Nutrient Dynamics on the NE Continental Shelf; Sample Analyses.

David Townsend, University of Maine

The accelerated melting of the Greenland ice sheet and the Arctic ice cap in recent decades are well documented climate change-related phenomena that are cause for a broad range of environmental concerns.  One aspect of these phenomena that appears to be influencing marine ecosystems far removed from the Arctic is an apparent associated change in the circulation of the Labrador Sea and the Northwest Atlantic continental shelf and slope waters, which in turn appears to have resulted in an increased baroclinic transport of low salinity shelf waters to regions farther south .  Consequently, those changes are altering the water properties and nutrient regime in the Gulf of Maine over the past several decades.  Our retrospective analyses of available hydrographic data back to the 1960s have revealed that deep water layers in the Gulf (>100m) have become fresher and cooler, with lower nitrate but higher and more variable silicate concentrations over a period coincident with recent, rapid melting in the Arctic (Townsend et al. 2010).  Those changes in the nutrient regime may also be forcing changes in the structure of the planktonic ecosystem.