Evidence for the inherent unsteadiness of a river plume: Satellite observations of the Niagara River discharge

Abstract

We present satellite data from the Niagara River plume showing that a large eddy, or bulge, forms and grows in the plume near the mouth of the river. The plume consists of a semicircular bulge region immediately offshore of the mouth and a narrow current that propagates east along the shoreline. During the low‐wind period from 27 to 29 May 1999, the width of the bulge more than doubled and the current width increased only slightly. Approximately one‐third of the Niagara River water accumulated in the bulge near the mouth during this period, implying that the transport rate in the shore‐parallel current was reduced to two‐thirds of the river discharge rate. The effective radius and the growth rate of the bulge computed from the satellite images was in good agreement with previous laboratory results and a numerical model of the Niagara River plume. This is the first field evidence of the unsteadiness of the bulge.