Photochemical reactions initiated by ultraviolet radiation remove the climate-active gas dimethylsulfide (DMS) from the ocean's surface layer. Here, we quantified DMS photolysis using a satellite-based model that accounts for spectral irradiance attenuation in the water column, its absorption by chromophoric dissolved organic matter, and the apparent quantum yields (AQYs) with which absorbed photons degrade DMS. Models with two alternative parameterizations for AQY estimate global DMS photolysis at between 17 and 20 Tg S yr⁻¹, equivalent to 13–15 Tg C yr⁻¹, of which ~ 73% occurs in the Southern hemisphere. This asymmetry results mostly from the high AQYs found south of 40° S, which more than counteract the prevailing low irradiance and deep mixing in that region. Simplified schemes currently used in biogeochemical models, whereby photolysis follows the vertical attenuation of visible radiation, overestimate DMS photolysis by around 150% globally. We propose relevant corrections and simple adjustments to those models.

中文翻译：

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使用光谱和垂直解析模型量化全球海洋二甲硫醚光解速率

紫外线辐射引发的光化学反应将气候活跃的气体二甲硫醚 (DMS) 从海洋表层去除。在这里，我们使用基于卫星的模型量化了 DMS 光解作用，该模型考虑了水柱中的光谱辐照度衰减、发色溶解有机物的吸收以及吸收光子降解 DMS 的表观量子产率 (AQY)。具有两种 AQY 替代参数化的模型估计全球 DMS 光解作用在 17 至 20 Tg S yr ⁻¹之间，相当于 13–15 Tg C yr ⁻¹，其中约 73% 发生在南半球。这种不对称性主要是由于南纬 40° 以南发现的高 AQY 造成的，这足以抵消该地区普遍存在的低辐照度和深度混合。目前生物地球化学模型中使用的简化方案（光解作用遵循可见辐射的垂直衰减）在全球范围内高估了 DMS 光解作用约 150%。我们对这些模型提出了相关的修正和简单的调整。