Shoaling Internal Waves

In collaboration with Stephen Monismith, Jeff Koseff (Stanford University), Jonathan Nash (OSU) and Brock Woodson (Georgia)

Internal tides are a generic feature of nearshore flows, playing a fundamental role in the ecology, biogeochemistry, and sedimentary environment of the nearshore. For example, on coral reefs, turbulent mixing, as modified by stratification, can determine the strength of coupling between the water column and the reef. In a like fashion, internal waves can also be important to such environments as kelp forests where they may be a critical means of cross-shore transport of larval organisms. Thus, understanding the behavior of internal waves and the mixing they produce in shallow water is a fundamental problem in coastal oceanography.

This work has focused on measurement of Reynolds stresses, turbulent buoyancy fluxes, and turbulence dissipation rates in the nearshore bottom boundary layer in the presence of shoaling internal tides and surface waves. Three sets of field experiments were completed on the south shore of Oahu, taking advantage of the capabilities of the Kilo Nalu Observatory operated by the University of Hawaii. The first set of observations was carried out at the KNO 12m node in 2009.  Full scale observations, which included deployment of an 8m tower were carried out in the vicinity of the KNO 20m node in Spring of 2010 and 2011. The objectives for the field measurements were to obtain a high quality turbulence data set, made in a setting for which we will have a fairly complete overall description of the mean flow.

8m ADV tower deployed near KNO 20m node

Top: Temperature time series from thermistor chain near KNO 20m node indicating

arrival of a baroclinic bore; Bottom: Bore velocities and density contours

Publications

Squibb, M.J., S.G. Monismith, J.D. Nash, G. Pawlak, C.B. Woodson. Observations of turbulent bottom boundary layers in the presence of shoaling internal tides in Mamala Bay, HI., In prep for J Geophys Res.