Let's learn about the fifth ocean in the world.

Jerash Strait is located on the west coast of Antarctic Peninsula, in the vast sea area around Antarctica. This sea area was reclassified as the Southern Ocean by the National Geographic Cartographer. The jerash Strait was once considered as a part of the Pacific Ocean. Photography: Jasper Doest, Nat Geo Image Collection

Sarah gibbons wrote it.

Anyone familiar with the Southern Ocean knows that this water body around Antarctica is very unique.

"It is difficult for people who have been there to explain its charm in words, but they all agree that compared with other places, the glaciers there are bluer, the air is colder, the mountains are more frightening and the scenery is more unforgettable," said Seth Sykora-Bodie, a marine scientist and national geographic explorer of the National Oceanic and Atmospheric Administration (NOAA).

19 15, National Geographic began to draw maps, and from then on, four oceans were identified: Atlantic Ocean, Pacific Ocean, Indian Ocean and Arctic Ocean. This year's World Ocean Day, National Geographic announced the recognition of the Southern Ocean, the fifth ocean in the world.

"Scientists have long announced the existence of the Southern Ocean, but we have never officially recognized it because there is no international agreement," said Alex Tait, a geographer at the National Geographic Society.

The focus of debate among geographers is whether the waters around Antarctica have enough features to be named separately, or whether this cold water is just the southern extension of the Pacific Ocean, Atlantic Ocean and Indian Ocean.

"In a sense, we are like geography nerds," Tate said. Over the years, scientists and the media have used the word "Southern Ocean" more and more, and he and the Map Policy Committee of the National Geographic Society have been thinking about this change.

He added that this trend is consistent with the National Geographic Society's advocacy of protecting the world's oceans and attracting public attention to areas in urgent need of protection.

"We've been labeling it, but the label is slightly different," Tate said. "This time we took the last step, which shows that we want to admit it because there is ecological isolation here."

Sylvia Earle, a marine biologist and national geographic explorer, praised the map update.

Ocean currents define the ocean.

Other oceans are defined by the continents around them, while the southern ocean is defined by ocean currents.

Scientists estimate that the Antarctic circumpolar current was formed about 34 million years ago, when Antarctica was separated from South America. Therefore, seawater can flow unimpeded in the Antarctic.

The Antarctic circumpolar current flows around the South Pole from west to east, forming a wave zone centered at about 60 degrees south latitude, which is now designated as the northern boundary of the Southern Ocean. Compared with the seawater in the north, the seawater in the Antarctic circumpolar current is colder and slightly lower in salinity.

The Antarctic circumpolar current extends from the sea surface to the seabed, transporting more seawater than any other ocean current. It absorbs seawater from the Atlantic Ocean, the Pacific Ocean and the Indian Ocean, and helps to drive a global circulation system called "conveyor belt" to transfer heat to the earth. Cold and dense seawater sinks into the Antarctic seabed, which helps to store carbon in the deep sea. From these two aspects, the southern ocean is of vital significance to the earth's climate.

At present, scientists are studying how climate change caused by human activities changes the southern ocean. Scientists have found that the sea water flowing through the Antarctic circumpolar current is warming, but they are not sure how much this will affect the Antarctic. In the Antarctic circumpolar current closest to the land, there is a phenomenon of rapid melting of continental ice sheets and ice shelves.

Unusual environment

At present, the Antarctic circumpolar current surrounds the cold southern waters, which helps to maintain the low temperature in Antarctica and the ecological uniqueness of the southern ocean. Thousands of species live here. They went to no way back.

Enrique Sala, resident explorer of National Geographic, said that the Southern Ocean "has a unique and fragile marine ecosystem and is home to wonderful marine life such as whales, penguins and seals".

More importantly, the Southern Ocean has also had an ecological impact on other places. Humpback whales, for example, feed on krill near the South Pole, migrate north in winter and spend their time in different ecosystems in South and Central America. Some seabirds pass through here when they migrate.

In the Southern Ocean, people have been worried about the impact of industrial fishing on species such as krill and chinchilla (also known as Chilean sea bass) for decades. 1982, local fishing is prohibited. In 20 16, the world's largest marine reserve was established in the Ross Sea in the west of Antarctica. Some organizations are trying to draw more marine protected areas to protect the most important feeding areas in the southern ocean, such as the waters near the Antarctic Peninsula.

"Many countries in the world support protecting these areas and banning industrial fishing," Sarah said.

Describe the real world

In the late 1970s, the National Geographic Society hired a geographer to review all changes and adjustments in the published map. 20 16, this important task was handed over to Tait.

"What's important is that this is a map policy, not a position policy of National Geographic on (geopolitical) disputes," he said. For example, the national geographic map shows that Britain controls the Falkland Islands, although Argentina also claims sovereignty. In disputed areas, Tait will work with geographers and editors to determine the most accurate description of an area.

There are some small changes every week or every two weeks, but there are few big changes like determining the southern ocean.

Generally speaking, National Geographic follows the rules of the International Hydrographic Organization (IHO) in naming oceans. Although IHO is not directly responsible for confirming geographical names, it cooperates with the United Nations Group of Experts on Geographical Names to standardize geographical names internationally. 1937, IHO recognized the Southern Ocean in its guide, but it was cancelled in 1953 due to disputes. Since then, this issue has been under consideration, but it has not been unanimously agreed by the members of the organization, so the name of the Southern Ocean has not been restored.

But since 1999, the United States Geographical Names Board has been using this place name. In February this year, NOAA officially recognized that the Southern Ocean is unique.

Tate said that the new policy of National Geographic will affect children in schools to see the world with maps.

"I think one of the biggest influences is education," he said. "We are studying the ocean, which opens the door for students to understand the ocean world. If the Southern Ocean is not included, then students cannot understand its uniqueness and importance. "

(Translator: Sky4)