Marine sediments and seafloor nutrient cycling in a changing Arctic

沉积物是所有海洋生态系统的关键组成部分。在海洋沉积物中，颗粒物质的沉积以及上覆水柱中溶解物质的扩散，加剧了生物地球化学过程的动态相互作用。这种相互作用转化了沉积物的很大一部分，因此，将营养物质，溶解的无机碳和碱度重新注入水柱。这些底栖生物循环通量可对中上层初级生产力和海洋酸化产生重要影响，过去的研究表明，在北极大陆架，底栖生物和中上层生物过程之间的耦合作用特别强烈。除其他因素外，北冰洋的温度和海冰范围，以及沉积通量、底层水条件和生物扰动等，都受到强烈的季节性和长期波动的影响。尽管对海洋生态系统很重要，但北极海底对这种强烈的季节性和长期波动的反应仍然没有得到充分的研究，本项目的目的是确定在季节性和气候相关时间尺度上北冰洋波动环境条件下海底生物地球化学过程和通量的时间和幅度的最重要控制因素。学生将使用反应传输模型（RTMs），通过进行全面的敏感性研究，并通过进行完全瞬态模拟和模型相互比较来探索这一挑战。学生还将能够使用从北极和其他高纬度实地考察中收集的样本生成自己的地球化学记录，以便进行数据模型比较研究。

Sediments are key components of all marine ecosystems. In marine sediments, a dynamic interplay of biogeochemical processes is fuelled by the deposition of particulate material, as well as the diffusion of dissolved species from the overlying water column. This interplay transforms a substantial part of the deposited material and, thus, recycles nutrients, dissolved inorganic carbon, and alkalinity back into the water column. These benthic recycling fluxes can exert an important influence on pelagic primary production and ocean acidification.Past research has indicated that the coupling between benthic and pelagic processes is particularly intense on Arctic shelves. The Arctic Ocean is subject to strong seasonal to long-term fluctuations in, among other factors, temperature and sea-ice extent and, so, deposition fluxes, bottom water conditions and bioturbation. Despite its importance for marine ecosystems, the benthic response to such strong seasonal and long-term fluctuations in the Arctic remains underexplored.The aim of this project is to identify the most important controls on the timing and magnitude of benthic biogeochemical processes and fluxes under fluctuating environmental conditions in the Arctic Ocean on both seasonal and climate relevant timescales. The student will use Reaction-Transport Models (RTMs) to explore this challenge by conducting comprehensive sensitivity studies and by carrying out fully transient simulations and model inter-comparisons. The student will also be able to generate their own geochemical records using samples collected in the field from Arctic and other high-latitude field expeditions, in order to carry out a data-model comparison study.