peat brgdgts based holocene temperature history of the altai mountains in arid central asia abstract due to their effects on snow ice melting in mountains and evaporation in basins temperature variations are an important influence on the hydrological cycle and water resources in arid central asia aca we present independently dated peat brgdgts based mbt mbt 5me records from an alpine sahara sand peatland ssp in the southern altai mountains in aca during the past 11 kyr the ssp mbt and mbt 5me profiles exhibit consistently increasing trends and they are significantly positively correlated using a global peat specific mbt 5me tempeature calibration the long term holocene warming trend indicated by the quantitative ssp mean annual temperature matpeat reconstruction is supported by the peat cellulose 13c summer temperature record from the ssp and by an independent peat cellulose 18o winter temperature record from a nearby site i e temporal validation the increasing trends are also evident in holocene peat mbt records from the hongyuan hy peatland in the ne tibetan plateau and in the shuizhuyang szy peatland in se china notably both the mbt data of the surface samples and the averaged mbt data of the holocene peat cores are consistent with the modern spatial temperature gradient at the ssp hy and szy i e spatial validation this evidence demonstrates the temperature significance of peat mbt mbt 5me records the long term holocene warming trend indicated by the ssp mbt mbt 5me records is supported by recently acquired holocene temperature records from the eurasian continent this trend is the opposite to the traditional viewpoint of a long term holocene cooling trend and it indicates that more effort is needed to obtain a reliable holocene temperature history

glacier fluctuations of muztagh ata and temperature changes during the late holocene in westernmost tibetan plateau based on glaciolacustrine sediment records late holocene glacier variations in westernmost tibetan plateau were studied based on the analysis of grain size magnetic susceptibility and elements from an 8 3 m long distal glaciolacustrine sediment core of kalakuli lake our results show that there are four glacier expansion episodes occurring in 4200 3700 calibrated years cal years b p 2950 2300 cal years b p 1700 1070 cal years b p and 570 100 cal years b p and four glacier retreat periods of 3700 2950 cal years b p 2300 1700 cal years b p 1070 570 cal years b p and 50 cal years b p present the four glacier expansion episodes are generally in agreement with the glacier activities indicted by the moraines at muztagh ata and kongur shan as well as with the late holocene ice rafting events in the north atlantic over the last 2000 years our reconstructed glacier variations are in temporal agreement with reconstructed temperature from china and the northern hemisphere indicating that glacier variations at centennial time scales are very sensitive to temperature in western tibetan plateau

grain size dependent geochemical characteristics of middle and upper pleistocene loess sequences from the junggar basin implications for the provenance of chinese eolian deposits abstract thick loess paleosol sequences are widely distributed in the arid inland basins of northwestern china the geochemical composition of these sediments provides important constraints on the provenance of chinese eolian deposits however grain size dependent geochemical characteristics of early middle pleistocene loess deposits from these arid inland basins have not been investigated the paucity of such studies hinders a full understanding of provenance changes of loess deposits from the chinese loess plateau clp in the present study we performed a detailed major trace and rare earth element analysis of multiple grain size fractions of middle pleistocene loess deposits from the dongwan section dw in the junggar basin we found that the major trace and rare earth element concentrations of the dw loess are grain size dependent with higher concentrations in the fine fraction in addition the 75 m from the dw section changed significantly at 0 5 ma which may have arisen from intensified physical erosion or increased wind speeds in the northern tianshan area

magnetic mineralogy of soils across the russian steppe climatic dependence of pedogenic magnetite formation formation of ferrimagnets in well drained buffered unpolluted soils appears to be related to climate and especially rainfall if robust this magnetism rainfall couple can be used to estimate past rainfall from buried soils particularly the multiple soils of the quaternary loess soil sequences of central asia however dispute exists regarding the role of climate vs dust flux for the magnetic properties of modern loessic soils here we examine the mineralogical basis of the magnetism rainfall link for a climate transect across the loess mantled russian steppe where critically dust accumulation is minimal at the present day magnetic and independent mineralogical analyses identify in situ formation of ferrimagnets in these grassland soils increased ferrimagnetic concentrations are associated with higher annual rainfall xrd and electron microscopy show the soil formed ferrimagnets are ultrafine grained 50 nm and pure ferrimagnetic contributions to ma ssbauer spectra range from 17 in the parent loess to 42 for a subsoil sample from the highest rainfall area total iron content varies little but the systematic magnetic increases are accompanied by decreased fe2 content reflecting increased silicate weathering for this region parent materials are loessial deposits topography is rolling to flat and duration of soil formation effectively constant the variations in soil magnetic properties thus predominantly reflect climate and its co variant organic activity statistical analysis identifies strongest relationships between rainfall and magnetic susceptibility and anhysteretic remanence this magnetic response correlates with that of the modern soils across the chinese loess plateau such correlation suggests that the rainfall component of the climate system not dust flux is a key influence on soil magnetic properties in both these regions

geochemical fluxes related to alteration of a subaerially exposed seamount nintoku seamount odp leg 197 site 1205 hole 1205a was drilled on nintoku seamount which lies in the midportion of the emperor seamount chain this seamount was emergent 56 myr ago but was submerged by 54 ma so the lavas have endured weathering in both subaerial and submarine environments we have studied the petrology mineralogy and geochemistry of intercalated altered basalts breccias and soil samples recovered at hole 1205a to quantify the chemical exchanges between the seamount and seawater and or meteoric fluids the secondary mineralogy is relatively uniform throughout the section and comprises smectite fe oxyhydroxides iddingsite and ca carbonates soils are composed of variably altered basaltic clasts in a matrix of kaolinite smectite and vermiculite with minor goethite hematite and magnetite throughout the basement section altered basalts breccias and soils are depleted in si mg ca na sr rb and ba and enriched in fe fe3 fet up to 1 18o up to 20 and 87sr 86sr ratios are strongly elevated relative to primary igneous values differences in the 87sr 86sr ratios define an upper alteration zone with 87sr 86sr close to 56 ma seawater 0 7077 from a lower alteration zone where 87sr 86sr are less elevated 0 704 the lower alteration zone likely reflects interaction with a subaerial oxidizing fluid at low temperature this zone probably retained most of the original subaerial weathering signature the upper alteration zone was altered through circulation of large quantities of cold oxidizing seawater that partially overprinted the subaerial weathering chemical characteristics altered samples were compared to estimated protolith compositions to calculate chemical gains and losses global chemical fluxes are calculated for the entire basement section using different lithological proportions models and different rates of oceanic island emplacement although the global construction rate of ocean islands is small compared to igneous accretion at mid ocean ridges the magnitude of the chemical changes indicates that ocean islands and seamounts may be a significant contributor to the chemical budget of the oceans

holocene temperature fluctuations in the northern tibetan plateau arid central asia aca lies on a major climatic boundary between the mid latitude westerlies and the northwestern limit of the asian summer monsoon yet only a few high quality reconstructions exist for its climate history here we calibrate a new organic geochemical proxy for lake temperature and present a 45 yr resolution temperature record from hurleg lake at the eastern margin of the aca in the northern tibetan plateau combination with other proxy data from the same samples reveals a distinct warm dry climate association throughout the record which contrasts with the warm wet association found in the asian monsoon region this indicates that the climatic boundary between the westerly and the monsoon regimes has remained roughly in the same place throughout the holocene at least near our study site six millennial scale cold events are found within the past 9000 yr which approximately coincide with previously documented events of northern high latitude cooling and tropical drought this suggests a connection between the north atlantic and tropical monsoon climate systems via the westerly circulation finally we also observe an increase in regional climate variability after the mid holocene which we relate to changes in vegetation forest cover in the monsoon region through a land surface albedo feedback

glacial activity reflected in a continuous lacustrine record since the early holocene from the proglacial laigu lake on the southeastern tibetan plateau abstract the southeastern tibetan plateau is an important area of monsoonal maritime glaciation and it serves as a watershed for several major asian rivers including the brahmaputra river and the lantsang river glacial activity is sensitive to climate change in this area however due to high annual ablation and accumulation in this region ice cores over long time scales are difficult to retrieve in addition reconstructed glacial activity from moraine dates is usually discontinuous here we use a sediment core retrieved from laigu lake which is a proglacial lake located in the headwaters of the parlung zangbo river the largest tributary of the brahmaputra river to reflect glacial activities over the last 8000 years in this area samples of the sediment core were analyzed for magnetic susceptibility xrf x ray florescence scanned elemental concentration and grain size the results indicated that the magnetic susceptibility and cps peak area counts per second of strontium sr could be used as proxies for glacial activity the cps of sr and the magnetic susceptibility were lower and the glacial activity was weak before 4 3 cal ka bp expansion of the glaciers in this area began from 4 3 cal ka bp and continued to develop after 3 3 cal ka bp from 2 2 cal ka bp to 1 6 cal ka bp the glaciers retreated substantially followed by another development period until the onset of modern global warming based on our findings and other climate records we concluded that glacial activity in the southeastern tibetan plateau areas was mainly influenced by northern hemisphere temperatures and summer insolation over a sub orbital time scale but did not respond to the indian monsoon

millennial scale hydroclimate variations in southwest china linked to tropical indian ocean since the last glacial maximum indian summer monsoon ism variations have been linked to the orbital scale boreal summer insolation and millennial scale north atlantic climates recent studies show the critical role of indian ocean sea surface temperatures ssts in affecting deglacial millennial scale monsoon oscillations however it is unclear whether ssts can affect monsoon rainfall and terrestrial hydroclimate during the holocene here we report multiproxy evidence of hydroclimate changes in southwest china since the last glacial maximum similar to the often documented gradual decrease in holocene monsoon rainfall with superimposed millennial scale variations our records particularly show pronounced hydroclimate fluctuations including wet conditions at 5000 4000 yr ago and perhaps over the past 1000 yr we also find coherent variations between our records and sea surface salinities in the eastern indian ocean suggesting that terrestrial hydroclimate and resultant continental drainage have affected surface ocean conditions these fluctuations are likely linked to changes in ssts downstream of the monsoon source in the tropical western indian ocean i e a warmer ocean and more monsoon rainfall we conclude that the influence of both insolation and tropical ssts on the ism has persisted from the last deglaciation into holocene

ti content in huguangyan maar lake sediment as a proxy for monsoon induced vegetation density in the holocene the provenance of element ti in huguangyan maar lake hgy sediment has been under debate since yancheva et al 2007a proposed its eolian source from the chinese loessplateau clp and applied it as a proxy for asian wintermonsoon we performed a comprehensive study on ti carryingminerals and ti uxes in lake sediments wall rocks andloess from the clp here we show that the chemicalcompositions and morphological features of magnetite the most important ti carrier in hgy surface sediments are identical to those in wall rocks around the lake butsubstantially different from those in clp loess samples ourcalculated modern eolian ti ux from the clp is negligiblecompared to the average total ti ux to hgy and ti uxfrom catchment erosion can provide enough ti indicating tiin hgy sediment are predominantly from wall rock erosion inverse correlation between total organic carbon toc vegetation density and ti ca ratio terrestrial input in theholocene suggests monsoon induced vegetation densitypredominates over runoff in controlling ti input to hgy s ratio represents toc directly mediated reductive diagenesisof iron oxides magnetite preservation rather than anoxic oxic condition at the bottom water induced by wintermonsoon our record shows a decreased vegetation density increased ti input and weakened reductive diagenesisthrough the holocene driven by a weakened summermonsoon

a 2700 year high resolution pollen record of climate change from varved sugan lake in the qaidam basin northeastern tibetan plateau abstract a 2700 year high resolution pollen record from annually varved sugan lake in the qaidam basin at 2793 m a s l was obtained to examine vegetation and climatic change on the ne tibetan plateau pollen data shows that sugan basin was constantly covered by open desert steppe vegetation dominated by chenopodiaceae artemisia poaceae and ephedra however large variations in artemisia chenopodiaceae a c ratios suggest regional moisture fluctuations over the last 2700 years including a dry and relatively stable climate prior to 300 ad relatively wet climate from 300 to 1200 ad with variability during 1100 1200 ad and unstable climate since 1200 ad with relatively moister climate during 1250 1400 ad and 1700 1800 ad however other proxies varve thickness chironomid taxa isotopes of oxygen in precipitated carbonate show fresher water when regional moisture was lower inferred from a c ratio this inconsistency suggests the possible difference of in lake lithology environment and regional moisture change fresh water into the lake from ice melting on the surrounding mountains might have contributed to the in lake lithology and environment variation the effective moisture changes in the basin are in opposite phases to snow accumulation records from dunde ice core 5325 m a s l and to the monsoon intensity inferred from dongge cave suggesting that the regional topography might have played an important role in mediating moisture changes at regional scale pollen data from sugan lake shows the shift of moisture at 1200 ad from stable to variable conditions this event is well correlated with other paleoclimate proxies in china and other parts of the world however the mechanisms behind these patterns require further investigation

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

radiometric ages for basement rocks from the emperor seamounts odp leg 197 1 the hawaiian emperor seamount chain is the type example of an age progressive hot spot generated intraplate volcanic lineament however our current knowledge of the age distribution within this province is based largely on radiometric ages determined several decades ago improvements in instrumentation sample preparation methods and new material obtained by recent drilling warrant a reexamination of the age relations among the older hawaiian volcanoes we report new age determinations 40ar 39ar incremental heating method on whole rocks and feldspar separates from detroit sites 1203 and 1204 nintoku site 1205 and koko site 1206 seamounts ocean drilling program odp leg 197 and meiji seamount deep sea drilling project dsdp leg 19 site 192 plateaus in incremental heating age spectra for site 1203 lava flows give a mean age of 75 8 0 6 2 ma which is consistent with the normal magnetic polarity directions observed and biostratigraphic age assignments site 1204 lavas produced discordant spectra indicating ar loss by reheating and k mobilization six plateau ages from lava flows at site 1205 give a mean age of 55 6 0 2 ma corresponding to chron 24r drilling at site 1206 intersected a n r n magnetic polarity sequence of lava flows from which six plateau ages give a mean age of 49 1 0 2 ma corresponding to the chron 21n 22r 22n sequence plateau ages from two feldspar separates and one lava from dsdp site 192 range from 34 to 41 ma significantly younger than the cretaceous age of overlying sediments which we relate to postcrystallization k mobilization combined with new dating results from suiko seamount dsdp site 433 and volcanoes near the prominent bend in the lineament sharp and clague 2002 the overall trend is increasing volcano age from south to north along the emperor seamounts consistent with the hot spot model however there appear to be important departures from the earlier modeled simple linear age progression which we relate to changes in pacific plate motion and the rate of southward motion of the hawaiian hot spot

low temperature alteration of the upper oceanic crust and the alkalinity budget of seawater abstract while the input of river alkalinity into seawater is relatively well known the complementary acidity production is poorly understood using the major element budget of seafloor alteration of the upper 500 m of 120 ma old oceanic crust at dsdp odp sites 417a 417d and 418a in the central western atlantic we estimate the acidity flux associated with the low temperature weathering of the upper oceanic crust the acidity flux is calculated based on major element fluxes and charge balance considerations the relevant chemical fluxes from seawater to the upper crust are 4 1 0 1 1 4 1 4 2 2 0 6 and 12 2 1011 mol yr 1 for k mg na and silicate ca respectively the associated acidity flux is 3 5 3 1011 eq yr 1 relative to continental weathering these fluxes are significant for k and silicate ca but are minor for na mg and acidity thus riverine fluxes of alkalinity are not significantly balanced by acidity fluxes from low temperature upper ocean crust alteration

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

holocene moisture and east asian summer monsoon evolution in the northeastern tibetan plateau recorded by lake qinghai and its environs a review of conflicting proxies abstract climatic and environmental changes in the northeastern tibetan plateau are controlled by the asian summer monsoon asm and the westerlies two key circulation components of the global climate system which directly affect a large human population and associated ecosystems in eastern asia during the past few decades a series of holocene palaeoclimatic records have been obtained from sediment cores from lake qinghai and from various other geological archives in the surrounding area of the northeastern tibetan plateau however because of uncertainties regarding the sediment chronologies and the climatic significance of the proxies used the nature of holocene climatic changes in the region remains unclear and even controversial here we review all major classes of the published data from drilled cores from lake qinghai as well as other evidence from lakes and aeolian deposits from surrounding areas in order to reconstruct changes in moisture patterns and possible summer monsoon evolution in the area during the holocene combining the results of moisture and precipitation proxies such as vegetation history pollen based precipitation reconstruction aeolian activity lake water depth lake level changes salinity and sediment redness we conclude that moisture and precipitation began to increase in the early holocene reached their maximum during the middle holocene and decreased during the late holocene similar to the pattern of the east asian summer monsoon easm in northern china it is clear that the region experienced a relatively dry climate and weak easm during the early holocene as indicated by relatively low tree pollen percentages and fluctuating pollen concentrations generally low lake levels of lake qinghai and the adjacent lake hurleg and lake toson in the qaidam basin and widely distributed aeolian sand deposition in the lake qinghai basin and the nearby gonghe basin to the south and in the eastern qaidam basin to the west we argue that the ostracod 18o record which is widely used as a proxy of effective moisture and summer monsoon intensity in lake sediments at least in lake qinghai and which exhibits light values in the early holocene and heavier values thereafter cannot be used to reflect the strength of the easm or the intensity of monsoon precipitation as is also the case for leaf wax 2h records rather we argue that as is the case of the chinese speleothem 18o record which also is often interpreted as an easm proxy it reflects variation in the 18o of precipitation overall we suggest that the easm significantly affected precipitation in the northeastern tibetan plateau during the holocene and that it increased in strength during the early holocene reached a maximum during the middle holocene and decreased during the late holocene

glacier mass variation and its effect on surface runoff in the beida river catchment during 1957 2013 using in situ measured data from qiyi glacier in combination with meteorological and runoff data from stations a distributed degree day model was developed for 631 investigated glaciers in the beida river catchment to explore glacier mass change and its effect on streamflow the results showed that the average mass balance was 272 67 mm w e a 1 with an ice loss of 3 99 gt during 1957 2013 assuming a continuous linear trend equilibrium line altitude rose by 242 m compared with morpho topographic variables climatic control is a more important factor affecting glacier change mass balance sensitivity to air temperature was 239 mm w e degrees c 1 a 1 while to precipitation it was 1 1 mm w e mm 1 a 1 that is a 210 mm increase in precipitation would be needed to compensate for the net mass loss induced by an air temperature increase of 1 degrees c average annual glacier meltwater runoff was 1 51 x 10 8 m 3 from 1957 to 2013 accounting for 15 2 of surface runoff the time series of meltwater runoff changed abruptly in 2000 and its contribution to surface runoff increased from 13 9 to 20 4

accretion of asian dust to hawaiian soils isotopic elemental and mineral mass balances hawaiian soils contain a mixture of material derived from in situ weathering of parent material plus atmospheric inputs including sea salt aerosols and asian dust we use soil mineralogy and radiogenic isotope geochemistry sr and nd to evaluate the impact of asian dust on a chronosequence of hawaiian soils dust becomes an important constituent of soils 20 ky and older near surface 50 cm depth horizons contain as much as 30 quartz a mineral absent from local parent material basaltic sr and nd isotope signatures in these horizons have been completely overprinted by asian dust signatures with 87sr 86sr ratios as high as 0 723 and end values as low as 7 ree patterns in these soils are indistinguishable from that of average upper continental crust quartz abundance and nd isotopes provide two independent tracers of long term dust additions to the chronosequence soils the two tracers indicate a minimum long term average dust accretion rate of 125 mg cm 2 ky 1 at the 150 ka chronosequence site roughly a factor of three higher than holocene dust accumulation rates estimated from north pacific sediment cores we find that the mass of dust preserved in these soil profiles does not increase with age in soils 150 ka and older requiring a loss mechanism for accreted dust on the basis of the geomorphic stability of these sites observed preferential loss of dust derived mica relative to quartz and estimates of soil si leaching rates we argue that chemical weathering is the dominant loss mechanism for dust from these soils dust has a profound effect on the budgets of elements that are susceptible to leaching losses dust becomes the dominant source of soil nutrients si and p in the oldest most intensely weathered soils we calculate a dust derived p input flux of 0 8 mg cm 2 ky 1 and a dust derived si input flux of 35 mg cm 2 ky 1 si leaching fluxes are high 1400 mg cm 2 ky 1 in the youngest 2 ka soils and drop systematically with soil age to a value that closely balances the dust derived si input flux by 4100 ka extremely refractory elements such as nb which are concentrated in soils by residual enrichment processes are much less readily impacted by dust addition although dust has had a pronounced impact on sr and nd isotopic budgets and on soil mineral composition at the 150 ka site dust cannot have contributed 4 of the total nb contained in this soil profile

glacial fluctuations over the last 3500 years reconstructed from a lake sediment record in the northern tibetan plateau abstract reconstructing glacial fluctuations can provide insights into glacial variations in response to climate change and can help predict future glacial changes in the context of global warming here we use an 2 yr resolution record of inert elements derived from a sediment core from tian e lake in the northern tibetan plateau together with proxies for magnetic susceptibility and n alkanes to reconstruct fluctuations of the qiyi glacier over the last 3500 years eight major glacial advances can be identified at 1450 1250 bce 1100 800 bce 250 100 bce and 200 300 ce 600 700 ce 1250 1350 ce 1600 1750 ce and 1850 1950 ce these glacial advances coincided with cold intervals such as the neoglaciation and the little ice age suggesting often mentioned temperature controls on glacial mass variations in the past moreover due to the wet cold climate combinations in the westerlies dominated areas these intervals can also be correlated with wet conditions as revealed by previously reported carbonate contents total organic carbon levels and artemisia amaranthaceae ratios from the same lake these results indicate that humid environments can also contribute to glacial advances in the northern tibetan plateau our study reveals a series of high magnitude multi decadal to multi centennial scale glacial fluctuations during the late holocene and suggests that wet conditions can also facilitate glacial advances in the westerlies dominated regions such as the northern tibetan plateau

possible orographic and solar controls of late holocene centennial scale moisture oscillations in the northeastern tibetan plateau 1 we present a record of lake level changes from hurleg lake a freshwater lake in the arid qaidam basin on the ne tibetan plateau an area with few high resolution paleoclimate records the carbonate percentage and ostracode abundance show a consistent pattern with 200 year moisture oscillations during the last 1000 years the moisture pattern in the qaidam basin is in opposite relation to tree ring based monsoon precipitations in the surrounding mountains suggesting that topography may be important in controlling regional moisture patterns as mediated by rising and subsiding air masses in this topographically complex region cross spectral analysis between our moisture proxies and solar activity proxy shows high coherence at the 200 year periodicity which is similar to chinese monsoon intensity records implying the possible solar forcing of moisture oscillations in the ne tibetan plateau

contribution of ice sheet and mountain glacier melt to recent sea level rise altimeter data suggest that sea level rose by about 2 4 mm per year from 2005 to 2011 but estimates of the relative contributions of ocean warming and increased ocean mass are equivocal an analysis of ocean temperature and satellite gravity data suggests that the delivery of meltwater from ice sheets and mountain glaciers contributed 75 of the observed sea level rise

general characteristics of temperature variation in china during the last two millennia three alternate china wide temperature composites covering the last 2000 years were established by combining multiple paleoclimate proxy records obtained from ice cores tree rings lake sediments and historical documents five periods of temperature variation can be identified a warm stage in ad 0 240 a cold interval between ad 240 and 800 a return to warm conditions from ad 800 1400 including the medieval warm period between ad 800 1100 the cool little ice age period between 1400 1920 and the present warm stage since 1920 regional temperature variation is found during ad 800 1100 when warm conditions occurred in eastern china and in the northeastern tibetan plateau and in ad 1150 1380 when the southern tibetan plateau experienced a warm interval in contrast evidence for cool conditions during the lia is more consistent among the proxy records the temperature reconstructions for china and the northern hemisphere show good agreement over the past millennium

indian summer monsoon variations and competing influences between hemispheres since 35 ka recorded in tengchongqinghai lake southwestern china abstract the southwestern yunnan province of china which is located at the southeastern margin of the tibetan plateau and close to bay of bengal is significantly influenced by the indian summer monsoon ism in this study we reconstruct proxies for the ism from 35 to 1 ka through detailed analysis of grain size distribution geochemical composition and environmental magnetism from a 7 96 m sediment core from tengchongqinghai lake yunnan province china globally recognized abrupt climatic events including heinrich events 0 3 h0 h3 and the bolling allerod b a warm period are identified in most of our proxies and the long term trend is consistent with other published records such as stalagmite oxygen isotopes 18o from sangxing cave northern hemisphere nh temperature which is influenced by nh solar insolation is commonly suggested to play a dominant role in controlling the ism a comparison of our record with the 18o variations of ice cores from greenland and antarctica a sea surface temperature sst record from the bay of bengal and summer solar insolation at 25 n latitude demonstrates that the general pattern of ism change does follow variations in summer insolation however the ism lags summer insolation by thousands of years while the ism fluctuations are highly correlated with nh temperature on shorter timescales centennial millennial the gradually weakened ism from 22 5 ka until the last glacial maximum lgm indicates a close relationship with the rise of southern hemisphere sh temperature and the relatively cold background of the sh our record expands on the findings of ism records from heqing paleolake basin in southwestern china and the arabian sea sediments suggesting that the nh and sh have a competitive influence on ism by controlling the cross equatorial pressure gradient this relationship means that when nh temperatures are relatively high it has a stronger influence on the ism than sh influences in contrast when the sh temperature is relatively low it has a dominant influence on ism in addition we speculate that the change of sh temperature not only influences the cross equatorial pressure gradient directly but also likely modulates the circulation system of ocean energy by influencing the atlantic meridional overturning circulation amoc

hydrothermal circulation through mid ocean ridge flanks fluxes of heat and magnesium thermally driven convection of seawater occurs through oceanic crust of all ages at the seafloor spreading axis on mid ocean ridge flanks and in the ocean basins at the ridge axis and on the flanks circulating seawater produces a major chemical exchange between the oceans and the crust based on heat budget constraints and the composition of hot springs between 10 and 40 of the river flux of mg can be taken up during high temperature alteration of the basaltic crust along the ridge axis most of the hydrothermal heat loss however occurs on the mid ocean ridge flanks where the temperatures are lower and the seawater flux correspondingly larger the estimated heat loss on the flanks is so large that upwelling must occur over a large fraction 5 30 of the seafloor less than 65 ma in age if temperatures are 20 c and seepage velocities are on the order of 10 to 100 cm y the circulating seawater needs to lose on average less than 1 2 of its mg content in order to solve the mg mass balance for the oceans chemical fluxes through mid ocean ridge flanks are poorly known because of the wide range of crustal conditions that prevail there and the paucity of study to date the most critical parameter for characterizing crustal conditions is temperature in basement which is a function of crustal age basement topography and sediment thickness and permeability basement temperature which can usually be inferred from heat flow and seismic reflection surveys largely determines the change in the composition of seawater circulating through basement this change can be inferred in turn from profiles of sediment porewater chemistry all sites studied to date with temperatures at the sediment basement interface 25 c have a large component of advective heat loss and show only a small 80 mg loss both types of sites may be important for chemical fluxes whether the cooler sites are important depends on how much the seawater changes in composition as it circulates through the crust only small changes are needed whether the warmer sites are important depends on how much heat is lost by advection in this type of setting the warmer sites could produce significant chemical fluxes even if they are scarce they could account for the entire river input of mg to the oceans even if they represent only 8 20 of the total advective heat loss on ridge flanks

the last glacial interglacial cycle at two sites in the chinese loess plateau mineral magnetic grain size and 10be measurements and estimates of palaeoprecipitation abstract to elucidate the way in which past climatic changes are encoded magnetically by wind blown silt we have investigated two stratigraphic sections in the chinese loess plateau xiagaoyuan in the cool dry western plateau and houzhuang in the warmer wetter central plateau in view of the anticipated importance of magnetic particle size we have determined grain size distributions from 50 m down to 10 nm by sequential sieving sedimentation and centrifugation of typical loess and palaeosol material from the two sites for the essentially unaltered loess the main susceptibility contribution lies in the 20 50 m fraction with only 20 of the signal residing in the 1 corresponding to oxygen isotope stage 5 at houzhuang and a peak value of 4 8 10 8 atoms g was observed almost identical to that found by other workers for the same horizon at luochuan a similar profile at xiagaoyuan reveals three peaks corresponding to palaeosols s 1 s 1 2 6 10 8 atoms g s 1 s 2 3 3 10 8 atoms g and s 1 s 3 3 3 10 8 atoms g conversion of these concentrations into 10 be fluxes indicates low dust accumulation during warmer climate episodes at these times pedogenic susceptibility enhancement is favoured the amounts of which imply palaeoprecipitation slightly higher than today for s 1 s 3 at xiagaoyuan but somewhat lower than today for s 1 at houzhuang

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