The fortnightly mean circulation of chesapeake bay

Data from several current measurement programmes were used to examine the temporal and spatial variability of Chesapeake Bay circulation at time scales of 15 days and longer. First, year-long current records from two stations were analysed for response to runoff, wind stress and gravitational forcing. A strong spring freshet in April resulted in an annual maximum in the longitudinal density gradient, yet the surface current at mid-bay actually declined at the time of this maximum. The reason for this response lies in a prolonged period of northward wind which effectively reduced the strength of the two-layer gravitational flow. This shows that seasonal changes in the wind field can modulate the gravitational flow and that these annual wind shifts are a significant factor in the circulation of this estuary. Statistical analysis also indicates correlation between surface current and longitudinal wind at time scales of 15 days and longer, implying that meteorological effects cannot be completely filtered out at these frequencies.