Assessing temperature changes in Central Africa since the Last Glacial Maximum using sediment cores from Lake Mahoma, Rwenzori Mountains, Uganda.
Abstract
Tropical mountains are thought to be particularly sensitive to anthropogenic climate change. In the Rwenzori Mountains of Uganda, in central Africa, climate change is already causing negative impacts on the local environment including rapid glacier retreat, fire, flooding, and drought. However, observational records of climate from these mountains are scarce, so it is difficult to test the predictions of climate models. Reconstructing the magnitude of temperature change during the last glacial termination (~21-8 kyr BP), the last time interval when global temperatures warmed significantly due to increasing atmospheric carbon dioxide concentrations, can help us to better understand how climate in these remote mountains will change as the global climate continues to warm. Here, we apply an organic geochemical proxy of temperature to lake sediment cores from Lake Mahoma (2990 m asl) in the Rwenzori Mountains to reconstruct changes in temperature since the Last Glacial Maximum (LGM). Specifically, we quantify the relative abundances of different branched glycerol dialkyl glycerol tetraethers (brGDGTs) to reconstruct temperature. Results show a ~7 °C to 8 °C ncrease in temperature from ~21.5 kry to ~4.5 kyr. This warming significantly exceeds the amplitude of warming observed at lower elevations (2 °C to 4 °C), confirming inferences from other high-elevation records and glaciological studies that mountain environments exhibit amplified warming. This warming exceeds the predictions of paleoclimate model simulations and suggests a steeper lapse rate over tropical African during the last ice age. Reconstruction of precipitation changes is ongoing and will allow us to examine precipitation gradients between easternmost and central Africa during the ice age.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC51L1064S
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 1621 Cryospheric change;
- GLOBAL CHANGE;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 1637 Regional climate change;
- GLOBAL CHANGE