Recent advances in processing velocity data from bottom-mounted Acoustic Doppler Current Profilers (ADCPs) offer the capability of partitioning directional wave spectra of surface wave height in order to separate the locally generated wind waves from incoming swells arriving from remote sources. In the study described here, we have partitioned directional wave spectra, derived from bottom-mounted ADCP measurements at the Martha's Vineyard Coastal Observatory (MVCO) south of Martha's Vineyard, MA, into dominant swell and locally generated wind-wave components. The partitioning was carried out following the method of Hanson and Phillips (2001). Because this is a relatively untested method, especially when applied to ADCP data, it was implemented by an exploratory, rather than a routine, approach. As part of this approach, we assessed the validity of the ADCP-derived wave spectra by comparing them with one-dimensional wave spectra derived from laser altimeter measurements. As will be shown, this comparison identified a frequency range over which the ADCP-derived wave field may be suspect. We also carried out a series of sensitivity tests in which we evaluated how the results of wave partitioning according to the Hanson and Phillips (2001) method is influenced by varying the parameters required to implement the method. In this report, we describe and assess the data sources used in our study, outline the methods employed for wave spectra partitioning and describe partitioning results (focusing on the sensitivity of these results to the partitioning parameters).

A moderate bandwidth observatory platform has been developed that integrates acoustic and satellite links to provide connectivity between sensors on the seafloor and investigators on shore. The system incorporates high-rate (5300 bps) acoustic modems, solar power generation, a low-power single board computer running Linux, and Iridium satellite modems to provide a lower cost, relocatable alternative to higher bandwidth systems. The prototype system, which supports an ocean bottom seismometer (OBS) and fluid-flow, temperature, and resistivity sensors, has been deployed near the Nootka Fault in 2326 m of water off the coast of Vancouver Island since May 2004. Since deployment, the system has transmitted more than 150 MB of data from the seafloor instruments.

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