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The article discusses the use of inter-genus oxygen isotope dendrochronology to date the keel of the Newport Medieval Ship, revealing a felling date of AD 1457/58 for the beech timber used in its construction. The study suggests that the ship's primary construction was a relatively rapid process, possibly completed within a year. The findings contribute to understanding timber sourcing and ship construction practices of the time, highlighting the value of isotopic dendrochronology in dating preserved maritime timbers. [Extracted from the article]

Since the discovery of the Newport Medieval Ship in 2002, many studies have tried to establish a chronology for its construction and subsequent abandonment. Whilst conventional ring-width dendrochronology has been able to identify the provenance and provide a terminus post quem for the ship, until now a felling date for timbers associated with the original construction of the vessel has proved elusive. This study reports results from the application of stable isotope dendrochronology to date timbers from the ship. Using a combination of dendrochronologically-dated timbers and stable oxygen isotopic data from dated and undated samples, we can provide an independent verification of the ring-width dendrochronology and to return the first felling dates for an assemblage of the ship's framing timbers. Our results indicate that the ship was likely constructed shortly after the winter of AD 1457/8 with an operational lifetime of less than a decade. The study highlights the potential for the use of stable isotope dendrochronology for the precise, absolute dating of archaeological ship remains where ring-width dendrochronology alone has not proved effective. [ABSTRACT FROM AUTHOR]

This paper presents results from a comparison of wholewood and cellulose carbon and oxygen isotope ratios for four UK tree species. These species occur within the historic buildings archive as both primary and supplementary construction materials and have been used to reconstruct the climate of the past. New advances in the application of stable isotopes have widened the scope of the isotope approach, but require the time-consuming purification of cellulose. Comparison of the oxygen and carbon isotope signals preserved in the wood and cellulose components confirms and builds upon previous research in this field and provides additional insight into the covariance of these two sample types between species, and the potential to employ wood isotope analysis for both pre-screening trees for palaeoclimatology and chronology research.

Stable carbon isotopes in plants can help evaluate and improve the representation of carbon and water cycles in land‐surface models, increasing confidence in projections of vegetation response to climate change. Here, we evaluated the predictive skills of the Joint UK Land Environmental Simulator (JULES) to capture spatio‐temporal variations in carbon isotope discrimination (Δ13C) reconstructed by tree rings at 12 sites in the United Kingdom over the period 1979–2016. Modeled and measured Δ13C time series were compared at each site and their relationships with local climate investigated. Modeled Δ13C time series were significantly correlated (p < 0.05) with tree‐ring Δ13C at eight sites, but JULES underestimated mean Δ13C values at all sites, by up to 2.6‰. Differences in mean Δ13C may result from post‐photosynthetic isotopic fractionations that were not considered in JULES. Inter‐annual variability in Δ13C was also underestimated by JULES at all sites. While modeled Δ13C typically increased over time across the UK, tree‐ring Δ13C values increased only at five sites located in the northern regions but decreased at the southern‐most sites. Considering all sites together, JULES captured the overall influence of environmental drivers on Δ13C but failed to capture the direction of change in Δ13C caused by air temperature, atmospheric CO2 and vapor pressure deficit at some sites. Results indicate that the representation of carbon‐water coupling in JULES could be improved to reproduce both the trend and magnitude of interannual variability in isotopic records, the influence of local climate on Δ13C, and to reduce uncertainties in predicting vegetation‐environment interactions. Plain Language Summary: Carbon has two stable isotopes, 12C and 13C. During the diffusion of carbon dioxide through the stomata of C3 plants, the lighter carbon isotope (12C) diffuses more easily resulting in leaf internal air that is depleted in 13C compared to the ambient air. Tree rings record this discrimination against 13C (noted Δ13C) which is used to decipher information about past climates, including atmospheric CO2 concentration when the rings formed. The Joint UK Land Environment Simulator (JULES) is a land‐surface model that predicts environmental processes (e.g., the carbon and water cycles). Comparing JULES estimates of Δ13C with tree‐ring measurements helps to improve simulations, leading to more accurate projections of ecosystem functioning under different climates. We found that JULES accurately predicted tree‐ring Δ13C in 8 out of 12 UK sites over a 38‐year period, with offsets in mean values of up to 2.6‰, but underestimated interannual variations in Δ13C at all sites. JULES captured the influence of environmental changes on tree‐ring Δ13C relatively well, although the trees' responses at individual sites varied. Results suggest that improvements are needed in JULES to reduce uncertainties in predicting the carbon and water cycles and therefore to produce more accurate projections of future climate‐vegetation interactions. Key Points: Joint UK Land Environmental Simulator (JULES) predicted well the tree‐ring Δ13C of oaks in eight out of 12 UK sites but underestimated inter‐annual variations and mean valuesJULES captured the environmental drivers of Δ13C, but the model failed to reproduce the direction of change in Δ13C at some individual sitesMore tree‐ring chronologies are needed to improve understanding of spatio‐temporal changes in Δ13C for UK broadleaf deciduous trees [ABSTRACT FROM AUTHOR]

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 [delta][sup.18][O.sub.precipitation] change, 4.53[per thousand] [+ or -] 1.05[per thousand] (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.

Interlaboratory comparisons involving nine European stable isotope laboratories have shown that the routine methods of cellulose preparation resulted in data that generally agreed within the precision of the isotope ratio mass spectrometry (IRMS) method used: [+ or -]0.2%0 for carbon and [+ or -]0.3%0 for oxygen. For carbon, the results suggest that holocellulose is enriched up to 0.39%0 in [sup.13]C relative to the purified ct-cellulose. The comparisons of IRMS measurements of carbon on cellulose, sugars, and starches showed low deviations from -0.23 to +0.23%0 between laboratories. For oxygen, IRMS measurements varied between means from -0.39 to 0.58 [per thousand], -0.89 to 0.42 [per thousand], and -1.30 to 1.16 [per thousand] for celluloses, sugars, and starches, respectively. This can be explained by different effects arising from the use of low- or high-temperature pyrolysis and by the variation between laboratories in the procedures used for drying and storage of samples. The results of analyses of nonexchangeable hydrogen are very similar in means with standard deviations between individual methods from [+ or -]2.7 to [+ or -]4.9 [per thousand]. The use of a onepoint calibration (IAEA-CH7) gave significant positive offsets in [[delta].sup.2]H values up to 6 [per thousand]. Detailed analysis of the results allows us to make the following recommendations in order to increase quality and compatibility of the common data bank: (1) removal of a pretreatment with organic solvents, (2) a purification step with 17% sodium hydroxide solution during cellulose preparation procedure, (3) measurements of oxygen isotopes under an argon hood, (4) use of calibration standard materials, which are of similar nature to that of the measured samples, and (5) using a two-point calibration method for reliable result calculation.

Developing a long‐term understanding of the cryosphere is important in the study of past climatic change. Here we used a nested approach combining diverse instrumental (monthly meteorological data from four weather stations, as well as gridded data) and proxy data (based on blue intensity measurements from local tree ring records) to create a reconstruction of past summer temperature for the central Jotunheimen area in southern Norway. This record was then used to reconstruct annual glacier mass balance from 1962, the start of the yearly measurements, back to 1722, immediately prior to the regional Little Ice Age maximum. Our reconstruction of the 'average' Jotunheimen cumulative glacier mass balance is based on three representative glaciers (Storbreen, Hellstugubreen and Gråsubreen) that were synthesized into one composite record which we term 'Gjennomsnittsbreen' ('mean glacier' in Norwegian) to filter out localized controls on the behaviour of individual glaciers. While not ignoring the role of precipitation on glacier mass balance, our reconstruction demonstrates that glaciers in this region exhibit a strong summer temperature control and appear to have been declining more or less continuously since the mid‐18th century. However, it also shows that this long‐term trend of overall retreat in Jotunheimen is punctuated by relatively short‐lived periods of neutral or occasionally positive glacier mass balance, signifying periods of stillstand or small‐scale glacier advance. These periods or 'events' in our reconstruction were compared with an independent record of 12 moraine‐building events developed using lichenometry. A minimum of 10 of the moraine‐building events identifiable in our reconstruction were also identifiable in the lichenometric data which affords confidence in the performance of our interrogative model. A critical implication of this successful glacier mass balance reconstruction based on just summer temperature is that for Jotunheimen – in contrast to Norwegian maritime glaciers further to the west – there is no need (as was proposed in some previous studies) to invoke large, prolonged increases in winter snowfall to explain glacier advances, not even for events such as the Little Ice Age. [ABSTRACT FROM AUTHOR]

Carbon and oxygen isotope ratios (δ13C and δ18O) were measured in annual tree-ring cellulose samples dated from 1756 to 2015 CE. These samples were extracted from Chinese pine (Pinus tabulaeformis Carr.) trees located in a semi-arid region of north-central China. We found that tree-ring δ13C and δ18O values both recorded similar climatic signals (e.g., temperature and moisture changes), but found that tree-ring δ13C exhibited a stronger relationship with mean temperature, precipitation, average relative humidity, self-calibrating Palmer drought severity index (scPDSI), and standard precipitation evaporation index (SPEI) than δ18O during the period 1951–2015 CE. The strongest correlation observed was between tree-ring δ13C and scPDSI (previous June to current May), which explains ~43% of the variance. The resulting 130-year reconstruction reveals severe drought events in the 1920s and a sustained drying trend since the 1980s. This hydroclimate record based on tree-ring δ13C data also reveals similar dry and wet events to other proxy data (i.e., tree-ring width and historical documentation) that have allowed reconstructions to be made across the northern fringe of the Asian summer monsoon region. Our results suggest that both large-scale modes of climate variability (e.g., El Niño-Southern Oscillation, Pacific Decadal Oscillation, and North Atlantic Oscillation) and external forcing (e.g., solar variability) may have modulated moisture variability in this region. Our results imply that the relationship between tree-ring δ18O and local climate is less well-characterized when compared to δ13C and may be affected more strongly by the influences of these different atmospheric circulation patterns. In this semi-arid region, tree-ring δ13C appears to represent a better tool with which to investigate historical moisture changes (scPDSI). [ABSTRACT FROM AUTHOR]

We here present a comparison of methods for the pretreatment of a batch of tree rings for high-precision measurement of radiocarbon at the Aarhus AMS Centre (AARAMS), Aarhus University, Denmark. The aim was to develop an efficient and high-throughput method able to pretreat ca. 50 samples at a time. We tested two methods for extracting α-cellulose from wood to find the most optimal for our use. One method used acetic acid, the other used HCl acid for the delignification. The testing was conducted on background 14C samples, in order to assess the effect of the different pretreatment methods on low-activity samples. Furthermore, the extracted wood and cellulose fractions were analyzed using Fourier transform infrared (FTIR) spectroscopy, which showed a successful extraction of α-cellulose from the samples. Cellulose samples were pretreated at AARAMS, and the graphitization and radiocarbon analysis of these samples were done at both AARAMS and the radiocarbon dating laboratory at Lund University to compare the graphitization and AMS machine performance. No significant offset was found between the two sets of measurements. Based on these tests, the pretreatment of tree rings for high-precision radiocarbon analysis at AARAMS will henceforth use HCI for the delignification. [ABSTRACT FROM AUTHOR]

We test a recent prediction that stable carbon isotope ratios from UK oaks will display age-trends of more than 4‰ per century by measuring >5400 carbon isotope ratios from the late-wood alpha-cellulose of individual rings from 18 modern oak trees and 50 building timbers spanning the 9th–21st centuries. After a very short (c.5 years) juvenile phase with slightly elevated values, the number of series that show rising and falling trends is almost equal (33:35) and the average trend is almost zero. These results are based upon measuring and averaging the trends in individual time-series; the 'mean of the slopes' approach. We demonstrate that the more conventional 'slope of the mean' approach can produce strong but spurious 'age-trends' even when the constituent series are flat, with zero slope and zero variance. We conclude that it is safe to compile stable carbon isotope chronologies from UK oaks without de-trending. The isotope chronologies produced in this way are not subject to the 'segment length curse', which applies to growth measurements, such as ring width or density, and have the potential to retain very long-term climate signals. [ABSTRACT FROM AUTHOR]

Oxygen isotope ratios from oak tree rings are used to extend the May–August precipitation totals of the England and Wales precipitation series back to 1201 ce. The agreement between instrumental and reconstructed values is unusually strong, with more than half of the variance explained and standard verification tests passed. The stability of this relationship is confirmed using split‐period calibration and verification. This allows the reconstruction to be variance‐scaled to the full length of the instrumental series back to 1766. Direct comparison with historical reports of very wet and dry summers show good agreement. Near‐constant replication, with a minimum of 10 timbers sourced from historic buildings across central southern England ensures signal strength does not change over time. Summers during the late 20th century appear anomalously dry and those of the 21st century very close to the pre‐20th century average with no evidence in the record of prolonged 'megadroughts' across England and Wales. [ABSTRACT FROM AUTHOR]

A tephra record is presented for a sediment core from Llyn Llech Owain, south Wales, spanning the early‐ to mid‐Holocene. Seven cryptotephra deposits are discovered with three thought to correlate with known eruptions and the remaining four considered to represent previously undocumented events. One deposit is suggested to correlate with the ~6.9 cal ka bp Lairg A tephra from Iceland, whereas more distant sources are proposed as the origin for two of the tephra deposits. A peak of colourless shards in early‐Holocene sediments is thought to tentatively correlate with the ~9.6 cal ka bp Fondi di Baia tephra (Campi Flegrei) and a second cryptotephra is tentatively correlated with the ~3.6 cal ka bp Aniakchak (CFE) II tephra (Alaska). The Fondi di Baia tephra has never been recorded beyond proximal sites and its discovery in south Wales significantly extends the geographical distribution of ash from this eruption. The remaining four cryptotephra deposits are yet to be correlated with known eruptions, demonstrating that our current understanding of widespread tephra deposits is incomplete. This new tephra record highlights the potential for sites at more southerly and westerly locations in northwest Europe to act as repositories for ash from several volcanic regions. [ABSTRACT FROM AUTHOR]