Accelerated carbon dioxide release from sedimentary rocks in a warming world

在变暖的世界中沉积岩加速二氧化碳释放

• 批准号: NE/Y000838/1
• 负责人: Robert Hilton
• 金额: $ 103.35万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FY000838%2F1
• 关键词: Accelerated; carbon; dioxide; release; sedimentary

Rocks contain a vast store of carbon locked in the ancient remains of plants and animals. In the upper metre of Earth's surface alone, there is estimated to be more than 1000 billion tonnes of carbon in rocks, which is similar to the amount of carbon found in plants alive today and more than is present in the atmosphere. Weathering processes, which break down rocks into pieces and result in chemical reactions, can release this carbon stored in rocks back to the atmosphere as carbon dioxide (CO2), a greenhouse gas that controls global temperature. Until recently, the stores of carbon in rocks were considered to be relatively unreactive, and thus viewed as a stable store of carbon. However, a new method developed by the team has directly measured CO2 emissions from rock weathering for the first time. This work shows that weathering can release CO2 rapidly, and that the rates of CO2 release increase with temperature. In addition, there is evidence that in mountain locations, the retreat of glaciers can expose these ancient carbon-containing minerals to weathering processes. This provides another link between climate warming and release of CO2 from rocks to the atmosphere.These recent findings lead us to question how the Earth's long term carbon cycle operates. Traditionally, chemical weathering of rocks is viewed as a CO2 sink via the weathering of silicate minerals. This process increases CO2 drawdown as temperature warms - a so called "negative feedback". However, it appears that weathering of sedimentary rocks acts in the opposite direction, raising fundamental questions on what controls the trajectory of atmospheric CO2 over Earth's history. In addition, the release of CO2 to the atmosphere from rock weathering may increase over the coming century. While the global fluxes are modest compared to fossil fuel CO2 emissions, they are currently very poorly constrained and will eat into our remaining carbon budget.This ambitious proposal will establish how CO2 emissions from sedimentary rock weathering respond to climate change. To do this, we will use the newly-devised methods to quantify CO2 release and assess how it changes with temperature. We will focus on areas of sedimentary rock exposure caused by melting glaciers. These areas, and rates of exposure over time, will be assessed in terms of the exposed rock types, elevations and land surface form. Having selected the best field areas to sample, we will use a combination of two novel approaches to quantify weathering of sedimentary rocks and CO2 release. Direct CO2 measurements will be made where rocks are exposed. Radiocarbon will be used to fingerprint the sources of CO2. In parallel, larger areas will be investigated by measuring the chemistry of streams and rivers, using novel trace element and isotope proxies to identify reactions and quantify CO2 fluxes. When combined with experiments in the laboratory, we will be able to assess how rock weathering is enhanced by climate change. We will use models to explore how this process may have controlled CO2 in the past, and also assess how the weathering of sedimentary rocks may impact the net carbon budget over the coming century. Only with this information of how the natural carbon cycle will respond can we best establish the most effective and feasible solutions to help mitigate the impacts of rising atmospheric CO2 concentrations.

岩石含有大量的碳，这些碳被锁定在植物和动物的古老遗迹中。仅在地球表面的上层仪表中，岩石中估计有超过1000亿吨的碳，这与当今活着的植物中发现的碳量相似，并且比大气中的碳含量超过。风化过程将岩石分解成碎片并导致化学反应，可以释放出将这种碳储存在岩石中，回到大气中，作为二氧化碳（CO2），这是一种控制全球温度的温室气体。直到最近，岩石中的碳存储被认为是相对不反应的，因此被视为稳定的碳储存。但是，团队开发的一种新方法已直接测量了首次从岩石风化中测量的二氧化碳排放。这项工作表明，风化可以快速释放CO2，并且二氧化碳释放速率随温度而增加。此外，有证据表明，在山区，冰川的撤退可以使这些古老的含碳矿物暴露于风化过程中。这提供了气候变暖与从岩石到大气的二氧化碳释放之间的另一个联系。这些发现使我们质疑地球的长期碳循环是如何运作的。传统上，岩石的化学风化被视为硅酸盐矿物质的风化。随着温度的温暖，此过程增加了二氧化碳的下降 - 一种所谓的“负反馈”。然而，似乎沉积岩的风化朝相反的方向起作用，提出了关于控制大气二氧化碳在地球历史上的轨迹的基本问题。此外，在岩石风化中将二氧化碳释放到大气中可能会在未来世纪增加。尽管与化石燃料二氧化碳排放相比，全球通量是适度的，但目前它们的限制非常差，并且会吞噬我们剩余的碳预算。这一雄心勃勃的提议将确定沉积岩石风化的二氧化碳排放如何对气候变化做出反应。为此，我们将使用新验证的方法来量化CO2释放并评估其随温度变化的变化。我们将重点关注由融化冰川引起的沉积岩石暴露区域。这些区域以及随时间的暴露率将根据裸露的岩石类型，高程和地表形式进行评估。选择了最佳的采样场所，我们将使用两种新型方法的组合来量化沉积岩和二氧化碳释放的风化。将在暴露岩石的情况下进行直接的二氧化碳测量。放射性碳将用于指示CO2的来源。同时，将使用新颖的痕量元素和同位素代理来识别反应并量化二氧化碳通量，从而通过测量流和河流的化学方法来研究较大的区域。当与实验室中的实验结合使用时，我们将能够评估气候变化如何增强岩石风化。我们将使用模型来探讨过去如何控制CO2，并评估沉积岩的风化如何影响未来世纪的净碳预算。只有了解自然碳循环将如何做出响应的信息，我们才能最好地建立最有效，最可行的解决方案，以帮助减轻大气中二氧化碳浓度上升的影响。