Surface albedo typically dominates the mass balance of mountain glaciers, though long-term trends and patterns of glacier albedo are seldom explored. We calculated broadband shortwave albedo for glaciers in the central Chilean Andes (33–34°S) using end-of-summer Landsat scenes between 1986 and 2020. We found a high inter-annual variability of glacier-wide albedo that is largely a function of the glacier fractional snow-covered area and the total precipitation of the preceding hydrological year (up to 69% of the inter-annual variance explained). Under the 2010–2020 ‘Mega Drought’ period, the mean albedo, regionally averaged ranging from ~0.25–0.5, decreased by −0.05 on average relative to 1986–2009, with the greatest reduction occurring 3500–5000 m a.s.l. In 2020, differences relative to 1986–2009 were −0.14 on average as a result of near-complete absence of late summer snow cover and the driest hydrological year since the Landsat observation period began (~90% reduction of annual precipitation relative to the 1986–2009 period). We found statistically significant, negative trends in glacier ice albedo of up to −0.03 per decade, a trend that would have serious implications for the future water security of the region, because glacier ice melt acts to buffer streamflow shortages under severe drought conditions.

中文翻译：

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1986-2020 年温带安第斯山脉冰川反照率降低和干旱效应

地表反照率通常在山地冰川的质量平衡中占主导地位，尽管很少探索冰川反照率的长期趋势和模式。我们使用 1986 年至 2020 年间的夏末 Landsat 场景计算了智利安第斯山脉中部（33-34°S）冰川的宽带短波反照率。我们发现冰川范围内反照率的年际变化很大，这在很大程度上是一个函数冰川部分积雪面积和前一个水文年的总降水量（高达解释的年际差异的 69%）。在 2010-2020 年“特大干旱”期间，区域平均反照率在 ~0.25-0.5 之间，相对于 1986-2009 年平均下降了 -0.05，降幅最大的是 3500-5000 m asl 2020 年，差异相对于 1986-2009 年为 -0。由于几乎完全没有夏末积雪和自 Landsat 观测期开始以来最干旱的水文年（与 1986-2009 年相比，年降水量减少约 90%），平均 14 年。我们发现冰川冰反照率的负趋势具有统计学意义，每十年高达 -0.03，这一趋势将对该地区未来的水安全产生严重影响，因为冰川融冰在严重干旱条件下起到缓冲水流短缺的作用。