ice moraine and landslide dams in mountainous terrain we review recent work on ice moraine and landslide dams in mountainous terrain thus complementing several comprehensive summaries on glacier dams in intracontinental and arctic areas of low relief we discuss the roles of tectonic and climatic forcing on ice moraine and landslide dam formation and sudden drainage and focus on similarities and differences between their geomorphic impacts on confined valleys drained by steep bedrock and gravel bed rivers despite numerous reported failures of natural dams in mountain belts throughout the world their relevance to long term dynamics of mountain rivers remains poorly quantified all types of dams exert local base level controls thus trapping incoming sediment and inhibiting fluvial bedrock incision pervasive geomorphic and sedimentary evidence of outburst events is preserved even in areas of high erosion rates suggesting that sudden dam failures are characterized by processes of catastrophic valley floor aggradation active channel widening and downstream dispersion of sediment during which little bedrock erosion seems to be achieved we find that in the absence of direct evidence of former dams a number of similarities among the geomorphic and sedimentologic characteristics of catastrophic outburst flows may give rise to ambiguous inferences on the dam forming process this is especially the case for tectonically active mountain belts where there is ample and comparable potential for the formation and failure of ice moraine landslide and polygenetic dams concomitant with climatic oscillations or earthquake disturbance hence the palaeoclimatic implications of erroneously inferring the cause of dam formation may be significant we recommend that future research on natural dams in mountainous terrain addresses a climate and earthquake controlled systematics in the pattern of formation and failure b quantification of response of mountain rivers to catastrophic outburst events and their concomitant process sequences c elaboration of a comprehensive classification of natural dams in mountainous terrain with special attention to polygenetic dams d physical based modelling of dam formation failure and routing of water and sediment outbursts and e quantitative controls on the contribution of natural dams to sediment budgets in mountainous terrain

ageostrophic geopotential fluxes in downstream and upstream development of baroclinic waves abstract with the use of a simple primitive equation model it is demonstrated that the convergence divergence of ageostrophic geopotential fluxes can be a major source sink of kinetic energy for both downstream and upstream development of baroclinic waves and can play a dominant role during the early stages of wave development it is also shown that both surface friction and effects lead to an asymmetry in the upstream versus downstream development with downstream development much stronger a total group velocity is defined based on ageostrophic fluxes and its relationship to the rate of wave packet spreading and to convective and absolute instability is discussed

integration of 3d geological modeling and gravity surveys for geothermal prospection in an alpine region abstract thermal sources are common manifestations of geothermal energy resources in alpine regions the up flow of the fluid is well known to be often linked to cross cutting fault zones providing a significant volume of fractures since conventional exploration methods are challenging in such areas of high topography and complicated logistics 3d geological modeling based on structural investigation becomes a useful tool for assessing the overall geology of the investigated sites geological modeling alone is however less effective if not integrated with deep subsurface investigations that could provide a first order information on geological boundaries and an imaging of geological structures with this aim in the present paper the combined use of 3d geological modeling and gravity surveys for geothermal prospection of a hydrothermal area in the western alps was carried out on two sites located in the argentera massif nw italy the geothermal activity of the area is revealed by thermal anomalies with surface evidences such as hot springs at temperatures up to 70 c integration of gravity measurements and 3d modeling investigates the potential of this approach in the context of geothermal exploration in alpine regions where a very complex geological and structural setting is expected the approach used in the present work is based on the comparison between the observed gravity and the gravity effect of the 3d geological models in order to enhance local effects related to the geothermal system it is shown that a correct integration of 3d modeling and detailed geophysical survey could allow a better characterization of geological structures involved in geothermal fluids circulation particularly gravity inversions have successfully delineated the continuity in depth of low density structures such as faults and fractured bands observed at the surface and have been of great help in improving the overall geological model

clastic lawsonite glaucophane and jadeitic pyroxene in franciscan metagraywackes from the diablo range california textural relationships and mineral chemistry identify a detrital origin for jadeitic pyroxene and some lawsonite and glaucophane in franciscan metagraywackes in the diablo range these clasts differ from the neometamorphic post depositional assemblage by having larger grain sizes and deformational features including bending cracking and optical strain polarization large strain polarized jadeitic pyroxenes contain inclusions of strained lawsonite and glaucophane but none of these minerals has grown across clast matrix boundaries by comparison neometamorphic lawsonite forms small unstrained tablets crossing the margins of large clasts and is associated with quartz albite chlorite white mica in recrystallized metagraywacke matrices similarly authigenic glaucophane forms discrete small prisms or euhedral outgrowths on large clasts of sodic amphibole jadeitic clasts in contact with metagraywacke matrices may be deeply embayed and show marginal recrystallization to fine grained mixtures of albite chlorite quartz or internally to pumpellyite albite backscatter electron imaging and microprobe analyses consistently show that the pyroxenes have extremely variable jd contents within a single clast compositional heterogeneity can be as much as jd 50 ac 39 aug 11 to jd 95 ac 4 aug 1 because their texture habit and chemical variability are similar to those of metasomatic jadeites from tectonic inclusions in serpentinite at new idria southern diablo range or to those of some jadeite quartz associations in extensively recrystallized metabasite knockers such a provenance is inferred for pyroxene clasts in the franciscan metasediments in metaconglomerates pebbles containing pyroxenes jd 59 98 formed original clasts that were overprinted later by the post depositional lawsonitic metamorphism metabasites at pacheco pass have compositionally variable na pyroxenes jd 30 92 which indicate tectonic emplacement of the igneous bodies within enclosing in some cases pyroxenefree metagraywackes the diablo range metagraywackes are weakly developed blueschist facies assemblages of lawsonite white mica albite chlorite titanite glaucophane aragonite pumpellyite which indicate minimum metamorphic conditions of p 3 5 5 0 0 5 kb at t 100 200 c

chemical microstructure of franciscan jadeite from pacheco pass california the chemical microstructure of five jadeitic pyroxenes from three franciscan quartzose metagraywacke samples was investigated by backscattered electron imagery element mapping and electron microprobe microanalysis these clinopyroxenes are neoblastic subhedral grains or subradial aggregates replacing albite for each compositionally zoned cpx grain a series of up to five parallel polished sections were cut essentially normal or parallel to the crystallographic c axis five investigated grains single and subradial aggregates were examined quantitatively and three dimensional chemical sections of the grains were constructed chemical zoning progresses from the na cpx core to rim in four distinct regions q l acm and t region q consists of microcrystalline blebs of quartz and jadeite chi jd 0 95 and has a bulk composition of nearly pure albite very rarely it contains albite l is jadeite chi jd 0 80 that contains lawsonite inclusions acm is acmite rich cpx chi jd 0 65 and t consists of tio 2 bearing jadeite 1 2 wt tio 2 chi jd 0 95 isolated cpx grains and prismatic aggregates display the same chemical architecture regardless of crystallographic orientation the earliest growth stage q represents a volume for volume replacement of pre existing albite by nearly stoichiometric jadeite plus quartz as prisms grew diffusion from the lithic matrix progressively enriched outer na cpx zones in fe super 3 ca and mg terminal stages of high pressure growth are represented by tio 2 bearing jadeitic pyroxenes possibly reflecting a temperature increase or relatively longterm annealing under the same conditions in the presence of titanite and rutile the core q and rim t regions represent a jadeite plus quartz assemblage and confirm our earlier notion that the jadeite zone of franciscan metamorphic rocks was subducted to depths where the assemblage jadeite and quartz was stable at pressures of more than 10 kbar

spatial distribution of sediment storage types and quantification of valley fill deposits in an alpine basin reintal bavarian alps germany spatial patterns of sediment storage types and associated volumes using a novel approach for quantifying valley fill deposits are presented for a small alpine catchment 17 km 2 in the bavarian alps the different sediment storage types were analysed with respect to geomorphic coupling and sediment flux activity the dominant landforms in the valley in terms of surface area were found to be talus slopes sheets and cones followed by rockfall deposits and alluvial fans and plains more than two thirds of the talus slopes are relict landforms completely decoupled from the geomorphic system notable sediment transport is limited to avalanche tracks debris flows and along floodplains sediment volumes were calculated using a combination of polynomial functions of cross sections seismic refraction and gis modelling a total of 66 seismic refraction profiles were carried out throughout the valley for a more precise determination of sediment thicknesses and to check the bedrock data generated from geomorphometric analysis we calculated the overall sediment volume of the valley fill deposits to be 0 07 km 3 this corresponds to a mean sediment thickness of 23 3 m the seismic refraction data showed that large floodplains and sedimentation areas which have been developed through damming effects from large rockfalls are in general characterised by shallow sediment thicknesses 20 m by contrast the thickness of several talus slopes is more than twice as much for some locations e g narrow sections of valley the polynomial generated cross sections resulted in overestimations of up to one order of magnitude whereas in sections with a moderate valley shape the modelled cross sections are in good accordance with the obtained seismic data for the quantification of valley fill deposits a combined application of bedrock data derived from polynomials and geophysical prospecting is highly recommended d 2003 elsevier b v all rights reserved

the integrated effect of condensation in numerical simulations of extratropical cyclogenesis abstract by combining traditional sensitivity studies with techniques that focus on the conservation and invertibility properties of ertel s potential vorticity pv we illustrate the effect of latent heating on the structure and evolution of three simulated extratropical cyclones the cases include one continental cyclone development 15 december 1987 which we examine extensively and two cyclones over the western atlantic ocean 6 january 1983 and 5 january 1985 of somewhat greater intensity which are diagnosed to assess the generality of our findings for the continental case each storm featured a weaker cyclonic low level circulation when latent heating was removed from the simulation but the magnitude of the effect varied greatly in all cases the difference in intensity was attributed to velocities associated with a positive condensation produced pv anomaly above the warm front the amplification of the surface thermal perturbations was not strongly altered in even the case most affected by

quantifying postglacial sediment storage at the mountain belt scale sediment storage is an often neglected term in sediment budgets despite being the crucial link between rates of erosion and sediment yield mountain belts in particular host large valley fills that modulate fluxes of water and sediment buffer the geomorphic coupling between hillslopes and river channels reduce local valley relief and protect bedrock from fluvial incision here we propose a region growing algorithm based on a slope gradient criterion to automatically extract areas of postglacial fluvial and lacustrine valley fills from digital topography at the mountain belt scale applying this method to the european alps we find that the size frequency relationship of 17 766 individual sediment storage units expressed by either area or volume follows a power law over four and five orders of magnitude with scaling exponents 1 77 and 1 71 respectively we show that 90 of the area covered by sediment storage is in the lower quartile of the mountain belt9s elevation and below the median local relief on average low gradient valley fill occupies 6 of the studied drainage basins this fraction increases with basin size likely reflecting the larger accommodation space of trunk valleys generated by multiple glacial interglacial cycles comparison with sediment storage mapped in the southern alps new zealand indicates that rates of uplift and precipitation control the extent and spatial distribution of sediment storage at the mountain belt scale

far upstream precursors of heavy precipitation events on the alpine south side this study examines the upper level flow pattern that foreshadows the comparatively frequent co occurrence of heavy precipitation events on the alpine south side together with potential vorticity pv streamers aloft over western europe it is hypothesized that each streamer is itself preceded by a dynamically distinctive and a thermodynamically active flow associated with the space time development and the ultimate breaking over europe of synoptic scale rossby waves the ecmwf european centre for medium range weather forecasts era 40 dataset is used to examine the nature of a streamer s coherent precursor pattern by deriving seasonal composites of refined hovmoller diagrams the upper level pattern of the pv and its gradient and mid tropospheric diabatic heating for the autumn and winter seasons the composites reveal a significant and coherent wave packet precursor signal in the pv field that can be traced back 1 week to the central and eastern pacific contemporaneously the coherent signatures in the composite pv gradient field and diabatic heating fields are conducive to triggering and or supporting the wave signal and also contribute to subsequent downstream wave breaking in spring the composite precursor pv signal appears over and propagates eastward from the atlantic basin and its limited zonal extent is attributed to the lack of a coherent pv waveguide in summer the signal appears essentially in situ in the hovmoller analysis but extends across the atlantic basin in the pv composite results an indication is also provided of the extent to which the composite characteristics are evident in two individual events and note is made of the study s implications for medium range forecasting copyright 2008 royal meteorological society

the impact of extratropical transition on the downstream flow an idealized modelling study with a straight jet the interaction of a tropical cyclone undergoing extratropical transition et with the midlatitude synoptic scale flow is investigated using full physics numerical experiments with idealized initial conditions the emphasis is on the impact on the midlatitude flow downstream of the et event the midlatitude flow is represented by a balanced straight jet stream as the tropical cyclone approaches the jet a ridge trough couplet and a distinct jet streak form in the upper level flow a midlatitude cyclone develops rapidly downstream of the et system and the further evolution is characterized by downstream baroclinic development based on hovmoller diagrams the upper level development is interpreted as the excitation and subsequent dispersion of a rossby wave train on the potential vorticity gradient associated with the jet the characteristics of this wave train are sensitive to the structure of the jet and to moist processes in the midlatitudes the tropical cyclone undergoing et acts as a sustained forcing for the wave train and the structure of the et system impacts the development most significantly one to two wavelengths downstream of et piecewise inversion of potential vorticity complemented by the partitioning of the flow into its rotational and divergent parts is applied to assess the impact of the et system quantitatively both the cyclonic circulation and the outflow of the tropical cyclone are important contributors to the formation and amplification of the ridge trough couplet the outflow anomaly reduces the eastward motion of the ridge trough couplet significantly and thus promotes phase locking between the tropical cyclone and the upper level pattern copyright 2008 royal meteorological society

synoptic features associated with temporally coherent modes of variability of the north pacific jet stream abstracttime extended eof te eof analysis is employed to examine the synoptic scale evolution of the two leading modes of the north pacific jet stream variability namely its zonal extension retraction te eof 1 and the north south shift of its exit region te eof 2 use of the te eof analysis enables a temporally coherent examination of the synoptic scale evolution preceding and following peaks in each of the two leading modes that provides insight into the preferred evolutions of the north pacific jet composite analyses are constructed based upon selecting peaks in the principal component time series of both phases of each te eof whose magnitude exceeded 1 5 standard deviations jet extension events are associated with an anomalous cyclonic circulation over the gulf of alaska that induces a low level warm anomaly over western north america jet retractions are associated with a nearly opposite configuration characterized by an anomalous anticyclonic circulation over the aleutians and anomalous low

persistent alluvial fanhead trenching resulting from large infrequent sediment inputs we present laboratory and field evidence that in mountainous catchment fan systems persistent alluvial fanhead aggradation and trenching may result from infrequent large sediment inputs we suggest that the river fan systems along the fault bounded range front of the western southern alps new zealand are likely to be in a dynamic equilibrium on 103 yr timescales superimposed on which their fanheads undergo long term cumulative episodic aggradation these fanheads are active only in rare events do not take part in the usual behaviour of the catchment fan system and require much longer to exhibit dynamic equilibrium than the rest of the fan these findings 1 increase our knowledge of the effects of extreme events on alluvial fan morphodynamics in humid climates 2 question the general applicability of inferring past climatic or tectonic regimes from alluvial fan morphology and stratigraphy and 3 provide a conceptual basis for hazard zonation on alluvial fans copyright 2006 john wiley sons ltd

rock type control on erosion induced uplift eastern swiss alps abstract there is growing evidence that quaternary rock uplift in parts of the european alps is a consequence of climate and erosion driven isostatic rebound contemporary rates of rock uplift u in the swiss alps show two distinctive dome like peak regions that attain 1 6 mm yr 1 we focus on the alpenrhein catchment and its surroundings where one of these peak regions spatially coincides with widely exposed cretaceous bundner schist and lower tertiary flysch field assessments and analyses of hillslope gradient distributions quantitatively demonstrate the low rock mass strength and high erodibility of these rocks this is reflected in mean postglacial catchment erosion rates d 4 mm yr 1 as opposed to 0 7 mm yr 1 in more resistant crystalline rocks though largely inferred from landslide and debris flow prone tributary catchments 2 the localised erosion rates in bundner schist and flysch are among the highest documented for the alps and corroborated by historic suspended sediment yields and thus export from the region we further find that the steepness of bedrock rivers the density of large landslides and d correlate with the highest values of u our observations highlight the possibility that erosion of mechanically weak bundner schist and flysch enhanced by large landslides may have contributed to regional crustal unloading and concomitant rock uplift irrespective of whether this is betraying a coupling between long term uplift and erosion modulated by rock type our findings indicate that long term 10 3 to 10 4 yr geomorphic signals contained in bedrock river steepness spatial density of large landslides and postglacial erosion rates strikingly correlate with regional gradients of historic 10 1 yr rock uplift rates

patterns of sediment slug translation and dispersion following typhoon induced disturbance oyabu creek kyushu japan a six year monitoring programme characterized the migration dispersion patterns of sediment slugs generated following typhoon induced disturbances in 1993 and 1997 along a single thread gravel bed stream oyabu creek on kyushu island japan this laterally con ned creek comprises rif e pool sequences with intervening bedrock outcrops the passage of sediment pulses associated with sediment slug processes re ected and was controlled by the rif e pool structures which provided channel bed roughness the volume of sediment stored along valley oors and the distribution of bedrock outcrops changes to bed material size following major sediment inputs during the disturbance events also exerted an in uence on subsequent sediment slug processes the sequence of rainfall events together with changes to channel bed structure induced different phases in the sediment slug processes the capacity of a reach to store or trap sediment as recorded by the longitudinal structure of the channel varied during these differing phases copyright 2004 john wiley sons ltd

reworking of basin fill deposits along a tributary of the upper yellow river implications for changes to landscape connectivity recent emphasis on sediment connectivity in the literature highlights the need for quantitative baseline studies on the patterns and distribution of sediment stores to facilitate understanding of how sediment moves through the landscape at various temporal and spatial scales this study evaluates the distribution and make up of sediment stores within the dramatically incised landscapes of the upper yellow river where basin fill deposits up to 1200 m in depth have been extensively reworked following incision by the yellow river field and gis analyses highlight the discontinuous distribution of sediment stores in garang catchment a 236 km2 tributary of the upper yellow river volumetric estimates of sediment storage were obtained through a combination of field mapping gpr transects and gis analyses sediment stores cover 20 of the garang catchment with an estimated volume of 474 0 x 106 m3 and inferred residence times from osl and 14c dating of 103 104 years fans and terraces reworked from basin fill deposits and associated cut and fill terrace features are the dominant forms of sediment storage 90 of total a space for time argument is used to assess stages of basin infilling and subsequent landscape responses to incision outlining a dramatic example of changes to sediment dynamics and connectivity relationships within the upper yellow river sediments within the upper catchment lie above the regional basin fill level offering a glimpse of pre incisional conditions this contrasts markedly with the enduring influence of basin incisional history seen within the middle catchment and the contemporary landscapes of the lower catchment where nearly all available sediment has been excavated from the basin and the landscape effectively operates under post incisional conditions the need to contextualize catchment scale studies in terms of landscape history is emphasized

sediment yield in europe spatial patterns and scale dependency abstract our understanding about the regional variation of sediment yield sy in europe and its scale dependency currently relies on a limited number of data for mainly larger river systems sy is the integrated result of all erosion and sediment transporting processes operating in a catchment and is therefore of high value for environmental studies and monitoring purposes most global assessments of sy consider catchment area a climate and topography as the main explanatory variables however it is still unclear if these factors also control regional variations of sy within europe this paper aims at bridging this gap therefore we i present a large database of sy values which was constructed through an extensive literature review ii describe the spatial patterns of sy across europe and iii explore its relation with a climate and topography in total sediment yield data from 1794 different locations throughout europe were collected 507 reservoirs and 1287 gauging stations representing a minimum of 29 203 catchment year data only sy data measured at gauging stations or derived from reservoir siltation rates over a period of a minimum of one year were included in the database this database comprises a large range of catchment areas a i e from small upland catchments 0 01 km to major european river basins 1 360 000 km an overview of the collected sy data is provided and sources of uncertainty on the available data are discussed despite potentially large uncertainties on several of the individual sy values analysis of this database indicates clear spatial patterns of sy in europe the temperate and relatively flat regions of western northern and central europe generally have relatively low sy values with ca 50 of the sy 40 t km 2 yr 1 and ca 80 of the data 2 yr 1 while mediterranean and mountainous regions generally have higher sy values with around 85 of the sy data 40 t km 2 yr 1 and more than 50 of the data 200 t km 2 yr 1 these differences are attributed to a combination of factors such as differences in climate topography lithology and land use although larger differences in sy were found between the climatic regions than between topographic zones it is currently difficult to identify the individual importance of the various controlling factors of sy sy a relationships were calculated for the entire dataset and for subgroups stratified according to the measurement method gauging stations or reservoir surveys range of the catchment area climatic region topographic zone of the river outlet and major european river system although typically a negative relationship between sy and a is expected due to a decrease in topsoil erosion rates on more gentle slopes and an increase in sediment deposition with an increase in catchment size this relationship was found to be generally very weak and subject to a lot of scatter furthermore results illustrate important differences in scale dependency whereas a weak but significant negative trend is generally observed for the temperate and relatively flat regions no significant or even positive trends were observed in mountain regions and mediterranean europe when only larger river catchments i e 100 km and especially 10 000 km are considered catchment area exerted a larger control on sy these findings confirm previous studies and indicate that the relationship between sy spatial scale and other controlling factors is often complex and non linear

kinematic evidence for extensional unroofing of the franciscan complex along the coast range fault northern diablo range california franciscan metagraywacke immediately below the del puerto ophiolite an outlier of the coast range ophiolite in the northern diablo range was sheared during top to the east displacement on the coast range fault this represents normal faulting and extensional offset it was accompanied by attenuation of the coast range ophiolite and great valley sequence in the hanging wall along layer parallel normal faults that sole into the coast range fault extension occurred as the franciscan complex moved relatively west out from under north american lithosphere and across the subducting ocean plate below this effected a lengthening and thinning in the wedge of material above the down going plate presumably in response to instability brought about by subduction shallowing krueger and jones 1989 and accretion of the franciscan central belt in the latest cretaceous to early paleocene as a result blueschist facies terranes of the uppermost part of the franciscan complex are now juxtaposed directly against hanging wall units that bear only low grade metamorphism

from gullies to mountain belts a review of sediment budgets at various scales this paper reviews the state of the art in the concept as well as in the application of sediment budgets in sedimentary research sediments are a product of mass dispersal at the earth surface and take part in global cycles sediment budgets aim at quantifying this mass transfer based on the principle of mass conservation and are the key to determine ancient fluxes of solid matter at the earth surface this involves fundamental questions about the interplay of uplift climate and denudation in mountain belts and transfer of sediments from the continents to the oceans as well as applied issues such as soil and gully erosion reservoir siltation and coastal protection first after introducing basic concepts relevant scales and methodologies the different components of quaternary routing systems from erosion in headwaters river systems glacial and paraglacial systems lakes deltas estuaries coasts shelves epicontinental seas and deep sea fans are discussed in terms of their sediment budget most suitable are sedimentologically closed or semi closed depositional environments e g alluvial fans lakes deltas and deep sea fans in a second step the dynamics of passive active and collisional tectonic settings and sediment budgets in related sedimentary basins are explored and new concepts of sediment portioning at large geodynamic scales are introduced ancient routing systems are more or less incomplete and may be intensively fragmented or destroyed in active tectonic settings in terms of sedimentary basin types rifts intracontinental and epicontinental settings are preferred objects of sediment budgets because of their persistence and relatively simple overall sedimentary architecture however closing basins such as foreland forearc retroarc piggy back and wedge top basins may provide excellent snapshots of orogenic sediment fluxes in a third step the large long lived routing systems of the amazon the ganges brahmaputra and the rhine are reviewed for each system estimates of either sediment volumes mass or sediment fluxes of continental and marine subsystems have been compiled in order to receive a complete routing in terms of mass conservation for specific time periods since the late glacial maximum as well as the cenozoic following lessons can be taken from these case studies i depositional centers and fluxes show strong shifts in space and time and call for caution when simply looking at subsystems ii the response times of these large systems are within the milankovich time interval thus lower than predicted from diffusion models iii cyclic routing of sediments in continental basins is much more dominated by climate human control than by eustacy and iv at long time scales ultimate sinks win over intermittent storage it is concluded from this review that the quantitative understanding of global sediment cycling over historic and geologic time and its response to allogenic forcing is still in its infancy and further research is needed towards a holistic view of sediment routing systems at various temporal and spatial scales and their coupling with global biogeochemical cycles this includes i to better determine response times of large routing systems by linking quaternary with cenozoic sediment budgets and continental with marine sub systems ii to combine advanced provenance techniques with sediment budgets in order to reconstruct ancient systems iii to study sediment partitioning at the basin scale iv to reconcile continental supply dominated sequence stratigraphy with the eustatic dominated marine concept and iv to account for non actualism of ancient systems with respect to their erosion and transport mode in particular during glaciations and pronounced arid intervals glacial and eolian sediment routing may cross over hydrologic boundaries of drainage basins thus challenging the principle of mass conservation

using piecewise potential vorticity inversion to diagnose frontogenesis part i a partitioning of the q vector applied to diagnosing surface frontogenesis and vertical motion abstract the technique of piecewise potential vorticity pv inversion is used to identify the nondivergent wind fields attributed to upper middle and lower tropospheric pv anomalies in addition to the irrotational wind with the goal of diagnosing the respective wind fields frontogenetic potentialities frontogenesis is diagnosed using a piecewise separation of the q vector into parts associated with the partitioned wind field partitioned geostrophic q vectors are used to diagnose the vertical motion attributed to the upper middle and lower tropospheric pv anomalies insight gained from this new diagnostic technique is demonstrated by examining a particular case of extratropical marine cyclogenesis resulting from the interaction of an upper tropospheric short wave trough with a surface thermal wave in the early stages of development the largest contributor to surface frontogenesis was associated with winds attributed to the lower tropospheric thermal wave as the cyclone matured the contribut

chemical fine structure of franciscan jadeitic pyroxene from ward creek cazadero area california jadeitic pyroxenes in two franciscan samples one a possible segregation vein in metabasite and another a metabasite both from ward creek cazadero area western california were examined with the electron microprobe the samples were collected from the area of type iii rocks the highest grade portion of the pumpellyite zone jadeitic pyroxenes from both samples are very heterogeneous and cannot be ascribed to crystallization under conditions of surface equilibrium with the coexisting phases two possibilities for their origin are suggested one is as tectonic blocks and the other as the highest grade rocks from the zone that crystallized close to or within the p t stability field of pure jadeite quartz

estimating the fill thickness and bedrock topography in intermontane valleys using artificial neural networks thick sedimentary fills in intermontane valleys are common in formerly glaciated mountain ranges but difficult to quantify yet knowledge of the fill thickness distribution could help to estimate sediment budgets of mountain belts and to decipher the role of stored material in modulating sediment flux from the orogen to the foreland here we present a new approach to estimate valley fill thickness and bedrock topography based on the geometric properties of a landscape using artificial neural networks we test the potential of this approach following a four tiered procedure first experiments with synthetic idealized landscapes show that increasing variability in surface slopes requires successively more complex network configurations second in experiments with artificially filled natural landscapes we find that fill volumes can be estimated with an error below 20 third in natural examples with valley fill surfaces that have steeply inclined slopes such as the unteraar and the rhone glaciers in the swiss alps for example the average deviation of cross sectional area between the measured and the modeled valley fill is 26 and 27 respectively finally application of the method to the rhone valley an overdeepened glacial valley in the swiss alps yields a total estimated sediment volume of 97 11 km3 and an average deviation of cross sectional area between measurements and model estimates of 21 5 our new method allows for rapid assessment of sediment volumes in intermontane valleys while eliminating most of the subjectivity that is typically inherent in other methods where bedrock reconstructions are based on digital elevation models

an automated method to extract fluvial terraces from digital elevation models the vesdre valley a case study in eastern belgium abstract fluvial terraces are a powerful tool for unraveling the combined tectonic and climatic conditions that controlled directly or indirectly the quaternary incision of rivers terrace long profiles are usually retrieved from sparse traces of ancient floodplains preserved in the present topography however when these traces classically collected from topographic maps aerial photographs and field analyses are too few the inferred profiles may be questionable yet the now available high quality and high resolution digital elevation models dems offer an opportunity to increase greatly the quantity of information usable to reconstruct terrace profiles therefore the purpose of this study was to develop a new dem based method of terrace recognition in order to create a larger database and better constrain the profile reconstruction moreover particular procedures of image and numerical processing were defined to fully automate the analysis basically our method relies on the production of bivariate scatter plots depicting the relation between slope and relative altitude i e the altitude above the current alluvial plain for all pixels of successive sections of the valley for each scatter plot the curve of the lowest slope values observed at every relative altitude is smoothed and its minima are assumed to locate the altitudes of the terrace elements preserved in the section we successfully tested this method in the vesdre valley incised in the ne ardenne massif e belgium notably identifying fault deformation of the profiles the main advantages of our approach are its objectivity exhaustiveness and rapidity allowing fast and coherent analysis of many rivers over extended regions

multivariate geostatistical modeling of the spatial sediment distribution in a large scale drainage basin upper rhone switzerland abstract there is a notable discrepancy between detailed sediment budget studies in small headwater catchments 103 km2 in higher order catchments applying modeling and or remote sensing based approaches for major sediment storage delineation to bridge the gap between these scales we compiled an inventory of sediment and bedrock coverage from field mapping remote sensing analysis and published data for five key sites in the upper rhone basin val d illiez val de la liene turtmanntal lotschental goms 360 3 km2 equivalent to 6 7 of the upper rhone basin this inventory was used as training and testing data for the classification of sediment and bedrock cover from a digital elevation model 2 2 m ground resolution and landsat imagery we derived 22 parameters characterizing local morphometry topography and position contributing area and climatic and biotic factors on different spatial scales which were used as inputs for different statistical models logistic regression principal component logistic regression generalized additive model best prediction results with an excellent performance mean auroc 0 8721 0 0012 and both a high spatial and non spatial transferability were achieved applying a generalized additive model since the model has a high thematic consistency the independent input variables chosen based on their geomorphic relevance are suitable to model the spatial distribution of sediment our high resolution classification shows that 53 5 21 7 of the upper rhone basin are covered with sediment these are by no means evenly distributed small headwaters

post collisional sediment budget history of the alps tectonic versus climatic control based on the sediment budget of the eastern swiss and western alps since the oligocene the regional tectonic evolution has been identified as the dominant factor it is superimposed on the influence of both regional and global climate change and global sea level change during late pliocene and pleistocene times climate became the dominant factor because of cyclic glaciations the early post collisional history of the alps is characterized by a doubling of sediment discharge rates around the rupelian chattian boundary this increase is attributed to isostatic re adjustment either after large scale thermal reorganization of the lithosphere related to slab break off or to crustal thickening as continental crust became subducted from middle oligocene to late miocene times the overall trend of sediment discharge rates in the entire alps was modified only during relatively short lived phases these are characterized by an increase in aquitanian ca 23 21 ma and late burdigalian times ca 18 16 4 ma and a decrease in early to middle burdigalian 21 19 ma and langhian to serravalian times 16 4 12 ma an important still ongoing period of uplift reflected by rapidly increasing sediment discharge rates started in latest miocene times in the swiss and western alps and affected the eastern alps some 2 million years later the reason for this uplift is not clear but deep seated lithospheric processes appear to be likely

sediment residence time and connectivity in non equilibrium and transient geomorphic systems abstract growing empirical evidence shows that many geomorphic systems are in transient state or out of equilibrium with respect to the external driving forces the transient state is often related to the dis connectivity of the many constituent parts of geomorphic systems as a result of sediment storage along the sediment flow path from its source to the final sink the response time of geomorphic systems to external changes is thus dependent on the residence time of sediment in various storage compartments here i present a mathematical concept based on reservoir theory to model residence time of sediment using millennial scale sediment budgets the framework sheds light on the limitation of the sediment delivery ratio which is often used as a measure of sediment connectivity in geomorphic systems and provides analytical information on process type pace of sediment flux and connectivity of storage compartments along the sediment cascade the application of the reservoir theory to geomorphic systems under agricultural land use shows that sediment delivery ratios are linked to the virtual velocity of the eroded sediment the time since the onset of agricultural land use and the size of the studied basins with respect to the temporal evolution of sediment storages that temporarily remove sediment from the conveyor belt the framework aims to estimate the sediment residence time in storages which is linked to the effective time scale of disconnectivity reanalysis of a long term empirical sediment budget from central europe reveals that the response to agricultural land use which started 5000 years bp is mainly buffered by the long residence time of sediment on hillslopes in the order of 10 3 years which results in a delayed floodplain aggradation furthermore the framework was applied to paraglacial mountain systems that inherit striking evidences of pleistocene glacial erosion and still recover from the change from glacial to interglacial conditions as a consequence of the reduced lateral and longitudinal connectivity i show that paraglacial response times of sediment flux in mountain headwater in the canadian rocky mountains range in the order of 100 400 ka the results indicate that response times at the transition from glacial to interglacial conditions are much longer than the return interval of the major glaciations causing a transient behavior of mountain headwater basins during interglacial periods the presented reanalysis of millennial scale sediment budgets of agricultural and mountain geosystems provides an integrative framework to link paleo environmental reconstructions and the connectivity of transient geomorphic system to external changes

sedimentology of archean greenstone belts signatures of tectonic evolution abstract stratigraphic styles in archean greenstone belts are compared to those of modern and phanerozoic depositional basins in order to test the conformity of tectonic style through time six lithological associations in greenstone belts are recognized 1 mafic ultramafic volcanic 2 calc alkaline volcanic 3 bimodal volcanic 4 quartz arenite iron formation or carbonate 5 conglomerate wacke and 6 conglomerate arenite examples of the associations are described from the kaapvaal superior and zimbabwe provinces and the pilbara block each association differs only slightly between the four regions thereby emphasizing a common tectonostratigraphic theme sedimentary rocks are a minor component of the mafic ultramafic volcanic association they were deposited in two types of volcanic basin environments one similar to barred lagoons and bays around oceanic volcanic islands and the other similar to sediment starved platforms adjacent to coalesced volcanoes in inter arc intra arc and back are basins in contrast sedimentary rocks in the calc alkaline volcanic association comprise thick wedges of epiclastic and volcaniclastic detritus deposited in elongate sedimentary basins and thick wedges of pyroclastic and volcaniclastic detritus deposited adjacent to volcanic centers sedimentary facies were identical to those of forearc trench and marine volcanoplutonic arc settings chemogenic lithofacies in both volcanic associations were deposited in shallow to deep marine waters although shallow water profiles were selectively preserved in some terrains sedimentary rocks of the bimodal volcanic association are thick wedges of siliciclastic and volcaniclastic deposits interbedded with subaerial to submarine erupted flows of komatiite basalt and rhyolite depositional environments ranged from braid plain and braid delta to coastal marine and submarine fan starved basin deposits include banded iron formation and sulfidic black shale the association is identical to that of cratonic extensional basins in arc continent and intracontinental rifts sedimentary rocks of the quartz arenite iron formation or carbonate association onlap weathered basement or bimodal volcanic association rocks depositional environments were either transitional from fluvial to siliciclastic and carbonate marginal marine to offshore pelagic hemipelagic or from inshore intrabasinal clastic and volcaniclastic to offshore pelagic hemipelagic siliciclastic deposits are supermature two tectonic sites are represented those with siliciclastic facies represent continent adjacent syn to post rift stable shelves and those dominated by banded iron formation with volcaniclastic deposits represent arc adjacent post rift stable shelves sedimentary rocks of the conglomerate wacke association are represented by thick wedges of siliciclastic or volcaniclastic sandstone with minor volcanic components these were deposited in braid plain braid delta and submarine fan environments within elongate sedimentary basins coastal plain and pelagic basin facies are also present siliciclastic detritus was derived from syndepositional magmatic and metasedimentary thrust belts two stratigraphic styles are preserved one that records a flysch like stage of deep to marginal marine environments and the other that records a molasse like stage of marginal marine to fluvial environments the association is identical to that of compressional foreland basins of arc continent collisional and compressional arc tectonic affinities the conglomerate arenite association is preserved in elongate structural basins that transgress crustal components and all other supracrustal units it is dominated by thick wedges of siliciclastic sandstone although bimodal volcanic and volcaniclastic rocks can also be present depositional environments ranged from talus and alluvial fan and braid plain to either lacustrine or coastal marine local basin margins often show lateral offsets from source terrains and vertically skewed facies patterns longitudinal facies geometries are typical the association is similar to that of strike slip collisional graben in hinterland tectonic escape and terrane accretion orogens the examples show that despite all the ramifications of secular geophysical geothermal and geochemical global change the stratigraphic style of sedimentary rocks in archean greenstone belts can be matched with modern tectonic analogues thereby emphasizing the conformity of stratigraphic style through time the inseparable link between stratigraphic and tectonic styles implies that the tectonic style of greenstone belts was not temporally unique major differences exist with regards to the chemical composition of certain magmatic and sedimentary products but these are compensated for by their constant stratigraphic function in terms of depositional processes depositional environments and tectonic sites

disequilibrium of holocene sediment yield in glaciated british columbia it is generally supposed that specific sediment yield the quantity of sediment passing a monitored river cross section per unit area drained upstream of that section declines as the area drained increases1 3 part of the sediment mobilized from the land surface is supposed to go back into storage at field edges and on footslopes and floodplains in contrast we show here that data from british columbian rivers reveal a pattern of increasing specific sediment yield at all spatial scales up to 3 104 km2 this results from the dominance of secondary remobilization of quaternary sediments along river valleys over primary denudation of the land surface the result controverts the conventional model which has been derived from studies of small highly disturbed agricultural catch ments the rivers are still responding to the last glaciation giving a landscape relaxation time greater than 10 kyr this holds pro found implications for geomorphological theory and for studies of erosion

a multiresolution index of valley bottom flatness for mapping depositional areas 1 valley bottoms function as hydrological buffers that significantly affect runoff behavior distinguishing valley bottoms from hillslopes is an important first step in identifying and characterizing sediment deposits for hydrologic and geomorphic purposes valley bottoms occur at a range of scales from a few meters to hundreds of kilometers in extent this paper describes an algorithm for using digital elevation models to identify valley bottoms based on their topographic signature as flat low lying areas the algorithm operates at a range of scales and combines the results at different scales into a single multiresolution index this index classifies degrees of valley bottom flatness which may be related to depth of deposit the index can also be used to identify groundwater constrictions and to delineate hydrologic and geomorphic units

using tropopause maps to diagnose midlatitude weather systems the use of potential vorticity pv allows the efficient description of the dynamics of nearly balanced atmospheric flow phenomena but the distribution of pv must be simply represented for ease in interpretation representations of pv on isentropic or isobaric surfaces can be cumbersome as analyses of several surfaces spanning the troposphere must be constructed to fully apprehend the complete pv distribution following a brief review of the relationship between pv and nearly balanced flows it is demonstrated that the tropospheric pv has a simple distribution and as a consequence an analysis of potential temperature along the dynamic tropopause here defined as a surface of constant pv allows for a simple representation of the upper tropospheric and lower stratospheric pv the construction and interpretation of these tropopause maps which may be termed isertelic analyses of potential temperature are described in addition techniques to construct dynamical representations of the lower tropospheric pv and near surface potential temperature which complement these isertelic analyses are also suggested case studies are presented to illustrate the utility of these techniques in diagnosing phenomena such as cyclogenesis tropopause folds the formation of an upper trough and the effects of latent heat release on the upper and lower troposphere

erosion and exhumation in the himalaya from cosmogenic isotope inventories of river sediments the outward erosional flux is a key factor in the tectonic evolution of mountain belts and there is much debate about the feedbacks between tectonics erosion and climate here we use cosmogenic nuclides 10be and 26al analysed in quartz from river sediments from the upper ganges catchment to make the first direct measurements of large scale erosion rates in a rapidly uplifting mountain belt the erosion rates are highest in the high himalaya at 2 7 0 3 mm yr 1 errors fall to 1 2 0 1 mm yr on the southern edge of the tibetan plateau and are 0 8 0 3 to 0 6 mm yr in the foothills to the south of the high mountains these relative estimates are corroborated by the nd isotopic mass balance of the river sediment analysis of sediment from an abandoned terrace suggests that similar erosion rates have been maintained for at least the last few thousand years the data presented here along with data recently published for european river catchments demonstrate that a log linear relationship between relief and erosion rate holds over three orders of magnitude variation in erosion rate and between very different climatic and tectonic regimes the erosion rate estimates from cosmogenic nuclides correlate well with exhumation rates calculated from previously published apatite fission track ages in the indian himalaya this confirms that much of the exhumation in the himalayan mountain chain is now balanced by erosion however exhumation rates calculated from high blocking temperature systems such as 40ar 39ar in muscovite imply lower exhumation rates rocks presently at the surface must have undergone a three to six fold increase in exhumation rate within the last few million years we show how this could be explained either by climatic forcing of erosion rate changes or by tectonics published evidence for equally rapid changes of exhumation rate in the past and the probable diachroneity in the time at which the present exhumation rates accelerated imply that tectonics has moderated at least some of the change in exhumation rates

subglacial basins their origin and importance in glacial systems and landscapes closed topographic basins are found beneath contemporary ice masses and within the footprint of former ice masses in all glaciated regions we present the first integrated review of subglacial basin occurrence and formation and the implications of such basins for glaciological processes and the evolution of landscape our purpose is to motivate research in areas where understanding of basin origin and process significance is weak basins on the order of 10 102 m deep and 102 103 m long are produced by glacial erosion of subglacial rock and or sediment and are known as overdeepenings outlet and valley glaciers can overdeepen their beds far below sea level or local fluviatile base level larger basins typically in ice sheet contexts may have a pre glacial usually tectonic origin subglacial basins are important glaciologically because they require ice water and sediment to ascend an adverse subglacial slope in order to exit the glacial system the efficiency of which is dependent upon the gradient of the adverse slope and that of the ice surface basins thus influence subglacial drainage system morphology and transmissivity the thickness and distribution of basal ice and sediment layers and the mechanisms and dynamics of ice flow adverse gradients that exceed 11 times that of the ice surface may even permit the formation of subglacial lakes we speculate that in comparison to ice masses with few or no subglacial basins those with numerous or very large basins may respond to climatic changes with unexpected vigour in addition erosion rates and transport pathways of water and sediment through the glacial system and the expression of these processes in the sediment and landform record may be unexpectedly complex further our review shows that in a warming climate ice masses resting on adverse slopes will be vulnerable to rapid and potentially catastrophic retreat new lakes in subglacial basins exposed by mountain glacier retreat will present an increasing hazard and subglacial lakes may drain catastrophically on even longer time scales we speculate that the glacial excavation and post glacial filling of basins in mountainous regions should contribute importantly to climate related changes in isostasy and relief although the controls on overdeepening and their influence on other glacial and landscape processes remain uncertain we hypothesise that overdeepened glacial systems reflect an equilibrium ice bed geometry that maximises the efficiency of ice discharge improved understanding of overdeepening processes especially overdeepened bed hydrology is therefore necessary to understand fully the dynamic behaviour of valley and outlet glaciers and thus the fate of earth s largest ice masses

sediment storage and evacuation in headwater valleys at the transition between debris flow and fluvial processes sediment from landscape disturbance often enters temporary storage in valleys and evacuates over longer times which in steeplands are poorly delimited we hypothesize that across process transitions e g debris fl ow versus fl uvial transport distributions of sediment transit times also change we use fi eld surveys and extensive radiocarbon dating to assess the distribution of transit residence times through the proxy measurement of ages of bank deposits in two mainstem reaches of a 2 23 km 2 watershed in the oregon coast range in the downstream reach debris fans impound fl uvial deposits debris fl ow fi ne fl uvial and coarse fl uvial deposits compose nearly equal parts of the valley fi ll and fl uvial erosion evacuates deposits transit times have a sample mean of 1 22 10 3 14 c yr and an exponential distribution indicating uniform probability of evacuation from storage in the upstream reach valleyspanning debris jams impound debris fl ow deposits composing 95 of the valley fi ll which is routinely scoured by debris fl ows transit times have a sample mean of 4 43 10 2 14 c yr and if 100 14 c yr a power law distribution indicating preferential evacuation of younger deposits and retention of older deposits in both reaches most sediment has short transit times 600 14 c yr but signifi cant volumes remain for millennia less than 20 of basin wide denudation passes through these reservoirs but the latter are still signifi cant buffers between hillslope disturbance and downstream aquatic habitat especially for coarse sediment

pv frontogenesis and upper tropospheric fronts abstract upper tropospheric fronts and frontogenesis are viewed from a potental vorticity pv perspective the rudiments of this approach are to regard such a front as a zone of strong pv gradient on isentropic surfaces and to treat the accompanying frontogenesis as the process whereby this gradient is enhanced on tropopause transcending isentropic surfaces a case study suggests that this concept of pv frontogenesis provides a concise dynamically based definition of upper level frontal zones and a compact and transparent approach for diagnosing the frontogenesis the concept provides fresh insight on the dynamics of the upper level fronts and has the potential to shed light on related phenomena and processes

the downstream impact of tropical cyclones on a developing baroclinic wave in idealized scenarios of extratropical transition the interaction of a tropical cyclone with a developing baroclinic wave is investigated in an idealized scenario of extratropical transition et the impact of et is examined by comparing and analyzing two numerical baroclinic wave experiments a traditional experiment in which baroclinic development is excited by a localized upper level perturbation on a realistic jet profile and an experiment in which additionally a model tropical cyclone is inserted south of the jet at the initial time et occurs in a wavy upper level flow while baroclinic surface systems are still weak the characteristic direct impact of et on the midlatitude flow is the formation of a distinct jet streak and the amplification of a ridge trough couplet in the adjacent downstream region the subsequent rapid cyclogenesis downstream is a direct consequence of these upper level flow modifications this faster and stronger development constitutes the amplification of the leading edge of downstream development both the upper level wave pattern and the surface development are subsequently amplified in the region further downstream the formation of the ridge adjacent to the intensified downstream cyclone is analyzed in detail to elucidate the next stage in the downstream dispersion of the et impact ridge building in the et scenario exhibits characteristics distinct from those in the life cycle experiment wave breaking feedback from the modified low level frontal structure and diabatic processes all contribute to the high amplitude wave pattern downstream of et the downstream impact of et is highly sensitive to the initial storm location and intensity the considerable amplification of the leading edge found in the reference experiment is the most widespread and rapidly propagating impact we thus speculate that this leading edge represents an optimal location of the midlatitude circulation where et can lead to the most significant impact on the downstream flow copyright 2010 royal meteorological society

trench and slope basin deposits in an archean metasedimentary belt superior province canadian shield the identification of a late archean arc trench assemblage in northwestern ontario provides the opportunity to compare depositional systems developed in a precambrian convergent setting with cenozoic examples two types of sedimentary associations exist in the accretionary complex medium to thick bedded bouma a ab and abc felsic turbidites dominate the belt these are primarily organized into unstructured sequences and reflect deposition in a ramp like environment with multiple feed points supplying sediment from a forearc basin mafic turbidites with possible shallow water reworked intervals form isolated pods within the metasedimentary belt erosion of upthrust blocks of sedimentary strata containing ultramafic masses supplied this sediment to elevated slope basins these types of depositional systems are similar in many respects to those developed in cenozoic and holocene arc trench settings

piecewise tendency diagnosis of dynamical processes governing the development of an upper tropospheric mobile trough abstract the intensification and evolution of midlatitude upper tropospheric mobile troughs may be viewed in terms of the isentropic advection and deformation of the tropopause potential vorticity gradient the potential vorticity viewpoint allows one to qualitatively assess observed events in the context of existing theories of mobile trough genesis such as baroclinic instability or downstream development in order to quantitatively determine the role of distinct dynamical process the method of piecewise tendency diagnosis or ptd is developed ptd is an extension of piecewise potential vorticity inversion applied to height tendencies with the forcing terms in the quasigeostrophic height tendency equation partitioned into potential vorticity advection associated with distinct dynamical processes a particular case of mobile trough genesis which occurred during 1 4 december 1980 over north america is diagnosed using ptd although about 20 of the intensification of the trough was due to superposition

downstream development associated with the extratropical transition of tropical cyclones over the western north pacific abstract the movement of a tropical cyclone into the midlatitudes involves interactions among many complex physical processes over a variety of space and time scales furthermore the extratropical transition et of a tropical cyclone may also result in a high amplitude rossby wave response that can extend to near hemispheric scales after an et event occurs over the western portion of a northern hemisphere ocean basin the high amplitude downstream response often forces anomalous midlatitude circulations for periods of days to a week these circulations may then be related to high impact weather events far downstream of the forcing by the et event in this study downstream development following et events over the western north pacific ocean is examined local eddy kinetic energy analyses are conducted on four cases of north pacific tropical cyclones of varying characteristics during et into varying midlatitude flow characteristics during 15 july 30 september 2005 the goal is to examine the impact of e

river loads and modern denudation of the alps a review this paper presents the first comprehensive analysis of sediment and dissolved load across an entire mountain range we investigate patterns and rates of modern denudation of the european alps based on a compilation of data about river loads and reservoir sedimentation from 202 drainage basins that are between ca 1 to 10 000 km2 large the study basins cover about 50 of the total area of the alps modern glaciated basins have the highest sediment yields of up to 7000 t km 2 a 1 which are on average 5 to 10 times higher than in non glaciated basins likewise sediment yield and glacial cover are positively correlated instead relief is a relatively weak predictor of sediment yield the strong glacial impact in the correlations is due to glacier recession since the 19th century as well as due to glacial conditioning during repeated quaternary glaciations which have produced the strong transient state of the alpine landscape we suggest that this is the major cause for ca 3 fold enhanced denudation of the western compared to the eastern alps chemical denudation rates are highest in the external alps dominated by carbonate sedimentary rocks where they make up about one third of total denudation the high rates cannot be explained without anhydrite dissolution we estimated that only 45 of the sediments mobilized in headwaters are exported out off the alps most sediments being trapped in artificial reservoirs the total amount of sediment annually trapped within the alps equates to 43 mt when corrected for sediment storage we obtain an area weighted mean total denudation rate for the alps of about 0 32 mm a 1 the pre dam rate might be as high as 0 42 mm a 1 in total ca 35 plus 23 mt of mass are exported each year out of the alps as solids and solutes respectively these rates are not enough to out pace modern rock uplift nevertheless pattern of sediment yield across the alps coincides roughly with the intensity of glacial conditioning and modern rock uplift supporting the hypothesis of an erosion driven uplift of the alps

erosion rates during rapid deglaciation in icy bay alaska 1 contemporary glacial erosion rates based on sediment yields in southeast alaska merit considerable attention because they are unsurpassed worldwide and they significantly exceed long term exhumation rates in the region two issues are likely to contribute to these high rates contemporary sediment yields in fjords 1 have generally been overestimated by failing to account for the considerable input of subaerially derived material and 2 are exceptionally high because tidewater glaciers in southeast alaska have been anomalously dynamic and erosive during the past century of rapid retreat to investigate these influences and to quantify the rate at which tyndall glacier erodes its basin we present seismic data defining the volume of sediments in taan fjord icy bay we subtract the contribution of subaerially derived sediments from the fjord sediment package to determine the sediment yield directly from tyndall glacier during the most recent period of retreat 1962 1999 using a numerical model of proglacial glacimarine sedimentation we then calculate the annual sediment yield from and the corresponding erosion rate of tyndall glacier during this period which averages 28 5 mma 1 a strong correlation emerges between glacial retreat rates and glacial sediment yields implying that most contemporary sediment yield data from retreating tidewater glaciers may correspond to contemporary erosion rates that are a factor of 3 5 1 5 higher than in the long term hence we estimate the long term erosion rate for tyndall glacier to be 9 2 mma 1

quaternary erosion induced isostatic rebound in the western alps the high elevation and deep incision of the alps have traditionally been used as an argument for recent tectonic activity that has elevated the belt and increased erosion rates normal faulting and horizontal extension however dominate current tectonic activity and isostatic compensation of thinning crust should lead not to increased but to decreased mean elevations here we test the idea that enhanced quaternary erosion of the alps and isostatic compensation of the mass removed can account for the distribution of present day geodetically measured rates of vertical movement in the western alps using geophysical relief and kuhlemann s estimated average erosion rate for the alps we quantify the spatial distribution of erosion and the volume of eroded rock respectively from these we obtain a map of rock eroded within a given time span the calculated isostatic response of the alpine lithosphere to erosional unloading for a variety of values of the flexural rigidity of the alpine lithosphere reaches a maximum of 500 m since 1 ma in the inner swiss alps and vertical movement extends across the entire belt including peri alpine basins assuming a steady erosion rate since 1 ma this rebound accounts for half of the measured vertical motion of 1 1 mm yr in the southern valais thus a significant fraction 50 of the present day vertical movement results from the isostatic response to enhanced erosion during plio quaternary time

tropical cyclone effects on arctic sea ice variability 1 in recent years increasing interest has been put on the role that intense tropical cyclones can play in the climate system the following study is aimed at highlighting the effects of strong tropical cyclones over the tropical atlantic on the mean climate their composite effect on the surface winds is made apparent by a wide cyclonic perturbation that affects a large portion of the atlantic tropical ocean teleconnection patterns which are visible in the sea level pressure anomalies associated with this tropical composite cyclone appear to link the activity of the hurricanes to the arctic ocean a significant negative correlation between the energy dissipated by hurricanes in the tropical atmosphere and the sea ice cover along the transpolar drift stream path has also been found

remote impact of north atlantic hurricanes on the mediterranean during episodes of intense rainfall in autumn 2012 autumn is the most favourable season for tropical cyclones to undergo extratropical transition and interact with the midlatitude flow over the north atlantic autumn is also the season when intense rainfall over the mediterranean is often triggered by rossby wave breaking the impact of tropical cyclones on downstream wave breaking is investigated here during three episodes of intense rainfall which were the target of hymex hydrological cycle in mediterranean experiment in autumn 2012 five day simulations of hurricanes leslie rafael and sandy were performed with the meso nh model in a domain encompassing the north atlantic and the mediterranean control simulations were compared to simulations in which the hurricanes were filtered out from the initial conditions in each case the hurricane locally impeded the forward progression of an upstream trough then reintensified as an extratropical cyclone during the wrap up of the trough the local impact of leslie and rafael on the midlatitude flow quickly propagated downstream along a polar jet and amplified rossby wave breaking but decreased the intensity of the forecast precipitation over the mediterranean the local impact of sandy propagated downstream along a subtropical jet in addition to the polar jet and resulted in a weak impact of the forecast precipitation on the mediterranean this study suggests that the interaction of tropical cyclones with the midlatitude flow over the western north atlantic may be considered a perturbation to rather than a source of downstream wave breaking

postglacial adjustment of steep low order drainage basins canadian rocky mountains 1 it is generally argued that pleistocene glaciation results in increased sediment flux in mountain systems an important but not well constrained aspect of pleistocene glacial erosion is the geomorphic decoupling of cirque basins from main river systems this study provides a quantitative link between glacier induced basin morphology postglacial erosion and sediment delivery for mountain headwaters with basin area 28 respectively and ii larger fan sizes at outlets of noncirque basins compared to cirques although small headwater basins represent the steepest part of mountain environments and erode significant postglacial sediment the majority of sediment remains in storage under interglacial climatic conditions and does not affect large scale mountain river systems

dynamics of a local alpine flooding event in october 2011 moisture source and large scale circulation alpine heavy precipitation events often affect small catchments although the circulation pattern leading to the event extends over the entire north atlantic the various scale interactions involved are particularly challenging for the numerical weather prediction of such events unlike previous studies focusing on the southern alps here a comprehensive study of a heavy precipitation event in the northern alps in october 2011 is presented with particular focus on the role of the large scale circulation in the north atlantic european region during the event exceptionally high amounts of total precipitable water occurred in and north of the alps this moisture was initially transported along the flanks of a blocking ridge over the north atlantic subsequently strong and persistent northerly flow established at the upstream flank of a trough over europe and steered the moisture towards the northern alps lagrangian diagnostics reveal that a large fraction of the moisture emerged from the west african coast where a subtropical upper level cut off low served as an important moisture collector wave activity flux diagnostics show that the ridge was initiated as part of a low frequency large scale rossby wave train while convergence of fast transients helped to amplify it locally in the north atlantic a novel diagnostic for advective potential vorticity tendencies sheds more light on this amplification and further emphasizes the role of the ridge in amplifying the trough over europe operational forecasts misrepresented the amplitude and orientation of this trough for the first time this study documents an important pathway for northern alpine flooding in which the interaction of synoptic scale to large scale weather systems and of long range moisture transport from the tropics are dominant moreover the trapping of moisture in a subtropical cut off near the west african coast is found to be a crucial precursor to the observed european high impact weather

sediment connectivity in the high alpine valley of val muschauns swiss national park linking geomorphic field mapping with geomorphometric modelling abstract the efficiency of sediment routing through mountain sediment cascades is controlled by the connectivity of hillslopes to the main river system a lack of connectivity may cause long term sediment storage and exclude large fractions of a basin from the sediment routing for several thousand years here we studied sediment dynamics in a small formerly glaciated valley in the swiss alps to characterise the sediment connectivity to the stream we calculated a morphometric index using a gis algorithm the modelling results were tested against a field based geomorphic mapping of sediment storages which were evaluated with respect to their state of de coupling in accordance to the field diagnostics the modelling results indicate very well that the present day sediment flux is conditioned by the glacial valley morphometry inherited through pleistocene glaciation especially in the upper hanging valleys the connectivity index is reduced noticeably due to the glacial cirque morphology based on the field mapping 30 of the hillslope sediment cascades are interrupted and 20 of the storage boundaries are currently affected by a lack of material transfer as a consequence 29 of the basin surface is currently disconnected from the main river nevertheless the gis algorithm overestimates the connectivity within the basin because it fails to calculate decoupling between neighbouring pixels in digital terrain models dtms around 35 of the basin surface which has been mapped in the field as being decoupled is related to relative high connectivity our study highlights the potential of morphometric gis modelling for studying sediment connectivity but additionally emphasises the indispensability of geomorphic field mapping for a holistic understanding of mountain cascading systems

sediment and rock strength controls on river incision into bedrock recent theoretical investigations suggest that the rate of river incision into bedrock depends nonlinearly on sediment supply challenging the common assumption that incision rate is simply proportional to stream power our measurements from laboratory abrasion mills support the hypothesis that sediment promotes erosion at low supply rates by providing tools for abrasion but inhibits erosion at high supply rates by burying underlying bedrock beneath transient deposits maximum erosion rates occur at a critical level of coarse grained sediment supply where the bedrock is only partially exposed fine grained sediments provide poor abrasive tools for lowering bedrock river beds because they tend to travel in suspension experiments also reveal that rock resistance to fluvial erosion scales with the square of rock tensile strength our results suggest that spatial and temporal variations in the extent of bedrock exposure provide incising rivers with a previously unrecognized degree of freedom in adjusting to changes in rock uplift rate and climate furthermore we conclude that the grain size distribution of sediment supplied by hillslopes to the channel network is a fundamental control on bedrock channel gradients and topographic relief

icesat validation of srtm c band digital elevation models 1 the geoscience laser altimeter system glas on the ice cloud and land elevation satellite icesat provides a globally distributed data set well suited for evaluating the vertical accuracy of shuttle radar topography mission srtm digital elevation models dems the horizontal error 2 4 7 3 m and vertical error 0 04 0 13 m per degree of incidence angle for the icesat data used are small compared to those for srtm using glas echo waveforms we document differences between the srtm c band phase center and the highest centroid and lowest elevations within icesat laser footprints in the western united states in areas of low relief and sparse tree cover the mean and standard deviation of elevation differences between the icesat centroid and srtm are 0 60 3 46 m the differences are 5 61 15 68 m in high relief sparse tree cover areas and 3 53 8 04 m in flat areas with dense tree cover the largest differences occur in rugged densely vegetated regions

sediment budget of the yangtze river the sediment budget is a method to study the distribution of sediment in different parts of a river basin this paper studies the sediment budget of the yangtze river by analyzing the data on soil erosion size distributions of sediment deposits sediment load and fluvial process a method to determine the sediment budget for the yangtze river is proposed in which the total soil erosion from the upstream reaches and tributaries is divided into two parts sediment load transported to the yichang station and sediment storage in the tributaries and gullies furthermore the sediment load is divided into three parts bed material load deposited in the middle and lower reaches for the fluvial process wash load transported to the estuary and sediment deposition in tongting lake the sediment transported into the estuary is further divided into two parts very fine sediment drifting to the ocean and sediment deposition in the estuary for land creation there is a large sediment demand for 1 the fluvial process to reach the minimum stream power in the middle and lower reaches 2 sediment mining for building material and 3 land creation in the estuary the riverbed profile in the middle and lower reaches is developing toward the equilibrium profile defined by the minimum stream power but the impoundment of the three gorges reservoir interrupts and modifies this fluvial process the annual sediment load in the yangtze river has reduced due to various human activities by about 100 x 10 6 t in the past 15 years thus there is a sediment shortage for land creation in the river mouth

a potential vorticity diagnostic approach to upper level frontogenesis within a developing baroclinic wave the process of tropopause folding is studied in the context of the life cycle of baroclinic waves previous studies of upper level frontogenesis have emphasized the role of the vertical circulation in driving stratospheric air down into the midtroposphere here a potential vorticity based approach is adopted that focuses on the generation of a folded tropopause to facilitate comparison of the two approaches the diagnosis is applied to the upper level front previously simulated and studied by rotunno et al the potential vorticity approach clarifies the primary role played by the horizontal nondivergent wind in producing a fold and explains why folding should be a common aspect of baroclinic development between the trough and upstream ridge prolonged subsidence within a region of weak system relative flow generates a tropopause depression oriented at an angle to the large scale flow the large scale vertical shear then locally increases the slope of the tropopause eventually leading to a tropopause fold in contrast tropopause folding in the base of the trough is caused by the nondivergent cyclonic circulation associated with the surface thermal wave the winds associated with the thermal wave amplify the potential vorticity wave aloft and these winds which decrease with height rapidly generate a tropopause fold within the trough

the influence of landscape configuration upon patterns of sediment storage in a highly connected river system abstract orthoimages are used to analyze the influence of valley width channel slope and the area of landslides that deliver sediment to valley floors upon the downstream pattern of sediment storage in the liwu basin eastern taiwan confined valley settings dominate this steep deeply dissected uplifting mountainous basin although they occupy 82 of the whole channel network sediment storage is limited in these reaches partly confined valley settings are restricted to relatively short reaches of two tributary systems over 95 of sediment storage in the liwu river is found within the short alluvial section of laterally unconfined valley close to the river mouth lateral bars are the primary features associated with sediment storage in confined reaches 54 in total volume while floodplains dominate the partly confined and laterally unconfined reaches 95 in total volume downstream patterns of sediment storage are controlled primarily by valley confinement i e valley width and landscape configuration channel slope and locations of contemporary landslides are not key determinants of sediment storage patterns sediment accumulation at confluence zones is not determined by the catchment area of tributaries or by landslide area rather it is determined by valley confinement of the trunk stream at the confluence and the associated downstream sequence of river types sediment conveyance is very effective within this highly connected river system

millennial lag times in the himalayan sediment routing system abstract any understanding of sediment routing from mountain belts to their forelands and offshore sinks remains incomplete without estimates of intermediate storage that decisively buffers sediment yields from erosion rates attenuates water and sediment fluxes and protects underlying bedrock from incision we quantify for the first time the sediment stored in 38 000 mainly postglacial himalayan valley fills based on an empirical volume area scaling of valley fill outlines automatically extracted from digital topographic data the estimated total volume of 690 242 452 km 3 is mostly contained in few large valley fills 1 km 3 while catastrophic mass wasting adds another 177 31 km 3 sediment storage volumes are highly disparate along the strike of the orogen much of the himalaya s stock of sediment is sequestered in glacially scoured valleys that provide accommodation space for 44 of the total volume upstream of the rapidly exhuming and incising syntaxes conversely the step like long wave topography of the central himalayas limits glacier extent and thus any significant glacier derived storage of sediment away from tectonic basins we show that exclusive removal of himalayan valley fills could nourish contemporary sediment flux from the indus and brahmaputra basins for 1 kyr though individual fills may attain residence times of 100 kyr these millennial lag times in the himalayan sediment routing system may sufficiently buffer signals of short term seismic as well as climatic disturbances thus complicating simple correlation and interpretation of sedimentary archives from the himalayan orogen its foreland and its submarine fan systems