A new analysis of satellite images shows that the sea ice around Antarctica has reached a record low.
According to an analysis by the National Snow and Ice Data Center in Boulder, Colo., ice covered 750,000 square miles around the coast, below the previous record low of 815,000 square miles.
Marilyn N. Raphael is a professor of geography at the University of California, Los Angeles. Warmer ocean temperatures may have played a role, but there are other factors that we will be working on in the next months.
Since the late 1970s, when satellite observations began, the overall sea ice extent has increased slightly. The sea ice extent in the Arctic, which is warming three times as fast as other regions, has decreased by more than 10 percent over the last decade.
The two regions are not the same. The North Pole is covered by the Arctic Ocean, which is hemmed in by land mass. The pole is covered in the Southern Hemisphere. The Southern Ocean is open to the north and begins at lower latitudes.
The effect of climate change on sea ice in the southern part of the world is less clear than in the northern part.
Many scientists think that global warming will lead to declines in sea ice in the southern hemisphere. He said that it is hard to connect the two, especially in terms of single events.
There are a lot of factors at play when it comes to sea ice. Local ocean currents and winds can all increase or decrease sea-ice coverage.
Some research suggests that a strong El NiF1;o in the tropical Pacific in 2015 and 2016 caused sea ice coverage to plummet.
The current minimum may have been caused by warmer than normal sea-surface temperatures in some areas around the world, according to an email message from a senior researcher at the Earth Science and Observation Center at the University of Colorado.
The area of the Amundsen Sea on the western side may have had an effect. She said that a region of low pressure air that develops over the sea was especially strong this year, and that may have caused more ice to move farther to the north.
Since the late 1970s, the sea ice extent has only slightly increased, but the rate of increase began to accelerate in 2000, and ice extent reached a record high in 2014). Dr. Raphael said something unexpected happened. It plummeted over the next three years to the lowest point in history.
Dr. Raphael said the sea ice extent would return to average levels by 2020.
She said that normally levels would have continued to be average or above average for several years. She said that the new sharp drop happened so quickly.
That is what makes this one unusual. The ice went back to normal but didn't stay that way.
The researchers will have to look at how the conditions changed last year to understand why the ice extent is so low.
Because of its circular current, the Weddell Sea has a low sea ice extent, which has been seen in other parts of the coast. A group of scientists and explorers encountered relatively mild ice conditions while searching for the wreck of Ernest Shackleton's ship, which sank in 1915.
The ice extent could be even lower this year, depending on the weather, but should soon start increasing as temperatures start to drop in the fall and winter. The maximum ice coverage is reached at the end of September. Over four decades, the maximum is more than 7 million square miles.
There is an opportunity for researchers to better understand the connection between climate change and sea ice.
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