wind control of storm triggered shallow landslides 1 heavy rainstorms are a major control of shallow landsliding in mountainous areas the influence of three dimensional 3 d variability of precipitation is analyzed by coupling a fine resolution atmospheric model rams with a fine resolution topographic model dem to represent the 3 d precipitation flux generating the catastrophic flood that occurred in versilia central italy on 19 june 1996 matching of this flux with the observed scars and debris shows that 92 of the mass movements occurred where the normalized precipitation flux exceeds 0 80 and less then 2 where this is null these results give an insight of the detected role of exposure in explaining the spatial variability of observed landslides as emerging from multivariate statistical analysis the interaction of the wind driven precipitation field with topography is an important control of shallow landslides triggered by convective storms in upland catchments

mechanisms of the 1997 1998 el nino la nina as inferred from space based observations 1 the intensity of the 1997 el nino and the 8 c sudden drop in sea surface temperature sst around 0 130 w during the turn into la nina in 1998 were a surprise to the scientific community this succession of warm and cold events was observed from start to finish with a comprehensive set of remotely sensed and in situ observations in this study we employ space based observations to demonstrate for the first time their maturity in capturing the preconditioning onset evolution and decay of the 1997 el nino and its transition into the 1998 la nina an accumulation of warm water in the west and equatorial wave reflection on the western ocean boundary appeared favorable for the development of el nino however the action of a series of westerly wind bursts from december 1996 to june 1997 notably in march 1997 was instrumental in setting up this huge el nino the westerly wind bursts excited equatorial downwelling kelvin waves and advected the eastern edge of the warm pool eastward which triggered a distinct warming over the central and eastern parts of the equatorial basin once these warmed regions joined the coupling between the sst and surface winds was fully effective and el nino reached its mature phase by that time much of the warm waters of the western equatorial pacific was transferred toward the east by surface eastward currents the demise of el nino and its turn into la nina in spring 1998 were due to the arrival in the east of various interrelated phenomena upwelling was brought from the west by favorable off equatorial wind stress curl and equatorial kelvin waves generated by easterly winds and wave reflection on the western ocean boundary additional upwelling was brought from the east by equatorial rossby waves generated by westerly winds these various upwelling signals were added to the general uplifting of the thermocline because of the slow discharge of the upper layer of the equatorial basin by diverging surface currents a series of equatorial kelvin and rossby waves characterized by upwelling and opposite surface currents led to the breakup of the warm waters the surfacing of the thermocline and the drastic drop in sst in may 1998 around 0 130 w with the arrival of cold water in the east the easterly winds expanded from the west and la nina turned into a growing mode this view of the 1997 1998 el nino la nina afforded from space enables the testing of various el nino theories

modelling landslide hazard soil redistribution and sediment yield of landslides on the ugandan footslopes of mount elgon in this study the lapsus ls landslide model together with a digital terrain analysis of topographic attributes is used as a spatially explicit tool to simulate recent shallow landslides in manjiya county on the ugandan slopes of mount elgon manjiya county is a densely populated mountainous area where landslides have been reported since the beginning of the twentieth century to better understand the causal factors of landsliding 81 recent landslides have been mapped and investigated through statistical analysis it was shown that steep concave slopes high rainfall soil properties and layering as well as human interference were the main factors responsible for landslides in the study area lapsus ls is used to construct a landslide hazard map and to confirm or reject the main factors for landsliding in the area the model is specifically designed for the analysis of shallow landslide hazard by combining a steady state hydrologic model with a deterministic infinite slope stability model in addition soil redistribution algorithms can be applied whereby erosion and sedimentation by landsliding can be visualized and quantified by applying a threshold critical rainfall scenario the model is tested in the manjiya study area for its ability to delineate zones that are prone to shallow landsliding in general and to group the recent landslides into a specific landslide hazard category the digital terrain analysis confirms most of the causal topographic factors for shallow landsliding in the study area in general shallow landslides occur at a relatively large distance from the water divide on the transition between steep concave and more gentle convex slope positions which points to concentration of sub surface flow as the main hydrological triggering mechanism in addition lapsus ls is capable to group the recent shallow landslides in a specific landslide hazard class critical rainfall values of 0 03 0 05 m day 1 by constructing a landslide hazard map and simulating future landslide scenarios with the model slopes in manjiya county can be identified as inherently unstable and volumes of soil redistribution can yield four times higher than currently observed more than half of this quantity can end up in the stream network possibly damming rivers and causing major damage to infrastructure or siltation and pollution of streams the combination of a high population density land shortage and a high vulnerability to landslides will likely continue to create a major sustainability problem 2007 elsevier b v all rights reserved

seasonal fluctuations in the advance of a tidewater glacier and potential causes hubbard glacier alaska usa satellite imagery has been used to acquire seasonal terminus positions of tidewater hubbard glacier alaska usa from 1992 to 2006 during this 15 year time period the width averaged advance of the entire terminus has been 620 m at a mean rate of 35 m a 1 seasonal fluctuation of the terminus ranges from 150 to 200 m on average and varies spatially a section of the terminus near a narrow gap where the glacier has now twice closed off 40 km long russell fiord exhibited little to no mean advance during this time period but displayed seasonal fluctuations of 300 500 m seasonal variability in surface ice speeds and surface sea water temperatures was also observed both are potential forcing mechanisms for terminus fluctuations seasonal changes in sea water temperature of 10 128c as well as seasonal changes in subglacial freshwater discharge are inferred to influence calving and submarine melting at the terminus driving seasonal variations displacements of the medial moraine separating hubbard and valerie glaciers at the terminus suggest surge like pulses of the latter with a periodicity of several years the timing of these pulses suggests they may influence the hubbard terminus near gilbert point and have implications for future closures of russell fiord

interannual variability of surface currents in the tropical pacific during 1987 1993 buoy drifts and current meter records between january 1987 and december 1993 are used to investigate the interannual variability of the equatorial pacific currents at a depth of 15 m the sampling is coarse until mid 1988 but more complete afterward so that the large scale features of the anomaly currents can be documented on the seasonal to yearly timescale using objective analysis bimonthly current anomalies are mapped between 20 n and 20 s on a 1 5 grid and the error covariance matrix of the analyzed fields are estimated the current anomalies are primarily zonal with largest amplitudes within about 8 from the equator and they are largely linked to the el nino southern oscillation phenomenon in particular broad basin wide westward anomaly currents were encountered during the 1988 la nina and strong eastward currents persisted from july august 1991 to january february 1992 followed by westward currents from may june to july august 1992 an empirical orthogonal function eof analysis shows that the first eof of zonal current anomaly is largely uniform in the equatorial band while the next two eofs describe large scale currents of opposite sign across the equator and across 160 w respectively the eofs are rather smooth and the errors on the principal component time series relatively small which indicates that the sampling is adequate to describe the large scale low frequency zonal current fluctuations as the dominant eofs of meridional current are noisy and the relative errors on the principal components larger the meridional current fluctuations are not as well captured by the data set correlation analysis and a singular value decomposition are used to investigate the influence of advection by the large scale low frequency currents on sea surface temperature sst anomalies during 1987 1993 although the data set is noisy and other terms play an important role in the sst anomaly equation the effect of zonal and to a lesser extent meridional advection is seen in much of the central and eastern equatorial pacific the dominant terms are the anomalous zonal advection of mean sst the mean zonal and intermittently meridional advection of sst anomalies

slope aspect affects geomorphic dynamics of coal mining spoil heaps in belgium abstract after the abandonment of coal mining in belgium in the 1960s 1980s many coal tips have been left to themselves increasingly these coal tips are regarded as socio cultural heritage and protected for their environmental value this research analyses the spatial distribution of the main geomorphic processes sheet and rill erosion landsliding rock fragment movement and root throw occurring on coal tips in belgium through mapping of the processes and their causal factors five spoil heaps spread over the major coal basins were studied in detail the spoil heaps were subdivided in homogeneous land units especially with regard to slope gradient vegetation cover and slope aspect qualitative and quantitative observations were done on processes and potential causal factors regressions showed that generally the expression of slope processes on the studied coal tips is 1 strongly dependent on westerly aspect of the slopes 2 independent of slope gradient which presents a narrow range 3 impeded by grass cover and 4 not fully predictable due to variability in type and age of dumped mine spoil

hazardous processes and events from glacier and permafrost areas lessons from the chilean and argentinean andes glacier and permafrost hazards such as glacial lake outburst floods and rock ice avalanches cause significant socio economic damages worldwide and these processes may increase in frequency and magnitude if the atmospheric temperature rises in the extratropical andes nearly 200 human deaths were linked to these processes during the twentieth century we analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio economic damages in this region in historic time including glacial lake outburst floods ice and rock ice avalanches and lahars to unravel their causes and geomorphological impacts in the extratropical andes at least 15 ice dammed lakes and 16 moraine dammed lakes have failed since the eighteenth century causing dozens of floods some floods rank amongst the largest events ever recorded 5000 106 m3 and 229 106 m3 respectively outburst flood frequency has increased in the last three decades partially as a consequence of long term decades to centuries climatic changes glaciers shrinkage and lake growth short term days to weeks meteorological conditions i e intense and or prolonged rainfall and high temperature that increased meltwater production have also triggered outburst floods and mass movements enormous mass failures of glaciers and permafrost 10 106 m3 have impacted lakes glaciers and snow covered valleys initiating chain reactions that have ultimately resulted in lake tsunamis and far reaching 50 km flows the eruption of ice covered volcanoes has also caused dozens of damaging lahars with volumes up to 45 106 m3 despite the importance of these events basic information about their occurrence e g date causes and geomorphological impact which is well established in other mountain ranges is absent in the extratropical andes a better knowledge of the processes involved can help to forecast and mitigate these events copyright 2014 john wiley sons ltd

calving processes and the dynamics of calving glaciers abstract calving of icebergs is an important component of mass loss from the polar ice sheets and glaciers in many parts of the world calving rates can increase dramatically in response to increases in velocity and or retreat of the glacier margin with important implications for sea level change despite their importance calving and related dynamic processes are poorly represented in the current generation of ice sheet models this is largely because understanding the calving problem involves several other long standing problems in glaciology combined with the difficulties and dangers of field data collection in this paper we systematically review different aspects of the calving problem and outline a new framework for representing calving processes in ice sheet models we define a hierarchy of calving processes to distinguish those that exert a fundamental control on the position of the ice margin from more localised processes responsible for individual calving events the first order control on calving is the strain rate arising from spatial variations in velocity particularly sliding speed which determines the location and depth of surface crevasses superimposed on this first order process are second order processes that can further erode the ice margin these include fracture propagation in response to local stress imbalances in the immediate vicinity of the glacier front undercutting of the glacier terminus by melting at or below the waterline and bending at the junction between grounded and buoyant parts of an ice tongue calving of projecting submerged ice feet can be regarded as a third order process because it is paced by first or second order calving above the waterline first order calving can be represented in glacier models using a calving criterion based on crevasse depth which is a function of longitudinal strain rate modelling changes in terminus position and calving rates thus reduces to the problem of determining the ice geometry and velocity distribution realistic solutions to the problem of modelling ice flow therefore depend critically on an appropriate choice of sliding law models that assume that basal velocities are controlled by basal drag can replicate much of the observed behaviour of calving glaciers with grounded termini but an important limitation is that they cannot be used to model floating glacier termini or ice shelves alternative sliding laws that parameterise drag from the glacier margins provide more flexible and robust ways of representing calving in ice sheet models such models can explain a remarkable range of observed phenomena within a simple unifying framework including downglacier increases in velocity and strain rates where basal and or lateral drag diminishes flow acceleration in response to thinning through time the tendency for glaciers to stabilise at pinning points in relatively shallow water or fjord narrowings the constraints on ice shelf stability and the contrasts in calving rates between tidewater and freshwater calving glaciers many unresolved issues remain however including the role played by the removal of backstress in the acceleration of retreating calving glaciers and the controls on melting at and below the waterline

mass fluxes and dynamics of moreno glacier southern patagonia icefield accumulation ablation calving and flow dynamics of moreno glacier one of the main outlet glaciers of the southern patagonia icefield were studied based on field campaigns and on spaceborne radar imagery acquired by sir c x sar ice velocities and ablation were measured through two summers and one winter the ice depth was sounded seismically at a transect 8 km above the calving front showing a maximum depth of 720 m the velocity field of the terminus was derived from sir c x sar data by means of interferometry and amplitude correlation the average specific annual net accumulation is 5540 500 mm water equivalent the bottom topography of the lake and the high ratio of calving flux to net accumulation explain the remarkable stability of moreno glacier throughout this century which is in contrast to the retreat of other glaciers in this region

glacial outburst flood sediments within disenchantment bay alaska implications of recognizing marine jokulhlaup deposits in the stratigraphic record abstract glacial outburst floods have been observed or inferred in most glaciated regions of the world outburst flooding events along past ice sheet margins have been discussed as possible causes for changes in ocean circulation while subglacial lake drainage under ice sheets may influence ice sheet stability the recognition of these geologically instantaneous events in the marine sediment or rock record is critical in order to characterize the magnitude and frequency of past outburst events as well as to predict the likelihood of future occurrences in this paper we characterize outburst lithofacies and infer depositional processes from two outburst floods within disenchantment bay alaska and compare these deposits to other recognized outburst deposits within marine depositional settings here we show that the outburst deposits are lithologically similar and are composed of stratified mud sand and diamicton we interpret these facies to have been formed by sediment gravity flows and hypopycnal plume sedimentation these results show that the volume of sediment lithofacies and inferred depositional processes cannot be easily distinguished from normal sediment accumulation within the proximal temperate glacimarine depositional environment the paucity of fluvial subglacial discharge in polar glacimarine environments suggests the potential for recognition of such deposits in the antarctic

documentary and tree ring evidence for a long term interval without ice impoundments from glaciar perito moreno patagonia argentina glaciar perito moreno hereafter gpm 50 30 s and 72 50 w is a major outlet glacier from the south patagonia icefield in contrast to most patagonian glaciers glaciological studies indicate that

the combined effect of wind and topography on rainfall distribution abstract the combined effect of wind and topography on rain motion and rainfall distribution is analyzed it is shown that the effect depends on the inclination angle of the raindrops at large heights and on a dimensionless number p which describes the ratio of the response distance of falling raindrops to the length scale of the topography two asymptotic solutions are derived for small and large values of p and it is proved that the hydrological rainfall intensity per projected unit area over large scale topographical configurations is uniform the rain motion and rainfall distributions over low hills for intermediate values of p are calculated numerically the analysis exhibits the features of the effect and its dependence on the raindrop size wind field and the scale of the topography

the north equatorial countercurrent and heat storage in the western pacific ocean during 1982 83 a sequence of extreme climate anomalies known as an el nino southern oscillation episode was observed in the tropical pacific ocean during 1982 831 2 models suggest that oceanic circulation has an important role in the formation of such anomalies1 3 4 by altering the pattern of sea surface temperature through advection the baroclinic structure of the upper 500 m of the ocean has been monitored routinely in the western pacific since 1979 providing indirect current measurements by the geostrophic method these observations reported here show large changes in the near equatorial currents during 1982 83 which are consistent with currents observed in the central and eastern pacific5 6 in particular the north equatorial countercurrent necc flowed with 25 50 increased strength during the early phase then weakened almost to zero flow the west pacific heat pool cooled by more than 1 c observed changes in circulation were large enough to alter surface heat storage by advection although other potentially important processes may not be negligible

the impact of eastern pacific versus central pacific el ninos on the north equatorial countercurrent in the pacific ocean 1 using a three dimensional ocean reanalysis data product the influence of two types of the el ninos on the north equatorial countercurrent necc across the pacific basin is examined in this study eastern pacific el ninos ep el ninos exert a significant impact on the interannual changes of the necc whereas central pacific el ninos cp el ninos have little influence from the developing to mature phase of the ep el ninos that occursfrequently in the latter half of a calendar year the necc tends to intensify and shift southward while the ep el nino related position changes of the necc is out of phase with its seasonal position changes the ep el nino related intensity variability of the necc is in phase with its seasonal modulation during both types of el ninos the el nino modulated wind stress curl forcing changes the upper ocean thickness modifying the necc intensity and central position the weaker and shorter fluctuations of wind stress curl forcing during the cp el nino events induce irregular and insignificant changes of the necc

an improved real time global sea surface temperature analysis abstract the monthly global sea surface temperature sst analysis of reynolds using real time in situ and satellite sst data has now been improved by using sea ice data to simulate ssts in ice covered regions the simulated ssts now become the external boundary condition for the analysis solution this technique eliminates any high latitude satellite biases and extends the analysis to the ice edge the analysis with the ice data has been computed for the period january 1982 to present

sand transport under increased lateral jetting of raindrops induced by wind abstract wind tunnel experiments for raindrop detachment and wind driven transport rd wdt process were conducted under improved lateral jetting induced by wind velocities of 6 4 10 and 12 m s 1 at nozzle operating pressures of 75 100 and 150 kpa wind driven rainfalls were also incident on the windward and leeward slopes of 4 and 9 to have a broad variation in the angle of incidence the objective of this experimental set up was to distinguish the roles of both impact components of obliquely striking wind driven raindrops on rd and wind on wdt raindrop impact components and reference horizontal wind were quantified by normal etz and horizontal etx kinetic energy fluxes and wind shear velocity u respectively to physically model the process of rd wdt the results showed at each level of u differential sand transport rates by rd wdt qm rd wdt occurred depending on the magnitude of raindrop impact components and qm rd wdt increased as the relative contribution of etz increased although etx was more correlated with qm rd wdt than etz the extreme increases in etx at the expense of etz brought about no increases but decreases in qm rd wdt an rd wdt model was built under the process of examining the discrete effects of etz and etx on rd together with u and resulted in a better coefficient of determination r2 0 89 than only total kinetic energy et did alone with u r2 0 84 in this study etx was strongly related to u and not to etz which was the principal difference from the previous rainsplash studies which relied on the compensatory lateral jet development by the compressive pressure build up at the raindrop soil interface including etx in the rd wdt model both separated the distinct role of each raindrop impact component in rd and improved the performance of u in wdt by better distinguishing its interaction with etx which was not explicitly separated in previous models of rd wdt

variations of zonal currents in the central tropical pacific during 1970 to 1987 sea level and dynamic height measurements the annual and interannual variations of the major zonal currents of the central tropical pacific for the period 1970 1987 are described by analyzing two data sets sea level data from a few selected island stations and ship of opportunity expendable bathythermograph xbt observations the annual cycles of geostrophic surface current indices dynamic height or sea level difference between the ridge and the trough defining the current in the north equatorial current nec and north equatorial countercurrent necc are found to be in phase maxima in november to be strong and to explain about 50 of the total variance the annual cycle of volume transport relative to 400 dbar in the necc is also strong but nec volume transport has a weak annual cycle the discrepancy between the nec surface current and the transport is due to the variation of the surface current being larger than that of the deep currents the annual cycle of the transport of the south equatorial current sec is 6 months out of phase with that of the nec and necc phases of the annual cycles of the sea level and dynamic height indices of flow agree well in general but there are significant differences between the annual amplitudes of the two types of measurements these differences arise from a variety of sources dynamic height reference level assumptions longitudinal spacing of sea level gauges meridional resolution of sea level array and different signal to noise ratios for the two sets of indices the necc shows marked flow maxima during the peaks of the strong ninos of 1972 and 1982 which were followed by near disappearance of the current the following year these fluctuations are clearly present in both the surface current indices and the volume transport in 1976 and 1986 1987 moderate ninos the same pattern is not marked the el nino signal in nec transport is weak there was a strong rise of equatorial sea level during the early phases of the 1972 and 1982 ninos followed by a fall the next year this resulted in a decrease of the transport of the sec in the first year followed by an increase to a maximum during the second year the maximum coincides with a minimum in necc transport

equatorial wave sequence associated with warm pool displacements during the 1986 1989 el nino la nina in the pacific equatorial band the zonal displacement of the eastern edge of the warm pool subject to insignificant seasonal variations is dominated by strong interannual variations almost in phase with the southern oscillation index over the 1971 1973 el nino la nina period gill 1983 suggested that such displacement was caused solely by horizontal advection by zonal current anomaly basin wide geosat derived zonal surface current anomalies are available during the 1986 1989 period and they agree quite well with observed equatorial currents in the western and central pacific within the 4on 4 s equatorial band the cumulative contribution of first baroclinic kelvin and first symmetric m 1 rossby modes to surface zonal equatorial current anomalies account for most of the geosat derived current variability from these geosat derived currents it is demonstrated that the eastward westward displacement of the eastern edge of the warm pool was primarily due to horizontal advection by zonal current anomalies during the 1986 1987 el nino 1988 1989 la nina as a corollary the el nino la nina warm cold sea surface temperature sst anomaly in the central western pacific was the result of anomalous zonal advection the 1986 1989 displacement of the warm pool appeared as a low frequency movement resulting from high frequency forcing i e a succession of local wind forcing and its remote kelvin and m 1 rossby wave responses in the equatorial waveguide in the central western pacific a in 1 downwelling rossby wave issued from the eastern pacific shifted the displacement from eastward to westward and therefore seems to have been the cause for el nino to turn to la nina in boreal fall 1987 in the eastern pacific the simultaneous occurrence of free propagating downwelling upwelling kelvin waves with the seasonal sst warming cooling appeared necessary for the development of local el nino la nina sst anomaly over most of the equatorial pacific slow migration of sst anomalies clearly showed up distinct during el nino and la nina these zonal migrations appeared to result from the delayed association of two phenomena the zonal advection in the central western pacific and the arrival of downwelling upwelling kelvin waves into the eastern pacific synchronous with the seasonal sst warming cooling albeit different in terms of equatorial wave action as compared to the delayed action oscillator theory our results suggest that zonal advection and wave dynamics were both important for the generation and migration of el nino southern oscillation sst anomalies in 1986 1989 finally our observational results about warm pool displacements equatorial wave sequence the shift from el nino to la nina and the slow sst migrations are presented in a schematic form involving sequential ocean atmosphere coupling which appears continuously over the november 1986 to a

intense surface currents in the tropical pacific during 1996 1998 tropical pacific ocean near surface currents and their momentum and temperature balances are investigated using several data sets including drifting buoy velocities and topex poseidon altimetry the data sets are combined to produce monthly surface current estimates on a uniform grid for the 6 year period 1993 1998 using multivariate optimal interpolation the analysis shows dramatic changes in current from december 1996 through august 1998 in response to the recent el nino southern oscillation event eastward current anomalies of 1ms 21 were recorded in december 1996 in the western pacific generated by sporadic westerly wind bursts by april 1997 these equatorial anomalies reached the eastern boundary and in the summer of 1997 a band of strong eastward flow formed across the basin this circulation pattern persisted until the beginning of 1998 when a westward equatorial jet appeared in january april interestingly the reversal of flow occurred prior to the restoration of the trade winds the timing of these events as well as the results of previous dynamical studies raise questions about the relative importance of terms in the zonal momentum and temperature balances we address the first of these questions by examining the applicability of a three term linear zonal momentum balance on the equator in all cases we focus on anomalies from the time mean our results show that local acceleration is reasonably well balanced by the difference between zonal pressure gradient anomaly and wind induced momentum flux this three term balance displays significant basin wide variations and is consistent with the conclusion that the equatorial pacific is not in equilibrium with local wind forcing due to the presence of propagating waves examination of the temperature balance shows that at the beginning of el nino the warming in the central pacific is mainly supported by horizontal temperature transport while the vertical heat exchange and transport become important in the eastern half of the equatorial pacific during the transition from el nino to la nina

synchronous retreat and acceleration of southeast greenland outlet glaciers 2000 06 ice dynamics and coupling to climate a large portion of the recent increase in the rate of mass loss from the greenland ice sheet is from increased outlet glacier discharge along its southeastern margin while previous investigations of the region s two largest glaciers suggest that acceleration is a dynamic response to thinning and retreat of the calving front it is unknown whether this mechanism can explain regional acceleration and what forcing is responsible for initiating rapid thinning and retreat we examine seasonal and interannual changes in ice front position surface elevation and flow speed for 32 glaciers along the southeastern coast between 2000 and 2006 while substantial seasonality in front position and speed is apparent nearly all the observed glaciers show net retreat thinning and acceleration with speed up corresponding to retreat the ratio of retreat to the along flow stress coupling length is proportional to the relative increase in speed consistent with typical ice flow and sliding laws this affirms that speed up results from loss of resistive stress at the front during retreat which leads to along flow stress transfer large retreats were often preceded by the formation of a flat or reverse sloped surface near the front indicating that subsequent retreats were influenced by the reversed bed slope many retreats began with an increase in thinning rates near the front in the summer of 2003 a year of record high coastal air and sea surface temperatures this anomaly was driven in part by recent warming suggesting that episodes of speed up and retreat may become more common in a warmer climate

sand detachment under rains with varying angle of incidence abstract in the case of wind driven rain as the angle of rain incidence increases greater force components act parallel to the surface and lower force components act perpendicular to the surface therefore raindrop impact angle could influence the detachment process in the existence of substantial lateral jet development this could be particularly significant for a cohesionless sand surface that has a weaker resistance to the dislodgement by a raindrop impact than a soil surface experiments of simulated wind driven rain were conducted to evaluate sand detachment rates under increased lateral jetting induced by wind velocities of 6 4 10 0 and 12 0 m s 1 at nozzle operating pressures of 75 100 and 150 kpa and incident on windward and leeward slopes of 4 and 9 with these set ups it was possible to have varying angles of incidence and to determine the effect of the compressive stress and shear stress evaluated by the horizontal and vertical kinetic energy fluxes e tx and e tz respectively on the detachment rates from the sand surface at the same vectorwise sum of e tz and e tx the results showed that there was for similar values of e tz and e tx in windward slopes more sand detachment rate however for dissimilar values of e tz and e tx in leeward slopes where e tx was significantly higher than e tz there was less sand detachment rate consequently with certain values of the compressive stress and shear stress the sand detachment rates under wind driven rains peaked and e tz was the limiting component since the rates significantly decreased as e tz particularly decreased in spite of very large values of e tx

alaska tidewater glacier terminus positions 1948 2012 a significant portion of the world s glacier ice drains through tidewater outlets though much remains unknown about the response to recent climate change of tidewater glaciers we present a 64 year record of length change for 50 alaska tidewater glaciers we use u s geological survey topographic maps to provide a base length for glaciers before 1970 using all available cloud free landsat images we manually digitize calving front outlines for each glacier between 1972 and 2012 resulting in a total of more than 10 000 outlines tidewater glacier lengths vary seasonally focusing on the 36 glaciers terminating in tidewater throughout the study period we find a mean standard deviation seasonal variation of 60 85 m a 1 we use these oscillations to determine the significance of interannual changes in glacier length all 36 glaciers underwent at least one period 1 year of significant advance or retreat 28 glaciers underwent at least one period of both significant advance and retreat over the entire period 1948 2012 24 of these glaciers retreated a total uncertainty of 107 95 0 29 km 11 advanced a total of 7 71 0 20 and one chenega glacier did not change significantly retreats and advances are highly variable in time several glaciers underwent rapid short term retreats of a few years duration these retreats occurred after large changes in summer sea surface temperature anomalies further study is needed to determine what triggered these retreats no coherent regional behavior signal is apparent in the length record although two subregions show a coherence similar to recent observations in greenland

rainfall redistribution over low hills due to flow perturbation abstract a simple potential flow model is developed for airflow over low hills the model readily allows incorporation of simple rain microphysics so that drop trajectories can be traced in the region of a hill complex rainfall intensity variations are found in the horizontal and in the vertical and a straightforward modification to the model allows for time dependence to be studied the model is shown to serve as a useful diagnostic tool to describe rain drop redistribution due to perturbed airflow in particular increased rainfall is predicted in the lee of hill peaks and depleted rainfall is predicted on ridges the redistribution effects dominate at low levels in contrast to predictions based on seeder feeder enhancement comparison with field measurements shows good qualitative agreement over low hills and in some cases close quantitative agreement redistribution of rain appears to be a significant process that should be considered in rainfall interpolation and prediction schemes involving hilly terrain

age of the fjord stade moraines in the disko bugt region western greenland and the 9 3 and 8 2 ka cooling events abstract retreat of the western greenland ice sheet during the early holocene was interrupted by deposition of the fjord stade moraine system the fjord stade moraine system spans several hundred kilometers of western greenland s ice free fringe and represents an important period in the western greenland ice sheet s deglaciation history but the origin and timing of moraine deposition remain uncertain here we combine new and previously published 10 be and 14 c ages from disko bugt western greenland to constrain the timing of fjord stade moraine deposition at two locations 60 km apart at jakobshavn isfjord the northern of two study sites we show that jakobshavn isbrae advanced to deposit moraines ca 9 2 and 8 2 8 0 ka in southeastern disko bugt the ice sheet deposited moraines ca 9 4 9 0 and 8 5 8 1 ka our ice margin chronology indicates that the greenland ice sheet in two distant regions responded in unison to early holocene abrupt cooling 9 3 and 8 2 ka as recorded in central greenland ice cores although the timing of fjord stade moraine deposition was synchronous in jakobshavn isfjord and southeastern disko bugt within uncertainties we suggest that jakobshavn isbrae advanced while the southeastern disko bugt ice margin experienced stillstands during the 9 3 and 8 2 ka events based on regional geomorphology and the distribution of 10 be ages at each location the contrasting style of ice margin response was likely regulated by site specific ice flow characteristics jakobshavn isbrae s high ice flux results in an amplified ice margin response to a climate perturbation both warming and cooling whereas the comparatively low flux sector of the ice sheet in southeastern disko bugt experiences a more subdued response to climate perturbations our chronology indicates that the western greenland ice sheet advanced and retreated in concert with early holocene temperature variations and the 9 3 and 8 2 ka events although brief were of sufficient duration to elicit a significant response of the western greenland ice sheet

interannual geostrophic current anomalies in the near equatorial western pacific abstract a network of island tide gauges is used to estimate interannual geostrophic current anomalies gcas in the western pacific from 1975 to 1997 the focus of this study is the zonal component of the current averaged between 160 e and 180 and 2 to 7 north and south of the equator in the mean flow regions associated with the north equatorial countercurrent necc and the south equatorial current sec respectively the tide gauge gca estimates agree closely with similarly derived currents from topex poseidon sea level anomalies the gcas in the western pacific relate to a basin scale adjustment associated with the el nino southern oscillation characterized here using empirical orthogonal functions of tide gauge and supporting sea surface temperature and heat storage data the dominant eof mode describes the mature phase of enso events and correlates 0 8 with the gca south of the equator the second mode describes transitions to and from enso events and correlates 0 9 with the gca north of th

airborne surface profiling of glaciers a case study in alaska a relatively lightweight and simple airborne system for surface elevation profiling of glaciers in narrow mountain valleys has been developed and tested the aircraft position is determined by kinematic global positioning system gps methods the distance to the glacier surface is determined with a laser ranger the accuracy is about 0 3 m sufficient to permit future changes to be observed over short time intervals long term changes can be estimated by comparison of profiles with existing maps elevation profiles obtained in 1993 94 from three glaciers in central and south central alaska are compared with maps made about 1950 the resulting area averaged seasonally corrected thickness changes during the interval are gulkana glacier central alaska range 11 m worthington glacier central chugach mountains 7 m and bear lake glacier kenai mountains 12 m all three glaciers retreated during the interval of comparison the estimated uncertainty in the average thickness change is 5 m which is mainly due to errors in the existing maps constraints on the accuracy of the maps are obtained by profiling in proglacial areas

impact of wind on the spatial distribution of rain over micro scale topography numerical modelling and experimental verification the wind driven rain effect refers to the redistribution of rainfall over micro scale topography due to the existence of local perturbed wind flow patterns rainfall measurements reported in the literature point to the fact that the wind driven rain distribution can show large variations over micro scale topography these variations should be taken into account in hillslope hydrology in runoff and erosion studies and in the design of rainfall monitoring networks in practice measurements are often not suitable for determining the wind driven rain distribution therefore a few researchers have employed numerical modelling in order to provide confidence in using numerical models experimental verification for a range of different topographic features is imperative the objective of this study is to investigate the adequacy of a two dimensional computational fluid dynamics cfd model to predict the wind driven rain distribution over small scale topography the numerical model is applied to a number of topographic features including a succession of cliffs a small isolated hill a small valley and a field with ridges and furrows the numerical results are compared with the corresponding measurement results reported in the literature it is shown that two dimensional numerical modelling can provide a good indication of the wind driven rain distribution over each type of micro scale topography that is considered in this study it is concluded that more detailed verification procedures are currently inhibited due to the lack of available and detailed spatial and temporal rainfall data from field measurements copyright 2005 john wiley sons ltd

factors controlling the spatial distribution of soil piping erosion on loess derived soils a case study from central belgium abstract collapsible loess derived soils are prone to soil piping erosion where enlargement of macropores may lead to a subsurface pipe network and eventually to soil collapse and gully development this study aims at understanding the main factors controlling spatial patterns of piping in loess derived soils under a temperate climate to map the spatial distribution of piping and identify the environmental controls on its distribution a regional survey was carried out in a 236 km2 study area in the flemish ardennes belgium orthophotos taken at optimal field conditions winter were analyzed to detect piping in open landscapes and ground thruthing was systematically done through field surveys in total 137 parcels having 560 collapsed pipes were mapped dimensions of the sinkholes and local slope gradient were measured in the field and topographical variables were derived from lidar data land use plays an important role as 97 of the sites with piping are found under pasture the probability of piping increases rapidly on hillslopes with gradients exceeding 8 and with a concave profile and plan curvature enhancing subsurface flow concentration the zones with soil profiles on shallow loess over a relatively thin layer of homogeneous blue massive clays aalbeke member are most prone to piping soil characteristics are of less importance to explain piping occurrence furthermore the topographical threshold line indicating the critical slope gradient for a given contributing drainage area was determined this threshold line negative power relation is similar to the threshold line for shallow gully initiation

where glaciers meet water subaqueous melt and its relevance to glaciers in various settings glacier change is ubiquitous but the fastest and largest magnitude changes occur in glaciers that terminate in water this includes the most rapidly retreating glaciers and also several advancing ones often in similar regional climate settings furthermore water terminating glaciers show a large range in morphology particularly when ice flow into ocean water is compared to that into freshwater lakes all water terminating glaciers share the ability to lose significant volume of ice at the front either through mechanical calving or direct melt from the water in contact here we present a review of the subaqueous melt process we discuss the relevant physics and show how different physical settings can lead to different glacial responses we find that subaqueous melt can be an important trigger for glacier change it can explain many of the morphological differences such as the existence or absence of floating tongues subaqueous melting is influenced by glacial runoff which is largely a function of atmospheric conditions this shows a tight connection between atmosphere oceans and lakes and glaciers subaqueous melt rates even if shown to be large should always be discussed in the context of ice supply to the glacier front to assess its overall relevance we find that melt is often relevant to explain seasonal evolution can be instrumental in shifting a glacier into a different dynamical regime and often forms a large part of a glacier s mass loss on the other hand in some cases melt is a small component of mass loss and does not significantly affect glacier response

average sand particle trajectory examined by the raindrop detachment and wind driven transport rd wdt process recent studies of soil loss by the integrated action of raindrop impact and wind transport have demonstrated the significance of this mechanism this paper presents data obtained during wind tunnel experiments examining the raindrop detachment and wind driven transport rd wdt process to investigate average sand particle trajectory and the spatial extent at which the process operates in the experimental design at the same time as the horizontal wind velocities of 6 4 10 and 12 m s 1 passed through the tunnel rainfall was simulated falling on very well sorted dune sand the aspect and slope of the sand bed was varied to reproduce both windward ww and leeward lw slopes of 4o and 9o with respect to the prevailing wind direction the average sand particle trajectories by the rd wdt process were estimated by a mass distribution function which was integrated over a 7 m uniform slope segment the results showed that depended statistically upon the wind shear velocity u and the effect of the slope gradient was insignificant on this was different from that of the windless rain process raindrop detachment and splash driven transport rd st the spatial range of which relies strongly on additionally was approximately 2 27 2 2 times greater than the average path of a typical saltating sand particle of the rainless wind wind erosion saltation transport we st copyright 2009 john wiley sons ltd

intraseasonal variability of the surface zonal currents in the western tropical pacific ocean characteristics and mechanisms abstractthe surface circulation of the tropical pacific ocean is characterized by alternating zonal currents such as the north equatorial current nec north equatorial countercurrent necc south equatorial current sec and south equatorial countercurrent secc in situ measurements of subsurface moorings and satellite observations reveal pronounced intraseasonal variability isv 20 90 days of these zonal currents in the western tropical pacific ocean wtpo the amplitude of isv is the largest within the equatorial band exceeding 20 cm s 1 and decreases to 10 cm s 1 in the necc band and further to 4 8 cm s 1 in the nec and secc the isv power generally increases from high frequencies to low frequencies and exhibits a peak at 50 60 days in the necc sec and secc these variations are faithfully reproduced by an ocean general circulation model ogcm forced by satellite winds and parallel model experiments are performed to gain insights into the underlying mechanisms it is found that large sca

topex poseidon the 2 cm solution the unprecedented accuracy of topex poseidon t p altimeter data warrants a new evaluation of the methods typically used to form time series of sea level change whereas explicit removal of orbit error has always been required as a first step in altimeter data processing the t p analysis presented here is based simply on unadjusted monthly averages this approach has the advantage of retaining the large scale ocean signal which would be distorted by orbit adjustment using 16 months of data we have evaluated the t p monthly means on spatial scales ranging from mesoscale to global in the tropical pacific comparisons with 17 island tide gauge records and dynamic height derived from 36 thermistor moorings show that the altimeter data have an accuracy of approximately 2 cm when averaged over spatial scales of a few hundred kilometers on basin scales in the northern hemisphere similar agreement is found between the t p data and the dynamic height climatology of levitus 1982 these new altimeter observations are thus providing the first reliable view of global sea level changes on seasonal to interannual timescales

structure and evolution of interannual variability of the tropical pacific upper ocean temperature n n yearly in situ temperature anomaly data for the period 1961 1990 are analyzed to reveal the dominant structure and evolution of interannual variability of the tropical pacific upper ocean we use multivariate empirical orthogonal function eof analyses to detect the principal three dimensional structure related to el nino there are well defined subsurface thermal patterns characterized by a prominent sea saw structure with opposite anomaly polarity in the equatorial and off equatorial tropical north pacific regions during an el nino year a positive temperature anomaly is found in the e astern and central tropical upper ocean this is accompanied by a corresponding negative anomaly at subsurface depths in the west with a maximum at 100 150 m off the equator unlike sea surface temperature whose variations are confined largely to the east with one dominant polarity temperature variations at 50 200 m depths have a dipole pattern with out of phase oscillations in the central equatorial pacific and in the western tropical north pacific a reverse pattern of these anomalies is observed during a la nina year evolution between el nino and la nina involves a significant zonal transfer of anomaly phase across the equatorial basin as well as across the off equatorial tropical north pacific showing consistent and coherent variations from west to east from subsurface to sea surface and from on the equator to off the equator this phase propagation is more evident at subsurface depths than that at the sea surface suggesting a continual movement of anomaly pattern in succession eastward along the equator and westward off the equator of the tropical north pacific with spatial inhomogeneities of zonal propagation in longitude our analyses present evidence of the manner in which temperature anomalies evolve at subsurface ocean depths in the tropical pacific thus providing an observational basis for evaluating theoretical studies and model simulations the dynamical implication of these results is also discussed

the influence of rainfall on transport of beach sand by wind this paper deals with the effect of rainfall on the process of wind erosion of beach sands and presents results from both field and wind tunnel experiments although sediment transport by splash is of secondary importance on coastal dunes splash saltation processes can move sediments in conditions where no motion is predicted by aeolian processes the effect of raindrop impact on the movement of soil particles by wind was measured on a sand beach plain using an acoustic sediment sampler in general an increase of particle movement by wind at the sensor heights was observed during rainfall rainfall also affected the wind erosion process during and after rain by changing the cohesive conditions of the surface the influence of the surface moisture content on the initiation of wind erosion and on the vertical distribution of transported sand particles was studied in a wind tunnel moisture significantly increased threshold wind velocities for the initiation of sediment transport and modified vertical sediment profiles

interannual north equatorial countercurrent variability and its relation to tropical atlantic climate modes 1 a synthesis product of the surface geostrophic circulation is used to quantify the interannual variability of the wind driven north equatorial countercurrent necc the first mode of a complex empirical orthogonal function ceof decomposition of zonal geostrophic velocity in the necc region reveals pronounced latitudinal displacements in addition to variations in current strength while north south migrations of the necc are mainly captured by the real pattern the imaginary pattern accounts for variations in its strength associated with these spatial patterns is prevailing propagation toward the northwest that is most pronounced northward of the mean necc position 6 n there is evidence that the zonal propagation characteristics are consistent with long rossby waves forced in the northeastern tropical atlantic the relationship between interannual necc variations and the tropical atlantic climate modes is investigated through regression and composite analyses sea surface temperature and wind stress patterns resembling the meridional and zonal modes are found for the ceof regression composite analysis further shows consistent patterns for warm phases of the meridional mode and cold phases of the zonal mode the response of the necc to a positive meridional and negative zonal mode event may be viewed as a northward shift of its core and a current strengthening respectively these results support a link between the two dominant tropical atlantic climate modes and show that the relation between interannual necc variability and the meridional and zonal modes can primarily be regarded as a response to changes in the wind field

the effect of oblique rain on inclined surfaces a nomograph for the rain gauge correction factor inclined rainfall leads to errors in the assessment of effective precipitation in areas with rugged relief this affects many hydrological studies such as hydrological forecasts water erosion determination of conditions for flash flood formation determination of cropping conditions etc in this paper a nomograph is presented for the rain gauge correction factor cgau by which rainfall measured in a standard horizontal rain gauge pgau may be corrected to obtain the rainfall flux actually received on the inclined surface under study pact cgau pgau the correction factor is assumed to be a function of wind with constant wind velocity type of rainfall and inclination and orientation of the sloping surface with respect to the oblique rain

glacial dynamics at the beginning of termination i in the eastern alps and their stratigraphic implications abstract results of a geological re investigation of the type localities of the buhl stadial the supposed first halt during ice decay of the inn glacier in the basin of hopfgarten and at the southern flank of the mountain range wilder kaiser northern tyrol austria are presented it is shown that in this region no stationary or advancing inn glacier tongue existed following the last glacial maximum lgm ice extent all sedimentary and morphological evidence indicates that large parts of the inn glacier and all other eastern alpine valley glaciers became stagnant followed by massive down wasting hence this period after the lgm at the beginning of termination i wurm lateglacial is best defined as phase of early lateglacial ice decay which can be tentatively correlated to greenland stadial 2c 21 2 19 5 kyr bp only smaller glaciers advanced towards their lateglacial maximum position lmp this happened mostly due to short lasting climatic oscillations as indicated in the windau valley hopfgarten and at steinach am brenner a mechanically induced glacier advance is reconstructed for the cirque glaciers of the wilder kaiser at an advanced stage of down melting they lost their blockade established by the inn glacier during lgm and advanced downvalley it is proposed to define the processes of this phase by lithostratigraphic type sections

freshwater calving and anomalous glacier oscillations recent behaviour of moreno and ameghino glaciers patagonia moreno glacier has been consistently advancing during a period of general glacier retreat this century and has repeatedly dammed an arm of lago argentino the most recent episode of ice dam failure and catastrophic lake drainage occurred in 1988 however the recent periodicity of this behaviour has now been interrupted and the current characteristics of the terminus suggest a future retreat because of the nature of calving dynamics such a retreat would be rapid and irreversible in the short term neighbouring ameghino glacier after almost a century of near stagnation commenced calving in a newly formed proglacial lake in about 1967 and then retreated 3 km at a mean rate of 334myr 1 for the next nine years in a fashion analagous to that predicted for moreno glacier the behaviour of these glaciers cannot be related directly to regional climate trends terminus response is more closely controlled by the interplay between calving dynamics and topography calving is therefore a potentially significant

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

impact of slope aspect on hydrological rainfall and on the magnitude of rill erosion in belgium and northern france abstract the impact of slope aspect on hydrological rainfall and on the magnitude of rill erosion has rarely been studied the dominant wind direction in belgium and northern france is the southwest which brings large amounts of rain with it we investigated whether this leads to greater rates of rill erosion on the southwestern slopes due to the greater amount of hydrological precipitation on these slopes the study was executed on six barren conical spoil heaps which are excellent study objects to bring the slope aspect in relation with rill erosion three indicators for rill erosion volume of rills drainage density and mean distance of the head cut of the five uppermost rills till the top of the spoil heap were associated with four explanatory factors slope gradient vegetation density rock fragment cover and slope aspect the amount of hydrological rainfall is the greatest on the western and southwestern slopes as a result the largest volume of rills was measured on the slopes facing the southwest 96 which indicates that there is a connection between the slope aspect and the magnitude of rill erosion on the northeastern 32 and eastern 36 slopes the volume of rills is lower due to the effect of rain shadow the other explanatory factors showed little influence on the magnitude of rill erosion as the spoil heaps were selected to be similar in as many parameters as possible

possible gyre gyre interaction in the pacific ocean the subtropical anticyclonic gyres of the north and south pacific ocean are among the largest circulation systems found in the ocean the gyres contain the warm waters of the warm water sphere1 2 and the rotation of these water masses is subject to low frequency variations3 the presence in these gyres of baroclinic rossby waves with periods of many years has been documented4 5 and this seems to be sufficient proof that the gyres undergo vacillations using sea level data we demonstrate here that the subtropical gyres of the north and south pacific oscillate with a period of about 4 years and that these oscillations are probably induced by the major el nino events

glaciar perito moreno patagonia climate sensitivities and glacier characteristics preceding the 2003 04 and 2005 06 damming events mass balance and climate sensitivity of glaciar perito moreno gpm one of the main outlet glaciers of hielo patagonico sur southern patagonia icefield were investigated field measurements were carried out from 1995 to 2003 including ice ablation and velocity at stakes seismic profiling bathymetry of the lake near the calving fronts and meteorological data the database was complemented by satellite observations to derive the motion field by interferometric data map glacier boundaries and snowlines from multi year time series of radar images and obtain glacier topography from the shuttle radar topography mission in september 2003 gpm started to dam the southern arm of lago argentino resulting in a maximum rise of the lake level of 9 35 m before the dam burst in march 2004 the ice dam formed again in august 2005 bursting in march 2006 analysis of mass fluxes indicates no long term trend in mass balance this behaviour contrasting with most retreating glaciers in the vicinity can be attributed to a particular glacier geometry monthly climate sensitivity characteristics for glacier mass balance were derived using a degree day model showing similar importance of both temperature and precipitation also the reconstruction of the mass balance for the last 50 years from local climate data shows a near steady state condition for gpm with some small fluctuations such as a slightly positive balance after 1998 that may have triggered the minor advance leading to damming events in 2003 and 2005