Please join us next Wednesday, October 9, at 2 pm for a Geochemistry Seminar by DEES alum Dr. Kassandra Costa (Ph.D. '18), an Assistant Scientist at the Woods Hole Oceanographic Institution. This is a special Lamont75 Seminar, where eminent alumni and former staff showcase their research and reflect on what makes LDEO special.
Reconstructing oxygen concentrations and carbon storage in the glacial Atlantic Ocean
Oxygen concentrations in seawater are sensitive to changes in carbon storage, and thus carbon sequestration in the deep ocean during the Last Glacial Maximum (LGM) is expected to coincide with lower glacial oxygen concentrations in deep waters. New and developing oxygen proxies have led to (semi-)quantitative estimates of glacial oxygen depletion, and these reconstructions have suggested more intense deoxygenation in the glacial deep Pacific (~100 umol/kg lower than Holocene) than in the glacial deep Atlantic (~50 umol/kg lower than Holocene). However, the water depth structure of oxygen concentrations in the past is poorly constrained. I will present the most highly resolved depth transect of glacial oxygen concentrations from the west equatorial Atlantic at the Demerara Rise (7-9˚N, 53-54˚W, 383 to 3328 m water depth) using the novel quantitative proxy U/Ba. The difference between the LGM and Holocene oxygen concentrations occurs from 1500-2500 m water depth, where glacial oxygen concentrations were 100 umol/kg or more lower than Holocene oxygen concentrations. We combine this new glacial depth profile of oxygen concentrations with carbon isotopes in order to investigate possible mechanisms, including enhanced carbon storage and changes in ocean circulation.
