title: Attenuation of sinking particulate organic carbon flux through the mesopelagic ocean.
abstract: The biological carbon pump, which transports particulate organic carbon (POC) from the surface to the deep ocean, plays an important role in regulating atmospheric carbon dioxide (CO2) concentrations. We know very little about geographical variability in the remineralization depth of this sinking material and less about what controls such variability. Here we present previously unpublished profiles of mesopelagic POC flux derived from neutrally buoyant sediment traps deployed in the North Atlantic, from which we calculate the remineralization length scale for each site. Combining these results with corresponding data from the North Pacific, we show that the observed variability in attenuation of vertical POC flux can largely be explained by temperature, with shallower remineralization occurring in warmer waters. This is seemingly inconsistent with conclusions drawn from earlier analyses of deep-sea sediment trap and export flux data, which suggest lowest transfer efficiency at high latitudes. However, the two patterns can be reconciled by considering relatively intense remineralization of a labile fraction of material in warm waters, followed by efficient downward transfer of the remaining refractory fraction, while in cold environments, a larger labile fraction undergoes slower remineralization that continues over a longer length scale. Based on the observed relationship, future increases in ocean temperature will likely lead to shallower remineralization of POC and hence reduced storage of CO2 by the ocean.
authors.affiliation: National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom; Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, SO14 3ZH, United Kingdom; and cmarsay@geol.sc.edu.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Marsay
authors.affiliation: National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom;
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Sanders
authors.affiliation: National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom;
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Henson
authors.affiliation: National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom; Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, SO14 3ZH, United Kingdom; and.
authors.forename: Katsiaryna
authors.initials: K
authors.lastname: Pabortsava
authors.affiliation: Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, SO14 3ZH, United Kingdom; and GEOMAR Helmholtz Centre for Ocean Research, 24148 Kiel, Germany.
authors.forename: Eric P
authors.initials: EP
authors.lastname: Achterberg
authors.affiliation: National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, United Kingdom;
authors.forename: Richard S
authors.initials: RS
authors.lastname: Lampitt
keywords: biological carbon pump; mesopelagic; particulate organic carbon; remineralization