Scientists have solved the Achaean paradox of a faint young Sun

(ORDO NEWS) — A new study by American, Canadian and Israeli scientists has made it possible to resolve the so-called paradox of the faint young Sun, which at the dawn of the Earth’s existence, in the Achaean, 4.0-2.5 billion years ago, shone 20% less brightly than at present, and nevertheless, stromatolites – cyanobacterial mats that produced oxygen – prospered in those days and did not suffer from low temperatures.

Existing fossil evidence shows that the planet then had warm shallow seas where stromatolites flourished, and the solution to the faint young Sun paradox may be the increased salinity of the oceans of that time, which prevented them from freezing 3 billion years ago.

Of course, the composition of the atmosphere, especially the abundance of greenhouse gases in it, plays a decisive role in mitigating the earth’s climate, but the composition of the oceans is also important.

To investigate this issue, the researchers used a model of the general circulation of the ocean and atmosphere to assess the influence of water salinity on these processes.

It has been shown that saltier oceans lead to warmer climates: this is partly because salt lowers the freezing point of seawater and therefore prevents the formation of reflective sea ice, but mainly another effect is at work: a greater density of salty water changes the circulation pattern ocean and thereby contributes to a more active transfer of heat to the poles.

The current salinity levels of the oceans should have led in the Achaean to a severe glaciation of the planet, on which only a narrow strip of open water at the equator would remain.

However, under the new Archean scenario, it is shown that a 40% increase in salinity compared to today resulted in a warmer climate with average water surface temperatures in excess of 20°C, with ice only able to form during winter seasons at the poles.


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