volume loss from antarctic ice shelves is accelerating the floating ice shelves surrounding the antarctic ice sheet restrain the grounded ice sheet flow thinning of an ice shelf reduces this effect leading to an increase in ice discharge to the ocean using 18 years of continuous satellite radar altimeter observations we have computed decadal scale changes in ice shelf thickness around the antarctic continent overall average ice shelf volume change accelerated from negligible loss at 25 64 cubic kilometers per year for 1994 2003 to rapid loss of 310 74 cubic kilometers per year for 2003 2012 west antarctic losses increased by 70 in the past decade and earlier volume gain by east antarctic ice shelves ceased in the amundsen and bellingshausen regions some ice shelves have lost up to 18 of their thickness in less than two decades

central zagros fold thrust belt iran new insights from seismic data field observation and sandbox modeling 1 we present five generalized cross sections across the central zagros fold and thrust belt iran these sections show that the fold geometry varies significantly both horizontally and vertically the style is closely related to the changes in the mechanical behavior of the lithostratigraphic horizons and in particular to the presence of intermediate decollements within the sedimentary pile restoration of the sections shows amounts of shortening of the same order from one section to the other however it appears to be unequally distributed suggesting variations in basal decollement shear strength analogue modeling has been performed to systematically investigate the effect of an intermediate decollement level at different depths on the style of folding the models demonstrate that the position of intermediate decollements is an important factor controlling both structural style and fold wavelength models with shallow intermediate decollement show regularly and widely spaced anticlines in these models the fold wavelength depends directly on the thickness of the dominant competent layer and short wavelength superficial structures mask broad anticlines at depth models with deep intermediate decollement are characterized by the rapid propagation of deformation with small rate of shortening along this decollement influencing localization of forthcoming anticlines in the upper levels such propagation favors the development of duplexes and multiwavelength folds on this basis fold kinematics in central zagros is discussed using the variation of structural style along different folds as an indicator of the sequence of deformation detachment folding is the main folding style at least for the initial stages of deformation and thrust faults developed only at later stages some of these faults branched on decollement levels express the progression of folding whereas others are linked to late basement faults cutting through early structures in general the decollement levels are activated sequentially from deeper horizons to shallower ones however in one case gachsaran decollement a shallow decollement is activated during the early stages of folding and then abandoned during the subsequent evolution

using a binary logistic regression method and gis for evaluating and mapping the groundwater spring potential in the sultan mountains aksehir turkey summary the purpose of this study is to produce a groundwater spring potential map of the sultan mountains in central turkey based on a logistic regression method within a geographic information system gis environment using field surveys the locations of the springs 440 springs were determined in the study area in this study 17 spring related factors were used in the analysis geology relative permeability land use land cover precipitation elevation slope aspect total curvature plan curvature profile curvature wetness index stream power index sediment transport capacity index distance to drainage distance to fault drainage density and fault density map the coefficients of the predictor variables were estimated using binary logistic regression analysis and were used to calculate the groundwater spring potential for the entire study area the accuracy of the final spring potential map was evaluated based on the observed springs the accuracy of the model was evaluated by calculating the relative operating characteristics the area value of the relative operating characteristic curve model was found to be 0 82 these results indicate that the model is a good estimator of the spring potential in the study area the spring potential map shows that the areas of very low low moderate and high groundwater spring potential classes are 105 586 km 2 28 99 74 271 km 2 19 906 101 203 km 2 27 14 and 90 05 km 2 24 671 respectively the interpretations of the potential map showed that stream power index relative permeability of lithologies geology elevation aspect wetness index plan curvature and drainage density play major roles in spring occurrence and distribution in the sultan mountains the logistic regression approach has not yet been used to delineate groundwater potential zones in this study the logistic regression method was used to locate potential zones for groundwater springs in the sultan mountains the evolved model was found to be in strong agreement with the available groundwater spring test data hence this method can be used routinely in groundwater exploration under favourable conditions

integration of ground subsidence hazard maps of abandoned coal mines in samcheok korea integrated techniques were developed applied and validated for the analysis of ground subsidence hazards by abandoned coal mines in samcheok korea using a geographic information system gis slope depth of drift distance from drift groundwater level permeability geology and land use were extracted or calculated from the digital elevation model topographic drift distribution borehole geologic and land use database by using the constructed spatial database the relations between the ground subsidence location and seven related factors were identified and quantified by frequency ratio fr weights of evidence woe logistic regression lr and artificial neural network ann models the relations were used as factor ratings in the overlay analysis to create ground subsidence hazard indices and maps the four ground subsidence hazard maps were reflected as the new input factors and integrated using fr woe lr and ann models to make a hazard map all of the subsidence hazard maps were validated by comparison with known ground subsidence locations that were not used in the analysis as a result the integrated ground subsidence hazard maps used four new subsidence related input factors that showed a greater accuracy 96 46 for fr 97 22 for woe 97 20 for lr and 96 70 for ann respectively than the individual ground subsidence maps 95 54 for fr 94 22 for woe 96 89 for lr and 94 45 for ann respectively using the first seven factors

potential sea level rise from antarctic ice sheet instability constrained by observations large parts of the antarctic ice sheet lying on bedrock below sea level may be vulnerable to marine ice sheet instability misi a self sustaining retreat of the grounding line triggered by oceanic or atmospheric changes there is growing evidence that misi may be underway throughout the amundsen sea embayment ase which contains ice equivalent to more than a metre of global sea level rise if triggered in other regions the centennial to millennial contribution could be several metres physically plausible projections are challenging numerical models with sufficient spatial resolution to simulate grounding line processes have been too computationally expensive to generate large ensembles for uncertainty assessment and lower resolution model projections rely on parameterizations that are only loosely constrained by present day changes here we project that the antarctic ice sheet will contribute up to 30 cm sea level equivalent by 2100 and 72 cm by 2200 95 quantiles where the ase dominates our process based statistical approach gives skewed and complex probability distributions single mode 10 cm at 2100 two modes 49 cm and 6 cm at 2200 the dependence of sliding on basal friction is a key unknown nonlinear relationships favour higher contributions results are conditional on assessments of misi risk on the basis of projected triggers under the climate scenario a1b ref 9 although sensitivity to these is limited by theoretical and topographical constraints on the rate and extent of ice loss we find that contributions are restricted by a combination of these constraints calibration with success in simulating observed ase losses and low assessed risk in some basins our assessment suggests that upper bound estimates from low resolution models and physical arguments up to a metre by 2100 and around one and a half by 2200 are implausible under current understanding of physical mechanisms and potential triggers

basal melting at the ekstrom ice shelf antarctica estimated from mass flux divergence we characterize the basal mass balance of the ekstr om ice shelf dronning maud land antarctica using interferometrically derived surface velocities and ice thickness measurements from radio echo sounding res the surface velocities are based on data from european remote sensing satellites 1 and 2 ers 1 2 during 1994 97 the ice thickness grid consists of 136 res profiles acquired between 1996 and 2006 mass fluxes are calculated along selected res profiles where possible to reduce uncertainties from ice thickness interpolation elsewhere large scale mass fluxes are calculated using interpolated ice thickness data themass flux into the ekstr om ice shelf from themain grounded drainage basins is estimated to be 3 19 0 4gt a 1 the mass flux near the ice shelf front is 2 67 0 3gt a 1 assuming steady state and based on the equation of continuity we interpret the residual mass flux as a combined effect of snow accumulation and subglacial melting refreezing using net snow accumulation rates from previous studies we link the mass flux divergence in irregular shaped polygons to processes beneath the ice shelf the highest subglacial melt rates of 1 1ma 1 are found near the grounding zone of two main inflow glaciers and around the german station neumayer iii the detection of unlikely refreezing in a small area 15 km west of neumayer iii is attributed to both dataset inaccuracies and a possibly past violation of the steady state assumption in general the method and input data allow mapping of the spatial distribution of basal melting and the results are in good agreement with several previous studies

antarctic thermocline dynamics along a narrow shelf with easterly winds abstractdetermining the role of southern ocean warm intermediate water for driving melting of the antarctic ice sheet is a major challenge in assessing future sea level rise analysis of 2859 ctd p

gis based assessment of risk due to salt mining activities at tuzla bosnia and herzegovina ground subsidence triggered by salt mining from deposits located beneath the city of tuzla bosnia and herzegovina is one of the major dangers acting on a very densely urbanized area since 1950 when the salt deposit exploitation by means of boreholes began as demonstrated in this paper subsidence induced several hazard factors such as severe ground deformations the arising of deep and superficial fractures and a very fast water table rise connected with the brine extraction now affecting several districts the above mentioned factors have been quantified by the use of geomatic methodologies including field surveys and analysis of geographical data in order to estimate the historical sinking rates authors processed the large and never before processed amount of topographical data collected during two periods from 1956 to 1991 and from 1992 to 2003 with only poor data collected afterward traditional surveys were completely and definitively stopped the analysis reveals a cumulative subsidence as high as 12 m during the whole period causing damage to buildings and infrastructures within an area that includes a large portion of the historical town at present almost entirely destroyed modern sinking rates have been monitored with static gps whereas the presence of superficial fractures monitored with kinematic gps factors related to the presence of deep fractures and water table rise have been evaluated by curvature analysis techniques and piezometric data respectively finally hazard factors have been combined in a risk map using the gis geographical information system map algebra capabilities and a simple multicriteria decision analysis mda in order to do that a vulnerability map has been derived on the basis of information reported on a couple of recently sensed high resolution satellite imageries the final risk arisen from the combination of single hazard factors and vulnerability map highlights critical scenarios and unsuspected threatening that are under consideration by the local decision makers and urban planners in particular as highlighted in the final risk map the present day water table rise triggered by the decrease in brine pumping is seriously posing a threat to a portion of the city which is not the most involved in ground deformations

prediction of ground subsidence in samcheok city korea using artificial neural networks and gis this study shows the construction of a hazard map for presumptive ground subsidence around abandoned underground coal mines aucms at samcheok city in korea using an artificial neural network with a geographic information system gis to evaluate the factors governing ground subsidence an image database was constructed from a topographical map geological map mining tunnel map global positioning system gps data land use map digital elevation model dem data and borehole data an attribute database was also constructed by employing field investigations and reinforcement working reports for the existing ground subsidence areas at the study site seven major factors controlling ground subsidence were determined from the probability analysis of the existing ground subsidence area depth of drift from the mining tunnel map dem and slope gradient obtained from the topographical map groundwater level and permeability from borehole data geology and land use these factors were employed by with artificial neural networks to analyze ground subsidence hazard each factor s weight was determined by the back propagation training method then the ground subsidence hazard indices were calculated using the trained back propagation weights and the ground subsidence hazard map was created by gis ground subsidence locations were used to verify results of the ground subsidence hazard map and the verification results showed 96 06 accuracy the verification results exhibited sufficient agreement between the presumptive hazard map and the existing data on ground subsidence area

reassembling gondwana a new high quality constraint from vibroseis exploration of the sub ice shelf geology of the east antarctic continental margin the breakup of gondwana is manifested by coeval early jurassic karoo magmatism in south africa and east antarctica in south africa the large volumes of volcanic rocks of the adjoining lebombo and mwenetzi save monoclines represent a volcanic rift margin and in east antarctica a corresponding feature the explora wedge is buried below sediments and floating ice shelves on the continental margin of dronning maud land we use the seismic vibrator source to explore the sub ice geology in antarctica and the new seismic reflection and available regional aeromagnetic data enable us to outline a dogleg landward extent of the explora wedge in dronning maud land the congruent inboard wedge geometries on the two continents define a high quality constraint which facilitate for the first time a geologically consistent and tight reconstruction of africa relative to east antarctica within gondwana the uncertainties in correlations of major geological features mobile belts from one continent to the other may now be of the order of ten s of kilometers rather than hundreds of kilometers

ross ice shelf response to climate driven by the tectonic imprint on seafloor bathymetry ocean melting has thinned antarctica s ice shelves at an increasing rate over the past two decades leading to loss of grounded ice the ross ice shelf is currently close to steady state but geological records indicate that it can disintegrate rapidly which would accelerate grounded ice loss from catchments equivalent to 11 6 m of global sea level rise here we use data from the rosetta ice airborne survey and ocean simulations to identify the principal threats to ross ice shelf stability we locate the tectonic boundary between east and west antarctica from magnetic anomalies and use gravity data to generate a new high resolution map of sub ice shelf bathymetry the tectonic imprint on the bathymetry constrains sub ice shelf ocean circulation protecting the ice shelf grounding line from moderate changes in global ocean heat content in contrast local seasonal production of warm upper ocean water near the ice front drives rapid ice shelf melting east of ross island where thinning would lead to faster grounded ice loss from both the east and west antarctic ice sheets we confirm high modelled melt rates in this region using rosetta ice radar data our findings highlight the significance of both the tectonic framework and local ocean atmosphere exchange processes near the ice front in determining the future of the antarctic ice sheet the boundary between west and east antarctica is a tectonic feature that bisects the ross ice shelf this boundary constrains ocean circulation under the ice which affects ice stability according to airborne survey data and ocean simulations

timing of thrust activity in the high zagros fold thrust belt iran from u th he thermochronometry 1 apatite and zircon u th he cooling ages are used to quantify the timing of exhumation associated with thrust faulting in the high zagros fold thrust belt single grain cooling age data were collected from 1 cambrian sandstone in various thrust sheets 2 sandstone and basement clasts derived from structurally controlled salt plugs or fault bounded slices and 3 syntectonic neogene siliciclastics strata in the northwestern kuhrang and central kuh e lajin high zagros apatite u th he ahe ages range from 26 7 to 0 38 ma most cooling and exhumation occurred in the early to middle miocene constrained by ahe ages 19 15 ma from the high zagros thrust sheet localized faults and reset cooling ages from bakhtiyari deposits in the southeastern high zagros kuh e dinar cooling occurred later with ahe ages ranging from 16 5 to 0 79 ma here most cooling and exhumation occurred in the late miocene constrained by ahe ages 12 8 ma from the high zagros fault and exhumed paleozoic clasts in synorogenic strata zircon u th he zhe ages from bedrock samples across the high zagros are reflective of the precollisional thermal history the preservation of precollisional zhe ages limits the pre miocene maximum burial temperature of the exhumed strata to 180 c and indicate 7 9 km of maximum exhumation in the central zagros this study shows that thrust activity in the high zagros and continental suturing along the zagros suture was underway by at least 19 ma and initiated no later than latest oligocene to early miocene time 23 ma

deep glacial troughs and stabilizing ridges unveiled beneath the margins of the antarctic ice sheet the antarctic ice sheet has been losing mass over past decades through the accelerated flow of its glaciers conditioned by ocean temperature and bed topography glaciers retreating along retrograde slopes that is the bed elevation drops in the inland direction are potentially unstable while subglacial ridges slow down the glacial retreat despite major advances in the mapping of subglacial bed topography significant sectors of antarctica remain poorly resolved and critical spatial details are missing here we present a novel high resolution and physically based description of antarctic bed topography using mass conservation our results reveal previously unknown basal features with major implications for glacier response to climate change for example glaciers flowing across the transantarctic mountains are protected by broad stabilizing ridges conversely in the marine basin of wilkes land east antarctica we find retrograde slopes along ninnis and denman glaciers with stabilizing slopes beneath moscow university totten and lambert glacier system despite corrections in bed elevation of up to 1 km for the latter this transformative description of bed topography redefines the high and lower risk sectors for rapid sea level rise from antarctica it will also significantly impact model projections of sea level rise from antarctica in the coming centuries a high resolution update of antarctic bed topography using mass conservation reveals broad stabilizing ridges for glaciers flowing across the transantarctic mountains and stabilizing slopes beneath moscow university totten and lambert glacier system

detailed seismic bathymetry beneath ekstrom ice shelf antarctica implications for glacial history and ice ocean interaction the shape of ice shelf cavities are a major source of uncertainty in understanding ice ocean interactions this limits assessments of the response of the antarctic ice sheets to climate change her

mining geohazards susceptibility and risk mapping the case of the amyntaio open pit coal mine west macedonia greece during the last decades numerous methodologies for the construction of both susceptibility and risk maps have been developed in order to identify and mitigate geohazards such as landslides and secondarily land subsidence phenomena caused by the collapse of natural or man made underground cavities according to literature review the conducted research concerning the assessment of land subsidence risk due to the overexploitation of the aquifer is still at an early stage this study focuses n the land subsidence phenomenon due to the overexploitation of the aquifer occurring in the amyntaio basin in west macedonia hosting the active amyntaio open pit coal mine this phenomenon has caused significant damage to settlements farmlands and infrastructure in order to construct susceptibility and risk maps knowledge of the geological geotechnical hydrogeological and tectonic settings of the study area is required the proposed methodology for the production of a susceptibility and a risk map of land subsidence was based on the semi quantitative method weighted linear combination wlc the results were evaluated with an extensive field survey action recording besides the above mentioned settings the spatial distribution of surface ruptures the excellent agreement between the produced maps and the findings of the field survey proved the added value of the maps assigning them as crucial tools for the management of land subsidence phenomena

assessment of ground subsidence using gis and the weights of evidence model abstract the weights of evidence model one of the bayesian probability models was applied in evaluating a ground subsidence spatial hazard near abandoned underground coal mines aucms at magyori area samcheok city in korea using gis using ground subsidence location and a spatial database containing information such as mining tunnel borehole topography geology and land use the weights of evidence model was applied to calculate each relevant factor s rating for the magyori area in korea seven major factors controlling or related to ground subsidence were determined from the probability analysis of the existing ground subsidence area depth of drift and distance from drift from the mining tunnel map slope gradient obtained from the topographical map ground water level and permeability from borehole data geology and land use tests of conditional independence were performed for the selection of factors allowing 6 combinations of factors to be analyzed for the analysis of mapping ground subsidence spatial hazard the contrast values w and w of each factor s rating were overlaid spatially the results of the analysis were validated using receiver operating characteristic roc with the previous ground subsidence locations in the case of all factor used the area under the roc curve auc showed 0 9667 which corresponds to an accuracy of 96 67 in the case of the combinations the case of distance from drift depth of ground water and land use used showed the 90 71 auc 0 9071 accuracy which is the best result produced in this analysis the results can be used for hazard prevention and land use planning near aucm areas

eddy overturning of the antarctic slope front controls glacial melting in the eastern weddell sea 1 the eastern weddell sea is characterized by narrow continental shelves and warm deep water wdw is located in close proximity to the ice shelves in this region the exchange of wdw across the antarctic slope front asf determines the rate of basal ice shelf melting here we present a unique data set consisting of 2351 vertical profiles of temperature and salinity collected by southern elephant seals mirounga leonina and a profile beneath the fimbul ice shelf fis obtained via drilling through 395 m of ice this data set reveals variations in salinity and temperature through winter and using a conceptual model of the coastal salt budget we quantify the main exchange processes our data show that modified wdw with temperatures below 1 5 c is advected onto the shelf and into the ice shelf cavities by an eddy overturning of the asf the onshore ekman flux of surface waters during summer is the main source of freshwater that leads to the formation of low salinity shelf waters in the region the modified wdw that reaches beneath the ice shelves is too cold for basal ice shelf melting to create such low salinity water a high resolution model of an idealized asf continental shelf ice shelf system supports the conclusions from the data analysis the inflow of wdw onto the continental shelf and into the ice shelf cavity occurs within a bottom boundary layer where the eddy advection in the model is particularly strong in close agreement with the observed vertical profile of temperature beneath the fis citation nost o a m biuw v tverberg c lydersen t hattermann q zhou l h smedsrud and k m kovacs 2011 eddy overturning of the antarctic slope front controls glacial melting in the eastern weddell sea j geophys res 116 c11014 doi 10 1029 2011jc006965

measurements beneath an antarctic ice shelf using an autonomous underwater vehicle the cavities beneath antarctic ice shelves are among the least studied regions of the world ocean yet they are sites of globally important water mass transformations here we report results from a mission beneath fimbul ice shelf of an autonomous underwater vehicle the data reveal a spatially complex oceanographic environment an ice base with widely varying roughness and a cavity periodically exposed to water with a temperature significantly above the surface freezing point the results of this the briefest of glimpses of conditions in this extraordinary environment are already reforming our view of the topographic and oceanographic conditions beneath ice shelves holding out great promises for future missions from similar platforms

measurements of ice thickness and seabed topography under the fimbul ice shelf dronning maud land antarctica 1 this paper presents results from seismic measurements of the ice and water column thickness of the fimbul ice shelf in the northeastern weddell sea seismic reflection measurements were conducted at 183 stations covering most of the ice shelf seismic velocities in the ice were derived from refraction measurements at 12 stations distributed evenly across the area as well as from temperature and density data from the fimbul ice shelf velocities in the water were derived from temperature and salinity data from beneath the fimbul ice shelf ice thicknesses were found to vary between 160 m and 550 m with uncertainties up to 10 m water column thicknesses up to 900 m were found within the central ice shelf cavity and values exceed 2000 m where the ice shelf overhangs the continental slope uncertainties in water column thickness are estimated to be 60 m and are dominated by the uncertainties in the shape of the seabed ice draft and seabed elevation was derived from ice and water column thickness assuming hydrostatic pressure the resulting map of seabed elevation and water column thickness suggests that the strong westward flowing coastal current will be steered under the ice shelf and thus drive a sub ice shelf flow warm deep water does not have direct access to the ice shelf cavity while relatively cold coastal waters shallower than 500 m will interact closely with the fimbul ice shelf

wind driven export of weddell sea slope water the export of waters from the weddell gyre to lower latitudes is an integral component of the southern subpolar contribution to the three dimensional oceanic circulation here we use more than 20 years of repeat hydrographic data on the continental slope on the northern tip of the antarctic peninsula and 5 years of bottom lander data on the slope at 1000 m to show the intermittent presence of a relatively cold fresh westward flowing current this is often bottom intensified between 600 and 2000 dbar with velocities of over 20 cm s 1 transporting an average of 1 5 1 5 sv by comparison with hydrography on the continental slope within the weddell sea and modeled tracer release experiments we show that this slope current is an extension of the antarctic slope current that has crossed the south scotia ridge west of orkney plateau on monthly to interannual time scales the density of the slope current is negatively correlated r 0 6 with a significance of over 95 with eastward wind stress over the northern weddell sea but lagging it by 6 13 months this relationship holds in both the high temporal resolution bottom lander time series and the 20 year annual hydrographic occupations and agrees with weddell sea export variability observed further east we compare several alternative hypotheses for this wind stress export relationship and find that it is most consistent with wind driven acceleration of the gyre boundary current possibly modulated by eddy dynamics and represents a mechanism by which climatic perturbations can be rapidly transmitted as fluctuations in the supply of intermediate level waters to lower latitudes

using maximum entropy modeling for landslide susceptibility mapping with multiple geoenvironmental data sets the potential of using maximum entropy modeling for landslide susceptibility mapping is investigated in this paper although the maximum entropy model has been applied widely to species distribution modeling in ecology its applicability to other kinds of predictive modeling such as landslide susceptibility mapping has not yet been investigated fully in the present case study of boeun in korea multiple environmental factors including continuous and categorical data were used as inputs for maximum entropy modeling from the optimal setting test based on cross validation the effective feature type for continuous data representation was found to be a hinge feature and its combination with categorical data showed the best predictive performance factor contribution analysis indicated that distances from lineaments and slope layers were the most influential factors from interpretations on a response curve steeply sloping and weathered areas that consisted of excessively drained granite residuum soils were very susceptible to landslides predictive performance of maximum entropy modeling was slightly better than that of a logistic regression model which has been used widely to assess landslide susceptibility therefore maximum entropy modeling is shown to be an effective prediction model for landslide susceptibility mapping

quantitative estimation of intertidal sediment characteristics using remote sensing and gis abstract high spatial resolution satellite data ikonos combined with in situ data was used to quantitatively estimate the spatial distribution of tidal flat characteristics for the hwangdo tidal flat cheonsu bay korea the classification result was accurate in terms of a comparison with the in situ data and the overall accuracy was 90 7 which confirmed the validity of the classification gis analysis based on a probabilistic model was applied to a quantitative estimation of the relationship between each surface sediment facies and the spectral reflectance mud flat facies showed a high positive correlation r 2 0 91 and sand flat facies showed a high negative correlation r 2 1 00 which was a good reflection of the sedimentary characteristics of hwangdo tidal flat relationships between each sediment facies and dem also showed good agreement with the topographic characteristics in the study area the study revealed that intertidal surface sediment classification using high resolution remote sensing imagery and in situ data successfully shows spectral and topographic characteristics of the study area it was noted that spectral reflectance was affected by a combination of environmental factors including grain size topography and remnant surface water it is possible to determine the type of tidal flat through quantitative estimates of the spatial distribution of surface sediments according to their spectral reflectance

wind driven spreading of fresh surface water beneath ice shelves in the eastern weddell sea solar heated fresh antarctic surface water asw is a permanent feature along the eastern weddell sea ews coast in summer down to a depth of roughly 200 m recently asw has been observed beneath the fimbul ice shelf suggesting that it might play an important role in basal melting we propose that wind driven coastal downwelling is the main mechanism that spreads asw beneath the ice shelf in this sector of antarctica we validate this hypothesis with observations scaling analyses and numerical modeling along three principle lines i data analyses of about 1500 salinity profiles collected by instrumented seals indicate that the observed freshening of the coastal water column is likely explained by the on shore ekman transport and subsequent downwelling of asw ii an analytical model of the coastal momentum balance indicates that wind driven downwelling is capable of depressing the buoyant surface water to a depth similar to the ice shelf draft and iii simulations from both idealized and regional eddy resolving numerical ice shelf ocean models support our proposition our main conclusion is that wind driven spreading of asw beneath the ice shelf occurs when downwelling exceeds the depth of the ice shelf base furthermore our study adds to the understanding of the oceanic processes at the antarctic slope front in the ews with possible implications for other sectors of antarctica

cenozoic exhumation history of the alborz mountains iran new constraints from low temperature chronometry the alborz mountains in the north of the turkish iranian plateau mainly developed in the cenozoic as a consequence of the closure of neo tethys and continental collision between arabia and eurasia cenozoic growth of the fold and thrust belt exploited an older palaezoic mesozoic crustal fabric but the extent to which this governed the overall form of the mountain belt is unclear to determine when and how the alborz mountain belt has grown apatite fission track aft and u th he ahe thermochronometry were performed on 46 bedrock samples collected along 8 transects across the range aft central ages range from 157 24 ma to 10 1 ma with most ages falling between 40 ma and 10 ma ahe ages range from 17 2 ma to 6 1 ma the data revealed enhanced exhumation ca 35 5 ma minor exhumation between ca 30 20 ma and an increase in exhumation thereafter this pattern matches the tripartite mid cenozoic stratigraphy of central iran where upper oligocene lower miocene carbonates are sandwiched between terrestrial clastic formations the most intriguing thermochronometric signal found is a major acceleration of exhumation that initiated in the late miocene to early pliocene recorded by the ahe data there does not appear to be a direct tectonic cause for pliocene intensified erosion as convergence rates between arabia and eurasia have remained relatively constant enhanced exhumation at this time may reflect a climatically induced intensification of erosion during caspian isolation and base level fall or a regional tectonic re organization of the arabia eurasia collision or both

assessing subsidence susceptibility to coal mining using frequency ratio statistical index and mamdani fuzzy models evidence from raniganj coalfield india raniganj an important coalfield in india is susceptible to mining subsidence ejection of toxicants in the environment and huge subsurface destruction mining with opencast method poses a great risk to the surrounding areas of this coalfield anthropogenic and natural activities have caused ground movement leading to subsidence in raniganj coalfield existing knowledge on subsidence susceptibility to coal mining in raniganj coalfield is scant the study makes an attempt to analyze mining subsidence susceptibility in raniganj coalfield using site specific parameters we first prepared subsidence inventory map to identify old subsidence locations and to construct the model it was later utilized for validating the models fifteen site specific parameters related to subsidence were chosen to analyze coal mining subsidence frequency ratio fr statistical index si and mamdani fuzzy mf models were utilized to assess their effectiveness in preparing susceptibility map findings of the study revealed very high susceptibility in the central part high susceptibility in north western part and moderate susceptibility in the eastern part of raniganj coalfield low and very low susceptibility was found in those parts having largest area under vegetation and water bodies the models were validated through roc curve seed cell area index scai and spatially agreed area approach mamdani fuzzy model with highest success rate 87 and prediction accuracy 85 was found the best fit model for analyzing mining subsidence susceptibility the framework of the methodology will be instructive for analyzing susceptibility at different geographical locations

retrodeforming the arabia eurasia collision zone age of collision versus magnitude of continental subduction the arabia eurasia collision has been linked to global cooling the slowing of africa mediterranean extension the rifting of the red sea an increase in exhumation and sedimentation on the eurasian plate and the slowing and deformation of the arabian plate collision age estimates range from the late cretaceous to pliocene with most estimates between 35 and 20 ma we assess the consequences of these collision ages on the magnitude and location of continental consumption by compiling all documented shortening within the region and integrating this with plate kinematic reconstructions shortening estimates across the orogen allow for 350 km of neogene upper crustal contraction necessitating collision by 20 ma a 35 ma collision requires additional subduction of 400 600 km of arabian continental crust using the oman ophiolite as an analogue ophiolitic fragments preserved along the zagros suture zone permit 180 km of subduction of the arabian continental margin plus overlying ophiolites wholesale subduction of this more dense continental margin plus ophiolites would reconstruct 400 500 km of postcollisional arabia eurasia convergence consistent with a ca 27 ma initial collision age this younger arabia eurasia collision suggests a noncollisional mechanism for the slowing of africa and associated extension

reconstruction of changes in the weddell sea sector of the antarctic ice sheet since the last glacial maximum the weddell sea sector is one of the main formation sites for antarctic bottom water and an outlet for about one fifth of antarctica s continental ice volume over the last few decades studies on glacial geological records in this sector have provided conflicting reconstructions of changes in ice sheet extent and ice sheet thickness since the last glacial maximum lgm at ca 23 19 calibrated kiloyears before present cal ka bp terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the weddell sea ice sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding line advance at the lgm other marine geological and geophysical studies concluded that subglacial bedforms mapped on the weddell sea continental shelf subglacial deposits and sediments over compacted by overriding ice recovered in cores and the few available radiocarbon ages from marine sediments are consistent with major ice sheet advance at the lgm reflecting the geological interpretations different ice sheet models have reconstructed conflicting lgm ice sheet configurations for the weddell sea sector consequently the estimated contributions of ice sheet build up in the weddell sea sector to the lgm sea level low stand of 130 m vary considerably in this paper we summarise and review the geological records of past ice sheet margins and past ice sheet elevations in the weddell sea sector we compile marine and terrestrial chronological data constraining former ice sheet size thereby highlighting different levels of certainty and present two alternative scenarios of the lgm ice sheet configuration including time slice reconstructions for post lgm grounding line retreat moreover we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research the aim of our study is to provide two alternative interpretations of glacial geological datasets on antarctic ice sheet history for the weddell sea sector which can be utilised to test and improve numerical ice sheet models

observations beneath pine island glacier in west antarctica and implications for its retreat thinning ice in west antarctica is currently contributing about 10 of the observed rise in global sea level observations obtained from an autonomous underwater vehicle operating beneath pine island glacier west antarctica reveal that the glacier was recently grounded on a transverse ridge in the sea floor but now warm sea water flows through the widening gap above the ridge thinning ice in west antarctica resulting from acceleration in the flow of outlet glaciers is at present contributing about 10 of the observed rise in global sea level1 pine island glacier in particular has shown nearly continuous acceleration2 3 and thinning4 5 throughout the short observational record the floating ice shelf that forms where the glacier reaches the coast has been thinning rapidly6 driven by changes in ocean heat transport beneath it as a result the line that separates grounded and floating ice has retreated inland7 these events have been postulated as the cause for the inland thinning and acceleration8 9 here we report evidence gathered by an autonomous underwater vehicle operating beneath the ice shelf that pine island glacier was recently grounded on a transverse ridge in the sea floor warm sea water now flows through a widening gap above the submarine ridge rapidly melting the thick ice of the newly formed upstream half of the ice shelf the present evolution of pine island glacier is thus part of a longer term trend that has moved the downstream limit of grounded ice inland by 30 km into water that is 300 m deeper than over the ridge crest the pace and ultimate extent of such potentially unstable retreat10 are central to the debate over the possibility of widespread ice sheet collapse triggered by climate change11 12

sensitivity analysis for the gis based mapping of the ground subsidence hazard near abandoned underground coal mines ground subsidence around abandoned underground coal mines can cause much loss of life and property we analyze factors that can affect ground subsidence around abandoned mines in jeongahm in kangwon do by sensitivity analysis in geographic information system gis spatial data for the subsidence area topography and geology and various ground engineering data were collected and used to make a factor raster database for a ground subsidence hazard map to determine the importance of extracted subsidence related factors frequency ratio model and sensitivity analysis were employed sensitivity analysis is a method for comparing the combined effects of all factors except one sensitivity analysis and its verification showed that using all factors provided 91 61 accuracy the best accuracy was achieved by not considering the groundwater depth 92 77 and the worst by not considering the lineament 85 42 the results show that the distance from the lineament and the distance from the drift highly affected the occurrence of ground subsidence and the groundwater depth land use and rock mass rating had the least effects thus we determined causes of ground subsidence in the study area and this information could help in the prediction of ground subsidence in other areas

two years of oceanic observations below the fimbul ice shelf antarctica 1 the mechanisms by which heat is delivered to antarctic ice shelves are a major source of uncertainty when assessing the response of the antarctic ice sheet to climate change direct observations of the ice shelf ocean interaction are extremely scarce and in many regions melt rates from ice shelf ocean models are not constrained by measurements our two years of data 2010 and 2011 from three oceanic moorings below the fimbul ice shelf in the eastern weddell sea show cold cavity waters with average temperatures of less than 0 1 c above the surface freezing point this suggests low basal melt rates consistent with remote sensing based steady state mass balance estimates for this sector of the antarctic coast oceanic heat for basal melting is found to be supplied by two sources of warm water entering below the ice i eddy like bursts of modified warm deep water that access the cavity at depth for eight months of the record and ii fresh surface water that flushes parts of the ice base with temperatures above freezing during late summer and fall this interplay of processes implies that basal melting at the fimbul ice shelf cannot simply be parameterized by coastal deep ocean temperatures but instead appears directly linked to both solar forcing at the surface as well as to the dynamics of the coastal current system

mapping hazardous mining induced sinkhole subsidence using unmanned aerial vehicle drone photogrammetry accurate subsidence inventory data based on an understanding of local topography are a crucial first step toward reliable subsidence prediction and mapping future subsidence hazards however conventional human based methods of surveying and mapping subsidence suffer from data omissions and errors due to problems regarding accessibility safety and manual digitization this study employed unmanned aerial vehicle photogrammetry to compile an accurate subsidence inventory map of abandoned mine areas a phantom 2 vision drone was used which is inexpensive yet appropriate for detailed topographic surveying of small sized mine sites with a history of subsidence an autonomous flight plan was designed taking into account the extent of target mapping areas a series of 29 aerial photographs were obtained within 2 min digitally georeferenced orthoimage and digital terrain model dtm with 5 cm resolution could be obtained by processing with coordinate information of pre installed ground control points gcps within 30 min sinkhole type subsidence including locational information was identified from the geocoded high resolution orthoimage and the dtm and its area and volume were calculated to be 427 m2 and 2323 m3 length 25 m width 23 m depth 9 1 m respectively from its modeled shape contour lines 10 cm interval slope and curvature were produced using the dtm validation using the gcp locations showed an error of approximately 14 cm in the generated dtm which was considered acceptable for subsidence mapping purposes the proposed approach enables accurate rapid low cost and safe surveying and mapping which complements conventional surveying methods at sites of mining subsidence

the international bathymetric chart of the southern ocean ibcso version 1 0 a new bathymetric compilation covering circum antarctic waters the international bathymetric chart of the southern ocean ibcso version 1 0 is a new digital bathymetric model dbm portraying the seafloor of the circum antarctic waters south of 60 degrees s

investigation of sinkholes spatial distribution using the weights of evidence method and gis in the vicinity of karapinar konya turkey abstract there are many sinkholes 182 in the vicinity of karapinar approximately 20 large sinkholes 10 m in diameter were formed within the obruk plateau between 1970 and 2012 the formation of sinkholes is the most important geological hazard in the study area because they can damage engineering structures settlements agricultural areas and eventually be a source of casualties to date no study has been conducted on the distribution of sinkholes in this region in this study the spatial distribution of the sinkholes and the factors controlling sinkhole development were studied through the use of geographical information systems using a sinkhole inventory and a spatial database containing information on the topography geology hydrogeology and land use initially 182 sinkholes were identified in the area by examining the digital elevation model produced for this study the sinkholes were verified in the field thirty two factor maps were produced to investigate their relationship with sinkholes using the weights of evidence method the sinkholes are mainly related to dissolution of the neogene age lacustrine insuyu formation consisting of limestone and clayey limestone sinkhole frequency increases in the vicinity of drainages 2000 3000 m and faults

improving antarctic tide models by assimilation of icesat laser altimetry over ice shelves 1 assimilation of laser altimeter data from the ice cloud and land elevation satellite icesat significantly improves the accuracy of ocean tide models for the ross ice shelf ris for the most energetic tidal harmonic k1 assimilation reduces the root mean square error rmse between the model and a set of 16 independent tide records on and near the ris from 6 0 to 2 8 cm and the combined rmse for the six most energetic tidal harmonics from 7 7 to 5 4 cm when only the six most recent and highest quality tide records are considered the combined rmse is 4 8 cm this value is close to the uncertainty expected from tidal analyses of the short 1 2 month validation records indicating that assessing further improvements in tide model accuracy will require development of a higher quality validation data set

gis based evaluation of mining induced subsidence susceptibility considering 3d multiple mine drifts and estimated mined panels this paper presents a case study of subsidence hazard mapping in the vicinity of an abandoned coal mine within geographic information system gis environment a geospatial database was constructed using mine drift maps topographic maps land use maps road maps building maps borehole data and subsidence inventory maps showing occurrences of past subsidence events six raster type factor layers i e an influential area instability iai layer calculated using multiple mine drifts and estimated mined panels land use distance from nearest railroad distance from nearest road and slope gradient were generated and extracted from the database to identify relationships between past subsidence occurrences and the factors two iai factors incorporate the complex effects of ground iai and are calculated using the depths of each underground cavity and its angle of draw a weight of evidence model was used to establish optimal correlations expressed as contrast values cvs for subsidence inventory data and inputs of all factors six cv layers one for each factor were linearly combined to generate a subsidence hazard map representing the relative vulnerability to subsidence in the study area the area under the cumulative frequency diagram technique was then used to verify predicted subsidence hazards by comparing estimated susceptibility rankings over the entire range of grid cells with actual subsidence occurrences the proposed gis analysis model showed an accuracy of 91 09 in the prediction of subsidence occurrences moreover field surveys showed buildings with severe subsidence related damage damage level 4 or 5 according to the national coal board in regions with very high subsidence hazard indices finally a factor negatively correlated with subsidence prediction slope angle was determined from the sensitivity analysis

antarctic ice sheet loss driven by basal melting of ice shelves accurate prediction of global sea level rise requires that we understand the cause of recent widespread and intensifying glacier acceleration along antarctic ice sheet coastal margins atmospheric and oceanic forcing have the potential to reduce the thickness and extent of floating ice shelves potentially limiting their ability to buttress the flow of grounded tributary glaciers indeed recent ice shelf collapse led to retreat and acceleration of several glaciers on the antarctic peninsula but the extent and magnitude of ice shelf thickness change the underlying causes of such change and its link to glacier flow rate are so poorly understood that its future impact on the ice sheets cannot yet be predicted here we use satellite laser altimetry and modelling of the surface firn layer to reveal the circum antarctic pattern of ice shelf thinning through increased basal melt we deduce that this increased melt is the primary control of antarctic ice sheet loss through a reduction in buttressing of the adjacent ice sheet leading to accelerated glacier flow the highest thinning rates occur where warm water at depth can access thick ice shelves via submarine troughs crossing the continental shelf wind forcing could explain the dominant patterns of both basal melting and the surface melting and collapse of antarctic ice shelves through ocean upwelling in the amundsen and bellingshausen seas and atmospheric warming on the antarctic peninsula this implies that climate forcing through changing winds influences antarctic ice sheet mass balance and hence global sea level on annual to decadal timescales

distribution and characteristics of overdeepenings beneath the greenland and antarctic ice sheets implications for overdeepening origin and evolution das thanks the national cooperative for the disposal of radioactive waste nagra switzerland for their role in stimulating new research on the topic of focused glacial erosion and das and hp further thank nagra for funding the quantitative study of overdeepening morphology on which this paper is based grant 11 716 fcu bys hp also acknowledges support by the research council of norway through its centres of excellence funding scheme grant 223259 and the petromaks project glaciations in the barents sea area glacibar grant 200672 j

the antarctic slope current in a changing climate the antarctic slope current asc is a coherent circulation feature that rings the antarctic continental shelf and regulates the flow of water towards the antarctic coastline the structure and variability of the asc influences key processes near the antarctic coastline that have global implications such as the melting of antarctic ice shelves and water mass formation that determines the strength of the global overturning circulation recent theoretical modeling and observational advances have revealed new dynamical properties of the asc making it timely to review earlier reviews of the asc focused largely on local classifications of water properties of the asc s primary front here we instead provide a classification of the current s frontal structure based on the dynamical mechanisms that govern both the along slope and cross slope circulation these two modes of circulation are strongly coupled similar to the antarctic circumpolar current highly variable motions such as dense overflows tides and eddies are shown to be critical components of cross slope and cross shelf exchange but understanding of how the distribution and intensity of these processes will evolve in a changing climate remains poor due to observational and modeling limitations results linking the asc to larger modes of climate variability such as el nino show that the asc is an integral part of global climate an improved dynamical understanding of the asc is still needed to accurately model and predict future antarctic sea ice extent the stability of the antarctic ice sheets and the southern ocean s contribution to the global carbon cycle

the fate of the southern weddell sea continental shelf in a warming climate abstractwarm water of open ocean origin on the continental shelf of the amundsen and bellingshausen seas causes the highest basal melt rates reported for antarctic ice shelves with severe consequences for the ice shelf ice sheet dynamics ice shelves fringing the broad continental shelf in the weddell and ross seas melt at rates orders of magnitude smaller however simulations using coupled ice ocean models forced with the atmospheric output of the hadcm3 sres a1b scenario run co2 concentration in the atmosphere reaches 700 ppmv by the year 2100 and stays at that level for an additional 100 years show that the circulation in the southern weddell sea changes during the twenty first century derivatives of circumpolar deep water are directed southward underneath the filchner ronne ice shelf warming the cavity and dramatically increasing basal melting to find out whether the open ocean will always continue to power the melting the authors extend their simulations applying twentieth century atmospheric

simple method for the identification of subsidence susceptibility above underground coal mines in korea estimation of subsidence susceptibility due to mining is a primary task for the effective and economical management of subsidence if the status of an underground mine is well known this process is simple and clear unfortunately in korea the excavation shape is typically complicated because of the complex geological characteristics and corresponding mining methods and relevant data on abandoned or closed coal mines are often deficient therefore estimation methods developed elsewhere are usually not suited to korean coal mines to solve this problem we developed a quick simple and quantitative method suitable for the estimation of subsidence susceptibility prior to the detailed field investigation of coal mines gangway depth from the surface and the attitude dip and dip direction of main geological features were selected as input data based on the degree of availability and reliability and the gangway was represented as a series of points instead of closed polygons for easy calculation two core assumptions of this method were that the susceptibility to subsidence within a unit area increases as i the depth of the gangway from the surface decreases and ii the number of gangways below the unit area increases in spite of the simplicity of this method it gave satisfactory results when applied to one virtual excavation model and two closed coal mines where subsidences had occurred

ice platelets below weddell sea landfast sea ice basal melt of ice shelves may lead to an accumulation of disc shaped ice platelets underneath nearby sea ice to form a sub ice platelet layer here we present the seasonal cycle of sea ice attached to the ekstrom ice shelf antarctica and the underlying platelet layer in 2012 ice platelets emerged from the cavity and interacted with the fast ice cover of atka bay as early as june episodic accumulations throughout winter and spring led to an average platelet layer thickness of 4m by december 2012 with local maxima of up to 10 m the additional buoyancy partly prevented surface flooding and snow ice formation despite a thick snow cover subsequent thinning of the platelet layer from december onwards was associated with an inflow of warm surface water the combination of model studies with observed fast ice thickness revealed an average ice volume fraction in the platelet layer of 0 25 0 1 we found that nearly half of the combined solid sea ice and ice platelet volume in this area is generated by heat transfer to the ocean rather than to the atmosphere the total ice platelet volume underlying atka bay fast ice was equivalent to more than one fifth of the annual basal melt volume under the ekstrom ice shelf

assessment of ground subsidence hazard near an abandoned underground coal mine using gis this study constructs a hazard map for ground subsidence around abandoned underground coal mines aucms at samcheok city in korea using a probability frequency ratio model a statistical logistic regression model and a geographic information system gis to evaluate the factors related to ground subsidence an image database was constructed from a topographical map geological map mining tunnel map global positioning system gps data land use map lineaments digital elevation model dem data and borehole data an attribute database was also constructed from field investigations and reports on the existing ground subsidence areas at the study site nine major factors causing ground subsidence were extracted from the probability analysis of the existing ground subsidence area 1 depth of drift 2 dem and slope gradient 3 groundwater level permeability and rock mass rating rmr 4 lineaments and geology and 5 land use the frequency ratio and logistic regression models were applied to determine each factor s rating and the ratings were overlain for ground subsidence hazard mapping the ground subsidence hazard map was then verified and compared with existing subsidence areas the verification results showed that the logistic regression model accuracy of 95 01 is better in prediction than the frequency ratio model accuracy of 93 29 the verification results showed sufficient agreement between the hazard map and the existing data on ground subsidence area analysis of ground subsidence with the frequency ratio and logistic regression models suggests that quantitative analysis of ground subsidence near aucms is possible

platelet ice the southern ocean s hidden ice a review basal melt of ice shelves is not only an important part of antarctica s ice sheet mass budget but it is also the origin of one of the most peculiar types of sea ice found in the polar oceans platelet ice in many regions around coastal antarctica tiny ice crystals form and grow in supercooled plumes of ice shelf water releasing heat into the surrounding ocean they usually rise towards the surface eventually becoming trapped under an ice shelf as marine ice frequently masses of those crystals are advected out of the ice shelf cavity and accumulate below a solid sea ice cover to form a semiconsolidated layer when the overlying sea ice grows into this so called sub ice platelet layer the loose crystals are consolidated adding additional thickness to the sea ice these phenomena are generally referred to as platelet ice although confusion about the terminology is widespread in the literature the presence of platelet ice has a profound impact on sea ice properties and processes in several regions of antarctica with numerous implications for the local polar marine biosphere most notably sub ice platelet layers provide a stable sheltered nutrient and food rich habitat which usually results in a highly productive and uniquely adapted ecosystem it has also been hypothesised that platelet ice may be an indicator of the state of an ice shelf although comprehensive time series are limited to the ross sea this paper clears up the terminology by providing exact definitions of the relevant terms we review platelet ice formation observational methods as well as geographical and seasonal occurrence the physical properties and ecological implications are merged in a way understandable for physicists and biologists alike to lay the foundation for the interdisciplinary research that is necessary to tackle the current knowledge gaps

synchronous intensification and warming of antarctic bottom water outflow from the weddell gyre 1 antarctic bottom water aabw the densest water in the global overturning circulation has warmed in recent decades most notably in the atlantic time series recorded within the boundary currents immediately upstream and downstream of the most significant outflow of aabw from the weddell sea indicate that raised outflow temperatures are synchronous with stronger boundary current flows these changes occur rapidly in response to changes in wind forcing suggesting that barotropic dynamics and the response of the bottom ekman layer are significant the observed synchronicity indicates that the previously detected weakening of the export of the colder forms of aabw from the weddell sea need not be associated with a reduction in the total flux of aabw exported via this route these points need careful consideration when attributing the observed aabw warming in the atlantic and when determining its contribution to global heat budgets and sea level rise citation meredith m p a l gordon a c naveira garabato e p abrahamsen b a huber l jullion and h j venables 2011 synchronous intensification and warming of antarctic bottom water outflow from the weddell gyre geophys res lett 38 l03603 doi 10 1029 2010gl046265