TEMPERATURE AND SALINITY CHANGES IN THE CARIBBEAN SEA DURING GLACIAL/INTERGLACIAL INTERVALS AS INFERRED FROM ELEMENTAL AND ISOTOPIC DATA
In parallel to the oxygen isotope analyses, magnesium/calcium (Mg/Ca) ratios were determined on foraminiferal tests to determine past changes in temperature and salinity of surface waters in the Caribbean Sea. Mg/Ca ratios range from 8.0 mmol/mol to 2.9 mmol/mol. Using published temperature calibrations, the obtained Mg/Ca ratios indicate that sea-surface temperatures have varied by up to 5˚C during the last 400,000 years. Because the oxygen-isotopic composition of foraminifera depends on that of seawater and temperature, the obtained Mg/Ca ratios can be used to assess the temperature-dependant isotope effect. Consequently the down-core residuals of oxygen isotope ratios of foraminifera reflect the variability in the oxygen isotopic composition of seawater through time. Residuals of isotope values for the studied core indicate significant changes in the isotopic composition of seawater that we correlate with the intensity of evaporation at the site. Since evaporation in the Caribbean Sea is closely coupled with the passage of the Inter-tropical Convergence Zone (ITCZ), we conclude that fluctuations in the intensity or zonality of the ITCZ exert a significant control on the amount of energy and moisture exported to mid-latidudes.