The Antarctic Circumpolar Current
With both southern gateways open, water begins circling Antarctica unobstructed — and the continent is thermally cut off.
- When
- —
- Duration
- 9 million years
- Known to
- ± 4 million years
- Era
- Oligocene, Cenozoic
Once Drake Passage and the Tasman gateway are both deep enough, nothing blocks a current running right round the globe at southern high latitudes. The ACC is the largest ocean current on Earth by volume transport, and by isolating Antarctic surface water from warm subtropical water it helps keep the continent frozen. Its timing is genuinely unsettled: a proto-current is argued for as early as 36 million years ago, a substantial strengthening for the latest Oligocene after about 24, and full modern configuration not until the late Miocene.