Sansone, F. J. University of Hawaii, sansone@soest.hawaii.edu
Falter, J. J. University of Hawaii, jfalter@soest.hawaii.edu
Haberstroh, P. R. Kapiolani Community College, phabers@leahi.kcc.hawaii.edu

 
WAVE-INDUCED POREWATER-SEAWATER MIXING IN PERMEABLE SEDIMENTS
 
Surface waves can greatly enhance porewater-seawater exchange in permeable sediments and submarine frameworks. The dynamic pressure field at the seafloor resulting from surface waves, which drives such exchange, can easily be measured using piezoelectric pressure gauges. These gauges, when attached to wells penetrating the seafloor, can also record the propagation of this pressure field through the seafloor and its resulting high frequency attenuation. Spectral analysis allows estimates of 1) wave-induced exchange across the sediment-water interface, and 2) the bulk modulus of the framework; the latter should provide a convenient means of comparing the hydrological characteristics of different systems. Pressure head variations in excess of several cm commonly occur at depths of up to 2 m within permeable sediments and frameworks, demonstrating the latter's high hydraulic conductivity despite, in some cases, a high degree of lithification. Computed mixing coefficients were several orders of magnitude higher than molecular diffusion coefficients, and were related to the direction and intensity of wind-driven waves. There was close agreement between exchange rates predicted by this technique and estimates from tracer experiments. Wave-driven mixing dominates reef porewater-seawater exchange, and can supply a significant fraction of the nutrients needed for upper-reef benthic primary production.
 
Day: Wednesday, Feb. 3
Time: 12:00 - 12:15pm
Location: Eldorado Hotel
 
Code: SS03WE1200E