Seasonal variations in the Amazon plume-related atmospheric carbon sink

• Main Authors: Cooley, S. R., Coles, V. J., Subramaniam, Ajit, Yager, P. L.
• Format: Text
• Language: unknown
• Published: Columbia University 2007
• Subjects: Carbon dioxide sinks; Oceanography; Biogeochemistry; North Atlantic
• Online Access: https://dx.doi.org/10.7916/d8pz58sd; https://academiccommons.columbia.edu/doi/10.7916/D8PZ58SD

The Amazon River plume is a highly seasonal feature that can reach more than 3000 km across the tropical Atlantic Ocean, and cover ∼2 million km². Ship observations show that its seasonal presence significantly reduces sea surface salinity and inorganic carbon. In the western tropical North Atlantic during April–May 2003, plume-influenced stations exhibited surface DIC concentrations lowered by as much as 563 μmol C kg⁻¹ (∼28%) and pCO₂ as low as 201 μatm. We combine our data with other data sets to understand the annual uptake and seasonal variability of the plume-related CO₂ sink. Using flux estimates from all seasons with monthly plume areas determined by satellite, we calculate the annual carbon uptake by the outer plume alone (28 < S < 35) to be 15 ± 6 TgC yr⁻¹. Diazotroph-supported net community production enhanced the air-sea CO₂ disequilibrium by 100x and reversed the typical CO₂ outgassing from the tropical North Atlantic. The carbon sink in the Amazon plume depends on climate-sensitive conditions that control river hydrology, CO₂ solubility, and gas exchange.