Kamazima M.M. Lwiza
Ph.D., 1990, University of Wales
Structure and dynamics of shelf-seas
and remote sensing oceanography.
I am a marine physicist. I study ocean processes that affect transport (e.g., currents and tides) and density distribution (e.g., mixing and heat balance). My research interests are the structure and dynamics of the shelf-seas, remote sensing oceanography and biological-physical interactions, which affect larval transport. I design field experiments to observe these processes by incorporating modern technology, with a particular emphasis on the acoustic Doppler current profiler (ADCP), GPS-tracked Lagrangian drifters, ocean gliders and satellites.
The study of the interaction of the lower Hudson estuary with adjacent waters of New York Bight has raised interesting questions on estuarine circulation, especially the fact that there was upstream non-tidal flow on both sides of the shoals near the banks. The results underscored the importance of bathymetry in controlling the structure of longitudinal flow. These results were confirmed by another study I did in the lower Chesapeake Bay in collaboration with Dr. Arnoldo Valle-Levinson (Old Dominion University).
My research in biological-physical interactions affecting larval transport began by collaborating with Dr. Eric Schultz (University of Connecticut) in studying processes responsible for larval transport in the lower Hudson River estuary. We used least squares method to extract amplitudes and phases of periodic signals in the larval concentrations. We showed that anchovy and goby larvae exhibit a depth distribution and vertical migration behavior that promotes upriver transport. Transport should be most rapid during neap tide periods. We have also used cohort analysis to show that the upriver shift in distribution of early-stage anchovy is not entirely due to changes in adult spawning behavior or to gradients in larval mortality, and must be partly the result of larval migration.
My students and I are currently working on three projects. In the first one we are using IKONOS satellite data (1-m resolution) to study vegetation changes in mosquito habitat in Suffolk County in New York. The second project involves analyzing all water column data in Long Island Sound collected on monthly basis by Connecticut DEP from 1991 to present. We have so far been able to demonstrate that horizontal heat exchange with the adjacent coastal ocean is more dominant (>80%) than local surface heat exchange in controlling the interannual variability of temperature. This result contradicts the traditional paradigm about heat balance in estuaries and most other places in the ocean that local heat exchange is considered to be the dominant process. Our results also show that the interannual variability of primary productivity in winter may be controlled by availability of light as much as grazing pressure, especially during warm winters. The third one, which will be starting in the summer of 2006, is in collaboration with a colleague, Dr. Dong-Ping Wang. We want to examine characteristics of internal waves in estuaries (our case study will be conducted in the Hudson River) produced by the small-amplitude topography regimes (h << U/N) where h is the topography amplitude, U the tidal velocity and N the buoyancy frequency. This problem has surprisingly received little attention compared to the case of internal waves generated over finite-amplitude topography (h ~ U/N), which typically applies to tidal currents crossing over sills. This project is bound to generate a lot of excitement in estuarine dynamics because for vertically propagating waves the horizontal pressure is higher on the upstream side of the topography than the downstream side. The pressure difference exerts a horizontal drag force on the topography, known as the form drag, which can be as large as friction drag. In addition, the momentum transported upward by internal waves may be an important mechanism for mixing in the water column.
I am the faculty director of the Environmental Living Learning Center. The Living Learning Center is the residential component of the environmental studies major program, which is housed in Hendrix College (Roth Quad) and is part of the Science and Technology College. The Living Learning Center offers special programs, such as a seminar series showcasing faculty research, selected courses in the major, and is also the home of the Stony Brook Environmental Club.
Lee, Y.J. and K.M.M. Lwiza, (In Press). Interannual variability of Temperature and salinity in shallow water: Long Island Sound, New York, J. Geophys. Res.
Schultz, E. T., K. M. M. Lwiza, J. Young, J. M. Martin. 2005. Tracking cohorts: analysis of migration in early life stages of an estuarine fish. Estuaries, Vol. 28, No. 3, p. 394–405.
Li, C., A. Valle-Levinson, L.P. Atkinson, and K.-C. Wong, K. M. M. Lwiza. 2004.Estimation of drag coefficient in James River Estuary using tidal velocity data from a vessel-towed ADCP. J. Geophys. Res.,109, C03034, doi:10.1029/2003JC001991.
Wang, Y.-H., L.-Y. Chiao, K.M.M. Lwiza and D.-P. Wang (2004) Analysis of flow at the gate of Taiwan Strait. J. Geophys. Res., 109, C02025, doi:10.1029/2003JC001937.
Schultz, E.T., Lwiza, K.M.M., Fencil, M.C., and Martin J.M. (2003) Mechanisms promoting upriver transport of larvae of two fish species in the Hudson River estuary. Mar Ecol-Prog. Ser. 251: 263-277
Paris, C.B., Cowen, R.K., Lwiza,K.M.M., Wang, D.P., and Olson, D.B. (2002) Multivariate objective analysis of the coastal circulation of Barbados, West Indies: implication for larval transport. Deep-Sea Res.,49(8), 1363-1386.
Sañudo-Wilhelmy, S.A., A. Kustka, C. Gobler, M. Yang, D. Hutchins, J. Burns, K. Lwiza, D. Capone, J. Raven and E. Carpenter. 2001. Phosphorus limitation of nitrogen fixation by Trichodesmium in the central Atlantic Ocean. Nature 411, 66-69.
Jordan, R.C., Gospodarek, A.M., Schultz, E.T., Cowen, R.K., and Lwiza,K. 2000
Spatial and Temporal Growth Rate Variation of Bay Anchovy (Anchoa mitchilli) Larvae in the mid Hudson River Estuary. Estuaries, 23 (5), pp. 683-689.
Valle-Levinson, A., Wong, K.C., and Lwiza,K.M.M. (2000) Fortnightly variability in the transverse dynamics of a coastal plain estuary. J. Geophys. Res. (C); 105(C2), 3413-3424;
Cowen, R.K., K.M.M. Lwiza, S. Sponaugle, C.B. Paris, D.B. Olson. (2000) Connectivity of marine populations: Open or closed? Science287(5454): 857-859.