The relationship between current flow direction and sediment distribution within slope-confined submarine canyons off the north coast of Moloka’i, HI

Abstract

Submarine canyons play an important role in transporting sediments from terrestrial sources to abyssal environments. Sediment can be transported along continental shelves and into submarine canyons through bottom currents and gravity flows. This study characterizes the variability of sediment deposition patterns within the intra-canyon and inter-canyon environments associated with submarine canyons along the north continental shelf and slope of Moloka’i Island, HI. Shallow seismic reflection and bathymetric surveys were conducted in order to visualize sediment deposition and morphologic patterns along the upper, middle, and lower courses of the canyons on the East Moloka’i Shelf and compared with a middle reach of the Central Moloka’i Shelf. The PacIOOS ROMS model was used to evaluate current direction and speed on both sides of the island and was compared with canyon sidewall slopes to differentiate possible current deposition from other sources that may not have representable patterns. Our results demonstrate that sediment is dominantly distributed along the intra-canyon environments and is not prevalent within the canyon axes. Canyon slope sidewalls off the Central Moloka’i Shelf are steeper with little differentiation compared to canyons on the East Moloka’i Shelf which have predominately steeper western sidewalls. Model data indicate a predominately NW current flow direction on the eastern shelf, which may contribute to shallower eastern slopes, while currents west of the Kalaupapa Peninsula exhibit eddy-like circulation, indicating a less consistent pattern. Submarine canyons off the north coast of Moloka’i are relatively understudied, so an understanding of their sediment deposition patterns plays a key role in evaluating sediment budgets in this region.