Antarctic circumpolar current developed in the Late Oligocene

In a recent issue of the journal Geology Lyle et al. present new sediment core data suggesting that deep flow in the South Atlantic ocean started as late as the late Oligocene. The Antarctic circumpolar current was thought to have thermally isolated Antarctica in the Eocene, so that an ice sheet could develop. Recent modeling studies, however, suggested that the story is more complex. Lyle et al. explain that shallow circulation may have existed earlier than the late Oligocene as indicated by Nd isotope studies, but that deep flow with vertical mixing was established by 23-25 Ma. These findings have consequences for studies of the evolutionary biology of the region as well. For more information read the abstract here

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