Submarine canyon sediment transport and accumulation during sea level highstand: Interactive seasonal regimes in the head of Astoria Canyon, WA

Lahr et al. (2025) use in-situ hydrodynamic data from a benthic tripod deployment in the head of Astoria Canyon to show that sediment resuspension and transport during summer is driven by internal tides and plume-associated nonlinear internal waves. Observations of shoreward-directed currents and low shear stresses (<0.14 Pa) along with sediment trap data suggest that seasonal loading of the canyon head occurs during summer. Nearby long-term wave data from the OOI Washington Shelf mooring shows that winter storm significant wave height often exceeds 10 m, driving shear stress capable of resuspending all grain sizes present within the canyon head. Swell events are generally concurrent with downwelling flows, providing a mechanism for episodic downcanyon sediment flux. This study indicates that canyon heads can continue to function as sites of sediment winnowing and bottom boundary layer export even with a detached, shelf-depth canyon head.

As part of this study, Lahr et al. (2025), used data from the OOI Washington Shelf Surface Mooring located 81 km north of the tripod site in Astoria Canyon. The 2019 benthic tripod deployment by Ogston was done as an ancillary activity on the Endurance 11B cruise aboard R/V Oceanus.  The data used were concurrent spectral surface wave and meteorological data near bed current velocity for 2016 (chosen for its complete records).  Figure xx shows the benthic tripod stress overlaid with the OOI Washington shelf mooring stress.  Over the summer, the benthic tripod stress and OOI estimated stress compare well.  Winter stresses (available from OOI mooring only) are much larger than those observed in summer.

Figure 1. Shear stress computed from the Astoria Canyon tripod deployment (black) and the OOI Shelf mooring (gray). Panels a) and b) depict relative stress contributions from waves and currents respectively, c) the distribution of total stresses, and d) maximum shear stresses from summer and winter on a Shields diagram. (Figure 3, Lahr et al., 2025)

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Reference:

Lahr, E.J., A.S. Ogston, J.C. Hill, H.E. Glover, and K.J. Rosenberger (2025). Submarine canyon sediment transport and accumulation during sea level highstand: Interactive seasonal regimes in the head of Astoria Canyon, WA. Marine Geology, no. (2025): 107516. https://www.sciencedirect.com/science/article/pii/S0025322725000416.