Investigator: Dr. Akihiko Murata Organization:Research Institute for Global Change (RIGC)/Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
Address: 2-15, Natsushima-cho, Yokosuka, Kanagawa, 237-0061, Japan
Vessel:
Vessel Name: Mirai
Vessel ID: JNSR
Country: Japan
Vessel Owner: JAMSTEC
Equilibrator Design:
Equilibrator type: Shower-head type equilibrator
Equilibrator volume (L): 1.2
Water_Flow_Rate (L/min): 5-8
Headspace_Gas_Flow_Rate (L/min): 0.6-0.8
Vented: During equilibrium, closed circulation of air. When measured by NDIR, vented to ambient air.
Measurement Method:
Continuous underway measurements of atmospheric and surface seawater pCO2 were made with the CO2 measuring system (Nippon ANS, Ltd) installed in the R/V Mirai of JAMSTEC. The system comprises of a non-dispersive infrared gas analyzer (NDIR; BINOSR model 4.1, Fisher-Rosemount) or the variations, an air-circulation module and a showerhead-type equilibrator. To measure concentrations (mole fraction) of CO2 in dry air (xCO2a), air sampled from the bow of the ship (approx. 30 m above the sea level) was introduced into the NDIR through a dehydrating route with an electric dehumidifier (kept at ~ 2 °C), a Perma Pure dryer (GL Sciences Inc.), and a chemical desiccant (Mg(ClO4)2). The flow rate of the air was 500 ml min-1. To measure surface seawater concentrations of CO2 in dry air (xCO2s), the air equilibrated with seawater within the equilibrator was introduced into the NDIR through the same flow route as the dehydrated air used in measuring xCO2a. The flow rate of the equilibrated air was 600 - 800 ml min-1. The seawater was taken by a pump from the intake placed at the approx. 4.5 m below the sea surface. The flow rate of seawater in the equilibrator was 500 - 800 ml min-1.
The CO2 measuring system was set to repeat the measurement cycle such as 4 kinds of CO2 standard gases (Table 1), xCO2a (twice), xCO2s (7 times). This measuring system was run automatically throughout cruises by a PC control. Effects of water temperature increased between the inlet of surface seawater and the equilibrator on xCO2s were adjusted based on Gordon and Jones (1973), although the temperature increases were slight, being ~ 0.5 °C at maximum.
Gordon, L. I. and L. B. Jones (1973), The effect of temperature on carbon dioxide partial pressure in seawater. Mar. Chem., 1, 317 - 322.
Manufacturer of Calibration Gas:
Concentrations of CO2 of the standard gases are listed in Table 1, which were calibrated by the JAMSTEC primary standard gases after 2000 (MR00-K01 and later). Before that time, the standard gases were calibrated against the scale of the Meteorological Research Institute, Tsukuba, Japan, and fitted to the 1985 World Meteorological Organization scale by using the equation of Inoue et al. (1995). The CO2 concentrations of the primary standard gases were calibrated by C. D. Keeling of the Scripps Institution of Oceanography, La Jolla, CA, USA. The values are 230.33 ppm (Cyl. No. 11325), 259.74 (11326), 279.67 (11327), 308.93 (11328), 328.25 (11329), 348.79 (11330), 369.55 (11331), 389.54 (11333), 411.60 (11334), 440.94 (11335), 460.42 (11336), and 478.54 (11337).
Since differences of concentrations of the standard gases between before and after the cruise were all allowable (< 0.1 ppmv), the averaged concentrations (Table 1) were adopted for the subsequent calculations.
Table 1. Concentrations of standard gases used in individual cruises.
Cruise #
STD1
STD2
STD3
STD4
Remark
MR98-06
-
-
-
-
No records left
MR98-K01
270.28
330.95
360.48
410.85
MR99-K02
270.28
330.95
360.48
410.85
MR99-K04
270.26
330.98
360.43
410.85
MR99-K05
247.74
304.98
333.32
382.57
MR00-K01
329.71
359.17
409.39
439.94
MR00-K03
269.60
329.71
359.17
439.94
269.60
329.71
359.17
409.39
MR00-K06
246.95
305.13
333.44
382.74
305.13
333.44
382.74
409.40
MR01-K02
269.60
329.74
359.22
409.39
MR01-K03
269.60
329.74
359.22
409.39
MR01-K04 Leg1
298.56
321.17
370.75
439.95
MR01-K04 Leg2
298.56
321.17
370.75
439.95
MR01-K05 Leg1-2
247.99
298.56
321.17
370.75
MR01-K05 Leg3-4
247.99
298.56
321.17
370.75
MR02-K03
269.20
329.52
359.11
408.76
MR02-K05 Leg1
246.69
297.83
320.05
391.66
MR03-K01
270.16
340.21
371.39
389.97
MR03-K02
270.08
328.87
359.10
409.23
MR03-K04 Leg1
270.08
328.87
359.10
409.23
MR03-K04 Leg2
270.08
328.87
359.10
409.23
MR03-K04 Leg4
270.08
328.87
359.10
409.23
MR03-K04 Leg5
268.84
330.16
369.37
414.39
MR04-04
268.85
328.87
369.39
414.43
MR04-05
268.84
330.16
369.37
414.39
MR05-02
262.94
320.42
381.04
420.76
MR05-05 Leg1
262.94
320.42
381.04
420.76
MR05-05 Leg2
262.94
320.42
381.04
420.76
MR05-05 Leg3
262.94
320.42
381.04
420.76
MR06-04 Leg1
289.76
349.00
393.75
439.72
MR06-04 Leg2
289.76
349.00
393.75
439.72
MR07-04
289.77
349.02
393.77
439.75
MR07-05
289.77
349.02
393.77
439.75
MR07-06 Leg1
270.02
330.40
369.28
419.68
MR07-06 Leg2
270.02
330.40
369.28
419.68
MR09-01 Leg1
270.22
330.43
360.04
420.32
MR09-01 Leg2
270.22
330.43
360.04
420.32
Inoue, H. Y., H. Matsueda, M. Ishii, K. Fushimi, M. Hirota, I. Asanuma, and Y. Takasugi (1995), Long-term trend of the partial pressure of carbon dioxide (pCO2) in surface waters of the western North Pacific 1984 - 1993. Tellus 47B, 391 - 413.