Eddy-Driven Subduction of Particulate Carbon During the North Atlantic Spring Bloom

传统上，海洋表层有机碳的输出是根据颗粒有机碳（POC）的沉降通量来测量和模拟的。 但是，有机碳库的很大一部分由小颗粒组成，这些小颗粒不会以显著的速度下沉。 从2008年北大西洋水华（NAB 08）研究中获得的滑翔机剖面的后向散射，荧光，温度和盐度的分析表明，小，中性浮力浮游植物细胞被向下运输沿着倾斜的等密度表面的入侵，表现出明显不同的水体特征，从周围的水。 这些特征也可以在高分辨率的三维模型中看到。 在这个项目中，伍兹霍尔海洋研究所的一个研究小组将探讨涡旋驱动的俯冲作用，作为北大西洋生物泵的一种贡献机制。 与季节性时间尺度上的大颗粒下沉或大规模俯冲不同，这种情况下的贡献是由于与1-10公里尺度上的涡旋和锋面相关的下沉或俯冲，在全球碳循环模型中通常无法解决。 具体而言，该小组将：（1）通过涡度、密度分层和锋面梯度、风和热通量，确定涡驱动俯冲的机制，并将其与流场联系起来;（2）追踪垂直通量的路径，确定将POC从混合层传递到深度的特征的年龄和起源，确定这些特征的普遍性，它们在空间和时间上的频率，以及它们输送碳的深度;以及（3）量化通过涡旋驱动的俯冲作用的POC通量，将其与表面POC分布和浓度以及再矿化、俯冲和下沉的时间尺度相关联，然后将该POC通量与北大西洋水华期间大POC输出的估计值进行比较。 这些目标将通过详细分析NAB 08数据集结合三维过程为基础的建模研究，这将有助于检查的机制，并与运输的动力学和表面POC的特性。更广泛的影响：这项工作将解决一个重要的问题，具有广泛的潜在影响的碳出口（包括出口溶解有机物），海气交换的CO2，氧气预算和通风的温跃层在短时间尺度上。 它将支持博士后研究员，并通过WHOI客座学生计划接待来自汉堡大学的访问学生，为期6个月。 PI和CoPI将继续通过当地博物馆和教师培训渠道参与外联活动。

Traditionally, export of organic carbon from the surface layer of the ocean has been measured and modeled in terms of the sinking flux of particulate organic carbon (POC). But, a large fraction of the organic carbon pool consists of small particles that do not sink at a significant rate. Analysis of backscatter, fluorescence, temperature and salinity in glider profiles obtained from the 2008 North Atlantic Bloom (NAB08) study reveals that small, neutrally buoyant phytoplankton cells are transported downward along sloping isopycnal surfaces in intrusions that show distinctly different water mass characteristics from the surrounding water. Such features are also seen in a high-resolution, three-dimensional model. In this project, a research team at the Woods Hole Oceanographic Institution will explore eddy-driven subduction as a contributory mechanism to the biological pump of the North Atlantic. Unlike the sinking of large particles or large-scale subduction on seasonal time scales, the contribution in this case, is due to downwelling or subduction associated with eddies and fronts on scales of 1-10 km, not usually resolved in global carbon cycle models. Specifically, the team will: (1) characterize the mechanism for eddy-driven subduction and relate it to the flow field, via vorticity, density stratification and frontal gradients, wind, and heat fluxes; (2) trace the pathways for vertical flux, identify the age and origin of features that convey the POC from the mixed layer to depth, ascertain the ubiquity of these features, their frequency in space and time, and the depth to which they transport carbon; and (3) quantify the flux of POC through eddy-driven subduction, relate it to the surface POC distribution and concentration and to time scales of remineralization, subduction and sinking, and then compare this POC flux to estimates for export of large POC during the North Atlantic bloom. These goals will be achieved through the detailed analysis of the NAB08 data set in conjunction with a three-dimensional process based modeling study that will help to examine the mechanisms and relate the transport of POC to the characteristics of the dynamics and surface POC. Broader Impacts: This work will address an important question with broad potential implications for carbon export (including export of dissolved organic matter), air-sea exchange of CO2, oxygen budgets, and ventilation of the thermocline on short time scales. It will support a postdoctoral investigator and host a visiting student from Hamburg University for a period of 6 months through the WHOI Guest Student program. Both the PI and CoPI will continue to be involved in outreach activities through local museums and avenues for teacher training.