Gondwana Tree Ring Laboratory

Little River, New Zealand

Gondwana Tree Ring Laboratory

Little River, New Zealand
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Villalba R.,CONICET | Lara A.,Austral University of Chile | Masiokas M.H.,CONICET | Urrutia R.,Austral University of Chile | And 17 more authors.
Nature Geoscience | Year: 2012

Recent changes in the summer climate of the Southern Hemisphere extra-tropics are primarily related to the dominance of the positive phase of the Southern Annular Mode. This shift in the behaviour of the Southern Annular Mode - essentially a measure of the pressure gradient between Southern Hemisphere mid and high latitudes - has been predominantly induced by polar stratospheric ozone depletion. The concomitant southward expansion of the dry subtropical belts could have consequences for forest growth. Here, we use tree-ring records from over 3,000 trees in South America, Tasmania and New Zealand to identify dominant patterns of tree growth in recent centuries. We show that the foremost patterns of growth between 1950 and 2000 differed significantly from those in the previous 250 years. Specifically, growth was higher than the long-term average in the subalpine forests of Tasmania and New Zealand, but lower in the dry-mesic forests of Patagonia. We further demonstrate that variations in the Southern Annular Mode can explain 12-48% of the tree growth anomalies in the latter half of the twentieth century. Tree-ring-based reconstructions of summer Southern Annular Mode indices suggest that the high frequency of the positive phase since the 1950s is unprecedented in the past 600 years. We propose that changes in the Southern Annular Mode have significantly altered tree growth patterns in the Southern Hemisphere. © 2012 Macmillan Publishers Limited. All rights reserved.

Boswijk G.,University of Auckland | Fowler A.M.,University of Auckland | Palmer J.G.,University of New South Wales | Fenwick P.,Gondwana Tree Ring Laboratory | And 5 more authors.
Quaternary Science Reviews | Year: 2014

Millennial and multi-millennial tree-ring chronologies can provide useful proxy records of past climate, giving insight into a more complete range of natural climate variability prior to the 20th century. Since the 1980s a multi-millennial tree-ring chronology has been developed from kauri (Agathis australis) from the upper North Island, New Zealand. Previous work has demonstrated the sensitivity of kauri to the El Niño-Southern Oscillation (ENSO). Here we present recent additions and extensions to the late Holocene kauri chronology (LHKC), and assess the potential of a composite master chronology, AGAUc13, for palaeoclimate reconstruction. The updated composite kauri chronology now spans 4491 years (2488 BCE-2002 CE) and includes data from 18 modern sites, 25 archaeological sites, and 18 sub-fossil (swamp) kauri sites. Consideration of the composition and statistical quality of AGAUc13 suggests the LHKC has utility for palaeoclimate reconstruction but there are caveats. These include: (a) differences in character between the three assemblages including growth rate and sensitivity; (b) low sample depth and low statistical quality in the 10th-13th century CE, when the record transitions from modern and archaeological material to the swamp kauri; (c) a potential difference in amplitude of the signal in the swamp kauri; (d) a westerly bias in site distribution prior to 911 CE; (e) variable statistical quality across the entire record associated with variable replication; and (f) complex changes in sample depth and tree age and size which may influence centennial scale trends in the data. Further tree ring data are required to improve statistical quality, particularly in the first half of the second millennium CE. © 2014 Elsevier Ltd.

D'Arrigo R.,Lamont Doherty Earth Observatory | Abram N.,Australian National University | Abram N.,Natural Environment Research Council | Ummenhofer C.,University of New South Wales | And 2 more authors.
Climate Dynamics | Year: 2011

The Citarum river basin of western Java, Indonesia, which supplies water to 10 million residents in Jakarta, has become increasingly vulnerable to anthropogenic change. Citarum's streamflow record, only ~45 years in length (1963-present), is too short for understanding the full range of hydrometeorological variability in this important region. Here we present a tree-ring based reconstruction of September-November Citarum streamflow (AD 1759-2006), one of the first such records available for monsoon Asia. Close coupling is observed between decreased tree growth and low streamflow levels, which in turn are associated with drought caused by ENSO warm events in the tropical Pacific and Indian Ocean positive dipole-type variability. Over the full length of record, reconstructed variance was at its weakest during the interval from ~1905-1960, overlapping with a period of unusually-low variability (1920-1960) in the ENSO-Indian Ocean dipole systems. In subsequent decades, increased variance in both the streamflow anomalies and a coral-based SST reconstruction of the Indian Ocean Dipole Mode signal the potential for intensified drought activity and related consequences for water supply and crop productivity in western Java, where much of the country's rice is grown. © 2009 Springer-Verlag.

Fowler A.M.,University of Auckland | Boswijk G.,University of Auckland | Lorrey A.M.,NIWA - National Institute of Water and Atmospheric Research | Gergis J.,University of Melbourne | And 5 more authors.
Nature Climate Change | Year: 2012

It is not known how global warming will affect the El Nià ±o/Southern Oscillation (ENSO). The instrumental record is too short to discern centennial-scale trends and modelling results are inconclusive. Proxy reconstructions indicate that ENSO activity was relatively high during the late twentieth century, but whether this was unusual in the millennial context remains uncertain. Here we present insights into these issues derived from rings of the kauri tree (Agathis australis), a rare long-lived conifer endemic to the forests of northern New Zealand. Our results indicate that the twentieth century was the most 'ENSO-active' century of the past 500 years, but may not be unique in the context of the past 700 years, and that ENSO activity comparable to or elevated above that experienced during the late twentieth century is plausible under warmer-than-present conditions. We also find evidence that there may have been significant changes in the ENSO teleconnection to the New Zealand region during the fourteenth and fifteenth centuries, and of multi-decadal fluctuations in ENSO-related activity building up to the present day. Although these two features may delay the expression of increased ENSO activity in the New Zealand region, our results indicate that New Zealand climate is likely to be more dominated by ENSO-related inter-annual variability as the world continues to warm. © 2012 Macmillan Publishers Limited. All rights reserved.

D'Arrigo R.,Columbia University | Palmer J.,Gondwana Tree Ring Laboratory | Ummenhofer C.C.,University of New South Wales | Kyaw N.N.,FRI Compound | Krusic P.,University of Stockholm
Geophysical Research Letters | Year: 2011

Asian monsoon extremes critically impact much of the globe's population. Key gaps in our understanding of monsoon climate remain due to sparse coverage of paleoclimatic information, despite intensified recent efforts. Here we describe a ring width chronology of teak, one of the first high-resolution proxy records for the nation of Myanmar. Based on 29 samples from 20 living trees and spanning from 1613-2009, this record, from the Maingtha forest reserve north of Mandalay, helps fill a substantial gap in spatial coverage of paleoclimatic records for monsoon Asia. Teak growth is positively correlated with rainfall and Palmer Drought Severity Index variability over Myanmar, during and prior to the May-September monsoon season (e.g., r = 0.38 with Yangon rainfall, 0.001, n 68). Importantly, this record also correlates significantly with larger-scale climate indices, including core Indian rainfall (23°N, 76°E; a particularly sensitive index of the monsoon), and the El Niño-Southern Oscillation (ENSO). The teak ring width value following the so-called 1997-98 El Niño of the Century suggests that this was one of the most severe droughts in the past ∼300 years in Myanmar. Evidence for past dry conditions inferred for Myanmar is consistent with tree-ring records of decadal megadroughts developed for Thailand and Vietnam. These results confirm the climate signature related to monsoon rainfall in the Myanmar teak record and the considerable potential for future development of climatesensitive chronologies from Myanmar and the broader region of monsoon Asia. Copyright © 2011 by the American Geophysical Union.

Duncan R.P.,Landcare Research | Duncan R.P.,Lincoln University at Christchurch | Fenwick P.,Gondwana Tree ring Laboratory | Palmer J.G.,Gondwana Tree ring Laboratory | And 2 more authors.
Climate Dynamics | Year: 2010

The warming trend over the last century in the northern hemisphere (NH) was interrupted by cooling from ad 1940 to 1975, a period during which the southern hemisphere experienced pronounced warming. The cause of these departures from steady warming at multidecadal timescales are unclear; the prevailing explanation is that they are driven by non-uniformity in external forcings but recent models suggest internal climate drivers may play a key role. Paleoclimate datasets can help provide a long-term perspective. Here we use tree-rings to reconstruct New Zealand mean annual temperature over the last 550 years and demonstrate that this has frequently cycled out-of-phase with NH mean annual temperature at a periodicity of around 30-60 years. Hence, observed multidecadal fluctuations around the recent warming trend have precedents in the past, strongly implicating natural climate variation as their cause. We consider the implications of these changes in understanding and modelling future climate change. © 2010 Springer-Verlag.

Cook E.R.,Lamont Doherty Earth Observatory | Palmer J.G.,University of New South Wales | Palmer J.G.,Gondwana Tree ring Laboratory | Ahmed M.,University of Karachi | And 5 more authors.
Journal of Hydrology | Year: 2013

Water wars are a prospect in coming years as nations struggle with the effects of climate change, growing water demand, and declining resources. The Indus River supplies water to the world's largest contiguous irrigation system generating 90% of the food production in Pakistan as well as 13. gigawatts of hydroelectricity. Because any gap between water supply and demand has major and far-reaching ramifications, an understanding of natural flow variability is vital - especially when only 47. years of instrumental record is available. A network of tree-ring sites from the Upper Indus Basin (UIB) was used to reconstruct river discharge levels covering the period AD 1452-2008. Novel methods tree-ring detrending based on the 'signal free' method and estimation of reconstruction uncertainty based on the 'maximum entropy bootstrap' are used. This 557-year record displays strong inter-decadal fluctuations that could not have been deduced from the short gauged record. Recent discharge levels are high but not statistically unprecedented and are likely to be associated with increased meltwater from unusually heavy prior winter snowfall. A period of prolonged below-average discharge is indicated during AD 1572-1683. This unprecedented low-flow period may have been a time of persistently below-average winter snowfall and provides a warning for future water resource planning. Our reconstruction thus helps fill the hydrological information vacuum for modeling the Hindu Kush-Karakoram-Himalayan region and is useful for planning future development of UIB water resources in an effort to close Pakistan's " water gap" Finally, the river discharge reconstruction provides the basis for comparing past, present, and future hydrologic changes, which will be crucial for detection and attribution of hydroclimate change in the Upper Indus Basin. © 2013 Elsevier B.V.

Hogg A.,University of Waikato | Palmer J.,Gondwana Tree Ring Laboratory | Boswijk G.,University of Auckland | Turney C.,University of New South Wales
Radiocarbon | Year: 2011

The best means for correcting Southern Hemisphere (SH) radiocarbon measurements, which are significantly influenced by temporal variations in the interhemispheric offset, is by the construction of a SH-specific calibration curve from dendrochronologically dated wood. We present here decadal 14C measurements on dendrochronologically secure New Zealand kauri (Agathis australis), covering the period 195 BC-AD 995, extending the range of calibration measurements from New Zealand tree rings to more than 2 millennia. Recently published Tasmanian huon pine (Lagarostrobos franklinii) data for the interval 165 BC to AD 1095 measured at the Center for Accelerator Mass Spectrometry (CAMS) have underestimated standard errors, which need to be re-assessed before the data can be considered for a Southern Hemisphere calibration curve update. The CAMS huon data, unlike the Waikato kauri data presented here, show a significant reduction in the SH offset for the interval AD 775-855. Although these data points are being checked, it is unlikely this represents a temporal geographic location-dependent offset. With re-assessed errors, the huon data set from 165 BC to AD 995 closely matches the new kauri data, with the combined data sets producing a mean interhemispheric offset with IntCal09 of 44 ± 17 yr for the time interval 195 BC-AD 1845. This SH offset is lower than the modeled offset of 55-58 yr used in the construction of SHCal04, and we recommend the lower value be used in future SHCal updates. Although there is an apparent increase in higher frequency events in the SH offset (NZ kauri plus Tasmanian huon) from 200 BC-AD 1000, the reason for this remains unclear. © 2011 by the Arizona Board of Regents on behalf of the University of Arizona.

Hogg A.,University of Waikato | Turney C.,University of New South Wales | Palmer J.,Gondwana Tree Ring Laboratory | Cook E.,Lamont Doherty Earth Observatory | Buckley B.,Lamont Doherty Earth Observatory
Radiocarbon | Year: 2013

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. © 2013 by the Arizona Board of Regents on behalf of the University of Arizona.

Hogg A.,University of Waikato | Lowe D.J.,University of Waikato | Palmer J.,Gondwana Tree Ring Laboratory | Boswijk G.,University of Auckland | Bronk Ramsey C.,Oxford Radiocarbon Accelerator Unit
Holocene | Year: 2012

Taupo volcano in central North Island, New Zealand, is the most frequently active and productive rhyolite volcano on Earth. Its latest explosive activity about 1800 years ago generated the spectacular Taupo eruption, the most violent eruption known in the world in the last 5000 years. We present here a new accurate and precise eruption date of ad 232 ± 5 (1718 ± 5 cal. BP) for the Taupo event. This date was derived by wiggle-matching 25 high-precision 14C dates from decadal samples of Phyllocladus trichomanoides from the Pureora buried forest near Lake Taupo against the high-precision, first-millennium ad subfossil Agathis australis (kauri) calibration data set constructed by the Waikato Radiocarbon Laboratory. It shows that postulated dates for the eruption estimated previously from Greenland ice-core records (ad 181 ± 2) and putative historical records of unusual atmospheric phenomena in ancient Rome and China (c. ad 186) are both untenable. However, although their conclusion of a zero north-south 14C offset is erroneous, and their data exhibit a laboratory bias of about 38 years (too young), Sparks et al. (Sparks RJ, Melhuish WH, McKee JWA, Ogden J, Palmer JG and Molloy BPJ (1995) 14C calibration in the Southern Hemisphere and the date of the last Taupo eruption: Evidence from tree-ring sequences. Radiocarbon 37: 155-163) correctly utilized the Northern Hemisphere calibration curve of Stuiver and Becker (Stuiver M and Becker B (1993) High-precision decadal calibration of the radiocarbon timescale, AD 1950-6000 BC. Radiocarbon 35: 35-65) to obtain an accurate wiggle-match date for the eruption identical to ours but less precise (ad 232 ± 15). Our results demonstrate that high-agreement levels, indicated by either agreement indices or χ 2 data, obtained from a 14C wiggle-match do not necessarily mean that age models are accurate. We also show that laboratory bias, if suspected, can be mitigated by applying the reservoir offset function with an appropriate error value (e.g. 0 ± 40 years). Ages for eruptives such as Taupo tephra that are based upon individual 14C dates should be considered as approximate only, and confined ideally to short-lived material (e.g. seeds, leaves, small branches or the outer rings of larger trees). © The Author(s) 2011.

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