Permafrost is a relevant component of the Pyrenean high mountains, triggering a wide range of geomorphological cryogenic processes. Although in the past decades there has been an increase in frozen ground studies in the Pyrenees, there are no specific studies about rock wall permafrost, its presence, distribution, thermal regime, or historical evolution. This work combines measured rock surface temperatures (RSTs, from August 2013 to April 2016) along an elevation profile (four sites) on the north facing the rock wall of the Vignemale peak (3,298 m a.s.l., 42°46′16″N/0°08′33″W) and temperature modeling (CryoGRID2) to determine the presence of permafrost and to analyze its evolution since the mid-20th century. Simulations are run with various RST forcings and bedrock properties to account for forcing data uncertainty and varying degrees of rock fracturing. Results reveal that warm permafrost may have existed down to 2,600 m a.s.l. until the early 1980s and that warm permafrost is currently found at ~2,800 m a.s.l. and up to 3,000 m a.s.l. Cold (<−2°C) permafrost may exist above 3,100–3,200 m a.s.l. Systematic investigations on rock wall permafrost must be conducted to refine those results in the Pyrenees. The elevation shift in warm permafrost suggests an imminent disappearance of permafrost in the Vignemale peak.

中文翻译：

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比利牛斯山岩壁永久冻土的第一个证据（Vignemale 峰，海拔 3,298 m，42°46′16″N/0°08′33″W）

永久冻土是比利牛斯山脉的一个相关组成部分，引发了广泛的地貌低温过程。尽管在过去的几十年里，比利牛斯山脉的冻土研究有所增加，但没有关于岩壁永久冻土、其存在、分布、热状况或历史演变的具体研究。这项工作结合了测量的岩石表面温度（RST，从 2013 年 8 月到 2016 年 4 月）沿 Vignemale 峰（3,298 m asl，42°46′16″N/0 °08′33″W) 和温度建模 (CryoGRID2) 以确定永久冻土的存在并分析其自 20 世纪中叶以来的演变。使用各种 RST 强迫和基岩属性运行模拟，以解释强迫数据的不确定性和不同程度的岩石破裂。结果表明，直到 1980 年代初期，暖永久冻土可能一直存在到 2,600 m asl，目前在 ~2,800 m asl 和高达 3,000 m asl 处发现了暖永久冻土 冷 (<-2°C) 永久冻土可能存在于 3,100–3,200 米以上必须对岩壁永久冻土进行系统调查，以完善比利牛斯山脉的这些结果。温暖的永久冻土层的海拔变化表明 Vignemale 峰的永久冻土层即将消失。100–3,200 m asl 必须对岩壁永久冻土进行系统调查，以完善比利牛斯山脉的这些结果。温暖的永久冻土层的海拔变化表明 Vignemale 峰的永久冻土层即将消失。100–3,200 m asl 必须对岩壁永久冻土进行系统调查，以完善比利牛斯山脉的这些结果。温暖的永久冻土层的海拔变化表明 Vignemale 峰的永久冻土层即将消失。