palaeo moisture evolution in monsoonal central asia during the last 50 000 years abstract the late quaternary climate history of monsoonal central asia was inferred from 75 palaeoclimatic records which provide information about moisture conditions in the last 50 ka or part of this period wet conditions occurred during middle and late marine isotope stage 3 while the last glacial maximum lgm was characterized by dry climate conditions in the region a stepwise climate amelioration is suggested by the climate records following the lgm several climate signals of this period which were reported from high latitude ice core records are preserved in archives from monsoonal central asia as well during the early holocene high effective moisture was inferred from most records from the area dominated by the indian monsoon e g the tibetan plateau suggesting that holocene optimal climate conditions occurred there during this period in contrast areas which are dominated by the south east asian monsoon se monsoon and the westerlies in north western and north central china mongolia do not uniformly show an early holocene climate optimum for this area optimal conditions prevailed during the mid holocene these apparent contradictions can possibly be explained by the regional uplift and descent of air masses in the holocene during the early holocene strengthened insolation possibly caused an enhanced low level convergence over the tibetan plateau which led to the intensification of the summer monsoon the strong air uplift caused intensified precipitation and air divergence in the upper troposphere over the tibetan plateau the areas adjacent to the north therefore experienced an intensified descent of air masses and consequently increased aridity the majority of the palaeoclimatic records suggest reduced effective moisture since the late holocene in the region

early holocene climate recorded in geomorphological features in western tibet cosmic ray exposure ages for formation of perched alluvial terraces and for abandonment of an alluvial debrisflow fan on opposite sides of the tangtse valley the outflow at the northwest end of lake panggong which is in the karakorum range of western tibet provide evidence of a humid period at v11 5 to v7 ka this is consistent with other regional records and supports a controversial chronology for the sedimentary record from lake panggong fan abandonment appears to have occurred at v11 5 ka as the climate presumably became more humid in response to initiation of enhanced monsoonal circulation consistent with previously reported onset of humid conditions in a sedimentary record from the easternmost basin of the lake in contrast the terraces did not form until about 7 ka with downcutting of the transverse valley by overflow from lake panggong this lag can be explained in light of the bathymetry of lake panggong the modern lake consists of five basins separated by shallow sills and outflow through the tangtse valley could not occur until the water level was substantially above its present level the easternmost basin receives the inflow of the major rivers feeding the lake making its chemistry highly sensitive to changes in precipitation however sustained wet conditions are required to fill the basins to the west to the sill depth necessary for overflow through the tangtse valley and resultant downcutting and terrace formation 2003 elsevier b v all rights reserved

topography relief and trmm derived rainfall variations along the himalaya 1 along the southern himalayan topographic front the indian summer monsoon modulates erosive processes and rates to investigate the influence of topography and relief on rainfall generation and resultant erosion we processed satellite rainfall amounts for the last 8 years 1998 2005 from the tropical rainfall measurement mission trmm based upon a spatial resolution of 5 5 km for the himalaya we identify 1 the spatial distribution of rainfall and 2 the large scale relationships between topography relief and rainfall locations our results show two distinct rainfall maxima along strike in the himalaya the first outer rainfall peak occurs along the southern margin of the lesser himalaya within a narrow band of mean elevation 0 9 0 4 km and mean relief 1 2 0 2 km the second discontinuous inner band typically occurs along the southern flank of the greater himalaya elevation and relief both 2 1 0 3 km

precipitation at lake qinghai ne qinghai tibet plateau and its relation to asian summer monsoons on decadal interdecadal scales during the past 500 years knowledge of the variability of precipitation at lake qinghai and its relation to the asian summer monsoons is helpful in constraining global climatic dynamics based on the high resolution precipitation indicators of 13 c of the organic matter 13 corg c n atomic ratio and the detrended total organic carbon content tocdetrended we found that the trend of precipitation at lake qinghai is inversely correlated to that of the indian summer monsoon ism inferred from layer thickness of a stalagmite s3 in southern oman on decadal interdecadal scales the chinese drought flood d f indices which can indicate the dryness wetness over large geographic areas are also used to indicate the intensity of the monsoon rainfall the d f index of xining near lake qinghai is synchronous with those of the regions in northern china where the east asian summer monsoon easm dominates while it is anti phase with those of southwestern china where ism prevails these materials suggest that during the past 500 years the source of moisture to lake qinghai on decadal interdecadal scales is controlled mainly by the easm but not by the ism it is also suggested that the intensity of easm is inversely related to that of the ism on decadal interdecadal scales the decadal interdecadal variability of enso may be responsible for the inverse relationship between the intensity of easm and that of ism 2007 elsevier b v all rights reserved

a 13 000 year climate record from western tibet although the tibetan plateau is important in influencing the atmospheric circulation of the northern hemisphere1 3 there are only a few continuous palaeoclimate records available and these are limited to the plateau s northeastern margin4 6 here we present a 13 000 yr record from sumxi co western tibet constructed from both lake core and shoreline studies which shows that conditions in the early middle holocene were warmer and wetter than at present these results confirm model predictions of an intensified monsoon over the region at 9 000 yr bp owing to an orbitally induced increase in summer insolation7 8 we also find evidence for warm humid pulses at 12 500 and 10 000 yr bp in phase with the steps of the last deglaciation and for a return to cold dry conditions at 11 10 000 yr bp none of which can be explained by orbital variations the existence of the cold episode confirms that the cooling associated with the younger dry as event occurred in continental china6 9 and provides further evidence of the global nature of this event10

interpreting stable isotope records from freshwater snail shell carbonate a holocene case study from lake golhisar turkey the oxygen and carbon stable isotope ratios from fossil snail shells within a small intramontane lake in southwest turkey are used to highlight the potential and problems of using freshwater snail carbonate as a palaeoenvironmental proxy two species gyraulus piscinarum and valvata cristata yielded different isotope ratios at the same sampling intervals probably due to differences in water isotope composition between different microhabitats isotope ratios from a number of individual shells from the same sampling intervals representing 7 25 years show large ranges up to 8 for 18o for each species only by analysis of a significant number of species specific shells 5 from each sampling interval can a true understanding of environmental change be obtained averages of the data provide an insight into longer term climatic variation while the ranges provide an estimate of short term decadal environmental variability

δ18o in mollusk shells from pliocene lake hadar and modern ethiopian lakes implications for history of the ethiopian monsoon abstract two of the five lacustrine intervals in the largely fluvial hadar formation afar ethiopia occur in the sidi hakoma member deposited 3 4 3 2 ma in a perspective of the 18o of 11 modern ethiopian lakes and their shells the 18o of the hadar fossil shells provide a snapshot of the nature of ancient lake hadar and ethiopia s climate in the pliocene ethiopia s modern lakes both in the rift and on the western plateau are fed by drainage of plateau rain with its well established barely negative 18osmow of 1 3 except for the man made lake koka reservoir all other ethiopian lakes are isotopically quite positive ranging from 5 4 to 16 0 indicating how significant evaporation is in their water budget shells from lakes with extant mollusk populations are mostly in isotopic equilibrium with the 18o and temperature of their lake water the upper transgressive interval in the sidi hakoma member is the largest one in the formation beginning at its base with the gastropod beds beach deposits mollusks from shell beds other than the gastropod beds show more positive and more variable 18o between shells with internal variations within shells as much as 7 at these times the site must have been underlain by a shallow partially isolated embayment of lake hadar which underwent rapid expansions and then contractions by evaporation within the few year lifetimes of the individual mollusks the results from the gastropod beds are of most significance for interpreting the overall paleoclimate at hadar their uniformly negative 18opdb shell values that average 6 7 represent a much less evaporated stage of lake hadar when its 18osmow was 8 lower than the spectrum of modern lakes in ethiopia and indeed even 3 or more lower than average modern plateau rain to explain such negative values we hypothesize that the atlantic derived air mass component to the ethiopian monsoon was persistently strengthened during pliocene summers which intensified the amount and the negative isotopic character of rainfall onto both the afar and the ethiopian plateaus that drained to lake hadar a similar phenomenon characterized the brief periodic pluvial episodes of the quaternary including the latest in the early holocene known as the african humid period in contrast to the hot semi desert steppe conditions of today s western afar the diverse abundant terrestrial fossil fauna at hadar including the early hominid australopithecus afarensis is explained by the wetter and probably cooler summers that persisted throughout the late pliocene

syncollisional extension along the india asia suture zone south central tibet implications for crustal deformation of tibet abstract crustal deformation models of the tibetan plateau are assessed by investigating the nature of neogene deformation along the india asia suture zone through geologic mapping in south central tibet 84 30 e our mapping shows that the suture zone is dominated by a system of 3 to 4 ene striking south dipping thrust faults rather than strike slip faults as predicted by models calling upon eastward extrusion of the tibetan plateau faults along the suture zone are not active as they are cut by a system of nnw striking oblique slip normal faults referred to herein as the lopukangri fault system fault slip data from the lopukangri fault system shows that the mean slip direction of its hanging wall is n36w we estimate the net slip on the lopukangri fault by restoring components of the thrust system we estimate that the fault has accommodated 7 km of right slip and 8 km of normal dip slip yielding a net slip of 10 5 km and 6 km of horizontal east west extension the lopukangri fault system is active and geomorphic offsets indicate right separations and westside down dip separation the mapview curviplanar geometry and geomorphic expression of the lopukangri fault system is similar to faults and rift basins to its east and west these extensional faults are en echelon in map view and encompass a region that is 200 km long east west and 95 km wide north south assuming our results for the lopukangri fault are applicable to the entire system we estimate a maximum of 18 extension across the zone all active faults in the system terminate southward adjacent to the india asia suture zone because the individual rift geometries are similar and suggest a common kinematic relationship we propose that the extensional system formed as a trailing extensional imbricate fan at the southern termination of the central tibet conjugate fault zone alternatively the extensional system may terminate to the north and represent a group of isolated crustal tears both kinematic interpretations imply a semi smooth north south variation in the magnitude of east west extension in southern tibet with higher magnitudes in the north along the bangong nujiang suture zone than in the south along the india asia suture zone our results from southern tibet show that deformation between southern tibet and the himalayas is broad 95 km wide and best described as a continuum possibly since the late miocene conversely the structural boundary between western tibet and the himalayas which is defined by the karakoram fault is presently a discrete boundary and probably has been since the middle miocene we think this variation in the displacement gradient and age of these structural boundaries within the interior of tibet is best explained by the fault patterns and strain history describing wholesale e w stretching and n s shortening of the tibetan crust

correlation between the oxygen isotope record from dasuopu ice core and the asian southwest monsoon during the last millennium long high resolution proxy records are valuable for understanding asian southwest monsoon asm dynamics on decadal to centennial timescales a millennium long d 18 o ice core record from the central himalayas provides an opportunity to study the asm variability on decadal to centennial timescales the dasuopu ice core d 18 o record indicates that a relatively warm period corresponding with the medieval warm period lasted from ad 1140s to 1390s a notable warming trend is apparent from 1800s to 1990s and several cool periods occurred between ad 1010 1130s 1290 1330s 1400 1460s 1520s 1590 1630s 1740s and 1770 1790s comparisons with other high resolution monsoon proxy records from the arabian sea south oman and southern china reveal a high correspondence between temperature changes in the central himalayas and the asm variability during the last 1000 years a pronounced warming trend since ad 1670 coincides with an abrupt transition from a weak to a strong intensity of the asm the thermal conditions in the himalayas and on the tibetan plateau and associated glacial boundary conditions may have been predominantly responsible for variations of the asm intensity and for a latitudinal movement in the mean position of the itcz on decadal to centennial timescales r 2007 elsevier ltd all rights reserved

a framework for late quaternary lake level fluctuations in lake karakul eastern pamir focusing on lake glacier landform interaction abstract this paper presents a framework for late quaternary lake level fluctuation in the closed basin lake lake karakul eastern pamir on the basis of the stereoscopic observation of remote sensing data field mapping and relative dating the palaeoshorelines approximately 60 in number observed around the lake karakul can be classified into four groups h shorelines m shorelines l shorelines and ll shorelines in the descending order of height the highest level of each of the above palaeoshoreline groups is 205 m 85 m 35 m and 10 m above the present lake level 3915 m asl from the glacial landform developments and related valley fill sedimentation patterns around the threshold of the present basin closure the lake level fluctuation defined by these palaeoshoreline groups was found to be a consequence of the water balance change within the closed basin with respect to the timing of the palaeolake highstands the relationship between lacustrine terraces and terminal moraines suggests the synchroneity of the highest stand of each palaeolake with the corresponding maximum glacier advance the tentative chronology of the lake level fluctuation was established from the synthesis of the style of geomorphic development and related glaciation relative dating on moraine gravels and the correlations to established glacial histories in and around the pamir the periods of the palaeolake highstands indicated by h m l and ll shorelines seem to be correlated with the antepenultimate glacial mis 8 penultimate glacial mis 6 early last glacial mis 4 and the late last glacial mis 2 periods respectively based on this chronology each of the 60 palaeoshorelines are expected to show stable lake surfaces during lake regressive stages toward the terminations from the glacial maxima of mis 8 6 4 and 2 given that the distinct landforms of each palaeoshoreline group were formed in association with the predominant stagnation or small re transgression of the palaeolake the short term cooling and or wetter episodes which turned positive lake hydrologic balances from negative ones were superimposed on the major palaeoclimate changes during the glacial termination periods

palaeoclimate interpretation of stable isotope data from lake sediment archives the isotope composition of authigenic and biogenic carbonates and diatom silica are commonly used as palaeoclimate proxies from lake sediments this article reviews the controls on the isotope composition of lacustrine skeletal and non skeletal deposits and illustrates how stable isotope studies contribute to an understanding of changes in temperature precipitation patterns evaporation and the carbon cycle it highlights the differences in the palaeoclimate potential of a wide range of lakes ranging from open to closed lake basins a large number of the case histories but not all are drawn from studies of temperate lakes from europe large closed lake systems in the tropics and elsewhere lose water predominantly through evaporation and contain sediments with variable and generally high 18o values fluctuations in the isotope composition of authigenic or biogenic minerals are mainly a function of long term changes in the precipitation evaporation ratio in contrast small open lakes which have a degree of through flow typically contain sediments with 18o values that vary by no more than a few these variations are generally ascribed to variations in temperature or the isotope composition of precipitation p from which either an annual or seasonally specific signal can be gained these types of lakes are common in northern europe and at high altitudes the interpretation of isotope data from a lacustrine succession requires a knowledge of the local processes that might control and modify the signal their effects need to be quantified and a robust calibration using the modern lake system is necessary to establish the relationship between the measured signal the isotopic composition of the host waters and climate

permafrost on the tibet plateau china abstract the tibet plateau represents a unique permafrost environment being a result of high elevation caused by land uplift in the order of 3000 m over the last 2 million years under present climatic conditions the lower altitudinal limit of permafrost in the north is at 4200 m a s l which means that if the plateau were 1000 m lower than present there would be hardly any permafrost the permafrost is ice poor because during the quaternary the area was unglaciated and little water was available for the formation of massive ground ice furthermore today s climate is arid and little moisture is available for segregated and pore ice formation as a result mid portion desiccation of the active layer does not occur to the same extent as in high latitudes permafrost temperature on the plateau depends mainly upon altitude and varies irregularly with latitude permafrost is warm and thin compared with high latitude polar permafrost in both north america and russia and thus more sensitive to changes in climate and surface conditions a recent warming trend in ground temperature has been monitored and if maintained permafrost will become relict within the next ca 150 years permafrost features are few due to the arid environment many of the pingos on the plateau are genetically associated with faults and therefore of the open system type faults are the most powerful factor disturbing the thermal regime of the plateau permafrost

reduced early holocene moisture availability in the bayan har mountains northeastern tibetan plateau inferred from a multi proxy lake record abstract a late glacial and holocene lake sediment record from the northeastern tibetan plateau was investigated using ostracod and geochemical analysis after lake koucha was established about 16 cal ka bp oligohaline conditions gradually converted to mesohaline conditions about 10 cal ka bp clearly suggesting that the water body was a closed basin lake from about 10 cal ka bp the salinity of the lake rose continuously until hyperhaline levels were reached about 7 5 cal ka bp this increase in salinity was accompanied by a falling lake level extreme rainfall and flooding events in a generally dry climate hit the shallow saline lake around 8 5 cal ka bp causing a unique thin gravel containing layer within the continuous fine grained lake sediments the age control of our record does not allow us to correlate this event exactly to the widely recorded 8 2 cal ka bp event however the recovered sediments from lake koucha provide strong evidence that climate changes around 8 5 cal ka bp had significant environmental implications in northeastern tibet after about 7 3 cal ka bp the available moisture significantly increased causing a continuous salinity decline until the present day freshwater conditions of a through flow lake were established about 6 5 cal ka bp in lake koucha this major shift from a shallow saline to a deeper freshwater lake was probably accompanied by a fundamental change from a macrophyte dominated to a phytoplankton dominated lake a slight reduction in available moisture in comparison to the periods before and afterward was recorded between 4 3 and 2 0 cal ka bp in phase with numerous records from monsoonal asia the reconstructed overall change in moisture availability from dry conditions before about 7 3 cal ka bp to wetter conditions afterwards contradicts most palaeoclimate records from the tibetan plateau and its surroundings which show that wetter conditions in the early holocene were replaced by drier and probably cooler conditions in the mid and late holocene however in the semi arid region of lake koucha with a mean annual precipitation of about 500 mm the insolation driven strengthened monsoon in the early holocene may have resulted in a temperature rise and higher evaporation rates which outweighed the increase in precipitation and therefore led to significantly lower moisture availability our record provides further evidence for a regionally non uniform response of the available moisture evolution to the overall monsoonal signal in the holocene climate history of central asia

oxygen and carbon isotope patterns archived in shells of the aquatic gastropod radix hydrologic and climatic signals across the tibetan plateau in sub monthly resolution abstract the tibetan plateau tp including its surrounding mountain ranges represents the largest store of ice outside the polar regions it hosts numerous lakes as well as the head waters of major asian rivers on which billions of people depend and it is particularly sensitive to climate change the moisture transport to the tp is controlled by the indian and pacific monsoon and the westerlies understanding the evolution of the interaction of these circulation systems requires studies on climate archives in different spatial and temporal contexts the objective of this study is to learn more about the interannual variability of precipitation patterns across the tp and how different hydrologic systems react to different climatic factors aragonite shells of the aquatic gastropod radix which is widely distributed in the region may represent suitable archives for inferring hydrologic and climatic signals in particularly high resolution therefore sclerochronological studies of 18 o and 13 c ratios in radix shells from seven lakes were conducted each representing a different hydrologic and climatic setting on a transect from the pamirs across the tp the shell patterns exhibit an increasing influence of precipitation and a decreasing influence of evaporation on the isotope compositions from west to east 18 o values of shells from lakes on the eastern and central tp donggi cona yamdrok yumco tarab co mirror monsoon signals indicated by more negative values and higher variabilities compared to the more western lakes karakul bangong nyak manasarovar in yadang co located on the central southern tp the monsoon rains did not reach the lake in the sampling year although it is located in a region which is usually affected by monsoon circulation the 18 o values are used to differentiate the annual hydrological cycle into ice cover period melt water period precipitation period and evaporation period 13 c compositions in the shells particularly depend on specific habitats which vary in biological productivity and in carbon sources 18 o and 13 c patterns show a positive covariance in shells originating from large closed basins the results show that radix shells mirror general climatic differences between the seven lake regions these differences reflect both regional and local climate signals in sub seasonal resolution without noticeable dependence on the particular lake system

the variation of summer monsoon precipitation in central china since the last deglaciation abstract two stalagmites c996 1 and c996 2 collected from the jiuxian cave in the shaanxi province in central china have been studied with u series dating and stable isotope analysis thirty eight 230 th dating results showed that the stalagmite c996 1 was continuously deposited through the last 8 5 ka bp thousand years before present present 1950 ad and c996 2 was deposited through the last 19 ka bp excluding two growth hiatuses between 8 3 and 5 7 ka bp and 15 4 and 11 9 ka bp with a relatively stable boundary condition we interpret the 18 o of speleothem calcite as most indicative of the amount of summer monsoon precipitation although temperature and other factors might have some minor impact the 18 o records show notable changes within the last glacial maximum lgm resembling other east asian monsoon records such as those from the hulu and sanbao caves suggesting that significant monsoonal climate changes occurred in eastern asia as far north as the qinling mountains during the lgm interval a comparison of our records to precisely dated contemporaneous speleothem records from other caves shows that the increasing trend of 18 o during the holocene commenced as early as 7 5 ka bp in the low latitude monsoonal area i e the hoti cave while at higher latitudes this shift occurred later such as 7 0 ka bp in the dongge cave 5 3 ka bp in the heshang cave 4 7 ka bp in the sanbao cave and 4 5 ka bp in the jiuxian cave these results imply an asynchronous change of the summer monsoon precipitation occurred in east asia during the holocene the asynchrony may be related to the responses of a coupled tropical and subtropical monsoon system to changes of the insolation and the differences in thermal forcing which result from the complex geographical configuration the variation of sea surface temperature sst in the western tropical pacific may also have important impacts on the summer monsoon precipitation changes in central and northern china because it affects the northwestern pacific subtropical high a monsoon front regulator more robust tests are needed to confirm this phenomenon and to evaluate the contribution of different factors in detail

summer monsoon precipitation variations in central china over the past 750 years derived from a high resolution absolute dated stalagmite abstract a 2 3 year resolution record of stalagmite oxygen isotope variations from the south flank of the qinling mountains central china has revealed the asian summer monsoon asm precipitation variations in the investigated area over the past 750 years the summer monsoon precipitation gradually increased since 1249 ad reaching its highest values in the period 1535 1685 ad and then decreased with substantial decadal to centennial scale fluctuations the monsoon precipitation increased again between 1920 and 1970 ad three intervals of high monsoon precipitation were identified 1535 1685 ad 1755 1835 ad and 1920 1970 ad three intervals of low precipitation were inferred in 1249 1325 ad 1390 1420 ad and 1890 1915 ad the 18 o composition and lithological features of the stalagmite coincidently indicate a wetter climate during the little ice age lia which is also confirmed by climate records from chinese historical documents within this area a comparison with other high resolution speleothem records indicates regional differences in monsoon precipitation variability from the south to the north of central china in the last 750 years on decadal to centennial scale power spectrum analysis of the 18 o record shows significant 117 8 34 6 14 10 3 and 6 year periodicities these periodicities are widely observed in the climate records from asm controlled areas of china and are consistent with the gleissburg periodicity br ckner periodicity sunspot periodicity of solar activity and el nino southern oscillation enso periodicity these correlations suggest that both solar activity and enso periodicity may have had important influences on asm precipitation in china over the past 750 years

climatic significance of tree ring δ18o in the qilian mountains northwestern china and its relationship to atmospheric circulation patterns it is important to understand the history and dynamics of climate in a transitional region between areas with different atmospheric circulation patterns where the vegetation and ecosystems are vulnerable to environmental change we investigated variations in the long term oxygen isotope composition delta 18 o in tree rings of qinghai spruce picea crassifolia and their relationships to climatic parameters in the and qilian mountains of northwestern china from 1870 to 2006 we found that the mean temperature from the previous november to the current february was significantly and positively correlated with the tree ring delta 18 o values the temperature effect the positive relationship between the temperature and the precipitation delta 18 o value can explain the connection between temperature and the tree ring delta 18 o values due to pooling of the earlywood and latewood into yearly tree ring samples it appears that the cellulose delta 18 o may be influenced by isotopically nonhomogeneous water sources and climatic conditions during the previous and current growing seasons subtle shifts and amplitude deviations in cellulose delta 18 o which abruptly became more positive around 1977 1978 may be attributed to the shifting climatic regime in china and to temperature variations respectively our results illustrated the potential for investigating climatic or atmospheric circulation patterns based on oxygen isotope records in tree rings in regions near the interface between different large scale synoptic circulations c 2009 elsevier b v all rights reserved

δ13c δ18c covariance as a paleohydrological indicator for closed basin lakes the relationship between 18o and 13c in a closed basin lake is a function of hydrological change vapor exchange lake productivity and total co2 or carbonate alkalinity concentration covariance of 18o and 13c usually occurs in lake sediments under the condition of hydrological closure for time periods of the order of 5000 yr or longer on shorter time scales however certain subtleties in the use of the 13c 18o covariance as a hydrology history indicator must be recognized the covariant trend may not be found in hyper alkaline lakes because of the insensitivity of 13c to lake volume changes for less alkaline closed basin lakes covariance of 13c 18o will result from relatively rapid increase or decrease of lake volume with the rapid decrease condition giving rise to heavy and narrow ranged isotopic values for both 13c and 18o due to the coupled evaporation productivity effect when the lake volume remains stable as is the case for an over flowing open lake poor 13c 18o covariance will ensue due to the effect of vapor exchange with the atmosphere we have used the measured 13c 18o covariance in carbonate sediments of mono lake california to deduce paleo hydrological and lake water alkalinity and salinity variations and found the results in consonance with holocene lake level history derived from the 18o and other information

a lateglacial and holocene lake record from the nianbaoyeze mountains and inferences of lake glacier and climate evolution on the eastern tibetan plateau abstract our 12 81 m long record from lake ximencuo provides insight into the lateglacial and holocene evolution of the lake and the nianbaoyeze glacier in its catchment and the regional climate history since 19 kyr lake ximencuo was a permanent deep lake throughout its history in contrast to numerous lakes on the tibetan plateau which experienced shallow lake levels or even desiccation during the lateglacial lake ximencuo was fed by large quantities of meltwater in the lateglacial the existence of glaciated upper catchment areas is apparently a prerequisite for lakes on the tibetan plateau which maintained relatively high water levels during the generally cold and dry periods following the global lgm 21 kyr a minor re advance of the nianbaoyeze glacier was recorded coeval with the greenland stadial 2a 16 4 and 14 5 kyr followed by rapid warming apparently synchronous with the greenland interstadial 1 warmest conditions were recorded at lake ximencuo during the early holocene which was punctured by a remarkable pulse of climate deterioration around 8 3 kyr this spell represents probably the 8 2 kyr event of the north atlantic region suggesting that it had a significant impact on the tibetan plateau colder conditions of longer duration occurred from 4 7 to 3 7 kyr apparently in phase with numerous records signalling colder and drier conditions on the tibetan plateau two minor spells of colder conditions and probably catchment erosion were recorded in the late holocene between 2 0 and 1 4 kyr and between 0 5 and 0 1 kyr with the latter representing the little ice age it is unclear whether human activities may have accelerated or even solely triggered the late holocene erosion events

el escondido a newly identified silicic quaternary volcano in the ne region of the northern volcanic segment central cordillera of colombia abstract el escondido 1650 m a s l is a silicic quaternary volcano recently identified on the central cordillera of colombian andes it is located about 50 km ne from the northern segment of active volcanoes it has been recognized as a polygenetic pyroclastic dome ring complex structure whose eruptive products derived from a crater like semi circular depression of 1 7 km in diameter this crater formed at the contact of the granitic florencia stock 54 9 1 8 my with the paleozoic metamorphic basement and at the intersection of the nnessw trending palestina fault system with an ew trending fault the preserved volcano morphology and the volcanic succession associated with it were defined as the el escondido volcanic center the eruptive products are alternating silicic mostly dacitic pyroclastic density current deposits pumice fall deposits and ballistic projectiles which suggest high explosiveness two 14c radiogenic dates obtained on carbonized wood fragments of the middle part of the eruptive sequence displayed ages of 36 030 380 bp and 33 550 280 bp suggesting two major eruptive episodes of the volcano about 2500 years apart the latest eruptive activity is inferred to be the emplacement of lava domes to the south of the crater like structure which are responsible for the partial destruction of the pyroclastic ring in that sector the products emitted by el escondido correspond to medium k andesites to dacites of the calc alkaline series and petrographically to amphibolic andesites towards the western and eastern sector of the volcano there are chlorinated thermal waters with temperatures up to 45 c the first monitoring of the volcanic activity carried out by the colombian geological survey cgs through the volcanological and seismological observatory of manizales vsom has not detected so far unusual volcano seismic activity the previously unreported el escondido volcano represents one of the northernmost occurrence of quaternary volcanism in the whole andean cordillera thus its study may have wide implications regarding the geodynamics of the region and subduction zone the correct assessment of geologic hazards and the identification of natural resources like geothermal reservoirs and mineral deposits of economic interest

dominant control of the south asian monsoon by orographic insulation versus plateau heating heat emitted from the tibetan plateau as dry heat and water vapour has long been assumed to be the main driver of the south asian summer monsoon but new work suggests that in fact it is the neighbouring mountains that are the major influence william boos and zhiming kuang use an atmospheric model to show that flattening the tibetan plateau has little effect on the monsoon so long as the himalayas and surrounding mountain ranges remain the plateau does boost rainfall locally along its southern edge but it is the build up of hot moist air over india insulated from colder drier air by the himalayas that drives large scale monsoon circulation the elevation of the tibetan plateau is thought to cause its surface to serve as a heat source that drives the south asian summer monsoon potentially coupling uplift of the plateau to climate changes on geologic timescales here however an atmospheric model is used to show that flattening of the tibetan plateau has little effect on the monsoon provided that the narrow orography of the himalayas and adjacent mountain ranges is preserved the tibetan plateau like any landmass emits energy into the atmosphere in the form of dry heat and water vapour but its mean surface elevation is more than 5 km above sea level this elevation is widely held to cause the plateau to serve as a heat source that drives the south asian summer monsoon potentially coupling uplift of the plateau to climate changes on geologic timescales1 2 3 4 5 observations of the present climate however do not clearly establish the tibetan plateau as the dominant thermal forcing in the region peak upper tropospheric temperatures during boreal summer are located over continental india south of the plateau here we show that although tibetan plateau heating locally enhances rainfall along its southern edge in an atmospheric model the large scale south asian summer monsoon circulation is otherwise unaffected by removal of the plateau provided that the narrow orography of the himalayas and adjacent mountain ranges is preserved additional observational and model results suggest that these mountains produce a strong monsoon by insulating warm moist air over continental india from the cold and dry extratropics these results call for both a reinterpretation of how south asian climate may have responded to orographic uplift and a re evaluation of how this climate may respond to modified land surface and radiative forcings in coming decades

influences of subtropical jet and tibetan plateau on precipitation pattern in asia insights from regional climate modeling abstract large topographic features like the tibetan plateau tp and the rocky mountains have significant impacts on earth s climate numerical experiments were carried out using a regional climate model in order to study the sensitivity of rainfall distribution to the tp s thermal dynamic effects and meridional position of the subtropical westerly jet the sensitivity experiments under the present winter conditions characterized by weaker solar radiation and westerly jet located to the south of the tp reveal that broad arid climate characterizes northeast asia covering north china and mongolia the results are consistent with previous studies indicating that tp dynamic forcing is dominant in winter in sensitivity experiments under present summer conditions characterized by stronger solar radiation and the westerly jet located to the north of tp a prominent subsidence occurred over north china where the taklimakan and gobi deserts are located in summer dynamic forcing of tp is very weak whereas the thermal forcing of tp mainly induces subsidence relatively smaller mountain ranges such as the tianshan mountains also modify the atmospheric circulation even during the summer season the active convection zone along the baiu front which produces an elongate rain belt that extends from east china to korea and japan is near the boundary of two moisture sources transported by the westerly wind over the eurasian continent and by the asian summer monsoon flow the millennial scale variation in the location of the boundary reflects corresponding changes in east asian climate including monsoon intensity storm activity and the subtropical jet

sub seasonal oxygen and carbon isotope variations in shells of modern radix sp gastropoda from the tibetan plateau potential of a new archive for palaeoclimatic studies carbon and oxygen isotope ratios have been measured for nine aragonite shells of the gastropod genus radix from the lake bangda co 30 29 n 97 04 e 4450 m a s l at the south eastern edge and from two characteristic sites at the lake kyaring co 31 09 n 88 17 e 4650 m a s l on the central tibetan plateau radix shells were sampled for isotope ratio analysis with high spatial resolution along the ontogenetic spiral of growth providing the basis of isotope records with a sub seasonal time resolution 18o values of shells from bangda co are on average 15 0 relative to pdb and the pattern exhibits a clear onset and progression of the summer monsoon precipitation indicated by a strong amount effect this pattern mirrors the precipitation pattern in the respective year and region as expected for a small surface area ca 0 3 km2 and shallow 5 m lake or habitat with short water residence times and little evaporative 18o enrichment of the lake water in contrast 18o values of radix shells from kyaring co habitat a which is connected to the deep several tens of metres and big surface area ca 660 km2 lake average at 13 0 consistent with a higher evaporation rate and longer water residence time the latter is supported by more 18o enriched water in this habitat the 18o values of radix shells from kyaring co habitat b are nearly as low as shells from bangda co due to the similar habitat characteristic but isotopic patterns of these shells exhibit a weaker amount effect in both lake systems 13c values of the shells are coupled with oxygen isotopes because a large amount of isotopically light carbon is washed from mountain slopes into the lake during the rainy season although other processes influence the isotopic patterns e g biological productivity 13c or temperature 18o these influences are minor compared with the monsoon signal or the effect of evaporation in the radix shell records the overall weaker amount effect in radix shells from kyaring co habitat b compared with shells from bangda co are consistent with a current decreasing monsoon influence from the south eastern edge towards the central tibetan plateau thus fossil shells of the gastropod genus radix are a valuable archive for reconstructing climatic and environmental changes on the tibetan plateau and provide information about former habitat sizes and depths

holocene environmental changes in bangong co basin western tibet part 3 biogenic remains abstract a 12 4 m core collected from the eastern part of lake bangong provided a continuous holocene record this core was analyzed for diatoms ostracods charophytes content in total organic carbon and identification of organic particles contained in the sediments the record is remarkable for the abundance and diversity of its microorganisms an oligo to mesosaline marsh occupied the core site before 9 5 ka b p bangong was most likely closed a sudden filling of the lake basin by dilute nutrient poor water occurs around 9 4 ka b p maximum lake extent seems to have occurred around 9 4 8 7 ka b p generally freshwater relatively deep conditions were maintained up to 6 3 ka b p although interrupted by short term regressive events between 8 6 and 7 5 ka b p a trend towards palustral conditions begins after 6 3 ka b p and the interval 3 9 3 2 ka b p rich in detrital organic material coincides with an extremely low lake level a last lacustrine episode of minor amplitude is recorded from about 3 to 2 ka b p before the closure of the system leading again to slightly saline conditions the resemblances and synchronism between environmental changes recorded at bangong and in lake sumxi situated 200 km northwards and 800 m higher in elevation indicate that regional climatic changes have been the major driving factor on ecological and hydrobiological changes in lakes of western tibet

c and o isotope compositions of modern fresh water mollusc shells and river waters from the himalaya and ganga plain the aim of this paper is to unfold the relationship between the o and c isotope compositions of modern fresh water mollusc shells and water in order to refine the basis of interpretation for paleoenvironnemental reconstruction in the sub himalayan river basins large number of mollusc shells and associated host water from both running water and closed body of water were analysed including intra shell variability in a few cases the o isotopic compositions of river waters in the himalaya and ganga plain have a large range from 18 in the north of the high range up to 8 to 4 in the ganga plain 18o of rivers are also seasonally variable especially in foothills rivers whereas the seasonal contrast is smoothed out for the main himalayan rivers having large catchments o isotopic compositions of bulk shells aragonite vary between 15 and 5 average 18oara values are consistent with precipitation at equilibrium with host waters at a temperature range of 20 25 c suggesting that shell growth may be favoured during non monsoon conditions shells collected along the main himalayan rivers have 18o values uniformly distributed within 11 and 6 reflecting the minimal seasonal contrast shown by these rivers in contrast o isotopic compositions of shells from foothills rivers vary only by 4 this shows that depending on the type of river where the molluscs grow the information in term of 18o amplitude will be different for identical climatic conditions in closed or pond water bodies significant enrichment in 18o due to evaporation is observed the c isotopic compositions of river dissolved inorganic carbon dic decrease downstream from 0 to 10 reflecting input of soil derived alkalinity and plant productivity in the river 13c of shells are systematically lower than compositions calculated for equilibrium with river dic indicating that in addition to dic a significant fraction of carbon is derived from metabolic sources intra shell 13c are stable compared to the seasonal variability of dic suggesting that the pool of organic carbon changes throughout year

holocene environmental changes in lake bangong basin western tibet part 1 chronology and stable isotopes of carbonates of a holocene lacustrine core abstract a 12 4 m core collected from the eastern part of lake bangong is analyzed for mineralogy radiometric chronology and stable isotope contents of authigenic inorganic carbonate isotopic compositions of the modern lake waters and of its major tributaries are first presented radiocarbon activity of these waters show that equilibrium with the atmospheric co2 is not reached because of admixture of dead carbon in solution in the system a model is thus developed to correct the radiocarbon ages of fossil material of aquatic origin for this ageing the core provides a continuous holocene record changes in mineralogy of bulk sediments and in 13c and 18o contents of authigenic carbonates reveal extremely large changes in environmental conditions induced by climate changes and or local hydrological factors e g closure opening of the lake system controlled by the altitude of the outflow sill the eastern basin of lake bangong was closed before 9 6 and after 1 2 ka b p in response to aridity on the catchment wet warm conditions attributed to the monsoon influence were established suddenly at 9 6 ka b p and maintained until 6 2 ka b p although minor reversal events occurred between 8 6 and 7 7 ka b p the return towards aridity is non linear dry spells at 6 2 3 9 3 2 and 1 3 ka b p are alternated with short term periods with positive precipitation evaporation balance

carbon isotopes in surface sediment carbonates of modern lake qinghai qinghai tibet plateau implications for lake evolution in arid areas to further investigate the significance of carbon isotopes of lake carbonates in arid areas we examined the carbon isotopic composition of ostracods bulk carbonate fine grained carbonates and associated water dic dissolved inorganic carbon from lake qinghai and several small lakes and ponds surrounding lake qinghai we obtained three major results 1 the carbon isotopic compositions of ostracods bulk carbonate and fine grained carbonates in the lakes and ponds are clearly correlated with water 13cdic values which vary with water salinity in the lake qinghai area 2 the variation in the 13cdic values of lake water is mainly controlled by co2 exchanges between the atmosphere and lake waters in the lake qinghai area 3 ostracods bulk carbonate and fine grained carbonates show consistent trends of isotopic composition in the study area and the differences in carbon isotopic composition between authigenic carbonates and ostracods may be explained by the differences in carbon isotopic composition between the dic of surface water and that of the water near to the sediment water interface as well as the vital offsets of ostracods our results suggest that variations in the 13c values of carbonates in lake qinghai and other lakes in this arid high altitude area are primarily controlled by the carbon isotope ratios of the lake water dic which in turn are related to water salinity therefore changes in carbonate 13c values may be used to indirectly indicate changes in water salinity in the lake qinghai area

deriving century long trends of surface temperature change from borehole temperatures we have employed a few parameter estimation fpe technique to derive information on past surface temperature variations from present day borehole temperatures synthetic experiments show that the fpe technique can separate reasonably well information on century long trends of surface temperature change from borehole temperatures within a wide range of noise levels the technique also allows a simple illustration and comparison of the inversion results both spatially and temporally we illustrate this technique by analyzing seventeen borehole temperature profiles from eleven sites in northeast usa and southeast canada utilizing a ground surface temperature model of five ramps of century long duration

new insights on late quaternary asian palaeomonsoon variability and the timing of the last glacial maximum in southwestern china abstract a 6 35 m core 06sd was retrieved from lake shudu yunnan province china the sediments spanning the period 22 6 10 5 kcal yr bp 6 35 1 44 m were analysed using a combination of variables including pollen charcoal particle size magnetic susceptibility and loss on ignition the resulting palaeorecord provides a high resolution reconstruction of late pleistocene to early holocene climatic and environmental changes in southwestern china our findings indicate that from c 22 6 to 17 7 kcal yr bp vegetation assemblages were primarily aligned to sparse xerophytic grassland tundra or cold tolerant boreal pinus forest indicating that climatic conditions in southwestern china were cold and dry however from c 17 7 to 17 4 kcal yr bp the lake shudu record is punctuated by marked environmental changes these include the establishment of denser vegetation cover a marked expansion of boreal pinus forest and enhanced hydrological activity in the catchment over centennial timescales perhaps suggesting that stepwise variations in the asian monsoon were triggering fundamental environmental changes over sub millennial timescales thereafter the pollen record captures a period of environmental instability reflected in fluctuations across all of the variables which persists until c 17 1 kcal yr bp after c 17 1 kcal yr bp the expansion of steppe vegetation cover and cold cool mixed forest consisting of mesophilous vegetation such as tsuga and picea thermophilous trees including ulmus and deciduous quercus inferred from the lake shudu pollen record point to the establishment of warmer wetter and perhaps more seasonal conditions associated with a strengthening asian summer monsoon during the shift from pleistocene to holocene climatic conditions

holocene monsoon climate documented by oxygen and carbon isotopes from lake sediments and peat bogs in china a review and synthesis there has been much recent debate about holocene climate variation in the monsoon region of china especially the temporal pattern of variations in precipitation the time transgressive nature of the holocene precipitation maximum and the extent to which variations in regions influenced by the indian summer monsoon ism and the east asian summer monsoon easm have been synchronous we summarize and compare carbonate oxygen isotope records delta o 18 carb from ten lakes within the present day ism region we discuss their paleoclimate significance considering the present day moisture source isotopic composition of precipitation and the hydrological setting the delta o 18 carb records are controlled mainly by the isotopic composition of lake water which in turn is a function of regional precipitation evaporation p e balance and the proportion of precipitation that is monsoon derived we normalized the delta o 18 carb data and used these records to generate an integrated moisture index this index along with oxygen isotope records from speleothems and carbon isotope records delta c 13 org from peats within the monsoon region suggests that holocene climate was broadly synchronous across the monsoon region and within the limits of accuracy of the existing age models provides no strong evidence for previously proposed anti phasing of the ism and the easm stable isotope records from lake sediments and peat bogs have excellent potential for providing high quality paleoclimate data for monsoon asia and complement high resolution speleothem sequences which are only found in certain localities c 2011 elsevier ltd all rights reserved

asynchronous evolution of the indian and east asian summer monsoon indicated by holocene moisture patterns in monsoonal central asia abstract the numerical meta analysis of 92 proxy records 72 sites of moisture and or temperature change confirms earlier findings that the dominant trends of climatic evolution in monsoonal central asia since the last glacial roughly parallel changes in northern hemisphere summer insolation i e the period following the last glacial maximum was characterized by dry and cold conditions until 15 cal kyr bp followed by a warm wet period coincident with the bolling allerod warm period and terminated by a cold dry reversal during the younger dryas period after an abrupt increase at the start of the holocene warm and wet conditions prevailed until ca 4 cal kyr bp when moisture levels and temperatures started to decrease ordination of moisture records reveals strong spatial heterogeneity in moisture evolution during the last 10 cal kyr the indian summer monsoon ism areas northern india tibetan plateau and southwest china exhibit maximum wet conditions during the early holocene while many records from the area of the east asian summer monsoon indicate relatively dry conditions especially in north central china where the maximum moisture levels occurred during the mid holocene we assign such phenomena to strengthened hadley circulation centered over the tibetan plateau during the early holocene which resulted in subsidence in the east asian monsoonal regions leading to relatively dry conditions our observations of the asynchronous nature of the two asian monsoon subsystems on millennial time scales have also been observed on annual time scales as well as implied through the spatial analysis of vertical air motion patterns after strong ascending airflows over the tibetan plateau area that were calculated from ncep ncar reanalysis data for the last 30 years analogous with the early holocene the enhancement of the ism in a future warming world will result in an increase in the asynchronous nature of the monsoon subsystems this trend is already observed in the meteorological data from the last 15 years

palaeoenvironment and palaeoclimate of the middle miocene lake in the steinheim basin sw germany a reconstruction from c o and sr isotopes of fossil remains a differentiated reconstruction of palaeolimnologic environmental and climatic conditions is presented for the middle miocene long term freshwater lake 14 3 to 13 5 ma of the steinheim basin on the basis of a combined c o and sr isotope study of sympatric skeletal fossils of aquatic and terrestrial organisms from the lake sediments the oxygen isotope composition for lake water of the steinheim basin 18oh2o 2 0 0 4 vsmow n 6 was reconstructed from measurements of 18opo4 of aquatic turtle bones the drinking water calculated from the enamel of large mammals proboscideans rhinocerotids equids cervids suids has 18oh2o values 18oh2o 5 9 1 7 vsmow n 31 typical for middle miocene meteoric water of the area this 18oh2o value corresponds to a mean annual air temperature mat of 18 8 3 8 c calculated using a modern day 18oh2o mat relation hence large mammals did not use the lake water as principal drinking water in contrast small mammals especially the then abundant pika prolagus oeningensis drank from 18o enriched water sources 18oh2o 2 7 2 3 vsmow n 7 such as the lake water differences in sr and o isotopic compositions between large and small mammal teeth indicate different home ranges and drinking behaviour and support migration of some large mammals between the swabian alb plateau and the nearby molasse basin while small mammals ingested their food and water locally changes in the lake level water chemistry and temperature were inferred using isotopic compositions of ostracod and gastropod shells from a composite lake sediment profile calcitic ostracod valves ilyocypris binocularis 18o 1 7 1 2 vpdb 13c 0 5 0 9 vpdb n 68 and aragonitic gastropod shells gyraulus spp 18o 2 0 1 3 vpdb 13c 1 1 1 3 vpdb n 89 have 18o and 13c values similar to or even higher than those of marine carbonates 13c values of the biogenic carbonates parallel lake level fluctuations while 18o values scatter around 2 2 and reflect the short term variability of meteoric water inflow vs longer term evaporation 87sr 86sr ratios of aragonitic gyraulus spp gastropod shells parallel the lake level fluctuations reflecting variable inputs of groundwater and surface waters using a water 18oh2o value of 2 0 vsmow water temperatures calculated from skeletal tissue 18o values of ostracods are 16 7 5 0 c gastropods 20 6 5 6 c otoliths 21 8 1 4 c and fish teeth 17 0 2 7 c the calculated mat 19 c lake water temperatures 17 to 22 c and the 18o enriched water compositions are indicative of warm temperate climatic conditions possibly with a high humidity during this period vegetation in the area surrounding the basin was largely of the c3 type as indicated by carbon isotopic compositions of tooth enamel from large mammals 13c 11 1 1 1 vpdb n 40

characteristics of isotope in precipitation river water and lake water in the manasarovar basin of qinghai tibet plateau the stable hydrogen and oxygen of lake river rain and snow waters were investigated to understand the water cycle characteristics of the drainage basin of manasarovar lake in tibet both d and 18o of river water are larger than those of lake water and the effect of altitude on both d and 18o is not very significant this phenomenon was suggested to occur because manasarovar basin is located in qinghai tibet plateau which has low latitude high altitude abundant glaciers thin air and intensive solar radiation resulting in higher evaporation in lake water

modern hydrology and late holocene history of lake karakul eastern pamirs tajikistan a reconnaissance study abstract lake karakul in the pamirs tajikistan is a deep brackish water lake in a closed basin at almost 4000 m above sea level water samples from the catchment area and lake karakul and a 104 cm sediment core from its shallow eastern sub basin were investigated and provide a first lake record from the region spanning the last 4200 cal yr bp multi proxy analyses revealed the following a relatively high meltwater inflow from glaciers snow fields and frozen ground in the catchment as a result of relatively warm conditions was reconstructed for the period between 4200 and 3500 cal yr bp the shift to colder climatic conditions around 3500 cal yr bp was probably abrupt total organic carbon values displayed the most dramatic drop for the entire core within less than 40 years in contrast the subsequent re establishment of warmer conditions occurred gradually over several centuries a higher meltwater supply to the lake and warmer conditions were recorded since ca 1900 cal yr bp with two slightly colder intervals between 1200 and 800 cal yr bp and between 400 and 100 cal yr bp the abrupt shift to significantly colder and drier conditions around 3500 cal yr bp in the eastern pamirs is seen also in records from the aral sea and the guliya ice core from the western tibetan plateau however more palaeoclimate studies in this highly continental part of central asia are needed to assess the spatial and temporal patterns of the holocene climate in the region

oxygen and carbon isotope ratios in gastropod shells as indicators of paleoenvironments in the afar region of ethiopia abstract the oxygen and carbon isotope ratios in the shells of ancient freshwater gastropods coupled with geological geographical and hydrological data from their area and time of origin can yield information concerning general climatic conditions prevailing at the time the gastropod lived in addition sequential oxygen isotope analyses along the growth spiral of the shell provides indications of seasonal variability in the life span of the organisms such data were collected for some freshwater gastropods collected from two lakes and two springs in the afar region of ethiopia spanning late pleistocene to modern age episodes of high rainfall in the ethiopian highlands were clearly evident in the depleted 18o values in some shells whiel arid spells produced enriched levels in others hot springs introduced an added complication to the isotope record this study on a region of particularly complex hydrology and highly variable environmental history indicates the utility of stable isotope analyses as proxies for past climates but also emphasizes the problems involved

late holocene temperature fluctuations on the tibetan plateau abstract proxy data of palaeoclimate like ice cores tree rings and lake sediments document aspects of climate changes on the tibetan plateau during the last 2000 years the results show that the tibetan plateau experienced climatic episodes such as the warm intervals during ad 800 1100 and 1150 1400 the little ice age between ad 1400 and 1900 and an earlier cold period between the 4th and 6th centuries in addition temperatures varied from region to region across the plateau a warm period from ad 800 to 1100 in the northeastern tibetan plateau was contemporaneous with cooling in the southern tibetan plateau which experienced warming between ad 1150 and 1400 large scale trends in the temperature history from the northeastern tibetan plateau resemble those in eastern china more than the trends from the southern plateau the most notable similarities between the temperature variations of the tibetan plateau and eastern china are cold phases during ad 1100 1150 1500 1550 1650 1700 and 1800 1850

a holocene molluscan succession from floodplain sediments of the upper lena river lake baikal region siberia floodplainsediments of the upperlenariver near basovo in south central siberia have yielded the most detailed holocenemolluscansuccession yet reported from the entire eastern palaearctic over 72 500 shells from at least 28 species of terrestrial and 23 species of freshwater mollusc have been recovered an abundance and diversity far higher than previously reported from the region the molluscan assemblages are dominated by land snails especially members of the genus vallonia represented by five species including vallonia tenuilabris and two poorly known species vallonia kamtschatica and vallonia cf chinensis other noteworthy species recovered include gastrocopta theeli carychium pessimum vertigo extima southernmost record vertigo microsphaera and the first asian records of three other taxa vertigo geyeri vertigo genesii and vertigo parcedentata illustrations are provided for the critical species since opinions differ about the status of various taxa and the correct names that should be used the molluscan assemblages show clear successional trends during the early to mid holocene reflecting episodes of dryness wetness on the floodplain drier conditions at ca 6350 14c yr bp coincide with major changes in the archaeological record seen at other sites in the region but it remains unclear whether the two are linked a prominent charcoal rich horizon dated to ca 2800 14c yr bp marks a burning event in the catchment which resulted in a two fold increase in sediment accumulation rate remains of small mammals occurred throughout the sequence including a tooth of microtus cf maximowiczii possibly the first occurrence of ungar vole west of lakebaikal the faunal analyses have been integrated with a detailed pedological study of the sedimentary profile and a chronology was obtained by means of 12 ams radiocarbon dates this study provides the first detailed palaeoecological information relating to holocenemolluscan assemblages from the cis baikalregion and lays the foundation for future work in the eastern palaearctic

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

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

catastrophic partial drainage of pangong tso northern india and tibet abstract catastrophic partial drainage of pangong tso one of the largest lakes in tibet is supported by the geomorphology of the tangtse valley ladakh northern india and cosmogenic 10be nuclide ages of roche moutonnees strath terraces and a flood deposit downstream from the former spillway the former spillway for pangong tso is 20 m high and likely allowed 18 km3 of water to drain catastrophically down the tangtse valley over a period of about 2 days sometime during the latest pleistocene to early holocene the largest flood deposit composed of imbricated granitic boulders up to 4 5 m in length is present 33 km downvalley of the spillway these boulders have a cosmogenic 10be exposure age of 11 1 1 0 ka the age of the outburst flood the minimum calculated discharge was 110 000 m3 s 1 one set of strath terraces upvalley of the flood deposit along the flood s drainage path shows that the rate of fluvial incision 0 3 0 1 mm y 1 during 122 10 5 ka increased to 1 5 0 5 mm y 1 during 10 5 ka to the present the temporal overlap of this increase in the rate of fluvial incision with the main flood deposit suggests that the flood was important in defining the incision along the tangste valley a second set of strath terraces shows little change in incision from 0 6 0 9 to 0 9 1 4 mm y 1 sometime between 18 and 27 ka roche moutonnees upvalley from strath terraces yield a cosmogenic 10be age of 35 8 3 0 ka defining the time when glaciers last occupied the tangtse valley however the lack of glacial sediment along the tangste valley suggests that the flood eroded glacial depositional landforms and sediments resulting in high sediment loads in the floodwater which in turn increased fluvial incision to form strath terraces much of the eroded glacial sediment was subsequently redeposited as the main flood deposit the catastrophic drainage of pangong tso may be the result of breaching of the pangong tangste spillway during very high lake levels in a period of intensified monsoon 10 7 9 6 ka and or possibly the consequence of seismic activity along the karakoram fault that is associated with the initial formation of pangong tso

evolution and variability of the asian monsoon system state of the art and outstanding issues the asian monsoon is comprised of the indian and east asian subsystems these two components are linked to one another in varying degrees by regions of strong sensible heating indo asian landmass and strong latent heat export the western pacific warm pool and the southern subtropical indian ocean variability within the indian and east asian subsystems interactions among them and the extent to which they interact with other climate phenomena e g enso are current topics of modern and paleoclimate research this work provides an overview of past and current paleomonsoon research on tectonic to interannual time scales with a primary focus on marine sediment records while past and current work has contributed greatly to our understanding of paleomonsoon variability at all time scales additional efforts are required to make further progress in two critical areas 1 additional efforts are needed in terms of proxy development and evaluation requiring concerted efforts at long term sediment trap deployments in key monsoon influenced regions as well as development of adequate and widely available core top databases these are necessary to assess the impact of modern oceanographic and seafloor processes on potential monsoon proxies 2 additional effort is also needed in acquiring a sufficient geographic distribution of downcore records to assess linkages among the subsystems and their role in the context of extratropical climate change these records should have high sedimentation rates including varved sections this requires substantial survey support to identify the most appropriate coring and drilling targets c 2004 elsevier ltd all rights reserved

glacial interglacial indian summer monsoon dynamics the modern indian summer monsoon ism is characterized by exceptionally strong interhemispheric transport indicating the importance of both northern and southern hemisphere processes driving monsoon variability here we present a high resolution continental record from southwestern china that demonstrates the importance of interhemispheric forcing in driving ism variability at the glacial interglacial time scale as well interglacial ism maxima are dominated by an enhanced indian low associated with global ice volume minima in contrast the glacial ism reaches a minimum and actually begins to increase before global ice volume reaches a maximum we attribute this early strengthening to an increased cross equatorial pressure gradient derived from southern hemisphere high latitude cooling this mechanism explains much of the nonorbital scale variance in the pleistocene ism record