Australasia

Observed changes and impacts Ongoing climate trends have exacerbated many extreme events (very high confidence). The Australian trends include further warming and sea level rise sea level rise (SLR), with more hot days and heatwaves, less snow, more rainfall in the north, less April–October rainfall in the southwest and southeast and more extreme fire weather days in the south and east. The New Zealand trends include further warming and sea level rise (SLR), more hot days and heatwaves, less snow, more rainfall in the south, less rainfall in the north and more extreme fire weather in the east. There have been fewer tropical cyclones and cold days in the region. Extreme events include Australia’s hottest and driest year in 2019 with a record-breaking number of days over 39°C, New Zealand’s hottest year in 2016, three widespread marine heatwaves during 2016–2020, Category 4 Cyclone Debbie in 2017, seven major hailstorms over eastern Australia and two over New Zealand from 2014–2020, three major floods in eastern Australia and three over New Zealand during 2019–2021 and major fires in southern and eastern Australia during 2019–2020

Radiocarbon/Tree-Ring Calibration, Solar Activity, and Upwelling of Ocean Water

From the 18th International Radiocarbon Conference held in Wellington, New Zealand, September 1-5, 2003.Least-squares fitted smooth curves to radiocarbon versus tree-ring calibration data for the period AD 1140 to 1950 are compared with climatic warming and cooling of the North Atlantic (Little Ice Age), and with recorded sunspot numbers over the period AD 1670 to 1950. Calibration curves from different parts of the globe are not identical, and appear to be determined by a combination of variable solar activity and variable oceanic upwelling of 14C-depleted water, with the variable upwelling itself partly determined by solar activity.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Least-Squares Fitting a Smooth Curve to Radiocarbon Calibration Data

We Fourier transformed and filtered calibration curve data to compensate for the averaging effect of radiocarbon-dating sets of adjacent tree rings. A Wiener Filter was also applied to minimize the effects of the counting errors of the dates on the resulting calibration curve and to produce a least-squares curve through the data. The method is illustrated using a short 14C-dated tree-ring sequence from New Zealand to produce a calibration curve at yearly intervals for New Zealand matai (Prumnopitys taxifolia). The resulting curve has a nominal standard error of 10 +/3 yr, which is ca. Half the average standard error of the original raw data.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Least-Squares Fitting Smooth Curves to Decadal Radiocarbon Calibration Data from AD 1145 to AD 1945

Smoothed curves are least-squares fitted to three sets of decadal radiocarbon calibration data from New Zealand and British Isles (AD 1725-1935) and western North America (AD 1145-1945). The curves are compared with each other and with a curve previously calculated from New Zealand data (AD 1335-1745). The smoothing procedure results in reduced standard deviations of the curves, but at the expense of time resolution. The comparison shows a variable 14C offset between the northern and southern hemispheres of 0-70 years (Southern Hemisphere older), and a Northern Hemisphere longitudinal variation of -20 to +60 years (British Isles generally older than western North America).The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Calibrating New Zealand Radiocarbon Dates of Marine Shells

Radiocarbon activity of 11 modern marine shell samples from the New Zealand region is enhanced compared with the surface layers of the average world ocean. The measured enhancement, Delta-R, is equivalent to -31 +/13 years. On this basis, the Institute of Nuclear Sciences will now use a value of -30 years in reporting calibrated ages for marine shell samples.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Radiocarbon Calibration Curve Variations and Their Implications for the Interpretation of New Zealand Prehistory

The shape of a distribution of calibrated 14C dates displays spurious peaks and troughs, brought about by changes in the slope of the calibration curve interacting with the spreading effect of the stochastic distribution of counting errors. The distortion results in a positive correlation between the numbers of dates per calendar year and the slopes of the calibration curves, for assemblages of archaeological dates from such widely separated areas as British Columbia, South Australia and New Zealand. The distortion also increases the possibility of date reversals, and increases the overall spread of calibrated 14C dates. After taking into account this systematic distortion and inbuilt age of charcoal and wood samples, we estimate dates for the initial settlement and first appearance of fortifications, and infer a likely trend of population growth for prehistoric New Zealand.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Geomorphology and accommodation space as limiting factors on tsunami deposition : Chatham Island, southwest Pacific Ocean

Chatham Island in the southwest Pacific Ocean is exposed on all sides to potential tsunami impact. In historical time, tsunamis are known to have inundated the coast on several occasions, with the largest event in 1868. Coastal dunes along the northeast coast of Chatham Island preserve sedimentary evidence of this and possibly earlier tsunami events, as localised gravel lags. However, these deposits lack a clear stratigraphic context and establishing their age is difficult. This study examines the sediment record in a freshwater wetland at Okawa Point, located directly landward of the dunes where apparent tsunami gravels occur. Sediment descriptions, pollen, foraminifera, chemical data and radiocarbon dates from cores are used to reconstruct the environmental history of the wetland. The record extends from ca >43. ka to the present and incorporates glacial, post-glacial and human-influenced phases. Throughout this time the wetland appears to have remained isolated from catastrophic marine inundation. The only evidence for saltwater intrusion is observed in the historic period, via geochemical, grain size and pollen data, which record a marine inundation event that forced the transport of a thin (cm-thick) deposit of dune and beach sand into the seaward edge of the wetland. This is interpreted as the signature of the 1868 tsunami. The lack of more widespread physical evidence for this and other tsunami events in the wetland is attributed to the morphological roughness afforded by coastal dunes and limited accommodation space for Holocene deposits.12 page(s