New Paper: Marine CO2 system variability along the northeast Pacific Inside Passage
Updated: May 24, 2022
Very little is known about the chemical oceanography in many regions of the Pacific coast of Canada. A few records in the Salish Sea existed, as well as records from an old NOAA mooring in Alaska (removed in 2016); however, these records give only a limited perspective of what conditions look like in simple parameters like temperature, salinity, CO2, and O2. The groundbreaking 2022 paper Marine CO2 system variability along the northeast Pacific Inside Passage determined from an Alaskan ferry is an observational study which allows us to view these parameters, and our North American Pacific coast like never before. This cutting edge 2-year project details how these parameters change along 1600km of coastline at high temporal resolution through the installation of equipment on the Alaska ferry the MV Columbia.
Dr Wiley Evans, the lead author of this paper, leads the Ocean Acidification program at the Hakai institute. His schooling and career have allowed him to study in many regions across the west coast of North America. He did not begin his career with a focus on Ocean Acidification; it was not until his post doc at the University of Alaska Fairbanks that he began his journey into the world of OA. He continued this focus during his time working at the NOAA Marine Pacific Environmental Lab in Seattle, before moving to the Haikai Institute where he works today.
The ideas for this project started simply with some local interest in one of Wiley’s previous projects in Prince William Sound while at the Pacific Marine Environmental Lab. Wiley explains, “Since part of my background is in underway CO2 measurements, we were interested in installing an instrument onto a tour vessel operated by Major Marine Tours. When we began this earlier project, which involved gliders and other sensors, it drew attention in Alaska because of how involved it was.” A colleague of Wiley’s from the Alaska Coastal Rainforest Center thought that projects like this could and should happen on Alaska Ferries. They thought that a project like this could mutually benefit from growing alongside the Alaska OA Network, which was still quite young at the time. The Alaska Department of Transportation agreed to install the project's instrumentation on their flagship vessel, the M/V Columbia, which runs a 1600 km transit from Bellingham WA in the Salish Sea to southeast Alaska (the latitudes that the transit runs through are represented in the image below).
“This research could not have been accomplished alone, teamwork drove the project at every stage.”
After 2 years of planning, preparing, and installing, the M/V Columbia began its 2-year task of collecting data along its transit of the Pacific Coast, taking measurements every 2 minutes, with the same locations sampled every 3 days to a week depending on their position along the transit. This project presented unique challenges to Wiley and his fellow researchers because the M/V Columbia is a working vessel. This means that the time that the research team has to service the equipment is limited. “Scheduling was key to ensuring this project was realized.” Wiley says, “This research could not have been accomplished alone, teamwork drove the project at every stage.”
When asked what scientific question drove the beginning of this research, Wiley explained, “We wanted to understand how ocean conditions varied and what this may mean for marine life.”
This research produced many insights into how oceanic conditions on the coast vary. The observations taken from the M/V Columbia show that the seasonal amplitude (the change of the factors over the course of a year) was the dominant signal. This pattern varied along the coast because of the effects of freshwater inputs, from rivers mouths; net community production, which is is the difference between O2 produced by primary producers (or CO2 drawdown) minus O2 respired (or CO2 produced) by consumers, i.e. the community metabolism.; and vertical mixing in the water column. Some regions undergo nearly constant vertical mixing, such as the Johnstone Strait along the northeast coast of Vancouver Island, which has narrow passages with a strong tidal current. The mixing keeps waters in these areas cold and salty for most of the year and creates a seasonal amplitude that is quite low. Seasonal changes are so dominant that even these areas with intense vertical mixing have a detectable seasonal signal. Areas with the largest seasonal variation are found outside of these mixing zones; an example of one of these areas is the Salish Sea in Southern BC. Low mixing in these regions create conditions for plenty of community production (increasing oxygen and drawing down more CO2). This production creates periods of CO2 drawdown which, in turn, increases the seasonal variability.
“Studies like this will help to inform about which areas of the coast can provide the best information"
Another factor Wiley and his team considered in this research is the extremes of the conditions (for example: when pH is at its highest/lowest value) that were measured and the seasonal timing of these extremes. Not all extremes are in the same direction (high or low) for the same factors at the same time of year. In areas with more mixing, like the Johnstone Strait, extremes occur at the same time of the year (in the fall). However, in some areas extremes do not occur during the same season, for example in the Lynn Canal located in southeast Alaska and the waters around Juneau. These areas have a large meltwater signal, which results in the largest declines of salinity of the entire transit. The melt water in this region has unique properties because it is exceptionally cold, maintains high pH conditions (non-acidic), and is undersaturated with respect to the atmosphere in pCO2. Despite these factors, this meltwater is corrosive for aragonite, a form of calcium carbonate used by some shell producers; this corrosiveness represents a decoupling of the CO2 system because the pCO2 is also low when it would usually be high in seawater corrosive to aragonite. This is very unusual in most coastal settings. The study detailed how these extremes differ between parameters and different timings across the transit of the MV Columbia.
“Studies like this will help to inform about which areas of the coast can provide the best information when thinking about the future of oceanographic observation along any coastline. Coastal waters are notorious for being highly variable and, because of this variability, it takes a long time to see any trends in the data. When you look at coastal waters on temporal and spatial scales that we did, you can see that this is not always the case. In some instances, we can select certain areas where there is less variability throughout the year and therefore less time needed to resolve trends in the data. If the goal of the future of the observing network is to observe long term change, then identifying these areas of low variability can give the future observing network a much better shot at seeing a signal in the observations within a reasonable amount of time. The realization of achieving observational goals in specific regions can be greatly aided by this type of research, through the identification of ideal locations for observation.”
“...it has taken 250 years for the acidity to go up 40% and these calculations predict that it will increase 17% more in just 13 years; that is an enormous change."
Tracking human or anthropogenic CO2 emissions inclusion into the marine environment is vital to the future of marine research and modeling. This paper estimated the amount of anthropogenic CO2 that was found in the waters along the transect. Through the use of observational data to estimate the first time-period the waters along the transit experienced undersaturation of aragonite.. The results of these estimates confirmed similar work that was done at the Hakai Institute’s Quadra Island Field Station in 2019, which found that undersaturation of aragonite (marine conditions became corrosive for aragonite) occurred for the first time around 1950 during the winter season in the Salish Sea. What was new in this study was the ability to look at how conditions have evolved over the entire transit. This showed that the coast is extremely variable in its susceptibility to undersaturation. Some areas like southeast Alaska did not become undersaturated during winter until the late 2000’s.
The data from this study was used to calculate how hydrogen ions, saturation state, and pH have changed from the industrial revolution to the present and projected the conditions to 2035; This is the year that the earth is predicted to reach its 1.5°C thresholds given consistently high CO2 emissions and presented in this study as the 1.5°C acidification level. What was found from these calculations was that, on average, this area of the coastline has seen a 40% increase in acidity since the beginning of the industrial era, which is 10% higher than the global average of a 30% increase (there is variation along the transit because of the factors that we discussed above). Looking forward to the 1.5°C acidification level we could see another increase of 17% on average in this region. “To put this in perspective it has taken 250 years for the acidity to go up 40% and these calculations predict that it will increase 17% more in just 13 years; that is an enormous change. We do have to keep in mind that these are just estimates and continued monitoring will determine if these estimates are realized.”
“These data have taken a lot of coordination and work to collect, but I think that these types of projects are very important to the future of global carbon research. We provided these data to the Surface Ocean CO2 Atlas, which is a global compilation of underway CO2 measurements. Data from researchers around the world are provided to the Atlas which in turn supports global projects like the creation of the annual Global Carbon Budget. It is a huge and very important piece of work, which has very few Canadian contributions.”
The next steps of this research are already underway and there is a want for it from members of the Alaskan community, who are voicing their interest in seeing the ferry running again, as there is potential the vessel may run again in late spring/early summer 2023. Additionally, a partnership with Seaspan was formed to outfit a tugboat which services Khidmat, Stewart, Haida Gwaii, Masset Inlet, Zeballos, around Vancouver Island, and into Vancouver itself, with a CO2 instrument package. The tugboat will allow for measurements over a large spatial scale, as well as add winter observations from these locations. “Growing the winter observation data set is important; we were fortunate with the winter data that was collected from Columbia.”
“When looking to the future, this type of work is incredibly important. Especially as we start to consider how we are going to use the oceans as part of the solution to climate mitigation”, says Wiley. He encourages the Canadian research community and the Government of Canada to expand these types of projects by outfitting more ships and other platforms with these types of instruments. Data like these with high spatial and temporal resolution will be needed from all 3 Canadian oceans to properly inform future decisions.
Read Evans et al., 2022, here:
Citation: Evans, W., Lebon, G. T., Harrington, C. D., Takeshita, Y., and Bidlack, A.: Marine CO2 system variability along the northeast Pacific Inside Passage determined from an Alaskan ferry, Biogeosciences, 19, 1277–1301, https://doi.org/10.5194/bg-19-1277-2022, 2022.
Acknowledgements: Thanks to Wiley Evans for his virtual “in-person” interview