Deep-water ocean circulation, marine biodiversity and climate change

A direct link has been shown between the greatest increase in Phanerozoic marine biodiversity and the onset of a sudden icehouse. The onset of sudden icehouse conditions during the Mid Ordovician was an abrupt change in climate. Prior to this, Earth was exposed to a prolonged super-greenhouse with sea surface temperatures estimated above 40 degree Celsius, thus, seriously affecting the ability of life to evolve and diversify. The researchers now speculate that the sudden emergence of icehouse conditions brought about fundamental changes in ocean circulation, instigating thermohaline circulation in the oceans.
Paleontology News — ScienceDaily