Arctic Ocean acidification from land-ocean carbon transfer during past and present climate change

The increasing uptake of CO2 by the Arctic Ocean leads to ocean acidification (OA) and may cause ecosystem and socio-economic stress within and beyond the Arctic.

Arctic warming and massive release of terrestrial organic carbon (terrOC) from rivers and collapsing permafrost may exacerbate OA by additional CO2 supply from mineralized terrOC. However, it is unclear how massive terrOC release affects the Arctic Ocean carbonate system.

This project investigates Arctic OA during past climate warming, when post-glacial warming 17.5-7.5 kyr ago triggered large-scale permafrost thawing and amplified terrOC transfer to the Arctic Ocean.

Past changes in ocean pH and CO2 will be studied using boron proxies (δ11B, B/Ca) in planktic and benthic foraminifera, as well as by microbial biomarkers, in three phases; 1. (2022) proxy calibration under modern conditions using surface sediments from the Siberian Arctic Ocean - key region of terrOC-induced OA today; 2. (2022-2023) reconstruct past pH and CO2 at the ocean surface during periods of known massive terrOC release, based on sediment archives from the Siberian continental slope with high temporal resolution; 3. (2023-2024) study past pH and carbonate system changes in surface and bottom water of the central Arctic at different sampling depths to decipher the impact of terrOC over a larger scale.

The results will constrain the contribution of terrOC to OA under warming climate and provide a benchmark for anticipating future Arctic OA.