Is the atmosphere's oxygen supply affected by an ice age? If a great deal of land dependent plant life is buried beneath miles of ice or subject to colder temperatures then surely there is less oxygen production. I am going to go out on a limb and suggest that plant life that is ocean born picked up the slack. I've read articles that say the oceans' microscopic plant life actually produces half of the world's oxygen. I've been trying to find out if there is any evidence that oxygen levels drop during an ice age or is the drop so insignificant that its hardly worth mentioning? Does the amount of photosynthesis taking place decrease? Has anyone seen any articles on this?