丹斯gaard-奥施格振荡期间的极端寒冷事件

中文摘要 AI 辅助

本文研究了经历突变的气候中地表极端低温的统计特征。我们采用CCSM4（社区气候系统模型第4版）对末次盛冰期条件的模拟结果作为数据，该模拟表现出冰阶（stadial）和间冰阶（interstadial）状态之间的快速切换。我们拟合了非平稳线性广义极值（GEV）分布，以找出变化最显著的区域并将其与物理过程关联起来。随后将结果与非线性模型进行比较，该模型提供了关于参数如何作为大西洋经向翻转环流（AMOC）强度的函数发生变化的更详细图景。尽管世界不同区域表现出不同的极端行为，但许多区域在冰阶和间冰阶状态内的GEV分布参数与AMOC强度之间呈现近似线性关系，在两者的过渡位置则存在一些非线性振荡或跳跃。海冰的扩张与退缩、洋流强度的相对变化等物理过程会影响极端事件的强度和变率，GEV的三个参数均观测到显著变化。这些过程还会产生遥相关，我们尽可能将其与各类空气和水温代用指标进行比较。我们表明，将GEV分布参数映射到AMOC强度为比较不同气候模型和不同气候状态的结果提供了一种方法，但这种比较需要关注状态的动力学特征和位置，才能具有意义。

英文摘要

This paper studies the statistics of extreme cold air surface temperatures in a climate that experiences abrupt changes. We employ a CCSM4 simulation of Last Glacial Maximum conditions that exhibits rapid switching between stadial and interstadial states as data. Non-stationary linear Generalized Extreme Value (GEV) distributions are fitted to find the regions that show the most prominent changes and associate them with physical processes. The results are then compared with a non-linear model, which gives a more detailed picture of how the parameters change as a function of the AMOC strength. While different regions of the world show different extremal behaviours, many regions show an approximately linear relationship between the parameters of the GEV distributions and the strength of the AMOC within the stadial and interstadial states, with some non-linear oscillation or jump where the transition between them takes place. Physical processes such as the expansion and retreat of the sea ice and the relative changes in the strength of the currents are shown to impact the magnitude and variability of the extremes, with significant changes observed in the three parameters of the GEV. They also create teleconnections that are compared whenever possible with various proxies for the temperature of the air and the water. We show how mapping the parameters of the GEV distributions into the AMOC strength gives a way to compare results between different climate models and different climate states. Comparisons, however, need to pay heed to the dynamical characteristics of the state and the location to be meaningful.

发表机构

• Niels Bohr Institute, University of Copenhagen（尼尔斯·玻尔研究所，哥本哈根大学）

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