Southern Ocean buoyancy forcing of ocean ventilation and glacial atmospheric CO2
Southern Ocean buoyancy forcing of ocean ventilation and glacial atmospheric CO2
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DOI：
10.1038/ngeo2538
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发表时间：
2015-11
影响因子：
18.3
通讯作者：
A. Watson;G. Vallis;M. Nikurashin
中科院分区：
文献类型：
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作者：
A. Watson;G. Vallis;M. Nikurashin
冰期-间冰期周期的大气二氧化碳浓度与南极的温度模式密切相关。这些与中北部纬度的温度变化不同，因此这表明南大洋在控制自然二氧化碳浓度方面起着关键作用。在这里，我们评估了大气二氧化碳浓度对海洋经向翻转环流中冰期-间冰期变化的敏感性，使用了一个环流模型，用于南大洋的上升流和涡旋输送，并结合简单的生物地球化学描述。在冰川条件下，相对于间冰期，更大范围的表面浮力丧失导致上升流向更北的方向上升。上升流的北部位置减少了二氧化碳的排放，加强了深海的碳封存：我们计算出，转向这种冰川式环流可以减少大气中30到60 的二氧化碳。因此，我们认为，温度对南大洋浮力强迫的直接影响，以及由此产生的剩余翻转环流，在很大程度上解释了南极温度变化与冰川-间冰期循环期间大气CO2浓度之间的强烈相关性。
Atmospheric CO2concentrations over glacial–interglacial cycles closely correspond to Antarctic temperature patterns. These are distinct from temperature variations in the mid to northern latitudes, so this suggests that the Southern Ocean is pivotal in controlling natural CO2concentrations. Here we assess the sensitivity of atmospheric CO2concentrations to glacial–interglacial changes in the ocean’s meridional overturning circulation using a circulation model,for upwelling and eddy transport in the Southern Ocean coupled with a simple biogeochemical description. Under glacial conditions, a broader region of surface buoyancy loss results in upwelling farther to the north, relative to interglacials. The northern location of upwelling results in reduced CO2outgassing and stronger carbon sequestration in the deep ocean: we calculate that the shift to this glacial-style circulation can draw down 30 to 60 ppm of atmospheric CO2. We therefore suggest that the direct effect of temperatures on Southern Ocean buoyancy forcing, and hence the residual overturning circulation, explains much of the strong correlation between Antarctic temperature variations and atmospheric CO2concentrations over glacial–interglacial cycles.