A leak in the biological pump may have caused atmospheric carbon dioxide levels to rise thousands of years ago, leading to a warm period conducive for human civilization.
An international team of researchers have found that the major upwelling taking place in Antarctica's Southern Ocean is responsible for releasing carbon dioxide into the air, thus warming the planet and stabilizing the planet for humans to start building their empires 11,000 years ago.
The findings provide new insight to the study of climate change and its effect on ocean circulation and predicting the carbon dioxide levels of the atmosphere.
Southern Ocean Leaks CO2 Into The Air
On a grand geological scale, the world's oceans are the largest storehouses for carbon dioxide. However, a team of geologists at Princeton University and the Max Planck Institute for Chemistry in Mainz, Germany, has found that parts of the ocean are actually leaking carbon dioxide into the atmosphere.
Experts have long proposed theories for a carbon dioxide increase that led to the rise of human civilizations but have failed to provide direct evidence for these.
In a new paper published in Nature Geoscience, researchers led by Princeton professor of geological and geophysical science Daniel Sigman say that activity within the depths of the southernmost ocean of the world may have given rise to civilization.
The researchers say that as the cold deep waters of the Southern Ocean rise to the surface, it creates a leak in the biological pump that lets off more carbon dioxide into the atmosphere. This caused a warmer, more stable climate during the Holocene, a geological period that took place 10,000 years ago up to the Industrial Revolution.
"This process is allowing some of that deeply stored carbon dioxide to invade back to the atmosphere," says Sigman. "We're essentially punching holes in the membrane of the biological pump."
What Made The Holocene Period Stable?
Phytoplankton growing in the oceans and sinking to the bottom pumps carbon dioxide into the deeper waters. Scientists call this the biological pump, which is most prominent in oceans in the lower latitudes.
However, closer to the poles, the biological pump weakens. In the Southern Ocean, the pump has a huge leak that released significant amounts of carbon dioxide into the air during the Holocene.
Experts have long known that the Holocene was critical for human civilization. The period is one of the rare interglacials, an interval between the ice ages that happened over the last million years.
Unlike other interglacials, however, the Holocene was unusually stable. Glaciers retreated, creating a vast expanse of land for human settlements to form. The rise in atmospheric carbon dioxide also enriched agriculture, allowing humans to leave their hunting-gathering lifestyles and live in more permanent areas.
Carbon dioxide levels during the Holocene rose by 20 parts per million from 260 to 280 ppm. For comparison, current atmospheric carbon dioxide level is at 400 ppm, an excessive increase attributed to the burning of fossil fuels.
It is unclear what caused the upwelling in the Southern Ocean, but the researchers believe it may have been caused by changes in the eastward blowing winds surrounding Antarctica.