variations in mode of formation and temperature of oceanic deep waters over the past 125 000 years marked changes in the deep water temperature of the different oceanic basins during the past 125 kyr are revealed by a detailed comparison of the oxygen isotopic composition ofbenthicforaminiferafrom sediment cores taken from the norwegian sea and the pacific atlantic and southern oceans the last interglacial deep water temperatures were similar to the modern ones at the 5e 5d transition around 115 kyr bp the deep water temperatures dropped below approximately 0 c in the pacific and southern indian oceans in the atlantic ocean the deep water temperature dropped in 2 successive steps at 115 and 75ky bp the global ocean deep water temperatures were in the 0 to 1 c range for the whole of the last ice age isotope stages 4 2

climate swings in the northern red sea over the last 150 000 years from end and mg ca of marine sediments abstract the end and mg ca compositions of terrigenous material from a meridional transect of seven marine sediment cores located between the northern red sea and the gulf of aqaba together with modern dust sample compositions reveal the temporal and spatial changes in precipitation and dust sources over the last 150 kyrs and are further used to discuss the late quaternary climate history of this region two recent glacial periods marine isotopes stages mis 6 and 2 are characterized by low end values associated with a saharan dust source 12 while mg ca ratios suggest increased transport of dust containing authigenic clays during the last deglacial which most likely originated from the arabian peninsula by contrast mis5e sediments are characterized by an abrupt basin wide shift of end values toward the local arabian nubian shield end member 2 that are exposed around the red sea this shift stems from intense fluvial events and is coeval with other regional paleo precipitation records that all point to an extensive northward shift of precipitation from the tropics during mis5e considering model simulations and regional precipitation dynamics we conclude that although the african summer monsoon probably intensified and extended somewhat northward during mis5e it was not the driver of significant precipitation and the main contribution of precipitation to the northern red sea was due to increased frequency and possible intensity of tropical plumes and red sea troughs that triggered massive fluvial floods within the red sea catchment considering mis5e as an analogue to a future warmer world this currently hyperarid region could be exposed over the coming decades to an increased impact of extreme rainfall events with critical implications for water availability and infrastructure sustainability

distinguishing climatic and tectonic signals in the sedimentary successions of marginal basins using sr isotopes an example from the messinian salinity crisis eastern mediterranean the evolution of oceanic 87 sr 86 sr through the tertiary has been sufficiently well documented to provide a useful stratigraphic tool for carbonate rich marine sediments which were deposited in basins connected to the global oceans in isolated basins sea water 87 sr 86 sr will diverge from coeval oceanic values thus if independent age information exists the geochemical signature can constrain the timing of isolation in marginal basins formed in tectonically active settings the timing of isolation is critical to the assessment of the relative importance of climate or tectonic controls on that event previously isolation has been assumed to coincide with the last occurrence of open marine fauna however in an example from the eastern mediterranean 87 sr 86 sr data challenge that assumption and can be interpreted as indicating a protracted period of isolation c 3 ma during which time marine conditions prevailed prior to the messinian salinity crisis at the end of the miocene this allows tectonic and climatic signals to be distinguished since although convergence of africa with eurasia was responsible for isolation of this part of the mediterranean it is more likely that later climatic change triggered desiccation

nannoplankton successions in the northern red sea during the last glaciation 60 to 14 5 ka bp reactions to climate change abstract due to its restricted connection with the indian ocean the desert enclosed red sea is extremely sensitive to global sea level changes and thus ideally suited for paleoceanographic studies of what occurred during the last glaciation the understanding of its glacial history is however still limited a serious obstacle to obtain satisfactory paleoecological information has been the rarity of microfossil proxy species caused by high salinities here we present a continuous and well dated calcareous nannoplankton record from the northern red sea covering the interval from 60 14 5 ka bp our investigation shows that the composition of the calcareous nannoplankton community varied between 32 ka bp and 14 5 ka bp in response to rapid environmental changes which are closely correlated to climatic fluctuations described from the north atlantic region heinrich events h3 h2 and h1 are dominated by emiliania huxleyi gephyrocapsa oceanica and especially gephyrocapsa ericsonii are abundant between h3 h2 and h2 h1 a less pronounced response of the calcareous nannoplankton to the high latitudinal climatic oscillations is documented prior to 32 ka bp suggesting that a strong atmospheric coupling between the northern red sea and the north atlantic realm was established in the late marine isotope stage 3 in contrast to the previously held view of a sea level related salinity increase as the major cause for changes of the plankton communities within the glacial red sea we interpret the documented variations as being caused by local hydrographic changes under the atmospheric control from the extratropics temperature changes and especially variations of the water stratification appear to be critical selective factors for the calcareous nannoplankton composition

milankovitch forcing of fluctuations in the level of tropical lakes from 18 to 0 kyr bp an atmospheric general circulation model has been used to simulate the climates of january and july at 3 000 yr intervals from 15 kyr bp onwards the model simulates a strengthened monsoon circulation and increased precipitation in the northern hemisphere tropics culminating at 9 6 kyr bp the computed hydrological budgets were used to estimate the area of closed lakes between 8 9 and 26 6 n giving with minor exceptions results in good agreement with geological evidence

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

laminar micrite crusts and associated foreslope processes red sea abstract forereef slopes in the red sea of sudan exhibit a uniform biozonation that is independent from the topography of the slopes below 120 m ledges protrude horizontally from sleep cliffs of barrier reefs and atolls as well as from patches of in situ lithified slope sediment on inclined fringing reef slopes free surfaces and cavities within these ledges are partly covered by laminar micrite crusts of 7 20 mm thickness the ledges are formed by an organic framework of living azooxanthellate corals bryozoans serpulids and fossil red algae they are affected by repeated episodes of boring infilling and cementation which obliterate much of the original fabric concomitant cementation and boring result in asymmetric cement linings which often show geopetal fabrics the laminar m crite crusts however show no significant traces of bioerosion which are a typical feature of fossil deep water stromatolites two types of lamination have been observed 1 vertically stacked irregular anastomosing laminate with ragged outlines and little lateral persistence which are often accentuated by iron staining and 2 0 5 mm thick laminae of light grey micrite rich in fine bioclasts showing smooth thin coatings of dark homogenous micrite which are weakly fluorescent in ultraviolet light no algal films are preserved but micritic tubes 10 30 m in diameter often bifurcated form a dense network on the upper surface of the crusts by overgrowing and binding particles associated aragonitic rosettes 30 40 m in diameter may represent calcified coccoid algae or bacteria if true these organisms suggest a formation of the latter type of crust by biogenic processes not related to the photic zone fenestral porosity and frutexites textures are absent radiocarbon dates from corals within the ledges provide ages of 10 500 ybp from the time related decrease in oxygen isotope ratios versus pdb of boring micrite 18o 3 72 micrite crusts 18o 1 69 and unlithified mud 18o 0 47 within the youngest voids of the hard substrates we conclude that crust formation must have taken place in shallower water when sea level was lower during the early holocene rise of sea level

mediterranean moisture source for an early holocene humid period in the northern red sea paleosalinity and terrigenous sediment input changes reconstructed on two sediment cores from the northernmost red sea were used to infer hydrological changes at the southern margin of the mediterranean climate zone during the holocene between approximately 9 25 and 7 25 thousand years ago about 3 per thousand reduced surface water salinities and enhanced fluvial sediment input suggest substantially higher rainfall and freshwater runoff which thereafter decreased to modern values the northern red sea humid interval is best explained by enhancement and southward extension of rainfall from mediterranean sources possibly involving strengthened early holocene arctic oscillation patterns and a regional monsoon type circulation induced by increased land sea temperature contrasts we conclude that afro asian monsoonal rains did not cross the subtropical desert zone during the early to mid holocene

reconstructing past planktic foraminiferal habitats using stable isotope data a case history for mediterranean sapropel s5 abstract a high resolution stable o and c isotope study is undertaken on all planktic foraminiferal species that are reasonably continuous through an eemian sapropel s5 from the western side of the eastern mediterranean the data are considered within a context of high resolution isotope records for two further s5 sapropels from the central and easternmost sectors of the basin alkenone based sea surface temperature records for all three sapropels and planktic foraminiferal abundance records for the same sample sets through all three sapropels results are compared with similar data for holocene sapropel s1 the adopted approach allows distinction between species that are most suitable to assess overall changes in the climatic hydrographic state of the basin including depth related differentiations and the main seasonal developments and species that are most affected by variable biological controls or local regional and transient physico chemical forcings it is found that a priori assumptions about certain species palaeohabitats based on modern habitat observations may become biased when non analogue conditions develop in the case of mediterranean sapropel s5 these consisted of enhanced freshwater dilution elevated productivity shoaling of the pycnocline between intermediate and surface waters and stagnation of the subsurface circulation under these conditions some species are found to shift into habitat settings that differ considerably from those occupied today the present multiple species approach can identify such anomalous responses and thus offers a sound background for further shell chemistry investigations and quantitative interpretation of the isotopic profiles we capitalise on the latter potential and offer the first quantitative estimates of monsoon flooding into the mediterranean during the deposition of eemian sapropel s5

distribution of crenarchaeota tetraether membrane lipids in surface sediments from the red sea abstract the red sea represents an extreme marine environment with high salinity high temperature and low level of nutrients complicating the application of standard geochemical palaeotemperature proxies in order to investigate the applicability of the tex 86 tetraether index of gdgts with 86 carbons proxy for sea surface temperature sst in the red sea the distribution of glycerol dialkyl glycerol tetraether membrane lipids gdgts in sediments from the red sea and the gulf of aden were examined against expectations tex 86 values for the red sea do not show a simple linear relationship with sst and deviate from the global core top calibration in the northern red sea at temperatures between 25 and 28 c the values increase linearly with sst whereas in the southern red sea at temperatures above 28 c tex 86 decreases with increasing temperature factors like seasonality and depth of production salinity and nutrient availability as well as diagenetic overprint or influence of allochtonous terrestrial lipids cannot explain this pattern however the observed tex 86 relationship with sst could be explained by the presence of a hypothetical endemic crenarchaeota population in the red sea with a specific tex 86 vs sst relationship in the southern red sea a two component mixing model implies an exponential decrease in the endemic population towards the gulf of aden thus the application of the tex 86 as a palaeotemperature proxy in the red sea is likely only possible for the northern red sea area with the specific sst vs tex 86 relationship determined in this study and potentially for the whole red sea basin during glacials when water exchange with the indian ocean was more restricted than today and the endemic archaeal lipid distribution was not affected by transport from the indian ocean our results suggest that distinct populations of crenarchaeota in extreme environments such as evaporitic basins may have different membrane composition necessitating application of another calibration than the global core top calibration for tex 86 palaeothermometry

paleoceanographic record of the last glacial interglacial cycle in the red sea and gulf of aden abstract hydrographic conditions in the red sea are strongly controlled by regional climatic conditions and the restricted water exchange with the gulf of aden indian ocean in turn intermediate and deep water masses in the gulf of aden reflect the nature of red sea outflow planktonic and benthic foraminiferal faunas and the lithology and mineralogy of red sea and gulf of aden sediments were studied in order to evaluate changes in water mass conditions in the two basins during the last 18 000 years the results indicate that changes in the local climate and circulation regime during this period resulted in significant hydrographic changes in surface and bottom waters in the red sea and intermediate waters in the gulf of aden during the last glacial maximum high aridity and glacio eustatic sea level lowering resulted in surface and bottom water salinities in the red sea which were considerably higher than at present in the gulf of aden glacial surface salinities and temperatures remained similar to holocene values while surface water productivity may have been lower surface salinities in the red sea decreased after 18 000 years b p as the connection between the red sea and gulf of aden was reestablished however bottom water salinities remained high until at least 11 000 years b p pluvial conditions during deglaciation enhanced the density difference between surface and bottom waters in the red sea and resulted in a decrease in the oxygen content of the bottom waters hydrographic conditions in the western gulf of aden reflect a change in the properties of outflowing red sea water during deglaciation

late quaternary changes in desert dust inputs to the red sea and gulf of aden from 87sr 86sr ratios in deep sea cores abstract strontium isotope ratios of the hcl insoluble residue isr and foraminifera of cores from the red sea and gulf of aden are used to monitor effects of hydrothermal fluvial and desert dust transport to these regions during the past 0 5 ma while the gulf of aden was open ocean during low glacial sea levels the red sea was a semi isolated basin allowing the possibility to study the effects regional versus global inputs during glacial interglacial cycles the isr from the gulf of aden and the red sea display different ranges of 87 sr 86 sr ratios of 0 7085 0 7107 and 0 7062 0 7085 respectively these reflect mixtures between three components granitic hydrothermal and loess strontium with representative 87 sr 86 sr of 0 711 0 706 and 0 7085 respectively gulf of aden isr represent mixtures of the loess and granitic sources while red sea isr are mixtures of the loess and sea floor hydrothermal sources in the gulf of aden loess sources dominate during glacials indicating intensification of the ne moonsonal wind regime and granitic sources dominate during interglacials reflecting wetter conditions related to an enhanced regional sw monsoon red sea isr show no clear glacial interglacial distinction but display a general temporal increase in 87 sr 86 sr ratios over the past 380 ka toward loess like values indicating increasing loess contributions toward the present day the ranges of isr 87 sr 86 sr ratios in the red sea and the gulf of aden were distinct prior to the last glacial period 87 sr 86 sr ratios following major climate transitions at 10 80 130 190 240 and 330 ka bp that coincide with sapropel episodes in the eastern mediterranean which originated from the african monsoonal system and indicate enhanced wetness in the desert belt 87 sr 86 sr ratios of foraminifera show a very narrow range from 0 70912 to 0 70917 over 530 ka and in most samples are consistent with the contemporaneous global ocean in the red sea foraminifera and pteropods show slightly more variability than the gulf of aden a few red sea samples fall slightly above the seawater trend in marine isotope stages 5 and 9 and below during the last deglaciation suggesting local effects that occurred when the flow of surface ocean water from the gulf of aden to the red sea was limited and the red sea behaved like an amplifier basin

the arid humid transition in the sahara and the sahel during the last deglaciation at the time of the last glacial maximum the sahara and sahel regions of north africa were extremely dry new records of rainfall show that during the subsequent deglaciation the transition from arid to humid conditions in these regions occurred synchronously in two main steps comparison with other records of palaeoclimate in europe and the north atlantic ocean shows that certain common factors controlled changes in ocean and atmosphere dynamics during the deglaciation

the structure of the southwest monsoon winds over the arabian sea during the late quaternary observations simulations and marine geologic evidence each summer strong southwest winds produced by the asian monsoon blow across the nw arabian sea creating a broad region of upwelling characterized by cool sea surface temperatures and enriched phytoplankton biomass the integrated history of the summer plankton blooms is preserved in the form of distinct plankton fossil assemblages and sediment facies forming a continuous geologic record of wind driven upwelling and thus changes in the sw monsoon winds sediments have been recovered from two regions in the nw arabian sea one located along the oman continental margin and another located approximately 400 km offshore over the late quaternary these two sites record time series of upwelling that are substantially different to understand the source of the differences we examined the relationship between wind stress and upwelling at these sites using historical observations and model simulated wind fields in the coastal region upwelling is directly related to the ekman transport offshore and is thus linearly proportional to the alongshore wind stress farther offshore open ocean upwelling is driven by the positive curl in the wind stress in historical records we found little correlation between stronger winds and increased open ocean upwelling in the region offshore where the sediment cores were recovered the year with the strongest winds was accompanied by weaker wind stress curl and diminished upwelling indicated by warmer sea surface temperatures and decreased phytoplankton pigment content because the region of maximum wind stress curl moved nw that year in atmospheric general circulation model experiments using a range of summer insolation forcing we found large changes in the wind stress curl occur over some areas of the nw arabian sea however the offshore core locations lies outside of the region where changes in the sw monsoon drive large changes in open ocean upwelling in contrast to the coastal sites where upwelling is directly related to the wind stress the offshore sites appear to be located in a region where the wind stress curl does not change much over a large range of summer insolation there is some evidence from both the interannual and model fields that this location is affected more by movements in the position of the low level jet than by changes in the over all strength of the sw monsoon although more data are required to define these patterns these results indicate that the time series of open ocean upwelling observed in the geologic record from offshore sites may differ substantially from the coastal time series

multidecadal variations in the early holocene outflow of red sea water into the arabian sea we present holocene stable oxygen isotope data from the deep arabian sea off somalia at a decadal time resolution as a proxy for the history of intermediate upper deep water these data show an overall 18o reduction by 0 5 between 10 and 6 5 kyr b p superimposed upon short term 18o variations at a decadal centennial timescale the amplitude of the decadal variations is 0 3 prior and up to 0 6 subsequent to 8 1 kyr b p we conclude from modeling experiments that the short term 18o variations between 10 and 6 5 kyr b p most likely document changes in the evaporation precipitation balance in the central red sea changes in water temperature and salinity cause the outflowing red sea water to settle roughly 800 m deeper than today

a study on the ambient noise field at a hydroacoustic array near robinson crusoe island continuous long term sound sources are recorded at hydroacoustic station h03s a threeelement hydrophone array south of robinson crusoe island between 2014 april 23 and 2017 august 20 the origin of the signal between 3 and 20 hz is investigated by using cross correlation array processing using plane wave beamforming and spectral analysis onebit normalization is successfully applied as a cross correlation pre processing step in order to suppress undesired earthquake events in the data traveltimes retrieved from averaged cross correlations do not yield a coherent array direction of arrival averaged envelopes of the cross correlations however indicate a coherent signal approaching h03s from a south southwest direction beamforming indicates two dominant backazimuth directions 172 224 antarctica and 242 monowai volcanic seamount this continuous source field creates possibilities to investigate the applicability of acoustic thermometry at hydrophones h03 s1 s2 cross correlation and array processing indicate significant directional variation in local propagation most likely related to the steep slope in the bathymetry near h03s in addition it is demonstrated that the ambient noise field is not sufficiently equipartitioned it is shown that this causes a large error in the estimated temperature primarily due to the short receiver spacing these large errors have not been addressed in previous studies on deep ocean acoustic thermometry hence it is shown that acoustic thermometry does not perform well on small arrays such as h03s the power spectral density yields a strong broadband signal in january march most likely related to iceberg noise a narrow banded signal around 17 hz between april and september corresponds to whale calls the best beam sound pressure levels towards antarctica are compared to era5 climatologies for sea ice cover and normalized stress into the ocean supporting the hypothesis of iceberg noise

stable oxygen isotope composition is biased by shell calcification intensity in planktonic foraminifera planktonic foraminifera are widely used for environmental reconstructions through measurements of their shell s geochemical characteristics including its stable oxygen and carbon isotope composition using these parameters as unbiased proxies requires a firm knowledge of all potential confounding factors influencing foraminiferal shell geochemistry one such parameter is the shell calcification intensity shell weight normalized for shell size that may influence the shell delta 18o value either bioenergetically by reducing energy available and required for equilibrium isotope fractionation during faster calcification or kinetically by influencing calcification depth through the shell s density contrast with seawater specimens from the globigerinoides ruber elongatus compound from a sediment trap in the north atlantic have been used to quantify the influence of shell calcification intensity on shell delta 18o values shell calcification intensity was found to have a significant effect on the shell stable oxygen isotope composition in all species through model fitting it is suggested that the effect size may be in a range of 1 to 2 depending on species depth migration and local oceanographic conditions we show that the confounding effect of shell calcification intensity on stable oxygen isotope composition can be of importance depending on the anticipated precision of the derived reconstructions a framework is provided to quantify this effect in future studies

dust transport and synoptic conditions over the sahara arabia deserts during the mis6 5 and 2 1 transitions from grain size chemical and isotopic properties of red sea cores abstract the red sea situated between the sahara and arabia deserts is a natural trap for fine grained particles transported by winds and floods from weathered materials in these deserts derived from the proterozoic crustal granitic and basaltic terrains and phanerozoic carbonates the accumulated fine particles provide valuable information on the climate conditions in the source regions and modes of atmospheric circulation over the red sea region here we report on the grain size mineralogy chemical composition and nd and sr isotope ratios of fine grained insoluble residues ir from acid leaching that were recovered from two deep sea cores kl23 and kl11 drilled in the northern and central red sea respectively we focus on the mis6 5 and mis2 1 transitions kl23 samples are closer to the sahara granitoids field and display significant variations during the mis6 5 transition between end of 7 to 2 and 87sr 86sr of 0 7096 to 0 7114 smaller variations occurred during the mis2 1 transition between end of 5 to 6 and 87sr 86sr of 0 7104 to 0 7118 the kl11 values are closer to the blue nile field which comprises mixtures of granitoid and basalt derived particles during the mis6 5 transition their end varies from 4 to 1 and in 87sr 86sr from 0 7059 to 0 7091 during periods equivalent to sapropels s5 and s1 both cores appear to converge to similar isotope ratios of e nd 2 and 87sr 86sr 0 7095 indicating derivation from the granitoid terrains of the arabian nubian shield occurring adjacent to the red sea and possibly distributed by runoff in terms of synoptic conditions the data indicate that during glacials dust was blown to the northern red sea from the northern sahara desert in association with the mediterranean winter cyclones and to the central red sea from the ethiopian plateau by southern winds that are associated with monsoonal circulation during interglacials especially sapropel intervals monsoonal rains caused erosion and flooding at the arabian nubian shield margins of the red sea during the heinrich events associated with the studied intervals h11 and h1 dust from mixed basaltic granitic terrains was blown from all of the regional sources in the red sea region reflecting severe regional aridity and transport of dust by regional winds when monsoonal activity and mediterranean cyclone activity were weak

regional monitoring of infrasound events using multiple arrays application to utah and washington state summary in this paper we present an integrated set of algorithms for the automatic detection association and location of low frequency acoustic events using regional networks of infrasound arrays here low frequency acoustic events are characterized by transient signals which may arise from a range of natural and anthropogenic sources examples of which include but are not limited to earthquakes volcanic eruptions explosions rockets and bolides first we outline a new technique for detecting infrasound signals that works successfully in the presence of correlated noise we use an f statistic sequentially adapted to ambient noise conditions in order to obtain detections at a given statistical significance while accounting for real background noise at each array individual arrivals are then grouped together based on measured delay times and backazimuths each signal is identified as either a first or later arrival first arrivals at spatially separated arrays are then associated using a grid search method to form events preliminary event locations are calculated from the geographic means and spreads of grid nodes associated with each event we apply the technique to regional infrasound networks in utah and washington state in utah over a period of approximately 1 month we obtain a total of 276 events recorded at three arrays in a geographic region of 6 4 for four groundtruth explosions in utah the automatic algorithm detects associates and locates the events within an average offset of 5 4 km to the actual explosion locations in washington state the algorithm locates numerous events that are associated with a large coalmine in centralia washington an example mining explosion from centralia is located within 8 2 km of the mine the methodology and results presented here provide an initial framework for assessing the capability of infrasound networks for regional infrasound monitoring in particular by quantifying detection thresholds and localization errors

three hundred eighty thousand year long stable isotope and faunal records from the red sea influence of global sea level change on hydrography stable isotope and faunal records from the central red sea show high amplitude oscillations for the past 380 000 years positive 18o anomalies indicate periods of significant salt buildup during periods of lowered sea level when water mass exchange with the arabian sea was reduced due to a reduced geometry of the bab el mandeb strait salinities as high as 53 and 55 are inferred from pteropod and benthic foraminifera 18o respectively for the last glacial maximum during this period all planktonic foraminifera vanished from this part of the red sea environmental conditions improved rapidly after 13 ka as salinities decreased due to rising sea level the foraminiferal fauna started to reappear and was fully reestablished between 9 ka and 8 ka spectral analysis of the planktonic 18o record documents highest variance in the orbital eccentricity obliquity and precession bands indicating a dominant influence of climatically driven sea level change on environmental conditions in the red sea variance in the precession band is enhanced compared to the global mean marine climate record specmap suggesting an additional influence of the indian monsoon system on red sea climates

synoptic conditions of fine particle transport to the last interglacial red sea dead sea from nd sr compositions of sediment cores abstract the sediments deposited at the depocenter of the dead sea comprise high resolution archive of hydrological changes in the lake s watershed and record the desert dust transport to the region this paper reconstructs the dust transport to the region during the termination of glacial marine isotope stage 6 mis 6 135 129 ka and the last interglacial peak period mis5e 129 116 ka we use chemical and nd and sr isotope compositions of fine detritus material recovered from sediment core drilled at the deepest floor of the dead sea the data is integrated with data achieved from cores drilled at the floor of the red sea thus forming a red sea dead sea transect extending from the desert belt to the mediterranean climate zone the dead sea accumulated flood sediments derived from three regional surface cover types settled desert dust mountain loess soils and loess soils filling valleys in the dead sea watershed termed here valley loess the valley loess shows a distinct 87sr 86sr ratio of 0 7081 1 inherited from dissolved detrital calcites that originate from dried waterbodies in the sahara and are transported with the dust to the entire transect our hydro climate and synoptic conditions reconstruction illustrates the following history during glacial period mis6 mediterranean cyclones governed the transport of saharan dust and rains to the dead sea watershed driving the development of both mountain soils and valley loess then at heinrich event 11 dry western winds blew saharan dust over the entire red sea dead sea transect marking latitudinal expansion of the desert belt later when global sea level rose the dead sea watershed went through extreme aridity the lake retreated depositing salt and accumulating fine detritus of the valley loess during peak interglacial mis 5e enhanced flooding activity flushed the mountain soils and fine detritus from all around the dead sea and red sea marking a significant contraction of the desert belt at the end of mis 5e the effect of the regional precipitation diminished and the dead sea and red sea areas re entered sever arid conditions with extensive salt deposition at the dead sea

late pleistocene variability of arabian sea summer monsoon winds and continental aridity eolian records from the lithogenic component of deep sea sediments the modern indian ocean summer monsoon is driven by differential heating between the asian continent and the indian ocean to the south this differential heating produces a strong pressure gradient which drives southwest monsoon winds during june july and august satellite and meteorological observations aerosol measurements sediment trap studies and mineralogical studies indicate an atmospheric mode of transport for modern lithogenic sediments in the northwest arabian sea analyses of lithogenic grain size and mass accumulation rate mar records from the owen ridge indicate that eolian transport has been the primary mode of transport for the past 370 kyr visual inspection shows that the mar record is positively correlated with global ice volume as indicated by the marine 18o record in contrast the grain size record varies at a much higher frequency showing little correlation to either the mar or the 18o records spectral analyses confirm these relationships indicating that the lithogenic grain size and mar records are coherent only over the precession band whereby the grain size leads the mar by 124 8 kyr we conclude that an eolian transport mechanism is the only mechanism that allows for this phase difference and at the same time is supported by comparison of the grain size and mar with independent eolian records we use lithogenic grain size as a paleoclimatic indicator of summer monsoon wind strength and lithogenic mar as a paleoclimatic indicator of source area aridity these interpretations are supported by comparison of the lithogenic records to independent indicators of wind strength globigerina bulloides upwelling record and aridity a loess record from central china such comparisons indicate high coherence and zero phase relationships our work supports the findings of previous studies which have documented the link between monsoon strength and the earth s axial precession cycles both the lithogenic mar and the grain size records have high coherency with precessional insolation maximum lithogenic mar source area aridity is in phase with 18o global ice volume and leads maximum precessional insolation by 88 6 kyr we attribute this lead to the influence of glacial conditions on the aridity and therefore the deflation potential of the source areas maximum lithogenic grain size summer monsoon wind strength lags maximum precession by 148 9 kyr we attribute this lag both to the influence of global and or local ice volume and to the availability of latent heat from the southern hemisphere indian ocean the two of which combine to determine the strength of the indian ocean monsoon

glacial conditions in the red sea in this paper results from previous studies on planktonic foraminifera 6 o and global sea level are combined to discuss climatic conditions in the red sea during the last glacial maximum 18 000 b p first the influence of 120 m sea level lowering on the exchange transport through the strait of bab el mandab is considered this strait is the only natural connection of the red sea to the open ocean next glacial red sea outflow salinity is estimated about 48 parts per thousand from the foraminiferal record combined these results yield an estimate of the glacial net water deficit which appears to have been quite similar to the present about 2 rn yf finally budget calculation of 6 o fluxes suggests that the glacial 6 o value of evaporation was about 50 of the present value this is considered to have resulted from substantially increased mean wind speeds over the glacial red sea which would have caused a rapid drop in the kinematic fractionation factor foro the sensitivity of the calculated values for water deficit and isotopic fractionation to the various assumptions and estimates is evaluated in the discussion improvents are to be expected especially through research on the glacial salinity contrast between the red sea and gulf of aden it is argued however that such future improvement will likely result in a worsening of the isotopic discrepancy thus increasing the need for an additional mechanism that influenced fractionation such as mean wind speed this study demonstrates the need for caution when calculating pal osaliniti s from 5 so records under the assumption that the modem s 5 so relation has remained constant through time previously overlooked factors such as mean wind speed may have significantly altered that relation in the past

messinian pre evaporite sapropels and precession induced oscillations in western mediterranean climate abstract cyclical fluctuations in planktic foraminiferal assemblages have been recognized in the pre evaporitic messinian in a marginal basin of the western mediterranean the fluctuations coincide with a dominantly precession controlled sedimentary cyclicity sapropels during sapropel deposition high planktic foraminiferal diversities are indicative of relatively stable marine conditions while during homogeneous marl deposition low diversities seem to indicate the presence of unfavourable more saline surface water conditions the dominance of a precession related signal indicates that regional climate oscillations rather than obliquity related glacio eustatically controlled influxes of atlantic and or mediterranean waters are responsible for the faunal fluctuations and sedimentary cyclicity our scenario links the persistence of normal marine conditions during sapropel formation with increased rainfall and run off along the western mediterranean at times that perihelion occurred in northern hemisphere summer less favourable highly saline surface water conditions prevailed during periods of drier climate induced by opposite precessional extremes the cyclical oceanographic fluctuations could also have governed periodic reef growth along the margins

the effect of paleo oceanographic changes on the sedimentary recording of hydrothermal activity in the red sea during the last 30 000 years abstract the restricted exchange of water with the indian ocean makes the red sea extremely sensitive to global oceanographic changes such as sea level variations linked with quaternary climate change the 120 m global sea level lowering during the last glacial maximum caused great reduction in water exchange with the open ocean at that time salinities reached 50 and were beyond the tolerance of planktonic foraminifera some topographic depressions located on the red sea axial zone are the centre of hydrothermal activity they are filled with hot brines and contain metalliferous sediments we studied three sediment cores in the axial part of the red sea one from the metal rich suakin deep depression and two cores sampled outside any deep at two different depths the sediment of the core located in the anoxic brine filled suakin deep contained no benthic foraminifera indicating the deep was filled by a brine pool during the recovered period of marine isotopic stages 1 2 and 3 the distribution of benthic foraminifera in the two other cores indicates that red sea waters were saltier during stage 2 and 3 than today and that at 2000 m depth red sea waters were anoxic during stage 2 and dysoxic during stage 3 profiles of fe mn and zn indicate that the sedimentary flux of metals was higher during stage 1 than during stage 2 in hydrothermal brine filled deeps in contrast the sedimentary flux of metal in cores outside the anoxic depressions was higher during stage 2 the shape of the metal profiles can be attributed to hydrological changes that induced variations of redox conditions in water column during isotopic stage 1 2 and 3 during interglacial periods metals dissolved in anoxic brines precipitated at the redox boundary that corresponded to the brine seawater interface so that metals precipitated only in the deeps during glacial period the deep water was anoxic and the redox boundary was located above the brine seawater interface therefore the hydrothermal metals could diffuse into the anoxic deep red sea water and be precipitated over a large area this interpretation suggests that the observed variations of metal concentrations are not only related to fluctuations of the hydrothermal fluid discharge but also to the varying redox conditions in the deep red sea water

stratigraphic and paleoceanographic significance of late quaternary pteropods from deep sea cores in the gulf of aqaba elat and northernmost red sea abstract the quantitative distribution of 16 thecosomatous pteropod species from four deep sea cores recovered from the gulf of aqaba elat and northernmost red sea is summarized the distribution facilitates a relatively high resolution stratigraphic subdivision of the 6 8 m long core sequences and their correlation the sequences of pteropod assemblages can be related to oxygen isotope curves and thus dated beyond the radiocarbon range the oldest strata penetrated are dated at about 150 000 yr b p considering the present day distribution of the species recognized the core assemblages are of a tropical subtropical character throughout the late quaternary on the basis of the composition of the living pteropod populations in the hypersaline 41 moderately oligotrophic and desert enclosed gulf of aqaba the pteropod core assemblages associated foraminiferal assemblages and the oxygen isotope values determined on both groups a sequence of paleoceanographic changes during the late quaternary is derived these changes are primarily influenced by productivity of the waters and pertain less to temperature and salinity the glacial periods isotope stages 2 3 4 and upper 6 were characterized by lower temperature than at present higher salinity and greater fertility of the waters during the glacial maxima monospecific creseis acicula assemblages characterize periods of metahaline more than 50 salinity conditions in highly productive waters although not identical in detail the last interglacial stage 5 assemblages are similar to the holocene warm water oligotrophic ones between 8000 and 3000 yr b p a short period of slightly higher productivity is indicated

impact of late quaternary environmental changes on deep sea benthic foraminiferal faunas of the red sea abstract fluctuations in abundance diversity and species composition of benthic foraminifera from two sites of the northern and southern red sea indicate strong variability of deep sea ecosystems during the last four glacial to interglacial cycles in total five and four different benthic foraminiferal assemblages have been identified in the northern core and southern core respectively comparison with recent faunas from the red sea and adjacent oceans allowed the reconstruction of temporal changes in deep water ventilation salinity and food availability at the seafloor generally the abundance of infaunal and miliolid taxa increase during glacial intervals indicating increased organic matter fluxes oxygen decrease and salinity increase in deep waters during these times these fluctuations are attributed to enhanced oxygen consumption rates and temporarily reduced deep water formation in the northern red sea during glacial intervals the recorded environmental changes are a reflection of both high and low latitude climate changes the northern red sea is mainly influenced by glacio eustatic sea level fluctuations that control deep water formation rates and by mid latitude climate changes of the mediterranean region that control surface productivity in contrast deep sea ecosystem variability of the southern red sea is additionally influenced by low latitude climate changes attributed to the ne monsoon intensity that drives the inflow of nutrient rich surface waters from the gulf of aden these results demonstrate the high sensitivity of deep sea ecosystems of the red sea to both global and regional climate changes

sensitivity of red sea circulation to monsoonal variability during the holocene an integrated data and modeling study received 20 october 2009 revised 6 march 2010 accepted 30 june 2010 published 4 november 2010 1 we used an oceanic general circulation model to evaluate the sensitivity of the hydrography and circulation of the red sea in response to reduced sea level and modified atmospheric conditions during the holocene with holocene sea level close to the modern level the red sea was sensitive to changes in atmospheric conditions and it only shows a relatively mild response to sea level change changes in the monsoon system influence the exchange flow through the strait of bab el mandab the meridional overturning circulation of the red sea and its hydrography forced by humid conditions the modeled red sea temperature increased by 1 5 c while when arid conditions were imposed the temperature decreased by 2 5 c similar heating and cooling events during the early and late holocene are seen in a sea surface temperature record from the northern red sea derived from the temperature sensitive tex86 molecular biomarker which suggests that humid conditions prevailed during the early holocene and more arid conditions prevailed during the late holocene the gradual decline in red sea temperature between these two time periods suggests a gradual decline in the summer monsoon strength this monsoon trend and the resulting changes in the red sea circulation are supported by the distribution of crenarchaea fossil lipids in red sea sediments from this period monsoon driven changes in the exchange flow through the strait of bab el mandab affected the crenarchaea population structure and therefore their molecular fossil distribution in the sediments of the red sea potentially provides an index for the summer monsoon strength during the holocene

formation of the late aptian niveau fallot black shales in the vocontian basin se france evidence from foraminifera palynomorphs and stable isotopes abstract we present paleoceanographic models for the formation of the marlstone facies and the most prominent black shale intervals of the late aptian niveau fallot black shale succession from the vocontian basin se france in the lower part of the succession the composition of benthic foraminiferal assemblages of the niveau fallot 2 and 2 black shales suggests an enhanced burial of organic matter due to more eutrophic conditions and resulting low oxygen conditions at the seafloor in the upper part of the succession including niveau fallot 3 and 4 a third order sea level fall indicated by a decrease in the stable carbon isotope values may have resulted in a reduced water mass exchange between the vocontian basin and the western tethyan ocean this may have led to dysoxic conditions at the seafloor of the vocontian basin and may have favored the formation of organic rich sediments as shown by benthic foraminiferal assemblages decreased evaporation however is proposed as the most important mechanism causing a restriction of deep water formation within the basin which finally led to the formation of the niveau fallot 3 and 4 black shales based on our investigations the formation of the niveau fallot black shales was caused by different factors the most prominent ones include sea level fluctuations increasing productivity and changes in precipitation and evaporation rates furthermore niveau fallot 3 can probably be correlated with the thalmann black shale event in california and a dark horizon at the mazagan plateau dsdp site 545

climatic changes in the northern red sea during the last 22 000 years as recorded by calcareous nannofossils 1 we present a high resolution record of calcareous nannofossils from the northern red sea for the last 22 kyr extreme conditions with enhanced salinities during the last glacial maximum are characterized by high values of gephyrocapsa ericsonii the dominance of emiliania huxleyi in heinrich event 1 indicates a climatic cooling favoring the bloom of opportunistic species the calcareous nannofossils record a two step onset of the postglacial humid climate punctuated by the younger dryas both steps show an early oligotrophic phase dominated by florisphaera profunda and gladiolithus flabellatus and a subsequent fertile phase characterized by e huxleyi the younger dryas is described by high values of gephyrocapsa oceanica indicating an increased mixing of the water column in the late holocene repetitive increases in abundance of f profunda and g flabellatus reflect restricted oligotrophic conditions caused by the high aridity following the holocene humid period

a seismoacoustic analysis of the gas pipeline explosion near ghislenghien in belgium a high pressure gas pipeline exploded near ghislenghien in belgium on 30 july 2004 seismic energy of this event was recorded at three nearby seismometers the origin time of the explosion was determined by analyzing the rayleigh waves and found to be 06h55m27 2sec coordinated universal time utc ground truth of the explosion was invoked to assess the accuracy of the location derived from infrasound data recorded over western europe different infrasonic phases were identified by using array processing techniques and raytracing through atmospheric models the analysis showed that the derived location was situated 13 km from the true location the total area of the uncertainty ellipse or area to be searched if the source was of unknown origin was 690 km 2 after the origin time and location the yield was calculated by comparing infrasonic stratospheric amplitudes with those from a high explosives dataset and was estimated at 40 9 tons high explosives equivalent in summary this study illustrates the capability of seismic and infrasound data in forensic investigations furthermore the potential of infrasound as a monitoring or verification technique is addressed

modelling the ocean climate for the early archaean abstract a solution to the enhanced surface temperature lowered solar luminosity paradox of the early archaean earth is presented in terms of albedo modifications due to the presence of a near global ocean and fewer clouds an interlinked suite of three ocean thermodynamic dynamic models is used to cross substantiate the viability of an oceanic climate in which zonal transports are enhanced pole to equator transports diminished and surface temperatures are only a few degrees below present day values throughout the year this provides substantiation for one of the two radiative explanations for the remarkable stability of the earth s surface temperature for the whole of the geological record although an alternative for the ocean dominated archaean earth to the previously well discussed radiation trapping by greenhouse gases mechanism it is likely that both mechanisms operated during the early phases of the earth s history

infrasonic propagation from the 2010 eyjafjallajokull eruption investigating the influence of stratospheric solar tides 1 the stratospheric infrasound duct formed between earth s surface and altitudes of 50 km is sensitive to spatiotemporal variations in stratospheric wind speed and temperature infrasound recorded at long range from the 2010 summit eruption of eyjafjallajokull volcano iceland exhibits temporal variability correlated with diurnal stratospheric solar tidal wind speed variations between 18 and 28 april 2010 signal observations at stations bkni u k range 1745 km and is18 greenland range 2285 km exhibit prominent diurnal variations in infrasonic amplitude bandwidth back azimuth and apparent speed which we identify using the clean spectral analysis algorithm for unevenly sampled time series results of 3 d acoustic ray tracing through operational atmospheric specifications indicate that tidal wind speed variations with amplitudes of 20 m s can generate diurnal variations in the proportion of the acoustic wavefield propagating within the stratospheric acoustic duct range dependent meteorology is required propagation modeling using averaged meteorological profiles fails to predict the leakage of acoustic energy out of the stratospheric acoustic duct at times of low observed signal amplitudes ray tracing correctly predicts the phase of the observed signal amplitude and apparent speed variations diurnal variability in ducting combined with diurnal variations in ambient noise at the sensors can explain the observed signal bandwidth variations back azimuth variations observed only along the eyjafjallajokull to bkni path are not predicted by 3 d ray tracing tidal variations have implications for models of infrasound array network detection capability and for studies that utilize amplitude and bandwidth measurements to make inferences about the acoustic source

an automatic seismic event processing for detection and location the p m c c method we present a new method for automatic detection and location of seismic events recorded on a network it is based on a progressive study of the interstation correlation functions which leads to a consistent set of time delays when a seismic phase is present three different examples are processed on networks of different sizes

global morphology of infrasound propagation i atmospheric sound waves in the 0 02 10 hz region also known as infrasound exhibit long range global propagation characteristics measurable infrasound is produced around the globe on a daily basis by a variety of natural and man made sources as a result of weak classical attenuation 0 01 db km 1 at 0 1 hz these acoustic signals can propagate thousands of kilometers in tropospheric stratospheric and lower thermospheric ducts to model this propagation accurately detailed knowledge of the background atmospheric state variables the global winds and temperature fields from the ground to 170 km is required for infrasound propagation calculations we have developed a unique atmospheric specification system g2s that is capable of providing this information using acoustic ray tracing methods and detailed g2s atmospheric specifications we investigate the major aspects of the spatiotemporal variability of infrasound propagation characteristics

acoustic propagation and atmosphere characteristics derived from infrasonic waves generated by the concorde infrasonic signals generated by daily supersonic concorde flights between north america and europe have been consistently recorded by an array of microbarographs in france these signals are used to investigate the effects of atmospheric variability on long range sound propagation statistical analysis of wave parameters shows seasonal and daily variations associated with changes in the wind structure of the atmosphere the measurements are compared to the predictions obtained by tracing rays through realistic atmospheric models theoretical ray paths allow a consistent interpretation of the observed wave parameters variations in the reflection level travel time azimuth deviation and propagation range are explained by the source and propagation models the angular deviation of a ray s azimuth direction due to the seasonal and diurnal fluctuations of the transverse wind component is found to be 5 from the initial launch direction one application of the seasonal and diurnal variations of the observed phase parameters is the use of ground measurements to estimate fluctuations in the wind velocity at the reflection heights the simulations point out that care must be taken when ascribing a phase velocity to a turning height ray path simulations which allow the correct computation of reflection heights are essential for accurate phase identifications

varying responses to indian monsoons during the past 220 kyr recorded in deep sea sediments in inner and outer regions of the gulf of aden although the climate in the arabian sea is controlled primarily by the southwest monsoon the southwest monsoon has little influence in the gulf of aden to examine the different responses to monsoons between the gulf of aden and areas outside the gulf a comprehensive data set of bulk organic and inorganic geochemistry sea surface temperature and 15n of pheopigments was obtained from deep sea sediment cores recovered from inner and outer regions of the gulf the results indicated that during the past 220 kyr the influence of the southwest monsoon was stronger in the outer region of the gulf than in the inner region which implies that the southwest monsoon trajectory has not changed substantially during that time period furthermore influxes of o2 depleted water from the southern ocean and the lateral advection of upwelled seawater also had limited influence in the inner region in contrast concentrations of lithogenic materials transported by the southwest monsoon were similar in the two regions 15n of pheopigments indicated that during the last glacial maximum the southwest monsoon was weaker and the northeast monsoon was stronger than at present a stronger southwest monsoon during interglacials enhanced primary productivity and may have caused anoxic conditions to develop in the arabian sea as indicated by redox proxies in the outer region anoxic conditions also formed during mis 3 but no increase in the primary productivity is indicated therefore another mechanism such as an influx of o2 depleted water from the southern ocean may have been the cause

continental oxygen isotopic record of the last 170 000 years in jerusalem abstract a long radiometrically dated oxygen isotopic record of continental climatic variations since the penultimate glaciation was obtained from a stalagmite deposited in a sealed cave in jerusalem this record shows that speleothems have the potential of assigning dates to long and short term climatic events with possible refining of milankovitch tuning of ice and marine records which themselves are not datable short term 1000 yr events are very significant in the region reaching 50 of glacial interglacial fluctuations the mediterranean sea was the most probable source of local precipitation throughout the last glacial cycle

seismo acoustic analysis of the buncefield oil depot explosion in the uk 2005 december 11 summary a massive vapour cloud explosion occurred at the buncefield fuel depot near hemel hempstead uk in the morning of 2005 december 11 the explosion was the result of an overflow from one of the storage tanks with the release of over 300 tons of petrol and generating a vapour cloud that spread over an area of 80 000 m2 before being ignited considerable damage was caused in the vicinity of the explosion and a total of 43 people were injured the explosion was detected by seismograph stations in the uk and the netherlands and by infrasound arrays in the netherlands we analysed the seismic recordings to determine the origin time of 06 01 31 45 0 5 s utc from p wave arrival times uncertainties in determination of origin time from acoustic arrival times alone were less than 10 s amplitudes of p lg and primary acoustic waves were measured to derive decay relationships as function of distance from the seismic amplitudes we estimated a yield of 2 10 tons equivalent to a buried explosion most seismic stations recorded primary and secondary acoustic waves we used atmospheric ray tracing to identify the various travel paths which depend on temperature and wind speed as function of altitude leading to directional variation refracted waves were observed from the troposphere stratosphere and thermosphere with a good match between observed and calculated traveltimes the various wave types were also identified through array processing which provides backazimuth and slowness of recordings from an infrasound array in the netherlands the amplitude of stratospheric refracted acoustic waves recorded by the array microbarometers was used to estimate a yield of 21 6 5 tons tnt equivalent we have demonstrated through joint seismo acoustic analysis of the explosion that both the seismic velocity model and the atmospheric model are sufficient to explain the observed traveltimes

glacio eustatic sea level control on red sea salinity previous studies of the red sea demonstrated that glacial surface and bottom water salinities in the basin were significantly higher than at present the very low abundance of planktonic foraminifera the so called aplanktonic zone during the last glacial indicates that surface water conditions approached or exceeded the tolerance limits of this plankton group1 2 glacial sediments are also characterized by high concentrations of magnesian calcite3 4 dolomite3 inorganically precipitated aragonite4 5 and benthic foraminifera typical of hypersaline environments3 6 additional evidence from oxygen isotope records of planktonic2 7 and benthic foraminifera8 9 as well as pteropods2 demonstrate that glacial interglacial contrasts in the red sea have an amplitude much larger than typically observed in open ocean records here we use both oxygen isotope data and a fractional overmixing model to estimate the impact of the most recent 18 000 yr bp pleistocene glacio eustatic sea level lowering on red sea salinity we estimate that during the last glacial maximum surface salinities in the central red sea were more than 10 0 higher than at present deep water salinities were also higher during the last glaciation and remained unusually high through deglaciation the combination of very high bottom salinities and the onset of pluvial conditions during deglaciation in the red sea region prevented ventilation of red sea bottom waters and resulted in the accumulation of organic rich sediments

new constraints on the timing of sea level fluctuations during early to middle marine isotope stage 3 1 to settle debate on the timing of sea level fluctuations during marine isotope stage mis 3 we present records of 18oruber sea level proxy and magnetic susceptibility from the same samples within the single sediment archive i e coregistered of central red sea core geotu kl11 core scanning x ray fluorescence and environmental magnetic data establish the suitability of magnetic susceptibility as a proxy for eolian dust content in red sea sediments the eolian dust data record similar variability as greenland 18oice during early to middle mis 3 in agreement with previous observations that regional arabian sea climate fluctuated with a timing similar to that of greenland climate variations in contrast the sea level record fluctuates with a timing similar to that of antarctic style climate variations the coregistered nature of the two records in core kl11 unambiguously reveals a distinct offset in the phase relationship between sea level and eolian dust fluctuations the results confirm that sea level rises indicated by shifts in red sea 18oruber to lighter values occurred during cold episodes in greenland during early to middle mis 3 this indicates that the amplitudes of the reconstructed mis 3 sea level fluctuations would not be reduced by inclusion of regional climate fluctuations in the red sea sea level method our analysis comprehensively supports our earlier conclusions of large amplitude sea level variations during mis 3 with a timing that is strongly similar to antarctic style climate variations

high rates of sea level rise during the last interglacial period sea level during the last interglacial stood at least 4 m higher than at present with evidence of short term fluctuations of up to 10 m a new continuous sea level record from the red sea and coral ages suggest that during these fluctuations sea level changes were on the order of 1 6 m per century

correlated oceanic and continental records demonstrate past climate and hydrology of north africa 0 140 ka analysis of pollen and dinocysts in a core from the eastern atlantic core v22 196 lat 13 degree 50 n long 18 degree 57 w provides the first continuous record of paleoclimate and paleohydrology for the latest climatic cycle during interglacial intervals increases in pollen input from humid vegetation zones are correlative with high dinocyst productivity this data shows a close coincidence of northward extensions of sudanian and guinean vegetation zones in north africa and increases in fresh water input into the atlantic direct evidence indicates positive hydroclimatic phases at 135 125 103 80 47 and 12 10 ka coincident with widespread continental records of high lake levels that confirm the validity of the u th chronology

controls on shell mg ca and sr ca in cultured planktonic foraminiferan globigerinoides ruber white mg ca and sr ca ratios were determined on a single species of planktonic foraminiferan globigerinoides ruber white collected from the gulf of eilat and cultured in seawater at five different salinities 32 to 44 five temperatures 18 to 30 c and four ph values 7 9 to 8 4 the mg ca temperature calibration of cultured g ruber with an exponential slope of 8 3 c agrees well with previously published calibrations from core tops and sediment traps however the dependence of mg ca on salinity with an exponential slope of 5 3 psu is also significant and should be included in the calibration equation with this purpose we calculated a calibration equation for g ruber dependent on both temperature and salinity within the 95 confidence limits mg ca mmol mol exp 0 06 0 02 s psu 0 08 0 02 t c 2 8 1 0 r2 0 95 the influence of ph on mg ca ratios is negligible at ambient seawater ph 8 1 to 8 3 however we observe a dominating ph control on shell mg ca when the ph of seawater is lower than 8 0 sr ca in g ruber shows a significant positive correlation with average growth rate presumably part of the variability in shell sr ca in the geological record is linked to changes in growth rates of foraminifera as a response to changing environmental conditions

mg ca paleothermometry in high salinity environments planktonic foraminiferal mg ca ratios have become a fundamental temperature proxy in past climate reconstructions however in the highly evaporative seas of the tropics and subtropics anomalously high planktonic foraminiferal mg ca ratios arise possibly linked to high salinities the extent to which salinity affects mg uptake into foraminiferal calcite remains disputed some studies suggest only minor salinity effects whereas others suggest a dominant role here we present new data from the highly saline 40 red sea which separate pure foraminiferal calcite from other phases the results show that high mg ca ratios 7 to 13 mmol mol found by conventional analysis of planktonic foraminifera from a red sea sediment core are not caused by increased mg uptake into foraminiferal calcite in a high salinity setting e g beyond those predicted by culturing studies but instead result from secondary high mg calcite overgrowths the overgrowths likely formed near the sediment seawater interface from caco3 supersaturated interstitial seawater

response of red sea deep water agglutinated foraminifera to water mass changes during the late quaternary abstract the distribution of deep water agglutinated foraminifera was determined in core material taken in the central red sea by the r v meteor cruise 5 leg 2 the sedimentary record represents the last 380 kyr which includes four glacial interglacial cycles the agglutinate assemblage is of low diversity and in general is a minor component of the benthic foraminifera it comprises 14 species belonging to the following genera ammobaculites lagenammina plotnikovina pseudogaudryina reophax sahulia siphotextularia spiroplectinella textularla and a doubtful genus of unknown taxonomic position psammosphaera three sub groups were identified in the core according to their occurrence either in interglacial stages or in both glacial and interglacial intervals reflecting mainly tolerance to salinity variations exceptional bottom water conditions during the last 60 kyr caused a remarkable decrease in the abundance and diversity of this group the development of dysaerobic bottom water between approx 60 and 26 kyr the presence of a deep water mass of extremely high salinity ca 55 between 26 and 13 kyr and the occurrence of anoxic bottom sediments between 12 9 and 9 6 kyr seem to have caused the extreme impoverishment during the last 9 6 kyr the agglutinated foraminifera gradually recolonized the deep water a diverse assemblage composed of the above mentioned genera is found in holocene sediments only in the core top sample in addition small 63 149 m noncanaliculate organic cemented agglutinated foraminifera belonging to the genera ammodiscus cribrostomoides eggerella glomospira haplophragmoides morulaeplecta spiroplectammina paratrochammina and trochammina are preserved preferentially only in the uppermost part of the core 0 28 cm depth in sediments younger than 3 kyr

african monsoons an immediate climate response to orbital insolation the croll milankovitch astronomical theory of climate1 3 has received strong support from the evidence of a linear climatic forcing by obliquity and precession although nonlinearity had to be assumed for eccentricity4 5 moreover interglacials have appeared to be controlled by the orbital insolation6 although a phase shift of 6 000 5 000 yr is seen between an astronomical climate index and terrestrial climate indicators dominated by the northern ice sheet dynamics climate proxy data of low latitudes are less directly dependent on the ice sheets here it is shown that during the past 464 000 yr african monsoons signalled by the east mediterranean sapropels were heaviest always and only when a northern summer monsoon index computed from the orbital variation of insolation reached maximum values this occurred during all the interglacials but also twice during glacial periods thus tropical aridity is not the single climatic pattern of glacial periods an immediate terrestrial climate response to orbital variations of insolation is established

detailed japan sea paleoceanography during the last 25 kyr constraints from ams dating and δ18o of planktonic foraminifera abstract we have reconstructed paleoceanographic changes in the japan sea for the period from the last glacial maximum lgm to the present using expanded paleoclimate proxy records from two cores together with previously published results from three others a suite of new accelerated mass spectrometer ams 14 c dates provides chronologies that differ from earlier age models and suggest correlation between conditions in the japan sea changes in the north pacific and global sea level and climate changes we present evidence that reduced salinity of the japan sea surface water during the late pleistocene was due primarily to the increased importance of the precipitation evaporation balance at a time when lowered sea level had reduced water exchange with the pacific to a few percent of the present value

paleoenvironmental events during the last 13 000 years in the central red sea as recorded by pteropoda a high resolution record was obtained by investigating a sedimentary sequence from two cores taken in the central red sea r v meteor cruise 5 leg 2 the numerical variations between nonmigratory and migratory pteropods and their stable isotopic record were studied together with variations in the carbonate and total organic carbon content in order to estimate changes in the structure of the water column during the last 13 kyr the results indicate the existence of a highly stratified water column during deglaciation and early holocene 13 8 5 ka during this period the depth of the mixed layer varied between less than 50 100 m at most and productivity was markedly reduced in comparison to the recent situation the intermediate and deep water were constantly highly depleted in oxygen a pronounced younger dryas event was recognized at 10 4 ka which coincides with an arid phase on the border land the oxygenation of the intermediate water improved remarkably after 7 5 ka and peaked during the period between 4 6 and 2 0 ka during this period the mixed layer reached its present depth and the productivity which was maximal during middle holocene attained present level during the last 4 6 kyr

red sea isolation history suggested by plio pleistocene seismic reflection sequences abstract high evaporation rates in the desert climate of the red sea ensure that during glacial sea level lowstands when water exchange with the indian ocean was more restricted water salinity and 18 o became unusually extreme modeling of the effect on red sea sedimentary 18 o has been used previously to reconstruct relative sea level to 500 ka and now poses the question of whether that sea level model could be extended if continuous core material of older sediment became available we attempt to address this question here by examining seismic reflection data the upper pleistocene hemipelagic sediments in the red sea contain intervals of inorganic aragonite precipitated during supersaturated conditions of sea level lowstands seismic impedance changes associated with boundaries to those aragonite rich layers appear to explain seismic reflection sequences a segment of chirp sediment profiler data from the central red sea reveals prominent reflections at 1 5 23 26 and 36 ms two way travel time twt from the seabed based on depths to the glacial marine isotope stages mis in cores we relate the upper three reflections to the tops of aragonite rich layers and hence the sea level rises immediately following mis 2 6 and 12 the reflection at 26 ms is related to an unusually rapid fall into mis 12 predicted by one sea level reconstruction which may have created an abrupt lower boundary to the mis 12 aragonite rich layer with the aid of seismogram modeling we tentatively associate the 36 ms reflection with the top of an aragonite rich layer formed during mis 16 furthermore some segments of lower frequency airgun and sparker seismic data from the central and southern red sea show a lower earlier plio pleistocene pp interval that is less reflective than the upper late pp interval this implies less variability in sediment impedance and that extreme variability in water salinity did not develop water exchange with the indian ocean likely continued throughout this interval these results suggest that viable relative sea level reconstructions may be recovered from red sea sediment 18 o data to at least mis 16 and perhaps even as far back as the early pliocene

quaternary paleo oceanography pteropod preservation and stable isotope record of the red sea abstract an abundance of pteropod species their mode of preservation and stable isotope ratios of carbon and oxygen in benthic and planktic foraminifera have been determined in core md76 140 from the northern red sea isotopic data and benthic foraminiferal species indicate changes in o2 concentration in the bottom sediments the glacial stages are characterized by an almost anoxic bottom while the interglacial bottom was generally well ventilated in general very well preserved pteropod shells occur in glacial oxygen depleted intervals and also on recent well ventilated bottoms in the interglacial stages the preservation deteriorates and in the most extreme cases there is a complete dissolution of the aragonitic shells in these cases most of the assemblage is lost and the only traces of the original shells are their internal molds these are cemented with high magnesium calcite hmc which is a more stable carbonate phase in bottom sediments of the interglacial dissolution of aragonite discriminates between large and small shells the latter tend to be removed completely while the larger ones may be preserved as internal hmc molds limacina inflata is more readily molded than l trochiformis and thus its relative abundance increases in poorly preserved assemblages the state of aragonitic shell preservation depends on the degree of organic matter combustion in the sediments well preserved shells occur in sediments where the supply of organic matter is limited and o2 levels are high preservation deteriorates with increasing supply of organic carbon o2 consumption and increasing production of co2 in this case the dissolved carbonate is reprecipitated as hmc cement with further increase in organic matter supply and reduced ventilation nearly all oxygen is consumed and no3 and subsequently so42 become the oxidizing agents this is followed by an increasing carbonate alkalinity and excellent aragonitic shell preservation

understanding the red sea response to sea level here we outline a new pragmatic methodology to derive relative sea level estimates from central red sea oxygen isotope records based on a previously published model in this paper the methodology is described in detail and it is shown that sea level change is the dominant factor responsible for the recorded variability in red sea 18o pdb for sea level changes greater than 12 m variables such as temperature or net evaporation are shown to have relatively small effects on the oxygen isotope record the modelled 18o pdb to sea level relationship is given in terms of a fifth order polynomial which may be used to describe relative sea level from central red sea oxygen isotope records we show how established sea level records from fossil reef terraces for the last 20 kyr are successfully simulated from central red sea oxygen isotope records we also examine the spatial variability of 18o pdb in the basin over the last 13 kyr

oxygenation changes in the deep western arabian sea during the last 190 000 years productivity versus deepwater circulation 1 fluctuations in the abundance of selected foraminiferal indicator species and diversity allowed the reconstruction of changes in deepwater oxygenation and monsoon driven organic matter fluxes in the deep western arabian sea during the last 190 kyr times of maximum surface production coincide with periods of intensified sw monsoon as shown by the abundance of globigerina bulloides and enhanced carbonate corrosion benthic ecosystem variability in the deep arabian sea is not exclusively driven by variations in monsoonal upwelling and related organic matter supply to the seafloor but also by changes in deepwater ventilation deepening of the base of the oxygen minimum zone omz below 1800 m water depth is strongly coherent on the precessional band but lags proxies of sw monsoon strength by 4 to 6 kyr the out of phase relationship between omz deepening and maximum sw monsoon strength is explained by temporal changes in the advection of oxygen rich deepwater masses of north atlantic and antarctic origin this process affected the remineralization and burial efficiency of organic matter in the deep arabian sea resulting in the observed phase lag between maximum monsoon strength and organic carbon preservation

carbon and oxygen isotope time series records of planktonic and benthic foraminifera from the arabian sea implications on upwelling processes abstract oxygen and carbon isotopic analyses have been performed on the tests of globigerina bulloides and pulleniatina obliquiloculata planktonic foraminifera and uvigerina excellens benthic foraminifer to study the evolution of surface and bottom water hydrographic changes associated with summer monsoon upwelling process at the oman margin over the last 19 kyr globigerina bulloides p obliquiloculata and u excellens show sharp depleted 18o excursions around 9 ka ascribed to the distribution of melt water flux of termination ib in this region a synchronous 18o shift in surface subsurface and bottom water living foraminifera around 9 ka reveals a rapid transfer of the termination ib signal through the vertical circulation of the arabian sea in response to peak monsoon intensity a steep increase in 13c values of u excellens between 9 and 8 ka reveals advection of red sea intermediate water into the arabian sea during peak monsoon intensity for the first time a drastic climatic shift at 4 ka is noticed in the arabian sea as evidenced by the lowest 18o values of both p obliquiloculata 1 10 and g bulloides 2 29 this points to reduced upwelling strength both planktonic foraminifer species 18o records suggest the establishment of modern surface water conditions after 3 ka at the oman margin

carbonate recrystallisation and organic matter maturation in heat affected sediments from the shaban deep red sea parasound profiles across the shaban deep in the red sea indicate turbiditic transport of surface sediments from the topographic hight basalt ridge into the interior of the deep this is supported by petrographical and isotope geochemical evidence in the east basin of the shaban deep where the presence of variable mixtures of authochtonous and allochthonous sediment compounds had been found the uppermost 170 cm of both sediment cores 17008 1 and 17009 3 reveal normal stable oxygen isotope values for the planktonic foraminifera g ruber near 1 which is indicative for carbonate formation in red sea surface water around 27 c however below 182 cm in core 17008 1 highly variable 18o values for g ruber between 0 26 and 10 68 occur which are not the result of temperature controlled oxygen isotope fractionation between foraminiferal carbonate and red sea surface water the lowest 18o values of 10 68 measured for highly altered foraminifera shells suggests carbonate precipitation higher than 90 c organic petrographical observations show a great diversity of marine derived macerals and terrigenous organic particles based on petrographical investigations sediment core 17008 1 can be subdivided in intervals predominantly of authochtonous character i e 1 3 5 corresponding to core depths 0 170 cm 370 415 cm 69 136 cm and allochthonous thermally altered character e g 2 4 corresponding to core depths 189 353 cm 515 671 cm allochthonous thermally altered material displays a wide to an extremely wide range of maturities 0 38 1 42 rr and also natural coke particles were found similarily the organic geochemical and pyrolysis data indicate the predominance of well preserved immature algal and bacterial remains with a minor contribution of land plant material sediments below 170 cm core 17008 1 contain contributions of re sedimented pre heated material most likely from the area of the basaltic ridge this is documented by individual coke particles reduced hydrogen indices and elevated tmax values up to 440 c an oil type contribution evidenced by mature biomarkers hopene hopane ratios elevated background fluorescence n alkane distribution is also present in the sediments which most likely originated at greater depth and impregnated the surface sediments the heat source responsible for recrystallisation of foraminiferal carbonate and maturation of organic particles in shaban deep sediments most likely is attributed to modern basalt extrusions which now separate the shaban deep subbasins

effect of interarray elevation differences on infrasound beamforming summary the international monitoring system infrasound network will upon completion contain 60 microbarometer arrays with apertures of between 1 and 4 km these arrays are located within a variety of terrains leading to large ratios of interelement elevation differences to array aperture for those arrays situated in areas of significant topography systematic errors in beamforming estimates caused by neglecting the vertical extent of the arrays are quantified for both signal backazimuth and apparent velocity of the 43 arrays certified as of 2011 january i14cl on juan fernandez island has the greatest topography across an array with a least squares fitted plane through the array elements having an 8 1 slope from the horizontal compared to a network mean of 1 6 beamforming errors both backazimuth and apparent velocity are a function of the arrival azimuth and become increasingly large for steeply inclined arrivals such that systematic errors will be significantly larger for signals returned from the thermosphere compared to those from the stratosphere at several arrays azimuthal errors due to array topography are comparable in magnitude to deviations often associated with atmospheric propagation these findings are illustrated using signals recorded in greenland at i18dk where differences between results processed using both full 3 d array geometry and the 2 d topography neglected approximation exhibit good correspondence to theoretical predictions

sea level reversal during termination ii the termination of the penultimate glacial period tii shows both similarities and differences to the last termination ti both terminations show significant cold reversals in the postglacial warming trend ti consists of a continuously increasing sea level trend whereas tii may demonstrate a sea level reduction midway through the termination we present a new continuous sea level record for tii derived from red sea 18 o records that supports the existence of the tii sea level reversal the record gives an unprecedented look at the structure of the tii sea level reversal which consists of an early highstand lasting several millennia in duration followed by a 30 12 m to 40 12 m reduction in sea level and a stillstand of several millennia before the final sea level rise to the marine oxygen isotope stage mis 5e interglacial we suggest that there is a link between the sea level reversal and internal millennial scale variability in the climate system

characterization of the 2008 kasatochi and okmok eruptions using remote infrasound arrays 1 the 2008 plinian eruptions of kasatochi and okmok volcanoes were recorded by six remote international monitoring system infrasound arrays high amplitude infrasound at these stations combined with remote sensing permits insight into important volcanic source parameters such as origin times durations and source characteristics infrasound from the 7 8 august kasatochi eruption consists of three well defined eruption pulses with the first two steam rich and the last ash rich pulse 2 is the most energetic and impulsive okmok produced over 9 h of continuous infrasound on 12 13 july acoustic propagation modeling for the okmok eruption and first kasatochi pulse predict thermospheric ducting and origin times consistent with seismic and satellite observations however theoretical acoustic origin times of pulses 2 3 are predicted to occur 15 min earlier than the seismic stratospheric ducting for these later pulses provides more consistent origin times although both volcanoes ejected ash into the stratosphere 15 km kasatochi produced higher amplitude infrasound than okmok previous studies have shown sustained infrasound with frequencies 2000 km and does not seem to be appreciably affected by changes in ash content between the eruption pulses

earthquake depth estimation using the f trace and associated probability determining the depths of seismic disturbances is of great importance when monitoring compliance with the comprehensive nuclear test ban treaty ctbt in plate tectonic studies and in seismic hazard assessments we have developed a semiautomated method that uses the output from the f detector a processing technique that detects correlated signals crossing a seismometer array as a tool for identifying candidate depth phases and hence estimating hypocenter depth the f trace can be interpreted approximately in terms of probability this can be used to help interpret signals and identify candidate depth phases here a method of calculating f probability traces that optimally highlight candidate depth phases is presented the values of the probability trace at the predicted times for pp and sp for a given depth are then weighted and summed over several high quality medium aperture array stations a clear maximum in the trace sum function with depth is interpreted as the probable hypocenter depth results for earthquakes from the lop nor and hindu kush regions indicate that this method of depth estimation is effective for many earthquakes with magnitude greater than about m b 4 0 and depths greater than around 10 km the method is best suited as a tool to be used by analysts to estimate the depths of individual seismic disturbances of special interest or groups of earthquakes in regions where there is a good azimuthal distribution of medium aperture array stations

red sea during the last glacial maximum implications for sea level reconstruction the red sea is connected to the indian ocean via a narrow and shallow strait and exhibits a high sensitivity to atmospheric changes and a reduced sea level we used an ocean general circulation model to investigate the hydrography and circulation in the red sea in response to reduced sea level and modified atmospheric conditions occurring during the last glacial maximum lgm the model salinity shows high sensitivity to sea level reduction together with a mild atmospheric impact sea level reduction affects the stratification and alters the circulation pattern at the strait of bab el mandab which experiences a transition from a submaximal flow to a maximal flow the best correlation to reconstructed conditions during lgm exists when the water depth of the hanish sill the shallowest part in the strait of bab el mandab is 33 10 75 m which would be affected by a sea level lowering of approximately 105 m our results support the reconstructed maximum salinity of around 57 practical salinity units because of a simple model that takes into account mixing processes along the strait and comparison of the surface salinity gradient to reconstructions based on isotopic records from sedimentary cores the salinity and 18o are sensitive to the mixing process at the strait and the sensitivity increases as the sea level is further reduced a local relative sea level reduction of approximately 105 m is also in close agreement with the inference of the lgm low stand of the sea at the location of the sill based on the ice 5g vm2 model

the 12 december 2017 baumgarten gas hub explosion a case study on understanding the occurrence of a large infrasound azimuth residual and a lack of seismic observations the baumgarten explosion occurred on 12 december 2017 at a gas storage site about 30 km east of vienna austria acoustic arrivals from this accidental surface explosion were detected at dozens of stations of the alparray seismic network to distances up to 150 km mainly in easterly directions thus it was expected that the hungarian infrasound array pszi located about 230 km to the east southeast of baumgarten would detect this acoustic wave as well standard progressive multichannel correlation processing and frequency wavenumber analysis identified a signal emerging at 7 57 55 utc from an azimuth of 296 300 and with trace velocity 400 m s the extraordinarily high trace velocity and excessive backazimuth residual relative to the explosion site direction of 282 however cast strong doubts on the arrival s connection to the baumgarten event accounting for the effect of non planar geometry of the infrasound array results in a reduction of the azimuth residual by half additionally 2d and 3d raytracing methods are used including the european centre for medium range weather forecasts ecmwf atmospheric model to further explain the remaining azimuth residual as well as to elucidate the large trace velocity estimates the prevailing stratospheric winds in excess of 150 m s are identified as the underlying cause including both factors the initial azimuth residual of up to 18 decreases to 4 allowing to associate the infrasound signal at pszi with the baumgarten event finally the data from a seismic station at 30 km range is re investigated for magnitude estimation the local magnitude of ml 1 0 explains well the scarcity of seismic observations within 50 km range where three or four stations show signals mainly consisting of rg type surface waves but no body waves

palaeoceanographic evolution of the central red sea during the late holocene three multicores were studied in the central red sea off port sudan at a w e transect in order to reconstruct palaeoceanographic conditions of the past 6000 years downcore fluctuations in the rel

antiphasing between rainfall in africa s rift valley and north america s great basin the beginning of the bolling allerod warm period was marked in greenland ice by an abrupt rise in 18o an abrupt drop in dust rain and an abrupt increase in atmospheric methane content the surface waters in the norwegian sea underwent a simultaneous abrupt warming at about this time a major change in the pattern of global rainfall occurred lake victoria latitude 0 which prior to this time was dry was rejuvenated the red sea which prior to this time was hypersaline freshened lake lahontan which prior to this time had achieved its largest size desiccated whereas the chronologic support for the abruptness of the hydrologic changes is firm only for the red sea in keeping with evidence obtained well away from the northern atlantic in the santa barbara basin and the cariaco trench the onset and end of the millennial duration climate events were globally abrupt if so the proposed linkage between the size of african closed basin lakes and insolation cycles must be reexamined

aplanktonic zones in the red sea abstract we use micropalaeontological and stable isotope results for a series of cores from north to south through the red sea to assess temporal and spatial patterns of change in planktonic foraminiferal faunas leading up to the remarkable full glacial red sea aplanktonic zones aplanktonic zones reflect salinities in the red sea in excess of the lethal 49 p s u limit caused by reduced exchange transport through the strait of bab el mandab due to glacial sea level lowering concerning the last glacial cycle aplanktonic conditions began at 39 ka bp in the north where salinities eventually reached 55 57 p s u paradoxically planktonic faunas are reported to have survived the last glacial maximum in the northern gulf of aqaba suggesting a poorly understood freshwater dilution at that time aplanktonic conditions s 49 p s u reached the south central red sea by 22 ka bp while planktonic foraminiferal faunas continued albeit in very low abundances and limited diversity s 45 p s u in the southernmost red sea during marine isotope stage mis 6 the 49 p s u isohaline appears to have resided in the central red sea between cores kl11 and md921017 we observe a systematic sequence of species disappearances before all glacial maxima of the last 500 kyr absence of a logical relationship with sea levels suggests that the disappearance sequences are not related to a general salinity increase instead we argue that the sequences were driven by complex reorganisations in hydrography stratification productivity food availability and subsurface oxygenation reproduction habitats the onset is marked by dramatic basin wide expansion of conditions that today are restricted to only the southern red sea suggesting an expansion of the dominance of ne monsoonal circulation over the entire red sea this expansion occurred 15 or more kyr before the aplanktonic zones of mis 12 6 and 2 and also before mis 10 and 8 which never reach the aplanktonic stage regarding the last glacial cycle this event occurred as early as 75 ka bp mis 4 5 boundary after this major climatic reorganisation we reconstruct progressive intensification of the new conditions especially marked by northward expansion and intensification of the subsurface oxygen minimum zone omz during the last glacial cycle a shallow and very distinct omz affected the central red sea as early as 68 ka bp and the north as late as 55 ka bp the omz expansion intensification appears to have been interrupted by episodes of increased ventilation

structural and kinematic analysis of eastern ovda regio venus implications for crustal plateau formation crustal plateaus on venus constitute one of that planet s most intriguing tectonic features they host so called tessera terrain or deformed crust exhibiting two or more sets of intersecting tectonic lineaments which comprises 8 of venus surface major questions surrounding crustal plateaus and tessera terrain include 1 what is the nature of crustal plateau deformation what structures are present and what are their spatial and temporal relations 2 what is the global distribution of tessera terrain does it form a global layer under the regional plains cropping out in crustal plateaus or is it confined to crustal plateaus and 3 what are the implications of 1 and 2 for understanding the processes responsible for formation and deformation of crustal plateaus structural and kinematic analyses reveal that deformation at ovda regio venus largest crustal plateau is characterized by linear shallow steep sided troughs ribbons long arcuate long wavelength folds short mid wavelength folds and wide complex graben temporal relations between structures lead to a three phase regional strain history consisting of 1 layer normal flattening of a thin competent membrane resulting in radially oriented distributed extension ribbon formation 2 modest contraction of a thicker layer concentric folding at plateau margins interference folding in the plateau interior and 3 limited extension localized at fold crests graben formation wavelength analysis of ribbons and folds places limits on the thickness of the competent layer during each stage of deformation and reflects an early shallow brittle ductile transition bdt that deepened with time ovda s deformation topography and gravity are all spatially correlated strongly suggesting a genetic relationship between surface deformation and processes causing crustal thickening and plateau uplift thus tessera terrain at ovda regio is likely confined to the topographically high plateau and does not extend beneath the surrounding regional plains similar patterns persist at other crustal plateaus indicating that tessera terrain is in general confined to crustal plateaus and does not form a globally continuous layer ovda s structures their spatial and temporal relations the resulting strain history and the behavior of the bdt through time support a model of mantle plume upwelling in a thin lithospheric regime for crustal plateau formation and contradict previous downwelling models similarities between structural and kinematic trends at ovda regio and other crustal plateaus lend support to this idea c 1999 academic press

organic rich sediments in brine filled shaban and kebrit deeps northern red sea the element compositions si ca and al of up to 2 1 1 ka old sediments in about 10 in long cores from the southern basin of the shaban and kebrit deeps in the northern red sea allowed a classification of major sediment types in carbonate sands and muds and siliceous oozes a feooh enriched sediment horizon and a few samples with high zn values in the kebrit core indicate a hydrothermal origin probably near the brine sea water interface with subsequent transport of hydrothermal compounds into the deep sediments high organic carbon contents up to 8 4 are positively correlated with the ba concentrations which suggests that high bioproductivity and rapid deposition c 14 dating suggests a sedimentation rate near 70 cm ka led to the formation of sapropelic sediments between 11 8 and 13 6 ka younger dryas organic petrological observations showed that the sediment organic material largely consists of 20 gm sized roundish fecal pellets intimate mixtures of organic matter and inorganic constituents and bituminite terrestrial organic matter pollens of land plants fusinite etc is very rare in the sediment cores from both deeps organic geochemical investigations of kerogens and organic extracts show that a significant hydrothermal hydrocarbon production did not occur in near surface sediments of the shaban and kebrit deeps rock eval pyrolysis of kerogens characterised the organic matter to be of type ii quality the delta c 13 values of the kerogens from the most prominent sapropel in the shaban deep indicate an enrichment of c 12 rich nutrients in the water column during postglacial sapropel formation in the younger dryas the n alkane spectra are dominated by short chain lengths between n c 15 and n c 25 prevailing n c 15 to n c 25 alkanes in low mature sediments are indicative of algal and microbial source pristane phytane ratios are generally low i to similar to 1 which suggests that anoxic conditions prevailed within the anaerobic brine filled deeps for the whole time covered by the sediments this again indicates that sapropel formation was caused by high bioproductivity in the northern red sea rather than episodic stagnation with better preservation of the organic matter long chain alkenones and sterols are the dominating compounds of the lipid fraction cholesterol contents in the sediment cores reflect phases of eukaryotes production in the water column whereas the positive correlations of dinosterol with toc and the amounts of total extract suggests that the major organic carbon source in the northern red sea during postglacial high productivity stages were dinoflagellates another important carbon source however is indicated by the occurrence of 22 29 30 trisnorhopan 21 one tnh although the formation of tnh from its precursors is not fully understood this compound probably results from microbial degradation of intact bacteriohopanepolyols bhp which can be used as indicators for bacterial abundances and phyla tnh is most likely produced at the brine sea water interface where sedimenting organic matter accumulates and if the redoxcline corresponds to the density gradient the organic matter is subjected to efficient aerobic bacterial degradation processes however during high bioproductivity stage younger dryas the redoxcline was probably higher in the water column and thus a significant tnh production at the brine sea water interface did not occur at times of sapropel formation in the northern red sea deeps c 2007 elsevier b v all rights reserved

paleosalinity and δ18o a critical assessment in paleoceanography a traditional application of oxygen isotope ratios in fossil carbonate from deep sea cores concerns the reconstruction of paleotemperatures recently isotopic data have been increasingly employed in the reconstruction of paleosalinities as well this application involves a number of basic assumptions a critical review of which is presented here as the calculation of paleosalinity from 18o residuals assumes constant and linear surface water salinity s 18o relationships we investigate this basic assumption for areas with important and variable freshwater budget and or sea ice influences we show that it is particularly unwarranted to assume such temporally invariant linearity in temperate and subpolar seas because of the effects of freezing and melting more critically we argue that the determinant of many regions s 18o is advection not the local water balance so that the basic 18o of seawater in many regions of the world ocean would likely have changed in a manner somewhat different from that expected from the ice volume record although the differences may not be significant for the gross reconstruction of such features as past sea level we believe they do potentially bias paleosalinity reconstructions mostly toward high salinities to fully exploit the potential of oxygen isotope records as quantitative paleosalinity indicators both the spatial and temporal variabilities need to be constrained hence we recommend that 1 for any time slice of specific interest to paleoceanographic and paleoclimatological studies a coupled ocean atmosphere isotope model or at least an ocean isotope model driven by a paleoclimate isotope model should be used to define the distribution of the base mixing end member 18o of sea water 2 much further regional scale research is needed on flux rates and isotopic compositions of the various terms in the freshwater budget as well as on the variability in the various advective terms the latter variability may be assessed from reconstructions of past seaice distributions and of volume fluxes isotopic compositions of outflow from marginal seas and through sea straits passages

stratigraphy palaeoenvironments and model for the deposition of the abdur reef limestone context for an important archaeological site from the last interglacial on the red sea coast of eritrea stone tools discovered within uplifted marine terraces along the red sea coast of eritrea at the abdur archaeological site dated to 125 7 ka the last interglacial marine isotope stage 5e show that early humans occupied coastal areas by this time walter et al 2000 nature 405 65 69 in the present paper the stratigraphy facies types and faunal composition from 25 measured sections of the tool bearing abdur reef limestone arl are documented in detail and interpreted to provide a palaeoenvironmental context for the stone artefacts and a model for the deposition of the arl the arl represents a complex marine terrace sequence erosional surfaces indicative of interrupted sedimentation are locally observed at two levels within the arl they subdivide the complex into three subunits named 5e1 5e2 and 5e3 representing different stages of the marine isotope stage 5e sea level highstand comprising six depositional phases i vi of the arl subunit 5e1 begins with the initial transgression of the 5e sea level highstand leading to the deposition of widespread lag gravels on which rich oyster beds developed in shallow water phase i it further records rapid deepening accompanied by the deposition of low energy carbonates with scarce corals phase ii and later shoaling characterised by local development of a fringing reef tract in a sedimented environment phase iii subunit 5e1 is capped locally by a burrowed hardground that is laterally equivalent to depositional discontinuities interpreted as caused by a globally recognised mid 5e sea level low stand phase iv extensive reef build up in response to sea level rise and improved conditions for coral growth characterises subunit 5e2 phase v a possible second sea level drop during the 5e highstand is inferred from the oyster encrusted upper surface of subunit 5e2 subunit 5e3 encompasses restricted coral patches that developed on the upper surface of the underlying subunit during the last stage of the 5e marine high stand phase vi two different toolkits are found in the arl one consists of bifacial hand axes and cores of the acheulian industry typically associated with the oyster beds encrusted on the transgressive lag deposits the other consists of middle stone age msa type obsidian flakes and blades mainly found in the nearshore and beach environments alongside debris from marine invertebrates and large land mammals the distribution of these tools suggests that foraging activities of early humans varied with environmental setting the abdur archaeological site represents a late example of the acheulian msa transition seen as a benchmark for early modern human behaviour and is to date the earliest well dated example of early human adaptation to marine food resources

a late pleistocene transgression in thailand a marine molluscan fauna from ban praksa samut prakan province abstract a late pleistocene molluscan fauna sampled at ban praksa near the chao phraya river mouth lower central plain of bangkok thailand is herein analyzed and paleoecologically characterized revealing a shallow infralittoral coarse hard bottomed environment the comparison of the ban praksa association with several coeval ones recovered from phra pradaeng formation seems to be evidence of a 10 000 year hiatus between two separate groups of marine faunas possibly belonging to different interstadial transgressive peaks that occurred during the long term sea level regression following the last interglacial

influence of seawater exchanges across the bab el mandeb strait on sedimentation in the southern red sea during the last 60 ka 1 the location of core md92 1008 close to the southern edge of the red sea is ideal to study the evolution of seawater exchanges with the northern indian ocean through the bab el mandeb narrow strait the present study was aimed at documenting the paleoceanographic evolution of this area over the past 60 ka using high resolution magnetic sedimentological and geochemical indicators two modes of variability dominate the records i long term glacial interglacial variations and ii rapid millennial scale variability dansgaard oeschger type during the last glacial period changes in magnetic concentration were documented from natural and laboratory magnetizations after proper normalization they are inversely correlated to the total organic carbon toc content pointing out the key role played by reductive dissolution of magnetite on the evolution of magnetic concentration based on the temporal evolution of toc caco3 and planktonic 13c we suggest that past changes in the organic matter content i were closely linked to glacio eustatic variations which modulated long term seawater exchanges and nutrient supplies to the red sea through the narrow bab el mandeb strait and ii reflect millennial scale changes in productivity driven by monsoon wind intensity which controlled the amount of nutrient rich intermediate waters upwelled in the gulf of aden during the summer season and advected into the southern red sea the sea level rise following the onset of deglaciation generated a rapid flush of detrital material that was accumulated on the continental margins and on the previously emerged zones of the bab el mandeb area

human occupation of the northern arabian interior during early marine isotope stage 3 the early part of marine isotope stage mis 3 ca 60 50 ka is a crucial period for studying human demography and behaviour in south west asia and how these relate to climatic changes however the archaeological and palaeoenvironmental records for mis 3 in critical areas such as the arabian peninsula remain poorly developed here we present findings from the al marrat basin in the nefud desert which provides the first clear evidence for both increased humidity and human occupation of the interior of northern arabia during early mis 3 a middle palaeolithic assemblage dated by optically stimulated luminescence to ca 55 ka was found stratified within a sequence of relict palustrine deposits indicative of shallow water body formation in the al marrat basin hominin presence in northern arabia at this time coincides with the intensification and northward displacement of monsoon rainfall systems during a period of maximum insolation these findings add to a growing corpus of palaeoenvironmental evidence which indicates that the arabian interior was neither arid nor unpopulated during early mis 3 and that hydrodynamic responses to enhanced moisture availability facilitated demographic expansions into the arabian interior

late quaternary biostratigraphy and paleotemperatures of the red sea and the gulf of aden based on planktonic foraminifera and pteropods abstract the quantitative distributions of planktonic foraminifera and pteropods were analyzed in seven red sea cores and two deep sea cores from the gulf of aden and off sokotra island biostratigraphic intervals were distin guished corresponding to oxygen isotope stages 1 5 in the red sea and stages 1 3 in the gulf of aden the faunal assemblages demonstrate that in the red sea hydrological conditions changed significantly during the late quaternary especially at the last glacial maximum when water exchange at the bab el mandeb straits was at a minimum and at the pleistocene holocene boundary at the end of deglaciation water exchange renewal and pluvial conditions resulted in surface salinity decrease and stable stratification which was followed by a rise in planktonic fauna abundance and stagnation of bottom waters the more constant composition of rather cold water subtropical faunal assemblages in the gulf of aden during the last 40 000 50 000 yrs points to more stable hydrological parameters and to local upwelling or influx of arabian upwelling waters during the last stadial mean annual sea surface temperatures fell by at least 5 c compared to the present in the central part of the red sea and by 3 5 c in the western gulf of aden

the significance of diatoms in the formation of laminated sediments of the shaban deep northern red sea laminated sediments spanning the last 20 000 years though not continuously in the shaban deep a brine filled basin in the northern red sea were analyzed microscopically and with backscattered electron imagery in order to determine laminae composition with emphasis on the diatomaceous component based on this detailed study we present schematic models to propose paleoflux scenarios for laminae formation at different time slices the investigated core geob 5836 2 26 12 61 n 35 21 56 e water depth 1475 m shows light and dark alternating laminae that are easily distinguishable in the mid holocene and at the end of the deglaciation 13 15 ka period light layers are mainly composed of coccoliths terrigenous material and diatom fragments while dark layers consist almost exclusively of diatom frustules monospecific or mixed assemblages the regularity in the occurrence of coccolith diatom couplets points to an annual deposition cycle where contrasting seasons and associated plankton blooms are represented diatoms fall winter deposition coccoliths summer signal we propose that for the past 15 000 years the laminations represent two season annual varves strong dissolution of carbonate with the concomitant loss of the coccolith rich layer in sediments older than 15 ka prevents us from presenting a schematic model of annual deposition however the diatomaceous component reveals a marked switch in species composition between last glacial maximum lgm sediments dominated by chaetoceros resting spores and sediments somewhat younger 18 19 ka dominated by rhizosolenia we propose that different diatom assemblages reflect changing conditions in stratification in the northern red sea strong stratification conditions such as during two meltwater pulses at 14 5 and 11 4 ka are reflected in the sediment by rhizosolenia layers while chaetoceros dominated assemblages represent deep convection conditions

coherent response of arabian sea upwelling and pollen transport to late quaternary monsoonal winds the indian summer monsoon causes large seasonal changes in the environments of both eastern africa and the arabian sea here we compare time series 140 kyr long of selected pollen types and foraminiferal upwelling faunas preserved in marine sediments to identify the frequencies of their variability and the coherence and phase of the terrestrial and marine responses to monsoonal circulation during interglacial intervals the pollen and upwelling records of the western arabian sea indicate stronger monsoons and are both coherent and in phase at periodicities near the precession of the earth s rotational axis 23 kyr we conclude that the strength of the monsoonal southwesterlies accounts for this high coherence of marine and terrestrial records during interglacial intervals low correlation during glacial phases indicates weaker monsoons and some decoupling of these two records these data indicate that two distinct modes of monsoon variability may exist an interglacial mode with strong monsoons and effective coupling of terrestrial and marine records and a glacial mode with both weaker monsoons and decreased linkage between arabian sea pollen and upwelling records