晴朗的天空導致格陵蘭冰蓋有史以來最大的下降

晴朗的天空導致格陵蘭冰蓋有史以來最大的下降

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，格陵蘭島晴朗的天空和更多的陽光，導致有史以來最大的冰蓋質量下降。

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.

哥倫比亞大學Lamont-Doherty地球觀測站的Marco Tedesco領導的一項研究表明，這一現(xiàn)象與一種特殊的高壓系統(tǒng)有關，該系統(tǒng)阻止了云層的形成。特德斯科在研究報告的評論中說，這表明，沒有納入大氣數(shù)據(jù)的氣候模型可能低估了未來冰川消融的一半。

“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.”

“在過去的幾十年里，這些大氣條件變得越來越頻繁，”他說。“對未來影響的模擬很可能低估了氣候變化造成的大規(guī)模損失。”

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.

科學家們密切監(jiān)測格陵蘭冰蓋的表面質量平衡，即融化造成的質量損失與降雪和其他積冰造成的質量損失之比。但是沒有云的時候，就沒有雪。結果，冰蓋上的降雪量比去年平均減少了500億噸。沒有了新的積雪，冰吸收了更多的熱量，最終融化到3200億噸，低于1981年至2010年的平均質量，這是自1948年有記錄以來的最大降幅。 它只回收了500億噸，大約是1981年到2010年平均增長量的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.

研究報告的合著者，列日大學的澤維爾·費特威斯在對論文的評論中說，增長如此之小可不是好消息。這部分是因為地表質量的損失并不是冰川縮小的唯一途徑。裂縫也會在冰中形成，導致大塊的冰裂入海洋，這一過程被稱為冰裂。在穩(wěn)定的條件下，表面質量平衡的增益將足夠高，以補償冰山崩解時失去的冰，但在目前的條件下不是這樣。

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.

同樣的天氣系統(tǒng)在格陵蘭島北部和西部造成了不同的破壞效果。來自低海拔的溫暖潮濕的空氣聚集形成了云，但這些云并沒有帶來降雪，而是吸收了通常會從冰反彈到大氣中的熱量，產生了小規(guī)模的溫室效應。

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

總的來說，格陵蘭冰蓋在2019年估計損失了6000億噸，相當于海平面上升約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.”

“你可以把格陵蘭島的總體平衡視為你的銀行賬戶，”特德斯科說。“有些時候你花得多，有的時候你賺得多。如果你花費太多，你就會變得消極。這就是發(fā)生在格陵蘭島的情況。”