Fall 2000

Title

Speaker

Institute

4:30pm, Thursday, Oct. 5, 2000

New Sensor Platforms for Moored and Underway Profiling

Geoff Lebans

Brooke Ocean Technology Ltd.

4:30pm, Thursday, Oct. 12, 2000

Abstract: The Bedford Institute of Oceanography/Fisheries and Oceans Canada have recently developed a pair of unique sensor platforms for both moored and underway ocean profiling. These are now manufactured under license by Brooke Ocean Technology Ltd. (BOT), who assisted with the development of both systems.

This seminar will review the development history of both platforms, including current and future applications. Also included is a brief overview of other projects completed by BOT, including launch/recovery systems developed for unmanned underwater vehicles and towed bodies, and a system to deliver emergency stores to a distressed submarine.

Limitations of conventional numerical methods in modelling the ocean

Frederic Dupont

Department of Atmospheric and Oceanic Sciences
McGill University

4:30pm, Thursday, Oct. 19, 2000

Title

Speaker

Institute

4:30pm, Thursday, Oct. 26, 2000

The Role of Gravity Waves in the Dynamics of the Atmosphere as Inferred From the Canadian Middle Atmosphere Model

Alexander Medvedev

York University

4:30pm, Thursday, Nov. 2, 2000

Abstract: Internal gravity waves (GW) can act to transport horizontal momentum, heat, and species in stably stratified regions of the atmosphere and oceans. Mesoscale GW generated by various meteorological processes in the atmosphere produce dynamical coupling between vertical layers from the ground to high altitudes. Comprehensive numerical models of the atmosphere demonstrate unrealistic simulations unless some account is taken of the effect of these subgrid-scale waves. A recently developed spectral gravity wave parameterization has been implemented in the Canadian Middle Atmosphere Model (CMAM) and improved significantly the simulated dynamics and climate. The talk will discuss the role of gravity waves as seen in the CMAM. This will include some aspects of a simulation of the polar night jet, stratospheric warmings, mesopause temperature, equatorial oscillations, winter stratospheric temperature, interactive ozone chemistry.

Title

Speaker

Institute

4:30pm, Thursday, Nov. 9, 2000

Dissipation of Turbulent Kinetic Energy in the Ocean Mixed Layer

Blair Greenan

Bedford Institute of Oceanography

4:30pm, Thursday, Nov. 16, 2000

Abstract: Some recent measurements of the mixed layer in oceans and lakes have indicated that the rate of the dissipation of turbulent kinetic energy is much higher than expected from a purely shear-driven wall layer. This enhancement has usually been attributed to wave breaking. In this study, measurements of dissipation in the open ocean mixed layer on the continental shelf off Nova Scotia are integrated with air-sea flux estimates and directional wave spectra to further study this issue. A microstructure profiler gliding quasi-horizontally provides estimates of TKE dissipation starting within 2 m of the ocean surface as it slowly descends through the mixed layer. Dissipation rates were found to be enhanced relative to the wind stress production and indicated that approximately 6% of the wind energy at 10 m is dissipated in the ocean mixed layer. In addition, results from this experiment demonstrate that the WAVES scaling for dissipation of TKE (Terray et al. 1996), based on wind and wave parameters, is valid for the case of a simple wind-sea in which the swell can be easily separated. In more complex wave conditions TKE dissipation remains enhanced relative to the classical wall layer, however, the WAVES scaling does not hold.

Title

Speaker

Institute

4:30pm, Thursday, Nov. 23, 2000

Joint Seminar with BOSS
THE EFFECTS OF INDUSTRIAL NOISE ON MARINE ANIMALS

Christine Erbe

Fisheries and Oceans Canada
Institute of Ocean Sciences
Sidney, BC

4:00pm, Wednesday, Nov. 29, 2000
LSC 5260
Please note special day, time, and room

Abstract: In recent decades, man-made noise emission in the world's oceans has steadily increased. Underwater noise has various effects on marine animals. These include behavioural disturbance; acoustic masking of communication, navigation signals, sounds of prey and sounds of predators; physiological damage to organs (e.g. ears) and tissues; and a reduction in prey availability. A software model is presented which predicts zones of impact on marine mammals around a noise source. This algorithm combines a sound propagation model and biological impact models. The software model is applied to the case of icebreakers affecting 'endangered' beluga whales, whale-watching boats affecting 'threatened' killer whales, and passenger ferries affecting whales, dolphins, porpoises, seals and sea lions. Noise effects on fish are less understood. Various mitigation methods are presented to reduce noise effects on marine life.

Coriolis Term Time Truncation Errors

Harold (Hal) Ritchie

Meteorological Service of Canada (MSC)

4:30pm, Thursday, Nov. 30, 2000

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Speaker

Institute

4:30pm, Thursday, Dec. 7, 2000

The spectral signatures of salt fingers and turbulence

Ray Schmitt

Dept. of Physical Oceanography Woods Hole Oceanographic Institution

4:30pm, Thursday, Dec. 14, 2000

Abstract: A new model of the horizontal wavenumber spectrum of scalar variables in salt fingers is contrasted with the Batchelor (1959) spectrum for turbulence. It predicts the observed +2 slope of the low wavenumber temperature gradient spectrum for salt fingers as well as the shape and amplitude of the spectral peak. Derived variables such as conductivity and optical index of refraction are also computed for the salt finger model and for turbulence where an important unknown is the T-S covariance spectrum. Here we employ the theory of Stern (1968) to estimate this quantity. Whereas gradient spectra of T, S and conductivity display low wavenumber slopes of +2 for salt fingers and +1 for turbulence, the spectra of refractive index is markedly steeper in the salt finger case, due to a spectral null caused by the "invisible finger" phenomena (Williams, 1975) which is predicted for wavenumbers near that of the fastest growing finger. This is consistent with the high wavenumber structure seen in shadowgraph imagery of salt fingers. It is suggested that small-scale sampling of both refractive index and conductivity from towed vehicles could provide a convenient method of discriminating between salt fingers and turbulence, as well as quantifying the rates of mixing.

Title

Speaker

Institute

4:30pm, Thursday, Dec. 21, 2000

University closed this week - No Seminar

Thursday, Dec. 28, 2000