Particle fluxes of thirteen sediment traps off Cape Blanc, Mauritania@en

Long-term data characterizing the oceans' biological carbon pump are essential for understanding impacts of climate variability on marine ecosystems. The 'Bakun upwelling intensification hypothesis' suggests intensified coastal upwelling due to a greater land-sea temperature gradient influenced by global warming. We present particle fluxes from ca. 1200-3600m water depth from a coastal and an offshore sediment trap setting located in the Canary Current upwelling. Organic carbon (Corg) and biogenic opal (BSi, diatoms) fluxes were two- to three-fold higher at the coastal upwelling site compared to the offshore site, respectively, and showed higher seasonality with flux maxima in spring. Fluxes of dust regularly showed maxima in winter when frequent low-altitude dust storms and deposition occurred, decreasing offshore by about three-fold. We obtained a high temporal match of short-term peaks of BSi and dust fluxes in winter-spring at the coastal site. Corg and BSi fluxes revealed a decreasing trend from 2006 to 2016 at the coastal site, pointing to coastal upwelling relaxation during the last two decades. The permanent offshore upwelling zone of the Canary Current showed no signs of increasing upwelling as well, which contradicts the Bakun hypothesis.