Simulation of oxygen isotopes in a global ocean model

• Main Authors: A. Paul, S. Mulitza, J. Pätzold, T. Wolff
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: Springer 1999
• Subjects: Antarctic; Antarc*; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.586.2306; http://www.geo.uni-bremen.de/~apau/publications/paul_et_al_1999.pdf

Abstract: We incorporate the oxygen isotope composition of seawater δ18Ow into a global ocean model that is based on the Modular Ocean Model (MOM, version 2) of the Geophysical Fluid Dynamics Laboratory (GFDL). In a first experiment, this model is run to equilibrium to simulate the present-day ocean; in a second experiment, the oxygen isotope composition of Antarctic Surface Water (AASW) is set to a constant value to indirectly account for the effect of sea-ice. We check the depth distribution of δ18Ow against observations. Furthermore, we computed the equilibrium fractionation of the oxygen isotope composition of calcite δ18Oc from a paleotemperature equation and compared it with benthic foraminiferal δ18O. The simulated δ18Ow distribution compares fairly well with the GEOSECS data. We show that the δ18Ow values can be used to characterize different water masses. However, a warm bias of the global ocean model yields δ18Oc values that are too light by about 0.5 ‰ above 2 km depth and exhibit a false vertical gradient below 2 km depth. Our ultimate goal is to interpret the wealth of foraminiferal δ18O data in terms of water mass changes in the paleocean, e.g. at the Last Glacial Maximum (LGM). This requires the warm bias of the global ocean model to be corrected. Furthermore the model must probably be coupled to simple atmosphere and sea-ice models such that neither sea-surface salinity (SSS) nor surface δ18Ow need to be prescribed and the use of present-day δ18Ow-salinity relationships can be avoided.