南极东部最大的冰川之一正在迅速消融

南极东部最大的冰川之一正在迅速消融

We interrupt coverage of the current disaster to inform you that a greater but slower-moving calamity has not taken a holiday. A major glacier in East Antarctica has retreated 5.4 kilometers (3.3 miles) in 22 years, satellite observations have revealed.

我们中断对当前这场灾难的报道，是为了告诉大家，一场规模更大但进展更缓慢的灾难还没有结束。卫星观测显示，南极洲东部的一个主要冰川在22年里退缩了5.4公里(3.3英里)。

Despite a handful of exceptions driven by local conditions, the vast majority of the planet's rivers of ice are in retreat. However, a finding from East Antarctica suggests more than half the world's ice is locked up in this one region – enough to raise sea levels by 1.5 meters (5 feet). Several factors also make it one of the most resistant parts of the planet to global heating-induced melting, so if glaciers are retreating there, nowhere is safe.

除了少数受当地条件影响的例外，地球上绝大多数的冰河都在退缩。然而，来自东南极洲的一项发现表明，世界上超过一半的冰被锁定在这一地区，足以使海平面上升1.5米(5英尺)。几个因素也使它成为地球上最能抵御全球变暖导致的融化的地区之一，所以如果冰川在那里融化，没有地方是安全的。

A paper in Geophysical Research Letters reports that the Denman Glacier has lost 5 kilometers (3 miles) of length between 1996 and 2018. Since 1979, 268 billion tons of the glacier's ice has melted, a volume sufficient to cover all of England more than 2 meters (7 feet) deep.

《地球物理研究快报》的一篇论文称，从1996年到2018年，丹曼冰川的长度已经减少了5公里(3英里)。自1979年以来，2680亿吨冰川的冰已经融化，其体积足以覆盖整个英格兰超过2米(7英尺)深。

Stephen Luntz

The Denman holds around 3 percent of East Antarctica's ice – on its own it could add 1.5 meters (5 feet) to global sea level. The expression “glacial pace” may need reworking.

丹曼冰库拥有南极洲东部约3%的冰——单是丹曼冰库就能使全球海平面上升1.5米(5英尺)。“缓慢的步伐”这个表达可能需要重新润色。

“East Antarctica has long been thought to be less threatened, but as glaciers such as Denman have come under closer scrutiny by the cryosphere science community, we are now beginning to see evidence of potential marine ice sheet instability in this region,” said Professor Eric Rignot of the University of California, Irvine, in a statement. “The ice in West Antarctica has been melting faster in recent years, but the sheer size of Denman Glacier means that its potential impact on long-term sea level rise is just as significant.”

“南极东部一直被认为是威胁较小,但随着冰川如Denman冰冻圈科学社区面临更严格的审查,我们现在开始看到证据的潜在海洋冰层不稳定在这个地区,”埃里克·里戈诺特教授说的加州大学欧文分校的一份声明中。“近年来，南极洲西部的冰融化得越来越快，但丹曼冰川的巨大规模意味着，它对长期海平面上升的潜在影响同样巨大。”

The retreat hasn't been noticed before because to most observers the boundary between the glacier itself and the Shackleton Ice Shelf is invisible. However, the Denman extends as much as 3.5 kilometers (2.2 miles) down into the deepest continental canyon on Earth, where it touches bedrock. As the planet heats up, it is this submarine component that is melting, leaving only a much thinner tongue of sea-ice extending into the ocean. Rignot and colleagues used the Italian Space Agency's COSMO-SkyMed satellites' radar capacity to study the depth beneath the glacier and compare its grounding line with older observations.

这种退缩以前没有被注意到，因为对大多数观察者来说，冰川本身和沙克尔顿冰架之间的边界是看不见的。然而，丹曼河延伸了3.5公里(2.2英里)到地球上最深的大陆峡谷，在那里它触及基岩。随着地球温度的升高，正是这种海底成分在融化，只留下一片更薄的海冰伸入海洋。里格诺特和他的同事利用意大利航天局的COSMO-SkyMed卫星的雷达能力来研究冰川下的深度，并将其接地线与以前的观测结果进行比较。

The retreat would have been even more extensive if a subglacial ridge was not holding the eastern flank in place. Unfortunately, the western flank not only lacks any similar stabilizing force at the glacier's current front but the underwater trough only gets deeper behind it, allowing the glacier to keep on retreating if warming continues.

如果冰川下的山脊没有把东翼固定住的话，撤退的范围会更大。不幸的是，西侧不仅在冰川当前的锋面缺乏任何类似的稳定力，而且水下的凹槽在它后面只会越陷越深，如果变暖继续下去，冰川就会继续后退。

A minor comfort is that smaller nearby glaciers that Rignot studied appear more stable.

令人稍感安慰的是，没有经过严格研究的附近较小的冰川似乎更稳定。