LATE GLACIAL AND EARLY HOLOCENE GLACIER FLUCTUATIONS IN THE RWENZORI MOUNTAINS, UGANDA-DEMOCRATIC REPUBLIC OF CONGO

The tropics are the locus of global atmospheric convergence and water vapor production, and as such have the potential to amplify – or trigger – global climate changes. However, the role of the tropics in the climate system is unclear. Both the magnitude and timing of warming in the tropics since the Last Glacial Maximum (LGM; ~26-19.5 ka) is uncertain, as is the question of whether temperatures across the tropics fluctuated synchronously following the LGM. Here we present a chronology of glaciation from the Rwenzori Mountains, Uganda-Democratic Republic of Congo, and compare these data to similar chronologies from elsewhere in the tropics. Using cosmogenic ¹⁰Be to date glacial deposits, we determined the timing and magnitude of ice fluctuations following the LGM. This chronology indicates that ice was more extensive prior to the Younger Dryas (YD; ~12.9-11.6 ka). No YD-age moraines are identified, but ice in the Rwenzori was inboard of its pre-YD extent throughout YD time. Rapid recession occurred between ~11.5 and ~10.0 ka during the early Holocene (~11.6-8.0 ka). When compared with similar datasets from tropical South America, there is a broad synchrony in both the timing and magnitude of ice recession across the tropics during the later stages of deglaciation and the early Holocene. This suggests that glaciers in both tropical Africa and South America responded to a common driver during this time. Because the hydrologic histories of tropical South America and Africa are distinct since the LGM, we suggest that temperature was the primary driver of glacier fluctuations in both regions.