Consistent CO2 release by pyrite oxidation on continental shelves prior to glacial terminations
Consistent CO2 release by pyrite oxidation on continental shelves prior to glacial terminations
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DOI：
10.1038/s41561-019-0465-9
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发表时间：
2019-11-01
影响因子：
18.3
通讯作者：
Zabel, Matthias
中科院分区：
文献类型：
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作者：
Koelling, Martin;Bouimetarhan, Ilham;Zabel, Matthias
先前的证据表明，在低海平面的冰期，暴露的大陆架上的黄铁矿氧化增强。虽然黄铁矿氧化直接消耗大气中的氧气，但该反应产生的酸会通过碳酸盐溶解增加CO2的释放。这种情况代表了一个气候控制循环，它可以缓和甚至阻止冰川，因为二氧化碳的增加会引发变暖和海平面上升。然而，在第四纪，海平面变化幅度增加，并且在过去80万年的大部分时间里，CO2浓度与海平面共同变化。只有在冰川高峰时期，二氧化碳水平才会达到与海平面下降无关的较低阈值。在最后9个冰期-间冰期旋回中，黄铁矿氧化驱动的CO2释放和O-2消耗发生在冰期终止前的10至40 kyr期间。我们证明了反复出现的海平面低洼迫使黄铁矿在暴露的陆架沉积物中氧化到更大的深度，并导致二氧化碳释放，这可以解释冰川二氧化碳阈值。当高海平面间冰期的持续时间不足以补充陆架黄铁矿库存时，这种二氧化碳释放过程代表放电的“酸电容器”。
Previous evidence suggests enhanced pyrite oxidation on exposed continental shelves during glacial phases of low sea level. While pyrite oxidation directly consumes atmospheric oxygen, acid generated by this reaction should increase the release of CO2 through carbonate dissolution. This scenario represents a climate control loop that could temper or even prevent glacials because increasing CO2 triggers warming and rising sea level. However, the amplitudes of sea-level changes increased over the Quaternary, and CO2 concentrations co-varied with sea level throughout most of the past 800,000 years. Only during peak glacial conditions did CO2 levels reach an apparent lower threshold independent of falling sea level. Here we suggest that during the last nine glacial-interglacial cycles, pyrite-oxidation-driven release of CO2 and consumption of O-2 occurred during 10 kyr to 40 kyr periods preceding glacial terminations. We demonstrate that repeated sea-level lowstands force pyrite oxidation to ever-greater depths in exposed shelf sediments and cause CO2 release that could explain the glacial CO2 threshold. When the duration of interglacials with high sea level is insufficient to restock the shelf pyrite inventory, this CO2-releasing process represents a discharging 'acid capacitor'.