Different types of sediment gravity flows detected in the Var submarine canyon (northwestern Mediterranean Sea)

Type Article
Date 2012-11
Language English
Author(s) Khripounoff AlexisORCID1, Crassous Philippe1, Lo Bue N.2, Dennielou BernardORCID3, Silva Jacinto Ricardo3
Affiliation(s) 1 : IFREMER Brest, Dep REM EEP LEP, F-29280 Plouzane, France.
2 : INGV, I-00143 Rome, Italy.
3 : IFREMER Brest, Dep REM GM, F-29280 Plouzane, France.
Source Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2012-11 , Vol. 106 , P. 138-153
DOI 10.1016/j.pocean.2012.09.001
WOS© Times Cited 32
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) 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. (C) 2012 Elsevier Ltd. All rights reserved.
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