The influence of the SML on trace gas biogeochemistry and air–sea gas exchange

我们的动机源于实验室和现场证据，即海洋表面微层（SML）极大地影响了气候活跃和大气重要微量气体的地球化学循环，如二氧化碳（CO2），一氧化碳（CO），甲烷（CH 4），一氧化二氮（N2 O）和二甲基硫（DMS）：（i）PASSME和SOPRAN项目最近的研究强调，表面活性物质的积累（即，表面活性剂）有一个强大的（阻尼）的影响，对CO2和N2 O通量在SML/大气界面，和（ii）微量气体可以产生和消耗（微）生物或（光）化学过程。因此，与混合层更深处的沃茨相比，包括SML在内的上层海洋可能是这些气体的独特来源或汇，这与BASS研究单位有着明显的相关性。二氧化碳、一氧化二氮和其他气体在海平面（或海洋上层厘米）的浓度已被证明与海平面以下的总体浓度不同。通常情况下，使用混合层中测量的浓度和不考虑SML的气体传输速度来计算大气中重要痕量气体的净源和汇。这些差异最终会导致通量值计算错误，从而导致地球系统模型中计算的气候强迫和空气质量存在很大的不确定性。通过将我们的痕量气体测量与以下测量相联系：（i）有机物和碳的动力学和分子特征，（SP1.1; SP1.5），㈡生物多样性和代谢活动（SP1.2），（iii）有机物的光学性质（SP1.3），（iv）有机物的光化学转化（SP1.4），和（v）物理传输过程（SP2.3），我们将获得一个全面的了解如何SML驱动痕量气体通量的变化。

Our motivation stems from laboratory and in situ evidence that the sea-surface microlayer (SML) greatly impacts the biogeochemical cycling of climate-active and atmospherically important trace gases, such as carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nitrous oxide (N2O), and dimethyl sulfide (DMS): (i) recent studies from the PASSME and SOPRAN projects have emphasized that accumulations of surface-active substances (i.e., surfactants) have a strong (dampening) effect on both CO2 and N2O fluxes across the SML/atmosphere interface, and (ii) trace gases can be produced and consumed by (micro)biological or by (photo)chemical processes. Therefore, the upper ocean, including the SML, can be a distinct source or sink for these gases, as compared to waters deeper in the mixed layer, with clear relevance to the BASS research unit. Concentrations of CO2, N2O, and other gases in the SML (or upper centimeters of the ocean) have been shown to be different from their bulk concentrations below the SML. Typically, the net sources and sinks of important trace gases to the atmosphere are computed using concentrations measured in the mixed layer and with gas transfer velocities that do not take the SML into account. These discrepancies will culminate in incorrectly calculated flux values, which can lead, subsequently, to large uncertainties in computed climate forcing and air quality in Earth system models. By linking our trace gas measurements with measurements of (i) the dynamics and molecular characteristics of organic matter and carbon specifically (SP1.1; SP1.5), (ii) biological diversity and metabolic activity (SP1.2), (iii) the optical properties of organic matter (SP1.3), (iv) the photochemical transformation of organic matter (SP1.4), and (v) physical transport processes (SP2.3), we will gain a comprehensive understanding of how the SML drives trace gas flux variability.