NOAA/WDS Paleoclimatology - Congo River Basin 25KYr MBT/CBT Data and Air Temperature Reconstruction

We analyzed the distribution of branched tetraether membrane lipids derived from soil bacteria in a marine sediment record that was recovered close to the Congo River outflow, and the results enabled us to reconstruct large-scale continental temperature changes in tropical Africa that span the past 25,000 years. Tropical African temperatures gradually increased from ~21° to 25°C over the last deglaciation, which is a larger warming than estimated for the tropical Atlantic Ocean. A direct comparison with sea-surface temperature estimates from the same core revealed that the land-sea temperature difference was, through the thermal pressure gradient, an important control on central African precipitation patterns. 25 ky MBT/CBT record for the Congo River Basin (central tropical Africa) obtained from marine core GeoB 6518-1 situated in the Congo deep sea fan. Annual mean air temperature and soil pH estimates have been obtained from branched tetraether membrane lipids derived from soil bacteria and analysed with high performance liquid chromatography / mass spectrometry (HPLC/MS). Core Location: GeoB 6518-1: 05°35.3'S, 11°13.3'E, 962m water depth (Congo Fan). Age calibration of core: Dating of core GeoB 6518-1 was carried out by means of fifteen 14C-AMS dates on mixed planktonic foraminifera fractions containing Globigerinoides ruber (white), Globigerinoides sacculifer and Orbulina universa. Radiocarbon ages were converted to calendar ages using the program CALIB 4.4 (using the marine calibration and applying a reservoir effect of 400 years) and were linearly interpolated to provide the core chronology. Uncertainties: The pH calibration range is from 3.3 to 8.2 and the temperature calibration range is from -6.7 to 27.0°C, which covers the entire range of pH and temperatures reconstructed from our core. The analytical reproducibility based on pooled standard deviations of duplicate measurements of samples is =< 0.01 units for the MBT index and ± 0.01 units for the CBT ratio, or ± 0.02 pH units and ± 0.2°C in the temperature estimates.