Investigating the impact of physical processes in the Southern Ocean on the carbon cycle during past, present and future climates

最近各种基于数据和模型的研究证明了南大洋对全球碳循环和大气二氧化碳的重要性。这包括现在和未来可能的二氧化碳吸收，以及最后一次冰川盛期大气二氧化碳的减少。特别是对于后者，已经提出了南大洋各种不同的机制来解释在冰芯中观察到的二氧化碳的一些变化，而到目前为止，还没有一项更令人信服的研究，将假设与我们基于海洋模型和古重建的物理知识联系起来。在这个项目中，我们将用一个成熟的海洋环流模型(MITgCM)来探索这些假设的物理基础，这些假说可以(部分)解释冰川PCO2值。我们将分析：(A)南大洋上空风场的时间和空间变化是否以及如何导致水柱层结的变化；(B)海冰覆盖率的变化(根据古重建或未来预测)对水性质的影响，从而对层化和海洋环流的影响；(C)风和海冰的变化对南大洋物理的相互影响。除了实际了解这些过程对南大洋二氧化碳汇能力的影响外，还将重点关注全球碳循环和对大气二氧化碳的影响。这些主题是在工业化前、现在和冰川边界条件下探讨的，也是针对气专委选定的未来气候变化情景而探讨的。

The importance of the Southern Ocean for the global carbon cycle and atmospheric CO2 has been demonstrated by various recent data- and model-based studies. This includes present and potential future CO2 uptake, as well as the reduction in atmospheric pCO2 during the Last Glacial Maximum. Especially for the latter, various different mechanisms in the Southern Ocean have been proposed to explain some of the changes in pCO2, which are observed in ice cores, while a more convincing study which brings hypotheses into context with our physical knowledge based on ocean models and paleo reconstructions remains elusive so far. In this project we will explore the physical basis of various of these hypothesis on the (partial) explanation of glacial pCO2 values with a well established ocean general circulation model (MITgcm). We will analyse (a) if and how temporal and spatial changes in the wind field over the Southern Ocean lead to variations in water column stratification; (b) the impact of changing sea ice coverage (based on paleo-reconstructions or future predictions) on water properties and thus on stratification and ocean circulation; (c) interacting effects of both changes in wind and sea ice on Southern Ocean physics. Besides a physical understanding of these processes their impact on the Southern Ocean CO2 sink capacities, the global carbon cycle and on atmospheric pCO2 will be in focus. These topics are explored under preindustrial, present-day and glacial boundary conditions, but also for selected IPCC scenarios of future climate change.