The largest increase in atmospheric CO2 in the recent geologic past occurred during the last deglaciation (from 20,000 to 10,000 years ago). As the large Northern Hemisphere ice sheets melted, atmospheric CO2 levels rose by ~30%. Despite extensive research, the underlying cause of the CO2 change has yet to be fully explained. Recent ice core results show that the CO2 rise coincided with a negative carbon isotopic excursion. Similar although larger carbon isotope anomalies occurred at surface and intermediate depths in multiple ocean basins, pointing to an oceanic source. The largest documented changes occurred from ~1 to 2 km in the Atlantic, suggesting that processes at mid-depth in this basin played a key role in the CO2 rise. Identifying the origin of the carbon isotope signal is essential to unraveling the mechanisms that drove atmospheric CO2 variability in the recent geologic past.

The primary goal of this project is to use data from the Southwest Atlantic to diagnose the source of the carbon isotope anomalies during the deglaciation. The researcher team will use a depth transect of high resolution sediment cores from the Brazil Margin to evaluate the relative timing of surface and deep water signals. The team will also use radiocarbon and other chemical analyses of microfossils to infer the origin of the carbon isotope anomaly. Work will focus on testing two competing hypotheses, one that calls for carbon originating from the abyssal ocean and the other that invokes carbon from a geological reservoir. The results could transform our understanding of the climate system by constraining the source of carbon isotopic minima and therefore the driver of atmospheric CO2 variability on glacial-interglacial timescales. The educational broader impacts of the proposed work include the participation of a graduate student and two undergraduates who will pursue independent research projects that complement the overall goals of the project.

Agency
National Science Foundation (NSF)
Institute
Division of Ocean Sciences (OCE)
Type
Standard Grant (Standard)
Application #
1404915
Program Officer
Candace Major
Project Start
Project End
Budget Start
2014-06-01
Budget End
2017-05-31
Support Year
Fiscal Year
2014
Total Cost
$313,060
Indirect Cost
Name
University of Connecticut
Department
Type
DUNS #
City
Storrs
State
CT
Country
United States
Zip Code
06269