MODELING GLACIAL EXTENT DURING THE LAST GLACIAL MAXIMUM IN UGANDA (Invited Presentation)

Paleoclimate records from tropical locations are relatively rare compared to extratropical regions, and often focus on hydroclimatic rather than thermal changes. Knowing the degree of cooling in low-latitude regions advances our understanding Earth's climate sensitivity to greenhouse gas forcing and internal feedbacks within the climate system. We use a 2-D ice flow and mass balance model to simulate glacier extents in the Rwenzori Mountains of Uganda and the Democratic Republic of Congo to estimate climate during the Last Glacial Maximum (LGM). Steady-state simulations of LGM glacier extents, which match moraines dated to ~20,000 years ago, can be obtained with a 20% reduction in precipitation and a 7°C cooling. Alternatively, using a paleo-lapse rate of 0.0067°C/m, which is slightly steeper than the modern lapse rate of 0.0058°C/m, and a 20% reduction in precipitation, the simulation requires only 3.5°C cooling for the glaciers to reach the mapped and dated LGM moraines. These results support the claim for large magnitude cooling at high elevations in tropical East Africa during the dry LGM and/or the possibility that some of that cooling resulted from a steepening of the lapse rate.