Scientists say the amount of sea ice around Antarctica has decreased from a record high to a record low in only a few years.
Sea ice is ice covering the ocean rather than land.
Ice floating in the waters around the Antarctic continent started increasing in 1979, about the time satellite observations first started.
The amount of Antarctic sea ice reached a record high in 2014. But a study of data gathered by satellites from the United States space agency NASA showed something different three years later. The data suggested that the yearly average amount of Antarctic sea ice reached its lowest level.
Scientists released the findings on July 1 in a study published in the Proceedings of the National Academy of Sciences.
National Snow and Ice Data Center director Mark Serreze said that, in recent years, “things have been crazy.” He told The Associated Press the quickly decreasing ice levels are a “white-knuckle ride.”
Serreze and other experts said they do not know what has caused the loss of ice. It could be a natural change, or a result of rising world temperatures caused by human activity.
“But the fact that a change this big can happen in such a short time should be viewed as an indication that the Earth has the potential for significant and rapid change,” said University of Colorado ice scientist Waleed Abdalati.
In the polar areas, sea ice levels increase during the winter and shrink in the summer. Around Antarctica, sea ice covered an average area of 12.8 million square kilometers in 2014. But the study shows that by 2017, only 10.7 million square kilometers of sea was covered by ice.
The difference represents an area bigger than the size of Mexico.
Claire Parkinson is the NASA climate scientist who wrote the report. She says losing that much sea ice in just three years “is pretty incredible” and faster than anything scientists have seen before.
Antarctic sea ice increased slightly in 2018. Although sea ice is expanding during the winter in Antarctica, levels in May and June of this year were the lowest on record, the ice data center reported.
Antarctica’s temperatures are generally lower than those near the North Pole. In the north, the Arctic is a floating collection of ice on an ocean surrounded by land. Antarctica, in the south, is just the opposite, with land surrounded by an ocean. That causes the ice to develop much farther out, Parkinson said.
When Antarctic sea ice was expanding, scientists pointed to changes in wind and air pressure or the movements of the ocean. They also considered natural ongoing changes in the climate.
Now, some of those explanations may need to be reconsidered, making what happens next a mystery, Parkinson said.
I’m Pete Musto.
Seth Borenstein reported this story for the Associated Press. Pete Musto adapted it for VOA Learning English. Mario Ritter Jr. was the editor.
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Words in This Story
crazy – adj. very unusual
white-knuckle ride – n. an experience marked by, causing, or experiencing intense worry or nervousness
indication – n. something, such as a sign or signal, that points out or shows something
potential – n. a chance or possibility that something will happen or exist in the future
significant – adj. large enough to be noticed or have an effect
rapid – adj. happening quickly
polar – adj. of or relating to the North or South Pole or the region around it
incredible – adj. difficult or impossible to believe