In this project, we will investigate how Atlantic Ocean circulation changed during the abrupt climate changes that occurred as the earth emerged from the last Ice Age. Our data will help to test the hypotheses that the Younger Dryas cold period was caused by a decrease in the strength of the Atlantic meridional overturning circulation and that the large discharges of freshwater into the North Atlantic during Heinrich Events shut down this overturning altogether. We will reconstruct the density structure of waters in the Florida Straits using oxygen isotope and Mg/Ca and measurements on benthic and deep dwelling planktonic foraminifera. This information will be combined to create a millennial scale transport history for the Florida Straits between 10,000 and 20,000 years ago, including the Younger Dryas/Bolling Allerod climate oscillation, Heinrich Event 1 and the last glacial maximum, using a novel geostrophic modeling method. The upper limb of the meridional overturning circulation passes through the Florida Straits as it travels along the western boundary towards the North Atlantic and any substantial reductions in the strength of the overturning will be reflected in a reduction of the flow through the straits. Understanding the past stability of the Atlantic meridional overturning circulation and its relationship to abrupt climate change is of great interest to society as we seek to understand the trajectory of climate over the next centuries. Undergraduate and graduate students will be trained as they collaborate on this project. The PI will communicate this research to a new generation of students at Georgia Tech and to the broader community through contacts with the media and local educational organizations.
