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首页> 外文期刊>Paleoceanography >Glacial onset predated Late Ordovician climate cooling
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Glacial onset predated Late Ordovician climate cooling

机译：冰川爆发早于奥陶纪晚期气候降温

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The Ordovician glaciation represents the acme of one of only three major icehouse periods in Earth's Phanerozoic history and is notorious for setting the scene for one of the big five mass extinction events. Nevertheless, the mechanisms that drove ice sheet growth remain poorly understood and the final extent of the ice sheet crudely constrained. Here using an Earth system model with an innovative coupling method between ocean, atmosphere, and land ice accounting for climate and ice sheet feedback processes, we report simulations portraying for the first time the detailed evolution of the Ordovician ice sheet. We show that the emergence of the ice sheet happened in two discrete phases. In a counterintuitive sequence of events, the continental ice sheet appeared suddenly in a warm climate. Only during the second act, and set against a background of decreasing atmospheric CO2, followed steeply dropping temperatures and extending sea ice. The comparison with abundant sedimentological, geochemical, and micropaleontological data suggests that glacial onset may have occurred as early as the Middle Ordovician Darriwilian, in agreement with recent studies reporting third-order glacioeustatic cycles during the same period. The second step in ice sheet growth, typified by a sudden drop in tropical sea surface temperatures by approximate to 8 degrees C and the further extension of a single, continental-scale ice sheet over Gondwana, marked the onset of the Hirnantian glacial maximum. By suggesting the presence of an ice sheet over Gondwana throughout most of the Middle and Late Ordovician, our models embrace the emerging paradigm of an early Paleozoic Ice Age.
机译：奥陶纪冰川活动代表了地球幻影史上仅有的三个主要冰屋时期之一，并以其为五个大灭绝事件之一奠定了基础而臭名昭著。然而，驱动冰盖生长的机制仍然知之甚少，并且冰盖的最终程度受到了严格限制。在这里，我们使用地球系统模型，结合海洋，大气层和陆地冰层之间的创新耦合方法来解释气候和冰原的反馈过程，我们首次报告了模拟，描绘了奥陶纪冰原的详细演化。我们表明，冰盖的出现发生在两个离散的阶段。在一系列与直觉相反的事件中，大陆冰盖在温暖的气候下突然出现。仅在第二幕中，并以大气CO2减少为背景，随后温度急剧下降并延伸了海冰。与丰富的沉积学，地球化学和微古生物学数据进行的比较表明，早在中奥陶纪达里维利人时期就可能发生了冰川爆发，这与最近的研究报告了同一时期的三阶冰川共生周期相一致。冰盖生长的第二步，以热带海面温度突然下降约8摄氏度，并在冈瓦纳上空扩展一个单一的大陆尺度冰盖为标志，这标志着赫南特冰川最大爆发的开始。通过暗示整个奥陶纪中晚期大部分时间都在冈瓦纳上空存在冰盖，我们的模型包含了早古生代冰河时代的新兴范例。

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