Rejuvenating the ocean: mean ocean radiocarbon, CO2 release, and radiocarbon budget closure across the last deglaciation
Rejuvenating the ocean: mean ocean radiocarbon, CO2 release, and radiocarbon budget closure across the last deglaciation
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DOI：
10.5194/cp-19-2177-2023
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发表时间：
2023-11
影响因子：
4.3
通讯作者：
L. Skinner;F. Primeau;A. Jeltsch-Thömmes;F. Joos;P. Köhler;E. Bard
中科院分区：
文献类型：
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作者：
L. Skinner;F. Primeau;A. Jeltsch-Thömmes;F. Joos;P. Köhler;E. Bard
抽象的。放射性碳是一种示踪剂，它为海洋从大气中隔离二氧化碳的能力提供了独特的见解。虽然海洋内部放射性碳的空间格局可以表明碳通过海洋运输的矢量和时间尺度，但对全球平均海洋-大气放射性碳年龄偏移量(B-ATM)的估计限制了全球碳循环的结束。在这里，我们将贝叶斯内插方法应用于编译的B-ATM数据，以生成全球内插场和最后一次冰川消融期间的一组时间片的平均海洋B-ATM估计。汇编的数据和内插证实了海洋的逐步和空间异质性的“复兴”，表明碳是通过北大西洋与南大洋和北太平洋之间的两次“通风跷跷板”的摆动而释放到大气中的。使用中等复杂性的Bern3D模型进行的灵敏度测试表明，重建的B-ATM退冰期变化的一部分可能反映了与海洋通风无关的“相位衰减”偏差，而是来自独立的大气放射性碳动力学。Bélling-allerød期间B-ATM补偿的消融最小值可能在一定程度上反映了这种偏见。然而，敏感性测试进一步表明，在修正这些偏差时，海洋的“通风”仍然可以解释至少三分之一的去冰期大气二氧化碳上升。这种对二氧化碳上升的贡献似乎一直持续到年轻的仙女木，尽管很大一部分影响可能是在伯林-阿勒德冰川结束时实现的，这表明海洋碳循环调整在去冰川过程的早期发挥了关键作用。我们的全球平均B-ATM估计对上一次冰川消融期间全球放射性碳预算关闭的长期谜团施加了进一步的新限制，并表明现有重建可能平均低估了冰川放射性碳的产量水平。
Abstract. Radiocarbon is a tracer that provides unique insights into the ocean's ability to sequester CO2 from the atmosphere. While spatial patterns of radiocarbon in the ocean interior can indicate the vectors and timescales for carbon transport through the ocean, estimates of the global average ocean–atmosphere radiocarbon age offset (B-Atm) place constraints on the closure of the global carbon cycle. Here, we apply a Bayesian interpolation method to compiled B-Atm data to generate global interpolated fields and mean ocean B-Atm estimates for a suite of time slices across the last deglaciation. The compiled data and interpolations confirm a stepwise and spatially heterogeneous “rejuvenation” of the ocean, suggesting that carbon was released to the atmosphere through two swings of a “ventilation seesaw” operating between the North Atlantic and both the Southern Ocean and the North Pacific. Sensitivity tests using the Bern3D model of intermediate complexity demonstrate that a portion of the reconstructed deglacial B-Atm changes may reflect “phase-attenuation” biases that are unrelated to ocean ventilation and that arise from independent atmospheric radiocarbon dynamics instead. A deglacial minimum in B-Atm offsets during the Bølling–Allerød could partly reflect such a bias. However, the sensitivity tests further demonstrate that when correcting for such biases, ocean “ventilation” could still account for at least one-third of deglacial atmospheric CO2 rise. This contribution to CO2 rise appears to have continued through the Younger Dryas, though much of the impact was likely achieved by the end of the Bølling–Allerød, indicating a key role for marine carbon cycle adjustment early in the deglacial process. Our global average B-Atm estimates place further new constraints on the long-standing mystery of global radiocarbon budget closure across the last deglaciation and suggest that glacial radiocarbon production levels are likely underestimated on average by existing reconstructions.