Breathing more deeply: Deep ocean carbon storage during the mid-Pleistocene climate transition
Breathing more deeply: Deep ocean carbon storage during the mid-Pleistocene climate transition
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DOI：
10.1130/g38636.1
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发表时间：
2016-12
期刊：
影响因子：
5.8
通讯作者：
C. Lear;K. Billups;R. Rickaby;L. Diester-Haass;E. Mawbey;S. Sosdian
中科院分区：
文献类型：
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作者：
C. Lear;K. Billups;R. Rickaby;L. Diester-Haass;E. Mawbey;S. Sosdian
∼100 K.Y.晚更新世冰期的旋回性始于中更新世过渡期(MPT)，当时冰盖变得更大，持续时间更长。负责引入这种非线性冰盖对太阳辐射轨道变化响应的气候系统反馈仍然不确定。本文介绍了北大西洋深海钻探计划第607点海底有孔虫的稳定同位素(δ18O，δ13C)和痕量金属记录(Cd/Ca，B/Ca，U/Ca)。在冰期-间冰期，δ13C值的冰期-间冰期变化与营养物质含量和碳酸盐饱和状态的变化有关，这与我们地点的水团从间冰期营养物质贫乏的北部来源到冰期期间营养丰富、具有腐蚀性的南部来源的变化是一致的。跨大西洋冰川深水的呼吸碳含量增加。在冰期期间，腐蚀性底水的优势增加会提高海洋的平均碱度，降低大气中的p CO2。δ13C的冰期-间冰期变化的幅度在整个最大冰期都有所增加，但这并没有反映在营养含量的变化上。我们用海-气CO2交换效应来解释这一现象，它改变了深水物质源区溶解无机碳的δ13C特征。冰川时期海冰覆盖或海洋层化的增加可能减少了南大洋的二氧化碳排放，为减少冰川大气中的二氧化碳提供了另一种机制。相反，在∼100 K.Y成立后。在冰川周期中，来自北方的间冰期水域的δ13C增加，这可能反映了MPT之后二氧化碳对北大西洋的入侵减少。
The ∼100 k.y. cyclicity of the late Pleistocene ice ages started during the mid-Pleistocene transition (MPT), as ice sheets became larger and persisted for longer. The climate system feedbacks responsible for introducing this nonlinear ice sheet response to orbital variations in insolation remain uncertain. Here we present benthic foraminiferal stable isotope (δ 18 O, δ 13 C) and trace metal records (Cd/Ca, B/Ca, U/Ca) from Deep Sea Drilling Project Site 607 in the North Atlantic. During the onset of the MPT, glacial-interglacial changes in δ 13 C values are associated with changes in nutrient content and carbonate saturation state, consistent with a change in water mass at our site from a nutrient-poor northern source during interglacial intervals to a nutrient-rich, corrosive southern source during glacial intervals. The respired carbon content of glacial Atlantic deep water increased across the MPT. Increased dominance of corrosive bottom waters during glacial intervals would have raised mean ocean alkalinity and lowered atmospheric p CO 2 . The amplitude of glacial-interglacial changes in δ 13 C increased across the MPT, but this was not mirrored by changes in nutrient content. We interpret this in terms of air-sea CO 2 exchange effects, which changed the δ 13 C signature of dissolved inorganic carbon in the deep water mass source regions. Increased sea ice cover or ocean stratification during glacial times may have reduced CO 2 outgassing in the Southern Ocean, providing an additional mechanism for reducing glacial atmospheric p CO 2 . Conversely, following the establishment of the ∼100 k.y. glacial cycles, δ 13 C of interglacial northern-sourced waters increased, perhaps reflecting reduced invasion of CO 2 into the North Atlantic following the MPT.