Bol Roséanne, Henson Stephanie A, Rumyantseva Anna, Briggs Nathan
School of Ocean and Earth Sciences University of Southampton Southampton UK.
Now at NIOZ Royal Netherlands Institute for Sea Research Texel The Netherlands.
Global Biogeochem Cycles. 2018 Dec;32(12):1803-1814. doi: 10.1029/2018GB005963. Epub 2018 Dec 18.
The biological carbon pump exports carbon fixed by photosynthesis out of the surface ocean and transfers it to the deep, mostly in the form of sinking particles. Despite the importance of the pump in regulating the air-sea CO balance, the magnitude of global carbon export remains unclear, as do its controlling mechanisms. A possible sinking flux of carbon to the mesopelagic zone may be via the mixed-layer pump: a seasonal net detrainment of particulate organic carbon (POC)-rich surface waters, caused by sequential deepening and shoaling of the mixed layer. In this study, we present a full year of daily small-particle POC concentrations derived from glider optical backscatter data, to study export variability at the Porcupine Abyssal Plain (PAP) sustained observatory in the Northeast Atlantic. We observe a strong seasonality in small-particle transfer efficiency, with a maximum in winter and early spring. By calculating daily POC export driven by mixed-layer variations, we find that the mixed-layer pump supplies an annual flux of at least 3.0 ± 0.9 g POC·m·year to the mesopelagic zone, contributing between 5% and 25% of the total annual export flux and likely contributing to closing a gap in the mesopelagic carbon budget found by other studies. These are, to our best knowledge, the first high-frequency observations of export variability over the course of a full year. Our results support the deployment of bio-optical sensors on gliders to improve our understanding of the ocean carbon cycle on temporal scales from daily to annual.
生物碳泵将光合作用固定的碳输出到海洋表层以下，并将其转移到深海，主要以沉降颗粒的形式。尽管碳泵在调节海气碳平衡方面具有重要作用，但其全球碳输出量的大小及其控制机制仍不明确。碳向海洋中层的一种可能沉降通量可能是通过混合层泵实现的：混合层的依次加深和变浅导致富含颗粒有机碳（POC）的表层水季节性净夹带。在本研究中，我们展示了源自滑翔器光学后向散射数据的一整年每日小颗粒POC浓度，以研究东北大西洋豪猪深海平原（PAP）长期观测站的输出变异性。我们观察到小颗粒转移效率存在强烈的季节性，在冬季和早春达到最大值。通过计算由混合层变化驱动的每日POC输出，我们发现混合层泵每年向海洋中层提供至少3.0±0.9 g POC·m²·年的通量，占年度总输出通量的5%至25%，并且可能有助于填补其他研究发现的海洋中层碳预算中的一个缺口。据我们所知，这些是全年出口变异性的首次高频观测结果。我们的结果支持在滑翔器上部署生物光学传感器，以增进我们对从每日到年度时间尺度上的海洋碳循环的理解。
