Dataset: Underway pH data near Line P
Deployment: Line-P_cruises

View Data: For data, See Dataset Metadata Page: https://www.bco-dmo.org/dataset/866582

Principal Investigator:

Phoebe J. Lam (University of California-Santa Cruz, UCSC)

Co-Principal Investigator:

Andrea J. Fassbender (National Oceanic and Atmospheric Administration, NOAA-PMEL)

Scientist:

Yuichiro Takeshita (Monterey Bay Aquarium Research Institute, MBARI)

Technician:

Jacqueline S. Long (Monterey Bay Aquarium Research Institute, MBARI)

BCO-DMO Data Manager:

Dana Stuart Gerlach (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Project:

Constraining Upper-Ocean Carbon Export with Biogeochemical Profiling Floats (EXPORTS BGC Floats)

Version:

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Description

Methods & Sampling

Dataset acquisition description

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.

Data Processing Description

Dataset Processing Description

Underway pH
Discrete pH and BGC-SUMO pH data were converted from pH values measured at the BGC-SUMO TSG temperature to in situ pH values using the ship-board TSG intake temperature. This pH temperature conversion calculation was performed using the program CO2SYSv3 (Lewis & Wallace, 1998; Sharp et al., 2020; van Heuven et al., 2011). An average of discrete TA samples (QF as good), also collected during these cruises, was used in the CO2SYSv3 calculations. The following constants were chosen for CO2SYSv3 input: K₁K₂ of Lueker et al (2000); K_SO4 of Dickson (1990); KF of Perez & Fraga (1987); TB of Lee (2010). The mean of pH residuals (BGC-SUMO pH – discrete pH, both at BGC-SUMO TSG temperature) was near zero for all cruises (4.5x10^-07, -1.0x10^-06, -3.3x10^-06; for cruises 2019-006, 2019-008, 2020-001, respectively).

Problem report
Underway pH measurements during the sensor warm-up phase for each cruise were given a Quality Flag (QF) of 4 or 3, determined based on comparison with in-line temperature and salinity data. During the return transits for cruises 2019-006 and 2020-001, large discrepancies between BGC-SUMO and discrete pH data were observed. These underway pH data were assigned a QF = 3. Unrealistic pH data for this region (values > 8.4 and < 7.6) were also assigned a QF of 4. A moving mean filter with a sliding window of 200 (~2 second resolution) was applied to the pH data to identify irregular spikes, which were assigned a QF = 3. When ship TSG temperature or salinity values were missing, BGC-SUMO pH data were set to NaN.

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BCO-DMO Processing:

Imported data from source file "combined_SUMO_data_FORMATTED.xlsx" into the BCO-DMO data system.
Data file imported using missing data identifiers "NaN”. The missing data identifier "NaN" in the original source file will be displayed as appropriate based on the type of file you download from the BCO-DMO data system. For example, missing data will be shown as blank (null) values in the csv files. In MATLAB .mat files it will be displayed as NaN. When viewing data at BCO-DMO the missing value will be shown as "nd" meaning "no data."
Converted separate date and time fields to single datetime column with ISO8601 format.
Added column for vessel/ship
Added conventional header with dataset name, PI name, version date.
Modified parameter (column) names to conform with BCO-DMO naming conventions. (The only allowed characters are A-Z,a-z,0-9, and underscores. No spaces, hyphens, commas, parentheses, or Greek letters).

More information about this dataset deployment

Funding

Award Number	Funding Source
OCE-1756932	NSF Division of Ocean Sciences
OCE-2032754	NSF Division of Ocean Sciences

Instruments

pH Sensor

Supplied Name: Deep-Sea DuraFET (DSD) sensor

Supplied Description:

pH was measured using a Deep-Sea Durafet (DSD) sensor

Instrument Type

Generic Name: pH Sensor

Generic Description:

An instrument that measures the hydrogen ion activity in solutions.

The overall concentration of hydrogen ions is inversely related to its pH. The pH scale ranges from 0 to 14 and indicates whether acidic (more H+) or basic (less H+).

pH Sensor

Supplied Name: BGC-SUMO

Supplied Description:

A prototype instrument (BGC-SUMO; Y. Takeshita - yui@mbari.org) for measuring seawater pH on underway ships was plumbed into the CCGS John P. Tully seawater intake line

Instrument Type

Generic Name: pH Sensor

Generic Description:

An instrument that measures the hydrogen ion activity in solutions.

The overall concentration of hydrogen ions is inversely related to its pH. The pH scale ranges from 0 to 14 and indicates whether acidic (more H+) or basic (less H+).

Sea-Bird SBE 45 MicroTSG Thermosalinograph

Supplied Name: SBE45 MicroTSG thermosalinograph

Supplied Description:

Underway temperature and salinity were measured near the pH sensor by an SBE45 MicroTSG thermosalinograph

Instrument Type

Generic Name: Sea-Bird SBE 45 MicroTSG Thermosalinograph

Acronym: SBE 45 MicroTSG

Community Identifier: http://vocab.nerc.ac.uk/collection/L22/current/TOOL0190/

Generic Description:

A small externally powered, high-accuracy instrument, designed for shipboard determination of sea surface (pumped-water) conductivity and temperature. It is constructed of plastic and titanium to ensure long life with minimum maintenance. It may optionally be interfaced to an external SBE 38 hull temperature sensor.

Sea Bird SBE 45 MicroTSG (Thermosalinograph)

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
ISO_DateTime_UTC	Date and time in ISO8601 standard format (YYYY-MM-DDThh:mm:ssZ)	unitless	ISO_DateTime_UTC
Vessel	Vessel	unitless	ship
Cruise_ID	Cruise	unitless	cruise_id
Latitude	Latitude of sample collection	decimal degrees	lat
Longitude	Longitude of sample collection	decimal degrees	lon
pH_in_situ	In situ pH value calculated using program CO2SYSv3 with conversion of discrete pH and SUMO pH data	unitless	pH
pH_QF	pH measurement quality flag where 2=acceptable; 3=questionable; 4=bad; 6=mean of replicate; 8=sample lost; 9=not sampled	unitless	q_flag
Temperature	Underway temperature as measured with TSG	degrees Celsius	temp
Salinity	Underway salinity as measured with TSG from the ship's intake about 5 meters below the surface	practical salinity unit (PSU)	sal_ss
Date	Date of sample collection	unitless	date

Database

Contribute Data

Dataset: Underway pH data near Line P
Deployment: Line-P_cruises

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: Underway pH data near Line PDeployment: Line-P_cruises

Dataset acquisition description

Dataset Processing Description

Dataset: Underway pH data near Line P
Deployment: Line-P_cruises