Model results of ocean physical field of the reference state and the targets in NetCDF format

In a feasibility study, the potential of proxy data for the temperature and salinity during the Last Glacial Maximum (LGM, about 19 000 to 23 000 years before present) in constraining the strength of the Atlantic meridional overturning circulation (AMOC) with a general ocean circulation model was explored. The proxy data were simulated by drawing data from four different model simulations at the ocean sediment core locations of the Multiproxy Approach for the Reconstruction of the Glacial Ocean surface (MARGO) project, and perturbing these data with realistic noise estimates. The results suggest that our method has the potential to provide estimates of the past strength of the AMOC even from sparse data, but in general, paleo-sea-surface temperature data without additional prior knowledge about the ocean state during the LGM is not adequate to constrain the model. On the one hand, additional data in the deep-ocean and salinity data are shown to be highly important in estimating the LGM circulation. On the other hand, increasing the amount of surface data alone does not appear to be enough for better estimates. Finally, better initial guesses to start the state estimation procedure would greatly improve the performance of the method. Indeed, with a sufficiently good first guess, just the sea-surface temperature data from the MARGO project promise to be sufficient for reliable estimates of the strength of the AMOC.

本可行性研究探讨了利用通用海洋环流模式，借助末次冰盛期（Last Glacial Maximum, LGM，约距今19000至23000年）的温度与盐度代用资料约束大西洋经向翻转环流（Atlantic meridional overturning circulation, AMOC）强度的潜力。上述代用资料的生成方式为：在冰川海洋表层重建多代用资料项目（Multiproxy Approach for the Reconstruction of the Glacial Ocean surface, MARGO）的海洋沉积物岩芯站位处，从4组独立的模式模拟结果中提取数据，并结合真实噪声估计对提取的数据施加扰动。研究结果显示，即便仅依赖稀疏的观测数据，本方法仍具备估算过去AMOC强度的潜力；但总体而言，若缺乏末次冰盛期海洋状态的额外先验知识，仅使用古海表温度数据不足以对模式实现有效约束。一方面，深海观测数据与盐度数据在冰盛期环流强度估算中被证实具有极高的重要性；另一方面，仅单纯增加表层观测数据的数量，似乎无法达成更精准的估算效果。最后，为状态估计流程提供更优质的初始猜测值，可显著提升本方法的性能。事实上，只要初始猜测足够精准，仅依靠MARGO项目提供的海表温度数据，便足以实现AMOC强度的可靠估算。