dansgaard oeschger and heinrich event imprints in alboran sea paleotemperatures past sea surface temperature sst evolution in the alboran sea western mediterranean during the last 50 000 years has been inferred from the study of c37 alkenones in international marine global change studies md952043 core this record has a time resolution of 200 years allowing the study of millennial scale and even shorter climatic changes the observed sst curve displays characteristic sequences of extremely rapid warming and cooling events along the glacial period comparison of this alboran record with 18o from greenland ice greenland ice sheet project 2 core shows a strong parallelism between these sst oscillations and the dansgaard oeschger events five prominent cooling episodes standing out in the sst profile are accompanied by an anomalous high abundance of neogloboquadrina pachyderma sinistral which is confined to the duration of these cold intervals these features and the isotopic record reflect drastic changes in the surface hydrography of the alboran sea in association with heinrich events hl 5

post calabrian sequence stratigraphy of the northwestern alboran sea southwestern mediterranean abstract the post calabrian sedimentary column of the northwestern alboran sea comprises three depositional sequences the two older depositional sequences are defined by lowstand systems tracts shelf margin deltas slope base of slope and basin deposits and the guadiaro channel levee complex in contrast the most recent depositional sequence also includes transgressive relict shelf facies and high stand the guadalmedina guadalhorce prodelta and hemipelagic facies systems tracts the stratigraphic architecture of these depositional sequences is controlled by the synchronism between high frequency sea level changes variations in sediment supply and sedimentary processes the configuration of the depositional sequences is variable and their distribution is complex as a result of the relative importance played by sea level changes and tectonism through the area the sequence boundaries are represented by polygenetic surfaces in the proximal margin and by monogenetic surfaces in the distal margin and basin each polygenetic surface results from the interaction between the sequence boundary with the lowstand erosional truncation surface and the transgressive surface both developed during the previous sea level cycle the monogenetic surfaces correspond to unconformities and their correlative conformities formed during sea level lowstands this pattern of depositional sequences developed in the margin and basin of the northwestern alboran sea shows differences with the exxon sequence stratigraphy model as traditionally applied sea level change control is essentially recognized through lowstand systems tracts and sequence boundary coincides with lowstand erosional truncation surface and transgressive surface both developed during the previous sea level cycle

effect of commercial trawling on the deep sedimentation in a mediterranean submarine canyon abstract in order to study sediment accumulation rates in the palamos submarine canyon northwestern mediterranean during the last century three sediment cores were extracted from the canyon axis at depths of 450 1200 and 1750 m respectively where instrumented moorings were previously located estimated sedimentation rates based on 210 pb and 137 cs profiles suggest that the contemporary trends of sediment transfer and accumulation in the canyon may be different from secular trends during the seventies a two fold increase of the sediment accumulation rate took place at the 1750 m depth site this change has been associated to trawling activities and is attributed to the rapid technical development that the local trawling fleet underwent during the seventies the surroundings and rims of submarine canyons are frequently targeted by commercial trawling fisheries an activity that may enhance the input of resuspended particles into canyons and eventually trigger sediment gravity flows our results suggest that the effects of trawling over the dynamics of the seafloor may extend further and deeper from the fishing grounds eventually extending to bathyal depths hence the anthropogenic influence on the sedimentary budget of some deep submarine environments may be more important than previously thought

210pb manganese and carbon indicators of focusing processes on the northwestern mediterranean continental margin abstract organic carbon contents 210 pb data and organic and oxidised forms of manganese in sediments are used for reconstructing the shelf and deep sea transport of particulate matter and for evaluating early diagenesis conditions the latter are used as indicators of focusing processes on the northwestern mediterranean continental margin twelve different physiographical sites were sampled between 400 and 2000 m in the pyrenean and golfe du lion canyon axes and on their open slopes in the canyon axes which indent the pyrenean slope 210 pb activities show a regular exponential decrease with sediment depth computed sedimentation rates range from 170 to 198 cm 10 3 yr for an identical regular exponential decrease in the golfe du lion canyon the sedimentation rate is lower 119 cm 10 3 yr on the lower open slopes and deep sea fans rapid deposition turbidites and surficial sliding occurs onto sediments that were deposited regularly at a rate of about 175 cm 10 3 yr a deposit enriched in organic carbon is identified at mid slope between 500 and 1300 m in this area surface sediments of the canyon axes are richer in organic carbon than at the adjacent open slope sites 0 9 against 0 6 dry weight canyon axes are more active than open slopes as channels for organic matter transfer in the axial channel of the pyrenean canyon organic carbon decreases exponentially in the uppermost 12 cm in the golfe du lion canyons only the upper 2 cm of sediment are enriched in organic carbon this is related to lower sedimentation rates in the golfe du lion area as compared to the pyrenean area on the upper and lower open slopes the organic carbon contents decrease rapidly within 1 2 cm of sediment there is no exponential evolution profile and the residence times at the sediment water interface are longer than in the canyons the highest surface mn concentrations are also found in the middle of the continental slope the average is 64 g g 1 for mn associated with the organic phase mn org and 1400 g g 1 for mn ox as for organic carbon contents canyons are areas of high concentrations the lowest values 4 g g 1 for mn org and 495 g g 1 for mn ox are found for the lower open slope 1200 1700 m where there is active surficial remobilisation and gravity mass movements moreover the vertical distribution of mn has allowed us to identify sites located at depths of about 1000 m where the redox discontinuity is located in the first few centimetres and where the mn ox and the mn org profiles display a positive gradient from the deepest layers to the sediment water interface the distribution of the various parameters was caused by three different mechanisms 1 bottom advection of particulate matter transferred from the continental shelf deposits to the slope along the canyon axes 2 scavenging of the dissolved phases of metals and 3 sedimentary focusing of the particles in a favoured area of the continental slope a mid slope depocenter these data contribute to our knowledge of the role of continental margins in the global recycling of carbon and other materials

increasing sediment accumulation rates in la fonera palamos submarine canyon axis and their relationship with bottom trawling activities previous studies conducted in la fonera palamos submarine canyon nw mediterranean found that trawling activities along the canyon flanks cause resuspension and transport of sediments toward the canyon axis 210pb chronology supported by 137cs dating applied to a sediment core collected at 1750 m in 2002 suggested a doubling of the sediment accumulation rate since the 1970s coincident with the rapid industrialization of the local trawling fleet the same canyon area has been revisited a decade later and new data are consistent with a sedimentary regime shift during the 1970s and also suggest that the accumulation rate during the last decade could be greater than expected approaching 2 4 cm yr 1 compared to 0 25 cm yr 1 pre 1970s these results support the hypothesis that commercial bottom trawling can substantially affect sediment dynamics and budgets on continental margins eventually initiating the formation of anthropogenic depocenters in submarine canyon environments

late holocene fine grained sediments of the balearic abyssal plain western mediterranean sea abstract the late holocene fine grained sedimentation in the deep central balearic abyssal plain western mediterranean sea has been studied after the analysis of high quality sediment cores from three multicoring stations named a b and c the coring stations are 25 km apart from each other and form a triangle that is at the greatest distance from the nearest landmasses the sediments consist of foraminifer pteropod oozes layers u1 and u4 from bottom to top two pteropod oozes u2 and u5 and a turbidite layer u3 the same sequence has been identified in the three cores the turbidite layer u3 that lies on top of u2 14 c ams dated at 1814 cal yrs bp ranges from 5 to 11 cm thick and is clearly distinguished from the dominating hemipelagic sediments by colour variations higher water content and the absence of planktonic foraminifer shells rather uniform values of organic carbon and nitrogen are also characteristic of the u3 turbidite unit likely because of homogenisation during transport and emplacement in addition u3 unit shows higher contents of terrigenous elements such as k and fe otherwise the presence of zeolites in the turbidite layer supports the hypothesis of the sardinian continental margin where pyroclastic deposits are known as the most likely source area for u3 our results demonstrate the ability of turbidity currents originating on the margins surrounding the balearic abyssal plain to reach the very centre of the basin during high sea level still stands as the present one

significance of bottom currents in deep sea morphodynamics an example from the alboran sea we present an interdisciplinary study of the geomorphology sedimentology and physical oceanography of the alboran sea south western mediterranean sea to evaluate the potential role of bottom currents in shaping the spanish and moroccan continental margins and adjacent basins bathymetric and seismic data have allowed the recognition of the contourite deposits including depositional plastered sheeted channel related mounded confined elongated and separated drifts erosive moats channels and furrows and mixed terraces and scarps features hydrographic data offer new insights into the distribution of the mediterranean water masses and reveal that bottom circulation of the western intermediate water wiw and the levantine intermediate water liw interact with the spanish slope and the western mediterranean deep water wmdw on the moroccan slope spanish base of slope and deep basins the integration of distinct datasets and approaches allows a proposal of a new sedimentary model for the alboran sea that details the significance of bottom current processes in shaping deep sea morphology this model considers the bottom circulation of water masses governs physiography that interface positions of water masses with contrasting densities sculpt terraces on a regional scale and that the morphologic obstacles play an essential role in the local control of processes and water mass distributions our findings demonstrate the pivotal role of bottom water circulation in seafloor shaping and sedimentary stacking patterns for continental margins establishing a new outlook for future studies of deep marine sedimentation

coherent millennial scale patterns in u37k and tex86h temperature records during the penultimate interglacial to glacial cycle in the western mediterranean 1 the tex86h temperature proxy is a relatively new proxy based on crenarchaeotal lipids and has rarely been applied together with other temperature proxies in this study we applied the tex86h on a sediment core from the alboran sea western mediterranean core odp 977a covering the penultimate climate cycle that is from 244 to 130 ka and compared this with previously published sea surface temperatures derived from the u37k of alkenones of haptophyta and mg ca records of planktonic foraminifera the tex86h temperature record shows remarkably similar stadial interstadial patterns and abrupt temperature changes to those observed with the u37k palaeothermometer absolute tex86h temperature estimates are generally higher than those of u37k though this difference 3 c in 81 of the data points is mainly within the temperature calibration error for both proxies suggesting that crenarchaeota and haptophyta experienced similar temperature variations during occasional events 5 of the analyzed time span however the tex86h exhibits considerably higher absolute temperature estimates than the u37k comparison with mg ca records of planktonic foraminifera as well as other mediterranean tex86 and u37k records suggests that part of this divergence may be attributed to seasonal differences that is with tex86h reflecting mainly the warm summer season while u37k would show annual mean biases in the global calibration of both proxies or specific biases in the mediterranean are an alternative though less likely explanation despite differences between absolute tex86h and u37k temperatures the correlation between the two proxies r2 0 59 95 significance provides support for the occurrence of abrupt temperature variations in the western mediterranean during the penultimate interglacial to glacial cycle

particle mixing rates in sediments of the eastern equatorial pacific evidence from 210pb 239 240pu and 137cs distributions at manop sites abstract particle mixing rates db calculated from excess 210pb gradients in sediments of the east equatorial pacific range from 0 04 to 0 5 cm2 y with variation of a factor of 3 4 at a single site diffusion of the 236ra daughter 222rn may affect 210pb distributions under conditions of slow mixing and low 210pb flux to the seafloor as shown by a siliceous ooze clay core which contained the fallout radionuclides 239 240pu and 137cs but no excess 210pb relative to 226ra there is no clear relationship between 210pbderived mixing rates and sediment type accumulation rate or organic carbon flux to the sediments comparison of 210pb mixing rates with those calculated from 239 240pu and 137cs distributions reveals better agreement for a pulse input of the fallout radionuclides db 0 03 0 4 cm2 y than for continuous input at a constant rate db 0 1 1 6 cm2 y although the pu and 137cs data are better fit by the latter model the agreement may be fortuitous because 239 240pu and 137cs appear significantly deeper than 210pb in at least one core tracer separation could be caused by particle size selective mixing by the benthic fauna or by chemical mobilization if the fallout radionuclides are scavenged from surface waters by large organic rich particles such as fecal pellets their release and migration may result from decomposition of the carrier in surface sediments either a relatively unreactive form of pu e g oxidized pu has been released by this process or a one dimensional model is inadequate to explain its observed penetration into the sediments activity ratios of 239 240 pu 137 cs in the sediments decrease with increasing north latitude and the trend reflects higher fluxes of 239 240pu near the weapons test site at christmas island 2 n the 239 240 pu 137 cs ratios and fluxes to the sediment assuming constant input at the siliceous ooze red clay site are consistent with published sediment trap data from a nearby site thus if fallout radionuclide fluxes to the sea floor were higher in the past both 239 240pu and 137cs have been released from sinking particles

paleobathymetric history of the western mediterranean sea shelf during the latest glacial period and the holocene quantitative reconstructions based on foraminiferal transfer functions abstract we present results of the palaeobathymetric evolution in cool water shelf carbonate environments of the western mediterranean sea during the latest glacial period and the holocene for this quantitative approach we used the weighted averaging partial least squares wa pls regression method for the development of benthic foraminifera based transfer functions and the modern analog technique mat to test the robustness of the models transfer functions were created on the basis of recent benthic foraminiferal assemblages in surface samples modern data sets and were then applied to fossil samples in sediment cores from the alboran platform the oran bight and the mallorca shelf the performance of the wa pls transfer functions suggests a close relationship between the observed and estimated water depths in the modern data sets with a precision of 11 m root mean squared error of prediction rmsep within water depths ranging from 38 to 160 m the estimated relative sea level histories of the alboran platform and the mallorca shelf show a total relative sea level rise of 50 m with sample specific errors of approximately 7 m and generally match the global and regional mediterranean sea records inconsistencies in the paleobathymetric estimates are strongly attributed to redeposition processes dating problems and to minor effects of an under representation of modern samples from shallower water depths

water masses and circulation in the western alboran sea and in the straits of gibraltar abstract some new elements of alboran sea circulation and water masses in close connection with flows through the straits of gibraltar are presented a general description is given of water masses found in 1981 during mediprod iv cruise from the gulf of cadiz to the gulf of lions followed by a brief review of the conditions found in the straits of gibraltar based on 1981 and 1961 observations the hydrological structure vertical and horizontal and surface and bottom currents typical of the western alboran sea are analysed we present some detailed observations about vertical currents in the deep waters near the straits and finally we analyse the characteristics of the mediterranean overflow through the straits our conclusions in part confirm those of bryden and stommel 1982 and in part shed light on the general pattern of the mediterranean currents entering the alboran sea from the east however considering the suggestion of stommel bryden and mangelsdorf 1973 that the deep currents in the interior of the western mediterranean basin are basically controlled by a bernoulli flow induced by the intense currents in the straits and the weak vertical stratification in the mediterranean we suggest that an interaction of a large scale circulation pattern and the topography of the alboran basin which is much shallower than the western mediterranean basin may play a major role in controlling hydraulically the deep mediterranean waters overflow a detailed water mass analysis of 1981 data and comparison with previous data revealed a time and space variability in the mediterranean waters the scales of this variability are unknown but the s variations make it difficult to make assumptions as to the depth of origin of the deep waters found in the alboran sea which flow into the atlantic ocean over the gibraltar sill

fluxes and budget of on the continental margin of the bay of biscay northeastern atlantic abstract as part of the ecofer experiment ecomarge program jgofs france concentrations of the natural radionuclide 210 pb were measured in particulate matter collected by sediment traps deployed for a 14 month period june 1990 august 1991 on two mooring lines within the cap ferret canyon on the french continental slope of the bay of biscay northeastern atlantic 210 pb concentrations range 63 218 dpm g 1 and fluxes range 0 1 11 2 dpm cm 2 yr 1 displayed typical gradients increasing with depth at both mooring sites also at equivalent trap depths 210 pb activities were systematically higher on the deep slope mooring 3000 m compared to the shallow one 2300 m fluxes of 210 pb generally decreased seaward and exhibited temporal variations but with no marked seasonal trend essentially matching variations in total mass flux various correlations between 210 pb activities and major constituents of trapped particles were examined 210 pb activities were independent of the particle composition indicating that in this area scavenging of this nuclide from the water column was not directly tied to the quality of settling particles the 210 pb budget as determined by the balance of local supply flux and fluxes to sediment traps and sediments implies important lateral inputs to both mooring sites 65 89 of the flux measured by traps a feature typical of continental margin environments on the basis of annual mean 210 pb activity in traps of the two mooring sites two particle sources are hypothesized the first source located in shallow waters of the shelf and upper slope supplies the entire slope region the second source probably composed of resuspended particles from upper slope sediments feeds essentially the upper and intermediate slope region maximum sedimentation rates determined on seven box cores decreased with bottom depth from 0 3 to 0 4 cm yr 1 at the canyon heads down to 0 06 cm yr 1 at 3000 m a good agreement was observed at both mooring sites between 210 pb fluxes registered by the near bottom traps and excess 210 pb inventories within the underlying sediments suggesting that nuclide fluxes measured by traps during this experiment are representative of fluxes on a longer time scale 10 100 yr nevertheless total mass fluxes measured by traps were 3 4 times lower than 210 pb determined sediment accumulation rates a discrepancy that may be more apparent than real given the possible errors in the latter due to bioturbation

deep sea circulation in the alboran sea alboran sea circulation between 220 and 1100 m depth is studied interaction between three types of water masses in this area causes a complicated flow pattern atlantic water flowing as a jet through the strait of gibraltar into the mediterranean often forms an anticyclonic gyre to the depth of 200 m and its features are now well documented a few works based on geostrophic calculations and bernoulli s equation treat the deep flow nine free floats were released at different depths and locations from january to may 1982 and acoustically tracked every 2 hours for 40 to 90 days acoustical tracking was done from three listening stations moored in the area the tracks of the floats at all depths from 220 to 1100 m revealed broad and slow approximately 2 5 cm s cyclonic circulation located under the surface anticyclonic gyre part of the flow following the bottom topography turned near the moroccan continental slope as a jet approximately 5 cm s to gibraltar and part turned to the east following the southern boundary of the deep channel to the isle of alboran

accumulation rates and sediment deposition in the northwestern mediterranean abstract as part of the eros 2000 programme sediment mixing and accumulation rates in the northwestern mediterranean sea were determined applying the 210 pb dating method to a total of 49 cores and the results from 29 sediment cores are presented here on the basis of the results from the 49 sediment cores an attempt was made to present a general picture of sediment accumulation for the area of the northwestern mediterranean the total deposition of sediment in the area is estimated to be of the order of 34 15 10 6 ton year 1 which is half the value reported earlier by got and aloisi 1990 continental shelf research 10 841 855 for the same region the activity depth profiles of 210 pb show the presence of intensive mixing in the upper layer of near shore sediments but little or no mixing is observed in the deep water sediments based on a diffusion model sediment mixing rates calculated from excess 210 pb gradients vary from 0 002 to 7 cm 2 year 1 and the deposition rates from 0 01 to 0 60 cm year 1 a linear dependence of sedimentation rate on water depth derived from the sediment cores indicates an inverse correlation between these two the relatively high sedimentation rates and mixing rates found near the rho ne river suggest that the contribution from the river dominates the deposition system in the northwestern mediterranean in the deep water basin however atmospheric input and biological production are clearly more important

circulation in the alboran sea as determined by quasi synoptic hydrographic observations part i three dimensional structure of the two anticyclonic gyres abstract the circulation and dynamics of the modified atlantic water have been studied using data from an intensive field experiment carried out between 22 september and 7 october 1992 data included 134 ctd casts adcp and satellite imagery a well defined wavelike front was observed with two significant anticyclonic gyres in the western and eastern alboran sea smaller scale cyclonic eddies were also observed the front separates the more saline older modified atlantic water s 38 in the northern region from the fresher more recent modified atlantic water s 36 8 in the south the associated baroclinic jet had a mean transport of 1 sv and maximum geostrophic velocities of 1 0 ms 1 the three dimensional structure and spatial scales of both gyres were similar that is 90 km long and 220 m deep in the eastern alboran northeast of oran the origin of the algerian current was also detected with an eastward transport of 1 8 sv the general picture can be presented as a structure formed by a wavelike

sediment accumulation rates and carbon fluxes to bottom sediments at the western bransfield strait antarctica abstract mean sediment and carbon accumulation rates in the western bransfield strait during the last ca 100 years were determined at three sites by using 210 pb as a radiotracer of sedimentation processes rates 210 pb profiles showed moderate mixing in the upper 8 5 12 cm which was attributed to bioturbation sediment accumulation rates calculated assuming no mixing below the surface mixed layer sml were found to be relatively high between 0 03 and 0 09 g cm 2 yr 1 in good agreement with previously reported data based on both 210 pb and 14 c dating in surrounding areas these results together with the calculated excess 210 pb fluxes to the bottom sediments and the 210 pb and 210 po distributions in the water column indicated the presence of a large net advective flux of material in the area highlighting the importance of glacial related sedimentation processes in this semi enclosed sea carbon in bottom sediments was mainly organic and its content was moderately low 0 65 1 25 being slightly higher within the sml reflecting the presence of inhabiting organisms however organic carbon oc accumulation fluxes 3 1 6 7 g c m 2 yr 1 were considerable due to the high sediment accumulation rates 210 pb dated profiles allowed us to estimate the amount of carbon exported from the water column and buried in the bottom sediment which represents about 3 7 of the mean annual primary production in the euphotic layer of the bransfield strait the burial efficiency of oc in the sediment was estimated to be approximately 60 80

the origin and characteristics of the algerian current satellite and ship data collected between may 1 and 22 1986 show that the algerian current originates in the almeria oran front and remains within 30 km of the algerian coast for over 300 km between oran and algiers the differences between the water masses of the current and the resident regional waters are clearly observed in the chlorophyll concentrations and optical characteristics thus permitting the resulting patterns to be used as tracers of the circulation during this field period the algerian current begins as an extension of the almeria oran front which is found at the western periphery of the eastern alboran gyre this major oceanographic salinity front s 1 km delineates the boundary of the algerian current which has average surface velocities of 40 cm s and maximum speeds reaching 80 cm s the current which has a volume transport between 0 4 and 0 5 sv is confined to the upper 150 m and is in geostrophic balance a sequence of coastal zone color scanner czcs and advanced very high resolution radiometer avhrr satellite imagery showing the rapidly evolving surface circulation features is augmented with in situ ship data of current and water mass characteristics rapid undulations and frontal movements of the current were observed during the study period however the flow remained unbroken between 1 and 3 e current instability increased eastward as the undulations were sharper and the current appeared to depart from the coast near algiers

paleoproductivity variations related to climatic conditions in the alboran sea western mediterranean during the last glacial interglacial transition the diatom record the present study addresses the analysis of changes in marine primary productivity derived from climatic variability over the last 30 000 yr the study area is the alboran sea this is the westernmost basin of the mediterranean sea and was a very sensitive area to changes in sea levels and atmospheric configuration during the last glacial interglacial transition we report the results from four sediment cores recovered in both the western and eastern alboran basins this allowed us to monitor the w e evolution of the hydrological structures the study is mainly based on the diatom record although total organic carbon toc isotopes and uk 0 37 sst were also used to gain further information paleoceanographic conditions favoured high paleoproductivity rates during the last glacial maximum although this occurred at termination 1a and during the younger dryas event yd increasing towards the easternmost sites during these periods meteorological conditions with increased westerlies intensified the flow to the east driving an eastward migration of the western anticyclonic gyre a possible displacement of the north alboran upwelling system is also considered the major component of the diatom assemblage during the yd are the resting spores of leptocylindrus danicus which suggest the presence of cooler and less saline surface waters the opposite behaviour between planktonic and benthic proxies in addition to the high toc values allows us to infer a phase of reduced deep water renewal between 16 5 and 9 cal ky bp fresh water diatoms and opal phytoliths were used as indicators of aridity and humid land conditions respectively during the glacial period and until 14 cal ky bp we observed a gradual climatic deterioration accompanied by a loss of grass belts climatic conditions were warmer and moister during the bolling allerod while the yd was dry the re establishment of vegetation belts and replenishment of lakes was observed at 8 cal ky bp q 2001 elsevier science b v all rights reserved

ground based observations during the period between two strong november 2004 storms attributed to steady magnetospheric convection 1 strong geomagnetic storms are of great scientific interest because they drive the magnetosphere to an extreme state and result in nontypical magnetosphere ionosphere coupling the present study examines the ground based signatures of the magnetosphere ionosphere disturbances during the recovery phase of the very intense storm on 7 8 november 2004 the recovery phase took place under steady and slightly negative 5 nt values of the imf bz we compare this event with previously documented storm recovery phases occurring under positive imf bz and accompanied by morning pc5 geomagnetic pulsations during the period studied in this article the strongest pulsation activity was recorded in the evening and midnight sectors of the earth we analyze observations from the scandinavian multipoint ground based instrumentation 1 geomagnetic variations and pulsations 2 auroras in visual wavelengths and 3 energetic particle precipitation riometer data we show that several enhancements in electrojet auroral and energetic precipitation activity were recorded at auroral latitudes the activations lasted 0 5 2 hours and the associated negative magnetic field deviations were often more than 1000 nt only one of these activations shows typical substorm behavior poleward expansion and geostationary particle injection we demonstrate remarkably good correlation between the magnetic variations and cosmic noise absorption variations in pulsations and slower variations as well as between the optical auroras and cosmic noise absorption imaging riometer for ionospheric studies riometer system both in time and in space thus the auroral precipitation revealed a very coherent behavior over a wide energy range 1 40 kev during the analyzed period the images acquired by the network of miracle all sky cameras show that the auroral distribution exhibited double oval configuration during our event double oval is often observed during so called steady magnetospheric convection smc episodes furthermore multiple auroral streamers were recorded implying probable occurrence of bursty bulk flows bbfs in the magnetotail the absence of recurrent geostationary injections the wide oval configuration and bbf signatures lead us to suggest that the intermediate period between the two november 2004 superstorms can be attributed to a smc period mapping the motion of ionospheric signatures to the magnetotail with the tsyganenko 96 models suggests bbf earthward speeds of 600 800 km s we suppose that the main drivers for the above described recurrent and intensive ionospheric phenomena are energy input from the solar wind due to slightly negative values of imf bz as well as huge energy storage in the magnetotail due to the previous storm main phase

yes some of the mediterranean outflow does come from great depth in 1973 stommel et al predicted that the western mediterranean deep water wmdw contributes directly to the mediterranean outflow through the strait of gibraltar strommel et al 1973 hydrographic data obtained in november 1985 showed unambiguous evidence of wmdw west of the major gibraltar sill thus confirming the prediction

accumulation rates of major constituents of hemipelagic sediments in the deep alboran sea a centennial perspective of sedimentary dynamics the accumulation rates of sediment and major constituents in three different geographic areas of the alboran sea have been assessed by means of 210pb and 137cs concentration profiles mixing is present in the top layer of the sedimentary column with mixing coefficients estimated to range from 0 2 to 15 cm2 yr 1 overall apparent sedimentation rates for the last 100 years range from 0 014 to 0 182 g cm 2 yr 1 and show a tendency to decrease with distance to the coast and water column depth however specific characteristics of the sea floor for each physiographic environment govern the actual patterns of sediment accumulation particularly noticeable are the feeding role of submarine canyons the trapping effect of slope terraces and the isolation caused by ridges sediment accumulation induced by turbiditic flows is also observed north of the almeria oran area excess 210pb inventories and surface concentrations reveal a net effect of sediment focussing and point to the role of bottom nepheloid layers in supplying a significant fraction of sediments to the deep areas this is also evidenced by comparison of bottom sediment with the sediment trap data available from the malaga area we estimate that the particle advective input below 30 m above the bottom accounts for as much as 50 70 of the material that is ultimately deposited onto the sea floor the greater abundance of lithogenic material in the malaga zone 80 reflects its larger input in the western alboran sea conversely carbonate contents increase from less than 20 in this area to about 30 in the almeria oran zone reflecting the lesser importance of the dilution by lithogenic components biogenic silica was only detected in some surface samples and no significant preservation was observed below the eh boundary abundance and accumulation rates of organic matter are in accordance with the spatial patterns of primary production in the alboran sea higher in the western part due to the presence of the western alboran gyre however near bottom redistribution leads to the homogenisation of organic matter concentrations in bottom sediments of any given area finally from comparisons with sediment trap data the degradation of organic matter has been estimated to be approximately 30 40 of what reaches the bottom

evidence of a high productivity area off the coast of malaga from studies of diatoms in surface sediments abstract the assemblages of diatoms contained in nineteen surface sediment samples recovered off the coast of malaga province spain between 5 w and 4 38 w have been analysed the variations observed in the diatom assemblage point to the presence of nutrient enriched waters transported laterally from the centre of an upwelling that occurs to the west of the study area the utility of species such as paralia sulcata thalassionema nitzschioides and the spores of chaetoceros spp in the reconstruction of physico chemical and biological characteristics and of the spatial structure of the upwelling is confirmed

satellite definition of the bio optical and thermal variation of coastal eddies associated with the african current the circulation of the african current along the north coasts of morocco algeria and tunisia is shown by seasonal satellite imagery to normally consist of a series of complex anticyclonic eddies that propagate eastward the large surface area associated with the eddy field illustrates significant amounts of coastal and modified atlantic waters that are entrained and the eddies compose the bulk of the net eastward transport analysis of the satellite imagery indicates that the turbulent shear produced by the current interacting with the african coast results in the advection of coastal waters into the modified atlantic water already contained in the eddy field the biological activity and chemical reactions spawned by the resultant mixing is clearly observed in the ocean color variations depicted in nimbus 7 coastal zone color scanner czcs visible imagery the extent of the offshore advection is indicated in the imagery by the high suspended sediment concentrations that border the periphery of the eddies sea surface temperature shown by both nimbus 7 czcs and noaa 7 avhrr advanced very high resolution radiometer infrared imagery also illustrate complex flow although in some imagery the ocean color imagery better defines the patterns applications of both visible ocean color and thermal imagery are suggested as a method of best determining the patterns of regional flow

particle mixing rates in deep sea sediments determined from excess 210pb and 32si profiles particle mixing rates have been determined for 5 south atlantic antarctic and 3 equatorial pacific deep sea cores using excess 210 pb and 32 si measurements radionuclide profiles from these siliceous calcareous and clay rich sediments have been evaluated using a steady state vertical advection diffusion model in antarctic siliceous sediments 210 pb mixing coefficients 0 04 0 16 cm 2 y are in reasonable agreement with the 32 si mixing coefficient 0 2 or 0 4 cm 2 y depending on 32 si half life in an equatorial pacific sediment core however the 210 pb mixing coefficient 0 22 cm 2 y is 3 7 times greater than the 32 si mixing coefficient 0 03 or 0 07 cm 2 y the difference in 210 pb and 32 si mixing rates in the pacific sediments results from 1 non steady state mixing and differences in characteristic time and depth scales of the two radionuclides 2 preferential mixing of fine grained clay particles containing most of the 210 pb activity relative to coarser particles large radiolaria containing the 32 si activity or 3 the supply of 222 rn from the bottom of manganese nodules which increases the measured excess 210 pb activity relative to 226 ra at depth and artificially increases the 210 pb mixing coefficient based on 32 si data and pore water silica profiles dissolution of biogenic silica in the sediment column appears to have a minor effect on the 32 si profile in the mixed layer deep sea particle mixing rates reported in this study and the literature do not correlate with sediment type sediment accumulation rate or surface productivity based on differences in mixing rate among three antarctic cores collected within 50 km of each other local variability in the intensity of deep sea mixing appears to be as important as regional differences in sediment properties

sedimentation rate dilution preservation and total organic carbon some results of a modelling study abstract a modelling exercise was undertaken to evaluate the positive preservational and negative diluent effects of sedimentation rate sr on the total organic carbon toc content of marine sediments and to use multiple regression analysis of modern data to predict toc data presented show the predicted marine toc using the carbon burial efficiency be versus sr relationship of betts and holland betts j n holland h d 1991 the oxygen content of ocean bottom waters the burial efficiency of organic carbon and the regulation of atmospheric oxygen palaeogeography palaeoclimatology palaeoecology global and planetary change section 97 5 18 calculated for a range of sr water depths primary productivities and four fixed be values the results suggest that the preservation effect of sr only enhances toc at 5 cm ka in oxic regimes after which dilution occurs if carbon supply is held constant above 35 cm ka there is no appreciable difference in toc regardless of whether the sea floor is anoxic or not below 10 cm ka there is a strong divergence in oxic and anoxic toc values observed positive correlations of sr and toc at 5 cm ka are largely an artefact of including sites from shallower depths and or higher productivities multiple regression analysis mra of modern marine sediment data suggests that once re scaled to allow for their non linear effect dissolved oxygen values may be a significant additional variable in determining the toc predicting an approximately 2 5 4 0 times higher toc in anoxic facies compared with fully oxic ones 4 ml l dissolved oxygen all other things being equal the mra also indicates a generally negative partial correlation between carbon delivery flux and be in modern sediments producing a significant moderating effect on the predicted toc

210pb activities in and fluxes to sediments of the washington continental slope and shelf abstract surface sediments of the washington coast have 210 pb activites which average 104 48dpm g for submarine canyon and slope regimes and 18 12dpm g for the continental shelf regime 210 pb sedimentary fluxes are also higher in canyons averaging 18 13dpm cm 2 per yr compared to 5 2 3 1 dpm cm 2 per yr for slope and 4 8 1 8dpm cm 2 per year for shelf regions these 210 pb activities and fluxes are 2 7 times greater than those reported for other coastal regions inputs from the atmosphere and the columbia river are not sufficient to supply the 210 pb but advection of seawater containing dissolved 210 pb produced in situ from 226 ra provides an input several times larger than the sedimentary fluxes the sedimentary 210 pb flux is limited by scavenging reactions rather than by supply of dissolved 210 pb calculations of maximum biological uptake and fluxes of 210 pb and selective chemical leaching experiments all show that the primary scavenging processes are due to hydrous mn and fe oxides rather than biological phases the pattern of higher 210 pb depositional fluxes in canyons than in nearby open slope areas of comparable water depth is most reasonably explained by enhanced scavenging of dissolved 210 pb near the sea floor rather than by processes operating throughout the water column relatively rapid removal of dissolved 210 pb from the near bottom nepheloid layer to slope and canyon sediments is shown by its mean residence time of less than two years in this layer

short term measurements of surface currents associated with the alboran sea gyre during donde va abstract during the period 6 18 october 1982 six flights by a u s navy research aircraft were made over the alboran sea gyre as part of the donde va experiment during five of these flights sonobuoys were dropped in a linear pattern designed to show the temporal and spatial variability of the currents that constitute the gyre a normal development consisted of approximately 15 sonobuoys dropped along the longitudinal line 4 45 w from the spanish coast to within 30 km of the moroccan coast during the following 4 hours the sonobuoys were relocated twice their positions noted and their individual drift speeds and directions derived aircraft precision radiation temperature and aircraft expendable bathythermograph data were collected concurrently with the sonobuoy drops to determine the thermal structure of the water during the drift period inertial navigation winds at the 300 m altitude of the aircraft as well as other meteorological data were also collected analysis of these data shows that at

the effect of sediment mixing on pb 210 accumulation rates for the washington continental shelf abstract nine cores from the washington continental shelf were examined by radiochemical techniques in order to evaluate the effect of mixing on the calculation of sediment accumulation rates from pb 210 profiles th 234 profiles indicate mixing coefficients of 140 cm 2 yr 1 for the seabed offshore from the columbia river and 47 cm 2 yr 1 for the seabed of the mid shelf silt deposit 75 km north of the columbia river these large mixing coefficients demonstrate that particles can penetrate to the base of the intensely mixed surface layer 10 cm within one year after emplacement at the seabed surface observed depths of cs 137 penetration within the seabed are compared with depths predicted from the surface mixed layer thickness and the pb 210 accumulation rate the observed and predicted depths agree well at all but one station at this station a combination of th 234 co 60 pb 210 and cs 137 profiles suggests that active mixing occurs below the intensely mixed surface layer the agreement of pb 210 and cs 137 data at the other stations however indicates a general absence of deep mixing on the washington shelf thus the apparent accumulation rates calculated from pb 210 profiles below the intensely mixed surface layer on the washington shelf generally reflect the true rates of sediment accumulation

a study of an intense density front in the eastern alboran sea the almeria oran front abstract studies of satellite imagery and space shuttle photographs of the western mediterranean have indicated that the main path of inflowing atlantic water is around two large anticyclonic gyres in the alboran sea and along the algerian coast these studies have also shown that a strong ocean front is present between almeria spain and oran algeria which is part of the easternmost segment of the eastern alboran gyre based on these satellite studies the first in situ investigation of the front called here the almeria oran front was conducted in march 1986 as part of the winter campaign of the western mediterranean circulation experiment wmce analyses of the resulting data show that the almeria oran front is a large scale density front formed by the convergence of two distinct water masses and controlled by the geographic position and strength of the eastern alboran gyre physical and biochemical data indicate that the front is limited to the upper 300 m with a strong southward baroclinic jet

sediment accumulation rates in the southern barcelona continental margin nw mediterranean sea derived from 210pb and 137cs chronology sediment cores were collected from the southern barcelona continental margin including the foix canyon in order to study sediment accumulation in this area for this purpose 210pb 137cs and to a lesser extent 239 240pu and heavy metals were determined in sediment sections using state of the art techniques 210pb concentration profiles and 137cs 239 240pu and heavy metals profile features were used to establish the sediment chronologies further information was also obtained from granulometric analyses the magnitudes studied and correlated in this work included surface activities mixing rates accumulation rates and inventories sediments on the continental shelf showed a varied degree of mixing except possibly cn 23 sedimentation rates were relatively small and the sedimentary material probably had a common origin cores from the slope showed less mixing and in cores cn 36 and eb 2 located in the foix canyon axis the 137cs signal vs depth was clear and well preserved accumulation rates and total 210pb inventories were maximum in core cn 36 at mid slope of the canyon which was considered to be an active depocenter core cn 38 collected on the open slope showed a much smaller accumulation rate therefore it was concluded that shelf material is being transported alongshore by the prevailing currents and becomes focused in the canyon which is acting as a natural trap within the canyon this material is preferentially deposited at a mid slope depocenter little extra material reaches the lower canyon area in this area core eb 2 appeared to show signs of the presence of resuspended material possibly derived from the canyon walls finally observed changes in sedimentation rates during the 1930s could not be explained on the basis of current knowledge and this is suggested to be an important subject for further research

time and space variability in the eastern alboran sea from march to may 1990 an intensive field experiment was carried out from march 6 to april 30 1990 in the eastern alboran sea to understand the relationship between the large scale circulation and the location of the transition zone between new and longer resident modified atlantic water maw the detection of a strong jet 80 cm s 1 of new maw with anticyclonic curvature near the morocco coast suggests that the eastern alboran gyre eag was not fully developed a new state of the circulation in the eastern alboran basin intermediate between the eag viudez et al 1995 and the lanoix 1974 state is presented also important is that the almeria oran front was not present in the upper layer that small scale instabilities were detected in the northern region and that significant nongeostrophic flows were observed all these features are clearly indicative of the high spatial and temporal variability of a region where complex adjustments among density velocity and topography occur

distribution of recent benthic foraminifera in shelf carbonate environments of the western mediterranean sea abstract the distribution of recent shallow water benthic foraminifera in surface sediment samples from cool water carbonate environments of the oran bight alboran platform and mallorca shelf in the western mediterranean sea was studied multivariate statistical analyses resulted in the identification of species assemblages representing different environmental settings in all three regions the assemblages show a distinct bathymetric zonation that is mainly attributed to the distribution of rhodoliths and related substrates but also to water turbulence and the availability of food at the sea floor the live assemblages rose bengal stained individuals are characterised by rather low diversity and low standing stocks likely reflecting seasonal population dynamics in the oran bight elevated standing stocks of high food taxa suggest the impact of anthropogenic eutrophication on the near coastal benthic ecosystems of this area the diversity of the dead assemblages is higher than in siliclastic shelf ecosystems of the mediterranean sea but lower when compared to carbonate environments of the levantine sea this regional difference is mainly attributed to lower sea surface temperatures and the lack of lessepsian invaders in the western mediterranean sea in all study areas a distinct faunal change occurs between approximately 80 90 m water depth this change coincides with the lower distribution limit of living rhodoliths at the shelf of mallorca providing coarse grained substrates that are dominated by attached taxa below this depth interval the fauna shows regional differences depending on the grain size and related accumulation of organic material fine grained substrates with infaunal niches are restricted to low energy environments on the deeper shelf southwest off mallorca

quaternary folding of the eastern tian shan northwest china abstract the tian shan east west trending more than 2000 km is one of most active intracontinental mountain building belts that resulted from india eurasia collision during cenozoic in this study quaternary folding related to intracontinental mountain building of the tian shan orogenic belt is documented based on geologic interpretation and analyses of the satellite remote sensing images landsat thematic mapper tm enhanced thematic mapper etm and india remote sensing irs pan combined with field geologic and geomorphic observations and seismic reflection profiles analyses of spatial temporal features of quaternary folded structure indicate that the early quaternary folds are widely distributed in both piedmont and intermontane basins whereas the late quaternary active folds are mainly concentrated on the northern range fronts field observations indicate that quaternary folds are mainly characterized by fault related folding the formation and migration of quaternary folding are likely related to decollement surfaces beneath the fold and fault zone as revealed by seismic reflection profiles moreover analysis of growth strata indicates that the quaternary folding began in late stage of early pleistocene 2 1 1 2 ma finally tectonic evolution model of the quaternary deformation in the tian shan is presented this model shows that the quaternary folding and faulting gradually migrate toward the range fronts due to the continuous compression related to india eurasia collision during quaternary time as a result the high topographic relief of the tian shan was formed