δ18O and Mg/Ca thermometry in planktonic foraminifera: a multi-proxy approach towards tracing coastal upwelling dynamics

Due to the complexity in the interpretation of planktonic foraminifera δ18O data with respect to past seawater temperatures, temperature determination based on the foraminifera shell Mg/Ca ratio is believed to be more accurate. However, scarce Mg/Ca calibration data exists for coastal upwelling regions, resulting in incoherent results of past seawater reconstructions.

The current study along the NW Iberia coastal upwelling system intends to define the best Mg/Ca temperature equation for the most representative species of this region (Neogloboquadrina incompta, Globigerina bulloides and Globorotalia inflata). Seawater temperature from δ18O and Mg/Ca of these three planktonic foraminifera species were compared with the surface sediments alkenone derived SST, and with the in-situ temperatures measured at the depths where these foraminifera species currently live and calcify.