The impact of atmospheric and oceanic heat transports on the sea-ice-albedo instability during the Neoproterozoic
The impact of atmospheric and oceanic heat transports on the sea-ice-albedo instability during the Neoproterozoic
复制标题
新元古代大气和海洋热传输对海冰反照率不稳定性的影响
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
A. Ganopolski
中科院分区：
文献类型：
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作者：
Y. Donnadieu;G. Ramstein;F. Fluteau;D. Roche;A. Ganopolski
摘要
为了模拟新元古代的气候条件，我们用一个中等复杂的海洋-大气耦合模式--REGREBER-2进行了一系列模拟，其中太阳常数减少了6%，二氧化碳浓度发生了变化。我们还测试了罗迪尼亚超大陆解体的影响，据推测，罗迪尼亚超大陆在冰盖地球的形成过程中发挥了重要作用。结果表明，在大气CO2浓度临界值为89ppm和149ppm时，雪球地球分别出现在超大陆情形和位错构型中。经向海洋能量输送对CO2浓度降低和超大陆位错的敏感性研究表明，动力海洋过程可以调节CO2阈值，低于该阈值可以找到滚雪球解，但不能阻止它。翻转环流和海洋热量输送的崩溃主要是由于海冰线到达30°纬度带后纬向温度梯度减小，同时也是由于海冰融化使热带海洋变得清新。在反馈方面，通过Hadley环流的经向大气热输送在整个CO2减少过程中起主要作用，它增加了海冰边缘前方的能量，但在这一贡献所测试的大陆构型的情况下，似乎不足以防止海冰反照率不稳定的发生。
Abstract
In order to simulate the climatic conditions of the Neoproterozoic, we have conducted a series of simulations with a coupled ocean–atmosphere model of intermediate complexity, CLIMBER-2, using a reduced solar constant of 6% and varied CO2 concentrations. We have also tested the impact of the breakup of the supercontinent Rodinia that has been hypothesized to play an important role in the initiation of an ice-covered Earth. Our results show that for the critical values of 89 and 149 ppm of atmospheric CO2, a snowball Earth occurs in the supercontinent case and in the dislocated configuration, respectively. The study of the sensitivity of the meridional oceanic energy transport to reductions in CO2 concentration and to the dislocation of the supercontinent demonstrates that dynamics ocean processes can modulate the CO2 threshold value, below which a snowball solution is found, but cannot prevent it. The collapse of the overturning cells and of the oceanic heat transport is mainly due to the reduced zonal temperature gradient once the sea-ice line reaches the 30° latitudinal band but also to the freshening of the tropical ocean by sea-ice melt. In term of feedbacks, the meridional atmospheric heat transport via the Hadley circulation plays the major role, all along the CO2 decrease, by increasing the energy brought in the front of the sea-ice margin but does not appear enough efficient to prevent the onset of the sea-ice-albedo instability in the case of the continental configurations tested in this contribution.