Ocean Circulation, Lateral Transfers of Nutrients, and the Air-Sea Flux of CO2

生物生产力是由必需营养物质的可用性调控的。在海洋中，下沉的有机颗粒的输出不可避免地将营养物质输送到密度更大的深海。最终，物理运输必须将这些营养物质返回到可以发生光合作用的较轻的地表水中。然而，在温跃层中观测到的底旋混合率太小，不足以平衡有机物的向下通量。因此，对营养物质的横向转移的一个重要的（也许是主要的）贡献必须发生在海洋表面的横向运输。这是由海气浮力通量促成的，并由海洋表面的残余平均流控制，残余平均流是侧向埃克曼和涡旋转移的净效应。在这项研究中，麻省理工学院的研究人员将使用一系列模型，从简化的尺度论证到海洋环流和生物地球化学循环的数值模型，来解决以下假设：地表剩余平均流量支持南极环极流的营养物质横向、纵向转移，并在长时间尺度上维持大西洋盆地的生产力。北大西洋环流间边界的类似过程有助于维持副热带环流的营养收支和生产力。2. 南极环极流和环流边界附近的海气碳通量分布可以通过残差平均流和等平涡搅拌的碳和营养物输运来理解和预测。3. 南大洋剩余环流对营养物和碳的运输在世纪和更长时间尺度上对全球海洋碳泵和大气二氧化碳水平具有重要控制作用，并受到海气动量和浮力通量的气候变化的调节。在这项研究的更广泛影响中，这项工作将导致麻省理工学院海洋环流和生物地球化学模型的持续发展。该模型是一种免费提供的工具，示踪剂和生物地球化学包的国际用户基础正在不断增长。这项工作也有很强的培训成分，包括对研究生的支持。此外，研究人员正在为研究生撰写一本跨学科的海洋生物地球化学循环书籍。

ABSTRACTOCE-0525974Biological productivity is regulated by the availability of essential nutrients. In the oceans, export of sinking organic particles inexorably transports nutrients towards the deep, denser ocean waters. Ultimately, physical transport must return those nutrients to the lighter, surface waters where photosynthesis can occur. However, observed diapycnal mixing rates in the thermocline are too small to balance the downward flux of organic matter. Therefore, a significant (perhaps dominant) contribution to the diapycnal transfer of nutrients must occur as lateral transport in the surface ocean. This is facilitated by air-sea buoyancy fluxes and governed by the residual mean flow, which in the surface ocean is the net effect of lateral Ekman and eddy transfers. In this research, researchers at the Massachusetts Institute of Technology will use a hierarchy of models, ranging from simplified scaling arguments to numerical models of ocean circulation and biogeochemical cycles, to address the following hypotheses: 1. The surface residual mean flow supports lateral, diapycnal transfers of nutrients across the Antarctic Circumpolar Current and sustains the productivity of the Atlantic Basin on long timescales. An analogous process at the inter-gyre boundary of the North Atlantic helps to sustain the nutrient budget and productivity of the subtropical gyre. 2. Patterns of air-sea carbon flux in the vicinity of the Antarctic Circumpolar Current and inter-gyre boundary can be understood and predicted in terms of the transport of carbon and nutrients by the residual mean flow and isopycnal eddy stirring. 3. The transport of nutrients and carbon by the residual circulation of the Southern Ocean has a significant control on the global ocean carbon pumps and atmospheric carbon dioxide levels on century and longer timescales, regulated by climatic changes in air-sea momentum and buoyancy fluxes. Among the broader impacts of the research, the work will lead to continued development of the MIT ocean circulation and biogeochemical model. The model is a freely available tool and there is a growing international user base for the tracer and biogeochemical packages. The work also has a strong training component that includes support for a graduate student. In addition, the investigators are engaged in writing an interdisciplinary book of ocean biogeochemical cycles for graduate students.