Hydrologic variability and sediment supply of the Xingu and Tapajós rivers: climate change and anthropogenic impacts in eastern Amazon rivers during Holocene

Abstract

The Amazon Rainforest and the Amazon River System are unique ecosystems supporting the world´s largest terrestrial and aquatic biodiversity. Those ecosystems also have an important role for the global climate system and precipitation distributionin South America. The Xingu and Tapajós Rivers are the largest clear water tributaries of the Amazon River. Both rivers stand out due to their specific biodiversity, unique landscape and as the main sources of surface water for agriculture and energy generation in eastern Amazon. Due to their socioeconomic importance, the Xingu andTapajós basins are threatened by the increasing anthropogenic impacts associated with the planning or building of hydropower dams and expansion of agropastoral activities. Future climate scenarios projected for eastern Amazon indicate increasing frequency of severe droughts and reduction of water availability. Thus, there construction of Holocene hydroclimate in the Xingu and Tapajós basins is a critical issue to understand the response of clear water Amazon rivers to future climate and anthropogenic changes. Severe hydroclimate and vegetation changes can threat surface water availability as well as promote shifts in sedimentation and carbon cycling, affecting ecosystems. This project will use sediment cores to reconstruct the Holocene hydroclimate in the Xingu and Tapajós watersheds through the application of proxies based on isotope analysis of organic specific-compounds, luminescence of minerals and inorganic geochemistry (major elements). These proxies will allow reconstructing changes in precipitation, vegetation and sediment supply. Age models will be constrained by radiocarbon and luminescence ages. Changes in precipitation, vegetation and sediment supply will be compared to global climate events and changes in the South American Monsoon System recorded by other climate records. Changes in the last century will be compared to deforestation rates in the Xingu and Tapajós Basins. (AU)