the vertical structure of shadow zone arrivals at long range in the ocean multimegameter range acoustic data obtained by bottom mounted sosus receivers show significant acoustic energy penetrating several hundred meters into the geometric shadow zones below cusps in the predicted acoustic time fronts much further than can be accounted for by diffraction dushaw et al ieee j oceanic eng 24 202 214 1999 acoustic data from two vertical line array receivers deployed in close proximity in the north pacific ocean together virtually spanning the water column show similar shadow zone arrivals for transmissions from broadband 250 hz sources moored at the sound channel axis 750 m and at surface conjugate depth 3000 m at ranges of 500 and 1000 km the vertical structure of the receptions will be compared to parabolic equation propagation simulations for sound speed fields constructed from high resolution underway conductivity temperature depth uctd data in the upper 400 m widely spaced deep ctd casts and climatological data predictions will be made i for the observed field ii for a smoothed field and iii for fields that include sound speed fines structure due to density variations internal waves or due to density compensated sound speed variations spice

36cl in chloride rich rainwater israel eleven rainwater samples from israel have been analyzed for their isotopic36cl cl ratios and their soluble salt content the rains display a range of36cl cl ratios between1 8 10 15 and50 10 15 and chloride ion concentrations of between 0 3 and 4 2 meqcl l the ratios between the concentrations of na mg2 and cl in the samples demonstrate a clear marine origin for these ions in the rainwater although the stable35cl isotope in rainwater is marine in origin while the accompanying36cl radioisotope is non marine both are linearly and positively correlated in chloride rich 1meqcl l rains the36clcl seawater solute relationship may be explained as result of a mixing process between two chloride bearing sources a sea spray laden air with a low36cl cl ratio and b a cl rich mineral dust reservoir with a high36cl cl ratio both are introduced and admixed into the atmosphere during storms the possibility of a high36cl cl ratio stratospheric end member is rejected in view of the non marine nature of the chlorine therein

vertical line array measurements of ambient noise in the north pacific shipping noise and wind are the dominant sources of ocean noise in the frequency band between 20 and 500 hz this paper analyzes noise in that band using data from the spicex experiment which took place in the north pacific in 2004 2005 and compares the results with other north pacific experiments spicex included vertical arrays with sensors above and below the surface conjugate depth facilitating an analysis of the depth dependence of ambient noise the paper includes several key results first the 2004 05 noise levels at 50 hz measured in spicex had not increased relative to levels measured by morris 1978 j acoust soc am 64 581 590 at a nearby north pacific site three decades earlier but rather were comparable to those levels second at 50 hz the noise below the conjugate depth decreases at a rate of 9 9 db km which is similar to the rate measured by morris and much less than the rate measured by gaul knobles shooter and wittenborn 2007 ieee j ocean eng 32 497 512 for the

a comparison of groundwater dating with 81kr 36cl and 4he in four wells of the great artesian basin australia the isotopic ratios 81 kr kr and 36 cl cl and the 4 he concentrations measured in groundwater from four artesian wells in the western part of the great artesian basin gab in australia are discussed based on radioactive decay along a water flow path the 81 kr kr ratios are directly converted to groundwater residence times results are in a range of 225 400 kyr with error bars in the order of 15 primarily due to counting statistics in the cyclotron accelerator mass spectrometer measurement additional uncertainties from subsurface production and or exchange with stagnant porewaters in the confining shales appear to be of the same order of magnitude these 81 kr ages are then used to calibrate the 36 cl and the 4 he dating methods based on elemental analyses of rock samples from the sandstone aquifer as well as from the confining bulldog shale the in situ flux of thermal neutrons and the corresponding 3 he 4 he and 36 cl cl ratios are calculated from a comparison of i the 3 he 4 he ratios measured in the groundwater samples with the calculated in situ ratios in rocks and ii the measured n 37 cl ratios with the 4 he concentrations measured in groundwater it is concluded that both helium and chloride are most likely added to the aquifer from sources in the stagnant porewaters of the confining shale by diffusion and or mixing based on this working hypothesis the 36 cl transport equation in groundwater is solved taking into account i radioactive decay ii subsurface production in the sandstone aquifer with an in situ 36 cl cl ratio of 6u10 315 and iii addition of chloride from a source in the confining shale with a 36 cl cl ratio of 13u10 315 lacking better information it is assumed that the chloride concentration increased linearly with time from an unknown initial value ci to its

surface gravity waves and their acoustic signatures 1 30 hz on the mid pacific sea floor in 1999 duennebier et al deployed a hydrophone and geophone below the conjugate depth in the abyssal pacific midway between hawaii and california real time data were transmitted for 3 yr over an abandoned att cable these data have been analyzed in the frequency band 1 to 30 hz between 1 and 6 hz the bottom data are interpreted as acoustic radiation from surface gravity waves an extension to higher frequencies of a non linear mechanism proposed by longuet higgins in 1950 to explain microseisms the inferred surface wave spectrum for wave lengths between 6 m and 17 cm is saturated wind independent and roughly consistent with the traditional phillips 4 wave number spectrum shorter ocean waves have a strong wind dependence and a less steep wave number dependence similar features are found in the bottom record between 6 and 30 hz but this leads to an enigma the derived surface spectrum inferred from the longuet higgins mechanism with conventional assumptions for the dispersion relation is associated with mean square slopes that greatly exceed those derived from glitter regardless of the generation mechanism the measured bottom intensities between 10 and 30 hz are well below minimum noise standards reported in the literature

a radiocarbon dated bat guano deposit from n w romania implications for the timing of the little ice age and medieval climate anomaly abstract there is considerable interest in the potential of bat guano as an alternative record of palaeoclimate in regions that are devoid of more commonly utilised archives in this study designed originally to evaluate the potential of cave hosted bat guano to preserve temporal variations in the flux of cosmogenic 36 cl it was found that the guano depositional history is strongly linked to climatic conditions radiocarbon measurements on a 2 7 metre long core of bat guano from m gurici cave n w romania indicate a maximum depositional age of 1195 ad for the base of the core deposition of the lowermost portion of the accumulation occurred during the medieval climate anomaly the cave roost was subsequently devoid of bats during a regional cold phase linked to the little ice age with bats returning when local temperatures increased the rate of guano accumulation then appears to increase in tandem with anthropogenic warming this indicates that bat occupation at this roost site in m gurici cave is strongly linked to regional climate variability with habitation during warm periods possibly associated with the abundance of insects upon which the bats feed comparison of large peaks in anthropogenic 14 c and 36 cl production associated with nuclear weapons testing indicates downward migration of 36 cl probably reflecting post depositional migration within the guano deposit elevated 36 cl cl at the top of the core in comparison with modern atmospheric values may indicate recycling of bomb 36 cl in vegetation therefore we show that while bat guano contains abundant atmospherically derived chloride it has severe limitations as a potential archive of atmospherically derived 36 cl a solar proxy because of post depositional mobility however separation of organically bound chloride or the use of an alternative cosmogenic isotope 10 be in bat guano may offer an unexploited solar proxy that contains contemporaneous environmental signals such as stable isotopes e g 13 c and pollen in association with radiocarbon dating

evidence for chlorine recycling hydrosphere biosphere atmosphere in a forested wet zone on the canadian shield abstract the ability to measure environmental levels of 36 cl by accelerator mass spectrometry and 3 h by 3 he ingrowth mass spectrometry has made it possible to use the pulses of these two isotopes released into the atmosphere during nuclear weapons testing as tracers of cl and water movement in soils and groundwater the authors have investigated the movement of these tracers below a forested wet zone and have found that both are retarded to a differing extent in the near surface because of vegetative uptake and recycling adsorption by clay particles followed by slow release to the groundwater may also be significant the data accumulated in this region of near vertical recharge have gone a considerable distance towards explaining the anomalously low concentrations of 36 cl measured in the 5 laurentian great lakes as well as indicating possible mechanisms for large scale cl recycling in the atmosphere and biosphere identification of the near term non conservative behaviour of the cl is significant since such a phenomenon could introduce errors in many watershed calculations e g water residence times evaporation rates and mixing calculations

the distribution of meteoric cl 36 in precipitation across europe in spring 2007 abstract the cosmogenic isotope 36 cl is a valuable tool for understanding many earth system processes but an improved knowledge of its spatial distribution at the earth s surface is critical for several applications meteoric 36 cl fallout reflects complex interactions between atmospheric production transport and deposition processes and predictive models require experimental validation this study investigates for the first time in a systematic way the spatial distribution of meteoric 36 cl on a continental scale within the european landmass using precipitation samples collected during spring 2007 36 cl cl ratios increase with distance inland and the new data exhibit a strong exponential relationship with 18 o values of precipitation r s 0 75 yielding a useful predictive framework for future studies precipitation events in central european regions are characterised by high 36 cl cl ratios with a maximum measured in lyon france of 746 134 10 15 the new data confirm models for the dependence of 36 cl fallout on latitude with the highest mean springtime fallout 53 6 atoms m 2 s 1 occurring in the 40 50 n latitudinal band with sharp decreases in fallout in high latitude regions and more gradual decreases towards the lower latitudes the 36 cl bomb pulse introduced by thermonuclear weapon testing predominantly in the 1950 s has persisted in the environment for c 50 years but the new data indicate that 36 cl fallout has now essentially returned to natural pre bomb values

origin of groundwater salinity current seawater vs saline deep water in a coastal karst aquifer based on sr and cl isotopes case study of the la clape massif southern france origin of groundwater salinity current seawater vs saline deep water in a coastal karst aquifer based on sr and cl isotopes case study of the la clape massif southern france a b s t r a c t in this study a typical coastal karst aquifer developed in lower cretaceous limestones on the western med iterranean seashore la clape massif southern france was investigated a combination of geochemical and isotopic approaches was used to investigate the origin of salinity in the aquifer water samples were collected between 2009 and 2011 three groundwater groups a b and c were identified based on the hydrogeological setting and on the cl a concentrations average and maximum cl a concentrations in the recharge waters were calculated cl ref and cl ref max to be 0 51 and 2 85 mmol l respectively group a includes spring waters with cl a concentrations that are within the same order of magnitude as the cl ref concentration group b includes groundwater with cl a concentrations that range between the cl ref and cl ref max concentrations group c includes brackish groundwater with cl a concentrations that are significantly greater than the cl ref max concentration overall the chemistry of the la clape groundwater evolves from dominantly ca hco 3 to nacl type on binary diagrams of the major ions vs cl most of the la clape waters plot along mixing lines the mixing end members include spring waters and a saline component current seawater or fossil saline water based on the br cl molar ratio the hypothesis of halite dissolution from triassic evaporites is rejected to explain the origin of salinity in the brackish groundwater groundwaters display 87 sr 86 sr ratios intermediate between those of the limestone aquifer matrix and current mediterranean seawater on a sr mixing diagram most of the la clape waters plot on a mixing line the end members include the la clape spring waters and saline waters which are similar to the deep geo thermal waters that were identified at the nearby balaruc site the 36 cl cl ratios of a few groundwater samples from group c are in agreement with the mixing hypothesis of local recharge water with deep saline water at secular equilibrium within a carbonate matrix finally phreeqc modelling was run based on cal cite dissolution in an open system prior to mixing with the balaruc type saline waters modelled data are consistent with the observed data that were obtained from the group c groundwater based on several trac ers i e concentrations and isotopic compositions of cl and sr calculated ratios of deep saline water in the mixture are coherent and range from 3 to 16 and 0 to 3 for groundwater of groups c and b respectively with regard to the la clape karst aquifer the extension of a lithospheric fault in the study area may favour the rise of deep saline water such rises occur at the nearby geothermal balaruc site along another lithospheric fault at the regional scale several coastal karst aquifers are located along the gulf of lion and occur in mezosoic limestones of similar ages the 87 sr 86 sr ratios of these aquifers tend toward values of 0 708557 which suggests a general mixing process of shallow karst waters with deep saline fossil waters the occurrence of these fossil saline waters may be related to the introduction of seawater during and after the flandrian transgression when the highly karstified massifs invaded by seawater formed islands and peninsulas along the mediterranean coast

effects of upper ocean sound speed structure on deep acoustic shadow zone arrivals at 500 and 1000 km range deep acoustic shadow zone arrivals observed in the late 1990s in the north pacific ocean reveal significant acoustic energy penetrating the geometric shadow comparisons of acoustic data obtained from vertical line arrays deployed in conjunction with 250 hz acoustic sources at ranges of 500 and 1000 km from june to november 2004 in the north pacific with simulations incorporating scattering consistent with the garrett munk internal wave spectrum are able to describe both the energy contained in and vertical extent of deep shadow zone arrivals incoherent monthly averages of acoustic timefronts indicate that lower cusps associated with acoustic rays with shallow upper turning points utps where sound speed structure is most variable and seasonally dependent deepen from june to october as the summer thermocline develops surface reflected rays or those with near surface utps exhibit less scattering due to internal waves than in later months when the utp deepens data collected in november exhibit dra

solar activity during the last 1000 yr inferred from radionuclide records identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors solar forcing prior to the period of direct solar observations radionuclide abundances in natural archives provide the best known proxies for changes in solar activity here we present two independent reconstructions of changes in solar activity during the last 1000 yr which are inferred from be 10 and c 14 records we analyse the tree ring c 14 data shcal intca104 from 1000 to 1510 ad and annual data from 1511 to 1950 ad and four be 10 records from greenland ice cores camp century grip milcent and dye3 together with two be 10 records from antarctic ice cores dome concordia and south pole in general the be 10 and c 14 records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates differences between be 10 records from antarctica and greenland indicate that climatic changes have influenced the deposition of be 10 during some periods of the last 1000 yr the radionuclide based reconstructions of past changes in solar activity do not always agree with the sunspot record which indicates that the coupling between those proxies is not as close as has been sometimes assumed the tree ring c 14 record and be 10 from antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr c 2006 elsevier ltd all rights reserved less

36cl in modern groundwater dated by a multi tracer approach 3h 3he sf6 cfc 12 and 85kr a case study in quaternary sand aquifers in the odense pilot river basin denmark abstract 36 cl produced by thermonuclear bomb testing has been proposed as an additional tool to date or at least to identify recent groundwater components in order to investigate the behaviour of 36 cl in shallow groundwater a multi tracer approach 3 h 3 he sf 6 cfc 12 and 85 kr was used to characterise and date the groundwater of a quaternary sands aquifer which is located on the island of funen near the city of odense denmark recharge to the semi confined shallow aquifer occurs through permeable sand windows and fractured tills at the surface locally however mixing with older pre bomb water from the underlying limestone aquifer may occur the integrated analyses of the available tracer data allowed a well constrained age structure determination of the investigated water system the 36 cl cl ratios measured in groundwater were used to reconstruct the fallout rates for radioactive 36 cl at odense the calculated fallout values exceeded the fallout estimated based on data from the dye 3 ice core in greenland recycling of the bomb peak fallout seems to be the most probable reason of the high values measured the local extent of this process is difficult to quantify which impedes the use of 36 cl for dating

dating rupture events on alluvial fault scarps using cosmogenic nuclides and scarp morphology scarp morphology evolution has commonly been used to estimate the timing of fault scarp rupture events however rates of scarp degradation depend strongly on the geomorphic diffusivity a parameter that is difficult to constrain independently this difficulty may lead to large uncertainties in the estimated ages of rupture events in this study we have coupled the accumulation of the cosmogenic nuclide 36cl to a model for scarp morphology in order to constrain the value of the geomorphic diffusivity and thus determine a more accurate rupture chronology than a rupture history based solely on scarp morphology we measured depth profiles of 36cl accumulated in situ within alluvial sediments beneath the surface of the socorro canyon fault scarp in central new mexico the material analyzed consisted of 150 individual gravel clasts from each depth interval amalgamated into a single sample the alluvium was sampled in three vertical profiles 4 m deep the first profile was 1 5 m downslope of the fault plane on the hanging wall the second 1 5 m upslope of the fault plane on the footwall and the third 27 m upslope of the fault plane on the footwall the third profile which served as a control and which soil geomorphic evidence indicated was beneath a stable surface showed a simple exponential 36cl profile from which a depositional age of 122 18 ka was calculated the second profile on the footwall showed a 36cl deficit relative to the control profile indicating net erosion the first profile on the hanging wall showed a 36cl excess relative to the control profile indicating net deposition stratigraphic evidence in the hanging wall indicated two rupture events prior to the late holocene we modeled the accumulation of 36cl in the vicinity of the scarp simulating erosional redistribution using a diffusion equation for scarp morphology the model accounted for redistribution of 36cl along with the sediment and the effects of the changing fault scarp morphology on the 36cl production by matching both the observed hanging wall and footwall 36cl profiles to profiles calculated by the model as well as the observed topographic profile we obtained ages of 92 16 13 and 28 18 23 ka for the two ruptures the results of our study indicate that cosmogenic nuclides can be useful in constraining rupture chronologies of fault scarps in alluvium

hypersalinity flushing and transient salt wedges in a tidal gulf an inverse estuary abstract because of high evaporation and low rainfall gulfs and embayments in the arid coastal regions of australia are endowed with highly saline water masses with salinities ranging from oceanic values at their mouths to values as high as 60 at their heads this presents the case of an inverse estuary in gulf st vincent of south australia an example of such an inverse estuary the salinity at the head ranges from 39 in winter to 42 in summer in sympathy with the seasonal changes of the local excess of evaporation over precipitation the salient characteristics of temperature salinity and density distributions in the gulf are here described despite a seasonal reversal of spatial temperature gradients the salinity gradient maintains the same sign and is strong enough to control a persistent density gradient from mouth to head in parallel with the case of estuaries a flushing time for salt is defined and estimated for the northern regions of the gulf although the water mass was initially assumed to be vertically well mixed because of tidally induced turbulence the present observations reveal the striking feature that at neap tides the horizontal density gradient forces a salt wedge from the north below the fresher water in the south

shale diapirism in the quaternary tectonic evolution of the northern apennine bologna italy 1 we use morphologic stratigraphic and structural data to identify a set of diapirs just southward uphill of the northern margin of the northern apennine range the diapirs consist mainly of ligurid chaotic shaley units that reach a maximum thickness of over 3 km we also reconstruct marine sedimentation abrasion surfaces that record a 1 cm a differential uplift induced by diapirism on the basis of this data we use the lubrication approximation of the navier stokes equations and analogue experiments to show that thrusting of the epiligurid units can be generated by diapirism of the underlying ligurid units in addition to regional compression owing to a gravity component parallel to the strata the structures formed by diapirism are similar to those generated by compressive tectonics differing in that thrusting is lubricated by diapiric rise using the analogue experiments we show that deformation begins with folding eventually evolving to thrusting and we derive an empirical relation to infer the time remaining to the end of deformation in our area diapiric deformation is still in the folding regime but it should eventually evolve to the thrusting regime and terminate in about 105 a we suggest that the whole northeastern slope of the northern apennine is controlled by diapiric tectonics our interpretation contrasts with the more traditional one which views regional tectonic compression as the only responsible for the structures observed in the field since our model is based on first principles it could be applied to other areas with similar geology and topography

cl deposition rate reconstruction from bomb pulse until present a study based on groundwater records the radioactive isotope 36 cl with a half life of 301 ka is a valuable chronometer for estimation of groundwater residence time up to 2 millions of years aerial thermonuclear fission bomb tests performed during the late 1950s injected a massive amount of this isotope into the atmosphere which exceeded the natural fallout signal since this bomb pulse atmospheric 36 cl deposition tends to return to natural fallout rate the monitoring of this attenuation can provide a good opportunity to extend the use of this chro nometer to shorter time spans venice s lagoon alimentation zone shows groundwaters with residence times distributed over last fifty years this permits the estimation of a continuous 36 cl deposition curve free from latitudinal and seasonal variations of the signal three old groundwater samples with residence times comprised in the range a900 to a8000 bp allow the estimation of a mean natural deposition of 49 at m a2 s a1 and are in good agreement with 36 cl fallout observed for the last 40 000 years by plummer et al 1997 for the bomb pulse period a fallout of 5300 at m a2 s a1 was calculated this was followed by a strong attenuation period taking place until the 1980s during which the fallout reached values ranging between 167 and 354 at m a2 s a1 the attenuation reached then a plateau it experienced a slower lowering until the actual deposition with fallout values calculated between 124 and 252 at m a2 s a1 this persistence of high deposition rate was classically attributed to biological and atmo spherical recycling processes or underestimation of the natural atmospheric production of the 36 cl additional source of 36 cl production has been envisaged through the activation of chlorine radicals from stratospherical cfcs leading to a 36 cl production rate comparable with that of ar spallation from the first approximation lastly the latitudinal factor of the attenuation of the fallout rate is discussed and the impact of the jet streams is proposed as an explanation for the discrepancies in the attenuation rate

cosmogenic 36cl in karst waters quantifying contributions from atmospheric and bedrock sources improved reconstructions of cosmogenic isotope production through time are crucial to understand past solar variability as a preliminary step to derive atmospheric 36 cl cl solar proxy time series from speleothems we quantify 36 cl sources in cave dripwaters atmospheric 36 cl fallout rates are a potential proxy for solar output however extraneous 36 cl derived from in situ production in cave hostrocks could complicate the solar signal results from numerical modeling and preliminary geochemical data presented here show that the atmospheric 36 cl source dominates in many but not all cave dripwaters at favorable low elevation mid latitude sites 36 cl based speleothem solar irradiance reconstructions could extend back to 500 ka with a possible centennial scale temporal resolution this would represent a marginal improvement in resolution compared with existing polar ice core records with the added advantages of a wider geographic range independent u series constrained chronology and the potential for contemporaneous climate signals within the same speleothem material

ratio of 36cl cl in ground ice of east siberia and its application for chronometry abundance of the cosmogenic nuclide chlorine 36 36cl was measured together with the chloride cl concentration in different horizons of quaternary permafrost samples collected from various types of ground ice in the northeastern part of siberia the 36cl cl in 32 samples ranged in value from 2 4 10 14 to 1 4 10 12 nonetheless after a few extreme values were excluded these 36cl cl ratios provided a local permafrost chronometry the general concordance of the modeled ages with geological expectations and other chronological methods supports the potential power of the proposed dating method however the large observed change in ratios from higher to lower values during the transition from last glacial maximum to holocene climatic conditions remains unexplained an attempt to make use of the corresponding beryllium 10 10be absolute concentrations in the same samples failed because input of 10be attached to particulate matter into permafrost is unknown further 36cl cl serial measurements of modern precipitation and fossil ground ice are needed to refine this dating method into a practical tool with a clear protocol

cosmogenic 36cl in karst waters from bunker cave north western germany a tool to derive local evapotranspiration abstract monthly rain and drip waters were collected over a period of 10 months at bunker cave germany the concentration of 36 cl and the 36 cl cl ratios were determined by accelerator mass spectrometry ams while stable 35 37 cl concentrations were measured with both ion chromatography ic and ams the measured 36 cl fluxes of 0 97 0 57 10 4 atoms cm 2 month 1 0 97 atoms m 2 month 1 in precipitation were on average twice as high as the global mean atmospheric production rate this observation is consistent with the local fallout pattern which is characterized by a maximum at mid latitudes the stable chloride concentration in drip waters ranging from 13 2 to 20 9 mg l and the 36 cl concentrations ranging from 16 9 10 6 to 35 3 10 6 atoms l are a factor of 7 and 10 above the values expected from empirical evapotranspiration formulas and the rain water concentrations respectively most likely the additional stable cl is due to human impact from a nearby urban conglomeration the large 36 cl enrichment is attributed to the local evapotranspiration effect which appears to be higher than the calculated values and to additional bomb derived 36 cl from nuclear weapons tests in the 1950s and 60s stored in the soil above the cave in the densely vegetated soil above bunker cave 36 cl seems not to behave as a completely conservative tracer the bomb derived 36 cl might be retained in the soil due to uptake by minerals and organic material and is still being released now based on our data the residence time of 36 cl in the soil is estimated to be about 75 85 years

tidal transformation and resonance in a short microtidal mediterranean estuary alfacs bay in ebre delta abstract tidal and subtidal waves are analyzed with sea level data and numerical modeling in a short and micro tidal embayment alfacs bay nw mediterranean sea data analysis exhibits tidal wave amplification and seiching characteristic period of 3 5 h along the bay numerical results show an eight fold increase in quarter wave resonant wave amplitudes from the mouth to the head of the bay this amplification follows the classical description of a standing wave moreover resonant wave velocities measured and computed at the bay mouth node location are about one order of magnitude higher than tidal currents analysis of astronomic tidal propagation in the bay reveals similar behavior for diurnal and semidiurnal constituents tidal waves amplify along the bay by 3 for diurnal and 10 for semidiurnal constituents numerical simulations conducted with different domains indicate that geometric effects dominate over frictional influences in causing the wave behavior this behavior is consistent with the existence of a quasi steady standing wave within the bay

cosmogenic nuclides during isotope stages 2 and 3 abstract changes in the concentration of cosmogenic nuclides measured in natural archives are related mainly to changes in the cosmic ray induced production rate in the atmosphere but also to the subsequent transport and deposition processes which depend on the geochemical properties of the nuclides a comparison of 10 be and 36 cl data from ice cores from greenland ice cores and 14 c data from tree rings and other archives provides the following information for the isotope stages 2 and 3 1 changes in the cosmogenic nuclide production rate on time scales longer than approximately 2 kyr agree well with paleomagnetic data derived from deep sea sediments in particular the geomagnetic excursions leading to weak fields around 40 kyr bp laschamp and 32 kyr bp mono lake can be clearly seen 2 production variations on shorter time scales contain information on solar variability as an example the 205 yr devries cycle already known from the analysis of 14 c tree ring data during the holocene is also present in the 10 be data of the time period 25 55 kyr bp 3 a comparison of 14 c calculated using 10 be data with the measured 14 c record points to a reduction of the global deep water formation during the younger dryas cold event 4 using information available on the production rates of cosmogenic nuclides in the past derived from paleomagnetic data the paleoprecipitation rate can be calculated this is crucial for establishing precise time scales

measurement and prediction of ultralow frequency ocean ambient noise off the eastern u s coast ultralow frequency 0 02 2 hz acoustic ambient noise was monitored from january to april 1991 at six ocean bottom stations off the eastern u s coast the depths of the stations ranged from about 100 m to 2500 m the measured spectra are in good agreement with predictions made using cato s theory j acoust soc am 89 1076 1095 1991 for noise generation by surface wave orbital motion after extending the calculations to incorporate horizontally stratified environments contributions from both the linear single frequency virtual monopole and the nonlinear double frequency dipole mechanisms are clearly recognizable in the data the predictions make use of directional wave data obtained from surface buoys deployed during the swade experiment and an ocean bottom model derived from compressional wave speed data measured during the edge deep seismic reflection survey the results demonstrate conclusively that nonlinear surface wave interactions are the dominant mechanism for generating deep ocean ulf noise in the band 0 2 0 7 hz

infragravity currents in a small ria estuary amplified coastal edge waves abstract observations are presented of estuarine infragravity oscillations in a very small estuary the ria de santiuste northern spain that discharges into a bay time scale calculations and measurements indicate that the most likely source of amplified infragravity waves within the estuary are coastal edge waves which appear to be resonating between the headlands of the bay and onshore offshore seiching of waters that may be resonating between the beach and the bay s seaward limit infragravity waves in the estuary have a narrow power dominant periodicity range of 4 3 4 8 min generally only very weak waves and at other periodicities occur within the tidal river when it is unaffected by the tide although infragravity water level amplitudes are small in the tidal river typically 0 01 m during high water the corresponding velocity amplitudes are significant typically 0 1 m s 1 despite the occurrence of high runoff conditions during these measurements within the estuary and close to the mouth near bed salinity shows considerable variability that is a consequence of salt wedge oscillations with periodicities that are within the range of 4 3 4 8 min model results for simulated neap to spring high water water levels show that wave periodicities in the range 3 5 4 5 min correspond approximately to 3 4 resonances the model also indicates that an effect of low runoff is to greatly enhance resonant behaviour within the estuary such that water level amplitudes of 0 02 m at the mouth can produce wave currents as fast as 0 4 m s 1 within the estuary compared with 0 1 m s 1 during high runoff

wind sea behind a cold front and deep ocean acoustics abstracta rapid and broadband 1 h 1 f 400 hz increase in pressure and vertical velocity on the deep ocean floor was observed on seven instruments comprising a 20 km array in the northeastern subtropical pacific the authors associate the jump with the passage of a cold front and focus on the 4 and 400 hz spectra at every station the time of the jump is consistent with the front coming from the northwest the apparent rate of progress 10 20 km h 1 2 8 5 6 m s 1 agrees with meteorological observations the acoustic radiation below the front is modeled as arising from a moving half plane of uncorrelated acoustic dipoles the half plane is preceded by a 10 km transition zone over which the radiator strength increases linearly from zero with this model the time derivative of the jump at a station yields a second and independent estimate of the front s speed 8 5 km h 1 2 4 m s 1 for the 4 hz spectra the source physics is taken to be longuet higgins radiation its strength depends on the qu

a review of the shelf slope circulation along australia s southern shelves cape leeuwin to portland abstract a review is presented of the ocean circulation along australia s southern shelves and slope uniquely the long zonal shelf is subject to an equatorward sverdrup transport that gives rise to the flinders current a small sister to the world s major western boundary currents the flinders current is strongest near the 600 m isobath where the current speeds can reach 20 cm s and the bottom boundary layer is upwelling favourable it is larger in the west but likely intermittent in both space and time due to possibly opposing winds thermohaline circulation and mesoscale eddies the flinders current may be important to deep upwelling within the ubiquitous canyons of the region during winter the leeuwin current and local winds act to drive eastward currents that average up to 20 30 cm s the currents associated with the intense coastal trapped wave field 6 12 day band are of order 25 30 cm s and can peak at 80 90 cm s wintertime winds and cooling also lead to downwelling to depths of 200 m or more and the formation of dense coastal water within the great australian bight and the south australian sea within the great australian bight the thermohaline circulation associated with this dense water is unknown but may enhance the eastward shelf edge south australian current the dense salty water formed within spencer gulf is known to cascade as a gravity current to depths of 200 m off kangaroo island this dense water outflow and meanders in the shelf circulation also fix the locations of a sequence of quasi permanent mesoscale eddies between the eyre peninsula and portland during summer the average coastal winds reverse and surface heating leads to the formation of warm water in the western great australian bight and the south australian sea no significant exchange of shelf water and gulf water appears to occur due to the presence of a dense nutrient rich sub surface pool that is upwelled off kangaroo island the winds lead to weak average coastal currents increasing evidence suggests that el nino events 4 7 year period can have a major impact on the winter and summer circulation these events propagate from the pacific ocean and around the shelf slope wave guide of west australia and into the great australian bight during winter el nino events the average shelf currents may be largely shut down during summer the thermocline may be raised by up to 150 m the nature and role of tides and surface waves is also discussed along with uncertainties in the general circulation and future research

tidal progression in a near resonant system a case study from south australia abstract detailed observations of the tide in a shallow southern hemisphere gulf are described the gulf is close to quarter wave resonance with the semi diurnal tide but the nature of the tide changes with distance from the head of the gulf near the head the tide behaves as a standing wave the phase is almost constant in this region and the tidal currents lead elevations by 90 near the entrance to the gulf the semi diurnal tide behaves more as a progressive wave there is a regular change in phase of elevation with distance and the phase difference between current and elevation is reduced it is shown here that this behaviour can be understood in terms of a simple conceptual model proposed by redfield 1950 papers in physical oceanography and meteorology 11 1 36 in this model friction causes the amplitude of the tidal wave to diminish exponentially with distance travelled near the gulf head the incident and reflected waves are of similar amplitude and a standing wave is produced further from the head the incident wave is considerably larger than the reflected wave and the resulting wave is predominantly progressive the observations presented here are in good agreement with this model if the tidal wave amplitude is allowed to fall by 1 e for every wavelength travelled this decay in wave amplitude implies a rate of energy loss in the region for the m2 tide of 135 mw a figure which is consistent with an independent estimate of energy dissipation