Benthic Records of Seawater Carbonate Ion and Temperature for the Past 30,000 Years in the Southwest Pacific Ocean
Friday, 18 December 2015: 13:40
2012 (Moscone West)
Records of past seawater temperature and carbonate chemistry from the interior ocean can provide insight into the role of changing ocean circulation and deep carbon storage in ice age cycles. Here we present trace element and stable isotope data from benthic foraminiferal calcite from sediment cores in New Zealand’s Bay of Plenty (~37˚S), a region that is influenced by deep waters derived from the Pacific and Southern Oceans. Large deglacial shifts in carbonate ion ([CO32-]) have been observed at ~1600m depth (Allen et al., 2015), likely reflecting a combination of shifting water mass boundaries and loss of CO2 from interior ocean waters. Extension of this record deeper into the ice age suggests that carbonate chemistry may also have shifted during HS2 (~23-26 ka). Mg/Ca records suggest that deep waters warmed gradually since the Last Glacial Maximum, with peak temperatures coinciding with peak [CO32-] at ~14.5 ka during the Antarctic Cold Reversal. We discuss these records in regional context and explore the implications for ocean-climate links on millennial and ice age timescales.