Title: Biological response to episodic wind events in Massachusetts Bay
Description: In this dissertation the biological response to wind-induced upwelling events in Massachusetts Bay is studied. Massachusetts Bay is a semi-enclosed embayment adjacent to a large shallow shelf-sea and is characterized by winds that vary frequently in magnitude and direction. To determine the biological response to episodic wind events 3-dimensional physical-biological simulations are carried out for June 6-26, 2001. During this time the ASCOT-01 combined physical and biological experiment took place in Massachusetts Bay and the Gulf of Maine and a large data set was collected for initialization, assimilation, and determination of biological parameters. Three wind forcings are used: (1) real winds from June 2001, (2) feature-model wind events of strong storms during 1985-2005, and (3) historical summer winds from the same period. During June 2001 the winds were unusually weak and hence caused very little upwelling. By modeling strong feature wind events we are able to amplify the biological responses.

The physical response to strong southerly wind events in Massachusetts Bay is characterized by three processes: 1) Upwelling along the mainland coast, (2) large off-shore currents near the surface, and (3) on-shore currents deeper in the water column. The deep on-shore current plays a crucial role as it advects nitrate from the Gulf of Maine into Massachusetts Bay, recharging the aphotic zone. After the upwelling event has subsided this nitrate can continue to enhance primary production in the overlying euphotic zone. The biological response to the wind event happens on two time scales. During the wind event the nutrients and biomass are redistributed mainly by advection and the only biological process of importance is ammonium uptake. After the wind event there is a phytoplankton bloom. Advective processes are weak and interactive biological processes dominate changes in nutrients and biomass.