Deep sea and seafloor ecosystem response to net-zero and negative emissions

With ongoing climate change, multiple stressors including ocean warming, deoxygenation, ocean acidification and limited nutrient availability will lead to large regime shifts within marine ecosystems^[1]. Deep-sea ecosystems are adapted to the stable ambient conditions of the deep ocean and are therefore likely highly vulnerable to human impacts and climate change. Future projections show considerable deep-water warming, acidification, and heat accumulation, and moreover, in strong overshoot scenarios, irreversibility is found in various properties in the deep ocean^[2]. Here, we compare rates of warming, acidification, and deoxygenation at depth and the seafloor for a range of emission driven idealized overshoot scenarios run with the fully coupled Norwegian Earth System Model version 2 (NorESM2). We discuss the impact that changing ambient conditions have for deep sea ecosystems at the example of Lophelia Pertusa, a common cold-water coral found in the North Atlantic. The continued exposure to calcium carbonate undersaturation and inhibited aerobic activity due to warming and deoxygenation lead to physiologically unsustainable conditions for cold water corals, which could be alleviated by sustained food supply, i.e., increased export production. We therefore conclude by showing different potential habitat extents in relation to environmental stressors under different evolving climates.

 

We acknowledge the project TipESM “Exploring Tipping Points and Their Impacts Using Earth System Models”. TipESM is funded by the European Union. Grant Agreement number: 101137673. DOI: 10.3030/101137673.

 

[1] Heinze et al., 2020, The quiet crossing of tipping points, PNAS, 118(9)

[2] Schwinger et al., 2022, Emit now, mitigate later? Earth system reversibility under overshoots of different magnitudes and durations, Earth Syst. Dynam., 13, 1641–1665