Article Dans Une Revue PNAS Nexus Année : 2024

Release of ballast material during sea-ice melt enhances carbon export in the Arctic Ocean

Steffen Swoboda
Thomas Krumpen
Eva-Maria Nöthig
Katja Metfies
Jutta Wollenburg
Kirsten Fahl
Ilka Peeken
Morten Iversen
  • Fonction : Auteur

Résumé

Abstract Globally, the most intense uptake of anthropogenic carbon dioxide (CO2) occurs in the Atlantic north of 50°N, and it has been predicted that atmospheric CO2 sequestration in the Arctic Ocean will increase as a result of ice-melt and increased primary production. However, little is known about the impact of pan-Arctic sea-ice decline on carbon export processes. We investigated the potential ballasting effect of sea-ice derived material on settling aggregates and carbon export in the Fram Strait by combining 13 years of vertical flux measurements with benthic eDNA analysis, laboratory experiments, and tracked sea-ice distributions. We show that melting sea-ice in the Fram Strait releases cryogenic gypsum and terrigenous material, which ballasts sinking organic aggregates. As a result, settling velocities of aggregates increased ≤10-fold, resulting in ≤30% higher carbon export in the vicinity of the melting ice-edge. Cryogenic gypsum is formed in first-year sea-ice, which is predicted to increase as the Arctic is warming. Simultaneously, less sea-ice forms over the Arctic shelves, which is where terrigenous material is incorporated into sea-ice. Supporting this, we found that terrigenous fluxes from melting sea-ice in the Fram Strait decreased by >80% during our time-series. Our study suggests that terrigenous flux will eventually cease when enhanced sea-ice melt disrupts trans-Arctic sea-ice transport and thus, limit terrigenous-ballasted carbon flux. However, the predicted increase in Arctic primary production and gypsum formation may enhance gypsum-ballasted carbon flux and compensate for lowered terrigenous fluxes. It is thus unclear if sea-ice loss will reduce carbon export in the Arctic Ocean.

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Dates et versions

hal-04681065 , version 1 (29-08-2024)

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Citer

Steffen Swoboda, Thomas Krumpen, Eva-Maria Nöthig, Katja Metfies, Simon Ramondenc, et al.. Release of ballast material during sea-ice melt enhances carbon export in the Arctic Ocean. PNAS Nexus, 2024, 3 (4), ⟨10.1093/pnasnexus/pgae081⟩. ⟨hal-04681065⟩
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