Abstract
Correlations between particulate organic carbon (POC) and mineral fluxes in the deep ocean have inspired the inclusion of “ballast effect” parameterizations in carbon cycle models. A recent study demonstrated regional variability in the effect of ballast minerals on the flux of POC in the deep ocean. We have undertaken a similar analysis of shallow export data from the Arctic, Atlantic, and Southern Oceans. Mineral ballasting is of greatest importance in the high-latitude North Atlantic, where 60% of the POC flux is associated with ballast minerals. This fraction drops to around 40% in the Southern Ocean. The remainder of the export flux is not associated with minerals, and this unballasted fraction thus often dominates the export flux. The proportion of mineral-associated POC flux often scales with regional variation in export efficiency (the proportion of primary production that is exported). However, local discrepancies suggest that regional differences in ecology also impact the magnitude of surface export. We propose that POC export will not respond equally across all high-latitude regions to possible future changes in ballast availability.
Highlights
The biological carbon pump (BCP) is an important component of the global carbon cycle, exporting 5 to 10 Gt C yrÀ1 from the surface ocean to the ocean’s interior [Henson et al, 2011]
Mineral ballasting is of greatest importance in the high-latitude North Atlantic, where 60% of the particulate organic carbon (POC) flux is associated with ballast minerals
It has been suggested that fluxes of minerals drive organic carbon flux, either by increasing particle density and sinking speed or possibly by physically protecting a proportion of the particulate organic carbon (POC) flux that leaves the surface from degradation [Armstrong et al, 2002; François et al, 2002; Klaas and Archer, 2002]
Summary
The biological carbon pump (BCP) is an important component of the global carbon cycle, exporting 5 to 10 Gt C yrÀ1 from the surface ocean to the ocean’s interior [Henson et al, 2011]. While this is the global Teff pattern reported by some studies [François et al, 2002; Henson et al, 2012; Lam et al, 2011], shipboard process studies have revealed that diatom blooms can lead to large export events characterized by high Teff [Buesseler and Boyd, 2009; Martin et al, 2011; Rynearson et al, 2013; Smetacek et al, 2012]. This basic disagreement about the effect of opal ballast underscores how limited our understanding of mineral ballast in the oceans is. We discuss the implications of our results for the role of minerals in the export of POC from the surface ocean
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