Browsing by Author "Rees, ABH"

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    Changes in biomass burning mark the onset of an ENSO-influenced climate regime at 42°S in southwest Tasmania, Australia
    (Elsevier, 2015-06-15) Fletcher, MS; Benson, A; Heijnis, H; Gadd, PS; Cwynar, L; Rees, ABH
    We use macroscopic charcoal and sediment geochemistry analysis of two proximal upper montane lakes located at 42°S in southwest Tasmania, Australia, to test the role of the southern hemisphere westerly winds (SWW) and the El Niño-Southern Oscillation (ENSO) in governing the climate of this sector of the southern mid-to high-latitudes. Inter-annual climate anomalies in the study area are driven by changes in both ENSO and the Southern Annular Mode (SAM - an index that describes seasonal to decadal shifts in the SWW), making it an ideal location to test assumptions about the varying influence of the SWW and ENSO, two important components of the global climate system, through time. We find multi-millennial scale trends in fire activity that are remarkably consistent with trends in hydroclimate reconstructed at the same latitude in southern South America, providing empirical support for the notion of zonally symmetric changes in the SWW governing the climate at this latitude in the Southern Hemisphere between 12 and 5 cal ka BP. A transition from multi-millennial scale to sub-millennial scale trends in fire activity occurs after ca 5 cal ka BP in concert with the onset of high frequency and amplitude ENSO variability in the tropical Pacific Ocean region. We conclude that the onset of sub-millennial scale trends in ENSO drove changes in fire activity in our study region over the last ca 5 cal ka. Geochemical data reveals divergent local impacts at the two study sites in response to these major climate transitions that are related to local topography and geography. © 2015 Elsevier Ltd.
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    Exploring the source-to-sink residence time of terrestrial pollen deposited offshore Westland, New Zealand
    (Elsevier, 2016-07-01) Ryan, MT; Newnham, RM; Dunbar, GB; Vandergoes, MJ; Rees, ABH; Neil, H; Callard, SL; Alloway, BV; Bostock, HC; Hua, Q; Anderson, BM
    The occurrence of terrestrial palynomorphs in Quaternary marine sedimentary sequences allows for direct land–sea correlations and provides a means for transferring Marine Isotope Stage chronologies to terrestrial records that extend beyond the range of radiocarbon dating. Both of these important applications require an implicit assumption that the lag between pollen release and final deposition on the seafloor – here referred to as source-to-sink residence time – is negligible in relation to the chronological resolution of the sedimentary sequence. Most studies implicitly assume zero lag, and where studies do take palynomorph residence time into account, its magnitude is rarely quantified. In Westland, New Zealand, fluvial transport is the main source of delivery of terrestrial pollen offshore to the adjacent East Tasman Sea. We radiocarbon-dated organic matter carried and deposited by contemporary Westland rivers that drain catchments with varying degrees of disturbance. The ages obtained ranged widely from essentially modern (i.e., − 57 ± 22 cal yr BP) to 3583 ± 188 cal yr BP, suggesting that precisely constraining the residence time in this region is unlikely to be achieved. We also compared the timing of four palynomorph events characterising Westland's late Pleistocene, along with the well-dated Kawakawa/Oruanui Tephra (KOT), between marine core MD06-2991 and four terrestrial records from Westland. Critically, all palynomorph events and the KOT are chronologically indistinguishable with respect to the independently dated marine and terrestrial records, supporting the general principle of transferring the marine chronology onto the terrestrial records in this setting. In other regions, particularly those lacking the high soil production and erosion rates that characterise Westland, we suggest that similar tests of marine residence time should be conducted before assumptions of zero or negligible lag are invoked.© 2016, Elsevier B.V.
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    A global database of holocene paleotemperature records
    (Springer Nature Limited, 2020-04-14) Kaufman, DS; McKay, N; Rouston, C; Erb, M; Davis, B; Heiri, O; Jaccard, SL; Tierney, J; Dätwyler, C; Axford, Y; Brussel, T; Cartapanis, O; Chase, BM; Dawson, A; de Vernal, A; Engels, S; Jonkers, L; Marsicek, J; Moffa-Sánchez, P; Morrill, C; Oris, A; Rehfeld, K; Saunders, KM; Sommer, PS; Thomas, E; Tonello, M; Tóth, M; Vachula, R; Andreev, A; Bertrand, S; Biskaborn, B; Bringué, M; Brooks, S; Caniupán, M; Chevalier, M; Cwynar, L; Emile-Geay, J; Fegyveresi, J; Feurdean, A; Finsinger, W; Fortin, MC; Foster, L; Fox, M; Gajewski, K; Grosjean, M; Hausmann, S; Heinrichs, M; Holmes, N; Ilyashuk, B; Ilyashuk, E; Juggins, S; Khider, D; Koinig, K; Langdon, P; Larocque-Tobler, I; Li, JY; Lotter, A; Luoto, T; Mackay, A; Magyari, E; Malevich, S; Mark, B; Massaferro, J; Montade, V; Nazarova, L; Novenko, E; Pařil, P; Pearson, E; Peros, M; Peinitz, R; Płóciennik, M; Porinchu, D; Potito, A; Rees, ABH; Reinemann, S; Roberts, SJ; Rolland, N; Salonen, S; Self, A; Seppä, H; Shala, S; St-Jacques, JM; Stenni, B; Syrykh, L; Tarrats, P; Taylor, K; van den Bos, V; Velle, G; Wahl, E; Walker, I; Wilmshurst, J; Zhang, E; Zhilich, S
    A comprehensive database of paleoclimate records is needed to place recent warming into the longer-term context of natural climate variability. We present a global compilation of quality-controlled, published, temperature-sensitive proxy records extending back 12,000 years through the Holocene. Data were compiled from 679 sites where time series cover at least 4000 years, are resolved at sub-millennial scale (median spacing of 400 years or finer) and have at least one age control point every 3000 years, with cut-off values slackened in data-sparse regions. The data derive from lake sediment (51%), marine sediment (31%), peat (11%), glacier ice (3%), and other natural archives. The database contains 1319 records, including 157 from the Southern Hemisphere. The multi-proxy database comprises paleotemperature time series based on ecological assemblages, as well as biophysical and geochemical indicators that reflect mean annual or seasonal temperatures, as encoded in the database. This database can be used to reconstruct the spatiotemporal evolution of Holocene temperature at global to regional scales, and is publicly available in Linked Paleo Data (LiPD) format. © 2020 The Authors