作为单稳态可激动力学导致的多尺度现象的冰川期气候突变
Glacial abrupt climate change as a multi-scale phenomenon resulting from monostable excitable dynamics
AI总结：
本研究提出基于多尺度单稳态可激动力学的模型，以噪声诱导的状态空间偏移解释丹斯高-厄施格事件，打破双稳态传统认知，准确复现其旋回特征与变率规律。
摘要：
古气候代用指标揭示了过去冰川期北大西洋气候的突变，即丹斯高-厄施格（Dansgaard--Oeschger，DO）事件。DO事件的核心特征是格陵兰地区约10°C的突然升温，标志着被称为间冰阶的相对温和阶段的开始。这些阶段会在数百年到数千年间逐渐降温，直至最终的突变下降使温度回到寒冷的冰阶水平。截至目前，这种千年尺度变率背后的确切机制仍无定论。在此，我们提出一个可激模型来解释丹斯高-厄施格旋回，其中间冰阶以噪声诱导的状态空间偏移的形式出现。我们的模型包含四个动力学变量之间的相互多尺度作用，这四个变量分别代表北极大气温度、北欧海温度与海冰覆盖，以及大西洋经向翻转环流（Atlantic Meridional Overturning Circulation）。模型的海-气热通量由海冰调节，而海冰又受到由快速演变的间歇性噪声动态生成的大扰动的影响。若扰动超过临界值，就会触发类似间冰阶的状态空间偏移，在此期间所有四个模型变量都会发生定性变化，与相应代用记录中间冰阶的特征一致。作为产生噪声的物理间歇性过程，我们提出了海洋中的对流事件或大气阻塞事件。我们的模型准确复现了DO旋回的形态、返回时间，以及间冰阶和冰阶持续时间对背景条件的依赖性。与普遍认为DO变率基于基础动力学中的双稳态的认知不同，我们表明多尺度单稳态可激动力学为解释与DO事件相关的千年尺度气候变率提供了一种有前景的替代方案。
英文摘要：
Paleoclimate proxies reveal abrupt transitions of the North Atlantic climate during past glacial intervals known as Dansgaard--Oeschger (DO) events. A central feature of DO events is a sudden warming of about 10$^{\circ}$C in Greenland marking the beginning of relatively mild phases termed interstadials. These exhibit gradual cooling over several hundred to a few thousand years until a final abrupt decline brings the temperatures back to cold stadial levels. As of now, the exact mechanism behind this millennia-scale variability remains inconclusive. Here, we propose an excitable model to explain Dansgaard-Oeschger cycles, where interstadials occur as noise-induced state space excursions. Our model comprises the mutual multi-scale interactions between four dynamical variables representing Arctic atmospheric temperatures, Nordic Seas' temperatures and sea ice cover, and the Atlantic Meridional Overturning Circulation. The model's atmosphere-ocean heat flux is moderated by the sea ice, which in turn is subject to large perturbations dynamically generated by fast-evolving intermittent noise. If supercritical, perturbations trigger interstadial-like state space excursions during which all four model variables undergo qualitative changes that consistently resemble the signature of interstadials in corresponding proxy records. As a physical intermittent process generating the noise we propose convective events in the ocean or atmospheric blocking events. Our model accurately reproduces the DO cycle shape, return times and the dependence of the interstadial and stadial durations on the background conditions. In contrast to the prevailing understanding that DO variability is based on bistability in the underlying dynamics, we show that multi-scale, monostable excitable dynamics provide a promising alternative to explain millennial-scale climate variability associated with DO events.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
