158
L. R. M. Maas et al.
Recall that the displacements defined above, present scaled pressure perturbations that can have different origins. BPRs, however, are not (or very marginally)
subject to blow-downs and the interpretation of pressure variations as being due to
surface tidal displacements is unambiguous, although we need to remember that an
upward sea surface elevation corresponds to a negative displacement. As Fig. 4f–
h show, blow-downs seem to be nearly absent at all depths on the most Eastern
mooring, lmc8. Together with the bottom-pressure records from two other periods
Table 4 Mean and standard deviation of the variance of the total HP-filtered signal, the tidal signal,
and the percent variance explained by the tides predicted from harmonic analyses of MC pressure
sensor measurements. Values were computed by averaging all estimates from MT_TIDE. The standard deviation for each estimate is also indicated. Notice that the BPR at lmc5a lasts only seven
months making it impossible to establish the evolution of its amplitude and phase. Recall that the
mean and trend were removed before the harmonic analysis
Mooring site –
Instrument depth (m)
Meters above bottom
(mab)
Total Var. (m 2 )
Tidal Var. (m 2 )
Tidal Var. (%)
lmc5 – 617 m
(1375 mab)
1.4369 ± 0.3655
1.1491 ± 0.1711
81.9529
lmc5 – 1020 m
(972 mab)
1.2545 ± 0.2763
1.0681 ± 0.1425
86.5204
lmc5 – 1520 m
(472 mab)
1.0815 ± 0.1708
0.9809 ± 0.0986
91.4791
lmc5 – 1966 m
(26 mab)
0.8823 ± 0.0100
0.8744 ± 0.0097
99.1022
lmctrap – 2200 m
(41 mab)
0.7923 ± 0.0106
0.7710 ± 0.0166
97.3134
lmc5a – 1520 m
(882 mab)
1.2189 ± 0.2256
1.0639 ± 0.1546
88.3847
lmc5a – 1975 m
(427 mab)
1.0412 ± 0.1270
0.9825 ± 0.1076
94.6039
lmc5a – 2375 m
(27 mab)
0.8669
0.8604
99.2438
lmc6 – 985 m
(1706 mab)
1.5220 ± 0.1595
1.0794 ± 0.1243
70.8571
lmc6 – 1960 m (731
mab)
1.2055 ± 0.0929
1.0133 ± 0.0802
84.0482
lmc6 – 2650 m (41
mab)
0.9243 ± 0.0165
0.9160 ± 0.0132
99.1108
lmc8 – 625 m (1574
mab)
0.9321 ± 0.0546
0.8158 ± 0.0239
87.7736
lmc8 – 1025 m (1174
mab)
0.9160 ± 0.0474
0.8206 ± 0.0224
89.7537
lmc8 – 2125 m (74
mab)
0.8293 ± 0.0073
0.8236 ± 0.0076
99.3154
L. R. M. Maas et al.
Recall that the displacements defined above, present scaled pressure perturbations that can have different origins. BPRs, however, are not (or very marginally)
subject to blow-downs and the interpretation of pressure variations as being due to
surface tidal displacements is unambiguous, although we need to remember that an
upward sea surface elevation corresponds to a negative displacement. As Fig. 4f–
h show, blow-downs seem to be nearly absent at all depths on the most Eastern
mooring, lmc8. Together with the bottom-pressure records from two other periods
Table 4 Mean and standard deviation of the variance of the total HP-filtered signal, the tidal signal,
and the percent variance explained by the tides predicted from harmonic analyses of MC pressure
sensor measurements. Values were computed by averaging all estimates from MT_TIDE. The standard deviation for each estimate is also indicated. Notice that the BPR at lmc5a lasts only seven
months making it impossible to establish the evolution of its amplitude and phase. Recall that the
mean and trend were removed before the harmonic analysis
Mooring site –
Instrument depth (m)
Meters above bottom
(mab)
Total Var. (m 2 )
Tidal Var. (m 2 )
Tidal Var. (%)
lmc5 – 617 m
(1375 mab)
1.4369 ± 0.3655
1.1491 ± 0.1711
81.9529
lmc5 – 1020 m
(972 mab)
1.2545 ± 0.2763
1.0681 ± 0.1425
86.5204
lmc5 – 1520 m
(472 mab)
1.0815 ± 0.1708
0.9809 ± 0.0986
91.4791
lmc5 – 1966 m
(26 mab)
0.8823 ± 0.0100
0.8744 ± 0.0097
99.1022
lmctrap – 2200 m
(41 mab)
0.7923 ± 0.0106
0.7710 ± 0.0166
97.3134
lmc5a – 1520 m
(882 mab)
1.2189 ± 0.2256
1.0639 ± 0.1546
88.3847
lmc5a – 1975 m
(427 mab)
1.0412 ± 0.1270
0.9825 ± 0.1076
94.6039
lmc5a – 2375 m
(27 mab)
0.8669
0.8604
99.2438
lmc6 – 985 m
(1706 mab)
1.5220 ± 0.1595
1.0794 ± 0.1243
70.8571
lmc6 – 1960 m (731
mab)
1.2055 ± 0.0929
1.0133 ± 0.0802
84.0482
lmc6 – 2650 m (41
mab)
0.9243 ± 0.0165
0.9160 ± 0.0132
99.1108
lmc8 – 625 m (1574
mab)
0.9321 ± 0.0546
0.8158 ± 0.0239
87.7736
lmc8 – 1025 m (1174
mab)
0.9160 ± 0.0474
0.8206 ± 0.0224
89.7537
lmc8 – 2125 m (74
mab)
0.8293 ± 0.0073
0.8236 ± 0.0076
99.3154