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

碳酸盐系统在海洋生物地球化学循环中具有关键作用。它是海洋和大气之间二氧化碳交换的核心，因此决定了大气中温室气体的负担和海洋酸化的程度。然而，对碳酸盐系统的研究忽略了海洋水柱的上部5米，包括其最高顶部，海面微层。这是因为研究船和玫瑰花采样器的干扰不允许在不破坏其integrity.I的采样区建议调查的碳酸盐系统和二氧化碳分压梯度在海洋表层（上5米），可能驱动的生物和物理过程。微层与大气直接接触，我假设微层中的CO2分压决定“真实的”海气通量，即与基于5米数据的通量相比。我将采用最先进的研究双体船，以高分辨率测量表层海洋和微层中碳酸盐系统的原位参数。在受控水槽实验中，我将评估既定的采样技术的测量气体的微层和相邻的底层薄层的不确定性，以修改相应的采样策略。与修改后的双体船和自主浮动室测量原位CO2通量，我将参加远征南太平洋收集现场数据，并调查近地表pCO2梯度的形成。有了高分辨率的数据，我将能够对表面梯度的形成提供一个机械的理解，并确定主要的潜在环境力量。结果将提供海气CO2通量的基础上近地表和微层水pCO2值，并通过计算通量从底层水体的偏见。总的来说，该项目将支持今后对与气候有关的气体的全球海气通量进行评估。此外，我将向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.