A northward shift of the Atlantic Intertropical Convergence Zone consistent with transient AMOC reinvigoration during Termination II

Termination II (T-II) has been considered a relatively smooth glacial–interglacial transition, punctuated by a single cold phase, Heinrich Stadial 11 (HS-11; ~136–129 ka), during which enhanced freshwater input from Northern Hemisphere ice sheets weakened the Atlantic Meridional Overturning Circulation (AMOC), thereby promoting a southward displacement of the Intertropical Convergence Zone (ITCZ). Here, we present oceanographic and runoff-sensitive proxy records from the Tobago Basin, north of the Orinoco Delta in the tropical Atlantic, that track meridional ITCZ migration during T-II. Consistent with expected effects of a southward ITCZ shift during HS-11, our records indicate reduced runoff and a deepened mixed layer. However, at ~134±1.4 ka, this pattern was reversed for several centuries, with increased runoff and a shallower mixed layer, suggesting a northward ITCZ shift that is at odds with the persistently southward position expected under a continuously weakened AMOC. This hydroclimate reversal coincided with North Atlantic sea-surface warming and reduced freshwater input from Northern Hemisphere ice sheets in other records, consistent with a centennial-scale reinvigoration of the AMOC during HS-11. Our findings add to recent evidence challenging the conventional view of HS-11 as an event with major AMOC weakening for ~7 kyr, and instead imply a more complex sequence of climate variability, with implications for understanding the evolution and dynamics of major deglaciations in general.