South of human civilization lies the vast Southern Ocean, the waters of which get swept around the globe by the Antarctic circumpolar current (ACC). This formidable current transports more than 100 million cubic metres of water per second. Connecting the Pacific, Indian and Atlantic ocean basins, it has a central role in the global circulation of the world’s oceans and in regulating climate1. Yet little is known about its history. Writing in Nature, Lamy et al .2present impr...