a comparison of terrasar x radarsat 2 and alos palsar interferometry for monitoring permafrost environments case study from herschel island canada abstract interferometric synthetic aperture radar insar data sets from terrasar x radarsat 2 and alos palsar are compared for their ability to detect ground movement over the continuous permafrost site of herschel island yukon territory canada all three sensors maintain good coherence within a summer season and can be used to create summer displacement products stacking is advantageous for the terrasar x and radarsat 2 data sets although mottling possibly an interaction of the sar with vegetation or residual tropospheric noise is visible reducing the reliability of the results radarsat 2 and alos palsar provide the most promising results with the ability to form one year interval interferograms palsar can also form two and three year interval interferograms long interval data sets spanning 2007 to 2010 identify a band of movement of 20 to 30 cm year along the north east coast and a region of movement of up to 5 cm year near the northern tip of the island the ability to form long interval displacement products holds the most promise for permafrost monitoring since long term trends are of greater interest for permafrost stability than short term seasonal changes terrasar x data have the disadvantage that year to year interferograms cannot be formed insar is not the ideal monitoring technique for the large thaw slumps of herschel island although general areas of instability can be identified specific slump detection is limited by radar look direction and the large and abrupt slump movement often accompanied by disintegration and collapse of slump sections causes loss of coherence in the insar data thaw slumps may require a different interferometric approach such as slump extent mapping from coherence loss or the installation of corner reflectors and point target techniques the frequent revisit and high spatial resolution of terrasar x provide the best chance of maintaining coherence over thaw slumps in general insar is more successful at identifying broad areas of subtle subsidence in gentle relief areas of terrain instability possibly due to permafrost thaw or ground ice melt and the removal of water volume and prior to significant slumping

the effect of soil hydrology on the oxygen and hydrogen isotopic compositions of plants source water abstract many studies have demonstrated that the isotopic composition of plants source water is the main factor affecting the isotopic composition of tree rings because of soil hydrological processes soil water as the source water for plants may isotopically differ from precipitation that contains climatic information such as surface temperature this study addresses the effects of soil hydrological processes on the isotopic compositions of soil water and discusses how these effects affect interpretations of tree ring data in isotopic dendroclimatology we collected precipitation soil gas at two depths 20 and 50 cm and twigs from a maple tree acer saccharum on a biweekly basis during the growing season in 1997 1999 at hanover nh usa water was extracted from the twig samples by vacuum distillation all water samples were analyzed for both d and 18 o soil co 2 was extracted from soil gas and measured for the 18 o values and using the soil temperature and assuming isotopic equilibrium between co 2 and h 2 o we calculated the 18 o values of soil water comparisons among the isotopic time series of each type of sample indicate the following 1 the isotopic composition of soil water is much less variable than that of precipitation suggesting isotopic mixing between waters of different precipitation events 2 in early spring soil water at all depths is isotopically similar to winter precipitation but with time the surface soil water becomes progressively enriched in deuterium and 18 o due to infiltration of summer rain and enrichment through soil water evaporation 3 the influence of summer precipitation decreases with increasing depth and soil at 50 cm can only receive water from large storms 4 replacement of old soil water with new infiltrating water is dependent upon frequency and intensity of growing season precipitation and it is generally more efficient in a wet year than in a dry year 5 the tree we studied uses water mainly from near surface soil layers 6 the d 18 o relationship in twig water indicates that soil water has experienced isotopic enrichment by evaporation these results have important implications for selecting sites for paleoclimatic studies using isotopic data of tree rings

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

insar measurements of surface deformation over permafrost on the north slope of alaska 1 ground based measurements of active layer thickness provide useful data for validating calibrating remote sensing and modeling results however these in situ measurements are usually site specific with limited spatial coverage here we apply interferometric synthetic aperture radar insar to measure surface deformation over permafrost on the north slope of alaska during the 1992 2000 thawing seasons we find significantly systematic differences in surface deformation between floodplain areas and the tundra covered areas away from the rivers using floodplain areas as the reference for insar s relative deformation measurements we find seasonally varying vertical displacements of 1 4 cm with subsidence occurring during the thawing season and a secular subsidence of 1 4 cm decade we hypothesize that the seasonal subsidence is caused by thaw settlement of the active layer and that the secular subsidence is probably due to thawing of ice rich permafrost near the permafrost table these mechanisms could explain why in situ measurements on alaskan north slope reveal negligible trends in active layer thickness during the 1990s despite the fact that atmospheric and permafrost temperatures in this region increased during that time this study demonstrates that surface deformation measurements from insar are complementary to more traditional in situ measurements of active layer thickness and can provide new insights into the dynamics of permafrost systems and changes in permafrost conditions

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

using tree ring cellulose as a tool to estimate past tritium inputs to the ocean tritium 3h concentrations in tree rings should reflect ambient precipitation thus to improve knowledge of the 3h input to the oceans we developed a new technique to measure 3h concentrations in annual tree rings measurements of 3h were made on cellulose the primary constituent of wood as the isotopic signal of its carbon bound hydrogen atoms should be unchanged since biosynthesis traditional cellulose extraction techniques from softwoods are slow and were found to not yield reproducibly pure cellulose therefore a new microwave method was developed which reduces extraction times from 3 5 days to approximately 3 h potential 3h contamination from the hydroxyl groups of the cellulose molecule was subsequently removed by exchange with 3h free naoh thus avoiding the dangers of working with large amounts of cellulose nitrate the validity of the technique was tested by presenting a 3h time series from a cedar tree which grew in tollymore forest park northern ireland for comparison with 3h data from the valentia weather station we find that the 3h in the cellulose clearly reflects the 3h in precipitation with no significant smearing of the bomb signal a simple box model illustrates that the maximum reservoir residence time of source water for the tree is less than 1 yr suggesting that groundwater is not a major source of water for this tree in general however the groundwater input needs to be quantified for accurate 3h reconstructions to be made this work demonstrates the potential of using 3h in wood cellulose as a proxy for 3h in precipitation and thus opens the door to reconstruction of past 3h inputs to the ocean

climatic implications of the natural variations of d h ratios in tree ring cellulose abstract natural variations in the deuterium composition of carbon bound hydrogen of cellulose nitrate from tree rings have been measured trees from edmonton have been analysed in detail and the d values of 5 year groups of rings show a strong temporal correlation with mean annual temperature at the growth site this is shown to result from the cellulose isotopic composition being related to the isotopic composition of soil water used during photosynthesis the soil water is in turn related to meteoric water which at this growth site appears to correlate temporally with mean annual temperature similar measurements from trees which grew in various areas of north america show a strong spatial correlation between d of cellulose and mean annual temperature the spatial functional relationship between d values and mean annual temperature at the growth site t is found to be d 5 5t 130 swhich compares with the spatial relationship between d of meteoric water and mean annual air temperature which is d 5 6t 100

mid holocene warming in the northwest kola peninsula russia northern pine limit movement and stable isotope evidence a set of 40 subfossil scots pines pinus sylvestris l was sampled in small lakes beyond the modernpine limit in the northwest kola peninsula russia radiocarbon dating suggests that the pine exp

using persistent scatterer interferometry to map and quantify permafrost thaw subsidence a case study of eboling mountain on the qinghai tibet plateau

medieval climate warming and aridity as indicated by multiproxy evidence from the kola peninsula russia data obtained from the low elevation khibiny mountains ca 67 68jn 33 34je on the kola peninsula northwest russia indicate a period of exceptionally warm and dry conditions commenced at ca ad 600 and was most pronounced between ca ad 1000 and 1200 warmer summer temperatures during this period coeval with the medieval warm period observed in other parts of europe are evident in a 100 140 m upward shift in the pine pinus sylvestris l limit in the khibiny mountains on average the cellulose of pine trees that grew between ca ad 1000 and 1300 is enriched by y 13 c values of around 1xcompared to the modern trees from the region further suggesting warmer summer climate than at present the medieval warm period was also accompanied by a steady decline in avalanche activity and the resulting formation of soils on the current avalanche cones in the khibiny mountains suggesting lower winter precipitation and thinner snow cover lower precipitation is also evident by currently submerged tree stumps dating to the medieval period that indicate lower lake levels on the kola peninsula in the middle of the peninsula at about ad 1000 the level of small closed basin lakes was f1 m lower than the modern time at some sites drier conditions may be attributable to decreased cyclonic activity the medieval warm and dry episode was followed at ca ad 1300 by the development of a colder climate with increased precipitation resulting in a decline in the alpine pine limits increased avalanche activity and higher lake levels that phase corresponds to the modern aeolian episode reconstructed in subarctic finland our results indicate that the medieval warm period on the kola peninsula

hydrogen isotope ratios of recent lacustrine sedimentary n alkanes record modern climate variability abstract hydrogen isotope ratios were measured on n alkanes n c12 to n c31 extracted from recent lake surface sediments along a n s european transect to test if modern climate variability is recorded in these biomarkers d values of the n alkanes are compared to d values of meteoric water from the iaea gnip database spanning a range from 119 in northern sweden to 41 in southern italy to lake water d values and to mean annual temperatures varying between 2 0 c in the north and 13 7 c in the south d values of the short chained n alkanes n c12 to n c20 excluding algal derived n c17 and n c19 are higher in the north and lower in the south the isotopic fractionation e for hydrogen between meteoric water and the short chained n alkanes is increasing from n to s by more than 100 and is significantly correlated to mean annual temperature for n c16 and n c18 this suggests that these n alkanes may originate from a different source in the northern lakes possibly due to petroleum contamination or are synthesized using a different biochemical pathway the n c17 and n c19 alkanes of algal origin the n c21 and n c23 alkanes originating from water plants and the long chain n alkanes n c25 n c27 n c29 and n c31 of terrestrial origin clearly correlate with d values of meteoric water lake water and mean annual temperature indicating that they excellently record the d value of meteoric water the mean hydrogen isotope fractionation ec17 w of 157 sd 13 between n c17 and meteoric water is fairly constant over the wide range of different climates and lake environments suggesting only minor influence of environmental factors on this biochemical fractionation this suggests that d values of n c17 are suitable to reconstruct the isotopic composition of source water the mean fractionation between the long chain n alkanes and water is 128 sd 12 the mean difference of 31 between both e values is likely due to evaporative enrichment of deuterium in the leaf water if this is the only influence on the enrichment the difference between the d values of terrestrial and aquatic compounds might be suitable to reconstruct terrestrial evapotranspiration of the lake environment

on the interference of man made em fields in the magnetotelluric dead band during processing of magnetotelluric mt data acquired in a survey carried out in southern italy a problem was encountered connected with the so called dead band of the mt signal around 1 hz in the apparent resistivity curves of some mt soundings a v shaped minimum appeared centred on the dead band frequency this phenomenon turned out to originate from a strong artificial source and was not due to a downward bias of the robust processing techniques adopted the source distance from the mt sounding locations was such that the v shaped minimum fell precisely in the dead band frequency range theoretical considerations about fields generated by an electric dipole led us to the probable identification of the source as the d c powered railway between naples and bari

deep electrical structure and geological significance of tongling ore district abstract the tongling ore district is one of the most important cu polymetal producers in the lower yangtze river metallogenic belt of china to understand deep crust structure beneath the tongling ore district more comprehensively and objectively and to explore important scientific issues such as characteristics of lithospheric evolution the relationship between the crustal structure and metallogenesis it is necessary to study the variation of crust electrical structure in the study area for this purpose six magnetotelluric mt sounding profiles have been completed by sinoprobe 03 project based on the imaging results of the six profiles electrical conductivity structure of the crust has been analyzed the result shows that the geology beneath the profiles is characterized by layering in vertical direction and block division in horizontal direction the high resistivity features are related to the transparent zones detected at the upper crust in reflection seismic surveys the absence of reflectivity from the depths indicates a homogeneous zone which could often be related to granitic intrusions combining the regional tectonic evolution mt and other geophysical data we suggest that the high resistivity bodies crossing the tongling uplift reveals the center of magma activity and the layering in vertical direction in the lower crust reveals a normal lower crust model and propose a small scale underplating model which is different with both the partial melting of a thickened or delaminated lower continental crust model and the oceanic ridge subduction the underplating might be related to small scale lithospheric or lower crust delamination controlled by deep fault during the early cretaceous the result of this mt survey is important for constraining lithospheric evolution and metallogenesis in the lower yangtze metallogenic belt such as collision of north china craton and yangtze craton underplating models deep structure mechanisms of ne sw trending rift as well as graben basin and probable metallogenesis

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

can magnetotelluric data resolve lower crustal conductors abstract it is commonly accepted that the lower crust is electrically conductive the most commonly used measurement technique is magnetotellurics mt using natural plane waves but also a few controlled source experiments have been carried out to study this problem previous work using mt and controlled source data has shown that in areas devoid of a sedimentary layer a hypothetical homogeneous lower crust can be resolved accurately adding a conductive surface layer degrades the resolving power of mt and controlled source data we have studied this problem quantitatively by varying the conductances product of the conductivity and thickness of the sedimentary and lower crustal layers both mt data and the data calculated with a controlled source grounded dipole technique are used for investigation we show that for sedimentary conductances of 200 2000 s mt data combined with controlled source data may identify a conducting lower crust provided its resistivity is less than a few hundred m but its thickness and resistivity cannot be resolved

hydrogen isotope ratios of palmitic acid in lacustrine sediments record late quaternary climate variations the rich paleoclimate information preserved in lacustrine sedimentary organic matter can be difficult to extract because of the mixed terrestrial and aquatic inputs herein we demonstrate that compound specific hydrogen isotope analysis of palmitic acid pa a ubiquitous compound in lacustrine sediments captures the d signals of lake water samples collected across a diverse range of 33 north american lakes show a strong correlation between water and dpa values at crooked pond massachusetts the dpa changes in a 14 k y sediment record parallel temperature trends inferred from fossil pollen downcore changes reveal differences between climatic trends in new england and in greenland that are consistent with important regional differences in climate controls

a climatic record from l4c dated wood fragments from southwestern colorado deuterium concentration in trees are related to the climatic temperature at which the trees grew deuterium analyses were made on all available 39 14 c dated all 14 c dates cited are uncorrected wood fragments collected from lake emma sediments the 14 c dates range from 9600 to 5400 b p tree line was above lake emma at 9600 b p was at lake emma at about 5000 b p and is 80 m below lake emma at the present time the isotopic records at the various intervals of time coincide very well with this history the range of d values is maximum at 9600 b p and is minimum at about 5400 b p these data allow us to estimate the temperature range for the area between tree line and lake emma between these times these results confirm previously observed cooling trends from several sources in the western hemisphere

post wildfire surface deformation near batagay eastern siberia detected by l band and c band insar thawing of ice rich permafrost and subsequent ground subsidence can form characteristic landforms and the resulting topography they create are collectively called thermokarst the impact of wild

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

geodetically accurate insar data processor we present a new interferometric synthetic aperture radar insar processing approach that capitalizes on the precise orbit tracking that is available with modern radar satellites our method uses an accurate orbit information along with motion compensation techniques to propagate the radar echoes to positions along a noninertial virtual orbit frame in which the location and focusing equations are particularly simple so that images are focused without requiring autofocus techniques and are computed efficiently motion compensation requires two additional focus correction phase terms that are implemented in the frequency domain if the images from an interferometric pair or stack are all computed along the same reference orbit flat earth topographic correction is not needed and image coregistration is simplified obviating many difficulties that are often encountered in insar processing we process several data sets collected by the alos palsar instrument and find that the geodetic accuracy of the radar images is 10 20 m with up to 20 m of additional image distortion needed to align 100 km 100 km scenes with reference digital elevation models we validated the accuracy by using both known radar corner reflector locations and by the registration of the interferograms with digital maps the topography corrected interferograms are free from all geometric phase terms and they clearly show the geophysical observables of crustal deformation atmospheric phase and ionospheric phase

multi interferogram method for measuring interseismic deformation denali fault alaska summary studies of interseismic strain accumulation are crucial to our understanding of continental deformation the earthquake cycle and seismic hazard by mapping small amounts of ground deformation over large spatial areas insar has the potential to produce continental scale maps of strain accumulation on active faults however most insar studies to date have focused on areas where the coherence is relatively good e g california tibet and turkey and most analysis techniques stacking small baseline subset algorithm permanent scatterers etc only include information from pixels which are coherent throughout the time span of the study in some areas such as alaska where the deformation rate is small and coherence very variable it is necessary to include information from pixels which are coherent in some but not all interferograms we use a three stage iterative algorithm based on distributed scatterer interferometry we validate our method using synthetic data created using realistic parameters from a test site on the denali fault alaska and present a preliminary result of 10 5 5 0 mm yr 1 for the slip rate on the denali fault based on a single track of radar data from ers1 2

can sedimentary leaf waxes record d h ratios of continental precipitation field model and experimental assessments abstract d h ratios of leaf waxes d wax derived from terrestrial plants and preserved in lake sediments can provide important information on past continental hydrology ideally d wax can be used to reconstruct precipitation d h ratios d p which is a well established paleoclimate proxy however many other factors such as vegetation and relative humidity rh also affect d wax variation how the combination of these factors affects sedimentary d wax is unclear here we use a transect of 32 lake surface sediments across large gradients of precipitation relative humidity and vegetation composition in the southwestern united states to study the natural factors affecting sedimentary d wax d values of c 28 n alkanoic acids show significant correlation with d p values r 2 0 76 with an apparent isotopic enrichment of 99 8 indicating that sedimentary d wax values track overall d p variation along the entire transect leaf waxes produced by plants grown under controlled conditions rh 80 60 40 show a small increase in d h ratios as rh decreases consistent with prediction from the craig gordon model however the isotopic effect of rh on d wax along the natural transect is partially countered by the opposing influence of vegetation changes the correlation between d wax and d p values is significantly higher r 2 0 84 in the drier portions of the transect than in the wetter regions r 2 0 64 this study suggests that d h ratios of sedimentary leaf waxes can be used as a proxy for precipitation d variations with particularly high fidelity in dry regions although more studies in other regions will be important to further test this proxy

sentinel 1 insar measurements of deformation over discontinuous permafrost terrain northern quebec canada abstract differential synthetic aperture radar interferometry d insar has been applied in permafrost environments to detect surface deformation caused by freeze thaw processes in the active layer and underlying permafrost the effectiveness of sentinel 1 insar in monitoring ground surface deformation over continuous permafrost terrain above the treeline has been proven the heterogeneous landscape and developed vegetation cover increase the difficulty of applying d insar in sub arctic discontinuous permafrost terrain the potential of sentinel 1 insar in such an environment has not been fully explored in this study we explore the capabilities and limitations of applying sentinel 1 time series data for monitoring surface deformation over discontinuous permafrost terrain the interferometric coherence time series from september 2016 to april 2018 were analyzed over typical landscapes in discontinuous permafrost environments and their thaw subsidence curves are revealed by the small baseline subset sbas insar technique the seasonal thaw subsidence in the summer of 2017 was in the range of 15 80 mm in the study area the land cover types with thaw subsidence magnitudes from low to high are exposed land peatland lichen low shrub lichen dominated and wetland low vegetation the difference in displacement pattern between lichen dominated and wetland low vegetation dominated permafrost terrains is especially clear at the end of the thawing stage in september and october the differences in thaw subsidence magnitude and pattern reveal the influence of the soil water content in the active layer and permafrost properties on the thaw subsidence patterns we also compared the sentinel 1 retrieved cumulative displacement with the x band terrasar x and l band alos palsar results the difference of retrieved deformation magnitude using the three sensors is amplified when shrubs are more developed the findings indicate that sentinel 1 time series with a 6 day or 12 day span work well over discontinuous permafrost terrain above the tree line i e tundra tundra wetlands and less developed shrub tundra environments during the thawed season but the results and accuracy are not promising over developed shrub tundra and especially forest tundra environments

large scale hydrological change drove the late miocene c4 plant expansion in the himalayan foreland and arabian peninsula carbon isotope changes in paleosols from siwalik pakistan and marine sediments from the bengal fan indicate a major c 4 plant expansion in the himalayan foreland during the late miocene however the timing and mechanisms behind the c 4 plant expansion remain enigmatic here we present high resolution 60 k y biomarker and compound specific isotope data spanning the past 11 m y from ocean drilling program site 722 in the arabian sea an 5 6 increase in leaf wax 13 c values indicates a marked rise of c 4 plants from 10 to 5 5 ma with accelerated expansion from 7 9 to 5 5 ma a concurrent 50 rise in leaf wax d values is attributed to a combined effect of changes in precipitation amount and evaporation indicating that source regions for the plant waxes became progressively drier from 10 to 5 5 ma in contrast to earlier reports our isotope records biomarker abundances alkenone u k 37 and globigerina bulloides abundance data do not suggest enhanced summer monsoon circulation during this time interval rather our results suggest that large scale hydrological changes drove the late miocene expansion of c 4 plants in the himalayan foreland and arabian peninsula

centennial scale compound specific hydrogen isotope record of pleistocene holocene climate transition from southern new england 1 northeastern north america experienced major climate shifts during the pleistocene holocene transition however there have been no high resolution isotopic records of climate change from this region here we present a centennial scale record of climate change during the transition based on d h ratios of behenic acid c22 nacid or ddba from a sediment core in blood pond massachusetts surface calibrations from a transect of 19 lakes in eastern north america show that ddba values track mean annual atmospheric temperature variations the abrupt climate events observed in blood pond records show remarkable similarity with greenland ice core d 18 o records during the pleistocene during the early holocene the northeastern north america ddba record was more variable than greenland possibly due to the close proximity of the laurentide ice sheet and impact of freshwater outbursts as the ice sheet rapidly retreated citation hou j y huang w w oswald d r foster and b shuman 2007 centennialscale compound specific hydrogen isotope record of pleistocene holocene climate transition from southern new england geophys res lett 34 l19706 doi 10 1029 2007gl030303

insar detects increase in surface subsidence caused by an arctic tundra fire wildfire is a major disturbance in the arctic tundra and boreal forests having a significant impact on soil hydrology carbon cycling and permafrost dynamics this study explores the use of the microwave interferometric synthetic aperture radar insar technique to map and quantify ground surface subsidence caused by the anaktuvuk river fire on the north slope of alaska we detected an increase of up to 8 cm of thaw season ground subsidence after the fire which is due to a combination of thickened active layer and permafrost thaw subsidence our results illustrate the effectiveness and potential of using insar to quantify fire impacts on the arctic tundra especially in regions underlain by ice rich permafrost our study also suggests that surface subsidence is a more comprehensive indicator of fire impacts on ice rich permafrost terrain than changes in active layer thickness alone

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

stable carbon and hydrogen isotope ratios of subfossil oaks in southern germany methodology and application to a composite record for the holocene the d ad values exist for the time interval 6470 bc to ad 905 not all records have the same time resolution and not all of them were prepared in the same way for isotope analysis however investigations on the influence of the preparation technique on the isotope values and on the isotope composition of different wood compartments latewood and earlywood respectively allowed us to homogenize the records the comparison of d values of wood with different cambial ages showed that hydrogen isotoperatios were affected by growth tre

correction to a statistical test of phase closure to detect influences on dinsar deformation estimates besides displacements and decorrelation noise two case studies in high latitude regions displacements of the earth s surface can be estimated using differential interferometric synthetic aperture radar the estimates are derived from the phase difference between two radar acquisitions when at least three such acquisitions are available one can compute the displacement between the first and the third acquisition and compare it with the sum of the two intermediate displacements these two are expected to be equal for a piston like spatially uniform deformation however this is not necessarily the case in measured data such lack of phase closure can be due to decorrelation noise alone it has also been attributed to complex scattering processes such as soil moisture changes or multiple scattering sources however the nature of these nonrandom effects is only poorly understood in cold regions as the role of snow and freeze thaw processes has not been studied to date to distinguish the noise like and the systematic effects an asymptotic wald significance test is proposed it detects situations when the observed closure error cannot solely be explained by noise such situations with p are observed at the ku band during snow metamorphism and melt and following a summer precipitation event in sodankyla finland they can also be prevalent 25 in the x band observations of ice rich permafrost regions in the lena delta russia indicating the presence of processes that can have systematic and deleterious impacts on the estimation of surface movements satellite based monitoring of these displacements is thus possibly subject to complex error sources in high latitude regions

electromagnetic outline of the solfatara pisciarelli hydrothermal system campi flegrei southern italy abstract we describe the results from a combined controlled source audio magnetotelluric csamt and natural source magnetotelluric mt survey carried out in the solfatara pisciarelli s p area located in the central part of the campi flegrei cf composite caldera west of naples southern italy the s p area represents the most active zone within the cf caldera in terms of hydrothermal manifestations and local seismicity since 1969 the cf caldera is experiencing ground deformation seismicity and geochemical fluid changes which are particularly evident in the s p area a 1 km long nearly w e directed csamt mt profile crossing the fumarole field was carried out in the s p area with the aim of deducting a resistivity model of the structural setting of the hydrothermal system in the first 3 km depth an interpretation of the modelled section across the profile is given in this paper taking advantage from already existing seismic gravity and geochemical data in the same area three well distinct zones have been outlined the first zone is a very shallow electrically conductive body localized beneath the westernmost segment of the profile which within a short distance of about 100 m dips westwards from near surface down to some hundred metres in depth mostly accounting for the very low resistivity 1 10 m and the exceedingly high values of v p v s 4 this shallow zone has been ascribed to a water saturated high pressurized geothermal reservoir the second zone which has been localized below the west central portion of the csamt mt transect appears as a composite body made up of a nearly vertical plumelike structure that escapes at about 2 25 km depth from the top edge of the east side of a presumably horizontal platelike body the plumelike structure rises up to the free surface in correspondence of the fumarole field whereas the platelike structure deepens at least down to the 3 km of maximum exploration depth the combined interpretation of resistivity 50 100 m body wave velocity ratio v p v s 3 and geochemical data indicates that the plumelike portion can likely be associated with a steam gas saturated column and the platelike portion with a high temperature 300 c over pressurized gas saturated reservoir finally the third zone which has been localized beneath the eastern half of the transect from about 1 2 km down to about 3 km of depth is also characterized by very low resistivity values 1 10 m jointly interpreted with seismic v p v s 0 g cm 3 data this last electrically conductive structure appears to be associated with a hydrothermally mineralized clay rich body

estimating 1992 2000 average active layer thickness on the alaskan north slope from remotely sensed surface subsidence 1 the measurement of temporal changes in active layer thickness alt is crucial to monitoring permafrost degradation in the arctic we develop a retrieval algorithm to estimate long term average alt using thaw season surface subsidence derived from spaceborne interferometric synthetic aperture radar insar measurements our algorithm uses a model of vertical distribution of water content within the active layer accounting for soil texture organic matter and moisture we determine the 1992 2000 average alt for an 80 100 km study area of continuous permafrost on the north slope of alaska near prudhoe bay we obtain an alt of 30 50 cm over moist tundra areas and a larger alt of 50 80 cm over wet tundra areas our estimated alt values match in situ measurements at circumpolar active layer monitoring calm sites within uncertainties our results demonstrate that insar can provide alt estimates over large areas at high spatial resolution

postglacial climate reconstruction based on compound specific d h ratios of fatty acids from blood pond new england we determined hydrogen isotope ratios of individual fatty acids in a sediment core from blood pond massachusetts usa in order to reconstruct climate changes during the past 15 kyr in addition to palmitic acid c16n acid which has been shown to record lake water d h ratios our surface sediments and down core data indicate that behenic acid c22n acid produced mainly by aquatic macrophytes is also effective for capturing past environmental change calibration using surface sediments from two transects across eastern north america indicates that behenic acid records d variation of lake water down core variations in d values of behenic acid and pollen taxa are consistent with the known climate change history of new england by evaluating the hypothesis that d h fractionations of long chain even numbered fatty acids c24 c32n acids relative to lake water provide independent estimates of relative humidity during the growing season we find that differences between lake level records and isotopically inferred humidity estimates may provide useful insight into seasonal aspects of the hydrologic cycle combined analyses of d h of short and long chain fatty acids from lake sediment cores thus allow reconstructions of both past temperature and growing season relative humidity comparison of d records from two lakes in new england provides critical information on regional climate variation and abrupt climate change such as the 8 2 ka event

tree ring d h ratio from kenya east africa and its palaeoclimatic significance the d h ratio of non exchangeable hydrogen atoms in tree rings is a reliable record of the stable isotope ratio of source water used by a given tree during its growth depending on the site of growth this source water has been shown to be the summer rains or groundwater or both because the isotope ratio of any of these source waters is influenced by climate tree ring isotope data provide a fine climatic signature in most cases however isotope dendroclimate studies so far have been focused mainly in north america and to a lesser degree in europe we report here analysis of a record spanning 145 yr from a tree juniperus procera from kenya in east africa the d h ratio correlates reasonably well with the recorded levels of the adjacent lake victoria and brings out interesting palaeoclimatic inferences from a region for which very little such data are available significantly the relatively severe arid conditions around 1920s and the record rainfall around 1961 are reflected in the tree ring isotope ratio this suggests that such tree ring isotope records could be used in the palaeoclimatic reconstruction of this area and could be applied to tropical environments

spatio temporal variability of x band radar backscatter and coherence over the lena river delta siberia abstract satellite based monitoring strategies for permafrost remain under development and are not yet operational remote sensing allows indirect observation of permafrost a subsurface phenomenon by mapping surface features or measuring physical parameters that can be used for permafrost modeling we have explored high temporal resolution time series of terrasar x backscatter intensity and interferometric coherence for the period between august 2012 and september 2013 to assess their potential for detecting major seasonal changes to the land surface in a variety of tundra environments within the lena river delta siberia the terrasar x signal is believed to be strongly affected by the vegetation layer and its viability for the retrieval of soil moisture for example is therefore limited in our study individual events such as rain and snow showers that occurred at the time of terrasar x acquisition or a refrozen crust on the snowpack during the spring melt were detected based on backscatter intensity signatures the interferometric coherence showed marked variability the snow cover onset and snow melt periods were identified by significant reduction in coherence principal component analysis provided a good spatial overview of the essential information contained in backscatter and coherence time series and revealed latent relationships between both time series and the surface temperature the results of these investigations suggest that although x band sar has limitations with respect to monitoring seasonal land surface changes in permafrost areas high resolution time series of terrasar x backscatter and coherence can provide new insights into environmental conditions

assessing meteoric water composition and relative humidity from18o and2h in wood cellulose paleoclimatic implications for southern ontario canada abstract an empirical model is presented that derives the initial isotopic composition of water used by terrestrial plants and the relative humidity that prevailed during photosynthesis from the isotopic composition of oxygen and carbon bound hydrogen in the plant cellulose the model uses fixed values for the fractionation factors that describe the evapotranspirative isotopic enrichment of leaf waters and the biochemical fractionations occurring during cellulose synthesis when applied to cellulose extracted from fossil plant matter the model can be used to generate quantitative estimates of the temperature and moisture regimes of the past the application of the model is demonstrated by consideration of 18o and 2h results on cellulose from fossil wood collected at brampton ontario the brampton data yield records of systematic changes in the temperature and moisture regimes of the eastern great lakes region over the past 11 500 a both mean annual temperature and photosynthetic humidity increased substantially from values much lower than the present at the end of the wisconsin stage to values higher than the present in the mid holocene the phase relation of the paleotemperature and paleohumidity curves engenders differentiation of the climatic history at brampton into four characteristic zones i a period of ameliorating climate predominantly much colder and drier than now lasting until about 7400 b p ii an early hypsithermal period of warm and dry conditions that transformed after 6000 a b p into iii the main hypsithermal time of warmth and pronounced moistness subsequent climatic detrioration led to establishment of iv cool moist conditions like the present sometime within the last few thousand years

climatic correlations in the stable isotope records of silver fir abies pindrow trees from kashmir india a high degree of coherence in the annual stable isotopic records along different radial directions of a silver fir tree and between two members of this species from the kashmir valley has recently been reported by us since such a common pattern of isotopic variability is most likely due to the climatic fluctuations in the site we have compared the mean d 13c and 18o records of these trees with instrumentally measured climatic parameters recorded in a nearby weather station to identify the climatic parameters predominantly influencing the isotopic record a multiple regression analysis of the two records for the period 1903 1932 yields the following 1 d is most sensitive to the amount of growing season precipitation followed by mean maximum temperature tree cellulose shows an amount effect analogous to precipitation samples the temperature coefficient for d is in good agreement with earlier estimates based on spatial correlations 2 13c is significantly related to humidity and cloud amount the signs of the regression coefficients are consistent with the recent model of francey and farquhar for13c 12c fractionation in c3 plants 3 18o of cellulose appears to be controlled significantly by relative humidity 18o shows less overall correlation with climatic parameters than d and 13c 4 d of carbon bound hydrogen and 18o of tree cellulose are linearly related with a slope of7 9 0 3 suggesting evaporative enrichment in leaf water

geophysical and hydrogeological experiments from a shallow hydrothermal system at solfatara volcano campi flegrei italy response to caldera unrest 1 integration of high resolution geophysical and hydrogeological investigations at solfatara volcano campi flegrei italy allowed us to 1 image the shallow and intermediate subsurface to the crater 2 elucidate patterns in the shallow subsurface degassing and 3 refine and upgrade volcano monitoring strategies for this dynamic area our results show that the subsurface to the crater can be divided roughly into two zones a dry outcropping layer overlying a horizon saturated by hydrothermal fluids within this saturated zone intersections of dominant nw and ene striking structural lineaments act as preferential escape conduits for the fluids which generate high microseismic noise amplitudes in the southeastern part of the crater hydrogeological data suggest an uprising of the isotherms below solfatara crater and a marked increment of fluid degassing over the last 40 years sudden variations of both seismic noise level and noise cycling are positively correlated with early stages of ground inflation during the ad 2000 uplift we believe therefore that monitoring of seismic noise can be used for upgrading early warning strategies in this sector of the campi flegrei volcanic system

δd values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record abstract the compound specific hydrogen isotope composition d of sedimentary n alkanes is increasingly used as a palaeoclimate proxy to explore the origin of the hydrogen isotope signal of n alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n alkane composition and d values of 31 plant biomass samples birch betula beech fagus oak quercus alder alnus hornbeam carpinus and myrtle myrtus as well as non stomata containing sphagnum cladonia and moss from 14 sites along a climatic gradient from northern finland to southern italy eleven of the sites were previously investigated for the n alkane d values in adjacent lake sediments and are compared to the leaf wax n alkane d values the distribution of terrestrial n alkanes in lake sediments was not found to be characteristic of the dominant vegetation around the lake evidently n alkane distributions within the same species at different sites were found to be variable these findings complicate the use of certain n alkane distributions in sediments as a palaeoenvironmental indicator d values of plant biomass n alkanes show a significant positive correlation with the precipitation d values biomass n alkane d values are in general less negative than the associated sedimentary n alkanes of terrestrial origin possibly due to the stronger evapotranspiration during the summer when sampling took place this suggests that n alkanes in leaves show seasonal variations and the sedimentary organic matter receives the lighter isotope signal of the autumn when most leaves are incorporated into the sediment the variability of the d values from non stomata containing plants is much higher than for broadleaf trees since stomata can regulate water loss through evapotranspiration the average chain length acl of n alkanes from deciduous tree leaves increases from north to south with increasing acl the hydrogen isotopic fractionation e between source water and n alkanes also increases our results prove that terrestrial n alkane d values record the d value of precipitation modified by the amount of isotope enrichment in the leaf water due to plant anatomy stomata vs no stomata and site specific meteorological conditions such as evapotranspiration relative humidity and soil moisture therefore terrestrial n alkanes in lake sediments can deliver information on changes in these parameters over geological timescales in lake sediments where aquatic n alkanes such as n c 17 record the lake water d value the isotopic difference between terrestrial and aquatic n alkanes could therefore be used to reconstruct changes in evapotranspiration

electric resistivity structure of the siljan impact region based on 65 magnetotelluric mt measuring stations a cross section of the electric conductivity structure in the siljan impact area located in the central part of sweden is presented static sh

relative humidity recorded in tree rings a study along a precipitation gradient in the olympic mountains washington usa abstract humidity is one of the fundamental variables controlling the energy balance of the climate and thus its reconstruction represents a significant aspect of paleoclimate studies we here report a study of oxygen and hydrogen isotopic compositions of tree ring cellulose along a precipitation gradient in the olympic mountains of washington usa to examine whether and how the relative humidity is recorded in the cellulose according to the physically based model described in this paper the relationship between d and 18 o of cellulose should have the same slope as that in the relationship between d and 18 o in the source water 8 8 for the local meteoric water if there is no systematic variation in the mean relative humidity among study sites and no physiologic differences among trees however our isotopic analyses of cellulose yielded a slope of 17 4 significantly greater than the slope of the local meteoric water line we show that to produce such a slope a positive covariation between the relative humidity and the d and 18 o in the source water is required across the precipitation gradient this work suggests that the d vs 18 o relationship in tree rings can be a useful tool for paleohumidity reconstruction

industrial interference magnetotellurics an example from the tangshan area china in order to attack the problem of industrial interference in magnetotellurics we apply the general theory of weidelt and christensen describing the electromagnetic fields of a grounded electric dipole over a horizontally stratified earth the impedance tensor for dipole fields is proven to be independent of the dipole orientation within the near field the elements of the impedance tensor are real quantities and are independent of period because of this the logarithm of the apparent resistivity versus the logarithm of period rises with a slope of 45 degrees and the phase is zero we study the inversion of the controlled source impedance tensor to reveal earth structure at a given distance from the source using a nonlinear least squares technique we present an interpretation of magnetotelluric data in the tangshan area of china as a practical application of the technique sedimentary thicknesses of about 600 m are estimated and agree well with conventional schlumberger soundings the upper resistive crust thickness about 13 km overlies a more conductive lower crust whose resistivity is below a few hundred omega m

ice loss in the northeastern tibetan plateau permafrost as seen by 16 yr of esa sar missions abstract insar time series of surface deformation from 16 yr of envisat 2003 2011 and sentinel 1 2014 2019 esa satellite radar measurements have been constructed to characterise spatial and temporal dynamics of ground deformation over an 80 000 km2 area in the permafrost of the northeastern tibetan plateau the regional deformation maps encompass various types of periglacial landforms and show that seasonal thaw effects are controlled by the sediment type and local topography high seasonal ground movements are concentrated on shallow slopes and poor drainage areas in unconsolidated frost susceptible and fine grained sediments within glacier outwash plains braided stream plains alluvial deposits or floodplains fast subsidence due to thaw settlement takes place during june july while frost heave is intense during december january when two sided freezing of pore water under pressure causes prolonged ice segregation near the permafrost table the analysis reveals pervasive subsidence of the ground of up to 2 cm yr and increasing by a factor of 2 to 5 from 2003 to today in high relief and well drained areas the findings suggest that seasonal thaw increasingly affects ice rich layers at the permafrost table as well as high rates of widespread mass movements of non consolidated sediments the latter amplified by an increase of effects from frost heave thaw settlement

large scale insar monitoring of permafrost freeze thaw cycles on the tibetan plateau multitemporal interferometric synthetic aperture radar insar observations are used to characterize spatial variations of the permafrost active layer and its temporal evolution in northwestern tibet we develop a method to enhance insar performances for such difficult terrain conditions and construct an 8 year timeline of the surface deformation over a 60 000 km2 area the ground movement induced by the active layer s response to climate forcing is limited to cenozoic sedimentary basins and is spatially variable in both its seasonal amplitude 2 5 12 mm and multiannual trend 2 to 3 mm yr a degree day integrated model adjusted to the data indicates that subsidence occurs when the surface temperature exceeds zero may to october over areas where seasonal movements are large 8 mm the period of subsidence is delayed by 1 2 months over areas where smaller seasonal movements are observed suggesting an unsaturated soil where water occurs in the deeper part of the active layer

remote sensing measurements of thermokarst subsidence using insar thawing of ice rich permafrost followed by surface subsidence results in irregular depressed landforms known as thermokarst many remote sensing studies have identified thermokarst landforms and mapped their changes however the intrinsic dynamic thermokarst process of surface subsidence remains a challenge to quantify and is seldom examined using remote sensing methods in this study we used spaceborne interferometric synthetic aperture radar insar data to map surface subsidence trends at a thermokarst landform located near deadhorse on the north slope of alaska a pipeline access road constructed in the 1970s triggered the thawing of the permafrost causing subsequent expansion of the thermokarst landform using phased array type l band synthetic aperture radar images acquired by the advanced land observing satellite 1 our insar analysis reveals localized thermokarst subsidence of 2 8 cm yr between 2006 and 2010 equivalent to an ice volume loss of about 1 2 107 m3 yr comparisons between insar subsidence trends and lidar microtopography suggest a characteristic time of 8 years of thermokarst development we also quantitatively explain the difficulty uncertainties and possible biases in separating thermokarst induced irreversible subsidence from cyclic seasonal deformation our study illustrates that insar is an effective tool for mapping and studying active thermokarst processes and quantifying ice loss

compound specific d h ratios and molecular distributions of higher plant leaf waxes as novel paleoenvironmental indicators in the chinese loess plateau abstract we measured d h ratios of individual long chain leaf wax n alkanes isolated from a loess profile spanning the last 130 ka from xifeng china the d values show large variation 140 to 200 for the past 130 ka and are highly correlated with changes in magnetic susceptibility ms an accepted proxy for past monsoon circulation in the chinese loess plateau peaks in high d values 140 to 160 coincide with low ms values for loess sections formed under relatively dry conditions marine isotope stages miss 2 and 4 whereas peaks in low d values 190 to 200 coincide with high ms values for paleosol sections formed under relatively wet conditions miss 1 3 and 5 we attribute the isotopic variations to the combined effects of varying aridity which controls the soil and leaf water evaporation and temperature and monsoon intensity which alter the d h ratios of precipitation we also discovered a strong negative correlation between the molecular distributions ratios of c31 c29 and c31 c27 n alkanes and the d values of n alkanes based on studies of modern plants and the xifeng loess sequence the complex relationship between ms and monsoon circulation has been difficult to understand mechanistically however the climatic controls on the d h ratios of individual long chain n alkanes and c31 c29 n alkane ratios can be readily demonstrated and calibrated from modern plants and surface soils therefore these new molecular and isotopic proxies have potential as quantitative proxies for paleoenvironmental reconstruction in the chinese loess plateau