The partial pressure of carbon dioxide (pCO₂) was surveyed across the Amazon River plume and the surrounding western tropical North Atlantic Ocean (15–0°N, 43–60°W) during three oceanic expeditions (May–June 2010, September–October 2011, and July 2012). The survey timing was chosen according to previously described temporal variability in plume behavior due to changing river discharge and winds. In situ sea surface pCO₂ and air-sea CO₂ flux exhibited robust linear relationships with sea surface salinity (SSS; 15 < SSS < 35), although the relationships differed among the surveys. Regional distributions of pCO₂ and CO₂ flux were estimated using SSS maps from high-resolution ocean color satellite-derived (MODIS-Aqua) diffuse attenuation coefficient at 490 nm (K_d490) during the periods of study. Results confirmed that the plume is a net CO₂ sink with distinctive temporal variability: the strongest drawdown occurred during the spring flood (−2.39 ± 1.29 mmol m⁻² d⁻¹ in June 2010), while moderate drawdown with relatively greater spatial variability was observed during the transitional stages of declining river discharge (−0.42 ± 0.76 mmol m⁻² d⁻¹ in September–October 2011). The region turned into a weak source in July 2012 (0.26 ± 0.62 mmol m⁻² d⁻¹) when strong CO₂ uptake in the mid-plume was overwhelmed by weak CO₂ outgassing over a larger area in the outer plume. Outgassing near the mouth of the river was observed in July 2012. Our observations draw attention to the importance of assessing the variable impacts of biological activity, export, and air-sea gas exchange before estimating regional CO₂ fluxes from salinity distributions alone.

中文翻译：

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受亚马逊河羽流影响的西热带北大西洋海气CO2通量的时间变化

在三个海洋探险期间（2010 年 5 月至 2010 年 6 月，9 月），对亚马逊河羽流和周围的热带北大西洋西部（15-0°N，43-60°W）的二氧化碳分压 ( p CO ₂ ) 进行了调查– 2011 年 10 月和 2012 年 7 月）。调查时间是根据先前描述的由于河流流量和风的变化而导致的羽流行为的时间变化来选择的。原位海面p CO ₂和海气-海 CO ₂通量与海面盐度（SSS；15 < SSS < 35）表现出稳健的线性关系，尽管这些关系在调查中有所不同。p CO ₂和CO _{2 的}区域分布在研究期间，使用来自高分辨率海洋彩色卫星 (MODIS-Aqua) 漫衰减系数的 SSS 地图估算了 490 nm (K _d 490) 的通量。结果证实，羽流是具有独特时间变异性的净 CO ₂汇：春季洪水期间出现最强的下降（2010 年 6 月-2.39 ± 1.29 mmol m ^-2  d ^-1），而具有相对较大空间变异性的中度下降是在河流流量下降的过渡阶段观察到（-0.42 ± 0.76 mmol m ^-2  d ^-1 2011 年 9 月至 10 月）。该区域在 2012 年 7 月变为弱源 (0.26 ± 0.62 mmol m ^-2  d ^-1) 当中间羽流中的强 CO ₂吸收被外部羽流中较大区域的弱 CO ₂释气所淹没。在 2012 年 7 月观察到河口附近的释气。我们的观察提请注意在仅从盐度分布估计区域 CO ₂通量之前评估生物活动、出口和海气交换的可变影响的重要性。