The approach is to measure the magnesium to calcium ratios (Mg/Ca) and oxygen isotopic composition (δ 18O) in planktic foraminifera deposited on the seafloor. The project is part of a collaborative effort to better understand how sea surface temperature and salinity have varied over the Holocene, or the past 10,000 years.

Petersburg Coastal and Marine Science Center, in collaboration with researchers at the Institute for Geophysics at University of Texas at Austin, have published a study in Nature Communications linking salinity changes in the Gulf of Mexico over the past 4 millennia to changes in rainfall patterns in the Western Hemisphere. Sediment cores holding 4,000 years’ worth of climate history from the Gulf of Mexico were used to link Atlantic surface currents to rainfall over continents. Correlations were performed with 8-year lowpass filters to reduce sensitivity to interannual variability, where black stippling indicates significance at the 5% confidence level. Proxy locations are marked with circles (sedimentary records), triangles (speleothems), dashed boxes (tree-ring compilations), stars (circulation proxies), and squares (additional proxies) with color fill indicating sign (fresh–blue dry/wet–brown/green purple–weakened poleward transport) during the Little Ice Age (1450–1850 C. Correlation map between northern Gulf of Mexico sea-surface salinity (SSS dashed red box) and global oceanic SSS (ORA-S4 data set red-blue scale), as well as continental precipitation (GPCC data set brown-green scale) with locations of proxy records used in the study. Long-term correlations between observed sea-surface salinity and rainfall.

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