“On the role of horizontal exchange in determining the interannual temperature
and salinity anomalies in shallow semi-enclosed waters”
Dr. Kamazima M.M. Lwiza
Marine Sciences Research Center
State University of New York, Stony Brook
Monday, February 21, 2005
3:30 PM
Room 109, Crittenton Hall
Abstract
The variabilities of temperature and salinity in Long Island Sound (LIS), New York, are examined using
observations from 1991 to 2002. There is a strong seasonal variation in the temperature, which also shows
a higher variance in winter than in summer at the central LIS, i.e., 1.9°C in February and 0.2°C in September.
The salinity exhibits regular seasonal patterns driven by the freshwater input, i.e., the salinity minimum in
spring and the maximum in fall, but there is a notable long-term change throughout the Sound: a decrease of
approximately 2 psu from 1991 until the spring of 1997, and then an increase of 3 psu by the end of record.
Maps of anomalies of both temperature and salinity indicate a strong longitudinal gradient along the Sound,
which is probably due frontal advection of gradients. Empirical orthogonal function analyses reveal that
most of the variability for both temperature and salinity anomalies can be explained by the first modes,
which contain 87% and 89% of the total variance, respectively. Quasi-biennial periodicities are contained
in the first mode principle components of temperature and salinity anomalies. The salinity also contains an
additional signal at a decadal time scale. The most exciting results of this analysis are: (1) the variability
in the horizontal exchange explains more than 75% of the variance in the interannual variability of temperature
and salinity. Missing portions of heat and salt balances can be explained by local processes, i.e., net surface
heat flux and river discharge; (2) warm winters tend to be associated with suppression of spring bloom; (3) the
salinity in LIS responds quickly (within a month) to the shifting of the Gulf Stream position, but the processes
that allow the salinity signal to be propagated that fast into shallow coastal waters are not clear.
Biography
Dr. Lwiza received M.Sc. and Ph.D. degrees in physical oceanography from the University of Wales, United Kingdom.
He is currently an Associate Professor at the Marine Sciences Research Center at Stony Brook University and Director
of the Environmental Living Learning Center. Dr. Lwiza’s research interests are in the areas of coastal dynamics,
estuarine physical processes, physical-biological processes involved in primary production and larval transport, and
remote sensing of aquatic environments.
Reception before seminar at 3:00 PM
Crittenton Hall
Old Dominion University
Norfolk, VA 23529
757-683-5548
Last updated 2/01/2005.
This page is maintained by
Gabriel Franke
Copyright Info: Old Dominion University 2005
