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How could the levels of seas and oceans in the next century and beyond? Reliable future predictions may come from Antarctica’s past. In fact, an international team of researchers has obtained one map of the temperatures ofAntarctic Ocean covering 45 million years: a tool that provides important information on mechanisms that drive the changes in the area and that affect the balance of the entire planet.
The variations
“The idea of the research was to study i ocean sediments collected in the Antarctic seabed to observe the molecules lipid of the membrane of microorganisms called Archea“explains a Wired Francesca Sangiorgifrom Utrecht University (Netherlands), which participated in the study published on Nature Geoscience. “The composition of the membranes, in fact, changes with the temperature of the sea water “.
Going up to ancient sediments 45 million years and resorting to machine learning algorithmsthe researchers thus made one map of the variations of temperature of the Ocean around Antarctica, which they were able to compare with the reconstructions of the levels of 2 2 CO2 atmospheric (obtained from previous studies), evaluating how these factors affected the growth and shrinkage of the ice sheets.
A critical threshold
It turned out that the withdraw of the Antarctic ice sheets, in general, is amplified by the ** increase in CO levels2 **and the temperatures of the sea waters, while when the levels of CO2 decrease and water temperatures drop, the formation of ice is favored. The results of the analyzes led the researchers to identify one critical threshold I say2 equal to 400 parts per million (ppm). “Below this value the part of the Antarctic sea ice cap that extends to the sea grows “, Sangiorgi points out. “Above ocean warming is such that sea ice melts faster”.
However, at some historical moments, particularly between 25 and 24 million years ago, the cooling of the oceans at the surface did not always correspond to the increase in Antarctic ice. Other non-climatic factorssuch as the tectonic lowering of West Antarctica, could have an impact by favoring the influx of warmer ocean waters that favor the expansion of sea ice.
The future of Antarctica (and beyond)
According to the researchers, the study emphasizes the crucial role of ocean temperatures and CO levels2 on the stability of the Antarctic ice sheets. “We have exceeded the critical threshold of 400 ppm of CO2 atmospheric in 2013“concludes Sangiorgi. “And what’s happening is that the Antarctic ice is already changing. Referring to what has happened in the past, we can say that if we fail to lower the temperatures of the seas by containing the levels of CO2 atmospheric, the melting of the Antarctic ice sheets that lean on the ocean will be a huge problem in the future: the prospect of raising 1 meter sea level by the end of the century it absolutely is realisticand if the West Antarctic sea caps melt completely, we could reach an increase of 2-4 meters “.
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