Capturing marine CO2 system variability & estimating change using observations from an Alaskan ferry (text & video)

OA Week 2021, North American Hub Session

Dr. Wiley Evans, Hakai Institute, Canada


Information on marine CO2 system variability has been limited along the Inside Passage of the Pacific Northwest despite the region’s rich biodiversity, abundant fisheries, and developing aquaculture industry. Beginning in 2017, the Alaska Marine Highway System M/V Columbia has served as a platform for surface underway data collection while conducting twice weekly ~1600-km transits between Bellingham, Washington and Skagway, Alaska. This effort provided the first characterization of the variability, severity, and timing of adverse pH and aragonite saturation state (Ωarag) conditions across the region. Lowest pH was seen in confined tidally-mixed zones in autumn; whereas lowest Ωarag was seen in areas of high glacial melt in summer. Time-of-detection estimates revealed the tidally-mixed zones to be sentinel observing sites with relatively short time spans of observation needed to capture seawater pCO2 increase equivalent to the contemporary atmospheric CO2 trend. Anthropogenic CO2 estimates showed large time and space variability, the impacts of which were greater change in winter pH and larger change in summer Ωarag. Differing spatial patterns of severe pH and Ωarag, and the differential response to anthropogenic CO2, likely have implications for vulnerable species and should be considered within the scope of tracking ocean acidification. Here we characterize the 1.5°C acidification level as the theoretical extent of acidification along the Inside Passage if society limits global warming to preferably 1.5°C as per the Paris Agreement, and show that half the acidification experienced thus far since the start of the industrial era is expected over the coming 15 years at our current atmospheric CO2 trajectory.

Ocean Acidification Week 2021 was sponsored by the following organizations:

(1) GOA-ON, the Global Ocean Acidification Observing Network,

(2) NOAA, the United States National Oceanic & Atmospheric Administration,

(3) IAEA OA-ICC, the International Atomic Energy Agency – Ocean Acidification International Coordination Centre, and

(4) IOC-UNESCO – the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific and Cultural Organization

For more information, please visit

GOA-ON, YouTube, 21 September 2021. Text and video.

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