Carbon microcycle: CO2 gradients in the ocean surface (CµC)

碳酸盐岩体系在海洋生物地球化学循环中起着关键作用。它是海洋和大气之间二氧化碳交换的核心，因此，它决定了大气中温室气体的负担和海洋酸化的程度。然而，碳酸盐岩体系的研究忽略了海洋水柱上5m的部分，包括其最上层——海表面微层。这是因为来自研究船和玫瑰花结采样器的干扰不允许在不破坏其完整性的情况下对该区域进行采样。我建议研究海洋表层（5米以上）的碳酸盐系统和二氧化碳分压梯度，可能是由生物和物理过程驱动的。微层与大气直接接触，我假设微层中二氧化碳的分压决定了“真实的”海气通量，即与基于5米数据的通量进行比较。我将采用最先进的研究双体船，在海洋表面和微层中以高分辨率就地测量碳酸盐系统的参数。在受控罐实验中，我将评估用于测量微层和相邻底层薄层中气体的既定采样技术的不确定性，以便相应地修改采样策略。我将利用改进后的双体船和一个自主浮动舱来测量现场二氧化碳通量，参加一次前往南太平洋的考察，收集实地数据，研究近地表二氧化碳分压梯度的形成。有了高分辨率的数据，我将能够提供对地表梯度形成的机制理解，并确定主要的潜在环境力。结果将提供基于近地表和微层水pCO2值的大气-海洋CO2通量，以及通过计算底层水团的通量而产生的偏差。总的来说，这个项目将支持未来对与气候有关的气体的全球海气通量的评估。此外，我将为欧洲航天局提供第一个具有足够分辨率的数据库，以调查是否可以通过卫星任务在全球范围内监测碳酸盐系统。

The carbonate system has a pivotal role in marine biogeochemical cycles. It is central to the exchange of CO2 between the ocean and atmosphere, and, therefore, determines the atmospheric burden with greenhouse gases and the extent of ocean acidification. However, research of the carbonate system has ignored the upper 5 m of the ocean’s water column, including its uppermost top, the sea-surface microlayer. This is because interferences from research vessels and rosette samplers do not allow sampling of this zone without disturbing its integrity.I propose to investigate the carbonate system and pCO2 gradients in the surface ocean (upper 5 meters), potentially driven by biological and physical processes. The microlayer is in direct contact with the atmosphere, and I hypothesize that partial pressures of CO2 in the microlayer determine “real” air-sea fluxes, i.e. compared to fluxes based on data from 5 meter. I will adapt a state-of the-art research catamaran to measure parameters of the carbonate system in situ in the surface ocean and in the microlayer at high resolution. In controlled tank experiments, I will assess uncertainties of established sampling techniques for measurements of gases in the microlayer and adjacent underlying thin layers, in order to modify the sampling strategy accordingly. With the modified catamaran and an autonomous floating chamber measuring in situ CO2 fluxes, I will participate in an expedition to the south Pacific to collect field data and to investigate the formation of near-surface pCO2 gradients. With data at high resolutions, I will be able to provide a mechanistic understanding on the formation of surface gradients and determine the main underlying environmental forces. Results will provide air-sea CO2 fluxes based on near-surface and microlayer aqueous pCO2 values, and biases by computing fluxes from underlying water masses. Overall, this project will support future assessment of global air-sea fluxes of climate-relevant gases. In addition, I will provide a first data base with sufficient resolution to the European Space Agency to investigate if the carbonate system can be monitored on a global scale from satellite missions.