VOA慢速英语2016 南极洲或因融水湖增多而不断瓦解（在线收听）

AS IT IS 2016-10-02 Meltwater Lakes in Antarctica Show Signs of Trouble 南极洲或因融水湖增多而不断瓦解

Antarctica is home to the largest ice mass on Earth.

The continent sits on 14 million square kilometers of rock. About 98 percent of the land surface is covered by ice.

Beautiful lakes have begun to appear on the top of the ice. They look like islands of deep blue in an ocean of white. These lakes are called supraglacial or meltwater lakes.

Although the lakes can be beautiful, the ones scientists studied are a sign of trouble. Amber Leeson is a scientist with Lancaster University in England.

"We really weren't expecting to find lakes as far inland as 20 kilometers, which was the furthest inland lake we found during the study. And it was important that we found the link between the atmospheric temperature and the depth, number, and size of the lakes..."

Scientists say Antarctica has always had supraglacial lakes appearing on the ice during the summer months. But the more lakes there are, the more unstable they make the continent’s ice shelf.

Ice shelves are permanent, but floating pieces of ice that connect to the land. They form where a glacier or ice sheet reaches a coastline and into the sea.

Leeson says water from the lakes can drip down through the glacier, causing the huge river of ice and snow to weaken.

"If they form on the grounded ice, which is the bit of the ice sheet that sits on the bedrock, then the water they contain can drain away through the ice to the base, where it can lubricate the flow of the ice and make it flow a bit faster. If they form on the floating part of the ice, which is where the ice shelf extends over the ocean and begins to float on the sea, by repeatedly filling and draining they can actually weaken the ice shelf."

Leeson and other scientists believe that lakes are partly responsible for the collapse of the Antarctica ice sheets.

"...the Larsen B ice shelf collapsed in 2002 and we think that this is because it was covered in lakes in the years prior to collapse, and that by repeatedly filling and draining, they weaken the ice sheet, leading to its eventual disintegration..."

And as temperatures rise, the team expects to see more and more lakes appearing in the continent. The scientists fear that all that meltwater could raise the world's sea levels.

南极洲有世界上最大的冰块。

南极洲大陆下面有1400万平方公里的岩石。其地表98%覆盖着冰。

很多美丽的湖泊逐渐在冰层上方显现，看起来就像一片白色海洋中的深蓝岛屿。这些湖泊叫做冰上湖或融水湖。

虽然这些融水湖很美，但有一些科学家发现了麻烦的迹象。其中的安布尔是伦敦兰卡斯特大学的一名科学家。

“我们根本没想到能在内陆20千里的地方发现湖泊，这也是我们本次研究中发现的最远的融水湖。找到气候温度与融水湖深度、数量和大小之间的关系十分重要”。

科学家称，南极洲夏季期间总会在冰面上出现融水湖。但融水湖数量越多，就会使得南极洲大陆的冰架越不稳固。

冰架是永久的，但浮动的冰块也与南极洲大陆相连。它们在冰川或冰原贴近海岸以及到达大海深处的地方形成。

安布尔称，融水湖的水会通过冰川滴落，瓦解融水湖的冰雪。

“如果融水湖在接近底层冰的地方形成，也就是在基岩上的冰原上形成，那么融水湖中的水就会通过冰层到达基部，会对冰块的流动起到润滑作用，加速其流动；如果融水湖在表层浮动的冰上形成，也就是冰架延伸到大海并向海深处浮动的地方，那么通过不断的填水和排水，这些融水湖也会瓦解冰架”。

安布尔和其他科学家认为，融水湖是南极洲冰架坍塌的原因之一。

“……拉森B冰架2002年坍塌过一次，我们认为这就是长年来融水湖覆盖的结果，因为不断的充水和排水会瓦解冰架，导致最终的分解”。

而且，随着气温的升高，该研究组认为会有越来越多的融水湖出现在南极洲大陆上。他们担心，这些融水会升高全球的海平面高度。

Words in This Story

ice mass - n. a large piece of ice

supraglacial lake – n. any pond of liquid water on the top of a glacier

ice sheet – n. a very large and thick area of ice that covers a region

ice shelf – n. a floating sheet of ice permanently attached to a land mass

glacier – n. an large areas of ice formed from falling snow and building up over the years