changes in planktonic assemblages during sapropel s5 deposition evidence from urania basin area eastern mediterranean 1 a micropaleontological study of planktonic assemblages on the partially laminated sapropel s5 late pleistocene marine isotope stage mis 5e was performed in two piston cores from urania basin area eastern mediterranean west of crete um94pc16 and um94pc31 recovered during a paleoflux project cruise the abundance of florisphaera profunda indicates the development of a deep chlorophyll maximum dcm before the anoxic condition at bottom were established whereas patterns of upper photic zone coccoliths suggest extreme oligotrophy in surface water the short appearance of globorotalia scitula and the presence of globigerinoides ruber in the lower part of sapropel testify to a thermal stratification also recorded by changes in primary producers during g scitula occurrence diatoms mainly represented by pseudosolenia calcar avis appear and bloom because of their capability in using nutrients from dcm scanning electron microscope analyses performed on selected intervals from um94pc16 show that the sapropel is organized in microlaminae mostly composed by siliceous microfossils in particular sapropel s5 could be related to an enhanced nutrient availability in the lower middle part of the photic zone stratified conditions and a higher continental input

geochemistry of surface sediments in the southwestern east japan sea abstract we analyzed 77 surface sediment samples collected in the southwestern east japan sea from the korea strait through the ulleung basin and the korea plateau for grain size calcium carbonate organic carbon and major na mg al fe k ca and ti and trace elements p mn sr li sc v cr co ni zn cu and pb the chemical composition of the surface sediments was found to be highly variable spatially cluster analysis of surface sediment chemical compositions indicated five major geochemical sedimentary environments basin lower slope coast and upper slope inner shelf and outer shelf continental shelf sediments were rich in shell fragments and had relict and coarse grained characteristics recent fine grained sediments were only distributed in coastal slope and basin areas concentrations of al k ca ti cr and sc were highest in the coastal and upper slope areas and decreased with water depth elemental ratios using major and trace elements indicated that coastal and upper slope detrital sediments were mixtures of sediments derived from the changjiang yangtze and nakdong rivers although the concentrations of organic carbon p mn v co ni cu and pb increased with water depth their distribution patterns indicated authigenic v cu and pb and diagenetic fe p mn co and ni origins the distribution pattern with water depth suggested that the chemical composition of surface sediment was determined by sedimentologic and geochemical processes such as the supply of detrital and biogenic materials and authigenic and post depositional diagenetic processes in sediments

metals in suspended sediments from the changjiang yangtze river and huanghe yellow river to the sea and their comparison thirty five samples of suspended sediments were collected at datong station and lijin station the basin wide control stations of the changjiang yangtze river and the huanghe yellow river during flood and dry seasons in 2000 and 2001 concentrations of 15 elements fe mg ca al na k ti mn ba sr pb cu zn v and ni in these samples were measured by icp aes the results indicated that fe al ti mn ba cu zn v and ni concentrations in the changjiang sediments in may flood season were quite close to those in november dry season whereas mg ca na k sr concentrations were slightly higher and pb was relatively lower in the dry season ti ba sr and zn concentrations in huanghe sediments varied little in august flood season and december dry season while mg ca al na and k concentrations were higher by approximately 30 and fe mn pb cu zn v and ni concentrations were lower in flood season concentrations of most metals except ca na and sr were much higher in changjiang sediments than those in the huanghe such differences of metal concentrations in sediments from these two rivers could be ascribed to their different sediment sources and weathering processes within their corresponding river basin particularly since the 1980s pb and zn concentrations in changjiang sediments have increased significantly due to the releases of waste contaminants from human activities while the variations for these two elements in the huanghe samples were very little due to the elevated river bed in the lower reaches

saturn s zonal winds at cloud level we present an analysis of new cloud motion measurements in saturn s atmosphere from voyager 1 and 2 images and define a nominal zonal wind velocity vs latitude profile for the cloud top level that can be used as reference for the upcoming cassini mission improvements over previous studies include i twice the number of wind vectors used ii independent measurements of cloud tracers iii extended latitudinal coverage iv strict error control and evaluation and v a new zonal averaging methodology mean zonal wind velocities are given for the latitude range 81 to 71 planetographic in steps of 0 5 with a gap between 0 and 10 due to ring shadowing this research also includes the study of the morphology and motions of cloud systems in the equator and in the southern hemisphere which have not been described previously we give an ephemeris motion equation for several long lived features that could be observable if they survive until cassini arrives on saturn the long term behavior of the zonal wind profile is studied by comparing it with a complete set of wind velocities compiled from historical and modern ground based and hst observations significant changes are noted in the equatorial jet between this set and the nominal voyager profile we discuss in detail the possible origin for such differences

chemical processes affecting the mobility of major minor and trace elements during weathering of granitic rocks abstract the behaviour of 38 major and trace elements as well as changes in the mineralogy have been examined in 10 weathering profiles developing on some portuguese granitic rocks element mobilities are calculated from geochemical data normalized with respect to ti in the fresh parent rock chemical elements are divided into two groups immobile and mobile on the basis of their geochemical distribution during weathering elements that are immobile during weathering are zr hf fe al th nb sc and the ree very mobile are ca na p k sr ba rb mg and si mobile elements are derived mainly from leachable minerals such as feldspars micas and apatites whereas immobile elements are either concentrated in resistate phases or strongly adsorbed by secondary minerals the geochemical behaviour of mn cr v fe and ce is very dependent on redox conditions redox transformations of these elements can be used to set limits on the oxidation state of a weathering suite the ree are mobilized or fractionated during late stages of weathering but not during moderate stages of weathering this fractionation is caused by selective leaching of rocks composed of both stable and unstable minerals containing ree

distribution and normalization of heavy metal concentrations in mangrove and lagoonal sediments from mazatlan harbor se gulf of california concentrations of heavy metals carbonates organic carbon and granulometry were examined in sediments from 60 sites within mazatlan harbor and adjacent areas regional distribution had a strong for al fe li and ni and weak for cd co cr pb v and zn seaward concentration gradient decreasing from the upper lagoon the highest concentrations for most metals occurred in fine grained sediments from infiernillo estuary the upper lagoon and the industrial zone in contrast lower levels were usually found in the sandy sediments of the navigation channel port entrance and an area associated with sewage outfall analysis of transects in mangrove and lagoonal sediments indicated that the amount of fine material and organic carbon increases towards the margins where mangrove sediments exist while metal variations were not clearly observed in most of the metals examined only ni v pb and cu showed a slight tendency to increase towards the margins sometimes lagoonal sediments had redox and texture characteristics comparable to those from mangrove substrate thus competing because of a similar capture capacity of metals metal data were normalized against al and li using a combination of normalization techniques 95 prediction intervals regional anomalies and enrichment factor it was found that al and li were good normalizers for most of the examined metals and they are important constituents of one or more of the major fine grained heavy metal carrier s and adequately reflect the granulometric variability in the sediments of the study area

ecologic interpretation of deep sea trace fossil communities abstract trace fossil types and their vertical arrangement tiering are closely related to the biotope and hence can provide information on ecological conditions especially on oxygenation benthic food content sedimentation rate and substrate consistency however to use the full potential of trace fossils for environmental analyses various ichnologic criteria are necessary in addition to trace fossil taxonomy based on a taxonomically oriented ichnologic evaluation of modern deep sea environments six ichnologic aspects to ecologic changes have been found to be of major importance 1 1 penetration depth of burrows is influenced by oxygenation benthic food availability and substrate consistency 2 2 the number and vertical extension of tiers varies due to environmental changes a decrease in the vertical extension of tiers telescoping indicates a decrease in oxygenation benthic food content and or sedimentation rate if shallow penetrating traces disappear oxygen may be depleted and if the deepest tiers disappear the benthic food content may be lowered 3 3 the size diameter of specific trace fossils can indicate oxygen and benthic food availability 4 4 degree of bioturbation is related to sedimentation rate and benthic food content and the diversity of the whole ichnocoenoses or within a specific tier is affected by oxygenation benthic food content sedimentation rate and substrate consistency 5 5 the type of burrow wall unlined mucus lined pellet lined mainly refers to substrate consistency and subordinately to pore water oxygenation 6 6 the type of sediment displacement by body appendages used for excavation ingestion sideward pressing or outside pumping is related to substrate consistency and grain size

drainage basin weathering and major element transport of two large chinese rivers huanghe and changjiang long term records show high concentrations of dissolved major elements in the changjiang yangtze river and the huanghe yellow river the huanghe drainage basin is characterized by intense weathering and erosion of carbonates and evaporites while weathering and erosion of carbonates and silicates over the drainage basin is the main source of major elements in the changjiang the rock soil composition and tectonics of the drainage basin are more important than atmospheric precipitation in affecting major element composition of these two rivers compared with other large rivers of the world the high suspended sediment and major element loads of the changjiang and huanghe reveal intense physical and chemical erosion over the chinese continent

saturn s cloud structure and temporal evolution from ten years of hubble space telescope images 1994 2003 abstract we present a study of the vertical structure of clouds and hazes in the upper atmosphere of saturn s southern hemisphere during 1994 2003 about one third of a saturn year based on hubble space telescope images the photometrically calibrated wfpc2 images cover the spectral region between the near uv 218 255 nm and the near ir 953 1042 nm including the 890 nm methane band using a radiative transfer code we have reproduced the observed center to limb variations in absolute reflectivity at selected latitudes which allowed us to characterize the vertical structure of the entire hemisphere during this period a model atmosphere with two haze layers has been used to study the variation of hazes with latitude and to characterize their temporal changes both hazes are located above a thick cloud putatively composed of ammonia ice an upper thin haze in the stratosphere between 1 and 10 mbar is found to be persistent and formed by small particles radii 0 2 m the lower thicker haze close to the tropopause level shows a strong latitudinal dependence in its optical thickness typically 20 40 at the equator but 5 at the pole at 814 nm this tropospheric haze is blue absorbent and extends from 50 to 100 mbar to about 400 mbar both hazes show temporal variability but at different time scales first there is a tendency for the optical thickness of the stratospheric haze to increase at all latitudes as insolation increases second the tropospheric haze shows mid term changes over time scales from months to 1 2 years in its optical thickness typically by a factor of 2 such changes always occur within a rather narrow latitude band width 5 10 affecting almost all latitudes but at different times third we detected a long term 10 year decrease in the blue single scattering albedo of the tropospheric haze particles most intense in the equatorial and polar areas long term changes follow seasonal insolation variations smoothly without any apparent delay suggesting photochemical processes that affect the particles optical properties as well as their size in contrast mid term changes are sudden and show various time scales pointing to a dynamical origin

a review on the provenance discrimination of sediments in the yellow sea the yellow sea has been extensively studied for the understanding of dispersal patterns and limits of sediments from neighboring countries including china and korea although sedimentological mineralogical and geochemical approaches have been tried to solve the problems especially including the identification of sediment sources in and around the yellow sea the published results are not enough for understanding them suggestions on sediment origins budgets sediment accumulation rates mineralogical and geochemical compositions are not coincident to each other and sometimes even controversial for example conflicts on the distribution patterns of smectite and calcium carbonate the provenance of the southeastern yellow sea mud and sedimentation rates in there the ratios of v al and mn al in korea and china river sediments the origin of ba and pb in sandy sediments of the northeastern yellow sea and so on various geochemical indicators from the literature for the provenance discrimination in the yellow sea are reviewed here in depth and corresponding discussions are described separately research topics for the future study also are suggested for the proper access to the understanding of the origin and dispersal patterns of the yellow sea sediments especially focusing on the geochemical approaches d 2003 elsevier science b v all rights reserved

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

why some mediterranean sapropels survived burn down and others did not abstract we have evaluated using a numerical model the burn down depth depth of post depositional oxygenation of organic matter rich sapropels under aerobic conditions at the seafloor the model suggests that sapropels may be erased by burn down to depths of at least 5 cm after 10 kyr of bottom water reoxygenation a test of the sensitivity shows that the parameters exerting a major control over the burn down process are the flux of freshly sedimenting organic carbon the oxygen concentration of the bottom water the amount of organic matter in the sapropel and the sedimentation rate in comparison bioturbation is of minor importance the result implies that burial of elevated concentrations of non refractory organic carbon is generally improbable when the sedimentation rate is lower than 1 2 cm kyr 1 the record of sapropel deposition in the mediterranean sea and elsewhere may thus be biased towards depositional environments where the sedimentation rate is large enough to shield the organic rich layer from oxygenation

discharge of metals from the st lawrence river the concentrations of dissolved and total al fe mn co ni cu zn and cd in st lawrence river water have been measured on a monthly basis over a 2 year period riverine suspended particulate matter was also analyzed for nondetrital mg ca si al fe mn co ni cu zn and cd and detrital mg ca si al fe and mn variability in the concentration of dissolved metals is unrelated to changes in water flow or suspended load particulate al fe mn and zn concentrations are related to water flow the metal aluminum ratios of particulate mn cu zn and cd are elevated with respect to crustal rocks or coastal marine sediments with the enrichment occurring in the nondetrital or weak acid soluble fraction annual dissolved metal discharges and nondetrital and total particulate metal discharges that take into account monthly variations in metal concentrations have been calculated for the st lawrence river these discharges have been used to estimate global annual river discharges of metals to the oce

trace element geochemistry in the upper amazon drainage basin bolivia abstract the distribution of trace elements sr mo ba rb u mn ni cu zn and cd was investigated in surface waters and associated particulates in two upper amazonian basins mamore and beni dissolved sr ba mo rb u and to a lesser extent zn and cd correlate with major ions and appear to be predominantly derived from soluble rocks carbonates evaporites or sulfides essentially contained in shales these elements are conservative in waters except in highly alkaline or sulfate rich waters where calcite and barite can precipitate the concentrations of transition element are generally not correlated with major ion chemistry their behaviour can be largely explained by equilibrium reactions in solution and solid liquid exchanges additionally the distribution of mn and cu reflects also the lithological differences between the mamore and beni basins the occurrence of mineralisation in the beni basin explains the high zn cd as well as the concentrations of cu in some rivers of the beni basin the higher content of mn in the mamore basin may reflects the predominance of carbonate rocks the fractionation of trace elements in spm has been attributed to the sorting of feldspars during transport in water and to the mixing between clay minerals and quartz these minerals refractory to weathering and introduced in water rivers by mechanical erosion have not contributed to the dissolved load

large scale storms in saturn s atmosphere during 1994 large scale storms are rarely observed in saturn s atmosphere but their appearance traces the wind velocity field providing information on the vertical structure of the clouds and on the dynamics of the atmosphere two large scale atmospheric disturbances formed by clouds highly reflective in the visible part of the spectrum were observed on saturn during 1994 an equatorial disturbance with a longitudinal size of 27 000 kilometers drifted in longitude with a velocity of 273 6 meters per second a second disturbance a rapidly evolving convective storm with an initial size 7000 kilometers was observed at 56 degrees south moving with a zonal velocity of 15 5 meters per second

particulate element inventory of the huanghe yellow river a large high turbidity river abstract suspended sediments from the river mouth to the upper portions of the huanghe yellow river were collected and analysed to determine their chemical composition comparison with other large world rivers indicates that trace element levels are relatively low in this high turbidity river natural weathering and erosion are of primary importance in controlling particulate element concentrations although the impact from anthropogenic activities is also visible finally input of particulate elements to the china sea is assessed from the river sediment load and compositions

iron and other transition metals in patagonian riverborne and windborne materials geochemical control and transport to the southern south atlantic ocean abstract the bulk of particulate transition metals transported by patagonian rivers shows an upper crustal composition riverine particulate 0 5 n hcl leachable trace metal concentrations are mainly controlled by fe oxides complexation of fe by dissolved organic carbon doc appears to be an important determinant of the phases transporting trace metals in patagonian rivers in contrast aeolian trace elements have a combined crustal and anthropogenic origin aeolian materials have fe mn and al contents similar to that found in regional topsoils however seasonal concentrations of some metals e g co pb cu and zn are much higher than expected from normal crustal weathering and are likely pollutant derived we estimate that patagonian sediments are supplied to the south atlantic shelf in approximately equivalent amounts from the atmosphere 30 10 6 t yr 1 and coastal erosion 40 10 6 t yr 1 with much less coming from the rivers 2 0 10 6 t yr 1 low trace metal riverine fluxes are linked to the low suspended particulate load of patagonian rivers inasmuch most of it is retained in pro glacial lakes as well as in downstream reservoirs based on our estimation of aeolian dust fluxes at the patagonian coastline the high nutrient low chlorophyll sub antarctic south atlantic could receive 1 0 to 4 0 mg m 2 yr 1 of leachable 0 5 n hcl fe past and present volcanic activity in the southern andes through the ejection of tephra must be highlighted as another important source of fe to the south atlantic ocean based on the 1991 hudson volcano eruption it appears that volcanic events can contribute several thousand fold the mass of leachable fe to the ocean as is introduced by annual patagonian dust fallout

spatially resolved methane band photometry of saturn ii cloud structure models at four latitudes abstract spatially resolved measurements of saturn s reflectivity in the 6190 7250 and 8996 a methane bands are analyzed to determine cloud vertical structures in the equatorial zone south equatorial belt and north and south temperate regions near latitudes 30 radiative transfer models are computed for a simple two parameter structure the parameters are a 0 the methane column abundance in an aerosol free layer at the top of the atmosphere and a 1 the specific abundance of methane in a semi infinite homogeneous gas and cloud mixture deep in the atmosphere for the equatorial zone a model with a 0 37 3 m am and a 1 26 2 m am fits all three bands for the north temperate region a model with a 0 39 m am and a 1 47 m am comes close to fitting all three bands for the south equatorial belt and south temperate region a single a 0 and a 1 do not fit all three bands the structure for the south equatorial belt resembles that for the north temperate region the level where unit cloud optical depth occurs in the south temperate region is deeper than the corresponding level at other latitudes some suggestions are proposed to explain differences between model parameters derived using different absorption bands

dynamics of jupiter s equatorial region at cloud top level from cassini and hst images abstract we present a study of the equatorial region of jupiter between latitudes 15 s and 15 n based on cassini iss images obtained during the jupiter flyby at the end of 2000 and hst images acquired in may and july 2008 we examine the structure of the zonal wind profile and report the detection of significant longitudinal variations in the intensity of the 6 n eastward jet up to 60 m s 1 in cassini and hst observations these longitudinal variations are in the hst case associated with different cloud morphology photometric and radiative transfer analysis of the cloud features used as tracers in hst images show that at most there is only a small height difference no larger than 0 5 1 scale heights between the slow 100 m s 1 and fast 150 m s 1 moving features this suggests that speed variability at 6 n is not dominated by vertical wind shears but instead we propose that rossby wave activity is the responsible for the zonal variability removing this variability we find that jupiter s equatorial jet is actually symmetric relative to equator with two peaks of 140 150 m s 1 located at latitudes 6 n and 6 s and at a similar pressure level we also study the local dynamics of particular equatorial features such as several dark projections associated with 5 m hot spots and a large long lived feature called the white spot ws located at 6 s convergent flow at the dark projections appears to be a characteristic which depends on the particular morphology and has only been detected in some cases the internal flow field in the white spot indicates that it is a weakly rotating quasi equatorial anticyclone relative to the ambient meridionally sheared flow

weathering and global denudation a negative correlation between sediment yield and weathering history as measured by the chemical alteration cia of the suspended sediment is observed for many of the world s major rivers and other regions of denudation the weathering history is a first order control on the sediment yield of such areas termed equilibrium denudation regions for other areas data scatter with either apparent increases or decreases of sediment yield for given cia values these areas are termed nonequilibrium denudation regions low sediment yields can be attributed to moderated erosion either natural or human induced and or the incorporation of unweathered glacial debris accelerated erosion resulting in high sediment yield is primarily human induced and results from cultivation and other land use each of these effects has a profound influence on global sediment discharge from the continents pre human suspended sediment discharge from the continents is estimated to be 12 6 times 10 15 g yr or about 0 6 the

element concentration and partitioning of loess in the huanghe yellow river drainage basin north china abstract loess samples from the middle reaches of the huanghe yellow river are analysed to determine the concentration and partitioning of fe mn cu pb zn cr co ni na and k very similar element concentrations are observed between the different areas of the loess plateau the relatively low trace element levels of loess as compared with the mean value of world soils are related to their wind borne origin and intense erosion over the loess plateau most of the studied elements are associated with mineral fractions carbonate aluminosilicates which account for 70 95 of total element concentrations low concentrations in the labile fractions suggest the weak element bioavailability to crop growth in this region

time variations of phosphorus and sources of sediments beneath the chang jiang yangtze river abstract depth dependent changes of different forms of sediment phosphorus in a 98 m drill core from near the mouth of the chang jiang yangtze river have been determined using a modified chemical extraction method results indicate that the dominant portion of the phosphorus is in inorganic form and that there is an upward increase in detrital apatite the concentration of phosphorus associated with hydrous ferric oxides fe p exhibits an excellent positive correlation with the fine size fraction of the sediments indicating the close association between ferric oxides and high surface area mineral grains most notable is a yellow clayey silt layer of low sand content at 39 5 m depth which is very rich in fe p four possibilities are presented to explain the possible source of the yellow layer one possibility is that the yellow layer may represent loess rich huang he yellow river sediment transported far to the south due to a large former shift of the huang he mouth the visual characteristics and chemical observations for the above core combined with some geological clues are in agreement with this hypothesis besides these geological observations chinese historical documents provide additional evidence for large former shifts of the mouth of the huang he

temporal behavior of cloud morphologies and motions in saturn s atmosphere saturn s atmosphere displays a variety of temporal changes in its cloud morphology at synoptic and planetary scales hemispheric long term albedo variations which are more pronounced at ultraviolet and blue wavelengths have been well established and are apparently linked to the seasonal insolation cycle short term changes of the order of months have been observed in the spectral reflectivity of the belt zone pattern mainly at mid latitudes some appear to be related to discrete spot activity but for the majority of the changes no such signs of spot activity were detected up to a resolution 2000 km in particular the ribbon structure at 45 n could have been affected by this activity and probably is a transient phenomenon the polar belts at 65 north and south and those at 75 north hexagon and south show a long term stability in their location perhaps for more than a century the most prominent belts located in the equator and the equatorial zone are persistent features of saturn s globe their main changes took place during the development of a rare planetary scale disturbance known as great white spots only five such events have been observed at repetitive regular intervals of about one saturn year since the first report in 1876 and at different latitudes from the equator to 60 n they are probably convective in origin with the seasonal heating of the upper atmosphere acting as a trigger mechanism during its life cycle of 2 3 years the disturbance shows turbulent planetary scale patterns of clouds that might be related to a wave dynamical phenomenon other distinct nonaxisymmetric cloud systems at synoptic scale are very scarce in saturn s atmosphere we observed new isolated features at several latitudes during 1990 and 1991 these spots together with those available from historical records are used as tracers for determining the latitude dependence and time variability of saturn s zonal winds the winds tend to exhibit a long term stability in their latitudinal positions and average wind speed although some significant departures from the zonal mean voyager profile have been detected during the development of the equatorial disturbance in 1990 and 1991

pyritization of tubes and burrows from late pleistocene continental shelf sediments off north norway four different types of pyritized tubes and three types of pyritized burrow fillings are described from pleistocene glaciomarine sediments in andfjorden northern norway the tubes and burrows probably originated from tubicolous and burrowing polychaetes respectively the decomposition of the organic matter in the tubes and burrows created a reducing micro environment favouring precipitation of pyrite by comparison with holocene tubes from marine sediments in andfjorden and fuglosyfjorden it is seen that pyritization commenced with isolated spherules these spherules with incipient pyrite crystals and framboids were formed mainly on the inner wall of the tube presence of a monosulphide in the holocene fugloyfjorden material suggests that the pyritization process has reached a later phase the final result would be a completely pyritized trace fossil it is shown that single pyrite crystals octahedra generally attain greater size in the burrow fillings than in the tubes the microstructure found in some of the pyritized tubes is interpreted as a reflection of the microstructure in the original wall finally the implications for the depositional environment in pleistocene in andfjorden is investigated with reference to the benthic skeletal macrofaunal assemblage in the sequence the pyritized trace fossils occur frequently in an opportunistic assemblage from a period c 14 000 13 000 yr bp characterized by some oxygen deficiency later 13 000 10 000 yr bp they play a minor role in an established assemblage under improved oxygen conditions

bed sediment particle size characteristics and its sources implication in the desert reach of the yellow river a 1000 km desert reach of the yellow river flows through an extensive aeolian desert region in recent years the river bed of this reach has shown an aggradational trend leading to substantial social economic and other environmental problems the desert reach of the yellow river provides an opportunity for us to study the sediment particle size characteristics and its sources transport and sedimentation processes in a large desert river to investigate this topic 111 shallow sediment core samples from the desert reach and some typical surface sediment samples were also systematically collected from the main reach and potential source areas in the upper yellow river basin for particle size analysis the analysis of sediment cores in the desert reach indicated that a fine sediment layer had developed over a coarse sediment layer in the 1 to 4 m thick bed deposits aeolian sand the ten tributaries and coarse fraction from the riverbank provide material for the development of the coarse sediment layer in the sediment cores while the relatively fine sediment 0 05 mm coming from the loess plateau our results provide a meaningful reference for the management of desert rivers around the world

sapropel burn down and ichnological response to late quaternary sapropel formation in two 400 ky records from the eastern mediterranean sea two approximately 400 ky long sedimentary records from the eastern mediterranean sea were used to study the factors determining why some sapropels are more or less completely erased while others are preserved x ray radiographs bulk density organic carbon content fe al and mn al ratios were used to reconstruct initial thickness and burn down ratios of sapropels s1 to s11 the results show that at the low sedimentation rate open ocean settings studied initial carbon content of the sapropel as well as post sapropel sedimentation rate and carbon flux have had only limited influence on the preservation of sapropels in contrast the regional position relative to the deep water source controlling bottom water current intensity and bottom water oxygenation played a major role in the preservation of the sapropels furthermore orbitally controlled variations in the intensity of subsequent summer insolation maxima also seem to play an important role in the preservation potential of sapropel layers subsequent strong insolation maxima resulting in thick sapropels tend to act as a lid preventing further burn down of the older sapropels below the long and well dated records also offer an opportunity to study the response of the benthic fauna to the drastic environmental changes related to the formation of sapropels the sediment in the two cores is generally characterized by mottled burrows with only scarce occurrences of distinct trace fossils such as scolicia thalassinoides chondrites and trichichnus the meager ichnofauna is attributed to the well oxygenated and warm bottom waters in an oligotrophic environment typical for non sapropel times the sparse ichnofauna and the lack of tiered ichnocoenosis render existing models of bioturbational response to changes in bottom water oxygenation unsuitable for this kind of environments however observations on individual traces support earlier studies that suggest that the trace fossils trichichnus and chondrites are the result of chemosymbiotic activities that benefit from reducing conditions in the pore water and that the producers of scolicia have a preference for well oxygenated conditions and sandy substrates c 2006 elsevier b v all rights reserved

the great white spot and disturbances in saturn s equatorial atmosphere during 1990 a giant storm the great white spot erupted at the end of september 1990 as a localized bright cloud system close to saturn s equator its evolution produced a complex planetary disturbance which affected the whole equatorial region a month later similar spots have appeared approximately once every saturnian year about 30 earth years implying that a seasonal change in solar heating for example may be responsible for their occurrence

shallow water simulations of saturn s giant storms at different latitudes abstract shallow water simulations are used to present a unified study of three major storms on saturn nicknamed as great white spots gws at different latitudes polar 1960 equatorial 1990 and mid latitude 2010 sanchez lavega 2004 sanchez lavega et al 2011 in our model the three gws are initiated by introducing a gaussian function pulse at the latitude of the observed phenomena with controlled horizontal size and amplitude this function represents the convective source that has been observed to trigger the storm a growing disturbance forms when the pulse reacts to ambient winds expanding zonally along the latitude band of the considered domain we then compare the modeled potential vorticity with the cloud field adjusting the model parameters to visually get the closest aspect between simulations and observations simulations of the 2010 gws planetographic latitude 40o zonal velocity of the source 30 m s 1 indicate that the coriolis forces and the wind profile structure shape the disturbance generating as observed a long region to the east of the convective source with a high speed peripheral anticyclonic circulation and a long lived anticyclonic compact vortex accompanied by strong zonal advection on the southern part of the storm forming a turbulent region simulations of the equatorial 1990 gws planetographic latitude 12o 5o zonal velocity of the source 365 400 m s 1 show a different behavior because of the intense eastward jet meridional shear at the equatorial region and low latitude dynamics a round shaped source forms as observed with the rapid growth of a kelvin helmholtz instability on the north side of the source due to advection and to the strong meridional wind shear whereas at the storm latitude the disturbance grows and propagates eastward the storm nucleus is the manifestation of a rossby wave while the eastward propagating planetary scale disturbance is a gravity rossby wave trapped around the equator the simulated 1960 gws disturbance planetographic latitude 56o zonal velocity 4 m s 1 formed a chain of periodic oval spots that mimic the few available observations of the phenomenon for the mid and high latitude storms simulations predict a strong injection of negative relative vorticity due to divergence of the upwelling storm material which may produce large anticyclones on the anticyclonic side of the zonal profile and a quick turbulent expansion on the background cyclonic regions in general simulations indicate that negative relative vorticity injected by storms determines the natural reaction to zonal winds at latitudes where coriolis forces are dominant

vertical cloud structure in saturn s 1990 equatorial storm abstract we present a model study of the evolution of the vertical cloud structure and aerosol optical characteristics of the giant storm that erupted in saturn s atmosphere in september 1990 this analysis is based on the photometric measurements of the reflected intensity of the equatorial region in the optical range 336 890 nm continuum and methane absorption bands that were previously published a sanchez lavegaet al 1994 icarus108 158 168 different stages of the storm evolution are analyzed preoutburst onset and mature october november 1990 and evolved july 1991 good fits between the observations and radiative transfer calculations are found using a three layer model a gas layer a haze layer and a semiinfinite cloud deck two term henyey greenstein and mie phase functions are used for the scattering particles according to the models the main change during the evolution of the disturbance took place in the altitude of the cloud layer cloud tops elevated by 1 2 1 5 scale heights during the onset and mature storm stage relative to the undisturbed atmosphere descending later during the evolved phase by 0 7 scale heights relative to the altitude of the mature clouds the altitude location of the haze layer did not change during the storm development but the single scattering albedo of the haze particles increased significantly during the onset and mature stages in the uv blue wavelengths if the haze particles are modeled as mie spheres their mean radius varied from 0 83 to 0 64 m with real refractive index 1 5 and extreme values of the imaginary index 0 01 370 nm and 0 0005 830 nm

hubble space telescope observations of the 1990 equatorial disturbance on saturn zonal winds and central meridian albedos abstract two sets of hubble space telescope hst data obtained in august 1990 and november 1990 are compared with voyager 1 and 2 data acquired in 1980 and 1981 a rare disturbance developed in the equatorial region of saturn in late september 1990 due to the large equatorial wind shear this disturbance generated inhomogeneous bright cloud structures in the equatorial region that extended to 25 north latitude in november 1990 meridional albedo scans and wind measurements from the voyager northern spring equinox and the hst northern summer observations are compared differences in average zonal winds in the images obtained with the green f547m and the methane f889n filters are interpreted as evidence of vertical shear in the zonal winds longitudinal variations in the equatorial zonal winds are interpreted as evidence of interaction between the storm nucleus generated during the disturbance and the local wind field

silicon isotopic composition of dissolved silicon and suspended particulate matter in the yellow river china with implications for the global silicon cycle abstract the silicon isotopic composition of dissolved silicon and suspended particulate matter spm were systematically investigated in water samples from the mainstem of the yellow river and 4 major tributaries the spm content of the yellow river varied from 1 4 to 38 560 mg l averaging 3568 mg l and the 30 si of suspended particulate matter 30 si spm varied from 0 3 to 0 4 averaging 0 02 the major factors affecting the spm content and the 30 si spm values in the yellow river were inferred to be the mineralogical chemical and isotopic characteristics of the sediments from the loess plateau and a combination of the climate and the flow discharge of the river the major ions in the yellow river water were na ca 2 mg 2 hco 3 so 4 2 and cl high salt concentration was observed in samples from the middle and lower reaches likely reflecting the effects of evaporation and irrigation because the na mg 2 so 4 2 and k concentrations were correlated with the cl concentration the dissolved si concentration d si increased downstream varying from 0 016 to 0 323 mm the 30 si of dissolved si 30 si diss varied from 0 4 to 2 5 averaging 1 28 the major processes controlling the d si and 30 si diss of the yellow river are a the weathering of silicate rocks b the formation of phytoliths in plants c the evaporation of water from and the addition of meteoric water to the river system which only affects concentrations d the adsorption and desorption of aqueous monosilicic acid on iron oxide and e the dissolution of phytoliths in soils the d si and 30 si diss values of global rivers vary spatially and temporally in response to changes in climate chemical weathering intensity and biological activity the moderately positive 30 si diss values observed in the yellow river may be attributed to the higher rates of chemical weathering and biological activities that have been observed in this catchment in comparison with those of other previously studied catchments excluding the yangtze river human activities may also potentially influence chemical weathering and biological activities and affect the d si and 30 si diss values of the major rivers of the world further river studies should be performed to gain a better understanding of the global si isotope budget

ree geochemistry of fine grained sediments from major rivers around the yellow sea abstract to investigate the distribution pattern and controlling factors of rare earth elements rees in riverine sediments river mouth sediments were collected at five geographically different rivers around the yellow sea two 1 m hcl leached and residual fractions and five step sequential extraction schemes the sedex method were applied to size separated sediments

geochemical elements characteristics and sources of the riverbed sediment in the yellow river s desert channel the yellow river flows through an extensive area of aeolian desert and extends from xiaheyan ningxia province to hekouzhen inner mongolia province for a total of 1 000 km in the desert channel of the yellow river the major chemical components are sio2 fe2o3 al2o3 ti cao mgo ba p mn ce co in which sio2 al2o3 fe2o3 and ti have significant value as indicators of the sources of the coarse sediment the spatial distribution of the elements weight percentages and the ratios of si ti si al between sediment sources and riverbed sediment of the gansu reach and the desert channel of the yellow river indicating that the coarse sediments deposited in the desert reach of the yellow river are mostly controlled by the local sediment sources and due to the higher mobility of the fine sediments they are primarily contributed by the local sediment sources and the tributaries that originate from the loess area of the upper reach of yellow river the results of r factor analysis illustrate that the first component score mainly shows negative values in the desert channel suggesting that the coarse sediments in this reach contain a higher content of si and a lower content of mg ca al fe which further proves that the ningxia hedong inner mongolian wulanbuhe and kubuqi deserts are the primary sources of the coarse sediment in the desert channel of the yellow river

hubble space telescope observations of the 1990 equatorial disturbance on saturn images albedos and limb darkening in september 1990 a major equatorial eruption on saturn produced a disturbance that spread in longitude until it completely girdled the planet we report here on 150 images recorded in six passbands with the wide field planetary camera wf pc aboard the hubble space telescope hst on 17 and 18 november 1990 for comparison we used hst wf pc observations of saturn obtained in three colors on 26 august 1990 before the onset of the disturbance and in six colors on 5 and 6 june 1991 when almost no evidence of the disturbance remained at both of those times the equatorial belt was normal in appearance four of the passbands with mean wavelengths of 336 435 546 and 716 nm were selected for photometric analysis and a patch of the b ring near the central meridian was used for photometric calibration using deconvolved images from all three epochs of observation we measured reflectivities i f of the disk along parallels of latitude as a function of longitudinal distance from the central meridian and also along the central meridian as a function of latitude from 0 to 90 the longitudinal measurements cover essentially the whole visible disk they were made at 1 intervals of planetographic latitude from 0 to 80 and the results are expressed in terms of minnaert coefficients k and minnaert albedos i f 0 we find that the cloud particles associated with the disturbance must differ in character from those that normally make up the visible cloud deck on saturn they were brighter and bluer they had greater limb darkening and their limb darkening was spectrally more neutral the mutual relationship of those properties is such that features which stand out strongly near the meridian fade to invisibility when near the limb

the low temperature geochemical cycle of iron from continental fluxes to marine sediment deposition suspended sediments from 34 major rivers geographically wide spread and 36 glacial meltwater streams have been examined for their variations in different operationally defined iron fractions fehr iron oxides soluble in dithionite fepr iron soluble in boiling hcl but not in dithionite and feu total iron less that soluble in boiling hcl river particulates show a close association between fehr and total iron fet reflecting the effects of chemical weathering which derive oxide iron from and retain it in close association with total iron consistent with this continental scale average fehr fet ratios vary with runoff ratios average river runoff per unit area average precipitation per unit area by contrast the diminished effects of chemical weathering produce no recognizable association of fehr with fet in glacial particulates and instead both fepr and feu are closely correlated with fet reflecting essentially pristine mineralogy a comparison of the globally averaged compositions of riverine particulates and marine sediments reveals that the latter are depleted in fehr fepr and fet but enriched in feu the river and glacial particulate data are combined with estimates of authigenic hydrothermal atmospheric and coastal erosive iron fluxes from the literature to produce a global budget for fehr f e pr f e u and fet this budget suggests that the differences between riverine particulates and marine sediments can be explained by i preferentially removing fehr from the riverine particulate flux by deposition into inner shore reservoirs such as floodplains salt marshes and estuaries and ii mixing the resulting riverine particulates with fehr depleted glacial particulates preliminary measurements of inner shore sediments are consistent with i above phanerozoic and modern normal marine sediments have similar iron speciation characteristics which implies the existence of a long term steady state for the iron cycle this steady state could be maintained by a glacioeustatic feedback where fehr enriched riverine particulates are either more effectively trapped when sealevel is high small ice masses diminished glacial erosion or are mixed with greater masses of fehr depleted glacial particulates when sealevel is low large ice masses enhanced glacial erosion further important controls on the steady state for fehr operate through the formation of euxinic sediments and ironstones which also provide sealevel dependent sinks for fehr enriched sediment

transport of heavy metals in the huanghe river estuary china surface water samples were taken from the huanghe river estuary in may and september 2009 pb cu zn cd as and hg in dissolved and particulate phase and physicochemical indexes of the water were determined to study the transport of metals the results show that dissolved metals in river water increased significantly in 2009 compared to late 1980 and metal content in suspended particulate matter in the river is still low compared to the world river average at the estuary the levels of particulate heavy metals decrease seaward with increasing salinity and have significant positive correlation with suspended particulate matter spm levels the concentrations of dissolved pb cu zn and as decrease as salinity levels increase but the levels of dissolved cd and hg increase seaward with increasing salinity the correlation analysis shows that spm salinity and do are the important factors that controlled the spatial distribution of heavy metals there is inverse linear relationship between metals log kd for pb cu and zn values and spm this relationship may be caused by particle concentration effect increased colloid concentration in the filtered fraction in proportion to the quantity of suspended particles spm salinity ph and do have significant p 0 01 correlation with kd partitioning coefficient of pb and cu spm has also significant p 0 05 correlation with kd of zn and hg and salinity has significant p 0 05 correlation with kd of zn and as however the kd of cd has no relation to the physicochemical indexes which means the behavior of cd in estuary is different spm and salinity are main parameters affecting the variance of kd in the estuary pollution and decrease of spm in the upper reaches of the huanghe have affected the transport behavior of trace elements at the estuary compared 1980

dating errors in high resolution stratigraphy a detailed x ray radiograph and ams 14 c study of zoophycos burrows abstract bioturbation in oxic deep sea settings is often considered if considered at all to consist of a 2 10 cm thick homogenized layer and some easily recognizable distinct burrows which could be avoided when sub sampling the sediment cores however there is one trace that is often difficult to discern in unlithified sediments that manifests transport of considerable amounts of sediment over large vertical distances and that is widely spread in deep sea sediments in all oceans this trace zoophycos is therefore predestined to cause errors and even age reversals in high resolution dating in order to better estimate the size of these age errors we have performed ams 14 c dating of the trace itself and of directly surrounding material in two gravity cores from the portuguese continental slope the results show an age falsification of 1110 2525 years at sedimentation rates of 10 20 cm ka 1 since zoophycos burrows are often poorly or not at all visible in fresh cores all observations of zoophycos were made on x ray radiographs to avoid dating errors of this kind an x ray radiograph study prior to sub sampling is strongly recommended

paleoclimatic and paleoceanographic conditions leading to development of sapropel layer s1 in the aegean sea abstract sapropel s1 occurs as 25 35 cm thick black weakly laminated muds in aegean sea cores s1 was deposited between 9600 and 6400 yr b p during a period of isotopically depleted and relatively cool surface waters micro faunal and floral data indicate a major reduction in surface waters salinity during the deposition of s1 and oxygen isotopic data show a northerly fresh water source relatively light 13 c org and high pollen spore concentrations in s1 suggest increased influx of terrestrial organic carbon probably supplied by major rivers draining into the northern aegean sea benthic foraminifera indicate high nutrient low oxygen bottom waters for s1 and together with silt sized hematite and manganese coatings suggest that during the deposition of s1 surface sediments were oxic visual and xrd evidence of pyrite in s1 together with enrichments in s cu zn as ni cr and fe suggest that subsurface conditions were sufficiently reducing for so 4 2 reduction to occur probably by diffusion from surface oxic into subsurface anoxic sediments palynomorphs in s1 show large increases in terrestrial pollen and spores with the floral assemblage indicating significant influx from northern european rivers and minor african components associated with increased summer monsoonal rain abundance of dinoflagellates and amorphogen suggests some increase in primary productivity in response to increased influx of humic compounds however there is no evidence of upwelling the clay fraction in s1 shows notable decreases in smectite and kaolinite and reciprocal increases in illite and chlorite the combined data suggested that the evolution of s1 in the aegean sea largely resulted from stagnation of the surface waters during the final disintegration of the continental ice sheets rather than an increase in primary productivity and higher preservation of organic carbon on the sea floor

bioturbation on the pelagian platform ichnofacies variations as paleoclimatic indicator abstract x radiographs of apparently structureless split cores collected on the outer pelagian platform tunisia display highly bioturbated sequences the study of these sequences enabled us to determine ichnofacies variations that might be related to hydrologic and climatic changes occurring in this area during the late quarternary epoch this interpretation is supported by mineralogic and paleontologic analyses and by the radiocarbon dating

the onset and growth of the 1990 equatorial disturbance on saturn abstract the development of cloud structures at low saturnian latitudes in september 1990 can be divided into three phases the onset and expansion of the initial disturbance popularly known as the great white spot the eastward and westward expansion of the bright cloud and the eventual formation of wave like structures encircling the equator the three phases of this storm are consistent with a single convective event this event is evaluated within the historical context of previous occurrences and general seasonal mechanisms are considered

saturn s zonal wind profile in 2004 2009 from cassini iss images and its long term variability abstract five years of cassini imaging science subsystem images from 2004 to 2009 are analyzed in this work to retrieve global zonal wind profiles of saturn s northern and southern hemispheres in the methane absorbing bands at 890 and 727 nm and in their respective adjacent continuum wavelengths of 939 and 752 nm a complete view of saturn s global circulation including the equator at two pressure levels in the tropopause 60 mbar to 250 mbar with the mt filters and in the upper troposphere from 350 mbar to 500 mbar with the cb filter set is presented both zonal wind profiles available at the supplementary material section show the same structure but with significant differences in the peak of the eastward jets and the equatorial region including a region of positive vertical shear symmetrically located around the equator between the 10 c

geochemistry of surface sediments off the southern and western coasts of korea abstract the continental shelf off the southern and western side of the korean peninsula is part of a modern epicontinental sea and is an effective sediment trap for clastic material derived from china and korea we have analyzed 179 surface sediment samples from this shelf for al fe na k mg ca ti p mn sr ba v cr co ni cu zn organic carbon and calcium carbonate in order to determine the geochemical characteristics of these sediments results showed a wide range of element contents which are mainly related to the textural variability of sediments exceptions to this were found in the contents of ca k sr and ba the ca and sr contents were largely determined by the amounts of carbonate present the k content on the other hand appeared to be influenced by both the contents of illite and feldspar and ba of potassium feldspar for muds i e sediments deposited under present day conditions it is possible to distinguish those in the central yellow sea from those in the keum estuary the former are characterized by high contents of fe na k mg ca and v and the latter by high contents of mn ba and co these differences become more apparent when these elements are normalized relative to al in order to minimize grain size effects the distribution of v al ratios is different from that of other elements the highest v al values occur in muds from the central yellow sea derived from the huanghe the yellow river in china whereas the highest values of mn al are found in the nearshore area adjacent to the korean peninsula based on these results it is suggested that the sources of fine sediments in the yellow and south seas can be distinguished from the geochemical characteristics of the surface sediments in the yellow sea two different sources of fine grained sediments can be seen the huanghe and the keum river the former is characterized by higher v contents and the latter by higher mn contents using the v al ratio as an end member component of the two source materials the dispersal patterns of the fine sediments 6o were also derived

discrimination of geochemical compositions between the changjiang and the huanghe sediments and its application for the identification of sediment source in the jiangsu coastal plain china concentrations of 25 elements in the fine grained fraction 6 63 wm of bottom sediments of the changjiang and the huanghe were determined to characterize the geochemical compositions of each riverine origin most of the elements except for alkali and alkaline earth elements na ca sr and ba are highly enriched in the changjiang sediments compared to those in the huanghe sediments differences in source rocks and weathering mechanisms between the two drainage basins are the major factors controlling those compositional characteristics the provenance index of core sediments from the northern jiangsu coastal plain calculated with nine elements with distinct compositional differences between both river sediments indicates that the changjiang had prevailed in the coastal plain sedimentation during the early stage of holocene while the huanghe dominated over the area during the late holocene however neither of the signatures of the modern changjiang and huanghe derived sediments is remarkable in the present day coastal plain 5 2002 elsevier science b v all rights reserved

motions in saturn s atmosphere observations before voyager encounters abstract a summary is presented of all the telescopic observations of the clouds in saturn s atmosphere made prior to the voyager encounters with the planet saturn displays a pattern of belts and zones like jupiter although they are practically constant in latitude and without significant changes over the last century some dark and white spots with diameters of about 6000 to 10 000 km have been observed allowing us to ascertain the atmospheric rotational period only a strong equatorial jet can be inferred from these measurements the most obvious features of saturn are the great white spots gws with diameters of 20 000 km or more but only five outbursts have been detected since 1876 corrected measurements have been obtained of the zonal velocities at different latitudes u with variations between 430 and 14 msec 1 with respect to the magnetic rotation of the planet m l kaiser m d desch j w warwick and j b pierce science 209 1238 1240 1980 the expansion velocities of some gws have been measured to be u 30 to 100 msec 1 and their lifetimes l from 30 to 150 days a possible subatmospheric origin for the gws is proposed in which it is due to a temporary and local anisotropy in the internal heat source a hot spot in the deeper atmosphere all the multiple features seen in both 1903 and 1933 appear to be linked to a unique system of longitudes rotating with the magnetic period

dynamics of saturn s great storm of 2010 2011 from cassini iss and rpws saturn s quasi periodic planet encircling storms are the largest convecting cumulus outbursts in the solar system the last eruption was in 1990 sanchez lavega a 1994 chaos 4 341 353 a new eruption started in december 2010 and presented the first ever opportunity to observe such episodic storms from a spacecraft in orbit around saturn fischer g et al 2011 nature 475 75 77 sanchez lavega a et al 2011 nature 475 71 74 fletcher l n et al 2011 science 332 1413 here we analyze images acquired with the cassini imaging science subsystem iss which captured the storm s birth evolution and demise in studying the end of the convective activity we also analyze the saturn electrostatic discharge sed signals detected by the radio and plasma wave science rpws instrument the storm s initial position coincided with that of a previously known feature called the string of pearls sops at 33 n planetocentric latitude intense cumulus convection at the westernmost point of the storm formed a particularly bright head that drifted at 26 9 0 8 m s 1 negative denotes westward motion on january 11 2011 the size of the head was 9200 km and up to 34 000 km in the north south and east west dimensions respectively rpws measurements show that the longitudinal extent of the lightning source expanded with the storm s growth the storm spawned the largest tropospheric vortex ever seen on saturn on january 11 2011 the anticyclone was sized 11 000 km by 12 000 km in the north south and east west directions respectively between january and september 2011 the vortex drifted at an average speed of 8 4 m s 1 we detect anticyclonic circulation in the new vortex the vortex s size gradually decreased after its formation and its central latitude shifted to the north the storm s head moved westward and encountered the new anticyclone from the east in june 2011 after the head vortex collision the rpws instrument detected that the sed activities became intermittent and declined over 40 days until the signals became undetectable in early august in late august the sed radio signals resurged for 9 days the storm left a vast dark area between 32 n and 38 n latitudes surrounded by a highly disturbed region that resembles the mid latitudes of jupiter using iss images we also made cloud tracking wind measurements that reveal differences in the cloud level zonal wind profiles before and after the storm

cassini imaging of saturn southern hemisphere winds and vortices high resolution images of saturn s southern hemisphere acquired by the cassini imaging science subsystem between february and october 2004 are used to create maps of cloud morphology at several wavelengths to derive zonal winds and to characterize the distribution frequency size morphology color behavior and lifetime of vortices nonequatorial wind measurements display only minor differences from those collected since 1981 and reveal a strong prograde flow near the pole the region just southward of the velocity minimum at 40 7 s is especially active containing numerous vortices some generated in the proximity of convective storms the two eastward jets nearest the pole display periodicity in their longitudinal structure but no direct analogs to the northern hemisphere s polar hexagon or ribbon waves were observed characteristics of winds and vortices are compared with those of saturn s northern hemisphere and jupiter s atmosphere

photometry of saturn s 1990 equatorial disturbance abstract multicolor ccd images at selected wavelengths from 370 to 900 nm obtained at pic du midi observatory during four different phases of the development of saturn s equatorial disturbance are used to analyze its photometric properties three epochs and four morphologically different regions were studied october 5 1990 the source of the event the great white spot properly october 6 and 8 1990 an undisturbed area in the same latitude far away from the gws november 17 1990 the mature phase of the planetary disturbance and july 7 1991 the declined phase but still active disturbance the absolute spectral reflectivity of the gws single feature showed a marked increase at all wavelengths with respect to the undisturbed neighbourings a simple interpretation of these data indicates that optically thick cloud tops in the gws nucleus were located at average pressures 200 mbar two scale heights above the expected ammonia cloud deck at 1 8 bar the particles forming the gws were very bright in the red and less contaminated by the blue absorbing impurities limb to limb scans at latitudes 5 13 and 20 n are used to characterize the temporal spectral dependence of the minnaert s limb darkening coefficient k and the normalized albedo i f 0 pronounced increases in k and i f 0 were noted at continuum wavelengths in november 1990 but only moderate changes were apparent in july 1991 both with respect to the undisturbed area observed in early october 1990 the particles constituting the upper cloud of the disturbance during its mature phase in november 1990 showed changes in their vertical distribution and had a higher single scattering albedo at blue and yellow wavelengths and were more forward scattering than those which normally form the equatorial haze and cloud of saturn

saturn s cloud structure inferred from cassini iss abstract using high resolution cassini iss images with wavelengths ranging from the ultraviolet to the near infrared we have retrieved saturn s atmospheric aerosol structure and properties for a broad range of latitudes in the southern hemisphere the observations are consistent with two distinct layers of haze above a scattered cloud each layer is characterized by a vertical location an optical thickness and an effective mean particle size all of which vary with latitude the tropospheric haze is optically thickest and extends to the greatest heights 40 mbar over the equator its top surface is at significantly greater depths 150 mbar at mid latitudes the height of the haze correlates well with position of the tropopause as indicated by the temperature field beneath this haze we find a scattered denser cloud responsible for small scale contrasts at an average depth of 1 75 0 4 bar with some features as deep as 2 5 bar or greater

atmospheric dynamics of saturn s 2010 giant storm great white spot a rare planet encircling storm raged on saturn in 2010 2011 analyses of high resolution spacecraft imagery and numerical modelling reveal a dynamic storm head powered by sustained convection in the zonal flow of saturn s atmosphere

thermal structure and dynamics of saturn s northern springtime disturbance saturn s slow seasonal evolution was disrupted in 2010 2011 by the eruption of a bright storm in its northern spring hemisphere thermal infrared spectroscopy showed that within a month the resulting planetary scale disturbance had generated intense perturbations of atmospheric temperatures winds and composition between 20 and 50 n over an entire hemisphere 140 000 kilometers the tropospheric storm cell produced effects that penetrated hundreds of kilometers into saturn s stratosphere to the 1 millibar region stratospheric subsidence at the edges of the disturbance produced beacons of infrared emission and longitudinal temperature contrasts of 16 kelvin the disturbance substantially altered atmospheric circulation transporting material vertically over great distances modifying stratospheric zonal jets exciting wave activity and turbulence and generating a new cold anticyclonic oval in the center of the disturbance at 41 n

cloud structure of saturn s 2010 storm from ground based visual imaging abstract we present a study of the vertical cloud structure for the initial stage of the great white spot gws a giant storm that developed in saturn in december 2010 using ground based visual images we focus in the characterization of the undisturbed atmosphere preceding the storm and the disturbed region in the wake of the gws the observations were taken at calar alto spain and pic du midi france observatories on 27 december 2010 and 13 january 2011 about 1 month after the detection of the outbreak they cover a spectral range from the ultraviolet at 375 nm to the near infrared at 954 nm including the deep methane absorption band at 890 nm and a number of increasingly weaker methane absorption bands limb to limb scans of the absolute reflectivity of the regions preceding and following the storm at different wavelengths are compared to those produced by a radiative transfer model atmosphere our model assumes three layers of gas and particles stratospheric and tropospheric hazes and a deep cloud we find that the most notorious changes in the wake of the gws occurred in the top level of the semi infinite bottom cloud which ascended from an altitude level p 1 bar in the undisturbed region to p 300 300 100 mbar in the stormy area representing a rise of more than 40 km the density of the tropospheric haze does not change substantially but tropospheric particles are found to be more reflectant at all wavelengths suggesting that they are coated by fresh material putatively coming from deeper levels of the atmosphere

review and new aspects concerning the formation of eastern mediterranean sapropels abstract in this paper it is proposed that the formation of eastern mediterranean sapropels occurred in an anti estuarine type of circulation which was to some degree weakened relative to the present in response to reduction of the eastern mediterranean excess of evaporation over freshwater input this reduction of excess evaporation would have been imposed by intensifications of 1 the indian ocean summer sw monsoon influencing the eastern mediterranean via increased nile discharge and 2 the system of mediterranean depressions an element of the westerly atlantic system causing increased precipitation and decreased evaporation both the indian ocean summer monsoon and the westerly atlantic system would be intensified in response to the occurrence of distinct minima in the cycle of precession it is demonstrated that reduced excess evaporation whether or not coinciding with global phases of deglaciation would lead to reduction of surface water salinities in the eastern mediterranean causing isolation of previously formed high salinity cooler deep water thus mixing was severely reduced possibly even restricted to eddy diffusion with only occasional convective events that because of the existing density gradient hardly ever would reach the deepest parts of the basin the consequently diminished oxygen advection down from a few hundred meters in the water column favoured preservation of the sinking organic matter this would however suffice only to enable the formation of sapropels with low organic carbon contents the high organic carbon contents observed in various sapropels are argued to reflect superimposed increases of export production the described scenario accounts for previously reported 1 increases of organic carbon content with increasing depth of deposition within individual sapropels and 2 asymmetrical sequences of sapropel deposition characterized by gradual build up and rather abrupt ending it is furthermore in agreement with 3 isotopic and faunal reconstructions of the history of exchange transports through both the strait of sicily and the strait of gibraltar and 4 faunal and floral reflections of the presence or absence of a distinct deep chlorophyll maximum with its associated increases in export production indicating the presence or absence of a shallow pycnocline within the euphotic layer moreover the described scenario 5 is in no way conflicting with the reports of sapropels in the western mediterranean and 6 seems to be endorsed by occasionally intercalated intervals suggestive of somewhat improved oxygenation amidst anoxic benthic desert levels a situation that has been observed in a few quaternary and pliocene sapropels

the 2009 2010 fade of jupiter s south equatorial belt vertical cloud structure models and zonal winds from visible imaging abstract the south equatorial belt seb of jupiter is known to alternate its appearance at visible wavelengths from a classical belt like band most of the time to a short lived zone like aspect which is called a fade of the belt hereafter sebf the albedo change of the seb is due to a change in the structure and properties of the clouds and upper hazes recent works based on infrared observations of the last sebf have shown that the aerosol density below 1 bar increased in parallel with the reflectivity change however the nature of the change in the upper clouds and hazes that produces the visible reflectivity change and whether or not this reflectivity change is accompanied by a change in the winds at the upper cloud level remained unknown in this paper we focus in the near ultraviolet to near infrared reflected sunlight 255 953 nm to address these two issues we characterize the vertical cloud structure above the ammonia condensation level from hubble space telescope images and the zonal wind velocities from long term high quality images coming from the international outer planet watch database both during the seb and sebf phases we show that reflectivity changes do not happen simultaneously in this wavelength range but they start earlier in the most deep sensing filters and end in 2010 with just minor changes in those sensing the highest particle layers our models require a substantial increase of the optical thickness of the cloud deck at 1 0 0 4 bar from cloud 6 2 in july 2009 seb phase to semiinfinite at visual wavelengths in 2010 sebf upper tropospheric particles 240 1400 mbar are also required to become substantially reflectant and their single scattering albedo in the blue changes from 0 0 905 0 005 in november 2009 to 0 0 95 0 01 in june 2010 no significant changes were found in the cloud top heights or in the particle density of the tropospheric haze the disturbance travels from the levels below 3 bar to a level about 400 100 mbar we derive an upward velocity of 0 15 0 05 cm s in agreement with a diffusive process in jupiter s upper troposphere requiring a mean eddy coefficient k 8 105 cm2 s 1 on the other hand cloud tracking on the iopw imaging showed no significant changes in the zonal wind profile between the seb and sebf stages as in other visually huge changes in jupiter s cloud morphology and structure the wind profile remains robust possibly indicating a deeply rooted dynamical regime