Browsing by Author "Corrick, E"

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    Characterising the expression of sub-millennial scale climate events in western Europe during the early last glacial period using multi-proxy speleothem records
    (Australasian Quaternary Association Inc., 2022-12-06) Corrick, E; Drysdale, RN; Hellstrom, JC; Couchoud, I; Wong, HKY; Didier, C; Hai, C; Jaillet, S; Tocino, S
    Past abrupt climate changes act as critical analogues for understanding how the climate system may respond to future abrupt changes. One of the best examples of naturally occurring abrupt climate change is the series of millennial-scale Dansgaard-Oeschger (D-O) events that took place during the last glacial period (115,000 – 11,500 years ago). D-O events are clearly recorded in ice-cores from Greenland, with coincident climate changes detected in marine and terrestrial records spanning a range of climate zones. Greenland ice cores also record shorter-lived ‘sub-millennial’ scale events that occur within the main D-O event sequence, particularly during the early last glacial period. To what extent these sub-millennial events were expressed outside of Greenland is currently poorly understood. Here we characterise the response to sub-millennial scale climate changes in western Europe using five multi-proxy (δ18O, δ13C, Mg and Sr) speleothem records from Saint-Marcel and Orgnac Caves, France, that collectively span 127 – 87 kyr BP. The replicated speleothem records clearly preserve both millennial D-O events and sub-millennial events, demonstrating the strong coupling between the climate of south-east France and the North Atlantic across both millennial and sub-millennial timescales. Interestingly, the multiproxy record reveals a decoupling between broad temperature (indicated by δ13C) and precipitation changes (indicated by δ18O) during some of these sub-millennial scale events. This suggests that climate teleconnections operating during sub-millennial events were in some ways different to those during the stronger millennial-scale D-O events.
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    Magnesium in subaqueous speleothems as a potential palaeotemperature proxy
    (Springer Nature, 2020-10-06) Drysdale, RN; Couchoud, I; Zanchetta, G; Isola, I; Regattieri, E; Hellstrom, JC; Govin, A; Tzedakis, PC; Ireland, T; Corrick, E; Grieg, A; Wong, HKY; Piccini, L; Holden, PJ; Woodhead, JD
    Few palaeoclimate archives beyond the polar regions preserve continuous and datable palaeotemperature proxy time series over multiple glacial-interglacial cycles. This hampers efforts to develop a more coherent picture of global patterns of past temperatures. Here we show that Mg concentrations in a subaqueous speleothem from an Italian cave track regional sea-surface temperatures over the last 350,000 years. The Mg shows higher values during warm climate intervals and converse patterns during cold climate stages. In contrast to previous studies, this implicates temperature, not rainfall, as the principal driver of Mg variability. The depositional setting of the speleothem gives rise to Mg partition coefficients that are more temperature dependent than other calcites, enabling the effect of temperature change on Mg partitioning to greatly exceed the effects of changes in source-water Mg/Ca. Subaqueous speleothems from similar deep-cave environments should be capable of providing palaeotemperature information over multiple glacial-interglacial cycles. © 2020 The Author(s)
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    Partitioning of Mg, Sr, Ba and U into a subaqueous calcite speleothem
    (Elsevier, 2019-11-01) Drysdale, RN; Zanchetta, G; Baneschi, I; Guidi, M; Isola, I; Couchoud, I; Piccini, L; Greig, A; Wong, HKY; Woodhead, JD; Regattieri, E; Corrick, E; Paul, B; Spötl, C; Denson, E; Gordon, J; Jaillet, S; Dux, F; Hellstrom, JC
    The trace-element geochemistry of speleothems is becoming increasingly used for reconstructing palaeoclimate, with a particular emphasis on elements whose concentrations vary according to hydrological conditions at the cave site (e.g. Mg, Sr, Ba and U). An important step in interpreting trace-element abundances is understanding the underlying processes of their incorporation. This includes quantifying the fractionation between the solution and speleothem carbonate via partition coefficients (where the partitioning (D) of element X (DX) is the molar ratio [X/Ca] in the calcite divided by the molar ratio [X/Ca] in the parent water) and evaluating the degree of spatial variability across time-constant speleothem layers. Previous studies of how these elements are incorporated into speleothems have focused primarily on stalagmites and their source waters in natural cave settings, or have used synthetic solutions under cave-analogue laboratory conditions to produce similar dripstones. However, dripstones are not the only speleothem types capable of yielding useful palaeoclimate information. In this study, we investigate the incorporation of Mg, Sr, Ba and U into a subaqueous calcite speleothem (CD3) growing in a natural cave pool in Italy. Pool-water measurements extending back 15 years reveal a remarkably stable geochemical environment owing to the deep cave setting, enabling the calculation of precise solution [X/Ca]. We determine the trace element variability of ‘modern’ subaqueous calcite from a drill core taken through CD3 to derive DMg, DSr, DBa and DU then compare these with published cave, cave-analogue and seawater-analogue studies. The DMg for CD3 is anomalously high (0.042 ± 0.002) compared to previous estimates at similar temperatures (∼8 °C). The DSr (0.100 ± 0.007) is similar to previously reported values, but data from this study as well as those from Tremaine and Froelich (2013) and Day and Henderson (2013) suggest that [Na/Sr] might play an important role in Sr incorporation through the potential for Na to outcompete Sr for calcite non-lattice sites. DBa in CD3 (0.086 ± 0.008) is similar to values derived by Day and Henderson (2013) under cave-analogue conditions, whilst DU (0.013 ± 0.002) is almost an order of magnitude lower, possibly due to the unusually slow speleothem growth rates (<1 μm a−1), which could expose the crystal surfaces to leaching of uranyl carbonate. Finally, laser-ablation ICP-MS analysis of the upper 7 μm of CD3, regarded as ‘modern’ for the purposes of this study, reveals considerable heterogeneity, particularly for Sr, Ba and U, which is potentially indicative of compositional zoning. This reinforces the need to conduct 2D mapping and/or multiple laser passes to capture the range of time-equivalent elemental variations prior to palaeoclimate interpretation. © 2019 Elsevier Ltd