strength and water weakening of mantle minerals olivine wadsleyite and ringwoodite rheological properties of olivine and its high pressure polymorphs both dry and hydrous have been studied by monitoring x ray diffraction peak broadening as a function of pressure temperature and time the measurements were carried out up to a pressure of 10 gpa and a temperature of 600 c for olivine and wadsleyite and a pressure of 20 gpa and a temperature of 1000 c for ringwoodite the observations indicate that olivine is much weaker than the other two minerals for this range of conditions and furthermore water weakens olivine dramatically but only slightly weakens wadsleyite and ringwoodite when the temperature increases from 25 c to 400 c the yield strength in the olivine drops by 39 without water and 62 with water however there is hardly any change in strength for wet or dry wadsleyite and ringwoodite

sound velocities and elastic constants of iron bearing hydrous ringwoodite the sound velocities and single crystal elastic constants of fo 89 hydrous ringwoodite mg1 7fe0 22h0 16sio4 containing 10 000 ppm by weight 1 wt h2o have been determined from seven separate pure mode travel time measurements using gigahertz ultrasonic interferometry the experiments feature a new yttrium aluminum garnet yag p to s conversion shear buffer rod br capable of producing pure ultrasonic shear waves with known polarization in the region of 0 5 2 0 ghz to our knowledge they are the first such single crystal ultrasonic measurements on a high pressure phase recovered from the multi anvil press the cubic single crystal elastic constants of hydrous fo 89 ringwoodite at ambient conditions are in gpa c11 298 13 c44 112 6 and c12 115 6 hydration of fo 90 ringwoodite to 1 wt h2o reduces the adiabatic bulk k0s 176 7 gpa and shear g 103 5 gpa moduli by about 6 and 13 roughly equivalent to raising the temperature at room pressure by 600 and 1000 c respectively assuming a linear trend with hydration we calculate that pand s wave velocities are reduced by about 40 m s for every 1000 ppm weight 0 1 wt h2o added to fo 90 ringwoodite p and s wave velocities of the lower transition zone in prem are consistent with a hydrated ringwoodite rich composition 2004 elsevier b v all rights reserved

the levantine intermediate water experiment liwex group levantine basin a laboratory for multiple water mass formation processes 1 in winter 1995 the last major field work of the physical oceanography of the eastern mediterranean poem program was carried out the levantine intermediate water experiment liwex in this study a thorough analysis is presented of the data set collected during three successive surveys in january february and march april 1995 the major overall result is that the levantine basin is shown to be the site for multiple and different water mass formation processes levantine deep water ldw was formed in the rhodes gyre with the preconditioning phase starting in december 1994 in late january the chimney was ventilating to the atmosphere in february the strong mixing phase is documented by the convective cell vertically homogeneous to 900 m depth in march april recapping has occurred in the upper 200 m ldw remained confined inside the rhodes gyre cyclonic circulation levantine intermediate water liw is instead deeply affected by the upper thermocline circulation shallow ventilating chimneys with the liw thermostads were found in the january survey inside the cyclonic region of the northern levantine the formation process of liw does not involve deep penetrative convection winter surface cooling and evaporation are sufficient to produce a surface mixed layer 100 m deep with liw characteristics at the mixed layer basis liw subducts and spreads along isopycnal surfaces along pathways determined by the cyclonic anticyclonic structures of the upper thermocline circulation

seasonal variability of water transport through the straits of gibraltar sicily and corsica derived from a high resolution model of the mediterranean circulation abstract the variability of the water transport through three major straits of the mediterranean sea gibraltar sicily and corsica was investigated using a high resolution model this model of the mediterranean circulation was developed in the context of the mercator project the region of interest is the western mediterranean between the strait of gibraltar and the strait of sicily the major water masses and the winter convection in the gulf of lions were simulated the model reproduced the meso scale and large scale patterns of the circulation in very good agreement with recent observations the western and the eastern gyres of the alboran sea were observed but high interannual variability was noticed the algerian current splits into several branches at the longitude of the strait of sicily level forming the tyrrhenian branch and the atlantic ionian stream and the atlantic tunisian current in the eastern mediterranean the north current retroflexed north of the balearic islands and a dome structure was observed in the gulf of lions the cyclonic barotropic algerian gyre which was recently observed during the mater and elisa experiment was evidenced in the simulation from time series of 10 day mean transport the three straits presented a high variability at short time scales the transport was generally maximum in april for the strait of gibraltar in november for the strait of sicily and in january for the strait of corsica the amplitudes of the transport through the straits of gibraltar 0 11 sv and sicily 0 30 sv presented a weaker seasonal variability than that of the strait of corsica 0 70 sv the study of the relation between transport and wind forcing showed that the transport through the strait of gibraltar is dependent on local zonal wind over short time scales 70 which was not the case for the other straits less than 30 the maximum minimum of the transport occurred for an eastward westward wind stress in the strait an interannual event was noticed in november december 2001 which corresponded to a very low transport 0 3 sv which was characterised by a cyclonic circulation in the western alboran sea that circulation was also reproduced by the model for other periods than winter during the interannual simulation the transport through the strait of sicily is not influenced by local wind the wind stress curl of the northwestern mediterranean influenced the transport through the strait of corsica

a synthesis of the levantine basin circulation and hydrography 1985 1990 abstract the levantine basin circulation derived from recent data consists of a series of sub basin scale to mesoscale eddies interconnected by jets the basin scale circulation is masked by eddy variability that modulates and modifies it on seasonal and interannual time scales long term qualitative changes in the circulation are reflected in the bifurcation pattterns of ther mid basin jets relative strengths of eddies and the hydrographic properties at the core of these eddies confinement within the basin geometry strongly influences the co evolution of the circulation features surface measurements satellite images and the mass field indicate an entire range of scales of dynamical features in the region the complexity of the circulation is consistent with the basin wide and mesoscale heterogeneity of the hydrographic properties the interannual variability of liw levantine intermediate water formation in the region appears correlated with the changes in the circulation wintertime convective overturning of water masses reach intermediate depths and constitute a dominant mechanism of liw formation especially in anticyclonic eddies and along the coasts of the northern levantine basin

variability of rhodes and ierapetra gyres during levantine intermediate water experiment observations and model results 1 this work is aimed at studying the variability of rhodes and ierapetra gyres during the levantine intermediate water experiment sea surface temperature maps derived from global area coverage advanced very high resolution radiometer avhrr data in the framework of the pathfinder project and sea level anomalies derived from topex poseidon altimeter were used to track the evolution both in terms of dimension and position of the cyclonic rhode gyre and ierapetra anticyclone the analysis was performed for the period from october 1994 to the end of april 1995 i e from the preconditioning to the spreading phase of levantine intermediate water the description of the surface fields was complemented by a temporal evolution study of the rhodes and ierapetra gyres hydrological vertical structure european centre for medium range weather forecasts avhrr derived fluxes have been used as forcing for a numerical model to study the variability of the mixed layer in both gyres the simulated upper layer dynamics remarkably matched remotely sensed and in situ observations this work shows that using a combined analysis of observational data and model simulations we were able to propose a dynamical scenario for the winter of 1995 where the levantine basin was characterized by short intense heat loss events occurring during at the beginning of december the intense air sea interaction contributed to deep instead of intermediate mixing as confirmed by remote sensing in situ data and model experiments a hypothesis on the role of the lateral contribution on the water column buoyancy content in the rhodes gyre was formulated

downwelling along the northeastern coasts of the eastern mediterranean abstract the most prominent winter storms in the eastern part of the eastern mediterranean are known as cyprus cyclones the surface wind speed is between 15 30 m s 1 and about five such cyclones occur in a typical winter the cyclone radius is between 500 and 1500 km the evolution of the sea structure under such atmospheric forcing is examined with a two dimensional numerical model in the vertical cross section perpendicular to the shore line two distinct regions result in the sea a downwelling zone near the coast about 100 km wide and a horizontally homogeneous zone in the open sea where vertical mixing is the important dynamical process in the open sea the final profiles turn out to be similar to those observed in the levantine intermediate water liw in their formation region we suggest that the liw forms in the region under the influence of these cyprus cyclones in the downwelling zone the 14 17 c isotherms decline by more than 250 m this water has the same t s properties as the water in

circulation and hydrography of the levantine basin results of poem coordinated experiments 1985 1986 abstract a brief review of the meteorological setting hydrography and the circulation in the levantine basin of the eastern mediterranean is given the recent high resolution data obtained in poem coordinated experiments of 1985 1986 are then used to optimally estimate the circulation in the basin in two different seasons and to describe the water mass distributions some of the features observed during the experiments support the historical knowledge on the locations of sub basin scale gyres and the general circulation in addition to which some new features are established details of the circulation such as the intensity the multiple scales and the three dimensional structure of the various vortices and the central levantine basin current are displayed extensively a variety of sub basin meso and sub mesoscale vortices occur with highly assymmetric baroclinic vertical structures some eddies split into multiple centres with depth interpreted as indicating possible coalescences a number of long lived eddies were persistent in both surveys the sub surface atlantic water aw is advected by and entrapped within the eddy field the levantine intermediate water liw at intermediate depths is shown to be maintained throughout the year in the northeastern sector of the levantine basin and along the periphery of the rhodes gyre the levantine intermediate water also has a patchy distribution owing to the advection and trapping by the eddy field which it helps to generate through adjustment processes

mediterranean sea large scale low frequency ocean variability and water mass formation rates from 1987 to 2007 a retrospective analysis abstract we describe a synthesis of the mediterranean sea circulation structure and dynamics from a 23 year long reanalysis of the ocean circulation carried out by adani et al 2011 this mesoscale permitting dynamical reconstruction of past ocean variability in the mediterranean sea allows the study of the time mean circulation and its low frequency decadal components it is found that the time mean circulation is composed of boundary and open ocean intensified jets at the border of cyclonic and anticyclonic gyres the large scale basin circulation is generally characterized in the northern regions by cyclonic gyres and in its southern parts by anticyclonic gyres and eddy dominated flow fields with the exception of the tyrrhenian and the northern ionian sea the time mean tyrrhenian sea circulation is dominated by cyclonic gyres of different intensity and intermittency the northern ionian sea circulation however reverses in sign in two ten year periods the first in 1987 1996 and the second in 1997 2006 which is here called the northern ionian reversal phenomenon this reversal is provoked by the excursion of the atlantic ionian stream from the middle to the northern parts of the basin the decadal variability of other parts of the basin is characterized by changes in strength of the basin scale structures the water mass formation rates and variability are dominated by event like periods where the intermediate and deep waters are formed for 2 3 years at higher rates the largest deep water formation events of the past 23 years occurred separately in the western and eastern mediterranean basin the first coincided with the eastern mediterranean transient roether et al 1996 and the second with the western mediterranean deep water formation event in 2005 2006 smith et al 2008 a new schematic of the basin scale circulation is formulated and commented

vertical distribution of marine cyanobacteria synechococcus spp in the black marmara aegean and eastern mediterranean seas abstract the vertical distributions of the unicellular cyanobacteria synechococcus were studied in several highly contrasting seas the black sea sea of marmara aegean sea and mediterranean sea cell abundances varied significantly on both vertical and horizontal scales in all physically and spatially discrete water masses epifluorescence microscope cell counts from all seas clearly showed that majority of the population remains suspended in the surface mixed layer and decreases gradually towards the base of the euphotic zone surface spatial distributions in the black sea were heterogeneous salinity rather than temperature seemed to have the greatest impact on the surface distribution of cells in this highly eutrophic sea changes in abundance in the mixed layer were small compared to the abrupt changes below the halocline especially in the black sea and the sea of marmara in contrast to the black sea the major population remains suspended above the depth of fluorescence maximum in the aegean and eastern mediterranean seas significant correlations r p 0 01 were observed between cell counts and physical and chemical parameters with depth in the black sea in all seas cells at subsurface chlorophyll a maximum layer scml reflected brighter and longer fluorescence than those present at the surface and below cell size derived from flow cytometry indicated the presence of larger cells at the surface mixed layer compared to those at depth

water transport into the deep mantle and formation of a hydrous transition zone abstract the phase relations in the peridotite water system to the top of the lower mantle reveal that a certain amount of water can be transported and stored in the transition zone by various hydrous minerals resulting in formation of a hydrous transition zone results of preliminary experiments to clarify the effect of water on kinetics of the olivine wadsleyite transformation are given and show that water enhances the transformation kinetics significantly there are potential dehydration sites in the deep mantle four sites along the descending slabs depending on their temperature profiles i e the mantle wedge of the subduction zone mantle transition zone top of the lower mantle where hydrous ringwoodite and superhydrous phase b decompose and deep in the lower mantle around 1200 1500 km depth where decomposition of phase d g occurs we also expect one site of dehydration melting at the base of the upper mantle where the hot mantle plume hydrated in the transition zone can be dehydrated the transition zone can serve as a water absorber for the mantle scale water circulation system some of the recent seismic works including the p wave tomography images reveal the existence of low velocity anomalies in the transition zone suggesting possibly a wet transition zone elevation of the 410 km discontinuity and lack of clear evidence for a metastable olivine wedge in cold slabs may be consistent with the equilibrium phase transformation from olivine to wadsleyite in cold and wet slabs on the basis of our kinetic study of the transformation under wet conditions

wintertime convection in warm core rings thermocline ventilation and the formation of mesoscale lenses large heat losses from warm core ring 82b during february march and april 1982 formed a 400 m thick thermostad in the center of the ring two different models were constructed to simulate the formation of the thermostad water mass properties a one dimensional vertical model forced with a meteorological time series and a volumetric mixing model with climatological input both models indicate that a flux of slope water into the ring is necessary to yield the observed thermostad salinities the subsequent slow decay of the ring core in the slope water suggests that such winter convected rings can easily maintain the warm band water identified by wright and parker 1976 the large loss of core water during interactions with the gulf stream suggests that the reabsorption of such winter cooled warm rings is an important source of high salinity high oxygen anomalies in the main thermocline of the sargasso sea the volume of water in a typical ring reabsorption is sufficient to generate many 20 intrathermocline eddies with t s properties close to those of recently reported lenses this suggests that many of these small eddies are much more local in origin and may be more highly dissipative than has previously been suggested an estimate of the flux of high salinity high oxygen water into the main thermocline by this mechanism leads to ventilation at a rate that is a significant fraction of the ekman pumping at these density levels thus the reabsorption of winter cooled warm core rings by the gulf stream is an important eddy ventilation mechanism for the sargasso sea

a geophysical perspective on mantle water content and melting inverting electromagnetic sounding data using laboratory based electrical conductivity profiles abstract this paper applies electromagnetic sounding methods for earth s mantle to constrain its thermal state chemical composition and water content we consider long period inductive response functions in the form of c responses from four stations distributed across the earth europe north america asia and australia covering a period range from 3 9 to 95 2 days and sensitivity to 1200 km depth we invert c responses directly for thermo chemical state using a self consistent thermodynamic method that computes phase equilibria as functions of pressure temperature and composition in the na 2 o cao feo mgo al 2 o 3 sio 2 model system computed mineral modes are combined with recent laboratory based electrical conductivity models from independent experimental research groups yoshino 2010 and karato 2011 to compute bulk conductivity structure beneath each of the four stations from which c responses are estimated to reliably allocate water between the various mineral phases we include laboratory measured water partition coefficients for major upper mantle and transition zone minerals this scheme is interfaced with a sampling based algorithm to solve the resulting non linear inverse problem this approach has two advantages 1 it anchors temperatures composition electrical conductivities and discontinuities that are in laboratory based forward models and 2 at the same time it permits the use of geophysical inverse methods to optimize conductivity profiles to match geophysical data the results show lateral variations in upper mantle temperatures beneath the four stations that appear to persist throughout the upper mantle and parts of the transition zone calculated mantle temperatures at 410 and 660 km depth lie in the range 1250 1650 c and 1500 1750 c respectively and generally agree with the experimentally determined temperatures at which the measured phase reactions olivine spinel and spinel ferropericlase perovskite occur the retrieved conductivity structures beneath the various stations tend to follow trends observed for temperature with the strongest lateral variations in the uppermost mantle for depths 300 km conductivities appear to depend less on the particular conductivity database conductivities at 410 km and at 660 km depth are found to agree overall with purely geophysically derived global and semi global one dimensional conductivity models both electrical conductivity databases point to 2 o in the upper mantle for transition zone minerals results from the laboratory database of yoshino 2010 suggest that a much higher water content up to 2 wt h 2 o is required than in the other database karato 2011 which favors a relatively dry transition zone 2 o incorporating laboratory measurements of hydrous silicate melting relations and available conductivity data allows us to consider the possibility of hydration melting and a high conductivity melt layer above the 410 km discontinuity the latter appears to be 1 regionally localized and 2 principally a feature from the yoshino 2010 database further there is evidence of lateral heterogeneity the mantle beneath southwestern north america and central china appears wetter than that beneath central europe or australia

elastic properties of hydrous ringwoodite γ phase in mg2sio4 abstract single crystal elastic properties of hydrous ringwoodite are reported for samples that were synthesized at 19 gpa and 1300 c the mg si ratio is determined to be 1 95 by epma which is slightly lower than that of ideal anhydrous ringwoodite the h 2 o content determined by sims is 2 2 wt resulting in the stoichiometry mg 1 89 si 0 97 o 4 h 0 33 the lattice parameter a 8 0786 4 a and elastic constants were determined from a single crystal with x ray diffractometry and brillouin scattering spectroscopy the crystal structure is cubic fd3m with a unit cell volume which is 0 51 larger than that of the anhydrous ringwoodite the adiabatic single crystal elastic moduli of hydrous ringwoodite in gpa are c 11 281 6 c 44 117 4 c 12 92 5 the isotropic properties of hydrous ringwoodite are k vrh 155 4 and g vrh 107 3 which are about 16 and 10 smaller than those of anhydrous ringwoodite thus hydrous ringwoodite if present drastically reduces the seismic velocity in the mantle transition zone relative to anhydrous ringwoodite in addition our results show that the anisotropy is enhanced relative to anhydrous ringwoodite using the present results we discuss the 520 km seismic discontinuity in a wet mantle transition zone

water partitioning in the earth s mantle abstract we have conducted h2o partitioning experiments between wadsleyite and ringwoodite and between ringwoodite and perovskite at 1673 k and 1873 k respectively these experiments were performed in order to constrain the relative distribution of h2o in the upper mantle the mantle transition zone and the lower mantle we successfully synthesized coexisting mineral assemblages of wadsleyite ringwoodite and ringwoodite perovskite that were large enough to measure the h2o contents by secondary ion mass spectrometry sims combining our previous h2o partitioning data chen et al 2002 with the present results the determined water partitioning between olivine wadsleyite ringwoodite and perovskite under h2o rich fluid saturated conditions are 6 30 15 1 respectively because the maximum h2o storage capacity in wadsleyite is 3 3 wt e g inoue et al 1995 the possible maximum h2o storage capacity in the olivine high pressure polymorphs are as follows 0 7 wt in olivine upper mantle just above 410 km depth 3 3 wt in wadsleyite 410 520 km depth 1 7 wt in ringwoodite 520 660 km depth and 0 1 wt in perovskite lower mantle if we assume 0 2 wt of the h2o content in wadsleyite in the mantle transition zone estimated by recent electrical conductivity measurements e g dai and karato 2009 the estimated h2o contents throughout the mantle are as follows 0 04 wt in olivine upper mantle just above 410 km depth 0 2 wt in wadsleyite 410 520 km depth 0 1 wt in ringwoodite 520 660 km depth and 0 007 wt in perovskite lower mantle thus the mantle transition zone should contain a large water reservoir in the earth s mantle compared to the upper mantle and the lower mantle

currents water masses eddies and jets in the mediterranean levantine basin abstract hydrographic measurements in the southeastern levantine basin are analyzed and the climatological water masses of the region and their seasonal variations are identified we observe the formation of the salty and warm levantine surface water layer lsw we characterize the subsurface atlantic water layer aw and we describe the properties of the thermocline waters called levantine intermediate waters liw the baroclinic dynamical modes are computed for the climatological stratification parameters the empirical orthogonal function eof analysis of the vertical shear profiles shows that considerable energy is contained in the second eof at the thermocline and deep levels maps of the baroclinic streamfunction field referred to 700 meters are displayed 16 instantaneous flow field realizations show an intense mesoscale eddy file never revealed before in the region the space scales of the eddies are about 100 km and a smaller scale 60 70 km variability is also evident the eddies are pres

small synoptic mesoscale eddies and energetic variability of the eastern levantine basin mesoscale eddies are energetically dominant over most of the world s ocean1 the local dynamics of eddies is now a central problem of physical oceanography2 and their statistics control aspects of the general circulation3 the horizontal scale of eddies is generally related to but somewhat larger than the rossby internal deformation radius the depth scale multiplied by the buoyancy frequency divided by the coriolis frequency in the eastern mediterranean which is not well explored or understood the internal radius is known to be 12 km or 4 times smaller than in the north atlantic the study of such eddies requires very fine sampling which hinders their accidental discovery by using a dedicated data set and objective analysis methods we have estab ished the existence of small synoptic mesoscale eddies and jets which constitute a variable and turbulent current regime and dominate the general circulation flow of the levantine basin their existence in the mediterranean has an impact on all aspects of basic and applied marine science there both conceptually and with respect to experimental and monitoring programme designs

a synthesis of the ionian sea hydrography circulation and water mass pathways during poem phase i abstract in this paper we revisit with a thorough in depth analysis the dataset collected in the hydrographic surveys of the international collaborative programme poem physical oceanography of the eastern mediterranean in the period 1986 1987 the work has two major objectives the first is to refine the dynamic picture of the ionian upper thermocline sub basin scale circulation rather less definitive than the dynamic picture of the levantine sea circulation the second is to identify the pathways of the major water masses of the basin not only in the near surface but also in the intermediate and deep layers to our knowledge this is the first work defining the pathways of the levantine intermediate water liw and of the adriatic deep water adw eastern mediterranean deep water emdw that characterize the intermediate and deep circulations the major novel results can be summarized as follows in the upper thermocline 1 the atlantic ionian stream ais jet entering the sicily straits bifurcates into two main branches at 37 n 17 e it advects the modified atlantic water maw into the ionian sea interior the first branch turning directly southward encloses an overall anticyclonic area comprising multiple centers around which the maw is advected 2 the second ais branch extends further into the northeastern ionian where it too turns southward before crossing the entire ionian sea meridionally advecting maw on its left side and ionian surface water isw on its right this branch of the jet is confined to the ionian margin and does not pass around the pelops gyre 3 a new water mass the lsw is formed in the levantine basin and enters the cretan passage then is first veered cyclonically south of crete by the cretan gyre and successively is entrained anticyclonically around the pelops gyre and then enters the aegean sea 4 a permanent cyclone located in the northeastern ionian determines the pathway of mixed adriatic surface water ionian surface water asw isw 5 a permanent cyclone is found in all the surveys near the tip of the italian boot this novel analysis of the liw pathways shows that 1 the major source of intermediate liw during the period 1986 1987 was actually in the levantine sea liw formed there entered the cretan passage was veered cyclonically by the cretan gyre south of crete and then entered the southern ionian sea the major liw pathway was westward directly to the sicilian straits 2 secondary important liw pathways were determined by the interior structures the strong pelops anticyclone was entraining liw around its periphery and was determining the liw northward pathway that closely followed the eastern greek coastline it was along this pathway that liw entered the otranto strait a further branch of liw was entrained and recirculated around the multiple ionian anticyclones ia of the western ionian sea 3 the cretan cyclone is a feature confined to the upper thermocline intermediate layer it disappears at 400 dbar while the pelops anticyclone is strongly barotropic below the upper 100 dbar and penetrates quite intense down to 800 dbar 4 a further completely novel result concerns the new water mass found in the deep layer that spreads on the 29 15 kg m3 isopycnal surface this water mass characterized by high salinity and high oxygen content is formed inside the aegean sea and is observed to spread out all around the cretan arc straits the final fully novel result is the demonstration of a second pathway for the adw exiting from the otranto strait that is transformed into emdw and occupies the abyssal layers of the ionian sea interior the traditional pathway for emdw is along the isobaths along the western side of italy but adw was observed to be exiting from the otranto strait in the eastern hellenic trench at 39 5 n both during poem on86 and poem as87 this second pathway for emdw follows isobath contours along the western side of greece the two emdw routes converge and merge between 36 n and 35 n so producing a deep layer of emdw that occupies uniformly the abyssal plain of the interior of the ionian sea

water mass properties and dynamic conditions of the eastern mediterranean in june 2007 abstract five locations in the eastern mediterranean situated in the ionian sea cretan passage and levantine basin were characterized for their physical and biogeochemical properties on the basis of the data collected during an oceanographic cruise in june 2007 basinwide subbasin and mesoscale surface dynamic features are described in terms of absolute dynamic topography of the sea surface sea surface temperature and chlorophyll a distribution additional information along the ship s track was acquired via the vessel mounted thermosalinograph and the acoustic doppler current profiler providing data on temperature salinity and marine current the latter helped identify the depth penetration

sound velocities of hydrous ringwoodite to 16 gpa and 673 k article i nfo 0 026 si1 00h0 179o4 with 1 1 wt h2o using brillouin scattering combined with x ray diffraction in an externally heated diamond anvil cell up to 16 gpa and 673 k up to 12 gpa at 300 k the presence of 1 1 wt h2o lowers the elastic moduli of ringwoodite by 5 9 but does not affect the pressure derivatives of the elastic moduli compared to anhydrous ringwoodite the reduction caused by hydration is significantly enhanced when temperatures are elevated at high pressures at 12 gpa increasing temperature by t 100 k leads to a 1 3 2 4 reduction in the elastic moduli c11 c12 and c14 comparing our results with seismic observations we have evaluated the potential h2o content in the lower part of the transition zone our results indicate that the observed seismic velocity anomalies and related depth depression of the 660 km discontinuity could be attributed to thermal variations together with the presence of 0 1 wt h2o 2012 elsevier b v all rights reserved

effect of water in depleted mantle on post spinel transition and implication for 660 km seismic discontinuity abstract we have determined the post spinel transition boundary in anhydrous and hydrous mg2sio4 in a temperature range from 1173 to 2023 k at 19 3 25 4 gpa using synchrotron in situ x ray diffraction measurements the phase boundary in mg2sio4 is located at 22 gpa and 1800 k and 22 1 gpa and 1500 k which is slightly lower 0 3 0 5 gpa than that determined in the previous in situ measurements using the same pressure scale e g katsura et al 2003 post spinel transition in mg2sio4 determined by high p t in situ x ray diffractometry phys earth planet inter 136 11 24 the clapeyron slope of mg2sio4 was found to be gentle i e between 0 4 and 0 7 mpa k which is also consistent with previous in situ measurements but inconsistent with diamond anvil cell experiments and theoretical estimations the phase boundary in mg2sio4 2 wt h2o which is relevant to fe free depleted harzburgitic composition is located between 23 4 and 23 6 gpa and 1500 k which shifts the hydrous boundary to the higher pressures relative to anhydrous mg2sio4 from 1 3 to 1 0 gpa the result for hydrous mg2sio4 shows steeper clapeyron slope between 3 2 and 3 1 mpa k compared with anhydrous mg2sio4 and hydrous pyrolite system the present data suggest that water has a strong influence on 660 km discontinuity and the depressions observed at this boundary in several regions especially related to subduction zones can be explained by the presence of water in depleted harzburgite component

first principles determination of the structure and elasticity of hydrous ringwoodite 1 the mechanism by which hydrogen is incorporated in ringwoodite affects the density composition and elasticity of the mineral with implications on the seismic velocities of earth s transition zone this study uses density functional theory to calculate the structure elasticity and energetics of each of three possible defect mechanisms for the incorporation of hydrogen in ringwoodite relative energetics of the defects predict that the three defects exist in ratios of 64 10 25 for the vmg 2h mgsi 2h and vsi 4h defects respectively results of a least squares fit to existing experimental data on hydrous ringwoodite produce a best fit model including each of the three defects in ratios of 75 11 14 therefore 51 66 of the hydrogen in hydrous ringwoodite is associated with vmg defects 8 10 is associated with mgsi defects and 24 41 is associated with vsi defects one wt h2o decreases seismic wave velocities by an amount equivalent to 200 350 k temperature increase the seismic parameter dlnvs dlnvp owing to hydration is twice that owing to temperature and reduces the impedance contrast at the 520 km boundary allowing for the separation of the effects of water and temperature in the lower transition zone

high water solubility of ringwoodite at mantle transition zone temperature abstract the mantle transition zone a potential water reservoir in the earth s interior is suggested to contain more than 1 wt of h2o at least locally by the natural water rich ringwoodite inclusion pearson et al 2014 and the mineral viscosity fei et al 2017 it is against the low h2o solubility of ringwoodite ohtani et al 2000 we revisited the h2o solubility in ringwoodite at 1600 2000 k showing that both iron free and iron bearing ringwoodite can store about 0 8 1 2 wt of h2o under mantle transition zone conditions temperature has a relatively small effect on the h2o solubility in iron bearing system but much larger in iron free one the high h2o solubility of ringwoodite is compatible with the water rich mantle transition zone the relatively low values reported previously is probably due to insufficient h2o source or unbuffered by sio2

surface circulation of the levantine basin comparison of model results with observations the eastern mediterranean levantine basin hydrography and circulation are investigated by comparing the results of a high resolution primitive equation model with observations after a 10 year integration the model is able to reproduce the major water masses and the circulation patterns of the eastern mediterranean comparisons with the poem hydrographical observations show good agreement the vertical distribution of the water masses matches that of the observations quite well in terms of monthly mean the model surface circulation is in agreement with circulation schemes derived from recent observations some well known mesoscale features of the upper thermocline circulation are also realistically reproduced in agreement with satellite observations the model shows that high energy mesoscale eddies dominate the upper thermocline circulation in the southern and the central parts of the levantine basin most of the atlantic water follows the north african coast and forms a strong coastal jet near the libyan coast rather than forming the mid mediterranean jet described by several authors the sub basin circulation shows a strong seasonal signal a strong and stable current flows along the isobaths in winter becoming weaker and with more meanders in summer the mesoscale eddies throughout the whole basin are more energetic in summer than in winter

effect of hydration on the single crystal elasticity of fe bearing wadsleyite to 12 gpa the single crystal elastic properties of fe bearing wadsleyite with 1 93 wt h2o mg1 634fe0 202h0 305sio4 have been determined by brillouin scattering at ambient conditions the aggregate bulk and shear moduli ks0 g0 of this wadsleyite are 156 2 5 and 98 0 3 gpa respectively compared to the corresponding anhydrous wadsleyite 1 93 wt h2o lowers ks0 and g0 by 8 1 and 9 3 respectively high pressure measurements up to 12 gpa show that the pressure derivative of

hydrogen site analysis of hydrous ringwoodite in mantle transition zone by pulsed neutron diffraction hydrogen site positions and occupancies in the crystal structure of synthetic hydrous ringwoodite have been determined for the first time by high resolution neutron powder diffraction conducted at the pulsed neutron source at japan proton accelerator research complex j parc it is demonstrated that hydrogen exchanges not only with mg or fe but also with si cations to form hydroxyl and hydrogen bonding both within the relevant octahedra or tetrahedra created by their surrounding oxygen anions the hydrated octahedra shrink whereas the hydrated tetrahedra expand the occurrence of simultaneous hydration of octahedra and tetraheda is thus unambiguously confirmed whereby the latter plays an especially unique role in reducing seismic velocity and for enhancing the electrical conductivity of ringwoodite at high pressures and temperatures these results provide distinctive implications for discussing the physical properties of hydrous ringwoodite occurring in the mantle transition zone and evaluating the actual water content in the zone

a synthesis of the circulation and hydrography of the south aegean sea and the straits of the cretan arc march 1994 january 1995 abstract four seasonal oceanographic cruises were carried out in the eastern mediterranean sea within the framework of the cec mast mtp project pelagos during 1994 1995 the surveys covered the south aegean sea and the adjacent open sea regions southeastern ionian northwestern levantine analysis of ctd data revealed that a multiscaled circulation pattern prevails in the area it differs from the circulations detected during the 1986 87 thus indicating interannual variability cyclonic and anticyclonic gyres and eddies are interconnected by currents and jets variable in space and time most of the features are persistent others seem transitional or recurrent the hydrological structure is also complex and apart from the upper layer does not present basinwide any significant seasonality dynamical and hydrological regimes are variable in the upper and intermediate layers at the straits of the cretan arc while the deep regime seems rather constant topographic control is evident on the flows through the straits the new very dense deep water mass namely the cretan deep water cdw and a well defined intermediate layer of minimum temperature and salinity the so called transition mediterranean water tmw consists the new important structural elements of the south aegean sea the cdw outflows towards the deep and bottom layers of the eastern mediterranean thus considerably contributing to the formation of the new denser deep and bottom water of the eastern mediterranean which sinks and displaces the eastern mediterranean deep water of adriatic origin in the adjacent sea regions outside the aegean sea

structure and evolution of warm core eddies in the eastern mediterranean levantine basin two recent cruises of the r v shikmona provided detailed coverage of a large portion of the levantine basin of the eastern mediterranean the first cruise was conducted in october 1985 corresponding to late summer and the second was in march 1986 corresponding to the following winter an objective analysis of the combined conductivity temperature depth and expendable bathythermograph data from these cruises reveals a variety of warm core and cold core mesoscale eddies during both seasons some of these features are unique to each cruise while others appear to retain their identities from summer to winter of the latter there are two intense anticyclonic eddies one of these appears to have formed off the coast of egypt as a meander of the north african current the other is a rather persistent quasi stationary feature to the southeast of cyprus which has been seen near this location for over 3 years lack of adequate satellite images for the period and region covered led us to use water mass properties to identify and track the development of these two eddies below the layer of seasonal influence it was found that each eddy had a unique signature in its ts diagram which changed very little over the 6 months covered by the two cruises and the period between them the water mass properties also provide additional evidence as to the possible formation regions for these two eddies

mean sea level and surface circulation variability of the mediterranean sea from 2 years of topex poseidon altimetry we describe the circulation and mean sea level variations of the mediterranean sea from 2 years of topex poseidon altimetric data it is first shown that the response of the mediterranean sea to atmospheric pressure forcing is close to an inverse barometer except at high frequencies which means that the adjustment is accompanied by a flow through the straits of sicily and gibraltar we then use topex poseidon to study the mean sea level variations representing steric effects and integrated large scale changes of the mass of the mediterranean sea we observe an annual cycle with a fast drop during winter steric effects account for about half of the observed variations the remaining signal is believed to be driven by evaporation minus precipitation e p forcing and internal hydraulic control in the straits of gibraltar using suboptimal space time objective analysis the classic components of the mediterranean surface circulation are recovered despite low signal to noise ratio the rms of sea level variability is less than 10 cm the variable mediterranean circulation is seen as a complex combination of mesoscale and large scale variations the surface circulation is more complex in the eastern basin than in the western basin in the east it is composed of subbasin scale gyres such as the so called mersa matruh and shikmona gyres which do not have an obvious recurrence period we also observe an intensification of the large scale cyclonic winter circulation in the western and in the ionian basins several mesoscale structures such as the alboran gyres and the ierepetra gyre show a clear seasonal cycle with a maximum in summer the good qualitative and quantitative agreement of the results with previous data from the mediterranean illustrates the improved accurary of topex poseidon over its predecessors

structure and dynamics of the rhodes gyre system and dynamical interpolation for estimates of the mesoscale variability abstract a coastal quasigeostrophic qg methodology is extended in an exploration of the mesoscale variability of the rhodes gyre region of the eastern mediterranean sea given multiscale data taken as part of the poem program standard objective analysis procedures are modified to include a coastal constraint that prohibits geostrophic flow normal to the coastline and imposes a characteristic nearshore variability in the coastal portion of the domain objectively analyzed fields are dynamically adjusted in short qg model integrations and then interpreted for the structure and characteristics of the subbasin scale flow system and the mesoscale two week simulations are then performed to explore the stability of the subbasin scale flow the dynamical balances and the variabilities and interactions of the mesoscale a matrix of simulation experiments is described to test the sensitivities to two variations in initial conditions and three parameterizations of the bottom topography an energy and vorticity

long term evolution and dynamics of a persistent warm core eddy in the eastern mediterranean sea abstract shipboard data from seven cruises covering april 1988 october 1990 are analyzed to follow the dynamical evolution of a persistent warm core eddy located to the southeast of cyprus the eddt is characterized by an isothermal isohaline lens of water wedged between the seasonal and permanent thermoclines in the winter this thermostad extends from the surface to a depth of nearly 400 m while in other seasons it lies in the layer from 200 to 400 m the data indicate that the temperature and salinity of the core of the eddy remained constant throughout most of 1989 and then increased abruptly with a slight increase in in the winter of 1989 1990 the velocity jet usually appears between the surface and 200 m at a mean distance of 35 km from the center of the eddy speeds in the jets typically exceed 25 cm s 1 and occasionally reach 50 cm s 1 during 1989 the eddy spins down as indicated by a loss of kinetic energy this weakening permits an abrupt renewal or exchange of core water during the winter of 1989 1990 the remnants of the previous core are apparently forced to sink into the permanent thermocline where the water may be free to spread laterally if the cross isopycnal gradient of potential vorticity is weak this process could explain the cycle of levantine intermediate water formation in the centers of warm core eddies and its eventual lateral spreading finally the eddy slowly begins to spin up again in 1990

oligocene to present shallow subduction beneath the southern puna plateau abstract the southern puna plateau is a conspicuous example of a high elevation orogenic plateau in a non collisional setting this orogenic sector is currently located above an anomalously shallow subduction segment in which timing and relation to upper plate tectonics have been widely overlooked this subduction segment here referred to as the southern puna shallow subduction spss is characterized by a 200 km wide shallow area located at 300 km from the trench at a depth of 100 120 km and dipping 10 12 to the east to determine the onset of the spss and its link to the tectonic and magmatic activity in this region we analyzed the tectonomagmatic record of the southern puna plateau from preexisting datasets also we present a new approach based on global subduction data that provides a straightforward methodology to extract potential paleo slab angles from the bedrock arc record this analysis reveals that a pronounced eastward arc front migration and magmatic broadening took place at 26 ma and was preceded by 4 ma of reduced magmatic activity which we link to the inception of the spss as expected in shallow subduction settings a change to basement cored distributed deformation south of 25 s in the southern puna plateau coincides with the beginning of shallow subduction also the spss is coincident with the enigmatic post eocene intraplate deformation of the otumpa hills located at 950 km from the trench we suggest that this succession of events is not fortuitous and that the development of the spss impacted directly the overriding plate since the oligocene contributing to the building of one of the largest topographies 3 km and thickest orogenic crusts 70 60 km on earth the shallow subduction would have acted jointly with cenozoic changes in plate kinematics and climate enhancing andean orogenesis at studied latitudes

continuing influence of the changed thermohaline circulation in the eastern mediterranean on the distribution of dissolved oxygen and nutrients physical and chemical characterization of the water masses 1 changes in the vertical distribution of the physical and chemical parameters observed during this study point to the continuing spatial and temporal evolution of the eastern mediterranean deep water emdw these changes influenced primarily the water column below 800 m and confined the old emdw of adriatic origin to the 1000 2000 m in the levantine uplifting the minimum oxygen maximum nutrient minox maxnut from 2500 m in 1995 to 1500 m in 1999 the denser and younger emdw of aegean origin emdwaeg appeared at the bottom layer more evident at the central eastern mediterranean and moving prevalently into the levantine basin younger water still intruded the central area at intermediate depths in the levantine intermediate waters liw oxygen decreased and nutrients increased westward in agreement with its pathway across the basin however a temporal decrease in oxygen and concurrent increase in nutrient was found in the liw because of its confinement in the levantine by anticyclonic features temporal changes were also found in the emdw at the western ionian and eastern cretan passage the differences in the vertical placement of the minox maxnut layer among the different areas were explained by the physical processes but the relative displacement of the extreme points within the same area were probably a result of oxidation of particulate matter poorer in nitrogen and phosphorus in the levantine than in the ionian maximal concentrations of silicic acid were located deeper than the other nutrients because of the slower chemical dissolution of silicious tests the n p molar ratios at the emdw were high 26 2 30 7 highest in the younger emdwaeg these differences could not be explained by different dissolved inorganic nutrients concentration at the sources nor by the composition of particulate matter in the euphotic zone it was suggested that dom may have a significant role in determining those differences however data on dom concentration and composition across the basin is lacking in order to test this hypothesis