decade 1 trends in melt onset are negative i e toward earlier melt the trends range from 1 0 d decade 1 for the bering sea to 7 3 d decade 1 for the east greenland sea except for the sea of okhotsk all areas also show a trend toward later autumn freeze onset the chukchi beaufort seas and laptev east siberian seas observe the strongest trends with 7 d decade 1 for the entire arctic the melt season length has increased by about 20 days over the last 30 years largest trends of over 10 d decade 1 are seen for hudson bay the east greenland sea the laptev east siberian seas and the chukchi beaufort seas those trends are statistically significant at the 99 level

arctic coastal retreat through block failure this study investigates the mechanics of block failure in frozen bluffs underlain by permafrost along arctic coasts different block failure modes with and without thermoerosional niches and ice we

fractal analysis of experimentally dynamically recrystallized quartz grains and its possible application as a strain rate meter abstract fractal analysis of experimentally recrystallized quartz grain shapes has been employed to study the relationship between the microstructures of dynamically recrystallized quartz grains and the deformation conditions such as temperature and strain rate samples used are quartz aggregates deformed under high temperature 800 c 900 c and 1000 c and high confining pressure 400 mpa the fractal dimension is useful to quantify the shapes of the recrystallized quartz grain boundaries at each set of conditions the fractal dimension is determined as the slope of a log log plot of the length of the grain boundaries perimeters against the grain size calculated as diameters of circles having the same areas as the actual grains the results show that the shapes of grains are self similar and the fractal dimensions d change systematically being dependent on both temperature and strain rate the skew of the grain boundary defined as d 1 and showing the degree of the serration may be proportional to the logarithm of the zener hollomon parameter that includes a component of the arrhenius term this relation indicates that strain rate can be calculated from the fractal dimension and the temperature it may therefore provide a new paleo strain rate meter for plastically deformed natural rocks

patterns and rates of riverbank erosion involving ice rich permafrost yedoma in northern alaska abstract yedoma a suite of syngenetically frozen silty ice and organic rich deposits with large ice wedges that accumulated during the late pleistocene is vulnerable to thermal degradation and erosion because of the extremely high ice contents this degradation can result in significant surface subsidence and retreat of coastal bluffs and riverbanks with large consequences to landscape evolution infrastructure damage and water quality we used remote sensing and field observations to assess patterns and rates of riverbank erosion at a 35 m high active yedoma bluff along the itkillik river in northern alaska the total volumetric ground ice content including wedge segregated and pore ice was estimated to be 86 the process of riverbank erosion and stabilization include three main stages typical of the areas with ice rich permafrost 1 thermal erosion combined with thermal denudation 2 thermal denudation and 3 slope stabilization active riverbank erosion at the main study site started in july 1995 when the itkillik river changed its channel the total retreat of the riverbank during 1995 2010 within different segments of the bluff varied from 180 to 280 m the average retreat rate for the most actively eroded part of the riverbank was almost 19 m y from august 2007 to august 2011 the total retreat varied from 10 to almost 100 m the average retreat rate for the whole 680 m long bluff was 11 m y for the most actively eroded central part of the bluff 150 m long it was 20 m y ranging from 16 to 24 m y more than 180 000 m3 of ground ice and organic rich frozen soil or almost 70 000 metric tons t of soil solids including 880 t of organic carbon were transported to the river from the retreating bank annually this study reports the highest long term rates of riverbank erosion ever observed in permafrost regions of eurasia and north america

fluvial thermal erosion investigations along a rapidly eroding river bank application to the lena river central siberia in central yakutia frozen river banks are affected by a combination of thermal and mechanical erosion exceptional bank retreat of up to 40 m per year is observed this results from ground thawing produced by heat transfer from the ow of water through the frozen ground followed by mechanical transport of the thawed sediments a one dimensional model is proposed to estimate the thermal erosion ef ciency a test of this model is a comparison of results obtained from experiments carried out in a cold room a hydraulic channel allows measurements of the thaw front propagation as well as the thermal erosion rate in simulated ground ice that is subjected to warm water ow various laboratory simulations demonstrate the validity of the mathematical model for the range of laboratory conditions a hierarchy of parameters reynolds number water and ground ice temperatures is proposed to explain the present ef ciency of thermal erosion along the siberian rivers from the characteristics of the lena river geometry temperature and discharge during the ood season the erosion of banks with different ice content predicted by the model is in agreement with eld observations copyright 2003 john wiley sons ltd

coastal changes in the arctic the arctic s climate system is changing air temperatures major river discharges and open water season length have increased and storm intensities and tracks are changing thirteen quantitative studies of the rates of coastline position change throughout the arctic show that recently observed changes have not increased coastal erosion rates which currently range between 0 and 2 m yr when averaged for the arctic shelf seas current data is probably insufficient both spatially and temporally however to capture change at decadal to sub decadal time scales in this context we describe the current understanding of arctic coastal geomorphodynamics with an emphasis on erosional regimes of coasts with ice rich sedimentary deposits in the laptev east siberian and beaufort seas where local coastal erosion can reach 30 m yr we also examine coasts with lithified rocky substrates where geomorphodynamics are intensified by rapid glacial retreat coastlines of svalbard greenland and the canadian archipelago are less frequently studied than ice rich continental coasts of north america and siberia and studies often focus on coastal sections composed of unlithified material as air temperature and sea ice duration and extent change longer thaw and wave seasons will intensify coastal dynamics in the arctic

multi scale site evaluation of a relict active layer detachment in a high arctic landscape abstract investigations into the susceptibility of permafrost landscapes response to thermokarst can be performed using various approaches depending on the scale of investigation in many cases point based field measurements are extrapolated to larger scales and vice versa the integration of scales often requires some form of ground control in addition to remote sensing surveys which are at times exclusively conducted as upscaling from discrete field measurements can provide spatial coverage and landscape scale significance downscaling from remote sensing can offer insight into processes and serve as calibration or verification here we present a multiple scale evaluation of an area initially interpreted as a relict active layer detachment slide before 1950 on melville island in the high arctic where differential interferometric synthetic aperture radar dinsar showed subsidence between 2013 and 2015 ground based cryostratigraphy measurements were combined with ground penetrating radar gpr to investigate permafrost ice content the results indicate greater subsidence within the relict active layer detachment as detected by dinsar gpr surveys and permafrost coring indicated the presence of an ice rich or massive ice layer near the base of the active layer in this area in addition cryostratigraphic evidences of thaw unconformity and of massive ice depth helped validate the interpretations of the geomorphology in the active layer detachment this combination of methods indicated a localized and inherited landform subsidence association which brought further insight into the interpretation of dinsar subsidence data the framework presented in this study demonstrates the importance of site specific investigations of thermokarst signal in order to understand the processes behind the remote sensing results

neural network retrieval of cloud parameters of inhomogeneous clouds from multispectral and multiscale radiance data feasibility study 1 in this paper we investigated the feasibility of retrieving cloud parameters of inhomogeneous and fractional clouds from simulated multispectral and multiscale radiometric data by using mapping neural networks a radiometric database prepared for neural network training consists of area averaged radiance data for two pixel scales i e 1 km 1 km and 0 25 km 0 25 km pixels respectively the cloud parameter retrieval assumes a vertically uniform inhomogeneous and fractional cloud defined with 6 parameters i e the mean and standard deviation of optical thickness the mean and standard deviation of effective radius the fractional cloud cover and the cloud top temperature all defined at a scale of cloud parameter retrieval the retrieval procedure comprises two separate steps the first one is relative to the angular interpolation and correction of radiance data surface reflection and thermal emission contribution the second step concerns the cloud parameter retrieval as such from interpolated and corrected radiance data the input vector to the retrieval mnns consists of 8 radiometric data in addition to a number of necessary ancillary data such as surface temperature and ground albedo the 8 radiometric data are 5 area averaged radiances over 1 km 1 km pixel and 3 standard deviations of radiance over 1 km 1 km pixel estimated from 0 25 km 0 25 km pixel radiances after evaluating the performance of the neural networks trained for each step we tested the whole retrieval procedure for three types of inhomogeneous and fractional clouds flat top bounded cascade clouds and flat top and non flat top gaussian process clouds all the cloud parameters of these clouds can be retrieved with reasonable accuracy in spite of the fact that the mean and standard deviation of optical thickness of non flat top clouds exhibit some dispersion the inclusion of 0 25 km 0 25 km pixel radiance data as input vector components improved significantly the performance of the cloud parameter retrieval finally we analyzed the consequences of some simplifying assumptions on the retrieved cloud parameters and discussed the perspectives of the cloud parameter retrieval based on the neural networks

different sources and degradation state of dissolved particulate and sedimentary organic matter along the eurasian arctic coastal margin the amount of organic carbon oc present in siberian arctic permafrost soils is estimated at twice the amount of carbon currently in the atmosphere the shelf seas of the arctic ocean receive large amounts of this terrestrial oc from eurasian arctic rivers and from coastal erosion degradation of this land derived material in the sea would result in the production of dissolved carbon dioxide and may then add to the atmospheric carbon dioxide reservoir observations from the siberian arctic suggest that transfer of carbon from land to the marine environment is accelerating however it is not clear how much of the transported oc is degraded and oxidized nor how much is removed from the active carbon cycle by burial in marine sediment using bulk geochemical parameters total oc d13c and d14c isotope composition and specific molecular markers of plant wax lipids and lignin phenols the abundance and composition of oc was determined in both dissolved and particulate carrier phases the colloidal oc coc part of the dissolved oc particulate oc poc and sedimentary oc soc statistical modelling was used to quantify the relative contribution of oc sources to these phases terrestrial oc is derived from the seasonally thawing top layer of permafrost soil topsoil oc and frozen oc derived from beneath the active layer eroded at the coast commonly identified as yedoma ice complex deposit oc yedoma icd oc these carbon pools are transported differently in the aquatic conduits topsoil oc was found in young doc and poc in the river water and the shelf water column suggesting long distance transport of this fraction the yedoma icd oc was found as old particulate oc that settles out rapidly to the underlying sediment and is laterally transported across the shelf likely dispersed by bottom nepheloid layer transport or via ice rafting these two modes of oc transport resulted in different degradation states of topsoil oc and yedoma icd oc terrestrial cuo oxidation derived biomarkers indicated a highly degraded component in the coc in contrast the terrestrial component of the soc was much less degraded in line with earlier suggestions the mineral component in yedoma icd functions as weight and surface protection of the associated oc which led to burial in the sediment and limited oc degradation the degradability of the terrestrial oc in shelf sediment was also addressed in direct incubation studies molecular markers indicate marine oc from primary production was more readily degraded than terrestrial oc degradation was also faster in sediment from the east siberian sea where the marine contribution was higher compared to the laptev sea although terrestrial carbon in the sediment was degraded slower the terrestrial component also contributed to carbon dioxide formation in the incubations of marine sediment these results contribute to our understanding of the marine fate of land derived oc from the siberian arctic the mobilization of topsoil oc is expected to grow in magnitude with climate warming and associated active layer deepening this translocated topsoil oc component was found to be highly degraded which suggests degradation during transport and a possible contribution to atmospheric carbon dioxide similarly the yedoma icd oc and or old mineral soil carbon may become a stronger source with accelerated warming but slow degradation may limit its impact on active carbon cycling in the siberian shelf seas

delta progradation in greenland driven by increasing glacial mass loss climate change has the potential to erode coastlines but a rediscovered archive of aerial photographs from the second world war shows that in southern greenland deltas have recently extended seaward climate change has the potential to erode coastlines for example as a result of increased wave activity but the net effect depends on the balance between creative and destructive forces mette bendixen and colleagues show that deltas in southwestern greenland have grown over the past few decades following a period of stability in the mid twentieth century the delta expansions occurred during periods of reduced sea ice and increased melt from the greenland ice sheet although many coastlines remain under threat these findings reveal the intimate interactions that arise in a warming climate a loss of ice seems to lead to increased sediment delivery which has resulted in the expansion rather than degradation of greenland s deltas climate changes are pronounced in arctic regions and increase the vulnerability of the arctic coastal zone1 for example increases in melting of the greenland ice sheet and reductions in sea ice and permafrost distribution are likely to alter coastal morphodynamics the deltas of greenland are largely unaffected by human activity but increased freshwater runoff and sediment fluxes may increase the size of the deltas whereas increased wave activity in ice free periods could reduce their size with the net impact being unclear until now here we show that southwestern greenland deltas were largely stable from the 1940s to 1980s but prograded that is sediment deposition extended the delta into the sea in a warming arctic from the 1980s to 2010s our results are based on the areal changes of 121 deltas since the 1940s assessed using newly discovered aerial photographs and remotely sensed imagery we find that delta progradation was driven by high freshwater runoff from the greenland ice sheet coinciding with periods of open water progradation was controlled by the local initial environmental conditions that is accumulated air temperatures above 0 c per year freshwater runoff and sea ice in the 1980s rather than by local changes in these conditions from the 1980s to 2010s at each delta this is in contrast to a dominantly eroding trend of arctic sedimentary coasts along the coastal plains of alaska2 siberia3 and western canada4 and to the spatially variable patterns of erosion and accretion along the large deltas of the main rivers in the arctic5 6 7 our results improve the understanding of arctic coastal evolution in a changing climate and reveal the impacts on coastal areas of increasing ice mass loss and the associated freshwater runoff and lengthening of open water periods

c axis fabrics and microstructures in quartz schist from the sambagawa metamorphic belt central shikoku japan an integrated study on c axis fabric and microstructure of plastically deformed and dynamically recrystallized quartz in quartz schist from the sambagawa metamorphic belt in central shikoku japan has revealed a correlation between c axis fabrics and three dimensional grain shape recrystallized quartz grains with prolate k 1 oblate 0 2 k 1 and uniaxially oblate k 0 2 shapes exhibit c axis fabric patterns of cleft girdles around the principal finite elongation direction x type i crossed girdles and small circle girdles around the principal finite shortening direction z respectively fabric intensity calculated from the eigenvalues of orientation tensors of the c axis fabrics increases with increasing magnitude of the apparent finite strain inferred from the shape of recrystallized quartz grains these results indicate that the development of recrystallized grain shape as well as c axis fabrics is primarily controlled by finite strain during progressive deformation however the finite strain estimated from three dimensional grain shape is systematically deviated toward the flattening field compared to that estimated from the c axis fabrics we investigated several possible causes for the discrepancy and propose that a scenario of coupled deformation and dynamic recrystallization in the quartz schist is responsible for the formation of these microstructures

soil carbon and material fluxes across the eroding alaska beaufort sea coastline 1 carbon nitrogen and material fluxes were quantified at 48 sampling locations along the 1957 km coastline of the beaufort sea alaska landform characteristics soil stratigraphy cryogenic features and ice contents were determined for each site erosion rates for the sites were quantified using satellite images and aerial photos and the rates averaged across the coastline increased from 0 6 m yr 1 during circa 1950 1980 to 1 2 m yr 1 during circa 1980 2000 soils were highly cryoturbated and organic carbon oc stores ranged from 13 to 162 kg oc m 2 in banks above sea level and averaged 63 kg oc m 2 over the entire coastline long term 1950 2000 annual lateral fluxes due to erosion were estimated at 153 gg oc 7762 mg total nitrogen 2106 tg solids and 2762 tg water total land area loss along the alaska beaufort sea coastline was estimated at 203 ha yr 1 we found coastal erosion rates bank heights soil properties and material stores and fluxes to be extremely variable among sampling sites in comparing two classification systems used to classifying coastline types from an oceanographic coastal morphology perspective and geomorphic units from a terrestrial soils perspective we found both systems were effective at differentiating significant differences among classes for most material stores but the coastline classification did not find significant differences in erosion rates because it lacked differentiation of soil texture

attenuation of ocean surface waves in pancake and frazil sea ice along the coast of the chukchi sea alaskan arctic coastlines are protected seasonally from ocean waves by presence of coastal and shorefast sea ice this study presents field observations collected during the autumn freeze up of 201

the fox permafrost tunnel a late quaternary geologic record in central alaska the fox permafrost tunnel which penetrates 110 m into frozen sediments of gold stream valley provides a continuous exposure of fossiliferous silt and alluvium above schistose bedrock deposition of fluvial gravel was followed by a long interval of loess accretion and permafrost aggradation that was punctuated by episodes of thaw and of gullying and redeposition of silt imbricated sandy gravel above the bedrock contains lenses of finer alluvium that contain wood fragments and some rooted stumps radiocarbon dates indicate that the gravel is older than 40 ka but absence of mature soil and weathering profiles at its upper contact indicates that fluvial activity must have continued until shortly before loess accretion began at the tunnel site silt is the most widespread depositional unit in the tunnel this deposit is of eolian origin loess but some has been redeposited by slope processes the silt units contain abundant ground ice as pore filings lenses wedges and buried pond ice loess accretion was interrupted by a period when little loess accumulated and when large ice wedges formed in the lower loess unit and subsequently were truncated by thaw loess began forming sometime before 40 ka and was rapidly accreting by 39 ka under xeric conditions with open vegetation a sharply decreased rate of loess accretion associated with local erosion and thaw between about 36 and 30 ka is marked by anomalous cation concentration values lenses of buried sod fossils indicative of moist to wet substrates and truncated ice wedges beneath small frozen ponds or streamlets that occupied ice wedge troughs a later episode of rapid loess influx under drier conditions began after 30 ka and coincided with glacial advances of late wisconsin age in the adjoining alaska range large ice wedges also formed in the upper loess unit but only their bases are exposed in the tunnel and their history of development is uncertain fanlike deposits of poorly sorted debris near the tunnel portal formed between about 12 5 and 11 ka during deep erosion of loess slopes under moister conditions the deposits locally form two subunits the younger over whelmed a stand of tall willows on the floor of goldstream valley between about 11 3 and 11 1 ka the older may have formed about 1 000 yr earlier stratigraphic records elsewhere in central alaska indicate variable middle wisconsin environments followed by colder and drier conditions that began between 30 and 25 ka and persisted until perhaps 12 5 ka widespread loess erosion and redeposition subsequently occurred under moister and probably warmer conditions renewed early holocene loess deposition may have been widespread but its exact environmental controls are uncertain our data challenge three generally accepted concepts of late quaternary periglacial processes in central alaska we contend that 1 many ice wedge systems may have formed under interstadial conditions rather than full glacial conditions 2 episodes of rapid loess influx may have been partly out of phase with episodes of glacier expansion and 3 redeposition of loess by solifluction sheetwash and gully formation may have been episodic and required conditions moister than those under which the loess initially accreted

microboudin structures of piemontite along the sambagawa metamorphic belt japan implications for lateral variation of differential stress during regional metamorphism evidence is presented of a lateral variation in differential stress during metamorphism along a regional metamorphic belt on the basis of the proportion of microboudinaged piemontite grains p in a quartz matrix in metacherts it is proposed that p is a practical indicator of relative differential stress analysis of 123 metacherts from the 800 km long sambagawa metamorphic belt japan reveals that p values range from 0 01 to 0 7 in this region most samples from wakayama in the mid belt area have p values of 0 4 0 6 whereas those from western shikoku have p values of 0 1 this difference cannot be explained by variations in metamorphic temperature and is instead attributed to a regional lateral variation in differential stress during metamorphism

fluvial sediment flux to the arctic ocean the paper presents an overview of recent publications on the fluvial suspended sediment flux to the arctic ocean the total suspended matter exported from the russian territory is 102 10 6 t year and from the canadian arctic is 125 10 6 t year the total suspended matter tsm flux to the arctic 227 10 6 t year is very low only about 1 of the global flux mean concentrations of suspended matter and specific sediment discharge are approximately one order of magnitude lower than the global concentration an analysis of the trends in the sediment loads based on records of up to 62 years in length shows decreases yenisey increases kolyma and stability ob among the reasons for the very low concentrations and fluxes of suspended sediment in the arctic rivers are thin weathering crusts on the arctic watersheds low precipitation extensive permafrost low temperatures for most of the year large areas of swamps and lakes and a low level of human activity a stochastic sediment transport model by morehead et al morehead m d syvitski j p hutton e w peckham s d 2003 modeling the temporal variability in the flux of sediment from ungauged river basins glob planet change 39 95 110 is applied to the arctic rivers to estimate the sediment load increase should the surface temperature of the drainage basin increase for every 2 c of warming a 30 increase in the sediment flux could result and for each 20 increase in water discharge a 10 increase in sediment load could follow based on this model an increase of the sediment flux of six largest arctic rivers yenisey lena ob pechora kolyma and severnaya dvina is predicted to range from 30 to 122 by 2100

on the nature and origin of muck deposits in the klondike area yukon territory organic rich muck deposits which blanket auriferous gravels in the klondike area yukon territory comprise two principal stratigraphic units i a silty late pleistocene deposit and ii holocene organics lying unconformably on the silt the deposits are found predominantly in valley bottoms and if undisturbed are normally perennially frozen field and laboratory investigations of particle size mineralogy and morphology as well as organic matter and sedimentary structures indicate that the silt is both primary massive and redeposited bedded loess by weight 87 medium and coarse silt and fine sand radiocarbon dates indicate that the loess was deposited during late wisconsinan mcconnell glaciation beginning after 27 000 14c years bp the loess was likely derived from the floodplain of the yukon river during periods of low flow turf in growth position and organic matter in the silt similar to that of loessal grasslands near kluane lake suggest a grassland environment for the area during

influence of ground ice and permafrost on coastal evolution richards island beaufort sea coast n w t a long term sediment budget 1947 1985 for northern richards island shows that when ground ice and offshore erosion are accounted for there is a near balance between headland erosion and coastal deposition excess ice constitutes about 20 of the total volume of eroded material from the headlands with massive ground ice contributing nearly 9 and segregated ice lenses and ice wedges making up the remainder coastal response to major storms in 1987 and 1993 suggests that erosion is episodic with short periods of intense disruption followed by readjustment of cliff profiles processes characteristic of this environment include mechanical erosion of ice bonded sediments creating unstable erosional niches mechanical failure of niches along ice wedge planes and longer term thermal erosion of ice bonded sediments where ice contents are high localized thaw slumps initiated by coastal erosion may retreat at rates substantially higher than those observed at other sections of the coast cliff top retreat r

observed changes in hurricane driven waves explain the dynamics of modern cuspate shorelines 1 a comparison between historical and recent shoreline change rates on the u s east coast based on observed shoreline positions from the last century and a half shows that emergent large scale cuspate coastline features are changing shape becoming more asymmetrical this change in coastline shape arises from spatial shifts in the location of erosion and accretion zones using a numerical model of coastline change forced by wave driven alongshore sediment flux we show that a previously identified shift in hurricane generated wave climate explains the patterns of coastline change we observe our results reveal a previously unrecognized type of large scale chronic landscape response to changing forcing though demonstrated here for a cuspate coastline similar large scale morphological adjustments are likely to occur along coastlines of varying morphology in the future as global warming continues along with the associated intensification of storms our approach allows for constraining and predicting future shifts in coastline shape

sea ice loss enhances wave action at the arctic coast 1 erosion rates of permafrost coasts along the beaufort sea accelerated over the past 50 years synchronously with arctic wide declines in sea ice extent suggesting a causal relationship between the two a fetch limited wave model driven by sea ice position and local wind data from northern alaska indicates that the exposure of permafrost bluffs to seawater increased by a factor of 2 5 during 1979 2009 the duration of the open water season expanded from 45 days to 95 days open water expanded more rapidly toward the fall 0 92 day yr 1 when sea surface temperatures are cooler than into the mid summer 0 71 days yr 1 time lapse imagery demonstrates the relatively efficient erosive action of a single storm in august sea surface temperatures have already decreased significantly by fall reducing the potential impact of thermal erosion due to fall season storm waves

the transition from brittle to ductile deformation in the sambagawa metamorphic belt japan the dominant deformation mechanism during the sambagawa metamorphism changes from brittle to ductile with increasing metamorphic temperature the magnitude of plastic strains inferred from the shapes of deformed radiolaria in metachert increases sharply across the boundary between the epidote pumpellyite actinolite zone and the epidote actinolite zone the synmetamorphic crack density of metachert is an indicator of the contemporaneous brittle strain of rocks and it decreases sharply as the grade reaches the epidote actinolite zone hence the ratio of the ductile strain to the brittle strain of metachert decreases rapidly across the transition to the epidote actinolite zone of the sambagawa metamorphic belt the sharp change of the ductile strain magnitude also takes place at the epidote actinolite grade in the shimanto metamorphic belt of japan an example of the intermediate pressure facies series of metamorphism it is concluded that the transition from brittle to ductile deformation takes place at about 300 400 c and is independent of pressure of metamorphism

deep yedoma permafrost a synthesis of depositional characteristics and carbon vulnerability abstract permafrost is a distinct feature of the terrestrial arctic and is vulnerable to climate warming permafrost degrades in different ways including deepening of a seasonally unfrozen surface and localized but rapid development of deep thaw features pleistocene ice rich permafrost with syngenetic ice wedges termed yedoma deposits are widespread in siberia alaska and yukon canada and may be especially prone to rapid thaw processes freeze locked organic matter in such deposits can be re mobilized on short time scales and contribute to a carbon cycle climate feedback here we synthesize the characteristics and vulnerability of yedoma deposits by synthesizing studies on the yedoma origin and the associated organic carbon pool we suggest that yedoma deposits accumulated under periglacial weathering transport and deposition dynamics in non glaciated regions during the late pleistocene until the beginning of late glacial warming the deposits formed due to a combination of aeolian colluvial nival and alluvial deposition and simultaneous ground ice accumulation we found up to 130 gigatons organic carbon in yedoma parts of which are well preserved and available for fast decomposition after thaw based on incubation experiments up to 10 of the yedoma carbon is considered especially decomposable and may be released upon thaw the substantial amount of ground ice in yedoma makes it highly vulnerable to disturbances such as thermokarst and thermo erosion processes mobilization of permafrost carbon is expected to increase under future climate warming our synthesis results underline the need of accounting for yedoma carbon stocks in next generation earth system models for a more complete representation of the permafrost carbon feedback

temporal and spatial variability in coastline response to declining sea ice in northwest alaska abstract arctic sea ice is declining in extent leaving coastlines exposed to more storm wave events there is an urgent need to understand how these changes affect geomorphic processes along arctic coasts here we describe spatial and temporal patterns of shoreline changes along two geomorphologically distinct storm wave dominated reaches of the chukchi sea coastline over the last 64 years one study area encompasses the west to southwest facing coarse clastic shoreline and ice rich bluffs of cape krusenstern cakr the other covers the north facing sandy shorelines on barrier islands ice rich bluffs and the cape espenberg spit in the bering land bridge national park bela both study areas lie within the zone of continuous permafrost which exists both on and offshore and outcrops as ice rich bluffs along the bela coast we mapped changes in coastal geomorphology over three observation periods 1950 1980 1980 2003 and 2003 2014 using aerial and satellite imagery we then compared these geomorphic changes to changes in sea ice coverage which declined 10 days per decade between 1979 and 2016 in the southern chukchi sea changes in coastal geomorphology in both bela and cakr exhibited high spatial variability over the study period between 2003 and 2014 shorelines of barrier islands in bela exhibited the highest mean rates of change 1 5 m yr 1 while coarse clastic barrier beaches in cakr showed only minimal change overall shorelines in both bela and cakr became more dynamic increasing erosion or increasing accumulation after ca 2003 with spatial variability in shoreline changes roughly doubling between the first period of observation 1950 1980 and the last 2003 2014 this increase in coastal dynamism may signal a transitional period leading to new state of geomorphic equilibria along these ice affected coastlines

the quartzite problem revisited abstract a review of past terminology and previous petrological studies suggests that quartzite should be classified descriptively as both a sedimentary and a metamorphic rock quartzite is identified in the field as a quartz rich rock exclusive of chert and vein quartz that is exceptionally hard and when broken by a rock hammer fractures irregularly through both grains and cement where present to form an irregular or conchoidal fracture surface quartzite is differentiated from quartzose sandstone arenite which is softer and fractures around individual grains and from chert and vein quartz by a bright vitreous luster quartzite is classified further on the basis of microscopic features into orthoquartzite and metaquartzite by the presence of clastic and metamorphic microtextures respectively low grade medium grade and high grade subtypes of metaquartzite are differentiated by mortar foam and porphyroblastic microtextures respectively composition is not used as a criterion for classifica

the role of intragranular fracturing on grain size reduction in feldspar during mylonitization abstract measurements of the size shape and orientation of k feldspar and plagioclase grains within a granitic mylonite in the kashio shear zone central honshu japan revealed that grain size was the most effective parameter controlling development of intragranular fracturing during mylonitization intragranular fractures are dominantly located near the centre of each grain and form preferentially along the 001 cleavage the grain size distribution of both feldspars is log normal with an average of 760 m the proportion of fractured grains expands dramatically to 100 as the grain size increases whereas few feldspar grains smaller than 300 m have been fractured during the mylonitization indicating that the fractures have preferentially developed in coarser grains furthermore the shape and shape preferred orientation of feldspar grains also affects the development of fractures the proportion of fractured grains not only increases up to 20 towards the extension direction but also rises slightly as the aspect ratio of feldspar grains increases it is therefore suggested that feldspar grains lying perpendicular to the extension direction may resist fracturing regardless of grain size unless their shape preferred orientations became sub parallel to the extension direction due to rotation or modification of their grain shapes during mylonitization the development of intragranular fractures could be statistically explained in terms of a fibre loading model although individual fractures may result from various fracture mechanisms

the effect of quaternary alluvium on strong ground motion in the coyote lake california earthquake of 1979 abstract the effect of alluvium on strong ground motion can be seen by comparing two strong motion records of the coyote lake california earthquake of 6 august 1979 m l 5 9 one record at a site on franciscan bedrock had a peak horizontal acceleration of 0 13 g and a peak horizontal velocity of 10 cm sec the other at a site 2 km distant on 180 meters of quaternary alluvium overlying franciscan had values of 0 26 g and 32 cm sec amplifications by factors of 2 and 3 horizontal motions computed at the alluvial site for a linear plane layered model based on measured p and s velocities show reasonably good agreement in shape with the observed motions but the observed peak amplitudes are greater by a factor of about 1 25 in acceleration and 1 8 in velocity about 15 per cent of the discrepancy in acceleration and 20 per cent in velocity can be attributed to the difference in source distance the remainder may represent focusing by refraction at a bedrock surface concave upward there is no clear evidence of nonlinear soil response fourier spectral ratios between motions observed on bedrock and alluvium show good agreement with ratios predicted from the linear model in particular the observed frequency of the fundamental peak in the amplification spectrum agrees with the computed value indicating that no significant nonlinearity occurs in the secant shear modulus computations show that nonlinear models are compatible with the data if values of the coefficient of dynamic shear strength in terms of vertical effective stress are in the range of 0 5 to 1 0 or greater the data illustrate that site amplification may be less a matter of resonance involving reinforcing multiple reflections and more the simple effect of the low near surface velocity application of traditional seismological theory leads to the conclusion that the site amplification for peak horizontal velocity is approximately proportional to the reciprocal of the square root of the product of density and shear wave velocity

synthesis of studies of palsa formation underlining the importance of local environmental and physical characteristics this review presents a synthesis of four decades of palsa studies based on field experiments and observations mainly in fennoscandia as well as laboratory measurements palsas are peat covered mounds with a permanently frozen core in finnish lapland they range from 0 5 to 7 m in height and from 2 to 150 m in diameter these small landforms are characteristic of the southern margin of the discontinuous permafrost zone palsa formation requires certain environmental conditions long lasting air temperature below 0 c thin snow cover and low summer precipitation the development and persistence of their frozen core is sensitive to the physical properties of peat the thermal conductivity of wet and frozen peat is high and it decreases significantly as the peat dries and thaws this affects the development of the active layer and makes its response to climate change complex the insulating properties of dry peat during hot and dry summers moderate the thawing of the active layer on palsas in contrast humid and wet weather during the summer causes deep thawing and may destroy the frozen core of palsas ice layers in palsas have previously been interpreted as ice segregation features but because peat is not frost susceptible the ice layers are now reinterpreted as resulting from ice growth at the base of a frozen core that is effectively floating in a mire

variability in rates of coastal change along the yukon coast 1951 to 2015 to better understand the reaction of arctic coasts to increasing environmental pressure coastal changes along a 210 km length of the yukon territory coast in north west canada were investigated shoreline positions were acquired from aerial and satellite images between 1951 and 2011 shoreline change rates were calculated for multiple time periods along the entire coast and at six key sites additionally differential global positioning system dgps measurements of shoreline positions from seven field sites were used to analyze coastal dynamics from 1991 to 2015 at higher spatial resolution the whole coast has a consistent spatially averaged mean rate of shoreline change of 0 7 0 2 m a with a general trend of decreasing erosion from west to east additional data from six key sites shows that the mean shoreline change rate decreased from 1 3 0 8 1950s 1970s to 0 5 0 6 m a 1970s 1990s this was followed by a significant increase in shoreline change to 1 3 0 3 m a in the 1990s to 2011 this increase is confirmed by dgps measurements that indicate increased erosion rates at local rates up to 8 9 m a since 2006 ground surveys and observations with remote sensing data indicate that the current rate of shoreline retreat along some parts of the yukon coast is higher than at any time before in the 64 year long observation record enhanced availability of material in turn might favor the buildup of gravel features which have been growing in extent throughout the last six decades

a microstructural sequence of quartz schists in central shikoku south west japan abstract this paper describes a microstructural sequence of quartz schists metamorphosed chert in the asemi river region of the sambagawa metamorphic terrain in central shikoku southwest japan the asemi river region is divided into three areas on the basis of characteristics of microstructures of quartz schists observed under the optical microscope areas i ii and iii in ascending order of metamorphic grade microstructures in area i consist of finer equant equidimensional and polygonal quartz grains free from internal deformation features microstructures in area ii are characterized by oblate or elliptical grains with remarkable undulatory extinction surrounded by serrated grain boundaries microstructures in area iii consist mainly of coarser and equant grains without distinct internal deformation features the formation conditions of these microstructures are discussed in the light of recent experimental results

retreat pattern of glaciers controls the occurrence of turbidity currents on high latitude fjord deltas eastern baffin island glacier and ice sheet mass loss as a result of climate change is driving important coastal changes in arctic fjords yet limited information exists for arctic coasts regarding the influence of glacial erosion and ice mass loss on the occurrence and character of turbidity currents in fjords which themselves affect delta dynamics here we show how glacial erosion and the production of meltwaters and sediments associated with the melting of retreating glaciers control the generation of turbidity currents in fjords of eastern baffin island canada the subaqueous parts of 31 river mouths along eastern baffin island were mapped by high resolution swath bathymetry in order to assess the presence or absence of sediment waves formed by turbidity currents on delta fronts by extracting glaciological and hydrological watershed characteristics of these river mouths we demonstrate that the presence and areal extent of glaciers is a key control for generating turbidity currents in fjords however lakes formed upstream during glacial retreat significantly alter the course of sediment routing to the deltas by forming temporary sinks leading to the cessation of turbidity currents in the fjords due to the different deglaciation stages of watersheds in eastern baffin island we put these results into a temporal framework of watershed deglaciation to demonstrate how the retreat pattern of glaciers through the formation and filling of proglacial lakes affects the turbidity current activity of deltas

coastal erosion vs riverine sediment discharge in the arctic shelf seas this article presents a comparison of sediment input by rivers and by coastal erosion into both the laptev sea and the canadian beaufort sea cbs new data on coastal erosion in the laptev sea which are based on field measurements and remote sensing information and existing data on coastal erosion in the cbs as well as riverine sediment discharge into both the laptev sea and the cbs are included strong regional differences in the percentages of coastal erosion and riverine sediment supply are observed the cbs is dominated by the riverine sediment discharge 64 45 106 t a 1 mainly of the mackenzie river which is the largest single source of sediments in the arctic riverine sediment discharge into the laptev sea amounts to 24 10 106 t a 1 more than 70 of which are related to the lena river in comparison with the cbs the laptev sea coast on average delivers approximately twice as much sediment mass per kilometer a result of higher erosion rates due to higher cliffs and seasonal ice melting in the laptev sea sediment input by coastal erosion 58 4 106 t a 1 is therefore more important than in the cbs and the ratio between riverine and coastal sediment input amounts to 0 4 coastal erosion supplying 5 6 106 t a 1 is less significant for the sediment budget of the cbs where riverine sediment discharge exceeds coastal sediment input by a factor of ca 10

fifty years of coastal erosion and retrogressive thaw slump activity on herschel island southern beaufort sea yukon territory canada abstract patterns of coastal erosion in the arctic differ dramatically from those coasts in more temperate environments thick sea ice and shore fast ice limit wave based erosional processes to a brief open water season however despite this permafrost coasts containing massive ice ice wedges and ice bonded sediments tend to experience high rates of erosion these high rates of erosion reflect the combined thermal mechanical processes of thawing permafrost melting ground ice and wave action climate change in the arctic is expected to result in increased rates of coastal erosion due to warming permafrost increasing active layer depths and thermokarst rising sea levels reduction in sea ice extent and duration and increasing storm impacts with the most ice rich permafrost in the canadian arctic the southern beaufort sea coast between the tuktoyaktuk peninsula and the alaskan border is subject to high rates of erosion and retrogressive thaw slump activity under many climate change scenarios this area is also predicted to experience the greatest warming in the canadian arctic this paper presents results of a remote sensing study on the long term patterns of coastal erosion and retrogressive thaw slump activity for herschel island in the northern yukon territory using orthorectified airphotos from 1952 and 1970 and an ikonos image from 2000 corrected with control points collected by kinematic differential global positioning system and processed using softcopy photogrammetric tools mean coastal retreat rates of 0 61 m yr and 0 45 m yr were calculated for the periods 1952 1970 and 1970 2000 respectively the highest coastal retreat rates are on north west facing shorelines which correspond to the main direction of storm related wave attack during the period 1970 2000 coastal retreat rates for south to south east facing shorelines displayed a distinct increase even though these are the most sheltered orientations however south to south east facing shorelines correspond to the orientations where the highest densities of retrogressive thaw slumps are observed differences in rates of headwall retreat of retrogressive thaw slumps and coastal erosion results in the formation of larger thermokarst scars and the development of polycyclic thaw slumps on south to south east exposures the number and the total area of retrogressive thaw slumps increased by 125 and 160 respectively between 1952 and 2000 as well the proportion of active retrogressive thaw slumps increased dramatically polycyclic retrogressive thaw slumps appear to develop in a periodic fashion related to retrogressive thaw slump stage and maximum inland extent

assessing patterns of annual change to permafrost bluffs along the north slope coast of alaska using high resolution imagery and elevation models abstract coastal permafrost bluffs at barter island on the north slope beaufort sea coast of alaska are among the most rapidly eroding along alaska s coast having retreated up to 132 m between 1955 and 2015 here we quantify rates and patterns of change over a single year using very high resolution orthophotomosaics and co registered surface elevation models derived from a survey grade form of structure from motion photogrammetry from a fixed wing manned aircraft the resulting elevation models were validated with over 10 000 ground check points and found that 95 agreed to within 20 cm before accounting for real differences in the ground surface due to seasonality vegetation and checkpoint acquisition errors this data set provides the most detailed and accurate measurements of coastal change to date along the alaskan coast and the method is scalable to more extensive coastlines between july 2014 and july 2015 the bluffs retreated an average of 1 3 m and a maximum of 8 1 m with an associated net volume loss of 38 100 300 m3 1 3 m3 m this average retreat over this single year was slightly less than the 60 year mean rate of change of 1 5 0 1 m yr suggesting the 2014 2015 year represented relatively typical to slightly below average conditions most of the bluff material 70 was lost during the 3 summer months july to sept of 2014 and the remaining 30 between the late summer and following winter spring the pattern of change was predominantly landward retreat of the top of the bluffs removal of the debris apron and subsequent niching at the base of the bluffs during mid to late summer july to sept followed by erosion of the bluff face and deposition of debris at the base of the bluff through the remainder of the year sept to the following july drivers of the observed change are likely a combination of thermal erosion on the bluff face throughout the summer and episodic thermo mechanical removal of material niching and undercutting of the base associated with high water levels driven by low pressure storms and westerly winds these patterns and high rates of change are believed to be broadly representative of coastal permafrost bluffs found along many high latitude coastlines worldwide

formation of thermoerosional niches into frozen bluffs due to storm surges on the beaufort sea coast an analysis is made of the formation of a thermoerosional niche into a frozen bluff due to a storm surge on the beaufort sea coast as a first attempt the problem is treated as a one dimensional unsteady problem in which the vertical melting front of the thermoerosional niche migrates into the frozen bluff under the thermoerosional action of breaking waves inside the surf zone during a storm the analysis examines the temporal and shore normal variations of the temperature and salinity of the seawater and the concentration of suspended sediment resulting from the migration of the melting front into the frozen bluff a simple analytical solution is obtained for the case where the mean water depth during a storm is approximately constant in the neighborhood of the frozen bluff an example computation based on the simple analytical solution indicates that the thermal driving of the ambient seawater the mechanical driving represented by the water depth and the duration of the storm surge are important in determining the degree of the thermoerosional niche formation into the frozen bluff the computed results are also shown to be in qualitative agreement with available field observations

use of misr measurements to study the radiative transfer of an isolated convective cloud implications for cloud optical thickness retrieval 1 radiative transfer simulations of an isolated deep convective cloud reconstructed with stereo techniques from the multiangle imaging spectroradiometer misr are compared with the reflectances measured at the nine misr viewing angles the simulations were done using a three dimensional monte carlo model in which ocean reflectance aerosol and rayleigh scattering were prescribed to match the surrounding clear sky misr measurements making reasonable assumptions regarding the vertical and horizontal distribution of the volume extinction coefficient we were able to reproduce the misr measurements with the 3d radiative calculations while the uniqueness of the these distributions cannot be proven they all lead to retrievals of much larger cloud optical thickness and cloud water content than for a 1d retrieval averaged over the cloud the difference was a factor of about 3 rising to 9 locally this is a consequence of horizontal photon transport that serves to highlight the inadequacy of 1d retrievals for the case of deep convective cloud concerning the internal cloud properties we noticed the angular distribution of modeled radiances did not match the measured radiances when an ice crystal phase function was applied better estimates of the optical depths and water contents of deep convective clouds appear to be obtainable by integrating an estimate of the extinction coefficient over the vertical cloud extent when this can assessed than by attempting to invert the radiance measured from a single angle view using 1d theory

seismic and ultrasonic velocities in permafrost we calculate the compressional and shear wave velocities of permafrost as a function of unfrozen water content and temperature unlike previous theories based on simple slowness and or moduli averaging or two phase models we use a biot type three phase theory that considers the existence of two solids solid and ice matrices and a liquid unfrozen water the compressional velocity for unconsolidated sediments obtained with this theory is close to the velocity computed with wood s model since biot s theory involves a wood averaging of the moduli of the single constituents moreover the model gives lower velocities than the well known slowness averaging theory wyllie s equation for consolidated berea sandstone the theory underestimates the value of the compressional velocity below 0 c computing the average bulk moduli by slowness averaging the ice and solid phases and wood averaging the intermediate moduli with the liquid phase yields a fairly good fit of the experimental data the proportion of unfrozen water and temperature are closely related fitting the wave velocity at a given temperature allows the prediction of the velocity at the whole range of temperatures provided that the average pore radius and its standard deviation are known