Self-sharpening induces jet-like structure in seafloor gravity currents

Dorrell, R. M.; Peakall, J.; Darby, S. E.; Parsons, D. R.; Johnson, J.; Sumner, E. J.; Wynn, R. B.; Özsoy, E.; Tezcan, D.. 2019 Self-sharpening induces jet-like structure in seafloor gravity currents. Nature Communications, 10 (1).

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Gravity currents are the primary means by which sediments, solutes and heat are transported across the ocean-floor. Existing theory of gravity current flow employs a statistically-stable model of turbulent diffusion that has been extant since the 1960s. Here we present the first set of detailed spatial data from a gravity current over a rough seafloor that demonstrate that this existing paradigm is not universal. Specifically, in contrast to predictions from turbulent diffusion theory, self-sharpened velocity and concentration profiles and a stable barrier to mixing are observed. Our new observations are explained by statistically-unstable mixing and self-sharpening, by boundary-induced internal gravity waves; as predicted by recent advances in fluid dynamics. Self-sharpening helps explain phenomena such as ultra-long runout of gravity currents and restricted growth of bedforms, and highlights increased geohazard risk to marine infrastructure. These processes likely have broader application, for example to wave-turbulence interaction, and mixing processes in environmental flows.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 2041-1723
Date made live: 07 May 2019 15:36 +0 (UTC)

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