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

Published online by Cambridge University Press:  02 December 2003

ALESSANDRA GIORGETTI
Affiliation:
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, I-34010 Sgonico (Trieste), Italy
ALESSANDRO CRISE
Affiliation:
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, I-34010 Sgonico (Trieste), Italy
ROBERTO LATERZA
Affiliation:
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, I-34010 Sgonico (Trieste), Italy
LUCIANO PERINI
Affiliation:
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, I-34010 Sgonico (Trieste), Italy
MICHELE REBESCO
Affiliation:
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, I-34010 Sgonico (Trieste), Italy
ANGELO CAMERLENGHI
Affiliation:
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, I-34010 Sgonico (Trieste), Italy

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.

Type
Research Article
Copyright
© Antarctic Science Ltd 2003

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