classification and snow line detection for glacial areas using the polarimetric sar image abstract snow cover and glaciers are sensitive indicators of the environment the vast spatial coverage of remote sensing data coupled with the tough conditions in areas of interest has made remote sensing a particularly useful tool in the field of glaciology compared to optical images synthetic aperture radar sar data are hardly influenced by clouds this is important because glacial areas are usually under cloud cover the dongkemadi glacier in the qinghai tibetan plateau was selected as the study area for this paper we use polarimetric sar polsar image for classification on and around the glacier the contrast between ice and wet snow is remarkable but it is difficult to distinguish the ice from the ground on sar images due to similar backscatter characteristics in former research in our study we found that this distinction can be achieved by target decomposition support vector machines svms are performed to classify the glacier areas using the selected features the glacial areas are classified into six parts wet snow ice river outwash soil land rocky land and others the polsar target decomposition svms pts method is proven to be efficient with an overall classification accuracy of 91 1 and a kappa coefficient of 0 875 moreover 86 63 of the bare ice and 96 76 of the wet snow are correctly classified the classification map acquired using the pts method also helps to determine the snow line which is an important concept in glaciology

peak metamorphic temperatures in type 6 ordinary chondrites an evaluation of pyroxene and plagioclase geothermometry quantifying the peak temperatures achieved during metamorphism is critical for understanding the thermal histories of ordinary chondrite parent bodies various geothermometers have been used to estimate equilibration temperatures for chondrites of the highest metamorphic grade type 6 but results are inconsistent and span hundreds of degrees because different geothermometers and calibration models were used with different meteorites it is unclear whether variations in peak temperatures represent actual ranges of metamorphic conditions within type 6 chondrites or differences in model calibrations we addressed this problem by performing twopyroxene geothermometry using quilf95 on the same type 6 chondrites for which peak temperatures were estimated using the plagioclase geothermometer nakamuta and motomura 1999 we also calculated temperatures for published pyroxene analyses from other type 6 h l and ll chondrites to determine the most representative peak metamorphic temperatures for ordinary chondrites pyroxenes record a narrow overlapping range of temperatures in h6 865 926 c l6 812 934 c and ll6 874 945 c chondrites plagioclase temperature estimates are 96 179 c lower than pyroxenes in the same type 6 meteorites plagioclase estimates may not reflect peak metamorphic temperatures because chondrule glass probably recrystallized to plagioclase prior to reaching the metamorphic peak the average temperature for h l and ll chondrites 900 c which agrees with previously published oxygen isotope geothermometry is at least 50 c lower than the peak temperatures used in current asteroid thermal evolution models this difference may require minor adjustments to thermal model calculations

slow energy transfer between regions supporting topographic waves in a recent paper jansons johnson 1988 the authors discuss topographic rossby waves over a random array of seamounts it is noted that resonance is possible between a hill and an equal and opposite dale but such resonances are mentioned only briefly due to the small likelihood of correctly matched topography in the ocean the present paper considers the resonances in detail showing how the normal modes formed by frequency splitting at resonance can be combined to give modes that slowly transfer energy from one region supporting topographic waves across a region where such weaves are evanescent to another region supporting waves in addition to the simplest case of a hill dale pair for which an exact energy transferring mode is obtained transferring modes are given for a three hill system for two hills near a coastal boundary and for two basin lakes the analysis is simplified and the results generalized by extensive use of the invariance of the governing equation under conformal mappings a transferring mode is given for a dale in a random array of seamounts showing energy leaking slowly from the dale to large distances and returning with the rate of leakage depending on the area fraction of seamounts it is concluded that although resonances and transferring modes are not likely to be important in random arrays on infinite planes they are relevant to numerical models which are necessarily restricted to finite domains to coastal seamount chains and to multi basin lakes

a method for monitoring glacier mass balance using satellite albedo measurements application to vatnajskull iceland we compare satellite albedo images of vatnajokull iceland with mass balance measurements for the years 1991 99 we find that the equilibrium line is mostly not visible when it is located above its position of the previous year s equilibrium line detection is further hindered by clouds and a gradual transition between ice and firn or snow consequently firn line elevation at the end of the melting season is not particularly useful for estimating the annual mass balance instead we propose to study the mean albedo of the entire ice cap throughout the melting season so that all available information about the surface albedo is taken into account the mean net potential global radiation which can be estimated from the mean surface albedo alone both depends on and influences summer melt it also depends on winter precipitation and integrated over the melting season is found to relate linearly to the specific mass balance b r 0 87 and 0 94 for different outlets of vatnajokull b can be estimated quantitatively when this relation is known and qualitatively when it is not the uncertainty in the satellite derived value of b is 0 5 0 8 m w e which for vatnajokull corresponds to about 27 of the interannual variability of b

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

greenland ice sheet surface properties and ice dynamics from ers 1 sar imagery c band synthetic aperture radar sar imagery from the european space agency s ers 1 satellite reveals the basic zonation of the surface of the greenland ice sheet the zones have backscatter signatures related to the structure of the snowpack which varies with the balance of accumulation and melt at various elevations the boundaries of zones can be accurately located with the use of this high resolution imagery the images also reveal a large flow feature in northeast greenland that is similar to ice streams in antarctica and may play a major role in the discharge of ice from the ice sheet

recognition of supraglacial debris in the tianshan mountains on polarimetric sar images abstract debris cover is widely present in the ablation areas of mountain glaciers such debris plays an important role in glacier mass balance but it complicates the glacier boundary and area estimation when using remotely sensed images automatic recognition of the debris is much more difficult than recognizing bare ice on optical remotely sensed images because the debris has almost the same spectral characteristics of the surrounding terrain in this paper the scattering characteristics of the debris on the c and l band polarimetric sar images are presented and analyzed to study the possibility of recognizing debris thickness and extent the koxkar glacier in the central tianshan mountain range was selected as the study area it was found that debris is distinct from bare ice in cross polarization hv of both the l and c bands the l band volume scattering component acquired from target decomposition increases with debris thickness when the debris is less than 25 cm deep but the volume scattering does not increases if the debris is thicker than 25 cm in contrast the c band sar data does not appear to be sensitive to debris thickness this difference may be caused by different radar penetration depth of the debris on the basis of the polarimetric property analysis two methods were developed to determine the extent of the debris in the first method the simple threshold to distinguish debris from non debris areas is presented using this threshold approximately 90 of the debris can be recognized in the second method by combining more polarimetric features and support vector machines recognition of debris reaches an accuracy greater than 95

measuring snow and glacier ice properties from satellite satellite remote sensing is a convenient tool for studying snow and glacier ice allowing us to conduct research over large and otherwise inaccessible areas this paper reviews various methods for measuring snow and glacier ice properties with satellite remote sensing these methods have been improving with the use of new satellite sensors like the synthetic aperture radar sar during the last decade leading to the development of new and powerful methods such as sar interferometry for glacier velocity digital elevation model generation of ice sheets or snow cover mapping some methods still try to overcome the limitations of present sensors but future satellites will have much increased capability for example the ability to measure the whole optical spectrum or sar sensors with multiple polarization or frequencies among the methods presented are the satellite derived determination of surface albedo snow extent snow volume snow grain size surface temperature glacier facies glacier velocities glacier extent and ice sheet topography in this review emphasis is put on the principles and theory of each satellite remote sensing method an extensive list of references with an emphasis on studies from the 1990s allows the reader to delve into specific topics

firn line detection on austre okstindbreen norway with airborne multipolarization sar we examine the ability of synthetic aperture radar sar to detect the equilibrium line on the glacier austre okstindbreen norway using multipolarization sar images in c and l band acquired with the electromagnetic institute of the technical university of denmark s airborne emisar sensor during the european multisensor airborne campaign emac 95 the late summer snowline approximating the equilibrium line cannot be seen on the sar images instead photographs from austre okstindbreen show that a distinct boundary visible on the c band sar images corresponds to the firn line created by old snow from many previous years this is better seen on the cross polarized sar images hv and vh which in general reveal more detail than the hh and vv polarized images we model the stratigraphy from net balance and glacier velocity data to calculate the firn line altitude fla modelled fla and the observed boundary are separated by 50 m in elevation but considering errors during co registration and modelling we conclude that the observed boundary on austre okstindbreen is the firn line monitoring fla rather than equilibrium line altitude ela for mass balance studies with remote sensing is therefore suggested

monitoring glacier zones and snow firn line changes in the qinghai tibetan plateau using c band sar imagery abstract small glaciers and ice caps in mountainous areas are often sensitive indicators of local and global climate change in this paper typical continental glaciers the dongkemadi and its neighbouring glaciers in the central area of the qinghai tibetan plateau are monitored using multi sensor c band synthetic aperture radar sar imagery the study includes analysis of the alternating processes of ablation and freezing the glacier zones detected on sar images and the changing snow firn line across different days seasons and years experiments show that in late summer the wet snow firn ice boundary which is termed the late summer wet snow firn line wsfl is easily detected on sar images and it is relatively stable over multiple days also the detected late summer wsfl and the recorded yearly equilibrium line which reflects glacier mass balance are close in a positive mass balance year but the detected late summer wsfl is lower than the equilibrium line in a negative mass balance year by combining pit and sar observations it was found that the firn can be divided into two parts on the glaciers the thick firn that lies in the neve basin is distinct on sar images in winter but the firn surrounding the basin with thickness ranging from 0 to 20 cm is difficult to recognize the thick firn line the lower boundary of neve basin is stable in observations eight years apart based on the c band vv polarization sar image experiments field work and existing records the spatiotemporal backscatter signature specific to the typical continental glacier is identified the spatiotemporal backscatter signature helps to understand mass balance proxies and surface melt patterns of the glaciers in sar images

radar enabled recovery of the sutter s mill meteorite a carbonaceous chondrite regolith breccia doppler weather radar imaging enabled the rapid recovery of the sutter s mill meteorite after a rare 4 kiloton of tnt equivalent asteroid impact over the foothills of the sierra nevada in northern california the recovered meteorites survived a record high speed entry of 28 6 kilometers per second from an orbit close to that of jupiter family comets tisserand s parameter 2 8 0 3 sutter s mill is a regolith breccia composed of cm mighei type carbonaceous chondrite and highly reduced xenolithic materials it exhibits considerable diversity of mineralogy petrography and isotope and organic chemistry resulting from a complex formation history of the parent body surface that diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to c class asteroids are interpreted

widespread evidence for high temperature formation of pentlandite in chondrites abstract by investigating the compositional and textural evolution of sulfides within a wide range of relatively pristine aqueously altered and thermally metamorphosed chondrites we constrain the equilibration temperatures of sulfide minerals and compare them to the metamorphic history of their host meteorite sulfides in mighei like carbonaceous chondrites are complex as they equilibrated mostly between 100 and 135 c but some may have equilibrated at temperatures up to 600 c this is consistent with some cm chondrite sulfides forming at high temperature during chondrule cooling and others during low temperature aqueous alteration and or annealing karoonda like carbonaceous chondrite sulfides equilibrated between 500 and 230 c which is consistent with formation during cooling and annealing after thermal metamorphism sulfides in the ll chondrites equilibrated between 600 and 230 c and are consistent with formation during chondrule cooling for semarkona ll3 00 and during cooling after thermal metamorphism for the equilibrated samples types 4 6 sulfides in the rumuruti like r chondrites equilibrated between 600 and 500 c and are consistent with formation after thermal metamorphism the sulfides within the brachinite equilibrated between 600 and 400 c consistent with formation during cooling after thermal metamorphism contrary to the assertion that pentlandite is solely the product of low temperature aqueous alteration in many chondrite groups this study suggests that most sulfides in chondrites are formed at or upon cooling from high temperature the evaluation of a single mineral system within samples that retain petrographic context is vital to the interpretation of formation and alteration processes recorded by small extraterrestrial samples such as those that have been returned by the spacecraft missions stardust and hayabusa and will be returned by osiris rex and hayabusa2

evaluation of remote sensing techniques to measure decadal scale changes of hofsjokull ice cap iceland dynamic surficial changes and changes in the position of the firn line and the areal extent of hofsjokull ice cap iceland were studied through analysis of a time series 1973 98 of synthetic aperture radar sar and landsat data a digital elevation model of hofsjokull which was constructed using sar interferometry was used to plot the sar backscatter coefficient vs elevation and air temperature along transects across the ice cap seasonal and daily patterns are caused by freezing or thawing of the ice cap surface and abrupt changes in are noted when the air temperature ranges from 5 to 0 c late summer 1997 sar and reflectance landsat boundaries agree and appear to be coincident with the firn line and a sar boundary that can be seen in the january 1998 sar image in january 1994 through 1998 the elevation of this boundary on the ice cap was quite stable ranging from 1000 to 1300 m while the equilibrium line altitude as measured on the ground varied considerably thus the equilibrium line may be obscured by firn from previous years techniques are established to measure long term changes in the elevation of the firn line and changes in the position of the ice margin

fe ni metal and sulfide minerals in cm chondrites an indicator for thermal history abstract cm chondrites were subjected to aqueous alteration and in some cases to secondary metamorphic heating the effects of these processes vary widely and have mainly been documented in silicate phases herein we report the characteristic features of fe ni metal and sulfide phases in 13 cm and 2 cm related chondrites to explore the thermal history of these chondrites the texture and compositional distribution of the metal in cm are different from those in unequilibrated ordinary and co chondrites but most have similarities to those in highly primitive chondrites such as ch cr and acfer 094 we classified the cm samples into three categories based on metal composition and sulfide texture fe ni metal in category a is kamacite to martensite category b is characterized by pyrrhotite grains always containing blebs or lamellae of pentlandite opaque mineral assemblages of category c are typically kamacite ni co rich metal and pyrrhotite these categories are closely related to the degree of secondary heating and are not related to degree of the aqueous alteration the characteristic features of the opaque minerals can be explained by secondary heating processes after aqueous alteration category a cm chondrites are unheated whereas those in category b experienced small degrees of secondary heating cms in category c were subjected to the most severe secondary heating process thus opaque minerals can provide constraints on the thermal history for cm chondrites

the use of remote sensing data for mass balance studies at mýrdalsjokull ice cap iceland a series of satellite images of myrdalsjokull iceland was analyzed in view of their value for mass balance investigations a combination of optical satellite images from the aster sensor and synthetic aperture radar data from ers 2 and envisat asar proved very useful the glacier margin of myrdalsjokull was delineated on aster images from summer and winter 2004 with a time series of summer asar images it was possible to monitor the temporal and spatial development of the transient snowline tsl throughout the year 2004 as well as the firn line fl at the end of the balance year an inverse function was applied to visually enhance detail in the radar imagery winter radar images were not useful for mass balance observations because of frequent surface melting which prevented the transparency of the snow cover for c band microwaves interannual mass balance fluctuations were observed by comparing three radar images acquired in late summer 1998 1999 and 2004 respectively these fluctuations follow the same trend as the annual mean air temperature which shows a strong increasing trend between 1999 and 2004 an accumulation area ratio of 0 43 was determined for 2004 indicating clear negative mass balance conditions monitoring the tsl fl with radar summer images for mass balance studies rather than the equilibrium line el is suggested for large ice caps in maritime climates

discrimination of glacier facies using multi temporal sar data glacier facies from the greenland ice sheet and the wrangell st elias mountains alaska are analyzed using multi temporal synthetic aperture radar sar data from the european space agency ers 1 satellite distinct zones and facies are visible in multi temporal sar data including the dry snow facies the combined percolation and wet snow facies the ice facies transient melt areas and moraine in greenland and south central alaska very similar multi temporal signatures are evident for the same facies although these facies are found at lower altitude in west greenland where the equilibrium line appears to be found at sea level at 71 30 n during the year analyzed 1992 93 probably because of the cooling effect of the eruption of mount pinatubo in greenland both the percolation and dry snow facies are excellent distributed targets for sensor calibration with backscatter coefficients stable to within 0 2 db however the percolation facies near the top of mount wrangell are more complex and less easily delineated than in greenland and at high altitude the glacier facies have a multi temporal signature which depends sensitively on slope orientation

glacier facies of vestfonna svalbard based on sar images and gpr measurements abstract the warming climate of the arctic affects the mass budget of glaciers and changes in the distribution of glacier facies are indicative of their response to climate change the glacial mass budget over large land ice masses can be estimated by remote sensing techniques but selecting an efficient remote sensing method for recognizing and mapping glacier facies in the arctic remains a challenge in this study we compared several methods of distinguishing the facies of the vestfonna ice cap svalbard based upon synthetic aperture radar sar images and terrestrial high frequency ground penetrating radar gpr measurements glacier zones as determined using the backscattering coefficient sigma0 of sar images were compared against gpr data and an alternative application of internal reflection energy ire calculated from terrestrial gpr data was also used for differentiating the extent of glacier facies the ire coefficient was found to offer a suitable method for distinguishing glacier zones and for validating sar analysis furthermore results of analysis of fully polarimetric phased array type l band synthetic aperture radar alos palsar and european remote sensing synthetic aperture radar ers 2 sar images were compared with the ire coefficient classification especially promising method is h segmentation where the glacier zone boundaries corresponded very well with both gpr visual interpretation and ire classification results the ire coefficient s simplicity of calculation makes it a good alternative to the subjective gpr visual interpretation method where results strongly depend on the operator s level of experience we therefore recommend for gpr profiles to be used for additional validation of sar image analysis in studies of glacier facies on the high arctic ice masses

two methods for firn area and mass balance monitoring of svalbard glaciers with sar satellite images this paper presents two methods for glacier monitoring on svalbard using synthetic aperture radar sar satellite images both methods were developed on glaciers in the kongsfjorden area the first method monitors the firn area extent and the firn line over time by thresholding and filtering the sar image manual detection of the threshold is preferable but using a constant threshold for all images also gives adequate results a retreat of the fire line position is visible especially on kongsvegen corresponding to consecutive years of negative mass balance the second method applies a k means classification to three clusters on the glacier surface the areal extent of the resulting class on the upper part of the glacier correlates remarkably well with the independently measured mass balance of kongsvegen having a correlation coefficient of around 0 89 for the various glaciers this is because the snow from the accumulation area influences the k means classification thus on glaciers where mass balance values are available new mass balance values can be predicted solely from sar images for glaciers where no mass balance is available the area change cannot be calibrated to absolute mass balance values but relative changes can be predicted

mineralogy and texture of fe ni sulfides in ci1 chondrites clues to the extent of aqueous alteration on the ci1 parent body to better understand the role of aqueous alteration on the ci1 parent body we have analyzed the texture composition and mineral associations of iron nickel sulfides in four of the five known ci1 chondrites the most commonly occurring sulfide present in the ci1 chondrites is the iron deficient fe ni sulfide pyrrhotite fe ni 1 xs that has a composition close to that of stoichiometric troilite fes three of the ci1s alais ivuna and tonk also contain pentlandite fe ni 9s8 although pentlandite is a rare phase in ivuna cubanite cufe2s3 was found in both alais and ivuna in this study although it has also been reported in orgueil macdougall and kerridge 1977 the pyrrhotite grains in all four chondrites form hexagonal rectangular or irregular shapes and show no evidence of ni or co zoning the pyrrhotite grains in orgueil and ivuna are in general smaller and show more corrosions or embayments than those in alais or tonk we suggest that the precursor sulfide present in the ci1 chondrites was troilite which during brecciation and oxidation on the parent body at a temperature of 100 c or less converted the troilite to magnetite and pyrrhotite with pentlandite inclusions subsequently continued alteration on the parent body removed pentlandite partially from alais tonk and ivuna completely from orgueil leaving behind pyrrhotite with spaces corrosions where the pentlandite had been ni derived from the pentlandite was incorporated into ferrihydrite onto the surface of which the ni na sulfate ni bloedite formed based on the size and abundant corrosions within pyrrhotite grains combined with observations from other authors we conclude that orgueil and ivuna have undergone a greater degree of alteration than alais and tonk further work is needed to assess the conditions under which pentlandite would be dissolved preferentially to pyrrhotite as the study of terrestrial literature indicates that the latter mineral is preferentially removed

interpretation of sar imagery of the greenland ice sheet using coregistered tm imagery abstract landsat thematic mapper tm images are coregistered with a seasat synthetic aperture radar sar image of the margin of the greenland ice sheet and used in the interpretation of features in the sar data a winter tm image is used to provide topographic information while a summer tm image provides information on the pattern of melt and the location of lakes many previous hypotheses are confirmed and some are rejected it is shown that 1 the snow line is easily d detectable in sar imagery 2 areas of higher radar backscatter in the bare ice zone most often correspond to areas full of crevasses too small to resolve in the sar image 3 subsurface scattering causes significantlblurring of features in sar imagery 4 the band of surface lakes occurring above the snow line corresponds to at least a portion of the wet snow zone 5 water is the cause of reduced radar backscatter above the snow line and 6 the fact that water causes reduced radar backscatter above the snow line permits the use of backscatter variations as a proxy indicator of surface topography in snow covered regions experiencing melt

analysis of glaciers and geomorphology on svalbard using multitemporal ers 1 sar images the all weather capability makes synthetic aperture radar sar interesting with respect to glaciological studies in remote arctic areas the aim of this project was to investigate how the european remote sensing satellite ers sar backscatter from certain glaciological and geomorphological structures varied with time and find out at which time of the year a sar acquisition will give the best result when observing certain features five ers 1 sar images one from the winter and four from the summer were acquired over the northwestern part of svalbard norway ground measurements and observations were made at the same time as one of the summer sar acquisitions the ground data as well as meteorological recordings were used to analyze the sar backscatter changes in the multitemporal data set a zonation on the glaciers representing snow firn superimposed ice and glacier ice was detected in the winter image only the equilibrium line could also be derived from this sar image information on drainage patterns distribution of wet and dry snow areas and the occurrence of crevasses was derived from the summer images changes in snow cover distribution was identified in the summer images the form and position of ice cored moraines fossil beach ridges and river channels were identified in all images early summer images showed the highest potential for identification of landforms small scale landforms such as patterned ground and tundra polygons could not be identified