Surface circulation patterns and the pathways of sea surface carbon dioxide (CO2) off northern Chile (~27.5° S) between 30 and 10 kyr BP: global and/or local forcing?
1Graduate Program in Oceanography, Department of Oceanography, University of Concepción, Concepción, Chile
2Department of Oceanography and Center for Oceanographic Research in the eastern South Pacific (FONDAP-COPAS), University of Concepción, Concepción, Chile
3Department of Environmental Chemistry, Faculty of Sciences, Universidad Católica de la Santísima Concepción, Concepción, Chile
4Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
5Centro de Investigación en Ecosistemas de la Patagonia (CIEP), Universidad Austral de Chile, Coyhaique, Chile
6MARUM Center for Marine Environmental Sciences, Bremen University, Bremen, Germany
Abstract. We present a reconstruction of past changes in partial pressure of CO2 (pCO2) from northern Chile (~27° S), between 10 and 30 kyr BP, based on carbon isotope composition of C37:2-alkenone. The high-pCO2 during the entire time series indicates that northern Chile upwelling system has been a permanent source of CO2 to the atmosphere. The multiproxy reconstruction suggests that the CO2 outgassing and sequestration pathways were modulated by local and global mechanisms. During global glacial conditions, an enhanced coastal upwelling forcing resulted in high-availability of deep water macronutrients and a CO2-supersaturated water column, which combined with high-inputs of iron from the continent, intensified the carbon sequestration pathway of the biological pump, through diatom biomass export. During the deglacial, a decrease in the upwelling forcing, an increment in water column stability and reduced continental inputs of iron are consistent with a larger role of calcifying organisms in the plankton assemblage in terms of carbon sequestration pathway through the carbonate system.