Abstract Lakes and permafrost on Qinghai-Tibet Plateau (QTP) are both important indicators of climate change. Previous literatures have shown the usefulness of optical remote sensing in lake expansion monitoring and the effectiveness of synthetic aperture radar (SAR) interferometry (InSAR) in retrieving permafrost deformation on QTP. However, none of them incorporated both optical remote sensing and InSAR to investigate an event that may exhibit causal links between lake outburst and permafrost degradation. This study integrated both the Google Earth Engine (GEE) analysis on optical images and the small baseline subset (SBAS) processing on SAR datasets to evaluate the potential impact of a lake outburst event on permafrost degradation. The outburst of Zonag Lake (headwater lake) that occurred on 14 September 2011 was focused, and its consequential influence on the permafrost degradation surrounding Salt Lake (tailwater lake) was investigated. The GEE processing on Landsat and HJ-1 imageries allowed an efficient monitoring of the Salt Lake expansion over past 20 years. In addition, the SBAS-InSAR analysis on temporal Envisat and Sentinel-1 datasets further discovered the accelerated permafrost degradation surrounding Salt Lake after 2014. The results provide an evidence that on QTP the outburst of a headwater lake may significantly accelerate the permafrost degradation surrounding the tailwater lake. Such degradation may be attributed to the thermal alteration of the permafrost thawing-freezing cycle and the melting ground ice, along with the subsequent changes on hydrological connectivity and soil permeability. With the continuous trend of the permafrost degradation surrounding Salt Lake, potential risks may be further exposed to the regional environment and infrastructures such as the Qinghai-Tibet railway and highway, thus deserving a particular attention in the near future. The novelties of this study are: 1) technically, the preliminary attempt to integrate the GEE and InSAR techniques for a joint analysis of lake expansion and permafrost degradation, and 2) scientifically, the finding that lake outburst may accelerate permafrost degradation on QTP.

中文翻译：

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湖泊溃决加速青藏高原多年冻土退化

摘要 青藏高原湖泊和多年冻土都是气候变化的重要指标。先前的文献已经表明光学遥感在湖泊扩张监测中的有用性以及合成孔径雷达 (SAR) 干涉测量 (InSAR) 在检索 QTP 永久冻土变形方面的有效性。然而，它们都没有结合光学遥感和 InSAR 来调查可能表现出湖泊溃决和永久冻土退化之间因果关系的事件。本研究整合了对光学图像的 Google Earth Engine (GEE) 分析和对 SAR 数据集的小基线子集 (SBAS) 处理，以评估湖泊溃决事件对永久冻土退化的潜在影响。发生在 2011 年 9 月 14 日的 Zonag 湖（源头湖）爆发的重点是，并研究了其对盐湖（尾水湖）周围多年冻土退化的影响。Landsat 和 HJ-1 图像上的 GEE 处理允许对过去 20 年盐湖扩张的有效监测。此外，SBAS-InSAR 对时态 Envisat 和 Sentinel-1 数据集的分析进一步发现了 2014 年后盐湖周围的多年冻土加速退化。结果提供证据表明，在青藏高原，源头湖的爆发可能会显着加速盐湖周围的多年冻土退化。尾水湖。这种退化可能归因于永久冻土融化-冻结循环和地冰融化的热变化，以及随后水文连通性和土壤渗透性的变化。随着盐湖周边多年冻土退化的持续趋势，潜在风险可能进一步暴露于区域环境和青藏铁路、公路等基础设施，在不久的将来值得特别关注。本研究的创新之处在于：1）在技术上，初步尝试将 GEE 和 InSAR 技术结合起来进行湖泊扩张和多年冻土退化的联合分析；2）在科学上，发现湖泊溃决可能会加速青藏高原多年冻土退化。