Moored Observations of Oceanographic Variability in the Columbia River Plume during the Summer of 2004

As part of the RISE (NSF CoOP) program, 3 moorings were placed over the Oregon and Washington shelves in the Columbia River plume from June to September 2004. The moorings were deployed north, south and immediately offshore of the Columbia River mouth at the 72 m isobath. The moored array was designed to sample the plume under various synoptic conditions. The distance between the northern and central moorings was 31 km and that between the central and southern mooring was 14 km. All moorings included anemometers, temperature loggers, acoustic Doppler current profilers (ADCPs) and near-surface salinity, fluorescence, light transmission, and dissolved inorganic nitrogen (DIN) measurements. The moored instruments were concentrated near the surface in order to sample the plume, which can be trapped very closely (5 m or less) to the surface. Salinity, fluorescence, and light transmission were measured 1, 5, and 20 m beneath the surface and DIN was measured 1 m beneath the surface. Temperature data were collected about every 5 m in the upper water column and at reduced resolution from 30-72 m. Each mooring included 2 ADCPs, a downward looking 300 kHz unit in the surface buoy, and an upward looking 1200 kHz ADCP moored 15 m beneath the surface. Moorings are scheduled for recovery in September, and preliminary results from them will be discussed.