Solibore‐induced sediment resuspension in the Faeroe‐Shetland Channel

Abstract

[1] High resolution measurements of temperature and current velocity over the seabed in the Faeroe-Shetland Channel (FSC) reveal an intense internal wave train, referred to as a solibore, propagating up the continental slope. In addition to enhancing turbulent mixing, a rotor formed at the leading edge of the solibore generates sediment fluxes O(10 2 ) greater than background levels. The interaction of solibores, which appear to evolve from baroclinic bores, with the seabed and the resulting rotor provides a dominant mechanism for the upward transport of sediment over continental slopes that may counteract downward avalanching of material by gravity. INDEX TERMS: 4211

High sampling rate thermistor string observations at the slope of Great Meteor Seamount

“…In detailed NIOZ2 observations like in Figs. 4b and 4c it appears that this ramp is extremely sharp, with a front passing the sensors with temperature dropping by 0.5 • C within 1 s. Such fronts or bores have been observed previously, in data sampled at a rate of once/30 s above the continental slopes of the Faeroe-Shetland Channel, where they appeared at a 4 days periodicity (Hosegood et al, 2004), and the Bay of Biscay, where tidal periodicity dominated (Gemmrich and van Haren, 2001 of several tens of meters thick as in flat-bottom tidal seas were not observed. With the varying stratification many small-scale features were observed ranging from overturns (Sect.…”

“…These thermistor strings had an accuracy of ∼10 −2 • C (Marmorino et al, 1987;Selschopp, 1997). As suggested from the "moored" observations by Thorpe (1987) and Hosegood et al (2004), such temperature variations can be expected even in deepocean environments, despite the local background buoyancy period, which is relatively large O(10-100 min). As a result, for monitoring such deep internal temperature variations standard moored thermistor strings sample too slow, typically once per minute at an accuracy of ∼5·10 −2 • C. To monitor the above variations and scales at an accuracy better than 10 −2 • C one should modify a string of the towed type to one that can be moored.…”

“…Specifically, we wanted to monitor over periods of a few weeks very fast (∼1 Hz) non-linear motions associated with internal "waves" in "solibore" form above sloping bottoms. Although such motions were captured with NIOZ1 (Hosegood et al, 2004), we wanted more detailed information, even more than presented by Thorpe (1987) who used an array of 11 thermisCorrespondence to: H. van Haren (hansvh@nioz.nl) tors at, on average, 10 m spacing, sampling every 10 s to a resolution of 10 −4 • C at ∼3000 m depth off Porcupine Bank.…”

Resuspension by fish facilitates the transport and redistribution of coastal sediments

“…At shallow depths, surface waves may cause resuspension (Mullenbach and Nittrouer 2000). In deeper waters, away from regions where surface waves break, sediment resuspension is commonly attributed to shear stress induced by strong bottom currents (Isla et al 2004) and internal waves (Puig et al 2001;Hosegood et al 2004). In Saanich Inlet, small surface waves (Fig.…”

“…To date, most studies attribute sediment focusing entirely to physical forces such as currents (Sayles et al 2001;Isla et al 2004), surface waves (Mullenbach and Nittrouer 2000), and internal waves (Hosegood et al 2004) or to slumping and seismic events (Dallimore et al 2005). However, significant and continuous sediment focusing also occurs in calm, deep marine environments where physical processes are weak or infrequent (Sugai 1990;Hales et al 2006).…”