the role of the barents sea in the arctic climate system present global warming is amplified in the arctic and accompanied by unprecedented sea ice decline located along the main pathway of atlantic water entering the arctic the barents sea is the site of coupled feedback processes that are important for creating variability in the entire arctic air ice ocean system as warm atlantic water flows through the barents sea it loses heat to the arctic atmosphere warm periods like today are associated with high northward heat transport reduced arctic sea ice cover and high surface air temperatures the cooling of the atlantic inflow creates dense water sinking to great depths in the arctic basins and 60 of the arctic ocean carbon uptake is removed from the carbon saturated surface this way recently anomalously large ocean heat transport has reduced sea ice formation in the barents sea during winter the missing barents sea winter ice makes up a large part of observed winter arctic sea ice loss and in 2050 the barents sea is projected to be largely ice free throughout the year with 4 c summer warming in the formerly ice covered areas the heating of the barents atmosphere plays an important role both in arctic amplification and the arctic heat budget the heating also perturbs the large scale circulation through expansion of the siberian high northward with a possible link to recent continental wintertime cooling large air ice ocean variability is evident in proxy records of past climate conditions suggesting that the barents sea has had an important role in northern hemisphere climate for at least the last 2500 years

past glacial and interglacial conditions in the arctic ocean and marginal seas a review past changes in the arctic ocean and its marginal seas have been profound even during the last 10 000 years understanding these changes such as those occurring during the transition from glacial to interglacial climates are important for research on modern processes because this knowledge provides a framework and unique perspective in which to view the modern physical and biological processes this paper discusses our current understanding of past environmental change and processes relative to those currently in progress special emphasis is placed on the most recent transition from a glacial state to the modern interglacial conditions

central arctic surface ocean environment during the past 80 000 years stable oxygen and carbon isotope and sedimentological paleontological investigations supported by accelerator mass spectrometry 14 c datings were carried out on cores from north of 85 degrees n in the eastern central arctic ocean significant changes in accumulation rates provenance of ice rafted debris ird and planktic productivity over the past 80 000 years are documented during peak glacials i e oxygen isotope stages 4 and 2 the arctic ocean was covered by sea ice with decreased seasonal variation limiting planktic productivity and bulk sedimentation rates in early stage 3 and during termination i major deglaciations of the circum arctic regions caused lowered salinities and poor oxygenation of central arctic surface waters a meltwater spike and an associated ird peak dated to similar to 14 12 14 c ka can be traced over the southern eurasian basin of the arctic ocean this event was associated with the early and rapid deglaciation of the marine based barents sea ice sheet a separate termination ib meltwater event is most conspicuous in the central arctic and is associated with characteristic dolomitic carbonate ird this lithology suggests an origin of glacial ice from northern canada and northern greenland where lower paleozoic platform carbonates crop extensively out

thermal models of oceanic crustal accretion linking geophysical geological and petrological observations 1 models of oceanic crustal accretion should be able to reproduce both petrological and geological observations from ophiolites and geophysical observations from active spreading ridges we have developed thermal models of crustal accretion at fast spreading ridges that incorporate petrological variation and allow for a variable vertical distribution of crystallization including petrological variation has a major effect on the distribution of melt within the crust and the consequent interpretation of model results in terms of geophysical observables in particular the narrow melt lens imaged by seismic reflection surveys can be produced by the presence of large scale compositional stratification within the crust such as that observed in the oman ophiolite controlling the vertical distribution of crystallization allows a range of crustal accretion mechanisms to be tested including the many sills and gabbro glacier models both gabbro glacier and many sills models can broadly match the geophysical observations but the preferred model is a hybrid where the uppermost 25 or more of the lower crust forms in a gabbro glacier and the lowermost 25 or more of the lower crust forms by crystallization in situ the success of all models is dependent on the strength and distribution of hydrothermal cooling

holocene paleoceanography of the northwest passage canadian arctic archipelago abstract a series of cores box and piston were collected at 2 key locations in lancaster sound cores 2004 804 009 bc and pc and barrow strait cores 2005 804 004 bc and pc in the canadian arctic archipelago to document the evolution of sea surface conditions in the main axis of the northwest passage during the holocene time period reconstruction of sea surface parameters summer temperature and salinity duration of sea ice cover were estimated based on transfer functions using dinoflagellate cyst assemblages as proxy indicators the chronology of these cores is based on calibrated ams 14c dates 210pb analyses and correlations between paleomagnetic secular variations of the geomagnetic field and a predicted spherical harmonic model of the geomagnetic field cals7 k 2 our age models for both cores indicate that 009 pc spans the last 11 100 cal bp while 004 pc encompasses the last 10 800 cal bp calculated sedimentation rates are in the range of 43 140 cm kyr for core 009 pc and 15 118 cm kyr for core 004 pc allowing for a millennial time scale resolution in each core our results indicate relatively harsh conditions in lancaster sound between 10 800 and 9000 cal bp summer temperatures 2 c cooler than at present which we associate with the presence of active ice streams in northernmost baffin bay and a weak west greenland current this is followed by a warming trend up to 3 c higher than present that took place between 8500 and 5500 cal bp which we associate with the holocene thermal maximum and to a large scale atmospheric pattern such as the arctic oscillation operating at the millennial time scale this is concomitant with an increase in the relative abundance of phototrophic dinoflagellate cyst taxa a gradual cooling of sea surface temperature and increased sea ice follow this from 5500 cal bp until the modern period in barrow strait harsh sea surface conditions prevailed from 11 100 to 5500 cal bp with summer temperatures as low as 4 c cooler than at present the warming trend occurred later in this region between 5500 and 1000 cal bp after which a gradual cooling is observed until the modern period the apparent shift or opposite warming trends between lancaster sound and barrow strait after 5500 cal bp could be the result of a change in atmospheric circulation patterns related to a possible shift in the ao mode from ao to ao comparison of ice core 18o record from devon island ice cap and the reconstructed sea surface temperature from core 009 pc suggests a strong atmospheric oceanic coupling throughout the holocene in this area

stages in gully evolution and self organized criticality the process of gully erosion at the active stage is far from equilibrium rather the gully shows the characteristics of a self organizing system that is close to crisis this qualitative description is similar to the understanding of open dynamic systems at a state of selforganized criticality soc we tried to find the quantitative attributes of soc in numerical simulations of gully evolution with a dynamic gully erosion model three scenarios were used 1 gully evolution is controlled by initial topography and texture when the discharge and base level are constant 2 discharge is constant and the base level lowers over time 3 the base level is constant and the discharge changes naturally the results of numerical simulations of gully evolution are consistent with the expectations of the soc theory under the first scenario when the gully was at the initial active stage of evolution the system showed all the soc attributes a fractal long profile a red noise spectrum and the power law frequency magnitude relationship fmr with gully stabilization the system had lost soc behaviour and became non fractal with a blue noise spectrum and exponential fmr for this scenario soc criteria can be used to find the boundary between active and stable states of gully evolution simulations under the second scenario showed that the riverbed incision made the active stage of the gully evolution with all soc attributes much longer than with a stable base level simulation under the third scenario with variable discharge with the elements of soc showed that the soc attributes of the hydrological system could be induced on the landform system while the gully had evidently reached the stable stage the process of gully volume change still indicated active stage soc attributes therefore some landform systems can really be in the soc stage which can diagnose their activity others only show soc attributes induced by climatic or hydrologic systems copyright 2006 john wiley sons ltd

middle to late pleistocene arctic paleoceanographic changes based on sedimentary records from mendeleev ridge and makarov basin abstract three sediment cores from the makarov basin and mendeleev ridge off the siberian margin were analyzed for a number of litho bio and magnetostratigraphic proxies correlation to previously studied arctic records from mendeleev to lomonosov ridges enables paleoceanographic reconstructions for the middle to late pleistocene estimated 0 8 ma on orbital time scales cyclic changes in lithology corroborated by multiple stratigraphic constraints were tuned to global climate variations based on the manganese content that increases during interglacials while calcium and zircon were used as proxies for the laurentide and eurasian ice sheet inputs the combined evaluation of glacial and interglacial proxy variabilities provides a coherent picture of the western arctic ocean development in the pleistocene we suggest that major cyclic changes were driven by summer processes such as sea ice retreat and enhanced biological production vs suppressed ice melt in warmer and colder summers respectively a potential link to low latitudes via atmospheric moisture and heat transport is indicated by similarities in the western arctic ocean and east asian monsoon records long term cooling is signified by biogenic proxies related to sea ice expansion over the western arctic ocean with step changes at mis 11 and 7 0 4 and 0 2 0 3 ma this transition also features better fossil preservation indicating less corrosive oxidative bottom waters probably resulting from a decrease in organic export production and or weakening of bottom water ventilation under perennial sea ice the latter was possibly enhanced by atmospheric cooling and increased meltwater fluxes with the growth of circum arctic ice sheets

evaluation of different machine learning models for predicting and mapping the susceptibility of gully erosion abstract gully erosion constitutes a serious problem for land degradation in a wide range of environments the main objective of this research was to compare the performance of seven state of the art machine learning models svm with four kernel types bp ann rf and brt to model the occurrence of gully erosion in the kashkan poldokhtar watershed iran in the first step a gully inventory map consisting of 65 gully polygons was prepared through field surveys three different sample data sets s1 s2 and s3 including both positive and negative cells 70 for training and 30 for validation were randomly prepared to evaluate the robustness of the models to model the gully erosion susceptibility 12 geo environmental factors were selected as predictors finally the goodness of fit and prediction skill of the models were evaluated by different criteria including efficiency percent kappa coefficient and the area under the roc curves auc in terms of accuracy the rf rbf svm brt and p svm models performed excellently both in the degree of fitting and in predictive performance auc values well above 0 9 which resulted in accurate predictions therefore these models can be used in other gully erosion studies as they are capable of rapidly producing accurate and robust gully erosion susceptibility maps gesms for decision making and soil and water management practices furthermore it was found that performance of rf and rbf svm for modelling gully erosion occurrence is quite stable when the learning and validation samples are changed

is the central arctic ocean a sediment starved basin abstract numerous short sediment cores have been retrieved from the central arctic ocean many of which have been assigned sedimentation rates on the order of mm ka implying that the arctic basin was starved of sediments during plio pleistocene times a review of both shorter term sedimentation rates through analysis of available sediment core data and longer term sedimentation rates through estimates of total sediment thickness and bedrock age suggests that cm ka scale rates are pervasive in the central arctic ocean this is not surprising considering the physiographic setting of the arctic ocean being a small land locked basin since its initial opening during early cretaceous times we thus conclude that the central arctic ocean has not been a sediment starved basin either during plio pleistocene times or during pre pliocene times rigorous chronstratigraphic analysis permits correlation of sediment cores over a distance of 2600 km from the northwestern amerasia basin to the northwestern eurasia basin via the lomonosov ridge using paleomagnetic biostratigraphic and cyclostratigraphic data

geomorphic changes in a complex gully system measured from sequential digital elevation models and implications for management high resolution digital elevation models dems were derived from sequential aerial photography of an active uvio mass movement gully complex in new zealand s north island east coast region to measure geomorphic changes over approximately one year the gully showed a complex behaviour combining uvial and mass movement erosion deposition and reworking of materials stored in an active debris fan during the measurement period 5200 1700 m3 of material were eroded from the 8 7 ha gully complex and 670 180 m3 from the 0 8 ha depositional fan giving a total of 5870 1710 m3 for the entire gully complex fan system the results provide a high resolution description of gully behaviour over a short time period and also demonstrate that mass movement slumping and debris ows accounted for almost 90 per cent 4660 200 m3 of the sediment generated this erosional response is described in terms of gully evolution by comparing the gully complex to other systems in the region in various stages of development the effect of gully evolution on geomorphic coupling between the gully complex and channel system is described and coupling is also shown to vary with the magnitude and frequency of rainfall events from a land management perspective the success of strategies such as tree planting to mitigate against gully erosion depends on the stage of gully development particularly on whether or not mass movement erosion has begun in contrast to gully rehabilitation efforts elsewhere basin wide afforestation in the early stages of gully incision is favoured over riparian planting given that mass movement assisted by excessive groundwater pressure is the main process leading to uncontrollable gully expansion to protect land effectively against continuing gully erosion of headwater catchments and resulting downstream aggradation it is necessary for land managers to understand the spatial and temporal variability of gully development fully so that mitigation efforts can be targeted appropriately copyright 2003 john wiley sons ltd

the younger dryas from whence the fresh water 1 oxygen isotopic records of meltwater outflow and records of sea level change do not support the idea that fresh waters derived solely from the melting of northern hemisphere ice sheets was likely to have stabilized the upper layers of the north atlantic ocean and prevented deep convection during the younger dryas yet there are paleoceanographic indicators that point to a pause in the formation of north atlantic deep water during the younger dryas this apparent conflict in evidence may be resolved by the existence of large relatively thick tabular icebergs that spilled out of the arctic and into the norwegian greenland sea and north atlantic the melting of large icebergs would have no impact on sea level but combined with meltwater runoff would provide enough fresh water to cap the north atlantic the timing of the start and the end of the younger dryas however may not have been directly related to freshwater supply

controls on 231pa and 230th in the arctic ocean the distributions of 230th and 231pa in the arctic ocean are not well understood in order to examine the arctic 231pa 230th system and therefore to shed light on the future use of arctic sedimentary 231pa 230th we developed a 2 d scavenging model modified from an atlantic model tuned with reasonable parameters that are consistent with eurasian basin geographic settings the model can reproduce most of the features of the 230th and 231pa water column profiles as well as the sedimentary 231pa 230th distribution patterns and suggests that the sedimentary 231pa 230th in the eurasian basin is mainly controlled by the deep water circulation in our attempt to reproduce the sedimentary 231pa 230th patterns during the last glacial we found that circulation strength in the eurasian basin at shallower depths may have been stronger than today

the younger dryas and the sea of ancient ice we propose that prior to the younger dryas period the arctic ocean supported extremely thick multi year fast ice overlain by superimposed ice and firn we re introduce the historical term paleocrystic ice to describe this the ice was independent of continental glacier ice and formed a massive floating body trapped within the almost closed arctic basin when sea level was lower during the last glacial maximum as sea level rose and the barents sea shelf became deglaciated the volume of warm atlantic water entering the arctic ocean increased as did the corresponding egress driving the paleocrystic ice towards fram strait new evidence shows that bering strait was resubmerged around the same time providing further dynamical forcing of the ice as the transpolar drift became established additional freshwater entered the arctic basin from siberia and north america from proglacial lakes and meltwater derived from the laurentide ice sheet collectively these forces drove large volumes of thick paleocrystic ice and relatively fresh water from the arctic ocean into the greenland sea shutting down deepwater formation and creating conditions conducive for extensive sea ice to form and persist as far south as 60 n we propose that the forcing responsible for the younger dryas cold episode was thus the result of extremely thick sea ice being driven from the arctic ocean dampening or shutting off the thermohaline circulation as sea level rose and atlantic and pacific waters entered the arctic basin this hypothesis focuses attention on the potential role of arctic sea ice in causing the younger dryas episode but does not preclude other factors that may also have played a role

assessment of gully erosion in eastern ethiopia using photogrammetric techniques abstract eastern ethiopia is severely affected by soil erosion as it is revealed by the commonly occurring deep and wide gullies these gullies are dynamically expanding into agricultural lands at an alarming rate they are also the chief sources of sediment causing siltation of lakes that are valuable sources of both drinking and irrigation water in the alemaya and harar areas a quantitative assessment of gully dynamics and the associated soil loss and a prognosis of areas susceptible to further gullying were deemed crucial aerial photographs from two different dates 1966 and 1996 with approximate scales of 1 45 000 were used to study the development and dynamics of gullies as indicated by volume changes between the two dates they were digitized at a pixel size of 20 m digital elevation models dem with grid widths of 20 and 2 m were derived from stereo image pairs separately gully breaklines and borderlines were measured for the identified gully systems gully profiles were positioned at regular intervals of 20 m along the gully length giving rise to gully sections that are portions of a gully between neighbouring profiles gully volume was computed for every gully section soil loss was estimated from the computed gully volumes using soil bulk density it showed that soil loss per unit of gully surface is very high 1 7 tons m 2 of gully surface over the 30 years time period indicating the severity of gully erosion in the subcatchment there was significant agreement between breakline measured and field measured gully depth and width for selected points this is an indication of the potential of the method for reliable gully volume estimation and hence quantification of soil loss due to gully erosion the possibility of predicting hill slope areas susceptible to further gullying based on the topographic attributes such as specific contributing area and local slope from an interpolated detailed dem with 2 m resolution was tested it was found that wetness index alone or a combination of the wetness index and the compound topographic index at the threshold values established in literature would give better results as viewed from better connectivity of flow lines and higher conformity of the predicted susceptible areas to natural gully headcut and expansion in a landscape reality

cooling of the west spitsbergen current isopycnal diffusion by topographic vorticity waves 1 we investigate the heat budget in the west spitsbergen current on the basis of theoretical considerations and current meter data across the slope at 78 83 n between september 1997 and september 1998 the dispersion relation for topographically trapped waves along the west spitsbergen slope with a barotropic along slope velocity is calculated by use of an idealized numerical model signal processing and coherence calculations of the current meter data show that barotropic vorticity waves with enhanced energy at the diurnal period exist along the slope a wave length of 32 km is given by the dispersion relation for the 24 hour period and a corresponding second mode with a 35 hour period coherence calculations and complex demodulations of the current meter time series confirm the spatial and temporal variations given by the dispersion relation the eddy characteristics of the first two modes are used to estimate the heat loss of the warm core of the west spitsbergen current by isopycnal eddy diffusion we present the first isopycnal heat loss estimates obtained through dynamical considerations of the west spitsbergen current and compare them with earlier diagnostic estimates for the mean heat loss in the subsurface layers within the standard errors we estimate the heat flux to be o 1000 w m2 throughout the year except for the summer months june july if the 9798 heat flux time series are representative for the subsurface layer between 100 and 500 m depth the heat loss is on the same order of magnitude as the mean winter value of 1050 w m2 from earlier diagnostic estimates

last glacial maximum and deglaciation of devon island arctic canada support for an innuitian ice sheet abstract the extent and origin of quarternary glaciers in the queen elizabeth islands of arctic canada especially during the last glacial maximum lgm has been debated for well over a century no consensus has yet emerged and the spectrum of interpretations within the last decade is the broadest ever the glacial geology of devon island strongly supports the late wisconsinan innuitian ice sheet hypothesis during lgm the southeastern part of the queen elizabeth islands was covered by an ice sheet flowing from a centre or a divide centrally located in the archipelago another ice divide extended from the centre across devon island flow from the innuitian centre and convergent flow from devon island and probably also from cornwallis and bathurst islands sustained an ice stream in wellington channel ice was locally advancing to its lgm limit about 23 ka bp recession in the vicinity of the present coastline was underway by 10 ka bp and final ice remnants west of the present devon ice cap vanished about 8 ka bp the island bears the same two part landscape zonation as do other islands and peninsulas in the region these reflect a cold based core and warm based periphery at lgm

early diagenesis and accumulation of redox sensitive elements in east siberian arctic shelves abstract the arctic shelf makes up half of the area within the arctic ocean it plays an important role in the global carbon cycle whilst its part in the recycling process of redox sensitive elements rses is still not clear this study has selected nine sediment cores 30 to 40 cm in length covering a wide area over the east siberian arctic shelves esas and analyzed a suite of rses s mn mo u v cd in the sediments along with al fe total organic carbon toc grain size and sedimentation rate the redox environment in surface sediments was clearly divided based on the s and mn contents of the cores ranging from being more oxidized on the western east siberian sea shelf to more reduced on the chukchi sea shelf toc also showed an increasing trend eastward in the study region statistically significant correlations were found between cd and s v and fe mo and mn and u and toc implying their close relationships during early diagenetic processes at the sediment water interface across the study area authigenic accumulation occurred for all rses except mn the estimated authigenic accumulation fluxes for mo u v and cd over the entire esas are 0 21 0 09 0 086 0 043 11 0 9 2 and 0 019 0 014 108 mol y 1 respectively which are comparable to values reported in suboxic marginal sediments for mo u and cd but exceptionally high for v although the sampling resolution was coarse and there are uncertainties in the sedimentation rates and detrital background values of v we propose the authigenic accumulation flux for v on the broad and shallow esas may be a significant but missing sink term for the global v cycle

paleoglaciology s grand unsolved problem the paleoglaciological concept that during the pleistocene glacial hemi cycles a super large structurally complex ice sheet developed in the arctic and behaved as a single dynamic system as the antarctic ice sheet does today has not yet been subjected to concerted studies designed to test the predictions of this concept yet it may hold the keys to solutions of major problems of paleoglaciology to understanding climate and sea level changes the russian arctic is the least known region exposed to paleoglaciation by a hypothetical arctic ice sheet but now it is more open to testing the concept implementation of these tests is a chaillenging task as the region is extensive and the available data are controversial well planned and coordinated field projects are needed today as well as broad discussion of the known evidence existing interpretations and new field results here we present the known evidence for paleoglaciation of the russian arctic continental shelf and reconstruct possible marine ice sheets that could have produced that evidence

a contemporary sediment and organic carbon budget for the kara sea shelf siberia it has recently been realized that the arctic undergoes drastic changes probably resulting from global change induced processes this acts on the cycling of matter and on biogenic elements in the arctic ocean having feedback mechanisms with the global climate for example by interacting with atmospheric trace gas concentration a contemporary budget for biogenic elements as well as suspended matter for the arctic ocean as a baseline for comparison with effects of further global change is thus needed available budgets are based on the late holocene sedimentary record and are therefore quiet different from the present which has already been affected by the intense anthropogenic activity of the last centuries we calculated a contemporary suspended matter and organic carbon budget for the kara sea utilizing the numerous available data from the recent literature as well as our own data from russian german sirro siberian river run off expeditions for calculation of the budgets we used a multi box model to simplify the kara sea shelf and estuary system input was assumed to comprise riverine and eolian input as well as coastal erosion output was assumed to consist of sedimentation and export to the arctic ocean exchange with the adjacent seas was considered in our budget and primary production as well as recycling of organic material was taken into account according to our calculations about 18 510 6 ty r 1 of sediments and 0 3710 6 t yr 1 of organic carbon are buried in the estuaries whereas 20 910 6 ty r 1 sediment and 0 3110 6 ty r 1 organic carbon are buried on the shelf most sources and sinks of our organic carbon budget of the kara sea are in the same order of magnitude making it a region very sensitive to further changes d 2005 elsevier b v all rights reserved

using 137cs technique to investigate the spatial distribution of erosion and deposition regimes for a small catchment in the black soil region northeast china abstract researches on the spatial distribution of erosion and deposition regimes are important to understand soil erosion mechanism and effectively implement soil and water conservation measures within watersheds however traditional monitoring techniques provide limited information for that at the catchment scale based on the 137cs tracer and gis technology this study clarified the spatial distribution of erosion and deposition regimes within a small catchment dongshan catchment which has typical representativeness in the black soil region of northeast china the local 137cs reference inventory was 2378 4 bq m 2 and the summit of convex slope was preferably taken as the reference site when undisturbed sites were inexistence in the study area estimates of soil redistribution rates derived from 137cs measurement ranged from 35 89 to 53 63 t ha 1 yr 1 with about 95 65 of the net soil loss coming from the slope surface the average soil erosion intensity within the catchment was 4 54 t ha 1 yr 1 and it was 1 51 t ha 1 yr 1 in the gully area but both were above the tolerance erosion rate in the black soil region of northeast china further gully head made the leading contribution to the gully erosion when the geographical location shifted from the upstream to the middle stream then to the down stream of the catchment the mainly erosion regimes changed from detachment dominant to coexisting detachment and deposition dominant and then deposition dominant regime along the slope length erosion rate increased from the summit to the shoulder and back slopes and then decreased at the foot slope while at the toe of slope deposition occurred however erosion pattern along the slope was affected by the slope shape for the convex slope the most severe erosion location was the back of slope while for the concave slope it was the shoulder of slope erosion rate of the summit and foot slope for the convex slope was 0 5 and 1 97 times that of the concave slope

the cycle of instability stress release and fissure flow as controls on gully head retreat gully head and wall retreat has commonly been attributed to fluvial scour and head collapse as a result of soil saturation sapping or piping the empirical evidence to substantiate these conceptual models is sparse however and often contradictory this paper explores the hydrological and mechanical controls on gully head and wall stability by modelling the hydrology stability and elastic deformation of a marl gully complex in granada province south east spain the hydrological and slope stability simulations show that saturated conditions can be reached only where preferential fissure flow channels water from tension cracks into the base of the gully head and that vertical or subvertical heads will be stable unless saturation is achieved owing to the high unsaturated strengths of marl measured in this research failure in unsaturated conditions is possible only where the gully head wall is significantly undercut head retreat thus requires the formation of either a tension crack or an undercut hollow finite element stress analysis of eroding slopes reveals a build up of shear stress at the gully head base and a second stress anomaly just upslope of the head wall although tension cracks on gully heads have often been attributed to slope unloading this research provides strong evidence that the so called sapping hollow commonly found in the gully headwall base is also a function of stress release although further research is needed it seems possible that pop out failures in river channels may be caused by the same process the hydrological analysis shows that once a tension crack has developed throughflow velocity in the gully headwall will increase by an order of magnitude promoting piping and enlargement of this weakened area it is therefore possible to envisage a cycle of gully expansion in which erosion channel incision or human action unloads the slope below a gully head leading to stress patterns that account for the tension crack and a stress release hollow the tension crack promotes faster throughflow encouraging hollow enlargement and piping which undercut the gully head the tension crack permits the development of positive pore water pressures behind the gully head leading either to failure or contributing to toppling finally the debris may be eroded by fluvial action unloading a new section of slope and completing the cycle of gully head retreat copyright 2001 john wiley sons ltd

high resolution gully erosion and sedimentation processes and land use changes since the bronze age and future trajectories in the kazimierz dolny area naleczow plateau se poland abstract this paper presents the results of 40 years of research on the gully system in the doly podmularskie catchment 0 35 km in size which is situated in the south western part of the loess covered naleczow plateau in se poland topographic stratigraphic and pedologic investigations and monitoring of a tributary gully gully area 0 7 ha catchment 2 5 ha were combined with historical archaeological and palaeoecological records the results reveal a long and complex history in terms of the temporal and spatial extent and the impact of land use on gully erosion and the long term feed back mechanisms between land use changes and natural processes since the end of the pleistocene phases of gully erosion and subsequent filling occurred in the bronze age and around the 10th to 11th centuries the most severe deepening and expansion of the gully took place in the 17th century the results also show that field structures and land use intensity had a significant influence on the frequency and magnitude of run off soil erosion piping and landslide events the last significant erosion phase started in the mid 19th century with renewed headward retreat and down cutting within older gully fills today most of the catchment is either forested or the land is covered in berry shrubs in the future the area will continue to produce sediments because of the steep slopes and because there are still areas of bare soil with a low resistance to erosion a legacy from past land uses which will remain a factor affecting soil erosion and sedimentation processes in the future this study is an example of how important it is to observe and understand slow geomorphologic processes and rare extreme events in the light of land use changes when investigating long term human environment interactions

using reservoir deposits to quantify the source contributions to the sediment yield in the black soil region northeast china based on the fingerprinting technique abstract identifying patterns of sediment dynamics is an important aspect of understanding soil erosion processes and developing reasonable management strategies to address environmental problems and assess the ecological functions of soil and water conservation measures in this study the sediment fingerprinting technique was applied in order to quantify the relative contributions of sediment to the hebei catchment in the black soil region of northeast china with the aim of determining the response of soil erosion to recent changes in land management within an area of approximately 28 km2 three potential sediment sources were identified based on land use types they included cultivated topsoil uncultivated topsoil and gullies a total of 69 sediment source samples were collected from potential sediment sources from 27 sampling sites for cultivated topsoil 18 sampling sites for uncultivated topsoil and 24 sampling sites for gullies six uniformly spatially distributed sediment cores were sampled from the liudui reservoir the walling collins model was optimized using a genetic algorithm combined with the latin hypercube sampling procedure the results indicated that cultivated topsoil and gullies were the primary sediment provenances and that gully erosion is as important as rill and interrill erosion according to the mean sediment contributions of the six deposited sediment cores the sediment contribution from cultivated topsoil was 50 6 ranging from 34 4 to 63 7 whereas gullies contributed 42 9 ranging from 30 1 to 57 8 however the sediment from uncultivated topsoil mainly containing forest and grassland contributed only 6 5 with a range of 5 0 to 7 8 over the last few decades with a mean absolute fit of 0 95 this indicated that caution is needed in when using only a single core to provide results for a reservoir over the 1976 2016 period rill and interrill erosion showed a general decreasing trend whereas gully erosion showed an increasing trend according to the sedimentation depth and time marks based on the 137cs and d50 peak horizon and decayed vegetation layer in the six sediment cores sedimentation rates during 1976 1998 and 1999 2016 were 1 6 cm yr 1 14 4 kg m 2 yr 1 and 0 9 cm yr 1 7 6 kg m 2 yr 1 respectively for the entire time series 1976 2016 the sedimentation rate was 1 2 cm yr 1 10 7 kg m 2 yr 1 a good correlation exists between the distance from the reservoir entrance and sediment contribution mean annual sedimentation rate r2 0 68 except uncultivated topsoil

testing the water hypothesis quantitative morphological analysis of terrestrial and martian mid latitude gullies abstract although martian gullies resemble terrestrial counterparts two conflicting hypotheses exist for their formation still invoke fluvial processes on the one hand or lubricated co 2 flows on the other in this work we compared the quantitative morphology of terrestrial gullies known to have formed by liquid water and mid latitude martian gullies in the martian southern hemisphere we also compared these results with measurements of martian dry ravines adjacent to the gullies our results show a similarity between martian and terrestrial gully formation supporting the hypothesis that liquid water was involved in their erosion our results show dry ravines differ morphologically from gullies further suggesting fluidised flows as a likely origin of the latter variations in the relationships across various terrestrial and martian gullies indicate the significance of local environmental and geological conditions our work supports the idea that martian gullies may not have been formed by just one single process but may have evolved through a more complex interaction of processes and environment

geochemical and geophysical evidence of methane release over the east siberian arctic shelf the east siberian arctic shelf esas which includes the laptev sea the east siberian sea and the russian part of the chukchi sea has not been considered to be a methane ch 4 source to hydrosphere or atmosphere because subsea permafrost which underlies most of the esas was believed first not to be conducive to methanogenesis and second to act as an impermeable lid preventing ch 4 escape through the seabed here recent observational data obtained during summer 2005 2006 and winter 2007 expeditions indicate the ubiquitous presence of elevated dissolved ch 4 and an elevated atmospheric ch 4 mixing ratio the ch 4 data were also analyzed together with high resolution seismic hrs data obtained by means of a sonic m 141 system consisting of a high resolution profiler and side scan sonar mounted in a towed fish during the transdrift x expedition 2004 onboard the r v yakov smimitskiy results show anomalously high concentrations of dissolved ch 4 up to 5 m and an episodically nongradually increasing atmospheric mixing ratio of ch 4 up to 8 2 ppm in some areas of the esas a most likely source is year round ch 4 release through taliks columns of thawed sediments within permafrost from seabed ch 4 reservoirs such as shallow hydrates and geological sources such releases occur not only within the areas underlain by fault zones but also outside of them this points to permafrost s failure to further preserve ch 4 deposits in the esas the total amount of carbon preserved within the esas as organic matter and ready to release ch 4 from seabed deposits is predicted to be 1400 gt release of only a small fraction of this reservoir which was sealed with impermeable permafrost for thousands of years would significantly alter the annual ch 4 budget and have global implications because the shallowness of the esas allows the majority of ch 4 to pass through the water column and escape to the atmosphere

using 137cs technique to quantify soil erosion and deposition rates in an agricultural catchment in the black soil region northeast china article i nfo soil erosion significantly affects the productive black soil region in northeast china quantification of the soil erosion is necessary for designing efficient degradation control strategies 137 cs measurements undertaken on 61 sampling points collected within a 28 5 ha agricultural catchment in the black soil region of northeast china were used to establish the magnitude and spatial pattern of soil redistribution rates as well as sediment budget within the catchment estimated soil redistribution rates using the mass balance model 2 mbm2 ranged from 56 8 to 171 4 t ha 1 yr 1 for the sampling points that were verified by means of both runoff plot data and pedological investigation erosion generally occurred behind the shelterbelts especially in the ephemeral gully susceptibleareas while deposition mainlyoccurred along the shelterbelts and atthe catchment outlet inthestudycatchment 69 oftheerodedsedimentscamefromtheslopes and31 theephemeral gullies sedimentsdepositedalongthe shelterbeltsatarateofca 78 t yr 1 andca 33 t yr 1 atthecatchmentoutlet the gross soil loss rate for the catchment was 4 4 t ha 1 yr 1 with a sediment delivery ratio of 53 the mean rate of 14 5 t ha 1 yr 1 in the erosion areas was much higher than the tolerable value suggesting that effective soilconservationmeasuresare urgentlyrequiredtoreducethesevere black soillossforsustainable management of the soil resource

experimental study on the development of collapse of overhanging layers of gully in yuanmou valley china the collapse of overhanging layers of the heads and sidewalls of gullies accelerates gully development thus the development features of the collapse of overhanging layers must be understood in this study the process of collapse of overhanging layers in man made soil bodies containing different soil layers was investigated by flow scouring experiments a soil body composed of a lower sandy layer and an upper layer of clay soil was evaluated and a field soil profile was modelled in a test tank with an open side the results revealed that the occurrence of the collapse of overhanging layers could be attributed to the development of a scour hole in the open side the greater the flow rate the lower the proportion of on wall runoff on wall runoff played a more important role in the development of scour holes than off wall runoff the shape of scour holes formed under different flow conditions was similar also the scour hole is not apparently related to the flow rate implicating that the collapse is more dependent on rainfall runoff time rather than rainfall runoff intensity in the studied region this is substantially different from other soil erosion types that are closely related to rainfall intensity moreover the maximum length s l and height s h of the scour holes increased gradually with accumulated flow and scouring time in addition the height of the hanging soil body h d gradually decreased and a linear relationship between sl and hd was observed h d 0 359 s l 117 3 r 2 0 861 p 0 003 after the seventh scour test the scour hole triggered the collapse of the upper clay layer the cantilever model was modified to predict the stability of the overhanging soil body it provided a satisfactory explanation of the static balance of the weight of the soil as well as the tensile strength after the seventh scour test the measured and predicted threshold values of h d s l and t c were nearly equal and a stable balance state was attained however when a 10 cm tension crack appeared in the overhanging soil body a stable balance state was obtained during the sixth scour test c 2013 elsevier b v all rights reserved

glacial geomorphology of the central arctic ocean the chukchi borderland and the lomonosov ridge the last decade of geophysical seafloor mapping in the arctic ocean from nuclear submarines and icebreakers reveals a wide variety of glaciogenic geomorphic features at water depths reaching 1000 in these findings provide new and intriguing insights into the quaternary glacial history of the northern hemisphere here we integrate multi and single beam bathymetric data chirp sonar profiles and sidescan images from the chukchi borderland and lomonosov ridge to perform a comparative morphological seafloor study this investigation aims to elucidate the nature and provenance of ice masses that impacted the arctic ocean sea floor during the quaternary mapped glaciogenic bedforms include iceberg keel scours most abundant at water depths shallower than similar to 350 400 m flutes and megascale glacial lineations extending as deep as similar to 1000 m below the present sea level small drumlin like features and morainic ridges and grounding zone wedges the combination of these features indicates that very large glacial ice masses extended into the central arctic ocean from surrounding north american and eurasian ice sheets several times during the quaternary ice shelves occupied large parts of the arctic ocean during glacial maxima and ice rises were formed over the chukchi borderland and portions of the lomonosov ridge more geophysical and sediment core data combined with modeling experiments are needed to reconstruct the timing and patterns of these events

an arctic ocean ice shelf during mis 6 constrained by new geophysical and geological data the hypothesis of floating ice shelves covering the arctic ocean during glacial periods was developed in the 1970s in its most extreme form this theory involved a 1000 m thick continuous ice shelf covering the arctic ocean during quaternary glacial maxima including the last glacial maximum lgm while recent observations clearly demonstrate deep ice grounding events in the central arctic ocean the ice shelf hypothesis has been difficult to evaluate due to a lack of information from key areas with severe sea ice conditions here we present new data from previously inaccessible unmapped areas that constrain the spatial extent and timing of marine ice sheets during past glacials these data include multibeam swath bathymetry and subbottom profiles portraying glaciogenic features on the chukchi borderland southern lomonosov ridge north of greenland morris jesup rise and yermak plateau sediment cores from the mapped areas provide age constraints on the glaciogenic features combining these new geophysical and geological data with earlier results suggests that an especially extensive marine ice sheet complex including an ice shelf existed in the amerasian arctic ocean during marine isotope stage mis 6 from a conceptual oceanographic model we speculate that the cold halocline of the polar surface water may have extended to deeper water depths during mis 6 inhibiting the warm atlantic water from reaching the amerasian arctic ocean and thus creating favorable conditions for ice shelf development the hypothesis of a continuous 1000 m thick ice shelf is rejected because our mapping results show that several areas in the central arctic ocean substantially shallower than 1000 m water depth are free from glacial influence on the seafloor

an arctic perspective on dating mid late pleistocene environmental history to better understand pleistocene climatic changes in the arctic integrated palaeoenvironmental and palaeoclimatic signals from a variety of marine and terrestrial geological records as well as geochronologic age control are required not least for correlation to extra arctic records in this paper we discuss from an arctic perspective methods and correlation tools that are commonly used to date arctic pleistocene marine and terrestrial events we review the state of the art of arctic geochronology with focus on factors that affect the possibility and quality of dating and support this overview by examples of application of modern dating methods to arctic terrestrial and marine sequences event stratigraphy and numerical ages are important tools used in the arctic to correlate fragmented terrestrial records and to establish regional stratigraphic schemes age control is commonly provided by radiocarbon luminescence or cosmogenic exposure ages arctic ocean deep sea sediment successions can be correlated over large distances based on geochemical and physical property proxies for sediment composition patterns in palaeomagnetic records and increasingly biostratigraphic data many of these proxies reveal cyclical patterns that provide a basis for astronomical tuning recent advances in dating technology calibration and age modelling allow for measuring smaller quantities of material and to more precisely date previously undatable material i e foraminifera for c 14 and single grain luminescence however for much of the pleistocene there are still limits to the resolution of most dating methods consequently improving the accuracy and precision analytical and geological uncertainty of dating methods through technological advances and better understanding of processes are important tasks for the future another challenge is to better integrate marine and terrestrial records which could be aided by targeting continental shelf and lake records exploring proxies that occur in both settings and by creating joint research networks that promote collaboration between marine and terrestrial geologists and modellers

holocene variability in sea ice cover primary production and pacific water inflow and climate change in the chukchi and east siberian seas arctic ocean in this study we present new detailed biomarker based sea ice records from two sediment cores recovered in the chukchi sea and the east siberian sea these new biomarker data may provide new insights on processes controlling recent and past sea ice changes the biomarker proxy records show i minimum sea ice extent during the early holocene ii a prominent mid holocene short term high amplitude variability in sea ice primary production and pacific water inflow and iii significantly increased sea ice extent during the last ca 4 5k cal a bp this late holocene trend in sea ice change in the chukchi and east siberian seas seems to be contemporaneous with similar changes in sea ice extent recorded from other arctic marginal seas the main factors controlling the millennial variability in sea ice and surface water productivity are probably changes in surface water and heat flow from the pacific into the arctic ocean as well as the long term decrease in summer insolation the short term centennial variability observed in the high resolution middle holocene record is probably related to solar forcing our new data on holocene sea ice variability may contribute to synoptic reconstructions of regional to global holocene climate change based on terrestrial and marine archives

observational and modeling evidence of seasonal trends in sediment derived material inputs to the chukchi sea author posting american geophysical union 2020 this article is posted here by permission of american geophysical union for personal use not for redistribution the definitive version was published in journal of geophysical research oceans 125 5 2020 e2019jc016007 doi 10 1029 2019jc016007

assessment of bank gully development and vegetation coverage on the chinese loess plateau abstract gully erosion is a serious environmental problem and the primary source of sediment loss on the loess plateau of china yet previous research focusing on bank gullies is limited an assessment of bank gully development is needed as a basis for predicting erosion rates under the effects of vegetation cover and land use change to estimate bank gully retreat rates under different land uses assess the factors leading to bank gully development and model gully area growth rate at the catchment scale 30 catchments with an average area of 39 0 ha were selected in the southeastern part of the loess plateau quickbird images 0 61 m resolution obtained in 2003 and 2010 were interpreted to delineate bank gully features and a 5 m resolution digital elevation model was used to extract topographic factors the results showed that from 2003 to 2010 the maximum retreat rates of bank gully heads in the 30 investigated catchments ranged between 0 23 and 1 08 m yr 1 with an average of 0 51 m yr 1 the ratio of bank gully growth area to valley area changed from 0 49 to 9 45 depending on land use with average increases of 3 94 4 00 and 2 09 for the three land use types identified i e mixed use grassland and forestland respectively correlation analysis indicated that the effects of topographic factors on bank gullies decreased as vegetation coverage increased in upslope drainage areas and that vegetation coverage exceeding 60 in upslope drainage areas can significantly control bank gully development a model was built to predict the bank gully area growth rate ra m2 yr 1 with upslope drainage area ai m2 local slope gradient s m m 1 and the proportion of the area with vegetation coverage below 60 in upslope drainage areas 0 6 at the catchment scale the regression equation is in the form ra 0 1540 0 6ai 0 24s 3 2588 compared with previous studies vegetation is a factor in this model which would be helpful for assessing the influence of vegetation cover on bank gully development

prehistoric and roman gullying in the european oess belt a case study from central belgium in contrast with the understanding of present day soil erosion processes knowledge on past soil erosion phenomena is still rather limited although some studies report on severe gully erosion phases during the fourteenth and eighteenth centuries almost no evidence is available that documents earlier gully erosion phases this study investigates the development and age of two old permanent gullies that are conserved in the ancient meerdaal forest in central belgium the development history of both gullies is very similar in the first gully archaeological evidence was found indicating an erosion phase during roman times followed by a partial infilling of the gully in the second gully radiocarbon dating provided evidence of the same roman activity phase cal yr 46 bc ad 78 but also of an earlier incision phase during the middle bronze age cal yr 1743 1602 1568 1533 bc also here the erosion phase was followed by a partial infilling this limited infilling indicates that the catchment of the gullies was reforested quite rapidly hereby cutting off all runoff and sediment production this has led to a unique situation in the meerdaal forest with the conservation of about 43 similar large gullies in an area of about 17 km 2 this area has a high geovalue as the studied gullies are among the oldest and best conserved gullies in northwestern europe

dynamic and static models of gully erosion abstract the main causes of gully formation are anthropogenic factors the clearing of native forests tilling of fallow lands and associated change of the hydrological conditions in the rainfall runoff system gully channels formation is very rapid during the period of gully initiation when morphological characteristics of a gully length depth width area and volume are far from stable this period is relatively short about 5 of a gully s lifetime for the most part of a gully s lifetime its size is near stable maximum value these two stages of gully development led to two types of gully erosion models 1 dynamic models to predict rapid changes of gully morphology at the first period of gully development 2 static models to calculate final morphometric parameters of stable gullies the dynamic gully model is based on the solution of the equations of mass conservation and gully bed deformation the model of straight slope stability was used for prediction of gully side walls inclination the static gully model is based on the assumption of final morphological equilibrium of a gully when averaged for several years elevations and width of gully bottom do not change this stability is associated with a negligible rate both of erosion and sedimentation at the gully bottom it means that flow velocity is less than the threshold value for erosion initiation but is more than the critical velocity of wash load sedimentation the dynamic and static gully models were verified on the data on gullies morphology and dynamics from yamal peninsula russia and new south wales australia

monitoring and modelling morphological change in a braided gravel bed river using high resolution gps based survey recent research in fluvial geomorphology has emphasized the direct monitoring of channel topography as a useful tool to better understand the interrelationship between river form and process and in particular to estimate bedload transport rates and reach scale sediment budgets until recently however this morphometric approach has been limited to comparison of repeatedly surveyed cross sections with the associated problems of low frequency sampling and an emphasis on cross stream as opposed to downstream morphological dynamics recent advances in analytical photogrammetry have however permitted the acquisition of data at sufficient resolutions to represent macroform 101 m and microform 10 m channel geometry in fully three dimensions while inherently spatially distributed the photogrammetric approach to land surveying is however restricted to observable areas of the channel and is thus of limited use in the subaqueous zone especially if flows are turbid or highly coloured this paper presents an alternative approach to the study of three dimensional morphological dynamics of a divided reach of the gravelly river feshie scotland in which topographic survey of both exposed and submerged areas of the reach was undertaken using the global positioning system gps survey results from two field programmes in 1998 and 1999 are presented in which a geotronics geotracer 2000 real time kinematic gps receiving unit was used to survey a 200 80 m reach rapid radial survey methods were employed permitting the collection of 2000 survey points per day giving a mean density over the 13 ha reach of 1 1 points per square metre a detailed assessment of survey errors and dem quality is presented and a limit of detection of c 10 cm proposed as an upper threshold for the identification of significant change between dems preliminary interpretation of channel dynamics in 1998 99 reveals relatively little change to the overall macroscale reach structure dem differencing techniques however highlight important local changes including the progradation of submerged bar fronts bar head aggradation and scour along major channel thalwegs and the erosion of fines from sloughs copyright 2000 john wiley sons ltd

sediment yield from gullies riparian mass wasting and bank erosion in the upper konto catchment east java indonesia abstract upland watershed rehabilitation programmes in indonesia have faced increased scrutiny for not delivering the desired reductions in downstream sedimentation rates partly this reflects the fact that conservation measures have not been widely adopted or maintained by upland farmers mainly for socio economic reasons another potential explanation is that sediment contributions by gullying riparian mass wasting and bank erosion have been seriously underestimated or even ignored this paper presents estimates of sediment contributions by gullies riparian mass wasting and bank erosion in the upland volcanic konto catchment east java runoff and sediment yield from gullies were studied in two areas with contrasting soils and land use gullies in the maron area few gullies andic cambisols maize and rice cultivation on stable broad based terraces were related to improper drainage of trails roads and yards in the binangsri area more widespread gullying eutric cambisols onion cultivation on forward sloping terraces gullying was further enhanced by the practice of downslope furrowing to promote field drainage estimated annual sediment yields from the two areas were strikingly different at 22 26 and 50 87 mg ha 1 respectively riparian mass wasting was estimated to contribute ca 4 of total sediment yield at maron and 8 19 in the main gully system at binangsri with the higher value in the latter case representing the effect of extreme rainfall in the latter half of the rainy season short term wet season rates of gully wall retreat at binangsri suggested a contribution by bank erosion of ca 3 8 including extreme events as such 11 27 of the annual sediment yield at binangsri was estimated to have come from sources other than surface erosion substantial volumes of sediment 29 107 mg km 1 of river length were also added to streams bordered by irrigated rice fields sawah in non gullied areas mainly through the collapse of the lowermost terraces due to undercutting

the distribution of neodymium isotopes in arctic ocean basins nd concentration and isotope data have been obtained for the canada amundsen and makarov basins of the arctic ocean a pattern of high nd concentrations up to 58 pm at shallow depths is seen throughout the arctic and is distinct from that generally seen in other oceans where surface waters are relatively depleted a range of isotopic variations across the arctic and within individual depth profiles reflects the different sources of waters the dominant source of water and so nd is the atlantic ocean with lesser contributions from the pacific and arctic rivers radiogenic isotope nd signatures up to epsilon nd 6 5 can be traced in pacific water flowing into the canada basin waters from rivers draining older terrains provide very unradiogenic nd down to epsilon nd 14 2 that can be traced in surface waters across much of the eurasian basin a distinct feature of the arctic is the general influence of the shelves on the nd concentrations of waters flowing into the basins either from the pacific across the chukchi sea or from across the extensive siberian shelves water shelf interaction results in an increase in nd concentration without significant changes in salinity in essentially all waters in the arctic through processes that are not yet well understood in estuarine regions other processes modify the nd signal of freshwater components supplied into the arctic basin and possibly also contribute to sedimentary nd that may be subsequently involved in sediment water interactions mixing relationships indicate that in estuaries nd is removed from major river waters to different degrees deep waters in the arctic are higher in nd than the inflowing atlantic waters apparently through enrichments of waters on the shelves that are involved in ventilating the deep basins these enrichments generally have not resulted in major shifts in the isotopic compositions of the deep waters in the makarov basin epsilon nd similar to 10 5 but have created distinctive nd isotope signatures that were found near the margin of the canada basin with epsilon nd similar to 9 0 the deep waters of the amundsen basin are also distinct from the atlantic waters with epsilon nd 12 3 indicating that there has been limited inflow from the adjacent makarov basin through the lomonosov ridge c 2009 elsevier ltd all rights reserved

modern dirty sea ice characteristics and sources the role of anchor ice extensive dirty ice patches with up to 7 kg m 2 sediment concentrations in layers of up to 10 cm thickness were encountered in 2005 and 2007 in numerous areas across the central arctic the fe grai

monitoring of gully erosion in the central ebro basin by large scale aerial photography taken from a remotely controlled blimp large deep gullies span barrancos are some of the most important sediment sources in the semi arid environment of the central ebro basin they are incised into the quaternary valley bottoms span vales which are characteristic landforms in this area in the research project eprodesert evaluation of processes leading to land degradation and desertification under extensified farming systems the development of a large barranco system is being investigated by different methods including documentation and monitoring by aerial photography geomorphological forms and processes such as sheet wash rill and gully erosion cannot be documented sufficiently by conventional remote sensing methods spatial and temporal resolution of satellite sensors as well as of conventional aerial photography do not correspond to the scale and dynamics of geomorphological processes with a specially designed hot air blimp as a sensor platform large scale aerial photographs were obtained from the barranco de las lenas specifically aimed at the scientific demands very high spatial and temporal resolution the development of the gully is documented and its dynamics are evaluated by a sequence of six aerial photographs taken between 1995 and 1998 d 2003 elsevier science b v all rights reserved

glacial freshwater discharge events recorded by authigenic neodymium isotopes in sediments from the mendeleev ridge western arctic ocean the freshwater budget of the arctic ocean is a key component governing the deep water formation in the north atlantic and the global climate system we analyzed the isotopic composition of neodymium end in authigenic phases of marine sediments on the mendeleev ridge in the western arctic ocean spanning an estimated time interval from present to about 75 ka bp this continuous record was used to reconstruct the end of the polar deep water pdw and changes in freshwater sources to the pdw through time three deviations in end from a long term average of 10 2 were identified at estimated 46 51 35 39 and 13 21 ka bp the estimated 46 51 ka bp event can be traced to bursting of ice dammed lakes accompanying the collapse of the barents kara ice sheet which would have released radiogenic nd to the eastern arctic ocean the cyclonic surface circulation in the eastern arctic ocean must have been stronger than at present for the event to be recorded on the mendeleev ridge for the 35 39 and 13 21 ka bp events it is likely that the laurentide ice sheet lis supplied the unradiogenic freshwater the configuration of the anticyclonic circulation in the western arctic was probably similar to today or expanded eastward our simple mass balance calculations suggest that large amounts of freshwater were released but due to significant deep water formation within the arctic ocean the effect on the formation of nadw was probably minor

a new bedrock and surface elevation dataset for modelling the greenland ice sheet a new digital elevation model of the surface of the greenland ice sheet and surrounding rock outcrops has been produced from a comprehensive suite of satellite and airborne remote sensing and cartographic data sets the surface model has been regridded to a resolution of 5 km and combined with a new ice thickness grid derived from ice penetrating radar data collected in the 1970s and 1990s a further data set the international bathymetric chart of the arctic ocean was used to extend the bed elevations to include the continental shelf the new bed topography was compared with a previous version used for ice sheet modelling near the margins of the ice sheet and in particular in the vicinity of small scale features associated with outlet glaciers and rapid ice motion significant differences were noted this was highlighted by a detailed comparison of the bed topography around the north east greenland ice stream

230th and 231pa in the arctic ocean implications for particle fluxes and basin scale th pa fractionation abstract we report concentrations of 231pa 230th and 232th measured in unfiltered seawater samples from three stations occupied during the 1994 arctic ocean section at the western edge of the canada basin in the makarov basin and in the amundsen basin at the north pole the north pole data agree well with previously published profiles from the amundsen basin 230th and 231pa concentrations in the canada and makarov basins are intermediate between those reported previously for the beaufort sea and the alpha ridge reinforcing the observation that scavenging rates are variable in the western and central arctic and can be as rapid as in the eurasian basin and other oceans thorium 232 data indicate that relatively high rates of scavenging under the permanent ice cover are driven at least in part by offshore transport of detrital particulate material a comparison of water column 230th 231pa ratios throughout the arctic suggests that there may be little basin scale fractionation of these two isotopes in this ocean contrary to expectations based on the relatively large area of the continental shelves and their contrasts with the deep basins models of shelf basin exchange and 230th 231pa scavenging incorporating available constraints support this suggestion and point to the need for more data from the arctic shelves where the imprint of th pa fractionation if any is expected be most pronounced

use of a total station to monitor post failure sediment yields in landslide sites of the shihmen reservoir watershed taiwan abstract landslides have both immediate and extended duration effects on sediment discharge examining the role of post failure soil loss sediment yield of landslides is essential for basin management purposes the comprehensive measurement of sediment production of existing landslides could provide a better understanding in this aspect this study investigated the post failure sediment yield of 13 landslide sites in the shihmen reservoir watershed taiwan during the rainy seasons of 2006 and 2007 using a total station our study showed that soil loss is mainly controlled by rainfall conditions and the geometric and geographic characteristics of each landslide can significantly influence the efficiency of sediment delivery we also observed that rainfall is important in determining landslide retrogression enlargement although vegetation in the landslide area increases with time we obtained a large amount of landslide measurement data which could be useful for future landslide modeling we suggest two regression models for estimating gross soil loss using cumulative rainfall the estimated gross soil loss values of 0 78 to 1 06 m yr 1 are equivalent to 18 096 to 24 592 t ha 1 yr 1 using these estimates we assessed the sources of sediment in the watershed and found that the ratio of landslide erosion soil loss after landsliding and soil erosion from other parts of the watershed was approximately 66 31 3 this study implies that remedying existing landslides is more effective than any other solution in reducing sediment production in the watershed

huge ice age lakes in russia during an early phase of the last ice age weichselian valdaian about 90 000 yr ago an ice sheet formed over the shallow barents and kara seas the ice front advanced on to mainland russia and blocked the north flowing rivers yenissei ob pechora dvina and others that supply most of the freshwater to the arctic ocean the result was that large ice dammed lakes were formed between the ice sheet in the north and the continental water divides to the south here we present reconstructions and calculations of the areas and volumes of these lakes the lake on the west siberian plain was nearly twice as large as the largest lake on earth today the well mapped lake komi in northeast europe and a postulated lake in the white sea basin would also rank before the present day third largest lake the lakes overflowed towards the south and thus the drainage of much of the eurasian continent was reversed the result was a major change in the water balance on the continent decreased freshwater supply to the arctic ocean and increased freshwater flow to the aral caspian black and baltic seas a sudden outburst of the lakes water to the arctic ocean when the ice sheet thinned is postulated copyright 2001 john wiley sons ltd

erosion processes and rates for gullies in granitic soils bathurst new south wales australia soil movement rates from fluted gully sides in new south wales were measured over three years by erosion pins and survey erosion rates varied considerably over short distances from 0 to 53 mm yr 1 with an average removal rate of 19 8 mm yr 1

early diagenesis and trace element accumulation in north american arctic margin sediments abstract concentrations of redox sensitive elements s mn mo u cd re were analyzed in a set of 27 sediment cores collected along the north american arctic margin naam from the north bering sea to davis strait via the canadian archipelago sedimentary distributions and accumulation rates of the elements were used to evaluate early diagenesis in sediments along this section and to estimate the importance of this margin as a sink for key elements in the polar and global oceans distributions of mn total s and reduced inorganic s demonstrated that diagenetic conditions and thus sedimentary carbon turnover in the naam is organized regionally undetectable or very thin layers

symmetric and baroclinic instability in dense shelf overflows abstractin this study we revisit the problem of rotating dense overflow dynamics by performing nonhydrostatic numerical simulations resolving submesoscale variability thermohaline stratification

patterns and controls of gully growth along the shoreline of lake huron an empirical approach was used to examine the morphology and behaviour of gullies along the eastern shoreline of lake huron canada gully and watershed dimensions and percentage vegetation cover of a sample of 44 gullies were measured from aerial photographs between 1930 and 1992 gullies with larger watersheds had higher area growth rates larger gullies continue to expand over time while small gullies are more likely to become stable growth rates increased between 1955 and 1978 because of increased snowfall extreme flow events the extension of municipal drains and the use of subsurface drainage after 1970 efforts to rehabilitate gullies using drain pipes and check dams contributed to a decrease in gully growth rates 1997 john wiley sons ltd

post glacial variability of sea ice cover river run off and biological production in the western laptev sea arctic ocean a high resolution biomarker study abstract multi proxy biomarker measurements were applied on two sediment cores ps51 154 ps51 159 to reconstruct sea ice cover ip25 biological production brassicasterol dinosterol and river run off campesterol sitosterol in the western laptev sea over the last 17 ka with unprecedented temporal resolution the absence of ip25 from 17 2 to 15 5 ka in combination with minimum concentration of phytoplankton biomarkers suggests that the western laptev sea shelf was mostly covered with permanent sea ice very minor river run off and restricted biological production occurred during this cold interval from 16 ka until 7 5 ka a long term decrease of terrigenous riverine organic matter and a coeval increase of marine organic matter reflect the gradual establishment of fully marine conditions in the western laptev sea caused by the onset of the post glacial transgression intensified river run off and reduced sea ice cover characterized the time interval between 15 2 and 12 9 ka including the bolling allerod warm period 14 7 12 9 ka prominent peaks of the dip25 index coinciding with maximum abundances of subpolar foraminifers are interpreted as pulses of atlantic water inflow on the western laptev sea shelf after the warm period a sudden return to severe sea ice conditions with strongest ice coverage between 11 9 and 11 ka coincided with the younger dryas 12 9 11 6 ka at the onset of the younger dryas a distinct alteration of the ecosystem reflected in a distinct drop in terrigenous and phytoplankton biomarkers was detected during the last 7 ka the sea ice proxies reflect a cooling of the laptev sea spring summer season this cooling trend was superimposed by a short term variability in sea ice coverage probably representing bond cycles 1500 500 ka that are related to solar activity changes hence atmospheric circulation changes were apparently able to affect the sea ice conditions on the laptev sea shelf under modern sea level conditions

seafloor evidence for ice shelf flow across the alaska beaufort margin of the arctic ocean new imagery of 14 100 km2 of seafloor along a 640 km stretch of the alaska and beaufort margins abm in water depths from 250 to 2800 m depicts a repetitive association of glaciogenic bedforms lineations and iceberg scours broad erosional bathymetric features and adjacent downslope turbidite gullies these bedforms have styles depths and orientations similar to features discovered earlier on the chukchi borderland up to 800 km northwest of the abm lineations occur across the surface of a flattened bathymetric bench interpreted to have formed by an ice shelf sliding along the continental slope and scraping the seafloor at temporary grounding locations the glacial geology of surrounding areas suggests that an ice shelf probably flowed from the mouths of overdeepened glacial troughs in the canadian arctic archipelago westward along the abm and across the chukchi borderland this curved pathway indicates an obstruction to ice flow in the central canada basin possibly caused by either a basin wide ice shelf or by a pile up of mega bergs originating from the eurasian side of the arctic ocean the ice shelf that affected the abm may have formed between oxygen isotopic stage 4 to 5b possibly correlating to an inferred intra stage 5 widespread beringian glaciation evidence for glaciogenic features on the abm corroborates suggestions that large ice volumes and extents existed in the arctic during pleistocene glacial periods these findings have far reaching implications for arctic climate studies ocean circulation sediment stratigraphy and the stability of circum arctic continental ice masses copyright 2007 john wiley sons ltd

rapid development and infilling of a buried gully under cropland central belgium abstract analysis of contemporary and past gully erosion and infilling processes allowed to reconstruct the long term evolution of a permanent gully system under cropland an active and a buried gully under cropland were investigated the recent sediment deposits within the active gully adjacent to the buried gully showed that the recent gully was filling in at a mean rate of 6 4 cm a 1 in the buried gully several erosion and deposition phases could be identified and the type of deposited sediments revealed a complex infilling history charcoal pottery and brick fragments of different sizes were found at all depths of the gully infilling their age indicates that the first gully incised after the midst of the 17th century most probably in the second half of the 18th century or the early 19th century gully morphology and analogy with the processes in the recent gully indicate that the buried gully filled in rapidly overall five cycles of cut and fill occurred in 350 years or less and four cycles even within little less than a few decades indicating that gully development and infilling under cropland can be very rapid processes

holocene sea ice history and climate variability along the main axis of the northwest passage canadian arctic 1 palynological geochemical and physical records were used to document holocene paleoceanographic changes in marine sediment core from dease strait in the western part of the main axis of the northwest passage core 2005 804 006 pc latitude 68 59 552 n longitude 106 34 413 w quantitative estimates of past sea surface conditions were inferred from the modern analog technique applied to dinoflagellate cyst assemblages the chronology of core 2005 804 006 pc is based on a combined use of the paleomagnetic secular variation records and the cals7k 2 time varying spherical harmonic model of the geomagnetic field the age depth model indicates that the core spans the last 7700 cal years b p with a sedimentation rate of 61 cm ka 1 the reconstructed sea surface parameters were compared with those from barrow strait and lancaster sound cores 2005 804 004 pc and 2004 804 009 pc respectively which allowed us to draw a millennial scale holocene sea ice history along the main axis of the northwest passage manwp overall our data are in good agreement with previous studies based on bowhead whale remains however dinoflagellate sea surface based reconstructions suggest several new features the presence of dinoflagellate cysts in the three cores for most of the holocene indicates that the manwp was partially ice free over the last 10 000 years this suggests that the recent warming observed in the manwp could be part of the natural climate variability at the millennial time scale whereas anthropogenic forcing could have accelerated the warming over the past decades we associate holocene climate variability in the manwp with a large scale atmospheric pattern such as the arctic oscillation which may have operated since the early holocene in addition to a large scale pattern more local conditions such as coastal current tidal effects or ice cap proximity may have played a role on the regional sea ice cover these findings highlight the need to further develop regional investigations in the arctic to provide realistic boundary conditions for climatic simulations

centroid depths and mechanisms of mid ocean ridge earthquakes in the indian ocean gulf of aden and red sea we have determined the centroid depths and source mechanisms of 14 earthquakes along spreading centers in the indian ocean gulf of aden and red sea the earthquakes are all characterized by normal faulting on planes dipping at about 45 and generally striking parallel to the local trend of the spreading center for the ridge axis earthquakes in the indian ocean gulf of aden and central red sea seismic moments range from 3 to 9 1024 dyn cm source time functions are all of simple form and centroid depths of events with adequate azimuthal coverage are all very shallow between 1 and 4 km beneath the seafloor if the centroid depth typically marks the mean depth of fault slip then earthquake faulting extended to 2 8 km beneath the seafloor during these earthquakes the centroid depths for two earth quakes near the mouth of the gulf of suez support the view that seismic faulting accompanying continental rifting generally extends to greater depth than does seismic faulting along the axes of oceanic spreading centers when these findings are combined with our earlier results from the mid atlantic ridge the greatest centroid depths of earthquakes with well constrained source mechanisms tend to shoal with increasing spreading rate this result supports a general decrease with spreading rate in the maximum thickness of the zone of brittle behavior for slow spreading ridges

plio pleistocene trends in ice rafted debris on the lomonosov ridge although more than 700 sediment cores exist from the arctic ocean the plio pleistocene evolution of the basin and its marginal seas remains virtually unknown this is largely due the shallow penetration of most of these records and difficulties associated with deriving chronologies for the recovered material the integrated ocean drilling program s iodp expedition 302 arctic coring expedition acex recovered 197 m of neogene quaternary sediment from the circumpolar regions of the lomonosov ridge as detailed analyses of this material emerge research is beginning to formulate a long term picture of paleoceanographic changes in the central arctic ocean this paper reviews the acex plio pleistocene age model identifies uncertainties and addresses ways in which these may be eliminated within the established stratigraphic framework a notable reduction in the abundance of ice rafted debris ird occurs in the early part of the pleistocene and persists until marine isotope stage 6 mis 6 therefore while global oceanographic proxies indicate the gradual growth of terrestrial ice sheets during this time ird delivery to the central arctic ocean remained comparatively low and stable within the resolution of existing data the pleistocene reduction in ird is synchronous with predicted changes in both the inflow of north atlantic and pacific waters which in modern times are known to exert a strong influence on sea ice stability

the history of human induced soil erosion geomorphic legacies early descriptions and research and the development of soil conservation a global synopsis abstract this paper presents a global synopsis about the geomorphic evidence of soil erosion in humid and semihumid areas since the beginning of agriculture historical documents starting from ancient records to data from the mid twentieth century and numerous literature reviews form an extensive assortment of examples that show how soil erosion has been perceived previously by scholars land surveyors farmers land owners researchers and policy makers examples have been selected from ancient greek and roman times and from central europe southern africa north america the chinese loess plateau australia new zealand and easter island furthermore a comprehensive collection on the development of soil erosion research and soil conservation has been provided with a particular focus on germany and the usa geomorphic evidence shows that most of the agriculturally used slopes in the old and new worlds had already been affected by soil erosion in earlier prehistoric times early descriptions of soil erosion are often very vague with regard to the roman times geomorphic evidence shows seemingly opposing results ranging from massive devastation to landscapes remaining stable for centuries unfortunately historical documentation is lacking in the following centuries historical records become more frequent and more precise and observations on extreme soil erosion events are prominent sometimes they can be clearly linked to geomorphic evidence in the field the advent of professional soil conservation took place in the late eighteenth century the first extensive essay on soil conservation known to the western world was published in germany in 1815 the rise of professional soil conservation occurred in the late nineteenth and early twentieth centuries soil remediation and flood prevention programs were initiated but the long term success of these actions remains controversial in recent years increasing interest is to recover any traditional knowledge of soil management in order to incorporate it into modern soil conservation strategies the study shows that local and regional variations in natural settings cultural traditions and socioeconomic conditions played a major role for the dynamics and the rates of soil erosion on a long term perspective geomorphic evidence and historical sources can often complement each other but there should be also an awareness of new pitfalls when using them together

231pa and 230th in surface sediments of the arctic ocean implications for 231pa 230th fractionation boundary scavenging and advective export abstract activities of 231pa and 230th in surface sediments from the arctic ocean and greenland norwegian seas are used to examine the redistribution of these water column produced tracers between the low productivity interior basins and high particle flux marginal areas sediment 231paxs 230thxs ratios throughout the canadian and eurasian basins and the high particle flux chukchi slope region are essentially invariant average 0 063 0 014 n 39 and significantly below the water column production ratio 0 093 231paxs 230thxs ratios are also below the production ratio in the seasonally high productivity greenland norwegian sea basins average 0 082 0 024 n 13 though they are 30 higher than the interior arctic the low sediment 231paxs 230thxs ratios are attributed to the net export of 39 of dissolved 231pa produced in intermediate deep waters as opposed to 10 of 230th through fram strait the negligible 230th export combined with the reported low 230thxs inventory of basin sediments and high 230thxs inventory in chukchi slope sediments points to significant boundary scavenging of 230th in the arctic the invariant 231paxs 230thxs ratios further indicate that scavenging of 230th is comparable to 231pa i e fractionation to a similar degree between the two nuclides in both the interior basins and margins thus while significant boundary scavenging of both 231pa and 230th occurs in the arctic there is a distinct lack of basin margin fractionation and a sizable export of 231pa there is also likely to be export of other similarly particle reactive radionuclides e g 10be pu isotopes out of the arctic

automatic processing of high rate high density multibeam echosounder data 1 multibeam echosounders mbes are currently the best way to determine the bathymetry of large regions of the seabed with high accuracy they are becoming the standard instrument for hydrographic surveying and are also used in geological studies mineral exploration and scientific investigation of the earth s crustal deformations and life cycle the significantly increased data density provided by an mbes has significant advantages in accurately delineating the morphology of the seabed but comes with the attendant disadvantage of having to handle and process a much greater volume of data current data processing approaches typically involve computer aided human inspection of all data with time consuming and subjective assessment of all data points as data rates increase with each new generation of instrument and required turn around times decrease manual approaches become unwieldy and automatic methods of processing essential we propose a new method for automatically processing mbes data that attempts to address concerns of efficiency objectivity robustness and accuracy the method attributes each sounding with an estimate of vertical and horizontal error and then uses a model of information propagation to transfer information about the depth from each sounding to its local neighborhood embedded in the survey area are estimation nodes that aim to determine the true depth at an absolutely defined location along with its associated uncertainty as soon as soundings are made available the nodes independently assimilate propagated information to form depth hypotheses which are then tracked and updated on line as more data is gathered consequently we can extract at any time a current best estimate for all nodes plus co located uncertainties and other metrics the method can assimilate data from multiple surveys multiple instruments or repeated passes of the same instrument in real time as data is being gathered the data assimilation scheme is sufficiently robust to deal with typical survey echosounder errors robustness is improved by pre conditioning the data and allowing the depth model to be incrementally defined a model monitoring scheme ensures that inconsistent data are maintained as separate but internally consistent depth hypotheses a disambiguation of these competing hypotheses is only carried out when required by the user the algorithm has a low memory footprint runs faster than data can currently be gathered and is suitable for real time use we call this algorithm cube combined uncertainty and bathymetry estimator we illustrate cube on two data sets gathered in shallow water with different instruments and for different purposes we show that the algorithm is robust to even gross failure modes and reliably processes the vast majority of the data in both cases we confirm that the estimates made by cube are statistically similar to those generated by hand

methane fluxes from the sea to the atmosphere across the siberian shelf seas the laptev and east siberian seas have been proposed as a substantial source of methane ch4 to the atmosphere during summer 2014 we made unique high resolution simultaneous measurements of ch4

a new bathymetric compilation for the south orkney islands region antarctic peninsula 49 39 w to 64 59 s insights into the glacial development of the continental shelf we present a new high resolution 300 m bathymetric grid of the continental shelf surrounding the south orkney islands northeast of the antarctic peninsula the new grid derived from a compilation of marine echo sounding data improves previous regional bathymetric representations and helps to visualize the morphology of the shelf in unrivalled detail the compilation forms important baseline information for a range of scientific applications and end users including oceanographers glacial modelers biologists and geologists in particular due to the limited understanding of glacial history in this region the bathymetry provides the first detailed insights into past glacial regimes the continental shelf is dominated by seven glacially eroded troughs marking the pathways of glacial outlets that once drained a former ice cap centered on the south orkney islands during previous glacial periods grounded ice extended to the shelf edge north of the islands a large 250 km long sediment depocenter interpreted as a maximum former ice limit of one or more cenozoic glaciations suggests that ice was only grounded to the 300 350 m contour in the south hypsometric analyses support this interpretation indicating that a significant proportion of the shelf has been unaffected by glacial erosion using these observations we propose a preliminary ice cap reconstruction for maximum glaciation of the south orkney plateau suggesting an ice coverage of about 19 000 km2 the timing of maximum ice extent number of past advances and pattern of subsequent deglaciation s remain uncertain and will require further targeted marine geological and geophysical investigations to resolve

monitoring of gully erosion on the loess plateau of china using a global positioning system abstract with the development of a technique global positioning system gps has become progressively less expensive lighter and easier to use the accuracy of gps has been improved and it appears applicable to the continuously monitoring morphology changes on the earth surface with small and slow change the objective of this study is to use gps to measure the morphology of gullies in a small catchment near suide shaanxi province china there are three main gully types in the study area bank gullies floor gullies and hill slope gullies and this study mainly focuses on the hill slope gullies the hill slope gullies in the study area are mainly discontinuous and are developing rapidly the gully density in the study area is very large the retreat rate of hill slope gullies is 0 16 2 02 m year 1 the relationships between the upslope drainage area a and the critical slope gradient s for hill slope gullies is s 0 1839a 0 2385 the values of as2 range from 41 to 814 m2 for the hill slope gully headcuts and most of them fell into the range of 100 300 m2 both of these relationships are suggested as indexes for estimating the location of gully headcuts

late pleistocene sea level variations derived from the argentine shelf 1 neritic littoral marine sedimentary deposits from the argentine shelf provide a record of late pleistocene sea level variation sediments interpreted to reflect the last glacial maximum low stand are 150 m below present using a simple airy isostatic model for hydroisostatic compensation and correcting for a minor tectonic component yields a local eustatic sea level lowering of 105 m at the last glacial maximum the deglacial sea level curve records two rapid sea level rises consistent with mwp1 a and 1 b as documented by the barbados coral based sea level curve comparison with relative sea level variations predicted by the ice4g vm2 viscoelastic model have highlighted a deficiency in the model s predicted sea level history for this region detailed data model comparisons of late pleistocene sea level variations are necessary in the face of climate change induced sea level perturbations to determine regional and or systematic biases in the treatment of lithosphere viscosity and accurate predictions of future sea level

medium term gully headcut retreat rates in southeast spain determined from aerial photographs and ground measurements this paper deals with gully retreat rates at different time scales whereby the short term time scale may span a time interval of 1 5 years the medium term time scale a time interval of 5 50 years and the long term time scale a time interval of more than 50 years an analysis of high altitude aerial photographs in combination with ground measurements allowed us to quantify volumetric gully head retreat rates for 12 permanent gullies in southeast spain guadalentin and guadix study areas over a 40 43 year time interval medium term time scale this resulted in an average retreat rate ve of 17 4 m3 year 1 a power relationship between drainage basin area a and medium term volumetric gully head retreat rate ve 0 069a0 380 r2 0 51 n 21 was found by combining the gully head retreat rates obtained in this study with those obtained by a dendrochronological method the exponent b and the coefficient of determination r2 of the power relationships ve aab increases from the short term to the long term time scale expressing the increasing importance of drainage basin area in gully development with time considerable differences between gully head retreat rates measured at the short and medium term time scales at individual gullies showed the importance of land use changes and unsuccessful management practices on gully head retreat and the episodic nature of gully head retreat when piping and tension cracking are involved higher gully head retreat rates are obtained at the medium term time scale compared to the short term time scale but the differences are not significantly different at 10 the medium term methods tend to measure proportionally more high gully retreat rates but less extreme values compared to the short term method this is explained by a more equal distribution of extreme rainfall events both in space and time at a longer term time scale and hence a higher probability of measuring the average effect of both small and extreme rainfall events at each gully

development of gullies and sediment production in the black soil region of northeastern china abstract gully erosion is an important environmental hazard in the black soil region of northeastern china it is a primary sediment source in the region which needs appropriate soil conservation practices gully incision in rolling hills typical of this region was monitored using real time kinematic gps to assess the rates of gully development and the resultant sediment production from 2002 to 2005 gully heads in the study area retreated between 15 4 and 33 5 m giving an average retreat rate of 8 4 m yr 1 field measurements showed that total sediment production due to gully erosion during the three years ranged between 257 and 1854 m3 yr 1 which is equivalent to 326 to 2355 t yr 1 with gully head retreat accounting for 0 to 21 7 4 4 in average the sediment delivery ratio was especially high during the summer rainy season 56 in average sediment production by ephemeral gullies and permanent gullies was 1 5 times greater than that from surface erosion gully heads retreated faster in the spring freeze thaw period than in the summer the stage of gully development could be identified based on short term changes in the gully erosion rate

comparison of gully erosion estimates using airborne and ground based lidar on santa cruz island california abstract gully erosion removes comparatively large volumes of soil from small areas it is often difficult to quantify the loss of soil because the footprint of individual gullies is too small to be captured by most generally available digital elevation models dems such as the usgs national elevation dataset airborne lidar light detection and ranging has the potential to provide the required data density but an even newer class of ground based sensors may provide better local resolution at lower cost in this study we compared digital elevation models produced by airborne and ground based lidar systems with ground based geomorphic and geodetic survey data to determine their utility in quantifying volumetric soil loss due to gully erosion in a heavily degraded watershed 7 55 10 2 km 2 on southwestern santa cruz island in southern california volumetric estimates of the eroded sediment were produced by comparing the lidar derived dems of the gully system to a modeled pre erosion surface average point densities were significantly higher for the ground based lidar system and provided more detailed information however its limited scanning footprint and side looking orientation presented serious challenges in collecting continuous data from deeply incised gullies making the airborne system preferable for this type of investigation and likely for most applications where heavy topographic shadowing is prevalent

testing the use of an image based technique to measure gully erosion at sparacia experimental area the first part of this investigation was aimed at testing the use of a three dimensional 3d digital terrain model dtm and a quasi tridimensional 2 5d digital elevation model dem obtained by a large series of oblique images of eroded channels taken from consumer un calibrated and non metric cameras for two closed earth channels having a different sinuosity the ground measurement of some cross sections by a profilometer p was carried out the real volume of each channel was also measured by waterproofing it by a plastic film and filling it with a known volume of water the comparison among the three methods 3d 2 5d and p pointed out that a limited underestimation of the total volume always occurs and that the 3d method is characterized by the minimum difference between measured and real volume this preliminary analysis allowed to conclude that 3d model can be used as benchmark and the 2 5d model is accurate enough to describe the investigated earth channels in the subsequent part of the investigation the three ground measurement methods were applied for surveying of an ephemeral gully eg channel at the sparacia area using the 3d model as benchmark the morphological and hydraulic variable values of the 24 surveyed cross sections determined by both 2 5d model and profilometer were compared this comparison showed that the estimate error is generally less than 10 the eg measurements carried out by the three methods agreed with the available literature measurements and supported the applicability both of the empirical relationship between eg length and its eroded volume and the theoretical dimensionless relationship among the morphological variables describing the channelized erosion process finally it was demonstrated that the effect of the distance interval on the eg volume measurement by 3d and 2 5d models is negligible for the investigated eg

seismological observations in and around the southern part of the gulf of suez egypt we have established a seismological network in the southern part of the gulf of suez at the northern end of the red sea in egypt the network consists of 10 satellite stations five in the southern tip of the sinai peninsula four on the african continent and one on shadwan island where a m s 6 6 earthquake occurred in march 1969 the first six stations were installed in august 1994 and the remaining four were added by june 1996 all data are radio transmitted to a central station in the city of hurghada each station consists of one 1 hz vertical component seismograph except for one three component station we use the iaspei software library for data acquisition and analysis seismic data are a d converted into 12 bit sampled at 100 hz and stored in desktop computers almost all earthquakes occurred at the center of the gulf of suez the center of the northern end of the red sea and the gulf of aqaba where old and new plate boundaries exist between the african and arabian plates three seismic zones are clearly observed along these boundaries three dominant earthquake swarms were also observed at the entrance of the gulf of suez the focal depths of almost all earthquakes observed in the network range mainly from 5 to 20 km the focal mechanisms of earthquakes show a variety of patterns the most predominant type is normal faulting along the ne sw tensional axes this is consistent with the mechanism of the 1969 earthquake and the opening of the red sea and the gulf of suez manuscript received 31 may 2000

gully head erosion processes on a semi arid valley floor in kenya a case study into temporal variation and sediment budgeting a three year monitoring programme of gully head retreat was established to assess the significance of sediment production in a drainage network that expanded rapidly by gully head erosion on the low angled alluvio lacustrine njemps flats in semi arid baringo district kenya this paper discusses the factors controlling the large observed spatial and temporal variation in gully head retreat rates ranging from 0 to 15 m a 1 the selected gullies differed in planform and in runoff contributing catchment area but soil material and land use were similar the data were analysed at event and annual timescales the results show that at annual timescale rainfall amount appears to be a good indicator of gully head retreat while at storm event timescale rainfall distribution has to be taken into account a model is proposed including only rainfall p and the number of dry days dd between storms which explains 56 per cent of the variation in retreat rate of the single headed gully of lam1 a detailed sediment budget has been established for lam1 and its runoff contributing area rca by measuring sediment input from the rca the sediment output by channelized flow and linear retreat of the gully head for nine storms it can be seen that erosion shifts between different components of the budget depending on the duration of the dry period dd between storms sediment input from the rca was usually the largest component for the smaller storms the erosion of the gully head occurred as a direct effect of runoff falling over the edge ghwaterfall and of the indirect destabilization of the adjacent walls by the waterfall erosion and by saturation ghmass storage the latter component ghmass storage was usually much larger that the former ghwaterfall the sediment output from the gully was strongly related to the runoff volume while the linear retreat because of its complex behaviour was not overall the results show that the annual retreat is the optimal timescale to predict retreat patterns more detailed knowledge about relevant processes and interactions is necessary if gully head erosion is to be included in event based soil erosion models copyright 2001 john wiley sons ltd

assessment of sidewall erosion in large gullies using multi temporal dems and logistic regression analysis although in the last decades gully erosion has been a thriving research field few studies have specifically addressed the contribution and location of sidewall erosion processes in gullies in this paper sidewall erosion in some large gullies in a mediterranean area anoia penedes ne spain is mapped and assessed for two time intervals 1975 1995 and 1995 2002 using detailed digital elevation models derived from aerial photographs at a scale of 1 5000 to 1 7000 logistic regression analysis is applied to compute the probability of occurrence of gully sidewall erosion from terrain variables the results confirm the complex nature of sidewall processes whose intensity is most probably related to rainfall characteristics prolonged wet soil conditions in the period 1995 2002 together with the large and high intensity rainfall of an extreme event occurred on 10th june 2000 help to explain the different sediment production rates 16 0 4 mg ha 1 year 1 in 1975 1995 and 83 6 3 mg ha 1 year 1 in 1995 2002 the logistic regression analysis revealed that gully wall slope angle was the main factor controlling gully sidewall failure in gully walls with high slope angles tension crack development is the main process promoting wall collapse the application of the logistic regression model showed a high overall accuracy 87 but over 50 of commission and omission errors for the class of interest sidewall erosion in agreement with the variance explained by the model

gully erosion impacts factors and control gully erosion attracts increasing attention from scientists as reflected by two recent international meetings poesen and valentin eds catena 50 2 4 87 564 li et al 2004 gully erosion under global change sichuan science technology press chengu china 354 pp this growing interest is associated with the increasing concern over off site impacts caused by soil erosion at larger spatial scales than the cultivated plots the objective of this paper is to review recent studies on impacts factors and control of gully erosion and update the review on dgully erosion and environmental change importance and research needst poesen et al 2003 catena 50 2 4 91 134 for the farmers the development of gullies leads to a loss of crop yields and available land as well as an increase of workload i e labour necessary to cultivate the land gullies can also change the mosaic patterns between fallow and cultivated fields enhancing hillslope erosion in a feedback loop in addition gullies tend to enhance drainage and accelerate aridification processes in the semi arid zones fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion in this respect tracers such as carbon nitrogen the nuclear bomb derived radionuclide 137 cs magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment recent studies conducted in australia china ethiopia and usa showed that the major part of the sediment in reservoirs might have come from gully erosion gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess european belt chinese loess plateau north america and sandy soils sahelian zone north east thailand or in soils prone to piping and tunnelling such as dispersive soils most of the time the gullying processes are triggered by

hypsometry and volume of the arctic ocean and its constituent seas 1 this paper presents an analysis of the arctic ocean and its constituent seas for seafloor area distribution versus depth and ocean volume the bathymetry from the international bathymetric chart of the arctic ocean ibcao is used together with limits defining this ocean and its constituent seas from the international hydrographic organization iho as well as redefined limits constructed to confine the seas to the shallow shelves ibcao is a bathymetric grid model with a resolution of 2 5 2 5 km which significantly improved the portrayal of the arctic ocean seafloor through incorporation of newly released bathymetric data including echo soundings from u s and british navies scientific nuclear submarine cruises and icebreaker cruises this analysis of seafloor area and ocean volume is the first for the arctic ocean based on this new and improved portrayal of the seafloor as represented by ibcao the seafloor area and volume are calculated for different depths starting from the present sea level and progressing in increments of 10 m to a depth of 500 m and in increments of 50 m from 550 m down to the deepest depth within each of the analyzed seas hypsometric curves expressed as simple histograms of the frequencies in different depth bins and depth plotted against cumulative area for each of the analyzed seas are presented the area and volume calculations show that the entire iho defined arctic ocean makes up 4 3 of the total ocean area but only 1 4 of the volume furthermore the iho arctic ocean is the shallowest mean depth 1201 m of all the major oceans and their adjacent seas the continental shelf area from the coasts out to the shelf break make up as much as 52 9 of the total area in the arctic ocean defined in this work as consisting of the oceanic deep arctic ocean basin the broad continental shelves of the barents kara laptev east siberian chukchi and beaufort seas the white sea and the narrow continental shelf off both the canadian arctic archipelago and northern greenland this result indicates that the arctic ocean has significantly larger continental shelves compared with all the other oceans where previous studies show that the proportion of shelves from the coasts out to the foot of the continental slopes only ranges between about 9 1 and 17 7 furthermore the derived hypsometric curves show that most of the arctic ocean shelf seas besides the barents sea beaufort sea and the shelf off northern greenland have a similar shape with the largest seafloor area between 0 and 50 m the east siberian and laptev seas in particular show area distributions concentrated in this shallow depth range and together with the chukchi sea they form a large flat shallow shelf province composing as much as 22 of the entire arctic ocean area but only 1 of the volume this implies that the circulation in the arctic ocean might be very sensitive to eustatic sea level changes one of the aims with this work is to make up to date high resolution area and volume calculations for the arctic ocean at various depths available for download

climatic limits on landscape development in the northwestern himalaya the interaction between tectonism and erosion produces rugged landscapes in actively deforming regions in the northwestern himalaya the form of the landscape was found to be largely independent of exhumation rates but regional trends in mean and modal elevations hypsometry frequency distribution of altitude and slope distributions were correlated with the extent of glaciation these observations imply that in mountain belts that intersect the snowline glacial and periglacial processes place an upper limit on altitude relief and the development of topography irrespective of the rate of tectonic processes operating

231pa and 230th in the arctic ocean implications for boundary scavenging and 231pa230th fractionation in the eurasian basin abstract 231pa 230th and 232th were analyzed in filtered seawater n 70 and suspended particles n 39 collected along a shelf basin transect from the barents shelf to the makarov basin in the arctic ocean during geotraces section gn04 in 2015 the distribution of dissolved 231pa and 230th in the arctic ocean deviates from the linear increase expected from reversible scavenging higher 232th concentrations were observed at the shelf slope and in surface waters in the deep basin pointing at lithogenic sources fractionation factors fth pa observed at the nansen margin were higher compared to fth pa in the central nansen basin possibly due to the residual occurrence of hydrothermal particles in the deep central nansen basin application of a boundary scavenging model quantitatively accounts for the dissolved and particulate 230th distributions in the nansen basin modelled dissolved 231pa distributions were largely overestimated which was attributed to the absence of incorporation of water exchange with the atlantic ocean in the model 231pa 230th ratios of the suspended particles of the nansen basin were below the 231pa 230th production ratio but top core sediments of the nansen margin and slope have high 231pa 230th ratios suggesting that scavenging along the nansen margin partly acts as a sink for the missing arctic 231pa

a method for dendrochronological assessment of medium term gully erosion rates abstract a method based on dendrochronology to estimate gully erosion rates was developed as an alternative of traditional methods for assessing medium term gully retreat rates such as field monitoring of headcuts or aerial photo interpretation of gully retreat the method makes use of trees or parts of a tree affected by gully erosion revealing information on the history of the erosion process by datable deviations of their normal growth pattern hence defined as datable objects these include roots exposed by erosion browsing scars made by ungulates on exposed roots or on above ground parts of fallen trees exposed and dead root ends root suckers stems branches and leading shoots of fallen trees and a sequence of trees within a gully the method is based on the differentiation between three main conditions depending on the relation between the dynamics of the datable object part of the tree and the development of the gully the first condition implies that the datable object was created before erosion of the gully volume to be dated e g exposed tree roots according to the second condition the datable object developed as an immediate consequence of the erosion event e g growth reactions of a fallen tree the third condition implies that the datable object was created some time after the erosion event took place e g trees colonising the gully bed each principle has consequences for the accuracy and the correct interpretation of the estimated erosion rate i e whether the true erosion rate is underestimated exact or overestimated in spite of methodological limitations and dendrochronological dating problems the method was successfully applied in southeast spain conservative estimations of gully head retreat rate resulted in an average medium term 3 46 years value of 6 m3 year 1 n 9 for gully sidewall processes the average minimum erosion rate per unit sidewall length amounted 0 1 m3 year 1 m 1 n 9 a strong correlation was found between the headcut retreat rate vm ortho m3 year 1 and the drainage basin area a m2 of the gullies expressed by vm ortho 0 02a0 57 r2 0 93 n 9 comparing the findings from this study with those obtained by short term headcut retreat monitoring suggests a high reliability of the estimated retreat rates supporting the applicability of the developed dendrochronological method

sources and cycling of mercury in the paleo arctic ocean from hg stable isotope variations in eocene and quaternary sediments abstract mercury stable isotopic compositions were determined for marine sediments from eight locations in the arctic ocean basin mass dependent fractionation mdf and mass independent fractionation mif of hg stable isotopes were recorded across a variety of depositional environments water depths and stratigraphic ages 202hg mdf ranges from 2 34 to 0 78 199hg mif from 0 18 to 0 12 and 201hg mif from 0 29 to 0 05 for the complete data set n 33 holocene sediments from the chukchi sea and morris jesup rise record the most negative 199hg values while pleistocene sediments from the central arctic ocean record the most positive 199hg values the most negative 202hg values are recorded in pleistocene sediments eocene sediments lomonosov ridge show some overlap in their hg isotopic compositions with quaternary sediments with a sample of the arctic ocean petm 56 ma most closely matching the average hg isotopic composition of holocene arctic marine sediments collectively these data support a terrestrially dominated hg source input for arctic ocean sediment through time although other sources as well as influences of sea ice atmospheric mercury depletion events amdes and anthropogenic hg in core top samples on hg isotopic signatures must also be considered