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.

在下一个资助期间，我的研究计划将集中在加拿大沿海沃茨（加拿大北极和圣劳伦斯系统）被人为CO2酸化的机制。我们将确定相对于文石和方解石的饱和深度在水柱中上升的速度，以及全球海洋如何，在哪里以及何时通过溶解富含CaCO 3的沉积物来应对或减轻这种环境压力。 海洋是地球上最大的二氧化碳储存库，因此，将吸收大部分人类排放到大气中的二氧化碳。富含CaCO 3的沉积物将最终中和大部分人为排放到海洋中的CO2。中和这种CO2所需的时间取决于CO2从表层海洋到深海的转移速率以及底栖CaCO 3的溶解动力学。为了预测溶解发生的时间尺度，我们需要准确地知道溶解动力学。我们通过实验确定，富方解石沉积物的溶解速率与上覆底层水的欠饱和度呈线性关系。这一发现挑战了方解石溶解速率遵循更高阶动力学的当前范例（3至4）。为了将我们的工作扩展到现场条件，我们设计了一个圆盘反应器，使我们能够准确地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（孔隙度）变量以及各种碳酸盐矿物（文石，镁方解石）和生物材料对碳酸盐溶解动力学的影响。鉴于溶解动力学，我们已经记录（水侧扩散控制）和溶解速率之间的关系，饱和状态，碳酸盐沉积物含量，并在沉积物-水界面的流体动力学，我们将能够开发一个全球模型来预测在哪里和多快深海将响应入侵的人为CO2在各种排放情景下。最后，我们将比较我们的结果与经历过去的温室期/事件的古代碳酸盐沉积物的矿物学和地球化学。后一项研究应该揭示现在的海洋是否像过去一样对酸化做出反应，它的反应有多快，以及从这些事件中完全恢复需要多长时间。 结合其他压力，如全球变暖和富营养化，海洋酸化影响碳酸盐分泌生物的生态（例如，颗石藻、翼足类、双壳类、珊瑚）以及非钙化生物。这是因为pH值在调节生理过程中起着关键作用，如生长，招聘和捕食。持续的海洋酸化可能会影响海洋生态系统的结构，海洋食物链，并威胁到我们自己的粮食安全。