Friday, February 06, 2015

Climate: Written in the Stars?

Well, not exactly, but the Milankovich theory of the ice ages has long been a major pillar of our understanding of natural climate changes in the past several million years. It's key idea is that natural variations in the Earth's orbit and inclination lead to changes in the amount of solar energy absorbed by the Earth and consequent changes in climate, including ice ages.

There are some unexplained details, including the difficulty in finding enough energy balance change to thaw a significantly frozen planet. It looks like marine geophysicist Maya Tolstoy may have found an important missing piece. Her experiment planted several seismographs on the East Pacific Rise, the most active site of sea floor spreading in the world. Her interesting discovery was that the rate of volcanism depended significantly on the positions of heavenly bodies, or, in plainer language, on the tides.

Although this makes good physical sense, it doesn't seem to have been considered much before, or in climate models. It makes sense because the rate of volcanism depends sensitively on pressure gradients in the lava column, so that changes in overpressure are important. This undersea volcanism affect climate because it releases significant CO2 into the ocean, which, over thousands of years, can migrate to the surface and into the atmosphere.

Ice ages produce large drops in sea level, 100 meters or more, and the pressure changes associated with this kind of drop would dwarf those associated with even the largest tide. Is it not plausible that such increased volcanism, acting over thousands of years, could pump up the CO2 enough to help the melting?