FY 1989

Lysocline, calcium carbonate compensation depth, and calcareous sediments in the north Pacific Ocean

Chen, C.T.A., R.A. Feely, and J.F. Gendron

Pac. Sci., 42(3–4), 237–252 (1988)

An extensive oceanographic investigation has been carried out in the North Pacific Ocean. The purpose of this report is to present the results of two cruises in which we participated and to report additional carbonate data from samples collected for us in the North Pacific. These data are combined with data from the literature to provide an overall picture of the carbonate system in the North Pacific. The degree of saturation of seawater with respect to calcite and aragonite was calculated from all available data sets. Four selected cross sections, three longitudinal and one latitudinal, and two three-dimensional graphs show that a large volume of the North Pacific is undersaturated with respect to CaCO. The saturation horizon generally shows a shoaling from west to east and from south to north in the North Pacific Ocean. It was found that the lysocline is at a depth much deeper (about 2500 m deeper) than the saturation horizon of calcite, and several hundred meters shallower than the calcium carbonate compensation depth. Our results appear to support the kinetic point of view of the CaCO dissolution mechanisms. Differences in the abundance of the calcareous sediments are explained by differences in the calcium carbonate compensation depth.