Glacial geomorphology of the Altai and Western Sayan Mountains, Central Asia

In this article, we present a map of the glacial geomorphology of the Altai and Western Sayan Mountains, covering an area of almost 600,000 km2. Although numerous studies provide evidence for restricted Pleistocene glaciations in this area, others have hypothesized the past existence of an extensive ice sheet. To provide a framework for accurate glacial reconstructions of the Altai and Western Sayan Mountains, we present a map at a scale of 1:1,000,000 based on a mapping from 30 m resolution ASTER DEM and 15 m/30 m resolution Landsat ETM+ satellite imagery. Four landform classes have been mapped: marginal moraines, glacial lineations, hummocky terrain, and glacial valleys. Our mapping reveals an abundance of glacial erosional and depositional landforms. The distribution of these glacial landforms indicates that the Altai and Western Sayan Mountains have experienced predominantly alpine-style glaciations, with some small ice caps centred on the higher mountain peaks. Large marginal moraine complexes mark glacial advances in intermontane basins. By tracing the outer limits of present-day glaciers, glacial valleys, and moraines, we estimate that the past glacier coverage have totalled to 65,000 km2 (10.9% of the mapped area), whereas present-day glacier coverage totals only 1300 km2 (0.2% of the mapped area). This demonstrates the usefulness of remote sensing techniques for mapping the glacial geomorphology in remote mountain areas and for quantifying the past glacier dimensions. The glacial geomorphological map presented here will be used for further detailed reconstructions of the paleoglaciology and paleoclimate of the region.

本文呈现阿尔泰山与西萨彦岭的冰川地貌（glacial geomorphology）图，覆盖面积近60万平方千米。尽管已有诸多研究证实该区域更新世（Pleistocene）冰川作用规模受限，但也有部分研究推测历史上曾存在大规模冰盖。为构建阿尔泰山与西萨彦岭精准冰川重建的研究框架，本研究基于30米分辨率ASTER数字高程模型（Digital Elevation Model, DEM）以及15米/30米分辨率Landsat ETM+卫星影像，绘制了比例尺为1:100万的冰川地貌图。本次制图共划分四类地貌类型：边缘冰碛垄（marginal moraines）、冰川线理（glacial lineations）、丘状地形（hummocky terrain）以及冰川谷（glacial valleys）。本次制图揭示了大量冰川侵蚀与沉积地貌。这些冰川地貌的分布特征表明，阿尔泰山与西萨彦岭以阿尔卑斯式冰川作用（alpine-style glaciations）为主，部分高海拔山峰周边存在小型冰盖。大型边缘冰碛垄复合体标志着山间盆地（intermontane basins）内的冰川进退过程。通过追踪现今冰川、冰川谷与冰碛垄的外围界限，本研究估算得到历史冰川总面积达6.5万平方千米（占制图区域的10.9%），而现今冰川总面积仅为1300平方千米（占制图区域的0.2%）。这一结果证实了遥感技术在偏远山区冰川地貌制图以及量化历史冰川规模方面的应用价值。本次呈现的冰川地貌图将为该区域古冰川学（paleoglaciology）与古气候学（paleoclimate）的后续精细化重建研究提供支撑。