Ocean sediment records document abrupt changes in glacial-to-deglacial circulation and mixing of the ocean, recorded as changes in ¹⁴C reservoir ages of surface waters.

Here we present ¹⁴C-based high-resolution age records of four sediment cores derived by means of ¹⁴C plateau tuning. This provides a detailed and precise stratigraphic correlation between the western and eastern South Pacific and paleoclimate records of Antarctic ice cores as well as ¹⁴C reservoir ages. The accuracy and precision of plateau tuning are confirmed in two sediment cores off Chile; in one core by independent land-based age control of four tephra layers, in a second core by a suite of glacial sediment varves. During glacial times, high reservoir ages reaching up to ~1500 yr may reflect

seasonal sea ice and/or a melt water lid at high latitudes both east of New Zealand and off southern Chile and may be linked to northward advection of upwelled old subsurface waters from the Polar Frontal Zone. Our results support the model of a bipolar seesaw at the onset of rapid deglacial Antarctic warming, moreover, they show that the Antarctic Cold Reversal immediately preceded the onset of the Younger Dryas cold spell.