Refining the planktic foraminiferal I/Ca proxy: Results from the Southeast Atlantic Ocean
Refining the planktic foraminiferal I/Ca proxy: Results from the Southeast Atlantic Ocean
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精炼浮游有孔虫 I/Ca 代理：来自东南大西洋的结果
DOI：
10.1016/j.gca.2019.10.025
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发表时间：
2019
影响因子：
5
通讯作者：
Lu, Zunli
中科院分区：
文献类型：
--
作者：
Lu, Wanyi;Dickson, Alexander J.;Thomas, Ellen;Rickaby, Rosalind E.M.;Chapman, Piers;Lu, Zunli
近几十年来，上层海洋氧合发生了深刻的变化，预计未来仍将持续，但驱动这些变化的过程的复杂性尚未完全揭开。浮游有孔虫 I/Ca 是重建过去上层海洋氧合程度的有前途的工具，但需要进行彻底的评估才能评估其潜力和局限性。我们使用全新世核心顶部（东南大西洋）的有孔虫来记录一系列海洋条件下的浮游 I/Ca。地下 O2 浓度可能是浮游有孔虫 I/Ca 的主要控制因素，浮游 I/Ca 在低 O2 条件下 (O2<∼70–100 µmol/kg) 迅速降低。因此，我们记录了低浮游 I/Ca 可以根据经验用于指示上层水体的缺氧，但对于海水碘形态变化、其 O2 阈值和有孔虫 I/Ca 之间关系的机械理解仍然存在问题。来自核心 GeoB1720-2（本格拉上升流系统，大西洋东南部）的浮游 I/Ca 记录表明，在过去 240ka 期间，该地点附近持续存在缺氧水域，没有明显的冰期-间冰期变化。
Profound changes in upper ocean oxygenation have taken place in recent decades and are expected to continue in the future, but the complexity of the processes driving these changes has yet to be fully unraveled. Planktic foraminiferal I/Ca is a promising tool to reconstruct the extent of past upper ocean oxygenation, but a thorough assessment is necessary to evaluate both its potential and its limitations. We used foraminifers from Holocene core-tops (Southeast Atlantic Ocean) to document planktic I/Ca across a range of oceanographic conditions. Subsurface O2concentrations may be the dominant control on planktic foraminiferal I/Ca and planktic I/Ca decreases rapidly at low O2conditions (O2< ∼70–100 µmol/kg). We thus document that low planktic I/Ca can be used empirically to indicate hypoxia in the upper water column, but questions remain as to the mechanistic understanding of the relation between seawater iodine speciation change, its O2threshold and foraminiferal I/Ca. Planktic I/Ca records from core GeoB1720-2 (Benguela Upwelling System, SE Atlantic) suggest that hypoxic waters were present near the site persistently during the last 240 ka, without clear glacial-interglacial variability.