HR: 0800h
AN: OS11A-0494    [Abstracts]
TI: Observations of Extreme Wave Events in a Shallow Coastal Embayment
AU: * Mulligan, R P
EM: mulligan@phys.ocean.dal.ca
AF: Department of Oceanography, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4J1 Canada
AU: Bowen, A J
EM: tony.bowen@phys.ocean.dal.ca
AF: Department of Oceanography, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4J1 Canada
AU: Hay, A E
EM: alex.hay@phys.ocean.dal.ca
AF: Department of Oceanography, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4J1 Canada
AB: Lunenburg Bay is a coastal inlet located on the southern shore of Nova Scotia, Canada, and is approximately 8 km long and 4 km wide. It has irregular and shallow bathymetry characterized by a typical depth of 10 m and is exposed to wave energy from the North Atlantic Ocean. Within the bay, an array of sensors has been deployed to collect physical, biological and atmospheric data as part of a real-time coastal observing system. The wave array consists of bottom-mounted instruments including two acoustic doppler current profilers capable of resolving wave spectra, two single-point velocimeters with co-located pressure sensors and standard acoustic doppler profilers, and a surface-moored directional wave-rider buoy. The set of instruments is capable of observing directional spectra at 0.5-hr intervals for wave events at 5 locations in Lunenburg Bay. This poster summarizes the dataset collected in fall 2002, summer-fall 2003 and summer-fall 2004. Extreme wave events are highlighted and compared with respect to differences in atmospheric forcing (wind, pressure, duration, storm type and scale) and attenuation within the bay from observed wave spectral properties (peak direction and directional spread, significant wave height and peak period). Extreme events include the close passage of several hurricanes (Gustav, Fabian, Juan), stronger but more distant hurricanes (Isabelle) and larger-scale mid-latitude low pressure systems. The most notable wave event in the bay was driven by Hurricane Juan with a deep-water significant wave height of 9 m, more than double that of the second largest event in the observation period. Strong attenuation between instrument locations inside the bay is attributed to refraction and breaking. Observed significant wave heights and near-bed orbital velocities are compared to numerical model simulations from the SWAN model for peak conditions for various extreme events and are in good agreement.
DE: 4546 Nearshore processes
DE: 4560 Surface waves and tides (1255)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting