THE ROLE OF VERTICAL CHEMICAL FRACTIONATION IN CONTROLLING LATE QUATERNARY ATMOSPHERIC CARBON-DIOXIDE
THE ROLE OF VERTICAL CHEMICAL FRACTIONATION IN CONTROLLING LATE QUATERNARY ATMOSPHERIC CARBON-DIOXIDE
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DOI：
10.1029/jc093ic12p15701
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发表时间：
1988-12-15
影响因子：
3.6
通讯作者：
BOYLE, EA
中科院分区：
文献类型：
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作者：
BOYLE, EA
在冰川最大期，大气中二氧化碳减少了30%，这一定是由海洋化学循环的某些变化引起的。本文提出了一个新的晚第四纪CO2变化模型，它解决了以往模型中存在的一些问题（包括CO2响应的时间和深海氧含量的变化）。在这个模型中的主要驱动因素是在海洋中的化学分布的重排，其中不稳定的营养物质和代谢CO2集中在深沃茨，而不是在中间沃茨中观察到的现代海洋。这种新的“底部重”化学结构不会直接影响大气中的二氧化碳。相反，二氧化碳引起的酸度降低了深海碳酸盐离子浓度，并暂时增加了碳酸盐溶解速率。海洋的碱度随后上升，直到深海碳酸盐离子恢复到其稳态值。由此产生的海洋碱性增加将二氧化碳从大气中吸入海洋。碱度和大气CO2滞后几千年后，在海洋化学结构的变化，这种延迟的反应是由大陆风化和深海碳酸盐溶解相对于海洋碱度库存有限的速度。据认为，海洋的冰消和冰前状态是驱动冰期-间冰期气候变化的主要因素。这一概念重新解释了地表水和深层沃茨之间的碳同位素对比[Δδ 13 C（B）]，因为轻代谢碳从中间沃茨转移到深层沃茨。这一过程在这里用一个简单的平衡五箱海洋模型来说明。观测到的中深层营养盐耗竭本身不足以确定几种可能的机制中的哪一种正在起作用，并且某些机制在改变大气CO2方面不如其他机制有效。最大的反应是从深化有机碳的再生循环，最小的反应是从北大西洋深水转化为中层水。
The 30% decrease in atmospheric carbon dioxide during glacial maxima must be driven by some change in the chemical circulation of the ocean. Here, a new model for late Quaternary CO2variability is presented which resolves some problems occurring in previous models (including the timing of carbon dioxide response and changes in the oxygen content of the deep ocean). The primary driving factor in this model is a rearrangement of chemical distributions in the ocean whereby labile nutrients and metabolic CO2are concentrated in deep waters rather than in intermediate waters as observed in the modern ocean. This new “bottom‐heavy” chemical structure does not affect atmospheric carbon dioxide directly. Instead, CO2‐induced acidity lowers the deep ocean carbonate ion concentration and temporarily increases carbonate dissolution rates. Oceanic alkalinity then rises until the deep ocean carbonate ion is restored to its steady state value. The resulting increase in oceanic alkalinity draws CO2out of the atmosphere into the ocean. Alkalinity and atmospheric CO2lag several thousand years behind the change in oceanic chemical structure; this delayed response is determined by the limited rate of continental weathering and deep ocean carbonate dissolution relative to the oceanic alkalinity inventory. It is proposed that characteristic deglacial and preglacial states of the ocean are leading factors driving glacial‐interglacial climate changes. This concept reinterprets the carbon isotope contrast between surface water and deep waters [Δδ13C(P‐B)] as due to a shift of light metabolic carbon from intermediate waters into deep waters. The process is illustrated here by a simple equilibrium five box ocean model. The observed intermediate‐depth nutrient depletion is not sufficient in itself to determine which of several possible mechanisms are operating, and some mechanisms are not as effective in changing atmospheric CO2as others. The largest response is seen from deepening the regeneration cycle of organic carbon; the least response is seen from converting North Atlantic Deep Water into intermediate water.