A potential suite of climate markers of long-chain n-alkanes and alkenones preserved in the top sediments from the Pacific sector of the Southern Ocean

Abstract

Abstract Investigating organic compounds in marine sediments can potentially unlock a wealth of new information in these climate archives. Here, we present pilot study results of organic geochemical features of long-chain n -alkanes and alkenones and individual carbon isotope ratios of long-chain n -alkanes from a newly collected, approximately 8 m long, located in the far reaches of the Pacific sector of the Southern Ocean. We analyzed a suite of organic compounds in the core. The results show abundant long-chain n -alkanes (C 29 – C 35 ) with predominant odd-over-even carbon preference, suggesting an origin of terrestrial higher plant waxes via long-range transport of dust, possibly from Australia and New Zealand. The δ 13 C values of the C 31 n -alkane range from − 29.4 to − 24.8‰, in which the higher δ 13 C values suggest more contributions from C 4 plant waxes. In the analysis, we found that the mid-chain n -alkanes (C 23 – C 25 ) have a small odd-over-even carbon preference, indicating that they were derived from marine non-diatom pelagic phytoplankton and microalgae and terrestrial sources. Furthermore, the C 26 and C 28 with lower δ 13 C values (~ − 34‰) indicate an origin from marine chemoautotrophic bacteria. We found that the abundances of tetra-unsaturated alkenones (C 37:4 ) in this Southern Ocean sediment core ranges from 11 to 37%, perhaps a marker of low sea surface temperature (SST). The results of this study strongly indicate that the δ 13 C values of long-chain n -alkanes and $$ {U}_{37}^{\mathrm{k}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>U</mml:mi> <mml:mn>37</mml:mn> <mml:mi>k</mml:mi> </mml:msubsup> </mml:math> index are potentially useful to reconstruct the detailed history of C 3 /C 4 plants and SST change in the higher latitudes of the Southern Ocean.

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