style and timing of glaciation in the lahul himalaya northern india a framework for reconstructing late quaternary palaeoclimatic change in the western himalayas

calibration of an ice core glaciochemical sea salt record with sea ice variability in the canadian arctic correlation between glaciochemical time series from an ice core collected on devon ice cap nunavut canada and gridded time series of sea ice concentrations reveals statistically significant inverse relationships between sea salt concentrations mainly na m g 2 and cl in the ice core and sea ice cover in baffin bay over the period 1980 97 an empirical orthogonal function eof analysis performed on all major ions shows that the dominant mode of glaciochemical variability eof1 represents a sea salt signal which correlates best with sea ice concentration in baffin bay on a seasonal basis the strongest and most spatially extensive anticorrelations are found in baffin bay during the fall followed by spring summer and winter these results support the notion that increased open water conditions in baffin bay during the stormy seasons fall and spring promote increased production transport and deposition of sea salt aerosols on devon ice cap comparison of ice core time series of eof1 d 18 o and melt percentage with air temperatures recorded in upernavik greenland suggests that ice cover variations in baffin bay over the past 145 years were dynamically rather than thermodynamically controlled with periods of strengthened cyclonic circulation leading to increased open water conditions and a greater sea salt flux on devon ice cap

effect of wind scouring on climatic records from ice core oxygen isotope profiles removal of winter snow by wind explains why the annual mean oxygen isotope ratio at an ice divide is 2 5 less negative than it is 1 2 km downslope cores from two sites on an ice cap ellesmere island canada show past variations in the difference depending on where the ice originated relative to the scoured zone some ice core climatic records may need correction for scouring

tectono climatic signatures during late quaternary in the yunam basin baralacha pass upper lahaul valley india derived from multi proxy records abstract this study provides evidence of the monsoon record over the past 25 ka from the kilang sarai palaeolake which is located in nw himalaya in the rain shadow zone of the indian summer monsoon ism the multi proxy study by using geomorphology carbon isotopes mineral magnetism clay mineralogy and elemental chemistry of a 8 m thick laminated lacustrine sediments indicates that the area experienced fluctuating precipitation conditions during the last 25 ka the time period between 12 and 5 ka bp can be regarded as a very wet interval of the last glacial to mid holocene due to a combined effect of ism and westerlies followed by aridity after 5 ka bp tectonic triggers may have caused the development of terraces and closure of lake at the millennial time scale a correlation of precipitation and vegetational changes between our data and other records from similar geographical settings suggests that kilang sarai basin responded to periods of strengthening in precipitation during the last glacial to early holocene

natural and anthropogenic levels of tritium in a canadian arctic ice core agassiz ice cap ellesmere island and comparison with other radionuclides

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

a record of holocene summer climate from a canadian high arctic ice core melt layers in ice cores are formed by melting on the snow pack surface which produces water that percolates down and refreezes in the colder snow layers below melt layers are distinguished by their bubble texture because more ice forms in the snow pack in warm summers than in cool summers the changing concentration with depth of melt layers in snow pits1 2 and ice cores3 5 is an indicator of past summer climate here we report on studies of melt layers in two canadian high arctic surface to bedrock ice cores although changes in elevation of the drill site owing to isostatic depression and uplift may contribute up to 40 of the total climatic signal recorded in the melt layers we interpret their varying concentrations in terms of changing summer temperatures over the past 10 000 years the warmest summers occurred 8 10 kyr ago and the coldest only 150 years ago the summers over the past 100 years have been the warmest for more than 1 000 years but are still not as warm as those of the early holocene the melt layer record is in broad agreement with geological records of glacier retreat during the holocene6 8 indicating that these data also contain information of regional significance

pollen and diatom inferred climatic and hydrological changes in sumxi co basin western tibet since 13 000 yr b p although the tibetan plateau greatly influences the atmospheric circulation of the nortbern hemisphere few continuous paleoclimatic records are available from the plateau a 13 000 yr pollen and diatom record from the sumxi longmu co basin in western tibet gives information on major changes both in regional vegetation and in local hydrology after the basin first filled ca 13 000 yr b p a dry spell occurred about 10 500 yr b p within the interval spanned by the european younger dryas chronozone a major environmental change occurred suddenly at 10 000 yr b p with the establishment of wet conditions and was followed by a long term trend toward maximum aridity which lasted approximately 6000 yr short term oscillations are superimposed on this general climatic change with a major reversal event about 8000 yr b p and a second wet pulse leading to a maximum lake volume ca 7500 6000 yr b p maximum aridity occurred 4300 yr b p the major environmental fluctuations recorded at sumxi longmu co appear in phase with climatic changes recognized in north tropical africa suggesting that the 8000 to 7000 yr b p event was caused by an abrupt disequilibrium in the climatic system as was the younger dryas and possibly the 4300 yr b p event

high resolution holocene environmental changes in the thar desert northwestern india sediments from lunkaransar dry lake in northwestern india reveal regional water table and lake level fluctuations over decades to centuries during the holocene that are attributed to changes in the southwestern indian monsoon rains the lake levels were very shallow and fluctuated often in the early holocene and then rose abruptly around 6300 carbon 14 years before the present 14c yr b p the lake completely desiccated around 4800 14c yr b p the end of this 1500 year wet period coincided with a period of intense dune destabilization the major harrapan indus civilization began and flourished in this region 1000 years after desiccation of the lake during arid climate and was not synchronous with the lacustral phase

monsoon reconstruction from radiocarbon dated tropical indian speleothems the potential of tropical speleothems as a climate proxy has been investigated amplitudes of 180 and 813c variations are found to be large and are likely to be primarily controlled by past rainfall contribution from past temperature variations seems to be relatively small the amount effect in rainfall has been observed and quantified by analysing rainwater samples collected during a monsoon season a tentative chronology to these speleothems is asssigned by the 14c radiometric dating method assuming that the variations in the 180 of cave carbonates are solely due to the past variations in rainfall a history of the latter has been reconstructed a high resolution rainfall reconstruction up to the last 3400 years is now available from gupteswar cave orissa subject to validation of dates by the u th method it is observed that in a tropical speleothem 513c is dominantly controlled by rainfall the study has shown that tropical indian speleothems faithfully record the annual monsoon rainfall in the

variability of southwest indian summer monsoon precipitation during the bolling allerod we have generated a high resolution 20 yr 2 3 0 th dated stalagmite oxygen isotope record from timta cave in the western himalaya in india that documents southwest indian summer monsoon ism precipitation variations during the bolling allerod interstadial from 15 2 to 11 7 ka compared with the glacial and younger dryas ism precipitation was enhanced during the bolling allerod ism precipitation was apparently coupled to variations in the east asian monsoon and north atlantic climate on millennial and multicentennial time scales during the deglaciation analyses of a high growth rate interval 2 5 yr resolution encompassing the late bolling early alterod suggest that multidecadal monsoon variability was an important aspect of ism behavior at that time the frequency spectrum of ism precipitation during this time interval is similar to that of the 1 4 c record and other ism precipitation records during the latest holocene this raises the hypothesis that multidecadal climate dynamics during the late boiling early allerod may have been similar to those that operated during the last several millennia even though the boundary conditions of these two time intervals were very different

holocene paleoclimates of india we present a comprehensive summary of the available palaeoclimate records from india and compare the results from different proxies the results indicate i fluctuating lake levels during the early holocene the period of relatively higher lake levels from increased precipitation efficiency was reached only 7 2 6 0 cal kyr bp possibly due to increased contribution from winter rainfall ii the onset of aridity in nw india could have begun as early as 5 3 cal kyr bp subsequently there were multiple wet events but of shorter duration and smaller magnitude than during the mid holocene iii there is evidence of several short term climate events in the proxy record however in the absence of a rigorous chronological framework a detailed regional correlation is not possible at this stage finally a comparison between marine and terrestrial records indicates that episodes of strongest and weakest monsoon winds were not always associated with wettest and driest episodes respectively in the nw indian lakes

oxygen isotopes in lacustrine carbonates of west china revisited implications for post glacial changes in summer monsoon circulation five lakes in the qinghai tibet plateau and north xinjiang have provided oxygen isotope records covering the past 17 11 cal kyr bp the modern lakes are first presented within the major atmospheric circulation and climate patterns of china with the climate related isotope composition of input water equations used to extract hydrological and climatic information from 18o in carbonates are then given after a discussion on potential causes for 18o changes each of the five isotope profiles is interpreted in the light of its specific environmental data the most significant event observed in all records occurred at 12 11 cal kyr bp an abrupt intensification of summer rainfall associated with an extremely rapid 1000 1500 km westward migration of the monsoon fronts the monsoon regime weakened in stages after 8 7 cal kyr bp holocene maximal aridity is recorded at all sites between about 4 5 and 3 5 cal kyr bp long term changes in monsoon strength as inferred from our isotopic interpretation are in good agreement with climate model reconstructions in the tibet qinghai plateau while observed hydrological changes in north xinjiang are not simulated by the models also the non linearity of the holocene monsoon variations cannot be accounted for by orbital forcing

late quaternary palaeoclimatic reconstruction from the lacustrine sediments of the sambhar playa core thar desert margin india the sambhar playa in rajasthan india located at the eastern fringe of the thar desert records multiple phases of clastic and evaporite dominated deposition as revealed from a 23 m deep core drilled in the center of the playa seven evaporite facies identified from the mineralogical data reflect variable brine chemistry throughout the history of the playa the complete absence of gypsum rich facies in the upper 5 m and dominance of carbonate and gypsum rich facies in the lower parts of the core reflect fluctuations in salinity level induced by climate change stable isotope data on carbonates d 18 o values correlate with the mgo mgo cao ratio geochemical ratios na al na ti na k and the evaporite mineralogy these data coupled with ams chronology of the organic fraction of the core sediments have been integrated to interpret evaporation inflow ratios which reflect humid and arid climatic conditions our data reconstruct the palaeoclimatic fluctuations in the thar desert margin for the last 30 ka and show significant spatial variation from the available lacustrine records from the thar desert the sambhar playa does not show any evidence of complete desiccation throughout its history although we record arid phases during the lgm and between ca 7500 and 6800 years d 2005 elsevier b v all rights reserved

the plio pleistocene geologic and climatic record of the kashmir valley india a review and new data abstract the kashmir valley located in the northwestern himalayas provides an intermontane valley fill comprising unconsolidated fluvio lacustrine sediments of more than a km thickness datable at 4 myr these sediments have been investigated for the last 7 years under an interdisciplinary multi agency project using a variety of proxy climatic data techniques and other analyses to decipher climatic change as a result of this study a variety of proxy climatic data from a long continental record is available now from northernmost south asia in this paper we briefly review the lithostratigraphic and chronologic framework of the sediment profile and proxy climatic data based on flora fauna stable isotopes pedology mineral magnetics and sedimentology lastly the climatic events are put in an absolute time frame for comparison with the global climatic trends the chronology is based on 14c thermoluminescence tl palaeomagnetic and fission track techniques

a review of palaeoclimates and palaeoenvironments in the levant and eastern mediterranean from 25 000 to 5000 years bp setting the environmental background for the evolution of human civilisation abstract the southern levant has a long history of human habitation and it has been previously suggested that climatic changes during the late pleistocene holocene stimulated changes in human behaviour and society in order to evaluate such linkages it is necessary to have a detailed understanding of the climate record we have conducted an extensive and up to date review of terrestrial and marine climatic conditions in the levant and eastern mediterranean during the last 25 000 years we firstly present data from general circulation models gcms simulating the climate for the last glacial maximum lgm and evaluate the output of the model by reference to geological climate proxy data we consider the types of climate data available from different environments and proxies and then present the spatial climatic picture for key climatic events this exercise suggests that the major northern hemisphere climatic fluctuations of the last 25 000 years are recorded in the eastern mediterranean and levantine region however this review also highlights problems and inadequacies with the existing data

vegetation and climate during the last 30 000 years in ladakh abstract pollen analysis was carried out from a 23 m core dating from about 30 000 to 9000 yr b p from the alpine tsokar lake about 4572 m above sea level in ladakh trans himalayan region this study reveals the continuation of the alpine steppe with four periods of expansion of juniperus communities during 28 000 30 000 yr b p 21 000 18 375 yr b p slightly before 15 800 yr b p and at 10 000 yr b p these phases of juniperus expansion were interpreted as events of amelioration of climate within the alpine steppe during the later part of the last weichselian glaciation in the alpine trans himalayan region

climatic and topographic controls on the style and timing of late quaternary glaciation throughout tibet and the himalaya defined by 10be cosmogenic radionuclide surface exposure dating abstract temporal and spatial changes in glacier cover throughout the late quaternary in tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region and the lack of numerical dating to help reconstruct the timing and extent of glaciation throughout tibet and the bordering mountains we use geomorphic mapping and 10 be cosmogenic radionuclide crn surface dating in study areas in southeastern gonga shan southern karola pass and central western nyainqentanggulha shan and tanggula shan tibet and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands each of the study regions receives its precipitation mainly during the south asian summer monsoon when it falls as snow at high altitudes gonga shan receives the most precipitation 2000 mm a 1 while near the margins of monsoon influence the karola pass receives moderate amounts of precipitation 500 600 mm a 1 and in the interior of the plateau little precipitation falls on the western nyainqentanggulha shan 300 mm a 1 and the tanggula shan 400 700 mm a 1 the higher precipitation values for the tanggula shan are due to strong orographic effects in each region at least three sets of moraines and associated landforms are preserved providing evidence for multiple glaciations the 10 be crn surface exposure dating shows that the formation of moraines in gonga shan occurred during the early mid holocene neoglacial and little ice age on the karola pass during the lateglacial early holocene and neoglacial in the nyainqentanggulha shan date during the early part of the last glacial cycle global last glacial maximum and lateglacial and on the tanggula shan during the penultimate glacial cycle and the early part of the last glacial cycle the oldest moraine succession in each of these regions varies from the early holocene gonga shan lateglacial karola pass early last glacial western nyainqentanggulha shan and penultimate glacial cycle tanggula shan we believe that the regional patterns and timing of glaciation reflect temporal and spatial variability in the south asian monsoon and in particular in regional precipitation gradients in zones of greater aridity the extent of glaciation has become increasingly restricted throughout the late quaternary leading to the preservation of old 100 ka glacial landforms in contrast in regions that are very strongly influenced by the monsoon 1600 mm a 1 the preservation potential of pre lateglacial moraine successions is generally extremely poor this is possibly because lateglacial and holocene glacial advances may have been more extensive than early glaciations and hence may have destroyed any landform or sedimentary evidence of earlier glaciations furthermore the intense denudation mainly by fluvial and mass movement processes which characterize these wetter environments results in rapid erosion and re sedimentation of glacial and associated landforms which also contributes to their poor preservation potential

signal and noise in four ice core records from the agassiz ice cap ellesmere island canada details of the last millennium for stable isotopes melt and solid conductivity four ice cores and two deep pit auger sequences from the top of the agassiz ice cap have been variously analysed for o18 ecm solid conductivity and ice melt layer stratigraphy the high resolution data are presented on time scales covering about the last 1000 years the 8 time series are compared and the noise examined in terms of snow drifting and wind scouring of winter snow from the higher exposed parts of flow lines the highly scoured 8 records reflect a mixture of summer biased conditions and the amount of winter scoured snow sites away from the ridges and domes are not scoured the signal part of the scoured and unscoured sites is obtained by stacking averaging normalized series the stacked unscoured series of 8 and accumulation are compared to similar stacked series from central greenland for the last century of annual averages the comparison is surprisingly good suggesting that at these resolutions low noise 8 series have some coherence over fairly large distances the percentage melt

timing and extent of late quaternary glaciation in the western himalaya constrained by 10be moraine dating in garhwal india glacial chronologies from the himalayan region indicate various degrees of asynchronous glacial behavior part of this has been related to different sensitivities of glaciers situated in contrasting climatic compartments of the orogen but so far field data in support for this hypothesis is lacking here we present a new 10 be derived glacial chronology for the upper tons valley in western garhwal india and initial results for the pin and thangi valleys in eastern himachal pradesh these areas cover a steep gradient in orographic precipitation and allow testing for different climatic sensitivities our data provide a record of five glacial episodes at w16 ka w11 12 ka w8 9 ka w5 ka and 1 ka in the thangi valley our results indicate a glacial episode at w19 ka but no data are available for younger glacial deposits in this valley at their largest mapped extent w16 ka the two main glaciers in the upper tons valley joined and descended down to w2500 m asl which represents a drop of w1400 m compared to the present day glacial extent during the holocene the two largest glaciers produced distinct glacial landforms that allowed us to reconstruct changes in the equilibrium line altitude ela over w20 km north south distance that is presently associated with a steep gradient in rainfall we observe that ela changes have been consistently w2 times higher for the glacier located in a presently wetter climate pointing at different climate sensitivities related to the amount of precipitation that they receive at regional scale our data is in reasonable agreement with other published glacial chronologies from the western himalaya and suggest that glacial advances during the holocene have been largely synchronous in this region comparison of glacial chronologies from the western himalaya with other palaeoclimatic proxy data suggests that long term changes in glacial extents are controlled by glacial interglacial temperature oscillations related to the waxing and waning of the large northern hemisphere ice sheets while the timing of millennial scale advance and retreat cycles are more directly related to monsoon strength

seasonal and spatial variations of snow chemistry on mount logan yukon canada three ice cores were recovered on or near mount logan yukon canada at 3017 4135 and 5340 ma s l in 2002 prior to ice core drilling we collected snow pit and shallow core samples from mount logan in 2001 to study seasonal and spatial variations of snow chemistry we dug snow pits at six sites between 2420 and 5340 m a s l before the beginning of the melt season with the exception of a pit at 3180 m a s l where the melt season had just started but had affected only the near surface stratigraphy three of the pits were extended deeper with a shallow core the snow pit and core samples were analyzed for ion chemistry and 18 o a series of depth profiles of ions and 18 o shows spatial variations though characteristic peaks can usually be traced across all the profiles concentrations and deposition fluxes of na and cl which are mainly of sea salt origin decrease with altitude on the other hand deposition fluxes of no 3 so 4 2 ca 2 and nh 4 show a weak positive relationship with elevation below the summit plateau stable isotopes 18 o decrease with altitude with a distinctive jump between 3200 and 4500 m a s l as was reported previously stable isotopes 18 o cl ch 3 so 3 msa na and ca 2 show clear seasonal variations which would enable us to date the cores by annual layer counting

analysis of vegetation and climate change during late pleistocene from ziro valley arunachal pradesh eastern himalaya region abstract vegetation and climate during later part of late pleistocene have been reconstructed from ziro valley arunachal pradesh eastern himalaya based on pollen data along with carbon isotope and magnetic susceptibility data the study reveals that the area and the vicinity is occupied by mixed broad leaved conifer forest and pine grass savanah at variable densities at least since 66 000yr bp the phases of expansions and declines of oaks with decline and increase of pines and grasses probably occurred under increase warm moist and decrease cool dry of s w monsoon precipitation respectively the increasing trend of s w monsoon and temperature is recorded during 44 000 to 34 000 cal yr bp synchronizing with the peat development and which peaked at around 35 000 cal yr bp this may link to the interstadial phase during the last major glacial cycle in the himalayan region it is also reflected in the decline of 13c value indicating dominance of c 3 type of vegetation the increased values of fd and lower values lf magnetic susceptibility recorded during the phase of the peat deposit further advocate s higher monsoon intensity impact of expansion of glacier felt with peak lgm around 20 000 cal yr bp is perceived tree line had moved to lower altitudes due to increased aridity and low temperature during this time existence of savannah type of vegetation is also evident by the increase of c4 taxa decreased fd and increased lf susceptibility also indicate reduced s w monsoon intensity

hydrological evolution during the last 15 kyr in the tso kar lake basin ladakh india derived from geomorphological sedimentological and palynological records abstract the tso kar lake basin in ladakh northwestern himalayas 33 18 n 78 e 4527 m a s l is located close to the modern boundary of effective moisture transport from the indian summer monsoon in order to reconstruct the possible monsoonal impact on the hydrology of the lake basin during the last 15 kyr we studied the geomorphology of the basin and combined the results with multi proxy records from tso kar lake sediments major analyses comprise geochemical data high resolution x ray fluorescence xrf mineral composition xrd aquatic pollen and non pollen palynomorphs npp although the chronological framework based on 41 14c ams dates remains speculative for the lateglacial and late holocene periods our results indicate major hydrological phases linked to regional climate variations and tectonic activity the maximum glacier advance falls within the period between the global lgm and ca 15 kyr bp while the basin remained open and may have drained along the paleo tso kar river tectonic pulses may have triggered terrace development and the closure of the lake the estimated mean vertical displacement rate accounts for 7 9 mm yr considerable summer monsoon moisture supply occurred for the periods around 12 5 kyr bp and between ca 11 5 and 8 6 kyr bp indicated by deposition of more profundal lake facies and the development of aquatic fauna and flora the lake level rise about 11 8 kyr bp was due to intensified glacier melt and summer monsoon effective moisture supply the lake reached its maximum level and extent between 8 5 and 7 kyr bp under warm moist climate conditions permafrost was absent from the basin summer monsoon influence weakened after 8 kyr bp with a short reverse trend at ca 5 6 kyr bp the lake shrank gradually after 7 kyr bp towards its lowest stand at about 4 2 kyr bp with return of permafrost activity subsequent terrace formation was probably amplified by tectonic movement the lake remained at a low level with minor fluctuations the results indicate that the orbitally driven regional climate variability is well reflected in the tso kar basin by hydrological variations considerable summer monsoon moisture seems to have influenced the area only during the early holocene the late quaternary evolution of the tso kar was controlled by the interplay of climate forces local morphodynamics and tectonic impact

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

holocene itcz and indian monsoon dynamics recorded in stalagmites from oman and yemen socotra abstract high resolution oxygen isotope 18o profiles of holocene stalagmites from four caves in northern and southern oman and yemen socotra provide detailed information on fluctuations in precipitation along a latitudinal transect from 12 n to 23 n 18o values reflect the amount of precipitation which is primarily controlled by the mean latitudinal position of the itcz and dynamics of the indian summer monsoon ism during the early holocene rapidly decreasing 18o values indicate a rapid northward displacement in the mean latitudinal position of the summer itcz and the associated ism rainfall belt with decadal to centennial scale changes in monsoon precipitation correlating well with high latitude temperature variations recorded in greenland ice cores during the middle to late holocene the summer itcz continuously migrated southward and monsoon precipitation decreased gradually in response to decreasing solar insolation a trend which is also recorded in other monsoon records from the indian and east asian monsoon domains importantly there is no evidence for an abrupt middle holocene weakening in monsoon precipitation although abrupt monsoon events are apparent in all monsoon records they are short lived and clearly superimposed on the long term trend of decreasing monsoon precipitation for the late holocene there is an anti correlation between ism precipitation in oman and inter monsoon spring autumn precipitation on socotra revealing a possible long term change in the duration of the summer monsoon season since at least 4 5 ka bp together with the progressive shortening of the ism season gradual southward retreat of the mean summer itcz and weakening of the ism the total amount of precipitation decreased in those areas located at the northern fringe of the indian and asian monsoon domains but increased in areas closer to the equator

seasonal variations of snow chemistry at neem greenland we conducted a pit study in july 2009 at the neem north greenland eemian ice drilling deep ice coring site in northwest greenland to examine the seasonal variations of snow chemistry and characteristics of the drill site we collected snow firn samples from the wall of a 2 m deep pit at intervals of 0 03 m and analyzed them for electric conductivity ph cl no3 so 4 2 ch 3 so 3 msa na k mg 2 ca 2 and stable isotopes of water 18 o and d pronounced seasonal variations in the stable isotopes of water were observed which indicated that the snow had accumulated regularly during the past 4 years concentrations of na cl and mg 2 which largely originate from sea salt peaked in winter to early spring while ca 2 which mainly originates from mineral dust peaked in late winter to spring slightly later than na cl and mg 2 concentrations of no 3 showed double peaks one in summer and the other in winter to spring whereas those of so 4 2 peaked in winter to spring the winter to spring concentrations of no 3 and so 4 2 seem to have been strongly influenced by anthropogenic inputs concentrations of msa showed double peaks one in spring and the other in late summer to autumn our study confirms that the neem deep ice core can be absolutely dated to a certain depth by counting annual layers using the seasonal variations of stable isotopes of water and those of ions we calculated the annual surface mass balance for the years 2006 08 the mean annual balance was 176 mm w e and the balances for winter to summer and summer to winter halves of the year were 98 and 78 mm respectively snow deposition during the winter to summer half of the year was greater than that during the summer to winter half by 10 20 mm for all three years covered by this study

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

timings and causes of glacial advances across the pep ii transect east asia to antarctica during the last glaciation cycle a comparison of glacial advances through the last glacial cycle between northern and southern hemispheres in the pep 2 transect east asia and australasia revealed 1 a relatively good synchrony of glacial advances during the lgm across the whole transect except antarctica 2 a rough synchrony in glacial advances in the karakorums himalayas japan and new zealand during marine isotope stages mis 3 and 4 although the age control is still poor and 1 a greater glacial extent in mis 3 and 4 than in mis 2 the lgm advances are driven by northern hemisphere temperature forcing but the mis 3 and or mis 4 advances appear to be dominantly controlled by the effects of moisture availability or lack of thereof in mainland australia and antarctica glaciers advanced only in the most humid phases in himalaya and karakorum where the moisture is supplied both by a summer monsoon and the westerlies timings of glacier advance coincide with both summer monsoon enhancement and westerly intensification in japan the glacier extent is controlled by monsoon changes sea surface temperatures ssts in the japan sea moisture source and by zonal shifts in westerly circulation in new zealand either insolalion changes or changes in the intensity of westerly circulation are invoked lis the main track of the westerlies did not change greatly during glacial times c 2003 elsevier ltd and inqua all rights reserved

holocene climate and cultural evolution in late prehistoric early historic west asia abstract the precipitation climatology and the underlying climate mechanisms of the eastern mediterranean west asia and the indian subcontinent are reviewed with emphasis on upper and middle tropospheric flow in the subtropics and its steering of precipitation holocene climate change of the region is summarized from proxy records the indian monsoon weakened during the holocene over its northernmost region the ganges and indus catchments and the western arabian sea southern regions the indian peninsula do not show a reduction but an increase of summer monsoon rain across the holocene the long term trend towards drier conditions in the eastern mediterranean can be linked to a regionally complex monsoon evolution abrupt climate change events such as the widespread droughts around 8200 5200 and 4200 cal yr bp are suggested to be the result of altered subtropical upper level flow over the eastern mediterranean and asia the abrupt climate change events of the holocene radically altered precipitation fundamental for cereal agriculture across the expanse of late prehistoric early historic cultures known from the archaeological record in these regions social adaptations to reduced agro production in both dry farming and irrigation agriculture regions are visible in the archaeological record during each abrupt climate change event in west asia chronological refinement in both the paleoclimate and archaeological records and transfer functions for both precipitation and agro production are needed to understand precisely the evident causal linkages

the southwest indian monsoon over the last 18 000 years previously published results suggest that the strength of the sw indian monsoon can vary significantly on century to millenium time scales an observation that has important implications for assessments of future climate and hydrologic change over densely populated portions of asia we present new well dated multi proxy records of past monsoon variation from three separate arabian sea sediment cores that span the last glacial maximum to late holocene to a large extent these records confirm earlier published suggestions that the monsoon strengthened in a series of abrupt events over the last deglaciation however our data provide a somewhat refined picture of when these events took place and suggest the primacy of two abrupt increases in monsoon intensity one between 13 and 12 5 ka and the other between 10 and 9 5 ka this conclusion is supported by the comparisons between our new marine data and published paleoclimatic records throughout the african asian monsoon region the comparison of data sets further supports the assertion that maximum monsoon intensity lagged peak insolation forcing by about 3000 years and extended from about 9 5 to 5 5 ka the episodes of rapid monsoon intensification coincided with major shifts in north atlantic european surface temperatures and ice sheet extent this coincidence coupled with new climate model experiments suggests that the large land sea thermal gradient needed to drive strong monsoons developed only after glacial conditions upstream of and on the tibetan plateau receded cold north atlantic sea surface temperatures european ice sheets and extensive asian snow cover it is likely that abrupt changes in seasonal soil hydrology were as important to past monsoon forcing as were abrupt snow related changes in regional albedo our analysis suggests that the monsoon responded more linearly to insolation forcing after the disappearance of glacial boundary conditions decreasing gradually after about 6 ka our data also support the possibility that significant century scale decreases in monsoon intensity took place during the early to mid holocene period of enhanced monsoon strength further highlighting the need to understand paleomonsoon dynamics before accurate assessments of future monsoon strength can be made

late glacial and holocene vegetation indian monsoon and westerly circulation in the trans himalaya recorded in the lacustrine pollen sequence from tso kar ladakh nw india abstract palynological investigation of a 410 cm long core section from tso kar 33 10 n 78 00 e 4527 m a s l an alpine lake situated in the arid ladakh area of nw india at the limit of the present day indian summer monsoon was performed in order to reconstruct post glacial regional vegetation and climate dynamics the area was covered with alpine desert vegetation from ca 15 2 to 14 kyr bp 1 kyr 1000 cal years reflecting dry and cold conditions high influx values of long distance transported pinus sylvestris type pollen suggest prevailing air flow from the west and northwest the spread of alpine meadow communities and local aquatic vegetation is a weak sign of climate amelioration after ca 14 kyr bp pollen data e g influx values of pinus roxburghii type and quercus suggest that this was due to a strengthening of the summer monsoon and the reduced activity of westerly winds the further spread of artemisia and species rich meadows occurred in response to improved moisture conditions between ca 12 9 and 12 5 kyr bp the subsequent change towards drier desert steppe vegetation likely indicates more frequent westerly disturbances and associated snowfalls which favoured the persistence of alpine meadows on edaphically moist sites the spread of chenopodiaceae dominated vegetation associated with an extremely weak monsoon occurred at ca 12 2 11 8 kyr bp during the younger dryas interstadial a major increase in humidity is inferred from the development of artemisia dominated steppe and wet alpine meadows with gentianaceae after the late glacial early holocene transition in response to the strengthening of the summer monsoon monsoonal influence reached maximum activity in the tso kar region between ca 10 9 and 9 2 kyr bp the subsequent development of the alpine meadow steppe and desert steppe vegetation points to a moderate reduction in the moisture supply which can be linked to the weaker summer monsoon and the accompanying enhancement of the winter westerly flow from ca 9 2 to 4 8 kyr bp the highest water levels of tso kar around 8 kyr bp probably reflect combined effect of both monsoonal and westerly influence in the region an abrupt shift towards aridity in the tso kar region occurred after ca 4 8 kyr bp as evidenced by an expansion of chenopodiaceae dominated desert steppe low pollen influx values registered ca 2 8 1 3 kyr bp suggest scarce vegetation cover and unfavourable growing conditions likely associated with a further weakening of the indian monsoon

lacustrine sedimentation in a semiarid alpine setting an example from ladakh northwestern himalaya abstract the lamayuru lacustrine strata in ladakh typify many of the carbonate rich pleistocene alpine lakes found in the semiarid environment of the northern himalaya created by a 200 m thick landslide the lake was in existence by at least 35 000 yr ago and may have persisted until 500 1000 yr ago represented in the center by thin turbidites and laminated muds the lacustrine sedimentation along the lake margins and low relief deltas characteristically displays a marked contrast between 1 clastic lenses representing rapid sporadic matrix poor debris flows and periglacial inputs from the alpine slopes and 2 abundant diverse shallow water biologically dominated carbonate strata among which organism rich chalky beds and oncolithic and encrusted stem rich strata predominate resemblances of the lamayuru lacustrine strata and their setting to those of former lakes throughout areas north of the greater himalayan crest suggest that the alpine semi arid environment would favor diversified spacially restricted carbonate sedimentation punctuated by occasional clastic influxes such a depositional regime contrasts strongly with that found immediately south of the himalayan crest where more humid conditions promote a more continuous clastic influx into intramontane lakes

late quaternary lake level record from northern eurasia lake records from northern eurasia show regionally coherent patterns of changes during the late quaternary lakes peripheral to the scandinavian ice sheet were lower than those today but lakes in the mediterranean zone were high at the glacial maximum reflecting the dominance of glacial anticyclonic conditions in northern europe and a southward shift of the westerlies the influence of the glacial anticyclonic circulation attenuated through the late glacial period and the westerlies gradually shifted northward such that drier conditions south of the ice sheet were confined to a progressively narrower zone and the mediterranean became drier the early holocene shows a gradual shift to conditions wetter than present in central asia associated with the expanded asian monsoon and in the mediterranean in response to local monsoon type circulation there is no evidence of mid continental aridity in northern eurasia during the mid holocene in contrast the circum baltic region was drier reflecting the increased incidence of blocking anticyclones centered on scandinavia in summer there is a gradual transition to modern conditions after ca 5000 yr b p although these broad scale patterns are interrupted by shorter term fluctuations the long term trends in lake behavior show a clear response to changes in insolation and glaciation

asynchronous glaciation at nanga parbat northwestern himalaya mountains pakistan we present a new glacial chronology demonstrating asynchroneity between advances of himalayan glaciers and northern hemisphere ice sheet volumes glaciers at nanga parbat expanded during the early to middle holocene ca 9 0 5 5 ka no major advances at nanga parbat during the last global glacial stage of marine oxygen isotope stage 2 mis 2 between 24 and 11 ka were identified preliminary evidence also indicates advances between ca 60 and 30 ka these periods of high ice volume coincide with warm wet regional climates dominated by a strong southwest asian summer monsoon the general lack of deposits dating from mis 2 suggests that nanga parbat was too arid to support expanded ice during this period of low monsoon intensity advances during warm wet periods are possible for the high altitude summer accumulation glaciers typical of the himalayas and explain asynchronous behavior however the holocene advances at nanga parbat appear to have been forced by an abrupt drop in temperature ca 8 4 8 0 ka and an increase in winter precipitation ca 7 5 5 ka these results highlight the overall sensitivity of himalayan glaciation to orbital forcing of monsoon intensity and on millennial or shorter time scales to changes in north atlantic circulation

seasonal and spatial variations in the chemistry of a high arctic supraglacial snow cover this paper describes the physical and chemical properties of the snowpack on john evans glacier ellesmere island canadian arctic archipelago and investigates the controls on snowpack solute concentrations and atmospheric deposition the snowpack contains three layers that are traceable across the whole glacier these represent fall accumulation that has been metamorphosed to depth hoar winter accumulation mixed with snow reworked by wind from the underlying depth hoar and spring accumulation mixed with wind reworked snow the seasonal cycle in snow chemistry closely reflects changes in the composition of the atmospheric aerosol at alert with some modification of no 3 concentrations by post depositional processes mean water weighted solute concentrations in the snowpack are largely independent of accumulation while atmospheric deposition tends to increase with accumulation this suggests that for most species wet deposition is the dominant depositional process throughout the year however concentrations of ca 2 and k increase with both accumulation and elevation implying an enhanced input from dry deposition of soil dust above 800 m elevation concentrations of so 4 2 are inversely related to accumulation especially in the winter layer suggesting a significant input from non precipitating events such as dry deposition or riming during this period of very limited snowfall

the last glacial maximum climate over europe and western siberia a pmip comparison between models and data under the framework of the palaeoclimate modelling intercomparison project pmip 17 climate models 16 of which are atmospheric general circulation models have been run to simulate the climate of the last glacial maximum 21 000 years ago using the same set of boundary conditions parallel to these numerical experiments new consistent data bases have been developed on a continental scale the present work compares the range of the model responses to the large perturbation corresponding to the conditions of the last glacial maximum with consistently derived climate reconstructions from pollen records over europe and western siberia it accounts for the differences in the model results due to the models themselves and directly compares this error bar due to the models to the uncertainties in the climate reconstructions from the pollen records overall the last glacial maximum climate simulated by the models over western europe is warmer especially in winter and wetter than the one depicted by the reconstructions this is the region where the reconstructed increase in temperature precipitation and moisture index from the last glacial maximum to the present conditions is largest the same disagreement but of smaller amplitude is found over central europe and the eastern mediterranean basin while models and data are in broad agreement over western siberia the numerous modelling results allow a study of the link between the changes in atmospheric circulation and those in temperature and an interpretation of the discrepancies in precipitation in terms of those in temperature

seasonal and spatial variability in snow chemistry at eclipse icefield yukon canada samples collected from four snow pits at eclipse icefield yukon canada were analyzed for stable isotopes and major ions to assess seasonal and spatial variability in snow chemistry accumulation since the end of the 2001 summer season over the 0 1 km 2 area sampled ranges from 0 77 to 1 16 m w e snow pit stratigraphy and chemical records demonstrate that the low accumulation at pit 3 is due to an under representation of winter snow accumulation at that site for all major ion species chemical concentrations are independent of snow accumulation rate seasonal variations are evident in the major ion records and can be divided between sea salt species na cl that peak in late fall to winter and dust ca 2 m g 2 k and other species nh4 n o 3 s o 4 2 c 2o2 2 that peak in late spring to summer the signal common to all four snow pits identified by empirical orthogonal function analysis ranges from 49 of the total variance for na and cl to as high as 80 of the total variance for so4 2 there is greater spatial variability in species associated with coarse mode particles na c l c a 2 m g 2 than in species present mainly in accumulation mode aerosols so4 2 n h 4 or in the gas phase no3

sharp decrease in summer monsoon strength 4000 3500 cal yr b p in the central higher himalaya of india based on pollen evidence from alpine peat age constrained pollen data and magnetic susceptibility of an alpine peat profile from the garhwal higher himalaya display a continuous record of climate and monsoon trends for the past 7800 yr about 7800 cal yr b p dominance of evergreen oak quercus semecarpifolia alder alnus and grasses in the pollen record reflect a cold wet climate with moderate monsoon precipitation from 7800 to 5000 cal yr b p vegetation was progressively dominated by conifers indicating ameliorated climate with a stronger monsoon a warm humid climate with highest monsoon intensity from 6000 4500 cal yr b p represents the mid holocene climatic optimum between 4000 and 3500 cal yr b p the abundance of conifers sharply decreased with the greatest increase in evergreen oak this trend suggests progressive cooling with a decrease in the monsoon to its minimum about 3500 cal yr b p two relatively minor cold dry events at ca 3000 and 2000 cal yr b p marked step wise strengthening of the monsoon until ca 1000 cal yr b p after a cold dry episode that culminated ca 800 cal yr b p the monsoon again strengthened and continued until today a sharp decrease in temperature and rainfall at 4000 3500 cal yr b p represents the weakest monsoon event of the holocene record this cold dry event correlates with proxy data from other localities of the indian subcontinent arabian sea and western tibet

classifying el nino modoki i and ii by different impacts on rainfall in southern china and typhoon tracks based on their opposite influences on rainfall in southern china during boreal fall this paper classifies el nino modoki into two groups el nino modoki i and ii which show different origins and patterns of sst anomalies the warm sst anomalies originate in the equatorial central pacific and subtropical northeastern pacific for el nino modoki i and ii respectively thus el nino modoki i shows a symmetric sst anomaly distribution about the equator with the maximum warming in the equatorial central pacific whereas el nino modokiii displays an asymmetric distribution with the warmsstanomaliesextending fromthe northeastern pacifictotheequatorialcentralpacific additionally thewarmsstanomaliesintheequatorialcentralpacific extend farther westward for el nino modoki ii than for el nino modoki i similar to the canonical el nino el nino modoki i is associated with an anomalous anticyclone in the philippine sea that induces south westerly wind anomalies along the south coast of china and carries the moisture for increasing rainfall in southern china for el nino modoki ii an anomalous cyclone resides east of the philippines associated with northerly wind anomalies and a decrease in rainfall in southern china the canonical el nino and el nino modoki i are associated with a westward extension of the western north pacific subtropical high wnpsh whereas el nino modoki ii shifts the wnpsh eastward differing from canonical el nino and el nino modoki i el nino modoki ii corresponds to northwesterly anomalies of the typhoon steeringflow which are unfavorable for typhoons to make landfall in china

snow chemistry of agassiz ice cap ellesmere island northwest territories canada pit wall samples were collected from two sites about 2km apart on agassiz ice cap ellesmere island northwest territories canada in 1992 1993 and 1994 and from a site a further 1 km distant in order to study spatial and seasonal variations in snow chemistry two of the pits were dug in wind scoured zones and one in an unscoured zone although a large part of the winter snow is removed fromt he scoured zones which do not show very negarive 18 o values the winter spring anion peaks are still evident this may be due to the predominance of dry deposition in mid winter the cl and so 4 2 ions peak in later winter early spring while no 3 peaks both in later winter early spring and in summer vertical concentration profiles of all anions did not significantly alter over a 2 year period indicating that there are no serious post depositional changes due to evaporation snow melting or photochemical reactions however comparisons between stake board snow accumulation measurements and those derived from the least scoured pit indicate that a single pit will represent annual accumulation rates for a local area only

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

holocene environmental changes in bangong co basin western tibet part 2 the pollen record abstract a better knowledge of environmental variations in key regions such as the tibetan plateau which plays a fundamental role in the indian monsoon dynamics and thus on the whole northern hemisphere atmospheric circulation is of great importance we present here a detailed paleoenvironmental study based on pollen analyses of a sediment core from lake bangong results on the modern pollen rain are also discussed as they give valuable information for the interpretation of the fossil pollen data the pollen results of the bangong sequence and their paleoclimatic interpretation are integrated into a chronological framework on the basis of palynostratigraphical methods because of dead carbon in the lake system it has been difficult to establish a reliable chronology of the bangong sequence using a geochemical model for correcting measured 14c ages the pollen record from lake bangong compares well with the record from lake sumxi in western tibet lake bangong core provides a continuous holocene pollen record before 9600 yr b p the dominance of desertic elements in the pollen record reflects an arid environment at about 9600 yr b p an abrupt shift to steppe vegetation suggests the onset of moister conditions and from 9500 to 6200 yr b p proxy data indicate conditions warmer and wetter than today proxy data also indicate short term changes during this interval climate instability is suggested by the development of a local palustral flora which peaks at 7700 yr b p and is interpreted as a lake regression in phase with increase in the percentage of littoral and saline water diatom species between 8600 and 7700 yr b p the first humid pulse culminating at 9000 8500 yr b p is thus followed by drier conditions around 8000 7700 yr b p the interval between 7200 and 6500 yr b p regarded as optimal for vegetation growth from the pollen record corresponds to a second humid pulse a trend towards aridity is observed during the following period with dry events centered around 5500 3900 3200 and 700 yr b p

late quaternary intensified monsoon phases control landscape evolution in the northwest himalaya the intensity of the asian summer monsoon circulation varies over decadal to millennial time scales and is reflected in changes in surface processes terrestrial environments and marine sedi ment records however the mechanisms of long lived 2 5 k y intensified monsoon phases the related changes in precipitation distribution and their effect on landscape evolution and sedimen tation rates are not yet well understood the arid high elevation sectors of the orogen correspond to a climatically sensitive zone that currently receives rain only during abnormal i e strength ened monsoon seasons analogous to present day rainfall anom alies enhanced precipitation during an intensified monsoon phase is expected to have penetrated far into these geomorphic threshold regions where hillslopes are close to the angle of failure we as sociate landslide triggering during intensified monsoon phases with enhanced precipitation discharge and sediment flux leading to an increase in pore water pressure lateral scouring of rivers and ov ersteepening of hillslopes eventually resulting in failure of slopes and exceptionally large mass movements here we use lacustrine deposits related to spatially and temporally clustered large land slides 0 5 km 3 in the sutlej valley region of the northwest him alaya to calculate sedimentation rates and to infer rainfall patterns during late pleistocene 29 24 ka and holocene 10 4 ka inten sified monsoon phases compared to present day sediment flux measurements a fivefold increase in sediment transport rates re corded by sediments in landslide dammed lakes characterized these episodes of high climatic variability these changes thus em phasize the pronounced imprint of millennial scale climate change on surface processes and landscape evolution

the effects of wind on δ 18o and accumulation give an inferred record of seasonal δ amplitude from the agassiz ice cap ellesmere island canada

quaternary geology tectonics and distribution of palaeo and present fluvio glacio lacustrine deposits in ladakh nw indian himalaya a study based on field observations abstract the ladakh region of the northwestern indian himalaya is rich in quaternary deposits but it has not received much attention previous quaternary research in the region has focused on the glacial sequences and only some scattered data of the lacustrine deposits are available this article addresses the reconstruction of the palaeo lacustrine deposits and the present day lakes and their distribution in the ladakh region the region was under the influence of tectonic activity and cold climate during the late quaternary times tectonic activity at 50 000 years bp 35 000 years bp and 25 000 years bp has been recorded we report the presence of three major lakes in the region in the late quaternary these formed due to the damming of the indus river and its tributaries by debris avalanches initiated mainly by tectonic activity along the indus suture shyok suture and the karakoram fault these are the spituk leh palaeolake formed 50 000 years bp the lamayuru palaeolake dated to 35 000 years bp in the indus valley and the khalsar palaeolake 60 km in length in the shyok valley vast exposures of the palaeolake deposits ranging from 25 to 150 m in thickness are reported spituk section 25 m lamayuru section 110 m and khalsar 150 m and hundri 100 m and which have a wide lateral extent a glacial lake basin at bhaktpur city north of baralacha la is now completely filled the tsokar lake has been subdivided into smaller units now and the water level is lowering other lakes in the region e g pangong tso tso morari the twin kyun tso lakes are confined to the western side of the study area limited chemical weathering rapid erosion and cold climatic conditions in late quaternary times are suggested by the stable illite values in the lamayuru section four levels of palaeoseismic structures convolute structures sand dykes intraformational folds micro faulting are present in the khalsar section and at three levels in the tirit section at shyok nubra confluence palaeoseismic activity was also prevalent after 25 000 years bp as is evident from the three levels of palaeoseismic structures in the younger sediments