geophysical imaging and thermal modeling of subsurface morphology and thaw evolution of discontinuous permafrost 1 despite our current understanding of permafrost thaw in subarctic regions in response to rising air temperatures little is known about the subsurface geometry and distribution of discontinuous permafrost bodies in peat covered wetland dominated terrains and their responses to rising temperature using electrical resistivity tomography ground penetrating radar profiling and thermal conduction modeling we show how the land cover distributions influence thawing of discontinuous permafrost at a study site in the northwest territories canada permafrost bodies in this region occur under forested peat plateaus and have thicknesses of 5 13 m our geophysical data reveal different stages of thaw resulting from disturbances within the active layer from widening and deepening of differential thaw features under small frost table depressions to complete thaw of permafrost under an isolated bog by using two dimensional geometric constraints derived from our geophysics profiles and meteorological data we model seasonal and interannual changes to permafrost distribution in response to contemporary climatic conditions and changes in land cover modeling results show that in this environment 1 differences in land cover have a strong influence on subsurface thermal gradients such that lateral thaw dominates over vertical thaw and 2 in accordance with field observations thaw induced subsidence and flooding at the lateral margins of peat plateaus represents a positive feedback that leads to enhanced warming along the margins of peat plateaus and subsequent lateral heat conduction based on our analysis we suggest that subsurface energy transfer processes and feedbacks at scales of 1 100 m have a strong influence on overall permafrost degradation rates at much larger scales

on the potential for a bottom active layer below coastal permafrost the impact of seawater on permafrost degradation imaged by electrical resistivity tomography hornsund sw spitsbergen this paper presents the results of two dimensional electrical resistivity tomography ert of permafrost developed in coastal zone of hornsund sw spitsbergen the measurements were made using the wenner schlumberger electrode array with an electrode spacing 5 m for overview and 1 5 or 1 m spacing for detailed imaging using the ert inversion results we studied the sea influence on deeper parts of the frozen ground during the investigations we tested hypotheses that the operation of seawater on shoreface may cause changes in the shape of the coastal permafrost base and that the impact of seawater on more inland permafrost depends on the shape of the shoreline differently in the embayment and differently in a headland exposed to the open sea our study was inspired by previous ground temperature measurements conducted in several boreholes located in study area which captured the propagation of ground heat waves from the base of permafrost our resistivity models indicate a major differentiation in terms of resistivity of permafrost in the coastal zone the resistivity measures obtained in deeper layers of ground were so low 100 m that in the warm permafrost conditions they exclude a possibility of freezing the coastal sediments and bedrock from the side of the sea low values continue further inland going down under the surface layer of permafrost with higher resistivity we interpret this situation as an influence of seawater s temperature and salinity on deeper parts of permafrost based on the measurements conducted within two years we stated a change in the distribution of resistivity both in the active layer and in coastal front of permafrost in deeper parts of the ground as observed in the inverse models the geometric arrangement between the fields of extreme resistivity indicates the existence of a bottom active layer by the permafrost base depending on thermal and chemical characteristics of seawater the measurements conducted in the embayment as well as on the headland exposed to the operation of storm waves proved strong differences in the scale of the impact of seawater on permafrost

linear filtering of vlf dip angle measurements the suggested interpretation technique is based on discrete linear filtering of vlf data the output of the described filtering results is expressed in terms of an equivalent current density at a specified depth that would cause the measured magnetic field the most practical six point filter gives an accuracy of 8 the filter is an extension of the commonly used fraser filter to process vlf dip angle data filtering the same data set for various depths gives an idea about the change of current density with depth areas with high current density correspond to good conductors the conductor dip can also be determined the use of the technique is illustrated on theoretical and field examples in all cases a good correlation with original models and other types of geophysical measurements was obtained as shown in the last example the filtering technique is also applicable in interpretation of other electromagnetic methods

permafrost and climate in europe monitoring and modelling thermal geomorphological and geotechnical responses we present a review of the changing state of european permafrost within a spatial zone that includes the continuous high latitude arctic permafrost of svalbard and the discontinuous high altitude mountain permafrost of iceland fennoscandia and the alps the paper focuses on methodological developments and data collection over the last decade or so including research associated with the continent scale network of instrumented permafrost boreholes established between 1998 and 2001 under the european union pace project data indicate recent warming trends with greatest warming at higher latitudes equally important are the impacts of shorter term extreme climatic events most immediately reflected in changes in active layer thickness a large number of complex variables including altitude topography insolation and snow distribution determine permafrost temperatures the development of regionally calibrated empirical statistical models and physically based process oriented models is described and it is shown that though more complex and data dependent process oriented approaches are better suited to estimating transient effects of climate change in complex mountain topography mapping and characterisation of permafrost depth and distribution requires integrated multiple geophysical approaches and recent advances are discussed we report on recent research into ground ice formation including ice segregation within bedrock and vein ice formation within ice wedge systems the potential impacts of climate change on rock weathering permafrost creep landslides rock falls debris flows and slow mass movements are also discussed recent engineering responses to the potentially damaging effects of climate warming are outlined and risk assessment strategies to minimise geological hazards are described we conclude that forecasting changes in hazard occurrence magnitude and frequency is likely to depend on process based modelling demanding improved understanding of geomorphological process response systems and their impacts on human activity

mars and earth comparison of cold climate features abstract on earth glacial and periglacial features are common in areas of cold climate on mars the temperature of the present day surface is appropriate for permafrost and the presence of water is suspected from data relating to the outgassing of the planet from remote sensing measurements over the polar caps and elsewhere on the martian surface and from recognition of fluvial morphological features such as channels these observations and the possibility that ice could be in equilibrium with the atmosphere in the high latitudes north and south of 40 latitude suggest that glacial and periglacial features should exist on the planet morphological studies based mainly on viking pictures indicate many features that can be attributed to the action of ice among these features are extensive talus aprons debris avalanches flows that resemble glaciers or rock glaciers ridges that look like moraines various types of patterned ground scalloped scarps and chaotically collapsed terrain that could be attributed to thermokarst processes and landforms that may reflect the interaction of volcanism and ice

a modified seismic reflection approach for engineering geology investigation in fractured rock zones abstract delineating soil rock interface is critical for geotechnical and tunnel site investigations in engineering geology in singapore we also need to draw attention to local faults and fractured rock zones because the regional geology of peninsular malaysia and singapore contains some minor steep and brittle faults propagating at some areas in the island city in addition to drilling boreholes seismic reflection survey is a viable option to mitigate the uncertainties in areas without boreholes however the current practice of seismic reflection still follows the methods used in the petroleum exploration community this investigation reviews and modifies the seismic reflection approach specifically customized for geotechnical and tunnel site investigation which is partly different from petroleum exploration we demonstrate the modified approach through a field testing in singapore the resultant image from the field test fairly captures the soil rock interface and it is validated based on the vertically drilled boreholes a local fault or a fracture rock zone is also identified in the migrated image the extent and location match with the record of horizontal directional coring hdc this addresses the concern of fracture rock zone raised from the regional and local geology and provides useful information for geotechnical and tunnel engineers in addition we further discuss the general challenges of using the modified seismic reflection approach this work aims to help the geotechnical and tunnel community better understand the non invasive seismic reflection survey

detecting unfrozen sediments below thermokarst lakes with surface nuclear magnetic resonance 1 a talik is a layer or body of unfrozen ground that occurs in permafrost due to an anomaly in thermal hydrological or hydrochemical conditions information about talik geometry is important for understanding regional surface water and groundwater interactions as well as sublacustrine methane production in thermokarst lakes due to the direct measurement of unfrozen water content surface nuclear magnetic resonance nmr is a promising geophysical method for noninvasively estimating talik dimensions we made surface nmr measurements on thermokarst lakes and terrestrial permafrost near fairbanks alaska and confirmed our results using limited direct measurements at an 8 m deep lake we observed thaw bulb at least 22 m below the surface at a 1 4 m deep lake we detected a talik extending between 5 and 6 m below the surface our study demonstrates the value that surface nmr may have in the cryosphere for studies of thermokarst lake hydrology and their related role in the carbon cycle

boundary shear stress in spatially varied flow with increasing discharge the distribution of the wall shear stress on the bed and sidewalls of an open channel receiving lateral inflow was obtained from experimental measurements of the distribution of the velocity in the viscous sublayer using a laser doppler velocimeter the experiments were conducted in a 0 4 m wide by 7 5 m long flume lateral inflow was provided into the channel from above via sets of nozzles positioned toward the downstream end of the flume lateral inflow was provided over a length of 1 9 m the results indicate that the local boundary shear stresses are significantly influenced by lateral inflow the significant variation occurs near and around the region where the lateral inflow enters the channel at various measurement positions along the lateral inflow zone mean boundary mean wall and mean bed shear stresses were obtained and compared the results indicate that the mean boundary shear stresses increase from the upstream to the downstream ends of the lateral inflow zone the results also indicate t

spatial variability of active layer thickness detected by ground penetrating radar in the qilian mountains western china the active layer plays a key role in geomorphic hydrologic and biogeochemical processes in permafrost regions we conducted a systematic investigation of active layer thickness alt in northeastern qinghai tibetan plateau by using ground penetrating radar gpr with 100 and 200 mhz antennas we used mechanical probing pit and soil temperature profiles for evaluating alt derived from gpr the results showed that gpr is competent for detecting alt and the error was 0 08 m at common midpoint co located sites considerable spatial variability of alt owing to variation in elevation peat thickness and slope aspect was found the mean alt was 1 32 0 29 m with a range from 0 81 to 2 1 m in eboling mountain in yeniu gou mean alt was 2 72 0 88 m and varied from 1 07m on the north facing slope to 4 86 m around the area near the lower boundary of permafrost alt in peat decreased with increasing elevation at rates of 1 31 m km eboling mountain and 2 1 m km yeniu gou and in mineral soil in yeniu gou the rate changed to 4 18 m km at the same elevation alt on the south facing slope was about 0 8m thicker than that on the north facing slopes while the difference was only 0 18 m in peat covered area within a 100 m 2 area with a local elevation difference of 0 8 m alt varied from 0 68 m to 1 25 m both field monitoring and modeling studies on spatial alt variations require rethinking of the current strategy and comprehensive design

comparison of geophysical investigations for detection of massive ground ice pingo ice 1 six different geophysical investigations 1 ground penetrating radar 2 dc resistivity sounding 3 seismic refraction 4 very low frequency vhf electromagnetic 5 helicopter borne electromagnetic hem and 6 transient electromagnetic tem techniques were employed to obtain information on the ice body properties of pingos near fairbanks alaska the surface nuclear magnetic resonance nmr data were also compared from similar sites near one of the study pingos the geophysical investigations were undertaken along with core sampling and permafrost drilling to enable measurement of the ground temperature regime drilling ground truthing results support field geophysical investigations and have led to the development of a technique for distinguishing massive ice and overburden material of the permafrost the two dimensional dc resistivity sounding tomography and ground penetrating radar profiling are useful for ice detection under heterogeneous conditions however the dc resistivity sounding investigation required high quality ground contact and less area coverage the active layer thickness and the homogeneous horizontal structure of the overburden material are important parameters influencing detection of massive ice in permafrost for most methods such as seismic tem or surface nmr

electromagnetic and geological transect across permafrost terrain mackenzie river delta canada the time domain electromagnetic tdem method provides a surface geophysical technique suitable for interpreting deep permafrost conditions this paper describes profiles collected in early spring in a transitional area of the mackenzie delta arctic canada with differing permafrost conditions and surficial geology these data augment previously published profiles and allow the construction of a 30 km long tdem transect from the holocene age mackenzie delta in the southwest to the pleistocene age tuktoyaktuk coastlands in the northeast the geoelectric section produced from the tdem data is interpreted in terms of permafrost distribution this interpretation provided a basis for inferring lithologic changes unconsolidated non ice bonded unfrozen sediment has resistivities less than 10 ohm m partially ice bonded sediment ranges in resistivity from 10 to 40 ohm m ice bonded frozen sediment has resistivities from 30 to 300 ohm m bedrock has low resistivities from 5 to 15 ohm m interpretation of the geoelectric section derived from both the shallow 500 m tdem data suggests that the main body of permafrost increases in thickness from 50 to 500 m over a few kilometers a horizontally persistent unfrozen zone talik is situated from 50 to 100 m in depth within the main body of permafrost ice bonding models derived from the tdem surveys provide constraints on the geologic history of the mackenzie delta

radar sounding of temperate permafrost in alaska analogy to the martian midlatitude to high latitude ice rich terrains 1 radar detection of subsurface ice on mars has been widely debated in part because the dielectric signature of ice as deduced from the dielectric constant can be confused with dry silicate rich materials to identify the ice dielectric signature it is crucial to estimate the imaginary part of the dielectric permittivity inferred from the dielectric attenuation after removing the scattering loss unfortunately the latter remains poorly quantified at both mars advanced radar for subsurface and ionospheric sounding marsis and shallow subsurface radar sharad frequencies to address this ambiguity we conducted multiple frequency ground penetrating radar and resistivity investigations in well characterized temperate permafrost in fairbanks alaska the area shows several geomorphologic similarities to midlatitude and high latitude terrains on mars this approach allowed us to quantify the dielectric and scattering losses in temperate permafrost over the 10 to 1000 mhz frequency band at 20 mhz our results suggest an average dielectric loss rate of 0 25 0 03 db m whereas the corresponding average scattering loss rate is 0 94 0 37 db m the scattering loss was found to represent 69 of the total signal attenuation considering this result and the study by heggy et al 2006a in volcanic environments we revised the interpretation of the attenuation coefficient calculated from sharad data over the deuteronilus mensae region and amazonis planitia we then used the reevaluated dielectric loss to estimate the imaginary part of the dielectric permittivity our results suggest that even if deuteronilus mensae deposits and the vastitas borealis formation may have similar dielectric constants their imaginary parts are different this implies that the two regions have different bulk compositions with the former being ice rich sediments and the latter being nonconsolidated volcanic deposits

ephemeral thermal and solute plumes formed by upwelling groundwaters near salt domes geochemical observations made by previous workers indicate that rapid upward advection of hot water has occurred along the flanks of some salt domes in the northern gulf of mexico basin and in the danish central trough the observations are based on pore fluid chemistry and on high temperatures of formation of metal sulfides and other diagenetic minerals near the crests of salt domes some of the diagenetic minerals formed at 40 c to 80 c above the ambient temperature of the host rocks numerical simulations of coupled heat and dissolved salt transport show that thermal perturbations in excess of 60 c can be repeatedly produced near the crest of a salt dome by focused dewatering of a thick strongly overpressured sedimentary interval around the dome in our simulations dewatering was triggered and stopped by cyclically changing the permeability at the salt sediment interface the thermal plumes dissipated within 100 kyr after dewatering ceased stratigraphically shallow brine plumes were also formed by dewatering and these gravitationally unstable plumes dissipated more slowly by sinking within 1 m y simulations showed that free thermohaline convection can also generate thermal perturbations near the crest of a dome in this mode of upwelling thermal perturbations reached 30 c when the vertical permeability of the hydrostatically pressured interval was 10 14 m2 10 mdarcy because such permeabilities seem large for the hydrostatically pressured interval as a whole in the northern gulf of mexico basin the formation of high temperature metal sulfide deposits near the crests of salt domes seems more likely to be due to dewatering of the overpressured interval with very strong focusing of expelled waters along the flanks of salt domes

the dielectric permittivity of terrestrial ground ice formations considerations for planetary exploration using ground penetrating radar 1 exploration of the polar ice caps and apparent glacial and periglacial landforms on mars will aid our understanding of its ancient climate conditions and the history of water on the planet given that ground penetrating radar gpr is likely to be used to understand these features we investigated the real component of the complex dielectric permittivity of stratified segregation ice non stratified segregation ice and polygonal ice wedge deposits in the canadian arctic we acquired moveout profiles with a 450 mhz gpr on ground ice formations that had active layer sediments excavated prior to surveying using ice core data collected from these sites we found that the volumetric fraction of ice plays the greatest role in defining the dielectric permittivity of the deposit and that it can be described using a modified complex refractive index method crim dielectric mixing model using the modified crim model we estimate the dielectric permittivity of several ground ice deposits on earth and present further estimates for similar features on mars using permittivity values for martian sediments derived from both theory and laboratory methods

the nature and dynamics of frozen ground in alpine and subarctic periglacial environments a spatial assessment of the complex discontinuous and sporadic permafrost distribution and characteristics in high altitude alpine and high latitude subarctic permafrost environments was achieved u

geophysical estimation of shallow permafrost distribution and properties in an ice wedge polygon dominated arctic tundra region abstractshallow permafrost distribution and characteristics are important for predicting ecosystem feedbacks to a changing climate over decadal to century timescales because they can drive active layer deepening and land surface deformation which in turn can significantly affect hydrologic and biogeochemical responses including greenhouse gas dynamics as part of the u s department of energy next generation ecosystem experiments arctic we have investigated shallow arctic permafrost characteristics at a site in barrow alaska with the objective of improving our understanding of the spatial distribution of shallow permafrost its associated properties and its links with landscape microtopography to meet this objective we have acquired and integrated a variety of information including electric resistance tomography data frequency domain electromagnetic induction data laboratory core analysis petrophysical studies high resolution digital surface models and color mosaics inferred from kite based

application of refraction seismics in alpine permafrost studies a review abstract refraction seismics is a common geophysical application to investigate permafrost in alpine studies this study reviews the physical basis of the use of refractions seismics and introduces the history of its application in alpine environments seismic properties are influenced by rock or soil properties and fluid or ice effects in laboratory measurements these influences are determined and linked to mechanical properties or used for calibration of field studies in field conditions supplementary environmental factors influence the seismic properties of landforms in this paper laboratory studies of rocks from different lithologies and with different properties as well as case studies on rock glaciers moraines talus slopes and debris covered slopes are collected and influencing factors quantitatively analyzed the data demonstrate how lithology porosity and anisotropy influence p wave velocity environmental factors result in a high variation of p wave velocities in landforms however p wave velocities enable the differentiation of active layer and permafrost in rock glaciers and moraines in talus slopes and debris covered slopes p wave velocity contrasts between active layer and permafrost layer might be insufficient and require the application of additional methods for a final differentiation

geoelectric observations of the degradation of nearshore submarine permafrost at barrow alaskan beaufort sea 1 submarine permafrost degradation rates may be determined by a number of interacting processes including rates of sea level rise and coastal erosion sea bottom temperature and salinity regimes geothermal heat flux and heat and mass diffusion within the sediment column observations of ice bearing permafrost in shelf sediments are necessary in order to determine its spatial distribution and to quantify its degradation rate we tested the use of direct current electrical resistivity to ice bearing permafrost in elson lagoon northeast of barrow alaska beaufort sea a sharp increase in electrical resistivity was observed in profiles collected perpendicular to and along the coastline and is interpreted to be the boundary between ice free sediment and underlying ice bearing submarine permafrost the depth to the interpreted ice bearing permafrost increases from 2 m below sea level to over 12 m below sea level with increasing distance from the coastline the dependence of the saline sediment electrical resistivity on temperature and freezing was measured in the laboratory to provide validation for the field measurements electrical resistivity was shown to be effective for detection of shallow ice bearing permafrost in the coastal zone historical coastal retreat rates were combined with the inclination of the top of the ice bearing permafrost to calculate mean vertical permafrost degradation rates of 1 to 4 cm yr 1

design and field experiments of a ground penetrating radar for mars exploration 1 we developed a wideband low power lightweight prototype ground penetrating radar gpr for subsurface exploration for mars the transmitter and receiver subsystems were constructed using a commercially available radio frequency rf and digital integrated circuits connectorized components and evaluation boards the transmit receive system antennas laptop controller and batteries are all accommodated on a 2 5 m sled field experiments were conducted in kansas and alaska the experiments in kansas tested the operation of the system the primary objective of the alaska experiments was to investigate the ability of a gpr to detect and distinguish between subsurface deposits of ice and ice cemented soils the investigation depths of these experiments ranged from 1 m to 30 m and the subsurface geology included near surface thaw discontinuous permafrost water saturated soils and lenses of pure ice dielectric contrasts within the ground were detected with near meter resolution however identifying the geologic context of an interface was difficult due to ambiguities associated with reflection data these investigations demonstrate some of the difficulties associated with inverting reflection data to obtain dielectric properties of the subsurface fortunately previous geophysical investigations such as drilled cores and seismic surveys helped to constrain the geology and numerical simulations provided an additional resource for the interpretations on mars additional geological context will be limited and numerical simulations will become extremely important for data interpretation due to these difficulties we demonstrate in one experiment how dielectric information can be obtained directly from bistatic measurements with a fixed transmitter and mobile receiver finally a comparison with a commercially available geophysical survey systems inc gssi radar system is presented and we discuss how the system can be modified and improved for future exploration on mars

an assessment of evidence for pingos on mars using hirise pingos are small hills with cores of ice formed by injection and freezing of pressurized water the possibility of pingos on mars is of particular interest because of the associated implications for liquid water we have systematically searched for candidate pingos using images from the high resolution imaging science experiment hirise camera since pingos are expected to develop surface fractures due to extension of the frozen ground over the ice core we have searched for fractured features and identified a variety of mounds these features are confined to the martian mid latitudes in the bands where gullies are also most common the observed fractured mounds have a variety of morphologies and are likely of multiple origins isolated fractured mounds found on the floors of gullied craters in the southern hemisphere match the general morphologic characteristics of terrestrial pingos and are the best candidates for martian pingos but there is currently no direct evidence for presence of ice cores and it is difficult to produce the necessary water volumes so these features should still be interpreted with caution other fractured mounds appear more likely to be erosional remnants of an unusual mantling layer or possibly thermokarst structures flat topped mounds in utopia have some characteristics fracture pattern and latitudinal distribution consistent with pingos but differ in other aspects such as shape and setting while we do not rule out a pingo origin we prefer an erosional model for these enigmatic features

possible frost mounds in an ancient martian lake bed abstract circular to elongated mounds are observed in gusev crater in the aeolis subquadrangle of mars they are arranged in a large cluster and show different stages of evolution from fresh to scar structures their morphology and morphometric ratios are comparable to those of terrestrial frost mounds this study shows how the paleolacustrine environment of the ma adim vallis gusev crater hydrogeologic system may have provided a suitable environment for the formation of frost mounds alternate hypotheses of formation including volcanism fluvial erosion and eolian erosion are discussed other features such as heavings curvilinear troughs hills ridges and depressions support the idea of a sediment ice interaction the typology of the mounds and plausible mechanisms for their formation are proposed their presence could support the model of a massive water body in gusev during the amazonian and provide indicators of paleoenvironmental conditions at the time of their formation

investigating internal structure of permafrost using conventional methods and ground penetrating radar at honhor basin mongolia a ground penetrating radar gpr survey was conducted at the end of august 2009 in the suburb region of ulaanbaatar honhor basin mongolia in combination with conventional methods such as borehole drilling and measurement of ground temperatures the interface of frozen and unfrozen sediment was distinctly resolved in the interpreted gpr images verified by the borehole drilling records and 6 month measurement of ground temperatures the location of the permafrost table was assessed to be at the depth of 2 4 m in the study region a conspicuous ice saturated soil layer massive ground ice was detected in the interpreted gpr images with a thickness of 2 5 m the gpr investigation results were consistent with the borehole drilling records and ground temperatures observation the borehole logs and ground temperatures profile in the borehole indicates that permafrost at honhor basin is characterized by high ground temperature and high ice content which implies that ongoing climatic warming would have great influence on permafrost dynamics the research results are of great importance to further assess permafrost dynamics to climatic change in the boundary of discontinuous and sporadic permafrost regions in mongolia in the future

possible pingos and a periglacial landscape in northwest utopia planitia hydrostatic closed system pingos are small elongate to circular ice cored mounds that are perennial features of some periglacial landscapes the growth and development of hydrostatic pingos is contingent upon the presence of surface water freezing processes and of deep continuous ice cemented permafrost other cold climate landforms such as small sized polygonal patterned ground also may occur in the areas where pingos are found on mars landscapes comprising small elongate to circular mounds and other possible periglacial features have been identified in various areas including utopia planitia where water is thought to have played an important role in landscape evolution despite the importance of the martian mounds as possible markers of water most accounts of them in the planetary science literature have been brief and or based upon viking imagery we use a high resolution mars orbiter camera image eo300299 and superposed mars orbiter laser altimeter data tracks to describe and characterise a crater floor landscape in northwest utopia planitia 64 8 n 292 7 w the landscape comprises an assemblage of landforms that is consistent with the past presence of water and of periglacial processes this geomorphological assemblage may have formed as recently as the last episode of high obliquity a similar assemblage of landforms is found in the tuktoyaktuk peninsula of northern canada and other terrestrial cold climate landscapes we point to the similarity of the two assemblages and suggest that the small roughly circular mounds on the floor of the impact crater in northwest utopia planitia are hydrostatic pingos like the hydrostatic pingos of the tuktoyaktuk peninsula the origin of the crater floor mounds could be tied to the loss of ponded local water permafrost aggradation and the evolution of a sub surface ice core

resurfacing history of the northern plains of mars based on geologic mapping of mars global surveyor data 1 geologic mapping of the northern plains of mars based on mars orbiter laser altimeter topography and viking and mars orbiter camera images reveals new insights into geologic processes and events in this region during the hesperian and amazonian periods we propose four successive stages of lowland resurfacing likely related to the activity of near surface volatiles commencing at the highland lowland boundary hlb and progressing to lower topographic levels as follows highest elevations indicated stage 1 upper boundary plains early hesperian 2 0 to 2 9 km stage 2 lower boundary plains and outflow channel dissection late hesperian 2 7 to 4 0 km stage 3 vastitas borealis formation vbf surface late hesperian to early amazonian 3 1 to 4 1 km and stage 4 local chaos zones early amazonian 3 8 to 5 0 km at acidalia mensa stage 2 and 3 levels may be lower 4 4 and 4 8 km respectively contractional ridges form the dominant structure in the plains and developed from near the end of the early hesperian to the early amazonian geomorphic evidence for a northern plains filling ocean during stage 2 is absent because one did not form or its evidence was destroyed by stage 3 resurfacing remnants of possible amazonian dust mantles occur on top of the vbf the north polar layered deposits appear to be made up of an up to kilometer thick lower sequence of sandy layers early to middle amazonian in age overlain by late amazonian ice rich dust layers both units appear to have outliers suggesting that they once were more extensive

3d ground penetrating radar imaging of ice complex deposits in northern east siberia abstractice complex deposits are characteristic ice rich formations in northern east siberia and represent an important part in the arctic carbon pool recently these late quaternary deposits are the objective of numerous investigations typically relying on outcrop and borehole data many of these studies can benefit from a 3d structural model of the subsurface for upscaling their observations or for constraining estimations of inventories such as the local carbon stock we have addressed this problem of structural imaging by 3d ground penetrating radar gpr which in permafrost studies has been primarily used for 2d profiling we have used a 3d kinematic gpr surveying strategy at a field site located in the new siberian archipelago on top of an ice complex after applying a 3d gpr processing sequence we were able to trace two horizons at depths below 20 m taking available borehole and outcrop data into account we have interpreted these two features as interfaces of major lithologic units and der

degrading permafrost mapped with electrical resistivity tomography airborne imagery and lidar and seasonal thaw measurements accurate identification of the relationships between permafrost extent and landscape patterns can help to develop airborne geophysical or remote sensing tools to map permafrost in remote locations or across large areas these tools will be particularly applicable in discontinuous permafrost where climate warming or disturbances such as human development or fire can lead to rapid permafrost degradation we have linked field based geophysical point scale and imagery surveying measurements to map permafrost at five fire scars 1930 1975 1988 2001 and 2010 on the tanana flats in central alaska ground based elevation surveys seasonal thaw depth profiles and electrical resistivity tomography ert measurements were combined with airborne imagery and light detection and ranging lidar to identify relationships between permafrost geomorphology and elapsed time since fire disturbance ert proved to be a robust technique for mapping the presence or absence of permafrost because of the marked difference in resistivity values for frozen versus unfrozen material there was no clear relationship between elapsed time since fire and permafrost extent at our sites however we have found that the transition zone boundaries between permafrost soils and unfrozen soils in the collapse scar bogs at our sites had complex and unpredictable morphologies this result suggested that attempts to quantify the presence or absence of permafrost using aerial measurements alone could lead to incomplete results taken in total the results from our study indicated that although ground based ert measurements were the most rapid means of mapping permafrost we were still limited in being able to apply airborne surveying measurements at the landscape scale toward accurately estimating permafrost extent