We report the discovery of an ancient forest bed near Stanley, on the Falkland Islands, the second such ancient deposit identified on the South Atlantic island archipelago that is today marked by the absence of native tree species. Fossil pollen, spores and wood fragments preserved in this buried deposit at Tussac House show that the source vegetation was characterized by a floristically diverse rainforest dominated by Nothofagus-Podocarpaceae communities, similar to cool temperate Nothofagus forests/woodlands and Magellanic evergreen Nothofagus rainforests. The age limit of the deposit is inferred from the stratigraphic distribution of fossil pollen species transported by wind, birds or ocean currents from southern Patagonia, as well as similar vegetation types observed across the broader region. The deposit is suggested to be between Late Oligocene and Early Miocene, making it slightly older than the previously analysed Neogene West Point Island forest bed (200 km west of Tussac House). The combined evidence adds to our current knowledge of the role of climate change and transoceanic dispersal of plant propagules in shaping high-latitude ecosystems in the Southern Hemisphere during the late Palaeogene and Neogene.

The IntCal family of radiocarbon (14C) calibration curves is based on research spanning more than three decades. The IntCal group have collated the 14C and calendar age data (mostly derived from primary publications with other types of data and meta-data) and, since 2010, made them available for other sorts of analysis through an open-access database. This has ensured transparency in terms of the data used in the construction of the ratified calibration curves. As the IntCal database expands, work is underway to facilitate best practice for new data submissions, make more of the associated metadata available in a structured form, and help those wishing to process the data with programming languages such as R, Python, and MATLAB. The data and metadata are complex because of the range of different types of archives. A restructured interface, based on the “IntChron” open-access data model, includes tools which allow the data to be plotted and compared without the need for export. The intention is to include complementary information which can be used alongside the main 14C series to provide new insights into the global carbon cycle, as well as facilitating access to the data for other research applications. Overall, this work aims to streamline the generation of new calibration curves.

Tree-ring series offer considerable potential for the development of environment-sensitive proxy records. However, with traditional increment cores, only small amounts of wood are often available from annual tree-ring sequences. For this reason, it is important to understand the reliability (and reproducibility) of radiocarbon measurements obtained from small-sized samples. Here we report the F14C results from the Chronos 14Carbon-Cycle Facility of modern tropical Australian tree samples over a range of four graphite target sizes from the same rings. Our study shows that similar precision can be obtained from full-sized, half-sized, as well as small-sized graphite targets using standard pretreatment and analysis procedures. However, with a decline in sample size, there was an increase seen in the associated variance of the ages and the smallest target weights started showing a systematic bias. Wiggle-matching accuracy tests, comparing the Southern Hemisphere post-bomb atmospheric calibration curve to the different sample weight sequences, were all significant except for the 200 μgC graphite targets. Our results indicate that samples smaller than 350 μgC have limited accuracy and precision. Overall, reliable measurements of F14C sequences from tree-ring records across a range of sample sizes, with best results found using graphitized samples >350 μgC.

Wetland sediments are valuable archives of environmental change but can be challenging to date. Terrestrial macrofossils are often sparse, resulting in radiocarbon (14C) dating of less desirable organic fractions. An alternative approach for capturing changes in atmospheric 14C is the use of terrestrial microfossils. We 14C date pollen microfossils from two Australian wetland sediment sequences and compare these to ages from other sediment fractions (n = 56). For the Holocene Lake Werri Berri record, pollen 14C ages are consistent with 14C ages on bulk sediment and humic acids (n = 14), whilst Stable Polycyclic Aromatic Carbon (SPAC) 14C ages (n = 4) are significantly younger. For Welsby Lagoon, pollen concentrate 14C ages (n = 21) provide a stratigraphically coherent sequence back to 50 ka BP. 14C ages from humic acid and >100 µm fractions (n = 13) are inconsistent, and often substantially younger than pollen ages. Our comparison of Bayesian age-depth models, developed in Oxcal, Bacon and Undatable, highlight the strengths and weaknesses of the different programs for straightforward and more complex chrono-stratigraphic records. All models display broad similarities but differences in modeled age-uncertainty, particularly when age constraints are sparse. Intensive dating of wetland sequences improves the identification of outliers and generation of robust age models, regardless of program used.

This paper presents a compilation of atmospheric radiocarbon for the period 1950–2019, derived from atmospheric CO2 sampling and tree rings from clean-air sites. Following the approach taken by Hua et al. (2013), our revised and extended compilation consists of zonal, hemispheric and global radiocarbon (14C) data sets, with monthly data sets for 5 zones (Northern Hemisphere zones 1, 2, and 3, and Southern Hemisphere zones 3 and 1–2). Our new compilation includes smooth curves for zonal data sets that are more suitable for dating applications than the previous approach based on simple averaging. Our new radiocarbon dataset is intended to help facilitate the use of atmospheric bomb 14C in carbon cycle studies and to accommodate increasing demand for accurate dating of recent (post-1950) terrestrial samples.

The Chronos 14Carbon-Cycle Facility is a new radiocarbon laboratory at the University of New South Wales, Australia. Built around an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) Accelerator Mass Spectrometer (AMS) installed in October 2019, the facility was established to address major challenges in the Earth, Environmental and Archaeological sciences. Here we report an overview of the Chronos facility, the pretreatment methods currently employed (bones, carbonates, peat, pollen, charcoal, and wood) and results of radiocarbon and stable isotope measurements undertaken on a wide range of sample types. Measurements on international standards, known-age and blank samples demonstrate the facility is capable of measuring 14C samples from the Anthropocene back to nearly 50,000 years ago. Future work will focus on improving our understanding of the Earth system and managing resources in a future warmer world.

Early researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14C yrs older.

Precise radiocarbon (14C) dating of sedimentary sequences is important for developing robust chronologies of environmental change, but sampling of suitable components can be challenging in highly dynamic landscapes. Here we investigate radiocarbon determinations of different peat size fractions from six peat sites, representing a range of geomorphological contexts on the South Atlantic subantarctic islands of the Falklands and South Georgia. To investigate the most suitable fraction for dating, 112 measurements were obtained from three components within selected horizons: a fine fraction <0.2 mm, a coarse fraction >0.2 mm, and bulk material. We find site selection is critical, with locations surrounded by high-ground and/or relatively slowly accumulating sites more susceptible to the translocation of older carbon. Importantly, in locations with reduced potential for redeposition of material, our results show that there is no significant or systematic difference between ages derived from bulk material, fine or coarse (plant macrofossil) material, providing confidence in the resulting age model. Crucially, in areas comprising complex terrain with extreme relief, we recommend dating macrofossils or bulk carbon rather than a fine fraction, or employing comprehensive dating of multiple sedimentary fractions to determine the most reliable fraction(s) for developing a robust chronological framework.

This research investigates two factors influencing the ability of tree-ring data to provide accurate 14C calibration information: the fitness and rigor of the statistical model used to combine the data into a curve; and the accuracy, precision and reproducibility of the component 14C data sets. It presents a new Bayesian spline method for calibration curve construction and tests it on extant and new Southern Hemisphere (SH) data sets (also examining their dendrochronology and pretreatment) for the post-Little Ice Age (LIA) interval AD 1500–1950. The new method of construction allows calculation of component data offsets, permitting identification of laboratory and geographic biases. Application of the new method to the 10 suitable SH 14C data sets suggests that individual offset ranges for component data sets appear to be in the region of ± 10 yr. Data sets with individual offsets larger than this need to be carefully assessed before selection for calibration purposes. We identify a potential geographical offset associated with the Southern Ocean (high latitude) Campbell Island data. We test the new methodology for wiggle-matching short tree-ring sequences and use an OxCal simulation to assess the likely precision obtainable by wiggle-matching in the post-LIA interval.

In ’Why didn't they ask Evans?’ (Turney, 2017), I draw together previously unpublished sources and new analyses of published material to cast further light on the circumstances that led to the fatal events surrounding the return of Captain Robert Falcon Scott's Polar Party on the British Antarctic Expedition (BAE, 1911–1913). Of particular importance are the notes on the meeting between the Royal Geographical Society's President Lord Curzon and the widows Kathleen Scott and Oriana Wilson in April 1913, which explicitly identify Lieutenant Edward ‘Teddy’ Evans as having removed food that exceeded his allocation as a member of the Last Supporting Party (Curzon, 1913), the establishment and almost immediate closure of a ‘Committee of Enquiry’ chaired by Lord Curzon (Beaumont, 1913a, b, c; Cherry-Garrard, 1913a; Darwin, 1913; Goldie, 1913), the recognition of missing food at key depots by the returning Polar Party on the 7, 24 and 27 February 1912 (Scott, 1913a; Wilson, 1912), Evans’ anger at not being selected as a member of the Polar Party and his early departure home (Evans, 1912), the revised timeline of when Evans fell down with scurvy on the Ross Ice Shelf to apparently align with when and where the food was removed (The Advertiser, 3 April 1912, Adelaide: 10) (Cherry-Garrard, 1922; Ellis, 1969; Evans, 1912, 1913a, 1943; Lashly, 1912; Scott, 1913a, 1913b), Evans’ failure to ensure Scott's orders regarding the return of the dog sledging teams had been acted on (Cherry-Garrard, 1922; Gran, 1961; Hattersley-Smith & McGhie, 1984) and the misunderstanding amongst senior Royal Geographical Society members during Evans’ recuperation in the UK that Apsley Cherry-Garrard ‘was to meet the South Pole party, with two teams of dogs, at the foot of the [Beardmore] glacier’ (Markham, 1913). I would like to thank May (2018) for her comment and acknowledge that Edward Wilson's sketchbooks of the expedition's logistics, scientific priorities, sketches and notes on the BAE comprise entries from 1911–1912 and not solely from 1912, which Turney (2017) used to denote the year of the last entry.

Arguably the best known scientific Antarctic venture was the British Antarctic Expedition of 1911–1913 led by Captain Robert Falcon Scott. Whilst the so-called race to the geographic South Pole with Roald Amundsen's Norwegian Antarctic expedition excited international interest, the tragic death of Scott and his returning Polar Party was a striking reminder of the hazards of operating in the south. Recent work has highlighted the possible role expedition second-in-command Lieutenant Edward ‘Teddy’ Evans played in the deaths of Scott and his men. Here I report newly discovered documents which, when placed in a wider context, raise significant questions over Evans’ behaviour during the expedition. The evidence focuses on the shortage of food at key depots, the apparently deliberate obfuscation of when Evans fell down with scurvy and the failure to pass on orders given by Scott. It is concluded that Evans actions on and off the ice can at best be described as ineffectual, at worst deliberate sabotage. Why Evans was not questioned more about these events on his return to England remains unknown.

New dating confirms that people occupied the Australian continent before the earliest time inferred from conventional radiocarbon analysis. Many of the new ages were obtained by accelerator mass spectrometry 14C dating after an acid–base–acid pretreatment with bulk combustion (ABA-BC) or after a newly developed acid–base–wet oxidation pretreatment with stepped combustion (ABOX-SC). The samples (charcoal) came from the earliest occupation levels of the Devil's Lair site in southwestern Western Australia. Initial occupation of this site was previously dated 35,000 14C yr B.P. Whereas the ABA-BC ages are indistinguishable from background beyond 42,000 14C yr B.P., the ABOX-SC ages are in stratigraphic order to ∼55,000 14C yr B.P. The ABOX-SC chronology suggests that people were in the area by 48,000 cal yr B.P. Optically stimulated luminescence (OSL), electron spin resonance (ESR) ages, U-series dating of flowstones, and 14C dating of emu eggshell carbonate are in agreement with the ABOX-SC 14C chronology. These results, based on four independent techniques, reinforce arguments for early colonization of the Australian continent.

Since the 1970s it has been recognised that Southern Hemisphere samples have a lower radiocarbon content than contemporaneous material in the Northern Hemisphere. This interhemispheric radiocarbon offset has traditionally been considered to be the result of a greater surface area in the southern ocean and high-latitude deepwater formation. This is despite the fact that the El Niño–Southern Oscillation (ENSO) is known to play a significant role in controlling the interannual variability of atmospheric carbon dioxide by changing the flux of ‘old’ CO2 from the tropical Pacific. Here we demonstrate that over the past millennium, the Southern Hemisphere radiocarbon offset is characterised by a pervasive 80-yr cycle with a step shift in mean values coinciding with the transition from the Medieval Warm Period to the Little Ice Age. The observed changes suggest an ENSO-like role in influencing the interhemispheric radiocarbon difference, most probably modulated by the Interdecadal Pacific Oscillation, and supports a tropical role in forcing centennial-scale global climate change.

AMS radiocarbon dates were obtained from Salix herbacea leaves, Carex seeds, and bulk organic detritus from a lake sediment profile of Wisconsinan (Weichselian) Lateglacial age in SW Ireland. There is a systematic age difference between the dated series from the two types of macrofossils, with ages obtained from Salix herbacea leaves being 900 to 1500 14C years younger than those obtained from Carex seeds. The latter tend to be more in accord with dates from the total organic detritus in the lake sediment, although the bulk organic fraction invariably registered the older ages. Intact survival of the fragile Salix leaves indicates that they are unlikely to have been physically transferred within the sediment matrix and/or otherwise reworked from the surrounding catchment. Hence, these macrofossils are the more likely to be contemporaneous with the time of deposition. However, there is no significant correlation between measured 14C age and depth in the Salix values, which scatter over a range of 700 14C years. In contrast, the age/depth relationship for Carex shows a significant reversal, possibly reflecting the redeposition of these macrofossils, and therefore giving radiocarbon ages that are anomalously old. The data have important implications for the dating of lake sediment sequences by AMS radiocarbon measurement of terrestrial plant macrofossils.

Lithology, pollen, macrofossils, and stable carbon isotopes from an intermontane basin bog site in southern New Zealand provide a detailed late-glacial and early Holocene vegetation and climate record. Glacial retreat occurred before 17,000 cal yr B.P., and tundra-like grassland"shrubland occupied the basin shortly after. Between 16,500 and 14,600 cal yr B.P., a minor regional expansion of forest patches occurred in response to warming, but the basin remained in shrubland. Forest retreated between 14,600 and 13,600 cal yr B.P., at about the time of the Antarctic Cold Reversal. At 13,600 cal yr B.P., a steady progression from shrubland to tall podocarp forest began as the climate ameliorated. Tall, temperate podocarp trees replaced stress-tolerant shrubs and trees between 12,800 and 11,300 cal yr B.P., indicating sustained warming during the Younger Dryas Chronozone (YDC). Stable isotopes suggest increasing atmospheric humidity from 11,800 to 9300 cal yr B.P. Mild (annual temperatures at least 1°C higher than present), and moist conditions prevailed from 11,000 to 10,350 cal yr B.P. Cooler, more variable conditions followed, and podocarp forest was completely replaced by montane Nothofagus forest at around 7500 cal yr B.P. with the onset of the modern climate regime. The Cass Basin late-glacial climate record closely matches the Antarctic ice core records and is in approximate antiphase with the North Atlantic.

The Last Glacial–Interglacial Transition (LGIT; 15,000–11,000 cal BP) was characterized by complex spatiotemporal patterns of climate change, with numerous studies requiring accurate chronological control to decipher leads from lags in global paleoclimatic, paleoenvironmental, and archaeological records. However, close scrutiny of the few available tree-ring chronologies and radiocarbon-dated sequences composing the IntCal13 14C calibration curve indicates significant weakness in 14C calibration across key periods of the LGIT. Here, we present a decadally resolved atmospheric 14C record derived from New Zealand kauri spanning the Lateglacial from ~13,100–11,365 cal BP. Two floating kauri 14C time series, curve-matched to IntCal13, serve as a 14C backbone through the Younger Dryas. The floating Northern Hemisphere (NH) 14C data sets derived from the YD-B and Central European Lateglacial Master tree-ring series are matched against the new kauri data, forming a robust NH 14C time series to ~14,200 cal BP. Our results show that IntCal13 is questionable from ~12,200–11,900 cal BP and the ~10,400 BP 14C plateau is approximately 5 decades too short. The new kauri record and repositioned NH pine 14C series offer a refinement of the international 14C calibration curves IntCal13 and SHCal13, providing increased confidence in the correlation of global paleorecords.

The arrival of iceberg B09B in Commonwealth Bay, East Antarctica, and subsequent fast ice expansion has dramatically increased the distance Adélie penguins (Pygoscelis adeliae) breeding at Cape Denison must travel in search of food. This has provided a natural experiment to investigate the impact of iceberg stranding events and sea ice expansion along the East Antarctic coast. As part of the Australasian Antarctic Expedition 2013–14, the Adélie penguin colony at Cape Denison was censused to compare to historic counts. Whilst some 5520 pairs still bred at Cape Denison there has been an order of magnitude decline in Adélie numbers in the area in comparison to the first counts a century ago and, critically, recent estimates based on satellite images and a census in 1997. In contrast, an Adélie population on the eastern fringe of Commonwealth Bay just 8 km from the fast ice edge was thriving, indicating the arrival of B09B and fast ice expansion was probably responsible for the observed recent population decline. In conclusion, the Cape Denison population could be extirpated within 20 years unless B09B relocates or the now perennial fast ice within the bay breaks out. Our results have important implications for wider East Antarctic if the current increasing sea ice trend continues.

Center for Accelerator Mass Spectrometry (CAMS) Tasmanian Huon pine (Lagarostrobos franklinii) decadal measurements for the interval AD 745–855 suggest a mean interhemispheric radiocarbon offset (20 ± 5 yr), which is considerably lower than the previously reported mean interhemispheric offset for the last 2 millennia (44 ± 17 yr). However, comparable University of Waikato (Wk) New Zealand kauri (Agathis australis) measurements show significantly higher values (56 ± 6 yr), suggesting the possibility of a temporary geographic (intrahemispheric) offset between Tasmania, Australia, and Northland, New Zealand, during at least 1 common time interval. Here, we report 9 new Wk Tasmanian Huon pine measurements from the decades showing the largest Huon/kauri difference. We show statistically indistinguishable Wk Huon and Wk kauri 14C ages, thus dispelling the suggestion of a 14C geographic offset between Tasmania and Northland.

Wc describe here the New Zealand kauri (Agathis australis) Younger Dryas (YD) research project, which aims to undertake Δ14C analysis of ∼140 decadal floating wood samples spanning the time interval ∼13.1–11.7 kyr cal BP. We report 14C intercomparison measurements being undertaken by the carbon dating laboratories at University of Waikato (Wk), University of California at Irvine (UCI), and University of Oxford (OxA). The Wk, UCI, and OxA laboratories show very good agreement with an interlaboratory comparison of 12 successive decadal kauri samples (average offsets from consensus values of –7 to +4 14C yr). A University of Waikato/University of Heidelberg (HD) intercomparison involving measurement of the YD-age Swiss larch tree Ollon505, shows a HD/Wk offset of ∼10–20 14C yr (HD younger), and strong evidence that the positioning of the Ollon505 series is incorrect, with a recommendation that the 14C analyses be removed from the IntCal calibration database.