Mechanisms and rate of anthropogenic CO2 uptake in Canadian coastal waters and the response of shallow and deep-ocean carbonate sediments to ocean acidification.

加拿大沿海水域人为二氧化碳吸收的机制和速率以及浅海和深海碳酸盐沉积物对海洋酸化的响应。

• 批准号: RGPIN-2018-04421
• 负责人: Mucci, Alfonso
• 金额: $ 6.27万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751016
• 关键词: Mechanisms; rate; anthropogenic; CO2; uptake

Over the next funding period, my research program will focus on the mechanisms by which Canadian coastal waters (Canadian Arctic and St. Lawrence system) are being acidified by anthropogenic CO2. We will determine how fast the saturation depths with respect to aragonite and calcite will rise in the water column, and how, where, and when the global ocean will respond to or mitigate this environmental stress through dissolution of CaCO3-rich sediments. The ocean is the largest reservoir of CO2 on Earth and, thus, will absorb much of the anthropogenic CO2 emitted to the atmosphere. CaCO3-rich sediments will ultimately neutralize most of the anthropogenic CO2 delivered to the ocean. The time required to neutralize this CO2 is predicated on the rate of transfer of CO2 from the surface ocean to the deep ocean as well as the dissolution kinetics of benthic CaCO3. To predict the timescale over which dissolution takes place, we need to know the dissolution kinetics accurately. We have determined experimentally that the dissolution rate of calcite-rich sediments varies linearly with the degree of undersaturation of the overlying bottom water. This finding challenges the current paradigm that the calcite dissolution rate follows higher order kinetics (3 to 4). To extend our work to in-situ conditions, we have designed a rotating-disk reactor that will allow us to accurately simulate the range of shear stresses encountered at the seafloor. We will investigate the effects of environmental (temperature, pressure) and lithological (porosity) variables as well as various carbonate mineralogies (aragonite, Mg-calcites) and biogenic materials on carbonate dissolution kinetics. Given the dissolution kinetics we have documented (water-side diffusion-controlled) and the relationships we will elucidate between dissolution rate, saturation state, carbonate sediment content, and hydrodynamics at the sediment-water interface, we will be able to develop a global model to predict where and how fast the deep-ocean will respond to the invasion of anthropogenic CO2 under various emission scenarios. Finally, we will compare our results with the mineralogy and geochemistry of ancient carbonate deposits that experienced past greenhouse periods/events. The latter study should reveal if the present ocean is responding to acidification as it did in the past, how fast it did so, and how long it took to fully recover from these events. In combination with other stresses, such as global warming and eutrophication, ocean acidification affects the ecology of carbonate-secreting organisms (e.g., coccolithophores, pteropods, bivalves, corals), as well as non-calcifiers. This is because pH plays a critical role in mediating physiological processes such as growth, recruitment, and predation. Ongoing ocean acidification may impact the structure of the marine ecosystem, the marine food chain, and threaten our own food security.

在下一个资金期间，我的研究计划将重点介绍加拿大沿海水域（加拿大北极和圣劳伦斯系统）的机制，该机制被人为的二氧化碳酸化。我们将确定在水柱中相对于文石和方解石的饱和深度的速度，以及通过富含CACO3的沉积物的溶解，全球海洋将如何，何时以及何时响应或何时缓解这种环境压力。 海洋是地球上二氧化碳的最大储层，因此，将吸收发射到大气中的大部分人为二氧化碳。富含CACO3的沉积物最终将中和大多数传递到海洋的人为二氧化碳。中和该二氧化碳所需的时间取决于二氧化碳从地面海洋到深海的转移速率以及底栖CACO3的溶解动力学。为了预测发生溶解的时间尺度，我们需要准确地了解溶解动力学。我们已经通过实验确定，富含方解石的沉积物的溶解速率随上覆底水的不饱和程度线性变化。这一发现挑战了有方解石溶解速率遵循高阶动力学的当前范式（3至4）。为了将工作扩展到原位条件，我们设计了一个旋转盘反应器，该反应器将使我们能够准确模拟海底遇到的剪切应力范围。我们将研究环境（温度，压力）和岩性（孔隙率）变量以及各种碳酸盐矿物质（aragonite，mg钙岩）和生物材料对碳酸盐溶解动力学的影响。鉴于我们已经记录了（水边扩散控制）的溶解动力学，以及我们将在沉积物 - 水界面上阐明溶解速率，饱和状态，碳酸盐沉积物含量和流体动力学之间的关系，我们将能够开发全球模型，以预测深度群体对人类侵害的侵害，以响应各种促进性毒素的侵害。最后，我们将将我们的结果与过去经历过温室时期/事件的古碳酸盐沉积物的矿物学和地球化学进行比较。后一项研究应揭示当前的海洋是否像过去一样对酸化作出反应，它的速度以及从这些事件中完全恢复的时间需要多长时间。 结合其他应力（例如全球变暖和富营养化），海洋酸化会影响碳酸盐分泌生物的生态（例如，cocolithophores，pteropods，pteropods，bivalves，bootalves，corals）以及非cal虫。这是因为pH在介导生长，募集和捕食等生理过程中起着至关重要的作用。持续的海洋酸化可能会影响海洋生态系统，海洋食物链的结构，并威胁我们自己的粮食安全。