Historic 2005 toxic bloom of Alexandrium fundyense in the western Gulf of Maine : 2. Coupled biophysical numerical modeling
McGillicuddy, Dennis J.
Keafer, Bruce A.
Anderson, Donald M.
MetadataShow full item record
A coupled physical/biological modeling system was used to hindcast a massive Alexandrium fundyense bloom that occurred in the western Gulf of Maine in 2005 and to investigate the relative importance of factors governing the bloom's initiation and development. The coupled system consists of a state-of-the-art, free-surface primitive equation Regional Ocean Modeling System (ROMS) tailored for the Gulf of Maine (GOM) using a multinested configuration, and a population dynamics model for A. fundyense. The system was forced by realistic momentum and buoyancy fluxes, tides, river runoff, observed A. fundyense benthic cyst abundance, and climatological nutrient fields. Extensive comparisons were made between simulated (both physical and biological) fields and in situ observations, revealing that the hindcast model is capable of reproducing the temporal evolution and spatial distribution of the 2005 bloom. Sensitivity experiments were then performed to distinguish the roles of three major factors hypothesized to contribute to the bloom: (1) the high abundance of cysts in western GOM sediments; (2) strong ‘northeaster' storms with prevailing downwelling-favorable winds; and (3) a large amount of fresh water input due to abundant rainfall and heavy snowmelt. Model results suggest the following. (1) The high abundance of cysts in western GOM was the primary factor of the 2005 bloom. (2) Wind-forcing was an important regulator, as episodic bursts of northeast winds caused onshore advection of offshore populations. These downwelling favorable winds accelerated the alongshore flow, resulting in transport of high cell concentrations into Massachusetts Bay. A large regional bloom would still have happened, however, even with normal or typical winds for that period. (3) Anomalously high river runoff in 2005 resulted in stronger buoyant plumes/currents, which facilitated the transport of cell population to the western GOM. While affecting nearshore cell abundance in Massachusetts Bay, the buoyant plumes were confined near to the coast, and had limited impact on the gulf-wide bloom distribution.
Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): C07040, doi:10.1029/2007JC004602.
Showing items related by title, author, creator and subject.
Reply to comment by M. Ortega-Sánchez et al. on “High-angle wave instability and emergent shoreline shapes : 1. Modeling of sand waves, flying spits, and capes” Ashton, Andrew D.; Murray, A. Brad (American Geophysical Union, 2008-01-26)
High-angle wave instability and emergent shoreline shapes : 1. Modeling of sand waves, flying spits, and capes Ashton, Andrew D.; Murray, A. Brad (American Geophysical Union, 2006-12-15)Contrary to traditional findings, the deepwater angle of wave approach strongly affects plan view coastal evolution, giving rise to an antidiffusional “high wave angle” instability for sufficiently oblique deepwater waves ...
Ganju, Neil K.; Schoellhamer, David H.; Jaffe, Bruce E. (American Geophysical Union, 2009-12-02)Hindcasting decadal-timescale bathymetric change in estuaries is prone to error due to limited data for initial conditions, boundary forcing, and calibration; computational limitations further hinder efforts. We developed ...