Slow-sinking particulate organic carbon in the Atlantic Ocean: Magnitude, flux, and potential controls
Slow-sinking particulate organic carbon in the Atlantic Ocean: Magnitude, flux, and potential controls
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DOI：
10.1002/2017gb005638
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发表时间：
2017-07-01
影响因子：
5.2
通讯作者：
Sanders, Richard
中科院分区：
文献类型：
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作者：
Baker, Chelsey A.;Henson, Stephanie A.;Sanders, Richard
从海洋表层输出的颗粒有机碳（POC）通量的矿化深度对大气CO2水平具有重要的控制作用。根据一个长期持有的范例，大多数输出到深度的POC与大颗粒有关。然而，最近的证据表明，缓慢下沉的POC（SSPOC）可能是一个重要的贡献者，这一流量。在这里，我们评估这种情况下发生的情况。我们的研究使用了从高纬度到中纬度的整个大西洋中使用海洋雪捕集器收集的样本。我们发现中位数SSPOC浓度为5.5 μ g L-1，13倍小于悬浮POC浓度和75倍高于中位数快速下沉POC（FSPOC）浓度（0.07 μ g L-1）。SSPOC的输出通量一般超过FSPOC通量，除了在南大洋采样的春季水华期间。在南大洋，SSPOC通量往往随着深度的增加，相对于FSPOC通量，可能是由于FSPOC的中层破碎，这一过程可能有助于POC的浅层矿化，从而减少碳储量。生物地球化学模型通常不会再现这种行为，这意味着它们可能高估了长期的海洋碳储存。
The remineralization depth of particulate organic carbon (POC) fluxes exported from the surface ocean exerts a major control over atmospheric CO2 levels. According to a long-held paradigm most of the POC exported to depth is associated with large particles. However, recent lines of evidence suggest that slow-sinking POC (SSPOC) may be an important contributor to this flux. Here we assess the circumstances under which this occurs. Our study uses samples collected using the Marine Snow Catcher throughout the Atlantic Ocean, from high latitudes to midlatitudes. We find median SSPOC concentrations of 5.5 mu g L-1, 13 times smaller than suspended POC concentrations and 75 times higher than median fast-sinking POC (FSPOC) concentrations (0.07 mu g L-1). Export fluxes of SSPOC generally exceed FSPOC flux, with the exception being during a spring bloom sampled in the Southern Ocean. In the Southern Ocean SSPOC fluxes often increase with depth relative to FSPOC flux, likely due to midwater fragmentation of FSPOC, a process which may contribute to shallow mineralization of POC and hence to reduced carbon storage. Biogeochemical models do not generally reproduce this behavior, meaning that they likely overestimate long-term ocean carbon storage.