3D map shows dead zones in the Pacific Ocean

3D map shows dead zones in the Pacific Ocean

Science

American researchers have mapped lifeless areas of the Pacific Ocean in 3D. The goal? Predict their evolution as a function of global warming. However, be aware that these areas generate nitrous oxide, a very powerful greenhouse gas.

Two gigantic dead zones

So-called dead zones are sea areas that are almost devoid of oxygen: hypoxic waters. Unfortunately, this results in the death by suffocation of biodiversity. These areas represent only 1% of the total volume of the Pacific Ocean, but the sediments found there generate nitrous oxide (or nitrous oxide – N2O), the heating power of which is 300 times greater than that of nitrogen dioxide. carbon (CO2). As it rises to the surface, N2O travels to the atmosphere and thus contributes to global warming. Moreover, if this phenomenon has a natural origin, it is accelerating due to the dumping of fertilizers and wastewater on the coastlines. The result is a proliferation of algae which eventually decomposes.

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In a study published in the journal Global Biogeochemical Cycles on December 27, 2021, a team from the Massachusetts Institute of Technology (MIT) explains that they have mapped these dead zones in 3D, one of the challenges being to know their extent. Two of these areas have been identified, the first representing 600,000 cubic kilometers. This volume still represents the equivalent of 240 billion Olympic swimming pools. The second is three times more important.

Work for the future

For the researchers, this work should serve as a basis for other subsequent work aimed at better understanding the phenomenon and possibly finding solutions to mitigate it. However, one of the other goals is to predict the changes to come.

In order to develop their maps, scientists processed more than four decades of data incorporating no less than fifteen million measurements at different depths. They focused their attention on data from sensors found on cylinders submerged in water or placed on robotic platforms capable of modifying their buoyancy. They made it possible to estimate the amount of dissolved oxygen by informing researchers about changes in electrical currents or in the light intensity of a photosensitive dye.

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Thus, the two maps produced by the researchers show hypoxic waters at several levels of depth. For scientists, the databases used are a wealth of information, including understanding the regulation of oxygen supply to the oceans.