The role of Antarctica in Pleistocene glacial history : Wilson's ice age theory revisited

Approximately 14,500 14C yr BP the major ice sheets of the Northern Hemisphere began melting and returning fresh water to the world's oceans. As the melt water was strongly depleted in 18O a distinctive geochemical signal was introduced into the North Atlantic Ocean which should then have been distributed via the reactivated oceanic conveyor belt to all of the worlds oceans, appearing in the deep Pacific Ocean about 1750 yrs after melting started, and in the surface waters even later. We have analysed planktic and benthic foraminifera from two cores from off the east coast of North Island, both of which had a good tephra chronology and high sedimentation rates. As expected the 18Omelt water signal first appeared in the benthic record between 1300 and 2000 yr before it appeared in the deep waters offf the east coast of New Zeland no later than it first appeared in the North Atlantic Ocean. Furthermore the shape of the changing 18O signal in the SW Pacific is quite different to that of the Atlantic and Indian Oceans which have a characteristic two step transition between glacial and interglacial values separated by temporary reversal of the Younger Dryas. For melting to start on the Antarctic Ice Sheets at the same time as if not before that of the Northern Hemisphere ice sheets requires a re-examination of the mechanism of ice age termination, such as instability of the marine based expanded Antarctic Ice Sheets. (author)