textural characteristics and genesis of the aeolian sediments in the kuwaiti desert several types of aeolian deposits have been recognized in kuwait a smooth sand sheets that resemble desert floor sand b immobile sands that include rugged vegetated sand sheets and wadi fill deposits and c mobile sands that form active sand sheets and sand dunes simple size frequency curves illustrate the genetic relationship between the various aeolian sediment types the four size parameters namely mean size sorting skewness and kurtosis were calculated scatter plot diagrams of sorting versus mean size and sorting versus kurtosis are effective in differentiating smooth sand sheet deposits from dune sands active sand sheet deposits can also be recognized because they are usually located between the two end members smooth sand sheets and dune sands size parameters change with location regardless of their types coarsening and positive skewness usually increase downwind mineralogical and textural characteristics of the aeolian deposits in kuwait revealed that they are mostly derived from the lower mesopotamian muddy flood plain deposits the sand fraction of the al dibdibba gravelly deposits and the disintegrated material from calcretic and gypcretic duricrusts distribution of depositional and deflational areas indicates that the northern desert of kuwait is characterized by a positive sand budget whereas the southern desert has a negative sand budget

an aerodynamic roughness length map derived from extended martian rock abundance data many boundary layer processes simulated within a mars general circulation model mgcm including the description of the processes controlling dust rising from the martian surface are highly sensitive to the aerodynamic roughness length z0 on the basis of rock size frequency distributions inferred from different martian landing sites and earth analog sites we have first established that lognormal modeled rock size frequency distributions are able to reproduce correctly the observed martian rock populations we have validated the hypothesis that the rock abundance of a given area could be estimated at a first order from its thermophysical properties namely its thermal inertia i and its albedo we have demonstrated the possibility of using rock abundance to estimate the roughness density on mars and to retrieve subsequently the aerodynamic roughness length by using semi empirical relationships based on terrestrial wind tunnel and field measurements by combining our methodology with remote sensing measurements of the thermal emission spectrometer aboard mars global surveyor we have derived a global map of the aeolian aerodynamic roughness length with a 1 8 1 8 resolution over the entire martian surface contrary to what is often assumed the martian aeolian aerodynamic roughness length is spatially highly heterogeneous at the fullest resolution the martian aerodynamic roughness length varies from 10 3 cm to 2 33 cm about 84 of the martian surface seems to be characterized by an aeolian aerodynamic roughness length value lower than 1 cm the spatially uniform value that most of the mgcms simulations have assumed recently since the aerodynamic roughness length z0 is a key parameter in deriving the erosion threshold wind velocities we anticipate a significant impact of our findings on the efficiencies for lifting dust in future mgcms

modeling the mineralogy of atmospheric dust sources the variability of atmospheric dust mineralogy influences the impact of desert dust on the earth s radiative budget and biogeochemical cycles until now atmospheric transport models have assumed that dust was a constant homogeneous mixture hence neglecting this variability the lack of mineralogical data in arid areas prevented a better description of the atmospheric dust composition and we propose here a new formulation to estimate the mineral content of arid surfaces on a global scale first we collect a database of arid soil surface mineralogy for eight major minerals quartz feldspar calcite gypsum illite kaolinite smectite and hematite both for the clay and silt fraction on the basis of this we formulate a mean mineralogical table that relates classical soil types to surface mineralogy we use this table and the geographical distribution of soil types given in the food and agriculture organization soil map of the world to obtain the mineralogy of arid surfaces globally in order to validate these results we present a compilation of measured mineralogical composition of dust samples with identified sources the correlation between observed dust mineralogy and those inferred from soil types in corresponding areas is between 0 70 and 0 94 we then calculate the maps of the single scattering albedo and of the ratio of infrared extinction to visible extinction for the erodible fraction of arid areas mineralogical maps presented here will be used in future studies with an emission scheme in a global transport model

barotropic tides on the north carolina shelf observations from 18 near bottom pressure sensors and 8 current meter moorings provide a characterization of the barotropic tides over the north carolina continental shelf between chesapeake bay and cape hatteras the largest tidal constituents in this region are the m2 sea level amplitude 47 cm n2 11 cm and s2 10 cm semidiurnal tides and the k1 p1 7 cm and o1 5 cm diurnal tides the barotropic tidal currents are small less than 3 cm s21 except for the m2 current which reaches 10 cm s21 at mid shelf cross shelf currents increase linearly from approximately zero near the coast to a maximum over the mid and outer shelf alongshelf currents are nonzero near the coast and increase to roughly twice the coastal value over the mid and outer shelf while bottom friction is weak over most of the shelf in water depths of less than 10 m bottom friction results in a rapid phase decrease toward the coast in the semidiurnal alongshelf velocities this phase difference is not observed in the k1 p1 alongshelf flow possibly because diurnal wind forcing causes an opposing phase increase toward the coast alongshelf variations in tidal amplitudes and phases near the coast are much larger than expected based on variations along the shelf break inferred from basin scale altimeter estimates the shelf width in this region increases from 25 to 100 km over an alongshelf distance of about 150 km results from an analytic flat bottom two dimensional model indicate that widening of the shelf toward the north causes the observed alongshelf increase in the semidiurnal amplitude and phase but does not explain alongshelf variations in the weaker diurnal constituents

a diagnostic model of summer circulation on the northwest shelf of the east china sea abstract hydrographic data and moored current meter records collected during a cruise of the china u s joint study in august 1981 were used to compute the circulation in the east china sea a steady state linear diagnostic model with a constant vertical eddy viscosity was developed lateral friction was ignored the taiwan warm current plays a dominant role in the survey area both the huanghai warm current and the cyclonic cold water gyre southwest of cheju island are closely related to the taiwan warm current

recent current observations in the eastern yellow sea observations of current velocity pressure and temperature in the eastern yellow sea from january 10 through april 12 1986 together with geostrophic winds calculated from surface atmospheric pressure distributions are analyzed for a study of the synoptic band response of the yellow sea to the wintertime winds north wind pulses in the winter monsoon are found to give rise to northward flow bursts in the yellow sea trough which appear to peak just as the wind relaxes and to be driven by a synoptic band north to south rise in bottom pressure synchronous with the north wind pulses the existence of a similar rise in coastal sea level indicates that the observed southward pressure rise is but an offshore extension of a setup along the west coast of south korea forced by the north wind pulses the advection by northward flow bursts of warm water from the south apparently causes the measured temperature to be substantially higher in the trough than in coastal waters at the same latitude and the observed rate of cooling in the trough to be less than half of that in coastal waters to the east a winter to spring transition is also found in the bottom pressure records obtained in the trough in which the mean north to south gradient in winter reverses suddenly in early march a similar reversal also appears in sea level records along the west coast of south korea the reversal appears to be triggered by the weakening of the north winds at the arrival of spring

studying solute and particulate sediment transfer in a small mediterranean mountainous catchment subject to land abandonment the sediment budget of the small research catchment of cal parisa vallcebre eastern pyrenees was studied by hydrological monitoring and assessment of the erosion rates in the major sediment sources this area is characterized by clayey mudrock prone to landsliding and badland erosion but the catchment was selected in an area free of major badland features as a representative of middle mountain regions where a system of terraces and drainage ditches had been built for agricultural use but is now abandoned streamwater chemistry is dominated by ca 2 and hco 3 at concentrations close to calcite saturation total dissolved solids show dilution during runoff peaks and positive hysteresis loops that support a slow contribution of subsurface water relative dissolved ion concentrations are different for each event analysed particulate sediment yield is very low and represents only about 1 per cent of gross erosion in the catchment mineralogical analysis of suspended sediments shows an enrichment in calcite because of precipitation chemical analysis of suspended sediments using common one litre water samples shows higher contents of ca p and mn in transported sediment than in sediment source areas attributed to the precipitation of calcite and enrichment in organic particulate matter during events respectively for the two first elements whereas enrichment in mn remains uncertain solid matter yield is therefore clearly dominated by dissolved transport as a result of both high calcium bicarbonate concentrations in runoff waters and strong suspended sediment conveyance discontinuities land conservation structures are very effective because they are in good condition whereas the soil is covered by dense permanent vegetation nevertheless this state is unstable because the network of drainage ditches needs maintenance its spontaneous breakdown after abandonment may result in the rearrangement of the elementary stream network and gullying of old fields in hollows 1997 john wiley sons ltd

wind driven effects on the yellow sea warm current the yellow sea is a shallow basin writh an average depth of 44 m located between china and the korean peninsula one of the dominant ocean circulation features of the yellow sea is a warm wrater intrusion known as the yellow sea warm current this feature is present throughout the year but reaches its farthest northward extension in winter the circulation of the yellow east china and bohai seas was modeled using the princeton ocean model to better understand the dynamics of the yellow sea warm current the horizontal resolution of the model varies from 8 km in the yellow sea to 25 km in the east china sea twenty four sigma levels are used to define the vertical structure the model uses daily atmospheric forcing from the navy operational global atmospheric prediction system for 1993 open boundary conditions are applied at the taiwan strait the tsushima korea strait an area south of taiwan and the tokara strait with a closed boundary south of the ryukyu islands the model results are examined to determine the effect of the wind on the northward extension of the warm water intrusion using both water mass characteristics and northward velocity components sensitivity tests and spectrum analyses performed to study the influence of the wind on the yellow sea warm current show that winds modify the pathway and extent of the yellow sea warm current the current s origin however appears to be due to external forcing from the current systems developed in the east china sea

study of the dynamics of wind driven transports into the yellow sea during winter synoptic wind stresses and surface heat flux force a three dimensional numerical ocean model of the yellow sea east china sea dynamics the basin response to winter winds is examined through the model output fields northerly wind bursts are a frequent winter occurrence in this region the wind bursts develop a southward flowing current along the chinese coast as the wind stress forces fluid out of the bohai sea a north south pressure gradient develops as surface water travels from the bohai sea southward decreasing the elevation in the north relative to the elevation in the south also a westward pressure gradient across the yellow sea basin develops in response to the wind forcing the southward pressure gradient forces a bottom flow in the direction opposite to the wind stress this return flow is concentrated in a deep trough located on the eastern side of the basin after the northerly wind ceases the northward transport increases pressure in the north with the result of slowing or stopping the flow northward at times pressure increases in the north sufficiently to force a southward flow in the trough following strong northerly wind events northward transport into the yellow sea occupies the entire trough and may extend into the northern yellow sea bohai sea during periods of calm winds northward flow usually does not penetrate beyond 34 n in the yellow sea this flow is northward on the western side of the island of cheju the flow turns eastward north of cheju and then southward passing through the cheju korea strait the wind stress along the korean coast often deviates from the northerly wind stress over the rest of the yellow sea thus the flow along the korean coast is not as closely related to the northerly wind bursts as the flow along the chinese coast the winter circulation in the yellow sea is predominately a barotropic response to winds with fluctuations due to ekman flow

the causes of piping in a set of abandoned agricultural terraces in southeast spain this study aims to identify some of the factors contributing to the piping process in abandoned terraces in seven sites located in the murcia region southeast spain the local landscape has the appearance of badland geomorphology possessing deep valleys which until the 1970s were terraced and cultivated the terraces have now been abandoned to the piping process the research focuses on the relationship between the size and position of pipes and the physical and geochemistry properties of the local highly dispersive marl lithology and the extent to which the reworking of the materials for terrace cultivation has exacerbated piping erosion morphologically the terracing in the stream beds has resulted in a series of gentle benches separated by steeper risers with variable drop riser height a series of flat infiltration surfaces result and because the resculpting produces a reduced bulk density infill with enhanced throughflow infiltrating water is forced along steep hydraulic gradients to a low outfall at the base of the riser paralleling studies of land levelling and terrace abandonment in similar materials elsewhere piping in the study area is shown to be closely related to the physical and chemical characteristics of the materials its sodicity and dispersive character considerable differences in structure texture mineralogical composition and material s surface crust and subsoil geochemical properties emerged from site signature plots and these results suggest that agricultural processes affect the dispersive character of the crust materials presumably because agricultural activity increases the buffering effect of organic acids on the dispersed clay this is supported by the observation that on the one site that was levelled but not used for agriculture a stable organically distinct crust like the abandoned agricultural sites has not formed the changes to the material s aggregate stability and bulk density properties when terracing occurs is examined but insufficient evidence is available from the data collected to unpick the causes of aggregate stability changes in the study plots the way in which differences between crust and subsoil enhance infiltration is discussed and the role of the terrace drop in influencing hydraulic gradients and pipe development is illustrated a possible index to describe the relationship between evacuated material volumes and the controlling parameters discussed above is tested it is concluded that terracing which is intended as a conservation practice has in dispersive materials actually enhanced piping leading to the abandonment of farming

on the branching of the kuroshio west of kyushu trajectories of satellite tracked surface drifters released in the continental margin area west of kyushu indicate a separation of the inshore side of the kuroshio that appears to form the beginning of the tsushima current the trajectories also indicate an anticyclonic sense of circulation in the area between the separated branch and the eastward directed kuroshio main stream consistent with long term geomagnetic electrokinetograph measurements of surface currents which show a broad southward flow along the west kyushu coast a theory is put forth that ties together these observed flow features in the theory the incidence is considered of an inertial current upon a step rise in topography characterized by a step depth of h0 to simulate the west kyushu coastal bathymetry in an f plane two layered inviscid ocean with a quiescent lower layer the inertial current is of a constant potential vorticity f h where h h0 is the undisturbed upper layer depth and is bounded inshore by a free streamline along which the upper layer depth is a constant hc h the steady state downstream configuration of a separation branch and a deflected main stream along the step is connected to the upstream approach current through the consideration of the constancy of the bernoulli function and the conservation of potential vorticity and mass in the immediate neighborhood of the incidence a complicated flow region is anticipated in which recirculation is featured and an anticyclonic gyre is expected further onto the step the volume integrated balance of along step momentum of the constant potential vorticity flow allows the determination of the angle the branch current makes with the step as a function of the angle of incidence and two depth ratios hc h and h0 h the bifurcation quotient defined as the ratio of the branch current transport to that of the approach current is found to be also such a function except it is independent of the incidence angle these functions yield results that are qualitatively in agreement with the observed bifurcation of the kuroshio west of kyushu that gives rise to the tsushima current

the effects of channels and shoals on exchange between the chesapeake bay and the adjacent ocean the role of bathymetric changes in determining the transport of water and salt in the lower chesapeake bay lcb was investigated using high resolution acoustic doppler current profiler adcp and conductivity temperature depth profiles a cross channel transect was repeated eight times during neap tides on october 6 7 1993 which illustrated the lateral structure of the longitudinal and transverse flow fields and the intratidal variations in the flow structure across the lcb amplitude and phase of the m2 tidal component as well as the mean flow velocity were calculated using least squares fitting at every point of a uniform grid obtained from the adcp data the results differ from the classical two layer pattern of estuarine circulation modified by coriolis effects but are consistent with recent hydrographic observations semidiurnal flow was highest over the navigational channels and lateral gradients were strongest in regions of sharp bathymetric changes the phase lag of the semidiurnal flow also showed lateral and vertical gradients that represented advances at the bottom with respect to the surface and over the shoals in relation to the channels the section of the water column measured indicated a mean outflow of 0 7 104 m3 s and a mean inflow of 1 3 104 m3 s the apparent gain of water by the estuary during the period of observation can be explained by meteorologically forced net barotropic inflow the depth averaged mean longitudinal flow consisted of inflow in the navigational channels and outflow over the shoals the mean transverse flow showed near surface convergence over the channels we propose a possible explanation for the observed flow and density structure as follows the barotropic and baroclinic forcing interact with the bathymetry to extend the inflow from the bottom to the surface thereby inducing a transverse circulation that yields near surface convergence over the channels

preferential dust sources a geomorphological classification designed for use in global dust cycle models received 11 april 2011 revised 28 september 2011 accepted 4 october 2011 published 24 december 2011 1 we present a simple theoretical land surface classification that can be used to determine the location and temporal behavior of preferential sources of terrestrial dust emissions the classification also provides information about the likely nature of the sediments their erodibility and the likelihood that they will generate emissions under given conditions the scheme is based on the dual notions of geomorphic type and connectivity between geomorphic units we demonstrate that the scheme can be used to map potential modern day dust sources in the chihuahuan desert the lake eyre basin and the taklamakan through comparison with observed dust emissions we show that the scheme provides a reasonable prediction of areas of emission in the chihuahuan desert and in the lake eyre basin the classification is also applied to point source data from the western sahara to enable comparison of the relative importance of different land surfaces for dust emissions we indicate how the scheme could be used to provide an improved characterization of preferential dust sources in global dust cycle models

soil loss and soil water content affected by land levelling in penedes vineyards ne spain abstract this paper analyses the differences in soil moisture runoff and sediment concentration resulting from land levelling works carried out before new vineyard establishment in a reference wine region of ne spain in low disturbed soils low differences in soil moisture were observed while in high disturbed soils soil moisture and water infiltration of the surface were always lower than in the low disturbed ones while soil sealing was higher in high disturbed than in the low disturbed soils differences in runoff and sediment concentrations were also observed the most disturbed plot showed a higher sediment concentration in runoff which together with higher runoff volumes gave higher erosion rates and soil losses than the low disturbed one the differences within the most disturbed soils were high after high intensity rainfall events while no significant variations were observed in the least disturbed ones

evaluation of a wind erosion model in a desert area of northern asia by eddy covariance for the first time vertical fluxes of mineral dust measured by eddy covariance in two desert sites of northern asia have been used to test the performances of a wind erosion model in the field soil parameters required by the model were obtained through field and laboratory determinations model predictions and direct measurements have been compared the main finding was that the direction of the horizontal wind relative to the orientation of nebkhas played a crucial role in determining the emission of particles in one of the investigated sites being unable to simulate such interaction the model generally overestimated the actual emission it provided instead reliable predictions r2 0 87 when the wind direction was suitable in detaching loose erodible elements placed on nebkhas thanks to their normal orientation copyright 2009 john wiley sons ltd

measurements of tidal flow around a headland with a shipboard acoustic doppler current profiler a shipboard acoustic doppler current profiler adcp and moored current meters were used to obtain detailed measurements of the spatial structure of the tidal flow around a headland in vineyard sound massachusetts where tidal currents typically range from 50 to 70 cm s 1 eight shipboard surveys were conducted each of which followed one of five trapezoidal tracks in the vicinity of the headland completing 11 12 circuits in the course of the tidal cycle 12 4 hours the measurements from the adcp compare favorably with moored velocity measurements at two locations rms deviations of 3 cm s 1 but the comparison showed more scatter at two other sites rms deviations of 7 cm s 1 the adcp measurements from separate cruises were merged to form a composite spatial representation of the tidal and residual currents providing resolution of the spatial structure of the flow around the headland at scales from several hundred meters to 10 km the semidiurnal tidal flow is relatively uniform in space roughly following the bathymetry around the headland while a residual current field consists of counterrotating eddies on either side of the headland with spatial scales of 5 8 km and velocities as high as 25 cm s 1 the instantaneous current field indicates the formation of transient eddies on the downstream side of the headland during flood and ebb with clear evidence of flow separation near the tip of the headland

intensive surveys of the azores front 2 inferring the geostrophic and vertical velocity fields the geostrophic and vertical velocity fields are inferred using density and horizontal velocity data from three seasoar acoustic doppler current profiler surveys of the azores front the analysis is a two step procedure consisting of 1 objective analyses to reflect the observed length scales and 2 dynamical adjustments so that the density field is statically stable and the velocity field is in geostrophic balance the vertical velocity is inferred using a version of the quasi geostrophic omega equation in which the stratification is allowed to vary in the horizontal the resulting vertical velocity peaks at 2 10 4 m s 1 at 200 300 m there is a tendency for the denser water to the north of the front to be downwelled while the warmer water to the south is upwelled the implied heat flux exceeds 10 w m 2 near 100 m depth so the upper 100 m is warmed while the lower water column is cooled tending to stratify the upper ocean ageostrophic horizontal flow is toward the dense side of the front at the surface the dominant terms in the density balance are time rate of change and horizontal advection the inferred circulation cells may be an important mechanism of subduction in the upper ocean

a numerical study of currents heat advection and sea level fluctuations in the yellow sea in winter 1986 abstract a vertically integrated model that incorporates horizontal temperature variations is used to study the circulation of the yellow sea in a wintertime period for which velocity and temperature measurements are available at several moorings locations along a central trough the model features realistic bottom topography and is forced with wind stress and heat flux fields from 13 january to 22 february 1986 the model also incorporates as a boundary condition sea level fluctuations derived from coastal and insular tide gauge stations along model boundaries in open waters the model reproduces well sea level fluctuations along the coasts of both china and korea the hindcast velocity time series particularly for the north south component track those obtained from direct measurements at the moorings the model momentum balance indicates that the northward flow in the trough is driven by a sea level setup to the south in response to northerly wind bursts in the winter monsoon the sea level fluctuat

hydro geomorphological consequences of the abandonment of agricultural terraces in the mediterranean region key controlling factors and landscape stability patterns abstract traditional cultivation terraces are one of the most ancient and conspicuous agricultural landscapes in mountain and hilly regions of the mediterranean basin spreading out from asia the first terraces in the mediterranean region date from the bronze age and the classical hellenic and roman periods reaching their greatest spatial extent during the eighteenth and nineteenth centuries under optimum management these systems contribute to the conservation of soil and water resources by increasing infiltration and decreasing sediment yield however traditional management and cultivation ceased on many terraced landscapes of the northern shore mediterranean countries during the twentieth century with variable results an extensive bibliographic review and meta analysis was carried out to explore the main effects of land abandonment of mediterranean agricultural terraces on local hydrological and geomorphological processes our results point to the development of vegetation cover and degradation of terraced structures e g walls terrace risers channels as the main critical factors controlling the hydrological behaviour i e runoff production and hydrological connectivity of abandoned terrace systems severe geomorphological problems in the form of intense surface erosion aggressive piping and gullying occurred under special climatic semi arid climate lithologic dispersive marls and structural high vertical hydraulic gradient conditions dense colonization by vegetation proved to be of major importance for controlling surface erosion vegetation however showed a limited capacity to control the activity of mass movements in most cases mass movements in the form of small soil slips primarily affected long abandoned terraces in hillslope concavities and valley bottom positions that concentrate surface and subsurface water fluxes and show recurrent soil saturation in humid terraced landscapes characterized by high hillslope gradients and terrace risers the most devastating effects of mass movements took place in the form of debris slips and terrace cascading landslides triggered by extreme rainfall a variety of management options non intervention stewardship of natural rewilding processes and active rehabilitation can be applied depending on vegetation development potential site hydro geomorphic vulnerability and local socio economic interests effective conservation approaches will be required to preserve the environmental socio cultural and historical values of these ancient anthropogenic landscapes

modelling runoff and erosion for a semi arid catchment using a multi scale approach based on hydrological connectivity runoff and erosion processes are often non linear and scale dependent which complicate runoff and erosion modelling at the catchment scale one of the reasons for scale dependency is the influence of sinks i e areas of infiltration and sedimentation which lower hydrological connectivity and decrease the area specific runoff and sediment yield the objective of our study was to model runoff and erosion for a semi arid catchment using a multi scale approach based on hydrological connectivity we simulated runoff and sediment dynamics at the catchment scale with the lapsus model and included plot and hillslope scale features that influenced hydrological connectivity the semi arid carcavo catchment in southeast spain was selected as the study area where vegetation patches and agricultural terraces are the relevant sinks at the plot and hillslope scales respectively we elaborated the infiltration module to integrate these runoff sinks by adapting the parameters runoff threshold and runoff coefficient which were derived from a rainfall simulation database the results showed that the spatial distribution of vegetation patches and agricultural terraces largely determined hydrological connectivity at the catchment scale runoff and sediment yield for the scenario without agricultural terraces were respectively a factor four and nine higher compared to the current situation distributed hydrological and erosion models should therefore take account of relevant sinks at finer scales in order to correctly simulate runoff and erosion sedimentation patterns

extraction of tidal streams from a ship borne acoustic doppler current profiler using a statistical dynamical model we present a method for extracting the barotropic tide directly from the time space series of horizontal velocity obtained by a ship borne acoustic doppler current profiler adcp the method is conceptually straightforward easy to implement and suitable for operational use it involves fitting a limited area tidal model based on the linearized depth averaged shallow water equations to the adcp record the flows across the open boundaries of the model domain are assumed periodic in time with known frequencies corresponding to the tidal constituents of interest the unknown tidal amplitudes and phases at the boundary are estimated from interior adcp velocities using an inverse method the solution of the shallow water equations is posed as a boundary value problem in the frequency domain and the estimation procedure is based on generalized least squares regression results obtained include tidal maps a tidal residual series and associated error estimates an application of the method to ship adcp data collected on a cruise to the western bank region of the scotian shelf off the east coast of canada is described the tidal estimates and the residual field obtained are verified by comparison to other data collected during the cruise the residual circulation shows an anticyclonic gyre centered on the crest of western bank and a northward current to the west of this region

high resolution observations of the intensity of secondary circulation along a curved tidal channel 1 high horizontal resolution moving vessel acoustic doppler current profiler adcp observations of the spatial pattern of cross stream velocities in a curved tidal channel show radially outward surface velocities up to 10 cm s 1 which are maximum midchannel consistent with helical secondary flow in a vertical plane normal to the depth averaged velocity the 30 m cross and 150 m along channel resolution observations are from a 2700 m long section of a 350 m wide horizontally and vertically well mixed tidal channel with a radius of curvature 1 5 km the along channel resolution allows the intensity of the curvature induced secondary flow to be estimated from the linear correlation between the observed cross channel component of vertical shear and the shear estimated from the streamwise velocity and its varying curvature using an existing analytic model the two shears are highly correlated and the regression line slope demonstrates that the observed curvature induced secondary flow is 30 more intense than that predicted by the model for a typical bottom drag coefficient the secondary flow is 50 more intense than that predicted using the drag coefficient which best fits the streamwise velocity profile numerical solutions demonstrate that the intensity of the secondary flow is sensitive to small changes in the shape of the eddy viscosity profile hence intensity may be sensitive to the way turbulence is modeled lagged correlation of the observations showed that the secondary flow adapts to changes in curvature and primary flow over a 300 m length scale or 20 water depths consistent with the existing model and laboratory studies

a model of the circulation on the outer scotian shelf with open boundary conditions inferred by data assimilation the circulation on western bank is described using data collected in spring 1991 and 1992 as part of an interdisciplinary study of the early life history of atlantic cod gadus morhua the mean circulation over the crest of the bank is weak of the order of a few centimeters per second and is flanked to the south and west by an anticyclonic flow with a speed of about 10 cm s 1 a thermal wind calculation shows the mean circulation is due primarily to horizontal variations in the density field the m2 tidal constituent is dominant and reaches speeds of about 20 cm s 1 the tidal residuals have a standard deviation of about 10 cm s 1 and characteristic time and length scales of several days and tens of kilometers respectively in order to help collect and interpret biological data from western bank we developed a hydrodynamic model of the near surface flow that could be used operationally the model is based on a decomposition of the flow into components driven by 1 local wind stress 2 horizontal density gradients and 3 flows through the open boundaries of the model the wind driven component is calculated using a simple slab model driven by the observed wind the other two components are estimated through the assimilation of observed bottom pressures dynamic heights and currents into the hydrodynamic model the hindcast skill of the model is quantified by cross validation and shown to be higher than that of four simple statistically based schemes

diurnal period continental shelf waves along vancouver island a comparison of observations with theoretical models abstract current and sea level data from the coastal oceanic dynamics experiment conducted of vancouver island from may 1979 to september 1980 reveal shelf waves of diurnal period whose motions dominate the flow over the continental shelf in this paper current meter data from mooring lines off brooks peninsula estevan point and carmanah point are compared with theoretical solutions for a combination of free shelf waves and barotropic kelvin waves over uniform alongshore topography use of brink s scheme for baroclinic shelf waves gives close agreement between the modeled and observed k1 period horizontal currents over the continental margin off central vancouver island and accurately predicts vertical velocities and sea levels the shelf waves am shown to be entirely dominated by the first baroclinic mode wavelength derived from the model closely approximate wavelenghts computed from the alongshore change in phase of the observed diurnal current ellipses the baroclinic model successfully predicts the

separation of tidal and subtidal currents in ship mounted acoustic doppler current profiler observations a simple method is developed to analyze current measurements obtained from a moving platform the need for this is motivated by the now common use of the ship mounted acoustic doppler current profiler adcp to acquire absolute velocity data during an oceanographic survey of a given region the full potential of this new measurement technique is severely hindered when the presence of high frequency phenomena e g tidal or inertial motions prevents a clear visualization of the lower frequency current structure of interest our analysis method is based on a spatial interpolation scheme using arbitrary functions that allows for the tidal current time variability which then permits the tide induced motions to be subtracted from the adcp data to yield the subtidal current field the method also allows nearby moored and drifter current measurements if available to be combined with the shipboard adcp observations in a single analysis to obtain the best description of the tidal and subtidal currents to illustrate this method we present results from the analysis of adcp data taken during oceanographic surveys in two different continental shelf regions the east china sea and the amazon shelf a 5 day conductivity temperature depth ctd and adcp survey was made in the east china sea near the mouth of the yellow sea during january 1986 there the currents were essentially barotropic and dominated by the semidiurnal tide the adcp derived cotidal chart for the m2 12 42 hours component agrees well with existing charts derived empirically from sea level observations or from regional numerical models the adcp derived steady flow is also consistent with the observed density field and indicates little flow in or out of the yellow sea and a transport of about 1 sv toward the tsushima strait two ctd adcp surveys lasting 21 and 23 days were conducted over the amazon shelf during march and may 1990 simultaneously moored current observations were also obtained at three locations along a cross shelf array 200 km north of the amazon river mouth for a common period of at least 2 months february 12 to april 13 over the shelf tidal and subtidal currents were comparable in magnitude our analysis indicates that the tidal currents were essentially barotropic semidiurnal and polarized in the cross shelf direction increasing in magnitude toward the inner shelf where current values of more than 2 m s are common the adcp derived steady currents were aligned in the along shelf direction and strongly influenced by the north brazil current nbc during both adcp surveys the northwestward flowing nbc was transporting more than 2 sv over the shelf at depths shallower than 100 m

factors controlling threshold friction velocity in semiarid and arid areas of the united states a physical model was developed to explain threshold friction velocities u t for particles of the size 60 120 m lying on a rough surface in loose soils for semiarid and arid parts of the united states the model corrected for the effect of momentum absorption by the nonerodible roughness for loose or disturbed soils the most important parameter that controls u t is the aerodynamic roughness height z0 for physical crusts damaged by wind the size of erodible crust pieces is important along with the roughness the presence of cyanobacteriallichen soil crusts roughens the surface and the biological fibrous growth aggregates soil particles only undisturbed sandy soils and disturbed soils of all types would be expected to be erodible in normal wind storms therefore disturbance of soils by both cattle and humans is very important in predicting wind erosion as confirmed by our measurements

assessing the microped size distributions of desert soils erodible by wind the microped size distribution of erodible soils is one of the main factors controlling the emissions of mineral aerosol to date the microped size distributions of desert soils in natural field conditions are not well known and thus the existing dust source models cannot be applied to natural sites based on dry sieving and elemental analysis of 26 soil samples collected in arid and semiarid regions it is shown that the microped size distributions of these desert soil samples involve a combination of four major mass size populations these four size populations correspond to salty soils fine quartz sand coarse dune sand and aluminosilicate silt we show that the microped size distributions of the various desert soils according to their mineralogical characteristics can be calculated by a mixture involving two or three of these four populations the main field of application for this scheme is the characterization of the erodible soil size distributions for modelling the atmospheric dust cycle

erosion in mediterranean landscapes changes and future challenges abstract intense erosion processes are widespread in the mediterranean region and include sheet wash erosion rilling gullying shallow landsliding and the development of large and active badlands in both subhumid and semi arid areas this review analyses the main environmental and human features related to soil erosion processes and the main factors that explain the extreme variability of factors influencing soil erosion particularly recent land use changes the importance of erosion in the mediterranean is related to the long history of human activity in a region characterized by low levels of annual precipitation the occurrence of intense rainstorms and long lasting droughts high evapotranspiration the presence of steep slopes and the occurrence of recent tectonic activity together with the recurrent use of fire overgrazing and farming these factors have resulted in a complex landscape in which intensification and abandonment wealth and poverty can co exist the changing conditions of national and international markets and the evolution of population pressure are now the main drivers explaining land use changes including farmland abandonment in mountain areas the expansion of some subsidized crops to marginal lands and the development of new terraces affected by landslides and intense soil erosion during extreme rainstorm events the occurrence of human related forest fires affecting thousands of hectares each year is a significant problem in both the northern and southern areas of the mediterranean basin here we highlight the rise of new scientific challenges in controlling the negative consequences of soil erosion in the mediterranean region 1 to reduce the effects and extent of forest fires and restructure the spatial organization of abandoned landscapes 2 to provide guidance for making the eu agricultural policy more adapted to the complexity and fragility of mediterranean environments 3 to develop field methods and models to improve the identification of runoff and sediment contributing areas 4 to contribute to the conservation of landscapes i e bench terraced fields having high cultural and productivity values 5 to improve knowledge of the hydrological and geomorphological functioning of badlands with the aim of reducing sediment yield and accessibility 6 to better understand the effect of climate change on soil erosion in the mediterranean region and 7 to improve quantitative information on long term soil erosion

numerical investigation of the generation of continental shelf waves and their role in the westward shift of the yellow sea warm current abstract the yellow sea warm current yswc which carries warm saline water into the yellow sea ys exhibits a typical northward upwind flow during winter observations have shown that the path of the yswc has shifted to the west from the deep trough and it has been suggested that continental shelf waves csws may play an important role in this westward shift however the source of southward propagating csws that drive the westward shift of the yswc remains unclear the objective of this study is to reveal the generative mechanism of csws and their role in driving the westward shift of the yswc numerical models with an idealised topography show that the westward shift of the northward flow propagates southward along the western slope offshore of china with a typical speed of 2 99 m s 1 comparable to the theoretical phase speed of a first mode csw csws driving the westward shift are generated on the northern slope primarily by the scattering of kelvin waves that develop due to northerly winds and propagate northward into the ys along the eastern boundary of the korean peninsula model experiments with a realistic topography consistently support the idea that kelvin wave scattering is a primary source of the southward propagation of the csws that drive the westward shift of the yswc

direct velocity observations of volume flux between iceland and the shetland islands atlantic waters flowing northward into the nordic seas are important for their role as an early indicator of changes to deepwater formation as such this requires a fundamental understanding of the pathways and volume fluxes through the primary passageways from the atlantic into the nordic seas a mean annual volume transport of 6 1 0 3 sv was observed flowing in above the t 27 8 isopycnal a proxy for the lower limit of atlantic water depth through the faroe shetland channel fsc and over the iceland faroes ridge ifr from march 2008 to june 2012 using repeat velocity sections obtained from a vessel mounted acoustic doppler current profiler adcp a new vessel route has expanded the spatial coverage of fsc observations and reveals a difference in average inflow transport which most likely results from an interannual variation in the total transport through the fsc which in turn is tied to a weakening of the southerly flow over the western slope of the channel this interannual variability has increased the mean transport through the fsc from 0 9 sv observed over the first 2 years of this program by rossby and flagg 2012 to a 4 5 year mean of 1 7 0 2 sv which emphasizes the importance of knowing the flow along the faroese shelf interannual fluctuations in transport observed over the ifr are related to the width of the inflow over the faroese half of the ridge

modeling temperature inversion in southeastern yellow sea during winter 2016 a significant temperature inversion with temperature differences larger than 3 c was observed in the southeastern yellow sea ys during february 2016 by analyzing in situ hydrographic profiles and results from a regional ocean model for the ys this study examines the spatiotemporal evolution of the temperature inversion and its connection with wind induced currents in winter observations reveal that in winter when the northwesterly wind prevails over the ys the temperature inversion occurs largely at the frontal zone southwest of korea where warm saline water of a kuroshio origin meets cold fresh coastal water our model successfully captures the temperature inversion observed in the winter of 2016 and suggests a close relation between northwesterly wind bursts and the occurrence of the large inversion in this respect the strong northwesterly wind drove cold coastal water southward in the upper layer via ekman transport which pushed the water mass southward and increased the sea level slope in the frontal zone in southeastern ys the intensified sea level slope propagated northward away from the frontal zone as a shelf wave causing a northward upwind flow response along the ys trough in the lower layer thereby resulting in the large temperature inversion diagnostic analysis of the momentum balance shows that the westward pressure gradient which developed with shelf wave propagation along the ys trough was balanced with the coriolis force in accordance with the northward upwind current in and around the inversion area

seasonal circulation patterns of the yellow and east china seas derived from satellite tracked drifter trajectories and hydrographic observations abstract we investigated seasonal circulation patterns of the yellow and east china seas yecs by reviewing previous works on the circulation and its dominant currents and taking into account newly compiled trajectories of satellite tracked drifters collected between the 1980s and 2000s the circulation patterns suggested before the 1990s can be categorized into two groups depending on the identified origin of the tsushima warm current in the korea tsushima straits i branching from the kuroshio southwest of kyushu or ii northeastward continuation of the taiwan strait throughflow the branching of the kuroshio southwest of kyushu and northeast of taiwan was clearly evidenced by current measurements and concurrent hydrographic surveys however there is still no clear evidence for the northeastward pathway of taiwan strait throughflow across the mid shelf area of the east china sea target oriented surveys in the 1990s and 2000s employing advanced instruments such as drifter tracking and acoustic doppler current profiler measurements now provide decisive proof of the clockwise rounding of the cheju warm current around jeju do throughout the year of the northeastward extension of changjiang discharge in summer and of the presence of the yellow sea warm current only in winter thus both coastal currents in shallow water and secondary branch currents of the kuroshio such as the yellow sea warm current are found to significantly change from winter to summer to better present the basic pattern of yecs circulation and its seasonality we have constructed seasonal circulations patterns based on review results on the newly compiled drifter trajectories and on hydrographic observations further investigations should be carried out in future with support of comprehensive current measurements on shelf areas and through elaborate numerical modeling

analysis of flow at the gate of taiwan strait 1 a field survey with ship borne acoustic doppler current profiler was carried out across the penghu channel the gate of taiwan strait from 17 to 20 of may 1999 a new method of least squares interpolation is used to separate the mean flow from tidal currents the technique uses gaussian interpolation functions with local support which also take into consideration the anisotropic nature of the flow structure optimal solution is obtained by determining the tradeoff between the misfit and the model order the analysis indicates that the currents in the penghu channel are essentially barotropic and characterized by strong semidiurnal tides and mean flow the along channel averaged tidal velocity amplitudes are 1 2 m s 1 and 0 32 m s 1 for semidiurnal and diurnal tides respectively the mean current is uniform with an average northward velocity of 0 73 m s 1 the total transport is about 1 6 sv which represents a significant mass and material flux into the east china sea

validation of a dust production model from measurements performed in semi arid agricultural areas of spain and niger abstract models of two processes saltation and sandblasting that lead to fine dust release in arid areas have recently been combined to form a dust production model dpm the physical bases of which are summarized in order to validate dpm at field scale its predictions in terms of horizontal and vertical mass fluxes are compared to direct measurements made in natural conditions on a silt loam soil in north east spain during wind erosion and loss of soil nutrients in semi arid spain welsons experiment and a sandy soil in niger during the programme soil and erosion prose experiment in the spanish case due to the formation of a coalescing crust after rainfall a limited supply of loose particles on the soil surface restricts the availability of soil aggregates for saltation once this supply limitation is taken into account in the saltation submodel the vertical fluxes predicted by dpm with the binding energies previously determined in a wind tunnel experiment agree well with the measured ones in the niger case the agreement is found to be directly satisfactory for unlimited saltation even in crusted conditions however in order to retrieve measured vertical fluxes the aggregate binding energies that constitute key factors involved in the sandblasting computation must be divided by 3 these results validate the sandblasting part of dpm but show that saltation has to be adequately tuned when a coalescing crust forms on loamy soils these results also show that the potential of soil for fine dust production does not increase with its clay content which rather tends to slightly reduce sandblasting efficiencies a high clay content favours formation of a coalescing crust that efficiently traps formerly loose soil aggregates the supply limitation resulting from this crust formation controls the importance of saltation and hence of fine dust production finally saltation clearly appears as the limiting factor for fine dust production

estimation of pm20 emissions by wind erosion main sources of uncertainties abstract the physics of the two processes saltation and sandblasting leading to fine mineral dust emissions by wind erosion in arid or semi arid areas has been detailed and modeled the combination of these two models has led to a physically explicit dust production model dpm in this work sensitivity tests are performed with the dpm to determine the nature of the main soil parameters that control dust emissions by sandblasting it is found that the soil roughness length and the dry size distribution of the soil aggregates constituting the loose wind erodible fraction of the topsoil have the greatest influence on the soil potential for mineral dust production contrary to what is often assumed soil texture is not a relevant parameter in the light of these new findings results of vertical flux measurements performed over a wide variety of sources in niger and the us south west 14 soils have been reanalyzed results show 1 that for the tested soils the dpm and hence sandblasting explain all dust emissions and 2 that 13 of the 14 soils that had been selected a priori for their high potential for dust emissions contained a fine soil aggregate component this is consistent with the sensitivity tests indicating that the presence of such a component could enhance dust emissions by one order of magnitude finally it can be concluded that most of the apparent scatter in the experimental results was in large part due to an inappropriate choice of soil parameters to interpret them

acoustic doppler current profiler measurements of possible lee waves south of key west florida acoustic doppler current profiler measurements made while underway in 200 240 m of water south of key west florida show wavelike signals with about 1 km horizontal wavelength and 3 5 cm s 1 amplitude vertical velocity vertical displacements of about 5 m are inferred from coherent oscillations in surfaces of constant acoustic backscatter in features associated with the width of the peak in the doppler spectrum and in fine structure of vertical current shear while the sampling was limited all the measurable waves occurred over irregular bathymetry in the presence of an east northeastward mean flow u 1 m s 1 averaged over 30 to 90 m depth the peak strain rate associated with the waves was nearly 1 10 3 s 1 at 12 m depth and this could have produced bands of smooth and rough water observed at the surface we tentatively identify the waves as being topographically forced by the florida current flowing over a rough continental margin

determination of winter temperature patterns fronts and surface currents in the yellow sea and east china sea from satellite imagery abstract a detailed winter sea surface temperature sst pattern in the yellow sea and east china sea is derived from meteorological satellite thermal infrared images the isotherms in the pattern are calibrated by temperature measurements in situ the features of sst patterns are analyzed using images taken from a variety of satellites dmsp noaa 5 6 gms 1 and tiros n over the last 10 years the winter sst pattern has a sandwich structure which implies that two warm tongues sandwich one cold tongue this pattern starts forming at the end of november has formed by the end of january begins to decline at the end of february and disappears at the end of april in the sst patterns strong coastal fronts can be discerned they are the shandong peninsula coastal front the zhejiang fujian coastal front and the south korean coastal front based on the features of sst patterns and these fronts the winter surface currents are discussed

threshold friction velocities and rupture moduli for crusted desert soils for the input of soil particles into the air desert soils having clay crusts mostly from the mojave desert were tested for threshold friction velocity the friction velocity at which soil erosion begins with an open bottomed wind tunnel the soils were also tested for content of clay water soluble material calcium carbonate organic material mineralogy of clay and of salts soil moisture modulus of rupture and crust thickness if no loose material existed on the soil surface crusts having modulus of rupture greater than 0 7 bar and crust thickness of 0 7 cm to 0 3 cm were effective in protecting against wind erosion disturbed clay crusts having modulus of rupture before disturbance greater than 2 bar with thickness less than 1 9 cm did not experience significant wind erosion modulus of rupture was related to composition of soil but was shown to depend mostly on clay content soil composition is related to modulus of rupture in an empirical equation

near inertial and tidal currents detected with a vessel mounted acoustic doppler current profiler in the western mediterranean sea 1 the objective of this study is to separate the subinertial inertial and tidal fields from vessel mounted acoustic doppler current profiler vm adcp observations acquired during six cruises in the catalan and alboran seas western mediterranean sea to fulfill this objective we use a method that successfully detects and filters out the main high frequencies that are present in the vm adcp data the resulting near inertial component has frequencies below the coriolis frequency f in the catalan sea and above f in the alboran sea the tidal component is consistent with observed and modeled tides in the catalan and alboran seas the steady component is highly correlated with the geostrophic field there is also a nonfitted or residual component which represents the misfit between the vm adcp data and the model proposed

observation of internal tidal currents in the kaoping canyon off southwestern taiwan abstract internal tidal currents and associated water mass displacements were investigated during multiple cruises in the kaoping submarine canyon off southwestern taiwan observations from both moored and shipboard acoustic doppler current profilers and hydrographic casts were conducted along the canyon the velocity data showed that in the lower layer the major axis of the tidal currents aligned with the orientation of the canyon and currents moved up canyon during flood and down canyon during ebb the vertical phase shift and amplitude of the currents indicated that the semidiurnal internal tide dominated with intensity increasing with depth toward the canyon head tidal energy was channeled from the shelf landward with a beamlike internal wave guided by bottom topography the estimated phase velocity was 1 4 1 7 m s 1 based on normal mode analysis and the phase lag between sampling stations empirical orthogonal function analysis of hydrographic profiles confirmed that the first mode m 2 internal tide explained 70 of the total variance the strong convergence of internal tidal currents near the canyon head during flood may play an important role in the daily migration of cherry shrimps which burrow along the canyon wall

an empirical model of the tidal currents in the gulf of the farallones abstract candela et al 1990 1992 showed that tides in an open ocean region can be resolved using velocity data from a ship mounted adcp we use their method to build a spatially varying model of the tidal currents in the gulf of the farallones an area of complicated bathymetry where the tidal velocities in some parts of the region are weak compared to the mean currents we describe the tidal fields for the m 2 s 2 k 1 and o 1 constituents and show that this method is sensitive to the model parameters and the quantity of input data in areas with complex bathymetry and tidal structures a large amount of spatial data is needed to resolve the tides a method of estimating the associated errors inherent in the model is described

a direct estimate of poleward volume heat and freshwater fluxes at 59 5 n between greenland and scotland the meridional overturning circulation moc in the north atlantic plays a major role in the transport of heat from low to high latitudes in this study we combine recent measurements of currents from the surface to 700 m from a shipboard acoustic doppler current profiler with argo profiles to 2000 m to estimate poleward volume heat and freshwater flux at 59 5 n between greenland and scotland this is made possible thanks to the vessel nuka arctica that operates on a 3 week schedule between greenland and denmark for the period late 2012 to early 2016 the de seasoned mean meridional overturning circulation reaches a 18 4 3 4 sv maximum at the 27 55 kg m 3 isopycnal which varies in depth from near the surface in the western irminger sea to 1000 m in rockall trough the total heat and fresh water fluxes across 59 5 n 399 74 tw and 0 20 0 04 sv where the uncertainties are principally due to that of the moc analysis of altimetric sea surface height variations along exactly the same route reveals a somewhat stronger geostrophic flow north during this period compared to the 23 year mean suggesting that for a long term mean the above flux estimates should be reduced slightly to 17 4 sv 377 tw and 0 19 sv respectively with the same estimate uncertainties the adcp program is ongoing

internal wave directional spectra using an acoustic doppler current profiler an acoustic doppler current profiler was deployed through land fast ice near resolute northwest territories it recorded a distinct train of high frequency periods 30 0 min horizontal flow without a corresponding coherent vertical velocity component attributed to a density driven along isopycnal flow created by salt rejection emanating from a broad shelf to the northeast

water characteristics and movements of the yellow sea warm current in summer water characteristics of the yellow sea warm current and its movement in summer are examined from the analysis of the recent hydrographic data collected in adjacent seas of cheju island it is suggested that the yellow sea warm current water in the northeastern china sea is a mixture of western north pacific central water and the yellow sea bottom cold water in the ratio of 7 to 3 it is characterized by salinities of 34 2 s 34 5 and temperatures of 13 t 15 c at depths below 50 m the yellow sea warm current does not seem to extend into the yellow sea as previously believed at least in summer but instead it turns eastward around cheju

taming the torrents the hydrological impacts of ancient terracing practices in jordan extensive terracing was an important component of the water and agricultural management regime of nabatean petra the exact function s of these terraces qualitatively and quantitatively is herein investigated field studies and computer modeling for two sites within the drainage basin of petra show that these terraces were highly effective at reducing surface runoff different design features seem to have been adapted in order to achieve different objectives at varying sites for example the beidha site in the lower reaches of the catchment area falls within the higher relief ordovician disi sandstone formation area here the terrace system was designed to slow water flow and trap sediments the terracing greatly reduced surface water flow through the entrapment of sandy loam sediments behind it on the other hand the baqa a site falls in the upper reaches of the drainage basin within the upper cretaceous amman silicified limestone formation the effect of the terrace system here on runoff is significant but less than that seen at beidha this system was more suited for soil conservation and agriculture as the soil here in its natural state already had a high infiltration rate neglect and abandonment of these terraces at both sites have led to increased runoff as evidenced by the development of gullies and by periodic flooding downstream in the core of the ancient city based on the six modeled cases terraces can minimize the surface flow by an average of 28 with values as high as 90 when 2010 precipitation data were used conducting an intensive survey within the catchment area surrounding the ancient city of petra mapping the ancient terraces and reviving their function may produce significant results in flood mitigation and control there

badlands in marl lithologies a field guide to soil dispersion subsurface erosion and piping origin gullies abstract field scientists studying badland processes in mediterranean and semi arid climates require assurances that the material in which gullies are presented is not dispersive a dispersive context means first infiltration rates may be radically changing in very short periods due to swelling and deflocculation of clays second surface crusts could be the result of translocation of sodium into subsurface positions third rills may be formed or at least exacerbated by shallow subsurface erosion fourth large gullies with substantial up channel headcuts including so called bank gullies may have formed because subsurface pipes have collapsed and fifth that network connectivity and evolution may be principally internal being effected by subsurface pipe capture network integration and most importantly the bulk of the sediment moving around in the landscape is not being lost from the surface this paper presents a decision support tool to assist the effective diagnosis of a landscape s principal genetic process suite the soil s behaviour in response to its geochemistry in marls with high exchangeable sodium percentages esps is outlined in simple terms with minimum use of laboratory or field chemical investigations using examples the paper then presents a simple set of form indicators that can be used in the field to diagnose the possibility that subsurface process are dominating landscape erosion surface crust character ephemeral rills and large subsurface tunnel settings are explained and classified in a final section the geomorphological implications of piping in gullied landscapes are explored by reference to the literature on connectivity

impact of lithology and soil properties on abandoned dryland terraces during the early stages of soil erosion by water in south east spain soil erosion by water in abandoned dry terraces is one of the most important environmental problems in semiarid areas enhancing biological degradation and reducing possible resources that can be obtained however little is known about the effects of the types of lithology and soil properties on the early stages of soil erosion therefore the main aim of this research was to assess the effect of different lithologies marls limestones and metamorphic phyllites schists and greywackes materials and soil properties on the early stages of soil erosion by water in abandoned dry terraces compared with similar terraces still in agricultural use soil analyses texture aggregate stability and bulk density and 22 rainfall simulations were carried out under dry conditions during the experiments local inclination vegetation and stone cover total organic matter and antecedent soil moisture were also quantified the results showed that the highest soil loss 41 41 g m2 in cultivated plots and 17 05 g m2 in the abandoned plots and runoff 3 79 l m2 in the abandoned plot occurred on marl substrata marls also showed the shallowest infiltration front 9 cm and lowest infiltration rate 4 3 cm min limestones and especially metamorphic areas showed a lower degree of soil erosion higher infiltration rates and deeper infiltration fronts

effects of the yellow sea warm current on the winter temperature distribution in a numerical model 1 the temperature distribution and circulation patterns in the yellow sea ys are examined by using a wave tide circulation coupled numerical model this model sufficiently reproduces the variation of the warm tongue structure of the yellow sea warm current yswc from the double branches flowing along the ys trough and the western 60 m isobath in january to the single stream along the western temperature front in march this is observed in both the long term monthly climatology and the satellite based sea surface temperature images in recent years examining the local heat balance in the numerical model during the entire cooling period it is found that the yswc has a very important influence on the ys warm tongue structure compared with the surface cooling the influence of the advection is small in the coastal shallow area but large in the deep warm tongue area up to 50 of the magnitude of heat flux although bathymetry is the essential factor which causes the temperature front the yswc is the key factor which positions shapes and maintains the warm tongue structure this helps to affirm the existence of the yswc at least as a monthly mean flow however more high resolution current observations in deeper layers west of cheju island and the western fork of the ys trough are needed to confirm the existence of the yswc and its characteristic timescale in the real ys

morphology and sedimentation of sand bodies in the tidal shelf sea of eastern taiwan strait abstract changyun ridge located in the central eastern part of the taiwan strait consists of sand bodies the eastern changyun sand ridge 65 km long and 13 km wide a sand shoal 53 km long and 22 km wide and a sand sheet 60 km long 40 km wide and 22 m in height the eastern changyun sand ridge and the sand sheet are oriented parallel to the coastline but the sand shoal is perpendicular to the coast the eastern changyun sand ridge is oriented oblique to the narrow reciprocal tidal ellipses the sand shoal and sand sheet are normal and oblique to the broad rotary tidal ellipses respectively surface sediments of the changyun ridge are composed of very fine to coarse sands in a progressive seaward decrease in grain size the configuration and spatial distribution of these three sand bodies with corresponding decrease in tidal speed and in grain size together suggest that the sand bodies developed sequentially from the near shore to the offshore area presumably in response to westward shifting of the north flowing tidal currents sand waves occur widespreadly on the sand shoal and seldom appear on the eastern changyun sand ridge occurrences of sand waves suggest that the sand shoal is considered to be active and the sand ridge to be moribund chirp sonar profiles reveal the internal structures of the sand shoal showing a relatively flat basal reflector underlying the sand body the thickness of the sand accumulation is about 22 25 m and it is firstly determined by the depth difference between the modern sea bed and the basal reflector to better describe morphology and document dimensions of these sand bodies the presence of several short inclined reflectors dipping northeast and down lapping the basal flat reflector indicate that sands are most likely transported from south to north for the sand shoal the sand bodies of the changyun ridge rest upon a relative flat basal reflector suggesting a mainly hydrodynamically controlled origin the variations of the hydrodynamic conditions mainly tidal currents on the central eastern taiwan strait shelf seem to be the primary control on sedimentary facies shift morphological changes and sand ridge growth for the changyun ridge the changyun ridge is ongoing to receive sands from the south in a transitional development stage as long as the sand supply continues and over a longer time period the sand bodies eventually will develop into three individual linear sand ridges separated by swales oriented parallel to the peak currents

open ocean modeling as an inverse problem m2 tides in bass strait abstract the solution of a linear model of barotropic m2 tides in bass strait is not consistent with new high quality tide gage and current meter data this is attributed to the method used to estimate the forcing due to incoming radiation at the open boundaries using only historical tide data the new data is assimilated into the model using a generalized inverse theory described by bennett and mcintosh the analysis establishes the consistency of the new data with the model dynamics of linearized shallow water waves and uses those dynamics to interpolate between the new data the dependence of the solution upon the estimated boundary forcing is reduced relaxation of the coastal rigid boundary condition within estimated model interpolation errors has a significant effect on the solution

transport processes in the kara sea field data from late summer cruises in 1993 1996 and results from a rotating laboratory model study are used to infer transport routes for contaminants in the kara sea on the western siberian coast the data show a circulation pattern that differs significantly from published concepts and contains a richer structure both the inflowing coastal water from the west and the modified atlantic water from the barents sea and the arctic ocean in the north affect the water properties of the east novaya zemlya trough through mixing intrusion and possible transformation during winter convection much of the current structure can be explained as a result of topographical steering of the throughflows weak summer winds of variable direction affect only the upper layer whereas persistent strong winds may affect long term circulation patterns and transports the main outflow routes are north to the santa anna trough and northeast to the voronin trough the outflowing surface water and ice to the north are expected to join the inflowing polar water from the arctic ocean that forms the persey current into the barents sea deeper outflows are expected to follow the continental slope to the east in the arctic ocean the laboratory model has been validated to earlier current measurements to the north and south of novaya zemlya and shows several of the features observed in the newer field measurements this suggests that the dynamic similitude and boundary forcing of the model are good two notable exceptions are the westward transport of drifting buoys to the north of novaya zemlya and the late winter hydrography to the north of the ob and yenisey estuaries both are probably due to persistent winds the conclusions from the measured and modeled currents are supported by measurements of 137cs in the seawater and sediments

on the spatial structure and temporal variability of poleward transport between scotland and greenland 1 the flow north of warm subtropical water though the northeastern atlantic is known to have many pathways that vary over time here we use a combination of upper ocean current measurements betwe

saltation threshold on earth mars and venus new formulations valid for wide ranges of particle diameter and density and gas density are presented for prediction of saltation threshold speed for small particles a low air density wind tunnel was used to extend the range of previous investigations and to separate the effects of reynolds number and interparticle forces of cohesion the new formulations are used to predict saltation threshold for atmospheric conditions on the surface of the earth mars and venus

does the yellow sea warm current really exist as a persistent mean flow does saline water of kuroshio origin intrude into the yellow sea interior by a persistent mean current through the yellow sea warm current or by an intermittently generated wind driven current this very fundamental question is discussed by analyzing comprehensive conductivity temperature depth data collected over the entire southern yellow sea basin and by analyzing satellite tracked drifter trajectories collected in 1996 and 1997 in the southwestern yellow sea relatively saline water 33 0 34 0 psu persists year round implying a northwestward intrusion of cheju warm current water cwcw this water is a mixture of saline cwcw with salinity higher than 34 0 psu and fresh yellow sea waters with salinity 33 0 psu during the winter monsoon the mixed water distribution is tongue shaped apparently intruding from the cwcw area at the same time a strong thermohaline front with a horizontal form similar to the greek letter forms across the southern entrance of the central yellow sea trough and separates the mixed water area from the cwcw during the summer monsoon the cwcw intrusion is weak and the mixed water that intruded in the previous winter monsoon remains inside the trough as its salinity decreases in winter occasional collapses of part of the front on the western side of the trough are observed presumably in response to an imbalance between northwest currents generated by strong northerly wind bursts and southeast tide induced residual currents saline water in the frontal zone may then flush into the southwestern yellow sea through the collapsed area of the front we conclude that the yswc is not a persistent mean current we also conclude that cwcw may be transported to the southwestern yellow sea in winter by the intermittently generated northwest currents on the western slope of the trough which override the tide induced residual currents that flow to the southeast in this part of the basin

an open ocean forcing in the east china and yellow seas 1 recent studies have demonstrated that the annual mean barotropic currents over the east china and yellow seas ecys are forced primarily by the oceanic circulation in the open ocean basin through the kuroshio current kc the western boundary current of the subtropical gyre in the north pacific ocean the local wind stress forcing plays an important but secondary role those previous results were mainly qualitative and from a simple barotropic model forced by a steady wind stress field they remain to be tested in a more complete 3 d model with both wind stress and buoyancy fluxes in addition the seasonal variability of major ecys currents may involve different forcing mechanisms than their annually averaged fields do and this can only be addressed when a seasonally varying forcing is used in the model in this paper we will address these issues by using a 3 d baroclinic model our results confirm the finding from the previous studies that the kc is the primary forcing mechanism for major annually mean currents in the ecys which include the taiwan strait current the tsushima warm current and the yellow sea warm current yswc etc however the local monsoonal forcing plays a prominent role in modulating the seasonal variability of all major currents in the region a deep northwestward intrusion of the yswc in winter for instance is mainly due to a robustly developed china coastal current and korea coastal current which draw water along the yellow sea trough to feed the southward flows along the west and east coasts of the yellow sea

direct measurement of volume flux in the faroe shetland channel and over the iceland faroe ridge 1 determining the exchange of water across the iceland faroe scotland ridge is of fundamental interest because it measures the rate of transformation of north atlantic water into dense water and thus the strength of the meridional overturning circulation moc here we study this exchange by monitoring all water flowing through the area east of iceland to near the bottom or 600 m depth using a 75 khz acoustic doppler current profiler adcp mounted on the high seas ferry m f norrona starting in march 2008 currents have been measured in the faroe shetland channel fsc and along the iceland faroe ridge ifr on the ferry s weekly round trips between iceland and denmark the detided average transports to the north across the two sections are 4 1 0 1 sv 106 m2s 1 through the fsc and 4 4 0 25 sv across the ifr this excludes 1 6 sv circulating around the faroes the norrona program is ongoing

sedimentation dynamics in the east china sea elucidated from and sedimentation dynamics in the east china sea was investigated based on profiles and inventories of 210 pb 137 cs and ex 239 240 pu in sediment cores collected from various settings in this marginal sea the derived sedimentation rates vary by two orders of magnitude from 2 to 0 02 cm yr y1 and generally decrease southward along the inner shelf and eastward offshore this pattern is consistent with the dispersal of yangtze river derived sediments by the current and tidal systems y2 y1 the weighted mean sedimentation rate over the shelf ca 0 3 g cm yr appears to be higher than fluvial inputs from the y2 y1 yangtze river and taiwan 0 14 g cm yr the discrepancy can be reduced by considering the effect of sediment mixing which renders sedimentation rates overestimated and the possibility of additional sediment input from the yellow river s dispersal system spatial variations of the observed nuclide inventories in sediments suggest extensive sediment redistribution boundary scavenging of 210 pb and large inputs of 137 cs and 239 240 pu from yangtze river s drainage basin

a description of tides near the chesapeake bay entrance using in situ data with an adjoint model 1 time series of surface elevation and current velocity in the vicinity of the chesapeake bay entrance are assimilated into a linear barotropic model using an iterative adjoint method tide surface elevations noaa nos tidal data moored acoustic doppler current profiler adcp and ocean surface current radar oscr data are included in the assimilation data are analyzed for three tidal constituents m2 s2 o1 tidal series are constructed from these constituents and then used in the model assimilations statistics of predicted currents compare favorably with those calculated from data not used in the assimilation an error analysis of the data distribution is performed for the m2 tidal component showing lower errors near assimilation data series but large errors particularly for velocity at some locations addition of a hypothetical current mooring dramatically reduces errors over most of the domain we believe these results give the most demonstrably accurate description now available of tidal currents for this region of strong currents and heavy shipping

a comparison of techniques for tide removal from ship mounted acoustic doppler measurements along the southwest coast of vancouver island two approaches are examined for the removal of tidal currents from acoustic doppler current profiler henceforth adcp measurements the first uses predictions from a numerical model foreman and walters 1990 whose domain includes the measurement region although the numerical model is barotropic adjustments are made to correct for baroclinicity in accordance with historical observations from stationary current meters in the region the second approach originally proposed by candela et al 1990 performs a least squares polynomial or biharmonic spline fit to the adcp data in order to determine the spatially varying amplitudes and phases of major tidal constituents and the magnitude of the residual flow both tide removal techniques are applied to adcp data taken during a 3 day cruise off the southwest coast of vancouver island and their relative effectiveness is compared some of the detided currents are seen to compare well with geopotential surfaces and clearly show the juan de fuca eddy freeland and denman 1982 a discussion of the results and limitations of each technique is also presented

a numerical model investigation of tides and diurnal period continental shelf waves along vancouver island abstract a numerical model study of the tidal regime west of vancouver island is presented ale model employed is a nonlinear barotropic two dimensional tidal model incorporating realistic bathymetry the m2 and k1 constituents are examined and comprehensive comparisons between computed and observed elevations and currents are given for m2 the model reproduces observed motion very accurately however k1 is of greater interest since it contains a substantial contribution in the form of a continental shelf wave csw the model correctly predicts the existence of the csw but consistent with the neglect of stratification and the influence of mean flows underestimates its wavelength it is shown that the csw component of k1 is generated by the tidal flow in juan de fuca strait the influence of mean currents on the tidal regime is investigated by including them in a further model solution consistent with theory the wavelength of the csw component of k1 is increased giving improved agreement with obser

summertime hydrographic features in the southeastern hwanghae abstract ctd casts in the southeastern hwanghae yellow sea were made in august 1983 and 1984 to describe the spatial structure of the summertime hydrographic features cold coastal water appeared around the southwestern coast of korea which was formed by strong tidal stirring tidal mixing in the study area seems to have been enhanced by the presence of many small islands in the deeper region beyond the tidal front stratification became much stronger and the bottom layer below seasonal thermocline was occupied mostly by the hwanghae cold water characterized by a temperature lower than 10 c and salinity of 32 5 33 0 the northeastward extension of the changjiang diluted water was shown by a tongue like plume of relatively warm fresh water confined to the thin surface layer 10 m thick there was no evidence for the hwanghae warm current carrying high salinity water into the eastern hwanghae along the korean coast the warm current was found to flow in a narrow band close to the west and north coast of chejudo cheju island and then to pass eastward through the cheju strait thus the eastern part of the cyclonic circulation in the surface layer cannot be considered to be a northward continuation of the hwanghae warm current the local salinity maximum in the lower layer off kunsan and the higher salinity on the west side of the central trough than on the east side would imply a northward flow on the west flank of the trough to compensate for the southward intrusion of the hwanghae cold water from which an anticyclonic circulation could be expected in the lower layer

tongue shaped frontal structure and warm water intrusion in the southern yellow sea in winter 1 in winter a thermohaline front forms at the yellow sea ys entrance where the warm and saline cheju warm current cwc water meets cold coastal water the frontal structure as well as the northwestward intrusion of the warm water was investigated by analyzing conductivity temperature depth ctd data tracks of drifting floats moored current data and satellite images the cwc water advances westward as a tongue with its tip heading westward across the ys entrance not intruding northward along the deepest part of the ys trough whereas a secondary warm water band is developed northwestward along the western flank of the trough floats in the warm tongue moved northwestward across the western frontal zone where the frontal structure was weak reflecting the northwestward intrusion along the 50 70 m isobaths through the frontal zone currents in the trough do not always meet the upwind flow theory that in an elongated basin the wind driven flow is upwind in the deep channel but rather show the predominance of the southward downwind flow model experiments show that on the western flank of the trough both the southeastward tide induced residual flow and the southeastward flow due to the nonlinear effect between tide and wind are generated at the same time thus the intermittent intrusion of the cwc across the western frontal zone may be closely associated with the predominance of the upwind flow over the southeastward nonlinear interacted flow

hydrodynamic processes and their impacts on the mud deposit in the southern yellow sea abstract the sedimentation processes of mud deposits on the continental shelves of the yellow sea ys are investigated using a combined data analysis and hydrodynamic modeling approach in order to identify the dominant factors that contribute significantly to the formation of these deposits the data analysis makes extensive use of existing data especially recently collected deep core data while the hydrodynamic and sediment transport processes are studied using a 3d hydrodynamics model that incorporates the effects of tides waves and wind the average deposit rate of the central yellow sea mud cs is estimated to be 3 6 107 t a 1 based on high resolution chirp sonar profiles combined with core data available sedimentological mineralogical geochemical and fluid flow data all indicate that the fine sediments discharged from huanghe river and changjiang river as well as the resuspended sediments from the old huanghe delta are the main sources for the mud deposits in the southern yellow sea sys this study confirms that tidal current flow is indeed the main agent for transporting the fine sediment to the mud patch in the central sys but wave effect is also significant as it is responsible for maintaining suspension concentration and causing sediment resuspension the wave influence is particularly notable around the old huanghe delta in winter storms as during these storm periods current circulation mainly caused by the asian monsoon can transport a large quantity of fine sediments from the old huanghe delta to the central sys under the present hydrodynamic conditions the modeling results showed that approximately 16 1 33 108 t a 1 of the huanghe river derived sediment is transported out of bohai strait of which around 44 5 72 107 t a 1 will finally be transported to the south yellow sea the corresponding values without accounting for the wave effects are 9 8 and 2 6 respectively it is noted that the deposition rate in the cs mud area over the past 12 kyr is virtually constant despite the significant rise in sea level and associated changes in the tidal current fields and wave distributions in the yellow sea the reason for this is believed to be that the weaker currents and waves during a lower water period is compensated by the shorter distance the suspended sediments have to travel from the paleo huanghe river to the cs mud area thus maintaining a nearly constant deposition rate in the cs mud area

temperature inversion in china seas temperature inversion was reported as a common phenomenon in the areas near the southeastern chinese coast region a west and south of the korean peninsula region b and north and east of the shandong peninsula region c during october may in the present study based on hydrographic data archived from 1930 through 2001 319 029 profiles the inversion was found to be remarkable with obvious temporal and spatial variabilities in both magnitude and coverage with higher probabilities in region a up to about 60 and region c 40 50 than in region b 15 20 the analysis shows that seasonal variation of the net air sea heat flux is closely related to the occurrence time of the inversion in the three areas while the yangtze and yellow river freshwater plumes in the surface layer and ocean origin saline water in the subsurface layer maintain stable stratification it seems that the evaporation excessive precipitation flux makes little contribution to maintaining the stable inversion advection of surface fresh water by the wind driven coastal currents results in the expansion of inversion in regions a and c the inversion lasts for the longest period in region a october may sustained by the taiwan warm current carrying the subsurface saline water while evolution of the inversion in region b is mainly controlled by the yellow sea warm current

influence of soil texture on the binding energies of fine mineral dust particles potentially released by wind erosion abstract models of the two aeolian processes saltation and sandblasting that lead to emission of fine dust particles pm20 by wind erosion in arid and semi arid areas have been combined to form the so called dust production model dpm in this model the size dependent binding energies of pm20 embedded within the wind erodible loose soil aggregates or in the soil surface itself are key input parameters indeed their values condition at the same time the intensity of emissions and their initial size distribution previous comparisons of vertical mass fluxes measured on field with the model predictions suggest that these energies might be relatively independent of soil texture and also probably composition because this would greatly facilitate application of the dpm at regional or global scale the objective of this work is to check experimentally the veracity of this result the strategy that has been designed for this has involved selecting four natural soil samples collected in various source areas of the world and covering a wide range of textures and compositions then these soil samples have been used to perform carefully controlled wind erosion simulations in a wind tunnel during the experiments which were carried out at different wind speeds with each soil the horizontal flux f h of saltating soil aggregates has been monitored at the same time number concentrations c i of pm20 released by the sandblasting process were recorded in the 6 size classes of an optical size analyzer thus the efficiency of the sandblasting process defined as the ratio of c i to f h could be determined for each of these size classes analysis of the results obtained in similar saltation conditions shows that for the four tested soils and within the range of contents in clay and other components favoring aggregation mostly organic matter and carbonates the influence of soil composition and texture on binding energies of the pm20 particles within soil aggregates is at best a second order effect that can be neglected in large scale modeling of wind erosion by the dpm

comparison of pi swerl with dust emission measurements from a straight line field wind tunnel 1 the portable in situ wind erosion lab pi swerl was developed to measure dust emissions from soil surfaces this small portable unit can test the emissivity of soils in areas that are difficult to access with a field wind tunnel and can complete a larger number of tests in less time the pi swerl consists of a cylindrical enclosure containing an annular flat blade that rotates at different speeds which generates shear stress upon the surface the shear stress generated by pi swerl results in the entrainment of particles including dust pi swerl was developed to provide an index of dust emission potential comparable to the field wind tunnel the pi swerl dust emission results were compared against those obtained from a 12 m long 1 m wide 0 75 m high straight line suction type portable field wind tunnel by conducting collocated tests at 32 distinct field settings and soil conditions in the mojave desert of southern california clay to sand rich soils that displayed a range of crusting gravel cover and disturbance were tested the correspondence between dust emissions mg m 2 s 1 for the two instruments is nearly 1 1 on most surfaces deviation between the two instruments was noted for densely packed gravel surfaces for rough surfaces a correction can be applied to the pi swerl that results in comparable dust emission data to the wind tunnel pi swerl can be used to complement research efforts in aeolian geomorphology aimed to quantify spatial and temporal patterns of dust emissions as well as air quality research related to dust emissions

structure of an eddy measured with drifters drifters are used to measure the structure of an eddy on western bank scotian shelf over a 5 day period a regression method that uses both the temporal and spatial structure of flow field observations is presented and used to analyze this eddy the eddy has vorticity 1 9 10 5 s 1 with divergence stretching deformation and shearing deformation smaller by more than an order of magnitude the eddy is centered on the crest of western bank the motion residual to the eddy had a slab like part that moved all points on a plane in a circle without rotation this latter type of motion can cause substantial error when vorticity and other eddy properties are estimated using methods that operate on a single drifter track the eulerian statistics of residual motion show correlations greater than 0 5 are restricted to spatial separations less than 2 km and temporal lags less than 3 h but motion directed along the vector separating two velocity measurements has a significant eulerian correlation for timescales of more than 40 hours and length scales of order 5 km transverse motion is positively correlated over lesser scales much cluster distortion results from subtidal frequency motion that has spatial scales that are seldom coherent over drifter separation scales greater than 2 3 km the long lagrangian timescale is inconsistent with a description of horizontal mixing in terms of an eddy diffusion coefficient rather we might picture drifters being dispersed by slowly evolving narrow streams of current that have larger spatial scales along their axis than across their axis