a general rule for synoptic eddy feedback onto low frequency flow in this study scale interaction between synoptic eddies and low frequency flow is investigated it is demonstrated here that there is a general rule the left hand rule that describes synoptic eddy feedback onto low frequency flow the rule is that low frequency anomalies systematically stir and deform the transient eddies in such a way that the irrotational eddy vorticity fluxes are directed preferentially about 90 toward the left hand side of the low frequency flow thus this eddy feedback plays a positive role in maintaining and prolonging low frequency flow under the stormy atmosphere similarly we show that the irrotational eddy temperature and moisture fluxes are also directed preferentially about 90 toward the left hand side of the low frequency flow in the northern hemisphere the eddy temperature fluxes and their vertical structure play a positive role in reinforcing the low frequency flow in the low levels the moisture fluxes play a role in enhancing low frequency flow by providing eddy induced moisture convergence and divergence

estimating the sensitivity of the atmospheric teleconnection patterns to sst anomalies using a linear statistical method abstractthe pacific north american pna pattern and the north atlantic oscillation nao are known to contain a tropical sea surface temperature sst forced component this study examines the sensitivity of the wintertime nao and pna to patterns of tropical sst anomalies using a linear statistical dynamic method the nao index is sensitive to sst anomalies over the tropical indian ocean the central pacific ocean and the caribbean sea and the pna index is sensitive to sst anomalies over the tropical pacific and indian oceans the nao and pna patterns can be reproduced well by combining the linear operator with the consistent sst anomaly over the indian ocean and the nino 4 regions respectively suggesting that these are the most efficient ocean basins that force the teleconnection patterns during the period of 1950 2000 the nao time series reconstructed by using sst anomalies over the indian ocean nino 4 region caribbean sea or the indian ocean nino 4 region is significantly correlated with t

erosion of modern terrestrial organic matter as a major component of sediments in fjords fjords have recently been recognized as hotspots of carbon burial in this study we investigated organic carbon oc and biomarker radiocarbon values in fjord sediments from new zealand our results showed that oc was mostly modern with the most aged oc in middle reaches of fjords likely related to hydrodynamic sorting and inputs along adjacent slopes radiocarbon ages of sedimentary oc increased from north to south consistent with the fiordland regional gradients of lower fjord slopes and less rainfall our biomarker results suggested that lignin and long chain fatty acids were preferentially linked with fresh terrestrial debris and degraded soil respectively likely due to their chemical and physical properties finally we propose that fjords are a significant sink of modern oc in contrast to large lowland coastal systems as a major sink of pre aged oc overall this study indicated that radiocarbon techniques are critical in investigating carbon dynamics in coastal systems

quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

biomarkers as proxies for plant inputs to peats an example from a sub boreal ombrotrophic bog lipid distributions in modern peat forming plants were determined and compared to biomarkers recovered from a ca 2800 year old peat deposited in a dutch ombrotrophic bog the peat section spans a well constrained shift in local hydrology and vegetation and potential molecular proxies for plant inputs were directly tested against the macrofossil record based on the analyses of modern plants low molecular weight lmw n alkanes c23 c25 and high molecular weight n alkanes c33 are proposed as potential biomarkers for sphagnum and non sphagnum inputs respectively consistent with this in the bargerveen peat core lmw n alkane abundances increase and hmw n alkane abundances decrease coincident with the shift to sphagnum dominated peat additional potential proxies include the abundances of c22 alkanedioic acid and phytenyl phytenoate as sphagnum indicators and the abundances of the triterpenoids taraxer 14 ene and taraxast 20 ene as biomarkers for ericaceae rootlets

the north atlantic oscillation and oceanic precipitation variability global north atlantic oscillation nao oceanic precipitation features in the latter half of the twentieth century are documented based on the intercomparison of multiple state of the art precipitation datasets and the analysis of the nao atmospheric circulation and sst anomalies most prominent precipitation anomalies occur over the ocean in the north atlantic where in winter a quadrupole like pattern is found with centers in the western tropical atlantic sub tropical atlantic high latitude eastern atlantic and over the labrador sea the extent of the sub tropical and high latitude center and the amount of explained variance over 50 are quite remarkable however the tropical atlantic center is probably the most intriguing feature of this pattern apparently linking the nao with itcz variability in summer the pattern is tripole like with centers in the eastern mediterranean sea the north sea baltic sea and in the sub polar atlantic in the eastern indian ocean the correlation is positive in winter and negative in summer with some link to enso variability the sensitivity of these patterns to the choice of the nao index is minor in winter while quite important in summer interannual nao precipitation anomalies have driven similar fresh water variations in these key regions in the sub tropical and high latitude atlantic in winter precipitation anomalies have been roughly 15 and 10 of climatology per unit change of the nao respectively decadal changes of the nao during the last 50 years have also influenced precipitation and fresh water flux at these time scales with values lower higher than usual in the high latitude eastern north atlantic labrador sea in the 1960s and the late 1970s and an opposite situation since the early 1980s in summer the north sea baltic region has been drier than usual during the period 1965 1975 when the nao was generally positive

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

spatial variations in geochemical characteristics of the modern mackenzie delta sedimentary system the mackenzie river in canada is by far the largest riverine source of sediment and organic carbon oc to the arctic ocean therefore the transport degradation and burial of oc along the land to ocean continuum for this riverine system is important to study both regionally and as a dominant representative of arctic rivers here we apply sedimentological grain size mineral surface area and organic and inorganic geochemical techniques oc 13c oc and 14c oc 143nd 144nd 2h and 18o major and trace elements on particulate bank channel and lake surface sediments from the mackenzie delta as well as on surface sediments from the mackenzie shelf in the beaufort sea our data show a hydrodynamic sorting effect resulting in the accumulation of finer grained sediments in lake and shelf deposits a general decrease in organic carbon oc to mineral surface area ratios from river to sea furthermore suggests a loss of mineral bound terrestrial oc during transport through the delta and deposition on the shelf the net isotopic value of the terrestrial oc that is lost en route derived from relationships between 13c oc and surface area is 28 5 for 13c and 417 for 14c we calculated that oc burial efficiencies are around 55 which are higher 20 than other large river systems such as the amazon old sedimentary oc ages up to 12 14c ky suggest the delivery of both a petrogenic oc source with an estimated contribution of 19 9 as well as a pre aged terrestrial oc source we calculated the 14c age of this pre aged biogenic component to be about 6100 yrs or 501 which illustrates that terrestrial oc in the watershed can reside for millennia in soils before being released into the river surface sediments in lakes across the delta n 20 showed large variability in oc 0 92 5 7 and 13c 30 7 to 23 5 high closure lakes flooding only at exceptionally high water levels hold high sedimentary oc contents 2 5 and young biogenic oc with a terrestrial or an autochthonous source whereas no closure lakes permanently connected to a river channel hold sediments with pre aged terrestrial oc the intermediate low closure lakes flooding every year during peak discharge display the largest variability in oc content age and source likely reflecting variability in for example the length of river lake connections the distance to sediment source and the number of intermediate settling basins bank channel and suspended sediment show variable 143nd 144nd values yet there is a gradual but distinct spatial transition in 143nd 144nd nearly three e units from 11 4 to 13 9 in the detrital fraction of lake surface sediments from the western to the eastern delta this reflects the input of younger peel river catchment material in the west and input of older geological source material in the east and suggests that lake sediments can be used to assess variability in source watershed patterns across the delta

extratropical impacts on atlantic tropical cyclone activity abstractwith warm sea surface temperature sst anomalies in the tropical atlantic and cold sst anomalies in the east pacific the unusually quiet hurricane season in 2013 was a surprise to the hurricane community the authors analyses suggest that the substantially suppressed atlantic tropical cyclone tc activity in august 2013 can be attributed to frequent breaking of midlatitude rossby waves which led to the equatorward intrusion of cold and dry extratropical air the resultant mid to upper tropospheric dryness and strong vertical wind shear hindered tc development using the empirical orthogonal function analysis the active rossby wave breaking in august 2013 was found to be associated with a recurrent mode of the midlatitude jet stream over the north atlantic which represents the variability of the intensity and zonal extent of the jet this mode is significantly correlated with atlantic hurricane frequency the correlation coefficient is comparable to the correlation of atlantic hurricane fre

climate change and cultural response around 4000 cal yr b p in the western part of chinese loess plateau new data suggest that dramatic environmental change in the western loess plateau of china corresponded with substantial changes in human demography ca 4000 cal yr b p these data demonstrate that a rapid climatic transition from wet to dry led to an ecologically devastated period between 4090 and 3600 cal yr b p the sudden reduction in the number of archaeological sites during this period namely a reduction in the total number of sites and a contraction of the areal distribution of sites points to declining agricultural productivity associated with widespread aridification beginning at 4000 cal yr b p 2005 published by university of washington

modelling the influence of north atlantic multidecadal warmth on the indian summer rainfall 1 ensemble experiments with an atmospheric general circulation model reveal that a positive warm ocean phase of the atlantic multidecadal oscillation amo increases indian summer rainfall the intensification is driven by extratropical north atlantic warmth with some cancellation associated with monsoon weakening in response to tropical north atlantic warmth mechanistically warm extratropical north atlantic ssts increase local rainfall inducing an arching extratropical wavetrain response the latter leads to intensified northern subsidence of monsoon mean meridional streamflow as well as widespread low surface pressure over north africa the middle east and the western indian ocean contributing to a strengthened indian monsoon trough and increased monsoon rainfall warm tropical north atlantic ssts primarily increase local tropical atlantic rainfall that induces a tropically confined response consisting of low level easterly wind anomalies over the indian ocean and dynamically induced subsident drying over india

evidence for a widespread climatic anomaly at around 9 2 ka before present 1 the 8 2 ka event was triggered by a meltwater pulse mwp into the north atlantic and resultant reduction of the thermohaline circulation thc this event was preceded by a series of at least 14 mwps their impact on early holocene climate has remained almost unknown a set of high quality paleoclimate records from across the northern hemisphere shows evidence for a widespread and significant climatic anomaly at 9 2 ka b p this event has climatic anomaly patterns very similar to the 8 2 ka b p event cooling occurred at high latitudes and midlatitudes and drying took place in the northern tropics and is concurrent with an mwp of considerable volume 8100 km3 as the 9 2 ka mwp occurs at a time of enhanced baseline freshwater flow into the north atlantic this mwp may have been despite its relatively small volume sufficient to weaken thc and to induce the observed climate anomaly pattern

testing the robustness of a precipitation proxy based north atlantic oscillation reconstruction abstract the reconstruction of past atmospheric circulation is crucial for the understanding of natural climate change and its driving factors a recent reconstruction suggests that during medieval times the european region was dominated by a persistent positive phase of the north atlantic oscillation nao followed by a shift to a more oscillatory behavior we test this hypothesis and the concept underlying the reconstruction in a pseudo proxy approach using instrumental records reanalysis data sets and millennial simulations with four different climate models while a shift from a more positive to a more negative phase of the nao seems to be likely the amplitude and persistence of the reconstructed positive phase cannot be reproduced by models the analysis further reveals that proxy locations that were used in the reconstruction are not always sufficient to describe the nao this is reflected in a failure of the reconstruction to verify against instrumental records of the nao in the 19th century by adding complementary proxies the robustness of an nao reconstruction can be improved to the degree that it would withstand the tests presented here

diagenetic trends in the phenolic constituents of sphagnum dominated peat and its corresponding humic acid fraction abstract models of peat accumulation assume that peat decomposition occurs mostly above the water table with little or no decomposition once it enters the deeper saturated anoxic zone few studies have used molecular biomarkers for tracing post depositional decomposition related trends in peat deposits we studied the major diagenetic changes in the phenolic constituents within a sphagnum dominated ombrotrophic bog deposit the yield of lignin derived phenols and degree of decomposition measured using alkaline cupric oxide oxidation of bulk peat samples and their corresponding humic acids revealed that most of the degradation takes place in the surface layers corresponding to the acrotelm in fact total phenolic constituents of peat samples decrease from 36 1 to 21 6 mg g 1 oc organic carbon over the first 36 cm whereas in the deeper anoxic layers phenolic constituents tend to accumulate reaching a highest concentration of 71 0 mg g 1 oc the diagenetic alteration of these phenolic constituents during peat accumulation involves significant demethoxylation and an increasing yield of vanillyl oxidation products despite the low redox potential syringyl phenols tend to be particularly resistant to diagenetic alteration and are significantly enriched within the humic acid fraction twofold with respect to the bulk peat this together with the higher degree of oxidation suggests that this organic matter fraction is enriched in more resistant but nonetheless diagenetically altered phenolic constituents this suggests that humic acids constitute a refractory pool of organic c with a relatively low turnover rate our results confirm that the major processes involved in the variation in phenolic constituents with depth are strongly related to the post depositional environment and that evaluation of diagenetic trends in phenolic constituents may provide molecular level information on the changes that fresh biomass undergoes during early diagenesis in peatlands

sediment and particulate organic carbon budgets of a subarctic estuarine fjard lake melville labrador abstract sediment and particulate organic carbon poc budgets constructed for oceanic regions provide a means to quantify the burial of poc providing a baseline against which future change can be measured here we developed the first mass balance budgets of sediment and poc terrestrial and marine for the lake melville system lms goose bay and lake melville in central labrador using previously published data 210pb based mass accumulation rates river discharge and total suspended solids together with measurements of oc and 13c signatures within dated sediment cores collected from the lms basins and water from main tributaries and groswater bay a two end member mixing model was used to establish fractions of terrigenous and marine poc overall our mass balance budgets show that the churchill river is the major supply of sediment 16 7 7 8 108 kg y 1 and pocterr 18 4 6 6 106 kg y 1 to the lms accounting for 47 and 56 of the total input to the system respectively although the churchill river drains directly into goose bay along with the smaller goose river the majority of sediment 12 9 7 8 108 kg y 1 and pocterr 11 8 7 0 106 kg y 1 is transported eastward through the surface water plume into lake melville inputs of pocmar from autochthonous primary production estimated by applying an empirical relationship between sediment surface flux of pocmar and water depth to goose bay 1 8 106 kg y 1 and lake melville 98 3 4 7 106 kg y 1 increase with increasing distance from the churchill river to investigate the potential changes to the sediment load of the churchill river to the lms following impoundment at muskrat falls we calculated the sediment increase using the median reservoir shoreline erosion potential this approach showed that the delivery of sediment and pocterr to the lms by the churchill river may double during the two years following impoundment of the lower churchill river

strong coherence between solar variability and the monsoon in oman between 9 and 6 kyr ago variations in the amount of solar radiation reaching the earth are thought to influence climate but the extent of this influence on timescales of millennia to decades is unclear a number of climate records show correlations between solar cycles and climate1 but the absolute changes in solar intensity over the range of decades to millennia are small2 and the influence of solar flux on climate is not well established the formation of stalagmites in northern oman has recorded past northward shifts of the intertropical convergence zone3 whose northward migration stops near the southern shoreline of arabia in the present climate4 here we present a high resolution record of oxygen isotope variations for the period from 9 6 to 6 1 kyr before present in a th u dated stalagmite from oman the 18o record from the stalagmite which serves as a proxy for variations in the tropical circulation and monsoon rainfall allows us to make a direct comparison of the 18o record with the 14c record from tree rings5 which largely reflects changes in solar activity6 7 the excellent correlation between the two records suggests that one of the primary controls on centennial to decadal scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation

centers of organic carbon burial and oxidation at the land ocean interface abstract continental margin systems collectively receive and store vast amounts of organic carbon oc derived from primary productivity both on land and in the ocean thereby playing a central role in the global carbon cycle the land ocean interface is however extremely heterogeneous in terms of terrigenous input marine primary productivity sediment transport processes and depositional conditions e g such as bottom water oxygen level continental margins are also highly dynamic with processes occurring over a broad range of spatial and temporal scales the rates of oc burial and oxidation are consequently variable over both space and time hindering our ability to derive a global picture of oc cycling at the land ocean interface here we review the processes controlling the fate of organic matter in continental margin sediments with a special emphasis on hot spots and hot moments of oc burial and oxidation we present a compilation of compositional data from a set of illustrative settings including fjords small mountainous river margins large deltaic systems and upwelling areas bulk oc stable isotope and radiocarbon compositions reveal the diversity and complexity characteristic of oc buried in marginal seas this primarily relates to differences in marine and terrestrial inputs the composition of the terrestrial component e g vascular plant oc soil and petrogenic oc inputs and processes modulating the fate of oc within the marine environment e g priming this widely contrasting behavior of oc among these systems illustrates that the reactivity of oc is a product of its chemical composition and regional conditions interpreted in the context of bulk compositional data as well as that obtained on specific molecular markers e g lignin derived phenols the possibility exists to tease apart complex mixtures of terrestrial and marine inputs and to shed light on the role of the myriad of depositional and post depositional processes finally we discuss a set of hot topics that warrant further investigation such as the role of photochemistry fungi halogenation and reactive iron in dictating the fate of oc in the changing coastal ocean

a link between fram strait sea ice export and atmospheric planetary wave phase 1 a link is found between the variability of fram strait sea ice export and the phase of zonal wave 1 in slp for the period 1958 1997 previous studies have found that the link between ice export through fram strait and the nao is inconsistent over time scales longer than the last two decades inconsistent and low correlations are also found between fram strait ice export and the ao index the phase of zonal wave 1 explains 60 70 of the simulated ice export variance after the removal of two anomalous phases in 1966 and 1967 unlike the nao and ao links these high variances are consistent for both the first and second halves of the 40 year period this consistency is attributed to the sensitivity of wave 1 phase to the presence of secondary low pressure systems in the barents sea that serve to drive arctic sea ice southward through fram strait

a sediment and organic carbon budget for the canadian beaufort shelf abstract the arctic ocean accounts for 20 of the world s continental shelves because the arctic is sensitive to global change budgets of organic carbon for its shelves are of immediate interest the mackenzie shelf of the canadian beaufort sea is the best north american proxy for the enormous eurasian shelves large area large river input and the only site for which a complete organic carbon budget can be attempted due to an extensive data base a mass balance for the mackenzie shelf has been constructed for sediments terrestrial organic carbon and primary produced carbon we have considered allochthonous inputs from the mackenzie river from coastal erosion from smaller rivers from groundwater from the atmosphere and import by ice the mackenzie river dominates the supply to the beaufort shelf of inorganic sediment 127 mt a 1 and paniculate and dissolved terrestrial carbon 2 1 mt a 1 poc 1 3 mt a 1 doc the combined input from all other sources contributes only about 5 of the mackenzie load using sediment accumulation data we estimate that about half of the sediment supply is trapped in the delta about 40 on the shelf and the remainder escapes the shelf edge by various processes autochthonous primary production in the delta and on the shelf adds a further 3 3 mt a 1 of particulate organic carbon a box model has been constructed to account for sediment terrestrial organic carbon and primary produced carbon whereas about 60 of the terrestrial poc is preserved in delta and shelf sediments it appears that most 97 of the primary produced carbon is recycled and not preserved in sediments confidence in the budget should be improved by focusing future research on the determination of modern sedimentation rates on the delta and shelf measurement of organic carbon content of deltaic sediments determination of primary production on the shelf and determination of the relative proportions of terrestrial and marine organic carbon preserved in sediments

lessons learned from oxygen isotopes in modern precipitation applied to interpretation of speleothem records of paleoclimate from eastern asia abstract variability in oxygen isotope ratios collected from speleothems in chinese caves is often interpreted as a proxy for variability of precipitation summer precipitation seasonality of precipitation and or the proportion of 18o to 16o of annual total rainfall that is related to a strengthening or weakening of the east asian monsoon and in some cases to the indian monsoon we use modern reanalysis and station data to test whether precipitation and temperature variability over china can be related to changes in climate in these distant locales we find that annual and rainy season precipitation totals in each of central china south china and east india have correlation length scales of 500 km shorter than the distance between many speleothem records that share similar long term time variations in 18o values thus the short distances of correlation do not support though by themselves cannot refute the idea that apparently synchronous variations in 18o values at widely spaced 500 km caves in china are due to variations in annual precipitation amounts we also evaluate connections between climate variables and 18o values using available instrumental measurements of 18o values in precipitation these data from stations in the global network of isotopes in precipitation gnip show that monthly 18o values generally do not correlate well with either local precipitation amount or local temperature and the degree to which monthly 18o values do correlate with them varies from station to station for the few locations that do show significant correlations between 18o values and precipitation amount we estimate the differences in precipitation amount that would be required to account for peak to peak differences in 18o values in the speleothems from hulu and dongge caves assuming that 18o scales with the monthly amount of precipitation or with seasonal differences in precipitation insofar as the present day relationship between 18o values and monthly precipitation amounts can be applied to past conditions differences of at least 50 in mean annual precipitation would be required to explain the 18o variations on orbital time scales which are implausibly large and inconsistent with published gcm results similarly plausible amplitudes of seasonal cycles in amounts or in seasonal variations in 18o values can account for less than half of the 4 5 difference between glacial and interglacial 18o values from speleothems in china if seasonal cycles in precipitation account for the amplitudes of 18o values on paleoclimate timescales they might do so by extending or contracting the durations of seasons a frequency modulation of the annual cycle but not by simply varying the amplitudes of the monthly rainfall amounts or monthly average 18o values amplitude modulation allowing that several processes can affect seasonal variability in isotopic content we explore the possibility that one or more of the following processes contribute to variations in 18o values in chinese cave speleothems different source regions of the precipitation which bring different values of 18o in vapor different pathways between the moisture source and the paleorecord site along which exchange of 18o between vapor surface water and condensate might differ a different mix of processes involving condensation and evaporation within the atmosphere or different types of precipitation each may account for part of the range of 18o values revealed by speleothems and each might contribute to seasonal differences between past and present that do not scale with monthly or even seasonal precipitation amounts

high precision and high resolution carbonate 230th dating by mc icp ms with sem protocols abstract to facilitate the measurement of u th isotopic compositions suitable for high precision and high resolution 230th dating of coral and speleothem carbonates secondary electron multiplier sem protocol techniques for multicollector inductively coupled plasma mass spectrometry mc icp ms have been developed the instrumental sensitivities are 1 2 with a precision of 1 2 2 for abundance determination of 50 200 fg 234u 1 4 ng 238u or 230th this method features chemistry refinements improvements to procedural and instrumental blanks spectral inference reductions and careful consideration of non linear sem behavior measurement consistency of this mc icp ms combined with previous mass spectrometric results on u th standards and a variety of carbonates demonstrates the validity of the sem protocol method for fossil corals a routine u th isotopic determination at permil level precision requires only 10 50 mg of carbonate as little as 200 mg of young coral with an age of less than 20 yr can be dated with a precision of 0 3 0 8 yr about 20 200 mg speleothem samples with sub ppm to ppm u are required to earn a 5 precision on ages from 5 to 100 kyr requirement of small sample size 10 100s mg carbonate can permit high temporal resolution to date speleothems with slow growth rates i e 1 10 mm kyr this high precision 230th chronology is critical to accurately establish age models date events and splice geochemical proxy time series records from multiple samples in the fields of paleoclimatology and paleoceanography the u th isotopic determination techniques described here can also be applied to different environmental samples such as waters rocks and sediments

preferential burial of permafrost derived organic carbon in siberian arctic shelf waters the rapidly changing east siberian arctic shelf esas receives large amounts of terrestrial organic carbon oc from coastal erosion and russian arctic rivers climate warming increases thawing of coastal ice complex deposits icd and can change both the amount of released oc as well as its propensity to be converted to greenhouse gases fueling further global warming or to be buried in coastal sediments this study aimed to unravel the susceptibility to degradation and transport and dispersal patterns of oc delivered to the esas bulk and molecular radiocarbon analyses on surface particulate matter pm sinking pm and underlying surface sediments illustrate the active release of old oc from coastal permafrost molecular tracers for recalcitrant soil oc showed ages of 3 4 13 14c ky in surface pm and 5 5 18 14c ky in surface sediments the age difference of these markers between surface pm and surface sediments is larger i in regions with low oc accumulation rates suggesting a weaker exchange between water column and sediments and ii with increasing distance from the lena river suggesting preferential settling of fluvially derived old oc nearshore a dual carbon end member mixing model showed that i contemporary terrestrial oc is dispersed mainly by horizontal transport while being subject to active degradation ii marine oc is most affected by vertical transport and also actively degraded in the water column and iii oc from icd settles rapidly and dominates surface sediments preferential burial of icd oc released into esas coastal waters might therefore lower the suggested carbon cycle climate feedback from thawing icd permafrost

asynchronous holocene climatic change across china a review of holocene climatic variations in different parts of china shows that they were asynchronous proxy data from ice cores pollen loess lacustrine sediments and changes of sea and lake levels demonstrate that many warm and cold oscillations have occurred in china during the holocene including a most important climatic event known as the holocene optimum a milder and wetter period and that the duration and amplitude of the optimum period as well as its start and end times differed in different parts of china uplift of the tibetan plateau over the past millions of years led to the development of the monsoon climate and to complex atmospheric circulation over continental china during the holocene as a result the holocene optimum began and terminated earlier in high altitude regions of western china than at lower elevations in eastern china and the amplitude of the variations was lower in the east this suggests that the western higher altitude areas were more sensitive to climatic change than were the eastern lower altitude areas holocene climatic records in the dunde and guliya ice cores do not correspond inverse 18o variations between the two cores indicate that the effects of climate and atmospheric processes on the stable isotopes at the two sites differed the correlation between the isotopic composition of carbonates in lake deposits in western china and climatic variations is similar to that in the ice cores the climatic resolution in ice cores and lake sediments is higher than that in other media the lack of precise correspondence of climatic records constructed on the basis of proxy data from different parts of china is a result of the different locations and elevations of the sampling sites the different resolutions of the source material and the varied climatic conditions within china further work is needed to confirm both the conclusions and the inferences presented here

modelling river discharge and precipitation from estuarine salinity in the northern chesapeake bay application to holocene palaeoclimate long term chronologies of precipitation can provide a baseline against which twentieth century trends in rainfall can be evaluated in terms of natural variability and anthropogenic influence howev

reconstruction of prehistoric pottery use from fatty acid carbon isotope signatures using bayesian inference abstract carbon isotope measurements of individual fatty acids c16 0 and c18 0 recovered from archaeological pottery vessels are widely used in archaeology to investigate past culinary and economic practices typically such isotope measurements are matched with reference to food sources for straightforward source identification or simple linear models are used to investigate mixing of contents however in cases where multiple food sources were processed in the same vessel these approaches result in equivocal solutions to address this issue we tested the use of a bayesian mixing model to determine the proportional contribution of different food sources to a series of different mixed food compositions using data generated both by simulation and by experiment the model was then applied to previously published fatty acid isotope datasets from pottery from two prehistoric sites durrington walls near stonehenge in southern britain and neustadt in northern germany we show that the bayesian approach to the reconstruction of pottery use offers a reliable probabilistic interpretation of source contributions although the analysis also highlights the relatively low precision achievable in quantifying pottery contents from datasets of this nature we suggest that with some refinement the approach outlined should become standard practice in organic residue analysis and also has potential application to a wide range of geological and geochemical investigations

fossil organic matter characteristics in permafrost deposits of the northeast siberian arctic 1 permafrost deposits constitute a large organic carbon pool highly vulnerable to degradation and potential carbon release due to global warming permafrost sections along coastal and river bank exposures in ne siberia were studied for organic matter om characteristics and ice content om stored in quaternary permafrost grew accumulated froze partly decomposed and refroze under different periglacial environments reflected in specific biogeochemical and cryolithological features om in permafrost is represented by twigs leaves peat grass roots and plant detritus the vertical distribution of total organic carbon toc in exposures varies from 0 1 wt of the dry sediment in fluvial deposits to 45 wt in holocene peats variations in om parameters are related to changes in vegetation bioproductivity pedogenic processes decomposition and sedimentation rates during past climate variations high toc high c n and low 13c reflect less decomposed om accumulated under wet anaerobic soil conditions characteristic of interglacial and interstadial periods glacial and stadial periods are characterized by less variable low toc low c n and high 13c values indicating stable environments with reduced bioproductivity and stronger om decomposition under dryer aerobic soil conditions based on toc data and updated information on bulk densities we estimate average organic carbon inventories for ten different stratigraphic units in northeast siberia ranging from 7 2 kg c m 3 for early weichselian fluvial deposits to 33 2 kg c m 3 for middle weichselian ice complex deposits to 74 7 kg c m 3 for holocene peaty deposits the resulting landscape average is likely about 25 lower than previously published permafrost carbon inventories

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

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

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

seasonality of the north atlantic oscillation abstract monthly sea level pressure slp data from the national centers for environmental prediction reanalysis for 1948 99 are used to develop a seasonally and geographically varying mobile index of the north atlantic oscillation naom naom is defined as the difference between normalized slp anomalies at the locations of maximum negative correlation between the subtropical and subpolar north atlantic slp the subtropical nodal point migrates westward and slightly northward into the central north atlantic from winter to summer the naom index is robust across datasets and correlates more highly than eof coefficients with historical measures of westerly wind intensity across north atlantic midlatitudes as measured by this mobile index the nao s nodes maintain their correlation from winter to summer to a greater degree than traditional nao indices based on fixed stations in the eastern north atlantic azores lisbon iceland when the naom index is extended back to 1873 its annual values during

a nonlinear expression of the north atlantic oscillation in the north pacific 1 the north atlantic oscillation nao has been identified as an important mode of variability in the climate system our knowledge of its impacts is based largely on linear analysis techniques as a result nonlinearities associated with it are largely unknown in this study we use recently proposed nonlinear compositing and one sided regression techniques as well as a new rectified regression technique to show that the nonlinear expression of the nao is fundamentally different from its linear expression in particular we show that its nonlinear expression is amplitude but not sign dependent and has a center of action in the north pacific sector that is associated with the east asia jet stream eajs and the aleutian low

reconstruction of climate and vegetation changes of lake bayanchagan inner mongolia holocene variability of the east asian monsoon a high resolution pollen and pediastrum record spanning 12 500 yr is presented for lake bayanchagan 115 21 e 41 65 n and 1355 m a s l southern inner mongolia individual pollen taxa pt mat and the pft affinity scores pft mat were used for quantitative climatic reconstruction from pollen and algal data both techniques indicate that a cold and dry climate similar to that of today prevailed before 10 500 cal yr b p the wettest climate occurred between 10 500 and 6500 cal yr b p at which time annual precipitation was up to 30 60 higher than today the early holocene increases in temperature and precipitation occurred simultaneously but mid holocene cooling started at approximately 8000 cal yr b p 1500 yr earlier than the drying vegetation reconstruction was based on the objective assignment of pollen taxa to the plant functional type the results suggest that this region was dominated by steppe vegetation throughout the holocene except for the period 9200 to 6700 cal yr b p when forest patches were relatively common inner mongolia is situated at the limit of the present east asian monsoon and patterns of vegetation and climate changes in that region during the holocene probably reflect fluctuations in the monsoon s response to solar insolation variations the early to middle holocene monsoon undoubtedly extended to more northern latitudes than at present

modes of climate variability synthesis and review of proxy based reconstructions through the holocene abstract modes of climate variability affect global and regional climates on different spatio temporal scales and they have important impacts on human activities and ecosystems as these modes are a useful tool for simplifying the understanding of the climate system it is crucial that we gain improved knowledge of their long term past evolution and interactions over time to contextualise their present and future behaviour we review the literature focused on proxy based reconstructions of modes of climate variability during the holocene i e the last 11 7 thousand years with a special emphasis on i proxy based reconstruction methods ii available proxy based reconstructions of the main modes of variability i e el nino southern oscillation pacific decadal variability atlantic multidecadal variability the north atlantic oscillation the southern annular mode and the indian ocean dipole iii major interactions between these modes and iv external forcing mechanisms related to the evolution of these modes this review shows that modes of variability can be reconstructed using proxy based records from a wide range of natural archives but these reconstructions are scarce beyond the last millennium partly due to the lack of robust chronologies with reduced dating uncertainties technical issues related to proxy calibration and difficulty elucidating their stationary impact or not on regional climates over time while for each mode the available reconstructions tend to agree at mutidecadal timescales they show notable disagreement on shorter timescales beyond the instrumental period the reviewed evidence suggests that the intrinsic variability of modes can be modulated by external forcing such as orbital solar volcanic and anthropogenic forcing the review also highlights some modes experience higher variability over the instrumental period which is partly ascribed to anthropogenic forcing these features stress the paramount importance of further studying their past variations using long climate proxy records for the progress of climate science

multidecadal variability of north atlantic temperature and salinity during the twentieth century abstract substantial changes occurred in the north atlantic during the twentieth century here the authors demonstrate through the analysis of a vast collection of observational data that multidecadal fluctuations on time scales of 50 80 yr are prevalent in the upper 3000 m of the north atlantic ocean spatially averaged temperature and salinity from the 0 300 and 1000 3000 m layers vary in opposition prolonged periods of cooling and freshening warming and salinification in one layer are generally associated with opposite tendencies in the other layer consistent with the notion of thermohaline overturning circulation in the 1990s widespread cooling and freshening was a dominant feature in the 1000 3000 m layer whereas warming and salinification generally dominated in the upper 300 m except for the subpolar north atlantic where complex exchanges with the arctic ocean occur the single signed basin scale pattern of multidecadal variability is evident from decadal 1000 3000 m temperature and salin

influence of the intertropical convergence zone on the east asian monsoon a palaeoclimate record spanning the past 16 000 years with nearly annual time resolution has been obtained from lake huguang maar in china the magnetic properties and titanium content of the lake sediments are thought to reflect changes in the east asian winter monsoon strength thus providing a complement to palaeoclimate archives that record the strength of the rain bearing summer monsoon the records point to an anti correlation between winter and summer monsoon strength best explained by migration of the intertropical convergence zone itcz a belt of low pressure air at the equator interestingly the decline of china s tang dynasty and the mayan civilization broadly coincide with drought periods recorded in lake huguang maar and cariaco basin sediments respectively did major shifts in the position of the itcz catalyse simultaneous events in civilizations on opposite sides of the pacific ocean the asian australian monsoon is an important component of the earth s climate system that influences the societal and economic activity of roughly half the world s population the past strength of the rain bearing east asian summer monsoon can be reconstructed with archives such as cave deposits1 2 3 but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct here we present high resolution records of the magnetic properties and the titanium content of the sediments of lake huguang maar in coastal southeast china over the past 16 000 years which we use as proxies for the strength of the winter monsoon winds we find evidence for stronger winter monsoon winds before the bolling allerod warming during the younger dryas episode and during the middle and late holocene when cave stalagmites suggest weaker summer monsoons1 2 3 we conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone similar migrations of the intertropical convergence zone have been observed in central america for the period ad 700 to 900 refs 4 6 suggesting global climatic changes at that time from the coincidence in timing we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the tang dynasty in china and the classic maya in central america

subannual to interannual variabilities of sst in the north atlantic ocean abstractbased on observational data this work examines the multi time scale feature of the sea surface temperature sst variability averaged in the whole north atlantic ocean to be referred to a

contrasting impacts of the arctic oscillation on surface air temperature anomalies in southern china between early and middle to late winter abstractin the boreal winter the arctic oscillation ao evidently acts to influence surface air temperature sat anomalies in china this study reveals a large intraseasonal variation in the relationship between the winter ao and southern china sat anomalies specifically a weak in phase relationship occurs in december but a significant out of phase relationship occurs in january and february the authors show that the linkage between the ao and southern china sat anomalies strongly depends on the ao associated changes in the middle east jet stream mejs and that such an ao mejs relationship is characterized by a significant difference between early and middle to late winter in middle to late winter the azores center of high pressure anomalies in the positive ao phase usually extends eastward and yields a significantly anomalous upper level convergence over the mediterranean sea which can excite a rossby wave train spanning the arabian sea and intensify the mejs in early winter however the azo

evidence for permafrost thaw and transport from an alaskan north slope watershed burial of organic carbon oc in marine sediments is one of the most important linkages between the short term biologic carbon cycle and the long term geologic carbon cycle yet much is still unknown about the fate of terrigenous oc in marine coastal margins here the delivery of particulate oc poc to the colville river deltaic region in the alaskan beaufort sea by particulates of varying densities is studied through the use of ramped temperature pyrolysis and radiocarbon analyses the colville river is the largest river in north america whose watershed is underlain completely by high arctic permafrost tundra a variety of sources of poc are considered including terrestrial soils pleistocene aged yedoma like sediments coastal peat erosion and marine poc we provide the first evidence that riverine poc from the colville river contains old pleistocene sourced oc suggesting ongoing thaw and mobilization of yedoma like permafrost oc from this northern alaskan watershed additionally much of this oc appears to be fairly labile and therefore could be readily oxidized and returned to the atmosphere

atmospheric circulation variability in the north atlantic european area since the mid seventeenth century based on monthly mean sea level pressure grids objectively reconstructed by luterbacher et al variations of dynamical modes of the atmospheric circulation for january and july are described by novel indices for running 31 year periods between 1659 and 1999 these indices reflect the continuous evolution of the atmospheric circulation not only with regard to frequency changes of major dynamical modes but also in terms of internal changes within each mode concerning both dynamic vorticity intensity and climatic properties central european temperature and precipitation during occurrence of each mode respectively results indicate the great importance of within mode variations the zonal circulation mode in january varying in frequency with long term cycles primarily changed its dynamic and climatic properties towards higher indices during the transition from the little ice age to modern conditions between 1800 and 1930 within the russian high mode of january a change in preference from easterly to westerly patterns above central europe occurred around 1850 for july a striking frequency maximum of the westerly mode at the end of the eighteenth century coincided with a period of marked summer warmth in central europe due to negative positive deviations in vorticity temperature during occurrence of this mode the long term evolution in july indicates a general increase of anticyclonic conditions strengthening during the last 50 years towards a unique phenomenon within the last centuries the strong increase in the winter time westerly circulation during the last decades however does not appear extraordinary in view of the low frequency variations of this mode

composition and fate of terrigenous organic matter along the arctic land ocean continuum in east siberia insights from biomarkers and carbon isotopes abstract climate warming is predicted to translocate terrigenous organic carbon terroc to the arctic ocean and affect the marine biogeochemistry at high latitudes the magnitude of this translocation is currently unknown so is the climate response the fate of the remobilized terroc across the arctic shelves represents an unconstrained component of this feedback the present study investigated the fate of permafrost carbon along the land ocean continuum by characterizing the terroc composition in three different terrestrial carbon pools from siberian permafrost surface organic rich horizon mineral soil active layer and ice complex deposit and marine sediments collected on the extensive east siberian arctic shelf esas high levels of lignin phenols and cutin acids were measured in all terrestrial samples analyzed indicating that these compounds can be used to trace the heterogeneous terrigenous material entering the arctic ocean in esas sediments comparison of these terrigenous biomarkers with other terroc proxies bulk 13c 14c and hmw lipid biomarkers highlighted contrasting across shelf trends these differences could indicate that terroc in the esas is made up of several pools that exhibit contrasting reactivity toward oxidation during the transport in this reactive spectrum lignin is the most reactive decreasing up to three orders of magnitude from the inner to the outer shelf while the decrease of hmw wax lipid biomarkers was considerably less pronounced alternatively degradation might be negligible while sediment sorting during the across shelf transport could be the major physical forcing that redistributes different terroc pools characterized by different matrix association despite the marked decrease shown by lignin the fingerprint of lignin phenols such as the acid aldehyde ratio of vanillyl and syringyl phenols showed a lack of any across shelf trends and exhibited an extremely wide range of values in all terrestrial samples by contrast the 3 5 dihydroxybenzoic vanillyl phenols ratio exhibited a clear across shelf trend suggesting either increasing degradation with distance from the coast or terroc sorting along the sediment dispersal system the ratio of syringyl vanillyl phenols indicated that gymnosperm tissues are more important than angiosperm tissues in surface sediments in particular off the lena river mouth consistent with the vegetation in its watershed conversely the fingerprint of p hydroxybenzenes suggests lack of substantial input of moss derived material finally autochthonous lipid and protein derived cuo reaction products displayed a strong along shelf gradient likely reflecting the inflow of nutrient rich pacific waters from the bering strait that stimulate primary productivity in the eastern esas in particular short chain fatty acids showed a clear frontal transition zone between pacific influenced and river influenced waters approximately along the 160 e longitude considering the labile nature of phytoplankton priming and co metabolism processes might stimulate degradation of terroc in the easternmost region of the siberian shelf this study demonstrated the need to consider multiple terroc proxies at isotopic molecular levels to differentiate the fate for different allocthonous components in arctic sediments and the need to assess how these terroc pools are distributed in different density size and settling fractions to better discriminate between the extent of hydrodynamic sorting versus degradation

multimolecular tracers of terrestrial carbon transfer across the pan arctic 14c characteristics of sedimentary carbon components and their environmental controls distinguishing the sources ages and fate of various terrestrial organic carbon oc pools mobilized from heterogeneous arctic landscapes is key to assessing climatic impacts on the fluvial release of carbon from permafrost through molecular 14c measurements including novel analyses of suberin and or cutin derived diacids das and hydroxy fatty acids fas we compared the radiocarbon characteristics of a comprehensive suite of terrestrial markers including plant wax lipids cutin suberin lignin and hydroxy phenols in the sedimentary particles from nine major arctic and subarctic rivers in order to establish a benchmark assessment of the mobilization patterns of terrestrial oc pools across the pan arctic terrestrial lipids including suberin derived longer chain das c24 26 28 plant wax fas c24 26 28 and n alkanes c27 29 31 incorporated significant inputs of aged carbon presumably from deeper soil horizons mobilization and translocation of these old terrestrial carbon components was dependent on nonlinear processes associated with permafrost distributions by contrast shorter chain c16 18 das and lignin phenols as well as hydroxy phenols in rivers outside eastern eurasian arctic were much more enriched in 14c suggesting incorporation of relatively young carbon supplied by runoff processes from recent vegetation debris and surface layers furthermore the radiocarbon content of terrestrial markers is heavily influenced by specific oc sources and degradation status overall multitracer molecular 14c analysis sheds new light on the mobilization of terrestrial oc from arctic watersheds our findings of distinct ages for various terrestrial carbon components may aid in elucidating fate of different terrestrial oc pools in the face of increasing arctic permafrost thaw

palaeoclimatic interpretation of high resolution oxygen isotope profiles derived from annually laminated speleothems from southern oman high resolution stable isotope profiles of three contemporaneously deposited stalagmites from a shallow cave in southern oman provide an annually resolved record of indian ocean monsoon rainfall variability for the past 780 years uranium series age dating and counts of annual growth bands enable an excellent age calibration although modern speleothems do not grow in perfect isotopic equilibrium oxygen isotope ratios 18o are a proxy for the amount of monsoon rainfall this is supported by the statistically significant correlation between 18o and the thickness of annual bands whereas 18o is inversely correlated with annual band thickness additionally overlapping 18o profiles are very similar in pattern and range indicating that sample specific noise did not blur the climatic signal the longest oxygen isotope profile derived from stalagmite s3 clearly shows the transition at 1320 ad from a generally wetter medieval warm period to a drier little ice age that lasted from approximately ad 1320 1660 in southern oman the decrease in monsoon rainfall since the 1960s is also obvious in meteorological records from northern africa and india indicating that our speleothem based rainfall records do not only reflect local monsoon rainfall variability

the fate of terrigenous dissolved organic carbon on the eurasian shelves and export to the north atlantic dissolved lignin phenols chromophoric dissolved organic matter cdom absorption and fluorescence were analyzed along cross slope mooring locations in the barents laptev and east siberian seas to gain a better understanding of terrigenous dissolved organic carbon tdoc dynamics in arctic shelf seas and the arctic ocean a gradient of river water and tdoc was observed along the continental shelf eastward into the east siberian sea correlations of carbon normalized yields of lignin derived phenols supplied by siberian rivers with river water fractions and known water residence times yielded in situ decay constants of 0 18 0 58 yr 1 calculations showed 50 of annual tdoc discharged by siberian rivers was mineralized in estuaries and on eurasian shelves per year indicating extensive removal of tdoc bioassay experiments and in situ decay constants indicated a reactivity continuum for tdoc cdom parameters and acid aldehyde ratios of vanillyl v and syringyl s lignin phenols showed biomineralization was the dominant mechanism for the removal of tdoc characteristic ratios of p hydroxy p s and v phenols p v s v also identified shelf regions in the kara sea and regions along the western laptev sea shelf where formation of low salinity halocline waters lshw and lower halocline water lhw occurred the efficient removal of tdoc demonstrates the importance of eurasian margins as sinks of tdoc derived from the large siberian rivers and confirms tdoc mineralization has a major impact on nutrients budgets air sea co2 exchange and acidification in the siberian shelf seas

the provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the ganges brahmaputra rivers organic matter carried by rivers and deposited in continental and marine sediments contains valuable information on past environmental conditions and their impact on the terrestrial biosphere in order to use sedimentary records to reconstruct past environmental conditions on the continents such as vegetation cover and type or precipitation intensity we need to understand the provenance of the organic signatures and how they are transferred and potentially modified by fluvial transport to the sedimentary reservoir in particular we need to understand how environmental conditions are imprinted in the composition of riverine particulate organic carbon here we investigate the stable carbon and hydrogen isotopic signatures of vascular plant leaf wax biomarkers in the modern day ganges and brahmaputra river complex one of the largest fluvial systems on earth the distribution of n alkanes and n alkanoic acids in ganges brahmaputra river sediments suggests that vascular plant inputs are consistently a significant component of the organic carbon pool molecular 13c measurements reveal that c3 vegetation inputs delivered by the himalayan rivers are partly degraded and replaced by mixed c3 c4 vegetation input in the floodplain the hydrogen isotopic composition of long chain c24 n alkanoic acids in combination with their stable c isotopic composition provides constraints on the isotopic composition of the environmental water used by higher plants within the drainage basin calculated compositions compare well with the depleted d isotopic ratios of the river water during the summer monsoon suggesting that h isotopic compositions of long chain alkanoic acids are a valuable proxy for the composition of summer monsoon moisture in the ganges brahmaputra basin detailed studies of the isotopic anatomy of modern river systems are critical for informed interpretation of marine sedimentary records in river influenced continental margins

river sediment discharge to the oceans present day controls and global budgets empirical relationships between river sediment yields and a large number of hydroclimatic biological and geomorphological parameters are investigated at the global scale for a set of 60 major world river basins the environmental characteristics were extracted from various global computer data sets and natural river sediment fluxes were taken from the literature it is found that sediment yields can be best correlated by forming the products of hydroclimatic and geomorphological factors that is runoff intensity basin slope an index characterizing rock hardness and an index characterizing rainfall variability over the year the best parameter combination varies to some extent when the rivers are grouped according to their average climatic situation but it is always a combination of the above mentioned parameters that yields the most significant models in arid climates however regression coefficients are greater than in humid climates indicating that erodibility is much greater than in arid climates when extrapolated to the total continental area on the basis of the corresponding data sets the empirical models result in a total sediment flux of about 16 gigatons discharged to the oceans every year which is in good agreement with previous estimates derived from compilations of world wide river data consequently two global maps are proposed showing the spatial distributions of river sediment yields on the continents as well as the inputs of these sediments to the oceans in a grid point scale by far most of the sediments originate from the young orogenic belts of the continents mainly due to a combination of steep morphologies and high runoff intensities

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

a 725 yr cycle in the climate of central africa during the late holocene high resolution analyses of the chemical and stable isotope composition of endogenic calcite from lake edward an equatorial rift lake in central africa reveal large oscillations in african climate and moisture balance over the past 5400 yr these oscillations indicate a series of droughts from 4900 to 400 yr b p that define a drought period of 725 yr this period may be correlated to variations in the indian ocean monsoons as documented by similar periods in sea surface salinity records from the northern indian ocean the similarities in periodicity of the lake edward and indian ocean records may indicate that low frequency variability within the indian and pacific oceans dominates millennial scale african moisture balance and the holocene climate of the tropical indian ocean

mg ca ratios in coralline algae record northwest atlantic temperature variations and north atlantic oscillation relationships climate variability in the north atlantic has been linked in part to the north atlantic oscillation nao the nao influences marine ecosystems in the northwestern atlantic and transport variability of the cold labrador current understanding historic patterns of nao variability requires long term and high resolution climate records that are not available from instrumental data here we present the first century scale proxy record of sea surface temperature sst variability from the newfoundland shelf a region from which other annual resolution shallow marine proxies are unavailable the 116 year record was obtained from three sites along the eastern newfoundland shelf using laser ablation inductively coupled mass spectrometry determined mg ca ratios in the crustose coralline alga clathromorphum compactum the alga is characterized by a high mg calcite skeleton exhibiting annual growth increments and a century scale lifespan results indicate positive correlations between interannual variations in mg ca ratios and both station based and gridded instrumental sst in addition the record shows high spatial correlations to sst across the newfoundland shelf and the gulf of st lawrence before 1950 the mg ca proxy record reveals significant departures from gridded temperature records while the newfoundland shelf is generally considered a region of negative correlations to the nao the algal time series as well as a recent modeling study suggest a variable negative relationship with the nao which is strongest after 1960 and before the mid 1930s

terrestrial plant biopolymers in marine sediments the vascular land plant biopolymers lignin and cutin were surveyed in the surface sediments of coastal and open ocean waters by controlled alkaline cuo oxidation reaction two contrasting oceanic regimes were studied the northwest mediterranean nwm sea which receives significant particulate terrigenous debris through riverine discharge and the northeast atlantic nea ocean with poorly characterised terrestrial carbon inputs in the nwm products of lignin and cutin co occurred at all stations elevated levels ca 0 5 3 0 mg lignin phenols 100 mg organic carbon ca 0 01 0 09 mg cutin acids 100 mg organic carbon were observed for near shore deltaic and shelf sediments the influence of terrestrial land plant inputs extended across the shelf and through the slope to the abyssal plain providing molecular evidence for advective offshore transfer of terrestrial carbon mass balance estimates for the basin suggest riverine inputs account for the majority of surface sedimentary lignin cutin most of which 90 is deposited on the shelf products of cuo oxidation of lignin and cutin were also detected in nea surface sediments at levels comparable to those observed for the nwm continental slope and were detectable at low concentrations ca 0 5 gg 1 in the sediments of the abyssal plains 4 000 m depth while atmospheric deposition of lignin cutin derived material cannot be discounted in this open ocean system lateral advective transfer of enriched shelf sediments is inferred as a possible transport process a progressive enrichment in cutin derived material relative to lignin was observed offshore with evidence of an increase in the degree of oxidative alteration of lignin residues to account for these observations preferential offshore transport of finer and more degraded material is proposed nonspecific oxidation products dominated the gas chromatograms of nea sediments which appear to originate from marine sources of sedimentary organic carbon preliminary mass balance calculations applied to the global ocean margin suggest riverine sources of both particulate lignin and cutin are important and that most 95 deposition of recognisable land plant biopolymers occurs in shelf seas

sub millennial variability of asian monsoon intensity during the early mis 3 and its analogue to the ice age terminations abstract although the initiation and continuation of orbital and millennial climate transitions were reported to be roughly similar little is yet known about the extent to which their sequences of climate events are linked together in the same physical processes here we present a stalagmite isotope record from wulu cave southwestern china based on 1200 oxygen isotope data and 15 230 th ages registering a detailed history of the asian monsoon am from 61 3 to 50 5 ka bp with an average resolution of 12 yr two replicated high resolution calcite 18 o profiles show four millennial scale strong summer monsoon events analogous in timing and structure to chinese interstadials a 17 a 14 cis a 17 a 14 as recorded elsewhere in china and greenland interstadials 17 14 gis 17 14 these events exhibit two distinct phases consistent with multi decadal centennial shifts in greenland temperature and storminess this relationship reveals a tight coupling between high and low latitude climates at sub millennial scales implying a role for westerly winds in linking greenland temperature and the am around the marine isotope stage mis 4 3 boundary successive am events resemble but in higher frequency structure of the bolling younger dryas yd surrounding termination i along with evidence from similar shifts in bipolar temperature and atmospheric ch 4 we suggest that the recurrence of similar climate structure worldwide is likely caused by changes in atlantic meridional overturning circulation amoc at various timescales under thresholds of global ice volume boundaries as predicted by the bipolar seesaw model

contrasting lipid biomarker composition of terrestrial organic matter exported from across the eurasian arctic by the five great russian arctic rivers contrasting lipid biomarker composition of terrestrial organic matter exported from across the eurasian arctic by the five great russian arctic rivers

terrestrial organic carbon contributions to sediments on the washington margin elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the columbia river basin and the washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments the biomarkers include an homologous series of long chain n alkanes derived from the surface waxes of higher plants phenolic and hydroxyalkanoic compounds produced by cuo oxidation of two major vascular plant biopolymers lignin and cutin all marine sediments including samples collected from the most remote sites in cascadia basin showed organic geochemical evidence for the presence of terrestrial organic carbon using endmember values for the various biomarkers determined empirically by two independent means we estimate that the terrestrial contribution to the washington margin is 60 for shelf sediments 30 for slope sediments and decreases further to 15 in basin sediments results from the same geochemical measurements made with depth in gravity core 6705 7 from cascadia seachannel suggest that our approach to assess terrestrial organic carbon contributions to contemporary deposits on the washington margin can be applied to the study of sediments depositing in this region since the last glacial period

sources of terrigenous inputs to surface sediments of the colville river delta and simpson s lagoon beaufort sea alaska 1 the provenance of sediments and particulate organic carbon poc in the colville river delta and adjacent simpson s lagoon in the alaskan beaufort sea was investigated using a variety of bulk and molecular techniques including stable and radiocarbon isotopes neodymium isotopes algal pigments and lignin phenols additionally stable carbon isotopes and lignin phenols were analyzed on four different density fractions from sediments the colville river the largest river in north america with a watershed exclusively located in the high arctic tundra was an important source of terrestrial poc to the western edge of the lagoon shown by extremely old radiocarbon ages fraction modern of 0 165 0 001 close to the river mouth up to 0 418 0 002 farther away stations without northern protective barrier islands had large amounts of marine poc input and evidence of benthic microalgae was found in one area of the lagoon chlorophyll a concentration 35 0 g goc 1 in the high algal biomass area compared to 1 to 7 g goc 1 outside of it stations in the middle and eastern end of the lagoon showed significant sediment input from coastal erosion input of peat indicating non lignin phenols 0 079 mg 100mgoc 1 in the eastern lagoon compared to 0 022 mg 100mgoc 1 near the colville delta and on the eastern end of the lagoon there was evidence of input of mackenzie river poc shown with neodymium isotopes and also cop poc inputs derived from rivers coastal erosion and marine productivity were quantified using a ternary mixing model and showed that fluvial supply and coastal erosion were the dominant carbon sources to the lagoon this constitutes the first study of poc delivery by the colville river into a nearshore region and illustrates that continued warming of the high arctic tundra will likely lead to increased riverine poc delivery to this region of the world

replicated stalagmite inferred centennial to decadal scale monsoon precipitation variability in southwest china since the mid holocene a lack of agreement between stalagmite records of the centennial to decadal scale asian summer monsoon asm variability since the mid holocene limited our understanding of forcings and the possible impacts on culture evolution here we present replicated high resolution stalagmite 18o profiles from dark cave in guizhou province southwest china established with 512 oxygen isotope data and 28 230th ages providing a continuous history of the asm precipitation from 6100 to 300 years before present yr bp before ad 1950 consistency of stalagmite 18o inferred long term decreasing asm trends since the mid holocene between caves at this site and others in the indian and east asian monsoon realms on orbital timescales supports the effect of primary orbital solar forcings on monsoonal precipitation the dark cave records display significant centennial to decadal scale variations more evident than previous stalagmite records spectral analysis of the dark cave 18o time series yields periodicities of 731

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

climate driven fluctuations in freshwater flux to sermilik fjord east greenland during the last 4000 years the freshwater runoff from the glaciated and snow covered sermilik fjord catchment se greenland was estimated at annual resolution for the period 1900 2008 and at decadal resolution for the past four millennia our simulations were forced with available meteorological station data 1900 2008 and greenland ice core estimated temperature data 1899 bc ad 1980 from dye3 and gisp2 time series of estimated ice discharge 2000 2009 for the three major outlet glaciers helheim fenris and midgard indicate that 53 74 of the ice discharge variations could be explained by variations in areally averaged glacier terminus surface supraglacial runoff based on these data and together with calculated subglacial geothermal and frictional melting as well as net precipitation for the fjord area the sermilik fjord freshwater flux was deduced for the period 1900 2008 our simulations indicated that during the last century surface freshwater runoff has equaled 13 of the sermilik fjord average freshwater flux of 33

sclerochronological records of arctica islandica from the inner german bight sclerochronological records of interannual shell growth variability were established for eight modern shells 26 to 163 years of age of the bivalve arctica islandica which were sampled at one site in the inner german bight the records indicate generally low synchrony between individuals spectral analysis of the whole 163 yr masterchronology indicated a cyclic pattern with a period of 5 and 7 years the masterchronology correlated poorly to time series of environmental parameters over the last 90 years high environmental variability in time and space of the dynamic and complex german bight hydrographic system results in an extraordinarily high noise level in the shell growth pattern of arctica islandica

organic matter compositions of rivers draining into hudson bay present day trends and potential as recorders of future climate change concentrations and compositions of particulate and dissolved organic carbon poc and doc respectively and aromatic compounds including lignin were analyzed in water samples from 17 rivers flowing into hudson bay northern canada these rivers incorporate basins to the south with no permafrost to basins in the north with continuous permafrost and dominant vegetation systems that include boreal forest the hudson plains taiga shield and tundra major latitudinal trends in organic carbon and lignin concentrations and compositions were evident with both doc and dissolved lignin concentrations dominating over their particulate counterparts and exhibiting significant correlations with total dissolved and suspended solids respectively the composition of lignin reaction products in terms of the syringyl cinnamyl and vanillyl compositions indicate mixed sources of vascular land plant derived organic carbon with woody gymnosperms contributions dominating in the southern river basins whereas nonwoody angiosperm sources were more important in the most northerly rivers the composition of nonlignin aromatic compounds which provides a tracer for nonvascular plant contributions suggests stronger contributions from sphagnum mosses to dissolved organic matter in rivers below the tree line including those with large peat bogs in their basins acid aldehyde ratios of the lignin products together with 14c data for doc in selected rivers indicate that doc has generally undergone greater alteration than poc interestingly several northern rivers exhibited relatively old doc according to the 14c data suggesting that either old doc is being released from permafrost or old doc survives river transport in these rivers

variable north atlantic climate seesaw patterns documented by a late holocene marine record from disko bugt west greenland abstract the reconstruction of past sea surface conditions in the labrador sea is essential for understanding climate fluctuations in the north atlantic region we here study late holocene sea surface conditions off west greenland in order to elucidate the possible relationship between a north atlantic seesaw and centennial to millennial scale climate fluctuations in the labrador sea region for that purpose we have studied the particulate organic matter especially dinoflagellate cysts and acritarchs from two marine sediment cores from disko bugt central west greenland our data show significant variations in sea surface temperature and sea ice cover during the last ca 3200 years after a cooling at ca 2 9 ka cal bp presumably related to the neoglacial cooling seen in large parts of the northern hemisphere the area was subjected to significant variability both in the entrainment of atlantic water west greenland current water and in atmospheric temperatures from 2 0 1 5 ka cal bp corresponding to the later part of the roman warm period the area experienced a return to a stronger influx of atlantic water and an increased fresh water influx from land probably related to increased precipitation or to melt water outflow from the nearby inland ice the dark ages 1 5 1 3 ka cal bp were characterised by an only minor cooling of the surface waters however as seen in other records from the labrador sea region the beginning of the medieval warm period 1 3 0 9 ka cal bp signified a severe cooling presumably due to a significant reduction in atlantic water entrainment the cold conditions continued through the little ice age after 0 9 ka cal bp although the area seems to have experienced a minor decrease in sea ice cover until 0 5 ka cal b p after which sea ice cover may again have increased the period of modern warming is not represented in our data our study shows that a north atlantic oscillation type pattern played a significant role in the late holocene centennial to millennial scale climate fluctuations in the labrador sea region however this cannot explain the full complexity of the climate signal the fact that a simple pattern of cold versus warm climate scenario does not exist demonstrates that it will hardly be feasible to select the correct baseline data set when modelling future climate development

a physical mechanism for north atlantic sst influence on the indian summer monsoon a link between the atlantic multidecadal oscillation amo and multidecadal variability of the indian summer monsoon rainfall is unraveled and a long sought physical mechanism linking atlantic climate and monsoon has been identified the amo produces persistent weakening strengthening of the meridional gradient of tropospheric temperature tt by setting up negative positive tt anomaly over eurasia during northern late summer autumn resulting in early late withdrawal of the south west monsoon and persistent decrease increase of seasonal monsoon rainfall on inter annual time scales strong north atlantic oscillation nao or north annular mode nam influences the monsoon by producing similar tt anomaly over eurasia the amo achieves the interdecadal modulation of the monsoon by modulating the frequency of occurrence of strong nao nam events this mechanism also provides a basis for explaining the observed teleconnection between north atlantic temperature and the asian monsoon in paleoclimatic proxies citation goswami b n m s madhusoodanan c p neema and d sengupta 2006 a physical mechanism for north atlantic sst influence on the indian summer monsoon

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

on the link between the subseasonal evolution of the north atlantic oscillation and east asian climate we analyse the impact of the north atlantic oscillation nao on the climate of east asia at subseasonal time scales during both winter and summer these teleconections have mainly been investigated at seasonal and longer time scales while higher frequency links are largely unexplored the nao is defined using extended empirical orthogonal functions on pentad mean observations which allows to elucidate the oscillation s spatial and temporal evolution and clearly separate the development and decay phases the downstream dynamical imprint and associated temperature and precipitation anomalies are quantified by means of a linear regression analysis it is shown that the nao generates a significant climate response over east asia during both the dry and wet seasons whose spatial pattern is highly dependent on the phase of the nao s life cycle temperature and precipitation anomalies develop concurrently with the nao mature phase and reach maximum amplitude 5 10 days later these are shown to be systematically related to mid and high latitude teleconnections across the eurasian continent via eastward propagating quasi stationary rossby waves instigated over the atlantic and terminating in the northeastern pacific these findings underscore the importance of rapidly evolving dynamical processes in governing the nao s downstream impacts and teleconnections with east asia

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

multidecadal mobility of the north atlantic oscillation abstractthe north atlantic oscillation nao is one of the most important modes of variability in the global climate system and is characterized by a meridional dipole in the sea level pressure field with centers of action near iceland and the azores it has a profound influence on the weather climate ecosystems and economies of europe greenland eastern north america and north africa it has been proposed that around 1980 there was an eastward secular shift in the nao s northern center of action that impacted sea ice export through fram strait independently it has also been suggested that the location of its southern center of action is tied to the phase of the nao both of these attributes of the nao have been linked to anthropogenic climate change here the authors use both the one point correlation map technique as well as empirical orthogonal function eof analysis to show that the meridional dipole that is often seen in the sea level pressure field over the north atlantic is not purely the

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

huge erratic boulders in tonga deposited by a prehistoric tsunami along some coastlines there are erratic boulders apparently emplaced by tsunamis or cyclonic storms evaluating their origin and time of emplacement places constraints on the frequency severity and location of coastal hazards seven such large coral limestone boulders are present near fahefa village on tongatapu island southwest pacific apparently emplaced by a prehistoric tsunami these boulders are 10 20 m above sea level and above any possible source and all are 100 400 m from the present shoreline coral 230th ages indicate that the limestone formed during the last interglacial sea level highstand ca 120 130 ka the largest boulder is 20 times more massive than any reported boulders emplaced by historically documented storms and may be the largest known tsunami or storm erratic worldwide situated above its source we performed computer simulations to assess whether tsunamis produced by earthquakes undersea landslides or volcanoes could emplace the boulders the simulations indicate that either volcanic flank collapse along the tofua arc 30 40 km to the southwest or undersea landslides on the submarine slopes of tongatapu could be responsible either could explain why these boulders are not widespread on tongatapu and instead occur in a localized group along the western coast this study demonstrates that small 1 km3 submarine slope failures sometimes generate locally large tsunamis the fahefa boulders are in a well studied and well populated area yet were unknown to the scientific community until recently this suggests that systematic searches elsewhere for erratic boulders and other tsunami deposits might provide new information for assessing the size and extent of prehistoric tsunamis

lipid and lignin cutin compounds in lake baikal sediments over the last 37 kyr implications for glacial interglacial palaeoenvironmental change abstract a stratigraphic study of total organic carbon toc concentration carbon isotopic composition of total organic matter tom lipids n alkanes n alkanols n alkanoic acids and sterols and lignin cutin compounds has been conducted for a lake baikal core 323 pc1 over the last glacial interglacial toc concentrations mg g 1 dry sediment are low 2 4 in the glacial sections but high 10 29 in the interglacial ones the concentrations of land plant derived compounds such as n c14 to c28 hydroxyalkanoic acids lignin phenols p hydroxyl vanillyl and syringyl total cutin acids normalized to toc in the interglacial are 5 6 times higher than those in the glacial carbon isotopic compositions of tom are 24 0 9 in the glacial while they are 27 1 3 in the interglacial the heavy isotope composition of tom in the glacial might be due to a contribution from submerged plants and or grasses the light isotopic composition of tom for the interglacial may be due to a contribution from both land plant and phytoplankton mainly diatom derived om autochthonous organic carbon contents were estimated from the c n ratio corrected for the effect of inorganic nitrogen and based on the assumption of c n values of 8 for autochthonous and 25 for allochthonous om the estimation indicates that autochthonous oc comprises 74 6 of toc for the glacial and 72 9 for the interglacial respectively primary palaeoproductivity was estimated to be below 20 gc m 2 y 1 in the glacial before 18 ka but high 100 120 gc m 2 y 1 in the interglacial 11 8 ka which is 10 30 higher than the modern values

climatic and environmental controls on speleothem oxygen isotope values variations in speleothem oxygen isotope values d 18 o result from a complicated interplay of environmental controls and processes in the ocean atmosphere soil zone epikarst and cave system as such the controls on speleothem d 18 o values are extremely complex an understanding of the processes that control equilibrium and kinetic fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem d 18 o as paleoclimate and paleoenvironmental proxies and is best complemented by study of site specific cave processes such as infiltration flow routing drip seasonality and saturation state and cave microclimate among others this review is a process based summary of the multiple controls on d 18 o in the atmosphere soil epikarst and speleothem calcite illustrated with case studies primary controls of d 18 o in the atmosphere include temperature and relative humidity through their role in the multiple isotope effects variability and modifications of water d 18 o values in the soil and epikarst zones are dominated by evaporation mixing and infiltration of source waters the isotopically effective recharge into a cave system consists of those waters that participate in precipitation of caco3 resulting in calcite deposition rates which may be biased to time periods with optimal dripwater saturation state recent modeling experimental and observational data yield insight into the significance of kinetic fractionation between dissolved carbonate phases and solid caco3 and have implications for the hendy test to assist interpretation of speleothem d 18 o time series quantitative and semi quantitative d 18 o climate calibrations are discussed with an emphasis on some of the difficulties inherent in using modern spatial and temporal isotope gradients to interpret speleothems as paleoclimate proxy records finally several case studies of globally significant speleothem paleoclimate records are discussed that show the utility of d 18 o to reconstruct past climate

chemical and isotopic characterization of size fractionated organic matter from cryoturbated tundra soils northern alaska 1 recent studies indicate a second layer of organic matter often accumulates in the lower active layer and upper permafrost in arctic tundra soils as a result of cryoturbation in this study cryoturbated organic matter was characterized using a combination of physical size fractionation and modern analytical techniques for elemental composition c and n stable isotopes 13c and 15n radiocarbon content 14c and molecular fingerprinting pyrolysis gas chromatography mass spectrometry py gc ms the results indicated that cryoturbated organic matter could be highly bioavailable soil organic matter som associated with fine sand particles was considered to be the organic carbon pool most sensitive to the changing climate more organic matter is stabilized on clay minerals in arctic tundra soils compared to those in temperate and tropical soils the bioavailable soluble organic matter extracted from cryoturbated soil was found to have significant long term effects on carbon cycling the similar molecular composition between cryoturbated and surface soil organic matter suggests that the vegetation cover has not significantly changed since the early holocene furthermore the som quality in moist acidic tundra was found to be higher than that of wet nonacidic tundra with thawing permafrost and a deepening of the active layer cryotrubated organic matter could reenter the biogeochemical cycles in the arctic resulting in a positive feedback to climate change