The upper reaches of Narragansett Bay have experienced episodic hypoxia during recent years. These events typically impact sub-pycnocline waters of the shipping channel in the Providence River as well as shallower areas such as Greenwich Bay. Hypoxic conditions generally develop during neap tide conditions following surface phytoplankton blooms (Bergondo et al., 2004), but the fact that hypoxia is not observed during all neap tide periods suggests an interplay with other forcing functions including freshwater runoff, nutrient input, and surface fluxes of heat and momentum.

As part of an interdisciplinary investigation of the hypoxia phenomenon in Upper Narragansett Bay, we have recently begun a study of the spatial and temporal variability of hydrography and turbulent mixing in the Upper Bay. The observations reported here were obtained during summer 2004 and 2005 during neap and spring tide periods. During each day of each 3-day period, an approximately 20 km transect was surveyed using an Acrobat towed undulating vehicle and a vessel-mounted 600 kHz ADCP.

The contour plots (see links above) display vertical sections of temperature, salinity, oxygen, nitrate, and chlorophyll along the transect, measured relative to the northern part of Narragansett Bay.