Over the past half-century, the oceans have contributed to slowing global warming. They absorbed about 40% of carbon dioxide emitted and more than 90% of excess heat retained in the atmosphere. However, according to a study published in Nature Communications, this contribution is not the same for all the oceans.
Using the global ocean circulation computer model, the researchers found that the Southern Ocean absorbed the most heat from the planet. This absorption would be the cause of the warming of almost all the oceans.
Heat retained in the depths of the ocean is only released into the atmosphere after millennia. It is therefore the future generation that will feel the consequences. Besides, these changes will only get worse, unless man stops emitting carbon dioxide.
Data on ocean warming are still insufficient
The warming of the oceans weakens the consequences of climate change. However, this causes sea levels to rise due to water expansion and melting ice. The marine ecosystems are under enormous heat stress. Also, meteorological phenomena are intensifying and becoming more and more frequent.
Temperatures at the surface of the ocean and in the atmosphere are getting closer, making it impossible to know the exact place where the excess heat enters. Moreover, few observations are made in the depths, around Antarctica and under the ice.
The researchers used a computer modeling approach to better understand this phenomenon. They simulated an ocean model with the climatic conditions of the 1960s. This approach revealed that although the Southern Ocean covers only 15% of the total ocean surface, it is the main heat absorber.
Wind circulation promotes heat input into the interior of the ocean
This warming of the Southern Ocean is claiming many victims, the Antarctic Krill being one of them. Too high a temperature causes them to move towards cooler waters. And since Krill is a key part of the food chain, the distribution and population of top predators will also be disrupted. Penguins and whales, already threatened today, will come under more stress.
If the Southern Ocean absorbs so much heat, it is mainly because of the geographical configuration of the region. The winds blow over a great distance uninterrupted, continually bringing masses of cold water to the surface. Cold water is pushed north, quickly absorbing large amounts of heat from the atmosphere. The excess is then retained in the ocean, furthered by wind circulation.