PIRE: DUST stimulated drawn-down of atmospheric CO2 as a trigger for Northern Hemisphere Glaciation

了解过去5000万年（myr）长期全球变冷背后的地质过程对于了解当今地球的气候条件非常重要。北半球在4万年前基本上是无冰的，随后在约3.6万年前全球温度下降加速，在约2.7万年前北半球大陆上形成大陆冰盖。有限的大气二氧化碳记录表明，在这段时间内，二氧化碳浓度从百万分之400下降到百万分之300，足以使地球冷却，使冰盖得以生长。然而，二氧化碳排放量下降的原因尚不清楚。这项由7个美国机构和3个中国机构组成的国际研究和教育合作将评估一个新的假设：来自中亚沙漠的大气尘埃为北太平洋提供了养分，刺激了藻类的繁殖，进而减少了大气中的二氧化碳，导致了北半球的冰川作用（NHG）。通过在中国的实地考察、对海洋和陆地沉积物的实验室分析以及大气和海洋模型研究，研究人员和学生将生成并比较来自不同地质档案的广泛古气候记录，以评估NHG开始时大气尘埃在二氧化碳下降和全球降温中的作用。这项研究项目的发现可能最终有助于形成具有全球政策影响的知识。通过评估大气尘埃在维持地球凉爽气候条件中的重要性，本研究有望阐明最近地质历史中气候冷却的机制。明确本研究将建立的记录:1)aridification中亚的历史,西藏北部和中国黄土高原(CLP)相关记录的变形和表面隆起高亚洲内部和这些地区的西部,2)风蚀中亚盆地和灰尘积累在CLP, 3)粉尘通量,藻类生产力,和海洋表面温度在北太平洋和南大西洋,和4)陆地二氧化碳的区间4.5 - -2.5 Ma。模拟和敏感性研究将(1)评估亚洲气候和沙尘循环对地形变化和背景全球气候的敏感性；(2)确定上新世尘埃向北太平洋输送可能导致的降温量；(3)评价亚洲扬尘对大气CO2的潜在影响。通过这一研究项目，美国研究生将有机会进入中国的研究设施和实地地点，否则将无法进入，并通过双边访问与中国合作伙伴进行互利的合作研究活动；美国本科生也将有机会参加暑期学校、研讨会和研究项目；调查人员将为博物馆开发外联工具，以提高公众对大气尘埃在气候变化中的作用的理解。

Understanding the geologic processes underlying the long-term global cooling over the past 50 million years (myr) is important for understanding the climate conditions on Earth today. The Northern Hemisphere was largely ice-free 4 myr ago followed by an acceleration of global temperature decline at ~3.6 myr ago, with continental ice sheets developing on northern hemisphere continents by ~2.7 myr ago. Limited atmospheric CO2 records suggest a decline in CO2 from ~400 to ~300 parts per million by volume (ppmv) during that time period could have cooled the Earth sufficiently to enable ice sheets to grow. Yet the cause for this decline in CO2 remains unknown. This international research and educational collaboration between 7 U.S. and 3 Chinese institutions will evaluate a new hypothesis: atmospheric dust derived from Central Asian deserts fertilized the North Pacific ocean, stimulating algal productivity, which in turn drew down atmospheric CO2 leading to Northern Hemisphere Glaciation (NHG). Through field work studies in China, laboratory analyses of ocean and terrestrial sedimentary deposits, and atmospheric and ocean modeling studies, the investigators and students will generate and compare a wide range of paleoclimate records from diverse geological archives to evaluate the role of atmospheric dust in CO2 decline and global cooling at the onset of NHG. The findings from this research project may ultimately contribute to knowledge with global policy implications.By evaluating the significance of atmospheric dust in sustaining cool climate conditions on Earth, this study is expected to elucidate the mechanisms of climate cooling in the recent geologic past. Specifically this study will establish records of: 1) the aridification history of Central Asia, northern Tibet, and the Chinese Loess Plateau (CLP) as related to records of deformation and surface uplift in high Asia within and to the west of these regions, 2) wind erosion of Central Asia basins and dust accumulation in the CLP, 3) dust flux, algal productivity, and sea surface temperature in the North Pacific and South Atlantic, and 4) terrestrial CO2 in the interval of 4.5-2.5 Ma. Modeling and sensitivity studies will (1) evaluate the sensitivity of Asian climate and the dust cycle to the growth of topography and to the background global climate; (2) determine the amount of cooling that could result from Pliocene dust transport to the North Pacific; (3) evaluate the potential influence of Asian dust on atmospheric CO2. Through this research program, US graduate students will gain access to research facilities as well as field localities in China that would otherwise be inaccessible and engage in mutually beneficial collaborative research activities with Chinese partners via bilateral visits; US undergraduate students will also have the opportunity to participate in summer schools, workshops, and research projects; the investigators will develop outreach tools for museums to increase public understanding of the role of atmospheric dust in climate change.