Terrawatch: saltier oceans could have prevented Earth from freezing

Study may have solved paradox of the faint young Sun – which shone 20% less bright in Archean times

The Sun shone 20% less brightly on early Earth, and yet fossil evidence shows that our planet had warm shallow seas where stromatolites – microbial mats – thrived. Now a study may have solved the “faint young Sun paradox”, showing that saltier oceans could have prevented Earth from freezing over during Archean times, 3bn years ago.

We all know that the composition of the atmosphere (particularly the abundance of greenhouse gases) plays a crucial role in tempering Earth’s climate, but what about the composition of the oceans? To answer this question researchers used an ocean-atmosphere general circulation model to investigate the impact of salinity. They show that saltier oceans result in warmer climates, partly because the salt depresses the freezing point of seawater and inhibits sea-ice formation, but mostly because the greater density of salty water alters ocean circulation patterns and aids heat transport to the poles.

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