全球增暖背景下大西洋经向翻转环流新型代用指标研究

大西洋经向翻转环流（AMOC: Atlantic meridional overturning circulation）是地球过去、现在和未来气候的重要调节器。众多气候模式研究指出，全球变暖背景下AMOC将减弱，但现实中AMOC的直接观测时间很短，现阶段难以分辨其在增暖背景下的长期响应特征。因此，寻找时间跨度较长的可靠AMOC代用指标，成为研究过去和现在AMOC变化的关键。以往AMOC代用指标受自然变率影响较大，在人为强迫作用下表现不佳。基于此，本项目从理论基础出发，结合海洋观测资料和新一代气候模式模拟，旨在提出一种具有更高可信度的新型AMOC代用指标。该新指标基于南大西洋副热带的盐度变化，在动力上与AMOC变化紧密联系，且赤道的低通滤波作用使其更能表征AMOC在人为强迫下的低频响应。该新指标将帮助我们更准确地理解工业革命以来AMOC的历史演变规律，进而更好地预测未来AMOC和气候的变化。

The Atlantic meridional overturning circulation (AMOC) is an important regulator of the Earth’s past, present and future climate. However, the long-term response of AMOC under global warming has been difficult to detect in reality, given the rather short observational record. Therefore, finding reliable longer-term proxy indicator for AMOC has become the key to studying the past and current AMOC changes. Previous indicators are largely subject to the local natural variability and perform poorly under human-induced external forcing. Based on theoretical studies, combining ocean observations and new generation of model simulations, this study will propose a more reliable proxy indicator for AMOC. The new indicator is based on the salinity change in the subtropical South Atlantic, which is shown to be closely related to AMOC. Furthermore, due to the low-pass filtering effect of equator, the new indicator highlights the low-frequency response of AMOC to human-induced forcing. This new AMOC indicator will help us to understand the historical evolution of AMOC since the Industrial Revolution and in turn better predict future changes of AMOC and climate.