There is much debate about when the Drake Passage was opened, due to deep currents like the Antarctic Circumpolar Current (ACC). This opening could have been a primary cause of changes in global circulation and climate, as well as the rapid expansion of Antarctic ice sheets, because as Antarctica was encircled by ocean currents it was cut from receiving heat from warmer regions. Precise dating of the earliest opening of the Drake Passage is complicated by the existence of plate fragments, which have been reconstructed to show the age of the earliest pathway.