Tidal Signals in Lake Michigan Water Level Data

• Activity Number: 24
• Type: Topic Contributed
• Date/Time: Sunday, August 3, 2014 : 2:00 PM to 3:50 PM
• Sponsor: Section on Physical and Engineering Sciences
• Author(s): David Riegert*+
• Keywords: multitaper ; signal processing ; Lake Michigan ; tide

Abstract

Water level data from monitoring stations surrounding Lake Michigan were obtained and analysed using the multitaper spectrum estimation technique. The expected high amplitude tidal signals were well identified, as were many minor tides that are typically only detected in oceans. In addition, spectral "hills" were present in data from all stations. These hills appear to be lake-specific resonance ("bathtub") modes. The phase of these resonance modes was examined using pairs of monitoring stations that sit opposite each other on the lake. If the origin of the resonance modes is meteorological, then a phase difference of 180 degrees is expected between stations. Conversely, if the cause of the modes is geological buckling of the substrate, then no phase difference is expected. We compare these hypotheses and discuss results in the context of the Lake Michigan environment.