October 01, 2016 from VOA
Meltwater Lakes in Antarctica Show Signs of Trouble
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.
I’m Marsha James.
Marsha James wrote this story for VOA Learning English. Her story includes information from an Associated Press report. George Grow was the editor.
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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