Fig. 1: Maps, sampling information, and hydographic properties from TReX Deep.

Maps (a) and (b) show the Gulf of St. Lawrence, TReX Deep sampling locations, and regional bathymetry. Black contour lines represent the injection depth bathymetric contour, h = 279 m. Abbreviated location names are: TS Tadoussac, QC Quebec, AI Anticosti Island, CS Cabot Strait, NL Newfoundland, BI Belle Ille Strait. The Lower St. Lawrence Estuary (LSLE), immediately east of Tadoussac, is shaded gray. Plot (c) shows hydrographic conditions from a single CTD profile immediately following the tracer injection with a dashed line indicating the injection depth. Shading represents the 95% confidence limits (mean conditions ± 2σ) of an October–December hydrography climatology from the Atlantic Zone Monitoring Program in the eastern Gulf between 1998 and 2022. Histogram (d) denotes the number of samples in z* = 10 m depth bins from Leg 1 and Leg 2 cruises.