Underway measurements of seawater pH and total alkalinity from the Ryder 2019 expedition

Adam Ulfsbo

Continuous, underway measurements of seawater pH and total alkalinity (TA) were collected from the surface seawater intake system on board the Swedish icebreaker Oden during the Ryder 2019 Expedition (August⁠ – ⁠September) from coastal waters along northwestern Greenland, from Thule in the south to Sherard Osborn Fjord in the north. More specifically, the observations cover Nares Strait, southern Lincoln Sea, Sherard Osborn Fjord (where Ryder Glacier drains), and Petermann fjord (where Petermann Glacier drains).

Seawater pH and TA were measured spectrophotometrically with automated analyzers (CONTROS HydroFIA pH and TA). The continuous observations of sea-surface pH (total pH scale, 25 °C, in situ salinity) and total alkalinity (µmol/kg-seawater) have a temporal resolution of 10 minutes and are accompanied by recordings of time, latitude, longitude, sea-surface salinity, and sea-surface temperature.

Seawater pH and TA are two key variables of the marine carbonate system. From these observations, together with concurrent measurements of temperature and salinity, the two other measureable variables of the marine carbonate system, i.e., dissolved inorganic carbon (DIC) and the partial pressure of carbon dioxide (pCO₂), can be calculated through thermodynamic models. Observations of any two of the four measureable variables of the the marine carbonate system are useful in assessing the seawater state with respect to, e.g., air-sea gas exchange, buffer capacity, and calcium carbonate mineral saturation.

Citation

Adam Ulfsbo (2021) Underway measurements of seawater pH and total alkalinity from the Ryder 2019 expedition. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-ryder-2019-surface-seawater-ph-alkalinity-1

References

Jakobsson M, Mayer LA, Farrell F, Ryder 2019 Scientific Party (2020) Expedition report: SWEDARCTIC Ryder 2019, Swedish Polar Research Secretariat, 455 pp, ISBN 978-91-519-5132-4

Data description

The underway measurements of seawater pH and TA are organized in a comma-separated values (csv) file and include the following parameters:

• Year
• Month
• Day
• Hour
• Minute
• Second
• Latitude (decimal degrees north)
• Longitude (decimal degrees east)
• Salinity (practical salinity, PSS-78) from the laboratory seawater intake system (SBE43)
• Temperature (°C) from the laboratory seawater intake system (SBE43)
• Temperature (°C) from the ship's hull (PT-100)
• Seawater pH on the total scale, at 25 °C, and 0 db pressure
• Total alkalinity (micromols per kilogram seawater)

Comments

The surface seawater intake system is situated at 8 meters depth on the Icebreaker Oden and is pumped up to the main laboratory on the main bow deck. The seawater from the intake system is sub-sampled for measurements of seawater pH and TA with a temporal resolution of 10 minutes. These observations are accompanied by recordings of time, latitude, longitude, salinity laboratory seawater intake temperature, and the vessel's hull temperature.

Seawater pH was measured spectrophotometrically with a CONTROS HydroFIA pH analyzer (Aßmann et al. 2011) on the total scale at a constant salinity of 35 and thermostated at 25 °C. The data were processed with in-situ salinites from the vessel's underway thermosalinograph (SBE43) post-cruise.

Total alkalinity was measured spectrophotometrically with a CONTROS HydroFIA TA analyzer (Seelmann et al. 2019) at a constant salinity of 35 and thermostated at 25 °C. The data were processed with in-situ salinites from the vessel's underway thermosalinograph (SBE43) post-cruise.

For more details, see the cruise report (Jakobsson et al. 2020).