testing the timing of radiocarbon dated events between proxy archives for interpreting past changes on a regional or global scale the timings of proxy inferred events are usually aligned with data from other locations however too often chronological uncertainties are ignored in proxy diagrams and multisite comparisons making it possible for researchers to fall into the trap of sucking separate events into one illusionary event or vice versa here we largely solve this suck in and smear syndrome for radiocarbon 14 c dated sequences in a bayesian framework millions of plausible age models are constructed to quantify the chronological uncertainties within and between proxy archives we test the technique on replicated high resolution 14 c dated peat cores deposited during the little ice age c ad 14001900 a period characterized by abrupt climate changes and severe 14 c calibration problems owing to internal variability in proxy data and uncertainties in age models these and possibly many more archives are not consistent in recording decadal climate change through explicit statistical tests of palaeoenvironmental hypotheses we can move forward to systematic interpretations of proxy data however chronological uncertainties of non annually resolved palaeoclimate records are too large for answering decadal timescale questions

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

mid late holocene climate variations in southeast china inferred by the intermountain peat records from fujian china abstract the climate of southeastern china is strongly influenced by the easm and tcs which produce most of the precipitation in this area and sustain large scale industrial and agriculture activities however proxy climate records from this area are sparse because of the dense population and intensive human activities in this study a total of ten well dated peat cores collected from the intermountain basins in fujian province were evaluated to explore the initiation histories of the peat bogs and 13 c c of cellulose extracted from four cores were further analyzed to investigate the precipitation history over the last thousand years lithological characteristics of the peat sections show that coarse gravel and sands occur at the bottom of each core which implies that erosion may be the constraint for the initiation of these peat bogs the formation of intermountain peatlands indicates rapidly weakening erosion which in turn suggests a decline in intensive rainfall and or total rainfall based on ams ages three cores show consistent basal ages of approximately 4 2 ka bp whereas five cores exhibit consistent basal ages centered at approximately 1 2 ka bp this staged increasing trend of peat bogs distribution since the mid holocene coincides with the gradual decline in the intensity of the easm intensity suggested by the chinese stalagmite 18 o records which indicates that intensive rainfall in the fujian area has decreased as the easm has weakened during the late holocene this long term change on insolation scale may be connected to insolation and sst of the western north pacific ocean the 13 c c exhibits large variability in amplitude from 27 5 to 11 3 and the periods of heavier 13 c c and lighter 13 c c corresponded to the layers of gray muddy silt and black peat respectively we interpret the large amplitude variability in 13 c c as a reflection of changes in the proportions of submerged plant matter which is rich in 13 c heavier 13 c c indicates a higher proportion of submerged plants with more detritus input and suggests wetter hydrological conditions with higher precipitation the changes in 13 c c over time show that there was a rapid decreasing trend of 13 c c around 800 yr bp which indicated that precipitation decreased since 800 yr bp this decrease in precipitation was consistent with the decrease in temperature from the mwp to the lia which implies that there was a wetter climate during the mwp and a less wet during the lia in southeastern china

multiproxy evidence of little ice age palaeoenvironmental changes in a peat bog from northern poland little ice age lia climatic deteriorations have been abundantly documented in various archives such as ice lake sediments and peat bog deposits palaeoecological analyses of peat samples have identified these climatic deteriorations using a range of techniques for example palynology plant macrofossils testate amoebae or carbon isotopic analyses the use of inorganic geochemistry and the reconstruction of dust fluxes has remained a challenge in tracing the nature of lia climatic changes although the idea of enhanced erosion conditions and storminess is commonly discussed the conditions for dust deposition in peatlands over europe during the lia are rarely favourable because the natural forest cover over europe was much more important than nowadays preventing dust deposition this intense forest canopy masks the deposition of dust in peatlands in northern poland near the baltic shore the slowin skie blota area was deforested around ad 1100 ie just before the lia and therefore constitutes a key area for the reconstruction of lia climatic change with the support of a well constrained chronology climatic fluctuations are recorded in an ombrotrophic bog using inorganic geochemistry plant macrofossils and carbon isotopic analyses the reconstruction of lia climatic changes is in good agreement with other records from poland and ne europe however a c 50 year discrepancy can be observed between various records this discrepancy is possibly due to progressive time dependent cooling gradient from north to south europe

radiocarbon dating of bulk peat samples from raised bogs non existence of a previously reported reservoir effect in 1995 an unexpected reservoir effect was reported in sequences of bulk c 14 dates of raised bog peat in most peat studies bulk c 14 dates are used for obtaining chronologies therefore it is important to confirm and quantify such a c 14 reservoir effect five bulk peat samples from the raised bog engbertsdijksveen were conventionally c 14 dated the same core had previously been precisely dated by c 14 ams dates of carefully selected above ground plant remains the existence of a reservoir effect in bulk peat c 14 samples could not be confirmed other explanations for the reported reservoir effect are discussed c 2004 elsevier ltd all rights reserved

carbon isotope variation in sphagnum from hummock hollow complexes implications for holocene climate reconstruction the interpretation of isotopic variation in sphagnum from holocene peat profiles rests upon several assumptions concerning physiological processes such as variation in co2 uptake and differences in the isotopic ratio of the source co2 to examine such variability sphagnum from hummock hollow complexes from two raised bogs florencecourt and clara in ireland was sampled for carbon isotope analysis samples were taken from relatively dry hummock tops margins and submerged hollows carbon isotope measurements on cellulose obtained from the sphagnum revealed a variation of 6 across the bog surface the mean values for florence court and clara bog are 25 6 and 26 5 pdb respectively which is consistent with the sphagna utilizing c3 photosynthesis to take up atmospheric co2 the hummock top species from both sites yielded lighter isotopic values than the hummock margin species which is consistent with the hummock top species photosyn thesizing under a lower water content and hence lower external diffu

last millennium palaeoenvironmental changes from a baltic bog poland inferred from stable isotopes pollen plant macrofossils and testate amoebae the baltic coast of northern poland is a region of considerable potential interest for paleoclimatic studies because this region is under the influence of both oceanic and continental climates and that these two influences have likely changed through time also unlike many more intensively studied regions of europe human impact was more limited until the 19th century we present a multiproxy high resolution record from st zki mire an ombrotrophic mire located in northern poland 35 km from the baltic sea coast we combined four proxies from the peat testate amoebae stable isotopes 13c of sphagnum stems pollen and plant macrofossils supported by dendroecological data to assess the palaeoenvironmental changes that took place during the last millennium the general aim of this study was to test if a range of proxies testate amoebae pollen plant macrofossils and tree rings could allow inferring a climatic signal from a peat monolith despite the considerable anthropogenic impact on the pomerania landscape since the early medieval period combining internal e g macrofossils and testate amoebae and external pollen signals is key to distinguishing human from climatic signals in palaeoenvironmental studies of peatlands our more specific aims were to a reconstruct the last millennium palaeoenvironment in a baltic raised bog and its surroundings b identify the major wet dry shifts and correlate those events with climate change and human impact c assess the resilience of the baltic bog ecosystem following human impact we noted two disturbance periods in the history of the mire the two major disturbances in the history of the mire were dry periods i 1100 1500 ad and ii 1650 1900 2005 ad these are reflected in all indicators and can be interpreted as the mixture of climate impact and human activities however the pollen record shows little evidence of human indicators during the first dry shift the second disturbance can be related to local peat exploitation of the mire and then in the 20th century with limited artificial drainage from 1500 ad all proxies show that the water table abruptly rose in the mire the beginning of this shift occurred during the little ice age and therefore it is likely a climatic signal alternatively this wet shift could have been interpreted as a re wetting mire surface after peat burning but this interpretation is rejected because there is no evidence of major local fire in the macrofossil record the macrofossil data shows that sphagnum fuscum dominated the pristine mire vegetation but then declined and finally disappeared this pattern is comparable with the timing of extinction of sphagnum austinii in western europe this study illustrated the value of palynological analysis of peat archives especially for last millennium to assess the magnitude of anthropogenic land use changes for example the comparison of fagus beech and carpinus hornbeam history with the palaeohydrological record allowed us to exclude climate change as the most important factor for the decline and expansion of these tree species this study is the first direct comparison of testate amoeba and stable isotope data

dating raised bogs new aspects of ams 14c wiggle matching a reservoir effect and climatic change abstract high resolution ams dating of holocene raised bog deposits engbertsdijksvenen the netherlands shows natural 14c variations wiggles which can be matched with the dendrochronological calibration curve comparison of our results with other conventionally dated peat cores and the 14c record shows an unexpected and as yet unreported reservoir effect and a marked and sudden wetting of the bog surfaces coinciding with the advent of a sporer type solar minimum the homeric minimum the potential of ams dating to vastly improve the accuracy of holocene chronologies is demonstrated

were last glacial climate events simultaneous between greenland and france a quantitative comparison using non tuned chronologies several large abrupt climate fluctuations during the last glacial have been recorded in greenland ice cores and archives from other regions often these dansgaard oeschger events are assumed to have been synchronous over wide areas and then used as tie points to link chronologies between the proxy archives however it has not yet been tested independently whether or not these events were indeed synchronous over large areas here we compare dansgaard oeschger type events in a well dated record from southeastern france with those in greenland ice cores instead of assuming simultaneous climate events between both archives we keep their age models independent even these well dated archives possess large chronological uncertainties that prevent us from inferring synchronous climate events at decadal to multi centennial time scales if possible comparisons between proxy archives should be based on independent non tuned time scales copyright 2009 john wiley sons ltd

evidence from northwest european bogs shows little ice age climatic changes driven by variations in solar activity fluctuations in holocene atmospheric radiocarbon concentrations have been shown to be due to variations in solar activity analyses of both 10 be and 14 c nuclides cone rm that production ratechanges during

changes in solar activity and holocene climatic shifts derived from 14c wiggle match dated peat deposits closely spaced sequences of accelerator mass spectrometer ams 14 c dates of peat deposits display century scale wiggles which can be e tted to the radiocarbon calibration curve by wiggle matching such sequences high precision calendar age chronologiescan be generated which show that changes in mire surface wetness during the bronze age iron age transition c 850 cal bc and the little ice age wolf sporer maunder and dalton minima occurred during periods of suddenly increasing atmospheric concentration of 14 c replicate evidence from peat based proxy climate indicators in northwest europe suggest these changes in climate may have been driven by temporary declines of solar activity carbon accumulation rates of two raised peat bogs in the uk and denmark record low values during the little ice age which ree ects reduced primary productivity of the peat forming vegetation during these periods of climatic deterioration

three dimensional structure and dynamics of african easterly waves part iii genesis this paper promotes the view that african easterly waves aews are triggered by localized forcing most likely associated with latent heating upstream of the region of observed aew growth a primitive equation model is used to show that aews can be triggered by finite amplitude transient and localized latent heating on a zonally varying basic state that is linearly stable heating close to the entrance region of the african easterly jet aej is shown to initiate aews downstream the heating leads to an initial trough that reaches the west african coast about 5 7 days later depending on the nature of the heating profile after this a structure that projects strongly onto the leading linear normal mode of the basic state becomes established characterized by a number of westward propagating disturbances that strongly resemble aews the sensitivity of the forced aews to the nature and location of the heating profile is examined aews are most efficiently triggered by heating profiles that establish lower tropospheric circulations close to the entrance region of the aej in the present study this was best achieved by lower tropospheric heating from shallow convection or upper level heating and lower level cooling from a stratiform precipitation profile both profiles have significant heating gradients in the vertical in the mid to lower troposphere this triggering paradigm for the genesis of aews has consequences for the variability and predictability of aews at weather and climate time scales in addition to the nature of the aej often emphasized it is crucial to consider the nature and variability of upstream heating triggers

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

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

a millennial record of environmental change in peat deposits from the misten bog east belgium in this study palaeoenvironmental changes recorded in the top metre of a peat profile misten bog east belgium were investigated using a multiproxy approach proxies include bulk density ti and si content pollen macrofossils d13c on specific sphagnum stems and d13ced18o on sphagnum leaves a highresolution chronology was generated using 210pb measurements and 22 14c ams dates on carefully selected sphagnum macrofossils d13c only records large change in mire surface wetness this is partly due to the fact that the core was taken from the edge of a hummock which may make it difficult to track small isotopic changes the d13c signal seems to be dependent upon the sphagnum species composition for example a change between sphagnum section cuspidata towards sphagnum imbricatum causes a significant drop in the d13c values on the whole the c and o isotopes record two shallow pool phases during the 8the9th and the 13th centuries pollen and atmospheric soil dust asd fluxes records increased human occupation in the area there may be some climatic signals in the asd flux but they are difficult to decipher from the increasing human impact land clearance agriculture during the last millennium the variations in the proxies are not always synchronous suggesting different triggering factors temperature wetness windiness for each proxy this study also emphasizes that compared to studies dealing with pollution using geochemical proxies palaeoclimatic inferences from peat bogs need as many proxies as possible together with highly accurate and precise age models in order to better understand climate variability and their consequences during the holocene

characterization of environmental conditions during microbial mg carbonate precipitation and early diagenetic dolomite crust formation brejo do espinho rio de janeiro brazil

the final meltdown of dead ice at the holocene thermal maximum 8500 7400 cal yr bp in western latvia eastern baltic it is commonly assumed that the majority of buried ice blocks in europe melted at the end of late glacial period and during the first part of the early holocene we show however that scattered dead ice blocks may have been preserved in the ground until 8500 cal yr bp we analysed thermokarst features in lake ikuru western latvia by means of a multi proxy approach pollen non pollen palynomorphs plant macrofossils diatoms loss on ignition magnetic susceptibility c n ratio carbon accumulation rate and radiocarbon dating abiotic and biotic processes following the ice block meltdown suggests abrupt development of a thermokarst from 8500 to 7400 cal yr bp important changes in local vegetation occurred with the deepening of a kettle hole during the transition from a fen to a lake that nearly coincided with the appearance of the first fish at 7800 cal yr bp thus forming a clear indication of a lacustrine environment our study shows that a thin peat layer formed at first and due to the meltdo

stable carbon and oxygen isotopes in sub fossil sphagnum assessment of their applicability for palaeoclimatology abstract to investigate the potential of stable isotopes of sphagnum peat deposits for palaeoclimate research and to inform sampling strategies we present results from a study of selected sphagnum plant constituents we report a combined stable carbon and oxygen isotope record of cellulose separately extracted from sphagnum branches and stem sections manually sampled from a 4000 year old peat deposited in a small dry maar crater located in the westeifel volcanic field germany we have determined the species composition of each individual sample of sphagnum branches to address the sensitivity of the stable isotope records to potential changes in sphagnum assemblages the youngest approximately 3000 years old peat section consists of scarcely decomposed sphagnum plant material from the bog s surface to a depth of 60 cm the predominant species is sphagnum magellanicum between 60 and 550 cm the peat predominantly consists of sphagnum capillifolium var rubellum at greater depths the decomposition status increases species identification is however solely achievable if the record under examination consists of moderately decomposed peat the stable carbon and oxygen isotope values of cellulose from sphagnum stem sections are significantly lighter than those of the branches both isotopic offsets between the different plant compounds exhibit a strong degree of correlation are statistically highly significant and observable down core the stable carbon isotope offset averages to 1 5 however presumably decreases with increasing age of the plant material in contrast the averaged oxygen isotope offset of 0 9 is consistent in time our results imply that if no differentiation into sphagnum branches and stem sections prior to stable isotope analyses is possible erroneous interpretations of the isotope records are likely since down core changes in the ratio of branches to stem sections in the peat profile are most likely this also implies that the removal of all non sphagnum plants or plant fragments is insufficient to retrieve stable isotope signals from peat deposits exclusively reflecting palaeo environmental conditions even isotopic records from bulk sphagnum cellulose comprise of two different signals firstly an environmental signal based on the plant response to external controls this signal is however masked by a second plant physiological signal originating from the isotopic offset between branches and stem sections

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

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

variations of 18o 16o in plants from temperate peat bogs switzerland implications for paleoclimatic studies despite the great potential of peat bogs as climatic archives to date only few studies have focused on the climatic controls on cellulose isotopic composition in modern bog plants this study attempts to calibrate plant climate relationships by sampling a set of modern plant species both vascular plants and mosses and bog surface waters along an altitude transect in switzerland isotopic analyses of water samples show that the 18o values of surface bog waters follow the trend of precipitation despite significant scatter in the data set detailed sampling of surface waters within one bog shows that 18o values vary widely and are closely related to the micro topography of the bog surface more enriched 18o 16o ratios in water samples collected from small raised hummocks than the ones collected from hollows are documented in both horizontal and vertical profiles a 18o d plot indicates that the process leading to the isotopic enrichment of the uppermost surface waters is evaporation greater above sphagnum covered hummocks than above open pools to investigate the implications of such high variability of source water for plant cellulose 18o values a detailed study of both surface water and cellulose 18o values within one site is conducted the large 18o variability observed in surface waters is found to be considerably smoothed in cellulose by a factor of 5 10 depending on the plant species this indicates that the water used by plant photosynthetic processes reflects the isotopic composition of the average annual precipitation this points to a source water level for plants of a few decimeters where the variations are smaller than at the air water interface the response of the cellulose 18o to the environmental gradient along the altitude transect varies considerably from species to species for most of the species studied the 18o values decrease with altitude following the trends of 18o values in precipitation and in surface water samples some species the cotton sedge eriophorum vaginatum and the moss sphagnum capillifolium show statistically significant 18o relationships to an altitude of 1 8 km and 2 9 km respectively however some other plant species calluna vulgaris vaccinium uliginosum andromeda poliflora carex pauciflora sphagnum cuspidatum and sphagnum magellanicum do not or only partially reflect changes in climatic parameters associated with an altitude increase furthermore changes in relative humidity which are not correlated with altitude are found to explain a large part of the variability in 18o values for the sedge carex pauciflora and the moss sphagnum cuspidatum therefore this study confirms the importance of species specific studies when interpreting 18o 16o ratios of macrofossils along a fossil peat sequence as a record of past climate changes our study allows to extend the mechanistic model that isotopically links source water and cellulose to the physiological specificities of sedges and mosses a comparison of the modeled and calculated net biological fractionation factors for eriophorum vaginatum and sphagnum capillifolium reveals that these two species appear to have a more homogeneous leaf reservoir than trees

paleodust deposition and peat accumulation rates bog size matters abstract we present a high resolution peat paleodust and accumulation rate record spanning the last 8300 years from draftinge mosse 400 ha southern sweden 57 06 27 6 n 13 42 54 1 e the record was analysed for peat accumulation rates par elemental concentrations mineralogy and plant macrofossil content five periods of increased mineral deposition were recorded the first event occurred between 6280 and 5570 cal bp during the fen to bog transition this is followed by four atmospheric mineral dust events de which were recorded in the ombrotrophic section of the sequence at cal bp 2200 1385 1150 830 590 and from 420 to the present statistical analysis and elemental ratios indicated that both the mineralogy and grain size shifted when the system transitioned from fen into bog showing that the governing transport process shifted with the peatland succession stages this highlights the importance of identifying peatland succession stages within peat paleodust studies following all four de increases in par were observed implying a coupling to dust deposition comparison of de and par with a paleodust record from store mosse a 20 times larger bog located ca 18 km away kylander et al 2016 showed that both par and dust deposition are largely represented by single core reconstructions indicating that they are driven by a common climate forcing mechanism however higher par and dust deposition rates were observed in the more moderately sized draftinge mosse suggesting that the size of the bog is important to consider in peat paleodust studies furthermore the smaller bog responded more rapidly to hydrological changes indicating that the size of the bog affects its buffering capacity authigenic carbonates observed here during episodes of rapid peat growth coincide with changes in ree ratios indicating that authigenic peat processes potentially cause ree fractionation