“Flow and density structure in a Magellan Glacial Fjord”
Dr. Arnoldo Valle-Levinson
Center for Coastal Physical Oceanography
Monday, January 24, 2005
3:30 PM
Room 109, Crittenton Hall
Abstract
Observations of water velocity and density profiles were obtained for the first time
in a Magellan glacial fjord, with the purpose of explaining the hydrodynamic processes
associated with the high primary productivity of the system. Underway and fixed current
velocity profiles were measured in combination with hydrographic profiles in Seno Ballena
off the Magellan Strait in southern Chile. This presentation will report on-going analyses
of data collected during weak wind conditions at the transition from austral spring to
summer, in December 2003 and 2004. Seno Ballena is ~15 km long and typically <1 km wide.
It is characterized by a glacier at the head of the fjord and a tall sill, < 3 m water
depth, located ~7 km from the glacier. Observations showed that the strongest longitudinal
gradients in density and flow were associated with the sill. Hydrography and flow also
exhibited lateral variability related to the transverse variations of the sill bathymetry.
Such a spatial structure translated into tidal and mean flows that displayed a rich
three-dimensional configuration. The most striking finding so far is that the interactions
between the semidiurnal tidal flow and bathymetry produced sixth-diurnal flows with a
magnitude that was one half of the semidiurnal flow magnitude. These relatively strong
sixth-diurnal flows generated frequent (~ every 4 hours) hydrographic fronts that may help
explain the high productivity of the system. Large numbers of zooplankton organisms
concentrated at these fronts, where many birds also congregated for a banquet.
Biography
Arnoldo Valle-Levinson is an Associate Professor at the Center for Coastal
Physical Oceanography, Department of Earth and Atmospheric Sciences at Old
Dominion University. His research concentrates on observations and modeling of
coastal hydrodynamics through studies in estuaries, coastal lagoons, bays, fjords
and continental shelves. In particular, his investigations focus on the factors that
shape the exchange of waters between basins.
Reception before seminar at 3:00 PM
Crittenton Hall
Old Dominion University
Norfolk, VA 23529
757-683-5548
Last updated 1/19/2005.
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