MERRIMACK RIVER STUDY AREA—The Merrimack flows about 100 miles from its source, Lake Winnipesaukee in New Hampshire, to the Atlantic, forming the boundary between Newburyport and Amesbury, Mass. As a source of waterpower, it enabled 19th-century industrial expansion in the mill towns in New Hampshire and northern Massachusetts. It meets the Atlantic in a broad expanse of tidal flats and salt marsh behind Plum Island, a barrier beach. In this map, orange, yellow and red tracklines denote paths following by R/V Tioga and Mytilus to record the evolution of currents, salinity, and temperature over tidal cycles. Current measurements were made with acoustic Doppler current profilers (ADCPs) mounted to the boats. Conductivity (to derive salinity), temperature and depth were measured by “tow-yo” method, in which the instrument is towed by a vessel and rapidly records as it follows a saw-tooth path from the bottom to near the surface. (Illustration by Jack Cook, WHOI)[back]
|
