Significance of millennial-scale coastal upwelling and Rio Loa variability for Atacama paleoclimate during MIS 2

The Atacama Desert located in northern Chile is one of the driest places on earth. The factors determining recent hyperarid climate conditions are known and their interplay and variability on interannual and decadal time scales are generally understood. Evidence for wetter (yet arid) conditions in the Atacama’s past is provided by episodic lacustrine and fluvial deposits. The main watercourse of the Atacama Desert is the Rio Loa sourced by rainfall in the Andean mountains. Information on changes of terrestrial supply to the ocean is recorded in marine sediments.

The sediment core SO-104-52KL has been collected on the upper continental slope (∼340 m water depth, 21°S) off the Rio Loa during a cruise with RV Sonne. The preliminary age model based on 14C-dating constrains the top and base of the core to 16 and 42 ka, respectively. Very high average sedimentation rates will allow paleoceaonographic and paleoclimatic studies of high resolution (millennial to centennial time scales) during the last glacial period. The location of the core on the continental slope off the Rio Loa mouth allows for the parallel evaluation of the Humboldt Current System and Andean rainfall as moisture sources for the Atacama Desert. Microfossils such as benthic foraminifera from this interval are abundant and well-preserved. Together with XRF-data, grain-size and lipid biomarker analyses, the expected proxy data will provide new insights into the dynamics of land-ocean coupling between the Atacama Desert and the eastern Pacific Ocean through characterization of coastal upwelling properties and Rio Loa runoff.