Terrawatch: saltier oceans could have prevented Earth from freezing | The sun

The Sun shone 20% less on early Earth, yet fossil evidence shows that our planet had warm, shallow seas where stromatolites (microbial mats) thrived. Now, a study may have resolved the “faint young Sun paradox,” showing that saltier oceans could have prevented Earth from freezing over during the archaic epoch, 3 billion years ago.

We all know that the composition of the atmosphere (particularly the abundance of greenhouse gases) plays a crucial role in moderating Earth’s climate, but what about the composition of the oceans? To answer this question, the 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 salt lowers the freezing point of seawater and inhibits the formation of sea ice, but mainly because the higher density of saltwater alters ocean circulation patterns. and helps transport heat to the poles.

Under their archaic scenario, they show that current salinity levels produce a severely glaciated world with only a narrow strip of open water at the equator. But raising the salinity to 40% higher than today revealed a warmer archaic world, with average surface temperatures of more than 20°C, and ice only appearing seasonally at the poles. Their findings are reported in Geophysical Research Letters.

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