use of terrestrial laser scanning tls for monitoring and modelling of geomorphic processes and phenomena at a small and medium spatial scale in polar environment scott river spitsbergen abstract the application of terrestrial laser scanning tls for precise modelling of land relief and quantitative estimation of spatial and temporal transformations can contribute to better understanding of catchment forming processes experimental field measurements utilising the 3d laser scanning technology were carried out within the scott river catchment located in the nw part of the wedel jarlsberg land spitsbergen the measurements concerned the glacier free part of the scott river valley floor with a length of 3 5 km and width from 0 3 to 1 5 km and were conducted with a state of the art medium range stationary laser scanner a leica scan station c10 a complex set of measurements of the valley floor were carried out from 86 measurement sites interrelated by the application of 82 common target points during scanning from 5 to 19 million measurements were performed at each of the sites and a point cloud constituting a model space was obtained by merging individual model spaces a digital surface model dsm of the scott river valley was obtained with a co registration error not exceeding 9 mm the accuracy of the model permitted precise measurements of dimensions of landforms of varied scales on the main valley floor and slopes and in selected sub catchments the analyses verified the efficiency of the measurement system in polar meteorological conditions of spitsbergen in mid summer

quantification of the ice cored moraines short term dynamics in the high arctic glaciers ebbabreen and ragnarbreen petuniabukta svalbard abstract extensive ice cored moraine complexes are common elements marking the last advance of many svalbard glaciers sediment gravity flows are among the most dynamic processes transforming these landforms the short term yearly and weekly dynamics of mass wasting processes were studied in a cm scale using repetitive topographic scanning we monitored several active sites on the forelands of two glaciers ebbabreen and ragnarbreen both of which are located near petuniabukta at the northern end of billefjorden in spitsbergen the surveys indicate high dynamic rates of landforms transformation the mean annual volume loss of sediments and dead ice for the most active parts of the moraines was up to 1 8 m a 1 however most of the transformation occurred during summer with the short term values of mean elevation changes as high as 104 mm day 1 in comparison the dynamics of the other i e non active parts of the ice cored moraines were much lower namely the mean annual lowering attributed mainly to dead ice downwasting was up to 0 3 m a 1 whereas lowering during summer was up to 8 mm day 1 our results indicate that in the case of the studied glaciers backwasting was much more effective than downwasting in terms of landscape transformation in the glacier forelands however despite the high activity of localised mass movement processes the overall short term dynamics of ice cored moraines for the studied glaciers were relatively low we suggest that as long as debris cover is sufficiently thick thicker than the permafrost s active layer depths the mass movement activity would occur only under specific topographic conditions and or due to occurrence of external meltwater sources and slope undercutting in other areas ice cored moraines remain a stable landsystem component in a yearly to decadal time scale

on the boundary conditions applied to the sea ice coupled model 1 the formulation of suitable boundary conditions at the water ice interface during ice formation melting is an important aspect of the sea ice coupled model the transfer of water and salt through the water ice can be posed as different boundary conditions behavior of the model under these boundary conditions is illustrated through simple analytical models and a numerical model based on pressure coordinate it is emphasized that the correct handling of the boundary conditions associated with sea ice formation requires an accurate treatment of the equivalent pressure on the top of water column and the total volume mass of the water column in the ice formation regime improper treatment of these boundary conditions may lead to an artificial loop current near the edge of ice in numerical simulations of oceanic circulation in the arctic ocean or near the antarctica

sea level variations induced by heating and cooling an evaluation of the boussinesq approximation in ocean models in this paper a sigma coordinate ocean model is modified to remove the commonly used boussinesq approximation so that the effect of thermal expansion is exactly included in the basic equations in order to cope with the seasonal heating cycle and the detection of climate change through variation in sea level height tests are performed to evaluate the differences between boussinesq and non boussinesq calculations under different heating and cooling conditions and different model domains for an idealized case of a flat bottom shallow ocean basin without wind forcing simulations of a warm eddy show that the non boussinesq dynamics have only a minor effect on the baroclinic current field however vertically averaged velocities though small compared with the baroclinic velocities are cyclonic for the boussinesq calculation and anticyclonic for the non boussinesq calculation the results indicate that global or closed basin boussinesq models should be able to simulate most of the observed steric sea level changes on seasonal or climate timescales when corrected by a spatially uniform time dependent factor calculated from the volume averaged density change the seasonal variation of the globally averaged sea level calculated from climatological data is small about 1 cm variations in steric sea level in regional models both boussinesq and non boussinesq may differ from those of global models owing to the unknown transport across their boundaries associated with the local heating and cooling a spatially uniform time dependent correction similar to that associated with thermal expansion is proposed to account for transport across open boundaries of regional models variations of sea level obtained from a boussinesq model of the atlantic ocean approximate the seasonal signal due to the heating cooling cycle of each hemisphere as observed by satellite altimeter data

paraglacial gullying of sediment mantled slopes a case study of colletthogda kongsfjorden area west spitsbergen svalbard this paper evaluates the paraglacial evolution of a sediment mantled slope in a polar maritime environment the intensity of paraglacial processes is estimated through quantifi cation of erosion and dating of fi eld sectors with the help of photographic archives gully erosion has been estimated using morphometric parameters and by surveys of vegetation cover the rapid melting of dead ice cores controls gully formation this leads to slope form modifi cation gully profi le gradients are reduced from a mean of 35 to a mean ranging between 10 and 15 profi le evolution results from the collapse of glacier lateral moraine all data mean slope angle of individual gullies frequency distribution of slope angles fractional distance to the apex gullying index volume of debris mobilized vertical erosion rate tend to increase with increasing deglaciation age and the duration of paraglacial activity vegetation colonization is a response to stabilization of the ground surface and the drying up of the ground surface due to dead ice melting the full sequence of paraglacial slope adjustment gully incision stabilization may occur rapidly at the study site i e within two decades finally a lateral morphogenic sequence is proposed showing the importance of paraglacial processes at the onset of the deglaciation

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

the goldsbrough stommel circulation of the world oceans abstract goldsbrough first showed how the mass flux at the ocean surface due to the difference between evaporation and precipitation could induce barotropic flow in the ocean interior through the requirement of vorticity conservation stommel proposed to close this circulation by adding the western boundary currents here a first otder description of the goldsbrough stommel circulation for the world oceans is presented using available climatologies while such flows are an order of magnitude smaller than the wind driven circulation the interaction between the goldsbrough stommel gyres and the wind driven and thermally driven circulation determines the salinity distribution of the world oceans therefore it is important to study the goldsbrough stommel circulation and its interaction with motions driven by other forcings in addition the western boundary currents required to close the goldsbrough interior and to satisfy interbasin mass transport can be substantial in the atlantic the southward wester

bering strait throughflow and the thermohaline circulation received 25 august 2005 revised 10 november 2005 accepted 14 november 2005 published 21 december 2005 1 in this study we employ a global coupled climate model to show that the bering strait is important to the variations of the thermohaline circulation three experiments are analyzed a present day control run and two freshwater hosing runs results show that as the thermohaline circulation weakens due to freshwater forcing in the northern north atlantic the bering strait throughflow weakens and even reverses its direction and the export of the arctic freshwater into the northern north atlantic is reduced or the arctic even takes freshwater from the latter thus helping the thermohaline circulation to recover relatively quickly after the end of the freshwater hosing citation hu a and g a meehl 2005 bering strait throughflow and the thermohaline circulation geophys res lett 32 l24610 doi 10 1029 2005gl024424

debris entrainment and landform genesis during tidewater glacier surges the englacial entrainment of basal debris during surges presents an opportunity to investigate processes acting at the glacier bed the subsequent melt out of debris rich englacial structures during the quiescent phase produces geometrical ridge networks on glacier forelands that are diagnostic of surge activity we investigate the link between debris entrainment and proglacial geomorphology by analyzing basal ice englacial structures and ridge networks exposed at the margins of tunabreen a tidewater surge type glacier in svalbard the basal ice facies display clear evidence for brittle and ductile tectonic deformation resulting in overall thickening of the basal ice sequence the formation of debris poor dispersed facies ice is the result of strain induced metamorphism of meteoric ice near the bed debris rich englacial structures display a variety of characteristics and morphologies and are interpreted to represent the incorporation and elevation of subglacial till via the squeezing of till into basal crevasses and hydrofracture exploitation of thrust faults reoriented crevasse squeezes and preexisting fractures these structures are observed to melt out and form embryonic geometrical ridge networks at the base of a terrestrially grounded ice cliff ridge networks are also located at the terrestrial margins of tunabreen neighboring von postbreen and in a submarine position within tempelfjorden analysis of network characteristics allows these ridges to be linked to different formational mechanisms of their parent debris rich englacial structures this in turn provides an insight into variations in the dominant tectonic stress regimes acting across the glacier during surges

a multi dimensional analysis of pro glacial landscape change at solheimajokull southern iceland proglacial landscapes are some of the most active on earth previous studies of proglacial landscape change have often been restricted to considering either sedimentological geomorphological or topographic parameters in isolation and are often mono dimensional this study utilised field surveys and digital elevation model analyses to quantify planform elevation and volumetric proglacial landscape change at solheimajokull in southern iceland for multiple time periods spanning from 1960 to 2010 as expected the most intense geomorphological changes persistently occurred in the ice proximal area during 1960 to 1996 the proglacial river was relatively stable however after 2001 braiding intensity was higher channel slope shallower and there was a shift from overall incision to aggradation attributing these proglacial river channel changes to the 1999 jokulhlaup is ambiguous because it coincided with a switch from a period of glacier advance to that of glacier retreat furthermore glacier retreat of 40 m yr 1 coincided with ice marginal lake development and these two factors have both altered the proglacial river channel head elevation from 2001 to 2010 progressive increase in channel braiding and progressive downstream incision occurred these together probably reflecting stream power due to increased glacier ablation and reduced sediment supply due to trapping of sediment by the developing ice marginal lake overall this study highlights rapid spatiotemporal proglacial landscape reactions to changes in glacial meltwater runoff regimes glacier terminus position sediment supply and episodic events such as jokuhlaups recognising the interplay of these controlling factors on proglacial landscapes will be important for understanding the geological record and for landscape stability assessments

resedimentation of debris on an ice cored lateral moraine in the high arctic kongsvegen svalbard abstract in ice cored landform assemblages the process of resedimentation via sediment flow is important in determining the morphology and sedimentary facies distribution after the ice core has melted this paper documents the sediment flow processes associated with the resedimentation of an ice cored lateral moraine at kongsvegen svalbard decay of the ice cored lateral moraine is dominated by the development of a sediment flow fan which has an hour glass form in plan the fan comprises a broad source area on the crest of the lateral moraine separated from the fan surface composed of tessellated flow lobes by a narrow ice floored channel system the principle sedimentary facies associated with this fan include matrix supported diamictons laminated silts and fine sands the evolution of this fan and the likely end products after complete deglaciation are discussed and this paper contributes modern analogue data relevant to the interpretation of the pleistocene landform and sediment record

younger dryas glacial landsystems in north west scotland an assessment of modern analogues and palaeoclimatic implications abstract by explicitly linking process to form landsystem models developed in modern environments provide powerful tools for the reconstruction of past environments from the sedimentological and geomorphological record some landform characteristics however may originate by more than one process equifinality so although a particular depositional model may fit the data it is not necessarily the correct one here we critically examine the use of modern analogues to interpret glacial landforms focusing on hummocky moraine a distinctive landform association consisting of numerous sharp crested moraine mounds and ridge fragments which occurs on many valley floors in upland britain detailed studies of examples of younger dryas age in the north west highlands of scotland show that they represent ice contact fans which have been affected to varying degrees by ice push and subglacial deformation and that they formed at active oscillating ice margins the sedimentological data are inconsistent with an origin by englacial thrusting as has been proposed for similar moraines elsewhere in upland britain on the basis of morphological criteria comparison with modern glacial landsystems shows that although aspects of hummocky moraines in the study area have close modern counterparts none provides an exact analogue in all respects this may reflect the distinctive climate of western scotland during the younger dryas estimates of mean july temperatures in the younger dryas in scotland based on chironomid assemblages are c 8 c at sea level when combined with reconstructed equilibrium line altitudes for contemporaneous glaciers these estimates indicate mean annual precipitation totals in the range of 2358 337 mm yr 1 at sea level in nw scotland c 26 higher than present day values the implied heavy snowfall suggests that glaciers in western scotland during the younger dryas were of high activity type unlike modern glaciers in svalbard for example high glacier velocities and high winter precipitation would suppress permafrost development despite low mean annual temperatures the climatic environment also favoured rapid oscillations of glacier margins during both glacier build up and retreat phases climatic factors combined with the availability of large quantities of subglacial debris led to the development of distinctive glacial landsystems which may have no direct modern analogue

ice cored moraine degradation mapped and quantified using an unmanned aerial vehicle a case study from a polythermal glacier in svalbard ice cored lateral frontal moraines are common at the margins of receding high arctic valley glaciers but the preservation potential of these features within the landform record is unclear recent climatic amelioration provides an opportunity to study the morphological evolution of these landforms as they de ice this is important because high arctic glacial landsystems have been used as analogues for formerly glaciated areas in the mid latitudes this study uses sfm structure from motion photogrammetry and a combination of archive aerial and uav unmanned aerial vehicle derived imagery to investigate the degradation of an ice cored lateral frontal moraine at austre lovenbreen svalbard across the study area as a whole over an 11 year period the average depth of surface lowering was 1 75 0 89 m the frontal sections of the moraine showed low or undetectable rates of change spatially variable rates of surface lowering are associated with differences in the quantity of buried ice within the structure of the moraine morphological change was dominated by surface lowering with limited field evidence of degradation via back wastage this permits the moraine a greater degree of stability than previously observed at other sites in svalbard it is unclear whether the end point will be a fully stabilised ice cored moraine in equilibrium with its environment or an ice free lateral frontal moraine complex controls on geomorphological change e g topography and climate and the preservation potential of the lateral frontal moraine are discussed the methods used by this research also demonstrate the potential value of sfm photogrammetry and unmanned aerial vehicles for monitoring environmental change and are likely to have wider applications in other geoscientific sub disciplines

response of thermohaline circulation to freshwater forcing under present day and lgm conditions responses of the thermohaline circulation thc to freshwater forcing hosing in the subpolar north atlantic ocean under present day and the last glacial maximum lgm conditions are investigated using the national center for atmospheric research community climate system model versions 2 and 3 three sets of simulations are analyzed with each set including a control run and a freshwater hosing run the first two sets are under present day conditions with an open and closed bering strait the third one is under lgm conditions which has a closed bering strait results show that the thc nearly collapses in all three hosing runs when the freshwater forcing is turned on the full recovery of the thc however is at least a century earlier in the open bering strait run than the closed bering strait and lgm runs this is because the excessive freshwater is diverged almost equally toward north and south from the subpolar north atlantic when the bering strait is open a significant portion of the freshwater flowing northward into the arctic exits into the north pacific via a reversed bering strait throughflow which accelerates the thc recovery when the bering strait is closed this arctic to pacific transport is absent and freshwater can only be removed through the southern end of the north atlantic together with the surface freshwater excess due to precipitation evaporation river runoff and melting ice in the closed bering strait experiments after the hosing the removal of the excessive freshwater takes longer and this slows the recovery of the thc although the background conditions are quite different between the present day closed bering strait run and the lgm run the thc responds to the freshwater forcing added in the north atlantic in a very similar manner

response of the nordenskiold land spitsbergen glaciers grumantbreen habergbreen and dryadbreen to the climate warming after the little ice age

origin evolution and dynamic context of a neoglacial lateral frontal moraine at austre lovenbreen svalbard moraines marking the neoglacial limits in svalbard are commonly ice cored investigating the nature of this relict ice is important because it can aid our understanding of former glacier dynamics this paper examines the composition of the lateral frontal moraine associated with the neoglacial limit at austre lovenbreen and assesses the likely geomorphological evolution the moraine was investigated using ground penetrating radar gpr with context being provided by structural mapping of the glacier based on an oblique aerial image from 1936 and vertical aerial imagery from 2003 multiple up glacier dipping reflectors and syncline structures are found in the gpr surveys the reflectors are most clearly defined in lateral positions where the moraine is substantially composed of ice the frontal area of the moraine is dominantly composed of debris the core of the lateral part of the moraine is likely to consist of stacked sequences of basal ice that have been deformed by strong longitudinal compression the long term preservation potential of the ice dominated lateral moraine is negligible whereas the preservation of the debris dominated frontal moraine is high a glacier surface bulge identified on the 1936 aerial imagery provides evidence that austre lovenbreen has previously displayed surge activity although it is highly unlikely to do so in the near future in its current state this research shows the value of relict buried ice that is preserved in landforms to aiding our understanding of former glacier characteristics

svalbard glacier elevation changes and contribution to sea level rise 1 we compare satellite altimetry from the ice cloud and land elevation satellite icesat 2003 2007 to older topographic maps and digital elevation models 1965 1990 to calculate long term elevation changes of glaciers on the svalbard archipelago results indicate significant thinning at most glacier fronts with either slight thinning or thickening in the accumulation areas except for glaciers that surged which show thickening in the ablation area and thinning in the accumulation areas the most negative geodetic balances occur in the south and on glaciers that have surged while the least negative balances occur in the northeast and on glaciers in the quiescent phase of a surge cycle geodetic balances are related to latitude and to the dynamical behavior of the glacier the average volume change rate over the past 40 years for svalbard excluding austfonna and kvitoya is estimated to be 9 71 0 55 km3 yr 1 or 0 36 0 02 m yr 1 w equivalent for an annual contribution to global sea level rise of 0 026 mm yr 1 sea level equivalent

svalbard surge dynamics derived from geometric changes geometric changes on a sample of svalbard glaciers were studied using subtraction of repeat digital terrain models to determine early surge stage dynamics changes in surface features were also analyzed a number of new surges were found for glaciers not known to have surged previously the surge development could be followed through three stages of which the first two had not been previously described in svalbard the first two stages are mainly identified from glacier thickness changes and showed little visual evidence in stage 1 initial surface lowering was found in the upper part of the glacier followed by a thickening further down glacier in stage 2 stage 3 represents the period of well developed surge dynamics that is usually reported some surges ceased at stage 2 as a partial surge and never developed into a fully active surge these partial surges could be misinterpreted as rapid response to climate change the results of this study further support previous findings that the majority of svalbard glaciers are of surge type data archives have greatly facilitated the search for signs of surges and the recapturing of the course of events in this paper we present a number of new observations of svalbard surge type behaviour based on evidence from geometric changes and complemented by observations of newly developed crevasse fields two criteria are used to identify a surge either individually or in combination 1 mass displacement from the upper to the lower glacier part and 2 presence of new crevasse fields which indicate rapid or strong changes in stresses the aims of our study are to contribute to a more complementary picture and better understanding of the transition from build up stage via initial surge dynamics to the previously described mature stage where the changes are more pronounced we also investi gate whether all surges develop fully the implications of partial surges for interpretation of surface lowering related to varying climate conditions and finally the large spread in estimates for the number of surge type glaciers in svalbard

quantification of historical landscape change on the foreland of a receding polythermal glacier horbyebreen svalbard the assessment of multidecadal scale change in a polythermal glacial landsystem in the high arctic is facilitated by a quantitative approach that utilises time series of aerial photographs satellite images digital elevation models and field geomorphological mapping the resulting spatiotemporal analysis illustrates a transition from glacial to proglacial paraglacial conditions indicating that 1 the areal coverage of ice between the maximum lia extent and 2013 decreased from 29 35 to 16 07 km2 which is a reduction in the glacierized area in the catchment from 62 to 34 2 the ice volume loss in the proglacial area amounted to 214 9 3 million m3 which was attributed mostly to ablation of the glacier snout but to a lesser extent the degradation of ice cored landforms 3 the transition from areas formerly covered by glacier ice to ice cored moraines glacifluvial deposits and other landforms was the most intense in the period 1990 2013 4 two end member scenarios polythermal glacial landsystem domains evolve during glacier recession each one dictated by the volume of debris in englacial and supraglacial positions and include a subglacial surfaces limited englacial and supraglacial debris related to temperate basal ice and b ice cored lateral moraines and moraine mound complexes significant supraglacial debris accumulations related to marginal cold based ice an additional assemblage of geometric ridge networks discrete or linear englacial and supraglacial debris concentrations relates to crevasse and hydrofracture infill branching out from an esker complex and is indicative of either surging or later rapid release of pressurised meltwater from temperate to cold based parts of the former glacier snout

recent high arctic glacial sediment redistribution a process perspective using airborne lidar abstract progressive glacier thinning retreat and mass loss in the high arctic is increasingly exposing forefield sediments to processes of mobilisation and redistribution in this paper we quantify forefield sediment redistribution at midtre lovenbreen svalbard using repeat light detection and ranging lidar surveys conducted in 2003 and 2005 in combination with field based observations average surface lowering of the forefield over the observation period identified from lidar surveys is 0 05 ma 1 and two primary areas of sediment reworking are identified active fluvial incision of proglacial streams by 2 m and lateral moraine downwasting of similar magnitude multivariate analysis of fluvial and climatological field data indicates that observed forefield sediment mobilisation is driven primarily by discharge forcing but with contributions from thermoerosive processes and stochastic autogenic sediment supply during the period of observation disparity between sediment loss in forefield fluvial systems as calculated from lidar data 3000 4000 103 kg and monitoring of fluvial sediment load 1600 3500 103 kg suggests the likely presence of significant quantities of buried ice beneath a thick debris mantle as evidenced by field observations relatively uniform lowering of the moraine crest identified from our repeat lidar surveys indicates thermoerosion of an ice core however simple debris layer thickness modelling indicates an increase in variation of debris layer thickness at lower elevations providing support for the assertion that moraine disintegration is driven by complex combinations of both thermal and mechanical processes this study demonstrates the viability of using lidar in conjunction with field monitoring to better understand sedimentary deglaciation dynamics and processes and also highlights the significance of forefield areas in controlling the sediment yield from deglaciating catchments

a general model of paraglacial landscape response a unifying attribute of all forms of paraglacial response is that deglaciation results in the exposure of unstable or metastable sediment sources that are subsequently tapped by a wide variety of processes over a wide range of timescales the paraglacial period in different geomorphological contexts is therefore con ditioned by two variables glacially conditioned sediment release and rate of sediment reworking under steady state conditions the latter may be approximated by an exhaustion model in which sediment yield is related to the amount of remaining available sediment by a negative exponential function this model offers an approximation for the behaviour of primary paraglacial systems in which glacigenic sediment sources are not replenished the long term behaviour of secondary primarily uvial paraglacial systems in which sediment inputs include both in situ and reworked glacigenic sediment appears intrinsically more complex but consistent with an exhaustion model if initial sediment avai

two configurations of the western arctic shelfbreak current in summer abstractdata from a closely spaced array of moorings situated across the beaufort sea shelfbreak at 152 w are used to study the western arctic shelfbreak current with emphasis on its configuration during the summer season two dynamically distinct states of the current are revealed in the absence of wind with each lasting approximately one month the first is a surface intensified shelfbreak jet transporting warm and buoyant alaskan coastal water in late summer this is the eastward continuation of the alaskan coastal current it is both baroclinically and barotropically unstable and hence capable of forming the surface intensified warm core eddies observed in the southern beaufort sea the second configuration present during early summer is a bottom intensified shelfbreak current advecting weakly stratified chukchi summer water it is baroclinically unstable and likely forms the middepth warm core eddies present in the interior basin the mesoscale instabilities extract energy from the mean flow such

eddy contributions to the meridional transport of salt in the north atlantic 1 the meridional transport of salt in the atlantic ocean is an important process for climate controlling the stability of the meridional overturning circulation the contribution of transient eddies to this transport is quantified in an eddy resolving north atlantic model at 1 12 resolution natl12 and compared with lower resolution north atlantic and global 1 4 models in natl12 between 10 n and 40 n there is a volume loss by evaporation of 0 6 sverdrups sv the divergence of the eddy flux of salt normalized by a reference salinity of 34 8 is 0 2 sv over the region a significant fraction of the total air seawater exchange but it is compensated by an opposite convergent transport of salt by the mean flow so that the total transport of salt is small the compensation between eddy and mean salt transport is almost complete in a multicentury long global model experiment but less effective in natl12 because the short integration time does not allow the salt content to equilibrate and the model drift is large eddies arising from baroclinic instability contribute to the meridional salt transports at the northern and southern boundary of the subtropical gyre where they appear consistent with a lateral diffusion acting on the mean salinity gradient however the eddy transport of salt is the sum of two terms an advective contribution arising from the correlations of velocity and isopycnal thicknesses and a diffusion along isopycnals both components have the same amplitude at the southern boundary of the subtropical gyre while diffusion is dominant at the northern boundary

controlled moraines origins characteristics and palaeoglaciological implications abstract controlled moraines are supraglacial debris concentrations that become hummocky moraine upon de icing and possess clear linearity due to the inheritance of the former pattern of debris rich folia in the parent ice linearity is most striking wherever glacier ice cores still exist but it increasingly deteriorates with progressive melt out as a result moraine linearity has a low preservation potential in deglaciated terrains but hummocky moraine tracts previously interpreted as evidence of areal stagnation may instead record receding polythermal glacier margins in which debris rich ice was concentrated in frozen toe zones recent applications of modern glaciological analogues to palaeoglaciological reconstructions have implied that a controlled moraine development can be ascribed to a specific process e g englacial thrusting or supercooling and b controlled moraine preservation potential is good enough to imply the occurrence of the specific process in former glacier snouts e g ancient polythermal or supercooled snouts these assumptions are tested using case studies of controlled moraine construction in which a wide range of debris entrainment and debris rich ice thickening mechanisms are seen to produce the same geomorphic features polythermal conditions are crucial to the concentration of supraglacial debris and controlled moraines in glacier snouts via processes that are most effective at the glacier permafrost interface end moraines lie on a process form continuum constrained by basal thermal regime the morphological expression of englacial structures in controlled moraine ridges is most striking while the moraines retain ice cores but the final deposits landforms tend to consist of discontinuous transverse ridges with intervening hummocks preserving only a weak impression of the former englacial structure these are arranged in arcuate zones of hummocky moraine up to 2 km wide containing ice walled lake plains and lying down flow of streamlined landforms produced by warm based ice a variety of debris entrainment mechanisms can produce the same geomorphic signature spatial and temporal variability in process form relationships will lead to the sequential development of different types of end moraines during the recession of a glacier or ice sheet margin

glacier retreat and landform production on an overdeepened glacier foreland the debris charged glacial landsystem at kviarjokull iceland glacier recession and landform development in a debris charged glacial landsystem characterized by an overdeepening is quantified using digital photogrammetry digital elevation model dem construction and mapping of the icelandic glacier kviarjokull for the period 1945 2003 melting of ice cores is recorded by surface lowering rates of 0 8 m yr 1 1945 1964 0 3 m yr 1 1964 1980 0 015 m yr 1 1980 1998 and 0 044 m yr 1 1998 2003 the distribution preservation of pushed and stacked ice cored moraine complexes are determined by the location of the long term glacial drainage network in combination with retreat from the overdeepening into which glacifluvial sediment is being directed and where debris rich ice masses are being reworked and replaced by esker networks produced in englacial meltwater pathways that bypassed the overdeepening and connected to outwash fans prograding over the snout recent accelerated retreat of kviarjokull potentially due to increased mass balance sensitivity has made the snout highly unstable especially now that the overdeepening is being uncovered and the snout flooded by an expanding pro glacial and partially supraglacial lake this case study indicates that thick sequences of debris charged basal ice controlled moraine have a very low preservation potential but ice cored moraine complexes can develop into hummocky moraine belts in de glaciated terrains because they are related to the process of incremental stagnation which at kviarjokull has involved periodic switches from transport dominant to ablation dominant conditions glacier recession is therefore recorded temporally and spatially by two suites of landforms relating to two phases of landform production which are likely typical for glaciers occupying overdeepenings an early phase of active temperate recession recorded by push moraines and lateral moraines and unconfined pro glacial meltwater drainage and a later phase of incremental stagnation and pitted outwash head development initiated by the increasing topographic constraints of the latero frontal moraine arc and the increasing importance of the overdeepening as a depo centre copyright 2012 john wiley sons ltd

ice marginal dynamics during surge activity kuannersuit glacier disko island west greenland the kuannersuit glacier surged 11 km between 1995 and 1998 the surge resulted in the formation of an ice cored thrust moraine complex constructed by subglacial and proglacial glaciotectonic processes four main thrust zones are evident in the glacier snout area with phases of compressional folding and thrusting followed by hydrofracture in response to the build up of compressional stresses and the aquicludal nature of submarginal permafrost and naled various types of stratified debris rich ice facies occur within the marginal zone the first facies i comprises laterally continuous strata of ice with sorted sediment accumulations and is reworked and thrust naled ice the second is laterally discontinuous stratified debris rich ice with distinct tectonic structures and is derived through subglacial extensional deformation and localised regelation facies ii whilst the third type is characterised by reworked and brecciated ice associated with the reworking and entrainment of meteoric ice facies iii hydrofracture dykes and sills facies iv cross cut the marginal ice cored thrust moraines with their sub vertically frozen internal contact boundaries and sedimentary structures suggesting supercooling operated as high pressure evacuation of water occurred during thrusting but this is not related to the formation of basal stratified debris rich ice linear distributions of sorted fines transverse to ice flow and small stratified sediment ridges that vertically cross cut the ice surface up ice of the thrust zone relate to sediment migration along crevasse traces and fluvial infilling of crevasses from a palaeoglaciological viewpoint marginal glacier tectonics ice sediment content and sediment delivery mechanisms combine to control the development of this polythermal surge valley landsystem the bulldozing of proglacial sediments and the folding and thrusting of naled leads to the initial development of the outer zone of the moraine complex this becomes buried in bulldozed outwash sediment and well sorted fines through surface ablation of naled up ice of this the heavily thrust margin becomes buried in sediment melted out from basal debris rich ice and subglacial diamicts routed along thrusts these mechanisms combine to deliver sediment to supraglacial localities and promote the initial preservation of structurally controlled moraines through insulation and the later development of kettled dead ice terrain

determining paleoceanographic circulations with emphasis on the last glacial maximum the inference from radiocarbon and other data that the north atlantic ocean circulation during the last glacial maximum was reduced is examined because glacial periods are thought to be windier than non glacial ones a reduced circulation is difficult to rationalize a first step is to note that the circulation of mass is unlikely to correspond simply to the circulation of heat or freshwater salt by merely permitting an enhanced input of southern hemisphere water into the north atlantic one can accommodate significantly increased radiocarbon ages such an input is equally interpretable as owing to an increased mass circulation rather than a decreased one inferred estimates from paleo shear estimates in the florida current are re interpreted as producing an indeterminate net flow there determination of the paleocirculation rates is not simpler than the problem in the modern ocean it is fully three dimensional and requires an adequate data base to determine the mass flux rates

10be concentrations and the long term fate of particle reactive nuclides in five soil profiles from california concentration depth profiles of cosmic ray produced 10 be t 1 2 1 5m y have been measured by accelerator mass spectrometry in five soil profiles these measurements were made in an effort 1 to understand the retentivity of soil surfaces for particle reactive tracers depositing from the atmosphere on time scales of 10 4 10 6 years and 2 to explore the application of 10 be as a chronometer of geomorphic surface age the profiles sampled are from two wave cut terraces located near mendocino california a table mountain top and an alluvial fan both located near friant california the ages of the mendocino terraces are inferred to be 1 5 10 5 years based on amino stratigraphic correlations and models of terrace evolution those of the table mountain top and alluvial fan are 9 5 10 6 years and 6 0 10 5 years respectively based on k ar analyses all the surfaces sampled are nearly flat and exhibit few erosional features in addition to 10 be we measured 210 pb 239 240 pu and 7 be to ascertain the retentivity of the soils for particle reactive nuclides and to assess the present day delivery rate of nuclides from the atmosphere the 7 be inventory is 4 0 dpm cm 2 similar to those observed at nearby locations the inventories of 210 pb and pu isotopes conform to those predicted from model calculations and suggest that the soil surfaces sampled retain the entire burden of particle reactive nuclides delivered to them over short time scales 100 years the 10 be concentrations in the sample range between 0 2 and 7 10 8 atoms g soil and show strong correlations with leachable fe and or al the inventory of 10 be in the soil domain sampled is 1 2 orders of magnitude lower than that expected from the geological age of the surface and an average delivery rate of 10 be from the atmosphere 5 2 10 5 atoms cm 2 yr the low inventory of 10 be is attributed to its loss from the soil domain sampled by solution transport based on a simple model type calculation with a first order removal process for 10 be the residence time of 10 be in the soil domains sampled is determined to be of the order of 10 4 years the low residence time of 10 be in the soil domains sampled requires that it be found either deeper in the regolith or in ground waters in either case the application of 10 be as a chronometer of geomorphic surface age is severely constrained however the study of 10 be in soils provides the only entry into the long term 10 4 10 6 years behavior of particle reactive nuclides in soils and hence could be important for understanding the behavior of analogous nuclides introduced into soils by natural and anthropogenic processes

recent elevation changes of svalbard glaciers derived from icesat laser altimetry abstract we have tested three methods for estimating 2003 2008 elevation changes of svalbard glaciers from multi temporal icesat laser altimetry a linear interpolation of crossover points between ascending and descending tracks b projection of near repeat tracks onto common locations using digital elevation models dems and c least squares fitting of rigid planes to segments of repeat track data assuming a constant elevation change rate the two repeat track methods yield similar results and compare well to the more accurate but sparsely sampled crossover points most glacier regions in svalbard have experienced low elevation thinning combined with high elevation balance or thickening during 2003 2008 the geodetic mass balance excluding calving front retreat or advance of svalbard s 34 600 km2 glaciers is estimated to be 4 3 1 4 gt y 1 corresponding to an area averaged water equivalent w e balance of 0 12 0 04 m w e y 1 the largest ice losses have occurred in the west and south while northeastern spitsbergen and the austfonna ice cap have gained mass winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast our findings are consistent with in situ mass balance measurements from the same period confirming that repeat track satellite altimetry can be a valuable tool for monitoring short term elevation changes of arctic glaciers

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

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

paraglacial slope adjustment since the end of the last glacial maximum and its long lasting effects on secondary mass wasting processes hauser kaibling austria abstract this study indicates the possible long lasting impacts of deep seated gravitational slope deformation dgsd on erosional and mass movement processes dgsd features are common large scale landforms in the crystalline basement rocks of the central alps of austria inactive forms are related to paraglacial nonglacial processes directly conditioned by former glaciation and deglaciation rock slope adjustment processes acting after glacier retreat towards the end of the late glacial period the near surface metamorphic bedrock of dgsd features is generally disintegrated such rock type favours erosion and the formation of small landslides field data laboratory analyses aerial photographs and gis based terrain analyses are used to describe the different geomorphic effects of an extremely disintegrated rock slope the studied dgsd hauser kaibling 13 6 km2 is located in central austria during the last glacial maximum the adjacent valley glacier reached an altitude of approximately 1900 m a s l glacier retreat in combination with the unfavourable tectono metamorphic setting caused gravity induced stresses to act subsequent sediment build up in the main valley restabilised the slope linear erosion cut a number of gullies into the lower part of the dgsd calculated mean erosional denudation rates at incised valley sections range from 0 5 to 2 6 mm a 1 since deglaciation smaller active landslides on the sides of the steep gullies draining the dgsd contribute to high denudation rates active landsliding is favoured by i fragmented rock ii steep slopes iii supply of surface and subsurface water by rain and snowmelt and iv human impact debris flows and debris charged flood events occurred frequently in the past during such events material was transported from the unstable slopes to the populated alluvial fans thus knowledge about the spatial distribution and the stage of development of dgsds active and currently inactive provides an important basis for risk management measures