BioGeoChemical-Argo Floats Reveal Stark Latitudinal Gradient in the Southern Ocean Deep Carbon Flux Driven by Phytoplankton Community Composition
BioGeoChemical-Argo Floats Reveal Stark Latitudinal Gradient in the Southern Ocean Deep Carbon Flux Driven by Phytoplankton Community Composition
复制标题
BioGeoChemical-Argo 浮标揭示了浮游植物群落组成驱动的南大洋深部碳通量明显的纬度梯度
DOI：
10.1029/2022gb007624
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发表时间：
2023
影响因子：
5.2
通讯作者：
Terrats L
中科院分区：
文献类型：
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作者：
Terrats L
中层（200- 1 000米）的颗粒重力下沉将浮游植物固定的一部分大气碳转移到深海。这一过程被称为重力泵，对大气中的CO2水平起到了重要的控制作用，但由于船基通量测量的时空覆盖范围有限，其特征仍然很差。在这里，我们在南大洋（一个严重采样不足的地区）用BioGeochemical-Argo浮标检查了重力泵。使用生物光学测量的时间序列，我们描述了生产区中颗粒的浓度，它们在底层中层区的输出和转移效率，以及1,000米处下沉通量的大小。我们将浮标观测分为六个环境，由纬度锋，海冰覆盖和天然铁施肥划定。结果表明，尽管生产层中的颗粒浓度相当，但随着纬度的增加，1,000米处的沉降颗粒通量显着增加。深层通量的变化是由通量转移效率的变化驱动的，与浮游植物群落的组成和颗粒的大小有关，强烈的通量与表面的微型浮游植物和大颗粒的优势有关。我们量化了表面颗粒的性质与1,000米处通量之间的关系，并利用这些结果，利用浮标和卫星的表面观测，扩大了我们在整个南大洋的通量调查。然后，我们估计了南大洋上空1,000米处的全流域春夏沉降颗粒通量（0.054 ± 0.021 Pg C）。
The gravitational sinking of particles in the mesopelagic layer (∼200–1,000 m) transfers to the deep ocean a part of atmospheric carbon fixed by phytoplankton. This process, called the gravitational pump, exerts an important control on atmospheric CO2levels but remains poorly characterized given the limited spatio‐temporal coverage of ship‐based flux measurements. Here, we examined the gravitational pump with BioGeoChemical‐Argo floats in the Southern Ocean, a critically under‐sampled area. Using time‐series of bio‐optical measurements, we characterized the concentration of particles in the productive zone, their export and transfer efficiency in the underlying mesopelagic zone, and the magnitude of sinking flux at 1,000 m. We separated float observations into six environments delineated by latitudinal fronts, sea‐ice coverage, and natural iron fertilization. Results show a significant increase in the sinking‐particle flux at 1,000 m with increasing latitude, despite comparable particle concentrations in the productive layer. The variability in deep flux was driven by changes in the transfer efficiency of the flux, related to the composition of the phytoplanktonic community and the size of particles, with intense flux associated with the predominance of micro‐phytoplankton and large particles at the surface. We quantified the relationships between the nature of surface particles and the flux at 1,000 m and used these results to upscale our flux survey across the whole Southern Ocean using surface observations by floats and satellites. We then estimated the basin‐wide Spring‐Summer flux of sinking particles at 1,000 m over the Southern Ocean (0.054 ± 0.021 Pg C).