南極東部最大的冰川之一正在迅速消融

南極東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.

我們中斷對(duì)當(dāng)前這場(chǎng)災(zāi)難的報(bào)道，是為了告訴大家，一場(chǎng)規(guī)模更大但進(jìn)展更緩慢的災(zāi)難還沒(méi)有結(jié)束。衛(wèi)星觀(guān)測(cè)顯示，南極洲東部的一個(gè)主要冰川在22年里退縮了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.

除了少數(shù)受當(dāng)?shù)貤l件影響的例外，地球上絕大多數(shù)的冰河都在退縮。然而，來(lái)自東南極洲的一項(xiàng)發(fā)現(xiàn)表明，世界上超過(guò)一半的冰被鎖定在這一地區(qū)，足以使海平面上升1.5米(5英尺)。幾個(gè)因素也使它成為地球上最能抵御全球變暖導(dǎo)致的融化的地區(qū)之一，所以如果冰川在那里融化，沒(méi)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.

《地球物理研究快報(bào)》的一篇論文稱(chēng)，從1996年到2018年，丹曼冰川的長(zhǎng)度已經(jīng)減少了5公里(3英里)。自1979年以來(lái)，2680億噸冰川的冰已經(jīng)融化，其體積足以覆蓋整個(gè)英格蘭超過(guò)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.

丹曼冰庫(kù)擁有南極洲東部約3%的冰——單是丹曼冰庫(kù)就能使全球海平面上升1.5米(5英尺)。“緩慢的步伐”這個(gè)表達(dá)可能需要重新潤(rùn)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.”

“南極東部一直被認(rèn)為是威脅較小,但隨著冰川如Denman冰凍圈科學(xué)社區(qū)面臨更嚴(yán)格的審查,我們現(xiàn)在開(kāi)始看到證據(jù)的潛在海洋冰層不穩(wěn)定在這個(gè)地區(qū),”埃里克·里戈諾特教授說(shuō)的加州大學(xué)歐文分校的一份聲明中。“近年來(lái)，南極洲西部的冰融化得越來(lái)越快，但丹曼冰川的巨大規(guī)模意味著，它對(duì)長(zhǎng)期海平面上升的潛在影響同樣巨大。”

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.

這種退縮以前沒(méi)有被注意到，因?yàn)閷?duì)大多數(shù)觀(guān)察者來(lái)說(shuō)，冰川本身和沙克爾頓冰架之間的邊界是看不見(jiàn)的。然而，丹曼河延伸了3.5公里(2.2英里)到地球上最深的大陸峽谷，在那里它觸及基巖。隨著地球溫度的升高，正是這種海底成分在融化，只留下一片更薄的海冰伸入海洋。里格諾特和他的同事利用意大利航天局的COSMO-SkyMed衛(wèi)星的雷達(dá)能力來(lái)研究冰川下的深度，并將其接地線(xiàn)與以前的觀(guān)測(cè)結(jié)果進(jìn)行比較。

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.

如果冰川下的山脊沒(méi)有把東翼固定住的話(huà)，撤退的范圍會(huì)更大。不幸的是，西側(cè)不僅在冰川當(dāng)前的鋒面缺乏任何類(lèi)似的穩(wěn)定力，而且水下的凹槽在它后面只會(huì)越陷越深，如果變暖繼續(xù)下去，冰川就會(huì)繼續(xù)后退。

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

令人稍感安慰的是，沒(méi)有經(jīng)過(guò)嚴(yán)格研究的附近較小的冰川似乎更穩(wěn)定。