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Jonathan G. Palmer

Jonathan G. Palmer
UNSW Sydney | UNSW · School of Biological, Earth and Environmental Sciences (BEES)

PhD

About

187
Publications
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Introduction
Jonathan currently works at the School of Biological, Earth and Environmental Sciences (BEES) , University of New South Wales, Sydney. Jonathan does research in Dendrochronology and Paleoclimatology. One current focus is the spatial field reconstruction of climate modes in Australasia. Another key area of interest are subfossil logs of kauri (Agathis australis) from northern New Zealand for radiocarbon calibration and palaeoclimate study.

Publications

Publications (187)
Article
Full-text available
Streamflow in Australia’s northern rivers has been steadily increasing since the 1970s, most likely due to increased intensity in the Indo‐Australian monsoon. However, because of limited data availability, it is hard to assess this recent trend and therefore contextualize potential future climatic changes. In this study, we used a network of 63 pre...
Preprint
Full-text available
Much of our knowledge about the impacts of volcanic events on climate comes from proxy records. However, little is known about the impact of volcanoes on trees from the Southern Hemisphere. We investigated whether volcanic signals could be identified in ring widths from eight New Zealand dendrochronological species, using superposed epoch analysis....
Article
Full-text available
We evaluate a range of blue intensity (BI) tree-ring parameters in eight conifer species (12 sites) from Tasmania and New Zealand for their dendroclimatic potential, and as surrogate wood anatomical proxies. Using a dataset of ca. 10–15 trees per site, we measured earlywood maximum blue intensity (EWB), latewood minimum blue intensity (LWB), and th...
Article
This paper presents a compilation of atmospheric radiocarbon for the period 1950–2019, derived from atmospheric CO 2 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 ( ¹⁴ C) data sets, with monthly data sets for...
Article
Full-text available
Our paper about the impacts of the Laschamps Geomagnetic Excursion 42,000 years ago has provoked considerable scientific and public interest, particularly in the so-called Adams Event associated with the initial transition of the magnetic poles. Although we welcome the opportunity to discuss our new ideas, Hawks' assertions of misrepresentation are...
Article
Full-text available
Our study on the exact timing and the potential climatic, environmental, and evolutionary consequences of the Laschamps Geomagnetic Excursion has generated the hypothesis that geomagnetism represents an unrecognized driver in environmental and evolutionary change. It is important for this hypothesis to be tested with new data, and encouragingly, no...
Article
Radiocarbon dating is the most widely applied and reliable dating technique for providing chronological control during Marine Isotope Stage 3 (MIS3; ∼60–27 cal kyr BP). Past variations in the atmospheric concentration of radiocarbon mean a calibration curve is required. IntCal20 and SHCal20 calibration curves covering MIS3 are presently largely bas...
Preprint
Full-text available
We evaluate a range of blue intensity (BI) tree-ring parameters in eight conifer species (12 sites) from Tasmania and New Zealand for their dendroclimatic potential, and as surrogate wood anatomical proxies. Using a dataset of ca. 10–15 trees per site, we measured earlywood maximum blue reflectance intensity (EWB), latewood minimum blue reflectance...
Article
The Chronos ¹⁴ Carbon-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 Archaeologica...
Article
Full-text available
Geological archives record multiple reversals of Earth’s magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the Laschamps Excursion [41 to 42 thousand years ago (ka)]. We use ancient New Ze...
Article
Full-text available
Supplementary Material for 'A global environmental crisis 42,000 years ago' Geological archives record multiple reversals of Earth’s magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the...
Article
The dynamics of the Late Glacial (LG) have been demonstrated by numerous records from the Northern Hemisphere (NH) and far fewer from the Southern Hemisphere (SH). SH paleoclimate records reveal a general warming trend, interrupted by a deglaciation pause (ACR: Antarctic Cold Reversal, ~14,700-13,000 cal BP). Here we present decadal tree-ring stabl...
Article
Full-text available
The lower Brahmaputra River in Bangladesh and Northeast India often floods during the monsoon season, with catastrophic consequences for people throughout the region. While most climate models predict an intensified monsoon and increase in flood risk with warming, robust baseline estimates of natural climate variability in the basin are limited by...
Article
An understanding of tropical hydroclimate variability, the associated drivers and how it is likely to change is a major scientific and societal challenge that is acutely hampered by short instrumental records. We present a 246-year tree-ring drought reconstruction of the Standardised Precipitation Evaporation Index (SPEI) for monsoonal northern Aus...
Article
Full-text available
Plain Language Summary South Pacific island communities experience significant variability in their rainfall between seasons, across years, and between decades. This variability is due to changes in the average position and intensity of the South Pacific Convergence Zone (SPCZ), the largest rain belt in the Southern Hemisphere. The SPCZ tends to mo...
Article
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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 tr...
Article
This study investigates if Blue Intensity (BI) parameters are capable of capturing enhanced climatic signals from a key New Zealand dendrochronological species when compared to ring-width (RW) measurements. Three BI parameters (earlywood mean, latewood mean and maximum latewood) recorded generally superior correlations to temperature than conventio...
Article
Irreversible shifts of large-scale components of the Earth system (so-called ‘tipping elements’) on policy-relevant timescales are a major source of uncertainty for projecting the impacts of future climate change. The high latitudes are particularly vulnerable to positive feedbacks that amplify change through atmosphere-ocean-ice interactions. Unfo...
Article
Full-text available
Radiocarbon (C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric C concentration. Although calibration curves are constructed from independently dated archives, they inva...
Preprint
Full-text available
The Taupo eruption deposit is an isochronous marker bed that spans much of New Zealand’s North Island and pre-dates human arrival. Holdaway et al. (2018, Nature Comms 9, 4110) propose that the current Taupo eruption date is inaccurate and that the eruption occurred “…decades to two centuries…” after the published wiggle-match estimate of 232 ± 10 C...
Conference Paper
Many parts of tropical and subtropical Australia lack both annually-resolved long-term instrumental climate data and proxy climate records. This limits our understanding of past climate patterns and impacts. There are however, remnant forest stands where dendroclimatology could be applied to extend the climate record. Early studies into tropical Au...
Article
Full-text available
Reconstructing past sea levels can help constrain uncertainties surrounding the rate of change, magnitude, and impacts of the projected increase through the 21 st century. Of significance is the mid-Holocene relative sea-level highstand in tectonically stable and remote (far-field) locations from major ice sheets. The east coast of Australia provid...
Article
This research investigates two factors influencing the ability of tree-ring data to provide accurate ¹⁴ C 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 ¹⁴ C data sets. It presents a new Bayesian spline method for calibra...
Article
Full-text available
The New Zealand subantarctic islands of Auckland and Campbell, situated between the subtropical front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind P...
Article
The ecology of the Australian monsoon tropics is fundamentally shaped by dry conditions between May and October followed by highly variable rainfall over the months of November to April. Due to its crucial ecological importance, a better understanding of past hydroclimate variability in the region is of great interest to land managers and custodian...
Article
Full-text available
The original version of this Article contained an error in the Data Availability section, which incorrectly read ‘All data will be freely available via https://www.ams.ethz.ch/research.html.’ The correct version states ‘http://www.ams.ethz.ch/research/published-data.html’ in place of ‘https://www.ams.ethz.ch/research.html’. This has been corrected...
Article
The late 16th-century North American megadrought was notable for its persistence, extent, intensity, and occurrence after the main interval of megadrought activity during the Medieval Climate Anomaly. Forcing from sea surface temperatures (SSTs) in the tropical Pacific is considered a possible driver of megadroughts, and we investigate this hypothe...
Article
Full-text available
Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the 14C content in 484 individual tree rings formed in the periods 770...
Article
Active traces of the reverse dextral Alpine Fault were poorly located on the true left (southwest) side of the Whataroa River. Mapping using airborne LiDAR-derived high resolution topographic data has identified a 300 m wide zone of partitioned faulting including the northeast-striking frontal trace of the Alpine Fault, c. 1.3 km northwest of the D...
Article
Coastal habitats are regarded to be highly vulnerable to the impacts of invasive alien species. These impacts can be particularly visible in areas of national cultural and heritage significance, raising public awareness of a growing global trend and often requiring urgent changes to management practices. New Zealand has a relatively long history of...
Article
Full-text available
Our understanding of the full range of natural variability in streamflow, including how modern flow compares to the past, is poorly understood for the Upper Indus Basin (UIB) because of short instrumental gauge records. To help address this challenge, we use Hierarchical Bayesian Regression (HBR) with partial pooling to develop six centuries long (...
Article
Full-text available
The New Zealand subantarctic islands of Auckland and Campbell, situated between the Subtropical Front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally-important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind P...
Article
Full-text available
Very few annually resolved millennial-length temperature reconstructions exist for the Southern Hemisphere. Here we present four 979-year reconstructions for southeastern Australia for the austral summer months of December–February. Two of the reconstructions are based on the Australian Water Availability Project dataset and two on the Berkeley Ear...
Article
New Zealand swamp kauri (Agathis australis) are relic trees that have been buried and preserved in anoxic bog environments of northern New Zealand for centuries through to hundreds of millennia. Kauri are massive in proportion to other native New Zealand trees and they can attain ages greater than 1000 years. The export market for swamp (subfossil)...
Article
Full-text available
Temporal stability of the relationship between a potential proxy climate record and the climate record itself is the foundation of palaeoproxy reconstructions of past climate variability. Dendroclimatologists have spent considerable effort exploring the issue of temporal instability of temperature records at high-latitude and −altitude Northern Hem...
Article
Full-text available
Anthropogenic activity is now recognised as having profoundly and permanently altered the Earth system, suggesting we have entered a human-dominated geological epoch, the ‘Anthropocene’. To formally define the onset of the Anthropocene, a synchronous global signature within geological-forming materials is required. Here we report a series of precis...
Article
Full-text available
However, for much of the Southern Hemisphere, the ability to identify spatial patterns of past climatic variability is constrained by the sparse distribution of proxy records. This is particularly true for mainland Australia, where relatively few proxy records are located. In this paper we (1) assess the potential to use existing proxy records in t...
Article
Full-text available
Eastern Australia is known to experience multi-decadal periods of flood and drought. Subtropical Southeast Queensland is one region where these devastating extreme events occur regularly yet a full understanding of their frequency and magnitude cannot be determined from the short duration (<100 years) climate data available for the region. Tree-rin...
Article
Full-text available
Water availability is fundamental to societies and ecosystems, but our understanding of variations in hydroclimate (including extreme events, flooding, and decadal periods of drought) is limited because of a paucity of modern instrumental observations that are distributed unevenly across the globe and only span parts of the 20th and 21st centuries....
Article
Full-text available
Invasive alien species (IAS) are a recognised threat to biodiversity and ecosystem services. With increasing tourism and projected 21st century climate changes across the mid-to high-latitudes of the southern hemisphere, subantarctic islands are potentially highly vulnerable to IAS, but suffer from a dearth of baseline monitoring. Here we report tr...
Article
Full-text available
Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water (the ‘bipolar seesaw’). Here we exploit a bidecadally resolved 14C data set obtained from New Zealand kauri (Agathis australi...
Article
Few Southern Hemisphere tree-ring chronologies exceed 1,000 years in length. We present a ca. 1,700 years of indexed values for the long-lived conifer Athrotaxis selaginoides at Cradle Mt in southeastern Australia and compare it with the only other published millennial-plus length tree-ring chronology for Australia: the nearby Mt Read Lagarostrobos...
Article
Full-text available
Satellite observations demonstrate Antarctic sea ice extent increased between late-1978 and 2015, with significant spatial and seasonal variability. Late spring retreat off George V Land is a major component of the observed increase, but the paucity of proxy records makes interpretation of trends (and impacts) challenging. Here Earth-system modelli...
Article
Full-text available
Water availability is fundamental to societies and ecosystems, but our understanding of variations in hydroclimate (including extreme events, flooding, and decadal periods of drought) is limited because of a paucity of modern instrumental observations that are distributed unevenly across the globe and only span parts of the 20th and 21st centuries....
Article
Full-text available
Occupying about 14 % of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine–atmosphere–ice domains interact o...
Article
Late-twentieth century changes in the intensity and migration of Southern Hemisphere westerly winds have been implicated in spatially complex variability in atmospheric and ocean circulation, and ice-sheet dynamics, across the mid- to high-latitudes. A major uncertainty, however, is whether present day hemispheric-wide symmetrical airflow is repres...
Article
The warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in Greenland (Greenland Stadial 1 or GS-1) and Europe (Younger Dryas Stadial or YD). This reversal to glacial-like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remain uncertain. Whilst th...
Article
Full-text available
div class="title">Decadally Resolved Lateglacial Radiocarbon Evidence from New Zealand Kauri–CORRIGENDUM - Volume 58 Issue 4 - Alan Hogg, John Southon, Chris Turney, Jonathan Palmer, Christopher Bronk Ramsey, Pavla Fenwick, Gretel Boswijk, Ulf Buntgen, Michael Friedrich, Gerhard Helle, Konrad Hughen, Richard Jones, Bernd Kromer, Amexandra Noronha,...
Article
Full-text available
Occupying 14% of the world’s surface, the Southern Ocean plays a fundamental role in global climate, ocean circulation, carbon cycling and Antarctic ice-sheet stability. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine-atmosphere-ice domains interact on mul...
Article
Eastern Australia recently experienced an intense drought (Millennium Drought, 2003–2009) and record-breaking rainfall and flooding (austral summer 2010–2011). There is some limited evidence for a climate change contribution to these events, but such analyses are hampered by the paucity of information on long-term natural variability. Analyzing a n...
Article
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...
Article
Full-text available
Determining the timing and impact of anthropogenic climate change in data-sparse regions is a considerable challenge. Arguably, nowhere is this more difficult than the Antarctic Peninsula and the subantarctic South Atlantic where observational records are relatively short but where high rates of warming have been experienced since records began. He...