We developed a simple method to refine existing open-ocean maps and extend them towards different coastal seas. Using a multi-linear regression we produced monthly maps of surface ocean fCO₂ in the northern European coastal seas (the North Sea, the Baltic Sea, the Norwegian Coast and the Barents Sea) covering a time period from 1998 to 2016. A comparison with gridded Surface Ocean CO₂ Atlas (SOCAT) v5 data revealed mean biases and standard deviations of 0 ± 26 µatm in the North Sea, 0 ± 16 µatm along the Norwegian Coast, 0 ± 19 µatm in the Barents Sea and 2 ± 42 µatm in the Baltic Sea. We used these maps to investigate trends in fCO₂, pH and air–sea CO₂ flux. The surface ocean fCO₂ trends are smaller than the atmospheric trend in most of the studied regions. The only exception to this is the western part of the North Sea, where sea surface fCO₂ increases by 2 µatm yr⁻¹, which is similar to the atmospheric trend. The Baltic Sea does not show a significant trend. Here, the variability was much larger than the expected trends. Consistently, the pH trends were smaller than expected for an increase in fCO₂ in pace with the rise of atmospheric CO₂ levels. The calculated air–sea CO₂ fluxes revealed that most regions were net sinks for CO₂. Only the southern North Sea and the Baltic Sea emitted CO₂ to the atmosphere. Especially in the northern regions the sink strength increased during the studied period.

中文翻译：

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北欧大陆架增加了CO _2的净汇

我们开发了一种简单的方法来完善现有的开放海洋地图，并将其扩展到不同的沿海海域。使用多元线性回归，我们绘制了北欧沿海海域（北海，波罗的海，挪威海岸和巴伦支海）1998年至2016年期间的月表海洋f CO _2图。比较使用网格化的表面海洋 CO ₂ Atlas（SOCAT）v5数据显示，北海的平均偏差和标准偏差为0  ±  26  µatm，挪威海岸为0  ±  16  µatm，巴伦支海为0  ±  19  µatm，2  ±  42 在波罗的海的µatm。我们使用这些地图调查了f CO ₂，pH和空气-海洋 CO ₂通量的趋势。在大多数研究区域中，表层海洋的f CO ₂趋势小于大气趋势。唯一的例外是北海的西部，海面f CO ₂增加2  µatm yr ^-1，这与大气趋势相似。波罗的海没有显示出明显的趋势。在这里，变异性远大于预期趋势。一致地，pH趋势小于f CO ₂增加的预期与大气中CO ₂水平的上升同步 。计算得出的海气CO ₂通量表明，大多数地区都是CO _2的净汇。只有南部的北海和波罗的海向大气中排放了CO ₂。在研究期间，特别是在北部地区，下沉强度增加了。