Research Interests
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.
Other Duties
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.
Courses Taught
ENS 101 Prospects to Planet Earth
MAR 334 Remote Sensing of the Environment
MAR 501 Physical Oceanography - co-taught /w Dong-Ping Wang and Bob Wilson
CEI 551 Global Change
Selected Recent Publications
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.
|
