scholarly journals Long Chain 1, 14-Diols as Potential Indicators for Upper Water Stratification in the Open South China Sea

2020 ◽  
Author(s):  
Xiaowei Zhu ◽  
Guodong Jia ◽  
Weihai Xu ◽  
Wen Yan
Keyword(s):  
South China Sea ◽  
South China ◽  
China Sea ◽  
Water Stratification ◽  
Long Chain

Long chain 1,14-diols as potential indicators for upper water stratification in the open South China Sea

2020 ◽  
Vol 110 ◽  
pp. 105900
Author(s):  
Xiaowei Zhu ◽  
Guodong Jia ◽  
Shengyi Mao ◽  
Yongge Sun ◽  
Nengyou Wu ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
China Sea ◽  
Water Stratification ◽  
Long Chain

Assessing the applicability of the long-chain diol (LDI) temperature proxy in the high-temperature South China Sea

2020 ◽  
Vol 144 ◽  
pp. 104017
Author(s):  
Yi Yang ◽  
Xiaoyan Ruan ◽  
Chao Gao ◽  
Xiaoxia Lü ◽  
Huan Yang ◽  
...  
Keyword(s):  
High Temperature ◽  
South China Sea ◽  
South China ◽  
China Sea ◽  
Temperature Proxy ◽  
Long Chain

scholarly journals Comparison of the U<sub>37</sub><sup>K′</sup>, LDI, TEX<sub>86</sub><sup>H</sup> and RI-OH temperature proxies in the northern shelf of the South China Sea

2019 ◽  
Author(s):  
Bingbing Wei ◽  
Guodong Jia ◽  
Jens Hefter ◽  
Manyu Kang ◽  
Eunmi Park ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Environmental Changes ◽  
The South China Sea ◽  
Nutrient Inputs ◽  
The South ◽  
Surface Cooling ◽  
Organic Input ◽  
China Sea ◽  
Long Chain

Abstract. The temperature proxies U37K′, LDI, TEX86H and RI-OH are derived from lipid biomarkers, namely long-chain alkenones from coccolithophorids, archaeal glycerol dialkyl glycerol tetraethers (GDGTs), long-chain diols ascribed tentatively to eustigmatophytes, and archaeal OH-GDGTs, respectively. The applicability of these proxies has been examined in the South China Sea (SCS), but most of these studies were focused on a single proxy and hence did not allow for a direct comparison between them. In this study, we investigated the above 4 proxies in the same set of surface sediment samples in the northern SCS shelf and related them to local sea surface temperature (SST), which allowed us to assess whether they represent certain seasons or are impaired by terrestrial influences, as well as to infer the preferred habitats of their source organisms. Terrestrial organic inputs appeared to have an impact on LDI, TEX86H and RI-OH proxies near the coast and lead to colder LDI and TEX86H derived temperatures, but a warmer RI-OH estimate in this region. After excluding samples influenced by terrestrial organic input, we found that LDI-derived temperature agreed well with annual SSTs, while U37K′ reflected mainly spring SST and both TEX86H and RI-OH indices were correlated with winter SST. The differential seasonal biases of these biomarker-derived temperatures observed here suggest that each biomarker’s source organism responds differently to regional marine environmental changes in an annual cycle. Specifically, marine eustigmatophytes are likely insensitive to nutrient variations and hence show the lowest seasonal variations, while coccolithophorids could have bloomed in late spring, when nutrient inputs by freshwater are usually highest. GDGT- and OH-GDGT-producing planktonic archaea likely thrive in winter, when conditions, such as relatively high nutrients levels, low light, and high concentrations of SPM in the upper water due to the enhancement of vertical mixing driven by a combination of surface cooling and strong winter monsoon winds, are favorable, although not clearly known.

Last glacial terrestrial vegetation record of leaf wax n-alcohols in the northern South China Sea: Contrast to scenarios from long chain n-alkanes

2020 ◽  
Author(s):  
Shengyi Mao ◽  
Xiaowei Zhu ◽  
Yongge Sun ◽  
Lihua Liu ◽  
Nengyou Wu
Keyword(s):  
South China Sea ◽  
South China ◽  
Northern South China Sea ◽  
C4 Plants ◽  
Interglacial Period ◽  
Terrestrial Vegetation ◽  
China Sea ◽  
Vegetation Reconstruction ◽  
Last Glacial ◽  
Long Chain

&lt;p&gt;Long chain n-alcohols and n-alkanes in core sediments from the northern South China Sea (SCS) were measured to make a comparison during terrestrial vegetation reconstruction from ~42 to ~7 ka. The results showed that terrestrial vegetation record from long chain n-alkanes matched well with previous studies in nearby cores, showing more C4 plants developed during the Last Glacial Maximum (LGM) and C3 plants dominated in the interglacial period. However, these scenarios did not occur during terrestrial vegetation reconstruction using long chain n-alcohols, i.e., showing C3 plant expansion during the LGM. The discrepancy during the interglacial period could be likely attributed to aerobic degradation of functionalized long chain n-alcohols due to the oxygen-rich SCS bottom water, resulting in the weak response of terrestrial vegetation signals. On the other hand, the difference between functionalized n-alcohols and non-functional n-alkanes to record local and distal vegetation signals, respectively might be a potential interpretation for the contradiction during the LGM when the SCS was characterized by low-oxygen deep water. Nevertheless, large variations on n-alkyl lipid compositions in C3/C4 plants could likely play a part in modulating sedimentary long chain n-alcohols and n-alkanes towards different vegetation signals, and caution must be taken in respect to the terrestrial vegetation reconstruction using long chain n-alkanes and long chain n-alcohols.&lt;/p&gt;

scholarly journals Comparison of the U<sub>37</sub><sup>K<sup>′</sup></sup>, LDI, TEX<sub>86</sub><sup>H</sup>, and RI-OH temperature proxies in sediments from the northern shelf of the South China Sea

2020 ◽  
Vol 17 (17) ◽  
pp. 4489-4508
Author(s):  
Bingbing Wei ◽  
Guodong Jia ◽  
Jens Hefter ◽  
Manyu Kang ◽  
Eunmi Park ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Seawater Temperature ◽  
Warm Season ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Asian Winter Monsoon ◽  
Terrestrial Inputs ◽  
Long Chain

Abstract. The temperature proxies U37K′, LDI, TEX86H, 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 U37K′ reflects annual mean SST with a slight bias toward the warm season. Terrestrial inputs appear to have a significant impact on LDI, TEX86H, and RI-OH proxies near the coast, leading to colder LDI- and TEX86H-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 TEX86H- 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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