Speaker
Description
Subsea permafrost thaw on the warming Arctic shelf could release up to ~2822 (1518–4982) Pg of organic carbon (OC) [1]. Microbial processes convert this OC into methane ($CH_4$) and dissolved inorganic carbon ($DIC$), which, if released to the Arctic Ocean, may intensify acidification and global warming. The impact depends on how much carbon escapes and in which form. In upper sediments, anaerobic methane oxidation ($AOM$) consumes $CH_4$ but raises $DIC$ and alkalinity ($TA$), influencing carbonate chemistry and favouring carbonate precipitation. This precipitation sequesters carbon but consumes $TA$. Thus, Arctic acidification and $CO_2$ fluxes depend not only on permafrost $CH_4$ and $DIC$ fluxes, but also on $AOM$ and authigenic carbonate precipitation rates, key regulators of benthic carbonate biogeochemistry.
We use a reaction-transport model on the pan-Arctic scale to quantify seafloor $DIC$ and $TA$ fluxes driven by subsea permafrost-derived $CH_4$ and $DIC$ inputs for three climate scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5) from 1900–2300. Across all scenarios, results confirm that $AOM$ is a highly effective microbial barrier consuming all dissolved $CH_4$. However, its regulating role on seafloor $DIC$ and $TA$ fluxes is dwarfed by high permafrost-derived $DIC$ fluxes. The model predicts subsea permafrost thaw could release 15 (SSP1)–95 (SSP5) TgC yr⁻¹ as $DIC$ and 10 (SSP1)–50 (SSP5) Teq yr⁻¹ as $TA$ by 2300. The pan-Arctic $TA/DIC$ efflux ratio, slightly below 1 for SSP1–2 and markedly lower for SSP5, indicates that permafrost thaw will amplify Arctic Ocean acidification and may weaken its $CO_2$ sink, especially under SSP5.
| If accepted by the Scientific Board, I agree to have my presentation/poster and abstract published on the Belgian Climate Centre websites and social media. | Yes |
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