Emergence of the Southeast Asian islands as a driver for Neogene cooling
Emergence of the Southeast Asian islands as a driver for Neogene cooling
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DOI：
10.1073/pnas.2011033117
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发表时间：
2020-09
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影响因子：
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通讯作者：
Yuem Park;P. Maffre;Y. Goddéris;F. Macdonald;E. Anttila;N. Swanson‐Hysell
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文献类型：
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作者：
Yuem Park;P. Maffre;Y. Goddéris;F. Macdonald;E. Anttila;N. Swanson‐Hysell
意义 东南亚岛屿是当今通过硅酸盐风化消耗二氧化碳的热点地区。自大约 1500 万年前以来，这些岛屿的面积一直在增大，同时地球气候也在变冷。在这里，我们检验了这样的假设：全球变冷可能是由东南亚岛屿的构造出现驱动的。通过对古海岸线的汇编，结合硅酸盐风化和气候模型，我们发现这种出现与 pCO2 的大幅下降有关。如果没有热带岛屿古地理的这些变化，过去 300 万年里就不会有巨大的北半球冰盖作为地球气候的决定性特征。陡峭的地形、热带气候和镁铁质岩性有助于东南亚岛屿有效的化学风化和碳封存。自中新世中期以来，巽他-班达弧系与澳大利亚之间持续不断的弧-大陆碰撞增加了该地区暴露于地面的土地面积。与此同时，自中新世气候最适期以来，地球气候已经变冷，导致南极冰盖的增长和北半球冰川的开始。我们试图评估东南亚岛屿的出现通过增加全球耐候性在推动这种降温趋势方面发挥了重要作用的假设。为此，我们编制了古海岸线数据并将其纳入 GEOCLIM，后者将全球气候模型与具有空间分辨岩性的硅酸盐风化模型结合起来。我们发现，如果新近纪上东南亚岛屿的面积没有增加，大气中的二氧化碳浓度将显着高于工业化前的值，仍然高于北半球冰盖形成所需的水平。
Significance The Southeast Asian islands are a modern-day hotspot of CO2 consumption via silicate weathering. Since ∼15 million years ago, these islands have been increasing in size at the same time that Earth’s climate has been cooling. Here, we test the hypothesis that this global cooling could have been driven by tectonic emergence of the Southeast Asian islands. Using a compilation of paleoshorelines, in conjunction with a coupled silicate weathering and climate model, we find that this emergence is associated with a large decrease in pCO2. Without these changes in tropical island paleogeography, there would not have been large Northern Hemisphere ice sheets as a defining feature of Earth’s climate over the past 3 million years. Steep topography, a tropical climate, and mafic lithologies contribute to efficient chemical weathering and carbon sequestration in the Southeast Asian islands. Ongoing arc–continent collision between the Sunda-Banda arc system and Australia has increased the area of subaerially exposed land in the region since the mid-Miocene. Concurrently, Earth’s climate has cooled since the Miocene Climatic Optimum, leading to growth of the Antarctic ice sheet and the onset of Northern Hemisphere glaciation. We seek to evaluate the hypothesis that the emergence of the Southeast Asian islands played a significant role in driving this cooling trend through increasing global weatherability. To do so, we have compiled paleoshoreline data and incorporated them into GEOCLIM, which couples a global climate model to a silicate weathering model with spatially resolved lithology. We find that without the increase in area of the Southeast Asian islands over the Neogene, atmospheric pCO2 would have been significantly higher than preindustrial values, remaining above the levels necessary for initiating Northern Hemisphere ice sheets.