@article{fdi:010070324,
  title = {{I}mproving the inverse modeling of a trace isotope : how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated ?},
  author = {{L}e {G}land, {G}. and {M}emery, {L}. and {A}umont, {O}livier and {R}esplandy, {L}.},
  editor = {},
  language = {{ENG}},
  abstract = {{R}adium-228 ({R}a-228), an almost conservative trace isotope in the ocean, supplied from the continental shelves and removed by a known radioactive decay ({T}-1/2 - 5.75 years), can be used as a proxy to constrain shelf fluxes of other trace elements, such as nutrients, iron, or rare earth elements. {I}n this study, we perform inverse modeling of a global {R}a-228 dataset (including {GEOSECS}, {TTO} and {GEOTRACES} programs, and, for the first time, data from the {A}rctic and around the {K}erguelen {I}slands) to compute the total {R}a-228 fluxes toward the ocean, using the ocean circulation obtained from the {NEMO} 3.6 model with a 2 degrees resolution. {W}e optimized the inverse calculation (source regions, cost function) and find a global estimate of the {R}a-228 fluxes of 8.01-8.49 x 10(23) atoms yr(-1), more precise and around 20% lower than previous estimates. {T}he largest fluxes are in the western {N}orth {A}tlantic, the western {P}acific and the {I}ndian {O}cean, with roughly two-thirds in the {I}ndo-{P}acific {B}asin. {A}n estimate in the {A}rctic {O}cean is provided for the first time (0.43-0.50 x 10(23) atoms yr(-1)). {L}ocal misfits between model and data in the {A}rctic, the {G}ulf {S}tream and the {K}uroshio regions could result from flaws of the ocean circulation in these regions (resolution, atmospheric forcing). {A}s radium is enriched in groundwater, a large part of the {R}a-228 shelf sources comes from submarine groundwater discharge ({SGD}), a major but poorly known pathway for terrestrial mineral elements, including nutrients, to the ocean. {I}n contrast to the {R}a-228 budget, the global estimate of {SGD} is rather unconstrained, between 1.3 and 14.7 x 10(13) m(3) yr(-1), due to high uncertainties on the other sources of {R}a-228, especially diffusion from continental shelf sediments. {B}etter precision on {SGD} cannot be reached by inverse modeling until a proper way to separate the contributions of {SGD} and diffusive release from sediments at a global scale is found.},
  keywords = {{MONDE} ; {OCEAN} {INDIEN} ; {ATLANTIQUE} ; {ARCTIQUE} ; {PACIFIQUE} ; {MEDITERRANEE} ; {INDONESIE} ; {OCEAN} {AUSTRAL}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {14},
  numero = {13},
  pages = {3171--3189},
  ISSN = {1726-4170},
  year = {2017},
  DOI = {10.5194/bg-14-3171-2017},
  URL = {https://www.documentation.ird.fr/hor/fdi:010070324},
}