Five million years of Antarctic Circumpolar Current strength variability (2024)
10 months ago
- #Climate Change
- #Paleoceanography
- #Antarctic Circumpolar Current
- The Antarctic Circumpolar Current (ACC) is the world's largest ocean-current system, influencing global ocean circulation, climate, and Antarctic ice-sheet stability.
- ACC dynamics are controlled by atmospheric forcing, oceanic density gradients, and eddy activity, with no linear long-term trend in strength over the past 5.3 million years.
- A reversal in ACC strength occurred from increasing during Pliocene global cooling to decreasing with further Early Pleistocene cooling, linked to Southern Ocean reconfiguration.
- ACC strength changes are closely tied to 400,000-year eccentricity cycles, influenced by tropical Pacific temperature variability and precessional changes in the South Pacific jet stream.
- A persistent link between weaker ACC flow, equatorward-shifted opal deposition, and reduced atmospheric CO2 during glacial periods emerged during the Mid-Pleistocene Transition (MPT).
- The strongest ACC flow occurred during warmer-than-present intervals of the Plio-Pleistocene, suggesting potential future increases in ACC flow with climate warming.
- ACC strength variations are relevant for Antarctic ice-sheet stability, with weaker ACC linked to ice-sheet advances and stronger ACC associated with retreats.
- The study provides geological evidence supporting future ACC acceleration under continued global warming, with implications for Southern Ocean carbon uptake.