constraints on the evolution of crustal flow beneath northern tibet crustal flow is an important tectonic process active in continent continent collisions and which may be significant in the development of convergent plate boundaries in this study the results from multidimensional electrical conductivity modeling have been combined with laboratory studies of the rheology of partially molten rocks to characterize the rheological behavior of the middle to lower crust of both the songpan ganzi and kunlun terranes in the northern tibetan plateau two different methods are adopted to develop constraints on melt fraction temperature and crustal flow velocity in the study area the estimates of these parameters are then used to evaluate whether crustal flow can occur on the northern margin of the tibetan plateau in the songpan ganzi crust all conditions are satisfied for topography driven channel flow to be dominant with partial melt not being required for flow at temperature above 1000 c further north the kunlun fault defines the southern boundary of a transition zone between the tibetan plateau and the qaidam basin constrained by the estimated melt fractions it is shown that channel injection across the fault requires temperatures close to 900 c the composition of igneous rocks found at the surface confirm those conditions are met for the southern kunlun ranges to the north the qaidam basin is characterized by colder crust that may reflect an earlier stage in the channel injection process in the study area at least 10 of the eastward directed tibetan crustal flow could be deflected northward across the kunlun fault and injected into the transition zone defining the northern margin of the tibetan plateau

laboratory measurements of electrical conductivity of hydrous and dry silicic melts under pressure an interpretation of the electrical signature of molten rocks within the earth s interior in terms of nature and temperature conditions of magma requires additional laboratory data on the electrical conductivity of silicate melts this paper describes an experimental setup and presents measurements of the electrical impedance of dry and hydrous 1 3 wt h2o metaluminous obsidians determined in an internally heated pressure vessel in the range of 50 400 mpa and 350 1325 c it is shown that the temperature and pressure dependences of electrical conductivity of both hydrous and dry obsidian can be fitted by an arrhenius law applying in the melt and the glass regions this suggests that a similar transport mechanism operates in both melt and glass the determined activation energies are 70 kj mol for the dry obsidian and 65 and 61 kj mol for the 1 and 3 wt h2o melts respectively the activation volume is 20 cm3 mol combination of tracer diffusion and electrical conductivity reveals that sodium is the dominant charge carrier in the hydrous and dry obsidians the temperature and pressure effects on conductivity are therefore interpreted in terms of activation energy and activation volume for na mobility in dry and hydrous rhyolites an increase in conductivity associated with addition of water was observed and is shown to reflect the effect of water incorporation in melts on the mobility of sodium as a prospective it is anticipated that both the mobility and content of sodium could control the electrical conductivity of most terrestrial silicate melts magma under differentiation becomes more conductive due to sodium and water enrichment associated with fractional crystallization therefore its electrical signature must reveal its nature and maturity

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

residual circulation in shallow estuaries 1 highly stratified narrow estuaries long wave theory and simple turbulence closures have been used to show that three distinct types of circulation highly stratified weakly stratified and partially mixed arise in narrow shallow estuaries from the finite amplitude of the tide and the interaction of stratification with vertical mixing each type has a different dominant process causing the vertical exchange of salt and fresh water on the flood and each gives rise to a characteristic residual circulation the tidal circulation in highly stratified shallow estuaries described herein is the result of a finite amplitude internal motion driven by the barotropic tide shear instabilities at the interface are the major vertical exchange mechanism the residual circulation is caused primarily by ebb flood asymmetry in interface position and thickness a model based on our theoretical analysis shows that the interface thickness on flood is much less than the depth of flow up to a critical tidal amplitude at which the two layer flow is destroyed and correctly predicts the tidal amplitude of the neap spring transition in the columbia river estuary tidal frequency internal wave motion is not found in weakly stratified and partially mixed estuaries because of the reduced tidal shear shear instabilities are weak or absent and the residual circulation assumes a very different character as described in part 2

partly pedogenic origin of magnetic variations in chinese loess quaternary sequences of interbedded aeolian silts loess and buried soils palaeosols potentially provide one of the best terrestrial records of past climates1 5 magnetic susceptibility variations in loess and palaeosol sequences from china are strongly correlated with climate induced fluctuations of oxygen isotope ratios in deep sea sediments2 4 6 8 as an explanation of this correlation it has been suggested that the recorded variations in magnetic susceptibility depend primarily on the degree of dilution by non magnetic bulk loess constituents of a uniform magnetic assemblage derived from remote but unknown sources6 8 it has also been suggested that such a model involving changes in the accumulation rate of loess superimposed on a constant flux of magnetic particles provides a relative geological timescale through the control of loess deposition by astronomically modulated climate fluctuations7 here we report a preliminary test of this model using rock magnetic properties especially sensitive to variations in magnetic grain size our results show that palaeosols are characterized by much finer magnetic grain size assemblages than are the intervening loess units this suggests that a simple model based on constant magnetic influx and dilution by variable amounts of non magnetic loess is inadequate our magnetic measurements establish the close comparability of the fine grained magnetic minerals in the palaeosol samples to those in contemporary soils and thus point to a partially pedogenic origin for the magnetic mineral assemblages in the palaeosols

loess deposits from the tajik depression central asia magnetic properties and paleoclimate abstract continuous accumulation of dust during the quaternary has formed widespread loess deposits in southern tajikistan the magnetic susceptibility variations of these aeolian sediments have recorded the paleoclimatic fluctuations in a similar direct and complete way to the well studied sediments from the central loess plateau in china 11 susceptibility measurements were carried out in situ at intervals of 10 cm along seven partly overlapping sections in the loess paleosol sequence of karamaidan ca 100 km east of dushanbe nearly 250 oriented samples were taken for rock magnetic investigations careful field observation revealed a total actual loess thickness of ca 100 m for a composite profile with thirteen intervening pedocomplexes pc standard demagnetization techniques yielded a characteristic component of natural remanent magnetization nrm which was used to obtain a well defined magnetostratigraphy the section covers a total timespan of approximately 1 m y including the brunhes and the youngest part of the matuyama polarity chron the susceptibility variations correlate excellently with those of the chinese loess record at xifeng 22 although minor differences in the relative amplitude of the susceptibility signal occur close correlation with the astronomically tuned oxygen isotope record 26 enables refined dating of the loess sequence at karamaidan and demonstrates the global significance of the recorded paleoclimatic variations especially with respect to paleoprecipitation on land during the quaternary

subtidal circulation in a deep silled fjord douglas channel british columbia douglas channel a deep fjord on the west coast of british columbia canada is the main waterway in the fjord system that connects the town of kitimat to queen charlotte sound and hecate strait a 200 m depth sill divides douglas channel into an outer and an inner basin this study examines the low frequency from seasonal to meteorological bands circulation in douglas channel from data collected at three moorings deployed during 2013 2015 the deep flows are dominated by a yearly renewal that takes place from may june to early september a dense bottom layer with a thickness of 100 m that cascades through the system at the speed of 0 1 0 2 m s 1 which is consistent with gravity currents estuarine flow dominates the circulation above the sill depth and the observed landward net volume flux suggests that it is necessary to include the entire complex channel network to fully understand the estuarine circulation in the system the influence of the wind forcing on the subtidal circulation is not only at the surface but also at middepth the along channel wind dominates the surface current velocity fluctuations and the sea level response to the wind produces a velocity signal at 100 120 m in the counter wind direction overall the circulation in the seasonal and the meteorological bands is a mix of estuarine flow direct wind driven flow and the barotropic and baroclinic responses to changes to the surface pressure gradient caused by the wind stress

a mechanism governing the estuarine circulation in deep strongly stratified fjords the estuarine circulation in deep strongly stratified fjords is discussed it is argued that a two layer description of the stratification in the fjord is correct in very wide fjords wide compared to the width of the mouth and possibly also in narrow fjords with high runoff and or weak mixing a theory for the thickness and the salinity of the brackish layer in a wide fjord was earlier developed by the present author and published in swedish 1975 and it is presented here among other findings in that theory we may mention that the thickness of the brackish layer is primarily determined by the internal hydraulic control for high specific runoff runoff unit horizontal surface area of the fjord and weak mixing in the other extreme with low specific runoff and strong mixing the thickness of the brackish layer is found to be proportional to the monin obukhov length the circulation in not very wide fjords is also discussed it is found that recirculation in the brackish layer may be expected whereby a two layer description of the flow field breaks down at least locally a critical rayleigh number that seems to control the recirculation of brackish water within the fjord is found a theory for the density difference between the mouth and the head in the brackish layer in the fjord is developed from the critical rayleigh number condition it is found that this density difference normally is proportional to the density difference between the brackish water at the mouth and the underlying sea water provided that the river runoff is not too heavy and or the mixing is not too weak this prediction is confirmed by extensive measurements from the nordfjord

winter spring precipitation as the principal control on predominance of c3 plants in central asia over the past 1 77 myr evidence from δ13c of loess organic matter in tajikistan abstract although changes in atmospheric co2 levels are thought to be the major factor driving long term c3 c4 vegetation evolution recent studies tend to emphasize the effect of regional climate conditions on c3 c4 variations the middle latitudes 30 45 in which c3 c4 plants are highly sensitive to environmental changes provide an optimal basis for the investigation of the relative impacts of climate and pco2 on shifts in c3 c4 cover in order to assess the factors controlling these shifts as well as the complex interactions between environmental factors the carbon isotopic composition of bulk organic matter from the chashmanigar loess section southern tajikistan was measured for the past 1 77 myr in general the 13c record shows mostly negative values throughout the sequence almost all 13c values falling between 23 and 26 indicating a predominance of c3 plants in central asia over this time period despite the presence of numerous glacial interglacial cycles from 0 85 myr to the present the 13c values become increasingly positive reflecting a growing c4 signal however this c4 component is not detectable prior to 0 25 myr after which minor peaks are evident at 228 171 and 18 kyr the 13c record from chashmanigar indicates that winter spring precipitation i e mediterranean climatic conditions have characterized central asia throughout the past 1 77 myr leading to the predominance of c3 vegetation in the context of glacial interglacial scale changes in atmospheric co2 therefore it is climate rather than pco2 that controls c3 c4 variations in asia s middle latitudes the gradual increase in the c4 component since 0 85 myr especially the notable peaks after 0 25 myr may have been caused by an increase in summer precipitation due to an enhanced southward shift of the climate zones

properties of magmatic liquids by molecular dynamics simulation the example of a morb melt abstract a new atom atom interaction potential is introduced for describing by classical molecular dynamics md simulation the physical properties of natural silicate melts the equation of state the microscopic structure the viscosity the electrical conductivity and the self diffusion coefficients of ions in a mid oceanic ridge basalt morb melt are evaluated by md over a large range of temperature and pressure 1673 3273 k and 0 60 gpa a detailed comparison with experimental data shows that the model reproduces the thermodynamic structural and transport properties of a morb with an unprecedented accuracy in particular it is shown that the morb melt crystallizes at lower mantle conditions into a perovskite phase whose the equation of state eos is compatible with those proposed in the experimental literature moreover in accordance with experimental findings the simulation predicts not only that the morb viscosity exhibits a slight minimum with the pressure but also that the viscosity at high temperature remains very low 2273 k even at high pressure up to 40 gpa however the evolution of the electrical conductivity with temperature and pressure is not always the symmetrical of that of the viscosity in fact the relationship between viscosity and electrical conductivity shows a crossover at around 2073 k

dry late glacial and early holocene climate in arid central asia indicated by lithological and palynological evidence from bosten lake china abstract stratigraphical and chronological investigations of four sediment cores from bosten lake the largest inland freshwater lake in china provide a reliable regional environmental evolution record since the late glacial the stratigraphy of the four cores has been well correlated according to their lithology and chronology osl and 14c dates pollen and grain size data from bosten lake show evidence for a dry regional climate during late glacial and early holocene 16 8 cal ka bp indicated by a thick layer of aeolian sand deposit 100 cm although the climate became humid after 8 cal ka bp analysis of pollen assemblages pollen a c ratio and ephedra percentage also indicates that the climate was relatively dry in the bosten lake area between 8 and 6 cal ka bp while afterwards more humid conditions ca 6 1 5 cal ka bp are assumed comparison with other lake records from arid central asia influenced by the westerly winds generally supports the assumption of late glacial to early holocene dry climates in westerly dominated regions hence they contrast the holocene climate development in monsoon asia relatively wet conditions during the late holocene 6 1 5 cal ka bp might be induced by stronger westerly circulation

a late pleistocene holocene lacustrine record from lake manas zunggar northern xinjiang western china information on the late quaternary palaeoclimate in the zunggar desert northern xinjiang is deduced from the study of three 5 m long cores taken from lake manas analyses including the mineralogical composition of bulk sediments stable isotope contents of carbonates organic matter pollen and diatoms were performed to help reconstruct the environmental evolution of the area the chronology is provided by 9 ams 14c dates done on carbonates or organic matter the record suggests a late pleistocene humid episode radiocarbon dated at 37 000 32 000 yr b p this episode is followed by a period of extreme aridity attributed to the last glacial maximum the early mid holocene record indicates conditions generally wetter than today as previously established for western china however our results show that the holocene period is rather complex after a minor wet warm pulse estimated to be around 12 000 yr b p the most important environmental change is recorded at 10 000 yr b p it led to the establishment of a steppic vegetation cover in the catchment and of a permanent lake which lasted 4000 years fluvial sedimentation took place between about 6000 and 4500 yr b p and it coincided with a decrease in moisture availability for vegetation growth a second lacustrine episode is recorded from about 4500 to 2500 yr b p although the pollen record and a sudden influx in detrital organic matter suggest a short term dry event around 3800 3500 yr b p the last 2500 years show climate unstability and the step wise establishment of hypersaline conditions in lake manas the major post glacial environmental changes appear to be roughly in phase with those observed in tibet

holocene climate and vegetation changes inferred from pollen records of lake aibi northern xinjiang china a potential contribution to understanding of holocene climate pattern in east central asia abstract this research focuses on the reconstructions of the lake hydrologic variations and the basin wide vegetation changes over past 13 870 years based on pollen data of 195 samples and the lithologic variations obtained from lake aibi in the western part of xinjiang area our results showed that lake or swamp environment did not come into existence until 13 870 cal bp and swamp or wetland environment dominated the depression of the basin between 13 870 and 7430 cal bp under ameliorated basin wide moisture conditions the following period between 7430 and 3620 cal bp witnessed lake transgression in the depression and vegetation amelioration within the basin the moisture conditions were continuously ameliorated from 3620 cal bp onward leading to further lake transgression and further basin wide vegetation amelioration a dry interval from 1400 to 1150 cal bp interrupted the late holocene wet epoch of the past 3600 years our synthesized regionally averaged moisture index of xinjiang area indicates that a gradual wetting climate dominated the mid to late holocene in xinjiang area this wetting trend in xinjiang area is hypothesized to have been associated with the winter warming and winter wetting trends in northern europe the gradual increase of winter insolation in mid to late holocene might have enhanced evaporation in the north atlantic ocean and injected more moisture to the westerlies system therefore bringing more precipitation to the downwind area including xinjiang

moisture dynamics in central asia for the last 15 kyr new evidence from yili valley xinjiang nw china based on high resolution palynological investigations and ams 14 c dating the continuous lacustrine sediments contained in yili valley xinjiang provide an opportunity to reconstruct the effective moisture changes for the last 15 kyr in central asia the relatively warm and humid climate of the bolling allerod 15 12 9 cal kyr bp is a generalization but it seems to show some fluctuations the time of the younger dryas yd interrupted the increasing trend of effective moisture in the study region the climate was cold and relatively dry in the early yd period 12 9 12 0 cal kyr bp whereas the desert vegetation community appeared around 11 8 cal kyr bp almost the driest time since the 15 cal kyr br a sharp increase in effective moisture marked the beginning of the holocene in the yili valley the early holocene 10 6 7 6 cal kyr bp was the wettest time with a developed temperate steppe a dry climate with desert vegetation arose in the early mid holocene 7 6 6 5 cal kyr bp spanning 1100 years a second humid phase emerged between 6 5 and 5 2 cal kyr bp whose vegetation community was represented by temperate steppe moisture was reduced again and the climate became drier between 5 2 and 3 3 cal kyr bp when vegetation was dominated by desert steppe in the yili valley regional comparisons indicate that the moisture changes in yili valley were mainly influenced by the north atlantic ocean ssts through the westerlies the mean position of the siberian high pressure cell probably made a great contribution to the drought between 7 6 and 6 5 cal kyr bp the climate changes were generally consistent between the westerly dominant central asia and asian monsoon regions since the last deglaciation possibly forced by summer insolation conditions in the northern hemisphere c 2011 elsevier ltd all rights reserved

structure of the central altyn tagh fault revealed by magnetotelluric data new insights into the structure of the northern margin of the india asia collision abstract the altyn tagh fault atf is a left lateral strike slip fault that forms the northern margin of the tibetan plateau and plays a significant role in accommodating the convergence between the colliding indian and eurasian plates as a part of the fourth phase of the indepth project magnetotelluric mt data were collected across the central segment of the atf to determine the lithospheric scale structure of the fault system dimensionality analyses demonstrated that the mt data can be interpreted using two dimensional approaches but some localized 3 d effects are seen consequently both 2 d and 3 d inversions were carried out and a joint interpretation was made on the basis of these two types of models inversion models revealed two major conductors beneath the qaidam basin qb and altyn tagh range atr respectively the conductive region beneath the qb was interpreted as a ductile layer in the lower crust to upper mantle that might represent flow beneath the western margin of the qb whereas the large scale south dipping conductor beneath the atr is interpreted as a region with high fluid content formed by metamorphism associated with the oblique underthrusting of the tarim block beneath the northern tibetan plateau these fluids migrate upwards through the fault system and have formed serpentinized zones in the crust combining these interpretations a structural model compatible with diverse geophysical observations is proposed in which we suggest the competing end member rigid block model and continuum model are reconcilable with the continuum model locally dominant for the study region as evidenced by a thickened crust

the dynamics of shelf forcing in greenlandic fjords abstractthe fjords that connect greenland s glaciers to the ocean are gateways for importing heat to melt ice and for exporting meltwater into the ocean the transport of heat and meltwater can be

out of phase evolution between summer and winter east asian monsoons during the holocene as recorded by chinese loess deposits we analyzed climate proxies from loessic soil sections of the southern chinese loess plateau the early holocene paleosol s0 is 3 2 m thick and contains six sub soil units co eval soils from the central loess plateau are thinner 1 m consequently higher resolution stratigraphic analyses can be made on our new sections and provide more insight into holocene temporal variation of the east asian monsoon both summer and winter monsoon evolution signals are recorded in the same sections enabling the study of phase relationships between the signals our analyses consist of i measurements of magnetic properties sensitive to the production of fine grained magnetic minerals which reflect precipitation intensity and summer monsoon strength and ii grain size analyses which reflect winter monsoon strength our results indicate that the holocene precipitation maximum occurred in the mid holocene 7 8 3 5 cal ka bp with an arid interval at 6 3 5 3 cal ka bp the winter monsoon intensity declined to a minimum during 5 0 3 4 cal ka bp these results suggest that the east asian summer and winter monsoons were out of phase during the holocene possibly due to their different sensitivities to ice and snow coverage at high latitudes and to sea surface temperature at low latitudes

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

3 d modeling of the deep electrical conductivity of merapi volcano central java integrating magnetotellurics induction vectors and the effects of steep topography we derive a 3 d model of the electrical conductivity structure of merapi volcano in central java from magnetotelluric mt sounding curves and geomagnetic induction vectors topography has been considered explicitly in the model the overall magnitude of the conductivities is constrained by mt measurements while lateral variations are mainly derived from geomagnetic induction vectors the resulting model is consistent with both the mt transfer functions apparent resistivities and phases and the magnetic transfer functions induction vectors the final model consists of two 3 d structures i e a central conductor and a second conductor lying to the southwest of the summit the high conductivity material is probably hot saline water as suggested by position and lateral extent of the high conductivity material

a numerical model of stratified circulation in indian arm british columbia a laterally integrated numerical model has been developed for the study of stratified circulation in inlets the model is time dependent and includes advective terms horizontal and vertical turbulent diffusion of momentum and salt and variations in width and depth initial and boundary conditions based on winter measurements in burrard inlet and indian arm were used to study the inlet s response to tidal forcing the friction term was tuned to match calculated and observed dissipation rates evidence for a standing wave pattern in the response of the m2 and k1 tidal constituents is discussed a comparison of model results with cyclesonde current meter time series at two locations in indian arm is consistent with resonance a modal decomposition of the calculated response shows that most of the energy is contained in the barotropic and first baroclinic modes with the former dominating near the sill and the latter dominating in the deep basin second mode energy was significant for the k1 at some locations

the investigation of magnetic susceptibility variation mechanism of tien mountains modern loess pedogenic or wind intensity model it had been widely accepted that in situ pedogenic enhancement of fine grained ferromagnetic content provides the well established patterns of magnetic susceptibility variation within mid latitude loess deposition such as those of chinese loess plateau and central europe an entirely different phenomenon is present in higher latitude loess deposition of alaska and siberia with high magnetic susceptibility in loess and low in soil this inverse relationship has suggested that magnetite grain size is related to wind velocity the tien mountains are located at the transition zone between the chinese loess plateau and siberia and have extensive loess deposits previous investigations have displayed a more complex correlation between pedogenesis and magnetic susceptibility with positive and negative relationships coexisting further research has indicated that a reducing environment must be an important influence in decreasing magnetic susceptibility of basal soil units in this area tien mountains loess has similar magnetic mineralogy to chinese loess plateau loess and pedogenic magnetite effectively influences magnetic properties however magnetic susceptibility does not perfectly correspond to weathering intensity change the result of high concentration and unstable primary magnetite among loess samples pedogenic magnetic material controls magnetic susceptibility variation gradually as pedogenic intensity increases magnetic susceptibility is not a great proxy of loessic soil unit pedogenic intensity in this region especially for weakly pedogenic soil units

linking bacterial community structure to advection and environmental impact along a coast fjord gradient of the sognefjord western norway abstract here we present novel data on bacterial assemblages along a coast fjord gradient in the sognefjord the deepest 1308 m and longest 205 km ice free fjord in the world data were collected on two cruises one in november 2012 and one in may 2013 special focus was on the impact of advective processes and how these are reflected in the autochthonous and allochthonous fractions of the bacterial communities both in november and may bacterial community composition determined by automated ribosomal intergenic spacer analyses arisa in the surface and intermediate water appeared to be highly related to bacterial communities originating from freshwater runoff and coastal water whereas the sources in the basin water were mostly unknown additionally the inner part of the sognefjord was more influenced by side fjords than the outer part and changes in bacterial community structure along the coast fjord gradient generally showed higher correlation with environmental variables than with geographic distances high resolution model simulations indicated a surprisingly high degree of temporal and spatial variation in both current speed and direction this led to a more episodic discontinuous horizontal current pattern with several vortices 10 20 km wide being formed from time to time along the fjord we conclude that during periods of strong wind forcing advection led to allochthonous species being introduced to the surface and intermediate layers of the fjord and also appeared to homogenize community composition in the basin water we also expect vortices to be active mixing zones where inflowing bacterial populations on the southern side of the fjord are mixed with the outflowing populations on the northern side on average retention time of the fjord water was sufficient for bacterial communities to be established

electrical conductivity of magma in the course of crystallization controlled by their residual liquid composition 1 the electrical conductivity of a magma in the course of crystallization was experimentally investigated in the temperature range of 1350 1018 c large samples of basaltic composition with a homogeneous crystal content were synthesized in a gas mixing furnace at 1 atm pressure the samples were analyzed by electron microprobe the relative proportions of the phases as a function of temperature were determined depending on temperature the phase assemblies included quenched silicate liquid plagioclase pyroxene fe ti oxides the crystal content varied from 0 to 80 wt in response to partial crystallization the residual liquid changed composition from basalt to andesite to dacite liquid the electrical conductivity of the partially crystallized basaltic samples was measured in addition above liquidus conductivity measurements were conducted on compositions matching the residual liquid at different temperature these supplemental electrical measurements allowed us to discriminate the effect of crystal content from the effect of changing liquid composition associated with partial crystallization combining with the modified archie s law a set of constraints describing the conductivity of the residual liquid versus chemical composition and temperature we propose an equation to calculate changes in conductivity associated with partial magma crystallization we showed how the composition of the residual liquid is critical on the electrical behavior of crystal liquid system the model overcomes the previous difficulties in finding a robust model for describing the electrical behavior of crystal liquid systems the effect of liquid composition on the electrical conductivity is related to diffusion mechanisms and transport properties in molten silicate combining known constraints on na tracer diffusion and our conductivity results confirms the statements that sodium is the dominant charge carrier silicate liquids from basalt to rhyolite these findings revealed that we need a comprehensive model that can predict the conductivity of molten silicate as a function of chemical composition

electrical conductivity of molten basalt and andesite to 25 kilobars pressure geophysical significance and implications for charge transport and melt structure electrical conductivities of molten hawaiian tholeiite and crater lake andesite were measured between 1200 c and 1400 c at atmospheric pressure and at pressures up to 17and 25 kbar respectively isobaric plots of log versus 1 t is electrical conductivity are linear with the exception of the zero pressure tholeiite melt data conductivities decrease with increasing pressure in both melts with the andesitic melt exhibiting a greater pressure dependence between 5 and 10 kbar abrupt decreases in the slopes of isothermal log versus p plots i e decreases in activation volume are observed for both rock melts this discontinuity probably reflects changes in melt structure as opposed to changes in conduction mechanism in each pressure range the data for each rock melt can be described reasonably well by an equation of the form 0 exp ea p v kt where 0 is a preexponential constant ea is the activation energy and v is the activation volume a qualitative model involving depolymerization of the melt with increased pressure leading to increased efficiency of packing can explain the observed discontinuity in activation volume as well as the observed pressure dependences of other melt physical properties such as viscosity and density conductivity versus melt fraction curves for partially molten peridotite are reevaluated using high pressure tholeiitic melt conductivities and crystalline conductivity values recently determined by other workers minimum melt fraction estimates of 5 10 are required to explain upper mantle regions of anomalously high electrical conductivity in terms of a partial melting hypothesis

trend of increasing holocene summer precipitation in arid central asia evidence from an organic carbon isotopic record from the ljw10 loess section in xinjiang nw china abstract due to the lack of reliable climatic proxies the variability of precipitation in westerlies dominated arid central asia aca during the holocene is debated here we present a high resolution ca 100 years per sample organic carbon isotopic composition 13corg record from bulk samples from the lujiaowan10 section in the northern piedmont of the tienshan mountains xinjiang province northwestern china a robust chronology is provided by k feldspar pirir dating during the early to middle holocene from 12 ka to 6 ka 1 ka 1000 years ago the 13corg values are relatively invariant with an average of around 22 5 after about 6 ka the 13corg values exhibit an overall negative trend with the most negative value of 25 2 occurring in the uppermost part of the section within the interval of holocene soil formation our investigation of the relationship between modern climatic variables and surface soil 13corg values from the region reveals a significant negative correlation between surface soil 13corg and summer precipitation amount june to august therefore we used the calibration model between summer precipitation amount and surface soil 13corg to quantitatively reconstruct the holocene summer precipitation history of the study area our results indicate that summer precipitation in the region was the lowest ca 85 mm during the early to middle holocene 12 6 ka however after 6 ka the precipitation increased continuously to about 137 mm per year at the present our reconstruction is generally consistent with climate simulation results and with regional effective moisture records thus we conclude that the highest summer precipitation and therefore the wettest climate occurred in the late holocene decreasing northern hemisphere summer insolation may have effected a change in the cgt circumglobal teleconnection from a positive to negative phase and together with more negative trends in ao arctic oscillation or nao north atlantic oscillation may have been responsible for the observed pattern of summer precipitation evolution

stratigraphies and chronologies of late quaternary loess paleosol sequences in the core area of the central asian arid zone abstract the sporadic distribution of the quaternary loess in central asia makes it hard to establish a regional pedostratigraphy through visual tracing of marker strata the pedostratigraphic correlation presented here is thus completely based on the radiocarbon chronologies of the four studied sections the first noticeable feature is that poorly drained conditions predominated in the period between 48 000 and 30 000 14 c bp during which three entisols developed at 45 000 14 c bp 40 000 14 c bp and 35 000 14 c bp after a period of loess deposition between 30 000 and 18 000 14 c bp under poorly drained conditions an entisol at the westernmost site valikhanov south central kazakhstan developed between 18 000 and 10 000 14 c bp also under poorly drained conditions the time equivalent deposits at romantic and zeketai sections to the east do not exhibit any soil forming characteristics although poorly drained conditions are also imprinted in the time equivalent loess the holocene sequences in the central asian domain consist of an early holocene loess unit deposited between 10 000 and 5 000 14 c bp and a late holocene soil formed during the past 5000 years in comparison the climate was also wet between 48 000 and 20 000 14 c bp during which three mollisols developed under well drained conditions in the chinese loess plateau of the east asian domain the loess deposited between 23 000 and 10 000 14 c bp in the chinese loess plateau has neither observable marks of soil formation nor imprints of poorly drained conditions the holocene sequence in the east asian domain exhibits an out of phase relationship with that in the central asian domain consisting of an early holocene soil formed between 9000 and 4000 14 c bp and a late holocene loess unit deposited during the past 4000 years

lower temperature as the main cause of c4 plant declines during the glacial periods on the chinese loess plateau abstract the distribution of c3 and c4 plants changed in regionally contrasting ways during the last glacial period c4 plant expansion in low latitude africa and america coincided with c4 plant decreases in mesoamerica and the us great plains this c4 plant expansion has been attributed to lower pco2 and increased aridity and the decline in c4 plants is believed to have been caused by increased winter precipitation and lower temperatures however it is still difficult to generalize whether pco2 temperature or aridity was mainly responsible for c3 vs c4 vegetation changes during glacial periods paleoclimate conditions on the chinese loess plateau clp offer opportunities to further evaluate the role of temperature in the c3 vs c4 competition detailed climate records have shown that the clp region was drier and colder during glacial periods with aridity favoring c4 expansion and lower temperatures favoring c3 expansion here we present two high resolution compound specific carbon isotope records of n alkanes from the clp as vegetation biomarkers to estimate the relative abundance of c4 plants during the last two glacial interglacial transitions more negative 13c values during the glacial periods from two clp sites clearly show that in contrast with low latitude sites c4 plants declined this decrease in c4 abundance was caused by lower temperature despite the lower pco2 and increased aridity on the clp during glacial time

a model for the rheology of particle bearing suspensions and partially molten rocks an edited version of this paper was published by agu copyright 2009 american geophysical union

transient simulation of last deglaciation with a new mechanism for bolling allerod warming we conducted the first synchronously coupled atmosphere ocean general circulation model simulation from the last glacial maximum to the bolling allerod ba warming our model reproduces several major features of the deglacial climate evolution suggesting a good agreement in climate sensitivity between the model and observations in particular our model simulates the abrupt ba warming as a transient response of the atlantic meridional overturning circulation amoc to a sudden termination of freshwater discharge to the north atlantic before the ba in contrast to previous mechanisms that invoke amoc multiple equilibrium and southern hemisphere climate forcing we propose that the ba transition is caused by the superposition of climatic responses to the transient co 2 forcing the amoc recovery from heinrich event 1 and an amoc overshoot

palaeoprecipitation reconstruction by inverse modelling using the isotopic signal of loess organic matter application to the nusloch loess sequence rhine valley germany a modified version of the biome4 vegetation model for simulation of the mean 13c of plant communities is presented and used to reconstruct palaeoprecipitation we treat all fractionations by c3 and c4 plants in all coexistent plant functional types weighted by their respective net primary production we constrain the range of variation in the intracellular versus atmospheric co2 concentration by fixing a lower limit finally we replace some constant parameters by functions of external forcing to account for their responses to environmental variation the new version of biome4 was applied as an inverse model and tested on three modern data sets the fit between observations and simulations is very close to the 1 1 relationship with respective slopes of 0 90 0 02 r2 0 98 n 29 for 13c and 0 97 0 06 r2 0 90 n 29 for precipitation inverse modelling was applied using the metropolis hastings algorithm to the nusloch loess sequence over the last glaciation simulated palaeoprecipitation varies between 240 mm year 1 and 400 mm year 1 this study clearly demonstrates atmospheric teleconnections with the greenland ice sheet extension by matching dansgaard oeschger events with precipitation increase of ca 100 200 mm year 1

variation and paleoclimatic significance of organic carbon isotopes of ili loess in arid central asia as an indicator for terrestrial paleovegetation the stable isotopic composition of total organic matter delta c 13 org in loess sediments has been widely used for paleoclimatic reconstruction in western europe the great plains of north america and the chinese loess plateau clp however little is known about the variation and paleoclimatic significance of the loess delta c 13 org in arid central asia aca we report delta c 13 org data from an axike axk loess paleosol profile from the eastern ili basin eastern central asia along the profile the delta c 13 org values were more negative in the paleosol layers observed in the field and were confirmed by environmental magnetic proxies and a higher concentration of total organic carbon toc consistent with results for western europe and the northwestern clp our results demonstrate that the loess delta c 13 org in this region documents mainly the response of delta c 13 of locally predominant c 3 plants to paleoclimatic variation especially paleoprecipitation our results also suggest that the loess delta c 13 org values in the area have the potential for quantitative paleoprecipitation reconstruction on the basis of detailed delta c 13 org results from modern plants and surface soils in the future c 2013 elsevier ltd all rights reserved

forcing mechanisms and hydrodynamics in loch linnhe a dynamically wide scottish estuary abstract hydrodynamic conditions in loch linnhe a dynamifcally wide estuary on the west coast of scotland are primarily influenced by wind forcing freshwater input and tides winds in the region are orographically steered along the axis of the estuary due to surrounding mountains a large rainfall catchment area results in a large freshwater inflow into loch linnhe which in turn produces low salinity waters at the head of the estuary this combined with a connection to the open sea with coastal salinities leads to salinity gradients in the horizontal and vertical even though a range of observational programmes have focussed on loch linnhe the literature still lacks an evaluation of its physical dynamics here we present a first description of the hydrodynamics in loch linnhe based on observations wind stress predominantly influences the surface layer especially at low frequencies and with a stronger influence than tides during neap tides the buoyancy driven flow due to the large river runoff influences the circulation independent of wind stress seasonal spring autumn and interannual 2011 2012 variability of water masses occur especially in the surface layer tides are dominated by the semi diurnal constituent m 2 with tidal ellipses aligned in the along estuary direction and a stronger influence during spring tides compared to wind an evaluation of dimensionless numbers reveal laterally and vertically sheared exchange flows compared to other scottish estuaries loch linnhe is wide enough to be influenced by the earth s rotation and demonstrates an enhanced freshwater outflow along its north western coast as the freshwater is diverted to the right in the direction of the flow these observed patterns are important for the sustainable environmental management of this socio economically valuable region e g through their relevance to aquaculture pathogen transmission patterns a thorough understanding of the dynamics of the system is essential for a successful evidence based marine planning framework

circumglobal teleconnection in the northern hemisphere summer analysis of the 56 yr ncep ncar reanalysis data reveals a recurrent circumglobal teleconnection cgt pattern in the summertime midlatitude circulation of the northern hemisphere this pattern represents the second leading empirical orthogonal function of interannual variability of the uppertropospheric circulation the cgt having a zonal wavenumber 5 structure is primarily positioned within a waveguide that is associated with the westerly jet stream the spatial phases of cgt tend to lock to preferred longitudes the geographically phase locked patterns bear close similarity during june august and september but the pattern in july shows shorter wavelengths in the north pacific north america sector the cgt is accompanied by significant rainfall and surface air temperature anomalies in the continental regions of western europe european russia india east asia and north america this implies that the cgt may be a source of climate variability and predictability in the above mentioned midlatitude regions the cgt has significant correlations with the indian summer monsoon ism and el nino southern oscillation enso however in normal ism years the cgt enso correlation disappears on the other hand in the absence of el nino or la nina the cgt ism correlation remains significant it is suggested that the ism acts as a conductor connecting the cgt and enso when the interaction between the ism and enso is active enso may influence northern china via the ism and the cgt additionally the variability of the cgt has no significant association with the arctic oscillation and the variability of the western north pacific summer monsoon the circulation of the wave train shows a barotropic structure everywhere except the cell located to the northwest of india where a baroclinic circulation structure dominates two possible scenarios are proposed the abnormal ism may excite an anomalous west central asian high and downstream rossby wave train extending to the north pacific and north america on the other hand a wave train that is excited in the jet exit region of the north atlantic may affect the westcentral asian high and thus the intensity of the ism it is hypothesized that the interaction between the global wave train and the ism heat source may be instrumental in maintaining the boreal summer cgt

the loess record in southern tajikistan and correlation with chinese loess in the present study the chashmanigar loess soil sequence in southern tajikistan is studied this loess section has a paleomagnetic basal age of about 1 77 myr magnetic susceptibility color reflectance and grain size were systematically measured for closely spaced samples from the section paleosols consistently have a finer grain size distribution higher magnetic susceptibility redder color reflectance and lower dust sedimentation rate than loess horizons suggesting a colder drier and dustier environment during glacial periods than in interglacial periods the grain size record was tuned to variations in obliquity and precession of the earth s orbit the resulting magnetic susceptibility grain size and color reflectance time series all show well expressed astronomical periodicities during the pleistocene the mid pleistocene climate transition characterized by a shift of dominant climatic periods from 41 kyr to 100 kyr at about 1 0 0 8 myr is clearly documented in these proxy records comparison of the chashmanigar loess record with the lingtai loess section in china and the odp site 677 n 18 o record shows that during the entire pleistocene the climate cycles recorded by the central asian loess can be well correlated to the chinese loess and deep sea oxygen isotope records it is suggested that alternations of loess and soil horizons both in central asia and china could be basically forced by global ice volume variations although different wind systems have controlled the pleistocene loess transport and sedimentation in the two areas 2002 elsevier science b v all rights reserved

δ13c of loess organic matter as a potential proxy for paleoprecipitation paleoprecipitation reconstructions on the basis of pollen are well known but they do not provide high temporal resolution for glacial periods high resolution paleoprecipitation reconstructions for the last glaciation based on the isotopic record organic matter in loess from nussloch rhine valley germany are consistent with paleoprecipitation inferred from peat in the same area using an independant method thus 13c of loess organic matter can be used as a proxy for paleoprecipitation

magnetic investigation of late quaternary loess deposition ili area china abstract a late quaternary loess section in ili river valley xinjiang northwest china has been studied magnetically samples from two sections exhibit variations in magnetic susceptibility which displays a positive relationship with pedogenesis intensity in s 0 and negative in s 1 and l 1 the detailed magnetic properties investigation reveals that concentration of initial magnetite and maghemite fm varies and may be dominated by wind intensity and source mineralogy furthermore this is the most important magnetic component influencing magnetic properties of loess paleosol sequences and controls magnetic properties of loess deposition in contrast concentration of pedogenic fm is low and has little influence on magnetic properties of loess however it is an ideal magnetic parameter to assess paleoclimate the magnetic minerals in s 1 soil units might be linked to reducing environments reflected by the enhancement of the coercive force of remanence

a high resolution record of holocene environmental and climatic changes from lake balikun xinjiang china implications for central asia a high resolution record of holocene environmental and climatic change in the balikun area was reconstructed from a sediment core from the lake balikun multiproxy data show that the climate was extremely arid during the early holocene before 8 6 cal ka bp moisture began to increase after 8 6 cal ka bp and the climate was humid between 7 9 and 4 3 cal ka bp a significant dry event occurred around 4 3 3 8 cal ka bp the climate became generally wet during the late holocene after 3 8 cal ka bp the holocene pollen and geophysical records do not indicate a wet early holocene making it evident that there was no early holocene humid period associated with peak asian monsoon strength regional comparisons indicate that this region has a different pattern of holocene environmental and climatic change from the asian monsoonal area and south siberia

a synthesis of abrupt changes in the asian summer monsoon since the last deglaciation we have compiled 36 previously published palaeoclimate records to determine the timing and spatial pattern of century scale abrupt changes in asian monsoon precipitation since the last deglaciation we identify abrupt events from 1 the interpretations of the authors of these records and 2 the more objective moving t test calculation our results indicate that abrupt climatic changes occurred at 11 5 cal ka 4 5 5 0 cal ka and ad 1300 at the start of the holocene 11 5 cal ka asian monsoon precipitation increased dramatically this climatic change is synchronous with an abrupt warming in the north atlantic during the middle holocene there was a time of preferred and widespread weakening in monsoon strength 4 5 5 0 cal ka this result contradicts previous notions of either a gradual trend towards drier conditions or a series of abrupt events that occurred in an unorganized fashion across space and time the middle holocene abrupt event could have been synchronous with an abrupt cooling event in the north atlantic as well as a warming and intensie cation of internannual variability in the tropical pacie c in contrast to previous periods precipitation changes at ad 1300 have a heterogeneous spatial pattern we e nd no conclusive evidence for a change in the asian monsoon at 8 2 cal ka as suggested by several previous studies more high resolution data may be needed to observe this short lived event overall our results attest to the potential for rapid and major shifts in asian monsoon precipitation that may be triggered by variations in other components of the climatic system

the molecular structure of melts along the carbonatite kimberlite basalt compositional joint co2and polymerisation transitional melts intermediate in composition between silicate and carbonate melts form by low degree partial melting of mantle peridotite and might be the most abundant type of melt in the asthenosphere their role in the transport of volatile elements and in metasomatic processes at the planetary scale might be significant yet they have remained largely unstudied their molecular structure has remained elusive in part because these melts are difficult to quench to glass here we use ftir raman 13c and 29si nmr spectroscopy together with first principle molecular dynamic fpmd simulations to investigate the molecular structure of transitional melts and in particular to assess the effect of co2on their structure we found that carbon in these glasses forms free ionic carbonate groups attracting cations away from their usual depolymerising role in breaking up the covalent silicate network solution of co2in these melts strongly modifies their structure resulting in a significant polymerisation of the aluminosilicate network with a decrease in nbo si of about 0 2 for every 5 mol co2dissolved this polymerisation effect is expected to influence the physical and transport properties of transitional melts an increase in viscosity is expected with increasing co2content potentially leading to melt ponding at certain levels in the mantle such as at the lithosphere asthenosphere boundary conversely an ascending and degassing transitional melt such as a kimberlite would become increasingly fluid during ascent hence potentially accelerate carbon rich transitional melts are effectively composed of two sub networks a carbonate and a silicate one leading to peculiar physical and transport properties

holocene environmental and climatic changes inferred from wulungu lake in northern xinjiang china abstract sedimentological geochemical and palynological data from wulungu lake in northern xinjiang china are used to reconstruct environmental and climate changes since 9550 cal yr bp high abundance of sparganium and poaceae low md median diameter and 13 c organic values indicate aridity between 9550 and 6730 cal yr bp high md and 13 c organic values and the prevalence of desert steppe and steppe vegetation between 4200 and 560 cal yr bp indicate that effective moisture increased after 6730 cal yr bp peaking at 4200 and 560 cal yr bp low md values a negative excursion of 13 c org and the transition from steppe to desert vegetation since 560 cal yr bp reflect a decrease in effective moisture during the latest holocene late holocene human activities were indicated by sharp increase in the abundance of pediastrum then variations in carbonate contents indicate that temperature was generally high between 9550 and 7740 cal yr bp low between 7740 and 6730 cal yr bp intermediate between 6730 and 560 cal yr bp and low during the last 560 yr regional comparison indicates that the asian monsoon did not extend to wulungu lake and westerlies were the main factor in determining the moisture availability during the holocene

physical mechanisms of summer precipitation variations in the tarim basin in northwestern china abstractthe tarim basin tb in northwestern china is one of the most arid regions in the middle latitudes where water is scarce year round this study investigates the variations of summer precipitation in the tb and their association with water vapor fluxes and atmospheric circulation the results suggest that the variations of summer precipitation in the tb are dominated by the water vapor fluxes from the south and east although the long term mean water vapor mostly comes from the west the anomalous water vapor fluxes are closely associated with the meridional teleconnection pattern around 50 80 e and the zonal teleconnection pattern along the asian westerly jet in summer the meridional teleconnection connects central asia and the tropical indian ocean the zonal teleconnection resembles the silk road pattern the two teleconnections lead to negative height anomalies in central asia and positive height anomalies in the arabian sea and india and in northern central china the anomalous pressure g

holocene east asian summer monsoon records in northern china and their inconsistency with chinese stalagmite δ18o records abstract monsoon precipitation over china exhibits large spatial differences it has been found that a significantly enhanced east asian summer monsoon easm is characterized by increased rainfall in northern china and by reduced rainfall in southern china and this relationship occurs on different time scales during the holocene this study presents results from a diverse range of proxy paleoclimatic records from northern china where precipitation variability is traditionally considered as an easm proxy our aim is to evaluate the evolution of the easm during the holocene and to compare it with all of the published stalagmite 18 o records from the asian monsoon region in order to explore the potential mechanism s controlling the chinese stalagmite 18 o we found that the intensity of the easm during the holocene recorded by the traditional easm proxy of moisture or precipitation records from northern china is significantly different from the chinese stalagmite 18 o records the easm maximum occurred during the mid holocene challenging the prevailing view of an early holocene easm maximum mainly inferred from stalagmite 18 o records in eastern china in addition all of the well dated holocene stalagmite 18 o records covering a broad geographical region exhibit a remarkably similar trend of variation and are statistically well correlated on different time scales thus indicating a common signal however in contrast with the clear consistency in the 18 o values in all of the cave records both instrumental and paleoclimatic records exhibit significant spatial variations in rainfall on decadal to centennial time scales over eastern china in addition both paleoclimatic records and modeling results suggest that holocene east asian summer monsoon precipitation reached a maximum at different periods in different regions of china thus the stalagmite 18 o records from the easm region should not be regarded as a reliable indicator of the strength of the east asian summer monsoon furthermore modern observations indicate that the moisture for precipitation in the east asian monsoon region is mainly derived from the indian ocean the moisture transport route from the indian ocean to the east asian monsoon region during the holocene is almost identical to that of modern precipitation therefore the strong correlation of 18 o records in the easm and indian summer monsoon ism regions and the similarity of the pattern of latitudinal changes in 18 o values in stalagmites and in modern meteoric precipitation along the water vapor transport route further suggests that the stalagmite 18 o records from the easm region are essentially a signal of the isotopic composition of precipitation which is determined mainly by changes in the 18 o of atmospheric vapor in the upstream source region over the indian ocean and indian monsoon region via the upstream depletion mechanism finally the main trends of the stalagmite 18 o records are strongly correlated with the known evolution of the ism and therefore these records reflect the history of the ism rather than that of the easm our findings support the conclusion that easm variability is mainly controlled by northern hemisphere summer insolation and was strongly modulated by ice volume during the last deglaciation and early holocene which delayed the response of the easm maximum to peak insolation forcing

summer monsoon intensity controls c4 c3 plant abundance during the last 35 ka in the chinese loess plateau carbon isotope evidence from bulk organic matter and individual leaf waxes the natural abundance of c3 and c4 plants is affected by multiple environmental factors including temperature moisture balance and atmospheric pco2 the relative importance of these factors is a subject of considerable debate and may vary in different natural ecosystems previous studies generally focus on single loess sequences in the chinese loess plateau and conflicting conclusions on c4 c3 have been reached when studying carbon isotope ratios in carbonate and organic matter in this paper we report a comprehensive carbon isotopic characterization of total organic carbon toc and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the chinese loess plateau clp the five coring sites encompass large gradients of annual mean temperature 9 2 13 9 c and precipitation 402 673 mm allowing us to assess the controlling mechanisms on c4 c3 plant ratios glacial interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility our results demonstrate that increased c4 c3 ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites we conclude c4 abundance increases from the last glacial to the holocene in response to greater monsoon activity and that the c4 expression is suppressed in the cold and drier intervals

ventilation of the miocene arctic ocean an idealized model study a model study of an idealized early miocene arctic ocean has been undertaken the work is motivated by the first drill core retrieved from the lomonosov ridge in the central arctic ocean which sug

late pleistocene and holocene palaeoenvironments in and around the middle caspian basin as reconstructed from a deep sea core this article has been made available through open access by the brunel open access publishing fund

holocene moisture evolution in arid central asia and its out of phase relationship with asian monsoon history we synthesize palaeoclimate records from the mid latitude arid asian region dominated today by the westerlies arid central asia aca to evaluate spatial and temporal patterns of moisture changes during the holocene sediment records from i i takes with reliable chronologies and robust proxies were selected to reconstruct moisture histories based on a five class ordinal wetness index with assigned scores from the driest to wettest periods at individual sites for 200 year time slices the proxies used in these records include pollen and diatom assemblages sediment lithology lake levels and geochemistry mainly isotope data the results of our synthesis show that aca as a whole experienced synchronous and coherent moisture changes during the holocene namely a dry early holocene a wetter less dry early to mid holocene and a moderately wet late holocene during the early holocene most of the lakes experienced very low water levels and even dried out before ca 8 ka 1 ka 1000cal a bp hence the effective moisture history in aca is out of phase with that in monsoonal asia as documented by numerous palaeoclimate records in monsoonal asia a strong summer monsoon and humid climate characterized the early holocene and a weakened summer monsoon and drier climate prevailed during the late holocene which were mainly controlled by changes in low latitude summer insolation in contrast we propose that the pattern of holocene effective moisture evolution in the westerly dominated aca was mainly determined by north atlantic sea surface temperatures ssts and high latitude air temperatures that affect the availability amount and transport of water vapor also topography of the tibetan plateau and adjacent asian highlands could have contributed to the intensification of dry climate in aca during the early holocene as a result of strengthening the subsidence of dry air masses associated with stronger uplift motion on the plateau by intense heating under a stronger summer insolation summer insolation might have played a key role in directly controlling moisture conditions in aca but only after the northern hemisphere ice sheets had disappeared in the mid and late holocene c 2007 elsevier ltd all rights reserved

variation in carbon isotopic composition over the past ca 46 000 yr in the loess paleosol sequence in central kazakhstan and paleoclimatic significance abstract we present a high resolution record of 13 c org variation from two loess sequences in central kazakhstan the variation shows that the vegetation was persistently dominated by c 3 plants over the past ca 46 000 yr the 13 c org signature was most likely an indicator of moisture and the moisture variation in central kazakhstan was associated with the precipitation in western europe the 13 c org indicated that moisture variation exhibited five stages decreasing during stage 1 ca 46 000 ca 31 500 yr bp increasing during stage 2 ca 31 500 ca 25 500 yr bp again decreasing during stage 3 ca 25 500 ca 19 000 yr bp fluctuating along a constant line during stage 4 ca 19 000 ca 5000 yr bp and increasing during stage 5 last ca 5000 yr our comparison demonstrated a general similarity between the 13 c org indicated moisture variation in central kazakhstan and the reconstructed precipitation variation in western europe the similarity implies that the moisture of the past ca 46 000 yr in central kazakhstan has been controlled or modulated by westerlies that brought water vapor from the north atlantic not only to western europe but also to central kazakhstan

dry early holocene revealed by sand dune accumulation chronology in bayanbulak basin xinjiang nw china understanding the holocene climate changes especially moisture variation and their mechanisms in the semiarid arid central asia sca is very important as water availability is crucial for sustainable developments in this area this study presents chronostratigraphy of an aeolian sedimentary sequence from bayanbulak basin xinjiang nw china aiming to infer the holocene moisture history in the sca luminescence dating technique was selected to construct the age framework of the study section since the luminescence signal intensity of quartz from the samples was too low to be detected feldspar was used as an alternative dosimeter a newly developed post infrared ir ir stimulated luminescence irsl pirir dating protocol on k feldspar was applied to determine the ages of samples a set of tests on luminescence characteristics was performed and demonstrate that this method is suitable and the resultant ages are reliable combined with the stratigraphic investigation on the sand dune palaeosol section the results imply a very dry climatic condition characterized by sand dune accumulation at similar to 9 8 kyr and a wet interval of 5 1 6 kyr when a soil layer was formed this moisture variation pattern is consistent with that inferred from many lacustrine records in the sca suggesting a widespread dry period at 11 8 kyr the present results appear to challenge a new stalagmite delta o 18 sequence located nearby to bayanbulak basin which instead suggested a humid early holocene

prediction of silicate melt viscosity from electrical conductivity a model and its geophysical implications 1 our knowledge of magma dynamics would be improved if geophysical data could be used to infer rheological constraints in melt bearing zones geophysical images of the earth s interior provide frozen snapshots of a dynamical system however knowledge of a rheological parameter such as viscosity would constrain the time dependent dynamics of melt bearing zones we propose a model that relates melt viscosity to electrical conductivity for naturally occurring melt compositions including h2o and temperature based on laboratory measurements of melt conductivity and viscosity our model provides a rheological dimension to the interpretation of electromagnetic anomalies caused by melt and partially molten rocks melt fraction 0 7

holocene moisture evolution across the mongolian plateau and its surrounding areas a synthesis of climatic records abstract based on the review of 26 high standard holocene climatic reconstructions mainly pollen based from the mongolian plateau and its surrounding areas temporal and spatial patterns of the holocene moisture evolution are synthesized the regionally averaged moisture history from the summer monsoon influenced semiarid belt in china i e region a demonstrates that the moisture index curve is broadly in agreement with the synthesized east asian monsoon strength curve both following the general trend of the west tropical pacific sst that is in turn the delayed response to the northern hemispheric summer solar insolation the regionally averaged moisture indices from the winter monsoon dominated southern siberia including lake baikal area and the altai mountains i e region b exhibit a general declining trends since 10 6 9 6 cal kyr bp being largely consistent with the trends of the annual precipitation and the warm season temperature in the russian plain the consistency might be attributable to the holocene declining trend of the warm season temperature in north atlantic region the predominant feature of the regionally averaged moisture index from the westerlies affected northern xinjiang i e region c is a persistent increasing trend since 8 cal kyr bp the wetting trend of northern xinjiang during the past 8000 years might be attributable to the increasing trend of winter insolation and to the associated increasing trend of cold season temperature in northwestern europe the chronological correspondences between dry phases and warm intervals in the arid areas of the mongolian plateau i e northern mongolian plateau within mongolia and southern mongolian plateau within china region d lend a support to the proposal that the mid holocene dry phase was most likely the result of mid holocene high warm season temperature

causes of early holocene desertification in arid central asia paleoclimate records of effective moisture precipitation minus evaporation or p e show a dry low effective moisture period in mid latitude arid semi arid central asia during the early holocene 11 000 8 000 years ago relative to the middle and late holocene in contrast to evidence for greater than present precipitation at the same time in the south and east asian monsoonal areas to investigate the spatial differences in climate response over mid latitude central asia and monsoonal asia we conducted a series of simulations with the community climate system model version 3 coupled climate model for the early middle and late holocene the simulations test the climatic impact of all important forcings for the early holocene including changes in orbital parameters the presence of the remnant laurentide ice sheet and deglacial freshening of the north atlantic model results clearly show the early holocene patterns indicated by proxy records including both the decreased effective moisture in arid central asia which occurs in the model primarily during the winter months and the increase in summer monsoon precipitation in south and east asia the model results suggest that dry conditions in the early holocene in central asia are closely related to decreased water vapor advection due to reduced westerly wind speed and less evaporation upstream from the mediterranean black and caspian seas in boreal winter as an extra forcing to the early holocene climate system the laurentide ice sheet and meltwater fluxes have a substantial cooling effect over high latitudes especially just over and downstream of the ice sheets but contribute only to a small degree to the early holocene aridity in central asia instead most of the effective moisture signal can be explained by orbital forcing decreasing the early holocene latitudinal temperature gradient and wintertime surface temperature we find little evidence for regional subsidence related to a stronger summer asian monsoon in forcing early holocene aridity in central asia as has been previously hypothesized

water mass modification in an arctic fjord through cross shelf exchange the seasonal hydrography of kongsfjorden svalbard 1 kongsfjorden and the west spitsbergen shelf is a region whose seasonal hydrography is dominated by the balance of atlantic water arctic waters and glacial melt regional seasonality and the cross shelf exchange processes have been investigated using conductivity temperature depth ctd observations from 2000 2003 and a 5 month mooring deployment through the spring and summer of 2002 modeling of shelf fjord dynamics was performed with the bergen ocean model observations show a rapid and overwhelming intrusion of atlantic water across the shelf and into the fjord during midsummer giving rise to intense seasonality pockets of atlantic water from the west spitsbergen current form through barotropic instabilities at the shelf front these leak onto the shelf and propagate as topographically steered features toward the fjord model results indicate that such cross front exchange is enhanced by north winds normally atlantic water penetration into the fjord is inhibited by a density front at the fjord mouth this geostrophic control mechanism is found to be more important than the hydraulic control common to many fjords slow modification of the fjord water during spring reduces the effectiveness of geostrophic control and by midsummer atlantic water intrudes into the fjord switching from being arctic dominant to atlantic dominant atlantic water continues to intrude throughout the summer and by september reaches some quasi steady state condition the fjord adopts a cold or warm mode according to the degree of atlantic water occupation horizontal exchange across the shelf may be an important process causing seasonal variability in the northward heat transport to the arctic

magma chamber properties from integrated seismic tomography and thermal modeling at montserrat it is widely believed that andesitic magmas erupted at arc volcanoes are stored in shallow reservoirs prior to eruption but high resolution images of focused regions of magma in the shallow crust are rare we integrate seismic tomography with numerical models of magma chamber growth to constrain the magma chamber beneath soufriere hills volcano montserrat our approach reveals the characteristics and dynamics of the magmatic system with a level of detail that no single method has yet achieved the integrated analysis suggests that a magma chamber of 13 km3 with over 30 melt fraction formed between 5 5 and at least 7 5 km depth a significantly higher melt fraction than inferred from the seismic data alone the magma chamber may have formed by incremental sill intrusion over a few thousand years and is likely to be a transient geologically short lived feature these volume and geometry estimates are critical parameters to model eruption dynamics which in turn are key to hazard assessment and eruption forecasting

climatic dependency of soil organic carbon isotopic composition along the s n transect from 34 n to 52 n in central east asia abstract we explored the relationships between surface soil 1 20 cm organic carbon isotopic signatures and associated climatic factors in central east asia in an attempt to develop transfer functions that can be used to retrieve the paleoclimatic information stored in the thick eolian paleosol sequences within the area our analysis shows that the negative correlation between the surface soil organic 13c values and the mean annual precipitation is robust r2 0 453 n 196 p

pleistocene climatic history of east and central asia based on paleopedological indicators in loess paleosol sequences a micromorphological comparison of the loess paleosol sequence of the karamaydan section central asia with the upper part of the luochuan section china clearly indicates that for the brunhes chron the sequence at karamaydan is more detailed than the corresponding section at luochuan single paleosols at luochuan correspond to pedocomplexes at karamaydan for example s 3 at luochuan corresponds to pk iii and s 4 to pk iv and both pks developed in a period longer than one interglacial about 104 years some pedocomplexes at luochuan are represented by more detailed successions at karamaydan for example the s 5 complex at luochuan corresponds to pedocomplexes v and vi the loess paleosol sequence at karamaydan should therefore be regarded as a key sequence for reconstructing the climatic history of the brunhes epoch correlation with the deep sea oxygen isotope record of bassinot et al which includes an accurate astronomical time scale allows a detailed chronostratigraphical subdivision of the loess paleosol sequence in karamaydan for the brunhes epoch the sequence in the central and lower parts of the chashmanigar section also in central asia shows much more pronounced paleosols than the equivalent sequence at luochuan although some ck or ckm horizons indicate the presence of hiatuses nevertheless for this part of the sequence it provides more paleoclimatic detail with cold dry stages represented by loess and warm humid stages interglacials by paleosols than even the deep sea cores

externally forced fluctuations in ocean temperature at greenland glaciers in non summer months the factors that control the submarine melt rate at greenland s glaciers are uncertain and largely inferred from brief summer surveys in the fjords where glaciers terminate continuous records of water properties and velocity for the months september to may from two large greenland fjords reveal strong variability on 3 to 10 day timescales as a result of pulses of water that are propagated from the shelf ocean

holocene vegetation history and sea level changes in the se corner of the caspian sea relevance to sw asia climate the palynological investigation of core tm 27 7 m long taken in a dried out lagoon reveals both holocene vegetation history in the north eastern foothills of the alborz mountains and past water level changes of the caspian sea cs the delay in woodland expansion at the beginning of the holocene which is typical of eastern turkey the iranian plateau and recorded in the cs south basin is only weakly felt as the region is close to glacial refugia of trees the succession of the main trees out of their refugia has been established as deciduous quercus carpinus betulus parrotia persica and fagus orientalis pterocarya fraxinifolia presenting therefore close affinities to south european interglacials of the early pleistocene this suggests a similarity in climate a pterocarya decline is observed after ad 495 the studied region is close to the easternmost tree distribution this could explain why it has been affected earlier than elsewhere in the northern alborz and the caucasus in addition human activities during the sasanian empire and the subsequent drying of the climate contributed to weakening the spread of this tree a maximal sea level occurs in the first part of the holocene from 10 6 to 7 2 cal ka it is suggested that the cs levels were significantly influenced by the monsoon precipitations over the western himalayas via the uzboy inflow this is followed by low levels from 7 2 to 3 5 cal ka with a minimum at 3 9 cal ka the neocaspian period should be considered a biozone rather than a chronozone as the environmental conditions reconstructed from dinocyst assemblages are different in shallow shelf waters and in the deep basins