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Carbon sources and sinks from an Ensemble Kalman Filter ocean data assimilation
Author(s) -
Gerber M.,
Joos F.
Publication year - 2010
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 - 10.1029/2009gb003531
Subject(s) - sink (geography) , climatology , equator , carbon flux , environmental science , southern hemisphere , latitude , carbon cycle , zonal and meridional , atmospheric sciences , ocean heat content , carbon sink , data assimilation , middle latitudes , flux (metallurgy) , oceanography , geology , thermohaline circulation , climate change , meteorology , geography , chemistry , ecology , cartography , geodesy , organic chemistry , ecosystem , biology
We quantify contemporary and preindustrial net air‐sea CO 2 fluxes by an Ensemble Kalman Filter assimilation of interior ocean observations and compare results with published estimates in the light of sensitivity to model transport and input data reconstructions. Four different published reconstructions of anthropogenic carbon and the Δ C gasex tracer are assimilated into different versions of the Bern3D ocean model. The two tracers represent the components of dissolved inorganic carbon due to the anthropogenic perturbation and the air‐sea gas exchange of preindustrial CO 2 . Contemporary air‐sea fluxes for broad latitudinal bands are consistent with those from earlier ocean inversions and the observed air‐sea CO 2 partial pressure differences. We infer modest meridional transport rates of up to 0.5 GtC yr −1 for the preindustrial and the contemporary ocean and a small carbon transport across the equator. The anthropogenic perturbation offsets the preindustrial net sea‐to‐air flux yielding a weak contemporary carbon sink in the Southern Ocean (south of 44°S) of 0.15 ± 0.25 GtC yr −1 . Preindustrial Southern Ocean outgassing varies by almost a factor of 2 among the four Δ C gasex reconstructions. Large differences in regional fluxes are found between an earlier ocean inversion using Green's function and this study for the same model and input data calculation. Systematic differences in assimilated and optimized Δ C gasex fields are large in both inversions, and the contemporary, anthropogenic, and preindustrial air‐sea CO 2 flux in the high‐latitude and midlatitude Southern Hemisphere remains uncertain.