Dataset Information

Role of oceanic abiotic carbonate precipitation in future atmospheric CO₂ regulation.

ABSTRACT: The oceans play a major role in the earth's climate by regulating atmospheric CO₂. While oceanic primary productivity and organic carbon burial sequesters CO₂ from the atmosphere, precipitation of CaCO₃ in the sea returns CO₂ to the atmosphere. Abiotic CaCO₃ precipitation in the form of aragonite is potentially an important feedback mechanism for the global carbon cycle, but this process has not been fully quantified. In a sediment-trap study conducted in the southeastern Mediterranean Sea, one of the fastest warming and most oligotrophic regions in the ocean, we quantify for the first time the flux of inorganic aragonite in the water column. We show that this process is kinetically induced by the warming of surface water and prolonged stratification resulting in a high aragonite saturation state (Ω_Ar ≥ 4). Based on these relations, we estimate that abiotic aragonite calcification may account for 15 ± 3% of the previously reported CO₂ efflux from the sea surface to the atmosphere in the southeastern Mediterranean. Modelled predictions of sea surface temperature and Ω_Ar suggest that this process may weaken in the future ocean, resulting in increased alkalinity and buffering capacity of atmospheric CO₂.

SUBMITTER: Bialik OM

PROVIDER: S-EPMC9509385 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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Role of oceanic abiotic carbonate precipitation in future atmospheric CO2 regulation.

Bialik Or M OM Sisma-Ventura Guy G Vogt-Vincent Noam N Silverman Jacob J Katz Timor T

Scientific reports 20220924 1

The oceans play a major role in the earth's climate by regulating atmospheric CO2. While oceanic primary productivity and organic carbon burial sequesters CO2 from the atmosphere, precipitation of CaCO3 in the sea returns CO2 to the atmosphere. Abiotic CaCO3 precipitation in the form of aragonite is potentially an important feedback mechanism for the global carbon cycle, but this process has not been fully quantified. In a sediment-trap stud ...[more]

PMID: 36153366

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Project description:Agricultural fields in drylands are challenged globally by limited freshwater resources for irrigation and also by elevated soil salinity and sodicity. It is well known that pedogenic carbonate is less soluble than evaporate salts and commonly forms in natural drylands. However, few studies have evaluated how irrigation loads dissolved calcium and bicarbonate to agricultural fields, accelerating formation rates of secondary calcite and simultaneously releasing abiotic CO2 to the atmosphere. This study reports one of the first geochemical and isotopic studies of such "anthropogenic" pedogenic carbonates and CO2 from irrigated drylands of southwestern United States. A pecan orchard and an alfalfa field, where flood-irrigation using the Rio Grande river is a common practice, were compared to a nearby natural dryland site. Strontium and carbon isotope ratios show that bulk pedogenic carbonates in irrigated soils at the pecan orchard primarily formed due to flood-irrigation, and that approximately 20-50% of soil CO2 in these irrigated soils is calcite-derived abiotic CO2 instead of soil-respired or atmospheric origins. Multiple variables that control the salt buildup in this region are identified and impact the crop production and soil sustainability regionally and globally. Irrigation intensity and water chemistry (irrigation water quantity and quality) dictate salt loading, and soil texture governs water infiltration and salt leaching. In the study area, agricultural soils have accumulated up to 10 wt% of calcite after just about 100 years of cultivation. These rates will likely increase in the future due to the combined effects of climate variability (reduced rainfall and more intense evaporation), use of more brackish groundwater for irrigation, and reduced porosity in soils. The enhanced accumulation rates of pedogenic carbonate are accompanied by release of large amounts of abiotic CO2 from irrigated drylands to atmosphere. Extensive field studies and modelling approaches are needed to further quantify these effluxes at local, regional and global scales.

Dataset Information

Role of oceanic abiotic carbonate precipitation in future atmospheric CO₂ regulation.

Publications

Role of oceanic abiotic carbonate precipitation in future atmospheric CO<sub>2</sub> regulation.

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