Although Antarctica is now covered by a layer of ice that is miles thick, was this once the case?
When did the continent with the lowest average temperature become completely devoid of ice?
The continent of Antarctica, which is approximately four times the size of the United States, is almost totally covered by a covering of ice that is miles thick.
The South Pole, on the other hand, has not always been frozen. But when was the last time that Antarctica was completely devoid of ice?
Using geological terminology, this ice cap was produced not too long ago, according to specialists who spoke with Live Science. According to Eric Wolff, a paleoclimatologist at the University of Cambridge, “I believe the majority of people would say that the first time the ice sheet formed in Antarctica was approximately 34 million years ago.” “[Previously] most of it would have been like northern Canada today — tundra and coniferous forest.”
One of the most important factors that determines the amount of ice covering is the global temperature. Approximately fifty million years ago, the temperature of the earth was approximately twenty-five degrees Fahrenheit (14 degrees Celsius) higher than it is now. However, temperatures then began to gradually fall during the subsequent sixteen million years. At a point in time known as the Eocene-Oligocene border, which occurred 34 million years ago, the temperature was 14.4 degrees Fahrenheit (8 degrees Celsius) higher than it is now.
What was the cause of this reduction in temperature, and was it the only thing that was required for the formation of the ice sheets?
“There are a couple of variables and probably all were in play,” Wolff said in his interview. “One of them is a change in the concentration of carbon dioxide in the atmosphere, and the other is the movement of the continents and, in specific, the opening up of the Drake Passage,” which is the strait that links the South Atlantic with the South Pacific. The Drake Passage is located between South America and Antarctica.
If there is a greater concentration of carbon dioxide in the atmosphere, then a greater amount of heat will be retained, resulting in a warmer world.
Approximately sixty million to fifty million years ago, the quantity of carbon dioxide in the atmosphere of the Earth was very high. According to Tina van de Flierdt, a geochemist at Imperial College London, the concentration was somewhere between two thousand and two thousand parts per million, which is equivalent to between two and five times the levels that are present now.
“But we know that the CO2 in the atmosphere came down across that Eocene-Oligocene boundary,” according to her interview with Live Science. She went on to say that this drop in atmospheric CO2 would have been followed by a lowering of the global temperature, which would have most likely caused the Earth to cross a threshold and allowed ice sheets to emerge.
As a result of plate tectonics, however, there was probably also a localized cooling that occurred on the Antarctic continent, according to Wolff. During this historical period, South America and Antarctica eventually parted ways, hence allowing for the formation of what is today known as the Drake Passage.
“This led to what we call a circumpolar current — water going right around Antarctica in a circle,” Wolff said to reporters. “This isolates Antarctica from the rest of the world and makes it much harder for warm air masses to get across the Southern Ocean and, therefore, makes Antarctica colder.”
In addition, he noted that plate tectonics had a direct impact on the levels of carbon dioxide. In light of the fact that rock weathering and volcanic activity are both components of the carbon cycle, geological activities have the potential to alter the equilibrium of gases in the atmosphere over the course of thousands of years.
As a result of the chemical traces found in rock deposits, researchers have a reasonable amount of confidence about this shift that occurred 34 million years ago, despite the fact that there is still some doubt. Both oxygen-16, sometimes known as common oxygen, and oxygen-18, also known as heavy oxygen, are both types of oxygen atoms. The seas, and therefore the shells of tiny marine animals, have a greater percentage of oxygen-18 when ice sheets are larger. This is because continental ice includes a higher proportion of the lighter oxygen-16 of the two types of oxygen.
“By looking at the oxygen isotopes in the carbonate shells of small sea creatures in ocean sediments, you see an increase around 34 million years ago, which people take as being because the [lighter] oxygen isotope is going onto the continent of Antarctica,” Wolff further said.
“It’s definitely possible,” van de Flierdt stated in response to the question of whether or not Antarctica might ever be free of ice to begin with. Planet Earth has been successful in the past. It’s possible that Planet Earth might do it again. She continued by saying that while it is very improbable that human activity would result in the entire melting of the ice sheet, it is imperative that we do all in our power to keep the loss of ice from the Antarctic region to a minimum right now. “We are in charge of preventing the worst-case scenario,” van de Flierdt added. “It is in our hands.”
