Baltimore Canyon as a modern conduit of sediment to the deep sea

https://doi.org/10.1016/0198-0149(89)90041-1Get rights and content

Abstract

An integrated study using moored current meters, transmissometers and sediment traps revealed that sediment in Baltimore Canyon was resuspended regularly when energy from internal tides was focused along the canyon axis. Such focusing occurred primarily during late winter and early spring. During resuspension events particle concentrations at 275 m in the canyon axis typically increased from a background level of 100 μg l−1 to over 1000 μg l−1 within a 5-min period and often exceeded 5000 μg l−1. Net transport of both water and sediment 5 m above bottom (mab) at 275 m in the canyon axis was consistently downcanyon, while 5 mab at 600 m in the canyon axis net transport was upcanyon, implying convergence between the two sites. The distribution of suspended sediment was determined using a CTD/transmissometer during hydrographic transects along the canyon axis and across the slope adjacent to either side of the canyon. Resuspension on the shelf, canyon walls, and along the slope was minimal, but in the canyon interleaving tongues of turbid water were always present between 200 and 800 m. Although concentrations of resuspended sediment were high, they were not sufficient to generate downcanyon flows. Turbid plumes moved seaward along density surfaces at the convergence between 275 and 600 m and other regions of the canyon. The passage of atmospheric storms and Gulf Stream rings may have changed the pattern of currents of resuspension in portions of the canyon sometimes, but not always. Fluxes of particles collected in sediment traps along the canyon axis increased exponentially toward the buttom, but the size of particles collected in traps decreased with distance from the canyon head, suggesting that resuspended sediment was advected, but depleted in larger, denser particles away from the canyon. An exponential increase with depth in trap fluxes at 1000 m, despite fairly uniform concentrations of suspended particles measured by transmissometers, suggests that many particles are advected as large aggregates (marine snow) that are not detected quantitatively by transmissometers. Currents outside the canyon walls quickly dilute and dissipate sediment moving out of the canyon. Subamrine canyons can act as conduits of sediment to the deep ocean not only by channeling turbidity currents, but also by focusing internal tides that resuspended sediment, after which it is advected to deeper water.

References (49)

  • B. Hickey et al.

    Suspended particle movement in and around Quinault Submarine Canyon

    Marine Geology

    (1986)
  • F.S. Hotchkiss et al.

    Internal waves in Hudson Canyon with geological implications

    Deep-Sea Research

    (1982)
  • M.J. Richardson

    Light scattering and composition of suspended particulate matter in the North Atlantic

    Deep-Sea Research

    (1987)
  • J.J. Walsh et al.

    The 1983–1984 Shelf Edge Exchange Processes (SEEP)—I experiment: hypotheses and highlights

    Continental Shelf Research

    (1988)
  • R.Y. Anderson

    Short-term sedimentation response in lakes in western United States as measured by automated sampling

    Limnology and Oceanography

    (1977)
  • E.T. Baker

    Distribution, composition and transport of suspended particulate matter in the vicinity of Willapa Submarine Canyon, Washington

    Geological Society of America Bulletin

    (1976)
  • E.T. Baker et al.

    The effect of particle size on the light attenuation coefficient of natural suspensions

    Journal of Geophysical Research

    (1984)
  • E.T. Baker et al.

    Field assessment of sediment trap efficiency in a high energy environment

    Journal of Marine Research

    (1988)
  • R. Bartz et al.

    A transmissometer for profiling and moored observations in water

    SPIE, Vol. 160 Ocean Optics

    (1978)
  • P.E. Biscaye et al.

    Suspended particulate concentrations and compositions in the New York Bight

  • J.K.B. Bishop

    The correlation and suspended mass calibration of Sea Tech transmissometer data

    Deep-Sea Research

    (1986)
  • D.E. Drake

    Distribution and transport of suspended particulate matter in submarine canyons off Southern California

  • D.E. Drake et al.

    Distribution and transport of suspended particulate matter in Hueneme, Redondo, Newport, and La Jolla submarine canyons, California

    Geological Society of America Bulletin

    (1973)
  • D.E. Drake et al.

    Suspended particulate matter and mud deposition in upper Hudson Submarine Canyon

  • Cited by (183)

    • Combining stratigraphic forward modeling and susceptibility mapping to investigate the origin and evolution of submarine canyons

      2022, Geomorphology
      Citation Excerpt :

      In addition, submarine canyons are initiated by mass movements and gravity flows. Hence, the morphology and evolution of submarine canyons could reveal the behaviors of these two dominant processes in deep-water settings (Gardner, 1989; Hui et al., 2019; Nelson et al., 2011; Normark et al., 2003; Qin et al., 2017). Due to the difficulty in directly measuring deep-water processes, especially in geological timescales, there still exists an unsettled debate between the upslope and downslope erosion models regarding submarine canyon evolution.

    • Turbidity Current

      2022, Treatise on Geomorphology
    • Distributions of microplastics and larger anthropogenic debris in Norfolk Canyon, Baltimore Canyon, and the adjacent continental slope (Western North Atlantic Margin, U.S.A.)

      2022, Marine Pollution Bulletin
      Citation Excerpt :

      These currents often originate in or near the heads of submarine canyons and are known to exist in Norfolk Canyon (Boggs, 2006; CSA et al., 2017). Baltimore Canyon also channels turbidity currents and focuses internal tides to transport sediments to the deep sea (Gardner, 1989). Sediments entrained in such currents generally settle within canyons in a “fining up” sequence, where larger coarse grain sediments are first to be deposited.

    View all citing articles on Scopus
    View full text