Browsing by Author "Hesse, PP"
Now showing 1 - 11 of 11
Results Per Page
Sort Options
- ItemBuilding a future on knowledge from the past: what paleo-science can reveal about climate change and its potential impacts in Australia(Commonwealth Scientific and Industrial Research Organisation, 2005-06) Harle, KJ; Etheridge, DM; Whetton, P; Jones, R; Hennessy, K; Goodwin, ID; Brooke, BP; van Ommen, TD; Barbetti, M; Barrows, TT; Chappell, J; De Deckker, P; Fink, D; Gagan, MK; Haberle, SG; Heijnis, H; Henderson-Sellers, A; Hesse, PP; Hope, GS; Kershaw, P; Nicholls, NIn Australia, high quality instrumental climate records only extend back to the late 19th century and therefore only provide us with a brief snapshot of our climate, its mean state and its short-term variability. Palaeo-records extend our knowledge of climate back beyond the instrumental record, providing us with the means of testing and improving our understanding of the nature and impacts of climate change and variability in Australia. There is a vast body of palaeo-records available for the Australian region (including Antarctica), ranging from continuous records of sub-decadal up to millennial scale (such as those derived from tree rings, speleothems, corals, ice cores, and lake and marine sediments) through to discontinuous records representing key periods in time (such as coastal deposits, palaeo-channels, glacial deposits and dunes). These records provide a large array of evidence of past atmospheric, terrestrial and marine environments and their varying interactions through time. There are a number of key ways in which this evidence can, in turn, be used to constrain uncertainties about climate change and its potential impacts in Australia.
- ItemContemporary versus long-term denudation along a passive plate margin: the role of extreme events(Wiley-Blackwell, 2007-06) Tomkins, KM; Humphreys, GS; Wilkinson, MT; Hesse, PP; Doerr, SH; Shakesby, RA; Wallbrink, PJ; Blake, WH; Fink, DShort-term (contemporary) and long-term denudation rates were determined for the Blue Mountains Plateau in the Western Sydney Basin, Australia, to explore the role of extreme events (wildfires and catastrophic floods) in landscape denudation along a passive plate margin. Contemporary denudation rates were reconstructed using 40 years of river sediment load data from the Nattai catchment in the south-west of the basin, combined with an analysis of hillslope erosion following recent wildfires. Long-term denudation rates (10 kyr-10 Myr) were determined from terrestrial cosmogenic nuclides, apatite fission track thermochronology and post-basalt flow valley incision. Contemporary denudation rates average several times lower than the long-term average (5(.)5 +/- 4 rum kyr(-1) versus 21(.)5 +/- 7 tmm kyr(-1)). Erosion of sediment following wildfires accounts for only a small proportion (5%) of the contemporary rate. Most post-fire sediment is stored on the lower slopes and valley floor, with the amount transported to the river network dependent on rainfall-run-off conditions within the first few years following the fire. Historical catastrophic floods account for a much larger proportion (35%) of the contemporary erosion rate, and highlight the importance of these events in reworking stored material. Evidence for palaeofloods much larger than those experienced over the past 200 years suggests even greater sediment export potential. Mass movement on hillslopes along valleys incised into softer lithology appears to be a dominant erosion process that supplies substantial volumes of material to the valley floor. It is possible that a combination of infrequent mass movement events and high fluvial discharge could account for a significant proportion of the discrepancy between the contemporary and long-term denudation rates. © 2007, Wiley-Blackwell.
- ItemExotic aerosols in the Falkland Islands: a record of South American dust and pollen transport to the South Atlantic since 13 ka(The AQUA Biennial Conference., 2016-12-05) Hesse, PP; Viehberg, F; Schittek, K; Ungrad, L; Hua, Q; White, DSouth America is thought to be a major contributor of dust to the Southern Ocean and Antarctica and therefore to affect the hemispheric energy balance and carbon cycle. However, Patagonia is an arid and deflated landscape without any continental records of dust flux. The Falkland Islands, downwind of Patagonia, offer an opportunity to recover such a record from the blanketing peat accumulation.A short peat core taken in 2013 from East Falkland was dated by 14C, analysed by iTrax XRF scanner, LOI and DBD, and pollen analysis. The peat extends back to approximately 13 ka and ceases at around 2 ka (probably due to turf cutting). LOI and iTrax confirm a component of inorganic, siliceous minerals which we infer to be dust transported from South America. The transport of aerosols from South America is confirmed by the presence of exotic pollen (e.g. Araucariaceae), also found by Turney et al. (2016) for the last 2.6 ka. mDust fluxes were high from 13 ka until around 10 ka and remained low except for a brief excursion around 8 ka. A similar pattern was found at a site in the Beagle Channel (Vanneste et al., 2016. Sci Reports), except that at the Falklands the post-ACR/YD decrease in dust flux was delayed by up to 1 kyr. The results support the Patagonian origin of dust to the South Atlantic and suggest a dominantly glacial origin.
- ItemIntegration of ice-core, marine and terrestrial records for the Australian Last Glacial Maximum and Termination: a contribution from the OZ INTIMATE group(Wiley, 2006-10) Turney, CSM; Haberle, SG; Fink, D; Kershaw, AP; Barbetti, M; Barrows, TT; Black, M; Cohen, TJ; Corrège, T; Hesse, PP; Hua, Q; Johnston, R; Morgan, VI; Moss, PT; Nanson, GC; van Ommen, TD; Rule, S; Williams, NJ; Zhao, JX; D'Costa, D; Feng, YX; Gagan, MK; Mooney, SD; Xia, QThe degree to which Southern Hemisphere climatic changes during the end of the last glacial period and early Holocene (30-8 ka) were influenced or initiated by events occurring in the high latitudes of the Northern Hemisphere is a complex issue. There is conflicting evidence for the degree of hemispheric ‘teleconnection’ and an unresolved debate as to the principle forcing mechanism(s). The available hypotheses are difficult to test robustly, however, because the few detailed palaeoclimatic records in the Southern Hemisphere are widely dispersed and lack duplication. Here we present climatic and environmental reconstructions from across Australia, a key region of the Southern Hemisphere because of the range of environments it covers and the potentially important role regional atmospheric and oceanic controls play in global climate change. We identify a general scheme of events for the end of the last glacial period and early Holocene but a detailed reconstruction proved problematic. Significant progress in climate quantification and geochronological control is now urgently required to robustly investigate change through this period. © 2006 John Wiley & Sons, Ltd.
- ItemLate quaternary fluvial incision and aggradation in the Lesser Himalaya, India(Elsevier, 2018-10-01) Dosseto, A; May, JH; Choi, JH; Swander, ZJ; Fink, D; Korup, O; Hesse, PP; Singh, T; Mifsud, C; Srivastava, PReconstructing how rivers respond to changes in runoff or sediment supply by incising or aggrading has been pivotal in gauging the role of the Indian Summer Monsoon (ISM) as a geomorphic driver in the Himalayas. Here we present new chronological data for fluvial aggradation and incision from the Donga alluvial fan and the upper Alaknanda River, as well as a compilation of previous work. In addition to conventional OSL-SAR (Single-Aliquot Regenerative-Dose) dating method, we have tested and applied pulsed OSL (POSL) dating for quartz samples that include K-rich feldspar inclusions, which is expected to improve the applicability and validity of OSL ages in the Lesser Himalaya. For previously dated deposits, our OSL ages are shown to be systematically older than previously reported ages. These results suggest periods of aggradation in the Alaknanda and Dehradun Valleys mainly between ∼25 and 35 ka. This most likely reflects decreased stream power during periods of weakened monsoon. In addition, in-situ cosmogenic beryllium-10 was used to infer bedrock surface exposure ages, which are interpreted as episodes of active fluvial erosion. Resulting exposure ages span from 3 to 6 ka, suggesting that strath terraces were exposed relatively recently, and incision was dominant through most of the Holocene. In combination, our results support precipitation-driven fluvial dynamics, which regulates the balance between stream power and sediment supply. On a larger spatial scale, however, fluvial dynamics are probably not spatially homogeneous as aggradation could have been taking place in adjacent catchments while incision dominated in the study area. © 2018 Elsevier Ltd.
- ItemLate quaternary palaeoenvironmental change in the Australian drylands(Elsevier, 2013-08-15) Fitzsimmons, KE; Cohen, TJ; Hesse, PP; Jansen, JD; Nanson, GC; May, JH; Barrows, TT; Haberlah, D; Hilgers, A; Kelly, T; Larsen, JR; Lomax, J; Treble, PCIn this paper we synthesise existing palaeoenvironmental data from the arid and semi-arid interior of the Australian continent for the period 40–0 ka. Moisture is the predominant variable controlling environmental change in the arid zone. Landscapes in this region respond more noticeably to changes in precipitation than to temperature. Depending on their location, arid zone records broadly respond to tropical monsoon-influenced climate regimes, the temperate latitude westerly systems, or a combination of both. The timing and extent of relatively arid and humid phases vary across the continent, in particular between the westerly wind-controlled temperate latitudes, and the interior and north which are influenced by tropically sourced precipitation. Relatively humid phases in the Murray-Darling Basin on the semi-arid margins, which were characterised by large rivers most likely fed by snow melt, prevailed from 40 ka to the Last Glacial Maximum (LGM), and from the deglacial to the mid Holocene. By contrast, the Lake Eyre basin in central Australia remained relatively dry throughout the last 40 ka, with lake high stands at Lake Frome around 35–30 ka, and parts of the deglacial period and the mid-Holocene. The LGM was characterised by widespread relative aridity and colder conditions, as evidenced by extensive desert dune activity and dust transport, lake level fall, and reduced but episodic fluvial activity. The climate of the deglacial period was spatially divergent. The southern part of the continent experienced a brief humid phase around ∼17–15 ka, followed by increased dune activity around ∼14–10 ka. This contrasts with the post-LGM persistence of arid conditions in the north, associated with a lapsed monsoon and reflected in lake level lows and reduced fluvial activity, followed by intensification of the monsoon and increasingly effective precipitation from ∼14 ka. Palaeoenvironmental change during the Holocene was also spatially variable. The early to mid-Holocene was, however, generally characterised by moderately humid conditions, demonstrated by lake level rise, source-bordering dune activity, and speleothem growth, persisting at different times across the continent. Increasingly arid conditions developed into the late Holocene, particularly in the central arid zone. © 2012 Elsevier Ltd.
- ItemMacro-charcoal accumulation in floodplain wetlands: problems and prospects for reconstruction of fire regimes and environmental conditions(PLOS, 2019-10-24) Graves, BP; Ralph, TJ; Hesse, PP; Westaway, KE; Kobayashi, T; Gadd, PS; Mazumder, DFloodplain wetland ecosystems respond dynamically to flooding, fire and geomorphological processes. We employed a combined geomorphological and environmental proxy approach to assess allochthonous and autochthonous macro-charcoal accumulation in the Macquarie Marshes, Australia, with implications for the reconstruction of fire regimes and environmental conditions in large, open-system wetlands. After accounting for fluvial macro-charcoal flux (1.05 ± 0.32 no. cm-2 a-1), autochthonous macro-charcoal in ~1 m deep sediment profiles spanning ~1.7 ka were highly variable and inconsistent between cores and wetlands (concentrations from 0 to 438 no. cm-3, mean accumulation rates from 0 to 3.86 no. cm-2 a-1). A positive correlation existed between the number of recent fires, satellite-observed ignition points, and macro-charcoal concentrations at the surface of the wetlands. Sedimentology, geochemistry, and carbon stable isotopes (δ13C range -15 to -25 ‰) were similar in all cores from both wetlands and varied little with depth. Application of macro-charcoal and other environmental proxy techniques is inherently difficult in large, dynamic wetland systems due to variations in charcoal sources, sediment and charcoal deposition rates, and taphonomic processes. Major problems facing fire history reconstruction using macro-charcoal records in these wetlands include: (1) spatial and temporal variations in fire activity and ash and charcoal products within the wetlands, (2) variations in allochthonous inputs of charcoal from upstream sources, (3) tendency for geomorphic dynamism to affect flow dispersal and sediment and charcoal accumulation, and (4) propensity for post-depositional modification and/or destruction of macro-charcoal by flooding and taphonomic processes. Recognition of complex fire-climate-hydrology-vegetation interactions is essential. High-resolution, multifaceted approaches with reliable geochronologies are required to assess spatial and temporal patterns of fire and to reconstruct in order to interpret wetland fire regimes. © 2019 Graves et al. This is an open access article distributed under the terms of the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproductionin any medium, provided the original author and source are credited.
- ItemMagnetic properties of uncultivated magnetotactic bacteria and their contribution to a stratified estuary iron cycle(Nature Publishing Group, 2014-09-01) Chen, AP; Berounsky, VM; Chan, MK; Blackford, MG; Cady, C; Moskowitz, BM; Kraal, P; Lima, EA; Kopp, RE; Lumpkin, GR; Weiss, BP; Hesse, PP; Vella, NGFOf the two nanocrystal (magnetosome) compositions biosynthesized by magnetotactic bacteria (MTB), the magnetic properties of magnetite magnetosomes have been extensively studied using widely available cultures, while those of greigite magnetosomes remain poorly known. Here we have collected uncultivated magnetite- and greigite-producing MTB to determine their magnetic coercivity distribution and ferromagnetic resonance (FMR) spectra and to assess the MTB-associated iron flux. We find that compared with magnetite-producing MTB cultures, FMR spectra of uncultivated MTB are characterized by a wider empirical parameter range, thus complicating the use of FMR for fossilized magnetosome (magnetofossil) detection. Furthermore, in stark contrast to putative Neogene greigite magnetofossil records, the coercivity distributions for greigite-producing MTB are fundamentally left-skewed with a lower median. Lastly, a comparison between the MTB-associated iron flux in the investigated estuary and the pyritic-Fe flux in the Black Sea suggests MTB play an important, but heretofore overlooked role in euxinic marine system iron cycle.© 2014, Nature Publishing Group.
- ItemPaleoclimate studies and natural-resource management in the Murray-Darling Basin I: past, present and future climates(Taylor & Francis, 2013-06-19) Mills, K; Gell, PA; Hesse, PP; Jones, R; Kershaw, P; Drysdale, RN; McDonald, JThis paper provides an incisive review of paleoclimate science and its relevance to natural-resource management within the Murray-Darling Basin (MDB). The drought of 1997–2010 focussed scientific, public and media attention on intrinsic climate variability and the confounding effect of human activity, especially in terms of water-resource management. Many policy and research reviews make statements about future planning with little consideration of climate change and without useful actionable knowledge. In order to understand future climate changes, modellers need, and demand, better paleoclimate data to constrain their model projections. Here, we present an insight into a number of existing long-term paleoclimate studies relevant to the MDB. Past records of climate, in response to orbital forcing (glacial–interglacial cycles) are found within, and immediately outside, the MDB. High-resolution temperature records, spanning the last 105 years, exist from floodplains and cave speleothems, as well as evidence from lakes and their associated lunettes. More recently, historical climate records show major changes in relation to El Niño–Southern Oscillation cycles and decadal shifts in rainfall regimes. A considerable body of research currently exists on the past climates of southeastern Australia but, this has not been collated and validated over large spatial scales. It is clear that a number of knowledge gaps still exist, and there is a pressing need for the establishment of new paleoclimatic research within the MDB catchment and within adjacent, sensitive catchments if past climate science is to fulfil its potential to provide policy-relevant information to natural-resource management into the future. © 2013, Taylor & Francis.
- ItemPaleoclimate studies and natural-resource management in the Murray-Darling Basin II: unravelling human impacts and climate variability(Taylor and Francis Group, 2013-08-09) Mills, K; Gell, PA; Gergis, J; Baker, PJ; Finlayson, CM; Hesse, PP; Jones, R; Kershaw, P; Pearson, S; Treble, PC; Barr, C; Brookhouse, MT; Drysdale, RN; McDonald, J; Haberle, SG; Reid, M; Thoms, M; Tibby, JThe management of the water resources of the Murray-Darling Basin (MDB) has long been contested, and the effects of the recent Millennium drought and subsequent flooding events have generated acute contests over the appropriate allocation of water supplies to agricultural, domestic and environmental uses. This water-availability crisis has driven demand for improved knowledge of climate change trends, cycles of variability, the range of historical climates experienced by natural systems and the ecological health of the system relative to a past benchmark. A considerable volume of research on the past climates of southeastern Australia has been produced over recent decades, but much of this work has focused on longer geological time-scales, and is of low temporal resolution. Less evidence has been generated of recent climate change at the level of resolution that accesses the cycles of change relevant to management. Intra-decadal and near-annual resolution (high-resolution) records do exist and provide evidence of climate change and variability, and of human impact on systems, relevant to natural-resource management. There exist now many research groups using a range of proxy indicators of climate that will rapidly escalate our knowledge of management-relevant, climate change and variability. This review assembles available climate and catchment change research within, and in the vicinity of, the MDB and portrays the research activities that are responding to the knowledge need. It also discusses how paleoclimate scientists may better integrate their pursuits into the resource-management realm to enhance the utility of the science, the effectiveness of the management measures and the outcomes for the end users. © 2020 Informa UK Limited
- ItemPast changes in sediment dynamics in the Himalayas inferred from uranium-series isotopes(Australian Geosciences Council, 2012-08-05) Dosseto, A; Hesse, PP; Fink, D; Srivastava, PClimate variability has been setting the rhythm of the Earth’s history, but how does the landscape, in particular rivers, adapt to these changes? One possible approach to tackle this question is to investigate how sedimentary deposits have recorded changes in fluvial dynamics. As a proxy for this dynamics, we use the sediment residence time, i.e. the time spent by sediments in a catchment before export (storage in soils + fluvial transport). Recently, it has been proposed that uranium-series isotopes can be used to quantify past variations in sediment residence time. In this study, this approach is applied to alluvial deposits from the upper Ganges River, the Yamuna River and the Dun valley in the foothills of the Himalayas. The age of these deposits has been previously constrained by optically-stimulated luminescence dating and range from 0 to 40 ka. Preliminary work using lithium isotopes has shown a strong link between monsoon activity and weathering intensity. Results from this study will investigate how hillslope erosion and fluvial transport may have responded to past climatic change.