Nearshore-Offshore Transport in the Great Lakes: Nearshore Physical Oceanography Measurements
C. R. Murthy, K. Miners, F. Chiocchio, J. Bull (CCIW)
Co-Principal Investigators: M.J. McCormick, D.J. Schwab, G. Miller, J. Saylor, and
Expected Project Duration: To coincide with EEGLE (2 field years '98-'99, '99-'00,
followed by 2 years for analyses and modelling)
It is our hypothesis that the episodic current reversals in the nearshore zone of Great
Lakes are one of the major mechanisms for nearshore-offshore transport of water masses and
sediments and biologically important materials (BIM).
Our experimental program is designed to test this hypothesis through the analysis of
carefully planned field measurements in collaboration with Saylor et al., and Eadie et al.,
measurements and the application of numerical models developed by Schwab and Beletsky, and
Bedford as outlined in the EEGLE program description. The specific mooring sites and the
measurements proposed here are designed to extend the measurements collected by the above
researchers into the high risk nearshore region in order to meet the following specific
The measurement set that will be collected by the NOAA/COP EEGLE program: (1) Physical
Oceanography Observations: Saylor, Miller, McCormick for the two field years (1998-2000)
will be extended shoreward from the 20 m contour to the 12 m contour by establishing 5 current
meter moorings inshore of stations V1,V4, A1, A4 and V9 (see EEGLE program description).
These moorings will each consist of a SACM current meter deployed in a bottom mounted
configuration with a measurement depth of 1 m off of the bottom. These instruments will
provide records of water currents and temperature at 15 minute intervals coincident with the
VACM and ADCP measurements that will be deployed by the NOAA researchers above. Although
these moorings are considered high-risk in terms of damage or loss should a major storm or
ice-scouring event occur during the deployments, the definition of the inshore flows is
considered essential to identify and quantify the physical transport processes during the
episodic current reversals responsible for nearshore-offshore transport of sediments. NWRI
will assume the risk associated with deploying these devices in a highly energetic zone. In
addition to the above moorings, a 1200Khz ADCP will be moored at site A2, alongside NOAA's
300Khz ADCP to collect bottom temperature with water current and backscatter data at 1 meter
intervals throughout the water column. The water current and temperature information from this
device will assist in the quantification of the physical transport processes while backscatter
data for two frequencies from the same site will enable researchers Bedford & McDonald to
estimate the vertical particle concentration profile.
- To identify and quantify the physical transport processes in shallow water during
episodic current reversals responsible for nearshore-offshore transport of BIM's during
winter/spring and summer conditions.
- To determine the climatology of coastal energetics of the episodic nearshore current
reversals during winter/spring and summer conditions.
- To establish the dominant temporal and spatial scales of episodic events from nearshore
current measurements (moored nearshore current meter array, shore based meteorological
stations and nearshore transmission measurement stations).
- To undertake a comparative study of coastal ocean processes from this program and past
programs undertaken in the Great Lakes.
- To establish and provide a data base of all our measurements and make them easily
accessible to other program participants.
In order to ensure that the local meteorological forcing is sufficiently delineated over
the spatial scales involved in the study area, meteorological stations will be set out at two
shore-based locations, one near St. Joseph and the other at a site near the Michigan-Indiana
border. Each site will record wind speed (WS), wind direction (WD), air temperature (AT) and
solar radiation (SR) on a Campbell 21x logger system as 15 minute averages.
In addition to the above instruments NWRI will establish 2 recording transmissometer
systems as part of the GLERL sediment traps (Eadie et al) each consisting of a SEATECH 25cm
transmissometers and a Brancker analogue recorder. Recordings will be made every 15 minutes
consistent with the rest of the physical instrumentation deployed for this study. These
systems will determine episodic events of high sediment loading at the sediment trap
The EEGLE program is the most intensive scientific program on the Great Lakes since the
Canadian initiated IFYGL program on Lake Ontario in 1972/73. In our opinion, Canadian
participation is crucial to maximizing the potential scientific benefits of this research
Our Canadian colleagues are highly experienced with making successful nearshore current
measurements. They have recognized a potentially major weakness in the EEGLE observation
strategy and have proposed a viable option for correction while assuming all of the
considerable risks associated with nearshore measurements. In addition, the results of the
research efforts proposed here directly addresses coastal concerns common to both of our
countries and all of the Great Lakes and if fully successful will generate tangible products
to aid resource management.