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

北大西洋春季水华期间涡流驱动的颗粒碳俯冲

• 批准号: 1260080
• 负责人: Amala Mahadevan
• 金额: $ 23.59万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-04-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1260080&HistoricalAwards=false
• 关键词: Eddy; Driven; Subduction; Particulate; Carbon

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.

传统上，从海洋表层输出的有机碳一直是根据颗粒有机碳（POC）的下沉通量进行测量和模拟的。但是，有机碳库的很大一部分是由小颗粒组成的，它们不会以显著的速度下沉。从2008年北大西洋水华（NAB08）研究中获得的滑翔机剖面的后向散射、荧光、温度和盐度分析表明，小的、中性浮力的浮游植物细胞沿着倾斜的等平面向下运输，这些侵入物显示出与周围水明显不同的水质量特征。在高分辨率的三维模型中也可以看到这些特征。在这个项目中，伍兹霍尔海洋研究所的一个研究小组将探索涡旋驱动的俯冲，作为北大西洋生物泵的一种促进机制。与季节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1-10公里尺度上与漩涡和锋面相关的下潜或俯冲，这通常在全球碳循环模式中无法解决。具体而言，研究小组将：(1)通过涡度、密度分层和锋面梯度、风通量和热通量，表征涡旋驱动俯冲的机制，并将其与流场联系起来；(2)追踪垂直通量的路径，确定从混合层向深度输送POC的特征的年龄和起源，确定这些特征的普遍性、时空频率和输送碳的深度；(3)量化涡旋俯冲过程中POC的通量，将其与地表POC的分布和浓度以及再矿化、俯冲和下沉的时间尺度联系起来，并将此POC通量与北大西洋水华期间大POC输出的估算值进行比较。这些目标将通过对NAB08数据集的详细分析以及基于三维过程的建模研究来实现，这将有助于检查POC的机制，并将POC的运输与动力学和表面POC的特征联系起来。更广泛的影响：这项工作将解决一个重要的问题，在短时间尺度上对碳输出（包括溶解有机物的输出）、二氧化碳的海气交换、氧气收支和温跃层通风具有广泛的潜在影响。它将通过WHOI客座学生计划支持一名博士后研究员，并接待一名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。