Collaborative Research: Disentangling physical and biological controls on Indian Ocean carbon storage during the last glacial-interglacial transition

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Evidence suggests more carbon dioxide was stored in deep ocean waters during the last ice age and released to the atmosphere as the Earth warmed. There are several ways that this might happen. Carbon dioxide could be released when the total amount of algae in ocean waters decreases after the last ice age. Or the amount of carbon dioxide stored in the deeper ocean waters could change with differing pathways of deep currents. Recent work suggest the Indian Ocean might play an important role in one or both of these processes. Newly collected sediment cores collected from the Indian Ocean will be examined for subtle changes in the chemistry that will provide scientists a way to document how carbon dioxide moves between the oceans and atmosphere over long periods of time. The social media platform of the American Museum of Natural History will be used to produce short video segments and visualizations of ocean circulation and climate to share with educators and the general public. The question of physical versus biological controls of CO2 sequestration in the glacial ocean remains unresolved after decades of research. During glaciations, changes in thermohaline circulation, Southern Ocean ventilation, and nutrient utilization are all believed to have played an important role in reducing atmospheric CO2. An improved understanding of the different roles of biological transfer versus physical transfer of CO2 requires examining multiple water masses in multiple ocean basins. The scientific objective is to reconstruct the magnitude and mechanisms driving carbon storage in the southern Indian Ocean by determining the temporal evolution and vertical distribution of Delta14C and oxygenation (using quantitative proxies: Delta-delta13Cwuel-globo, and alkenone preservation) in Indian Ocean interior water masses across the last glacial-interglacial transition. These proxies have been chosen to distinguish between the rate of water mass circulation and respiration-driven CO2 accumulation to assess the roles these mechanisms played in CO2 sequestration. The use of multiple sediment cores across latitude and longitude has been fundamental in determining that critical indicators of oceanic CO2 storage (Delta14C and oxygenation) differed substantially in the Atlantic and Pacific through time. Work proposed here will fill a substantial gap in our knowledge by making use of the first new core material from the Southern Indian Ocean in nearly 30 years. We have selected a suite of three suitable cores from depths (1,118 to 3,164 m) that are bathed by the major interior water masses that reflect both respiration and circulation driven CO2 storage in the region today. Results created here will be the first from this area using these techniques to determine the magnitude and mechanisms of Southern Indian Ocean CO2 storage.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.