Planktic foraminifera-based sea-surface temperature record in the Tasman Sea and history of the Subtropical Front around New Zealand, over the last one million years

Planktic foraminiferal assemblages in a composite section from two cores (MD06-2989/2986) off the west coast of New Zealandʹs South Island (42–43.5°S) provide a 1 myr (MIS 31–1) sea-surface temperature (SST) record (~ 3–4 kyr resolution) in the Tasman Sea. A significant overall faunal change occurred near the end of the mid-Pleistocene Climate Transition (MPT) at ~ 600 ka (MIS 15). Mean annual SSTs were estimated using the Artificial Neural Network (ANN) method. Glacial–interglacial (G–I) cycles in the MPT had ~ 9 °C SST range, whereas in the post-MPT SST range was ~ 6–7 °C. The SST and faunal changes imply that the Subtropical Front (STF) migrated ~ 6° in latitude to lie just north of the sites in MPT glacials (MIS 28–16), but only migrated 3–5° north in post-MPT glacials. These G–I latitudinal migrations of the STF west of New Zealand contrast with the situation east of New Zealand, where migrations of both the STF and Subantarctic Front were prevented by the Chatham Rise and Campbell Plateau. Subtropical Water is inferred to have only flowed around the south of New Zealand (as it does today) during MIS 11 and the Late Pleistocene–Holocene (MIS 5–1).