annual net balance of north cascade glaciers 1984 94 annual net balance on eight north cascade glaciers during the 1984 94 period has been determined by measurement of total mass loss from firn and ice melt and of residual snow depth at the end of the summer season overall spatial density of measurement points is 200 points km 2 mean annual balance of north cascade glaciers from 1984 to 1994 has been 0 38 m a 1 the resulting 4 2 m loss in water equivalent thickness is significant since north cascade glaciers have an average thickness of 30 50 m cross correlation of annual net babance for eight glaciers ranges from 0 83 to 0 97 this indicates the mass balances of the eight glaciers have been responding similarly to climate conditions despite their range of topographic and geographic characteristics annual net balance of individual glaciers was correlated with climate records the highest ablation season correlation coefficient is mean may august temperature ranging from 0 63 to 0 84 the highest accumulation season correlation coefficient is total accumulation season precipitation ranging from 0 35 to 0 59

plateau icefields as contributing areas to valley glaciers and the potential impact on reconstructed elas a case study from the lyngen alps north norway

postglacial topographic evolution of glaciated valleys a stochastic landscape evolution model the retreat of valley glaciers has a dramatic effect on the stability of glaciated valleys and exerts a prolonged influence on the subsequent fluvial sediment transport regime we have studied the evolution of an idealized glaciated valley during the period following retreat of ice using a numerical model the model incorporates a stochastic process to represent deepseated landsliding non linear diffusion to represent shallow landsliding and an approximation of the bagnold relation to represent fluvial sediment transport it was calibrated using field data from several recent surveys within british columbia canada we present ensemble model results and compare them with results from a deterministic linear diffusion model to show that explicit representation of large landslides is necessary to reproduce the morphology and channel network structure of a typical postglacial valley our model predicts a rapid rate of fluvial sediment transport following deglaciation with a subsequent gradual decline similar to that inferred for holocene time we also describe how changes in the model parameters affect the estimated magnitude and duration of the paraglacial sediment pulse

europe s southernmost glaciers response and adaptation to climate change the southernmost glaciers in europe are located on the iberian apennine and balkan peninsulas in mid latitudes between 41 n and 44 n at altitudes ranging from 2000 to 3000 m a s l all these glaciers are a legacy of the little ice age lia they survive in a relatively warm environment mean annual temperature 0 ct o 1 c due to local topographic controls and high levels of accumulation as a result of avalanche and wind blown snow in the pirin mountains bulgaria snezhnika glacieret has been cored providing an archive of recent climate change small glaciers such as this respond quickly to climatic extremes since the lia maximum during the 19th century all southern european glaciers have retreated losing 30 100 of their volume however despite the trend towards warmer years since the late 1970s some glaciers still survive even after some of the hottest summers on record predicted future warming especially in summer and drier conditions in the mediterranean basin may result in the disappearance of all glacier features at these latitudes in europe within the next few decades

quaternary glaciation in africa key chronologies and climatic implications multiple episodes of quaternary glaciation are evidenced on 10 distinct mountain localities throughout africa with the best dated sites from kilimanjaro and mt kenya in equatorial east africa a general paucity of radiogenic dates constrains the glacial chronology and regional sequences have largely been based on correlations by relative weathering of features excellent glacial moraine preservation and other features of erosion put limits on the spatial extent of palaeoglaciers and have facilitated advances in palaeo equilibrium line altitude ela analyses all radiocarbon dates n 30 provide minimum ages of deglaciation and are consistent with a widespread synchronous advance during the last glacial maximum lgm 21 2 ka k ar dates on kilimanjaro lava flows initially recognised up to three glaciations prior to the lgm over 100 cosmogenic radionuclide crn 36 cl exposure ages on glacial erratics and bedrock from kilimanjaro and mt kenya date 16 landforms confirming maximum glacial extent prior to marine isotope stage mis 10 no glacial geological features have been dated to mis 6 while on kilimanjaro the crn ages confirm a clear lgm mis 2 maximum mt kenya lacks definitive lgm moraines lateglacial advances or stillstands on both mountains are suggested by low relief moraines dating to 14 6 1 2 ka two boulders on mt kenya and 16 3 1 9 ka and 15 8 2 5 ka on kilimanjaro multiple moraines upvalley have early holocene ages ranging from 11 2 0 8 to 8 6 0 2 ka isolated and equivocal dates on both mountains also provide speculative evidence that the maximum extent since mis 5e may have occurred close to 30 ka similar to sites in south america new palaeoclimatic understanding from lake and ocean proxies suggests hypotheses for the source of low latitude climate changes causing the advances that can be tested with improved dates a high degree of intra regional variance in ela is observed with differences by aspect reflecting precipitation gradients future work should include more crn dates improved mapping and inverse climate mass balance modelling copyright 2008 john wiley sons ltd

speleothem u th age constraints for the last glacial conditions in the apuan alps northwestern italy abstract during the quaternary several glaciations occurred in the mountain regions around the mediterranean and in recent years new ages have better constrained their timing however this is not the case for the apuan alps a high rainfall mountain chain adjacent to the mediterranean sea here in spite of the widespread evidence for glaciers the complete lack of geochronological information hinders our understanding of glaciation history in this paper we utilize speleothem ages to better constrain the timing of these glacial features we re examine 293 uranium thorium ages from 19 speleothems collected in five caves at different elevations after a period of very low growth between 160 and 132 ka the analysed speleothems grew almost continuously to 75 ka this period was followed by intermittent growth with lower deposition rate and presence of hiatuses until 12 5 12 ka this is consistent with an ice coverage persisting over the apuan alps inhibiting or interrupting the growth of speleothems via the limited availability of groundwater and the scarcity absence of soils this interval is much greater than the time interval that has previously been attributed to the existence of glaciers on the apuan alps which has been assumed to be restricted to marine isotope stage mis 2 instead ice cover probably also appeared in the apuan alps during mis 4 the phase of restarting of growth which may implies the definitive or substantial glacier melts seem to predate the holocene

numerical modeling of stress and topography coupling during subduction inferences on global vs regional observables interpretation abstract the mechanical strength of the oceanic lithospheres exerts a fundamental control on the dynamics and tectonics of convergent margins here we use numerical models of coupled subducting upper plates and mantle to investigate the impact of the subducting lithosphere properties on the parameters commonly measured at subduction zones the models predict a correlation among parameters such as subducting and convergence velocities slab dip and curvature and stress coupling with the upper plates such signature emerges in a dynamic system through the slab buoyancy similar trends are found when assessing the impact of laboratory constrained non linear rheologies uncertainties on the mechanical strength and mantle flow although some features are more affected when the role of upper plate thickness is tested we find a positive correlation of upper plate subsidence and fore arc topography with the buoyancy of the down going plate however plasticity in the crust limits the development of topography becoming increasingly relevant with thinner upper plates so that no correlation can be established similar control is found on the width of the long wavelength dynamic subsidence due to flexure which increases non linearly with the upper plate thickness the models constrain relations among parameters within the dynamic system driven that allow inferences on the observable parameters the comparisons supports the idea that the subduction dynamics emerges as a global phenomenon in plate motions bending and dynamic subsidence yet andean type margin tectonics is best addressed in a regional context

the impact of the north atlantic ocean on the younger dryas climate in northwestern and central europe the main results of multiproxy climate reconstructions for the younger dryas and experiments carried out with an atmospheric general circulation model are discussed quantitative temperature inferences for northwestern and central europe show that winter conditions were remarkably extreme with values of 20 30 c below that of today annual temperature ranges with a continental signature 30 34 c were reconstructed for the entire study area compared with today the greatest cooling was experienced in the seaboard area the comparison of the climate reconstructions and simulation experiments indicates that sea ice in the north atlantic ocean played a decisive role in the climate of the study area by cooling the surface air temperatures and by controlling the position of the storm track surface air circulation was westerly even during younger dryas winters a slight northward shift of the mean atlantic sea ice margin during winter may explain the proposed subdivision of the younger drays into a phase of maximum cold and humidity succeeded by a less cold and relatively dry phase 1998 john wiley sons ltd

timing of glaciation during the last glacial cycle evaluating the concept of a global last glacial maximum lgm abstract it has long been known that mountain glaciers and continental ice sheets around the globe reached their respective maximum extent at different times during the last glacial cycle often well before the global last glacial maximum lgm c 23 19 ka which is formally defined by peaks in global sea level and marine oxygen isotope records however there is increasing evidence from around the world that it was not only mountain glaciers which were asynchronous with the global lgm but also some regions of the large continental glaciers the barents kara ice sheet in northern eurasia together with a majority of ice masses throughout asia and australasia reached their maximum early in the last glacial cycle a few thousand years before the global lgm period the east antarctic ice sheet also reached its maximum extent several millennia before the global lgm in numerous mountainous regions at high mid and low latitudes across the world glaciers reached their maximum extent before marine isotope stage mis 2 in mis 5 4 and 3 this is in contrast to most sectors of the laurentide ice sheet the cordilleran ice sheet the se sector of the fennoscandinavian ice sheet and the alpine ice sheet in central europe which appear to have reached their maximum close to the global lgm in mis 2 the diachronous maximum extents of both mountain glaciers and continental ice sheets during the last glacial cycle means that the term and acronym last glacial maximum lgm has limited chronostratigraphical meaning when correlating glacial deposits and landforms

the influence of alpine glaciation on the relief of tectonically active mountain belts a surface processes model incorporating large scale fluvial processes local hill slope processes and glacial erosion is used to investigate the effect of glaciation on the relief of a fast growing narrow orogen the results of several simulations show that glaciers concentrate erosion near peaks fluvial erosion is reduced downstream of glaciers glaciers with frozen bases can lead to an increase in relief and the net affect of glaciation in the absence of widespread basal freezing is to reduce relief

abrupt onset and termination of the african humid period rapid climate responses to gradual insolation forcing a detailed ca 100 yr resolution and well dated 18 ams 14 c dates to 23 cal ka bp record of latest pleistocene holocene variations in terrigenous eolian sediment deposition at odp site 658c off cap blanc mauritania documents very abrupt large scale changes in subtropical north african climate the terrigenous record exhibits a well defined period of low influx between 14 8 and 5 5 cal ka bp associated with the african humid period when the sahara was nearly completely vegetated and supported numerous perennial lakes an arid interval corresponding to the younger dryas chronozone punctuates this humid period the african humid period has been attributed to a strengthening of the african monsoon due to gradual orbital increases in summer season insolation however the onset and termination of this humid period were very abrupt occurring within decades to centuries both transitions occurred when summer season insolation crossed a nearly identical threshold value which was 4 2 greater than present these abrupt climate responses to gradual insolation forcing require strongly non linear feedback processes and current coupled climate model studies invoke vegetation and ocean temperature feedbacks as candidate mechanisms for the non linear climate sensitivity the african monsoon climate system is thus a low latitude corollary to the bi stable behavior of high latitude deep ocean thermohaline circulation which is similarly capable of rapid and large amplitude climate transitions

temperature and precipitation climate at the equilibrium line altitude of glaciers expressed by the degree day factor for melting snow several authors relate accumulation or precipitation at the glacier equilibrium line altitude ela to summer mean temperature using exponential or power law functions i analyze the accumulation temperature relation at the ela with a degree day model using data from the 1992 paper by a ohmura and others the dataset includes estimates at the ela of winter balance and of winter balance plus summer precipitation which represent respectively low and high estimates of annual accumulation which is seldom measured the ohmura dataset only lists summer mean temperature but i recover monthly temperatures for the whole year for 66 of the glaciers by assuming sinusoidal temperature variation through the year and using annual temperature range from a gridded climatology monthly degree day sums are then estimated from monthly mean temperature and summed to give annual totals so degree day factors for melting snow at the ela are obtained the degree day factors fall close to those reported in the literature for glacier snowmelt with averages of 3 5 1 4 and 4 6 1 4 mm d 1 k 1 for low and high accumulation estimates on the 66 glaciers the degree day model gives a family of accumulation temperature curves that depend upon the annual temperature range representing the contrast between maritime and continental climates

controls on modern tributary junction alluvial fan occurrence and morphology high atlas mountains morocco abstract modern tributary junction alluvial fans cone shaped depositional landforms formed in confined valley settings were analysed from a 20 km long reach of the dades river in the distal part of the fold thrust belt region in the south central high atlas mountains of morocco here a deeply dissected network of ephemeral tributary streams and a perennial trunk drainage characterised by an arid mountain desert climate are configured onto a folded and thrust faulted mesozoic sedimentary sequence out of 186 tributary streams only 29 16 generated alluvial fans at their tributary junctions the fan generating catchments possess higher relief longer lengths lower gradients and larger areas than nonfan generating catchments whilst geologically fan generating catchments are underlain by folded steeply dipping weak bedrock conducive to high sediment yield tributary junction fans are built from debris flow or fluvial processes into open or confined canyon trunk valley settings the proximity of the perennial trunk drainage combined with the valley morphology produces lobate or foreshortened trimmed fan forms analysis of fan area gradient process catchment area relief length gradient and tributary valley width variables reveals weak morphometric relationships highlighted by residual plots that show dominance of smaller and lower gradient than expected fan forms these morphometric relationships can be explained by interplay between the catchment and trunk drainage geology morphology climate and flood regime that are combined into a conceptual build and reset model ephemeral tributary junction fans develop progressively during annual localised winter spring storm events attempting to build towards a morphological equilibrium however the fans never reach an equilibrium morphological form as they are reset by rare 10 year large floods along the river dades that are linked to regional incursions of atlantic low pressure troughs the model highlights the spatial and temporal variability of tributary junction fan building and illustrates the connectivity coupling importance of such features in dryland mountainous terrains

longitudinal to transverse drainage network evolution in the high atlas morocco the role of tectonics the high atlas of morocco is a still active linear intracontinental mountain chain in the nw african plate which results from weak crustal thickening associated with rift inversion during the cenozoic and from uplift related to mantle thermal doming a striking morphological feature of the high atlas is the occurrence of both transverse and longitudinal i e strike parallel drainage characterized by deep fluvial incision of more than 1000 m in low relief topography of the axial zone of the chain most of the transverse component of the drainage appears to postdate the longitudinal component as indicated by recent or incipient captures and wind gaps the longitudinal drainage is inherited from an early stage of fluvial organization controlled by the tectonic structures developed during upper crustal folding and thrusting in the post paleozoic cover amplification of n s regional slope in the western high atlas by continued crustal shortening and thickening triggered i higher erosion rates in transverse than in longitudinal catchments and ii captures of longitudinal streams by transverse ones creating a new organization of the drainage system toward the regional slope such evolution from a longitudinal to a transverse dominated drainage may represent a common mechanism of fluvial network development in mountain belts where the amplification of the regional slope results from long lived lithospheric convergence

transpressional tectonics in the marrakech high atlas insight by the geomorphic evolution of drainage basins the ouzzelarh massif extends across the marrakech high atlas mha and forms the highest elevated mountain belt to better understand the evolution of collision related topography we present the results of a geomorphological study in which elevation changes generated by reactivated pre alpine variscan and triassic jurassic faults drive a landscape evolution model we aim to evaluate the relationship between the geometry of the drainage network and the main fault systems in this region new insight into geomorphological changes in drainage patterns and related landforms is based on geological fieldwork combined with dem analysis to quantitatively measure landscape features we used several classical geomorphic indices spacing ratio hypsometric curves and integral stream frequency drainage stream length gradient the ouzzelarh massif is bounded to the north by the tizi n test fault zone ttfz and to the south by the sour fault zone sfz these faults delimit a pop up structure by using the above geomorphic parameters we ascertained that the ouzzelarh massif is affected by a high spatial variability of uplift the actual landscape of the ouzzelarh massif reveals remnants of an uplifted ancient erosional surface and the heterogeneity of exposed rocks in the range explaining the possibility that the topographic asymmetry between north and south flanks is due to differences in lithology controlled resistance to erosion drainage topography and fault pattern all concur to show uplifted rhomboidal shaped blocks it exhibits high stream frequency drainage and uplift in separate tectonically uplifted blocks such as jebel toubkal which is characterized by asymmetric drainage basins

glaciological conditions in seven contrasting regions estimated with the degree day model we apply the degree day model to seven glacial regions that offer contrasting conditions and are well documented in the world glacier inventory the regions are axel heiberg island in arctic canada svalbard northern scandinavia southern norway the alps the caucasus and new zealand we estimate the average equilibrium line altitude ela for each half degree latitude longitude grid square from the median elevations of glaciers within the square and we extrapolate temperature from the uea cru climate research unit of the university of east anglia gridded climatology using the degree day model we calculate annual accumulation at the ela equal to ablation at the ela and other quantities like summer mean temperature length of melt season balance gradients and the sensitivity of mass balance to temperature and or precipitation changes glaciers can be characterized on a scale from cold dry axel heiberg island to warm wet new zealand corresponding to the contrast between maritime and continental climates mass balance sensitivities to temperature and or precipitation changes are relatively small for dry cold climate and relatively high for warm wet climate we could extend the approach to other glacier regions but we note that there are large areas for which ela data are not available as they are still not covered by the world glacier inventory

pleistocene plateau ice fields in the high atlas morocco large ice fields 25 km2 formed over the tazaghart and iouzagner plateaux of the high atlas morocco during the late pleistocene the plateau ice fields were drained by large valley glaciers forming a series of moraine assemblages four moraine units have been mapped and subdivided on the basis of morphostratigraphy and the degree of soil weathering soil profile development index pdi values indicate that the moraine units are widely separated in time with the oldest moraines deeply weathered and degraded whereas soils are absent on the youngest moraines the highest moraine unit was formed by a small niche glacier which was present as recently as the mid 20th century pleistocene glaciers are likely to have been associated with wetter conditions than today in addition to colder air temperatures combined with ice in neighbouring areas such as the toubkal massif the sw high atlas supported some of the largest glaciers in africa during the pleistocene the extent of glaciation with ice exploiting and breaching drainage divides has major implications for landscape development the evolution of the high atlas is therefore strongly shaped by glaciation and this is closely intertwined with tectonic fluvial and slope processes

the nicola group late triassic and early jurassic subduction related volcanism in british columbia mafic lavas of the nicola group are divided into three distinct petrographic and geochemical types type 1 lavas are strongly augite porphyritic picrites basalts and andesites that belong to a high potassium to shoshonitic rock series type 2 lavas are augite and plagioclase porphyritic basalts and andesites that belong to a low potassium calc alkaline series and type 3 lavas are petrographically variable tholeiitic to transitional basalts and andesites low concentrations of ti zr y and nb and moderate to high concentrations of k rb ba and sr in type 1 and 2 lavas clearly indicate a subduction related tectonic setting of eruption type 3 lavas show chemical affinities intermediate between modern day island arc and intraplate volcanics type 1 shoshonitic lavas generally lie east of and are younger than type 2 calc alkaline lavas a relationship that implies an east dipping early mesozoic subduction zone beneath the nicola arc these interpretations resolve previous uncertainties regarding th

active and passive tectonic controls for transverse drainage and river gorge development in a collisional mountain belt dades gorges high atlas mountains morocco abstract transverse drainages are discordant river patterns whose flow directions cut across geological structures such as faults folds and the regional tectonic fabric strike of mountain belts such drainages can form spectacular geomorphological features with reaches often occupying narrow and deeply dissected canyons gorges that cut through prominent topographic barriers within collisional plate margins e g foreland basin systems studies have frequently examined transverse drainage development in response to active tectonics e g thrusting here transverse drainage will develop via incision or become deflected and fixed in response to oblique fault fold growth structures particularly within wedge top thrust front and foredeep basin settings within this paper the development of transverse drainage within the little studied fold thrust component of an orogen is examined using a spectacular series of river gorges along the river dades from the high atlas mountains of morocco integrated field derived geological and geomorphological data are used to explore the interplay between active tectonics lithology and structural configuration passive tectonics of bedrock for the creation of transverse drainage and associated river gorge reaches at the southern edge of the high atlas fold thrust belt the river dades passes through the deeply dissected tarhia n dades and main dades gorges before emerging into the ait seddratt wedge top basin fluvial incision is principally controlled by plio quaternary uplift of the high atlas mountains the larger main dades gorge has formed a deeply dissected antecedent course via drainage inheritance into structurally thickened jurassic bedrock via uplift between two key structural components of the foreland basin system the fold thrust belt and the wedge top basin the smaller tarhia n dades gorge involves a more complex interplay between active tectonics and the passive structural arrangement of an asymmetric plunging syncline combined with the stratigraphic arrangement and strength of the jurassic bedrock the drainage network is configured to the fold and associated fault joint structures to form respective nw se and ne sw orientated dip slope and strike drainage progressive incision by tributary dip slope streams cutting down through resistant limestone bedrock into underlying weaker mudstone bedrock has resulted in accelerated headward erosion and drainage network expansion by river captures this has resulted in a minor re routing of the river dades as a transverse drainage through a former dip slope tributary stream to form the tarhia n dades gorge

preliminary results of mass balance observations of yala glacier and analysis of temperature and precipitation gradients in langtang valley nepal monitoring the glacier mass balance of summer accumulation type himalayan glaciers is critical to not only assess the impact of climate change on the volume of such glaciers but also predict the downstream water availability and the global sea level change in future to better understand the change in meteorological parameters related to glacier mass balance and runoff in a glacierized basin and to assess the highly heterogeneous glacier responses to climate change in the nepal himalaya and nearby ranges the cryosphere monitoring project cmp carries out meteorological observations in langtang valley and mass balance measurements on yala glacier a debris free glacier in the same valley a negative annual mass balance of 0 89 m w e and the rising equilibrium line altitude of yala glacier indicate a continuation of a secular trend toward more negative mass balances lower temperature lapse rate during the monsoon the effect of convective precipitation associated with mesoscale thermal circulation in the local precipitation and the occurrence of distinct diurnal cycles of temperature and precipitation at different stations in the valley are other conclusions of this comprehensive scientific study initiated by cmp which aims to yield multi year glaciological hydrological and meteorological observations in the glacierized langtang river basin

relative size of fluvial and glaciated valleys in central idaho quantitative comparisons of the morphometry of glaciated and fluvial valleys in central idaho were used to investigate the differences in valley relief and width in otherwise similar geologic and geomorphic settings the local relief width and cross sectional area of valleys were measured using gis software to extract information from usgs digital elevation models hillslope gradients were also measured using gis software power law relationships for local valley relief width and cross sectional area as a function of drainage area were developed local valley relief in glaciated valleys relates to drainage area with a power law exponent similar to fluvial valleys but glaciated valleys are deeper for a given drainage area local valley width in glaciated valleys is greater than in fluvial valleys but the exponent of the power law relationship to drainage area is similar in both valley types local valley cross sectional area in glaciated valleys increases with drainage area with a power law exponent similar to fluvial valleys however glacial valleys have roughly 80 greater cross sectional area steep valley walls in glaciated basins increase the potential for bedrock landsliding relative to fluvial basins both the olympic mountains of washington and valleys in central idaho show relationships in which glaciated valleys are up to 30 deeper than fluvial valleys despite differences in lithology tectonic setting and climate

glacial trimlines to identify former ice margins and subglacial thermal boundaries a review and classification scheme for trimline expression abstract reconstructions of former ice sheets and glaciers provide important palaeoglaciological information about their behaviour in response to climate changes glacial trimlines record both the margin positions and palaeo ice thickness enabling the production of empirically constrained 3 dimensional reconstructions however the literature review into the characteristics interpretation and use of glacial trimlines here presented shows that these features have been under utilised and are poorly described in the existing literature with a confusing terminology currently in use a new classification scheme and terminology for trimline identification and interpretation is developed to better facilitate further research into these common features of glacierised and formerly glaciated landscapes

glacial activity and catchment dynamics in northwest greece long term river behaviour and the slackwater sediment record for the last glacial to interglacial transition woodward j c hamlin r h b macklin m g hughes p d lewin j 2008 glacial activity and catchment dynamics in northwest greece long term river behaviour and the slackwater sediment record for the last glacial to interglacial transition geomorphology 101 1 2 44 67 sponsorship uk science and engineering research council woodward the school of geography at the university of leeds hamlin and the university of cambridge hughes the uk natural environment research council gr9 2916 and ip 754 0302 funded the bulk of the analyses reported here specialissue sp iss si

defining modern day area altitude balance ratios aabrs and their use in glacier climate reconstructions abstract with the increasing use of digital elevation models in palaeo glacier reconstructions and the availability of freeware spreadsheets the area altitude balance ratio aabr and balance ratio br methods are becoming increasingly used in palaeo glacier reconstruction for estimating equilibrium line altitudes ela and subsequently deriving quantitative estimates of palaeo climate while there are many data detailing contemporary accumulation area ratios there are still only a few studies that have established from contemporary environments aabr br ratios publicly available glacier mass balance world glacier monitoring service us geological survey and norwegian water directorate and spatial extent datasets provided the basis for this research from a time series of mass balance regressing specific net balance against ela allows the zero net balance ela to be identified once the zero balance ela is established the glacier hypsometry above and below the ela is defined the aabr br is calculated by using the right hand side the following aabr b n a b b n a c z a c a a c z a b a a b where b nab and b nac are the net mass balance gradients in the ablation and accumulation zones respectively z a c and z a b are the area weighted mean altitudes of the accumulation and ablation areas respectively and a ac and a ab are the areas of the accumulation and ablation areas respectively aabrs are calculated for a suite of glaciers located across a range of climatic zones and glacier types with antarctica being excluded the following representative aabrs are found a global aabr 1 75 0 71 mid latitude maritime 1 9 0 81 high latitude 2 24 0 85 north america west coast 2 09 0 93 north america eastern rockies 1 11 0 1 canadian arctic 2 91 0 35 svalbard 2 13 0 52 western norway 1 5 0 4 european alps 1 59 0 6 central asia 1 75 0 56 kamchatka 3 18 0 16 this study provides an empirically derived dataset characterising aabr ratios which may be used for ela estimation in palaeo glacier reconstructions and for palaeo climate quantification

age and significance of the quaternary cemented deposits of the duje valley picos de europa northern spain abstract cemented calcareous breccias appear in the picos de europa cantabrian mountains spain resting on glacially abraded surfaces and covered by moraines u th dating of the calcite coating the clasts was successful in two samples the oldest one indicating that the breccias accumulated during or prior to marine isotope stage mis 11 and the youngest indicating later cementation during mis 8 the former introduces a limit for the age of the glaciation preceding the breccias which cannot correspond to an event younger than mis 12 this is the oldest absolute age so far obtained for intercalated glacial interglacial deposits of the iberian peninsula

little ice age glaciers in the balkans low altitude glaciation enabled by cooler temperatures and local topoclimatic controls moraine ridges are present in the highest cirques of the durmitor massif in montenegro and post date the widespread pleistocene moraines of this area lichenometry suggests that at least eight glaciers were present in the 19th century and correlate with the culmination of the little ice age in the european alps cooler temperatures combined with local topoclimatic controls including windblown and avalanching snow as well as shading were crucial for the formation and survival of these glaciers below the regional equilibrium line altitude the resultant regional equilibrium line altitude ela was positioned close to the highest peaks between 2400 and 2500 m with local controls such as avalanche windblown snow and shading depressing the ela in the northern cirques to 2130 2210 m this ela position was very low for this latitude and lower than for most glaciers in the european alps at any time during the holocene and even equivalent to many alpine glaciers during the younger dryas today one glacier still survives in montenegro in a deep northeast facing cirque characterized by the largest combined areas of potential avalanche and windblown snow copyright 2009 john wiley sons ltd

middle and late pleistocene glaciations in the campo felice basin central apennines italy the present paper refers to research conducted in the tectonic karst depression of campo felice in the central apennines italy in which glacial alluvial and lacustrine sediments have been preserved stratigraphic interpretations of sediments underlying the campo felice plain are based on evidence obtained from nine continuous core boreholes the boreholes reach a depth of 120 m and provide evidence of five sedimentation cycles separated by erosion surfaces each cycle is interpreted as an initial response to a mainly warm stage characterized by low energy alluvial and colluvial deposition pedogenesis and limited episodes of marsh formation in turn a mainly cold stage follows during which a lake formed and glaciers developed and expanded leading to deposition of glacial and fluvioglacial deposits the chronological framework is established by eleven accelerator mass spectrometer 14c ages and three 39ar 40ar ages on leucites from interbedded tephra layers these age determinations indicate five glacial advances that respectively occurred during marine oxygen isotope stages 2 3 4 6 10 and 14

estimating equilibrium line altitude ela from glacier inventory data a glacier s most fundamental altitude is the equilibrium line altitude ela because it divides the glacier into ablation and accumulation areas the best parameterization of the ela for glacier inventory is the balanced budget ela we discuss direct estimation of balanced budget ela from mass balance data for individual glaciers and indirect estimation of balanced budget ela from simple topographic parameters available from the world glacier inventory wgi i e the area median and maximum and minimum altitudes mass balance and ela for individual glaciers are usually strongly correlated and we calculate balanced budget ela from the regression equation linking the two we then compare balanced budget ela with area median and mid range altitudes for the 94 glaciers for which we have all the necessary data the different ela estimates agree well enough 82 to 125 m to describe geographical variations in ela and for application of glacier climate models to glacier inventory data mid range and area median altitudes are already available for tens of thousands of glaciers in the current wgi and should be evaluated in future inventories

catastrophic rock avalanches in a glaciated valley of the high atlas morocco 10be exposure ages reveal a 4 5 ka seismic event surface modification processes leading to large debris accumulations in high relief mountain areas are important for understanding landscape evolution especially in some of earth s most active orogens the arroumd rock avalanche at the foot of the nw face of mount aksoual 3912 m above sea level masl in the jebel toubkal area of the high atlas morocco represents one of the largest mass movement landforms in north africa the age and origin of this extensive feature have been contested for over a century late pleistocene moraines are also present in the same valley adjacent to the avalanche debris the mean of six 10 be cosmogenic exposure ages shows that a series of catastrophic rock slope failures occurred at 4 5 0 5 ka while a set of eight exposure ages from two of the three mapped moraines has a far larger spread from 1 5 to 7 5 ka this suggests that the avalanche events were effective agents in modifying the true surface exposure age of the pleistocene moraines in the arroumd valley this has resulted in similar mean 10 be apparent exposure ages for the preexisting late pleistocene moraine surfaces and holocene catastrophic rock slope failures similar rock avalanche deposits are present in other glaciated valleys in the high atlas we conclude that the trigger for collapse was seismic activity related to proximity of the major tizi n test fault these findings have important implications for interpreting and dating glacial landforms in tectonically active settings

numerical simulation of selforganized stone stripes geometrically regular stripes of stones are found on many unvegetated alpine and polar hillslopes known as sorted stripes because of the characteristic textural sorting between surface stones and fine grained soil they contrast markedly with the lack of order typical of natural landscapes the spacing of the stripes can range from centimetres to metres about 10 20 times the average stone diameter1 2 with individual stripes extending down slope for many tens of metres fig 1 a variety of formative mechanisms have been proposed3 but it is still unclear how such orderly stripes can arise spontaneously and what dictates the spacing here we present two dimensional computer simulations in which the displacement of surface stones is governed by the preferential growth of needle ice in stone free regions of soil during each freezing cycle regular patterns of stones and soil that closely resemble natural stripes are found to emerge spontaneously from the model as a result of identifiable feedbacks between soil texture ice growth and local slope

medial moraines of the haut glacier d arolla valais switzerland debris supply and implications for moraine formation the haut glacier d arolla displays three medial moraines an ablation dominant moraine east of the glacier centre line an ice stream interaction moraine west of the glacier centre line and a medial lateral supraglacial moraine complex along the western margin of the glacier the eastern moraine is formed by the emergence of coarse angular clasts from a series of short longitudinal debris bands 1 km from the glacier terminus this debris is derived from rock falls at the glacier head wall and follows a low level transport path through the glacier the western moraine is formed partly by the direct fall of weathered debris on to the ice surface at a point 2 6 km from the snout but it receives further increments of sediment from extensive longitudinal englacial debris bands developed from the convergence of two ice streams with lateral englacial debris septa the medial lateral moraine complex is formed largely by rock falls from the western valley wall but is also nourished by a debris layer developed at the base of the small tributary glacier de la mitre this layer crops out at the eastern margin of the re sultant inset ice stream and releases more rounded abraded and comminuted rock fragments to supplement the surface debris cover of supraglacial origin

permafrost conditions in the mediterranean region since the last glaciation the relatively warm climate conditions prevailing today in the mediterranean region limit cold geomorphological processes only to the highest mountain environments however climate variability during the late pleistocene and holocene has led to significant spatio temporal variations of the glacial and periglacial domain in these mountains including permafrost conditions here we examine the distribution and evolution of permafrost in the mediterranean region considering five time periods last glaciation deglaciation holocene little ice age lia and present day the distribution of inactive permafrost derived features as well as sedimentary records indicates that the elevation limit of permafrost during the last glaciation was between 1000 m and even 2000 m lower than present permafrost was also widespread in non glaciated slopes above the snowline forming rock glaciers and block streams as well as meter sized stone circles in relatively flat summit areas as in most of the northern hemisphere the onset of deglaciation in the mediterranean region started around 19 20 ka the ice free terrain left by retreating glaciers was subject to paraglacial activity and intense periglacial processes under permafrost conditions many rock glaciers protalus lobes and block streams formed in these recently deglaciated environments though most of them became gradually inactive as temperatures kept rising especially those at lower altitudes following the younger dryas glacial advance the early holocene saw the last massive deglaciation in mediterranean mountains accompanied by a progressive shift of permafrost conditions to higher elevations it is unlikely that air temperatures recorded in mediterranean mountains during the holocene favoured the existence of widespread permafrost regimes with the only exception of the highest massifs exceeding 2500 3000 m lia colder climate promoted a minor glacial advance and the spatial expansion of permafrost with the development of new protalus lobes and rock glaciers in the highest massifs finally post lia warming has led to glacial retreat disappearance enhanced paraglacial activity shift of periglacial processes to higher elevations degradation of alpine permafrost along with geoecological changes

glaciokarst landforms and processes of the southern dinaric alps glaciokarst is a landscape which combines karst features and hydrology as well as inherited glacial features it is a result of glaciation upon a karst geomorphological system the relationship between glaciers and karst is rather poorly known and inadequately recognized this research focuses on three distinct karst areas along the adriatic coast in the southern dinaric alps that were affected by the quaternary glaciations an insight into specific glaciokarst processes and surface features was provided through the study of the areas of the lovcen orjen and vele mountains a glaciokarst geomorphology is in general well preserved due to the prevailing vertically oriented chemical denudation following de glaciation and almost the entire absence of other surface processes typical glacial erosional features are combined by a variety of depressions which are the result of a karstic drainage of sub glacial waters the majority of glacial deposits occur as extensive lateral terminal moraine complexes which are often dissected by smaller breach lobe moraines on the external side of the ridge those moraine complexes are likely to be a product of several glacial events which is supported by complex depositional structures according to the type of glacial depositional features the glaciers in the study areas were likely to have characteristics of moraine dammed glaciers due to vertical drainage ice marginal fluvial processes were unable to evacuate sediment fluvial transport between glacial and pro glacial systems in karst areas is inefficient nevertheless some sediment from the glacier margin is washed away by the pro glacial streams filling the karst depressions and forming piedmont type poljes copyright 2015 john wiley sons ltd

debris entrainment and transfer in polythermal valley glaciers hambrey mj bennett mr dowdeswell ja et al 1999 debris entrainment and transfer in polythermal valley glaciers journal of glaciology 45 149 69 86 published 1999

a stratigraphical basis for the last glacial maximum lgm abstract the last glacial maximum lgm is widely used to refer to the episode when global ice volume last reached its maximum and associated sea levels were at their lowest however the boundaries of the interval are ill defined and the term and acronym have no formal stratigraphical basis this is despite a previous proposal to define it as a chronozone in the marine records on the basis of oxygen isotopes and sea levels spanning the interval 23 19 or 24 18 ka and centred on 21 ka in terrestrial records the lgm is poorly represented since many sequences show a diachronous response to global climate changes during the last glacial cycle for example glaciers and ice sheets reached their maximum extents at widely differing times in different places in fact most terrestrial records display spatial variation in response to global climate fluctuations and changes recorded on land are often diachronous asynchronous or both leading to difficulties in global correlation however variations in the global hydrological system during glacial cycles are recorded by atmospheric dust flux and this provides a signal of terrestrial changes whilst regional dust accumulation is recorded in loess deposits global dust flux is best recorded in high resolution polar ice core records providing an opportunity to define the lgm on land and establish a clear stratigraphical basis for its definition on this basis one option is to define the global lgm as an event between the top end of greenland interstadial 3 and the base onset of greenland interstadial 2 spanning the interval 27 540 23 340 ka greenland stadial 3 this corresponds closely to the peak dust concentration in both the greenland and antarctic ice cores and to records of the global sea level minima this suggests that this definition includes not just the coldest and driest part of the last glacial cycle but also the peak in global ice volume the later part of the lgm event is marked by heinrich event 2 which reflects the onset of the collapse of the laurentide at c 24 ka together with other ice sheets in the north atlantic region a longer and later span for the lgm may be desirable although defining this in chronostratigraphical terms is problematic whichever formal definition is chosen this requires the contribution of the wider quaternary community

middle pleistocene cold stage climates in the mediterranean new evidence from the glacial record abstract a major reduction in summer temperatures during a middle pleistocene glacial cycle caused the most extensive glaciation recorded in the mediterranean region glaciers in the mountains of greece formed during marine isotope stage mis 12 474 000 427 000 years bp under climatic conditions characterised by mean summer temperatures at least 11 c cooler than today and annual precipitation of 2300 mm at the equilibrium line altitude 1741 m a s l this represents the coldest mean summer temperatures recorded in greece during at least the last 430 000 years later pleistocene glaciations mis 6 and 5d 2 were characterised by warmer summer temperatures and higher annual precipitation

the late quaternary glaciation of africa a regional synthesis abstract there are numerous mountain ranges in africa which carry evidence of quaternary glaciation though few have glaciers now and these are rapidly disappearing the best studied sites are in east africa and ethiopia in east africa the three highest mountains kilimanjaro kenya and the rwenzori each have evidence of 3 5 major glaciations dating back to an estimated 400 000 bp one of which is dated to the last glacial maximum lgm by radiocarbon or cosmogenic radionucleide crn methods two other mountains have similar large moraine systems inferred to date to the lgm in ethiopia three mountains have clear evidence of glaciation and on two of them radiocarbon dates give minimum ages which suggest that these are lgm features in north africa the atlas and other groups of mountains have evidence of glaciation but in the absence of any dating it is unclear whether these sites were glaciated at the lgm although geomorphic features resembling moraines and protalus ramparts have been described from the drakensberg mountains south africa it is still unclear whether these features indicate glaciation and can be attributed to the lgm thus although circumstances for fieldwork on african mountains are very difficult in many cases investigations for more than a century provide an extensive picture of quaternary glaciation in some cases there has been an increasingly detailed mapping of field evidence and the first crn dates were carried out recently thus improving the global picture considerably particularly in east africa and ethiopia there is sufficiently reliable field information to make useful estimates of equilibrium line altitude changes at the provisionally identified lgm but this age needs confirmation by further crn dating by making some hypothetical assumptions inferences can be drawn that indicate a temperature lowering of 5 6 c during the lgm elsewhere in africa further field surveys are required

timing of pleistocene glaciations in the high atlas morocco new 10be and 36cl exposure ages abstract this paper presents data from 42 new samples yielding late pleistocene cosmogenic 10be and 36cl exposure ages of moraine boulders across a series of glaciated valleys in the toubkal massif 4167 m a s l high atlas morocco this represents the first comprehensive pleistocene glacial chronology in north africa and one of the largest datasets from the mediterranean region the timing of these glacier advances has major implications for understanding the influence of atlantic depressions on moisture supply to north africa and the mediterranean basin during the pleistocene the oldest and lowest moraines which span elevations from 1900 to 2400 m a s l indicate that the maximum glacier advance occurred from mis 5 to 3 with a combined mean 10be and 36cl age of 50 2 19 5 ka 1 sd n 12 7 outliers the next moraine units up valley at higher elevations 2200 2600 m a s l yielded exposure ages close to the global last glacial maximum lgm with a combined mean 10be and 36cl age of 22 0 4 9 ka 1 sd n 9 7 outliers the youngest exposure ages are from moraines that were emplaced during the younger dryas with a combined mean 10be and 36cl age of 12 3 0 9 ka 1 sd n 7 no outliers and are found in cirques at the highest elevations ranging from 2900 to 3300 m a s l from moraines predating the younger dryas a large number of young outliers are spread evenly between 6 and 13 ka suggesting a continuing process of exhumation or repositioning of boulders during the early to mid holocene this attests to active seismic processes and possibly intense erosion during this period

combined numerical and geomorphological reconstruction of the serra da estrela plateau icefield portugal abstract the paper focuses on reconstructing a plateau icefield surface from field geomorphological data and a physical based glacier model the results allow the analysis of the patterns of glacial erosion and the estimation of the palaeo equilibrium line altitudes ela the study area is the serra da estrela a plateau in central portugal rising to 2000 m asl the glaciated area during the last maximum of the serra da estrela glaciation lmgse was 66 km 2 the reconstruction of the topography of the icefield and valley glaciers in the lmgse is based on the schilling and hollin model it iterates along the valley longitudinal profile and is based on the gradient on valley shape indices and on yield basal shear stresses these variables influence ice thickness and therefore also the slope of the ice surface allowing for its reconstruction the key variable is basal yield shear stress and its value was included in the model manually starting from the points of maximum extent of the valley glaciers and following a range known to occur in contemporary conditions the input values are validated by matching the resulting ice surface to geomorphological features where these are absent a constant value of 100 kpa was used the icefield was reconstructed from a radiating set of long sections along which ice thicknesses were calculated a dem of the ice surface was constructed allowing the estimation of the hypsometric curves of the distinct glacier catchments and the calculation of the palaeo elas the results show a regional ela at 1650 m asl with spatial variations across the icefield reflecting mainly the effect of eastward snow drift the lmgse glaciers were very sensitive to minor climatic changes especially due to the large area of the plateau icefield and to the positioning of the elas close to or in the flat part of the hypsometric curve the model of the ice surface is of significant value for the analysis of the patterns of glacial erosion at the landscape level in the serra da estrela most of the glacial erosion occurred near the plateau margins and in valley heads where glacier surface slope was steeper allowing for a faster ice flow and where ice flow concentrated strong glacier erosion in the zezere valley is linked to the tectonic setting but also to the confluence of glaciers and to the overfeeding of snow from the plateau

glaciers and rivers pleistocene uncoupling in a mediterranean mountain karst abstract large scale coupling between headwater catchments and downstream depocentres is a critical influence on long term fluvial system behaviour and on the creation of the fluvial sedimentary record however it is often difficult to examine this control over multiple quaternary glacial cycles and it has not been fully explored in karst basins by investigating the pleistocene glacial and fluvial records on and around mount orjen 1894 m in montenegro we show how the changing connectivity between glaciated mountain headwater source zones and downstream alluvial basins is a key feature of long term karst system behaviour especially in relation to the creation and preservation of the surface sedimentary record middle and late pleistocene glacial deposits are well preserved on mount orjen uranium series dating of 27 carbonate cements in fluvial sediments shows that many alluvial depocentres were completely filled with coarse glacial outwash before 350 ka during the largest recorded glaciation this major glaciation is correlated with the skamnellian stage in greece and marine isotope stage 12 mis 12 c 480 420 ka this was a period of profound landscape change in many glaciated catchments on the balkan peninsula later glaciations were much less extensive and sediment supply to fluvial systems was much diminished the extreme base level falls of the late miocene produced the world s deepest karst networks around the mediterranean after mis 12 the subterranean karst of mount orjen formed the dominant pathway for meltwater and sediment transfer so that the depositional basins below 1000 m became disconnected uncoupled from the glaciated headwaters there is little evidence of post mis 12 aggradation or incision in these basins this absence of later pleistocene and holocene fluvial activity means these basins contain some of the thickest and best preserved outwash deposits in the mediterranean

quaternary evolution of the marrakech high atlas and morphotectonic evidence of activity along the tizi n test fault morocco here we consider the ourika and rheraia drainage basins on the tizi ntest fault zone in the mountains of the marrakech high atlas western morocco with regard to late pleistocene tectonic activity new insights into geomorphological changes in drainage patterns and related landforms are based on geological fieldwork in conjunction with dem analysis lithological and structural data combined with certain geomorphometric indices provide clues to the ongoing uplift of quarternary surfaces in this region five geomorphological indices are utilized 1 drainage network 2 shape of stream long profiles 3 hypsometric integral and curves 4 valley floor width valley height ratio vf index and 5 stream gradient index sl index we also considered the temporal evolution of alluvial deposit complexes with diverse lithofacies such as debris flows channel gravels rockslide debris avalanche stratified slope deposits terrace gravels and fan deposits in the ourika and rheraia valleys pleistocene talus deposits and fluvial sediments are offset by the tizi n test fault in the upper ourika and upper rheraia valleys such deformation of thick continental deposits strongly points to thrust reactivation along the tizi n test fault we define the chronology and overall aggradation phases or lateral incision phases showing how they are the consequences of variations in tectonic uplift and climate as a result we are better able to access recent morphotectonic evolution in part of the marrakech high atlas

equilibrium line altitudes and paleoenvironment in the merchants bay area baffin island n w t canada the fiordlands south of merchants bay contain an extensive well preserved moraine record of a late foxe advance of local valley glaciers this has allowed accurate reconstruction of former glacier margins and computation of former equilibrium line altitudes elas by a variety of methods statistical comparison of three methods maximum lateral moraine elevation median elevation and accumulation area ratio aar shows that different techniques can give different results for the same glaciers lateral moraines gave estimates that were too low probably due to post glacial erosion or to non deposition median elevations and the aar method produced statistically similar results but only for glaciers of simple geometry the median elevation method fails to take into account variations in valley morphology and glaciological parameters and so is not reliable in all situations the aar method is supported by empirical evidence and is the best of the three methods for estimating former elas analysis of trend surfaces of present and late foxe elas shows changes in elevation and orientation through time due to changing environmental factors present elas are strongly influenced by local factors southerly storm tracks and warm maritime conditions paleo elas do not show this influence suggesting that davis strait may have been ice covered during the late foxe stade and that storm tracks were from the north

the glacial history of the pindus mountains greece abstract geomorphological evidence for pleistocene glaciation has been mapped in the pindus mountains of northwest greece and the chronology of glaciation in this area has been established through soil profile analysis and u series dating of secondary carbonates calcite formed within glacial deposits three glacial stages are evident in the sedimentological and geomorphological records the earliest and most extensive recorded glaciation predates 350 000 yr b p and was characterized by extensive valley glaciers and ice fields a more recent glaciation occurred before the last interglacial and was characterized by glaciers that reached midvalley positions the last phase of glaciation in greece is recorded by small cirque glacier moraines and relict periglacial rock glaciers the glacial and periglacial sequence on mount tymphi has been used in conjunction with a reference parastratotype the long lacustrine sequence at ioannina to provide a chronostratigraphical framework for cold stage deposits in g

the geomorphological impact of loch lomond younger dryas stadial plateau icefields in the central lake district northwest england detailed geomorphological mapping has revealed evidence for the development of plateau icefields in the central fells of the english lake district during the loch lomond younger dryas stadial ca 12 9 11 5 ka the largest plateau icefield system which covered an area of approximately 55 km2 including outlet glaciers was centred on high raise to the west smaller plateau icefields developed on grey knotts brandreth and dale head covering areas of 7 km2 and 3 km2 respectively the geomorphological impact of these plateau icefields appears to have been minimal on the summits where the survival of blockfields and other frost weathered debris mostly peat covered implies the existence of at least patches of protective cold based ice ice moulded bedrock at some plateau edges however documents a transition to wet based erosive conditions prominent moraine systems were produced by outlet glaciers which descended into the surrounding valleys where their margins became sediment traps for supraglacial debris and inwash in some valleys ice marginal moraines record successive positions of outlet glaciers which actively back wasted towards their plateau source this interpretation differs from that of previous workers who assumed an alpine style of glaciation with reconstructed glaciers emanating from corries and valley heads it is likely that plateau icefields were more common at this time in upland britain than hitherto has been appreciated

simulation of an abrupt change in saharan vegetation in the mid holocene climate variability during the present inter glacial the holocene has been rather smooth in compar ison with the last glacial nevertheless there were some rather abrupt climate changes one of these changes the desertication of the saharan and arabian region some 4 6 thousand years ago was presumably quite important for human society it could have been the stimulus leading to the foundation of civilizations along the nile euphrat and tigris rivers here we argue that saharan and arabian de sertication was triggered by subtle variations in the earth s orbit which were strongly amplied by atmosphere vegeta tion feedbacks in the subtropics the timing of this tran sition however was mainly governed by a global interplay between atmosphere ocean sea ice and vegetation

geomorphology and style of plateau icefield deglaciation in fjord terrains the example of troms finnmark north norway in spite of a widespread distribution the way in which plateau icefields affect the glaciation and deglaciation of adjacent terrains is not particularly well known this paper aims to identify how the deglaciation of the fjord and plateau terrain of north norway has influenced the glacial geomorphology and relative sea level history of both local and adjacent areas and so serve as a model for interpreting similar areas along the continental margins of northwest europe and elsewhere the identification of moraines and their relationships with the main shoreline of northern norway allows the margins of the oksfjordjokelen svartfjelljokelen and langfjordjokelen plateau icefields to be identified in the adjacent terrains in locations where ice margins are uncertain it is also possible to reconstruct ice limits by means of glacier models appropriately constrained by known local conditions and dates earlier glacier margins characterised in north norway by ice shelves floating in the local inlets of major fjords also can be related to known regional shorelines the distribution of high shoreline fragments augmented by radiocarbon dates helps show the extent to which inter island channels and outermost parts of fjords can become deglaciated relatively early in comparison with published maps of regional deglaciation plateau icefield centred glaciation became important sometime after 14 000 14c yr bp and was characterised by glacier readvances up to and in some locations beyond earlier moraines and raised marine features although overlooked until recently the identification of the influence of plateau icefields on local glaciation and their interaction with local and regional marine limits is of great importance in accurate palaeoenvironmental reconstruction copyright 2002 john wiley sons ltd

preservation of landforms under ice sheets and ice caps abstract this article addresses the question of whether or not distinct glacial and non glacial landforms can survive beneath ice sheets and ice caps with little or no morphological alteration a review of recent work documents the existence of pre last stadial landforms and landscapes in areas covered by the fennoscandian and laurentide ice sheets a substantial number of independent works indicate that landforms such as eskers drainage channels and boulder fields have escaped destruction despite complete ice overriding during several tens of millenia full preservation of former ground surfaces or delicate landforms probably is linked to areas where the ice sheet base was continuously frozen to its bed larger robust landforms such as large drumlins appear to have been preserved even under wet based conditions in glaciated areas patches preserved under dry cold based conditions provide important windows towards the past showing landscapes that were destroyed in surrounding areas affected by wet based and eroding ice some consequences for the research fields of non glacial geomorphology archaeology and botany include the possibility of subglacial museums and refugia a time space model describes geomorphological access to information from older events in glaciated areas

anthropogenic trigger for late holocene soil erosion in the jebel toubkal high atlas morocco abstract the assif n imserdane valley located in the jebel toubkal area of the high atlas morocco is a highly dynamic geomorphological setting the valley was glaciated during the late pleistocene and subsequently experienced a catastrophic rock avalanche leading to the formation of one of the largest mass movement landforms in north africa recent research hughes et al gsa bulletin 126 1093 1104 has dated the formation of the rock avalanche to the mid holocene at 4 5 0 5 ka in this paper we examine the sedimentological organic matter content magnetic susceptibility particle size and xrf and palaeoecological pollen and spores non pollen palynomorphs npps microcharcoal and conifer tracheid fragments record of a small infilled basin located adjacent to a late pleistocene moraine and close to the rock avalanche in the arroumd sector the deposits primarily fine grained and minerogenic with a low concentration of organic microfossils including pollen coprophilous ascospores wood and charcoal microfragments are enriched in fine silts and ferrimagnetic minerals consistent with erosional sources from surrounding slope soils three radiocarbon dates from the deposit indicate that the infill event occurred during the first millennium ad after 430 640 ad as such the deposits point to a phase of slope instability and erosion that is not linked to either deglaciation processes or to the mid holocene rock avalanche instead the nature and timing suggest that an anthropogenic trigger of degradation to the natural vegetation cover may be implicated consistent with an increasing scale and intensity of pastoral activity in the southern high atlas during the early islamic period in morocco the record casts light on a previously undocumented phase of landscape instability in the dynamic setting of the assif n imserdane valley and highlights the potential for further exploration of small infilled basins in the high atlas to illuminate the geoecological history of the region

sediments and landforms at kviarjokull southeast iceland a reappraisal of the glaciated valley landsystem abstract eyles identified kviarjokull an outlet of the icecap oraefajokull southeast iceland as an exemplar of the glaciated valley landsystem emphasising rockfall debris supply passive transport and reworking of a thick cover of supraglacial morainic till in this paper we take a fresh look at the sediments and landforms of kviarjokull focusing on clast form analysis to reconstruct primary transport pathways new data demonstrate the importance of active transport of debris derived from the glacier bed substantial portions of the supraglacial debris cover can be traced back to englacial channel fill deposits or anomalously thick exposures of basal ice these two types of sediments also make up much of kviarjokull s large neoglacial moraine rampart we attribute the abundance of these non rockfall sediments to the presence of a terminal overdeepening and the switch from predominantly subglacial to predominantly englacial drainage that this induces this hydrological switch enhances retention of debris within ice transport preventing it from being washed away and making it available to feed ice marginal moraine formation the complexity of sediment transport processes observed at kviarjokull and the contrast between it and alpine glaciers undermines any single concept of the glaciated valley landsystem accordingly we propose kviarjokull as the type example of a distinct subclass defined by its moderate relief high debris turnover and drainage behaviour characteristic of an overdeepened basin

reconstructing the transport history of glacigenic sediments a new approach based on the co variance of clast form indices abstract two indices are used to describe the aggregate shape and roundness characteristics of glacially transported clasts the c40 index the percentage of clasts with c a ratios 0 4 and the ra index the percentage of very angular and angular clasts in a sample analysis of the between and within sample co variance of these indices provides a powerful tool for discriminating actively and passively transported clasts in glacigenic deposits use of these indices is illustrated in an analysis of the form characteristics of clasts from lateral and frontal moraines at storbreen jotunheimen these fall between those of actively transported clasts in basal till low c40 and ra values and those of unmodified frost weathered clasts high c40 and ra values both indices decline down moraine within sample analyses of clast shape demonstrates that these aggregate clast form gradients reflect changes in the relative proportions of actively and passively transported debris on the moraines rather than progressive modification of actively transported clasts these analyses also indicate that actively transported clasts form the dominant component of the moraines particularly near the former glacier terminus further applications of the approach developed here are suggested

climate evolution and forcing during the last 40 ka from the oscillations in apennine glaciers and high mountain lakes italy the results of studies carried out on the variations of glaciers and lakes in the higher apennines during the last 40 ka are considered for correlation with some climate forcing agents e g changes in insolation variations in origin of the air masses carrying moisture and north atlantic events acting both at regional and hemispheric scales the origin of air masses was assessed using the apennine equilibrium line altitude pattern the presence of a quartz rich loess in the former glacial environment and the sedimentation rate of sahara quartz in maar lakes temperature and humidity variations have been deduced from glacier expansions and retreats and lake oscillations the data discussed in the paper show that variations in insolation have driven climatic changes in the apennines for most of the considered time span producing gradual changes that took place during periods lasting several thousand years however during some periods insolation seems to have been of minor importance compared to variations in frequency and intensity of southern air currents and to the influence of north atlantic events the data as a whole allow us to highlight the climatic evolution of the high apennine mountains during the last 40k cal a bp

pleistocene ice caps on the coastal mountains of the adriatic sea ice caps once covered large areas of mount orjen 1894 m on the adriatic coast of montenegro bosnia herzegovina croatia the largest ice cap covered an area of c 165 km2 and reached a maximum ice thickness of c 450 m in some areas reaching down to 500 m above modern sea level u series dating of secondary carbonates within moraines indicates that the most extensive glaciation occurred during the middle pleistocene correlating with a major phase of glaciation in greece to the south during mis 12 c 480 430 ka later less extensive glaciations are also recorded in the cirques and valleys and correlate with glaciations during mis 6 190 130 ka and mis 5d 2 110 11 7 ka each phase of glaciation would have required large amounts of snow accumulation under modern precipitation values which at c 5000 mm are some of the highest in europe mean annual temperatures would need to be only c 5 6 c lower in order to form similar sized glaciers today a mean annual temperature depression of 12 13 c would still require 1000 mm of snow accumulation water equivalent to balance ablation suggesting sustained moisture supply during pleistocene cold stages such sustained precipitation supply during pleistocene cold stages is likely to have been facilitated by major temperature contrasts between the european landmass and the mediterranean sea which are likely to have sustained lee side vortices to the south of the alps in the gulf of genoa and adriatic sea forming weak moisture bearing depressions which tracked across the eastern adriatic coastal mountains large ice caps on the dinaric alps would have blocked the inland penetration of these depressions resulting in much drier conditions in the balkan interior creating favourable conditions for the deposition of thick accumulations of loess the last glaciers on orjen formed during the younger dryas 12 9 11 7 ka and confirm the influence of north atlantic ocean circulation on pleistocene climate change in this part of the mediterranean

the upper pleistocene on the northern face of the guadarrama mountains central spain palaeoclimatic phases and glacial activity abstract the present paper provides new information on pleistocene glacial activity in a mountainous area of the iberian central system a sediment analysis associated with pleistocene modelling was carried out using 1 granulometric and morphometric procedures 2 quartz grain microtexture techniques sem to discriminate between glacial and no glacial origins of sediments 3 clay x ray diffraction study to determine intra pleistocene climate variability and 4 optically stimulated luminescence osl absolute dating the results show that the sediments were formed in two different phases associated with glacial dynamics one of them was 35 30 ky bp and another was 25 20 ky bp separated by a short intermediate warm wet period identification of glacial phenomena is new for the northern slopes of the guadarrama mountains facing the north meseta duero basin although they are not unusual within the general context of the iberian central system from the data provided we deduce that glaciation in these mountains was much more intense and widespread than had previously been thought because on the northern slopes glaciers occupied large areas reaching the base of the mountains the evidence favours new interpretations of pleistocene morphology in the centre of the iberian peninsula and by extension on the southwestern edge of europe it also highlights the sensitivity of mountainous areas with regard to quaternary climate changes

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

little ice age nivation activity in northeast greenland during the little ice age lia the periglacial landscape in northeast greenland responded rela tively quickly to the climatic deterioration with increased nivation activity resulting nivation landforms and associated sediment basins are used as palaeoclimatic archives documenting the significant geomorphological effect of nivation during the lia period in the zackenberg area a nival basin studied in detail showed the onset and dominance of niveo fluvial sedimentation in the period ad 1250 1420 followed by increasing niveo aeolian sedimentation between ad 1420 1500 1580 finally very rapid niveo aeolian sedimentation prevailed during the period ad 1500 1580 1690 in the same period some large nival fans accumulated in the zackenberg lowland as a result of increased niveo fluvial activity and niveo fluvial sediments were also deposited in pre existing fluvial valleys demonstrating the large areal extension of the nivation activity the chronology is based on nine ams 14c determinations the inte

numerical modeling of the development of u shaped valleys by glacial erosion the steep sided valleys and overdeepened basins of alpine landscapes are well known products of glaciation yet relatively little is known about how the dynamics of ice flow and glacial erosion interact to give rise to such landforms by linking a finite element model for ice flow through a glacier cross section with an erosion model it is possible to investigate the development of one of the most striking glacial landforms the u shaped valley in addition to providing a detailed understanding of landform development such modeling provides a way to test current understanding of the controls on glacial sliding and erosion to simulate valley development i first model flow through an initial glacier cross section and calculate the glaciological parameters that govern erosion i then numerically simulate erosion to produce a modified transverse profile for which a new flow field and erosion pattern are computed a number of iterations permits examination of the progressive transformation of cross section form which can be compared with field data model predictions of the cross section flow field are in close accord with data from the athabasca glacier and include marked lateral variations in sliding velocity with an erosion law dependent on basal velocity the model predicts the rapid transformation of a v shaped cross section into a recognizably glacial form over a time period on the order of 10 4 yr and the eventual development of a steady state quasi parabolic glacier cross section better agreement with empirical data from glaciated valleys is obtained by including temporal variations in ice discharge in order to mimic the characteristics of 100 000 yr glacial cycles the high discharge phase dominates form development and at low discharges cross section form is essentially inherited from the central part of the form that developed during the preceding high discharge phase

quantifying climate and glacier mass balance in north norway during the younger dryas abstract oksfjordjokelen is located at 70 n on the troms finnmark border in north norway during the younger dryas it was decoupled from and sat just beyond the margin of the scandinavian ice sheet at this time the major fjords in troms and finnmark were ice free with outlet glaciers from the icefield filling a number of smaller side valleys only one outlet from the icefield sorfjorddalen is temporally well constrained by 14 c dating and association with the main shoreline associated with a period of minimal crustal rebound dated to the younger dryas sorfjorddalen is reconstructed using a valley centre line iterative model and assuming a no slip basal boundary condition this assumption of cold based ice is supported by the geomorphological evidence of angular bouldery fronto lateral moraines formed during the younger dryas the equilibrium line altitude for the sorfjorddalen is calculated using both the balance ratio and accumulation area ratio methods and this is used to constrain the snout positions generally to mapped moraines of the other outlets this approach assumes similarity of mass balance gradients and geometries of the outlet glaciers which is supported by present day symmetry of the icefield this method is extremely useful in such environments where dateable material is often difficult if not impossible to find some margins terminated in deep water where bathymetry was lacking making calving quantification problematic with subsequent impacts on equilibrium line altitudes poorly constrained these deep water terminating snouts were discounted from subsequent palaeo climate reconstructions an empirical equilibrium line altitude temperature precipitation relationship was used to define limits of climate change required to sustain the reconstructed icefield palaeo precipitation estimates were refined using a palaeo temperature estimate for the younger dryas from andoya calculations of ice flux through the equilibrium line altitude were used to further constrain the mass balance characteristics of the reconstructed icefield and these suggest similarities with ice masses found in the northern nordaustlandet regions of svalbard

last glacial maximum glaciers in the northern apennines reflect primarily the influence of southerly storm tracks in the western mediterranean abstract during the local last glacial maximum llgm the northern apennines hosted more than 100 valley and mountain glaciers covering collectively more than 260 km2 cosmogenic 10be exposure ages obtained for the first time along the apenninic range constrain the age of the llgm to pre date ca 21 ka the estimated volumes of these late pleistocene glaciers exceeded 9 1 km3 w e their reconstructed equilibrium line altitudes elas range from ca 1200 m a s l for northerly facing compound basin valley glaciers to ca 1620 m a s l for southerly facing mountain glaciers reconstructed elas in the western sector of the northern apennines were among the lowest recorded for the whole of the italian peninsula including the alps and also when compared with other mountain chains in the surrounding mediterranean basin these probably reflect exceptionally high accumulation rates fed by storm tracks in the western mediterranean which in turn has implications for the atmospheric circulation pattern that prevailed in the region at the time