Southern Ocean upwelling, Earth's obliquity, and glacial-interglacial atmospheric CO change.

Previous studies have suggested that during the late Pleistocene ice ages, surface-deep exchange was somehow weakened in the Southern Ocean's Antarctic Zone, which reduced the leakage of deeply sequestered carbon dioxide and thus contributed to the lower atmospheric carbon dioxide levels of the ice ages. Here, high-resolution diatom-bound nitrogen isotope measurements from the Indian sector of the Antarctic Zone reveal three modes of change in Southern Westerly Wind-driven upwelling, each affecting atmospheric carbon dioxide. Two modes, related to global climate and the bipolar seesaw, have been proposed previously.

Glacial heterogeneity in Southern Ocean carbon storage abated by fast South Indian deglacial carbon release.

Past changes in ocean C disequilibria have been suggested to reflect the Southern Ocean control on global exogenic carbon cycling. Yet, the volumetric extent of the glacial carbon pool and the deglacial mechanisms contributing to release remineralized carbon, particularly from regions with enhanced mixing today, remain insufficiently constrained. Here, we reconstruct the deglacial ventilation history of the South Indian upwelling hotspot near Kerguelen Island, using high-resolution C-dating of smaller-than-conventional foraminiferal samples and multi-proxy deep-ocean oxygen estimates.

Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age.

The Southern Ocean regulates the ocean's biological sequestration of CO and is widely suspected to underpin much of the ice age decline in atmospheric CO concentration, but the specific changes in the region are debated. Although more complete drawdown of surface nutrients by phytoplankton during the ice ages is supported by some sediment core-based measurements, the use of different proxies in different regions has precluded a unified view of Southern Ocean biogeochemical change. Here, we report measurements of the N/N of fossil-bound organic matter in the stony deep-sea coral , a tool for reconstructing surface ocean nutrient conditions.