Atmospheric carbon dioxide and ocean circulation changes during the middle Miocene climate transition

在最近的一项基于浮游有孔虫硼同位素的研究中，我们发现中新世中期南极冰期后，大气pCO2迅速上升，然后恢复到冰期前的值，这是令人惊讶的，因为它与文献中广泛假设的相反。我们得出结论，二氧化碳分压的短暂上升可能是由经向深海环流增强引起的。然而，我们需要通过研究来自不同地区和不同深度的中新世沉积物岩心来验证我们的假设，以便(1)最终从底栖生物记录中观察海洋环流的变化，(2)从浮游生物记录中巩固二氧化碳分压记录。中新世中期仍然是古气候学家研究的热点，它可能为南极冰与全球碳循环之间的紧密耦合提供洞见。这个时间间隔特别有趣，因为大气二氧化碳分压似乎与今天相似，我们将面临中新世中期气候转变的逆转，即南极冰量的大幅减少。因此，了解中新世中期冰量和全球碳循环之间相互作用的过程，可能对未来预测地球变暖很重要。

In a recent study based on boron isotopes in planktic foraminifera, we found that after the mid-Miocene Antarctic glaciation atmospheric pCO2 rose rapidly before returning to pre-glaciation values, which is surprising since it is opposite to what was widely assumed in the literature. We conclude that this transient rise in pCO2 is supposedly caused by enhanced meridional deep-ocean circulation. We need, however, to verify our hypothesis by investigating Miocene sediment cores from different areas and different depths to (1) eventually observe changes in ocean circulation from benthic records, and (2) to consolidate pCO2 records from the planktic records. The middle Miocene is still a hot topic among paleoclimatologists, and may provide insights into the tight coupling between Antarctic ice and the global carbon cycling. This time interval is especially interesting, because atmospheric pCO2 appears to have been similar to today and we are going to face the reversal of the middle Miocene climate transition, i.e. a substantial reduction in Antarctic ice volume. Hence the knowledge of processes involved in the interaction between mid-Miocene ice volume and global carbon cycle may be important for future predictions of our warming planet.