coastal southerlies and alongshore surges of the west coast of north america evidence of mesoscale topographically trapped response to synoptic forcing abstract one of the most important warm season weather phenomena of the west coast of north america is the temporal transition from northerly to southerly flow within a few hundred kilometers offshore from the coastal mountains such wind shifts are often accompanied by cooler temperatures higher pressure and a change from nearly cloud free to low overcast conditions the more vigorous coastal transitions termed alongshore surges are characterized by an abrupt change in wind direction a sudden increase in wind speed to 15 m s 1 or more a precipitous temperature drop exceeding 10 c and a sharp rise in sea level pressure this paper presents two detailed case studies of topographically trapped coastal southerlies the strong surge event of 15 17 may 1985 and the far weaker case of 3 7 may 1982 it is shown that coastal southerlies and alongshore surges are controlled by the alongshore pressure gradients created by the synoptic scale flow at low levels and within approximately one rossby radius of th

decadal evolution of a very small heavily debris covered glacier in an alpine permafrost environment glacier response to climate forcing can be heterogeneous and complex depending on glacier system characteristics this article presents the decadal evolution of the tsarmine glacier swiss alps a very small and heavily debris covered cirque glacier located in the alpine periglacial belt archival aerial photogrammetry and autocorrelation of orthophotos were used to compute surface elevation volume and geodetic mass changes as well as horizontal displacement rates for several periods between 1967 and 2012 a gpr survey allowed us to investigate glacier thickness 15 m mean and volume 4 10 6 m 3 in 2015 and to anticipate its future evolution different dynamics occurred in recent decades because of the heterogeneous surface characteristics the climate sensitive upper debris free zone contrasts with the progressively stagnant heavily debris covered glacier tongue between 1967 and 2012 the glacier lost 1 3 of its initial volume 2 10 6 m 3 the average mass balance stabilised at 0 3 m w e a 1 since 1999 compared with other local glaciers the tsarmine glacier shows a particular decadal behaviour both in time divergence of mass balance since the 2000s and space inverted ablation pattern this might be explained by the combined influence of debris cover shadow snow redistribution and permafrost conditions on this very small glacier

permafrost activity and atmospheric warming in the argentinian andes abstract rock glaciers are permafrost or glacial landforms of debris and ice that deform under the influence of gravity recent estimates hold that in the semiarid chilean andes for example active rock glaciers store more water than glaciers however little is known about how many rock glaciers might decay because of global warming and how much this decay might contribute to water and sediment release we investigated an inventory of 6500 rock glaciers in the argentinian andes spanning the climatic gradient from the desert andes to cold temperate tierra del fuego we used active rock glaciers as a diagnostic of permafrost assuming that the toes mark the 0 c isotherm in climate scenarios for the twenty first century and their impact on freezing conditions near the rock glacier toes we find that under future worst case warming up to 95 of rock glaciers in the southern desert andes and in the central andes will rest in areas above 0 c and that this freezing level might move up more than twice as much 500 m as during the entire holocene 200 m many active rock glaciers are already well below the current freezing level and exemplify how local controls may confound regional prognoses a bayesian multifactor analysis of variance further shows that only in the central andes are the toes of active rock glaciers credibly higher than those of inactive ones elsewhere in the andes active and inactive rock glaciers occupy indistinguishable elevation bands regardless of aspect the formation mechanism or shape of rock glaciers the state of rock glacier activity predicts differences in elevations of toes to 140 m at best so that regional inference of the distribution of discontinuous permafrost from rock glacier toes cannot be more accurate than this in the argentinian andes we conclude that the central andes where rock glaciers are largest cover the most area and have a greater density than glaciers is likely to experience the most widespread disturbance to the thermal regime of the twenty first century

models of coastally trapped disturbances during the spring and summer the climatological northerly flow along the u s west coast is occasionally interrupted by transitions to southerly flow that have a limited offshore scale and appear to be manifestations of marine layer flow that is rotationally trapped by the coastal mountains existing climatological and observational studies suggest that a synoptic scale offshore flow initiates these coastally trapped disturbances ctds using idealized simulations produced with a 3d nonhydrostatic model the authors find that an imposed offshore flow will produce ctds in idealized coastal environments the imposed flow first weakens the prevailing northerly flow in the marine layer and lowers the pressure at the coast the marine layer flow around this low pressure evolves toward geostrophic balance but is retarded as it encounters the coastal mountains to the south of the low and subsequently deepens the marine layer in this region the elevated marine layer then begins progressing northward as a kelvin wave and later may steepen into a bore or gravity current this progression being the ctd many observed features accompanying ctds are found in the numerical simulations including the formation of a mesoscale pressure trough offshore and deep southerlies in the ctd at the coast stability in the atmosphere above the marine layer can give rise to topographically trapped rossby waves and stronger ctd winds in these stable conditions propagation of wave energy away from the disturbance does not preclude strong quasi steady propagating ctds

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

climate tectonics and the morphology of the andes large scale topographic analyses show that hemisphere scale climate variations are a first order control on the morphology of the andes zonal atmospheric circulation in the southern hemisphere creates strong latitudinal precipitation gradients that when incorporated in a generalized index of erosion intensity predict strong gradients in erosion rates both along and across the andes cross range asymmetry width hypsometry and maximum elevation reflect gradients in both the erosion index and the relative dominance of fluvial glacial and tectonic processes and show that major morphologic features correlate with climatic regimes latitudinal gradients in inferred crustal thickening and structural shortening correspond to variations in predicted erosion potential indicating that like tectonics nonuniform erosion due to large scale climate patterns is a first order control on the topographic evolution of the andes

rock glaciers and mountain hydrology a review abstract in mountainous regions climate change threatens cryospheric water resources and understanding all components of the hydrological cycle is necessary for effective water resource management rock glaciers are climatically more resilient than glaciers and contain potentially hydrologically valuable ice volumes and yet have received less attention even though rock glacier hydrological importance may increase under future climate warming in synthesising data from a range of global studies we provide the first comprehensive evaluation of the hydrological role played by rock glaciers we evaluate hydrological significance over a range of temporal and spatial scales alongside the complex multiple hydrological processes with which rock glaciers can interact diurnally seasonally annually decadally and both at local and regional extents we report that although no global extent complete inventory for rock glaciers exists currently recent research efforts have greatly elaborated spatial coverage using these research papers we synthesise information on rock glacier spatial distribution morphometric characteristics surface and subsurface features ice storage and hydrological flow dynamics water chemistry and future resilience from which we provide the first comprehensive evaluation of their hydrological contribution we identify and discuss long intermediate and short term timescales for rock glacier storage allowing a more balanced assessment of the contrasting perspectives regarding the relative significance of rock glacier derived hydrological contributions compared to other water sources we show that further empirical observations are required to gain a deeper hydrological understanding of rock glaciers in terms of i their genesis and geomorphological dynamics ii total ice water volume iii water discharge and iv water quality lastly we hypothesise that at decadal and longer timescales under future climate warming degradation of ice within rock glaciers may represent an increasing hydrological contribution to downstream regions and thus increased hydrological significance while rock glacier water stores persist

a continuous 770 year record of volcanic activity from east antarctica a 100 m ice core from site g 15 accumulation rate 0 1 m water yr 1 mean annual temperature 38 c on the mizuho plateau dronning maud land east antarctica has been analysed using the dielectric profiling dep technique the capacitance and conductance of the core were measured at ac frequencies 20 hz 300 khz the high frequency conductivity profile shows variations that are primarily related to the strong acids derived from volcanic activity the tambora 1815 eruption can be identified with the aid of an approximate chronology based on the firn densification rate other historic eruptions can then be recognised beyond about 300 years historical observations are very few however if a constant overall accumulation rate is assumed a well known eruption of 1259 a d can be found near the bottom of the core other peaks in the conductivity profile can then be assigned dates accurate to within a few years using the conductivity profile it is possible to estimate the relative acid deposition fluxes produced by the main eruptions with reasonable accuracy the estimated acid deposisition fluxes realtive to the tambora 1815 eruption of agung 1963 is 27 krakatoa 1883 25 the signal of 1601 28 and that of 1259 53

chronological and geomorphological investigation of fossil debris covered glaciers in relation to deglaciation processes a case study in the sierra de la demanda northern spain abstract in this study fossil debris covered glaciers are investigated and dated in the sierra de la demanda northern spain they are located in glacial valleys of approximately 1 km in length where several moraines represent distinct phases of the deglaciation period several boulders in the moraines and fossil debris covered glaciers were selected for analysis of 10 be surface exposure dating a minimum age of 17 8 2 2 ka was obtained for the outermost moraine in the san lorenzo cirque and was attributed to the global last glacial maximum lgm or earlier glacial stages based on deglaciation dates determined in other mountain areas of northern spain the youngest moraines were dated to approximately 16 7 1 4 ka and hence correspond to the gs 2a stadial oldest dryas given that the debris covered glaciers fossilize intermediate moraines it was deduced that they developed between the lgm and the oldest dryas coinciding with a period of extensive deglaciation during this deglaciation phase the cirque headwalls likely discharged large quantities of boulders and blocks that covered the residual ice masses the resulting debris covered glaciers evolved slowly because the debris mantle preserved the ice core from rapid ablation and consequently they remained active until the end of the late glacial or the beginning of the holocene for the san lorenzo cirque and the holocene thermal maximum for the mencilla cirque the north facing part of the mencilla cirque ensured longer preservation of the ice core

a simple model to estimate ice ablation under a thick debris layer this paper presents a simple model to estimate ice ablation under a thick supraglacial debris cover the key method employed in the model is to establish a link between the debris heat flux and the debris temperature at a certain depth when the heat transfer in the debris is described by a diffusion process given surface temperature debris thermal properties and relevant boundary conditions the proposed model can estimate mean debris temperature at interfaces of different debris layers using an iterative procedure and then the heat flux for ice ablation the advantage of the proposed model is that it only requires a few parameters to conduct the modeling which is simpler and more applicable than others the case study on koxkar glacier west tien shan china shows in general that the proposed model gives good results for the prediction of debris temperatures except for an apparent phase shift between modeled and observed values we suggest that this error is mainly due to complex phase relations between debris temperature and debris heat flux the modeled ablation rates at three experimental sites also show good results using a direct comparison with observed data and an indirect comparison with a commonly used energy balance model

numerical modeling of a coastal trapped disturbance part i comparison with observations abstract the coastal trapped disturbance ctd of 15 17 may 1985 represents an example of a strong mesoscale trapped event along the west coast of north america with abrupt transitions in many basic meteorological parameters in this study a comparison between observations and a numerical simulation of this event using the regional atmospheric modeling system rams is presented the model is shown to realistically reproduce ctd characteristics such as the coastal transition from northerly to southerly flow as a mesoscale coastal ridge of higher pressure with associated drops in marine layer temperature propagates northward along the west coast of north america simulated sea level pressure and temperature fields near the surface match well with observations especially at the synoptic scale the model realistically simulates mesoscale sea level pressure and 6 h pressure changes during the event the modeled hourly time evolution of sea level pressure and the southerly transitions at a series of coastal

properties of natural supraglacial debris in relation to modelling sub debris ice ablation as debris covered glaciers become a more prominent feature of a shrinking mountain cryosphere there is increasing need to successfully model the surface energy and mass balance of debris covered glaciers yet measurements of the processes operating in natural supraglacial debris covers are sparse we report measurements of vertical temperature profiles in debris on the ngozumpa glacier in nepal that show i conductive processes dominate during the ablation season in matrix supported diamict ii ventilation may be possible in coarse surface layers iii phase changes associated with seasonal change have a marked effect on the effective thermal diffusivity of the debris effective thermal conductivity determined from vertical temperature profiles in the debris is generally 30 higher in summer than in winter but values depend on the volume and phase of water in the debris surface albedo can vary widely over small spatial scales as does the debris thickness measurements indicate that debris thickness is best represented as a probability density function with the peak debris thickness increasing down glacier the findings from ngozumpa glacier indicate that the probability distribution of debris thickness changes from positively skewed in the upper glacier towards a more normal distribution nearer the terminus although many of these effects remain to be quantified our observations highlight aspects of spatial and temporal variability in supraglacial debris that may require consideration in annual or multi annual distributed modelling of debris covered glacier surface energy and mass balance copyright 2012 john wiley sons ltd

sensitivity of coastally trapped disturbance dynamics to barrier height and topographic variability in a numerical model abstract the sensitivity of a coastally trapped disturbance ctd to topographic height is examined using simulations of the 15 18 may 1985 ctd these simulations include three with uniform topography in which the north american west coast mountains are represented by a three piece uniform ramp at the coast leading to a constant plateau inland and three with realistic topography in each trio of uniform and realistic topography simulations there is a control case in which the terrain height closely approximates reality and two variations in which the topography is multiplied everywhere by a topographic multiplication factor tmf of 1 5 and 0 5 to assess the sensitivity of the simulation to the barrier height average propagation speeds increased decreased by 15 20 with the increased decreased tmf it was found that the position of the ctd leading edge generally followed close behind a leading pressure trough minimum which propagated northward along the coast in a manner similar to a topographi

response of debris covered glaciers in the mount everest region to recent warming and implications for outburst flood hazards abstract in areas of high relief many glaciers have extensive covers of supraglacial debris in their ablation zones which alters both rates and spatial patterns of melting with important consequences for glacier response to climate change wastage of debris covered glaciers can be associated with the formation of large moraine dammed lakes posing risk of glacier lake outburst floods glofs in this paper we use observations of glaciers in the mount everest region to present an integrated view of debris covered glacier response to climate change which helps provide a long term perspective on evolving glof risks in recent decades debris covered glaciers in the everest region have been losing mass at a mean rate of 0 32 m yr 1 although in most cases there has been little or no change in terminus position mass loss occurs by 4 main processes 1 melting of clean ice close to glacier elas 2 melting beneath surface debris 3 melting of ice cliffs and calving around the margins of supraglacial ponds and 4 calving into deep proglacial lakes modelling of processes 1 and 2 shows that everest region glaciers typically have an inverted ablation gradient in their lower reaches due to the effects of a down glacier increase in debris thickness mass loss is therefore focused in the mid parts of glacier ablation zones causing localised surface lowering and a reduction in downglacier surface gradient which in turn reduce driving stress and glacier velocity so the lower ablation zones of many glaciers are now stagnant model results also indicate that increased summer temperatures have raised the altitude of the rain snow transition during the summer monsoon period reducing snow accumulation and ice flux to lower elevations as downwasting proceeds formerly efficient supraglacial and englacial drainage networks are broken up and supraglacial lakes form in hollows on the glacier surface ablation rates around supraglacial lakes are typically one or two orders of magnitude greater than sub debris melt rates so extensive lake formation accelerates overall rates of ice loss most supraglacial lakes are perched above hydrological base level and are susceptible to drainage if they become connected to the englacial drainage system speleological surveys of conduits show that large englacial voids can be created by drainage of warm lake waters along pre existing weaknesses in the ice roof collapses can open these voids up to the surface and commonly provide the nuclei of new lakes thus by influencing both lake drainage and formation englacial conduits exert a strong control on surface ablation rates an important threshold is crossed when downwasting glacier surfaces intersect the hydrological base level of the glacier base level lakes formed behind intact moraine dams can grow monotonically and in some cases can pose serious glof hazards glacier termini can evolve in different ways in response to the same climatic forcing so that potentially hazardous lakes will form in some situations but not others additionally the probability of a flood is not simply a function of lake volume but depends on the geometry and structure of the dam and possible trigger mechanisms such as ice or rockfalls into the lake satellite based measurements of glacier surface gradient and ice velocities allow probable future locations of base level lakes to be identified a base level lake has begun to grow rapidly on ngozumpa glacier west of mount everest and could attain a volume of 10 8 m 3 within the next 2 or 3 decades unless mitigation efforts are undertaken this lake could pose considerable glof hazard potential

slow dynamics in debris covered and rock glaciers in hofsdalur trollaskagi peninsula northern iceland abstract the results of previous work on the dynamics of the debris covered and rock glaciers in trollaskagi are contradictory to improve our knowledge of these dynamics and determine the origin and evolution of these landforms we analyzed two case studies located in the hofsdalur valley the hofsjokull debris covered glacier and the jullogil rock glacier using digital photogrammetry combined with gis techniques our most accurate results were obtained for the period 1980 1994 as follows for the hofsjokull debris covered glacier a mean block displacement velocity of 0 22 m yr 1 a block elevation difference of 0 36 m and a horizontal displacement of linear ridges of 0 21 m yr 1 for the jullogil rock glacier a mean block displacement velocity of 0 15 m yr 1 a block elevation difference of 0 63 m and a horizontal displacement of linear ridges of 0 16 m yr 1 the limits of these glaciers remained stable for 70 years from 1946 to 2017 all our data support the fact that these landforms are stable and having lost their ice accumulation sources their dynamics are fundamentally related to subsidence processes therefore they are relict landforms whose origin seems to be related to paraglacial processes after rapid deglaciation of the valleys and their stagnated ice is preserved as it is above the permafrost level

logistic regression modeling of rock glacier and glacier distribution topographic and climatic controls in the semi arid andes abstract logistic regression is applied to a random sample of surface points in the semi arid andes of santiago and mendoza chile argentina 32 45 34 30 s 12 000 km 2 above 3000 m a s l to identify local and regional controls on rock glacier and glacier distribution the study area is among the areas with the greatest abundance of rock glaciers worldwide the explanatory variables used for model selection are related to local and regional morphometric and climatic characteristics the models achieve a very good fit area under the roc curve 0 84 for rock glaciers and 0 95 for glaciers and are able to reproduce the regional distribution pattern model results are used to determine the optimal morphographic and climatic niche of rock glaciers and glaciers in the study area and help explain the presence of low elevation rock glaciers under favorable topoclimatic conditions

dynamics and gpr stratigraphy of a polar rock glacier on james ross island antarctic peninsula we describe field measurements ground penetrating radar gpr geodetic survey and ice core drilling to provide new information on the movement mechanism and internal structure of a polar rock glacier on james ross island antarctic peninsula we collected gpr data along longitudinal and transverse profiles the longitudinal gpr profiles identify inter bedded debris rich layers that dip up glacier similar to the thrust structures in the compression zone of a valley glacier the transverse gpr profiles indicate a syncline structure inclined towards the central part of the rock glacier resembling the transverse foliation of a valley glacier the stratigraphy of two boreholes shows that the rock glacier consists primarily of bubbly ice with thin debris rich layers an internal structure similar to the nested spoons structure common in the interior of valley glaciers these results indicate that the glacier motion is controlled by shear movement common in valley glaciers the geodetic survey confirms that flow velocities decrease towards the lower part of the rock glacier such heterogeneous movement causes longitudinal compression and forms thrusts which then create the debris rich layer by uplifting basal ice and debris pushing of the upstream ice against the downstream ice bends the surface layers forming transverse ridges on the rock glacier surface

interpretation age and significance of a relict paraglacial and periglacial boulder dominated landform assemblage in alnesdalen romsdalsalpane southern norway abstract a boulder dominated landform assemblage in an alpine setting in norway is described interpreted and dated using a combination of schmidt hammer exposure age dating shd and cosmogenic 10be surface exposure dating the origin and formation of these features is determined from their morphology topographic setting and age three main components of the assemblage are recognized first a 300 m long and 160 m wide tongue shaped rock slope failure with a shd age of 11 49 0 82 12 96 0 86 ka is identified on the basis of its planform thickness runout distance and association with a fractured backing scarp this is interpreted as a relict paraglacial landform triggered by deglaciation second a 400 m long unequivocal pronival protalus rampart with an shd age of 6 95 0 97 8 35 1 21 ka is identified on the basis of its narrow ridge form aligned close to the foot of an extensive talus slope although formation of the rampart probably commenced with deglaciation the younger shd ages indicate formation at a diminishing rate through the holocene third a 550 m by 150 m lobate component with transverse ridges longitudinal and transverse depressions and enclosed pits previously identified as a rock glacier is dated to 11 33 0 83 13 33 0 90 ka with the schmidt hammer and between 13 3 2 0 14 7 2 0 ka with 10be this third component may also be a product of rock slope failure but attribution to rock glacier creep associated with either interstitial ice permafrost or buried glacier ice during the allerod interstadial younger dryas stadial and to which one or more rock slope failures contributed debris cannot be rejected the advantages and limitations of compiling such evidence for identifying differentiating and classifying apparently similar boulder dominated colluvial landforms are exemplified

the little ice age glacier advance in the central andes 35 s argentina abstract this paper documents the occurrence of the little ice age lia in the el azufre and el penon glaciers at 35 s and in the las choicas and las damas glaciers at 34 55 s in the headwaters of the rio grande basin in the central andes of argentina moraine morphology stratigraphic relationships radiocarbon ages obtained from peat on these glacial deposits and the proximity to the active glaciers enabled us to reconstruct the lia advance in this area the lia maximum advance occurred between cal yr 1550 and 1720 ad and a readvance occurred around cal yr 1830 ad in addition glacier fluctuations of the las vacas and gussfeltd glaciers 33 s and el penon and el azufre glaciers were documented from the end of the 19th century to the present based on historical and aerial photographs and satellite images the glaciers showed a marked retreat during 1894 2007 minor readvances occurred in the 1980s and 1990s which could be related with strong warm enso events during these decades our results are consistent with observations made by other authors in the region

analyses of uav and gnss based flow velocity variations of the rock glacier lazaun otztal alps south tyrol italy abstract flow velocities were measured on the active rock glacier lazaun by eleven gnns 2006 2018 and six uav campaigns 2016 2018 to better understand the flow pattern and its possible causes this medium sized active rock glacier is located w of kurzras maso corto in the schnals senales valley in the southern otztal alps south tyrol northern italy the uav data were used to generate displacement maps by image correlation techniques to analyse surface lowering and accumulation processes and to interpret the geomorphology base on shaded relief images the spatial information from uav contributes much more to the understanding of the rock glacier flow patterns as the point based gnss measurements even when the uav based horizontal displacement analyses are less precise the level of detection lod for the absolute horizontal displacements derived by image correlation from uav data ranges between 0 05 and 0 15 m a comparison of the displacement lengths shows that the uav derived displacement vectors deviate in average about 0 05 m from the gnss measured displacement lengths the deviation in the displacement directions is smaller when the absolute displacement is higher and ranges in zones with an absolute displacement higher than 0 3 m in dependence to the data quality between 0 and 4 consequently when planning a uav based rock glacier monitoring the achievable data accuracy rock glacier flow velocity and the time span must be considered analyses of the rock glacier velocities from gnss and uva data show that the calculated horizontal mean velocity increased significantly from 2 mm day in 2006 up to 6 mm day in the period 2012 to 2016 and then decreased to values of 3 4 mm day until 2018 we assume that internal structures and hydrogeology are essential parameters that control the flow mechanism of rock glacier lazaun particularly the shear horizon composed of debris and banded ice that is present at the base of the permafrost body and the unfrozen groundwater bearing sediment layer between the shear horizon and the bedrock we conclude that climate warming caused increased infiltration of meltwater into the shear horizon and that this is the main driving force for the movement of the rock glacier increased meltwater infiltration as result of climate warming caused an increase of flow velocity until 2016 the observed thickness loss near the front of the rock glacier indicates increased melting of permafrost ice resulting in a significant loss of permafrost ice during the last years this process that particularly occurs in the lower part of the rock glacier is believed to be responsible for the decrease in flow velocity since 2017

preliminary results from the lichenometric study of the nautardalur rock glacier trollaskagi northern iceland preliminary results from the lichenometric dating studies undertaken using the collective lichen species rhizocarpon geographicum sensu lato are presented and applied to the establishment of a rock glacier developmental chronology for the nautardalur rock glacier trollaskagi northern iceland absolute dates are tentatively postulated based on the application of the largest lichen thalli diameters to a regional trollaskagi r geographicum s l growth rate of 40 mm 100 yr lichenometric ages on the nautardalur rock glacier range over a continuum from approximately 200 yr bp to present a time frame suggestive of rock glacier development initiated during or immediately after the little ice age when a small come glacier was inundated with rock debris which formed an insulating skin over the ice and permitted its preservation until present lichenometric dating therefore provides an independent means of dating rock glacier deposits which agrees well with relative ages postulated by other palaeo reconstructional methods

an inventory and estimate of water stored in firn fields glaciers debris covered glaciers and rock glaciers in the aconcagua river basin chile abstract an inventory of firn fields glaciers debris covered glaciers and rock glaciers was conducted in the aconcagua river basin of the semiarid andes of central chile a total of 916 landforms were identified of which rock glaciers were the most abundant 669 and occupied the most total area glaciers and debris covered glaciers were less numerous but were about five times larger in comparison the total area occupied by glaciers and debris covered glaciers was roughly equivalent to the total area of rock glaciers debris covered glaciers and rock glaciers were subcategorized into six ice content classes based on interpretation of surface morphology with high resolution satellite imagery over 50 of rock glaciers fell within a transitional stage 85 of debris covered glaciers were either fully covered or buried most landforms occupied elevations between 3500 and 4500 m glaciers and firn occurred at higher elevations compared to rock glaciers and debris covered glaciers rock glaciers had a greater frequency in the northern part of the study area where arid climate conditions exist firn and glaciers were oriented south debris covered glaciers west and rock glaciers southwest an analysis of water contribution of each landform in the upper andes of the aconcagua river basin was conducted using formulas that associate the size of the landforms to estimates of water stored minimum and maximum water storage was calculated based on a range of debris to ice content ratios for debris covered glaciers and rock glaciers in the aconcagua river basin rock glaciers accounted for 48 to 64 of the water stored within the landforms analyzed glaciers accounted for 15 to 25 debris covered glaciers were estimated at 15 to 19 firn fields contained only about 5 to 8 of the water stored expansion of agriculture prolonged drought and removal of ice rich landforms for mining have put additional pressure on already scarce water resources to develop long term sustainable solutions the importance of the water stored in rock glaciers or other alpine permafrost landforms such as talus slopes must be weighed against the economic value of mineral resources

status and evolution of the cryosphere in the andes of santiago chile 33 5 s in the context of a general retreat of glaciers in the dry andes this study focuses on the state and recent evolution of debris covered glaciers and permafrost related landforms especially rock glaciers in the semiarid to semihumid laguna negra catchment a part of the andes of central chile at 33 5 s that is a key contributor of drinking water for the city of santiago we conducted catchment scale geomorphological mapping diachronic analysis of 1955 and 1996 orthophotographs and digital elevation models dems and the analysis of ground temperatures and their sensitivity to climate variation rock glaciers dominate spatially and in terms of water storage over glaciers area ratio 1 7 1 ratio of water equivalents 1 5 1 an intense downwasting has affected both debris covered and exposed glacier components in the punta negra subcatchment a process that is associated with the growth of numerous thermokarst depressions the altitudinal transect of ground temperature suggest that permafrost is widespread above 4000 m asl although it can also occur at lower elevations on sheltered footslopes and within rock glaciers the sensitivity analysis indicates that the near surface ground thermal regime at high altitudes is strongly influenced by the snow cover disappearance date which may therefore constitute an important control on the effect of climatic warming

ducted coastal ridging over s e australia the intense and rapidly established coastal ridging which is a regular occurrence over south eastern australia during the warm seasons is investigated using a detailed case study and mesoscale numerical model simulations we suggest that the ridge is initiated by a forced kelvin type edge wave which forms on the south western edge of the great dividing range and is ducted in an anticlockwise sense around the coast the ridge is then stabilized by inertial modification and decays over a synoptic time scale of a few days our results apply to similar phenomena in other parts of the world notably southern africa and south america

geomorphology internal structure and successive development of a glacier foreland in the semiarid chilean andes cerro tapado upper elqui valley 30 08 s 69 55 w we use geomorphological analysis sedimentological survey remote sensing and ground penetrating radar gpr in order to understand the complex landform assemblage found in front of the cerro tapado glacier in the upper elqui river catchment semiarid andes of chile the geomorphological analysis highlights prominent boundaries dividing the landform assemblage into from the upper part to the lower part an upper latero frontal moraine complex an upper debris covered glacier a lower debris covered glacier two rock glaciers and a lower morainic complex the sedimentological survey highlights the rather small size of the surface debris in general 400 m receding of the glacier occurred along with downslope displacements dm m y 1 of most of the landform units and a significant evolution of the thermokarst features on the debris covered glaciers considerable surface lowering occurred in the upper part of the assemblage while localized bulging is seen along the morphological boundaries in the lower units the gpr profiles highlight spectacular internal structure in the upper debris covered glacier with up to 80 m of buried ice in the other landform units the internal structure is less visible and more heterogeneous the analysis of the radar wave velocity along the gpr profiles reveals the occurrence of air filled and moist zones in the internal structure the geomorphological assemblage is fundamentally characterized by its morphological structural and dynamical boundaries and defined as a young probably 2000 years polygenetic construction with landform units having added to overlapped one another the rock glaciers do not derive from the present debris covered glacier but preexist to it

an inventory driven rock glacier status model intact vs relict for south tyrol eastern italian alps ice presence in rock glaciers is a topic that is likely to gain importance in the future due to the expected decrease in water supply from glaciers and the increase of mass movements originating in periglacial areas this makes it important to have at ones disposal inventories with complete information on the state of rock glaciers this study presents a method to overcome incomplete information on the status of rock glaciers i e intact vs relict recorded in regional scale inventories the proposed data driven modelling framework can be used to estimate the likelihood that rock glaciers contain frozen material potential predictor variables related to topography environmental controls or the rock glacier appearance were derived from a digital terrain model dtm satellite data and gathered from existing data sets an initial exploratory data analysis supported the heuristic selection of predictor variables three classification algorithms namely logistic regression glm support vector machine svm and random forest rf were trained on the basis of the available information on the status of rock glaciers within the territory of south tyrol eastern italian alps the resulting classification rules led to assign a binary label intact or relict to 235 unclassified rock glaciers present in the inventory all models were validated quantitatively on spatially independent test samples spatial cross validation and achieved highly satisfactory performance scores hereby the less flexible statistically based classifier glm performed slightly better than the more flexible machine learning algorithms svm and rf spatial permutation based variable importance assessment revealed that elevation and vegetation cover based on ndvi were the most relevant predictors for more than 80 of the unclassified rock glaciers all of the three models agreed on the spatially predicted rock glacier status only for a minor portion 12 3 one model differed from the remaining two

an empirical relation between overburden pressure and firn density two empirical equations for firn densification have been obtained considering firn porosity as a function of overburden pressure in the first equation thereduction ratio of porosity in firn is assumed to be proportional to the increasing ratioof overburden pressure and the mth power of the porosity the porosity exponent m should be close to 2 so as to have a best fit with 14 depth density profiles fromgreenland and antarctica in the second equation the reduction ratio of porosity wasassumed to increase proportionally to the increment of overburden pressure and thenth power of the porosity the most satisfactory values of the exponent range from 1 to 1 it has been suggested that firn density determined primarily by overburdenpressure and firn temperature contribute to a lesser degree

the age of the air in the firn and the ice at summit greenland in the framework of the eurocore drilling project 1989 at summit central greenland air samples were collected from a drill hole in the firn at several depth levels the samples have been analyzed for 85kr co2 ch4 cfc s f 11 and f 12 contents and for the isotopic composition of nitrogen and oxygen the measured data are compared with the results of a diffusion model co2 for example takes 12 years with a standard deviation of 7 5 years to diffuse from the surface to the firn ice transition under the present climatic conditions at summit the difference between the age of the ice and the mean age of the occluded air is approximately 210 years an enrichment of the heavier isotopes due to separation by gravity has been observed molecular diffusion alone suffices to explain the observed concentration trends in the firn column we can however not exclude the existence of a convective zone below the surface we have also measured the density and closed porosity along the firn core that has been retrieved when drilling the hole the porosity data reveal that the air is occluded into bubbles mainly between 65 and 80 m corresponding to densities of 790 and 830 kg m3 respectively

glaciation of alpine valleys the glacier debris covered glacier rock glacier continuum abstract alpine ice varies from pure ice glaciers to partially debris covered glaciers to rock glaciers as defined by the degree of debris cover in many low to mid latitude mountain ranges the few bare ice glaciers that do exist in the present climate are small and are found where snow is focused by avalanches and where direct exposure to radiation is minimized instead valley heads are more likely to be populated by rock glaciers which can number in the hundreds these rock cloaked glaciers represent some of the most identifiable components of the cryosphere today in low to mid latitude settings and the over steepened snouts pose an often overlooked hazard to travel in alpine terrain geomorphically rock glaciers serve as conveyor belts atop which rock is pulled away from the base of cliffs in this work we show how rock glaciers can be treated as an end member case that is captured in numerical models of glaciers that include ice dynamics debris dynamics and the feedbacks between them specifically we focus on the transition from debris covered glaciers where the modern equilibrium line altitude ela intersects the topography to rock glaciers where the modern ela lies above the topography on debris covered glaciers i e glaciers with a partial rock mantle rock delivered to the glacier from its headwall or from sidewall debris swept into the glacier at tributary junctions travels englacially to emerge below the ela there it accumulates on the surface and damps the rate of melt of underlying ice this allows the termini of debris covered glaciers to extend beyond debris free counterparts thereby decreasing the ratio of accumulation area to total area of the glacier aar in contrast rock glaciers i e glaciers with a full rock mantle occur where and when the environmental ela rises above the topography they require avalanches and rockfall from steep headwalls the occurrence of rock glaciers reflects this dependence on avalanche sources because they are most common on lee sides of ridges and peaks where wind blown snow enhances the strength of the avalanche source to maintain positive mass balance the avalanche cone developed in the winter must be sufficiently thick not to melt entirely in the summer thus providing an ice accumulation area for the rock glacier in the absence of rockfall this would support a short cirque glacier the presence of debris however facilitates the development of rock glaciers with lengths of hundreds of meters thicknesses of tens of meters and speeds of meters per year that are well described by numerical models numerical models are used to explore the alpine glacier response to its climate history in warming climates a debris covered glacier can transform into a much shorter rock glacier leaving in its wake a thinning ice cored moraine rock glaciers will persist in landscapes well beyond debris free counterparts because they have much longer response times to climate change the headwaters of alpine basins with steep headwalls will therefore oscillate between glacier and rock glacier occupation over glacial interglacial cycles maintaining a means by which rock from the headwall can be conveyed away this enhances the asymmetry of alpine ridgelines with downwind valleys biting deeply into the range crests as originally noted by g k gilbert

the dynamics of coastally trapped mesoscale ridges in the lower atmosphere abstract the dynamics of coastally trapped ridges that propagate in the marine layers of western north america and southeastern australia is examined a nonlinear semigeostrophic theory shows that the coastal ridges develop initially as an alongshore intrusion of denser marine air that is driven by the synoptic scale pressure gradient nonlinear kelvin waves evolve with the intruding flow on a slower time scale governed by the dynamic parameters if dispersive effects balance the nonlinearities then these waves evolve into solitary form otherwise the nonlinear waves steepen so that the leading edge of the ridge eventually propagates as a shock the theory is applied to two ridging events in california and one in southeastern australia in each case good agreement is found between theory and observations of the evolution times and propagation speeds of the coastal ridges the theory also explains the observed behavior of the events at prominent convex bends and gaps in the coastal topography

possible role of gravity currents in northern california s coastal summer wind reversals north winds along the northern california coast in the summer of 1982 were interrupted by six events with southerly winds four of these events occurred under similar circumstances one of these four events is presented in detail at the start of this event the marine layer is thickened in the southern california bight a couple of days later the marine layer thickens from point conception to monterey then the marine layer thickness increase surges to the north along the coast to point arena where progression stopped and an eddy formed in this surging stage winds switched to southerlies as the leading edge of the event passed a day later the leading edge surged further to the north inshore winds were southerly and the lifted marine layer extended to cape blanco in oregon this event is interpreted as a gravity current surging up the coast the basic reservoir is the thickened marine layer in the southern california bight northerly progression is interrupted by a blocking wave near point arena where an eddy forms it is hypothesized that most of the major wind reversals along the northern california coast during the summer are gravity currents or kelvin waves in the marine layer that are formed to the south

enclosure of air during metamorphosis of dry firn to ice if cold firn has reached a density of about 0 55 mg m 3 further densificaron occurs by a sintering process which increases the contact surface between the firn grains the pore volume is decreasing continuously but the firn remains permeable to air up to a density of 0 82 mg m 3 at about this density the remaining air in the pore volume is closed off in isolated bubbles we are interested in the age and the age distribution of the air enclosed in bubbles relative to the age of the surrounding ice and are investigating the development of the pore volume in firn a newly constructed measuring device allows the field measurement of the amount of air which is already enclosed in bubbles of firn samples measurements have been made during summer 1983 in greenland and during winter 1983 84 at the south pole the results are discussed and compared with results obtained with a simplified statistical sintering model using some results of percolation theory

mountain permafrost development and challenges of a young research field an overview is given of the relatively short history important issues and primary challenges of research on permafrost in cold mountain regions the systematic application of diverse approaches and technologies contributes to a rapidly growing knowledge base about the existence characteristics and evolution in time of perennially frozen ground at high altitudes and on steep slopes these approaches and technologies include 1 drilling borehole measurement geophysical sounding photogrammetry laser altimetry gps sar surveying and miniature temperature data logging in remote areas that are often difficult to access 2 laboratory investigations e g rheology and stability of ice rock mixtures 3 analyses of digital terrain information 4 numerical simulations e g subsurface thermal conditions under complex topography and 5 spatial models e g distribution of permafrost where surface and microclimatic conditions are highly variable spatially a sound knowledge base and improved understanding of governing processes are urgently needed to deal effectively with the consequences of climate change on the evolution of mountain landscapes and especially of steep mountain slope hazards as the stabilizing permafrost warms and degrades interactions between glaciers and permafrost in cold mountain regions have so far received comparatively little attention and need more systematic investigation

the geomorphic significance of rock glaciers estimates of rock glacier debris volumes and headwall recession rates in west greenland to obtain knowledge on rockwall retreat rates at sites with rock glaciers an inventory of about 400 individual rock glacier sites in west greenland was carried out by means of field studies and using aerial photographs and topographic maps a number of sites with ice cored moraines beyond normal glaciers were included in the analysis for comparative purposes the estimated debris volume was compared with the size of the source headwall the result of the inventory suggests that the presence of rock glaciers indicates extraordinary high retreat rates for rock free faces above especially headwalls above glacier derived rock glaciers are exposed to high weathering rates and thereby presumably delimit critical ranges regarding altitude for headwall retreat rates the relation of such a critical altitudinal range to other regional concepts such as glaciation level gl and glacier equilibrium line is discussed from this comments are also made on the relation between various permafrost zones and the typical regional climate within the maximum headwall weathering altitude at sites with active rock glaciers finally the potential importance of this range of maximum weathering for understanding the long term evolution of high relief cold climate landscapes is emphasised

magnetotelluric evidence for crustal suture zones bounding the southern great valley california a geoelectric section inferred from a regional magnetotelluric study across the coast ranges the great valley and the sierra nevada reveals significant variations in electrical resistivity zones of lower resistivity interpreted at depths from 10 km to at least 30 km lie near mapped geologic boundaries between the coast ranges and the great valley and beneath the eastern side of the great valley the former boundary is inferred by others to separate the subduction complex of the coast ranges from the mafic basement of the great valley the lower resistivities are most likely associated with metasediments trapped between the coast ranges ophiolite and the former oceanic crust beneath the great valley the latter boundary is problematic but may be evidence for a deep metasedimentary section trapped between the ophiolites beneath the great valley and the granitic rocks of the sierra nevada the lack of change in the magnetotelluric phase across the great valley indicates that a suture zone marked by lower resistivities is unlikely to be present beneath the valley however this does not preclude the existence of a resistive suture zone

evidence of kelvin waves in california s marine layer and related eddy generation abstract evidence suggests that an internal solitary kelvin wave exists in the marine layer along california the marine layer is lifted over the central coast by a weak cyclonic circulation this bump initially 850 m high moves to the north along the coast at 6 m s 1 the undisturbed layer depth is 100 200 m thick the crest height of the wave decreases to 500 m farther north winds under the raised marine layer are southerly the leading edge of the wave is easily followed by satellite as the thickened marine layer is marked by overcast stratus a greatly curved offshore leading edge indicates that nonlinear effects are important offshore scale in the overcast is about 300 km in the south and 50 km in the north surface pressure gradient alongshore is closely related to the marine layer depth the surface wind shifts when the leading and trailing edge of the wave passes northerly wave progression ceases at the sharp bend formed by cape mendocino at this time a vortex is formed in the marine laye

interrogating the time and processes of development of the las liebres rock glacier central chilean andes using a numerical flow model the las liebres rock glacier is a large 2 2 km long andean rock glacier whose internal composition and kinematics are known from previous studies we investigate its development by posing and testing the following null hypothesis the rock glacier has developed from a constant supply of debris and ground ice in periglacial conditions and resulting creep of the ice rock mixture a rheological model was formulated based on recent advances in the study of ice rock mixture rheology and calibrated on the known surface velocities and internal composition of the rock glacier we show that the rock glacier viscosity is inversely related to both water and debris fractions in agreement with recent field and theoretical studies of ice rock mixture rheology taking into account the possible variations in water fraction the model was used to estimate the time spans of development 0 91 7 11 ka rates of rock wall retreat 0 44 4 18 mm a and rates of ground ice formation 0 004 0 026 m a for the rock glacier these results support the null hypothesis of a periglacial origin of the las liebres rock glacier copyright 2016 john wiley sons ltd

australian southerly busters part i analysis of a numerically simulated case study abstract a diagnostic study of the australian southerly buster is performed using a numerical weather prediction model it is demonstrated that the model run at 50 km resolution is capable of capturing the transition of a cold front into a southerly buster as it traverses the cut coast of the australian continent the main features of the modified front am identified through comparison of the simulation with an adiabatic simulation from which precipitation and surface processes including orography have been removed from this comparison the southerly buster effect is defined in terms of the deformation of the front from its adiabatic ostentation and in terms of enhancement of temperature gradients and southerly winds along the coastal strip sensitivity experiments are then analyzed with a view to objectively determining the relative roles of mountains precipitation and land sea contrasts of heating and friction in bringing about these perturbations the major conclusions are that i the primary e

a nonhydrostatic mesoscale simulation of the 10 11 june 1994 coastally trapped wind reversal abstract during the summer months the california coast is under the influence of persistent northwesterly flow several times each summer this regime is disrupted by coastally trapped wind reversals ctwr in which the northwesterly flow is replaced by southerlies in a narrow zone along the coast controversy exists as to the physical mechanisms responsible for initiation and maintenance of ctwrs while it is clear that coastal terrain is important in creating the trapped response the precise role played by terrain is unclear in the present study these issues are investigated using a nonhydrostatic mesoscale model to simulate the 10 11 june 1994 ctwr event the results show that the model successfully reproduces many of the observed features of this event including anomalous vertical structure involving the relatively shallow boundary layer with a warm nearly neutral layer above the northward propagation of southerly flow in advance of a tongue of coastal stratus fog and a substantial reduction i

age difference between polar ice and the air trapped in its bubbles air entrapped in bubbles formed in cold ice has essentially the same composition as that of the atmosphere at the time of bubble formation the analysis of dated ice samples therefore enables the history of atmospheric composition to be investigated 1 3 the age of the entrapped air is however not the same as that of the surrounding ice because air bubbles only become isolated from the atmosphere during the transition from firn to ice typically the age of the ice at this transition is between 100 and 3 000 yr depending mainly on firn temperature and snow accumulation rate the mean age difference between ice and enclosed air as well as the age distribution width for a given sample are especially important for the investigation of the anthropogenic increase of co2 and trace gases in the atmosphere over the last centuries and for the comparison of climatic parameters recorded in the ice with parameters recorded in the bubbles for siple station antarctica this age difference and age distribution width were deduced from the bubble volume measured as a function of depth the values are 95 yr and 22 yr respectively

internal structure and composition of a rock glacier in the andes upper choapa valley chile using borehole information and ground penetrating radar this study uses boreholes ground temperature monitoring and ground penetrating radar gpr in order to understand the internal structure and composition of a rock glacier in the upper choapa valley northern chile the rock glacier is a small valley side feature 200 m long and ranging between 3710 and 3780 m a s l two boreholes were drilled down to depths of 20 and 25 m respectively using the diamond drillhole technique an ice rock mixture was encountered in the boreholes with heterogeneous ice content averaging 15 30 data from common midpoint cmp and constant offset co gpr surveys acquired respectively near the boreholes and across the whole rock glacier were processed to highlight the internal stratigraphy and variations in the radar wave velocity the gpr profiles depict a rock glacier constituted of stacked and generally concordant layers with a thickness ranging from 10 m in its upper part to 30 m towards its terminus the cmp analysis highlights radar wave velocities of 0 13 0 16 m ns 1 in the first 20 m of the structure larger vertical and lateral velocity variations are highlighted from co data reflecting the heterogeneous composition of the rock glacier and the likely presence of unfrozen water in the structure given the average air temperature registered at the site 0 58c the near melting point temperature registered in the boreholes over more than a year and the presence of locally high water content inferred from gpr data it is thought that the permafrost in the rock glacier is currently degrading

development of tongue shaped and multilobate rock glaciers in alpine environments interpretations from ground penetrating radar surveys abstract rock glaciers occur as lobate or tongue shaped landforms composed of mixtures of poorly sorted angular to blocky rock debris and ice these landforms serve as primary sinks for ice and water storage in mountainous areas and represent transitional forms in the debris transport system accounting for 60 of all mass transport in some alpine regions observations of active flowing alpine rock glaciers indicate a common association between the debris that originates from cirque headwalls and the depositional lobes that comprise them the delivery of this debris to the rock glacier is regulated primarily by the rate of headwall erosion and the point of origin of debris along the headwall these factors control the relative movement of individual depositional lobes as well as the overall rate of propagation of a rock glacier in recent geophysical studies a number of alpine rock glaciers on prins karls forland and nordenskioldland svalbard norway and the san juan mountains of southwest colorado usa have been imaged using ground penetrating radar gpr to determine if a relationship exists between the internal structure and surface morphology results indicate that the overall morphologic expression of alpine rock glaciers is related to lobate deposition during catastrophic episodes of rockfall that originated from associated cirque headwalls longitudinal gpr profiles from alpine rock glaciers examined in this study suggests that the difference in gross morphology between the lobate and tongue shaped rock glaciers can be attributed primarily but not exclusively to cirque geometry frequency and locations of debris discharge within the cirque and the trend and magnitude of valley gradient in relation to cirque orientation collectively these factors determine the manner in which high magnitude debris discharges which seem to be the primary mechanism of formation accumulate to form these rock glaciers

deglaciation history at the alpine mediterranean transition argentera mercantour sw alps from 10be dating of moraines and glacially polished bedrock estimating the extent and age of the last glacial maxima as well as the chronology of glacial recessions in various environmental contexts is key to source to sink studies and paleoclimate reconstructions the argentera mercantour massif being located at the transition between the alps and the mediterranean sea its deglaciation chronology can be compared to the sediment budget of the var river marine delta in this paper the deglaciation is constrained by 13 new and 22 reassessed cosmic ray exposure cre 10be datings of moraines and polished crystalline bedrocks these data allow for the first time to fully reconstruct the deglaciation history at the scale of the entire massif in agreement with a major glacier recession at ca 15 ka at the onset of bolling transition this contribution reveals a glacier climate relationship more sensitive to warming phases in the southern alps highlighted by a major decrease of glaciers after ca 15 ka this major deglaciation is correlated with a 2 5 fold decrease of sediment discharge of rivers into the mediterranean sea main deglaciation of the massif upper slopes 2 700 2 800 m a s l occurred after the lgm at 20 8 18 6 ka followed by the lower slopes 2 300 m a s l at 15 3 14 2 ka finally the flat polished surfaces above 2 600 m a s l and the zones confined within narrow lateral valleys were likely affected by progressive ice melting of remaining debris covered glaciers and moraine erosion following the younger dryas re advance stage between 12 and 8 9 ka at lower elevations a sediment core in the vens lake located at 2 300 m a s l shows onset of lake sedimentation at ca 14 ka and a transition towards a vegetated environment after 8 ka final stabilization of moraines occurred at 5 ka which might reflect denudation acceleration during the holocene humid phase

modeling past and future alpine permafrost distribution in the colorado front range rock glaciers a feature associated with at least discontinuous permafrost provide important topoclimatic information active and inactive rock glaciers can be used to model current permafrost distribution relict rock glacier locations provide paleoclimatic information to infer past conditions future warmer climates could cause permafrost zones to shrink and initiate slope instability hazards such as debris flows or rockslides thus modeling change remains imperative this research examines potential past and future permafrost distribution in the colorado front range by calibrating an existing permafrost model using a standard adiabatic rate for mountains 0 5 c per 100 m for a 4 c range of cooler and warmer temperatures according to the model permafrost currently covers about 12 per cent 326 1 km2 of the entire study area 2721 5 km2 in a 4 c cooler climate 73 7 per cent 2004 4 km2 of the study area could be covered by permafrost whereas in a 4 c warmer climate almost no permafrost would be found permafrost would be reduced severely by 93 9 per cent a loss of 306 2 km2 in a 2 0 c warmer climate however permafrost will likely respond slowly to change relict rock glacier distribution indicates that mean annual air temperature maat was once at least some 3 0 to 4 0 c cooler during the pleistocene with permafrost extending some 600 700 m lower than today the model is effective at identifying temperature sensitive areas for future monitoring however other feedback mechanisms such as precipitation are neglected copyright 2005 john wiley sons ltd

australian southerly busters part ii the dynamical structure of the orographically abstract a methodology is presented for comparing nonlinear 3d model output to the physical principles embodied in idealized and analytical models through the use of the transformation of wind components v vg va to accelerations k f fk v p dv dt this methodology is applied to numerical simulations of the interaction of a cold front with coastal topography leading to the formation of a southerly busier current along australia s east coast it is found that while the front is moving along the south coast mountain chain the dynamics of the perturbation are similar in character to an orographically trapped density current type perturbation on the background front along the east coast however the southerly busier current bears no dynamical relationship to either an orographically trapped density current or a kelvin wave the balance of forces here being dominated by inertial terms

observations and analysis of the 10 11 june 1994 coastally trapped disturbance abstract a coastally trapped disturbance ctd characterized by southerly flow at the surface on 10 11 june 1994 was observed from the california bight to bodega bay during a field experiment along the california coast north south approximates the coast parallel direction data from a special observational network of wind profilers radio acoustic sounding systems special surface data balloon ascents and a research aircraft were used with satellite and synoptic data to explore both the ctd structure and the regional scale changes before the event the disruption of the climatological northerly flow along the central california coast which preconditioned the area for the development of a ctd began with the eastward movement of a surface high into washington and oregon and the amplification of a thermal low in northern california as with most ctds in the region this occurred over the 2 3 days preceding the ctd s initiation these large scale changes caused westward advection of warm continental

rock glaciers and protalus landforms analogous forms and ice sources on earth and mars 1 the basic features and terminology of terrestrial rock glaciers are reviewed together with associated forms termed protalus lobes and protalus ramparts two basic models of rock glacier formation and flow invoke either the creep of ice derived from permafrost or glacial former glacial activity a third possible mechanism invokes landslide emplacement observations on terrestrial rock glaciers and similar forms suggest that the ice component can be produced via ground ice or from a glacier system finite element modeling of simple slope systems containing 1 a continuous ice layer buried by debris and 2 a mixture of ice and rigid blocks can both show creep but with very low rates especially at low temperatures possible martian examples of rock glacier and protalus lobe features are identified from candor chasma by wide angle mars orbiter camera moc imagery although the topography does not allow unambiguous interpretation some possible ways in which moc and mars orbiter laser altimeter mola and other mars orbiter data could help future interpretation of rock glaciers related protalus landforms and ice presence are discussed

rock glaciers and the geomorphological evolution of deglacierizing mountains abstract rock glaciers are an important geomorphic element of glaciated mountain landscapes but our understanding of their distribution and ages controls on their development and their importance in regional mountain hydrology and mountain geomorphic evolution is incomplete in part this incomplete knowledge arises through problems associated with identifying rock glaciers on a morphological basis alone amplified by the multiple ways in which rock glaciers can form in different glacial periglacial and paraglacial settings this study focuses on rock glaciers as a paraglacial mountain landscape element and considers the relationships between rock glaciers and glacial periglacial and paraglacial processes new geomorphic and sedimentary data on different rock glaciers from the khumbu region of nepal are presented these data show that even within a single region rock glaciers may have varied origins and thus likely ages and different climatic and environmental controls we argue that rock glaciers in deglacierizing mountains may have a long residence time in the landscape unlike many other glacially influenced mountain landforms and can undergo significant morphodynamic changes as glaciated landscapes transition into paraglacial landscapes

numerical modeling of a coastal trapped disturbance part ii structure and dynamics abstract a detailed analysis of a simulation of a coastal trapped disturbance ctd using the colorado state university regional atmospheric modeling system rams is presented the ctd considered 15 18 may 1985 represents an example of a strong mesoscale trapped event with abrupt gravity current like transitions in many meteorological parameters and which was closely tied to the synoptic forcing propagation of this event along the west coast of north america occurred from initiation in the southern california bight baja california coastal region to the northern tip of vancouver island and the event appeared to have no difficulty in negotiating significant bends or gaps in the coastal mountains unlike some other events that have ceased or stalled near cape mendocino point arena and the mouth of the columbia river it is found that warm offshore flow ahead of the ctd and cool onshore flow in the southern california bight northern baja california coastal region both driven by the westward tracking

glacier meltwater flow paths and storage in a geomorphologically complex glacial foreland the case of the tapado glacier dry andes of chile 30 s summary the tapado catchment is located in the upper elqui river basin 4000 5550 m in northern chile it comprises the tapado glacial complex which is an assemblage of the tapado glacier and the glacial foreland debris covered glacier rock glacier and moraines although the hydrological functioning of this catchment is poorly known it is assumed to actively supply water to the lower semi arid areas of the elqui river basin to improve our knowledge of the interactions and water transfers between the cryospheric compartment glacier debris covered glacier and rock glacier and the hydrological compartment aquifers streams the results of monitoring of meteorological conditions as well as discharge conductivity and temperature of streams and springs located in the tapado catchment were analyzed the hydrological results are compared to results inferred from a ground penetrating radar gpr survey of the underground structure of the glacial foreland water production from the tapado glacier was shown to be highly correlated with daily and monthly weather conditions particularly solar radiation and temperature the resulting daily and monthly streamflow cycles were buffered by the glacial foreland where underground transfers took place through complex flow paths however the development of a thermokarst drainage network in a portion of the glacial foreland enabled rapid concentrated water transfers that reduced the buffer effect the glacial foreland was shown to act as a reservoir storing water during high melt periods and supplying water to downstream compartments during low melt periods gpr observations revealed the heterogeneity of the internal structure of the glacial foreland which is composed of a mixture of ice and rock debris mixture with variable spatial ice content including massive ice lenses this heterogeneity may explain the abovementioned hydrological behaviors finally calculation of a partial hydrological budget confirmed the importance of the tapado catchment in supplying water to lower areas of the elqui river basin water production from and transfer through cryospheric compartments and its subsequent interactions with hydrological compartments are key processes driving the summer water supply from the tapado catchment

a numerical study of a southeast australian coastal ridging event abstract a numerical study of the 9 11 november 1982 southeast australian coastal ridging event is presented the mesoscale coastal features of this event have been previously described as a coastally trapped disturbance ctd however the analysis presented in this paper shows that the model coastal trapping is of secondary importance in generating the coastal ridging given the potential controversy particular emphasis in this paper is placed on identifying the causes of the ridging the paper follows a previous study by the authors in which a colorado state university regional atmospheric modeling system simulation of this event was validated in this event contributions to ridging along the southeastern australian coast came from both synoptic and mesoscale phenomena in the model a southern ocean anticyclone that tracked east from the great australian bight toward the southern tasman sea led to a large scale steady pressure increase over the entire southeast australian region ridging at the victo

distribution of debris thickness and its effect on ice melt at hailuogou glacier southeastern tibetan plateau using in situ surveys and aster imagery debris cover is widely present in glacier ablation areas of the tibetan plateau and its spatial distribution greatly affects glacier melt rates high resolution in situ measurements of debris thickness on hailuogou glacier mount gongga southeastern tibetan plateau show pronounced inhomogeneous debris distribution an analysis of transverse and longitudinal profiles indicates that the ground surveyed debris thicknesses and advanced spaceborne thermal emission and reflection radiometer aster derived thermal resistances of debris layers correlate strongly over the entire ablation area across and along glacier patterns of aster derived thermal resistance correspond well with spatial patterns of debris thickness which may reflect large scale variations in the extent and thickness of the debris cover the ice melt rate variability over the ablation area simulated by a surface energy balance model that considered thermal resistance of the debris layer indicates clearly the crucial role of debris and its spatial continuity in modifying the spatial characteristics of melt rates because of the inhomogeneous distribution of debris thickness about 67 of the ablation area on hailuogou glacier has undergone accelerated melting whereas about 19 of the ablation area has experienced inhibited melting and the sub debris melt rate equals the bare ice melt rate in only 14 of the ablation area

kelvin waves and internal bores in the marine boundary layer inversion and their relationship to coastally trapped wind reversals abstract detailed observations of a coastally trapped disturbance or wind reversal on 10 11 june 1994 along the california coast provide comprehensive documentation of its structure based on aircraft wind profiler radio acoustic sounding system and buoy measurements unlike the expectations from earlier studies based on limited data which concluded that the deepening of the marine boundary layer mbl was a key factor the 1994 data show that the perturbation was better characterized as an upward thickening of the inversion capping the mbl as the event propagated over a site the reversal in the alongshore wind direction occurred first within the inversion and then 3 4 h later at the surface a node in the vertical structure defined here as the altitude of zero vertical displacement is found just above the inversion base with up to 200 m upward displacements of isentropic surfaces above the node and 70 m downward displacements below although this is a single event it is shown that the vertic

comments on debris covered glaciers in the sierra nevada california and their implications for snowline reconstruction by d h clark m m clark and a r gillespie

constraints on the timing of debris covered and rock glaciers an exploratory case study in the holar area northern iceland abstract eighteen samples for 36cl cosmic ray exposure cre dating were taken from glacially polished bedrocks moraine boulders fossil active rock glaciers and debris covered glaciers in fremri grjotardalur and holadalur cirques in the vi inesdalur hofsdalur and he insdalur valleys close to holar village in the trollaskagi peninsula northern iceland boulder sampling was preceded by a study of the boulder stability with the twofold aim of ensuring that the surfaces to be sampled were stable enough for the reliable application of cre dating and to better understand the relation between the glacier dynamics and exposition history the results show that the glaciers which occupy the valleys in trollaskagi began their retreat around 16 ka later the glaciers advanced again around 11 ka within the cirques and small moraines were formed thereafter these small glaciers retreated and evolved into rock glaciers as debris from paraglacial processes accumulated on the glacier surface the fronts of these rock glaciers stabilized definitively shortly after their formation and became eventually fossil after the melting of their internal ice new rock glaciers and debris covered glaciers formed afterwards which still have internal ice at present although their current dynamics are mostly related to subsidence the stabilization of these rock glaciers and debris covered glaciers is dated to the period between 7 and 3 ka although they may have been reactivated during cold neoglacial periods this research demonstrates the potential interest in applying cre dating methods to debris covered glaciers and rock glaciers to determine their origin evolution and phase of cessation of internal movement until they finally lost their internal ice and became fossil

reconsidering the glacier to rock glacier transformation problem new insights from the central andes of chile abstract the glacier to rock glacier transformation problem is revisited from a previously unseen angle a striking case in the juncal massif located in the upper aconcagua valley chilean central andes is documented there the presenteseracae debris covered glacier has advanced several tens of metres and has developed a rock glacier morphology in its lower part over the last 60 years the conditions for a theoretically valid glacier to rock glacier transformation are discussed and tested permafrost probability in the area of the studied feature is highlighted by regional scale spatial modelling together with on site shallow ground temperature records two different methods are used to estimate the mean surface temperature during the summer of 2014 and the sub debris ice ablation rates are calculated as ranging between 0 05 and 0 19 cm d 1 i e 0 04 and 0 17 m over the summer these low ablation rates are consistent with the development of a coherent surface morphology over the last 60 years furthermore the rates of rock wall retreat required for covering the former glacier at presenteseracae lie within the common 0 1 2 mm y 1 range assuming an average debris thickness and a range of debris covering time intervals the integration of the geomorphological observations with the numerical results confirms that the studied debris covered glacier is evolving into a rock glacier

physical and climatic parameters which influence the air content in polar ice abstract under present day climatic conditions the air content of polar ice v generally shows a high sensitivity to the atmospheric pressure and hence to the surface elevation of the ice sheet wherethe ice is formed the results presented here are from sixteen different sites fourteen in antartica one in greenland and one in the yukon territories canada and they allow a better understanding of the parameters which influence the air content in ice it is demonstrated the v can be expressed very simply as a function of the atmospheric pressure p i the temperature t i and the porous volume of ice v i at which the air in the firn becomes isolated in terms of pressure from the atmosphere during the process of pore close off our results confirm a v i increase with temperature and show no clear v i dependence on snow accumulation rate the possible non linearity of the v i t i relation we obtain could be due to a wind influence on v i and or to a second order effect of the accumulation rate our v i results are compared to measurements of the volume of closed pores versus depth in the firn to close we discuss the parameterization that we can obtain to interpret the air content variations observed in deep ice cores over periods covering glacial interglacial transitions in terms of paleoclimatic conditions prevailing at the surface of the ice sheet

australian southerly busters part iii the physical mechanism and synoptic conditions contributing to development abstract the physical mechanism responsible for the formation of the southerly busier is investigated using simulations from a version of the australian bureau of meteorology s numerical weather prediction model froude number calculations are performed on a numerically simulated event to determine the blocking capacity of the mountains while the separate roles of the southern and eastern topography are explored through a series of idealized topography simulations it is found that the topography along the southern coastline plays a crucial role in the formation of the southerly buster through blocking of the cold air and subsequent channeling around to the east coast where the southerly surge occurs the interaction of four other summertime cold fronts with the southeastern australian topography is studied only two of these events in reality produced southerly busters on the east coast the model demonstrates ability to simulate the additional fronts accurately and hence distinguish between the southerl

a new model of rock glacier dynamics abstract rock glaciers have traditionally been described as periglacial landforms and thus associated genetically with the presence of permafrost and a seasonal active layer they have also been described as glacigenic in origin in which the main rock glacier body contains glacier ice at depth other rock glaciers can be considered as relict where they contain no interstitial ice and are functionally inactive although all rock glaciers are to some extent polygenic there is no clear simple test that can be used to distinguish between different rock glacier types this study proposes a simple and testable model for rock glacier classification based on their behaviour from evidence reported from the literature the study then proposes an interpretive evolutionary model describing the temporal evolution of rock glacier surface movement through the year that can inform on its dynamical controls this analysis provides an easily deployed interpretive framework for the origins of rock glaciers

the problem of hidden ice in glacier mapping lee can become hidden i e buried by the superimposition of rock debris on a glacier or where rock debris may incorporate interstitial ice because it is obscured problems result from a lack of understanding of the extent and continued activity of such ice landforms may be associated with this phenomenon and can be used as indirect evidence of its existence a rock glacier can contain glacially derived buried ice as well as interstitial ice we show with examples how such rock glaciers can be identified and provide information on the extent and possible volume of hidden ice in marginally glacierized and permafrost areas in most cases recognition of topography is sufficient although time separated aerial photographs may be necessary to locate the extent of ice these are generally preferable to and more cost effective than most detailed on site determinations of ice extent it is possible to incorporate and extend knowledge of hidden ice in glacier mapping and inventory projects

an energy balance model for debris covered glaciers including heat conduction through the debris layer extensive covers of supraglacial debris are often present in glacier ablation areas and it is essential to assess exactly how the debris affects glacier melt rates this paper presents a physically based energy balance model for the surface of a debris covered glacier the model is driven by meteorological variables and was developed using data collected at miage glacier italy during the ablation seasons of 2005 2006 and 2007 the debris surface temperature is numerically estimated by considering the balance of heat fluxes at the air debris interface and heat conduction through the debris is calculated in order to estimate melt rates at the debris ice interface the predicted hourly debris surface temperatures and debris internal temperatures provide a good fit to temperatures measured on rock covered miage glacier r 2 0 94 and the tephra covered glacier on villarrica volcano chile r 2 0 82 the model can also be used to reproduce observed changes in melt rates below debris layers of varying types and thicknesses an important consideration for the overall mass balance of debris covered glaciers

calculating ice melt beneath a debris layer using meteorological data generalized numerical models of sub debris ice ablation are preferable to empirical approaches for predicting runoff and glacier response to climate change as empirical methods are site specific and strongly dependent upon the conditions prevailing during the measurement period we present a modified surface energy balance model to calculate melt beneath a surface debris layer from daily mean meteorological variables despite numerous simplifications the model performs well and modelled melt rates give a good match to observed melt rates suggesting that this model can produce reliable estimates of ablation rate beneath debris layers several decimetres thick this is a useful improvement on previous models which are inappropriate for thick debris cover

debris covered glaciers in the sierra nevada california and their implications for snowline reconstructions abstract ice walled melt ponds on the surfaces of active valley floor rock glaciers and matthes little ice age moraines in the southern sierra nevada indicate that most of these landforms consist of glacier ice under thin ca 1 10 m but continuous covers of rock fall generated debris these debris blankets effectively insulate the underlying ice and greatly reduce rates of ablation relative to that of uncovered ice such insulation explains the observations that ice cored rock glaciers in the sierra actually debris covered glaciers are apparently less sensitive to climatic warming and commonly advance to lower altitudes than do adjacent bare ice glaciers accumulation area ratios and toe to headwall altitude ratios used to estimate equilibrium line altitudes elas of former glaciers may therefore yield incorrect results for cirque glaciers subject to abundant rockfall inadvertent lumping of deposits from former debris covered and bare ice glaciers partially explains an apparently anomalous regional ela gradient reported for the pre matthes recess peak neoglacial advance distinguishing such deposits may be important to studies that rely on paleo ela estimates moreover matthes and recess peak ela gradients along the crest evidently depend strongly on local orographic effects rather than latitudinal climatic trends indicating that simple linear projections and regional climatic interpretations of ela gradients of small glaciers may be unreliable

recent glacier variations at the aconcagua basin central chilean andes the majority of glaciers in central chile have receded in recent decades from 50 m to only a few meters per year mainly in response to an increase in the 08c isotherm altitude the aconcagua river basin 338 s is one of the major glaciated basins in central chile with 121 km 2 of ice in 2003 an earlier inventory using 1955 aerial photographs yielded a total surface area of 151 km 2 implying a reduction in glacier area of 20 0 63 km 2 a 1 over the 48 years photographic stereo models high resolution satellite images landsat aster and srtm data have been used to delineate glacier basins a focus on glaciar juncal norte one of the largest glaciers in the basin allows a more detailed analysis of changes the glacier has exhibited a smaller reduction 14 between 1955 and 2006 and the resulting elevation changes over this smaller period are not significant the above reduction rates are lower than in other glaciers of central chile and argentina this trend emphasizes water runoff availability in a river where most of the water in the dry summers is generated by glaciers and snowpack and where most of the superficial water rights are already allocated ongoing hydrological research including modelling of future water runoff will improve our understanding