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Browsing Conference Publications by Author "Abram, NJ"

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    The CoralHydro2k Database: a global compilation of coral δ18O and Sr/Ca records for reconstructing tropical hydroclimate over the common era
    (American Geophysical Union (AGU), 2021-12-18) Sayani, HR; Walter, R; Felis, T; Cobb, KM; Abram, NJ; Atwood, AR; Arzey, A; Brenner, LD; Dassie, EP; DeLong, KL; Ellis, B; Goodkin, N; Hargreaves, J; Kilbourne, KH; Krawczyk, H; Fischer, MJ; Murty, SA; Moore, AL; Ramos, RDP; Reed, E; Samanta, D; Zinke, J
    Shallow-water corals provide annual to subannual -resolution climate reconstructions from normally data-scarce locations in the tropical to subtropical oceans, enabling us to extend the modern-day observational records back to the preindustrial era, contextualize anthropogenic climate change, and improve the skill of future climate projections. The majority of these coral-based reconstructions utilize oxygen isotope ratios (δ18O), a proxy that tracks the combined change in sea surface temperature (SST) and the oxygen isotopic composition of seawater (δ18Osw) and/or strontium-to-calcium ratios (Sr/Ca), which primarily track SST variability. Paired coral δ18O and Sr/Ca records can be combined to isolate δ18Osw variability, which like salinity reflects changes in the local hydrologic budget. Recently, the PAGES Ocean2k project used published coral records to reconstruct regional SST variability across the tropical oceans (Tierney et al., 2015, Abram et al., 2016). Building on this work, the PAGES CoralHydro2k team has compiled a more comprehensive, machine-readable, and metadata-rich network of paired coral δ18O and Sr/Ca records to help facilitate tropical hydroclimate reconstructions across recent centuries. The CoralHydro2k database currently contains 227 coral proxy records from 120 unique locations that are organized into seven tiers based on the availability of paired proxy data, temporal coverage, and record resolution. The metadata for the new database follows PACTs 1.0 recommendations (Khider et al., 2019), and the database is built using LiPD (McKay and Emile-Geay, 2016) with available R, MATLAB, and Python serializations. Here we describe the structure and spatiotemporal characteristics of this new database and outline a crowdsourced data-submission process to ensure active-curation of records and future updates to the database.
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    Past hydroclimatic variability from southwest Australian speleothems during the last millennium
    (Australiasian Quaternary Association Inc., 2018-12-10) Treble, PC; Baker, AA; Griffiths, AD; Hellstrom, JC; Bajo, P; Abram, NJ; Fairchild, IJ; Borsato, A; Markowska, M; Gagan, MK
    Speleothems from Golgotha Cave in SW Western Australia have been investigated to extend our knowledge of past climate variability for this region during the last millennium. O isotopic datasets, the primary paleoclimate proxy used for speleothems, were constructed for four stalagmites. A challenge in their interpretation has been the disagreement between these records, despite representing coeval growth from within the same cave. Resolving this conundrum has necessitated the characterisation of the hydrology, hydrochemistry, rainfall isotopes7 and development of proxy system forward models1,8 for Golgotha Cave. The findings of these studies will be summarised as a conceptual model in order to present the main karst hydrological features that give rise to each stalagmite’s isotopic response to hydroclimatic forcing. The paleoclimate interpretation will focus on the two continuous stalagmite records that were fed predominately by diffuse flow. This will be supported by evidence from the two stalagmites predominantly fed by fracture flow, which has resulted in a non-linear response to hydroclimatic forcing.
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    Speleothem ‘uptick’ supports reduction in rainfall recharge to groundwater is unprecedented for last 800 years, SW Western Australia
    (Australasian Quaternary Association, 2022-12-06) Priestley, SC; Treble, PC; Baker, AA; Griffiths, AD; Abram, NJ; Meredith, KT
    Southwestern Australia relies significantly on groundwater for domestic and industrial purposes. As water availability has decreased and is projected to continue to decrease with climate change, it is critical to understand the impacts of climate change on groundwater recharge for this region. Speleothem (e.g. cave stalagmites) deposition is directly related to groundwater recharge, as they form from rainfall which has infiltrated into the vadose zone and represent periods of potential aquifer recharge. In this study, modern speleothems from five caves record a consistent response to a sustained decrease in rainfall across south-west Australia that began in the 1970s, characterised by an ‘uptick’ in the speleothem oxygen isotopic composition (Priestley et al., 2022). It is demonstrated that the ‘uptick’ is in response to the shallow karst aquifers becoming disconnected from rainfall recharge due to regional drying. As the coastal caves are located in highly permeable host rock along the wettest zone of the region, our findings imply that rainfall recharge to groundwater across the southwest Australian region may no longer be reliably occurring. The paleo-record for speleothems from south-west Australia (Treble et al., 2022) provides a longer-term context to assess the recent isotopic uptick against and confirms that no similar events are seen in the last 800 years in stalagmites from the region.