1,721,056 research outputs found
Geochemical, age model and pollen data for the SEK2016 sequence from the Sekhokong Mountain Range, Lesotho
No full textWe present data from a sequence from a well-stratified sedimentary infill occupying a lower slope basin which covers 17,060 to 13,400 cal yr BP with the aim to reconstruct paleoclimatic variability in the high Drakensberg during the Late Glacial. We use a combination of pollen, total organic carbon and nitrogen, δ13C, Fourier transform infrared spectroscopy attenuated total reflectance (FTIR-ATR) spectral and elemental data on contiguous samples with high temporal resolution (10 to 80 years per sample)
Eastern Mediterranean hydroclimate reconstruction over the last 3600 years based on sedimentary n-alkanes, their carbon and hydrogen isotope composition and XRF data from the Gialova Lagoon, SW Greece
No full textUnderstanding past hydroclimate variability and related drivers is essential to improve climate forecasting capabilities especially in areas with high climatic sensitivity, such as the Mediterranean. This can be achieved by using a broad spectrum of high resolution, multiple proxy records which can also allow us to assess linkages between regional hydroclimate variability and shifts in the large-scale atmospheric patterns. Here, we present a multiproxy reconstruction of the central-eastern Mediterranean hydro climate changes over the last 3600 years based on a sediment core from the Gialova Lagoon, a shallow coastal ecosystem in SW Peloponnese, Greece. Our combined dataset consists of the distribution and compound-specific carbon and hydrogen isotope (delta C-13 and 8D) composition of n-alkanes, bulk organic matter properties and X-ray fluorescence (XRF) core scanning data. This approach was complemented with a semi-quantitative analysis of plant remains in the core. The results indicate a high contribution of local aquatic vegetation to organic matter. Large delta C-13 variations in predominantly aquatic plant-derived mid-chain alkanes (C23-23) mainly reflect changes in the aquatic plant abundance and their carbon source. Our data suggest that higher delta C-13(23-25) values (up to 19 parts per thousand) largely correspond to expansion of aquatic vegetation during wet and/or cold periods causing carbon-limiting conditions in the water and assimilation of isotopically-enriched bicarbonate by the plants. The 8D records of the individual n-alkanes (C-17 to C-31) exhibit a nearly identical pattern to each other, which implies that they all reflect changes in the source water isotope composition, driven by hydroclimate variability. In addition, the 8D profiles are consistent with the XRF data with both proxies being driven by a common hydroclimate signal. We observe two major shifts from dry and/or warm periods at ca 3600-3000 cal BP and ca 17001300 cal BP to wet and/or cold episodes at ca 3000-2700 cal BP and ca 1300-900 cal BP. The period ca 700-200 cal BP is the wettest and/or coldest in our record and coeval with the Little Ice Age. The climatic fluctuation reported in this study can be explained by the relative dominance of high-latitude (e.g. North Atlantic Oscillation during winters) and the low-latitude atmospheric patterns (Intertropical convergence zone, Subtropical High and the effects of Asian monsoons during summers) which suggests an Atlantic-Mediterranean-Monsoon climate link in this area for the late Holocene.</p
Peat properties (radiocarbon dating, bulk density analysis, and peat accumulation rates) obtained from a peat sequence reaching ~10 000 years BP in Store Mosse bog, south-central Sweden
No full textPeat properties from an ombrotrophic bog (Store Mosse bog) located in south-central Sweden. The data include peat bulk density analysis, peat accumulation rates (peat-AR), and an age model based on 16 radiocarbon dates, on a 678 cm long peat sequence which was collected in November 2018 (using a Russian corer) and reaches almost 10000 cal years BP in basal age. The peat sequence is based on 9 consecutive peat cores (of 1 m each) obtained from two alternating holes in the southern part of Store Mosse bog. The peat cores were subsampled into 1 cm slices and then stored in a cold room before analysis. The bulk density analysis was made at a 1 cm resolution by taking a cube of peat (roughly 1 cubic cm) from each subsampled slice to be freeze-dried, then weighed and measured (using a caliper) to calculate its density - these values were then used to align the cores to obtain one composite peat sequence with a depth of 678 cm. The age model was created using R_Bacon which utilizes the IntCa13.14C calibration curve, based on 16 radiocarbon age dates of hand-picked plant macrofossil remains. Using the bulk density data and the ages from the age model, the peat accumulation rates (peat-AR) were calculated at 1 cm resolution by dividing the total mass (g/m²) by time between each sample, presented as g/m²/a
Postglacial vegetation data obtained using macrofossil analysis on a peat sequence reaching ~10 000 years BP in Store Mosse bog, south-central Sweden
No full textPeatland vegetation from an ombrotrophic bog (Store Mosse bog) located in south-central Sweden. The data include an Age & Peat Properties Dataset (peat bulk density analysis, peat accumulation rates (peat-AR), and an age model based on 16 radiocarbon dates) and a Plant Macrofossil Analysis Dataset, on a 678 cm long peat sequence which was collected in November 2018 (using a Russian corer) and reaches almost 10000 cal years BP in basal age. The plant macrofossil analysis includes 119 samples; 5 cubic cm of fresh peat per sample was gently cleaned using a 120 µm mesh sieve under running water (no pre-analysis treatment was required). The samples were analysed using a stereomicroscope (magnification ranging X10-40) for plant coverage percentages using a petri dish with a 10 x 10 mm grid as scale, and species identification was made using a high-power light microscope (based on stem and branch leaves for Sphagnum species)
Global perspectives on natural and anthropogenic controls on atmospheric lead and dust cycling using peat bog archives
Full text linkDisentangling seasonal and annual precipitation signals in the tropics over the Holocene: Insights from δD, alkanes and GDGTs
Full text linkUnidad de excelencia María de Maeztu CEX2019-000940-MRainfall seasonality in the tropics has a substantial impact on both ecosystems and human livelihoods. Yet, reconstructions of past rainfall variability have so far generally been unable to differentiate between annual and seasonal precipitation changes. Past variations in seasonality are therefore largely unknown. Here, we disentangle hydrogen isotopic (δD) signals from terrestrial leaf waxes and algae in an 8000-year peat core from Sumatra, which reflect annual versus wet season rainfall signals, respectively. We validate these results using lipid biomarkers by reconstructing vegetation dynamics via n-alkane distributions and peatland hydrological conditions using glycerol dialkyl glycerol tetraethers (GDGTs), as well as biomass burning using levoglucosan concentrations in the core. Finally, we compare our proxy results to a transient climate model simulation (MPI-ESM1.2) to identify the mechanism for seasonality changes. We find that algal δD indicates stronger Indonesian-Australian Summer Monsoon (IASM) precipitation in the Mid-Holocene, between 8 and 4.2 cal ka BP. A period of alternating flooding, droughts and wildfires is reconstructed between 6 and 4.2 cal ka BP, implicating very strong monsoonal precipitation and drying out and burning during a longer and intensified dry season. We attribute this strong rainfall seasonality in the Mid-Holocene mainly to orbitally forced insolation seasonality and a strengthened IASM, consistent with the modeling results. In terms of annual rainfall, terrestrial plant δD, vegetation composition and GDGTs all indicate wetter conditions peaking between 3 and 4.5 cal ka BP, preceded by drier conditions, followed by drastic and rapid drying in the late Holocene from around 2.8 cal ka BP. Our multiproxy annual precipitation reconstruction thereby indicates the wettest overall conditions approximately 1500-2000 years later than a nearby speleothem δ18O record, which instead follows the seasonally biased algal δD in our record. We, therefore, hypothesize that speleothem reconstructions over the Holocene in parts of the tropics with low but significant seasonality may carry a stronger seasonal component than previously suggested. The data presented here contribute with new insights on how isotopic rainfall proxies in the tropics can be interpreted. Our findings resolve the seasonal versus annual components of Holocene rainfall variability in the Indo-Pacific Warm Pool region, highlighting the importance of considering seasonality in rainfall reconstructions
Global perspectives on natural and anthropogenic controls on atmospheric lead and dust cycling using peat bog archives
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
Bulk density, ash, absorbance and net peat accumulation rates of Store Mosse peat bog
No full textBulk density, ash, absorbance and net peat accumulation rates of Store Mosse peat bo
Bulk density, ash content, humification, peat accumulation and selected lithogenic data of Store Mosse peat bog
No full textThis datafile presents chemical and physical as well as age dating information from the Store Mosse peat bog in southern Sweden. This record dates back to 8900 cal yr BP. The aim of the research was to reconstruct mineral dust deposition over time. As such we have only presented the lithogenic element data (Al, Ga, Rb, Sc, Ti, Y, Zr, Th and the REE) as the sample preparation method was tailored to these. This data is supported by parameters describing the deposit including bulk density, humification, ash content and net peat accumulation rates
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