Abstract The glacier surface ice velocity (SIV) is important in understanding the glacier state. This study presents results on the SIV of the 18 glaciers spread over the Indian central Himalaya (ICH). The SIV was computed by applying Co-registration of Optically Sensed Images and Correlation (COSI-Corr) technique on the Landsat time series data (1993–2017). Results show that the average SIV of all glaciers was 22.63 ± 5.8 m a−1 in 1993/94, which decreased (by ~23%) to 17.32 ± 3.1 m a−1 in 2000/01 and further declined (by ~33%) to 11.50 ± 1.7 m a−1 in 2015/16. Though a secular decline in average SIV is observed, rates of slowdown are considerably heterogeneous for the studied glaciers being largely determined by glaciers size, orientation, altitude and debris cover. Slope was found to have comparatively low influence on the glacier movement. Inter-regional comparison reveals that average SIVs of the ICH glaciers were slightly but consistently lower than that of the western and eastern Himalayan glaciers. Nonetheless, though moving slowly, ICH glaciers are more active than nearby Everest region glaciers with sufficient proportion of active glaciers (referred as Type-I; 39%). However, the point of concern is that owing to declining health, ICH-glaciers are progressively converting from Type-I to partially active (referred as Type-II), and Type-II to entirely stagnant (referred as Type-III). This observed slowdown coupled with negative mass balance and continuous debris growth (as reported in previous studies) may form favorable conditions for supraglacial lake development. We thereby recommend regular monitoring of glacier dynamics in this region for tenable assessment of climatic change impacts.

中文翻译：

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印度喜马拉雅冰川中部表面冰速的时空趋势

摘要 冰川表面冰速（SIV）对于了解冰川状态很重要。本研究展示了分布在印度喜马拉雅中部 (ICH) 上的 18 条冰川的 SIV 结果。SIV 是通过对 Landsat 时间序列数据 (1993–2017) 应用光学传感图像和相关联配准 (COSI-Corr) 技术来计算的。结果表明，1993/94 年所有冰川的平均 SIV 为 22.63 ± 5.8 ma-1，2000/01 年下降（约 23%）至 17.32 ± 3.1 ma-1，并进一步下降（约 33%）至2015/16 年为 11.50 ± 1.7 ma−1。尽管观察到平均 SIV 的长期下降，但所研究的冰川的减缓速度相当不均匀，这主要取决于冰川的大小、方向、高度和碎片覆盖。发现坡度对冰川运动的影响相对较小。区域间比较表明，ICH 冰川的平均 SIV 略低于喜马拉雅西部和东部冰川，但始终低于。尽管如此，虽然移动缓慢，但 ICH 冰川比附近的珠穆朗玛峰地区冰川更活跃，拥有足够比例的活动冰川（称为 I 型；39%）。然而，令人担忧的是，由于健康状况下降，ICH冰川逐渐从I型转变为部分活跃（称为II型），以及II型转变为完全停滞（称为III型）。这种观察到的放缓加上负的质量平衡和持续的碎片增长（如先前研究报告的那样）可能为冰上湖的发展形成有利条件。