Understanding the dynamics of submarine density flows through direct observations from modern systems

Abstract

Submarine density flows are the volumetrically most important process for
transporting sediment across our planet and form the largest sediment
accumulations on Earth. Current models for turbidity currents are largely based
on experimental and numerical models, and inferences from deposits in the
geological record. This thesis provides a new understanding of the structure of
submarine density flows through the analysis of direct measurements of
submarine density currents near the seafloor. This is achieved by the analysis of
datasets of density flows collected in two submarine channel systems: Congo
Submarine Canyon and a channel on the Black Sea Shelf. The analysis of new
measurements of submarine density flows suggests a new structure for
submarine density flows that contrasts with previous models. The new structure
shows that the flow front is the fastest part of the flow that outruns the rest of
the flow. The difference in velocities between the front and end of the flow
results in a flow stretching. This model contrasts with previous field observations of submarine flows collected in coarser sediment submarine channel systems.
This thesis also analyses the cross-stream evolution of submarine density flows
through meandering submarine channel systems. This new model studies the evolution of the flow processes around meanders, and suggests different
scenarios of the flow structure based on the dominant process. This document
links the evolving structure of the flow around bends with the sediment
distribution of the submarine channel systems, and reconciles discrepancies
among earlier models. This thesis provides a better understanding of the
complexity of the system formed by submarine density flows and the interaction
of these flows with seafloor sediment and channel morphology.

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