Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

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.

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).

OCE-1756932 Start Date: 2018-03-01
OCE-2032754 Start Date: 2020-05-28

NSF abstract:
A goal in chemical oceanography is to advance our understanding of the global carbon cycle, specifically to quantify the transfer of carbon from the surface ocean to depth through the sinking of particles produced by marine organisms. Yet, modern global estimates of this process (commonly called carbon export) differ by over 100%. These estimates are often derived from regional relationships between ocean measurements and satellite observations that are then applied globally. Persistent differences between the satellite and field-based estimates of carbon export have been found throughout the ocean, suggesting that improvements are needed. This project will determine whether profiling floats equipped with chemical sensors can be used to estimate the export of carbon in the ocean. Floats will be deployed at Ocean Station Papa, but the approach is scalable in nature and could be used to validate and improve the satellite algorithms used for global carbon export determinations. The project will support a female, early career scientist and a postdoc, as well as facilitate international collaboration with Canadian scientists. Additionally, the results may assist the National Aeronautics and Space Administration (NASA) EXPORTS campaign as well as other satellite carbon export development efforts.

Modern global estimates of the biological pump differ by over 100% (~5 to >12 Pg C yr-1) making it challenging to determine the role of marine biogeochemical (BGC) cycling in modern climate and climate variability. Global carbon export estimates are often derived from regional empirical relationships between field and satellite observations that are then applied globally. Persistent discrepancies between unique satellite algorithms and unique geochemical approaches suggest that accurately quantifying the biological pump remains a fundamental research goal. This project will assess the capability of using BGC profiling floats to estimate the export of distinct biogenic carbon pools (dissolved and particulate organic carbon, and particulate inorganic carbon). By using BGC floats to close multiple upper ocean tracer budgets this project will address two known issues common to other geochemical approaches: assumptions about (1) dissolved organic carbon cycling and (2) the integration depth used for annual carbon export assessments. The method will be tested at Ocean Station Papa, but is scalable in nature and could be used to develop a carbon export database suitable for the validation and training of satellite algorithms required for global carbon export determinations. Results from the floats will be compared to satellite carbon export algorithm estimates over the 5-year float lifetimes. Ten years of existing BGC data from profiling floats and a mooring in the region will also be used to provide further context about interannual variability.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.