FESD Type I Proposal: Continent-island arc fluctuations: Linking deep Earth dynamics to long-term climate

FESD I 类提案：大陆岛弧波动：将地球深层动力学与长期气候联系起来

• 批准号: 1338842
• 负责人: Cin-Ty Lee
• 金额: $ 421万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1338842&HistoricalAwards=false
• 关键词: FESD; Type; Proposal; Continent; island

The over-arching theme of this study is to better understand what drives long-term climate change, specifically oscillations between greenhouse and icehouse states over timescales of 100 My. These climatic oscillations, integrated over Earth?s history, profoundly influenced the evolution of life and the surface of the Earth. To first order, variations in the CO2 budget of the ocean-atmosphere-biosphere system drive climatic variation over timescales greater than 10 My: because of the greenhouse effect of CO2 in the atmosphere, Earth?s surface temperature warms when atmospheric CO2 is high and cools when CO2 levels are low, all other variables (like albedo) being equal. The C content of the Earth?s exogenic system, over long timescales, is controlled by volcanic inputs from the Earth?s interior and outputs from the exogenic system via sediment burial and subduction. Long-term climate variability is thus intimately linked to whole Earth carbon cycling, that is, the cycling of C between the endogenic and exogenic systems. Exactly how and why these inputs and outputs have changed through time is the question. This study will focus on the most recent greenhouse-icehouse transition. This begins with the Cretaceous to early Cenozoic (150-60 My) greenhouse interval when dinosaurs roamed the Earth, atmospheric CO2 pressure was possibly 4-8 times higher than today, polar ice caps were absent, and much of Earth?s economically viable hydrocarbon source rocks were generated. In contrast, the mid-Cenozoic (~55 My to present) was characterized by cooler surface temperatures, polar ice sheets, lower atmospheric CO2, and the proliferation of mammals. We will evaluate a number of hypotheses for elevated CO2 during the Cretaceous. These include enhanced carbonate subduction and subsequent output of CO2 through arc volcanoes, enhanced oceanic crust production, and an increase in the frequency of episodic flood basalts. In particular, we will also explore a new hypothesis that CO2 inputs into the exogenic system are strongly influenced by secular changes in the nature of subduction zone volcanoes. During periods of enhanced continental arc activity, carbonate sediments stored on the continents over Earth?s history, are magmatically liberated, whereas during periods dominated by island arc activity the CO2 inputs return to baseline levels because of the smaller volumes of carbonates in the oceanic upper plate. The transition from Cretaceous greenhouse to mid-Cenozoic icehouse conditions may have coincided with a decline in the number of continental arc volcanoes, suggesting that there may also be a mechanism driving long term oscillations between the nature of subduction zones. The goal of this study is to evaluate the relative importance of all these potential sources of CO2 so that a more complete model of the whole Earth carbon cycle can be developed. We are specifically interested in how deep Earth dynamics modulates these sources of CO2. To test these hypotheses and place bounds on each of these processes, we have assembled an interdisciplinary team to quantify the stability of carbonates in the shallow crust and in the deep parts of subduction zones, map out how the distribution of arc volcanoes and the extent of magmatic decarbonation has changed through time, quantify global volcanic inputs of CO2, and develop a model for long-term climate evolution coupled to the cycling of C between the deep Earth and the exogenic system.

这项研究的架构主题是更好地了解是什么导致了长期气候变化的原因，特别是在100 MY的时间尺度上，温室和Icehouse国家之间的振荡。 这些气候振荡在地球历史上融为一体，深刻影响了生命的演变和地球表面。 首先，海洋 - 大气 - 双层层系统的二氧化碳预算变化驱动大于10 my的时间尺度上的气候变化：由于二氧化碳在大气中的温室效应，当二氧化碳水平很低时，大气表面温度较高，而大气中的二氧化碳则变暖，其他变量（如ARDOABLES）是相等的。 地球的C含量在长时间的尺度上，由地球内部的火山输入控制，并通过沉积物埋葬和俯冲从外来源系统输出。 因此，长期气候变异性与整个地球碳循环密切相关，即内源性和外源系统之间C的循环。 这些输入和输出随着时间的流逝而发生的方式和原因是问题。这项研究将侧重于最新的温室冰屋过渡。 这始于恐龙漫游地球时的白垩纪至早期的新生代（150-60 MY）温室间隔，大气中的二氧化碳压力可能比今天高4-8倍，没有极地冰盖，地球上的大部分经济上可行的碳氢化合物源是产生的。相比之下，中元（〜55我的目前）的特征是表面温度较低，极性冰盖，低大气二氧化碳和哺乳动物的增殖。 我们将评估白垩纪期间二氧化碳升高的许多假设。其中包括增强的碳酸盐俯冲以及随后通过弧火山的二氧化碳输出，增强的海洋壳产生以及发作性洪水盆地的频率增加。特别是，我们还将探讨一个新的假设，即二氧化碳输入到外来源系统中受到俯冲带火山性质的世俗变化的强烈影响。在增强的大陆弧活性的时期，碳酸盐沉积物存储在地球历史上，岩浆式释放，而在岛弧活动主导的时期，二氧化碳的输入返回基线水平，因为海洋上层板中的碳酸盐量较小。 从白垩纪温室到中期冰屋中的过渡可能与大陆弧火山的数量减少相吻合，这表明也可能存在一种机制，促进了俯冲带的性质之间的长期振荡。 这项研究的目的是评估所有这些潜在二氧化碳来源的相对重要性，以便可以开发出整个地球碳循环的更完整的模型。 我们对深层动力学如何调节CO2的来源特别感兴趣。 To test these hypotheses and place bounds on each of these processes, we have assembled an interdisciplinary team to quantify the stability of carbonates in the shallow crust and in the deep parts of subduction zones, map out how the distribution of arc volcanoes and the extent of magmatic decarbonation has changed through time, quantify global volcanic inputs of CO2, and develop a model for long-term climate evolution coupled to the在深地球和外部系统之间循环C。