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Fill, flush, or shuffle: how is sediment carried through submarine channels to build lobes?

Fill, flush, or shuffle: how is sediment carried through submarine channels to build lobes?
Fill, flush, or shuffle: how is sediment carried through submarine channels to build lobes?

Submarine channels are the primary conduits for land-derived material, including organic carbon, pollutants, and nutrients, into the deep-sea. The flows (turbidity currents) that traverse these systems can pose hazards to seafloor infrastructure such as cables and pipelines. Here we use a novel combination of repeat seafloor surveys and turbidity current monitoring along a 50 km-long submarine channel in Bute Inlet, British Columbia, and discharge measurements from the main feeding river. These source-to-sink observations provide the most detailed information yet on magnitude-frequency-distance relationships for turbidity currents, and the spatial-temporal patterns of sediment transport within a submarine channel-lobe system. This analysis provides new insights into mass redistribution, and particle residence times in submarine channels, as well as where particles are eventually buried and how that is recorded in the deposits. We observe stepwise sediment transport down the channel, with turbidity currents becoming progressively less frequent with distance. Most flows dissipate and deposit within the proximal (< 11 km) part of the system, whilst longer run-out flows then pick up this sediment, ‘shuffling’ it further downstream along the channel. This shuffling occurs mainly through upstream migration of knickpoints, which can generate sediment bypass along the channel over timescales of 10–100 yrs. Infrequent large events flush the channel and ultimately transport sediment onto the lobe. These flushing events can occur without obvious triggers, and thus might be internally generated. We then present the first ever sediment budget analysis of an entire submarine channel system, which shows that the river input and lobe aggradation can approximately balance over decadal timescales. We conclude by discussing the implication of this sediment shuffling for seafloor geohazards and particle burial.

bypass, flushing, lobe, source to sink, submarine channel, turbidity current
0012-821X
Heijnen, Maarten
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Clare, Michael
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Cartigny, M.J.B.
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Talling, Peter J.
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Hage, Sophie
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Pope, Ed
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Bailey, Lewis
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Sumner, Esther
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Lintern, Gwyn
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Stacey, Cooper
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D., Parsons
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Simmons, S.
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Chen, Y.
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HUBBARD, S.
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Eggenhuisen, Joris T.
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Kane, Ian A.
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Hughes Clarke, J.E.
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Heijnen, Maarten
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Clare, Michael
b26da858-9c08-4784-aaa9-7092efcd94bd
Cartigny, M.J.B.
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Talling, Peter J.
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Hage, Sophie
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Pope, Ed
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Bailey, Lewis
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Sumner, Esther
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Lintern, Gwyn
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Stacey, Cooper
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D., Parsons
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Simmons, S.
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Chen, Y.
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HUBBARD, S.
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Eggenhuisen, Joris T.
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Kane, Ian A.
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Hughes Clarke, J.E.
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Heijnen, Maarten, Clare, Michael, Cartigny, M.J.B., Talling, Peter J., Hage, Sophie, Pope, Ed, Bailey, Lewis, Sumner, Esther, Lintern, Gwyn, Stacey, Cooper, D., Parsons, Simmons, S., Chen, Y., HUBBARD, S., Eggenhuisen, Joris T., Kane, Ian A. and Hughes Clarke, J.E. (2022) Fill, flush, or shuffle: how is sediment carried through submarine channels to build lobes? Earth and Planetary Science Letters, 584, [117481]. (doi:10.1016/j.epsl.2022.117481).

Record type: Article

Abstract

Submarine channels are the primary conduits for land-derived material, including organic carbon, pollutants, and nutrients, into the deep-sea. The flows (turbidity currents) that traverse these systems can pose hazards to seafloor infrastructure such as cables and pipelines. Here we use a novel combination of repeat seafloor surveys and turbidity current monitoring along a 50 km-long submarine channel in Bute Inlet, British Columbia, and discharge measurements from the main feeding river. These source-to-sink observations provide the most detailed information yet on magnitude-frequency-distance relationships for turbidity currents, and the spatial-temporal patterns of sediment transport within a submarine channel-lobe system. This analysis provides new insights into mass redistribution, and particle residence times in submarine channels, as well as where particles are eventually buried and how that is recorded in the deposits. We observe stepwise sediment transport down the channel, with turbidity currents becoming progressively less frequent with distance. Most flows dissipate and deposit within the proximal (< 11 km) part of the system, whilst longer run-out flows then pick up this sediment, ‘shuffling’ it further downstream along the channel. This shuffling occurs mainly through upstream migration of knickpoints, which can generate sediment bypass along the channel over timescales of 10–100 yrs. Infrequent large events flush the channel and ultimately transport sediment onto the lobe. These flushing events can occur without obvious triggers, and thus might be internally generated. We then present the first ever sediment budget analysis of an entire submarine channel system, which shows that the river input and lobe aggradation can approximately balance over decadal timescales. We conclude by discussing the implication of this sediment shuffling for seafloor geohazards and particle burial.

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Accepted/In Press date: 1 March 2022
Published date: 15 April 2022
Additional Information: Funding Information: MSH was supported by European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 721403 . MSH and MAC acknowledge funding through Climate Linked Atlantic Sector Science - NERC National Capability programme ( NE/R015953/1 ). MAC, MJCB, and PJT acknowledge funding from the Natural Environment Research Council (NERC), including “Environmental Risks to Infrastructure: Identifying and Filling the Gaps” ( NE/P005780/1 ), and “New field-scale calibration of turbidity current impact modelling” ( NE/P009190/1 ). MJBC was support by a Royal Society Research Fellowship ( DHF﹨R1﹨180166 ). Talling was supported by a NERC and Royal Society Industry Fellowship hosted by the International Cable Protection Committee. The authors also acknowledge discussions with collaborators as part of Talling's NERC International Opportunities Fund grant ( NE/M017540/1 ) “Coordinating and pump-priming international efforts for direct monitoring of active turbidity currents at global test sites”. ELP was supported by a Leverhulme Trust Early Career Fellowship ( ECF-2018-267 ). SH has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 899546 . We further thank the Canadian Geological Survey and Canadian Hydrographic Survey for data collection and processing, in particular Peter Neelands and Brent Seymour. We also thank the captains and crew of CCGS Vector. We thank two reviewers and the editor for helpful and constructive comments that improved the manuscript. Funding Information: MSH was supported by European Union's Horizon 2020 research and innovation programme under the Marie Sk?odowska-Curie grant agreement No. 721403. MSH and MAC acknowledge funding through Climate Linked Atlantic Sector Science - NERC National Capability programme (NE/R015953/1). MAC, MJCB, and PJT acknowledge funding from the Natural Environment Research Council (NERC), including ?Environmental Risks to Infrastructure: Identifying and Filling the Gaps? (NE/P005780/1), and ?New field-scale calibration of turbidity current impact modelling? (NE/P009190/1). MJBC was support by a Royal Society Research Fellowship (DHF?R1?180166). Talling was supported by a NERC and Royal Society Industry Fellowship hosted by the International Cable Protection Committee. The authors also acknowledge discussions with collaborators as part of Talling's NERC International Opportunities Fund grant (NE/M017540/1) ?Coordinating and pump-priming international efforts for direct monitoring of active turbidity currents at global test sites?. ELP was supported by a Leverhulme Trust Early Career Fellowship (ECF-2018-267). SH has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 899546. We further thank the Canadian Geological Survey and Canadian Hydrographic Survey for data collection and processing, in particular Peter Neelands and Brent Seymour. We also thank the captains and crew of CCGS Vector. We thank two reviewers and the editor for helpful and constructive comments that improved the manuscript. Publisher Copyright: © 2022 The Author(s)
Keywords: bypass, flushing, lobe, source to sink, submarine channel, turbidity current

Identifiers

Local EPrints ID: 457622
URI: http://eprints.soton.ac.uk/id/eprint/457622
ISSN: 0012-821X
PURE UUID: 7b6f6adc-ca64-4459-a2b3-6df0f4500aa3

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Date deposited: 14 Jun 2022 16:43
Last modified: 14 Jun 2022 16:44

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Contributors

Author: Maarten Heijnen
Author: Michael Clare
Author: M.J.B. Cartigny
Author: Peter J. Talling
Author: Sophie Hage
Author: Ed Pope
Author: Lewis Bailey
Author: Esther Sumner
Author: Gwyn Lintern
Author: Cooper Stacey
Author: Parsons D.
Author: S. Simmons
Author: Y. Chen
Author: S. HUBBARD
Author: Joris T. Eggenhuisen
Author: Ian A. Kane
Author: J.E. Hughes Clarke

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