Changes in bay circulation in an evolving multiple inlet system

Abstract

Observations and numerical model (ADCIRC) simulations are used to quantify the changes in circulation within the evolving, shallow, two-inlet tidal Katama system, Martha's Vineyard, MA. From 2011 to 2013, Katama Inlet, connecting Katama Bay to the Atlantic, became 5 times longer, 1/3 as wide, and 1/3 as deep as the inlet migrated and rotated. This morphological evolution caused a significant loss of energy throughout Katama Bay and Edgartown Channel, which connects the bay to Vineyard Sound. The decrease in energy as the inlet evolved between 2011 and 2013 was not monotonic. Model simulations suggest bathymetric changes caused by Hurricane Irene (August 2011) resulted in a temporary increase in circulation energy throughout the inlets and bay. Changes in the M4 and M6 tidal constituents, harmonics of the primary M2 tidal forcing, suggest the changes in the observed circulation patterns primarily were owing to changes in friction, and not to changes in advection resulting from the evolving inlet location, orientation, or geometry, consistent with previous results.