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Publication Abstracts

Lerner et al. 2025, in press

Lerner, P., M. Grenier, O. Marchal, and P. van Beek, 2025: An inverse modelling approach to constrain Be cycling in the subpolar North Atlantic. Deep Sea Res. I, in press, doi:10.1016/j.dsr.2025.104465.

Beryllium-7 is a short-lived cosmogenic radionuclide that has been used as a tracer of atmospheric deposition at the sea surface and of physical processes in the upper ocean. These applications generally assume that (i) the fraction of marine ⁷Be in particulate form is negligible, and/or (ii) the interactions between the particulate and dissolved forms of ⁷Be in seawater can be neglected. In this study, we test different steady-state models of upper ocean ⁷Be cycling from measurements of total ⁷Be and particulate ⁷Be activities collected at two stations of the GEOVIDE cruise in the subpolar North Atlantic (May-June 2014). The most complete model includes vertical advection, vertical diffusion, gravitational settling, radioactive decay, atmospheric deposition, and the reversible exchange between dissolved ⁷Be (⁷Be_d) and particulate ⁷Be (⁷Be_p). This model reproduces the measured ⁷Be activities at both stations to within their uncertainties (±1 standard deviation). In the East Greenland-Irminger Current (station 51/60), models that do not consider adsorption and/or desorption can still reproduce the measured activities, while in the southern Labrador Sea (station 69) models that neglect reversible exchange or desorption poorly fit the data. Thus, ⁷Be_d at station 51/60 could have been supplied entirely by surface deposition, whereas ⁷Be_d at station 69 originated at least partly from the release of particulate ⁷Be into solution. The subsurface ⁷Be_p maxima, present at both stations, seem to require a flux of ⁷Be between particles and solution at station 69 but not at station 51/60. At both stations, most of the total ⁷Be deposited at the ocean surface was removed by radioactive decay, with at most 5% removed by sinking of ⁷Be_p, suggesting that reversible exchange can be neglected in applications of total ⁷Be as a tracer for atmospheric deposition. However, reversible exchange is important to consider in applications of ⁷Be_d as a deposition tracer, with a maximum bias of 40% when reversible exchange is neglected. The steady state assumption does not alter our results regarding the solid-solution exchange of ⁷Be, but it does result in a significant bias when deriving atmospheric ⁷Be_tot deposition fluxes from water column ⁷Be_tot inventories Overall, our findings suggest that reversible exchange could significantly influence the oceanic cycling of ⁷Be at some locations, and should not be systematically neglected when using ⁷Be_d as an oceanic tracer.

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@unpublished{le03010z,
  author={Lerner, P. and Grenier, M. and Marchal, O. and van Beek, P.},
  title={An inverse modelling approach to constrain Be cycling in the subpolar North Atlantic},
  year={2025},
  journal={Deep Sea Research Part I},
  doi={10.1016/j.dsr.2025.104465},
  note={Manuscript accepted for publication}
}

TY  - INPR
ID  - le03010z
AU  - Lerner, P.
AU  - Grenier, M.
AU  - Marchal, O.
AU  - van Beek, P.
PY  - 2025
TI  - An inverse modelling approach to constrain Be cycling in the subpolar North Atlantic
JA  - Deep Sea Res. I
JO  - Deep Sea Research Part I
DO  - 10.1016/j.dsr.2025.104465
ER  -

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