There are many different methods that scientists use to measure pH, pCO₂, DIC, and TA. Scientists choose their methodology carefully to help them answer specific questions about ocean acidification.

Seawater carbonate chemistry measurements can be collected using the following methodologies:

• Continuous sensors: These sensors are used to automatically measure seawater carbonate chemistry in situ. Commonly used sensors can measure pH or pCO₂, alongside other water quality characteristics like temperature and salinity. Sensors can be applied to different platforms:
  
  • Moored Continuous Sensors: affixed to buoys or docks, moored sensors measure seawater carbonate chemistry in one place over time
  • Underway Cruise: sensors can also be attached to ships, collecting data at the ocean surface as the ship moves along its route
  • Continuous Ocean Gliders: ocean gliders are autonomous, underwater vehicles that collect data across large areas and at varying depths as they “swim” through the ocean.
• Discrete sampling: Discrete sampling involves scientists collecting a single data point at a time, either by collecting a water sample or using a handheld probe. This can be done in several ways:
  
  • Discrete Bottle Sampling: water samples are collected, preserved, and then brought back to a lab for analysis. Most methodologies for measuring DIC and TA require benchtop lab equipment, so bottle samples are commonly collected for these two parameters.
  • Rosette Sampler: device that makes bottle sampling possible in the open ocean and deep ocean.
  • Handheld Probe: handheld sensor that is operated by a user to record discrete measurements.