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http://hdl.handle.net/2122/8650
Authors: | Khripounoff, A.* Crassous, P.* Lo Bue, N.* Dennielou, B.* Silva Jacinto, R.* |
Title: | Different types of sediment gravity flows detected in the Var submarine canyon (northwestern Mediterranean Sea) | Journal: | Progress in Oceanography | Series/Report no.: | /106 (2013) | Publisher: | Elsevier Science Limited | Issue Date: | 19-Sep-2012 | DOI: | 10.1016/j.pocean.2012.09.001 | Keywords: | submarine canyon gravity flows |
Subject Classification: | 03. Hydrosphere::03.02. Hydrology::03.02.02. Hydrological processes: interaction, transport, dynamics | 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. |
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