Glacial-interglacial changes in Antarctic Intermediate Water advection in the Southeast Pacific during the last 787 kyr

Southern-sourced intermediate waters play a central role in global ocean oxygenation and nutrient transport to low latitudes. However, the glacial-interglacial variability in their formation rate and geometry are not well constrained. Here we present a new ca. 787 thousand years-long benthic foraminifera stable carbon isotopic record from the Southeast Pacific, near the main formation region of Antarctic Intermediate Water (AAIW), which allows the investigation of changes in the formation rate and transport of AAIW over the last 787 kyr. Our results show glacial-interglacial changes in AAIW transport, with more AAIW being exported towards the Atlantic Ocean during interglacials, and to the low-latitude Pacific Ocean during glacials. We hypothesize that the AAIW exportation from the Pacific to the Atlantic Ocean is controlled by transport through the Drake Passage, which is reduced (increased) during glacial (interglacial) periods. The observed pattern is probably related to a combination of factors, including reduced (increased) sea-ice extent and southward (northward) shift of oceanic fronts and/or the westerlies during interglacials (glacials). Our mechanism reconciles the greater influence of AAIW in the northern Chilean margin during glacial periods, concurrent with the previously suggested decrease in formation rate and shallowing of this water mass. Ultimately, the glacial-interglacial variability in AAIW exportation to the Atlantic Ocean may be closely linked with changes in the stability of Atlantic Meridional Overturning Circulation during these distinct climate background states.