in the ocean mixed surface layer. This effect was somewhat moderated by the deep oceans' elevated temperatures during this period. In the late Eocene the transition from a greenhouse to an icehouse Earth coincided with a deepened CCD. John Murray investigated and experimented on the dissolution of calcium carbonate and was first to identify the carbonate compensation depth in oceans. Climate change impacts Increasing atmospheric concentration of from combustion of fossil fuels are causing the CCD to rise, with zones of downwelling first being affected. Ocean acidification, which is also caused by increasing carbon dioxide concentrations in the atmosphere, will increase such dissolution and shallow the carbonate compensation depth on timescales of tens to hundreds of years. Sedimentary ooze On the sea floors above the carbonate compensation depth, the most commonly found ooze is calcareous ooze; on the sea floors below the carbonate compensation depth, the most commonly found ooze is siliceous ooze. While calcareous ooze mostly consists of Rhizaria, siliceous ooze mostly consists of Radiolaria and Diatom. See also Carbonate pump Lysocline Ocean acidification References Oceanography