arenigian early ordovician sea level history and the response of conodont communities western newfoundland four cluster analyses were performed which recognized 17 conodont communities in the arenigian lower ordovician of western newfoundland the analyses include 69 598 identifiable conodont specimens recovered from 153 conodont bearing samples from four stratigraphical sections representing the environmental settings of the platform upper proximal slope lower proximal slope and distal slope the distribution of conodont communities along the platform to slope environmental gradient shows that sea level changes simultaneously affected the development and replacement of the conodont communities in the different facies the pattern of change in conodont communities allows an interpretation of sea level change that is correlated precisely into the detailed graptolite biozonation a gradual transgression lasted most of tetragraptus approximatus zone time which was followed by a brief regression a transgression regression cycle occurred in the t akzharensis zone time a major transgression caused a highst

sea ice production over the laptev sea shelf inferred from historical summer to winter hydrographic observations of 1960s 1990s the winter net sea ice production nsip over the laptev sea shelf is inferred from continuous summer to winter historical salinity records of 1960s 1990s while the nsip strongly depends on the assumed salinity of newly formed ice the nsip quasi decadal variability can be linked to the wind driven circulation anomalies in the laptev sea region the increased wind driven advection of ice away from the laptev sea coast when the arctic oscillation ao is positive implies enhanced coastal polynya sea ice production and brine release in the shelf water when the ao is negative the nsip and seasonal salinity amplitude tends to weaken these results are in reasonable agreement with sea ice observations and modeling

influence of storm related sediment storage on the sediment delivery from tributary catchments in the upper waipaoa river new zealand although much is known about overall sediment delivery ratios for catchments as components of sediment production and sediment yield little is known about the component of temporary sediment storage sediment delivery ratios focused on the influence of storm related sediment storage are measured at matakonekone and oil springs tributaries of the waipaoa river basin east coast of new zealand the terrace deposits of both tributaries show abundant evidence of storm related sedimentation especially sediment delivered from cyclone bola a 50 year return rainfall event which occurred in 1988 the sediment delivery ratio is calculated by dividing the volume of sediment transported from a tributary to the main stream by the volume of sediment generated at erosion sites in the tributary catchment because the sediment delivery volume is unknown it can be calculated as the difference between sediment generation volume and sediment storage volume in the channel reach of the tributary the volume of sediment generated from erosion sites in each tributary catchment was calculated from measurements made on aerial photographs dating from 1960 1 44 000 and 1988 1 27 000 the volume of sediment stored in the tributary can be calculated from measurements of cross sections located along the tributary channel which are accompanied by terrace deposits dated by counting annual growth rings of trees on terrace surfaces sediment delivery ratios are 0 93 for both matakonekone catchment and oil springs catchment results indicate that oil springs catchment has contributed more than twice the volume of sediment to the waipaoa river than the matakonekone catchment 2 75 106 m3 vs 1 22 106 m3 although large volumes of sediment are initially deposited during floods subsequent smaller flows scour away much of these deposits the sediment scouring rate from storage is 1 25 104 m3 a 1 for matakonekone stream and 0 83 104 m3 a 1 for oil springs stream matakonekone and oil springs channels respond to extreme storms by instantaneously aggrading then gradually excavating the temporarily stored sediment results from matakonekone and oil springs streams suggest a mechanism by which event recurrence interval can strongly influence the magnitude of a geomorphic change matakonekone stream with its higher stream power is expected to excavate sediment deposits more rapidly and allow more rapid re establishment of storage capacity copyright 1999 john wiley sons ltd

spatial modelling and uncertainty assessment of pyroclastic cover thickness in the sorrento peninsula assessing spatial variability of soil thickness is a critical issue for understanding and predicting slope processes the present work was aimed at estimating the spatial scales at which the variation of pyroclastic cover thickness occurs in a sample area in the sorrento peninsula italy stochastic simulation was used to understand the spatial variability of pyroclastic cover thickness on mount pendolo and to assess its spatial uncertainty in the study area covering about 0 7 km2 thickness measurements were collected using electrical resistivity tomography profiles continuous core drillings and steel rod penetrometric tests variographic analysis revealed the occurrence of an anisotropic behaviour along the n50 and n140 directions in the latter anisotropic direction a nested variogram was fitted including 1 a long range component which could be related to large scale factors like the curvature of the slope and contributing area and 2 a shorter scale variation which is probably associated with the occurrence of denudation processes or to the articulate cover bedrock interface to assess the spatial variability and uncertainty of pyroclastic cover thickness a stochastic simulation algorithm was used and 500 equally probable images of cover thickness were yielded the results showed that a better thickness distribution map can be drawn by simulating the data collected on the slope and at the footslope separately the approach also allowed delineating the areas characterized by greater uncertainty suggesting supplementary measurements to further improve the cover thickness distribution model thus reducing the uncertainty

possible dynamic and thermal causes for the recent decrease in sea ice in the arctic basin 1 a dynamic thermodynamic sea ice model with 50 km spatial and 24 hour temporal resolution was used to investigate the spatial and temporal variability of the sea ice cover and the surface energy exchange in the arctic basin daily surface level air temperature and pressure data from national centers for environmental prediction for 1958 1997 and climatic data for cloudiness relative humidity snow precipitation and the heat flux from the deep ocean in the greenland barents and bering seas were used as external forcing the model is integrated using the method of large particles belotserkovskii 1984 the model satisfactorily reproduces the seasonal and interannual variability of the main characteristics of the sea ice the sea ice extent and exchange through the main straits and the surface heat exchange for different parts of the arctic basin in particular estimates of the year to year difference between mean sea ice thickness in september show good agreement with the essential thinning of sea ice in the canadian basin that rothrock et al 1999 found most of the decrease in sea ice thickness is caused by a decrease in ridge concentration and an increase in the area covered by undeformed ice numerical experiments show that only 20 of the ice decrease can be explained by an increase in surface level air temperature model results for the canadian and eurasian basins allow us to determine the main trends in the temporal variability of ice thickness in these regions our model results suggest that the recent thinning of the sea ice correlates with a decrease in the concentration of ridged ice in turn the concentration of ridged ice and the total sea ice volume in the canadian basin correlate with cyclonic and anticyclonic regimes of the wind driven ice motion the sharp decrease in modeled ice volume in the canadian basin after 1987 also coincides with a significant increase in the mean atmospheric vorticity index for the central arctic ocean

semidiurnal tides on the laptev sea shelf with implications for shear and vertical mixing the arctic continental shelf seas hold a globally significant source of freshwater that impacts arctic ocean stratification circulation and climate this freshwater can be injected below the surface mixed layer by intense turbulent kinetic energy dissipation events as resolved by laptev sea microstructure observations the tides provide a major source of energy that can be dissipated and hence drive diapycnal mixing in the laptev sea multiyear adcp mooring records from locations across the shelf reveal that semidiurnal tides are dominated by them2 and s2 constituents with the largest amplitudes on the outer shelf throughoutmost of the shelf tides are clockwise polarized and sheared by stratification as characteristic near the m2 critical latitude interannual variations of the tidal and shear structures on the inner shelf aremainly determined by the stratification setting lena river freshwater plume in all locations m2 tides are enhanced under sea ice and therefore changes in the seasonal ice cover may lead to changes in tides and water column structure the main conclusions of this study are that i tides play a comparatively greater role year round on the outer shelf relative to the inner shelf ii a sea ice reduction will overall decrease the predictability of the currents especially on the inner shelf and iii the freshwater distribution directly impacts diapycnal mixing by setting the vertical tidal structure these combined effects imply that future sea ice loss will increase the variability and vertical mixing of freshwater particularly on the inner shelf where the lena river first enters the laptev sea

effects of ice coverage and ice rafted material on sedimentation in the fram strait as little is known about pelagic sedimentation processes in arctic environments1 the interpretation of biological and chemical processes as well as the reconstruction of ancient conditions including those in the glacial north atlantic is difficult here we provide sediment trap results which show that the position of the sea ice boundary significantly influences the particle flux the seasonal variability of the particle flux differed markedly in the various sediment trap sites in fram strait depending on the behaviour of the sea ice under complete ice cover sedimentation is very low whereas maximum sedimentation is found at the ice margin the highest particle flux observed showing a large lithogenic component was observed at the ice edge where the water was warmer 2 c we find that high biogenic opal fluxes are characteristic of the summer ice margin indicating that the sedimentary record of opal fluxes may allow the position of ice margins in the past to be reconstructed

a key source area and constraints on entrainment for basin scale sediment transport by arctic sea ice combining field measurements remote sensing and numerical modelling a key site for ice entrainment and basinwide dispersal of sediments by sea ice has been identified near the new siberian islands the total ice bound sediment export of 18 5 x 10 6 t for an entrainment event documented in 1994 95 is of the same order of magnitude as annual sediment supply to the deep sea sector of the eurasian arctic and the greenland sea satellite imagery and ancillary data indicate that ice advection from this source may play an important role in sedimentation downstream in the transpolar drift

medium term effects of two landsliding episodes on channel storage of sediment two landsliding episodes between late 1973 and early 1975 delivered about 60000 m3 of sediment to six small deeply incised streams draining a 2 7 km2 area about 4700 m3 of logs in the landslide debris formed major log jams in five streams which impounded large volumes of landslide derived sediment five years after the landsliding 42 per cent 25000 m3 of sediment was still in storage behind 35 log jams ranging from 1 4 8 2 m high the landsliding episodes have produced multi stepped stream profiles aggradation of channel reaches up to 150 m long to mean depths between 1 2 and 4 1 m reductions in gradient fining of bed material size and related changes in bedforms and channel width depth ratios that seem likely to persist for at least several decades sediment presently stored behind log jams is equivalent to between 50 and 220 years normal supply of sediment from hillslopes to stream channels long delayed large magnitude impacts on higher order channels may occur if sudden failure of log jams is induced by a large storm at some future date

fram strait satellite image derived ice motions in order to develop an operational method for the u s navy noaa joint ice center to extract ice velocity vectors from sequential advanced very high resolution radiometer avhrr imagery we have combined the maximum cross correlation mcc method with a spatial filtering technique on the image inferred ice motion vectors we compute the cross correlations between images directly from the image brightness values rather than computing ffts the direct method allows greater flexibility in computational parameter settings and allows one to compute motion vectors near coastlines where irregular windows are required by using a combination of statistical and spatial filters we can then retrieve coherent ice motion vectors in the presence of cloud contaminated imagery a series of six satellite images of the fram strait region from april 1986 was used to compute sea ice motion from pairs of sequential images the resulting ice motion vectors were taken as a representation of the surface flow field derived objectively from the satellite imagery resulting vector motion fields were found to match well with manually tracked vectors for the same images thus verifying the validity of the objective mcc method of computing ice motion these techniques were applied to both the visible and infrared avhrr channels and to images with different spatial resolutions yielding an overall bias accuracy of about 0 5 cm s and standard deviations of about 0 9 cm s the mcc ice motion results were also compared with wind driven numerical model simulations of the region marked differences between the mcc image derived velocities and those from the numerical model were thought to be primarily due to a stronger ocean current than was present in the model

two circulation regimes of the wind driven arctic ocean the major goal of this paper is to demonstrate the existence in the arctic ocean of two regimes of wind forced circulation we simulated the vertically averaged currents sea level heights and ice drift in the arctic ocean from 1946 to 1993 using a two dimensional wind forced barotropic model that includes frictional coupling between the ocean and ice the model has a spatial resolution of 55 5 km and is driven by winds river runoff and an imposed but realistic sea level slope between the pacific and the atlantic oceans there is a good agreement between velocities from observed buoy motions and velocities of modeled ice drift even though the model lacks ocean baroclinicity and ice thermodynamics the results indicate that wind driven motion in the central arctic alternates between anticyclonic and cyclonic circulation with each regime persisting for 5 7 years based upon our analysis of the modeled sea level and ice motion anticyclonic wind driven motion in the central arctic appeared during 1946 1952 1958 1963 1972 1979 and 1984 1988 and cyclonic motion appeared during 1953 1957 1964 1971 1980 1983 and 1989 1993 shifts from one regime to another are forced by changes in the location and intensity of the icelandic low and the siberian high the two regimes may help explain the significant basin scale changes in the arctic s temperature and salinity structure observed recently the great salinity anomaly and the variability of ice conditions in the arctic ocean

silurian devonian active margin deep marine systems and palaeogeography alai range southern tien shan central asia analysis of mid palaeozoic successions in the northern part of the alai range kyrgyzstan and bordering uzbekistan southern tien shan central asia has identified a silurian devonian deep marine depositional system of basin slope facies associations here we document the stratigraphy and sedimentology of a region in central asia that through conflict has become inaccessible for geological research the turbidite dominated pul gon formation silurian accumulated in sea floor depressions and within the inferred basin axis the large scale coarse clastic lenses of the dzhidala formation mostly devonian represent the fills of submarine channels canyons or gullies of the palaeoslope other slope apron processes include sediment slides debris flows and olistoliths the partly time equivalent condensed sequences of the mid to late silurian kursala formation and early devonian tamasha formation represent graptolitic mudstone and chert accumulation respectively together with thin dolomitic limestones that accumulated over c 10 15 ma probably on seamounts in the turkestan fergana ocean between the continental margin of kazakhstania and the alai microcontinent the graptolitic shale rich chakush formation early silurian is geographically and petrographically different from the pul gon and dzhidala formations and suggests a different provenance opposing continental margin or seamount talus

post deforestation soil loss from steepland hillslopes in taranaki new zealand soil erosion on steepland hillslopes in taranaki new zealand where landsliding is the dominant erosion form was investigated by comparing mean regolith depths between first order basins that have had their forest cover removed for different periods of time regolith depth and slope angle data were collected along 19 profile lines and 30 profile lines from steepland basins that had been deforested for 10 and 85 years respectively these profile lines were subdivided into a total of 236 profile segments of relatively linear slope angle and uniform regolith depth that averaged 17 5 m in length the depth of pre existing regolith on post deforestation landslide sites is estimated from a regression of regolith depth on slope angle for undisturbed non landslide profile segments regolith depletion on landslide sites is in turn estimated by subtracting the depth of regolith on landslide sites from the estimate of pre existing regolith depth regolith depletion by post deforestation landslides averaged over the entire length of profile lines gives an estimate of average surface lowering for the area deforested for 85 years average surface lowering by post deforestation landslides is 0 15 0 04 m and is the same as the difference in mean depth of 0 15 0 11 m between this area and the area deforested for 10 years erosion of regolith from hillslopes by processes other than landsliding appears to be minimal the 0 15 m average surface lowering represents a regolith depletion rate of 1 8 0 5 mm yr 1 for hillslopes steeper than 28 where all post deforestation landslides occur average surface lowering is 0 20 0 05 m and the regolith depletion rate is 2 4 0 6 mm yr 1 average surface lowering is greatest at 0 23 0 07 m on hillslopes steeper than 32 where most post deforestation landslides occur here the regolith depletion rate is 2 7 0 8 mm yr 1 a large magnitude low frequency storm in march 1990 produced an average surface lowering of 0 041 m there were proportionately more landslides in the area deforested for 10 years illustrating the importance of previous erosion history of hillslopes on the spatial distribution of landslides there were also comparatively few landslides on steeper hillslopes because previous lower magnitude storms had already removed much of the deeper regolith

assessment of rainfall induced shallow landslide susceptibility using a gis based probabilistic approach abstract this study proposes a probabilistic analysis method to assess shallow landslide susceptibility over an extensive area by integrating an infinite slope model with gis geographic information system and monte carlo simulation taking into consideration the inherent uncertainty and variability in input parameters the mechanical parameters of soil materials such as cohesion and friction angle used in the infinite slope analysis have been identified as the major source of uncertainty because of their spatial variability therefore these parameters were considered as random variables in this probabilistic landslide analysis to properly account for the uncertainty in input parameters the probabilistic analysis method used was monte carlo simulation the process was carried out in a gis based environment because gis has effective spatial data processing capacity over broad areas in addition the hydrogeological model was coupled with the infinite slope model to evaluate increases in pore water pressure caused by rainfall the proposed approach was applied to a practical example to evaluate its feasibility the landslide inventory map and the spatial database for input parameters were constructed in a grid based gis environment and a probabilistic analysis was implemented using monte carlo simulation to evaluate the performance of the model the results of the probabilistic landslide susceptibility analysis were compared with the landslide inventory the probabilistic approach demonstrated good predictive performance when compared with the landslide occurrence location in addition deterministic analysis was carried out using fixed single input data for comparison with the results from the proposed approach in this comparison the probabilistic analysis showed better performance than the deterministic analysis in addition the results showed that proper consideration and understanding of uncertainties play an important role in accurately predicting shallow landslide susceptibility

influences of spatial distribution of soil thickness on shallow landslide prediction abstract shallow landslides usually occur during hevy rainfall and result in casualties and property losses thus the possible locations where landslides are likely to occur must be identified in advance in order to avoid or reduce the harm they cause when performing a slope instability analysis soil thickness is an important factor however soil thickness information from landslide prone areas is rarely obtained the objective of this study is to realize the influences of spatial distribution of soil thickness on shallow landslide prediction three different spatial soil thickness distributions were applied to perform a slope instability analysis and uniform distributed soil thicknesses from 0 4 m to 2 0 m were also applied for comparison geomorphologic information and hydrological records from a landslide prone area in southern taiwan were collected results show that the spatial distribution of soil thickness related to wetness index provides a reasonable estimation in order to avoid an over prediction for landslide prone areas or an under prediction for stable areas the analytical procedure used in this study is a simple way for assessing hillslope instability for shallow landslide prediction

sediments in arctic sea ice implications for entrainment transport and release despite the arctic sea ice cover s recognized sensitivity to environmental change the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood sea ice sediment inclusions were studied in the central arctic ocean during the arctic 91 expedition and in the laptev sea east siberian arctic region expedition 1992 results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central arctic ocean this study documents the regional distribution and composition of particle laden ice investigates and evaluates processes by which sediment is incorporated into the ice cover and identifies transport paths and probable depositional centers for the released sediment in april 1992 sea ice in the laptev sea was relatively clean the sediment occasionally observed was distributed diffusely over the entire ice column forming turbid ice observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment in the central arctic ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes the surface sediment accumulation in central arctic multi year sea ice exceeds by far the amounts observed in first year ice from the laptev sea in april 1992 sea ice sediments are generally fine grained although coarse sediments and stones up to 5 cm in diameter are observed component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles the biogenous components namely shells of pelecypods and benthic foraminiferal tests point to a shallow benthic marine source area apparently sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing clay mineralogy of ice rafted sediments provides information on potential source areas a smectite maximum in sea ice sediment samples repeatedly occurred between 81 n and 83 n along the arctic 91 transect indicating a rather stable and narrow smectite rich ice drift stream of the transpolar drift the smectite concentrations are comparable to those found in both laptev sea shelf sediments and anchor ice sediments pointing to this sea as a potential source area for sea ice sediments in the central arctic ocean sea ice clay mineralogy is significantly different from deep sea clay mineral distribution patterns the contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms

sea ice circulation in the laptev sea and ice export to the arctic ocean results from satellite remote sensing and numerical modeling sea ice circulation in the laptev sea and ice exchange with the arctic ocean have been studied based on remote sensing data and numerical modeling ice drift patterns for short and long term periods were retrieved from successive okean radar images and special sensor microwave imager data for the winters 1987 1988 and 1994 1995 seasonal and interannual variabilities of ice drift in the laptev sea and ice exchange with the arctic ocean during the period from 1979 to 1995 were studied with a large scale dynamic thermodynamic sea ice model during an average year sea ice was exported from the laptev sea through its northern and eastern boundaries with maximum and minimum export occurring in february and august respectively the winter ice outflow from the laptev sea varied between 251 000 km2 1984 1985 and 732 000 km2 1988 1989 with the mean value of 483 000 km2 sea ice was exported into the east siberian sea mostly in summers with the mean value of 69 000 km2 out of the 17 investigated summers 12 were characterized by sea ice import from the arctic ocean into the laptev sea through its northern boundary magnitude and direction of ice export from the laptev sea corresponded with the large scale arctic ocean drift patterns during periods of prevailing cyclonic or anticyclonic circulation based on a semiempirical method that has been validated with the large scale model and satellite data ice exchange between the laptev sea and the arctic ocean during the period from 1936 to 1995 has been estimated as 309 000km2 with strong interannual variability and no significant trend apparent

transient deterministic shallow landslide modeling requirements for susceptibility and hazard assessments in a gis framework abstract application of transient deterministic shallow landslide models over broad regions for hazard and susceptibility assessments requires information on rainfall topography and the distribution and properties of hillside materials we survey techniques for generating the spatial and temporal input data for such models and present an example using a transient deterministic model that combines an analytic solution to assess the pore pressure response to rainfall infiltration with an infinite slope stability calculation pore pressures and factors of safety are computed on a cell by cell basis and can be displayed or manipulated in a grid based gis input data are high resolution 1 8 m topographic information derived from lidar data and simple descriptions of initial pore pressure distribution and boundary conditions for a study area north of seattle washington rainfall information is taken from a previously defined empirical rainfall intensity duration threshold and material strength and hydraulic properties were measured both in the field and laboratory results are tested by comparison with a shallow landslide inventory comparison of results with those from static infinite slope stability analyses assuming fixed water table heights shows that the spatial prediction of shallow landslide susceptibility is improved using the transient analyses moreover results can be depicted in terms of the rainfall intensity and duration known to trigger shallow landslides in the study area

an estimate of the mean field of arctic sea ice motion the observational basis for our understanding of sea ice motion comes from the trajectories of particular ice floes these ice floes may have been marked by a manned research station or more recently by an automatic data buoy since 1893 almost 100 station years of drift data have been recorded using the principles of optimal linear estimation these data are used to obtain a quantitative estimate of the field of mean motion

hydro geomorphological modelling of ash fall pyroclastic soils for debris flow initiation and groundwater recharge in campania southern italy abstract carbonate mountain ranges surrounding volcanic centers in the campania region of southern italy are covered by discontinuous ash fall pyroclastic deposits of variable thicknesses the cover thickness and stratigraphy are relevant to hydrological controls on both rainfall induced landslides and groundwater recharge to improve understanding of the hydrologic regimes within the pyroclastic soil mantle a hydrological monitoring station was installed upslope of a debris flow source area in the sarno mountains monitoring results demonstrate consistently unsaturated conditions strong seasonal and inter annual variations in pressure head and delayed and damped dynamics at different depths related to rainfall and evapotranspiration patterns frequencies of recorded pressure head time series were analyzed to quantify the seasonal hydrological regime of the cover as a whole as well as variations within individual soil horizons for the whole ash fall pyroclastic soil cover variable seasonal frequencies of pressure head were recognized exceeding landslide alert and groundwater recharge threshold values analysis of frequencies for individual soil horizons showed a strongly delayed timing determining in winter and summer an opposite hydrological behavior between the shallowest and deepest soil horizons a model that accounts for topographic variations in cover thickness and these hydrological regimes is proposed to quantify hydro geomorphological controls on debris flows triggering and groundwater recharge the model is based on the estimation of ash fall pyroclastic soil thickness along slopes by the total thickness fallen in a given area and an inverse relationship with slope angle allowing the assessment at the distributed scale over peri volcanic mountainous areas moreover it links the spatially variable thicknesses of ash fall pyroclastic soils to the amount of soil water storage allowing the assessment of frequency of hydrological conditions leading to debris flow initiation and groundwater recharge

sediment budget to assess the geomorphic effect of a cyclonic storm new zealand abstract a short term sediment budget was constructed to assess the erosion response of a soft rock hill country watershed to an intense rainstorm event the watershed is located in a landslide prone area on the east coast of the north island new zealand during march 1988 753 mm of rain was recorded over a four day period with 320 mm and 329 mm on successive days known as cyclone bola this was the largest rainstorm event in the tutira watershed in the 93 year rainfall record the budget quantifies the total sediment generated during the storm the relative contribution of erosion processes involved the amount of sediment held in storage and the amount discharged into two lakes within the watershed a landform map of the watershed was constructed and the contribution of each landform type to the total budget was calculated a total of 1 35 0 13 million m3 of sediment was generated during the storm at an average of 420 m3 ha this is equivalent to a denudation value of 42 mm for the total watershed 3208 ha and 83 mm for the landforms severely affected by landsliding 1427 ha of the sediment generated 21 remained on hillslopes 22 was deposited on valley floors 51 was deposited on the lakebeds and the remaining 6 was discharged from the watershed via the lake outlet most of the sediment generated during the storm was from primary source areas on hill slopes with sediment in secondary storage providing only a small contribution landslide erosion was the main process accounting for 89 of the sediment generated channel tunnel gully and sheet erosion were only minor contributors to the budget six hillslope landforms which occupy only 44 of the watershed generated 90 of the sediment the results of this sediment budget when put in context with the storm magnitude frequency history being analysed from lake cores contribute to the identification of sustainable land use and management of soft rock hill country

seismogenic deformation structures in microbialites and mudstones silurian lockport dolomite northwestern ohio u s a syndepositional deformation structures are present at two different stratigraphic levels in the silurian lockport dolomite at a quarry in maumee ohio such structures are absent in this unit at twelve other quarries in northwestern ohio the structures at maumee present within stromatolites thrombolites and variably bedded mudstones include convolute layers homogenization of bedding and breccia clasts clasts of stromatolites boudinage structures normal reverse and thrust faults and discordant and concordant breccias the distribution of deformation structures within beds suggests substantial control from substrate rheology possibly resulting from differences in degrees of lithification and from variations in water content the extensive variety of syndepositional deformation structures juxtaposed evidence for nearly synchronous compression and dilation proximity 4 5 km of the structures to the largest fault in northwestern ohio the bowling green fault and the restricted geographic distribution of the deformation structures suggest seismic shaking as a probable mode of genesis similarities between features produced by seismogenic deformation of siliciclastic sediments and deformation features in the lockport dolomite provide additional evidence that the latter features are seismogenic it is postulated that two earthquakes one with a magnitude 5 caused the formation of the syndepositional deformation structures present in the youngest facies in the lockport dolomite at maumee quarry the bowling green fault 4 5 km west of maumee was a growth fault during formation of the lockport dolomite and is considered to have been the source of earthquakes that created the syndepositonal deformation structures in this unit at maumee quarry evidence from the lockport dolomite in northwestern ohio suggests that seismogenic deformation structures created by two earthquakes along the bowling green fault with magnitudes of 5 did not form in this unit over large areas i e all of northwestern ohio this evidence challenges the suggestion that syndepositional seismogenic deformation structures are always formed over a large area

automated extraction of pack ice motion from advanced very high resolution radiometer imagery multiple subarea cross correlations have been computed from visible advanced very high resolution radiometer images of the beaufort sea in an automated technique to detect pack ice motion the computational method is an application of the well known matched filter and consists of subdividing the first image into a set of subareas and correlating each reference subarea against the appropriate region of the second image the correlation functions are processed to determine a set of local maxima which define end point vectors of ice displacements from the subarea centers resulting velocities agree well with estimates of ice movement obtained by manually measuring invariant ice feature displacements the velocity fields show the spatial structures of ice motion over scales of 100 500 km with a high degree of pattern consistency and agreement with simple surface wind driving

cosmogenic nuclides topography and the spatial variation of soil depth abstract if the rate of bedrock conversion to a mobile layer of soil depends on the local thickness of soil then hillslopes on uniform bedrock in a landscape approaching dynamic equilibrium should be mantled by a uniform thickness of soil conversely if the depth of soil varies across an actively eroding landscape then rates of soil production will also vary and consequently the landscape will not be in morphologic equilibrium the slow evolution of hillslopes relative to the tempo of climatic variations and tectonic adjustments would suggest that local morphologic disequilibrium may be expected in many landscapes here we explore this issue of equilibrium landscapes through a previously developed model that predicts the spatial variation in thickness of soil as a consequence of the local balance between soil production and erosion first we confirm the assumption in the model that soil production varies inversely with the thickness of soil using two independent methods one method uses the theoretical prediction that at local steady state soil production equals removal the depth of soil should vary inversely with hillslope curvature the second method relies on direct measurements of in situ produced concentrations of cosmogenic 10 be and 26 al in bedrock at the base of the soil column for our study site in northern california the two methods agree and yield the expression that the rate of soil production declines exponentially with the thickness of soil from 0 077 mm year with no soil mantle to 0 0077 mm year under 1 m of soil we then use this function of soil production in a coupled production and diffusive model of sediment transport to explore the controls on the spatial variation of the depth of soil on four separate spur ridges noses where we measured the data for the function of soil production model predictions are sensitive to boundary conditions grid scale and run time nonetheless we found good agreement between predicted and observed depths of soil as long as we used the observed function of soil production the four noses each have spatially varying curvature and consequently have varying depths of soil implying morphologic disequilibrium we suggest that our study site has been subjected to a wave of incision and varying intensities of erosion because of tectonic and climatic oscillations that have a frequency shorter than the morphologic response time of the landscape

carbonate debris flows cow head group western newfoundland abstract the cow head group is an allochthonous cambro ordovician sequence of deep water limestone conglomerates mudstones to grainstones minor quartz sandstones siltstones and shales platy clast conglomerates and boulder rich megaconglomerates as much as 100 m thick exhibit features similar to those described for subaerial debris flows that is flat sharp bases with only minor evidence for erosion poorly developed clast fabric with tilting of platy clasts at right angles to the flow direction boulders floating within flows or projecting above the tops of flows irregular flow tops indicating primary relief above the sea floor and tapered flow margins snouts snout geometry and the extent of boulder projection both allow calculation of debris static strength these results combined with measured flow thickness permit calculation of minimum and maximum paleoslope gradients original debris static strengths were in the range of 103 to 105 dynes cm2 similar to the observed range in subaerial flows calculations yield bottom gradients of l l 8 but independent field data suggest that the paleoslope dip was on the order of only a few degrees this constraint suggests that debris strength was substantially reduced during flow probably by excess pore fluid pressures thus permitting flow on very gentle slopes the paleoslope orientations used in this study are substantially different from those previously published by hubert et at 1977

relative instability of colluvium filled bedrock depressions regolith landslides commonly occur in colluvium filled bedrock depressions rather than on ridges spurs or sites with planar bedrock surfaces drained direct shear tests of colluvium from bedrock depressions in wellington new zealand indicate the presence of cohesion in all samples suggesting that thickness of accumulated deposits may become a limiting factor for stability critical depths for a range of slope angles were calculated assuming conditions of infinite limiting equilibrium and compared to the depth angle relationships for depression and interdepression regolith occurring in the field the results indicate that under saturated conditions interdepression regolith is not thick enough to permit the development of landslides colluvium filled bedrock depressions on the other hand generally exceed critical depth and must be considered susceptible to landsliding in the absence of any significant root cohesion the age of deposits and the abundance of unfailed colluvium filled bedrock depressions suggest that they have been inactive for most of post glacial time stability analysis verified by observing the occurrence of landslides indicates that recent instability has been brought about by deforestation

contrasts in arctic shelf sea ice regimes and some implications beaufort sea versus laptev sea the winter ice regime of the 500 km from the mainland than in the beaufort sea as a result the annual freeze up does not incorporate old deep draft ice and with a lack of compression such deep draft ice is not generated in situ as on the beaufort sea shelf the laptev sea has as much as 1000 km of fetch at the end of summer when freezing storms move in and large 6 m waves can form also for the first three winter months the polynya lies inshore at a water depth of only 10 m turbulence and freezing are excellent conditions for sediment entrainment by frazil and anchor ice when compared to conditions in the short fetched beaufort sea we expect entrainment to occur yearly different from the intensely ice gouged beaufort sea shelf hydraulic bedforms probably dominate in the laptev sea corresponding with the large volume of ice produced more dense water is generated in the laptev sea possibly accompanied by downslope sediment transport thermohaline convection at the midshelf polynya together with the reduced rate of bottom disruption by ice keels may enhance benthic productivity and permit establishment of open shelf benthic communities which in the beaufort sea can thrive only in the protection of barrier islands indirect evidence for high benthic productivity is found in the presence of walrus who also require year round open water by contrast lack of a suitable environment restricts walrus from the beaufort sea although over 700 km farther to the south we could speculate on other consequences of the different ice regimes in the beaufort and laptev seas but these few examples serve to point out the dangers of exptrapolating from knowledge gained in the north american arctic to other shallow arctic shelf settings

large scale drift of arctic sea ice retrieved from passive microwave satellite data a method of determining the large scale sea ice drift using 85 5 ghz special sensor microwave imager data are presented a cross correlation method is applied to sequential images of gridded data covering the entire arctic individual correlation results are validated with ice velocities derived from buoy data the satellite derived mean drift values and the variabilities of the ice drift correspond closely with the buoy data similarly time series of buoy data and associated satellite data are in good agreement even over large time periods an example of a satellite retrieved 3 day mean drift field demonstrates the potential of the method for providing large scale ice circulation patterns mean drift fields of the winter periods 1987 1988 and 1992 1993 indicate a considerable interannual variability of the sea ice drift pattern in the arctic ocean the arctic region is divided into seven larger areas and the area flux between these regions has been derived the kara sea and the laptev sea show the largest area ice export with 0 02 and 0 015 km 2 s 1 respectively the central arctic export through fram strait amounts to 0 12 sv during the winter of 1992 1993 with a maximum of 0 15 sv in january

reconstructing the origin and trajectory of drifting arctic sea ice recent studies have indicated that drifting arctic sea ice plays an important role in the redistribution of sediments and contaminants here we present a method to reconstruct the back ward trajectory of sea ice from its sampling location in the eurasian arctic to its possible site of ori gin on the shelf based on historical drift data from the international arctic buoy program this method is verified by showing that origins derived from the backward trajectories are generally con sistent with other indicators such as comparison of the predicted backward trajectories with known buoy drifts and matching the clay mineralogy of sediments sampled from the sea ice with that of the seafloor in the predicted shelf source regions the trajectories are then used to identify regions where sediment laden ice is exported to the transpolar drift stream from the new siberian islands and the central kara plateau calculation of forward trajectories shows that the kara sea is a major contributor of ice to the barents sea and the southern limb of the transpolar drift stream

a new 14 c age for the oruanui wairakei eruption new zealand the oruanui eruption was the largest known outburst of taupo volcano new zealand and is among the larger quaternary eruptions documented the eruption deposits are variously known as the oruanui wairakei kawakawa tephra or aokautere ash formations and represent a bulk volume probably exceeding 500 km 3 four new 14 c age determinations on carbonized vegetation in the non welded oruanui ignimbrite are combined to give a conventional age of 22590 230 yr b p compared with the previously accepted figure of 20000 yr b p this new age resolves the anomaly of apparently older 14 c ages being obtained from a demonstrably younger new zealand deposit and strengthens correlation of this eruption with an antarctic ice core acid anomaly the trace of this eruption has great potential as a time plane marker in the antarctic just prior to the last glacial maximum the close similarity in ages between the oruanui and a comparable sized eruption ito aira tn in japan suggests that this period of activity may represent the best chance of resolving any linkages between large scale explosive silicic volcanism and climate changes

circulation and transformation of atlantic water in the eurasian basin and the contribution of the fram strait inflow branch to the arctic ocean heat budget abstract the inflows of atlantic water from the nordic seas to the arctic ocean through fram strait and over the barents sea are examined and their pathways and transformations in the eurasian basin are described based primarily on hydrographic observations from two cruises with rv polarstern in 2007 and 2011 the contrast between the high salinity atlantic water core in the nansen basin and the lower atlantic water salinity in the amundsen basin combined with a salinity minimum below the atlantic layer suggest that the fram strait branch mainly remains in the nansen basin while the barents sea branch continues along the continental slope enters the amundsen basin and provides most of the atlantic water in the makarov and canada basins to examine the consequences of such a circulation pattern recently published estimates of the in and outflows of volume and liquid freshwater through the barents sea bering strait and the canadian arctic archipelago as well as river runoff net precipitation and ice export are reviewed and added together to achieve volume and freshwater balances net outflows through fram strait of 2 3 sv and 100 msv respectively are required this is reasonably close to the recently reported fram strait transport estimates the net outflows are separated into two parts upper layer transports less dense than the entering atlantic water and lower layer transports as dense as or denser than the atlantic water the largest net volume outflow occurs in the lower layer 1 65 sv while the liquid freshwater is almost exclusively exported in the 0 64 sv net outflow in upper layer leading to unrealistically low salinities in the upper layer compared with observations atlantic water is north of svalbard transformed into less saline surface water through melting of sea ice which can supply the necessary higher salinity halocline water to the upper layer 1 23 sv of halocline water of salinity 34 2 must be added to obtain a more realistic salinity of 33 1 leading to a total export of 1 84 sv upper layer water in the east greenland current existing observations of the net transports into and out of the arctic ocean through fram strait in different temperature classes are used to estimate the heat loss of the atlantic water entering the arctic ocean through fram strait about 10 tw are supplied to the atmosphere in addition to the loss of 24 tw occurring in connection with the formation of the halocline water if the hypothesis that the fram strait branch remains in the nansen basin is true it implies a heat loss between 5 and 15 w m 2 in the nansen basin depending upon how much heat is temporarily stored in the water column this is high compared to the 2 w m 2 commonly cited as the ocean heat flux to the atmosphere in the arctic ocean

cross shelf transport of warm and saline water in response to sea ice drift on the laptev sea shelf 1 oceanographic moorings and conductivity temperature depth ctd surveys from september 2009 to september 2010 are used to describe recent changes in the laptev sea hydrography and to highlight wind and ice driven surface ekman transport as the mechanism to translate these changes from the outer to the inner shelf bottom waters in february 2010 moored oceanographic instruments recorded a sudden increase in temperature 0 8 c and salinity 3 near the bottom of the inner laptev sea shelf such warm and saline waters had not been previously observed on the inner shelf in winter they likely originated from the basin and were first observed during a summer 2009 ctd survey in the northwestern shelf break region subsequently spreading east and shoreward across the laptev sea shelf the changes were introduced to the mooring site by the first of a series of bottom intensified flow events with velocities reaching 20 cm s 1 topographically guided along a relic submarine river valley each of the flow events coincided with negative pressure anomalies at the mooring site and offshore directed upwelling favorable winds and ice drift we suggest that the observations to first order resemble a simplified two dimensional two layered ocean where offshore surface ekman transport is compensated for by a barotropic shoreward response flow near the bottom in this paper we use one of the first comprehensive long term laptev sea datasets to highlight ice ocean atmosphere interactions in early and late winter and discuss the role of freshwater stratification and ice mobility on under ice circulation on the laptev sea shelf

soil depth age relationship of landslides on deforested hillslopes taranaki new zealand a soil chronosequence was examined on landslide scars of different ages in the taranaki hill country this area underlain by tertiary silty sandstone was deforested 90 years ago sequential aerial photographs historical terrestrial photographs and documented erosion events were used to date landslide scars formed since forest removal and establish age control for the chronosequence soil depth increased with landslide age and was used as an index of soil formation mean soil depth increased from 5 cm on 15 year old scars to 20 cm on 82 year old scars measures soil depths were attributed to rafted soil colluvium and bedrock weathering a chronofunction was derived by regressing mean soil depth against the logarithm of known scar age similarly a second chronofunction was derived by excluding depths of rafted soil from the calculation of mean soil depth to describe soil accumulation on exposed bedrock within the landslide scar this chronofunction showed a better correlation r2 0 92 compared with r2 0 79 and can give an estimate of the age of other landslide scars to within 27 for ages up to 90 years the rate of soil depth increase averaged 3 5 mm yr 1 over the first 40 years after slipping but dropped to 1 2 mm yr 1 over the following 50 years the logarithmic chronofunction suggests that the rate of soil formation further decreases beyond 90 years soil formation is primarily a result of bedrock weathering and accumulation of colluvium derived from surface fragmentation of exposed bedrock and crumbling scar margins

dynamic preconditioning of the minimum september sea ice extent abstractthere has been an increased interest in seasonal forecasting of the arctic sea ice extent in recent years in particular the minimum sea ice extent here a dynamical mechanism based on winter preconditioning is found to explain a significant fraction of the variance in the anomaly of the september sea ice extent from the long term linear trend to this end a lagrangian trajectory model is used to backtrack the september sea ice edge to any time during the previous winter and quantify the amount of sea ice advection away from the eurasian and alaskan coastlines as well as the fram strait sea ice export the late winter anomalous sea ice drift away from the coastline is highly correlated with the following september sea ice extent minimum it is found that the winter mean fram strait sea ice export anomaly is also correlated with the minimum sea ice extent the following summer to develop a hindcast model of the september sea ice extent which does not depend on a priori knowledge of the minimu

geomorphic change implied by regolith slope relationships on steepland hillslopes taranaki new zealand abstract slope angle and regolith depth were measured along profile lines covering a range of hillslopes in several small neighbouring drainage basins in taranaki hill country new zealand slope measurements show a cyclic variation along the length of broadly rectilinear profiles variation in slope on the lower portion of profiles adjacent to stream channels indicates that hillslopes have undergone phases of accelerated downcutting and hillslope rejuvenation a recent phase of increased erosion and hillslope rejuvenation is suggested for hillslopes steeper than 31 by the steep lowerslope and incised stream channel hillslope evolution occurs primarily by parallel retreat of steeper swale sites and slope decline during pauses in the rate of downcutting all slope profiles show a large range in regolith depth mean regolith depth of swale sites is highly correlated with mean profile slope angle mean regolith depth decreases and the frequency of landslides increase with increasing mean profile slope angle microtopographic variation in regolith depth is attributed mainly to vegetation effects recurrent landsliding and in part to bedrock curvature hillslope position and slope angle shallowing of regolith is caused by recurrent landsliding on steep swale sites fluvial erosion at the base of steep profiles and surface erosion on extremely convex spur sites the very shallow soil on the steep lowerslope portion of profiles suggests a phase of soil removal consistent with hillslope rejuvenation average depth of regolith is least at 97 cm and variability greatest on hillslopes with a profile mean exceeding 31 erosion rates are greater on these sites where soil is derived predominantly from underlying tertiary sandstone this is attributed to a greater frequency of landsliding compared to hillslopes with a profile slope less than 31 where a more regular and deeper average regolith of 153 cm infers a longer period of hillslope stability consistent with the high volcanic ash content of soils airfall andesitic volcanic ash deposited throughout the holocene has largely been removed from steeper sites the work demonstrates the need to interpret the frequency and distribution of landslides in context with natural geomorphic changes in order to assess the effect that landuse changes has on erosion rates

prediction of landslide occurrence based on slope instability analysis and hydrological model simulation summary hillslope failure usually occurs as soil resistance deteriorates in the presence of the acting stress developed by a rising groundwater level during rainstorms the present study adopted a slope instability analysis and a hydrological model for landslide prediction during heavy rainstorms variation of the groundwater table on hillslope was simulated by using the hydrological model and then the temporal groundwater level at each grid was substituted into the slope instability analysis to determine the instability of the grids in watersheds for prediction of massive landslides hydrological records from two landslide prone areas in northern taiwan were collected digital elevation model was adopted to obtain the geomorphologic factors required for the slope instability analysis and the hydrological model the spatial distribution of soil thickness required for performing the infinite slope model was estimated by using a wetness index results showed that the temporal variation of the percentage of unstable grids in the study watersheds basically followed the variation of rainfall hyetographs the percentage of the unstable grids reached a maximum value when the centroid of the hyetograph passed a comparison between the landslide records and the model analytical results revealed that a massive landslide might occur if more than 50 of the grids in the subwatershed were classified as unstable in the study areas the predicted time and location of landslide occurrence were consistent with those obtained from field investigations it is therefore considered promising to apply the developed analytical method for landslide warning to alleviate the loss of lives and property

asymmetry in holocene river deltas patterns controls and stratigraphic effects abstract understanding controls on sediment distribution in river deltas is paramount to predicting facies relationships and stratal architecture most classifications of deltas have focused on subaerial plan morphology as a simplistic function of river tide and wave energy new work however is revealing the importance of subaqueous deposits and in particular shore parallel sediment redistribution in the shaping of delta planform delta asymmetry has emerged as an important characteristic reflective of patterns of alongshore sediment dispersal asymmetry has been described from onshore and offshore environments from several different types of modern deltas but aspects of asymmetry have not been fully documented and the degree to which these patterns are recorded in deltaic strata is not yet known this study is a comprehensive literature review of sediment distributions in modern deltas focusing on studies with high resolution geomorphic geophysical and geochronological datasets we reviewed 27 deltas using over 100 papers primarily from the past 15 20 years morphological facies and stratigraphic aspects were analyzed across the entire spectrum of deposits from the delta apex to the most distal muds of the prodelta we define quantifiable indices of asymmetry describing upcurrent vs downcurrent distribution of sediment volume sediment area sediment caliber and distributary channels most deltas are asymmetrical to some degree with respect to one or more of these parameters many deltas are increasingly skewed toward the downcurrent side from proximal to distal sub environments i e delta plain delta front prodelta some deltas are skewed toward the upcurrent side in one sub environment and toward the downcurrent side in another sub environment sand is preferentially deposited on the downcurrent side of most deltas but distributary channels tend to develop toward the upcurrent side the highest sand mud ratios are often on the upcurrent side in the lower delta plain but in the delta front these ratios are highest on the downcurrent side these complex patterns of asymmetry reflect different combinations of controls including discharge partitioning lobe abandonment and localized transgression plume deflection by coastal currents dominance of longshore current direction variable subsidence and other factors these processes may result in upcurrent downcurrent variations in clinoform geometry rates of progradation and stratal lapping relationships asymmetry has multiple aspects manifestations and controls even within a single delta but the long term preservation potential of these patterns likely varies depending on depositional setting and shoreline trajectory studies of ancient deltas will be better informed by recognizing the wide variety of controls on sediment distribution and avoiding the tendency toward a single model of delta asymmetry

patterns of sea ice retreat in the transition to a seasonally ice free arctic abstractthe patterns of sea ice retreat in the arctic ocean are investigated using two global climate models gcms that have profound differences in their large scale mean winter atmospheric circulation and sea ice drift patterns the community earth system model large ensemble cesm le presents a mean sea level pressure pattern that is in general agreement with observations for the late twentieth century the community climate system model version 4 ccsm4 exhibits a low bias in its mean sea level pressure over the arctic region with a deeper icelandic low a dynamical mechanism is presented in which large scale mean winter atmospheric circulation has significant effect on the following september sea ice extent anomaly by influencing ice divergence in specific areas a lagrangian model is used to backtrack the 80 n line from the approximate time of the melt onset to its prior positions throughout the previous winter and quantify the divergence across the pacific and eurasian sectors of the arctic i

resistance to shallow landslide failure through root derived cohesion in east coast hill country soils north island new zealand measured shear strength cohesion and friction of airfall derived east coast hill country regolith is insufficient for the maintenance of existing regolith depth slope angle relationships in the catchment of lake waikopiro in northern hawke s bay new zealand if these regoliths are attributed with an additional increment of cohesion derived mechanically from a turf mat membrane existing depth slope angle distributions are explicable sites where failure has occurred have been measured and back analysis used to derive a range of values for additional mechanical cohesion values are in the range 0 2 7 6 kpa consistent with earlier findings this range is narrowed further to 0 7 6 9 kpa with assumptions regarding soil moisture status at failure copyright 1999 john wiley sons ltd

winter coastal divergence as a predictor for the minimum sea ice extent in the laptev sea abstractseasonal predictability of the minimum sea ice extent sie in the laptev sea is investigated using winter coastal divergence as a predictor from february to may the new ice forming in wi

selecting and weighting spatial predictors for empirical modeling of landslide susceptibility in the darjeeling himalayas india in this paper we created predictive models for assessing the susceptibility to shallow translational rocksliding and debris sliding in the darjeeling himalayas india by empirically selecting and weighting spatial predictors of landslides we demonstrate a two stage methodology 1 quantifying associations of individual spatial factors with landslides of different types using bivariate analysis to select predictors and 2 pairwise comparisons of the quantified associations using an analytical hierarchy process to assign predictor weights we integrate the weighted spatial predictors through multi class index overlay to derive predictive models of landslide susceptibility the resultant model for shallow translational landsliding based on selected and weighted predictors outperforms those based on all weighted predictors or selected and unweighted predictors therefore spatial factors with negative associations with landslides and unweighted predictors are ineffective in predictive modeling of landslide susceptibility we also applied logistic regression to model landslide susceptibility but some of the selected predictors are less realistic than those from our methodology and our methodology gives better prediction rates although previous predictive models of landslide susceptibility indicate that multivariate analyses are superior to bivariate analyses we demonstrate the benefit of the proposed methodology including bivariate analyses

satellite derived maps of arctic and antarctic sea ice motion 1988 to 1994 standard image processing methods applied to 85 5 ghz special sensor microwave imager ssm i data provide previously unseen details about sea ice motion in the arctic and southern oceans means calculated from daily ice motions for 1988 1994 confirm the basic circulation patterns established from drifting stations and buoys but extend these observations to illustrate less well known transport patterns in the arctic coastal zones and sub arctic seas in the antarctic the gridded motion fields show a nearly continuous westward transport along the antarctic coast with well defined regions of exchange between this east wind drift and the antarctic circumpolar current this detailed view of mean ice motion in the southern ocean is unique and presents a comprehensive overview not previously available for antarctic ice motions

gis fuzzy logic technique in modeling soil depth classes using parts of the clay belt and hornepayne region in ontario canada as a case study abstract globally there is a growing desire to predict and map the spatial distribution of soil depth on the landscape due to its numerous roles in areas such as agriculture forestry hydrology and ecological land classification the aim of this study was to develop a technique to model and map soil depth classes based on gis fuzzy logic modeling approach and to examine the mapping accuracy of this technique with the accuracy of soil depth classes derived using randomforest modeling approach this was carried out for a portion of the clay belt and hornepayne region in ontario canada as a case study the gis fuzzy logic approach was performed based on the soil environment model case based reasoning and rule based reasoning using a 10 m lidar derived digital elevation model dem and derivatives such as curvature slope aspect slope position classification smooth multi path wetness index and surface roughness in combination with mode of deposition and spatial observations of soil depth information a digital soil depth map with classes of deep 120 cm moderately deep 60 and 120 cm shallow 15 and 60 cm and very shallow 15 cm was predicted across 430 076 ha an overall mapping accuracy of 94 in validation was obtained from the gis fuzzy logic modeling approach relative to 88 derived from the randomforest modeling technique the gis fuzzy logic modeling approach could be readily implemented to predict and map the spatial distribution of soil depth classes on various landscapes

a process based model for colluvial soil depth and shallow landsliding using digital elevation data a model is proposed for predicting the spatial variation in colluvial soil depth the results of which are used in a separate model to examine the effects of root strength and vertically varying saturated conductivity on slope stability the soil depth model solves for the mass balance between soil production from underlying bedrock and the divergence of diffusive soil transport this model is applied using high resolution digital elevation data of a well studied site in northern california and the evolving soil depth is solved using a finite difference model under varying initial conditions the field data support an exponential decline of soil production with increasing soil depth and a diffusivity of about 50 cm 2 yr the predicted pattern of thick and thin colluvium corresponds well with field observations soil thickness on ridges rapidly obtain an equilibrium depth which suggests that detailed field observations relating soil depth to local topographic curvature could further test this model bedrock emerges where the curvature causes divergent transport to exceed the soil production rate hence the spatial pattern of bedrock outcrops places constraints on the production law the infinite slope stability model uses the predicted soil depth to estimate the effects of root cohesion and vertically varying saturated conductivity low cohesion soils overlying low conductivity bedrock are shown to be least stable the model may be most useful in analyses of slope instability associated with vegetation changes from either land use or climate change although practical applications may be limited by the need to assign values to several spatially varying parameters although both the soil depth and slope stability models offer local mechanistic predictions that can be applied to large areas representation of the finest scale valleys in the digital terrain model significantly influences local model predictions this argues for preserving fine scale topographic detail and using relatively fine grid sizes even in analyses of large catchments

correlation of river water and local sea ice melting on the laptev sea shelf siberian arctic hydrographic and stable isotope 18o data from 4 summer surveys in the laptev sea are used to derive fractions of sea ice meltwater and river water sea ice meltwater fractions are found to be correlated to river water fractions while initial heat of river discharge is too small to melt the observed 0 158 km3 of sea ice meltwater arctic rivers contain suspended particles spm and colored dissolved organic material cdom that preferentially absorb solar radiation accordingly heat content in surface waters is correlated to river water fractions but in years when river water is largely absent within the surface layer absolute heat content values increase to considerably higher values with extended exposure time to solar radiation and sensible heat nevertheless no net sea ice melting is observed on the shelf in years when river water is largely absent within the surface layer the total freshwater volume of the central eastern laptev sea 72 76 n 122 140 e varies between 1000 1500 km3 34 92 reference salinity it is dominated by varying river water volumes 1300 1800 km3 reduced by an about constant freshwater deficit 350 400 km3 related to sea ice formation net sea ice melt 109 158 km3 is only present in years with high river water budgets intermediate to bottom layer 25 salinities contain 60 and 30 of the river budget in years with low and high river budgets respectively the average mean residence time of shelf waters was 2 3 years during 2007 2009