TThe sun shone 20% less clearly on the 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 “weak young solar paradox” that shows that saltier oceans could have prevented the Earth from freezing to during the Archaic time, 3 billion years ago.
We all know that the composition of the atmosphere (especially the abundance of greenhouse gases) plays a crucial role in tempering the Earth’s climate, but what about the composition of the oceans? To answer this question, researchers used an ocean-atmosphere general circulation model to study the effect of salinity. They show that saltier oceans result in warmer climates, partly because the salt lowers the freezing point of seawater and inhibits the formation of sea ice, but mostly because the greater density of salt water changes the ocean’s circulation patterns and helps heat transport to the poles.
Under their archaic scenario, they show that today’s salinity levels produce a severely icy world with only a narrow strip of open water at the equator. But pushing salinity up to 40% higher than today revealed a warmer archaic world with average surface temperatures of more than 20C, and ice appearing only seasonally at the poles. Their findings are reported in Geophysical Research Letters.