The Consequences for the North American Shelf of a Shift Toward a Heightened Gulf Stream Presence at the Tail of the Grand Banks

Observed changes in temperature, salinity, oxygen concentration, and fish distribution along the Northeast US and Canadian Shelves appear to be correlated with shifts of the large-scale ocean circulation. Specifically, the interaction between the Gulf Stream and the Labrador Current near the Grand Banks of Newfoundland may influence water mass properties along the shelf. These currents interact at the Southeast Newfoundland Ridge (SENR), a topographic feature that extends southeastward from the Tail of the Grand Banks. In this work, we use a suite of observational data to understand how the impingement of the Gulf Stream on the SENR influences the water properties on the shelf. Our analysis of long-term hydrography suggests that the waters at the SENR experienced two step-like changes towards warmer and more saline waters: first in the 1970s and, again, after 2010. An examination of the satellite altimeter record (1992-present) shows that the latter shift was associated with the Gulf Stream meandering onshore from its mean position along the 4,000 m isobath to impinge on the 3,000 m isobath near the Tail of the Grand Banks. The presence of the Gulf Stream so close to the slope may represent a dynamical constraint for the Labrador Current, potentially blocking its southwestward transport around the Grand Banks and along the North American continental slope. We examine the changes associated with this shift, including the arrival time for anomalies as a function of distance along the continental slope and their correspondence to documented changes in the spatiotemporal distributions of fish and invertebrates on the Northeast US and Canadian Shelves.