NOAA/WDS Paleoclimatology - Lake Edward, East Africa 5400 Year Calcite Mg Data

High-resolution analyses of the chemical and stable isotope composition of endogenic calcite from Lake Edward, an equatorial rift lake in central Africa, reveal large oscillations in African climate and moisture balance over the past 5400 yr. These oscillations indicate a series of droughts from 4900 to 400 yr B.P. that define a drought period of ~725 yr. This period may be correlated to variations in the Indian Ocean monsoons, as documented by similar periods in sea-surface salinity records from the northern Indian Ocean. The similarities in periodicity of the Lake Edward and Indian Ocean records may indicate that low-frequency variability within the Indian and Pacific Oceans dominates millennial-scale African moisture balance and the Holocene climate of the tropical Indian Ocean. Stacked and detrended Mg in authigenic, inorganic calcite from AMS 14C dated cores 1P, 5M, and 6M from Lake Edward, East African Rift Valley, Uganda/Democratic Republic of the Congo. Lake Edward: 0° 25'S, 29° 45' E, 917m elev, 117m max depth, ~2400km2. Mg percentage in calcite is used to reconstruct lacustrine paleohydrology and climate history. The Mg percentage in calcite rises during evaporative concentration of a lake because of increases in the [Mg2+]/[Ca2+] ratio in lake water. This ratio rises during evaporation because of (1) Ca loss by precipitation and sedimentation of endogenic calcite in the evaporating water body and (2) rising salinity that concentrates dissolved Mg.