Very Large Crack Creating Iceberg in Antarctica

 

Researchers say part of a very large shelf of ice on Antarctica could soon break off – and become an iceberg¹.

A team of scientists is closely watching part of the Larsen Ice Shelf, off the coast of northwestern Antarctica. The area is connected to land, but floats on seawater instead of sitting on top of the continent.

The piece of ice, known as Larsen C Ice Shelf, caught the attention of researchers a few years ago. There are many cracks, or signs of weakness, in the ice. In 2010, the scientists found that one crack was getting bigger.

Martin O’Leary is with Swansea University in Wales. He spoke² with VOA about the work he does with Project MIDAS, the British group studying Antarctica.

“We became concerned in 2014 when it started to become obvious that this crack was going to produce a particularly large iceberg, much larger than we had initially³ expected.”

Icebergs⁴ are huge masses of ice that break off from glaciers⁵ in coastal⁶ areas. Glaciers begin as fallen snow. Over time, the weight of the snow creates large, thickened ice masses. When the ice becomes too heavy, pieces break off and float in the sea.

The crack on the Larsen C Ice Shelf has been growing quickly -- by an estimated 18 kilometers just in the second half of December.

And how large will this future iceberg be?

Martin O’Leary thinks it will be between nine to 12 percent of the ice shelf, which is about the size of some countries.

The iceberg will be “around 5,000 square kilometers,” he says.

That would be about the size of Lebanon. Now, only 20 kilometers of ice still connects the iceberg to the shelf.

What is causing the break?

By nature, ice is brittle⁷ and can break easily. O’Leary says the process that is opening the large crack is a natural one.

“The crack is a natural phenomenon, the ice by its nature is quite brittle, it tends to crack quite a lot. What happens is that snow and bits of debris⁸ fall into the crack and that pushes the crack open even wider, so the force of that crack ratchets the crack open and that’s what causes it to get longer and longer."

He adds that “to the best of our knowledge,” this break is not a product of climate change. Some studies have linked rising temperatures to human activities.

The new iceberg is not expected to change ocean levels around the world. That is because the iceberg is already sitting in the sea and it will not displace⁹ more water.

Once it breaks off, the iceberg will slowly move away. Over time, it will break into smaller pieces, which will move north, and eventually melt away.

What is the Larsen Ice Shelf?

The Larsen Ice Shelf is a series of shelves, all of which are linked together. They may be connected to the land, but float out over the sea. They grew out from the Antarctic mainland over tens of thousands of years. And over time, pieces have broken off.

Larsen A, the most northern and smallest part, broke free from the continent in 1995.

There was the larger Larsen B Ice Shelf. It was an estimated 3,200 square kilometers of ice, and about 220 meters thick. But it broke up into the sea in 2002.

Now, Larsen C is larger still, with ice thickness averaging 350 meters. This is where the piece is that is about to break off of the ice shelf.

O’Leary says “the honest answer is we don’t know” when the iceberg will break off. But scientists think it will probably be in the next few months.

While they call this a “natural process,” O’Leary explains that this break could make the area more vulnerable¹⁰ to climate change in the future.

“What we’re worried about is that this will put the ice shelf in a more unstable¹¹ position, which will mean that the effects of climate change, such as melting of the ice, thinning of the ice, those can have a stronger effect now.”

And that means there could be more events like this one, with large parts of the ice shelf falling into the sea. It could lead to the collapse¹² of the whole shelf.

There is not enough information to predict if or when that might happen. But if it does, it is possible that the ice, which the Larsen shelf holds on the land, could start sliding into the sea.

Predictions suggest that could raise world sea levels by as much as 10 centimeters.

Words in This Story

crack – n. a line in the surface of something that is broken but not separated into pieces

obvious – adj. easy to see or notice

initially – adv. occurring at the beginning of something

phenomenon – n. something that can be observed and studied that is unusual or difficult to understand or explain fully¹³

ratchet – v. to increase or decrease something by a series of small amounts

vulnerable – adj. easily hurt or harmed physically, mentally or emotionally

1 iceberg   

n.冰山，流冰，冷冰冰的人

参考例句：

• The ship hit an iceberg and went under.船撞上一座冰山而沉没了。
• The glacier calved a large iceberg.冰河崩解而形成一个大冰山。

2 spoke   

n.（车轮的）辐条；轮辐；破坏某人的计划；阻挠某人的行动 v.讲，谈（speak的过去式）；说；演说；从某种观点来说

参考例句：

• They sourced the spoke nuts from our company.他们的轮辐螺帽是从我们公司获得的。
• The spokes of a wheel are the bars that connect the outer ring to the centre.辐条是轮子上连接外圈与中心的条棒。

3 initially   

adv.最初，开始

参考例句：

• The ban was initially opposed by the US.这一禁令首先遭到美国的反对。
• Feathers initially developed from insect scales.羽毛最初由昆虫的翅瓣演化而来。

4 icebergs   

n.冰山，流冰( iceberg的名词复数 )

参考例句：

• The drift of the icebergs in the sea endangers the ships. 海上冰山的漂流危及船只的安全。 来自《简明英汉词典》
• The icebergs towered above them. 冰山高耸于他们上方。 来自辞典例句

5 glaciers   

冰河，冰川( glacier的名词复数 )

参考例句：

• Glaciers gouged out valleys from the hills. 冰川把丘陵地带冲出一条条山谷。
• It has ice and snow glaciers, rainforests and beautiful mountains. 既有冰川，又有雨林和秀丽的山峰。 来自英语晨读30分（高一）

6 coastal   

adj.海岸的，沿海的，沿岸的

参考例句：

• The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
• This country will fortify the coastal areas.该国将加强沿海地区的防御。

7 brittle   

adj.易碎的；脆弱的；冷淡的；(声音)尖利的

参考例句：

• The pond was covered in a brittle layer of ice.池塘覆盖了一层易碎的冰。
• She gave a brittle laugh.她冷淡地笑了笑。

8 debris   

n.瓦砾堆，废墟，碎片

参考例句：

• After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
• Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上，导致蛀牙。

9 displace   

vt.取代，迫使...离开家园，使离开原位

参考例句：

• The extraordinary thing was that french did not displace English.奇特的是，法语没有取代英语。
• At present,obviously,nevertheless,he was not likely to displace himself.但时至今日，很清楚，他不可能再迁徙了。

10 vulnerable   

adj.易受伤的，脆弱的，易受攻击的

参考例句：

• He volunteered to protect her as she looked so vulnerable.她看上去很脆弱，他就主动去保护她。
• The company is in an economically vulnerable position.该公司目前经济状况不稳定。

11 unstable   

adj.不稳定的，易变的

参考例句：

• This bookcase is too unstable to hold so many books.这书橱很不结实，装不了这么多书。
• The patient's condition was unstable.那患者的病情不稳定。

12 collapse   

vi.累倒；昏倒；倒塌；塌陷

参考例句：

• The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做了一次彻底的调查分析。

13 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。