modulation of boreal summer intraseasonal oscillations over the western north pacific by enso abstractthe authors investigate the effects of el nino and la nina on the intraseasonal oscillation iso in the boreal summer may october over the western north pacific wnp it is found that during el nino summers the iso is dominated by a higher frequency oscillation with a period of around 20 40 days whereas during la nina summers the iso is dominated by a lower frequency period of around 40 70 days the former is characterized by northwestward propagating convection anomalies in the wnp and the latter is characterized by northward and eastward propagating convective signals over the tropical indian ocean maritime continent the possible mechanisms through which el nino southern oscillation enso induced background mean state changes influence the iso behavior are examined through idealized numerical experiments it is found that enhanced weakened mean moisture and easterly westerly vertical wind shear in the wnp during el nino la nina are the main causes of the strengthened weakened 2

topographically controlled fronts in the ocean and their biological influence headlands islands and reefs generate complex three dimensional secondary flows that result in physical and biological fronts mixing and diffusion processes near these reefs and headlands are quite different from these processes in the open sea and classical advection diffusion models that were developed for the open sea are not valid near shore topographically generated fronts affect the distribution of sediments and they aggregate waterborne eggs larvae and plankton this aggregation influences the distribution and density of benthic assemblages and of pelagic secondary and tertiary predators

onset of the summer monsoon over the indochina peninsula climatology and interannual variations abstract the temporal and spatial structures of the atmospheric circulation associated with the climatology and interannual variations of the summer monsoon onset over the indochina peninsula were studied using the observed daily rainfall at 30 stations and the ncep ncar reanalysis from 1951 to 1996 the climatological monsoon onset over indochina is on 9 may with a standard deviation of 12 days the monsoon onset is characterized by the pronounced northeastward progression of the low level southwesterlies over the indian ocean and the intensification and northward extension of the tropical convection from sumatra it coincides with the weakening of the midlatitude westerly over south asia and the westward propagation of the intraseasonal oscillation iso originated in the south china sea scs and the western pacific with a dominant timescale of 12 25 days a close relationship between the interannual variations of the monsoon onset and el nino la nina was identified years with warm cold sea surfac

new views of lunar geoscience an introduction and overview beyond the earth the moon is the only planetary body for which we have samples from known locations the analysis of these samples gives us ground truth for numerous remote sensing studies of the physical and chemical properties of the moon and they are invaluable for our fundamental understanding of lunar origin and evolution prior to the return of the apollo 11 samples the moon was thought by many to be a primitive undifferentiated body e g urey 1966 a concept shattered by the data returned from the apollo and luna missions ever since new data have helped to address some of our questions but of course they also produced new questions in this chapter we provide a summary of knowledge about lunar geologic processes and we describe major scientific advancements of the last decade that are mainly related to the most recent lunar missions such as galileo clementine and lunar prospector 1 1 the moon in the planetary context compared to terrestrial planets the moon is unique in terms of its bulk density its size and its origin fig 1 1a c all of which have profound effects on its thermal evolution and the formation of a secondary crust fig 1 1d numerous planetary scientists considered the moon as an endmember among the planetary bodies in our solar system because its lithosphere has been relatively cool rigid and intact throughout most of geological time a one plate planet and its surface has not been affected by plate recycling an atmosphere water or life therefore the moon recorded and preserved evidence for geologic processes that were active over the last 4 4 5 b y and offers us the unique opportunity to look back into geologic times for which evidence on earth has long been erased fig 1 1c d impact cratering an exterior process is considered the most important surface process on the moon internal

comparison of sediment plate methods to measure accretion rates in an estuarine mangrove forest new zealand abstract sedimentation is a fundamental process in aquatic receiving environments including vegetated habitats such as mangroves selection of appropriate methods to measure sedimentation depends on time scales of interest due to the variable nature of this process our study considers the appropriateness of methods to measure sediment accretion over time scales of months to years in estuarine mangroves sediment accretion has commonly been measured using marker horizons sediment erosion pins and buried plates bioturbation and erosion can make application of these methods problematic here sediment accretion rates for porous plastic mesh and impervious ceramic plates of two sizes 0 023 and 0 16 m2 were compared replicate plates of each type were installed on the substrate surface at nine rod surface elevation table rset sites distributed along a shore normal sedimentation gradient the plates were progressively buried by sedimentation 17 41 mm yr 1 measurements were made at seasonal to annual intervals over a seven year period 2012 2019 comparison of accretion rates on the plastic mesh with both types of ceramic plates showed strong positive correlations r2 0 96 with slopes close to unity mean 0 95 range 0 68 1 09 sediment accretion rates measured on the large and small ceramic plates were not measurably different from rates for the plastic mesh these results show that sediment accretion rates were spatially homogenous at sub metre to metre scales in the mangroves and sediment accretion rates did not measurably vary between different sediment plate methods the sediment plate method has a number of advantages over marker horizons for long term measurements of sediment accretion particularly where bioturbation alters the sediment profile mesh plates are easily maintained and provide a cost effective flexible precise and reproducible alternative to sediment marker horizons and solid plates for long term monitoring sediment accretion in mangroves and unvegetated intertidal habitats future studies including those employing rset should consider incorporating mesh plate measurements of sediment accretion

sea level and turbidity controls on mangrove soil surface elevation change increases in sea level are a threat to seaward fringing mangrove forests if levels of inundation exceed the physiological tolerance of the trees however tidal wetlands can keep pace with sea level rise if soil surface elevations can increase at the same pace as sea level rise sediment accretion on the soil surface and belowground production of roots are proposed to increase with increasing sea level enabling intertidal habitats to maintain their position relative to mean sea level but there are few tests of these predictions in mangrove forests here we used variation in sea level and the availability of sediments caused by seasonal and inter annual variation in the intensity of la nina el nino to assess the effects of increasing sea level on surface elevation gains and contributing processes accretion on the surface subsidence and root growth in mangrove forests we found that soil surface elevation increased with mean sea level which varied over 250 mm during the study and with turbidity at sites where fine sediment in the water column is abundant in contrast where sediments were sandy rates of surface elevation gain were high but not significantly related to variation in turbidity and were likely to be influenced by other factors that deliver sand to the mangrove forest root growth was not linked to soil surface elevation gains although it was associated with reduced shallow subsidence and therefore may contribute to the capacity of mangroves to keep pace with sea level rise our results indicate both surface sedimentation and subsurface root growth processes can influence mangrove capacity to keep pace with sea level rise within the same geographic location and that current models of tidal marsh responses to sea level rise capture the major feature of the response of mangroves where fine but not coarse sediments are abundant

fluxes and exchange of suspended sediment in tidal inlets draining a degraded mangrove forest in kenya abstract this study focuses on sediment exchange in the degraded mwache mangrove forest wetland located in southern kenya it involved measurement of total and particulate organic suspended sediment concentrations tssc and posc tidal water elevation and current velocities results showed that in the heavily degraded backwater zone mangrove forest the ebb and flood tide total sediment fluxes were of same order of magnitude however flood tide sediment fluxes were slightly higher than the ebb ones in the moderately degraded frontwater zone mangrove forest the flood tide sediment fluxes were more than 50 higher than the ebb tide fluxes the peak net sedimentation in the highly degraded backwater zone was 4 g m 2 tide 1 but that in the moderately degraded frontwater zone was 63 g m 2 tide 1 in the frontwater zone of the mangrove forest the peak instantaneous ebb tide sediment flux was 3206 kg tide 1 equivalent to 35 6 g m 2 tide 1 and the flood one 8574 kg tide 1 95 g m 2 tide 1 the peak instantaneous flood and ebb tide particulate organic sediment pos fluxes in the frontwater zone mangrove forest were 1316 kg tide 1 15 g m 2 tide 1 and 587 kg tide 1 6 5 g m 2 tide 1 respectively the peak ebb and flood tide sediment fluxes in the backwater mangrove forest were 3206 kg tide 1 36 g m 2 tide 1 and 3305 kg tide 1 36 7 g m 2 tide 1 respectively in case of pos fluxes in the backwater zone mangrove forest the peak flood period pos flux was 969 kg tide 1 10 7 g m 2 tide 1 while the ebb period one was 484 kg tide 1 5 4 g m 2 tide 1 in both highly degraded backwater and moderately degraded frontwater zone of the mangrove forest there is net import of sediments however the net import is relatively lower in the backwater zone forest where the trapping efficiency is 27 in the moderately degraded frontwater zone of the mangrove forest the sediment trapping efficiency is 65 the net sediment import occurs mainly in periods of high river discharge in both neap and spring tides but occurs only in spring tides during dry season the net accretion rates in the backwater and frontwater zone mangrove forests are 0 25 and 3 5 cm year 1 respectively

morphology hydrography and sediment dynamics in a mangrove estuary the konkoure estuary guinea the konkoure estuary in the republic of guinea is a poorly understood atypical mangrove system sediment dynamics in tropical estuaries are controlled by a combination of processes including river discharge morphology salinity erosion and deposition processes the settling of mud physico chemical processes and mangrove swamps here we present a consistent set of data aimed at characterising the estuary and thus increasing our understanding of tropical systems as well as studying the impact of human intervention in the region water elevations current measurements salinity suspended sediment concentrations bathymetry and sediment cover are presented following a 3 year survey of the konkoure estuary here we provide conclusive evidence that the lower konkoure is a shallow funnel shaped mesotidal mangrove fringed tide dominated estuary well mixed during low river discharge the estuary becomes stratified during high river flows and spring tides whereas a salt wedge appears during neap tides the konkoure estuary has been described as hypersynchronous and has three terminal outlets two of which are landward directed attesting to a tidal pumping effect while the third one is seaward directed and is controlled by the mangrove the suspended matter is transported by the tidal effect within the middle estuary and is therefore trapped in the turbidity maximum zone tmz the location of the tmz is river controlled and is correlated with residual currents but not with salinity front a dam constructed 130 km upstream impacts on the hydrodynamics and reduces the salinity intrusion by about 25 it causes an increased low river discharge whereas its efficiency over high river flows is unclear

currents and sediment transport in mangrove forests abstract a field study of the tidal currents cohesive sediment dynamics and transport of organic carbon in a highly vegetated mangrove swamp was carried out at middle creek cairns australia the interaction of tidal currents and the vegetation generated jets eddies and zones of stagnant waters which were numerically modelled a high value of the manning friction coefficient n 0 1 was derived by the dense vegetation about 80 of the suspended sediment brought in from coastal waters at spring flood tide was trapped in the mangroves corresponding to about 10 12 kg of sediment m 1creek length spring tide resulting in a rise of the substrate by about 0 1 cm year 1 the selective trapping of clay was caused by flocculation of the finer particles in the mangroves there was an indication of a slight inwelling of organic carbon creek water was readily differentiated from mangrove water by large differences in the molecular weight distribution of the dissolved organic carbon

shock metamorphism of planetary silicate rocks and sediments proposal for an updated classification system we reevaluate the systematics and geologic setting of terrestrial lunar martian and asteroidal impactites resulting from single or multiple impacts for impactites derived from silicate rocks and sediments we propose a unified and updated system of progressive shock metamorphism shock metamorphosed rocks occur as lithic clasts or melt particles in proximal impactites at impact craters and rarely in distal impactites they represent a wide range of metamorphism typically ranging from unshocked to shock melted as the degree of shock metamorphism at a given shock pressure depends primarily on the mineralogical composition and the porosity of a rock or sediment sample different shock classification systems are required for different types of planetary rocks and sediments we define shock classification systems for eight rock and sediment classes which are assigned to three major groups of rocks and sediments 1 crystalline rocks with classes f m a and u 2 chondritic rocks class c and 3 sedimentary rocks and sediments with classes sr se and re the abbreviations stand for felsic f mafic m anorthositic a ultramafic u sedimentary rocks sr unconsolidated sediments se and regoliths re in each class the progressive stages of shock metamorphism are denominated s1 to sx these progressive shock stages are introduced as s1 s7 for f s1 s7 for m s1 s6 for a s1 s7 for u s1 s7 for c s1 s7 for sr s1 s5 for se and s1 s6 for re s1 stands for unshocked and sx variable between s5 and s7 stands for whole rock melting we propose a sequence of symbols characterizing the degree of shock metamorphism of a sample i e f s1 to f s7 with the option to add the tabulated pressure ranges in gpa in parentheses

structure and origin of the quasi biweekly oscillation over the tropical indian ocean in boreal spring abstract the structure and evolution features of the quasi biweekly 10 20 day oscillation qbwo in boreal spring over the tropical indian ocean io are investigated using 27 yr daily outgoing longwave radiation olr and the national centers for environment prediction national center for atmospheric research ncep ncar reanalysis data it is found that a convective disturbance is initiated over the western io and moves slowly eastward after passing the central io it abruptly jumps into the eastern io meanwhile the preexisting suppressed convective anomaly in the eastern io moves poleward in the form of double cell rossby gyres the analysis of vertical circulation shows that a few days prior to the onset of local convection in the eastern equatorial io an ascending motion appears in the boundary layer based on the diagnosis of the zonal momentum equation a possible boundary layer triggering mechanism over the eastern equatorial io is proposed the cause of the boundary layer convergence and ver

evaluating deep subsidence in a rapidly accreting mangrove forest using gps monitoring of surface elevation benchmarks and sedimentary records abstract ultimately the fate of mangrove forests depends on substrate elevation gains keeping pace with relative sea level rise rslr some of the world s largest mangrove forests occur on tectonically active margins river deltas and sedimentary basins where sea level trends are largely controlled by vertical land motion i e subsidence so that rslr can be markedly higher than sea level rise induced by climate warming the rod surface elevation table marker horizon rset mh method has been applied globally to evaluate coastal wetland resilience to slr by quantifying net rates of elevation change relative to a benchmark a limitation of the rset method is that the stability of the benchmark i e vertical trend is unknown and rslr in wetlands is typically inferred from regional tide gauge records in the present study we evaluate rslr in a rapidly subsiding avicenna marina mangrove forest with a large terrigenous sediment supply firth of thames new zealand using independent and complimentary methods 1 campaign gps surveys of the stability of three rset benchmarks driven 18 m into unconsolidated sediment a tide gauge some 10 km distant and a reference station located on basement rock 2007 2016 that are tied to a network of satellite based geodetic sites and 2 137cs validated 210pb sediment accumulation rates sar measured in cores as a proxy for rslr the similarity of deep subsidence rates at the rset benchmarks located several hundred metres apart 7 7 0 5 to 9 4 0 5 mm yr 1 provides confidence in these results these subsidence rates are two to five fold higher than recorded at the nearby tide gauge 3 6 0 7 mm yr 1 and reference station 1 6 0 5 mm yr 1 weighted average 210pb sar of 9 9 mm and 9 3 mm yr 1 yield similar estimates of deep subsidence i e 8 4 and 6 9 mm yr 1 slr adjusted for vertical land motion indicating that this geological process is the major driver of the long term sea level trend in the mangrove forest our findings suggest that regional tide gauge records may not provide reliable estimates of rslr for all coastal wetlands due to local subsidence associated with natural processes and human activities subsidence rates and rslr within coastal wetlands can be evaluated using campaign gps surveys of rset benchmarks and independently from longer term sedimentary records finally evaluations of the resilience of coastal wetlands to rising sea levels over the coming decades must be based on measurements of rslr from these systems themselves

modulation of the mjo intensity over the equatorial western pacific by two types of el nino the modulation of the madden julian oscillation mjo intensity by eastern pacific ep type and central pacific cp type of el nino was investigated using observed data during the period of 1979 2013 mjo intensity is weakened strengthened over the equatorial western pacific from november to april during ep cp el nino the difference arises from distinctive tendencies of column integrated moist static energy mse anomaly in the region a larger positive mse tendency was found during the convection developing period in the cp mjo than the ep mjo the tendency difference is mainly caused by three meridional moisture advection processes the advection of the background moisture by the intraseasonal wind anomaly the advection of intraseasonal moisture anomaly by the mean wind and the nonlinear eddy advection the advections differences are primarily caused by different intraseasonal perturbations and high frequency activity whereas the background flow and moisture gradient are similar the amplitudes in the intraseasonal suppressed convection anomaly over the central pacific is critical in modulating the three meridional moisture advection processes the influences on the central pacific convection anomaly from seasonal mean moisture in two types of el ninos are discussed

evolution of the madden julian oscillation in two types of el nino abstractevolution characteristics of the madden julian oscillation mjo during the eastern pacific ep and central pacific cp types of el nino have been investigated mjo activities are strengthened over the western pacific during the predeveloping and developing phases of ep el nino but suppressed during the mature and decaying phases in contrast mjo activities do not show a clear relationship with cp el nino before their occurrence over the western pacific but they increase over the central pacific during the mature and decaying phases of cp el nino lag correlation analyses further confirm that mjo activities over the western pacific in boreal spring and early summer are closely related to ep el nino up to 2 11 months later but not for cp el nino ep el nino tends to weaken the mjo and lead to a much shorter range of its eastward propagation anomalous descending motions over the maritime continent and western pacific related to el nino can suppress convection and moisture flux convergence the

on upper mantle seismic heterogeneities beneath fennoscandia abstract three dimensional seismic mapping of the upper mantle beneath fennoscandia baltic shield using an ach type of inversion technique in combination with p wave travel time residual observations from the local seismograph network gave the following results the central parts of the baltic shield are characterized by relatively high seismic velocities down to approximately 300 km those parts of the shield most affected by the caledonide orogeny exhibit relatively low velocities particularly in the uppermost 100 km depth interval the lower part of the upper mantle 300 600 km does not exhibit pronounced seismic velocity anomalies and in this respect is in contrast to results from similar studies in regions subjected to neotectonic processes like parts of central and southeastern europe the seismic anomaly pattern in the presumed thickened lithosphere is in quantitative agreement with similar ones derived from surface wave dispersion analysis and inversion of electrical measurements the general orientation of these anomalies coincides with that of the glacial uplift

estimating shallow subsidence in microtidal salt marshes of the southeastern united states kaye and barghoorn revisited abstract simultaneous measurements of vertical accretion and change in surface elevation relative to a shallow 3 5 m subsurface datum were made in selected coastal salt marshes of louisiana florida and north carolina to quantitatively test kaye and barghoorn s contention that vertical accretion is not a good surrogate for surface elevation change because of autocompaction of the substrate rates of subsidence of the upper 3 5 m of marsh substrate were calculated for each marsh as the difference between vertical accretion and elevation change measured with feldspar marker horizons and a sedimentation erosion table surface elevation change was significantly lower than vertical accretion at each site after 2 years indicating a significant amount of shallow subsidence had occurred ranging from 0 45 to 4 90 cm the highest rate of shallow subsidence occurred in the mississippi delta results confirm kaye and barghoorn s contention that vertical accretion is not generally a good surrogate for elevation change because of processes occurring in the upper few meters of the substrate including not only compaction but also apparently shrink swell from water storage and or plant production decomposition at some sites indeed surface elevation change was completely decoupled from vertical accretion at the florida site the assumption of a 1 1 relationship between vertical accretion and surface elevation change is too simplistic a generalization of the complex interactions between accretionary and substrate processes consequently the potential for coastal marsh submergence should be expressed as an elevation deficit based on direct measures of surface elevation change rather than accretion deficits these findings also indicate the need for greater understanding of the influence of subsurface and small scale hydrologic processes on marsh surface elevation

a decade of progress in earth s internal properties and processes a major component of the inter union commission on geodynamics project labeled internal properties and processes included certain experimental and theoretical research in tectonophysics seismology geochemistry petrology volcanology and planetology this review focuses on a few research areas in which there have been surprises and reversals in particular attention is given to the attempts to quantify the thermal profile in the earth s interior and the material properties of the earth s interior

high surface elevation gains and prediction of mangrove responses to sea level rise based on dynamic surface elevation changes at dongzhaigang bay china abstract mangrove forest responses to sea level rise slr are likely misestimated in many studies because current assessment methods often assume a constant rate of surface elevation change along the intertidal profile most studies also neglect the ecogeomorphic feedback process known to accelerate soil building with slr here an empirical dynamic model that accounts for the above processes is constructed for the intertidal zone of a mangrove bay in hainan china the model allows us to explore the response of a tide dominated mangrove forest to different rates of slr rod surface elevation table marker horizon rset mh data 2015 2018 indicate rather high rates of surface accretion 13 3 57 9 mm yr 1 and surface elevation changes 7 9 35 5 mm yr 1 surface accretion and surface elevation change decreased exponentially with increasing ground elevation our model showed that slr at rates of 4 and 16 mm yr 1 would not lead to the loss of mangrove cover but that it could alter mangrove species zonation along the intertidal profile by 2100 due to a rich sediment supply and ecogeomorphic feedback importantly rapid slr and landward barriers can pose a considerable threat to the high intertidal community by causing increased inundation of the high intertidal zone subsequent shifts in species zones and the loss of mangrove biological and structural diversity along the intertidal profile overall this study predicts probabilities of habitat suitability for mangrove species under slr and expands our current understanding of the impacts of slr on tide dominated mangrove forests in sediment rich systems incorporation of extensive long term rset data into this kind of dynamic model could contribute to the better prediction of mangrove responses to slr at large scales in the future

the extreme cold anomaly over southeast asia in february 2008 roles of iso and enso a record breaking long persisting extreme cold anomaly eca over southeast asia accompanied by an intraseasonal convection over the maritime continent is identified during the la nina mature phase in february 2008 the cause of the eca in particular the role of the intraseasonal oscillation iso and el nino southern oscillation enso on the eca is investigated by diagnosing observations and con ducting numerical experiments the eca is associated with an enhanced prolonged siberian high sh and a persistent northerly anomaly over southeast asia in contrast to conventional cold surges which are characterized by a synoptic time scale less than 10 days the northerly anomaly associated with the eca persisted for a month or so the onset of the northerly anomalyis concurrent with a phase change of an iso over sumatra unlike the normal iso that continues its eastward journey the convection associated with this iso stationed there during all of february 2008 numerical experiments with an anomaly atmospheric gcm suggest that the iso heating over the maritime continent is responsible for initiating and maintaining the northerly anomaly the westward progression of the la nina is crucial for blocking the iso the circulation and sst anomalies associated with the la nina moved westward at a speed of about 158 longitude per month by early february the suppressed convective anomaly had moved to the far western pacific the westward shift of the cold episode prevented the iso from moving farther eastward in addition to its blocking effect the la nina also enhanced the heating over the maritime continent through the anomalous walker circulation therefore it is the combined effect of the iso and enso that maintained a prolonged positive heating anomaly which resulted in a persistent northerly anomaly and thus the eca

effects of air sea coupling on the boreal summer intraseasonal oscillations over the tropical indian ocean the effects of air sea coupling over the tropical indian ocean tio on the eastward and northward propagating boreal summer intraseasonal oscillation bsiso are investigated by comparing a fully coupled ctl and a partially decoupled indian ocean pdio experiment using sintex f coupled gcm air sea coupling over the tio significantly enhances the intensity of both the eastward and northward propagations of the bsiso the maximum spectrum differences of the northward eastward propagating bsiso between the ctl and pdio reach 30 25 of their respective climatological values the enhanced eastward northward propagation is related to the zonal meridional asymmetry of sea surface temperature anomaly ssta a positive ssta appears to the east north of the bsiso convection which may positively feed back to the bsiso convection in addition air sea coupling may enhance the northward propagation through the changes of the mean vertical wind shear and low level specific humidity the interannual variations of the tio regulate the air sea interaction effect air sea coupling enhances reduces the eastward propagating spectrum during the negative indian ocean dipole iod mode positive indian ocean basin iob mode and normal years during positive iod and negative iob years such phase dependence is attributed to the role of the background mean westerly in affecting the wind evaporation sst feedback a climatological weak westerly in the equatorial indian ocean can be readily reversed by anomalous zonal sst gradients during the positive iod and negative iob events although the ssta is always positive to the northeast of the bsiso convection for all interannual modes air sea coupling reduces the zonal asymmetry of the low level specific humidity and thus the eastward propagation spectrum during the positive iod and negative iob modes while strengthening them during the other modes air sea coupling enhances the northward propagation under all interannual modes due to the persistent westerly monsoon flow over the northern indian ocean

effects of sea level rise and climatic changes on mangroves from southwestern littoral of puerto rico during the middle and late holocene abstract we evaluated the response to sea level rise and climatic changes of the northeastern caribbean by establishing a palaeoenvironmental reconstruction of the flamenco lagoon located in the coastal side of the guanica dry forest a mab unesco reserve in the semi arid southwestern coast of puerto rico 17 57 10 31 n 66 50 39 30 w the reconstruction was based on pollen records sediments analysis 13 c 15 n c n data and ams 14 c dating of one sediment core the geology of the area is rocky calcareous karst with rocky outcrops and canyons with intermittent streams that move water during periods of high run off conditions the present lagoon is surrounded by rocky outcrops where dry forest vegetation is present on the terrestrial sides and sand dunes on the coastal side we propose that the studied lagoon developed after the stabilization of sea level rise in the region following three main stages 1 before 5400 cal yr bp sediments were accumulated according to small channels dynamics and trees shrubs and herbs were present the sedimentary organic matter was mainly sourced from terrestrial c 3 and c 4 plants 2 between 5400 and 4400 cal yr bp tidal flats were established and mangroves mainly represented by rhizophora trees migrated landward with sea level rise and established in the area and the sedimentary organic matter was sourced from terrestrial c 3 plants 3 around 4400 cal yr bp sea level was near the stabilization the endorheic minibasin was closed when a coastal sand dune was established as a result of drier climatic conditions mangroves were eliminated from the system as a result of the closure of the area by sand dunes and increased salinity in water due to high evaporative demand of the climate the pollen dominance of herbaceous and shrubby vegetation prevails until present throughout the lagoon development sedimentary organic matter was sourced from c 3 and c 4 plants as well as phytoplankton organic matter the closure of the lagoon and the drier conditions prevalent in the region during the late holocene which lasts until the present day and increased the contribution of salinity tolerant phytoplankton that characterizes the current conditions of the flamenco lagoon

biophysical controls on accretion and elevation change in caribbean mangrove ecosystems abstract habitat stability of coastal ecosystems such as marshes and mangroves depends on maintenance of soil elevations relative to sea level many such systems are characterized by limited mineral sedimentation and or rapid subsidence and are consequently dependent upon accumulation of organic matter to maintain elevations however little field information exists regarding the contribution of specific biological processes to vertical accretion and elevation change this study used biogenic mangrove systems in carbonate settings in belize bz and southwest florida fl to examine biophysical controls on elevation change rates of elevation change vertical accretion benthic mat formation and belowground root accumulation were measured in fringe basin scrub and dwarf forest types plus a restored forest elevation change rates mm yr 1 measured with surface elevation tables varied widely bz dwarf 3 7 bz scrub 1 1 fl fringe 0 6 fl basin 2 1 bz fringe 4 1 and fl restored 9 9 root mass accumulation varied across sites 82 739 g m 2 yr 1 and was positively correlated with elevation change root volumetric contribution to vertical change mm yr 1 was lowest in bz dwarf 1 2 and fl fringe 2 4 intermediate in fl basin 4 1 and bz scrub 4 3 and highest in bz fringe 8 8 and fl restored 11 8 sites surface growth of turf forming algae microbial mats or accumulation of leaf litter and detritus also made significant contributions to vertical accretion turf algal mats in fringe and scrub forests accreted faster 2 7 mm yr 1 than leaf litter mats in basin forests 1 9 mm yr 1 but similarly to microbial mats in dwarf forests 2 1 mm yr 1 surface accretion of mineral material accounted for only 0 2 3 3 of total vertical change those sites with high root contributions and or rapid growth of living mats exhibited an elevation surplus 2 to 8 mm yr 1 whereas those with low root inputs and low or non living mat accumulation showed an elevation deficit 1 to 5 7 mm yr 1 this study indicates that biotic processes of root production and benthic mat formation are important controls on accretion and elevation change in mangrove ecosystems common to the caribbean region quantification of specific biological controls on elevation provides better insight into how sustainability of such systems might be influenced by global e g climate atmospheric co2 and local e g nutrients disturbance factors affecting organic matter accumulation in addition to relative sea level rise

el nino and la nina sea surface temperature anomalies asymmetry characteristics associated with their wind stress anomalies 1 the asymmetric nature of el nino and la nina sea surface temperature sst anomalies is investigated by the use of national centers for environmental prediction reanalysis data and various ocean and atmosphere models it is demonstrated that the relatively weak sst anomalies during la nina compared with those of el nino are related to the westward shift of wind stress anomalies by 10 15 the asymmetric characteristics of atmospheric responses are confirmed by the general circulation model experiments with the two different sst anomalies which have equal amplitude but are of opposite sign from each other the experiments with an intermediate ocean model and a hybrid coupled model clearly show that the sst anomalies over the equatorial pacific become weaker as the zonal wind stress shifts to the west not only the amplitude but also the oscillation timescale of the sst anomaly is shown to be sensitive to the location of wind stress anomalies the duration of la nina which is rather shorter than that of el nino is also related to the longitudinal displacement of the wind stress anomaly

low frequency equatorial waves in vertically sheared zonal flow part i stable waves abstract the mechanism by which a vertically sheared zonal flow affects large scale low frequency equatorial waves is investigated with two level equatorial plane and spherical coordinates models vertical shears couple barolinic and barotropic components of equatorial wave motion affecting significantly the rossby wave and westward propagating yanai wave but not the kelvin wave this difference results from the fact that the barotropic component is a modified rossby mode and can be resonantly excited only by westward propagating internal waves the barotropic components emanate poleward into the extratropics with a pronounced amplitude while the baroclinic components remain equatorially trapped a westerly vertical shear favors the trapping of rossby and yanai waves in the upper troposphere whereas an easterly shear tends to confine them in the lower troposphere as such their westward propagation is slowed down by both westerly and easterly shears when the strength of the vertical shear varies w

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

a spatial analysis of the relationship between mangrove avicennia marinavar australasica physiognomy and sediment accretion in the hauraki plains new zealand the relationship between mangrove avicennia marina var australasica physiognomy and forest bed accretion was quantified using experimental and field measurements at the piako river mouth firth of thames new zealand sediment accretion under six densities of artificial pneumatophores was monitored for 13 weeks in an experimental plot while accretion was simultaneously monitored for 5 months at 102 locations along two parallel 500 m transects experimental results demonstrated that accretion increases with pneumatophore density this was supported by bivariate analyses of cumulative accretion and avicennia marina stem density basal area and pneumatophore density along the transects only the latter is significantly correlated with accretion geostatistical analyses showed that variation in sediment accretion occurs at the same spatial scale as pneumatophore density accretion and pneumatophore density are spatially autocorrelated over distances 70 m and have fractal dimensions of 1 5 1 6 it is proposed that avicennia marina grow pneumatophores at a density that balances the benefits of aeration with the drawbacks of sediment accretion these results are compared with the concept of positivefeedback switches in plant communities 1996 academic press limited

stratigraphical and palynological appraisal of the late quaternary mangrove deposits of the west coast of india the organic deposits derived from the mangrove swamps form reliable stratigraphic markers within the late quaternary sequence of kerala konkan basin three generations of such deposits have been identified the older one is dated to around 43 000 40 000 14c yr b p with a few dates beyond the range of radiocarbon the younger ones date from the middle holocene to latest pleistocene 10 760 4540 14c yr b p and the late holocene 4000 14c yr b p pollen analyses confirm that the deposits are mostly derived from the mangrove vegetation peat accumulation during the period 40 000 28 000 14c yr b p can be correlated with the excess rainfall 40 100 greater than modern values of the asian summer monsoon the low occurrence of mangrove between 22 000 and 18 000 14c yr b p can be attributed to the prevailing aridity and or reduced precipitation associated worldwide with last glacial maximum because exposure surfaces and ferruginous layers are commonly found in intervals representing this period the high rainfall of 11 000 4000 14c yr b p is found to be the most significant as the mangrove reached an optimum growth around 11 000 14c yr b p but with periods of punctuated weaker monsoons from the present and previous studies it has been observed that after about 5000 or 4000 14c yr b p the monsoons became gradually reduced leading to drying up of many of the marginal marine mangrove ecosystems a case study of hadi profile provided an insight to the relevance of magnetic susceptibility to record the ecological shift in late holocene

balancing aggradation and progradation on a vegetated delta the importance of fluctuating discharge in depositional systems vegetation is an important component of constructional landscapes as plants enhance deposition and provide organic sediment that can increase aggradation rates to combat land loss we conducted two sets of laboratory experiments using alfalfa medicago sativa to determine the effects of plants on channel organization and large scale delta dynamics in the first set we found that rapid vegetation colonization enhanced deposition but inhibited channelization via increased form drag that reduced the shear stress available for sediment entrainment and transport a second set of experiments used discharge fluctuations between flood and base flow or interflood interfloods were critical for reworking the topset via channel incision and lateral migration to create channel relief and prevent rapid plant colonization these low flow periods also greatly reduced the topset slope in the absence of vegetation by removing topset sediment and delivering it to the shoreline floods decreased relief by filling channels with sediment resulting in periods of rapid progradation and enhanced aggradation over the topset surface which was amplified by vegetation the combination of discharge fluctuations and vegetation thus provided a balance of vertical aggradation and lateral progradation we conclude that plants can inhibit channelization in depositional systems and that discharge fluctuations encourage channel network organization to naturally balance against aggradation thus variations in discharge are an important aspect of understanding the ecomorphodynamics of aggrading surfaces and modeling vegetated deltaic systems and the combined influences of plants and discharge variations can act to balance vertical and lateral delta growth

structures and mechanisms of the northward propagating boreal summer intraseasonal oscillation abstract the spatial and temporal structures of the northward propagating boreal summer intraseasonal oscillation bsiso are revealed based on the analysis of both the echam4 model simulation and the ncep ncar reanalysis the bsiso structure and evolution characteristics simulated by the model bear many similarities to those derived from the ncep ncar reanalysis the most notable features are the remarkable meridional asymmetries relative to the bsiso convection in the vorticity and specific humidity fields a positive vorticity perturbation with an equivalent barotropic structure appears a few latitude degrees north of the convection center the maximum specific humidity also shows a clear northward shift in the lower troposphere two internal atmospheric dynamics mechanisms are proposed to understand the cause of the northward propagation of the bsiso the first is the vertical shear mechanism the key process associated with this mechanism is the generation of barotropic vorticity due to the couplin

gravitational circulation in the upper mantle implications for crustal and mantle evolution abstract officer and drake 1983 have given an quantitative description of upper mantle convection and related plate dynamics in which the principal driving force is the longitudinal density gradient within the upper mantle between the spreading ridge and the subduction zone the principal objective here is to consider an additional component of flow in the upper mantle between the warmer and less dense spreading ridge and the cooler and more dense deep continental regions

composition of the upper mantle geophysical tests of two petrological models the elastic properties of candidate mantle phases are used to test the viability of olivine rich pyrolitic and cao al 2o 3 rich eclogitic assemblages for the mantle high temperature adiabats for each phase of interest are constructed and compared to mantle seismic properties both pyrolitic and eclogitic assemblages satisfy the seismic properties between 200 and 400 km between 400 and 670 km depth an eclogitic assemblage yields a superior match to velocities and velocity gradients the 400 km seismic discontinuity may represent a chemical boundary between pyrolite and picritic eclogite piclogite or phase transformations in the olivine orthopyroxene components of a piclogitic assemblage containing about 16 olivine high velocity gradients in the transition zone may be explained by the transformation of ca rich cpx to majorite garnet seismic properties at the top of the lower mantle are consistent with pyrolite piclogite or perovskite implying that the 670 km discontinuity may be a chemical boundary

energy spectrum characteristics of boreal summer intraseasonal oscillations climatology and variations during the enso developing and decaying phases the geographic dependence characteristics of the energy spectrum of the boreal summer intraseasonal oscillation bsiso may october over the indo western pacific region were analyzed using 25 yr 1979 2003 observational data the bsiso energy spectrum distribution exhibits a distinctive regional characteristic the stationary and eastward propagating modes are most pronounced at the equator 5 s 5 n while the westward propagating modes are dominant in the off equatorial region 10 20 n while the eastward intraseasonal oscillation iso spectrum agglomerates on the 30 60 day period and zonal wavenumber 1 the westward mode covers wider spatial wavenumber and temporal period range along the arabian sea bay of bengal and south china sea scs latitudes the dominant wavenumber 1 mode is the eastward westward propagation at the 30 60 day 10 20 day period for zonal wavenumber 2 the dominant mode is the westward propagation at both the 30 60 day and 10 20 day periods compared to the absolute amplitude of both zonal and meridional mode energy spectrum northward propagation is the most predominant mode in boreal summer over the indo western pacific regions the strongest northwardpropagating bsiso signal appears in the eastern tropical indian ocean the variation of bsiso differs significantly in the el nino and la nina developing and decaying phases during the el nino la nina developing summer the eastward propagation is enhanced weakened at the equator while the northward propagation is also strengthened weakened over the western pacific east of 140 e during the el nino la nina decaying summer the eastward propagation weakens strengthens at the equator opposite to that in the developing summer the westward propagation off the equator and the northward propagation over scs and the western pacific are suppressed enhanced the amplitude of the bsiso variation is stronger in the decaying summer than that in the developing summer this asymmetry in bsiso variations is primarily attributed to the asymmetry of the background mean flow change associated with the developing and decaying phases of enso

the weakened intensity of the atmospheric quasi biweekly oscillation over the western north pacific during late summer around the late 1990s abstractthe interdecadal pacific oscillation ipo shifted to a negative phase around the late 1990s its impact on the atmospheric quasi biweekly oscillation qbwo intensity over the western north pacific wnp during late summer was investigated corresponding to the phase transition of the ipo la nina like sst anomalies and an enhanced walker circulation appeared in the tropical pacific which led to decreased precipitation over the equatorial central and eastern pacific the decreased precipitation induced a gill response with an anomalous anticyclone cyclone in the lower upper troposphere over the wnp this resulted in anomalous background westerly vertical shear over the tropical wnp furthermore the anomalous anticyclone induced anomalous horizontal divergence and descent motion in the planetary boundary layer which led to decreased background surface moisture over the tropical wnp these changes in background atmospheric conditions suppressed the development of qbwo perturbations over the

differential rates of vertical accretion and elevation change among aerial root types in micronesian mangrove forests abstract root systems in mangrove swamps have captured the attention of scientists for decades among the postulated roles of root structures include a contribution to the geomorphological stability of mangrove soils through sediment trapping and binding in this study we used feldspar marker horizons and sediment pins to investigate the influence of three different functional root types prop roots in rhizophora spp root knees in bruguiera gymnorrhiza and pneumatophores in sonneratia alba on vertical accretion and elevation change in three mangrove forests in the federated states of micronesia prop roots facilitated vertical accretion 11 0 mm year 1 more than pneumatophores or bare soil controls mean 8 3 mm year 1 sediment elevation on the other hand increased at an average rate of only 1 3 mm year 1 across all root types with rate differences by root type ranging from 0 2 to 3 4 mm year 1 being detected within river basins this investigation demonstrates that prop roots can assist in the settling of suspended sediments from estuarine waters yet prop root structures are not as successful as pneumatophores in maintaining sediment elevation over 2 5 years as root densities increase over time an increase in turbulence induced erosion and in shallow subsidence as organic peat layers form is expected in micronesian mangrove forests

the 30 50 day variation of convective activity over the western pacific ocean with emphasis on the northwestern region abstract coherent 30 50 day oscillations between regions north and south of 20 n were observed using the latitude time y t diagram of a convective index ic along 140 e over the entire 1979 summer may september the oscillation in the northern region exhibits a relatively regular north south movement of deep convective clouds while the oscillation in the southern region shows enhancement or suppression fluctuations of broad and intensive deep convective clouds with a period of 30 50 days the southward northward movement of the midlatitude oscillation coincides with the suppression enhancement of the tropical deep convective clouds the midlatitude deep convective clouds are usually maintained by the divergent circulation and are associated with fronts the empirical orthogonal function eof analysis of velocity potential at 200 mb shows that the north south 30 50 day oscillation of deep convective clouds over the northwestern pacific is a response of the regional weather system to the eastwar

seasonal variation abrupt transition and intraseasonal variability associated with the asian summer monsoon in the gla gcm abstract in this paper a description of the global and regional features of the asian summer monsoon in the goddard laboratory atmospheres gla general circulation model gcm is presented based on a 10 yr 1979 1988 integration of the model under the atmospheric model intercomparison project it is found that the earliest signal of onset of the asian monsoon is represented by the emergence of convection over the indo china land bridge in early may followed by the sudden jump of the equatorial itcz intertropical convergence zone to 10 n over the south china sea and indian ocean in mid may this sudden jump is linked to an abrupt northward shift of the ascending branch of the local hadley circulation possibly stemming from symmetric instability of the basic flow in may in agreement with observations the model shows a pronounced intraseasonal oscillation along the equator and enhanced synoptic scale activities identified as easterly waves in the tropical and subtropical western pacific these int

speculations on the thermal and tectonic history of the earth summary the connection between the earth s thermal history and convection in the mantle is exploited to elucidate the early evolution of the earth it appears probable that convection extending over almost all of the mantle has dominated vertical heat transport throughout the whole of the earth s history only in boundary layers at the surface and at a depth of 650 700 km is conduction likely to be important the resulting evolution appears to be consistent with geological observations on early precambrian rocks various arguments are put forward in favour of two horizontal scales of convective flow in the mantle at depths less than 650 km the large scale flow is related to the motion of major plates and must be ordered over distances of more than 5000 km its evolution and energetics are discussed and there are no obvious problems in maintaining the proposed convective motions small scale flow with an extent of the order of 500 km appears necessary both to explain the heat flow through older parts of the earth s surface and to reconcile the geophysical observations with the results of numerical experiments though the existence of the small scale flow is at present speculative various tests of its presence are proposed

tidal scale flow routing and sedimentation in mangrove forests combining field data and numerical modelling tidal scale biophysical interactions establish particular flow routing and sedimentation patterns in coastal mangroves sluggish water flows through the mangrove vegetation and enhanced sediment deposition are essential to maintain these valuable ecosystems thereby enabling their contribution to coastal protection and stabilization spatially explicit field observations of tidal scale flow routing and sediment deposition were obtained in an elevated mangrove stand dissected by tidal creeks located in the trang river estuary at the thai andaman coast an accurate and efficient depth averaged process based numerical model of this field site was developed in delft3d to study the contributions of various biogeophysical mangrove settings to the observed tidal dynamics and to study the impacts of changes of these environmental conditions the creeks are found to form the major pathway for the tidal inflow during the lower tides while the sheltered interior of the forest is an effective sediment sink during the higher tides a numerical sensitivity analysis of the initial response or adaptive capacity of the studied mangrove system to instantaneous environmental changes reveals the stable state of the study site deposition rates are largely imposed by the topography and relative elevation while they are rather independent of the vegetation density deeper inundations of the mangroves favor sheet flows through the forest and spatially averaged deposition rates decrease particularly when this coincides with decreasing vegetation densities moreover the sediment trapping efficiency is found to reduce significantly with diminishing sediment inputs and with mangrove area losses these results clearly indicate the sensitivity of mangroves ecosystem engineering ability in terms of sedimentation to climate change and anthropogenic threats

efficient three dimensional reconstruction of aquatic vegetation geometry estimating morphological parameters influencing hydrodynamic drag abstract aquatic vegetation can shelter coastlines from energetic waves and tidal currents sometimes enabling accretion of fine sediments simulation of flow and sediment transport within submerged canopies requires quantification of vegetation geometry however field surveys used to determine vegetation geometry can be limited by the time required to obtain conventional caliper and ruler measurements building on recent progress in photogrammetry and computer vision we present a method for reconstructing three dimensional canopy geometry the method was used to survey a dense canopy of aerial mangrove roots called pneumatophores in vietnam s mekong river delta photogrammetric estimation of geometry required 1 taking numerous photographs at low tide from multiple viewpoints around 1 m2 quadrats 2 computing relative camera locations and orientations by triangulation of key features present in multiple images and reconstructing a dense 3d point cloud and 3 extracting pneumatophore locations and diameters from the point cloud data step 3 was accomplished by a new sector slice algorithm yielding geometric parameters every 5 mm along a vertical profile photogrammetric analysis was compared with manual caliper measurements in all 5 quadrats considered agreement was found between manual and photogrammetric estimates of stem number and of number mean diameter which is a key parameter appearing in hydrodynamic models in two quadrats pneumatophores were encrusted with numerous barnacles generating a complex geometry not resolved by hand measurements in remaining cases moderate agreement between manual and photogrammetric estimates of stem diameter and solid volume fraction was found by substantially reducing measurement time in the field while capturing in greater detail the 3d structure photogrammetry has potential to improve input to hydrodynamic models particularly for simulations of flow through large scale heterogenous canopies

the 30 50 day mode at 850 mb during monex abstract the analyzed wind field at 850 mb during the summer monsoon experiment monex is subjected to a time series analysis to confirm the existence of a peak in the time range of 30 50 days having established that this study presents a mapping of the motion field for this time scale in this short paper we illustrate the steady meridional propagation of a train of troughs and ridges that seem to form near the equator and dissipate near the himalayas the meridional scale of this mode is around 300 km and its meridional speed of propagation is 0 75 latitude per day the amplitude of the wind for this mode is around 3 6 m s 1 the salient contributions here are the mapping and the demonstration of a very regular behavior of this mode its existence is here noted from a period well before the onset of monsoon i e from early may to late july three major storms during monex were noted to form within the trough line of this system and the period of major cessation of rains over the indian subconti

intraseasonal behavior of clouds temperature and motion in the tropics abstract the spectral character of tropical convection is investigated in an 11 yr record of outgoing longwave radiation from the advanced very high resolution radiometer to identify interaction with the tropical circulation along the equator in the eastern hemisphere the space time spectrum of convection possesses a broad peak at wave numbers 1 3 and eastward periods of 35 95 days significantly broader than the dynamical signal of the madden julian oscillation mjo this quasi discrete convective signal is associated with a large scale anomaly that propagates across and modulates time mean or climatological convection over the equatorial indian ocean and western pacific outside that region the convective signal is small even though under amplified conditions coherence can be found east of the date line and in the subtropics having a zonal scale of approximately wavenumber 2 anomalous convection propagates eastward at some 5 m s 1 and suppresses as well as reinforces climatological convection

northern hemisphere summer monsoon singularities and climatological intraseasonal oscillation abstract using climatological pentad mean outgoing longwave radiation olr and european centre for medium range weather forecasts analysis winds the authors show that the northern hemisphere summer monsoon displays statistically significant climatological intraseasonal oscillations cisos the extreme phases of ciso characterize monsoon singularities monsoon events that occur on a fixed pentad with usual regularity whereas the transitional phases of ciso represent the largest year to year monsoon variations the ciso results from a phase locking of transient intraseasonal oscillation to annual cycle it exhibits a dynamically coherent structure between enhanced convection and low level convergent upper level divergent cyclonic anticyclonic circulation its phase propagates primarily northward from the equator to the northern philippines during early summer may july and westward along 15 n from 170 e to the bay of bengal during august and september the propagation of ciso links monsoon singular

variations in the lithosphere thickness and vertical neotectonic movements abstract thermal changes and mechanical deformation of the lithospheric thickness are presumed to cause vertical neotectonic movements it is established that heterochronous fragments of the continental lithosphere respond differently to cenozoic thermotectonic activation lithospheric segments which had consolidated in the archean were less mobile in the cenozoic those of riphean ma and late phanerozoic age were mobile the archean fragments comprise the stable blocks of ancient and young continental platforms the riphean and late phanerozoic fragments comprise orogenic belts these regional differences may be due to different degrees of cratonization of the continental lithosphere

the 30 60 day convection seesaw between the tropical indian and western pacific oceans abstract the tropical indian and western pacific oceans are two prominent action centers for tropical 30 60 day convective variability when convection is enhanced over the equatorial indian ocean the tropical western pacific often experiences an abnormal dry condition phase i whereas the development of the convection over the tropical western pacific tends to be accompanied by suppressed convection in the equatorial indian ocean phase ii this convection seesaw is a fundamental characteristic of the tropical 30 60 day oscillation the seesaw is intimately associated with the activity of propagating low frequency convective systems lfcss its formation process is season dependent typical boreal summer seesaw results from a time lagged development of two systems a western system that originates in the equatorial indian ocean and moves eastward and or northward and an eastern system that develops in the western pacific monsoon region and moves westward and or northward the boreal winter seesaw o

reflection properties of phase transition and compositional change models of the 670 km discontinuity seismic observations of the amplitude ratio amplitude p 670p amplitude p p suggest a reflection coefficient r 7 13 for reflections from the underside of the 670 km discontinuity this can be compared with calculated reflection coefficients to constrain the nature of the mantle transition region velocity and density profiles through the transition region were calculated for olivine pyroxene garnet and olivine garnet model mineral assemblages for models with identical upper and lower mantle compositions the computed reflection coefficients from the phase transitions pertinent to the 670 km discontinuity are less than 0 5 these phase transitions produce their maximum r if they are effectively discontinuous which gives r 2 3 except for the garnet to perovskite transformation which gives r 8 in general given realistic impedance contrasts across a phase transition the change in material properties must occur over a region less than 3 km thick for r to be of the order of 5 a discontinuous change in chemical composition at 670 km depth coupled with a change in phase can also produce a reflection coefficient of the observed magnitude r 2 3 for a first order change in phase at 670 km with different iron concentrations on each side of the discontinuity and r 4 6 for cases with a discontinuous increase in silica content based on our analysis the thermal and chemical boundary layers which would occur across such a chemical discontinuity would probably have negligible effects on the reflection coefficient thus although limited by considerable uncertainties the mineralogical and seismic data suggest a two layered model of the mantle with a discontinuous change in both phase and composition at 670 km

patterns of tidal flooding within a mangrove forest coombabah lake southeast queensland australia tidal flooding and surface drainage patterns have often been used to describe mangrove species zonation however in mangrove forests exhibiting little topography ambiguous species distributions and or few species such approaches are ineffective we identified four physiognomic mangrove forest types riverine fringing overwash and basin at coombabah lake a tidal lake in southeast queensland australia and investigated tidal flooding patterns using synoptic surveys of tidal observations at the local standard port combined with local water depth observation subsequently three sub types of the basin forest type were identified 1 deep basin forest with mature trees 50 cm standing water and 3 tides per year 2 medium depth basin forest with intermediate tree development 15 30 cm standing water and 20 40 tides per year and 3 shallow basin forest with relatively recent mangrove establishment 5 15 cm standing water and 80 tides per year these three basin sub types were found to flood at different tide heights with the shallow basin flooding for tides above mean high water springs and the deep basin flooding only for tide heights approaching the highest astronomical tide we propose that these basin types represent a succession in mangrove forest development that corresponds with increasing water depth and tree maturation over time the succession not only represents increasing age but also change in basin substrate composition this is manifest as increasing pneumatophore density and an increasing area of basin surface occupied by contiguous pneumatophore cover as a result it seems that mangrove development is able to modify tidal flooding into the basin by increasingly impeding water movement

a model for the boreal summer intraseasonal oscillation abstract the tropical intraseasonal oscillation iso exhibits pronounced seasonality the boreal summer iso is more complex than its winter counterpart due to the coexistence of equatorial eastward off equatorial westward and northward propagating low frequency modes and their interactions based on observational evidence and results obtained from numerical experiments a mechanism is proposed for the boreal summer iso in which the northern hemisphere summer monsoon nhsm circulation and moist static energy distribution play essential roles with a climatological july mean basic state the life cycle of model low frequency waves consists of four processes an equatorial eastward propagation of a coupled kelvin rossby wave packet an emanation of moist rossby waves in the western pacific a westward propagation and amplification of the rossby waves in south asian monsoon regions and a reinitiation of the equatorial disturbances over the central indian ocean the life cycle spans about one month and p

further efforts to limit lunar internal temperatures from electrical conductivity determinations a monte carlo procedure is used to generate a representative set of eighteen electrical conductivity profiles that are consistent with previously published lunar transfer function data in the frequency range 10 5 to 10 3 hz the electrical conductivity is most strongly constrained by these data in the approximate depth range 450 to 1350 km published laboratory electrical conductivity versus temperature data extrapolated to higher and lower temperatures are applied to convert the eighteen electrical conductivity profiles into temperature profiles for a series of radially homogeneous olivine pyroxene mixtures ranging from 100 olivine mg mg fe 0 91 to 100 aluminous orthopyroxene 6 8 wt al2o3 the 100 olivine composition yields selenotherms that approach the ringwood essene solidus at depths near 500 km while the addition of aluminous orthopyroxene either 1 9 or 6 8 wt al2o3 in concentrations exceeding 15 30 vol leads to cooler selenotherms that approach the solidus only at depths greater than about 1000 km the shape of the temperature depth profiles is not found to be strongly sensitive to the olivine pyroxene ratio if the assumption of radial homogeneity is valid at depths greater than 450 500 km on the basis of independent geophysical constraints low seismic shear wave attenuation in the upper mantle maintenance of mascon anisostasy over 3 4 b y locations of the deep moonquake foci the profile envelopes for compositions containing more than 15 30 vol aluminous orthopyroxene are considered to be most probable a comparison of the latter with present day selenotherms calculated according to thermal history models indicates the greatest consistency with the model of toksoz et al 1978 which assumed initial partial melting and differentiation to a depth of 500 km and significant radial heat transport by subsolidus convection only during the first few b y of lunar history

the influence of sea surface temperature on the tropical intraseasonal oscillation a numerical study abstract the development and movement of the tropical intraseasonal system tis exhibit remarkable annual variations it was hypothesized that spatial and temporal variation in sea surface temperature sst is one of the primary climatic factors that are responsible for the annual variation of tiss this paper examines possible influences of sst on the tis through numerical experiments with a 2 5 layer atmospheric model on an equatorial plane in which sst affects atmospheric heating via control of the horizontal distribution of moist static energy and the degree of convective instability the gradient of the antisymmetric with respect to the equator component of sst causes a southward propagation of the model tis toward northern australia in boreal winter and a northward propagation over the indian and western pacific oceans in boreal summer the phase speed of the meridional propagation increases with the magnitude of antisymmetric sst gradients the poleward propagation of the equatorial disturba

sticky waters in the great barrier reef the great barrier reef is a mosaic of regions of high and low reef density current meter observations upstream from a region of high reef density revealed that the tidal and low frequency currents were steered away from the region during spring tides but not during neap tides a mathematical model suggests that this effect was due to both tidal friction and to the dissipation of energy by eddies behind reefs at spring tides for a high reef density region this results in a longer residence time at spring tides than at neap tides conversely this effect also diminishes connectivity between regions of high and low reef density at spring tides this process may affect the recruitment and dispersion of fish and other larvae in the great barrier reef it may also invalidate the use of satellite altimetry and tidal harmonic analysis for currents in the great barrier reef

estuarine flocs their size settling velocity and density the size and settling velocity of flocs of suspended sediments from the chesapeake bay were measured in laboratory experiments and in the field the curves between floc diameter and settling velocity showed a non stoke s relationship that was best described by the following settling velocity cm s 1 73 floc diameter cm 0 78 furthermore the relationship between floc diameter and settling velocity indicated that the floe density decreased as the floes increased in size in addition to changing density a cylinder shape was found to be the best shape factor