RECONSTRUCTION OF THE AMAZON DRAINAGE BASIN, RIVER DISCHARGE, AND BASIN-SCALE EROSION RATES SINCE THE LAST GLACIAL MAXIMUM

The Amazon River system has the largest discharge and drainage area in the world, and is estimated to carry ~550-1500 Mt/yr (Wittmann et al., 2011) of sediment to the sea. Since the Last Glacial Maximum, ~21,000 years before present, changes in global climate and sea level influenced the Amazon and other tropical river systems. Large fluctuations in precipitation over South America were driven by the movement of the Intertropical Convergence Zone (ITCZ) and South Atlantic Convergence Zone (SACZ), and these impacted erosion rates and river discharge over time. At the same time, rising sea level moved the mouth of the Amazon River landward.

We present a time series of synthetic paleohydrographs and drainage basin maps from the Last Glacial Maximum (LGM) to the present for the Amazon River. These are based on modelled changing topography, climate, and sea level over the past 21000 years. We compare these to climate reconstructions from speleothems, deposition rates and paleodischarge proxy data from off-shore sediment cores, and measured modern discharge and erosion. These assorted data sources combine to form a picture of evolving water discharge and erosion rates across a massive continental-scale drainage basin during the rapid environmental change of the last deglaciation.