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Physical pathways for carbon transfers between the surface mixed layer and the ocean interior
Author(s) -
Levy M.,
Bopp L.,
Karleskind P.,
Resplandy L.,
Ethe C.,
Pinsard F.
Publication year - 2013
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/gbc.20092
Subject(s) - mixed layer , subduction , carbon cycle , dissolved organic carbon , carbon fibers , obduction , carbon sink , geology , environmental science , atmospheric sciences , oceanography , materials science , climate change , oceanic crust , ecosystem , biology , composite number , composite material , tectonics , paleontology , ecology
Although they are key components of the surface ocean carbon budget, physical processes inducing carbon fluxes across the mixed‐layer base, i.e., subduction and obduction, have received much less attention than biological processes. Using a global model analysis of the preindustrial ocean, physical carbon fluxes are quantified and compared to the other carbon fluxes in and out of the surface mixed layer, i.e., air‐sea CO 2 gas exchange and sedimentation of biogenic material. Model‐based carbon obduction and subduction are evaluated against independent data‐based estimates to the extent that was possible. We find that climatological physical fluxes of dissolved inorganic carbon (DIC) are two orders of magnitude larger than the other carbon fluxes and vary over the globe at smaller spatial scale. At temperate latitudes, the subduction of DIC and to a much lesser extent (<10%) the sinking of particles maintain CO 2 undersaturation, whereas DIC is obducted back to the surface in the tropical band (75%) and Southern Ocean (25%). At the global scale, these two large counter‐balancing fluxes of DIC amount to +275.5 PgC yr −1 for the supply by obduction and −264.5 PgC yr −1 for the removal by subduction which is ∼ 3 to 5 times larger than previous estimates. Moreover, we find that subduction of organic carbon (dissolved and particulate) represents ∼ 20% of the total export of organic carbon: at the global scale, we evaluate that of the 11 PgC yr−1 of organic material lost from the surface every year, 2.1 PgC yr −1 is lost through subduction of organic carbon. Our results emphasize the strong sensitivity of the oceanic carbon cycle to changes in mixed‐layer depth, ocean currents, and wind.