Resonant seiche motion in the Chesapeake Bay

Chesapeake Bay is a long and narrow estuary in which seiche motions are common phenomena. These motions are generally driven by the longitudinal (N‐S) wind at 2‐ to 3‐day time scales and are characterized by a node at the mouth and an antinode at the head of the bay. Recent observations revealed a burst of seiche activity which was, however, related to the lateral (E‐W) wind. The amplitude of current fluctuations was about 50 cm s−1 and was not simply related to the winds. The period was about 1.6 days, which was less than the natural period of the whole bay. Since the optimum wind was aligned with only a small portion of the bay (the lower reaches of the bay, about 40 km long), the primary wind effect may be active only at the entrance region. Nevertheless, it appeared that the wind‐driven current was able to trigger a resonant seiche motion in the rest of the bay. The coupled response was modeled through a two‐section conceptual model, and the results compare well with the observations.