reduction in northward incursions of the south asian monsoon since 1400 ad inferred from a mt everest ice core 1 a highly resolved mt everest ice core reveals a decrease in marine and increase in continental air masses related to relatively high summer surface pressure over mongolia and reduction in northward incursions of the summer south asian monsoon since 1400 ad previously published proxy records from lower sites south of the himalayas indicate strengthening of the monsoon since this time these regional differences are consistent with a south north seesaw in convective activity in the asian monsoon region and reflect a southward shift in the mean summer position of the monsoon trough since 1400 ad the change in monsoonal circulation at 1400 ad is synchronous with a reduction in solar irradiance and the onset of the lia this demonstrates a hemispheric scale circulation reorganization at this time and the potential for future large shifts in monsoonal circulation

tree ring δ 18 o a tool to crack the paleo hydroclimatic code in subtropical china abstract tree ring plays an important role in deciphering the paleoclimatic signals although tree ring width trw has obvious advantages in studying the hydroclimatic history in the middle high latitudes it has certain limitation in hydroclimatic signal extraction in the tropical to subtropical areas which greatly limits our fully understanding about the hydroclimatic history in these areas in this work tree ring 18o 18otree records from five independent tree ring cores were measured and a composite 18otree record 1939 2014 was developed in guilin subtropical southwest china no juvenile effect existed in this 18otree record and no relationship was found between 18otree and trw correlation analysis with the climatic parameters demonstrated that the 18otree record significantly p

measurement of eolian sand ripple cross sectional shapes assuming that the profiles of eolian sand ripples remain constant over a short distance it is possible to measure their shapes by casting a shadow perpendicular to the ripple crests we describe a method whereby this can be done accurately and easily tests of the method demonstrate that accuracies on the order of one sand grain diameter can be achieved

planetary dune analogues a special issue on integrating models remote sensing and field data this article reports on the special issue of earth surface processes and landforms dedicated to planetary dune analogues and the advances that have been made through the integration of remote sensing and terrestrial field data to better model and understand aeolian systems the 11 articles presented demonstrate a spectrum of analytical techniques that are employed to investigate ripples dunes draa and ergs across a variety of spatial and temporal scales nine of the papers involve innovative research about aeolian bedforms and processes while the final two papers are examples of how vast quantities of data may be organized and scrutinized using a giscience approach based on these 11 papers and the many abstracts archived in a series of three planetary dunes workshops at the lunar planetary institute http www lpi usra edu publications abstracts shtml lpi contributions 1403 1552 and 1673 it is evident that there exists diverse and complementary approaches to the comparative study of landforms and processes for terrestrial and extra terrestrial aeolian landscapes that is driven by a vibrant international community of scientists and educators that engage in the cross fertilization of ideas copyright 2014 john wiley sons ltd

seasonal incursion of indian monsoon humidity and precipitation into the southeastern qinghai tibetan plateau inferred from tree ring δo18 values with intra seasonal resolution abstract incursion of the indian monsoon flow onto the qinghai tibetan plateau is an important regional moisture delivery mechanism but the causes of intra seasonal and longer term variations are poorly understood we observed a clear intra seasonal cycle in the oxygen isotope composition 18o of smith fir abies forrestii var georgei growing at two different altitudes high elevation site 29 39 n 94 42 e 4200 m a s l low elevation site 29 39 n 94 43 e 3800 m a s l on a se facing slope in the sygera mountains southeastern qinghai tibetan plateau mechanistic modeling suggests that 18o of precipitation which in turn depends on relative humidity and precipitation amount is important in controlling the intra seasonal tree ring isotopic cycle and we speculate that the same controls also operate on interannual and longer time scales if so multi century 18o records with intra seasonal resolution may enable us to infer long term variations in the incursion of the indian monsoon onto the qinghai tibetan plateau

patterns of earthquakes and the effect of solid earth and ocean load tides at mount st helens prior to the may 18 1980 eruption seismographs near mount st helens volcano recorded an earthquake swarm lasting nearly 2 months prior to the catastrophic may 18 1980 eruption the earthquakes are divided into four classes based on station cpw 116 km seismogram characteristics 1 events with sv p amplitude ratio 3 and dominant frequency 3 hz 2 events with sv p ratio between 1 and 3 and dominant frequency 2 hz 3 events similar to characteristic 2 but with a strong probably surface wave phase just after the s phase and 4 events with frequencies between 1 and 2 hz lacking a clear s phase the seismicity pattern for each of the four classes is unique and we assume each group of events with similar wave forms represents a common physical process depth source area or fault orientation maximum likelihood b values range between 0 97 0 05 and 1 81 0 09 for the four groups we calculate solid earth stress and strain tides at the average hypocentral depth of 4 km we also calculate stress and strain tides induced by ocean loading their amplitudes are typically 20 40 those of the solid earth tides at the location of mount st helens a weak but significant correlation exists between the latter two classes of events and the tides for a time interval of about 5 days preceding the first onset of volcanic tremor and about 5 days thereafter the polarity of the correlation is opposite for the two classes of events in each case the phase of the correlation changes systematically with time the changes coinciding with the onset of tremor on march 31 and with a pronounced decrease in earthquake energy release rate on april 3 there are no significant correlations between the tides and the number of events or energy release of these two classes of earthquakes during any other interval between march 20 and may 18 1980 the first two classes of events show no evidence of significant tidal correlation at any time during the study period

latitude dependent nature and physical characteristics of transverse aeolian ridges on mars 1 narrow angle images from the mars orbiter camera moc have revealed the common occurrence of small scale 100 m wavelength bright transverse aeolian ridges tars on the surface of mars moc images were used to assess the broad distribution of tars from 90 n to 90 s between 180 e and 240 e to investigate their relationship to latitude elevation thermal inertia geologic units local slopes and surface roughness out of 5112 examined images from the primary mission 520 10 contain evidence of tars 92 of the images with tars are located between 50 latitude and very few occur in the middle to upper latitudes or polar regions of either hemisphere tars are observed at elevations from 5 km to 3 km with the highest frequency 26 between 1 and 0 km there is no systematic relationship between the distribution of tars and global thermal inertia measurements most tars occur in geologic units associated with the channel system materials 39 and the olympus mons aureole 33 at a length scale of 1 85 km pixel the average local slopes for images with and without tars are 1 92 and 1 36 respectively of the parameters investigated the latitudinal trend of tars in both hemispheres appears to be predominantly related to surface roughness with a positive linear correlation between the surface roughness of geologic units and frequency of tars r2 0 87 factors affecting the semiglobal distribution of tars are likely related to the climate and wind regimes in which they formed but do not provide definitive evidence for either saltation or reptation formation mechanisms

modeling of surface deformation in volcanic areas the 1970 1972 and 1982 1984 crises of campi flegrei italy campi flegrei is a densely inhabited volcanic area within a caldera 12 14 km in diameter immediately west of naples italy in 1970 1972 and in 1982 1984 campi flegrei experienced considerable ground surface deformation producing a bulge about 3 5 m high at its peak in the two inflation episodes the point of maximum uplift did not change coinciding with the caldera center about which the displacements exhibited radial symmetry the 1982 1984 uplift was accompanied by considerable seismic activity gravity changes have been interpreted as reflecting the occurrence of a subvertical magmatic intrusion volcanological petrological and geophysical data point to the existence of a shallow magma chamber just beneath the center of the caldera we assume that the observed surface displacements are the response of an essentially elastic medium to a pressure increase in the magma chamber static deformation is calculated by using a finite element method assuming axial symmetry around a vertical axis through the caldera center the role played by various components of the model geometry boundary conditions elastic properties is analyzed it is shown that models assuming uniform elasticity are inadequate therefore the major volcanotectonic features as well as the influence of temperature and pressure on the elastic properties are taken into account the results of various more complex models are presented it is suggested that a progressively fractured zone whose size and shape depend also on the possible occurrence of magmatic intrusions may explain the observed surface displacements and the other data collected at campi flegrei it is suggested that the 1970 1972 uplift was possibly accompanied by larger scale changes in the stress field

spatial analysis of sand dunes with a new global topographic dataset new approaches and opportunities on june 29 2009 version 1 of the aster gdem advanced spaceborne thermal emission and reflection radiometer global digital elevation model was made available at no cost or restrictions to users worldwide via electronic download the aster gdem provides expanded spatial coverage and better resolution than other global digital elevation models dems in this paper we demonstrate how the aster gdem provides new opportunities for investigating large aeolian sand dunes in three dimensions two dune specific spatial analysis methods are presented to illustrate potential applications of these data for discriminating dune generations and quantifying spatial variations of sediment supply moreover we review how existing and emerging fields of dune pattern analysis and simulation modeling will be able to make significant advances through application of these data potentially leading to future progress in studies of dune morphodynamics environmental controls and paleoenvironmental reconstructions copyright 2010 john wiley sons ltd

changes in active eolian sand at northern coachella valley california abstract climate variability and rapid urbanization have influenced the sand environments in the northern coachella valley throughout the late 20th century this paper addresses changes in the spatial relationships among different sand deposits at northern coachella valley between two recent time periods by using satellite data acquired from the advanced spaceborne thermal emission and reflection radiometer aster the approach employed here involving multispectral thermal infrared tir data and spectral mixture analysis has shown that the major sand deposits can be spatially modeled at northern coachella valley the coarse grained quartz rich sand deposit is associated with active eolian sand and the mixed sandy soil and fine grained quartz rich sand deposits are associated with inactive eolian sand the fractional abundance images showed a significant decrease between 2000 and 2006 in the percentage of active sand in the major depositional area for fluvial sediment the whitewater river but also in two downwind areas the whitewater and willow hole reserves the pattern of the active sand appears to be related to variations in annual precipitation wet and dry years and river discharge in the northern coachella valley we suggest here that recent human modifications to the major watercourses that supply sand affect the capability of fluvial deposition areas to restore sediments over time and consequently the responses of the sand transport system to climate change becoming more sensitive to dry years where areas of active sand may shrink degrade and or stabilize faster the approach utilized in this study can be advantageous for future monitoring of sand in the northern coachella valley for management of these and similar environments

megaripple flattening due to strong winds abstract megaripples in nahal kasuy in the southern negev desert of israel are characterized by a mean wavelength of about 70 cm and by a bimodal distribution of coarse and fine particle sizes the latter property being a pre requisite for their formation in our three year project megaripple development was monitored using a digital elevation model dem constructed from above ground stereo digital photographs temporal dynamics of wind power drift potential dp were measured and grain size analyses were performed on samples taken from different parts of the megaripple the coarse grains that protect the crest enable the ripple to grow but when ripple height becomes too high the bed shear stress increases thus allowing the wind to move the armoring layer when this happens during strong wind storms the megaripple will flatten and even disappear as was observed in our field study we present measurements that for the first time directly show the megaripple to normal ripple transition and we suggest two possible physical processes as potential causes of this phenomenon megaripple flattening can occur either when the wind exceeds the fluid threshold for a sufficient length of time or after a sequence of storms with winds blowing from the same direction

transverse aeolian ridges tars on mars aeolian processes are probably the dominant ongoing surface modification process on mars as demonstrated by observations of dunes ripples yardangs ventifacts wind streaks dust devils and dust storms large dark dunes ldds are particularly common and were first recognized in the 1960 s from mariner data however another population of smaller often brighter ripple like aeolian bed forms that are morphologically distinct from ldds has been observed in recent higher resolution images calculations of saltation path length under martian conditions suggest these small bed forms could have formed as small barchanoid dunes or as mega ripples also known as granule ripples these features have therefore been called transverse aeolian ridges tars as this label has no genetic inference we have begun a study of tars that examines all high resolution mars orbiter camera data 1 5 to 8 m pixel resolution in a 45o longitude wide pole to pole swath we aim to determine the geographic distribution of tars assess whether they are active and to identify possible sediment sources we have already made some key observations first we present a new classification of tar deposits based on crest ridge morphology of individual forms and the size and degree of topographic control of the entire sediment mass second we present associations of tars with ldds slope streaks dust devils tracks and small impact craters that provide clues as to whether tars are currently active finally we present preliminary pole to pole survey results for the northern hemisphere that show clusters of tar deposits in the low latitudes suggesting possible unique sediment sources in these regions

modelling of surface ground deformations in the phlegraean fields volcanic area italy a preliminary finite elements model of the ground deformations observed at phlegraean fields is proposed the model assumes an oblate spheroid magma chamber at the depth of 5 4 km with major semiaxis of 1 5 km and minor semiaxis of 0 75 kin the dimensions of the magma chamber have been evaluated by using a thermal model based on the assumptions that a progressively cooling huge magmatic body is responsible for the volcanic activity at phlegraean fields in the last 35 000 years surface deformations caused by an overpressure of 30 mpa in the magma chamber have been calculated constant and temperature dependent elastic parameters of the surrounding medium have been considered vertical displacements of the order of those presently observed at phlegraean fields can be obtained only with temperature dependent elastic properties of the medium

the rate of granule ripple movement on earth and mars abstract the rate of movement for 3 and 10 cm high granule ripples was documented in september of 2006 at great sand dunes national park and preserve during a particularly strong wind event impact creep induced by saltating sand caused 24 granules min 1 to cross each cm of crest length during wind that averaged 9 m s 1 at a height well above 1 m which is substantially larger than the threshold for saltation of sand extension of this documented granule movement rate to mars suggests that a 25 cm high granule ripple should require from hundreds to thousands of earth years to move 1 cm under present atmospheric conditions

transverse aeolian ridges tars on mars ii distributions orientations and ages transverse aeolian ridges tars 10 m scale ripple like aeolian bedforms with simple morphology are widespread on mars but it is unknown what role they play in mars wider sediment cycle we present the results of a survey of all mars global surveyor narrow angle images in a pole to pole study area 45 longitude wide following on from the classification scheme and preliminary surveys of balme et al balme m r berman d c bourke m c zimbelman j r 2008a geomorphology 101 703 720 and wilson and zimbelman wilson s a zimbelman j r 2004 j geophys res 109 e10 doi 10 1029 2004je002247 we searched more than 10 000 images and found that over 2000 reveal at least 5 areal cover by tars the mean tar areal cover in the study area is about 7 3 in the northern hemisphere and 11 in the southern hemisphere but tars are not homogenously distributed they are concentrated in the mid low latitudes and almost absent poleward of 35 n and 55 s we found no clear correlation between tar distribution and any of thermal inertia kilometer scale roughness or elevation we did find that tars are less common at extremes of elevation we found that tars are most common near the equator especially in the vicinity of meridiani planum in which area they have a distinctive barchan like morphology and in large southern hemisphere impact craters tars in the equatorial band are usually associated with outcrops of layered terrain or steep slopes hence their relative absence in the northern hemisphere tars in the southern hemisphere are most commonly associated with low albedo intercrater dune fields we speculate that the mid latitude mantling terrain e g mustard j f cooper c d rifkin m k 2001 nature 412 411 414 kreslavsky m a head j w 2002 j geophys res 29 15 doi 10 1029 2002gl015392 could also play a role in covering tars or inhibiting saltation we compared tar distribution with general circulation model gcm climate data for both surface wind shear stress and wind direction we performed gcm runs at various obliquity values to simulate the effects of changing obliquity on recent mars climate we found good general agreement between tar orientation and gcm wind directions from present day obliquity conditions in many cases but found no good correlation between wind shear stress and tar distribution we performed preliminary high resolution crater count studies of tars in both equatorial and southern intracrater dunefield settings and compared these to superposition relationships between tars and large dark dunes our results show that tars near dunefield appear to be younger than tars in the equatorial regions we infer that active saltation from the large dunes keeps tars active but that tars are not active under present day condition when distal to large dunes perhaps supporting the interpretation that tars are granule ripples we conclude that local geology rather than wind strength controls tar distribution but that their orientation matches present day regional wind patterns in most cases we suggest that tars are likely most perhaps only active today when they are proximal to large dark dune fields

the time evolution of vertical ground movements in the campei flegrei caldera a kinetic phenomenological model abstract several ground uplift episodes accompanied by an increase of fumarolic and seismic activity took place in recent times in the campi flegrei volcanic area close to naples although many researchers have focused their efforts on this highly hazardous area complexities are such that a detailed understanding of the uplift crises in terms of cause effect is still to come we present a new global phenomenological approach based on the kinetics of irreversible processes we consider the whole campi flegrei volcanic and subvolcanic system as a thermodynamic system whose equilibrium or steady state corresponds to a resting state of the ground a ground uplift crisis takes place when a thermodynamic instability forms in one or more subsystems and the whole system moves toward a new equilibrium or steady state under these assumptions the time evolution of the ground level in campi flegrei can be described as relaxation kinetics we use a theoretical equation that was derived by non equilibrium thermodynamics for autocatalytic or self cooperative processes we analyze in detail the 1982 1985 period one of the characteristics is that seismic activity began several months later than the onset of the ground uplift we describe the ground level evolution as the sum of three consecutive long steps and the and steps are positive i e represent uplift episodes the step is negative and represents the subsidence which followed the uplift the growth pulse of the ground uplift which is more self cooperative than the step appears to describe surprisingly well also the seismic energy release moreover a preliminary analysis shows that the 1970 1972 uplift crisis took place with the same sequence of steps each step being characterized by the same time constant 2 as in 1982 1985 it thus seems that the and steps reflect different processes in the subvolcanic system and that the step is responsible for the seismic activity

ground deformation measurements in active volcanic areas using tide gauges a new method of tide gauge data analysis is described for detecting ground deformation in active volcanic areas this method was tested in the phlegraean fields an active volcanic area near naples where in 1970 after a large ground uplift a dense tide gauge network was installed

seasonal temperature and precipitation recorded in the intra annual oxygen isotope pattern of meteoric water and tree ring cellulose abstract modern and ancient wood is a valuable terrestrial record of carbon ultimately derived from the atmosphere and oxygen inherited from local meteoric water many modern and fossil wood specimens display rings sufficiently thick for intra annual sampling and analytical techniques are rapidly improving to allow for precise carbon and oxygen isotope measurements on very small samples yielding unprecedented resolution of seasonal isotope records however the interpretation of these records across diverse environments has been problematic because a unifying model for the quantitative interpretation of seasonal climate parameters from oxygen isotopes in wood is lacking towards such a model we compiled a dataset of intra ring oxygen isotope measurements on modern wood cellulose 18ocell from 33 globally distributed sites five of these sites represent original data produced for this study while the data for the other 28 sites were taken from the literature we defined the intra annual change in oxygen isotope value of wood cellulose 18ocell as the difference between the maximum and minimum 18ocell values determined within the ring then using the monthly resolved dataset of the oxygen isotope composition of meteoric water 18omw provided by the global network of isotopes in precipitation database we quantified the empirical relationship between the intra annual change in meteoric water 18omw and 18ocell we then used monthly resolved datasets of temperature and precipitation to develop a global relationship between 18omw and maximum minimum monthly temperatures and winter summer precipitation amounts by combining these relationships we produced a single equation that explains much of the variability in the intra ring 18ocell signal through only changes in seasonal temperature and precipitation amount r2 0 82 we show how our recent model that quantifies seasonal precipitation from intra ring carbon isotope profiles can be incorporated into the oxygen model above in order to separately quantify both seasonal temperature and seasonal precipitation determination of seasonal climate variation using high resolution isotopes in tree ring records makes possible a new understanding of the seasonal fluctuations that control the environmental conditions to which organisms are subject both during recent history and in the geologic past

controls on the height and spacing of eolian ripples and transverse dunes a numerical modeling investigation abstract ripples and transverse dunes in areas of abundant sand supply increase in height and spacing as a function of time grain size and excess shear velocity how and why each of these factors influence ripple and transverse dune size however is not precisely known in this paper the controls on the height and spacing of ripples and transverse dunes in areas of abundant sand supply are investigated using a numerical model for the formation of eolian bedforms from an initially flat surface this bedform evolution model combines the basic elements of werner s werner b t 1995 eolian dunes computer simulations and attractor interpretation geology 23 1107 1110 cellular automaton model of dune formation with a model for boundary layer flow over complex topography particular attention is paid to the relationship between bed shear stress and slope on the windward stoss side of evolving bedforms nonlinear boundary layer model results indicate that bed shear stresses on stoss slopes increase with increasing slope angle up to approximately 20 then decrease with increasing slope angle as backpressure effects become limiting in the bedform evolution model the linear boundary layer flow model of jackson and hunt jackson p s hunt j c r 1975 turbulent wind flow over a low hill quarterly journal of the royal meteorological society 101 929 955 generalized to 3d is modified to include the nonlinear relationship between bed shear stress and slope bed shear stresses predicted by the modified jackson and hunt flow model are then used to predict rates of erosion and deposition iteratively through time within a mass conservative framework similar to werner werner b t 1995 eolian dunes computer simulations and attractor interpretation geology 23 1107 1110 beginning with a flat bed the model forms ripples that grow in height and spacing until a dynamic steady state condition is achieved in which bedforms migrate downwind without further growth the steady state ripple spacing predicted by this model is approximately 3000 times greater than the aerodynamic roughness length of the initially flat surface which is a function of grain size and excess shear velocity once steady state ripples form they become the dominant roughness element of the surface the increase in roughness associated with ripple formation triggers the same bedform instability that created ripples causing dunes to form at a larger scale in this way the numerical model of this paper suggests that ripples and dunes are genetically linked transverse dunes in this model have a steady state height and spacing that is controlled by the effective roughness length of the rippled surface which is shown to be on the order of 500 times greater than the original roughness length but varies significantly with the details of ripple morphology the model predictions for ripple and dune spacing and their controlling variables are consistent with field measurements from the published literature the model of this paper provides a preliminary process based understanding of the granulometric control of ripples and dunes in areas of abundant sand supply and unidirectional prevailing winds and it argues for a genetic linkage between ripples and dunes via a scaling relationship between eolian bedform size and the aerodynamic roughness length

relations between dune morphology air flow and sediment flux on reversing dunes silver peak nevada relations between wind speed sediment flux and dune morphology were measured for two reversing dunes situated in the south western part of the silver peak dunefield in clayton valley west central nevada the larger dune was 120 m in length with a height of 12ae5 m and the smaller dune 80 m long and 6 m high both dunes were sharp crested aligned approximately e w perpendicular to the dominant wind direction and had slightly concave stoss profiles twenty seven rotating cup anemometers were placed 0ae3 m elevation along n s transects on each of the dunes at each anemometer site a passive wedge shaped sediment trap was used to measure sediment flux amplification of wind speed was observed towards the crest on the stoss side of both dunes with speed up factors ucrest ubase ranging from 1ae50 3ae19 with a corresponding increase in sediment flux by 1 2 orders of magnitude in general the ratio of crest flux to base flux qc qb increased with increasing incident basal wind speed on both dunes direct measurements of the stoss slope variation in sediment flux relative to the dune crest are in good agreement with owen s transport model friction speed u was approximated from near surface 0ae3 m point wind speed although not all assumptions of the owen model are upheld the modified model performance is sufficiently robust to predict short term variation in stoss sediment flux on the study dunes improved models that adequately account for variation in sediment flux under changing air flow and transport conditions are necessary for the prediction of longterm evolution of dunes in this regard further progress in model development will require increased understanding of the spatial and temporal variability of airflow and the short term response of sediment flux to these flow conditions

a preliminary study of stress pattern at phlegraean fields as inferred from focal mechanisms thirty seven selected earthquakes which occurred in phlegraean fields from april to december 1983 are investigated from the focal mechanism point of view in order to attempt a preliminary representation of the stress pattern in the area from 37 earthquakes 15 reliable solutions were obtained ten mechanisms for events located around the solfatara crater are of tensional type 2 located in the gulf of pozzuoli seem to be compressive no predominant orientation ofp andt axes seem to occur evidently a more accurate analysis with a greater number of data in particular for compressive events is necessary in order to resolve a detailed map of stress pattern

geothermal energy release at the solfatara of pozzuoli phlegraean fields phreatic and phreatomagmatic explosion risk implications the h2o co2 and h2s outputs at the solfatara of pozzuoli have been measured and a map of the exhaling areas has also been made the energy released at the surface by the fluids has been estimated to be 1019 ergs day

grainfall processes in the lee of transverse dunes silver peak nevada grainfall deposition and associated grainflows in the lee of aeolian dunes are important in that they are preserved as cross beds in the geological record and provide a key to the interpretation of the aeolian rock record despite their recognized importance there have been very few field laboratory or numerical simulation studies of leeside depositional processes on aeolian dunes as part of an ongoing study the relationships among grainfall wind speed and direction stoss sand transport rates and dune morphometry height and aspect ratio were investigated on four relatively small straightcrested transverse dunes at silver peak nevada between 55 and 95 of the total grainfall was found to be deposited within 1 m of the crest and 84 99 within 2 m depending primarily on dune size and shape grainfall decay rates on high dunes of large aspect ratio were observed to be very consistent with a weak positive dependence on wind speed for small dunes with low aspect ratios grainfall deposition was more varied and decreased rapidly within 1 m of the dune crest whereas at increased distance from the dune crest it eventually approached the smaller decay rates observed on the large dunes no dependence of grainfall on wind speed was observed for these small dunes comparison of field data with predictions from anderson s 1988 saltation model of grainfall based on the computation of saltation path lengths indicates lack of agreement in the following areas 1 deposition rate magnitude 2 variation in decay rate with wind speed and 3 the magnitude and location of the localized lee slope depositional maxima the silver peak field results demonstrate the importance of dune aspect ratio and related wake effects in determining the rate and pattern of grainfall this work confirms earlier speculation by mcdonald anderson 1995 that temporary turbulent suspension or modified saltation of relatively large grains does occur within the dune wake so that transport distances generally are larger than predicted by numerical simulations of true saltation

medium and long period ground oscillatory pattern inferred by borehole tiltmetric data new perspectives for the campi flegrei caldera crustal dynamics abstract we analyse tiltmetric time series recorded at borehole instruments recently installed at campi flegrei caldera italy a volcanic area subjected to the phenomenon of bradyseism which consists in fast ground uplift phases alternated to slow subsidence for the first time we evaluate the crustal response in terms of ground tilting of the entire caldera to external excitations such as long medium period tidal constituents by adopting independent component analysis indeed we recognize diurnal solar and long period fortnightly and monthly components superimposed to the normal deformation trend of the area they show well defined polarization directions and are associated with an oscillatory deformation pattern with the same periodicity of the corresponding tidal constituents the comparison with the local geology evidences that the tidal tilting is controlled by the local stress field distribution and the rheology thus inducing structural and thermoelastic site effects

strong influence of water vapor source dynamics on stable isotopes in precipitation observed in southern meghalaya ne india to calibrate 18o time series from speleothems in the eastern indian summer monsoon ism region of india and to understand the moisture regime over the northern bay of bengal bob we analyze the 18o and d of rainwater collected in 2007 and 2008 near cherrapunji india d values range from 18 5 to 144 4 while 18o varies between 0 8 and 18 8 the local meteoric water line lmwl is found to be indistinguishable from the global meteoric water line gmwl late ism september october rainfall exhibits lowest 18o and d values with little relationship to the local precipitation amount there is a trend to lighter isotope values over the course of the ism but it does not correlate with the patterns of temperature and rainfall amount 18o and d time series have to be interpreted with caution in terms of the amount effect in this subtropical region we find that the temporal trend in 18o reflects increasing transport distance during the ism isotopic changes in the northern bob surface waters during late ism and vapor re equilibration with rain droplets using an isotope box model for surface ocean waters we quantify the potential influence of river runoff on the isotopic composition of the seasonal freshwater plume in the northern bob temporal variations in this source can contribute up to 25 of the observed changes in stable isotopes of precipitation in ne india to delineate other moisture sources we use backward trajectory computations and find a strong correlation between source region and isotopic composition palaeoclimatic stable isotope time series from northeast indian speleothems likely reflect changes in moisture source and transport pathway as well as the isotopic composition of the bob surface water all of which in turn reflect ism strength stalagmite records from the region can therefore be interpreted as integrated measures of the ism strength

precipitation stable isotope records from the northern hengduan mountains in china capture signals of the winter india burma trough and the indian summer monsoon abstract this project reports results of the first precipitation stable isotope 18 o and d time series produced for qamdo in the northern hengduan mountains in the southeastern tibetan plateau the data showed that the fluctuations of precipitation stable isotopes at qamdo during the different seasons revealed various moisture sources the westerlies and local recycling moisture dominated at the study area before the pre monsoon and after the post monsoon seasons which resulted in similar trends of both precipitation stable isotopes and temperature the marine moisture was transported to the northern hengduan mountains by the winter india burma trough combined with convection consequently stable isotopes in subsequent precipitation were occasionally observed to decrease suddenly however 18 o and d values of precipitation at qamdo were lower during the monsoon period and the duration of those low values was longer because of the effects of the indian summer monsoon and the strengthening convection our findings indicate that the effects of seasonal precipitation differences caused by various climate systems including the winter india burma trough and indian summer monsoon need to be considered when attempting to interpret tree ring and ice core records for the hengduan mountains

formation of the highest sand dunes on earth characterization of dune morphology has historically been based on relationships between dune forms and wind regimes with dune height shown to be sensitive to atmospheric boundary layer depth sand availability and sediment properties while these parameters have been used in numerical simulations to model the occurrences of some types of dunes they cannot alone explain the great diversity in form and size seen on earth and on other solar system bodies here we present results from our studies of dune formation in the badain jaran desert in western china where earth s tallest dunes occur we measured the variability of the dune morphology in this desert on the basis of landsat etm data and we detected the bedrock landforms beneath the aeolian sands by applying gravity methods wind records from stations at the periphery of the desert and srtm topographical data were examined also to augment the interpretation our studies demonstrate that in addition to average wind parameters dune height is highly sensitive to local geology subsurface characteristics and topography and interactions between changing climate conditions and aeolian and fluvial processes these additional factors need to be considered in the interpretation and simulation of dunes on earth we anticipate that analysis of anomalous dune heights like those seen in the badain jaran may also provide critical information on subsurface characteristics and environmental conditions on earth and on other planetary bodies

high resolution investigations of transverse aeolian ridges on mars abstract transverse aeolian ridges tars are the most pervasive aeolian feature on mars their small size requires high resolution data for thorough analyses we have utilized mars reconnaissance orbiter mro context camera ctx and high resolution image stereo experiment hirise images along with mro compact reconnaissance imaging spectrometer for mars crism spectroscopic data to study tars in detail tar deposits along with related dark dune material and layered terrains have been mapped in six study areas in order to identify sediment pathways and determine whether tars are sourced locally or from global wind borne materials tar morphology and orientation were mapped in grids within each study area the results show that tars are probably locally sourced we constructed four hirise digital terrain models dtms to measure tar heights widths spacing areas symmetry and to calculate sediment volumes results show that tars have average heights of 1 5 m are very symmetrical and are similar in form to terrestrial megaripples orthorectified hirise images taken 3 years apart were analyzed for tar movement and none was found superposed craters on equatorial tars give ages of 2 ma suggesting that these are relatively ancient and generally inactive aeolian deposits crism data were analyzed over tar deposits dark dune material and light toned terrains although the surfaces were somewhat obscured by dust cover the results did not show any remarkable difference between tars and other deposits we conclude that tars may be sourced from local materials and form in a similar way to terrestrial megaripples

aerodynamic roughness height for gravel mantled megaripples with implications for wind profiles near tars on mars abstract aerodynamic roughness heights of 1 3 cm were obtained from measured wind profiles collected among fields of gravel mantled megaripples in the high desert of the puna region of northwestern argentina roughness height appears to be relatively insensitive to the angle at which the wind was incident upon the bedforms throughout the study sites the results represent the first wind profiling measurements for large megaripples but they also demonstrate the importance of a careful evaluation of many potential effects that can influence the utility of wind profiling data the same effects that influence collection of fieldwork data must also be considered in any prediction of wind profiles anticipated to occur near transverse aeolian ridges and other aeolian features on mars that are intermediate in scale between wind ripples and small sand dunes

cross sectional profiles of sand ripples megaripples and dunes a method for discriminating between formational mechanisms cross sectional profiles of sand ripples megaripples and sand dunes provide a useful tool for discriminating between formation by ripple and dune processes feature width defined as the basal break in slope along the profile to either side of the crest represents a good standard for comparison of profile attributes across more than three orders of magnitude aspect ratio height width as a function of log width separates measurements into clusters representing differing mechanisms of formation scaling both height and distance for individual profiles by feature width facilitates comparison of profile shapes across three orders of magnitude in width the data presented here should prove useful for evaluating possible mechanisms of origin for aeolian features observed remotely including on planetary bodies copyright 2012 john wiley sons ltd

sampling strategy and climatic implications of tree ring stable isotopes on the southeast tibetan plateau we explore the potential of tree ring cellulose d18o and d13c records for reconstructing climate variability in the southeast tibetan plateau our sampling strategy was designed to investigate intra and inter tree variability and the effects of the age of tree on d18o variation we show that intra tree d13c and d18o variability is negligible and inter tree coherence is sufficient to build robust tree ring d18o or d13c chronologies based on only four trees there is no evidence of an age effect regarding d18o in contrast with tree ring width in our warm and moist sampling site young tree d13c is not clearly correlated with monthly mean meteorological data tree ring d18o appears significantly anti correlated with summer precipitation amount regional cloud cover and relative humidity simulations conducted with the orchidee land surface model confirm the observed contribution of relative humidity to tree cellulose d18o and explain the weak correlation of d13c with climate by the non linear integration linked with photosynthesis altogether the tree ring cellulose d18o is shown to be a promising proxy to reconstruct regional summer moisture variability prior to the instrumental period 2010 elsevier b v

modelling transverse dunes transverse dunes appear in regions of mainly unidirectional wind and high sand availability a dune model is extended to two dimensional calculation of the shear stress it is applied to simulate dynamics and morphology of three dimensional transverse dunes in the simulations they seem to reach translational invariance and do not stop growing hence simulations of two dimensional dune elds have been performed characteristic laws were found for the time evolution of transverse dunes bagnold s law of the dune velocity is modi ed and reproduced the interaction between transverse dunes led to the interesting conclusion that small dunes can travel over bigger ones copyright 2004 john wiley sons ltd

aeolian processes across transverse dunes ii modelling the sediment transport and profile development this paper discusses a model which simulates dune development resulting from aeolian saltation transport the model was developed for application to coastal foredunes but is also applicable to sandy deserts with transverse dunes sediment transport is calculated using published deterministic and empirical relationships describing the influence of meteorological conditions topography sediment characteristics and vegetation a so called adaptation length is incorporated to calculate the development of transport equilibrium along the profile changes in topography are derived from the predicted transport using the continuity equation vegetation height is incorporated in the model as a dynamic variable vegetation can be buried during transport events which results in important changes in the sediment transport rates the sediment transport model is dynamically linked to a second order closure air flow model which predicts friction velocities over the profile influenced by topography and surface roughness modelling results are shown for a the growth and migration of bare initially sine shaped dunes and b dune building on a partly vegetated and initially flat surface results show that the bare symmetrical dunes change into asymmetric shapes with a slipface on the lee side this result could only be achieved in combination with the secondorder closure model for the calculation of air flow the simulations with the partly vegetated surfaces reveal that the resulting dune morphology strongly depends on the value of the adaptation length parameter and on the vegetation height the latter result implies that the dynamical interaction between aeolian activity and vegetation reaction to burial growth rates is highly relevant in dune geomorphology and deserves much attention in future studies copyright 1999 john wiley sons ltd

analysis of transverse aeolian ridge profiles derived from hirise images of mars photoclinometry was used to analyze selected high resolution imaging science experiment hirise images of transverse aeolian ridges tars on mars sixty mars profiles have been assessed and a summary of their morphologic characteristics compiled measurements collected quantified the symmetry of the feature the curvature of the crest flank slopes width height and several comparative ratios results show that small tars have physical characteristics generally similar to measurements obtained from lower resolution images of mars the hirise image data allow for much improved sampling along each feature the improved resolution reveals relatively few features not seen in earlier studies but is well suited for topographic sampling measured tar profiles when scaled by the width of the feature can be compared to similarly scaled profiles for terrestrial dunes and megaripples published 2012 this article is a u s government work and is in the public domain in the usa

recent ground movement and seismic activity in campi flegrei southern italy episodic growth of a resurgent dome leveling surveys in campi flegrei an active volcanic caldera in southern italy show that this caldera has undergone both subsidence and uplift of a few meters during the past 85 years a single source located at a depth of about 3 km beneath the center of the caldera can account for almost all elevation changes recorded in campi flegrei since the first leveling survey conducted in 1905 1907 this includes leveling surveys that span periods of subsidence such as between 1905 1907 and 1919 and between january 1985 and october 1986 and periods of rapid uplift between march 1970 and october 1971 and between january 1981 and december 1984 a possible geometry for the source of uplift and subsidence beneath campi flegrei is a rectangular horizontal sheet located at a depth of about 3 km and centered a few hundred meters east of the city of pozzuoli the horizontal dimensions of this sheet are about 1 5 km by 3 0 km the long axis is oriented n70 w this sheet lies adjacent to the most intense area of seismicity that occurred from mid 1983 to december 1984 during an uplift episode this sheet may represent the top of a magma body undergoing internal pressure changes possibly by intrusion of additional magma subsidence is caused by groundwater removal from the water saturated deposits that fill this caldera to a depth of a few kilometers a temporary increase in subsidence rate after an uplift episode is caused by increased rate of groundwater removal from newly fractured regions that lie immediately above the magma body the close proximity of this water saturated region and the magma body makes it impossible to separate the depth to these two sources from the results of leveling surveys two observations indicate that uplift has occurred in the center of campi flegrei for at least the past several thousand years first marine deposits in the center of campi flegrei were uplifted at least 40 m between 4000 and 8000 years ago second continuous seismic profiles of the undersea portion of campi flegrei have identified only one region where rocks are fractured and faulted adjacent to the uplifted marine deposits that surround the point of maximum uplift indicated by recent leveling surveys on the basis of these observations and the historical record of activity we suggest that campi flegrei caldera is in a stage of growing a resurgent dome the present diameter of the resurgent dome is about 4 km and the maximum amount of vertical uplift during the past 10 000 years has probably not exceeded 100 m the episodes of rapid uplift and shallow earthquake swarms during the past 20 years are probably related to the growth of this resurgent dome

on the origin and age of the great sand dunes colorado abstract over the past 100 yr several hypotheses have been proposed for the origin and age of the great sand dunes these hypotheses differ widely in the descriptions of dune morphometry the immediate source of eolian sand and when sand transport occurred the primary purpose of this paper is to evaluate these hypotheses and where warranted to present new ideas about the origin and age of the great sand dunes to evaluate the previous hypotheses we had to develop more detailed information about the surficial geology of the northern san luis valley thus we mapped the surficial geology of an area extending several tens of kilometers north south and west of the great sand dunes and examined subsurface stratigraphy in more than 200 wells and borings in addition we used relative dating criteria and several radiocarbon and osl ages to establish the chronology of surficial deposits and we determined the u pb ages of detrital zircons to obtain information about the sources of the sand in the great sand dunes the first principal finding of this study is that the lower part of the closed basin north of the rio grande referred to here as the sump is the immediate source of the sand in the great sand dunes rather than the late pleistocene flood plain of the rio grande the most widely accepted hypothesis a second principal finding is that the great sand dunes are older than late pleistocene they postdate the draining of lake alamosa which began 440 ka and predate the time when streams draining the west flank of the sangre de cristo mountains were deflected by incipient dunes that formed near the mountain front geomorphic and stratigraphic evidence indicate that this deflection occurred prior to the end of the next to last glaciation bull lake i e prior to 130 ka

the development of large aeolian bedforms abstract large aeolian bedforms complex and compound varieties of dunes or draas dominate over wide areas of many sand seas and are well represented in the rock record analyses of allometric relationships between dune height and spacing in several sand seas suggest that draas develop by vertical growth of existing dunes in the namib and other sand seas draa tend to occur in areas of low total and net sand transport rates the distribution of such bedforms in a sand sea reflects long term patterns of deposition which are related to regional scale changes in wind regimes and sand transport rates superimposed bedforms are almost ubiquitous on draa and develop only after a minimum size of draa has been reached formation of superimposed dunes reflects spatial and temporal variations in secondary flow patterns developed on the draa measurements of winds and depositional patterns on complex linear dunes in the namib sand sea suggest that an important mechanism for their growth is the migration of superimposed dunes from areas of high to low wind velocity on draa flanks leading to the deposition of sediment by bedform climbing

complex systems in aeolian geomorphology aeolian geomorphology provides a rich ground for investigating earth surface processes and landforms as complex systems sand transport by wind is a classic dissipative process withnon linear dynamics while dunefield evolution is a prototypical self organisation phenomenon bothofthesebroadareasofaeoliangeomorphologyarediscussedandanalysedinthecontextofcomplexityandasystems approach afeedbackloopanalysisoftheaeolianboundary layer flow sediment transport bedforminteractions basedoncontemporary physicalmodels revealsthatthesystemisfundamentallyunstable oratmostmeta stable andlikelytoexhibitchaoticbehaviour recent field experimental research on aeolian streamers and spatio temporal transport patterns however indicates that sand transport by wind may be wholly controlled by a self similar turbulence cascade in the boundary layer flow and that key aspects of transport event timeseriescanbefullyreproducedfromacombinationof self organised 1 fforcing motionthreshold andsaltationinertia theevolutionof various types of bare sand dunes and dune field patterns have been simulated successfully with self organising cellular automata that incorporateonlysimplifiedphysically basedinteractions rules becauseoftheirundefinedphysicalscale however itnotclearwhether they in fact simulate ripples bedforms or dunes landforms raising fundamental cross cutting questions regarding the difference between aeolian dunes impact ripples and subaqueous current ripples and dunes an extended cellular automaton ca model currently under development incorporates the effects of vegetation in the aeolian environment and is capable of simulating the development of nebkhas blow outs and parabolic coastal dunes preliminary results indicate the potential for establishing phase diagrams and attractor trajectories for vegetated aeolian dunescapes progress is limited however by a serious lack of appropriate concepts for quantifying meaningful state variables at the landscape scale state variables currently used in the bare sand models are far from capturing the rich 3d topography and patterns and are not sufficiently discriminative to distinguish different attractors the vegetationcomponentintheextendedmodel andindeedecogeomorphicsystemsingeneral poseevengraverchallengestoestablishing

toward forward modeling for paleoclimatic proxy signal calibration a case study with oxygen isotopic composition of tropical woods a forward model of the oxygen isotopic composition 18o of wood cellulose is parameterized for time series prediction in tropical environments and driven with meteorological data observed at la selva biological research station costa rica for 1985 2001 monthly resolution model results correlate modestly r 0 34 p 0 05 with observed isotopic data with higher correlation r 0 45 p 0 01 over the earliest 10 years of comparison and nonsignificant correlation over the most recent 6 years of record analysis of model output for la selva suggests that isotopic variations are strongly controlled by rainfall amount the model simulates an analogous but stronger than observed negative isotopic anomaly associated with positive july september rainfall anomalies during el nino southern oscillation enso warm phase event years simulated tree isotope data for the global tropics suggest that a network of well replicated data series from selected locations may resolve the large scale precipitation anomaly pattern associated with enso

secondary airflow and sediment transport in the lee of a reversing dune lee side windspeed and sediment transport were measured over a small 1 2 m transverse ridge in the silver peak dunefield west central nevada usa using an intensive array of 25 cup anemometers and seven total flux traps during crest transverse and transporting flow conditions u0 3crest 8 4 m s 1 windspeed near the surface of the lee slope averaged half 48 per cent that of crest speeds dimensionless speeds in the separation zone ranged from 0 2 to 0 8 that of the outer flow u12 along the boundary of the separation cell windspeed increased by 10 per cent of the crest speed before separation equilibrium of upper and lower wake regions was not observed by the documented eight dune heights suggesting that wake recovery may not occur over closely spaced dunes sediment transport measured directly on both the lee slope and interdune surfaces averaged approximately 15 per cent of crest inputs this suggests that a significant amount c 70 95 per cent of sediment transported over the crest moved as fallout for this data set flux was approximately proportional to the cube of the near surface windspeed u0 3 and in general there was an order of magnitude difference between flux measured at the crest and that measured within the separation zone transport direction in the separation zone was acutely oblique to the incident direction owing to secondary flow deflection beyond the interdune transport direction progressed from oblique to crest transverse this indicates that an appreciable amount of sediment may move laterally along the lee slope and interdune corridor under crest transverse flows regarding the grain size and sorting properties of transported sediment there was no significant difference in mean grain size over the dune although in general particles were finer and more poorly sorted in the lee copyright 1999 john wiley sons ltd

sand dune movement in the victoria valley antarctica we use vertical aerial photographs and lidar topographic survey data to estimate dune migration rates in the victoria valley dunefield antarctica between 1961 and 2001 results confirm that the dunes migrated an average of 1 5 m year these values are consistent with other estimates of dune migration from cold climate deserts and are significantly lower than estimates from warm deserts dune migration rates are retarded by the presence of entrained ice soil moisture and a reversing wind regime dune absorption merging and limb extension are apparent from the time series images and account for significant changes in dune form and the field scale dune pattern dune field pattern analysis shows an overall increase in dune field organization with an increase in mean dune spacing and a reduction in total crest length and defect density these data suggest that dunes in other cold desert environments on earth mars or titan that may also have inter bedded frozen laminae still have the potential to migrate and organize albeit at lower rates than dunes in warm deserts

a terrestrial analog for transverse aeolian ridges tars environment morphometry and recent dynamics abstract transverse aeolian ridges tars are a distinct aeolian bedform found on mars the formative processes evolution and geological significance of tars is poorly understood fundamentally it is unknown whether tars are dunes mega ripples or another bedform type we examined aeolian bedforms in the lut desert of iran as a terrestrial analog for martian tars from an objective sampling strategy with high resolution satellite imagery we developed a large morphometric dataset for comparison with existing martian tars we also examined the dynamics of the lut bedforms between 2004 and 2012 to determine if they were static or migrating results indicate that the range in the dimensions length width height and wavelength of the lut bedforms and martian tars overlap suggesting lut bedforms are a viable terrestrial tar analog our sample yielded median values of 55 18 m 9 80 1 02 m and 20 m for length longest planview axis width shortest planview axis height and wavelength respectively cumulative log frequency plots of morphometric parameters suggest the sample is from a single population and process mechanism although the vast majority of lut bedforms examined were static between 2004 and 2012 some migrated up to 0 09 myr 1 on average this is much slower than nearby dunes 4 12 myr 1 but is explained by the existence of a surface lag of coarse particles on the tar like bedforms the combination of morphometry surface sedimentology and slow migration rate indicate the lut bedforms are mega ripples which provides evidence supporting interpretation of martian tars as mega ripples testing the mega ripple hypothesis for martian tars requires measurements of their sedimentology which may be possible with the mars science laboratory rover curiosity as well as expanded measurements of tar morphometry to constrain their size shape and scaling

precision topography of a reversing sand dune at bruneau dunes idaho as an analog for transverse aeolian ridges on mars abstract ten high precision topographic profiles across a reversing dune were created from a differential global position system dgps the shapes of the profiles reveal a progression from immature to transitional to mature characteristics moving up the dune when scaled by the basal width along each profile shape characteristics can be compared for profiles whose horizontal scales differ by orders of magnitude the comparison of width scaled bruneau dunes profiles to similarly scaled profiles of transverse aeolian ridges tars on mars indicates that many tars are likely similar to transitional or mature reversing sand dunes

mega ripples in iran a new analog for transverse aeolian ridges on mars abstract a new terrestrial analog site for transverse aeolian ridges tars is described in this study the lut desert of iran hosts large ripple like aeolian bedforms with the same horizontal length scales and patterns of tars on mars different classes of tars and different types of other aeolian features such as sand dunes zibars dust devil tracks and yardangs can be found in this area which signify an active aeolian region this area represents a unique site to study the formation and evolution of these enigmatic features with potential relevance toward a better understanding of tars on mars

the phlegraean fields structural evolution volcanic history and eruptive mechanisms abstract the main event within the volcanic history of the phlegraean fields was the eruption about 35 000 years ago of a huge alkali trachytic ignimbrite 80 km 3 dre followed by caldera collapse the pre caldera activity evidence from geothermal wells and surface outcrops changed from submarine to subaerial shortly before the ignimbrite eruption the caldera was subsequently invaded by the sea and became progressively filled with tuffites and subordinate submarine flows in its northern half the last submarine explosive activity dates back to 12000 10500 yr with the eruption of mostly hydroplinian yellow tuffs recent mostly subaerial activity consists of a series of explosive eruptions whose volume decreases with time until the last eruption of mt nuovo in 1538 a d two peaks in recent activity occur at 10000 8000 and 4700 3000 years ago during post caldera activity eruptive vents migrated from the caldera rim toward the center where there are two distinct zones of recent vents minor collapses occurred within the caldera after the main eruptions often they are eccentric to the vent and displaced toward the caldera center phlegraean explosive activity is characterized by water magma interaction eruptive events without a hydromagmatic component are extremely rare in most cases the evolved trachytic magmas interacted with surface water either the sea or intracaldera lakes however there is evidence of interaction of magma with deep seated aquifers for some plinian events explosivity i e the efficiency of the transformation of thermal into kinetic energy during magma water interaction is largely controlled by the primary fragmentation of the magmatic melt

temperature signals in tree ring oxygen isotope series from the northern slope of the himalaya abstract oxygen isotope ratios 18 o are the most commonly used parameters recorded in paleoclimate archives since they link different natural archives via the water cycle tree ring 18 o 18 otr has been widely used for hydroclimate reconstructions in the himalaya however few of them record temperature signals which are dominant in himalaya ice core 18 o we hypothesize that the precipitation amount effect due to the south asian summer monsoon sasm may overprint temperature signals in 18 otr series the purpose of this study is to investigate whether temperature signals could be found in the 18 otr in locations where the influence of sasm is weak we developed a 105 yr 18 otr chronology from the northern slope of the western himalaya which greatly blocks the sasm our 18 otr clearly shows stronger correlations with temperature dominant winter and weak summer than summer precipitation signals it also agrees well with summer soil moisture 18 o simulated by the global isotope model lmdz4 r 0 72 1979 2010 in lmdz4 low winter temperature was found to increase winter snowfall and subsequent snow melt and thus to increase the contribution of winter snowfall to soil moisture in summer at the expense of summer precipitation since winter snowfall is more depleted than summer precipitation this leads to lower summer soil moisture 18 o the temperature signals found in our 18 otr series are consistent with those found in the dasuopu ice core 18 o this implies that 18 otr series from the southwest tibetan plateau tp with a weak monsoon hold great potential to capture temperature signals climate interpretations of 18 o proxies in the himalaya largely depend on the influence of seasonal water from the dominant atmosphere circulation systems of the westerlies or monsoon the 18 o proxies from the monsoon affected region have a higher potential for the reconstruction of boreal summer hydroclimate whereas 18 o proxies from westerly affected sites have a higher potential for temperature reconstructions

spatial grain size sorting in eolian ripples and estimation of wind conditions on planetary surfaces application to meridiani planum mars the landscape seen by the mars exploration rover mer opportunity at meridiani planum is dominated by eolian wind blown ripples with concentrated surface lags of hematitic spherules and fragments these ripples exhibit profound spatial grain size sorting with well sorted coarse grained crests and poorly sorted generally finer grained troughs these ripples were the most common bed form encountered by opportunity in its traverse from eagle crater to endurance crater field measurements from white sands national monument new mexico show that such coarse grained ripples form by the different transport modes of coarse and fine grain fractions on the basis of our field study and simple theoretical and experimental considerations we show how surface deposits of coarse grained ripples can be used to place tight constraints on formative wind conditions on planetary surfaces activation of meridiani planum coarse grained ripples requires a wind velocity of 70 m s at a reference elevation of 1 m above the bed from images by the mars orbiter camera moc of reversing dust streaks we estimate that modern surface winds reach a velocity of at least 40 m s and hence may occasionally activate these ripples the presence of hematite at meridiani planum is ultimately related to formation of concretions during aqueous diagenesis in groundwater environments however the eolian concentration of these durable particles may have led to the recognition from orbit of this environmentally significant landing site

high elevation shrub ring δ18o on the northern slope of the central himalayas records summer may july temperatures abstract the potential of shrub ring oxygen isotopes sro as a paleoclimatic proxy is not well demonstrated in this study we explored the climate signals embedded in an sro chronology from saga on the northern slope of the central himalayas by correlation analysis with climate variables and comparison with tree ring and or ice core 18o records the saga sro had significant and positive correlations with may july temperatures in both local r 0 43 and moisture source areas r 0 49 during the period 1955 2015 ce while no significant correlations were found with hydroclimatic variables it is also in good agreement with two tree ring 18o series from the southern slope of the central himalayas the source of moisture to the site the temperature signals are further verified by an ice core 18o record from the tanggula mountains on the central tibetan plateau however it shows little similarity with the nearest himalayan ice core 18o record from dasuopu demonstrating temperature signals of different seasons this study suggests that sro could be used as an acceptable climate proxy like tree ring and ice core 18o to broaden the spatial extent of the paleoclimatic records network however we should be cautious when combining different proxies with climate signals of different seasons in paleoclimate studies

simulation of the effect of wind speedup in the formation of transverse dune fields a computer simulation model for transverse dune field dynamics corresponding to a uni directional wind regime is developed in a previous formulation two distinct problems were found regarding the cross sectional dune shape namely theerosionintheleeofdunesandthesteepnessofthewindwardslopes thefirstproblemissolvedbyintroducingnoerosion inshadowzones thesecondissueisovercomebyintroducingawindspeedup shearvelocityincrease factor whichcanbe accountedforbyaddingatermtotheoriginaltransportlength whichisproportionaltothesurfaceheight byincorporating these features we are able to model dunes whose individual shape and collective patterns are similar to those observed in nature moreoverweshowhowtheintroductionofanon linearshear velocity increasetermleadstothereductionofdune height andthismayresultinanequilibriumdunefieldconfiguration thisisthoughttobebecausethenon linearincreaseof thetransportlengthmakesthesandtrappingefficiencylowerthanunity evenforhigherdunes sothattheincomingandthe outgoingsandfluxareinbalance tofullydescribetheinter dunemorphologymoreprecisedynamicsintheleeofthedune must be incorporated copyright 2000 john wiley sons ltd

particle size and sorting characteristics of sand in transport on the stoss slope of a small reversing dune studies of the particle size and sorting characteristics of sand on the stoss slope of a 6 m high reversing dune show that the sand in transport is generally finer and better sorted than surface sand at the same position on the slope the sand in transport becomes coarser and more poorly sorted as wind speed and rates of mass transport increase toward the dune crest these patterns reflect changes in the competence of the wind which is capable of transporting larger grains and a wider range of grain sizes as its speed increases in space and time our field observations suggest that the particle size and sorting characteristics of surface sand are highly dependent on antecedent wind conditions and are not an invariant property of the dune as is widely assumed the wide range of particle sizes on the surface as well as its change through time also has important implications for modeling sediment transport on dunes transport thresholds may vary by as much as 30 on the stoss slope of the study dune

a theoretical model for aeolian impact ripples new insights into the grain bed impact process arising from both numerical and physical experiments involving single grain impacts lead to a more complete conceptual model of the aeolian saltation process that in turn allows a simple model of aeolian impact ripples to be developed the saltating population may be idealized as consisting of 1 long trajectory high impact energy constant impact angle successive saltations and 2 short trajectory low impact energy reptations it is argued that the spatial variations in mass flux due to the reptating population lead to the growth and translation of impact ripples using the sediment continuity equation an expression for the spatial variation in the ejection rate of reptating grains from a sinusoidally perturbed bed and a probability distribution for the reptation lengths a simple stability analysis demonstrates that the flat bed is unstable to small amplitude perturbations a fastest growing wavelength emerges that is roughly six times the mean reptation length and is only weakly dependent upon the detailed shape of the probability distribution of reptation lengths the results match well with the observed initial wavelengths in wind tunnel experiments

tidal signal in the recent dynamics of campi flegrei caldera italy abstract this paper presents periodicities in geophysical measurements made during recent activity in campi flegrei caldera this caldera located west of naples in southern italy is well known for the slow vertical ground movement known as bradyseism the maximum rate of movement occurrs near the city of pozzuoli near the caldera center a monitoring system of geophysical instruments has been in operation since 1970 to record activity in campi flegrei we analyze the time series and frequency spectra of vertical ground movement seismicity and gravity changes associated with a strong episode of unrest occurred between 1982 and 1984 our purpose is to investigate the influence of the earth tide on some aspects of the unrest our results reveal periodicities coincident with some tides which range from semidiurnal to annual components some of these periodicities has already been identified during an earlier episode of activity in campi flegrei

transverse aeolian ridges on mars first results from hirise images abstract three images obtained by the high resolution imaging science experiment hirise were analyzed for the information they could provide regarding transverse aeolian ridges tars on mars tars from five locations in a hirise image of the floor of ius chasma show remarkably symmetric cross sectional profiles with average slopes for the entire feature of 15 these results apply to tars that span an order of magnitude in wavelength and a factor of 6 in height a hirise image of gamboa impact crater in the northern lowlands shows low albedo sand patches

a model of the phlegraean fields magma chamber in the last 10 500 years volcanological and petrological data suggest that the phlegraean fields volcanic activity has been fed at least in the last 10 500 years by a not refilled magma chamber where trachytic residual liquids were produced by fractionation of a trachybasaltic magma using estimated volumes of the erupted products andp t data obtained through petrological studies a conductive thermal model of the chamber was built up in order to estimate its past and present size results suggest a volume decrease from approximately 14 to 1 4 km3 of the trachybasaltic magma in 10 500 years trachytic liquid would also be present in the chamber in a minimum amount of 0 4 km3 the model allowed some insights on the petrogenesis of the phlegraean trachytes suggesting that they were erupted as liquids because thermally buffered within the magma chamber

thermal history of phlegraean fields italy in the last 50 000 years a schematic numerical model an attempt is made to reproduce by numerical simulation the last 50 000 years of the phlegraean fields volcanic history in terms of a magma chamber with volume progressively reduced by magma extraction to the surface and without refillings from depth since the aim is just to verify the plausibility of such an assumption attention is focused on the major volcanic events and a rather crude model is adopted it turns out that the main features of the phlegraean fields thermal history namely the campanian ignimbrite the yellow tuffs emission and the high temperatures measured in the geothermal wells drilled inside the caldera can reasonably be reproduced under the not refilled system assumption the magmatic body is predicted to have an average temperature of 1000 c at present

tibetan plateau summer monsoon northward extent revealed by measurements of water stable isotopes a program of individual precipitation events and river water sampling and of water isotopic measurements d 18o was carried out during summer 1996 along a northeast southwest transect of the tibetan plateau the spatial distribution of both 18o and deuterium excess d d 8 18o of the precipitation reveals three distinct regions simulations with a simple isotopic model and seasonal isotopic variations measured at two extreme south and north locations support our interpretation in terms of different summer moisture origins 1 south of the himalayan mountains the moisture provided by the indian monsoon has been recycled over the indian peninsula 2 between the himalayas and the tanggula mountains the oceanic moisture is directly transported from the bay of bengal along the brahmaptra river valley 3 north of the tanggula mountains the moisture is not provided by the monsoon anymore but by continental water recycling

synchronization between tides and sustained oscillations of the hydrothermal system of campi flegrei italy 1 long continuous seismic data recorded at five broadband seismic stations during 2006 at campi flegrei caldera have been analyzed introducing a coarse grained method we evaluate the time evolution of amplitude and polarization of the seismic noise in the frequency band common to long period events the series are modulated on tidal time scales the root mean square is basically dominated by solar contribution while the azimuth of the polarization vector shows lunar diurnal and semidiurnal constituents in addition we find that in the frequency band common to long period events the azimuths are polarized toward a specific area suggesting that these persistent oscillations can be induced by the activity of the shallow geothermal reservoir

spatial and temporal variability in the stable isotope systematics of modern precipitation in china implications for paleoclimate reconstructions the stable isotopic composition of materials such as glacial ice tree rings lake sediments and speleothems from low to mid latitudes contains information about past changes in temperature t and precipitation amount p however the transfer functions which link 18op to changes in t or p d 18op dt and d 18op dp can exhibit significant temporal and spatial variability in these regions in areas affected by the southeast asian monsoon past variations in 18o and d of precipitation have been attributed to variations in monsoon intensity storm tracks and or variations in temperature proper interpretation of past 18op variations here requires an understanding of these complicated stable isotope systematics since temperature and precipitation are positively correlated in china and have opposite effects on 18op it is necessary to determine which of these effects is dominant for a specific region in order to perform even qualitative paleoclimate reconstructions here we evaluate the value of the transfer functions in modern precipitation to more accurately interpret the paleorecord the strength of these transfer functions in china is investigated using multiple regression analysis of data from 10 sites within the global network for isotopes in precipitation gnip 18op is modeled as a function of both temperature and precipitation the magnitude and signs of the transfer functions at any given site are closely related to the degree of summer monsoon influence 18op values at sites with intense summer monsoon precipitation are more dependent on the amount of precipitation than on temperature and therefore exhibit more negative values in the summer in contrast 18op values at sites that are unaffected by summer monsoon precipitation exhibit strong relationships between 18op and temperature the sites that are near the northern limit of the summer monsoon exhibit dependence on both temperature and amount of precipitation comparison with simple linear models 18op as a function of t or p and a geographic model 18op as a function of latitude and altitude shows that the multiple regression model is more successful at reproducing 18op values at sites that are strongly influenced by the summer monsoon the fact that the transfer function values are highly spatially variable and closely related to the degree of summer monsoon influence suggests that these values may also vary temporally since the southeast asian monsoon intensity is known to exhibit large variations on a number of timescales annual to glacial interglacial and the magnitude and sign of the transfer functions is related to monsoon intensity we suggest that as monsoon intensity changes the magnitude and possibly even the sign of the transfer functions may vary therefore quantitative paleoclimate reconstructions based on 18op variations may not be valid