Observations of ice sheet stability in Antarctica in the past, during significantly warmer climatic periods than today, are hampered by a paucity of continental outcrops but they are essential if we are to test and more fully understand established concepts of ice sheet growth and decay and robustly predict Earth's future during rapid global warming. In this paper we use the unique terrestrial record preserved in the three most southerly volcanoes on Earth to reconstruct Antarctica's environmental landscape in the Transantarctic Mountains for three time slices (at 20.1, 19.31 and c. 17 Ma). We demonstrate that the East Antarctic Ice Sheet margin was highly dynamic and fluctuated greatly during the Early Miocene. The period included a much-reduced ice cover that left the southern Transantarctic Mountains virtually ice-free, although a few tidewater glaciers reached the shores of the Early Miocene Ross Sea (Sheridan Bluff; 20.1 Ma); and a substantially thicker, much more voluminous ice mass (represented by volcanism at Mount Early; 19.31 Ma). An intermediate stage of ice retreat is also indicated (at c. 17 Ma), when the East Antarctic Ice Sheet had again withdrawn to behind the Transantarctic Mountains. It is represented by a subglacial volcanic centre identified remotely by aerogeophysics and sampled only as glacial erratics. The associated ice cover at c. 17 Ma had a relatively low surface elevation but it was confluent with thin ice domes that covered the adjacent mountains. Although the ice margin probably did not extend down to the Ross Sea coast, several glaciers fed icebergs into the Ross Sea. The large ice sheet indicated by the Mount Early volcanic centre is the only known physical record of a significant glacial event that took place at 19.31 ± 0.32 Ma (‘Mount Early glacial’). The records examined at the other two volcanic sites correspond to eruptions during periods of substantially reduced ice in Antarctica, of which that at 20.1 ± 0.4 Ma is the most remarkable (‘Sheridan Bluff interglacial’). The causes of the extreme variations in ice sheet thickness and extent indicated are uncertain but they occurred during a period of rapidly fluctuating atmospheric CO compositions. Although Milankovitch astronomical forcing probably also played a significant part, the results suggest that the East Antarctic Ice Sheet was highly susceptible to comparatively slight changes in CO during the warm Early Miocene.

中文翻译：

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中新世早期（约 20-17 Ma）南横贯南极山脉的地貌演化以及来自世界最南端火山（南纬 87°）的东南极冰盖边缘高度动态的证据


过去，在比现在温暖得多的气候时期，对南极洲冰盖稳定性的观测受到了大陆露头匮乏的阻碍，但如果我们要测试和更全面地理解冰盖生长和衰变的既定概念，并稳健地进行测试和更全面地理解，它们是至关重要的。预测全球快速变暖期间地球的未来。在本文中，我们利用地球最南端三座火山保存的独特陆地记录，重建了横贯南极山脉三个时间切片（20.1、19.31 和约 17 Ma）的南极洲环境景观。我们证明，在早中新世期间，东南极冰盖边缘高度动态且波动很大。这一时期的冰盖大大减少，使得横贯南极山脉南部几乎没有冰，尽管一些潮水冰川到达了早中新世罗斯海的海岸（谢里登布拉夫；20.1 Ma）；以及更厚、体积更大的冰块（以厄尔利山的火山活动为代表；19.31 Ma）。还表明了冰退缩的中间阶段（大约17Ma），此时东南极冰盖再次退缩到横贯南极山脉后面。它以通过航空地球物理学远程识别的冰下火山中心为代表，并且仅作为冰川不稳定物进行采样。 c处相关的冰盖。 17 Ma 的地表海拔相对较低，但与覆盖邻近山脉的薄冰穹顶交汇。尽管冰缘可能没有延伸到罗斯海沿岸，但一些冰川将冰山注入罗斯海。厄尔利山火山中心所指示的大冰盖是 19.31 ± 0 发生的重大冰川事件的唯一已知物理记录。32 Ma（‘早期冰川’）。在另外两个火山地点检查的记录对应于南极洲冰层大幅减少期间的喷发，其中 20.1 ± 0.4 Ma 的喷发最为引人注目（“谢里登布拉夫间冰期”）。冰盖厚度和范围极端变化的原因尚不确定，但它们发生在大气二氧化碳成分快速波动的时期。尽管米兰科维奇天文强迫也可能发挥了重要作用，但结果表明，在温暖的早中新世期间，东南极冰盖极易受到相对较小的二氧化碳变化的影响。