Two YSI Inc. probes (#13341 and #13251) were used in a dual-sensor configuration during the 1996 cruises. The new procedures implemented in late 1995 to check for possible sensor problems (Section 4.7), were followed during 1996, and in-lab checks of atmospheric oxygen level recommended by Sea-Bird were performed before every cruise. Sensor #13251 was calibrated and its membrane and electrolyte were replaced at Sea-Bird on 15 December 1995, in addition replacement of the membrane and electrolyte were performed in our lab on sensor #13251 before cruise HOT-70 and replacement of electrolyte on both sensors before cruise HOT-76. These measures have resulted in oxygen traces with less drift throughout cruises than in previous years.

     Only the data from sensor #13251 are reported here for all cruises, the other sensor (#13341) showed a slight drift during some of the cruises.

     Two sets of calibration parameters were usually obtained per cruise, corresponding to the casts at Stations 1 and 2. During HOT-70, there was a slight drift in the CTD oxygen sensor throughout Station 2 casts. This cruise required two sets of calibration parameters at Station 2. Cruise ALOHA-Climax 1 (AC-1) required five sets of calibration coefficients. Each set of coefficients was obtained from stations grouped in adjacent geographical locations as follows: station 1; stations 2 and 9; stations 3, 7 and 8; stations 4 and 6; and station 5.

     Table 4.8a gives the means and standard deviations for the final calibrated CTD oxygen values minus the water sample values for the regular HOT cruises and Table 4.8b for the ALOHA-Climax cruise.

Table 4.8a: CTD-Bottle Dissolved Oxygen per Cruise (µmol kg-1)

 

 

 

Station 1, Kahe Point

Station 2, ALOHA

 

 

0 to 1500 dbar

0 to 4700 dbar

500 to 4700 dbar

Cruise

Sensor #

Mean

SD

Mean

SD

Mean

SD

69

13251

0.01

1.12

0.01

1.98

0.16

0.97

70

13251

0.01

0.80

-0.02

1.51

-0.07

1.27

71

13251

0.01

1.26

0.30

1.88

0.65

1.41

72

13251

0.00

1.00

0.16

1.32

0.43

0.85

73

13251

-0.01

1.79

0.07

1.19

0.19

0.72

74

13251

0.00

1.37

0.12

1.64

0.28

0.91

75

13251

0.34

1.80

0.12

1.46

0.25

1.18

76

13251

0.01

2.13

0.16

1.43

0.15

0.99

77

13251

0.01

1.60

0.18

1.18

0.20

0.84

78

13251

0.02

1.46

0.08

1.04

0.07

0.80

Table 4.8b: CTD-Bottle Dissolved Oxygen during AC-1 (µmol kg-1)

AC-1

 

0-1500 dbars

Stations

Sensor #

Mean

SD

1

13251

0.00

1.08

2, 9

13251

-0.01

1.71

3, 7, 8

13251

0.02

2.29

4, 6

13251

0.04

2.42

5

13251

-0.01

1.13

Figure 4.9 shows the CTD oxygen data quality for every 2-dbar bin in each cast at Station ALOHA for cruises 69 through 78.

Figure 4.9. CTD oxygen data quality per cast (vertical bars) and per 2-dbar bin at Station ALOHA during HOT cruises 69 through 78. The tick marks along the x-axis separate different casts. Casts from the same cruise are separated by vertical black lines.

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