2024/11/12 by Jens Müller, Jens Daniel Müller, Nicolas Gruber +9 · 1 voice
Environmental Science · #Methane Hydrates and Related Phenomena #Atmospheric and Environmental Gas Dynamics
paper · pdf · doi:10.21203/rs.3.rs-5198321/v1
Abstract In 2023, sea-surface temperatures (SST) reached record highs. Based on historical responses, this SST anomaly would suggest an increased oceanic CO2 uptake (-0.11±0.03 PgC yr-1). In contrast, our observation-based estimates reveal that the global non-polar ocean absorbed about 10% less carbon than expected (+0.16±0.28 PgC yr-1). This weakening occurred despite reduced CO2 outgassing in the tropics associated with El Niño. Hence, the decline in CO2 uptake in 2023 materialised entirely in the extratropics, driven primarily by elevated SSTs in the Northern Hemisphere. Two ocean biogeochemical models demonstrate that in the subtropical North Atlantic the thermally-induced reduction in CO2 uptake was strongly mitigated by the depletion of dissolved inorganic carbon in the surface mixed layer. Such negative feedbacks cause an overall muted response of the ocean carbon sink to the record high SSTs, but this resilience may not persist under long-term warming or more severe SST extremes.