Transition of a Hyperpycnal Flow Into a Saline Turbidity Current Due to Differential Diffusivities

Abstract. Turbidity currents are one of the main drivers for sediment transport from the continental shelf to the deep ocean. The resulting sediment deposits can reach hundreds of kilometres into the ocean. Computer models that simulate turbidity currents and the resulting sediment deposit can help to understand their general behaviour. However, in order to recreate real-world scenarios, the challenge is to find the turbidity current parameters that reproduce the observations of sediment deposits. This paper demonstrates a solution to the inverse sediment transportation problem: for a known sedimentary deposit, the developed model reconstructs details about the turbidity current that produced these deposits. The reconstruction is constrained here by a shallow water sediment-laden density current model, which is discretised by the finite element method and an adaptive time-stepping scheme. The model is differentiated using the adjoint approach and an efficient gradient-based optimisation method is applied to identify turbidity parameters which minimise the misfit between modelled and observed field sediment deposits. The capabilities of this approach are demonstrated using measurements taken in the Miocene-age Marnoso Arenacea Formation (Italy). We find that whilst the model cannot match the deposit exactly due to limitations in the physical processes simulated, it provides valuable insights into the depositional processes and represents a significant advance in our toolset for interpreting turbidity current deposits.

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TURBIDITY-CURRENT DEPOSITS IN SAN PEDRO AND SANTA MONICA BASINS OFF SOUTHERN CALIFORNIA

Geological Society of America Bulletin ◽

10.1130/0016-7606(1959)70[279:tdispa]2.0.co;2 ◽

1959 ◽

Vol 70 (3) ◽

pp. 279 ◽

Cited By ~ 99

Author(s):

DONN S. GORSLINE ◽

K. O. EMERY

Keyword(s):

Southern California ◽

Turbidity Current ◽

San Pedro ◽

Santa Monica

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Modeling of Breaching-Generated Turbidity Currents Using Large Eddy Simulation

Journal of Marine Science and Engineering ◽

10.3390/jmse8090728 ◽

2020 ◽

Vol 8 (9) ◽

pp. 728

Author(s):

Said Alhaddad ◽

Lynyrd de Wit ◽

Robert Jan Labeur ◽

Wim Uijttewaal

Keyword(s):

Experimental Data ◽

Numerical Model ◽

Large Eddy Simulation ◽

Flow Characteristics ◽

Turbidity Current ◽

Turbidity Currents ◽

Eddy Simulation ◽

Failure Evolution ◽

Large Eddy ◽

Flow Slides

Breaching flow slides result in a turbidity current running over and directly interacting with the eroding, submarine slope surface, thereby promoting further sediment erosion. The investigation and understanding of this current are crucial, as it is the main parameter influencing the failure evolution and fate of sediment during the breaching phenomenon. In contrast to previous numerical studies dealing with this specific type of turbidity currents, we present a 3D numerical model that simulates the flow structure and hydrodynamics of breaching-generated turbidity currents. The turbulent behavior in the model is captured by large eddy simulation (LES). We present a set of numerical simulations that reproduce particular, previously published experimental results. Through these simulations, we show the validity, applicability, and advantage of the proposed numerical model for the investigation of the flow characteristics. The principal characteristics of the turbidity current are reproduced well, apart from the layer thickness. We also propose a breaching erosion model and validate it using the same series of experimental data. Quite good agreement is observed between the experimental data and the computed erosion rates. The numerical results confirm that breaching-generated turbidity currents are self-accelerating and indicate that they evolve in a self-similar manner.

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