2012: Advent Atmosphere: Carbonic Acid

by on December 5, 2012

Earth’s oceans did more for us than just sit there being wet. We started off the right temperature to have oceans in the first place, reaching enough pressure to make it rain before the planet was too hot for liquid water. And the oceans have kept us that temperature. Oceans capture carbon dioxide.

The runaway greenhouse effect that makes Venus hot enough to boil lead is due to the makeup of its atmosphere: mostly carbon dioxide. With no liquid oceans, the process that removed the carbon dioxide from our atmosphere just couldn’t happen.

Carbon dioxide reacts with liquid water to produce a solution of carbonic acid. The carbonic acid reacts with metals like calcium. So if you have an atmosphere rich in carbon dioxide, and liquid water lying around the place, and some metals on the seabed, those two reactions happen, and you end up with less carbon dioxide in the atmosphere and a bunch of new rocks. The Earth got lucky – our mass and distance from the sun gave us oceans, and our oceans turned carbon dioxide into rocks, and that kept the temperature low enough for us to keep the oceans.

There’s only so much carbon dioxide that any given amount of water can hold, and the surface water of the oceans has long since reached that point. Transferring water from the surface to the deep oceans is a surprisingly slow process, one we’ll look at later.

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