enhanced turbulence and energy dissipation at ocean fronts the ocean surface boundary layer mediates air sea exchange in the classical paradigm and in current climate models its turbulence is driven by atmospheric forcing observations at a 1 kilometer wide front within the kuroshio current indicate that the rate of energy dissipation within the boundary layer is enhanced by one to two orders of magnitude suggesting that the front rather than the atmospheric forcing supplied the energy for the turbulence the data quantitatively support the hypothesis that winds aligned with the frontal velocity catalyzed a release of energy from the front to the turbulence the resulting boundary layer is stratified in contrast to the classically well mixed layer these effects will be strongest at the intense fronts found in the kuroshio current the gulf stream and the antarctic circumpolar current all of which are key players in the climate system

assessment of multiple and interacting modes of soil loss in the karst critical zone southwest china swc abstract in southwest china swc soil loss is becoming a serious threat to the sustainable development of resources and the health of the environment a large number of studies have been conducted to investigate the causes e g environmental factors and human activities and impacts e g karst rocky desertification of soil loss however the following are some important problems related to soil loss in the karst of swc 1 although soil loss is caused by chemical weathering gravity and water interaction in karst the mechanisms by which soil loss takes place in the swc and their interaction are still not clear 2 subsurface soil loss varies under different geological and hydrological conditions and there is still no consensus on the common the ratio between surface soil erosion and underground soil loss 3 traditional methods for soil loss risk assessment are difficult to apply over the whole of swc and 4 a large number of studies have been published only in chinese and remain inaccessible to the international science community therefore a review paper is needed to address this gap and introduce the contributions of chinese researchers to soil loss in karst this paper proposes a novel modelling approach for the grouped soil loss styles and presents a comprehensive discussion for the mechanism causes and risk assessment of the various soil loss styles in swc karst

the soil leakage ratio in the mudu watershed china soil leakage in karst areas is an important geomorphic agent of environmental interest there are several viewpoints concerning soil leakage ratios one viewpoint states that the soil leakage ratio is high in karst regions whereas others consider that it is very low this paper s objective is to describe the soil leakage phenomena qualitatively and quantitatively in the chongqing karst china by conventional methods such as monitoring runoff plots and paint traces drawn on piles and walls found within runoff plots and by measuring the activity of the isotope 137cs at small medium and large spatial scales this paper s results show that soil filled karst cracks occurred at a small spatial scale with soil leakage ratios ranging from about 3 to about 34 at two abandoned quarries and six soil profiles with rock karst crack development the soil leakage ratio was almost zero at the medium spatial scale the soil leakage ratio was 4 50 and the surface soil erosion ratio was 95 50 of the total soil erosion at the large spatial scale it is concluded that soil leakage ratios in the study area were low at a large spatial scale and that cracks in karst were filled with soil at small spatial scales this paper s results indicate that soil leakage phenomena vary depending on the processes acting at the small medium and large spatial scales

identifying marine incursions into the paleogene bohai bay basin lake system in northeastern china abstract the extent of marine influence on the paleogene bohai bay basin in northeastern china which accumulated mainly continental e g fluvial and lacustrine facies remains under debate evidence from geochemical paleontological and lithological data have documented several marine incursions but no systematic study has been conducted to investigate their timing and frequency and their significance for understanding the paleogene tectonic evolution of northeastern china in order to address the marine influence on sediment accumulation and to identify variations in paleosalinity during deposition of the mid eocene lower es3 es3l member of the shahejie formation this study analyzed multiple paleosalinity proxies b ga sr ba and s toc in fine grained siliciclastic argillaceous sediments of the luo 69 drillcore from the dongying depression all three proxies yielded similar paleosalinity interpretations with peak salinity and marine influence i e maximum b ga sr ba and s toc values occurring at the base of the es3l member and progressively declining salinities representing a shift toward brackish conditions upsection over an interval of 185 5 m representing 2 2 myr of sedimentation this paleosalinity record suggests gradual long term variations that were probably due to changes in tectonically controlled gateways linking the bohai bay basin to the yellow sea in addition to analysis of the mid eocene es3l member published data on the stratigraphic distribution of marine fossils glauconite and elemental paleosalinity proxies are applied to evaluate the history of marine incursions into the bohai bay lake system throughout the mid to late paleogene 50 24 ma this analysis revealed four intervals of probable major marine incursions dating to the early eocene the middle eocene the early oligocene and the late oligocene

relations between interrill erosion processes and sediment particle size distribution in a semiarid mediterranean area of se of spain abstract erosion and sediment characteristics were measured using simulated rainfall on two cultivated soils of contrasting lithology quaternary calcareous colluvium and tertiary marls in a semiarid mediterranean area of se spain two rainfall intensities high 56 0 2 4 mm h 1 and medium 31 4 1 4 mm h 1 were used in order to know the mechanisms involved in each selected condition for each simulated event runoff and sediment were sampled at 1 min intervals on a 1 m wide by 2 m long erosion plot the erosion rate was calculated as the total amount of soil lost divided by the time period of the test the duration of the test was that needed to reach steady state runoff an average time of 24 5 min for quaternary calcareous colluvium and 17 7 min for tertiary marls the size distribution of the transported sediment in the field effective size distribution was compared with equivalent measurements of the same samples after chemical and mechanical dispersion ultimate size distribution to investigate the detachment and transport mechanisms involved in sediment mobilisation the results showed that the soil type determined the hydrological response regardless of the rainfall intensity the erosional response was however determined by the rainfall and soil surface characteristics in quaternary calcareous colluvial soils the predominant erosion process depended on the rainfall intensity with a prevailing detachment limited condition in high intensity events and prevailing transport limited conditions in those events of medium intensity these differences in the main erosion processes were reflected in the size of the transported material and in the change in sediment size within the storm thus a time dependent size distribution of the eroded material decreasing coarse fractions and increasing fine fractions with runoff time was observed for high intensity events in medium intensity events on the other hand the time independent size distribution of the eroded material indicated transport limited erosion due to the rapid surface crusting on the tertiary marl soil no differences in the main erosion processes or in the sediment size distribution occurred for the different rainfall intensities tested the erosion of marl soils was determined mainly by the limited quantity of available sediment the effective size of material was a more sensitive parameter than the ultimate size of the sediment to study the way in which the sediment was transported

two dimensional kinematic wave model of overland flow a two dimensional kinematic wave model was developed for simulating runoff generation and flow concentration on an experimental infiltrating hillslope receiving artificial rainfall experimental observations on runoff generation and flow concentration on irregular hillslopes showed that the topography of the slope surface controlled the direction and flow lines of overland flow the model simulated results satisfactorily compared with experimental observations the erosive ability of the concentrated flow was found to mainly depend on the ratio of the width and depth of confluent grooves

observations of energetic high wavenumber internal waves in the kuroshio abstract intense and spatially coherent shear layers were detected in and under the kuroshio in an april 2000 survey in the east china sea the sloping layers revealed by shipboard doppler sonars on the r v roger revelle appeared to cross isopycnal surfaces except in a small region near the kuroshio shelfbreak front the rms finescale shear associated with the layers significantly exceeded the geostrophic shear an april 2002 follow on cruise was organized to establish whether these motions were propagating internal waves shipboard and lowered adcps were both operated from the r v melville in addition to ctd sonar transects a 30 h time series of currents and shear was obtained in the core of the kuroshio near the island of kyushu japan the shear structures were indeed found to be propagating with both up and down going internal wave motions present in comparison with the nearby open ocean the finescale 160 m vertical shear variance is increased by a factor of 3 in the kuroshio and by a fact

particle size distribution of sediment transported by shallow flow abstract a small laboratory flume on a 0 035 m m 1 slope was used to examine particle selection in shallow flows initial experiments were carried out on smooth surfaces to measure travel rates of different sediment sizes grain size fractions were introduced by hand into 1 37 10 4 to 3 96 10 4 m2 s 1 flows and clear selective mobility occurred with slowest transport in the 63 90 m range following those experiments a sediment mixture was introduced a selectively from a vibrating overhead hopper into 1 39 10 4 to 8 16 10 4 m2 s 1 flows on roughened surfaces the highest discharge had sufficient energy to transport all particle sizes but 355 595 m were preferentially transported none of the lower discharges were competent to transport the full range of particles injected and 45 125 m grains were always preferentially transported sediment finer than the median bed grain diameter was entrapped in micro bed pockets the progressively coarsening of transported material in time observed for all flow conditions may be related to progressive filling of micro bed pockets by fines both transport and entrapment selectivity is strongly related to the ability of flow to transport the full range of grains present as well as to the relationship of the bed roughness to the particles transported

numerical paleoceanographic study of the early jurassic transcontinental laurasian seaway the forces governing marine circulation of a meridional transcontinental seaway is explored with the princeton ocean model the jurassic laurasian seaway which connected the low latitude tethys ocean with the arctic sea is modeled quantitatively the global ocean is found to have a profound influence on seaway dynamics a north south density difference and hence sea level difference of the global ocean was probably the main factor in forcing the seaway flow when the tethys waters were the denser water the net seaway flow was southward and conversely it was northward for denser arctic waters marine bioprovincial boundaries and sediment data indicate that the seaway probably was dominated by boreal faunal groups and reduced salinities several times in the jurassic the model results suggest that this can be explained by southward flowing seaway currents which may have been related to an oceanic thermohaline circulation where no northern high latitude deep convection occurred

evidence of enhanced turbulent dissipation in the frontogenetic kuroshio front thermocline 1 enhanced turbulent dissipation o 10 8 10 7 wkg 1 in the thermocline on the cyclonic side of the kuroshio front was observed during a period of frontogenesis using a microstructure profiler xbt and adcp along 143 e across the kuroshio front in august 2008 the eddy diffusivity corresponding to the mixing below the central jet is estimated to be o 10 4 10 3 m2 s 1 the strong turbulent mixing we observed in the kuroshio is in sharp contrast to previous field measurements which found that small scale diapycnal mixing in western boundary currents remains at levels typically measured in the open ocean thermocline the turbulence in the kuroshio is attributed to frontogenesis arising out of an estimated confluence rate of o 10 5 s 1 based on satellite altimeters suggesting the ubiquity of a forward energy cascade from mesoscale to microscale turbulence near ocean fronts as indicated by recent theoretical studies

hydrological response and soil detachment rate from dip anti dip slopes as a function of rock strata dip in karst valley revealed by rainfall simulations rock dip angle plays a significant role in surface hydraulic characteristics and leads to different spatial distribution of water and soil loss in karst trough valleys in this study the rock dip angle effect on the hydraulic characteristics and soil detachment rate on dip anti dip slopes was explored via rainfall simulations and a steel experimental flume the rainfall intensities ranged from 30 to 90 mm h and the rock dip angles varied from 10 to 60 the results revealed that i surface runoff on the dip slope was higher than that on the anti dip slope whereas underground runoff presented opposite results the 30 rock dip angle presented the critical flow velocity for the anti dip slope and the flow velocity reduced as the rock dip angle of the dip slope increased ii laminar water flow occurred on the dip anti dip slope re was 500 in all cases for the anti dip slope the re value reduced by 3 53 89 79 the fr value reduced by 34 13 73 04 and the f value increased by 61 07 93 78 compared with that of the dip slope iii a linear function model can describe the relationship between the soil detachment rate and hydrodynamic parameters w and e it was found that w was the best of the hydrodynamic parameters to describe the soil detachment rate these results could provide valuable information for establishing a national scale empirical soil erosion model for karst trough valley

paleosalinity determination in ancient epicontinental seas a case study of the t oae in the cleveland basin uk abstract the early jurassic toarcian oceanic anoxic event t oae was marked by deposition of organic rich sediments and a pronounced negative carbon isotope excursion across the northwest european sea nwes representing a signal that was stronger regionally than globally various models for the t oae have been proposed some focusing on general atmospheric oceanic controls to reflect its global character and others emphasizing local or regional factors to account for its strong expression in the nwes in this study we evaluate watermass dynamics of the early jurassic cleveland basin uk during the t oae using a combination of paleosalinity proxies b ga sr ba and s toc these proxies suggest that brackish conditions existed prior to onset of the t oae with a shift to nearly freshwater conditions during the t oae reflecting a large increase in terrestrial runoff due to a stronger hydrological cycle possibly combined with shallowing of the marginal sill of the cleveland basin through sea level fall following the t oae basinal salinity conditions first returned to brackish and then gradually shifted to fully marine this hydrographic history accounts for low mo concentrations in t oae sediments of the cleveland basin demonstrating control by watermass restriction and local rather than global aqueous mo drawdown these findings demonstrate the importance of local hydrographic controls on the sedimentary expression of the t oae the more general significance of this study is that it highlights the need for application of paired salinity and redox proxies in order to correctly interpret paleoenvironmental variations in marginal marine basins

the early toarcian early jurassic and the cenomanian turonian late cretaceous mass extinctions similarities and contrasts abstract the early toarcian eto and cenomanian turonian c t mass extinctions are comparable from a wide range of scales and perspectives from a broad standpoint their similarities include virtually identical extinction intensity at the familial and generic levels widespread basinal facies deposited during sea level highstands an overall greenhouse climate and anoxia as an important causal mechanism the high resolution macroinvertebrate data analyzed here consisting of stratigraphic ranges diversity and abundance point to smaller scale similarities the two events resulted in significant ecological disruption and in both cases the biotic responses were very similar taxa inhabiting the upper water column were unaffected by anoxia and included ammonites and in the eto belemnites in addition epifaunal taxa adapted to low oxygen conditions such as the buchiids posidoniids and inoceramids flourished in the post extinction environment during the survival interval as conditions ameliorated the biota became more diverse and gradually began to resemble pre extinction biotas furthermore the 13c curves predict the end of the survival interval and suggest that the period characterized by carbon isotope excursions represent disrupted environmental conditions this points to the potential application of 13c as a tool for determining the repopulation modes and timing for other mass extinctions

erosion creep collapse mechanism of underground soil loss for the karst rocky desertification in chenqi village puding county guizhou china carbonate rocks distribute widely in china the total area of the carbonate rocks is about 3 430 000 km 2 and the exposed area of the carbonate is approximately 13 of china s territory in 2003 soil loss in yunnan guizhou and guangxi provinces reached 179 600 km 2 which is almost 40 1 of the total area causing rocky desertification in this study the erosion creep collapse mechanism of underground soil loss for the karst rocky desertification in chenqi village puding county guizhou province is proposed the mechanism occurs under the following geological environment slope surface undulation underlying bedrock surface fluctuation and thin and inhomogeneous soil overlying overlying soil generation by bedrock weathering underground karst development and large groundwater depth and lying water table under the bottom of soils the erosion creep collapse mechanism of underground soil loss in the karst slopes is explained as follows power loss due to human cultivation activities that destroy the soil structure hydraulic force formed by rainfall infiltration wet dry cycle generated by rainfall erosion effect caused by rainfall penetration creeping and flowing of plastic stream soil and collapse the erosion creep collapse mechanism of underground soil loss has seven steps disturbance of soils filled in underground karst cave by human activities internal soil erosion and partial collapse caused by hydraulic power internal free surface formation within the soil in the filled karst cave internal soil creeping soil pipe formation soil pipe collapse and ground surface collapse and filling soil loss develops slowly and sudden transportation occurs by collapse soil loss can be explained by the proposed mechanism and soil loss can be prevented by controlling soil collapse

paleoceanographic changes of the late pliensbachian early toarcian interval a possible link to the genesis of an oceanic anoxic event abstract secular records of the elemental and isotopic composition of belemnite calcite were studied in pliensbachian and toarcian sections from the yorkshire coast uk and southern germany to investigate oceanographic change during an interval prior to and including the toarcian oceanic anoxic event oae records from southern germany are correlated to the uk stratigraphy using strontium isotope stratigraphy the geochemical trends measured from belemnite calcite are consistent between the two sections and are interpreted in terms of temperature and salinity of the northwest european epi continental sea the data suggest that a dramatic environmental change coincided with the toarcian oae belemnite mg ca sr ca and na ca ratios increase by a factor of between 1 7 and 2 coincident with a 3 negative shift in 18o from the mid tenuicostatum zone until the lower falciferum zone of the uk ammonite biostratigraphy a period of 0 6 0 7 myr taken at face value the mg ca and 18o data argue for an abrupt warming of 6 7 c and substantial freshening during this interval global warming accompanied by an accelerated hydrological cycle and increased runoff is proposed to explain these changes prior to these events data from lower in the yorkshire section suggest a possible cooling accompanied by a shift to more saline waters during the period from the upper pliensbachian margaritatus zone to the toarcian lower tenuicostatum zone this earlier event may also have been important in causing density stratification in the northwest european epi continental sea

characteristics of red clay creep in karst caves and loss leakage of soil in the karst rocky desertification area of puding county guizhou china the loss of surface soil and water in the karst rocky desertification area of carbonate rock in chenqi village puding county guizhou province was monitored in this study the results show that the major form of surface soil loss in the area is the loss of soil through underground channels a creep test of red clay formed by loss through underground channels was conducted the results of the test show that the creep curve of the red clay samples includes two stages attenuation creep stage and stable creep stage the creep law for the red clay samples in the karst cave can be described by buger s model the parameters of buger s equation were deduced by fitting the creep curve which provides the reference for analyzing the surface soil loss leaking through the underground channels

coral record of variability in the upstream kuroshio current during 1953 2004 the kuroshio current kc one of the most important western boundary currents in the north pacific ocean strongly affects regional hydroclimate in east asia and upper ocean thermal structure limited by few on site observations the responses of the kc to regional and remote climate forcings are still poorly understood here we use monthly coral 18o data to reconstruct a kc transport record with annual to interannual resolution for the interval 1953 2004 the field site is located in southern taiwan on the western flank of the upstream kc increased reduced kc transport would generate strong weak upwelling resulting in relatively high low local coral 18o the upstream kc transport and downstream transport off tatsukushi bay japan covary on interannual and decadal timescales this suggests common forcings such as meridional drift of the north equatorial current bifurcation or zonal climatic oscillations in the pacific the intensities of kc transport off southeastern and northeastern taiwan are in phase before 1990 and anti phase after 1990 this difference may be due to a poleward shift of the subtropical western boundary current as a response to global warming

fine and microstructure observations in the urup strait kuril islands during august 2006 1 for the first time we performed continuous observations of turbulent mixing upon the sill of the urup strait kuril islands for a period of 1 day during august of 2006 time series of velocity profiles water properties and isopycnal depths show variability with a period of about 1 day however the water mass variability is not explained by simple water exchange between the sea of okhotsk and the north pacific empirical orthogonal function eof analysis of isopycnal coordinates extracted variability presumed to represent tidal flows as major eofs in profiles of the residual flow after subtracting the mean flow and major eofs we detected phase propagations consistent with internal gravity waves with an approximate period of 9 1 11 4 h the turbulent energy dissipation rate and vertical diffusivity k ranged from 1 10 9 to 3 10 8 w kg 1 and from 3 10 5 to 2 10 3 m2s 1 respectively occurrences of high dissipation rates generally corresponded to either strong shear or weak stratification a significant contribution of shear s to the dissipation rate was indicated with a relationship of s1 4 s1 8 probably related to propagating internal waves a strong mixing event was observed within the water column with extremely weak stratification and a richardson number below the critical value of 0 25 when the flow direction changed from up sill to down sill

significance of preferential flow at the rock soil interface in a semi arid karst environment abstract in many semi arid environments the surface materials are frequently characterized by thin soils and large proportions of bare rock both of which are expected to considerably influence infiltration and groundwater recharge processes in this study small plot scale irrigation experiments in combination with dye tracer application as well as real time and subsequent soil moisture measurements and soil particle size analysis were conducted to investigate the significance of preferential flow at the rock soil interface large scale assessments of soil depth and surface type distribution were used to upscale the findings of the irrigation experiments to the scale of a complete hillslope and further to estimate percolation properties of a hypothetical rainfall event the two experimental plots were each located in the west bank mountains close to ramallah each irrigation experiment was designed with 50 mm of precipitation applied on an area of 1 m 2 during the course of ca 2 5 h each irrigation plot had a surface share of approximately 50 rock outcrop and 50 soil surface percolation properties were investigated by subsequent soil moisture measurements at high spatial resolution on vertical soil profiles on the irrigated plot dye tracer application on the rock outcrop during the sprinkling allowed for tracking of resulting outcrop runoff in the subsurface the soil depth survey included 2100 measurement points on 7 transects which allowed the estimation of local soil depth distribution results of the irrigation experiments showed that precipitation induced runoff from rock outcrops continued below ground as preferential flow along the rock soil interface while water from the soil surface percolated mainly vertically and much more homogeneously this was evident from the high density soil moisture measurements as well as from the dye tracer patterns outcrop runoff percolated faster and to greater depths than water infiltrating directly from the soil surface thus possessing a greater potential for groundwater recharge

effects of rock fragments on soil erosion by water at different spatial scales a review this paper reviews the various effects of rock fragments on soil erosion by water since these effects are scale dependent they are investigated at three different nested spatial scales the microplot 4 10 6 100m2 the mesoplot 10 2 102 m2 and the macroplot 101 104 m2 for each scale the corresponding process mechanisms are discussed particular attention is paid to the effects of rock fragment cover on the intensity of soil erosion processes at the mesoplot scale i e on interrill areas rock fragments at the soil surface can have negative as well as positive effects on sediment yield these ambivalent effects are conditioned by the type of fine earth porosity soil surface slope vertical position and size of rock fragments and by the occurrence of horseshoe vortex erosion at the microplot scale i e the soil surface area which is covered by a single rock fragment and at the macroplot scale i e upland areas where both interrill and rill erosion takes place rock fragments at the soil surface have a negative effect on sediment yield in these two scales rock fragments can thus be considered as natural soil surface stabilizers at the macroplot scale the mean decrease of relative interrill and rill sediment yield with rock fragment cover can be expressed by an exponential decay function the scatter of the data indicates that a given rock fragment cover can have different efficiencies in reducing interrill and rill sediment yield depending on the varying intensities of the hydrological and erosion subprocesses these findings have implications for erosion modelling and soil conservation

role of underground fissure flow in near surface rainfall runoff process on a rock mantled slope in the karst rocky desertification area abstract because of the complex near surface double layer geologic structure i e surface and underground fissures of slopes in karst regions it is difficult to collect data on all flows especially the flows generated in underground fissures this lack of information leads to a poor understanding of the rainfall runoff process associated with soil loss in karst landscapes the goal of this study was to determine the output characteristics of surface subsurface and underground fissure flows and their conversion relationships as well as the role of underground fissure flow in the near surface rainfall runoff process using rainfall experiments the results revealed the following findings light rainfall intensities 15 and 30 mm h generated subsurface lateral flow and underground fissure flow whereas greater rainfall intensities generated surface runoff in addition to subsurface and underground flows ii the runoff drainage depths of all the above flows increased with increasing rainfall intensity while the runoff drainage coefficient exhibited no obvious regular change except for the surface runoff moreover the distribution ratio of surface runoff to total flow also increased with increasing rainfall intensity but decreased with increasing underground fissure degree while the distribution ratio of underground fissure flow exhibited the opposite trend iii underground fissure flow with distribution ratios of 27 8 78 0 dominated the total flow yield this study has significance for controlling soil erosion and water shortage in the karst rocky desertification region and also improves the understanding of the near surface rainfall runoff process in this region

dating reservoir deposits to reconstruct sediment yields from a small limestone catchment in the yimeng mountain region china abstract in this study we use reservoir deposits to reconstruct sediment yields over the past 50 years from the quananzi catchment a small limestone catchment in the yimeng mountain region china three sediment cores were collected from the reservoir and the chronology of each core was established using 137cs and 210pbex dating the area specific sediment yields ssy for different time periods since dam construction were estimated from each core by referring to the original capacity curves of the reservoir the estimated ssy from the quananzi catchment in each core for each period ranged between 0 9 0 3 and 2 6 0 9 t ha 1 y 1 with a mean value of 1 8 0 6 t ha 1 y 1 which is low compared with reported ssy from catchments worldwide the mean value was only about 1 7 of the equivalent value reported from the jiangzhang catchment in the granite area of the yimeng mountain region this low ssy reflects the shortage of erodible luvisols resistance to erosion and the limited effect of human disturbance in this small limestone catchment the decrease in ssy from 1959 to1972 suggests that the effect of the deforestation that occurred in 1958 on soil erosion decreased with time the continual increase of ssy through the two subsequent periods after 1972 reflects the expansion and intensification of cultivation during this time however the decreased ssy over the latest period of 1998 2012 can be related to the limitations imposed by the karst landscape on cultivation and to the impact of increasing numbers of residents leaving the area since the end of the 1990s to become temporary migrant workers elsewhere resulting in a decrease in human activity in the area overall the trend in ssy reflects the general history of changing human disturbance in this small limestone catchment over the past 50 years the results indicate that reservoir deposits provide a means of estimating the historical sediment yields from a karstic environment

occurrence mechanism and prediction of rocky land degradation in karst mountainous basins with the aid of gis technology a study case in houzhai river basin in southwestern china rocky desertification is a severe ecological issue threatening and constraining regional sustainable development in karst mountainous areas like houzhai river basin in southwestern china the results indicate that slope gradient and altitude are closely associated with occurrence of rocky desertification in the study region and there are some significant correlations between rock outcrop and slope gradient r 0 363 p 0 001 and between rock outcrop and altitude r 0 0 336 p 0 001 slope gradient and altitude are key factors contributing to rocky desertification in the studied basin therefore special attention should be paid to sloping lands that have greater slope gradients or altitudes to prevent and control the rocky desertification in a karst mountainous basin as the houzhai river basin furthermore it might be possible to predict the occurrence of rocky desertification using neural networks on the basis of geographical characteristics and human disturbance the correlation coefficients between observed values and predicted values ranged from 0 728 to 0 905 with a mean value of 0 851 ten times repeats the present study also indicates that human disturbance has little effect on rocky desertification however further studies should be conducted to interpret the effects of agricultural activities on the occurrence of rocky desertification

modeling evidences for global warming arctic seawater freshening and sluggish oceanic circulation during the early toarcian anoxic event 1 the paleoecological disturbances recorded during the early toarcian warming event 183 myr ago including marine anoxia sea level rise seawater acidification carbonate production crisis and species extinctions are often regarded as past examples of earth s possible responses to the rapid emergence of super greenhouse conditions however physical mechanisms explaining both the global and local expressions of paleoenvironmental events are still highly debated here we analyze the paleoclimatic and paleoceanographic consequences of increases in atmospheric pco2 levels at a multiscale resolution using a fully coupled ocean atmosphere model foam we show that in association with stronger high latitude precipitation rates and enhanced continental runoff the demise of polar sea ice due to the global warming event involved a regional freshening of arctic surface seawaters these disturbances lead to progressive slowdowns of the global oceanic circulation accountable for widespread ocean stratification and bottom anoxia processes in deep oceanic settings and epicontinental basins in agreement with very negative oxygen isotope values measured on fossil shells from the nw tethys our simulations also show that recurrent discharges of brackish and nutrient rich arctic surface waters through the viking corridor could have led to both vertical and geographical gradients in salinity and seawater 18o in the nw tethyan seas locally contrasted conditions in water mass density and rises in productivity rates due to strong nutrient supplies could partly explain the regional severity of the anoxic event in the restricted euro boreal domains as it has been previously suggested and modeled regionally

carbon isotope record of the early jurassic toarcian oceanic anoxic event from fossil wood and marine carbonate lusitanian basin portugal thetoarcianoceanicanoxicevent oae intheearlyjurassic 183maago wascharacterizedbywidespreadnear synchronous deposition of organic rich shales in marine settings as well as perturbations to several isotopic systems characteristically two positive carbon isotope excursions in a range of materials are separated by an abrupt negative shift carbon isotope profiles from toarcian fossil wood collected in england and denmark have previously been shown to exhibit this large drop 7 i n 13 c values interpreted as due to an injection of isotopically light co2 into the ocean atmosphere system however the global nature of this excursion has been challengedonthebasisofcarbon isotopedatafromnektonicmarinemolluscs belemnites whichexhibitheavierthanexpectedcarbonisotope values here we present new data principally from fossil wood and bulk carbonate collected at centimetre scale from a hemipelagic section at peniche coastal portugal this section is low in organic carbon average toc 0 5 and the samples should not have suffered significant diagenetic contamination by organic carbon of marine origin the carbon isotope profile based on wood shows two positive excursions separated by a large and abrupt negative excursion which parallels exactly the profile based on bulk carbonate samples from the same section albeit with approximately twice the amplitude 8 in wood versus 3 5 in carbonate these data indicate thatthe negative carbon isotope excursion affected the atmosphereand by implication the global ocean as well the difference in amplitude between terrestrial organic and marine carbonate curves can be explained by greater water availability in the terrestrial environment during the negative excursion for which there is independent evidence from marine osmiumisotope records and plausibly changes in atmospheric co2 content for which independent evidence is also available the peniche succession is also notable for the occurrence of re deposited sediments their lowest occurrence coincides with the base of the negative excursionandtheirhighestoccurrencecoincideswithitstop thus slopeinstabilityandsedimentsupplycouldhavebeenstronglylinked to the global environmental perturbation an association that may misleadingly simulate the effects of sea level fall

observations of the structure of turbulent mixing across the kuroshio 1 the mean structure of turbulence intensity across the kuroshio in spring is presented by compositing microstructure profiles on a stream coordinate the composite mean of turbulent energy dissipation rate e was high near fronts on both cyclonic and anticyclonic sides on the cyclonic side e 10 8 w kg 1 vertical diffusivity of 3 10 5 m2 s 1 was observed in the region of strong vertical shear of geostrophic velocity depth averaged e within the depth range 50 150 m 150 250 m was significantly higher at 0 to 50 km 25 to 50 km compared with 50 km from the axis although lower than on the cyclonic side e at depths of 50 150 m on the anticyclonic side near the front was again enhanced on this side the total vertical shear of horizontal velocity was strong whereas the geostrophic shear was weak

soil erosion rates in two karst peak cluster depression basins of northwest guangxi china comparison of the rusle model with 137cs measurements reliable estimation of erosion in karst areas is difficult because of the heterogeneous nature of infiltration and subsurface drainage understanding the processes involved is a key requirement for managing against karst rock desertification this study used the revised universal soil loss equation rusle to estimate the annual soil erosion rates on hillslopes and compared them with cs 137 budget in the depressions at two typical karst peak cluster depression basins in northwest guangxi southwestern china runoff plots data were used to calibrate the slope length factor l of the rusle model by adjusting the accumulated area threshold the rusle model was sensitive to the value of the threshold and required dems with 1 m resolution due to the discontinuous nature of the overland flow the average annual soil erosion rates on hillslopes simulated by the rusle were 0 22 and 0 10 mg ha 1 y 1 2006 through 2011 in the partially cultivated gz1 and the undisturbed gz2 basins respectively the corresponding deposition rates in the depressions agreed well with the cs 137 records when recent changes in precipitation and land use were taken into consideration the study suggests that attention should be given to the rusle l factor when applying the rusle on karst hillslopes because of the discontinuous nature of runoff and significant underground seepage during storm events that effectively reduces the effects of slope length c 2015 elsevier b v all rights reserved

research on soil detachment rate and hydrodynamic parameters of dip anti dip slope in simulated karst trough valley bedding dip has an important influence on soil detachment and flow hydrodynamics in a karst trough valley the laboratory rainfall simulation was conducted with three bedding dips bare slope dip slope and anti dip slope under three rainfall intensities 30 60 90 mm h 1 the characteristics of soil detachment and hydrodynamic parameters were assessed including water flow shear stress stream power unit stream power and unit flow energy the significant effects of bedding dips and rainfall intensities and their interactions on soil detachment and hydrodynamic parameters were examined the results showed that 1 the soil detachment rate decreased with increasing rainfall duration and the soil detachment rate in 30 bedding dip of dip slope was much larger than those in bare slope and anti dip slope in most rainfall intensities 2 the 60 bedding dip of dip slope was the threshold that controlled the stream power unit stream power and unit flow energy increased or decreased under different rainfall intensities and 3 the soil detachment rate had extremely significant positive power relationships with water flow shear stress stream power unit stream power and unit flow energy meanwhile the stream power was the most suitable parameter for predicting soil detachment in a karst trough valley slope therefore these results could provide useful information for soil erosion prediction in a karst trough valley

the implications of spatial variability in surface seal hydraulic resistance for infiltration in a mound and depression microtopography abstract soil surface crusting has a major impact on water infiltration and erosion in many soils considerable progress has been made in describing crusting processes and in modelling the impact of crusting on infiltration most studies however have neglected the high spatial variability in crust characteristics observed in the field the objective of this experiment was to determine the influence of runoff depth on infiltration rate in the presence of a surface seal varying in hydraulic characteristics with microtopography the blosseville silt loam has a low aggregate stability and forms crusts readily the villamblain silty clay loam has a greater aggregate stability due to its greater clay and organic matter contents and it is more resistant to aggregate breakdown processes under rainfall samples of the soils were sieved to retain aggregates less than 2 0 cm and packed in 50 50 15 cm soil trays the trays were surrounded by a 10 cm soil border to compensate for splash loss after molding the surface into a mound and depression microtopography the samples were subjected to simulated rainfall at an intensity of 22 8 mm h 1 hourly measurements of surface roughness showed that the original roughness was smoothed out due to the infilling of depressions by sediments detached from the mounds for the final hour runon was added to the top of the soil tray to increase the runoff rate and depth for both soils infiltration rate increased more than could be attributed to the increased ponding pressure head the change in infiltration rate was particularly great for villamblain the measurements of hydraulic resistance showed that structural crusts had a lower hydraulic resistance than sedimentary crusts they also showed that the crusts formed on villamblain were of a lower hydraulic resistance than those of blosseville it appears that small changes in runoff depth can significantly increase infiltration rate when structural crusts of lower hydraulic resistance are inundated the effect was less important in blosseville which formed seals of relatively high hydraulic resistance everywhere the results provide a suitable explanation for field observations of increasing infiltration rate with either increasing rainfall intensity or runoff rate the results also have implications for the relationships between surface roughness surface water storage and infiltration

new range data for marine invertebrate species across the early toarcian early jurassic mass extinction abstract we have reinvestigated the marine mass extinction interval that occurred during the early toarcian which was a time of widespread marine anoxia the ranges of marine benthic invertebrates are significantly altered using new observations from the cleveland basin uk goniomya rhombifera is reported for the first time from the whitby mudstone formation and together with an increased epifaunal bivalve diversity indicates a brief relatively oxygenated period towards the end of the event the new data together with published results suggest three apparent extinction horizons on a global scale the first is just above the pliensbachian toarcian boundary and the following two are in the semicelatum ammonite subzone as a result of the signor lipps effect there may be only one or possibly two true extinctions the youngest extinction horizon coincides with the first of the abrupt carbon isotope shifts that characterize this interval and with increases in sea surface temperature continental weathering rates and seawater anoxia pseudomytiloides dubius is the only abundant benthic macroinvertebrate during the most hostile environmental conditions but it and all other benthic species are almost entirely absent for many thousands of years immediately after each abrupt negative carbon isotope shift supplementary material a compilation of the late pliensbachian and early toarcian marine biotic changes and a discussion of the systematics of the key faunal elements are available at http www geolsoc org uk sup18353

effects of land use land cover and rainfall regimes on the surface runoff and soil loss on karst slopes in southwest china abstract surface runoff and soil loss from 2007 to 2010 related to land use and rainfall regimes in karst hill slopes in guizhou province southwest china were analyzed using the hierarchical clustering method sixty one rainfall events under the subtropical monsoon climate condition were classified into 5 types of rainfall regimes according to the depth maximum 30 min intensity and duration of rainfall in our study we first demonstrated that the amounts of surface runoff and soil loss on the karst hill slopes were very small compared to the non karst areas because the dual hydrological structure in the karst region including ground and underground drainage systems could influence the processes of rainfall recharge and runoff generation most rainfall water was transported underground through limestone fissures and fractures while little was in the form of surface runoff second the runoff and soil loss were affected by land use management and vegetation cover soil loss was intensified in a descending order to five types of land uses pastureland burned area cropland combination vegetation land young forestland third the runoff and soil loss exhibited remarkable variances among different rainfall regimes large runoff and soil loss were mainly created by heavy rainfall storms with a rainfall depth of more than 40 mm and a maximum 30 min rainfall intensity of over 30 mm h 1 in addition rainfall storms with large antecedent precipitations could also produce large runoff and soil loss these observations indicated that limestone fissures and fractures play important roles in surface runoff generation on karst limestone slopes due to their large storage capacity and high infiltration rate lastly the soil erosion risk in the karst pure limestone slope is quite high and should be paid particular attention especially in regards to over grazing because the soil loss created by a single heavy rainstorm in pastureland was 5 times the annual soil loss tolerance

runoff and erosion processes on bare slopes in the karst rocky desertification area underground pore fissure and bedrock bareness are the main factors that lead to complicated mechanisms of soil erosion in karst regions the objectives of this study were as follows a to measure runoff and sediment generated from the surface and underground in the karst bare slope and b to analyse the impacts of underground pore fissures and bedrock bareness rates on soil erosion to achieve these objectives we designed an experiment in which underground pore fissure degrees and bedrock bareness rates were varied and their impacts on soil erosion were measured the results showed that runoff and sediment yields from the surface and underground increased with increasing rainfall intensity and the surface runoff was much more easily generated when the rainfall intensity was greater ii surface runoff yield first increased and then decreased with increasing bedrock bareness rates while the runoff yield in underground pore fissures increased with increasing bedrock bareness rates thus sediment production on the surface and in underground pore fissures showed the same pattern i e first decreased and then increased iii the surface runoff and sediment generally decreased with increasing degrees of underground pore fissures while that of underground pore fissures presented a different pattern and iv rainfall intensity bedrock bareness rates and underground pore fissure degrees were the important factors affecting soil erosion processes in karst bare slopes because the bedrock bareness rates and underground pore fissure degrees were the main factors causing the uneven distribution of runoff and sediment on soil surfaces and underground therefore soil and water loss in underground pore fissures was the special pattern and main difference in soil erosion processes in the karst region compared with other regions these results have theoretical and practical significance for understanding soil erosion mechanisms and controlling soil and water loss in karst regions

assessment of the interrill and rill contributions to total soil loss from an upland field plot abstract govers g and poesen j 1988 assessment of the interrill and rill contributions to total soil loss from an upland field plot geomorphology 1 343 354 erosion measurements were carried out on an upland field plot in the loam region of belgium the sediment being detached by splash on interrill areas is transported to the channel system mainly by interrill wash over the entire 7500 m field plot rill and gully erosion is more important than interrill erosion however the relative importance of interrill erosion varies in time and in space due to changes of the interrill surface characteristics and the activation of sidewall and gullying processes in the channel network these factors should be taken into account in a realistic rill interrill erosion model introduction at present few available field data permit the separation of rill and or gully and interrill contributions to sediment removal from arable land the scarcity of this type of field data is a major factor inhibiting the validation and fur ther development of recently developed physi cally based models describing upland erosion by water e g foster 1982 rose et al 1983 knowledge of the contribution of rill and inter rill processes to total soil loss has also some practical interest if the ratio between rill and interrill erosion were known even approxi mately it would be possible to obtain a quick estimate of total erosion by making a volumet ric recording of rill patterns plot measure

observation of frontal waves and associated salinity minimum formation along the kuroshio extension 1 high resolution observations with a towed conductivity temperature depth system were conducted along the kuroshio extension where the kuroshio and the oyashio merge and new north pacific intermediate water npiw is formed large amplitude frontal waves at an intermediate depth corresponding to a density range of npiw 26 6 26 9 were discovered here along the main stream of the kuroshio extension a remarkable salinity minimum due to the intense intrusions of oyashio water was observed near the trough of the frontal wave with an apparent wavelength of 100 km around the troughs crests of the frontal waves the horizontal velocity in the intermediate layer was directed to the southern kuroshio water side northern oyashio water side relative to the upper layer horizontal velocity fields converged diverged around the wave trough crest indicating downwelling upwelling the amplitude of the frontal waves was observed to grow in the downstream direction where isolated eddies were observed this suggests that the development of frontal waves and wave breaking enhance isopycnal mixing and cross frontal exchange across the main stream of the kuroshio extension

depressional storage for markov gaussian surfaces processes during rain events such as infiltration runoff soil erosion and crust formation are influenced in part by depressional storage and surface roughness if the surface topography is known its potential depressional storage can be calculated the objective of this paper was to relate the statistical parameters for quantifying surface roughness to depressional storage analysis of topographic data sets digitized at millimeter grids by a laser scanner showed that soil roughness can be quantified by a markov gaussian m g type random process a monte carlo simulation procedure was used to find the mean ponding characteristics from simulated m g surfaces depressional storages were found to be functions of two m g parameters two sample length scales and the slope steepness the markov parameters are the global variance 2 and the correlation length scale l and the sample length scales are grid spacing x and side length ls after proper scaling all storage functions collapsed into two nondimensional relationships 1 storage at zero slope as a function of relative sample length scale and 2 storage as a function of scaled slope when l 0 simulated surfaces followed the random gaussian model and the nondimensional storage was only a function of scaled slope storages calculated from digitized elevation data sets with m g type statistics agreed well with results obtained from simulated surfaces

geomorphic inheritance and the development of tower karst four genetic types of tower karst are identified the most typical consisting of residual hills protruding from a planed carbonate surface veneered by alluvium two extreme possibilities for tower karst evolution are recognized a direct development that is independent of any previous morphology and a sequential development that depends explicitly on the morphological characteristics of a previous cockpit karst phase examples of both are described although the latter appears the more common south china tower karst is examined in this light palaeomagnetic analysis of cave deposits in a tower near guilin indicate the feature to be a time transgressive landform four principal controls of tower development are discussed and a model of tower evolution is presented

soil structure and nutrient contents in underground fissures in a rock mantled slope in the karst rocky desertification area near surface karst fissures are filled with soils these soils are often derived from the erosion and transport of surface soil but have different properties than the surface soil in karst rocky desertification regions this study was undertaken to determine the soil structure and nutrient contents in underground fissures with different grades of rocky desertification no potential mild moderate and severe based on field surveys near surface karst fissures were selected in a typical karst plateau area soil particle compositions particularly nutrient characteristics were determined through field sampling and laboratory experiments the results indicated that the higher the rock desertification grade was the higher the soil sand 0 02 2 mm content and the lower the clay 0 002 mm content the soil in both limestone and dolomite fissures was basically neutral to weakly alkaline the surface soil in dolomite fissures presented a higher soil organic matter content than that in limestone fissures but the opposite was true for the subsurface soil from the surface to the lower layer the total nitrogen content generally decreased and the total phosphorus content generally decreased in dolomite fissures but exhibited a more complex pattern in limestone fissures the total phosphorus content of the surface soil was higher than that of the subsurface soil but the total potassium content was lower there was no significant difference among different soil layers near surface fissures are a good place to promote vegetation restoration projects because they provide good soil structure and nutritional conditions for plant growth

effect of a jurassic oceanic anoxic event on belemnite ecology and evolution the toarcian oceanic anoxic event t oae 183 million y ago is possibly the most extreme episode of widespread ocean oxygen deficiency in the phanerozoic coinciding with rapid atmospheric pco2 increase and significant loss of biodiversity in marine faunas the event is a unique past tipping point in the earth system where rapid and massive release of isotopically light carbon led to a major perturbation in the global carbon cycle as recorded in organic and inorganic c isotope records modern marine ecosystems are projected to experience major loss in biodiversity in response to enhanced ocean anoxia driven by anthropogenic release of greenhouse gases potential consequences of this anthropogenic forcing can be approximated by studying analog environmental perturbations in the past such as the t oae here we present to our knowledge the first organic carbon isotope record derived from the organic matrix in the calcite rostra of early toarcian belemnites we combine both organic and calcite carbon isotope analyses of individual specimens of these marine predators to obtain a refined reconstruction of the early toarcian global exogenic carbon cycle perturbation and belemnite paleoecology the organic carbon isotope data combined with measurements of oxygen isotope values from the same specimens allow for a more robust interpretation of the interplay between the global carbon cycle perturbation environmental change and biotic response during the t oae we infer that belemnites adapted to environmental change by shifting their habitat from cold bottom waters to warm surface waters in response to expanded seafloor anoxia

influence of bare rocks on surrounding soil moisture in the karst rocky desertification regions under drought conditions abstract a large number of bare rocks exposed in the field represent one of the most spectacular scenes of the karst rocky desertification krd process the presence of bare rocks modifies the microenvironment an understanding of soil moisture variability is necessary to characterize the linkages between a region s hydrology ecology and physiography the objective of the study was to determine the influence of those exposed bare rocks on soil moisture in the surrounding area in a typical krd region the forest station of sandoqing in fu yuan county yun nan province southwest china dynamic soil moisture was quantified in feb 2010 during an extreme drought period results showed that during the drought period soil moisture on the north side of the rocks was significantly higher than those on the east west and south sides p

geometric morphology and soil properties of shallow karst fissures in an area of karst rocky desertification in sw china abstract serious soil erosion and an extremely low rate of soil formation leads to a thin layer of surface soil that makes tree growth difficult in areas of karst meanwhile surface soil driven by runoff enters shallow karst fissures skfs these skfs filled with soil have become the major habitat type in the area here we explore the morphological characteristics of shallow karst fissures as well as the soil physical and chemical properties of the skfs and comprehensively analyse the factors that influence the soil properties three key results are presented first a high heterogeneity of morphological characteristics exists for shallow karst fissures according to the different characteristics of the vertical section the skfs can be divided into 5 types these types are rectangle type pyramid type funnel type net type and diamond type in addition the skf dip angles were mainly between 60 and 90 76 39 the width of the top aperture was mainly between 20 and 40 cm 51 39 and the trace lengths were mainly between 80 and 160 cm 76 39 second compared with their characteristics of surface soil the bulk density and fractal dimension of soil particles of the skfs were both large and the main composition of the skf soil was clay third the soil nutrients of the skfs the organic matter total nitrogen and total phosphorus were lower than the surface soil nutrients but not significantly so the total potassium tk of the skfs was greater than that observed for the surface and increased as the depth of the skf increased the soil nutrients of the skfs were significantly affected by the fissure morphology the poorly connected fissures had better soil fertility when the morphological characteristics and soil properties of the skfs were comprehensively considered the vegetation types that were determined to be the best for use in the ecological restoration of areas of karst rocky desertification were deep rooted plants with especially strong root penetration the result of this study can supply some reference for future studies of karst rocky desertification control and vegetation restoration in the karst area of southwest china in the south claw silicon island in yogyakarta province indonesia and in other karst regions with the same ecological background

molybdenum isotope chemostratigraphy and paleoceanography of the toarcian oceanic anoxic event early jurassic molybdenum mo isotope chemostratigraphy of organic rich mudrocks has been a valuable tool for testing the hypothesis that the toarcian oceanic anoxic event t oae early jurassic 183 ma was characterized by the spread of marine euxinia and organic matter burial at a global scale however the interpretation of existing mo isotope data for the t oae from yorkshire cleveland basin u k is equivocal in this study three new mo isotope profiles are presented from dotternhausen quarry south german basin germany the rijswijk core west netherlands basin netherlands and the dogna core belluno basin northern italy precise bio and chemo stratigraphic correlation between the three sites allows a direct comparison of the data enabling some key conclusions to be reached i the mo isotope composition of seawater during the peak of the t oae was probably close to 1 45 implicating a greater removal flux of sulphides from seawater and a larger extent of global seafloor euxinia compared to the present day ii mo isotope cycles previously identified in the yorkshire sedimentary succession are attributed to changes in the degree of local mo drawdown from overlying cleveland basin seawater iii the consistency of the new multi site mo isotope dataset indicates a secular reduction in the burial of sulphides globally in the late stages of the t oae implying a contraction in the extent of global marine euxinia iv subtle differences in the mo isotope composition of deposits formed in different euxinic sub basins of the european epicontinental shelf were probably governed by local variations in basin hydrography and rates of water renewal

evolution of the toarcian early jurassic carbon cycle and global climatic controls on local sedimentary processes cardigan bay basin uk the late early jurassic toarcian stage represents the warmest interval of the jurassic period with an abrupt rise in global temperatures of up to 7 c in mid latitudes at the onset of the early toarcian oceanic anoxic event t oae 183 ma the t oae which has been extensively studied in marine and continental successions from both hemispheres was marked by the widespread expansion of anoxic and euxinic waters geographically extensive deposition of organic rich black shales and climatic and environmental perturbations climatic and environmental processes following the t oae are however poorly known largely due to a lack of study of stratigraphically well constrained and complete sedimentary archives here we present integrated geochemical and physical proxy data high resolution carbon isotope data 13c bulk and molecular organic geochemistry inorganic petrology mineral characterisation and major and trace element concentrations from the biostratigraphically complete and expanded entire toarcian succession in the llanbedr mochras farm borehole cardigan bay basin wales uk with these data we 1 construct the first high resolution biostratigraphically calibrated chemostratigraphic reference record for nearly the complete toarcian stage 2 establish palaeoceanographic and depositional conditions in the cardigan bay basin 3 show that the t oae in the hemipelagic cardigan bay basin was marked by the occurrence of gravity flow deposits that were likely linked to globally enhanced sediment fluxes to continental margins and deeper marine shelf basins and 4 explore how early toarcian tenuicostatum and serpentinum zones siderite formation in the cardigan bay basin may have been linked to low global oceanic sulphate concentrations and elevated supply of iron fe from the hinterland in response to climatically induced changes in hydrological cycling global weathering rates and large scale sulphide and evaporite deposition

elevated mixing at a front 1 the mesoscale submesoscale and microscale structure of a front in the california current was observed using a towed vehicle outfitted with microconductivity sensors thirteen 60 km cross front sections from 0 to 350 m in depth were covered in 3 5 days objectively mapped data are fit via the omega equation to obtain vertical velocity a composite cross front section shows elevated mixing on the dense side within 10 20 km of the front water downwells and gradients are elevated there i e rossby number ro horizontal strain spice gradients and microscale thermal dissipation thermal eddy diffusivity kt reaches 10 3 m2 s 1 and increases 3 10 from the anticyclonic to the cyclonic side with a depth mean of 10 4 m2 s 1 the spatial structure of kt ro and are similar on the dense side suggesting an energy cascade from the mesoscale via the submesoscale to the microscale however it is unclear whether frontogenesis internal wave blocking by elevated vorticity or internal wave trapping by large produces the elevated mixing the mean turbulent heat flux opposes the mean restratifying mesoscale heat flux of 10 w m 2 and may allow the front to persist turbulent nitrate fluxes are 0 1 0 3 mmol m 2 s 1 chlorophyll fluorescence and beam transmission reveal a 6 km wide 100 km long alongfront streamer which is a deep biomass maximum time scales for mixing and nutrient fluxes are 0 3 3 days which are similar to phytoplankton growth rates and the time scale for frontal evolution

effect of microrelief on water erosion and their changes during rainfall soil surface roughness contains two elementary forms depressions and mounds which affect water flow on the surface differently while depressions serve as temporary water storage mounds divert water away from their local summits although roughness impacts on runoff and sediment production have been studied almost no studies have been designed explicitly to quantify the evolution of depressions and mounds and how this impacts runoff generation and sediment delivery the objectives of this study were to analyze how different surface forms affect runoff and sediment delivery and to measure the changes in surface depressions and mounds during rainfall events a smooth surface was used as the control both mounds and depressions delayed the runoff initiating time but to differing degrees and slightly reduced surface runoff when compared to the runoff process from the smooth surface surface mounds significantly increased sediment delivery whilst depressions provided surface storage and hence reduced sediment delivery however as rainfall continued and rainfall intensity increased the depression effect on runoff and erosion gradually decreased and produced even higher sediment delivery than the smooth surface depressions and mounds also impacted the particle size distribution of the discharged sediments many more sand sized particles were transported from the surface with mounds than with depressions the morphology of mounds and depressions changed significantly due to rainfall but to different extents the difference in change had a spatial scale effect i e erosion from each mound contributed to its own morphological change while sediments deposited in a depression came from a runoff contributing area above the depression hence a much greater source area than a single mound the results provide a mechanistic understanding of how soil roughness affects runoff and sediment production copyright 2015 john wiley sons ltd

molybdenum isotope evidence for global ocean anoxia coupled with perturbations to the carbon cycle during the early jurassic relatively brief periods of severe paleoenvironmental change during the jurassic and cretaceous were associated with the widespread accumulation of organic rich marine deposits termed oceanic anoxic events oaes these intervals involved abrupt global warming of 5 10 c higher rates of continental weathering elevated extinction rates and large scale perturbations to the global carbon cycle the major oaes also overlapped temporally the emplacement of large igneous provinces however despite being known as oaes the extent of seawater anoxia at those times is undefined and the causative processes remain unclear here we show how changes in seawater molybdenum isotope ratios a proxy for seawater anoxia during the toarcian early jurassic oae define the onset and expansion of oxygen deficient conditions our data also place constraints on the areal extent of marine anoxia during the event and demonstrate that anoxia expanded and contracted periodically broadly in line with precession driven changes in 13 corg despite their intermittent occurrence over geological history oaes have an important contemporary relevance because the magnitude and high rates of environmental change then were broadly similar to those occurring at the present day

role of rock dip angle in runoff and soil erosion processes on dip anti dip slopes in a karst trough valley abstract due to the great difficulty of monitoring surface and underground runoff and sediment yield directly the surface and underground hydrological processes associated with soil leakage loss in karst trough valleys remain unknown the objective of this study was to analyse the role of the rock dip angle in the water and soil leakage loss processes to assess the characteristics of surface and underground runoff and soil erosion and to investigate their conversion relationships using rainfall experiments the results showed the following i at a steep rock dip angle 60 the underground runoff yield had a shorter stabilization time than the surface runoff yield and that the underground runoff coefficient of the dip slope exceeded 0 5 ii the surface sediment yield could be divided into the suspended load and the bed load and the underground sediment yield included only the suspended load on the anti dip slope the surface erosion modulus was 0 83 2 50 times the underground erosion modulus iii the surface and underground cumulative runoff was linearly correlated with the cumulative sediment yield the rock dip angle had a significant quadratic relationship with the surface and underground runoff and sediment yield these results improve the understanding of the surface underground runoff and soil erosion processes and have significance for preventing water and soil leakage loss on the slopes of karst trough valleys

assessing soil erosion in mediterranean karst landscapes of lebanon using remote sensing and gis abstract maps showing the potential for soil erosion at 1 100 000 scale are produced in a study area within lebanon that can be used for evaluating erosion of mediterranean karstic terrain with two different sets of impact factors built into an erosion model the first set of factors is soil erodibility morphology land cover use and rainfall erosivity the second is obtained by the first adding a fifth factor rock infiltration high infiltration can reflect high recharge therefore decreasing the potential of surface runoff and hence the quantity of transported materials infiltration is derived as a function of lithology lineament density karstification and drainage density all of which can be easily extracted from satellite imagery the influence of these factors is assessed by a weight rate approach sharing similarities between quantitative and qualitative methods and depending on pair wise comparison matrix the main outcome was the production of factorial maps and erosion susceptibility maps scale 1 100 000 spatial and attribute comparison of erosion maps indicates that the model that includes a measure of rock infiltration better represents erosion potential field investigation of rills and gullies shows 87 5 precision of the model with rock infiltration this is 17 5 greater than the precision of the model without rock infiltration these results indicate the necessity and importance of integrating information on infiltration of rock outcrops to assess soil erosion in mediterranean karst landscapes

on internal waves propagating across a geostrophic front abstractreflection and transmission of normally incident internal waves propagating across a geostrophic front like the kuroshio or gulf stream are investigated using a modified linear internal w

comments on paleosalinity determination in ancient epicontinental seas a case study of the t oae in the cleveland basin uk by remirez m n and algeo t j

the early toarcian jurassic anoxic event stratigraphic sedimentary and geochemical evidence detailed paleogeographic studies in the southern alps suggest that an oxygen minimum model is appropriate for interpreting conditions on tethyan continental margins advection of manganese in this low oxygen layer may explain the local occurrence of carbonate ores of this element carbon sulfur and iron sulfur ratios although showing considerable scatter suggest that bottom waters at this time were locally euxinic containing free hydrogen sulfide this oceanic anoxic event was preceded by significant faunal turnover of ammonites in tethys and accompanied by widespread extinction of benthos in northern europe in response to the lateral spread of anoxic bottom waters during transgression similar changes may be recognized in other parts of the world other anoxic events may have taken place during the jurassic but documentation is as yet meagre furthermore models for such phenomena remain largely speculative although upwelling and increased planktonic productivity commencing in pre toarcian time are favored for the falciferum zone event documented here from author

superficial and subterranean soil erosion in tabasco tropical mexico development of a decision tree modeling approach tropical countries suffer from a lack of financial resources to monitor and model sources and outcomes of soil degradation and therefore a scarcity of data in this study it was tried to model superficial and subterranean water erosion based on basic environmental variables such as geological formation soil type or vegetation cover data which are potentially available even in developing countries different forms of water erosion and karst or pseudokarst formations in tabasco southeastern mexico were estimated the study region 3500 km 2 consists of plain and hilly areas with an annual precipitation ranging from 2000 to 4000 mm main land use form is rangeland the area is geologically composed of sedimentary rocks limestone sandstone and conglomerates collecting data by field observations over the entire study area a cartography of different soil loss forms such as rill and gully erosion mass movement sinkholes and tunnels was created including field data from available maps of geological formation soil type precipitation and former land use 20 years ago additionally data collected in the field such as actual land use vegetation cover and inclination were added in the entire study area 1039 sites were affected by soil erosion with 2435 single manifestations of soil erosion 482 sites were found with one gully each 57 sites with erosion rills with a total of 416 392 sites with one mass movement each 85 sites with sinkholes with a total of 1122 and 23 sites with one tunnel each rendzic leptosols over oligocene limestone are strongly affected by sinkholes and tunnels in regions with inclinations of less than 5 this phenomenon is explained by karstic and pseudokarstic formation superficial erosion forms are mainly found on rendzic leptosols over shale sandstone and on eutric or peli eutric vertisols on andesit in areas with inclinations between 5 and 30 the application of classification trees allowed to successfully predict the occurrence of sinkholes and tunnels degree of agreement between prediction and observation very good to excellent even in areas with scarce data bases this could allow for easy identification of high risk areas predictive success of the occurrence of the different forms of superficial soil losses however is low superficial erosion seems to be mainly caused by more specific pedological factors nevertheless automated induction of classification trees can be a valuable tool for preliminary data analysis and hypothesis generation in areas with lack of local expertise and can guide erosion risk mapping and soil conservation planning 2007 elsevier b v all rights reserved

organic geochemistry of the early toarcian oceanic anoxic event in hawsker bottoms yorkshire england a comprehensive organic geochemical investigation of the hawsker bottoms outcrop section in yorkshire england has provided new insights about environmental conditions leading into and during the toarcian oceanic anoxic event t oae 183 ma rock eval and molecular analyses demonstrate that the section is uniformly within the early oil window hydrogen index hi organic petrography polycyclic aromatic hydrocarbon pah distributions and tricyclic terpane ratios mark a shift to a lower relative abundance of terrigenous organic matter supplied to the sampling locality during the onset of the t oae and across a lithological transition unlike other ancient intervals of anoxia and extinction biomarker indices of planktonic community structure do not display major changes or anomalous values depositional environment and redox indicators support a shift towards more reducing conditions in the sediment porewaters and the development of a seasonally stratified water column during the t oae in addition to carotenoid biomarkers for green sulfur bacteria gsb we report the first occurrence of okenane a marker of purple sulfur bacteria psb in marine samples younger than 1 64 ga based on modern observations a planktonic source of okenane s precursor okenone would require extremely shallow photic zone euxinia pze and a highly restricted depositional environment however due to coastal vertical mixing the lack of planktonic okenone production in modern marine sulfidic environments and building evidence of okenone production in mat dwelling chromatiaceae we propose a sedimentary source of okenone as an alternative lastly we report the first parallel compound specific c13 record in marine and terrestrial derived biomarkers across the t oae the c13 records of short chain n alkanes acyclic isoprenoids and long chain n alkanes all encode negative carbon isotope excursions cies and together they support an injection of isotopically light carbon that impacted both the atmospheric and marine carbon reservoirs to date molecular c13 records of the t oae display a negative cie that is smaller in magnitude compared to the bulk organic c13 excursion although multiple mechanisms could explain this observation our molecular petrographic and rock eval data suggest that variable mixing of terrigenous and marine organic matter is an important factor affecting the bulk organic c13 records of the t oae

spatial distribution of rock fragments on steep hillslopes in karst region of northwest guangxi china abstract rock fragments 5 mm in diameter at the soil surface and within the topsoil have a large effect on the intensity of various hydrologic and geomorphic processes however little information is available on the spatial distribution of rock fragments in subtropical regions the objective of this paper was to investigate the relationship between the spatial distribution of rock fragments and landforms on two different steep karst hillslopes in northwest guangxi southwest china on the first hillslope a disintegrated landslide failure with the presence of several large rock outcrops 2 m in height the spatial distribution of rock fragment cover had no obvious relationship with topographic position except that the mean cover percentage of small rock fragments 5 20 mm decreased from bottom to top on the second hillslope an avalanche slope without the presence of large rock outcrops the mean total rock fragment cover 5 600 mm increased from bottom 5 to top 21 with decreasing variability and rock fragments with various sizes 5 20 20 75 and 75 250 mm showed a similar increasing trend the mean total rock fragment cover increased linearly with slope gradient on the second hillslope and tended to increase and then decrease with gradient but their relationship was not obvious on the first hillslope this indicated that the spatial distribution of surface rock fragment cover had a close relationship with the presence of large rock outcrops and slope gradient however the median diameter d50 of the surface rock fragments had an increase decrease trend with slope gradient but there was no obvious relationship on both hillslopes with low overland flow therefore the dominant factor for the spatial distribution of rock fragment cover and size at the soil surface might not be soil erosion by water but slope gradient vegetation and geomorphologic condition of the slope the mean total volumetric rock fragment content 5 250 mm within the topsoil 10 20 cm thick increased linearly from bottom 16 to top 39 with slope gradient on the first hillslope and had a logarithmic increase from bottom 10 to top 27 with gradient on the second hillslope this suggested that rock fragment content within the topsoil was mostly controlled by slope gradient and topographic positions and had not a close relationship with the presence of large rock outcrops

mixing in the main thermocline abstract a series of profiles of velocity microstructure along 152 e in the western north pacific ocean were collected in may june 1982 large averaged turbulent dissipation rates found in the main thermocline 400 to 1000 m were determined by a combination of large independent estimates of and a greater rate of occurrence of turbulent events in the main thermocline than elsewhere concurrently we find that averaged values of exhibit a positive dependence on the buoyancy frequency n and that form an is best fit by 1 when only the data below 400 m are considered of the more than 5000 m of data collected below 1000 m depth 12 showed measurable turbulence and dominated the depth averages a deep ocean estimate of an upper bound to the eddy coefficient for vertical diffusion k is 10 4 m2 s 1 and not significantly different from the value estimated by munk the inferred dependence of the mass flux with depth indicates the relative significance of vertical mixing in the main thermocli

soil surface roughness measurement methods applicability and surface representation abstract in a laboratory rainfall simulator study soil surface roughness was measured using contact roller chain pin meter and noncontact devices laser scanner photogrammetry soil surfaces with two initial roughness conditions aggregates as for the contact methods resolution cm range and precision mm range is limited which constrains their application to calculation of simple surface parameters resolution and precision in the sub millimeter range could be obtained with the laser scanner while for the photogrammetric method the measurement uncertainty was approximately 1 2 mm measurement time was highest 90 min for the pin meter technique though data were ready to use for analyses laser scanner measurements took 34 min several steps of data post processing required 30 more minutes data acquisition was fastest for photogrammetry 5 min but expert knowledge as well as special hard and software were necessary for time consuming photo analyses taking about 120 min the chain and pin meter were compared using a profile index profile lengths matched well for smooth surfaces on rough surfaces the chain meter gave shorter profile lines between profile index from chain measurements and the random roughness derived from pin meter data a polynomial regression could be found parameters of distributions of elevations as well as inclinations and depressions were used to compare the laser scanner and the photogrammetric technique generally the laser scanner was able to reproduce small aggregates as well as voids in between them while dem from stereophotos was smoothed between major aggregates this led to skewed distributions of elevations and inclinations as well as to a lower surface area up to 39 and a lower depression volume up to 68 shapes of depressions were significantly different as well the used photogrammetric technique is supposed to be successful in producing adequate dems for already smoothed surfaces e g after rainfall events the study revealed different fields of application and limitations of the compared devices using a non adequate technique for certain situations will definitely have implications on further analyses concerning connectivity of runoff pathways surface protection from raindrop impact or runoff detachment and sediment transport

particle size characteristics of suspended sediment in hillslope runoff and stream flow this study examines the particle size characteristics of hillslope soils and fluvial suspended sediments in an agricultural catchment samples of surface runoff and stream flow were collected periodically and analysed for the size distributions of the effective undispersed sediment this sediment was subsequently dispersed and the ultimate size distributions determined the median effective particle size of stream suspended sediment was considerably coarser than the median ultimate particle size indicating that most of the load included a substantial proportion of aggregates moreover the proportion of fine material i e silt and clay increased and the proportion of sand sized material decreased with increasing discharge this decrease in sediment size with increased flow which is contrary to the traditional assumption of a positive discharge particle size relationship is thought to reflect i the influx of silt and clay predominantly the former originating on the catchment slopes and brought to the stream by overland flow along vehicle wheelings roads and tracks and ii erosion of fine material from the channel bed and banks during large storms however the proportion of sand sized sediment increased during the rising limb of the hydrograph as a result of the entrainment of coarser source material from the valley floor during overbank flooding the stream suspended sediment was finer than the catchment soils and considerably finer than material eroding from the catchment slopes during storms the degree of clay and silt enrichment in the suspended sediments was largely the result of preferential deposition of the coarser fraction during the transport and delivery of sediment from its source to basin outlet the data from this study confirm that a significant mode of sediment transport in fluvial systems is in the form of aggregates and that the dispersed sediment size distribution is inappropriate for determining the transportability of sediment by flow 1997 by john wiley sons ltd

controls of infiltration runoff processes in mediterranean karst rangelands in se spain semiarid karst landscapes represent an important ecosystem surrounding the mediterranean basin for which little is known on runoff generation knowledge of the sources and patterns of variation in infiltration runoff processes and their controls is important for understanding and modelling the hydrological functions of such ecosystems the objectives of this paper are to determine the infiltration rates and their controls in a representative mountain karst area sierra de gador se spain at micro plots and to investigate the integrated response of rainfall on a typical hillslope rainfall simulations in micro plots and natural rainfall runoff monitoring on a hillslope were carried out complementarily we investigated the role of soil surface components vegetation rock outcrop fracture and soil crust topographic position antecedent soil moisture and rainfall characteristics in regulating infiltration runoff processes results of rainfall simulation revealed the importance of vegetation cover and the presence of rock fractures in promoting the infiltration in the limestone karst landscape while bare patches and rock outcrops acted as sources for runoff all plots with 50 vegetation cover had no runoff with up to 55mmh 1 of simulated rain in contrast nearly all bare plots had runoff under the same simulated rain with runoff coefficients ranging from 3 1 to 20 6 on dry soil surface conditions and from 2 0 to 65 4 on wet soil surfaces runoff coefficients amounted to 59 0 79 5 for rock outcrops without cracks but were drastically reduced by the presence of cracks the surfaces with rock fragments resting on the soil generally located in the middle of the slopes prevented more effectively the runoff generation than those surfaces where rock fragments were embedded in the top soil antecedent soil moisture had significant impact on runoff generation with wet soil having doubled runoff coefficient shortened time to runoff and increased runoff rate compared to the same but dry soil linear regressions indicated that the main controls for constant infiltration rate were the cover percentages of vegetation and litter plus rainfall intensity while the major controls for runoff coefficient were the bare soil and vegetation coverage plus rainfall intensity high infiltration rates measured at the micro plots agreed with low intra event runoff coefficients mostly below 1 observed under natural rainfalls at the hillslope runoff depth and coefficient at the hillslope was significantly correlated with rainfall depth maximum hourly rainfall intensity and antecedent precipitation over 20days ap20 during the 1 5 year monitoring period from sep 2003 to mar 2005 the overall infiltration was 41 of the total rainfall amount and the maximum infiltration rate was almost 94 of the largest single rainfall event the results from this study contribute to improved understanding of the magnitude and controls of the surface runoff in semiarid karst mountain areas 2011 elsevier b v