Additional co-authors: TJ Heaton, AG Hogg, KA Hughen, KF Kaiser, B Kromer, SW Manning, RW Reimer, DA Richards, JR Southon, S Talamo, CSM Turney, J van der Plicht, CE Weyhenmeyer

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IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP

The age calibration program, CALIB (Stuiver & Reimer 1986), first made available in 1986 and subsequently modified in 1987 (revision 2.0 and 2.1), has been amended anew. The 1993 program (revision 3.0) incorporates further refinements and a new calibration data set covering nearly 22,000 cal yr (≈18,400 14C yr). The new data, and corrections to the previously used data set, derive from a 6-yr (1986–1992) time-scale calibration effort of several laboratories.

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Extended 14C Data Base and Revised Calib 3.0 14C Age Calibration Program

If radiocarbon measurements are to be used at all for chronological purposes, we have to use statistical methods for calibration. The most widely used method of calibration can be seen as a simple application of Bayesian statistics, which uses both the information from the new measurement and information from the 14C calibration curve. In most dating applications, however, we have larger numbers of 14C measurements and we wish to relate those to events in the past. Bayesian statistics provides a coherent framework in which such analysis can be performed and is becoming a core element in many 14C dating projects. This article gives an overview of the main model components used in chronological analysis, their mathematical formulation, and examples of how such analyses can be performed using the latest version of the OxCal software (v4). Many such models can be put together, in a modular fashion, from simple elements, with defined constraints and groupings. In other cases, the commonly used "uniform phase" models might not be appropriate, and ramped, exponential, or normal distributions of events might be more useful. When considering analyses of these kinds, it is useful to be able run simulations on synthetic data. Methods for performing such tests are discussed here along with other methods of diagnosing possible problems with statistical models of this kind.

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Bayesian analysis of radiocarbon dates

[1] We present a 53-Myr stack (the “LR04” stack) of benthic δ18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm This is the first benthic δ18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the δ18O stack to a simple ice model based on 21 June insolation at 65°N Stacked sedimentation rates provide additional age model constraints to prevent overtuning Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 53 Myr and in the precession band for more than half of the record The LR04 stack contains significantly more variance in benthic δ18O than previously published stacks of the late Pleistocene as the result of higher-resolution records, a better alignment technique, and a greater percentage of records from the Atlantic Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of δ18O from 27–16 Ma is primarily a deep-water temperature signal and that the phase of δ18O precession response changed suddenly at 16 Ma

/pdf/a-pliocene-pleistocene-stack-of-57-globally-distributed-n5iphe7mt2.pdf

A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records

The use of stable isotopes to solve biogeochemical problems in ecosystem analysis is increasing rapidly because stable isotope data can contribute both source-sink (tracer) and process information: The elements C, N, S, H, and all have more than one isotope, and isotopic compositions of natural materials can be measured with great precision with a mass spectrometer. Isotopic compositions change in predictable ways as elements cycle through the biosphere. These changes have been exploited by geochemists to understand the global elemental cycles. Ecologists have not until quite recently employed these techniques. The reasons for this are, first, that most ecologists do not have the background in chemistry and geochemistry to be fully aware of the possibilities for exploiting the natural variations in stable isotopic compositions, and second, that stable isotope ratio measurements require equipment not normally available to ecologists. This is unfortunate because some of the more intractable problems in ecology can be profitably addressed using stable isotope measurements. Stable isotopes are ideally suited to increase our understanding of element cycles in ecosystems. This review is written for ecologists who would like to learn more about how stable isotope analyses have been and can be used in ecosystem studies. We begin with an explanation of isotope terminology and fractionation, then summarize isotopic distributions in the C, N, and S biogeochemical cycles, and conclude with five case studies that show how stable isotope measurements can provide crucial information for ecosystem analysis. We restrict this review to studies of natural variations in C, N, and S isotopic abundances, cxcluding from consideration ~5N enrichment studies and hydrogen and oxygen isotope studies. Our focus on C, N, and S derives in part from our

Stable isotopes in ecosystem studies

Two cores which had been drilled to a depth of over 200 m were recovered near Amundsen-Scott South Pole Station during the 1980-82 field seasons. A firn core drilled from 3 to 19 m depth was taken in December 1982 from a site about 5 km distant from the two others. The cores cannot be used to study the seasonal 6 180 cycle, because: (i) detailed sampling (1-2 cm increments) provides evidence of isotopic enrichment in the I m core sections during storage, both in the field and in the laboratory cold-room, and (ii) low accumulation (9.2 g cm-2 aI, given by Jouzel and others 1983) led to missing years or parts thereof. Estimates of the proportion of missing years range from I in 10 (J.R . Petit, quoted in Mosley-Thompson and Thompson 1982) to 1 in 20 (Jouzel and others 1983). The cores are still useful for studies on a decadal or longer time-scale. The average 6180 value of detailed measurements of the upper 40 m of the 1980 firn core differs by only 0. 14 ± 0.05~ from the average of measurements made about 16 months earlier. Thus, although storage in the cold-room changed the isotopic composition of the outer firn layer, the bulk of the firn core was unaffected. The two measurement series of this profile show a high correlation (r2 = 0.75, P < 10-6) when smoothed with a I m moving average (equivalent to 4-7 years' accumulation) in order to reduce noise and the effect of enrichment at the ends of the I m sections. In both long cores and in the short core which was taken in 1982 the 6 180 depth profile shows a long-term trend with superimposed shorter fluctuations. The seasonal signal soon disappears but variability of up to 2~ on a 3-5 year time-scale persists at depth . Linear-correlation analysis shows a significant correlation between the 198'0 firn core and the 1982 short core (r2 = 0.32, P = 0.0 11) for a I m moving average of samples 0.25 m long. Some correlation is also observed between the deeper ice parts of the 1982 core (106-227 m) and the 1981 core (100-202.4 m) (r2 = 0.087, P = 0.00043, I m moving average), if the relative depths are shifted by 3.75 m. A firm time-scale for both cores is needed to determine whether such a shift corrects for an artefact of the depth logs of the cores, or proves that no real correlation exists between the two cores. Comparison of the long-term trend of the two South Pole cores with the 2.5 ka isotope climatic record from the 1979 Dome C core (Benoist and others 1982) and with the Law Dome core BHD record (Morgan 1985) again suggests possible correlation, but cannot prove it for lack of a firm time-scale. Collaboration with other investigators which brings together data on visible stratigraphy and density (personal communication from A.J. Gow), solid conductivity (Schwander unpublished), acid horizons (Langway and others 1988, this volume) and microparticles may solve this problem. REFERENCES Benoist J P, Jouzel J, Lorius C, Merlivat L, Pourchet M 1982 Isotope climatic record over the last 2.5 ka from Dome C, Antarctica ice cores. Annals of Glaciology 3: 17-22 Jouzel J, Merlivat L, Petit J R, Lorius C 1983 Climatic information over the last century deduced from a detailed isotopic record in the South Pole snow. Journal of Geophysical Research 88(C4): 2693-2703 Langway C C Jr, Clausen H B, Hammer C U 1988 An inter-hemispheric volcanic time-marker in ice cores from Greenland and Antarctica. Annals of Glaciology ]0: 102-108 Morgan V I 1985 An oxygen isotope .... dimate record from the Law Dome, Antarctica. Climatic Change 7(4): 415-426 Mosley-Thompson E, Thompson L G 1982 Nine centuries of microparticle deposition at the South Pole. Quaternary Research 17( I): 1-13 Schwander J Unpublished Lufteinschluss im Eis von Gronland und der Antarktis; Messung der elektrischen Leitfahigkeit von Eisproben fur klimatologische Anwendungen. (PhD thesis , Universitat Bern, 1984)

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Oxygen-isotope records covering the last 2 ka at South Pole

by Paul A. Mayewski, W. Berry Lyons, M.). Spencer and Mark S. Twickler (Glacier Research Group and Earth Science Department, University of New Hampshire, Durham, NH 03824, U.S.A.) and Pieter M. Grootes and Minze Stuiver (Quaternary Isotope Laboratory, University of Washington, WA 98195, U.S.A.) The production of climatic-change records using glaciochemical time series has seen minimal application in the Transantarctic Mountains. This is true despite the fact that glacial geologic studies in this area are the primary basis for understanding the glacial history of East Antarctica and thus provide an excellent potential framework for the more detailed records obtainable from glaciochemical studies. Numerous sites within the Transantarctic Mountains fit the requirements necessary for the retrieval of ice cores, and pilot studies have been conducted in both southern Victoria Land (Mayewski and Lyons 1982) and northern Victoria Land (Alien and others 1985). These pilot studies have validated the hypothesis that glaciochemical records retrieved from appropriately chosen ice-core sites in the Transantarctic Mountains can be used for: (I) assessing the current stability of the East Antarctic ice sheet, (2) validating models concerning the recent glacial history of the Transantarctic Mountains, (3) searching for relatively high-frequency (i-lOO year) climatic signals, (4) determining changes in the relative geography (ocean -land - ice) of a region, and (5) defining the relative importance of the chemical species source areas (i.e. volcanic, biogenic, anthropogenic, marine, crustal) that provide precipitation to the Transantarctic Mountains. During the 1984-85 austral summer, a combined University of New Hampshire - Polar Ice Coring Office effort resulted in the recovery of a 20 I m long core from a 2800 m high snow massif atop the Dominion Range (85

Minze Stuiver

Papers

Oxygen-isotope records covering the last 2 ka at South Pole

A Climatic Record Using An Ice Core from the Transantarctic Mountains, Antarctica (Abstract)