the sensitivity of the late saalian 140 ka and lgm 21 ka eurasian ice sheets to sea surface conditions this work focuses on the late saalian 140 ka eurasian ice sheets surface mass balance smb sensitivity to changes in sea surface temperatures sst an atmospheric general circulation model agcm forced with two preexisting last glacial maximum lgm 21 ka sst reconstructions is used to compute climate at 140 and 21 ka reference glaciation contrary to the lgm the ablation almost stopped at 140 ka due to the climatic cooling effect from the large ice sheet topography late saalian sst are simulated using an agcm coupled with a mixed layer ocean compared to the lgm these 140 ka sst show an inter hemispheric asymmetry caused by the larger ice albedo feedback cooling climate the resulting late saalian ice sheet smb is smaller due to the extensive simulated sea ice reducing the precipitation in conclusion sst are important for the stability and growth of the late saalian eurasian ice sheet

assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures though many studies on the mg contents in the calcitic tests of foraminifers exist the processes controlling its uptake are still a matter of debate laboratory cultures offer an excellent opportunity to reveal these mechanisms the mg concentrations within single chambers of the planktic foraminifer globigerinoides sacculifer brady maintained under controlled laboratory conditions were measured 1 at variable temperatures 19 5 29 5 c and constant salinity and 2 at variable salinity 22 45 and constant temperature the experimental results suggest that under natural conditions temperature is the leading mechanism controlling the mg ca ratio temperature and magnesium are related proportionally a temperature increase of ca 10 c gives rise to an increase of the magnesium concentrations of ca 130 drastic unnatural salinity changes dominate the effects of temperature a 110 change in the mg ca ratio was observed when salinity was elevated or reduced by more than ca 10 specimens which underwent gametogenesis reveal significantly higher mg concentrations than specimens that did not release gametes partition coefficients for mg in foraminiferal calcite are orders of magnitude lower than values from inorganically precipitated calcite when comparing observed mg ca ratios of foraminiferal tests with predicted mg ca ratios calculated according to empirical equations it becomes evident that foraminiferal tests are undersaturated with respect to mg for the water temperature they have experienced apparently foraminifers are capable of controlling their mg concentration the physiological processes presumably responsible for such depressed mg ca ratios appear to be temperature controlled as deduced from the close relationship of the observed mg ca ratios and water temperature this study demonstrates that variations in temperature and salinity are definitely reflected in the mg content of foraminiferal tests magnesium may thus serve as a paleo proxy for past surface water temperatures as long as postdepositional changes and salinity variations are of subordinate importance or can be excluded

modern distribution patterns of planktonic foraminifera in the south china sea and western pacific a new transfer technique to estimate regional sea surface temperatures abstract we present 30 new planktonic foraminiferal census data of surface sediment samples from the south china sea recovered between 630 and 2883 m water depth these new data together with the 131 earlier published data sets from the western pacific are used for calibrating the simmax 28 transfer function to estimate past sea surface temperatures this regional simmax method offers a slightly better understanding of the marginal sea conditions of the south china sea than the linear transfer function fp 12e which is based only on open ocean data however both methods are biased toward the tropical temperature regime because of the very limited data from temperate to subpolar regions the simmax formula was applied to sediment core 17940 from the northeastern south china sea with sedimentation rates of 20 80 cm ka results revealed nearly unchanged summer temperatures around 28 c for the last 30 ky while winter temperatures varied between 19 5 c in the last glacial maximum and 26 c during the holocene during termination 1a the winter estimates show a younger dryas cooling by 3 c subsequent to a temperature optimum of 24 c during the bolling allerod estimates of winter temperature differences between 0 and 100 m water depth document the seasonal variations in the thickness of the mixed layer and provide a new proxy for estimating past changes in the strength of the winter monsoon

intertropical latitudes and precessional and half precessional cycles a mcintyre and b molfino in their report about the forcing of atlantic equatorial and subpolar millennial cycles by precession suggest that climatic changes in high polar latitudes which are related to heinrich iceberg surges may be caused by events that occur in low latitudes 1 1 this

a study of cleaning procedures used for foraminiferal mg ca paleothermometry the various cleaning steps required for preparation of foraminiferal samples for mg ca and sr ca analysis are evaluated for their relative importance and effects on measured elemental ratios it is shown that the removal of silicate contamination is the most important step for the measurement of mg ca ratios in an example bulk sample mg ca decreases from 10 5 to 2 5 mmol mol 1 during clay removal oxidation of organic material causes a lowering of sample mg ca in the order of 10 or approximately 1 c when converted to temperature use of dilute acid leaching to remove adsorbed contaminants causes partial dissolution of the sample carbonate and a corresponding decrease in mg ca reductive treatment also causes dissolution of the sample and a decrease in the mg ca ratio of up to 10 15 sample preparation for sr ca analysis does not require the same degree of rigor as is necessary for mg ca work the within run reproducibility of the method described here for g ruber in a core top sample from the arabian sea was 1 8 mean sample ratio was 4 72 mmol mol 1 when converted to temperature this becomes 28 0 2 c the equivalent result for sr ca was 0 5 mean ratio 1 44 mmol mol 1

deep sea records of the continental weathering and erosion response to east asian monsoon intensification since 14 ka in the south china sea we analyzed sediment from ocean drilling program odp site 1144 in the northern south china sea to examine the weathering response of se asia to the strengthening of the east asian monsoon eam since 14 ka our high resolution record highlights the decoupling between continental chemical weathering physical erosion and summer monsoon intensity mass accumulation rates ti ca k rb hematite goethite and sr 87 sr 86 show sharp excursions from 11 to 8 ka peaking at 10 ka clay minerals show a shorter lived response with a higher kaolinite illite chlorite ratio at 10 7 9 5 ka however not all proxies show a clear response to environmental changes magnetic susceptibility rises sharply between 12 and 11 ka grain size becomes finer from 14 to 10 ka and then coarsens until similar to 7 ka but is probably controlled by bottom current flow and sealevel sr and nd isotopes show that material is dominantly eroded from taiwan with a lesser flux from luzon while clay mineralogy suggests that the primary sources during the early holocene were reworked via the shelf in the taiwan strait rather than directly from taiwan erosion was enhanced during monsoon strengthening and caused reworking of chemically weathered pleistocene sediment largely from the now flooded taiwan strait which was transgressed by similar to 8 ka cutting off supply to the deep water slope none of the proxies shows an erosional response lasting until similar to 6 ka when speleothem oxygen isotope records indicate the start of monsoon weakening although more weathered sediments were deposited from 11 to 8 ka when the monsoon was strong these are reworked and represent more weathering during the last glacial maximum lgm when the summer monsoon was weaker but the shelves were exposed c 2012 elsevier b v all rights reserved

patterns of deglacial warming in the pacific ocean a review with emphasis on the time interval of heinrich event 1 abstract based on a compilation of currently available records of past sea surface temperature sst variability estimated from a variety of different proxies the regional scale deglacial sst development in the pacific ocean is tentatively classified into four endmember types the subtropical and tropical pacific is characterized by a continuous deglacial warming without marked interruption during the time interval of heinrich event 1 h1 whereas the subarctic north pacific exhibits centennial scale warm cold oscillations during this time interval sst records from marginal seas of the pacific show a deglacial warming interrupted by a cooling event coeval with h1 followed by a marked bolling sst increase a single sst record from the southwestern subantarctic pacific displays a continuous deglacial warming across h1 followed by an antarctic cold reversal type cooling during the allerod thus in contrast to the deglacial sst development in the atlantic which has been inferred to be overwhelmingly driven by the redistribution of heat through changes in the meridional overturning circulation moc none of the open oceanic pacific sst records reviewed here displays any obvious and or dominant response to the reduction of the moc and or the reorganization of atmospheric circulation during h1 within the limits of absolute chronologies all tropical and subtropical pacific sst records show an onset of deglacial warming at 19 1 ka coeval with the onset of the deglacial rise in sea level

sea surface temperature history of the low latitude western pacific during the last 5 3 million years abstract the late neogene was a time of cryosphere development in the northern hemisphere the present study was carried out to estimate the sea surface temperature sst change during this period based on the quantitative planktonic foraminiferal data of 8 dsdp sites in the western pacific target factor analysis has been applied to the conventional transfer function approach to overcome the no analog conditions caused by evolutionary faunal changes by applying this technique through a combination of time slice and time series studies the sst history of the last 5 3 ma has been reconstructed for the low latitude western pacific although the present data set is close to the statistical limits of factor analysis the clear presence of sensible variations in individual sst time series suggests the feasibility and reliability of this method in paleoceanographic studies the estimated sst curves display the general trend of the temperature fluctuations and reveal three major cool periods in the late neogene i e the early pliocene 4 7 3 5 ma the late pliocene 3 1 2 7 ma and the latest pliocene to early pleistocene 2 2 1 0 ma cool events are reflected in the increase of seasonality and meridional sst gradient in the subtropical area the latest pliocene to early pleistocene cooling is most important in the late neogene climatic evolution it differs from the previous cool events in its irreversible steplike change in sst which established the glacial climate characteristic of the late pleistocene the winter and summer sst decreased by 3 3 5 4 c and 1 0 2 1 c in the subtropics by 0 9 c and 0 6 c in the equatorial region and showed little or no cooling in the tropics moreover this cooling event occurred as a gradual sst decrease during 2 2 1 0 ma at the warmer subtropical sites while that at cooler subtropical site was an abrupt sst drop at 2 2 ma in contrast equatorial and tropical western pacific experienced only minor sst change in the entire late neogene in general subtropics was much more sensitive to climatic forcing than tropics and the cooling events were most extensive in the cooler subtropics the early pliocene cool periods can be correlated to the antarctic ice volume fluctuation and the latest pliocene early pleistocene cooling reflects the climatic evolution during the cryosphere development of the northern hemisphere

bayesian hierarchical regression analysis of variations in sea surface temperature change over the past million years statistical challenges often preclude comparisons among different sea surface temperature sst reconstructions over the past million years inadequate consideration of uncertainty can result in misinterpretation overconfidence and biased conclusions here i apply bayesian hierarchical regressions to analyze local sst responsiveness to climate changes for 54 sst reconstructions from across the globe over the past million years i develop methods to account for multiple sources of uncertainty including the quantification of uncertainty introduced from absolute dating into inter record comparisons the estimates of local sst responsiveness explain 64 62 to 77 95 interval of the total variation within each sst reconstruction with a single number there is remarkable agreement between sst proxy methods with the exception of mg ca proxy methods estimating muted responses at high latitudes the indian ocean exhibits a muted response in comparison to other oceans i find a stable estimate of the proposed universal curve of change in local sst responsiveness to climate changes as a function of sin2 latitude over the past 400 000 years sst change at 45 n s is larger than the average tropical response by a factor of 1 9 1 5 to 2 6 95 interval and explains 50 35 to 58 95 interval of the total variation between each sst reconstruction these uncertainty and statistical methods are well suited for application across paleoclimate and environmental data series inter comparisons

archaeal tetraether lipids record subsurface water temperature in the south china sea abstract the south china sea scs is the largest tropical marginal sea in the western pacific ocean while the u 37 k proxy is known to reflect the sea surface temperature sst of the 0 30 m mixed layer in the scs little is known about the applicability of the tex86 proxy here we present results from paired analyses of tex 86 h a modified version of tex86 and u 37 k from core top sediment samples from the scs tex 86 h based sst calculated from the global regression exhibited slightly higher values avg 28 7 c range 27 1 30 3 c than values from the world ocean atlas 1994 avg 27 4 c range 26 1 28 6 c and u 37 k based temperature values avg 27 3 c range 26 1 29 0 c moreover the linear relationship between tex 86 h and sst was poor r2 0 44 correlation analysis of tex 86 h with annual temperature and seasonal temperature at various depths revealed that tex 86 h correlated better with annual sea temperature at 30 125 m r 0 89 than with temperature in the 0 30 m mixed layer r 0 69 this suggests that tex 86 h reflects a deeper and cooler subsurface temperature rather than surface or mixed layer temperature in the scs as a result the global regression which results in higher sst values could not be applied to predict subsurface temperature in the scs and a local calibration of tex 86 h vs 30 125 m subsurface temperature was tentatively established furthermore the difference between u 37 k and tex 86 h derived temperature talkenone gdgt correlated moderately r 0 62 with the depth of the thermocline of the 18 c isotherm in the scs suggesting that the difference may provide a proxy for upper ocean vertical thermal gradient in this marginal sea

the ti al molar ratio as a new proxy for tracing sediment transportation processes and its application in aeolian events and sea level change in east asia abstract ti al molar ratios of sediments in various sedimentary environments are used to explain sediment transportation from source regions to sink areas samples were collected from outcrops soils fluvial lake and marine sediment environments initial ti al molar ratios of sediments are controlled by those of parent soils or rocks these ratios tend to decline gradually as a result of heavy mineral gravity fractionation during transportation sedimentary ti al molar ratios in sink areas such as lakes and pelagic environments are lower than those in source regions in this study for the changjiang river huanghe river and kaoping river ti al molar ratios decline considerably from downstream to estuary environments additionally well sorted aeolian sands have extremely low ti al molar ratios in northern china the ti al molar ratios of aerosol particles found in taiwan and the east china sea show reduced ratios as a result of asia dust storm episodes furthermore lower ti al molar ratios in deep ocean sediments were discovered by tracing the distribution of sedimentary ti al molar ratios in the south china sea when sea levels dropped during glacial periods the river estuary was closer to deep marine areas and carried more terrestrial sediments into deep marine environments the closer estuary with relatively higher ti al ratio would lead increase of ti al molar ratios in deep sea sediments in this study ti al molar ratio is promoted as a new proxy to help with understanding changes in sedimentary environments

paleosecular variations of the geomagnetic field during the holocene from eastern asia abstract high resolution paleomagnetic secular variation psv records bear great information of dynamics processes of the earth s geomagnetic field and can be further used for inter profile correlation and for dating sediments however effects of changes in the depositional environment on psv records have not been fully determined this study constructed holocene psv records for the gravity piston core zsqd34 obtained from the northern south china sea rock magnetic and transmission electron microscope tem results indicate that single sd and psd domain magnetites are the main carrier of the natural remanent magnetization comparable to the records derived from the freshwater lakes and the modeling results we observed that direction curves from these two environments of contrasting salinity content are rather consistent the direction curves are independent of the constructed salinity however the gradual increasing trend of relative intensity since about 5 kyr might be related to the decreasing sea surface salinity furthermore on the centennial and millennial time scale the relative intensity and salinity show some positive relation suggesting a potential contribution of salinity to the paleomagnetic relative intensity recording processes

marine palynological record for tropical climate variations since the late last glacial maximum in the northern south china sea the upper part 191 1439 cm of the marine sediment core md05 2906 from the northern south china sea scs was palynologically investigated the chronology suggested that it covered the record since 19 calendar kiloyears before present cal ka bp and revealed a detailed environmental change history since the late last glacial maximum lgm during the late lgm due to the lowered sea level 100 m lower and the shortened distance from the shore to the study site the pollen concentration was very high the pollen assemblages were dominated by non arboreal taxa especially artemisia pollen before 15 cal ka bp abundant subtropical and tropical pollen taxa were still important components and a south subtropical climate prevailed during the late lgm the coexistent rich artemisia pollen possibly was not derived from near shores but was derived mainly from the northern exposed continental shelf in the east china sea ecs after 15 cal ka bp with the rise in the sea level and enhanced distance from the pollen source areas to the core site pollen concentrations started to decline gradually however during the late deglaciation and early holocene the higher concentrations of many pollen taxa reoccurred which cannot be attributed to the sea level changes pinus pollen deposited in the core which is considered to be mostly water carried based on many modern pollen surveys also started to dramatically increase at the same time therefore the higher pollen concentration with more pinus and typha an aquatic plant pollen indicated a notably enhanced terrestrial runoff and precipitation during the last deglaciation holocene transition 11 3 9 4 cal ka bp we inferred that a strong summer monsoon occurred at this time during the late lgm deglaciation transition period the pollen assemblage reflected a gradually warming climate and the climate fluctuations derived from the high latitudes were not well identified this study suggests that solar insolation played a crucial role in controlling the east asian monsoon and hydrological cycle in the northern scs

forcing of atlantic equatorial and subpolar millennial cycles by precession abundance cycles of the marine alga florisphaera profunda centered on a period of 7600 carbon 14 years 8400 calendar years are present in high resolution records from the equatorial atlantic spanning 0 to 45 000 years ago these cycles correlate with heinrich events 1 through 5 which document rapid changes in continental ice melting around the subpolar north atlantic these variations in f profunda are a direct response to modulation in zonal wind driven divergence produced by a precessional component of orbital variation during a time of reduced eccentricity modulation

mg ca ratios of two globigerinoides ruber white morphotypes implications for reconstructing past tropical subtropical surface water conditions 1 tests of the planktonic foraminifer globigerinoides ruber white d orbigny have become a standard tool for reconstructing past oceanic environments paleoceanographers often utilize the mg ca ratios of the foraminiferal tests for reconstructing low latitude ocean glacial interglacial changes in sea surface temperatures sst we report herein a comparison of mg ca measurements on sample pairs n 20 of two g ruber white morphotypes g ruber sensu stricto s s and g ruber sensu lato s l from surface and downcore samples of the western pacific and indian oceans g ruber s s refers to specimens with spherical chambers sitting symmetrically over previous sutures with a wide high arched aperture whereas g ruber s l refers to a more compact test with a diminutive final chamber and small aperture the g ruber s s specimens generally show significantly higher mg ca ratios compared to g ruber s l our results from the mg ca ratio analysis suggest that g ruber s l specimens precipitated their shells in slightly colder surface waters than g ruber s s specimens this conclusion is supported by the differences in 18o and 13c values between the two morphotypes although it is still unclear if these two morphotypes represent phenotypic variants or sibling species our findings seem to support the hypothesis of depth and or seasonal allopatry within a single morphospecies

high resolution uk 37 temperature reconstructions in the south china sea over the past 220 kyr past sea surface temperatures sst in the northern and southern areas of the south china sea have been reconstructed for the past 220 kyr using the uk37 alkenone index the sst profiles follow the glacial interglacial pattern exhibiting differences between last glacial maximum and holocene that are 1 3 c larger than those observed at the same latitudes in the atlantic and pacific oceans in termination i both planktonic foraminiferal 18o and sst exhibit well defined bolling allerod and younger dryas events with temperature differences between both periods of 0 8 and 0 4 c in north and south respectively ssts record a constant north south difference of 1 c in the interglacials and nearly 2 5 c in the glacial stages these differences define two distinct climatic and water circulation patterns that correspond with glacial interglacial sea level oscillations which opened and closed water exchange with the tropical indo pacific ocean through the present sunda shelf

accurate estimation of sea surface temperatures using dissolution corrected calibrations for mg ca paleothermometry 1 paired 18o and mg ca measurements on the same foraminiferal shells offer the ability to independently estimate sea surface temperature sst changes and assess their temporal relationship to the growth and decay of continental ice sheets the accuracy of this method is confounded however by the absence of a quantitative method to correct mg ca records for alteration by dissolution here we describe dissolution corrected calibrations for mg ca paleothermometry in which the preexponent constant is a function of size normalized shell weight 1 for g ruber 212 300 m mg ca ruber 0 025 wt 0 11 e0 095t and b for g sacculifer 355 425 m mg ca sacc 0 0032 wt 0 181 e0 095t the new calibrations improve the accuracy of sst estimates and are globally applicable with this correction eastern equatorial atlantic sst during the last glacial maximum is estimated to be 2 9 0 4 c colder than today

paleo sea surface temperature calculations in the equatorial east atlantic from mg ca ratios in planktic foraminifera a comparison to sea surface temperature estimates from u37k oxygen isotopes and foraminiferal transfer function we present two 270 kyr paleo sea surface temperature sst records from the equatorial divergence and the south equatorial current derived from mg ca ratios in the planktic foraminifer globigerinoides sacculifer the present study suggests that the magnesium signature of g sacculifer provides a seasonal sst estimate from the upper 50 m of the water column generated during upwelling in austral low latitude fall winter common to both down core records is a glacial interglacial amplitude of 3 3 5 c for the last climatic changes and lower holocene and glacial oxygen isotope stage 2 temperatures compared with interglacial stage 5 5 and glacial stage 6 temperatures respectively the comparison to published sst estimates from alkenones oxygen isotopes and foraminiferal transfer function from the same core material pinpoints discrepancies and conformities between methods

temporal and spatial variabilities of the south china sea surface temperature anomaly in this study we use the national centers for environmental prediction ncep monthly sea surface temperature sst fields 1982 1994 to investigate the temporal and spatial wriabilities of the south china sea scs warm cool anomalies three steps of analysis were performed on the data set ensemble mean t composite analysis to obtain the monthly mean anomaly relative to the ensemble mean t and empirical orthogonal function eof analysis on the residue data relative to t t the ensemble mean sst field t has a rather weak horizontal gradient 29oc near the borneo cost to 25o 26oc near the southeast chincoast two areas of evident sst anomalies were found in the monthly t variation west of borneo palawan islands wbp and southeast of the southern vietnam coast svc four patterns monsoon and transition each with two out of phase structures were found during the spring to summer transition march to may the warm anomaly is formed in the northern scs with t 1 8oc located at 112o 119o30 e 15o 19o30 n during the fml to winter transition october to november the northern scs north of 12on cool anomaly is formed in november with t 0 6oc located at 108o 115oe 13o 20on we performed an eof analysis on the residue data relative to t t in order to obtain transient and interannual variations of the sst fields eof1 accounts for 47 of the variance and represents the northern scs warm cool anomaly pattern eof2 accounts for 14 of the variance and represents the southern scs dipole pattern strong northern scs wrmnommy ioc wrmer ppers during october november 1987 nd jnury february 1988 and strong northern scs cool anomaly ioc cooler occurs during march 1986 and november 1992 furthermore strong cross correlation between wind stress curl and sst anomalies computed from the european centre for medium range weather forecast analyzed wind stress data and the n cep sst data for different lags shows the existence of an air sea feedback mechanism in the scs deep basin

rapid analysis of high precision sr ca ratios in corals and other marine carbonates a method for rapid determination of high precision sr ca ratios in scleractinian corals is presented using an inductively coupled plasma atomic emission spectrophotometer samples are corrected for instrument drift using a reference solution similar to the approach used for analysis of stable isotopes using gas source mass spectrometry further correction for variation of the sr ca ratio with ca concentration is accomplished using internal standards the precision once all corrections have been made is better than 0 1 relative standard deviation 1 for samples of similar ca concentration and better than 0 2 for samples with variable ca concentrations this method increases the sample throughput by approximately a factor of 20 relative to thermal ionization mass spectrometry and significantly reduces instrument and per sample costs comparison of sr ca data for a coral from the galapagos islands with an instrumental temperature record shows excellent agreement and demonstrates the potential for application of this technique to samples of modern and fossil scleractinian corals and other marine carbonates including foraminifera

paleoclimate history of galapagos surface waters over the last 135 000 yr abstract records of planktonic and benthic foraminiferal 18 o and planktonic mg ca from core tr163 22 just northwest of the galapagos islands reveal a detailed 250 450 year resolution climate history of the region over the last 135 thousand years kyr sea surface temperatures ssts reconstructed from g ruber mg ca averaged 24 3 0 4 c during the holocene 22 6 0 6 c during marine isotope stage mis 2 3 and 4 and 26 0 0 9 c during mis 5e changes in sst lead changes in both planktonic and benthic 18 o by an average 3 kyr suggesting that sst changes in this region predated continental ice volume changes changes in sst display clear millennial scale variability especially in marine isotope stage 3 with behavior somewhat similar to antarctic proxy air temperature and south pacific sst records removal of the temperature component from the planktonic 18 o record demonstrates that glacial interglacial 18 o water changes at this site were 1 0 0 2 similar to estimates for mean ocean shifts implying that salinity changes due to regional hydrological variation between the last glacial maximum and holocene in the galapagos region were minimal comparison between the tr163 22 sst record and an sst record from core tr163 19 north of the equatorial front reveals a largely similar broad scale climate history suggesting that changes in the galapagos region were caused by large scale forcing rather than by local or regional dynamical changes changes in atmospheric greenhouse forcing are the most plausible explanation for the observed large scale climate changes in the eastern equatorial pacific

astronomical forcing of terrestrial climate recorded in the pleistocene of the western tarim basin nw china abstract astronomically forced variations of climate are well documented in lacustrine and marine settings however few studies have examined astronomical forced cycles within quaternary fluvial fan successions to explore whether milankovitch cyclicity might also be present in fluvial fan successions we carried out high resolution gamma ray gr from downhole logging magnetic susceptibility ms rb sr and total organic carbon toc analysis of a core from an 800 m borehole kt11 from the kashgar region in the western tarim basin china spectral analyses of the gr ms and rb sr data reveal cycles with 70 m 30 m and 14 m wavelengths these pertain to relative variations in grain size electron spin resonance esr dating and magnetostratigraphy imply that the cored interval spans the past 1 1 myr this age span constraint coupled with the comparison of the ratios of these cycle wavelengths to expected ratios of milankovitch frequencies suggests that these cycles represent 100 kyr short eccentricity 40 kyr obliquity and 20 kyr precession frequencies respectively we constructed an astronomical time scale ats spanning the past 1 13 myr using the 100 kyr short eccentricity period the average accumulation rate is about 70 cm kyr for this 800 m core succession and the evolutive spectrum emphasizes that long term sedimentation rates were stable we also applied correlation coefficient coco analysis to identify the astronomical forcing thus we conclude that orbitally forced climate change was the main driver of stratigraphic alternations between sand and clay rich intervals in the kashgar region during maxima of the 100 kyr short eccentricity cycles which correspond to interglacial intervals more chemical weathering and increased seasonal runoff delivered a larger amount of relatively coarser grained sediments to the fluvial fan in the kashgar region and vice versa the mid pleistocene transition mpt at ca 0 9 to 0 65 ma is also well recorded in our gr and rb sr data and is characterized by a shift in dominant cycle period from 41 kyr obliquity to 100 kyr eccentricity after 0 65 ma the average toc content decreases whilst rb sr values increase which suggests that there was an increase in regional aridity of the kashgar region in the western tarim basin following the mpt this regional change is synchronous with the trend toward aridification observed throughout central asia

amplitude and timing of sea surface temperature change in the northern south china sea dynamic link to the east asian monsoon magnesium calcium mg ca ratios of foraminiferal shells from a sediment core from the northern south china sea a semi enclosed basin in the western tropical pacific document variations in sea surface temperature sst during the past 145 k y glacial ssts were 4 c colder than interglacial ssts during the last deglaciation most of the warming was accomplished in a single abrupt step after continental ice sheet decay had already begun but warming and ice sheet demise were nearly synchronous during the penultimate deglaciation abrupt sst changes of the past 15 k y were apparently synchronous with events in east asian monsoon rainfall suggesting that variations in monsoon winds and their influence on surface circulation of the western pacific exerted a strong control on northern south china sea ssts we suggest that this link persisted for the previous 130 k y during which time orbital scale 2 3 c sst changes and several small 2 c abrupt sst events occurred in the northern south china sea the similar timing of northern south china sea sst on a benthic 1 8 o time scale to a well dated speleothem record from eastern china suggests that the demise of ice sheets associated with the penultimate deglaciation did not precede northern hemisphere summer insolation increase our results suggest that surface waters had higher 1 8 o values during times of strong summer monsoon than during times of weak monsoon likely reflecting a redistribution of 1 8 o depleted rainfall from land during times of strong summer monsoons to the western pacific during times of weaker summer monsoons

distributions of branched gdgts in soils and lake sediments from western uganda implications for a lacustrine paleothermometer bacterially produced branched glycerol dialkyl glycerol tetraethers gdgts are ubiquitous in soils and lake sediments and can potentially be used to reconstruct past temperatures in lakes however it is still unclear if these compounds are derived from eroded soils or if they are produced in situ to better understand environmental controls on the distributions of these compounds and the sources of branched gdgts to lake sediments we compare branched gdgt distributions and concentrations in lake sediments and catchment soils within a 3600 m altitudinal transect in western uganda reconstructed mean annual air temperature maat determined from the degree of methylation mbt and cyclisation cbt of branched gdgts in soils decreases with increasing altitude as is expected from the air temperature gradient in our transect however we observe significant offsets between observed and reconstructed temperatures in soils from wet high elevation soils but not in most dry low elevation soils branched gdgt distributions differ significantly between lake sediments and soils at all elevations with greater differences at low elevations than at high elevations these data support previous hypotheses that branched gdgts are produced in situ in lakes and suggest that the abundance of water in soil environments may play a role in controlling the distribution of branched gdgts while branched gdgts in lacustrine sediments can be used to reconstruct temporal temperature variations in lakes we urge caution in utilizing this proxy in lacustrine systems with high soil loadings especially if there is evidence of changing clastic fluxes through time

incorporation and preservation of mg in globigerinoides sacculifer implications for reconstructing the temperature and 18o 16o of seawater using bathymetric transects of surface sediments underlying similar sea surface temperatures but exposed to increasing dissolution we examined the processes which affect the relationship between foraminiferal mg ca and 18o we found that globigerinoides saccculifer calcifies over a relatively large range of water depth and that this is apparent in their mg content on the seafloor foraminiferal mg ca is substantially altered by dissolution with the degree of alteration increasing with water depth selective dissolution of the chamber calcite formed in surface waters shifts the shell s bulk mg ca and 18o toward the chemistries of the secondary crust acquired in colder thermocline waters the magnitude of this shift depends on both the range of temperatures over which the shell calcified and the degree to which it is subsequently dissolved in spite of this shift the initial relationship between mg ca and 18o determined by their temperature dependence is maintained we conclude that paired measurements of 18o and mg ca can be used for reconstructing 18owater though care must be taken to determine where in the water column the reconstruction applies

past methane release events and environmental conditions at the upper continental slope of the south china sea constraints by seep carbonates authigenic carbonates and seep biota are archives of seepage history and record paleo environmental conditions at seep sites we obtained the timing of past methane release events at the northeastern slope of the south china sea based on u th dating of seep carbonates and seep bivalve fragments from three sites located at 22 02 22 09 n 118 43 118 52 e water depths from 473 to 785 m also we were able to reconstruct the paleo bottom water temperatures by calculating the equilibrium temperature using the ages the corresponding past 18o of seawater 18osw and the 18o of the selected samples formed in contact with bottom seawater with negligible deep fluid influence a criterion consists of mineralogy redox sensitive trace elements and u th isotope systematics is proposed to identify whether the samples were formed from pore water or have been influenced by deep fluid our results show that all methane release events occurred between 11 5 0 2 and 144 5 12 7 ka when sea level was about 62 104 m lower than today enhanced methane release during low sea level stands seems to be modulated by reduced hydrostatic pressure increased incision of canyons and increased sediment loads the calculated past bottom water temperature at one site site 3 water depth 767 771 m during low sea level stands 11 5 and 65 ka ago ranges from 3 3 to 4 0 c i e 1 3 to 2 2 c colder than at present the reliability of 18o of seep carbonates and bivalve shells as a proxy for bottom water temperatures is critically assessed in light of 18o enriched fluids that might be emitted from gas hydrate and or clay dehydration our approach provides for the first time an independent estimate of past bottom water temperatures of the upper continental slope of the south china sea

variations in mg ca and sr ca ratios of planktonic foraminifera caused by postdepositional dissolution evidence of shallow mg dependent dissolution a comparative study has been made of two species of planktonic foraminifera g tumida and g sacculifer in a depth transect on the ontong java plateau western equatorial pacific g tumida tests from core top sediments showed decreasing mg ca 2 65 1 25 mmol mol and sr ca 1 50 1 16 mmol mol ratios with increasing water depth 1600 4400 m while no such variation was found in g sacculifer tests in excess of 355 m average mg ca 3 6 mmol mol sr ca 1 4 mmol mol artificial dissolution of g tumida tests led to a decrease in both mg ca and sr ca but in g sacculifer there was no significant change in the ratios analyses by electron microprobe revealed that mg ca of the inner chamber calcite in g tumida tests was much higher than that of the calcite crust keel whereas sr ca was only slightly elevated there were no consistent spatial differences in either mg ca or sr ca for g sacculifer tests dissolution in the oceans gives rise to the removal of the chamber calcite in g tumida about 30 of the total calcite leaving the keel calcite although g tumida is thought of as a dissolution resistant form the majority of mg ca and sr ca depletion and chamber loss occurs above the lysocline it is also possible that much of the mg enriched gametogenic calcite has been lost by dissolution from g sacculifer above 1600 m mg content has a significant effect on the dissolution susceptibility of planktonic foraminifera calculations show that the saturation horizon for mg rich parts of tests may be elevated by several hundred meters compared with normal calcite

east asian winter monsoon variability over the last glacial cycle insights from a latitudinal sea surface temperature gradient across the south china sea article i nfo high resolution planktonic foraminifer mg ca sea surface temperature sst and 18 o records of images core md052896 from the southern south china sea scs provide a history of east asian winter monsoon variability over the past 23 kyr specifically we find that the latitudinal sst gradient of the north south scs shows promise as a useful proxy of east asian winter monsoon changes the sst record of core md052896 from the southern scs and odp site 1145 from the northern scs documents several positive anomalies indicating east asia winter monsoon maxima during cold periods of the past 23 kyr including the h1 and younger dryas events the sst record also indicates that after 8 5 ka the east asian winter monsoon strengthened relative to the deglaciation reaching levels of the last glacial period comparison of the scs sst record with stalagmite 18 o records suggests that both the east asian summer and winter monsoons strengthened from the last glacial to the holocene and that summer and winter monsoon strength probably are not anti correlated at least over the last glacial interglacial cycle

core top calibration of mg ca in tropical foraminifera refining paleotemperature estimation 1 optimal use of mg ca as a paleotemperature proxy requires establishing calibrations for different species of foraminifera and quantifying the influence of dissolution to achieve this goal we have measured mg ca and 18o in a series of tropical and subtropical core tops including four depth transects the ceara rise the sierra leone rise and the rio grande plateau in the atlantic and the ontong java plateau in the pacific focusing on spinose mixed layer dwelling species globigerinoides ruber and globigerinoides sacculifer and nonspinose thermocline dwelling neogloboquadrina dutertrei shell mg ca in g sacculifer is 5 15 lower than in g ruber while n dutertrei mg ca is 49 55 lower than in g ruber this statistically significant offset has allowed us to establish different calibrations for each species multilinear regression analysis was used to develop calibration equations that include a correction term for the dissolution effect on mg ca in foraminiferal calcite presented in this paper are two sets of calibrations one set using core depth as a dissolution correction and another using co32 as a dissolution parameter the calibrations suggest that g ruber is the most accurate recorder of surface temperature while g sacculifer records temperatures below the surface at 20 30 m the depth habitat of n dutertrei is more uncertain owing to the wide range in habitat depths depending on hydrographic conditions but on average mg ca and 18o data suggest it is at 50 m of the three species n dutertrei is the most sensitive to dissolution up to 23 decrease in shell mg ca per km while g sacculifer is the most resistant

estimating the time of pockmark formation in the sw xisha uplift south china sea using reaction transport modeling carbon cycling and fluid seepage in marine sediments over the late quaternary were investigated at a now extinct pockmark located in a mega pockmark field in the sw xisha uplift nw south china sea measured particulate organic carbon poc content and porewater sulfate so4 2 dissolved inorganic carbon dic concentrations and 34s so4 2 distributions were used to constrain a non steady state reaction transport model and quantify poc mineralization rates as well as estimate the time when fluid flow ceased at the investigated pockmark an increase in poc content and 34s so4 2 and a decrease in sulfate concentrations in the upper ca 2m at the pockmark and a reference core implied an increase in the flux and reactivity of organic matter during the early holocene around 10kyrb p caused by enhanced primary productivity during the strengthened southwestern summer monsoon these features were simulated with the model assuming a holocene increase in poc flux and reactivity subsequently starting from an initial condition reminiscent of a modern active cold seep hydrate ridge hindcast simulations showed that fluid seepage at the pockmark ceased ca 39kyr ago this corresponds to a relative sea level high stand which is believed to be associated with gas hydrate stabilization the non steady state model presented in this contribution can also be used to constrain the time when fluid seepage ceased at other presently extinct cold seeps when suitable sediment and porewater data are available

tropical limestone forest resilience and late pleistocene foraging during mis 2 in the trang an massif vietnam abstract in this paper we present a multi proxy study of tropical limestone forest and its utilization by human groups during the significant climatic and environmental upheavals of mis 2 29 11 7 kbp our data are drawn from new field research within the trang an world heritage property on the edge of the red river delta northern vietnam key findings from this study include 1 that limestone forest formations were resilient to the large scale landscape transformation of the sunda continent at the end of the last glaciation 2 that prehistoric human groups were probably present in this habitat through out mis 2 and 3 that the forested insular karst of trang an provided foragers with a stable resource base in a wider changing landscape during the late pleistocene and into the holocene these results have implications for our understanding of the prehistoric utilization of karst environments and resonance for their conservation in the face of climate and environmental change today

cadmium zinc copper and barium in foraminifera tests the concentrations of cadmium zinc copper and barium have been determined on 2 mg samples of single species foraminifera populations cleaning techniques were tested using north atlantic core tops and followed by a detailed downcore study for the last 30 000 years in south atlantic core v22 174 raw foram tests cleaned by crushing followed by ultrasonic removal of fine grained material and dissolved in a ph 5 5 acetate buffer contain appreciable amounts of trace elements associated with ferromanganese and alumino silicate contaminants a reductive complexing cleaning treatment reduces ferromanganese contamination by 1 2 orders of magnitude acetate buffers at ph 5 5 complex iron and raise the solubility of ferromanganese oxides these buffers are unsuitable for separating carbonate lattice bound trace elements from the fraction associated with ferromanganese phases improved mechanical and ultrasonic reductive cleaning combined with a mild dissolution in distilled water under 1 atm pco2 reduces contaminant levels another order of magnitude the cd and zn concentrations order 10 8 mole cd mole ca and 10 5 mole zn mole ca of species with low surface area show an increase with decreasing isotopic temperatures this increase is consistent with the increasing concentrations of these metals from low values in surface waters to higher values at depth the variance of cd and zn over the last 30 000 years in the central south atlantic is consistent with the probable variability of the dissolved trace elements at the calcification levels of the species analyzed cu and ba are irreproducible and probably sensitive to residual contaminant phases the trace element content of the tests differs from levels observed in a recent coprecipitation study foraminifera may be a significant vector in zinc cycling in the ocean

enhanced silicate weathering of tropical shelf sediments exposed during glacial lowstands a sink for atmospheric co2 atmospheric co2 and global climate are closely coupled since 800 ka co2 concentrations have been up to 50 higher during interglacial compared to glacial periods because of its dependence on temperature humidity and erosion rates chemical weathering of exposed silicate minerals was suggested to have dampened these cyclic variations of atmospheric composition cooler and drier conditions and lower non glacial erosion rates suppressed in situ chemical weathering rates during glacial periods however using systematic variations in major element geochemistry sr nd isotopes and clay mineral records from ocean drilling program sites 1143 and 1144 in the south china sea spanning the last 1 1 ma we show that sediment deposited during glacial periods was more weathered than sediment delivered during interglacials we attribute this to subaerial exposure and weathering of unconsolidated shelf sediments during glacial sealevel lowstands our estimates suggest that enhanced silicate weathering of tropical shelf sediments exposed during glacial lowstands can account for 9 of the carbon dioxide removed from the atmosphere during the glacial and thus represent a significant part of the observed glacial interglacial variation of 80 ppmv as a result if similar magnitudes can be identified in other tropical shelf slope systems the effects of increased sediment exposure and subsequent silicate weathering during lowstands could have potentially enhanced the drawdown of atmospheric co2 during cold stages of the quaternary this in turn would have caused an intensification of glacial cycles

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

a last glacial and deglacial pollen record from the northern south china sea new insight into coastal shelf paleoenvironment this study presents a marine palynological record of the asian summer monsoon and sea level change in the last glacial maximum lgm and the deglacial period in the northern south china sea scs a fossil core std 235 855 cm in length and 273 surface sediment samples from the northern scs were pollen analysed to reconstruct the paleoenvironment of the continental shelf during the last glacial period results from fossil pollen show that the main pollen source region fundamentally changed from the lgm to the deglacial period as sea level rapidly rose the modern marine surface samples show that pollen concentrations in the estuary of the pearl river are extremely high and modern pollen assemblages are in good agreement with the regional vegetation however wind transport becomes more important in the deeper ocean as the percentages of pinus a taxon with very high pollen production and dispersal capacity is highest in these sediments which otherwise have very low pollen concentrations the concentration of total pollen between surface and fossil pollen samples is compared in order to determine the possible vegetation sources areas for the marine core pollen concentration as high as 100 grains g at the lgm suggested that the paleo shoreline was located within 80 km of the core consequently pollen would mostly have derived from the exposed continental shelf in the northern scs by contrast pollen concentrations were very low due to a much greater transport distance 318 km at present core std 235 under higher sea levels and windblown pollen played a more important role because of the limitation of riverine input into the deep ocean during this highstand period such alternation of pollen flux and source distance should be repeated during all glacial interglacial cycles reflecting closely sea level and climate dynamics according to fossil pollen assemblages from core std 235 we conclude that wetland and or grassland communities with sparse subtropical trees dominated most of the exposed shelf during the lgm rather than forest that characterizes the region today the existence of a predominantly open landscape on the exposed continental shelf suggests lower precipitation during the lgm which in turn indicates a weaker asian summer monsoon this finding is supported by other records from the okinawa trough and the east china sea suggesting that a weaker summer monsoon was a key characteristic of the lgm in east asia

pollen record in the northwestern continental shelf of the south china sea in the past 82 ka paleoenvironmental changes in the last glacial period abstract the northwestern continental shelf of the south china sea scs is in a geographic location that was sensitive to the global paleoenvironmental change during the last glacial period here we present a high resolution palynological record of core zbw 100 65 m in length from the continental shelf of the scs in the past 82 ka in contrast to results for the northern scs the core s pollen assemblage was dominated by arboreal trees between mis5a and mis1 even during the glacial period pollen provenance analyses indicated it was mainly from the drainage basin of the red river the yungui plateau and tibetan plateau between 66 and 64 ka the contribution of pinus fell while that of cyclobalanopsis and trilete spores increased indicating a drier and cooler climate conversely during mis3 the contributions of pinus and lowland trees were high indicating a warm and wet climate the sedimentary environment in core zbw alternated between coastal marine and river alluvial or shore facies a sedimentary hiatus between 42 and 13 ka coincided with a significant fall in sea levels seismic data indicate that the hainan paleo river delta hprd process occurred at the core site between 65 and 56 ka with extremely high rates of sediment deposition pollen data indicate the hprd process was coincided with a transition period from cooler and drier climate to warmer and wetter climate and lower sea levels to higher sea levels

reconstruction of the 30 40 ka bp enhanced indian monsoon climate based on geological records from the tibetan plateau abstract multi proxy records from ice caps lakes and pollen records from the tibetan plateau are used to reconstruct the palaeoclimate during the period 30 40 ka bp lake geomorphological and lacustrine sedimentological studies show that numerous high lake level stands and or freshwater lakes occurred in large areas of western china at this time including over the tibetan plateau where the area contains mostly shallow water and saline hypersaline water lakes under extremely dry conditions of today pollen based reconstruction of tibetan vegetation shows systematic differences from the present alpine steppe forests were shifted ca 400 km further north and the alpine conifer forest extended ca 400 800 km beyond their present western limits variations in 18 o curves from ice cores from the plateau suggest that the temperature was 2 4 c higher and precipitation was 40 to over 100 higher than today all of the evidence consistently suggests the existence of an exceedingly strong summer monsoon climate over the plateau the vigorous evaporation of the tropical ocean surface would also play an important role in promoting the penetration of moisture rich southwest monsoon over the tibetan plateau these climate patterns with strong summer monsoon circulation during the period 30 40 ka bp reflect the 20 ka earth orbital precessional cycle when the tibetan plateau region received greater solar radiation which thus enlarged the thermodynamical contrast between the plateau and the mid south portion of the indian ocean

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

source processes for archean au ag vein deposits evidence from lithophile element systematics of the hollinger mcintyre and buffalo ankerite deposits timmins potassic alteration domains of archean greenstone belt lode gold deposits typified by the hollinger mcintyre and buffalo ankerite mines timmins are characterized by systematic partitioning between different groups of incompatible elements such that al ga th u ti and v are decoupled from k rb ba li cs and tl the former group of elements has concentrations and interelement ratios in alteration domains that reflect host rock control implying approximately isochemical behaviour in contrast the lithophile elements k rb and ba are generally coenriched and are linearly correlated over three orders of magnitude in abundance where k rb 230 380 r 0 92 0 99 and k ba 34 97 r 0 82 0 99 values close to average crustal ratios of 285 and 36 respectively k rb and k ba ratios trend towards higher values with respect to increasing concentrations of rb and ba possibly because of mixing between host rock and hydrothermal reservoirs of the lithophile elements cs and tl contents average 1 4

foraminiferal responses to major pleistocene paleoceanographic changes in the southern south china sea a detailed age model for core 17957 2 of the southern south china sea was developed based on delta 18 o coarse fraction magnetostratigraphy and biostratigraphy for the last 1500 kyr the delta 18 o record has clear similar to 100 kyr cycles after the mid pleistocene revolution mpr at the entrance of marine isotopic stage mis 22 planktonic foraminifera responded to the mpr immediately showing the increased sea surface temperature sst and dissolution after the mpr benthic foraminifera did not respond to it until the brunhes matuyama boundary since the mpr the depth of thermocline gradually became shallower until miss 6 5 this major change within miss 6 5 was also reflected in the decreased ssts and increased productivity and deep water mass thus two major pleistocene paleoceanographic changes were found one was around the mpr the other occurred within miss 6 5 which speculatively might be ascribed to the reorganization of surface and deep circulation possibly induced by tectonic forces

sea level changes since the last glacial maximum an appraisal of the ipcc fourth assessment report the ipcc fourth assessment report ar4 stated that global sea level rose by about 120 m between the last glacial maximum lgm and 3 2 ka and did not rise again until the late 19th century a review of relevant literature demonstrates that the rise may have been larger by 10 15 m that the timing of stabilisation is poorly constrained within the last 7 ka bp and that the onset of modern rates of sea level rise is not synchronous and uniform across the globe the lgm lowstand as defined in the ar4 is based on the classic barbados sea level history but the sea level curve from this island may not be an accurate eustatic approximation if glacial isostatic adjustment gia processes were significant as suggested by various authors the barbados sea level curve revealed the existence of meltwater pulse mwp 1a at around 14 000 cal a bp questions about the source and causal mechanism of mwp 1a are still being explored by field scientists and gia modellers these problems have direct relevance for contemporary measurements of ice mass changes because space geodetic measurements rely on information provided by gia models to separate land motion from ice mass changes global patterns of holocene sea level change are controlled by regional sea level variability not only through isostatic and tectonic processes but also through steric effects longer wavelength gravitational changes produced by changing ice ocean mass flux and hemispheric scale perturbations in the earth s rotation eustasy is therefore merely a concept not a measurable quantity constraining the late holocene ice melt contribution to global sea level rise and determining regional sea level rise patterns in the 18th and 19th centuries are important future tasks for sea level scientists these will establish the baseline contributions to 20th and 21st century sea level rise and will help to determine the causes of modern rates of sea level rise constraining historical sea level accelerations and short term ice mass flux will aid models of ice sheet dynamics and help to reduce current uncertainties in future sea level predictions the ar4 shows that regional sea level variability is clearly present in sea level change patterns for the past 50 a and an important challenge for the next ipcc assessment is to incorporate this variability into regional future sea level rise scenarios copyright 2009 john wiley sons ltd

molecular biomarker record of sea surface temperature and climatic change in the south china sea during the last 140 000 years the d 18 oa ndd 18 c isotopic composition of globigerinoides ruber the concentration of c37 alkenones n nonacosane and n hexacosan 1 ol and the populations of coccolith species in core 17961 2 have been used to characterize the climatic changes which occurred in the south china sea scs during the last climatic cycle the relative composition of diand triunsaturated c37 alkenones the u k index has been used to estimate the variation in sea surface temperatures the concentrations of the terrigenous markers n nonacosane and n hexacosan 1 ol have allowed to infer changes in continental water dynamics during the glacial and interglacial times the stratigraphic record of these compounds has shown that the influence of continental waters i e the molengraaff river and restricted water circulation in scs gave rise to a marginal system of higher but slower response to climatic change both in terminations i and ii the change from glacial to interglacial conditions involves a considerable reduction of continental water input into this semi enclosed system the high resolution study of the biomarker proxies in termination i has shown that the sst increase lagged about 2 3 ky the d 18 o isotopic decrease of cibicidoides wuellerstorfi probably the sst increase corresponds to the period of the sunda shelf inundation onset 1999 elsevier science b v all rights reserved

high resolution sea surface temperature records derived from foraminiferal mg ca ratios during the last 260 ka in the northern south china sea abstract high resolution sea surface temperatures sst derived from mg ca ratios of globeriginoides sacculifer at odp site 1144 were reported to reveal the sst changes during the last 260 ka in the northern south china sea scs the results indicate an average holocene sst of about 26 7 c about 3 6 c increase from lgm to the holocene and higher temperature during mis 5 5 than the holocene these agree well with other foraminifer mg ca and uk37 sst records in this region the mg ca records suggest warmer ssts during mis 3 in the northern scs compared with those in the eastern pacific strong east asian summer monsoon during mis 3 indicated by paleoclimate records from nearby continents may account for it step wise increases during terminations are shown in our sst record and the beginning of deglacial warming occurs at about 19 ka which precedes the change of oxygen isotopes suggesting a tropical driven forcing for the sst change in the northern scs this is further supported by a robust semi precessional cycle centering at 9 1 ka in the spectra of the sst record which is absent in that of the oxygen isotopes however tropical driven forcing seems not to be indicated in another mg ca sst record in the northern scs oppo d w and sun y b 2005 amplitude and timing of sea surface temperature change in the northern south china sea dynamic link to the east asian monsoon geology 33 10 785 788 the discrepancy may be caused by different post deposition dissolutions of foraminifer tests at these two sites details about the modification of foraminifer mg ca ratios after burial however are not well known in this region and further studies are needed

deep sea pollen from the south china sea pleistocene indicators of east asian monsoon abstract a high resolution pollen record sampling interval averages 820 years has been obtained from odp site 1144 water depth 2037 m northern south china sea the 504 m sequence in composition length covers the last 1 03 million years according to micropaleontological and isotopic stratigraphy the pollen assemblages are characterized by high proportions of pinus and herb pollen and by their frequent alternations based on these alternations 29 pollen zones have been recognized that are closely correlated to the marine oxygen isotope stages mis 1 29 pinus dominant pollen zones correspond to interglacial periods with lighter 18o values while herb marked ones relate to the heavier 18o stages assigned to glacials judging from the pollen data the exposed northern continental shelf of the south china sea during the glacials was covered by grassland and the extensive northern shelf has formed only since mis 6 ca 150 ka probably as a result of tectonic subsidence tree pollen influx values are indicative of winter monsoon which began to intensify 600 ka ago the summer monsoon variations can be approximated by the fern percentage within the total pollen and spore abundance and the result shows high values in general occurring at interglacials with the maxima at mis 15 5e and 1 the relatively high fern percentage with smaller amplitude in variations before 600 ka might suggest more stable humid conditions before the intensification of winter monsoon

decreasing intensity of the last glacial stadials in low latitude terrestrial east asia inferred by a new observation of pollen records in central taiwan abstract the cold intensity of the last glacial stadials corresponding to marine isotope stage mis 5d or 5b mis 4 and mis 2 in terrestrial east asia monsoon area is not discussed much due to the paucity of long continuous pollen records a palynological study of drilling cores from three closely linked intramontane basins toushe sun moon lake and yuchi in central taiwan provides a history of shifting altitudinal vegetation zones in surrounding mountains during late quaternary climate changes by integrating these records we found that the alpine conifer forest approached its lowest altitude about 614 m during the earliest stadial mis 5d or 5b and 745 m during the early stadial mis 4 based on records of yuchi basin and sun moon lake in addition the pollen records of toushe basin and sun moon lake show more temperate conditions for the late stadial mis 2 than the early stadial mis 4 this leads to an interpretation of a decreasing intensity of stadials during the last glaciation which might follow the regional insolation amplitude such a decreasing trend in coldness during the last glacial stadials does not exist in the record for the south china sea which reflects a different sensitivity and response to climatic forcings between terrestrial and marine

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

high resolution benthic foraminifer δ13c records in the south china sea during the last 150 ka abstract high resolution 13c ratios of benthic foraminifer cibicidoides wuellerstorfi in core md97 2151 from the southern south china sea scs and core so50 31kl from the northern scs indicate deep water variations in the scs during the last 150 ka the 13c records of both show a general variation pattern with higher 13c during interglacial periods than glacial periods and rapid increases during terminations this variation pattern resembles those of the west pacific intermediate deep water the sources of the scs deep water and the general variation of global deep water indicating that the variation of the scs deep water is largely controlled by global factors such as carbon cycles and global deep water circulation spectra analysis exhibits robust milankovitch cycles in the scs deep water 13c again supporting global controls significant semi precession cycles can also be seen in the spectra implying that changes of local surface productivity also influence the scs deep water 13c

mobilization and re distribution of major and trace elements during extreme weathering of basalt in hainan island south china major trace and organic elements of a laterite profile developed on neogene basalts in northern hainan island south china were reported in this paper the aim of which was to investigate element mobilization and re distribution during extreme weathering the results indicate that most of the elements have been mobilized and transferred downwards along the profile by aqueous solution organic matter om can significantly improve the transport of insoluble elements among all the elements th is the least mobile as for the general conservative elements during incipient chemical weathering such as fe ti zr hf nb and ta the removals are up to 20 40 in the upper profile however these elements behave as conservatively as th in the lower profile in the middle profile oxic environment occurs accompanied with significant om decomposition the mn and ce transferred downward are readily oxidized into insoluble mn iv and ce iv and precipitate in the oxic front important om decomposition decreases the capacity of transfer of insoluble elements in aqueous solution consequently al significantly precipitates in the oxic front and rees with the exception of ce precipitate largely in the omdepleted layers co and u are also concentrated in the oxic front in association with mn and ce respectively however cr shows a negative correlation with mn because its response to redox condition changes is reversed from that of mn mn oxides hydroxides fe oxides hydroxides and secondary phosphate minerals other than clay minerals are potential hosts for rees except for ce in the profile rees with high concentrations in the profile seem closely associated with mn oxides hydroxides remarkable highly correlated ce and gd anomalies are observed in the profile ce anomalies are caused by ce precipitation in the oxic environment and successive decomposition of organic matter gd anomalies are likely to have resulted from lower stability constants of gd om complexes compared to those of neighboring rees the overall elemental behaviors in this profile suggest that organic matter plays a very important role in the mobilization and re distribution of the elements during extreme weathering

quantitative reconstruction of palaeoclimate from pollen profiles in northeastern japan and the timing of a cold reversal event during the last termination we reconstructed quantified palaeoclimate changes within two japanese pollen profiles spanning the last termination lt 18 10 cal ka in an attempt to better understand past monsoon activity the reconstructed winter climate at the tashiro mire which is strongly influenced by the siberian air mass showed a weak and a short lived cooling event at 11 8 10 6 cal ka this event spans part of the younger dryas yd cooling event in the north atlantic region suggesting the latter influenced the siberian high pressure system in contrast the summer climate at the komado mire which is more influenced by the pacific air mass experienced a strong and a prolonged cooling event at 15 5 13 0 cal ka the latter event is broadly synchronous with the antarctica cold reversal acr event and suggests that the pacific high pressure system weakened during this period the pattern of climate change across east asia shows that the yd event did not extend beyond the east asian monsoon front while the acr event strongly affected the pacific high pressure system during the lt we suggest the east asian monsoon front is an important geo climatic boundary between yd like and acr like deglacial climate changes copyright 2009 john wiley sons ltd

a high resolution sea surface temperature record from the tropical south china sea 16 500 3000 yr b p the timing and magnitude of sea surface temperature sst changes in the tropical southern south china sea scs during the last 16 500 years have been reconstructed on a high resolution c 14 dated sediment core using three different foraminiferal transfer functions simmax28 ram fp 12e and geochemical u 37 k sst estimates in agreement with climap reconstructions both the fp 12e and the u 37 k sst estimates show an average late glacial interglacial sst difference of 2 0 degreesc whereas the ram and simmax28 foraminiferal transfer functions show only a minor 0 6 degreesc or no consistent late glacial interglacial sst change respectively both the u 37 k and the fp 12e sst estimates as well as the planktonic foraminiferal delta o 18 values indicate an abrupt warming ca 1 degreesc in 200 yr at the end of the last glaciation synchronous within dating uncertainties with the bolling transition as recorded in the greenland ice sheet project 2 gisp2 ice core whereas the ram derived deglacial sst increase appears to lag during this event by ca 500 yr the similarity in abruptness and timing of the warming associated with the bolling transition in greenland and the southern scs suggest a true synchrony of the northern hemisphere warming at the end of the last glaciation in contrast to the foraminiferal transfer function estimates that do not indicate any consistent cooling associated with the younger dryas yd climate event in the tropical scs the u 37 k sst estimates show a cooling of ca 0 2 0 6 degreesc compared to the bolling allerod period these u 37 k sst estimates from the southern scs argue in favor of a northern hemisphere wide synchronous cooling during the yd period c 2001 university of washington

comparison and implication of tex86 and u37k temperature records over the last 356kyr of odp site 1147 from the northern south china sea abstract proxy records from the south china sea scs have played an important role in understanding late quaternary scs environmental changes and the east asian monsoon eam variations but few long sea surface temperature sst records have been generated from the scs the recently established tex86 index provides an opportunity to generate long sst records especially for tropical oceans but the applicability and climatic interpretation of the tex86 index for the scs need further study we report and compare orbital scale resolution ca 5 3 kyr tex86 and u37k temperature records of the past 356 kyr for odp site 1147 from the northern scs both records display clear and similar glacial interglacial patterns the u37k sst fluctuated between 22 3 c and 28 3 c with a glacial interglacial difference of 4 5 c while the tex86 temperature fluctuated between 20 3 c and 25 4 c with a slightly smaller glacial interglacial difference of ca 4 c the tex86 temperature has been consistently lower than the u37k temperature over the past 356 kyr consistent with previous studies suggesting that the u37k index is a proxy for sst but the tex86 index is a proxy for subsurface temperature thus it is proposed that the temperature difference t between the u37k and tex86 records reflects mixed layer depth mld changes in the northern scs which fluctuated between 0 3 and 4 0 c with high values mostly during interglacials and lower values mostly during glacial stages mld changes in the northern scs are interpreted to be driven by eam changes with stronger winter monsoon resulting in a deeper mld and a smaller t thus the combination of u37k and tex86 records and their t can be used to reconstruct east asian winter monsoon variations as well as their influences on the hydrographic structure of the scs

high resolution palynological record for vegetation and environment change during mis 2 in the southern south china sea abstract vegetation evolution and corresponding climate changes during marine isotope stage mis 2 on the exposed shelves in the southern south china sea scs region are still controversial palynomorph data including percentage concentration and influx were used to reconstruct the history of vegetation and environment changes during mis 2 and mis 1 it recommends three significant changes occurred during these periods at 21 51 cal kyr b p 17 82 cal kyr b p and 12 36 cal kyr b p the findings indicate that during mis 2 and the start of mis 1 the northeastern part of exposed shelves were covered with tropical rainforests ferns were present in ground flora and sub canopy of tree cover in the rainforests in the coastal areas mangrove forests survived up to the start of mis 1 and then disappeared due to the rapid rise in sea level grassland was present to a limited extent and probably in the beach areas only winter monsoon was strong although the temperature was lower than at present from 11 70 cal kyr b p ferns were the dominating vegetation while herbs disappeared completely trees of lower and upper montane rainforests were present to some extent the climate was warm sea level rose the continental shelf was submerged in the ocean and the summer monsoon became stronger than in previous times this study supports the previous works from the southern scs region and suggests that a combination of pollens with other proxies give a better understanding of vegetation and climatic dynamics in the past

relocation and focal mechanisms of earthquakes in the south central sector of the aeolian archipelago new structural and volcanological insights abstract to recognize possible spatial clusters and identify active seismogenic zones and structures in the aeolian archipelago in the south of italy we analyzed the spatial pattern of seismicity between 1993 and 2010 in a selected area comprising vulcano lipari salina and filicudi and calculated 22 fault plane solutions fpss for shocks with magnitude greater than 2 7 first we computed a 1 d velocity model for this area including information from recorded earthquakes by a joint hypocenter velocity inversion kissling et al 1994 successively we applied the double difference approach of waldhauser and ellsworth 2000 finding that a certain part of the scattered epicenter locations collapse in roughly linear features relocated seismicity evidenced three main alignments oriented nnw sse and ne sw at different depths that concur well with the known tectonic lineaments and focal mechanisms a detailed discussion is focused on a seismogenetic structure ne sw oriented 3 8 km deep located in the northern area of vulcano island this recognized element could represent a link between magma accumulation zones thus representing a possible preferential pathway along which magma may intrude two earthquake clusters located south west and east of vulcano with their focal mechanisms highlight the aeolian tindari letojanni fault system seismic activity and the existence of a transitional zone going from the n s compressive domain that dominates the aeolian islands to the nw se extensional domain characterizing the south eastern tyrrhenian

summer monsoon induced upwelling dominated coastal sea surface temperature variations in the northern south china sea over the last two millennia the south china sea scs situated to the north of the indo pacific warm pool ipwp is under the strong influence of the asian monsoon system however coastal sea surface temperature sst reco

precise magnesium isotope measurements in core top planktic and benthic foraminifera 1 this study presents a new methodology to obtain highly precise measurements 0 1 of magnesium isotope ratios in very small samples of foraminiferal carbonate 40 50 g here this technique is used to examine mg isotopic variation among different species of core top foraminifera over a range of different ambient conditions despite the high degree of temperature control on the abundance of elemental mg incorporated into foraminiferal tests analyses of surface dwelling globigerinoides ruber and g sacculifer from five cores with associated sea surface temperatures ranging from 20 to 31 c show no significant temperature dependent variations in their mg isotope ratios analyses of different size fractions of g sacculifer show an increase in mg ca with test size but no variation of mg isotope ratio in all nine planktic and benthic species were analyzed all show identical mg isotope ratios with a mean of 26mg 4 72 apart from small differences in three species namely o universa g sacculifer which are both 0 4 lighter than the average and p obliquiloculata which is 0 4 heavier these results highlight the constancy of foraminiferal mg isotope ratios despite changing environmental conditions which dominate mg ca variation and arguably affect ca isotope fractionation this is an important observation which needs to be included in any model of foraminiferal calcification the insusceptibility of 26mg values to external parameters makes mg isotopes ideally suited to constraining past variations in the mg isotope budget of the oceans and the information this carries about the history of oceanic dolomitization continental weathering and hydrothermal behavior

identification and removal of mn mg rich contaminant phases on foraminiferal tests implications for mg ca past temperature reconstructions 1 the geochemical composition of foraminifera shells from an ocean drilling program site in the panama basin has been analyzed by several analytical techniques la icp ms icp ms xrd sem edx in order to identify and evaluate the occurrence of contaminant phases which may bias paleoenvironmental reconstructions la icp ms results on uncleaned tests indicate the presence of mnmg rich contaminant phases at the inner surfaces of the foraminiferal shells which have mn ca ratios up to 400 mmol mol 1 and mg ca ratios up to 50 mmol mol 1 we have rigorously assessed the ability of different cleaning protocols to remove these contaminant phases and have obtained satisfactory results only when a reductive step is included the analysis of cleaning residuals collected after each of the different cleaning steps applied reveals that high mn values are associated with at least two different contaminant phases of which only one is linked to high mg values xrd analysis further reveals that the mn mg rich phase is the ca mn mg carbonate kutnahorite ca mn mg co3 2 our results demonstrate that the presence of kutnahorite like minerals can bias mg ca ratios toward higher values by 7 36 and lead to significant overestimation of past seawater temperatures by 0 9 up to 6 2 c in the case of these panama basin samples components 11 867 words 13 figures 3 tables

glacial interglacial changes in subantarctic sea surface temperature and δ18o water using foraminiferal mg laboratory culturing experiments with living globigerina bulloides indicate that mg ca is primarily a function of seawater temperature and suggest that mg ca of fossil specimens is an effective paleotemperature proxy using culturing results and a core top neogloboquadrina pachyderma calibration we have estimated glacial interglacial changes in sea surface temperature sst using planktonic mg ca records from core rc11 120 in the subantarctic indian ocean 43 s 80 e and core e11 2 in the subantarctic pacific ocean 56 s 115 w our results suggest that glacial sst was about 4 c cooler in the subantarctic indian ocean and 2 5 c cooler in the subantarctic pacific comparison of sst and planktonic 18o records indicates that changes in sst lead changes in 18o by on average 1 3 kyr the glacial interglacial temperature change indicated by the subantarctic mg ca records suggests that temperature accounts for 40 60 of the foraminiferal 18o change we have used the mg ca based sst estimates and 18o determinations to generate site specific seawater 18o records which suggest that seawater 18o was on average 1 more positive during glacial episodes compared with interglacial episodes

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

comparison of foraminiferal cleaning procedures for mg ca paleothermometry on core material deposited under varying terrigenous input and bottom water conditions a down core comparison of two commonly applied foraminiferal cleaning procedures for mg ca paleothermometry has been conducted using well preserved globigerinoides ruber white 250 300 mm from core material deposited under varying terrigenous input and bottom water conditions this study demonstrates that in the majority of investigated core materials both cleaning methods yield fairly comparable results of mg ca ratios however fe and mn phases are effectively removed by the cleaning procedure containing a reductive step in a core interval indicating gradual transition of terrigenous deposition and pore water conditions the cleaning procedure without a reductive step results in anomalously higher mg ca ratios accompanied by high fe ca and mn ca ratios indicating the presence of high mg contaminants considering that the mg ca deviation of the comparison study is the cumulative sum of 1 the difference in cleaning efficiency of the applied methods 2 the cleaning method dependent partial dissolution of mg and 3 the heterogeneity of subsamples we suggest that selective mg loss from well preserved globigerinoides ruber shells caused by the reductive sample treatment is not substantial enough to significantly bias paleotemperature estimation thus for core material deposited under varying sources and amounts of terrigenous material and bottom water conditions favorable for formation of authigenic mineral phases the use of cleaning methods that do include a reductive step yields more effective cleaning results by successful removal of mineral phases that may contain high mg

geochemical and nd isotopic variations in sediments of the south china sea a response to cenozoic tectonism in se asia secular variations in geochemistry and nd isotopic data have been documented in sediment samples at odp site 1148 in the south china sea major and trace elements show significant changes at ca 29 5 ma and 26 23 ma whereas ond values show a single change at ca 26 23 ma increases in al ti al k rb sr and la lu ratios and a decrease in the th la ratio of the sediments beginning at 29 5 ma are consistent with more intense chemical weathering in the source region the abrupt change in nd isotopes and geochemistry at ca 26 23 ma coincides with a major discontinuity in the sedimentology and physical properties of the sediments implying a drastic change in sedimentary provenance and environment at the drill site comparison of the nd isotopes of sediments from major rivers flowing into the south china sea suggests that pre 27 ma sediments were dominantly derived from a southwestern provenance indochina sunda shelf and possibly northwestern borneo whereas post 23 ma sediments were derived from a northern provenance south china this change in provenance from southwest to north was largely caused by ridge jumping during seafloor spreading of the south china sea associated with a southwestward expansion of the ocean basin crust and a global rise in sea level thus the geochemical and nd isotopic changes in the sediments at odp site 1148 are interpreted as a response to a major plate reorganization in se asia at ca 25 ma b 2003 elsevier science b v all rights reserved

synchronous tropical south china sea sst change and greenland warming during deglaciation the tropical ocean plays a major role in global climate it is therefore crucial to establish the precise phase between tropical and high latitude climate variability during past abrupt climate events in order to gain insight into the mechanisms of global climate change here we present alkenone sea surface temperature sst records from the tropical south china sea that show an abrupt temperature increase of at least 1 c at the end of the last glacial period within the recognized dating uncertainties this sst increase is synchronous with the bolling warming observed at 14 6 thousand years ago in the greenland ice sheet project 2 ice core

new oceanic proxies for paleoclimate environmental variables such as temperature and salinity cannot be directly measured for the past such variables do however influence the chemistry and biology of the marine sedimentary record in a measurable way reconstructing the past environment is therefore possible by proxy such proxy reconstruction uses chemical and biological observations to assess two aspects of earth s climate system the physics of ocean atmosphere circulation and the chemistry of the carbon cycle early proxies made use of faunal assemblages stable isotope fractionation of oxygen and carbon and the degree of saturation of biogenically produced organic molecules these well established tools have been complemented by many new proxies for reconstruction of the physical environment these include proxies for ocean temperature mg ca sr ca 44ca and ocean circulation cd ca radiogenic isotopes 14c sortable silt for reconstruction of the carbon cycle they include proxies for ocean productivity 231pa 230th u concentration nutrient utilization cd ca 15n 30si alkalinity ba ca ph 11b carbonate ion concentration foraminiferal weight zn ca and atmospheric co2 11b 13c these proxies provide a better understanding of past climate and allow climate model sensitivity to be tested thereby improving our ability to predict future climate change proxy research still faces challenges however as some environmental variables cannot be reconstructed and as the underlying chemistry and biology of most proxies is not well understood few proxies have been applied to pre pleistocene times another challenge for future research only by solving such challenges will proxies provide a full understanding of the range of possible climate variability on earth and of the mechanisms causing this variability

foraminiferal magnesium in globeriginoides sacculifer as a paleotemperature proxy foraminiferal magnesium shows increasing promise as a paleothermometer but the accuracy and precision are limited by biases introduced by partial dissolution salinity variations mg rich gametogenic calcite and contaminant phases we improved cleaning methods and reduced errors introduced by partial dissolution by sampling from well preserved cores in the equatorial atlantic and the caribbean sea with different dissolution histories all cores reveal a synchronous 25 increase in mg ca from the stage 2 3 boundary to the holocene core top indicating that dissolution is not a controlling factor modern temperatures estimated from core top mg ca are 24 5 25 0 c equal to mean annual water temperatures at 50 100 m we estimate that sea surface temperature increased by 2 6 c 1 3 from the last glacial maximum to the holocene holocene values were comparable to those during isotope stage 5e our data indicate that biases from contaminant phases and partial dissolution can be reduced this paleothermometer holds promise if uncertainties introduced by salinity variations and gametogenic calcite can be constrained

orbital scale timing and mechanisms driving late pleistocene indo asian summer monsoons reinterpreting cave speleothem δ18o 1 southeast china cave 18o often interpreted as a pure east asian summer monsoon proxy lags maximum northern hemisphere summer insolation by 2 9 0 3 kyrs at the precession cycle the arabian sea summer monsoon stack lags by 8 1 kyr consistent with 13 other indian and east asian summer monsoon proxies from marine lake and terrestrial archives this 5 kyr phase difference cannot be attributed to age control inadequacies in the marine chronology it requires reconciliation in the context of proxy interpretation both of these lags are incompatible with a direct response to northern hemisphere summer insolation implicating additional forcing mechanisms analysis of heterodynes in the cave 18o spectrum demonstrates that variance contained in the arabian sea summer monsoon proxies also resides in the cave 18o record this variance is subtracted from the cave 18o record yielding a residual that is highly coherent and in phase with precession minima reflecting the impact of winter temperature change on cave 18o meteorological precipitation under cold conditions thus we argue that the timing of light cave 18o peaks cannot be interpreted as reflecting the timing of strong summer monsoons alone the 2 9 kyr precession band phase lag of cave 18o reflects the combined influence of summer monsoon forcing with a phase lag of 8 kyrs relative to precession minima and winter temperature forcing that is in phase with precession minima this interpretation is consistent with modern seasonality in the amount and isotopic composition of rainfall in southeast china

tectonics and seismicity of the tindari fault system southern italy crustal deformations at the transition between ongoing contractional and extensional domains located above the edge of a subducting slab 1 the tindari fault system southern tyrrhenian sea italy is a regional zone of brittle deformation located at the transition between ongoing contractional and extensional crustal compartments and lying above the western edge of a narrow subducting slab onshore structural data an offshore seismic reflection profile and earthquake data are analyzed to constrain the present geometry of the tindari fault system and its tectonic evolution since neogene including the present seismicity results show that this zone of deformation consists of a broad nnw trending system of faults including sets of right lateral left lateral and extensional faults as well as early strike slip faults reworked under late extension earthquakes and other neotectonic data provide evidence that the tindari fault system is still active in the central and northern sectors and mostly accommodates extensional or right lateral transtensional displacements on a diffuse array of faults from these data a multiphase tectonic history is inferred including an early phase as a right lateral strike slip fault and a late extensional reworking under the influence of the subduction related processes which have led to the formation of the tyrrhenian back arc basin within the present regional geodynamic context the tindari fault system is interpreted as an ongoing accommodation zone between the adjacent contractional and extensional crustal compartments these tectonic compartments relating to the complex processes of plate convergence occurring in the region the tindari fault system might also be included in an incipient oblique extensional transfer zone linking the ongoing contractional belts in the calabrian ionian and southern tyrrhenian compartments

northern south china sea sst changes over the last two millennia and possible linkage with solar irradiance abstract high resolution surface temperature records over the last two millennia are crucial to understanding the forcing and response mechanism of earth s climate here we report a bidecadal resolution sea surface temperature sst record based on long chain alkenones in a gravity sediment core retrieved from the northern south china sea sst values varied between 26 7 and 27 5 c with a total variability 1 c over the last 2000 years the general sst variation pattern matches well with total solar irradiance tsi changes relatively warm period between 800 and 1400 ad and cool period 1400 1850 ad could be identified in agreement with the commonly defined periods of medieval warm period and little ice age within chronological uncertainty notable short cooling events at 640 670 ad 1030 1080 ad 1260 1280 ad and 1420 1450 ad coincide with large volcanic eruption events the general coincidence of sst changes with tsi and volcanic eruption events suggests strong impact of external forcing on sea surface conditions in the studied area in addition to the direct tsi changes volcanic eruptions might have induced oceanic and atmospheric circulation adjustments which might be responsible for the short cooling events as revealed in the alkenone sst record

significant sst differences between peak mis5 and mis1 along the low latitude western north pacific margin abstract the peak period of marine isotope stage 5 mis5e is the most recent warm period largely comparable to the present interglacial marine isotope stage 1 mis1 the spatial variations in sea surface temperature sst between mis5e and mis1 can reveal the important differences in the effects of insolation and oceanographic conditions between the two warm periods which in turns help refine global climate models in order to quantify the differences this study calculated the sst for the peak periods of mis5e c 128 113 ka bp and mis1 c 8 3 ka bp along the low latitude western north pacific margin 18 on to 26 on together with the previously published data from the south china sea 9 on to 19 on the results indicate a generally northwards decreasing trend in the two interglacial periods this latitudinal sst trend in both peak mis 1 and mis 5e can be attributed to the strong influence of ocean currents in the studied region secondly the average sst of peak mis5e is 1 3 0 2 c higher than that of peak mis1 suggesting a higher level of insolation during the previous interglacial however the above general pattern is complicated by the near shore and offshore difference in the effects of winter monsoon on oceanic conditions around 20 22 on the coastal upwelling near 26 on during peak mis5e reduced the sst whilst the sst was raised as the upwelling ceased during peak mis1 finally the ssts of the two warm periods are significantly higher than the present sst from 20 on northwards implying the influence of winter monsoon cold current in the taiwan strait

constraint on the penultimate glacial maximum northern hemisphere ice topography 140 kyrs bp abstract the penultimate glacial maximum pgm 140 kyrs bp is known to be the most extensive glaciation on record that occurred during the last 400 kyrs over eurasia we used a coupled atmosphere ocean sea ice land model to simulate the climate of the pgm accounting for a reconstruction of the large pgm eurasian ice sheet due to uncertainties in the pgm laurentide ice sheet topography two simulations with different ice sheet topographies over north america large as for the last glacial maximum lgm and small as for 13 kyrs bp are performed results show that the simulated pgm glacial maximum climates are of comparable magnitude with previous simulations of the lgm in both cases assuming a small laurentide ice sheet instead of the lgm one in our pgm simulations results in a shift in the planetary waves this causes an increase in storm track activity over the north atlantic as well as higher temperatures and precipitation rates over north america north atlantic and over the eurasian ice sheet in addition it induces a negative temperature anomaly over east siberia yielding a thick snow cover which seems to be in agreement with data from recent arctic campaigns suggesting that an ice cap developed over beringia during the pgm all together the changes in large scale circulation and regional climate simulated using a small laurentide ice sheet match the proxies well based on our findings we suggest that the laurentide ice sheet might have been smaller during the pgm than during the lgm in turn also implying a larger eurasian ice sheet than during the lgm which is supported by various geological evidence of the pgm

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr