analysis and modeling of atmospheric gravity waves observed in radarsat sar images four case studies of radarsat synthetic aperture radar sar observations of atmospheric gravity waves are presented to demonstrate sar s capability to measure associated near surface wind field variations a brief review of the main characteristics and scales of atmospheric gravity waves agws first establishes their importance in atmospheric dynamics the shape and scale of the wave patterns observed in successive sar images are compared with those calculated from agw models there is agreement between the small scale wind variations across wave patterns in sar images and the larger scale wind field that plays a role in the generation of the observed waves

space time description of nonstationary trapped lee waves using st radars aircraft and constant volume balloons during the pyrex experiment abstract the third intensive observation period iop3 of pyrex was a case of strong lee waves generated by a southerly wind crossing the pyrenees chain upstream radiosounds and measurements obtained by aircraft along the chain transect and by constant volume balloons launched near the crest provided spatial characteristics of the lee wave at different times and heights values ranging from 7 to 14 km for the horizontal wavelength and from 3 to 5 m s 1 for the maximum amplitude of the air vertical velocity were observed the lee wave horizontal extent measured from the crest line reached 30 to 55 km in addition two very high frequency stratosphere troposphere vhf st radars one on the mountain mean axis and another downstream in the lee wave field observed the temporal variations of the vertical profiles of the vertical velocity the analysis of those observed variations and their vertical distribution allowed the stationarity of the wave to be studied the lee wave was found to be far from stat

offshore breaking of impact tsunami the van dorn effect revisited 1 we report on calculations of the shoaling and off shore breaking of typical wavetrains from sub km impactors into the deep ocean we use the coulwave code to compute the propagation of waves through simple bathymetry profiles typical of the north american pacific coast and the gulf of mexico numerical results are consistent with those predicted by nonlinear shoaling theory our primary result is that large long period waves of the type considered should indeed break far offshore as suggested by w g van dorn for similar waves generated by underwater explosions typical breaking distances range from 3 17 km for the pacific coast and up to 200 km for the gulf coast the inclusion of bottom friction affects the results for very gentle slopes like the gulf coast a modest amount of bottom friction supplies enough dissipation to suppress wave breaking

tsunami in coastal zone due to meteorite impact the impact of a meteorite into the ocean surface is a rare phenomenon however it can be catastrophic especially for the coastal area the aim of the paper is to describe the evolution of the tsunami impulse due to meteorite impact in shallow water including energy dissipation due to bottom friction and wave breaking as the exact nonlinear solutions for tsunami transformation with energy loss due to wave breaking are not known the linearised equations of motion are used and energy loss is parameterised accordingly to describe the evolution of tsunami impulse in shallow water the hilbert transform technique was introduced it facilitates considerably the evaluation of the tsunami impulse transformation its run up and coast inundation range examples are included to illustrate the applicability of the theoretical derivations

a global morphology of gravity wave activity in the stratosphere revealed by the gps occultation data gps met using temperature profiles obtained by the gps met gps meteorology experiment from april 1995 to february 1997 we have extracted mesoscale temperature perturbations with vertical wavelengths ranging from 2 to 10 km and background brunt vaisala frequency squared n2 for each occultation event we can evaluate a potential energy ep which is assumed to be caused by atmospheric gravity waves the monthly mean values of ep at 15 20 km around japan showed an annual variation with an enhancement in winter which is consistent with the climatological behavior of the kinetic energy of gravity waves observed with the mu middle and upper atmosphere radar 34 9 n 136 0 e from 1985 to 1989 we have then derived the global distribution of ep at 20 30 km during northern hemisphere winter from november to february our analysis shows that the largest ep values are generally centered around the equator between 25 n and 25 s with considerable longitude variations longitudinal variations of ep at 20 30 km in a latitude range of 30 60 n are also analyzed resulting in larger ep values over the continents than over the pacific ocean using gps met data without antispoofing latitudinal variations of ep are determined in 15 45 km although large ep values are concentrated near the equator at 20 30 km ep tends to become larger at midlatitudes at 30 40 km and higher altitude regions at midlatitudes ep is found to be larger in winter months in both hemispheres height variations of ep indicate a decrease at 25 30 km and a monotonic increase above 30 km

the southern ocean s biological pump during the last glacial maximum ice core records from antarctica show large 80 ppm and regular climate related changes in atmospheric co2 with minimum values during glacial periods and maximum values during peak interglacials the suggested role of the southern ocean in driving these changes is based on either the potential for increased utilization of surface nutrients or the potential for decreased ventilation of deep waters during glacial times several recent studies have invoked increased stratification of the southern ocean to explain lower glacial atmospheric co2 levels in terms of reduced exchange of co2 between the deep sea and the atmosphere a northward displacement and or substantial weakening of the westerly winds during glacial periods are implicit in the scenarios that invoke enhanced stratification however both circulation models and proxy results argue against a weakening of the westerlies in fact the mean flow of the antarctic circumpolar current and wind driven upwelling during the last glacial maximum lgm are thought to be at least as vigorous as those which exist today given these boundary conditions we offer two competing scenarios for ecosystem structure and export production of the glacial southern ocean the first scenario satisfies all proxy records for nutrient utilization and phytoplankton growth rate and requires increased relative to today nitrate utilization south of the antarctic polar front apf by phytoplankton other than diatoms together with a shift in the zone of maximum diatom growth from south interglacials to north glacials of the apf the second scenario has reduced growth of all phytoplankton species south of the apf during glacials and a shift in the zone of maximum export production to the north of the polar front the principal weakness of the first scenario is that there is little sedimentary evidence to support the increased export of particulate organic carbon required by the inferred increase in nitrate utilization south of the apf the principal weakness of the second scenario is that it requires a change in the isotopic fractionation of nitrogen by phytoplankton growing south of the polar front for reasons presently unknown the southern ocean s biological pump at the lgm has yet to be characterized unequivocally

impact tsunami eltanin employing classical tsunami theory and elementary assumptions about the initial shape of impact cavities we compute tsunami from the eltanin asteroid collision at 2 15 ma an eltanin impactor 4 km in diameter would have blown an initial cavity as deep as the ocean and 60 km wide into the south pacific and delivered a 200 300 m high tsunami to the antarctic peninsula and the southern tip of south america 1200 1500 km away new zealand 6000 km distant would have met 60 m waves generalizing these results to other size impactors we fit simplified tsunami attenuation laws to maximum tsunami heights extracted from the full wave calculations if eltanin was 1 km in diameter instead of 4 km its waves would have been at least five times smaller an asteroid the size of chicxulub 10 km diameter had it fallen into water deeper than 1000 m would have sent a 100 m tsunami out to 4000 km distance even if shoaling amplifications are neglected r 2002 elsevier science ltd all rights reserved

run up from impact tsunami summary we report on calculations of the on shore run up of waves that might be generated by the impact of subkilometre asteroids into the deep ocean the calculations were done with the coulwave code which models the propagation and shore interaction of non linear moderate to long wavelength waves kh using the extended boussinesq approximation we carried out run up calculations for several different situations 1 laboratory scale monochromatic wave trains onto simple slopes 2 10 100 m monochromatic wave trains onto simple slopes 3 10 100 m monochromatic wave trains onto a compound slope representing a typical bathymetric profile of the pacific coast of north america 4 time variable scaled trains generated by the collapse of an impact cavity in deep water onto simple slopes and 5 full amplitude trains onto the pacific coast profile for the last case we also investigated the effects of bottom friction on the run up for all cases we compare our results with the so called irribaren scaling the relative run up r h0 s h0 l0 1 2 where the run up is r h0 is the deep water waveheight l0 is the deep water wavelength s is the slope and is a dimensionless quantity known as the irribaren number our results suggest that irribaren scaling breaks down for shallow slopes s 0 01 when 0 1 0 2 below which r h0 is approximately constant this regime corresponds to steep waves and very shallow slopes which are the most relevant for impact tsunami but also the most difficult to access experimentally

the earthquake and tsunami of 1865 november 17 evidence for far field tsunami hazard from tonga summary historical reports of an earthquake in tonga in 1865 november identify it as the only event from that subduction zone which generated a far field tsunami observable without instruments run up heights reached 2 m in rarotonga and 80 cm in the marquesas islands hydrodynamic simulations require a moment of 4 1028 dyn cm a value significantly larger than previous estimates of the maximum size of earthquake to be expected at the tonga subduction zone this warrants an upwards re evaluation of the tsunami risk from tonga to the cook islands and the various polynesian chains which had hitherto been regarded as minor

advances in the study of mega tsunamis in the geological record abstract extreme geophysical events such as asteroid impacts and giant landslides can generate mega tsunamis with wave heights considerably higher than those observed for other forms of tsunamis in this paper we review recent advances in the study of mega tsunamis in the geological record focusing on well documented examples that have captured particular attention over the past decade we provide up to date background on the source mechanisms of tsunami generation during asteroid impacts and ocean island landslides which are the largest landslides on earth we also discuss the main sources of uncertainty for modelling such mega tsunamis and for addressing associated hazards

vertical wind disturbances in the afternoon of mid summer revealed by the mu radar this paper reports a kind of vertical wind disturbances which appear daily in the afternoon of mid summer in the troposphere a detailed analysis was made of wind data monitored by the mu radar 35 n 136 e shigaraki shiga japan for about five days in july 1987 as a typical example the disturbances propagate upward up to sometimes over the tropopause level with a speed of 0 4 1 8 m s 1 as a packet the timing of generation and propagation suggests that they are convective motions of cumulus clouds generated by solar heating on the ground a map of cloud top height with high horizontal resolution of about 1 km provided by a satellite of noaa 9 supports this inference the structures near the tropopause and spectral characteristics are shown

gravity wave interactions around the jet stream 1 vhf radar measurements have been applied to study the interaction between a mountain wave and an inertia gravity wave above the jet stream in the tropopause region the mountain wave was observed to break and generate turbulence at a critical level that was induced by the inertia gravity wave this indicates that wave wave interactions can be an important source of turbulence and consequently mixing in the tropopause region

biogenic budgets of particle rain benthic remineralization and sediment accumulation in the equatorial pacific abstract budgets of organic c corg cac03 and opal have been constructed for the palisades ny pacific equatorial region at 140 w between 5 n and 5 s measurements of the rain and benthic remineralization rate of biogenic materials have been adjusted and normalized to account for sampling biases sea surface temperature serves as a master variable in normalizing sediment trap and benthic remineralization data to average conditions the rain and remineralization rates for corg are nearly equal 0 40 0 05 and 0 46 0 06 mmol m 2 d 1 respectively thus only a minor fraction of this constituent is buried rain and dissolution rates for biogenic opal are similarly balanced 0 3 0 06 and 0 36 0 01 mmol m 2 d 1 and consistent with the value for opal burial 0 0 0 004 the cac03 budget appears to have changed during the holocene the best estimates of modern cac03 dissolution 0 58 0 03 mmol m 2 d 1 and rain rate 0 61 0 06 are consistent with230th normalized carbonate accumulation rates for the late holocene 0 1 mmol m 2 d 1 however the balance between dissolution and rain is not consistent with early holocene carbonate accumulation 0 3 mmol m 2 d 1 and this imbalance suggests 1 a recent increase in the rate of cac03 dissolution on the sea floor or 2 a decrease in the rain rate of carbonate particles modeling230th profiles in sediments from this region define the last 3000 years as the duration of increased dissolution or decreased particle rain 231pa 230th ratios in sediments indicate that particle rain rates have remained constant or possibly increased slightly through the holocene two potential causes for increased dissolution were investigated a change in deep water carbonate saturation or a change in co g cac03 rain ratios a model describing carbonate dissolution as a function of the degree of undersaturation and the amount of organic carbon oxidation within sediments indicates that the recent increase in dissolution is more likely due to changes in bottom water chemical composition we propose that pacific ocean bottom water carbonate ion concentration has decreased by 10 15 m over the last 3000 years

gravity wave characteristics in the southern hemisphere revealed by a high resolution middle atmosphere general circulation model abstractgravity wave characteristics in the middle to high latitude southern hemisphere are analyzed using simulation data over 3 yr from a high resolution middle atmosphere general circulation model without using any gravity wave parameterizations gravity waves have large amplitudes in winter and are mainly distributed in the region surrounding the polar vortex in the middle and upper stratosphere while the gravity wave energy is generally weak in summer the wave energy distribution in winter is not zonally uniform but it is large leeward of the southern andes and antarctic peninsula linear theory in the three dimensional framework indicates that orographic gravity waves are advected leeward significantly by the mean wind component perpendicular to the wavenumber vector results of ray tracing and cross correlation analyses are consistent with this theoretical expectation the leeward energy propagation extends to several thousand kilometers which explains part of the gravity wave distribution aro

seasonal variation of gravity wave activity at 5 20 km observed with vhf radar at white sands missile range new mexico wind observations at altitudes from 5 to 20 km obtained from the vhf wind profiler radar at the white sands missile range ws new mexico are used to construct a climatology of gravity wave intensities over ws during the nearly 6 year period from january 1991 through september 1996 the kinetic energy densities for both high frequency gravity waves ground based period of 6 min to 2 hours and low frequency gravity waves period from 2 to 21 hours are considered these results are compared to earlier results from the middle and upper atmosphere mu radar in japan comparisons of gravity wave variability at high and low frequency reveal both similarities and differences between the two sites the primary differences occur at high frequency the seasonal cycle in the high frequency gravity waves is less pronounced and less regular at ws compared to mu the magnitude of the high frequency kinetic energy density is generally larger at ws compared to mu and the relationship between the upper tropospheric jet stream winds and the high frequency gravity wave activity is not nearly so strong at ws as at mu the primary high frequency gravity wave excitation mechanism at ws appears to change with season there is evidence of a connection in winter and spring between the wind speeds in the middle troposphere and the high frequency gravity wave activity suggesting a topographic source for these waves strong summertime high frequency variability at ws in the upper troposphere is most likely linked to waves launched by deep convection during the monsoon season in new mexico the results for low frequency gravity waves are more consistent between ws and mu similarities appear in the kinetic energy density the nature of the seasonal cycle and the correlation between the kinetic energy density and the mean winds

characteristics of oceanic impact induced large water waves re evaluation of the tsunami hazard the potential hazard of a meteorite impact in the ocean is controversial with respect to the destructive power of generated large ocean waves tsunamis we used numerical modeling of hypervelocity impact to investigate the generation mechanism and the characteristics of the resulting waves up to a distance of 100150 projectile radii the wave signal is primarily controlled by the ratio between projectile diameter and water depth and can be roughly classified into deep water and shallow water impacts in the latter the collapse of the crater rim results in a wave signal similar to solitary waves which propagate and decay in agreement with shallow water wave theory the much more likely scenario for an asteroid impact on earth is a relatively small body much smaller than the water depth striking the deep sea in this case the collapse of the transient crater results in a significantly different and much more complex wave signal that is characterized by strong nonlinear behavior we found that such waves decay much more rapidly than previously assumed and cannot be treated as long waves for this reason the shallow water theory is not applicable for the computation of wave propagation and more complex models full solution of the boussinesq equations are required

observations simulations and analysis of nonstationary trapped lee waves abstract although considerable understanding of mountain waves has been gained with the aid of the steady state assumption it is clear that mountain waves evolve over time group velocity arguments indicate that this evolution can occur in less than 1 h this study uses observations of trapped lee waves to measure the rate at which their horizontal wavelengths change including a detailed analysis of two events in which such changes are clearly documented in one case doppler lidar observations show a steady increase in horizontal wavelength of 6 h 1 over 4 h and clearly illustrates the relationship between the wave clouds and wave motions in a second case visible satellite imagery reveals an increase in wavelength of 14 h 1 which is related to temporal changes in vertical air motions measured by wind profilers within the wave field hourly vertical profiles of wind and virtual temperature measured by radio acoustic sounding systems rass and wind profilers reveal important changes in the wave env

impact of a cosmic body into earth s ocean and the generation of large tsunami waves insight from numerical modeling 1 the strike of a cosmic body into a marine environment differs in several respects from impact on land oceans cover approximately 70 of the earth s surface implying not only that oceanic impact is a very likely scenario for future impacts but also that most impacts in earth s history must have happened in marine environments therefore the study of oceanic impact is imperative in two respects 1 to quantify the hazard posed by future oceanic impacts including the potential threat of large impact generated tsunami like waves and 2 to reconstruct earth s impact record by accounting for the large number of potentially undiscovered crater structures in the ocean crust reconstruction of the impact record is of crucial importance both for assessing the frequency of collision events in the past and for better predicting the probability of future impact we summarize the advances in the study of oceanic impact over the last decades and focus in particular on how numerical models have improved our understanding of cratering in the oceanic environment and the generation of waves by impact we focus on insight gleaned from numerical modeling studies into the deceleration of the projectile by the water cratering of the ocean floor the late stage modification of the crater due to gravitational collapse and water resurge furthermore we discuss the generation and propagation of large tsunami like waves as a result of a strike of a cosmic body in marine environments

glacial holocene calcium carbonate dissolution at the central equatorial pacific seafloor holocene sediments in the central equatorial pacific have lower caco3 burial rates relative to sediments deposited during the last glacial period this change could be related to shifts in the deep sea carbonate system and ultimately to the glacial interglacial atmospheric co2 cycle in this study the glacial holocene sedimentation in the central equatorial pacific is investigated using a numerical model applied to caco3 carbonate 14c and excess 230th we also employ excess 231pa to 230th ratios as proxies of past particle fluxes although the caco3 burial rates decreased by 0 7 2 0 g cm 2 kyr 1 the 231pa to 230th ratios indicate that particle and caco3 fluxes have either remained nearly constant or increased since the last glacial this suggests that the reduction in caco3 burial rates resulted from an intensification of caco3 dissolution a small to moderate decrease in bottom water carbonate concentration rather than an increase in sedimentary respiratory co2 production is the most plausible mechanism for driving the sedimentation changes

the tsunami phenomenon abstract with human activity increasingly concentrating on coasts tsunamis from japanese tsu harbour nami wave are a major natural hazard to today s society stimulated by disastrous tsunami impacts in recent years for instance in south east asia 2004 or in japan 2011 tsunami science has significantly flourished which has brought great advances in hazard assessment and mitigation plans based on tsunami research of the last decades this paper provides a thorough treatise on the tsunami phenomenon from a geoscientific point of view starting with the wave features tsunamis are introduced as long shallow water waves or wave trains crossing entire oceans without major energy loss at the coast tsunamis typically show wave shoaling funnelling and resonance effects as well as a significant run up and backflow tsunami waves are caused by a sudden displacement of the water column due to a number of various trigger mechanisms such are earthquakes as the main trigger submarine and subaerial mass wastings volcanic activity atmospheric disturbances meteotsunamis and cosmic impacts as is demonstrated by giving corresponding examples from the past tsunamis are known to have a significant sedimentary and geomorphological off and onshore response so called tsunamites form allochthonous high energy deposits that are left at the coast during tsunami landfall tsunami deposits show typical sedimentary features as basal erosional unconformities fining upward and landward a high content of marine fossils rip up clasts from underlying units and mud caps all reflecting the hydrodynamic processes during inundation the on and offshore behaviour of tsunamis and related sedimentary processes can be simulated using hydro and morphodynamic numerical models the paper provides an overview of the basic tsunami modelling techniques including discretisation guidelines for appropriate temporal and spatial resolution as well as the nesting method furthermore the boussinesq approximation a simplification of the three dimensional navier stokes equations is presented as a basic theory behind numerical tsunami models which adequately reflects the non linear dispersive wave behaviour of tsunamis the fully non linear boussinesq equations allow the simulation of tsunamis e g in the form of n waves based on the various subtopics presented recommendations for future multidisciplinary tsunami research are made it is especially discussed how the combination of sedimentary and geomorphological tsunami field traces and numerical modelling techniques can contribute to derive locally relevant tsunami sources and to improve the assessment of tsunami hazards considering the individual pre history and physiogeographical setting of a specific region

ritter island volcano lateral collapse and the tsunami of 1888 summary in the early morning of 1888 march 13 roughly 5 km 3 of ritter island volcano fell violently into the sea northeast of new guinea this event the largest lateral collapse of an island volcano to be recorded in historical time flung devastating tsunami tens of metres high on to adjacent shores several hundred kilometres away observers on new guinea chronicled 3 min period waves up to 8 m high that lasted for as long as 3 h these accounts represent the best available first hand information on tsunami generated by a major volcano lateral collapse in this article we simulate the ritter island landslide as constrained by a 1985 sonar survey of its debris field and compare predicted tsunami with historical observations the best agreement occurs for landslides travelling at 40 m s 1 but velocities up to 80 m s 1 cannot be excluded the ritter island debris dropped little more than 800 m vertically and moved slowly compared with landslides that descend into deeper water basal friction block models predict that slides with shorter falls should attain lower peak velocities and that 40 ms 1 is perfectly compatible with the geometry and runout extent of the ritter island landslide the consensus between theory and observation for the ritter island waves increases our confidence in the existence of mega tsunami produced by oceanic volcano collapses two to three orders of magnitude larger in scale

a study of mountain lee waves using clear air radar the tropospheric and lower stratospheric response to flow over complex terrain is investigated using observations of vertical and horizontal motions made by a clear air doppler radar stationed at toulon in southern france analysis of the data has disclosed that episodic enhancements in the variability of vertical and horizontal velocities are due to lee waves excited by obstacles located within 5 km of the radar three separate cases of lee wave activity are studied two dimensional linear perturbation theory and existing three dimensional simulation results for appropriate parameter values are used as guides to check against the vertical structure observed by radar the magnitudes of vertical velocities observed during lee wave incidence are well within the range reported in previous observational and numerical simulation studies from a detailed examination of one of the cases of trapped waves the time variation observed by the radar of timescales of less than an hour has emerged as the likely result of small directional changes in the upstream winds causing a bodily rotation of the downstream three dimensional wave pattern centred on the wave generating obstacle the observed tendency of the vertical velocity perturbation to change sign with time above the radar location follows as a consequence of the presence of large horizontal gradients in the motion field which are inherent in the structure of three dimensional lee waves the temporal variability of the lee wave pattern has allowed the radar to sweep out a partial horizontal cross section revealing vertical circulation features that are broadly consistent with gravity wave behaviour however analysis of the effects of finite antenna beam spacing on the sampled data indicates that a spurious phase shift might have been introduced between the vertical and horizontal velocity perturbations observed in the cross section in contrast the measured vertical velocities are not seriously affected by finite beam width effects the lee waves examined in this study are quite moderate nevertheless this circumstance has provided a favourable opportunity to conduct a critical evaluation of the capabilities and limitations of this radar technique for observing lee wave phenomena in general we have been able to show clearly how the incidence and vertical structure of the waves respond to the synoptic scale situation in particular we have been able to distinguish between trapped and vertically propagating waves and to relate a transition between these wave types to synoptic scale changes in the static stability structure

do geochemical estimates of sediment focusing pass the sediment test in the equatorial pacific 1 the paleoceanographic recording fidelity of pelagic sediments is limited by chemical diagenesis and physical mixing bioturbation and horizontal sediment transport diagenesis and bioturbation are relatively well studied but the effects of physical sedimentation have been largely ignored modeling u series isotopes e g 230th can potentially quantify horizontal sediment movement but model horizontal sediment focusing often equals or exceeds the vertical particle rain we find no evidence of this level of sediment focusing in the equatorial pacific from geophysical data or sediment core comparisons the overestimate of sediment focusing by 230th is probably caused by poor model assumptions that sediment does not fractionate does not sort according to size during transport and that 230th cannot leak from slowly accumulating sediments both assumptions are weak u series methods do hold promise to quantify sediment focusing if properly calibrated with calibration the trade offs between seeking high sedimentation rates for better time resolution and the blurring by horizontal sediment focusing can be better assessed

layered structure associated with low potential vorticity near the tropopause seen in high resolution radiosondes over japan horizontal wind and temperature data obtained from operational radiosondes over japan have recently been available with high vertical resolution analyzing these data over 4 yr has indicated horizontal velocity layers with vertical scales of about 5 km lasting for a week or more the layers appear frequently in winter at several stations simultaneously and are dominant in the height range of 8 16 km an empirical orthogonal function eof analysis for the time series of layered disturbance amplitude in winter indicates that there are two dominant principal components the first component eof1 describes layered disturbances in the middle of japan 308 378n and the second one eof2 describes disturbances in the south of japan 238 308n using global analysis data the background field of the layered disturbances was examined an interesting result is that the background potential vorticity pv is approximately zero or negative for eof2 disturbances even though located in a relatively high latitude region this fact suggests that the eof2 disturbances are due to inertial instability it is also shown that negative pv occurs more than 30 of the time in winter in a zonally elongated region of 238 298n in the western pacific on an isentropic surface of 345 k 10 km altitude such a high frequency of negative pv is not observed at other longitudes in this latitude band to determine the origin of the anomalous pv backward trajectories were analyzed for eof2 disturbances air parcels having mostly negative pv are traced back to the equatorial region in the longitude band 208w 1408e within a few days this is due to a strong northward branch of the hadley circulation associated with deep convection over the maritime continent and a strong northeastward subtropical jet stream on the other hand the background pv is low but scarcely negative for eof1 disturbances air parcels at eof1 stations are traced back to the far west because they are advected mostly by a strong eastward jet stream thus it is inferred that the eof1 disturbances may be due to inertia gravity waves trapped in a duct of the westerly jet core

230th normalization an essential tool for interpreting sedimentary fluxes during the late quaternary there is increasing evidence indicating that syndepositional redistribution of sediment on the seafloor by bottom currents is common and can significantly affect sediment mass accumulation rates notwithstanding its common incidence this process generally referred to as sediment focusing is often difficult to recognize if redistribution is near synchronous to deposition the stratigraphy of the sediment is not disturbed and sediment focusing can easily be overlooked ignoring it however can lead to serious misinterpretations of sedimentary fluxes particularly when past changes in export flux from the overlying water are inferred in many instances this problem can be resolved at least for sediments deposited during the late quaternary by normalizing to the flux of 230th scavenged from seawater which is nearly constant and equivalent to the known rate of production of 230th from the decay of dissolved 234u we review the principle advantages and limitations of this method notwithstanding its limitations it is clear that 230th normalization does provide a means of achieving more accurate interpretations of sedimentary fluxes and eliminates the risk of serious misinterpretations of sediment mass accumulation rates

assessment of gravity wave momentum flux measurement capabilities by meteor radars having different transmitter power and antenna configurations 1 measurement capabilities of five meteor radars are assessed and compared to determine how well radars having different transmitted power and antenna configurations perform in defining mean winds tidal amplitudes and gravity wave gw momentum fluxes the five radars include two new generation meteor radars on tierra del fuego argentina 53 8 s and on king george island in the antarctic 62 1 s and conventional meteor radars at socorro new mexico 34 1 n 106 9 w bear lake observatory utah 41 9 n 111 4 w and yellowknife canada 62 5 n 114 3 w our assessment employs observed meteor distributions for june of 2009 2010 or 2011 for each radar and a set of seven test motion fields including various superpositions of mean winds constant diurnal tides constant and variable semidiurnal tides and superposed gws having various amplitudes scales periods directions of propagation momentum fluxes and intermittencies radars having higher power and or antenna patterns yielding higher meteor counts at small zenith angles perform well in defining monthly and daily mean winds tidal amplitudes and gw momentum fluxes though with expected larger uncertainties in the daily estimates conventional radars having lower power and a single transmitting antenna are able to describe monthly mean winds and tidal amplitudes reasonably well especially at altitudes having the highest meteor counts they also provide reasonable estimates of gw momentum fluxes at the altitudes having the highest meteor counts however these estimates are subject to uncertainties of 20 to 50 and uncertainties rapidly become excessive at higher and lower altitudes estimates of all quantities degrade somewhat for more complex motion fields

impact of the tropopause on upward propagation of mountain waves the vertical propagation of mountain waves into the stratosphere is investigated with reference to the scorer parameter profile in the troposphere and the change in brunt vaisala frequency at the tropopause vhf radar provides data on the vertical and horizontal wind velocities and echo power while radiosondes supply temperature profiles in studies of four large amplitude mountain wave events where the wave phase remains nearly constant throughout the troposphere partial reflection at a sharp tropopause offers a better explanation than wave trapping below a minimum in the scorer parameter

interface dissolution control of the 14c profile in marine sediment abstract the process of carbonate dissolution at the sediment water interface has two possible endmember boundary conditions either the carbonate particles dissolve mostly before they are incorporated into the sediment by bioturbation interface dissolution or the vertical mixing is rapid relative to their extermination rate homogeneous dissolution in this study a detailed radiocarbon profile was determined in deep equatorial pacific sediment that receives a high rate of carbonate supply in addition a box model of sediment mixing was used to simulate radiocarbon carbonate content and excess thorium profiles that result from either boundary process following a dissolution increase results from homogeneous dissolution imply a strong very recent erosional event while interface dissolution suggests that moderately increased dissolution began about 10 000 years ago in order to achieve the observed mixed layer radiocarbon age increased homogeneous dissolution would concentrate a greater amount of clay and 230th than is observed while for interface dissolution the predicted concentrations are too small these results together with small discontinuities beneath the mixed layer in 230th profiles suggest a two stage increase in interface dissolution in the deep pacific the first occurring near the beginning of the holocene and the second more recently roughly 5000 years ago

vertical wind disturbances in the troposphere and lower stratosphere observed by the mu radar abstract an analysis is made of vertical wind disturbances vwds observed by the mu radar shigaraki shiga japan in terms of the wave structures sources and vertical momentum flux first it is shown through spectral and lag correlation analyses that there are several common features in three observation periods when the vwds appeared large power in the vertical wind fluctuations exists below a height of 20 km and is distributed largely at lower frequencies the decrease in power near 20 km is sharp and the correlation between vertical winds above and below the level is very small suggesting that the height of 20 km is a special level for the vwds such as a critical level the disturbances below 20 km consist of several modes in a height frequency space some of which oscillate almost in phase in a wide height range spanning 8 km at the maximum second using eight sets of the mu radar data the relationship between vertical wind activity and horizontal wind near the surface is examined in order

global measurements of stratospheric mountain waves from space temperatures acquired by the cryogenic infrared spectrometers and telescopes for the atmosphere crista during shuttle mission sts 66 have provided measurements of stratospheric mountain waves from space large amplitude long wavelength mountain waves at heights of 15 to 30 kilometers above the southern andes mountains were observed and characterized with vigorous wave breaking inferred above 30 kilometers mountain waves also occurred throughout the stratosphere 15 to 45 kilometers over a broad mountainous region of central eurasia the global distribution of mountain wave activity accords well with predictions from a mountain wave model the findings demonstrate that satellites can provide the global data needed to improve mountain wave parameterizations and hence global climate and forecast models

scavenged excess aluminum and its relationship to bulk titanium in biogenic sediment from the central equatorial pacific ocean we present results from chemical analyses of al and ti in surface sediment sampled along two cross equator latitudinal transects at 135w and 140w in the central equatorial pacific ocean although traditionally both al and ti are considered to reside exclusively within terrigenous phases in marine sediment these sediments present extremely high al ti ratios that are several times that of average shale and other potential crustal sources a sharp maximum in al ti is observed slightly south of the equator where sedimentary bulk accumulation rate bar is also highest reflecting elevated productivity in the overlying water caused by surface water divergence bulk al ti decreases sharply away 2 latitude to near crustal values at 4 north and south the latitudinal profiles of al ti are entirely unrelated to the concentration of the biogenic components as well as to the absolute accumulation of al and ti these results indicate the presence of a significant scavenged component of al sourced directly from seawater during particle settling the data from the two transects analytically and oceanographically confirms our earlier work that was based on the single 135w transect calculations of alexcess indicate that the highest al ti ratios correspond to 50 of the total al being unsupported by the small amount of terrigenous phases present these results are consistent with previous and ongoing studies of biogenic sediment suspended particulate matter and sediment trap material quantitative use of al as an index of terrigenous material may therefore lead to an overestimation by a factor of two of the true terrigenous load in marine sediment sedimentary rock and settling particles because bulk al ti appears to respond to sedimentary bar which in biogenic regimes is linked to surface water productivity downcore records of al ti in biogenic sediment may track productivity changes through time such al ti proxy records may be applicable in sediment of all ages unlike radionuclide tracers which are limited by radioactive decay to use over the past hundreds of kyr

deep tropospheric gravity waves created by leeside cold fronts abstract the water vapor channel of the geostationary operational environmental satellite goes 8 reveals narrow 30 km wide elongated 500 1000 km bands that propagate southward on the eastern side of the rocky mountains from colorado to texas two events in which surface and wind profiler observations show that these bands are associated with leeside cold fronts are documented in detail and several other cases are summarized the wind profilers observe vertical motions exceeding 1 m s 1 in narrow plumes at the leading edge of the fronts in broader zones in the upper troposphere and in the lower stratosphere these cause vertical displacements of up to 1 km and are responsible for the signature in water vapor images the bands occur when the rocky mountains block either arctic leeside cold fronts coming from the north or northeast or pacific cold fronts coming from the northwest the blocking changes the frontal orientation and disrupts geostrophic thermal wind balance near the terrain modified fron

the meteorite impact induced tsunami hazard when a cosmic object strikes the earth it most probably falls into an ocean depending on the impact energy and the depth of the ocean a large amount of water is displaced forming a temporary crater in the water column large tsunami like waves originate from the collapse of the cavity in the water and the ejecta splash because of the far reaching destructive consequences of such waves an oceanic impact has been suggested to be more severe than a similar sized impact on land in other words oceanic impacts may punch over their weight this review paper summarizes the process of impact induced wave generation and subsequent propagation whether the wave characteristic differs from tsunamis generated by other classical mechanisms and what methods have been applied to quantify the consequences of an oceanic impact finally the impact induced tsunami hazard will be evaluated by means of the eltanin impact event

volcano collapse and tsunami generation in the bismarck volcanic arc papua new guinea during a cruise on the r v kilo moana in 2004 we mapped 12 debris avalanches from volcanoes in the bismarck volcanic arc estimated their sizes and computed the size of potential tsunami run up in major local population centers from these features we used the towed side scan instrument hawaii mr1 the hull mounted em120 system for swath bathymetry and backscatter intensity a shallow penetration chirp system several bottom camera tows and selected cores we calibrate our computations with the known tsunami run up of the ritter collapse even the small collapses may have had significant run up on near by coastlines had any of the collapses we have identified occurred in modern times each would affect a presently populated region of the coastline to a moderate or significant degree

a comparison between excess barium and barite as indicators of carbon export 1 since dymond et al 1992 proposed the paleoproductivity algorithm based on bio ba which relies on a strong correlation between ba and organic carbon fluxes in sediment traps this proxy has been applied in many paleoproductivity studies barite the main carrier of particulate barium in the water column and the phase associated with carbon export has also been suggested as a reliable paleoproductivity proxy in some locations we demonstrate that baexcess total barium minus the fraction associated with terrigenous material frequently overestimates babarite barium associated with the mineral barite most likely due to the inclusion of barium from phases other than barite and terrigenous silicates e g carbonate organic matter opal fe mn oxides and hydroxides a comparison between overlying oceanic carbon export and carbon export derived from baexcess shows that the dymond et al 1992 algorithm frequently underestimates carbon export but is still a useful carbon export indicator if all caveats are considered before the algorithm is applied babarite accumulation rates from a wide range of core top sediments from different oceanic settings are highly correlated to surface ocean 14 c and chlorophyll a measurements of primary production this relationship varies by ocean basin but with the application of the appropriate f ratio to 14 c and chlorophyll a primary production estimates the plot of babarite accumulation and carbon export for the equatorial pacific atlantic and southern ocean converges to a global relationship that can be used to reconstruct paleo carbon export index terms 3022 marine geology and geophysics marine sediments processes and transport 4267 oceanography general paleoceanography 4825 oceanography biological and chemical geochemistry keywords paleoproductivity barite export production excess barium marine sediments citation eagle m a paytan k r arrigo g van dijken and r w murray a comparison between excess barium and barite as indicators of carbon export paleoceanography 18 1 1021 doi 10 1029 2002pa000793 2003

terrigenous fe input and biogenic sedimentation in the glacial and interglacial equatorial pacific ocean many ocean regions important to the global carbon budget including the equatorial pacific ocean have low chlorophyll concentrations despite high levels of conventional nutrients iron may instead be the limiting nutrient and elevated input of terrigenous fe during windy glacial episodes has been hypothesized to stimulate oceanic productivity through time and thus regulate the oceanic and atmospheric co2 balance to test whether particulate fe input is related to the accumulation of biogenic matter in one important low chlorophyll high nutrient area that is the equatorial pacific ocean we present results from a suite of sediment cores that collectively record biogenic deposition through the last six glacial interglacial cycles 600 000 years our data set includes new chemical data on total fe terrigenous and biogenic components in three cores as well as previously published mineralogic records of coljan input to the region chemical spectral and stratigraphic analysis indicates that 1 terrigenous input to the region shows no consistent pattern of either glacial or interglacial maxima 2 the accumulation of particulate fe is closely related to the accumulation of terrigenous matter linear r 2 0 81 0 98 3 there are no coherent spectral relationships between fe input and glacial periodicity i e 5180 in any of the orbital frequency bands 4 the linear and cross spectral correlations between fe or coljan input and caco3 concentration are most commonly the strongest observed relationships between fe and any biogenic component yet indicate a largely inverse pattern with higher fe being associated with low caco3 5 there is no consistent linear r 2 correlation or spectral coherence between the accumulation of fe and that of caco3 corg or opal thus in total there is no relationship between terrigenous fe input and sedimentary sequestering of carbon additionally although we cannot specifically address the potential for changes in solubility of the terrigenous fraction that may be driven by a terrigenous compositional change the fe ti ratio which monitors first order mineralogic changes records only slight variations that also are linearly and spectrally unrelated to glacial periodicity the bulk fe flux and the accumulation of any biogenic component finally we find that the paleoceanographic flux of fe is several order of magnitudes larger than modem observations of coljan fe input suggesting that the long term importance of fe input by dust storms which deliver fe on the order of the sedimentary burial may be underestimated the removal of particulate terrigenous fe from the recently discovered source within the equatorial undercurrent however remains unquanfified and may also prove significant

dust sources and deposition during the last glacial maximum and current climate a comparison of model results with paleodata from ice cores and marine sediments mineral dust aerosols in the atmosphere have the potential to affect the global climate by influencing the radiative balance of the atmosphere and the supply of micronutrients to the ocean ice and marine sediment cores indicate that dust deposition from the atmosphere was at some locations 2 20 times greater during glacial periods raising the possibility that mineral aerosols might have contributed to climate change on glacial interglacial time scales to address this question we have used linked terrestrial biosphere dust source and atmospheric transport models to simulate the dust cycle in the atmosphere for current and last glacial maximum lgm climates we obtain a 2 5 fold higher dust loading in the entire atmosphere and a twenty fold higher loading in high latitudes in lgm relative to present comparisons to a compilation of atmospheric dust deposition flux estimates for lgm and present in marine sediment and ice cores show that the simulated flux ratios are broadly in agreement with observations differences suggest where further improvements in the simple dust model could be made the simulated increase in high latitude dustiness depends on the expansion of unvegetated areas especially in the high latitudes and in central asia caused by a combination of increased aridity and low atmospheric co2 the existence of these dust source areas at the lgm is supported by pollen data and loess distribution in the northern continents these results point to a role for vegetation feedbacks including climate effects and physiological effects of low co2 in modulating the atmospheric distribution of dust

does strong tropospheric forcing cause large amplitude mesospheric gravity waves a deepwave case study the deepwave deep propagating wave experiment campaign was designed for an airborne and ground based exploration of gravity waves from their tropospheric sources up to their dissipation at high altitudes it was performed in and around new zealand from 24 may till 27 july 2014 being the first comprehensive field campaign of this kind a variety of airborne instruments was deployed onboard the research aircraft nsf ncar gulfstream v gv and the dlr falcon additionally ground based measurements were conducted at different sites across the southern island of new zealand including the dlr rayleigh lidar located at lauder 45 04 s 169 68 e we focus on the intensive observing period iop 10 on the 4 july 2014 when strong wsw winds of about 40 m s at 700 hpa provided intense forcing conditions for mountain waves at tropopause level the horizontal wind exceeded 50 m s and favored the vertical propagation of gravity waves into the stratosphere the dlr rayleigh lidar measured temperature fluctuations with peak to peak amplitudes of about 20 k in the mesosphere 60 km to 80 km msl over a period of more than 10 hours two research flights were conducted by the dlr falcon falcon flight 04 and 05 during this period with straight transects mt aspiring 2a over new zealand s alps at three different flight levels around the tropopause approx 11 km msl these research flights were coordinated with the gv research flight 16 where the largest mountain wave amplitudes at flight level approx 13 km msl were measured during deepwave additionally a first analysis of falcon s in situ flight level data revealed amplitudes in the vertical wind larger than 4 m s at all altitudes in the vicinity of the highest peaks of the southern alps here we present a comprehensive picture of the gravity wave characteristics and propagation properties during this interesting gravity wave event we use the airborne observations combined with a comprehensive set of ground based measurements consisting of 13 radiosoundings 1 5 hourly interval together with the dlr rayleigh lidar to cover the altitude range from the troposphere to the mesosphere high resolution 1 hourly ecmwf analyses and forecasts are used to estimate the propagation conditions of the excited mountain waves the goal of our investigation is to find out whether the large amplitude mesospheric gravity waves are caused by the strong tropospheric forcing

southern argentina agile meteor radar initial assessment of gravity wave momentum fluxes 1 the southern argentina agile meteor radar saamer was installed on tierra del fuego 53 8 s in may 2008 and has been operational since that time this paper describes tests of the saamer ability to measure gravity wave momentum fluxes and applications of this capability during different seasons test results for specified mean tidal and gravity wavefields including tidal amplitudes and gravity wave momentum fluxes varying strongly with altitude and or time suggest that the distribution of meteors throughout the diurnal cycle and averaged over a month allows characterization of both monthly mean profiles and diurnal variations of the gravity wave momentum fluxes applications of the same methods for real data suggest confidence in the monthly mean profiles and the composite day diurnal variations of gravity wave momentum fluxes at altitudes where meteor counts are sufficient to yield good statistical fits to the data monthly mean zonal winds and gravity wave momentum fluxes exhibit anticorrelations consistent with those seen at other midlatitude and high latitude radars during austral spring and summer when no strong local gravity wave sources are apparent when stratospheric variances are significantly enhanced over the drake passage hot spot during austral winter however mlt winds and momentum fluxes over saamer exhibit very different correlations that suggest that mlt dynamics are strongly influenced by strong local gravity wave sources within this hot spot saamer measurements of mean zonal and meridional winds at these times and their differences from measurements at a conjugate site provide further support for the unusual momentum flux measurements

secondary generation of gravity waves associated with the breaking of mountain waves abstract the generation of small scale gravity waves associated with the breaking of mountain waves in the stratosphere has been simulated within a fully compressible nonhydrostatic two dimensional numerical model the model includes the mesosphere and offers sufficiently high spatial resolution to characterize the breaking and generation of gravity waves in the stratosphere the mean flow is initialized by cira86 at 40 n in february a bell shaped mountain with 30 km half width and 1 5 km height is located in the bottom of the modeled domain the primary wave forced by the mountain propagates into the stratosphere with amplitude increasing with height and subsequently breaks in the lower stratosphere after the primary wave breaking significant wave activity is simulated in the stratosphere these secondary waves are generated at both the upstream and the downstream edges of the breaking zone analysis is mostly focused on downstream small scale waves the horizontal and vertical wavelengths of the se

geological record and reconstruction of the late pliocene impact of the eltanin asteroid in the southern ocean in 1995 an expedition on board the research vessel fs polarstern explored the impact site of the eltanin asteroid in the southern ocean the only known asteroidimpact into a deep ocean basin analyses of the geological record of the impact region place the event in the late pliocene 2 15 myr and constrain thesize of the asteroid to be 1 km the explosive force inferred for this event places it at the threshold of impacts believed to have global consequences and its studyshould therefore provide a baseline for the reconstruction and modelling of similar events which are common on geological timescales

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

a 20 km diameter multi ringed impact structure in the north sea most craters found on earth are highly eroded poorly preserved and only exposed on land here we describe a multi ringed impact structure discovered in the north sea from the analysis of three dimensional seismic reflection data the structure is 20 km in diameter and has at least ten distinctive concentric rings located between 2 and 10 km from the crater centre the structure affects cretaceous chalk and jurassic shales and is well preserved below several hundred metres of post impact tertiary strata which constrains its age to be 60 65 myr old the formation of concentric ringed impact structures at this relatively small scale had not previously been thought possible especially on the terrestrial planets we have mapped the ring structures at a resolution of tens of metres both laterally and in depth and show that the rings are fault bounded graben structures similar to fault arrays formed in low strain rate detachment tectonic settings strata deeper than 500 m palaeodepth appear unfaulted and we infer that the concentric ring structures may have accommodated post impact extension towards the excavated crater through detachment on weak layers within the chalk

the runup of solitary waves this is a study of the runup of solitary waves on plane beaches an approximate theory is presented for non breaking waves and an asymptotic result is derived for the maximum runup of solitary waves a series of laboratory experiments is described to support the theory it is shown that the linear theory predicts the maximum runup satisfactorily and that the nonlinear theory describes the climb of solitary waves equally well different runup regimes are found to exist for the runup of breaking and non breaking waves a breaking criterion is derived for determining whether a solitary wave will break as it climbs up a sloping beach and a different criterion is shown to apply for determining whether a wave will break during rundown these results are used to explain some of the existing empirical runup relationships

dynamics and coastal effects of tsunamis generated by asteroids impacting the black sea two dimensional 2d and one dimensional 1d shallow water models are used to evaluate the seashore effects of the tsunami generated by an asteroid impacting the western regions of the black sea about 208 km from the coast the tsunami s speed and the effects on the coastal regions depend on many factors among which the most important is asteroid size the tsunami generated by a 250 m asteroid reaches the nearest land location in 24 min and needs about 2 h to arrive at all black sea coast the run up value is about 7 m high on the turkish and crimean coasts in the western black sea regions the wave height is two or three times smaller the run up values strongly depend on bathymetry and topography peculiarities the run in value in case of the tsunami generated by a 1 000 m asteroid is up to eight times larger than in case of a 250 m impactor depending on location the results reported herein are upper limit values in case of the 250 m asteroid the real wave amplitude may be up to two times smaller the uncertainty factor decreases in case of larger asteroids ways of diminishing the social consequences are briefly discussed

export production and carbonate dissolution in the central equatorial pacific ocean over the past 1 myr in order to quantify changes in export production and carbonate dissolution over the past 1 myr in the central equatorial pacific ocean we analyzed ba p a1 ti and ca in 1106 samples from five piston cores gathered from 5os to 4on at 140ow we focused on ba ti a1 ti and p ti ratios as export proxies and employed areally integrated time slice as well as time series strategies carbonate maxima from 0 560 kyr are characterized by 15 30 greater export than carbonate minima the increases in export fall on glacial 5180 transitions rather than glacial maxima from 560 800 kyr overlapping with the mid pleistocene transition there is a very large increase in total export yet no glacial interglacial variability the highest latitudes 5os and 4on record minimal absolute export change from glacials to interglacials and yet record the most extreme minima in percent caco3 indicating that carbonate records there are dominated by dissolution whereas near the equator they are more influenced by changes in export

new evidence on the size and possible effects of a late pliocene oceanic asteroid impact debris from a late pliocene asteroid impact is spread across at least 600 kilometers of the ocean floor in the southeast pacific on the basis of iridium concentrations in sediments from six deep sea cores the asteroid diameter was at least 0 5 kilometer the impacting projectile may have been one of the largest in the last few million years the stratigraphic age of this impact is the same as that inferred for the onset of northern hemisphere glaciation

numerical simulations of the mjolnir marine impact crater 1 the 40 km diameter mjolnir crater in the barents sea was created by a meteoroid impact into a 400 m shallow sea about 142 ma we have used a multimaterial hydrocode with depth depending target strength to model numerically the cratering and early modification stages of the mjolnir impact our models are constrained by the observed crater morphology and structure the best results were obtained for a composite target strength structure very low strength for the upper 3 km of sedimentary rocks and gradual increase from 3 to 6 5 km depth before using strength values typical for granitic rocks at greater depths the low strength of the target sediments at shallow depths led to exceptionally intensive slumping and gravitational collapse of the order of 2 0 2 5 considerably larger than the average expected values for typical terrestrial craters as a result we obtain a crater collapse in between simple and complex where slumping and gravitational collapse counteract the crater floor uplift and lead to suppression and burial of the central high the mjolnir impact in a shallow sea was responsible for a major disturbance of the water column following the impact induced outward water surge large amplitude tsunamis were formed and the rapid resurge of seawater into the excavated crater transported large amounts of ejecta and crater wall material back into the crater accounting for the redestribution of ejecta material and extensive infilling

radiosonde observations of equatorial atmosphere dynamics over indonesia 2 characteristics of gravity waves this paper discusses the characteristics of gravity waves in the equatorial region revealed by analyzing radiosonde measurements of wind velocity and temperature fluctuations at 0 35 km with a height resolution of 150 m made every 5 7 hours between february 27 and march 22 1990 in east java indonesia we conducted hodograph analysis to delineate vertical and horizontal propagation characteristics and found that most gravity waves were generated in the middle of the troposphere and that they propagated upward into the stratosphere the amplitudes of wind velocity and temperature fluctuations due to gravity waves were larger in the stratosphere than in the troposphere the direction of horizontal propagation of gravity waves was rather uniformly distributed in the troposphere but it became eastward in the lower stratosphere being opposite to that of the mean winds because of quasi biennial oscillation the vertical wavenumber spectra of wind velocity were described fairly well by a saturated model spectrum although their amplitudes were smaller in the stratosphere a typical vertical wavelength was 2 2 5 km while the horizontal phase velocities were 5 7 and 12 m s in the troposphere and stratosphere respectively the amplitudes of small scale gravity waves were significantly larger in the equatorial stratosphere than at middle latitudes time height variation of the wind velocity variance due to gravity waves showed a clear correlation with that for high relative humidity which implies that cloud convection is an important mechanism of gravity wave generation in the equatorial region

frequency spectra and vertical profiles of wind fluctuations in the summer antarctic mesosphere revealed by mst radar observations continuous observations of polar mesosphere summer echoes at heights from 81 93 km were performed using the first mesosphere stratosphere troposphere incoherent scatter radar in the antarctic over the three summer periods of 2013 2014 2014 2015 and 2015 2016 power spectra of horizontal and vertical wind fluctuations and momentum flux spectra in a wide frequency range from 8 min 1 to 20 days 1 were first estimated for the antarctic summer mesosphere the horizontal vertical wind power spectra obey a power law with an exponent of approximately 2 1 at frequencies higher than the inertial frequency of 13 h 1 and have isolated peaks at about 1 day and a half day in addition an isolated peak of a quasi 2 day period is observed in the horizontal wind spectra but is absent from the vertical wind spectra which is consistent with the characteristics of a normal mode rossby gravity wave zonal meridional momentum flux spectra are mainly positive negative and large fluxes are observed in a relatively low frequency range from 1 day 1 to 1 h 1 a case study was performed to investigate vertical profiles of momentum fluxes associated with gravity waves and time mean winds on and around 3 january 2015 when a minor stratospheric warming occurred in the northern hemisphere a significant momentum flux convergence corresponding to an eastward acceleration of 200 m s 1 d 1 was observed before the warming and became stronger after the warming when mean zonal wind weakened the strong wave forcing roughly accorded with the coriolis force of mean meridional winds

a comparison of gravity wave energy observed by vhf radar and gps met over central north america monthly mean values of the kinetic energy at frequencies associated with gravity waves based on wind observations made with the vhf radar at white sands missile range new mexico are compared with potential energies determined using gps met soundings the monthly mean curves of e k and e p are highly correlated and both show minimum values in the summer season with summer to winter increases of about a factor of 2 the observed ratio e k e p agrees very closely with the prediction of a linear gravity wave model these observations support previous comparisons of e k with e p made using the middle and upper atmosphere radar in japan

asteroid impact tsunami of 2880 march 16 summary nasa scientists have given a 1 1 km diameter asteroid 1950 da a 0 0 to 0 3 per cent probability of colliding with the earth in the year 2880 this article examines a scenario where 1950 da strikes the sea 600 km east of the united states coast travelling at 17 8 km s 1 the asteroid would blow a cavity 19 km in diameter and as deep as the ocean 5 km at the impact site tsunami waves hundreds of metres high would follow as the transient impact cavity collapses the tsunami disperses quickly but because the waves are so large initially destructive energy carries basin wide within two hours of the scenario impact 100 m waves make landfall from cape cod to cape hatteras within 12 hours 20 m waves arrive in europe and africa water velocity at the deep ocean floor exceeds 1 m s 1 to 800 km distance strong enough to leave a widespread tsunami signature in the sedimentary record

chemical transport to the seafloor of the equatorial pacific ocean across a latitudinal transect at 135 w tracking sedimentary major trace and rare earth element fluxes at the equator and the intertropical convergence zone we have analyzed the major trace and rare earth element composition of surface sediments collected from a transect across the equator at 135 w longitude in the pacific ocean comparing the behavior of this suite of elements to the caco3 opal and corg fluxes which record sharp maxima at the equator previously documented at the same sampling stations enables us to assess the relative significance of the various pathways by which trace elements are transported to the equatorial pacific seafloor the 1 1 high biogenic source at the equator associated with equatorial divergence of surface water and upwelling of nutrient rich water and 2 2 high aluminosilicate flux at 4 n associated with increased terrigenous input from elevated rainfall at the intertropical convergence zone itcz of the tradewinds are the two most important fluxes with which elemental transport is affiliated the biogenic flux at the equator transports ca and sr structurally bound to carbonate tests and mn primarily as an adsorbed component trace elements such as cr as pb and the rees are also influenced by the biogenic flux at the equator although this affiliation is not regionally dominant normative calculations suggest that extremely large fluxes of ba and p at the equator are carried by only small proportions of barite and apatite phases the high terrigenous flux at the itcz has a profound effect on chemical transport to the seafloor with elemental fluxes increasing tremendously and in parallel with ti normative calculations however indicate that these fluxes are far in excess of what can be supplied by lattice bound terrigenous phases the accumulation of ba is greater than is affiliated with biogenic transport at the equator while the p flux at the itcz is only 10 less than at the equator this challenges the common view that ba and p are essentially exclusively associated with biogenic fluxes many other elements including mn pb as and rees also record greater accumulation beneath the itcz than at the equator thus adsorptive scavenging by terrigenous paniculate matter or phases intimately associated with them appears to be an extremely important process regulating elemental transport to the equatorial pacific seafloor these findings emphasize the role of vertical transport to the sediment and provide additional constraints on the paleochemical use of trace elements to track biogenic and terrigenous fluxes

a comparison of multiple proxies for export production in the equatorial pacific 1 several commonly used paleoproductivity proxies were compared to evaluate the validity of assumptions and limitations associated with each proxy export production fluxes cexport over glacial interglacial timescales were calculated from previously developed proxy specific algorithms at ttn013 pc72 and ttn013 pc114 both located in the equatorial pacific comparison of data from the same core intervals yields conflicting results despite calibrations based on the same core top samples the periodicity of marine barite excess ba and excess al based cexport records is similar the relative magnitude of cexport when calculated using excess ba and algorithms based on sediment trap data is significantly different than records based on core top calibrations particularly during glacial intervals at both sites bulk sedimentary al ti and ba ti ratios covary however these ratios do not correspond with the downcore records of their respective excess concentrations and their accumulation rates or with contemporaneous records based on marine barite excess ba and excess al accumulation although downcore records based on sediment mass accumulation rates may be compromised by sediment focusing this process cannot explain all the differences observed among the various data sets presented here this implies that some or all of these proxies do not exclusively respond to changes in export production the contradictions among these data highlight the importance of addressing inconsistencies among paleoproxies and re examining assumptions imbedded in proxy fundamentals prior to applying paleoproductivity proxies and interpreting paleoceanographic records

constraints on interpretation of the eltanin impact from numerical simulations the results of numerical simulations of the eltanin impact are combined with the available geological data in order to reconstruct the impact dynamics and to get some constraints on the impact parameters numerical simulations show that the eltanin projectile size should be less than 2 km for a 45 oblique impact and less than 1 5 km for a vertical impact on the other hand we demonstrate that the projectile diameter cannot be considerably smaller than 1 km otherwise the impact induced water flow cannot transport eroded sediments across large distances the maximum displacement approximately equals the water crater radius and rapidly decreases with increasing distances numerical simulations also show that ejecta deposits strongly depend on impact angle and projectile size and therefore cannot be used for reliable estimates of the initial projectile mass the initial amplitudes of tsunami like waves are estimated the presence of clay rich sediments typical for the abyssal basins in cores ps2709 and ps2708 on the freeden seamounts bellingshausen sea southern ocean combined with numerical data allow us to suggest a probable point of impact to the east of the seamounts the results do not exclude the possibility that a crater in the ocean bottom may exist but such a structure has not been found yet