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

• Published in: Antarctic Science
• Main Authors: GIORGETTI, ALESSANDRA, CRISE, ALESSANDRO, LATERZA, ROBERTO, PERINI, LUCIANO, REBESCO, MICHELE, CAMERLENGHI, ANGELO
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2003
• Subjects: Geology; Ecology, Evolution, Behavior and Systematics; Oceanography; Antarctic; The Antarctic; Antarctic Peninsula; Pacific; Antarc*; Antarctic Science
• Online Access: http://dx.doi.org/10.1017/s0954102003001652; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102003001652

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.