text: Tides in the Chesapeake Bay exhibit an interesting and unique behavior due to the nature of the topography (both horizontal and vertical shape), wind-driven circulation, and how the Bay interacts with oceanic tides. Research into the peculiar behavior of tides both at the northern and southern extents of the Bay began in the late 1970s. One study noted sea level fluctuations at periods of 5 days, driven by sea level changes at the Bay's mouth on the Atlantic coast and local lateral winds, and 2.5 days, caused by resonant oscillations driven by local longitudinal winds, while another study later found that the geometry of the Bay permits for a resonant period of 1.46 days.
  A good example of how the different Chesapeake Bay sites experience different tides can be seen in the tidal predictions published by the National Oceanographic and Atmospheric Administration (NOAA) (see figure at right).
  At the Chesapeake Bay Bridge–Tunnel (CBBT) site, which lies at the southernmost point of the Bay where it meets the Atlantic Ocean near Norfolk, Virginia, and the capes of Charles and Henry, there is a distinct semi-diurnal tide throughout the lunar month, with small amplitude modulations during spring (new/full moon) vs. neap (one/three quarter moon) tidal periods. The main forcing of the CBBT tides are typical, semi-diurnal ocean tides that the East Coast of the United States experiences.
  Baltimore, in the northern portion of the Bay, experiences a noticeable modulation to form its mixed tidal nature during spring vs. neap tides. Spring tides, when the sun-earth-moon system forms a line, cause the largest tidal amplitudes during lunar monthly tidal variations. In contrast, neap tides, when the sun-earth-moon system forms a right angle, are muted, and in a semi-diurnal tidal system (such as that seen at the CBBT site) this can be seen as a lowest intertidal range.
  Two interesting points that arise from comparing these two sites at opposite ends of the Bay are their tidal characteristics - semi-diurnal tide for CBBT and mixed tide for Baltimore (due to resonance in the Bay) - and the differences in amplitude (due to dissipation in the Bay).