Two of the instruments on this mooring carried pressure sensors that
worked - the two shallowest MicroCats. The pressure records from these
instruments were consistent in two important ways: they showed that
1. Both instruments were initally about 27 meters deeper than
the values that appear in the installation and recovery logs
(the "nominal depths").
2. The mooring slid deeper during the year. Most of the depth
change occurred around 19 August 2004. By 26 August the mooring
was about 27 meters deeper than at installation, and it remained
at that depth for the rest of the year.
Note that the number 27 occurs twice: the actual initial depth was 27
meters greater than the nominal value, and then subsequent to installation
the mooring slid a further 27 meters deeper.
The initial depth of the top MicroCat (s/n 2504) is calculated as
follows: This instrument recorded a minimum pressure of 394.0 db, which
corresponds to a depth of 390.7 meters using the Reid pressure-depth
relationship. The second MicroCat (s/n 2532) recorded a minimum pressure
of 493.5 db which corresponds to a depth of 489.2 meters. Rounding and
splitting the difference, we can put the two MicroCats, which were 100
meters apart, at 390 and 490 meters respectively (initially), which is
27 meters greater than their given depths.
This implies that the initial seafloor depth, given as 664 meters,
should really be 691 meters. That is the depth used in this data report.
In general, the depths given here, in cases where the mooring moved, are
initial depths.
Move up one level.