Articles | Volume 11, issue 3
Ocean Sci., 11, 439–453, 2015
Ocean Sci., 11, 439–453, 2015

Research article 08 Jun 2015

Research article | 08 Jun 2015

Water level oscillations in Monterey Bay and Harbor

J. Park1, W. V. Sweet2, and R. Heitsenrether3 J. Park et al.
  • 1National Park Service, 950 N. Krome Ave, Homestead, FL, USA
  • 2NOAA, 1305 East West Hwy, Silver Spring, MD, USA
  • 3NOAA, 672 Independence Parkway, Chesapeake, VA, USA

Abstract. Seiches are normal modes of water bodies responding to geophysical forcings with potential to significantly impact ecology and maritime operations. Analysis of high-frequency (1 Hz) water level data in Monterey, California, identifies harbor modes between 10 and 120 s that are attributed to specific geographic features. It is found that modal amplitude modulation arises from cross-modal interaction and that offshore wave energy is a primary driver of these modes. Synchronous coupling between modes is observed to significantly impact dynamic water levels. At lower frequencies with periods between 15 and 60 min, modes are independent of offshore wave energy, yet are continuously present. This is unexpected since seiches normally dissipate after cessation of the driving force, indicating an unknown forcing. Spectral and kinematic estimates of these low-frequency oscillations support the idea that a persistent anticyclonic mesoscale gyre adjacent to the bay is a potential mode driver, while discounting other sources.

Short summary
Seiches in coastal bays can produce significant water level oscillations that impact maritime operations and introduce ecological stress. Monterey Bay, California, is found to have wave-driven short-period oscillations that can reinforce themselves, resulting in water level amplification. At longer periods the oscillations are not wave-driven and several potential forcing mechanisms are examined. A gyre offshore the bay is suggested as the driver, while other potential drivers are discounted.