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Water masses and bottom boundary layer dynamics above a sediment drift of the Antarctic Peninsula Pacific Margin

  • ALESSANDRA GIORGETTI (a1), ALESSANDRO CRISE (a1), ROBERTO LATERZA (a1), LUCIANO PERINI (a1), MICHELE REBESCO (a1) and ANGELO CAMERLENGHI (a1)...
Abstract

Data from eight CTD casts and two one-year long current time series collected at 8 and 60 m above the seafloor of a sediment drift, off the Pacific Margin of the Antarctic Peninsula are presented, with special emphasis on bottom boundary layer dynamics and processes relevant to sediment settling and re-suspension. The water masses over the drift are characterized, including also a comparison with other measurements available from that region. The south-westward flow along the continental rise exhibits a strong topographic (bathymetric) control in the near-bottom current regime. A consistent mean flow deflection between an upper and lower current regime suggests that only the lower regime falls within a bottom (turbulent) Ekman layer. The bottom current regime is not energetic enough to maintain the coarse sediment fraction in suspension. The absence of evidence for a nepheloid layer justifies the assumption that most sediment was supplied to the margin during glacial periods. Two events, with peak velocities of up to 20 cm s−1, are associated with barotropic eddies shown as negative (cyclonic) mean sea level anomalies detected by ERS/TOPEX satellite altimeters. These energetic bottom current pulses may give way to episodic sediment re-suspensions of the sortable (non-cohesive) part of the sediment, thus exerting a minor role in redistributing fine sediments through the mean flow regime.

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Corresponding author
agiorgetti@ogs.trieste.it
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Antarctic Science
  • ISSN: 0954-1020
  • EISSN: 1365-2079
  • URL: /core/journals/antarctic-science
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