electromagnetic and geoelectric investigation of the gurinai structure inner mongolia nw china abstract in three field campaigns between the years 2000 and 2004 geophysical measurements were conducted in the ejina basin nw china research work in the year 2004 which is described in this paper was concentrated on the gurinai structure 101 25 e 41 n situated in the southeastern part of the ejina basin in transition to the dune fields of the badain jaran shamo on satellite images the gurinai structure can be identified by two almost 100 km long subparallel n s striking lineaments which may indicate tectonic deformations of late quaternary sediments to get a coherent picture of the structure a geophysical survey employing three electromagnetic methods magnetotellurics mt transient electromagnetics tem and geoelectrics dc has been conducted to map the subsurface resistivity at different depth scales the geophysical data interpretation for shallow and intermediate depth down to a few hundred meters links the subsurface distribution of electric resistivity to geomorphological units known from field work in reference with satellite images the westerly lineament of the gurinai structure coincides with a subvertical change in electric resistivity together with geomorphological indications from fieldwork and the analysis of elevation data srtm a tectonic deformation of unconsolidated sediments along a fault with an extensional component is interpreted in the central and eastern part of the gurinai structure a shallow resistive subsurface layer can be traced into the first dunes of the badain jaran shamo this resistive subsurface layer is linked to the presence of fresh water indicating infiltration from the dune field also in the eastern part of the gurinai structure a resistive approximately ene striking feature can be seen at intermediate depth which is interpreted as a crystalline basement ridge towards the southern margin of the gurinai structure a trough shaped unit with low resistivities and a thickness of about 1 km is identified and can be explained by a sediment package saturated with fluids of high salinity or substantial amounts of clay the strike direction of the structure can be connected to the regional pattern of tectonic faults and seismicity the interpretation of electromagnetic data at various depth scales contributes to the general understanding of the ejina basin s buildup and tectonic setting in the vicinity of the gurinai structure

the bi decadal rainfall cycle southern annular mode and tropical cyclones over the limpopo river basin southern africa the association between bi decadal rainfall variability over southern africa and the rainfall contributed by tropical cyclonic systems from the southwest indian ocean swio provides a potential means towards understanding decadal scale variability over parts of the region a multi decadal period is considered focusing on the anomalous tropospheric patterns that induced a particularly wet 8 year long sub period over the limpopo river basin the wet sub period was also characterized by a larger contribution to rainfall by tropical cyclones and depressions the findings suggest that a broadening of the hadley circulation underpinned by an anomalous anticyclonic pattern to the east of southern africa altered tropospheric steering flow relative vorticity and moisture contents spatially during the sub period of 8 years these circulation modulations induced enhanced potential for tropical systems from the swio to cause precipitation over the limpopo river basin the same patterns are also conducive to increasing rainfall over the larger subcontinent therefore explaining the positive association in the bi decadal rainfall cycle and rainfall contributed by tropical cyclonic systems from the swio an overview of regional circulation anomlies during alternating near decadal wet and dry epochs is given the regional circulation anomalies are also explained in hemispheric context specifically in relation to the southern annular mode towards understanding variation over other parts of the southern hemisphere at this time scale

heat balance and regime shifts of the mixed layer in the kuroshio extension abstract we investigated the seasonal variations of the mixed layer depth and temperature in the kuroshio extension region 145 180 e 30 36 n and studied the causes of the mixed layer depth and temperature regime shifts which occurred in the late 1980s using upper ocean thermal and heat flux datasets incorporated with a bulk mixed layer model the mixed layer from fall to winter is cooled by the net surface heat flux the ekman transport and the entrainment and warmed by the horizontal heat convergence resulting from the kuroshio heat advection the mixed layer depth is controlled by the entrainment and the horizontal transport divergence convergence which act to slow the mixed layer deepening from fall to early winter and then in winter deepen the mixed layer the entrainment velocity is significantly influenced by the temperature difference between the mixed layer and the layer below the mixed layer shift from its deep to shallow phase occurred in 1985 this shift is preceded the sst shift in 1988 by three years and was caused by the horizontal transport divergence anomaly the horizontal heat convergence of the kuroshio extension caused the sst shift in 1988 whereas its anomaly had been already positive since 1983 the delay from 1983 to 1987 can be attributed to the effects of the negative fall sst anomaly stronger surface heat flux and ekman cooling and the shoaling of the mixed layer depth it is suggested that the kuroshio current system plays a major role in forcing the sst shift and thus the subsequent climate regime shift

atmosphere ocean mechanisms of climate anomalies in the angola tropical atlantic sector abstract interannual variations in the large scale atmospheric and oceanic fields over the tropical atlantic are studied in relation to rainfall anomalies on the angola coast departure patterns are constructed by stratification with respect to extremely dry and wet years and by correlation with rainfall in angola which is concentrated in march april the analysis suggests a causality chain of atmospheric oceanic anomalies variations of westward wind stress on the western equatorial atlantic constitute an early link in this chain the annual cycle is characterized by a relaxation of the wind stress from september november to february march anomalous seasonal relaxation of easterly wind stress over the western equatorial atlantic remotely forces the sea surface temperature sst departures in the eastern south atlantic a large relaxation being followed by positive sst departures sea surface temperature modulates the rainfall over downstream angola by controlling the atmospheric moisture and stability

paleoenvironmental and archaeological investigations at qinghai lake western china geomorphic and chronometric evidence of lake level history abstract qinghai lake located on the northeastern qinghai tibet plateau qing zang gaoyuan is china s largest extant closed basin lake its position relative to major asian climate systems makes it sensitive to global climate change the lake has been the subject of numerous paleoenvironmental investigations including dating of shoreline features around the lake basin here we report new age estimates of shoreline features geomorphic exposures and archaeological sites that contribute to the development of a lake level history for qinghai lake and a landscape model of the qinghai lake basin lake highstands above 3230 m 36 m above the modern lake level appear to date to late mis 5 70 110 ka the lake has had much more modest highstands since then no evidence of mis 3 lake stands higher than modern were found and early holocene highstands are no more than 12 m above modern if the age of highstands greater than 3230 m is confirmed through future work then the qinghai lake basin hydrologic balance prior to 70 ka was dramatically different than after that time including during the holocene a simple hydrologic balance model provides insights into the combination of precipitation evaporation and runoff generation needed to sustain the lake at 3260 m the highest shoreline observed a range of factors may explain the difference primarily the relative strength of the east asian monsoon the basin was apparently subject to extensive alluviation during mis 3 interrupted by widespread erosion and development of cryogenic features before and during the last glacial maximum lgm loess that presently drapes much of the lower basin landscape began to be deposited after the lgm 16 18 ka the landscape model outlined here has implications for archaeological visibility of early human occupation of the qinghai tibet plateau

orbital scale lake evolution in the ejina basin central gobi desert china revealed by k feldspar luminescence dating of paleolake shoreline features abstract the ejina basin in the central gobi desert contains the terminal lakes of the heihe river paleoenvironmental changes in the basin are important since its deposits are a significant source of northern hemisphere dust in this study we employed a k feldspar pirir dating technique to date shoreline features 940 m at multiple locations in the ejina basin 45 50 m above the modern basin floor internal checks of luminescence characteristics were employed to test the reliability of the pirir dating in combination with our previously reported stratigraphy and chronology of shorelines at 927 m in the ejina basin these results imply that a paleolake was present in the basin prior to 350 ka other high stands in the basin occurred at 320 310 ka 240 180 ka 120 80 ka and 5 ka corresponding to mis 9 mis 7 mis 5 and the mid holocene mis 1 respectively indicating a strong link with glacial interglacial cycles extensions of the east asian summer monsoon easm during interglacial periods possibly interacting with the westerlies apparently caused higher precipitation and lake formation the impact of orbital eccentricity on the easm westerlies appears to be responsible for the formation of major lake desert cycles on the northeastern margin of the tibetan plateau

seasonal variations in the southern hemisphere storm tracks and jet streams as revealed in a reanalysis dataset abstract regional characteristics of the climatological seasonal variations in southern hemisphere sh storm tracks are examined based on a reanalysis dataset when differences in vertical structure between the subpolar and subtropical jet streams spj and stj respectively are considered the regional characteristics can be interpreted reasonably well from a potential vorticity perspective of baroclinic eddy growth and downstream development of a baroclinic wave packet eddy activity in the upper and lower tropospheres is strongest in the core region of the spj over the eastern south atlantic and indian ocean throughout the year even in austral winter when the intense stj forms over the indian ocean and south pacific showing its eddy driven nature the spj accompanies the strong surface westerlies along a well defined baroclinic zone above an intense oceanic frontal zone in this core region of the storm track low level eddy activity is strongly correlated with the local near surface baroclinicity

imprint of the el nino modoki on decadal sea level changes 1 decadal variation in sea level is shown to manifest as higher than normal sea level in the central pacific flanked by lower than normal sea level on either side of the basin during the early 21st century this abnormal condition is evidently aided by frequent occurrences of el nino modoki events and associated wind convergence to the dateline during 2000 2004 the sea level rise in central pacific succeeded a phase of lower than normal sea level associated with la nina modoki events toward the end of 20th century a correlation analysis confirms the dominant influence of el nino la nina modoki on the sea level rise in the central pacific as compared to that of the el nino la nina this influence can even be seen in remote regions such as the coasts of california and mauritius through atmospheric teleconnections

yardangs on earth and implications to mars a review abstract yardangs as typical aeolian landforms are extensively identified in arid hyper arid areas on earth and other terrestrial bodies in this review based on analyses of morphology distribution age climate and geologic condition of yardangs worldwide we 1 assess the impacts of various controlling factors on yardang development to generalize a model based on morphology 2 illustrate the climate driven mechanism for yardangs 3 propose a geomorphological evolutionary model of yardang fields and 4 discuss potential implications of the above two models of yardang evolution on earth to mars it is demonstrated that both deflation and abrasion work on yardang development and it is the lithology to determine which one will be more effective in addition the wind action dominates the general aerodynamic form of yardangs while non aeolian factors account for the diversity in yardang morphology thus a model including four stages and initiating mechanisms is generalized for yardang processes from initiation to demise the synthetic analyses of meteorological data chronology and paleoclimatic proxies show that yardang development is mostly controlled by westerlies and would be accelerated during glacial periods and interrupted by lake formation during interglacial periods due to dry humid fluctuations and changes in atmospheric circulation driven by variations in solar radiation at orbital scales this leads to the zonal distributions of yardangs near 30 in both hemispheres depressions would be created or enlarged in yardang fields during glacial period along with activities of dust release and transport leading to aeolian deposition e g loess downwind the depressions then could be turned into lakes during wet phase of interglacial period and evolved into new yardangs in the following glacial period due to wind erosion this climate controlled geomorphological process under glacial interglacial cycles suggests that high accumulation rate in sediments from enclosed inland basins e g the qaidam basin doesn t mean high resolution climatic record due to the hiatus by wind erosion indicating the significance of robust chronology establishment before any climatic correlation under the rules of earth based yardang evolution it is potential to identify the specific level of development and explore the geomorphological processes as well as the climatic background for yardangs on mars

quartz and k feldspar optical dating chronology of eolian sand and lacustrine sequence from the southern ulan buh desert nw china implications for reconstructing late pleistocene environmental evolution the ulan buh desert ubd in southwestern inner mongolia is one of the main dune fields and dust source areas in northern china in the southern ubd consisting primarily of high pyramidal and complex sand dunes the process of desert evolution remains unclear due to a lack of depositional records and adequate age controls in this study we present the stratigraphic record of a 120 5 m deep core wl12zk 1 collected in this sandy desert region a 22 6 m thick deposit of lacustrine clay silty clay bracketed between 37 m top and 54 7 m bottom thick layers of eolian sand provides evidence of a desert lake desert sequence in the southern ubd quartz optical stimulated luminescence osl and k feldspar multi elevated temperature post ir irsl met pirir dating technologies were employed to provide a chronology for this sequence internal checks of the quartz osl dating indicate that the quartz single aliquot regenerative dose protocol is appropriate for equivalent dose determination and that the quartz ages younger than 60 ka are acceptable the reliability of the k feldspar ages is confirmed by both internal checks and an age temperature plot the combined stratigraphy and chronology indicate a sand desert landscape developed in the southern ubd at least similar to 232 ka ago and that a paleolake was present beginning sometime before similar to 155 ka and lasting until similar to 87 ka with several possible lake level fluctuations desert landforms developed synchronously in the southern and northern ubd after the paleolake regressed a combination of tectonic activity and climate change may be responsible for this sequence c 2013 elsevier b v all rights reserved

luminescence chronology and palaeoenvironmental significance of limnic relics from the badain jaran desert northern china abstract the badain jaran desert in northern china is well known for the highest mega dunes on earth and unique alternating megadune lake landform and various formation mechanisms have been proposed although the relics of interdune lakes are generally considered as good palaeoenvironmental records their evolutions and relevance to paleoenvironment change are poorly understood due to limited age control in this study quartz optically stimulated luminescence osl and k feldspar post infrared infrared stimulated luminescence pirir were used to establish a chronological framework for limnic relics in order to reconstruct the evolution of interdune lakes our results indicate that limnic relics were deposited in mis 5 and mis 1 due to a lake level transgression and humid environmental condition during the holocene humid conditions occurred at early to middle holocene immediately preceded and followed by aridity the last 600 years have been characterized by high rates of aeolian activity based on field observation and luminescence ages we propose that climate fluctuations since the late pleistocene have played a pivotal role in the formation of the unique landform assemblages

high resolution osl dating of a late quaternary sequence from xingkai lake ne asia chronological challenge of the mis 3a mega paleolake hypothesis in china in this paper a combined osl 49 samples and 14c 14 samples dating study was conducted on a sediment core from xingkai lake ne asia a single aliquot regenerative dose protocol was used to determine the equivalent dose dede of the extracted fine grained fg quartz fraction the suitability of the measurement procedure was confirmed by a set of luminescence tests e g preheat plateau and dose recovery measurements in addition a post ir infrared stimulated luminescence protocol at 290 c pirir290 was applied to the polymineral fg fraction of seven samples our results can be summarized as follows 1 the uppermost sample was dated to 110 a indicating that the osl signal of fg quartz has been well bleached this has been further confirmed by the consistency of osl ages and pirir290 ages within 80 ka the resulting osl ages generally increased with depth and the lowermost samples of core xk08 reached back to the last interglacial although the pirir290 dating suggested that the quartz osl ages likely begin to be underestimated beyond 80 ka 2 the comparison of osl and 14c ages suggested that the radiocarbon dating technique may significantly underestimate the age of sediments for samples older than 30 cal ka bp corresponding to 25 14c ka bp and thus it is necessary to pay attention when using such old 14c dates for paleoclimatic archaeological interpretation 3 this study challenges the radiocarbon based chronology of the mis 3a mega paleolake hypothesis which had been reiterated for many years and extensively reported across northern and western china and 4 the current high resolution osl dating record one age 5 10 cm showed clear sedimentation rate changes down the core the identified variations in the sedimentation processes at the orbital timescale may be related to regional global climatic changes during the past 130 ka and the high sedimentation rate during the last 0 4 ka has probably been caused by intensified human activities in the xingkai lake catchment

east asian monsoon variability over the last seven glacial cycles recorded by a loess sequence from the northwestern chinese loess plateau a 180 m thick loess paleosol sequence from the northwestern chinese loess plateau was investigated to construct a high resolution record of the east asian monsoon variability over the last seven glacial interglacial cycles the low field magnetic susceptibility mass specific and the mean grain size are used as proxies for changes in the intensity of the east asian summer and winter monsoon respectively because of the weaker pedogenesis at the northwestern chinese loess plateau compared to the central chinese loess plateau our and mean grain size records show a muted glacial interglacial contrast for the asian summer monsoon but an enhanced contrast for the asian winter monsoon although better resolved most orbital scale east asian monsoon variations captured by our and grain size records are similar to those reported from the central chinese loess plateau nevertheless variations in exhibit clear precessional cycles in three paleosol layers i e s1 s2 and s3 corresponding with solar insolation maxima furthermore unlike records at the central chinese loess plateau where is dramatically enhanced at paleosol s5ss1 corresponding to marine isotope stage 13 our new record shows a major enhancement at paleosol s4 corresponding to marine isotope stage 11 which indicates geographic differences in the timing of local monsoon precipitation in the two regions

observed relationships between the el nino southern oscillation and the extratropical zonal mean circulation abstract there is increasing evidence indicating that the climate response to variations in the el nino southern oscillation enso includes not only thermally forced zonal wind anomalies in the subtropics but also eddy driven zonal wind anomalies that extend into the mid high latitudes of both hemispheres in this study new insights into the observed seasonally varying signature of enso in the extratropical zonal mean circulation are provided and the associated linkages with the dominant patterns of extratropical variability are examined the zonal mean extratropical atmospheric response to enso is characterized by two principal features an equivalent barotropic dipole in the southern hemisphere sh zonal mean zonal flow with centers of action located near 40 and 60 during austral summer and a weaker but analogous dipole in the northern hemisphere nh with centers of action located near 25 and 45 during early and late boreal winter both structures are accompanied by eddy momentum flux ano

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

age constraints on the late quaternary evolution of qinghai lake tibetan plateau dating and geomorphology of shoreline features in the qinghai lake basin of northwestern china suggest that contrary to previous interpretations the lake likely did not reach levels 66 140 m above modern within the past 90 000 yr maximum highstands of 20 66 m above modern probably date to marine isotope stage mis 5 mis 3 highstands are undated and uncertain but may have been at or below post glacial highs the lake probably reached 3202 3206 m 8 12 m during the early holocene but stayed below 3202 m after 8 4 ka this shoreline history implies significantly different hydrologic balances in the qinghai lake basin before 90 ka and after 45 ka possibly the result of a more expansive asian monsoon in mis 5

south pacific origin of the decadal enso like variation as simulated by a coupled gcm 1 the hypothesis of the south pacific origin of the decadal 7 35 years enso like variation is investigated based on 200 year outputs of the echam4 opa oasis coupled gcm associated with the decadal warm cold sst anomalies in the tropical pacific an anomalous cyclonic anticyclonic circulation which is tilted in a southeast northwest direction appears in the south pacific this results in anomalous upward downward ekman pumping along the northeastern edge of the anomalous circulation and hence shallowing deepening the oceanic thermocline there such an external source of heat content tends to slowly discharge recharge the tropical ocean on the decadal timescale the above result is consistent with the observational study of luo and yamagata 2001 besides the model reproduces amazingly a high lagged correlation between the global land surface temperature and the decadal nino3 sst despite the model biases this suggests a potential prediction skill of the global warming based on the enso like decadal variation

last deglacial and holocene lake level variations of qinghai lake north eastern qinghai tibetan plateau qinghai lake is of significance for paleoclimate research because it lies in a pivotal region that is influenced by both the mid latitude westerlies and the low latitude asian summer monsoon asm most published lake level histories of qinghai lake are interpreted from drill core proxies here we combine geomorphic shoreline investigations with optically stimulated luminescence dating to constrain lake level variations since the last deglacial the results indicate that two periods of highstands occurred during the last deglacial approximate to 16 14 9 and approximate to 12 6 12 2 ka and that lake levels were 6 7 4m higher than at present lake levels dropped abruptly during the younger dryas and were generally low with frequent fluctuations during the early holocene qinghai lake reached its highest holocene level 9 1m higher than modern at approximate to 5 ka and has regressed during the past 2 ka we propose that high lake levels during the last deglacial were due mainly to melting glacial and permafrost waters supplemented by enhanced westerlies precipitation and decreased evaporation during heinrich event 1 approximate to 16 14 9 ka and increased asm rainfall during the bolling allerod warm period approximate to 14 12 ka lake level fluctuations during the holocene were generally in accordance with moisture variations in the marginal monsoon zones of inland china

hydrological changes and holocene climate variations in nw china inferred from lake sediments of juyanze palaeolake by factor analyses abstract the eastern juyanze palaeolake in hyperarid north western china 41 75 42 n 101 5 102 e provides evidence of a complex hydrological pattern during the holocene multivariate statistics based on lithological geochemical and mineral data from the reference site g36 in the centre of the lake were performed to reconstruct the interrelation between lake hydrology and climate variability of the last 11 000 yr principal component analyses pca analyses enabled us to extract the three system variables runoff lake level water budget and salinity as the major factors which have influenced the lake history during a highly variable holocene climate we can also demonstrate that the independent variable total organic carbon toc is not only a function of bio productivity in lakes under warm wet climate conditions but more frequently related to surface runoff processes which can result in over estimation of pollen types used for climate reconstructions a combined consideration of all system variables with lithological parameters catchment characteristics and the local groundwater situation show that lake formation and its persistence strongly depended on local rainfall runoff and the status of the underlying aquifer our results indicate remarkable differences between the early holocene and mid to late holocene lake formation owing to changes in the aquifer system beneath the lake at about 10 700 cal bp freshwater lake formation starts with extreme runoff events under a wet climate repeated dry climate spells of reduced runoff the overall climate during the early holocene points to wet conditions with frequent phases of very high runoff and highest lake levels until about 8900 cal bp extremely low runoff occurred between 8900 and 8100 cal bp indicating already dry climate conditions some hundred years prior to the worldwide recorded responses of the 8 2 ka cold dry event a second period of major dry climate conditions with generally low but fluctuating runoff unstable water budget and deposition of aeolian sand lasted for about 2100 yr between 7500 and 5400 cal bp these climate conditions corroborate previous assumptions of a mid holocene dry period in arid north western china increased runoff after 5400 cal bp under wet climate conditions led to a complete refill of the aquifer at about 5000 cal bp and favoured the development of a saline lake for about 3500 yr in terms of hydrology the time between 5400 and 4000 cal bp appears to be the climate optimum compared with the early holocene wet climate the mid to late holocene local rainfall was less pronounced and displays a general decreasing trend towards complete desiccation of the lake our results indicate an extremely variable moisture availability in arid regions of north western china during the entire holocene owing to the interplay of the east asian summer monsoon with the westerly waves at the boundary of the summer monsoon limit variations from dry to wet climate conditions seem to have been more pronounced than in other monsoon regions of china

atmosphere ocean coupled variability in the south atlantic abstract the climate variability of the south atlantic region is determined from 40 yr 1953 92 of comprehensive ocean atmosphere data set monthly sea surface temperature sst and sea level pressure slp data using the empirical orthogonal function eof and the singular value decomposition svd analysis methods the eof method is applied to each field separately whereas the svd method is applied to both fields simultaneously the significance of the atmosphere ocean interaction is revealed by a strong resemblance between individual eof and coupled svd modes of sst and slp the three leading modes of coupled variability on interannual and interdecadal timescales are discussed in some detail the first coupled mode which accounts for 63 of the total square covariance represents a 14 16 yr period oscillation in the strength of the subtropical anticyclone accompanied by fluctuations of a north south dipole structure in the sst the atmosphere ocean coupling is strongest during the southern summe

impacts of sst anomalies in the agulhas current system on the regional climate variability abstractthe potential impact of the variability in the agulhas current system on the large scale atmospheric state in the southern hemisphere is examined using the monthly near surface baroclinicity as the key parameter for the period between september 1980 and august 2002 dominant patterns of anomalous near surface baroclinicity found from empirical orthogonal function eof analyses in the region that includes most of the agulhas current system show a wide variety of anomaly patterns some of which indicate spatial shifts in the position of the agulhas retroflection and or agulhas return current composited anomalies in various atmospheric fields sea surface temperature and the net surface heat flux at the air sea boundary based on the signals in the eofs suggest that sea surface temperature anomalies in the agulhas current system thermally force the atmosphere on the synoptic scale via modification of the near surface baroclinicity in march and april and possibly in january and february as well

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

luminescence dating of the stratzing loess profile austria testing the potential of an elevated temperature post ir irsl protocol abstract feldspar infrared stimulated luminescence irsl signals saturate at 2000 gy i e 500 700 ka assuming a dose rate of 3 4 gy ka typical for loess and it is therefore theoretically possible to date middle pleistocene loess however the accuracy of age estimates is hampered by anomalous fading which leads to significant age underestimation fading corrections have been proposed but these corrections are reliant on inherent assumptions and in any case are inapplicable at large doses as the growth curve approaches saturation recent studies have identified a post ir irsl signal that shows less fading and is thus less dependent on accurate fading corrections this study builds upon these investigations and applies a post ir irsl sar dating protocol to polymineral fine grain samples of the loess palaeosol sequence in stratzing lower austria after a preheat at 320 c 60 s and an ir bleach at 50 c 200 s irsl was measured at 290 c for 200 s the same set of conditions were used to measure the response to a test dose recycling ratios recuperation and dose recovery tests show that this protocol is suitable for the loess under investigation although finite residual doses of up to 20 gy are observed for the oldest samples the natural signal is in or close to saturation indicating that fading is negligible in nature this observation is inconsistent with the measured laboratory fading rates of 1 1 5 decade and needs further investigation

magmatism and extension the thermal and mechanical effects of the yellowstone hotspot currently there is a parabolic shaped pattern of seismicity and latest quaternary faulting which centers on the axis of the eastern snake river plain srp and has its apex at the yellowstone plateau the pattern of activity surrounds a region of aseismicity that includes the eastern srp geologic evidence suggests that this pattern has migrated in tandem with rhyolitic volcanism induced by the yellowstone hotspot during its 16 m y trek across western north america similarly there is a migration in the onset of basaltic lava flows and the emplacement of up to 12 km of midcrustal mafic intrusions that follows the track of rhyolitic volcanism these observations suggest that the intrusion of magmas has a significant influence on the pattern of seismicity and faulting we present a one dimensional finite difference thermomechanical model that accounts for the observed pattern of increased faulting followed by fault quiescence within the circum eastern srp in this model mafic magmas are intruded into a lithosphere that is already extending the intrusions heat the surrounding rocks resulting in locally increased strain rates as the intruded magmas solidify the length of time required to return strain rates to their pre intrusion level is then determined the model assumes constant horizontal tectonic forces and maps strain rate as a function of yield strength and time since intrusion we vary model parameters such as crustal thickness initial geothermal gradient and amount of magma intruded in order to assess how they affect turnaround time for strain rates the amount and timing of intruded material allowed by the model are constrained by seismic refraction data as well as by regional geochronologic and petrologic studies we assume intruded rock rheology to be a maryland diabase mantle rheology we base on dry olivine we represent the crust by both dry granite and dry anorthosite rheologies our results suggest that 2 to 3 m y appears to be a reasonable length of time for strain rates to return to levels present before a midcrustal mafic intrusion equivalent in magnitude to the yellowstone intrusion this corresponds closely to the length of time between the onset of along axis accelerated faulting and subsequent fault quiescence assuming a hotspot velocity of 3 5 to 4 0 cm yr relative to the north american plate

holocene shorelines and lake evolution in juyanze basin southern mongolian plateau revealed by luminescence dating holocene environment change in the gobi desert of mongolia and northwestern china is of global significance as it is one of the key dust source areas of the world the juyanze basin located in the central gobi desert of southern mongolian plateau is one of the three terminal basins of the heihe river that flows north from the qilian mountain a series of geomorphic shorelines at different elevations around the basin indicate that large lake levels fluctuated during the past in this study we measured the exact elevation of shorelines in the juyanze basin using digital global positioning system and found seven shorelines at 37 36 34 30 28 24 and 22 m above modern basin floor a m b f optically stimulated luminescence dating was employed to date the deposition of beach sand and gravel sequences at these shorelines results indicate a paleolake developed in the basin at 5 ka when lake levels reached 26 m a m b f the lake level then gradually increased to 29 m a m b f at 3 3 ka and r

electrical resistivity image of the jingsutu graben at the ne margin of the ejina basin nw china and implications for the basin development 1 magnetotelluric and transient electromagnetic data reveal the graben geometry of a nne striking depression within crystalline basement at the ne margin of the ejina basin we interpret this structure as a late mesozoic pull apart basin which is delineated by nne striking normal faults to the east and west satellite imagery srtm elevation data and previously published geophysical data of our work group suggest that the graben is part of normal fault system that continues at least 140 km farther to the south thus forming the eastern margin of the ejina basin nne striking normal faults are atypical in a regional context where nw striking and ene striking fault systems prevail thus this feature marks a distinct difference of the ejina basin when compared to other basin structures in the china mongolia border region

the geometry kinematics and rates of deformation within an en echelon normal fault segment boundary central italy abstract the geometry kinematics and rates of deformation have been investigated within an en echelon fault segment boundary between two left stepping major normal faults in the central apennines italy examination of faulted post glacial sediments and geomorphic features attributed to glacial retreat 18 ka reveals that the two major faults dominate the recent slip with rates that are 5 10 times greater than the other faults at the centres of the major faults slip is parallel to the regional extension direction ne sw defined by focal mechanisms and borehole breakouts slip vector azimuths defined by striations on faults in the stepover zone indicate ne sw extension on nw se faults sub parallel to the regional extension direction together with significant and contemporaneous nw se extension along the strike of the apennines on ese wnw and ene wsw faults thus distributed three dimensional strain occurs in the stepover between the two major bounding faults extension rates summed across the stepover are 0 68 mm y parallel to the regional extension compared to 2 mm y at the centre of one of the major faults extension rates along strike of the fault zone are 0 14 mm y within the stepover and zero at the centres of the two major bounding faults the above information is used to discuss how extension is partitioned between different structures during the growth and linkage of normal faults

deformation from 1973 to 1987 in the epicentral area of the 1959 hebgen lake montana earthquake ms 7 5 a 40 km aperture trilateration network centered on the 1959 hebgen lake earthquake epicenter has been surveyed in 1973 1974 1976 1978 1981 1984 and 1987 the deformation inferred from those surveys is described roughly by a uniaxial 0 266 0 014 strain yr n15 e 1 extension that is uniform in both time and space that extension is orthogonal to the strike n78 w 5 of the 1959 rupture plane inferred from focal mechanism solutions the absence of strain accumulation in the n75 w direction suggests that the source of deformation must be greatly elongated in that direction looked at in greater detail the deformation is found to be concentrated in the northern part of the network the zone of concentrated deformation coincides with a part of a well defined trend in seismicity that extends at least 100 km n75 w from the sour creek resurgent dome in the yellowstone caldera extension perpendicular to that trend is indicated by focal mechanism solutions thus the zone of rifting identified within the hebgen lake network apparently extends east southeast to the yellowstone caldera about 8 mm yr extension is observed across a 20 km width within the zone

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

asian provenance of glacial dust stage 2 in the greenland ice sheet project 2 ice core summit greenland samples of dust from the greenland ice sheet project 2 gisp2 ice core summit greenland dated within marine isotope stage 2 between 23 340 and 26 180 calendar years b p around the time of the coldest local last glacial temperatures have been analyzed to determine their provenance to accomplish this we have compared them with approximately coeval aeolian sediments mostly loesses sampled in possible source areas psas from around the northern hemisphere the 5 m grain size fraction of these samples was analyzed on the basis that it corresponds to the atmospheric dust component of that time and locale which was sufficiently fine grained to be transported over long distances on the basis of comparison of the clay mineralogy and sr nd and pb isotope composition with ice dust and psas and assuming that we have sampled the most important psas we have determined that the probable source area of these gisp2 dusts was in eastern asia the dust was not derived from either the midcontinental united states or the sahara two more proximal areas that have been suggested as potential sources based on atmospheric circulation modeling except for a brief period during an interstadial when dust transport was exceptionally low for glacial times and had a mineralogical composition indicative of a slightly more southern provenance the source area of the dust did not change significantly during times of variably higher fluxes of dust with larger mean grain size or lower fluxes of dust with smaller mean grain size this includes the high dust period that correlates with the heinrich 2 period of major iceberg discharge into the north atlantic variable wind strengths must therefore be invoked to account for these abrupt and significant changes in dust flux and grain size

comparison of surface slip and focal mechanism slip data along normal faults an example from the eastern gulf of corinth greece abstract focal mechanism and surface slip data are used to investigate whether kinematics are similar at depth and at the surface along an active normal fault in the gulf of corinth greece we present a new database of slip data from the lateral termination of the south alkyonides fault segment safs and the en echelon stepover between it and an adjacent fault and use published data on surface slip and focal mechanism data pertaining to slip at depth during the 1981 alkyonides earthquake sequence the focal mechanisms exhibit similar fault plane orientations and kinematics to those measured at the surface within the stepover both data sets show that contemporaneous c n s and c e w extension is being accommodated by c e w and c n s oriented normal faults and the overall deformation is distributed oblate vertical flattening the deviation of the surface slip direction from 350 increases with distance from the centre of the safs the deviation of the focal mechanism t axes from 350 fit well with the surface data implying that the coseismic slip on the safs at depths of 7 10 km exhibits a similar kinematic pattern as that observed at the surface our results imply that it is critical to know the along strike position of data on a fault if either focal mechanisms or surface slip are to be used to infer regional strain and stress trajectories

the south indian convergence zone and interannual rainfall variability over southern africa abstract the south indian convergence zone sicz is identified in this paper as a region of enhanced precipitation extending off the southeast coast of southern africa during austral summer unlike the south pacific convergence zone the sicz is a land based convergence zone lbcz with position and intensity at least partially determined by surface conditions over southern africa an idealized gcm simulation is used to explore the basic dynamics of lbczs in the tropics and subtropics output from a realistic gcm simulation and the national centers for environmental prediction national center for atmospheric research 40 year reanalysis are analyzed to apply this basic dynamical framework to the case of the sicz in contrast to the intertropical convergence zone where column moisture convergence is primarily due to meridional wind convergence in the moist environment precipitation within the sicz and the lbczs in general is also supported by zonal wind convergence moisture convergence by transient eddy

late quaternary lake evolution in the gaxun nur basin central gobi desert china based on quartz osl and k feldspar pirir dating of paleoshorelines paleoenvironmental changes in the gobi desert of mongolia are of global significance because fluvial and lacustrine deposits in the region constitute one of the dominant sources of northern hemisphere dust a series of well preserved geomorphic shoreline features at different elevations around the gaxun nur basin central gobi desert indicate past fluctuations of the basin s terminal lake we measured the exact elevation of shorelines in the basin using a differential global positioning system and found six shorelines at similar to 24 similar to 20 similar to 18 similar to 16 similar to 15m and similar to 8m above the modern basin floor quartz optically stimulated luminescence and k feldspar postinfrared infrared stimulated luminescence methods were used to date these shoreline features the reliability of the dates was confirmed using internal checks of luminescence characteristics and by comparing the quartz and kfeldspar ages our results suggest a lake developed in the gaxun nur basin by at least similar to 121 ka lake levels increased from similar to 8 to similar to 24m from similar to 121 to similar to 85 ka a 20 13 m deep lake again formed in the basin between similar to 8 4 and 0 8 ka monsoonal precipitation and temperature variations during marine isotope stage 5 and the mid late holocene were the likely causes of paleolake formation and lake level fluctuations copyright c 2017 john wiley sons ltd

quartz and k feldspar luminescence dating of a marine isotope stage 5 megalake in the juyanze basin central gobi desert china abstract the juyanze basin in the central gobi desert of china contains one of three terminal lakes of the heihe river the second largest inland river in china the paleoenvironmental record of the region is important since it is a significant global dust source region in this study a newly developed post infrared ir stimulated luminescence irsl pirir dating technique together with traditional quartz optically stimulated luminescence osl dating was applied to shoreline and deep water sediments obtained from a buried shoreline at 927 m in the ejina basin 33 m above the basin floor the reliability of k feldspar pirir dating was confirmed by internal checks of a dose recovery test an anomalous fading test and a residual dose test internal checks of the quartz osl dating and comparison to k feldspar pirir ages indicate that the single aliquot regenerative dose protocol was reliable for samples from the shoreline but that quartz ages older than 60 ka may be underestimated our results indicate that three lacustrine sequences separated by erosional unconformities and eolian deposition span a period from 122 to 73 ka covering most of marine isotope stage mis 5 at a depth of 33 m 927 m elevation the paleolake covered more than 1800 km2 in the juyanze basin during this period but fluctuated frequently whether or not this mis 5 lake filled the entire ejina basin or merely overflowed the juyanze basin to partially fill the other ejina sub basins remains unknown regardless the presence of such a large mis 5 paleolake in the ejina basin suggests its lake history closely matches those from other closed basin drainages originating in the qilian mountains we suggest that the high stands appearing during mis 5 in the juyanze basin likely were a response to moist climatic conditions during the last interglacial period

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

subtropical indian ocean sst dipole events and southern african rainfall an atmospheric general circulation model agcm is used to examine how the regional atmospheric circulation and rainfall over southern africa respond to a recently observed dipole in subtropical sea surface temperature sst over the south indian ocean observations suggest that when sst is warm to the south of madagascar and cool off western australia increased summer rains occur over large areas of southeastern africa the model results suggest that this sst pattern leads to increased rainfall via enhanced convergence of moister than average air over the region increased evaporation occurs over the warm pole in the south west indian ocean and this moist air is advected towards mozambique and eastern south africa as a result of the low pressure anomaly generated over this pole which strengthens the onshore flow

potential sources of decadal climate variability over southern africa abstractpotential sources of decadal climate variability over southern africa are examined by conducting in depth analysis of available datasets and coupled general circulation model cgcm experiments the observational data in recent decades show a bidecadal variability noticeable in the southern african rainfall with its positive phase of peak during 1999 2000 it is found that the rainfall variability is related to anomalous moisture advection from the southwestern indian ocean where the anomalous sea level pressure slp develops the slp anomaly is accompanied by anomalous sea surface temperature sst both slp and sst anomalies slowly propagate eastward from the south atlantic to the southwestern indian ocean the analysis of mixed layer temperature tendency reveals that the sst anomaly in the southwestern indian ocean is mainly due to eastward advection of the sst anomaly by the antarctic circumpolar current the eastward propagation of slp and sst anomalies are also confirmed in the 270 yr outp

remote effects of el nino and modoki events on the austral summer precipitation of southern africa abstractremote effects modulating the austral summer precipitation over southern africa during el nino el nino modoki events are investigated by analyzing the observed events during december february of the years from 1982 83 to 2010 11 based on the composite analyses it is found that southern africa experiences significantly below normal precipitation during el nino events compared to el nino modoki events during these latter events precipitation anomalies are not so significant although southern africa as a whole receives below normal precipitations the differences in the spatial distribution of precipitation over southern africa are seen to be related to the sea surface temperature sst anomalies of the equatorial pacific through atmospheric teleconnections the low level 850 hpa matsuno gill response to anomalously high precipitation over the pacific during el nino events results in an anomalous anticyclone extending from the equatorial to the subtropical south indian ocean these anomalous ant

eastward propagating decadal temperature variability in the south atlantic and indian oceans the origin and structure of eastward propagating decadal temperature variability in the south atlantic and indian oceans are investigated by using long term output of coupled general circulation model composite analysis during the warm southwest indian ocean swio years shows that decadal temperature anomalies in the swio region originate in the south atlantic and are associated with density anomalies since the density anomalies propagate at the speed of a few cm s 1 slower than the speed of the background eastward antarctic circumpolar current and exhibit a surface intensified equivalent barotropic structure the eastward propagation of the density anomalies may be attributed to quasi stationary oceanic rossby waves the density anomalies are also accompanied with anomalous ekman pumping indicating an important contribution from the overlying atmospheric variability the role of atmospheric variability is further examined by evaluating the mixed layer heat balance it is found that the warm temperature anomalies in the south atlantic are due to anomalous entrainment and meridional advection these results suggest that the atmospheric variability plays an important role through the ocean mixed layer in generating the eastward propagation of decadal temperature variability from the south atlantic besides the internal ocean variability as suggested in previous studies

luminescence dating of the pasado core 5022 1d from laguna potrok aike argentina using irsl signals from feldspar in this paper we develop and test a luminescence chronology for the pasado core 5022 1d taken in the laguna potrok aike maar lake because of unsuitable quartz osl characteristics sand sized k feldspar extracts were chosen as a dosimeter and the dose was measured using a recently developed post ir irsl pirir290 measurement protocol using this approach we were able to access a stable signal and thus avoid the ubiquitous problem of signal instability in feldspar dating extensive laboratory tests show that the chosen pirir290 protocol is applicable to these samples we also develop a new criterion based on the known relative bleaching rates of the conventional irsl signal ir50 and the pirir290 signals and the relationship between the resulting equivalent doses this is used to identify and reject poorly bleached samples fourteen samples out of 35 were rejected based on this criterion the resulting age depth profile is self consistent increases smoothly with depth and is in agreement with the independent age control reclus mt burney and hudson tephras at the top of the core our new luminescence chronology suggests the 5022 1d core reaches back to 65 ka at 96 m below lake floor