The 5.2 ka climate event: Evidence from stable isotope and multi-proxy palaeoecological peatland records in Ireland

AbstractEvidence for a major climate event at 5.2 ka has been reported globally and is associated with considerable societal disruption, but is poorly characterised in northwest Europe. This event forms part of a broader period of re-organisation in the Earth's ocean-atmosphere circulation system between 6 and 5 ka. This study tests the nature and timing of the event in northwest Europe, a region highly sensitive to change in meridional overturning circulation and mid-latitude westerly airflow. Here we report three high-resolution Irish multi-proxy records obtained from ombrotrophic peatlands that have robust chronological frameworks. We identify the 5.2 ka event by a sustained decrease in δ18Ocellulose at all three sites, with additional and parallel changes in δ13Ccellulose and palaeoecological (testate amoebae, plant macrofossil and humification) data from two sites in northern Ireland. Data from Sluggan Moss demonstrate a particularly coherent shift towards wetter conditions. These data support the hypothesis that the event was caused by a prolonged period of positive North Atlantic Oscillation conditions, resulting in pervasive cyclonic weather patterns across northwest Europe, increasing precipitation over Ireland

Local and indigenous knowledge as an emergent property of complexity : a case study in the Solomon Islands

Doctor of Philosoph

Estimating uncertainty in pooled stable isotope time-series from tree-rings

Stable carbon isotope time-series (δ13C) from tree-rings are capable of providing valuable palaeoclimatic information, but analysis of individual tree-rings is time consuming and expensive. Pooling material from several tree-rings prior to isotopic analysis reduces costs, but does not allow the magnitude of uncertainty in the mean δ13C chronology to be calculated unless the pool is broken and each tree-ring measured individually at regular intervals. Here we use a comparison of pooled and mean individual (the arithmetic mean of isotopic data from tree series measured individually) δ13C records between AD 1650 and 2007, comprising cores from 21 Scots pine (Pinus sylvestris L.) trees growing in the western Highlands of Scotland. The aim is to determine whether the true error structure of the time series is better captured by using the overall mean error estimate for the entire time series or by linear interpolation between the equally spaced measurements. We conclude that where autocorrelation exists within the error structure of a chronology, annual estimates of 95% confidence intervals, developed through linear interpolation at 5-year or 10-year intervals, are preferable to using the overall mean uncertainty. The method outlined increases the viability of pooled δ13C records for palaeoclimatic research by retaining error structure whilst reducing analytical time and costs. The method is applied here using tree-ring data, but could theoretically be applied to any well-replicated time-series

Combined theoretical and computational study of interstrand DNA guanine–guanine cross-linking bytrans-[Pt(pyridine)2] derived from the photoactivated prodrugtrans,trans,trans-[Pt(N3)2(OH)2(pyridine)2]

Molecular modeling and extensive experimental studies are used to study DNA distortions induced by binding platinum(II)-containing fragments derived from cisplatin and a new class of photoactive platinum anticancer drugs. The major photoproduct of the novel platinum(IV) prodrug trans,trans,trans-[Pt(N3)2(OH)2(py)2] (1) contains the trans-{Pt(py)2}2+ moiety. Using a tailored DNA sequence, experimental studies establish the possibility of interstrand binding of trans-{Pt(py)2}2+ (P) to guanine N7 positions on each DNA strand. Ligand field molecular mechanics (LFMM) parameters for Pt–guanine interactions are then derived and validated against a range of experimental structures from the Cambridge Structural Database, published quantum mechanics (QM)/molecular mechanics (MM) structures of model Pt–DNA systems and additional density-functional theory (DFT) studies. Ligand field molecular dynamics (LFMD) simulation protocols are developed and validated using experimentally characterized bifunctional DNA adducts involving both an intra- and an interstrand cross-link of cisplatin. We then turn to the interaction of P with the DNA duplex dodecamer, d(5′-C1C2T3C4T5C6G7T8C9T10C11C12-3′)·d(5′-G13G14A15G16A17C18G19A20G21A22G23G24-3′) which is known to form a monofunctional adduct with cis-{Pt(NH3)2(py)}. P coordinated to G7 and G19 is simulated giving a predicted bend toward the minor groove. This is widened at one end of the platinated site and deepened at the opposite end, while the P–DNA complex exhibits a global bend of 67° and an unwinding of 20°. Such cross-links offer possibilities for specific protein–DNA interactions and suggest possible mechanisms to explain the high potency of this photoactivated complex

NOAA/WDS Paleoclimatology - European Tree-Ring Oxygen Isotope Network from 1600-2013 CE

This archived Paleoclimatology Study is available from the NOAA National Centers for Environmental Information (NCEI), under the World Data Service (WDS) for Paleoclimatology. The associated NCEI study type is Climate Reconstruction. The data include parameters of instrumental with a geographic location of Europe. The time period coverage is from 350 to -70 in calendar years before present (BP). See metadata information for parameter and study location details. Please cite this study when using the data