Our lab group seeks to understand the role of the global-scale ocean circulation in past climate change over a range of timescales. The deep ocean interacts and feeds back on many other key parts of the Earth's climate system, including the carbon cycle, atmosphere, and cryosphere. Understanding these interactions in the past will help us better understand how climate may change in the future.
Deep-sea corals as paleoceanographic archives
Fossil deep-sea corals are an exciting and unique paleoceanographic archive. We primarily use the species Desmophyllum dianthus (pictured to the left). Deep-sea corals incorporate sufficient uranium from seawater to be precisely U/Th-dated, the inherent stratigraphy of their skeletons allow for resolution of decadal changes in ocean biogeochemistry, and their large size accommodates multiple geochemical measurements on the same samples (e.g. radiocarbon, temperature, and neodymium isotopes). We are in the process of obtaining funding to collect some of these corals along the Walvis Seamounts in the Southeast Atlantic. This will help us investigate changes in intermediate water circulation over the most recent glacial termination.
Interocean exchange via the Agulhas Leakage and its connection to global ocean circulation
The 'Great Ocean Conveyor' connects the shallow and deep ocean circulation and plays a crucial role in global climate. A key part of this is the formation of North Atlantic Deep Water in the high-latitude North Atlantic, supplied by shallow feed water via Drake Passage (the cold route) and the Agulhas Leakage (the warm route). We have been investigating variations in the Agulhas Leakage over the glacial cycles of the past million years and how they connect to changes in North Atlantic Deep Water circulation. This is part of a collaborative project with researchers at Lamont-Doherty Earth Observatory, Scripps Institution of Oceanography, Hostos Community College, and Cardiff University.
Modeling neodymium cycling in the modern ocean
The isotope ratios of neodymium in seawater have the potential to provide key information about ocean circulation, both today and in the past, and can help shed light on the underlying drivers of global climate. However, uncertainties in our understanding of neodymium cycling in the modern ocean have limited the widespread use of this tracer. We have developed a model of the modern marine neodymium cycle, GNOM v1.0, that uses observations to constrain modeled processes, simultaneously optimizing ~40 parameters. Due to its architecture, this model is both high-resolution and incredibly fast to run. This project is pending funding through the NSF Chemical Oceanography Program, with co-PIs at Lamont-Doherty Earth Observatory and collaborators at University of Southern California.
Radiocarbon changes in the Southern Ocean over the past 30,000 years
The Southern Ocean is uniquely important in the global overturning circulation, as it is the only place where there is both deep water formation and upwelling. Radiocarbon is a powerful tracer of deep ocean circulation, but due to the dynamics of the Southern Ocean, radiocarbon values at the surface are not spatially uniform, leading to uncertainty in deep ocean reconstructions. This project seeks to reconstruct radiocarbon values in subantarctic surface water to reduce these uncertainties. It is led by PI Christopher Charles at Scripps Institution of Oceanography.