Active-layer detachments (ALD) and retrogressive thaw slumps (RTS) are landslides that occur as a result of thaw in permafrost regions. I mapped the extent of bare soil exposed in these thaw-related slope failures in four study areas with continuous permafrost in Alaska’s Arctic National Parks, on mosaics of aerial photographs from 1977–1985 (sampling episode 1), satellite images from 2006–2009 (sampling episode 2), and satellite images from 2018–2019 (sampling episode 3). In all four study areas the count of ALD and RTS, and the area of bare soil they exposed, was greater during the first or second sampling episode than the third sampling episode, in spite of record high mean annual temperatures in 2014–2019. One study area had frozen debris lobes (FDL) in addition to ALD and RTS. In that study area the bare ground exposed by destabilization and rapid movement of FDL was greatest in the third sampling episode, probably as a result of deep thaw and talik formation. The destabilization of FDL in episode 3 was probably a long-term consequence of warming and permafrost loss, while the observed pulses of ALD and RTS in episodes 1 and 2 were closely tied to short-term deep thaw events in areas where the underlying permafrost remained stable.

中文翻译：

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阿拉斯加北极国家公园中与永久冻土融化相关的斜坡破坏，c。1980-2019 年

活动层脱离 (ALD) 和倒退性融化塌落 (RTS) 是由于多年冻土地区融化而发生的滑坡。我根据 1977 年至 1985 年的航空照片马赛克（采样第 1 集）和 2006 年至 2009 年的卫星图像，绘制了阿拉斯加北极国家公园中具有连续永久冻土层的四个研究区域中这些与解冻相关的斜坡破坏中裸露土壤的范围（采样第 2 集）和 2018-2019 年的卫星图像（采样第 3 集）。在所有四个研究区域中，尽管 2014-2019 年平均气温创历史新高，但在第一次或第二次采样期间，ALD 和 RTS 的数量以及它们暴露的裸土面积都大于第三次采样。除了 ALD 和 RTS 之外，一个研究区域还有冷冻碎片裂片 (FDL)。在该研究区域，由于 FDL 的不稳定和快速移动而暴露的裸露地面在第三次采样事件中最大，这可能是深度解冻和 talik 形成的结果。第 3 集 FDL 的不稳定可能是变暖和永久冻土流失的长期后果，而第 1 集和第 2 集观察到的 ALD 和 RTS 脉冲与潜在永久冻土仍然存在的地区的短期深度解冻事件密切相关稳定的。