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Efficient burial of carbon in a submarine canyon

Efficient burial of carbon in a submarine canyon
Efficient burial of carbon in a submarine canyon
Burial of organic carbon (OC) in marine sediments moderates atmospheric CO2 levels on geological time scales, but uncertainties remain about how much OC is buried and about the efficiency of OC burial, particularly in heterogeneous seafloor environments such as ocean margins. Here we describe OC burial in Nazaré submarine canyon and the adjacent continental slope off Portugal, an area within which sedimentation rates vary by three orders of magnitude. Using a nested series of observations at different scales, ranging from regional bathymetry to sediment cores, we estimate the annual sediment and OC deposited in the canyon at 620,000 t and 12,500 t, respectively. Nazaré Canyon is thus a significant sink of both sediment and OC. Canyon sediments typically contain ~2% OC, both in surface sediments and at depth, and there is a limited correlation between sedimentation rate and OC content. The likely explanation is that the OC has already survived a lengthy period of degradation prior to deposition in the canyon, such that additional exposure to oxygenated water has minimal effect. Burial efficiency is difficult to calculate because of extensive resuspension and reworking of OC in the upper canyon, but probably exceeds 30% in areas of high sedimentation. These areas are shown to be 30 times more effective in burying OC than adjacent areas of the continental slope, indicating that Nazaré Canyon is a hitherto overlooked sink of OC on a continental margin where OC burial is otherwise low.
0091-7613
831-834
Masson, D.G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45
Huvenne, V.A.I.
f22be3e2-708c-491b-b985-a438470fa053
de Stigter, H.C.
678af78b-39eb-49f2-af00-cb0c00f20cc5
Wolff, G.A.
3a42c086-8356-449b-9d40-9b16758733c2
Kiriakoulakis, K.
d9834ec4-e9a3-4dd3-8226-fe1da2514471
Arzola, R.G.
403ebca0-9574-4cfa-bbe5-03ba68731df0
Blackbird, S.
3b14f07c-a7d3-4567-b10a-37a722cf83f7
Masson, D.G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45
Huvenne, V.A.I.
f22be3e2-708c-491b-b985-a438470fa053
de Stigter, H.C.
678af78b-39eb-49f2-af00-cb0c00f20cc5
Wolff, G.A.
3a42c086-8356-449b-9d40-9b16758733c2
Kiriakoulakis, K.
d9834ec4-e9a3-4dd3-8226-fe1da2514471
Arzola, R.G.
403ebca0-9574-4cfa-bbe5-03ba68731df0
Blackbird, S.
3b14f07c-a7d3-4567-b10a-37a722cf83f7

Masson, D.G., Huvenne, V.A.I., de Stigter, H.C., Wolff, G.A., Kiriakoulakis, K., Arzola, R.G. and Blackbird, S. (2010) Efficient burial of carbon in a submarine canyon. Geology, 38 (9), 831-834. (doi:10.1130/G30895.1).

Record type: Article

Abstract

Burial of organic carbon (OC) in marine sediments moderates atmospheric CO2 levels on geological time scales, but uncertainties remain about how much OC is buried and about the efficiency of OC burial, particularly in heterogeneous seafloor environments such as ocean margins. Here we describe OC burial in Nazaré submarine canyon and the adjacent continental slope off Portugal, an area within which sedimentation rates vary by three orders of magnitude. Using a nested series of observations at different scales, ranging from regional bathymetry to sediment cores, we estimate the annual sediment and OC deposited in the canyon at 620,000 t and 12,500 t, respectively. Nazaré Canyon is thus a significant sink of both sediment and OC. Canyon sediments typically contain ~2% OC, both in surface sediments and at depth, and there is a limited correlation between sedimentation rate and OC content. The likely explanation is that the OC has already survived a lengthy period of degradation prior to deposition in the canyon, such that additional exposure to oxygenated water has minimal effect. Burial efficiency is difficult to calculate because of extensive resuspension and reworking of OC in the upper canyon, but probably exceeds 30% in areas of high sedimentation. These areas are shown to be 30 times more effective in burying OC than adjacent areas of the continental slope, indicating that Nazaré Canyon is a hitherto overlooked sink of OC on a continental margin where OC burial is otherwise low.

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Published date: September 2010
Organisations: Marine Geoscience

Identifiers

Local EPrints ID: 162575
URI: http://eprints.soton.ac.uk/id/eprint/162575
ISSN: 0091-7613
PURE UUID: 4608cc19-1453-4541-a10f-76a18b12e088
ORCID for V.A.I. Huvenne: ORCID iD orcid.org/0000-0001-7135-6360

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Date deposited: 24 Aug 2010 10:20
Last modified: 14 Mar 2024 02:49

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Contributors

Author: D.G. Masson
Author: V.A.I. Huvenne ORCID iD
Author: H.C. de Stigter
Author: G.A. Wolff
Author: K. Kiriakoulakis
Author: R.G. Arzola
Author: S. Blackbird

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