An Integrated Study of the Middle Miocene Climate Transition.

东南极冰盖在中新世中期，大约1400万年前完全形成。目前尚不清楚冰盖为什么会在这个时候增长，尽管人们认为冰盖的扩张是在200万到300万年之间“断断续续”发生的。这段时间被称为中中新世气候转变。地球化学记录显示，大气中的二氧化碳水平在气候转变后并没有明显低于以前。然而，这并不一定意味着这种重要的温室气体在地球历史上的这个关键时刻没有影响气候。事实上，海洋中碳同位素组成的巨大变化表明，在气候转型期间，全球碳循环发生了巨大变化，这与冰盖快速增长的间隔有关。该提案旨在确定大气中二氧化碳的水平是否在气候转型期间发生了变化，这与冰盖的突然增长和衰退有关。我们将构建二氧化碳趋势的记录（即，增加/减少二氧化碳）和海面温度。我们还将从不同的地点生成详细的地层，这将使我们能够将这些记录与冰量，深海温度和风化的其他记录联系起来。这将为中新世中期气候转变提供第一个真正完整的记录。这将提供关于南极冰盖形成的原因和影响的宝贵资料。这些记录应该能揭示气候转变的不稳定性。长期的气候转变似乎被气候改善和冰川消退的间隔所打断。在这种间隔期间运行的过程与我们对现代南极冰盖及其在未来全球变暖情景下的行为的理解直接相关。

The East Antarctic ice sheet became fully established in the middle Miocene, about 14 million years ago. It is not known why the ice sheet grew at this time, although it is believed that the ice sheet expansion happened in 'fits and starts', over 2 to 3 million years. This time interval is known as the middle Miocene climate transition. Geochemical records show that levels of atmospheric carbon dioxide were not noticeably lower after the climate transition than before. However, this does not necessarily imply that this important greenhouse gas did not influence the climate at this crucial time in Earth's history. Indeed, large changes in the isotopic composition of carbon in the ocean suggest that there were large changes in the global carbon cycle associated with the intervals of rapid ice sheet growth within the climate transition. This proposal aims to determine whether levels of atmospheric carbon dioxide changed within the climate transition, in association with the bursts of ice sheet growth and decay. We will construct records of carbon dioxide trends (i.e., increasing/decreasing carbon dioxide) and sea surface temperatures. We will also generate detailed stratigraphies from different sites, which will enable us to link these records with other records of ice volume, deep sea temperatures and weathering. This will provide the first truly integrated record of the middle Miocene climate transition. This will provide valuable information on the causes and effects of the establishment of the Antarctic ice sheet. The records should shed light on the erratic nature of the climate transition. The long term climate transition appears to have punctuated by intervals of climatic amelioration and deglaciation. The processes operating during such intervals have direct relevance to our understanding of the modern day Antarctic ice sheet and its behaviour under future global warming scenarios.