depth dependent acoustic features of diving sperm whales physeter macrocephalus in the gulf of mexico three dimensional dive trajectories of three sperm whales in the gulf of mexico have been obtained by measuring the relative arrival times and bearings of the animals acoustic multipath reflections using two elements of a towed hydrophone array deployed at an unknown depth and orientation within the first 6 12 min of the start of a dive the intervals between successive clicks of all three whales corresponded closely with the two way travel time of an acoustic pulse traveling vertically between the animals position and the ocean bottom the click spectra contained multiple peaks including a faint band of energy originally centered near 10 khz as the animals descended over 500 m in depth the center frequency of this band shifted to nearly 15 khz but subsequently remained near this value during the rest of the dive this frequency shift is consistent with that expected from energy scattering from an ensemble of incompressible small scale air filled resonators with diameters on the order of 4 mm one possible candidate for such an ensemble is proposed to reside in the collapsed frontal sac of the animal a comparison of the received levels for the bottom and direct multipath arrivals indicates that the whales acoustic directivity must range between 10 30 db in the 5 20 khz region

modeling substorm current systems using conductivity distributions inferred from de auroral images images of auroral emissions observed with dynamics explorer 1 de 1 are used to calculate ionospheric conductivities over the polar region the combination of ground based magnetometer data and the inferred conductivities enables us to estimate on a global scale the distributions of ionospheric electric fields and currents and field aligned currents as well as the joule heating production rate with a time resolution of 12 min although our inference of the conductivity distribution requires further improvements the following conclusions may be drawn from this work 1 the westward electrojet is in general collocated with the region of high auroral luminosity while the region of relatively low luminosity in the evening sector is collocated with the eastward electrojet 2 the upward field aligned currents exist in the brightest auroral region on the poleward side of the evening auroral oval and on the equatorward side of the morning oval however the magnitudes of these upward currents are not in proportion to the auroral luminosities suggesting that the characteristic energies of precipitating electrons carrying the upward currents and generating the auroral luminosities may be different 3 a significant amount of ionospheric currents can flow in regions where there are no bright auroral emissions an example of this effect is found over the poleward half of the westward electrojet in the morning sector where the electric field is the main contributor to the ionospheric currents 4 the distribution of calculated field aligned currents displays many localized structures which characterize the development of the substorm current system previous satellite observations may represent gross time averages of such complicated distributions

off axis effects on the multipulse structure of sperm whale usual clicks with implications for sound production sperm whales physeter macrocephalus produce multipulsed clicks with their hypertrophied nasal complex the currently accepted view of the sound generation process is based on the click structure measured directly in front of or behind the whale where regular interpulse intervals ipis are found between successive pulses in the click most sperm whales however are recorded with the whale in an unknown orientation with respect to the hydrophone where the multipulse structure and the ipi do not conform to a regular pulse pattern by combining far field recordings of usual clicks with acoustic and orientation information measured by a tag on the clicking whale we analyzed clicks from known aspects to the whale we show that a geometric model based on the bent horn theory for sound production can explain the varying off axis multipulse structure some of the sound energy that is reflected off the frontal sac radiates directly into the water creating an intermediate pulse p1 2 seen in off axis recordings the powerful p1 sonar pulse exits the front of the junk as predicted by the bent horn model showing that the junk of the sperm whale nasal complex is both anatomically and functionally homologous to the melon of smaller toothed whales

glacial advance and retreat sequences in a permo carboniferous section central transantarctic mountains episodes of glacial advance and retreat can be recognized through analysis of vertical facies sequences in the permo carboniferous pagoda formation of the beardmore glacier area antarctica the formation includes a remarkably complete record of continental sedimentation near the terminus of a temperate glacier facies sequence is pre eminent for inferring glacial advance and retreat other important criteria are abundance and geometry of sandstone interbedded with diamictite diamictite character and nature of bed contacts using these characteristics advance and retreat sequences 5 60 m thick are recognized a sharp contact with a striated surface and erosional relief overlain by structureless diamictite lodgement till is typical of grounded ice advance grounded ice retreat is characterized by structureless diamictite lodgement till overlain by crudely stratified diamictite melt out till and then by diamictite interbedded with sandstone and conglomerate flow till and glacio fluvial or glacio lacustrine deposits gradational contacts between shale overlain by diamictite and diamictite overlain by shale characterize advance and retreat respectively in subaqueous settings pauses in sediment accumulation minor fluctuations of the ice margin and or changes in subglacial dynamics are indicated by specific features within diamictite units such as probable frost wedge casts single layer boulder beds sharp sedimentary contacts and changes in diamictite character these minor events are superimposed upon the main advance retreat cycles study of both the overall facies sequence and of individual diagnostic structures albeit in an incomplete stratigraphic record permits a distinction between major and minor advance retreat events as many as six major advance retreat cycles exist in some pagoda sections but the number of cycles present varies in different sections

the monopulsed nature of sperm whale clicks traditionally sperm whale clicks have been described as multipulsed long duration nondirectional signals of moderate intensity and with a spectrum peaking below 10 khz such properties are counterindicative of a sonar function and quite different from the properties of dolphin sonar clicks here data are presented suggesting that the traditional view of sperm whale clicks is incomplete and derived from off axis recordings of a highly directional source a limited number of assumed on axis clicks were recorded and found to be essentially monopulsed clicks with durations of 100 micros with a composite directionality index of 27 db with source levels up to 236 db re 1 micropa rms and with centroid frequencies of 15 khz such clicks meet the requirements for long range biosonar purposes data were obtained with a large aperture gps synchronized array in july 2000 in the bleik canyon off vesteralen norway 69 degrees 28 n 15 degrees 40 e a total of 14 h of sound recordings was collected from five to ten independent simultaneously operating recording units the sound levels measured make sperm whale clicks by far the loudest of sounds recorded from any biological source on axis click properties support previous work proposing the nose of sperm whales to operate as a generator of sound

processes and products of grounding line fans from the permian pagoda formation antarctica insight into glacigenic conditions in polar gondwana abstract glacimarine grounding line fans are subaqueous depositional features that form due to the expulsion of sediment laden subglacial waters at the grounding lines of temperate tidewater glaciers few studies of ancient grounding line fans exist this study describes and interprets several ancient glacimarine grounding line fans and their physical characteristics using the lower permian pagoda formation along tillite glacier in the central transantarctic mountains antarctica as a deep time example wedge shaped sandstone bodies are used to identify major depositional processes and products that occurred during fan formation the depositing processes on these fans operated in tandem as tractive freshwater discharge from beneath the glacier s was progressively replaced down the fans in the direction of flow by buoyant upwelling and the development of overflow plumes tractive flow deposits are characterized by trough and climbing cross stratification while deposits resulting from settling from meltwater plumes consist of horizontal laminations and abundant soft sediment deformational structures load flame and diapiric structures secondary features such as thrust and normal faults resulted from advance and retreat dynamics of the ice front whereas mass flow deposits convolute bedding recumbent and s shaped folds slumps and slides resulted from resedimentation because glacimarine grounding line fans require specific depositional conditions to develop their identification is useful in constraining environmental conditions in the rock record for the pagoda formation the occurrence of grounding line fan deposits is significant as these strata were originally interpreted as deposits of a large terrestrial ice sheet centered over the location of the present transantarctic mountains that extended outward and covered much of gondwana for up to 90 million years however this study demonstrates that these rocks were deposited in a glacimarine setting results combined with other recent studies suggest that multiple small temperate ice sheets occurred in south polar antarctica during the late paleozoic ice age rather than a single massive ice sheet

three dimensional passive acoustic tracking of sperm whales physeter macrocephalus in ray refracting environments a wide aperture towed passive acoustic array is used to obtain ranges and depths of acoustically active sperm whales in the gulf of mexico in june 2004 by extending a technique previously reported thode j acoust soc am 116 245 253 2004 to explicitly account for ray refraction effects arising from a depth dependent sound speed profile under this expanded approach three quantities are measured from an impulsive sound the time difference between direct path arrivals on a forward and rear subarray the time difference between the direct and surface reflected paths on the rear subarray and the acoustic bearing measured on the rear subarray these quantities combined with independent measurements of hydrophone depths and cable inclination are converted into range depth position fixes by implementing an efficient numerical procedure that uses a ray tracing code to account for ray refraction effects caused by depth dependent sound speed profiles analytic expressions that assume a constant waterb

lithofacies and origin of the buckeye formation late paleozoic glacial and glaciomarine sediments ohio range transantarctic mountains antarctica up to 300 m of glaciogenic late paleozoic buckeye formation rest unconformably upon an erosional surface cut on and in places through early devonian horlick formation in the ohio range antarctica the diamictite exhibits a gradual transition upsection from direct glacial to subsequent glaciomarine deposition lowermost beds include diamictite deposited directly from grounded ice numerous striated pavements indicate paleo ice flow from west to east upsection many beds are internally stratified and this with the presence of fine laminated interbeds provides evidence of subaqueous deposition geochemical textural and paleontological data suggest a marine influence towards the top of the buckeye most diamictite horizons are horizontally stratified with a decreasing proportion of small dropstones buckeye formation is conformably overlain by discovery ridge formation beds of probable shallow marine origin

using a coherent hydrophone array for observing sperm whale range classification and shallow water dive profiles sperm whales in the new england continental shelf and slope were passively localized in both range and bearing and classified using a single low frequency 2500 hz densely sampled towed horizontal coherent hydrophone array system whale bearings were estimated using time domain beamforming that provided high coherent array gain in sperm whale click signal to noise ratio whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements multiple concurrently vocalizing sperm whales in the far field of the horizontal receiver array were distinguished and classified based on their horizontal spatial locations and the inter pulse intervals of their vocalized click signals the dive profile was estimated for a sperm whale in the shallow waters of the gulf of maine with 160 m water column depth located close to the array s near field where depth estimation was feasible by employing time difference of arrival of the direct and multiply reflected click signals received on the horizontal array by accounting for transmission loss modeled using an ocean waveguide acoustic propagation model the sperm whale detection range was found to exceed 60 km in low to moderate sea state conditions after coherent array processing

localization and tracking of phonating finless porpoises using towed stereo acoustic data loggers cetaceans produce sound signals frequently usually acoustic localization of cetaceans was made by cable hydrophone arrays and multichannel recording systems in this study a simple and relatively inexpensive towed acoustic system consisting of two miniature stereo acoustic data loggers is described for localization and tracking of finless porpoises in a mobile survey among 204 porpoises detected acoustically 34 individuals similar to 17 were localized and 4 of the 34 localized individuals were tracked the accuracy of the localization is considered to be fairly high as the upper bounds of relative distance errors were less than 41 within 173 m with the location information source levels of finless porpoise clicks were estimated to range from 180 to 209 db re 1 mu pa pp at 1 m with an average of 197 db n 34 which is over 20 db higher than that estimated previously from animals in enclosed waters for the four tracked porpoises two dimensional swimming trajectories relative to the moving survey boat absolute swimming speed and absolute heading direction are deduced by assuming the animal movements are straight and at constant speed in the segment between two consecutive locations

hemispheric asymmetries in the ionospheric response observed in the american sector during an intense geomagnetic storm 1 the main purpose of this investigation is to study the ionospheric f region response induced by the intense geomagnetic storm that occurred on 7 8 september 2002 the geomagnetic index dst reached a minimum of 181 nt at 0100 ut on 8 september in this study we used observations from a chain of 12 gps stations and another chain of 6 digital ionosonde stations it should be mentioned that soon after the sudden commencement sc at 1637 ut on 7 september the tec variations at midlatitude stations in both hemispheres showed an f region positive storm phase however during the recovery phase a strong hemispheric asymmetry was observed in the ionospheric response while a tid type soliton was observed to propagate in the southern american sector no tid activity was seen in the northern american sector also in the southern hemisphere the tec variations were less affected by the geomagnetic storm the northern hemisphere observations showed a strong and long lasting negative f region storm phase starting at about 1000 ut on 8 september lasting for about 24 h a perusal of tec phase fluctuations and equatorial spread f esf ionospheric sounding data indicates that on the disturbed night of 7 8 september some stations showed the occurrence of esf starting at about 0000 ut 2000 lt on 8 september whereas other stations showed that the esf occurrence started much later at about 0800 ut 0500 lt this hemispheric asymmetric response of the ionospheric f region possibly indicates the presence of different mechanisms for the generation of esf along the various latitudinal regions during the disturbed period

first e region observations of mesoscale neutral wind interaction with auroral arcs we report the first observations of e region neutral wind fields and their interaction with auroral arcs at mesoscale spatial resolution during geomagnetically quiet conditions at mawson antarctica this was achieved by using a scanning doppler imager which can observe thermospheric neutral line of sight winds and temperatures simultaneously over a wide field of view in two cases the background e region wind field was perpendicular to an auroral arc which when it appeared caused the wind direction within 50 km of the arc to rotate parallel along the arc reverting to the background flow direction when the arc disappeared this was observed under both westward and eastward plasma convection the wind rotations occurred within 7 16 min in one case as an auroral arc propagated from the horizon toward the local zenith the background e region wind field became significantly weaker but remained unaffected where the arc had not passed through we demonstrate through modeling that these effects cannot be explained by height changes in the emission layer the most likely explanation seems to be the greatly enhanced ion drag associated with the increased plasma density and localized ionospheric electric field associated with auroral arcs in all cases the f region neutral wind appeared less affected by the auroral arc although its presence is clear in the data

coherent radar estimates of average high latitude ionospheric joule heating the scandinavian twin auroral radar experiment stare and sweden and britain radar experiment sabre bistatic coherent radar systems have been employed to estimate the spatial and temporal variation of the ionospheric joule heating in the combined geographic latitude range 63 8 72 6 corrected geomagnetic latitude 61 5 69 3 over scandinavia the 173 days of good observations with all four radars have been analyzed during the period 1982 to 1986 to estimate the average ionospheric electric field versus time and latitude the ae dependent empirical model of ionospheric pedersen conductivity by spiro et al 1982 has been used to calculate the joule heating the latitudinal and diurnal variation of joule heating as well as the estimated mean hemispherical heating of 1 7 1011 w are in good agreement with earlier results average joule heating was found to vary linearly with the ae au and al indices and as a second order power law with kp the average joule heating was also examined as a function of the direction and magnitude of the interplanetary magnetic field it has been shown for the first time that the ionospheric electric field magnitude as well as the joule heating increase with increasingly negative southward bz

echolocation clicks of free ranging cuvier s beaked whales ziphius cavirostris strandings of beaked whales of the genera ziphius and mesoplodon have been reported to occur in conjunction with naval sonar use detection of the sounds from these elusive whales could reduce the risk of exposure but descriptions of their vocalizations are at best incomplete this paper reports quantitative characteristics of clicks from deep diving cuvier s beaked whales ziphius cavirostris using a unique data set two whales in the ligurian sea were simultaneously tagged with sound and orientation recording tags and the dive tracks were reconstructed allowing for derivation of the range and relative aspect between the clicking whales at depth the whales produced trains of regular echolocation clicks with mean interclick intervals of 0 43 s 0 09 and 0 40 s 0 07 the clicks are frequency modulated pulses with durations of 200 s and center frequencies around 42 khz 10 db bandwidths of 22 khz and q3 db of 4 the sound beam is narrow with an estimated directionality index of more than 25 db

off axis effects on the multi pulse structure of sperm whale coda clicks sperm whale physeter macrocephalus clicks have a multi pulse structure a result of the reflection of sound energy between air sacs in the spermaceti organ although previous research revealed that usual clicks used for echolocation recorded away from a vocalizing whale s longitudinal axis have waveforms with poorly defined pulse structures it has been unknown whether sperm whale coda clicks used for communication show similar off axis effects to address this knowledge gap a hydrophone array was used to localize vocalizing sperm whales and the waveforms of coda clicks recorded from different aspects were examined coda clicks recorded close to the whale s acoustic axis showed well defined multi pulsed waveforms while those recorded off axis did not as for usual clicks this suggests that sound energy radiates directly into the water upon reflection off the frontal sac

tectonic and denudational history of the rennick graben north victoria land implications for the evolution of rifting between east and west antarctica 1 the tectonic depression of the rennick graben northern victoria land antarctica is a key element for deciphering the cenozoic separation history between east and west antarctica and evolution of the west antarctic rift system the geometry kinematics and timing of the boundary faults of the rennick graben are presented on the basis of a detailed structural study of the major fault segments combined with apatite fission track data the structural architecture of the rennick graben is controlled by distributed and partitioned right lateral strike slip faulting fission track data indicate that the last significant denudation stage of the rennick graben shoulders started from eocene times with increasing cooling and denudation since 40 50 ma a direct structural connection is then established between cenozoic denudation and the activation of the dextral strike slip regime in north victoria land during the cenozoic in this framework the rennick graben is interpreted as a localized tectonic depression generated as a displacement accommodation area of the regionally sized dextral strike slip shearing the results of this study 1 invalidate the commonly assumed link between mesozoic ross sea rifting and opening of the rennick graben 2 argue against orthogonal rifting models for the cenozoic evolution of the ross sea region and 3 provide constraints to the modalities and timing of the separation between the east antarctic craton and the west antarctica extensional province

sperm whale clicks directionality and source level revisited in sperm whales physeter catodon l 1758 the nose is vastly hypertrophied accounting for about one third of the length or weight of an adult male norris and harvey in animal orientation and navigation nasa sp 262 1972 pp 397 417 ascribed a sound generating function to this organ complex a sound generator weighing upward of 10 tons and with a cross section of 1 m is expected to generate high intensity directional sounds this prediction from the norris and harvey theory is not supported by published data for sperm whale clicks source levels of 180 db re 1 pa and little if any directionality either the theory is not borne out or the data is not representative for the capabilities of the sound generating mechanism to increase the amount of relevant data a five hydrophone array suspended from three platforms separated by 1 km and linked by radio was deployed at the slope of the continental shelf off andenes norway in the summers of 1997 and 1998 with this system source levels up to 223 db re 1 pa perms were recorded also source level differences of 35 db for the same click at different directions were seen which are interpreted as evidence for high directionality this implicates sonar as a possible function of the clicks thus previously published properties of sperm whale clicks underestimate the capabilities of the sound generator and therefore cannot falsify the norris and harvey theory

the diurnal and latitudinal variation of auroral zone ionospheric conductivity the great spatial and temporal variability of auroral ionospheric conductivity significantly influences the ionospheric closure path for high latitude field aligned currents because these closure paths can extend to low latitudes changes in auroral zone conductivity can influence the global electric field distribution in this paper synoptic chatanika radar observations of auroral zone conductivity that cover 62 to 68 geomagnetic latitude are presented they are representative of quiet winter active winter and equinoctial conditions during the daytime the solar contribution to the height integrated conductivity is well represented by p h 5 10 cos1 2 where is the solar zenith angle the nighttime height integrated pedersen and hall conductivities p and h in the electron density trough are at times below our detection threshold of 0 5 mho following magnetic substorm onset enhanced conductivity regions move southward and intensify as the recovery phase begins the conductivity pattern recedes northward and diminishes the onset and cessation of precipitation associated with these events can be as abrupt as a few minutes in one example the behavior of p and h are examined in the vicinity of the harang discontinuity which was quite sharp 30 min in local time at the harang discontinuity on that day the ratio of h to p decreased indicating a softening of the precipitating energy distribution

a new radar auroral backscatter experiment in 1982 a new radar auroral backscatter system sabre sweden and britain radar experiment commenced operation in northern europe observations with this ground based system allow estimates to be made of the electric fields in the auroral e region as an electric field probe the coherent radar technique is unique in that measurements are made over a large area 200 000 km2 with good spatial resolution 20 20 km2 and with a temporal resolution of typically 20 s the system field of view covers an l value range 4 3 5 8 this region in the magnetosphere ionosphere system is now accessible for the first time for detailed electric field studies we present here observations of two pulsation events

a large aperture low cost hydrophone array for tracking whales from small boats a passive sonar array designed for tracking diving sperm whales in three dimensions from a single small vessel is presented and the advantages and limitations of operating this array from a 6 m boat are described the system consists of four free floating buoys each with a hydrophone built in recorder and global positioning system receiver gps and one vertical stereo hydrophone array deployed from the boat array recordings are post processed onshore to obtain diving profiles of vocalizing sperm whales recordings are synchronized using a gps timing pulse recorded onto each track sensitivity analysis based on hyperbolic localization methods is used to obtain probability distributions for the whale s three dimensional location for vocalizations received by at least four hydrophones these localizations are compared to those obtained via isodiachronic sequential bound estimation results from deployment of the system around a sperm whale in the kaikoura canyon in new zealand are shown

modeling acoustic propagation of airgun array pulses recorded on tagged sperm whales physeter macrocephalus in 2002 and 2003 tagged sperm whales physeter macrocephalus were experimentally exposed to airgun pulses in the gulf of mexico with the tags providing acoustic recordings at measured ranges and depths ray trace and parabolic equation pe models provided information about sound propagation paths and accurately predicted time of arrival differences between multipath arrivals with adequate environmental information a broadband acoustic pe model predicted the relative levels of multipath arrivals recorded on the tagged whales however lack of array source signature data limited modeling of absolute received levels airguns produce energy primarily below 250hz with spectrum levels about 20 40db lower at 1khz some arrivals recorded near the surface in 2002 had energy predominantly above 500hz a surface duct in the 2002 sound speed profile helps explain this effect and the beampattern of the source array also indicates an increased proportion of high frequency sound at near horizontal launch angles these findings indicate that airguns sometimes expose animals to measurable sound energy above 250hz and demonstrate the influences of source and environmental parameters on characteristics of received airgun pulses the study also illustrates that on axis source levels and simple geometric spreading inadequately describe airgun pulse propagation and the extent of exposure zones

upper paleozoic glacigenic deposits of gondwana stratigraphy and paleoenvironmental significance of a tillite succession in northern victoria land antarctica abstract late paleozoic glacial deposits are widespread in gondwana in antarctica the best outcrops occur in the central transantarctic mountains ellsworth mountains pensacola mountains and in southern victoria land whereas they are rare and very scattered in northern victoria land which represents a linkage sector with tasmania and eastern australia the aim of the present research is to define the stratigraphic setting and the environmental interpretation of a poorly studied lower permian glacigenic succession located near orr glacier in the lanterman range in northern victoria land it has great importance because it represents the only significant glacigenic succession for this wide area marking and defining time and modality of a glacial postglacial transition during the early permian a critical time interval in the paleoenvironmental evolution of southern gondwana this succession named here as the lanterman formation lies directly on to crystalline basement and is overlain by a thick permian fluvial succession takrouna formation the results provided by sedimentological facies analysis and palynological analysis integrated with a limited petrographic characterization show a correlation framework between two isolated successions outlining their stratigraphic architecture and subdivided into a lower glacial portion and an upper postglacial portion the former asselian in age is dominated by diamictite sandstone mudstone with lonestones and carbonate deposits suggesting repeated advance and retreat of a terrestrial glacier with facies associations indicating environmental changes from subglacial to glaciofluvial to glaciolacustrine the latter is dominated by lacustrine mudstone with decreasing lonestones upward thin bedded sandstone conglomerate and a thick fluvial sandstone and pebbly sandstone succession at the top signalling the transition to a fluvial system through time the overall dataset suggests that the late paleozoic glacigenic deposits of northern victoria land record the evolution from a setting characterized by a terrestrial small ice cap that underwent repeated advances and retreats due to climate cycles in a lacustrine setting into a postglacial paleoenvironmental scenario with a wide fluvial system draining northwards from victoria land towards the tasmanian basin the results contribute to increasing knowledge of the timing and modalities of the late paleozoic ice age in gondwana particularly for polar regions such as antarctica

mesoscale observations of joule heating near an auroral arc and ion neutral collision frequency in the polar cap e region 1 we report on the first mesoscale combined ionospheric and thermospheric observations partly in the vicinity of an auroral arc from svalbard in the polar cap on 2 february 2010 the eiscat svalbard radar employed a novel scanning mode in order to obtain f and e region ion flows over an annular region centered on the radar simultaneously a colocated scanning doppler imager observed the e region neutral winds and temperatures around 110 km altitude using the 557 7 nm auroral optical emission combining the ion and neutral data permits the e region joule heating to be estimated with an azimuthal spatial resolution of 64 km at a radius of 163 km from the radar the spatial distribution of joule heating shows significant mesoscale variation the ion neutral collision frequency is measured in the e region by combining all the data over the entire field of view with only weak aurora present the estimated ion neutral collision frequency at 113 km altitude is in good agreement with the msis atmospheric model

three dimensional beam pattern of regular sperm whale clicks confirms bent horn hypothesis the three dimensional beam pattern of a sperm whale physeter macrocephalus tagged in the ligurian sea was derived using data on regular clicks from the tag and from hydrophones towed behind a ship circling the tagged whale the tag defined the orientation of the whale while sightings and beamformer data were used to locate the whale with respect to the ship the existence of a narrow forward directed p1 beam with source levels exceeding 210 db peak re 1 pa at 1 m is confirmed a modeled forward beam pattern that matches clicks 20 off axis predicts a directivity index of 26 7 db and source levels of up to 229 db peak re 1 pa at 1 m a broader backward directed beam is produced by the p0 pulse with source levels near 200 db peak re 1 pa at 1 m and a directivity index of 7 4 db a low frequency component with source levels near 190 db peak re 1 pa at 1 m is generated at the onset of the p0 pulse by air resonance the results support the bent horn model of sound production in sperm whales while the sperm whale nose appears primarily adapted to produce an intense forward directed sonar signal less directional click components convey information to conspecifics and give rise to echoes from the seafloor and the surface which may be useful for orientation during dives

subglacial carbonate deposition an isotopic study of a present day case abstract different types of calcite deposits may be formed in the subglacial environment patchy coatings on polished and striated bedrock pavements occur on outcrops recently exposed by retreating temperature glaciers coated pebbles and thin limestone crusts in fissures are present in recent basal till exposures freezing of meltwater is the main process susceptible to explain most of these carbonate deposits partial freezing is accompanied by a rejection of ions from the growing ice and a concentration increase in the residual water eventually until saturation is reached glacier sliding over a protuberance by pressure melting on the stoss side and refreezing on the lee side is likely to be responsible for subglacial carbonate deposition a fixed bedrock protuberance will give rise to fluted and furrowed coatings on its lee side a mobile protuberance like a pebble at the ice bedrock interface because it is susceptible to rotate while in traction will have a coating on most of its surface a present day case in the swiss alps is studied by a comparison of the isotopic composition of calcite deposits ice and meltwater from the glacier this study indicates that melting of the basal ice layer not of glacier ice is at the origin of the initial water giving rise to the precipitate since the basal ice layer is formed in the marginal zone of the glacier subglacial carbonate deposition is a marginal feature in this case

ionospheric electron number densities from cutlass dual frequency velocity measurements using artificial backscatter over eiscat using quasi simultaneous line of sight velocity measurements at multiple frequencies from the hankasalmi cooperative uk twin auroral sounding system cutlass on the super dual auroral radar network superdarn we calculate electron number densities using a derivation outlined in gillies et al 2010 2012 backscatter targets were generated using the european incoherent scatter eiscat ionospheric modification facility at tromso norway we use two methods on two case studies the first approach is to use the dual frequency capability on cutlass and compare line of sight velocities between frequencies with a mhz or greater difference the other method used the khz frequency shifts automatically made by the superdarn radar during routine operations using ray tracing to obtain the approximate altitude of the backscatter we demonstrate that for both methods superdarn significantly overestimates ne compared to those obtained from the eiscat incoherent scatter radar over the same time period the discrepancy between the ne measurements of both radars may be largely due to superdarn sensitivity to backscatter produced by localized density irregularities which obscure the background levels

delphinid echolocation click detection probability on near seafloor sensors the probability of detecting echolocating delphinids on a near seafloor sensor was estimated using two monte carlo simulation methods one method estimated the probability of detecting a single click cue counting the other estimated the probability of detecting a group of delphinids group counting echolocation click beam pattern and source level assumptions strongly influenced detectability predictions by the cue counting model group detectability was also influenced by assumptions about group behaviors model results were compared to in situ recordings of encounters with risso s dolphin grampus griseus and presumed pantropical spotted dolphin stenella attenuata from a near seafloor four channel tracking sensor deployed in the gulf of mexico 25 537 n 84 632 w depth 1220 m horizontal detection range received level and estimated source level distributions from localized encounters were compared with the model predictions agreement between in situ results and model predictions suggests that

thermospheric winds at high latitudes from chemical release observations wind measurements from 39 chemical release rockets launched from auroral belt and polar cap sites between 1967 and 1979 are summarized and interpreted multipoint measurements between 200 and 320 km altitude were obtained from all flights by tracking the neutral strontium clouds produced as by products of ba cuo releases these releases producing ba clouds also provided the simultaneous measurements of ion drift that are needed for wind analysis trail releases of trimethylaluminum and lithium provided measurements between 90 and 200 km from 19 rockets the wind measurements at different local times and latitudes are disorganized when presented in geographic and solar local time coordinates an organized wind system at altitudes above 160 km emerges when wind vectors are presented in magnetic local time and invariant latitude coordinates the dominant role of electric field ion drag as a driving force and the inertial characteristics of the wind system are clearly illustrated when the wind vectors are superposed on model patterns of the global high latitude ion convection at altitudes above the 110 km shear region and below a transitional zone in the 140 160 km range relationships between the observed winds and the causative mechanisms become less apparent as a consequence of the slower response to changing ion drag conditions a notable exception occurs in the polar cap where high velocity winds are observed at all altitudes under the influence of continuous antisolar ion flow a key factor affecting the wind pattern is the formation of a pressure ridge along the interface zone between the polar cap and the auroral belt in the evening hours back pressures from this ridge suppress the coriolis forces in the adjacent regions and contribute to the development of a dusk to dawn component in the antisolar polar cap flow the observations clearly indicate that the antisolar polar cap wind loses momentum and deposits energy in the early morning auroral belt at high altitudes i e 160 320 km there is directional continuity but a velocity loss as the polar cap wind inertially penetrates the morning auroral region at lower altitudes i e 140 km the observations are less definitive but indicate that the wind is discontinuous along the morning auroral belt interface in general the observations do not reveal wind characteristics that can be attributed to pressure gradients from joule heating or heating by precipitating particles a possible but speculative exception is that the perturbing effects of heating may explain why observed velocities tend to be lower than velocities calculated for model ion drag conditions other wind effects from high latitude heating apparently have less influence than the time space variability of the electric field and are thus obscured by these variations the existence of the classical day night flow from dayside euv heating is demonstrated by measurements from three rockets launched at subauroral latitudes on the dayside the influence of this flow at higher latitudes is similarly not identifiable in the presence of the ion drag winds a number of the gross characteristics of the observed high latitude wind pattern are simulated reasonably well by fuller rowell and rees recent model