The evolution of pCO2, ice volume and climate during the middle Miocene
The evolution of pCO2, ice volume and climate during the middle Miocene
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DOI：
10.1016/j.epsl.2012.06.007
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发表时间：
2012-08-01
影响因子：
5.3
通讯作者：
Rae, James W. B.
中科院分区：
文献类型：
--
作者：
Foster, Gavin L.;Lear, Caroline H.;Rae, James W. B.
中新世中期气候适宜期（17-15 Ma; MCO）是全球变暖和相对高CO2的时期，被认为与南极冰盖（AIS）的显著退缩有关。我们在这里提出了一个新的南极有孔虫三角洲B-11记录从16.6至11.8 Ma的两个深海站点目前在平衡与大气中的CO2。这些新的数据表明，在中新世中期全球气候的演变（反映在cyrosphere的变化）是很好的相关性，在大气中的CO2浓度的变化。更重要的是，在我们的采样分辨率（类似于每300 kyr 1个样本）有没有证据表明，在中新世中期的冰量对CO2强迫的响应滞后，相反，从冰盖建模研究南极冰盖的理解。与以前的数据一致，我们表明，在MCO期间的二氧化碳的绝对水平相对温和（350-400 ppm）和水平的MCO的两侧是类似的或低于工业化前（200-260 ppm）。这些新的数据意味着在中新世中期，在相对较低的CO2下，存在非常动态的AIS，或者存在显著的北方半球冰的进退。最近在南极边缘的钻探和基于海岸的研究表明，在中新世中期，AIS确实发生了超过现代界限的显著后退和前进，但AIS的完全丧失是不可能的。因此，似乎冰量和气候变化在中新世中期可能涉及一个更动态的AIS比现代，但也有一些成分的陆基冰在北方半球。(C)2012爱思唯尔有限公司版权所有。
The middle Miocene Climatic Optimum (17-15 Ma; MCO) is a period of global warmth and relatively high CO2 and is thought to be associated with a significant retreat of the Antarctic Ice Sheet (AIS). We present here a new planktic foraminiferal delta B-11 record from 16.6 to 11.8 Ma from two deep ocean sites currently in equilibrium with the atmosphere with respect to CO2. These new data demonstrate that the evolution of global climate during the middle Miocene (as reflected by changes in the cyrosphere) was well correlated to variations in the concentration of atmospheric CO2. What is more, within our sampling resolution (similar to 1 sample per 300 kyr) there is no evidence of hysteresis in the response of ice volume to CO2 forcing during the middle Miocene, contrary to what is understood about the Antarctic Ice Sheet from ice sheet modelling studies. In agreement with previous data, we show that absolute levels of CO2 during the MCO were relatively modest (350-400 ppm) and levels either side of the MCO are similar or lower than the pre-industrial (200-260 ppm). These new data imply the presence of either a very dynamic AIS at relatively low CO2 during the middle Miocene or the advance and retreat of significant northern hemisphere ice. Recent drilling on the Antarctic margin and shore based studies indicate significant retreat and advance beyond the modern limits of the AIS did occur during the middle Miocene, but the complete loss of the AIS was unlikely. Consequently, it seems that ice volume and climate variations during the middle Miocene probably involved a more dynamic AIS than the modern but also some component of land-based ice in the northern hemisphere. (C) 2012 Elsevier B.V. All rights reserved.