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Different types of sediment gravity flows detected in the Var submarine canyon (northwestern Mediterranean Sea)
Language
English
Obiettivo Specifico
1.8. Osservazioni di geofisica ambientale
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/106 (2013)
ISSN
0079-6611
Electronic ISSN
1873-4472
Publisher
Elsevier Science Limited
Pages (printed)
138-153
Issued date
September 19, 2012
Keywords
Abstract
Current velocities and vertical sediment fluxes in the Var submarine canyon were assessed at three stations
respectively at 800 m, 1200 m and 1800 m depth, using moorings deployed for 4 months during
winter 2008–2009. During this period, we observed three major sediment gravity flows, all characterized
by sudden increases in current velocity that lasted 2–5 h and by downward particle fluxes. Each gravity
flow, described using a high frequency current meter and two Acoustic Doppler Current Profiler (75 and
300 kHz ADCP) showed distinctive features. The first event, triggered during a flood of the Var River, was
determined to be a hyperpycnal current with a large vertical extent (>100 m high) and relatively low
velocity (40 cm s 1). The second event, observed after a Var River flood, was more energetic with a maximum
horizontal current peak of 60 cm s 1 but with a low vertical extent (30 m high). This event was
considered to be a turbidity landslide. The third was the result of a local canyon wall failure. It was characterized
by a speed of >85 cm s 1. These peaks of current speed were associated with large clouds of
material that transported sediment along the canyon and reached up to 200 g m 2 d 1 of sediment
(>1 g m 2 d 1 of organic carbon). Our measurements in the Var canyon show the important role of gravity
flows transporting particulate matter to the deep-sea floor. These large inputs of sediment and organic
carbon may have a significant impact on deep-sea carbon storage in the Mediterranean Sea.
respectively at 800 m, 1200 m and 1800 m depth, using moorings deployed for 4 months during
winter 2008–2009. During this period, we observed three major sediment gravity flows, all characterized
by sudden increases in current velocity that lasted 2–5 h and by downward particle fluxes. Each gravity
flow, described using a high frequency current meter and two Acoustic Doppler Current Profiler (75 and
300 kHz ADCP) showed distinctive features. The first event, triggered during a flood of the Var River, was
determined to be a hyperpycnal current with a large vertical extent (>100 m high) and relatively low
velocity (40 cm s 1). The second event, observed after a Var River flood, was more energetic with a maximum
horizontal current peak of 60 cm s 1 but with a low vertical extent (30 m high). This event was
considered to be a turbidity landslide. The third was the result of a local canyon wall failure. It was characterized
by a speed of >85 cm s 1. These peaks of current speed were associated with large clouds of
material that transported sediment along the canyon and reached up to 200 g m 2 d 1 of sediment
(>1 g m 2 d 1 of organic carbon). Our measurements in the Var canyon show the important role of gravity
flows transporting particulate matter to the deep-sea floor. These large inputs of sediment and organic
carbon may have a significant impact on deep-sea carbon storage in the Mediterranean Sea.
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