The Effect of Cosmic Dust on Southern Ocean Biogeochemistry is Small but Non-Negligible
The Effect of Cosmic Dust on Southern Ocean Biogeochemistry is Small but Non-Negligible
Abstract:
Input of iron from cosmic dust particles has been hypothesized to be a significant contribution to phytoplankton requirements of iron in the Southern Ocean. Due to its remoteness, the ocean south of 50S receives little iron from the deposition of terrestrial dust, and iron availability limits phytoplankton growth is in large parts. Although globally the iron flux into the ocean from meteoric smoke, the ablation product of cosmic dust, is small compared to that from terrestrial dust, it might be an important contribution here. This conjecture has, however, not been quantified and compared to the influence of other external iron sources and the effect of oceanic transport.
Here we use a new estimate of the spatial distribution of meteoric smoke particle deposition, and ocean biogeochemical models to quantify the relative role of cosmic dust for total iron fluxes to the Southern Ocean, and to its biological productivity.
We show that compared to terrestrial dust, the deposition of meteoric smoke particles indeed dominates the atmospheric iron supply to large parts of the Southern Ocean. Nevertheless, its effect on primary production, nutrient drawdown, and on the vertical sinking flux of organic carbon is small, albeit non-negligible. This is mainly due to upwelling and vertical mixing, both driven by the strong winds around Antarctica, dominating the total iron supply. As there is some uncertainty in the magnitude of other oceanic iron sources, e.g. from sediments and hydrothermal fluxes, it is important that these results have been robustly obtained using several models that use different assumptions on the strength of these other iron sources.
Here we use a new estimate of the spatial distribution of meteoric smoke particle deposition, and ocean biogeochemical models to quantify the relative role of cosmic dust for total iron fluxes to the Southern Ocean, and to its biological productivity.
We show that compared to terrestrial dust, the deposition of meteoric smoke particles indeed dominates the atmospheric iron supply to large parts of the Southern Ocean. Nevertheless, its effect on primary production, nutrient drawdown, and on the vertical sinking flux of organic carbon is small, albeit non-negligible. This is mainly due to upwelling and vertical mixing, both driven by the strong winds around Antarctica, dominating the total iron supply. As there is some uncertainty in the magnitude of other oceanic iron sources, e.g. from sediments and hydrothermal fluxes, it is important that these results have been robustly obtained using several models that use different assumptions on the strength of these other iron sources.