Reverse and Submarine Weathering in Glacially Influenced Arctic Fjords

当矿物颗粒到达海底时，它们经常经历生物或化学转化，将它们变成新的矿物相，并导致从周围海水中吸收或释放元素。其中一组反应涉及硅酸盐矿物，它由二氧化硅、氧和一系列其他元素组成，如铁和铝。这些海底反应很重要，因为它们会影响海洋的化学成分及其ph值。在这个项目中，我们的目标是研究北极峡湾的这些反应。峡湾是长而窄的海洋入口，是由冰川在过去的地形上移动而形成的。如今，许多峡湾的内端仍有冰川，这些冰川将融水和沉积物输送到峡湾水域。气候变化导致这些冰川迅速融化。我们感兴趣的是了解正在发生的特定硅酸盐矿物反应，它们吸收或释放什么元素，以及气候变化如何影响这些过程。我们将为这个项目从斯瓦尔巴群岛的kongsjorden收集海底沉积物样本，并使用一系列化学方法进行分析。此外，我们将进行实验室孵化研究，将海洋藻类形成的硅酸盐矿物添加到峡湾沉积物中，观察它们会发生什么变化。在很长的时间尺度上，河流和热液喷口向海洋输入的主要元素和次要元素必须通过海洋领域中这些元素的去除机制来平衡，以便海洋化学保持相对恒定。一个长期争论的过程是将海洋海底沉积物中的元素隔离并影响海水pH值的反向风化作用，它涉及将硅藻等生物源二氧化硅转化为新的硅酸盐（粘土矿物）。这一过程的许多方面仍然未知，如反应速率和产物，以及全球分布。以前对这一过程的研究主要集中在热带沿海海洋系统。沿海极地地区，包括受冰川影响的峡湾，可能是逆风化的另一个热点，因为它们接受了大量关键“成分”的输入：生物硅和活性铁和氧化铝矿物。与此同时，气候变化推动了北极冰川的退缩，预计将强烈改变这些峡湾的沉积物输送和碳循环。该项目将填补我们在沉积物中涉及硅酸盐矿物的反应途径和产物的知识方面的关键空白，以及这些过程对冰川影响峡湾海水中溶解离子的去除的影响。我们将在斯瓦尔巴群岛的kongsjorden收集沉积物样本，并使用一系列地球化学技术对其进行分析。此外，我们将使用硅藻体和峡湾沉积物进行孵化研究。本研究结果将有助于准确地约束快速变化的北极沿海环境中气候变化对更大规模海洋过程的可能影响，并构建未来海洋元素循环和生物地球化学响应的预测模型。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

When mineral particles reach the ocean floor, they often undergo biological or chemical transformations that turn them into new mineral phases and also result in the uptake from or release of elements to the surrounding seawater. One set of these reactions involve silicate minerals, which are composed of silica and oxygen and a range of other elements, such as iron and aluminum. These seafloor reactions are important because they affect the chemical composition of the ocean and its pH. In this project, we aim to study these reactions in Arctic fjords. Fjords are long, narrow ocean inlets that were formed by glaciers moving over the landscape in the past. Many fjords still have glaciers located at their inner end today which deliver meltwater and sediment to fjord waters. Climate change is resulting in the rapid melting of these glaciers. We are interested in understanding the specific silicate mineral reactions that are occurring, what elements they are taking up or releasing, and how climate change may affect these processes. We will collect seafloor sediment samples for this project from Kongsfjorden, Svalbard, and analyze them using a range of chemical methods. Additionally, we will carry out laboratory incubation studies where we will add silicate minerals formed by ocean algae to fjord sediments and observe what happens to them. Over long time scales, the inputs of major and minor elements to the ocean by rivers and hydrothermal vents has to be balanced by removal mechanisms of these elements in the marine realm in order for ocean chemistry to remain relatively constant. A long-debated process that sequesters elements in ocean seafloor sediments and affects seawater pH is reverse weathering which involves the transformation of biogenic silica, such as diatom frustules, to new silicate (clay) minerals. Many aspects of this process still remain unknown, such as reaction rates and products, and global distribution. Previous studies of this process have focused mainly on tropical coastal ocean systems. Coastal polar regions, including glacially influenced fjords, likely represent another hotspot of reverse weathering because they receive high inputs of key “ingredients”: biogenic silica and reactive iron and aluminum oxide minerals. At the same time, climate change drives the retreat of Arctic glaciers and is expected to strongly modify sediment delivery to and carbon cycling in these fjords. This project will fill key gaps in our knowledge of the pathways and products of the reactions involving silicate minerals in sediments and the impacts of these processes on the removal of dissolved ions from seawater in glacially influenced fjords. We will collect sediment samples for this project from Kongsfjorden, Svalbard, and analyze them using a range of geochemical techniques. Additionally, we will carry out incubation studies using diatom frustules and fjord sediments. The outcomes of this study will help accurately constrain the possible impacts that climate change in rapidly changing Arctic coastal environments has on larger scale oceanic processes and construct predictive models of elemental cycling and biogeochemical responses in the future ocean.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.