Younger Dryas drought and IPO climate modulation during the Antarctic Cold Reversal in New Zealand.

We present an environmental magnetic record from a 6.1 metre sediment core from Lake Hayes, Te Waipounamu, South Island, New Zealand that spans the last c. 16.5 kyr and contains a logical progression of climate events. Periods of anoxia are identified from greigite that formed during reducing conditions whereas magnetite-dominated intervals indicate an oxygenated, well mixed water column. Before c. 15.5 ka, magnetite was eroded from schist and transported to the lake by glaciers. During the Antarctic Cold Reversal (between c. 14.7-13.0 ka), redox oscillations were modulated by the long term Interdecadal Pacific Oscillation (IPO) control on precipitation and wind strength. Later, during the Younger Dryas (c. 12.9-11.7 ka), the lake became anoxic suggesting less rain and wind and persistent drought conditions. In this region, the Younger Dryas was warmer than today which may indicate persistent drought conditions may return as the climate warms, in contradiction to projections from numerical climate models.