paraglacial rock slope stability glaciation and deglaciation along with their associated climatic and non climatic processes modify slope stresses and influence slope stability paraglacial slope failures are those that are a part of or influenced by the transition from glacial conditions to non glacial conditions gravitational failure of rock slopes is a primary and dominant process of slope evolution in mountainous terrain and is the subject of this paper which 1 reviews the approaches taken for researching paraglacial rock slope failure patterns and processes 2 summarises the spatial and temporal patterns of post glacial failures 3 assesses the factors influencing slope stability during glaciation and deglaciation 4 explores some of the applications of paraglacial research and 5 highlights some of the outstanding issues to be resolved and provides recommendations for terminology relating to paraglacial slope processes

ice front variations and speed changes of calving glaciers in the southern patagonia icefield from 1984 to 2011 patagonian icefields are losing volume and their loss is due partly to rapid changes in their outlet glaciers that terminate in lakes or the ocean despite this key influence from outlet glaciers relatively few of these calving glaciers have had high frequency measurements on their frontal variations and ice speed changes we describe here recent frontal variations and ice speed changes of all 28 major calving glaciers in the southern patagonia icefield spi including ice speed maps covering approximately half of the entire icefield the analysis is based on satellite data from 1984 to 2011 over this period only the two termini of glaciar pio xi advanced of the remaining glacial fronts 12 changed less than 0 5 km but 17 retreated at least 0 5 km in the latter group three glacial fronts glaciar jorge montt hps12 and upsala retreated over 6 km averaged over all 31 glacial fronts of the calving glaciers the front positions retreated 1 56 km median is 0 71 km along the flowline within 20 km of the front the ice speeds up to 5900 200 m a 1 except for regions showing large acceleration or deceleration the mean speed over the measured area decreased by 30 m a 1 from 1984 to 2011 the three most rapidly retreating glaciers showed much larger acceleration near the calving front suggesting that ice dynamics drive their rapid retreat thus we see retreat as a long term trend for the calving glaciers in the spi with behavior that implies a dynamically controlled rapid recession that may explain the recently reported volume change of the spi

calving rates in fresh water new data from southern patagonia data relating to calving dynamics in fresh water are scarce especially for deep water sites a linear dependence of calving velocity vc onwater depth hw is commonly accepted for both tidewater and fresh water calving glaciers herewe use recent data from temperate patagonian glaciers to propose a revised relationship for calving in fresh water the new ratio is derived from glaciers calving rapidly into deep water documented using sequential satellite images and depth soundings the main data source is a detailed remotely sensed dataset of the rapidly retreating glaciarupsala complementedwith global positioning system field surveys and precise ice proximal bathymetric surveys the areaintegrated mean water depth between glacier positions in 1996 and 2000 is 490m with a maximum recorded depth of4700m in the same period image analysis reveals surface area loss of 1 37 km a 4 8 km and an average calving rate of 1880ma the resulting vc hw ratio is of a similar order of magnitude to that recently derived for nearby glaciar moreno but is well above the range of values commonly reported for lacustrine calving

ice loss from the southern patagonian ice field south america between 2000 and 2012 1 a time series composed of 156 aster derived digital elevation models dems and a radar penetration bias corrected version of the shuttle radar topography mission srtm dem is used to derive ice surface height and volume changes at the southern patagonian ice field spi in southern south america the observations made between february 2000 and march 2012 indicate that the ice field is rapidly losing volume at many of the largest outlet glaciers and in most cases thinning extends to the highest elevations of the ice field mass loss is occurring at a rate of 20 0 1 2 gt a 1 which when summed with mass loss at the adjacent northern patagonian ice field results in a combined rate of 24 4 1 4 gt a 1 equivalent to 0 067 0 004 mm a 1of sea level rise our decade long mass loss rates are substantially higher than those derived during the last three decades of the 20th century but are in good agreement with recent grace observations our volume loss estimate is sensitive to constraints applied to the amount of thickening in the accumulation zone new field measurements and a continued dem time series will be required to refine our estimates

an objective cyclone climatology for the southern hemisphere abstract an objective method is developed and used to derive a climatology of centers of cyclonic vorticity for the southern hemisphere based on twice daily european centre for medium range weather forecasts ecmwf 1000 hpa analyses during 1980 86 these centers were computed as local minima of geostrophic relative vorticity g extending previous studies based on pressure minima this use of g avoids a bias favoring slower and or deeper cyclones that occurs when pressure is used and includes a large number of additional mobile vorticity centers in the 45 55 s band that are missed where a local pressure minimum cannot be found an automated tracking algorithm similar to that of murray and simmonds is used to match predicted location pressure and g from previous track history with available centers large numbers of g centers were found south of 60 s and near the midlatitude continents as in previous studies these were a mixture of migratory centers and other fixed topographic features the maxi

recent accelerating mass loss of southeast tibetan glaciers and the relationship with changes in macroscale atmospheric circulations the mass balance history 1980 2010 of a monsoon dominated glacier in the southeast tibetan plateau is reconstructed using an energy balance model and later interpreted with regard to macroscale atmospheric variables the results show that this glacier is characterized by significant interannual mass fluctuations over the past three decades with a remarkably high mass loss during the recent period of 2003 2010 analysis of the relationships between glacier mass balance and climatic variables shows that interannual temperature variability in the monsoonal season june september is a primary driver of its mass balance fluctuations but monsoonal precipitation tends to play an accentuated role for driving the observed glacier mass changes due to their covariation concurrence of warm dry and cold wet climates in the monsoon influenced southeast tibetan plateau analysis of the atmospheric circulation pattern reveals that the predominance of anticyclonic cyclonic circulations prevailing in the southeastern northern tibetan plateau during 2003 2010 contributes to increased air temperature and decreased precipitation in the southeast tibetan plateau regionally contrasting atmospheric circulations explain the distinct mass changes between in the monsoon influenced southeast tibetan plateau and in the north tibetan plateau tien shan mountains during 2003 2010 the macroscale climate change seems to be linked with the europe asia teleconnection

climatology of tropopause folds at midlatitudes a statistical analysis of a 25 years time series of routine ozone soundings at uccle 51 48 n 4 21 e reveals that the frequency of tropopause folds is within the limits of uncertainty similar for all seasons on the average 4 8 of the ozone profiles show the presence of a fold whereas a shorter time series of soundings 1985 1993 obtained at the observatoire de haute provence 43 54 n 5 45 e yields only a 2 fraction of folds the difference between both stations is however riot entirely statistically significant the average wet and dry artificial radioactivity deposition in the sixties and early seventies was at a maximum at uccle around june in good agreement with global sr 90 wet deposition measurements volchok and kleinman 1971 suggesting that stratosphere troposphere exchange is more important during spring compared to the rest of the year this leads to the hypothesis that if tropopause folds are the major agent of stratosphere troposphere exchange ste they may be more efficient in spring than in autumn

gis based landslide susceptibility mapping using analytical hierarchy process and bivariate statistics in ardesen turkey comparisons of results and confirmations abstract the ardesen area is prone to landslides because of the climate conditions geologic and geomorphologic characteristics of the region as in previous years in 2001 due to heavy rainfall there were many landslides resulting in damage and human casualties there is still a great danger of further landslides in the region therefore it is vitally important to prepare a landslide susceptibility map of the region in this study the analytical hierarchy process ahp the statistical index wi and weighting factor wf methods were used to produce and later compare three susceptibility maps for this purpose thematic layers including landslide inventory lithology weathering slope aspect land cover distance to stream drainage density and distance to road were used in this study area 98 of landslides occurred in highly or completely weathered units lithology weathering land cover and slope data layers were found to be important factors in the study area to confirm the practicality of the three susceptibility maps were compared with a landslide activity map containing 16 active landslide zones the outcome was that the active landslide zones do not completely fit into the high and very high susceptibility classes but 81 3 of these landslide zones fall into the high and very high susceptibility zones of the ahp method while this is 62 5 in the case of wi method and 68 8 with the wf method in spite of the results obtained in this study the development of a susceptibility map is usually determined by the needs and available resources the results showed that the ahp method gave a more realistic picture of the actual distribution of landslide susceptibility than the wi and wf methods

a landslide susceptibility model using the analytical hierarchy process method and multivariate statistics in perialpine slovenia abstract landslides cause damage to property and unfortunately pose a threat even to human lives good landslide susceptibility hazard and risk models could help mitigate or even avoid the unwanted consequences resulted from such hillslope mass movements for the purpose of landslide susceptibility assessment the study area in the central slovenia was divided to 78 365 slope units for which 24 statistical variables were calculated for the land use and vegetation data multi spectral high resolution images were merged using principal component analysis method and classified with an unsupervised classification using multivariate statistical analysis factor analysis the interactions between factors and landslide distribution were tested and the importance of individual factors for landslide occurrence was defined the results show that the slope the lithology the terrain roughness and the cover type play important roles in landslide susceptibility the importance of other spatial factors varies depending on the landslide type based on the statistical results several landslide susceptibility models were developed using the analytical hierarchy process method these models gave very different results with a prediction error ranging from 4 3 to 73 as a final result of the research the weights of important spatial factors from the best models were derived with the ahp method using probability measures potentially hazardous areas were located in relation to population and road distribution and hazard classes were assessed

assessment of shallow landslide susceptibility by means of multivariate statistical techniques several multivariate statistical analyses have been performed to identify the most influential geological and geomorphological parameters on shallow landsliding and to quantify their relative contribution a data set was first prepared including more than 30 attributes of 230 failed and unfailed slopes the performance of principal component analysis t test and one way test allowed a preliminary selection of the most significant variables which were used as input variables for the discriminant analysis the function obtained has classified successfully 88 5 per cent of the overall slope population and 95 6 per cent of the failed slopes slope gradient watershed area and land use appeared as the most powerful discriminant factors a landslide susceptibility map based on the scores of the discriminant function has been prepared for ensija range in the eastern pyrenees an index of relative landslide density shows that the results of the map are consistent copyright 2001 john wiley sons ltd language en

a gis based landslide susceptibility evaluation using bivariate and multivariate statistical analyses bivariate and multivariate statistical analyses were used to predict the spatial distribution of landslides in the cuyahoga river watershed northeastern ohio u s a the relationship between landslides and various instability factors contributing to their occurrence was evaluated using a geographic information system gis based investigation a landslide inventory map was prepared using landslide locations identified from aerial photographs field checks and existing literature instability factors such as slope angle soil type soil erodibility soil liquidity index landcover pattern precipitation and proximity to stream responsible for the occurrence of landslides were imported as raster data layers in arcgis and ranked using a numerical scale corresponding to the physical conditions of the region in order to investigate the role of each instability factor in controlling the spatial distribution of landslides both bivariate and multivariate models were used to analyze the digital dataset the logistic regression approach was used in the multivariate model analysis both models helped produce landslide susceptibility maps and the suitability of each model was evaluated by the area under the curve method and by comparing the maps with the known landslide locations the multivariate logistic regression model was found to be the better model in predicting landslide susceptibility of this area the logistic regression model produced a landslide susceptibility map at a scale of 1 24 000 that classified susceptibility into four categories low moderate high and very high the results also indicated that slope angle proximity to stream soil erodibility and soil type were statistically significant in controlling the slope movement

rapid retreat acceleration and thinning of glaciar upsala southern patagonia icefield initiated in 2008 the patagonia icefields are characterized by a large number of outlet glaciers calving into lakes and the ocean in contrast to the recent intensive research activities on tidewater glaciers in other regions very few observations have been made on calving glaciers in patagonia we analysed satellite images of glaciar upsala the third largest freshwater calving glacier in the southern patagonia icefield to investigate changes in its front position ice velocity and surface elevation from 2000 to 2011 our analyses revealed a clear transition from a relatively stable phase to a rapidly retreating and fast flowing condition in 2008 the glacier front receded by 2 9 km and the ice velocity increased by 20 50 over the 2008 11 period we also found that the ice surface lowered at a rate of up to 39 m a 1 from 2006 to 2010 this magnitude and the rate of changes in the glacier front position ice velocity and surface elevation are greater than previously reported for glaciar upsala and comparable to recent observations of large tidewater glaciers in greenland our data illustrate details of a rapidly retreating calving glacier in patagonia that have been scarcely reported despite their importance to the mass budget of the patagonia icefields

a comparison of the gis based landslide susceptibility assessment methods multivariate versus bivariate the purpose of this study is to evaluate and to compare the results of multivariate logical regression and bivariate landslide susceptibility methods in geographical information system gis based landslide susceptibility assessment procedures in order to achieve this goal the asarsuyu catchment in nw turkey was selected as a test zone because of its well known landslide occurrences interfering with the e 5 highway mountain pass

a northern hemispheric climatology of cross tropopause exchange for the era15 time period 1979 1993 1 a 15 year climatology of cross tropopause exchange in the extratropical northern hemisphere is presented based upon a previously developed lagrangian methodology and reanalysis data from the european centre for medium range weather forecasts ecmwf for the years 1979 1993 for this time period no apparent trends exist for upward troposphere to stratosphere tst and downward stratosphere to troposphere stt cross tropopause transport the seasonal cycles of hemispherically integrated tst and stt and the zonally integrated meridional exchange distributions show relatively little interannual variability the 15 year averaged geographical distribution of stt reveals significant deviations from zonal symmetry and pronounced seasonal variability stt occurs predominantly over the atlantic and pacific storm track regions during winter spring and autumn and also over the mediterranean in winter and spring in contrast during summer stt maxima are located over the continents particularly over southeastern europe and central asia tst is less variable and is strongest near the southern tip of greenland and the aleutian islands during all seasons aspects of the interannual variability of the geographical exchange distributions are investigated over the atlantic stt varies significantly in line with the changing storm tracks during different phases of the north atlantic oscillation nao whereas tst does less so special consideration is given to vertically deep exchange where the exchange air parcels transfer rapidly from the lowermost stratosphere to the boundary layer or vice versa these processes occur mainly during winter and exhibit pronounced maxima over the north american west deep stt and east deep tst coasts

fragmentation of stratospheric intrusions evidence is presented pointing to the existence of rich and coherent subsynoptic and mesoscale flow features at tropopause levels these features are related to and evolve from the classical v shaped intrusions of stratospheric air down to tropospheric elevations it is shown that intrusions can develop into elongated 2000 3000 km and slender 200 km streamers and that thereafter such a streamer can roll up to form a train of stalactite shaped vortex subentities with an accompanying substantial thinning of the intervening filament in addition there are indications that the vortices themselves can develop a spirallike interior structure of interleaved stratospheric and tropospheric air these inferences are based upon two independent but complementary sources analysis of the potential vorticity distribution on tropopause transcending isentropic surfaces derived from the analysis fields of the european centre for medium range weather forecasts either directly or indirectly using a contour advection technique and imagery from the water vapor channel of the european space agency meteosat 4 satellite streamers were observed to occur with a frequency of approximately one per week over central and southern europe during the winter of 1991 1992 the fragmentation is linked to the instability or self development of a filament of enhanced potential vorticity and it can modify or instigate surface weather systems moreover by inducing a substantial and rapid enlargement of the intrusion s surface area it greatly enhances the potential for local irreversible mixing of stratospheric and tropospheric air

dynamical aspects of the life cycle of the winter storm lothar 24 26 december 1999 dynamical aspects of the life cycle of the winter storm lothar 24 26 december 1999 are investigated with the aid of the european centre for medium range weather forecasts analysis data and mesoscale model simulations neither of these datasets capture the full amplitude of the observed extreme pressure fall and surface wind speeds but they do help identify a range of key dynamical and physical features that characterize the development of this unusual event the analysis and interpretation is primarily based upon the evolution of the lower and upper level potential vorticity pv field complemented by three dimensional trajectory calculations lothar originated in the western atlantic and travelled as a shallow low level cyclone of moderate intensity towards europe this translation took place below and slightly to the south of a very intense upper level jet and was accompanied by continuous and intense condensational heating that sustained a pronounced positive low level pv anomaly not unlike the concept of a diabatic rossby wave no significant pv anomalies were evident at the tropopause level during this early phase of the life cycle the surface cyclone intensified rapidly when the shallow cyclone approached the jet stream axis the circulation induced by the diabatically produced low tropospheric pv anomaly on steeply sloping isentropic surfaces that transect the intense upper level jet contributed significantly to the rapid formation of a narrow and deep tropopause fold this stratospheric pv anomaly virtually merged with the diabatically produced ephemeral pv feature to form a vertically aligned tower of positive pv at the time of maximum storm intensity a sensitivity study with a dry adiabatic hindcast simulation shows no pv tower configuration and only a very weak surface development and confirms the primary importance of the cloud diabatic heating for the tropopause fold formation and the rapid bottom up intensification of lothar a comparison of the anomalously high atlantic sea surface temperatures in december 1999 with the water vapour source regions for the latent heat release that accompanied the rapid intensification phase of lothar shows a close relationship this is of importance when discussing the possible implications of climate variability and change on the development of north atlantic winter storms copyright 2002 royal meteorological society

changes in the velocity structure of the greenland ice sheet using satellite radar interferometry observations of greenland we detected widespread glacier acceleration below 66 north between 1996 and 2000 which rapidly expanded to 70 north in 2005 accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year as more glaciers accelerate farther north the contribution of greenland to sea level rise will continue to increase

landslide susceptibility certainty mapping by a multi method approach a case study in the tertiary basin of puy en velay massif central france the present study discusses the use of integrated variables along with a combination of multi method forecasts for landslide susceptibility mapping the study area is located in the south eastern french massif central a volcanic region containing tertiary sedimentary materials that are prone to landslides the flowage type landslides within the study area are very slow moving phenomena which affect the infrastructures and human settlements the modelling process is based on a training set of landslides 70 of total landslides and a set of controlling factor slope lithology surficial formation the topographic wetness index the topographic position index distance to thalweg and aspect we create a composite variable or integrated variable corresponding to the union of geology and surficial formation in order to avoid the conditional dependence between these two variables and to build a geotechnical variable we use five classical modelling methods index weight of evidence logistic regression decision tree and unique condition unit with the same training set but with different architectures of input data made up of controlling factors all the models are tested with a validation group 30 of total landslides using the area under the receiver operating characteristic curve auc to quantify their predictive performance we finally select a single best model for each method however these five models are all equivalent in quality despite their differences in detail so no single model stands out against another finally we combine the five models into a unique susceptibility map with a calculation of median susceptibility class the final auc value of this combined map is better than that for a single model except for unique condition unit and we can evaluate the certainty of the susceptibility class pixel by pixel in agreement with the sparse literature on this topic we conclude that i integrated variables increase the performance of classical modelling processes and ii the combination of multi method forecasts is a pragmatic solution to the inherent problem of choosing the most suitable method for the available data and geomorphological context

statistical approaches for the definition of landslide rainfall thresholds and their uncertainty using rain gauge and satellite data abstract models for forecasting rainfall induced landslides are mostly based on the identification of empirical rainfall thresholds obtained exploiting rain gauge data despite their increased availability satellite rainfall estimates are scarcely used for this purpose satellite data should be useful in ungauged and remote areas or should provide a significant spatial and temporal reference in gauged areas in this paper the analysis of the reliability of rainfall thresholds based on rainfall remote sensed and rain gauge data for the prediction of landslide occurrence is carried out to date the estimation of the uncertainty associated with the empirical rainfall thresholds is mostly based on a bootstrap resampling of the rainfall duration and the cumulated event rainfall pairs d e characterizing rainfall events responsible for past failures this estimation does not consider the measurement uncertainty associated with d and e in the paper we propose i a new automated procedure to reconstruct ed conditions responsible for the landslide triggering and their uncertainties and ii three new methods to identify rainfall threshold for the possible landslide occurrence exploiting rain gauge and satellite data in particular the proposed methods are based on least square ls quantile regression qr and nonlinear least square nls statistical approaches we applied the new procedure and methods to define empirical rainfall thresholds and their associated uncertainties in the umbria region central italy using both rain gauge measurements and satellite estimates we finally validated the thresholds and tested the effectiveness of the different threshold definition methods with independent landslide information the nls method among the others performed better in calculating thresholds in the full range of rainfall durations we found that the thresholds obtained from satellite data are lower than those obtained from rain gauge measurements this is in agreement with the literature where satellite rainfall data underestimate the ground rainfall registered by rain gauges

the landslide response of alpine basins to post little ice age glacial thinning and retreat in southwestern british columbia abstract the role of post little ice age lia neoglacial retreat on landslide activity is investigated in 19 alpine basins along the upper lillooet river valley british columbia we examine how neoglacial scouring and glacial recession have modified hillslope form and slope stability and construct a decision making flowchart to identify landslide hazards associated with glacial retreat this work is based on field mapping gis analysis statistical associations between landslides and terrain attributes and a comparison between neoglaciated and non neoglaciated terrain within each basin the bedrock landslide response to glacial retreat varies appreciably according to lithology and the extent of glacial scour below the lia trimline valleys carved in weak quaternary volcanics show significant erosional oversteepening and contain deep seated slope movement features active rock fall rock slides and rock avalanches near glacial trimlines basins in stronger granitic rock rarely show increased bedrock instability resulting from post lia retreat except for shallow seated rock slides along some trimlines and failures on previously unstable slopes in surficial materials landslides associated with post lia retreat originate in till or colluvium as debris slides or debris avalanches and are concentrated along lateral moraines or glacial trimlines significant spatial association was also observed between recent catastrophic failures gravitational slope deformation and slopes that were oversteepened then debuttressed by glacial erosion eight out of nine catastrophic rock slope failures occurred just above glacial trimlines and all occurred in areas with a previous history of deep seated gravitational slope movement implying that this type of deformation is a precursor to catastrophic detachment

southern patagonia s perito moreno glacier lake argentino and santa cruz river hydrological system an overview summary an overview of the hydrological data from patagonia s perito moreno glacier lake argentino and santa cruz river system reinforces our previous assertion that the el nino southern oscillation enso and the antarctic oscillation aao are teleconnected with the rupture sequence when the glacier s snout harmonically dams during certain interannual periods the rico branch of lake argentino it is clear however that the incidence of interannual climatic anomalies is not uniform in time and appears embedded in decadal or quasi bidecadal periods of relative damming inactivity the use of nonparametric tests shows that there are no significant positive trends in the river s annual discharge with the only exception of the yearly snowmelt ice melt periods september october when riverine flow appears to increase with statistical significance the question of the glacier s stability looks like a complex multivariate process although we do not rule out the occasional role of enso aao a longer hydrological data series i e 100 years would prove useful in casting some light on this intriguing process surely accounting for the glacier s response time

the retreat of glaciers in response to recent climate warming in western china glaciers in china are primarily located in the tibetan plateau tp and surrounding high mountains the chinese glacier inventory indicates that there are 46 377 glaciers in western china meteorological records indicate that air temperature in western china has risen by 0 2 c per decade since 1951 and 1998 was the warmest year precipitation in the region increased by 5 10 per decade from 1953 to 1997 using remote sensing and geographic information system methods we have monitored the changes in 5000 glaciers over the past 50 years we conclude that 80 of glaciers in western china have retreated losing 4 5 of their combined areal coverage although some glaciers have advanced in addition regional differences characterize glacier changes over the past few decades for example glaciers in the central and northwestern tp were relatively stable while glaciers in the mountains surrounding the tp experienced extensive wastage mass balance variations for some glaciers show accelerated ice shrinkage in the last two decades

assessment of different topographic corrections in landsat tm data for mapping vegetation types 2003 different methods for topographic correction of landsat thematic mapper images have been assessed in the context of mapping vegetation types the best results were obtained with a variation of the c method which takes into account the overcorrection of low illuminated slopes by the original c method the performance of this method was tested using two criteria the changes in the spectral characteristics of the image and the reduction in standard deviation of each vegetation type after the correction

holocene glacier history of the lago argentino basin southern patagonian icefield abstract we present new geomorphic stratigraphic and chronologic data for holocene glacier fluctuations in the lago argentino basin on the eastern side of the southern patagonian andes chronologic control is based on 14c and surface exposure 10be dating after the lateglacial maximum at 13 000 cal yrs bp the large ice lobes that filled the eastern reaches of lago argentino retreated and separated into individual outlet glaciers this recession was interrupted only by a stillstand or minor readvance at 12 200 cal yrs bp the eight largest of these individual outlet glaciers are from north to south upsala agassiz onelli spegazzini mayo ameghino perito moreno and grande formerly frias holocene recession of upsala glacier exposed brazo cristina more than 10 115 100 cal yrs bp and reached inboard of the holocene moraines in agassiz este valley by 9205 85 cal yrs bp ice remained in an inboard position until 7730 50 cal yrs bp several subsequent glacier readvances are well documented for the upsala and frias glaciers the upsala glacier readvanced at least seven times the first being a relatively minor expansion documented only in stratigraphic sections between 7730 50 and 7210 45 cal yrs bp the most extensive holocene advances of upsala glacier resulted in the deposition of the pearson 1 moraines and related landforms which are divided into three systems the pearson 1a advance occurred about 6000 5000 cal yrs bp and was followed by the slightly less extensive pearson 1b and 1c advances dated to 2500 2000 and 1500 1100 cal yrs bp respectively subsequent advances of upsala glacier resulted in deposition of the pearson 2 moraines and corresponding landforms also separated into three systems pearson 2a 2b and 2c constructed respectively at 700 400 and

tropopause folds and cross tropopause exchange a global investigation based upon ecmwf analyses for the time period march 2000 to february 2001 1 a new methodology is proposed to identify folds of the dynamical tropopause taken as the 2 potential vorticity pv units pvu isosurface from global analysis data sets from the european centre for medium range weather forecasts ecmwf it consists of a three dimensional subdivision of the atmosphere into stratospheric and tropospheric parts and a subsequent examination of multiple tropopause crossings in vertical profiles of the analyses the method is applied to a 1 year period starting in march 2000 seasonal mean fold frequency distributions show that folds occur preferentially in the subtropics with maximum frequencies of about 30 pronounced maxima are located in the subtropical bands that extend from 20 e to 120 e on both hemispheres during summer generally subtropical folds are comparatively shallow deep folds occur most frequently in midlatitudes during winter over eastern north america and the western north atlantic with maximum frequencies of about 1 detailed investigation of the relationship between individual folds and cross tropopause exchange events reveals that on the average individual folds in the extratropics are associated with larger exchange mass fluxes compared to the subtropics however due to the much higher frequency of subtropical folds the percentage of exchange events that are associated with tropopause folds is larger near 20 40 latitude 50 70 than further poleward 20 30 during winter and 10 20 during summer this indicates that tropopause folds are the key feature for cross tropopause exchange in the subtropics whereas in the extratropics other tropopause structures are at least of equal importance

assessing the validity of the channel model of fracture aperture under field conditions in recent investigations of fluid and solute movement in discrete fractures spatial heterogeneity of the fracture aperture has been conceptualized as a series of noninterconnecting constant aperture flow paths or channels two methods of estimating the distribution of the aperture sizes are presented using information from a single hole pumping test and a radially converging tracer test the first method uses the transmissivity of the fracture and mean arrival time of the tracer while the second method uses the mean and variance of the solute arrival time if the fracture can be conceptualized as a series of nonintersecting flow paths of constant aperture the two methods should yield identical estimates for the parameters of the distribution the validity of the channel model can be assessed by comparing the parameters of the distribution that are estimated by the two methods this technique was demonstrated using hydraulic and tracer tests conducted in a discrete areally extensive horizontal fracture in the silurian dolomite in the northeastern illinois a lognormal and a truncated gamma distribution were used to describe the distribution of constant aperture flow paths the lognormal distribution could not reproduce the abrupt rising limb and maximum rate of mass arrival that characterized the tracer tests the gamma distribution more accurately predicted the shape of the breakthrough curves however the two methods of estimating the parameters of the distribution provided significantly different estimates of the variances of the aperture sizes the mean aperture as estimated by the two methods was similar the difference in the variance of the aperture as estimated by the two methods indicates that alternative conceptual models of aperture heterogeneity are required to more accurately describe both fluid and solute movement in this field situation

thermal structure of proglacial lakes in patagonia calving glaciers are rapidly retreating in many regions under the influence of ice water interactions at the glacier front in contrast to the numerous researches conducted on fjords in front of tidewater glaciers very few studies have been reported on lakes in which freshwater calving glaciers terminate to better understand ice water interactions at the front of freshwater calving glaciers we measured lakewater temperature turbidity and bathymetry near glaciar perito moreno upsala and viedma large calving glaciers of the southern patagonia icefield the thermal structures of these lakes were significantly different from those reported in glacial fjords there was no indication of upwelling subglacial meltwater instead turbid and cold glacial water discharge filled the region near the lake bottom this was because water density was controlled by suspended sediment concentrations rather than by water temperature near surface wind driven circulation reaches a depth of 180 m forming a relatively warm isothermal layer mean temperature of 5 6 c at perito moreno 3 4 c at upsala and 6 7 c at viedma which should convey heat energy to the ice water interface however the deeper part of the glacier front is in contact with stratified cold water implying a limited amount of melting there in the lake in front of glaciar viedma the region deeper than 120 m was filled entirely with turbid and very cold water at pressure melting temperature our results revealed a previously unexplored thermal structure of proglacial lakes in patagonia suggesting its importance in the subaqueous melting of freshwater calving glaciers

a model aided study of the origin and evolution of the anomalously high potential vorticity in the inner region of a rapidly deepening marine cyclone abstract high spatial and temporal resolution fields generated by a mesoscale prediction model are used to study a case of rapid marine cyclogenesis 26 mb in 12 h within the context of potential vorticity pv thinking the case which occurred on 23 february 1987 near the east coast of the united states was well simulated by the model as was verified by ship reports and satellite imagery three components of the cyclone were investigated 1 a surface thermal anomaly or surrogate pv anomaly 2 a low level diabatically produced pv anomaly in and near the frontal cloud band and 3 a dry pv anomaly of upper tropospheric and lower stratosphoric origin trajectory tracing revealed that the surface thermal anomaly was caused primarily by northward transport of warm air into the central region of the low although surface sensible heat flux also contributed to the warm anomaly a sensitivity experiment run with the flux withheld showed that it had little impact on the depth of the storm furthermore

slope instability analysis in south patagonia applying multivariate and bivariate techniques on landsat images during 2001 2015 period abstract we present results of the estimation of surface changes associated with slope instability processes on the upsala channel by remote sensing and statistic techniques hillslopes involving lateral moraines of upsala channel at the argentino lake have become potentially unstable due to the retreat of upsala glacier during the last century the glaciation and deglaciation processes modify the tensions on the slope stability and may generate landslide processes a landslide movement destroyed the western edge of the upsala channel in february 2013 in addition the region represents a great tourist attraction usually ships navigate through the upsala channel seeing impressive landscapes especially the upsala glacier stand out due to this risky situation the necessity of increasing the knowledge in the area has arisen but has not been addressed yet therefore the main goal of the present study is to investigate the multivariate statistical techniques by the principal component analysis pca and discriminative analysis da in four testing areas tasn besides we include pearson s correlation coefficient pcc and normal distribution nd to determine whether the testing areas suffered slope movements or were temporally stable the study is based on landsat optical satellite images acquired during the period from october 2001 to april 2015 the results show that tas1 2 4 are less stable whereas tas5 is a more stable area as compared to another tas the pc1 and pc2 principal components explained the total variability of the 76 data the total apparent error of da reached 2 2 points the pcc achieved a positive trend during the years when movement on the slope surface was not observed while during the periods when slope instability was observed the correlation showed a negative trend the tasn that had shown a different behavior presented contrasted gaussian bells they are more flattened in those years with instability events

substructure of a map streamer a study is undertaken of the substructure of an upper level potential vorticity streamer that approached the european alps during the field phase of the mesoscale alpine programme map the diagnosis is based upon a lagrangian forward projection lfp technique which can provide a spatial refinement of the operational european centre for medium range weather forecasts analysis fields the reconstructed fields capture several notable fine scale features of the streamer s structure that include spiral arms of a vortex like feature and a richly structured western flank to the streamer comprising a deep primary fold surmounted by a significant secondary fold with an intermediate distinctive striation that extends back into the stratosphere these features are not at variance with independent high resolution satellite water vapour images and measurements gathered during a flight mission using an airborne water vapour differential absorption lidar dial instrument and hence lend a measure of credence to both the lfp approach and the dial measurements moreover the analysis sheds light on the evolution and dynamics of the streamer s vortices the origin of the folds the mismatch between the satellite observations and fields from other sources and also has implications for stratosphere troposphere exchange and the accompanying chemical mixing copyright 2003 royal meteorological society

calculating change curves for multitemporal satellite imagery mount st helens 1980 1995 abstract we developed and tested a method for analyzing multitemporal satellite imagery using change curves the method is flexible and allows an analyst to extract specific change parameters from the curves depending on the research question of interest eight landsat tm images of the mount st helens washington blast zone from 1984 to 1995 were geometrically and radiometrically corrected they were then transformed to estimates of green vegetation cover unsupervised clustering was performed on the set of eight transformed images and polynomial curves were fit to the cluster means from these fitted curves parameters of interest were extracted and returned to gis layers including number of years to reach 10 cover the greatest rate of cover increase during the study period and time integrated cover statistical analysis indicated that the curves did a good job of representing the change trajectories of unclustered pixels we demonstrated the use of change curve analysis by analyzing the importance in the revegetation of mount st helens of the different types of disturbance resulting from the volcanic eruption the change curve analysis is useful in a variety of applications where the data are continuous more than two dates of data are available and the underlying question of interest relates to trends in the data

global sea level contribution from the patagonian icefields since the little ice age maximum the melting of mountain glaciers and ice caps is expected to contribute significantly to sea level rise in the twenty first century 1 3 although the magnitude of this contribution is not fully constrained glaciers in the patagonian icefields of south america are thought to have contributed about 10 of the total sea level rise attributable to mountain glaciers in the past 50 years 3 however it is unclear whether recent rates of glacier recession in patagonia are unusual relative to the past few centuries here we reconstruct the recession of these glaciers using remote sensing and field determinations of trimline and terminal moraine location we estimate that the north patagonian icefield has lost 103 20 7 km 3 of ice since its late holocene peak extent in ad 1870 and that the south patagonian icefield has lost 503 101 1 km 3 since its peak in ad 1650 this equates to a sea level contribution of 0 0018 0 0004 mm yr 1 since 1870 from the north and 0 0034 0 0007 mm yr 1 since 1650 from the south the centennial rates of sea level contribution we derive are one order of magnitude lower than estimates of melting over the past 50 years 3 even when we account for possible thinning above the trimline we conclude that the melt rate and sea level contribution of the patagonian icefields increased markedly in the twentieth century

glacier fluctuations during the past 2000 years abstract a global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions excluding antarctica highlights the nature of glacier fluctuations during the late holocene the dataset includes 275 time series of glacier fluctuations based on historical tree ring lake sediment radiocarbon and terrestrial cosmogenic nuclide data the most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and when available winter precipitation reconstructions the most important parameters for glacier mass balance in many cases major glacier advances correlate with multi decadal periods of decreased summer temperature in a few cases such as in arctic alaska and western canada some glacier advances occurred during relatively warm wet times the timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region however the number of glacier advances shows a clear pattern for the high mid and low latitudes and hence points to common forcing factors acting at the global scale globally during the first millennium ce glaciers were smaller than between the advances in 13th to early 20th centuries ce the precise extent of glacier retreat in the first millennium is not well defined however the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th early 21st centuries other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the european alps in the 3rd 6th and 9th centuries in norway during the 10th 13th centuries in southern alaska and in the 18th century in spitsbergen however no single period of common global glacier retreat of centennial duration except for the past century has yet been identified in contrast the view that the little ice age was a period of global glacier expansion beginning in the 13th century or earlier and reaching a maximum in 17th 19th centuries is supported by our data the pattern of glacier variations in the past two millennia corresponds with cooling in reconstructed temperature records at the continental and hemispheric scales the number of glacier advances also broadly matches periods showing high volcanic activity and low solar irradiance over the past two millennia although the resolution of most glacier chronologies is not enough for robust statistical correlations glacier retreat in the past 100 150 years corresponds to the anthropogenic global temperature increase many questions concerning the relative strength of forcing factors that drove glacier variations in the past 2 ka still remain

correlation of satellite image time series for the detection and monitoring of slow moving landslides abstract slow moving landslides are widespread in many landscapes with significant impacts on the topographic relief sediment transfer and human settlements their area wide mapping and monitoring in mountainous terrain however is still challenging the growing archives of optical remote sensing images offer great potential for the operational detection and monitoring of surface motion in such areas this study proposes a multiple pairwise image correlation mpic technique to obtain a series of redundant horizontal displacement fields and different multi temporal indicators for a more accurate detection and quantification of surface displacement the technique is developed and tested on a series of monoscopic and stereoscopic pleiades satellite images at a test site in the south french alps empirical tests confirm that mpic significantly increased detection accuracy f measure 0 85 and that the measurement error can be reduced by averaging velocities from all pair combinations covering a given time step i e when stereo pairs are available for at least one date the derived inventory and displacement fields of 169 slow moving landslides show a positive relationship between the landslide size and velocities as well as a seasonal acceleration of the largest landslides in response to an increase in effective precipitation the processing technique can be adapted to better exploit increasingly available time series from a variety of optical satellites for the detection and monitoring of landslide displacement

image enhancements of landsat 8 oli and sar data for preliminary landslide identification and mapping applied to the central region of kenya image enhancements lead to improved performance and increased accuracy of feature extraction recognition identification classification and hence change detection this increases the utility of remote sensing to suit environmental applications and aid disaster monitoring of geohazards involving large areas the main aim of this study was to compare the effect of image enhancement applied to synthetic aperture radar sar data and landsat 8 imagery in landslide identification and mapping the methodology involved pre processing landsat 8 imagery image co registration despeckling of the sar data after which landsat 8 imagery was enhanced by principal and independent component analysis pca and ica a spectral index involving bands 7 and 4 and using a false colour composite fcc with the components bearing the most geologic information the sar data were processed using textural and edge filters and computation of sar incoherence the enhanced spatial textural and edge information from the sar data was incorporated to the spectral information from landsat 8 imagery during the knowledge based classification the methodology was tested in the central highlands of kenya characterized by rugged terrain and frequent rainfall induced landslides the results showed that the sar data complemented landsat 8 data which had enriched spectral information afforded by the fcc with enhanced geologic information the sar classification depicted landslides along the ridges and lineaments important information lacking in the landsat 8 image classification the success of landslide identification and classification was attributed to the enhanced geologic features by spectral textural and roughness properties

historically unprecedented global glacier decline in the early 21st century observations show that glaciers around the world are in retreat and losing mass internationally coordinated for over a century glacier monitoring activities provide an unprecedented dataset of glacier observations from ground air and space glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass balance data relating to the impact that glaciers exercise on global sea level fluctuations or on regional runoff in this study we provide an overview and analysis of the main observational datasets compiled by the world glacier monitoring service wgms the dataset on glacier front variations 42000 since 1600 delivers clear evidence that centennial glacier retreat is a global phenomenon intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the little ice age or holocene glaciological and geodetic observations 5200since 1850 show that the rates of early 21st century mass loss are without precedent on a global scale at least for the time period observed and probably also for recorded history as indicated also in reconstructions from written and illustrated documents this strong imbalance implies that glaciers in many regions will very likely suffer further ice loss even if climate remains stable

a three dimensional view of the evolution of midlatitude stratospheric intrusions abstract three dimensional views of midlatitude stratospheric intrusions are presented the views are obtained by plotting a surface of constant potential vorticity pv where the pv is diagnosed from a 6 day run of the u k universities global atmospheric modelling project general circulation model the pv 1 10 6 k kg 1 m2 s 1 1 pvu isosurface is chosen as representative of the tropopause the evolution of this surface is examined during the development of baroclinic waves in the northern hemisphere during october 1990 the developments show a number of features expected during the evolution of upper level troughs such as vortex roll up and the generation of tropopause folds in which air from the stratosphere intrudes downward into the troposphere however it is shown that the combined effects of deformation and convergence lead to the rapid collapse of folded features to leave low level tubes of pv together with higher level filaments the result is that the air intruded in the vicinity of

attribution and its application to mesoscale structure associated with tropopause folds it is important in meteorology to be able to establish a link between various features this link in its strongest form would be referred to as cause and effect but this is extremely difficult to establish for atmospheric flows a weaker but nonetheless powerful link is attribution which attempts to provide a way to associate various fundamental features such as potential vorticity anomalies to weather events involving regions of ascent attribution is not new and it is implicit in the way that atmospheric evolution is usually described in this paper an attempt is made to define more precisely what are the steps and assumptions being made in such a method these ideas become more concrete by applying them to a simple model of a two dimensional front at which there is a tropopause fold the aim is to find the vertical motion attributable to the descended tropopause fold in an extra tropical cyclone this is the first step in a longer programme of research designed to provide a test of the hypothesis that such a descended tropopause can trigger mesoscale phenomena such as convection and cyclones

contemporary glacier retreat triggers a rapid landslide response great aletsch glacier switzerland the destabilization and catastrophic failure of landslides triggered by retreating glaciers is an expected outcome of global climate change and poses a significant threat to inhabitants of glaciated mountain valleys around the globe of particular importance are the formation of landslide dammed lakes outburst floods and related sediment entrainment based on field observations and remote sensing of a deep seated landslide located at the present day terminus of the great aletsch glacier we show that the spatiotemporal response of the landslide to glacier retreat is rapid occurring within a decade our observations uniquely capture the critical period of increase in slope deformations onset of failure and show that measured displacements at the crown and toe regions of the landslide demonstrate a feedback mechanism between glacier ice reduction and response of the entire landslide body these observations shed new light on the geomorphological processes of landslide response in paraglacial environments which were previously understood to occur over significantly longer time periods

large scale control on the patagonian climate abstractpatagonia located in southern south america is a vast and remote region holding a rich variety of past environmental records but a small number of meteorological stations precipitation over this region is mostly produced by disturbances embedded in the westerly flow and is strongly modified by the austral andes uplift on the windward side leads to hyperhumid conditions along the pacific coast and the western slope of the andes in contrast downslope subsidence dries the eastern plains leading to arid highly evaporative conditions the authors investigate the dependence of patagonia s local climate precipitation and near surface air temperature year to year variability on large scale circulation anomalies using results from a 30 yr long high resolution numerical simulation variations of the low level zonal wind account for a large fraction of the rainfall variability at synoptic and interannual time scales zonal wind also controls the amplitude of the air temperature annual cycle by changi

landslide characteristics and slope instability modeling using gis lantau island hong kong steep terrain and high a frequency of tropical rainstorms make landslide occurrence on natural terrain a common phenomenon in hong kong this paper reports on the use of a geographical information systems gis database compiled primarily from existing digital maps and aerial photographs to describe the physical characteristics of landslides and the statistical relations of landslide frequency with the physical parameters contributing to the initiation of landslides on lantau island in hong kong the horizontal travel length and the angle of reach defined as the angle of the line connecting the head of the landslide source to the distal margin of the displaced mass are used to describe runout behavior of landslide mass for all landslides studied the horizontal travel length of landslide mass ranges from 5 to 785 m with a mean value of 43 m and the average angle of reach is 27 7 this gis database is then used to obtain a logistic multiple regression model for predicting slope instability it is indicated that slope gradient lithology elevation slope aspect and land use are statistically significant in predicting slope instability while slope morphology and proximity to drainage lines are not important and thus excluded from the model this model is then imported back into the gis to produce a map of predicted slope instability the results of this study demonstrate that slope instability can be effectively modeled by using gis technology and logistic multiple regression analysis