detection and classification of surface roughness in an arctic marginal sea ice zone sea ice dynamic and thermodynamic processes are important and highly variable elements of the marginal ice zone miz this study examines the detection and classification of statistically separable sea ice classes in the miz through a range of temporal and spatial scales a helicopter based laser system was used to obtain large scale and a ship based laser profiler to identify small scale roughness types respectively the analysis of variance of surface height data from helicopter and ship based laser systems active microwave amw c band backscattering data and passive microwave pmw 37 and 89 ghz brightness temperature data reveal different classes that statistically differ from one another we found significant statistical difference in variances in amw data with six classes that differ in vv polarization three classes in vh polarization and five classes in hh polarization in the miz e g snow covered first year ice ice rubble pancake ice frost flowers melt pond flooded ice and ice edge of southeastern beaufort sea the pmw emission was not as effective at discrimination yielding only one statistically separable class the results can potentially be extended to satellite based investigations of the miz at regional scales copyright 2012 john wiley sons ltd

deep seismic reflectivity patterns in specific tectonic units of western and central europe a systematic comparative study of the reflectivity of the continental crust is undertaken made possible by the expanded data basis of deep seismic reflection profiles in europe the reflectivity is not at all the same but can change dramatically from one seismic line to the next different seismic reflectivity patterns independent of applied techniques are observed correlations between these seismic patterns and specific tectonic units have been found

thinning and volume loss of the arctic ocean sea ice cover 2003 2008 1 we present our best estimate of the thickness and volume of the arctic ocean ice cover from 10 ice cloud and land elevation satellite icesat campaigns that span a 5 year period between 2003 and 2008 derived ice drafts are consistently within 0 5 m of those from a submarine cruise in mid november of 2005 and 4 years of ice draft profiles from moorings in the chukchi and beaufort seas along with a more than 42 decrease in multiyear my ice coverage since 2005 there was a remarkable thinning of 0 6 m in my ice thickness over 4 years in contrast the average thickness of the seasonal ice in midwinter 2 m which covered more than two thirds of the arctic ocean in 2007 exhibited a negligible trend average winter sea ice volume over the period weighted by a loss of 3000 km3 between 2007 and 2008 was 14 000 km3 the total my ice volume in the winter has experienced a net loss of 6300 km3 40 in the 4 years since 2005 while the first year ice cover gained volume owing to increased overall area coverage the overall decline in volume and thickness are explained almost entirely by changes in the my ice cover combined with a large decline in my ice coverage over this short record there is a reversal in the volumetric and areal contributions of the two ice types to the total volume and area of the arctic ocean ice cover seasonal ice having surpassed that of my ice in winter area coverage and volume became the dominant ice type it seems that the near zero replenishment of the my ice cover after the summers of 2005 and 2007 an imbalance in the cycle of replenishment and ice export has played a significant role in the loss of arctic sea ice volume over the icesat record

sea ice thickness retrieval in the sea of okhotsk using dual polarization sar data we investigated the feasibility of using multi polarization synthetic aperture radar sar data to estimate the thickness of undeformed first year ice analysis of the radar signatures for the c and l bands showed that the correlation between the ice thickness and vv to hh backscattering ratio is larger than the correlation between the ice thicknesses and the backscattering coefficients this is in part because the ice surface salinity and hence the surface reflection coefficient decreases as the ice thickens the backscattering ratio had low sensitivity to the small scale ice surface roughness for the c band and is almost independent of roughness at l band given that the ratio is most sensitive to ice surface dielectric constants which depend on salinity we developed an algorithm for retrieving the ice thickness that is based on the backscattering ratio and on the integral equation method iem surface scattering model comparison of the observed and estimated ice thicknesses showed that the correlation was much better when the thicknesses were estimated using the backscattering ratio than when the backscattering coefficient was used directly the algorithm also performed better than previous retrievals using an empirical technique

observations of sea ice thickness surface roughness and ice motion in amundsen gulf 1 ice thickness and surface roughness measurements of first year fy sea ice were collected with a fix mounted helicopter borne electromagnetic hem laser system in amundsen gulf in april to may 2004 the modal ice thickness values are in good qualitative agreement with different ice types identified in synthetic aperture radar sar imagery and shown on ice charts produced by the canadian ice service modal ice thickness values which generally represent level ice thicknesses were about 2 0 m over landfast ice a large range of modal ice thicknesses was observed in the mobile ice region with values of about 0 2 m young ice in leads where there was high radar backscatter 0 6 m thin fy ice in the polynya where there was medium to high backscatter and about 1 1 1 9 m thick fy ice elsewhere high surface roughnesses are strongly associated with high radar backscatter in sar imagery and are observed in areas of large shear the ratio of the standard deviations of ice draft and averaged roughness in an area of landfast ice is in good agreement with the ratio of the standard deviations of ice draft and ice equivalent roughness expected from isostasy with constant level ice and snow thickness however the standard deviation of ice equivalent roughness may be significantly underestimated due to differences in snow thickness between level and deformed ice and limitations of the laser processing method modal ice plus snow thicknesses measured with the hem system are within the range of historical values measured at cape parry

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

snow mapping in alpine regions with synthetic aperture radar active microwave sensors can discriminate snow from other surfaces in all weather conditions and their spatial resolution is compatible with the topographic variation in alpine regions using data acquired with the nasa airsar in the otztal alps in 1989 and 1991 the authors examine the usage of synthetic aperture radar sar to map snow and glacier covered areas by comparing polarimetric sar data to images from the landsat thematic mapper obtained under clear conditions one week after the sar flight the authors found that sar data at 5 3 ghz c band can discriminate between areas covered by snow from those that are ice free however they are less suited to discrimination of glacier ice from snow and rock the overall pixel by pixel accuracies 74 from vv polarization alone with topographic information 76 from polarimetric sar without any topographic information and 79 from polarimetric sar with topographic information are high enough to justify the use of sar as the data source in areas that are too cloud covered to obtain data from the thematic mapper this is especially true for snow discrimination where accuracies exceed 80 because mapping of a transient snow cover during a cloudy melt season is often difficult with an optical sensor the airsar survey was carried out in summer during a heavy rainstorm when the snow surfaces were unusually rough even better results for snow discrimination can be expected for mapping in the spring when snow is usually smoother

characterization of arctic sea ice thickness using high resolution spaceborne polarimetric sar data in this paper we have investigated the relationship between the depolarization effects and the wintertime sea ice thickness in the landfast ice region where smooth thick first year ice fyi and deformed old ice coexisted by using c and x band spaceborne polarimetric synthetic aperture radar sar data radarsat 2 and terrasar x we have found a strong correlation between the in situ sea ice thickness and the sar derived depolarization factors copolarized correlation and cross polarized ratio the observed relationships have demonstrated not only a categorical difference between fyi and multiyear ice myi but also a one to one continuity in the scatter plots rather than being clustered it clearly shows that the observed correlations are not merely from the categorical difference in scattering mechanism between fyi and myi and that there might exist a one to one relationship between thickness and depolarization factors at least in our deformed ice case this suggests that depolarization factors could be effective sar parameters in the estimation of wintertime sea ice thickness numerical model simulations explained some portions of the correlation by employing multiple scattering on the sea ice surface and volume scattering within the low density subsurface layer

continental collisions and seismic signature processes active during continental collisions and orogenic collapse create distinct structures which are imaged by reflection seismic profiling examples are shown and discussed

observations of brine drainage networks and microstructure of first year sea ice brine drainage networks and the microstructure of first year sea ice have been examined at two locations near barrow northern alaska a method for obtaining full depth sections of ice sheets up to 1 8 m thick is presented and shown to provide information on the spatial distribution and geometry of brine drainage networks on a scale of meters a number of such sections from the two test sites are presented which reveal a greater variety of main channel and side branch configurations than is typically observed in ice grown in the laboratory vertical and horizontal micrographs and thin section photographs were obtained in november 1993 and march and may 1994 at a test site in the relatively protected elson lagoon the resulting time series of photographic records provide detailed information on the size shape and spatial distribution of the brine and gas filled inclusions and a means to quantify their size and shape changes with time an example of the changes with time in inclusion sizes and aspect ratios in the vertical and horizontal directions for a depth of 0 2 m with a given thermal history is also presented

comparison of sea ice thickness measurements under summer and winter conditions in the arctic using a small electromagnetic induction device drillhole determined sea ice thickness was compared with values derived remotely using a portable smalloffset loop loop steady state electromagnetic em induction device during expeditions to fram strait and the siberian arctic under typical winter and summer conditions simple empirical transformation equations are derived to convert measured apparent conductivity into ice thickness despite the extreme seasonal differences in sea ice properties as revealed by ice core analysis the transformation equations vary little for winter and summer thus the em induction technique operated on the ice surface in the horizontal dipole mode yields accurate results within 5 to 10 of the drillhole determined thickness over level ice in both seasons the robustness of the induction method with respect to seasonal extremes is attributed to the low salinity of brine or meltwater filling the extensive pore space in summer thus the average bulk ice conductivity for summer multiyear sea ice derived according to archie s law amounts to 23 ms m compared to 3 ms m for winter conditions these mean conductivities cause only minor differences in the em response as is shown by means of 1 d modeling however under summer conditions the range of ice conductivities is wider along with the widespread occurrence of surface melt ponds and freshwater lenses underneath the ice this causes greater scatter in the apparent conductivity ice thickness relation this can result in higher deviations between em derived and drillhole determined thicknesses in summer than in winter

limex 87 ice surface characteristics implications for c band sar backscatter signatures ice surface characterization data collected in 1987 during the labrador ice margin experiment are analyzed to estimate the changes in snow and ice properties at the onset of melt surface measurements were made from an ice research vessel on several days some of which had coincident remote sensing flights at a number of locations in the marginal ice zone these data are used as input parameters in a simple scattering model to simulate the effects of variations in material properties upon c band scattering signatures

observation of sea ice thickness in the sea of okhotsk by using dual frequency and fully polarimetric airborne sar pi sar data to investigate the possibilities of using dual frequency multipolarization synthetic aperture radar sar data to monitor sea ice we derived the relationship between various polarization characteristics and the physical parameters of sea ice we discuss the frequency and polarization characteristics of the backscattering coefficients of sea ice and then characterize its thickness by comparing the corresponding backscattering coefficient for each polarization with the physical parameters of the ice we first propose a methodology for classifying sea ice types by using a polarimetric decomposition technique before comparing an estimation of the sea ice thickness with the corresponding dual frequency multipolarization sar data we utilized the backscattering ratio to estimate the thickness of the sea ice this ratio canceled the effect of roughness on the backscattering the method was validated using pi sar polarimetric and interferometric airborne sar observation data obtained at ground truth sites

about the lithospheric structure of central tibet based on seismic data from the indepth iii profile signals from 11 shots and 8 earthquakes and numerous teleseismic events were recorded along the 400 km seismic line indepth iii in central tibet and interpreted together with previous seismic and tectonic data the abnormal behavior of various mantle phases reveals a complex moho transition zone especially in the northern part of the line in the changtang block where the lower crust and the mantle show unusually low velocities a shingled appearance of pn and no low velocity layer in the upper crust the strong east west anisotropy in the changtang block is related to an easterly escape movement of the whole lithosphere facilitated by the warm and weak layers in the lower crust and the upper mantle bounded apparently by two prominent west east running fault zones

indirect measurements of the mass balance of summer arctic sea ice with an electromagnetic induction technique abstract in the framework of the surface heat budget of the arctic ocean sheba study indirect non invasive icemass balance measurements were carried out at a drifting station in the northern chukchi sea between mayand august of 1998 ice thickness was derived from electromagnetic induction em measurements ofapparent conductivity along 13 profiles 60 to 900 m long as shown through sensitivity studies with a 1 d model the apparent conductivity data from individual points can be inverted to yield estimates of icethickness and ablation with an accuracy of approximately 0 05 m for 2 m thick level ice ablation ratesranged between 8 and 18 mm d 1 with total ablation amounting to roughly 0 9 to 1 2 m measurements ofthickness and melt rates along different profiles in undeformed multi year ice corresponded closely indicating that the sampling statistics are adequate the roughness of undeformed ice has been found toincrease during the summer due to deepening of melt ponds and enhanced bottom melt ice under melt pondswas disproportionately thinner most likely a result of thicker snow cover reducing winter accretion

polarimetric characteristics of sea ice in the sea of okhotsk observed by airborne l band sar the phased array l band sar palsar aboard the advanced land observing satellite alos is capable of globally acquiring fully polarimetric data in order to confirm the ability of l band polarimetric synthetic aperture radar sar to investigate sea ice before the alos launch we conducted a field experiment using an airborne polarimetric and interferometric sar pi sar in the sea of okhotsk in 1999 this paper presents the analyzed results of data acquired in that experiment the extracted polarimetric parameters of several ice types suggested that polarimetric coherences and phase differences between right right rr and left left ll are good candidates for discriminating ice types the polarimetric anisotropy as well as the beta angle of the first eigenvector calculated in the polarimetric decomposition procedure are alternative parameters that are sensitive to ice type differences due to the low depolarization characteristics of open water it could be discriminated from sea ice by scattering entropy in all incidence angle ranges from the relation between ice thickness and the polarimetric parameters we found that backscattering coefficients and vertical vv to horizontal hh backscattering ratio are highly correlated with ice thickness since the ratio is sensitive to ice surface dielectric constants a simple simulation using the integral equation method surface model was conducted by using the physical parameters of typical sea ice a two dimensional ice thickness map was derived from an empirical relation between the vv to hh backscattering ratio and ice thickness

c band polarimetric backscattering signatures of newly formed sea ice during fall freeze up a study of the polarimetric backscattering response of newly formed sea ice types under a large assortment of surface coverage was conducted using a ship based c band polarimetric radar system polarimetric backscattering results and physical data for 40 stations during the fall freeze up of 2003 2006 and 2007 are presented analysis of the copolarized correlation coefficient showed its sensitivity to both sea ice thickness and surface coverage and resulted in a statistically significant separation of ice thickness into two regimes ice less than 6 cm thick and ice greater than 8 cm thick a case study quantified the backscatter of a layer of snow infiltrated frost flowers on new sea ice showing that the presence of the old frost flowers can enhance the backscatter by more than 6 db finally a statistical analysis of a series of temporal spatial measurements over a visually homogeneous frost flower covered ice floe identified temperature as a significant but not exclusive factor in the backscattering measurements

rupture creep lamellae and crocodiles happenings in the continental crust from the observation of certain seismic reflectivity patterns in phanerozoic continental crusts a relationship is suggested between 1 rupture and seismicity generally restricted to the upper crust 2 crocodile tectonics a kind of vertical indentation observed by diverging plane reflectors preferably in the middle crust 3 creep and the formation of reflecting lamellae in the lower crust based on these observations and on viscosity depth estimates a conceptual model for the above mentioned structures is presented which is also compatible with observations in older crusts boundary conditions are given for rupture as well as for lamellae forming creep

seismic lamination and anisotropy of the lower continental crust abstract seismic lamination in the lower crust associated with marked anisotropy has been observed at various locations three of these locations were investigated by specially designed experiments in the near vertical and in the wide angle range that is the urach and the black forrest area both belonging to the moldanubian a collapsed variscan terrane in southern germany and in the donbas basin a rift inside the east european ukrainian craton in these three cases a firm relationship between lower crust seismic lamination and anisotropy is found there are more cases of lower crustal lamination and anisotropy e g from the basin and range province western us and from central tibet not revealed by seismic wide angle measurements but by teleseismic receiver function studies with a p s conversion at the moho other cases of lamination and anisotropy are from exhumed lower crustal rocks in calabria southern italy and val sesia and val strona ivrea area northern italy we demonstrate that rocks in the lower continental crust apart from differing in composition differ from the upper mantle both in terms of seismic lamination observed in the near vertical range and in the type of anisotropy compared to upper mantle rocks exhibiting mainly orthorhombic symmetry the symmetry of the rocks constituting the lower crust is either axial or orthorhombic and basically a result of preferred crystallographic orientation of major minerals biotite muscovite hornblende we argue that the generation of seismic lamination and anisotropy in the lower crust is a consequence of the same tectonic process that is ductile deformation in a warm and low viscosity lower crust this process takes place preferably in areas of extension heterogeneous rock units are formed that are generally felsic in composition but that contain intercalations of mafic intrusions the latter have acted as heat sources and provide the necessary seismic impedance contrasts the observed seismic anisotropy is attributed to lattice preferred orientation lpo of major minerals in particular of mica and hornblende but also of olivine a transversely isotropic symmetry system such as expected for sub horizontal layering is found in only half of the field studies azimuthal anisotropy is encountered in the rest of the cases this indicates differences in the horizontal components of tectonic strain which finally give rise to differences in the evolution of the rock fabric

multiple cycles of wave dominated estuarine deposits in low accommodation settings cretaceous j sandstone northwestern nebraska the j sandstone comprises less than 46 m 151 ft of sandstone dominated strata within the mudrock dominated lower upper cretaceous succession of northwestern nebraska the unit is a prolific hydrocarbon producer in this region denver julesburg basin but its lithostratigraphic and sequence stratigraphic framework critical for reservoir characterization and mapping is poorly known we have achieved an improved understanding of depositional history and sequence stratigraphy by describing and correlating cores and wireline logs from wells within sioux dawes and box butte counties nebraska and niobrara and goshen counties wyoming coals paleosols fluvial or inner estuarine sandstones estuarine mudstones fluvial conglomerate shoreface sandstone and reworked volcanic fallout bentonite lithofacies were identified trace fossil assemblages representing stressed expressions of the skolithos and cruziana ichnofacies are common these lithofacies are arranged vertically into three erosionally based cycles each less than 28 m 92 ft thick and each grade upward from fluvial or inner estuarine sandstones into estuarine mudstones and in turn into shoreface sandstones the lateral and vertical stacking patterns of the lithofacies are complex however and the upper cycles appear to fill space eroded into the underlying ones northeast southwest elongate isochore trends appear in all three cycles lithofacies transition downdip from inner estuarine sandstones in the northeast to estuarine basin mudstones and shoreface sandstones toward the southwest detrital mineralogy indicates an easterly cratonic provenance for the entire unit our data suggest that the j sandstone in northwestern nebraska accumulated in wave dominated estuarine settings as part of a long lived transgressive systems tract the unit as a whole occupies a complexly incised landscape cut during a third order lowstand ca 98 ma coeval cycles of similar magnitude throughout the western interior suggest that the three cycles represent eustatic fluctuations the highest quality reservoirs occur at the base of the unit in inner estuarine lithofacies in the central and southwestern parts of the study area

increasing mobility of high arctic sea ice increases marine hazards off the east coast of newfoundland heavy ice conditions along canada s east coast during spring 2017 presented hazardous conditions for the maritime industry and required the canadian coast guard to pull its research icebreaker ccgs amundsen off its scientific cruise to provide ice escort services and conduct search and rescue operations along newfoundland s northeast coast greater ice concentrations and a thicker ice pack than are typical of this area created the anomalous ice cover within this paper we present in situ observations of the ice cover confirming that pieces of multiyear sea ice from the high arctic were present within the ice cover and subsequently examine the transport pathway that connects the export of thick multiyear sea ice from the lincoln sea and canadian arctic archipelago to coastal communities in newfoundland we conclude with a discussion on how an increasingly mobile arctic sea ice cover may increase these ice hazards in the south

global correlation of cenomanian upper cretaceous sequences evidence for milankovitch control on sea level we have investigated the sequence stratigraphy of two widely separated marine cenomanian successions in southeast india and northwest europe and used high resolution ammonite biostratigraphy to demonstrate that sea level changes are globally synchronous and therefore must be eustatically controlled sequence scale sea level changes in the cenomanian were driven by the long eccentricity cycle 400 k y in the milankovitch band we hypothesize that during pre quaternary time the third order sequences of vail and haq are essentially a sediment response to sea level changes driven by the 400 k y cycle construction of a relative sea level curve for the marginal marine succession in india demonstrates that the short term sea level changes are rapid 10 100 m m y and have a magnitude of 2 20 m glacioeustasy is a possible but unproven driving mechanism