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Slow‐sinking particulate organic carbon in the Atlantic Ocean: Magnitude, flux, and potential controls
Author(s) -
Baker Chelsey A.,
Henson Stephanie A.,
Cavan Emma L.,
Giering Sarah L. C.,
Yool Andrew,
Gehlen Marion,
Belcher Anna,
Riley Jennifer S.,
Smith Helen E. K.,
Sanders Richard
Publication year - 2017
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1002/2017gb005638
Subject(s) - oceanography , environmental science , marine snow , biogeochemical cycle , particulate organic carbon , flux (metallurgy) , particulates , remineralisation , spring bloom , atmospheric sciences , carbon cycle , middle latitudes , sediment trap , total organic carbon , water column , phytoplankton , geology , environmental chemistry , nutrient , ecosystem , chemistry , ecology , biology , inorganic chemistry , fluoride , organic chemistry
The remineralization depth of particulate organic carbon (POC) fluxes exported from the surface ocean exerts a major control over atmospheric CO₂ levels. According to a long‐held paradigm most of the POC exported to depth is associated with large particles. However, recent lines of evidence suggest that slow‐sinking POC (SS POC ) may be an important contributor to this flux. Here we assess the circumstances under which this occurs. Our study uses samples collected using the Marine Snow Catcher throughout the Atlantic Ocean, from high latitudes to midlatitudes. We find median SS POC concentrations of 5.5 μg L −1 , 13 times smaller than suspended POC concentrations and 75 times higher than median fast‐sinking POC (FS POC ) concentrations (0.07 μg L −1 ). Export fluxes of SS POC generally exceed FS POC flux, with the exception being during a spring bloom sampled in the Southern Ocean. In the Southern Ocean SS POC fluxes often increase with depth relative to FS POC flux, likely due to midwater fragmentation of FS POC , a process which may contribute to shallow mineralization of POC and hence to reduced carbon storage. Biogeochemical models do not generally reproduce this behavior, meaning that they likely overestimate long‐term ocean carbon storage.