Fig. 3: Paleoceanographic evolution of the Southern Ocean.
From: Gateway-driven weakening of ocean gyres leads to Southern Ocean cooling
a–f Model-data comparison and proposed paleoceanographic evolution of the surface Southern Ocean from the Late Eocene to Early Oligocene (41–30 million years ago, Ma). The left column presents the comparison of observed and modelled surface temperature differences (δ SST, both datasets use the same colour scale, see legend). Modelled differences in sea-surface temperatures result from the: a Drake Passage (DP) deepening from 300 to 1000 m (Tasmanian Gateway (TG) remaining at 300 m), TG deepening from: b 300 to 600 m and c 600 to 1500 m (DP at 1000 m). Contours indicate 0.5 °C intervals. The inner part of the triangles shows relative changes of paleo sea-surface temperature proxy records from sediment drill cores within the geological time slices2,21,29,30,31,32,33,34,35,36,42,43. The outer part of the triangles shows the modelled SST changes at these drill sites. The right column presents the comparison of observed and modelled current pattern. Modelled stream function pattern (bold contours show 10 Sverdrup (Sv) and −10 Sv; fine lines show >10 Sv and <−10 Sv; colour scale, see legend, ACC = Antarctic Circumpolar Current) are taken from simulations with: b TG at 300 m, d TG at 600 m and f TG at 1500 m (DP at 1000 m; Fig. 2). Pie charts present plankton biogeographic patterns in proportions (colours and affinities, see legend)5,19,21,42,43,44,45 found in sediment drill cores as proxy for surface current pattern. Details of the sites’ paleolocations, recorded geological time periods, as well as all data used in this study are collated in the SI.
