mapping of a major paleodrainage system in eastern libya using orbital imaging radar the kufrah river paillou p schuster m tooth s farr t rosenqvist a lopez s malezieux j m 2009 mapping of a major paleodrainage system in eastern libya using orbital imaging radar the kufrah river earth and planetary science letters 277 3 4 327 333 sponsorship french space agency cnes centre national d etudes spatiales

the use of sequential extraction techniques for sedimentary phosphorus in eastern mediterranean sediments abstract the sedex method a sequential extraction scheme for sedimentary phosphorus phases was tested for use on eastern mediterranean sediments using two in house reference sediments in addition a 2 m nh4cl and a 0 1 m naoh extraction were tested to extract caco3 associated and iron bound p respectively these methods were then applied to samples of a sediment core from the eastern mediterranean abc26 the sum of extracted p phases of the reference sediments and core abc26 was not significantly different from total p and precision of each extraction was better then 17 1s except for detrital p and iron bound p extracted by cdb the naoh extraction dissolved only iron oxides associated with the surface of minerals while the cdb extraction dissolved a much larger fraction in core abc26 p produced in the sapropel layer s1 appeared to have diffused both upwards and downwards this p is now found as exchangeable loosely bound p and as iron oxide bound p in the adjacent oxic sediments there was evidence that p was released from caco3 p in the burn down zone which was affected by sulfide oxidation the organic c p molar ratio was 400 1 in the sapropel while it was indeterminate for the oxic layers

the use of multifrequency and polarimetric sir c x sar data in geologic studies of bir safsaf egypt abstract bir safsaf within the hyperarid core of the sahara in the western desert of egypt was recognized following the sir a and sir b missions in the 1980s as one of the key localities in northeast africa where penetration of dry sand by radar signals delineates previously unknown sand buried paleodrainage valleys radar rivers of middle tertiary to quaternary age the bir safsaf area was targeted as a focal point for further research in sand penetration and geologic mapping using the multifrequency and polarimetric sir c x sar sensors analysis of the sir c x sar data from bir safsaf provides important new information on the roles of multiple sar frequency and polarimetry in portraying specific types of geologic units materials and structures mostly hidden from view on the ground and on landsat tm images by a relatively thin but extensive blanket of blow sand basement rock units granitoids and gneisses and the fractures associated with them at bir safsaf are shown here for the first time to be clearly delineated using c and l band sar images the detectability of most geologic features is dependent primarily on radar frequency as shown for wind erosion patterns in bedrock at x band 3 cm wavelength and for geologic units and sand and clay filled fractures in weathered crystalline basement rocks at c band 6 cm and l band 24 cm by contrast quaternary paleodrainage channels are detectable at all three radar frequencies owing among other things to an usually thin cover of blow sand the sir c x sar data investigated to date enable us to make specific recommendations about the utility of certain radar sensor configurations for geologic and paleoenvironmental reconnaissance in desert regions

stable isotope anomalies in mediterranean pleistocene records oxygen and carbon isotope records of twelve mediterranean cores raised from west alboran sea to east off israel and of four atlantic cores raised from the western side of gibraltar and located respectively inside below and beyond the modern mediterranean outflow are compared to open ocean records of core 71 139c from the north atlantic and core v19 30 from the east pacific oxygen isotope stratigraphies can be established for deep mediterranean records and the major events of the last 150 ka are easily identifiable for instance the five substages of stage 5 or the 18 ka event stage 2 are identified but the 10 ka event younger dryas is only recorded by globigerina bulloides and benthic foraminifera suggesting that the cooling affected only winter sst 14c dates for the two terminations ia and ib of the last deglaciation which are recorded in sediment cores from areas with high sedimentation rates faro ridge alboran sea sicilian strait are in good agreement with the dates published for the same termination in atlantic cores an intermediate step however has been identified in some cores at 14 ka and divides termination ia into two phases oxygen isotope anomalies are recorded by the shallow water species globigerinoides ruber they correspond to 1 a higher amplitude glacial interglacial change in 18o values which exceeds that of the open ocean by 1 in the western basin and by 1 7 in the eastern basin 2 large isotopic depletions during the deposition of sapropel s1 s3 and s5 they are interpreted as the result of fresh water run off responsible for a strong dilution in the shallower layers of the east mediterranean waters the isotopic effect of this dilution averages 0 75 for sapropel s1 and 1 6 for sapropel s5 during the last glacial maximum the mediterranean still acted as a concentration basin and a gradient of 18o values similar to the modern one 0 75 existed from west to east in the deep waters apparently deep water temperatures were lower during the last glacial but the decrease did not exceed 4 c in the eastern basin major anomalies are also contained in the 13c records of g bulloides and benthic foraminifera the 13c records from surface intermediate and deep waters of the eastern basin and from intermediate and deep waters of the western basin are opposite to that of the open ocean during glacial time 13c values were higher in intermediate and deep waters of the whole mediterranean and also in surface water of the eastern basin at the same time the 13c gradient of surface to deep waters was low this gradient increased during the last deglaciation while 13c values of g bulloides and benthic foraminifera decreased this decrease interrupted at 10 ka may have been related to increased fresh water run off from the bordering contintents due to increased precipitation especially in the tropical belt the 13c depletion is clearly recorded in the levantine and deep water masses and can be traced westward in the mediterranean outflow oxygen and carbon isotope anomalies recorded simultaneously in the east mediterranean by the shallow water species globigerinoides ruber during sapropel deposition indicate that increased precipitation on the bordering continents and strong fresh water run off during the time of the last deglaciation may have caused a density stratification and deep stagnation in the eastern basin uncertainties arise from the fact that in the mixing model deglacial mediterranean waters are mixed with continental fresh waters the isotopic characteristics of which are not entirely understood although increased surface water production of biogenic material can not be excluded as a possible cause of 13c depletion it appears that the river discharge including the nile as well as black sea input are also plausible sources for the fresh water layering

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

a comparison of several methods for the determination of iron hydroxides and associated orthophosphates in estuarine particulate matter abstract five different methods commonly used for the extraction and the determination of iron hydroxides and or the associated phosphorus held in marine seston or in sediments have been tested on single phase minerals goethite and apatite on reference minerals so1 and so2 and on suspended matter samples from the st lawrence estuary and from the estuary of the eastmain river a major james bay affluent in northern quebec canada the citrate dithionite bicarbonate cdb procedure generally seemed to be more reproducible and more specific the validity of the other methods respectively using as extracting reagents ammonium oxalate oxalic acid hydroxylamine hydrochloride calcium nitrilotriacetic acid and acetate tartrate is discussed the cdb extraction is included in an analytical scheme which allows to distinguish between three fractions of phosphorus this chemical speciation is applied to the study of p retention on fe hydroxides and to its potential desorption

elevation modelling and palaeo environmental interpretation in the siwa area egypt application of sar interferometry and radargrammetry to cosmo skymed imagery abstract digital elevation models produced from cosmo skymed imagery were used to delineate palaeo drainage in a wide area surrounding the siwa and al jaghbub oases of the western sahara desert egypt and libya this new generation of synthetic aperture radar imagery is suitable for this purpose because of its high spatial resolution and capacity to penetrate dry surface sediments different techniques such as radar interferometry and radargrammetry were used to produce digital elevation models these were assessed for accuracy and then combined to produce a single elevation model of the area the resulting elevation model was used to support the geological study and palaeo environmental interpretation of the area it revealed buried features of the landscape including inactive palaeo drainage systems drainage features were extracted from the elevation model using geographical information systems results were combined and assessed with respect to geological field data as well as data from the literature previous studies in the area suggest that a wide river probably the old nile river flowed into the libyan palaeo sirte before the late messinian drawdown of the mediterranean sea during the late messinian lowering of the sea the fluvial system changed shape and carved deep canyons throughout north eastern africa the reported findings on the key siwa area were used to precisely delineate the physiography of the modern drainage network and to confirm findings from our previous geological research in the area

mesoscale spectral analysis of in situ horizontal and vertical wind measurements at 6 km as part of the aloha anlc 93 campaign to investigate atmospheric dynamics in situ wind measurements collected at 6 km with the gust probe sensor attached to the national center for atmospheric research electra aircraft were analyzed for 16 flight segments between 61 n and 14 s and between 92 w and 170 w over land and water horizontal wavenumber spectra for the vertical wind and both zonal and meridional horizontal wind components were calculated the zonal and meridional wavenumber spectra exhibited a decrease in the spectral slope from 1 98 0 02 for wavelengths between 2 km and 100 km to 3 18 0 06 for the longer wavelengths between 100 km and 330 km the wavenumber spectrum for the vertical wind component showed a 2 power law dependence for wavelengths in excess of 5 km and a generally flat shape at shorter wavelengths an increase in power at the wavelength of 10 km was detected for the meridional wavenumber spectrum these results were compared with predictions from two spectral models and with spectral results from other observations

aeolian erosional lineations in the libyan desert dakhla region egypt abstract this paper presents results of a study of aeolian erosion at the landscape scale there have been few such studies in desert geomorphology compared to those focused on individual landforms and on rock surface sculpture the present study area lies in the southern part of the libyan desert in south central egypt between 25 and 27 n 29 and 30 e bedrock comprises paleogene limestone of various lithologies climate is hyperarid the following topics are treated i correspondences between rock outcrop belts and belts of terrain lineated by aeolian erosion and unlineated terrain ii the effect of lithology on aeolian lineation which works through the presence or absence of chert in the limestones lineation is produced by aeolian erosion in chert free poor rocks whereas erosion of chert rich rocks produces a desert pavement that armors the surface suppressing erosion iii the effect of large valleys eroded upwind of lineated terrain which deflect winds and trap sand ending erosion so that downwind lineations are reduced and finally erased by weathering iv sample lineated landscapes in the area show stages of evolution arranged in the time domain into a proposed cycle of aeolian erosion the cycle progresses from initial smooth plain to grooves separating long blade shaped ridges to segmentation of ridges into shorter blades along diagonal joints to streamlining of shorter blades and size reduction to final planation in any one wind parallel swath of lineated terrain stages in the cycle progress downwind in the space domain so that upwind landscapes are more advanced in the cycle v the structure of air flow responsible for lineation is still uncertain but initial grooving may respond to stable longitudinal horseshoe vortices or self organized regularity of erosion by random vortices subsequently the erosion pattern is fixed by evolving relief vi large smooth basins within the lineated terrain were carved by aeolian erosion before oxygen isotope stage ois 5 70 130 ka as were similar basins along the dakhla piedmont below the scarp little geomorphic change has occurred since so in this field of aeolian erosional lineations aels the aeolian erosion cycle may have occupied 10 times as long since continental scale aridity set in at ca 2 4 ma there have been only two cycles in this area a completed cycle earlier than the current incomplete one is indicated by rare small yardangs riding piggyback on larger ones

the horizontal kinetic energy spectrum and spectral budget simulated by a high resolution troposphere stratosphere mesosphere gcm abstract horizontal kinetic energy spectra simulated by high resolution versions of the geophysical fluid dynamics laboratory skyhi middle atmosphere general circulation model are examined the model versions considered resolve heights between the ground and 80 km and the horizontal grid spacing of the highest resolution version is about 35 km tropospheric kinetic energy spectra show the familiar 3 power law dependence on horizontal wavenumber for wavelengths between about 5000 and 500 km and have a slope of 5 3 at smaller wavelengths qualitatively similar behavior is seen in the stratosphere and mesosphere but the wavelength marking the transition to the shallow regime increases with height taking a value of 2000 km in the stratosphere and 4000 km in the mesosphere the global spectral kinetic energy budget for various height ranges is computed as a function of total horizontal wavenumber contributions to the kinetic energy tendency from nonlinear advective processes from conversion of avai

biological productivity during sapropel s5 formation in the eastern mediterranean sea evidence from stable isotopes of nitrogen and carbon we determined 15n 14n ratios in modern surface and sapropel s5 sediments of the mediterranean sea to clarify differences in the nutrient regime associated with sapropel formation in the modern situation high 15n of unused nitrate 15 20 remaining in the surface waters during the winter phytoplankton bloom evidences p limitation of biological production in winter 15n of surface sediments decrease towards the east of the basin 5 to 2 5 this is a consequence of either eastward increasing nitrogen fixation during the summer months or of particulate matter being supplied predominantly by the p limited winter bloom very low 1 1 15n values in sapropel s 5 from four locations require a very light source of nutrient n assimilated at a minimum of ten times the modern export flux because the isochronous records show no spatial gradient in 15n we exclude both ekman type upwelling and direct riverine discharge as likely sources of nutrients our data are consistent with an anti estuarine thermohaline circulation in the upper 500m during s5 time allowing for the trapping of nutrients in the eastern basin the most likely scenario for s5 is that phosphorus release from a relatively shallow redox boundary resulted in an imbalanced supply of n p 16 1 to the photic zone the result was a slow assimilation of carbon during summer stratification and extensive n2 fixation providing the majority of the export flux from a n limited system

mesoscale dynamical regimes in the midlatitudes the atmospheric mesoscales are characterized by a complex variety of meteorological phenomena that defy simple classification here a full space time spectral analysis is carried out based on a 7 day convection permitting simulation of springtime midlatitude weather on a large domain the kinetic energy is largest at synoptic scales and on the mesoscale it is largely confined to an advective band where space and time scales are related by a constant of proportionality which corresponds to a velocity scale of about 10 m s 1 computing the relative magnitude of different terms in the governing equations allows the identification of five dynamical regimes these are tentatively identified as quasi geostrophic flow propagating gravity waves stationary gravity waves related to orography acoustic modes and a weak temperature gradient regime where vertical motions are forced by diabatic heating

the marine phosphorus cycle phosphorus introduced to the ocean must ultimately be removed if a steady state is to be maintained over geologic time aeolian input is insignificant and there is evidently no hydrothermal contribution rivers dominate p input to the ocean the fluvial p flux is poorly quantified due to the interactions of two factors 1 man s influence on river nutrient fluxes and 2 inherent complexities in understanding the biological and inorganic associations of p in estuarine and coastal waters our best estimate of the natural or pre man p input flux is about 10 x 10 sup 9 moles p cm sup 2 ocean surface year of the identified flux of phosphorus to the sediments about 90 percent is in the form of biogenic debris or its regeneration products the burial of phosphatic fish debris is negligible p removal by direct reaction of phosphate in seawater with sea floor basalts during mid ocean ridge hydrothermal circulation is insignificant p removal by processes such as sorption on clay surfaces or formation of authigenic fe and al phosphate phases is presently unquantified and remains a serious uncertainty in the phosphorus cycle the identified sources and sinks approximately balance yielding a residence time for p in the oceans of about 10 sup 5 yrs

stratospheric gravity wave fluxes and scales during deepwave abstractduring the deep propagating gravity wave experiment deepwave project in june and july 2014 the gulfstream v research aircraft flew 97 legs over the southern alps of new zealand and 150 legs over the tasman sea and southern ocean mostly in the low stratosphere at 12 1 km altitude improved instrument calibration redundant sensors longer flight legs energy flux estimation and scale analysis revealed several new gravity wave properties over the sea flight level wave fluxes mostly fell below the detection threshold over terrain disturbances had characteristic mountain wave attributes of positive vertical energy flux efz negative zonal momentum flux and upwind horizontal energy flux in some cases the fluxes changed rapidly within an 8 h flight even though environmental conditions were nearly unchanged the largest observed zonal momentum and vertical energy fluxes were mfx 550 mpa and efz 22 w m 2 respectively a wide variety of disturbance scales were found at flight level over

the late neogene sahabi rivers of the sahara and the hamadas of the eastern libya chad border area abstract this paper contributes to the concept that during the late tortonian messinian and early pliocene c 7 5 4 6 ma in addition to the nile the sahabi rivers also crossed the sahara having originated from tropical neogene lake chad examination of two hamadas lying just to the north of the libya chad border using landsat images and srtm topographic data enables one of them hamada ibn battutah west to be recognised as an uplifted palaeosurface which preserves late miocene early pliocene fluvial activity this surface is referred to as the yangara palaeosurface of particular interest on the hamada are two long c 50 km wide c 4 km channels a 50 km 2 relic landscape and a short well defined 5 km channel about 1 km wide the location of hamada ibn battutah west is significant because the hamada provides evidence of extensive fluvial activity part way between the place of origin of the sahabi rivers and their preserved record at the gulf of sirt the yangara palaeosurface is considered to extend southwards to the adjacent hamada in northeastern chad the total palaeosurface extends 165 km in an approximate north south direction and averages 45 km in width it lies in the central part of an area of complex post miocene uplift involving four hamadas at the libya chad border

subsurface valleys and geoarcheology of the eastern sahara revealed by shuttle radar the shuttle imaging radar sir a carried on the space shuttle columbia in november 1981 penetrated the extremely dry selima sand sheet dunes and drift sand of the eastern sahara revealing previously unknown buried valleys geologic structures and possible stone age occupation sites radar responses from bedrock and gravel surfaces beneath windblown sand several centimeters to possibly meters thick delineate sand and alluvium filled valleys some nearly as wide as the nile valley and perhaps as old as middle tertiary the now vanished major river systems that carved these large valleys probably accomplished most of the erosional stripping of this extraordinarily flat hyperarid region underfit and incised dry wadis many superimposed on the large valleys represent erosion by intermittent running water probably during quaternary pluvials stone age artifacts associated with soils in the alluvium suggest that areas near the wadis may have been sites of early human occupation the presence of old drainage networks beneath the sand sheet provides a geologic explanation for the locations of many playas and present day oases which have been centers of episodic human habitation radar penetration of dry sand and soils varies with the wavelength of the incident signals 24 centimeters for the sir a system incidence angle and the electrical properties of the materials which are largely determined by moisture content the calculated depth of radar penetration of dry sand and granules based on laboratory measurements of the electrical properties of samples from the selima sand sheet is at least 5 meters recent september 1982 field studies in egypt verified sir a signal penetration depths of at least 1 meter in the selima sand sheet and in drift sand and 2 or more meters in sand dunes

eastern mediterranean palaeoclimates from 26 to 5 ka b p documented by pollen and isotopic analysis of a core in the anoxic bannock basin continuous pollen and isotopic records were established for core ban 84 09 gc retrieved from the anoxic bannock basin in the eastern mediterranean on the basis of two 14c dates they document the palaeoclimate between about 25 7 ka b p and 5 2 ka b p in the northern borderlands of the ionian basin the upper half of the core has been redeposited the isotopic record displays a correlation with pollen percentages that is strong and positive for artemisia sage brush and negative for quercus oak the last glacial maximum and the deglaciation are identified by these combined taxa together with chenopodiaceae the glacial maximum around 18 ka b p which has elsewhere been dated from 20 to 15 ka b p has pollen percentages that are high for artemisia and low for quercus the climate in the pollen source area was arid cold in winter briefly warm in summer and sustained the vegetation of a semi desert the onset of deglaciation after 18 ka b p coincides with that of the decline in artemisia pollen percentage however this decline does not indicate reduced aridity because it is accompanied by a pollen percentage rise of the even more arid herbs chenopodiaceae and ephedra throughout the deglaciation from 18 to 11 ka b p the aridity progressively increases culminating at 11 ka b p this trend is briefly interrupted by a more humid event shown by a peak in artemisia pollen percentage and a smaller peak in oak these two peaks are coeval with the bolling allerod chronozone 13 11 ka b p maximum aridity occurs during the younger dryas chronozone 11 10 ka b p afterwards the oak pollen percentage begins a steady increase and its maximum value is coeval with the lowest isotopic value dated at 8760 170 yr b p this period was one of high moisture warm summers and according to altitude mild to cool winters this climate sustained forests that were mediterranean in the lowlands and warm temperate in the uplands a high pollen concentration is observed during this period and reveals the presence of sapropel s1 which is otherwise unrecognizable in this entirely black core during the following period between 8760 170 and 5200 yr b p the 180 reverts to slightly higher values and the quercus pollen percentage decreases while the pollen percentage of the wetter ostrya the oriental hornbeam increases the high pollen concentration during the deposition of sapropel s1 cannot have been caused by increased pollen input into the sea this pollen being wind borne nor by increased pollen production for all taxa both trees and herbs we conclude that it is entirely due to increased preservation of this allochtonous organic material by the deep anoxia of the bottom water below a thick anoxic water column the coincidence of sapropel deposition with warm and humid local climate as well as with the second global meltwater pulse suggests that the cessation of bottom water ventilation was due to decreased surface water density resulting from less saline incoming atlantic surface water increased local runoff and warmer winters

modification and complete removal of eastern mediterranean sapropels by postdepositional oxidation sapropels unusually dark organic rich sediment layers whose origin is controversial are widespread in the eastern mediterranean the upper surfaces of these layers appear sharp and show little evidence of bioturbation it has been suggested that postdepositional oxidation may have removed the dark coloration from the upper part of the original layer so that the top of the visible layer now lies somewhat below the original position of the sapropel top such a diagenetic alteration has considerable implications for the interpretation of the sedimentary record where the tops of dark layers are usually correlated with the cessation of sapropel formation geochemical data demonstrate that all visual evidence of a thin example of the most recent eastern mediterranean sapropel has been removed from the sedimentary record by oxidation processes such a process may have thinned all sapropel units by several centimetres the most recent period of sapropel formation probably ended as recently as 5 ka cf cited values between 6 0 and 7 6 ka

distribution of various extracted phosphorus compounds in the interbedded turbiditic pelagic sediments of the madeira abyssal plain eastern north atlantic abstract a sequential extraction scheme was used to differentiate different p fractions in the interbedded turbiditic pelagic sediments of the madeira abyssal plain these fractions were carbonate associated exchangeable phosphate pex iron and aluminium associated phosphate poh calcium associated phosphate apatite phcl organic phosphorus porg and remaining phosphorus pr the pex forms a minor fraction of the total sedimentary phosphorus ptot whereas for most samples phcl represents near 80 of the ptot the amount of p in most fractions appears to be determined by the composition and provenance of the various turbidites the relatively high pex and the moderately high apatite p phcl for the sediment of turbidite e organicrich turbidite provenance group may point to a source area that is possibly upwelling related on the other hand the high phcl for the sediments of the turbidites b g n o p corresponds nicely to their volcanic and near coastal provenance area in contrast to this major impact of inherited p only a small contribution comes from p that is associated to post depositional re allocation of fe poh this results in a poh concentration that is slightly higher in the upper post depositionally oxidized layer of a turbidite than it is in the lower still un oxidized layer of the same turbidite in addition this postdepositional oxidation of the upper layer of a turbidite may also result in enhanced fe and p levels in the overlying pelagic interval the c p molar ratio for organic matter in these sediments is much higher than that reported for more recent sediments and for average marine plankton 1200 versus 500 and 106 respectively which may be caused by postdepositional differential decomposition of organic matter

active post depositional oxidation of the most recent sapropel s1 in sediments of the eastern mediterranean sea abstract over a wide area of the eastern mediterranean basin two mn rich layers have been observed above the most recent sapropel s1 one immediately above the sapropel top and one a few centimetres closer to the sediment surface different mechanisms have been proposed to explain the occurrence of these two mn peaks either both peaks have a diagenetic origin in which case the upper mn peak is actively forming or the lower peak is actively forming and the upper peak has a different formation mechanism high resolution porewater including a gel sampler used for the first time in marine sediments and solid phase data are now used to demonstrate that the oxidation front is located at the level of the lower mn peak which therefore is presently being formed a barium organic carbon relationship is used to calculate the initial organic carbon profile of the s1 sapropel the palaeoproductivity profiles generated by this method demonstrate that the original sapropel unit was bounded by the upper mn peak this implies that the interval between the two mn peaks where a low organic carbon content is now observed was originally part of the sapropel the initially deposited organic carbon has been oxidised by a progressive downwards moving oxidation front the penetration depth of this oxidation front i e the distance between the two mn peaks is mainly determined by the organic carbon content the sediment accumulation rate and the bioturbation depth the upper mn peak appears to have formed as a result of either mn precipitation upon oxygenation of previously anoxic eastern mediterranean deep water or preservation of a surficial mn peak at the end of the high productivity episode in either case the upper mn peak marks the end of sapropel formation as indicated by the ba profiles this means that formation of the s1 sapropel ceased more recently than is indicated by radiocarbon dating of the visible top of s1

the influence of gravity waves on the slope of the kinetic energy spectrum in simulations of idealized midlatitude cyclones abstractthe influence of gravity waves generated by surface stress and by topography on the atmospheric kinetic energy ke spectrum is examined using idealized simulations of a cyclone growing in

atmospheric conditions during the deep propagating gravity wave experiment deepwave abstractthis paper describes the results of a comprehensive analysis of the atmospheric conditions during the deep propagating gravity wave experiment deepwave campaign in austral winter 2014 different datasets and diagnostics are combined to characterize the background atmosphere from the troposphere to the upper mesosphere how weather regimes and the atmospheric state compare to climatological conditions is reported upon and how they relate to the airborne and ground based gravity wave observations is also explored key results of this study are the dominance of tropospheric blocking situations and low level southwesterly flows over new zealand during june august 2014 a varying tropopause inversion layer was found to be connected to varying vertical energy fluxes and is therefore an important feature with respect to wave reflection the subtropical jet was frequently diverted south from its climatological position at 30 s and was most often involved in strong forcing events of mountain waves at t

the diagenesis of phosphorus in a nearshore marine sediment abstract chemical analyses have been made for total inorganic phosphorus total organic phosphorus and organic carbon in plankton and in anoxic sediments from long island sound u s a when combined with laboratory experiments the measurements of other studies on the same sediments and mathematical modelling the results indicate that 1 1 a large proportion of dissolved phosphate in the upper 10 cm of sediment zone of bioturbation is provided by the release of adsorbed phosphate during the reduction of ferric oxyhydroxides 2 2 below the zone of bioturbation phosphate is liberated to solution solely via organic matter decomposition and the release is stoichiometrically coupled to bacterial sulfate reduction and ammonia formation 3 3 a steady state diagenetic model can be used to predict the profile of organic phosphorus from that of dissolved phosphate at depths below the zone of bioturbation 4 4 the flux of dissolved phosphate out of the sediment must arise largely from phosphate liberation occurring very close 5 5 there is a large preferential loss of phosphorus relative to carbon from organic matter at the time of or prior to burial whereas after burial phosphorus is not lost preferentially at this location

mesoscale spectrum of atmospheric motions investigated in a very fine resolution global general circulation model 1 the horizontal spectrum of wind variance conventionally referred to as the kinetic energy spectrum is examined in experiments conducted with the atmospheric gcm for the earth simulator afes global spectral general circulation model we find that the control version of afes run at t639 horizontal spectral resolution simulates a kinetic energy spectrum that compares well at large scales with global observational reanalyses and at smaller scales with available aircraft observations at near tropopause levels specifically there is a roughly 3 power law dependence on horizontal wave number for wavelengths between about 5000 and 500 km transitioning to a shallower mesoscale regime at smaller wavelengths this is seen for both one dimensional spectra and for the two dimensional total wave number spectrum based on a spherical harmonic analysis the simulated spectrum at midtropospheric levels is similar in that there is a transition to a shallower mesoscale regime but the spectrum in the mesoscale is clearly steeper at midtroposphere than near the tropopause there seem to be no extensive observations of horizontal spectra available in the midtroposphere so it is not known whether the contrast seen in the model between upper and mid tropospheric levels is realistic the dependence of the model simulated variability on the subgrid scale moist convection parameterization is examined the space time variability of rainfall is shown to depend strongly on the convection scheme employed the tropospheric kinetic energy spectrum in the mesoscale seems to be correlated with the precipitation behavior so that in a version with a more variable precipitation field the kinetic energy in the mesoscale is enhanced this suggests that the mesoscale motions in the model may be directly forced to a significant extent by the variability in the latent heating field experiments were also performed with a dry dynamical core version of the model run at both t639 and t1279 resolutions this version also simulated a shallow mesoscale range supporting the view that the mesoscale regime in the atmosphere is energized at least in part by a predominantly forward i e downscale nonlinear spectral cascade experiments with various formulations of the hyperdiffusion horizontal mixing parameterization show that the kinetic energy spectrum over about the last half of the resolved wave number range is under strong control by the parameterized mixing however the t1279 model simulates almost a decade of the shallow mesoscale regime i e for horizontal wavelengths from about 80 to 500 km that appears to be fairly independent of the diffusion employed finally experiments are conducted in the dry version to see the effects on the kinetic energy spectrum of changing the thermal rossby number for the simulations

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

relation between sedimentation rate and burial of organic phosphorus and organic carbon in marine sediments organic carbon and organic phosphorus concentrations in marine sediment cores with known sedimentation rates were determined and collected from the literature with the exception of organic rich sediments from upwelling areas organic phosphorus concentrations in marine sediments do not correlate linearly with organic carbon concentrations the c p ratios of organic matter buried in marine sediments vary systematically with sedimentation rate over the range studied 0 0001 to 2 5 cm y low c p ratios 200 atomic occur in sediments with sedimentation rates both less than 0 002 cm y and greater than 1 cm y higher c p ratios up to 600 are found at intermediate sedimentation rates a simple steady state model is developed for the early diagenesis of organic carbon and organic phosphorus in marine sediments the processes included are sediment burial pore water diffusion and bacterial decomposition of organic matter by oxic respiration and sulfate reduction preferential regeneration of phosphorus relative to carbon is assumed to take place during oxic respiration the modeling shows that both organic matter preservation and the degree of elemental fractionation between phosphorus and carbon depend strongly on the overall sedimentation rate very high sedimentation rates coastal deltaic environment result in a good preservation of deposited organic matter with an initial c p ratio close to the redfield value at very slow sedimentation rates pelagic environment the oxidation of the sedimentary organic matter is nearly complete and produces a low c p residual organic material this residual organic matter may represent either refractory detrital organic compounds enriched in phosphorus or in situ synthesized low c p bacterial remains the high c p ratios at intermediate sedimentation rates slope and shelf environment reflect the preferential regeneration of phosphorus during the incomplete decomposition of the metabolizable organic matter

sources of mesoscale variability of gravity waves part i topographic excitation abstract aircraft measurements of winds and temperatures collected during the gasp program are used to study the effects of topography as a source of mesoscale variability variances of fluctuations at the mesoscale over rough terrain are enhanced up to nearly two orders of magnitude compared to nonsource regions in some cases and are frequently enhanced by an order of magnitude the implications of these episodic enhancements of variances for the vertical transports of energy and momentum are considered in the framework of gravity wave theory the observed flight data are used to estimate the momentum flux u w on several flight segments results show that the flux is generally negative with mean value 0 26 m2 s 2 and with magnitudes ranging up to 1 5 m2 s 2 spectral analysis shows that the largest contributions to the net flux come from horizontal scales of 25 x 60 km finally the observed momentum fluxes are used to infer the anisotropy factor of gravity waves over rough terrain which is foun

seasonal salinity changes during mediterranean sapropel deposition 9000 years b p evidence from isotopic analyses of individual planktonic foraminifera using stable isotopic analyses of individual tests of planktonic foraminifera with different seasonal and depth habitats we have investigated temporal variations in surface water salinities in the eastern mediterranean during the past 13 000 years low oxygen isotopic values document the presence of anomalously low salinity conditions in the eastern mediterranean at about 13 000 years b p 4000 years before the deposition of the youngest sapropel by 11 000 years b p during the deposition of presapropel sediments low salinity surface waters were more pervasive but were restricted to summer months and only affected the surface of the water column at the onset of sapropel deposition about 9000 years b p surface salinities in the eastern mediterranean had decreased by almost 4 and had extended to depths of at least 75 m the low salinity surface lens was not however a permanent feature of the eastern mediterranean during sapropel deposition low salinity surface conditions occurred in the fall and winter seasons but normal sea surface salinities returned during spring months on a seasonal and or interannual basis thus a low salinity surface lens could have existed continuously for months or decades at a time but would have been interrupted intermittently by a return to normal conditions any triggering mechanism proposed for mediterranean sapropels must account for the seasonal fluctuations and ephemeral nature of low salinity conditions in the eastern mediterranean despite normal salinities returning occasionally during spring months a low salinity surface lens may have greatly inhibited the production of levantine intermediate water prevented the formation of adriatic deep water and consequently reduced ventilation of the eastern mediterranean

further study of terrain effects on the mesoscale spectrum of atmospheric motions abstract wind and temperature data collected on commercial airliners are used to investigate the effects of underlying terrain on mesoscale variability these results expand upon those of nastrom et al by including all available data from the global atmospheric sampling program gasp and by more closely focusing on the coupling of variance with the roughness of the underlying terrain over mountainous regions the earlier results showing that variances are larger over mountains than over oceans or plains with greatest increases at wavelengths below about 80 km are confirmed statistical tests are used to confirm that these differences are highly significant over mountainous regions the roughness of the underlying terrain was parameterized from topographic data and it was found that variances are highly correlated with roughness and in the troposphere with background wind speed average variances over the roughest terrain areas range up to about ten times larger than those over the oceans these re

late pleistocene variability of the carbon isotopic composition of organic matter in the eastern mediterranean monitor of changes in carbon sources and atmospheric co2 concentrations the organic carbon isotopic record of the sapropels s1 and s3 s10 and intercalated marl oozes has been determined in a 12 m piston core from the eastern mediterranean the 13corganic values are systematically lighter mean 21 0 0 82 in all sapropels and heavier mean 18 8 1 07 in the marl oozes these differences are not due to variable marine and terrestrial organic matter mixtures because all values are heavier than modern plankton in the mediterranean there is no relationship between the corganic n ratios and the isotopic values and published information on the abundance and distribution of organic biomarkers shows that terrestrial material constitutes a minor fraction of the total organic matter temperature effects on isotope fractionation are also discounted because the change in 13corganic values between glacial and interglacial horizons is in the opposite sense diagenesis which can produce relatively small changes in the carbon isotopic composition of sedimentary organic matter under certain circumstances is unlikely to have caused the observed differences because this mechanism would cause an enrichment in 12c implying that all values were even heavier originally and there is no secular trend in the 13corganic record the observed differences in 13corganic between the two lithologies are probably produced by changes in the isotopic composition and the concentration of dissolved co2 first freshwater flooding during the formation of the sapropels caused the isotopic composition of the dissolved inorganic carbon in the surface waters of the mediterranean to become lighter because of the 13c deficiency in fresh waters hence photosynthesis would have produced isotopically lighter organic material second changes in atmospheric pco2 between glacial and interglacial periods as shown by the vostok ice core caused marked changes in the concentration of free dissolved co2 in the mixed layer lower values during glacial maxima caused a smaller fractionation of the carbon isotopes by phytoplankton whereas levels were less limiting during the interglacials concentrations of dissolved co2 could also have been much higher during the deposition of the sapropels because of the supply of regenerated co2 to the mixed layer by upwelling and this could have further lightened the 13corganic values in the sapropels themselves carbon isotope records may provide an alternative method for estimating atmospheric pco2 levels over longer time periods than can be obtained from ice cores

hydrostatic vertical velocity and incompressibility in the northern hemisphere the vertical velocity w is evaluated for the northern hemisphere from reanalysis data and two forms of the richardson equation this equation is based on the hydrostatic assumption and the thermodynamic energy equation the standard form of the richardson equation allows one to quantify the contributions to the vertical velocity of the horizontal divergence

the horizontal spectrum of vertical velocities near the tropopause from global to gravity wave scales abstractvertical motions are fundamental for atmospheric dynamics compared to horizontal motions the horizontal spectrum of vertical velocity w is less well known here w spectra are related to

geochemistry of eastern mediterranean sediments primary sediment composition and diagenetic alterations abstract two cores recovered in the eastern mediterranean were analysed for major minor and trace elements the primary chemical composition of the sediment is different at each location probably because the lithological sources and the relative biogenic contributions differ carbonates are important for the concentration of ca mg and sr whereas aluminosilicates determine the concentration of si al k li y and be and to a lesser extent that of fe cr ti mg zn and zr in sapropels organic carbon and sulphur seem to be closely related bromine mo p fe v cu zn co ni and cr are closely associated with organic and sulphidic compounds the concentration versus depth profile for organic carbon in two sapropels points to a rapid establishment of conditions that gave rise to sapropel formation followed by a gradual transition back to normal conditions the primary composition is overprinted by diagenetic processes sulphate reducing conditions occurred during and just after sapropel deposition a progressive oxidation front mechanism which became active after sapropel deposition is responsible for additional major geochemical changes this diagenetic phenomenon has strong implications for the chemistry of fe mn ni co zn cu cr v u as and sb

the use of structure functions and spectra from numerical model output to determine effective model resolution abstract the effective model resolution of three numerical weather prediction nwp models is determined from analyses of spatial structure functions and spatial spectra in this paper the effective resolution is defined as the dimensions of the rectangular spatial filter that describes the net effect of all of the nwp model s numerical filtering and smoothing effects these effects are determined by comparison of spatial statistics of the nwp model output with statistical climatologies derived from aircraft data for the upper troposphere and lower stratosphere the comparisons are based on both spatial structure functions and spatial spectra the structure function approach has fewer assumptions and fewer numerical artifacts accurate estimates of nwp effective model resolution require a robust climatology of the spatial statistics which are a function of latitude and location such as over mountainous regions an artifact in the climatology of the velocity statistics resulting from mountain waves is i

measuring area averaged vertical motions with dropsondes abstractmeasurements of vertical profiles of areal mean mass divergence vorticity and vertical velocity based on dropsondes distributed over an area of 25 000 km2 are presented the dropsondes

paleodrainages of the eastern sahara the radar rivers revisited sir a b implications for a mid tertiary trans afnrcan drainage system a complex history of cenozoic fluvial activity in the presently hyperarid eastern sahara is inferred from sir data and postflight field investigations in southwest egypt and northwest sudan sir images were coregistered with landsat and existing maps as a guide to exploration of the buried paleodrainages radar rivers first discovered by sir a field observations explain the radar responses of three types of radar rivers rr 1 rr 2 and rr 3 rr 1 broad aggraded valleys or basins filled with alluvium generally give a dark response relative to the surrounding radar bright tone of the wind roughened discontinuously sand covered bedrock of the remnant interfluves the alluvial fill in some of the rr 1 valleys gives a locally intermediate to bright response where cemented by diagenetic caco3 caliche the rr 2 type braided channels inset in the rr 1 valleys are filled with noncalichified loose sediment and are visible on sir because of the caliche effect the dark response of unconsolidated alluvium in the inset channels contrasts with the brighter response of calichified alluvium in the broad valleys the third type rr 3 narrow long bedrock incised channels which are partly visible on the ground and on landsat in areas where the sand sheet is patchy are conspicuous on sir because the dark response of their unconsolidated channel fill contrasts with the brighter response of the surrounding bedrock disconformably overlying and concealing the rr 1 valleys the rr 2 channels and parts of the rr 3 channels are eolian sand sheet sheet de deposits which in turn are locally overridden by trains of barchan dunes

redistribution and geochemical behaviour of redox sensitive elements around s1 the most recent eastern mediterranean sapropel the youngest eastern mediterranean sapropel s1 is generally believed to have formed 7 9 14c ky b p the distribution of redox sensitive elements above in and below the sharply defined organic rich unit reveal that s 1 has already suffered heavy diagenetic alteration its present thickness based on its dark colour is only a fraction of its original thickness in one core visual evidence of s1 with an inferred initial thickness of 6 cm has been destroyed and a similar thickness appears to have been lost from the tops of another two examples this is caused by oxidation of the upper reaches of s 1 by a progressive oxidation front which commenced 5 2 5 4 14c ky ago and still appears to be active in the three cores studied diagenetic relocation of many redox sensitive elements has occurred most elements expected to be enriched in sapropels or sulphide rich sediments already have maximum concentrations above or below rather than in the present s 1 layers similarities are observed in the geochemical behaviour of as fe and p of co cu mn ni and zn and of cd mo sb ti u and v the behaviour of ba is distinctive and its immobility as barite makes it an indicator for palaeoproductivity and the original high s1 corg content the elements se and i exhibit particularly large sharp concentration peaks and together are proposed as useful indicators of the present boundary between oxic and post oxic conditions

the dynamics of mesoscale winds in the upper troposphere and lower stratosphere spectral analysis is applied to infer the dynamics of mesoscale winds from aircraft observations in the upper troposphere and lower stratosphere two datasets are analyzed one collected aboard commercial aircraft and one collected using a dedicated research aircraft a recently developed wave vortex decomposition is used to test the observations consistency with linear inertia gravity wave dynamics the decomposition method is shown to be robust in the vicinity of the tropopause if flight tracks vary sufficiently in altitude for the lower stratosphere the decompositions of both datasets confirm a recent result that mesoscale winds are consistent with the polarization and dispersion relations of inertia gravity waves for the upper troposphere however the two datasets disagree only the research aircraft data indicate consistency with linear wave dynamics at mesoscales the source of the inconsistency is a difference in mesoscale variance of the measured along track wind component to further test the observed flow s consistency with linear wave dynamics the ratio between tropospheric and stratospheric mesoscale energy levels is compared to a simple model of upward propagating waves that are partially reflected at the tropopause for both datasets the observed energy ratio is roughly consistent with the simple wave model but wave frequencies diagnosed from the data draw into question the applicability of the monochromatic theory at wavelengths smaller than 10 km

the diagenetic formation of metal rich layers in sapropel containing sediments in the eastern mediterranean two cores recovered from different locations in the eastern mediterranean contain intercalations of organic rich sapropels in organic poor hemipelagic sediments in both cores enrichments of mn and fe were found in the oxidised section of the sediment above the sapropel s1 the sediments followed a diagenetic cycle which began after the sapropel formation finished about 7000 years ago first during a non steady state diagenetic phase metal rich layers were formed at a downward moving oxidation front the front decelerated at the top of the sapropel as a consequence of increasing amounts of corg and sulphides that had to be oxidised during the second part of this non steady state phase the oxidation front starts moving upwards with respect to the sapropel manganese is remobilised in preference to iron due to thermodynamics reinforced by kinetics when the upward movement of the oxidation front becomes equal to the sedimentation rate steady state is established with respect to the new organic poor sedimentary circumstances at location 31g1 the system is at or close to steady state at location 9g1 however this steady state phase has never been reached between 1900 and 1350 years bp the organic carbon accumulation rate probably increased suddenly inducing a retreat of the oxidation front and the non steady state formation of double peaks

dynamical structure and turbulence in cirrus clouds aircraft observations during fire abstract aircraft data collected during the first international satellite cloud climatology project regional experiment fire i are used to examine dynamical processes operating in cirrus cloud systems observed on 19 and 28 october 1986 measurements from lagrangian spiral soundings and constant altitude flight legs are analyzed comparisons are made with observations in clear air each cirrus case contained a statically stable layer a conditionally unstable or neutrally stratified layer ice pseudoadiabatic in which convection was prevalent and a neutral layer in which convection was intermittent the analysis indicates that a mixture of phenomena occurred including small scale convective cells gravity waves 2 9 km quasi two dimensional waves 10 20 km and larger two dimensional mesoscale waves 100 km the intermediate scale waves observed both in clear air and in the cloud systems likely played an important role in the development of the cloud systems given the magnitude of the associ

state of disequilibrium between 238u 234u 226ra and 222rn in groundwater from bedrock abstract approximately one thousand drilled wells were investigated for their natural radioactivity the determinations of 238u 234u 226ra and 222rn from 310 samples showed a high state of radioactive disequilibrium between the members of the uranium series present in water the 238 u 226 ra activity ratio usually fell in the range 1 20 and the 238 u 222 rn activity ratio in the range 1 20 10 4 the highest activity ratios being from samples with an elevated uranium content the 234 u 238 u activity ratio varied between 0 76 and 4 67 the most frequent values showing a 60 excess of 234u in the samples most of the 234 u 238 u activity ratios near unity were found in samples with a high uranium content several drilled wells with anomalously high uranium contents were found in southern finland the average 226ra and 222rn contents of these wells were not exceptionally high which suggests high mobility of uranium in groundwater from the areas involved

vertical resolution requirements in atmospheric simulation abstractthe role of vertical mesh spacing in the convergence of full physics global atmospheric model solutions is examined for synoptic mesoscale and convective scale horizontal resolutions usi

influence of water column anoxia on the burial and preservation of carbon and phosphorus in marine shales abstract organic p and organic c concentrations were measured in several well characterized phanerozoic marine shale sequences with the primary focus being the camp run member of the devonian mississippian new albany shale sequences were selected with close spatial association of bioturbated and laminated sediments which reflect deposition from oxic and anoxic waters respectively average organic c p mole ratios calculated from the data are 150 for bioturbated shales and 3900 for the laminated shales of the new albany differences in the extent and mechanisms of early diagenesis related to the oxygenation of waters at the sediment water interface can account for the c p ratios of buried organic matter low c p ratios of bioturbated sediments are attributed to 1 1 the increased ability of bacteria to store p in well oxygenated environments which leads to the production of low c p ratio bacterial biomass and 2 2 the extensive oxidation of sedimentary organic matter resulting in the formation of residual organic phases with low c p ratios high organic c p ratios of laminated sediments are explained by a combination of 1 1 the limited ability of bacteria to store p under anoxic conditions 2 2 extensive p regeneration from sedimentary organic matter 3 3 enhanced c preservation relative to the bioturbated shales it is also shown that relative to organic c laminated shales are not as effective a p sink as are bioturbated shales this provides a mechanism in anoxic environments for burying large quantities of organic matter without simultaneously sequestering the p needed to sustain further productivity

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

phosphorus forms related to sediment grain size and geochemical characteristics in french coastal areas abstract phosphorus forms with respect to sediment characteristics such as grain size and major chemical elements were studied in french coastal marine areas the bay of seine and the loire and gironde estuaries in the three areas fe al bound phosphate fe al p and exchangeable phosphate exch p were significantly related to the proportion of fine fraction calcium bound phosphate ca p was found in all grain size classes with comparable concentrations in the bay of seine where there was no correlation between ca p and ca this corresponded to the calcium s marine origin shells in the bay of seine in contrast the correlation of ca p with ca and the fine fraction of the sediment in the loire and gironde estuaries was characteristic of the predominant metamorphic origin of ca p in these areas useful information for interpretation of p forms can be obtained from major sediment characteristics thus for areas where specific relationships have previously been established good estimates of p forms could be predicted from sediment properties

an investigation of terrain effects on the mesoscale spectrum of atmospheric motions abstract wind and temperature data collected on commercial aircraft during the global atmospheric sampling program gasp are used to investigate the effects of underlying terrain on mesoscale variability and the observational results are interpreted within the theories of gravity wave motions and quasi two dimensional turbulence the data show the variances are up to six times larger over mountainous terrain than over oceans or plains with the most striking differences at horizontal scales from 4 to 80 km results were subdivided between the stratosphere and troposphere and between high and low background wind speed cases and show basically the same response to topography in all cases the linear theory of gravity waves is found to predict correctly the scaling of wave amplitude with background stability in the case of low background wind speeds while the two dimensional turbulence theory correctly predicts the shape of the variance spectrum and the observed amplitude scales with as required by t