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Antarctic Science

Table of Contents - 2003 - Volume 15, Issue 04  


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

ALESSANDRA GIORGETTI a1c1, ALESSANDRO CRISE a1, ROBERTO LATERZA a1, LUCIANO PERINI a1, MICHELE REBESCO a1 and ANGELO CAMERLENGHI a1
a1 Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, I-34010 Sgonico (Trieste), Italy

Article author query
giorgetti a   [PubMed][Google Scholar] 
crise a   [PubMed][Google Scholar] 
laterza r   [PubMed][Google Scholar] 
perini l   [PubMed][Google Scholar] 
rebesco m   [PubMed][Google Scholar] 
camerlenghi a   [PubMed][Google Scholar] 

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.

(Received February 11 2003)
(Accepted August 22 2003)


Key Words: Bellingshausen Sea; bottom current; oceanography; sediment mound; turbulent Ekman layer.

Correspondence:
c1 agiorgetti@ogs.trieste.it

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