Variations in GDGT distributions through the water column in the South East Atlantic Ocean
Variations in GDGT distributions through the water column in the South East Atlantic Ocean
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DOI：
10.1016/j.gca.2014.02.009
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发表时间：
2014-05
影响因子：
5
通讯作者：
M. Hernández-Sánchez;E. Woodward;K. Taylor;G. Henderson;R. Pancost
中科院分区：
文献类型：
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作者：
M. Hernández-Sánchez;E. Woodward;K. Taylor;G. Henderson;R. Pancost
TEX 86温度代用指标广泛应用于过去海表温度的重建。大多数目前的校准是基于表面沉积物分布的甘油二烷基甘油四醚脂质（GDGT），包括TEX 86，并假设这些GDGT从上混合层输出。然而，GDGT输出从较深的沃茨可能会影响沉积GDGT的分布，因此TEX 86古测温。在这里，我们研究GDGT分布在悬浮颗粒物（SPM）和底层沉积物收集从东南大西洋。我们的研究结果揭示了不同的GDGT分布-特别是带有2与3个环戊基部分的GDGT之间的比率，[2/3]比率-在表面，地下（>50-200 m）和深水（>200 m）SPM之间，这表明在考虑TEX 86时不明显的原位（深部）生产的发生。GDGT在沉积物中的分布相匹配的地下沃茨，而不是地表沃茨，这表明他们没有优先来自上层混合层，这是一致的GDGT丰度最高的浅层地下SPM（100至200米）。目前还不清楚是什么控制了整个水柱的不同[2/3]比例，但它可能与温度和thaumarchaeotal群落结构的结合有关。
The TetraEther indeX of 86 carbon atoms (TEX86) temperature proxy is widely used in reconstructions of past sea surface temperature. Most current calibrations are based on surface sediment distributions of the glycerol dialkyl glycerol tetraether lipids (GDGTs) that comprise TEX86and assume that these GDGTs are exported from the upper mixed layer. However, GDGT export from deeper waters could impact sedimentary GDGT distributions and therefore TEX86paleothermometry. Here we examine GDGT distributions in suspended particulate matter (SPM) and underlying sediments collected from the Southeast Atlantic Ocean. Our results reveal different GDGT distributions – specifically the ratio between GDGTs bearing 2 vs. 3 cyclopentyl moieties, [2/3] ratios – between surface, subsurface (>50–200 m) and deep water (>200 m) SPM, which suggests the occurrence of in situ (deep) production that is not apparent when considering TEX86. The GDGT distributions in sediments match those of subsurface waters rather than surface waters, suggesting that they have not been preferentially derived from the upper mixed layer; this is consistent with GDGT abundances being highest in shallow subsurface SPM (∼100 to 200 m). It remains unclear what governs the different [2/3] ratios throughout the water column, but it is likely related to a combination of temperature and thaumarchaeotal community structure.