The Southern Ocean’s greenhouse gases uptake has been reinvigorated after a period when it seemed that its role as a major carbon sink was wearing off.
During the 1990s, the Southern Ocean’s ability to absorb heat-trapping gases was observed to have waned off. It seemed that the carbon sink had reached saturation. Now, according to the outputs of a new scientific research, the Southern Ocean is back on track.
A nexus of conditions have prompted the Antarctic Ocean to absorb 1.2 billion tonnes of carbon in 2011. According to researchers, this enormous amount of carbon absorbed in the ocean is two times higher than the lowest level of carbon absorption in the 1990s. In other words, in 2011, the Southern Ocean absorbed roughly as much carbon as the European Union produces in one year.
Oceans are crucial to carbon sinking. Without this resource, approximately one quarter of the carbon emitted throughout the world would be left in the atmosphere, leading to an ever-accelerated climate change. Of all the oceans, the Southern Ocean sinks 40 percent of the carbon present in the atmosphere as a result of human activity.
Looking at model results, scientists have warned that the level of carbon sinking had failed to increase since the late 1980s. This thesis was difficult to grasp. There should have been a direct relation between the concentration of CO2 in the atmosphere and the amount of CO2 absorbed by the ocean. It was difficult to grasp that there could be a saturation point.
The latest research, led by Nicolas Gruber who is a professor of Environmental Physics with ETH Zurich explains why there could be a saturation point and why is it reversible. For the Southern Ocean and for us, the combination of weather patterns occurring in the region was the lucky draw.
While over the Pacific there’s a specific area of low pressure, the Southern Ocean’s Atlantic sector is dominated by a high pressure system. These atmospheric pressure systems and their development make models and predictions rather difficult.
At the same time they cause wind patterns to shift. During the 1990s, the wind pattern followed most times the west-east axis. Now, they follow undulating patterns. Also, during the 1990s, the winds over the Southern Ocean were much stronger. As such, they led to water being circulated from the depth to the surface.
The carbon concentration is higher in depth waters than in surface waters. When depth waters are upwelled to the surface, more carbon and other greenhouse gases are released in the atmosphere. Overall, this led to observation that the Southern Ocean’s carbon intake had stagnated.
The study is published in the Science journal.
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