【每天一篇经济学人】Ice and fire 冰与火（2023年第53期）
文章来源：《经济学人》Sep 30th 2023 期 Science & technology 栏目 Ice and fire 冰与火
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Mapping glaciers was once a difficult and arduous job. So was monitoring volcanoes for the grumblings and rumblings that might herald an eruption. In recent decades, the old methods of hiking boots and mountaineering gear have been joined by satellites and remote sensing, making things both easier and safer.
绘制冰川地图曾经是一项困难而艰巨的工作。同样，监测火山喷发前的咆哮与轰鸣也很艰巨。近几十年来，徒步登山装备与卫星遥感技术相结合，使得这些任务更容易、更安全。
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But looking from afar has its drawbacks too. If a volcano is high enough to sport glaciers on its flanks (and many are), then the thick layer of ice can make it harder, or impossible, to get accurate temperature readings from the rock beneath.
但远观方法也有缺点。如果火山的侧面高到被冰川覆盖（很多火山都是这样），那么厚厚的冰层会使监测冰下岩石温度读数变得更加困难，甚至不可能。
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And that is a particular problem, for glacier-topped volcanoes are some of the most dangerous of all. If they do erupt, the heat can melt the glaciers, forming torrents of fast-moving mud called lahars that can flatten anything in their path. In 1985 the Nevado del Ruiz volcano in western Colombia erupted. The glaciers on its summit and flanks formed several gigantic lahars, one of which buried the nearby town of Armero, killing more than 20,000 of its inhabitants. It remains the worst natural disaster in the country’s history.
这是一个特殊的问题，因为冰川覆盖的火山极其危险。如果火山爆发，热量会融化冰川，形成快速流动的泥流，称为“火山泥流”，可以毁了所到之处的一切。1985年，哥伦比亚西部的内瓦多德尔鲁伊斯火山爆发。火山顶与侧面的冰川形成了几条巨大的火山泥流，其中一条火山泥流掩埋了附近的阿尔梅罗镇，导致2万多居民死亡。这仍然是哥伦比亚历史上最严重的自然灾害。
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In a paper published last month in Geology, Matteo Spagnolo and Brice Rea, a pair of volcanologists at the University of Aberdeen, suggest a possible solution to the problem. The internal heat of volcanoes, they conclude, has a notable impact on the glaciers that sit on top of them.Monitoring those glaciers, rather than the volcano itself, may serve as an early-warning system for anyone living nearby.
上个月《地质学》杂志发表了一篇论文，作者是阿伯丁大学的两位火山学家马特奥.斯帕尼奥洛和布莱斯.雷亚，他们提出了一个可能的火山预警方案。他们得出结论，火山的内部热量对火山顶部的冰川有着显著影响。监测火山表面的冰川，而不是火山本身，可能作为附近居民的早期预警系统。
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The researchers and their colleagues studied 600 glaciers in the Andes (including those on Nevado del Ruiz) of which 74, being less than a kilometre from the mouth of an active volcano, were classed as “volcanic”. One of the main features the scientists were looking for was the “equilibrium line”. This is the point on a glacier that separates the “accumulation zone”, where snow adds to the glacier’s mass, from the “ablation zone”, where melting subtracts from it. One of the things that affects the equilibrium line is the weather. Plenty of snowfall, or a cool summer, and the line will move downhill. A dry winter or a scorching summer will move it higher.
研究人员及其同事们研究了安第斯山脉上 600 座山峰冰川（包括了内瓦多德尔鲁伊斯火山上的冰川），其中有74 座山的冰川距离活火山口不到一公里，被归类为 "火山冰川”。科学家们寻找的主要特征之一是“平衡线”，即火山冰川上的 "积雪区 "和 "消融区 "之间的分界线。"积雪区 "的积雪增加了冰川的质量，而 "消融区 "的融雪则减少了冰川的质量。影响平衡线的因素之一是天气。如果降雪量大或夏季凉爽，平衡线就会向下移动。而干燥的冬季或炎热的夏季则会使平衡线上移。
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In theory, though, any source of heat—including volcanic heat from beneath the ground—ought to affect the height of the equilibrium line. When the researchers examined the data, that is exactly what they found. Glaciers on volcanoes had equilibrium lines notably higher than those on ordinary mountains. In some cases, as on Copahue, a volcano on the border between Chile and Argentina, which last had a major eruption in 2016, the difference could be several hundred metres. Glaciers on quiescent volcanoes, such as Parinacota, a 6,400-metre mountain that sits between Bolivia and Chile, had equilibrium lines similar to glaciers on mountains that had never been volcanic at all.
然而，从理论上讲，任何热源——包括地下的火山热——都会影响平衡线的高度。当研究人员研究数据时，他们正是发现了这一点。火山上的冰川平衡线明显高于普通山脉上的冰川平衡线。例如，位于智利和阿根廷边境的科帕韦火山，它的平衡线与普通山脉的平衡线高度相差数百米。该火山最近一次大规模喷发是在 2016 年。死火山上的冰川（例如位于玻利维亚和智利之间的一座 6,400 米高的帕里纳科塔山），它们的平衡线与普通山脉上的冰川平衡线高度相似。
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With so many glaciers in their sample, the researchers were able to rule out other explanations, such as differences in the local microclimate. And on the 13 volcanoes for which the best data were available, they were able to map the correlation in detail. Those data showed a strong link between changes in the amount of volcanic heat seeping to the surface and the movements of the equilibrium line.
由于样本中的冰川数量非常之多，研究人员能够排除其他解释，如当地微气候的差异。根据13 座火山的最佳数据，他们成功绘制出了相关性图表。这些数据表明，渗入地表的火山热量变化与平衡线移动之间存在密切相关性。
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This means, say the researchers, that, although volcanic glaciers obscure what is going on underneath, they could themselves serve as telltales. Sudden changes in the equilibrium line, particularly if they are out of kilter with those of other glaciers nearby, could be evidence that something is brewing beneath the surface, and that further attention is warranted. Although they are getting better, volcanologists still cannot predict exactly when eruptions will occur. But a rise in heat suggests more magma is accumulating below, and makes a valuable early-warning sign.
研究人员说，这意味着尽管火山冰川掩盖了地表下的情况，但它们本身可以作为线索。平衡线的骤然变化，特别是如果它们与附近其他冰川的变化不一致时，可能表明地表下的岩浆正在酝酿，需要进一步关注。尽管火山学日益完善，但火山学家仍然无法预测火山爆发的准确时间。但热量的上升表明有更多的岩浆正在地表下积聚，这是一种有价值的提前预警信号。
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The findings have implications beyond volcanology and warning nearby inhabitants of a looming disaster. Measurements of glaciers around the world provide one way for climate researchers to track the long-term effects of climate change. A warmer planet should mean that glaciers are receding everywhere, and by and large they are. But Dr Spagnolo and Dr Rea’s results suggest that not all glaciers make equally reliable thermometers. Those on the sides of volcanoes can advance and recede for reasons entirely unrelated to global warming. Climate scientists, they argue, should consider excluding such glaciers from their databases.
这项研究的意义除了给附近居民提供火山预警信号，意义还超越了火山学的范围。世界各地冰川的测量为气候研究人员提供了一种追踪气候变化长期影响的方法。地球变暖意味着各地的冰川都在消退，而且大体上确实如此。但斯帕尼奥洛博士和雷亚博士的研究结果表明，并非所有冰川都能提供同样可靠的温度数据。火山侧面的冰川可能会增加和消退，但可能与全球变暖完全无关。他们认为，气候科学家应该考虑删除研究数据库中的火山冰川的温度数据。
