Click on figures for larger images

Figure 1. Satellite photograph of Martha's Vineyard and Cape Cod (inset), Massachusetts. Study site is indicated by "C" and is 2 kilometers offshore, to the south of Martha's Vineyard.

Figure 2. Schematic illustration of profiling tripod with instruments on cantilever arm for profiling particle distributions in the bottom boundary layer. Refer to the Abbreviations and Symbols section.

Figure 3. Front view of the tripod with the profiling arm; frame-mounted instruments are labeled. Profiling arm is in the up position. See the Instrumentation section for a complete description of these instruments.

Background

The data described here were obtained as part of the Optics, Acoustics, and Stress In Situ (OASIS) Project, a cooperative effort between the U.S. Navy Office of Naval Research (ONR) and the U.S. Geological Survey (USGS). Field data were collected in September and October 2011 near the Martha's Vineyard Coastal Observatory (MVCO; fig. 1) in collaboration with other OASIS investigators.

Objectives

The goal of the project was to measure optical and acoustical characteristics of particles suspended near the seafloor under a variety of wave and current conditions. In particular, we wanted to measure vertical profiles of acoustic and optical backscatter and attenuation, along with estimates of particle size. Profiles of acoustic properties can be made with readily available instruments, but because light is attenuated in marine environments, profiles of optical properties are more difficult to measure. To obtain both optical and acoustic profiles, we designed and built a tripod-mounted profiler to move a package of optical and acoustic sensors up and down through the bottom 2 meters (m) of the water column (figs. 2 and 3). This report describes the profiler, associated instrumentation, field program, and resulting data.