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This pocket is located in the so-called Southern Ocean, which wanders through Antarctica. More specifically, between Tasmania and Antarctica, between 54 and 62 degrees latitude. Scientists claim that the boundary layer at this latitude, located just above the water’s surface and feeding low clouds, appears to be generally free of aerosols from other parts of the world. This means that most of the pollutants generated by human activities are simply not present in that area.
Scientists base their conclusions on the calculation of bacteria in the air: in the southern regions of the planet, closest to Antarctica, their diversity is greatly reduced. In that part of the ocean, essentially the entire variety of bacteria is made up of microorganisms sprayed by marine animals.
“We were able to use the bacteria in the air over the Southern Ocean as a diagnostic tool to assess the essential properties of the lower atmosphere,” said Thomas Hill, an expert in microbiological ecology at Colorado State University in the United States.
“For example, we have found that aerosols that determine cloud properties in the Southern Ocean are highly involved in ocean biological processes and that Antarctica appears to be isolated from the spread of microorganisms and their nutrients from the southern hemisphere,” explained the scientific.
This is the first time that bioaerosol samples have been taken in the Southern Ocean so close to Antarctica. Scientists have been very surprised by the cleanliness of the air in this part of the world, especially when they realize that the global climate system is extremely interconnected.
Windborne microorganisms can travel vast distances, but only a very small proportion appears to be able to reach Antarctica. Experts determined the origin of all the particles by combining DNA sequencing methods, source tracking, and lawn path models.
All samples were also divided into latitude zones to assess changes as they moved south. And the results of the microbial journey in these latitudes contradict what scientists have found in the northernmost latitudes: the subtropics and the northern hemisphere, where microbes travel freely and mix with each other.
Incidentally, this study is important not only because it has given the South Ocean air the title of “cleaner”, but it will also contribute to climate and climate modeling. The aerosol composition of the boundary layer determines the composition of clouds and precipitation, which in turn determines the amount of sunlight that reaches the Earth’s surface.
In fact, there are fewer ice crystal core particles, those solid particles surrounded by cloud droplets that generally originate from plants or soil, over the Southern Ocean than anywhere else in the world. This has already been established in previous studies.
Taken together, these studies show that the Southern Ocean is one of the few places in the world that is minimally affected by anthropogenic activities, “Hill said.
The peer-reviewed study was published in the PNAS journal.
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