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Lookup NU author(s): Dr Aleksandra Svalova
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© Copyright: The West Antarctic Ice Sheet (WAIS) is one of the largest potential sources of future sea-level rise, with glaciers draining the WAIS thinning at an accelerating rate over the past 40 years. Due to complexities in calibrating palaeoceanographic proxies for the Southern Ocean, it remains difficult to assess whether similar changes have occurred earlier during the Holocene or whether there is underlying centennial- to millennial-scale forcing in oceanic variability. Archaeal lipid-based proxies, specifically glycerol dialkyl glycerol tetraether (GDGT; e.g. TEX86 and TEXL 86), are powerful tools for reconstructing ocean temperature, but these proxies have been shown previously to be difficult to apply to the Southern Ocean. A greater understanding of the parameters that control Southern Ocean GDGT distributions would improve the application of these biomarker proxies and thus help provide a longer-term perspective on ocean forcing of Antarctic ice sheet changes. In this study, we characterised intact polar lipid (IPL)-GDGTs, representing (recently) living archaeal populations in suspended particulate matter (SPM) from the Amundsen Sea and the Scotia Sea. SPM samples from the Amundsen Sea were collected from up to four water column depths representing the surface waters through to Circumpolar Deep Water (CDW), whereas the Scotia Sea samples were collected along a transect encompassing the sub-Antarctic front through to the southern boundary of the Antarctic Circumpolar Current. IPL-GDGTs with low cyclic diversity were detected throughout the water column with high relative abundances of hydroxylated IPLGDGTs identified in both the Amundsen and Scotia seas. Results from the Scotia Sea show shifts in IPL-GDGT signatures across well-defined fronts of the Southern Ocean. Indicating that the physicochemical parameters of these water masses determine changes in IPL-GDGT distributions. The Amundsen Sea results identified GDGTs with hexosephosphohexose head groups in the CDW, suggesting active GDGT synthesis at these depths. These results suggest that GDGTs synthesised at CDW depths may be a significant source of GDGTs exported to the sedimentary record and that temperature reconstructions based on TEX86 or TEXL 86 proxies may be significantly influenced by the warmer waters of the CDW.
Author(s): Spencer-Jones CL, McClymont EL, Bale NJ, Hopmans EC, Schouten S, Muller J, Abrahamsen EP, Allen C, Bickert T, Hillenbrand C-D, Mawbey E, Peck V, Svalova A, Smith JA
Publication type: Article
Publication status: Published
Journal: Biogeosciences
Year: 2021
Volume: 18
Issue: 11
Pages: 3485-3504
Online publication date: 11/06/2021
Acceptance date: 23/03/2021
Date deposited: 28/06/2021
ISSN (print): 1726-4170
ISSN (electronic): 1726-4189
Publisher: Copernicus GmbH
URL: https://doi.org/10.5194/bg-18-3485-2021
DOI: 10.5194/bg-18-3485-2021
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