Non Linearity Between Seasonal and Interannual Oxygen Isotopes Measured on Coral Skeleton
Abstract
Oxygen isotopic ratio from coral skeleton is regarded for a long time as promising climate archives at seasonal scale. Although in isotopic disequilibrium relative to seawater, it was supposed to obey to the isotope thermometer. This did not take into account vital effects due to biogenic origin of the mineral. Coral aragonite is composed of two crystal types showing different shapes, well arranged and differently oriented. Measurements at micrometer scale revealed two different fractionations. Isotopic signature of the most abundant crystal type suggested that it is likely deposited following kinetic process biologically controlled. Thus, the oxygen fractionation does not obey to the classical isotopic thermometer. Coral cultures enabled to relate metabolic activity to oxygen isotopic variability. This confirmed that seasurface temperature is the major environmental factor acting on the proxy according to several mechanisms. However, experiments suggested that temperature might act on isotopic oxygen ratio and linear extension through photosynthesis, inversely than direct temperature effect. The growth mode understanding should allow the time data series to be correctly interpreted.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMPP51D..05R
- Keywords:
-
- 0419 Biomineralization;
- 1615 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 4805;
- 4912);
- 1721 Nonlinear geophysics;
- 4916 Corals (4220)