Particle Export Fluxes in the Southern Ocean: Importance of Nonheterotrophic Processes in POC Flux Attenuation

IF 3.3 2区 地球科学 Q1 OCEANOGRAPHY
Frédéric A. C. Le Moigne, Katsiaryna Pabortsava, María Villa-Alfageme, Nathan Briggs, Chelsey A. Baker, Heather A. Bouman, Chance J. English, Sabena Blackbird, Stephanie A. Henson, Hugh Venables, Craig A. Carlson, C. Mark Moore, Jack Williams, Adrian P. Martin
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Abstract

The ocean contributes to regulating atmospheric CO2 levels via the biological carbon pump (BCP). One critical aspect of the BCP is the depth at which sinking particulate organic carbon (POC) remineralizes in the mesopelagic zone (200–1,000 m). In the Southern Ocean, the circulation is such that the products generated from POC remineralization may have drastically different fates depending on (a) the latitude at which sinking particulate material is produced and (b) the depth at which its remineralization occurs. Here, we assess latitudinal and depth variations of POC export marine aggregate abundance and composition in the Southeast Pacific sector of the Southern Ocean. We show changes in flux attenuation depth horizons in the upper mesopelagic in the subantarctic zone. These correspond to rapid particle accumulation below the depth of the euphotic zone followed by abrupt export. We believe that such rapid changes may be linked to diatom life cycles, including resting cell and spore formation and resulting changes in particle sinking velocities rather than attenuation due to heterotrophic degradation or solubilization in the upper mesopelagic zone. We further discuss the occurrence of such features in the Southern Ocean and at the global scale. Our results highlight the importance of alternative flux attenuation processes, such as sudden changes in particles sinking velocities, in explaining variability in organic carbon sequestration by the ocean's BCP.

Abstract Image

南大洋颗粒输出通量:非异养过程在POC通量衰减中的重要性
海洋通过生物碳泵(BCP)调节大气中的二氧化碳水平。BCP的一个关键方面是下沉颗粒有机碳(POC)在中层带(200-1,000 m)再矿化的深度。在南大洋,环流是这样的,POC再矿化产生的产物可能有截然不同的命运,这取决于(a)下沉颗粒物质产生的纬度和(b)再矿化发生的深度。在此,我们评估了南大洋东南太平洋区域POC出口海洋聚集物丰度和组成的纬度和深度变化。我们显示了亚南极区中上层通量衰减深度层的变化。这对应于粒子在透光区深度以下的快速积聚,然后突然输出。我们认为,这种快速变化可能与硅藻的生命周期有关,包括静止细胞和孢子的形成,以及由此导致的颗粒下沉速度的变化,而不是由于中层上部异养降解或增溶而导致的衰减。我们进一步讨论了这些特征在南大洋和全球范围内的出现。我们的研究结果强调了替代通量衰减过程的重要性,例如粒子下沉速度的突然变化,在解释海洋BCP对有机碳封存的可变性方面。
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来源期刊
Journal of Geophysical Research-Oceans
Journal of Geophysical Research-Oceans Earth and Planetary Sciences-Oceanography
CiteScore
7.00
自引率
13.90%
发文量
429
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