a 4500 year proxy climate record from peatlands in the north of ireland the identification of widespread summer drought phases abstract mid to late holocene high resolution testate amoebae derived water table reconstructions from two peatlands in the north of ireland are presented the proxy climate records are dated and correlated using a combination of ams 14 c dating spheroidal carbonaceous particles and tephrochronology the reconstructions start prior to the hekla 4 tephra isochron 2395 2279 bc and thus span the last 4500 years the records are compiled by the process of tuning within chronological errors standardisation and stacking comparisons are made to existing palaeoclimate records from peatlands in northern britain and ireland and the compiled lake level record for mid latitude europe four coherent dry phases are identified in the records at ca 1150 800 bc 320 bc ad 150 ad 250 470 and ad 1850 2000 recent research has shown that peat derived water table reconstructions reflect summer water deficit and therefore the dry phases are interpreted as periods with a higher frequency and or greater magnitudes of summer drought these drought phases occur during periods of relatively low 14 c production which may add support to the hypothesis of persistent solar forcing of climate change during the holocene any relationship with the north atlantic stacked drift ice record is less clear

quantitative reconstruction of mid to late holocene climate in ne china from peat cellulose stable oxygen and carbon isotope records and mechanistic models there has been an increasing need to reconstruct past climate from proxy records quantitatively and mechanistically the inverse proxy modeling method stands out as a novel approach to quantitative palaeoclimate reconstructions through integrating process based models and proxy records representing a major progress in quantitative palaeoclimatology it has been proposed to incorporate multiple proxy records to produce a more robust constraint on the climate parameters sought for estimation and most of the work has been conducted using pollen records in conjunction with vegetation models here i show a worked example of using paired stable oxygen and carbon isotope records of peat cellulose from one single core to infer the climate history in ne china for the last 6000 years through solving a well posed inverse problem using bayesian statistics the quantitative palaeoclimate data obtained in this study may deepen our insight into the dynamics of the east asian summer monsoon mean growing season temper

stable carbon and oxygen isotopes in sphagnum fuscum peat from subarctic canada implications for palaeoclimate studies stable carbon and oxygen isotope ratios in single plant components in sphagnum peat have a good potential to reveal environmental changes in peat archives two peat profiles covering the past 600

stable isotopes in sphagnum fuscum peat as late holocene climate proxies in northeastern european russia the environment of the northern taiga to tundra transition is highly sensitive to climate fluctuations in this study from northeastern european russia stable carbon and oxygen isotope ratios 13

model evaluation for reconstructing the oxygen isotopic composition in precipitation from tree ring cellulose over the last century the oxygen isotope composition of tree rings is controlled by many factors including temperature amount of precipitation and changes in relative humidity in this study we present a modified leaf water model from dongmann et al radiation and environmental biophysics 11 1974 41 that can be used to calculate the isotopic composition of the source water and thus of precipitation that a tree used during the growing season the calibration of the model was accomplished by comparing a previously measured oxygen isotope tree ring chronology from central switzerland with the swiss network for isotopes in the hydrologic cycle station at bern from 1971 to 1995 and integrating temperature relative humidity data and ring width in particular our efforts focused on understanding the significance of the dampening factor f which we relate to changes in humidity and its variability over both the calibration period 1971 to 1995 and the study period 1913 to 1995 our results indicate that f ranging between 0 27 to 0 49 is variable based on correlation with relative humidity average daily temperature and ring width index using this model we have constructed a record of the oxygen isotope composition of precipitation during the growing season may through september for the last century in central western europe this approach can be potentially used in other locations where isotopic and meteorological data are available to extend records of the isotopic composition of precipitation back in time beyond observational records

terrestrial climate signal of the 8200 yr b p cold event in the labrador sea region accelerated melting of greenland ice has raised concern about the future impact of enhanced freshwater discharge on regional climate through its effect on ocean circulation an abrupt cooling event ca 8200 cal yr b p has been linked to meltwater from the decaying north american ice sheet oxygen isotopic analyses of cellulose from subfossil sphagnum mosses isolated from a newfoundland peat core reveal a pronounced anomaly ca 8350 yr b p with a duration of 150 years the maximum estimated 18 o precipitation change 4 53 1 05 vienna standard mean ocean water is the largest observed in the circum north atlantic region the magnitude of change exceeds that predicted by recent paleoclimate simulations comparisons with recent records of surface and deep ocean proxies in the labrador sea and the wider north atlantic region suggest synchroneity however an 200 year delay between the responses of the labrador sea region and the greenland ice sheet to the effects of meltwater release remains to be explained

a holocene paleoclimate reconstruction for eastern canada based on δ18o cellulose of sphagnum mosses from mer bleue bog we present a 9200 yr high resolution oxygen isotope record of plant cellulose 18ocel from the peat deposits of mer bleue bog ontario and apply it as a proxy for paleotemperature reconstruction in eastern canada the results show that 18ocel of sphagnum follows the general pattern of the northern hemisphere reconstructed paleotemperature record for the last 2000 years at a ratio of 2 18ocel c the 18ocel record of ombrotrophic phase of mer bleue bog is also in accordance with major features of the holocene sunspot number reconstruction three distinct time intervals have low 18ocel values 200 800 cal bp little ice age 2800 3400 cal bp synchronous to a cooling period reported elsewhere in north america and 4200 4600 cal bp corresponding to a cooling interval in the north atlantic region these cooling periods also correlate well with negative excursions in the holocene sunspot and cosmogenic 10be records a fourth period of low 18ocel values between ad 1810 and 1820 may be related to t

temperature responses to quasi 100 yr solar variability during the past 6000 years based on δ18o of peat cellulose in hongyuan eastern qinghai tibet plateau china abstract during the past 6000 years the temperature variation trend inferred from 18o of peat cellulose in a peat core from hongyuan eastern qinghai tibet plateau southwestern china is similar to the atmospheric 14c concentration trend and the modeled solar output trend the general trend of hongyuan 18o during the past millennium also coincides well with the atmospheric 14c concentration trend the 10be concentration trend in an ice core from the south pole the reconstructed total solar irradiance trend as well as the modeled solar output trend in addition temperature events also correspond well to solar perturbations during the past 6000 years therefore the driving force of holocene temperature variations should be properly ascribed to solar activity the spectrum analysis further illustrates that quasi 100 yr fluctuation of solar activity was probably responsible for temperature variations in northeast qinghai tibet plateau during the past 6000 years

can oxygen stable isotopes be used to track precipitation moisture source in vascular plant dominated peatlands a b s t r a c t variations in the isotopic composition of precipitation are determined by fractionation processes which occur during temperature and humidity dependent phase changes associated with evaporation and condensation oxygen stable isotope ratios have therefore been frequently used as a source of palaeoclimate data from a variety of proxy archives which integrate this signal over time applications from ombrotrophic peatlands where the source water used in cellulose synthesis is derived solely from precipitation have been mostly limited to northern hemisphere sphagnum dominated bogs with few in the southern hemisphere or in peatlands dominated by vascular plants new zealand nz provides an ideal location to undertake empirical research into oxygen isotope fractionation in vascular peatlands because single taxon analysis can be easily carried out in particular using the preserved root matrix of the restionaceous wire rush empodisma spp that forms deep holocene peat deposits throughout the country furthermore large gradients are observed in the mean isotopic composition of precipitation across nz caused primarily by the relative influence of different climate modes here we test whether 18o of empodisma cellulose from ombrotrophic restiad peatlands in nz can provide a methodology

a deglacial and holocene record of climate variability in south central alaska from stable oxygen isotopes and plant macrofossils in peat we used stable oxygen isotopes derived from bulk peat d 18 otom in conjunction with plant macrofossils and previously published carbon accumulation records in a w14 500 cal yr bp peat core ht fen from the kenai lowlands in south central alaska to reconstruct the climate history of the area we find that patterns are broadly consistent with those from lacustrine records across the region and agree with the interpretation that major shifts in d 18 otom values indicate changes in strength and position of the aleutian low al a semi permanent low pressure cell that delivers winter moisture to the region we find decreased strength or a more westerly position of the al relatively higher d 18 otom values during the bolling allerod holocene thermal maximum htm and late holocene which also correspond to warmer climate regimes these intervals coincide with greater peat preservation and enhanced carbon c accumulation rates at the ht fen and with peatland expansion across alaska the htm in particular may have experienced greater summer precipitation as a result of an enhanced pacific subtropical high a pattern consistent with modern d 18 o values for summer precipitation the combined warm summer temperatures and greater summer precipitation helped promote the observed rapid peat accumulation a strengthened al relatively lower d 18 otom values is most evident during the younger dryas neoglaciation and the little ice age consistent with lower peat preservation and c accumulation at the ht fen suggesting less precipitation reaches the leeward side of the kenai mountains during periods of enhanced al strength the peatlands on the kenai peninsula thrive when the al is weak and the contribution of summer precipitation is higher highlighting the importance of precipitation seasonality in promoting peat accumulation this study demonstrates that d 18 otom values in peat can be applied

comparison of stable carbon and oxygen isotopes in picea glauca tree rings and sphagnum fuscum moss remains from subarctic canada stable isotope ratios from tree rings and peatland mosses have become important proxies of past climate variations we here compare recent stable carbon and oxygen isotope ratios in cellulose of tr

the little ice age in the southern hemisphere in the context of the last 3000 years peat based proxy climate data from tierra del fuego the so called little ice age lia of the 15th to 19th centuries ad is well attested from much of europe and from some other parts of the northern hemisphere it has been attributed to solar forcing associated with reduced solar activity notably during the sporer maunder and dalton solar minima although other causes have also been proposed and feature strongly in recent papers detection of the lia in some proxy climate records from the southern hemisphere is less clear leading to suggestions that the lia was perhaps not a global phenomenon resolving this issue requires more data from the southern hemisphere we present proxy climate data plant macrofossils peat humification covering the past three millennia from an ombrotrophic mire peat bog in tierra del fuego southern south america but focus our discussion on the period traditionally associated with the lia during parts of this time the mire surface was apparently relatively dry compared with much of its 3000 year record it was report

seismic anisotropy in granite at the underground research laboratory manitoba the shear wave experiment at atomic energy of canada limited s underground research laboratory was probably the first controlled source shear wave survey in a mine environment taking place in conjunction with the excavation of the mine by test tunnel at 420 m depth the shear wave experiment was designed to measure the in situ anisotropy of the rockmass and to use shear waves to observe excavation effects using the greatest variety of raypath directions of any in situ shear wave survey to date inversion of the shear wave polarizations shows that the anisotropy of the in situ rockmass is consistent with hexagonal symmetry with an approximate fabric orientation of strike 023 degree and dip 35 degree the in situ anisotropy is probably due to microcracks with orientations governed by the in situ stress field and to mineral alignment within the weak gneissic layering however there is no unique interpretation as to the cause of the in situ anisotropy as the fabric orientation agrees approximately with both the orientation expected from extensive dilatancy anisotropy and that of the gneissic layering eight raypaths with shear waves propagating wholly or almost wholly through granodiorite rather than granite do not show the expected shear wave splitting and indicate a lower in situ anisotropy which maymore be due to the finer grain size and or the absence of gneissic layering within the granodiorite these results suggest that shear waves may be used to determine crack and mineral orientations and for remote monitoring of a rockmass this has potential applications in mining and waste monitoring less

protracted and polyphased gold mineralisation in the agnew district yilgarn craton western australia abstract the archean orogenic gold deposits exhibits common characteristics including coeval emplacement age often proposed to be associated with a single late tectonic gold mineralisation event although valid for a large majority of deposits in the yilgarn craton this model does not account for certain atypical gold deposits in the world class agnew district yilgarn craton western australia structural and paragenetic relationships combined with a compilation of geochronology and multiple sulfur isotopes indicate that mineralisation developed during a two stage process involving different fluid sources the initial event dated at c 2660 ma is related to the onset of folding during kalgoorlie orogeny and presents characteristics compatible with magmatic intrusion related mineralisation a second mineralisation event dated at c 2630 ma presents a mineral and metal inventory typical to archean orogenic like gold mineralisation and developed at a later stage of the orogenesis measurements of 34s and 33s from spatially constrained samples from the two temporally distinct mineralising events further ascertain contrasting fluid compositions and or reservoirs combined with geochronological data obtained on the poly magmatic lawlers granitic complex we argue for a protracted ore forming process the first stage of mineralisation has a magmatic affinity and is followed by a second stage of mineralisation whereby au bearing hydrothermal solution incorporated an archean sedimentary sulfur reservoir we propose that the change in source reservoir for sulfur in hydrothermal fluids may reflect a regional change in tectonic regime from convergent to transcurrent motion allowing fluids to be first sourced from mantle derived magmas followed later by metamorphic fluids

paleoclimatic implications of the relationship between oxygen isotope ratios of moss cellulose and source water in wetlands of lake superior abstract groundwater dominated wetlands contain abundant peat deposits but few studies have addressed the potential of using the oxygen isotopic composition 18 o of fen peat cellulose to evaluate past changes in climate here we investigated the relationship between 18 o values of pond water and those of moss cellulose from species inhabiting different micro environments in three different swales near lake superior united states isotope results over two growing seasons indicate a negligible effect of evaporation on the studied fens and the strong control of groundwater on the isotopic composition of swale water isotopic values for groundwater show a small seasonal variability and their low values suggest the influence of snowmelt our results show a consistent offset of 27 1 between average swale water 18 o and cellulose 18 o values for hollow sphagnum species reflecting the fractionation associated with cellulose biosynthesis when sphagnum species from hummocks are included the offset shows a larger variability 27 3 pointing to evaporative effects affecting hummock species this evaporative effect is more pronounced in emerged mosses which show the largest difference 30 relative to their source water the smaller variability associated with hollow species points to the possibility of performing species specific analyses from peat cellulose for improved paleoclimatic reconstructions

synchronous climate anomalies in the western north pacific and north atlantic regions during the last 14 000 years abstract a peat cellulose 18 o record spanning around 14 000 years from the hani peat mire in northeastern china reveals several abrupt temperature anomalies in the period from the last deglaciation through the holocene the timing of these anomalies coincides well with the notable cooling events recorded respectively using the gisp2 ice core and ice rafted sediment of the north atlantic ocean such as the older dryas inter allerod younger dryas and the nine ice rafted debris events the results demonstrate that this repeating pattern of abrupt temperature deterioration is not limited to the north atlantic area at high latitude but also exists in the western north pacific region at middle latitude the synchronous temperature anomalies possibly are resulted from the joint effects of meltwater discharge into the north atlantic ocean and reduced solar activity in the period from around 8600 to 8200 cal yrs bp the hani peat record shows a broad 18 o peak that may reflect compound climate signals resulting from the two kinds of forcing factors the temperature drop related to reduced solar activity at around 8600 8250 cal yrs bp and the temperature anomaly attributed to the meltwater effect at around 8220 70 cal yrs bp this result may provide palaeo temperature evidence for existence of the sharp 8 2 k event in the western north pacific region in addition our results have revealed that in the period from the last deglaciation through the holocene the synchronous temperature anomalies before and after the 8 2 k event seem to be related to meltwater outflow and reduced solar activity respectively it is important that the all temperature anomalies whether because of reduced solar activity in the late holocene or from meltwater discharge in the early holocene are accompanied by an abrupt decline in the indian ocean summer monsoon and abrupt strengthening of the east asian summer monsoon it is likely that reduced solar activity and meltwater outflow appear to modulate earth system changes in the same direction the influences could be compounded reduced solar activity and meltwater outburst both appear to act as triggers for occurrence of the el nino phenomenon in the equatorial pacific ocean which may result in broad teleconnections between the temperature anomaly in the northern hemisphere and abrupt variation of the asian monsoon

characterizing carbon isotopic variability in sphagnum to understand more fully the nature of isotopic fractionation in mosses and to explore the potential of stable isotope analyses of selected peat constituents for palaeoenvironmental research we present results from a study of inter and intra plant 13c variability in sphagnum spp subdivisions of stem pendant and horizontal branch elements of modern sphagnum capillifolium plants revealed consistent and statistically significant differences in their isotopic composition sequential downstem analysis of a further cohort of four modern sphagnum capillifolium plants also reveals evidence of common forcing on the isotopic composition of sequentially formed stem and branch increments this relationship was tested further by analysis of a series of branch and stem samples manually recovered from sphagnum fuscum preserved within a late holocene ad 2003 1970 peat monolith from a european mire the high degree of isotopic coherence observed between plants supports the analysis of sphagnum in palaeoecological

decrypting stable oxygen isotope variability in modern plants of the dajiuhu peatland from hubei province china implications for palaecology and palaeoenvironments abstract stable oxygen isotopes 18o from cellulose of peatland plants represent a widely used tool for studying ecological processes and palaeoenvironmental evolution however comparison of different regions shows that the climate drivers of 18o from peat cellulose vary by location in addition controversy remains about the parts of plants that are most suitable for analysis in this study 18o from different parts of modern plants in the peatland of dajiuhu hubei province china were determined to better understand the environmental factors that influence 18o in this area and at a seasonal scale results show that 18o values do not significantly differ in different parts of the plants whole sample stem and leaf correlation analyses indicate that the major factor contributing to 18o variability is the 18o value of peatland water under the influence of monsoons in addition significant negative correlations exist between 18o of plants and mean monthly temperature therefore results demonstrate that 18o of plants may preserve the 18o isotopic signatures of the peatland water and mean monthly temperature signals irrespective of the plant organ analysed our findings provide a reference and basis for a modern process that uses cellulose 18o in plants to study palaeoenvironmental changes

sphagnum δ13c values as indicators of palaeohydrological changes in a peat bog late holocene peat stratigraphy of a canadian boreal peat bog was examined to evaluate the poten tial of sphagnum 13 c values as surface moisture proxy indicators isotopic measurements were compared to tes tate amoebae inferred water table depth reconstructions plant macrofossil assemblages and past decompo sition levels inferred by colorimetric humification ams radiocarbon dates were coupled with 210 pb dates to establish peat chronology although the mechanisms underlying carbon fractionation processes in peatlands are not well understood we demonstrate that sphagnum 13 c values have potential for palaeohydrological recon structions since variations presented by the isotopic values can generally be correlated with the other proxy records especially during drier episodes

differential hydrogen isotopic ratios of sphagnum and vascular plant biomarkers in ombrotrophic peatlands as a quantitative proxy for precipitation evaporation balance abstract we have developed a new approach to quantitatively reconstruct past changes in evaporation based on compound specific hydrogen isotope ratios of vascular plant and sphagnum biomarkers in ombrotrophic peatland sediments we show that the contrast in h isotopic ratios of water available to living sphagnum top 20 cm and in the rooting zone of peatland vascular plants can be used to estimate the fraction of water remaining after evaporation vascular plant leaf waxes record h isotopic ratios of acrotelm water which carries the d h ratio signature of precipitation and is little affected by evaporation whereas the sphagnum biomarker c 23 n alkane records h isotopic ratios of the water inside its cells and between its leaves which is strongly affected by evaporation at the bog surface evaporation changes can then be deduced by comparing h isotopic ratios of the two types of biomarkers we calibrated d h ratios of c 23 n alkane to source water with lab grown sphagnum we also tested our isotopic model using modern surface samples from 18 ombrotrophic peatlands in the midwestern united states finally we generated a 3000 year downcore reconstruction from minden bog michigan usa our new record is consistent with records of other parameters from the same peatland derived from different proxies and allows us to differentiate precipitation supply and evaporative loss

holocene climate variability revealed by oxygen isotope analysis of sphagnum cellulose from walton moss northern england abstract stable isotope analyses of sphagnum alpha cellulose precipitation and bog water from three sites across northwestern europe raheenmore ireland walton moss northern england and dosenmoor northern germany over a total period of 26 months were used to investigate the nature of the climatic signal recorded by sphagnum moss the 18o values of modern alpha cellulose tracked precipitation more closely than bog water with a mean isotopic fractionation factor cellulose precipitation of 1 0274 0 001 1 27 sub samples of isolated sphagnum alpha cellulose were subsequently analysed from core wlm22 walton moss northern england yielding a sphagnum specific isotope record spanning the last 4300 years the palaeo record calibrated using the modern data provides evidence for large amplitude variations in the estimated oxygen isotope composition of precipitation during the mid to late holocene estimates of palaeotemperature change derived from statistical relationships between modern surface air temperatures and 18oprecipitation values for the british isles give unrealistically large variation in comparison to proxies from other archives we conclude that use of such relationships to calibrate mid latitude palaeo data must be undertaken with caution the 18o record from sphagnum cellulose was highly correlated with a palaeoecologically derived index of bog surface wetness bsw suggesting a common climatic driver

chinese stalagmite δ 18 o controlled by changes in the indian monsoon during a simulated heinrich event carbonate cave deposits in india and china are assumed to record the intensity of monsoon precipitation because the 18 o of the carbonate tracks the isotopic signature of precipitation these records show spatially coherent variability throughout the last ice age and suggest that monsoon strength was altered during the millennial scale climate variations known as dansgaard oeschger events and during the heinrich cooling events here we use a numerical climate model with an embedded oxygen isotope model to assess what caused the shifts in the oxygen isotope signature of precipitation during a climate perturbation designed to mimic a heinrich event our simulations show that a sudden increase in north atlantic sea ice extent during the last glacial period leads to cooling in the northern hemisphere reduced precipitation over the indian basin and weakening of the indian monsoon the precipitation is isotopically heavier over india and the water vapour exported to china is isotopically enriched our model broadly reproduces the enrichment of 18 o over northern india and east asia evident in speleothem records during heinrich events we therefore conclude that changes in the 18 o of cave carbonates associated with heinrich events reflect changes in the intensity of indian rather than east asian monsoon precipitation