Overview
- New research in PNAS reports that opening the Drake Passage and Tasman Gateway was necessary but not sufficient to launch the Antarctic Circumpolar Current.
- The study finds the current only matured once strong westerly winds blew directly through the Tasman Gateway after Australia had moved farther from Antarctica.
- Researchers ran coupled climate and Antarctic ice-sheet models using Oligocene-era geography and then checked the results against geological reconstructions.
- The early current was not a single continuous loop, with strong flow in the southern Atlantic and Indian Oceans and a much weaker Pacific sector.
- The team links the current’s growth to greater Southern Ocean carbon uptake and planetary cooling during the Oligocene, while noting other CO2 sinks such as mountain building, and they caution that past climates do not map 1:1 onto future high-CO2 worlds.