The pH (in situ, total scale) of near surface seawater was measured from the CCGS John P. Tully while underway during three Canadian Line P cruises conducted from 2019 through 2020. A prototype instrument, BGC-SUMO (Y. Takeshita, MBARI), was plumbed into the ship's seawater intake line to measure near surface pH while a collocated thermosalinograph measured near surface salinity and temperature from the same flow stream. This dataset provides information on these properties.
Underway measurements were made aboard the CCGS John P. Tully during three Canadian Line P cruises (2019-2020) in the northeast Pacific from Vancouver Island to Station P (50°N, 145°W).
Fisheries and Oceans Canada (DFO) Cruise numbers: 2019-006, 2019-008, 2020-001
pH
A prototype instrument (BGC-SUMO) developed by Dr. Yui Takeshita at MBARI was plumbed into the CCGS John P. Tully seawater intake (~5 m below the surface) line in the wet lab. Underway in situ pH on the total hydrogen ion concentration scale was measured with an ion-sensitive field-effect transistor (ISFET) pH sensor (Deep-Sea DuraFET; Johnson et al., 2016). The instrument was powered through an isolation transformer to prevent ground loop issues. The system was polled using a LabView interface and pH measurements were made every 10 milliseconds. pH sensor data were calibrated using discrete pH samples collected from the underway line (near BGC-SUMO) during the three cruises: 2019-006, 2019-008, and 2020-001 (n= 19, n= 5, n= 5, respectively)
Temperature and Salinity
Underway temperature and salinity were measured by a Sea-Bird Scientific SBE45 MicroTSG thermosalinograph located directly downstream (< 10 cm) of the BGC-SUMO pH sensor that was plumbed into the CCGS John P. Tully seawater intake (~5 m below the surface) line in the wet lab. Underway temperature and salinity were also measured with a CCGS John P. Tully thermosalinograph at the seawater intake location. These data were used to correct for warming between the seawater intake and the location where the instruments were plumbed into the underway line. The CCGS John P. Tully thermosalinograph data can be accessed through the Canadian Line P Program data archive (https://waterproperties.ca/linep/2019-001/index.php). The instrument was powered through an isolation transformer to prevent ground loop issues. The system was polled using a LabView interface and pH measurements were made every 10 milliseconds.
Fassbender, A. J., Long, J. S., Takeshita, Y. (2021) Underway pH of seawater sampled during CCGS John P. Tully cruises in the northeast Pacific Ocean from Vancouver Island to Station P from 2019 to 2020. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2021-12-13 [if applicable, indicate subset used]. doi:10.26008/1912/bco-dmo.866582.1 [access date]
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