W2: How to constrain oxygen 18-based water-mass reconstructions

(G. Ganssen, Amsterdam; A. Paul, Bremen)

With the advent of independent temperature reconstructions, e.g., from transfer functions based on foraminiferal assemblages, alkenone concentrations, or Mg/Ca ratios, it has become possible to estimate variations in water-mass properties (such as paleosalinity or paleodensity) from the oxygen-isotope ratio as preserved in foraminiferal carbonate. However, the propagation of the analytical errors as well as the uncertainties in the paleotemperature equation and the local relationship between salinity and the oxygen-isotope ratio of seawater must be carefully accounted for. Furthermore, there are constraints from physical oceanography and climatology that must be satisfied to assure the plausibility of the reconstructed changes. We would like to discuss with the workshop participants questions such as: How can the »oxygen-18 community« contribute to reduce the present uncertainties? To what degree can we reconstruct paleodensity? Do we need an oxygen-18 database for the past?