Glacier algae foster ice-albedo feedback in the European Alps
Glacier algae foster ice-albedo feedback in the European Alps
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DOI：
10.1038/s41598-020-61762-0
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发表时间：
2020-03-16
影响因子：
4.6
通讯作者：
Rossini, M.
中科院分区：
文献类型：
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作者：
Di Mauro, B.;Garzonio, R.;Rossini, M.
如今，冰川和冰原的融化被认为是气候变化的象征。冰的融化涉及许多复杂的机制，在这些过程中，由于裸露冰上的有机物质造成的表面变暗最近受到了科学界的关注。冰川上微生物的存在已被证明可以降低冰的反照率并促进融化。尽管在喜马拉雅、格陵兰、安第斯和阿拉斯加进行了一些研究，但在欧洲阿尔卑斯山还没有进行过定量研究。在本文中，我们利用DNA测序，显微镜和场光谱描述了在欧洲阿尔卑斯山冰川（Vadret da Morteratsch）发现的冰川藻类的性质，并评估了它们对冰反照率反馈的影响。在样本中鉴定出的不同藻类物种中，我们发现了大量的北棘龙藻，这是一种在阿尔卑斯山脉从未被定量记录过的物种，在格陵兰冰盖上的藻华中占主导地位。研究结果表明，在消融季节结束时，冰川表面上的褐藻（anylonema nordenskioeldii）浓度高于其他藻类（如Mesotaenium berggrenii）。利用现场光谱数据，我们发现反射率（750nm/650nm）与藻类浓度之间存在显著相关性。利用Sentinel-2卫星上的多光谱仪器（MSI）的波段6 （740nm）和波段4 （665nm）的遥感数据，该反射率比值可用于未来的冰川藻类制图。研究表明，冰川的生物变暗（即生物反照率反馈）也发生在欧洲阿尔卑斯山脉，因此，在考虑与冰川融化有关的正反馈机制时，必须考虑到这是一个全球性的过程。
The melting of glaciers and ice sheets is nowadays considered a symbol of climate change. Many complex mechanisms are involved in the melting of ice, and, among these processes, surface darkening due to organic material on bare ice has recently received attention from the scientific community. The presence of microbes on glaciers has been shown to decrease the albedo of ice and promote melting. Despite several studies from the Himalaya, Greenland, Andes, and Alaska, no quantitative studies have yet been conducted in the European Alps. In this paper, we made use of DNA sequencing, microscopy and field spectroscopy to describe the nature of glacier algae found at a glacier (Vadret da Morteratsch) of the European Alps and to evaluate their effect on the ice-albedo feedback. Among different algal species identified in the samples, we found a remarkable abundance of Ancylonema nordenskioeldii, a species that has never previously been quantitatively documented in the Alps and that dominates algal blooms on the Greenland Ice Sheet. Our results show that, at the end of the ablation season, the concentration of Ancylonema nordenskioeldii on the glacier surface is higher than that of other algal species (i.e. Mesotaenium berggrenii). Using field spectroscopy data, we identified a significant correlation between a reflectance ratio (750nm/650nm) and the algae concentration. This reflectance ratio could be useful for future mapping of glacier algae from remote sensing data exploiting band 6 (740nm) and band 4 (665nm) of the MultiSpectral Instrument (MSI) on board Sentinel-2 satellite. Here we show that the biological darkening of glaciers (i.e. the bioalbedo feedback) is also occurring in the European Alps, and thus it is a global process that must be taken into account when considering the positive feedback mechanisms related to glacier melting.