晴朗的天空导致格陵兰冰盖有史以来最大的下降

晴朗的天空导致格陵兰冰盖有史以来最大的下降

Clear skies and more sunlight over Greenland last summer resulted in the biggest drop in the ice sheet’s mass ever recorded, new research shows.

新的研究表明，去年夏天，格陵兰岛晴朗的天空和更多的阳光，导致有史以来最大的冰盖质量下降。

The phenomenon was linked to an exceptional high-pressure system that prevented the formation of clouds, according to a study led by Marco Tedesco from Columbia University’s Lamont-Doherty Earth Observatory. That suggests climate models that don’t incorporate atmospheric data could be underestimating future melting by about half, Tedesco said in commentary accompanying the research.

哥伦比亚大学Lamont-Doherty地球观测站的Marco Tedesco领导的一项研究表明，这一现象与一种特殊的高压系统有关，该系统阻止了云层的形成。特德斯科在研究报告的评论中说，这表明，没有纳入大气数据的气候模型可能低估了未来冰川消融的一半。

“These atmospheric conditions are becoming more and more frequent over the past few decades,” he said. “Simulations of future impacts are very likely underestimating the mass loss due to climate change.”

“在过去的几十年里，这些大气条件变得越来越频繁，”他说。“对未来影响的模拟很可能低估了气候变化造成的大规模损失。”

Scientists closely monitor the surface mass balance of Greenland’s ice sheet—that is, how much mass is lost due to melting compared with how much is gained due to snowfall and other accumulation. But when there are no clouds, there’s no snow. As a result, about 50 billion fewer tons of snowfall fell over the ice sheet than average last year. Without the fresh snow cover, the ice absorbed more heat, eventually melting down to 320 billion tons below the average mass for 1981 to 2010, the biggest drop since record-keeping began in 1948. It gained back just 50 billion tons, about 13% of the average increase between 1981 and 2010.

科学家们密切监测格陵兰冰盖的表面质量平衡，即融化造成的质量损失与降雪和其他积冰造成的质量损失之比。但是没有云的时候，就没有雪。结果，冰盖上的降雪量比去年平均减少了500亿吨。没有了新的积雪，冰吸收了更多的热量，最终融化到3200亿吨，低于1981年至2010年的平均质量，这是自1948年有记录以来的最大降幅。 它只回收了500亿吨，大约是1981年到2010年平均增长量的13% 。

Such a small increase is not good news said the study’s co-author, the University of Liege’s Xavier Fettweis, in commentary on the paper. That’s in part because surface mass losses aren’t the only way glaciers shrink. Fissures also form in the ice, causing large chunks to break off into the ocean, a process known as calving. Under stable conditions, the gains in surface mass balance would be high enough to compensate for the ice that’s lost when icebergs calve off, but not under current conditions.

研究报告的合著者，列日大学的泽维尔·费特威斯在对论文的评论中说，增长如此之小可不是好消息。这部分是因为地表质量的损失并不是冰川缩小的唯一途径。裂缝也会在冰中形成，导致大块的冰裂入海洋，这一过程被称为冰裂。在稳定的条件下，表面质量平衡的增益将足够高，以补偿冰山崩解时失去的冰，但在目前的条件下不是这样。

The same weather system caused a different damaging effect in the northern and western parts of Greenland. Warm, moist air from the lower altitudes gather there and formed clouds, but instead of bringing snowfall, these clouds trapped the heat that would normally bounce off of the ice into the atmosphere, creating a small-scale greenhouse effect.

同样的天气系统在格陵兰岛北部和西部造成了不同的破坏效果。来自低海拔的温暖潮湿的空气聚集形成了云，但这些云并没有带来降雪，而是吸收了通常会从冰反弹到大气中的热量，产生了小规模的温室效应。

Overall, the Greenland ice sheet lost an estimated 600 billion tons in 2019, representing a sea level rise of about 1.5 millimeters.

总的来说，格陵兰冰盖在2019年估计损失了6000亿吨，相当于海平面上升约1.5毫米。

“You can see the mass balance in Greenland as your bank account,” Tedesco said. “In some periods you spend more, and in some periods you earn more. If you spend too much you go negative. This is what happened to Greenland.”

“你可以把格陵兰岛的总体平衡视为你的银行账户，”特德斯科说。“有些时候你花得多，有的时候你赚得多。如果你花费太多，你就会变得消极。这就是发生在格陵兰岛的情况。”