4.7. Year 7, 1995

Two YSI Inc. probes (#13341 and #13251) were used in a dual-sensor configuration during the 1995 cruises. The sensors were empirically calibrated following procedures described previously. Two sets of calibration parameters were usually obtained per cruise, corresponding to the casts at Stations 1 (Kahe) and 2 (ALOHA). In some of the 1995 cruises there was an obvious drift in the CTD oxygen sensors throughout Station 2 casts, apparently due to sensor electrolyte depletion. These cruises required more than one set of calibration parameters at Station 2.

During some of the 1995 cruises, scientists from the University of Washington obtained additional bottle oxygen measurements. These data were also used in the CTD sensors calibrations.

A new procedure has been implemented to check for possible sensor problems. The data from the sensor pair is plotted after each cast. In addition, before each cruise the sensor's membrane is inspected closely for wrinkles or tears, and for air bubbles in the electrolyte reservoir. Replacement of the membrane and electrolyte was performed on both sensors before cruises HOT-64 and HOT-66, on sensor #13251 before HOT-60, and on sensor #13341 before HOT-62.

Only the data from sensor #13341 are reported here for all cruises. This sensor showed less drift during cruises than sensor #13251. Table 4.7 gives the means and standard deviations for the final calibrated CTD oxygen values minus the water sample values.

Table 4.7: CTD-bottle Dissolved Oxygen per Cruise.

Mean and standard deviation (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
60	13341	0.03	1.38	0.17	1.87	0.32	1.53
61	13341	-0.35	1.41	-0.06	1.53	0.02	1.51
62	13341	-0.29	2.42	-0.23	2.18	0.00	1.90
63	13341	-0.41	1.71	-0.01	2.23	0.32	2.52
64	13341	0.11	2.26	-0.35	2.18	-0.37	2.18
65	13341	0.01	1.98	0.45	2.24	0.51	1.73
66	13341	0.01	1.83	-0.41	2.07	0.02	1.32
67	13341	0.01	2.58	0.41	2.20	0.82	1.76
68	13341	0.01	1.57	-0.01	1.84	0.24	2.13

Figure 4.8 shows the CTD oxygen data quality for every 2-dbar bin in each cast at Station ALOHA for cruises 60 through 68.

Figure 4.8. CTD oxygen data quality per cast (vertical bars) and per 2-dbar bin at Station ALOHA during HOT cruises 60 through 68. The tick marks along the x-axis separate different casts. Casts from the same cruise are separated by vertical black lines.

Back to Table of Contents