relative weathering intensity of calcite versus dolomite in carbonate bearing temperate zone watersheds carbonate geochemistry and fluxes from catchments within the st lawrence and danube river basins 1 calcite and dolomite solubilities in open weathering environments are proportional to pco2 and inversely proportional to temperature and dolomite solubility is progressively greater than calcite below 25 c the continent scale weathering budget reveals the significance of the northern hemisphere nh to globally integrated riverine fluxes of ca2 mg2 and hco3 the nh contributes 70 of the global hco3 flux while only 54 of the riverine discharge we present results of a comparative hydrogeochemical study of carbonate mineral equilibria and weathering fluxes in two nh carbonate rich river basins surface water geochemistry and discharge were determined for headwater streams in michigan and slovenia within the st lawrence and danube river basins michigan watersheds are established atop carbonate bearing glacial drift deposits derived from erosion of paleozoic strata with thick soil horizons 100 300 cm slovenia watersheds drain mesozoic bedrock carbonates in alpine and dinaric karst environments with thin soil horizons 0 70 cm carbonate weathering intensity is a parameter that normalizes river runoff and hco3 concentration to catchment area meq hco3 km 2 s 1 summing calcite and dolomite contributions and is used to gauge the effects of climate land use and soil thickness on organic inorganic carbon processing rates importantly michigan riverine discharge is one tenth of slovenian rivers providing the opportunity to evaluate the kinetics of carbonate mineral equilibration the study rivers are hco3 ca2 mg2 waters supersaturated for calcite at pco2 values in excess of the atmosphere as discharge varies hco3 concentrations differ by less than 20 for any location and mg2 ca2 remains relatively fixed for michigan 0 5 and slovenia streams 0 4 requiring that dolomite dissolution exceed calcite on a mole basis the ability of calcite and dolomite dissolution to keep pace with increased discharge indicates carbonate weathering is limited only by water flux and temperature dependent solubility in these watersheds carbonate weathering intensity in michigan and slovenia exceeds the world average by factors between 2 and 20 and dolomite weathering intensity estimated from riverine mg2 fluxes exceeds the world average by factors between 2 and 15 thus global fluxes of carbonate related weathering products appear heavily skewed toward carbonate bearing environments at higher latitudes with relatively low mean annual temperatures and high discharge

upper stratosphere polar jet instability in the southern hemisphere synoptic scale zonal eddies longitudinal disturbances confines to polar latitudes in the southern hemisphere sh upper stratosphere have been observed in fourier analyses of temperature measurements from the limb infrared monitor of the stratosphere lims experiment during april may 1979 eddy activity at 60 degree s 1 mb is characterized by a fourier zonal wavenumber 5 wavelength approximately 4 000 km disturbance of amplitude 2 3 k which exhibits intermittent eastward propagation substantial meridional phase tilt and little vertical phase tilt these wave properties along with evidence of pronounced latitudinal variations in the upper stratosphere zonal wind distribution suggest that the synoptic scale modes may arise from a latitudinal wind shear barotropic instability of the sh polar jet stream this analysis apparently represents the first identification of polar upper stratosphere synoptic scale disturbances from satellite based information heretofore only seen in rocketsonde measurements in northern hemisphere nh polar regions and also predicted by linear model studies the ability to discern these disturbances in satellite temperature data sets offers an opportunity for future studies of the interhemispheric and interannual variability of synoptic scale eddy activity in the stratosphere however and unambiguous determination of dominant wavelength and phase speed in such studies will be precluded by the fact that satellite data alwaysmore will suffer from a certain degree of aliasing if disturbances exist with scales unresolved by the asynoptic satellite sampling less

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

origin of calcium in pedogenic carbonate nodules from silicate watersheds in the far north region of cameroon respective contribution of in situ weathering source and dust input significant amounts of pedogenic ca carbonate nodules have been observed in the far north region of cameroon in the carbonate free watershed of the mayo tsanaga thus a priori not favourable for carbonate nodules accumulations these nodules are associated with a clay rich parent material crpm covering either a granitic upstream or a greenstone bedrock downstream in this peculiar context the amount of pedogenic carbonate nodules represents large quantities of ca and c therefore determining the ca sources for pedogenic carbonate nodules is a key point regarding the mechanisms leading to carbonate nodule precipitation and their role in the biogeochemical cycle of ca three sites two on granite and one on greenstone were studied by combining sr et nd isotope systematics in order to assess the ca sources of carbonate nodules and the origin of the crpm associated with nodules carbonate nodules have a distinct sr isotopic composition in each profile pointing to the contribution of a local source for ca sr isotopic compositions of plagioclases and carbonate nodules display a concomitant variation in each profile indicating that plagioclases acted as a sr and thus ca source for the carbonate nodules nevertheless carbonate nodules have a higher sr isotopic signature than plagioclases implying the contribution of another more radiogenic sr source sr and nd isotope data from the crpm show that it is a mixture of weathered bedrock compounds and saharan dust this result highlights two other potential sr and ca sources biotite and saharan dust calculations of their respective contributions demonstrate that in situ weathering significantly adds to the ca source of nodules this result contrasts with many other studies from similar settings that highlight the importance of allochthonous marine aeolian inputs this conclusion points out that a substantial part of ca is transferred from the local bedrock to the carbonate nodules this mechanism seems to have been possible as peculiar edaphic conditions preserved the primary ca sources making in situ weathering a significant process for providing ca

a comparative study of mesospheric solar tides observed at adelaide and kyoto observations of winds in the upper mesosphere and lower thermosphere 80 110 km measured at the geographically conjugate locations of adelaide 35 s 138 e and kyoto 35 n 136 e in the years 1983 1985 are used to study hemispheric differences in the behavior of the solar diurnal and semidiurnal tides comparisons of the tidal amplitude and phase parameters show that there are distinct hemispheric asymmetries the diurnal tide is usually much larger in amplitude at adelaide and it exhibits a height structure which indicates a relatively larger contribution from the propagating 1 1 mode at this location comparisons with recent theoretical work suggest that while some of these differences may be due to hemispheric differences in forcing and or to interactions between the tide and the background winds in the middle atmosphere it is also possible that they indicate weaker turbulent induced damping of the 1 1 mode in the southern hemisphere the characteristics of the semidiurnal tide agree well at the two locations it is found that the zonal wind components are about 6 hours out of phase and the meridional components are in phase in all seasons this behavior taken together with the inferred vertical wavelengths which are greater than 100 km in summer and 45 80 km in winter indicates that there are strong contributions from the antisymmetric 2 3 mode probably forced by wind induced mode coupling from the symmetric 2 2 mode the phases near 90 km exhibit a bimodal or two state behavior with the phases being almost constant in one state near the june solstice and then making a rapid transition of between 4 and 6 hours to another phase stable state near the december solstice the duration of the state near the june solstice 6 8 months is longer than the duration of the state at the december solstice although the agreement between recent models and our observations is relatively good better agreement may be expected when more realistic wind distributions especially for the southern hemisphere are used in the models

a raised ois 3 sea level recorded in coastal sediments southern changjiang delta plain china abstract the distribution of marine influenced oxygen isotope stage ois 5 to ois 1 sediments was examined in several late quaternary boreholes from the southern changjiang yangtze delta plain china using different dating methods including osl u series ams 14c and paleomagnetism results demonstrate that coastal and estuarine deposition during ois 5 and ois 3 occurred throughout the study area however holocene transgressive sediments were absent on the taihu block the burial depth of intertidal to subtidal sediment deposited during ois 5e records 30 80 m subsidence caused by sediment compaction and tectonic movement since that time however coastal sediments formed during the late phase of ois 3 were buried to a depth of ca 6 15 m in the taihu lake area while the burial depth increased eastward to ca 45 60 m on the coastal plain this phenomenon combined with the distribution of holocene marine strata indicates at least 25 30 m uplift of the taihu block since the end of ois 3 we suggest that this uplift was mainly caused by the differential subsidence due to substantial amount of post glacial deposition by the changjiang and huanghe rivers on the continental shelf of east china marginal sea

worldwide initiation of holocene marine deltas by deceleration of sea level rise radiocarbon dated deltaic sequences of holocene age from different parts of the world began to accumulate within a restricted time range from about 8500 to 6500 years ago evaluation of major delta processes indicates that deceleration in sea level rise was the key factor in holocene delta formation within many deltas there is as much as a 2000 year age range between basal deposits in seaward and landward cores this age difference records the progressive landward migration of near mean sea level depositional environments during the lower to mid holocene establishment of a chronostratigraphic framework for holocene delta development provides a fundamental global baseline for distinguishing sea level change from vertical land motion by tectonism and isostasy and for evaluating rates of future marine incursion into low lying deltas

yangtze delta eastern china 1 geometry and subsidence of holocene depocenter abstract stratigraphic analysis of 59 borings serves to define the subsurface configuration of late quaternary deposits of the outer yangtze delta including both subaerial lower plain and its contiguous submerged sector isopachous maps of the holocene sediment section reveal a linear thickened trend parallel to the lower yangtze estuary chongming island which extends seaward southeast to the mid shelf maps depicting depths of the holocene to late pleistocene contact also highlight this thickened northwest to southeast trend and a deep downward bowing depression formed by the sedimentary sequence seaward of the yangtze mouth radiocarbon dated facies in the cores serve to calculate long term averaged subsidence rates for the holocene section 0 1 to 3 0 mm year on land and 1 6 to 4 4 mm year at sea this preliminary information is vital for planning coastal protection erosion salt water intrusion in this densely populated low lying region vulnerable to marine inundation

elliptical diagnostics of stratospheric polar vortices diagnostics based on the spatial moments of isopleths of a long lived tracer or of potential vorticity are presented that enable the structure and evolution of stratospheric polar vortices to be concisely summarized and quantified the area centre aspect ratio and orientation of the equivalent ellipse of the vortex on an isentropic surface are defined using the second and lower order spatial moments of contours within the vortex edge region by examining the variations of these elliptical diagnostics with time and altitude the temporal evolution and vertical structure of the polar vortices can be quantified the usefulness of the diagnostics is assessed by examining nitrous oxide data from the geophysical fluid dynamics laboratory skyhi general circulation model the diagnostics show and quantify several differences between the arctic and antarctic vortices in the skyhi model the arctic vortex moves further off the pole is generally more elongated and has a more complicated vertical structure than the antarctic vortex with larger variations of both the vortex centre and elongation with height the elliptical diagnostics also identify the occurrence of large scale rossby wave breaking events both at the vortex edge and in the subtropics in the model

sedimentary facies of the tide dominated paleo changjiang yangtze estuary during the last transgression abstract a large estuary was formed by marine inundation of the paleo changjiang yangtze incised valley during the transgression after the last glacial maximum this paper presents the sedimentary facies and architecture of the estuary fill based on the analysis of three sediment cores cm97 js98 and hq98 obtained from the present changjiang delta plain estuary fill deposits showing an upward fining succession were grouped into five depositional facies tidal river distributary channel muddy intertidal to subtidal flats transgressive lag and estuary front based on sedimentary textures lithology and physical sedimentary structures sand mud couplets are common in these deposits indicating that tides played a significant role in producing these sedimentary structures and that the estuary type was tide dominated some of the successive sand mud couplets probably recorded neap spring cycles as well as semidiurnal tidal cycles the nature of the estuary was very different from other representative tide dominated estuaries in sediment facies its distribution and sediment source for estuarine fill unlike the other estuaries that receive sediments mainly from the sea the paleo changjiang estuarine fill deposits were supplied largely from the river this difference would also have a great influence on the sedimentological and morphological component in the estuary the sediment distribution of the estuary showed fining seaward and estuary mouth sand bodies fed by marine source sand were absent the architecture model of tide dominated estuaries should be divided into two types by the degree of fluvial sediment supply the paleo changjiang estuary shows a good example for an estuary of large rivers

origin of strontium and calcium in pedogenic needle fibre calcite nfc abstract strontium sr and calcium ca isotopic compositions and sr ca ratios have been analysed in different fractions of pedogenic needle fibre calcite nfc from the swiss jura mountains villiers neuch tel switzerland in order to determine their ca sources and to investigate the potential role of fungi in the origin of nfc 87sr 86sr ratios have been measured to trace the ca trapped within different pedogenic carbonate this ratio was compared for previously identified microscopic morphological groups of nfc the bulk soil fine earth

evolution of the coastal depositional systems of the changjiang yangtze river in response to late pleistocene holocene sea level changes abstract the paleo changjiang yangtze incised valley fills approximately 80 90 m thick provide an opportunity to document the evolution of coastal depositional systems with large sediment supply in response to late pleistocene holocene sea level fluctuations on time scales of 103 to 104 years the sedimentary facies of the incised valley fills record three main depositional systems fluvial tide dominated estuary and tide dominated delta radiocarbon ages for the incised valley fills suggest that these depositional systems developed before about 11 ka between 11 and 8 ka and after approximately 8 ka respectively by applying sequence stratigraphic concepts the evolution of the depositional systems can be divided into three systems tracts a lowstand systems tract lst a transgressive systems tract tst and a highstand systems tract hst sea level changes on a 104 year time scale controlled the basic architecture of the sequence of the incised valley fill on the other hand sea level changes on a millennial time scale affected the stacking pattern of the systems tracts in particular the continuous sea level rise with episodic rapid rises during the last deglaciation affected the stacking pattern of the tst which is characterized by a combination of aggradation and backstepping the aggradation of fluvial and estuarine systems was dominant and the shoreline migrated only gradually landward under the relatively slow rise in sea level and a very rapid sea level rise around 12 and 10 ka caused the system to migrate abruptly landward unlike the transgressive estuarine phase the stacking pattern of the regressive tide dominated delta hst which developed within the almost filled incised valley and on the surrounding interfluve zones was characterized by seaward progradation with clinoform architecture it was initiated with aggradational and progradational stacking about 8 ka during the last phase of decelerated sea level rise and was followed by a progradational phase after the highest sea level about 6 ka

yangtze delta eastern china 2 late quaternary subsidence and deformation abstract late quaternary deposits examined on high resolution seismic profiles provide evidence of recent subsidence of the outer yangtze delta in the east china sea deformed late pleistocene strata and mud diapirs tilted bedding and gas deformed structures in holocene sequences record remobilization of underconsolidated sediment within and adjacent to the yangtze depocenter deformation types and their specific position relative to the depocenter record displacement of sediment as a result of quaternary overburden and probable compaction and deep seated tectonic motion the configuration of depositional sequences demonstrates that subsidence in the outer yangtze delta has continued from the late pleistocene to the present

how stable is the mississippi delta large deltas are commonly believed to exhibit rapid rates of tectonic subsidence largely due to sediment loading of the lithosphere as a result deltaic plains are prone to accelerated relative sea level rise coastal erosion and wetland loss hurricane katrina s devastation testifies to the severe threat that these processes pose to the mississippi delta but the relative role of tectonics versus other mechanisms causing land subsidence remains elusive relative sea level records derived from basal peat have the potential to quantify differential crustal movements over holocene time scales with exceptionally high accuracy and precision here we present new sea level index points from two study areas in the southwestern mississippi delta that essentially coincide with a recently published detailed relative sea level record from the eastern part of the delta our results show that differential vertical movements among the three study areas have been only 0 1 mm yr 1 w e compare our evidence with a recent sea level compilation from the caribbean to a large extent based on data from areas that are tectonically stable our sea level index points nearly coincide with the caribbean data showing surprising tectonic stability for considerable sections of the mississippi delta however the well documented high subsidence rates in and near the birdfoot of the mississippi delta indicate that different conditions prevail there the rapid wetland loss in coastal louisiana is likely due to a considerable extent to the compaction of holocene strata

origin of abundant moonmilk deposits in a subsurface granitic environment subsurface granitic environments are scarce and poorly investigated a multi disciplinary approach was used to characterize the abundant moonmilk deposits and associated microbial communities coating the granite walls of the 16th century paranhos spring water tunnel in porto city north west portugal it is possible that this study is the first record of moonmilk in an urban subsurface granitic environment the morphology and texture mineralogical composition stable isotope composition and microbial diversity of moonmilk deposits have been studied to infer the processes of moonmilk formation these whitish secondary mineral deposits are composed of very fine needle fibre calcite crystals with different morphologies and density calcified filaments of fungal hyphae or bacteria were distinguished by field emission scanning electron microscopy stable isotope analysis revealed a meteoric origin of the needle fibre calcite with an important contribution of atmospheric co2 soil respiration and hco3 from weathering of ca bearing minerals the dna based analyses revealed the presence of micro organisms related to urban contamination including actinobacteria mainly represented by pseudonocardia hispaniensis thaumarchaeota and ascomycota dominated by cladosporium this microbial composition is consistent with groundwater pollution and contamination sources of the overlying urban area including garages petrol stations and wastewater pipeline leakage showing that the paranhos tunnel is greatly perturbed by anthropogenic activities whether the identified micro organisms are involved in the formation of the needle fibre calcite or not is difficult to demonstrate but this study evidenced both abiotic and biogenic genesis for the calcite moonmilk in this subsurface granitic environment this article is protected by copyright all rights reserved

climatology of the stationary planetary waves seen in the saber timed temperatures 2002 2007 1 the paper focuses on the global spatial structure seasonal and interannual variability of the stationary planetary waves spw with zonal wavenumber s 1 spw1 and s 2 spw2 derived from the saber timed temperature measurements for 6 full years january 2002 december 2007 the monthly mean climatological multiyear average 2002 2007 depictions of spw temperature field extending between 20 and 120 km altitude and 50 latitude are derived a special attention is paid to the spw temperature field in the lower thermosphere where the spw1 amplifies in may and december january in the northern hemisphere nh and in april may and november in the southern hemisphere sh amplitudes in both hemispheres are similar in strato mesosphere however in the lower thermosphere sh amplitudes are significantly larger 30 k than those in nh 20 k the nh spw1 is able to propagate up to 115 km altitude contributing to the winter amplification of the lower thermospheric spw1 but that from the sh cannot penetrate above 90 100 km in the lower thermosphere above h 100 km mainly trapped spw signal is observed the spw1 are almost out of phase in both hemispheres the average 2002 2007 phases are 100 w in nh and 120 e in sh strong evidence indicates that auroral heating is a main origin of the lower thermospheric spw temperature field

inorganic carbon isotope systematics in soil profiles undergoing silicate and carbonate weathering southern michigan usa abstract the upper midwest usa features glacial derived till materials enriched in carbonate minerals but with the uppermost soil layer progressively leached of carbonates in the interval since glaciation groundwaters and groundwater fed surface waters are profoundly influenced by carbonate mineral dissolution stable carbon isotope compositions of soil waters and groundwaters in two southern michigan watersheds huron and kalamazoo were studied as a function of ph 13cco2 types of weathering reactions silicate vs carbonate and degree of isotope equilibration this comprehensive study of carbon isotope biogeochemistry in the vadose zone including soil gas soil water groundwater and soils organic matter carbonate phases elucidates relations between the chemical weathering rates and co2 fluxes in the soil zone such information is important to evaluate responses of terrestrial ecosystems to global climate change in shallow soil zones where only silicate weathering was occurring respiratory co2 was the major source of soil water dic with little addition from the atmospheric co2 isotopic equilibration between 13cdic and 13cco2 occurred in an open system with respect to soil co2 in the deeper soil horizons carbonate dissolution dominated soil water chemistry and saturation with respect to calcite and dolomite was attained rapidly mass balance calculation showed that large amounts of soil co2 were consumed by carbonate dissolution such that the deeper soil zone may not have been an open system with respect to co2 constant 13cdic values 11 were observed in these deep soil waters and also in shallow groundwaters of the huron watershed thus isotopic equilibrium might not be reached between dic and co2 possibly due to a rapid kinetics of carbonate dissolution and limited gas water exchange in the soils if so dic was equally contributed by carbonate minerals 13ccaco3 0 in reaction with soil co2 13cco2 22 soils beneath an agricultural site with a wheat corn soybean rotation the kalamazoo watershed displayed a wide range in 13cco2 values 22 to 12 and the 13cdic of deeper soil waters in contact with carbonate minerals was controlled by seasonal variations of 13cco2 as well as by strong acids produced by nitrification and to a lesser degree by pyrite oxidation both of which could react to dissolve carbonate minerals in addition to carbonic acid dissolution

stable carbon and oxygen isotope signatures of pedogenic needle fibre calcite abstract carbon and oxygen isotope compositions of the needle fibre calcite nfc from two soils observed in quarries villiers and savagnier in the swiss jura mountains are used to investigate the processes involved in the formation of these calcite crystals in pedogenic environments nfc occurs in soils with different macroscopic and microscopic morphologies three groups of microscopic morphologies are distinguished simple needles sn simple needles with overgrowths sno and simple needles with nanofibres snn nanofibres being either organic or mineral in nature these groups correspond to different stages in the formation and evolution of nfc evaluation of the 13c and 18o values of nfc and late calcite cements lcc in relationship to the composition of the carbonate host rock chr and 13cdic from the soil waters indicate that both nfc and lcc are precipitated in isotopic equilibrium with the soil waters similar 13c and 18o values of the elongated nfc and the rhombohedral calcite crystals of the lcc suggest that the precipitation of these different calcite habits is not due to changes in physicochemical conditions the growth of nfc crystals inside an organic mould formed by the fungal hyphae could explain the formation of calcite crystals in the shape of a needle in isotopic equilibrium with the local environment the comparison of the 13c and 18o signatures of the various nfc morphological groups suggests that they likely evolve in the soil solution from calcite crystals liberated during the degradation of fungal hyphae walls the nfc may be a proxy of the soil conditions temperature and vegetation during its precipitation and also an indicator of biogenic fungal activity

climatological features of mesosphere and lower thermosphere stationary planetary waves within 40 latitude 1 zonal and meridional wind measurements from the high resolution doppler imager hrdi and wind imaging interferometer windii instruments on the upper atmosphere research satellite uars are used to construct monthly average stationary planetary wave spw structures from 15 km to 110 km over the period december 1991 to september 1994 because of viewing constraints of the instruments intercomparisons between northern hemisphere nh and southern hemisphere sh structures and seasonal evolutions are mainly confined to 40 latitude the largest zonal wave number s 1 amplitudes 10 25 m s 1 in the stratosphere and mesosphere at 40 exist in the zonal wind fields and occur during september january in the nh and july october in the sh spw s 2 structures are much less prevalent especially above 80 km because of more restrictive filtering effects due to the mean winds above about 70 km s 1 wave amplitudes 5 10 m s 1 are more uniform extending over all nonsummer months in both hemispheres up to 80 90 km with similar amplitudes existing throughout the year at higher altitudes our interpretation is that the spw above about 80 90 km during summer owe their existence to ducting from the winter hemisphere in agreement with numerical simulations by pogoreltsev and sukhanova 1993 the origin of spw above about 80 km during winter at midlatitudes is not possible to determine unambiguously phase structures undergo a transition from vertical propagation with long vertical wavelengths hundreds of kilometers below 80 km to either evanescent behavior or an extreme shortening of vertical scale at higher altitudes this change in phase behavior may be connected with negative values in refractive index q for quasi geostrophic wave propagation which occur over a narrow height region near 80 km during almost every month this interruption of normal phase progression makes it impossible to distinguish the origin of the planetary wave oscillations from 1 those that tunnel through the q 0 region and 2 those that might be excited in situ by zonally asymmetric momentum deposition from gravity waves which have undergone filtering by the stratospheric planetary wave wind field in addition quantitative estimates of aliasing due to the diurnal tide indicate that it may be of sufficient magnitude to contaminate retrieved spw structures between 80 90 km and 100 110 km where local time coverages are incomplete comparisons are made between the observed spw structure and those from the horizontal wind model hedin et al 1993 1996 this model is found to provide a reasonable approximation to nh winter spw s 1 structures below 80 km but severely underestimates the amplitudes of spw in the sh

eastern mississippi delta late wisconsin unconformity overlying transgressive facies sea level and subsidence abstract analysis of 92 engineering core logs located in the balize sector of the eastern mississippi delta focuses on the late wisconsin unconformity and lithofacies of strata lying immediately below and above this stratigraphic horizon this major sequence boundary is a key feature used to correlate strata across shelf and slope to the basin observations emphasize lithofacies distributions of the latest pleistocene sediments underlying the unconformity the late pleistocene to early holocene transgressive facies and the immediately overlying deltaic deposits maps and a cross section compiled with this information highlight the critical relation between lithofacies distributions and late wisconsin sea level oscillations core analysis reveals that the transgressive facies comprises distinct environments of deposition offshore to onshore findings identify criteria to determine the approximate position of the shoreline at the late wisconsin maximum sea level lowstand and at the extent of early holocene maximum marine inundation in the balize complex mapping of lithologies along the late wisconsin unconformity serves to improve correlation of sediment facies with changes in acoustic response along high resolution seismic profiles an estimate of long term averaged land subsidence suggests lowering of at least 1 mm year near the shelfedge during the past 18 000 years this mapping also refines sea level response models for the mississippi delta including criteria to locate key paleogeographic features such as shelfedges and maximum flooding surfaces in other recent marine deltas and in older stacked deltaic sequences

carbon dioxide in scree slope deposits a pathway from atmosphere to pedogenic carbonate abstract a continuum of carbon from atmospheric co2 to secondary calcium carbonate has been studied in a soil associated with scree slope deposits in the jura mountains of switzerland this approach is based on former studies conducted in other environments this c continuum includes atmospheric co2 soil organic matter som soil co2 dissolved inorganic carbon dic in soil solutions and secondary pedogenic carbonate soil parameters pco2 temperature ph cmin and corg contents soil solution chemistry and isotopic compositions of soil co2 dic carbonate and soil organic matter 13cco2 13cdic 13ccar and 13csom values have been monitored at different depths from 20 to 140 cm over one year results demonstrated that the carbon source in secondary carbonate mainly needle fiber calcite is related to the dissolved inorganic carbon which is strongly dependent on soil respiration the heterotrophic respiration rather than the limestone parent material seems to control the pedogenic carbon cycle the correlation of 13corg values with rock eval hi and oi indices demonstrates that in a soil associated to scree slope deposits the main process responsible for 13c enrichment in som is related to bacterial oxidative decarboxylation finally precipitation of secondary calcium carbonate is enhanced by changes in soil pco2 associated to the convective movement of air masses induced by temperature gradients heat pump effect in the highly porous scree slope deposits the exportation of soil c leachates from systems such as the one studied in this paper could partially explain the gap in the european carbon budget reported by recent studies

radar observations of prevailing winds and waves in the southern hemisphere mesosphere and lower thermosphere hf radar stations utilizing the spaced antenna partial reflection technique located at adelaide 35 s 138 e and mawson station 67 s 63 e have observed horizontal mesospheric winds continuously since mid 1984 observations in the period 1984 87 are compared with the northern hemisphere latitude conjugate stations of kyoto 35 n 136 e and poker flat 65 n 147 w and with satellite derived circulation models particular reference is made to the equinoctial changeovers in zonal flow and to the temporal and altitude variations in the planetary wave activity at mawson and adelaide

process based morphodynamic modeling of the yangtze estuary at a decadal timescale controls on estuarine evolution and future trends abstract understanding the decadal morphodynamic evolution of estuaries and deltas and their controls is of vital importance regarding management for estuarine function and sustainable development this work addresses this issue by applying a process based model system delft3d to hindcast and then forecast the morphodynamic evolution of the yangtze estuary at a decadal timescale forced by the river and tides the model considers sand mud mixture and the variations of river water discharge and sediment discharge the morphodynamic model is validated against three periods i e an accretion period 1958 1978 an erosion period 1986 1997 and a recent accretion period with human activities 2002 2010 model results show good performance with respect to spatial erosion and deposition patterns sediment volume changes and hypsometry curves the model reveals quite different behaviors for mud transport between the dry and wet seasons which is subject to the prescription of river boundary conditions and bed composition we define six scenarios to project evolution to the year 2030 under decreased river inputs and increased relative sea level the simulations reveal that overwhelming amount of erosion will likely occur in the inner and mouth bar area of the estuary particularly the mouth zone will shift from net deposition before 2010 to net erosion by 2030 mainly because of decreasing sediment supply changes in water discharge have minor effects on the projected trend net erosion will be considerable when the sediment supply is extremely low 100 mt yr 1 due to the abundance of erodible modern sediment in the yangtze estuary erosion within the mouth bar area may be unexpected including the deepening of the tidal inlet at east chongming mudflat and the formation of a flood channel on the seaward side of jiuduansha shoal overall the model results provide valuable information for sustainable delta management under changing conditions for both the yangtze system and other similar estuaries and deltas with diminishing sediment supplies

upper stratospheric circulations in the two hemispheres observed by satellites a global analysis is made of upper stratospheric circulations with the aid of nimbus 5 and tiros n satellite observations in order to make a comparison of characteristics between the northern hemisphere nh and the southern hemisphere sh it is shown that the reversal of north south gradient of the zonal mean temperature at the stratopause level is always observed in higher latitudes of the sh winter while the temperature gradient of the nh winter is variable because of the occurrence of sudden warmings consequently due to the thermal wind relation the polar night westerlies of the sh stratosphere are generally stronger than those of the nh stratosphere in association with this difference the activity of transient planetary waves of wavenumber 2 is striking in the sh in contrast to the predominance of steady waves in the nh finally the interrelation between the zonal mean field and planetary waves in the upper stratosphere is briefly discussed

weathering processes in superficial deposits regolith and their influence on pedogenesis a case study in the swiss jura mountains abstract the last glacial period left a mantle of freshly reworked sediments covering the european landscape glacial periglacial fluvio glacial and aeolian dynamics enhanced transportation and mixing of materials generating new superficial deposits in which holocene soils developed these assorted surface sediments often differed from the underlying bedrock in their lithological composition and texture and were delimited by lithological discontinuities in the swiss jura mountains the mesozoic limestone bedrocks are covered by various superficial deposits moraines cover beds loess deposits cryoclasts etc which reduce or even suppress the influence of limestone on present day soil development in this context soils and their underlying bedrock no longer present a genetic continuity the nature and relationships between these deposits is studied within a toposequence of soils in terms of their mineralogical and geochemical compositions three main superficial deposits limestone bedrock clasts loess and non carbonate moraine are used as reference materials in order to characterize the complex mixing of sediments through the toposequence soils with limestone clasts undergo decarbonation and decalcification processes iron rich alpine loess deposits composed of fine silicate particles enhance brunification process in soils a non carbonate alpine moraine displays the most acidic conditions within the toposequence due to enhanced leaching clay and ions processes consequently the reworked surface sediments including limestone cryoclasts moraines and cover beds have a prevailing influence on pedogenesis compared to the hard underlying bedrock

the seasonal cycle of planetary waves in the winter stratosphere a simple mechanistic model with time independent planetary wave forcing at the lower boundary is used to investigate the observed differences between the northern hemisphere nh and southern hemisphere sh stratospheric evolution considered here are differences in both the zonal mean and the zonal wavenumber 1 structure of the winter vortex throughout its seasonal evolution in particular for small and intermediate forcing values the model robustly produces the midwinter minimum in geopotential wavenumber 1 amplitudes observed in the sh lower and middle stratosphere this feature is considered from the different viewpoints of transitions between stable equilibria wave transmission properties of the mean flow and resonant type interactions with the lower boundary wave forcing to assess the extent to which these viewpoints previously studied in the context of models representing variation with height only are relevant to a more complicated model representing variation in both height and latitude results show that resonance with the lower boundary forcing in early and late winter leading to early and late winter wave maxima and hence to an associated midwinter minimum is the dominant mechanism in the model considered for large forcing amplitudes more typical of the nh two possible winter and late winter evolutions are found to exist for the same forcing amplitudes which of these is selected depends on the details of the forcing in early winter note that there is no constant value of wave forcing amplitude that produces both a sh like undisturbed winter evolution as well a strong final warming suggesting that time varying lower boundary wave forcing is necessary to simulate these aspects of the sh evolution

a robust geochronology of the yangtze river delta based on magnetostratigraphy and cyclostratigraphy of sediment core zka2 abstract studying the evolution of sea level fluctuations climate oscillations and tectonic movements in the yangtze river delta requires a reliable chronology here we present the results of a comprehensive study of the magnetostratigraphy and cyclostratigraphy of a 295 m long sediment core zka2 recovered from nantong city jiangsu province china anisotropy of magnetic susceptibility ams studies reveal that the petrofabrics are mainly primary based on rock magnetic and thermal demagnetization analyses the major magnetic minerals in the studied sediments are magnetite hematite and greigite but only magnetite and hematite carry the primary remanence the magnetostratigraphy reveals seven reversed polarity intervals nine normal polarity intervals and one interval of mixed polarity variations in natural gamma ray activity reflect variable continental weathering in the sediment source regions and are paced by earth orbital cycles notably a prominent 405 kyr long eccentricity cycle and 100 kyr short eccentricity cycle are evident which allow us to constrain the basal age of core zka2 to 3 1 ma the magnetostratigraphic and cyclostratigraphic results together enable us to define the depths of key chronostratigraphic and magnetostratigraphic boundaries they include the late middle pleistocene boundary at 18 m depth the brunhes matuyama boundary at 88 m depth and the matuyama gauss boundary at 254 m depth according the new chronology we find that although clear long eccentricity 405 kyr and short eccentricity cycles 100 kyr cycles are evident in the magnetic susceptibility record they are not well matched with cycles of natural gamma ray activity this suggests the source and post depositional process of the magnetic particles is complicated and it should be cautious to choose magnetic properties for cyclostratigraphic analysis

morphodynamic impacts of large scale engineering projects in the yangtze river delta morphodynamics of world s river deltas are increasingly affected by human activities which are of great ecological economic and social implications however impacts of human interventions in deltaic regions are insufficiently understood especially superimposed upon diminishing sediment supplies this study uses the heavily interfered yangtze river delta as an example to address this issue the morphodynamic impacts of the deepwater navigation channel project dncp during 1997 2013 are investigated through process based modeling approach delft3d and bathymetric data analysis the dncp was implemented in the mouth bar area of the yangtze river delta including the twin dikes and 19 groynes with the total length of 132 0 km hydrodynamic simulations indicate that the training walls resulted in weaker tidal flow and longer slack period at the east hengsha shoal ehs and stronger tidal flow at the subaqueous delta thus the ehs is characterized as a sediment accumulation zone after the completion of the training walls subsequently morphological modeling shows enhanced accretion at the ehs and enhanced erosion at the subaqueous delta when the training walls are taken into account numerical experiments further demonstrate that the above changes are mainly attributed to the seaward half of the northern training walls constructed in 2002 2005 this is probably the reason for the observed accretion peak of the ehs in 2002 2007 and the gradual increase in the erosion rate of the subaqueous delta after 2002 the schematized paths of sediment transport after the dncp indicate that sediment eroded from the subaqueous delta serves as an important source for accretion of the mouth bar area it is suggested that siltation promoting projects within the mouth bar area increased shallow shoal accretion and aggravated erosion at the subaqueous delta with the overall erosion of the yangtze river delta due to river sediment reduction large scale estuarine engineering projects substantially increase the complicacy of its morphodynamic pattern which merits close attention for sustainable delta management

the oceanic contribution to the earth s seasonal angular momentum budget seasonal variations in the speed of the earth s rotation manifest themselves as fluctuations in the length of the day lod with an amplitude of about 1000 microseconds s we know from previous work that at least 95 of these variations can be accounted for in terms of angular momentum exchanged between the atmosphere and the solid earth here we examine the respective contributions of the antarctic circumpolar current acc and the global oceans to the earth s seasonal angular momentum budget using in situ data from the drake passage and results from both the oceanic regional model fine resolution antarctic model fram of webb et al 1991 and the global oceanic model of maier reimer et al 1993 as analyzed by brosche et al 1990 the estimated annual contribution of the acc 2 4 s is much smaller than the total variation in the oceanic models or the existing lod aam residual both 15 20 s the estimated semi annual acc contribution 3 8 s is offset by counter currents further north in both oceanic models which exhibit larger semi annual variations in planetary angular momentum further refinements in the earth s seasonal angular momentum budget therefore will require the full planetary plus relative contribution of the global oceans in addition to that of the acc

lims limb infrared monitor of the stratosphere observation of traveling planetary waves and potential vorticity advection in the stratosphere and mesosphere eastward and westward traveling waves were observed by the nimbus 7 limb infrared monitor of the stratosphere lims during the northern winter 1978 1979 eastward waves were prevalent in early winter and were involved in a minor canadian warming in december 1978 a large westward traveling wave as described by previous authors was observed in january 1979 during a series of minor warmings by comparing these two events it is shown that in both cases the superposition of traveling and quasi stationary waves led to constructive interference that was responsible for the warmings however there was significant asymmetry between eastward and westward traveling components eastward disturbances were confined mostly within the polar vortex whereas quasi stationary and westward traveling components propagated to the vortex periphery and beyond into the tropics and mid latitude mesosphere this behavior is consistent with rossby wave propagation and indicates that the location and magnitude of planetary wave breaking is sensitive to the frequency spectrum entering the middle atmosphere however this asymmetry is also a signature of the nonlinear critical layer as it projects onto the frequency spectrum both interpretations are shown to be valid during wave events observed by lims a local eulerian analysis of potential vorticity pv transport indicates that adiabatic geostrophic advection by the resolvable scales of motion explains qualitatively but not quantitatively the observed potential vorticity tendencies in the lims northern hemisphere winter in particular calculated advection explains the eastward rotation of the main vortex intrusion of low pv air into the polar cap and formation of high pv filaments at the vortex periphery

sedimentary facies and holocene progradation rates of the changjiang yangtze delta china abstract the changjiang yangtze river one of the largest rivers in the world has formed a broad tide dominated delta at its mouth during the holocene sea level highstand three boreholes cm97 js98 and hq98 were obtained from the changjiang delta plain in 1997 1998 to clarify the characteristics of tide dominated delta sediments and architecture based on sediment composition and texture and faunal content core sediments were divided into six depositional units in ascending order they were interpreted as tidal sand ridge prodelta delta front subtidal to lower intertidal flat upper intertidal flat and surface soil deposits the deltaic sequence from the prodelta deposits to the delta front deposits showed an upward coarsening succession overlain by an upward fining succession from the uppermost part of the delta front deposits to the surface soil thinly interlaminated to thinly interbedded sand and mud sand mud couplets and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of changjiang deltaic facies sediment facies and their succession combined with ams 14c dating revealed that isochron lines cross unit boundaries clearly and delta progradation has occurred since about 6000 to 7000 years bp when the rising sea level neared or reached its present position the average progradation rate of the delta front was approximately 50 km kyear over the last 5000 years the progradation rate however increased abruptly ca 2000 years bp going from 38 to 80 km kyear the possible causes for this active progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid holocene

link between east asian summer monsoon and sedimentation in river mouth sandbars since the early holocene preserved in the yangtze river subaqueous delta front this paper presents geochemical and grain size records since the early holocene in core ecs0702 with a fine chronology frame obtained from the yangtze river subaqueous delta front since 9500 cal yr bp the proxy records of chemical weathering from the yangtze river basin generally exhibit a holocene optimum in the early holocene a weak east asian summer monsoon easm period during the middle holocene and a relatively strong easm period in the late holocene the 8 2 and 4 4 cal ka bp cooling events are recorded in core ecs0702 the flooding events reconstructed by the grain size parameters since the early holocene suggest that the floods mainly occurred during strong easm periods and the yangtze river mouth sandbar caused by the floods mainly formed in the early and late holocene the yangtze river mouth sandbars since the early holocene shifted from north to south affected by tidal currents and the coriolis force and more importantly controlled by the easm our results are of great significance for enriching both the record of holocene climate change in the yangtze river basin and knowledge about the formation and evolution progress of the deltas located in monsoon regions

on the seasonal cycle of stratospheric planetary waves quasi stationary planetary waves exhibit different seasonal behaviour in the two winter stratospheres whereas in a climatological sense wave amplitudes are large throughout northern winter in the southern hemisphere there is a climatological minimum in midwinter it is suggested here that the southern hemisphere behaviour is basically linear the midwinter minimum arising from the opacity of the strong westerlies of southern midwinter to stationary wave propagation on the other hand it is further suggested that in the northern hemisphere winter the westerlies are prevented from becoming so strong in a climatological sense by the action of the waves themselves on the mean state and that the penetration of large scale waves into the midwinter northern stratosphere thus depends on a nonlinear feedback process preliminary tests of this hypothesis are conducted using a highly truncated beta plane model of the stratospheric flow

initiation of the changjiang yangtze delta and its response to the mid holocene sea level change abstract the changjiang yangtze delta in eastern china is one of the largest tide dominated deltas in the world to obtain a more detailed information on its initiation we drilled three sediment cores pk01 hg01 and xj03 from the uppermost region of the delta plain on the basis of sedimentary facies and ams 14c dating we identified three depositional systems 1 a fluvial system 2 an estuarine system and 3 a deltaic system including an initial delta estuary delta transition and a typical delta the maximum flooding surface separates the estuarine and deltaic systems and occurred at ca 8 0 cal kyr bp when brackish water intruded landward and reached the nanjing area the changjiang delta was initiated at the area between nanjing and yizheng when the sea level rise decelerated after the rapid rise in sea level during 9 0 8 2 cal kyr bp the subsequent evolution of the changjiang delta has been shown as a seaward development model of river mouth bars with shoreline migration the oldest river mouth bar called hongqiao sand body which is located most landward was dated at 6 0 5 5 cal kyr bp in this study nearly one thousand years younger than the previous estimates a tide dominated funnel shaped estuary was formed at 8 0 cal kyr bp and lasted until the hongqiao sand bar became exposed this stage is regarded as an aggradation dominated initial stage of the changjiang delta followed by a progradation dominated stage that is characterized by the formation of a series of seaward migrating river mouth bars a relative sea level highstand in the mid holocene may be associated with glacio hydro isostatic tilting

modeling the growth limit of the changjiang delta river deltas grow in response to sediment discharge from the land it is not clear however whether or not there is a limit for such growth conceptual geometric models are used in this paper in association with the principle of mass conservation in an attempt to answer this question preliminary analyses of the changjiang delta indicate that delta growth is constrained by a number of factors the original topography bathymetry sediment supply sediment retention in the estuary sea level rise ground subsidence the quantity of sediment supply per unit area and the sediment retention index for the subaqueous delta decrease as the delta progrades towards deeper water resulting in a decreasing rate of growth the limit of growth is reached when the index approaches zero i e the shoreline reaches the shelf edge if the combined effect of sea level rise and ground subsidence is considered together with decrease in the sediment discharge from land the limit is reached at an earlier stage for the changjiang delta the model output using hypothesized sediment retention index estimates implies that the delta growth will reach its limit in the near future this will occur sooner if the sediment output of the river is reduced to 60 of its original level in response to the upstream basin changes further knowledge however is required of the retention index together with the information on future changes in river input and the character of the sediments in order to improve the accuracy of the simulations

morphology and isotope heterogeneity of late quaternary pedogenic carbonates implications for paleosol carbonates as paleoenvironmental proxies abstract stable isotope values and radiocarbon ages were determined for pedogenic carbonate microsamples from relict soils and palaeosols from the rio grande rift region of new mexico carbonate nodules and clusters were sampled from fluvial and piedmont soils and palaeosols with widely varying exposure durations 7 900 ky pedogenic carbonates from individual soils exhibited irregular relationships between age and depth ranging in radiocarbon age by 13 ky at individual depths 18 o values and to a lesser extent 13 c values likewise had wide ranges within soils however comparing the stable isotope values of carbonates with similar radiocarbon ages within and between soils revealed consistent trends in stable isotope values over time 18 o values of pedogenic carbonates tended to decrease with decreasing age 25 17 radiocarbon ka and increased with decreasing age 13 c values with either depth or age although the oldest palaeosol piedmont carbonates radiocarbon ages of 24 5 19 2 ka are 1 more negative than the younger piedmont palaeosol carbonates pedogenic carbonates in the relict fluvial soil which has by far the longest exposure period showed the greatest range in 13 c values comparing the 13 c values of samples of similar radiocarbon age from the relict fluvial soil indicates a transition from a mixed c 3 c 4 ecosystem at 11 ka to an effectively pure c 3 ecosystem at 9 ka followed by a return to mixed vegetation by 5 ka thus although c 4 vegetation persisted in southern new mexico through the last glaciation drought resistant c 3 vegetation became dominant at 9 ka prior to significant strengthening of the summer monsoon this study illustrates that the stable isotope values of carbonate nodules and clusters from relict soils and or slowly buried palaeosols can be used for palaeoenvironmental reconstructions in the context of a detailed chronologic framework

recent subsidence and northeast tilting of the nile delta egypt abstract sediment borings collected in the nile delta of egypt many of them radiocarbon dated indicate that the entire northern sector of this major depositional center in the eastern mediterranean is presently subsiding mapping of the base of the holocene deltaic facies which is dated at about 8000 6500 yrs b p reveals that differential lowering of the northern delta plain is preferentially accentuated toward the northeast long term subsidence rates at or near the coast averaged for the mid to upper holocene range from about 0 1 to 0 25 cm yr between alexandria and the north central delta margin rates increase markedly eastward to a maximum of about 0 5 cm yr in the port said manzala lagoon region and this rapid lowering explains the presence of thick marine delta lobe sequences of holocene age in cores in the northeastern delta in contrast only reworked remnants of holocene marine delta lobe deposits of the earlier river nile branches which once flowed to the north and northwest are preserved seaward of the present north delta coast subsidence has induced marked environmental changes particularly with respect to coastal erosion and salt water incursion the asymmetric pattern of saline ground water here attributed in part to the northeast tilt of the delta plain has serious implications for agricultural development in this intensely cultivated region

the seasonal evolution of planetary waves in the southern hemisphere stratosphere and troposphere seasonality in planetary wave structure in the southern hemisphere stratosphere and troposphere 1000 1 mb is studied based on eight years 1979 1986 of daily geopotential data emphasis is placed on the distinctive seasonality in the stratosphere along with tracing the stratospheric fluctuations into the troposphere time filtering is used to separate stationary and transient components maximum geopotential height variance is observed in the middle to upper stratosphere in late winter spring with a distinct secondary smaller maximum in late fall early winter these maxima sandwich the strongest mid winter zonal winds this sequence occurs approximately one month earlier in the upper stratosphere two corresponding peaks are observed in stratospheric zonal mean wind and temperature fluctuations the two maxima in stratospheric wave variance are not in agreement with observed seasonal changes in quasi geostrophic refractive index of the zonal mean flow the stratospheric geopotential variance maxima result from nearly equal amounts of stationary and transient zonal wave 1 fluctuations with transient wave 2 also contributing during late winter stationary wave 1 shows intriguing seasonal evolution the early winter maximum is predominantly equivalent barotropic whereas that of late winter spring is highly baroclinic in the stratosphere stratospheric poleward fluxes of heat and momentum both exhibit pronounced maxima during september october these result primarily from the stationary wave 1 contributions and the transients assume a secondary role although not as pronounced as the stationary wave seasonality seasonal differences in transient wave behaviour are also documented including three dimensional propagation characteristics and wave mean flow interaction diagnostics

bedrock versus superficial deposits in the swiss jura mountains what is the legitimate soil parent material soils are generally considered to be the result of in situ weathered products of geological substrata nevertheless the earth s surface is mainly composed of superficial deposits made of sediments reworked during periods of climate instability glaciation aridification flooding etc but to what extent do these deposits influence present day soil development and or lessen the contribution of the geological substratum in the swiss jura mountains characterization and distribution of superficial deposits along a toposequence are used in order to decipher the polygenic sources of soil parent materials and question the importance of lithodependence in soil development the in situ weathering material and the allochtonous deposits are discriminated through analysis of mineralogical composition grain size distribution of the soil mineral fraction and multivariate statistical treatment as expected calcite is dominant in the autochonous mineral phase leading to high ph values in deep soil layers however the mineralogical composition of the surficial deposits is made of local mineral components mixed with allochtonous aeolian deposits this exogenous material is dominated by quartz and phyllosilicates and is reflected by low ph values in soil surficial horizons the grain size distribution curves of the insoluble residue from bedrocks are unimodal and dominated by fine loam and clays in contrast surficial deposits display polymodal curves demonstrating the contribution of various aeolian episodes and or sources analysis of the surface texture of quartz sand grains shows glacial marks intersected by aeolian shock marks indicating the posteriority of wind transportation loess material originates from alpine moraines of the swiss plateau and is mixed with deposits originating from more proximal jura moraines diluting the alpine signature consequently the soil development does not follow the expected and conventional decalcification process but is directly influenced by the origin of the primary sediments even when present only in small amounts and their evolution copyright 2012 john wiley sons ltd

architectural stacking patterns of the ebro delta controlled by holocene high frequency eustatic fluctuations delta lobe switching and subsidence processes abstract during the late pleistocene and holocene 125 ka b p to present a type 1 4th order depositional sequence comprising regressive lowstand transgressive and highstand system tracts formed worldwide the holocene 10 ka b p to present part of this contains the latest and present highstand systems tract hst within this and the underlying transgressive systems tract tst of the ebro delta in northeastern spain higher frequency 5th to 6th order sea level fluctuations are recognised these form retrogradational and progradational high frequency depositional sequence sets within the tst and hst respectively each high frequency sequence comprises 1 a basal highly reflective shell lag associated with an erosional transgressive surface 2 aggradational deposits which seawards consist of a wedge of marine clays with transparent seismic facies but inland are represented by thick peats 3 progradational deposits composed of sandy delta front facies displaying slope clinoforms these pass seawards into prodeltaic grey silts and landwards into red silts and pebbly sands of delta plain facies the progradational deposits downlap towards their bases the aggradational deposits formed in response to a period of rising sea level and a rapid increase in accommodation space progradation began when sediment supply to the delta exceeded accommodation space as a result of relative sea level fall the relative sea level curve for the delta has a stepped character caused by the punctuation of the 4th order sea level trend by higher frequency eustatic fluctuations as well as by high subsidence rates of about 1 75 mm per year the tst comprises retrogradational parasequences that onlap the underlying pleistocene gravels the maximum flooding surface separating the tst from the hst was formed about 6900 yrs b p on the basis of14c dating of peats the hst comprises progradational deltaic and aggradational units stacked as progradational high frequency parasequence sets the hst of the ebro delta is compared with other deltaic sequences around the world in particular with that of the mississippi delta a tentative chronology of the high frequency climatic and eustatic oscillations influencing deltaic sedimentation globally over the last 7000 years is presented

interannual variability of the 4 day wave and isentropic mixing inside the polar vortex in midwinter of the southern hemisphere upper stratosphere 1 interannual variations of the flow field and large scale horizontal transport and mixing inside the wintertime polar vortex of the southern hemisphere upper stratosphere are investigated using isentropic winds obtained from the u k met office assimilated data for nine years of 1992 2000 we focused on the midwinter july when the polar vortex is not much distorted although an eastward propagating wave called the 4 day wave is observed in some years in the polar region finite time lyapunov exponents are computed and contour advections are done to examine stirring and mixing in the polar region when the 4 day wave has a large amplitude effective mixing through a stretching and folding process is seen inside the polar vortex finite time lyapunov exponents are sometimes as large as the midlatitudes and the material contours of small areas grow exponentially in time on the poleward side of 70 s such mixing properties are not uniform inside the vortex when the wave is not clearly seen on the other hand wind fields are close to a solid body rotation around the pole and mixing is very small lyapunov exponents are small and the material contours grow linearly in time by the stretching due to the meridional shear of the polar night jet such interannual variability of the strength of the mixing is correlated with the variability of the perturbation amplitude of potential vorticity in the polar region

seismic framework and the holocene morphological evolution of the changjiang river mouth china abstract acoustic profiling in combination with coring has been used to examine the recent evolution of river mouth of the changjiang two acoustic facies are present petrologic radiometric and seismic analyses show that the upper facies i of 10 20 m thick fine sand and silt represents the sandy shoals of late holocene age in the distributary and the 5 20 m thick lower facies ii of fine grained silty clay with abundant marine microfossils represents the mid holocene prodelta facies deposited as fillings in the former large estuarine valley of late pleistocene to early holocene origin rapid accumulation during the holocene has led to some instability of unconsolidated sedimentary strata in the distributary such as strata collapse and mud diaper formation the existence of large cross beddings such as tabular and trough stratification in facies i identifies the sediment transport as predominantly bed load driven by runoff and tidal currents two sets of discrete flood ebb flow troughs oriented nw and se reflect controls by tidal waves generated from the sea and the superimposition of runoff and ebb flows symmetrical sand waves that appear at the northern trough of one of the distributaries also indicate the balancing sediment dynamics between runoff ebb and flood currents whereas the asymmetrical ones in the southern trough indicate superimposed sedimentation by runoff and ebb flows a large quantity of sediment has been deposited in the slack water region between the discrete flood and ebb flows to form sandy shoals the principal mechanism of the evolution of estuarine islands in the holocene changjiang mouth the morphology of the extended river mouth to the southeast possibly indicates an external driving force such as the coriolis effect nw prevailing wind and longshore currents

barotropic stability of realistic stratospheric jets abstract the stability of realistic jets is examined in a linearized barotropic model on a sphere approximately non dispersive modes associated with a region of negative basic state absolute vorticity gradient on the poleward side of the jet are examined in detail as in previous studies broader jets and those which peak at higher latitudes produce poleward modes that are less dispersive jet profiles derived from observational data at 10 5 and 2 mb for three southern hemisphere winter months are used in the model and the results are compared with quasi nondispersive features qndf which have been observed in satellite data in the southern hemisphere winter stratosphere characteristics of the barotropically unstable modes compare remarkably well with those of the observed modes the barotropic model results for a month in which these features are not observed indicate the presence of equatorward modes at wavenumbers 3 and 4 which grow considerably faster than the quasi nondispersive poleward modes

intercomparison of planetary scale diagnostics derived from separate satellite and radiosonde time mean temperature fields the planetary scale components of the extratropical northern hemisphere troposphere stratosphere 1973 74 winter circulation are diagnosed using separate time mean temperature fields based on radiosonde and satellite observations meridional cross sections of zonal wind together with for zonal wavenumbers 1 2 and 3 the streamfunction amplitude phase and eliassen palm flux are displayed with the relative accuracy of the satellite derived diagnostics assessed through comparison with the ground truth radiosonde information the satellite and radiosonde diagnostics compare most favourably in terms of zonal wind speed and shear direction of wave propagation and meridional wave structure all of which are closely related to the differential properties of the atmospheric temperature field the intensity of the satellite derived patterns of tropospheric wave propagation is underestimated due to the effects of spatial smoothing and residual cloud contamination present in the satellite radiance measurements

planetary wave mean flow interaction in the stratosphere a comparison between northern and southern hemispheres by the use of stratospheric height and temperature field data obtained from the tiros satellite dynamical interaction between planetary waves and mean zonal winds in the stratosphere is investigated special attention is paid to differences between northern and southern hemispheres an analysis is made for pressure levels from 70 to 0 4 mb during the period from june 1981 to may 1982 eliassen palm e p flux diagnostics are used as a powerful and useful tool to investigate the wave mean flow interaction from winter to summer the seasonal marches of wave activity measured by the e p flux and of mean zonal wind are different between the two hemispheres in the nh wave activity varies intermittently with a characteristic timescale of about two weeks once the core of the stratospheric westerly jet shifts poleward due to a minor warming the subsequent wave activity breaks the westerlies dramatically to replace them by the easterlies in association with the sudden warming whilst in the sh wave activity in mid winter is quiet corresponding to small time variations of the maximum westerly speed in late winter the core of the stratospheric westerly jet suddenly shifts poleward and downward due to a wavenumber 2 minor warming after the shifting of the westerly jet the wave activity of wavenumber 1 is enhanced and continues until early summer on the basis of this observational evidence we discuss i the seasonal evolutions of wave activity and the mean zonal wind ii the interannual variability of the stratospheric circulations and iii the time variation of wave activity

some comparisons between the middle atmosphere dynamics of the southern and northern hemispheres comparisons are drawn between certain middle atmosphere dynamical processes in the southern hemisphere and the northern hemisphere attention is focused on the zonal mean climatological state stationary waves transient waves of various types stratospheric sudden warmings and polar ozone minima observations of the similarities and differences between the hemispheres are mentioned and ways in which these comparisons may be used to enhance our dynamical knowledge of the whole middle atmosphere are discussed

deltaic land subsidence and sea level fluctuations along the east coast of india since 8 ka a palynological study the consequences of climate change and land subsidence are often related to sea level rise fall mangrove extinction and migration were assessed through palynological studies in two sedimentary cores in order to address climate relative sea level rsl and its relation to geomorphology since 8420 cal yr bp from kanuru 500 cm deep and since 5850 cal yr bp from machilipatnam 118 cm deep krishna delta india four units nine phases of sediment depositional environment were identified on the basis of marine terrestrial palynomorphs in unit 1 the marine palynomorphs indicate palaeoshoreline in kanuru from 8420 to 8300 cal yr bp which is now 4 5 km from the present day shoreline but after a short span a retreat in sea level took place between 8300 and 7040 cal yr bp about three to four short term intermittent rise fall in rsl were recorded in unit 2 between 7040 and 3980 cal yr bp in kanuru and between 5225 and 3240 cal yr bp in machilipatnam during this period the diversity of mangroves was

dating modern deltas progress problems and prognostics 1 abstract radiocarbon dating is the method most frequently used to date holocene deltaic sequences but less than one quarter of 14c dates are within 500 years of predicted age such dates tend to be unreliable in other words often too old and commonly inverted upsection and core sample dates obtained near deltaic plain surfaces may be as old as mid to late holocene stratigraphic irregularities result primarily from downslope reworking of upland alluvial sediment with displacement of old carbon in the sediment that accumulates in lower valleys and deltaic plains use of dates that are too old results in inaccurately calculated rates most often too low of relative sea level rise and or land subsidence more reliable timing of deltaic sediment requires a multiple method dating approach including where possible identification of associated archaeological material developing an accurate dating strategy is a critical step for implementing reliable coastal protection measures needed for the rapi

environmental change in the yangtze river delta since 12 000 years b p abstract a 52 m core from qidong at the tip of the yangtze river chang jiang delta provides a history of sea level change deltaic development and vegetational and climatic changes during the last 12 000 yr about 12 000 yr ago when sea level was about 60 m below the present level the coring site was situated in the innermost part of the exposed continental shelf the late pleistocene vegetation on the uplands of the lower yangtze river valley was a mixed forest of deciduous and broadleaved evergreen trees in which betula ulmus tsuga and cupressaceae were slightly more abundant than at present abies and picea were probably present as relict populations on mountains bordering the region rapidly rising sea level converted the qidong area to a coastal or estuarine environment between 11 000 and 10 800 yr b p leading to widespread development of wetlands dominated by gramineae and cyperaceae during the next 2500 yr coastal erosion due to marine transgression obliterated the sedimentary record deltaic sedimentation predominated from 8300 to 3800 yr b p as the yangtze river delta prograded by successively building a series of estuarine sand bars during the mid holocene the climate was slightly warmer and more humid than at present allowing the subtropical broadleaved evergreen trees to increase their populations pinus and quercus became more abundant after 3800 yr b p in response to climatic cooling the present deltaic plain in qidong formed less than 200 yr ago

the huanghe yellow river and changjiang yangtze river deltas a review on their characteristics evolution and sediment discharge during the holocene abstract today asian rivers play an important role in delivering sediment from the land to the oceans however past sediment discharge before human activities modified the landscape is not well known and is estimated to have been roughly one third to one half of the present level chinese rivers have been strongly influenced by human activities and their sediment discharge has changed over the last 6000 years for the study of the long term human impact on rivers and catchment basins chinese rivers provide excellent examples because continuous historical records are available here the characteristics evolution and sediment discharge during the holocene of the deltas of two large chinese rivers huanghe yellow river and changjiang yangtze river are summarized the huanghe and changjiang deltas are different with respect to coastal environments water and sediment discharge the pattern of development of the delta lobe thickness of holocene sediments and basal topography of the incised valleys formed during the last glacial period the huanghe delta is characterized by a high concentration of sediment huge sediment discharge thin holocene deltaic sediments a lateral delta lobe shift and a steep longitudinal profile in its lower reaches the changjiang delta is characterized by a large water discharge a large interseasonal water level change a tide dominated coastal environment continuous seaward progradation with isolated river mouth sand bodies thick holocene sediments and a deep incised valley formed during the last glacial period based on the sediment volume of prograding deltaic sediments over the last 6000 years the sediment discharge of huanghe 1000 years ago is estimated to have been 1 10 8 tons year 1 10 of the present level an abrupt increase occurred at ca 1000 years ago as a consequence of human activities on the loess plateau especially involving cultivation and deforestation moreover the estimated sediment load of huanghe at sanmenxia station prior to 1000 years was 2 7 4 0 10 8 tons year or about 20 15 25 of the present level our recent study estimated that the sediment discharge of changjiang before 2000 years bp was ca 2 4 10 8 tons year total sediment discharge of both rivers before 2000 years bp is estimated to have been 3 4 10 8 tons year or only about 20 of the present level moreover the total sediment load to the lower reaches is estimated to have been 5 6 10 8 tons year or one fourth the present level

observations of the 5 day wave in the mesosphere and lower thermosphere the 5 day planetary wave has been detected in the winds measured by the high resolution doppler imager hrdi on the upper atmosphere research satellite uars in the mesosphere and lower thermosphere 50 110 kin the appearances of the 5 day wave are transient with a lifetime of 10 20 days in the two year data set the structures of selected 5 day wave events are in generally good agreement with the 1 1 rossby normal mode for both zonal and meridional components a climatology of the 5 day wave is presented for an altitude of 95 km and latitudes mainly between 40os and 40on

soil development on sediments and evaporites of the messinian crisis abstract vast areas in the mediterranean are characterised by evaporite deposits of the messinian crises c 6 5 3 ma bp during this period large deposits were built up in shallow lagoon like systems and are now found in southern italy albania cyprus and turkey so far soil formation on evaporites has been studied predominantly in subarid to arid environments although the formation of soils has received new significance little is known about the evolutional trajectories on evaporites of the mediterranean we therefore studied soil formation in the caltanissetta basin sicily where evaporites are most widespread the lithologies included the sequence marine clay deposits laminated marl diatomite tripoli sediments calcare di base limestone detritic deposits gypsum selenite the chemical signature immobile elements rare earth elements indicated that they all have a similar origin surprisingly both an increasing corg and carbonate content in the soils caused a decrease in the 13c signal in carbonates and in part in the bulk soil the low 13c and 18o values of carbonates in the parent material indicate a high rock water or meteoric water interaction that has occurred during sedimentation and diagenesis organic matter was oxidised into the shallow lagoon like systems and its carbon incorporated in the limestone elemental leaching from silicates during pedogenesis was most intense in the soils that developed on clays and tripoli sediments vertisols and mollisols have evolved together with a high amount of oxyhydroxides non crystalline and crystalline forms and kaolinite only weak soil formation was recognisable at sites having gypsiferous parent material the presence of a high amount of selenite hindered a more advanced evolution the soils developed on detritic and gypsiferous material exhibited some palygorskite that was inherited from the parent material at sites having selenite or limestone shallow aridisols or mollisols are found weathering is weakly pronounced e g indicated by a high proportion of trioctahedral minerals besides inheritance from the parent material smectite and kaolinite are also actively formed in the soils with increasing weathering plagioclase and mica are the main sources of smectite and k feldspar is a main source of kaolinite neo formation the evaporite deposits vary greatly within short distances causing a high spatial diversity of soils consequently soil quality strongly varies which challenges agricultural use well developed soil profiles and advanced weathering stages are only possible when marine clays tripoli sediments or detritic deposits are the parent material limestone calcare di base and gypsiferous sediments selenite strongly limit soil formation and mineral transformation

interannual variability of the vertical descent rate in the antarctic polar vortex to investigate a descent rate in the antarctic polar vortex we analyzed the long lived trace gas data derived from the halogen occultation experiment on board the upper atmosphere research satellite during the 6 year period from 1992 to 1997 by comparing the antarctic fall february and march and spring september and october methane profiles we estimated the middle stratospheric descent for each of the six winters large year to year variations are seen 1 2 1 8 km month 1 at 0 6 ppmv which consist of a biennial oscillation and a decreasing trend for the period analyzed the descent rate is larger in the even years 1992 1994 and 1996 than in the odd years 1993 1995 and 1997 dynamical fields for the 6 years are also analyzed using the united kingdom meteorological office assimilation data the differences between the even and odd years are clear in the midwinter in the even years the downward and poleward movement of the westerly jet occurs earlier the thermal wind relation infers that this event is associated with the development of a warm pool around the antarctic stratopause resulting from adiabatic heating due to the downward motion of air planetary wave activity over the winter season is more vigorous in the even years than in the odd years suggesting a close relationship between the mean flow and planetary waves

neolithic agriculture freshwater resources and rapid environmental changes on the lower yangtze china analyses of sedimentary evidence in the form of spores pollen freshwater algae dinoflagellate cysts phytoliths and charcoal from ams 14c dated holocene aged sequences provide an excellent opportunity to examine the responses of neolithic agriculturalists in the lower yangtze to changing environments evidence from two sites close to the southern margin of the yangtze delta and separated by what is now hangzhou bay attests the critical importance to early attempts at food production of access to freshwater resources more readily if episodically available freshwater resources during the early to mid holocene on the hangjiahu plain may have encouraged an early reliance on rice based agriculture which in turn facilitated the accumulation of agricultural surpluses and cultural diversification cultural change was relatively attenuated and human population pressures possibly lower on the ningshao plain seemingly because of much more profound environmental impacts of variations in local hydrological conditions and because predominantly saline conditions associated with rising relative sea level hampered the early development of irrigated agriculture the evidence although largely dating to the early and middle parts of the holocene provides a timely warning of the complexity of vulnerability to climate change induced processes of agriculture and indeed human activities more generally on megadeltas in asia

upward decrease of organic c n ratios in the okinawa trough cores proxy for tracing the post glacial retreat of the continental shore line abstract six piston cores were collected along the nw se line in the okinawa trough close to the chinese continental shelf edge and dated by 23 ams 14 c measurements along with planktonic 18 o stratigraphy and an ash layer dated as 6 3 ka on a time scale to 19 ka the ratio of total organic carbon to total nitrogen concentration c n ratio displays gradual decreases toward the present and suggests the decrease of vascular plant fragment input to the trough from continental rivers this suggestion is confirmed by similar decreases of lignin phenol content and ratio of c 28 fatty acid to c 16 fatty acid content in core rn93 pc3 the gradual decrease of land plant fragment input is interpreted to be a consequence of the retreat of the continental coastline during the deglacial period

transparent heavy minerals and magnetite geochemical composition of the yangtze river sediments implication for provenance evolution of the yangtze delta abstract heavy mineral and detrital magnetite geochemistry were analyzed to extract sediment provenance indexes from different reaches of the modern yangtze river which were used to trace sediment source of the yangtze delta and to speculate its geomorphology change since the pliocene our results show that diagnostic heavy minerals of the upper yangtze sediment are characterized by clinopyroxene 12 on average and magnetite 7 on average the middle reaches by ilmenite zircon and tourmaline and the local small rivers by fluorite detrital magnetite composition of ti mg v and cr is high in the upper yangtze from the underlying basalt these diagnostic indexes are then used in the pliocene sediment core to extract provenance signal of different yangtze reaches analysis of core sediment of the yangtze delta reveals that sediment provenance of the pliocene was from local small rivers since the beginning of the pleistocene core sediments provenance was similar to that of the middle yangtze tributaries after 1 2 ma high content of pyroxene and magnetite grains that are rich in ti mg v cr imply sediment provenance signals from the upper yangtze sediment provenance shift from short distance sources to more distant sources indicates that the geomorphology of the yangtze delta region has undergone a great transformation since the pliocene this dramatic landform change is likely in response to continuous uplift of the tibetan plateau and accelerated subsidence of the east china coast since the pliocene

impacts of human activity on the late holocene development of the subaqueous yangtze delta china as shown by magnetic properties and sediment accumulation rates development of the yangtze delta during the late holocene and its relationship to human activities in the drainage basin was analyzed using data from 16 cores collected from distributaries to the

seasonal bias in the formation and stable isotopic composition of pedogenic carbonate in modern soils from central new mexico usa in order to better calibrate pedogenic carbonate as a proxy for past environments we compared the stable isotopic composition of soil co 2 soil water and pedogenic carbonate in young soils from central new mexico usa seasonal changes in the 13 c value of soil co 2 the 18 o value of soil water and the soil temperature were monitored to establish the timing of isotopic equilibrium with the carbonate calcite solubility was calculated from measured temperatures and co 2 concentrations in the soil this approach allowed us to determine the conditions associated with pedogenic carbonate formation carbon isotope equilibrium oxygen isotope equilibrium and minimum calcite solubility all occurred simultaneously during warm dry conditions in may 2008 when soil co 2 concentrations were low it is therefore concluded that pedogenic carbonate forms during warm dry periods and does not record mean growing season conditions as typically assumed the seasonal bias in pedogenic carbonate formation may explain the occurrence of pedogenic carbonate in monsoon climates and its absence in regions where annual precipitation is more uniformly distributed the implications of the seasonal bias for stable isotope based paleoenvironmental reconstructions are that paleoelevations may have been previously over or underestimated paleoatmospheric co 2 concentrations likely have been signifi cantly overestimated and pedogenic carbonate provides a c 4 biased record of paleovegetation especially in dry soils

the biogenic origin of needle fibre calcite needle fibre calcite is one of the most ubiquitous habits of calcite in vadose environments caves deposits soil pores etc its origin either through inorganic indirect or direct biological processes has long been debated in this study investigations at 11 sites in europe africa and central america support arguments for its biogenic origin the wide range of needle morphologies is the result of a gradual evolution of the simplest type a rod this rod is the elementary brick which by aggregation and welding builds more complex needles the absence of cross welded needles implies that they are welded in a mould or under a longitudinal and unidirectional constraint before being released inside the soil pores the difference between the lengthening of the needles and the c axis can be explained by the existence of needles observed under a scanning electron microscope in organic sleeves which can act as a mould during rod growth complex morphologies with epitaxial outgrowths on straight rods cannot have grown entirely inside organic microtubes they must result from soil diagenesis after the release of straight rods in a soil free medium whisker crystals are interpreted as the result of growth and coalescence of euhedral crystals on a rod rhomb chains are considered to be the consequence of successive epitaxial growth steps on a needle during variations in growth conditions isotopic signatures for needle fibre calcite vary from 16 63 to 1 10 and from 8 63 to 2 25 for 13c and 18o respectively the absence of high 18o values for needle fibre calcite precludes a purely physicochemical origin evaporative for this particular habit of calcite as epitaxial growth cannot precipitate in the same conditions as initial needles needle fibre calcite stable isotopic signatures should be used with caution as a proxy for palaeoenvironmental reconstructions in addition it is suggested that the term needle fibre calcite should be kept for the original biogenic form the other habit should be referred to as epitaxial forms of needle fibre calcite

a sudden warming in the middle atmosphere of the southern hemisphere this paper presents a case study of a wave mean flow interaction or minor warming near the southern hemisphere stratopause for 15 30 july 1974 the analysis is based mainly on data from the selective chopper radiometer carried by nimbus 5 a deceleration of the zonal mean wind of 70 m s 1 from 20 to 25 july is observed in middle latitudes at 0 5 mb with an acceleration further south the polar vortex is however not disrupted eliassen palm cross sections are presented for the event and a good correlation found between the e p flux convergence and the deceleration the channelling of the e p fluxes from the tropopause to the convergent region is in broad agreement with the distribution of refractive index but there is a region of e p flux divergence at high levels in polar latitudes suggesting a source of wave activity there the residual circulation is calculated both from the momentum budget and from an omega equation both methods diagnosing a region of modest equatorward flow near the region of e p flux divergence embedded in the stronger poleward flow elsewhere maps of potential vorticity on the isentropic surface of 0 1640 k are presented and the evolving pattern related to zonal mean and isobaric descriptions the event is shown to be associated with an incursion of low latitude air into middle latitudes with a corresponding irreversible mixing of potential vorticity reminiscent of the wave breaking in northern hemisphere events reported by mcintyre and palmer j at ter ph 46 825 but of much smaller amplitude

interannual variability of the stratospheric circulation in the southern hemisphere the variability from year to year of the seasonal evolution in the southern hemisphere stratosphere over a period of 10 years from 1980 to 1989 is investigated using the global geopotential height derived from the data from the stratospheric sounding unit on board the tiros noaa satellites as a measures of interannual variability the variance of the zonal mean geostrophic wind over the 10 years was calculated for each day although the major warming hardly occurs in the southern hemisphere stratosphere large variances can be observed during the winter and spring the maximum variances appear at low latitudes in late autumn move towards mid latitudes in midwinter and remain near 60 s in spring the seasonal movement of the zonal mean westerly jet in the southern hemisphere stratosphere can be classified into two categories in terms of the location of the maximum westerlies at the 1 mb level in midwinter namely hlj high latitude jet years with maximum westerlies around 50 s llj low latitude jet years with maximum westerlies around 40 s during the late winter the core of the westerly jet moves polewards earlier in hlj years in llj years in association with this earlier movement the growth of the amplitudes of planetary waves 1 and 2 during the period from winter to spring occurs earlier in hlj years than in llj years in autumn however the wave 1 amplitude only for llj years develops vigorously in the stratosphere and even the troposphere before the seasonal movement of the zonal mean westerly jet branches off into the two categories the appearances of hlj and llj years occur in groups of a few years this is quite different from the behaviour of the equatorial quasi biennial oscillation

low latitude mesospheric mean winds observed by gadanki mesosphere stratosphere troposphere mst radar and comparison with rocket high resolution doppler imager hrdi and mf radar measurements and hwm93 1 low latitude mesospheric winds are investigated using data collected from 1995 to 2006 11 years by indian mst radar located at gadanki 13 5 n 79 2 e clear eastward and westward flow in zonal wind is noticed during solstices and equinoxes respectively the meridional wind shows equatorward flow below 75 km and poleward flow above 75 km quite consistent with that observed with other techniques the winds show a clear semiannual oscillation sao with maxima during equinoxes the strength of the sao during spring is larger than that of fall equinox and the first peak occurs at higher altitudes than the second peak the observed features are compared with other techniques namely rocket high resolution doppler imager hrdi and medium frequency mf radar and also with horizontal wind model hwm93 in general good comparison is seen among various techniques with some discrepancy observed in amplitudes interestingly decrease in eastward wind with time during winter months is noticed the significance of the present results lies in showing the consistency inconsistency of various experimental techniques to measure the middle atmospheric winds which are very important to assess the climate variability

seasonal variation of isentropic transport out of the tropical stratosphere the seasonal variation of the isentropic transport out of the tropical stratosphere is examined using contour advection calculations with winds from meteorological analyses for the period july 1991 to june 1994 calculations using winds from three different meteorological analyses are compared there is good qualitative agreement between the different calculations for extratropical structures but not for structures in the tropics there is also reasonable agreement between area diagnostics for transport out of the tropics derived from these calculations transport out of the tropics occurs in rossby wave breaking events in which filaments of tropical air are drawn into middle latitudes in all years these wave breaking events occur during the fall to spring period when there are westerlies throughout middle latitudes late september to early may in the northern hemisphere this includes periods before the formation of and after the breakup of the polar vortex in the northern hemisphere the rate of transport out of the tropics during fall to spring fluctuates around a constant value whereas in the southern hemisphere there is a relatively quiet midwinter period with maxima in the transport in early and late winter