A clue to why ice ages got much longer

The culprit could also lie in the ocean, where circulation changes or increases in the wind-blown dust that fertilizes plankton growth could pull greenhouse gas out of the atmosphere, making the ice ages icier.A new study led by Adam Hasenfratz and Samuel Jaccard at the University of Bern may have found a piece of the puzzle at the bottom of the ocean around Antarctica.The core of seafloor sediment collected there—spanning 1.5 million years of history—targets a location where surface water and deep water mix. Where that water mixes up toward the surface in places like this, the gas has an opportunity to vent (perhaps complaining about how dark it is down there as it makes its way into the atmosphere).This release of carbon dioxide is one of the keys to the ice ages. The movement of CO2 into and out of the ocean is a huge part of this, strengthening or weakening Earth’s greenhouse effect.This means that anything that influences the exchange of CO2 between the ocean and atmosphere can have a big impact on the dynamics of ice ages.The researchers analyzed the shells of tiny critters called forams, some of which live as floating plankton near the surface and some of which live down on the seafloor. The shallow and deep water shells diverged, implying that deep water had a harder time mixing up toward the surface after that.If significantly less CO2 was being vented from the deep ocean to the atmosphere, the slight warming nudge from the 41,000-year cycle might not have been enough to kick off a full-blown global warming.