a numerical study on convergence of alongshore flows over the texas louisiana shelf 1 a hydrodynamic model is used to investigate convergent alongshore flows over the texas louisiana shelf characterized by down coast flows over the northern shelf encountering up coast flows over the southern shelf the model s ability to reproduce realistic current salinity and surface elevation fields is demonstrated through positive model skill scores when comparing model simulations to observational data the convergent flows are explored on both weather band and seasonal time scales for weather band scales this study focuses on wintertime convergent events the model predicted locations of convergent flows are supported by current measurements we find that the formation of convergent flows is primarily caused by along coast variation in the alongshore component of wind forcing which in turn is due to the curvature of the texas louisiana coastline in general the alongshore currents are well correlated with alongshore winds however the convergence points of currents and winds are not colocated but rather convergence points in ocean currents typically occur down coast of convergence points in the wind this offset is demonstrated to be mainly caused by buoyancy forcing that can drive the convergence location in the currents farther down coast no specific temporal pattern is found for the weather band convergence locations whereas at seasonal time scales the monthly mean convergence exhibits a prominent seasonal pattern with up coast migration of convergence locations in spring and summer and down coast migration in fall and winter

forced oscillations near the critical latitude for diurnal inertial resonance abstract oscillations at or close to the inertial frequency are widely observed in shelf seas where frictional damping is weak in the vicinity of latitudes 30 n and s such motions may become significantly enhanced by a resonance in which the local inertial frequency coincides with that of diurnal forcing under these conditions regular daily variations in wind stress tend to produce large anticyclonic motions that may extend throughout the water column as shown in the analytical theory of craig here the authors examine new observations from a location close to the critical latitude on the namibian shelf in the southern hemisphere the measurements cover almost the full depth 175 m of the water column by using upward and downward looking adcps suspended in midwater the observed flow involves a steady drift to the north maximum 11 cm s 1 at 40 m but the kinetic energy budget is dominated by anticyclonic circular motions with speeds in the surface layers exceeding 40 cm s 1 at times comparably e

a sensitivity analysis of meteoric infrasound 1 we perform a multicomponent sensitivity analysis of how the physical and dynamical parameters that characterize a meteor in fall affect the ground overpressure and period of a plausible emitted n wave signal the nonlinear propagation model used throughout is based upon whitham s nonlinearization method which is modified to take into account a stratified atmosphere we use sensitivity indices derived using a fourier amplitude sensitivity test to measure how the meteor parameters uncertainties affect the uncertainty in the overpressure and period of an emitted n wave the investigated parameters include the azimuth entry angle diameter drag coefficient density and initial velocity of the meteor as well as the atmosphere the method is used to re examine the crater forming meteorite fall near carancas peru 2007 we obtain good agreement between the simulated signals and observed waveforms it is shown that ground overpressure uncertainty depends on the atmospheric uncertainties that are strongly correlated with the unknown trajectory whereas the period is governed by the diameter uncertainties finally we consider new waveform parameters that help characterize the meteor

observed energy exchange between low frequency flows and internal waves in the gulf of mexico abstracta long term mooring array deployed in the northern gulf of mexico is used to analyze energy exchange between internal waves and low frequency flows in the subthermocline 245 450 m there

thermoluminescence dating of the kamil impact crater egypt thermoluminescence tl dating has been used to determine the age of the meteorite impact crater at gebel kamil egyptian sahara previous studies suggested that the 45 m diameter structure was produced by a fall in recent times less than 5000 years ago of an iron meteorite impactor into quartz arenites and siltstones belonging to the lower cretaceous gilf kebir formation the impact caused the complete fragmentation of the impactor and the formation of a variety of impactites e g partially vitrified dark and light materials present as ejecta within the crater and in the surrounding area after a series of tests to evaluate the tl properties of different materials including shocked intra crater target rocks and different types of ejecta we selected a suite of light colored ejecta that showed evidence of strong thermal shock effects e g partial vitrification and the presence of high temperature and pressure silica phases the abundance of quartz in the target rocks including the vitrified impactites allowed tl dating to be undertaken the variability of radioactivity of the intracrateric target rocks and the lack of direct in situ dosimetric evaluations prevented precise dating it was however possible to constrain the impact in the 2000 bc 500 ad range if as we believe the radioactivity measured in the fallback deposits is a reliable estimate of the mean radioactivity of the site the narrower range 1600 400 bc at the 2 confidence level can be realistically proposed

inertial currents in the caspian sea 1 we present the first simulation of near inertial oscillations in the caspian sea model amplitude is in good agreement with observations annual mean near inertial oscillations are found to be up to 14 cm s with a seasonal maximum in the summer approximately twice as great as in the winter the energy increases away from the coast at a rate of up to 0 8 cm2 s 2 km 1 the strongest relationship is with distance from the 50 m depth contour the peak amplitude also occurs later further from the coastline with a delay of the order of 1 day per 100 km distance these features are consistent with propagating baroclinic and barotropic waves

redistribution of energy available for ocean mixing by long range propagation of internal waves ocean mixing which affects pollutant dispersal marine productivity and global climate1 largely results from the breaking of internal gravity waves disturbances propagating along the ocean s internal stratification a global map of internal wave dissipation would be useful in improving climate models but would require knowledge of the sources of internal gravity waves and their propagation towards this goal i present here computations of horizontal internal wave propagation from 60 historical moorings and relate them to the source terms of internal waves as computed previously2 3 analysis of the two most energetic frequency ranges near inertial frequencies and semidiurnal tidal frequencies reveals that the fluxes in both frequency bands are of the order of 1 kw m 1 that is 15 50 of the energy input and are directed away from their respective source regions however the energy flux due to near inertial waves is stronger in winter whereas the tidal fluxes are uniform throughout the year both varieties of internal waves can thus significantly affect the space time distribution of energy available for global mixing

geological and geophysical investigation of kamil crater egypt we detail the kamil crater egypt structure and refine the impact scenario based on the geological and geophysical data collected during our first expedition in february 2010 kamil crater is a model for terrestrial small scale hypervelocity impact craters it is an exceptionally well preserved simple crater with a diameter of 45 m depth of 10 m and rayed pattern of bright ejecta it occurs in a simple geological context flat rocky desert surface and target rocks comprising subhorizontally layered sandstones the high depth to diameter ratio of the transient crater its concave yet asymmetric bottom and the fact that kamil crater is not part of a crater field confirm that it formed by the impact of a single iron mass or a tight cluster of fragments that fragmented upon hypervelocity impact with the ground the circular crater shape and asymmetries in ejecta and shrapnel distributions coherently indicate a direction of incidence from the nw and an impact angle of approximately 30 to 45 newly identified asymmetries including the off center bottom of the transient crater floor downrange maximum overturning of target rocks along the impact direction and lower crater rim elevation downrange may be diagnostic of oblique impacts in well preserved craters geomagnetic data reveal no buried individual impactor masses 100 kg and suggest that the total mass of the buried shrapnel 100 g is approximately 1050 1700 kg based on this mass value plus that of shrapnel 10 g identified earlier on the surface during systematic search the new estimate of the minimum projectile mass is approximately 5 t

the flux of small near earth objects colliding with the earth asteroids with diameters smaller than approximately 50 100 m that collide with the earth usually do not hit the ground as a single body rather they detonate in the atmosphere these small objects can still cause considerable damage such as occurred near tunguska siberia in 1908 the flux of small bodies is poorly constrained however in part because ground based observational searches pursue strategies that lead them preferentially to find larger objects a tunguska class event the energy of which we take to be equivalent to 10 megatons of tnt was previously estimated to occur every 200 300 years with the largest annual airburst calculated to be approximately 20 kilotons kton tnt equivalent ref 4 here we report satellite records of bolide detonations in the atmosphere over the past 8 5 years we find that the flux of objects in the 1 10 m size range has the same power law distribution as bodies with diameters 50 m from this we estimate that the earth is hit on average annually by an object with approximately 5 kton equivalent energy and that tunguska like events occur about once every 1 000 years

shear and baroclinic energy flux on the summer new england shelf observations are presented of internal wave properties and energy fluxes through a site near the 70 m isobath on the new england shelf in late summer data collected from a shipboard adcp and microstructure profiler over a three week period and projected onto dynamic vertical modes reveals large variations in the magnitude and vertical structure of internal waves baroclinic energy and shear were primarily associated with low mode near inertial and semidiurnal waves and at times high frequency solibores the energies in each mode varied by factors from 2 to 10 over several days and were not significantly correlated with one another the associated shear variance was concentrated in the thermocline however the strength and vertical range of shear varied significantly throughout the research period and depended sensitively on both the magnitude and evolving vertical mode content of the wave field shear during the quasi two layer solibores was strong enough to temporarily lower the 4 m richardson number below the threshold for shear instability energy flux through the site came primarily from the mode 1 internal tide in both linear and nonlinear solibore forms the average energy flux from the first five baroclinic modes was 130 w m 21 a comparison of energy fluxes from each mode and locally measured average dissipation rates suggests that near inertial and high mode waves were generated near the experimental site

diurnal sea breezes force near inertial waves along rottnest continental shelf southwestern australia abstractobservations of upper ocean dynamics close to the critical latitude ratio of the local inertial to diurnal frequency is 0 94 from a range of platforms surface currents using hf radar moored instruments and satellite remote sensing data off southwest australia indicated the presence of energetic near inertial waves generated through the diurnal inertial resonance during the austral summer when southerly winds and land sea breeze lsb system dominated the wind regime strong counterclockwise diurnal motions amplitudes surpassing 0 3 m s 1 penetrated to 300 m depth with diurnal vertical isotherm fluctuations up to 60 m the upward phase propagation speed of 140 m day 1 deep penetration of diurnal currents below the mixed layer and the 180 phase difference between the upper and lower water column suggested that the local lsb system caused the resonant diurnal motions relative vorticity fluctuations along two cross shore transects indicated changes to the local effective coriolis freq

enhanced vertical mixing in coastal upwelling systems driven by diurnal inertial resonance numerical experiments the land sea breeze is resonant with the inertial response of the ocean at the critical latitude of 30a n s 1d vertical numerical experiments were undertaken to study the key drivers of enhanced diapycnal mixing in coastal upwelling systems driven by diurnal inertial resonance near the critical latitude the effect of the land boundary was implicitly included in the model through the craig approximation for first order cross shore surface elevation gradient response the model indicates that for shallow water depths 100 m bottom shear stresses must be accounted for in the formulation of the craig approximation as they serve to enhance the cross shore surface elevation gradient response while reducing shear and mixing at the thermocline the model was able to predict the observed temperature and current features during an upwelling mixing event in 60 m water depth in st helena bay 32 5a s southern benguela indicating that the locally forced response to the land sea breeze is a key driver of diapycnal mixing over the event alignment of the sub inertial ekman transport with the surface inertial oscillation produces shear spikes at the diurnal inertial frequency however their impact on mixing is secondary when compared with the diurnal inertial resonance phenomenon the amplitude of the diurnal anticlock wise rotary component of the wind stress represents a good diagnostic for the prediction of diapycnal mixing due to diurnal inertial resonance the local enhancement of this quantity over st helena bay provides strong evidence for the importance of the land sea breeze in contributing to primary production in this region through nutrient enrichment of the surface layer

wind modulated buoyancy circulation over the texas louisiana shelf this numerical investigation examines buoyancy driven circulation on the texas louisiana shelf modulated by seasonal winds in wintertime with downcoast in the direction of kelvin wave propagation wind forcing the mississippi atchafalaya river plume exhibits a bottom advected pattern the plume is fairly wide and the horizontal density gradients span almost across the entire shelf inshore of 50 m within the plume vertical shear of alongshore flow is in thermal wind balance with the cross shore density gradient and the shear causes a slight reversal of alongshore flow near the bottom an alongshore flow estimated by the thermal wind relation along with an assumption of zero bottom velocity generally well agrees with the actual flow near the surface in regions deeper than 20 m in spring and summer the thermal wind balance derived flow deviates from the actual alongshore flow and an ekman flow driven by strong onshore wind makes the major contribution to the deviation besides the summertime upcoast wind component transforms the plume to a surface advected state resulting in reduced cross shore density gradients and increasing the relative importance of wind driven barotropic alongshore flow which contributes to the remaining deviation

ams radiocarbon analyses from lake baikal siberia challanges of dating sediments from a large oligotrophic lake abstract a suite of 146 new accelerator mass spectrometer ams radiocarbon ages provides the first reliable chronology for late quaternary sediments in lake baikal in this large highly oligotrophic lake biogenic and authigenic carbonate are absent and plant macrofossils are extremely rare total organic carbon is therefore the primary material available for dating several problems are associated with the toc ages one is the mixture of carbon sources in toc not all of which are syndepositional in age this problem manifests itself in apparent ages for the sediment surface that are greater than zero however because most of the organic carbon in lake baikal sediments is algal autochthonous in origin this effect is limited to about 1000 500 years which can be corrected at least for young deposits the other major problem with dating lake baikal sediments is the very low carbon contents of glacial age deposits which makes them extremely susceptible to contamination with modern carbon this problem can be minimized by careful sampling and handling procedures the ages show almost an order of magnitude difference in sediment accumulation rates among different sedimentary environments in lake baikal from about 0 04 mm year on isolated banks such as academician ridge to nearly 0 3 mm year in the turbidite depositional areas beneath the deep basin floors such as the central basin the new ams ages clearly indicate that the dramatic increase in diatom productivity in the lake as evidenced by increases in biogenic silica and organic carbon began about 13 ka in contrast to previous estimates of 7 ka for the age of this transition holocene net sedimentation rates may be less than equal to or greater than those in the late pleistocene depending on the site this variability reflects the balance between variable terrigenous sedimentation and increased biogenic sedimentation during interglaciations the ages reported here and the temporal and spatial variation in sedimentation rates that they imply provide opportunities for paleoenvironmental reconstructions at different time scales and resolutions

potential of pollen and non pollen palynomorph records from tso moriri trans himalaya nw india for reconstructing holocene limnology and human environmental interactions the high altitude lake tso moriri 32 55 46 n 78 19 24 e 4522 m a s l is situated at the margin of the indian summer monsoon and westerly influences in the trans himalayan region of ladakh human settlements are rare and domestic and wild animals are concentrated in the alpine meadows a set of modern surface samples and fossil pollen from a deep water core was evaluated with focus on indicator types revealing human impact grazing activities and lake system development during the last ca 12 cal ka bp the non pollen palynomorph npp record comprising remains of limnic algae and invertebrates as well as fungal spores and charred plant tissue fragments were examined in order to attest palaeolimnic phases and human impact respectively changes in the early and middle holocene limnic environment are mainly influenced by regional climatic conditions and glacier fed meltwater flow in the catchment area the npp record indicates low lake productivity with high influx of freshwater between ca 11 5 and 4 5 cal ka bp which is in agreement with the regional monsoon dynamics and published climate reconstructions geomorphologic observations suggest that during this period of enhanced precipitation the lake had a regular outflow and contributed large amounts of water to the sutlej river the lower reaches of which were integral part of the indus civilisation area the inferred minimum freshwater input and maximum lake productivity between ca 4 5 1 8 cal ka bp coincides with the reconstruction of greatest aridity and glaciation in the korzong valley resulting in significantly reduced or even ceased outflow we suggest that lowered lake levels and river discharge at a larger regional scale may have caused irrigation problems and harvest losses in the indus valley and lowlands occupied by sedentary agricultural communities this scenario in turn supports the hypothesis that mature harappan urbanism ca 4 5 3 9 cal ka bp emerged in order to facilitate storage protection administration and redistribution of crop yields and secondly the eventual decline of the harappan culture ca 3 5 3 cal ka bp was promoted by prolonged aridity there is no clear evidence for human impact around tso moriri prior to ca 3 7 cal ka bp with a more distinct record since ca 2 7 cal ka bp this suggests that the sedimentary record from tso moriri primarily archives the regional climate history

gebel kamil the iron meteorite that formed the kamil crater egypt abstract the 45 m in diameter kamil impact crater was formed 10 g inferred from the density map compiled in this study is 3400 kg field data indicate that the iron bolide approached the earth s crust from the northwest 305 340 n travelling along a moderately oblique trajectory upon hypervelocity impact the projectile was disrupted into thousands of fragments shattering was accompanied by some melting of the projectile and of the quartz arenite target rocks which also suffered shock metamorphism

a numerical study of wind induced near inertial oscillations over the texas louisiana shelf the wind induced near inertial oscillations over the texas louisiana shelf were studied using a two dimensional primitive equation model forced by an impulse of the surface wind numerical experiments reproduced the cross shelf structure of observed near inertial oscillations for a given spatially uniform impulse of the wind the model predicted the large near inertial oscillations that were surface intensified and characterized by a first baroclinic mode in the vertical the oscillations reached a maximum kinetic energy near the shelf break and decayed gradually toward the coast but rapidly offshore the magnitude and cross shelf distribution of the wind induced near inertial energy changed with wind direction effects of nonlinear advection on near inertial oscillations were largest near the shelf break and decreased both onshore and offshore where the bottom topography was gentle or flat they were stronger during the wind event and weaker after the wind ceased nonlinear interaction of tides and wind was weak on the shelf however it tended to provide a positive net contribution to near inertial currents for both cases where tides were in and out of phase with winds a simple theory suggests that the cross shelf variation of near inertial oscillations was controlled by the cross shelf gradient of surface elevation and the vertical gradient of reynolds stress

shock metamorphism and impact melting in small impact craters on earth evidence from kamil crater egypt kamil is a 45 m diameter impact crater identified in 2008 in southern egypt it was generated by the hypervelocity impact of the gebel kamil iron meteorite on a sedimentary target namely layered sandstones with subhorizontal bedding we have carried out a petrographic study of samples from the crater wall and ejecta deposits collected during our first geophysical campaign february 2010 in order to investigate shock effects recorded in these rocks ejecta samples reveal a wide range of shock features common in quartz rich target rocks they have been divided into two categories as a function of their abundance at thin section scale 1 pervasive shock features the most abundant including fracturing planar deformation features and impact melt lapilli and bombs and 2 localized shock features the least abundant including high pressure phases and localized impact melting in the form of intergranular melt melt veins and melt films in shatter cones in particular kamil crater is the smallest impact crater where shatter cones coesite stishovite diamond and melt veins have been reported based on experimental calibrations reported in the literature pervasive shock features suggest that the maximum shock pressure was between 30 and 60 gpa using the planar impact approximation we calculate a vertical component of the impact velocity of at least 3 5 km s 1 the wide range of shock features and their freshness make kamil a natural laboratory for studying impact cratering and shock deformation processes in small impact structures

the importance of independent chronology in integrating records of past climate change for the 60 8 ka intimate time interval this paper provides a brief overview of the most common dating techniques applied in palaeoclimate and palaeoenvironmental studies including four radiometric and isotopic dating methods radiocarbon 230th disequilibrium luminescence cosmogenic nuclides and two incremental methods based on layer counting ice layer varves for each method concise background information about the fundamental principles and methodological approaches is provided we concentrate on the time interval of focus for the intimate integrating ice core marine and terrestrial records community 60 8 ka this dating guide addresses palaeoclimatologists who aim at interpretation of their often regional and local proxy time series in a wider spatial context and therefore have to rely on correlation with proxy records obtained from different archives from various regions for this reason we especially emphasise scientific approaches for harmonising chronologies for sophisticated and robust proxy data integration in this respect up to date age modelling techniques are presented as well as tools for linking records by age equivalence including tephrochronology cosmogenic 10be and palaeomagnetic variations finally to avoid inadequate documentation of chronologies and assure reliable correlation of proxy time series this paper provides recommendations for minimum standards of uncertainty and age datum reporting

target projectile interaction during impact melting at kamil crater egypt abstract in small meteorite impacts the projectile may survive through fragmentation in addition it may melt and chemically and physically interact with both shocked and melted target rocks however the mixing mingling between projectile and target melts is a process still not completely understood kamil crater 45 m in diameter egypt generated by the hypervelocity impact of the gebel kamil ni rich ataxite on sandstone target allows to study the target projectile interaction in a simple and fresh geological setting we conducted a petrographic and geochemical study of macroscopic impact melt lapilli and bombs ejected from the crater which were collected during our geophysical campaign in february 2010 two types of glasses constitute the impact melt lapilli and bombs a white glass and a dark glass the white glass is mostly made of sio 2 and it is devoid of inclusions its negligible ni and co contents suggest derivation from the target rocks without interaction with the projectile 2 o 3 0 84 18 7 wt feo t 1 83 61 5 wt and nio 2 melt that eventually solidified as white glass behaved as an immiscible liquid and did not interact with the projectile during the excavation stage dark glass melt engulfed and coated the white glass melt target fragments and got stuck to iron meteorite shrapnel fragments this model could also explain the common formation of white and dark glasses in small impact craters generated by iron bodies e g wabar

formation of a small impact structure discovered within the agoudal meteorite strewn field morocco a relic impact structure was recognized within the strewn field of the agoudal iron meteorite the heavily eroded structure has preserved shatter cones in a limestone basement and remnants of autochthonous and allochthonous breccias fragments of iron incorporated into the allochthonous breccia have a chemical composition ni 5 16 wt ir 0 019 ppm similar to that of the agoudal meteorite supporting a syngenetic origin of the strewn field and the impact structure the total recovered mass of agoudal meteorite fragments is estimated at approximately 500 kg the estimated size of the se nw oriented strewn field is 6 2 km model calculations with minimal preatmospheric size show that a similar meteorite strewn field plus one small crater with observed shock effects could be formed by fragmentation of a meteoroid approximately 1 4 m in diameter with an impact angle of approximately 60 from the horizontal however the most probable is an impact of a larger 3 4 m diameter meteoroid resulting a strewn field with approximately 10 craters 10 30 m in diameter each plus numerous meteorite fragments the calculated scattering area of meteorite shrapnel ejected from these impact craters could completely cover the observed strewn field of the agoudal meteorite

role of near inertial internal waves in subthermocline diapycnal mixing in the northern gulf of mexico abstractmoored adcp data collected in the northern gulf of mexico are analyzed to examine near inertial internal waves and their contribution to subthermocline diapycnal mixing based on a finescale parameterization of deep ocean mixing the focus of the study is on the impact of near inertial internal waves generated by an extreme weather event that is hurricane katrina and by month to month variation in weather patterns on the diapycnal mixing the inferred subthermocline diapycnal mixing exhibits pronounced elevation in the wake of katrina both the increased near inertial 0 8 1 8f where f is the coriolis frequency and superinertial 1 8f shear variances contribute to the elevated diapycnal mixing but the former plays a more dominant role the intense wind work on near inertial motions by the hurricane is largely responsible for the energetic near inertial shear variance energy transfer from near inertial to superinertial internal waves however appears to play an important role in elevating th

orbital and solar forcing of shifts in mid to late holocene flood intensity from varved sediments of pre alpine lake ammersee southern germany abstract microfacies analyses and x ray fluorescence scanning xrf at sub mm resolution were conducted on the varved mid to late holocene interval of two sediment profiles from pre alpine lake ammersee southern germany the coring sites are located in a proximal as10prox and distal as10dist position towards the main tributary river ammer in 1 8 km distance from each other to shed light on sediment distribution within the lake particular emphasis was 1 the detection of intercalated detrital layers and their micro sedimentological features and 2 intra basin correlation of these event deposits detrital layers were dated by microscopic varve counting verified by accelerator mass spectrometry 14c dating of terrestrial plant macrofossils since 5500 varve years vyr bp in total 1573 detrital layers were detected in either one or both of the investigated sediment profiles based on their microfacies geochemistry and proximal distal deposition pattern detrital layers were interpreted as river ammer flood deposits earlier studies on flood layer seasonality have proven that flood layer deposition occurs predominantly during spring and summer the flood season at lake ammersee most prominent features of the record are the onset of regular flood layer deposition at 5500 vyr bp in as10prox and 2800 vyr bp in as10dist as well as three major increases in mean flood layer thickness at 5500 2800 and 400 vyr bp integrating information from both sediment profiles allowed to interpret these changes in terms of shifts towards higher mean flood intensity proposed triggering mechanisms are gradual reduction in northern hemisphere orbital summer forcing and superimposed centennial scale solar activity minima likely responses to this forcing are enhanced equator to pole temperature gradients and changes in synoptic scale atmospheric circulation the consequences for the ammersee region are more intense cyclones leading to extremer rainfall and flood events in spring and summer

boils and turbulence in a weakly stratified shallow tidal sea abstract measurements of turbulence are made in a weakly but variably stratified region of tidal straining in the eastern irish sea using turbulence sensors profiling vertically through the water column on the fast light yo yo fly profiler and horizontally on the autonomous underwater vehicle auv autosub the tidal currents exceed 1 m s 1 at the location of the measurements in water of a depth of about 43 5 m and result in turbulence extending from the seabed to the surface with a cycle period that is half that of the tides as previously observed the time of onset of enhanced turbulence that is measured by the sensors on fly and autosub as the speed of tidal currents increases are in good agreement as are their mean levels boils on the sea surface are identified using the autonomously recording inverted echo sounder version 2 aries ii a two beam upward pointing side scan sonar mounted on a rig resting on the seabed the boils have mean horizontal dimensions of about 25 m they are continually

pollen event stratigraphy of the varved sediment of lake suigetsu central japan from 15 701 to 10 217 sg vyr bp suigetsu varve years before present description interpretation and correlation with other regions high resolution pollen data average interval between samples 15 years are reported on part of a varved sediment core from lake suigetsu japan spanning the interval 15 701 to 10 217 sg vyr bp suigetsu varve years before present this new record is compared with a previously proposed event stratigraphy based on pollen based reconstructed changes of mean annual temperature the deglacial climate history reconstructed at lake suigetsu resembles that observed in the north atlantic although the major boundaries of pollen zones are asynchronous with those in the north atlantic event stratigraphy by several centuries the onset of the late glacial interstadial occurred earlier in japan than in the north atlantic this demonstrates that the climate in japan was closely linked to the low latitude pacific sea surface temperatures that first reacted to orbital forcing conversely the onset of the subsequent cold reversal phase in japan lagged that of the north atlantic younger dryas by several centuries the duration of this cold phase was about the same as the younger dryas event but the amplitude was much reduced 4 2 c in mean annual temperature these findings support the hypothesis that this pan hemispheric cooling event was triggered by north atlantic forcing most probably by a meltwater pulse and an associated change in the north atlantic thermohaline circulation however the mechanism which transmitted the change in the north atlantic to the far east is unknown

analysis of a prehistoric egyptian iron bead with implications for the use and perception of meteorite iron in ancient egypt tube shaped beads excavated from grave pits at the prehistoric gerzeh cemetery approximately 3300 bce represent the earliest known use of iron in egypt using a combination of scanning electron microscopy and micro x ray microcomputer tomography we show that microstructural and chemical analysis of a gerzeh iron bead is consistent with a cold worked iron meteorite thin fragments of parallel bands of taenite within a meteoritic widmanstatten pattern are present with structural distortion caused by coldworking the metal fragments retain their original chemistry of approximately 30 wt nickel the bulk of the bead is highly oxidized with only approximately 2 4 of the total bead volume remaining as metal our results show that the rst known example of the use of iron in egypt was produced from a meteorite its celestial origin having implications for both the perception of meteorite iron by ancient egyptians and the development of metallurgical knowledge in the nile valley

palaeoecology of late glacial and holocene profundal ostracoda of pre alpine lake mondsee austria a base for further palaeo biological research succession of profundal ostracod palaeoassemblages in response to environmental changes during the late glacial and holocene was studied in a similar to 15 m long sediment sequence from pre alpine lake mondsee austria first local ostracod assemblage zone loaz 1 prior to 15 700 a bp with low abundances of leucocythere mirabilis and limnocytherina sanctipatricii followed by cytherissa lacustris corresponds to the pleniglacial phase of clastic detrital sedimentation at relatively high rates most of the key species of loaz 2 15 590 to 13 940 a bp including the pleniglacial late glacial transition i e limnocytherids fabaeformiscandona cf harmsworthi f tricicatricosa c lacustris and candona candida reveal the significant association with high al contents and low sedimentation rates and are classified as preferring low productivity conditions in contrast candona neglecta dominant in loaz 3 13 820 to 9960 a bp palynologically defined as balling early holocene and in the last loaz 4 9780 a bp to present as well as cypria ophtalmica second key species in loaz 4 show relationship with higher productivity elevated sedimentation rates and decreasing al contents furthermore valve biodegradation and shape disparity at different time periods and in relation to sedimentation rate changes were investigated in a 3 juveniles of candona neglecta the highest percentage of valves biodegraded by actinobacteria was recorded during the allerod younger dryas and early holocene when the lowest sedimentation rates occurred whereas significantly lower frequencies of biodegraded valves were recorded during the mid holocene and late holocene when sediment accumulation was much higher it is also hypothesised that the degree of the valve shape variation was related to the lake productivity during the allerod younger dryas and early holocene a valve shape variation significantly lower than that recorded during late holocene intervals characterised by intensified lake productivity was observed additionally an agenda of potential questions and approaches that should be considered and form the core of further palaeo biological research projects is offered c 2014 elsevier b v all rights reserved

mid to inner shelf coupled roms swan model data comparison of currents and temperature diurnal and semidiurnal variability abstractaccurately representing diurnal and semidiurnal internal variability is necessary to investigate inner shelf to midshelf exchange processes here a coupled regional ocean model system roms simulating waves nearshore swan model is compared to observed diurnal and semidiurnal internal tidal variability on the mid and inner shelf 26 8 m water depth near san pedro bay california modeled mean stratification is about one half of that observed modeled and observed baroclinic velocity rotary spectra are similar in the diurnal and semidiurnal band modeled and observed temperature spectra have similar diurnal and semidiurnal band structure although the modeled is weaker the observed and modeled diurnal and semidiurnal baroclinic velocity and temperature dominant vertical structures are similar and consistent with mode one internal motions both observed and modeled diurnal baroclinic kinetic energy are strongly correlated to diurnal wind forcing and enhanced by subtidal vorticity induced reduc

model studies of near inertial motion on the continental shelf off northeast spain a three dimensional two dimensional one dimensional model comparison study 1 a three dimensional nonlinear model of the balearic sea region is used to examine the spatial distribution of wind induced near inertial internal waves results from the model are compared with those from two dimensional cross section and single point models in the case of motion induced by a wind pulse there is no significant along shelf flow and comparable solutions are obtained from the three and two dimensional models however when forced with a realistic wind a significant along shelf flow is produced that is larger in the cross section model than in the three dimensional model because of the absence of an along shelf pressure gradient associated with this change in flow are important differences in across shelf currents and temperature fields that influence the distribution of near inertial motion since the point model cannot take account of internal pressure gradients near inertial internal waves are absent however when some account of barotropic pressure gradients related to local wind stress are included currents and inertial oscillations were in better agreement with the three dimensional model than with the cross section model although the major features of the wind induced deepening of the thermocline could be reproduced by the single point model the absence of internal waves and mixing associated with them lead to a sharper thermocline than in the three dimensional model comparison of two and one dimensional models with the full three dimensional model shows some severe limitations in the simpler models

the last interglacial glacial cycle in the eastern alps abstract investigation of several localities in the eastern alps has resulted in the recognition of the effects of the last interglacial glacial cycle large volumes of sediments with high sedimentation rates resulting from debris input to the main valleys from grasscovered slopes characterise cool phases during warmer periods arboreal vegetation on the slopes was more developed and the debris input was reduced under these climatic conditions similar to those of today plant detritus formed organic beds the chronological succession as given by radiometric dating at several sites shows a good correlation with the well dated profile of grande pile two major cool phases are indicated with an intervening warm phase within the alps as indicated by the pollen record some contradictions exist in the available climatic record which can only be resolved with data from new localities

the cycle of turbulent dissipation in the presence of tidal straining in regions of large horizontal density gradient tidal straining acts to produce a periodic component of stratification that interacts with turbulent mixing to control water column structure and flow a 25 h series of measurements of the rate of dissipation of turbulent kinetic energy e in the liverpool bay region of freshwater influence rofi have revealed the form of this interaction and indicate substantial differences from regions where horizontal gradients are weak in the rofi system there is a pronounced difference between flood and ebb regimes during the ebb the water column stratifies and strong dissipation is confined to the lower half of the water column by contrast during the flood stratification is eroded with complete vertical mixing occurring at high water and high values of dissipation 3 mw m23 extending throughout the water column the cycle of dissipation is therefore predominantly semidiurnal in the upper layers whereas near the bottom boundary the principal variation is at the m4 frequency as observed in regions of horizontal uniformity toward the end of the flood phase of the cycle tidal straining produces instabilities in the water column that release additional energy for convective mixing confirmation of increased vertical motions throughout the water column during the late flood and at high water is provided by measurements of vertical velocity and the error velocity from a bottom mounted acoustic doppler current profiler

on the behavior of internal waves in the wakes of storms abstract the rossby adjustment process in the wake of a storm is studied with a view to finding within the context of linear theory how wave dispersion in both the vertical and meridional directions spreads energy which is initially confined entirely to the mixed layer comparisons are made between three cases 1 a periodic storm on the f plane where dispersion is purely vertical 2 a bounded storm on the f plane and 3 a bounded storm centered 2700 km from the equator on an equatorial beta plane particular attention is paid to the initial rate of loss of energy from the mixed layer and some simple formulas which work very well in the cases studied are derived these show that the rate of loss goes up when the mixed layer depth is increased and also that the rate scales as the square of the wavenumber values of the rates are sufficient to provide a major source of energy for internal waves below the mixed layer the often observed tendency for phase lines to propagate upward is found in all case

microscopic impactor debris in the soil around kamil crater egypt inventory distribution total mass and implications for the impact scenario we report on the microscopic impactor debris around kamil crater 45 m in diameter egypt collected during our 2010 geophysical expedition the hypervelocity impact of gebel kamil ni rich ataxite on a sandstone target produced a downrange ejecta curtain of microscopic impactor debris due se sw of the crater extending 300 000 m2 up to 400 m from the crater in agreement with previous determination of the impactor trajectory the microscopic impactor debris include vesicular masses spherules and coatings of dark impact melt glass which is a mixture of impactor and target materials si fe and al rich glass plus fe ni oxide spherules and mini shrapnel documenting that these products can be found in craters as small as few tens of meters in diameter the estimated mass of the microscopic impactor debris 20 t likely 50 60 t

model studies of near inertial waves in flow over the oregon continental shelf abstract two dimensional primitive equation model studies of wind forced flow over a continental shelf show that under upwelling conditions high levels of near inertial wave energy are found in the interior over the shelf the regions of elevated wave energy with maximum wave amplitudes of around 0 2 m s 1 persist for up to two weeks and have spatial scales of 20 40 m vertically and 5 20 km horizontally relatively high dissipation levels are associated with these concentrations of wave energy when forced with downwelling favorable winds model results show very little subsurface inertial energy on the shelf a comparison of inertial wave propagation using the primitive equation model and a linearized version of the model demonstrates strong dependence on the background flow field the behavior of inertial waves using the linearized model is completely different very little subsurface inertial energy is seen on the shelf in either upwelling or downwelling conditions except where the bottom slope

diurnal period wind stress and current fluctuations over the continental shelf off northern california diurnal period wind stress and current fluctuations measured over the continental shelf off northern california during the coastal ocean dynamics experiment in the summers of 1981 and 1982 are examined the diurnal currents are strongly surface intensified with amplitudes of up to 20 cm s 1 at depths of less than 35 m the diurnal currents are nonstationary and their amplitude is well correlated with the amplitude modulation of the local diurnal wind stress beneath the surface layer the diurnal current vectors rotate clockwise with ellipse semi major axes of 1 to 3 cm s 1 a mixed layer model driven with diurnal wind stress and surface heat flux produces currents similar to those observed in the upper water column the deeper currents are consistent with the combination of a freely propagating kelvin and first mode coastal trapped wave and over the inner shelf with the interior flow forced by the diurnal wind stress in the presence of a coast

anatomy of a young impact event in central alberta canada prospects for the missing holocene impact record small impact events recorded on the surface of earth are signifi cantly underrepresented based on expected magnitude frequency relations we report the discovery of a 36 m diameter late holocene impact crater located in a forested area near the town of whitecourt alberta canada although undetectable using visible imagery the presence of the crater is revealed using a bare earth digital elevation model obtained through airborne light detection and ranging lidar the target material comprises deglacial quaternary sediments with impact ejecta burying a late holocene soil dated to ca 1100 14 c yr b p most of the 74 iron meteorites 0 1 1196 g recovered have an angular exterior morphology these meteorites were buried at depths 25 cm and are interpreted to result from fragmentation of the original projectile mass either at low altitude or during the impact event impact of the main mass formed the simple bowl shaped impact structure associated with an ejecta blanket and crater fi ll the increasing availability of lidar data for many terrestrial surfaces will serve as a useful tool in the discovery of additional small impact features

longitudinal and topographic variations in north atlantic tidal and inertial energy around latitudes 30 10 n 1 open ocean kinetic energy is investigated at dominant inertial and semidiurnal tidal frequencies using historic current observations from the north atlantic ocean around midlatitudes focus is on possible energy variations due to major topography changes between the eastern canary and western hatteras sohm basins thereby crossing the mid atlantic ridge mar while in open basins on both sides of mar semidiurnal kinetic energy drops in magnitude by some 50 between latitudes 20 n 28 n in agreement with tpxo elevation data an even larger longitudinal dependence is observed west of mar semidiurnal energy is up to 30 times less than east of it inertial kinetic energy is either decreasing by a factor of 2 4 westward or more or less independent of longitude this contrasts strongly with westward intensified near surface inertial energy fluxes previously found the latter fluxes also did not show an increase by a factor of 5 10 for 25 n 30 n as observed here for inertial energy in both basins west of mar the internal wave background level for frequencies up to sixth diurnal is much less by a factor of 3 10 at tidal inertial interaction frequencies than east of mar no significant atmospheric or large scale vorticity influence or seasonal variations therein is found on inertial energy content across the basin as no individual peaks are observed at frequencies k1 o1 and m1 s1 direct diurnal tidal forcing and subharmonic resonance must be accompanied by nonlinear interactions in possibly enhancing inertial energy at the critical diurnal latitude

holocene vegetation and climate dynamics of ne china based on the pollen record from sihailongwan maar lake abstract high resolution palynological analysis on annually laminated sediments of sihailongwan maar lake shl provides new insights into the holocene vegetation and climate dynamics of ne china the robust chronology of the presented record is based on varve counting and ams radiocarbon dates from terrestrial plant macro remains in addition to the qualitative interpretation of the pollen data we provide quantitative reconstructions of vegetation and climate based on the method of biomization and weighted averaging partial least squares regression wa pls technique respectively power spectra were computed to investigate the frequency domain distribution of proxy signals and potential natural periodicities pollen assemblages pollen derived biome scores and climate variables as well as the cyclicity pattern indicate that ne china experienced significant changes in temperature and moisture conditions during the holocene within the earliest phase of the holocene a large scale reorganization of vegetation occurred reflecting the reconstructed shift towards higher temperatures and precipitation values and the initial holocene strengthening and northward expansion of the east asian summer monsoon easm afterwards summer temperatures remain at a high level whereas the reconstructed precipitation shows an increasing trend until approximately 4000 cal yr bp since 3500 cal yr bp temperature and precipitation values decline indicating moderate cooling and weakening of the easm a distinct periodicity of 550 600 years and evidence of a mid holocene transition from a temperature triggered to a predominantly moisture triggered climate regime are derived from the power spectra analysis the results obtained from shl are largely consistent with other palaeoenvironmental records from ne china substantiating the regional nature of the reconstructed vegetation and climate patterns however the reconstructed climate changes contrast with the moisture evolution recorded in s china and the mid latitude semi arid regions of n china whereas a clear insolation related trend of monsoon intensity over the holocene is lacking from the shl record variations in the coupled atmosphere pacific ocean system can largely explain the reconstructed changes in ne china

quantifying the role of biosphere atmosphere feedbacks in climate change coupled model simulations for 6000 years bp and comparison with palaeodata for northern eurasia and northern africa the lmd agcm was iteratively coupled to the global biome1 model in order to explore the role of vegetation climate interactions in response to mid holocene 6000 y bp orbital forcing the sea surface temperature and sea ice distribution used were present day and co2 concentration was pre industrial the land surface was initially prescribed with present day vegetation initial climate anomalies differences between agcm results for 6000 y bp and control were used to drive biome1 the simulated vegetation was provided to a further agcm run and so on results after five iterations were compared to the initial results in order to identify vegetation feedbacks these were centred on regions showing strong initial responses the orbitally induced high latitude summer warming and the intensification and extension of northern hemisphere tropical monsoons were both amplified by vegetation feedbacks vegetation feedbacks were smaller than the initial orbital effects for most regions and seasons but in west africa the summer precipitation increase more than doubled in response to changes in vegetation in the last iteration global tundra area was reduced by 25 and the southern limit of the sahara desert was shifted 2 5 n north to 18 n relative to today these results were compared with 6000 y bp observational data recording forest tundra boundary changes in northern eurasia and savana desert boundary changes in northern africa although the inclusion of vegetation feedbacks improved the qualitative agreement between the model results and the data the simulated changes were still insufficient perhaps due to the lack of ocean surface feedbacks

a numerical study of sea breeze driven ocean poincare wave propagation and mixing near the critical latitude abstract near the vicinity of 30 latitude the coincidence of the period of sea breeze and the inertial period of the ocean leads to a maximum near inertial ocean response to sea breeze this produces a propagating inertial internal poincare wave response that transfers energy laterally away from the coast and provides significant vertical mixing in this paper the latitudinal dependence of this wave propagation and its associated vertical mixing are investigated primarily using a nonlinear numerical ocean model three dimensional idealized simulations show that the coastal oceanic response to sea breeze is trapped poleward of 30 latitude however it can propagate offshore as poincare waves equatorward of 30 latitude near 30 latitude the maximum oceanic response to sea breeze moves offshore slowly because of the near zero group speed of poincare waves at this latitude the lateral energy flux convergence plus the energy input from the wind is maximum near the critical latitude leading to increa

subtropical catastrophe significant loss of low mode tidal energy at 28 9 1 an idealized numerical study of a northward propagating internal tide reveals a dramatic loss of energy to small scale subharmonic instabilities near 28 9 n inspired by observations of the internal tide radiating northward from the hawaiian ridge a three dimensional numerical model is initialized with a northward baroclinic tidal flux of approximately 1 7 kw m after an initial spinup period energy is quickly transferred from the baroclinic tide to subharmonic motions with half the horizontal tidal wavenumber and small vertical scales through nonlinear advection of horizontal tidal velocity gradients potential oceanic implications are twofold first once a steady state has been reached the instability acts as a partial filter of northward tidal flux between 27 5 and 29 5 n in rough agreement with some altimetric tidal observations second elevated shear of the subharmonic motions suggests the potential for elevated near surface dissipation rates near the critical latitude that may be important for upper ocean mixing

delayed hydrological response to greenland cooling at the onset of the younger dryas in western europe during the younger dryas cold event about 12 800 years ago environmental change in western europe seems to occur 170 years after cooling over greenland lake sediment analyses confirm this delay and suggest european hydrological and vegetation change occurred only after the build up of sea ice in the north atlantic pushed the westerly wind system south

earth impact effects program a web based computer program for calculating the regional environmental consequences of a meteoroid impact on earth we have developed a web based program for quickly estimating the regional environmental consequences of a comet or asteroid impact on earth www lpl arizona edu impacteffects this paper details the observations assumptions and equations upon which the program is based it describes our approach to quantifying the principal impact processes that might affect the people buildings and landscape in the vicinity of an impact event and discusses the uncertainty in our predictions the program requires six inputs impactor diameter impactor density impact velocity before atmospheric entry impact angle the distance from the impact at which the environmental effects are to be calculated and the target type sedimentary rock crystalline rock or a water layer above rock the program includes novel algorithms for estimating the fate of the impactor during atmospheric traverse the thermal radiation emitted by the impact generated vapor plume fireball and the intensity of seismic shaking the program also approximates various dimensions of the impact crater and ejecta deposit as well as estimating the severity of the air blast in both crater forming and airburst impacts we illustrate the utility of our program by examining the predicted environmental consequences across the united states of hypothetical impact scenarios occurring in los angeles we find that the most wide reaching environmental consequence is seismic shaking both ejecta deposit thickness and air blast pressure decay much more rapidly with distance than with seismic ground motion close to the impact site the most devastating effect is from thermal radiation however the curvature of the earth implies that distant localities are shielded from direct thermal radiation because the fireball is below the horizon

efficient disruption of small asteroids by earth s atmosphere accurate modelling of the interaction between the atmosphere and an incoming bolide is a complex task but crucial to determining the fraction of small asteroids that actually hit the earth s surface most semi analytical approaches have simplified the problem by considering the impactor as a strengthless liquid like object pancake models1 2 but recently a more realistic model has been developed that calculates motion aerodynamic loading and ablation for each separate particle or fragment in a disrupted impactor3 4 here we report the results of a large number of simulations in which we use both models to develop a statistical picture of atmosphere bolide interaction for iron and stony objects with initial diameters up to 1 km we show that the separated fragments model predicts the total atmospheric disruption of much larger stony bodies than previously thought in addition our data set of 1 000 simulated impacts combined with the known pre atmospheric flux of asteroids with diameters less than 1 km5 6 7 8 9 10 11 12 elucidates the flux of small bolides at the earth s surface we estimate that bodies 220 m in diameter will impact every 170 000 years

internal tides in monterey submarine canyon abstract the m2 internal tide in monterey submarine canyon is simulated using a modified version of the princeton ocean model most of the internal tide energy entering the canyon is generated to the south on sur slope and at the head of carmel canyon the internal tide is topographically steered around the large canyon meanders depth integrated baroclinic energy fluxes are up canyon and largest near the canyon axis up to 1 5 kw m 1 at the mouth of the upper canyon and increasing to over 4 kw m 1 around monterey and san gregorio meanders the up canyon energy flux is bottom intensified suggesting that topographic focusing occurs net along canyon energy flux decreases almost monotonically from 9 mw at the canyon mouth to 1 mw at gooseneck meander implying that high levels of internal tide dissipation occur the depth integrated energy flux across the 200 m isobath is order 10 w m 1 along the majority of the canyon rim but increases by over an order of magnitude near the canyon head where internal ti

stable vegetation and environmental conditions during the last glacial maximum new results from lake kotokel lake baikal region southern siberia russia abstract this paper presents a new decadal resolution fossil pollen record from lake kotokel 52 47 n 108 07 e 458 m a s l and provides a reconstruction of the last glacial maximum lgm vegetation and environments in the study area during this interval of globally harsh climate lake kotokel is situated close to the eastern shoreline of lake baikal in the boreal forest zone of southern siberia the analysed 190 cm long section 6 of the bottom core ktk10 ktk10 6 consists of compact undisturbed greenish grey to dark grey slightly laminated silty clay indicating continuous lacustrine sedimentation throughout the lgm period ca 26 8 19 1 cal ka bp the age model is supported by 11 calibrated ams dates the results of pollen analysis and pollen based biome reconstruction show that steppe and tundra vegetation composed of grasses and various herbs dominated ca 26 8 19 1 cal ka bp occurrence of conifer tracheids and stomata throughout the record together with small quantities of boreal conifer and broadleaf tree and shrub taxa pollen suggests the presence of single trees or small forest stands in the lake vicinity most likely in the river valleys application of the biomisation method and the resulting numerical scores of the most characteristic biomes steppe tundra and cold deciduous forest show minor fluctuations signifying stability of the regional vegetation cover during the analysed lgm interval in contrast to the regional biomes the local environmental indicators demonstrate greater sensitivity of the lake system to decadal and century scale climate variability the highest pollen percentages of ranunculaceae representing littoral meadow vegetation communities are registered ca 23 8 23 4 cal ka bp this and an increase in coarse grained sand particles together with slightly increased total inorganic carbon tic values representing calcite in the ktk10 6 sediment provide evidence of a much shorter than present distance between the coring site and the shoreline and a reduced lake area in line with a drier than present lgm climate a general stability of the grassland vegetation in the study region ca 26 8 19 1 cal ka bp and relatively constant total organic carbon toc values support the hypothesis that this productive vegetation could stably serve as a perennial food resource for large populations of herbivores thus providing favourable environments for the local hunter gatherers inhabiting the lake baikal region during the lgm interval

vegetation and fire history of the euganean hills colli euganei as recorded by lateglacial and holocene sedimentary series from lago della costa northeastern italy we reconstruct the vegetational and fire history of the colli euganei and northeastern po plain from c 16 500 cal bp to the present using ams dated sedimentary pollen microscopic and macroscopic charcoal records our study site lago della costa is the only natural water basin with an undisturbed late quaternary sediment accumulation in the northeastern po plain mixed coniferous deciduous forests occurred since at latest 14 500 cal bp gradual expansion of e g alnus glutinosa and carpinus betulus is documented after c 11 000 cal bp a further expansion of abies alba and alnus at 9200 cal bp coincided with a population buildup of these species in the insubrian region c 200 km northwest of our site a further increase of alnus about 6400 cal bp was accompanied by an expansion of castanea sativa and juglans regia as well as meadow and field plants this vegetational change was contemporaneous with a huge increase of regional and local fire activity our data suggest that fire disturbance favoure

environmental responses to lateglacial climatic fluctuations recorded in the sediments of pre alpine lake mondsee northeastern alps investigation of the sedimentary record of pre alpine lake mondsee upper austria focused on the environmental reaction to rapid lateglacial climatic changes results of this study reveal complex proxy responses that are variable in time and influenced by the long term evolution of the lake and its catchment a new field sampling approach facilitated continuous and precisely controlled parallel sampling at decadal to sub annual resolution for mu xrf element scanning carbon geochemistry stable isotope measurements on ostracods pollen analyses and large scale thin sections for microfacies analysis the holocene chronology is established through microscopic varve counting and supported by accelerator mass spectrometric 14 c dating of terrestrial plant macrofossils whereas the lateglacial age model is based on delta 18 o wiggle matching with the greenland ngrip record using the gicc05 chronology microfacies analysis enables the detection of subtle salimentological changes proving that depositional processes even in rather large lake systems are highly sensitive to climate forcing comparing periods of major warming at the onset of the lateglacial and holocene and of major cooling at the onset of the younger dryas reveals differences in proxy responses reflecting threshold effects and ecosystem inertia temperature increase vegetation recovery decrease of detrital flux and intensification of biochemical calcite precipitation at the onset of the holocene took place with only decadal leads and lags over a ca 100 a period whereas the spread of woodlands and the reduction of detrital flux lagged the warming at the onset of the lateglacial interstadial by ca 500 750a cooling at the onset of the younger dryas is reflected by the simultaneous reaction of delta 18 o and vegetation but sedimentological changes reduction of endogenic calcite content increase in detrital flux were delayed by about 150 300 a three short term lateglacial cold intervals corresponding to greenland isotope substages gl 1d gl 1c2 and gl 1b also show complex proxy responses that vary in time copyright c 2011 john wiley sons ltd

a simple analytical model of periodic coastal upwelling abstractan existing reduced gravity model that reproduces the response of the coastal sea to alongshore wind forcing at subinertial frequencies is extended by allowing for cross shore wind forcing and by considering superinertial frequencies the obtained explicit solution shows that the wind driven currents are predominantly controlled by friction and the coriolis force at subinertial frequencies and by friction and local acceleration at superinertial frequencies the effect of the coast is manifested by coastal trapped variability at subinertial frequencies and baroclinic inertia gravity waves propagating away from the coast at superinertial frequencies the pycnocline oscillates at the coast not only at subinertial but also at superinertial frequencies with the alongshore wind contributing more to the former and the cross shore wind influencing more the latter the oscillations are most pronounced when the periodic wind forcing is resonantly coupled to the local inertial oscillations but only if the

near resonant ocean response to sea breeze on a stratified continental shelf abstract the spatial structure and temporal characteristics of sea breeze and the associated coastal ocean response in the northwest gulf of mexico are investigated using moored instruments hydrographic stations and wind measurements near the study area of 30 n motions in the diurnal inertial band dib may be significantly enhanced by a near resonant condition between local inertial and diurnal forcing frequencies wavelet analysis is used to quantify the results results indicate that diurnal sea breeze variability peaks in summer and extends at least 300 km offshore with continuous seaward phase propagation the maximum dib oceanic response occurs in june when there is a shallow mixed layer strong stratification and an approximately 10 day period of continuous sea breeze forcing dib current variance decreases in july and august as the consequence of the deepening of the mixed layer and a more variable phase relationship between the wind and current river discharge varies interannually and can s

the kamil crater in egypt we report on the detection in southern egypt of an impact crater 45 meters in diameter with a pristine rayed structure such pristine structures are typically observed on atmosphereless rocky or icy planetary bodies in the solar system this feature and the association with an iron meteorite impactor and shock metamorphism provides a unique picture of small scale hypervelocity impacts on earth s crust contrary to current geophysical models ground data indicate that iron meteorites with masses of the order of tens of tons can penetrate the atmosphere without substantial fragmentation

resonant near surface inertial oscillations in the northeastern gulf of mexico the inertial frequency is nearly diurnal at 30 n latitude which transects the northeastern gulf of mexico negom at this latitude near surface inertial oscillations can amplify due to resonance with diurnal wind forcing diurnal oscillations have also been attributed to diurnal tidal forcing in this region because tidal forcing wind forcing and inertial oscillations are nearly diurnal a unique series of comparative analyses are required to determine their relative influence on surface circulation by comparing surface currents obtained by hf radar to predictions of the inertial response to wind forcing and barotropic tidal currents it is found that diurnal oscillations in the negom were predominantly due to wind forced inertial oscillations in june 2010 the analyses provide a unique spatiotemporal perspective of inertial oscillations in the negom where there is evidence of propagation frequency and phase shifts and amplitude variability because inertial oscillations mix the ocean differently than the tides these results provide insight into how inertial oscillations potentially mixed oil from the deepwater horizon spill in june 2010 near diurnal oscillations during the winter were found to be predominantly due to tidal forcing when wind driven inertial oscillations were diminished due to a presumably deeper mixed layer

onset and termination of the late glacial climate reversal in the high resolution diatom and sedimentary records from the annually laminated sg06 core from lake suigetsu japan high resolution diatom sediment and pollen analyses of two sections from the annually laminated sg06 core from lake suigetsu were used to study the onset and termination of the late glacial climate reversal in central japan its broadly recognised counterpart is the younger dryas or greenland stadial 1 ca 12 85 11 65 cal kyr bp based on the ngrip ice core records our study suggests that accumulation of the analysed late glacial sediments occurred in a deep and relatively cold water meso eutrophic lake with a strong mixing regime and relatively high silica content combining these results together with available pollen based environmental reconstructions we suggest that climate cooling together with an intensified winter monsoon and thicker snow cover could influence changes in regional vegetation sedimentation processes and trophic status of the lake during the transition from the last interstadial to stadial around lake suigetsu a decrease in total pollen concentration and increase in fagus pollen percentage indicate local vegetation stress disturbances and suggest that cooling started at least 2 3 decades prior to the major shift in the inorganic sediment accumulation of detrital layers and in diatom assemblages change from aulacoseira ambigua to aulacoseira subarctica dominance which took about 10 years the transition from the last stadial to the holocene again shows that vegetation in the lake catchment area reacted first to the regional climate change i e to the weakening of the winter monsoon and decrease in winter snow accumulation the increase in the vegetation cover density and reduced volume of surface runoff associated with the decrease in melt water supply is likely responsible for the reduced soil erosion activity which caused the cessation in detrital layer accumulation and consequent decrease in the amount of nutrients brought to the lake and lowering of the water nutrient status the latter process finally influenced changes in the diatom assemblages including the return to dominance of a subarctica ca 30 years after the virtual disappearance of detrital layers from the sediment our results demonstrate the rapid response of the lake suigetsu system to the global cooling and subsequent warming and allow clear definition of the onset and termination of the late glacial climate reversal despite the fact that the lake system shows a more abrupt shift from the warm to cold and cold to warm environments than terrestrial records of vegetation demonstrate we do not see any delayed response of local vegetation to the climate change this last conclusion is of particular importance for application of the sg06 pollen record for quantitative climate reconstruction

anthropogenic and climate controls on vegetation changes between 1500 bce and 500 ce reconstructed from a high resolution pollen record from varved sediments of lake mondsee austria abstract this study reports a precisely dated pollen record with a 20 year resolution from the varved sediments of lake mondsee in the north eastern european alps 47 49 n 13 24 e 481 m above sea level the analysed part of core spans the interval between 1500 bce and 500 ce and allows changes in vegetation composition in relation to climatic changes and human activities in the catchment to be inferred intervals of distinct but modest human impact are identified at ca 1450 1220 740 490 and 340 190 bce and from 80 bce to 180 ce while the first two intervals are synchronous with prominent salt mining phases during the bronze age and early iron age at the nearby unesco world heritage site of hallstatt the last two intervals fall within the late iron age and roman imperial era respectively comparison with published records of extreme runoff events obtained from the same sediment core shows that human activities including agriculture and logging around lake mondsee were low during intervals of high flood frequency as indicated by a higher number of intercalated detrital event layers but intensified during hydrologically stable intervals comparison of the pollen percentages of arboreal taxa with the stable oxygen isotope and potassium ion records of the ngrip and gisp2 ice cores from greenland reveals significant positive correlations for fagus and negative correlations for betula and alnus this underlines the sensitivity of vegetation around lake mondsee to temperature fluctuations in the north atlantic as well as to moisture fluctuations controlled by changes in the intensity of the siberian high and the north atlantic oscillation nao regime

crater morphology in sandstone targets the memin impact parameter study hypervelocity 2 5 7 8 km s 1 impact experiments into sandstone were carried out to investigate the influence of projectile velocity and mass target pore space saturation target projectile density contrast and target layer orientation on crater size and shape crater size increases with increasing projectile velocity and mass as well as with increasing target pore space saturation craters in water saturated porous targets are generally shallower and larger in volume and in diameter than craters from equivalent impacts into dry porous sandstone morphometric analyses of the resultant craters 5 40 cm in diameter reveal features that are characteristic of all of our experimental craters regardless of impact conditions i a large central depression within a fragile light colored central part and ii an outer spallation zone with areas of incipient spallation two different mechanical processes grain fragmentation and intergranular tensile fracturing are recorded within these crater morphologies zone i approximates the shape of the transient crater formed by material compression displacement comminution and excavation flow whereas ii is the result of intergranular tensile fracturing and spallation the transient crater dimensions are reconstructed by fitting quadric parabolas to crater profiles from digital elevation models the dimensions of this transient and of the final crater show the same trends both increase in volume with increasing impact energy and with increasing water saturation of the target pore space the relative size of the transient crater in percent of the final crater volume decreases with increasing projectile mass and velocity signifying a greater contribution of spallation on the final crater size when projectile mass and velocity are increased

resonant diurnal oscillations and mean alongshore flows driven by sea land breeze forcing in the coastal southern california bight abstractthis study presents observations of the cross sectional structure of resonant response to sea land breezes slbs off huntington beach hb in the southern california bight scb a resonant response to local diurnal wind stress fluctuations associated with slb forcing occurs intermittently and produces strong diurnal oscillations of flow and temperature resulting from enhanced work of the diurnal local wind on the sea surface at nighttime daytime a coherent cross sectional circulation with offshore onshore currents in the surface layer upper 15 m and onshore offshore currents in the intermediate layer around 20 m are generated with a three layered vertical structure on the outer shelf the authors find a net cross shore eddy heat flux net cooling of nearshore water during the period of strong response to slb that is a rectified mean heat flux and steeper isotherms resulting from the diurnal slb fluctuations the steepened mean isotherms are also found to be in thermal wind balance

characterization of the principal tidal current constituents on the texas louisiana shelf we analyzed 81 current meter records of varying lengths 3 to 30 months to describe the principal diurnal o1 k1 p1 and q1 and semidiurnal s2 m2 k2 and n2 tidal current constituents on the texas louisiana continental shelf the louisiana texas shelf physical oceanography program latex had 81 current meters at 31 sites and varying depths from april 1992 to december 1994 the local inertial period range across the shelf 24 4 hours to 26 2 hours and thermal diurnal cycling during the summer season make it difficult to estimate the diurnal tidal constituents dominant tidal modes on the shelf are k1 o1 and m2 absolute and relative energy contained in each tidal constituent varies with shelf location the northeast corner of the shelf near atchafalaya bay has the largest tidal currents with maximum surface current amplitudes at 3 m depth of about 9 cm s 1 while typical maximum tidal surface currents near the shelf break are between 1 and 2 cm s 1 for each of the k1 o1 and m2 components in general the surface tidal currents decrease in magnitude as water depth increases toward the shelf break although the semidiurnal components are amplified more at midshelf locations than the diurnal components examination of tidal ellipses at different depths suggests that the m2 tide has less vertical structure while the diurnal tides exhibit more shear particularly at the more shallow locations sea surface height constituents estimated at five locations along the texas louisiana coast are in agreement with historical values

cosmic ray exposure and pre atmospheric size of the gebel kamil iron meteorite cosmogenic he ne and ar as well as the radionuclides 10be 26al 36cl 41ca 53mn and 60fe have been determined on samples from the gebel kamil ungrouped ni rich iron meteorite by noble gas mass spectrometry and accelerator mass spectrometry ams respectively the meteorite is associated with the kamil crater in southern egypt which is about 45 m in diameter samples originate from an individual large fragment individual as well as from shrapnel concentrations of all cosmogenic nuclides stable and radioactive are lower by a factor 3 4 in the shrapnel samples than in the individual assuming negligible 36cl decay during terrestrial residence indicated by the young crater age 85 cm i e a pre atmospheric mass 20 tons with a preferred radius of 115 120 cm 50 60 tons the analyzed samples came from a depth of approximately 20 cm individual and approximately 50 80 cm shrapnel the size of the gebel kamil meteoroid determined in this work is close to estimates based on impact cratering models combined with expectations for ablation during passage through the atmosphere folco et al 2010 2011

sg06 a fully continuous and varved sediment core from lake suigetsu japan stratigraphy and potential for improving the radiocarbon calibration model and understanding of late quaternary climate changes abstract the high potential of the varved sediments of lake suigetsu central japan to provide a purely terrestrial radiocarbon calibration model and a chronology of palaeoclimatic changes has been widely recognised for the last two decades however this potential has not been fully realised since the only available long sediment core from the lake sg93 was extracted from a single bore hole and was therefore interrupted by gaps of unknown duration between successive core sections in the summer of 2006 a new sediment core sg06 was recovered from the lake four separate boreholes were drilled and the parallel sets of cores recovered were found to overlap completely without gaps between segments this new record provides the ability to test existing atmospheric radiocarbon calibration models as well as to assess the scale of inter regional leads and lags in palaeoclimatic changes over the last glacial interglacial cycle multi disciplinary analyses from sg06 are still ongoing but a reliable description of the sedimentary sequence needs to be provided to the wider science community before major outputs from the project are released thereby allowing fully informed critical evaluation of all subsequent releases of data based on the sg06 record in this paper we report key litho stratigraphic information concerning the sg06 sediment core highlighting changes in the clarity of annual laminations varves with depth and possible implications for the mechanism of the climate change we also discuss the potential of the sg06 record to meet the fundamental goals of the inqua intimate project