development and demise of a fringing coral reef during holocene environmental change eastern ningaloo reef western australia abstract reefs lining the western exmouth gulf located at the northern limit of the 300 km long ningaloo reef in western australia represent modern incipient coral reefs and veneers of non reef building coral algal communities on exposed pleistocene or give up holocene reef surfaces acquisition of sixteen cores alongside u series tims dates were used to confirm the nature of the pleistocene foundation and characterise holocene reef development three calcretised pleistocene units were identified as 1 the last interglacial mis 5e reef directly underlying holocene units 2 a mid pleistocene mis 7 bioclastic conglomerate unit and 3 a pleistocene alluvial fanglomerate eight holocene reef facies total thickness of 1 8 5 3 m included coral framework facies domal arborescent mixed tabulate and encrusting and detrital facies carbonate sand skeletal rubble and alluvial fan deposits holocene ages range from 7 93 to 5 8 ka bp with vertical accretion ranging from 1 46 to 9 88 mm year avg 4 11 mm year highest rates of accretion and thickest accumulation occurred in the most seaward and deepest cores composed of massive coral framestone and coralline algal crusts a six stage holocene chronology is proposed including 1 coastal inundation from 8 to 8 5 ka bp 2 initiation start up from 8 to 7 5 ka bp 3 rapid growth catch up and back step from 7 5 to 7 ka bp 4 rapid aggradational growth catch up from 7 to 6 5 ka bp 5 reef decline give up and detrital buildup from 6 5 to 5 8 ka bp and 6 detrital buildup and progradation from 5 8 ka bp to present changes in reef facies and the ultimate demise of the holocene reef probably involved a combination of increased sea level coastal flooding and erosion during the mid holocene highstand with associated increase in sedimentation turbidity and decline in water quality burial by sediment buildup during the mid holocene highstand and detrital progradation during the mid to late holocene regression and the introduction of alluvial sediment during cyclones and other severe storms to an already stressed community modern communities have thus shifted from coral dominated to bored macroalgal pavements this study shows that integration of reef development processes with response to environmental change can be used to assess future pressures on coral reef ecosystems globally

holocene reef growth dynamics on kodakara island 29 n 129 e in the northwest pacific abstract the spatial distribution of modern coral reefs in the northwest pacific nwp is restricted to approximately 30 n understanding the high latitude reef growth process and its correlation to climate change may provide important insights into future reef growth at even higher latitudes in response to global warming we conducted field surveys and obtained seven cores from the raised reefs of kodakara island 29 n 129 e in the nwp to determine the changes in and response of reef growth dynamics to millennial scale climate change through the holocene to reconstruct the timing of the reef growth 37 coral ages were determined using accelerator mass spectrometry ams radiocarbon dating the island is characterized by three holocene reef terraces terraces i to iii which were uplifted ca 2 4 ka 1 0 0 4 ka and in the modern era three growth hiatuses occurred circa 5 9 5 8 ka 4 4 4 0 ka and 3 3 3 2 ka which correlate with millennial scale climate changes hamanaka et al 2012 the reef growth began at least 8 ka relatively rapid vertical growth of 3 6 3 3 m kyr 1 occurred between 8 and 6 ka the reef started growing near land and then gradually extended seaward the reef growth around the reef slope decelerated after 6 ka and most likely coincided with the first and second hiatuses detected landward in contrast with the reef flat which resumed its growth after the third hiatus event the reef mound accretion on the slope ceased definitively terrace i was uplifted ca 2 4 ka the reef growth reactivated ca 1 3 ka and the reef grew at a rate of 9 1 m kyr 1 between 1 3 and 1 0 ka this rate is the fastest growth recorded in this study this time interval corresponds to the medieval climatic anomaly mca the cause of the delayed reef growth between 2 4 and 1 4 ka remains unclear but it may imply the existence of a late holocene hiatus due to a weaker kuroshio current kc ca 1 7 ka and to strong el nino southern oscillation enso activity between 2 and 1 5 ka in the east pacific the timing of the hiatuses agrees with the weakening of the kc and the more frequent el nino events during the positive phase of the pacific decadal oscillation pdo whereas the rapid growth coincides with la nina conditions such as the mca during the negative phase of the pdo our results indicate that the climate event at approximately 4 ka caused the largest change in the reef growth and it may have affected reefs throughout the pacific region specifically the enso and pdo phases may have impacted the reef growth and kc behavior

textured dust storm activity in northeast amazonis southwest arcadia mars phenomenology and dynamical interpretation abstractdust storms are mars s most notable meteorological phenomenon but many aspects of their structure and dynamics remain mysterious the cloud top appearance of dust storms in visible imagery varies on a continuum between diffuse hazy and textured textured storms contain cellular structure and or banding which is thought to indicate active lifting within the storm some textured dust storms may contain the deep convection that generates the detached dust layers observed high in mars s atmosphere this study focuses on textured local dust storms in a limited area within northeast ne amazonis and southwest sw arcadia planitiae 25 40 n 155 165 w using collocated observations by instruments on board the mars global surveyor mgs and mars reconnaissance orbiter mro satellites in northern fall and winter this area frequently experiences dust storms with a previously unreported ruffled texture that resembles wide mixed layer rolls in earth s atmosphere a resemblance that is supported by h

holocene turn on and evolution of the southern great barrier reef revisiting reef cores from the capricorn bunker group abstract extensive drilling of the great barrier reef gbr in the 70s and 80s illuminated the main factors controlling reef growth during the holocene however questions remain about 1 the precise nature and timing of reef turn on or initiation 2 whether consistent spatio temporal patterns occur in the bio sedimentologic response of the reef to holocene sea level rise then stability and 3 how these factors are expressed in the context of the different evolutionary states juvenile mature senile reefs combining 21 new c 14 ams and 146 existing re calibrated radiocarbon and u th ages we investigated the detailed spatial and temporal variations in sedimentary facies and coralgal assemblages in fifteen cores across four reefs wreck fairfax one tree and fitzroy from the southern gbr our newly defined facies and assemblages record distinct chronostratigraphic patterns in the cores displaying both lateral zonation across the different reefs and shallowing upwards sequences characterised by a transition from deep porites faviids to shallow acropora isopora coral types the revised reef accretion curves show a significant lag period ranging from 0 7 2 ka between flooding of the antecedent pleistocene substrate and holocene reef turn on this lag period and dominance of more environmentally tolerant early colonizers e g domal porites and faviids suggests initial conditions that were unfavourable for coral growth we contend that higher input of fine siliciclastic material from regional terrigenous sources exposure to hydrodynamic forces and colonisation in deeper waters are the main factors influencing initially reduced growth and development all four reefs record a time lag and we argue that the size and shape of the antecedent platform is most important in determining the duration between flooding and recolonisation of the holocene reef finally our study of capricorn bunker group holocene reefs suggests that the size and shape of the antecedent substrate has a greater impact on reef evolution and final evolutionary state mature vs senile than substrate depth alone

observational analysis of a gust front to bore to solitary wave transition within an evolving nocturnal boundary layer abstract the evolution of a gust front to bore to solitary wave transition and comprehensive information on the evolving nocturnal boundary layer nbl associated with this change are described with analysis of radar and profiler measurements the observations were obtained on 21 june 2002 in the oklahoma panhandle during the international h2o project the evolution of this system from a strong bore initiated by a vigorous gust front to a solitary wave was observed over a 4 h period with doppler radar and surface measurements detailed information on the mature bore structure was obtained by a cluster of profiling instruments including two boundary layer wind profilers a lidar ceilometer and a microwave profiling radiometer a strong bore was initiated by an extensive gust front that perturbed an incipient nbl whose development prior to sunset was enhanced by shading from the parent mesoscale convective system at the time of bore formation the nbl was about 300 m deep and exhibited a surface t

martian north polar cap summer water cycle abstract a key outstanding question in martian science is are the polar caps gaining or losing mass and what are the implications for past current and future climate to address this question we use observations from the compact reconnaissance imaging spectrometer for mars crism of the north polar cap during late summer for multiple martian years to monitor the summertime water cycle in order to place quantitative limits on the amount of water ice deposited and sublimed in late summer we establish here for the first time the summer cycle of water ice absorption band signatures on the north polar cap we show that in a key region in the interior of the north polar cap the absorption band depths grow until l s 120 when they begin to shrink until they are obscured at the end of summer by the north polar hood this behavior is transferable over the entire north polar cap where in late summer regions flip from being net sublimating into net condensation mode this transition or mode flip happens earlier for regions closer to the pole and later for regions close to the periphery of the cap the observations and calculations presented herein estimate that on average a water ice layer 70 microns thick is deposited during the l s 135 164 period this is far larger than the results of deposition on the south pole during summer where an average layer 0 6 6 microns deep has been estimated by brown et al 2014 earth planet sci lett 406 102 109

late quaternary reef growth and sea level in the maldives indian ocean abstract based on rotary drilling and radiometric and u series dating we present the first comprehensive data on holocene reef anatomy and sea level rise as well as nature and age of underlying pleistocene limestone in the maldives holocene reefs in rasdhoo atoll central maldives are composed of four facies including 1 robust branching coral facies 2 coralline algal facies 3 domal coral facies and 4 detrital sand and rubble facies branching coral and coralline algal facies predominate the marginal reefs and domal corals and detrital facies preferentially occur in a lagoon reef in addition microbialite crusts are found in lower core sections of marginal reefs microbialites formed during the early holocene in reef cavities holocene reef thickness ranges from 14 5 m to 22 m reef growth started as early as 8 5 kyr bp marginal reefs accreted in the keep up mode with rates of 15 m kyr rate of sea level rise significantly slowed down from 7 6 kyr bp and subsequently gradually rose with rates

hubble space telescope observations of the martian aphelion cloud belt prior to the pathfinder mission seasonal and interannual variations the presence of a globally extant equatorial belt of water ice clouds on mars is quantitatively investigated using data from three seasons of our hubble space telescope synoptic monitoring program 1993 1997 a subset of the 1996 1997 images covers the landing site of the mars pathfinder including a set of images taken after touchdown using multicolor imaging from the wide field planetary camera and the wide field planetary camera 2 we characterize both water ice cloud and dust optical depths as a function of latitude at several local times for each observing epoch the analysis technique models calibrated data using a multiple scattering radiative transfer code our results support the initial results of clancy et al 1996a regarding changes between the aphelion and perihelion climate of mars and provide a more detailed look at the development and decay of the cloud belt comparing our dust optical depths to those of the viking landers for the same seasons we note a trend toward lower dust loading in late northern winter and in spring our observations of the pathfinder site in july 1997 reveal a dust opacity in good agreement with that reported by pathfinder smith et al 1997b in addition the serendipitous occurrence of a dust storm in valles marineris in late june 1997 allows us to derive a set of dust single scattering albedos for use in more accurately modeling the dust s radiative properties and effects

discovery of lower cretaceous synmetamorphic thrust tectonics in french lesser antilles la desirade island guadeloupe implications for caribbean geodynamics located east of guadeloupe the island of la desirade exhibits the oldest rocks of the lesser antilles arc and the eastern caribbean plate an old magmatic basement is composed of 1 late jurassic ophiolitic complex with meta basaltic pillow lavas and interbedded radiolarites 2 acid igneous complex comprising meta quartz diorite and meta rhyolitic lavas flows and 3 meta diabasic microdioritic dyke swarm complex we present and discuss the discovery of synmetamorphic thrust tectonics in this island based on detailed structural analysis we evidenced two main compressive events the first event d1 is characterized by pervasive folding associated with thrust development in the northeastern part of the island a major thrust fault the grand abaque thrust has been discovered which displaces for several kilometers the acid igneous complex onto the ophiolitic unit the second deformation event d2 is featured by a main pervasive cleavage s2 observed at the regional scale associated with upright folding f2 and by the development of two sets of conjugated steeply dipping strike slip shear zones dextral 130 n and sinistral 20 n striking respectively microstructural observations indicate that greenschist facies metamorphism is clearly contemporaneous with the development of d1 and d2 superimposed tectonic structures ar ar geochronology was performed on two bulk of adularia minerals sampled in the northeast volcanic complex within a deformed zone related to a d2 event these analyses yield well defined and concordant plateau ages at 106 2 1 7 ma and 107 2 1 8 ma thus shortening and thickening tectonics occurred during lower cretaceous albian in the available framework of caribbean geodynamics the synmetamorphic thrust tectonics we discovered in the french lesser antilles is related to the collision between an aptian albian oceanic plateau and the andean cordilleran east dipping subduction zone our results support subduction polarity reversal during lower cretaceous

an observational overview of dusty deep convection in martian dust storms abstractdeep convection as used in meteorology refers to the rapid ascent of air parcels in earth s troposphere driven by the buoyancy generated by phase change in water deep convection undergir

spatial variations in wave transformation and sediment entrainment on a coral reef sand apron abstract waves are the main hydrodynamic force acting on coral reefs and are crucial in driving the evolution of reef systems previous research has mainly focused on wave breaking and transformation on the reef flat but often neglected the spatial variation of reformed wave characteristics once they have propagated into the back reef environment this study examines wave conditions on a reef flat and the adjacent back reef sand apron specifically focusing on the transformation of wave height period and spectra including changes to long period and incident wave height the ability of reformed waves in the back reef environment to entrain sediment is also investigated wave conditions were found to be distinctly different on the sand apron compared to the reef flat with the majority of wave energy dissipated during initial breaking and transformation almost all incident waves are dissipated on the reef flat under a depth threshold of 0 5 m before reaching the back reef with long period motions dominating in the back reef during these tidal stages at higher tidal stages incident waves are capable of propagating into the back reef but they are very low energy with under 1 of all waves capable of entraining sediment this suggests that higher energy events such as high frequency storms are required to significantly transport sediment and change reef geomorphology smaller scale spatial changes in wave height were observed on the sand apron that shows the influence of both cross and along reef attenuation processes a distance parameter x pd is introduced that combines the cross reef distance from the reef crest x d and the temporally specific along reef distance from the first point of wave breaking on the reef rim x p where x pd x d x p x pd is shown to accurately describe the changes in wave height and sediment entrainment if deep water significant wave height wave direction and depth over the reef flat are known the results in this study shows that wave conditions sediment entrainment and longer term trends in sediment characteristics can be predicted in back reef environments from a few simple geomorphic inputs

spectral imaging of martian water ice clouds and their diurnal behavior during the 1999 aphelion season ls 130 abstract we report high spectral resolution 800 2300 near infrared mapping observations of mars at ls 130 april 1999 which were obtained by drift scanning the cryogenic long slit spectrometer at the kpno 2 2 m telescope across the disk data were reformatted into calibrated spectral image cubes x y spanning 2 19 to 4 12 m which distinguish atmospheric co2 features solar lines and surface and aerosol features maps of relative band depth between 3 0 and 3 5 m trace water ice clouds and show the diurnal evolution of features in the persistent northern summer aphelion cloud belt which was mapped contemporaneously but at fixed local time by the mars global surveyor thermal emission spectrometer mgs tes cloud optical depth particle sizes and ice aerosol content were estimated using a two stream single layer scattering model with mie coefficients derived from recently published ice optical constants followed by a linear spectral deconvolution process a comparison of data and model spectra shows evaporating nighttime clouds in the morning followed by afternoon growth of a prominent orographic cloud feature on the west flank of elysium mons cloud optical depth at 3 2 m evolved to 0 28 0 13 and ice aerosol column abundance to 0 9 0 3 pr m in the afternoon column abundances as large as 0 17 pr m were retrieved in nonorographic clouds within the aphelion cloud band around midday these clouds exhibit a modest decline in optical depth during the afternoon results show that ice particle radii from 4 m exist in both cloud types however large particles dominate the spectra consistent with recent mgs tes emission phase function measurements of aphelion cloud aerosol properties

sublimation and transport of water from the north residual polar cap on mars several features of the viking mars atmospheric water detection observations have suggested that the residual north polar cap on mars is a major source of atmospheric water during northern summer and that the water it supplies to the atmosphere is transported equatorward to low northern latitudes by summer s end we have explored the role of the north residual cap in the current martian water cycle by constructing models to assess the ability of the cap to supply water to the atmosphere and the ability of the atmosphere to transport it out of the polar regions from our sublimation model we conclude that the residual cap can sublime the 7 1014 g of water that appears in the atmosphere after ls 80 provided surface winds are high 10 m s the cap emissivity is low 0 9 or the exposed soil in polar regions contains ice that is accessible to the atmosphere in our view these requirements seem unlikely and we are drawn to the conclusion that other sources of water exist this conclusion is further supported by the results of two dimensional transport simulations which show that most of the water sublimed from the cap remains at high latitudes the polar circulation simply lacks the intensity and scale to move water very far from the cap a weak circulation places additional constraints on cap sublimation rates since abundant clouds and significant ice deposits would form just equatorward of the cap edge according to the model if the cap is allowed to sublime 7 1014 g of water such predictions are inconsistent with available data we suggest that the nature of the additional source is water desorbing from the nonpolar regolith

mesoscale spectra of mars s atmosphere derived from mgs tes infrared radiances wavenumber spectra of the atmospheric potential energy of mars at mesoscales wavelengths of 64 957 km were obtained as a function of latitude season and martian year using infrared radiance data obtained by the thermal emission spectrometer tes onboard the mars global surveyor mgs spacecraft spectral slopes tend to be flatter at smaller scales and the slopes are usually flatter than 1 near small scale ends near large scale ends the spectra sometimes show prominent steepening with slopes from 2t o3 the power peaks in the high latitudes in winter and equinoxes suggesting that eddies are generated preferentially in baroclinic zones the seasonal variation at each latitude band on the other hand tends to be obscured by large interannual variability an enhancement in the power was observed around the storm tracks in the southern hemisphere spectra of the terrestrial stratosphere were also obtained with a similar method from data taken by the aura satellite and compared to the results for mars

multi stage reef development on barbados during the last interglaciation by mapping the vertical and lateral distribution of reefal facies on the west and south coast of barbados we have produced a revised model of reef development for the last interglaciation we find that reef architecture around barbados has significant complexity including evidence for wave exposure related variations in reef geometry and at least 3 stages of reef development that were controlled by variations in sea level during the main stage of development an acropora palmata dominated reef crest aggraded 22 m in response to a minimum sea level rise of 20 m during stage 2 a sea cave was cut 3 4 m above the fossil reef crest possibly indicating that reef growth was terminated before sea level reached the highstand similar sequences elsewhere in the caribbean indicate that this early reef demise may not be a local phenomenon several reefs apparently stopped growing between 2 and 4 m and only in sheltered areas did they reach the highstand at 6 m as recorded by intertidal notches this pattern of reef demise has previously been related to rapid sea level rise at the end of the interglacial but stratigraphic data are equivocal the final stage of reef development on barbados occurred when sea level began to fall this fall was rapid leaving a thin but widespread veneer of reef crest deposits over the proximal reef front and discontinuous intertidal and shallow subtidal deposits capping the distal reef front although further dating is required to differentiate these three stages our only reliable u th tims date indicates that almost 50 of the exposed reef had accreted by 129 ka giving an estimate of 15 ka for the main aggradational stage furthermore reports of relict reef crests buried beneath these exposed deposits indicate that our revised model is incomplete and that earlier stages of reef growth occurred during the last interglaciation these earlier stages imply that sea level was at an interglacial level for as long as 20 ka supporting the devils hole record of interglacial duration unfortunately these estimates could not be verified directly because most of our u th data show major stratigraphic age reversals attributed to diagenesis this pattern is also evident in all other well dated reefal units in the caribbean and leads us to conclude that only diagenetically screened precise stratigraphically consistent coral dates can be used to directly estimate the duration of the last interglaciation

the martian surface the past four years have been particularly fruitful for martian research as the enormous volumes of data collected during the viking mission became readily available to the general science community and as reformatting of the remote sensing data into cartographic products made the data more useable the 1 5 000 000 scale map series is complete and 1 2 000 000 scale controlled mosaics of the entire planet are nearing completion in addition 1 500 000 scale mosaics have been prepared of about thirty local areas a uniform scale digital imaging data base is in preparation batson 1986 and the infrared data have been reformatted to make it more accessible to the general user martin and kieffer 1985

mars aerosol studies with the mgs tes emission phase function observations optical depths particle sizes and ice cloud types versus latitude and solar longitude 1 emission phase function epf observations taken in 1999 2001 by mars global surveyor thermal emission spectrometer mgs tes support the broadest study of martian aerosol properties to date tes solar band and infrared ir spectral epf sequences are analyzed to obtain first time seasonal latitudinal distributions of visible optical depths particle sizes and single scattering phase functions this combined angular and wavelength coverage enables identification of two distinct ice cloud types over 45 s 45 n type 1 ice clouds exhibit small particle sizes reff 1 2 m and a distinctive backscattering increase they are most prevalent in the southern hemisphere during aphelion but also appear more widely distributed in season and latitude as topographic and high altitude 20 km ice hazes type 2 ice clouds exhibit larger particle sizes reff 3 4 m a distinct side scattering minimum at 90 100 phase angles characteristic of a change in particle shape relative to the type 1 and appear most prominently in the northern subtropical aphelion cloud belt the majority of retrieved dust visible to ir optical depth ratios are indicative of reff 1 5 0 1 m consistent with pathfinder and viking mariner 9 reanalyses however increased ratios 2 7 versus 1 7 appear frequently in the northern hemisphere over ls 50 200 indicating substantially smaller dust particles sizes reff 1 0 0 2 m at this time in addition larger reff 1 8 2 5 m dust particles were observed locally in the southern hemisphere during the peak of the 2001 global dust storm detailed spectral modeling of the tes visible band pass indicates agreement of epf derived dust single scattering albedos 0 92 0 94 with the spectrally resolved results from pathfinder observations

the morning glory an extraordinary atmospheric undular bore summary observations made during an expedition in october 1980 to study morning glory wind squalfs in the gulf of carpentaria region of northern australia are described during a ten day period in burketown north queensland six squalls were documented on consecutive mornings 8 1 3 october including two moving from the south an apparently unusual direction the unique data gathered from the latter confirm that these have the same character as their north easterly counterparts that is they are undular bores the origin of southerly glories remains uncertain but at least in some cases appears to be linked with the northeast advance of a frontal trough across central australia while the data are equivocal it seems possible that the motion of the front into the developing nqcturnal inversion could generate waves or hydraulic type disturbances which run along the inversion layer ahead of the front as proposed by tepper 1950 the efficacy of such a mechanism is demonstrated by a simple laboratory experiment evidence is presented which suggests that morning glory type events occur elsewhere in the world sometimes as precursors to cold fronts observations in the gulf of carpentaria region show that they are effective triggers of deep convection when they advance into air with a sufficient degree of conditional instability

relationship between frontal dust storms and transient eddy activity in the northern hemisphere of mars as observed by mars global surveyor we have compiled a catalog of frontal dust storms in the northern hemisphere using mars orbiter camera daily global maps spanning 2 3 martian years of mars global surveyor mgs observations from 1999 to 2003 the most vigorous frontal storms that flush dust to the low latitudes occur in early mid fall and mid late winter away from the northern winter solstice while many streaks are observed in the polar hood during the winter solstice period no frontal dust storms are observed in the vicinity of the north polar region we have also analyzed simultaneous mgs thermal emission spectrometer tes temperature data and found statistically significant negative temperature anomalies associated with frontal storms in the lowest scale height of the atmosphere the geographical and seasonal distributions of temperature standard deviations associated with transient variations agree well with the distributions of frontal storms the correlation deteriorates with increasing altitude suggesting that lower level temperature waves are associated with the frontal dust storms specifically eastward traveling m 3 waves with periods of 2 3 sols appear to be closely related to the development of flushing frontal storms

measuring coral reef terrain roughness using structure from motion close range photogrammetry our understanding of earth surface processes is rapidly advancing as new remote sensing technologies such as lidar and close range digital photogrammetry become more accessible and affordable a very high spatial resolution digital terrain model dtm and orthophoto mosaic mm scale were produced using close range digital photogrammetry based on structure from motion sfm algorithms for a 250 m transect along a shallow coral reef flat on heron reef great barrier reef the precise terrain data were used to characterise surface roughness a critical factor affecting ecological and physical processes on the reef three roughness parameters namely the root mean square height tortuosity or rugosity and fractal dimension were derived and compared in order to asses which one better characterises reef flat roughness the typical relief across the shallow reef flat was 0 1 m with a maximum value of 0 42 m coral reef terrain roughness as characterised by the three chosen parameters generally increased towards the middle of the transect where live coral covers most of the reef flat and decreases towards the edges of the transect the fractal dimension values ranging from 2 2 to 2 59 best characterised reef roughness as evidenced by a closer agreement with the distribution of known coral benthic substrates this is the first study quantifying scale independent roughness of a coral reef at benthic and biotope patch levels cm m the readily available and cost effective methods presented are highly appropriate for data collection processing and analysis to generate very high spatial resolution dtms and orthophoto mosaics of shallow and energetic coral reefs

some observational constraints on the global scale wind systems of mars wind direction measurements from a variety of indicators taken over several mars years and covering the entire planet have been collected these include observations of lee wave clouds not previously studied the data exhibit a high degree of consistency and seasonal reproducibility making it possible to interpret most of the observations in terms of the zonally symmetric circulation of mars we examine these data in the context of the constraints the observed wind directions place upon the thermal and polar cap mass flux fields which force the flows within the limitations of the data set mid and high latitude winds appear to be controlled by the thermal field during mid and late summer and winter and in the northern hemisphere during early spring and early summer at other times the cap flows dominate at high latitudes the strongest yearly winds are probably generated by cap formation in the north and cap recession in the south the hemispheric asymmetry seems to result primarily from the effects of global dust storms on the north polar cap turning of the prograde wind from poleward to equatorward in midautumn is observed consistent with reduced poleward mass flux and increased meridional temperature gradient at that time the latitudinal extent of the equatorial hadley cell when observed is probably larger than that predicted by nearly inviscid models of low latitude circulation the cross equational hadley cell and high latitude poleward flows which occur in both hemispheres during the summer seasons may set additional constraints on the thermal forcing mechanisms at these times

the spatial and seasonal distribution of martian clouds and some meteorological implications the spatial and seasonal distributions of martian atmospheric clouds organized according to simple morphologic criteria exhibit distinct patterns when interpreted self consistently using analogies to terrestrial cloud forms and martian temperature wind direction and water vapor measurements patterns of cloud occurrence provide some loose constraints on global scale near surface wind speed static stability and humidity we have examined all mariner 9 and viking orbiter images for this study we concentrate primarily on the larger viking data set whenever observations are possible relatively high near surface winds appear to follow the seasonal cap edges during early fall late winter and spring moderate to high winds are also inferred in mid latitudes for mid southern winter and in low latitudes mainly in the steeply sloping areas of tharsis near the solstices at other times lower winds are suspected hemispheric asymmetries are traced to differences in atmospheric hydration state and to global dust storm related effects on the atmospheric temperature structure and the north polar cap recession schedule cloud occurrence data suggest that the near surface daytime static stability is low in the northern hemisphere during summer and at low latitudes during mid northern spring relatively high static stability is deduced near the winter poles and globally during the dust storm season in spite of low atmospheric temperatures the correspondingly low absolute humidity apparently precludes the formation of thick water ice clouds at high latitudes in mid to late autumn and winter in both hemispheres and in southern mid latitudes during early winter during northern spring and summer saturation conditions seem to be easily achieved at mid latitudes and condensate clouds are abundant the situation is complicated by atmospheric dust in southern spring and summer low latitudes generally appear to be farther from saturation than mid latitudes and clouds generally form more easily in the northern hemisphere than in the south during corresponding seasons

analysis of a lower tropospheric gravity wave train using direct and remote sensing measurement systems abstracton 10 august 2014 a gravity wave complex generated by convective outflow propagated across much of oklahoma the four dimensional evolution of the wave complex was analyzed using a synthesis of near surface and vertical observations from the oklahoma mesonet and atmospheric radiation measurement arm southern great plains networks two atmospheric emitted radiance interferometers aeri one located at the arm sgp central facility in lamont oklahoma and the other in norman oklahoma were used in concert with a doppler wind lidar dwl in norman to determine the vertical characteristics of the wave complex hydraulic theory was applied to the aeri derived observations to corroborate the observationally derived wave characteristics it was determined that a bore soliton wave packet initially formed when a density current interacted with a nocturnal surface based inversion and eventually propagated independently as the density current became diffuse the soliton propagated within an elevated invers

observation of pressure variations in the martian atmosphere 1 pressure waves in the martian atmosphere could so far be observed only in the presence of clouds thanks to the mars global surveyor mars orbiter laser altimeter mgs mola a direct observation is now possible with the method presented here many more events are thus potentially observable we compare altimetry measurements from mgs mola and spectral observations from ism the infrared spectrometer aboard the phobos 2 spacecraft to infer pressure variations in the martian atmosphere we identify variations of pressure above martian volcanoes and we observe lee vortices of wavelength 200 250 km and amplitude 0 05 mbar in two different occasions the application of this technique should constrain martian meteorology with data from future imaging spectrometers

pliocene lower pleistocene shallow water mixed siliciclastics and carbonates yanigua and los haitises formations in eastern hispaniola dominican republic the virtually unfolded sedimentary cover of the cordilleras central and oriental in the eastern dominican republic eastern hispaniola tropical north atlantic largely consists of pliocene to early pleistocene mixed siliciclastics and carbonates these deposits have been grouped into two laterally interfingering mapping units the yanigua and los haitises formations the former mainly siliciclastics comprises marl marly limestone and minor conglomerate sandstone lignite and carbonaceous clay and crops out closest to the basement the los haitises formation mainly consists of limestone and intercalating beds of marly limestone and marl lithological mapping at the 1 50 000 scale and facies analysis of twelve measured sections and of additional fourteen outcrops suggest that these deposits mainly formed on a shallow water marine platform fringing the precursor reliefs of the cordillera oriental and the southeastern end of the cordillera central only a limited proportion of sediment formed in floodplains and marshes marl and marly limestone dominated the inner platform sediments terrigenous mud decreased away from the emergent basement and carbonate sedimentation dominated the more external platform corals molluscs echinoids foraminifers bryozoans coralline algae and halimeda are the main components with varying amounts of carbonate mud the platform was generally a low energy environment with seagrass patches in the inner platform corals grew as isolated colonies or as small patch reefs dominated by porites in marly and bioclastic substrates branching corals stylophora and acropora grew in extensive carpets in more distal areas at least in the last stage of its development early pleistocene the platform was rimmed by a reef barrier similar to the holocene caribbean barrier reefs with acropora gr palmata a cervicornis porites montastrea siderastrea and diploria as the main reef builders

structure of an atmospheric undular bore generated from colliding boundaries during cape abstract a case study of a sea breeze front originating from the east coast of florida colliding with a gust front moving toward the southeast is presented single and multi doppler radar analyses combined with serial balloon ascents suggest that the denser sea breeze flow undercut the cold pool behind the gust front and may have generated a westward propagating undular bore in addition another undular bore was generated by the collision and propagated eastward through the cape network the latter bore propagated upstream against the southeasterly flow behind the sea breeze front and was apparent as a narrow band 5 6 km wide of near zero radial velocities embedded within an overall flow that was positive as seen by the cp 4 doppler radar as the eastern bore propagated through the dual doppler lobe defined by the ncar cp 3 and cp 4 radars a detailed and unique wind synthesis revealed its three dimensional kinematic structure significant along bore variability was shown in the convergence and verti

long cloud observations on mars and implications for boundary layer characteristics over slopes viking orbiter images of mars show several instances of long continuous cloud formations on the slopes of arsia and pavonis mons we have searched all the images of the planet for occurrences of such formations only in the tharsis region were long clouds unambiguously identified we have measured the times and locations of occurrence the wavelengths and when possible the apparent velocity of motion of these clouds we have also tabulated the wavelengths of patches of ripple clouds that are often found with the long formations the long clouds are observed only in the early morning hours suggesting that they are associated with drainage winds due to a cold planetary boundary layer we develop simple mathematical models to examine various aspects of such boundary layer winds these allow us to construct a complete and self consistent explanation of all the observed features of the cloud formations we use the results to characterize some physical properties of the mars boundary layer there is strong downslope flow in the boundary layer on the high slopes of both volcanos in the saddle region between the peaks the flow slows and undergoes a hydraulic jump producing the long clouds downstream of the jump standing internal gravity waves can exist and are excited by flow over surface irregularities small variations in their observed wavelengths behind the jump may be attributed to variation in the flow speed and depth finally we can account for the location of the jumps by the variation of relative strength of the boundary layer flows on the two volcanos

thermal inertia mapping of mars from 60 s to 60 n twenty micrometer brightness temperatures are used to derive the thermal inertia for 81 of the martian surface between latitudes 60 these data were acquired by the two viking infrared thermal mappers in 1977 and 1978 following the two global dust storms of 1977 the spatial resolution used is 2 in latitude by 2 in longitude and the total range in derived inertia is 1 to 15 10 3 cal cm 2 sec 12 k 1 the distribution of thermal inertia is strongly bimodal with all values of thermal inertia less than 4 10 3 cal cm 2 sec 12 k 1 being associated with three disjoint bright regions mostly in the northern hemisphere sufficient dust is raised in global storms to provide fine material adequate to produce these low inertia areas but the specific deposition mechanism has not been defined at the low resolution used no complete exposures of clean rock were found there is some tendency for darker material to be associated with higher thermal inertia although the trend is far from one to one the distribution of high and low inertia areas is sufficiently nonrandom to produce a variation in whole disk brightness temperature with central meridian longitude this variation and the change in surface kinetic temperature associated with dust storms are factors in establishing the whole disk brightness temperature at radio and infrared wavelengths and will be important for those who use mars as a calibration source

reworking processes and deposits in coral reefs during very high energy events example from a pleistocene coral formation 125 ka la desirade island lesser antilles abstract abundant literature has documented the ecological impact of very high energy hurricane type events and high energy storm type events on modern coral reefs and sediment transport in previous studies sedimentary processes are often deduced from geophysical image analysis and scuba diving observations few field based studies have been devoted to the impact of very high energy disturbance on the structure and ecology of holocene and pleistocene coral reefs and very few to the sedimentary processes acting around these reefs this research examines the structure of the late pleistocene end of mis5e stage reefs of la desirade island guadeloupe archipelago lesser antilles and focuses on the poorly known reworking processes and related coral breccia sedimentation surrounding these reefs fieldwork was performed to document two coral fragment rich breccia interbedded with coral patches the breccia predominantly show the same petrography but differ in their internal structure showing a massive breccia type and a stratified breccia type this work infers that these breccia are the result of gravity induced high density mass flows triggered by high to very high energy events such as storms and hurricanes damage and reworking vary according to the type of very high energy event prior to transport storms are thought to have broken the heads of branching and columnar coral colonies and broken and overturn isolated lamellar and massive colonies hurricanes particularly their eye walls may have reworked much more sediment than storms and may have also destabilised entire several metre sized columnar colonies from the flank of coral patch reefs we propose the name coral debrite for these coral breccia deposits caused by gravity induced debris flows the reworked deposits are interbedded between two coral reef levels of which the main coral species vertical succession should record the end of marine isotope stage 5e sea level rise thus reworking is believed to occur during the transitional stage between a glacial and an interglacial period

two mars years of clouds detected by the mars orbiter laser altimeter 1 the mars orbiter laser altimeter mola instrument operated as an atmospheric lidar system as well as an altimeter detecting absorptive clouds in northern latitudes shortly after orbit insertion in october 1997 and reflective clouds over the north polar cap at the start of the science phasing orbits in march 1998 global cloud measurements commenced with the primary mapping mission in march 1999 with nearly continuous coverage for 1 25 mars years mola tracked several dust storms culminating with a major dust storm in june 2001 reflective clouds exhibiting distinctive patterns governed by insolation and the dynamics of the atmosphere were detected at elevations up to 20 km above the surface chiefly in the polar winter night mola distinguishes cloud returns by pulse width and energy measurements unusually strong and brief reflections with minimal extinction suggest precipitation of co2 snow under supercooled conditions weaker cloud reflections occurred at all latitudes some reflective daylight clouds at low latitudes suggested convective vortices or dust devils ground fogs composed of dust and h2o ice formed at night along the seasonal frost line absorptive clouds while not resolved altimetrically tracked the advancing and receding edges of the seasonal polar caps the absorptive and reflective clouds provide a seasonal profile of atmospheric activity spanning two martian years winter reflective cloud activity declined to background levels earlier in the second year at both poles suggesting interannual warming

western boundary currents in the martian atmosphere numerical simulations and observational evidence western boundary currents hereafter wbcs are an intensification of meridional fluid flow along the eastward facing flank of a boundary they occur in the earth s oceans the best known instance being the gulf stream and in the terrestrial atmosphere an example of which is the east african jet we have investigated wbcs in numerical simulations of the martian atmosphere where they occur in the presence of large longitudinal topographical gradients combined with the effect we suggest that wbcs have already been simulated by other martian atmospheric models although not identified as such the intensity of these currents is dependent on basic model parameters notably surface drag we show that for physically reasonable values of drag frictional forces dominate the wbcs behavior the requirement of zero net cross equatorial time mean mass flow produces a return flow in simulations with relatively low surface drag which acts in opposition to the tharsis wbc we also show that the intense flow associated with wbcs advects potential vorticity across the equator although the presence of strong radiative damping inhibits low level inertial instabilities that might result from this slope winds are found to have a profound effect on wbc structure especially where they have a component parallel to the jet in these cases slope winds can cancel out or reinforce wbcs depending on their direction enhanced low level winds associated with wbcs may be a factor that influences the locations of dust storm generation the high vertical shear associated with wbcs may also play a role in the maintenance and subsequent decay of these dust storms some observational evidence may exist for wbcs in the form of the alignment of bright depositional dust streaks wave clouds and in wind measurements taken during the parachute descent phase of viking lander 1 through the planetary boundary layer

a global compilation of coral sea level benchmarks implications and new challenges i present a quality controlled compilation of sea level data from u th dated corals encompassing 30 studies of 13 locations around the world the compilation contains relative sea level rsl data from each location based on both conventional and open system u th ages i have applied a commonly used age quality control criterion based on the initial 234u 238u activity ratios of corals in order to select reliable ages and to reconstruct sea level histories for the last 150 000 yr this analysis reveals scatter of rsl estimates among coeval coral benchmarks both within individual locations and between locations particularly during marine isotope stage mis 5a and the glacial inception following the last interglacial the character of data scatter during these time intervals imply that uncertainties still exist regarding tectonics glacio isostacy u series dating and or coral position to elucidate robust underlying patterns with confidence limits i performed a monte carlo style statistical analysis of the compiled coral data considering appropriate age and sea level uncertainties by its nature such an analysis has the tendency to smooth obscure millennial scale and finer details that may be important in individual datasets and favour the major underlying patterns that are supported by all datasets this statistical analysis is thus functional to illustrate major trends that are statistically robust what we know trends that are suggested but still are supported by few data what we might know subject to addition of more supporting data and improved corrections and which patterns data are clear outliers unlikely to be realistic given the rest of the global data and possibly needing further adjustments prior to the last glacial maximum and with the possible exception of the 130 120 ka period available coral data generally have insufficient temporal resolution and unexplained scatter which hinders identification of a well defined pattern with usefully narrow confidence limits this analysis thus provides a framework that objectively identifies critical targets for new data collection improved corrections and integration of coral data with independent stratigraphically continuous methods of sea level reconstruction

high resolution atmospheric observations by the mars odyssey thermal emission imaging system high resolution observations of atmospheric phenomena by the mars odyssey thermal emission imaging system themis during its first mapping year are presented an atmospheric campaign was implemented on the basis of previous spacecraft imaging this campaign however proved of limited success this appears to be due to the late local time of the odyssey orbit the locations of activity at 4 6 p m appear to be different from those at 2 p m ironically images targeting the surface were more useful for study of the atmosphere than those images specifically targeting atmospheric features while many previously recognized features were found novel themis observations included persistent clouds in the southern polar layered deposits dust or condensate plumes on the northern polar layered deposits dust plumes as constituent parts of local dust storms and mesospheric clouds the former two features tend to be aligned parallel and normal to polar troughs respectively suggesting a wind system directed normal to troughs and radially outward from the center of the polar deposits this is consistent with katabatic drainage of air off the polar deposits analogous to flow off antarctica the observation of dust lifting plumes at unprecedented resolution associated with local dust storms not only demonstrates the importance of mean wind stresses as opposed to dust devils in initiation of dust storms but is also seen to be morphologically identical to dust lifting in terrestrial dust storms as odyssey moves to earlier local times we suggest that the atmospheric campaign from the first mapping year be repeated

evolution and vertical structure of an undular bore observed on 20 june 2015 during pecan abstractthis study documents the evolution of an impressive largely undular bore triggered by an mcs generated density current on 20 june 2015 observed as part of the plains elevated convection at night pecan experiment the university of wyoming king air with profiling nadir and zenith viewing lidars sampled the south bound bore from the time the first bore wave emerged from the nocturnal convective cold pool and where updrafts over 10 m s 1 and turbulence in the wave s wake were encountered through the early dissipative stage in which the leading wave began to lose amplitude and speed through most of the bore s life cycle its second wave had a higher or equal amplitude relative to the leading wave striking roll clouds formed in wave crests and wave energy was detected to about 5 km agl the upstream environment indicates a negative scorer parameter region due to flow reversal at midlevels providing a wave trapping mechanism the observed bore strength of 2 4 2 9 and speed of 15 16 m s 1 agree

a revised morpho and chronostratigraphy of the late and middle pleistocene coral reef terraces on southern barbados west indies the barbados coral reef terraces are one of the few type localities worldwide that provide insights into interglacial sea level change during the late and middle pleistocene several sea level estimates have been established since the late 1960s and each has contributed to the barbados model of sea level change this paper presents new morpho and chonostratigraphic data from the barbados coral reef terraces developed over the last 12 years the work is based on significant advances in electron spin resonance esr dating of fossil coral air photo interpretation and a greatly improved geomorphic map of preserved fossil beach formations and reef terraces above present sea level the need for a revision of past published morpho and chronostratigraphies is best demonstrated on the southern part of the island the morpho and chronostratigraphic sequence in this region is both more complex and diverse than has been assumed so far the revised morphostratigraphy presented here includes a differentiation of coral reef terraces wave cut platforms and other erosive features such as notches and cliffs our study of these geomorphic features combined with new numeric dating results esr u th enable a revised estimate of the spatial and temporal variation in tectonic uplift rate within south barbados these new rates are an essential requirement for more precise glacio eustatic sea level reconstructions during the late and middle pleistocene from this region

curvilinear features in the southern hemisphere observed by mars global surveyor mars orbiter camera abstract we have used the complete set of mars global surveyor mgs mars daily global maps mdgms to study martian weather in the southern hemisphere focusing on curvilinear features including frontal events and streaks frontal events refer to visible events that are morphologically analogous to terrestrial baroclinic storms mdgms show that visible frontal events were mainly concentrated in the 210 300 e 60 150 w sector and the 0 60 e sector around the southern polar cap during l s 140 250 and l s 340 60 the non uniform spatial and temporal distributions of activity were also shown by mgs thermal emission spectrometer transient temperature variations near the surface streaks refer to long curvilinear features in the polar hood or over the polar cap they are an indicator of the shape of the polar vortex streaks in late winter usually show wavy segments between the 180 meridian and argyre model results suggest that the zonal wave number m 3 eastward traveling waves are important for their formation

review of wave turbulence interactions in the stable atmospheric boundary layer flow in a stably stratified environment is characterized by anisotropic and intermittent turbulence and wavelike motions of varying amplitudes and periods understanding turbulence intermittency and wave turbulence interactions in a stably stratified flow remains a challenging issue in geosciences including planetary atmospheres and oceans the stable atmospheric boundary layer sabl commonly occurs when the ground surface is cooled by longwave radiation emission such as at night over land surfaces or even daytime over snow and ice surfaces and when warm air is advected over cold surfaces intermittent turbulence intensification in the sabl impacts human activities and weather variability yet it cannot be generated in state of the art numerical forecast models this failure is mainly due to a lack of understanding of the physical mechanisms for seemingly random turbulence generation in a stably stratified flow in which wave turbulence interaction is a potential mechanism for turbulence intermittency a workshop on wave turbulence interactions in the sabl addressed the current understanding and challenges of wave turbulence interactions and the role of wavelike motions in contributing to anisotropic and intermittent turbulence from the perspectives of theory observations and numerical parameterization there have been a number of reviews on waves and a few on turbulence in stably stratified flows but not much on wave turbulence interactions this review focuses on the nocturnal sabl however the discussions here on intermittent turbulence and wave turbulence interactions in stably stratified flows underscore important issues in stably stratified geophysical dynamics in general

martian north polar hazes and surface ice results from the viking survey completion mission viking infrared observations of the martian north polar regions taken during the 1979 1980 viking survey completion mission have been used to determine the location and nature of the retreating polar cap edge and of an accompanying atmospheric ice haze the haze is composed of water ice and its visible opacity is approximately unity equivalent to 1 2 precipitable microns of water ice during the polar cap retreat aerocentric longitude ls 340 60 the haze is nearly always present and extends from at most a few degrees south of the polar cap edge to an undetermined distance over the cap interior the transition from ice free ground to a predominantly ice covered surface at the cap edge spans 5 10 of latitude the ability of the viking infrared observations to distinguish haze from surface condensate yields a more accurate seasonal regression for the polar cap than can be determined from visual images generally the infrared observations presented here yield a regression similar to those determined from earth based and or spacecraft visual data for the same and for previous northern springs however there are differences concerning details of the cap retreat the thermal data indicate that the martian seasonal polar cap did extend south of 60 n during this particular late winter and that the midspring resumption of the cap retreat occurs at ls 50

marci and moc observations of the atmosphere and surface cap in the north polar region of mars abstract we used mgs moc and mro marci daily mapping images of the north polar region of mars from 16 august 2005 ls 270 to 21 may 2009 ls 270 covering portions of three consecutive martian years my 27 my 29 to observe the seasonal behavior of the polar ice cap and atmospheric phenomena the rate of cap regression was similar in my 28 and my 29 but was advanced by 3 5 of ls 7 8 sols in my 29 the spatial and temporal behaviors of dust and condensate clouds were similar in the two years and generally in accord with prior years dust storms 100 km2 were observed in all seasons with peak activity occurring at ls 10 20 from 50 n to 70 n and at ls 135 140 from 70 n to 90 n the most active quadrant was 0 90 w in my 28 shifting to 180 270 w in my 29 the majority of regional storms in both years developed in longitudes from 10 w to 60 w during late summer the larger storms obscure the north polar region in a cloud of dust that transitions to north polar hood condensate clouds around autumnal equinox changes in the distribution of perennial ice deposits especially in olympia planum were observed between the 2 years with the my 29 ice distribution being the most extensive observed to date modeling suggests that the small bright ice patches on the residual cap are not the result of slope or elevation effects rather we suggest that they are the result of local meteorological effects on ice deposition the annual darkening and brightening of peripheral areas of the residual cap around summer solstice can be explained by the sublimation of a brighter frost layer revealing an underlying darker ice rich layer that itself either sublimes to reveal brighter material below or acts as a cold trap attracting condensation of water vapor that brightens the surface an alternative explanation invokes transport and deposition of dust on the surface from the cap interior and later removal of that dust the decrease in cap albedo and accompanying increase in near surface atmospheric stability may be related to the annual minimum of polar storm activity near northern summer solstice

a local dust storm in the chryse region of mars viking orbiter observations a local dust storm was observed near the viking lander 1 site by viking orbiter l in september 1977 when the areocentric longitude of the sun ls was 340 shortly before vernal equinox the orbiter observations which consisted of a time sequence of pictures show that the storm moved at about 50 m sec to the ene from the lunae planum region into the chryse basin both baroclinic waves and topography may have been associated with the generation of the storm

surface ages and resurfacing rates of the polar layered deposits on mars interpretation of the polar stratigraphy of mars in terms of global climate changes is complicated by the significant difference in surface ages between the north and south polar layered terrains inferred from crater statistics we have reassessed the cratering record in both polar regions using viking orbiter and mariner 9 images no craters have been found in the north polar layered terrain but the surface of most of the south polar layered deposits appears to have been stable for many of the orbital axial cycles that are thought to have induced global climate changes on mars the inferred surface age of the south polar layered deposits about 10 ma is two orders of magnitude greater than the surface age of the north polar layered deposits and residual cap at most 100 ka similarly modeled resurfacing rates are at least 20 times greater in the north than in the south these results are consistent with the hypotheses that polar layered deposit resurfacing rates are highest in areas covered by perennial ice and that the differences in polar resurfacing rates result from the 6 4 km difference in elevation between the polar regions deposition on the portion of the south polar layered deposits that is not covered by the perennial ice cap may have ceased about 5 million years ago when the obliquity of mars no longer exceeded 40

geomorphology and sediment transport on a submerged back reef sand apron one tree reef great barrier reef back reef sand aprons are conspicuous and dynamic sedimentary features in coral reef systems the development of these features influences the evolution and defines the maturity of coral reefs however the hydrodynamic processes that drive changes on sand aprons are poorly understood with only a few studies directly assessing sediment entrainment and transport current and wave conditions on a back reef sand apron were measured during this study and a digital elevation model was developed through topographic and bathymetric surveying of the sand apron reef flats and lagoon the current and wave processes that may entrain and transport sediment were assessed using second order small amplitude stokes wave theory and shields equations the morphodynamic interactions between current flow and geomorphology were also examined the results showed that sediment transport occurs under modal hydrodynamic conditions with waves the main force entraining sediment rather than average currents a morphodynamic relationship between current flow and geomorphology was also observed with current flow primarily towards the lagoon in shallow areas of the sand apron and deeper channel like areas directing current off the sand apron towards the lagoon or the reef crest these results show that the short term mutual interaction of hydrodynamics and geomorphology in coral reefs can result in morphodynamic equilibrium

differential uplift and tilt of pleistocene reef platforms and quaternary slip rate on the morne piton normal fault guadeloupe french west indies 1 the guadeloupe islands are cut by normal faults that accommodate oblique convergence between the north american and caribbean plates such faults are responsible for part of the shallow seismicity and have produced m 5 damaging earthquakes to better assess the seismic hazard in guadeloupe we quantify the slip rate on one of the largest fault morne piton this roughly e w fault crosses the island of marie galante and uplifts a flight of reef terraces from geomorphic analysis we mapped three main terraces new u th datings show that they formed during the latest interglacials 120 and 240 kyr ago correlation with specmap isotopic records implies that the marie galante plateau emerged during the 330 ka highstand topographic profiles show that the terraces and the plateau are deformed by faulting elastic modeling of their shape constrains the geometry of the fault 70 80 dip 5 km depth and its slip rate 0 5 0 2 mm yr given its length 50 km depth and slip rate this fault might produce maximum m 6 5 earthquakes with a recurrence time of 1400 to 3300 years or more likely smaller events such as the m 5 5 16 may 1851 and 3 august 1992 shocks that might recur every 400 to 1000 years we also show that all the islands and terraces are tilted westward perpendicularly to the trench la desirade closest to the trench is uplifted by 276 m whereas subsidence 70 m is observed 10 km east of the volcanic arc this tilt probably resulted from a transient deformation episode at the subduction interface that predated the late pleistocene

the spectacular undular bore in iowa on 2 october 2007 a visually impressive undular bore moved across much of iowa on 2 october 2007 and video animations were captured by numerous webcams the bore was sampled very well by doppler radar at close range and also by the high density mesoscale network of surface stations in place over iowa and 1 min automated surface observing system asos surface data at des moines iowa radar and surface observations are presented along with a brief analysis of the structure of the bore

loss of fine scale surface texture in viking orbiter inages and implications for the inferred distribution of debris mantles abstract the absence of fine scale surface features in viking orbiter images must be interpreted with caution a reduction in contrast due to the presence of atmospheric haze will preferentially obscure small features two sets of images of the same region taken with similar viewing geometry but under different atmospheric conditions allow us to demonstrate that a single scattering model quantitatively accounts for the effects of the atmosphere craters five to seven times the size of the camera picture element should be resolved in viking orbiter images if the atmosphere is clear when atmospheric haze effects dominate larger craters are obscured and crater size frequency distributions appear to be depleted in small sized craters in a predictable way twelve crater size frequency counts in the northern hemisphere behave in the manner predicted for hazy conditions their characteristics also follow the pattern of increasing atmospheric opacity with latitude in spring and summer deduced from other measurements of cloudiness loss of surface resolution due to the nearly ubiquitous atmospheric obscuration in the northern mid to high latitudes makes it difficult to assesst with existing images the validity of suggestions that fine scale surface features have been preferentially degraded by surface processes however the atmosphere in the southern mid and high latitudes is relatively clear during autumn and winter and a preliminary review of existing image data suggests that features with sizes down to five to seven picture elements can be detected in this region no evidence for a recent circumpolar debris mantle can be found in the southern hemisphere data because the smallest craters that can be resolved in viking images are several tens of meters in diameter we cannot rule out the occurrence of debris deposits less than a few tens of meters thick regardless of atmospheric clarity

thermal and albedo mapping of the polar regions of mars using viking thermal mapper observations 1 north polar region we present the first maps of the apparent thermal inertia and albedo of the south polar region of mars the observations used to create these maps were acquired by the infrared thermal mapper irtm instruments on the two viking orbiters over a 30 day period in 1977 during the martian late southern summer season the maps cover the region from 60 s to the south pole at a spatial resolution of 1 of latitude thus completing the initial thermal mapping of the entire planet the analysis and interpretation of these maps is aided by the results of a one dimensional radiative convective model which is used to calculate diurnal variations in surface and atmospheric temperatures and brightness temperatures at the top of the atmosphere for a range of assumptions concerning dust optical properties and dust optical depths the maps show that apparent thermal inertias of bare ground regions decrease systematically from 60 s to the south pole in unfrosted regions close to the south pole apparent thermal inertias are among the lowest observed anywhere on the planet on the south residual cap apparent thermal inertias are very high due to the presence of co2 frost in most other regions of mars best fit apparent albedos based on thermal emission measurements are generally in good agreement with actual surface albedos based on broadband solar reflectance measurements however in the frost free region poleward of 75 s best fit apparent albedos are significantly higher than measured lambert albedos implying that measured brightness temperatures in this area are up to 15 k colder than would be expected for surfaces with the same measured albedos during this season the one dimensional atmospheric model calculations also predict anomalously cold brightness temperatures close to the pole during late summer and after considering a number of alternatives it is concluded that the net surface cooling due to atmospheric dust is the best explanation for this phenomenon the observed systematic decrease in apparent thermal inertia from 60 s to the south pole during this season is also consistent with the predictions of atmospheric model calculations the region of lowest apparent thermal inertia close to the pole which includes the south polar layered deposits is interpreted to be mantled by a continuous layer of aeolian material that must be at least a few millimeters thick the low thermal inertias mapped in the south polar region imply an absence of surface water ice deposits which is consistent with viking mars atmospheric water detector mawd measurements which show low atmospheric water vapor abundances throughout the summer season however these observations do not necessarily imply a complete absence of water thermal model calculations that can reproduce observed diurnal temperature variations in the south polar region show that annual maximum subsurface temperatures at depths ranging from 4 to 20 cm are cold enough to permit the stability of ground ice deposits even if they are in excellent diffusive contact with the atmosphere therefore the presence of near surface ground ice in the south polar region is not inconsistent with the viking irtm and mawd observations

structure and development of detrital reef deposits in turbid nearshore environments inhaca island mozambique coral communities are intermittently developed along the seaward margins of wide up to 500 m intertidal flats that fringe the western margins of inhaca island southern mozambique the coral communities occur in an environment that can be considered as marginal for coral growth in the sense that they are subject to high turbidity levels which results in rapid light attenuation and to the effects of periodic smothering and burial associated with a mobile siliciclastic dominated sediment substrate these constraints limit coral community development both spatially and bathymetrically in addition historical evidence suggests that the main sites of coral growth shift over decadal timescales due to periodic sediment remobilisation such rapid rates of turnover restrict the development of rigid framework deposits and in contrast the main depositional product of coral growth is an abundance of branched mainly acropora sp coral rubble rubble production is aided both by intense internal bioerosion sponge bivalve and worm traces and by periodic storm damage much of this rubble accumulates along the channel margins and provides a substrate for subsequent coral recruitment the deposits can be distinguished from those associated with clear water reef environments by 1 the lack of a rigid reef framework either comprising of in situ coral or encrusted coral rubble 2 the distinct lack of rubble encrustation syn depositional cementation and 3 the predominance of a siliciclastic rich sediment matrix the deposits indicate however a long term history of coral community occurrence in sites dominated by siliciclastic sedimentation cores recovered from a transect across the tidal flats identify a coral rubble floatstone facies extensively developed along the western margins of the island it comprises mainly branched coral rubble often heavily bioeroded but sparsely encrusted along with spheroidal rhodoliths and molluscan fragments set within a poorly sorted mixed siliciclastic carbonate sediment matrix 14c dating indicates that most of the rubble deposits date from the period 6500 4700 years bp which corresponds to a period of regional sea level highstand a detailed growth chronology cannot be established due to the lack of in situ coral but rapid rubble deposition and reef flat progradation around 350 m can be inferred for this period equivalent to an average progradation rate of around 0 2 m year 1 over the subsequent 4700 years progradation of only around 25 m has occurred this may be attributed to reworking and erosion of the seaward margin of the deposits during periods of fluctuating sea level between 4700 and 900 years bp or to a lack of seaward accommodation space

the vertical structure of limb hazes in the martian atmosphere abstract profiles of scattered light above the planetary limb from over 100 viking orbiter images are used to constrain the temporal and spatial behavior of earosols suspended in the martian atmosphere the data cover a wide range of seasons locations and viewing geometry providing information about the aerosol optical properties and vertical distribution the vertical resolution of the data is about 1 5 km with an absolute elevation accuracy of 1 to 4 km viking orbiter camera colibration algorithms provided reflectance accuracies to 7 absolute allowing meaningful radiometric analysis the typical atmospheric column contains one or more discrete optically thin ice like haze layers between 30 and 90 km elevation depending on season whose composition is inferred to be water ice below the detached hazes there is a continuous haze extending to the surface the continuous haze is rarely observed above 50 km and is much redder in color than the detached hazes above implying a composition that has a strong dust component the aerosol distribution exhibits a strong seasonal control inferred to be driven by the variable solar flux around the orbit of mars

winter clouds over the north martian polar cap the mars orbiter laser altimeter mola experiment carried on the mars global surveyor spacecraft has observed echoes from cloud tops on roughly 2 5 of the total data taken above 70 n over the northern winter martian polar hood from march to june 1998 sloping wavefronts are commonly seen at latitudes above 70 n implying the presence of propagating buoyancy waves since these wavefronts frequently extend from the surface up to 10 km at a time when co2 is known to be condensing on the polar surface it seems likely that the laser scattering particles consist primarily of co2 ice and that the near surface temperature lapse rate is 0 85 k km 1 set by the vapor pressure of dry ice from the observed wavelengths where available we have calculated the corresponding phase velocities some of these waves appear to be correlated with surface discontinuities and may represent lee waves

martian clouds observed by mars global surveyor mars orbiter camera we have made daily global maps that cover both polar and equatorial regions of mars for ls 135 360 and 0 111 using the mars global surveyor mgs mars orbiter camera moc red and blue wide angle swaths taken from may 1999 to january 2001 we study the seasonal distribution of condensate clouds and dust clouds during roughly 1 martian year using these daily global maps we present the development and decay of the tropical cloud belt and the polar hoods the spatial and temporal distributions of lee waves and spiral clouds and an unusual aster cloud above the volcanoes consisting of rays around a central disk like the flower the tropical cloud belt contains mostly fibrous clouds during northern spring early summer and convective clouds during middle late northern summer the detailed development and decay of the tropical cloud belt is nonuniform in longitude two distinct stormy periods in late summer precede the formation of the north and south circumpolar hoods the north polar storms in late summer resemble baroclinic frontal systems on earth but contain both dust and condensate clouds spiral clouds occur only in the northern high latitudes and only during northern spring and summer the north polar hood displays a stationary wave number two structure during the fall and winter the south polar hood has fewer streak clouds and lee wave clouds than the north polar hood during this particular year the lee wave cloud abundance in the south had two peaks in early fall and late winter and the lee wave cloud abundance in the north had one peak in early fall

a multiannual record of gravity wave activity in mars s lower atmosphere from on planet observations by the mars climate sounder abstract gravity waves in mars s atmosphere strongly affect the general circulation as well as middle atmospheric cloud formation but the climatology and sources of gravity waves in the lower atmosphere remain poorly understood at earth the statistical variance in satellite observations of thermal emission above the instrumental noise floor has been used to enable measurement of gravity wave activity at a global scale here is presented an analysis of variance in calibrated radiance at 15 4 m 635 665 cm 1 from off nadir and nadir observations by the mars climate sounder mcs on board mars reconnaissance orbiter mro a major expansion in the observational data available for validating models of martian gravity wave activity these observations are sensitive to gravity waves at 20 30 km altitude with wavelength properties h 10 100 km z 5 km that make them likely to affect the dynamics of the middle and upper atmosphere we find that 1 strong moderately intermittent gravity wave activity is scattered over the tropical volcanoes and throughout the middle to high latitudes of both hemispheres during fall and winter 2 gravity wave activity noticeably departs from climatology during regional and global dust storms and 3 strong intermittent variance is observed at night in parts of the southern tropics during its fall winter but frequent co 2 ice clouds prevents unambiguous attribution to gw activity the spatial distribution of wave activity is consistent with topographic sources being dominant but contributions from boundary layer convection and other convective processes are possible

aphelion water ice cloud mapping and property retrieval using the omega imaging spectrometer onboard mars express mapping of the aphelion clouds over tharsis and retrieval of their particle size and visible opacity are made possible by the omega imaging spectrometer aboard mars express observations cover the period from my26 ls 330 degree sign to my29 ls 180 degree sign and are acquired at various local times ranging from 8am to 6pm cloud maps of the tharsis region constructed using the 3 1 m ice absorption band reveal the seasonal and diurnal evolution of aphelion clouds four distinct types of clouds are identified morning hazes topographically controlled hazes cumulus clouds and thick hazes the location and time of occurrence of these clouds are analyzed and their respective formation process is discussed an inverse method for retrieving cloud particle size and opacity is then developed and can only be applied to thick hazes the relative error of these measurements is less than 30 for cloud particle size and 20 for opacity two groups of particles can be distinguished the first group is found over flat plains and is composed of relatively small particles ranging in size from 2 to 3 5 m the second group is characterized by particle sizes of 5 m which appear to be quite constant over ls and local time it is found west of ascraeus and pavonis mons and near lunae planum these regions are preferentially exposed to anabatic winds which may control the formation of these particles and explain their distinct properties the water ice column is equal to 2 9pr m on average and can reach 5 2pr m in the thickest clouds of tharsis

the influence of the rocky mountains on the 13 14 april 1986 severe weather outbreak part ii evolution of a prefrontal bore and its role in triggering a squall line abstract in this paper part ii of a series the evolution of a prefrontal bore on the leeside of the rockies and its subsequent propagation and initiation of convection farther downstream over eastern colorado and western nebraska are investigated the observational evidence for this sequence of events was obtained from combined analyses of high resolution goes satellite imagery and program for regional observing and forecasting services mesonetwork data over the colorado region for the severe weather event that occurred during 13 14 april 1986 a 2d nonhydrostatic numerical model is used to further understand the initiation of the bore and its ability to propagate farther downstream and trigger convection analysis of satellite imagery and mesonet data indicated that an internal bore ahead of a cold front a moderate downslope windstorm and a quasi stationary hydraulic jump were generated within a few hours along the iceslope as a pacific cold front and its attendant upper level jet streak advanced o

retrieval of atmospheric temperatures in the martian planetary boundary layer using upward looking infrared spectra abstract we present an algorithm for the retrieval of temperature in the planetary boundary layer lowest few kilometers of the martian atmosphere using upward looking infrared spectra from a mars lander temperature profiles retrieved from an orbiting or passing spacecraft do not have adequate vertical resolution to provide significant information within the planetary boundary layer by using spectra taken from a surface lander looking upward toward zenith and by transforming to a vertical coordinate that stretches out the atmosphere just above the surface where the contribution to the observed radiation peaks we find that an efficient algorithm can be formulated with adequate vertical resolution to successfully retrieve temperature profiles that exhibit the major features of the diurnal cycle of planetary boundary layer temperatures we expect that this technique can be extended to simultaneously retrieve the opacity and possibly the scattering properties of atmospheric aerosols as well although no upward looking martian infrared spectra yet exist demonstration of the abilities of a lander based infrared spectrometer is important for the planning of future missions to mars

the seasonal behavior of water ice clouds in the tharsis and valles marineris regions of mars mars orbiter camera observations abstract the mars global surveyor mars orbiter camera was used to obtain global maps of the martian surface with equatorial resolution of 7 5 km pixel in two wavelength ranges blue 400 450 nm and red 575 625 nm the maps used were acquired between march 15 1999 ls 110 and july 31 2001 ls 205 corresponding to approximately one and a quarter martian years using the global maps cloud area in km2 has been measured daily for water ice clouds topographically corresponding to olympus mons ascraeus mons pavonis mons arsia mons alba patera the western valles marineris canyon system and for other small surface features in the region seasonal trends in cloud activity have been established for the three tharsis volcanoes olympus mons and alba patera olympus ascraeus and pavonis mons show cloud activity from about ls 0 220 with a peak in cloud area near ls 100 one of our most interesting observational results is that alba patera shows a double peaked feature in the cloud area with peaks at ls 60 and 140 and a minimum near ls 100 arsia mons shows nearly continuous cloud activity the altitudes of several of these clouds have been determined from the locations of the visual cloud tops and optical depths were measured for a number of them using the disort code of stamnes et al 1988 appl opt 27 2502 2509 several aspects of the observations e g cloud heights effects of increased dust on cloud activity are similar to simulations in richardson et al 2002 j geophys res 107 5064 a search for short period variations in the cloud areas revealed only indirect evidence for the diurnal cloud variability in the afternoon hours unambiguous evidence for other periodicities was not found

detection and monitoring of h2o and co2 ice clouds on mars we have developed an observational scheme for the detection and discrimination of mars atmospheric h2o and co2 clouds using ground based instruments in the near infrared we report the results of our cloud detection and characterization study using mars near ir images obtained during the 1990 and 1993 oppositions we focused on specific wavelengths that have the potential based on previous laboratory studies of h2o and co2 ices of yielding the greatest degree of cloud detectability and compositional discriminability we have detected and mapped absorption features at some of these wavelengths in both the northern and southern polar regions of mars compositional information on the nature of these absorption features was derived from comparisons with laboratory ice spectra and with a simplified radiative transfer model of a co2 ice cloud overlying a bright surface our results indicate that both h2o and co2 ices can be detected and distinguished in the polar hood clouds the region near 3 00 m is most useful for the detection of water ice clouds because there is a strong h2o ice absorption at this wavelength but only a weak co2 ice band the region near 3 33 m is most useful for the detection of co2 ice clouds because there is a strong relatively narrow co2 ice band at this wavelength but only broad continuum h2o ice absorption weaker features near 2 30 m could arise from co2 ice at coarse grain sizes or surface dust minerals narrow features near 2 00 m which could potentially be very diagnostic of co2 ice clouds suffer from contamination by mars atmospheric co2 absorptions and are difficult to interpret because of the rather poor knowledge of surface elevation at high latitudes these results indicate that future ground based earth orbital and spacecraft studies over a more extended span of the seasonal cycle should yield substantial information on the style and timing of volatile transport on mars as well as a more detailed understanding of the role of co2 condensation in the polar heat budget

dating open systems by the 238 u 234 u 230 th method application to quaternary reef terraces abstract the sedimentation conditions and diagenetic processes of biogenic and inorganic carbonates are such that the assumptions of a closed system evolution and the absence of initial th invoked in classical 238 u 234 u 230 th dating methods are very often not fulfilled for such material this problem is of interest for all studies requiring accurate dating of corals or aragonite rich sediments as in palaeoclimatology or neotectonics extending the approach of henderson and slowey nature 404 2000 61 66 we propose a consistent model that takes into account possible initial 230 th excess and where continuous selective redistribution gain or loss of 234 u 234 th and 230 th is controlled by recoil processes this model applied to quaternary marine terraces in barbados marie galante lesser antilles arc and pacific islands is able to explain the large scatter in isotopic compositions observed in the series of cogenetic corals or sediments we show that recoil processes generally tend to increase the 234 u 238 u and 230 th 234 u ratios with time leading to an overestimation of the apparent ages calculated using classical methods on the basis of simple assumptions identical marine initial 234 u 238 u 0 and 230 th 232 th 0 ratios we propose a method for calculating a best estimate of the age of cogenetic series our model offers an alternative way to date old reef terraces where corals are almost systematically altered and where classical dating methods do not apply it may also explain the apparent variations of the 234 u 238 u seawater initial ratio estimated from corals formed in the last 300 ka and the apparent uncoupling between sea level highstands and high latitude northern hemisphere summer insolation our set of equations can be applied to all weathering processes where the mobility of u series isotopes is controlled by recoil

observations of martian ice clouds by the mars global surveyor thermal emission spectrometer the first martian year successful operation of the mars global surveyor spacecraft beginning in september 1997 ls 184 has permitted extensive observations over more than a martian year initially thin normal optical depth 0 06 at 825 cm 1 ice clouds and hazes were widespread showing a distinct latitudinal gradient with the onset of a regional dust storm at ls 224 ice clouds vanished in the southern hemisphere to reappear gradually after the decay of the storm the zonally averaged cloud opacities show little difference between the beginning and end of the first martian year a broad low latitude cloud belt with considerable longitudinal structure was present in early northern summer apparently characteristic of the northern summer season it vanished between ls 140 and 150 the latitudinal extent of this feature is apparently controlled by the ascending branch of the hadley circulation the most opaque clouds optical depth 0 6 were found above the summits of major volcanic features these showed spatial structure possibly associated with wave activity variety among low lying late morning clouds suggests localized differences in circulation and microclimates limb observations showed extensive optically thin optical depth 0 04 stratiform clouds at altitudes up to 55 km considerable latitude and altitude variations were evident in ice clouds in early northern spring ls 25 near 30 km thin clouds extended from just north of the equator to 45 n nearly to the north polar vortex a water ice haze was present in the north polar night ls 30 at altitudes up to 40 km because little dust was present this probably provided heterogeneous nucleation sites for the formation of co2 clouds and snowfall at altitudes below 20 km where atmospheric temperatures dropped to the co2 condensation point the relatively invariant spectral shape of the water ice cloud feature over space and time indicates that ice particle radii are generally between 1 and 4 m

structure of an internal bore and dissipating gravity current as revealed by raman lidar abstract detailed moisture observations from a ground based raman lidar and special radiosonde data of two disturbances associated with a dissipating gust front are presented a synthesis of the lidar data with conventional meteorological data in conjunction with theoretical calculations and comparison to laboratory studies leads to the conclusion that the disturbances seen in both the lidar and accompanying barograph data represent a weak gravity current and an associated undular bore the disturbances display excellent coherence over hundreds of kilometers upstream of the lidar site bore formation occurs at the leading edge of the gust front coincidentally with the rapid weakening of the gravity current analysis suggests that the bore was generated by the collapse of the gravity current into a stable nocturnal inversion layer and subsequently propagated along this wave guide at nearly twice the speed of the gravity current the raman lidar provided detailed measurements of the vertical structure o

a comparison of the finescale structures of a prefrontal wind shift line and a strong cold front in the southern plains of the united states abstractthe objectives of this study are to determine the finescale characteristics of the wind and temperature fields associated with a prefrontal wind shift line and to contrast them with those associated with a strong cold front data from a mobile polarimetric x band doppler radar and from a surveillance s band radar temperature profiles retrieved from a thermodynamic sounder and surface observations from the oklahoma mesonet are used to analyze a prefrontal wind shift line in oklahoma on 11 november 2013 data from the same mobile radar and the oklahoma mesonet are used to identify the finescale characteristics of the wind field associated with a strong surface cold front in oklahoma on 9 april 2013 it is shown that the prefrontal wind shift line has a kinematic and thermodynamic structure similar to that of an intrusion elevated density current while the cold front has a kinematic structure similar to that of a classic density current other characteristics of the prefrontal wind shift line

amazonian northern mid latitude glaciation on mars a proposed climate scenario recent geological observations in the northern mid latitudes of mars show evidence for past glacial activity during the late amazonian similar to the integrated glacial landsystems in the dry valleys of antarctica the large accumulation of ice many hundreds of meters required to create the observed glacial deposits points to significant atmospheric precipitation snow and ice accumulation and glacial flow in order to understand the climate scenario required for these conditions we used the lmd laboratoire de meteorologie dynamique mars gcm general circulation model which is able to reproduce the present day water cycle and to predict past deposition of ice consistent with geological observations in many cases prior to this analysis however significant mid latitude glaciation had not been simulated by the model run under a range of parameters in this analysis we studied the response of the gcm to a wider range of orbital configurations and water ice reservoirs and show that during periods of moderate obliquity 25 35 and high dust opacity sdust 1 5 2 5 broad scale glaciation in the northern mid latitudes occurs if water ice deposited on the flanks of the tharsis volcanoes at higher obliquity is available for sublimation we find that high dust contents of the atmosphere increase its water vapor holding capacity thereby moving the saturation region to the northern mid latitudes precipitation events are then controlled by topographic forcing of stationary planetary waves and transient weather systems producing surface ice distribution and amounts that are consistent with the geological record ice accumulation rates of 10 mm yr

the mars observer laser altimeter investigation the primary objective of the mars observer laser altimeter mola investigation is to determine globally the topography of mars at a level suitable for addressing problems in geology and geophysics secondary objectives are to characterize the 1064 nm wavelength surface reflectivity of mars to contribute to analyses of global surface mineralogy and seasonal albedo changes to assist in addressing problems in atmospheric circulation and to provide geodetic control and topographic context for the assessment of possible future mars landing sites the principal components of mola are a diode pumped neodymium doped yttrium aluminum garnet laser transmitter that emits 1064 nm wavelength laser pulses a 0 5 m diameter telescope a silicon avalanche photodiode detector and a time interval unit with 10 ns resolution mola will provide measurements of the topography of mars within approximately 160 m footprints and a center to center along track foot print spacing of 300 m along the mars observer subspacecraft ground track the elevation measurements will be quantized with 1 5 m vertical resolution before correction for orbit and pointing induced errors mola profiles will be assembled into a global 0 2 deg x 0 2 deg grid that will be referenced to mars center of mass with an absolute accuracy of approximately 30 m other data products will include a global grid of topographic gradients corrected individual profiles and a global 0 2 deg x 0 2 deg grid of 1064 nm surface reflectivity

possible effects of breaking gravity waves on the circulation of the middle atmosphere of mars a simplified quasi geostrophic beta plane dynamical model of the zonal mean flow is used to investigate the possible effects of breaking internal gravity waves on the circulation in the middle atmospheric region 10 100 km altitude of mars the gravity wave parameterization employed is basically the saturation parameterization of lindzen 1981 which has been utilized in several terrestrial modeling studies numerical simulations are performed for a range of plausible values of the gravity wave parameters and for different representations of the mean flow thermal forcing with a focus on the effects of topographically forced stationary gravity waves on the winter hemisphere circulation the results of the model simulations show that breaking gravity waves of intermediate horizontal scales 100 1000 km wavelengths could act to close off the winter westerly circumpolar jet in the 40 80 km altitude region and induce strong high latitude warming at these levels the latter could explain recent thermal measurements indicating that martian winter polar latitudes may be very warm far above radiative equilibrium in this middle atmospheric region deming et al 1986 for the most plausible range of parameter values breaking gravity waves do not induce much warming below 40 km consistent with available data showing that winter high latitudes are normally very cold at lower levels several dust storm cases indicate that breaking gravity waves possibly could act to induce a very large polar warming at relatively low altitudes such as was observed during the 1977 winter solstice dust storm however quite large gravity wave amplitudes and or relatively long horizontal wavelengths are required for such strong low level effects thermal forcing associated with dust heating might be a source for such anomalous gravity wave activity during a global dust storm summer simulations indicate that breaking gravity waves might alter the mean flow at somewhat higher levels than in the winter hemisphere as a consequence of the presence of westerlies in the lower atmosphere this could explain the presence of a warm summer pole in the recent 50 80 km thermal measurements of deming et al several aspects of the results relating to the middle atmospheric circulation and the polar warming phenomenon are discussed the possible importance of breaking gravity waves for constituent transports in the middle atmosphere of mars is also briefly considered

persistent dust cloud activity on mars near echus chasma in 1978 abstract clouds were recorded by viking cameras during five out of six observations over the same side canyon of echus chasma during a period of over 3 1 2 months in 1978 although these clouds were different from one another in appearance all were bright through a red filter and are believed to be at least partially composed of dust two of them were also imaged in violet light in which they were also bright therefore they may also have contained condensate a plausible explanation for the formation of the dust clouds is drainage winds which are also known to be active to the west in the tharsis region during this season in this case winds may have been flowing downslope from the north rim of tithonium chasma

south polar layered deposits of mars the cratering record data from the mars orbiter laser altimeter mola and mars orbiter camera moc instruments aboard the mars global surveyor mgs were used in a detailed search of a selected part of the south polar layered deposits spld for impact craters impact craters with diameters from 0 8 to 5 km were identified from a mola derived shaded relief map and were primarily validated using individual mola tracks and in select cases moc narrow angle images the resultant crater population determined in this study is at least four times the density of the crater population previously recognized from these new statistics we estimate the mean apparent surface age of the spld to be 30 100 ma depending on the established production model isochrons used all of these craters are considerably shallower than other martian craters in the same diameter range we attribute this shallowness to be the cause of the lower detection rates of previous studies there is a correlation between crater depth and rim height which suggests that both erosion and infilling have affected the crater forms a similar study of the north polar layered deposits uncovered no craters in this diameter range a limited population of craters smaller than 800 m was uncovered in higher resolution moc narrow angle images these do not appear to have been degraded to the same degree this separate population implies a surface exposure age of only 100 000 years and perhaps indicates an event that erased all small craters and degraded and infilled the larger ones

martian south polar cap boundary 1971 and 1973 data abstract international planetary patrol photographs of mars obtained during the 1971 and 1973 apparitions have been used to produce regression curves for the martian south polar cap for those years useful data span the range in areocentric longitude l s 186 261 in 1971 and l s 255 301 in 1973 these regression curves are compared to the 1977 regression curve obtained from viking observations and to the results of 1956 observations there is remarkable consistency between the 1971 ipp and 1977 viking data points and the 1973 regression does not appear to have differed significantly from those of 1971 or 1977

radar and profiler analysis of colliding boundaries a case study abstract the kinematics of a head on collision between two gust fronts followed by a secondary collision between a third gust front and a bore generated by the initial collision are described using analyses of weather surveillance radar 1988 doppler wsr 88d and mobile integrated profiling system mips data each gust front involved in the initial collision exhibited a nearly north south orientation and an east west movement the eastward moving boundary was 2 c colder and moved 7 m s 1 faster than the westward moving boundary two dimensional wind retrievals reveal contrasting flows within each gravity current one exhibited a typical gravity current flow structure while the other assumed the form of a gravity wave current hybrid with multiple vortices atop the outflow one of the after collision boundaries exhibited multiple radar finelines resembling a solitary wave shortly after the collision about 1 h after the initial collision a vigorous gust front intersected the eastward moving bore severa

viking era water ice clouds we have spatially and temporally mapped water ice clouds on mars for 1 25 martian years using the viking infrared thermal mapper irtm data our technique compares brightness temperatures in the 11 and 20 m irtm channels utilizing the 11 m water ice absorption feature a complication arises because of the surface nonunit and wavelength dependent emissivities we developed a technique for removal of this effect using a surface thermal model we calculated brightness temperatures and their differences for the irtm channels resulting from the surface emissivity effect alone these were then subtracted from the measured brightness temperatures yielding brightness temperature differences dominated by atmospheric effects the ability to identify water ice clouds in the infrared provides potential new information about particle size and physical processes by comparing these clouds to those seen in visible wavelengths we found that water ice clouds were more widespread and frequent during the viking period than had been previously recognized with the northern spring and summer being the cloudiest periods on mars we interpret some of the identified cloudy zones as the southern and northern solstice season upwelling branches of the hadley cell although these were shifted 15 20 southward from model predictions additionally the transition between the two branches occurred later in time than in the model predictions we observed the extension of the north polar hood below 60 n in longitudes 120 200 we did not find evidence for a south polar hood north of 60 s nor any evidence for interannual variability within our limited data set

the morning glory of the gulf of carpentaria an atmospheric undular bore abstract this paper presents the results of a field expedition mounted in late september early october 1979 to investigate the structure and origin of the morning glory of the gulf of carpentaria in northern australia the morning glory is a line wind squall accompanied by a pressure jump and often by a long roll cloud or series of such clouds it frequently occurs in the early morning especially in october in the gulf area a light aircraft fitted with a temperature and humidity probe was flown in two glories to determine their thermodynamic structure and wind fields wore obtained principally by tracking pilot balloons using the double theodolite method data also were obtained from a network of surface stations recording wind velocity and pressure installed at locations across cape york peninsula which is believed to be the area of genesis the morning glory is identified as an internal undular bore propagating on the nocturnal and or maritime inversion its origin appears to lie frequently

la desirade island lesser antilles revisited lower cretaceous radiolarian cherts and arguments against an ophiolitic origin for the basal complex la desirade island in the guadeloupe archipelago is a keystone of the structural framework of the lesser antilles island arc hypothetical ophiolitic series and wide discrepancy in the radiometric datings of its igneous basement have raised considerable debate concerning the structural significance of this island and the geodynamic constraints for the caribbean plate recent detailed field work leads to a reconsideration of the problem the volcanic basement of la desirade can be subdivided into three independent units the cherts interbedded in the unit 2 basalts contain hauterivian barremian radiolarians that represent the oldest biostratigraphic assemblage found in the lesser antilles this affirms the jurassic radiometric age of the unit 1 trondhjemite outcrop observations and analyses allow us to discard the concept of an ophiolitic origin for la desirade whose basement was generated like the northern half of the lesser antilles arc by island arc processes during the mesozoic

valles marineris cloud trails 1 distinctive cloud trails are identified in mars reconnaissance orbiter mars color imager marci images over specific locations associated with valles marineris and noctis labyrinthus and at perihelion solar longitudes l s 230 260 high contrast surface shadows are well defined as cast from their eastern margins supporting altitude and optical depth determinations these relatively high altitude clouds 40 50 km exhibit narrow latitudinal widths 25 75 km in comparison to extended longitudinal dimensions 400 1000 km marci multispectral imaging of cloud surface shadows in five wavelength channels 260 320 437 546 and 653 nm yields the wavelength dependence of cloud extinction optical depth revealing a range of small cloud particle sizes r eff 0 2 0 5 m and moderate cloud optical depths 0 03 0 10 visible and 0 1 0 2 ultraviolet local time and temporal sampling characteristics of marci cloud images indicate that these clouds develop very rapidly in afternoon hours 1300 1500 lt reach their full longitudinal extents within 2 h time scales and often reoccur on successive afternoons mars global surveyor mars orbital camera imaging in previous mars years indicates these clouds are annually repeating these observed characteristics suggest a cloud formation mechanism that is specific to 50 km horizontal and vertical scales transports water vapor and dust upward from lower levels exists during the afternoon and is likely associated with the mesoscale atmospheric circulations induced by the near equatorial canyons of mars cloud particles formed in such updrafts would then be rapidly transported westward in the strong retrograde zonal circulation of the subsolar middle atmosphere in this season

hurricane control on shelf edge reef architecture around grand cayman rimming the outer shelf of grand cayman is a submerged 87 km long shelf edge reef that rises to within 12 m of mean sea level it consists of an array of coral armoured buttresses aligned perpendicular to shore and separated by steep sided sediment floored canyons individual buttresses have a diverse coral dominated biota and consist of three architectural elements a shield like front wall colonized by platy corals a dome shaped crown colonized by head corals and a shoreward projecting spur covered by varying amounts of branching coral buttresses are commonly fronted by coral pinnacles that in some areas have amalgamated with buttress walls to produce pinnacle and arch structures as margin orientation changes shelf edge reef architecture shows systematic variations that are consistent with changes in fetch and height of hurricane waves along margins exposed to fully developed storm waves shelf edge reef buttresses are deep have large amplitudes and are dominated by robust head corals these characteristics are consistent with hurricane induced pruning of branching corals and the flushing of significant quantities of sand from buttress canyons by return flows along margins impacted by fetch limited storm waves reef buttresses are shallower have intermediate amplitudes and have a significantly higher proportion of branching corals these characteristics are consistent with less coral pruning and sand flushing by weaker hurricane waves along margins fully protected from storm waves the buttresses canyon architecture of the shelf edge reef breaks down producing a series of shallow undulating branching coral dominated ridges that merge laterally into an unbroken belt of coral these characteristics correspond with negligible amounts of pruning and flushing during hurricanes in addition to differences between margins local intra marginal changes in shelf edge reef architecture are consistent with changes in the angle of hurricane wave approach open sections of the shelf edge reef which face directly into storm waves are pruned of branching corals and the fragments swept back onto the shelf producing extensive spurs by contrast on more sheltered obliquely orientated sections storm waves sweep debris along and off shelf producing little or no spur development instead the debris shed seawards accumulates in front of the buttress walls and initiates the development of coral pinnacles over time repeated buttress pruning and canyon flushing during hurricanes not only controls reef architecture but may also influence accretion patterns vertical accretion is limited by the effective depth of storm wave fragmentation once this hurricane accretion threshold is reached the reef moves into a shedding phase and accretes laterally via pinnacle growth amalgamation and infilling consequently the reef steps out over its own debris in a kind of balancing act between lateral growth and slope failure a pattern widely recognized in ancient reefs

coral reefs and sea level change abstract coral reefs provide significant evidence for former sea level positions because of their geological preservation and suitability for dating interpretation of this evidence presumes an understanding of reef geomorphology modern reef organism distributions and environmental factors influencing them fossil reef terraces formed during the last interglacial marine oxygen isotope mis substage 5e 128 116 ka are prevalent on many tropical shorelines and there has been ongoing debate as to the height reached by sea level during that highstand observations from numerous last interglacial sites suggest that sea level was at least 3 m above present sea level implying less extensive icesheets than at present an elevation of 6 m has commonly been adopted when correcting tectonically active sites for uplift recent compilations suggest elevations up to 8 9 m but incorporate few observations from reefs where the last interglacial is found below sea level oscillation of sea level during mis 5e has been interpreted from several sites with recent studies inferring rapid rise of several metres at the end of the interglacial these interpretations are at the limits to the precision with which corals can currently be dated and their palaeo water depths inferred it is not surprising that constraining last interglacial sea level changes within uncertainties of less than 1 2 m remains controversial considering sea level variations recognised between reef sites in the holocene and observed geographical variation in isostatic or flexural adjustments fossil coral reefs on uplifting margins also provide clear evidence for mis substages 5c and 5a and those on huon peninsula indicate fluctuations related to heinrich events mis 3 interpretations show considerable variability between sites with still greater uncertainties about sea level timing and elevation during previous interglacials future study of extensive sequences of fossil reefs preserved on rapidly subsiding margins could address these uncertainties submerged reefs have already yielded important information about sea level rise during the last deglaciation coring around barbados and tahiti as well as on the huon peninsula has produced a broadly consistent picture of ice melt reflecting eustatic change since the last glacial maximum these studies have shown the sensitivity of reefs to rapid sea level rise associated with meltwater pulses with some reefs drowning while others back stepped integrated ocean drilling program iodp expeditions to tahiti and recently the great barrier reef extended these records but details of timing nature and impact of deglacial meltwater pulses remain elusive studies of holocene reefs have indicated different growth strategies some kept up with sea level while others caught up when sea level decelerated holocene sea level appears to have experienced a gradual rise up to present across the caribbean providing accommodation space for reefs to accrete vertically whereas in the indo pacific sea level has been near its present level since 7 ka with many reef flats emergent following a slight fall of sea level caused by ocean siphoning microatolls on reef flats provide perhaps the clearest evidence of past sea level position but in their absence novel biological or other sea level indicators are required to better constrain palaeo water depths there is an urgent need for further research from additional key reef locations not only to decipher processes driving past sea level change and its geographical variability but also to better understand how coral reefs will respond in the context of future sea level rise

mars observer camera the mars observer camera moc is a three component system one narrow angle and two wide angle cameras designed to take high spatial resolution pictures of the surface of mars and to obtain lower spatial resolution synoptic coverage of the planet s surface and atmosphere the cameras are based on the push broom technique that is they do not take frames but rather build pictures one line at a time as the spacecraft moves around the planet in its orbit moc is primarily a telescope for taking extremely high resolution pictures of selected locations on mars using the narrow angle camera areas ranging from 2 8 km 2 8 km to 2 8 km 25 2 km depending on available internal digital buffer memory can be photographed at about 1 4 m pixel additionally lower resolution pictures to a lowest resolution of about 11 m pixel can be acquired by pixel averaging these images can be much longer ranging up to 2 8 500 km at 11 m pixel high resolution data will be used to study sediments and sedimentary processes polar processes and deposits volcanism and other geologic geomorphic processes the moc wide angle cameras are capable of viewing mars from horizon to horizon and are designed for low resolution global and intermediate resolution regional studies low resolution observations can be made every orbit so that in a single 24 hour period a complete global picture of the planet can be assembled at a resolution of at least 7 5 km pixel regional areas covering hundreds of kilometers on a side may be photographed at a resolution of better than 250 m pixel at the nadir such images will be particularly useful in studying time variable features such as lee clouds the polar cap edge and wind streaks as well as acquiring stereoscopic coverage of areas of geological interest the limb can be imaged at a vertical and along track resolution of better than 1 5 km different color filters within the two wide angle cameras permit color images of the surface and atmosphere to be made to distinguish between clouds and the ground and between clouds of different composition

the formation of internal bores in the atmosphere a laboratory model summary recently several atmospheric observations have been interpreted as internal undular bores or internal solitary waves evolving from internal bores that propagate along low level temperature inversions it has been speculated that such disturbances are generated by some type of gravity current such as cold fronts sea breeze fronts and thunderstorm outflows interacting with an existing temperature inversion in this paper we describe a systematic laboratory study in a water channel of internal bores and their generation by the movement of gravity currents through a two layer model of the atmosphere we compare the results of our laboratory experiments with previous theories and numerical simulations and with several detailed atmospheric observations of internal bores at different stages of development

global patterns in cloud forms on mars abstract mariner 9 images and all viking orbiter images through july 1979 were searched for cloud forms a computer accessible catalog was assembled consisting of a classification of cloud type lee wav wave for example and properties directionality wavelength for example lee wave directionality shows a pattern and seasonal variation at high latitudes which is consistent with predictions of theoretical modeling fog and haze occurrence shows no obvious correlation with water abundance or any other simple causal factor lee waves are rare at equatorial latitudes plumes probably dust occur preferentially at locations where strong boundary layer convection is expected