Figure 6.

Schematic of potential changes to surface and intermediate water circulation in the southwest Pacific since the late Pliocene. Sites which inform the conceptual framework for each time interval are shown. (a) Late Pliocene, with amplified EAC and poleward displacement of the Tasman Front (from DSDP Site 590B) and equatorward displacement of the STF (from DSDP Site 593 and ODP Site 1172) relative to modern, whereas warmer IWTs than modern and reduced sea ice extent [Barron, 1996a, 1996b] suggest an overall poleward displacement of the SAF. Cooling in SSTs and IWT at DSDP Site 593 from ~3 Ma suggests ongoing subantarctic cooling and/or equatorward migration of the STF and SAF (blue arrows). (b) Early Pleistocene, with the Tasman Front still displaced poleward and a strong EAC (DSDP Site 590B). Cooling in SSTs and IWTs at DSDP Site 593 indicates poleward migration of the STF and SAF, but the STF remains north of ODP Site 1172. (c) Late Pleistocene glacial stages, which are marked by large equatorward displacements of the STF and SAF, as well as increased bathymetric control over front positions to the east of New Zealand (constrained by multiple sites in Hayward et al. [2012] and Sikes et al. [2009], site numbers not shown here). The TF also migrated northward but some influence of subtropical water to the northern Tasman Sea is hypothesized (orange arrows [Hayward et al., 2012]). For the modern positions of the fronts please refer to Figure 1.