Investigation of Long-Term Fluctuations in the Georges Bank, Gulf of Maine Water Mass Structure
Charles N. Flagg, Marine Sciences Research Center, Stony Brook University
Stony Brook, NY 11794, cflagg@ms.cc.sunysb.edu

	Physical and biological low frequency processes clearly affect the Georges Bank, Gulf of Maine system and these appear to be related to large scale atmospheric and oceanic processes.  The apparent dependence of GOM plankton abundance on changes in the large scale weather systems of the North Atlantic is, on the face of it, simply a statistical result.  However, it points to the existence of a large-scale interdependence of the entire region that dictates not only the physical system but through as yet unresolved mechanisms, the biological processes (nutrient supply, productivity and recycling) as well.  The goal in this investigation is to see if we can define some of the relevant mechanisms responsible for these linkages through a study of the temporal and spatial relationship between the nutrients in the Gulf of Maine and the larger scale distribution of water masses with their attendant nutrient signatures.  
	To establish these linkages, we have assembled all the available data west of Greenland and north of Cape Hatteras from the NODC and the Canadian MEDS data bases.  These data goes back to the 1930s for temperature and salinity but significant amounts of nutrient data do not start until the late 1950s. Of the stations with a complete suite of variables (T, S, NO3 (or NO3+NO2), PhO4, SiO4, O2) 3762 lie to the south and west of the Grand Banks, excluding the Gulf of St. Lawrence, and 811 lie to the north of the Grand Banks and west of Greenland.  The end-point waters of interest are those typical of the Maine Bottom Water found in the Georges Basin and Northeast Channel (sill depth of ~220 m) below the most obvious seasonal cooling (~100m) and above the maximum historical ?? of about ~27.3 kg/m3.  The investigation includes examinations of the temporal T, S and nutrient variations in the GOM and surrounding regions, the spatial distribution of properties on density surfaces that intersect with Maine Bottom Water and a combined spatial/temporal EOF analyses on a series of potential density surfaces.  The study is not complete as yet although substantial interannual variations have been identified in all the large-scale indices that we have examined although the potential linkages between these indices have not unambiguously resolved.