Arctic neoglaciation following the Holocene Thermal Maximum is an important feature of late-Holocene climate. We investigated this phenomenon using a transient 6000-year simulation with the CESM-CAM5 climate model driven by orbital forcing, greenhouse gas concentrations, and a land use reconstruction. During the first three millennia analyzed here (6–3 ka), mean Arctic snow depth increases, despite enhanced greenhouse forcing. Superimposed on this secular trend is a very abrupt increase in snow depth between 5 and 4.9 ka on Ellesmere Island and the Greenland coasts, in rough agreement with the timing of observed neoglaciation in the region. This transition is especially extreme on Ellesmere Island, where end-of-summer snow coverage jumps from nearly 0 to virtually 100% in 1 year, and snow depth increases to the model’s imposed maximum within 15 years. This climatic shift involves more than the Milankovitch-based expectation of cooler summers causing less snow melt. Coincident with the onset of the cold regime are two consecutive summers with heavy snowfall on Ellesmere Island that help to short-circuit the normal seasonal melt cycle. These heavy snow seasons are caused by synoptic-scale, cyclonic circulation anomalies over the Arctic Ocean and Canadian Archipelago, including an extremely positive phase of the Arctic Oscillation. Our study reveals that a climate model can produce sudden climatic transitions in this region prone to glacial inception and exceptional variability, due to a dynamic mechanism (more summer snowfall induced by an extreme circulation anomaly) that augments the traditional Milankovitch thermodynamic explanation of orbitally induced glacier development.

中文翻译：

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中晚期全新世瞬态气候模型模拟中夏季降雪增强促进了埃尔斯米尔岛的快速新冰川作用

全新世极热期之后的北极新冰川作用是晚全新世气候的一个重要特征。我们使用由轨道强迫、温室气体浓度和土地利用重建驱动的 CESM-CAM5 气候模型的瞬态 6000 年模拟研究了这种现象。在此处分析的前三千年（6-3 ka）中，尽管温室强迫增加，但平均北极雪深增加。叠加在这种长期趋势上的是埃尔斯米尔岛和格陵兰海岸 5 到 4.9 ka 之间的雪深突然增加，与该地区观察到的新冰川作用的时间大致一致。这种转变在埃尔斯米尔岛尤为极端，那里的夏末积雪覆盖率在 1 年内从接近 0 跃升至几乎 100%，并且雪深在 15 年内增加到模型规定的最大值。这种气候变化所涉及的不仅仅是米兰科维奇对夏季凉爽导致融雪减少的预期。与寒冷状态的开始同时发生的是埃尔斯米尔岛连续两个夏天的大雪，这有助于缩短正常的季节性融化周期。这些大雪季是由北冰洋和加拿大群岛上空的天气尺度气旋环流异常引起的，包括北极涛动的极端正相位。我们的研究表明，气候模型可以在该地区产生突然的气候转变，容易发生冰川开始和异常变化，