Planktonic Foraminiferal Shell Weight Variability From The Cariaco Basin: Insights Into Carbon Dioxide Concentrations During The Last Glacial Period

Here we present decadal scale records of sediment color reflectance, planktonic foraminiferal shell weight variability, and planktonic foraminiferal carbon isotope composition (δ13C) from the Cariaco Basin, Venezuela for the last glacial period (Marine Isotope Stage 3; ~32-55kyrBP) and demonstrate that the temporal variability in the records is associated with established stadial/interstadial climate oscillations. Sediment trap results from the Cariaco Basin suggest that the shell weight variability is driven, in part, by changes in the surface water carbonate ion concentration [CO3=]. Using the modern relationship between shell weight and [CO3=] for this location, we estimate down-core [CO3=] variability during MIS 3 in order to assess past changes in the surface seawater partial pressure of carbon dioxide (pCO2). This record also provides insight into past changes in pH. We find that the Cariaco Basin was a source for atmospheric carbon dioxide during this time interval and that pCO2 underwent large stadial/interstadial oscillations with higher values during interstadials than during stadials.