Abstract Ground ice is a key component of permafrost, and its melt induced by climate change and anthropogenic disturbance has been causing increased ground surface subsidence, thermal erosion, and engineering problems. However, the distribution and quantity of ground ice in permafrost have yet to be investigated in detail on the Qinghai-Tibet Plateau (QTP), and consequently, an assessment of the nature of impacts associated with permafrost degradation is challenging. In this study, variation in near-surface ground ice content of the upper 2–3 m of the permafrost layer was examined by drilling 72 boreholes at eight sites in Beiluhe Basin, QTP, an area with relatively warm (near 0 °C) permafrost. High ground ice contents occur at most sites, but visible ice was absent at one site, where the vegetation cover has transitioned from a meadow to a sparsely-covered grassland. The moisture content within the active layer (surface to 2 m depth) increases with depth at most sites, and the higher moisture contents were associated with greater near-surface ground ice contents. The gravimetric moisture content (Mg) in permafrost typically ranged from 8% to 500%, and ~76% of samples were classified as ice rich (Mg ≥ 20%). The mean excess-ice content in near-surface permafrost was ~19% for all boreholes. At six flat sites, the minimum mean excess-ice content was about zero, and the mean maximum was ~22% at an alpine grassland site. The mean excess-ice content at a sunny sloping site was much higher (~27%) than at a north-facing shady site (10%) and the ice was distributed differently with depth. The mean subsidence ratio at the eight sites was from 0.05 to 0.44. The volumetric ice content varied from 1% to 70% in samples from the different sites, with an average value of ~16%. Topographically controlled moisture availability, slope direction, and fine-particle content are important controls on ground ice content in Beiluhe Basin. This study provides fundamental information about the spatial distribution of ground ice on QTP, which is important for future assessments of thermal erosion potential and infrastructure instability in the region.

中文翻译：

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青藏高原北麓河盆地暖冻土区近地表地冰特征控制因素

摘要 地冰是永久冻土的重要组成部分，由气候变化和人为干扰引起的地冰融化导致地表沉降加剧、热侵蚀和工程问题。然而，青藏高原（QTP）永久冻土中地冰的分布和数量尚待详细调查，因此，评估与永久冻土退化相关的影响性质具有挑战性。在这项研究中，通过在青藏高原北麓河盆地的八个地点钻探 72 个钻孔，研究了多年冻土层上部 2-3 m 近地表地面冰含量的变化，该地区具有相对温暖（接近 0 °C）的多年冻土. 大多数地点都存在高地冰含量，但在一个地点没有可见的冰，植被覆盖从草甸过渡到稀疏覆盖的草原。在大多数地点，活动层内的水分含量（表层到 2 m 深）随着深度的增加而增加，并且较高的水分含量与较大的近地表地面冰含量有关。永久冻土中的重量含水量 (Mg) 通常介于 8% 到 500% 之间，约 76% 的样本被归类为富含冰（Mg ≥ 20%）。所有钻孔的近地表永久冻土中的平均过量冰含量约为 19%。在六个平坦地点，最小平均过量冰含量约为 0，而在高山草原地点平均最大值约为 22%。阳光充足的斜坡场地的平均过量冰含量（~27%）比朝北的阴凉场地（10%）高得多，而且冰的分布随深度不同。八个地点的平均沉降率为 0.05 至 0.44。来自不同地点的样品的体积冰含量从 1% 到 70% 不等，平均值约为 16%。地形控制的水分有效性、坡向和细颗粒含量是北陆河盆地地面冰含量的重要控制因素。这项研究提供了关于青藏高原地冰空间分布的基本信息，这对于未来评估该地区的热侵蚀潜力和基础设施不稳定性非常重要。