Detrital Carbonate Minerals in Earth's Element Cycles. Issue 5 (17th May 2022)

• Record Type: Journal Article
• Authors: Müller, Gerrit; Börker, Janine; Sluijs, Appy; Middelburg, Jack J.
• Is Part Of: Global biogeochemical cycles. Volume 36:Issue 5(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-17
• Subjects: detrital carbonate -- particulate inorganic carbon -- alkalinity -- calcium -- biogeochemical cycling -- river sediment; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1029/2021GB007231
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: We investigate if the commonly neglected riverine detrital carbonate fluxes might reconciliate several chemical mass balances of the global ocean. Particulate inorganic carbon (PIC) concentrations in riverine suspended sediments, that is, carbon contained by these detrital carbonate minerals, were quantified at the basin and global scale. Our approach is based on globally representative data sets of riverine suspended sediment composition, catchment properties, and a two‐step regression procedure. The present‐day global riverine PIC flux is estimated at 3.1 ± 0.3 Tmol C/y (13% of total inorganic carbon export and 4% of total carbon export) with a flux‐weighted mean concentration of 0.26 ± 0.03 wt%. The flux prior to damming was 4.1 ± 0.5 Tmol C/y. PIC fluxes are concentrated in limestone‐rich, rather dry and mountainous catchments of large rivers near Arabia, South East Asia, and Europe with 2.2 Tmol C/y (67.6%) discharged between 15°N and 45°N. Greenlandic and Antarctic meltwater discharge and ice‐rafting additionally contribute 0.8 ± 0.3 Tmol C/y. This amount of detrital carbonate minerals annually discharged into the ocean implies a significant contribution of calcium (∼4.75 Tmol Ca/y) and alkalinity fluxes (∼10 Tmol (eq)/y) to marine mass balances and moderate inputs of strontium (∼5 Gmol Sr/y) based on undisturbed riverine and cryospheric inputs and a dolomite/calcite ratio of 0.1. Magnesium fluxes (∼0.25 Tmol Mg/y), mostly hosted by less‐soluble dolomite, are rather negligible. These unaccounted fluxes help in elucidating respective marine mass balances and potentially alter conclusions based on these budgets. Plain Language Summary: Earth surface conditions, including climate and sea level, are largely controlled by the cycling of carbon and biogeochemically coupled elements. However, most elemental budgets cannot be consentaneously balanced for the present state. Here, we investigate the possible role of riverine carbonate minerals in biogeochemical cycles. We derive individual river basin export fluxes, the global export flux to the ocean, and its reduction by human influence, utilizing state‐of‐the‐art regression techniques and published global‐scale data sets. Results point to a significance of riverine detrital carbonates for the global mass balances of carbon, calcium, alkalinity, and strontium, which might help in solving this long‐standing problem. Abstract :