indian ocean summer monsoon iosm dynamics within the past 4 ka recorded in the sediments of lake nam co central tibetan plateau china abstract in september 2008 several cores 68 cm 115 cm length water depth 93 m were retrieved from lake nam co southern central tibetan plateau 4718 m a s l this study focuses on the interpretation of high resolution partly 0 2 cm data from three gravity cores and the upper part of a 10 4 m long piston core i e the past 4000 cal bp in terms of lake level changes hydrological variations in the catchment area and consequently variations in monsoon strength a wide spectrum of sedimentological geochemical and mineralogical investigations was carried out results are presented for xrf core scans grain size distribution xrd measurements and sem image analyses these data are complemented by an age depth model using 210pb and 137cs analyses as well as eleven ams 14c ages this model is supported by excellent agreement between secular variations determined on one of the gravity cores to geomagnetic field models this is a significant improvement of the chronology as most catchments of lacustrine systems on the tibetan plateau contain carbonates resulting in an unknown reservoir effect for radiocarbon dates the good correlation of our record to the geomagnetic field models confirms our age depth model and indicates only insignificant changes in the reservoir effect throughout the last 4 ka high summer monsoonal activity i e moist environmental conditions was detected in our record between approximately 4000 and 1950 cal bp as well as between 1480 and 1200 cal bp accordingly lower monsoon activity prevails in periods between the two intervals and thereafter this pattern shows a good correlation to the variability of the indian ocean summer monsoon iosm as recorded in a peat bog 1000 km in ne direction from lake nam co this is the first time that such a supra regional homogenous monsoon activity is shown on the tibetan plateau and beyond finally our data show a significant lake level rise after the little ice age lia in lake nam co which is suggested to be linked to glacier melting in consequence of rising temperatures occurring on the whole tibetan plateau during this time

unusual radar echoes from the greenland ice sheet airborne radar images of part of the greenland ice sheet reveal icy terrain whose radar properties are unique among radar studied terrestrial surfaces but resemble those of jupiter s icy galilean satellites the 5 6 and 24 centimeter wavelength echoes from the greenland percolation zone like the 3 5 and 13 centimeter wavelength echoes from the icy satellites are extremely intense and have anomalous circular and linear polarization ratios however the detailed subsurface configurations of the galilean satellite regoliths where heterogeneities are the product of prolonged meteoroid bombardment are unlikely to resemble that within the greenland percolation zone where heterogeneities are the product of seasonal melting and refreezing

water balance observations reveal significant subsurface water seepage from lake nam co south central tibetan plateau summary hydrological observations including precipitation runoff evaporation and lake level were performed in detail in the basin of the lake nam co in the southern central tibetan plateau from 2007 to 2011 two runoff coefficients at differing catchment scales were obtained and applied to derive the surface water inflow to the lake from the non glaciated areas total runoff was partitioned into contributions from glaciated and non glaciated areas at two additional catchment scales the runoff from the non glaciated areas amounted to 1400 mm lake depth during the observation period from may 18 to october 17 2008 during which the most complete set of observations was obtained neglecting groundwater contributions this amount accounted for 55 65 of the total water input to the lake nam co the precipitation contribution and the meltwater inflow from the glaciers accounted for 23 28 and 7 22 of the total water input to the lake respectively the water input was found to be 810 1220 mm lake depth 1 63 109 2 47 109 m3 more than the output of the lake during a 5 month period in 2008 similar results were obtained for the years 2007 and 2009 2011 as there is no surface outflow from the lake the large water imbalance can only be explained by water seepage corresponding to an average outflow of 120 190 m3 s 1 or 5 8 mm lake water depth per day it is likely that the main pathway for lake water seepage is through the sub surface fault system which is known to exist in the area

stable isotope and radiocarbon balances of two tibetan lakes sumxi co longmu co from 13 000 bp hydrologic and climatic changes in western tibet since 13 000 bp are inferred from mineralogical and isotopic analyses of lacustrine sediments from the sumxi longmu co basin the interpretation is based on isotope data from the modern system carbon isotope chemistry is complex because of the presence of old limestones on the watershed sediments contain detrital and authigenic calcites the proportions of which are quantitatively estimated by x ray diffractometry stable isotope contents of the authigenic calcite are reconstructed from mass balance equations the high 13c contents up to 6 are attributed to an enhancement of calcite precipitation from water surface during freezing periods the 18o content is related to residence time and evaporation the validity of 14c dates obtained from different types of material is discussed our record in good agreement with paleobiological data from the same material shows the sudden establishment of wet warm conditions at 10 000 bp which culminated at 7500 6000 bp after a brief reversal event at 7900 bp maximum aridity for the whole holocene is recorded at 4300 bp

review of holocene glacial chronologies based on radiocarbon dating in tibet and its surrounding mountains a compilation of 53 14c ages on moraines constrains the holocene glacial history of tibet and the surrounding mountains several holocene glacial stages are identified the little ice age had three substages at 1 0 0 13 cal ka bp however the glacial advances may have occurred 200 600 a earlier in southern and eastern bordering mountains than in the northern bordering mountains the earlier glacial advance might have been driven by humid conditions in bordering areas of tibet most glacial advances in the neoglaciation occurred at 3 5 1 4 cal ka bp they can be identified in almost every mountain range an early holocene glacial advance occurred 9 4 8 8 cal ka bp in both central tibet and bordering mountains the timings of holocene glacial advances are synchronous with the cooling periods in the 18o record from ice cores and with the results of optically stimulated luminescence dating and cosmogenic exposure dating in tibet copyright 2008 john wiley sons ltd

500 2000 mhz brightness temperature spectra of the northwestern greenland ice sheet an ultra wideband radiometer has been developed to measure subsurface properties of the cryosphere including ice sheets and sea ice the radiometer measures brightness temperature spectra from 0 5 to 2 ghz using 12 channels each of which measures scene brightness temperatures over an 88 mhz bandwidth resolved into 0 24 mhz intervals the instrument was flown over northwestern greenland in september 2016 and acquired the first wideband low frequency brightness temperature spectra over the ice sheet and coastal region the results reveal strong spatial and spectral variations that correlate well with the physical properties of the surface encountered along the flight path which started over ocean then passed the rock near the coast and then up onto the ablation wet percolation and dry snow zones of the interior ice sheet in particular strong spectral responses in percolation and dry snow zones are observed and plausibly explained by varying the distribution of horizontal density layers and isolated icy bodies in the upper portion of the firn the success of the airborne deployment of the instrument and subsequent implementation of algorithms to limit radio frequency interference in unprotected bands is motivating continued airborne investigations as well as stimulating research into the feasibility of a spaceborne instrument

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

palaeo water depth estimation for a 600 year record from nam co tibet using an ostracod based transfer function a modern training set of ostracods from the large slightly saline lake nam co on the southeastern tibetan plateau is presented in total 44 samples covering the largest part of the lake and water depth from 2 to 93 m were taken there are eight ostracod species in surface sediments of nam co leucocytherella sinensis leucocythere dorsotuberosa fabaeformiscandona gyirongensis candona xizangensis candona candida ilyocypris cf mongolica eucypris gyirongensis and limnocythere inopinata in order of mean dominance a morphological variant of l dorsotuberosa the forma postilirata is an indicator form of deep water below the thermocline the 36 samples comprise a sufficient number of ostracods for analysis covering water depths between 3 7 and 89 3 m two transfer function models based on weighted average binomial regression wa br and weighted average partial least square regression wa pls using the programs excel and c2 were established to estimate past water depths of nam co transfer functions were applied to ostracod data from two short cores from nam co covering approximately the past 600 years model results show a lake level minimum occurring during the little ice age lia between about 1490 and 1760 ad this minimum corresponds to results from previous stable isotope analysis and indicates a lake level which was about 5 m below the present day level the more exact transfer function model wa pls was set up using c2 and revealed a higher correlation index r o f 0 91 and a lower standard error of 6 7 m however the more selective because of using indicator taxa only wa br model using excel r 0 88 standard error 10 6 m seems to represent palaeo water depths better at least for the studied short cores

environmental changes since 8 4 ka reflected in the lacustrine core sediments from nam co central tibetan plateau china the tibetan plateau induces and enhances the asian monsoon that influences the plateau itself east china and even the whole of asia pursuing the changing monsoon history and its impact in this environment sensitive area is a key for understanding the climatic changes here we present the initial results from core sed iments in nam co central tibet to elucidate the holocene environment changes in this area the studied lake nam co is the second largest lake with an elevation of 4718 m water area of 2015 km 2 and catchment area of 10 610 km 2 by using echo seismic profiling and hydro echosounding we investigated the bathymetric dis tribution of the whole lake one 332 cm long piston core was successfully taken in the east part of the lake at 60 m water depth twelve ams 14 c dates from top to bottom of this core established a good time sequence toc tn n alkanes grain size clay minerals fe mn sr ba and caco3 content were analysed with sampling intervals from 1 cm to 10 cm results showed that since 8400 yr bp the environment changes in this region indicate three stages the early stage 8400 6900 yr bp was characterized by slight shifting from warm to cold with a cold dry interval at 8100 7800 yr bp the middle stage was from 6900 to 2900 yr bp during which cli mate changed from warm humid to cold dry however around 2900 yr bp the climate once was slightly cold but strongly dry the late stage from 2900 yr bp to present was characterized by a general tendency toward cold dry the first temperature decline was around 1700 1500 yr bp following which temperature increased once before decreasing again around 600 300 yr bp which might be the result of the little ice age

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

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

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

holocene aridification of india 1 spanning a latitudinal range typical for deserts the indian peninsula is fertile instead and sustains over a billion people through monsoonal rains despite the strong link between climate and society our knowledge of the long term monsoon variability is incomplete over the indian subcontinent here we reconstruct the holocene paleoclimate in the core monsoon zone cmz of the indian peninsula using a sediment core recovered offshore from the mouth of godavari river carbon isotopes of sedimentary leaf waxes provide an integrated and regionally extensive record of the flora in the cmz and document a gradual increase in aridity adapted vegetation from 4 000 until 1 700 years ago followed by the persistence of aridity adapted plants after that the oxygen isotopic composition of planktonic foraminiferglobigerinoides ruberdetects unprecedented high salinity events in the bay of bengal over the last 3 000 years and especially after 1 700 years ago which suggest that the cmz aridification intensified in the late holocene through a series of sub millennial dry episodes cultural changes occurred across the indian subcontinent as the climate became more arid after 4 000 years sedentary agriculture took hold in the drying central and south india while the urban harappan civilization collapsed in the already arid indus basin the establishment of a more variable hydroclimate over the last ca 1 700 years may have led to the rapid proliferation of water conservation technology in south india

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

interplay between redox conditions and hydrological changes in sediments from lake nam co tibetan plateau during the past 4000 cal bp inferred from geochemical and micropaleontological analyses abstract this study focuses on the analysis of lake sediments retrieved from the deepest part of lake nam co tibetan plateau one gravity core of 115 cm length covering the last 4000 cal bp was analyzed for geochemical and biological parameters high organic content at 4000 cal bp and the coinciding presence of pyrite framboids until 2000 cal bp point to hampered decomposition of organic material due to anoxic conditions within the lake sediments at the same time sedimentological and biological proxies suggest a rather high lake level but still 5 m below the recent one with less saline lake water due to enhanced monsoonal activity during this time a change in the source of organic matter to lowered input of terrestrial components is observed a rather quick shift to a dry environment with less monsoonal influence and a lake level 15 m lower than today at 2000 cal bp lead to the oxygenation of sediment the degradation of organic matter and the absence of pyrite oscillations of the lake level thereafter were of minor amplitude and not able to establish anoxia at the lake bottom again a wet spell between 1500 cal bp and 1150 cal bp is visible in proxies referring to catchment hydrology and the ostracod based water depth transfer function gives only a slightly elevated lake level the last 300 years are characterized by low toc and rising tn values reflecting enhanced nutrient supply and hence an advancing influence of human activity in the catchment decreasing toc tn values point to a complete shift to almost solely aquatic biomass production these results show that hydrological variations in terms of lake level change based on monsoonal strength can be linked to redox conditions at the lake bottom of nam co comparison with other archives over larger parts of the tibetan plateau and beyond exhibits a rather homogeneous climatic pattern throughout the late holocene

remote sensing of sea ice thickness and salinity with 0 5 2 ghz microwave radiometry an ultrawideband radiometer was used to measure microwave brightness temperature spectra over arctic sea ice in the lincoln sea near the north coast of greenland spectra over the range of 0 5 2 ghz were compared to thermal infrared images collected during the airborne campaign and also compared to nearly concurrent sentinel 1 c band synthetic aperture radar sar data based on those comparisons spectral signatures were associated with thick multiyear ice and thin ice a radiative transfer rt model consisting of a homogeneous slab of sea ice bounded by sea water and air was then used to invert the spectra for sea ice thickness and salinity inferred thicknesses were consistent with ice thickness climatology for ice floes in the lincoln sea salinities are higher than expected which may be a consequence of neglecting surface and volume scattering contributions in the models

correlation between indian ocean summer monsoon and north atlantic climate during the holocene there has been a number of investigations for the correlation between the asia monsoon and the north atlantic climate for the last glacial however little research has been done for the present interglacial the holocene here we present for the first time a high resolution composite proxy record for the indian ocean summer monsoon spanning around 12 000 years based on the 13c time series of both a single plant species carex mulieensis remains cellulose and the total plant assemblage cellulose in the hongyuan peat bog from the tibet plateau the records show that the strength of the indian ocean summer monsoon had abrupt variations during the last 12 000 years the weakest monsoon occurred in the younger dryas period following rapid strengthening from around 11 200 to 10 800 a bp the monsoon kept a generally strong level for around 5300 years from around 5500 a bp onwards the monsoon strength tended to gradual decrease in addition there are a series of abrupt variation events of the monsoon strength on centennial to millennial time scales which superimpose the general tendency of the monsoon variation in every case when the ice rafted debris events in the north atlantic occurred the summer monsoon strength decreased correspondingly these evidences show that teleconnection between the indian ocean summer monsoon and the north atlantic climate is present not only in the last glacial but also in the holocene which may be linked to abrupt reorganizations of the ocean thermohaline circulation leading to redistribution of energy changing temperature and moisture gradient over the southern subtropical indian ocean and eventually controlling the variability of the indian ocean summer monsoon

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

the huguang maar lake a high resolution record of palaeoenvironmental and palaeoclimatic changes over the last 78 000 years from south china abstract a series of seven piston cores from the huguang maar lake situated near the south china sea coastline provides insight into regional palaeoenvironmental and palaeoclimatic changes in southern china over the last 78 000 years the data set comprises a high resolution record of magnetic susceptibility dry density and water content total organic carbon and inorganic carbon total nitrogen biogenic silica bsio2 and palynological results the time scale was developed by ams 14c dating of 17 terrestrial plant macro fossils during the last glacial the huguang record is characterised by an alternation of more temperate and humid periods from 78 to 58 and 48 to 40 5 ka bp and periods with predominance of grassland vegetation and possibly lowered lake level from 58 to 48 and ca 40 5 to 15 ka bp the huguang data have been compared to regional marine and terrestrial records in order to discuss variability of the south east asian monsoon system for most of the last glacial period the huguang proxies do not exhibit marked millennial scale variability as known from some long se asian and many north atlantic records this picture changes at about 15 cal ka bp when the huguang and greenland records appear to correlate well a short climatic reversal which is assumed to reflect a younger dryas type event is well recorded in the huguang record during the holocene the huguang multi proxy data show a much higher variability than during the last glacial stage probably reflecting at least for the early mid holocene fluctuations in monsoon activity however the last 4000 years of the sediment record are clearly influenced by enhanced human activity and thus difficult to interpret in terms of palaeoclimate change

a long and winding road towards a palethnograpic interpretation of the middle gravettian site of la picardie indre et loire france abstract after nine years of excavation 1998 2008 the site of la picardie has delivered a significant lithic collection more than 13 000 artefacts coordinated chronologically related to the raysse burin phase of the gravettian second phase of middle gravettian ca 25 23 ky bp uncal the study of the lithic material has provided several important results including the chronological attribution of the site the description of a new type of retouched bladelet and the reconstruction of the flint knapping process for blade and bladelet production on site the palethnographic study and interpretation of the site have however not been discussed to date in spite of some taphonomic issues the coalescence of different studies has allowed us to further our understanding of the site notably via the functional analysis of stone tools the evaluation of different skill levels in flint knapping the vertical and horizontal distributions of artefacts and tools and finally the study of the different organised structures made of limestones blocks using several examples we will describe in a step by step manner the various elements that helped us to rebuild the probable function s of the site and propose a first palethnographic assessment

use of stable oxygen isotope determinations from brachiopod shells in palaeoenvironmental reconstruction abstract stable oxygen isotope analyses were obtained from fossil brachiopod shells from a shallow marine deposit of upper pleistocene age approximately 80 ka in new zealand as part of a palaeoenvironmental investigation bulk analyses of entire shells of calloria inconspicua yielded highly variable results a range of 2 30 rendering these data of limited use as palaeoenvironmental proxies attempts to obtain consistent oxygen isotope values by removing areas of the brachiopod shell thought to be prone to oxygen isotope disequilibrium effects vital effects revealed that the matching anterior portions of ventral and dorsal valves from the same individual which were secreted at the same time also yielded different oxygen isotope ratios the dorsal valve 18o values were higher and less variable than those obtained from the ventral valve of the same individual the investigation was then extended to living representatives of the same species from a similar shallow water habitat from the south island of new zealand the pattern of dorsal valves yielding higher and less variable oxygen isotope values than matching areas of the ventral valves was repeated in seven out of eight individuals investigated although there was considerable variation in the absolute values from specimen to specimen contrary to common practice therefore it seems that in this species it is the much thinner and lighter dorsal valve that provides a more consistent isotopic measurement if converted into absolute temperature estimates the dorsal valve measurements correspond to a temperature midway between the mean and maximum annual temperature experienced by this species in its present day habitat which may make it acceptable as a palaeoenvironmental indicator the high level of variation between individuals including an inferred temperature from one ventral valve above the mean maximum temperature experienced indicates that a range of individuals needs to be investigated in any palaeoenvironmental investigation to avoid misleading interpretations however intra and inter specimen variation in isotopic composition may provide valuable palaeobiological information on growth rates metabolism and possibly also pathological conditions in the past

greenland ice sheet surface properties and ice dynamics from ers 1 sar imagery c band synthetic aperture radar sar imagery from the european space agency s ers 1 satellite reveals the basic zonation of the surface of the greenland ice sheet the zones have backscatter signatures related to the structure of the snowpack which varies with the balance of accumulation and melt at various elevations the boundaries of zones can be accurately located with the use of this high resolution imagery the images also reveal a large flow feature in northeast greenland that is similar to ice streams in antarctica and may play a major role in the discharge of ice from the ice sheet

radar measurements of melt zones on the greenland ice sheet surface based microwave radar measurements were performed at a location on the western flank of the greenland ice sheet here firn metamorphosis is dominated by seasonal melt which leads to marked contrasts in the vertical structure of winter and summer firn this snow regime is also one of the brightest radar targets on earth with an average backscatter coefficient of 0 db at 5 3 ghz and an incidence angle of 25 by combining detailed observations of firn physical properties with ranging radar measurements we find that the glaciological mechanism associated with this strong electromagnetic response is summer ice lens formation within the previous winter s snow pack this observation has important implications for monitoring and understanding changes in ice sheet volume using space borne microwave sensors

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 impact of periglacial processes on palaeolithic sites the case of sorted patterned grounds during the last glaciation western europe witnessed recurrent millennial scale episodes of periglacial climates that had significant impact on palaeolithic site preservation after a review on the genesis and climatic meaning of sorted patterned grounds examples of polygons stripes and stone banked solifluction lobes taken from archaeological contexts are described sorted features in palaeolithic sites imply that caution should be taken in site patterning analysis for reconstructing past human behaviours since spatial alteration of the original anthropogenic pattern took place on low gradients artefact movements remain limited but may increase dramatically on slopes when solifluction adds to sorting processes although these features are widespread in modern periglacial environments archaeological examples remain scarce multiple factors are probably involved including lack of knowledge of periglacial processes and landforms by archaeologists leading to misinterpretation but also more or less complete obliteration of surface features by sedimentary processes upon burial however it is assumed that scarcity of clear anthropogenic patterning in french palaeolithic sites before the late glacial is due for a large part to post depositional disturbance by periglacial processes

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

analysis of synthetic aperture radar data collected over the southwestern greenland ice sheet analyses of the first aircraft multi frequency polarimetric synthetic aperture radar sar data acquired over the southwestern greenland ice sheet are presented data were collected on 31 august 1989 by the jet propulsion laboratory sar using the nasa dc 8 aircraft along with curvilinear patterns associated with large scale morphologic features such as crevasses lakes and streams frequency and polarization dependencies are observed in the p l and c band image products

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

analyzing and modeling the smos spatial variations in the east antarctic plateau abstract the smos brightness temperature t b collected on the east antarctic plateau revealed spatial signatures at l band that have never before been observed when only higher frequency passive microwave observations were available and this has opened up a new field of research because of the much greater penetration depth modeling the microwave ice sheet emission requires taking into account not only snow conditions on the surface but should also include glaciological information even if the penetration depth of the l band is not well known due to the uncertainty on the imaginary part of the ice permittivity it is likely to be of the order of several hundreds of meters which means that the temperature of the ice over a depth of nearly 1000 m influences the emission over such a depth the temperature is related to both the surface conditions and to the ice sheet thickness which in turn depends on the bedrock topography and on other glaciological variables the present paper aims to provide a thorough theoretical explanation of the observed t b spatial variation close to the brewster angle at vertical polarization in order to limit the effect of surface and vertical density variability in the firn in order to provide reliable inputs to the microwave emission models used for simulating t b data an in depth analysis of the temperature profiles was performed by means of glaciological models the comparison between simulated and observed data over three transects totalling 2000 km in east antarctica pointed out that whereas the emission models are capable of explaining the t b spatial variations of several kelvins 0 7 and 2 9 k they are unable to predict its absolute value correctly this study also shows that the main limiting factor in simulating low frequency microwave data is the uncertainty in the currently available imaginary part of the ice permittivity

the effect of fluctuations in surface density accumulation and compaction on elevation change rates along the egig line central greenland repeated measurements of density profiles and surface elevation along a 515 km section of the greenland ice sheet have been used to determine elevation change rates and the error in determining mass balance from these rates which arises from short term fluctuations in mass input compaction and surface density over the 28 months from spring 2004 to summer 2006 the average error over 100 km sections of the traverse ranged from 0 006 to 0 100 m a 1 the lowest values comparable with the system accuracy of the cryosat radar altimeter 0 033 m a 1 were found below 3000 m the surface density required to translate the elevation change into mass change decreased from 0 40 g cm 3 at an elevation of 2348 m to 0 33 g cm 3 at an elevation of 3264 m from the density profiles the equivalent values for a time period of 10 years were found to be 0 48 and 0 38 g cm 3 respectively

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

constraining holocene lake level highstands on the tibetan plateau by 10be exposure dating a case study at tangra yumco southern tibet abstract many lakes on the tibetan plateau are surrounded by palaeo shorelines that document former lake level highstands and hence past changes in climate establishing accurate chronologies for these shorelines is crucial to correlate lake level fluctuations with palaeo environmental histories that are commonly inferred from lake sedimentary records here we apply surface exposure dating to constrain the age of two lake level highstands at one of the largest tibetan lakes tangra yumco which has well developed palaeo shorelines located up to 185 m above the current lake for sampling we focussed on wave cut bedrock terraces that vary considerably in width because they were carved into rocks of different erodibility samples from the highest strath terrace 180 185 m above the lake at three different sites yield tightly clustered 10 be ages between 7 39 0 19 ka and 7 87 0 27 ka internal errors which constrain the end of an early holocene lake level highstand at 7 6 0 6 ka external error the consistency of the 10 be ages indicates that bedrock erosion by wave attack reduced the inherited 10 be component to negligible amounts because otherwise samples would show considerable age scatter two bedrock samples from a lower terrace 140 145 m above the lake and one amalgamated clast sample from a beach ridge on the same terrace yield 10 be ages between 4 04 0 14 ka and 4 50 0 15 ka these ages document that the lake level dropped by 40 m between 7 6 ka and 4 3 ka granite boulders from the two investigated terraces yield apparent 10 be ages that are 6 ka and 27 ka older than the ages of the respective terraces indicating that this sample type is not reliable in this setting overall our results demonstrate that exposure dating of bedrock terraces provides a valuable tool to reconstruct lake level histories on the tibetan plateau

holocene lake level changes of hurleg lake on northeastern qinghai tibetan plateau and possible forcing mechanism the palaeoshorelines of a lake are the direct geomorphic evidences to reflect past water levels and record information on palaeoclimatic changes previous research indicates that the timing and forcing mechanisms of climatic change on the northeastern qinghai tibetan plateau ne qtp are still controversial here we report quartz optically stimulated luminescence osl ages for beach deposits and accelerator mass spectrometry ams 14c age for plant remains shoreline features and geomorphic exposures that contribute to a reconstruction of the lake level history of hurleg lake on the ne qtp the results imply that 1 three high lake levels are dated to 6 8 6 4 5 0 4 7 and 2 2 1 4 kyr corresponding to relatively wet and stable climate from pollen records of sediment core in this lake during mid late holocene 2 the highest lake level period occurred at 5 0 4 7 kyr which is almost synchronous with the highest effective moisture phase from synthesized lake records influenced by the westerlies and 3

palaeoclimatic interpretation of a topographic profile across middle holocene regressive shorelines of longmu co western tibet most lakes and closed basins in tibet are surrounded by abandoned shorelines attesting for high water levels in the past two such lakes longmu co and sumxi co western tibet were the focus of detailed palaeoclimatic work during the 1989 sino french expedition based on the study of lake sediments and analysis of a piston core here it is shown that additional information may be deduced from the abandoned shorelines around longmu co a 1800 m long topographic profile was levelled from 75 m up to 230 m above the present lake elevation 5008 m on which the shorelines form a flight of horizontal terraces separated by more or less degraded scarps the elevations of the terraces were spaced regularly about 1 35 m except for 3 5 m high lacunae reccurring every 15 16 m the potential annual evapo transpiration was computed based on meteorological data collected at tien shui hai from 13 08 89 to 11 09 90 using a modified penman formula a value of 1 60 0 3 m yr was obtained under close system conditions no outlet and a synthetic curve of lake regression was derived which appears to be consistent with the measured shoreline heights it is concluded that the 1 35 m terraces represent annual regression of the lake level by contrast the 3 5 m high lacunae might reflect the periodic return about every 9 12 yr of particular climatic conditions responsible for a perturbation of the annual process of shoreline formation all the shorelines of this profile have formed probably within one century during a continuous and abrupt regression of the lake such evolution has also been identified in the sediments of a piston core collected at sumxi co and dated at about 6 5 5 kyr b p the lake level must have been at its highest stand shortly before that major regression the mechanism responsible for this middle holocene high stand and for the major sudden drop of the lake level remains uncertain

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

potential forcing mechanisms of holocene lake level changes at nam co tibetan plateau inferred from the stable isotopic composition of shells of the gastropod radix the timing of lake level fluctuations on the tibetan plateau and their relationship with climatic changes is still under debate and the main reason for this is the lack of suitable archives for reconstructing the paleohydrology and paleoclimatology of the lakes here we present the results of analyses of the shell geochemistry of radix sp from an exposed terrace of nam co lake on the south central tibetan plateau optically stimulated luminescence osl dating reveals that deep water lacustrine sediments formed between ca 4 4 and 2 2 ka suggesting a high and stable lake level significantly above the present the results of sr ca 13c and 18o analyses of the fossil shells of radix sp indicate that during the mid to late holocene lake level variations in nam co were mainly controlled by variations in the indian summer monsoon a trend of decreasing evaporation also played an important role comparison with other results suggests a consistent pattern of mid to late holocene lake level changes acro

thermoluminescence dating of the malan loess at zhaitang china although the widespread loess deposits of north china have been well described there has been limited information on the absolute age of the various layers loess a wind carried deposit exposed to sunlight and subsequently buried should be amenable to dating by thermoluminescence through use of the fine grain technique ages from 18 to 84 ka have been obtained for a sequence in the malan loess exposed in the zhaitang section near beijing the dates are consistent with the evidence from geology and magnetostratigraphy and provide a chronology for the zhaitang section

fabric of palaeolithic levels methods and implications for site formation processes fabric analysis in archaeological contexts i e the study of the orientation and dip of artefacts has been significantly improved during the last decade mainly with respect to the statistical treatment of data the development of a reference base for natural sedimentary processes as well as the increased number of data for palaeolithic levels these works show that fabrics are an efficient tool for assessing site formation processes fabrics allow discrimination between i undisturbed or minimally disturbed levels ii levels that have undergone strong pedoturbations due to biological activity or to shrinking and swelling of clayey sediments and iii levels that have been significantly reworked by slope processes such as periglacial solifluction or overland flow however in the present state of knowledge fabrics do not allow precise estimation of the degree of perturbation if not associated with other archaeological and geological criteria from the set of data on french palaeolithic sites used here it is demonstrated that slope dynamics and particularly solifluction for sites predating the late glacial may have played an important role in site formation

late quaternary hydrological changes inferred from lake level fluctuations of nam co tibetan plateau china abstract this paper discusses the range of lake level changes using hydro acoustic techniques and sediment core data for lake nam co in central tibet china this second largest tibetan lake is situated at an elevation of 4718 m a s l lake level changes with different high stands documented by beach remnants are widespread on the tibetan plateau and also in lake nam co they indicate significant changes in the hydrological system triggered by the monsoonal circulation using hydro acoustic techniques submerged beach remains at approximately 10 15 m 30 m 45 m 70 m and 95 m below present day lake level were detected indicating a more negative water balance than today the 10 15 m lake level is dated to an age equal to the little ice age all deeper lake levels are assumed to have been formed prior to 10000 cal bp folded older sediments detected in the hydro acoustic profiles indicate a possible larger extent of the glaciers during or prior to the last glacial maximum lgm this is followed by a low stand or even by possible desiccation of the entire lake basin during or after the lgm

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

hydrological variations on the central tibetan plateau since the last glacial maximum and their teleconnection to inter regional and hemispheric climate variations decadal to sub decadal variability of inflow evaporation and biological productivity derived from lake nam co was used to reconstruct hydrological changes for the past ca 24 k cal a bp the timing of these variations corresponds to known climatic shifts on the northern hemisphere after a dry and cold last glacial maximum the lake level of nam co initially rose at ca 20 k cal a bp moist but further cold conditions between ca 16 2 and 14 k cal a bp correspond to heinrich event 1 a warm and moist phase between ca 14 and 13 k cal a bp is expressed as a massive enhancement in inflow and biological productivity and might be associated with a first intensification of the indian ocean summer monsoon coinciding with the bolling allerod complex a two step decrease in inflow and a contemporaneous decline in biological productivity until ca 11 8 k cal a bp points to cool and dry conditions during the younger dryas lake levels peak at ca 9 4 k cal a bp although hydrological conditions remain relatively stable during the holocene with only low amplitude variations observed

prolonged monsoon droughts and links to indo pacific warm pool a holocene record from lonar lake central india abstract concerns about the regional impact of global climate change in a warming scenario have highlighted the gaps in our understanding of the indian summer monsoon ism also referred to as the indian ocean summer monsoon and the absence of long term palaeoclimate data from the central indian core monsoon zone cmz here we present the first high resolution well dated multiproxy reconstruction of holocene palaeoclimate from a 10 m long sediment core raised from the lonar lake in central india we show that while the early holocene onset of intensified monsoon in the cmz is similar to that reported from other ism records the lonar data shows two prolonged droughts pd multidecadal to centennial periods of weaker monsoon between 4 6 3 9 and 2 0 6 cal ka a comparison of our record with available data from other ism influenced sites shows that the impact of these pd was observed in varying degrees throughout the ism realm and coincides with intervals of higher solar irradiance we demonstrate that i the regional warming in the indo pacific warm pool ipwp plays an important role in causing ism pd through changes in meridional overturning circulation and position of the anomalous walker cell ii the long term influence of conditions like el nino southern oscillation enso on the ism began only ca 2 cal ka bp and is coincident with the warming of the southern ipwp iii the first settlements in central india coincided with the onset of the first pd and agricultural populations flourished between the two pd highlighting the significance of natural climate variability and pd as major environmental factors affecting human settlements

the late solutrean open air site of landry aquitaine france a preliminary spatio temporal analysis the upper palaeolithic open air site of landry near perigueux in the aquitaine region of southwestern france lies on an alluvial plain of the isle river the site contains two stratified late solutrean levels preserved over 300 m2 within aeolian silts and dated by optically stimulated luminescence osl to between 27 and 16 ky only lithic material was present in both levels with organic material having been destroyed by post depositional processes the upper level associated with a thermoluminescence tl date of 21 ky obtained from burnt flint produced the remains of a hunting camp organised into different sectors containing cobble reserves features in large alluvial blocks or heated cobbles and specialised activity zones for the production and use of highly varied domestic as well as hunting tools the lithic assemblage comprises more than a hundred laurel leaf points bifacial tools and shouldered points that reflect either considerably different degrees of technical knowledge and know how amongst the group s who occupied the site and or highly diversified needs the importation and circulation of flint points in non local raw materials likely suggests the occupation to have been connected with other late solutrean sites within an expansive subsistence and raw material provisioning territory the remarkable preservation of habitation features the varied composition of the toolkit and the exceptional presence of mobiliary art makes landry a benchmark for better understanding the technology and socio cultural organisation of late solutrean groups in the aquitaine basin

interaction of geomorphological processes on the north eastern tibetan plateau during the holocene an example from a sub catchment of lake donggi cona abstract geomorphological landforms on a large alluvial fan and neighboring areas on the eastern side of the donggi cona show a complex spatial pattern sediment availability is an important factor in the formation of these archives and is partly associated with lake level fluctuation different sedimentary archives therefore show a similar geomorphological signal while in some cases similar archives are related to different forcing the chronology of the processes is based on 22 optical stimulated luminescence osl ages obtained from coarse grained quartz or potassium feldspar the base of the alluvial fan formed during the late pleistocene but deposition of cover sediments on the fan only started at around 7 ka ago silty sediments form a thin cover on the uppermost terraces and have been available only during short timespans most of the sediments are sandy deposits which form an internal sediment cycle on the fan they developed throughout the holocene sandy deposits on the footslopes of the neighboring hills have been preserved since the pleistocene holocene transition thicker eolian deposits accumulated during the late holocene these sediments were washed into the donggi cona and formed sandy lake sediments which were susceptible to remobilization during lower lake levels in combination with drier climatic conditions during the late holocene these sediments formed small dunes on the fan sediments on the alluvial fan are highly active for which erosion and deposition vary in space and time the interaction of fluvial and eolian processes is an important part of this dynamic high mountain system

mollusca stable isotope record of a core from lake frassino northern italy hydrological and climatic changes during the last 14 ka a core retrieved from lake frassino northern italy provided evidence of palaeohydrological change in this area during the last 14 ka lithological malacological and in particular stable isotope composition of freshwater shells allowed the delineation of the main phases of lake evolution between the lateglacial and holocene lateglacial conditions were drier than the holocene although a wetter period was inferred before c 14 ka according to the oxygen isotope composition of freshwater shells the holocene showed a clear bipartition the first part which lasted from 9100 to 7000 yr bp was drier and was followed by a rapid increase in humidity at 7000 6800 yr bp between 6800 and 5000 yr bp there were wetter and more stable conditions as indicated by smaller 18 o oscillations of pisidium and valvata shells from c 5000 to 2600 yr bp the record is characterized by larger fluctuations which may indicate that short term and particularly pronounced alternation of wet and dry periods occurred

inverse phase oscillations between the east asian and indian ocean summer monsoons during the last 12 000 years and paleo el nino abstract the inverse phase variations between the east asian and indian ocean summer monsoons on the interannual timescale result from the el nino southern oscillation activity in the tropical pacific which potentially provides a new way for studying paleo enso here we reconstruct a 12 000 yr proxy record for the east asian summer monsoon from 13 c time series of the plant cellulose of the hani peat bog in the northeastern china the comparison of it with the peat proxy record of the indian ocean summer monsoon suggests that the el nino conditions are coincident with strong east asian summer monsoons weak indian summer monsoons and drift ice events in the north atlantic at both orbital and millennial time scales the orbital scale inverse phase relationships between the monsoons indicate the occurrence of a long term enso like pattern confirming the sensitivity of the monsoon systems associated with enso to insolation forcing the nine inverse phase variations on the millennial time scales may suggest the nine el nino like patterns superimposing the long term enso like pattern the inverse phase variations between the monsoons also show close correspondence to the drift ice events at high northern latitudes in every case when the abrupt ice rafted debris events occurred in the north atlantic the inverse phase relationship established and the el nino like pattern occurred in the tropical pacific correspondingly the discussions on the influence of ocean thermohaline circulation on these global linkages have been made

late quaternary transition from lacustrine to a fluvio lacustrine environment in the north western nam co tibetan plateau china abstract holocene sediments from a 9 m high outcrop at the gangyasang qu s entry into lake nam co on the south eastern tibetan plateau were studied in a multiproxy approach the lowermost part of the section is of early holocene age and consists of varved sediments deposited in a proglacial lake geomorphological investigations of fossil beach ridges and fossil cliff lines in the littoral zone of nam co indicate a late pleistocene lake level high of 29 m above the present level a warming is visible in ostracode rich silts deposited after 9 6 ka bp an ostracode based transfer function estimates a lake level 28 m higher than today from this time until about 5 2 ka bp a late pleistocene lake level high was accompanied by an increase in lake size causing nam co to overflow into the lower course of gangyasang qu where a bay with slack water conditions formed between 4 2 and 1 3 ka bp the lake level was approximately 10 m higher than today the progradation of the gangyasang qu delta into nam co and the decreasing lake level shifted the study site into a fluvio lacustrine environment the sandy character and relatively low numbers of ostracode valves in the topmost sediments indicate increased fluvial activity possibly due to a temporary increase in flood frequency this facies lasted at least until 1 3 ka bp when the lake level of nam co dropped again and the river incised more than 10 m into the underlying fluvio lacustrine and lacustrine sediments

radiometric approach for estimating relative changes in intraglacier average temperature we investigate the degree to which ultrahigh frequency radio emission can be used to estimate subsurface physical temperature in the polar ice sheets we combine electromagnetic emission forward models with plausible models of depth dependent physical properties in the ice sheet temperature models are parameterized with variables including accumulation rate geothermal heat flux and surface temperature scattering is parameterized using empirical observations of grain growth combined with measured densities electromagnetic absorption is modeled using dielectric dispersion processes and semiempirical models based on observations our models illustrate that information about east antarctic ice sheet temperature from near the surface to near the base can be gleaned from ultrawideband radiometer data based on our modeling study we illustrate an instrument concept to measure ice sheet temperature profiles comprising a novel ultrawideband radiometer

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

quaternary paleoenvironmental change on the tibetan plateau and adjacent areas western china and western mongolia abstract this paper summarises the nature of climatic change during the last glacial interglacial cycle on the tibetan plateau and adjacent areas the results are derived from inland glacier fluctuations lake level changes and dust loess records of central asia including tibet these are based on our field investigations from 1988 to 1998 and literature surveys the changing extents of different climatic controlled geomorphic landscapes and vegetation zones help to provide estimates of the magnitude of climatic change features such as ice wedge casts loess and palaeosols ela reconstruction s and palaeobotanical data are used to help reconstruct palaeoprecipitation and palaeotemperatures weathering characteristics the overlying strata and some luminescence dates indicate that there are two main glacial ice advances during the last glacial cycle these correspond to marine oxygen isotope stages ois 2 and 4 in some areas as the eastern or northern margin of the tibetan plateau remnants of older glaciations are preserved higher lake levels in the deserts of central asia and on the tibetan plateau are dated to 40 to 25 ka ois 3 and to late glacial early to mid holocene periods our work supports the view that in many areas of central asia cold phases during the last glacial correspond with the maximum extent of glaciers and the periglacial activity the last glaciation produced large alluvial fans alternating with periods of high lake stands on the tibetan plateau however at the northern margin of the plateau in the qaidam basin and in some particular desert areas in western china high lake levels occurred also during the pleistocene and are related with alluvial fans

les bossats ormesson paris basin france a new early gravettian bison processing camp abstract in the paris basin the gravettian techno complex is documented by a limited number of sites and radiocarbon dates are available for only three locations arcy sur cure grande grotte and grotte du renne yonne la pente des brosses montigny sur loing seine et marne and chamvres yonne this period of human prehistory is poorly known in the region the recently discovered open air site of les bossats at ormesson seine et marne includes an early gravettian occupation with well preserved faunal remains this allows for radiocarbon dating and provides information on the ecological context that was previously inaccessible located on the southern limit of the maximum extension of loess deposits ormesson also provides a well developed pleistocene sedimentary sequence the peculiar geomorphological context of the gravettian occupation opens new avenues of investigation regarding taphonomy and the possible anthropogenic intra site spatial organisation here we present the primary results of excavations that began in 2009 the strategic location of the site the richness of the lithic industry the presence of two well preserved hearths and associated maintenance features near which were found both perforated and non perforated shells as well as the few elements of bone technology all suggest that the site was occupied for a relatively long period of time flint nodules are primarily obtained from local sources and were used to produce blades and bladelets the tool kit is however dominated by blades likely used in butchering activities as well as armature and burin production the occupants of ormesson seem to have killed and butchered bison near site and imported the most nutritious parts portions of reindeer and horse were also imported the gravettian occupation at ormesson thus appears to have been a medium to short term multi purpose campsite likely occupied for the time it took to process imported bison carcasses

paleoenvironmental significance of compound specific δ13c variations in n alkanes in the hongyuan peat sequence from southwest china over the last 13 ka abstract compound specific 13c 12c ratios of the c23 c25 c27 c29 and c31 n alkanes in the hongyuan peat sequence from southwest china were measured to decipher paleoenvironmental information recorded in the 13c variations over the last 13 ka the 13c values of the n alkanes range between 35 4 and 30 5 falling within the range of those from modern c3 peat forming vegetation however the vertical trends do not match with those of the 13c value for the c3 peat forming plant cellulose such a discrepancy between the 13c profiles implies that the n alkane 13c values are unlikely to reflect signals from emerged aquatic plants in the bog because submerged floating aquatic plants are major contributors of mid chain c23 and c25 n alkanes in the sequence the decoupling between the c23 and c25 n alkanes and the peat cellulose likely reflects the situation that these mid chain homologues primarily record the isotopic signals of submerged floating aquatic plants the stratigraphic profile of 13c values of submerged floating aquatic plant n alkanes c23 and c25 reveals two prominent positive excursions 0 8 2 4 during the early to middle holocene the excursions coincide with peat accumulation maxima and stronger indian monsoon activity in southwest china indicating that the 13c variations in submerged floating aquatic plants are closely related to changes in bog primary productivity controlled by the asian monsoon activity