The Southern Ocean around Antarctica plays a decisive role in the global carbon cycle – and thus in the climate system.
The Southern Ocean around Antarctica plays a decisive role in the global carbon cycle – and thus in the climate system. This is supported by a new study involving the GEOMAR Helmholtz Centre for Ocean Research Kiel, published today in Nature Communications. An international team has demonstrated that between 800,000 and 430,000 years ago, a stronger layering of the Southern Ocean prevented carbon dioxide from rising from the deep ocean into the atmosphere. As a result, temperatures were significantly lower than in later warm periods.
The Earth’s climate has fluctuated between cold and warm periods for millions of years. During the so-called “lukewarm interglacials” – warm phases between 800,000 and 430,000 years ago – atmospheric CO2 concentrations were only around 240 to 260 ppm (parts per million, i.e. molecules per one million molecules of air). Later interglacials reached values of 280 to 300 ppm. By comparison, today’s concentration has already exceeded 420 ppm due to human emissions. Why these earlier warm periods were cooler remained unclear until now. A new study now highlights the Southern Ocean, the ocean surrounding the South Pole, as a decisive factor.
“Our data show for the first time that stronger stratification of the Southern Ocean was crucial for the comparatively cool interglacials before the Mid-Brunhes Event,” says Dr Huang Huang, the study's lead author. He completed his PhD at GEOMAR in 2019 and now works at the Laoshan Laboratory in Qingdao (China). The Mid-Brunhes Event refers to a significant climate change that occurred around 430,000 years ago. Following this event, the interglacial periods became warmer, longer and had higher CO2 levels in the atmosphere. “With our new methodological approach, we were even able to detect shorter-term variations in the ocean – providing us with a much more detailed view of Southern Ocean dynamics.”
Read more at: GEOMAR Helmholtz Centre for Ocean Research Kiel
The Southern Ocean surrounding Antarctica plays a decisive role in the global carbon cycle – and thus in the climate. (Photo Credit: Huang Huang, GEOMAR)
