How high seas rise and how soon has a lot to do with what happens here.

海面上升的高度跟速度與這裡發生的一切有很大關聯。

Antarctica holds the largest chunk of ice on Earth.

南極洲擁有地球上最大面積的冰量。

Its western portion alone contains enough ice to raise sea levels by more than 3 meters.

光是它在西部地區的冰量就足以讓海平面上升超過三公尺。

And it's in big trouble. Largely because of this, the Thwaites glacier.

而這是一個很大的問題，很大一部分的原因是它，思韋茨冰川。

Its face towers as high as a six-story building, and extends for 120 kilometers across the coast of West Antarctica, making it about the size of Florida.

它高聳得像一棟六層樓高的大樓，橫跨西南極洲的海岸長達 120 公里，面積跟一個佛羅里達州的大小一樣。

It's a humongous glacier that reaches right into the heart of West Antarctica.

它是一個直通西南極洲中心的巨大冰山。

And that's a major problem, because in the past couple decades, it's become increasingly clear the Thwaites glacier is falling apart.

而這是一個很嚴重的問題，因過去幾十年來，思韋茨冰川正在崩塌的現象越來越明顯。

These are portraits of a vast, rugged, treacherous continent.

這是一個廣闊、荒蕪崎嶇、危機四伏的大陸。

Which has challenged man since first he could sail beyond the limits of his horizon.

自從人類可以划過地平線的極限後，就在挑戰人類。

Antarctica.

南極洲。

This is the Antarctic ice sheet.

這是南極洲的冰蓋。

It's thickest in the middle, where years and years of snowfall compacts into ice.

中間最厚，因為年復一年的降雪會結實成冰。

As the middle builds, it pushes ice out towards the oceans via glaciers.

當中間形成之後，它會透過冰山將冰往兩邊的海推去。

And the part of a glacier that floats on water is its “ice shelf.”

而浮在海面上的一部分冰山被稱作「冰棚」。

Today, man-made climate change is warming the air and water around Antarctica, causing each side of the ice sheet to melt, but at very different speeds.

時至今日，人為的氣候變遷讓南極洲附近的空氣及海水越來越溫暖，造成冰棚的每一側以非常不同的速度融化。

The Eastern ice sheet lies mostly on high ground, above sea level, which keeps it relatively safe from warm ocean water.

東部冰蓋大部分位於海拔較高的高地上，相對地使其免受溫暖海水的傷害。

That means it's melting slowly and remains relatively stable.

它融化的速度很慢且相對地比較穩定。

But West Antarctica is different; most of it lies below sea level.

但是西南極洲就不一樣了；冰蓋大部分位於海平面以下。

That means as it thins, water can undermine it, possibly kick-starting a more rapid collapse.

如果它變薄了，海水可以融化它，甚至造成更快速的崩塌。

It's why West Antarctica is considered the most important piece of ice in the world when it comes to climate change.

這就是為什麼提到氣候變遷時，西南極洲會被認定是世界上最重要的冰山。

Here's another view of the bedrock underneath Antarctica's ice sheet.

這是另一幅顯示南極洲冰蓋下的基岩圖示。

The green, yellow, and red parts are land above sea level. Like in East Antarctica.

綠色、黃色，跟紅色的部分是海平面以上的陸地，就像東南極洲。

But these blue areas in West Antarctica are all below sea level.

但是在西南極洲的藍色的區域全都在海平面以下。

This area, where the bedrock slopes continuously for more than a mile down and deep into the center of Antarctica, is the Thwaites Glacier. And it could be the most dangerous glacier in the world.

在這個地區，連續的向下傾斜一英里以上並深入南極洲中心的就是思韋茨冰川，而它可能是世界上最危險的冰川。

Surrounded by three mighty oceans, the seas are as much a part of Antarctica, as her highest mountains.

被三個廣闊的海洋包圍，這些海洋跟南極洲的距離就跟它最高的山脈一樣遠。

Right now, Thwaites is barely hanging on.

思韋茨冰川現在已經快撐不住了。

In the past 30 years, the front of Thwaites' ice shelf has lost a lot of ice, causing it to retreat backwards.

過去 30 年來，思韋茨冰川前側的冰棚已流失很多的冰，造成它往後退。

With a smaller ice shelf to slow the flow of ice, the flow of the glacier speeds up.

隨著較小塊的冰架減緩冰的流動，冰川的流失會得更快。

But the bigger problem is the glacier's "grounding line", the final point where the glacier rests on the bedrock.

但是更大的問題是冰川的「基線」，就是冰川停留在基岩上的最終點。

That grounding line has been shifting backwards as warm ocean water reaches underneath the ice shelf.

隨著溫暖的海水流到冰架下方，基線一直向後移動。

It's moved 14 kilometers since 1992.

自 1992 年起，已經移動了 14 公里了。

So ice that used to be on land becomes ice that is floating on water, raising sea levels.

所以原本應該在陸地上的冰變成在海上漂流，造成海平面上升。

The downhill slope of the bedrock means that as the grounding line moves back, it lifts an even bigger slice of ice behind it off the land and into the water.

基岩的下坡坡度意味著，隨著基線往後移，它會將更大的冰塊從陸地上抬到水中。

And that accelerates the flow of the glacier into the sea.

而這會加快冰川流進海水裡的速度。

The amount of ice flowing from Thwaites has doubled over the past 30 years.

過去 30 年來，從思韋茨冰川流失的冰量已增加一倍。

And already contributes 4 percent to global sea level rise.

且已經為全球的海平面上升貢獻 4%。

And scientists have recently detected a huge cavity two-thirds the size of Manhattan down here.

最近，科學家們在這裡發現了一個巨大的洞，其大小相當於曼哈頓的三分之二。

Scientists believe this could mean Thwaites' collapse is inevitable.

科學家認為，這可能意味著思韋茨冰川的崩塌是不可避免的。

How soon that happens is hotly debated.

而他們正在激烈討論到底會有多快。

The sleeping continent is awakening, slowly at first, but with ever-gathering momentum.

沈睡的大陸正在甦醒。剛開始很緩慢，但是力量正在增長。

The complete collapse of Thwaites will take centuries and its affected by many different things, from the temperature of the ocean currents to the makeup of the bedrock.

思韋茨冰川的徹底崩塌將持續好幾個世紀，受到許多不同因素的影響，像是從海洋的溫度到基岩的構造。

But the research shows that humans can possibly slow or even stall its collapse by curbing greenhouse gas emissions soon.

但是研究顯示，人類可以透過盡快地抑制溫室氣體排放來減緩甚至阻止冰川崩塌。

That's important because some scientists believe collapse could start this century, while others say it's already underway.

這很重要，因為有些科學家認為崩塌可能將於這個世紀開始，而另一些科學家則認為已經開始了。

The collapse of Thwaites would add about half a meter of sea level rise.

思韋茨冰川的崩塌將為海平面添加半公尺的高度。

And trigger a much bigger catastrophe.

且引發更大的災難。

Because Thwaites reaches into the middle of West Antarctica, its collapse could cause the rest of the ice sheet to collapse with it, resulting in more than 3 meters of sea level rise in the next few centuries.

因為思韋茨冰川長達西南極洲中部，它的崩塌可能會導致其它冰蓋一起崩塌，造成未來幾個世紀的海平面上升超過3米。

That would submerge not only Miami and southern Bangladesh but also parts of the Netherlands and New York City.

這不僅將淹沒邁阿密和孟加拉南部，還將淹沒荷蘭和紐約市的部分地區。

So while there's still a lot of uncertainty around Thwaites, one thing is clear: once it starts to collapse, it won't stop.

因此，儘管思韋茨冰川周圍仍然存在很多不確定性，但很明顯地，一旦它開始崩塌就不會停止。