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

New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally rati- fied to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0-26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision, and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically-dated tree-ring samples, converted with a box diffusion model to marine mixed-layer ages, cover the period from 0-10.5 cal kyr BP. Beyond 10.5 cal kyr BP, high-res- olution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific 14C reservoir age information to provide a single global marine mixed-layer calibration from 10.5-26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring data sets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al. (this issue). ABSTRACT. New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally rati- fied to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0-26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision, and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically-dated tree-ring samples, converted with a box diffusion model to marine mixed-layer ages, cover the period from 0-10.5 cal kyr BP. Beyond 10.5 cal kyr BP, high-res- olution marine data become available from foraminifera in varved sediments and U/Th-dated corals. The marine records are corrected with site-specific 14C reservoir age information to provide a single global marine mixed-layer calibration from 10.5-26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring data sets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al. (this issue).

/pdf/marine04-marine-radiocarbon-age-calibration-0-26-cal-kyr-bp-3xfuopbcek.pdf

Marine04 marine radiocarbon age calibration, 0-26 cal kyr BP

The 3-km-long Greenland Ice Sheet Project 2 (GISP2) ice core presents a 100,000 +- year detailed oxygen isotope profile covering almost a full glacial-interglacial cycle. Measuranents of isotopic fluctuations in snow, frost, and atmospheric water vapor samples collected during summer field seasons (up to 20%0) are compatible with the large and abrupt 80/160 changes observed in accumulated tim. Snow pit 1580 profiles from the GISP2 summit area, however, show rapid smoothing of the 180/160 signal near the surface. Beyond about 2-m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate. The longer climate fluctuations also have regional and often global significance. In the older part of the record, corresponding to marine isotope stages (MIS) 5a to 5d, the effect of orbital climate forcing via the 19- and 23-kyr precession cycles and the 41-kyr obliquity cycle is obvious. From the end ofMIS 5a, at about 75,000 years B.P., till the end of the glacial at the Younger Dryas-Preboreal transition, at 11,650 years B.P., the O180/160 record shows frequent, rapid switches between intermediate interstadial and low stadial values. Fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1.5 kyr, a broad peak at 4.0 kyr, and additional shorter periods. Detailed comparison of the GISP2 180/160 record with the Vostok, Antarctica, 15D record; Pacific Ocean foraminiferal 180/160; Grande Pile, France, tree pollen; and insolation indicates that a counterpart to many of the rapid 180/160 fluctuations of GISP2 can be found in the other records, and that the GISP2 isotopic changes clearly are the local expression of climate changes of worldwide extent. Correlation of events on the independent GISP2 and SPECMAP time scales for the interval 10,000-50,000 years B.P. shows excellent chronometric agreement, except possibly for the event labeled 3.1. The glacial to interglacial transition evidently started simultaneously in the Arctic and the Antarctic, but its development and its expression in Greenland isotopes was later suppressed by the influence of meltwater, especially from the Barents Sea ice sheet, on deep water formation and ocean circulation. Meltwaters from different ice sheets bordering the North Atlantic also influenced ocean circulation during the Bolling-Allerod interstadial complex and the Younger Dryas and led to a distinct development of European climate and Greenland 180/160 values. The Holocene interval with long-term stable mean isotopic values contains several fluauations with periods from years to millennia. Dominant is a 6.3-year oscillation with amplitude up to 3 to 4%0. Periodicities of 11 and 210 years, also found in the solar-modulated records of the cosmogenic isotopes 1oBe and 14C, suggest solar processes as the cause of these cycles. Depression of180/160 values (cooling) by volcanic eruptions is observed in stacked GISP21580 records, but the effect is small and not likely to trigger major climate changes.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/97JC00880

Oxygen 18/16 variability in Greenland snow and ice with 10 -3- to 105-year time resolution

Viewed from a geological perspective, present-day animal and plant communities in many parts of the world have a remarkably short history. The environmental revolution at the end of the Pleistocene, a mere 10 000 years ago, triggered major shifts in the ranges of species and hence composition of communities. Present-day communities in the boreal and temperate zones assembled at this time by combining species that survived the northern environment of the Last Cold Stage with those returning from more temperate refugia. Increasing evidence suggests that the well-studied European southern and eastern refugia for thermophilous animal and plant taxa were supplemented by cryptic refugia in northern Europe during the Late Pleistocene. These northern refugia would have been in areas of sheltered topography that provided suitable stable microclimates, and could partially explain the ‘nonanalogue' mammalian assemblages of the Late Pleistocene. They also have implications for phylogeography and speciation.

Cryptic northern refugia and the origins of the modern biota

In the last decade, palaeolimnology has shifted emphasis from being a predominantly qualitative, descriptive subject to being a quantitative, analytical science with the potential to address critical hypotheses concerning the impacts of environmental changes on limnic systems. This change has occurred because of (1) major developments in applied statistics, some of which have only become possible because of the extraordinary developments in computer technology, (2) increased concern about problem definition, research hypotheses, and project design, (3) the building up of high quality modern calibration data-sets, and (4) the narrowing of temporal resolution in palaeolimnological studies from centuries to decades or even single years or individual seasons. The most significant development in quantitative palaeolimnology has been the creation of many modern calibration data-sets of biotic assemblages and associated environmental data. Such calibration sets, when analysed by appropriate numerical procedures, have the potential to transform fossil biostratigraphical data into quantitative estimates of the past environment. The relevant numerical techniques are now well developed, widely tested, and perform remarkably well. The properties of these techniques are becoming better known as a result of simulation studies. The advantages and disadvantages of the preferred technique (weighted averaging partial least squares) are reviewed and the problems in model selection are discussed. The need for evaluation and validation of reconstructions is emphasised. Several statistical surprises have emerged from calibration studies. Outstanding problems remain the need for a detailed and consistent taxonomy in the calibration sets, the quality, representativeness, and inherent variability of the environmental variables of interest, and the inherent bias in the calibration models. Besides biological- environmental calibration sets, there is the potential to develop modern sediment-environment calibration sets to link sedimentary properties to catchment parameters. The adoption of a ‘dynamic calibration set’ approach may help to minimise the inherent bias in current calibration models. Modern regression techniques are available to explore the vast amount of unique ecological information about taxon-environment relationships in calibration data-sets. Hypothesis testing in palaeolimnology can be attempted directly by careful project design to take account of ‘natural experiments’ or indirectly by means of statistical testing, often involving computer- intensive permutation tests to evaluate specific null hypotheses. The validity of such tests depends on the type of permutation used in relation to the particular data-set being analysed, the sampling design, and the research questions being asked. Stratigraphical data require specific permutation tests. Several problems remain unsolved in devising permutation designs for fine-resolution stratigraphical data and for combined spatial and temporal data. Constrained linear or non-linear reduced rank regression techniques (e.g. redundancy analysis, canonical correspondence analysis and their partial counterparts) provide powerful tools for testing hypotheses in palaeolimnology. Work is needed, however, to extend their use to investigate and test for lag responses between biological assemblages and their environment. Having developed modern calibration data-sets, many palaeolimnologists are returning to the sedimentary record and are studying stratigraphical changes. In contrast to much palynological data, palaeolimnological data are often fine-resolution and as a result are often noisy, large, and diverse. Recent developments for detecting and summarising patterns in such data are reviewed, including statistical evaluation of zones, summarisation by detrended correspondence analysis, and non-parametric regression (e.g. LOESS). Techniques of time-series analysis that are free of many of the assumptions of conventional time-series analysis due to the development of permutation tests to assess statistical significance are of considerable potential in analysing fine-resolution palaeolimnological data. Such data also contain a wealth of palaeopopulation information. Robust statistical techniques are needed to help identify non-linear deterministic dynamics (chaos) from noise or random effects in fine-resolution palaeolimnological data.

D.G. Frey and E.S. Deevey Review 1: Numerical tools in palaeolimnology – Progress, potentialities, and problems

Apparent radiocarbon ages of recent marine shells from Norway, Spitsbergen, and Arctic Canada

Marine 14C reservoir ages for 19th century whales and molluscs from the North Atlantic

New Radiocarbon Dates for the Vedde Ash and the Saksunarvatn Ash from Western Norway

Estimates of the radiocarbon age of seawater are required in correlations between marine and terrestrial records of the late Quaternary climate. We radiocarbon-dated marine shells and terrestrial plant remains deposited in two bays on Norway's west coast between 11,000 and 14,000 years ago, a time of large and abrupt climatic changes that included the Younger Dryas (YD) cold episode. The radiocarbon age difference between the shells and the plants showed that sea surface reservoir ages increased from 400 to 600 years in the early YD, stabilized for 900 years, and dropped by 300 years within a century across the YD-Holocene transition.

https://science.sciencemag.org/content/sci/312/5779/1514.full.pdf

Changes in North Atlantic radiocarbon reservoir ages during the Allerod and Younger Dryas

Cores representing a 5.5m long sequence recovered from lake AErasvatnet have been investigated for lithostratigraphy, micro- and macrofossils and radiocarbon chronology. For the first time in Fennoscandia the maximum Weichselian advance has been closely bracketed with radiocarbon datings (19,000–18,500 B.P.). A continuous stratigraphy from 18,500 B.P. and onwards, partly marine and partly lacustrine, discloses the local shoreline displacement, the palaeovegetation, the palaeoclimate and, together with other data, the deglaciation history. Two phases with a prevailing High Arctic climate have occurred: 18,000 to 16,000 B.P. and 13,700 to 12,800 B.P. Important climatic amelioration accelerating the deglacial recession occurred 16,000, 12,800 and 12,000 B.P. The continental ice sheet was situated close to its maximum position until about 16,000 B.P. The following deglaciation was interrupted by (a minor ?) readvance/halt about 15,000 B.P. (the Flesen event), 13,700-13,000 B.P. (the D-event), 12,500 B.P. (the Skarpnes event) and 11,000–10,000 B.P. (the TromsO-Lyngen event). The deglaciation chronology and pattern can be correlated with the suggested deep-sea-stratigraphy-based stepwise pattern relying on the old age alternative for termination IA.

Steinar Gulliksen

Papers

Apparent radiocarbon ages of recent marine shells from Norway, Spitsbergen, and Arctic Canada

Marine 14C reservoir ages for 19th century whales and molluscs from the North Atlantic

New Radiocarbon Dates for the Vedde Ash and the Saksunarvatn Ash from Western Norway

Changes in North Atlantic radiocarbon reservoir ages during the Allerod and Younger Dryas

The last deglaciation (20,000 to 11,000 B. P.) on Andoya, northern Norway