Half-precessional orbital forcing, the Congo Air Boundary, and geographical diversity in Africa's post-glacial climate history

Documenting the spatial variability of past climate change is critical for understanding how external climate forcing, such as long-term changes in solar insolation or today’s anthropogenic increase in atmospheric greenhouse gases, affect earth’s climate at the regional scale. In contrast to the data-rich middle and high latitudes of the northern hemisphere, high-quality climate records from equatorial regions are scarce, especially from regions with bimodal rainfall seasonality associated_with a twice-annual overhead passage of the Intertropical Convergence Zone. Recent data show_that the portion of equatorial Africa situated east of the Congo Air Boundary (CAB) has experienced_a succession of wet and dry periods at half-precessional (~11,500-year) intervals, i.e. twice the_frequency common to (sub-) tropical regions north and south of the equator. The principal aim of this project is to better constrain the area of East Africa which has experienced this truly low-latitude climate history, impacted only modestly by the history of northern high-latitude glaciation. Resolving this question will reveal long-term variability in the mean annual position of the CAB, and thus in the relative strength of Atlantic and Indian Ocean monsoon circulation during critical time windows in the past. This understanding is crucial for improvement of climate models aiming to predict whether East African nations must mainly prepare for higher rainfall or more severe droughts in the next century.