Variable C : N : P stoichiometry of dissolved organic matter cycling in the Community Earth System Model

[摘要] Dissolved organic matter (DOM) plays an important role in the ocean'sbiological carbon pump by providing an advective/mixing pathway for~ 20% of export production. DOM is known to have astoichiometry depleted in nitrogen (N) and phosphorus (P) compared to theparticulate organic matter pool, a fact that is often omitted frombiogeochemical ocean general circulation models. However the variable C : N : Pstoichiometry of DOM becomes important when quantifying carbon export fromthe upper ocean and linking the nutrient cycles of N and P with that ofcarbon. Here we utilize recent advances in DOM observational data coverageand offline tracer-modeling techniques to objectively constrain the variableproduction and remineralization rates of the DOM C : N : P pools in a simplebiogeochemical-ocean model of DOM cycling. The optimized DOM cyclingparameters are then incorporated within the Biogeochemical Elemental Cycling(BEC) component of the Community Earth System Model (CESM) and validated againstthe compilation of marine DOM observations. The optimized BEC simulationincluding variable DOM C : N : P cycling was found to better reproduce theobserved DOM spatial gradients than simulations that used the canonicalRedfield ratio. Global annual average export of dissolved organic C, N, andP below 100 m was found to be 2.28 Pg C yr⁻¹ (143 Tmol C yr⁻¹,16.4 Tmol N yr⁻¹, and 1 Tmol P yr⁻¹, respectively, with an averageexport C : N : P stoichiometry of 225 : 19 : 1 for the semilabile (degradable) DOMpool.Dissolved organic carbon (DOC) export contributed ~ 25% of the combined organicC export to depths greater than 100 m.

[学科分类] 地球化学与岩石