unsaturated zone hydrostratigraphies a novel archive of past climates in dryland continental regions natural chemical tracers contained in moisture within unsaturated zone usz sediments have very significant potential as a novel archive of past climate and palaeoenvironmental conditions in dryland environments however this potential has yet to be fully realised the tracer signature is established in the near surface zone with evapotranspiration processes enriching the concentration inherited from input from atmospheric deposition predominantly rainfall this pore moisture tracer signature then moves vertically through the usz sediments toward the water table producing a hydrostratigraphy that with increasing depth records changes to the moisture balance at the surface through time the small fluxes of water through the usz in dryland climates means that this hydrostratigraphy approach is particularly valuable in these environments for providing climate records longer than the instrumental data period this paper sets out the current state of the art in the use of the usz as an archive we explain the nature of the usz the basis of the tracer technique and also the field and sampling methodologies employed examples of application worldwide by broad geographic region are also evaluated this shows that the usz hydrostratigraphy approach can be used across three key timescales i decadal to multi decadal resolution records covering hundreds of years that provide information about recent climate fluctuations and patterns of land use change ii multi decadal through to millennial scale length records which may record wetter and drier events down to decadal scale resolution and iii last interglacial through to the holocene records of lower resolution that indicate broad shifts over multi millennial timescales we also explore the questions and challenges surrounding the depositional flux of tracer inputs and the extent to which infiltration is non uniform before setting the agenda for their future potential use alongside related proxies for palaeohydrology

holocene climate variability archived in the puruogangri ice cap on the central tibetan plateau two ice cores 118 4 and 214 7 m in length were collected in 2000 from the puruogangri ice cap in the center of the tibetan plateau tp in a joint us chinese collaborative project these cores yield paleoclimatic and environmental records extending through the middle holocene and complement previous ice core histories from the dunde and guliya ice caps in northeast and northwest tibet respectively and dasuopu glacier in the himalaya the high resolution puruogangri climate record since ad 1600 details regional temperature and moisture variability the post 1920 period is characterized by above average annual net balance contemporaneous with the greatest 18 o enrichment of the last 400 years consistent with the isotopically inferred warming observed in other tp ice core records on longer timescales the aerosol history reveals large and abrupt events one of which is dated 4 7 kyr bp and occurs close to the time of a drought that extended throughout the tropics and may have been associated with centuries long weakening of the asian indian african monsoon system the puruogangri climate history combined with the other tp ice core records has the potential to provide valuable information on variations in the strength of the monsoon across the tp during the holocene

flood drought variability in the yangtze delta and association with the climatic changes from the guliya ice core a wavelet approach abstract correlativity between flood drought variability in the yangtze delta and temperature precipitation changes reconstructed from the oxygen isotope 18 o 16 o and ice accumulation were detected using continuous wavelet transform cross wavelet and squared wavelet coherence approaches research results indicate that 1 significant wavelet variance fluctuations occurred during 1115 1315 ad and 1415 1715 ad in terms of larger time scales the significant wavelet variance fluctuations can be identified during 1115 1315 ad and 1715 1865 ad 2 cross wavelet analysis and wavelet coherence analysis demonstrate concurrent correlations between flood drought variability in the yangtze delta and temperature changes reconstructed from the guliya ice core but are varying over time and in different time scales generally relatively stable relations are found in the larger time scales and ambiguous ones in the shorter time scales 3 in phase relations in 4 8 year time scales and anti phase relations in 8 16 year time scales are identified between flood drought variability in the yangtze delta and temperature changes reconstructed from the guliya ice core the correlativity between flood drought changes and precipitation changes reconstructed from the guliya ice core is relatively weak and ambiguous without obvious changing patterns

stable isotope time series and precipitation origin from firn core and snow samples altai glaciers siberia in the summers of 2001 and 2002 glacio climatological research was performed at 4110 4120ma s l on the belukha snow firn plateau siberian altai hundreds of samples from snow pits and a 21m snow firn core were collected to establish the annual seasonal monthly depth accumulation scale based on stable isotope records stratigraphic analyses and meteorological and synoptic data the fluctuations of water stable isotope records show well preserved seasonal variations the d 18 o and dd relationships in precipitation snow pits and the snow firn core have the same slope to the covariance as that of the global meteoric water line the origins of precipitation nourishing the belukha plateau were determined based on clustering analysis of d 18 o and d excess records and examination of synoptic atmospheric patterns calibration and validation of the developed clusters occurred at event and monthly timescales with about 15 uncertainty two distinct moisture sources were shown oceanic sources with d excess 12 two thirds of the annual accumulation was from oceanic precipitation of which more than half had isotopic ratios corresponding to moisture evaporated over the atlantic ocean precipitation from the arctic pacific ocean had the lowest deuterium excess contributing one tenth to annual accumulation

tree ring evidence of little ice age glacier advances in southern tibet the history of late holocene glacier fluctuations in eastern tibet was studied by determining the ages of trees growing on glacier deposits maximum tree ages yield minimum ages of ad 1760 and 1780 for moraine formation at the maximum extent of the little ice age glacier advances in two glacier forefields subsequent moraines could be dated to the beginning of the nineteenth and the beginning of the twentieth century larch trees from a third glacier forefield in southeastern tibet show evidence of glacier activity from 1580 to 1590 from the end of the eighteenth to the beginning of the nineteenth century and from 1860 to 1880 one glacier at mt gyalaperi recently advanced in both 1951 and 1987 periods of glacier advances can partly be correlated with periods of growth reductions in chronologies of total ring width and maximum latewood density derived from trees growing on slopes above the glacier valleys correlation functions with meteorological data suggest that maximum latewood density of subalpin

climatic oscillations over the past 120 kyr recorded in the guliya ice core china recently several ice cores were drilled on the tibetan plateau to examine climate and environmental changes based on the temperature proxy records in the guliya ice core climate oscillations over the past 120 kyr were examined using wavelet analysis and singular spectrum analysis methods the results showed two main milankovitch type oscillatory modes 22 and 44 kyr the 22 kyr period corresponds to the precession period and 44 kyr period corresponds to the earth axis s obliquity inclination period the two periods combined explain 43 of the variance in addition there are millennial and 10 thousand years time scales periods which may be related to the dansgaard oeschger d o cycles and the heinrich h events r 2006 elsevier ltd and inqua all rights reserved

dynamics of surge type glaciers in west kunlun shan northwestern tibet here we examine 31 glaciers in the west kunlun shan of the northwestern tibetan plateau and identify 9 as surge type the method is based on satellite synthetic aperture radar and landsat optical images the former going back to 1992 the latter to 1972 to identify surge type glaciers we consider temporal changes in velocity changes in glacier terminus position propagation of a surge bulge presence of looped and or contoured medial moraines and extensive crevassing other than the nine surge type glaciers we identify two that have likely surged and six that may be surge type but no glacier surges more than once during the observation period meaning that the recurrence interval exceeds 42 years in addition we examine the evolution of the surface velocities at two surging glaciers with the unprecedented temporal resolution of down to 11 days over 7 years the results show clear seasonal modulations by as much as 200 in early winter against those in early summer this seasonal modulation in surface velocity suggests the presence of surface meltwater that reroutes through the englacial and subglacial drainage systems thus our findings suggest that the hydrological processes originating in the surface meltwater play an important role in maintaining the yearlong active surging phase

association between atmospheric circulation patterns and firn ice core records from the inilchek glacierized area central tien shan asia 1 glacioclimatological research in the central tien shan was performed in the summers of 1998 and 1999 on the south inilchek glacier at 5100 5460 m a 14 36 m firn ice core and snow samples were collected and used for stratigraphic isotopic and chemical analyses the firn ice core and snow records were related to snow pit measurements at an event scale and to meteorological data and synoptic indices of atmospheric circulation at annual and seasonal scales linear relationships between the seasonal air temperature and seasonal isotopic composition in accumulated precipitation were established changes in the 18o air temperature relationship in major ion concentration and in the ratios between chemical species were used to identify different sources of moisture and investigate changes in atmospheric circulation patterns precipitation over the central tien shan is characterized by the lowest ionic content among the tien shan glaciers and indicates its mainly marine origin in seasons of minimum precipitation autumn and winter water vapor was derived from the arid and semiarid regions in central eurasia and contributed annual maximal solute content to snow accumulation in tien shan the lowest content of major ions was observed in spring and summer layers which represent maximum seasonal accumulation when moisture originates over the atlantic ocean and mediterranean and black seas

a 700 year history of groundwater recharge in the drylands of nw china a 700 year semi quantitative history of diffuse groundwater recharge in the badain jaran desert inner mongolia is proposed on the basis of solute data from multiple unsaturated zone groundwater profiles using mass balance of chloride to establish recharge rates and profile chronologies four relatively humid 1330 1430 1500 1620 1700 1780 and 1950 1990 and three relatively arid phases 1430 1500 1620 1700 and 1900 1950 are discernable across the profiles the recharge history broadly reflects multidecadal to centurial timescale precipitation changes in the northern tibetan plateau and suggests that variations in east asian summer monsoon intensity affect desert recharge rates uncertainties in the records owing to assumptions about the cl inputs are examined by comparing deterministic and stochastic cl input scenarios such records are valuable for assessing spatial aspects of climate changes in the region as well as for informing sustainable water resource management strategies for northwestern china s drylands

late holocene hydroclimatic variation in central asia and its response to mid latitude westerlies and solar irradiance abstract hydroclimatic variations in central asia are widely recognized to be tele connected with the north atlantic climate via the mid latitude westerlies however the long term hydroclimatic variation and its response to north atlantic climate changes are not fully understood here we report multi decadal and centennial hydroclimatic variations in central asia during the late holocene using high resolution oxygen and carbon isotopes of bulk carbonate from a remote hydrologically closed alpine lake in tianshan mountains northwestern china the hydroclimatic variations inferred from the covariance between 18ocarb and 13ccarb and published multi proxy in the lake sayram together agree well with the records from the central asia showing enhanced effective moisture at the intervals of 4000 3780 3590 3210 2800 2160 1700 1370 and 890 280 cal yr bp during the negative phase of north atlantic oscillation nao comparison with european hydroclimatic changes on centennial scale our records not only provide valuable insight into the hydroclimatic variations in central asia but also indicate all broadly contemporaneous changes with that of southern europe whereas antiphase with that of northern europe we then conclude that the observed antiphase hydroclimatic pattern between northern europe and southern europe central asia on centennial time scale during the late holocene were persistently controlled by the north south migration of mid latitude westerlies and changes of nao phase in response to solar irradiance forcing however further research is necessary to fully disentangle the natural and anthropogenic forcing mechanisms for enhanced effect moisture and or precipitation in central asia

tropical glaciers potential for ice core paleoclimatic reconstructions the objective of this work is to evaluate the potential of tropical glaciers and ice caps for the reconstruction of past climatic conditions by the analysis of firn and ice cores samples were collected in pits and from cores retrieved on three snow fields in the south american andes quelccaya ice cap and huascaran in peru and chimborazo in ecuador these are compared with results from west africa and indonesia measurements include the microparticle concentration oxygen isotopic abundance ratios and total beta radioactivity which in polar regions often exhibit seasonal depositional cycles annual variations in these three parameters are fairly well defined on quelccaya and huascaran and are apparently absent on chimborazo the quelccaya ice cap contains the best preserved annual signal for all three parameters and although in some instances the annual cycle is difficult to distinguish the measurement of more than one stratigraphic parameter aids in the interpretation of the firn core records the relatively flat bottom topography under quelccaya suggests a simple ice flow regime and depth age calculations indicate that an ice core to bedrock should contain a record of 600 to 1300 years this inference was confirmed by drilling to bedrock in 1983 this investigation of tropical glaciers indicates that the quelccaya ice cap on the eastern edge of the peruvian andes has excellent potential to contain a lengthy and interpretable record of climatic conditions within the tropics of south america

correlation between precipitation and temperature variations in the past 300 years recorded in guliya ice core china the guliya ice cap on the crest of the kunlun shan central asia is an ideal site for acquiring ice cores for climate change studies detailed analyses of the precipitation index glacier accumulation and the temperature proxy do recorded in the guliya ice core since 300 years bp show that precipitation correlates with temperature in this region climate conditions in the guliya region since 300 years bp can be separated into three periods warm and wet from ad1690 to the end of the 18th century cold and dry from the 19th century to the 1930s and warm and wet again since the 1940s during this period the climate exhibits just two phases warm wet and cold dry comparison of the temperatures and the precipitation recorded in the guliya ice core shows that variations of temperature and precipitation in the region correlate quite well however changes in the precipitation regime appear to lag behind those of the temperature by 20 40 years we believe this results from the larger heat capacity of the ocean relative to that of the land hence ocean temperatures and corresponding evaporation rates change more slowly than do continental conditions additionally however positive feedback processes such as increasing temperatures and precipitation improving vegetation moisture retention and hence local convective precipitation probably play an important role in this paper we explain how the timescale of evolving vegetation and the feedback mechanism between precipitation and the temperature could help explain why the changes in precipitation lag those of temperature by 20 40 years over long periods taking this time lag into account we should be able to predict future precipitation trends based on observed temperature trends

microparticle content records of the dunde ice core and dust storms in northwestern china abstract dust storms are important atmospheric phenomenon in central asia particularly in the regions bordering deserts arid and semi arid regions dust storms occur quite often in northwestern china there are some research results about past dust storm events using historical archives in china however the archives used cover limited time and area microparticle concentrations in the dunde ice cap qilian mountain of northwestern china represent a continuous record of past dust storms comparison between dust rain frequency reconstructed from historical archives and the ice core record from the dunde ice cap demonstrate that the microparticle record in the dunde ice core is a good indicator of dust storms in northwest china according to the ice core records we can reconstruct the dust storm chronology for historical time during the past 700 years the dust content fluctuated with time and lower frequency variations existed although the linear trend increased over the past 700 years dust content was decreasing since the early 1700s during the little ice age it was slightly higher corresponding to the cold period

climate changes reconstructed from a glacial lake in high central asia over the past two millennia abstract climatic changes in arid central asia aca over the past two millennia have been widely concerned however less attention has been paid to those in the high central asia hca where the asian water tower nurtures the numerous oases by glacier and or snow melt here we present a new reconstruction of the temperature and precipitation change over the past two millennia based on grain size of a well dated glacial lake sediment core in the central of southern tianshan mountains the results show that the glacial lake catchment has experienced cold wet climate conditions during the dark age cold period 300 600 ad dacp and the little ice age 1300 1870 ad lia whereas warm dry conditions during the medieval warm period 700 1270 ad mwp integration of our results with those of previously published lake sediment records stalagmite 18o records ice core net accumulation rates tree ring based temperature reconstructions and mountain glacier activities suggest that there has a broadly similar hydroclimatic pattern over the hca areas on centennial time scale during the past two millennia comparison between hydroclimatic pattern of the hca and that of the aca areas suggests a prevailing warm dry and cold wet hydroclimatic pattern over the whole westerlies dominated central asia areas during the past two millennia we argue that the position and intensity of the westerlies which are closely related to the phase of the north atlantic oscillation nao and the strength of the siberian high pressure sh could have jointly modulated the late holocene central asia hydroclimatic changes

multicomponent ocean bottom cable data in gas hydrate investigation offshore of norway 1 a multicomponent seismic ocean bottom cable obc line from the northern flank of the storegga slide offshore of norway is the first obc line ever acquired over a gas hydrate related bottom simulating reflector bsr the seismic data are of very good quality and display strong p s converted wave reflections for the whole sediment column all p s reflections follow the sediment layers and are therefore interpreted to be caused by increased shear modulus and density due to sediment compaction no p s reflections are associated with the bsr along this line indicating that the gas hydrate bearing sediments at the base of the hydrate stability zone are not stiff enough to increase the shear modulus of the sediments to produce p s converted wave reflections seismic interpretation and seismic stratigraphic modeling suggest that the bsr in this area is a contrast in compressional wave velocity only mainly caused by small amounts of free gas confined to dipping sediment layers beneath the bsr gas hydrate saturation above the bsr tentatively estimated to be about 1 1 5 of the sediment pore space is most likely too low to distinguish between different models for microscale gas hydrate distribution

seasonal variability of ionic concentrations in surface snow and elution processes in snow firn packs at the pgpi site on urumqi glacier no 1 eastern tien shan china to investigate the effects of both non meltwater and meltwater related post depositional processes on chemical species within the snow firn pack a research program the program for glacier processes investigation was initiated in july 2002 by the tien shan glaciological station chinese academy of sciences the seasonal variability of the ionic concentrations in surface snow samples and ion elution behavior in the snow firn pack were assessed from surface samples collected year round and 1011 samples collected from a snow pit at weekly intervals from september 2003 through september 2004 the results indicate that elevated ionic concentrations in spring and summer result from asian dust storm derived aerosol input and other aerosols entrained in precipitation potential sources of these chemical species are explored using correlation and factor analyses the elution sequence through the snow firn pack was determined to be so4 2 c a 2 n a n o3 c l k m g 2 n h4 the elution of ions at the sampling site was found to be driven primarily by air temperature and became evident when a diurnal mean temperature of 3 68c was attained at 0 38c all of the year round new ionic input was leached from the snow

hydroclimatic changes in china and surroundings during the medieval climate anomaly and little ice age spatial patterns and possible mechanisms abstract investigating hydroclimatic changes during key periods such as the medieval climate anomaly mca 1000 1300 ad and the little ice age lia 1400 1900 ad is of fundamental importance for quantifying the responses of precipitation to greenhouse gas induced warming on regional and global scales this study synthesizes the most up to date and comprehensive proxy moisture precipitation records during the past 1000 years in china and surroundings the proxy data collected include 34 records from arid central asia aca and 37 records from monsoonal asia our results demonstrate a pattern of generally coherent regional moisture variations during the mca and lia in mid latitude asia north of 30 n monsoonal northern china north china and northeast china was generally wetter while aca northwest china and central asia was generally drier during the mca than in the lia a west east mode the boundary between wetter northern china and drier aca was roughly consistent with the modern summer monsoon boundary in monsoonal china to the east of 105 e the northern part was generally wetter while the southern part was generally drier during the mca than in the lia a north south mode with a boundary roughly along the huai river at about 34 n these spatial patterns of moisture precipitation variations are also identified by instrumental data during the past 50 years in order to understand the possible mechanisms related to the moisture variations during the mca and lia we investigate the major sst and atmospheric modes e g the el nino southern oscillation enso the atlantic multidecadal oscillation amo and the north atlantic oscillation nao which affect the moisture precipitation variations in the study region using both the instrumental data and the reconstructed time series it is found that the enso may play an important role in determining hydroclimatic variability over china and surroundings on a multi centennial time scale and that the foregoing spatial patterns could be attributed to the la nina like el nino like condition during the mca lia in addition amo and nao may also have their own contributions

a 1000 year climate ice core record from the guliya ice cap china its relationship to global climate variability in 1992 an american chinese expedition successfully recovered three ice cores 308 6 93 2 and 34 5m from the guliya ice cap summit 6710 m a s l in the far western kunlun on the qinghai tibetan plateau china guliya resembles a polar icecap with 10 m 200 m and basal temperatures of 15 6 5 9 and 2 1 c respectively the 308 6 m core to bedrock is the longest ice core retrieved from an elevation greater than 4000 m a s l and provides the first ice core history from the western side of the qinghai plateau the plateau experiences a pronounced annual precipitation cycle during which 70 80 of annual total precipitation falls in the summer monsoon season this leads to a marked visible stratigraphy in the glaciers which allows accurate dating of the ice cores and reconstruction of the net mass accumulation this paper presents 1 the results of the geophysical program to determine ice thickness ice flow and surface topography 2 an assessment of net accumulation from stake measurements snow pits and shallow core samples and 3 the analyses of the upper 100 m of the 308 6 m core which provide a 1000 year history including the little ice age which is compared with chinese historical records extended periods of positive accumulation on guliya are closely contemporaneous with dry periods in eastern china a trans pacific teleconnection is suggested by the strong temporal coherence between extended wet and dry phases on guliya and on the quelccaya ice cap peru

evidence for a late holocene warm and humid climate period and environmental characteristics in the arid zones of northwest china during 2 2 1 8 kyr b p 1 natural archives like ice cores tree rings river and lake sediments lake terraces and paleosols and also historical documents witness aspects of climate change in northwestern china during the western and eastern han dynasties 206 b c 220 a d reconstructions of decadal averages of annual mean temperature and precipitation fluctuations were derived from variations of 18o and net accumulation rates in the guliya ice core they revealed a period of higher temperatures and higher precipitation than today which affected vast areas of northwestern china during the period of interest until the fifth century a d these conditions resulted in a marked increase in the discharge of big endorheic river systems such as the tarim the keriya and the manas rivers as a consequence water levels in appendant terminal lakes rose e g at lop nor manas lake and baijian hu lake surface areas expanded and lake desalting occurred also at lakes in intermontane basins such as balikun hu and qinghai lake the warm and moist conditions during the western and eastern han dynasties might have been responsible for the large scale agricultural production and the local socioeconomic boom that is documented by the occurrence of the famous ruin groups of loulan niya and keriya the following desiccation phase led to a deterioration of water resources and most oases tended to dry out and were finally abandoned the appearance development flourishing and final abandonment of each great ruin group are closely associated with regional climate change at that time

pre incan agricultural activity recorded in dust layers in two tropical ice cores in south america no documentary records survive from before the incursion of the spaniards in the mid sixteenth century knowledge of pre hispanic civilizations in this region comes largely from archaeological excavations which may now be supplemented by information recorded in two ice cores drilled in the quelccaya ice cap in southern peru fig 1 1 2 a 1 500 year record of particle concentrations and conductivity in these cores shows two major dust episodes each lasting about 130 years centred at ad 920 and 600 here we examine these dust events in the light of oxygen isotope and net accumulation records and suggest a correlation with pre incan agricultural activity the annual net accumulation record for ad 1915 1984 compares well with annual changes in lake titicaca water levels and with annual precipitation at el alto lapaz bolivia suggesting that the 1 500 year net accumulation record from quelccaya may serve as a proxy for water level changes in lake titicaca the ice core record suggests that climatic variability reflected in lake level changes has strongly influenced fluctuations in agricultural activity in southern peru

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

high resolution temperature and evaporation changes during the late holocene in the northeastern arabian sea in order to reconstruct the monsoonal variability during the late holocene we investigated a complete annually laminated sediment record from the oxygen minimum zone omz off pakistan for oxygen isotopes of planktic foraminifera and alkenone derived sea surface temperatures sst significant sst changes of up to 3 c which cannot be explained by changes in the alkenone producing coccolithophorid species inferred from the gephyrocapsa oceanica emiliania huxleyi ratio suggest that sst changes are driven by changes in the monsoon strength our high decadal resolution data indicate that the late holocene in the northeastern arabian sea was not characterized by a stable uniform climate as inferred from the greenland ice cores but by variations in the dominance of the sw monsoon conditions with significant effects on temperatures highest sst fluctuations of up to 3 0 c and 2 5 c were observed for the time interval from 4600 to 3300 years b p and during the past 500 years the significant short term sst changes during the past 500 years might be related to climatic instabilities known from the northern latitudes little ice age and confirm global effects surface salinity values reconstructed from 18o records after correction for temperature related oxygen isotope fractionation suggest that in general the past 5000 years were characterized by higher than recent evaporation and more intense sw monsoon conditions however between 4600 and 3700 years b p evaporation dropped sw monsoon weakened and ne monsoon conditions were comparatively enhanced for the past 1500 years we infer strongly fluctuating monsoon conditions comparisons of reconstructed salinity records with ice accumulation data from published tibetan ice core and tibetan tree ring width data reveal that during the past 2000 years enhanced evaporation in the northeastern arabian sea correlates with periods of increased ice accumulation in tibet and vice versa this suggests a strong climatic relationship between both monsoon controlled areas

recent increases in atmospheric concentrations of bi u cs s and ca from a 350 year mount everest ice core record 1 high resolution major and trace elements sr cs ba la ce pr nd sm eu tb dy ho er tm yb lu bi u tl al s ca ti v cr mn fe and co quantified in a mount everest ice core 6518 m above sea level spanning the period 1650 2002 ad provides the first asian record of trace element concentrations from the pre industrial era and the first continuous high resolution asian record from which natural baseline concentrations and subsequent changes due to anthropogenic activities can be examined modern concentrations of most elements remain within the pre industrial range however bi u and cs concentrations and their enrichment factors ef have increased since the 1950s and s and ca concentrations and their efs have increased since the late 1980s a comparison of the bi u cs s and ca data with other ice core records and production data indicates that the increase in atmospheric concentrations of trace elements is widespread but that enrichment varies regionally likely sources for the recent enrichment of these elements include mining metal smelting oil and coal combustion and end uses for bi and mining and refinement for u and cs the source of the synchronous enrichment of ca and s is less certain but may be related to land use and environmental change

late holocene climatic and environmental changes in arid central asia abstract late holocene climate and environmental changes in arid central asia were analyzed using various paleoclimate archives such as ice cores tree rings lake sediments historical documents glacial fluctuations and archeological data over the last 2000 years arid central asia witnessed three humid periods from ad 0 410 650 890 and 1500 1820s dry periods occurred in 420 660 and in 900 1510s concerning temperature the most striking features are the existence of the medieval warm period mwp and the little ice age lia the mwp was recorded in the 9 12th centuries and was accompanied by an anomalously dry climate whereas the lia extended from the 15 18th centuries and was accompanied by pluvial conditions temperature and precipitation show significantly negative correlations on annual decadal and centennial timescales temperature was generally above average when dry climate conditions predominated on decadal to centennial timescales during the last 1000 years the coldest decades of the last millennium the period 1630 1650s matched with an anomalously wet episode the combination of paleoclimatic evidence clearly suggests that the combination of cold and wet climate condition during the lia was responsible for the strong glacial advances in several mountain systems of central asia

monsoon and dust signals recorded in dasuopu glacier tibetan plateau during summer 1997 a 15 m firn core was recovered from dasuopu glacier 28 23 n 85 44 e 7000 m a s l on the northwest margin of xixabarngma feng in the central himalaya oxygen isotope values and concentrations of ca 2 mg 2 nh 4 so 4 2 and no 3 were measured over the 10 years of snow accumulation captured in the firn core the seasonal variations of 18 o values and major ion concentrations in the dasuopu core indicate that summer monsoon and dust signals are clearly recorded in dasuopu glacier annual variations in 18 o values are controlled by the amount effect with more negative i e lighter 18 o values representing summer monsoon precipitation characteristic of tropical regions higher concentrations of ca 2 mg 2 and so 4 2 reflect the influx of mineral aerosols from the vast arid and semi arid desert regions to the north and west during the spring dust storm period high spring concentrations of nh 4 and no 3 appear to reflect changes in regional biogenic source strength

climate since ad 1510 on dyer plateau antarctic peninsula evidence for recent climate change a 480 year record of the oxygen isotope ratios dust content chemical species and net accumulation from ice cores drilled in 1989 90 on dyer plateau in the antarctic peninsula is presented the continuous analyses of small sub annual samples reveal well preserved annual variations in both sulfate content and 18o thus allowing an excellent time scale to be established this history reveals a recent pronounced warming in which the last two decades have been among the warmest in the last five centuries furthermore unlike in east antarctica on dyer plateau conditions appear to have been fairly normal from ad 1500 to 1850 with cooler conditions from 1850 to 1930 and a warming trend dominating since 1930 reconstructed annual layer thicknesses suggest an increase in net accumulation beginning early in the 19th century and continuing to the present this intuitive conflict between increasing net accumulation and depleted 18o cooler climate in the 19th century appears widespread in the peninsula region and challenges our understanding of the physical relationships among moisture sources air temperatures and snow accumulation the complex meteorological regime in the antarctic peninsula region complicates meaningful interpretation of proxy indicators and results in a strong imprint of local high frequency processes upon the larger scale climate picture

westerlies asia and monsoonal asia spatiotemporal differences in climate change and possible mechanisms on decadal to sub orbital timescales abstract the westerlies dominated climatic regime wdcr in the present interglacial period was proposed because precipitation moisture variations between arid central asia and mid latitude monsoonal asia are out of phase or anti phased on different timescales during the holocene in this study we first review the development of the theoretical framework of the wdcr and then outline the boundary of its core area from the caspian sea in the west to the western hexi corridor in the east with the northern and southern limits coinciding with the domain of arid central asia next we present a synthesis of multiple lines of evidence for the occurrence of the wdcr on multi millennial sub orbital herein to decadal timescales during the holocene finally we examine the possible physical mechanisms responsible for the wdcr we find that external factors insolation changes induced by orbital factors generated the wdcr on a sub orbital timescale whereas a circum global teleconnection silk road pattern was the most significant factor responsible for the wdcr on centennial and decadal timescales the study provides a comprehensive summary of the development of our knowledge of the wdcr over the past several decades together with a tentative theoretical framework for understanding climatic and environmental changes within its region of influence in addition it forms a scientific basis for environmental management and ecological restoration in this arid region in the context of global warming

mass balance and a glacier surge of guliya ice cap in the western kunlun shan between 2005 and 2015 abstract contemporary estimates of glacier changes are necessary to assess the impact of climate change associated hazards and water resources management glaciers in high mountain asia hma are mostly retreating except the karakoram and western kunlun shan confirmed by remote sensing measurements however ground validation with precise measurements of these mass balance estimates are scarce this study selected guliya ice cap in the western kunlun shan to observe its recent changes regarding surface dynamics and mass balance using aster dem of 2005 and 2015 our findings indicate that one of the north facing glaciers surged with no previous surging history during july and early november 2015 advancing at about 8 m per day on average the mass balance shows a balance condition 0 01 0 02 m w e a 1 the icesat data 2004 2008 at selected locations compared to dgps data collected in the field during 2015 indicating a minute difference of 0 03 0 05 m a 1 with aster data in the same area our findings suggest that guliya ice cap in the western kunlun shan is in equilibrium state following a similar pattern mass gain or stable conditions as observed previously

the little ice age as recorded in the stratigraphy of the tropical quelccaya ice cap the analyses of two ice cores from a southern tropical ice cap provide a record of climatic conditions over 1000 years for a region where other proxy records are nearly absent annual variations in visible dust layers oxygen isotopes microparticle concentrations conductivity and identification of the historical a d 1600 huaynaputina ash permit accurate dating and time scale verification the fact that the little ice age about a d 1500 to 1900 stands out as a significant climatic event in the oxygen isotope and electrical conductivity records confirms the worldwide character of this event

reliability analysis for design of stake networks to measure glacier surface velocity measurement of glacier surface velocity provides some constraint on glacier flow models used to date ice cores recovered near the flow divide of remote high altitude ice caps the surface velocity is inferred from the change in position of a network of stakes estimated from the least squares adjustment of geodetic observations terrestrial and or spaced based collected approximately 1 year apart the lack of outliers in and the random distribution of the post fit observation residuals are regarded as evidence that the observations contain no blunders however if the network lacks sufficient geometric redundancy the estimated stake positions can shift to fit erroneous observations to determine the maximum size ofthese potential undetected shifts given the covariance of the observations and the approximate network geometry expressions are developed to analyze a network for redundancy number and marginally detectable blunders internal reliability and the position shifts from marginally detectable blunders external reliability two stake networks one on the col of huascaran 9 07 s 77 37 w 6050 m a s l in the north central andes of peru and one on the guliya ice cap 35 17 n 81 29 e 6200 m a s l on the qinghai tibetan plateau in china are examined for precision and internal and external reliability

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

seismic images of a grenvillian terrane boundary a series of gently dipping reflection zones extending to mid crustal depths is recorded by seismic data from lakes ontario and erie these prominent reflection zones define a broad complex of southeast dipping ductile thrust faults in the interior of the grenville orogen one major reflection zone provides the first image of a proposed grenvillian suture the listric boundary zone between allochthonous terranes of the central gneiss and central metasedimentary belts curvilinear bands of reflections that may represent ramp folds and ramp anticlines that originally formed in a deep crustal scale duplex abut several faults vertical stacking of some curvilinear features suggests coeval or later out of sequence faulting of imbricated and folded thrust sheets grenvillian structure reflections are overlain by a thin wedge shaped package of shallow dipping reflections that probably originates from sediments deposited in a local half graben developed during a period of post grenville extension this is the first seismic evidence for such extension in this region which could have occurred during terminal collapse of the grenville orogen or could have marked the beginning of pre appalachian continental rifting

changes in vegetation and environment in yamzhog yumco lake on the southern tibetan plateau over past 2000 years abstract high resolution palynological analyses of the sediment of yamzhog yumco lake can potentially provide new insight into vegetation change and climate dynamics of the southern tibetan plateau over the past 2000 years the chronology presented herein is based on 210pb and ams 14c dates from the macro remains of plants reconstruction of vegetation types temperature and moisture indices indicate that the vegetation was alpine meadow under relatively wet and cool conditions from approximately 100 to 780 ce later the vegetation between approximately 780 and 1400 ce was alpine steppe with a warmer and drier climate prevailing during the medieval warm period mwp then the vegetation during the period from approximately 1400 to 1890 ce reverted back to alpine meadow under relatively cold and moist climate conditions which may have corresponded to the little ice age lia since the 20th century an alpine steppe has dominated the landscape developed under a dry climate with a lower effective moisture climate records from yamzhog yumco lake have confirmed a cold moist warm dry climate oscillation on the southern tibetan plateau over the past 2000 years comparison of pollen records with other climatic records suggests that the climate changes in the southern tibetan plateau were generally similar to those in the northern tibetan plateau as well as those in westerly dominated central asia additionally climate patterns were found to be the opposite of those in the east asian monsoon controlled region the temperature variations inferred from the records correlate well with changes in the solar irradiance and northern hemispheric temperature which suggests a possible link between solar forcing and climate variabilities over the last 2000 years on the southern tibetan plateau in addition the enhancement and southward shift of the westerlies is determined to have significantly contributed to the high moisture conditions on the southern tibetan plateau during the lia

late holocene variation of the raigorodskogo glacier and climate change in the pamir alai central asia during the late holocene the raigorodskogo glacier in the pamir alai central asia expanded before 3215 after 1545 and at 310 cal years bp as dated by the 14c calibrated ages of wood samples from moraine deposits and terrace exposures the glacier expansions which were accompanied by increased melt water run off over the terrace surface were confined to the proglacial area the terrace deposits with intercalated buried soil layers provide evidence of two obvious warm periods when the glacier abruptly retreated during the late holocene shortly before 1545 cal years bp and again sometime before ca 500 cal years bp fallen juniperus turkestanica broken by moraine deposits suggests that the largest glacial expansion during the little ice age occurred 310 cal years bp the glacier expansion in the little ice age was on roughly the same scale as that which occurred in the cold period after 1545 cal years bp observational records of the glacier terminus and moraine positions indicate that recent glacier advances occurred in the years 1908 1911 sometime in 1911 1934 and in 1960 1977 these advances were small while the glacier recessions were larger in the 1900s with large recessions also sometime in 1911 1934 and in 1977 1998 the glacier recession rate of 27 m year in 1911 1934 was faster than the rates of 13 m year in 1977 1990 and 21 m year in 1990 1998 however the glacier recession rate has been accelerating recently particularly after 1990 this recession reflects recent climate warming in inland asia

glacier surface motion pattern in the eastern part of west kunlun shan estimation using pixel tracking with palsar imagery mountain glacier is considered as one of the most sensitive natural indicators of climate change glacier surface motion distribution in west kunlun shan wks has been attracting considerable attention and represents a fundamental glacier parameter for better understanding glacier dynamics ice mass balance and even for the climate change this paper would present the accurate ice motion observation of mountain glacier in eastern part of wks by the refined pixel tracking method with phased array type l band synthetic aperture radar images acquired on december 13 2008 and january 28 2009 the standard deviation values in nonglacial area before after topographic effect compensation are 0 61 and 0 43 m respectively during 46 day temporal interval in addition the terrain almost is a determining factor of ice velocity distribution in study area because the elevation of topography is generally shown to be positive correlated with glacier surface velocity along the central line furthermore with estimated detailed glacier surface movement distribution pattern we found that the continental glaciers were actively moving with spatially variable ice motion while the icecaps maintain the stable status without apparent motion on most part of surface therefore the refined sar based pixel tracking method including topographic effect compensation operation provides a useful and robust tool to map and measure the glacier motion in mountain area with complex terrain

fractal geometry in the san andreas fault system it has been noted that the spatial distribution of earthquakes and the mode of strain release in the san andreas fault system is related to the complexity of fault geometry because of their rough appearance over many length scales faults can be regarded as fractal surfaces direct estimates of fractal dimension d of portions of the san andreas fault system between the northern gabilan range and the salton sea including the postulated extent of the great 1857 fort tejon earthquake are obtained from measured fault lengths analogous to the lengths of coastlines as discussed by mandelbrot regions characterized by complicated fault geometry are associated with larger values of d based on fault traces mapped at a scale of 1 750 000 d is 1 3 for this reach of the fault defined as a 30 km wide band about a main fault trace for that part near parkfield which could be associated with the nucleation of the 1857 earthquake d is 1 1 at this same scale d is 1 4 for the san andreas and related faults near san bernardino where the 1857 rupture stopped compared to 1 2 for the san andreas san juan fault segments near the point of arrest of the 1966 parkfield earthquake at finer map scales 1 24 000 and 1 62 500 critical lengths of 500 m and 1 km are identified which might relate to the extent of off san andreas fault offsets the critical lengths also suggest that fault geometry is not self similar if this fractal geometry persists through the seismic cycle it may be possible to use a quantitative measure of complexity to explain the occurrence of great and characteristic earthquakes along a given reach of fault

dating of an alpine ice core from the interior of the tibetan plateau abstract accurate archive based paleoclimate reconstruction requires precise dating however the dating of mid and low latitude alpine ice cores is in challenge in particular for the lower parts of ice cores here we present a new dating work for a 109 m ice core collected to bedrock from the qiangtang no 1 glacier central tibetan plateau annual layer counting based on seasonal indicators in combination with absolute dating of radioactivity peaks indicates that the upper part 0 79 m captures a period of 678 years from 1334 2011 ad with an uncertainty of 20 years at 79 m in the lower part 79 109 m we dated by visible annual layer thickness depth relationships and found the lower ice core captures 665 years of deposition and can be dated back to 669 66 ad at 109 m this new method reduces the ambiguity of utilizing glacier flow models that have been widely used in previous study on the presence of observable optical annual layers the polynomial fitting method based on annual layer thickness depth relationships is a superior method to obtain reliable chronology in the lower parts furthermore this method has the potential to improve the dating of other alpine ice cores with similar settings

wavelet analysis reveals periodic oscillations in a 1700 year ice core record from guliya china ice cores contribute important records of past climate changes as one of the thickest ice caps in central asia the guliya ice cap 35817 0 n 81829 0 e provides valuable information for this critical region about the past climate and environment changes we used wavelet analysis to examine periodic temperature and precipitation oscillations over the past 1700 years recorded in the guliya ice core the results show non linear oscillations in the ice core records with multiple timescales temperature records indicate persistent oscillations with periodicities of approximately 200 150 and 70 years precipitation records show significant periodicities at 200 100 150 and 60 years however the amplitude modulation and frequency vary with time wavelet analysis can explore these time series in greater detail and furnish additional useful information

climate of the last 500 years high resolution ice core records precipitation accumulating on the earth s ice sheets and ice caps records a variety of physical and chemical information about the atmosphere and in some cases provides unique insight to both the history and the mechanics of the earth s environmental system high resolution well dated dust records from both polar ice sheets suggest a linkage between increased atmospheric dust and cooler temperatures over antarctica but a similar relationship is not observed in ice cores from either greenland or china net accumulation histories for the last 490 years reveal no discemible global pattern although interesting regional differences and similarities exist excess non sea salt sulfate profiles provide

time marker of 137cs fallout maximum in lake sediments of northwest china abstract caesium 137 137cs has no natural source and is commonly employed in establishing the chronology of recent lake sediments in the anthropocene epoch because of their location in the northern mid latitude westerlies circulation region downwind of the chernobyl accident and their proximity to the lop nur chinese nuclear testing cnt site lake sediments in nw china record a137cs fallout maximum of global atmospheric thermonuclear weapon tests gtwt in 1963 1964 common era ce with probably local fallout subpeaks due to the chernobyl accident in 1986 ce and cnt in 1976 ce this complexity means that the use of 137cs fallout maximum in lake sediments as a time marker in nw china is thus far not well constrained impeding assessment of recent and future changes in paleoclimate and human activities to identify the 137cs time marker and provide a reliable chronology of surface lake sediments for investigating paleoclimatic changes and for defining the anthropocene epoch in nw china during the last 50 100 years here we describe chronologies of 6 near surface sediment cores from nw china based on 137cs and 210pb activities and review the chronology of 23 lake sediments and 10 ice cores from nw china and central asia based on 137cs 210pb 239 240pu 3h 241am and beta activity dating methods and annual layer counting as well as 240pu 239pu isotopic ratios based on the potential influence of radioactivity transport from the chernobyl accident and cnt and the comparison with deposition records of 26 european lake sediments and 5 alpine ice cores we propose that the 137cs fallout maximum of lake sediments in nw china and central asia is primarily attributable to gtwt and that there is no unambiguous evidence to confirm the chernobyl and cnt derived 137cs local fallout subpeaks taking into account the approximately one year delay between injection of 137cs into the atmosphere and its incorporation in lake sediment records we conclude that the 137cs fallout maximum in lake sediments of nw china provides a reliable gtwt time marker for 1964 ce

changes on ionic concentrations and delta o 18 in the snowpack of zhadang glacier nyainqentanglha mountain southern tibetan plateau to investigate the effects of depositional and post depositional processes on chemical records in the snowpack seven monthly snow pits were sampled at the same site on the pass of zhadang zd glacier 30828 079 0 n 90839 032 0 e 5800 m a s l nyainqentanglha mountain southern tibetan plateau between april and october 2006 meteorological data from an automatic weather station at the sampling site showed that the annual mean air temperature was 5 68c on the pass and that monthly air temperature was above 08c from june to august indicating that snowmelt could occur in this high elevation region during the summer an analysis of d 18 o and major ion variability in snow pits suggests that glaciochemical records were influenced by both meltwater percolation in mid summer july and august and seasonal deposition less negative d 18 o values and high concentrations of major ions occurred during the spring the trends of d 18 o variations in the zd snow pits were consistent with those in precipitation sampled at the nearby nam co station for all months except for july and august suggesting that climate signals are well preserved in the snow pit d 18 o records during the non summer months however these climate signals were destroyed by strong percolation of meltwater during mid summer

circular polarization radar properties of high altitude ice western kunlun shan and central andes full polarization synthetic aperture radar images of high altitude glaciers and ice fields in the western kunlun shan of tibet and the central andes near santiago chile made with the shuttle imaging radar display regions with circular polarization ratios c in excess of unity the mountainous topography at both locales allows reconstruction of the angular scattering behavior the behavior is very similar to that displayed by greenland s percolation zone glaciologic evidence from the tibetan site confirms ice pipes and lenses embedded in the firn which have been identified as the scatterers producing c 1 in greenland this demonstrates that the cold snow percolation facies radar signature exists outside of greenland the greenland radar behavior had been suggested as an analogue for that of the icy galilean satellites we like previous workers find that the near nadir backscatter is too specular to be considered analogous to that of the jovian moons we also present a crevasse region in tibet that exhibits c 1 and a possible detection of the ice substrate of a rock covered glacier in the andes

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago

palaeoenvironmental change and glacier fluctuations in the high tian shan mountains during the last millennium based on sediments from lake ala kol kyrgyzstan abstract a suite of limnological proxies measured in clastic sediments of the glacier fed lake ala kol ne kyrgyzstan document palaeoenvironmental change and glacier fluctuations in the central tian shan over the last millennium rock magnetic and geochemical data provide supporting evidence for three glacier expansion episodes occurring in 1200 1400 ce 1500 1850 ce and 1900 1950 ce and glacier retreat periods during 1000 1200 ce and the intervening periods the maximal glacier extent as inferred from high lf si inc coh ca inc coh and low arm30 arm is recorded between 1500 and 1850 ce and corresponds to cold and wet conditions during the little ice age in the high central tian shan periods of glacier waxing and waning recorded at lake ala kol present a close correspondence to ice accumulation rate in the northern tibetan plateau suggesting that precipitation changes are the main driver of glacier fluctuations in central tian shan during the last millennium although temperature may have exerted a more complex influence on centennial timescales

short term glacier velocity changes at west kunlun shan northwest tibet detected by synthetic aperture radar data abstract seasonal glacier velocity changes across the high arctic including the greenland ice sheet have been observed and have attracted significant attention over the past decade however it remains uncertain how much short term variability exists in other polythermal glaciers particularly those in high asia here we report satellite radar image analyses that reveal diverse glacier surface velocities and their evolution in west kunlun shan wks nw tibet where little is known about glacier dynamics on the basis of radar images obtained from 2003 to 2011 we examined 36 glaciers and classified them into two classes according to their multi temporal velocity profiles 25 as normal flow type surface velocity reaches maxima around the middle part and gradually approaches zero toward downstream and upstream and four as surging type surface velocities are greater than 150 m yr and or the terminus advance is recognized from the radar images seven other glaciers do not fit the former two classes and reveal stagnant velocity profiles that are nearly zero in the lower part but are similar to those of the normal type in the upper part although these glaciers could be just stagnant tongues indicative of receding normal type glaciers given the temporal evolution at the zhongfeng glacier the stagnant type possibly represents a quiescent phase of the surging type glaciers while glacier surfaces are mostly clean with limited debris cover except near the termini surge type glaciers might be common in wks the observed short term velocity changes provide us with evidence for efficient basal slip even at the high elevation polythermal glaciers this study demonstrates that frequent radar image acquisitions are helpful to understand short term velocity changes at remote glaciers in detail

oxygen isotopic and soluble ionic composition of a shallow firn core inilchek glacier central tien shan oxygen isotopic and soluble ionic measurements made on snow pit 2 m depth and firn core 12 4 m depth samples recovered from the accumulation zone 5100 m of inilchek glacier 43 n 79 e provide information on recent 1992 98 climatic and environmental conditions in the central tien shan region of central asia the combined 14 4 m snow pit firn core profile lies within the firn zone and contains only one observed melt feature 10 m temperature 12 c although some post depositional attenuation of the sub seasonal 18 o record is possible annual cycles are apparent throughout the isotope profile we therefore use the preserved 18 o record to establish a depth age scale for the core mean 18 o values for the entire core and for summer periods are consistent with 18 temperature observations and suggest the 18 o record provides a means to reconstruct past changes in summer surface temperature at the site major ion na k mg 2 ca 2 nh 4 cl no 3 so 4 2 data from the core demonstrate the dominant influence of dust deposition on the soluble chemistry at the site and indicate significant interannual variability in atmospheric dust loading during the 1990s anthropogenic impacts on nh 4 concentrations are observed at the site and suggest a summer increase in atmospheric nh 4 that may be related to regional agricultural nitrogen rich fertilizer use activities

application of pollen analysis to dating of ice cores from lower latitude glaciers 1 ice cores from temperate regions have long been expected to be useful for understanding local climate trends but a reliable dating method has proved difficult here we show that measurements of pollen using samples with only 10 ml of water can give an accurate measure of the annual ice accumulation in addition two major types of pollen allow us to estimate the summer ice accumulation as well as the annual accumulation

late holocene coupled moisture and temperature changes on the northern tibetan plateau the northern tibetan plateau involves complex interactions between the mid latitude westerly circulation and the subtropical asia monsoon circulation acting as a bridge communicating high and low latitude climatic processes previous studies from the region suggest relatively wet conditions in cold periods during the late holocene for instance the little ice age lia however the inference of such temperature moisture association is subject to the large uncertainty in lacustrine 14c chronology due to the particularly large lake reservoir effect in the region here we take a different approach by reconstructing paired temperature and moisture records from the same sediment cores to assess the temperature moisture association independent of chronology uncertainty we use alkenone indices uk 37 and c37 4 to reconstruct high resolution temperature and moisture changes simultaneously from two lakes in the qaidam basin northern tibetan plateau over the last 2500 years characterized by marked climatic variability our paired records confirm the warm dry and cold wet association in arid northwestern china during the late holocene opposite to the warm wet and cold dry association in subtropical asian monsoonal regions our moisture records further suggest substantially drier conditions during the medieval warm period mwp than the current warm period lastly the temperature and moisture changes inferred from our records can be well correlated with solar irradiance changes suggesting a possible link between solar forcing and natural climate variability during the late holocene on the northern tibetan plateau