Comparison of the U 37K, LDI, TEX 86H, and RI-OH temperature proxies in sediments from the northern shelf of the South China Sea

Wei, Bingbing; Jia, Guodong; Hefter, Jens; Kang, Manyu; Park, Eunmi; Wang, Shizhu; Mollenhauer, Gesine

The temperature proxies inline-formula M5inlinescrollmathml normal U normal 37 normal K 19pt18ptsvg-formulamathimg99fc2d8179091d08156d907117c54287 bg-17-4489-2020-ie00007.svg19pt18ptbg-17-4489-2020-ie00007.png , LDI, inline-formula M6inlinescrollmathml normal TEX normal 86 normal H 32pt17ptsvg-formulamathimg63b4ac3c59c15036b71aa213380ff8c2 bg-17-4489-2020-ie00008.svg32pt17ptbg-17-4489-2020-ie00008.png , and RI-OH are derived from lipid biomarkers, namely long-chain alkenones from coccolithophorids and long-chain diols ascribed tentatively to eustigmatophytes, as well as glycerol dialkyl glycerol tetraethers (GDGTs) and OH-GDGTs produced by Archaea. The applicability of these proxies in the South China Sea (SCS) has been investigated previously. However, in each study only one or two of the proxies were compared, and the recently updated calibrations or new calibrating methods such as BAYSPAR and BAYSPLINE were not applied. Here, we investigate four proxies in parallel in a set of surface sediment samples from the northern SCS shelf and relate them to local sea surface temperature (SST), which allows for us to compare and assess similarities and differences between them and also help improve regional multiproxy seawater temperature reconstructions. Our results indicate that inline-formula M7inlinescrollmathml normal U normal 37 normal K 19pt18ptsvg-formulamathimg4c05c5c9a363482b3530a89f3cc72440 bg-17-4489-2020-ie00009.svg19pt18ptbg-17-4489-2020-ie00009.png reflects annual mean SST with a slight bias toward the warm season. Terrestrial inputs appear to have a significant impact on LDI, inline-formula M8inlinescrollmathml normal TEX normal 86 normal H 32pt17ptsvg-formulamathimg80afcf95cfc3b13c7a7482ef01974818 bg-17-4489-2020-ie00010.svg32pt17ptbg-17-4489-2020-ie00010.png , and RI-OH proxies near the coast, leading to colder LDI- and inline-formula M9inlinescrollmathml normal TEX normal 86 normal H 32pt17ptsvg-formulamathimgb7d669ee194078bb8eef72a2172aab4a bg-17-4489-2020-ie00011.svg32pt17ptbg-17-4489-2020-ie00011.png -derived temperatures but a warmer RI-OH temperature estimate. After excluding samples influenced by terrestrial materials, we find that LDI-derived temperature agrees well with annual SST, while inline-formula M10inlinescrollmathml normal TEX normal 86 normal H 32pt17ptsvg-formulamathimg9c565ff346b90ce7b7ddbfcd6489e76f bg-17-4489-2020-ie00012.svg32pt17ptbg-17-4489-2020-ie00012.png - and RI-OH-derived temperature estimates are close to SSTs in seasons dominated by the East Asian winter monsoon and summer monsoon, respectively. The different seasonal biases of these temperature proxies provide valuable tools to reconstruct regional SSTs under different monsoonal conditions.

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Wei, Bingbing / Jia, Guodong / Hefter, Jens / et al: Comparison of the U37K′, LDI, TEX86H, and RI-OH temperature proxies in sediments from the northern shelf of the South China Sea. 2020. Copernicus Publications.

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