Global patterns in efficiency of particulate organic carbon export and transfer to the deep ocean

• Published in: Global biogeochemical cycles 2012-03, Vol.26 (1), p.n/a
• Main Authors: Henson, Stephanie A., Sanders, Richard, Madsen, Esben
• Format: Article
• Language: English
• Subjects: Algorithms; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biological oceanography; Calcite; Calcium carbonate; Carbon; Carbon cycle; carbon export; Chemical oceanography; Earth sciences; Earth, ocean, space; Ecological function; Efficiency; Estimates; Exact sciences and technology; Fluctuations; Fundamental and applied biological sciences. Psychology; General aspects; Geochemistry; global; Hypotheses; Latitude; Marine; Marine ecosystems; Minerals; Nitrogen; Organic matter; Particulate organic carbon; POC flux; Primary production; satellite data; Sediments; Synecology; Upper ocean
• ISSN: 0886-6236; 1944-9224
• DOI: 10.1029/2011GB004099

The ocean's biological carbon pump is a key component of the global carbon cycle. Only a small fraction of the carbon fixed by primary production is exported to the deep ocean, yet this flux sets to first order the efficiency with which carbon is sequestered out of further contact with the atmosphere on long time scales. Here we examine global patterns in particle export efficiency (PEeff), the proportion of primary production that is exported from the surface ocean, and transfer efficiency (Teff), the fraction of exported organic matter that reaches the deep ocean. Previous studies have found a positive correlation between Teff and deep ocean calcite fluxes recovered from sediment traps, implying that ballasting by calcium carbonate may play an important role in regulating Teff. An alternative explanation is that this correlation is not causative, as regions where the dominant biomineral phase is calcite tend to be subtropical systems, which are hypothesized to produce sinking aggregates highly resistant to degradation. We attempt to distinguish between these alternative hypotheses on the control of Teff by examining the relationship between Teff and biomineral phases exported from the upper ocean, rather than those collected in deep traps. Global scale estimates derived from satellite data show, in keeping with earlier studies, that PEeff is high at high latitudes and low at low latitudes, but that Teff is low at high latitudes and high at low latitudes. However, in contrast to the relationship observed for deep biomineral fluxes in previous studies, we find that Teff is strongly negatively correlated with opal export flux from the upper ocean, but uncorrelated with calcium carbonate export flux. We hypothesize that the underlying factor governing the spatial patterns observed in Teff is ecosystem function, specifically the degree of recycling occurring in the upper ocean, rather than the availability of calcium carbonate for ballasting. Key Points Global maps of export efficiency and transfer efficiency are presented Upper ocean export flux of CaCO3 is not correlated with transfer efficiency Ecosystem structure, particularly extent of recycling, drives transfer efficiency