Carbon cycle feedbacks during the Oligocene-Miocene transient glaciation
Carbon cycle feedbacks during the Oligocene-Miocene transient glaciation
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渐新世-中新世短暂冰川作用期间的碳循环反馈
作者：
Mawbey E
冰盖模型表明，由于其寒冷的上表面，大的、高海拔的东南极冰盖一旦形成，相对来说是自稳定的。冰盖滞后问题是由于无法将这一预期与冰盖退缩的地质证据相协调而造成的。这个问题的一个经典例子表现在渐新世-中新世边界（约23 Ma）的底栖有孔虫氧同位素记录中，它们显示出向更高值的短暂偏移~ 1‰。推断出的冰量的增加和随后的减少与南极冰盖在大陆架上的进退有关。然而，氧同位素记录本身并不能提供温度和冰体积的明确记录，从而阻碍了对这些变化驱动机制的评估。在这里，我们提出了新的底栖有孔虫Mg/Ca， Li/Ca和U/Ca记录，这些记录跨越渐新世-中新世边界，来自海洋钻探计划地点926和929。我们的记录表明，大西洋底水的温度是周期性变化的，主要的冷却和变暖步骤分别是冰的生长和腐烂。我们认为，随着气候变冷，有机碳埋藏的增加起到了正反馈作用。几条线索的证据表明，冰川消融与向海洋-大气系统输入碳有关，最终导致了以前未被确认的海底溶解事件。我们认为碳的最初来源之一是海洋沉积物中的有机物氧化。该研究表明，在评估古冰盖稳定性时应考虑碳循环反馈。
Ice sheet models suggest that once formed, the large, high-altitude East Antarctic Ice Sheet was relatively self-stabilizing, due to its cold upper surface. The ice sheet hysteresis problem results from an inability to reconcile this expectation with geological evidence for episodes of ice sheet retreat. A classic example of this problem is manifested in benthic foraminiferal oxygen isotope records across the Oligocene-Miocene boundary (ca. 23 Ma), which display a transient∼ 1‰ excursion to higher values. The inferred increase and subsequent decrease in ice volume has been linked to advance and retreat of the Antarctic ice sheet across the continental shelf. However, oxygen isotope records alone do not provide unambiguous records of temperature and ice volume, hindering assessment of the driving mechanism for these variations. Here we present new benthic foraminiferal Mg/Ca, Li/Ca, and U/Ca records across the Oligocene-Miocene boundary from Ocean Drilling Program Sites 926 and 929. Our records demonstrate that Atlantic bottom-water temperatures varied cyclically, with the main cooling and warming steps followed by ice growth and decay respectively. We suggest that enhanced organic carbon burial acted as a positive feedback as climate cooled. Several lines of evidence suggest that the deglaciation was associated with an input of carbon to the ocean-atmosphere system, culminating in a previously unidentified seafloor dissolution event. We suggest that one of the initial sources of carbon was organic matter oxidation in ocean sediments. This study demonstrates that carbon cycle feedbacks should be considered when evaluating the stability of ancient ice sheets.
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DOI：
--
发表时间：
2005
期刊：
影响因子：
--
作者：
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通讯作者：
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影响因子：
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作者：
Elderfield, H.;Yu, J.;Nyland, B.
通讯作者：
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影响因子：
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作者：
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DOI：
--
发表时间：
2012
期刊：
影响因子：
--
作者：
P. Bart;L. D. Santis
通讯作者：
L. D. Santis
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DOI：
--
发表时间：
1997
期刊：
影响因子：
--
作者：
N. Shackleton;M. Hall
通讯作者：
M. Hall