Fig. 1

Location of sites and modern ocean surface temperature and phosphate concentrations. Temperature (a) and phosphate (b) concentration fields are plotted with the Ocean Data View (ODV) software68 with WOA0969. Solid black lines represent the: Subtropical (STF), Subantarctic (SAF), Polar (PF) and Subantarctic Circumpolar Current (SACCF) Fronts70. The Polar Frontal and Subantarctic Zones are the regions between the PF and SAF, and between the SAF and the STF respectively. a Solid white circles symbolize the geographic location of sediment cores MD07-3088 (46.1°S, 75.7°W, 1536 m), TN057-13-4PC30 (53.2°S, 5.1°E, 2850 m), and sites ODP 123329 (41.0°S, 74.4°W, 838 m) and 123815 (1.5°S, 82.5°W, 2203 m). The solid white square highlights the West Antarctic Ice Sheet Divide ice core56 (WDC, 79.5°S, 112.1°W, 1766 m above sea level)