Scripps Institute of Oceanography

ALACE PLOTS FROM DRAKE PASSAGE DEPLOYMENT

by Russ Davis
 
In January 1990 ten Autonomous Lagrangian Circulation Explorer (ALACE) floats were 
deployed from the Meteor in Drake Passage, north of the Polar Front, at a nominal 
depth of 750m. Ten floats were deployed; two failed to report after their first or 
second ascent and the remaining eight are still functioning nominally in September 
1990.  

These floats remained submerged for 14 days and were on the surface for almost 24 
hours.  The float rise velocity is greater than a kilometer per hour but the des-
cent velocity varies from 700 m/hour near the surface to near zero at the equili-
brium depth. ALACE position reports are presented as vector displacements between 
the dive position and the surfacing position, that is the displacement while sub-
merged over a period of 14 days. These positions are estimated by fitting the ob-
served surface positions to a model of a steady current plus an inertial motion & 
extrapolating to the dive and surfacing times. The gaps between displacement vec-
tors represent the on-surface motion over a 24 hour period. 

The floats report battery voltage and their depth. Seven of the floats are report-
ing depths between 720 and 770 meters; one reports 825 m. Battery voltage change 
is as expected but a prediction of life hinges on knowing the minimum operating 
voltage. This has been estimated from a realistic laboratory simulation and in-
dicates that the design life of 50 cycles (here over 2+ years) will be achieved.