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。

基本信息

批准号：
RGPIN-2018-04421
负责人：
Mucci, Alfonso
金额：
$ 3.13万
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：
2020
资助国家：
加拿大
起止时间：
2020-01-01 至 2021-12-31
项目状态：
已结题

来源：
https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=712590
关键词：
Mechanisms rate anthropogenic CO2 uptake

项目摘要

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.

在下一个资助期内，我的研究项目将重点研究加拿大沿海水域（加拿大北极和圣劳伦斯系统）被人为二氧化碳酸化的机制。我们将确定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、在何处以及何时通过溶解富含碳酸钙的沉积物来响应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为排放到大气中的二氧化碳。富含碳酸钙的沉积物最终将中和大部分人为排放到海洋的二氧化碳。中和二氧化碳所需的时间取决于二氧化碳从表层海洋转移到深海的速率以及底栖碳酸钙的溶解动力学。为了预测溶解发生的时间尺度，我们需要准确地了解溶解动力学。我们通过实验确定，富含方解石沉积物的溶解速率与上覆底层水的欠饱和程度呈线性变化。这一发现挑战了方解石溶解速率遵循高阶动力学（3 至 4）的当前范式。为了将我们的工作扩展到现场条件，我们设计了一个转盘反应器，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（孔隙度）变量以及各种碳酸盐矿物学（文石、镁方解石）和生物材料对碳酸盐溶解动力学的影响。鉴于我们记录的溶解动力学（水侧扩散控制）以及我们将阐明的溶解速率、饱和状态、碳酸盐沉积物含量和沉积物-水界面的流体动力学之间的关系，我们将能够开发一个全局模型预测在各种排放情景下深海对人为二氧化碳入侵的反应地点和速度。最后，我们将我们的结果与经历过过去温室时期/事件的古代碳酸盐矿床的矿物学和地球化学进行比较。后一项研究应该揭示当前的海洋是否像过去那样对酸化做出反应，反应的速度有多快，以及从这些事件中完全恢复需要多长时间。与全球变暖和富营养化等其他压力相结合，海洋酸化影响碳酸盐分泌生物（例如颗石藻、翼足类、双壳类、珊瑚）以及非钙化生物的生态。这是因为 pH 在调节生长、补充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，并威胁我们自身的粮食安全。