Table of Contents

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

In situ biogeochemical measurements including pCO2, pH, alkalinity, oxygen, temperature and salinity for a time-series in Bermuda, September 2017.

The instruments were deployed on Hog Reef, Bermuda (32.46 oN, 64.83 oW), attached to the PMEL MAPCO2 buoy for the surface measurements, and anchored to the reef below the buoy at ~7 meters depth.

Real-time temperature, pCO2, pH, salinity, alkalinity and dissolved oxygen were determined in situ. Discrete samples were collected and stored in glass bottles, preserved with HgCl2.

SAMI-CO2 sampled on a 15 minute interval. SAMI-CO2 ran a non-absorbing blank measurement every 3.5 days. 

SAMI-pH sampled on a 15 minute interval.

SAMI-Alk sampled on a 2 hour interval. SAMI-Alk ran a non-absorbing blank measurement for every measurement. A standard was run every 22 hours.

Dissolved oxygen was sampled on a 15 minute interval.

Temperature was recorded with SAMI-CO2, SAMI-pH on a 15 minute interval and with CTD on a 15 minute interval.

Salinity was recorded with CTD on a 15 minute interval.

SAMI data were processed through a custom-written Matlab QC program.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- commented out units row
- reduced precision of temperature and pCO2 to 2 decimals, pH to 4 places, alkalinity to 1 place.

NSF abstract:
The ocean inorganic carbon system is of great interest to marine scientists, and indeed all people, because it contains important information about ocean productivity, the sources and sinks of anthropogenic carbon dioxide, and ocean acidification. Total alkalinity is one of the critical inorganic carbon parameters and has been widely measured through ship and laboratory-based methodologies. At this time, there are no commercially-available in situ sensors for total alkalinity. In this project, researchers at the University of Montana will further develop and test a new autonomous system, known as the SAMI-alk, for measuring total alkalinity. This new system will expand understanding of total alkalinity and the inorganic carbon cycle by making near continuous measurements in locations not frequented by ships. The development of this instrument will have important broader implications for the oceanographic community and ocean acidification research by providing a novel instrument for ocean research. This project will also provide training opportunities to graduate and undergraduate students, and will continue to support public outreach on ocean acidification through a university-affiliated museum.

Studies focused on the marine carbon cycle and ocean acidification pose a number of measurement challenges. While pH is the ocean acidification "smoking gun" and partial pressure of CO2 is critical for gas exchange calculations, the full inorganic carbon system must be quantified for most inorganic carbon studies. Using autonomous sensors to accurately and precisely quantify all of the inorganic carbon species has been a long-standing objective for marine biogeochemists, but full characterization of the inorganic carbon system has, until recently, been limited to ship and laboratory-based measurements. Total alkalinity is one such parameter as its research has been limited by the lack of instrument capable of making in situ measurements. This research will address this problem and advance inorganic carbon studies through the further development of an autonomous, in situ system to measure seawater total alkalinity, known as the submersible autonomous moored instrument for total alkalinity (SAMI-alk). Preliminary testing of the instrument showed great promise, and through this project, researchers will conduct lab experiments to improve its performance. Two new prototype instruments will be tested in laboratory and field evaluations.