Monitoring OAE Efforts in Halifax: Fighting Climate Change with Emerging mCDR Strategies

Marine carbon dioxide (CO2) removal (mCDR) is an emerging strategy that aims to fight climate change by taking advantage of the carbon capture potential of our oceans. There are multiple types of mCDR approaches being evaluated globally, one of which is ocean alkalinity enhancement (OAE).

According to NOAA, OAE aims to increase the pH of water by either adding alkaline material to ocean surface waters or by removing acid from seawater. Due to the change in acidity, the chemistry of seawater changes, making it capable of absorbing greater volumes of CO2.

Once absorbed, the CO2 can be converted into more stable forms of carbon, which are then potentially stored on the ocean floor and are expected to remain there for thousands of years, as stated by Columbia Law.

As a still-emerging strategy, there is much to learn about how effective mCDR is and asking questions is an essential component of building a better understanding of how removal occurs. Such unknowns limit the ability for OAE strategies to be implemented at a large scale.

Sequoia team members installing the NexSens X3 datalogger to enable remote monitoring of sensor outputs. (Credit: Darren Calabrese / Carbon to Sea)

The team at Sequoia Scientific, Inc., overseeing the deployment of some of their instruments in an OAE field trial in Halifax, Nova Scotia, explains, “Some open questions around OAE involve the fate of alkalinity added to the water: How does the distribution and dissolution of the alkaline material match up with models? What potential secondary effects, such as aggregation or secondary precipitation, may be occurring?”

They continue, “By deploying sensors to directly measure particles in the water, we aim to provide in-situ data that can help ground-truth these models and answer these questions.”

Studying OAE and Testing mCDR in Nova Scotia

In the summer of 2024, Carbon to Sea and COVE announced a Joint Learning Opportunity (JLO) seeking proposals for additional research, instrument testing, and other activities to support an already-funded OAE field trial being led by Planetary Technologies and Dalhousie University in Halifax. 

OAE field trial site at Tufts Cove in Halifax, Nova Scotia, Canada. (Credit: Darren Calabrese / Carbon to Sea)

Sequoia, who is a globally recognized leader in submersible instrumentation for particle analysis, felt their instruments were uniquely suited to study particles and water optical properties in-situ to support the scientific investigation around alkalinity dosing. 

Upon hearing about the JLO, Sequoia submitted a proposal to deploy several of their sensors throughout the field trial this fall and winter, and was then selected as one of the four research projects to be funded.

The Sequoia team prepared the sensors and delivered them to Halifax in late September, after which Kirby Simon, Science & Technology Lead, and Ole Mikkelsen, President and CEO, traveled to Halifax to help deploy the sensors and train researchers on how to deploy, operate, and maintain the different instruments.

Currently, Sequoia provides remote support to researchers in Halifax from their office in Bellevue, WA and periodically archives, cleans, and analyzes measurements from their sensors as they continue to operate in the OAE field trial.

Sequoia and Planetary personnel mounting the LISST-OST and LISST-Tau sensors to the mooring. (Credit: Darren Calabrese / Carbon to Sea)

In terms of sensors, the Sequoia team has contributed their LISST-200X submersible particle size analyzer, LISST-Tau beam transmissometer, and newly developed LISST-OST (Optical Sediment Trap) under the JLO. 

The LISST-Tau and LISST-OST are connected to a NexSens X3 datalogger. The logged data from these sensors are transmitted to WQData LIVE, where the Sequoia team can monitor the sensor performance remotely.

The team explains, “Our LISST-Tau and LISST-OST are deployed near the alkalinity addition site and perform measurements every 5 minutes, logging and transmitting data through the NexSens X3. Our LISST-200X is being profiled during boat surveys performed by Dalhousie and Planetary personnel throughout the Bedford Basin and surrounding waters.”

LISST-200X submersible particle size analyzer in profiling cage. (Credit: Sequoia Scientific, Inc.)

“We hope the instrumentation we contribute to this JLO can provide in-situ data to help address unanswered questions regarding the effectiveness and potential environmental impacts of alkalinity addition and build upon the growing body of research surrounding mCDR,” they elaborate.

While an initial concern was that the Sequoia team was based out of Washington while the other stakeholders were based closer to the OAE field trial site, the telemetric capabilities of the X3 data logger resolved concerns about data access and troubleshooting.

Additionally, the dedicated team of researchers from Planetary Technologies and Dalhousie University helped deploy the system and have been trained on necessary maintenance procedures.

Sequoia and Planetary personnel adjusting the LISST-OST positioning before deployment. (Credit: Darren Calabrese / Carbon to Sea)

At the conclusion of the study, Sequoia plans to release the collected data to the public for use in research studies involving OAE and other mCDR research.

“We aim to provide open-source datasets from our sensors that can be used by researchers for a variety of studies ranging from particle fate and transport to model validation. We also aim to help integrate measurements from our sensors with studies by other JLO participants to maximize synergies among our research efforts,” states the Sequoia team.

Conclusion

The data collected by the Sequoia/NexSens system is fundamental to learning more about mCDR and OAE treatments. Results of the study will help lead to new developments in reducing global CO2 levels and fighting climate change.

“Supporting research efforts in this emerging field is exciting and provides a novel opportunity for learning, and we hope the research we are contributing to now can help build a knowledgebase to support future research in mCDR and other climate mitigation strategies to come,” states the team.

They continue, “Additionally, getting to work with such a diverse team of passionate and purposeful researchers under this JLO who all are fervently committed to fighting climate change is truly inspiring.”

Sequoia team demonstrating a profiling deployment of the LISST-200X. (Credit: Sequoia Scientific, Inc.)