An integrated carbon and oxygen isotope approach to reconstructing past environmental variability in the northeast Atlantic Ocean

摘要

The combined influence of temperature and the isotopic composition of the seawater (delta O-18(w)) often precludes the use of oxygen isotope (delta O-18) records, derived from marine carbonates, to reconstruct absolute seawater temperatures, without the application of an independent delta O-18(w) proxy. Here we investigate the application of carbon isotope records (delta C-13(shell)), derived from the long-lived marine bivalve Glycymeris glycymeris, as a proxy for delta O-18(w) variability. Our analyses indicate G. glycymeris delta C-13(shell) data derived from growth increments > 20 years of age contain strong ontogenetic trends (-0.013 parts per thousand yr(-1), R = 0.98, P < 0.001, N = 51). These analyses demonstrate that, coupled with the ontogenetic trends, 54% of the variability in G. glycymeris delta C-13(shell) records can be explained by a combination of the marine Suess effect and physical (salinity and riverine input) and biological processes (primary production). The application of these delta C-13(shell) data in conjunction with co-registered delta O-18(shell) and growth increment width series, each of which have been shown to be sensitive to seawater temperature and primary productivity respectively, can therefore provide new insights into past environmental variability and help constrain uncertainties on reconstructions of past seawater temperature variability.