[PHOTO] Alex Hay

Department of Oceanography
Dalhousie University
Halifax, NS
B3H 4J1

e-mail: Alex.Hay@Dal.Ca
Phone: (902) 494-6657
FAX: (902) 494-2885

Biennial Report, 1999-2000

Research Interests

The continuing primary focus of the group is the dynamic response of mobile seabed sediments in sandy coastal and continental shelf environments to storm forcing, including turbulence production and suspension mechanisms at the bed, bedform genesis and evolution, and the roles of non-linear wave-wave and wave-current interactions in sediment transport. Acoustic remote sensing techniques are particularly well suited to these studies, because the measurements can be made with minimal disturbance to the nearbed flow. Quantitative measurements now being made at scales not possible even a few years ago are contributing new insights into turbulent flow-particle-mobile bed interaction and the friction between the ocean and the seabed, both fundamental oceanographic and unsolved basic science questions. We have also recently become actively involved in the study of microbubbles in the near surface layer of the ocean, and in the use of passive acoustics to locate right whales within the Bay of Fundy. The microbubble project is a natural extension of particle dynamics and turbulence in the bottom boundary layer, with bubbles taking the place of sand grains, and has as its goal determining the contribution from microbubble scattering to ocean color. The right whale project is aimed at determining the feasibility of using passive acoustic arrays for real-time tracking of right whales through locating their sounds, as a means for reducing ship-strikes, a major cause of documented mortality in this highly-endangered species.

The overall approach to the sediment dynamics and bottom boundary layer turbulence questions combines theory and experiment as well as the development of new measurement technologies. The theory encompasses both acoustic scattering and propagation theory, and the theory of the relevant fluid motions and sediment response. The technologies are mainly high frequency (MHz-range) acoustic systems capable of resolving the several-mm spatial and O(10ms) temporal scales of interest. The need to connect these high-resolution small-scale observations to the response at larger scales necessitates the use of spatially-extended instrument arrays. We also use optical imaging systems when appropriate: for example, video imaging using diode lasers to provide structured lighting.

Our interests in the seabed response during energetic conditions have taken us in recent years to the U.S. Army Corps of Engineers Field Research Facility in Duck, North Carolina, on the Carolina Outer Banks north of Cape Hatteras. The special logistics facilities at this site, and its broad exposure to the Northwest Atlantic, have made it the centre for major international nearshore dynamics experiments over the past decade. In 1994 we participated in a pilot experiment (Duck94), and returned in 1997 for the primary experiment, SandyDuck97. Analysis of the results from these experiments represents a continuing focus of activity within the group.

Participation in international experiments continues to be an ongoing feature of our research efforts. Two separate experiments were carried out at the Longterm Environmental Observatory (LEO-15) in 15-m water depth on the open shelf off the New Jersey coast, operated by Rutgers University: a bottom boundary layer and sediment dynamics experiment with Drs. Peter Traykovski and Jim Irish from the Woods Hole Oceanographic Institution (WHOI) in 1999; and a first microbubble experiment as part of the Hyperspectral Coastal Ocean Dynamics Experiment (HyCODE) with colleagues from Dalhousie, Drs. Marlon Lewis and Bruce Johnson, in 2000.

We are becoming increasingly involved in web-based experimental oceanography through the use of long-term ocean observing systems like LEO, which provide real-time access through the internet to our sensor systems deployed at distant locations. We used this capability in the 1999 experiment to monitor sensor operation and to adjust the data acquisition protocol. The group has a significant role in the recently-funded initiative within this Department to develop a Marine Environmental Prediction System, which will in part involve the implementation of a range of real-time measurement systems, including acoustic sensors, in Lunenburg Bay, NS, using high-speed telemetry systems including wireless Ethernet. Real-time observation systems also find application in the right whale project, and wireless Ethernet is being implemented for the prototype tracking system.

The Chair in Ocean Acoustics at Dalhousie entered its fourth and fifth years. The Chair is jointly funded by NSERC and Satlantic Inc., a Halifax-based ocean technology company. The goal is to provide graduate and senior undergraduate students with opportunities to study and carry out research in the area of Acoustical Oceanography. The program has links to the Defence Research Establishment Atlantic (DREA), in the area of Mine Counter Measures to which seabed imaging and seabed dynamics have application, and in the Dalhousie/DREA right whale project. This combination creates a broader range of research projects and future career choices for program graduates, with opportunities in industry and defence as well as university and government.

The Ocean Acoustics Laboratory at Dalhousie has continued to develop. This large laboratory has a 10-m long flume and a 2-m sediment suspension tank for instrument testing and calibration. Several advanced capabilities have been added in the past 2 years, realized through the efforts of Wes Paul with assistance from Walter Judge and now Doug Schillinger, including a new 16-frequency, broad-band, coherent acoustic backscatter system, and a system for acquiring and processing low-frequency acoustic signals (i.e. right whale sounds). Through the efforts of Todd Mudge, assisted by David Jackson, we have also made major improvements to our data processing and modelling capability. The group currently works with distributed processing nodes consisting of 6 SUN Ultra workstations, one dual-processor SUNBlade workstation, a SUN Ultra80 server, and multiple high-end PC's, all on a high speed local area network with 500 Gbytes of mass storage and a 30-platter CD-ROM server.

Funding for this research is provided by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) through its Research Grants, Collaborative Special Projects, and Industrial Research Chair programmes, from the U.S. Office of Naval Research (ONR) Coastal Sciences Program, from the U.S. National Oceanic and Atmospheric Administration (NOAA) National Underwater Research Program, and from the World Wildlife Fund's Endangered Species Research Fund, by a Collaborative Research Agreement with the Environment Canada/Department of Fisheries and Ocean's Habitat Stewardship Fund, and by contracts from the Canadian Department of National Defense.

Collaborative Research

Current collaborations are listed below, by research area.

Coastal and Continental Shelf Sediment Dynamics

Dr. A. J. Bowen, Dalhousie
Dr. A. M. Crawford, DREA
Dr. J. Irish, WHOI
Dr. K. Thompson, Dalhousie
Dr. P. Traykovski, WHOI

Microbubbles and Ocean Colour

Dr. Marlon Lewis, Dalhousie
Dr. Bruce Johnson, Dalhousie

Dalhousie/DREA Right Whale Project

Ms. F. Desharnais, DREA
Dr. C. Taggart, Dalhousie
Dr. K. Louden, Dalhousie

Pulse Coherent Doppler Profiling

Dr. L. Zedel, Memorial University of Newfoundland

Marine Environmental Prediction System (MEPS)

Dr. J. Cullen (Dalhousie, bio-optical properties)
Dr. J. Sheng (Dalhousie, bottom friction and numerical model verification)
Dr. H. Ritchie (Meteorological Service of Canada, wind and wave prediction verification)
Drs. P. Hill and A.J. Bowen (Dalhousie, bottom boundary layer and sediment transport)

This page last updated May 14, 2001.

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