Research Identifies Major Sediment Transport Process
in Shallow Waters
This story entered on 18th Jan, 2005 10:48:56 AM PST
Recent NURP-supported research, published in Science,
suggests that Langmuir supercells are an important mechanism for
major sediment resuspension events on the extensive shallow shelves
off the eastern U.S. coast. A Langmuir cell is a circular current
oriented parallel with wind direction that forms quickly as a result
of wind and evaporative cooling at the water's surface. Langmuir
supercells are Langmuir circulations that, during extended storms,
achieve vertical scales equal to the full depth of the water column.
Because resuspension moves sediments out of low speed,
near-bottom flow and into stronger interior flows, supercell events
are associated with major sediment transport in shallow environments.
Excessive amounts of sediments can potentially smother and kill
coral tissue and reduce light levels and food supplied to the coral
by symbiotic algae. Research results can be applied towards better
differentiating sedimentation resulting from anthropogenic versus
Research data was collected off the New Jersey
shore with a cabled seafloor node, part of the Long-term Ecosystem
Observatory (LEO-15) operated by NURP's Undersea Research Center
at Rutgers University. The supercells were observed first near the
sea surface and only progressively extended to the bottom, indicating
that they were not generated by normal bottom boundary layer processes.
Six months of data revealed that major sediment resuspension occurred
only during supercell episodes, which lasted from 9 to 42 hours.
A. Gargett, J. Wells, A. E. Tejada-Martinez, C.E. Grosch (2004).
Langmuir Supercells: A Mechanism for Sediment Resuspension and Transport
in Shallow Seas. Science. Vol 306, Issue 5703, December 10, 2004,