Théau Leclercq, a former student of Québec-Océan researcher Cédric Chavanne, recently published an article on the Gaspé Current in Regional Studies in Marine Science.
Here's a summary of the article, and to read the full article, click here!
The Gaspé Current is the most prominent current in the surface circulation of the Gulf of St. Lawrence. It drains water from the St. Lawrence estuary into the Gulf along the Gaspé coast. It can reach speeds of up to 1 m/s in summer, is 10 to 20 km wide and occupies the top 40 m of the water column. It is separated from the waters of the Gulf by a salinity front, which can become unstable and generate meanders several tens of kilometers apart. Upwelling of nutrient-rich deep waters along this front has been observed in the past, and a theoretical model was proposed by Tang in 1982 to explain these vertical movements. This model predicted permanent upwelling of deep waters located offshore of the front, accompanied by downwelling of surface waters below the front, but these predictions had never been tested experimentally.
By analyzing in-situ observations of temperature, salinity and currents collected along the Gaspé Current between 1991 and 1993, Leclercq, Chavanne and Larouche (2023) show that vertical movements are often present near the front of the Gaspé Current, but are neither permanent nor always located offshore of the front, challenging Tang's (1982) model. Two other potential mechanisms for generating frontal vertical motions are tested: frontogenesis (strengthening of the front) or frontolysis (weakening of the front) caused by meandering of the front, and non-linear Ekman pumping caused by wind stress. The results show that the vertical movements observed are mainly caused by frontogenesis and frontolysis, with Ekman pumping playing a secondary role near the surface.
Deep-water upwelling associated with the Gaspé Current front provides near-surface nutrients that support primary production and thus the entire regional food chain. These upwellings are mainly associated with the meandering Gaspé Current, and their occurrence varies in time and space, impacting the regional variability of primary production.
Summary by Théau Leclercq and Cédric Chavanne
