A review of the Australian-New Zealand sector of the Southern Ocean over the last 30 ka (Aus-INTIMATE project)

• Published in: Quaternary Science Reviews
• Main Authors: Bostock, HC, Barrows, TT, Carter, L, Chase, Z, Cortese, G, Dunbar, GB, Ellwood, M, Hayward, B, Howard, W, Neil, HL, Noble, TL, Mackintosh, A, Moss, PT, Moy, AD, White, D, Williams, MJM, Armand, LK
• Format: Article in Journal/Newspaper
• Language: English
• Published: Pergamon-Elsevier Science Ltd 2013
• Subjects: Earth Sciences; Physical geography and environmental geoscience; Palaeoclimatology; Antarctic; New Zealand; Pacific; Southern Ocean; The Antarctic; Antarc*; Antarctica; Iceberg*; Sea ice
• Online Access: https://doi.org/10.1016/j.quascirev.2012.07.018; http://ecite.utas.edu.au/79528

The Australia/New Zealand region of the Southern Ocean is influenced by several of the major globalwater masses of the oceans and is the prime entry point for cold deep waters into the Pacific basin.During the last glacial there was increased sea-ice extent around Antarctica (as far north as 55 degree S), as wellas increased iceberg presence inferred from ice-rafted debris. Evidence from microfossil assemblagessuggests that sea surface temperatures (SST) were up to 7 Celsius degree cooler, consistent with recent estimates ofcooling for New Zealand derived from glacier modelling and other terrestrial proxies. The SubtropicalFront (STF), Subantarctic Front (SAF) and Polar Front (PF) had migrated north, except where the positionof the fronts were controlled bathymetrically. Despite the potential for iron fertilisation by increased dustinput into the ocean during the glacial, there is limited evidence for higher total biological productivity inthe Pacific sector of the Southern Ocean. The altered oceanic circulation during the glacial also decreasednutrients in the surface waters and affected the outgassing of CO 2 . This contributed to an increasedstorage of CO 2 in the deep waters and lowering of the carbonate lysocline. During the deglaciation, sea-ice retreat and SST increased rapidly at ~ 18 ka, roughly synchronous withthe reinvigoration of deep water circulation in the Southern Ocean and the release of CO 2 stored in thedeep waters. The gradient in carbon isotopes ( 13 O benthic ) between Antarctic Intermediate Water (AAIW)and lower Circumpolar Deep Water (LCDW) was greatest at the start of the deglaciation, suggesting thatthe AAIW ventilation preceded LCDW ventilation, or there was a significant change in air-sea fractionationof o 13 O benthic . There was a slight enrichment in o 18 O planktic , decrease in SSTs and a reduction in intermediateand deep water circulation between ~ 14 and 12.5 ka BP during the Antarctic Cold Reversal(ACR), coincident with glacier advances in the New Zealand Southern Alps and ...