Variability and wind forcing of ocean temperature and thermal fronts in the Slope Water region of the Northwest Atlantic

Ingrid Peterson, Fisheries and Oceans Canada
Blair Greenan, Fisheries and Oceans Canada
Denis Gilbert, Maurice Lamontagne Institute, Fisheries and Oceans Canada
Dave Hebert, Fisheries and Oceans Canada

Document Type Article


Subsurface temperatures in the Slope Water region of the Northwest Atlantic from Argo profiling floats and on the adjacent continental shelf from ship-based measurements are compared with the latitudinal position of the Shelf-Slope Front (SSF) and the Gulf Stream North Wall (GSNW). The Slope Water and shelf temperature anomalies at 200 m depth are in agreement for the period, 2002–2015. For the period 1978–2015, shelf temperatures are significantly correlated with the SSF position, and to a lesser extent with the GSNW position. Annual SSF position anomalies near the Grand Banks at 50°W–55°W lead anomalies to the west at 65°W–75°W by 1–2 years. Wind stress curl is compared with the annual change in the SSF and GSNW latitudinal positions, rather than with the positions directly. Changes in the mean position of the SSF are related to the wind stress curl pattern in the mid-Atlantic, with an 8 month lag. It is suggested that a wind pattern favoring a southward shift of the SSF is associated with a southward shift of the zero-curl line near 40°W, resulting in an expanded subpolar gyre and enhanced flow of Labrador Current Water westward from the Tail of the Grand Banks. However, changes in the GSNW position are related to an NAO-like wind stress curl pattern in the eastern Atlantic in the winter-spring period, in agreement with other studies. High sea surface temperatures in the Gulf of Maine and on the Scotian Shelf in recent years can be largely attributed to positive local onshore wind anomalies.