Preprints
https://doi.org/10.5194/bg-2022-228
https://doi.org/10.5194/bg-2022-228
 
25 Nov 2022
25 Nov 2022
Status: this preprint is currently under review for the journal BG.

Assessing global-scale organic matter reactivity patterns in marine sediments using a lognormal reactive continuum model

Sinan Xu1,2, Bo Liu2, Sandra Arndt3, Sabine Kasten2,4, and Zijun Wu1 Sinan Xu et al.
  • 1State Key Laboratory of Marine Geology, School of Ocean and Earth Science, Tongji University, Shanghai, 200092, P.R. China
  • 2Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 275706 Bremerhaven, Germany
  • 3Department of Geosciences, Environment and Society, Université Libre de Bruxelles, Avenue Franklin Roosevelt 50, 1050 Brussels, Belgium
  • 4Faculty of Geosciences, University of Bremen, 28359 Bremen, Germany

Abstract. Organic matter (OM) degradation in marine sediments is largely controlled by its reactivity and profoundly affects the global carbon cycle. Yet, there is currently no general framework that can constrain OM reactivity on a global scale. In this study, we propose a reactive continuum model based on a lognormal distribution (l-RCM) that is fully described by the mean μ and standard deviation σ of the sedimentary OM reactivity distribution. We use the l-RCM to inversely determine μ and σ at 123 sites across the global ocean. The results find that the apparent OM reactivity (<k>=μ·exp(σ2/2)) decreases with decreasing sedimentation rate (ω) and show that OM reactivity is more than three orders of magnitude higher in shelf than that in abyssal regions. Despite the general global trends, higher than expected OM reactivity is observed in certain deeper ocean regions, such as the Eastern-Western Coastal Equatorial Pacific and the Arabian Sea, emphasizing the complex control of the depositional environment (e.g., OM flux, oxygen content in the water column) on benthic OM reactivity. Notably, the l-RCM can also highlight the variability of OM reactivity in these regions. Based on inverse modeling results in our database, we establish the significant statistical relationships between <k> and ω, and further map the global OM reactivity distribution.

Sinan Xu et al.

Status: open (until 06 Jan 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-228', Anonymous Referee #1, 03 Dec 2022 reply

Sinan Xu et al.

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Short summary
We use a reactive continuum model based on a lognormal distribution (l-RCM) to inversely determine model parameters μ and σ at 123 sites across the global ocean. Our results show organic matter (OM) reactivity is more than three orders of magnitude higher in shelf than that in abyssal regions. In addition, OM reactivity is higher than predicted in some specific regions, yet the l-RCM can still capture OM reactivity features in these regions.
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