- Associate Marine Research Scientist
- Physical Oceanography
- Phone: 401.874.6138
- Email: email@example.com
- Office Location: 210 Watkins
Circulation, Coastal and estuarine health, Coastal and estuarine physical oceanography, Coastal circulation and mixing, Coastal water circulation, Current measurements, Estuarine circulation and mixing, Estuarine oceanography, Instrumentation, Small-scale ocean dynamics, Measurements from ships of opportunity, Observational physical oceanography, Observations of mixing circulation, ROV sensing.
I am a physical oceanographer focusing on circulation and mixing processes in the coastal ocean and estuarine systems, in particular those along the U.S. east coast. I address these problems using both observational and numerical modeling approaches. Much of my work has an applied flavor with strong connections to societally relevant scientific problems. I am a 100% grant funded researcher, which means that I work on a wide range of projects, often juggling many projects at the same time.
For several years, I have been working with an interdisciplinary team to improve our understanding of the processes that lead to summertime hypoxia in Narragansett Bay. One component of this project has been the development and implementation of an ecological box model of the Bay that is coupled with a realistically-forced high-resolution hydrodynamic model. My focus on this project has been the hydrodynamic modeling and the problem of how to use dye tracers in the model to specify the physical mixing that must be parameterized in the coarsely resolved ecological model. In addition to the practical contribution towards the simulations of the ecology of the Bay, including oxygen concentration, this work has helped improve our understanding of physical mixing processes in the Bay.
I have also used the Narragansett Bay hydrodynamic model to investigate the dispersion of planktonic hard clam larvae within the Bay. The larval stage is the only period of the hard clam life cycle in which the organism is mobile and it is thought that clams spawning in areas of the Bay that are closed to harvesting may serve to replenish populations Bay-wide. The results of particle trajectory modeling using current fields provided by the hydrodynamic model have shown that some potential spawning sanctuaries in the Upper Bay and within Greenwich Bay may be very effective in seeding the Bay whereas the larvae spawned at other sites are likely to be transported out of the Bay and thus these sites will not be effective as spawning sanctuaries.
In addition to numerical modeling, my research program also includes a sea-going observational component. One such project, funded by the state as part of its offshore wind-farm planning, was aimed at providing a basic description of the circulation and hydrographic variability in Rhode Island Sound (RIS). The observational component of this project included placement of moored current and hydrographic sensors as well as the carrying out of periodic shipboard surveys. We fortuitously captured an important cross-shelf exchange event: an intrusion into RIS of warm, salty water normally found seaward of the continental shelf break. Although much is still to be learned about this mechanism of cross-shelf exchange of water and the biologically relevant substances within it, the large size of the intrusion (> 40 km) suggests a significant impact on RIS water properties.
Because many biological processes occur on timescales of days (e.g. duration of clam larvae planktonic stage), currents that vary slowly with time, so-called residual currents are often more important than rapidly varying tidal currents in producing net transport. The interaction of tidal processes and bathymetry in generating residual currents in estuaries was the focus of a recent project focused on the Long Island Sound estuary. From shipboard measurements we have shown that cross-estuary tidal currents appear to be rectified to produce along-estuary residual currents in the eastern portion of the estuary.
In collaboration with colleagues at the University of Connecticut I have operated a surface current mapping system (CODAR) in the Block Island Sound region. This system, which is funded by the Mid-Atlantic Regional Association Coastal Ocean Observing System, has been providing hourly maps of surface currents over the past 13 years. These observations are sent to the national surface current archive and are used, for example, in U.S. Coast Guard search and rescue planning.
Ph.D Coastal Oceanography, State University of New York, 1996
M.S. Coastal Oceanography, State University of New York, 1984
B.S. Mechanical Engineering, Stevens Institute of Technology, 1981
Ullman, D. S., D. L. Codiga, A. Pfeiffer-Herbert, and C. R. Kincaid (2014), An anomalous cross-shelf intrusion of slope water on the southern New England continental shelf, J. Geophys. Res. Oceans, 119, doi:10.1002/2013JC009259.
Ullman, D. S. and D. Hebert (2014), Processing of underway CTD data, J. Atmos. Oceanic Tech., 31, 984-998, doi:10.1175/JTECH-D-13-00200.1.
Ullman, D. S., D. L. Codiga, D. Hebert, L. B. Decker, and C. R. Kincaid (2012), Structure and dynamics of the midshelf front in the New York Bight, J. Geophys. Res., 117, C01012, doi:10.1029/2011JC007553.
Whitney, M. M., D. L. Codiga, D. S. Ullman, P. M. McManus, and R. Jiorle (2012), Tidal cycles in stratification and shear and their relationship to gradient Richardson number and eddy viscosity variations in estuaries, J. Phys. Oceanogr., 42, 1124-1133, doi:10.1175/JPO-D-11-0172.1
Stachelhaus, S. L., S. B. Moran, D. S. Ullman, and R. P. Kelly (2012), Cross-shelf mixing and mid-shelf front dynamics in the Mid-Atlantic Bight evaluated using the radium quartet, J. Mar. Res., 70(1), 141-172.
Ho, D. T., C. L. Sabine, D. Hebert, D. S. Ullman, R. Wanninkhov, R. C. Hamme, P. G. Strutton, B. Hales, J. B. Edson, and B. R. Hargreaves (2011), Southern Ocean Gas Exchange Experiment: Setting the stage, J. Geophys. Res., 116, C00F08, doi:10.1029/2010JC006852.
Ho, D. T., R. Wanninkhov, P. Schlosser, D. S. Ullman, D. Hebert, and K. F. Sullivan (2011), Toward a universal relationship between wind speed and gas exchange: Gas transfer velocities measured with 3He/SF6 during the Southern Ocean Gas Exchange Experiment, J. Geophys. Res., 116, C00F04, doi:10.1029/2010JC006854.
Kremer, J. N., J. M. P. Vaudrey, D. S. Ullman, D. L. Bergondo, N. LaSota, C. Kincaid, D. L. Codiga, and M. J. Brush (2010), Simulating property exchange in estuarine ecosystem models at ecologically appropriate scales, Ecological Modelling, 221, 1080-1088, doi: 10.1016/j.ecolmodel.2009.12.014.
Mau, J.-C., D.-P. Wang, D. S. Ullman, and D. L. Codiga (2008), Model of the Long Island Sound outflow: Comparison with year-long HF radar and Doppler current observations, Continental Shelf Research, 28, 1791-1799.
Ullman, D. S., J. O’Donnell, J. Kohut, T. Fake, and A. Allen (2006), Trajectory prediction using HF radar surface currents: Monte Carlo simulations of predicition uncertainties, Journal of Geophysical Research, 111, C12005, doi: 10.1029/2006JCoo3715.