WINTER-SPRING STORMS AND THEIR INFLUENCE ON SEDIMENT RESUSPENSION, TRANSPORT, AND ACCUMULATION PATTERNS IN SOUTHERN LAKE MICHIGAN

The Episodic Events-Great Lakes Experiment was designed to quantify the impacts of major late winter-early spring storms on sediment-water exchange, sediment, and associated constituent transport and resultant influence on well-characterized sediment distributions in southern Lake Michigan. Prior to this project, only very sparse data were available during the late winter-early spring period for any of the Great Lakes, primarily because of strong storms and ice conditions. The observation strategy consisted of moored arrays of current meters, thermistors, and sequencing traps, along with shipboard surveys. In addition, process measurement cruises were conducted along with special cruises for sediment-water interface sampling using a remotely operated vehicle, particle transformation measurements, and sediment collection. A summary of conclusions include: (1) particles, predominantly from the western shore of the lake, are resuspended and transported in a coastal band toward the major sediment depositional region in the southeastern portion of the lake, (2) transport rates, measured by234Th, are on the order of kilometers per day, (3) the magnitude of resuspended sediments from a single major storm is 1–5 × 10⁶ kg, larger than annual external input of fine-grained materials to the southern basin, (4) resuspension surrogates based on 50 years of wave data show an interannual variability in major storm events that ranges over an order of magnitude, and (5) trap and ⁷Be evidence indicates that the events appear to be primarily responsible for the complicated sediment accumulation patterns in the southern basin of Lake Michigan.