Ocean Acidification in the SIberian Seas (OASIS): The impact of permafrost thaw and methane release

Ocean acidification by rising atmospheric CO2 is a tipping point of the carbon-climate system, limits future ocean CO2 uptake and threatens ocean fauna.

The Siberian Arctic Ocean is a hot spot of acidification, driven by additional and likely increasing CO2 production from (1) decomposition of organic matter released from thawing land permafrost and (2) oxidation of CH4 released from subsea sources. OASIS will quantify the impact of both on ocean acidification.

Central questions:To what extent does degradation of permafrost-released organic matter contribute to ocean acidification?

How sensitive is degradation to projected increases in ocean productivity (“priming effect”)?To what extent does CH4 oxidation accelerate ocean acidification but also mitigate CH4 emissions?

What is the potential of CH4 oxidation to reduce emissions in case of CH4 hydrate collapse?Two expeditions provide rare access to the Siberian Arctic Ocean: the ISSS-2020 expedition (successfully executed in 2020) and the EURASIAN ARCTIC C4 expedition (scheduled 2023 on ice breaker Oden).

OASIS will combine on-board and laboratory experiments, 14C-dating, 13C- and 3H-labelling, as well as large, existing databases to answer these questions.The generated quantitative data and systems understanding will facilitate estimates of how permafrost thaw and CH4 release accelerate acidification of the Siberian Arctic Ocean, and contribute to a SYNTHESIS REPORT on tipping points in the ocean-cryosphere-climate system.