One year sediment trap fluxes from a mooring in the western tropical North Atlantic

Abstract:

Particle fluxes in the oceans are determined by environmental circumstances and differ from site to site. In the western tropical North Atlantic the particle flux is considered to be rather low since there is low nutrient input and low productivity. It is, however, influenced by atmospheric dust deposition, Amazon River discharge, and nitrogen fixation. This brings both refractory lithogenic material and new nutrients into the system, affecting primary production and particle export. Particle export in particular has attracted attention since it is potentially partially responsible for atmospheric CO₂ sequestration. Here we present one year (October 2012 until November 2013) flux data collected by two sediment traps at 1200 m and 3500 m depth in the western tropical North Atlantic (12⁰N, 49⁰W), combined with satellite data, giving information about environmental circumstances and particle export fluxes from the surface to the deep ocean. Average total mass fluxes vary between 40 – 270 mg/m²/d and 30 - 170 mg /m²/d at the upper and lower depths, respectively. Peak fluxes during the second half of April and by the end of October/start of November 2013 are notable since they differ in nature; carbonaceous material dominates fluxes in spring and biogenic opal in fall. While the fall peak seems related to Amazon River dispersal, the spring peak appears to arise due to changing environmental conditions; rising SST possibly combined with dry dust deposition, causing a spring bloom. Both peak fluxes go along with elevated organic matter and lithogenic fluxes in the upper trap at 1200 m. At this depth, additional individual elevated lithogenic fluxes are also accompanied by raised organic matter. The lithogenic and opal fractions are considered to be the main ballast components for organic carbon aggregates, or vice versa.

See: www.nioz.nl/dust