Ocean chemistry and deep-sea sediments

We now know that:• The rate of carbonate dissolution increases with depth.• The Pacific shows more carbonate dissolution than the Atlantic.• The CCD is depressed beneath the equator because of highbiological productivity and increased flux of calcarous materialto the seabed.• If calcite concentrations in sediments are more than 20% thanthe area is above the CCD; if they contain less, it is below it.• The CCD rises towards the continental margins, where biologicalproductivity is in general greater than in open oceans.This seems to contradict point three! However, rich supply oforganic matter causes a consumption of organic matter at theseabed. As a result, CO 2 is released, and thus CO 2 increases inthe bottom water, thus it becomes more acid.• The CCD changes in space and time since the oceanproductivity, depth, temperature, and water mass ventilationchanges.