Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene
Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene
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DOI：
10.1016/j.gloplacha.2005.01.001
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发表时间：
2005-05
影响因子：
3.9
通讯作者：
J. Zachos;L. Kump
中科院分区：
文献类型：
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作者：
J. Zachos;L. Kump
在渐新世早期（约34 Ma），南极冰川作用的开始表现为海洋δ 18 O记录（Oi-1）的明显正异常，并伴随着海洋溶解无机碳和生物沉积物积累速率的δ 13 C平均值的正偏移。在Oi-1爆发后的400 ky内，气候系统进入了一个更加温和但稳定的“冰川”状态。在这里，通过建模，我们调查了两个主要的地球化学过程中参与这种反应：硅酸盐风化和海洋有机碳循环。我们开始的事件与大气中的CO2迅速下降导致增加与喜马拉雅山脉的大陆的耐候性。由于冰盖覆盖、硅酸盐风化速率和大气CO2之间的反馈，这种扰动触发了δ 18 O记录的超调和调整。该系统是一个阻尼振荡器，其强度取决于化学风化率对气候变化的敏感性和气候对大气CO2变化的敏感性。与最初过渡到冰川世界相关的海洋混合增加，加速了生物生产力和碳埋藏的速度，降低了大气CO2，加速了全球冷却和冰盖生长，并产生了粗略近似于观察到的碳同位素反应。Oi-1超调似乎需要快速（<100万年）应用强迫（例如，大气CO2的构造下降）。虽然进一步的调查和更复杂的模型最终可能会显示，其他触发和反馈盛行在Oi-1，这里提出的建模表明，简单的反馈在气候系统中可以解释的超调和调整响应早渐新世气候强迫。
The initiation of Antarctic glaciation in the early Oligocene (∼34 Ma) is represented by a distinct positive anomaly in the marine δ18O record designated Oi-1 and accompanied by positive excursions in the mean δ13C of oceanic dissolved inorganic carbon and biogenic sediment accumulation rates. Within 400 ky of the onset of Oi-1, the climate system settled into a more moderate but stable “glacial” state. Here, through modeling, we investigate two of the principal biogeochemical processes involved in this response: silicate weathering and marine organic carbon cycling. We initiate the event with a rapid drawdown in atmospheric CO2resulting from increased weatherability of the continents associated with Himalayan orogeny. This perturbation triggers the overshoot and adjustment of the δ18O record because of feedback among ice-sheet coverage, silicate weathering rates, and atmospheric CO2. The system is a damped oscillator, the strength of which depends on the sensitivity of chemical weathering rates to climate change and climate to changes in atmospheric CO2. Increased oceanic mixing associated with initial transition into a glacial world accelerates the rates of biological productivity and carbon burial, lowering atmospheric CO2and accelerating global cooling and ice-sheet growth, and generating a carbon isotope response that crudely approximates that observed. The Oi-1 overshoot appears to require a rapid (<1 million year) application of the forcing (e.g., tectonic drawdown of atmospheric CO2). Although further investigation and more sophisticated models ultimately may show that other triggers and feedbacks prevailed during Oi-1, the modeling presented here demonstrates that simple feedbacks in the climate system can explain the overshoot and adjustment response to early Oligocene climate forcing.