Semiannual patterns of erosion and deposition in upper Monterey Canyon from serial multibeam bathymetry

Abstract

Recently acquired 3-m-resolution 244 kHz multibeam seafl oor bathymetry (0.5 m depth precision) reveals geomorphology at suffi cient detail to interpret small-scale features and short-term processes in the upper 4 km of Monterey Canyon, California. The study area includes the continental shelf and canyon features from 10 m to 250 m depth. The canyon fl oor contains an axial channel laterally bounded by elevated complex terrace surfaces. Sand waves with 2 m height and 35 m average wavelength dominate the active part of the canyon fl oor. The sand waves are strongly asymmetrical, indicating net downcanyon sediment transport in this reach. Terraces, including a broad 25-m-tall terrace complex near the head of the canyon, bear evidence of recent degradation of the canyon fl oor. Slump scars and gullies having a variety of sizes and relative ages shape the canyon walls. Serial georeferenced digital elevation models were analyzed to detect net changes in bathymetry or morphology occurring during both a six month period (September 2002 to March 2003) and a 24-h period (24 March to 25 March). Signifi cant changes over the six month period include: (1) complete reorganization of the sand waves on the channel fl oor, (2) local channel degradation creating new 2-m-tall erosional terraces on the channel margins, (3) local channel widening that laterally eroded older channel margin terraces, and (4) 60 m extension of one minor gully head on a steep canyon wall. There were no discernable changes in morphology during the 24-h study period. Raster subtraction of serial bathymetric grids provides estimates of sediment erosion and deposition that occurred between the canyon head and a point 2 km down canyon during the six month study. Erosion of 320,000 m 3 (±80,000 m 3) of sediment occurred mainly in the tributaries, along the margins of the axial channel, and in the lowest 700 m of the analyzed reach. This eroded volume was approximately balanced by 260,000 m 3 (±70,000 m 3) of sediment deposition that was concentrated in the nearshore region along the rim of the canyon head. There was no measurable sediment gain or loss during the 24-h study period.

Connections Between Fluvial To Shallow Marine Environments and Submarine Canyons: Implications For Sediment Transfer To Deep Water

“…The canyon head comes within 0.1 to 0.2 km of the shoreline (Table 2), sand is fed into the upper reaches of the canyon primarily by longshore drift with subordinate direct fluvial input (Smith et al 2005), and current meters indicate that turbidity flows competent to transport sand in Monterey Canyon are commonly triggered by winter storms (Paull et al 2003).…”

“…With improved technology for imaging the sea floor, and the deployment of current monitors and sediment traps in some submarine canyons, the scale and distribution of these canyons has become better defined and their role as conduits for transferring sediment from terrestrial sources into the deep basin has become better understood (e.g., Piper and Savoye 1993;Khripounoff et al 2003;Paull et al 2003;Smith, et al 2005;Oliveira et al 2007;Harris and Whiteway 2011). Indeed, as observed by Normark and Carlson (2003), every major submarine fan in the world is fed by a submarine canyon.…”

More than a century of bathymetric observations and present-day shallow sediment characterization in Belfast Bay, Maine, USA: implications for pockmark field longevity

“…Such offsets are common in difference analyses of steeply sloping features (cf. Smith et al 2005;Hughes Clarke et al 2009), and are particularly evident when data are not collected using RTK positioning (this study). That such artifacts exist even in studies using high-quality modern swath bathymetry data underscores the need for caution when interpreting "change" among datasets of varying resolution and quality, especially in areas with complex seafloors.…”

From the Ground Up: Building an Undergraduate Earth Systems Curriculum

“…For example, Maria Ferdin was senior author on a research paper that identified a new indicator species for the detection of domoic acid in California coastal waters (Ferdin, et. al., 2002); Kate Thomas was senior author on a research paper that analyzed the effects of human activity on the foraging behavior of sanderlings (Thomas et al, 2003); Greg Ruiz coauthored a paper on erosion and deposition in a submarine canyon using serial multibeam bathymetry (Smith et al, 2005); Erica Morris coauthored a paper on genus-specific marine habitat mapping using high-resolution multibeam bathymetry (Iampietro et al, 2005); and Ryan Lockwood coauthored a paper on mapping the geothermal surface heat flux from Yellowstone National Park (Watson et al, in press). …”